Thermochemical conversion of biomass to produce drop-in quality biofuels typically involves hydrodeoxygenation (HDO) steps following catalytic fast pyrolysis (CFP) to remove excess oxygen and create a more stable bio-oil product [1]. HDO reactions are performed by co-feeding the vapor-phase product from CFP and H2 gas over a bi-functional catalyst [2]. Noble-metal catalysts supported on reducible metal oxides (e.g., Pt/TiO2) have been shown to be active and selective toward these HDO reactions, with recent work aiming to elucidate the role of the various Pt/TiO2 actives sites (i.e., Pt-metal, TiO2-support, Pt-TiO2-interfacial sites) in the competing desired deoxygenation and undesired decarboxylation/decarbonylation reactions for important classes of CFP vapor model compounds [3, 4]. Carboxylic acids are one important class of bio-derived compounds that has not been studied extensively for HDO on Pt/TiO2, particularly at the atomic level. Past experimental work evaluating both Pt/C and Pt/TiO2 catalysts for acetic acid HDO demonstrated that the former is more selective toward C-C bond-dissociation products, whereas the latter favors C-O bond-dissication products [5]. The work summarized in this presentation builds off of these studies, utilizing atomic-scale modeling to discern the role of Pt-metal and Pt-TiO2-interfacial sites in promoting key C-C bond-breaking, C-O bond-breaking, and (de)hydrogenation steps in acetic acid HDO. By considering Pt(111) and Pt-TiO2-interface surface models, adsorption and reaction energetics calculated by density funcational theory provide fundamental insights into the role of both interfacial sites and oxygen vacancies in promoting desired deoxygenation pathways over undesired decarboxylation/decarbonylation pathways.

Assessing the role of interfacial and metal sites in Pt/TiO2-catalyzed acetic acid hydrodeoxygenation

ACS Spring Meeting 2021

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