Activity and stability of Mo₂C/ZrO₂ as catalyst for hydrodeoxygenation of mixtures of phenol and 1-octanol

Mo₂C/ZrO₂ was investigated as catalyst for hydrodeoxygenation (HDO) of phenol in 1-octanol as a simplified bio-oil model system in a fixed-bed setup at 100bar. Mo₂C/ZrO₂ selectively converted phenol to benzene above 320°C. During long-term testing, limited stability of the catalyst was observed, with the conversion of 1-octanol and phenol decreasing from 70% to 37% and from 37% to 19%, respectively, over 76h of operation. Repeating the experiment but also co-feeding 30% water, the catalyst deactivated completely within 12h of operation. Thermodynamic calculations and in situ XRD analysis showed that Mo₂C is transformed to MoO₂ in the presence of water at the given conditions, and this was probably the source of deactivation in the experiments. Thus, Mo₂C-based catalyst for HDO seems interesting, but requires further stabilization or regeneration of the carbide phase as bio-oil contains high levels of water and water is a by-product during HDO.