摘要
采用ONIOM2(B3LYP/6-31G(d):UFF)计算方法研究了H-ZSM-5分子筛上苯与乙醇和乙烯烷基化反应历程.选取40T簇模型模拟了H-ZSM-5分子筛位于孔道交叉点的酸性位.从生成能和反应活化能角度分析并比较了苯与乙醇和乙烯烷基化反应机理.结果表明,苯与乙醇的烷基化按照分步机理进行,速控步骤的活化能为170.34kJ/mol.而乙烯作为烷基化剂与苯反应时同时存在联合机理和分步机理,且二者之间存在一定程度的竞争,其中联合机理的活化能为167.24kJ/mol,分步机理速控步骤的活化能为155.20kJ/mol.比较苯与乙醇和乙烯发生烷基化反应的机理可以看出,二者作为烷基化试剂对烷基化反应性能影响不大.
Alkylation of benzene with ethanol and ethylene over H-ZSM-5 zeolite has been studied theoretically by the ONIOM2 （B3LYP/ 6-3 IG（d）：UFF） method, A 40T cluster model was selected to simulate the acidic sites located at the intersection of channels in ZSM-5 zeo- lite. The difference of the reaction mechanisms using the two kinds of alkylation reagents has been analyzed and compared according to the formation energy and reaction activation energy （Ea）. The results showed that alkylation of benzene with ethanol occurred via stepwise mechanism. The Ea for the formation of ethoxide intermediate was 170.34 kJ/mol. Alkylation of benzene with ethylene occurred through both concerted mechanism and stepwise mechanism, and they were competitive to each other. These two paths were only slightly different in the activation energy. Ea for the concerted mechanism was 167.24 k J/mol, while it was 155.20 kJ/mol for the formation of ethoxide intermediate in the stepwise mechanism.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2009年第5期453-458,共6页
基金
新世纪优秀人才支持计划(NCET-04-0268)
高等学校学科创新引智计划(111计划)
国家自然科学基金(20573013)
大连理工大学青年教师培养基金(2007009)
