A First-Principle Study of Oxonium Ylide Mechanism over HSAPO-34 Zeolite

Based on density functional theory calculation with periodic boundary conditions, the possibility of the direct coupling of methanol into ethene by oxonium ylide mechanism was investigated. The calculated results indicate that the energy barriers for the formation of dimethyl ether and trimethyl oxonium ion inside HSAPO-34 zeolite are 1.68 and 0.93 eV, respectively. The suggested intermediate oxonium ylide is very unstable and the energy barriers for the formation of C-C bond are over 3.0 eV by concerted pathway. It is thus concluded that the methanol to olefin reaction cannot follow the oxonium ylide mechanism.

摘要䜕采用基于周期性边界条件的密度泛函理论研究了䜕HSAPO-34䜕分子筛上甲醇通过氧鎓叶立德机理直接耦合生成乙烯的可能性.䜕䜕结果表明,䜕二甲醚和三甲基氧鎓离子在䜕HSAPO-34䜕分子筛上的生成能垒分别为䜕1.68䜕和䜕0.93䜕eV,䜕中间体氧鎓叶立德不能稳定存在,䜕同时表明䜕C–C䜕键通过协同反应形成的能垒均超过䜕3.0䜕eV.䜕䜕因此䜕甲醇制烯烃催化过程不可能遵循氧鎓叶立德机理.䜕

A first-principle study indicated that the production of light olefins such as ethene from methanol over HSAPO-34 zeolite cannot follow oxonium ylide mechanism in the methanol to olefin reaction.Figure optionsDownload as PowerPoint slide