The cost-effective Cu-based catalysts for the efficient removal of acetylene from ethylene: The effects of Cu valence state, surface structure and surface alloying on the selectivity and activity

Cost-effective Cu-based catalysts with high activity and selectivity towards C2H4 formation are vital for the efficient removal of C2H2 from C2H4 in industry. A comprehensive understanding about the effects of Cu-based catalyst properties, including the valence state, surface structure and surface alloying, on the selectivity and activity towards C2H4 formation is essential for developing any novel Cu-based catalysts. In this work, C2H2 hydrogenation to C2H4 over various Cu-based catalysts, including Cu(0), Cu(I), Cu(II), and alloyed MCu(M = Ni, Pd, N, Au), were systematically investigated. The results indicated that the activity and selectivity of Cu catalysts with different oxidation states towards C2H4 formation are very different. Cu(I) led to the highest selectivity, while Cu(0) led to the highest activity. Moreover, the catalytic performances of Cu(I) and Cu(0) catalysts are closely related to their surface structures, especially their defective and stable (111) surfaces. For the most stable Cu(0) catalyst in reducing atmosphere, the activity and selectivity towards C2H4 formation on M-doped Cu(111) (M = Ni, Pd, N, Au) surface are affected by the surface d-band center, PdCu(111) surface with d-band center at the middle site has the best activity and selectivity towards C2H4 formation compared to the individual Cu(111) and Pd(111) surfaces. Thus, the activity of Cu-based catalysts and the selectivity of C2H2 hydrogenation towards C2H4 formation are determined by the valence state, surface structure, and surface d-band center of Cu catalysts. The catalytic activity and selectivity of all active surfaces can be predicted by analyzing the catalyst surface characteristics. The results are considerably beneficial to the development of new generation of Cu-based catalysts in the selective hydrogenation of C2H2.