Combined preparation of at least butene and octene from ethene

1. A process for the combined preparation of at least butene and octene from ethene, the process comprising:

a) providing an inert solvent;

b) mixing ethene having a purity of more than 99.9% and said inert solvent to provide a first feed mixture comprising said inert solvent and ethene dissolved therein;

c) in a first synthesis, oligomerizing at least a portion of the ethene present in the first feed mixture in the presence of a first heterogeneous catalyst to obtain a first reaction mixture comprising said inert solvent, butenes, hexenes and octenes;

d) working-up of the first reaction mixture and/or a stream based thereon into a low boiler fraction comprising the inert solvent, at least one C 4 -fraction comprising butenes, a C 6 -fraction comprising hexenes, a C 8 -fraction comprising octenes and into a C 8+ -fraction comprising hydrocarbons having more than eight carbon atoms;

e) recycling at least a portion of the low boiler fraction to the first feed mixture;

f) mixing hexene and ethene to provide a second feed mixture comprising ethene dissolved in the hexene wherein hexene is provided using at least a portion of the C 6 -fraction;

g) in a second synthesis, reacting at least a portion of the ethene present in the second feed mixture with at least a portion of the hexene present in the second feed mixture in the presence of a second heterogeneous catalyst to obtain a second reaction mixture comprising at least octene, wherein the second synthesis is spatially separated from the first synthesis; and

h) feeding the second reaction mixture to the working-up of said first reaction mixture;

wherein said inert solvent has a boiling point or boiling range below any butene formed in said first synthesis;

a solid is used as the first heterogenous catalyst and/or the second heterogenous catalyst which comprises at least two components,

wherein a first component comprises at least one element selected from the group consisting of Ni, Cr, Fe, and Ti, which is present in a metallic and/or oxidic and/or hydridic form, and

wherein a second component comprises at least one metal oxide selected from the group consisting of Al 2 O 3 , SiO 2 , TiO 2 , and ZrO 2 and mixtures thereof.

2. The process according to claim 1 , wherein the low boiler fraction is separated at the top from the first reaction mixture or from the substance stream based on the first reaction mixture using a first distillation column to obtain an essentially solvent-free bottom product from which in turn the C 4 -fraction, the C 6 -fraction, the C 8 -fraction and the C 8+ -fraction are separated.

3. The process according to claim 2 , wherein the low boiler fraction in the first synthesis and/or in the second synthesis comprises unreacted ethene in addition to said inert solvent.

4. The process according to claim 1 , wherein said inert solvent is propane or isobutane or a mixture thereof.

5. The process according to claim 1 said first synthesis is carried out at the following conditions with the provision that said inert solvent is present in a liquid phase in said oligomerizing:

Temperature: 20° C. to 150° C.,

Pressure: 1*10 5 Pa to 50*10 5 Pa,

Weight hourly space velocity: 3 to 50 h −1 , and

a molar ratio of ethene to said solvent in the first feed mixture is adjusted to a value of 0.1 to 0.5.

6. The process according to claim 5 , wherein the ethene is completely dissolved in the liquid inert solvent at the first synthesis conditions.

7. The process according to claim 5 , wherein the ethene is partially dissolved in the liquid inert solvent and is present partially in the gas phase at the first synthesis conditions.

8. The process according to claim 1 , wherein the second feed mixture comprises ethene at a proportion of from 0.1% by weight to 30% by weight and wherein the second synthesis is carried out at a temperature of from 20° C. to 150° C. and at a pressure of from 1*10 5 Pa to 50*10 5 Pa, wherein the proportion of ethene in the second feed mixture and the reaction conditions of the second synthesis are selected so that the hexene is present in a liquid phase and the ethene is completely dissolved therein.

9. The process according to claim 1 , wherein the second reaction mixture is provided exclusively using at least a portion of the C 6 -fraction and by adding ethene.

10. The process according to claim 9 , wherein the second reaction mixture is provided exclusively using a first portion of the C 6 -fraction and by adding ethene and that a second portion of the C 6 -fraction is discharged.

11. The process according to claim 9 , wherein the second reaction mixture is provided exclusively using the entire C 6 -fraction and by adding ethene.

12. The process of claim 1 , wherein said first reaction mixture further comprises ethene and said low boiler fraction comprises ethene and said inert solvent.

13. The process of claim 1 , further comprising discharging the first reaction mixture from a reactor with said inert solvent as a transport medium after the first synthesis.

14. A process for the combined preparation of at least butene and octene from ethene, the process comprising:

a) providing an inert solvent;

b) mixing ethene having a purity of more than 99.9% and said inert solvent to provide a first feed mixture comprising said inert solvent and ethene dissolved therein;

c) in a first synthesis, oligomerizing at least a portion of the ethene present in the first feed mixture in the presence of a first heterogeneous catalyst to obtain a first reaction mixture comprising said inert solvent, butenes, hexenes and octenes;

d) working-up of the first reaction mixture and/or a stream based thereon into a low boiler fraction comprising the inert solvent, at least one C 4 -fraction comprising butenes, a C 6 -fraction comprising hexenes, a C 8 -fraction comprising octenes and into a C 8+ -fraction comprising hydrocarbons having more than eight carbon atoms;

e) recycling at least a portion of the low boiler fraction to the first feed mixture;

f) mixing hexene and ethene to provide a second feed mixture comprising ethene dissolved in the hexene wherein hexene is provided using at least a portion of the C 6 -fraction;

g) in a second synthesis, reacting at least a portion of the ethene present in the second feed mixture with at least a portion of the hexene present in the second feed mixture in the presence of a second heterogeneous catalyst to obtain a second reaction mixture comprising at least octene, wherein the second synthesis is spatially separated from the first synthesis; and

h) feeding the second reaction mixture to the working-up of said first reaction mixture;

wherein said inert solvent has a boiling point or boiling range below any butene formed in said first synthesis;

a solid is used as the first heterogenous catalyst which comprises at least two components,

wherein a first component comprises at least one element selected from the group consisting of Ni, Cr, Fe, and Ti, which is present in a metallic and/or oxidic and/or hydridic form, and

wherein a second component comprises at least one metal oxide selected from the group consisting of Al 2 O 3 , SiO 2 , TiO 2 , and ZrO 2 and mixtures thereof.

15. The process of claim 14 , wherein a solid is used as the second heterogenous catalyst which comprises at least two components,

wherein a first component of said second heterogeneous catalyst comprises at least one element selected from the group consisting of Ni, Cr, Fe, and Ti, which is present in a metallic and/or oxidic and/or hydridic form, and

wherein a second component of said second heterogeneous catalyst comprises at least one metal oxide selected from the group consisting of Al 2 O 3 , SiO 2 , TiO 2 , and ZrO 2 and mixtures thereof.

16. The process of claim 14 , further comprising discharging the first reaction mixture from a reactor with said inert solvent as a transport medium after the first synthesis.

17. The process of claim 14 , wherein said first reaction mixture further comprises ethene and said low boiler fraction comprises ethene and said inert solvent.