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  • 1
    Electronic Resource
    Electronic Resource
    Preparation and characterization of hydroxysilicoaluminum pillared clays (1992)
    s.l. : American Chemical Society
    Inorganic chemistry 31 (1992), S. 4727-4732 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00049a003
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  • 2
    Electronic Resource
    Electronic Resource
    carbon monoxide/CO Molecular Exchange and Its Relation with Desorption of CO/Metal (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 7175-7181 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100080a013
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  • 3
    Electronic Resource
    Electronic Resource
    Dehydrogenation and aromatization of methane in the absence of oxygen on Mo/HZSM-5 catalysts before and after NH4OH extraction (1996)
    Springer
    Catalysis letters 40 (1996), S. 207-214 
    Details
    ISSN: 1572-879X
    Keywords: Mo/HZSM-5 ; Mo species ; MoO3 crystallites ; Al2(MoO4)3 crystallites ; methane activation ; NH4OH extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mo/HZSM-5 catalysts show good catalytic reactivity in the absence of oxygen for the dehydrogenation and aromatization of methane at 973 K. The active Mo species were investigated by combining catalytic studies on Mo/HZSM-5 catalysts before and after NH4OH extraction with XRD, BET, NH3-TPD and TPR analysis. The XRD patterns show that Mo species are well dispersed on the zeolite surface. The specific surface areas decrease with increasing Mo loading but they can be restored to a large extent by NH4OH extraction. NH3-TPD results suggest that the Mo species prefer to deposit on the strong acid sites of HZSM-5 zeolite. TPR profiles show that there is a kind of Mo species which is easily reduced. No TPR peaks could be obviously observed if the Mo/ HZSM-5 catalysts were extracted by NH4OH solution. The results of NH4OH extraction experiment and other relevant characterization studies suggest that there are several kinds of Mo species deposited on the surface. By referring to the Mo species on Al2O3 supported MoO3 samples, we propose that the dissolvable Mo species in NH4OH solution are MoO3 crystallites and their aggregates in octahedral coordination, while the unsoluble Mo species mainly are Al2(MoO4)3 and MoO 4 2− in tetrahedrally coordinated form. The catalytic performance of Mo/HZSM-5 catalysts before and after NH4OH extraction illustrates that Mo species in small MoO3 crystallites with octahedral coordination form are active for methane activation in the absence of oxygen on Mo/HZSM-5 catalysts, while Mo species in tetrahedrally coordinated form is less active for the reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00815284
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  • 4
    Electronic Resource
    Electronic Resource
    Acid-base properties and the directions of oxidative transformation of methane over nickel-based catalysts (1996)
    Springer
    Catalysis letters 41 (1996), S. 165-169 
    Details
    ISSN: 1572-879X
    Keywords: acid-base properties ; oxidative transformation of methane ; nickel-based catalysts ; oxidative coupling of methane ; C2 hydrocarbon ; partial oxidation of methane ; syngas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two completely different behaviors of the oxidative transformation of methane (OTM) were performed on nickel-based catalysts because of different acid-base properties of those catalysts. The relatively acidic LaNiOx and LiNiLaOx/Al2O3 catalysts exhibit excellent performances in the partial oxidation of methane to syngas (POM). However, the relatively basic LiNiLaOx catalyst has a good performance in the oxidative coupling of methane to C2 hydrocarbons (OCM). The redox behaviors of those catalysts and the states of the nickel present were investigated by TPR techniques. TPR results indicated that the active component nickel of the working LaNiOx and LiNiLaOx/Al2O3 catalysts existed in the reduced state, and that of the working LiNiLaOx catalyst existed in the oxidized state under the same reaction conditions. It can be concluded that the acidic property favors keeping the reduced nickel and the reduced nickel is necessary for the POM reaction, whereas the basic property favors keeping the oxidized nickel and the oxidized nickel is necessary for the OCM reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811485
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  • 5
    Electronic Resource
    Electronic Resource
    Methane and ethane activation without adding oxygen: promotional effect of W in Mo-W/HZSM-5 (1996)
    Springer
    Catalysis letters 38 (1996), S. 39-43 
    Details
    ISSN: 1572-879X
    Keywords: acid-assisted heterolytic splitting of methane ; Mo/HZSM-5 ; W/HZSM-5 ; Mo-W/HZSM-5 ; promotional effect of tungsten
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The conversions of methane and ethane over Mo/HZSM-5 and W/HZSM-5 catalysts are compared. A reaction model for hydrocarbon formation over Mo/HZSM-5 catalysts is proposed, which involves heterolytic splitting of methane and a molybdenum-carbene intermediate. Ethene is shown to be the initial product of methane conversion, and it undergoes further reaction to form aromatics in a solid acid environment. The promotional effect of addition of tungsten in the Mo-W/HZSM-5 catalyst in methane conversion reaction suggests the formation of Mo-W mixed oxide. The product selectivity patterns of Mo/HZSM-5 and W/HZSM-5 catalysts in ethane conversion reaction are consistent with a dual-path model involving dehydrogenation and cracking (or hydrogenolysis) of ethane. The rates of both these reactions over Mo/HZSM-5 are higher than over W/HZSM-5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806897
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  • 6
    Electronic Resource
    Electronic Resource
    Oxidative coupling of methane by carbon dioxide: a highly C2 selective La2O3/ZnO catalyst (1996)
    Springer
    Catalysis letters 42 (1996), S. 149-153 
    Details
    ISSN: 1572-879X
    Keywords: carbon dioxide as the oxidant ; oxidative coupling of methane ; La2O3/ZnO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In the oxidative coupling of methane by carbon dioxide, La2O3/ZnO catalysts were found to have high C2 selectivity and good stability. The coupling selectivity on La2O3/ZnO is about 90%, which is much higher than that on pure La2O3 or ZnO. The consumption ratio of carbon dioxide to methane is approximately one. X-ray diffraction analysis reveals that the structural forms of the oxides are unchanged during the reaction. The reaction mechanism for C2 formation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810680
