Aromatic-based hydrocarbon pool mechanism for methanol-to-olefins conversion in H-SAPO-18: A van der Waals density functional study

作者：Wang Chuan Ming^*; Wang Yang Dong; Liu Hong Xing; Yang Guang; Du Yu Jue; Xie Zai Ku

来源：Chinese Journal of Catalysis, 2015, 36(9): 1573-1579.

DOI：10.1016/S1872-2067(15)60891-9

• Methanol-to-olefins conversion
• Zeolite catalysis
• Density functional theory
• H-SAPO-18 zeotype
• Reaction mechanism
• Aromatic-based cycle

The reaction mechanism of zeolite-catalyzed methanol-to-olefins (MTO) conversion is still debated. Aromatics and/or olefins themselves may act as hydrocarbon pool species in the reaction. In this work we used periodic density functional theory calculations with the van der Waals density functional to study the aromatic-based hydrocarbon pool mechanism in H-SAPO-18 zeotype with eight-membered ring openings. The distribution of different polymethylbenzenes (MBs) in H-SAPO-18 was evaluated from adsorption and interconversion analysis. Hexamethylbenzene was calculated to be the primary component of MBs in H-SAPO-18. Gibbs free energy analysis on the process of ethyl side chain propagation indicated that hexamethylbenzene was not more reactive than pentamethylbenzene and tetramethylbenzene. The overall Gibbs free energy barriers were calculated to be more than 200 kJ/mol at MTO reaction temperature (673 K). These calculated results would provide some implications for understanding the reaction mechanism and the role of aromatics in MTO conversion.

• 出版日期2015-9
• 单位中国石油化工股份有限公司上海石油化工研究院