GB781578A - Improvements relating to processes for the refining of naphthenic acids by distillation - Google Patents

Abstract

Crude naphthenic acid is refined by distilling it under reduced pressure using a fractionating column, a temperature of from 280 DEG to 370 DEG F., and a pressure of from 5 to 25 mm. Hg being maintained at the top of the column, so as to remove the more volatile hydrocarbon impurities in the overhead fraction, and then submitting the bottom fraction to straight distillation whereby a pale-coloured product of enhanced acid-value, suitable for use in the paint industry, is obtained as distillate. The fractionation step may be carried out in the presence of steam. The overhead fraction may be saponified to recover from it the valuable low molecular weight naphthenic acids. In an example, crude naphthenic acid having an acidvalue of 158.3 and an unsaponifiable content of 23.6 per cent was preheated to 195 DEG F. and submitted to distillation in a still surmounted by a column packed with ceramic rings and equivalent to 6 theoretical plates. The still was divided into sections heated at progressively higher temperatures, that of the last section being 435 DEG F. The pressure at the top of the column was maintained at 10 mm. Hg; and about one-fifth of the feed was taken off in the overhead fraction. The liquid withdrawn from the last section of the still was submitted to straight distillation at a pressure of 5 mm. Hg, giving a distillate (66 per cent yield) having an acid-value of 188 and an unsaponifiable content of 10 per cent.