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

The methylation of 4-methylbiphenyl (4-MBP) can yield 4,4ʹ-dimethylbiphenyl (4,4ʹ-DMBP), an important precursor for advanced polymers. The reaction mechanism of 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. 4,4ʹ-DMBP is kinetically favored by both mechanisms. Transition state selectivity accounts for the preferential methylation to 4,4ʹ-DMBP. The 56 LI Ling-Ling et al.: Reaction Mechanism of Methylation of 4-Methylbiphenyl with Methanol over H-ZSM-5 Zeolite No.1