Hydrodeoxygenation of phenolic compounds and raw lignin-oil over bimetallic RuNi catalyst: An experimental and modeling study focusing on adsorption properties

Bimetallic catalysts are usually superior to monometallic catalysts due to the synergistic effect of two metal species, and the enhanced adsorption properties by the interaction between two metal species played an important role in catalytic reaction. In this study, the promotion relationship between the adsorption properties and the hydrodeoxygenation (HDO) performances of a bimetallic RuNi/SiO2-ZrO2 catalyst were investigated based on an experimental and modeling study, by comparison to the monometallic catalysts. RuNi catalyst presented a much better performance on guaiacol HDO than Ru and Ni catalysts, with the yield of cyclohexane product close to 100%. Characterization results exhibited a strong interaction between two metal species and an electron transfer from Ru to Ni, which led to a higher spin-up d-band center value of surface atoms and thereby a different adsorption property from the monometallic catalysts. Adsorption property mainly included the adsorption of substrate and the adsorption of hydrogen. The former one is the first step, and the latter one is the second step to trigger the occurrence of HDO reaction. The good adsorption of substrate and the strong adsorption of hydrogen in RuNi catalyst were the crucial factors for its better catalytic HDO performance than the monometallic catalysts. The modeling results by DFT calculation confirmed the experimental results and revealed the promotion mechanism. Moreover, bimetallic RuNi catalyst also showed a good performance on the HDO of other phenolic compounds and raw lignin-oil. This work highlighted the promotion effect of adsorption properties on the HDO reaction.