Lowering nitrogen-containing Lewis bases in molecular sieve oligomerisation

Abstract

Nitrogen-containing Lewis bases act as poisons for molecular sieve catalysts used in oligomerisation reactions. A lowering of their presence in the feed prior to the contacting thereof with the molecular sieve brings a significant extension of catalyst life. Excessive elimination of these poisons may be disadvantageous. Lowering the levels of these catalyst poisons to more manageable concentrations is therefore preferred.

Description

Claims

1. A process for the oligomerisation of olefins comprising: (a) treating an olefin-containing hydrocarbon stream comprising an organic nitrogen-containing Lewis base to thereby lower the concentration of the organic nitrogen-containing Lewis base in the olefin-containing hydrocarbon stream; and(b) subsequently contacting the treated olefin-containing hydrocarbon stream with a molecular sieve oligomerisation catalyst.

2. The process according to claim 1 wherein the concentration of said Lewis base is lowered to a concentration that is not less than 0.1 ppm by weight based on the total treated hydrocarbon stream.

3. The process according to claim 1 wherein the concentration of said Lewis base prior to said treatment step is at least 1 ppm by weight, based on the total hydrocarbon stream, and at most 40 ppm by weight on the same basis.

4. The process according to claim 1 wherein the concentration of said Lewis base is lowered to a concentration of at most 5 ppm by weight based on the total hydrocarbon stream.

5. The process according to claim 4 wherein the concentration of said Lewis base is lowered to a concentration of at most 2 ppm by weight.

6. The process according to claim 5 wherein the concentration of said Lewis base is lowered to a concentration of at most 1 ppm by weight.

7. The process according to claim 1 wherein the concentration of said Lewis base in the hydrocarbon stream being contacted with said oligomerisation catalyst is from 0.1 to 2.0 ppm by weight based on the total hydrocarbon stream.

8. The process according to claim 1 wherein the concentration of said Lewis base in the hydrocarbon stream being contacted with said oligomerisation catalyst is from 0.1 to 1.0 ppm by weight, based on the total hydrocarbon stream.

9. The process according to claim 8 wherein the concentration of said Lewis base in the hydrocarbon stream being contacted with said oligomerisation catalyst is from 0.2 to 0.8 ppm by weight, based on the total hydrocarbon stream.

10. The process according to claim 1 wherein said Lewis base comprises acetonitrile, propionitrile, dimethylformamide or N-methyl-pyrrolidone.

11. The process according to claim 1 wherein the olefin is selected from the group consisting of ethylene, propylene, butene-1, isobutylene, trans-butene-2, cis-butene-2, normal pentene-1, normal pentene-2,3-methyl-butene-1,3-methyl-butene-2,2-methyl-butene-1,2-methyl-butene-2 and mixtures of any two, three, four or more olefins selected therefrom.

12. The process according to claim 1 wherein the olefin-containing hydrocarbon stream is obtained by catalytic cracking, steamcracking, or dehydrogenation of a hydrocarbon starting material.

13. The process according to claim 1 wherein the olefin-containing hydrocarbon stream further comprises a diene and/or acetylene, and the concentration of diene and/or acetylene is lowered prior to oligomerisation.

14. The process according to claim 13 wherein the diene is butadiene and the butadiene concentration is lowered by an extraction step.

15. The process according to claim 14 wherein the extraction step utilises a compound selected from the group of dimethylformamide, N,N-dimethyl acetamide, β-methoxy propionitrile and N-methyl-pyrrolidone, and is performed prior to said Lewis base lowering treatment step.

16. The process according to claim 13 wherein the concentration of said diene and/or acetylene is lowered by a hydrogenation step.

17. The process according to claim 13 wherein the concentration of said diene and/or acetylene is lowered by a fractionation step.

18. The process according to claim 1 wherein the olefin-containing hydrocarbon stream comprises isobutylene, said process further comprising lowering the concentration of isobutylene prior to oligomerisation.

19. The process according to claim 18 wherein the concentration of isobutylene is lowered by a process selected from conversion to MTBE, conversion to ETBE, conversion to DIB or another oligomer of isobutylene, conversion to polyisobutylene (PIB), and conversion to a higher carbon number hydrocarbon boiling in the boiling range of gasoline, distillate or lubricant oil.

20. The process according to claim 1 wherein the treatment step to lower the concentration of said Lewis base comprises an extraction step.

21. The process according to claim 20 wherein the extraction step comprises a plurality of extraction steps.

22. The process according to claim 21 wherein the extraction is performed in a multistage countercurrent extraction column.

23. The process according to claim 22 wherein the column comprises from 4 to 8 theoretical stages.

24. The process according to claim 20 wherein the extraction step is a water wash, which produces a waste water byproduct.

25. The process according to claim 24, wherein the water used in the water wash has a pH of at most 9.5.

26. The process according to claim 24 wherein the waste water byproduct is reused as process water in a different process or process step.

27. The process according to claim 24 wherein the wash water is not treated with a corrosion inhibitor.

28. The process according to claim 24 wherein the wash water is demineralised water.

29. The process according to claim 24 wherein the water wash operates with a ratio of wash water flow to hydrocarbon flow of 0.1 to 1.7 on a liquid volume basis.

30. The process according to claim 20 wherein the extraction step operates at a temperature from 5 to 50° C.

31. The process according to claim 1 wherein the treatment step to lower the concentration of said Lewis base comprises the use of a solid material, catalytic or non catalytic, acting as a sorbent capable of adsorbing said Lewis base.

32. The process according to claim 1 wherein the oligomerisation produces an oligomer having an atmospheric boiling point that is within the boiling range of gasoline or distillate.

33. The process according to claim 32 further comprising blending the oligomer into motor gasoline or distillate.

34. The process according to claim 32 further comprising hydroformylating the oligomer to produce a hydroformylation product comprising an aldehyde.

35. The process according to claim 34 further comprising oxidising the aldehyde to produce an acid.

36. The process according to claim 35 further comprising esterifying the acid to produce an ester.

37. The process according to claim 36 further comprising blending the ester into a lubricant.

38. The process according to claim 34 further comprising hydrogenating the aldehyde to produce an alcohol.

39. The process according to claim 32 further comprising hydroformylating the oligomer to produce a hydroformylation product comprising an alcohol.

40. The process according to claim 38 further comprising esterifying the alcohol to produce an ester.

41. The process according to claim 40 wherein the ester is selected from the group consisting of an ortho-phthalate di-ester, a terephthalate di-ester, an isophthalate di-ester, an adipate di-ester, a trimellitate tri-ester, a benzoate ester, a cyclohexanoate mono-ester and a cyclohexanoate di-ester.