Adipic acid prepn. by oxidising cyclohexane with oxygen

摘要

Prepn. of adipic acid (I) involves single-stage oxidn. of cyclohexane (II) with oxygen in presence of acetic acid and a cobalt salt catalyst (III). All of the (III) used is recovered by: (i) cooling the mixt. from the oxidn. reactor and isolating the pptd. (I) by filtration; (ii) separating the obtd. filtrate into a non-polar phase (A) rich in (II) and a polar phase (B) contg. acetic acid, (III), (I), cyclohexanone, cyclohexanol, cyclohexyl ester and other by-products, the whole of phase (A) and part of phase (B) being recycled (opt. after isolation of (I) in (B)) to the start of the process; and (iii) isolating (III) from the non-recycled part (B') of (B). the novelty is that either: (a) (B') is mixed with 1-10 times its vol. of an inert solvent (IV) for the organic components of (B) (excluding (III)) of b.pt. /-130 deg C under normal pressure, the HOAc in the obtd. mixt. is distilled. off and the (III) which crystallises out is recovered by filtration; or (b) 20-95% of the HOAc in (B') is distilled. off, the ester in the distn. residue is hydrolysed, the organic components of the obtd. aq. phase (excluding (III)) are extd. with a water-immiscible extractant (V) and (III) is recovered from or as the aq. soln..