KR101177684B1 - Selective catalytic reduction catalyst using LPG as a reductant for removing NOx - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SCR catalyst using LPG as a reducing agent. Compared with the catalyst using the active ingredient of the component shows an excellent NOx reduction efficiency over low and high temperatures.

Description

Selective catalytic reduction catalyst using LPG as a reductant for removing NOx}

The present invention relates to a SCR catalyst for NOx removal using LPG as a reducing agent. In particular, the present invention relates to an SCR catalyst for NOx removal in which a noble metal and a transition metal active component of three components are supported on a zeolite carrier.

The exhaust gases of automobiles, which are considered the main causes of air pollution, are carbon monoxide, carbon dioxide, nitrogen oxides (NOx), hydrocarbons, particulate matter (PM), ozone, sulfur dioxide (SOx), and aldehydes. The present invention relates to a catalyst for removing nitrogen oxides (NOx) in the exhaust gas.

NOx is a generic term for nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ). When combustion, oxygen and nitrogen in air react with high heat, and ozone is generated by photochemical reaction with sunlight in the air. NO is a colorless, odorless gas that reacts with air to oxidize to NO ₂ , and NO ₂ has a reddish-brown irritating odor and penetrates lung cells in the body when adsorbed to mucous secretions to form strong nitric acid. May cause lung edema, bronchitis, and pneumonia. More than 50% of the NOx emissions come from the transportation sector.

Methods for removing NOx can be divided into a pretreatment method of pretreating fuel to reduce the amount of NOx itself and a post-treatment method of converting the generated NOx into harmless components. Since the pretreatment method does not have a large effect, the post-treatment method is mainly used, and the post-treatment method is divided into a wet method and a dry method. Among the wet methods, a dry method is mainly used because secondary environmental pollutants are generated. Catalytic cracking and catalytic reduction are typical of the dry process. Catalytic cracking is a method of directly decomposing NOx into N ₂ and O ₂ by using a catalyst. The reaction occurs at a very high temperature and has a low decomposition rate. have. Catalytic reduction is typical of selective catalytic reduction techniques (hereinafter referred to as "SCR", Selective Catalytic Reduction). Although ammonia (NH ₃ ) is mainly used as the SCR reducing agent, ammonia is known to be difficult to be applied to a vehicle that is a mobile source due to ammonia slip problem. In addition, the ammonia used as the reducing agent may react with hydrocarbons, NOx, SOx, and the like in the exhaust gas, thereby causing corrosion of the device. In order to solve this problem, researches for reducing NOx by hydrocarbon reducing agents such as propane, propene, and methane are being conducted as reducing agents having less risk than ammonia.

SCR method using hydrocarbon as reducing agent also generates carbon monoxide due to incomplete oxidation, and hydrocarbon is O ₂ Alternatively, there is a problem of reacting with H ₂ O to generate CO or a new type of substance, which prevents the progress of the NOx removal reaction. In the case of hydrocarbon-based non-ammonia-based catalysts, reducing agents and carriers which have high desired temperature ranges or satisfactory high activity are not yet developed to reduce nitrogen compounds. Until now, many studies have been conducted around Cu / ZSM5 and Fe / ZSM5 systems, but there are problems of toxicity to sulfur or preparation of carriers is too complicated, and Pt-based catalysts have low selectivity. In the case of Ag / alumina system, the operating temperature is rather high, and there are technical problems such as the use of oxygenated compounds (oxygenated compound) as the reducing agent.

The present invention relates to a novel SCR catalyst capable of efficiently removing NOx using LPG as a reducing agent in a hydrocarbon-based reducing agent.

An object of the present invention is to develop an SCR catalyst using LPG fuel as a reducing agent to reduce NOx emitted from a vehicle using LPG as fuel.

The present invention provides an SCR catalyst for removing NOx using LPG as a reducing agent, characterized in that Pd, Fe and Cu are supported on a zeolite carrier.

The zeolite carrier is preferably ZSM5.

In particular, the zeolite carrier ZSM5 is more preferably Fe-ZSM5 in which Fe is ion-exchanged.

