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Nanocrystalline Zeolite Tetraethylammonium-Beta Membrane for Preferential Sorption and Transport of CO2 over N2 (2013)

P. S. Singh, T. Selvam, S. Reuß, A. Avhale, S. Lopez-Orozco, W. Schwieger

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2013-06-07

Beschreibung: CO 2 /N 2 gas separation was performed over a nanocrystalline zeolite tetraethylammonium (TEA)-beta membrane prepared on a stainless-steel porous disc by repeated hydrothermal crystallization. Two to three consecutive hydrothermal syntheses were required to form a membrane comprised of a continuous and compact layer of zeolite beta nanocrystals on the support. The membrane TEA-BEA3 obtained by three consecutive syntheses, in which the membrane from two consecutive syntheses was used as support, exhibited the highest structural order. When the separation experiment was performed over this membrane without applying any external applied pressure, 100 % selectivity of CO 2 over N 2 was observed. The separation was driven by differences in chemical potentials of the molecules generated only by the adsorption-desorption behavior of the gases into the membrane. The novel zeolite TEA-beta membrane provided promising results for the separation of small gas molecules due to the combined influence of diffusion and sorption selectivity. Nanocrystalline zeolite tetraethylammonium (TEA)-beta membranes were prepared by repeated coating of zeolite nanocrystals via hydrothermal crystallization from a colloidal solution over a porous stain-less-steel disc support. When the separation experiment was performed without applying any external pressure, a CO 2 selectivity over N 2 of 100 % could be achieved.

Print ISSN: 0930-7516

Digitale ISSN: 1521-4125

Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

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Effects of Aromatics on the Stability and Product Distribution of the Methanol to Olefin Process (2011)

S.-H. Zhang; Z.-X. Gao; S.-Y. Liu; Y.-Z. Han; Y.-S. Zhao

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2011-09-28

Beschreibung: Methanol to olefin process was investigated over a steam-treated Ca-ZSM-5 catalyst in a flow-type fixed bed reactor by adding aromatics to the methanol feed. As a comparison, the catalytic performance in the presence of nitrogen and water was also investigated. The experimental results exhibit that in the presence of aromatics, the total light olefin selectivity and the ethylene selectivity increased, while propylene selectivity increased with adding o- xylene and m -xylene to the methanol feed, but decreased with adding benzene, toluene, p -xylene and ethylbenzen to the methanol feed. The catalyst was characterized by temperature-programmed desorption of ammonia, N 2 adsorption, and scanning electron microscope. The adsorption of water and aromatics on the catalyst was also studied. Based on the results, it is concluded that aromatics may be responsible for the formation of light olefins and be more favorable for ethylene than propylene in methanol conversion. The methanol to olefin process was investigated over a steam-treated Ca-ZSM-5 catalyst in a flow-type fixed bed reactor by adding aromatics to the methanol feed. High light-olefin selectivity was gained. Further experimental data suggested that aromatics enhanced the formation of light olefins in methanol conversion.

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Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

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Moisture Distribution in Fluidized Beds with Liquid Injection (2011)

L. Fries; M. Dosta; S. Antonyuk; S. Heinrich; S. Palzer

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2011-06-08

Beschreibung: Coupled discrete element method-computational fluid dynamics (DEM-CFD) simulations have been performed to study the fluid and particle dynamics in a fluidized-bed granulator on the scale of individual particles. Simulation of the gas and particle dynamics is combined with heat and mass transfer mechanisms, as the moisture distribution is a key parameter for the functionality of a fluidized-bed spray granulator. The model allows monitoring the moisture content and temperature of each individual particle as well as the temperature and humidity of the surrounding gas phase. A novel modeling approach is presented to describe the process dynamics of a fluidized bed in full detail for a reference time interval using coupled DEM-CFD simulations. The motion profile of gas and particles is extrapolated to larger time scales and used for the calculation of heat and mass transfer. Through this multiscale approach, a step forward is taken towards a physically based description of the microprocesses in granulation. Coupled discrete element method-computational fluid dynamics (DEM-CFD) simulations of the fluid and particle dynamics in a fluidized-bed granulator have been performed and combined with a model of heat and mass transfer. According to a novel multiscale modeling approach the process dynamics of a fluidized bed can be described in full detail for a reference time interval using DEM-CFD.

