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 biooil containing large amounts of phenolic compounds into renewable hydrocarbon products.