Sites for the selective hydrogenation of ethyne to ethene on supported NiO/Au catalysts

Au, NiO, and NiO/Au clusters of 2.5–16 nm, supported on Al2O3, ZrO2, TiO2, and ZnO, were studied in the purification of ethene feedstock from ethyne by hydrogenation at 357 K. The Au, NiO, and NiO/Au catalysts possessed 100 % selectivity to ethene. As the size of NiO clusters decreased from 7 to 3 nm, the turnover frequency (TOF) decreased from 812–1,023 to 276 h 1. In contrast with NiO, Au activity increased with decreasing particle size. NiO/Au catalysts possessed higher stability and activity in comparison with Au and NiO catalysts. The synergistic gain on NiO/Au clusters (SG) calculated as TOFNiO/Au – TOFAu – TOFNiO was 1,466; 1,147; 563; and 569 h 1 for NiO/Au/Al2O3, NiO/Au/TiO2, NiO/Au/ZnO, and NiO/Au/ZrO2, respectively. The reasons of the observed catalytic trends and the origin of the most active and selective sites are discussed.