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Study of Theoretical Calculation of Ethylene Dimerization Reaction on Ga(Al)/HZSM-5 Zeolite

Author: LiJingHong
Tutor: ZhouDanHong
School: Liaoning Normal University
Course: Physical and chemical
Keywords: Ethene ZSM-5 zeolite Br (?) Nsted acid sites Confinement effect Density functional theory
CLC: O621.25
Type: Master's thesis
Year: 2011
Downloads: 16
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Abstract


In this paper, theoretical calculations of the the zeolite Ga/HZSM-5 and Al/HZSM-5 ethylene dimerization reaction complete acid-catalyzed course , the dimerization process in accordance with the step-by-step mechanism and collaborative mechanism are surface -butyl alkoxy The intermediate product generated after deprotonation of 1 - butene and adsorbed on the molecular sieve acidic sites . 11T cluster model and 76T cluster model is divided into two layers were used , and the application of quantum mechanics and molecular mechanics union ONIOM2 (B3LYP/6-31G (d, p): UFF) method compares Ga the molecular sieve acidic Al substitution confinement effect of the change of the reaction process and energy and skeleton , the details are as follows : 1 , application ONIOM2 method to study the adsorption of NH3 and C2H4 molecules zeolite Ga/HZSM-5 and Al/HZSM-5 , compare Ga molecular sieve of the acidic and Al substitution , the results showed that the adsorption of NH3 and C2H4 in Ga/HZSM-5 zeolites , Description Ga/HZSM-5 zeolite acidic than on Al/HZSM-5 zeolite low weaker . 2, the method of application ONIOM2 ethylene dimerization reaction Ga/HZSM-5 , and Al/HZSM-5 Zeolite complete catalytic course , compare the dimerization reaction stepwise mechanism , a synergistic mechanism, and dehydrogenation reaction mechanism , the results showed that the step-by-step the intrinsic activation energy of dimerization Ga/HZSM-5 zeolite is 62.55 kJ than Al/HZSM-5 ? mol ? 1, the dimerization reaction synergistic activation energy 21.97 kJ than aluminum center ? mol ? weakly acidic not conducive ethylene dimerization reaction proceeds . For the two types of molecular sieves, the activation energy of the intermediate surface butyl alkoxy deprotonation is almost the same , and was significantly higher than the other steps , indicating that the process is a speed control step of the entire reaction , and means that the intermediate product of the surface - butyl alkoxy relatively stable intermediates. 3 DFT and ONIOM2 methods , 11T and 76T zeolite cluster model on ethylene dimer acid-catalyzed course , discuss the molecular sieve confinement effect on the reaction from the energy point of view . The results show that the skeleton presence of the stabilizing effect of the different degrees of adsorption complexes , transition states and products , which contribute more to the van der Waals interaction , the favorable order : adsorption complexes gt ; product gt ; transition state .

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Properties of organic compounds > Chemical properties of organic reactions
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