Poisoning of Pt/γ-AlO Aqueous Phase Reforming Catalysts by Ketone and Diketone-Derived Surface Species.

Strong adsorption of ketone and diketone byproducts and their fragmentation products during the aqueous phase reforming of biomass derived oxygenates is believed to be responsible for the deactivation of supported Pt catalysts. This study involves a combined experimental and theoretical approach to demonstrate the interactions of several model di/ketone poisons with Pt/γ-AlO catalysts. Particular di/ketones were selected to reveal the effects of hydroxyl groups (acetone, hydroxyacetone), conjugation with C=C bonds (mesityl oxide), intramolecular distance between carbonyls in diketones (2,3-butanedione, 2,4-pentanedione), and length of terminal alkyl chains (3,4-hexanedione).

Differences in solvation thermodynamics of oxygenates at Pt/AlO perimeter versus Pt(111) terrace sites.

A prominent role of water in aqueous-phase heterogeneous catalysis is to modify free energies; however, intuition about how is based largely on pure metal surfaces or even homogeneous solutions. Using multiscale modeling with explicit liquid water molecules, we show that the influence of water on the free energies of adsorbates at metal/support interfaces is different than that on pure metal surfaces. We specifically compute free energies of solvation for methanol and its constituents on a Pt/AlO catalyst and compare the results to analogous values calculated on a pure Pt catalyst.

Influence of an electrified interface on the entropy and energy of solvation of methanol oxidation intermediates on platinum(111) under explicit solvation.

Liquid water and electric fields play significant roles in phenomena occurring at catalytic and electrocatalytic interfaces; however, how their interplay influences interfacial energetics remains uncertain. Electric fields control the orientations of water molecules, which we hypothesized would influence the solvation thermodynamics of surface species. To explore this hypothesis, we used multiscale simulations involving density functional theory and classical molecular dynamics.