K. Joseph Antony Raj

Single-Step Synthesis and Structural Study of Mesoporous Sulfated Titania Nanopowder by a Controlled Hydrolysis Process

An environmentally benign route for the single-step synthesis of mesoporous sulfated titania is described by a seeding method using titanium oxysulfate as the titania source. The hydrolysis was performed in the presence of NaOH and seed under constant-volume conditions around 98 degrees C. The XPS and DRIFT spectra show the existence of a bridged bidentate sulfate complex on the surface of titania. The elimination of sulfur on heat treatment showed a characteristic change in mesoporosity, specific surface area, and crystallinity of the material. The transformation of sulfated titania to anatase was incomplete at 900 degrees C, showing a delay in crystallization due to the presence of sulfur. Studies on the thermal stability of the sulfated titania showed that the material obtained can be used for various applications at temperatures below 300 degrees C. The ammonia-TPD and catalytic performance studies of the sulfated titania samples showed the presence of strong acid sites.

Liquid Phase Hydrogenation of Nitrobenzene over Nickel Supported on Titania

The catalytic hydrogenation of nitrobenzene to aniline employing nickel impregnated on rutile, anatase, and high surface area titania supports has been investigated. The nickel is present in elemental state as fcc phase on the catalyst as evidenced by X-ray diffraction results. The Ni crystallite size was found to be greater for Ni/anatase. The temperature-programmed reduction results suggest a greater metal-support interaction for Ni/rutile. The observed order of catalytic activity for the hydrogenation of nitrobenzene is Ni/rutile > Ni/anatase > Ni/TiO2. A conversion of 99% was observed for Ni/rutile at 140°C and hydrogen pressure of 1.96 MPa. Interestingly, aniline is the only product formed which demonstrates the catalytic hydrogenation of nitrobenzene proceeds with atom economy. Both Ni/rutile and Ni/anatase exhibited a better stability than Ni/TiO2. The hydrogenation proceeds with the preferential adsorption of hydrogen on nickel present in the catalyst surface, possibly assisted by TiOx species.

Selective hydrogenation of acetophenone over nickel supported on titania

The catalytic activity of Ni impregnated on various phases of titania, viz. rutile, anatase and high surface area, has been investigated for the hydrogenation of acetophenone. The TPR profile of Ni/rutile suggests a strong metal–support interaction. The observed catalytic activity order is Ni/rutile > Ni/anatase > Ni/TiO2. The greater activity of Ni/rutile is attributed to higher concentration of Ni on the surface and SMSI. The catalyst samples showed sintering of Ni when calcined at 900 °C, which resulted in a drop in their catalytic activity. The catalyst stability studies showed that activity is lost only marginally in rutile and anatase. The electronic interaction between Ni and rutile promotes the formation of electron enriched Ni–H species which interact with the carbonyl group of acetophenone. The hydrogenation proceeds with atom economy to form phenylethanol irrespective of the reaction conditions suggesting that these catalysts are of significant importance in green chemistry. The results obtained in this investigation clearly establish that Ni/rutile, a non-porous support, is better for this class of reaction.

Selective orthobutylation of phenol over sulfated Fe2O3–TiO2

Sulfated Fe2O3–TiO2 (SFT) has been synthesized by an organic-free method employing ilmenite ore. Various SFT samples were prepared by drying and calcining over 100–900 °C. The XRD patterns of the system showed the presence of anatase and rutile phases of TiO2 and Fe2O3. The XRF analysis and DRIFT spectra demonstrated the presence of sulfate moieties, with their content being ≥8.1 wt% for samples calcined at ≤500 °C. The number of Bronsted and Lewis acid sites of the samples calcined at ≤500 °C was found to be nearly the same as that observed from pyridine adsorption measurements. The SFT samples were found to be thermally stable up to 500 °C. The SFT samples exhibited catalytic activity for the ortho-alkylation of phenol with tert-butanol. The activity for the SFT samples calcined at ≤500 °C was 5–8 times greater than that for the samples calcined at 700 and 900 °C. The decrease in the catalytic activity of the samples in the latter cases is due to the decreased acidity of the catalysts arising from the removal of sulfate species on calcination. The sulfated Fe2O3–TiO2 catalyst exhibited greater activity than similar higher surface area materials.