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Thermodynamic calculation, ab initio molecular dynamics (AIMD) and vacuum decomposition experiments were performed to study the volatilization behaviors of Mo and S from molybdenite concentrate by vacuum decomposition. In thermodynamic calculation, starting decomposition temperatures of reactions were calculated, and saturated vapor pressures of Mo, S and MoS2 were also analyzed. In AIMD, geometries of the S n (n≤8), Mo m (m≤8) and Mo m S n (m+n≤8) clusters have been optimized using density functional theory (DFT) with generalized gradient approximation (GGA). And these clusters were simulated in DFT with Cambridge Sequential Total Energy Package (CASTEP) code of Material Studio software. Structures and stabilities of these clusters before and after molecular dynamics simulations were discussed, and diffusion coefficients were also calculated. In vacuum decomposition experiments, relationship between heat preservation time and volatilization rate of Mo and S was obtained, while the constant temperature and chamber pressure were 1823 K and 5–35 Pa, respectively. Above all, both the theoretical and experimental results showed that volatilization behaviors of Mo and S during vacuum decomposition process of molybdenite concentrate were as follows: Mo could partly evaporate into the condensate in the form of clusters, and S could easily evaporate into the condensate.

In this paper, thermal decomposition process of molybdenum concentrate in vacuum was thermodynamically analyzed, and decomposition mechanism of Mo S system in molybdenum was mainly studied. To further investigate and analyze the electronic properties in different temperature, the simulation calculations of MoS 2 (0 0 1) surface and Mo 2 S 3 (0 0 1) surface density of states, electron density difference, electronic orbital and Mulliken overlap population were carried out by density functional theory(DFT) formalism. The dynamics simulations results of MoS 2 (0 0 1) surface and Mo 2 S 3 (0 0 1) surface were obtained the temperature range of phase transforming are 1573 K–1673 K and from 1473 K to 1573 K at 20Pa, respectively. The interaction of MoS 2 and Mo 2 S 3 shows that thermal-decomposition of MoS 2 and Mo 2 S 3 does react, when new S S bonds and Mo Mo bond are formed instead of Mo S bond fracture. The experimental results of the thermal decomposition of MoS 2 and Mo 2 S 3 were in accordance with the thermodynamics theoretical calculation results and ab-initio molecular dynamics simulation results.

In this work, new experimental vapor–liquid equilibrium (VLE) data of lead-antimony alloy (Pb-Sb alloy) in vacuum distillation are reported. The activity coefficients of components of Pb-Sb alloy were calculated by using the NRTL model. The calculated average relative deviations were ±0.1425 and ±0.2433 pct, and the average standard deviations were ±0.0009 and ±0.0007, respectively, for Pb and Sb. The VLE phase diagrams, such as the temperature composition (T-x) and pressure composition (P-x) diagrams of Pb-Sb alloy in vacuum distillation were predicted based on the NRTL model and VLE theory. The predicted results are consistent with the new experimental data indicating that VLE phase diagrams obtained by this method are reliable. The VLE phase diagrams of alloys will provide an effective and intuitive way for the technical design and realization of recycling and separation processes. The VLE data may be used in separation processes design, and the thermodynamic properties as the key parameters in specific applications.

Vacuum distillation experiments were conducted for tin-antimony alloy (Sn–Sb alloy) under the system pressure of 5 Pa. The content of Sb (mole fraction) in crude Sn, viz., xSb was reduced from 0.5000 to 0.0619 in a single stage distillation process under the condition of residual pressure of 5–10 Pa, distillation temperature of 1373 K and distillation time of 60 min. The activity coefficients of components of Sn–Sb alloy were calculated by using the molecular interaction volume model (MIVM), and the calculated average relative deviation and the average standard deviation were ±0.00039 and ± 0.173%, respectively for both Sn and Sb. The vapor–liquid equilibrium (VLE) phase diagrams, including the temperature-composition (T-x) and pressure-composition (p-x) diagrams of Sn–Sb alloy in vacuum distillation were calculated based on VLE theory and the MIVM. A reasonable agreement between the calculated results and the experimental data indicates that VLE phase diagrams obtained by this method are reliable. The VLE phase diagrams of alloys will provide an effective and convenient way for the designing of the process parameters of industrial production of vacuum metallurgy, and for the prediction of the needed product component dependence of temperature and pressure during the process of vacuum distillation.

