Monometallic Ru and Os catalysts and bimetallic Ru-Os catalysts with molar ratios (8:1 4:1 and 1:1) supported on a mesoporous silica doped with zirconium (molar ratio Si/Zr = 5) with a total metal loading of 5 wt.% were prepared by the wet incipient impregnation method, then dried at 120degreesC and finally reduced with hydrogen at 400degreesC. After a complete characterisation with XRD, XPS, N-2 adsorption-desorption volumetry, H-2-TPR and NH3-TPD, the catalysts were tested in the hydrogenation and ring opening of tetralin at high hydrogen pressure. Catalysts with a high Ru content display excellent hydrogenation properties even at low reaction temperatures (200-295degreesC). However, catalysts with a high Os content display weak hydrogenation activity but a very good hydrogenolysis/hydrocracking activity (30-40% of cracking compounds). This high level of activity is explained by the strength of the acid centres. Catalysts with a high Ru content maintain their catalytic performance in the presence of 600 ppm of dibenzopthiophene in the feed at 320 degreesC, but all other catalysts are partially or totally deactivated. All catalysts are irreversibly poisoned with a feed containing 1000 ppm of dibenzothiophene. (C) 2004 Elsevier B.V. All rights reserved.