Hydrodeoxygenation of Guaiacol over Ceria-Zirconia Catalysts

The hydrodeoxygenation of guaiacol is investigated over bulk ceria and ceria-zirconia catalysts with different elemental compositions. The reactions are performed in a flow reactor at 1atm and 275-400 degrees C. The primary products are phenol and catechol, whereas cresol and benzene are formed as secondary products. No products with hydrogenated rings are formed. The highest conversion of guaiacol is achieved over a catalyst containing 60mol% CeO2 and 40mol% ZrO2. Pseudo-first-order activation energies of 97-114kJmol(-1) are observed over the mixed metal oxide catalysts. None of the catalysts show significant deactivation during 72h on stream. The important physicochemical properties of the catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction, titration of oxygen vacancies, and temperature-programmed desorption of ammonia. On the basis of these experimental results, the reasons for the observed reactivity trends are identified.