Activity, selectivity and regeneration of copper molybdate as a catalyst for the hydrodeoxygenation under flow conditions

Chemical processing of biomass derived feedstocks is one of the main vectors for the sustainable production of chemicals and fuels. Hydrodeoxygenation of oxygenated bio-based intermediates using molecular hydrogen is particularly attractive to sustainably produce aromatics and fuels. Herein we investigated catalytic performance of CuMoO4, benchmarked to MoO3 and NiMoO4 catalysts, in the hydrodeoxygenation of anisole under flow conditions, focusing on activation / re-activation cycles. Present results indicated a superior activity of the CuMoO4 phase and more importantly higher product selectivity to oxygen-free aromatics associated with limited activity toward the hydrogen-assisted decomposition of aromatic rings to methane. The regeneration experiments depicted a decisive role of an oxidative step followed directly by an additional reductive step to bring the catalyst to its highest catalytic activity again after on stream deactivation. Based on a multitude of surface/bulk-sensitive characterizations including in situ X-ray diffraction, Raman and X-ray photoelectron spectroscopy measurements, supported by thermal analysis of fresh and spent catalysts, it can be concluded, that the highest activity is correlated with the formation of a molybdenum oxycarbohydride phase which is promoted by Cu. Surface segregation of Cu species and build-up of surface carbon can be correlated to deactivation which can be reverted by the oxidative treatment.