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

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 hydroge-nation at room temperature. It was shown that the freshly reduced catalyst contains PdIn intermetallic nano-particles that demonstrate excellent selectivity in the diphenylacetylene selective hydrogenation to diphenylethylene similar to 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.

Automated summary

A bimetallic PdIn/Al2O3 catalyst was prepared and characterized, and its activity and selectivity changes in the diphenylacetylene hydrogenation were investigated. It was found that oxidative treatment modified the catalyst active sites structure, leading to a decrease in selectivity, but this effect was reversible and reproducible. This catalyst is of great significance for balancing activity and selectivity.