Process for oligomerization of isobutene

1. A process for producing diisobutene comprising:

performing an oligomerization of isobutene in the absence of an oxygenate over an acid catalyst in at least one reaction stage which in each case contains at least one reactor and at least one distillation column,

wherein an isobutene-containing input stream, which comprises an isobutene-containing hydrocarbon stream as feed and a recirculated stream as recycle, is converted in the at least one reactor of the at least one reaction stage to obtain a product mixture containing at least the diisobutene formed having a proportion of 2,4,4-trimethylpent-1-ene of at least 75 mol %, and unconverted isobutene, and an obtained product mixture is supplied to the at least one distillation column,

wherein at the top of the distillation column a residual hydrocarbon stream depleted in the diisobutene formed based on the obtained product mixture is withdrawn and at least partially recirculated to the at least one reactor as recycle,

wherein a ratio of recycle to feed is at least 4, whereby the selectivity of the oligomerization is increased such that the diisobutene formed has said proportion of 2,4,4-trimethylpent-1-ene.

2. The process according to claim 1 , wherein the ratio of recycle to feed is at least 5.

3. The process according to claim 2 , wherein the ratio of recycle to feed is at least 6.

4. The process according to claim 1 , wherein the isobutene-containing hydrocarbon stream is a C 4 -hydrocarbon stream.

5. The process according to claim 1 , wherein the isobutene-containing hydrocarbon stream is a pure isobutene stream.

6. The process according to claim 1 , wherein the residual hydrocarbon stream withdrawn at the top of the distillation column is completely recirculated to the at least one reactor.

7. The process according to claim 1 , wherein the at least one reaction stage comprises at least two reactors which are connected in series or parallel relative to one another.

8. The process according to claim 1 , wherein the oligomerization is performed in a liquid phase.

9. The process according to claim 1 , wherein the acid catalyst is an acidic ion exchange resin in which a portion of acidic protons have been exchanged for metal ions.

10. The process according to claim 9 , wherein 0.1% to 70% of the acidic protons of the acidic ion exchange resin have been exchanged for metal ions.

11. The process according to claim 9 , wherein the metal ions are ions of alkali metals, alkaline earth metals, and/or rare earths.

12. The process according to claim 1 , wherein the at least one reactor is a flow reactor.

13. The process according to claim 1 , wherein the at least one reactor is operated adiabatically, polytropically, or virtually isothermally using a coolant.

14. The process according to claim 1 , wherein the oligomerization is performed at a temperature between 5° C. and 160° C.

15. The process according to claim 1 , wherein a first reaction stage is run with a total feed of the is butene-containing input stream of at least 2.5 t per t of catalyst and hour (h) (unit t/(t*h)).

16. The process according to claim 1 , wherein the product mixture containing at least the diisobutene formed has proportion of 2,4,4-trimethylpent-1-ene of at least 78 mol %.

17. The process according to claim 10 , wherein 30% to 60% of the acidic protons of the acidic ion exchange resin have been exchanged for metal ions.

18. The process according to claim 12 , wherein the flow reactor is a fixed bed reactor, a tube bundle reactor, a continuous stirred tank reactor, or a loop reactor.

19. The process according to claim 14 , wherein the oligomerization is performed at a temperature between 40° C. and 90° C.

20. The process according to claim 15 , wherein the first reaction stage is run with a total feed of the isobutene-containing input stream of at least 3.5 t per t of catalyst and hour (h).