Mixtures of TiO2 and Al2O3 (0, 5, 10 and 20 mol% Al2O3) were prepared by reaction of metal salts with molten alkali metal nitrates. The powders are constituted from nanosized anatase crystallites and amorphous alumina. Physico-chemical characterizations reveal the powders to be homogeneous. Ni-Mo sulphide catalysts were elaborated using these powders as supports and tested in the reaction of hydrogenation of tetralin. The decrease of the intrinsic catalytic activity per Mo atom, related to the alumina content, is higher than expected for a regular mixing of oxides, suggesting that alumina coats the anatase particles. On the contrary, it was found that changing the aluminium precursor salt leads to a metastable solid solution which increases significantly the intrinsic activity.