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  • 1
    Electronic Resource
    Electronic Resource
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of chemical reactor engineering 5.2007, 1, A66 
    ISSN: 1542-6580
    Source: Berkeley Electronic Press Academic Journals
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The technological development of catalytic processes under rapid deactivation requires the rigorous calculation of the deactivation kinetic equation in order to be useful in the simulation and optimization of industrial processes. Accordingly, suitable equipment for reaction and product analysis and a rigorous methodology for kinetic data analysis are required. These aspects are approached in this paper using the transformation of methanol into olefins on a SAPO-18 as the model reaction. In this reaction, deactivation is rapid and there is also an initiation period depending on process conditions. The correct use of gas chromatography allows for improving the collection of experimental data of composition with time-on-stream, given that, on the one hand, it minimizes the time required for analysis (4 min), and on the other, a better homogenization of the reaction product sample is achieved, which allows for a more accurate determination of the composition corresponding to a given time-on-stream. Furthermore, the rigorous kinetic modelling of deactivation requires a data analysis methodology that considers the past history of the catalyst and an activity to be defined based on a rigorous physical meaning. Accordingly, the concept of the integrated kinetic model has been used in this paper, whose basis is the calculation of kinetic parameters by simultaneously solving the zero time-on-stream kinetic model and the kinetic equation for deactivation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of chemical reactor engineering 5.2007, 1, A60 
    ISSN: 1542-6580
    Source: Berkeley Electronic Press Academic Journals
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: A study has been carried out on the effect of acid catalyst properties and operating conditions (methanol/n-butane ratio in the feed, temperature, space time, time on stream) on the yield of light olefins (C2-C4) in the simultaneous cracking of n-butane and methanol. The operation has been carried out in an isothermal fixed bed reactor in the 400-575 °C range, using catalysts prepared based on HZSM-5 zeolites (with different Si/Al ratio), HY, Ni/HZSM-5 and SAPO-18. The results are evidence of a synergism between the transformation reactions of both reactants, whose consequence is an increase in the yield of olefins that correspond to the transformation of methanol and the cracking of n-butane. Furthermore, catalyst deactivation by coke is significantly attenuated compared to the corresponding transformation of methanol. Based on the effect of operating conditions on product distribution, a kinetic model is proposed by combining the schemes corresponding to the transformation of individual components.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 32 (1993), S. 2542-2547 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 32 (1993), S. 588-593 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 32 (1993), S. 458-465 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0268-2575
    Keywords: skeletal isomerization ; isobutene ; shape selectivity ; acidity ; chlorinated alumina ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect upon kinetic behaviour (activity and selectivity) of the physical properties (pore volume distribution) and acidic characteristics (nature of acidic sites and acidic strength distribution) of acidic catalysts in the skeletal isomerization of n-butenes has been studied. The catalysts studied are the following: γ-alumina, alumina modified by introduction of F, Cl and Br, silica-alumina, HZSM-5 zeolite-based catalyst and SAPO-34-based catalyst. It has been proven that the selectivity of acidic catalysts towards the skeletal isomerization of n-butenes is the result of a compromise between pore shape selectivity and intrinsic selectivity of the acidic sites of different strength, this latter property being more significant. Strong acidic sites are needed for the skeletal isomerization, but sites which are too strong produce important amounts of byproducts. A chlorinated alumina is a highly active and selective catalyst for skeletal isomerization. © 1998 SCI.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    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
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  • 8
    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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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 60 (1994), S. 141-146 
    ISSN: 0268-2575
    Keywords: catalysts acidity ; acidic strength distribution ; bases adsorption ; calorimetry ; thermogravimetry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The measurement of the adsorption equilibrium constants of the bases and the total mass of base adsorbed at 200°C are proposed as reproducible indices of average acidity strength and of total acidity of the solid, respectively. The adsorption of different bases (ammonia, n-butylamine, tert-butylamine, pyridine) in gas phase on solid acidic catalysts (silica-alumina and zeolite catalysts and a silica gel) has been studied, by applying the calorimetric method in flow regime through an isothermal bed of solid. Both the conditions under which the adsorption is exclusively chemical as well as those under which the adsorption is not limited by the internal diffusion of the base have been determined. For these acidity measurements tert-butylamine behaves well and is an alternative base to ammonia.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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