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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 65 (1996), S. 186-192 
    ISSN: 0268-2575
    Keywords: MTG process ; HZSM5 zeolite ; catalyst acidity ; activity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of Si/Al ratio of HZSM5 zeolite-based catalysts on surface acidity and on selectivity in the transformation of methanol into hydrocarbons has been studied. The acidic strength distribution (measured by combining the differential scanning calorimetry and the chromatographic analysis) and the total acidity (measured by calorimetry and temperature programmed desorption), using ammonia and tert-butylamine, have been studied as acidity measurements. The nature of the acidic sites has been determined by FTIR analysis of both the surface OH groups and the interaction of Brönsted and Lewis sites with pyridine. The increase in light olefin selectivity and the decrease in methanol conversion with increasing Si/Al ratio are a consequence of the kinetic scheme of the reaction, which has steps in series, and can be explained by the decrease in total acidity. The same acidic sites are responsible for the formation of light olefins and for the transformation of these olefins into higher hydrocarbons.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 66 (1996), S. 183-191 
    ISSN: 0268-2575
    Keywords: Brönsted/Lewis acidity ; H-ZSM5 zeolites ; MTG process ; primary products ; MTG mechanism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: From experiments in a chromatographic reactor, under conditions of incipient reaction, the effect of the Si/Al ratio of H-ZSM5 zeolites on the nature of the primary products has been proven in the transformation of methanol into gasoline. It has been determined that alkenes (ethene, propene and butenes) are the first reaction products, the proportion of heavier alkenes being greater as the Brönsted/Lewis ratio increases and as total acidity decreases (decrease in acidic site density). By in-situ FTIR analysis of the adsorbed phase, the presence of surface methoxy groups has been determined. By virtue of the results, a mechanism of propagation-decomposition of oxonium ions has been proposed. This mechanism basically occurs in a phase adsorbed on the zeolite and explains the formation of the first C—C bond and the presence in the gas phase of the first products according to a reaction-diffusion compromise for each one of the intermediate products of the mechanism.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The recovery of the acidic structure and activity during the regeneration step by coke combustion of an HZSM-5 zeolite-based catalyst used in the methanol-to-gasoline (MTG) process in reaction-regeneration cycles was studied. The reactivation kinetics (activity us. coke combustion time) was determined as a function of temperature and time on stream of the reaction step. The validity of the reactivation kinetic model was proven by using it for the simulation of the cyclic operation under conditions of catalyst partial reactivation, together with the kinetic model for the MTG process.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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