Hydrodeoxygenation of Guaiacol on Ru Catalysts: Influence of TiO₂-ZrO₂ Composite Oxide Supports

TiO₂-ZrO₂ composite oxides with a series of different Ti/Zr atomic ratios were synthesized by using a deposition precipitation method and employed as supports to prepare Ru catalysts. The physicochemical characteristics of Ru catalysts were tested by N₂ adsorption, CO chemisorption, X-ray diffraction, H₂ temperature-programmed reduction, scanning electron microscopy, transmission electron microscopy, NH₃ adsorption, and X-ray photoelectron spectroscopy, and their catalytic hydrodeoxygenation (HDO) performance was evaluated by using guaiacol as a model compound. The Ru/TiO₂ catalyst exhibits low HDO activity due to the surface modification of Ru particles with Ti³⁺ species formed during the reduction of Ru/TiO₂. The HDO activity of Ru catalysts was significantly promoted by ZrO₂ in the supports because it can hinder the migration of Ti³⁺ species onto the surface of Ru particles and thus more Ru active sites are exposed. The higher selectivity of benzene for Ru catalysts supported on TiO₂-ZrO₂ composite oxides suggests that they are promising supports for Ru catalysts in the HDO reaction of guaiacol.