Chemistry of sodium lactate formation under simulated alumina refinery conditions

The formation of sodium lactate, sodium acetate, and sodium formate under laboratory-simulated conditions for the production of alumina from organic-contaminated bauxite by dissolution in hot (145 C) sodium hydroxide (3 M) has been studied. Not unexpectedly, sodium lactate, sodium acetate, and sodium formate are shown to arise from glucose. Studies up to 14 h show that, once formed, sodium acetate and sodium formate are stable. Sodium L-(+)-lactate, however, decomposes to sodium carbonate and ethanol under these conditions, but it reaches a constant concentration that appears to be dependent on the initial lactate and sodium hydroxide concentrations. Sodium [1-13C]L-lactate studies showed that 13C-labeled carboxylate (COO-) is scrambled among the carbonate and both of the carbons in the ethanol produced. A 1,2,3-trihydroxycyclopropane intermediate is proposed. In the presence of 2-methoxyphenol, a lignin degradation product, sodium lactate decomposition is enhanced, and the sodium acetate and formate yields are also affected.