ALBERT

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Priscilla M. de Souza, Carlos V.M. Inocêncio, Victoria I. Perez, Raimundo Crisostomo Rabelo-Neto, Vinicius Ottonio O. Gonçalves, Gary Jacobs, Frédéric Richard, Victor Teixeira da Silva, Fabio B. Noronha〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work studied the performance of nickel phosphide phases supported on various supports (SiO〈sub〉2〈/sub〉, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, TiO〈sub〉2〈/sub〉, CeO〈sub〉2〈/sub〉 and CeZrO〈sub〉2〈/sub〉) for the hydrodeoxygenation of phenol in gas phase at 300 °C and 1 atm. The nature of the phosphide phase obtained by the temperature programmed reduction at 700 °C depended on the type of support. Only Ni〈sub〉2〈/sub〉P was formed on SiO〈sub〉2〈/sub〉, TiO〈sub〉2〈/sub〉, and CeZrO〈sub〉2〈/sub〉, whereas the Ni〈sub〉12〈/sub〉P〈sub〉5〈/sub〉 was the preferred phase on Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. A mixture of both Ni〈sub〉2〈/sub〉P and Ni〈sub〉12〈/sub〉P〈sub〉5〈/sub〉 phases was obtained on CeO〈sub〉2.〈/sub〉 Unsupported Ni〈sub〉2〈/sub〉P exhibited high selectivity to benzene (95%), indicating that the Ni〈sub〉2〈/sub〉P phase is responsible for the direct deoxygenation of phenol. Ni〈sub〉12〈/sub〉P〈sub〉5〈/sub〉 phase promoted the formation of cyclohexanone, cyclohexane and cyclohexene. However, the supported catalysts showed lower selectivity to benzene, even when the Ni〈sub〉2〈/sub〉P was the only phase present. The supports favored the formation of hydrogenation products via the tautomerization route. All catalysts only slightly deactivated with time on stream, which is likely due to the high activity of the phosphide phase.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304602-ga1.jpg" width="279" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Jose L. Diaz de Tuesta, Asuncion Quintanilla, Jose A. Casas, Sergio Morales-Torres, Joaquim L. Faria, Adrián M.T. Silva, Helder T. Gomes〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉P, B and N-doped carbon blacks prepared with H〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉, urea and H〈sub〉3〈/sub〉BO〈sub〉3〈/sub〉 were tested as catalysts in the wet peroxide oxidation of a concentrated 4-nitrophenol (4-NP) model solution (〈em〉C〈sub〉4-NP〈/sub〉〈/em〉 = 5 g·L〈sup〉-1〈/sup〉). The highest catalytic activity was found for P-doped carbon black (complete removal of 4-NP after 4 h at 80 °C, 〈em〉C〈sub〉cat〈/sub〉〈/em〉 = 2.5 g·L〈sup〉-1〈/sup〉, 〈em〉C〈sub〉H2O2〈/sub〉〈/em〉 = 17.8 g·L〈sup〉-1〈/sup〉 and initial pH 3, whereas 44-19% removals were reached with the other catalysts). That was ascribed to the strongest acidity (〈em〉pH〈sub〉PZC〈/sub〉〈/em〉 = 3.5) and hydrophilic character of the catalyst. Initial pH affected the oxidation, allowing to increase strongly the conversion of 4-NP with the P-doped catalyst decreasing the initial pH from 4 to 2 (4-NP removal from 20% to 99% after 8 h of reaction time at 50 °C, 〈em〉C〈sub〉cat〈/sub〉〈/em〉 = 2.5 g·L〈sup〉-1〈/sup〉 and 〈em〉C〈sub〉H2O2〈/sub〉〈/em〉 = 17.8 g·L〈sup〉-1〈/sup〉). An autocatalytic-power-law kinetic model was developed to predict the observed induction period and the dependence on the pH of the 4-NP oxidation, H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 consumption and pH evolution (〈em〉k〈sub〉4-NP〈/sub〉〈/em〉 = 2.2·10〈sup〉-5〈/sup〉 M〈sup〉-2〈/sup〉 min〈sup〉-1〈/sup〉, 〈em〉k 〈sub〉H2O2〈/sub〉〈/em〉 = 4.0·10〈sup〉-6〈/sup〉 M〈sup〉-3〈/sup〉· min〈sup〉-1〈/sup〉 and 〈em〉k〈sub〉H+〈/sub〉〈/em〉 = 5.1·10〈sup〉-3〈/sup〉M〈sup〉-0.23〈/sup〉 min〈sup〉-1〈/sup〉 at 80 °C).〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304663-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): J.J. Ternero-Hidalgo, F.F. Budihardjo, K.L. Yeung〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rapid synthesis of zeolite thin film coating on metal surface was demonstrated for LTA, FAU, EMT, SOD, CAN and JBW on stainless steel. The direct heating of LTA-seeded stainless steel was achieved in a specially made synthesis reactor enabling rapid heat transfer that promote zeolite deposition and growth. Microns thick zeolite film can be grown on the stainless steel with an acceptable degree of intercrystalline defects in a relatively short crystallization time (i.e., 45 min). The type of zeolite deposited can be controlled from the starting composition of the synthesis mixture, the ageing time and substrate temperature enabling the preparation of both pure and mixed phase zeolites.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304894-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Hung Hai Pham, Ngoc Thuy Nguyen, Kang Seok Go, Sunyoung Park, Nam Sun Nho, Gyoo Tae Kim, Chul Wee Lee, Guillermo Felix〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a five-lump model was proposed for kinetic modeling of asphaltene placed in a batch reactor with a commercial slurry-phase catalyst (Mo-octoate). Asphaltene was separated from vacuum residue using normal pentane. The kinetic experiments were carried out at 380∼430℃ for 1∼20 hours together with a 1,000 ppm concentration of Molybdenum in thermal and catalytic hydrocracking reaction modes. The results showed that the coke induction period and maximum maltene yield are changed with reaction temperature and time at thermal and catalytic hydrocracking. In addition, a linear relationship between coke and liquid (maltene + asphaltene remains) yields was shown so that the critical gas amount could be found as a criterion for determining the end of the coke induction period. Significantly, the kinetic model fit the experimental data well and, moreover, was found to be able to predict the moment when coke begins to form as well as maximum maltene yields.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092058611930464X-ga1.jpg" width="245" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Mohamed M.A. Soliman, Anirban Karmakar, Elisabete C.B.A. Alegria, Ana P.C. Ribeir, Guilherme M.D.M. Rúbio, Marta S. Saraiva, M. Fátima C. Guedes da Silva, Armando J.L. Pombeiro〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pure ZnO nanoparticles were synthesized by a sustainable precipitation method using zinc nitrate and sodium hydroxide in aqueous medium at room temperature. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis) spectroscopy and Brunauer-Emmett-Teller (BET) analysis. The XRD patterns indicate the formation of the hexagonal wurtzite phase with high purity and SEM-EDS analysis confirm the purity and a homogenous distribution of the nanostructures. The ZnO nanostructures present plate-like agglomerates, resulting in a quasi-spherical morphology. The catalytic activity of the formed ZnO nanoparticles was evaluated towards the transesterification reaction of different carboxylic esters in the presence of various alcohols. This catalyst is highly selective for the transesterification of 〈em〉α〈/em〉-keto carboxylic ester (methyl benzoylformate) and leads to 〈em〉ca〈/em〉. 97% of product yield within 24 h of reaction time.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304869-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Lina Mahardiani, Abhijit Shrotri, Hirokazu Kobayashi, Atsushi Fukuoka〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Diels-Alder reaction is a useful method for modifying the surface of carbon materials. In this work, we functionalized activated carbon with a large number of carboxyl groups using the Diels-Alder reaction. Polyaromatic structure of activated carbon acted as a diene for addition of maleic anhydride (MA) that acted as a dienophile. Upon hydrolysis of the anhydride group in the adduct, vicinal carboxyl groups were formed. The formation of carboxyl groups by Diels-Alder reaction was proved by FTIR, solid-state 〈sup〉13〈/sup〉C NMR, CO and CO〈sub〉2〈/sub〉 evolution from TPD and Boehm titration. Titration results showed that the number of carboxyl groups increased from 0.09 mmol g〈sup〉-1〈/sup〉 to 3.06 mmol g〈sup〉-1〈/sup〉. DFT calculation showed that the concave site of the armchair edge on carbon surface was the most favorable for the Diels-Alder addition. The formation of exo-adduct was preferred with a reaction energy (Δ〈em〉E〈/em〉) of −24 kJ mol〈sup〉-1〈/sup〉. The synthesized catalyst was tested for acid-catalyzed hydrolysis of cellobiose. The catalyst showed higher activity than a catalyst prepared by oxidation in the presence of air.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304882-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Jorge Ramírez, Perla Castillo-Villalón, Aída Gutiérrez-Alejandre, Alejandro Ayala, Oscar Cruz-Garduza, Mónica Ayala, Patricia Quintana-Owen, Adolfo Romero-Galarza〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the search of insight concerning the interaction of molecules of different complexity with the desulfurization and hydrogenation sites, a series of NiMo sulfided catalysts with active particles of different morphology were tested in the hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and in the hydrogenation of naphthalene and cyclohexene. The size and stacking of the NiMoS nanoparticles were modified both by increasing the Mo loading and by decreasing the metal-support interaction. The results show that not all the hydrogenation reactions take place at the same type of site, and that the hydrogenating sites at the top basal plane have greater hydrogenating power than those at the edge. The direct desulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene takes place at coordinatively unsaturated sites (CUS), whereas for the hydrogenation-desulfurization reaction route, the site where the rate controlling step takes place is influenced by the structure and reactivity of the reacting molecule. For dibenzothiophene, the rate controlling step takes place at hydrogenating sites at the top basal plane while for 4,6-dimethyldibenzothiophene it takes place at CUS. Therefore, to efficiently eliminate sulfur from molecules like 4,6-dimethyldibenzothiophene, as required in ultra-low sulfur fuels, the catalyst must have good hydrogenating capacity but more importantly, a high number of CUS.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304651-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): E. Blanco, C. Sepulveda, K. Cruces, J.L. García-Fierro, I.T. Ghampson, N. Escalona〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present work, the preparation and use of new supported transition metal carbides as catalyst for the conversion of guaiacol was investigated. Several metals (Mo, Re, Ru, Ni, Fe, and Cu) were impregnated over activated carbon and carburized under a mixture of H〈sub〉2〈/sub〉/C〈sub〉2〈/sub〉H〈sub〉4〈/sub〉 at 700 °C. Catalysts were characterized by XRD, N〈sub〉2〈/sub〉 physisorption, XPS, CO chemisorption, and TPR-MS. Evidence for carbide formation was obtained in the case of Mo, Re, Ni and Ru, based primarily on CO formation during the TPR-MS analysis. It was found that carbides were mainly active for primary guaiacol conversion to phenol and catechol through demethoxylation and demethylation. Completely deoxygenated products such as benzene and cyclohexane were also formed. The highest selectivity in benzene was obtained for the Re-TPR catalyst while Ni-TPR was the most hydrogenative one.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304614-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 337〈/p〉 〈p〉Author(s): 〈/p〉

Beschreibung: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Iskra Z. Koleva, Hristiyan A. Aleksandrov, Georgi N. Vayssilov〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Using periodic density functional calculations we clarified the variations of the electronic structure of platinum clusters and nanowires upon their deposition on reducible and on non-reducible oxide as well as upon adsorption of carbon monoxide. Three models of platinum clusters and nanowires deposited on ceria surface and one on gamma-alumina surface were studied. At high CO coverage, when the metal cluster or nanowire is completely covered by CO, there is clear depletion of the occupied Pt 5d-projected states close to the Fermi level and appearance of a new state at lower energies, in the region around −1.5 eV below the Fermi level. Thus, in total the 5d states are stabilised and the d-band center in all systems shifts to lower energies, which is an indication that the reactivity of the platinum clusters decreases upon adsorption of carbon monoxide. According to the calculated d-band center value, the metal cluster on gamma-alumina is the most reactive (in terms of electron-donating properties) as its d-band center is located at higher energy compared to platinum on ceria. For most of the models the most stable adsorption position of CO is linear to a platinum atom from the upper part of the platinum moiety, while for the largest model the most stable position is bridging between two platinum atoms.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304092-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): D. Grigoriou, D. Zagoraios, A. Katsaounis, C.G. Vayenas〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The reaction of CO〈sub〉2〈/sub〉 hydrogenation is of high environmental interest since it allows for the transformation of the logistically challenging H〈sub〉2〈/sub〉, gained from renewable sources, to the much more manageable hydrocarbons. Ruthenium is a catalyst widely used to produce methane from CO〈sub〉2〈/sub〉. In this study we present an example of how Electrochemical Promotion of Catalysis (EPOC) can elucidate the role of solid electrolytes (YSZ, BZY) supporting Ru porous films or nanoparticles. It is found that the sign of the charge (-/+) of the current-conducting species of the electrolyte has a profound effect on the selectivity of Ru during CO〈sub〉2〈/sub〉 hydrogenation. Using this insight, we have developed and tested a new supported Ru-Co catalyst for the production of higher hydrocarbons.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119300318-ga1.jpg" width="237" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Chanon Auepattana-aumrung, Kongkiat Suriye, Bunjerd Jongsomjit, Joongjai Panpranot, Piyasan Praserthdam〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Na〈sup〉+〈/sup〉 and H〈sup〉+〈/sup〉 of ZSM-5 having three Si/Al molar ratios (20, 35, and 50) were synthesized to investigate and illustrate 1-butene cracking mechanism. The physical and chemical properties of ZSM-5 were described by XRD, SEM-EDX, N〈sub〉2〈/sub〉 physicsorption, FT-IR, pyridine-IR, 〈sup〉1〈/sup〉H MAS NMR, TPO, and NH〈sub〉3〈/sub〉-TPD techniques. For the characterization, the Na-ZSM-5 consisted of two main types of acid sites (weak and medium acid sites), whereas strong, medium, and weak acid sites were detected on H-ZSM-5. For H-ZSM-5, the Si-(OH)-Al site (strong Brønsted site) was an active site for 1-butene cracking reaction, while the active site of Na-ZSM-5 in the reaction was silanol nest (moderate Brønsted site). The 1-butene cracking reaction on H-ZSM-5 and Na-ZSM-5 was studied under the operating condition of temperature =500 °C, pressure =1 atm, and WHSV =3 h〈sup〉−1〈/sup〉. The oligomerization, cracking, and hydrogen transfer were three main reactions in the 1-butene cracking mechanism. The alkenes excluding propylene occurred on weak acid site, while the formation of propylene underwent on medium acid site of ZSM-5 catalyst. The presence of strong acid site on ZSM-5 catalyst promoted the hydrogen transfer reaction, which provoked the alkane formation. The hydrogen transfer index in 1-butene reaction of Na-ZSM-5 was less than H-ZSM-5 in all Si/Al molar ratios because of the absence of strong acid. The Na-ZSM-5 (Si/Al molar ratio = 20) reached the highest propylene selectivity at 31.73 C-wt.% and the Na〈sup〉+〈/sup〉 ion could block the strong acid site. At low Si/Al molar ratio, the stability of Na-ZSM-5 was higher than H-ZSM-5 because of the lower coke formation. Therefore, the Na-ZSM-5 was more suitable catalyst than H-ZSM-5 for propylene formation in 1-butene cracking reaction.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092058611930433X-ga1.jpg" width="350" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Arturo Claudio-Piedras, Rosa Ma. Ramírez-Zamora, Brenda C. Alcántar-Vázquez, Albina Gutiérrez-Martínez, Gilberto Modragón-Galicia, Fernando Morales-Anzures, Raúl Pérez-Hernández〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pt nanocatalysts supported on CeO〈sub〉2〈/sub〉-NR (CeO〈sub〉2〈/sub〉-nanorods) were synthesized and evaluated in the steam reforming of methanol reaction (SRM) for hydrogen production. The effect of Pt precursor was investigated using tetraaminplatinum nitrate (Pt(NH〈sub〉3〈/sub〉)〈sub〉4〈/sub〉(NO〈sub〉3〈/sub〉)〈sub〉2〈/sub〉), platinum acetylacetonate (CH〈sub〉3〈/sub〉-COCHCO-CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉Pt and hexachloroplatinic acid (H〈sub〉2〈/sub〉PtCl〈sub〉6〈/sub〉*6H〈sub〉2〈/sub〉O). The catalysts were characterized by N〈sub〉2〈/sub〉 Adsorption-Desorption (BET), MEB, DRX, TPR, HAADF-STEM, Mass Spectroscopy (MS) and DRIFT. All samples showed typical diffraction peaks of the fluorite CeO〈sub〉2〈/sub〉 phase cubic structure. TPR profiles of Pt/CeO〈sub〉2〈/sub〉-NR(Nit) and Pt/CeO〈sub〉2〈/sub〉-NR(Acac) catalysts, showed reduction peaks at temperatures lower compared with those of Pt/CeO〈sub〉2〈/sub〉-NR(Cl) catalysts. STEM-HAADF characterization revealed the presence of small Pt nanoparticles on Pt/CeO〈sub〉2〈/sub〉-NR(Nit) but not for Pt/CeO〈sub〉2〈/sub〉-NR(Acac); this finding was associated with the catalysts synthesis solvent used. Pt/CeO〈sub〉2〈/sub〉-NR(Nit) sample showed the best performance on methanol conversion than other catalysts, this result was associated with a larger number Pt nanoparticles distributed along the CeO〈sub〉2〈/sub〉-NR. Low catalytic activity observed on the Pt/CeO〈sub〉2〈/sub〉-NR(Cl) sample, was associated with formation of oxychlorinated Pt〈sub〉x〈/sub〉O〈sub〉y〈/sub〉Cl〈sub〉z〈/sub〉 species. Although MS technique showed stable methanol conversion during the reaction, no further changes in the outlet signals on the real-time monitoring analysis by MS was observed, this indicates that the catalyst was very stable during the reaction.