Preparation of new oxidic precursors based on heteropolyanions for efficient hydrocracking catalysts

摘要

Hydrocracking catalysts are bifunctional, associating a hydro—deshydrogenating function with an acidic one. If gas oil is the required product, NiW/silica—alumina is the most appropriate catalyst. It is obtained through the sulfidation of an oxidic precursor that is prepared by incipient wetness impregnation of the support by ammonium metatungstate and nickel nitrate solution. After impregnation the solid is matured, dried and calcined. We focused here on the use of tungsten heteropolyanions as NiW6O_(24)H_6~(4-) (Anderson-type) or SiW_(12)O_(40)~(4-) PW_(12)O_(40)~(3-) and PW_(11)NiO_(40)H~(6-) (Keggin-type) to prepare the impregnating solution. Nickel salts of the Keggin hetero-polytungstate were synthesized in order to associate W and Ni in the same entity. The first catalytic results in toluene hydrogenation showed the efficiency of the Keggin-type HPA NiW/ASA catalysts.