Conversion of Methanol to Alkenes over Medium-and Large-Pore Acidic Zeolites : Steric Manipulation of the Reaction Intermediates Governs the Ethene/Propene Product Selectivity
Conversion of Methanol to Alkenes over Medium-and Large-Pore Acidic Zeolites : Steric Manipulation of the Reaction Intermediates Governs the Ethene/Propene Product Selectivity
复制标题
DOI：
10.1021/jp077331j
复制
发表时间：
2007-11
影响因子：
3.7
通讯作者：
S. Svelle;U. Olsbye;A. Joensen;M. Bjørgen
中科院分区：
文献类型：
--
作者：
S. Svelle;U. Olsbye;A. Joensen;M. Bjørgen
比较了h- β和H-ZSM-5沸石催化剂在相同反应条件下（温度= 350℃，WHSV = 7.0 gg-1 h-1）的甲醇转化率，发现H-ZSM-5的乙烯产率是h- β产率的7倍。通过从12C甲醇进料切换到13C甲醇，甲醇中的13C原子进入位于沸石空隙中的气相产物和反应中间体中。对于h - β，五甲基苯和六甲基苯参与了烃池型机制，主要导致丙烯和高级烯烃，而对于H-ZSM-5，低甲基苯是中间产物，代表了乙烯的唯一生成途径。这项工作概述了沸石拓扑结构如何决定参与催化循环的中间体类型，从而控制甲醇制烯烃反应中乙烯/丙烯产物的选择性。
Methanol conversion over H-beta and H-ZSM-5 zeolite catalysts is compared at identical reaction conditions (temperature = 350 °C, WHSV = 7.0 gg-1 h-1), and it is found that H-ZSM-5 yields seven times more ethene relative to propene than H-beta yields. By switching from a 12C methanol feed to 13C methanol, the transient incorporation of 13C atoms from methanol into the gas-phase products and reaction intermediates located within the zeolite voids is followed. For H-beta, penta- and hexamethylbenzene are involved in a hydrocarbon-pool-type mechanism, leading predominantly to propene and the higher alkenes, whereas for H-ZSM-5, the lower methylbenzenes are the intermediates and represent the only route for ethene formation. This work outlines how the zeolite topology determines the type of intermediate participating in the catalytic cycle, thereby controlling the ethene/propene product selectivity in the methanol to olefins reaction.