Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (1): 56-66.doi: 10.3866/PKU.WHXB201411052

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

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.

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