Ni2P and CoP catalysts prepared from phosphite-type precursors for HDS–HDN competitive reactions Original Research Article

Silica-supported nickel and cobalt phosphide catalysts were synthesized with low metal-loading (5 wt%). The formation of Ni2P and CoP phases was achieved by temperature-programmed reduction of phosphite-based precursors, Ni(HPO3H)2 and Co(HPO3H)2, respectively. The catalysts were characterized by X-ray fluorescence (XRFS), N2 adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and elemental analysis (CNHS). These catalysts were tested in the individual reactions of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of quinoline (Q), and also in the simultaneous HDS and HDN reactions. These tests were conducted by feeding 3000 ppm of DBT or 3000 ppm of Q. Additional tests were performed with the aim to evaluate S-removal capability by keeping constant Q concentration in the feed (3000 ppm) and varying DBT concentration (200 and 2000 ppm). The catalytic results show that these phosphide catalysts achieve high DBT and Q conversion values at high temperatures though the rate of HDS reaction is higher than that of HDN. In all cases Ni2P is more active than CoP. Moreover, the presence of N-containing molecules in the feed does not affect the S-removal as sulfur is almost completely removed after 48 h on-stream.