GB565636A - Improvements in or relating to the manufacture of aliphatic dibasic acids - Google Patents

Abstract

Aliphatic dibasic acids are produced by liquid phase oxidation of a saturated alicyclic alcohol in a solvent therefor with an oxygen-containing gas in the presence of an oxidation catalyst, and an oxidation initiator consisting of a peroxide or a compound capable of forming a peroxide under the reaction conditions. Cyclohexanol or its homologues yield adipic acid or substituted adipic acid, cyclopentanols give glutaric and cyclobutanols succinic acid or substituted acids. Temperature is about 60-160, generally 80-130 DEG C., and pressure is preferably above atmospheric, e.g. 2-100 or even up to 1000 atm. The solvent may be, for example, carbon tetrachloride or benzene, but is preferably an organic acid such as acetic, propionic, butyric, trimethylacetic, isobutyric, phenylacetic and methoxyacetic acids in an amount of, say, 1-99, and preferably at least 20 per cent by weight of the reaction mixture. The catalyst may be a solid polyvalent metal of atomic weight between 50 and 200 or a salt or oxide thereof, with or without inorganic acids. Specified catalysts are chlorides of V, Ce and Co, acetates of Mn and Ba, permanganates of Ba and Co, sodium cobalti nitrite, and mixtures thereof, the preferred catalyst being a mixture of the Co, Cu and Mn salts of organic acids, especially acetic. Promoters such as Ba, Mg and K acetates, butyrates or propionates may also be used. The initiator may be a peroxide, such as sodium, hydrogen or benzoyl peroxide, a peracid, e.g. peracetic or perbenzoic, an aldehyde, ketone, ether or olefine, e.g. cyclohexene or octylene. It may be added only at the start, a ketonic initiator being formed, for example, during the oxidation of cyclohexanol, or continuously during the oxidation. If desired, oxidation may be commenced at such a temperature and pressure that products capable of oxidation to, or acting as, oxygen carriers are formed and act as initiators in the oxidation of further alicyclic alcohol at the lower reaction temperature. The amount of initiator may be about 0.1-10 per cent by weight of the reaction mixture. The preferred initiator is cyclohexanone. The process may be a batch or continuous one, the oxygen-containing gas being passed through a body of liquid or in counter- or co-current with the liquid through a tube or tower of acid-resisting material, such as stainless steel, aluminium or tantalum. In examples: isobutyric acid and a mixture of Co, Cu and Mn acetates is heated to 110 or 115 DEG C. in an autoclave, and air introduced to give a pressure of 150 lbs./sq. in. Air is continuously bubbled through while gas is vented at the top, and cyclohexanone is first injected followed by cyclohexanol. Air flow is continued until oxidation is complete. Adipic acid is crystallized from the product, and cyclohexanol and cyclohexanone recovered from the product and the off-gas. Specification 534,525 is referred to.