Ru0.05Ce0.95O2 Solid Solution Derived Ru Catalyst Enables Selective Hydrodeoxygenation of m-Cresol to Toluene

Selective hydrodeoxygenation (HDO) of biomass lignin-derived phenolic compounds to aromatics is a demanding reaction. Oxophilic Ru based catalysts can catalyze direct deoxygenation but suffer from competing C-C hydrogenolysis to CH4 at 350 degrees C and hydrogenation of phenyl ring at 250 degrees C under atmospheric pressure. In this work, a solid solution Ru0.05Ce0.95O2 catalyst was hydrothermally synthesized, characterized and tested for HDO of m-cresol. The Ru species 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. In contrast to nonselective Ru/SiO2, Ru0.05Ce0.95O2 selectively catalyzes deoxygenation to toluene while significantly inhibits C-C hydrogenolysis and hydrogenation. Moreover, the overall intrinsic HDO rate on Ru0.05Ce0.95O2 is 2.2 and 8.8 times higher than those on Ru/CeO2 and Ru/SiO2, respectively. The Ru-O-V-Ce sites were proposed to be the active sites for deoxygenation. Inhibition of C-C hydrogenolysis and phenyl hydrogenation can be ascribed to the reduced size of the Ru ensembles due to the strong interaction in the solid solution.

Automated summary

In this study, a solid solution Ru0.05Ce0.95O2 catalyst was used for the selective hydrodeoxygenation of m-cresol, demonstrating high oxygen vacancy concentration and the ability to catalyze toluene production with significant inhibition of competing hydrogenolysis and hydrogenation reactions. The active sites for deoxygenation were proposed to be Ru-O-V-Ce sites, and the inhibition of C-C hydrogenolysis and phenyl hydrogenation was attributed to the reduced size of the Ru ensembles due to strong interaction in the solid solution.