GB705862A - Improvements in or relating to the production of benzene carboxylic acids and estersthereof - Google Patents

Abstract

In the production of benzene carboxylic acids and esters thereof by the treatment of fossilized or more recent combustible deposits such as bituminous coal, lignites, peat or carbonization products thereof such as coke tar and pitch with oxidizing agents in an aqueous acidic or alkaline medium, e.g. nitric acid, the crude product after separation of the chemicals used in oxidation is heated with sulphuric acid, density 1.8-1.84, to a temperature below the boiling point of the sulphuric acid, the mixture is allowed to cool and is diluted with water, and the benzene carboxylic acids are separated from the mixture by extraction with an organic solvent and if desired are subsequently esterified. Suitably the benzene carboxylic acids are extracted with an alcohol preferably a low-boiling mono alcohol, e.g. an aliphatic or aromatic monohydric alcohol of 3-8 carbon atoms, and are then esterified with the same alcohol. The alcohol may be unsaturated and the amount of alcohol may be such that an acid mixture of esters is obtained. In further modifications the benzene carboxylic acids may be recrystallized from dilute nitric acid and subjected to a second treatment with sulphuric acid, density 1.8-1.84, or the crude product may be freed from nitrogenous compounds by extraction with an organic solvent, e.g. benzene, chloroform or ethylene trichloride prior to treatment with sulphuric acid. In examples (1) the product obtained by oxidizing bituminous coal with nitric acid is heated with concentrated sulphuric acid, cooled and diluted with water, the benzene carboxylic acids are extracted with ether, recrystallized from dilute nitric acid and subjected to further treatment with sulphuric acid; (2) from a raw product obtained by treating a gas coal with nitric acid, nitrogenous matter is extracted with benzene and the purified product is heated to 170 DEG C. with sulphuric acid and worked up as in (1); (3) the raw product obtained by oxidizing bituminous coal with nitric acid is heated with sulphuric acid, diluted with water, extracted with butyl alcohol and esterified to give a mixture of butyl esters; (4) the product obtained by oxidizing coals by air in the presence of aqueous sodium carbonate and separating by electrodialysis is heated with sulphuric acid and worked up as in (1); (5) the product obtained by oxidizing high temperature tar-pitch with nitric acid is treated as in (1) and (6) the product obtained by oxidizing coking coal with nitric acid is treated as in (1) and the resulting benzene carboxylic acids partially esterified with allyl alcohol.