Catalytic reduction of acetic acid, methyl acetate, and ethyl acetate over silica-supported copper

The selective reduction of acetic acid, methyl acetate, and ethyl acetate over silica-supported copper catalysts was studied by combining microcalorimetric, IR spectroscopic, and reaction kinetics measurements with quantum-chemical calculations based on density-functional theory (DFT). Experimental values of initial heats for adsorption were 124, 130, 130, 128, and 140 kJ/mol for methyl acetate, ethyl acetate, acetaldehyde, methanol, and ethanol on silica-supported copper, respectively. These values were consistent with adsorption energetics estimated by DFT calculations on Cu13 clusters. Results from kinetic analyses and DFT calculations showed that the rate of dissociation on copper increases in the order from acetic acid to methyl acetate to ethyl acetate. The experimental values of the activation energies were 83, 67, and 62 kJ/mol, respectively. Kinetic analyses indicated that the rate of reduction of n-alkyl acetates is dictated by the dissociative adsorption of the molecules and by the surface hydrogenation of surface acyl species.

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