KR100888018B1 - A catalyst for treating exhaust gas of diesel lng dual fuel vehicles - Google Patents

Abstract

An exhaust gas purifying catalyst for a vehicle using both diesel and LNG is provided to dip platinum as well as palladium for a catalyst and control weight ratio of the platinum and the palladium, thereby suppressing a poisoning phenomenon caused by sulfur. An exhaust gas purifying catalyst for a vehicle using both diesel and LNG comprises the following steps. A ceramic support is coated with alumina, dried and plasticized. The support coated with a carrier is manufactured and dipped in a catalyst solution containing platinum and palladium, dried and plasticized. The platinum is dipped to weight ratio of 0.1~0.5 on a basis of 1 of the palladium.

Description

A catalyst for treating exhaust gas of diesel LNG dual fuel vehicles}

The present invention relates to a catalyst for purifying exhaust gas for diesel LNG mixed-vehicle vehicles, and more particularly, to an exhaust gas purifying catalyst having an effective removal of methane from exhaust gas and an excellent anti-toxic effect on sulfur.

Natural gas vehicles can be divided into CNG and LNG according to the fuel supply method. CNG stores and uses compressed gas at about 200 atm in a high-pressure container. LNG supplies ultra-low temperature fuel around -130 ℃ as automotive fuel. The reason why CNG accounts for most of natural gas fuel at home and abroad is that LNG is more difficult to apply than CNG and there is insufficient infrastructure to supply LNG. In Korea, the supply of CNGV (CNG vehicle) is showing good response in the market and it is considered to be mature stage, but LNGV (LNG vehicle) is now undergoing development and testing.

On the other hand, depending on the combustion ignition method, natural gas engines can be divided into dedicate and dual fuel types. In the case of burned-up methods, the ignition method by electric method is the combustion method of gasoline engines, and the fusion method is diesel fuel. It is used as an ignition source. In case of converting existing diesel vehicle to natural gas engine, if mixed gas is applied, only natural gas supply system is installed without changing ignition system, so it is relatively simple to convert fuel.

Natural gas vehicles have methane as their main component. Methane is a potential greenhouse gas substance with a very long lifespan and a greater effect than carbon dioxide. Natural gas vehicle emissions Due to the environmental impact of methane gas, emission regulations are expected to be enforced in the future, and 60% of the current methane gas must be treated with a low temperature post-treatment device to implement the strongest regulations in Europe. I can hit it.

Currently, a catalyst in which palladium is supported as an active ingredient is used as a catalyst for oxidizing methane. However, palladium has a problem that the catalytic activity is significantly lowered when sulfur (S) is present.

On the other hand, LNG does not contain sulfur, but diesel contains sulfur. In the case of diesel-LNG mixed vehicles, the catalytically active material for oxidizing methane in the exhaust gas is poisoned by sulfur (S) contained in diesel. There is a need for the development of a suitable methane removal catalyst.

An object of the present invention is to provide a catalyst for purifying a diesel-LNG mixed vehicle exhaust gas which can efficiently remove methane from the exhaust gas of a diesel-LNG mixed vehicle.

In addition, another object of the present invention is to provide a catalyst for purifying a diesel-LNG mixed vehicle exhaust gas which has high methane removal efficiency and suppresses poisoning by sulfur.

The present inventors have carried out research to achieve the above object, and found that it is possible to support the platinum in addition to the palladium catalyst component to suppress the poisoning phenomenon by sulfur by adjusting the weight ratio of palladium and platinum to complete the present invention. Reached.

Diesel fuel is usually managed at 50ppm or less in Korea. Therefore, the concentration of sulfur present in the exhaust gas of the diesel LNG mixed vehicle is 10 ppm or less, 0.1 to 10 ppm, more specifically 0.1 to 5 ppm, depending on the mixing ratio of the diesel-LNG mixed vehicle. In the present invention, as described above, the loading ratio of palladium (Pd) and platinum (Pt) was adjusted to have excellent methane oxidation activity under the conditions of diesel LNG mixed vehicle exhaust gas, and as a result, palladium: platinum component is 1: 0.1 to 0.5 by weight ratio. It was found that the poisoning effect on sulfur contained in the exhaust gas of diesel LNG mixed-vehicle vehicle was excellent and the methane oxidation activity was high.

Hereinafter, the present invention will be described in detail.

The present invention relates to a catalyst for diesel LNG mixed vehicle exhaust gas purification, in which a catalyst active component is supported by palladium (Pd): platinum (Pt) in a weight ratio of 1: 0.1 to 0.5. More preferably, the present invention relates to a catalyst for purifying exhaust gas for diesel LNG mixed vehicle, in which palladium (Pd): platinum (Pt) is supported at a weight ratio of 1: 0.1 to 0.5 as an acid treated carrier and a catalytically active component on a ceramic support.

