In this thesis, Ni-Mo and Co-Mo nanocatalysts supported on the hexagonal mesopores silica (HMS) and ?-Al 2 O 3 were prepared via the supercritical fluid deposition method (SCFD) using supercritical CO 2 -methanol solution. In this route, the supports were impregnated with Ni(NO 3 ) 2 .6H 2 O, Co(NO 3 ) 2 .6H 2 O and Mo(CO) 6 . The resulting composites were converted to Ni-Mo and Co-Mo nanocatalysts via calcinations. Methanol as co-solvent enhanced the dissolution of the precursors in supercritical CO 2 . In addition, for study of the effect of this method some samples were prepared using conventional impregnation (IMP). For characterization of the prepared samples, adsorption-desorption of nitrogen, oxygen chemisorpsion, XRD, TEM, EDAX and TPR were applied. The results showed high and uniform dispersed deposition of metal oxides on the supports for the SCFD nanocatalysts. The hydrodesulfurization of fuel model, dibenzothiophene in n-heptane, was used for catalytic activity evaluation of the SCFD nanocatalysts, IMP and commercial (COM) catalysts. The results indicated that supercritical impregnation method of metal precursors into support has a positive effect on the catalyst activity. The results showed higher conversion for the nanocatalysts in contrast to IMP and COM catalysts in hydrodesulfurization of dibenzothiophene. The kinetic analysis of the reaction data was carried out to calculate the reaction rate constant of the catalysts in the temperature range of 260-330 o C. The frequency factor and activation energy of the hydrodesulfurization were calculated for the all catalysts using Arrhenius' law. Furthermore, addition of toluene as an aromatic compound in the feed showed less inhibition effect of SCFD nanocatalysts with respect to those of the IMP and COM catalysts.
