Oxygenate Chemistry on Platinum-Molybdenum Bimetallic Surfaces

Biomass-derived compounds are highly functionalized, making them difficult to selectively process into a desired product because they can interact with the surface in multiple ways. Addition of oxophilic metals such as molybdenum to supported catalysts has been shown to facilitate C-O bond activation and influence selectivity for a number of deoxygenation reactions. However, the mechanism for the improvements is not known, hampering efforts to design better catalysts. Surface science techniques using single crystals can provide a fundamental understanding of the role of oxophilic metals as promoters to platinum group catalysts for deoxygenation reactions.

Our recent studies have focused on how oxophilic modifiers influence oxygenate chemistry. Temperature programmed desorption (TPD), Auger electron spectroscopy, and X-ray photoelectron spectroscopy have been used to investigate surface chemistry of simple probe molecules (hydrogen, oxygen, CO, water) as well as model compounds for biorefinery streams (2-methoxyethanol, cresol) on unmodified and Mo-coated Pt(111) surfaces. The results indicate that modifier sites influence the adsorption energies of both oxygenates and their decomposition intermediates. These results have been used to help explain observed trends from complementary investigations on supported bimetallic PtMo catalysts that show improved hydrodeoxygenation selectivity.