Influence of Al2O3 on the reoxidation of aluminum in molten cryolite

The influence of Al₂O₃ content on the reoxidation reaction at 1293 K between CO₂ and Al dissolved in molten cryolite was examined. The rate and extent of the reaction were evaluated as the concentration of Al₂O₃ was varied from 0 to 12 wt pct at 4 pct intervals. The cryolite, under an argon atmosphere, was saturated with Al before CO₂ was introduced. High initial reaction rates were observed with a quasisteady state condition established 30 to 60 min after beginning an experiment. Increasing the Al₂O₃ content of the melt significantly reduced the initial rate, but it was not found to alter the steady rate for a given flow system. This phenomenon was observed for systems where CO₂ was passed over or bubbled through the molten cryolite. Bubbling the CO₂ through the molten cryolite led to increases in both the initial and steady state rates. M. K. Han, formerly a Graduate Fellow with the University of Washington.