The feasibility study of the AlCl(g) generated by Al2O−AlCl2−C system under vacuum was carried out by thermodynamic analysis and CASTEP package of the Material Studio program which was based on density functional theory (DFT) formalism. Thermodynamic calculations indicate that AlCl and CO molecules can be formed under conditions of temperature 1760 K and the pressure of 60 Pa. The interaction of Al2O and AlCl2 with C shows that the chemical adsorption of Al2O and AlCl2 does take place on C(001) crystal plane, and at the same time, new chemical bond is formed between Al atom in Al2O and Cl atoms from one of the Al—Cl bonds in AlCl2. The results, after 1.25 ps dynamics simulation, indicate that adsorbed AlCl molecules are generated and CO molecule will be formed in this system, and they will escape from C(001) surface after a longer period of dynamic simulation time. It means that the reaction of Al2O and AlCl2 with C can be carried out under given constraint condition.

Vacuum decomposition process of molybdenite concentrate was investigated under pressure of 5–35 Pa for 15–120 min at the temperature range 1473 K–1973 K. The theoretical and experimental results showed that Gibbs free energy of vacuum decomposition reactions and evaporation rate of pure sulfur provided the theoretical calculation basis for temperature and heat preservation time selection in vacuum decomposition experiments of molybdenite concentrate. Melting points and saturated vapor pressures of pure substances and compounds predicted the evaporation behavior of impurity elements and its compounds during the experimental process. Both Cu and Fe could partly evaporate into condensate and Cu had better evaporation ability than Fe. MoO3 could easily and Al2O3, SiO2 could partly evaporate into the condensate. Kilo-scale experiment was performed based on the small experiments and its results showed that the Mo content of molybdenum metal product was 92.38% and the S content of sulfur product was 96.28%, and the molybdenum recovery rate reached to 95.94%. Both the theoretical and experimental results proved that it was feasible to produce crude molybdenum and sulfur from molybdenite concentrate through vacuum decomposition.

AlN chlorination route, in the present work, was proposed to extract Aluminum from aluminum nitride under vacuum. Density functional theory (DFT) were implemented to study the interaction of AlCl 3 molecule and AlN ( 10 1 ¯ 0 ) surface. The results of DFT indicate that chemisorbed AlCl 3 adsorption configuration was observed on the clean AlN ( 10 1 ¯ 0 ) surface after structure optimization, and adsorbed AlCl molecules were generated after 1 ps dynamic simulation time. The phase and composition of condensate were examined by means of XRD and EDS. It was found that 97.76 wt% of Al metal was obtained in the experiment B (in the presence of AlCl 3 ), however, no condensate was collected in the experiment A (without AlCl 3 ) at 1760 K under pressure of average 60 Pa. The results show that AlN chlorination route is an alternative Al production method from aluminum nitride.

A novel process that the combination of vacuum decomposition and acid leaching was proposed. The influence of distillation times, diameter and thickness of the feeding material on the mass fraction of Molybdenum (Mo) and sulphur (S) in residual was investigated. The influence of leaching temperature, leaching time, concentration of hydrochloric acid solution, and ratio of liquid to solid on leaching rates of Mo and S in acid leaching process was also investigated. Due to the fact that SO2 emission happening in the long process of traditional molybdenum metallurgy could be avoided in this novel method, this combination process was environmentally-friendly. Molybdenum powder was obtained through handling molybdenite concentrate under the optimal condition parameters, and the mass fraction of Mo reached 98.29 wt%. So it’s feasible to produce molybdenum powder from molybdenite concentrate by using this new method.

In this research, thermodynamic analysis and CASTEP package of the Material Studio program which is based on density functional theory (DFT) formalism were used to study the carbothermic-chlorination (AlCl3) reaction of Al2O under vacuum. Thermodynamic calculations indicated that AlCl(g) can be generated by carbothermic-chlorination process at 1760K and 60Pa. The interaction of Al2O and AlCl3 with C showed that the chemical adsorption of Al2O and AlCl3 did take place on C(001) crystal plane, at the same time, new chemical bond have been formed between Al atom dissociated from Al2O and Cl atom dissociated from AlCl3 molecule. The result, after 1ps dynamics simulation, indicated that adsorbed AlCl and CO molecules have been generated in Al2O-AlCl3-C system, and they would escape from C surface after a longer period of dynamics simulation time. It means that the reaction of Al2O and AlCl3 with C can be carried out under given constraint condition.