Hydrogenation of organic acids is an important step in the conversion and upgrading of biomass-derived feedstock for the production of valuable liquid fuels and chemical intermediates. To develop a fundamental understanding for this class of reaction, we are investigating the aqueous-phase hydrogenation of acetic acid, one of the simplest carboxylic acids, to ethanol, by a combined experimental and theoretical approach. The catalytic activity of monometallic Ni, Cu, Ru, Rh, Pd, Ir, and Pt catalysts have been measured in a fixed bed reactor and found to be distinctly different. In agreement with previous studies of the hydrogenation of organic acids,1-4 Ru is by far the most active and selective catalyst, with the rest of the metals being at least an order of magnitude less active. For additional mechanistic insight, periodic density functional theory calculations have been performed to investigate the activation and subsequent hydrogenation of acetic acid on the seven metals. Our results suggest that the different activity is dictated largely by the first C-O bond scission step of acetic acid forming acetyl (CH3CO)5-7 across the metals. A simple reaction model allows the rate of acetic acid conversion to be estimated based on readily calculated reactivity parameters. Further investigation suggests that the selectivity for ethanol on Ru is controlled by reaction conditions. Our study provides insight for the challenging task of developing new catalysts for efficient biomass feedstock processing.
Work at UMass was supported with a grant from the ACS Petroleum Research Fund. The Center for Nanophase Materials Sciences is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy.
(1) Varadarajan, S.; Miller, D. J. Biotechnol. Prog. 1999, 15, 845.
(2) Chen, Y. Q.; Miller, D. J.; Jackson, J. E. Ind. Eng. Chem. Res. 2007, 46, 3334.
(3) Dalavoy, T. S.; Jackson, J. E.; Swain, G. M.; Miller, D. J.; Li, J.; Lipkowski, J. J. Catal. 2007, 246, 15.
(4) Garcia, A. R.; da Silva, J. L.; Ilharco, L. M. Surf. Sci. 1998, 415, 183.
(5) Santiago, M. A. N.; Sánchez-Castillo, M. A.; Cortright, R. D.; Dumesic, J. A. J. Catal. 2000, 193, 16.
(6) Pallassana, V.; Neurock, M. J. Catal. 2002, 209, 289.
(7) Alcala, R.; Shabaker, J. W.; Huber, G. W.; Sanchez-Castillo, M. A.; Dumesic, J. A. J. Phys. Chem. B 2005, 109, 2074.
See more of this Group/Topical: Catalysis and Reaction Engineering Division