Selective Deoxygenation of Aldehydes: The Reaction of Acetaldehyde and Glycolaldehyde on Zn/Pt(111) Bimetallic Surfaces

Temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) were used to characterize the adsorption and reaction of acetaldehyde and glycolaldehyde on Zn-modified Pt(111) surfaces. The barriers for both C-H and C-C bond cleavage in adsorbed aldehydes were found to be higher on Pt(111) decorated with Zn adatoms or containing a PtZn near-surface alloy, compared to Zn-free Pt(111). This results in stabilization of aldehydes adsorbed in an eta(2)(C,O) bonding configuration and hinders formation of acyl intermediates as typically occurs on group 10 metals. Adsorbed eta(2)(C,O) acetaldehyde and glycolaldehyde on Zn-modified Pt(111) were found to undergo selective C-O bond scission to produce adsorbed hydrocarbon intermediates and hydroxyl groups, while decarbonylation of acyl species to produce CO and hydrocarbon fragments was the primary pathway on the Zn-free surface. These results provide mechanistic insights that are useful for the design of hydrodeoxygenation catalysts for the upgrading of oxygenates derived from biomass, such as glucose and furfural.