GB851562A - Process for the production of terephthalic acid - Google Patents

Abstract

A process for the production of terephthalic acid by interaction in the liquid phase of an aliphatic para disubstituted benzene and molecular oxygen in the presence of bromine and a catalyst containing cobalt or manganese at a temperature above 165 DEG C. is characterised in that there is added at least one of the following:-nickel, copper, zinc, tin and iron, or a compound of one of these metals, in such amount as provides in the reaction mixture a concentration of nickel exceeding 100 parts per million, or a concentration of copper between 25 and 150 p.p.m., or of zinc between 1,000 and 5,000 p.p.m., or of tin between 100 and 1,000 p.p.m., or of iron not more than 1,000 p.p.m. Preferably an excess of oxygen is maintained continuously in the reaction system. Preferably a catalyst containing both cobalt and manganese is used and the reaction is carried out in an inert medium such as acetic acid or water. The reaction may be carried out in titanium, silver, or glass lined equipment, or in steel reactors, e.g. of nickelsteel alloys. Examples describe the production of terephthalic acid from mixtures of p-xylene, glacial acetic acid, cobalt bromide, manganese bromide or acetate, and various proportions of nickel carbonate or acetate, copper sulphate, zinc acetate, stannous chloride, and ferric acetate. When the reaction is carried out in a steel reactor it is not necessary to add iron directly but the content of iron in the reaction mixture should be controlled within the specified limit, e.g. by by-passing mother liquors through an ionexchange resin before re-cycling. Specifications 737,439, 787,937, 804,612, 807,091, 810,020, 841,246 and 850,960 are referred to.