CA1166617A - Procedure to improve the ageing characteristics of catalysts applied in the oxidative purification of exhaust gases originating from combustion engines fuelled with leaded gasoline - Google Patents
Procedure to improve the ageing characteristics of catalysts applied in the oxidative purification of exhaust gases originating from combustion engines fuelled with leaded gasolineInfo
- Publication number
- CA1166617A CA1166617A CA000386496A CA386496A CA1166617A CA 1166617 A CA1166617 A CA 1166617A CA 000386496 A CA000386496 A CA 000386496A CA 386496 A CA386496 A CA 386496A CA 1166617 A CA1166617 A CA 1166617A
- Authority
- CA
- Canada
- Prior art keywords
- exhaust gases
- catalyst
- air
- combustion engines
- fuel ratio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
- F01N2430/06—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by varying fuel-air ratio, e.g. by enriching fuel-air mixture
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention provides a method of improving the ageing characteristics of catalysts used for the oxidative purification of exhaust gases from combustion engines fuelled with leaded gasoline, wherein the engines are kept running, essentially, at the stoichiometric air/fuel ratio.
The invention provides a method of improving the ageing characteristics of catalysts used for the oxidative purification of exhaust gases from combustion engines fuelled with leaded gasoline, wherein the engines are kept running, essentially, at the stoichiometric air/fuel ratio.
Description
1 16661~
The present invention relates to a method for extending the effective service life of catalysts, especially precious metal catalysts, which are used in the oxidative purification of exhaust gases from internal combustion engines fuelled with leaded gasoline.
The exhaust gases from internal combustion engines con-tain as noxious components carbon monoxide, oxides of nitrogen, partially oxidised hydrocarbons, polynuclear hydrocarbons and aldehydes and nitrogen and water vapour, which are harmless to living beings.
It is well known that these noxious ingredients present in the exhaust gases from internal combustion engines can be eliminated to a large extent with the aid of catalysts which include precious metals and/or non-precious metals. So called oxidation catalysts are needed, for instance to remove carbon monoxide and hazardous hydrocarbons from exhaust gases to which secondary air has been added, such that the air number Lambda is raised to values, which are above 1.01, whereby these environmental poisons may be converted into carbon dioxide and water vapour.
Such an arrangement will, in the long run, however, only be suc-cessful as long as the internal combustion engine is fuelled with lead-free gasoline. It is well known that under normal con-ditions of operation of an internal combustion engine equipped with a system to supply the exhaust gases with secondary air and equipped with oxidation catalysts the lead compounds which form during the combustion of tetraalkyl lead present in the fuel will deactivate the catalyst in a short period of time. The higher the lead content of the gasoline ~he faster the catalyst will lose its power to oxidise to a sufficient degree of the carbon '~
1 16661~
monoxide, the hydrocarbons and the aldehydes.
It is suggested in West German "Offenlegungsschrift" No.
28 28 805 to operate with the oxidation catalyst at the highest possible temperature t~ avoid its poisoning by lead compounds and to re-evaporate lead compounds which have already been deposited on it. Lead oxide which is formed in the combustion process from lead tetraethyl, and the lead halides, which result from the re-action of lead oxide with alkyl halides, the so called scavengers, dibromomethane and dichloroethane for instance, are converted, in an oxidising atmosphere, by the oxides of sulphur primarily into lead sulphate (PbSO4) and basic lead sulphate (nPbO.PbSO~).
These lead sulphates cannot be removed from the catalysts even at the highest temperature level the catalyst will function, as the decomposition temperature of lead sulphate is 1100~C. Eleva-ted temperatures of the catalyst accelerate the reduction in acti-vity of the catalyst due to its thermal impairment as well as by the thermodynamically favoured formation of lead sulphate.
U.S. patent No. 3,072,457 describes a process with which catalysts, which have been poisoned with lead, can be partially reactivated. The catalyst is alternatively treated under oxidising conditions followed by a treatment with reducing gases. This is accomplished by cutting off for a period of time the supply of secondary air when the engine is operated with an air/gasoline mixture enriched in fuel (air/fuel ratio = 12), and when the function of the catalyst is transferred to a second catalyst unit.
This method requires, however, rather costly installations and quite a complicated control mechanism. In addition the adjust-ment required to operate the engine with an enriched carburant will lead to high fuel consumption figures.
The present inve~tion provides for the prevention of rapid deactivation of the catalyst when in contact with the ex-haust gases from an engine fuelled with leaded gasoline, whereby 1 16661~
the disadvantages described above can be avoided.
