Process for preparing 4-aminodiphenylamine

1. A method for refining an organic composition comprising 4-aminodiphenylamine, aniline, azobenzene, and phenazine, comprising

feeding the organic composition to a first rectification column;

producing a first effluent composition at a top of the first rectification column and a second effluent composition at a bottom of the first rectification column, wherein the first effluent composition comprises aniline, azobenzene, phenazine, and a small amount of 4-aminodiphenylamine, and the second effluent composition comprises mostly 4-aminodiphenylamine;

feeding the second effluent composition to a second rectification column; and

producing a 4-aminodiphenylamine composition at a top of the second rectification column and a residual composition at a bottom of the second rectification column,

wherein the first rectification column is operated at a vacuum degree ranging from about 0.08 MPa to about 0.1 MPa, a reflux ratio of about 0.2:1 to about 10:1, a column top temperature of from about 70° C. to about 170° C., and a still temperature of from about 230° C. to about 310° C.

2. The method of claim 1 , wherein the reflux ratio in the first rectification column is about 0.2:1 to about 4:1.

3. The method of claim 2 , wherein the reflux ratio in the first rectification column is about 0.5:1 to about 2:1.

4. The method of claim 1 , wherein the column top temperature in the first rectification column is about 80° C. to about 150° C.

5. The method of claim 1 , wherein the column still temperature in the first rectification column is about 230° C. to about 290° C.

6. The method of claim 1 , wherein the second rectification column is operated at a vacuum degree ranging from about 0.08 MPa to about 0.1 MPa, a column top temperature of from about 140° C. to about 230° C., and a still temperature of from about 250° C. to about 310° C.

7. The method of claim 6 , wherein the column top temperature in the second rectification column is from about 180° C. to about 230° C.

8. The method of claim 7 , wherein the column top temperature in the second rectification column is from about 190° C. to about 220° C.

9. The method of claim 6 , wherein the second rectification column is operated at a reflux ratio of about 0.25:1 to about 2:1.

10. The method of claim 6 , wherein the second rectification column uses an internal reflux.

11. The method of claim 1 , wherein the second effluent composition is conveyed to the second rectification column via a pump.

12. The method of claim 1 , wherein the second effluent composition is conveyed to the second rectification column via pressure difference.

13. The method of claim 1 , further comprising

feeding the first effluent composition to a third rectification column; and

producing a third effluent composition at a top of the third rectification column and a fourth effluent composition at a bottom of the third rectification column, wherein the third effluent composition comprises aniline, and the fourth effluent composition comprises azobenzene, phenazine, and a small amount of 4-aminodiphenylamine.

14. The method of claim 13 , wherein the third effluent composition comprises about 99% pure aniline.

15. The method of claim 13 , wherein the third rectification column is operated at a vacuum degree ranging from about 0.04 MPa to about 0.1 MPa, a reflux ratio of from about 0.5:1 to about 4:1, a column top temperature of from about 70° C. to about 140° C., and a still temperature of from about 120° C. to about 260° C.

16. The method of claim 15 , wherein the reflux ratio in the third rectification column is about 0.5:1to about 2:1.

17. The method of claim 15 , wherein the still temperature in the third rectification column is from about 120° C. to about 250° C.

18. The method of claim 15 , further comprising

feeding the fourth effluent composition to a phenazine distillation column, and

producing a seventh effluent composition at a top of the phenazine distillation column and an eighth effluent composition at a bottom of the phenazine distillation column, wherein the seventh effluent composition comprises mostly phenazine and a small amount of 4-aminodiphenylamine and azobenzene, and the eighth effluent composition comprises mostly 4-aminodiphenylamine and a small amount of phenazine and azobenzene.

19. The method of claim 18 , further comprising

conveying and mixing the eighth effluent composition with fresh organic composition, and

feeding and refining the mixed eighth effluent composition and organic composition in the first rectification column.

20. The method of claim 18 , wherein the phenazine distillation column is operated at a vacuum degree ranging from about 0.08 MPa to about 0.1 MPa, a column top temperature of from about 195° C. to about 205° C., and a still temperature of from about 235° C. to about 245° C.

21. The method of claim 18 , wherein the phenazine distillation column uses internal reflux.

22. The method of claim 1 , further comprising

conveying the residual composition from the bottom of the second rectification column to be mixed with fresh organic composition,

feeding and refining the mixed organic composition and the residual composition in the first rectification column.

23. The method of claim 1 , further comprising

accumulating the residual composition at the bottom of the second rectification column,

feeding the accumulated residual composition to a batch rectification column,

producing a fifth effluent composition at a top of the batch rectification column, and

discharging residues and waste at a bottom of the batch rectification column, wherein the fifth effluent composition comprises residual 4-aminodiphenylamine.

