Influência das condições operacionais na conversão de eteno em propeno e aromáticos catalisada por HZSM-5

• Ano de defesa: 2016
• Autor(a) principal: Fernandes, Débora da Silva
• Orientador(a): Henriques, Cristiane Assumpção
• Banca de defesa: Araujo, Lucia Regina Raddi de , Sousa, Zilacleide da Silva Barros , Mello, Leonardo Fialho de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade do Estado do Rio de Janeiro
• Programa de Pós-Graduação: Programa de Pós-Graduação em Engenharia Química
• Departamento: Centro de Tecnologia e Ciências::Instituto de Química
• País: BR
• Palavras-chave em Português: Eteno; Zeólita ZSM-5; Propeno; Aromáticos
• Palavras-chave em Inglês: Ethylene; ZSM-5 zeolite; Propylene; Aromatics
• Área do conhecimento CNPq: CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA::TECNOLOGIA QUIMICA
• Link de acesso: http://www.bdtd.uerj.br/handle/1/12071

The search for renewable raw materials in order to reduce oil dependence and comply with environmental preservation issues has been encouraged. In this context, ethanol is a promising alternative for producing petrochemicals, especially propylene and aromatics such as benzene, toluene and xylenes, via ethanol catalytic conversion. The ethylene is the major primary product of this reaction and the intermediate for formation of other olefins and aromatics. For understanding the ethanol processing routes in hydrocarbons, a thorough study is essential to elucidate the formation of olefins and aromatics from ethylene. In this work, the influence of operating conditions in the catalytic conversion of ethylene into propylene and aromatics was investigated. A commercial HZSM-5 zeolite with SiO2/Al2O3 molar ratio equal to 30 was used as catalyst, and the reaction was conducted at atmospheric pressure for 4.5 h. The ethylene partial pressure (0.12, 0.20, 0.35 atm), reaction temperature (300, 400, 450, 500 °C) and contact time (0.15, 0.20, 0.40, 0.67 h) were varied to identify their effects on ethylene conversion and product yield. The proposed mechanism of olefin formation is based on carbene species formed from ethylene to produce propene and on ethylene dimerization to form butenes. For aromatic formation the dehydrocyclization reaction is favored over hydrogen transfer. The higher propylene formation was obtained at high reaction temperature, using low values of contact time and ethylene partial pressure (p = 0.12 atm,  = 0.15 h, and T = 500 °C). Furthermore, the optimum conditions for the formation of aromatics are p = 0.35 atm,  = 0.20 h, and T = 400 °C. At the optimal conditions to produce propylene and aromatics, the comparison of the performance of zeolites with different SiO2/Al2O3 molar ratio (30, 80, 280) revealed that HZSM-5 (280) zeolite was not catalytic active, while the others presented different conversion and yield due to the acidity of the materials. The long term reactions were performed for 20 h to verify catalyst stability, as well as product yields variation. The yield of aromatics decreased and in contrast the propylene yield increased as a result of zeolite deactivation. To investigate the influence of water in zeolite deactivation, ethylene conversion and product yield were compared when water was fed to the reactor with different concentrations (18 and 36 %). The presence of water intensified the deactivation process, but the increasing of water concentration did not promote significant changes