The role of water in the adsorption of oxygenated aromatics on Pt and Pd.

Catalytic processing of biomass-derived oxygenates to valuable chemical products will contribute to a sustainable future. To provide insight into the conversion of processed sugars and lignin monomers, we present density functional theory studies of adsorption of phloroglucinol, a potentially valuable biomass derivative, on Pt(111) and Pd(111) surfaces. A comprehensive study of adsorption geometries and associated energies indicates that the bridge site is the most preferred adsorption site for phloroglucinol, with binding energies in the range of 2-3 eV in the vapor phase. Adsorption of phloroglucinol on these metal surfaces occurs via hybridization between the carbon p(z) orbitals and the metal d(z(2)) and d(yz) orbitals. With explicit solvent, hydrogen bonds are formed between phloroglucinol and water molecules thereby decreasing binding of phloroglucinol to the metal surfaces relative to the vapor phase by 20-25%. Based on these results, we conclude that solvent effects can significantly impact adsorption of oxygenated aromatic compounds derived from biomass and influence catalytic hydrogenation and hydrodeoxygenation reactions as well.