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The Reaction Mechanisms of Ethylene Aromatization in H-ZSM-5 Zeolite: from C4 to C6 Intermediates

Author: CaoLiang
Tutor: ZhouDanHong
School: Liaoning Normal University
Course: Physical and chemical
Keywords: Density functional theory Ethylene aromatization H-ZSM-5 zeolite Reaction Mechanism Confinement effect
CLC: O643.12
Type: Master's thesis
Year: 2010
Downloads: 63
Quote: 0
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Abstract


In this thesis through theoretical calculations to study the reaction mechanism of the H-ZSM-5 zeolite ethylene aromatization reaction C4 to benzene . Study the structure of the zeolite channels 78T cluster model , the method of application of the combination of quantum mechanics and molecular mechanics ONIOM2 (B3LYP/6-31G (d, p): UFF) . Mainly made ??the result of the following aspects : (1 ) the surface of n-butyl the alkoxy complex (C4) as the product of ethylene dimerization reaction , and to follow the course of a batch reaction , first deprotonated to produce 1 - butene , and then 1 - D ene zeolite acidic sites with the addition of ethylene , been incorporated into the zeolite surface - methylpentene base alkoxy complex intermediates . Removal of the alkoxy oxygen complexes proton to the molecular sieve cyclization to methyl cyclopentane , which then jointly with the molecular sieve acidic proton removal of hydrogen gas , generating unstable carbocation intermediate , and then re - constituted cyclohexane positive ions. 1 - butene and ethylene addition reaction activation energy is 130.71 kJ / mol; 3 - methyl amyl alkoxy complex dehydrogenation cyclization the methylcyclopentane of activation energy for generate 122.06 kJ / mol . (2) cyclohexane Carbocations as intermediates of (C6) , and then with the zeolite series of dehydrogenation proton , de - hydrogen in the reaction , and finally generate benzene . Zeolite acidic sites as catalytic centers , repeated a proton donor and acceptor , and adjacent basic skeleton oxygen synergistic . This process , the activation energy of the dehydrogenation of protons was 41.8 kJ / mol , 49.03 kJ / mol and 18.31 kJ / mol the the dehydrogenation activation energy of 205.95 kJ / mol and 264.97 kJ / mol respectively . (3 ) the use of different methods of calculation , analysis and comparison of the role of the van der Waals and electrostatic interactions between the reactant molecules and the backbone atoms of the confinement effect of the zeolite pores , and its role of shape selectivity of ethylene aromatization .

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Chemical kinetics > The mechanism and kinetics of chemical reactions
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