Dsm N.v.

Veerle Cauwenberg

Franciscus H Vergossen

Peter J Maas

Process for recovering a pyridine-2,3-dicarboxylic acid from a process stream in the preparation process of the pyridine-2,3-dicarboxylic acid in which the process stream is subjected to nanofiltration at a pH higher than 4.5 and the pyridine-2,3-dicarboxylic acid-containing concentrate is utilised. Preferably, the pH is chosen to be between 7 and 9 and the concentration factor in nanofiltration greater than 3. In a suitable embodiment the process stream is formed by the mother liquor obtained in the preparation of pyridine-2,3-dicarboxylic acid by oxidising a suitable quinoline or the corresponding 2,3-lutidine and separating the solid material.

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Leuven, Belgium

Veerle Cauwenberg