High-Loading Nickel Phosphide Catalysts Supported on SiO2–TiO2 for Hydrodeoxygenation of Guaiacol

High-loading Ni x P y catalysts supported on SiO2–TiO2 binary oxides with different Si/Ti atomic ratios were prepared by liquid-phase phosphidation using triphenylphosphine (PPh3) and valued for the hydrodeoxygenation (HDO) of guaiacol. The samples synthesized were characterized by N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and ammonia temperature-programmed desorption. The XRD and XPS results showed that the Ni2P/Ni12P5 mixed phase was formed when SiO2–TiO2 binary oxides were employed as supports, whereas only Ni2P and Ni12P5 phases were produced on SiO2 and TiO2 single oxides, respectively. XPS analysis showed that TiO2–x species were generated on the surface of the catalyst during the reduction of the precursor, and the electron transfer occurred from TiO2–x species to the Ni x P y surface. TiO2–x species on the Ni x P y surface would contribute to the high HDO activity of guaiacol on Ni x P y catalysts because the presence of TiO2–x species promoted the adsorption of guaiacol and activation of the C–O bond in the guaiacol molecule. HDO reaction of guaiacol on Ni x P y catalysts dramatically followed the hydrogenation path owing to the high hydrogenation activity of Ni x P y catalysts.