Process for obtaining adipic acid

US5587511A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Herbert Salzburg · Leichlingen, DE
• Georg Steinhoff · Unterhaching, DE
• Andreas Gosch · Bochum, DE
• Gerd Hufen · Duisburg, DE

Key dates

• Filing date: Nov 13, 1995
• Grant date: Dec 24, 1996
• Expiry date: Nov 13, 2015

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C51/43
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The present invention relates to a process for obtaining adipic acid from the aqueous nitric acid mother liquors that arise during industrial adipic acid production by PA1 (i) removing nitric acid from the aqueous mother liquor by evaporation to a concentrate having a residual content of at most about 2.5 wt. % of HNO.sub.3, PA1 (ii) mixing the concentrate obtained according to step (i) with water or dilute aqueous nitric acid in a quantity corresponding to a weight ratio of solid to liquid of about 1:2.1 to about 1:1.2, PA1 (iii) allowing the water added in step (ii) or the nitric acid added in step (ii) to act upon the concentrate for at least about 10 minutes at about 20.degree. to about 80.degree. C., and PA1 (iv) separating adipic acid as crystals that are formed (1) during step (iii) at temperatures of no more than about 35.degree. C. or (2) after step (iii) by cooling the mixture from step (iii) to about 10.degree. to about 35.degree. C.