Process for purifying crude hydrochloric acid

US5174865A · kind A · utility

Assignees

• Dow Deutschland Inc. · DE
• THE DOW CHEMICAL COMPANY · US

Inventors

• Jeff H. Stultz · Freeport, US
• Heinz Rorup · Fredenbeck, DE
• Siegfried Unger · Buxtehude, DE
• Edmund R. Nettersheim · Dollern, DE
• Bernd Wottawa · Himmelpforten, DE

Key dates

• Filing date: Jan 25, 1991
• Grant date: Dec 29, 1992
• Expiry date: Jan 25, 2011

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S159/19
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Aqueous hydrochloric acid of very high purity can be obtained in a process for purifying crude aqueous 5 to 20 wt. % hydrochloric acid. In the purification, process water or a water/HCl mixture is evaporated from the crude aqueous hydrochloric acid at a pressure of from 0.01 to 1.0 bar and a temperature of from 10.degree. to 100.degree. C. until a crude, azeotropic mixture of water and HCl is obtained. The crude, azeotropic mixture of water and HCl is distilled in a distillation apparatus at a pressure of from 0.1 to 1.5 bar and a temperature of from 50.degree. to 110.degree. C. A purified gaseous, azeotropic mixture of water and HCl is recovered from the head of the distillation apparatus and a liquid mixture is left at the bottom of the distillation apparatus. The liquid mixture which is left at the bottom of the distillation apparatus is distilled at a pressure of from 0.5 to 2.5 bar and a temperature of from 80.degree. to 130.degree. C.