A highly dispersed Co/SiO₂–Al₂O₃ catalyst for hydrodeoxygenation of guaiacol to cyclohexane

Highly efficient and low-cost bio-oil upgrading process is critical for the realization of renewable biomass as the substitution for fossil oil in the production of biofuel. In this study, a highly dispersed Co/SiO₂–Al₂O₃ catalysts were prepared by simple wet impregnation, and its catalytical activity in the hydrodeoxygenation of guaiacol, one of the most key reactions of bio-oil upgrading, was evaluated. The as-prepared catalyst could provide a full conversion of guaiacol (100%) and 96.8% selectivity of cyclohexane under relatively mild conditions (250 °C, 2-MPa H₂, 1 h). The characterizations of the as-prepared Co/SiO₂–Al₂O₃ catalyst confirmed a highly dispersed Co particle with the SiO₂–Al₂O₃ support, which favored the selectivity of cyclohexane. In addition, both the synergy of Co⁰ and Co^δ+ species and the medium-strength acidic sites contributed to the high catalytical performance of the catalyst. According to the distribution of the products, the reaction path from guaiacol to cyclohexane was speculated. Furthermore, the Co/SiO₂–Al₂O₃ catalyst also possessed high stability and versatility. The above properties together with the easy preparation method entitled the Co/SiO₂–Al₂O₃ catalyst great potential as a non-noble metal catalyst for the scale-up applications in bio-oil upgrading process.