Highly active NiMo/TiO2-Al2O3 catalysts:: Influence of the preparation and the activation conditions on the catalytic activity

NiMo/TiO2-Al2O3 catalysts were prepared over a TiO2-Al2O3 mixed oxide (5% of Al2O3) by impregnation with nickel and molybdenum salts precursors at different pH solution and the catalysts have been activated by several calcination-sulfidation procedures. Evaluation of the catalysts in tetraline hydrogenation under pressure indicated that the sample obtained after impregnation under basic condition and sulfided without any previous calcination presents the highest activity. Characterizations of the samples by Raman and UV-vis diffuse reflectance spectroscopies, XPS and HRTEM allowed to follow the evolution of the Ni and Mo species along the different steps of the preparation and to understand how to get a high promoting effect of Ni over such a TiO2 rich support. (c) 2007 Elsevier B.V. All rights reserved.