Cost-effective promoter-doped Cu-based bimetallic catalysts for the selective hydrogenation of C2H2 to C2H4: the effect of the promoter on selectivity and activity

Abstract

In order to probe into the effect of the promoter on the selectivity and activity towards C₂H₄ formation in the selective hydrogenation of C₂H₂ over cost-effective Cu-based bimetallic catalysts, different metal promoter M-modified Cu catalysts including Ni, Ag, Au, Pt, Pd and Rh have been employed to fully investigate the selective hydrogenation of C₂H₂ using density functional theory calculations together with microkinetic modeling. The results show that the adsorption ability of C₂H₂ is far stronger than that of C₂H₄ on different Cu-based catalysts, which favors the activation and hydrogenation of C₂H₂. The type of promoter obviously affects the preferable pathway of C₂H₂ selective hydrogenation, and ultimately alters the selectivity of the products; only on PdCu(211) and AgCu(211) surfaces, the C₂H₄ desorption pathway is the most favorable for gaseous C₂H₄ formation, suggesting that the promoter Pd or Ag has good selectivity towards C₂H₄ formation. The catalytic activity towards C₂H₄ formation follows the order PdCu(211) > PtCu(211) > NiCu(211) > RhCu(211) > AgCu(211) > AuCu(211) > Cu(211), indicating that the promoter can obviously increase the catalytic activity towards C₂H₄ formation compared to the Cu catalyst alone. Thus, the promoter Pd-modified Cu catalysts exhibit the highest catalytic activity and selectivity for C₂H₂ hydrogenation to C₂H₄. This work provides a method to evaluate and obtain the type of promoter with the best activity and selectivity in the selective hydrogenation of C₂H₂.