Method for replacement of phosgene synthesis column catalyst

Patent metadata

Field	Value
Publication number	US-10046289-B2
Application number	US-201515536425-A
Country	US
Kind code	B2
Filing date	Jan 16, 2015
Priority date	Jan 7, 2015
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

The present invention discloses a method of quickly desorbing phosgene from a catalyst in a phosgene synthesizing tower when the catalyst in the phosgene synthesizing tower is replaced. The method is carried out by first purging out easily-desorbed phosgene from the catalyst activated carbon in the phosgene synthesizing tower with nitrogen gas, then purging with ammonia gas, and the ammonia gas is reacted with the hardly-desorbed phosgene in the catalyst of the phosgene synthesizing tower. Then the phosgene synthesizing tower is rinsed with a water gun and then dried with hot gas. The phosgene content at an outlet of the phosgene synthesizing tower after purging is below 0.5 ppm, which can significantly save the time of the phosgene synthesizing tower for purging the phosgene, greatly reduce the amount of nitrogen gas consumed, and improve the safety of the process operation.

First claim

The invention claimed is:

1. A method of quickly desorbing phosgene from a catalyst in a phosgene synthesizing tower having a bottom inlet and an outlet before the catalyst in the phosgene synthesizing tower is replaced, comprising:
(A) purging with nitrogen gas: after feeding of carbon monoxide and chlorine to the phosgene synthesizing tower is discontinued, nitrogen gas is introduced into the bottom of the phosgene synthesizing tower for purging, the phosgene in the phosgene synthesizing tower is purged to a phosgene decomposition tower until the phosgene concentration at the outlet of the phosgene synthesizing tower is measured as 0.05-0.5% (v/v), relative to the overall volume of gas; and
(C) purging with ammonia gas: ammonia gas is continuously introduced into the bottom of the phosgene synthesizing tower for purging.

2. The method of claim 1 , further comprising:
(D) replacing catalyst:
the catalyst is taken out from the phosgene synthesizing tower, and the fresh catalyst is loaded therein; or
when a tubular phosgene synthesizing tower is used, the catalyst is taken out from tubes of the phosgene synthesizing tower, and then the tubes of the phosgene synthesizing tower are rinsed with a water gun, and then dried with hot gas, and finally the fresh catalyst is filled into the tubes of the phosgene synthesizing tower.

3. The method of claim 1 , wherein, in step (A), the temperature of the nitrogen gas for purging is from 80 to 160° C. and/or the content of moisture in the nitrogen gas is below 500 ppm.

4. The method of claim 1 , wherein, in step (A), the flow of the nitrogen gas for purging is from 50 to 500 Nm3/h, the time for purging with nitrogen gas is from 1 to 10 days and the pressure for purging with nitrogen gas is from 0.05 to 1.0 MPa.

5. The method of claim 1 , wherein, in step (C), purging with ammonia gas is conducted until the phosgene concentration at the outlet of the phosgene synthesizing tower is below 1 ppm.

6. The method of claim 1 , wherein, in step (B), ammonia gas is introduced into the phosgene synthesizing tower for building up the pressure, such that the pressure in the phosgene synthesizing tower reaches from 0.11 to 5 MPa; and/or, two operations including building up the pressure and opening the outlet of the phosgene synthesizing tower are repeated 3 to 10 times.

7. The method of claim 1 , wherein, in step (C) of purging with ammonia gas, the flow of the ammonia gas for purging the phosgene synthesizing tower is from 50 to 200 Nm3/h, and/or the pressure of the ammonia gas is from 0.05 to 1.0 MPa, and/or the temperature of the ammonia gas is from 30 to 100° C.

8. The method of claim 1 , wherein, in the step (C) of purging with ammonia gas, the time for purging with ammonia gas is from 1 to 10 days.

9. The method of claim 1 , wherein, the phosgene purged out by the phosgene synthesizing tower and excess ammonia gas are transferred to a phosgene decomposition tower and are decomposed by inorganic acids with the catalysis of an activated carbon.

10. The method of claim 8 , further comprising adding inorganic acids, wherein the inorganic acids are hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid.

11. The method of claim 9 , wherein the concentration of the inorganic acids is from 0.5 to 10% by mass.

12. The method of claim 2 , wherein the hot gas used in step (D) is one of air, nitrogen gas, and CO2, and/or the temperature of the hot gas is from 100 to 200° C., and/or the pressure of the hot gas is from 0.05 to 1.0 MPa, and/or the flow of the hot gas is from 200 to 1000 Nm3/h.

13. The method of claim 2 , wherein, after the phosgene synthesizing tower is dried with the hot gas, the dew point measured therein is below −30° C.

14. The method of claim 1 , wherein the catalyst in the phosgene synthesizing tower or the catalyst filled into the tubes of the phosgene synthesizing tower is activated carbon.

15. The method of claim 1 , further comprising:
(B) building the pressure: phosgene synthesizing tower is closed, ammonia gas in introduced into the bottom of the phosgene synthesizing tower to build up pressure in the phosgene synthesizing tower, and then the outlet of the phosgene synthesizing tower is opened to discharge gas from the phosgene synthesizing tower, wherein two operations including building up pressure and opening the outlet of the phosgene synthesizing tower are carried out once or several times repeatedly, wherein step (B) is performed after step (A) and prior to step (C).

Assignees

• Wanhua Chemical Group Co Ltd

Inventors

• Zhang Hongke
• Yao Yu
• Zhao Dongke
• Cao Guanyi
• Liu Xiaogao
• Cao Younian
• Li Chong
• Ma Yabo

Classifications

• B01J2208/06

  Details of tube reactors containing solid particles · CPC title

• B01J8/0292

  with stationary packing material in the bed, e.g. bricks, wire rings, baffles · CPC title

• B01J8/06 Primary

  in tube reactors; the solid particles being arranged in tubes · CPC title

• B01J27/20

  Carbon compounds · CPC title

• B01J8/0278

  Feeding reactive fluids (for solid material B01J8/0015) · CPC title