Hydroprocessing of dibenzothiophene, 1-methylnaphthalene and quinoline was studied in a batch reactor at 340 degreesC and 7 MPa H-2, over sulfided NiO-MoO3 catalysts supported on calcium-deficient hydroxyapatite, materials, enriched or not with Al ions, and aluminium phosphate AlPO4. On those catalysts, reaction schemes for hydrodesulfurization of dibenzothiophene, hydrogenation of 1-methyinaphthalene and hydrodenitrogenation of quinoline were found to be similar to those already reported for sulfided NiMo catalysts supported on gamma-alumina. However, the catalytic activity was significantly improved by using calcium-deficient apatites, particularly for the catalyst referred to as NiMo/ACP-1.5 that contains 1.5 wt.% Al ions, although its specific surface area was lower than that of an industrial alumina supported catalyst. This increase in activity would result from the presence of superficial defects oxygen vacancies and HPO42- species, which would ease the dispersion of the NiMo phase. Moreover, the existence of correlations between the reaction rates for hydrodesulfurization of dibenzothiophene, hydrogenation of 1-methylnaphthalene, hydrodenitrogenation of quinoline and reduction of dimethyldisulfide into methanethiol confirm that the nature of the catalytic sites was the same, whatever the chemical reaction concerned, hydrogenation of aromatic rings or hydrogenolysis of C-S, C-N and S-S bonds. (C) 2004 Elsevier B.V. All rights reserved.