GB1013617A - Improved process for recovery of adipic acid precursors - Google Patents

Abstract

<PICT:1013617/C2/1> In the manufacture of adipic acid by oxidizing cyclohexane with molecular oxygen in the liquid phase and further oxidizing the primary oxidation products so obtained, the primary oxidation products are mixed with water and then separated into an organic phase and an aqueous phase before they are further treated to produce a product suitable for further oxidation to adipic acid. The further oxidation is preferably effected in two stages with nitric acid. As shown, cyclohexane is oxidized in a vessel 2 with air supplied through a pipe 3, and the oxidation products are treated with water fed through a pipe 4. The mixture is separated in a decanter 6 into an organic layer and an aqueous layer, which pass to vessels 7, 8, respectively. The organic layer passes to a drystripper 10 from which unoxidized cyclohexane is passed back to the vessel 2 by pipe 13. The distillation residue from the dry stripper 10 passes to a wet stripper 18 to which water is supplied from a concentrator 35 (see below), and the distillate from the wet stripper is separated in decanter 14 into cyclohexane, which is returned to the vessel 2, and an aqueous layer which is sent to waste, wholly or in part, through pipe 15. The distillation residue from the wet stripper passes to the adipic acid precursor storage vessel 25 either directly or by way of a refiner 22 in which a final distillation is effected and from which the distillation products pass via a decanter 12 to the vessel 25. The aqueous portion of the cyclohexane oxidation product collected in the vessel 8 passes to a concentrator 35, the distillate from which is fed to the wet stripper 18 (see above). The residue from the concentrator 35 passes to a crystallizer 27, from which the crystals pass to a filter 30, the filter cake being transferred to the vessel 25. Comparative experimental results are given. Specifications 1,013,618 and 1,013,619 are referred to.