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.