物理化学学报 >> 2015, Vol. 31 >> Issue (1): 56-66.doi: 10.3866/PKU.WHXB201411052

理论与计算化学 上一篇    下一篇

H-ZSM-5分子筛催化4-MBP与甲醇甲基化的反应机理

李玲玲1,2, JANIK J. Michael2,3,4, 聂小娃5, 宋春山2,3,4, 郭新闻2   

  1. 1. 辽宁科技学院冶金工程学院, 辽宁 本溪 117004;
    2. 大连理工大学化工学院, 精细化工国家重点实验室, PSU-DUT联合能源研究中心, 辽宁 大连 116024;
    3. 宾夕法尼亚州立大学能源与矿物工程系能源研究所, PSU-DUT联合能源研究中心, 宾夕法尼亚 16802, 美国;
    4. 宾夕法尼亚州立大学化学工程系, 宾夕法尼亚 16802, 美国;
    5. 佐治亚理工学院化学与生物工程学院, 亚特兰大 30332-0100, 美国
  • 收稿日期:2014-09-16 修回日期:2014-11-05 发布日期:2014-12-25
  • 通讯作者: JANIK J. Michael, 郭新闻 E-mail:mjanik@engr.psu.edu;guoxw@dlut.edu.cn
  • 基金资助:

    辽宁省教育厅科学研究一般项目基金(L2014503), 辽宁科技学院博士科研启动基金项目(1406B08), 新世纪优秀人才项目(NCET-04-0268)及教育部111计划工程基金和大连理工大学网络与信息化中心高性能计算部资助

Reaction Mechanism of Methylation of 4-Methylbiphenyl with Methanol over H-ZSM-5 Zeolite

LI Ling-Ling1,2, JANIK J. Michael2,3,4, NIE Xiao-Wa5, SONG Chun-Shan2,3,4, GUO Xin-Wen2   

  1. 1. Department of Metallurgical Engineering, Liaoning Institute of Science and Technology, Benxi 117004, Liaoning Province, P. R. China;
    2. State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning Province, P. R. China;
    3. EMS Energy Institute, PSU-DUT Joint Center for Energy Research and Department of Energy & Mineral Engineering, Pennsylvania State University, University Park, PA 16802, USA;
    4. Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802, USA;
    5. School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0100, USA
  • Received:2014-09-16 Revised:2014-11-05 Published:2014-12-25
  • Contact: JANIK J. Michael, GUO Xin-Wen E-mail:mjanik@engr.psu.edu;guoxw@dlut.edu.cn
  • Supported by:

    The project was supported by Scientific Research Foundation for the General Program of Department of Education of Liaoning Province, China (L2014503), Research Fund for the Doctoral Programof Liaoning Institute of Science and Technology, China (1406B08), Programfor New Century Excellent Talent in Universities, China (NCET-04-0268), Plan 111 Project of the Ministry of Education of China, and High Performance Computing Department of Network and Information Center, Dalian University of Technology, China.

摘要:

4,4'-二甲基联苯(4,4'-DMBP)是生产高性能聚合物材料的重要前驱体, 可以通过4-甲基联苯(4-MBP)甲基化制得.本文采用“our own-N-layered integrated molecular orbital+molecular mechanics”(ONIOM)和密度泛函理论(DFT)方法研究H-ZSM-5分子筛孔内4-MBP和甲醇择形甲基化的反应机理, 考虑了分步和协同反应机理. 分步机理的活化能低于协同机理. 在两种反应机理中, 4,4'-DMBP为动力学优先生成产物. 过渡态择形的特征也使甲基化更容易生成4,4'-DMBP. 在分子筛孔内, 4-MBP异构化生成3-甲基联苯(3-MBP)的反应被抑制. 在分子筛外表面, 4-MBP异构化生成3-MBP比甲基化反应更有动力学优势, 导致4,4'-DMBP选择性降低.对外表面进行改性将会抑制4-MBP异构化反应, 并使反应在分子筛孔内进行, 因此可以提高4,4'-DMBP的选择性. H-ZSM-5催化择形和非择形反应的计算结果与实验现象一致.

关键词: ONIOM, 甲基化, 甲醇, 4-MBP, H-ZSM-5

Abstract:

Themethylation of 4-methylbiphenyl (4-MBP) can yield 4,4'-dimethylbiphenyl (4,4'-DMBP), an important precursor for advanced polymers. The reaction mechanismof the shape-selective methylation of 4-MBP with methanol within the pores of H-ZSM-5 zeolite was studied, using“our own-N-layered integrated molecular orbital+molecular mechanics”(ONIOM) and density functional theory (DFT) methods. Stepwise and concerted mechanisms were considered, with the former having a lower activation energy. 4,4'-DMBPis kinetically favored by both mechanisms. Transition state selectivity accounts for the preferential methylation to 4,4'-DMBP. The isomerization of 4-MBPto 3-methylbiphenyl (3-MBP) is restricted within the zeolite. The isomerization of 4-MBP to 3-MBPis kinetically favored over methylation on the external zeolite surface, which causes a decrease in 4, 4'-DMBP selectivity. Passivating the external surface will suppress 4-MBP isomerization, therefore increasing 4,4'-DMBP selectivity by restricting reaction within the zeolite. The computational results of shape-selective and non-selective reactions over H-ZSM-5 zeolite well account for the experimental observations.

Key words: ONIOM, Methylation, Methanol, 4-MBP, H-ZSM-5

MSC2000: 

  • O641