Purification of indigo

US5109137A · kind A · utility

Assignee

• BASF SE

Inventors

• Reinhold Kohlhaupt · Bischofswerda, DE
• Manfred Gaeng · Frankenthal (Pfalz), DE
• Lothar Haas · Schifferstadt, DE
• Guenter Engelhardt · Mannheim, DE
• Walter Bieg · Grünstadt, DE
• Matthias Fankhaenel · Ludwigshafen, DE

Key dates

• Filing date: Jul 15, 1991
• Grant date: Apr 28, 1992
• Expiry date: Jul 15, 2011

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09B7/02
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

A process for the preparation of purified indigo comprises extracting the aqueous alkaline indoxylate solution arising from the synthesis with an inert water-insoluble solvent in the absence of oxygen before oxidizing the indoxylate solution to give indigo.