THE FUNCTION OF PHOSPHORUS , NICKEL AND H2S IN THE HDN OF PIPERIDINE AND PYRIDINE OVER NiMoP/Al2O3 CATALYSTS
The effect of phosphorus in the hydrodenitrogenation (HDN) of piperidine and pyridine over NiMo/Al2O3 catalysts was studied. In the absence of H2S no effect of P was found, but in the presence of H2S the HDN activity of NiMo/Al2O3 catalysts decreased as the P content in the catalysts increased. It is concluded that phosphorus has a negative effect on the C-N bond cleavage in piperidine, as well as on the subsequent hydrogenation of the C5 alkene intermediates. Also the influence of Ni was found to depend on the reaction conditions. A substantial promotion effect of Ni could only be observed in the presence of H2S, both in the C-N bond cleavage of piperidine and in the pyridine hydrogenation. The activity for the HDN of piperidine of NiMo(P)/Al2O3 catalysts increased with increasing H2S concentration up to H2S/H2 = 12.5 × 10−3 mol/mol.