Promotion of imine formatin via cationic resin catalyst

1. A method for purifying a crude aniline, comprising contacting a crude aniline comprising aniline, water, and cyclohexanone with a cation exchange resin to produce a cyclohexanone-lean product that contains less cyclohexanone than the crude aniline, wherein the cation exchange resin is a solid, a semi-solid, or a combination thereof.

2. The method of claim 1 , further comprising:

hydrogenating nitrobenzene to produce the crude aniline;

separating at least a portion of the water from the crude aniline to produce a dehydrated crude aniline; and

contacting the dehydrated crude aniline with the cation exchange resin to produce the cyclohexanone-lean product.

3. The method of claim 2 , further comprising:

cooling the dehydrated crude aniline to produce a cooled dehydrated crude aniline;

contacting the cooled dehydrated crude aniline with the cation exchange resin to produce the cyclohexanone-lean product; and

introducing the cyclohexanone-lean product to a separation column to produce a purified aniline product.

4. The method of claim 3 , wherein the crude aniline comprises about 85 wt % to about 99 wt % of aniline, about 1 wt % to about 15 wt % of water, and about 100 ppmw to about 15,000 ppmw of cyclohexanone, wherein the dehydrated crude aniline comprises about 98 wt % to about 99.9 wt % of aniline, less than 0.5 wt % of water, and about 100 ppmw to about 5,000 ppmw of cyclohexanone, and wherein the purified aniline product comprises about 99 wt % to about 99.99 wt % of aniline, less than 0.5 wt % of water, and less than 100 ppmw of cyclohexanone.

5. The method of claim 1 , wherein the crude aniline is contacted with the cation exchange resin at a temperature of about 50° C. to about 150° C. for a time period of about 1 minute to about 15 minutes, and wherein the cyclohexanone-lean product contains at least 30% less cyclohexanone as compared to the crude aniline.

6. The method of claim 1 , wherein the crude aniline is contacted with the cation exchange resin at a temperature go about 50° C. to about 150° C. for a time period of less than 60 minutes, and wherein the cyclohexanone-lean product contains at least 50% less cyclohexanone as compared to the crude aniline.

7. The method of claim 1 , wherein the cation exchange resin comprises H + functional groups, sulfuric acid, HSO 4 − functional groups, or any combination thereof.

8. The method of claim 1 , wherein the cation exchange resin is in the form of pellets, beads, granules, flakes, spheres, cubes, blocks, fibers, filaments, threads, or any mixture thereof.

9. The method of claim 1 , wherein the cation exchange resin comprises a polymer based on a cross-linked styrene divinylbenzene copolymer containing sulfuric acid and HSO 4 − functional groups.

10. The method of claim 1 , wherein the cation exchange resin has an average pore diameter of about 100 Å to about 500 Å, a pore volume of about 0.1 mL/g to about 1 mL/g, and a surface area of about 10 m 2 /g to about 50 m 2 /g.

11. The method of claim 1 , wherein at least a portion of the crude aniline is contacted with the cation exchange resin at a rate of about 0.1 m 3 crude aniline per 1 m 3 of cation exchange resin per hour to about 30 m 3 of crude aniline per 1 m 3 of cation exchange resin per hour.

12. A method for purifying a crude aniline, comprising:

hydrogenating an aromatic nitro compound to produce a crude aniline comprising about 85 wt % to about 99 wt % of aniline, about 1 wt % to about 15 wt % of water, and about 100 ppmw to about 15,000 ppmw of cyclohexanone;

separating at least a portion of the water from the crude aniline to produce a dehydrated product comprising about 98 wt % or more of aniline, less than about 5,000 ppmw of water, and about 100 ppmw to about 5,000 ppmw of cyclohexanone;

reacting a portion of the cyclohexanone with a portion of the aniline in the dehydrated product to produce a cyclohexanone-reduced product comprising less cyclohexanone than the dehydrated product; and

contacting the cyclohexanone-reduced product at a temperature of about 50° C. to about 150° C. with a cation exchange resin to produce a cyclohexanone-lean product that comprises less cyclohexanone than the cyclohexanone-reduced product, wherein the cation exchange resin is solid, semi-solid, or a combination thereof.

13. The method of claim 12 , wherein the cyclohexanone-reduced product is contacted with the cation exchange resin for a time period of about 1 minute to about 15 minutes, and wherein the cyclohexanone-lean product contains at least 30% less cyclohexanone as compared to the cyclohexanone-reduced product.

14. The method of claim 13 , wherein the cation exchange resin comprises H + functional groups, sulfuric acid, HSO 4 − functional groups, or any combination thereof.

15. The method of claim 12 , wherein the cation exchange resin comprises a polymer based on a cross-linked styrene divinylbenzene copolymer containing sulfuric acid, HSO 4 − , functional groups.

16. The method of claim 12 , wherein the portion of the cyclohexanone reacted with the portion of the aniline is reacted at a temperature of about 100° C. to about 170° C.

17. A system for purifying a crude aniline, comprising:

a hydrogenation reactor configured to hydrogenate an aromatic nitro compound to produce a crude aniline comprising aniline, water, and cyclohexanone; and

a cation exchange unit configured to contact the crude aniline with a cation exchange resin to produce a cyclohexanone-lean product that contains less cyclohexanone than the crude aniline, wherein the cation exchange resin is solid, semi-solid, or a combination thereof.

18. The system of claim 17 , further comprising a dehydration unit configured to separate water from the crude aniline to produce a dehydrated crude aniline containing less water than the crude aniline, wherein the dehydration unit is located upstream of the cation exchange unit.

19. The system of claim 18 , further comprising a reactor configured to react a portion of the cyclohexanone in the dehydrated crude aniline to produce a cyclohexanone-reduced crude aniline, wherein the reactor is located upstream of the cation exchange unit and downstream of the dehydration unit.

20. The system of claim 19 , further comprising a separator configured to separate at least a portion of any impurities from the cyclohexanone-lean product to produce a purified aniline product.