SEPARATION OF N-METHYLETHYLENEDIAMINE FROM EDA-CONTAINING MIXTURES

Abstract

A process for producing EDA from a mixture comprising water (H2O), ethylenediamine (EDA) and N-methylethylenediamine (NMEDA) by feeding the mixture into a rectification column, wherein the rectification column is operated at the top pressure in the range of 5.0 to 7.5 bar.

Claims

1.-15. (canceled)

16. A process for producing EDA from a mixture comprising water (H2O), ethylenediamine (EDA) and N-methylethylenediamine (NMEDA) by feeding the mixture into a rectification column, wherein the rectification column is operated at the top pressure in the range of 5.0 to 7.5 bar and the weight ratio EDA to NMEDA in the mixture comprising water (H2O), ethylenediamine (EDA) and N-methylethylenediamine (NMEDA) fed into the rectification column is 1:0.0005 to 1:0.2.

17. The process according to claim 16, wherein the pressure at the top of the rectification column is in the range of 5.1 to 7.0 bar.

18. The process according to claim 16, wherein the rectification column has 40 to 90 theoretical plates.

19. The process according to claim 16, wherein the reflux ratio in the column is in the range of 2:1 to 4:1.

20. The process according to claim 16, wherein the rectification is a tray column.

21. The process according to claim 16, wherein the mixture comprising water, EDA and NMEDA is introduced in a spatial region between 60 to 80% of the theoretical plates.

22. The process according to claim 16, wherein the mixture comprising EDA, water and NMEDA is obtained from an ethylenamine producing process.

23. The process according to claim 16, wherein the mixture comprising EDA, water and NMEDA is obtained by the reaction of monoethanolamine and ammonia.

24. The process according to claim 16, wherein a mixture comprising EDA and higher boiling amines is obtained as a higher boiling fraction at the bottom of the rectification column and wherein the higher boiling fraction is fed into a rectification column in which EDA and PIP are obtained as the lower boiling fraction and the higher boiling amines are obtained as the higher boiling fraction and wherein the mixture of EDA and PIP is fed to a rectification column in which EDA is obtained as the lower boiling fraction and PIP is obtained as the higher boiling fraction.

25. The process according to claim 16, wherein the rectification column is operated at a top pressure at which EDA and water form a zeotropic mixture.

26. The process according to claim 16, wherein a mixture of water and NMEDA is obtained as a lower boiling fraction at the top of the rectification column.

27. The process according to claim 26, wherein the mixture obtained at the top of the rectification column is fed to a waste water treatment column and is separated into a high boiling fraction comprising water and NMEDA and a low boiling fraction comprising water.

28. The process according to claim 16, wherein ammonia and/or hydrogen has been removed from the mixture comprising water (H2O), ethylenediamine (EDA) and N-methylethylenediamine (NMEDA) before feeding the mixture into the rectification column.

29. The process according to claim 16, comprising the step of producing EDA according claim 16 and further converting the EDA to polyamides, electronic chemicals, crop protection agents, pesticides, epoxy resins, complexing agents, leather chemicals, paper chemicals, textile resins, fuel and gasoline additives, lubricants, bleach additives or detergents.

30. The process according to claim 28, wherein the mixture obtained after the removal of ammonia comprises 20 to 75 percent by weight of EDA.

Description

EXAMPLE 1

[0250] The examples are bases on calculation performed on the basis of a thermodynamic model using the NRTL model for the description of the vapour-liquid equilibrium of water, EDA, NMEDA and other higher boiling amines.

[0251] A feed of 17800 kg/h comprising 25 wt.-% water, 33 wt.-% EDA, 1400 wt.-ppm NMEDA, high boiling amines like DETA, AEEA, TETA and TEPA was fed on the 34th theoretical plate of a column with a total of 47 theoretical plates. The pressure at the top of the column was varied from 4.6 to 8.8 bar.

[0252] The concentration of NMEDA as function of the tower pressure in the top of the water separation tower is depicted in FIG. 1. With decreasing top pressure, the concentration of NMEDA in the process water is increasing until nearly all NMEDA is separated from the other amines. FIG. 1 also shows the reflux ration required to maintain an EDA concentration of less than 100 ppm in the distillate removed at the top of the distillation tower. With decreasing pressure, the separation is becoming more difficult expressed by the increasing reflux ratio of the tower.

[0253] FIG. 2 depicted the NMEDA concentration in the product EDA as function of the top pressure of the EDA-water separation. With decreasing pressure, the concentration of NMEDA in EDA is decreasing.

[0254] It can be seen, that above a pressure of 7.0 bar, the NMEDA concentration rises to values which make it difficult to obtain the EDA specifications demanded in the market. Under the pressure of 5.0 bar it's difficult to separate EDA from process water. Surprisingly, the separation is best affected at a top pressure in the narrow range of 5.0 to 7.5 bar.