摘要
用周期性密度泛函理论方法(PBC-DFT)研究了SAPO-34分子筛中甲基萘催化甲醇制烯烃(MTO)反应的侧链烃池机理.在侧链烃池机理中,甲基化用于烷基侧链的增长,通过间接质子转移消除烷基侧链得到乙烯丙烯产物.计算结果表明在不考虑旋转限制的情况下二甲基萘的MTO催化活性高于多甲基苯,催化生成丙烯的选择性比生成乙烯的高.生成乙烯的控速步骤是乙基侧链的消除,而生成丙烯的控速步骤是具有环外双键中间体的甲基化.但是SAPO-34分子筛对反应中间体的旋转限制作用可能降低多甲基萘的MTO催化活性.
The side-chain hydrocarbon pool mechanism for the methanol-to-olefins（MTO） conversion catalyzed by methylnaphthalene in SAPO-34 zeolite was investigated by means of periodic density functional theory calculations.The alkyl side-chain was propagated by the methylation step and was eliminated into ethene and propene by the indirect proton shift steps in the mechanism.As shown,dimethylnaphthalene is more active than methylbenzenes for the MTO reaction when the organic intermediates are not rotationally limited inside the pore of catalyst.Propene is intrinsically more favorable than ethene as the product.The rate-determining step to produce ethene is the elimination of side ethyl chain,while that to produce propene is the methylation of exocyclic double bond in the reaction intermediates.However,the MTO activity of methylnaphthalene may be decreased by the limitation of SAPO-34 zeolite for the rotation of organic intermediates.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2010年第22期2312-2318,共7页
Acta Chimica Sinica
基金
973国家重点基础研究发展计划(No.2009CB623504)
中国博士后科学基金(No.20080440568)资助项目
关键词
甲醇制烯烃
SAPO-34分子筛
甲基萘
烃池机理
密度泛函理论
methanol-to-olefins reaction
SAPO-34 zeolite
methylnaphthalene
hydrocarbon pool mechanism
density functional theory