It has now been found that an internal combustion engine fuelled with leaded gasoline is nln under conditions in which the air/fuel ratio is maintained at the stoichiometric proportion or very close to the stoichiometric proportion, the rate of deac-tivation of the oxidation catayst is much less than in the hither-to used practice of running the engine under oxidising conditions.
Furthermore, the oxidation catalyst can be operated in the tem-perature range which is most favourable for its performance, i.e.
in the temperature range of between 400 and 850C.,preferentially of between 500 and 700C., and it is not exposed to temperatures which exceed 800C., which temperatures would be required to evaporate deposited lead compounds, and temperatures, which by themselves would readily impair the endurance ' catalyst.
According to the present invention therefore there is provided a method of improving the agelng characteristics of catalysts used in the oxidative purification of exhaust gases from internal combustion engines fuelled with leaded gasoline, in which the engine is run with an essentially stoichiometric air/fuel ratio. Desirably, the air/fuel ratio is maintained thereby at a C ~ Lambda which remains within the limits of 0.98 and ~_e}4, particu-larly within the limits of 0.99 and 1.00.
A particular advantage of the method of the present inven-' tion is that the costly mechanism needed to supply secondary air to the oxidation system for exhaust gases can be eliminated. The elimination of a mechanical air pump driven by the engine, for instance, brings with it an increase of power available for driving and a reduction in gasoline,consumption.
By the use of the method of the present invention compli-cated mechanisms needed for the cyclic regeneration of the catalyst can be avoided.
6 1 ~
Again, with a lean and a fat mixture of exhaust gases, the second eatalyst, which takes over the eatalytic oxidation task during the regeneration of the first eatalyst may be avoided.
Gasoline eonsumption considerably decreases when the air/fuel ratio is raised to a value which is greater than 12 to bring it to the stoichiometric ratio, i.e. when the combustion mixture is made leaner. This follows also from the publication:"Abgasemis-sionen von Xraftfahrzeugen in Gro~st~dten und industriellen sallungsgebietQn", by Prof. Dr. Ing. Hans May 1973, published by TUV Rheinland GmbH , Cologne, Federal Republic of Germany.
The present invention will be further illustrated by way of the following Examples in conjunctionwith the accompanying drawings in which:-Figs. 1 to 4 are graphs of conversion efficiency of theeatalysts of the Examples with time under the conditions of operations speeified in the Examples.
xample 1 A preeious metal eatalyst (platinum) of honey-eomb strue-ture with 400 eell units per square inch having alumina as earrier material and a eontent of preeious metal of 70 grams per cubie foot, mounted on a metallie support was plaeed into an exhaust gas stream from an Otto engine and aged therein for 150 hours.
The parameters of the ageing procedure were as follows:
-4-eylinder injeetion motor with K-jetronies -Temperature at the inlet of the eatalyst: 630C.
-spaee veloeity = 108,000 .h -Lambda = 0.990 -gasoline with 0.4 g./l lead, "Motormix"
The results from these tests are shown in Figure 1 under the designation "catalyst (1)". The conversion efficiency attain-ed at an air number Lambda = 1.0 was checked every 25 hours.
116661~
Example 2 A catalyst similar to the one in Example 1 was placed ~ o+to into the stream of exhaust gases from an ~h~ engine. This time C however a mixture of platinum and rhodium was used as the pre-cious metal catalyst. All the other characteristics of the cata-lyst and the parameters of operating remained the same. The re-sults are presented in Figure 1. The graph designated as (2) shows the ageing characteristics of this catalyst.
Example 3 (comparative example) A catalyst, identical to the ones which were used in Examples 1 and 2, respectively, were exposed to ageing tests at an air-number Lambda - 1.015. All the other operational parame-ters remained the same. The results are summarised in Figure (2).
Figures (1) and (2) distinctly show that the resistivity of the catalysts against ageing is substantially enhanced when the engine is running at an air-number Lambda of 0.990 when compared to being run at an air-number Lambda of 1.015. Thus in Examples 1 and 2 practically no reduction in carbon monoxide oxidation at the catalyst can be observed over the test period of 150 hours.
In the comparative Example it reduced to values of around 65%.
The.oxidation of hydrocarbons with the catalysts shows the same trend, but not in quite such a distinct manner.
Example 4 A catalyst, identical to the one used in Example 1, of honey-comb structure with 400 cell units per square foot, this time however mounted on a support of cordierite was exposed to the same conditions of testing as described in Example 1. The results are given in Figure (3). The graph designated as (3) shows the ageing of the catalyst used in this example.
