Active sites of Ni2P/SiO2 catalyst for hydrodeoxygenation of guaiacol: A joint XAFS and DFT study

[Display omitted] •Ni2P/SiO2 catalyst was active for guaiacol hydrodeoxygenation (HDO).•HDO followed direct deoxygenation or prehydrogenation pathway.•Threefold hollow Ni site and neighboring P site in Ni2P were active in HDO.•Distribution of H and OH groups on Ni2P surface influenced HDO pathways. A Ni2P/SiO2 catalyst was prepared by temperature-programed reduction (TPR), and applied for the hydrodeoxygenation of guaiacol. The physical properties of the catalyst samples were characterized by N2 adsorption/desorption isotherms and CO uptake chemisorption. X-ray diffraction (XRD) and extended X-ray absorption fine structure (XAFS) spectroscopy were used to obtain structural properties for the supported Ni2P catalysts. Hydrodeoxygenation (HDO) tests were performed in a continuous flow fixed-bed reactor at 523–573K, and 1 or 8atm, and an LHSV of 2.0h−1. The Ni2P/SiO2 gave an HDO conversion over 90% with two different reaction pathways being identified; at 1atm direct deoxygenation was dominant to produce benzene, and at 8atm prehydrogenation followed by deoxygenation was preferred to produce cyclohexane. A combined X-ray absorption fine structure spectroscopy and density functional theory analysis revealed that the active site of Ni2P catalysts is composed of threefold hollow Ni and P sites which lead to adsorption of H or OH groups. These results suggest that relative populations of H or OH groups on Ni or P sites of Ni2P surface have an impact on overall reaction pathways of the HDO.