(195b) Reaction of Sugar Derivatives On Metal Surfaces

Over the past decade, the interest in theoretical methods to aid catalyst design has grown with the advances in computational resources.  In this research, we apply such state-of-the-art theory to describe the adsorption and the reaction kinetics of biomass derivatives on transition metal surfaces to gain mechanistic insights into this complex chemistry.  Specifically, we looked at furfural hydrogenation to methylfuran, which can be used as an additive in transportation fuel.  In this work, we performed a density functional theory (DFT) study on the adsorption of furan, furfuryl alcohol, furfural, and methylfuran, which are the main products in furfural reaction on Pd.  For the first time in modeling reactions on transition metal surfaces, we applied the recently-developed DFT-D3 method, which combines the standard DFT functionals with a correction for weak long-range interactions.  This correction is essential in modeling multi-metallic catalysts, because these weak interactions have shown to be the dominating forces on some catalysis-relevant metals.  As a part of this work, we have shown that DFT-D3 performs well in predicting geometric adsorption parameters regardless of the type of interactions involved.

Following the adsorption study, we explored the furfural interconversion on Pd surface.  We obtained the heats of reaction and performed transition state search to obtain the activation energies for each reaction.  The results showed that despite decarbonylation being thermodynamically favored, the hydrogenation activation energy is lower, thus allowing the chemical upgrade of the biomass derivative.  This explains the hydrogenation products that were experimentally observed in Pd-catalyzed furfural reaction.  Further mechanistic analysis showed full consistency with the recently reported ultra-high vacuum (UHV) experimental findings. As such, this work constitutes a great starting point in the development of predictive models for biomass derivatives’ reactions on transition metal surfaces.