Selective Hydrogenation of Nitrobenzene to para-Aminophenol on a Zirconium-Phosphate-Supported Platinum Catalyst

In this work, zirconium-phosphate-supported plati-num catalysts have been prepared by a wetness impregnation method and characterized thoroughly by various methods. The 1% Pt/ZrP catalyst displayed superior catalytic performance for the selective hydrogenation of nitrobenzene. It was found that the formation rate of para-aminophenol was much higher than that of aniline over the catalyst in the presence of inorganic acid and DMSO. A full conversion of nitrobenzene and high selectivity to para-aminophenol (89%) were achieved under mild reaction conditions (80 degrees C, 0.6 MPa H2). Also, the catalyst can be recycled in 14 consecutive catalytic runs without any obvious decrease in activity and selectivity for the hydrogenation of nitrobenzene. The electron transfer interaction of Pt(0) species with zirconium phosphate accounted for the high dispersion and leaching resistance of the Pt sites, leading to excellent recyclability of the catalysts. The further characterization by in situ DRIFT demonstrated that the nitro functional group was dominantly adsorbed on acid sites of zirconium phosphate and reduced to N-phenylhydroxylamine by spillover hydrogen, followed by rearrangement to afford para-aminophenol.