Pd is preferably 0.01 to 0.1% by weight, Fe to 1 to 3% by weight and Cu to 2 to 8% by weight in the total weight of the SCR catalyst.

As the method of supporting Pd, Fe and Cu on the zeolite carrier, an impregnation method or an ion exchange method is preferably used.

The catalyst developed in the present invention is composed of a noble metal and a transition metal, and synergistic action is performed by each component to further improve the NOx removal performance in the exhaust gas, and a zeolite catalyst using a conventional metal active ingredient of one component as a catalyst. Compared to the high nitrogen oxide removal efficiency. In particular, it can exert up to 60% NOx removal effect even in harsh experimental conditions.

Since the zeolite catalyst of the present invention shows excellent performance in removing nitrogen oxides emitted from an LPG engine, it can be widely used as an SCR catalyst for removing nitrogen oxides using LPG fuel as a reducing agent.

The present invention relates to the development of an SCR catalyst for NOx removal using LPG as a reducing agent. The present invention provides an SCR catalyst for NOx removal using LPG as a reducing agent, characterized in that Pd, Fe and Cu are supported on a zeolite carrier. In addition, the present invention provides an SCR catalyst for removing NOx further adding Ce in addition to the Pd, Fe, and Cu.

The total weight of the SCR catalyst is preferably 0.01 to 0.1% by weight, 2 to 8% by weight of Cu, 1 to 3% by weight of Fe, and 0.5 to 2% by weight of Ce. Occupy. When each metal component is excessively used, it should be uniformly dispersed on the zeolite carrier, but when used below the above range, the dispersion degree becomes low and shows low performance. On the other hand, when used excessively above the above range, aggregation or overlapping phenomenon between the metals is observed. As a result, the active surface of the metal may be deposited, thereby degrading performance. However, the above range is merely an example of a preferable content, and may be used outside the above range depending on the driving conditions of the LPG vehicle.

As a result of our research, ZSM5 is preferred among various zeolite carriers. In particular, it is preferable to use Fe-ZSM5 in which Fe is substituted by Fe in the carrier ZSM5 in advance by carrying out the ion exchange method before supporting the metal active ingredients. Of course, even when Fe-ZSM5 is used as a carrier, Fe is separately supported by impregnation or ion exchange to increase the content of Fe in the entire SCR catalyst.

In the following examples and comparative examples, the SCR catalyst of the present invention was directly synthesized in a honeycomb for the NOx removal experiment.

[ Example ]

Example  One

( carrier  : ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

ZSM5 was added to 60 g of distilled water at 60 ° C., 40 g of mass of distilled water was stirred for 2 hours, coated on a ceramic honeycomb, and dried at 150 ° C. for 6 hours. To 30 g of water, add 0.08 g of palladium nitrate, 4.6 g of kappa nitrate, 2.95 g of iron nitrate, and 0.55 g of cerium nitrate and stir for 2 hours. This stirred solution was prepared by a double coating impregnation method coated on a dried honeycomb, dried at 120 ° C. for 12 hours, and calcined at 500 ° C. for 3 hours in air.

Example  2

( carrier  : ZSM5 , metal : Pd - Cu - Fe - Ce )

In Example 1 was prepared in the same manner as in Example 1 except that the caffeite is 3.06g.

Example  3

( carrier  : ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

In Example 1, palladium nitrate was prepared in the same manner as in Example 1 except that 0.2g, carfanite was 3.06g, and iron nitrate was 8.85g.

Example  4

( carrier  : ZSM5 , metal : Pd - Cu - Fe , Impregnation method )

In Example 1, palladium nitrate was prepared in the same manner as in Example 1 except that 0.4 g, iron nitrate was 5.9 g, and cerium nitrate was not added.

Example  5

( carrier  : Fe - ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

In Example 1 was prepared in the same manner as in Example 1, except that Fe-ZSM5 in which ZSM5 was exchanged with iron ions.

Example  6

( carrier  : Fe - ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

In Example 1 was prepared in the same manner as in Example 1 except that iron nitrate is 5.9g, the carrier is Fe-ZSM5.

Example  7

(carrier : Fe - ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

In Example 1 was prepared in the same manner as in Example 1 except that the carbanitrate is 6.13g, the carrier is Fe-ZSM5.

