EFFECT OF CALCINATION AND WATER EXTRACTION ON THE DISTRIBUTION OF THE ACTIVE COMPONENTS IN THE OXIDE FORM OF PHOSPHORUS-NICKEL-MOLYBDENUM ALUMINA CATALYSTS FOR HYDRODESULFURIZATION

A series of co-impregnated P-Ni-Mo/Al2O3 catalysts of varying phosphorus content is studied. The dispersion of the active components in the oxide form of the samples is evaluated by XPS. Calcination of the samples increases the dispersion of molybdenum. This effect is most strongly manifested for samples with phosphorus concentrations of 1.4 and 2.7 wt.-% P2O5. Phosphorus impedes the diffusion of nickel in the bulk of the support during calcination. The largest amount of removed molybdenum, nickel and aluminium during water extraction is observed in the samples containing 2.7 and 4.2 wt.-% P2O5. The distribution of molybdenum in these samples is close to a monolayer. Only a small amount of phosphorus participates in the formation of water-soluble heteropoly compounds. The amount of extracted phosphorus is independent of its initial content. Phosphorus distribution is in the form of a monolayer for a phosphorus-to-aluminium concentration ratio of 6·10-2, both for P-Ni/Al2O3 and P-Ni-Mo/Al2O3 samples. © 1990.