Elucidating the dominant reaction mechanism of methanol-to-olefins conversion in H-SAPO-18: A first-principles study

作     者：Chuan-Ming Wang Yang-Dong Wang Zai-Ku Xie 王传明;王仰东;谢在库

作者机构：State Key Laboratory of Green Chemical Engineering and Industrial Catalysis SINOPEC Shanghai Research Institute of Petrochemical TechnologyShanghai 201208China 

基　　金：supported by the National Key Research and Development Program of China (2016YFB0701100, 2017YFB0702800) the National Natural Science Foundation of China (21673295) 

出 版 物：《Chinese Journal of Catalysis》 (催化学报（英文）)

年 卷 期：2018年第39卷第7期

页      码：1272-1279页

摘      要：The reaction mechanism of zeolite- or zeotype-catalyzed methanol-to-olefins（MTO） conversion is still a subject of debate. Employing periodic density functional theory calculations, the olefin-based cycle was studied using tetramethylethene（TME） as a representative olefinic hydrocarbon pool in H-SAPO-18 zeotype. The overall free energy barrier at 673 K was calculated and found to be less than 150 kJ/mol in the TME-based cycle, much lower than those in the aromatic-based cycle（〉 200 kJ/mol）, indicating that olefins themselves are the dominant active hydrocarbon pool species in H-SAPO-18. The similarity of the intermediates involved between the aromatic-based cycle and the olefin-based cycle was also highlighted, revealing that both cycles were pattern-consistent. The selectivity related to the distribution of cracking precursors, such as higher olefins or carbenium ions, as a result of the olefin-based cycle for the MTO conversion. The enthalpy barrier of the crack-ing step scaled linearly with the number of carbon atoms of cracking precursors to produce ethene or propene with ethene being much less favored than propene for cracking of C7 and higher pre-cursors. This work highlighted the importance of the olefin-based cycle in H-SAPO-18 for the MTO conversion and established the similarity between the olefin-based and aromatic-based cycles.

主 题 词：Methanol-to-olefins conversion Hydrocarbon pool reaction mechanism Olefin-based hydrocarbon pool Density functional theory H-SAPO-18 zeotype 

学科分类：081702[081702] 081704[081704] 07[理学] 070304[070304] 08[工学] 0817[工学-轻工类] 0703[理学-化学类] 

核心收录：

D　O　I：10.1016/S1872-2067(18)63064-5

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