Liquid phase in situ hydrodeoxygenation of biomass-derived phenolic compounds to hydrocarbons over bifunctional catalysts

The objective of this study was to find an effective method for converting renewable biomass-derived phenolic compounds into hydrocarbons bio-fuel via in situ catalytic hydrodeoxygenation. The in situ hydrodeoxygenation of biomass-derived phenolic compounds was carried out in methanol-water solvent over bifunctional catalysts of Raney Ni and HZSM-5 or H-Beta. In the in situ hydrodeoxygenation, the hydrogen was donated by aqueous phase reforming of methanol without external hydrogen gas. This reaction pathway for liquid-phase in situ hydrodeoxygenation of phenolic monomers was based on methanol-water as a solvent, stepwise metal-catalyzed hydrogenation, acid-catalyzed dehydration, and metal-catalyzed hydrolysis. The three-step conversion process can be achieved by a one-pot procedure. When HZSM-5 (Si/Al ratio of 25) and Raney Ni were used as the bifunctional catalysts of in situ hydrodeoxygenation, more than 90% conversion of phenolic monomers and dimers, approximately 70-90% selectivity of cyclohexanes and hydrocarbons could be obtained at 220 °C with a reaction time of 7 h. The bifunctional catalysts combined Raney Ni with HZSM-5 can achieve the aqueous-phase reforming of methanol, which coupled with the in situ hydrodeoxygenation of phenolic compounds. Therefore, this in situ hydrodeoxygenation process with bifunctional catalysts provided an efficient route for upgrading bio-oil containing large amounts of phenolic compounds into renewable hydrocarbon products.