Example 5 The catalyst described in Example 4, carrying however a mixture of platinum and rhodium as the precious metal component, 1 16661~
was exposed to the ageing test performed as described in Example 1. Fiqure (3) shows the performance of this catalyst designated as (4) at an air-number Lambda of 0.990.
Example 6 (comparative example) Catalysts, identical to the ones used in the Examples 4 and 5, were aged at an air number Lambda of 1.015. The conversion of carbon monoxide (CO) and of hydrocarbons (HC) are given, graphical-ly, in Figure 4.
When the engine is running at an air-number Lambda of 0.990 or of 1.015, respectively, the precious metal catalysts show, in each of the exhaust gasenvironments equal but specific ageing characteristics not affected by being mounted on metallic or on ceramic supports.
The present invention relates to a method for extending the effective service life of catalysts, especially precious metal catalysts, which are used in the oxidative purification of exhaust gases from internal combustion engines fuelled with leaded gasoline.
The exhaust gases from internal combustion engines con-tain as noxious components carbon monoxide, oxides of nitrogen, partially oxidised hydrocarbons, polynuclear hydrocarbons and aldehydes and nitrogen and water vapour, which are harmless to living beings.
It is well known that these noxious ingredients present in the exhaust gases from internal combustion engines can be eliminated to a large extent with the aid of catalysts which include precious metals and/or non-precious metals. So called oxidation catalysts are needed, for instance to remove carbon monoxide and hazardous hydrocarbons from exhaust gases to which secondary air has been added, such that the air number Lambda is raised to values, which are above 1.01, whereby these environmental poisons may be converted into carbon dioxide and water vapour.
Such an arrangement will, in the long run, however, only be suc-cessful as long as the internal combustion engine is fuelled with lead-free gasoline. It is well known that under normal con-ditions of operation of an internal combustion engine equipped with a system to supply the exhaust gases with secondary air and equipped with oxidation catalysts the lead compounds which form during the combustion of tetraalkyl lead present in the fuel will deactivate the catalyst in a short period of time. The higher the lead content of the gasoline ~he faster the catalyst will lose its power to oxidise to a sufficient degree of the carbon '~
1 16661~
monoxide, the hydrocarbons and the aldehydes.
It is suggested in West German "Offenlegungsschrift" No.
28 28 805 to operate with the oxidation catalyst at the highest possible temperature t~ avoid its poisoning by lead compounds and to re-evaporate lead compounds which have already been deposited on it. Lead oxide which is formed in the combustion process from lead tetraethyl, and the lead halides, which result from the re-action of lead oxide with alkyl halides, the so called scavengers, dibromomethane and dichloroethane for instance, are converted, in an oxidising atmosphere, by the oxides of sulphur primarily into lead sulphate (PbSO4) and basic lead sulphate (nPbO.PbSO~).
These lead sulphates cannot be removed from the catalysts even at the highest temperature level the catalyst will function, as the decomposition temperature of lead sulphate is 1100~C. Eleva-ted temperatures of the catalyst accelerate the reduction in acti-vity of the catalyst due to its thermal impairment as well as by the thermodynamically favoured formation of lead sulphate.
U.S. patent No. 3,072,457 describes a process with which catalysts, which have been poisoned with lead, can be partially reactivated. The catalyst is alternatively treated under oxidising conditions followed by a treatment with reducing gases. This is accomplished by cutting off for a period of time the supply of secondary air when the engine is operated with an air/gasoline mixture enriched in fuel (air/fuel ratio = 12), and when the function of the catalyst is transferred to a second catalyst unit.
This method requires, however, rather costly installations and quite a complicated control mechanism. In addition the adjust-ment required to operate the engine with an enriched carburant will lead to high fuel consumption figures.
The present inve~tion provides for the prevention of rapid deactivation of the catalyst when in contact with the ex-haust gases from an engine fuelled with leaded gasoline, whereby 1 16661~
the disadvantages described above can be avoided.
It has now been found that an internal combustion engine fuelled with leaded gasoline is nln under conditions in which the air/fuel ratio is maintained at the stoichiometric proportion or very close to the stoichiometric proportion, the rate of deac-tivation of the oxidation catayst is much less than in the hither-to used practice of running the engine under oxidising conditions.
