Exploring Furfural Catalytic Conversion on Cu(111) from Computation

The full potential energy surface of the catalytic conversion of furfural to 2-methylfuran on the Cu(111) surface has been systematically computed on the basis of density functional theory, including dispersion and zero-point energy corrections. For furfuryl alcohol formation, the more favorable step is the first H addition to the carbon atom of the C=O group, forming an alkoxyl intermediate (F-CHO +H -> F-CH2O); the second H atom addition, leading to furfuryl alcohol formation (F-CH2O + H -> F-CH2OH), is the rate-determining step. For 2-methylfuran formation from furfuryl alcohol dissociation into surface alkyl (F-CH2) and OH groups, H2O formation is the rate-determining step (OH + H -> H2O). Our results explain perfectly the experimentally observed selective formation of furfuryl alcohol and the equilibrium of furfural/furfuryl alcohol conversion under hydrogen-rich conditions as well as the effect of H2O suppressing furfural conversion. In addition, it is found that dispersion correction (PBE-D3) overestimates the adsorption energies of furfural, furfuryl alcohol, and 2-methylfuran considerably, whereas those of H-2 and H2O can be reproduced nearly quantitatively. Our results provide insights into Cu-catalyzed furfural selective conversion and broaden our fundamental understanding into deoxygenation reactions of oxygenates involved in the refining of biomass-derived oils.