TY - JOUR
T1 - Reaction mechanism of methylation of 4-methylbiphenyl with methanol over H-ZSM-5 zeolite
AU - Li, Ling Ling
AU - Janik, Michael J.
AU - Nie, Xiao Wa
AU - Song, Chun Shan
AU - Guo, Xin Wen
N1 - Publisher Copyright:
© Editorial office of Acta Physico-Chimica Sinica.
PY - 2015
Y1 - 2015
N2 - The methylation 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.
AB - The methylation 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.
UR - http://www.scopus.com/inward/record.url?scp=84921749891&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84921749891&partnerID=8YFLogxK
U2 - 10.3866/PKU.WHXB201411052
DO - 10.3866/PKU.WHXB201411052
M3 - Article
AN - SCOPUS:84921749891
SN - 1000-6818
VL - 31
SP - 56
EP - 66
JO - Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica
JF - Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica
IS - 1
ER -