Reduction Of MoS2 Research Articles

Study on the molybdenum electro-extraction from MoS2 in the molten salt

In this study, the electrochemical behavior of MoS2 in NaCl-KCl eutectic system was revealed by transient electrochemical techniques, using a homemade Mo metallic cavity electrode (MCE). In order to investigate the difference between MoS2 and molybdenum free ions in the molten salt, a metallic molybdenum electrode was electro-dissolved into the electrolyte in the form of molybdenum ions. The valence of molybdenum free ions was estimated to be in form of Mo6+ through the XPS analysis. The results of the electrochemical tests show that the reduction steps for MoS2 in NaCl-KCl salt was two and the corresponding reduction potentials were −0.37 V and −0.65 V (vs. Pt), respectively. A three-step reduction was found while investigating molybdenum free ions and the corresponding reduction potentials were 0.15 V, −0.40 V and −0.54 V (vs. Pt), respectively. The results of electrochemical impedance spectroscopy (EIS) analysis on the MoS2 pellet show a decreasing resistance with the increasing of potential. Moreover, potentiostatic electrolysis processes under different potentials were also carried out. Na2Mo3S4 was found to be the intermediate product during the reduction of MoS2 and Mo powder with residual sulfur content of 372 ppm was obtained as the cathode product after the electrolysis under 2.60 V for 20 h. At the same time, elemental sulfur was collected as the anodic product with a self-design condense apparatus.

The effect of Al2O3 and CaO presence on the kinetics of mechanochemical reduction of MoS2 by Zn

Abstract In this research, a new mechanochemical route has been introduced for solid-state reduction of MoS2 using metallic Zn powder as reductant. Nano particles of Mo and ZnS were synthesized as final product. When MoS2 and Zn were used as the starting mixture, the reaction was completed after 12 h. Whereas this reaction was completed after 5 h and 8 h of milling in presence of Al2O3 and CaO respectively. In this research X-ray powder diffraction (XRD) was employed for studying the reactions’ progress. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and laser particle size analyzing techniques were employed for studying the morphology and size distribution of the ball-milled powders. Results have shown that decreasing in size of particles in presence of Al2O3 and CaO was the main reason of improving kinetic of the reaction.

Modeling of Noncatalytic Hydrogen Reduction of Molybdenum Disulfide in the Presence of Lime, by Complex Multistep Gas–Solid Reactions

Direct reduction of molybdenum disulfide (MoS2) by hydrogen in the presence of lime is an alternative method for producing molybdenum metal. Such a process can be envisaged to have many advantages, including decreased number of operating stages and elimination of SO2 emissions. A mathematical model for predicting behavior of reduction of MoS2 with hydrogen in the presence of lime is presented in this work. And finally, the results predicted by the model have been evaluated and validated using experimental data.

Effect of Supported Pt on Reduction and Sulfidation of Mo Based Catalysts

Effect of supported Pt on reduction and sulfidation for Pt/MoO3 and Pt/MoS2 catalysts were studied by pulse reduction-sulfidation, flow reduction-sulfidation, temperature programmed electrical conductivity, temperature programmed reduction technique and X ray diffraction analysis. It was found that, for Pt/MoO3 the addition of Pt greatly promoted the reduction and sulfidation of MoO3, it was also shown that, for Pt/MoS2 Pt obviously facilitated the reduction of MoS2 to form S-vacancy, leading to an increment of the concentration of coordinative unsaturated molybdenum.

Reduction of molybdenite with carbon in the presence of lime

The thermodynamics of the MoS2-C-CaO system has been studied in order to understand the carbothermic reduction of molybdenite in the presence of CaO. Kinetic studies were also conducted with mixtures of MoS2+C+CaO in the temperature range of 900 °C 1200 °C. The reduction of MoS2 with carbon in the presence of lime proceeds through the direct oxidation of MoS2 by CaO to form intermediate molybdenum oxidized species, MoO2 and CaMoO4, which subsequently undergo reduction by CO to yield mixtures of Mo, Mo2C, and CaS. Complete conversion of MoS2 can be obtained at 1200 °C in less than 20 minutes for molar concentrations of MoS2:C:CaO=1:2:2. The kinetic model ln (1−X)=kt was used to determine the rate constants. The activation energy found for the temperature range studied was 218.8 kJ/mol.

Direct Synthesis of Molycarbide by Molybdenite-Carbon Monoxide Reaction in the Presence of Lime

Studies have been conducted on the lime-scavenged reduction of molybdenite (MoS2) by carbon monoxide. The effects of quantity of CaO, CO gas flow rate, temperature and time have been investigated. Results indicate that lime can enhance MoS2 conversion by over 20 times and sulfur emission into off-gas can be as low as 12–15 ppm. These exploratory tests also show that it is feasible to achieve 99% reduction-conversion of MoS2 by its CO treatment in the presence of CaO (e.g. at 1273 K for 6.6 ks and 3.33 cm3 s−1 CO gas flow rate). After separating the unreacted CaO and CaS, the carbide product has been found to be of 98% purity. As compared to the traditional methods of producing molycarbide, this lime-scavenged CO reduction of MoS2 is suggested to be a simple and non-polluting route suitable for the direct synthesis of Mo2C.

Studies on the Hydrodesulfurization(II)

Sulfurization and reduction of V2O3-MoO2 catalyst have been studied kinetically.V2O3 is not sulfurized with H2S at lower temperature than 480°C, but MoO2is sulfurized to MoS2+x (x=0.3) with CS2, H2S, and thiophene in the temperature range 400∼480°C.The reduction of MoS2+x with H2 is difficult at 400°C, but it proceeds slowly to MoS1.86at 600°C.Sulfurization rate of this MoS1.86were measured.The kinetic orders of sulfurization were1.2th, 0.5th and 0.9th for CS2, H2S and thiophen respectively, and the reactivities of these compounds decreased in the preceding order.The catalyst of molar ratio V2O3/MoO2=6was sulfurized most easily, so it was understood that the sulfurization process was the main step in the mechanism of hydrodesulfurization, for the desulfurization activity per unit area of catalyst was maximum at this composition as shown in the preceding paper.Further, from the results of electric conductivity measurements of the catalyst, it was supposed that the catalysis displayed activity under the co-operation betweenV2O3 (n-type semiconductor) and MoS2-x (p-type semiconductor).