Thermodynamics and Kinetics of Aluminothermic Reduction of NEU-1 Lunar Soil Simulant

The molten salt electrolysis method is suitable for in-situ resource utilization of lunar soil to simultaneously produce metals and oxygen. However, the complex composition of lunar soil leads to intricate electrolyte components, thereby necessitating studies on the thermite reduction of simulated lunar soil for the removal of Si, Fe, and Ti. NEU-1 simulated lunar soil is used as the raw material in this paper to investigate the thermodynamic and kinetic processes of thermite reduction. Thermogravimetric analysis results indicate that the differential thermal curve of thermite-reduced simulated lunar soil exhibits two exothermic peaks at 1039 ℃ and 1258 ℃, with apparent activation energies of 375 kJ/mol and 324 kJ/mol, respectively, and reaction orders of 2.87 and 2.85. The phase evolution mechanism of simulated lunar soil at high temperatures was studied, revealing that the phase of simulated lunar soil remains unchanged below 1100 ℃. Above 1200 ℃, most of the simulated lunar soil transforms into an amorphous state, while at 1500 ℃, most of the simulated lunar soil decomposes into CaAl₂O₄, SiO₂, Fe₂O₃, and Fe₃O₄. Finally, the influence of reaction temperature on the phase of thermite-reduced simulated lunar soil products was investigated. The results show that silicon-containing minerals in simulated lunar soil can be reduced to elemental silicon above 1000 ℃. Iron-containing minerals can be reduced to Al₃FeSi₂ above 1200 ℃, and calcium-containing minerals can be reduced to Al₂Ca above 1300 ℃. Increasing temperature facilitates the thermite reduction reaction of simulated lunar soil, but the separation of metal products from slag phases remains challenging.