(177c) Exploring Pt-Wox Interactions in Hydrodeoxygenation Catalysts for Lignin Upgrading | AIChE

(177c) Exploring Pt-Wox Interactions in Hydrodeoxygenation Catalysts for Lignin Upgrading


Marlowe, J. - Presenter, Rutgers, The State University of New Jersey
Christopher, P., University of California-Riverside
Abu-Omar, M., University of California, Santa Barbara
The valorization of biomass-derived lignin holds great potential as a potential route for the sustainable production of primary chemicals such as benzene, toluene, and xylenes (BTX), but requires selective hydrodeoxygenation (HDO). To date, a catalytic system of acceptable selectivity and activity without also catalyzing over-hydrogenation to lower value alkanes has yet to be discovered. The most promising catalysts for this process are inverse oxide-on-metal MOx/Pt (M = W, Mo) catalysts, though the active site remains unidentified.

To elucidate the unique active site for HDO on these materials, Pt nanoparticles size and subsequent WOx coverage are varied on an inert silica support. CO probe molecule DRIFTS and CO chemisorption measurements give insight into the behavior of sub-monolayer oxide structures on Pt under reducing conditions, showing WOx migrated to preferentially decorate well-coordinated Pt sites, leaving under-coordinated Pt sites free for CO adsorption and presumably reactivity.

To connect this behavior to selective HDO, a series of Pt and WOx/Pt catalysts with Pt crystallite size from 1.1 nm to 5+ nm are investigated in the HDO reaction of a lignin model compound, dihydroeugenol (DHE). The results over monometallic Pt catalysts indicate that small Pt particles without WOx modification effectively catalyze deoxygenation, whereas large particles preferentially catalyze hydrogenation of the aromatic ring. This implicates that under-coordinated Pt sites, the same sites exposed at low coverages of WOx, are the likely active site for deoxygenation, whereas well-coordinated Pt sites are primarily active for hydrogenation.

HDO results over WOx/Pt catalysts varying both Pt size and WOx coverage elucidate 1.) the influence of Pt particle size on WOx-Pt interactions and 2.) the influence of WOx on HDO chemistry. This will shed light on whether the unique WOx/Pt reactivity in HDO stems from blocking hydrogenation sites or creating novel reactivity at WOx-Pt interfaces, driving C-O cleavage.