Catalytic Reduction of Acetic Acid, Methyl Acetate, and Ethyl Acetate over Silica-Supported Copper

Abstract

Microcalorimetric, infrared spectroscopic, and reaction kinetics measurements are combined with quantum-chemical calculations based on density-functional theory to investigate the selective reduction of acetic acid, methyl acetate, and ethyl acetate over silica-supported copper catalysts. Experimental values for initial heats of dissociative adsorption of methyl acetate, ethyl acetate, acetaldehyde, methanol, and ethanol on silica-supported copper are estimated to be 124, 130, 130, 128, and 140 kJ mol−1, respectively. These values are in agreement with adsorption energies predicted from DFT calculations using Cu13 clusters. Experimental values of activation energies for the dissociation of acetic acid, methyl acetate, ethyl acetate, and acetaldehyde on copper are estimated to be 83, 67, 62, and 75 kJ mol−1, respectively. Results from DFT calculations also indicate that the activation energy for dissociation decreases from acetic acid to methyl acetate to ethyl acetate. The rate of reduction of n-alkyl acetates appears to be determined by the dissociative adsorption of these molecules and by the hydrogenation of surface acyl species.