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  • 7
    Electronic Resource
    Electronic Resource
    Interaction between ammonium heptamolybdate and NH4ZSM-5 zeolite: the location of Mo species and the acidity of Mo/HZSM-5 (1995)
    Springer
    Catalysis letters 35 (1995), S. 233-243 
    Details
    ISSN: 1572-879X
    Keywords: Mo/HZSM-5 ; NH4ZSM-5 ; zeolite ; BrØnsted acid sites ; methane activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mo/HZSM-5 catalysts show high reactivity and selectivity in the activation of methane without using oxidants. Mo/HZSM-5 catalysts with Mo loading ranging from 0 to 10% were prepared by impregnation with an aqueous solution of ammonium heptamolybdate (AHM). The samples were dried at 393 K, and then calcined at different temperatures for 4 h. The interaction between Mo species and NH4ZSM-5 zeolite was characterized by FT-IR spectroscopy, differential thermal analysis (DTA) and temperature programmed decomposition (TPDE) and NH3-TPD at different stages of catalyst preparation. The results showed that if Mo/HZSM-5 catalysts were calcined at a proper temperature, the Mo species will interact with acid sites (mainly with BrØnsted acid sites) and part of the Mo species will move into the channel. The Mo species in the form of small MoO3 crystallites residing on the external surface and/or in the channel, and interacting with BrØnsted acid sites may be responsible for the methane activation. Strong interaction between Mo species and the skeleton of HZSM-5 will occur if the catalyst is calcined at 973 K. This may lead to the formation of MoO 4 2− species, which is detrimental to methane activation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807179
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic study of gas-surface molecular exchange between CO/CO on metals (1992)
    Springer
    Catalysis letters 12 (1992), S. 7-15 
    Details
    ISSN: 1572-879X
    Keywords: Kinetics of CO exchange ; kinetics of CO desorption ; CO desorption from metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Isotopic switching technique has been used to study the exchange of gaseous CO* with chemisorbed CO molecules on metal surface. The kinetic curves observed on Re(0001) exhibit a nonlinear dependence of desorption rate on the surface coverage of CO. However, the desorption rate for CO on Rh(111) in the same temperature range is strictly linear with the coverage of CO. A concerted adsorption-desorption mechanism is postulated which emphasizes that the desorption of CO in enhanced by the pressure of gas phase CO* on the one hand, and may be retarded by the screening effect of the CO* molecule chemisorbed on the surface on the other hand. It is pointed out that the adsorption of CO* (or CO) and the desorption of CO (or CO*) on a surface at high coverage, i.e. the molecular exchange processes, are primarily taking place simultaneously and concertedly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00767184
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation and characterization of three pure magnesium vanadate phases as catalysts for selective oxidation of propane to propene (1994)
    Springer
    Catalysis letters 23 (1994), S. 321-337 
    Details
    ISSN: 1572-879X
    Keywords: Citrate method ; magnesium vanadates ; redox property ; selective oxidation of propane to propene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three magnesium vanadate phases, i.e., MgV2O6 (metavanadate), α-Mg2V2O7 (pyrovana-date) and Mgs V2O8 (orthovanadate), have been successfully prepared with high purity by the citrate method at a relatively low temperature (550°C). FT-IR, LRS, XRD and SEM techniques have been used to characterize these vanadate phases. The effect of calcination temperature has also been investigated. It was found that the particle size and morphology of the MgV2O6 phase, which is a function of calcination temperature, appear to have a strong effect on the infrared spectra. Furthermore, the catalytic properties of the three phases were examined in the oxidative dehydrogenation of propane. The propene selectivity follows the order: α-Mg2V2O7 〉 Mg3 Vg2O8 〉 MgV2O6, which is consistent with their redox properties. This fact suggests that there is some correlation between the catalytic and redox properties of these magnesium vanadate phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811367
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  • 10
    Electronic Resource
    Electronic Resource
    Methane activation without using oxidants over Mo/HZSM-5 zeolite catalysts (1994)
    Springer
    Catalysis letters 30 (1994), S. 135-149 
    Details
    ISSN: 1572-879X
    Keywords: methane activation ; without using oxidants ; heterolytic splitting of methane ; molybdenum carbene-like complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of Mo loading, calcination temperature, reaction temperature and space velocity on the catalytic performance of methane dehydrogenation and aromatization without using oxidants over Mo/HZSM-5 has been studied. The XRD and BET measurements show that Mo species are highly dispersed in the channels of the HZSM-5 zeolite, resulting from the interaction between the Mo species and the zeolite, which also leads to a decrease in its crystallinity. The Brønsted acidity, the channel structure and the state and location of Mo species in the zeolite seem to be crucial factors for its catalytic performance. It was found that 2% Mo/HZSM-5 calcined at 773 K showed the best aromatization activity among the tested catalysts, the methane conversion being 9% at 1013 K with the selectivity to aromatics higher than 90%. The experimental results obtained from the variation of space velocity gave evidence that ethylene is an initial product. On the basis of these results a possible mechanism for methane dehydrogenation and aromatization has been proposed in which both the heterolytic splitting of methane in a solid acid environment and a molybdenum carbene-like complex as an intermediate are of significance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813680
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