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304341-ga1.jpg" width="378" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): E.V. Parkhomchuk, K.V. Fedotov, V.S. Semeykina, A.I. Lysikov〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Polystyrene microsphere-template method was used to prepare a range of hierarchically porous alumina samples. Different ways for creating hierarchical porosity were implemented, including mixing of alumina precursor with dry powder of PS microspheres and with PS water suspension, followed by extruding the resulting composite and its calcination. The samples were studied by BET technique, Hg porosimetry and scanning microscopy, mechanical strength of alumina pellets was also measured. In comparison with the “dry” method, the “wet” one gives pellets with a narrower distribution of macropores in size and the greater material mechanical strength. In whole the approach allows tuning textural parameters of hierarchically porous alumina samples in the following range: BET specific surface area 90–300 m〈sup〉2〈/sup〉/g, mesopore volume 0.30–0.65 cm〈sup〉3〈/sup〉/g, total pore volume 0.50–1.20 cm〈sup〉3〈/sup〉/g, mechanical crushing strength of 10–35 MPa. Ordered macroporosity of alumina was obtained by the impregnation of dry PS colloidal crystal by ethanol-water solution of aluminum oxalate; this method can be used only to produce small quantities or films of the material.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119303876-ga1.jpg" width="269" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Fei Yan, Yushuai Sang, Yunfei Bai, Kai Wu, Kai Cui, Zhe Wen, Fuhang Mai, Zewei Ma, Linhao Yu, Hong Chen, Yongdan Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Re〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 is used to convert guaiacol in alcohols at 280–320 °C. In ethanol, guaiacol is deoxygenated and alkylated, and the major products are phenol and alkylphenols (including ethylphenol, diethylphenol, diisopropylphenol, di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol), accounting for 97 mol% of all products after 6 hour reaction at 320 °C. Both catechol and phenol are the intermediates of guaiacol demethoxylation. Among the substituents, ethyl is directly provided by ethanol while isopropyl and tert-butyl are formed by the addition of methyl to ethyl step by step. In addition, Re〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 has negligible activity for the saturation of benzene ring so it does not cause considerable over-consumption of reductant. The actual catalyst for guaiacol demethoxylation is likely a Re〈sup〉IV−VI〈/sup〉 species.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119303785-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Alechine E. Ameh, Chuks P. Eze, Edith Antunes, Mero-Lee U. Cornelius, Nicholas M. Musyoka, Leslie F. Petrik〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coal fly ash (class F) was used as feedstock to extract silica for the indirect synthesis of BEA zeolite via a hydrothermal process. The extraction steps selectively retained major components of Si 〉 Al 〉 Na and eliminated the need for the addition of an extra silica source in the zeolite synthesis mixtures. The stability of BEA zeolite was studied in hot liquid phase at different exposure times (6, 12 and 24 h) and temperatures (150 and 200 °C). The structural changes in the framework of the treated zeolite was determined with X-ray diffraction, thermogravimetric analysis, N〈sub〉2〈/sub〉 adsorption–desorption and 〈sup〉27〈/sup〉Al and 〈sup〉29〈/sup〉Si magic-angle spinning nuclear magnetic resonance. Structural degradation of the treated zeolite depended on prolonged exposure time and high temperature, reduced crystallinity and framework Si/Al ratio, the degree of desilication, and the presence of silanol defects. The relative crystallinity and changes in framework Si/Al ratio were shown to depend on the exposure time and temperature in hot liquid phase. With prolonged exposure time, the surface area and micropore volume decreased with an increase in the mesopore volume. The stability of BEA zeolite was influenced by the hydrolysis of Si-O-Si bonds (siloxane) through desilication which eventually caused the formation of structural defects at elevated treatment time and temperature, however, the crystal structure remained intact. Herein, the stability of fly ash based BEA zeolite in hot liquid shows its potential use as a catalyst for liquid phase reactions, considering the exposure time and temperature investigated.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304274-ga1.jpg" width="373" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Yanning Qu, Renliang Huang, Wei Qi, Mingbo Shi, Rongxin Su, Zhimin He〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Zinc oxide (ZnO) nanomaterials are functional photocatalysts that show excellent photocatalytic activity, among which diverse morphologies, such as nanospheres, nanorods, nanoleaves, nanodisks, or nanoflowers, often possess different photocatalytic activities. In this study, we employed a simple ultrasonic treatment to controllably synthesize three types of three-dimensional (3D) fluffy ZnO nanoflowers with different nanostructures. Specifically, one nanoflower with smooth edges was formed via direct hydrothermal reaction without ultrasonic treatment (denoted as ZnO-0), and the other two with different jagged margins were obtained by ultrasonic treatment at 250 W and 950 W, respectively, before the hydrothermal procedure (denoted as ZnO-250 and ZnO-950). The results showed that the size, specific surface area, crystallite dimension, intrinsic donor defects and the signals of reactive radicals of ZnO nanoflowers all decreased with increasing ultrasonic intensity. Furthermore, the photocatalytic performance of such ZnO nanoflowers with similar morphologies but different nanostructures was investigated using methyl orange (MO) as a model pollutant. As expected, ZnO-0 possessed the highest photocatalytic activity with a kinetic constant of 0.0478 min〈sup〉−1〈/sup〉, while the value decreased to 0.0251 min〈sup〉−1〈/sup〉 and 0.013 min〈sup〉−1〈/sup〉 for ZnO-250 and ZnO-950 under simulated sunlight irradiation, respectively, suggesting that the photocatalytic efficiency of ZnO nanoflowers decreased due to the ultrasonic treatment. These findings provide structural insight into the photocatalytic activity of ZnO nanoflowers.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304171-ga1.jpg" width="324" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 30 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): M. Tsvetkov, J. Zaharieva, M. Milanova〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ferrites of the type MFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉, where M = Zn, Co, and Mg, were prepared 〈em〉via〈/em〉 a sol-gel procedure using propylene oxide as a gelating agent. Silver nanoparticles with an average size of 6 nm were prepared in the presence of the ferrite powders in suspension using raffinose as a reducing agent in a basic water solution. Nine samples of the ferrite/silver nanoparticles nanocomposites were prepared in this way with different Ag content. The composites obtained were characterized by XRD, TEM, and UV/Vis spectroscopy. The size distribution of the particles was determined using the data from TEM. By TEM-EDAX, the location of the silver nanoparticles on the ferrite surfaces was determined. Using UV/Vis spectra, the band gap energies for the pure ferrites and the nanocomposites were calculated; the calculated band gap energies were influenced by the presence of the silver nanoparticles. The photocatalytic activity of the silver nanoparticles/ferrite nanocomposites for decomposition of Malachite Green in model water solutions under UV and visible light irradiation was determined. The ZnFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/Ag-NPs nanocomposites were found to be active under visible light irradiation, while the MgFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/silver nanoparticles composites especially active more than the pure MgFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉. The presence of silver nanoparticles did not influence the very low photocatalytic activity of CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Mechanism of the Malachite Green degradation under light irradiation in the presence of Ag-NPs modified ferrites MFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 (M = Mg, Zn).〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304080-ga1.jpg" width="310" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Anup Kumar Sasmal, Arun Kumar Sinha, Kaushik Mallick, Tarasankar Pal〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Chromism from phosphomolybdate – malachite green dye moiety through hydrogen bonding interaction with water molecules is reported. Interestingly, the substance with bound di-nitrogen or di-oxygen together with water molecules also exhibits color change. N〈sub〉2〈/sub〉 or O〈sub〉2〈/sub〉 binding vis-à-vis chromism is a new insight.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304377-ga1.jpg" width="249" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 13 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Guangyuan Zhao, Miaomiao Li, Liyin Wang, Dongzhe Wang, Jinsheng Liang, Gang Xue〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The tourmaline/manganese-iron-cerium-oxide composites prepared by the hydrothermal method was investigated for NOx removal in simulated flue gas. The microstructure of the catalyst has been characterized by X-ray diffractometer (XRD), temperature-programmed reductions (TPR) and X-ray photoelectron spectra (XPS). The incorporation of tourmaline could remarkably enhance the activity of tourmaline/Mn-Fe-Ce catalyst at low temperature. H〈sub〉2〈/sub〉-TPR results indicated that H〈sub〉2〈/sub〉 adsorption amount decreased after the incorporation of tourmaline. The XPS results revealed that the incorporation of tourmaline could enhanced the contents of high valence 〈em〉O〈/em〉〈sub〉α〈/sub〉 (〈em〉O〈/em〉〈sub〉α〈/sub〉/〈em〉O〈/em〉) in the composite catalysts, which is favorable for oxidation process of elemental manganese. Overall, the catalytic performance of tourmaline/Mn-Fe-Ce was closely related to the addition of tourmaline. When the addition of tourmaline was 2%, the composite catalyst showed the best catalytic performance: The NOx conversion of the composite catalyst is 100% at 170–230 °C. Moreover, the denitrification mechanism of composites was studied. The addition of tourmaline improved the catalytic process, and stable bidentate nitrate species was activated at low temperature during the denitrification reaction. As a mineral material, tourmaline has excellent far-infrared properties and spontaneous polarization properties, which can significantly improve the denitration performance of the catalyst. The use of mineral materials as raw materials to prepare denitration catalysts provides new ideas for future research.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304390-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 2 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Seunghyun Jo, JunHwa Kwon, Ki-Yeop Cho, Dong Hyeon Kim, KwangSup Eom〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, the effect of a predeposited Co-Ni layer on the catalytic activity and long-term durability of the quaternary Co-Ni-P-B catalyst for the hydrogen evolution reaction (HER) is investigated. To study the effect of predeposition of the Co-Ni layer for the Co-Ni-P-B catalyst, both Co-Ni-P-B/Co-Ni/Cu and Co-Ni-P-B/Cu catalysts are prepared. The current density for HER of the Co-Ni-P-B/Co-Ni/Cu catalyst at −0.5 V〈sub〉RHE〈/sub〉 is 36.1% higher than that of Co-Ni-P-B/Cu in 0.5 M H〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 solution at 18 °C. This is because the porous morphology of the Co-Ni-P-B/Co-Ni/Cu catalyst leads to a 10.6% larger electrochemical surface area and higher atomic ratio for both the P and B contents, which act as a proton acceptor and a supplier of electrons to the d orbital of the transition metals, respectively, compared to Co-Ni-P-B/Cu on the catalytic surface. Furthermore, the Co-Ni-P-B/Co-Ni/Cu catalyst retains 94.5% of the catalytic activity during durability test of 1 h owing to its higher adhesion strength between the substrate and catalyst and rougher morphology, whereas the Co-Ni-P-B/Cu catalyst shows a retention of only 64.4%.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119303566-ga1.jpg" width="431" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 2 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Dong Wook Kwon, Somin Lee, Jongsik Kim, Kwan-Young Lee, Heon Phil Ha〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The roles of WO〈sub〉3〈/sub〉 and SiO〈sub〉2〈/sub〉 in Ce-V catalysts supported on TiO〈sub〉2〈/sub〉 comprised tungsten-silica were investigated systematically for NH〈sub〉3〈/sub〉-SCR (selective catalytic reduction) and NH〈sub〉3〈/sub〉-oxidation at high temperatures. When SiO〈sub〉2〈/sub〉 and WO〈sub〉3〈/sub〉 were added to TiO〈sub〉2〈/sub〉, the surface area of Ce-V/TWS was maximized and the formation of Ti〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Si bond reduced nanoparticle size compared to without SiO〈sub〉2〈/sub〉. The Ce-V/TWS surface had greater abundance of catalytic defects and surface oxygen species 〈em〉via〈/em〉 XPS results. Increasing the (V〈sup〉4+〈/sup〉 + V〈sup〉3+〈/sup〉) fraction increased the catalytic activity, which is attributed to the enhanced SCR performance at a wide temperature range due to the addition of WO〈sub〉3〈/sub〉 and SiO〈sub〉2〈/sub〉 to TiO〈sub〉2〈/sub〉. The catalysts using the TWS supports exhibit high catalytic activity, since WO〈sub〉3〈/sub〉 and SiO〈sub〉2〈/sub〉 can promote redox properties. It was shown that Ce-V/TWS was the most suitable catalyst for selectively producing N〈sub〉2〈/sub〉 〈em〉via〈/em〉 thermodynamically unavoidable NH〈sub〉3〈/sub〉 direct oxidation as the temperature increased. In addition, hydrothermal aging effects were investigated for the Ce-V/TWS catalyst prepared by TiO〈sub〉2〈/sub〉 supports including WO〈sub〉3〈/sub〉 and SiO〈sub〉2〈/sub〉 (comparison with vanadium-tungsten/titania). This study demonstrates the feasibility of utilizing WO〈sub〉3〈/sub〉 and SiO〈sub〉2〈/sub〉 in the TiO〈sub〉2〈/sub〉 support as a possible way to increase catalytic activity and N〈sub〉2〈/sub〉 selectivity in NH〈sub〉3〈/sub〉-SCR at high temperatures.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119303554-ga1.jpg" width="268" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): J.E. Samaniego-Benitez, L. Lartundo-Rojas, A. García-García, H.A. Calderón, A. Mantilla〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉ZnS/MoS〈sub〉2〈/sub〉 composite material was prepared by one-step solvothermal method at different molybdenum concentration. The structural properties of the composite material were analyzed by XRD, UV–vis DRS, TEM and XPS techniques, and the photocatalytic was evaluated for the hydrogen production under UV irradiation. The hydrogen yield reaches 606 μmol h〈sup〉−1〈/sup〉 g〈sup〉−1〈/sup〉 for the material with 10% of molybdenum, which was 30 and 50% superior than that obtained using MoS〈sub〉2〈/sub〉 and ZnS as photocatalyst, respectively. The increase in the photocatalytic activity may be associated to a synergistic effect produced by the interaction between ZnS and MoS〈sub〉2〈/sub〉, as well as the formation of defects in the structure of ZnS, due to sulfur vacancies produced during the synthesis, which could be observed in the TEM analysis of the composite material.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304328-ga1.jpg" width="374" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): G. Bonura, C. Cannilla, L. Frusteri, E. Catizzone, S. Todaro, M. Migliori, G. Giordano, F. Frusteri〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A significant boost to the catalytic technology of CO〈sub〉2〈/sub〉-to-DME hydrogenation in a single step was recently given by the design of novel hybrid multimetallic/zeolite systems. However, a significant drop of catalyst activity after few hours of operation time pushes now the research interest towards the development of more stable multifunctional systems, suitable to ensure activity, selectivity and lifetime under typical industrial conditions. In this work, the influence of different home-made zeolite samples (〈em〉i.e.〈/em〉, Sil-1, MFI, Y, FER, BEA, MOR), integrated in a weight ratio of 1:1 with a CuO-ZnO-ZrO〈sub〉2〈/sub〉 metal-oxide(s) phase, was investigated under long-term stability tests in a fixed bed reactor during CO〈sub〉2〈/sub〉 hydrogenation reaction to assess the activity-selectivity pattern of the hybrid catalyst as well as their deactivation trend during operation time. The individuation of key structure-activity relationships helped to explain how the extent of interaction between the metal-oxides phase with the zeolite surface as well as the strength of the acid sites significantly control the catalyst stability.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304353-ga1.jpg" width="182" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈p〉Deactivation rate and interface metal-to-zeolite contact area (〈em〉θ〈/em〉〈sub〉M/Z〈/sub〉).〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 13 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Mingxiu Liu, Ondřej Veselý, Pavla Eliášová, Mariya Shamzhy, Pengbo Lyu, Lukáš Grajciar〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tetrahydropyranylation (THP) has been extensively studied experimentally with both Brønsted and Lewis acid-based catalysts, such as zeolites, considered. However, our atomic-level understanding of the underlying mechanisms of different types of catalytic sites remains limited, particularly regarding zeolites. Thus, we combined an experimental catalytic study with density functional theory (DFT) calculations to identify the active sites and corresponding reaction mechanism in MFI zeolite. Both experimental and computational data clearly show that Brønsted acid sites are more reactive than Lewis acid sites. Furthermore, calculated reaction barriers for Brønsted acid site catalysis (5 kcal mol〈sup〉-1〈/sup〉) are much lower than those for the diffusion of bulky products in microporous channels (approximately 20 kcal mol〈sup〉-1〈/sup〉). In full agreement with theoretical calculations, the results of Madon-Boudart test clearly show that the effect of diffusion on the H-MFI catalysts performance cannot be neglected even at low temperature. Therefore, the diffusion becomes the rate-determining step. Overall, our findings suggest that designing zeolites with improved THP catalysis performance requires focusing on acid zeolites with Brønsted acid sites of average strength with facilitated diffusion, e.g., due to auxiliary mesoporous system.