Effect of Pr and Ce on the activity of Ni₂P catalyst prepared by low temperature reduction in hydrodesulphurization

The Ni₂P-L, Pr-Ni₂P-L and Ce-Ni₂P-L catalysts were prepared by thermal decomposition of hypophosphites and reduced at low temperature; they were characterized by X-ray diffraction (XRD), temperature programmed reduction with hydrogen (H₂-TPR), nitrogen physisorption, CO adsorption, and X-ray photoelectron spectroscopy (XPS). The effect of the rare earth praseodymium (Pr) or cerium (Ce) elements on the activity of Ni₂P-L catalyst in hydrodesulfurization (HDS) was investigated with dibenzothiophene (DBT) as a model compound. The results indicated that the addition of Pr and Ce can suppress the formation of Ni₅P₄ and other mixed crystal phases and then promote the formation of Ni₂P phase. After adding the rare earth metals, the selectivity to BP over the Ni₂P catalyst is enhanced greatly, though the total HDS activity is decreased slightly.