HIGH TEMPERATURE CATALYST AND PROCESS FOR SELECTIVE CATALYTIC REDUCTION OF NOX IN EXHAUST GASES OF FOSSIL FUEL COMBUSTION

• US 20090196813A1
• Filed: 02/01/2008
• Published: 08/06/2009
• Est. Priority Date: 02/01/2008
• Status: Active Grant

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Siemens Power Generation, Inc.
• Inventors: Rossin, Joseph A., Knapke, Michael J., Sobolevskiy, Anatoly
• Granted Patent: US 7,695,703 B2
• Time in Patent Office: Days
• US Class Current: 423/239.2
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: B01D 2255/206 Rare earth metals
• CPC Class Codes: B01D 2255/20715 Zirconium
• CPC Class Codes: B01D 2255/20738 Iron
• CPC Class Codes: B01D 2255/20776 Tungsten
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/502 Beta zeolites
• CPC Class Codes: B01D 2258/012 Diesel engines and lean burn gasoline engines
• CPC Class Codes: B01D 2258/018 Natural gas engines
• CPC Class Codes: B01D 53/9418 for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
• CPC Class Codes: B01J 2229/186 not in framework positions
• CPC Class Codes: B01J 2229/36 Steaming
• CPC Class Codes: B01J 2229/40 Special temperature treatment, i.e. other than just for template removal
• CPC Class Codes: B01J 29/072 Iron group metals or copper
• CPC Class Codes: B01J 29/076 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
• CPC Class Codes: B01J 29/7615 Zeolite Beta
• CPC Class Codes: B01J 29/7815 Zeolite Beta
• CPC Class Codes: B01J 37/0246 Coatings comprising a zeolite
• CPC Class Codes: B01J 37/038 to form slurries or suspensions, e.g. a washcoat
• CPC Class Codes: B01J 37/28 Phosphorising

Abstract

A process for producing a stable high-temperature catalyst for reduction of nitrogen oxides in combustion exhaust gases at operating temperatures from 300° C. to over 700° C. without the need for exhaust dilution. A zeolite material is steam-treated at a temperature and duration sufficient to partially de-aluminize the zeolite to approximately a steady state, but not sufficient to fully collapse its chemical structure. Iron is added to the zeolite material. The zeolite material is calcined at a temperature, humidity, and duration sufficient to stabilize the zeolite material. Examples and specifications for ranges, order, and durations of steaming, calcining, and other steps are provided.

Claims

1. A process of selective catalytic reduction of NOx in a combustion exhaust stream comprising:

preparing a catalyst by the steps of

a) steam treating a zeolite material at about 500 C-600 C for about 5-15 hours;

b) adding iron to the zeolite material at a loading between 0.01% and 10% iron; and

c) calcining the zeolite material at about 750-900 C for about 1-5 hours;

wherein the order of steps a) and b) may vary, followed by step c);

mixing 60-82 ppm of ammonia into a combustion exhaust stream at over 500°

C.;

contacting the combustion exhaust stream at 500°

C.-650°

C. with the catalyst in a manner necessary to facilitate a reaction between NO and NO₂ in the exhaust stream and the ammonia.

7. The process of claim 2, further comprising:

mixing the catalyst prepared according to claim 1 with a liquid to form a slurry;

washcoating a catalytic converter bed form with the slurry; and

calcining the washcoated bed form to make a catalyst bed for a catalytic converter apparatus.

2. A process for preparing a catalyst for reduction of NOx in combustion exhaust, comprising:

steam treating a zeolite material at about 400-800 C;

adding iron to the zeolite material at a loading between 0.01% and 10% iron; and

calcining the zeolite material at about 500-1100 C;

wherein the order of the above steps may vary.

3. The process of claim 2, wherein at least one steam treating is performed at 500 C-600 C for about 5-15 hours, followed at a later time by at least one calcining performed at 800 C-900 C for 1-5 hours.

4. The process of claim 2, comprising at least two calcining steps, at least one of which being performed in the range of 750-900 C for about 1-5 hours, and at least a final one of which being performed after the iron adding step.

5. The process of claim 2, further comprising adding tungsten and/or phosphorus to the zeolite material prior to the calcining step.

6. The process of claim 2, wherein the steam treating is performed at about 500-600 C in air with about 10-25% water vapor for about 5-15 hours, and the calcining is performed at about 750-900 C in air with less than about 2% water vapor for about 1-5 hours.

