Bayer Aktiengesellschaft

Horst Karkossa

Gerhard Stopp

Viktor Trescher

Hans Uhlemann

Karl Mannes

Burkhard Braun

Hans-Joachim Laakmann

Karl-Heinz Kreutzer

Heinz Heusmann

A new process for continuously preparing granules having narrow grain size distribution, comprising

Process for preparing granulates

Particulate material is discharged continuously from fluidized bed reactors by passing the material emerging at the lowest point of the fluidized bed through a zone which is narrower than the fluidized bed and in which a gas stream flows counter-current to the material, the pressure of the gas stream being above the pressure of the fluidized zone.

Process for the simultaneous classification and regulated, continuous

Aromatic hydroxycarboxylic acids are prepared by reacting an alkali metal salt of an aromatic hydroxy compound in solid phase with carbon dioxide, by reacting an alkali metal salt of an aromatic hydroxy compound in the form of granules in a fluidized bed with carbon dioxide, if desired under elevated pressure, at first at temperatures of 20.degree. to 130.degree. C. until at least 40% of the hydroxy compound has been converted into the corresponding carbonate, then completing the reaction at temperatures of 135.degree. to 300.degree. C., and then converting the reaction product obtained into the free acid.

Process for preparing 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 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.

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Leichlingen, Germany

Horst Karkossa