Example  8

(carrier : Fe - ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

In Example 1 was prepared in the same manner as in Example 1 except that the carbanitrate is 7.66g, the carrier is Fe-ZSM5.

Example  9

(carrier : Fe - ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

In Example 1, it was prepared in the same manner as in Example 1 except that the carbanitrate was 9.2 g and the carrier was Fe-ZSM5.

Example  10

(Carrier: Fe - ZSM5, metals: Pd - Cu - Fe - Ce , impregnation)

In Example 1, it was prepared in the same manner as in Example 1 except that 9.2 g of carbanitrate, 1.1 g of cerium nitrate, and Fe-ZSM5.

Example  11

(carrier : Fe - ZSM5 , metal : Pd - Cu - Fe - Ce , Impregnation method )

In Example 1, it was prepared in the same manner as in Example 1 except that the carpanitrate is 7.66g, cerium nitrate is 1.1g, the carrier is Fe-ZSM5.

Example  12

(Carrier: Fe - ZSM5, metals: Pd - Cu - Fe - Ce , impregnation)

Cerium nitrate in Example 1 was 1.1g, and was prepared in the same manner as in Example 1 except that the carrier is Fe-ZSM5.

Example  13

(carrier : Fe - ZSM5 , metal : Pd - Cu - Fe - Ce , Ion exchange method)

7.66 g of carbanitrate was added to 60 g of 60 ° C. distilled water, followed by stirring for 20 minutes. Then, a solution (A) was prepared by adding zeolite Fe-ZSM5 with a mass equal to 2/3 of the mass of distilled water. A solution (B) was prepared by adding 0.08 g of palladium nitrate, 2.95 g of iron nitrate, and 0.55 g of cerium nitrate to 60 ° C. in distilled water at 20 ° C., wherein the total mass of the solution (B) was (A) 2/3 of the amount of distilled water. The prepared solutions (A) and (B) were combined and stirred for 2 hours. The stirred solution was coated on a ceramic honeycomb, dried at 120 ° C for 12 hours, and calcined at 500 ° C for 3 hours.

Comparative example  One

( carrier  : ZSM5 , metal : Cu , Impregnation method )

40 g of ZSM5 was added to 60 g of 60 ° C. distilled water, stirred for 2 hours, coated on a ceramic honeycomb, and dried at 150 ° C. for 6 hours. Again, 12.26 g of carfanite was added to 30 g of water and stirred for 2 hours. The stirred solution was prepared by a double coating impregnation method coated on a dried honeycomb, dried at 120 ° C. for 12 hours, and calcined at 500 ° C. for 3 hours in air.

Comparative example  2

( carrier  : ZSM5 , metal : Pd , Impregnation method )

40 g of ZSM5 was added to 60 g of 60 ° C. distilled water, stirred for 2 hours, coated on a ceramic honeycomb, and dried at 150 ° C. for 6 hours. Again, 0.04 g of palladium nitrate was added to 30 g of water, followed by stirring for 2 hours. The stirred solution was prepared by a double coating impregnation method coated on a dried honeycomb, dried at 120 ° C. for 12 hours, and calcined at 500 ° C. for 3 hours in air.

Comparative example  3

( carrier  : ZSM5 , metal : Fe , Impregnation method )

40 g of ZSM5 was added to 60 g of 60 ° C. distilled water, stirred for 2 hours, coated on a ceramic honeycomb, and dried at 150 ° C. for 6 hours. Again, 1.47 g of iron nitrate was added to 30 g of water, followed by stirring for 2 hours. The stirred solution was prepared by a double coating impregnation method coated on a dried honeycomb, dried at 120 ° C. for 12 hours, and calcined at 500 ° C. for 3 hours in air.

Comparative example  4

( carrier  : Ferrilite , metal : Pd - Cu - Fe - Ce , Impregnation method )

  It was prepared in the same manner as in Example 1 except that iron nitrate is 3.06 g in Example 1, and the carrier is ferrilite.

