XAFS Characterization of Highly Active Alumina-Supported Molybdenum Phosphide Catalysts (MoP/Al2O3) for Hydrotreating

Alumina-supported molybdenum phosphide (MoP/Al2O3) catalysts were prepared by temperature-programmed reduction of supported phosphate precursors in H2 at 0.083 K s-1 to 1123 K. The catalysts had excellent activity in the simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene at realistic conditions [P = 3.1 MPa (450 psig) and T = 643 K (370 °C)]. The catalysts surpassed the performance of a sulfided commercial Ni−Mo−S/Al2O3 catalyst in both HDN and HDS. X-ray absorption fine structure (XAFS) analysis of the supported samples indicated the presence of dispersed species retaining metallic bonding with a characteristic Mo−P distance of 0.243 nm but showing considerable attenuation in Mo−Mo linkages.