8. A process for preparing a catalyst for reduction of NOx in combustion exhaust, comprising:

adding iron to an alumino-silicate zeolite material;

steam treating the zeolite material at a temperature and duration sufficient for partial de-alumination of the zeolite material to approximately a steady state, but not sufficient to fully collapse the chemical structure of the zeolite material;

calcining the zeolite material at a temperature, humidity, and duration sufficient to stabilize the zeolite material; and

wherein the order of the above steps may vary;

whereby the process creates a stable and efficient catalyst for converting NO to N2 and H2O in combustion exhaust at temperatures from 300 C to over 700 C.

9. The process of claim 8 wherein at least one steam treating is performed at 500 C-600 C for about 5-15 hours, followed at a later time by at least one calcining performed at 800 C-900 C for about 1-5 hours.

10. The process of claim 8, comprising:

steam treating a zeolite beta material at about 525 C for about 5 hours;

calcining the zeolite beta material at about 825 C for about 2 hours;

mixing the zeolite beta with iron (III) nonahydrate in water to form a slurry;

after about 1 hour, mixing zirconium acetate into the slurry;

washcoating a catalytic bed form with the slurry; and

calcining the washcoated catalytic bed form at about 525 C for about 1 hour, forming a catalyst bed.

11. The process of claim 8, comprising:

steam treating a zeolite beta material at about 525 C for about 5 hours;

mixing the zeolite beta material with iron (III) nonahydrate in water to form a first slurry;

heating the first slurry to about 90 C;

after about 3 hours, calcining the first slurry at about 825 C for about 2 hours to form an iron-containing zeolite material.

12. The process of claim 11, further comprising:

mixing the iron-containing zeolite material with zirconium acetate in water to form a second slurry;

washcoating a catalytic bed form with the second slurry; and

calcining the washcoated catalytic bed form at about 525 C for about 1 hour, forming a catalyst bed.

13. The process of claim 8, comprising:

mixing a zeolite beta material with lanthanum nitrate nonahydrate in water to form a first slurry;

heating the first slurry to about 95 C for about 6 hours;

mixing the resulting zeolite material with iron (III) nonahydrate in water to form a second slurry;

heating the second slurry to about 90 C for about 2 hours;

steam treating the resulting zeolite material at about 500 C for about 14 hours;

calcining the resulting zeolite material at about 825 C for about 2 hours to form a lanthanum zeolite beta material.

14. The process of claim 13, comprising:

mixing the lanthanum zeolite beta material and additional iron (III) nitrate nonahydrate with water to form a third slurry;

heating the third slurry to about 90 C;

after about 3 hours, steam treating the resulting zeolite material at about 525 C for about 5 hours; and

calcining the resulting zeolite material at about 825 C for about 2 hours to form an iron-lanthanum-containing zeolite material.

15. The process of claim 14, further comprising:

mixing the iron-lanthanum-containing zeolite material with zirconium acetate in water to form a fourth slurry;

washcoating a catalytic bed form with the fourth slurry; and

calcining the washcoated catalytic bed form at about 525 C for about 1 hour, forming a catalyst bed.

16. The process of claim 8, comprising:

steam treating a pre-calcined zeolite beta material at about 525 C for about 5 hours;

mixing the resulting zeolite material with iron (III) nonahydrate and ammonia metatungstate in water to form a first slurry;

heating the first slurry to about 90 C for about 3 hours; and

calcining the resulting zeolite material at about 825 C for about 2 hours to form an iron-tungsten-containing zeolite material.

17. The process of claim 16, further comprising:

mixing the iron-tungsten-containing zeolite material with zirconium acetate in water to form a second slurry;

washcoating a catalytic bed form with the second slurry; and

calcining the washcoated catalytic bed form at about 525 C for about 1 hour, forming a catalyst bed.

18. The process of claim 8, comprising:

steam treating a zeolite beta material at about 525 C for about 5 hours;

mixing the zeolite beta material with iron (III) nonahydrate and ammonium phosphate in water to form a first slurry;

heating the first slurry to about 90 C for about 3 hours;

calcining the resulting zeolite material at about 825 C for about 2 hours to form an iron-phosphorus-containing zeolite material.

19. The process of claim 18, further comprising:

mixing the iron-phosphorus-containing zeolite material with zirconium acetate in water to form a second slurry;

washcoating a catalytic bed form with the second slurry; and

calcining the washcoated catalytic bed form at about 525 C for about 1 hour, forming a catalyst bed.

20. The process of claim 101 further comprising:

mixing 60-82 ppm of ammonia into a combustion exhaust stream at over 500°

C.; and

contacting the combustion exhaust stream at 500°

C.-650°

C. with the catalyst bed in a manner necessary to facilitate a reaction between NO and NO₂ in the exhaust stream and the ammonia.