(729d) Theoretical Study of the Effects of Co-Adsorbed Water on Acetic Acid Decomposition.

Acetic acid decomposition on metal surfaces and the effects of co-adsorbed water on the decomposition are good model systems for solvent effects on small oxygenates with applications in biomass conversion. Numerous studies have found that solvents influence the selectivity and rate of heterogeneous catalytic reactions. Fundamental understanding of how water affects acetic decomposition on metal surfaces gives us valuable insight into how water changes the selectivity of decomposition reactions on different metals, further enabling bottom up design of effective catalyst and catalyst system. Here we present a density functional theory (DFT) calculations and microkinetic analysis of the effects of co-adsorbed water on acetic acid decomposition over Pd (111) and Pt (111). Our results suggest that in the absence of co-adsorbed water, the decarboxylation pathway (CO₂) is more favorable than decarbonylation pathway (CO) on both Pt (111) and Pd (111) but in the presence of co-adsorbed water, the decarboxylation pathway is more favored on Pd (111) than on Pt (111). Co-adsorbed water has more effect on OC-O cleavage on Pd (111) than on Pt (111), while for OC-OH bond cleavage, co-adsorbed water has more effect on Pt (111) than on Pd (111). These calculations give insight into how water affects different bond cleavages differently on these two metals and how that affect the overall selectivity of the reaction.