Molten salt preparation of stabilized zirconia catalysts : characterization and catalytic properties

Abstract Supports of Mo and NiMo catalysts were prepared and tested in hydrotreatment model reactions. These supports, composed of zirconia and various amounts of yttria, were obtained by synthesis in molten salts. It was found that the distribution of yttrium in zirconium oxide was homogeneous. Moreover, it was shown that the crystalline structure as well as the textural properties (especially the porosity) were stabilized. These solids were then used as supports of Mo and NiMo sulphides and their activities were compared to those of a commercial NiMo alumina catalyst. In biphenyl hydrogenation, with the same coverage of Mo (2.8 at/nm 2 ), the activities per gram of both catalysts (supported on zirconia and alumina) were similar, while the activity per atom of Mo of the catalyst supported on ZrO 2 Y 2 O 3 was twice the activity of the catalyst supported on alumina. For NiMo catalysts, a ratio r= Ni/(Ni+Mo)=0.4 with Mo = 2.8 at/nm 2 and a co-impregnation of the Mo and Ni were required to have a good synergetic effect. The activity per atom of Mo in biphenyl hydrogenation was then enhanced more than twofold when compared to the NiMo/alumina catalyst. In an HDN model reaction (conversion of diethylanyline in the presence of quinoline) the results obtained with zirconia were much better than with alumina.