A novel hydrothermal method for the preparation of nano MoS2 for hydrodesulfurization (HDS) with MoO3 as a precursor is presented. The redox reaction mechanism is, for the first time, revealed. It is shown to involve the oxidation of S2− to SO42− while hexavalent Mo is reduced to quadrivalent Mo to form MoS2. The HS− group is identified to play a key role in the reduction of MoO3. The interaction between Na2S and the HS− group and the yield of the resulting MoS2 are controlled via the pH of the synthesis solution. Various characterization methods, e.g. XRD, TEM, SEM, BET, TPR, XPS, XANES, EXAFS, etc., are employed for the characterization of the synthesized MoS2. The results show that high purity MoS2 is obtained. The ratio of precursors, MoO3 and Na2S, influences the crystal structure and catalytic activity. A slightly less amount of sulfur than the stoichiometric ratio of S/Mo produces defect sites, which promote catalyst activities in the hydrodesulfurization of real light cycle oil (LCO).
