Molybdenum-oxide (MoO3) is a promising catalyst candidate for hydrodeoxygenation (HDO) of pyrolysis vapor or liquefaction products to renewable fuels or value-added chemicals. Density functional theory is used to study the mechanism and active site requirements for HDO of furan over the MoO3(010) facet and contrast our results with prior work on hydrodesulfurization (HDS) of thiophene over MoS2 model catalysts. The potential energy diagram for HDO over a realistically terminated MoO3(010) surface facet reveals that the elementary reaction steps for deoxygenation are facile, but the formation of oxygen-vacancies is slow and endothermic. In general, HDO over MoO(3 )and HDS over MoS2 exhibit mechanistic similarities, which suggests that knowledge transfer from the mature HDS system to the emerging field of HDO catalysis is possible. For example, transition metal promotion of MoO3 resulted in an improvement of the kinetics and thermodynamics of oxygen vacancy formation, similar to Co and Ni promotion of MoS2. (C) 2018 American Institute of Chemical Engineers