GB594983A - Improvements relating to aromatic hydrocarbons - Google Patents

Abstract

Pure aromatic hydrocarbons are prepared from mixtures containing them, together with indene and non-aromatic hydrocarbons, such as petroleum and coal tar naphthas, by contacting with 65-85 per cent sulphuric acid, separating the hydrocarbon layer, producing an aromatic concentrate therefrom, and recovering the pure aromatic hydrocarbons by controlled sulphonation and hydrolysis of the sulphonic acids. The acid to hydrocarbon ratio is generally between 1 : 1 and 1 : 10 by volume. Feedstocks consisting of aromatic fractions or aromatic extracts obtained by solvent extraction, and generally boiling at about 160-185 DEG C., are treated batchwise or continuously with about 80 per cent acid, and the hydrocarbon layer steam distilled to remove polymer material. If desired, a solvent extraction may be effected to separate aromatics. Preferably, however, the hydrocarbons are treated with 96 per cent sulphuric acid to sulphonate the aromatics, the acid layer then being diluted, heated to about 90 DEG C. and steam distilled. Hydrocarbons distil over at about 140-185 DEG C. Fractionation yields crude mesitylene, pseudocumene, and hemimellitene fractions from which the pure hydrocarbons are recovered by controlled sulphonation and hydrolysis, alone or combined with fractional distillation and crystallization. In an example, the indene fraction from coal tar naphtha, B.R. 170-180 DEG C., is treated with an equal volume of 80 per cent acid for 30 mins., and the separated hydrocarbon layer again treated similarly. Sulphonation followed by hydrolysis and fractionation yields, inter alia, hemimellitene-containing fractions from which the pure hydrocarbon is recovered by controlled sulphonation and hydrolysis.