KR100230874B1 - Method for purifying exhaust gases of cng automobiles - Google Patents

Abstract

An object of the present invention is to provide a catalyst for CNG vehicle exhaust gas purification and a CNG vehicle exhaust gas purification method capable of efficiently purifying methane which occupies most of the compressed natural gas (CNG) vehicle exhaust gas. CNG automobile exhaust gas purification catalyst is 50 to 200 g of γ-Al ₂ O ₃ , 10 to 100 g of CeO ₂ , 1 to 10 g of ZrO ₂ and 0.1 to 10 g of precious metals per 1 liter of the carrier. It is characterized by being supported. In addition, the CNG automobile exhaust gas purification method is 50 to 200 g of γ-Al ₂ O ₃ , 10 to 100 g of CeO ₂ , 1 to 10 g of ZrO ₂ and 0.1 to 10 g of precious metal as a catalytically active material per liter of the carrier. Each of these catalysts is characterized in that two types of catalysts having different compositions of the catalytically active substance are provided at the front and rear portions of the CNG automobile catalytic converter, respectively.

Description

Catalyst for exhaust gas purification for compressed natural gas and its purification method

The present invention relates to a catalyst for purifying exhaust gas of a compressed natural gas (hereinafter referred to as 'CNG') and a purification method thereof.

Recently, as the regulations on environmental pollution become more strict, active researches on CNG vehicles are being conducted as low-polluting vehicles.

CNG, which is used as fuel for such CNG vehicles, is made up of almost all of them, usually about 70% or more. Therefore, there is a need for a catalyst for CNG automobile exhaust gas purification and a purification method thereof capable of efficiently purifying methane which occupies most of the CNG automobile exhaust gas.

Accordingly, an object of the present invention is to provide an exhaust gas purifying catalyst and a method for purifying the same, which can efficiently purify methane, which is a main component of CNG automobile exhaust gas.

1 is a diagram for demonstrating the CNG automobile exhaust purification efficiency of the method according to the embodiment of the present invention.

In order to achieve the above object, the catalyst for CNG vehicle exhaust gas purification of the present invention is 50-200g γ-Al ₂ O ₃ , 10-100g CeO ₂ , 1-10g ZrO ₂ and It is characterized in that 0.1 to 10 g of precious metal is supported as a catalytically active material. Wherein the catalytically active material is selected from the group consisting of palladium, platinum, rhodium and combinations of two or more thereof.

In addition, an object of the present invention is 50 to 200 g of γ-Al ₂ O ₃ per 10 liter of the carrier, 10 to 100 g of CeO ₂ , 1 to 10 g of ZrO ₂ and 0.1 to 10 g of precious metal as a catalytically active material. It is achieved by providing a CNG automobile exhaust gas purification method, characterized in that two kinds of catalysts each supported and having different compositions of catalytically active materials are provided on the front and rear portions of the CNG automobile catalytic converter, respectively.

As used herein, the term “front portion” means a portion corresponding to the distance from the portion of the catalytic converter at which the gas exiting the engine begins to flow from the portion of the catalytic converter along the longitudinal direction of the catalytic converter. "Rear portion" means a portion corresponding to a distance from a portion of the catalytic converter at which gas starts to be discharged toward the muffler to a point about an intermediate point along the longitudinal direction of the catalytic converter. Thus, the term "front catalyst" as used hereinafter means a catalyst that is installed in the front portion and a "rear catalyst" means a catalyst that is installed in the rear portion.

The precious metal supported on the catalyst used in the process of the present invention and serving as a catalytically active component is selected from the group consisting of palladium, platinum, rhodium and combinations of two or more thereof. Further, sources of precious metals for supporting the ceramic carrier include noble metal chlorides, nitrates and acetates.

In addition, sources of active alumina (γ-Al ₂ O ₃ ) used as a supporting layer in the catalyst and CeO ₂ and ZrO ₂ used as cocatalysts include oxides, nitrates, acetates, sulfates, and the like.

Hereinafter, the present invention will be further described through examples.

EXAMPLE

For use in Examples 1-2 and Comparative Examples 1-3 below, noble metal supported catalysts were prepared as follows.

[Production of Palladium (Pd) Supported Catalyst]

Lanthana (La ₂ O ₃₎ of 5% has been doped with a specific surface area of 100m ² / g of activated alumina (γ-Al ₂ O ₃₎ powder with a specific surface area of the CeO ₂ powder and ZrO ₂ powder are each 4m ² / g The slurry was prepared by wet grinding. Thereafter, the slurry was applied for supporting on the ceramic carrier, and the supporting amount was 100 g of activated alumina, 60 g of CeO ₂ , and 3 g of ZrO ₂ per liter of the ceramic carrier. Subsequently, the applied ceramic carrier was dried and then fired at a temperature of 500 ° C. Then, the calcined ceramic sesame was impregnated with palladium chloride (H ₂ PdCl ₆ ), dried, and calcined at a temperature of 500 ° C. to prepare a catalyst having 3.2 g of Pd per liter of the ceramic carrier.

