Catalytic study of cobalt modified titanium silicalites-1 in the hydroxylation of toluene to cresol by hydrogen peroxide

Abstract

This research investigated the hydroxylation of toluene by hydrogen peroxide in a bubble reactor using titanium silicalite-1 (TS-1) catalysts modified with Co. The reaction is carried out at 70C and atmospheric pressure. Parameters investigated are hydrogen peroxide concentration, appropriate amount of cobalt, crystallization time, and effects of treatment (washing with nitric acid solution). The experimental results show that the addition of too much cobalt salt before catalyst crystallization results in the separation of cobalt cation from the catalyst crystal structure. Such excess cobalt will form a cobalt compound which can be washed off with nitric acid solution. The washing of such cobalt compound can increase the catalytic activity of the catalyst. Reaction study shows that the formation of cresol prefers a low hydrogen peroxide concentration. At 3wt% hydrogen peroxide concentration, selectivity toward cresol up to 100% can be achieved. At a too high hydrogen peroxide concentration, benzaldehyde becomes the main reactor product.