Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
1998-12-11
2001-05-15
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C422S180000, C502S327000, C502S346000
Reexamination Certificate
active
06231817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust emission control device for internal combustion engines, and a method of manufacturing the same, and more particularly to an exhaust emission control device which is capable of simultaneously combustion-removing toxic components, such as particulate substances (which will hereinafter be referred to as particulates), CO and hydrocarbon compounds (which will hereinafter be abbreviated to as HC), and which has a high durability, and a-method of manufacturing the same.
2. Description of the Prior Art
In recent years, particulates and NOx contained in exhaust gas discharged from internal combustion engines, especially, diesel engines have become an issue as toxic substances to the environment. Especially, particulates contain particles of an average grain size of not more than 1 &mgr;m, and such particles float in the atmospheric air and are easily taken into human bodies by respiration. Moreover, it has been ascertained by recent clinical test results that these particles contain carcinogens. Therefore, the tightening of the control of the regulations concerning the discharge of these particulates is being discussed mainly in Japan, the U.S.A. and European countries.
Employment of DPF (Diesel Particulate Filter) as a particulate removing means which is adapted to remove particulates by filtering exhaust gas by using a heat-resistant porous body, such as a metal foam, a wire mesh, steel wool, a cell-sealed type ceramic honeycomb, a ceramic foam and open flow type ceramic honeycomb and metal honeycomb as a filter has been discussed. As particulates are collected by DPF, the pressure drop increases, so that a decrease in the engine output and deterioration of the fuel consumption occur. Therefore, the collected particulates are combustion-removed by a burner, an electric heater or a catalyst, thereby regenerating the filter.
The catalysts for burning particulates are roughly divided into noble-metal catalysts and base metal catalysts. A noble metal catalyst has a high durability and a high CO and HC removing performance but the particulate burning effect thereof has a problem. A base metal catalyst has a good particulate burning effect but it has a problem regarding its durability. Namely, the characteristics of the catalyst supported on a filter decrease due to SO
2
in the exhaust gas.
The catalysts comprising a combination of a noble metal catalyst and a base metal catalyst include a catalyst comprising a combination of rhodium, copper, silver, iron, magnesium and zinc and disclosed in Japanese Patent Laid-Open No. 169534/1984, a catalyst comprising a combination of palladium and copper oxide and disclosed in Japanese Patent Laid-Open No. 64741/1993, and a catalyst comprising a metal oxide layer of oxides of Cu, Mn, Ni, Fe and Co and a catalyst metal such as platinum supported on the metal oxide layer, and disclosed in Japanese Patent Laid-Open No. 138026/1993.
Among these conventional catalysts, a catalyst having a practicality as well as a durability against SO
2
-containing exhaust gas has not yet been found out. The exhaust gas temperature of a diesel engine is lower that of a gasoline engine, so that the former engine requires a low-temperature activity of the catalyst correspondingly to this. It has been found out that, when a conventional catalyst is used in a diesel engine exhaust emission control device, the low temperature activity is a problem.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an exhaust emission control device having a function of effectively removing toxic components, such as particulates, CO and HC, and having a high durability.
The inventors of the present invention have earnestly studied these problems. Consequently, they have discovered that a combination of copper oxide and platinum the grain sizes of which are within predetermined ranges brings about an excellent-exhaust emission control performance and a high durability and completed the present invention, achieving the present invention.
The present invention provides an exhaust emission control device which is provided in a container disposed in an intermediate portion of an exhaust system, wherein the exhaust emission control device comprises (1) a heat-resistant porous body having communicating pores, (2) a mixture of copper oxide and aluminum oxide supported on the surface of the porous body, and (3) platinum supported on the surface and the inner portion of the mixture, the grain size of the copper oxide being not less than 0.1 &mgr;m and not more than 50 &mgr;m.
One of the methods of manufacturing an exhaust emission control device according to the present invention comprises the steps of (1) preparing a heat-resistant porous body having communicating pores; (2) applying to the heat-resistant porous body a slurry obtained by dispersing in a liquid a mixture of copper oxide and aluminum oxide and/or compounds from which the oxides are produced by slight firing, and baking the mixture and/or compounds; and (3) applying a water-soluble platinum compound to the heat-resistant porous body on which the mixture of the copper oxide and the aluminum oxide has been supported, and baking the platinum compound.
Another method of manufacturing an exhaust emission control device according to the present invention comprises the steps of (1) preparing a heat-resistant porous body having communicating pores, and (2) applying to the heat-resistant porous body a slurry obtained by dispersing in a liquid a mixture of copper oxide and aluminum oxide and/or compounds from which the oxides are produced by slight firing, and a water-soluble platinum compound, and baking the oxide mixture and compounds.
Still another method of manufacturing an exhaust emission control device according to the present invention comprises (1) preparing a heat-resistant porous body having communicating pores; and (2) mixing a mixture of copper oxide and aluminum oxide and/or compounds from which the oxides are produced by slight firing, and a water-soluble platinum compound, drying, firing, and dispersing the mixture in a liquid to obtain a slurry, and applying the slurry to the heat-resistant porous body, and baking the mixture of oxides and the compounds.
REFERENCES:
patent: 3844980 (1974-10-01), Sakai et al.
patent: 3929671 (1975-12-01), Nakamura et al.
patent: 4274981 (1981-06-01), Suzuki et al.
patent: 4956331 (1990-09-01), Tsurumi et al.
patent: 5108978 (1992-04-01), Durand et al.
patent: 5264186 (1993-11-01), Harada et al.
patent: 0 727 248 (1996-08-01), None
patent: 59-169534 (1984-09-01), None
patent: 5-64741 (1993-03-01), None
patent: 5-138026 (1993-06-01), None
Ihara Tomohiko
Nakagama Syoji
Shimoda Kouhei
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
Tran Hien
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