KR20120004253A - Oxidation catalyst - Google Patents

Abstract

PURPOSE: An oxidization catalyst is provided to oxidize hydrocarbon and carbon monoxide contained in exhaust gas and to reduce fuel consumption by reducing the occurrence of sulfur-based pollution with respect to other catalytic components. CONSTITUTION: An oxidization catalyst includes a nitrogen oxide purifying catalyst, a smoke filter, and an oxidization catalyst. The nitrogen oxide purifying catalyst is installed at one side of an exhaust line. The nitrogen oxide purifying catalyst absorbs and eliminates nitrogen oxide contained in exhaust gas. The smoke filter is installed at another side of the exhaust line and filters particulates contained in the exhaust gas. The oxidization catalyst is installed other side of the exhaust line and oxidizes harmful materials contained in the exhaust gas. The oxidization catalyst includes catalytic components containing Pt, Pd, and M. The M is one selected from a group including Co, Cr, Cu, Fe, Mo, Ni, and W.

Description

Oxidation catalyst {OXIDATION CATALYST}

The present invention relates to an oxidation catalyst, and more particularly, to an oxidation catalyst for oxidizing hydrocarbons and carbon monoxide contained in exhaust gas.

In general, the exhaust gas discharged from the engine through the exhaust manifold is guided and purified by a catalytic converter formed in the middle of the exhaust pipe, is discharged to the atmosphere through the tail pipe after the noise is attenuated while passing through the muffler.

On the other hand, the purification catalyst contains a catalyst component, the catalyst component functions to purify the harmful substances contained in the exhaust gas, the function is degraded (deteriorated) or lost due to sulfur components contained in the fuel periodically, the temperature Desulfurization regeneration to remove sulfur is carried out.

However, when desulfurization and regeneration is performed, the durability of the catalyst unit decreases due to the high temperature, and fuel consumption increases.

Accordingly, it is an object of the present invention to provide an oxidation catalyst which is less polluted by sulfur components contained in the exhaust gas, which has good purification performance and improved durability and reduces fuel consumption.

The oxidation catalyst according to the present invention is a nitrogen oxide purification catalyst installed on one side of the exhaust line to adsorb and remove nitrogen oxides contained in the exhaust gas, and the particulate matter contained in the exhaust gas on the other side of the exhaust line is filtered. A soot filtration filter, and an oxidation catalyst installed at the other side of the exhaust line to oxidize harmful substances contained in the exhaust gas, wherein the oxidation catalyst is Pt (platinum), Pd (palladium), and M. Comprising a catalyst component, wherein M is selected from Co, Cr, Cu, Fe, Mo, Ni, W.

Pt (platinum), Pd (palladium), and M have a mass ratio of x: y: z, x is in the range of 0 to 1, y is in the range of 0.01 to 1, and z is in the range of 0.01 to 1 to be.

The catalyst component is composed of Pt, Pd, and Fe, and the mass ratio of each component is 4 (Pt): 1 (Pd): 10 (Fe).

The catalyst component is supported on alumina (Al 2 O 3), and is formed by firing in the range of 700 ° C. to 900 ° C.

Among the catalyst components, Pt and Pd have a mass ratio of 1% to the total catalyst, and Fe has a mass ratio of 2% to the total catalyst.

As described above, in the oxidation catalyst according to the present invention, the iron component included in the catalyst component is oxidized with the sulfur component to prevent other catalyst components (Pt, Pd) from being contaminated with sulfur, and reacts with alumina to produce aluminum sulfate. It prevents it from becoming and improves durability.

1 is a schematic diagram of an exhaust gas aftertreatment system according to an exemplary embodiment of the present invention.
2 is a flow chart of the oxidation catalyst provided in the exhaust gas aftertreatment system according to an embodiment of the present invention.
3 is a graph showing the purification performance according to the combination of the catalyst component of the oxidation catalyst according to an embodiment of the present invention.
4 is a graph showing the purification performance according to a specific catalyst component of the oxidation catalyst according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of an exhaust gas aftertreatment system according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the exhaust gas aftertreatment system includes an engine 100, an oxidation catalyst 110, a soot filter 120, and a nitrogen oxide purification catalyst 130.

The oxidation catalyst 110 oxidizes / reduces hydrocarbons and carbon monoxide contained in the exhaust gas discharged from the engine 100, and the soot filter 120 filters and removes particulate matter contained in the exhaust gas. .

The nitrogen oxide purification catalyst 130 adsorbs the nitrogen oxide contained in the exhaust gas under a condition rich in oxygen, and desorbs and reduces it under a condition in which oxygen is low.

On the other hand, the oxidation catalyst 110 is contaminated by the sulfur component contained in the exhaust gas, the performance is degraded by this contaminated sulfur component. In addition, the fuel consumption is increased by additionally injecting fuel to desulfurize to remove the attached sulfur component.

