(98a) Surface Chemistry of Furanic Species On the (111) Surfaces of Pd and Pt

The surface reactions of furanic compounds ? five-membered ether or ester rings that may contain a variety of additional functional groups ? have become the focus of increasing interest because of the prevalence of these compounds in routes for production of fuels and chemicals from biomass. Lactones such a 2(5H)-furanone (25HF) and furans such as hydroxymethylfurfural (HMF) are intermediates in processes such as biomass pyrolysis and sugar reforming pathways. Despite their growing importance, fundamental investigations of these highly functional molecules on key catalyst surfaces are rare. Design of catalysts for selective upgrading of furanic compounds to desired products requires an improved understanding of their interactions with transition metal surfaces.

In this contribution, we report on experimental and computational investigations of a variety of furanic compounds, including 2(5H)-furanone, gamma-butyrolactone, 2,3-dihydrofuran, 2,5-dihydrofuran, tetrahydrofuran, furfural, and furfuryl alcohol, on the (111) surfaces of Pd and Pt. Temperature programmed desorption, high resolution electron energy loss spectroscopy, and density functional theory calculations were employed to map out adsorption and reaction pathways for these compounds. These studies reveal that the reactivity of the furan rings is strongly affected by the presence and position of unsaturated C=C bonds as part of the ring, as well as by the oxygenated functional group (ester versus ether). They also show that furanic ?ligands? attached to key reactive functional groups, such as alcohols and aldehydes, strongly influences the reactivity of those groups. Implications of these findings for reactions of furanic compounds over heterogeneous catalysts will be discussed.