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.