[Experimental Example]

Below, the NOx removal efficiency of each Example and the comparative example was measured through the experimental example. LPG was used as a reducing agent in Experimental Example 1 and Experimental Example 2 below. Experimental Example 2 is a result of testing the removal efficiency of NOx in harsh conditions compared to Experimental Example 1.

Experimental Example  One

In order to measure the nitrogen oxide removal efficiency of the catalyst prepared in Examples 1 to 6 and Comparative Examples 1 to 4, 500 ppm of 10% oxygen (O ₂ ), 500 ppm nitrogen monoxide (NO), and a reducing agent was injected, and a balance gas was used. Was taken as nitrogen (N ₂ ). The catalyst was inserted into a fixed bed continuous flow reactor, and the NOx removal rate was measured at a space velocity of 20,000 h ⁻¹ and a reaction temperature of 25 to 600 ° C. As a result, the same result as in Table 1 was obtained.

As a result of Table 1, when the catalyst of the present invention (Examples 1 to 6) was used, the NOx reduction efficiency was excellent at all temperatures as compared with the SCR catalyst using the catalysts of Comparative Examples 1 to 4. In particular, it can be seen that the NOx reduction efficiency of the catalyst of the present invention is noticeable at a high temperature rather than a low temperature.

In addition, Examples 5 and 6 are better than Examples 1 to 4 because the Fe-ZSM5 in which Fe is ion-exchanged is used in Examples 5 and 6. In the case of using Fe-ZSM5 as a carrier, since Fe is already uniformly distributed in the carrier ZSM5, it is presumed to exhibit an excellent NOx removal rate as compared with supporting Fe by the impregnation method.

Experimental Example  2

In order to measure the nitrogen oxide removal efficiency of the prepared catalysts of Examples 5 and 7 to 13, 6% oxygen (O ₂ ), 500 ppm nitrogen monoxide (NO), which are conditions for increasing the test severity, and butane 70 for winter as a reducing agent. %, the injection of LPG B7P3-propane 30% composition 500ppm, and was a balance gas of nitrogen (N _2). The catalyst was inserted into a fixed bed continuous flow reactor, the space velocity was 50,000 h ^-1 , and the reaction temperature was 25-600 ° C.

Comparing the NOx removal rate of Table 2, which summarizes the results of Experimental Example 2, and Table 1, which summarizes the results of Experimental Example 2, the overall NOx removal efficiency of Table 2 is inferior. In particular, Example 5 was all tested under the conditions of Experimental Example 1 and Experimental Example 2, as expected, it was found that the NOx removal efficiency in Experimental Example 2, which is a severe operating condition, is somewhat reduced. This is because in the case of Table 2, NOx removal efficiency was measured under harsher operating conditions than the experiments in Table 1.

On the other hand, even in the results of Experimental Example 2 for the examples of Examples 5, 7 to 13 tested under harsh experimental conditions, it shows that the NOx removal efficiency superior to Comparative Examples 1 to 4 of Table 1 tested under less severe experimental conditions Could know.

In addition, in the case of Example 13, Pd, Fe, Cu, Ce supported on the Fe-ZSM5 carrier through the ion exchange method, compared to the other examples 5, 7 to 12 produced through the impregnation method, the NOx removal efficiency is excellent I could see it. It is assumed that this is because the ion exchange method rather than the impregnation method can uniformly distribute each metal component to the carrier without aggregation.

Claims (5)

SCR catalyst for removing NOx having Pd, Fe and Cu supported on a zeolite carrier, wherein Pd is 0.01 to 0.1% by weight, Fe is 1 to 3% by weight and Cu is 2 to 8% by weight of the total weight of the SCR catalyst SCR catalyst for removing NOx using LPG as a reducing agent.
The SCR catalyst for removing NOx using LPG as a reducing agent according to claim 1, wherein the zeolite carrier is ZSM5.
The SCR catalyst for removing NOx using LPG as a reducing agent according to claim 2, wherein the zeolite carrier ZSM5 is Fe-ZSM5 in which Fe is ion-exchanged.
delete 2. The SCR catalyst for removing NOx using LPG as a reducing agent according to claim 1, wherein the method of supporting Pd, Fe and Cu on the zeolite support is carried out by impregnation or ion exchange.