Process for purifying and concentrating spent sulfuric acids

US6156288A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Heiko Beckhaus · Leverkusen, DE
• Jurgen Munnig · Kaarst, DE
• Dieter Grenner

Key dates

• Filing date: Dec 4, 1998
• Grant date: Dec 5, 2000
• Expiry date: Dec 4, 2018

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01B17/90
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A process is provided for the purification of sulfuric acid contaminated with impurities, such as nitric acid, nitrosylsulfuric acid, dinitrotoluenes and mononitrotoluenes, wherein this contaminated sulfuric acid was obtained from the production of nitrated toluene using toluene and nitric acid. The contaminated sulfuric acid is preheated to a temperature in the range of 50 to 180.degree. C. in a heat exchanger. The heated, contaminated sulfuric acid is freed from steam-volatile impurities, such as dinitrotoluenes and mononitrotoluenes, and the nitrogen-containing compounds within the sulfuric acid are decomposed by counter currently contacting the contaminated sulfuric acid with steam and vapors from a downstream concentration step in a steam stripper, which is operated at a pressure ranging from 300 to 1,000 mbars. The steam-stripped sulfuric acid is fed into a first concentration stage, which is operated at the same pressure used in the steam stripper. The concentrated sulfur acid is then fed into a vacuum concentration process which produces a sulfuric acid having a concentration of 88 to 97 percent by weight. By using the same pressure that the steam stripper operates at in th…