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304389-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 30 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Anchittha Liu, Supareak Praserthdam, Suphot Phatanasri〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The carbon dioxide reforming of methane is one of the processes used to tackle global warming by reducing carbon dioxide, one of the most harmful greenhouse gases through the catalytic reaction with methane which produces syngas. Although the noble metals are good candidates for such a process, the cost and scarcity limit their uses. The non-noble metals on the other hand, with satisfactory activity and cost, are of interest except their stability against the coke formation, the main deactivation scheme during the dry reforming reaction. Therefore, the study of the enhanced stability found in the bi-metallic system of Ni catalysts via the introduction of Co was carried out in this work. The activity and coke resistance were studied on both mono and bi-metallic system of the Ni-based catalysts (10%wt) supported on γ-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-HY zeolite prepared via the sol-gel method. The activity testing was performed in a fixed-bed reactor with a unity feed volume ratio under atmospheric pressure at 973 K, where the Ni–Co bi-metallic system exhibits higher activity than both mono-metallic of either pure Ni or Co due to a higher number of active sites confirmed by the CO chemisorption. On the stability testing, the high stability was found on the bi-metallic system as verified by the time-on-stream testing. In addition, the higher reduction temperature for the bi-metallic system via the analysis using H〈sub〉2〈/sub〉-TPR also suggested stronger metal-support interaction which may decrease the bonding strength of the coke on the surface leading to lower deactivation.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304031-ga1.jpg" width="350" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Ren Wei Chang, Chin Jung Lin, Sofia Ya Hsuan Liou, Miguel A. Bañares, M. Olga Guerrero-Pérez, Rosa María Martín Aranda〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The modification of ordered mesoporous carbon (OMC) via NH〈sub〉3〈/sub〉 heat treatment and subsequent amine refluxing at increased temperature was investigated to improve their performances for cyclic CO〈sub〉2〈/sub〉/N〈sub〉2〈/sub〉 separation stability and kinetics. Characterizations conducted with nitrogen adsorption/desorption isotherm, Fourier transform infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy demonstrated that the porosity and surface chemistry of the OMCs were tuned by modification. Adsorption evaluation with volumetric and gravimetric methods under various conditions indicated that the resulting amine-introduced N-doped OMC presented a high CO〈sub〉2〈/sub〉 adsorption capacity with fast kinetics, outstanding selectivity at 50 °C and maintained superior separation performance after 20 cycles. The presence of accessible amino groups in considerable amounts renders the modified mesoporous carbon a promising candidate for CO〈sub〉2〈/sub〉 capture from flue gas by using the temperature swing adsorption.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304250-ga1.jpg" width="230" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Silvia Carlotto, Girolamo Casella, Luca Floreano, Alberto Verdini, Ana P.C. Ribeiro, Luísa M.D.R.S. Martins, Maurizio Casarin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Fe(II) spin state in the condensed phase of [Fe(II)Cl2(tpm)] (tpm = [tris(pyrazol-1-yl)methane]; 1) catalyst has been determined through a combined experimental and theoretical investigation of X-Ray Absorption Spectroscopy (XAS) at the 〈sup〉Fe〈/sup〉L〈sub〉2,3〈/sub〉-edges and 〈sup〉N〈/sup〉K-edge. Results indicated that in this phase a mixed singlet/triplet state is plausible. These results have been compared with the already know Fe singlet spin state of the same complex in water solution. A detailed analysis of the electronic structure and bonding mechanism of the catalyst showed that the preference for the low-spin diamagnetic ground state, strongly depends upon the ligands, the bulk solvent and the interaction of the complex’s vacant site (the sixth) with a further ligand. Moreover, comparison of the electronic properties of the complex in condensed phase and water solution showed an increased Lewis acidity of the catalyst in solution phase, due to a decreasing of the LUMO energy of about 8 kcal/mol. These results gave an overall picture of the electronic behavior of the complex investigated, on going from condensed to water solution phase, explaining the preferred use of 1 as catalyst in homogeneous catalysis. The N〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Fe(II) interaction has been thoroughly investigated by means of DFT Kohn-Sham and EDA bond analysis applied to i) the isolated [Fe(II)Cl〈sub〉2〈/sub〉(tpm)] and ii) the [Fe(II)Cl〈sub〉2〈/sub〉(tpm)] interacting with water as a solvent within the Conductor-like Screening Mode (COSMO) framework. Results showed that both tpm→Fe(II) σ and tpm⟵Fe(II) π Charge Transfer (CT) interactions characterize the Fe(II)–tpm interaction. Moreover, the three tpm N atoms do not equally interact with the Fe(II) and one of them shares a suitable available iron-based d virtual orbital, to bind a further ligand in trans position.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304316-ga1.jpg" width="268" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 30 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Humayun Shariff, Muthanna H. Al-Dahhan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A steady-state diffusion model comprising of diffusion and reaction in a catalyst pellet was used to study and understand the effect of the approximation of the catalyst effectiveness factor in the modeling of trickle bed reactors. The hydrogenation of alpha-methylstyrene was chosen as the case study reaction from literature for liquid-limited reaction conditions. The effectiveness factor values in this study were sensitive to reactor scale equations during the prediction of reactor performance. The approximation of accounting the overall catalyst effectiveness factor in the reactor scale model equations from different models and solving the reactor scale model equations by different modeling approaches was assessed. These modeling simulations were compared against the experimental results. It was observed that evaluating the overall effectiveness factor from pellet scale model equations and integrating the parameter in the reactor scale axial dispersion model at every local axial collocation point to simulate the reactor performance showed better agreement to the experimental data. This approach evaluates the effectiveness factor locally at different axial points across the reactor rather than using one value for the entire reactor. The approach of using a single effectiveness factor for the whole bed and using the effectiveness factor approximated as a fitted polynomial to the reactant concentrations did not properly predict the reactor performance.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119303931-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 2 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): L. Satish K. Achary, Pratap S. Nayak, Bapun Barik, Aniket Kumar, Priyabrat Dash〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A facile chemical synthetic route has been demonstrated for the synthesis of copper oxide nanoparticles decorated phosphate functionalized graphene oxide (〈em〉CuO/PGO〈/em〉). The synthesized nanocatalyst was used as an efficient and active candidate for the synthesis of β-amino carbonyl compounds via a green synthetic ultrasonic route. The structural properties of the samples were investigated by means of a number of sophisticated techniques like X-ray diffraction (XRD), Fourier-transform Infrared (FTIR) spectroscopy, High Resolution Transmission Electron Microscope (HRTEM), N〈sub〉2〈/sub〉 adsorption-desorption measurements, X-ray photoelectron spectroscopy (XPS) analysis, Ammonia temperature programmed desorption analysis (NH〈sub〉3〈/sub〉-TPD) and Raman spectroscopy. HRTEM analysis confirmed the presence of spherical CuO nanoparticles distributed uniformly throughout the PGO surface. XPS analysis demonstrated the presence of Cu〈sup〉2+〈/sup〉 species and minor reduction of oxygen functional groups on GO. A higher surface area of 162 m〈sup〉2〈/sup〉/g for 〈em〉CuO/PGO〈/em〉 was found from N〈sub〉2〈/sub〉 adsorption-desorption isotherms. Later on, the presence of acidic groups on 〈em〉CuO/PGO〈/em〉 that play an essential role in the catalytic activity was examined by NH〈sub〉3〈/sub〉-TPD and pyridine adsorbed IR analysis. The total acidity on the surface of synthesized nanocatalyst was found to be of 0.59 mmol g〈sup〉−1〈/sup〉 which includes both Lewis as well as Brönsted acidic sites. A higher product yield of 95% in a shorter period of time of 15 min was achieved which is superior to many reported catalytic systems. A combined strategy involving greener and easier ultrasonic route and use of an efficient acidic graphene oxide-based catalyst resulted in higher catalytic activity and stability with with good recyclability.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉Highly efficient and active CuO nanoparticle decorated Phosphate functionalised graphene oxide (PGO-CuO) nanocomposite has been synthesized in a water-isopropanol system and used as an active catalyst for the synthesis of β-amino carbonyl compounds via Mannich reaction by using a greener ultrasonic method.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304067-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 30 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Sanchari Basu, Narayan C. Pradhan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vapor phase hydrogenation of acetone was carried out over Cu-Al mixed oxide catalysts. The catalysts were synthesized via co-precipitation method with Cu:Al atomic ratio varied from 0.25 to 1. The characterization of the catalysts was done by using XRD, BET, FESEM (coupled with EDS), FTIR, H〈sub〉2〈/sub〉-TPR, NH〈sub〉3〈/sub〉-TPD and CO〈sub〉2〈/sub〉-TPD. The performance of the synthesized catalysts was evaluated in a continuous packed bed reactor by varying parameters such as temperature (150 to 225 °C), H〈sub〉2〈/sub〉/acetone mole ratio (0.5 to 1.25) and space-velocity (0.09 to 0.145 kmol acetone/kg cat. h). Along with direct hydrogenation, condensation of acetone also occurred due to the presence of basic and acidic sites in the catalysts. The catalyst having Cu:Al atomic ratio of 0.5 showed highest selectivity (98%) to isopropyl alcohol at 175 °C. Kinetic study was conducted at different temperatures by varying space-velocity. LHHW type model rate equations were fitted with the kinetic data obtained at three different temperatures. The activation energy of the reaction was determined to be 44.3 kJ/mol.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304079-ga1.jpg" width="258" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Toru Murayama, Satoshi Ishikawa, Norihito Hiyoshi, Yoshinori Goto, Zhenxin Zhang, Takashi Toyao, Ken-ichi Shimizu, Shutoku Lee, Wataru Ueda〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High dimensionally structured W-V-O catalysts (HDS-WVO) were synthesized by hydrothermal method and catalyst structures were investigated by HAADF-STEM analysis. HDS-WVO were rod-shaped crystals and the cross-sections were constituted by W〈sub〉6〈/sub〉O〈sub〉21〈/sub〉 pentagonal units and MO〈sub〉6〈/sub〉 octahedra (M = V, W), forming heptagonal and hexagonal channels. HDS-WVO catalysts showed excellent catalytic performance for selective oxidation of toluene to benzoic acid, and the activity and the selectivity to benzoic acid were superior to those of state-of-the-art catalysts. After the ion exchange using Cs〈sup〉+〈/sup〉, the catalytic activity over HDS-WVO was significantly decreased. Since HAADF-STEM analysis and N〈sub〉2〈/sub〉 adsorption revealed that Cs〈sup〉+〈/sup〉 was located mainly at the heptagonal channel of HDS-WVO, it can be concluded that toluene oxidation takes place at the heptagonal channel site of HDS-WVO.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119300793-ga1.jpg" width="211" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Lorena P. Rivoira, Verónica A. Valles, María L. Martínez, Yanika Sa-ngasaeng, Siriporn Jongpatiwut, Andrea R. Beltramone〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The catalytic oxidation of different sulfur compounds, commonly present in liquid fuel, was studied over a series of ceria and ceria-zirconium based oxidation mesoporous catalysts. SBA-15 was synthesized using sol-gel method and Ce and Ce-Zr were added by two different procedures: i) directly during the synthesis and ii) via post-synthesis method. The catalysts were characterized by XRD, N〈sub〉2〈/sub〉 adsorption isotherms, XPS, DRUV-Vis, TEM, SEM and Py-FTIR. Low angle XRD, N〈sub〉2〈/sub〉 isotherms and TEM confirmed that the structure was not changed after metal incorporation. Wide angle XRD, UV–vis-DRS, XPS and TEM determined that the catalysts prepared by direct synthesis presented higher dispersion of Ce oxides, smaller particle size and isolated Zr〈sup〉4+〈/sup〉 species. FTIR of adsorbed/desorbed pyridine indicated that zirconium as promoter increases the Lewis acidity of the catalysts, especially during direct synthesis. Ce-Zr-SBA-15 catalyst prepared by direct synthesis was very active in the oxidation of dibenzothiophene, 4,6-dimethyl dibenzothiophene and benzothiophene using hydrogen peroxide (H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉) as oxidant agent and acetonitrile as polar solvent. The effect of acidity in the catalyst, hydrogen peroxide concentration and temperature was studied. The deactivation test demonstrated that the catalyst is stable and adequate for the industrial process.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304262-ga1.jpg" width="425" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 31 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Fuping Li, Min Ao, Gia Hung Pham, Yun Jin, Minh Hoang Nguyen, Nabil Majd Alawi, Moses O. Tade, Shaomin Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Dimethyl ether (DME) has received great attention as a promising clean fuel and industrially important intermediate. Tremendous efforts have been made to develop highly active and stable catalysts for DME production. Here, we present the first example of the application of metal-organic framework (MOF) catalyst in DME synthesis from syngas. A Zr-MOF (UiO-66) was selected as the catalyst host and support owing to its exceptionally high stability and porosity. UiO-66 was firstly functionalized by silicotungstic acid (H〈sub〉4〈/sub〉SiW〈sub〉12〈/sub〉O〈sub〉40〈/sub〉, STA) via a one-pot synthesis method and then loaded with Cu by a facile solid grinding method. The prepared catalysts were characterized using XRD, TGA, FT-IR, N〈sub〉2〈/sub〉 adsorption and TEM. The high porosity and thermal stability of acidified UiO-66 were maintained after 15% wt STA incorporation without any destruction of the Keggin structure of STA. The catalyst was tested for one step DME synthesis from syngas, showing higher DME selectivity and space-time yield than control catalysts. The superior activity of Cu/STA-UiO was attributed to the uniform dispersion of active centres with close intimacy and high density of Brønsted acid sites, as well as strong metal support interaction between Cu and Zr oxide SBU evidenced by XPS analysis.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304183-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): O.A.L. Galán, G. Carbajal-Franco〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉It is known that a given material can exhibit different catalytic performances by deploying different crystallographic orientations on the surface, which can increase the reactivity of the system. This work is based on the experimental results of a previous work, where a ZnO thin film presented a (103) preferred orientation, raising the interest to investigate its catalytic performance on NO and CO by using DFT calculations. Three different conditions of the surface are considered in this work: a defect-free surface, pre-adsorption of O〈sub〉2〈/sub〉 and pre-adsorption of OH molecules. Calculations demonstrated that CO and NO catalytic reactions are improved primordially by the pre-adsorbed species on the material. ZnO (103) defect-free surface presents higher affinity to NO on the three tested sites. In the case of pre-adsorbed oxygen, the surface presented higher reaction energies for CO. In both conditions, the gases were oxidized to NO〈sub〉2〈/sub〉 and CO〈sub〉2〈/sub〉 respectively. In the case of pre-adsorbed OH radicals, the final products were nitrous acid (HNO〈sub〉2〈/sub〉) and carboxyl groups (COOH), bonded to the surface with different energies depending on the adsorption site. ZnO (103) surface proved to be reliable for using it in reactions involving pre-adsorbed oxygen and OH molecules.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304249-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Heon Lee, Byung-Joo Kim, Young-Kwon Park, Jung-Sik Kim, Sang-Chul Jung〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To improve the photocatalytic performance of TiO〈sub〉2〈/sub〉 photocatalysts, a new method, liquid phase plasma (LPP) method, was used to introduce nitrogen and iron oxide. Interstitial or substitutional nitrogen and Fe〈sup〉3+〈/sup〉 iron nanoparticles were impregnated on the surface of TiO〈sub〉2〈/sub〉 by LPP reaction without additional chemical reduction agent and the amount of iron of modified TiO〈sub〉2〈/sub〉 photocatalysts was affected by the amount of initial precursor. The adsorption edge of modified TiO〈sub〉2〈/sub〉 photocatalysts was shifted to the visible region in proportion to the amount of nitrogen and iron oxide, and the band gap energy was decreased, and the photocatalytic activity was confirmed by PL and EPR analysis. The photocatalytic activities of modified TiO〈sub〉2〈/sub〉 photocatalysts were measured under UV and blue LED lamps and compared with pure TiO〈sub〉2〈/sub〉 powder (P-25). The modified TiO〈sub〉2〈/sub〉 exhibited better photocatalytic degradation performance than pure TiO〈sub〉2〈/sub〉 under blue LED light conditions, but exhibited low degradation activity under UV LED light conditions. Through GC–MS analysis, it was found that the methylene blue was finally decomposed into an inorganic substance through intermediates such as benzene sulfonic acid and phenol by OH radicals. From these results, we found that the modified TiO〈sub〉2〈/sub〉 photocatalysts can be easily prepared using the LPP method and can be used in the visible region.