Metal phosphide catalysts for the hydrotreatment of non-edible vegetable oils

Silica-supported catalysts of nickel, cobalt, iron, molybdenum, and tungsten metal phosphides (NiP/SiO2, CoP/SiO2, FeP/SiO2, MoP/SiO2, and WP/SiO2) with a metal-loading of 15 wt%, were synthesized by reduction of the corresponding phosphite precursors. The catalysts were characterized by N-2 adsorption-desorption, X-ray diffraction (XRD), CO pulse chemisorption, NH3 temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS). The activity of these catalysts was measured at 573 K, a liquid flow of 0.3 mL min(-1), a pressure of 2.0 MPa and a H-2/liquid ratio of 300 in a three-phase, trickle-bed reactor in the hydrotreatment of methyl laurate. The MoP/SiO2 catalyst was found to exhibit the best catalytic performance based on its higher active phase dispersion as measured by XRD, CO chemisorption and XPS analyses, along with its moderate acidity, which is higher with respect to the other studied catalysts. The reaction conditions using the MoP/SiO2 catalyst, the most active and selective to C-12 and C-11 hydrocarbons, were optimized. Optimal results can be obtained under the following conditions: 573 K, 2.0 MPa, and a liquid flow of 0.3 mL min(-1). Moreover, long-run experiments showed that the MoP/SiO2 catalyst exhibits stable catalytic behavior for at least 96 h.