(521c) Transition-Metal-Phosphide-Decorated De-Aluminated Zeolites As Regenerable and Deactivation-Resistant Biomass Pyrolysis Catalysts.

Biomass pyrolysis like wood is a potential strategy for converting abundant, renewable resources into a liquid fuel and chemical precursor called bio-oil. In the absence of a catalyst or hydrogen co-feed, the resulting bio-oil typically contains up to 50wt% oxygen atoms, and is highly corrosive and thermally unstable; together, these qualities make non-catalytically-produced bio-oil unusable as a liquid fuel, and difficult to upgrade using conventional refining technologies. Catalysts such as zeolites or hydrodeoxygenation-active materials can be utilized to effect partial oxygen removal during the initial biomass conversion step via dehydration and/or hydrodeoxygenation reactions, resulting in bio-oils with improved properties that are more readily upgraded into finished products using conventional refinery infrastructure. However, alkali and alkaline earth metal contaminants entrained in natural biomass resources quickly deactivate conventional catalysts; this dynamic has prevented catalytic biomass pyrolysis technologies from being meaningfully scaled-up. In this work, we report a novel series of catalyst formulations comprising dealuminated zeolites decorated with transition-metal phosphides. The dealuminated zeolites contain silanol nests which retain partial Bronsted acidity vs. their parent aluminosilicates, so that acid-catalyzed dehydration reactions of the oxygenated biomass molecules are still enabled, though entrained alkali and alkaline earth metal poisons are bound to Bronsted sites more weakly. The transition metal phosphide sites, together with a hydrogen co-feed, facilitate further deoxygenation of the biomass-derived molecules via hydrodeoxygenation reactions. Importantly, the dealuminated zeolites and transition metal phosphides are hydrothermally stable at low pH, allowing for regeneration of the catalysts via leaching of the basic metal poisons in concentrated nitric acid. Together, these characteristics represent a new family of biomass conversion catalysts which resist deactivation by the high concentrations (~ wt%) of catalyst poisons entrained in biomass, while allowing for regeneration of reuse of the catalysts and the recovery of valuable biomass nutrients in the form of metal nitrate fertilizers.