Support Effects of Ni2P Catalysts on the Hydrodeoxygenation of Guaiacol: In Situ XAFS Studies

The hydrodeoxygenation (HDO) of guaiacol was investigated over SiO2, ZrO2, and active carbon (AC) supported Ni2P catalysts. The physical properties of the catalysts were analyzed by temperature-programmed reduction (H-2-TPR), CO-uptake chemisorption, and N-2 physisorption. X-ray diffraction and extended X-ray adsorption fine structure spectroscopy were used to obtain structural properties for the supported Ni2P catalysts. The HDO was tested in a batch reactor at 573 K and 30 atm. The Ni2P/SiO2 catalyst underwent a decrease in the HDO conversion from 87 to 30 % for the first and second run of reaction. However, the Ni2P/ZrO2 and Ni2P/AC catalysts showed a little low but stable HDO conversions of 72 and 46 %, respectively. The in situ XAFS analysis revealed that differently from the cases of Ni2P/ZrO2 or and Ni2P/AC catalysts, the local structure of the Ni2P on SiO2 support underwent an oxidation to form nickel phosphate during the reaction, demonstrating that the SiO2 based Ni2P was vulnerable to the water or hydroxyl group of the reactant due to the hydrophilic nature of SiO2 support.