Hydrodeoxygenation of Guaiacol over Ceria-Zirconia Catalysts

• Published in: ChemSusChem 2015-06, Vol.8 (12), p.2073-2083
• Main Authors: Schimming, Sarah M., LaMont, Onaje D., König, Michael, Rogers, Allyson K., D'Amico, Andrew D., Yung, Matthew M., Sievers, Carsten
• Format: Article
• Language: English
• Subjects: arenes; bio-oil; Catalysis; Cerium - chemistry; Guaiacol - chemistry; heterogeneous catalysis; hydrodeoxygenation; Oxygen - chemistry; oxygen vacancies; Temperature; Zirconium - chemistry
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201500317

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 1 atm and 275–400 °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 60 mol % CeO2 and 40 mol % ZrO2. Pseudo‐first‐order activation energies of 97–114 kJ mol−1 are observed over the mixed metal oxide catalysts. None of the catalysts show significant deactivation during 72 h 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. Guaiacol to action: Ceria–zirconia catalysts catalyze the hydrodeoxygenation of guaiacol in the absence of reduced metal particles. The functional groups are removed, but the aromatic ring is not hydrogenated. Oxygen vacancies are the active sites for hydrodeoxygenation.