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119303621-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Sasithorn Kuhaudomlap, Piyasan Praserthdam, Masayuki Shirai, Joongjai Panpranot〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nickel-doped spherical silica (SSP) catalysts with ca. 10 wt% Ni were prepared via a sol-gel method using cetyltrimethyl ammonium bromide as the structure directing agent with different loading sequences of Ni and Si sources (Si1_Ni2, Ni1_Si2, and Ni_Alt_Si). For comparison purposes, the SSP supported Ni catalysts were also prepared by impregnation method (Ni/SSP (Imp)). All the prepared catalysts showed spherical shape with high specific surface area (357-868 m〈sup〉2〈/sup〉/g). The X-ray diffraction and H〈sub〉2〈/sub〉-temperature programmed reduction results revealed the stronger interaction between Ni and SiO〈sub〉2〈/sub〉 in the form of nickel silicate for all the Ni-doped SSP catalysts except Ni/SSP (imp), in which only NiO species were detected. For the reaction temperature 350 ̊C, the CO〈sub〉2〈/sub〉 conversion was in the order: Ni〈sub〉_〈/sub〉Alt〈sub〉_〈/sub〉Si (51%) 〉 Ni1〈sub〉_〈/sub〉Si2 (49%) 〉 Si1〈sub〉_〈/sub〉Ni2 (28%) 〉 Ni/SSP (Imp) (10%) with methane selectivity 80–95%. The superior performances of the Ni_Alt_Si catalyst were correlated well to the higher electron density of Ni on the surface and higher CO〈sub〉2〈/sub〉 adsorption ability as revealed by the X-ray photoelectron spectroscopy and CO〈sub〉2〈/sub〉-temperature program desorption results.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119303979-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Rocío Magdalena Sánchez-Albores, Bianca Yadira Pérez-Sariñana, C.A. Meza-Avendaño, P.J. Sebastian, Odín Reyes-Vallejo, J. Billerman Robles-Ocampo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study synthesized powders of bismuth vanadate-alumina (BiVO〈sub〉4〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) by means of the microwave-assisted hydrothermal method. The powders prepared were characterized by X-ray diffraction, scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the synthesized powders was determined via the oxidative degradation of methylene blue (MB) in aqueous solution under the irradiation of visible light. The effect of parameters such as alumina concentration, synthesis temperature and reaction time was examined in order to determine their influence on crystal size, morphology, photocatalytic activity and the type of crystal structure. The sample prepared under conditions of 160 °C, 60 min and 1.5 wt % Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, presented the highest percentage of degradation and photonic efficient of all samples, which was close to 86% and 4.86 × 10〈sup〉−6〈/sup〉 respectively, under the parameters of the experimental design proposed for this research.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉The particles synthesized from BiVO〈sub〉4〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 with a mixture of monocyclic-tetragonal structure, showed better removal of the blue methylene dye, than the pristine form BiVO〈sub〉4〈/sub〉.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304006-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): M. Pérez-González, S.A. Tomás〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Photocatalytic Ag-loaded (TiO〈sub〉2〈/sub〉)〈sub〉0.95〈/sub〉-(ZnO)〈sub〉0.05〈/sub〉 thin films were synthesized by the sol-gel dip-coating method, with the Ag content varying in the range 1–4 mol%. The films were deposited on glass substrates at room temperature and then annealed at 500 °C. Raman spectroscopy disclosed basically the anatase phase of TiO〈sub〉2〈/sub〉. Secondary ion mass spectrometry measurements proved the incorporation of Ag in the films, revealing its diffusion to the film surface as a consequence of thermal treatments. X-ray photoelectron spectroscopy (XPS) was used to study in detail the chemical composition and electronic structure of the samples. The O 1s, Ti 2p, and Zn 2p core level spectra indicated Ti〈sup〉4+〈/sup〉 and Zn〈sup〉2+〈/sup〉 states associated with TiO〈sub〉2〈/sub〉 and ZnO regions. The chemical species identification was confirmed by calculating the modified Auger parameter for O, Ti, and Zn. In addition, an XPS depth profile analysis using an Ar〈sup〉+〈/sup〉 ion gun showed the formation of Ti〈sup〉+2〈/sup〉 and Ti〈sup〉+3〈/sup〉 oxidation states as a consequence of the Ar〈sup〉+〈/sup〉 bombardment. The photocatalytic activity under UV irradiation was evaluated by the degradation of methylene blue aqueous solutions, with the best response corresponding to (TiO〈sub〉2〈/sub〉)〈sub〉0.95〈/sub〉-(ZnO)〈sub〉0.05〈/sub〉 thin films doped with 2 mol% Ag.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304304-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): José Valecillos, Eva Epelde, Jonathan Albo, Andrés T. Aguayo, Javier Bilbao, Pedro Castaño〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The benefits of H-ZSM-5 zeolite modification with H〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 or ZnCl〈sub〉2〈/sub〉 have been analyzed during the methanol to olefins (MTO) reaction. The catalysts were prepared, characterized and tested using three different reactors: fixed-bed, operando FTIR and UV–vis. The spent catalysts were further characterized for analyzing the nature and location of the species trapped. The results show that the zeolite modified with H〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 has suffered a simultaneous dealumination, leading to a decrease of number of acid sites and activity. However, the zeolite modified with ZnCl〈sub〉2〈/sub〉 shows the inclusion of Zn transforming Brønsted into Lewis acid sites, leading to reaction intermediates (hydrocarbon pool species) that decreases the rate of reaction but improves propylene selectivity (+10%), slows downs coke formation (-42%) and expands catalytic lifetime (+80%). The distinct effect of Zn modification, typically associated with the promotion of aromatics, is explained on the grounds of the severe transformation of the strong and Brønsted acid sites.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304201-ga1.jpg" width="371" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 17 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Li Chen Kao, Wen Chen Kan, Rosa Maria Martin-Aranda, Maria Olga Guerrero-Perez, Miguel Á. Bañares, Sofia Ya Hsuan Liou〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The silica supported niobium oxide catalysts with abundant acid active sites were successfully fabricated and demonstrated catalytic activity in the acetalization of glycerol with acetone to produce solketal. Although Niobium pentachloride which was used as the niobium precursor preferred to aggregate on the surface, the chemical vapor deposition method was introduced to remove the surface chloride. The synthesis parameter of the material affects the structure and the type of the supported niobium oxide on the carrier, and directly changes the amounts of catalytic sites. The effect of calcination temperature/time and loading amount of hydrated niobium oxide on the catalytic performance was investigated. The properties of acid sites on catalysts were characterized, and the catalytic process was directly observed by operando Raman. These in-situ experimental trials could provide deep insight to understand the catalytic mechanism.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304286-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Yury I. Bauman, Ilya V. Mishakov, Yuliya V. Rudneva, Anton A. Popov, David Rieder, Denis V. Korneev, Alexandra N. Serkova, Yury V. Shubin, Aleksey A. Vedyagin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A series of micro-disperse Ni〈sub〉1-x〈/sub〉Pt〈sub〉x〈/sub〉 alloys with the sponge-like structure was prepared by a simultaneous precipitation method with subsequent sintering of the sediment in H〈sub〉2〈/sub〉 atmosphere at 800 °C. The formation of single-phase solid solution Ni〈sub〉1-x〈/sub〉Pt〈sub〉x〈/sub〉 was confirmed by powder XRD analysis for entire range of Pt concentrations (1.3–75.9 wt.%). The synthesized samples were studied in a process of catalytic decomposition of C〈sub〉2〈/sub〉H〈sub〉4〈/sub〉Cl〈sub〉2〈/sub〉 at 600 °C. In situ kinetic studies of the carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. Interaction of Ni-Pt alloys with reaction mixture is characterized by an induction period (18–32 min) followed by rapid disintegration of the bulk alloys with intensive growth of carbon fibers. The stage of the induction period was explored in detail by means of XRD and SEM techniques. According to XRD data, the interaction of Ni-Pt alloys with C〈sub〉2〈/sub〉H〈sub〉4〈/sub〉Cl〈sub〉2〈/sub〉 vapors is accompanied by formation of Ni〈sub〉1-x〈/sub〉Pt〈sub〉x〈/sub〉C〈sub〉δ〈/sub〉 interstitial solution due to entry of carbon into the crystal lattice of the alloy. The effect of Pt addition on catalytic activity of Ni in CCVD process was also studied. It was found that the yield of carbon product depends extremely on Pt concentration with a maximum at C〈sub〉Pt〈/sub〉 =4.3 wt.% (26 g/g〈sub〉Ni〈/sub〉 for 120 min). The impact of Pt concentration upon morphology and structural features of the produced carbon fibers was investigated by SEM and TEM techniques.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304365-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Yuan-Yuan Geng, Chun-Lan Tao, Shi-Fang Duan, Jovan San Martin, Yixiong Lin, Xiaolin Zhu, Qian-Qian Zhang, Xiong-Wu Kang, Sui-Sui He, Yi-Xin Zhao, Xin Li, Li Niu, Dong-Dong Qin, Yong Yan, Dong-Xue Han〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 is a n-type (negative type) semiconductor that has a narrow band gap and an ideal band edge position for hydrogen generation. However, high charge recombination rate, low photoelectrochemical (PEC) efficiency and poor stability are of major concerns of Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 as a photoelectrode. Herein, we report an efficient Vanadium-rich Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 nanowires (atomic ratio of V to Bi is 1/22) that have been prepared on fluorine-doped tin oxide (FTO) substrate by an in-situ solution-processed reaction with BiVO〈sub〉4〈/sub〉 film as precursor. The resulting V-rich photoelectrode demonstrates notably high charge separation efficiency and fast charge transport with respect to pristine Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 nanowires. As a result, the photocurrent density of ca. 10 mA·cm〈sup〉-2〈/sup〉 at -0.2 V vs Ag/AgCl is obtained under visible light illumination. In addition, V-rich Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 generates IPCE (incident photocurrent-to-current conversion efficiency) of 50% at 460 nm and 45% at 760 nm, demonstrating a 2.0 and 2.8-fold increase, respectively, when compared with pristine Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉. This enhancement is probably due to increased light absorption, less charge recombination, and faster charge transfer. More importantly, in contrast to pristine Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 sample that suffers detrimental photocorrosion in sulfide containing electrolyte, V-rich Bi〈sub〉2〈/sub〉S〈sub〉3〈/sub〉 nanowires retain 84.6% of its initial photocurrent over the course of 1 h. These findings are expected to shed light on engineering high-performance and robust metal sulfide materials for photoelectrochemical application.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304298-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈p〉Highlights〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Mathias Barreau, Xavier Courtois, Fabien Can〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Selective Catalytic Reduction (SCR) is one of the most efficient process for NO〈sub〉x〈/sub〉 removal from Diesel exhaust gas. However, the urea/NH〈sub〉3〈/sub〉-SCR process implemented in recent vehicles still suffers from a poor activity in the low temperature range (T 〈 250°C). One main reason is its dependency against the NO〈sub〉2〈/sub〉/NO〈sub〉x〈/sub〉 ratio, limiting the expected fast-SCR reaction in this temperature range. Recently, we shown that the addition of ethanol to ammonia led to a significant increase of the activity of a Ag/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 catalyst in this low temperature range. Moreover, in a dual-bed configuration (Ag/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉+WO〈sub〉3〈/sub〉/Ce〈sub〉x〈/sub〉-Zr〈sub〉y〈/sub〉O〈sub〉2〈/sub〉), a remarkable improvement was achieved at low temperature using only NO as NO〈sub〉x〈/sub〉. The present work aims to highlight the DeNO〈sub〉x〈/sub〉 chemistry encountered over the WO〈sub〉3〈/sub〉/Ce〈sub〉x〈/sub〉-Zr〈sub〉y〈/sub〉O〈sub〉2〈/sub〉 catalyst in a bifunctional (EtOH+NH〈sub〉3〈/sub〉) mixture. In addition to the fact that this process takes advantage of the low temperature NO〈sub〉2〈/sub〉 formation over the upstream Ag/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 catalyst, this work also puts in evidenced unexpected interactions between NO〈sub〉2〈/sub〉 and CH〈sub〉3〈/sub〉CHO (resulting from ethanol oxidation over Ag/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) thus leading to NO emission.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304407-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Jorge E. Ramos-Sanchez, R. Camposeco, Soo-Whon Lee, Vicente Rodríguez-González〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉SrTiO〈sub〉3〈/sub〉-cubic-like photocatalysts with average size of 35–40 nm were synthesized in 2 h without further calcination treatment. Structural defects or contamination were negligible according to the DRX and FTIR analyzes. The H〈sub〉2〈/sub〉 generation rates were 386 and 463 μmol h〈sup〉−1〈/sup〉 g〈sup〉〈sub〉−〈/sub〉1〈/sup〉 using an ethanol-water scavenger suspension with the SrTiO〈sub〉3〈/sub〉 and Ag/SrTiO〈sub〉3〈/sub〉 oxides, respectively. In comparison with other works reported in the literature, the hydrothermal synthesis of SrTiO〈sub〉3〈/sub〉 and the UV-pen lamp radiation used for the H〈sub〉2〈/sub〉 production may open a new strategy for the sustainable synthesis of 3-dimensional photoactive nanomaterials. The functionalization of nanocubes with highly monodispersed silver or rhodium nanoparticles provided an additional increase in the hydrogen photoproduction rate. In this sense, the silver nanoparticles (AgNPs) act as a sink for the photogenerated electrons through a Schottky barrier in the metal-perovskite contact region, boosting up the separation of the charge carriers. The identification of the surface species by XPS as well as the Rhodamine B photo-oxidation were performed to better understand the surface backward reaction in the photocatalytic production of hydrogen. The AgNPs worked as co-catalysts, preserving the stability of the most photoactive catalysts for 32 h.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304419-ga1.jpg" width="244" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 31 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Mun Kyoung Kim, Woo Hyeong Sim, Miri Choi, Hyungseob Lim, Youngkook Kwon, Hyung Mo Jeong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alkali metal ion intercalation into TiO〈sub〉2〈/sub〉 photocatalysts is a well-known method for obtaining enhanced photocatalytic properties. Herein, an effective electrochemical lithiation method is proposed for the synthesis of lithium-intercalated TiO〈sub〉2〈/sub〉 nanoparticles (NPs) suitable for high performance photocatalytic production of hydrogen. The electrochemical lithiation of TiO〈sub〉2〈/sub〉 induces partial reduction of Ti ions in the crystal lattices, which introduces additional energy states within the band edge of TiO〈sub〉2〈/sub〉, resulting in the improved optical properties. Consequently, Li-intercalated TiO〈sub〉2〈/sub〉 NPs exhibit almost 60-times improved hydrogen generation activity under both UV and visible light exposure compared to those of commercial TiO〈sub〉2〈/sub〉 NPs (P25).〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304195-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 31 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Gilliani Peixoto Miranda, Virgílio José Martins Ferreira Neto, Alexandre Ferreira Young, Erika Batista Silveira, Paulo Gustavo Pries de Oliveira, Fabiana Magalhães Teixeira Mendes〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Catalysts containing V-Mg-O species supported on activated carbon (AC), obtained from sugar-cane straw, were prepared and evaluated in the propane ODH reaction. Two conditions containing different molar amounts of Mg and V where prepared, one (condition II) with higher molar amounts of magnesium and vanadium than condition I, but the ratio of Mg/V = 1:2 was kept constant. For comparison purposes, the same preparation methodology was used but with MCM-41 as support, instead. The physicochemical properties of these catalysts were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Laser Raman spectroscopy (RS) and Scanning electron microscopy, coupled with energy dispersive microscopy (SEM-EDS). For the first time the nature of V-Mg-O species on an activated carbon surface was investigated. The electron environment around vanadium was evaluated by XPS, revealing the coexistence of V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 crystallites with highly dispersed species of Mg-V-O and P-V linkages on the surface. Vanadium enrichment was observed on the surface of those supported on activated carbon, especially for the preparation containing higher amounts of V and Mg. All the AC and MCM-41 supported catalysts were active and selective in ODH of propane into propylene and were stable for, at least 24 h, of reaction. The stability was attributed to the presence of the Mg-V linkages at the catalysts surface, while Phosphate CPO groups still exists, despite of the formation of V-P linkages.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304213-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 30 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Jing Ning, Yan Zhou, Aling Chen, Yong Li, Shu Miao, Wenjie Shen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cu species in the forms of layers, clusters and particles were dispersed on a rod-shaped ceria by a deposition-precipitation method and the resulting Cu/CeO〈sub〉2〈/sub〉 catalysts were tested for the low-temperature water-gas shift reaction. The structural, chemical and surface properties of the Cu/CeO〈sub〉2〈/sub〉 catalysts were analyzed by spectroscopic and microscopic techniques. It was identified that dispersion of copper on the rod-shaped ceria strongly depended on the metal loading (1–28 mol%): lower contents resulted in copper monolayers and/or bilayers while higher loadings led to multi-layered clusters and faceted particles. The copper-ceria interface was constructed by an intimate bonding of positively-charged copper atoms with oxygen vacancies on ceria, in a form of Cu〈sup〉+〈/sup〉-O〈sub〉v〈/sub〉-Ce〈sup〉3+〈/sup〉, involving the electronic and geometric interactions between the copper atoms in the metal species and the oxygen vacancies on ceria. The overall activity increased linearly with the copper content in the range of 1–15 mol%, contributed mainly by copper monolayers and/or bilayers. Further increasing Cu loading up to 28 mol% only slightly enhanced the activity because of the presence of multilayered and crystalline Cu particles. This finding demonstrates that the dispersion of copper on the rod-shaped ceria depends on the loading of copper in the Cu/CeO〈sub〉2〈/sub〉 catalysts, which is associated with the number and density of the active sites.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304043-ga1.jpg" width="450" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 336〈/p〉 〈p〉Author(s): 〈/p〉

