Method and device for producing an aqueous acrylamide solutions using a biocatalysts

1 . Method for producing an aqueous acrylamide solution by the hydration of acrylonitrile in an aqueous solution in the presence of a biocatalyst, characterised in that the biocatalyst is separated from the aqueous acrylamide solution within ≦2 hours, preferably within ≦1 hour of the end of the reaction.

2 . Method according to claim 1 , characterised in that the biocatalyst is separated with a tubular centrifuge.

3 . Method according to claim 1 , characterised in that the biocatalyst is separated with an at least partially continuously operating, self-draining centrifuge.

4 . Method according to claim 3 , characterised in that the centrifuge is an annular gap centrifuge.

5 . Method according to any one of claims 2 to 4 , characterised in that the clear discharge from the centrifuge is preferably monitored using an optical means, particularly preferably a light barrier.

6 . Method according to claim 5 , characterised in that the monitoring is used to control the centrifuges.

7 . Method according any one of claims 1 to 6 , characterised in that the biocatalyst is flocculated before the separation.

8 . Method according to claim 7 , characterised in that aluminium sulphate is used as the flocculation agent.

9 . Method according to claim 7 , characterised in that an anionic polymer is used as the flocculation agent.

10 . Method according to any one of claims 7 to 9 , characterised in that the flocculation is performed at a pH value of 6.8 to 8.0, preferably 7.0 to 7.5.

11 . Method according to any one of claims 1 to 10 , characterised in that the aqueous acrylamide solution freed of biocatalyst is set to a pH value of 4.5 to 7.0, preferably 5.5 to 6.5.

12 . Method according to any one of claims 1 to 11 , characterised in that the separated biocatalyst is freed of acrylamide by at least a single, preferably multiple washing and separation.

13 . Method according to claim 12 , characterised in that the washing is performed with deionised water.

14 . Method according to claim 12 or 13 , characterised in that the acrylamide concentration in the biocatalyst is <10 ppm, preferably <5 ppm.

15 . Method according to any one of claims 12 to 14 , characterised in that the washing water is recycled in the process.

16 . Method according to any one of claims 12 to 15 , characterised in that the biocatalyst is sterilised after the washing.

17 . Method according to any one of claims 1 to 16 , characterised in that the biocatalyst is Rhodococcus rhodochrous filed under the deposition number 14230 with DSMZ, Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Maschroder Weg 1b, D-38124 Braunschweig, Germany.

18 . Device for the production of an aqueous acrylamide solution by the hydration of acrylonitrile in an aqueous solution in the presence of a biocatalyst with a reactor and a tubular centrifuge for separating the biocatalyst from the aqueous acrylamide solution.

19 . Device for the production of an aqueous acrylamide solution by the hydration of acrylonitrile in an aqueous solution in the presence of a biocatalyst with a reactor and a self-draining, at least partially continuously operating centrifuge, to separate the biocatalyst from the aqueous acrylamide solution.

20 . Device according to claim 19 , characterised in that the centrifuge is an annular gap centrifuge.

21 . Device according to any one of claims 18 to 20 , characterised in that the clear discharge from the centrifuge is monitored using an optical means.

22 . Device according to claim 21 , characterised in that a signal is used to control the centrifuge.