It is preferable that it is 1: 0.1-0.5, and, as for the weight ratio of the said palladium (Pd): platinum (Pt), it is more preferable that it is 1: 0.1-0.3.

The catalytic activity of oxidizing methane is superior to that of palladium, but palladium is easily poisoned by sulfur and loses catalytic activity. Therefore, in order to have a poisoning inhibitory effect on sulfur, a promoter must be introduced in addition to palladium. Platinum has a superior effect as a cocatalyst having a poisoning inhibitory effect on sulfur while maintaining methane oxidation activity, but platinum has a lower methane oxidation activity than palladium, and thus platinum has a poisoning inhibitory effect on sulfur and excellent methane oxidation activity. And the proportion of palladium is important. In addition, as a result of researches to have a poisoning inhibitory effect and excellent methane oxidation activity for the sulfur content of the exhaust gas in diesel LNG mixed-vehicle vehicle, the ratio of palladium to platinum is 1: 0.1 to 0.5 by weight, more preferably When the ratio is 1: 0.1 to 0.3 by weight, it was confirmed that it has an anti-toxic effect on sulfur and excellent methane oxidation activity under exhaust gas conditions of diesel LNG mixed vehicle. When the content of platinum is lower than 0.1 weight ratio with respect to palladium, the poisoning inhibitory effect on sulfur is remarkably reduced, and when the content of platinum is 0.5 weight ratio with respect to palladium, catalytic activity is lowered. Therefore, it should be adjusted to the above range in the diesel LNG mixed vehicle can have a poisoning inhibitory effect on sulfur and high methane oxidation activity.

The catalyst for purifying exhaust gases according to the present invention is a palladium and platinum component supported as a carrier and a catalytically active material on a ceramic support. The ceramic support may be a honeycomb monolith type made of a heat resistant ceramic material such as cordierite. As the carrier, alumina, zirconia, silica, ceria, or the like may be used alone or in combination. The use of alumina is more preferred in view of catalytic activity. The carrier may be used by acidic treatment with an acid such as sulfuric acid.

The amount of the carrier supported on the ceramic support is preferably 0.5 to 4 g / in ³ . When the content of the carrier is less than 0.5 g / in ³ , the performance of the catalyst is remarkably reduced, and when the content of the carrier exceeds 4 g / in ³ , the catalyst performance no longer increases and at the same time, the production is not easy.

In addition, the content of the catalytically active material supported on the catalyst in the present invention is in the range of 0.1 to 20% by weight, more preferably 1 to 15% by weight, based on the total weight of the carrier and the catalytically active material. If the content is less than 0.1 wt%, the performance of the catalyst is significantly reduced, and if it exceeds 20 wt%, no further catalyst activity is increased, which may be economically disadvantageous.

In the catalyst active material according to the present invention, the carrier may first be coated on a support, and then the catalyst active material may be supported on the support coated with the carrier. The catalyst active material may be supported on the support to prepare a carrier on which the catalyst active material is supported. It may then be washcoated onto the support.

Diesel LNG mixed-vehicle vehicle exhaust gas purification catalyst according to the present invention can be prepared by a manufacturing method comprising the following steps.

Washing the alumina on the ceramic support, drying and calcining to prepare a support coated with a support; And

The support is coated with a carrier in a catalyst solution containing palladium (Pd) and platinum (Pt), followed by drying and baking.

Palladium precursors used in the preparation of the catalyst solution may be used, such as palladium nitrate, palladium chloride, tetraminpalladium dichloride, and as platinum precursor, tetraminplatinum nitride (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ). ) Or hexachloroplatinic acid (H ₂ PtCl ₆ ) may be used, but compared to the tetraminplatinum nitride (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ), hexachloroplatinic acid (H ₂ PtCl _6). ) Is more preferable because it is remarkably excellent in catalytic activity.

The method of washing the carrier to the support, the drying and the firing method may be accomplished by conventional methods used in the art.

The catalyst for purification of diesel LNG mixed vehicle exhaust gas according to the present invention not only shows excellent methane oxidation activity, but also has an excellent anti-toxic effect by sulfur.

The present invention will be described in more detail with reference to the following Examples. However, the following examples are merely examples of the present invention, and the claims of the present invention are not limited thereto.

[Examples 1 to 7] Preparation of Catalyst Supported with Pd and Pt Components

A mixture of acetic acid and distilled water (1: 3.5 weight ratio) was mixed with gamma alumina powder [SASOL, Germany, surface area: 210m ² / gr, pore volume: 0.5cc / gr, specific gravity: 0.8g / cc], followed by a wet ball mill. 12 hours to grind to prepare a uniform alumina slurry. The content of gamma alumina powder in the slurry was 50% by weight, and the average particle size of alumina ground through a wet ball mill was 3 micrometers.