Beschreibung: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 336〈/p〉 〈p〉Author(s): M.O. Guerrero-Pérez, R. López-Medina, E. Rojas-Garcia, M.A. Bañares〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A XANES study under reaction conditions has been performed with two different V-based catalytic systems, Mo-V-Nb-Te-O and V-Sb-O. For this study, an alumina-supported nanoscaled bulk catalyst has been used. In all cases XANES determined the average vanadium oxidation state during reaction. XANES also demonstrated that the nanosized phases are more dynamic, and able to participate in the redox catalytic cycle without significant changes either in their structure or in the overall vanadium oxidation state. Such a stability is also apparent under oxidizing conditions.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586117308350-fx1.jpg" width="419" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Arun Kumar, Nishith Verma〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Emerging organic pollutants and heavy metals are the most common co-contaminants in water bodies. Efficacy of the Cu-Fe bimetals-dispersed carbon nanofibers (CNFs) grown over activated carbon beads (ACBs) was investigated for remediation of wastewater co-contaminated with dichlorvos (DDVP) (pesticide) and toxic Cr(VI) at moderate temperature and pressure (200 °C and 25 bar) using air as an oxidant. The experimental data showed that ˜95 and 80% degradation of DDVP (single feed) was achieved in 3 h over Cu-CNF/ACB and Fe-CNF/ACB, respectively, whereas complete degradation was measured during the identical time over Cu-Fe-CNF/ACB. In case of mixed feed (DDVP and Cr), complete degradation of DDVP as well as reduction of Cr(VI) was achieved in only 1 h. DDVP was degraded or mineralized by the hydroxyl radicals (〈sup〉〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/rad"〉〈/sup〉OH) through oxidation, whereas Cr(VI) was reduced to Cr(III). Further analysis indicated that reduction of Cr(VI) to Cr(III) was facilitated by the transformed intermediate products of DDVP, which were recognized as the formic and acetic acids. Analysis of the spent water showed complete mineralization of DDVP with simultaneous reduction of Cr(VI) to Cr(III). The toxicity tests showed the spent water to be non-toxic. This is the first study to indicate the successful remediation of wastewater co-contaminated with a recalcitrant organic pollutant and a heavy toxic metal over the catalytic Cu-Fe-CNF/ACB.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Simultaneous oxidation of DDVP and reduction of Cr(VI) to Cr(III) over Cu-Fe dispersed carbon nanofiberous catalytic beads in wet air.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304481-ga1.jpg" width="401" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Sang-Chul Jung, Heon Lee, Seo Jin Ki, Sun-Jae Kim, Young-Kwon Park〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding the performance and mechanism of the degradation of various contaminants is essential for the effective design of wastewater treatment systems. This study examined the degradation of 1,4-dichlorobenzene in a photocatalytic system, which embedded TiO〈sub〉2〈/sub〉 particles (as a thin film) on alumina balls (as a solid support). Decomposition of the parent compound was assessed by introducing a TiO〈sub〉2〈/sub〉 photocatalyst, microwave irradiation, and ultraviolet irradiation jointly or separately (in terms of the system configuration) with and without an adjustment for the microwave intensity, pH, and hydrogen peroxide levels (in terms of the operating conditions) to the photocatalytic system. The results showed that the photocatalytic system adopting multiple processes concomitantly improved the degradation performance of the parent compound that was resistant to the single-unit processes. On the other hand, the decomposition efficiency was increased further with the sophisticated control of the operating conditions, specifically the pH and hydrogen peroxide levels. A dechlorination process as well as substitution and addition reactions involving the hydroxyl radical appeared to occur in the degradation pathway to produce four degradation products from the parent compound. The significance of this study lies in the introduction of a systematic approach to optimizing the operating conditions that facilitate the decomposition efficiency in a given photocatalytic system at no extra cost.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304420-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 13 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Zhou-jun Wang, Runduo Zhang, Zhigang Lei, Claude Descorme, Michael S. Wong〈/p〉

Beschreibung: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Marina Godino-Ojer, Mariya Shamzhy, Jiři Čejka, Elena Pérez-Mayoral〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report here efficient synthesis of quinoxalines from o-phenylendiamine and α-hydroxy ketones over commercial Basolites. The concentration and type of acid centres, as CUS sites, together with the porosity of the samples strongly influence the resulting conversion and selectivity. Our results indicate that the formation of quinoxalines preferentially follows a new route, in which tautomerization reactions are also involved.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304237-ga1.jpg" width="256" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 336〈/p〉 〈p〉Author(s): Casey P. O’Brien, Ivan C. Lee〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pd and PdCu alloy membranes are promising candidates for separating hydrogen from mixed gas streams due in part to their infinite selectivity to hydrogen separation. However, other gases such as CO can inhibit hydrogen transport across Pd-based membranes. In this work, the mechanism by which CO inhibits hydrogen transport across a 25 μm-thick Pd〈sub〉47〈/sub〉Cu〈sub〉53〈/sub〉 (mol%) membrane is investigated by 〈em〉operando〈/em〉 infrared-reflection absorption spectroscopy (IRAS) in the 373–533 K temperature range. In the absence of hydrogen, CO adsorbs on three different sites on the PdCu surface: (1) bridging between contiguous Pd atoms, (2) on top of isolated Pd atoms surrounded by Cu atoms, and (3) on top of oxidized Cu atoms. CO induces agglomeration of isolated Pd atoms on the PdCu surface, which is driven by the higher stability of CO adsorbed on bridging sites between Pd atoms than on isolated Pd atoms surrounded by Cu atoms. The rate of hydrogen permeation across the PdCu alloy membrane decreases with increasing CO concentration in the feed gas, and the poisoning effect of CO is more severe at lower temperatures. CO inhibits hydrogen transport across the membrane by adsorbing only on Pd sites on the PdCu surface and blocking H〈sub〉2〈/sub〉 dissociation on these sites. Due to the weaker interaction of CO with PdCu alloy surfaces than with Pd, the PdCu alloy is more resistant to CO poisoning than pure Pd.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586117306545-fx1.jpg" width="454" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): M.M. Ramirez-Corredores, Dong Ding, Anne M. Gaffney〈/p〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118315591-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 336〈/p〉 〈p〉Author(s): 〈/p〉

Beschreibung: 〈p〉Publication date: Available online 30 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Long-Fei Xie, Yu-Ping Xu, Xian-Lei Shi, Feng Wang, Pei-Gao Duan, Shi-Chang Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydrothermal liquefaction of 〈em〉Auxenochlorella pyrenoidosa〈/em〉 (AuP) and 〈em〉Arthrospira platensis〈/em〉 (ArP) at 350 °C for 1 h produced algal biocrudes (BCs), BC(AuP) and BC(ArP), with yields of 41.82 and 36.60 wt.%, respectively. These two algal BCs were cut into five distillate fractions (DFs) of 25-100 °C (DF0), 101-200 °C (DF1), 201-300 °C (DF2), 301-400 °C (DF3), and ≥401 °C (DR) using atmospheric distillation under N〈sub〉2〈/sub〉 atmosphere. The total yields of DF1, DF2, and DF3 from either BC(AuP) or BC(ArP) are at least 60 wt.%. All the DFs, from either AuP or ArP, showed different yields and elemental and molecular compositions. Next, the DF1, DF2, and DF3 DFs were each blended with used engine oil (UEO) at a mass ratio of 1:1 and treated at 400 °C for 4 h with an additional 0.1 kg〈sub〉Pt/C〈/sub〉/kg〈sub〉feed〈/sub〉 under 4 MPa H〈sub〉2〈/sub〉. The presence of UEO could dilute the DF, avoid solvent extraction of the product oil, favor desulfurization of the upgraded oil, and be directly recovered as a major part of the product oil. Catalytic hydrotreatment of the DF and UEO blends led to a higher upgraded oil yield (〉79 wt.%) and lower coke (〈12 wt.%) and gas (〈9 wt.%) yields compared with those from the BCs alone under the same process conditions, and higher upgraded oil yields were achieved when using the DFs with high boiling point ranges. The upgraded oil had a lower total acid number and oxygen, nitrogen, and sulfur contents than those of the BC. The sulfur contents of the upgraded oil produced from the DF and UEO blends were much lower than those from the BCs alone, and the lowest sulfur content of 12 ppm (〈em〉w/v〈/em〉) was achieved. The high abundance of unsaturated hydrocarbons and nitrogen- and oxygen-containing compounds in the BC were replaced by a high abundance of hydrocarbons and benzene derivatives in the upgraded oil. The heating value of the upgraded oil (˜48 MJ/kg) was higher than that of the BC. The main gas-phase products were H〈sub〉2〈/sub〉, CH〈sub〉4〈/sub〉, C〈sub〉2〈/sub〉H〈sub〉6〈/sub〉, and C〈sub〉3〈/sub〉H〈sub〉8.〈/sub〉 Overall, many of the properties of the upgraded oils obtained from the catalytic hydrotreatment of the DF and UEO blends were similar to those of hydrocarbon fuels derived from fossil fuel resources.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119301294-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Tianyu Gao, Yongxuan Yin, Guanghui Zhu, Qiue Cao, Wenhao Fang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oxidative transformations of HMF are key routes toward a wide variety of chemicals and biofuels through an environmental friendly process. Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs decorated Mn-Co-O solid solution, donated as Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉/Mn〈em〉〈sub〉X〈/sub〉〈/em〉Co, was prepared by co-precipitation method and used as non-precious metal catalyst for base-free oxidation of HMF to FDCA in the presence of O〈sub〉2〈/sub〉 and water. Comprehensive characterizations such as XRD, H〈sub〉2〈/sub〉-TPR, O〈sub〉2〈/sub〉-TPD, XPS, NH〈sub〉3〈/sub〉/CO〈sub〉2〈/sub〉-TPD and TEM were used to study materials properties especially the oxygen mobility and acidity-basicity. The effect of Mn/Co molar ratio in catalyst and the reaction conditions were investigated and optimized. In addition, the kinetics of the reaction was monitored to reveal the reaction route and rate-determining step. The variation of Mn/Co molar ratio was found to affect not only HMF conversion but also distribution of products. When the Mn/Co ratio was of 0.2, the Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉/Mn〈sub〉0.2〈/sub〉Co catalyst showed the optimal catalytic performance (i.e., 〉99% yield of FDCA obtained under 1 bar O〈sub〉2〈/sub〉 at 140 °C after 24 h) due to the highest content of both Lewis and Brønsted acid sites on the surface, leading to the strongest ability of HMF adsorption and COOH group formation, as well as the enhanced oxygen mobility. This catalyst was shown stable after a minor deactivation (≤8%) during six recycling uses and its activity can be entirely regenerated by calcination in air.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119301452-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Vasiliy Yu. Evtushok, Olga Yu. Podyacheva, Arina N. Suboc, Nataliya V. Maksimchuk, Olga A. Stonkus, Lidiya S. Kibis, Oxana A. Kholdeeva〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we present a new methodology for the preparation of highly active, selective, leaching-tolerant and recyclable catalysts on the basis of polyoxometalates (POM) and nitrogen-doped carbon nanomaterials. A divanadium-substituted γ-Keggin phosphotungstate [γ-PW〈sub〉10〈/sub〉O〈sub〉38〈/sub〉V〈sub〉2〈/sub〉(μ-O)(μ-OH)]〈sup〉4-〈/sup〉 (PV〈sub〉2〈/sub〉), was immobilized on two types of supports – N-doped carbon nanofibers (N-CNFs) having herring-bone packing of graphite layers and bamboo-like N-doped carbon nanotubes (N-CNTs). Two series of catalysts have been prepared and characterized by elemental analysis, N〈sub〉2〈/sub〉 adsorption, TEM, XPS and FTIR techniques. Their catalytic performance was assessed in the liquid-phase selective oxidation of two representative organic substrates, 2,3,6-trimethylphenol and cyclohexene, with aqueous H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 as the green oxidant. The presence of nitrogen in the supports ensures strong binding and quasi-molecular dispersion of POM on the carbon surface, which is crucial for the catalytic performance and catalyst stability. The catalysts reveal truly heterogeneous nature of the catalysis and can be easily recovered and reused without loss of the catalytic performance. The morphology of the support has a significant impact on the catalytic performance: the supported PV〈sub〉2〈/sub〉 catalysts prepared using N-CNTs are more active and, in general, more selective than the catalysts prepared with N-CNFs.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092058611831441X-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Gaurav Sharma, Dionysios D. Dionysiou, Shweta Sharma, Amit Kumar, Ala’a H. Al-Muhtaseb, Mu. Naushad, Florian J. Stadler〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present paper, we report the synthesis of activated carbon supported strontium/cerium bimetallic nanocomposite (Sr/Ce/AC BNC) that has been prepared by simple microwave reduction method. X- Ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-Ray diffraction (XRD) and Transmission electron microscopy (TEM) analyses were performed to characterize the fabricated Sr/Ce/AC BNC. Sr/Ce/AC BNC has been found to be efficient photocatalyst and being explored for the degradation of rhodamine B under natural sunlight irradiation. The photocatalytic activity of Sr/Ce/AC was evaluated based on reaction kinetics to remove rhodamine B, chemical oxygen demand (COD), and total organic content (TOC). Hydroxyl radicals have been found to be the active participating species which was confirmed by using appropriate radical scavengers. Degradation intermediate products of rhodamine B were identified using LC-MS and the reaction pathways were proposed and discussed in the manuscript. In short, this work provides a deep insight into the utilization of Sr/Ce/AC BNC as effective photocatalyst.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118317371-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Priyanka Verma, Yasutaka Kuwahara, Kohsuke Mori, Hiromi Yamashita〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The localized surface plasmon resonance (LSPR) mediated enhanced chemical activity can be entitled as a promising strategy for efficient solar to chemical energy conversion. To tune the selectivity of a desired product in a chemical reaction is of paramount importance yet a great challenge. In this paper, a new strategy to effectively enhance the selectivity of the product formation under visible light irradiation is reported. A series of Ag catalysts deposited on metal oxide support materials (TiO〈sub〉2〈/sub〉, ZrO〈sub〉2〈/sub〉, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and CeO〈sub〉2〈/sub〉) along with their preparative techniques, optimum metal content ratio and effect of different wavelength of light is explored for the chemoselective reduction of 〈em〉p〈/em〉-nitrostyrene to 〈em〉p〈/em〉-aminostyrene under visible light irradiation. The prepared catalysts were characterized by a range of physicochemical techniques including UV-vis, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The reduction reaction was carried out in ethanolic suspension at room temperature and pressure utilizing ammonia borane (AB) as an in-situ source of H〈sub〉2〈/sub〉. The reaction results displayed 100 % conversion with a maximum chemoselectivity of 81 % shown by Ag/TiO〈sub〉2〈/sub〉 under light irradiation conditions. The high chemoselectivity could be attributed to the preferential alignment of polar nitro group on the surface of plasmonic silver under light irradiation conditions.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119301439-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 26 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Frederik Tielens, Maciej Gierada, Jarosław Handzlik, Monica Calatayud〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Much of our current understanding of catalytic activity is derived from materials with well-defined structures, either molecular (i.e., homogeneous catalysts) or extended, ordered solids (i.e., heterogenous catalysts and surface science), and active sites in real catalysts are often assumed to closely resemble structures found in such ordered materials, at least locally. Yet many real catalysts involve amorphous materials and are much more active than their well-ordered counterparts would suggest. This implies that at least some active sites in amorphous materials are intrinsically different. One of these important and versatile amorphous materials is silica.〈/p〉 〈p〉The materials properties are based in many cases on the way molecules interact with the silica surface. Since several years we investigate silica and its role as support of transition metal oxide catalysts, but also the interaction with bio-organic systems, and this at different levels: from the phenomenological description of the interaction at the interface substrate-adsorbate (adsorption and self-assembling of biomolecules) to technologic applications (catalysis, ionic liquids), pharmaceutical (controlled delivery of drug molecules) and their plausible role in different scenarios in the origin of life. For this we use the tools of quantum chemistry combined with experimental back up with the aim to improve the understanding of the complex chemical behavior of these silica based materials.