GB1359879A - Preparation of organic acids and esters - Google Patents

Abstract

1359879 Hydroxycaproic acid; adipic acid; formyl valeric acid; esters thereof TEIJIN Ltd 4 Nov 1971 [28 July 1971] 51390/71 Heading C2C A mixture of #-hydroxycaproic acid, adipic acid, and #-formylvaleric acid is produced continuously by oxidizing cyclohexane with O 2 , withdrawing at least part of the reaction mixture, extracting the acids from the withdrawn reaction mixture such that under steady state conditions the COOH concentration is reduced to not more than 1À2 gm. equ./litre, and recycling part or all of the extraction residue containing cyclohexane, cyclohexanol and cyclohexanone to the reaction system. Extraction may be effected by countercurrent contact with an aqueous solution of product acids containing 4-7 gm. equ./litre COOH, recycled from the foot of the contact tower, water also being fed in at the top (1/30-1/5 parts by volume). The extraction residue may then be passed to a second stage where it is contacted with water or acids containing 0-1À5 gm. equ./litre COOH. 1-5% of the extraction residue may be withdrawn and distilled to separate cyclohexane &c. which is recycled. Alternatively, extraction may be effected with 1,2-propane diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, or diethylene glycol, alone or in aqueous solution. The glycol is then extracted from the extraction residue by washing with water. The oxidation reaction may be carried out at 120-150‹ C. and 3-30 atm. pressure.