Acylation of biphenyl with acetic anhydride and carboxylic acids over zeolite catalysts

Acylation of biphenyl with acetic anhydride and carboxylic acids over zeoli te catalysts is investigated. Acylation of biphenyl with acetic anhydride o ver zeolite HY and zeolite beta at 83 degreesC gives 4-acetylbiphenyl as th e main product. The selectivity to 4-acetylbiphenyl is always higher than 9 8% and the highest yields are obtained over zeolite beta. An increase of th e Si/Al ratio in zeolite beta leads to slightly higher rates of 4-acetylbip henyl formation, however, the final yields are always within the range 8-10 %. Catalyst deactivation occurs and is mainly due to product inhibition, i. e. 4-acetylbiphenyl strongly competes for the adsorption sites on the zeoli te. Acylation of 4-acetylbiphenyl yielded less than 38 diacylated products, with a 4,4 ' -diacetylbiphenyl selectivity below 12%. Solventless acylatio n of biphenyl with hexanoic acid at 150 degreesC produces 4-hexanoylbipheny l (selectivity > 98%) at a yield of 8-14% and the best results are obtained over zeolite HY. An increase in temperature enhances the yield of 4-hexano ylbiphenyl (53% at 200 degreesC) but decreases slightly the selectivity (si milar to 92%). Acylation with a bulky acid (trimethyiacetic acid) in an att empt to obtain shape selective e acylation led to the formation of 4-t-buty lbiphenyl as main product (yield similar to9%) instead of the acylated prod uct. (C) 2001 Elsevier Science B.V. All rights reserved.