Nickel promoter effect in rhenium catalysts for valorization of bio-oil model molecules

In the present work, the promoter effect of nickel over rhenium-supported catalysts was studied for the valorization of bio-oil model compounds. The catalysts were characterized by X-ray diffraction, N₂ adsorption isotherms at −196 °C, temperature programmed reduction, NH₃-temperature programmed desorption, CO chemisorption, and X-ray photoelectron spectroscopy. The catalytic performance was evaluated in a batch reactor at 350 °C and 50 bar of H₂. The characterization results show that two phenomena occur with the inclusion of Ni through post-impregnation: A higher exposure of rhenium phases and formation of ReC and metallic Re at higher Ni contents and an electronic transfer from Ni to Re. The catalysts were evaluated for the hydrodeoxygenation reaction (HDO) of guaiacol used as a bio-oil model compound. The most active catalysts were the Re-Ni(3 %)/AC and Re-Ni(5 %)/AC samples. Cyclohexanol and cyclohexane were the main products obtained from the hydrogenation of phenol promoted by the reduced rhenium species.