Hydrogenation of benzoic acid (BA) to cyclohexanecarboxylic acid (CCA) has important industrial and academic significance, however, the electron deficient aromatic ring and catalyst poisoning by carboxyl groups make BA hydrogenation a challenging transformation. Herein, we report that Pt/TiO2 is very effective for BA hydrogenation with, to our knowledge, a record TOF of 4490 h−1 at 80 °C and 50 bar H2, one order higher than previously reported results. Pt/TiO2 catalysts with electron-deficient and electron-enriched Pt sites are obtained by modifying the electron transfer direction between Pt and TiO2. Electron-deficient Pt sites interact with BA more strongly than electron-rich Pt sites, helping the dissociated H of the carboxyl group to participate in BA hydrogenation, thus enhancing its activity. The wide substrate scope, including bi- and tri-benzoic acids, further demonstrates the high efficiency of Pt/TiO2 for hydrogenation of BA derivatives.

The hydrogenation of benzoic acid (BA) to corresponding cyclohexanecarboxylic acid has important industry and academia significance, however, the electron deficient aromatic ring and the catalyst “poison” by carboxyl group make BA hydrogenation as one of the most challenging transformations. Herein, we found that Pt NPs deposited on TiO2 were very effective for BA hydrogenation with a record TOF of 4490 h− 1 under 80 oC and 50 bar H2 in hexane, one order higher than the reported results. DFT calculation showed that Pt NPs had a weaker interaction with BA than Ru and Pd NPs commonly used for BA hydrogenation, which improved the toxicity resistance of catalyst to BA. Pt/TiO2 catalysts with electron deficient and electron enriched Pt sites were successfully synthesized by modifying the electron transfer direction between Pt and TiO2. Isotopic experiments suggested the participation of dissociated H from carboxyl group in BA hydrogenation. Consequently, the electron deficient Pt sites with stronger adsorption of BA were more active than electron rich Pt sites in BA hydrogenation. In addition to BA, terephthalic acid, iso-phthalic acid, trimesic acid and other BA derivatives could also be efficiently converted to corresponding aromatic saturated products, demonstrating the wide substrate scope of Pt/TiO2.