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Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

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Indirect Synthesis of Bis(2-PhInd)ZrCl2 Metallocene Catalyst, Kinetic Study and Modeling of Ethylene Polymerization (2011)

S. Ahmadjo; H. Arabi; M. Nekoomanesh; S. M. M. Mortazavi; G. Zohuri; M. Ahmadi; S. Bolandi

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2011-01-25

Beschreibung: Bis(2-phenylindenyl)zirconium dichloride (bis(2-PhInd)ZrCl 2 ) catalyst was synthesized via the preparation of bis(2-phenylindenyl)zirconium dimethyl (bis(2-PhInd)ZrMe 2 ) followed by chlorination to obtain the catalyst. Performance of the catalyst for ethylene polymerization and its kinetic behavior were investigated. Activity of the catalyst increased as the [Al]:[Zr] molar ratio increased to 2333:1, followed by reduction at higher ratios. The maximum activity of the catalyst was obtained at a polymerization temperature of 60 °C. The rate-time profile of the reaction was of a decay type under all conditions. A general kinetic scheme was modified by considering a reversible reaction of latent site formation, and used to predict dynamic polymerization rate and viscosity average molecular weight of the resulting polymer. Kinetic constants were estimated by the Nelder-Mead numerical optimization algorithm. It was shown that any deviation from the general kinetic behavior can be captured by the addition of the reversible reaction of latent site formation. Simulation results were in satisfactory agreement with experimental data. Bis(2-PhInd)ZrCl2 catalyst was synthesized using an indirect method which has the advantage of preparing the catalyst at room temperature. For better identification of the catalyst behavior, the kinetic constants were estimated and evaluated by quantitative modeling of the polymerization mechanism.

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Atrazine Removal in Municipal Secondary Effluents by Fenton and Photo-Fenton Treatments (2013)

A. De Luca, R. F. Dantas, A. S. M. Simões, I. A. S. Toscano, G. Lofrano, A. Cruz, S. Esplugas

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2013-10-16

Beschreibung: Alternative water sources, including effluents from municipal wastewater treatment plants (MWTP) are necessary to meet increasing water demand. Advanced oxidation processes based on the Fenton reaction were applied to remove atrazine from the secondary effluents of a MWTP that uses activated sludge. Fenton, UV-A photo-Fenton, and UV-C photo-Fenton treatments were tested. Atrazine removal percentages were around 20 % for Fenton, 60 % for UV-A photo-Fenton and 70 % for UV-C photo-Fenton treatments, respectively. Organic matter mineralization by Fenton treatment was monitored and no significant reduction was observed. However, organic matter oxidation in terms of COD reduction of around 30 and 40 % were achieved by Fenton and photo-Fenton processes, respectively. The photo-Fenton process with UV-C is a useful technique for atrazine degradation, leading to higher degradation than with UV-A while also being more attractive in an economic point of view. Wastewater treatment plant effluents are increasingly used as non-potable water sources to meet increasing water demands, and therefore, efficient removal of pollutants is needed. Atrazine is used as a probe molecule for the comparison of Fenton, UV-A photo-Fenton, and UV-C photo-Fenton treatment. The study includes economical evaluations of all options.

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Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

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Effect of process parameters on properties of colloids in continuous flow microreactor system (2015)

M. L. Bari, P. L. Suryawanshi, B. A. Bhanvase, S. H. Sonawane, J. S. Narkhede, S. Mishra

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2015-09-04

Beschreibung: The effect of reactant concentration, flow rate and surfactant type on the size and distribution of the synthesized nanoparticles was studied. Two tubular microreactors, made up of PVC and SS, were used for production of iron oxide nanoparticles from FeCl 3 and NaBH 4 as precursors by a chemical reduction route. It was observed that the diameter of microreacrtor and process parameter influence the size and size distribution of iron oxide nano particles. The axial dispersion in PVC microreactor was less than in SS microreactor due the large ratio of volume of microreactor to flow rate. The formation of iron oxide was confirmed by FTIR, XRD and EDAX. It was confirmed that the stable colloidal iron oxide nanoparticles with narrow size distribution were synthesized in contentious microreactor system.

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Influence of the Sparger Type and Added Alcohol on the Gas Holdup of an External-Loop Airlift Reactor (2015)

Predrag S. Kojić, Milenko S. Tokić, Ivana M. Šijački, Nataša Lj. Lukić, Dragan Lj. Petrović, Dragica Z. Jovičević, Svetlana S. Popović

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2015-02-25

Beschreibung: The influences of alcohol adding and three different gas spargers (single orifice, perforated plate, and sinter plate) on the gas holdup in an external-loop airlift reactor were studied. The experimental results show that the gas holdup can be increased by mutual influence of both the alcohol adding and the sparger type. The presence of small amounts of normal aliphatic alcohols caused an increase of the gas holdup compared to the air-water system, due to their coalescence-inhibiting nature. The sinter plate was the most efficient sparger, followed by the perforated plate and the single orifice. A proposed artificial neural network (ANN) has the potential to predict gas holdup values in airlift reactors for various alcohols and types of gas spargers. The effects of alcohol and three different gas spargers on the gas holdup in external-loop airlift reactors were studied. The sinter plate turned out to be the most efficient sparger. Small amounts of common aliphatic alcohols increased the gas holdup due to their coalescence-inhibiting nature. The proposed artificial neural network has the potential to predict the gas holdup in airlift reactors.

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Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

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