| 摘要 |
<p>Pure racemic tartaric acid and mesotartaric acid are prepd. by reaction of an alakali metal maleate with aq. H2O2 in the presence of an alkali metal tungstate with a mole ratio of H2O2:maleic acid greater than 1 and the alkali salts of cis-epoxysuccinic acid formed with the alkali metal tungstate, opt. after decompsn. of excess H2O2, are converted to free cis-epoxysuccinic acid and free tungstic acid by passage through a strong acid cation-exchanger and hydrolysis of the cis-epoxysuccinic acid into the desired prodt. is effected either in the presence or absence of the tungstic acid, the tungstic acid being sepd. by an anion-exchanger, and the racemic tartaric acid is then sepd. by crystallisation in known manner from the hydrolysate free of tungstic acid, opt. by evapn. of water and lowering of the temp., after which the mesotartaric acid remaining in the mother-liquor is obtd. by crystallisation by evapn. to dryness opt. in a mixt. with racemic tartaric acid, unreacted cis-epoxy-succinic acid and maleic acid, whilst the anion-exchanger charged with tungstic acid is regenerated in known manner by a dilute alkali soln. and the alkali metal tungstate obtd. is opt. directly recycled to the epoxidation stage, after treatment with active carbon. The mole ratio of H2O2:maleic acid is pref. 1.01-5:1 esp. 1.1-1.3:1. The process is pref. carried out in a series of circulating reactors. Suitable alkali metal maleates and tungstates are of K, Na and ammonium. Racemic tartaric acid is obtd. at very pure state suitable for use in foodstuffs and in high yield.</p> |