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118313725-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Filip Zasada, Joanna Gryboś, Camillo Hudy, Janusz Janas, Zbigniew Sojka〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mechanistic investigations based on combination of catalytic isotopic experiments with DFT modeling were used to probe the pathways by which CH〈sub〉4〈/sub〉 in transformed into H〈sub〉2〈/sub〉O and CO〈sub〉2〈/sub〉 over cobalt spinel nanocubes exposing the (100) surface exclusively. The catalyst synthetized by the hydrothermal method was thoroughly characterized by means of XRD, XRF, Raman and SEM techniques. Combustion of methane was performed in a TPSR mode using sole 〈sup〉16〈/sup〉O〈sub〉2〈/sub〉 or a 1:1 mixture of 〈sup〉16〈/sup〉O〈sub〉2〈/sub〉 and 〈sup〉18〈/sup〉O〈sub〉2〈/sub〉. Two distinct mechanistic pathways of the C–H bond activation, and subsequent oxidation of the consecutive intermediates involve a suprafacial mechanism operating in the oxygen covered surface and an interfacial mechanism operating on the oxygen depleted/bare surface. It was found that depending on the conditions they may act separately in the early and late stages of the reaction, and simultaneously in the middle phase, in response to differences in the nature and accessibility of the surface and lattice oxygen species, however the activation of the first C– bond remains the kinetically relevant step. The cobalt-oxo Co〈sup〉T〈/sup〉〈sub〉2c〈/sub〉–O species exhibit the highest activity in the suprafacial C–H bond breaking, and the peroxo O〈sub〉2〈/sub〉〈sup〉2–〈/sup〉 species are engaged in the intermediate reaction steps leading to formation of final H〈sub〉2〈/sub〉O and CO〈sub〉2〈/sub〉 products. On the oxygen exhausted surface, where the interfacial mechanism operates, dual Co–O sites constituted by Co〈sup〉O〈/sup〉〈sub〉5c〈/sub〉–O〈sub〉3O〈/sub〉 and Co〈sup〉T〈/sup〉〈sub〉2c〈/sub〉–O〈sub〉2O,1T〈/sub〉 pairs may activate the C–H bond in a concerted way, with the former being more active. For all the mechanistic steps the transition and stable states of the involved intermediates and products were identified and quantified in terms of their structure and the associated free enthalpy profiles. The three dimensional (log(〈em〉k〈/em〉〈sup〉intra〈/sup〉/〈em〉k〈/em〉〈sup〉supra〈/sup〉) versus (Δ〈em〉G〈/em〉〈sub〉a〈/sub〉〈sup〉supra〈/sup〉-Δ〈em〉G〈/em〉〈sub〉a〈/sub〉〈sup〉supra〈/sup〉) and 〈em〉Θ〈/em〉〈sub〉O〈/sub〉) diagrams were constructed to discriminate between the suprafacial (Eley-Rideal/Langmuir-Hinshelwood) and interfacial (Mars-van Krevelen) mechanism of CH〈sub〉4〈/sub〉 combustion. It is believed that the main features of the established mechanism are also applicable in the case of the methane oxidation over other electron rich transition metal oxides.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118317152-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Hyeonkwon Lee, Vijay S. Kumbhar, Jaewon Lee, Hyunchul Oh, Kiyoung Lee〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The formation of well aligned TiO〈sub〉2〈/sub〉 nanotubes with suitable inner diameters is a pre-requisite for photocatalytic application. The inner diameters can be tuned by the composition of electrolyte, anodization temperature, and applied potential. Here, we have successfully formed the TiO〈sub〉2〈/sub〉 nanotubes with wide inner diameters by controlling the anodization potential of the Ti metal substrate. The anodizations were performed in the aqueous solution of ethylene glycol mixed with hydrofluoric acid as an electrolyte at potentials of 150-240 V at 40 ℃. It resulted into TiO〈sub〉2〈/sub〉 nanotubes with inner diameters in the range of 160-400 nm and lengths about 6-8 µm, respectively. Moreover, the TiO〈sub〉2〈/sub〉 nanotubes were sputter coated with thin layers (1-5 nm) of Pt and Au nanoparticles. Finally, we compared the photocatalytic behavior of the as-prepared TiO〈sub〉2〈/sub〉 nanotubes and those coated with Au and Pt nanoparticles. Interestingly, 1 nm Pt coated 300 and 400 nm inner diameter TiO〈sub〉2〈/sub〉 nanotubes showed highest H〈sub〉2〈/sub〉 production rate of 25 µL h〈sup〉-1〈/sup〉 cm〈sup〉-2〈/sup〉 under a 10 h of light illumination.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119301476-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Wei-Chung Wen, Shawn C. Eady, Levi T. Thompson〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There is significant interest in the use of H〈sub〉2〈/sub〉O as a reactant for production of commodity chemicals and fuels, in particular from water-laden biomass-derived feedstocks. In this paper, we describe results for the aldehyde water shift (AWS), a reaction where aldehydes are partially oxidized by water to produce the corresponding carboxylic acid and H〈sub〉2〈/sub〉, over a series of CeO〈sub〉2〈/sub〉, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and SiO〈sub〉2〈/sub〉 supported Cu, Pt, and Au catalysts. The effects of support were further investigated by evaluating the performances of a Cu-Zn-Al water gas shift catalyst and bulk Cu nanoparticles. The supported Cu catalysts were more active than the supported Pt and Au catalysts, and the reducible oxide (CeO〈sub〉2〈/sub〉) supported Cu catalyst had the highest AWS activity. The high activity of Cu/CeO〈sub〉2〈/sub〉 catalyst is believed to derive from coupling H〈sub〉2〈/sub〉O dissociation and aldehyde oxidation. The two major side reactions, aldol condensation and aldehyde disproportionation, appeared to be catalyzed by acid and Cu sites, respectively. The results indicate that both the admetal and support play critical roles in catalyzing the AWS reaction and provide guidance for the design of highly active AWS catalysts.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119301440-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: 1 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 329〈/p〉 〈p〉Author(s): Derek Bradley, Joaquim Casal, Adriana Palacios〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydrogen jet flames, as a consequence of their greater reactivity, have a number of characteristics that are different from other flames. These are reviewed, as are the various attempts that have been made to characterise, and generalise, the lift-off distance at the base of jet flames. There has been a consistent improvement in the accuracy of the expressions for the prediction of lift-off distance. In addition to the greater reactivity that creates a small laminar flame thickness, allowance must be made for the significantly smaller air requirement for each mole of hydrogen fuel. The evolution of an expression for the lift-off distance is discussed and a new expression is provided. Alongside the blow-off data for lifted flame regimes, this enables hydrogen lifted flames to be fully characterised.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586117307885-fx1.jpg" width="178" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Denzil Moodley, Michael Claeys, Eric van Steen, Pieter van Helden, Deshen Kistamurthy, Kees-Jan Weststrate, Hans Niemantsverdriet, Abdool Saib, Willem Erasmus, Jan van de Loosdrecht〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sintering of supported cobalt catalysts is an important deactivation mechanism at play at realistic Fischer-Tropsch synthesis conditions. The traditional ways of studying the mechanism of sintering by looking at cobalt particle size distributions derived from transmission electron microscope images on porous supported catalysts, does have its drawbacks. In this mini-review, we show collaborative work between Sasol and its academic partners at the University of Cape Town and Eindhoven University of Technology, in which a two-pronged approach was used to study the topic of sintering. This included the use of model systems (model catalysts and theory) as well as 〈em〉in-situ〈/em〉 monitoring of real (industrial) systems for understanding this practical problem in industry. We also show with new data, that the understanding generated can be used in the mitigation of sintering by using either process conditions, catalyst design or catalyst regeneration.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118309088-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: 1 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 329〈/p〉 〈p〉Author(s): Alexander S. Noskov, Andrey N. Zagoruiko, Oleg Klimov, Christophe Geantet, Tatyana Zamulina〈/p〉

Beschreibung: 〈p〉Publication date: 1 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 329〈/p〉 〈p〉Author(s): 〈/p〉

Beschreibung: 〈p〉Publication date: Available online 3 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Daniela Pietrogiacomi, Maria Cristina Campa, Leandro Ardemani, Manlio Occhiuzzi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Co-, Fe- or Ni-exchanged Na-MOR (Si/Al = 9.2) were prepared by ion-exchange method. The catalytic activity of Fe-MOR catalyst for the simultaneous selective catalytic reduction of NO〈sub〉x〈/sub〉 and N〈sub〉2〈/sub〉O with CH〈sub〉4〈/sub〉 in the presence of excess O〈sub〉2〈/sub〉 (SCR〈sub〉sim〈/sub〉) and for the related reactions (SCR〈sub〉N2O〈/sub〉, SCR〈sub〉NO〈/sub〉, N〈sub〉2〈/sub〉O decomposition, N〈sub〉2〈/sub〉O decomposition in the presence of NO and CH〈sub〉4〈/sub〉 combustion) was investigated and compared with that previously measured for Co-MOR and Ni-MOR. The evolution of the surface species on Co-, Fe- or Ni-MOR (tmi-MOR) in the presence of flowing reactant mixtures during the SCR〈sub〉NO〈/sub〉 and the SCR〈sub〉sim〈/sub〉 were investigated by 〈em〉operando〈/em〉 FTIR experiments and compared with that previously studied during SCR〈sub〉N2O〈/sub〉. The correlation between the results of both 〈em〉operando〈/em〉 FTIR and catalytic activity study gave an insight into the active sites and the pathway of the simultaneous abatement in tmi-MOR catalysts.〈/p〉 〈p〉〈em〉Operando〈/em〉 FTIR experiments under SCR〈sub〉NO〈/sub〉 feed allowed to identify on Co-MOR and Ni-MOR, both active for NO reduction, isocyanate species and monodentate tmi-nitrates, whereas on inactive Fe-MOR NO〈sup〉+〈/sup〉 and bridged tmi-nitrates. The SCR〈sub〉NO〈/sub〉 pathway consisted of CH〈sub〉4〈/sub〉 activation by NO〈sup〉+〈/sup〉 yielding Al〈sup〉3+〈/sup〉-isocyanates, that together with monodentate tmi-nitrates on nearby sites were involved in the pathway leading to the N-N pairing. 〈em〉Operando〈/em〉 FTIR experiments under SCR〈sub〉sim〈/sub〉 feed on tmi-MOR identified the same NO〈sub〉y〈/sub〉 species as in SCR〈sub〉NO〈/sub〉 feed and no CH〈sub〉x〈/sub〉O〈sub〉y〈/sub〉 species, intermediates of SCR〈sub〉N2O〈/sub〉. The formation of CH〈sub〉x〈/sub〉O〈sub〉y〈/sub〉 species was hindered by the active sites coverage due to nitrates.〈/p〉 〈p〉We concluded that the simultaneous NO and N〈sub〉2〈/sub〉O abatement occurred 〈em〉via〈/em〉 two independent processes (NO reduction and N〈sub〉2〈/sub〉O decomposition). The zeolite MOR structure, allowing the location of working sites in different confined positions, guaranteed the simultaneous but independent pathways for the two abatements. Co-MOR alone was effective for the simultaneous abatement, because it combined the proper location with the suitable properties (nuclearity, coordination and electron charge mobility) of active sites.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118309076-ga1.jpg" width="491" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 2 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Ó. Benito-Román, M.T. Sanz, A.E. Illera, R. Melgosa, S. Beltrán〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present work, High Pressure Carbon Dioxide (HPCD) has been used to inactivate the enzymes Polyphenol Oxidase (PPO) and Pectin Methylesterase (PME). The work has been done in two stages: in the first one, fundamental knowledge about the inactivation mechanism induced by HPCD was obtained using pure commercial enzymes. The influence of the main process parameters was studied: pressure, temperature, time and ratio CO〈sub〉2〈/sub〉/volume of enzymatic solution. The changes in the tertiary structure of the enzymes after the HPCD treatment were analyzed by fluorescence spectroscopy running two different tests: intrinsic fluorescence measurement and ANS binding. In the second stage, the acquired knowledge was used to study the inactivation pattern of these two enzymes in liquid and solid natural products, including fruit and vegetable juices or shrimps. The results revealed differences in the inactivation pattern of the enzymes in these substrates compared to the pure commercial enzymes, but the applicability of HPCD technology for the inactivation of enzymes in real substrates at industrial scale was also revealed.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118313841-ga1.jpg" width="406" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 26 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Chelsea L. Tucker, Eric van Steen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of the harsh conditions achieved when operating the Fischer-Tropsch synthesis at high conversion on the activity and selectivity of Pt-Co/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 were studied in a slurry bed reactor at T = 220 °C, P = 20 bar, with a feed simulating synthesis gas generated by air-blown gasification (H〈sub〉2〈/sub〉: CO: N〈sub〉2〈/sub〉 = 4:2:6). The rate of CO consumption decreased with increasing conversion. Decreasing the space velocity and thus increasing the CO conversion was found to have slight effect on CO〈sub〉2〈/sub〉 selectivity until a conversion of CO of 75%, after which a strong increase was observed. The production of CO〈sub〉2〈/sub〉 raised the H〈sub〉2〈/sub〉/CO ratio within the reactor resulting in a large increase in methane selectivity. An increase in CO conversion resulted in a decrease in chain growth probability and C〈sub〉5+〈/sub〉 selectivity. The link between the change in the methane selectivity, chain growth probability and C〈sub〉5+〈/sub〉 selectivity and the presence of carbonaceous species on the surface is explored.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118306862-ga1.jpg" width="352" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 26 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): A.M. Díez, M. Pazos, M.A. Sanromán〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, magnetic iron particles doped with TiO〈sub〉2〈/sub〉 were synthetized to be used as a photo electro Fenton catalyst, being easily eliminated from the treated solution. Thus, the synergistic and scarcely reported combination of photocatalyst with electro Fenton process was evaluated for the degradation of an emerging pollutant: the ionic liquid 1-butyl-2, 3-dimethyl imidazolium chloride. To increase the radiation leverage, a cyclic two-cell configuration reactor was set, so the photolysis is applied directly and without obstacles in one cell and the electrolysis in another. The effect of the catalyst synthesis method and the ratio Fe/TiO〈sub〉2〈/sub〉 were evaluated. With the most active bifunctional catalyst, a deep study of the two-cell reactor was done in terms of recirculation flow, applied intensity and catalyst dosage. Under the best conditions (respectively, 480 mL min〈sup〉−1〈/sup〉, 70 mA and 1 g L〈sup〉−1〈/sup〉), complete pollutant removal (in 10 min) and high mineralization (100% in 2 h) was achieved. Encouragingly, the results were almost equal when degrading the model pollutant on a real wastewater matrix. The reusability of the catalyst was also confirmed after three trials without almost no detriment on the performance.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118311064-ga1.jpg" width="267" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 26 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Sun Hee Yoon, Unseock Kang, Hyunwoong Park, Ahmed Abdel-Wahab, Dong Suk Han〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study examines the reaction pathways for the selective conversion of CO〈sub〉2〈/sub〉 to formate on the surface of mixed CuFeO〈sub〉2〈/sub〉 and CuO (CFO) by employing density functional theory (DFT) calculation of the reaction energy and activation energy barrier. Two different systems were employed to model the CFO structure: homogeneous structures (HMS) of uniformly mixed 40% CuFeO〈sub〉2〈/sub〉 (012) and 60% CuO (111), and a heterogeneous structure (HTS) created with CuO (111) clusters intermittently supported on the CuFeO〈sub〉2〈/sub〉 (012) surface. The monodentate and bidentate oxygen coordinations (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mi mathvariant="normal"〉O〈/mi〉〈mrow〉〈mi mathvariant="normal"〉C〈/mi〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉O〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉) in possible CO〈sub〉2〈/sub〉 adsorption configurations were investigated for the preferential reduction of CO〈sub〉2〈/sub〉 to formate on the surface Cu sites constrained by dense electron density. In the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mi mathvariant="normal"〉O〈/mi〉〈mrow〉〈mi mathvariant="normal"〉C〈/mi〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉O〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉-monodentate configuration, the reaction energy and activation barrier for formate formation using PBE + D3 were −0.41 eV and 0.28 eV, respectively, for the HTS and −0.69 eV and 0.72 eV, respectively, for the HMS. In the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mi mathvariant="normal"〉O〈/mi〉〈mrow〉〈mi mathvariant="normal"〉C〈/mi〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉O〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉-bidentate configuration, the corresponding values were −0.58 eV and 0.53 eV, respectively, for the HTS and −1.17 eV and 0.54 eV, respectively, for the HMS. Consequently, the conversion of CO〈sub〉2〈/sub〉 to formate in the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mi mathvariant="normal"〉O〈/mi〉〈mrow〉〈mi mathvariant="normal"〉C〈/mi〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉O〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉-monodentate mode was kinetically more advantageous in the HTS. This result indicated that the heterogeneity of the CFO structure, as well as the CO〈sub〉2〈/sub〉 adsorption configuration, would change the rate-limiting energy barrier through the reaction coordinates, ultimately supporting the selective conversion of CO〈sub〉2〈/sub〉 on HTS.