Process for preparing 1-butene from technical mixtures of C4 hydrocarbons

1. A process for preparing 1-butene from a technical mixture of C 4 hydrocarbons I, wherein the technical mixture of C 4 hydrocarbons comprise at least 1-butene, isobutene, n-butane and cis and trans 2-butenes, comprising

a) reacting a portion of the isobutene present in the technical mixture to give at least one product II which boils at higher than 30° C. at standard pressure, and unconverted C 4 hydrocarbons III,

b) removing the unconverted C 4 hydrocarbons III from a) by a thermal separation process,

c) distillatively separating the C 4 hydrocarbons III into a fraction IV comprising the 1-butene and the isobutene, and a virtually isobutene-free fraction V comprising the cis and trans 2-butenes and the n-butane,

d) reacting the isobutene present in fraction IV with at least one alcohol VI in the presence of at least one acidic catalyst to give at least one tert-butyl ether VII, and unconverted C 4 hydrocarbons VIII,

e) removing the unconverted C 4 hydrocarbons VIII from d) and

f) distillatively removing the 1-butene from the C 4 hydrocarbons VIII obtained in e).

2. The process of claim 1 ,

wherein

the acid-catalyzed etherification in d) is carried out in at least one reaction stage, and wherein one reaction stage of the at least one reaction stage comprises a reactive distillation.

3. The process according of claim 1 ,

wherein

the acid-catalyzed etherification in d) is carried out in at least two reaction stages, and wherein at least the last reaction stage of the at least two reaction stages comprises a reactive distillation.

4. The process of claim 1 ,

wherein

the at least one alcohol in d) is methanol or ethanol.

5. The process of claim 4 ,

wherein

the at least one alcohol in d) is methanol.

6. The process of claim 4 ,

wherein

the at least one alcohol in d) is ethanol.

7. The process of claim 1 ,

wherein

the unconverted C4 hydrocarbons VII in e) comprise a residual amount of alcohol, and

wherein

the residual amount of alcohol is scrubbed out, in e), in an extraction step with water.

8. The process of claim 1 , further comprising an additional purification,

wherein

the polyunsaturated hydrocarbons present in the C 4 hydrocarbon stream are hydrogenated catalytically, and

wherein the additional purification is preceded by at least one of a), b), c) or d).

9. The process of claim 8 ,

wherein

the catalytic hydrogenation of the polyunsaturated hydrocarbons comprises at least two reaction stages, and

wherein

at least the last reaction stage is carried out in the presence of from 0.05 to 100 ppmw of CO.

10. The process of claim 1 ,

wherein

the reaction of a portion of the isobutene, in a), results in a conversion of the portion of the isobutene of over 70%.

11. The process of claim 1 ,

wherein

the reaction of the portion of the isobutene in a) is carried out with water or an alcohol as a co-reactant and

wherein

the reaction of a portion of the isobutene results in a conversion of the portion of isobutene of over 75%.

12. The process of claim 1 ,

wherein

the portion of isobutene reacted in a) is reacted under acidic catalysis with at least one alcohol to give at least one alkyl tert-butyl ether (ATBE) or

wherein

the portion of isobutene reacted in a) is reacted with water under acidic catalysis to give a tertiary butyl alcohol (TBA).

13. The process of claim 12 ,

wherein

the acidic catalyst comprises at least one ion exchange resin.

14. The process of claim 12 ,

wherein

the portion of isobutene reacted in a) is reacted with water under acidic catalysis to give a tertiary butyl alcohol (TBA).

15. The process of claim 12 ,

wherein

the portion of isobutene reacted in a) is reacted under acidic catalysis with at least one alcohol to give at least one alkyl tert-butyl ether (ATBE).

16. The process of claim 15 ,

wherein the at least one alcohol is methanol.

17. The process of claim 15 ,

wherein the at least one alcohol is ethanol.

18. The process of claim 15 ,

wherein,

after the portion of the isobutene has been reacted with the at least one alcohol in a), the thermal separation process in b) comprises

removal, by distillation, of the unconverted C 4 hydrocarbons together with a residual amount of the at least one alcohol, and

removal of the residual amount of the at least one alcohol, by extraction, from the unconverted C 4 hydrocarbons.

19. The process of claim 18 ,

wherein

the same at least one alcohol is used in stage a) and in stage d).

20. The process of claim 19 ,

wherein

the tert-butyl ether VII obtained in e), in the course of removal of the C 4 hydrocarbons VIII, is returned together with excess alcohol fully or partly into a), b), or a) and b).

21. The process of claim 14 ,

wherein

after the portion of the isobutene has been reacted with water in a), the thermal separation process, in b) is a distillation

wherein

the unconverted C 4 hydrocarbons are removed from the products II.

22. The process of claim 21 ,

wherein

after the portion of the isobutene has been reacted with water in a), the unconverted C 4 hydrocarbons, in b), are removed together with a little water.

23. The process of claim 1 ,

wherein

the reacting of a portion of the isobutene in a) comprises converting the portion of the isobutene to diisobutene.

24. The process of claim 23 ,

wherein

the reacting in a) is effected under acidic catalysis.

25. The process of claim 23 ,

wherein

the reacting in a) is effected in the presence of a cation exchanger.

26. The process of claim 25 ,

wherein

the cation exchanger comprises acidic hydrogen atoms, and

wherein

a portion of the acidic hydrogen atoms have been exchanged for metal ions of at least one metal of Groups 1 to 12 of the Periodic Table.

27. The process of claim 26 ,

wherein

from 1 to 70% of the acidic hydrogen atoms of the ion exchanger have been exchanged for metal ions of at least one metal of Groups 1 to 12 of the Periodic Table.

28. The process of claim 27 ,

wherein

the thermal separation in b) comprises distillation of the unconverted C 4 hydrocarbons III from the products II.

29. The process of claim 1 ,

wherein

the portion of the isobutene is reacted in a) with formaldehyde to give 4,4-dimethyl-1,3-dioxane or 3-methyl-3-buten-1-ol.

30. The process of claim 29 ,

wherein

the portion of the isobutene is reacted in a) with formaldehyde to give 4,4-dimethyl-1,3-dioxane.

31. The process of claim 29 ,

wherein

the portion of the isobutene is reacted in a) with formaldehyde to give 3-methyl-3-buten-1-ol.

32. The process of claim 1 ,

wherein

the 1-butene obtained by distillation in f) has an isobutene content of less than 5000 ppmw.