Deliberate control of the structure-specific active sites in PdIn bimetallic catalysts using adsorbate induced segregation effects

Abstract

A bimetallic PdIn/Al2O3 catalyst has been prepared, characterized by diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO (DRIFTS CO), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and tested towards the liquid-phase diphenylacetylene hydrogenation at room temperature. It was shown that the freshly reduced catalyst contains PdIn intermetallic nanoparticles that demonstrate excellent selectivity in the diphenylacetylene selective hydrogenation to diphenylethylene ∼ 98 % at 90 % conversion. An oxidative treatment of the catalyst induces preferential oxidative leaching of the In component from the intermetallic compound, modifying the catalyst active sites structure to the state with a high hydrogenation activity but poor stilbene selectivity. The changes upon the redox treatments are essentially reversible and reproducible. This effect can be intentionally used to get an optimum balance between activity and selectivity of the catalyst.