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) ≈ 70 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.