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

High-loading NixPy 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 N-2 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 NixPy surface. TiO2-x species on the NixPy surface would contribute to the high HDO activity of guaiacol on NixPy 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 NixPy catalysts dramatically followed the hydrogenation path owing to the high hydrogenation activity of NixPy catalysts.