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US4046888A
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Methods for catalytic reduction of nitrogen oxides
Assignee: Tonen General Sekiyu KK
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Filing: 1976-03-11
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Granted: 1977-09-06
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Expires: 1996-03-11
Abstract
Abstract Process for removing nitrogen oxides from gaseous mixtures comprising the same. Ammonia in an amount excessive over the stoichiometric amount necessary for reducing the nitrogen oxides is introduced into a reaction zone containing a catalyst. Then, ammonia in a minimum amount necessary for reduction of the nitrogen oxides is introduced into the reaction zone.
Inventors
- 👤 Tsugio Maeshima
- 👤 Eiichiroh Nishikawa
- 👤 Mitsuko Nakamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 15:19
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/34; B01D53/74; B01D53/86; B01D53/8621; B01D53/8625; B01D53/8628
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
142 words
A process for reducing the concentration of nitrogen oxides in a gaseous mixture which comprises (A). introducing ammonia in an amount between about 1.2 and 3.0 times the stoichiometric amount necessary for reducing the nitrogen oxides into a reaction zone containing a catalyst said catalyst comprising an active metal component and natural or synthetic zeolite having an SiO 2 /Al 2 O 3 molar ratio of at least about 2 and an alkali metal content within the range from 0.2 to 0.6 equivalents per gram atom of alumina, the introduction of ammonia at this rate continuing for at least about 20 minutes and then (B). contacting the nitrogen oxides containing gas with the catalyst in the presence of ammonia in an amount between about 0.7 and 1.0 times the stoichiometric amount necessary for reducing the nitrogen oxides. C. repeating step (A) periodically.
Claim 2
Dependent Claim
142 words
A process for reducing the concentration of nitrogen oxides in a gaseous mixture which comprises (A). introducing ammonia in an amount between about 1.2 and 3.0 times the stoichiometric amount necessary for reducing the nitrogen oxides into a reaction zone containing a catalyst said catalyst comprising an active metal component and natural or synthetic zeolite having an SiO 2 /Al 2 O 3 molar ratio of at least about 2 and an alkali metal content within the range from 0.2 to 0.6 equivalents per gram atom of alumina, the introduction of ammonia at this rate continuing for at least about 20 minutes and then (B). contacting the nitrogen oxides containing gas with the catalyst in the presence of ammonia in an amount between about 0.7 and 1.0 times the stoichiometric amount necessary for reducing the nitrogen oxides. C. repeating step (A) periodically.
Claim 3
Dependent Claim
17 words
The process of claim 1 wherein the reaction temperature is between about 200° C. and 500° C.
Claim 4
Dependent Claim
18 words
The process of claim 2 wherein the temperature range is from about 250° C. to about 450° C.
Claim 5
Dependent Claim
20 words
The process of claim 1 wherein the catalyst has a pore diameter of from about 3 to about 15 A.
Claim 6
Dependent Claim
22 words
The process of claim 1 wherein about 1 to about 30% by weight of a refractory substance is incorporated in the catalyst.
Claim 7
Dependent Claim
25 words
The process of claim 1 wherein the active metal component of the catalyst is taken from the group consisting of copper, iron, chromium and vanadium.
Claim 8
Dependent Claim
19 words
The process of claim 6 wherein the amount of metal component is about 1 to about 20% by weight.
Claim 9
Dependent Claim
19 words
The process of claim 1 wherein the catalyst is molded into a shape having a large contact surface area.
Claim 10
Dependent Claim
14 words
The process of claim 1 wherein the catalyst is arranged in a fixed bed.
Claim 11
Dependent Claim
15 words
The process of claim 1 wherein the nitrogen oxides containing gas is a flue gas.
Claim 12
Dependent Claim
23 words
The process of claim 1 wherein the catalyst activation is accomplished before the gaseous mixture containing nitrogen oxides is contacted with the catalyst.
References Cited (Backward Citations)
US3689212A
Cited
US3895094A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-09-05 | 1981-03-07 | 1981-09-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-09-05 | 1985-03-07 | 1985-09-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-09-05 | 1989-03-07 | 1989-09-06 | $7700.00 | Window Closed / Lapsed |