A method of reducing nitrogen oxide compounds

Patent metadata

Field	Value
Publication number	US-2019282959-A1
Application number	US-201716335399-A
Country	US
Kind code	A1
Filing date	Sep 25, 2017
Priority date	Sep 26, 2016
Publication date	Sep 19, 2019
Grant date	—

Abstract

The invention provides a method of reducing the amount of nitrogen oxide components in a process gas stream comprising: a) contacting a deNOX catalyst with the process gas in the presence of ammonia which results in the conversion of nitrogen oxide components as well as a decline in the NOX conversion over the deNOX catalyst; and b) regenerating the deNOX catalyst to improve the NOX conversion by contacting the deNOX catalyst at a temperature in the range of from 250 to 390° C. with a flow of ammonia that is reduced relative to the flow of ammonia in step a) and process gas, air or a mixture thereof.

First claim

1 . A method of reducing the amount of nitrogen oxide components in a process gas stream comprising:
a. contacting a deNO X catalyst with the process gas in the presence of ammonia which results in the conversion of nitrogen oxide components as well as a decline in the NO X conversion over the deNO X catalyst; and b. regenerating the deNO X catalyst to improve the NO X conversion by contacting the deNO X catalyst at a temperature in the range of from 250 to 390° C. with a flow of ammonia that is reduced relative to the flow of ammonia in step a) and process gas, air or a mixture thereof.

2 . The method of claim 1 wherein step a) is carried out at a temperature in the range of from 140 to 300° C.

3 . The method of claim 1 wherein the flow of ammonia in step b) is reduced to less than 50% of the flow of ammonia used in step a).

4 . The method of claim 1 wherein the flow of ammonia in step b) is reduced to less than 10% of the flow of ammonia used in step a).

5 . The method of claim 1 wherein the flow of ammonia in step b) is reduced to less than 2% of the flow of ammonia used in step a).

6 . The method of claim 1 wherein the regeneration is carried out at a temperature in the range of from 260 to 350° C.

7 . The method of claim 1 wherein the deNO X catalyst is not contacted with process gas.

8 . The method of claim 1 wherein the NO X is at least partially converted to water and nitrogen.

9 . The method of claim 1 wherein steam is present in the process gas.

10 . The method of claim 1 wherein the process gas comprises at least 10 vol % steam.

11 . The method of claim 1 wherein the process gas comprises at least 20 vol % steam.

12 . The method of claim 1 wherein additional steam is added to the process gas.

13 . The method of claim 1 wherein the process gas additionally comprises sulfur compounds.

14 . The method of claim 13 wherein the sulfur compounds comprise sulfur dioxide and/or sulfur trioxide.

15 . The method of claim 1 wherein the decline in NO X conversion is at least partially caused by the presence of sulfur and/or sulfur compounds on the deNO X catalyst.

16 . The method of claim 15 wherein the deNO X catalyst after step a) has a sulfur content of at least 0.6 wt %.

17 . The method of claim 1 wherein the sulfur content on the deNO X catalyst is reduced in step b) to less than 0.6 wt %.

18 . The method of claim 1 wherein sulfur in the form of ammonium sulfate and/or ammonium bisulfate is removed from the catalyst in step b).

19 . The method of claim 1 wherein the regeneration is carried out for a time period of from 5 to 168 hours.

20 . The method of claim 1 wherein the regeneration is carried out for a time period of from 24 to 48 hours.

21 . The method of claim 1 wherein the deNO X catalyst comprises one or several of the following elements: titanium, tungsten, molybdenum, vanadium or other compounds known to be suitable for the conversion of nitrogen oxides to nitrogen and water.

22 . A method of regenerating a deNO X catalyst that has been deactivated while contacting the catalyst with a stream comprising process gas and ammonia, comprising: reducing the flow of ammonia and continuing to contact the catalyst with process gas.

23 . The method of claim 22 wherein the flow of process gas is reduced.

24 . The method of claim 22 wherein the ammonia flow is reduced to less than 1%.

Assignees

• Shell Oil Co

Inventors

• Zhang Wenzhong
• Bakker Geert Marten

Classifications

• B01J21/20

  Regeneration or reactivation · CPC title

• B01D2257/404

  Nitrogen oxides other than dinitrogen oxide · CPC title

• B01D2251/2062

  Ammonia · CPC title

• B01D53/8625 Primary

  Nitrogen oxides · CPC title

• B01J23/22

  Vanadium · CPC title