| 摘要 |
A process for the purification of mixed tolylene diamines obtained by the reduction of the dinitro compounds produced by the direct nitration of toluene comprises treating the diamines with a solvent of a temperature of from 20 DEG C. to -20 DEG C. preferably from 0 DEG C. to -20 DEG C. and removing the undissolved purified aromatic diamines from the solution. Suitable solvents are water, alcohols such as methanol, ethanol and isopropanol, and mixtures of such alcohols with water, and mixtures of chloroform, carbon tetrachloride and aromatic hydrocarbons such as benzene, toluene and xylene, with aliphatic hydrocarbons such as hexane, heptane, isooctane, cyclohexane and mixtures thereof, for example light petroleum (boiling point 40 DEG to 60 DEG C.) and o-dichlorobenzene. The solvent is preferably used in an amount from half to ten times the weight of the diamines to be purified. The process may be carried out by mixing the aromatic diamines, preferably in a finely divided form, with the solvent at the desired temperature, and agitating the mixture until all soluble material has dissolved. Alternatively the diamines and solvent may be mixed at an elevated temperature, for example at 50 DEG to 100 DEG C. until all soluble material has dissolved, and then cooling the mixture to the desired temperature range, when the undissolved purified diamines are removed by, for example, filtration or centrifugal means. Examples are given of removing the ortho isomers as impurities in a mixture of 2:4 and 2:6 isomers of diaminotoluenes using isopropanol and ortho-dichlorobenzene as solvents.
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