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118315268-ga1.jpg" width="451" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 31 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Liliana Lukashuk, Nevzat Yigit, Hao Li, Johannes Bernardi, Karin Föttinger, Günther Rupprechter〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In contrast to Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉, CoO has been much less studied for CO oxidation. Herein, the phase changes of commercial mesoscopic CoO (particle size ˜1 μm) and nanosized CoO (20–50 nm particle size), the latter prepared by vacuum reduction of commercial Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉, were examined by operando X-ray absorption (XAS) and near-ambient pressure X-ray photoemission (NAP-XPS) spectroscopy during CO oxidation, as well as ex situ by transmission electron microscopy and diffraction (TEM/SAED).〈/p〉 〈p〉Commercial mesoscopic CoO exhibited CO oxidation activity at ˜200 °C, but even up to 530 °C in pure O〈sub〉2〈/sub〉 no substantial (bulk) oxidation was observed by operando XAS, likely due to the large grains and bulk nature of CoO. After pre-oxidation at 400 C, electron diffraction detected thin surface layers of Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉. This increased activity but the activity of nanosized Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 of equal surface area was still not reached. For nanosized CoO (surface layers on vacuum-reduced Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉), operando NAP-XPS/XAS, acquired during CO oxidation, revealed oxidation of CoO to Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 above 150 °C, yielding the activity of nanosized Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉. Evidently, the nanoscale CoO shell on a Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 core with small grains more easily and more completely transformed to Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 than mesoscopic (bulk) CoO with large grains.〈/p〉 〈p〉Our study demonstrates how flexible and dynamic surfaces of cobalt oxide materials adjust to various reaction environments, which also depends on grain size and morphology (bulk vs. thin layers), illustrating the importance of operando techniques to determine active catalyst phases under reaction conditions.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092058611831527X-ga1.jpg" width="305" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 26 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Yanjie Wang, Hongjia Wang, Abebe Reda Woldu, Xuehua Zhang, Tao He〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Photoelectrochemical reduction of CO〈sub〉2〈/sub〉 is an efficient way to overcome the limited supply of fossil fuels and mitigate the greenhouse effect, as well as produce carbonaceous fuels from the sunlight. CuBi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 is a 〈em〉p〈/em〉-type semiconductor with conduction band potential negative enough for CO〈sub〉2〈/sub〉 reduction. Nanoporous CuBi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 photocathodes are prepared by electrodeposition with subsequent annealing and are comprised of well-crystallized nanoparticles, which exhibit good visible-light response. The film thickness can be adjusted readily by changing the deposition time. The charge behavior in the CuBi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 photocathodes and its relationship with the film thickness are thoroughly investigated by using photocurrent and intensity modulated photocurrent spectroscopy. It is found that CuBi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉-4 min possesses the optimized charge generation and transfer performance, and shows the highest activity with CO as the only product of photoelectrochemical reduction of CO〈sub〉2〈/sub〉 under 0 V vs Ag/AgCl. The results indicate that CuBi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 can be a promising photocathode for CO〈sub〉2〈/sub〉 photoelectrochemical reduction under low bias.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118309398-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 2 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): G. Latini, M. Signorile, V. Crocellà, S. Bocchini, C.F. Pirri, S. Bordiga〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tackling global warming through the reduction of greenhouse gases is a key challenge mankind is called to face in the close future. Carbon dioxide is one of the main causes of such temperature increase, thus avoiding its release in the atmosphere through capture and/or utilization strategies is a valuable tool to limit greenhouse effect. Presently, the applied technology for sequestrating CO〈sub〉2〈/sub〉 relies on its reaction with amines in aqueous solutions, giving rise to the formation of carbamates and carbonates. However, due to the energy intensive release step, toxicity and corrosiveness, amine scrubbing could not represent a long-term solution in CO〈sub〉2〈/sub〉 capture. Ionic liquids (ILs), organic salts in the liquid state near room temperature, are a class of emerging materials with a great potential towards CO〈sub〉2〈/sub〉 capture. Recently the combination of the choline cation with amino acids based anions gave rise to a wide set of bio-inspired ILs with low toxicity, that, due to the presence of amino groups in the amino acid moiety, are optimal candidates for CO〈sub〉2〈/sub〉 capture. In the present work, two choline-amino acids ILs were synthesized, containing glycine and proline, according to an innovative procedure, overcoming some drawbacks proper of the classical methods. A throughout IR operando study of the CO〈sub〉2〈/sub〉 absorption process in these amino acids based ILs was performed. Even though elementary reactions are the same for all the investigated systems, different absorption pathways were recognized depending on the amino acid based anion. The reversibility of the absorption process differs between the two systems as well, further remarking the role played by the selected amino acid in the overall absorption performances. Such fundamental information, still missing in the literature, will contribute to rationally develop choline-amino acids ILs with optimal CO〈sub〉2〈/sub〉 absorption/activation properties.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118307612-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 325〈/p〉 〈p〉Author(s): Benjaram M. Reddy, Goutam Deo〈/p〉

Beschreibung: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today, Volume 324〈/p〉 〈p〉Author(s): Jong-San Chang, Benjaram M. Reddy, Rosa Maria Martin-Aranda, Ajayan Vinu, Jiří Čejka〈/p〉

Beschreibung: 〈p〉Publication date: Available online 26 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Davide Ottaviani, Vanmira Van-Dúnem, Ana P. Carvalho, Angela Martins, Luísa M.D.R.S. Martins〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The hydrotris(3,5-dimethylpyrazol-1-yl)borate dioxido-vanadium(V) complex [VO〈sub〉2〈/sub〉{HB(3,5-Me〈sub〉2〈/sub〉pz)〈sub〉3〈/sub〉}] (〈strong〉V〈/strong〉, pz = pyrazol-1-yl) immobilized at hierarchical MOR zeolite modified through surfactant mediated technology using NaOH as alkaline agent, 〈strong〉V〈/strong〉@MOR_NaOH, provides an efficient (TON up to 5.2 × 10〈sup〉2〈/sup〉) catalyst for the peroxidative oxidation of cyclohexane with 〈em〉tert〈/em〉-butyl hydroperoxide to KA oil (52% yield), at room temperature, and is easily recovered and reused up to four consecutive catalytic cycles with no significant leaching of vanadium. The textural modifications performed on the zeolitic matrix produced an effective support for the anchorage of the vanadium complex allowing an improved catalytic performance and reusability. This work constitutes an unprecedented use of supported vanadium B-scorpionate complexes as catalysts for the oxidation of alkanes.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305310-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 11 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): R. Cuevas-García, J.G. Téllez-Romero, J. Ramírez, P. Sarabia-Bañuelos, I. Puente-Lee, C. Salcedo-Luna, S. Hernández-González, V.A. Nolasco-Arizmendi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Three Ni catalyst supported on mordenite zeolite with the same content of nickel, ∼2 wt.%, were prepared by incipient wetness impregnation (IWI), ionic exchange (IE), and deposition-precipitation (DP) methods. The catalysts were characterized by, X-ray diffraction (XRD), textural properties, temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and scanning electron microscopy / energy-dispersive spectroscopy (SEM/EDS). For all the catalysts conversion and selectivity were studied in naphthalene hydrogenation without or with thiophene in the feedstock. Despite the low nickel content, the three preparations showed a high initial total naphthalene conversion up to 94%. The Ni-IWI catalyst exhibited high selectivity to tetralin and deactivated very fast. Ni-IE catalyst had good activity; however, it shows deactivation and the main products are related to acid reactions. The Ni-DP shows high hydrogenation activity and was the most active catalyst, it generated decalins, especially cis-decalin and at a long reaction time on stream, the catalyst remains active. TEM and TPR results suggest that this behavior is related to the crystal sizes related with the preparation method. In presence of thiophene, all the catalysts deactivate; but the Ni-DP deactivation was slower.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119304778-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Katarzyna Stawicka〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mesoporous silica MCF and metalosilicates Nb/MCF-14 and Ce/MCF-14 were modified with anchoring of melamine followed by (3-chloropropyl)trimethoxysilane functionalization. The texture/structure parameters, chemical composition and surface properties of synthesized samples were investigated by XRD, N〈sub〉2〈/sub〉 adsorption/desorption, XPS, UV–vis, TG, elemental analysis and 2-propanol dehydration and dehydrogenation, whereas the activity of obtained catalysts was tested in the Knoevenagel condensation between benzaldehyde and malononitrile. The Knoevenagel reaction required the presence of basic active sites or a pair of acid-base active centers. The novelty of the presented work was the use of mesoporous cellular foam (MCF) also modified with niobium (Nb/MCF-14) or cerium species (Ce/MCF-14) as supports for melamine anchoring. The use of the mentioned supports allowed the investigation of the role of open structure of MCF and metal dopant on melamine loading, its stability and reactivity in the Knoevenagel condensation. The obtained results clearly demonstrate that cerium and niobium species loaded into MCF increase significantly the efficiency of melamine loading as well as its stability. The anchoring of melamine to silica and metalosilicates increase the activity of this modifier as a result of formation of secondary amine species. The presence of defected ceria in Mel/Ce/MCF-14 raises the basicity of anchored melamine due to the electron donating effect of ceria. Consequently, the amine species in melamine are more active in the Knoevenagel condensation than those in Mel/Nb/MCF-14 because niobium species do not change oxidation state as easily as defected ceria.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118314214-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 10 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Chunghyeon Ban, Seungdo Yang, Hyungjoo Kim, Do Heui Kim〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ruthenium supported on nitrogen-doped mesorporous carbons (NMC) catalyzed hydrolytic hydrogenation of alginic acid to produce C6 sugar alcohols, mainly sorbitol and mannitol. Nitrogen contents were controlled by changing the weight ratio of urea/glucose and carbonization temperature. The highest yield of target C6 sugar alcohols was 50.3% (sorbitol: 24.3% and mannitol: 26.0%) at 180 °C for 1 h over Ru(5)/NMC(0.1)(600), where 0.1 and 600 were the urea/glucose ratio and carbonization temperature (°C), respectively. The intimate interaction between Ru and the support induced by nitrogen doping resulted in suppression of byproduct formation such as C4-C5 sugar alcohols and galactitol. Moreover, the interaction as evidenced by various analytical techniques resulted in the excellent durability of the catalyst after repeated reactions without severe leaching or aggregation of Ru.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Ruthenium on N-doped mesoporous carbon successfully hydrogenated alginic acid into sorbitol and mannitol, suppressing byproduct formation with excellent hydrothermal stability.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305061-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): G. Beltrami, T. Chenet, L. Pasti, L. Gigli, S. Pollastri, A. Martucci〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gallium substituted L, mordenite and ferrierite zeolites, obtained through wet impregnation, were characterized combining adsorption isotherms, X-ray powder diffraction (XRPD) and X-ray adsorption spectroscopy (XAS) to elucidate nature and structure of the Ga〈sup〉3+〈/sup〉 sites of the materials. The saturation capacity of L was higher than those of mordenite and ferrierite. Rietveld refinements on saturated materials confirm the presence of Ga〈sup〉3+〈/sup〉 within the zeolites pores system. Besides, the analysis of the structural features (〈em〉i.e.〈/em〉, lightening of tetrahedral bond distances and narrowing of interthetraedral angles) suggest that small fractions of metal cation have been also incorporated in tetrahedral sites. This is corroborated by XAS analysis, which confirms the effective inclusion of gallium into the zeolites frameworks, thus indicating that the incorporation of Ga〈sup〉3+〈/sup〉 from wet impregnation within the zeolite structures occurs in both framework and non-framework positions.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305085-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): H. Vargas-Villagrán, D. Ramírez-Suárez, G. Ramírez-Muñoz, L.A. Calzada, G. González-García, T.E. Klimova〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The hydrogenation of naphthalene was performed with nickel catalysts (4 wt. % of Ni) supported on SBA-15 and Al-SBA-15 in order to evaluate the effect of the support’s acidity on the activity and selectivity of the catalysts. The incorporation of aluminum into the SBA-15 support was performed during the hydrothermal synthesis of the material with the aim to reach the isomorphic substitution of Si〈sup〉4+〈/sup〉 by Al〈sup〉3+〈/sup〉 leading to the generation of Brönsted acid sites. Two different precursors (nickel nitrate and a Ni:EDTA complex) were used for the preparation of the catalysts on each support. Catalysts were characterized by nitrogen physisorption, powder X-ray diffraction, temperature programmed reduction, temperature programmed desorption of ammonia, scanning and high-resolution transmission electron microscopy. The Al-SBA-15 support was characterized by solid state 〈sup〉27〈/sup〉Al MAS-NMR. The results showed that the intrinsic activity of the catalysts (TOF) increased when the Al-SBA-15 support and the Ni:EDTA complex were used in the catalyst’s preparation. The catalysts prepared using the Ni:EDTA complex showed high selectivity to decalins and higher proportion of 〈em〉trans〈/em〉-decalin in the products than the catalysts prepared with nickel nitrate, which was attributed to a higher dispersion of the metallic Ni species and the larger total amount of acid sites.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305103-ga1.jpg" width="362" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 12 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): R. de la Serna Valdés, J. Agúndez, C. Márquez-Álvarez, J. Pérez-Pariente〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanosized gold entities immobilized on short-channel SBA-15 mesoporous materials functionalized solely with mercaptopropyl groups and together with propyl and octyl moieties have been prepared following a two-steps procedure. These materials have been used as catalysts for the oxidation of cyclohexene with molecular oxygen in liquid phase at atmospheric pressure. First, SBA-15 materials functionalized only with mercaptopropyl groups and with a combination of these groups with two hydrophobic moieties, namely propyl and octyl, have been synthesized in the presence of the non-ionic surfactant P104. Small particles having short channel length have been identified by TEM and SEM. In order to study the influence of the nature of the sulphur functional group, these S-bearing materials were also oxidized with hydrogen peroxide or dimethyldioxirane (DMD) to sulfonic groups prior to gold immobilization. The effectiveness of these oxidation methods was assessed by 〈sup〉29〈/sup〉Si MAS NMR, 〈sup〉13〈/sup〉C CP MAS NMR, XPS, chemical and thermal analysis, and it has been found that DMD oxidized efficiently thiol groups to sulfonic groups, but H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 leaves a fraction of unreacted thiol. In a second step, nanosized gold entities have been prepared by a two-liquid phases route involving rosemary oil as organic phase and an aqueous phase formed by dissolving gold in a solution of ammonium chloride in concentrated nitric acid (〈em〉aqua regia〈/em〉). Following this method, a fraction of the Au dissolved in the 〈em〉aqua regia〈/em〉 solution is spontaneously reduced and transferred to the essential oil phase. Upon contacting the gold-bearing organic layer with the mesoporous materials, gold is actually immobilized on them, rendering metal contents in the range 1.1-0.2 wt.%, being those functionalized with alkyl chains the least efficient in capturing gold from the organic phase. No surface plasmon resonance band at 520 nm characteristic of gold nanoparticles has been detected by UV–vis spectroscopy in these Au-containing materials. All of them are active and selective for the allylic oxidation of cyclohexene, but their specific activity varies as a function of the nature of the functional groups. It has been found that the most active catalysts are those pre-oxidized with DMD. The presence of hydrophobic octyl groups increases substantially the turnover number of the reaction (TON), while the short-chain propyl moieties hardly affect the activity. It has been found that the nanosized gold entities initially present in the catalysts evolve in the reaction medium towards the formation of nanoparticles.