A route to form initial hydrocarbon pool species in methanol conversion to olefins over zeolites

• Published in: Journal of catalysis 2014-08, Vol.317, p.277-283
• Main Authors: Li, Junfen, Wei, Zhihong, Chen, Yanyan, Jing, Buqin, He, Yue, Dong, Mei, Jiao, Haijun, Li, Xuekuan, Qin, Zhangfeng, Wang, Jianguo, Fan, Weibin
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Chemical bonds; Chemistry; Direct reaction mechanism; Exact sciences and technology; General and physical chemistry; Hydrocarbons; Ion-exchange; Methanol; Methanol conversion to olefins; Methoxymethyl cation; Original C–C bond; SAPO-34; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites; Zeolites: preparations and properties
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2014.05.015

[Display omitted] •The existence of the direct mechanism in initial MTO process was evidenced.•A critical intermediate of CH3OCH2+ was detected and theoretically verified.•A convincing route for formation of original C–C bond in MTO process was proposed.•Propene was found to be the initial olefin product in the MTO process. The formation mechanism of the original C–C bond in methanol conversion to hydrocarbons over zeolite catalysts remains a grand challenge, although many researchers have done a lot of work and made significant progress. Here, a convincing route for formation of initial hydrocarbon pool (HCP) species involving original C–C bonds from dimethyl ether (DME) and/or methanol is illustrated by combining coincident experimental and theoretically calculated results. Elaborate experimental results gave strong evidence for predominant direct mechanism in the initial methanol-to-olefins process catalyzed by SAPO-34. A critical intermediate of the methoxymethyl cation was detected and theoretically verified through the reaction of the methoxy group and DME. This intermediate species subsequently reacted with DME or methanol to produce C–C bond-containing compounds 1,2-dimethoxyethane or 2-methoxyethanol. Further formation of oxonium cations led to generation of ethers or alcohols, and further to propene as the primary alkene product that induced the occurrence of the HCP mechanism.