Journal of Physical Chemistry B, Vol.105, No.21, 4961-4966, 2001
XAFS characterization of highly active alumina-supported molybdenum phosphide catalysts (MoP/Al(2)0(3)) for hydrotreating
Alumina-supported molybdenum phosphide (MoP/Al2O3) catalysts were prepared by temperature-programmed reduction of supported phosphate precursors in H-2 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 degreesC)]. 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.