Process for the preparation of aromatic monocarboxylic acids from toluene and substituted toluenes

Abstract

In a process for preparing aromatic monocarboxylic acids by oxidation of toluene or of toluenes substituted in the nucleus, the starting substances are reacted in the liquid phase with oxygen or with a gas containing oxygen, at a temperature of 80.degree.-180.degree. C. and a pressure of 5 to 50 bar in the presence of acetic acid as diluent and a soluble cobalt and/or manganese salt in combination with a bromide, and the aromatic monocarboxylic acids are then obtained by solid-liquid separation of the cooled reaction mixture. To reduce the dimensions of the oxidation reactor, for which particularly corrosion-resistant materials are necessary, and to isolate the target products in high yield and purity, as well as to reduce the technical complexity and cost of the treatment of the amounts of solvents that are yielded, relatively small amounts of acetic acid are used as solvents or diluents, namely at a ratio by weight of the alkyl aromatic being oxidized and acetic acid of 0.5:1 to 6:1. Not until the reaction has ended is the dilution, which is necessary for the isolation of the target product by solid-liquid separation of the cooled reaction mixture, performed by the addition of dilute aqueous acetic acid or of the washing filtrate from a preceding oxidation run. A typical example is the preparation of p-tert-butylbenzoic acid from p-tert-butyltoluene by the method described.

Dependencies are inferred from the claim text.