Characterization And Catalytic Performance Of RuCeO₂ Solid Solution For Hydrodeoxygenation Of M-Cresol

As a renewable energy resource,biomass has extensive application in replacing fossil energy such as coal,petroleum,and natural gas.The bio-oils obtained by fast pyrolysis of lignin could be used for producing fuels and valuable products,but it contains a large amount of guaiacol,phenol,ketones,and other oxygen-containing compounds.Therefore,the upgrading of bio-oil is an important processing goal for application of biomass.Recently,noble metal catalysts which have high hydrodeoxygenation reaction rates have attracted more attention around the world.However,the reaction mechanism of phenolics hydrodeoxygenation is not clear yet.In this work,we developed RuCeO₂ solid solution catalysts,using m-cresol as model compound,to explore the reaction mechanism of RuCeO₂ solid solution catalyzing the hydrodeoxygenation of m-cresol.Indeed,we also studied the relationship between the different Ru/Ce ratios of RuCeO₂ solid solution and m-cresol deoxygenation reactivity.RuCeO₂ solid solution were prepared by modified hydrothermal method and evaluated in vapor phase hydrodeoxygenation of m-cresol at 350℃ and atmospheric pressure.The results showed that RuCeO₂ catalyst was more than 2 times active than the Ru/Ce O₂ and larger yield of toluene than that over Ru/Si O₂ at the same space time.These results suggest that RuCeO₂ solid solution is highly dispersed in the solid solution as isolated atoms and/or subnanometer clusters as a result of strong Ru-O-Ce interaction,and the catalyst shows high concentration of oxygen vacancies,which is essential for promoting the reaction rates of direct deoxygenation.The catalytic performance of different Ru/Ce ratios of Ru_xCe_1-xO₂ solid solution catalysts have been studied.We found that the direct deoxygenation of m-cresol to toluene mainly occurs at low m-cresol conversion,while methane is the dominate product at high m-cresol conversion.With the amount of Ru increasing,some Ru species of Ru_xCe_1-xO₂ form agglomerated clusters on the surface of Ce O₂ which promotes the C-C hydrolysis path of m-cresol to form methane.