Compositional variations in highly active PtSn/Al2O3 catalysts derived from molecular complexes

Abstract

We investigated the industrially important PtSn/Al2O3 catalysts prepared with uniform particle sizes (∼ 1 nm) and varied compositions using molecular complexes of Pt(II) and Sn(II). Our best catalyst, with a Sn:Pt ratio of around 2, exhibited a high initial propylene productivity of about 1.1 mol C3H6 (g catalyst)−1 h−1. Elaborate electron microscopy studies revealed significant compositional variations in the catalyst, highlighting the practical challenges in achieving or confirming the theoretically predicted optimum Sn:Pt ratio. It is also found that the catalytic activities correlate well with the Pt dispersion, suggesting the structure-insensitive nature of the dehydrogenation reaction applies to these ultrasmall Pt-Sn nanoparticles. The presence of Pt-rich particles in the catalysts did not produce noticeable degradations in the reaction selectivity, indicating a wide composition range for Pt-Sn nanoparticles to be effective at the 1 nm size range. These findings emphasize the importance of detailed analysis of compositional distributions for understanding and optimizing nanoalloys.