GB536172A - Purification of aromatic hydrocarbons by azeotropic distillation - Google Patents

Abstract

536,172. Distilling hydrocarbons. WOODALLDUCKHAM (1920), Ltd., SPIERS, H. M., and SUTTLE, H. K. Oct. 26, 1939, No. 28710. [Class 32] Pure or nitration pure aromatic hydrocarbons boiling below 150‹C. e.g. benzene, toluene, xylenes, are obtained from impure raw material. comprising mainly one such hydrocarbon and a plurality of non-aromatic hydrocarbons, by azeotropic distillation with an aliphatic alcohol containing not more than three carbon atoms in the molecule, e.g. methyl alcohol, so that the non-aromatic hydrocarbons having boiling points up to about 15‹C. higher than the boiling point of the aromatic hydrocarbon are vaporized at a temperature below the boiling point of the latter and removed with the alcohol, while a residue is obtained of the aromatic hydrocarbon and impurities boiling more than 15‹C. above the boiling point of the aromatic hydrocarbon, which impurities are removed by simple fractional distillation. In a modification methyl alcohol is added to the impure raw material in an amount less than that required to bring over all the hydrocarbons and the mixture is fractionally distilled to obtain at progressively increasing temperatures mixtures containing alcohol and low boiling non-aromatic hydrocarbons, a mixture of water and pure aromatic hydrocarbon, and a residue of aromatic hydrocarbon and high boiling hydrocarbons. The water is separated from the aromatic hydrocarbon which is added to the residual fraction which is then re-fractionated. The free-runnings containing alcohol may be used for treating a further batch of raw material. Examples are given of the distillation of impure toluoles. Specifications 464,307 and 513,566 are referred to.