US5078982A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reduction of nitrogen oxide in effluent gases using formaldehyde
Assignee: Noxtech Inc
•
Filing: 1990-09-20
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Granted: 1992-01-07
•
Expires: 2010-09-20
Abstract
Abstract A method is described for reducing the nitrogen oxide content of an effluent gas stream which comprises contacting the effluent gas with an amount of formaldehyde which is effective in reducing the nitrogen oxide content of the gas. In one preferred embodiment, the formaldehyde is contacted with the effluent stream in the presence of a catalyst which promotes the reaction between the formaldehyde and the nitrogen oxide contained in the gas stream. Preferred catalysts comprise zirconium, cerium, or mixtures thereof. Catalysts comprising zirconium in the plus four oxidation state, cerium in the plus four oxidation state, or mixtures thereof are particularly preferred catalysts.
Inventors
- 👤 Ralph A. Gardner-Chavis
- 👤 Micahel P. May
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 06:13
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/34; B01D53/92; B01D53/94; B01D53/9404; B01D53/9409
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
48 words
A method for reducing the nitrogen oxide content of an effluent gas stream comprising contacting the gas stream with formaldehyde in the presence of a catalyst which promotes a reaction between the formaldehyde and nitrogen oxide in the gas at a temperature of at least about 700° F.
Claim 2
Independent Claim
48 words
A method for reducing the nitrogen oxide content of an effluent gas stream comprising contacting the gas stream with formaldehyde in the presence of a catalyst which promotes a reaction between the formaldehyde and nitrogen oxide in the gas at a temperature of at least about 700° F.
Claim 3
Dependent Claim
17 words
The method of claim 1 conducted at a temperature from about 700° F. to about 2000° F.
Claim 4
Dependent Claim
17 words
The method of claim 1 conducted at a temperature from about 700° F. to about 1200° F.
Claim 5
Dependent Claim
14 words
The method of claim 1 wherein the catalyst comprises zirconium, cerium, or mixtures thereof.
Claim 6
Dependent Claim
27 words
The method of claim 1 wherein the catalyst comprises zirconium in the plus four oxidation state, cerium in the plus four oxidation state, or a mixture thereof.
Claim 7
Dependent Claim
27 words
The method of claim 1 wherein the catalyst comprises a mixture of zirconium in the plus four oxidation state and cerium in the plus four oxidation state.
Claim 8
Dependent Claim
15 words
The method of claim 1 wherein the formaldehyde is obtained from the oxidation of methanol.
Claim 9
Dependent Claim
10 words
The method of claim 3 wherein the catalyst comprises zirconium.
Claim 10
Dependent Claim
19 words
The method of claim 8 wherein at least some of the zirconium is in the plus four oxidation state.
Claim 11
Dependent Claim
11 words
The method of claim 3 wherein the catalyst comprises zirconium oxide.
Claim 12
Dependent Claim
10 words
The method of claim 3 wherein the catalyst comprises cerium.
Claim 13
Dependent Claim
19 words
The method of claim 11 wherein at least some of the cerium is in the plus four oxidation state.
Claim 14
Dependent Claim
11 words
The method of claim 3 wherein the catalyst comprises cerium oxide.
Claim 15
Dependent Claim
12 words
The method of claim 3 wherein the catalyst comprises zirconium and cerium.
Claim 16
Dependent Claim
24 words
The method of claim 3 wherein the catalyst comprises zirconium in the plus four oxidation state and cerium in the plus four oxidation state.
Claim 17
Dependent Claim
14 words
The method of claim 3 wherein the catalyst comprises zirconium oxide and cerium oxide.
Claim 18
Dependent Claim
15 words
The method of claim 3 wherein the gas stream contains at least some nitric oxide.
Claim 19
Dependent Claim
12 words
The method of claim 3 wherein the formaldehyde is produced from methanol.
Claim 20
Independent Claim
105 words
A method of reducing the nitrogen oxide content of a combustion gas comprising the steps of (A) converting methanol to formaldehyde; (B) advancing the formaldehyde to a reaction zone containing a catalyst which promotes a reaction between formaldehyde and nitrogen oxides, said catalyst comprising zirconium in the plus four oxidation state, cerium in the plus four oxidation state, or mixtures thereof; and (C) contacting the formaldehyde with the combustion gas in the presence of the catalyst in the reaction zone at a temperature of at least about 700° F. for a period of time sufficient to reduce the nitrogen oxide content of the combustion gas.
Claim 21
Independent Claim
105 words
A method of reducing the nitrogen oxide content of a combustion gas comprising the steps of (A) converting methanol to formaldehyde; (B) advancing the formaldehyde to a reaction zone containing a catalyst which promotes a reaction between formaldehyde and nitrogen oxides, said catalyst comprising zirconium in the plus four oxidation state, cerium in the plus four oxidation state, or mixtures thereof; and (C) contacting the formaldehyde with the combustion gas in the presence of the catalyst in the reaction zone at a temperature of at least about 700° F. for a period of time sufficient to reduce the nitrogen oxide content of the combustion gas.
Claim 22
Dependent Claim
21 words
The method of claim 19 wherein the catalyst comprises a mixture of zirconium and cerium in the plus four oxidation state.
Claim 23
Dependent Claim
14 words
The method of claim 19 wherein the catalyst comprises zirconium oxide and cerium oxide.
Claim 24
Dependent Claim
15 words
The method of claim 19 wherein the combustion gas contains at least some nitric oxide.
Claim 25
Dependent Claim
24 words
The method of claim 19 wherein the contact in step (C) is at a temperature of from about 700° F. to about 1200° F.
Claim 26
Dependent Claim
14 words
The method of claim 19 wherein the combustion gas is an engine exhaust gas.
Claim 27
Dependent Claim
22 words
The method of claim 19 wherein the combustion gas is a smokestack, boiler exhaust gas, gas turbine exhaust, or diesel engine exhaust.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-01-06 | 1995-07-08 | 1996-01-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-01-06 | 1999-07-08 | 2000-01-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-01-06 | 2003-07-08 | 2004-01-07 | $7700.00 | Window Closed / Lapsed |