Process for the preparation of phosphorous acid

US5147625A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Alexander Tapper · Mönchengladbach, DE
• Horst Buhl · Waiblingen, DE
• Josef Holz · Lechenich, DE

Key dates

• Filing date: Aug 2, 1991
• Grant date: Sep 15, 1992
• Expiry date: Aug 2, 2011

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01B25/163
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

In a continuous process for the preparation of phosphorous acid with simultaneous production of hydrochloric acid, a reaction zone is provided which is in open communication with a first scrubbing zone. A portion of the reaction product is recycled from the bottom of the reaction zone into the top of the scrubbing zone and phosphorous acid is removed from the circulation. Hydrogen chloride gas escaping from the top of the first scrubbing zone is brought into contact, in a cooled, second scrubbing zone, with an overstoichiometric amount of water. Hydrochloric acid is obtained which is passed as starting material into the reaction zone or into the top of the first scrubbing zone. The external cooling of the second scrubbing zone is controlled such that the temperature in the reaction zone is kept constant at a desired value between 90.degree. and 130.degree. C. without adding any external cooling or heating energy. Pure hydrochloric acid is recovered in an absorption zone.