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. The hydrogenation of nitrobenzene on nickel supported titania catalysts takes place with the preferential adsorption of hydrogen to form nickel hydride species. Ni/rutile catalyst is found to possess better activity and stability. Aniline is formed exclusively suggesting the reduction proceeds with atom economy.