RuPd Alloy Nanoparticles Supported on N-Doped Carbon as an Efficient and Stable Catalyst for Benzoic Acid Hydrogenation

RuPd alloy nanoparticles (3.6 nm) uniformly dispersed on N-doped carbon (RuPd/CN) was prepared via a simple ultrasound-assisted coreduction method. The RuPd/CN is highly active, selective, and stable in the hydrogenation of benzoic acid to cyclohexanecarboxylic acid under mild conditions with a TOF up to 2066 h–1. It was found that the bimetallic RuPd/CN catalyst exhibited a substantially enhanced activity in comparison with the monometallic catalysts (Ru/CN and Pd/CN). The reason for the higher performance of the RuPd/CN catalyst is considered to be the increased Ru0 /Run+ ratio induced by the electronic interaction between Ru and Pd, as evidenced by various characterizations. Notably, the different phenomenon of activity platform on different catalysts ascribed to the effect of hydrogen pressure was newly observed and further explained by first-principle studies. Moreover, the factors influencing the adsorption modes of BA, especially the configuration of the carboxyl group, have been investigated preliminarily in first-principle studies, giving a distinct insight from the former work. The reason the carboxyl group in benzoic acid does not undergo hydrogenation, which results in superior selectivity (>99%), is also revealed by a comparison of the thermodynamics of hydrogenation and dissociation of the carboxyl group.