Studies on anion promoted titania. 1: Preparation, characterization, and catalytic activity toward alcohol and cumene conversion reactions of phosphated titania

Abstract

Phosphate impregnated titania samples with varying amount of phosphate have been prepared by solid-solid kneading as well as aqueous impregnation method. All the samples are characterized by XRD, TG-DTA, and N-2 adsorption-desorption isotherm. Surface area is found to increase with the increase in phosphate content up to 7.5 wt% loading and thereafter decreases. The average pore diameter and crystallite size of titania decreases with the addition of phosphate, However, total acidity (determined by base adsorption method) and the catalytic activity increases with the increase in phosphate content up to 10 wt%, Phosphated samples prepared using phosphoric acid as the source of phosphate exhibit higher acidity compared to the samples prepared using (NH4)(3)PO4. However, the sample prepared from (NH4)(3)PO4 shows the presence of both, acid and basic sites. Though from the cumene conversion study it is understood that phosphated samples contain both Lewis and Bronsted acid sites, the latter predominates over the:former. (C) 1999 Academic Press.