| 摘要 |
The invention relates to a method for the purification of crude diacerein by means of toluene. The inventive method consists in dissolving the crude diacerein in acetone/water (1:1) using approximately 13 volumes of mixture in relation to the diacerien. The pH is adjusted to between 6.6 and 7.2 and, preferably, to between 7 and 7.2, with a tertiary amine in acetone, whereby any trialkylamine with C1-4 alkyl groups can be used as the tertiary amine, preferably the trimethylamine, triethylamine, tripropylamine, methyldiethylamine, diethylpropylamine group and, more preferably, trimethylamine. The aforementioned mixture is stirred until the diacerein has dissolved completely. A water-immiscible organic solvent is subsequently added and the mixture is stirred. According to the invention, between 5 and fifteen continuous extractions are made with the water-immiscible organic solvent and the organic phase is separated each time. The diacerein crystallises in the acetone/water phase when the neutral pH is changed to acid pH with a strong mineral acid which is selected from chlorohydric, sulphuric and phosphoric acid. The crystallised product is centrifuged or filtered, washed with water and dried. The aforementioned method can be used to obtain diacerein with a yield of between 90 and 93 %, average purity of 99.17 %, an aloe-emodin content of between 7 and 10 ppm and a chromium content of between 20 and 25 ppm.
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