Cordierite honeycomb monolith (1in ³ , 400 cpsi) wasolated on the alumina slurry prepared above, coated with alumina so that the loading amount of alumina was 2 g / in ³ , and then dried at 120 ° C. for 2 hours, followed by 550 ° C. The honeycomb monolith coated with an alumina was prepared by baking at 3 hours.

Pd (NO ₃ ) ₂ aqueous solution (10% by weight) as a palladium precursor, H ₂ PtCl ₆ as a platinum precursor was dissolved in distilled water to have a content as shown in Table 1 below to prepare 80g of catalyst solution, respectively The honeycomb monolith coated with the prepared alumina was impregnated with each catalyst solution for 1 minute, and then subjected to air-blowing to remove the excess solution, followed by drying at 120 ° C. for 2 hours at 600 ° C. Firing at 4 ° C. for 4 hours yielded a catalyst carrying Pd and Pt.

Example 8

A catalyst was prepared in the same manner as in Example 7, except that tetraminplatinum nitride (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ) was used as the platinum precursor.

TABLE 1

Test Example 1 Evaluation of Catalyst Activity

After fixing the honeycomb monolith catalyst prepared in Examples 1 to 4 in the catalytic reactor, methane (CH ₄ ) oxidation experiment was performed.

The model gas having the composition shown in Table 2 was mixed by controlling the flow rate using an MFC (mass flow controller), and then injected into the catalytic reactor. The flow rate of the model gas is 13.6 l / min, and the space velocity is GHSV 50,000hr ^-1 . Thermocouples were placed at the top and bottom of the reactor to control and measure the temperature. The reaction temperature range was 150-600 ° C., and the temperature was raised to 5 ° C./min to confirm catalytic activity. The concentrations of NO, CO, and CH ₄ reactant gases before and after the reaction were confirmed through a gas analyzer.

TABLE 2

1 is a result of evaluating methanation activity while adjusting the ratio of palladium and platinum. Referring to the results of FIG. 1, the catalyst of Example 4 having a palladium: cobalt weight ratio of 1: 0.2 showed the best catalytic activity.

Test Example 2 Evaluation of Resistance to Sulfur Resistance

Injecting the model gas shown in Table 3 for the catalysts of Examples 5 to 8, the methane conversion rate was evaluated at 500 degrees with time, and the results are shown in FIG. 2.

TABLE 3

Referring to the results of FIG. 2, the methane conversion was higher in the condition of Pd: Pt = 1: 0.2 (weight ratio) than in the case of Pd: Pt = 1: 0.5 (weight ratio), and the methane conversion was higher as the loading amount was increased. . In terms of catalytic activity according to the platinum precursor, the use of hexachloroplatinic acid (H ₂ PtCl ₆ ) is more excellent than that of tetraminplatinum nitride (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ). Preferred.

1 is a result of activity evaluation of a methane oxidation catalyst in which palladium and platinum are supported as catalytic active components,

2 is a result of evaluation of catalyst resistance to sulfur.

Claims (6)

A catalyst for the purification of diesel LNG mixed vehicle exhaust gas, wherein the catalyst for treating the diesel LNG mixed vehicle vehicle exhaust gas in which palladium (Pd): platinum (Pt) is supported at a weight ratio of 1: 0.1 to 0.5 as a catalyst active component. The method of claim 1, A catalyst for purifying exhaust gas of a diesel LNG mixed-vehicle vehicle having a weight ratio of palladium (Pd): platinum (Pt) of 1: 0.1 to 0.3. The method of claim 2, The catalyst is a catalyst for purifying exhaust gas of diesel LNG mixed vehicle with palladium and platinum supported as a carrier and a catalytically active material selected from alumina, zirconia, silica, ceria and mixtures thereof on a ceramic support. The method of claim 3, wherein The carrier is alumina diesel LNG mixed vehicle exhaust gas purification catalyst. The method of claim 4, wherein The diesel LNG mixed-vehicle exhaust gas purification catalyst Washing the alumina on the ceramic support, drying and calcining to prepare a support coated with a support; And Supporting the carrier-coated support in a catalyst solution containing palladium (Pd) and platinum (Pt), followed by drying and baking;  Catalyst for exhaust gas purification of diesel LNG mixed vehicle manufactured by The method of claim 5, wherein The catalyst liquid is a diesel LNG mixed-vehicle exhaust gas purification catalyst containing hexachloroplatinic acid (H ₂ PtCl ₆ ) as a platinum precursor.

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