Several supported Ru catalysts, Ru/TiO2, Ru/ZrO2, Ru/SiO2, Ru/gamma-Al2O3 and Ru/SiO2-Al2O3, were prepared and investigated for propanoic acid aqueous-phase hydrogenation. H-2-TPR, NH3-TPD, pyridine-FTIR and propanoic acid-DRIFTS techniques were performed to explore the metal-support interaction, acid sites and key adsorption species. The effect of support on the reaction pathway of C=O hydrogenation and decarbonylation of acyl species was discussed. Compared with Ru/ZrO2 and Ru/SiO2 catalysts, high selectivity of C=O hydrogenation was obtained over the catalysts with more Lewis acid sites, such as Ru/gamma-Al2O3 and Ru/SiO2-Al2O3 catalysts. The DRIFTS results suggest that the formation of adsorption species (acyl, carboxylate and carboxylic acid) is strongly depended on the nature of support. The metal-acid bifunctional sites are indispensable for the C=O hydrogenation of acyl. However, the decarbonylation of acyl on the metal sites requires the relatively weak metal-support interaction and few of Lewis acid sites. (C) 2014 Elsevier B.V. All rights reserved.