Thioreduction of cyclopentanone and hydrodesulfurization of dibenzothiophene over sulfided nickel or cobalt-promoted molybdenum on alumina catalysts

Two series of sulfided Ni or Co promoted Mo/alumina catalysts, having diffe rent Ni or Co loadings, were characterized by their activities for the tran sformation of cyclopentanone into cyclopentanethiol (flow reactor, 220 degr ees C, atmospheric pressure) and for the hydrodesulfurization of dibenzothi ophene (flow reactor, 340 degrees C, 3 MPa hydrogen pressure). The addition of the promoter increased significantly the activity of the Mo/alumina cat alyst for both reactions, up to a maximum obtained with the catalysts havin g a (promoter)/(promoter+Mo) molar ratio equal to 0.3-0.4. This increase in activity was due in part to an increase in the hydrogenating properties of the Mo/alumina catalyst. However, an additional modification of the cataly st (basic and nucleophilic properties) must be considered to account for th e spectacular effect of the promoter on the rate of the dibenzothiophene di rect desulfurization reaction. (C) 1999 Elsevier Science B.V. All rights re served.