Santosh Kumar Samantaray

Studies on anion promoted Titania: 2: Preparation, characterisation and catalytic activity towards aromatic alkylation over sulfated titania

Abstract Sulfated titania samples with varying amounts of sulfate have been prepared by solid–solid kneading, as well as aqueous impregnation method, and are characterized using X-ray diffraction (XRD), FT-IR and N 2 adsorption–desorption isotherm. Surface area, average pore diameter and total pore volume are found to increase with the increase in sulfate content up to 7.5 wt.%, and thereafter decreases. 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, wt.% and source of sulfate ion. Among all the catalysts, the sample with 7.5 wt.% sulfate loading prepared from H 2 SO 4 impregnation exhibits highest selectivity and yield towards alkylation of aromatic compounds to their corresponding isopropylated products.

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 (PO 4 3− /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)3PO4, 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.

Effect of anions on the textural and catalytic activity of titania

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.

SO4 2-/TiO2-SiO2 mixed oxide catalyst, 3. An eco-friendly catalyst for esterification of acetic acid

The effect of addition of titania to silica was examined by various characterization techniques such as FT-IR, BET surface area, surface acid strength/acid sites by the Hammett indicator method and Brönsted/Lewis acid sites by pyridine adsorbed IR study. Ti-O-Si bond is formed in case of TiO2-SiO2 sample, as observed from FT-IR data. Acid strength, surface acid sites, and rate constant for esterification of acetic acid are increased with Ti-O-Si bonding and sulfate impregnation. Both Brönsted and Lewis acid sites are responsible for catalysing the esterification reaction.