Effect of anions on the textural and catalytic activity of titania

Abstract

An attempt has been made to review and studied the effect of ions ( phosphate and sulfate) on titania samples. Surface area, average pore diameter and total pore volume increases however crystallite size decreases with increase in anion contents ( both phosphate and sulfate case) up to 7.5 wt%, and thereafter decreases on further loading. TG-DTA and XRD patterns showed that phosphate stabilizes the anatase phase of TiO2 up to 1173 K. FT-IR result showed that both phosphate and sulfate species strongly bound bidentately on TiO2 support. Total acidity increases with increase in phosphate content up to 10.0 wt%, however, it increases up to 7.5 wt% in case of sulfated samples and thereafter decreases. Samples prepared at pH 3 and aqueous impregnation method exhibit higher acidity than the samples at pH 7 and solid-solid kneading method. Alkylation of benzene gives highest product ( cumene) approximate to70 mol% compared to others. Alkylation of aromatic compounds ( benzene, toluene and chlorobenzene) with isopropanol is carried out in a fixed bed flow reactor over these catalysts as a function of benzene to isopropanol molar ratio, reaction temperature, percentage and source of sulfate ion. (C) 2003 Kluwer Academic Publishers.