title: Theoretical insights into the mechanism of olefin elimination in the methanol-to-olefin process over HZSM-5, HMOR, HBEA, and HMCM-22 zeolites.
abstract: The mechanism of olefin elimination in the process of methanol-to-olefins (MTO) over a series of zeolites like HZSM-5, HMOR, HBEA, and HMCM-22 was investigated by DFT-D calculations, which is a crucial step that controls the MTO product distribution. The results demonstrate that the manners of olefin elimination are related to the pore structure of zeolite catalyst and the interaction between proton transfer reagent (water or methanol) and zeolite acidic framework. The indirect spiro mechanism is preferable to the direct mechanism over HMOR, HBEA, and HMCM-22 zeolites with large pores, as suggested by the energy barrier of rate-determining step and the potential energy surface (PES), but is unfavorable over HZSM-5 with medium-sized pores due to the steric hindrance of spiro intermediates. Over various zeolites, water and methanol perform differently in proton transfer to form the spiro intermediates; over HMOR and HBEA with strong acidity, water is superior to methanol in promoting propene elimination, whereas over HMCM-22 with relatively weaker acidity, methanol is more favorable as a proton transfer reagent.
authors.affiliation: State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences , P.O. Box 165, Taiyuan, Shanxi 030001, PR China.
authors.forename: Sen
authors.initials: S
authors.lastname: Wang
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Chen
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Wei
authors.forename: Zhangfeng
authors.initials: Z
authors.lastname: Qin
authors.forename: Jialing
authors.initials: J
authors.lastname: Chen
authors.forename: Hong
authors.initials: H
authors.lastname: Ma
authors.forename: Mei
authors.initials: M
authors.lastname: Dong
authors.forename: Junfen
authors.initials: J
authors.lastname: Li
authors.forename: Weibin
authors.initials: W
authors.lastname: Fan
authors.forename: Jianguo
authors.initials: J
authors.lastname: Wang