Furthermore, the oxidation catalyst can be operated in the tem-perature range which is most favourable for its performance, i.e.
in the temperature range of between 400 and 850C.,preferentially of between 500 and 700C., and it is not exposed to temperatures which exceed 800C., which temperatures would be required to evaporate deposited lead compounds, and temperatures, which by themselves would readily impair the endurance ' catalyst.
According to the present invention therefore there is provided a method of improving the agelng characteristics of catalysts used in the oxidative purification of exhaust gases from internal combustion engines fuelled with leaded gasoline, in which the engine is run with an essentially stoichiometric air/fuel ratio. Desirably, the air/fuel ratio is maintained thereby at a C ~ Lambda which remains within the limits of 0.98 and ~_e}4, particu-larly within the limits of 0.99 and 1.00.
A particular advantage of the method of the present inven-' tion is that the costly mechanism needed to supply secondary air to the oxidation system for exhaust gases can be eliminated. The elimination of a mechanical air pump driven by the engine, for instance, brings with it an increase of power available for driving and a reduction in gasoline,consumption.
By the use of the method of the present invention compli-cated mechanisms needed for the cyclic regeneration of the catalyst can be avoided.
6 1 ~
Again, with a lean and a fat mixture of exhaust gases, the second eatalyst, which takes over the eatalytic oxidation task during the regeneration of the first eatalyst may be avoided.
Gasoline eonsumption considerably decreases when the air/fuel ratio is raised to a value which is greater than 12 to bring it to the stoichiometric ratio, i.e. when the combustion mixture is made leaner. This follows also from the publication:"Abgasemis-sionen von Xraftfahrzeugen in Gro~st~dten und industriellen sallungsgebietQn", by Prof. Dr. Ing. Hans May 1973, published by TUV Rheinland GmbH , Cologne, Federal Republic of Germany.
The present invention will be further illustrated by way of the following Examples in conjunctionwith the accompanying drawings in which:-Figs. 1 to 4 are graphs of conversion efficiency of theeatalysts of the Examples with time under the conditions of operations speeified in the Examples.
xample 1 A preeious metal eatalyst (platinum) of honey-eomb strue-ture with 400 eell units per square inch having alumina as earrier material and a eontent of preeious metal of 70 grams per cubie foot, mounted on a metallie support was plaeed into an exhaust gas stream from an Otto engine and aged therein for 150 hours.
The parameters of the ageing procedure were as follows:
-4-eylinder injeetion motor with K-jetronies -Temperature at the inlet of the eatalyst: 630C.
-spaee veloeity = 108,000 .h -Lambda = 0.990 -gasoline with 0.4 g./l lead, "Motormix"
The results from these tests are shown in Figure 1 under the designation "catalyst (1)". The conversion efficiency attain-ed at an air number Lambda = 1.0 was checked every 25 hours.
116661~
Example 2 A catalyst similar to the one in Example 1 was placed ~ o+to into the stream of exhaust gases from an ~h~ engine. This time C however a mixture of platinum and rhodium was used as the pre-cious metal catalyst. All the other characteristics of the cata-lyst and the parameters of operating remained the same. The re-sults are presented in Figure 1. The graph designated as (2) shows the ageing characteristics of this catalyst.
Example 3 (comparative example) A catalyst, identical to the ones which were used in Examples 1 and 2, respectively, were exposed to ageing tests at an air-number Lambda - 1.015. All the other operational parame-ters remained the same. The results are summarised in Figure (2).
Figures (1) and (2) distinctly show that the resistivity of the catalysts against ageing is substantially enhanced when the engine is running at an air-number Lambda of 0.990 when compared to being run at an air-number Lambda of 1.015. Thus in Examples 1 and 2 practically no reduction in carbon monoxide oxidation at the catalyst can be observed over the test period of 150 hours.
In the comparative Example it reduced to values of around 65%.
The.oxidation of hydrocarbons with the catalysts shows the same trend, but not in quite such a distinct manner.
Example 4 A catalyst, identical to the one used in Example 1, of honey-comb structure with 400 cell units per square foot, this time however mounted on a support of cordierite was exposed to the same conditions of testing as described in Example 1. The results are given in Figure (3). The graph designated as (3) shows the ageing of the catalyst used in this example.
Example 5 The catalyst described in Example 4, carrying however a mixture of platinum and rhodium as the precious metal component, 1 16661~
was exposed to the ageing test performed as described in Example 1. Fiqure (3) shows the performance of this catalyst designated as (4) at an air-number Lambda of 0.990.