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586118317188-ga1.jpg" width="286" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 25 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Thien An Le, Jieun Kim, Jong Kyu Kang, Eun Duck Park〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Core–shell Al@Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, which was obtained by hydrothermal surface oxidation of Al metal particles, was used as the support in supported Ni catalysts for CO and CO〈sub〉2〈/sub〉 methanation. The core–shell micro-structured support (Al@Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) helped develop a highly efficient Ni-based catalyst compared with conventional γ-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 for these reactions. Moreover, the deposition–precipitation method was shown to outperform the wet impregnation method in the preparation of the active supported Ni catalysts. The catalysts were characterized using various techniques, namely, N〈sub〉2〈/sub〉 physisorption, H〈sub〉2〈/sub〉 chemisorption, CO〈sub〉2〈/sub〉 chemisorption, temperature-programmed reduction with H〈sub〉2〈/sub〉, temperature-programmed desorption after CO〈sub〉2〈/sub〉 adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, high-resolution transmission electron microscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Higher Ni dispersion when using Al@Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 as the support and the deposition–precipitation method resulted in better catalytic performance for CO methanation. Furthermore, the higher density of medium basic sites and enhanced CO〈sub〉2〈/sub〉 adsorption capacity observed for Ni/Al@Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 helped increase catalytic activity for CO〈sub〉2〈/sub〉 methanation.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305255-ga1.jpg" width="312" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): R. Turco, B. Bonelli, M. Armandi, L. Spiridigliozzi, G. Dell’Agli, F.A. Deorsola, S. Esposito, M. Di Serio〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ce〈sub〉0.75〈/sub〉Zr〈sub〉0.25〈/sub〉O〈sub〉2〈/sub〉 supports were prepared by precipitation in the presence of either ammonia or urea as precipitating agents. Mo(VI) oxide was dispersed onto the supports by either co-precipitation or wet impregnation, using ammonium eptamolybdate tetrahydrate as the Mo precursor. In all the cases, the nominal Mo content was 6.6 wt.%, selected to be under the value of the reported monolayer capacity of molybdenum oxide. The catalysts prepared by using ammonia as precipitating agent showed a superior catalytic activity in the cyclooctene epoxidation, with cumene hydroperoxide as oxidizing agent. The stability of the catalysts was confirmed by multiple runs and the absence of leaching was verified according to the Sheldon method. Physico-chemical characterization of the catalysts revealed that urea promotes the formation of hydrated cerium(III) oxycarbonate, which likely hampers a homogeneous distribution of active MoO〈sub〉x〈/sub〉 species that, conversely, are fairly stabilized on the support when ammonia is used as precipitating agent.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119306029-ga1.jpg" width="456" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 16 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Xiangjie Gong, Anni Li, Junbin Wu, Junying Wang, Congwei Wang, Junzhong Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Increasing green energy demands and environmental concerns have promoted extensive research on the development of next-generation energy technologies with high efficiency and environmental friendliness. One big challenge of electrochemical energy conversion and storage is to facilitate the core electrocatalytic oxygen reactions, including oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which commonly suffering from slow kinetics. In the past decade, great effort has been devoted to the development of next-generation oxygen electrocatalysts based on transition metals, among which cobalt-based compounds stand out as one of the most promising candidates for precious metals, as exhibiting highly efficiency, excellent stability, plus low-cost and earth-abundance. Here, recent progresses on the synthesis, structure and performance of various oxygen electrocatalysts of cobalt related, including metallic Co, Co-nonmetallic compounds, Co-metallic compounds and Co single-atom catalysts, are summarized, and the perspectives on the future developments are discussed.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305875-ga1.jpg" width="497" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 19 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Dhara H. Morawala, Dharmesh R. Lathiya, Ajay K. Dalai, Kalpana C. Maheria〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present work is focusing on the improvement of catalytic characteristics of zeolite. In the present endeavor, zeolite H-BEA has been modified using sol-gel route by making use of tetradecyltrimethyl ammonium bromide (TTAB) surfactant as a structure directing agent. The synthesized mesozeolite was characterized by SEM, HRTEM, 〈sup〉29〈/sup〉Si and 〈sup〉27〈/sup〉A1 MAS-NMR, small and wide-angle XRD, FT-IR, TGA, NH〈sub〉3〈/sub〉-TPD, ICP-OES and BET surface area analysis. The synthesized materials were found to exhibit mesoporosity along with microporosity of parent H-BEA. The utility of modified H-BEA as heterogeneous catalyst was demonstrated in the production of value added chemical, n-butyl levulinate from biomass derived feedstock, levulinic acid (LA) via esterification reaction. n-butyl levulinate is one of the significant industrial chemical and has wide use as plasticizing agent, solvent and odorous substance. Various process variables such as molar ratio (LA to n–butanol), catalyst concentration (%) and reaction time (h) were optimized by response surface methodology (RSM), using the Box–Behnken Design (BBD). Analysis of variance (ANOVA) has been performed to investigate the suitability and significance of the quadratic model.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305632-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 8 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): A. Erigoni, M.C. Hernández-Soto, F. Rey, C. Segarra, U. Díaz〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉New base hybrid catalysts, based on silyl-derivatives of molecules carrying amino, diamino, pyrrolidine, pyrazolium and imidazolium functionalities have been successfully achieved through post synthetic grafting onto M41S-type support. Different characterization techniques were implemented to study the characteristics of the materials, such as elemental analysis, solid state MAS NMR and FTIR spectroscopies, X-ray diffraction (XRD), thermogravimetric and differential thermal analyses (TGA-DTA) and textural properties through N〈sub〉2〈/sub〉 physisorption analysis. The catalytic activity and recyclability of these compounds as base catalysts was demonstrated for C〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉C bond forming reactions such as Knoevenagel condensations and Michael additions rationalizing the differences observed as function of the reaction mechanisms. An enamine mechanism was proposed for Knoevenagel condensations and an enolate mechanism for Michael additions.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119305383-ga1.jpg" width="476" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 3 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Anjali Pal, Nishith Verma〈/p〉

Beschreibung: 〈p〉Publication date: Available online 28 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Tomoko Yoshida, Yuhei Misu, Muneaki Yamamoto, Tetsuo Tanabe, Jun Kumagai, Satoshi Ogawa, Shinya Yagi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉We have succeeded to prepare Au nanopareticle deposited TiO〈sub〉2〈/sub〉 photocatalysts (Au/TiO〈sub〉2〈/sub〉) with control of Au nanoparticle size to be around 8 nm and variation of number density using a colloid photodepostion method. The prepared Au/TiO〈sub〉2〈/sub〉 exhibits activity on decomposition (oxidation) of formic acid by thermally activated and photo-activated catalytic reactions. The thermally activated catalytic decomposition gradually increases with increasing the number density of deposited Au NPs and saturated, suggesting that the decomposition occurs on Au NPs surface and/or near the interface of TiO〈sub〉2〈/sub〉 and Au NPs. On the other hand, the photocatalytic decomposition is significantly improved with rather small number density deposition of Au NPs and disappeared with high number density deposition.〈/p〉 〈p〉ESR measurements of Au/TiO〈sub〉2〈/sub〉 in the surrounding similar to the photocatalytic decomposition suggests that electrons excited by plasmon resonance absorption in the Au NPs transfer to TiO〈sub〉2〈/sub〉 to promote the decomposition. However, high number density deposition enhances electron capture by neighboring Au NPs and reduces the photocatalytic activity. Thus there should be the optimum number density of Au NPs on TiO〈sub〉2〈/sub〉 for photocatalytic decomposition of formic acid.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119306984-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈p〉Decomposition of formic acid under visible light irradiation was conducted to understand the effects of the number density of deposited same sized Au nanoparticles.〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Yanjie Wu, Huaqin Yang, Wei Li, Carlos Mattea, Siegfried Stapf, Letian Zhang, Chunlin Ye, Xiaofeng Ye〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Building the desirable superstructure of polyethylene is one of the important topics for developing high value-added products, which brings potential benefits for society and sustainable development. Crystalline order is the ubiquitous superstructure for enhancing mechanical properties of polymeric materials. In this work, polystyrene copolymers (〈em〉c〈/em〉-PS) are incorporated into pores of silica through the wet-impregnation procedure of styrene and 〈em〉p〈/em〉-chloromethyl styrene followed by the 〈em〉in-situ〈/em〉 free-radical copolymerization. Metallocene catalyst is further immobilized on supported silica. This incorporated 〈em〉c〈/em〉-PS is proved to be coated on the surface of silica pore walls rather than blocking the interparticle channels. The swelling behavior of 〈em〉c〈/em〉-PS inside the pores are performed by pulsed field gradient NMR (PFG-NMR) and thermoporosimetry (TPM-DSC), where a swelling behavior is shown in the toluene owing to the matched solubility parameters between the 〈em〉c〈/em〉-PS and toluene. According to the swelling behavior of 〈em〉c〈/em〉-PS confined in the pores, a compartmentalization is created hindering the formation of chain overlaps and increasing the crystallinity order of nascent polymers. As a result, the nascent polyethylene with a high crystallinity (〈em〉i.e.〈/em〉, bulk crystallinity 〈em〉X〈sub〉c,DSC〈/sub〉〈/em〉 = 72.9 % and linear crystallinity 〈em〉X〈sub〉c,WAXD〈/sub〉〈/em〉 = 90.5 %) is synthesized. There is a considerable activity (i.e., 3.8 × 10〈sup〉6〈/sup〉 g PE·(molZr·h)〈sup〉-1〈/sup〉) at 70 °C. Finally, the particle morphology of the nascent polyethylene is investigated based on the swelling behavior of 〈em〉c〈/em〉-PS.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119306959-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈p〉Ethylene polymerization is conducted based on the swollen behaviors of polystyrene in the confined pores, where the disentangled UHMWPE with highly crystalline order is successfully synthesized.〈/p〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Wonjin Jeon, Il-Ho Choi, Ji-Yeon Park, Jin-Suk Lee, Kyung-Ran Hwang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alkaline wet oxidation of lignin was performed to study the effect of Cu-Mn mixed oxide catalysts on the production of vanillin at between 120–180 °C using H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 as an oxidizing agent. The mixed oxide catalysts were prepared by a sol-gel method with mixing ratios of Cu to Mn between 0.25 and 0.75 and characterized by XRD, XPS, N〈sub〉2〈/sub〉-physisorption, SEM-EDS, and H〈sub〉2〈/sub〉-TPR. The XRD and N〈sub〉2〈/sub〉-physisorption analyses showed a non-stoichiometric spinel structure (Cu〈sub〉1.5〈/sub〉Mn〈sub〉1.5〈/sub〉O〈sub〉4〈/sub〉) and a relatively high BET surface area of the mixed oxides compared with pure Cu and Mn oxides, respectively. In addition, the Cu-Mn mixed oxide catalysts exhibited better redox properties and a higher catalytic performance for lignin oxidation to vanillin and other aromatic oxygenates. Higher Cu contents in the mixed oxide catalysts promoted the over-oxidation of vanillin producing vanillic acid along with the formation of more surface oxygen species on the catalyst surface. Finally, a possible reaction pathway for the catalytic conversion of lignin to vanillin was proposed.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092058611930700X-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Mi Yeon Byun, Dae-Won Park, Man Sig Lee〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High dispersion of Pt on carbon supports is expected to provide improved catalytic performance. In this study, Pt/C catalysts have been prepared by a deposition–precipitation method with different concentrations of sodium propionate (SP) as a stabilizer. Carbon black (CB), multiwall carbon nanotubes (MWCNTs), and carbon nanofibers (CNFs) have been used as catalyst supports. The dispersion and particle size of Pt have been shown to depend on the type of carbon support and the concentration of SP. The addition of SP can increase the ionic strength and thus improve the dispersion of Pt via the formation of Pt complexes, which prevents the aggregation of Pt nanoparticles. The activities of the prepared catalysts for D-glucose hydrogenation have been investigated. Both D-glucose conversion and D-sorbitol selectivity have been found to increase with increased Pt dispersion. The Pt/CB_SP0.5 catalyst with the highest Pt dispersion (59%) has been shown to exhibit the best catalytic performance. Further investigations revealed that the product distribution is strongly affected by the surface acidity and the reaction conditions. Thus, SP can be used as a stabilizer to obtain highly dispersed Pt/C catalysts with good D-glucose conversion and D-sorbitol selectivity.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119307023-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 28 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Kaiqi Xu, Athanasios Chatzitakis, Sanne Risbakk, Mingyi Yang, Paul Hoff Backe, Mathieu Grandcolas, Magnar Bjørås, Truls Norby〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, Co-based cocatalysts are electrodeposited on mesoporous Ta〈sub〉3〈/sub〉N〈sub〉5〈/sub〉 nanotubes. The electrodeposition time is varied and the optimized photoelectrode reaches a photocurrent density of 6.3 mA/cm〈sup〉2〈/sup〉 at 1.23 V vs. SHE, under simulated solar illumination of 1 Sun, in 1 M NaOH. The best performing electrode, apart from the high photocurrent density, shows improved stability under intense photoelectrochemical water splitting conditions. The dual function of the cocatalyst to improve not only the photoelectrochemical performance, but also the stability, is highlighted. Moreover, we adopted a simple protocol to assess the toxicity of Co and Ta contained nanostructured materials (representing used photoelectrodes) employing the human cell line HeLa S3 as target cells.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119306947-ga1.jpg" width="293" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 27 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Guoqiang Shu, Kui Ma, Siyang Tang, Changjun Liu, Hairong Yue, Liang Bin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A highly selective CuAl/SiO〈sub〉2〈/sub〉 catalyst was investigated for the hydrogenation of dimethyl oxalate (DMO) and ethylene carbonate (EC) to ethylene glycol (EG) and ethanol. Aluminum modified silica sol was used to prepare CuAl/SiO〈sub〉2〈/sub〉 catalysts by a hydrothermal method. The catalytic performance of the CuAl/SiO〈sub〉2〈/sub〉 catalysts with varying aluminum content was investigated at the conditions of 280 ℃ and 2.5 MPa for DMO hydrogenation, while 180 ℃ and 3 MPa for EC hydrogenation. The results showed that the Cu1.0Al/SiO〈sub〉2〈/sub〉 catalyst exhibited the highest selectivity of ethanol (∼94%) in the DMO hydrogenation, while the Cu0.5Al/SiO〈sub〉2〈/sub〉 catalyst exhibited the highest selectivity of EG (∼95%) and methanol (65%) in the EC hydrogenation. Characterizations (e.g., TPD, TPR and XANES) indicated that the moderate aluminum modification on SiO〈sub〉2〈/sub〉 in the form of ≡Si-OH-Al bond could not only tune the support acidity to polarize the C = O bond of esters, but also intrinsically facilitate the dispersion of Cu active species to activate H〈sub〉2〈/sub〉, which thus facilitated the selective hydrogenation reaction to EG, ethanol and methanol.〈/p〉〈/div〉 〈h5〉Graphic Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119306972-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 26 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Catalysis Today〈/p〉 〈p〉Author(s): Joachim Pasel, Dirk Schmitt, Heinrich Hartmann, Astrid Besmehn, Jürgen Dornseiffer, Jonas Werner, Joachim Mayer, Ralf Peters〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vehicles that run on natural gas must be equipped with an exhaust gas after-treatment system to burn their unavoidable CH〈sub〉4〈/sub〉 slip, which must not be released into the environment as CH〈sub〉4〈/sub〉 is a potent greenhouse gas. Pd is known as a highly active catalyst material for CH〈sub〉4〈/sub〉 oxidation. For this study, Pd was deposited on a γ-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 support and the as-received samples were pre-reduced and pre-oxidized, respectively. Near-Ambient Pressure Photoelectron Spectroscopy and the Temporal Analysis of Products methodology were combined to understand that both electronic states, namely PdO and Pd〈sup〉0〈/sup〉, are active for the CH〈sub〉4〈/sub〉 oxidation reaction, whereby the superior activity of the pre-reduced Pd/γ-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 catalyst was ascribed to the spill-over of OH-groups from the support to Pd. It was found that the reaction products, CO, CO〈sub〉2〈/sub〉 and H〈sub〉2〈/sub〉, were strongly and, to a large extent, adsorbed on the catalyst surface and were involved in reversible chemical interactions on the catalyst surface during the CH〈sub〉4〈/sub〉 oxidation reaction on the Pd/γ-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 catalyst.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920586119306753-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