ETHENE HYDROGENATION OVER SILICA-SUPPORTED RU AND RU-CU BIMETALLIC CATALYSTS - THE ROLE OF DEFECTS AND SPECIAL SITES

H-1 NMR of chemisorbed hydrogen and solid state C-13 NMR were used to investigate ethene hydrogenation and decomposition on Ru/SiO2 and Ru-Cu/SiO2 catalysts. H-1 NMR results on Ru/SiO2 catalysts indicate that the weakly adsorbed hydrogen is more concentrated on defect-like Ru sites, and it is suggested to be thermodynamically more accessible than strongly adsorbed hydrogen for ethene hydrogenation under typical reaction conditions. Results from H-1 NMR also indicate that addition of Cu reduces the amount of the weakly bound hydrogen. Addition of Cu to Ru/SiO2 catalysts suppresses the activity of ethene hydrogenation as observed by C-13 NMR. This effect may be due to preferential population of defect-like edge and comer Ru sites by Cu, subsequently limiting the amount of the weakly bound hydrogen on the metal surfaces necessary for ethene hydrogenation.