Preparation and performance of noble metal phosphides supported on silica as new hydrodesulfurization catalysts

Preparation of noble metal (NM) (Rh, Pd, Ru, Pt) phosphide species and their catalytic activities for hydrodesulfurization (HDS) of thiophene were investigated. Noble metal phosphides (NMXPY) catalysts were prepared by reduction of P-added NM (NM-P) supported on silica (SiO_2) with hydrogen. Hydrogen consumption peaks at around 350–700 °C, which were attributed to the formation of NMXPY, were observed in temperature-programmed reduction (TPR) spectra of all NM-P/SiO_2. Furthermore, X-ray diffraction (XRD) patterns of NM-P/SiO_2 indicate that NMXPY (Rh_2P, Pd_P, Ru_2P, PtP_2) were formed by hydrogen reduction at high temperature. The reduction temperature strongly affected HDS activities of NM-P/SiO_2 catalysts. The NM-P/SiO_2 catalysts, other than Pt, showed higher HDS activities than NM/SiO_2 catalysts. The HDS activity of the Rh-P/SiO_2 catalyst was the highest among those of NM-P/SiO2 catalysts. This activity was higher than that of the Ni-P catalyst and was the same as that of pre-sulfided CoMoP/Al_2O_3 catalyst. Furthermore, the Rh-P/SiO_2 catalyst showed stable activity even after reaction for 30 h. The XRD, transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) results revealed that the formation of small Rh_2P particles and suitable P addition to form Rh_2P caused the high HDS activity of the Rh-P catalyst.