Analysis of KF behavior and inverse reaction molecular kinetics simulation in the vacuum carbothermic reduction of magnesium oxide

Abstract

As a new generation of structural materials, magnesium-based materials are expected to replace steel and aluminum. Vacuum carbothermic reduction of magnesium smelting is a novel green technique that has received extensive attention in recent years. For this method, the study of catalysts and the reverse reaction mechanism is crucial. In this paper, the behavior of KF during the vacuum carbothermic reduction of magnesium oxide is thermodynamically analyzed. The experimental findings are characterized using X-ray diffraction (XRD), X-ray photon energy spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and chemical analysis. Furthermore, the molecular dynamics simulation of the inverse reaction are investigated. According to thermodynamic calculations, the reaction temperature for the vacuum carbothermic reduction of magnesium oxide is higher than 1463 K at 80 Pa. Furthermore, KF is not involved in the reaction during the reduction in which F- plays the major role. The experimental analysis shows that the addition of KF and CaF2 significantly improved the reduction, and the degree of KF promotion is higher. The degree of reduction of magnesium oxide is higher under higher addition and lower system pressure conditions. The mass loss rate increases with increasing addition and holding time, and tends to level off when the addition amount is greater than 7 % due to the limited impact of F-. The KF reduction experiment crystallized magnesium with a purity of 90.21 %, with good crystallization and structure. It is notable that KF remains in the residue and functions as a catalyst, and is not involved in the vacuum carbothermic reduction of magnesium oxide. According to the reverse reaction mechanism, when the three CO molecules interact on the surface of Mg(100) to form a carbon chain, oxygen atoms separate from the carbon chain, and the released oxygen atoms combine with magnesium atoms to form MgO.