Process for the preparation of aromatic hydroxycarboxylic acids

US4508920A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Gerhard Stopp · Leverkusen, DE
• Horst Karkossa · Leichlingen, DE
• Viktor Trescher · Leverkusen, DE

Key dates

• Filing date: Mar 7, 1983
• Grant date: Apr 2, 1985
• Expiry date: Mar 7, 2003

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C51/15
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

Aromatic hydroxycarboxylic acids are prepared by reacting alkali metal salts of aromatic hydroxy compounds in the solid phase with carbon dioxide in a process in which the alkali metal salt of the aromatic hydroxy compound is reacted at temperatures of 120.degree. to 300.degree. C., in the form of granules, in a fluidized bed with carbon dioxide, if appropriate under elevated pressure and, if appropriate, in the presence of the aromatic hydroxy compound in the form of vapor, with continuous removal, by means of excess carbon dioxide, of the aromatic hydroxy compound which is formed, until at least 40% of the hydroxy compound have been converted into the alkali metal salt of the corresponding hydroxycarboxylic acid, and, if appropriate, the resulting alkali metal salt of the hydroxycarboxylic acid is reacted further in a subsequent stage at temperatures of 150.degree. to 300.degree. C. and under elevated pressure, in the presence of carbon dioxide, with the aromatic hydroxy compound formed, and the resulting reaction product is then converted in a customary manner into the free acid.