Catalysts based on Co/zirconium doped mesoporous silica MSU for the hydrogenation and hydrogenolysis/hydrocracking of tetralin

Zirconium doped mesoporous silica (MSU) has been used as a support of Co catalysts with different Co-loadings. These catalysts have been characterised by several techniques such as XRD, XPS, textural properties, H-2-TPR, NH3-TPD, chemisorption of H-2, DRIFTS and FT-IR of adsorbed NO. The performance in the hydrogenation and hydrogenolysis/hydrocracking of tetralin at different temperatures has been examined in a high-pressure fixed-bed continuous-flow stainless steel catalytic reactor operating at 6.0 MPa of pressure. The incorporation of cobalt by using the incipient wetness method with an aqueous solution of cobalt nitrate is effective for preparing catalysts with 5-20 wt.% Co. The behaviour of these catalysts demonstrates that the higher the metallic loading, the contact time between catalyst and reactants, and the H-2/tetralin molar ratio, the better the results with conversions in the steady-state near to 100% and better the yields of hydrogenation and hydrogenolysis/hydrocracking products. Thus, the catalyst with 15 wt.% of Co, operating at 315 degrees C, with a contacttime of 3.6 s and an H-2/tetralin molar ratio of 15, gives rise to a conversion of tetralin of nearly 100%, yields of hydrogenation of 71%, and of hydrogenolysis/hydrocracking of 28% after 6 h on-stream. In addition, the thiotolerance of these catalysts has been tested with a feed of 425 and 850 ppm of dibenzothiophene (DBT). With 425 ppm of DBT, the performance of the best catalyst is only reduced by 17% after 5 h on-stream. However, with 850 ppm of DBT, a dramatic decrease in the activity is observed, although this activity can be recovered after new thermal and reduction treatments. (c) 2005 Elsevier B.V. All rights reserved.