Título:	Aspectos energéticos e eletrônicos da zeólita H-ZSM-5 na ação catalítica da reação de desidratação de álcoois
Autor(es):	Sousa, Gustavo Gomes de
Orientador(es):	Politi, José Roberto dos Santos
Assunto:	zeólita H-ZSM-5 ONIOM Desidratação Alcoois
Data de publicação:	29-Jun-2020
Data de defesa:	31-Jan-2020
Referência:	SOUSA, Gustavo Gomes de. Aspectos energéticos e eletrônicos da zeólita H-ZSM-5 na ação catalítica da reação de desidratação de álcoois. 2020. 44 f., il. Dissertação (Mestrado em Química)—Universidade de Brasília, Brasília, 2020.
Abstract:	Because the future depletion of oil supplies and environmental concerns, the need for the use of sustainable raw materials and chemical reactions that promote the reduction of dependence on society with this energy matrix appeared. The dehydration of alcohols by acid catalysis has been employed for the production of various hydrocarbons of great economic importance which were obtained from petroleum. Among the most effective acid catalysts employed in this reaction, the zeolite H-ZSM-5 stands out due to its high acidity, reaction selectivity, high thermal stability and catalytic properties. Thus, the study of alcohol dehydration reaction is of great importance for both the academic and productive means, especially in relation to its stages and the exact participation of the catalyst used. In this work we studied the catalytic behavior of the H-ZSM-5 zeolite in the dehydration reaction of various alcohols (ethanol, propanol, isopropanol, butanol and iso- butanol), by modeling of the adsorption process, protonation and dehydration of these alcohols within the cavity of the zeolite. The hybrid ONIOM methodology was used to optimize the reaction steps of the catalytic conversion of alcohols to hydrocarbons within the catalyst cavity. The study was divided into 3 stages. The first stage corresponded to the study of the adsorption and protonation of alcohols by zeolite. The intermediate step described the hydroxyl exit, while the final step was the formation of the double bond. The analysis of the results indicates that the first stage of the reaction occurs with the contact of the alcohol with the zeolite cavity, in which the acid hydrogen protons the alcohols. This protonation occurs differently, depending on the molecular structure of alcohol. Dehydration happens via an E2 type elimination mechanism. However, the energy curve profile indicates that for larger alcohols, the mechanism is basically of second order but presents first order elimination characteristic. Therefore, we observed that zeolite converts alcohols to hydrocarbons in a specific way. The lower chain primary alcohols follow one reaction mechanism, while secondary alcohols and longer chain react in a slightly different mechanism.
Unidade Acadêmica:	Instituto de Química (IQ)
Informações adicionais:	Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2020.
Programa de pós-graduação:	Programa de Pós-Graduação em Química
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