Shape-selective synthesis of 4,4′-dimethylbiphenyl.: 1.: Methylation of 4-methylbiphenyl over modified zeolite catalysts

Methylation of 4-methylbiphenyl with methanol was carried out using zeolites HY, HM, and HZSM-5 as catalysts under fixed-bed down-flow conditions. HY and HM display no shape selectivity, but HZSM-5 shows moderate selectivity to the target product, 4,4'-dimethylbiphenyl (4,4'-DMBP) under proper reaction conditions. Modification of the surface of HZSM-5 zeolite can improve the selectivity to 4,4'-DMBP, especially the simultaneous modification of external and internal surface with inorganic P compound. The selectivity to 4,4'-DMBP can be increased to as high as 65% over the HZSM-5 modified with a small amount of ammonium hydrogen phosphate.