Theoretical Study on Structures and Reaction Mechanisms of Ethylene Oxide Hydration over H-ZSM-5: Ethylene Glycol Formation
Theoretical Study on Structures and Reaction Mechanisms of Ethylene Oxide Hydration over H-ZSM-5: Ethylene Glycol Formation
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DOI：
10.1021/jp8034677
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发表时间：
2008-07
影响因子：
3.7
通讯作者：
T. Maihom;S. Namuangruk;Tanin Nanok;J. Limtrakul
中科院分区：
文献类型：
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作者：
T. Maihom;S. Namuangruk;Tanin Nanok;J. Limtrakul
采用ONIOM（B3 LYP/6- 31 G（d，p）：UFF）和embedded-ONIOM（B3 LYP/6 - 31 G（d，p）：UFF）方法，对H-ZSM-5分子筛中环氧乙烷水合反应的分步协同机理进行了研究.对于逐步机理，环氧乙烷的水合反应从环氧乙烷的开环开始，通过破坏C-O键以形成醇盐中间体，然后醇盐中间体水合以产生作为反应产物的乙二醇。计算的活化能计算为34.4和14.5千卡/摩尔的开环和水合步骤，分别。对于协调机制，开环和水合同时发生，具有13.3 kcal/mol的小活化势垒。该反应是目前环氧乙烷非催化水合反应的一种更经济的替代方法。
Stepwise and concerted mechanisms of the ethylene oxide hydration reaction within a cluster model covering the nanocavity, where the straight and zigzag channels intersect, of H-ZSM-5 have been proposed and investigated by means of the ONIOM(B3LYP/6-31G(d,p):UFF) and embedded-ONIOM(B3LYP/6-31G(d,p):UFF) methods. For the stepwise mechanism, the hydration reaction of ethylene oxide starts from the ring opening of ethylene oxide by breaking of the C−O bond to form the alkoxide intermediate followed by hydration of the alkoxide intermediate to produce ethylene glycol as the product of the reaction. The calculated activation energies are computed to be 34.4 and 14.5 kcal/mol for the ring-opening and hydration steps, respectively. For the concerted mechanism, the ring opening and hydration take place simultaneously with a small activation barrier of 13.3 kcal/mol. This reaction is suggested as a more economical alternative to the present noncatalytic hydration of ethylene oxide via the concerted mechanism for p...