Method for obtaining alcohols from aldehydes III

1. A method for preparing saturated C n - and C 2n -alcohols where n=4, 5 and 6, the method comprising the method steps of

a) providing a mixture of isomeric C n -aldehydes comprising unbranched aldehydes, wherein the proportion of unbranched aldehydes is at least 20% by weight, based on the C n -aldehydes, wherein the C n -aldehydes were prepared by hydroformylation of isomeric olefins having 3 to 5 carbon atoms with synthesis gas in the presence of a hydroformylation catalyst to form the aldehydes specified, and wherein the proportion of unbranched aldehydes is from 40 to 99.5% by weight, based on the C n -aldehydes, wherein the hydroformylation comprises a catalyst system comprising rhodium as central atom and is complexed with the ligand (1)

and an organic amine of formula (2)

in which Ra, Rb, Rc, Rd, Re and Rf represent identical or different hydrocarbon radicals which may also be bonded to one another,

b) carrying out a distillation for the at least partial separation of the isomeric C n aldehydes into a first stream having a higher proportion of linear aldehydes than the mixture provided in a) and into a second stream having a higher proportion of branched aldehydes than the mixture provided in a),

c) carrying out an aldol condensation in a tubular reactor of the aldehydes present in the first stream having a higher proportion of linear aldehydes than the mixture provided in a) to obtain a mixture of C n - and α,β-unsaturated C 2n -aldehydes wherein the tubular reactor comprises a mixing module which disperses the reactant aldehyde into droplets having an average diameter (Sauter diameter) of 0.2 mm to 2 mm in a process liquor comprising aqueous sodium hydroxide solution and sodium salts of carboxylic acids and has a sodium content of 0.6 to 1.75%,

d) mixing the mixture of C n - and α,β-unsaturated C 2n -aldehydes obtained in c) with the second stream, provided in b), having a higher proportion of branched C n aldehydes than the mixture provided in a),

e) hydrogenating the mixture of C n - and α,β-unsaturated C 2n -aldehydes and C n -aldehydes obtained in d) with hydrogen to obtain a mixture of saturated C n and C 2n -alcohols, and

f) separating the mixture of C n and C 2n -alcohols.

2. The method according to claim 1 , wherein the ligand (1) is 3,3′-di-tert-butyl-5,5′-dimethoxy-[1,1′-biphenyl]-2,2′-diyltetrakis(2,4-dimethylphenyl)bis(phosphite).

3. The method according to claim 2 , wherein the organic amine comprises at least one 2,2,6,6-tetramethylpiperidine

4. The method according to claim 1 , wherein the aldol condensation in step a) is carried out in the presence of aqueous sodium hydroxide solution, and wherein the proportion of unbranched aldehydes is from 95 to 99.5% by weight, based on the C n -aldehydes.

5. The method according to claim 1 , wherein the process liquor has a pH in the range from 12.5 to 13.5.

6. The method according to claim 1 , wherein the aldol condensation of the C n -aldehydes according to step a) is carried out in a temperature range from 100 to 150° C.

7. The method according to claim 1 , wherein a reaction pressure in the tubular reactor during the aldol condensation of the C n -aldehydes according to step a) is in a range from 0.2 to 1.0 MPa.

8. The method according to claim 1 , wherein the hydrogenation according to step b) is carried out in a temperature range from 170° C. to 200° C. at a pressure of 15*10 5 Pa to 30*10 5 Pa over a supported catalyst which contains at least nickel and copper as active components.

9. The method according to claim 1 , wherein the hydrogenation according to step b) is carried out with hydrogen in a pressure range from 5 to 100 bar and the hydrogenation temperatures are between 120 and 220° C.

10. The method according to claim 1 wherein n=5.

11. The method according to claim 2 , wherein the aldol condensation in step a) is carried out in the presence of aqueous sodium hydroxide solution.

12. The method according to claim 3 , wherein the aldol condensation in step a) is carried out in the presence of aqueous sodium hydroxide solution.

13. The method according to claim 2 , wherein the process liquor has a sodium content of 1.1 to 1.20% by mass and a pH in the range from 12.5 to 13.5.

14. The method according to claim 3 , wherein the process liquor has a sodium content of 1.1 to 1.20% by mass and a pH in the range from 12.5 to 13.5.

15. The method according to claim 2 , wherein the aldol condensation of the C n -aldehydes according to step a) is carried out in a temperature range from 100 to 150° C.

16. The method according to claim 3 , wherein the aldol condensation of the C n -aldehydes according to step a) is carried out in a temperature range from 100 to 150° C.

17. The method according to claim 2 , wherein a reaction pressure in the tubular reactor during the aldol condensation of the C n -aldehydes according to step a) is in a range from 0.2 to 1.0 MPa.

18. The method according to claim 2 , wherein the hydrogenation according to step b) is carried out in a temperature range from 170° C. to 200° C. at a pressure of 15*10 5 Pa to 30*10 5 Pa over a supported catalyst which contains at least nickel and copper as active components.

19. The method according to claim 1 , wherein the hydrogenation according to step b) is carried out with hydrogen in a pressure range from 5 to 100 bar and the hydrogenation temperatures are between 120 and 220° C.

20. The method according to claim 2 , wherein n=5.