For the aqueous-phase hydrodeoxygenation (APHDO) of carboxylic acids over the Ru/C, Ru/ZrO(2) and Ru/Al(2)O(3) catalysts, the C=O hydrogenation and C-C bond cleavage reactions were studied by collecting reaction kinetics data and the measures of DRIFTS. The C-C bond cleavage was improved at high temperature and with high metal loadings. The acidic supports in combination with Ru metal can favor the C=O hydrogenation of carboxyl. The C-C bond cleavage derived from the decarbonylation of acyl on the catalyst was studied by the measures of DRIFTS. The APHDO and DRIFTS results demonstrated that the C-C bond cleavage was favored in the order of Ru/C>Ru/ZrO(2)>Ru/Al(2)O(3). The catalysts were characterized by multiple methods (H(2)-TPR, NH(3)-TPD, CO-FTIR and DRIFTS of propanoic acid). It is concluded that the effect of support on the reaction routes may be attributed to these factors of catalysts, i.e., surface acidity, metal-support interaction and electronic state of Ru species. (C) 2011 Elsevier B.V. All rights reserved.