(120e) Ethylene Glycol Reforming over Pt (111): Modeling of C-C Versus C-O Bond Cleavage Selectivity in Vapor and Aqueous Environments

Catalytic conversion of biomass-derived oxygenates to fuels and value-added chemicals is a promising strategy in the search for renewable and sustainable energy sources. Decomposition chemistry on a metal catalyst is a complex network of multiple series and parallel pathways leading to formation of hydrogen, alkanes, and lighter oxygenates. The final product distribution ultimately depends on the sequence and competition of C-C, C-O, C-H, and O-H bonds scissions. Ethylene glycol (EG) is the simplest such molecule to contain all of C-C, C-O, C-H, and O-H bonds and a C/O stoichiometry of 1:1, and has received significant attention as a model molecule of larger biomass-derived polyols. While the reaction mechanism of EG reforming is to some degree understood at the metal-gas interface, lack of a well-established methodology for describing the influence of a complex liquid phase on a reaction across a solid-liquid interface has hindered similar theoretical studies in an aqueous environment.

            In this talk, we present an application of our recently developed iSMS¹ methodology to study the mechanism of EG reforming over Pt (111) in water. Reaction free-energies and free-energy barriers for all elementary reactions in vapor phase are computed within the framework of periodic planewave DFT calculations. The effect of water is then included through a combination of Gaussian-type orbital calculations and COSMO-RS calculations as required by iSMS. Finally, detailed microkinetic models are developed for both vapor and aqueous phases to provide insights into the effect of an aqueous environment on the activity and selectivity of the metal catalyst.

1.            Faheem, M.; Suthirakun, S.; Heyden, A. J. Phys. Chem. C 2012, 116, 22458-22462.