Selective hydrogenation of high concentration acetylene over the well-defined crystalline sites of Pd₁Cu₁ and Pd₁Cu₃

Specific structures of PdCu bimetallic catalysts have been reported to exhibit superior performance in the hydrogenation of acetylene; however, the performance and the underlying mechanism of the conventional catalysts with comparable Pd/Cu ratios remain unknown. In this work, the well-defined crystalline sites of Pd₁Cu₁ and Pd₁Cu₃ are investigated in the hydrogenation of high concentration acetylene, and the corresponding conventional catalysts prepared by incipient wetness impregnation are compared. By correlating the theoretical and experimental results, the electronic effect is found to be present on the bimetallic structures, which results in better inhibition of excessive hydrogenation. The oligomerization reaction is better controlled over Pd/SiO₂(NS) and Pd₁Cu₁/SiO₂(NS), and Pd₁Cu₃/SiO₂(NS) exhibits the highest selectivity to oligomers and the largest amount of green oil accumulation. Among the well-defined structures, Pd₁Cu₁/SiO₂(NS) shows similar activity and stability to Pd/SiO₂(NS), but better suppression of the excessive hydrogenation reaction. Due to the existence of various sites, the conventional bimetallic catalysts show different properties from the corresponding well-defined crystalline catalysts. The performances of the well-defined alloy structures allow us to understand and analyze the actual properties of the surface sites over the conventional catalysts, and inspire further work to design optimum catalysts in different reaction environments.