269199 Shape-Selective Alkylation of Biphenyl with Propylene by Using Zeolite Catalysts
The alkylation of biphenyl with propylene is a reaction of practical interest since it produces the 4, 4΄-diisopropylbiphenyl (4, 4΄-DIPB) . 4, 4΄-DIPB is a promising precursors for biphenyl-4, 4΄-dicarboxylic acid, which is an intermediate for polyester fibers, engineering plastics, and liquid crystalline polymers for electronic and mechanical devices and films with high heat resistance and strength . Selective synthesis of 4, 4΄-DIPB is not possible on traditional Friedel–Crafts , since catalysts such as Lewis acids or silica/alumina  are generally produce products large amount of undesired products with low para-selectivity. In contrast, zeolites, being micro porous and crystalline, may be shape-selectively and yield the less bulky para-isomers.
The present work aims to study the influence of zeolite structure for alkylation of biphenyl with propylene over various zeolites such as HY, HZSM-5, HMOR-40 and amorphous SiO2-Al2O3 in a stirred tank reactor. Biphenyl conversion was found to be increased with reaction time for HZSM-5 and HMOR-40 zeolites, whereas for HY and amorphous SiO2-Al2O3 catalysts conversion increased up to certain time and then reached a steady state conversion. The selectivities for 4, 4ʹ-DIPB for HY, HZSM-5 and amorphous SiO2-Al2O3 was in the range of 10-35%: they are much lower than that of HMOR-40. These differences in selectivity might be due to the zeolite structure, pore channel and SiO2/Al2O3 ratio. HMOR-40 was found to be an active catalyst in the alkylation of biphenyl with propylene. The selectivity for 4-isopropylbiphenyl (4-IPBP) and (4, 4ʹ-DIPB) was high among IPB and DIPB isomers, respectively, indicating HMOR-40 shows shape-selective catalysis.
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