PROCESS FOR THE PREPARATION OF AROMATIC HYDROXYCARBOXYLIC ACIDS

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.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 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 hydroxycarboxylic acid, and, if appropriate, the resulting alkali metal slat of the hydroxycarboxylic acid is reacted further in a subsequent stage at temperatures of 150 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.