Carbothermal reduction−chlorination−disproportionation of alumina in vacuum
(1. Faculty of Science, Kunming University of Science and Technology, Kunming 650500, China;
2. National Engineering Laboratory of Vacuum Metallurgy, Faculty of Metallurgy and Energy Engineering,
Kunming University of Science and Technology, Kunming 650093, China)
2. National Engineering Laboratory of Vacuum Metallurgy, Faculty of Metallurgy and Energy Engineering,
Kunming University of Science and Technology, Kunming 650093, China)
Abstract: The carbothermal reduction−chlorination−disproportionation of alumina in vacuum was investigated by XRD and thermodynamic analysis. The experiments on alumina and graphite at 1643−1843 K in vacuum were carried out. The results demonstrate that AlCl3(g) reacts with Al2O(g) or Al(g) generated from the carbothermal reduction of alumina to form AlCl(g), and the AlCl(g) disproportionates to aluminum and AlCl3(g) at a lower temperature and the reaction rate of AlCl(g) reaches 90% at 980 K and 100 Pa. The aluminum can absorb CO to catalyze its disproportionation to C and CO2, and react backward with CO to form Al4C3, Al2O3, C and CO2, resulting in the aluminum product containing C, Al4C3 and Al2O3. The impurities in the aluminum product decrease as the AlCl(g) disproportionation temperature decreases. AlCl3 condenses at a temperature approximated to the room temperature.
Key words: carbothermal reduction; Al2O3; AlCl; vacuum; disproportionation