Method for producing 2-methylbutanal from the secondary flows arising in the production of mixtures of isomeric alpha, beta-unsaturated decenals

1. A process for preparing 2-methylbutanal from the secondary streams obtained in the preparation of mixtures of isomeric α,β-unsaturated decenals, characterized in that

a) a mixture comprising linear butenes is reacted in the presence of transition metal compounds of group VIII of the Periodic Table of the Elements with carbon monoxide and hydrogen at elevated temperature and elevated pressure to give a pentanal mixture;

b) the pentanal mixture obtained in step a) is converted in the presence of basic compounds to a mixture of isomeric α,β-unsaturated decenals; and

c) the mixture obtained in step b) is separated into a stream enriched with unconverted 2-methylbutanal and a stream enriched with a mixture of isomeric α,β-unsaturated decenals; with the proviso that the stream which has been separated off in step c) and is enriched with unconverted 2-methylbutanal is reacted with formaldehyde.

2. The process as claimed in claim 1 , characterized in that the reaction with formaldehyde is effected in the presence of a secondary amine and a mono-, di- or polycarboxylic acid.

3. The process as claimed in claim 2 , characterized in that distillation is effected in the course of the reaction with formaldehyde.

4. The process as claimed in claim 1 , characterized in that the 2-methylbutanal obtained in step c) is oxidized to 2-methylbutyric acid, hydrogenated to 2-methylbutanol or reductively aminated to 2-methylbutylamines.

5. The process as claimed in claim 1 , characterized in that the mixture of isomeric α,β-unsaturated decenals obtained in step c) is completely hydrogenated to give a mixture of isomeric decanols or selectively hydrogenated to give a mixture of isomeric decanals.

6. The process as claimed in claim 5 , characterized in that the mixture of isomeric decanals is oxidized to give a mixture of isomeric decanoic acids or reductively aminated to give a mixture of isomeric decylamines.

7. A process for preparing 2-methylbutanal from the secondary streams obtained in the preparation of mixtures of isomeric decanals, characterized in that

a) a mixture comprising linear butenes is reacted in the presence of transition metal compounds of group VIII of the Periodic Table of the Elements with carbon monoxide and hydrogen at elevated temperature and elevated pressure to give a pentanal mixture;

b) the pentanal mixture obtained in step a) is converted in the presence of basic compounds to a mixture of isomeric α,β-unsaturated decenals;

c) the mixture obtained in step b) is selectively hydrogenated in the presence of a hydrogenation catalyst with hydrogen at elevated temperature and elevated pressure to give a mixture of isomeric decanals; and

d) the mixture obtained in step c) is separated into a stream enriched with unconverted 2-methylbutanal and a stream enriched with a mixture of isomeric decanals; with the proviso that the stream which has been separated off in step d) and is enriched with unconverted 2-methylbutanal is reacted with formaldehyde.

8. The process as claimed in claim 7 , characterized in that the reaction with formaldehyde is effected in the presence of a secondary amine and a mono-, di- or polycarboxylic acid.

9. The process as claimed in claim 8 , characterized in that distillation is effected in the course of the reaction with formaldehyde.

10. The process as claimed in claim 7 , characterized in that the 2-methylbutanal obtained in step d) is oxidized to 2-methylbutyric acid, hydrogenated to 2-methylbutanol or reductively aminated to 2-methylbutylamines.

11. The process as claimed in claim 1 , characterized in that the reaction with formaldehyde is followed by distillative removal of 2-methylbutanal.

12. The process as claimed in claim 11 , characterized in that the 2-methylbutanal obtained is oxidized to 2-methylbutyric acid, hydrogenated to 2-methylbutanal or reductively aminated to 2-methylbutylamines.

13. The process as claimed in claim 7 , characterized in that the mixture of isomeric decanals obtained in step d) is hydrogenated to give a mixture of isomeric decanols, oxidized to give a mixture of isomeric decanoic acids or reductively aminated to give a mixture of isomeric decylamines.

14. The process as claimed in claim 2 , characterized in that the 2-methylbutanal obtained in step c) is oxidized to 2-methylbutyric acid, hydrogenated to 2-methylbutanol or reductively aminated to 2-methylbutylamines.

15. The process as claimed in claim 3 , characterized in that the 2-methylbutanal obtained in step c) is oxidized to 2-methylbutyric acid, hydrogenated to 2-methylbutanol or reductively aminated to 2-methylbutylamines.

16. The process as claimed in claim 2 , characterized in that the mixture of isomeric α,β-unsaturated decenals obtained in step c) is completely hydrogenated to give a mixture of isomeric decanols or selectively hydrogenated to give a mixture of isomeric decanals.

17. The process as claimed in claim 3 , characterized in that the mixture of isomeric α,β-unsaturated decenals obtained in step c) is completely hydrogenated to give a mixture of isomeric decanols or selectively hydrogenated to give a mixture of isomeric decanals.

18. The process as claimed in claim 8 , characterized in that the 2-methylbutanal obtained in step d) is oxidized to 2-methylbutyric acid, hydrogenated to 2-methylbutanol or reductively aminated to 2-methylbutylamines.

19. The process as claimed in claim 9 , characterized in that the 2-methylbutanal obtained in step d) is oxidized to 2-methylbutyric acid, hydrogenated to 2-methylbutanol or reductively aminated to 2-methylbutylamines.

20. The process as claimed in claim 7 , characterized in that the reaction with formaldehyde is followed by distillative removal of 2-methylbutanal.