Benzoylation of toluene with p-toluoyl chloride over triflic acid functionalized mesoporous Zr-TMS catalyst

Abstract

Abstract The catalytic liquid phase benzoylation of toluene (Tol) to 4,4′-dimethylbenzophenone (4,4′-DMBP) with para -toluoyl chloride ( p -T-Cl) has been studied in a batch reactor at atmospheric pressure in the presence of different loadings of triflic acid (TFA) functionalized on the walls of mesoporous Zr-TMS (f-Zr-TMS/Zr-TMS-O-SO 2 -CF 3 /mesoporous Zr-O-SO 2 -CF 3 ) catalysts. Conventional catalysts, CF 3 SO 3 H and Zr-TMS (zirconium oxide with a mesostructured framework; TMS is transition metal oxide mesoporous molecular sieves) are also included for comparison. Under identical reaction conditions, f-Zr-TMS is considerably more active than Zr-TMS, whereas CF 3 SO 3 H shows higher activity. The conversion of p -T-Cl, rate of p -T-Cl conversion (turn over frequency (TOF)), selectivity to 4,4′-DMBP and 4,4′-DMBP/2,4′-DMBP ratio over f-Zr-TMS-15, after 8 h of reaction time and at 403 K are ca. 50.7%, 14.5 (10 −1 h −1 mol −1 S), 73.5% and 3.2, respectively. Acidity and mesoporosity of the f-Zr-TMS catalyst play an important role in the conversion of p -T-Cl, rate of p -T-Cl conversion and product distribution. The effect of various parameters such as duration of run, reaction time, catalyst concentration, reaction temperature, Tol/ p -T-Cl molar ratio and re-use of catalyst, on the catalyst performance is examined in order to optimize the conversion of p -T-Cl and selectivity to 4,4′-DMBP. The conversion of p -T-Cl using f-Zr-TMS-15 is increased significantly with the increases in reaction time, catalyst concentration, reaction temperature and Tol/ p -T-Cl molar ratio. f-Zr-TMS-15 catalyst is recycled one time (fresh + one cycle) and a decrease in p -T-Cl conversion is observed after one cycle, which is related to the minor leaching of anchored CF 3 SO 3 H by HCl (formed during reaction).