TiO2-Modified Pd/SiO2for Catalytic Hydrodeoxygenation of Guaiacol

TiO2-modified Pd/SiO2catalysts (TixPd/SiO2) have been prepared using wet impregnation and characterized with N2adsorption, X-ray diffraction, transmission electron microscopy, and temperature-programmed reduction. Their catalytic performance was examined for hydrodeoxygenation (HDO) of guaiacol as a model component of bio-oil. A smaller Pd particle size was obtained by the addition of TiO2, which may contribute to the high conversion of guaiacol on TixPd/SiO2. A strong interaction between TiO2and Pd occurred when the catalysts were reduced with H2at 500 °C. TiOxcovered on Pd particles can coordinate the oxygen atom in hydrogenation intermediates and activate the C–O bond that could contribute to the significantly enhanced deoxygenation activity. The results suggest that the catalytic HDO proceeds through hydrogenation of the benzene ring of guaiacol on Pd sites to form 2-methoxycyclohexanol, followed by deoxygenation on the sites at a reduced TiOx–Pd interface to generate cyclohexane.