Kinetics and mechanism of hydrogenation of furfural on Cu/SiO2 catalysts

The hydrogenation/hydrodeoxygenation of furfural was studied on a Cu/SiO2 catalyst at 230–290 °C. Detailed kinetics, density function (DFT) calculations, and spectroscopic studies were combined to investigate this reaction. A Langmuir–Hinshelwood model was found to fit the kinetic data well and provided the parameters of physical significance. The heat of adsorption (ΔHads) of furfural, derived from the fitting, was found to be significantly higher than those of furfuryl alcohol and 2-methyl furan. Activation energies for the conversion of furfural and furfuryl alcohol were both about 12 kcal/mol. DFT calculations and DRIFTS provided guidance about the nature of the surface species. Accordingly, the most likely species adsorbed on the Cu surface is suggested to be a top η1(O)-aldehyde. DFT calculations of the reaction path show that the predicted energy barriers are of the same order as the experimental values and suggest that the hydrogenation of furfural can occur via either an alkoxide or ahydroxyalkyl intermediate.

Graphical abstractFurfural on a copper surface. The most likely species adsorbed on the Cu surface is a top η1(O)-aldehyde species. Hydrogenation of this species occurs via H attack on the carbonyl C or carbonyl O, resulting in an alkoxide or a hydroxyalkyl intermediate, respectively. DFT calculations indicate that the first attack on the carbonyl O is energetically more favorable.Figure optionsDownload full-size imageDownload high-quality image (37 K)Download as PowerPoint slide