Example 6 (comparative example) Catalysts, identical to the ones used in the Examples 4 and 5, were aged at an air number Lambda of 1.015. The conversion of carbon monoxide (CO) and of hydrocarbons (HC) are given, graphical-ly, in Figure 4.
When the engine is running at an air-number Lambda of 0.990 or of 1.015, respectively, the precious metal catalysts show, in each of the exhaust gasenvironments equal but specific ageing characteristics not affected by being mounted on metallic or on ceramic supports.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for improving the aging characteristics of a catalyst for the oxidative purification of the exhaust gases of internal combustion engines, when using leaded motor fuels, which comprise operating an internal combustion engine with an es-sentially stoichiometric air/fuel ratio.
2. The process according to Claim 1, wherein the air/
fuel ratio is kept within the range of lambda equals from 0.98 to 1.1.
fuel ratio is kept within the range of lambda equals from 0.98 to 1.1.
3. The process according to Claim 2, wherein the air/
fuel ratio is kept within the range of lambda equals from 0.99 to 1.00.
fuel ratio is kept within the range of lambda equals from 0.99 to 1.00.
4. A method for the oxidative purification of exhaust gases of internal combustion engines comprising contacting said gases with a noble metal catalyst capable of converting environ-mentally harmful components into harmless components said noble metal being supported by an inert support, and operating an in-ternal combustion engine with leaded motor fuel with an air/fuel ratio of 0.98 to 1.01.
5. The method of Claim 4, wherein the temperature of the catalyst is less than 800°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19803036130 DE3036130A1 (en) | 1980-09-25 | 1980-09-25 | METHOD FOR IMPROVING THE AGING BEHAVIOR OF CATALYSTS FOR THE OXIDATIVE PURIFICATION OF THE EXHAUST GASES FROM COMBUSTION ENGINES WITH THE USE OF LEADED FUELS |
| DEP3036130.9 | 1980-09-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1166617A true CA1166617A (en) | 1984-05-01 |
Family
ID=6112815
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000386496A Expired CA1166617A (en) | 1980-09-25 | 1981-09-23 | Procedure to improve the ageing characteristics of catalysts applied in the oxidative purification of exhaust gases originating from combustion engines fuelled with leaded gasoline |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0048808A1 (en) |
| JP (1) | JPS5786543A (en) |
| AU (1) | AU7564081A (en) |
| BR (1) | BR8106013A (en) |
| CA (1) | CA1166617A (en) |
| DE (1) | DE3036130A1 (en) |
| ES (1) | ES504050A0 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5073289A (en) * | 1989-11-02 | 1991-12-17 | The Curators Of The University Of Missouri | Paint stripper composition having reduced volatility containing decanolactone, n-methylpyrrolidone and butyrolactone and method of use |
| DE19510642C2 (en) * | 1994-12-02 | 1997-04-10 | Volkswagen Ag | Method for reducing pollutants in the exhaust gas of an internal combustion engine having multiple cylinders |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3599427A (en) * | 1969-09-22 | 1971-08-17 | Ford Motor Co | Exhaust gas purification |
| DE2146084A1 (en) * | 1971-09-15 | 1973-03-29 | Aerolyt Vertriebsgesellschaft | Exhaust gas detoxification unit - has afterburner sepd from catalyst section by air venturi and nozzle tube |
| JPS51117234A (en) * | 1975-04-08 | 1976-10-15 | Nissan Motor Co Ltd | Process of air-fuel ratio control in internal-combustion engine |
-
1980
- 1980-09-25 DE DE19803036130 patent/DE3036130A1/en not_active Withdrawn
-
1981
- 1981-07-17 ES ES504050A patent/ES504050A0/en active Granted
- 1981-08-07 EP EP81106184A patent/EP0048808A1/en not_active Withdrawn
- 1981-09-21 BR BR8106013A patent/BR8106013A/en unknown
- 1981-09-23 CA CA000386496A patent/CA1166617A/en not_active Expired
- 1981-09-24 AU AU75640/81A patent/AU7564081A/en not_active Abandoned
- 1981-09-25 JP JP15082581A patent/JPS5786543A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| AU7564081A (en) | 1982-04-01 |
| EP0048808A1 (en) | 1982-04-07 |
| ES8205940A1 (en) | 1982-06-16 |
| BR8106013A (en) | 1982-06-08 |
| DE3036130A1 (en) | 1982-05-06 |
| JPS5786543A (en) | 1982-05-29 |
| ES504050A0 (en) | 1982-06-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |