Designing nanoscopic, fluxional bimetallic Pt–Ru alloy hydrogenation catalysts for improved sulfur tolerance

Supported Pt and Ru mono- and bimetallic alloy catalysts, with promising potential applications in biomass processing, were investigated for their tolerance to sulfur poisoning using the batch hydrogenation of cyclohexene to cyclohexane in the presence of thiophene as a screening reaction. Compared to their monometallic counterparts, the bimetallic catalysts exhibited higher turnover frequencies, both in the absence and presence of sulfur. XRD analysis of changes in the Pt unit cell size suggest that the observed restructuring of the metal nanoparticles results from increasing amounts of sulfur species being coordinated to the ruthenium during poisoning, leading to at least a partial separation of the alloy. However, regeneration of the catalyst in pure H2 at 300 °C shows this to be a reversible process. The sulfur tolerance observed for catalysts with certain Ru to Pt ratios might be due to sulfur and hydrogen intra-particle spillover.