Amino:benzoic acid prodn. from nitrotoluene - by oxidn. to nitrobenzoic acid and electrochemical redn. to amino:benzoic acid with simultaneous regeneration of oxidising agent

摘要

Process for the preparation of aminobenzoic acids comprises a first stage in which nitro toluenes are oxidised to nitrobenzoic acids, followed by a second stage in which the nitrobenzoic acids are electrochemically reduced is characterised in that the oxidising agent used in the first stage is regenerated at the anode of the electrolyser in the second stage, simultaneously with the electrochemical reduction. The preferred oxidising agent is a sulphochromic solution, esp. an aqueous solution of 3-20 wt.% of chromic oxide and 10-95 wt.% of sulphuric acid, which optionally contains chromium sulphate and other additives. Preparation of amino-benzoic acid, esp. para-amino-benzoic acid, which are useful in the pharmaceutical and dyestuff industry. The present invention simultaneous reduction of the nitrobenzoic acids and regeneration of the oxidising agent gives excellent yields of pure product and avoids the cost and toxicity problems in recycling the chromium salts, in addition to needed only one electrolyser reducing electric energy requirements.