Method and apparatus for denenoxing waste gases from nitration

Patent metadata

Field	Value
Publication number	US-9346012-B2
Application number	US-201414300504-A
Country	US
Kind code	B2
Filing date	Jun 10, 2014
Priority date	Jun 10, 2014
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

The invention relates to a method for reducing the concentration of nitrogen oxides in waste gases released dating the production of organic amino compounds, wherein an organic compound is first reacted with NO x and/or nitric acid to form an organic nitro compound with the formation of an NO x -containing waste gas stream and the organic nitro compound is converted to the organic ammo compound by means of hydrogen-containing reaction gas, the reaction of the organic nitro compound with the hydrogen-containing reduction gas taking place with the formation of a hydrogen-containing waste gas stream, the method being characterised in that the NO x -containing waste gas stream is combined with the hydrogen-containing waste gas stream and/or an externally supplied hydrogen stream and is reacted at a temperature of 800 to 1700° C. for the at least partial reduction of the NO x concentration. The invention additionally relates to an apparatus for carrying out the method.

First claim

The invention claimed is:

1. A method for reducing the concentration of nitrogen oxides in waste gases released during the production of organic amino compounds, comprising:
(1) reacting an organic compound with NO x and/or nitric acid to form an organic nitro compound wherein an NO x -containing waste gas stream is formed and the organic nitro compound is converted to the organic amino compound by means of a hydrogen-containing reaction gas, the reaction of the organic nitro compound with the hydrogen-containing reduction gas taking place with the formation of a hydrogen-containing waste gas stream,
(2) combining the NO x -containing waste gas stream with the hydrogen-containing waste gas stream and/or an externally supplied hydrogen stream, and
(3) reacting the NO x -containing waste gas stream with the hydrogen-containing waste gas stream and/or an externally supplied hydrogen stream at a temperature of 800 to 1700° C. for the at least partial reduction of the NO x concentration.

2. The method according to claim 1 , wherein the externally supplied hydrogen stream consists of at least 70 vol. % pure hydrogen, the externally supplied hydrogen stream comprising technical-grade hydrogen.

3. The method according to claim 1 , wherein the hydrogen-containing waste gas stream consists of at least 70 vol. % pure hydrogen.

4. The method according to claim 1 , wherein the organic compound is an aromatic compound.

5. The method according to claim 4 , wherein the organic compound is selected from the group consisting of aniline, benzene, monochlorobenzene, toluidine, nitrobenzene, mononitrotoluene and dinitrotoluene.

6. The method according to claim 3 , wherein the hydrogen-containing waste gas stream comprises by-products carrying amino groups.

7. The method according claim 1 , further comprising reducing the NO x concentration further by adding one or more hydrocarbon compounds to the NO x -containing waste gas stream before or during step (2) or during or after step (3).

8. The method according to claim 7 , wherein the hydrocarbon compound is added before, during and/or after the reaction of the NO x -containing waste gas stream with the hydrogen-containing waste gas stream and/or the externally supplied hydrogen stream.

9. The method according to claim 7 , further comprising determining the NO x concentration during the reaction of the NO x -containing waste gas stream with the hydrogen-containing waste gas stream and/or the externally supplied hydrogen stream and optionally controlling the hydrocarbon compound and the metering of the hydrocarbon compound as a function of the measured reaction temperature and/or the NO x concentration.

10. The method according to claim 1 , further comprising adding air, oxygen-containing waste gases and/or oxygen to the NO x -containing waste gas stream before or during step (2) or during or after step (3).

11. The method according to claim 1 , wherein the reaction of the NO x -containing waste gas stream with the hydrogen-containing waste gas stream and/or the externally supplied hydrogen stream and optionally the hydrocarbon compound takes place at a temperature of 1000 to 1700° C.

12. The method according to claim 1 , wherein the reaction of the NO x -containing waste gas stream with the hydrogen-containing waste gas stream and/or the externally supplied hydrogen stream takes place with a hyperstoichiometrie amount of substance of hydrogen and further comprising at least partially oxidizing the excess hydrogen with air and/or oxygen.

13. The method according to claim 12 , further comprising adding a compound selected from the group consisting of ammonia, urea and/or another ammonia-releasing compound to the NO x -containing waste gas stream.

14. The method according to claim 1 , further comprising recovering at least a portion of any heat of reaction released during the reaction of the NO x -containing waste gas stream with the hydrogen-containing waste gas stream and/or the externally supplied hydrogen stream, and/or any heat of reaction released while the excess hydrogen is reacted off, with the aid of heat exchangers.

Assignees

• Bayer Materialscience Llc
• Bayer Materialscience Ag
• Covestro Llc
• Covestro Deutschland Ag

Inventors

• Pennemann Bernd
• Westphal Ulrich
• Foertsch Dieter
• Miller Spotswood

Classifications

• B01D53/77

  Liquid phase processes · CPC title

• C07C209/36 Primary

  by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings {in presence of hydrogen-containing gases and a catalyst} · CPC title

• B01D53/76

  Gas phase processes, e.g. by using aerosols · CPC title

• B01D53/343

  Heat recovery · CPC title

• B01D2251/202

  Hydrogen · CPC title