Novel shape-selective catalysts for synthesis of 4,4′-dimethylbiphenyl

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Shape-selective methylation of 4-methylbiphenyl was studied using zeolites HY, HM and HZSM-5 under the 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). Increasing the crystal size and modifing the surface of HZSM-5 zeolite can improve the selectivity to 4,4′-DMBP. The modification of external and internal surface with inorganic P compound was found to be very effective. 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.