ACETYLATION OF BENZENE TO ACETOPHENONE OVER ZEOLITE CATALYSTS

The vapour phase acetylation of benzene has been investigated over var ious zeolite catalysts using acetic acid as acetylating agent in a tub ular reactor and at atmospheric pressure. The rate of acetic acid conv ersion (TOF = m mol s(-1) mol(-1) Al x 10(-3)) is found to be about el even times higher over H-ZSM-5 (TOF = 45.2) compared to the H-mordenit e (TOF = 4.3). HY and REY do not catalyze the reaction. The acidity of the catalysts is evaluated by the temperature programmed desorption o f ammonia. NH3-TPD results show that the presence of strong Bronsted a cid sites are desired for the acetylation of benzene by acetic acid. T he effects of time on stream (TOS), degree of Na-exchange, SiO2/Al2O3 molar ratios, reaction temperature, weight hourly space velocity (WHSV h(-1)) and molar ratios of benzene/CH3COOH upon the conversion of ace tic acid and product yields are investigated in the acetylation of ben zene using H-ZSM-5 zeolite. H-ZSM-5 is partially deactivated under the se reaction conditions. Acetic acid conversion increased with reaction temperature and benzene/CH3COOH molar ratios, whereas it decreased wi th the increase in reaction time, degree of Na-exchange, WHSV (h(-1)) and SiO2/Al2O3 molar ratio. Presumably, the acetylation proceeds by th e attack of an electrophile (CH3CO+) on the benzene ring resulting in the formation of acetophenone. (C) 1997 Published by Elsevier Science B.V.