GB1294744A - Process for the recovery of pure trimellitic anhydride - Google Patents

Abstract

1294744 Trimellitic anhydride CHEMIEBAU DR A ZIEREN GmbH & CO KG 25 March 1970 [29 March 1969] 14477/70 Heading C2C Pure trimellitic anhydride (containing at least 99.0% by wt. trimellitic anhydride and not more than 0.02% by wt. nitrogen) is recovered from crude trimellitic anhydride, obtained by nitric acid oxidation of a 1,2,4-trialkylbenzene and subsequent elimination of water, by distillation at no more than 20 torr and no more than 250‹ C. to distil 2-20% by wt. of crude product in a first stage, to obtain a fraction containing more volatile nitrogen-containing impurities, and distilling, under the same pressure and temperature limitations as the first stage, in a second stage a main fraction consisting of pure anhydride, leaving a residue of not more than 12% by wt. containing less volatile impurities. It is preferred to remove 3-5% by wt. of crude product in the first stage under a pressure of 5-15 torr and conduct the second stage at 3-10 torr. The crude anhydride may be freed from 1-10% by wt. of the residue prior to the two-stage distillation, e.g. by thin-layer evaporation. Pseudocumene is the preferred trialkylbenzene. An arrangement of apparatus for carrying out the process is described (not shown).