[Preparation of Platinum (Pt) / Rhodium (Rh) Supported Catalyst]

That sikyeotdaneun carrying a weight ratio of 1: slurry of Pt and Rh of 1.6g per 1ℓ ceramic carrier 5 by combining the coating and the fired ceramic carrier for platinum chloride (H ₂ PtCl ₆₎ and rhodium hydrochloride (H ₂ RhCl ₆₎ Except, a Pt / Rh supported catalyst was prepared according to the same process as the preparation of the Pd supported catalyst.

[Preparation of Platinum (Pt) / Piladium (Pd) / Rhodium (Rh) Supported Catalyst]

The slurry was applied and calcined, and the ceramic carrier was impregnated with palladium chloride, platinum chloride and rhodium chloride to support 3.2 g of Pt, Pd and Rh per liter of the ceramic carrier in a weight ratio of 1: 14: 1. A Pt / Pd / Rh supported catalyst was prepared according to the same process as the preparation of the Pd supported catalyst.

Example 1

Sweep test and light-off test in the fresh state of the catalyst using the Pd-supported catalyst prepared as described above as the front catalyst and the Pt / Rh supported catalyst as the rear catalyst. Test) was performed.

In the sweep test, a model gas having the composition shown in Table 1 was used, and the CH ₄ purification rate was measured while changing the oxygen concentration from the rich region to the lean region. It is shown as a symbol-(square).

TABLE 1

Composition of Model Gas

The temperature of the gas introduced during the sweep test was 500 ° C., the space velocity was 30,000 / hr, and the stoichiometric ratio of the model gas was adjusted as a change in the redox ratio as follows (1).

Further, in the light-off test, the temperature at which CH ₄ is purified by 50% while changing the temperature of the gas flowing into the catalyst at the theoretical air-fuel ratio composition (redox ratio = 1) within a range of 100 ° C to 700 ° C (LOT ₅₀ ) Was measured.

LOT ₅₀ was 335 ° C.

Example 2

Using the prepared Pd supported catalyst as the front catalyst and the Pt / Pd / Rh catalyst as the rear catalyst, the sweep test and the light-off test were carried out under the same conditions as described in Example 1. The sweep test results are shown as symbols-Δ- in FIG. 1 and LOT ₅₀ is 332 ° C.

Comparative Example 1

Using the Pd-supported catalyst prepared as described above as the front catalyst and the rear catalyst, the sweep test and the light-off test were conducted according to the same conditions as described in Example 1. The sweep test results are shown as symbols--in FIG. 1 and LOT ₅₀ was 353 ° C.

Comparative Example 2

Using the Pt / Rh supported catalyst prepared as described above as the front catalyst and the rear catalyst, the sweep test and the light-off test were conducted according to the same conditions as described in Example 1. Sweep test results are shown as symbol- ◆-in FIG. 1 and LOT ₅₀ was 417 ° C.

Comparative Example 3

Using the Pt / Pd / Rh catalyst prepared as above as the front catalyst and the rear catalyst, the sweep test and the light-off test were conducted according to the same conditions as described in Example 1. The sweep test results are shown as symbols --- in FIG. 1, and LOT ₅₀ was 396 ° C.

The results of Examples 1-2 and Comparative Examples 1-3 are comprehensively described. As shown in FIG. 1, the composition of the catalytically active material of the front catalyst and the catalytically active material of the rear catalyst is different from that of the catalytically active component. It can be seen that not only can the methane purification rate be further improved than the same, but the LOT ₅₀ can be further reduced.

As described above, the CNG vehicle exhaust gas purification catalyst of the present invention is used, and according to the method of the present invention, the composition of the catalytically active substance of the front catalyst and the catalytically active substance of the rear catalyst is different for most of the CNG automobile exhaust gas. It can efficiently purify the methane which occupies.

Claims (6)

50 to 200 g of γ-Al ₂ O ₃ , 10 to 100 g of CeO ₂ , 1 to 10 g of ZrO _2, and 0.1 to 10 g of precious metal are supported on the ceramic carrier, respectively. A method for purifying exhaust gas for a CNG vehicle, characterized in that two kinds of catalysts having different compositions are provided at the front and rear portions of the catalytic converter of the CNG vehicle, respectively. The method of claim 1, wherein the catalytically active material is selected from the group consisting of palladium, platinum, rhodium, and combinations of two or more thereof. The catalyst installed in the front portion of the catalytic converter is supported by palladium as a catalytically active material, and the catalyst installed in the rear portion is supported by platinum and rhodium as a catalytically active material. How to Clean CNG Vehicle Exhaust? The catalyst installed in the front portion of the catalytic converter has palladium supported as a catalytically active material, and the catalyst installed in the rear portion has platinum, palladium and rhodium as the catalytically active material. CNG automobile exhaust gas purification method to use. The method of claim 3, wherein the weight ratio of platinum and rhodium supported on the catalyst installed in the rear portion is 5: 1. The method of claim 4, wherein the weight ratio of platinum, palladium, and rhodium supported on the catalyst installed at the rear portion is 1: 14: 1.

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