Characterization of unsupported NiMo hydrodesulfurization catalysts by oxygen chemisorption

Abstract

The hydrodesulfurization (HDS) of the refractory compound 4,6-dimethyldibenzothiophene (DMDBT) normally proceeds through a hydrogenation pathway that removes the planarity of the ring system and makes the hindered sulfur atom more accessible to the desulfurization centers. In this study, a highly active dispersed bimetallic NiFeP catalyst is found to have high selectivity for a direct desulfurization pathway, which does not require prior hydrogenation. The compound has equal numbers of Ni and Fe atoms which extended X-ray absorption fine structure analysis indicates are distributed randomly in the hexagonal Fe2P structure, with just a slight enrichment of Fe on the surface. This is supported by density functional theory calculations. The remarkable properties of the catalyst are ascribed to a ligand effect of Fe on the active Ni atoms.