In the embodiment of the present invention, in order to prevent the oxidation catalyst 110 from being contaminated by sulfur components, it is composed of palladium (Pd), platinum (Pt), and iron (Fe).

The oxidation catalyst 110 is a catalyst component supported on a carrier composed of at least one component selected from alumina, ceria, zirconia, and zeolite. The catalyst component includes palladium and platinum as precious metals, and as a transition metal. Cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), molybdenum (Mo), nickel (Ni), and tungsten (W).

2 is a flow chart of the oxidation catalyst provided in the exhaust gas aftertreatment system according to an embodiment of the present invention.

Referring to FIG. 2, the method for preparing the oxidation catalyst 110 includes preparing a catalyst raw material (S300), dissolving raw materials (S310), preparing a carrier (S320), and supporting a catalyst component. Step S330, drying the catalyst S340, and calcining (heating) the catalyst S350.

The raw material of the oxidation catalyst 110 using hexachloroplatinate (H ₂ PtCl ₆ ), palladium chloride (PdCl ₂ ), and iron nitrate (Fe (NO ₃ ) ₃ ) as precursors of platinum, palladium, and iron. Alloys of, platinum, palladium, and iron are formed and dissolved / mixed in distilled water.

After stirring for a set time (about 1 hour), it is evenly supported on the alumina carrier by the initial impregnation method.

Platinum and palladium account for 1% by mass ratio of the total catalyst (wash coat), and platinum and palladium are mass ratios, which are variously modified into 0 to 1, 4 to 1, 1 to 4, and 1 to 0. Can be. In this embodiment, the mass ratio of platinum to palladium is preferably 4 to 1.

The oxidation catalyst 110 loaded with the catalyst is dried for 24 hours in an atmosphere of 100 degrees Celsius, and again heated to 500 degrees Celsius at a rate of 5 ^o C / min, heat-treated in an air atmosphere for 3 hours, and then slowly cooled. .

The oxidation catalyst 110 thus prepared is heated to 300 degrees Celsius at a rate of 5 ^o C / min in accordance with experimental conditions (vehicle exhaust gas temperature), and then reduced by heat treatment in a hydrogen atmosphere for 3 hours.

In addition, after the heat treatment for 24 hours in a 750 degrees Celsius air atmosphere to deteriorate the oxidation catalyst 110 in harsh conditions, in order to expose to sulfur components, flows 1000 ppm SO ₂ in an air atmosphere of 350 degrees Celsius for 24 hours Add.

In an embodiment of the present invention, an oxidation catalyst including platinum, palladium and iron was prepared, but the oxidation catalyst includes a catalyst component consisting of Pt (platinum), Pd (palladium), and M, wherein M is Co , Cr, Cu, Fe, Mo, Ni, W, Pt (platinum), Pd (palladium), and M has a mass ratio of x: y: z, x is in the range of 0 to 1 , y is in the range of 0.01 to 1, and z may be included in the range of 0.01 to 1.

3 is a graph showing the purification performance according to the combination of the catalyst component of the oxidation catalyst according to an embodiment of the present invention.

Referring to FIG. 3, the horizontal axis represents temperature and the vertical axis represents the purification rate of carbon monoxide.

As shown in the figure, when only platinum (Pt) is applied to the oxidation catalyst, the purification rate increases rapidly at around 150 degrees Celsius.

When platinum and palladium (Pd) are further applied to the oxidation catalyst, the purification rate is increased at around 130 degrees Celsius, and the purification rate is slowed down at around 150 degrees Celsius, and rises again at 200 degrees Celsius.

When platinum, palladium, and iron components are further applied to the oxidation catalyst, the purification rate increases at around 130 degrees Celsius, and the overall stable purification rate is obtained.

In this embodiment, when only platinum is applied to the oxidation catalyst, alumina and a sulfur dioxide (SO ₂ ) component as a carrier react with each other to produce aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), thereby degrading the performance of the catalyst. In addition, when only palladium is applied to the catalyst, the initial reactivity is high and does not produce aluminum sulfate, but the sulfur dioxide component reacts with the palladium to rapidly attach, thereby rapidly deteriorating the performance of the catalyst.

Therefore, when platinum and palladium are appropriately applied to the oxidation catalyst, the production of aluminum sulfate is reduced, and the initial reactivity and the reactivity at high temperature are improved.

However, even if platinum and palladium are applied to the catalyst, the sulfur dioxide component cannot completely block the formation of aluminum sulfate and the catalyst component cannot be completely blocked from sulfur contamination.

In this embodiment, the iron (Fe) component is added to the catalyst component so that the iron component is oxidized with the sulfur component, thereby substantially minimizing the reaction of the sulfur component with the catalyst or with the alumina.

