Process for the preparation of aromatic hydroxycarboxylic acids

Abstract From the Canadian patent

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 slat of the aromatic hydroxy comound is reacted at temperatures of 120 to 300°C in the, form of granules, in a fluidized bed with carbon dioxide if appropriate under elevated pressure and if appro-, priate, in the presence of the aromatic hydroxy compound in the form of vapour, with continuous removal by means, of excess carbon dixoide, of the aromatic hydroxy compound which is formed, until at least 40% of the hydroxy compound have been converted into the alkali metal salt at the corresponding …