Journal of the American Chemical Society, Vol.133, No.50, 20528-20535, 2011
Glycolaldehyde as a Probe Molecule for Biomass Derivatives: Reaction of C-OH and C=O Functional Groups on Monolayer Ni Surfaces
Controlling the activity and selectivity of converting biomass derivatives to syngas (H(2) and CO) is critical for the utilization of biomass feedstocks as renewable sources for chemicals and fuels. One key chemistry in the conversion is the selective bond scission of the C-OH and C=O functionalities, which are present in many biomass derivatives. Because of the high molecular weight and low vapor pressure, it is relatively difficult to perform fundamental surface science studies of C6 sugars, such as glucose and fructose, using ultrahigh vacuum techniques. Glycolaldehyde (HOCH(2)CH=O) is the smallest molecule that contains both the C-OH and CO functional groups, as well as the same C/O ratio as C6 sugars, and thus is selected as a probe molecule in the current study to determine how the presence of the C=O bond affects the reaction mechanism. Using a combination of density functional theory calculations and experimental measurements, our results indicate that the reaction pathway of glycolaldehyde to produce syngas can be enhanced by supporting monolayer Ni on a Pt substrate, which shows higher activity than either of the parent metals. Furthermore, the Pt substrate can be replaced by tungsten monocarbide to achieve similar activity and selectivity, indicating the possibility of using Ni/WC to replace Ni/Pt as active and selective catalysts with higher stability and lower cost.