24. The method of claim 23 , wherein the batch rectification column is operated at a vacuum degree ranging from about 0.08 to about 0.1 MPa, a column top temperature of from about 200° C. to about 250° C., and a still temperature of from about 250° C. to about 350° C.

25. The method of claim 23 , wherein the 4-aminodiphenylamine composition comprises no less than about 96% of the amount of the 4-aminodiphenylamine in the organic composition.

26. The method of claim 23 , further comprising

conveying the residual 4-aminodiphenylamine from the top of the batch rectification column to the second rectification column, and

refining the residual 4-aminodiphenylamine in the second rectification column.

27. The method of claim 23 , further comprising

conveying the residual 4-aminodiphenylamine from the top of the batch rectification column to be mixed with fresh organic composition, and

feeding and refining the mixed organic composition and the residual 4-aminodiphenylamine in the first rectification column.

28. A method for refining an organic composition comprising 4-aminodiphenylamine, aniline, azobenzene, and phenazine, comprising the steps of

continuously feeding the organic composition to a first rectification column;

continuously producing a first effluent composition at a top of the first rectification column and a second effluent composition at a bottom of the first rectification column, wherein the first effluent composition comprises aniline, azobenzene, phenazine, and a small amount of 4-aminodiphenylamine, and the second effluent composition comprises 4-aminodiphenylamine;

continuously feeding the second effluent composition to a second rectification column;

continuously producing a 4-aminodiphenylamine composition at a top of the second rectification column and a residual composition at a bottom of the second rectification column;

continuously feeding and refining the residual composition to the first rectification column;

continuously feeding the first effluent composition to a third rectification column; and

continuously producing a third effluent composition at a top of the third rectification column and a fourth effluent composition at a bottom of the third rectification column, wherein the third effluent composition comprises aniline, and wherein the fourth effluent composition comprises azobenzene, phenazine, and a small amount of 4-aminodiphenylamine,

wherein the first rectification column is operated at a vacuum degree ranging from about 0.08 MPa to about 0.1 MPa, a reflux ratio of about 0.2:1 to about 10:1, a column top temperature of from about 70° C. to about 170° C., and a still temperature of from about 230° C. to about 310° C.

29. The method of claim 28 , further comprising

conveying the fourth effluent to a phenazine distillation column,

producing a seventh effluent composition at a top of the phenazine distillation column and an eighth effluent composition at a bottom of the phenazine distillation column, wherein the seventh effluent composition comprises mostly phenazine and a small amount of 4-aminodiphenylamine and azobenzene, and the eighth effluent composition comprises mostly 4-aminodiphenylamine and a small amount of phenazine and azobenzene,

mixing the eighth effluent composition with fresh organic composition, and

feeding and refining the mixed eighth effluent composition and the organic composition in the first rectification column.

30. A method for refining an organic composition comprising 4-aminodiphenylamine, aniline, azobenzene, and phenazine, comprising

continuously feeding the organic composition to a first rectification column;

continuously producing a first effluent composition at a top of the first rectification column and a second effluent composition at a bottom of the first rectification column, wherein the first effluent composition comprises aniline, azobenzene, phenazine, and a small amount of 4-aminodiphenylamine, and the second effluent composition comprises 4-aminodiphenylamine;

continuously feeding the second effluent composition to a second rectification column;

continuously producing a 4-aminodiphenylamine composition at a top of the second rectification column and a residual composition at a bottom of the second rectification column;

continuously feeding the first effluent composition to a third rectification column;

continuously producing a third effluent composition at a top of the third rectification column and a fourth effluent composition at a bottom of the third rectification column, wherein the third effluent composition comprises aniline, and wherein the fourth effluent composition comprises azobenzene, phenazine, and a small amount of 4-aminodiphenylamine;

feeding the residual composition to a batch rectification column; and

producing a fifth effluent composition comprising residual 4-aminodiphenylamine at a top of the batch rectification column and discharging residues and waste at a bottom of the batch rectification column,

wherein the first rectification column is operated at a vacuum degree ranging from about 0.08 MPa to about 0.1 MPa, a reflux ratio of about 0.2:1 to about 10:1, a column top temperature of from about 70° C. to about 170° C., and a still temperature of from about 230° C. to about 310° C.

31. The method of claim 30 , further comprising

conveying the fifth effluent composition to the first rectification column, and

refining the fifth effluent composition in the first rectification column.

32. The method of claim 30 , further comprising

conveying the fifth effluent composition to the second rectification column, and

refining the fifth effluent composition in the second rectification column.