Hydroxylation of alkyl benzenes in a bubble reactor using ts-1 and modified ts-1 catalysts

Abstract

This research has investigated the hydroxylation of alkyl benzenes (toluene and ethyl benzene) over TS-1 and modified TS-1 (Al-TS-1, Co-TS-1, Fe-TS-1 and V-TS-1) catalysts in a bubble reactor using hydrogen peroxide (3, 7.5 and 30 wt%) as an oxidant. In the reactor, reactant (toluene or ethyl benzene) was fed in gas phase, hydrogen peroxide was in aqueous phase, and catalyst which was immersed in hydrogen peroxide solution, was solid. The routes of product formation from the hydroxylation reaction have two paths, the ring oxidation that produces interested products, and another path is the side chain oxidation. The toluene hydroxylation gives cresol (ring oxidation product) and benzaldehyde (side chain oxidation product). In the case of hydroxylation of ethyl benzene acetophenone and 1-phenyl ethanol (both are side chain oxidation products) are observed in trace amount. The main products, benzaldehyde and o-cresol, are formed in meso pore system whereas p-cresol, found in a significant amount of Al-TS-1 and Co-TS-1 at 30 wt% H2O2, is formed in micro pore system. Co and V cation enhance the formation of ring oxidation product and inhibit the formation of side chain oxidation product. In addition, at high H2O2 concentration (30 wt%) Al cation promote the formation of ring oxidation product and inhibit the ring oxidation product at low H2O2 concentration (3 and 7.5 wt%). The products from hydroxylation of ethyl benzene are found in trace amount due to low solubility in water which leads to a fewer amount of ethyl benzene on catalyst surface.