Hydrodeoxygenation of phenolic model compounds over zirconia supported Ir and Ni-catalysts

The hydrodeoxygenation (HDO) of three different phenolic model compounds, isoeugenol, guaiacol and vanillin was investigated using Ir/ZrO2 and Ni/ZrO2 as heterogeneous catalysts. The catalysts were prepared by incipient wetness impregnation and characterized by transmission electron microscopy, nitrogen adsorption, FTIR pyridine adsorption–desorption. The organic material in the spent catalysts was analyzed by organic elemental analysis and thermogravimetry. The results revealed that in guaiacol HDO at 250 °C under 30 bar total pressure the main product was cyclohexanol with 36% yield over Ni/ZrO2 while the total deoxygenation forming cyclohexane was limited to 2%. Ir/ZrO2 exhibited higher HDO activity compared to Ni/ZrO2 giving 14% yield of cyclohexane. Extensive formation of methane and ethane was also observed in guaiacol HDO. Hydrodeoxygenation of isoeugenol over Ir/ZrO2 resulted in maximally 33% yield of propylcyclohexane due to a low liquid phase mass balance. The main products in vanillin HDO at 100 °C in water was vanillyl alcohol.