Pd3Sn nanoparticles on TiO2 and ZnO supports as catalysts for semi-hydrogenation: synthesis and catalytic performance

The two catalysts Pd₃Sn/TiO₂ and Pd₃Sn/ZnO were prepared via a one-pot procedure based on the “polyol method” with the addition of a capping agent (polyvinylpyrrolidone) to control the particle size distribution. The same procedure was used to prepare Pd/TiO₂ and Pd/ZnO for comparison. All four catalysts showed high activity and selectivity for the selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) in the liquid phase under identical conditions. However, Pd₃Sn/TiO₂ and Pd₃Sn/ZnO show selectivities to alkene significantly higher than that of the Pd catalysts. Specifically, the selectivity increases from 96.4% to 97.4% on TiO₂ support, and 96.2% to 97.6% on ZnO support, at 90% conversion. Transition electron microscopy shows nanoparticles evenly dispersed on the support, with mean particle sizes as low as 4.1 (±0.8) nm when Sn is incorporated into the catalyst. Unsupported Pd₃Sn was prepared using the same method and characterised by powder X-Ray diffraction followed by the Rietveld refinement. Pd₃Sn was found to be single-phase and isostructural to Pd metal with a face centred cubic unit cell.