Studies on anion-promoted titania 3. Effect of concentration and source of phosphate ion, method of preparation, and activation temperature on redox, acid-base, textural and catalytic properties of titania

The effect of phosphate concentration, source of phosphate ion, method of preparation and activation temperature on the redox, acid-base, textural, and catalytic properties of phosphated titania (PO43-/TiO2) toward alcohol and cumene conversion reactions has been described. The characterisation of the catalyst was performed using X-ray powder diffraction (XRD), infra-red spectroscopy (IR), thermal analysis (TG-DTA), nitrogen adsorption-desorption methods, surface redox, acid-base and phosphate content by spectrophotometric method. TG.-DTA and XRD patterns show that phosphate stabilises the anatase phase of TiO2 UP to 1173 K and decreases its crystallite size. IR result shows that phosphate species strongly bound bidentately on TiO2 supports. Surface area is found to increase with the increase in phosphate content up to 7.5 wt.% loading and thereafter decreases. However, total acidity and the catalytic activity increases with the increase in phosphate content up to 10.0 wt.%. Phosphated samples (PH = 3) prepared using H3PO4 as the source of phosphate ion exhibit higher acidity than the samples (PH = 7) using H3PO4 and (NH4)(3)PO4, though all the three samples contain same amount of phosphate ion (10.0 wt.%). Among the 573, 773, 973, and 1173 K activated samples, the 573 K sample has shown maximum activity toward the above reactions. (C) 2001 Elsevier Science B.V. All rights reserved.