(704c) Evaluating Tungsten Doped Molybdenum Carbide for the Selective Hydrodeoxygenation of Real Bio-Oil: A DFT Study Using Lignin and Carbohydrates Derived Bio-Oil Components

Catalytic upgrading is one of the viable ways to improve the quality of bio-oil, generated via pyrolysis of lignocellulosic biomass. Recently, transition metal carbides attracted significant attention owing to their noble metal-like properties. Monometallic carbide, especially, Mo₂C, showed promising results in the hydrodeoxygenation (HDO) of bio-oil-derived compounds. However, it results in a mixture of deoxygenated and saturated products resulting in unnecessary high consumption of H₂. In this regard, bimetallic carbides have recently drawn much attention to selectively enhance the deoxygenation characteristics of monometallic carbides. In this work, a novel tungsten doped molybdenum carbide (MoWC), synthesized and characterized using theory and experiments is examined. This study investigated the HDO performance of the MoWC catalyst and compares it to that of its monometallic counterpart using six major compounds that constitute bio-oil derived from pyrolysis of real biomass: 5-HMF, Acetic acid, Guaiacol, Eugenol, Levoglucosan, Methyl glyoxal, and Vanillin. Furthermore, they encompass the vast majority of oxygen-containing functional groups present in bio-oil components. The generally accepted mechanism for HDO includes two major pathways: i) direct deoxygenation (DDO) and ii) hydrogenation–dehydration (HYD). The presence of oxophilic tungsten in MoWC significantly reduces the DDO barriers for different bond types, specifically C_aryl– O /C – O /C = O bonds (E_barriers= 4 - 60 kJ/mol) in comparison to the corresponding monometallic catalyst Mo₂C, which is relatively less active, particularly for C = O bonds. We also examined the alternative route (HYD), and demonstrated that MoWC has a strong preference for DDO over HYD than Mo₂C, widening the gap between the two competing pathways and reducing excessive hydrogen utilization. This work illustrates that MoWC catalyst could be potentially used for the HDO of real bio-oil mixture.