4 is a graph showing the purification performance according to a specific catalyst component of the oxidation catalyst according to an embodiment of the present invention.

Referring to Figure 4, the horizontal axis represents the temperature, the vertical axis represents the content of sulfur dioxide (SO ₂ ).

4 is to determine the amount of iron in the catalyst component, consequently, the iron component preferably has a ratio of 2% of the total catalyst.

That is, under the condition that the mass ratio of platinum (4Pt) and palladium (1Pd) constituting the total catalyst is 1%, as shown, 0.5Fe means that the mass ratio of iron to the total catalyst is 0.1%.

In addition, 1Fe is the mass ratio of iron to the total catalyst is 0.2%, such as palladium (Pd), 10Fe means that the mass ratio of iron to the total catalyst is 2%, 20Fe is the mass ratio of iron to the total catalyst 4%, 30Fe is 6% of the mass ratio of iron to the total catalyst.

As shown, it can be seen that the content of sulfur dioxide in the 10Fe state is lowered. On the other hand, as with 20Fe and 30Fe, when iron content becomes high too much, it turns out that reactivity with sulfur dioxide is inferior. The reason for this is that iron particles aggregate together and the reactivity thereof is rather deteriorated.

As described above, the catalyst component used in the oxidation catalyst 110 preferably has a structure of 4Pt1Pd10Fe. Here, 4, 1, and 10 represent mass ratios, and since 4Pt1Pd occupies 1% of the total catalyst component, 10Fe occupies 2% of the total catalyst component.

In the present embodiment, the iron component contained in the catalyst component of the oxidation catalyst reacts with alumina to have a FeAlO ₃ form, but this FeAlO ₃ is hardly generated at 700 degrees Celsius or less. In addition, the FeAlO ₃ is produced in a large amount of more than 900 degrees Celsius, but the phase deformation of gamma alumina into alpha alumina, the specific surface area is sharply reduced, the carrier function is drastically reduced.

Therefore, when the catalyst component is supported on the support and calcined, it is preferable to maintain the temperature range within the range of 700 to 900 degrees Celsius.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

100: engine
110: oxidation catalyst
120: soot filter
130: nitrogen oxide purification catalyst

Claims (10)

A nitrogen oxide purification catalyst installed at one side of the exhaust line to adsorb and remove nitrogen oxide contained in the exhaust gas;
A soot filtration filter installed at the other side of the exhaust line to filter particulate matter contained in the exhaust gas; And
It is installed on the other side of the exhaust line and includes an oxidation catalyst for oxidizing harmful substances contained in the exhaust gas,
The oxidation catalyst includes a catalyst component composed of Pt (platinum), Pd (palladium), and M, wherein M is one selected from Co, Cr, Cu, Fe, Mo, Ni, and W. catalyst. In claim 1,
Pt (platinum), Pd (palladium), and M have a mass ratio of x: y: z, x is in the range of 0 to 1, y is in the range of 0.01 to 1, and z is in the range of 0.01 to 1 An oxidation catalyst characterized by the above-mentioned. In claim 1,
The catalyst component is composed of Pt, Pd, and Fe, and the mass ratio of each component is 4 (Pt): 1 (Pd): 10 (Fe). In claim 1,
The catalyst component is supported on alumina (Al 2 O 3), the oxidation catalyst, characterized in that formed by firing in the range of 700 to 900 degrees Celsius. 4. The method of claim 3,
Pt and Pd in the catalyst component is a mass ratio of 1% to the total catalyst, the Fe is an oxidation catalyst, characterized in that the mass ratio of 2% to the total catalyst. It is installed on the other side of the exhaust line includes a catalytic unit for removing harmful substances contained in the exhaust gas,
The catalyst unit includes a catalyst component composed of Pt (platinum), Pd (palladium), and M, wherein M is one selected from Co, Cr, Cu, Fe, Mo, Ni, and W. catalyst. In claim 6,
Pt (platinum), Pd (palladium), and M have a mass ratio of x: y: z, x is in the range of 0 to 1, y is in the range of 0.01 to 1, and z is in the range of 0.01 to 1 An oxidation catalyst characterized by the above-mentioned. In claim 6,
The catalyst component is composed of Pt, Pd, and Fe, and the mass ratio of each component is 4 (Pt): 1 (Pd): 10 (Fe). In claim 6,
The catalyst component is supported on alumina (Al 2 O 3), the oxidation catalyst, characterized in that formed by firing in the range of 700 to 900 degrees Celsius. 9. The method of claim 8,
Pt and Pd in the catalyst component is a mass ratio of 1% to the total catalyst, the Fe is an oxidation catalyst, characterized in that the mass ratio of 2% to the total catalyst.

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