Bimetallic Phosphide Catalysts for Biomass Upgrading Reactions

This thesis focuses on the synthesis and detailed characterizations of various bimetallic phosphides as well as their catalytic evaluation for hydrodeoxygenation and hydrogenation reactions of oxygenated biomass compounds. Extensive studies on the oxidation state of Mo-based bimetallic phosphides MMoP (M = Fe, Co, Ni) with x-ray photoelectron spectroscopy and x-ray absorption near edge spectroscopy show the relative oxidation of (i.e., Mo^δ+) is highly dependent on the charge transfer between the atoms in MMoP and most likely is the site for the interaction between the lone pair oxygen in phenol and the catalyst surface. Other bimetallic phosphides such as RuMoP are found to be active for low temperature hydrogenation reactions (<125°C) for various functionalized aromatics. Kinetic evaluations on monometallic and bimetallic Ru and Mo phosphides for furfural hydrogenation provide evidence for catalytic enhancement in bimetallic phosphides with a Ru:Mo:P ratio of 1:1:1 as the optimum composition for selective aldehyde conversion to alcohol. Lastly, bimetallic NiMoP and RuMoP are evaluated for a more complicated molecule such as cinnamaldehyde with conjugated C=C and C=O bond. NiMoP shows favorable selectivity to the hydrogenation of thermodynamically favored C=C bond. Meanwhile, bimetallic RuMoP favors the hydrogenation of C=O bond due to its surface electronics in combination with surface crowding by the products that prevents C=C adsorption. The studies in thesis emphasize the importance of finding the optimum surface electronics through material modifications in bimetallic phosphides for biomass upgrading reactions.