KR100349451B1 - FABRICATION METHOD OF DeNOx CATALYST - Google Patents
FABRICATION METHOD OF DeNOx CATALYST Download PDFInfo
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- KR100349451B1 KR100349451B1 KR1019950007558A KR19950007558A KR100349451B1 KR 100349451 B1 KR100349451 B1 KR 100349451B1 KR 1019950007558 A KR1019950007558 A KR 1019950007558A KR 19950007558 A KR19950007558 A KR 19950007558A KR 100349451 B1 KR100349451 B1 KR 100349451B1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/30—Ion-exchange
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/064—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing iron group metals, noble metals or copper
- B01J29/068—Noble metals
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
Abstract
Description
본 발명은 질소산화물(NOx) 정화용 촉매의 제조방법에 관한 것으로, 좀 더 상세하게는 질소산화물 정화용 촉매의 제조시 제올라이트에 귀금속 이온을 이온교환시키는 방법을 변화시켜 열적내구성을 향상시킨 NOx 정화용 촉매의 제조방법에 관한 것이다.The present invention relates to a method for preparing a catalyst for purifying nitrogen oxides (NOx), and more particularly, to a method for purifying a catalyst for NOx purification by changing a method of ion-exchanging noble metal ions to zeolite during production of a catalyst for purifying nitrogen oxides. It relates to a manufacturing method.
급속한 산업경제 발전에 따른 자동차 보유대수의 증가와 이에 따른 유해 배기가스의 증가는 지구환경을 크게 손상시켜 심각한 사회문제로 대두되고 있다. 이러한 문제를 해결하기 위해서 미국, 일본을 비롯한 자동차 선진각국 뿐만 아니라 국내 자동차 산업계에서도 연비규제와 배기가스 규제를 동시에 만족시키기 위한 일환으로 희박연소 엔진(lean burn engine)의 개발과 상용화에 관심을 집중시키고 있으며, 이와 함께 희박연소 엔진의 배기가스 처리용 촉매의 연구개발에 박차를 가하고 있다.The increase in the number of cars owned by the rapid development of the industrial economy and the increase in the amount of harmful exhaust gases are seriously damaging the global environment and are becoming a serious social problem. In order to solve these problems, the automobile industry in the United States, Japan and other countries as well as the domestic automotive industry focus on the development and commercialization of lean burn engines as a part of satisfying fuel economy and emission regulations simultaneously. At the same time, the research and development of catalysts for exhaust gas treatment of lean burn engines is being accelerated.
현재, 승용차 엔진의 배기가스 정화용 촉매로서 HC(Hydrocarbons)와 CO의 산화와 NOx의 환원을 동시에 정화시키는 3원촉매가 알려져 있는데, 이 3원촉매는 허니컴(Honeycomb)에 γ-Al2O3에 Pt, Pd 및 Rh를 담지시켜 엔진의 공연비(공기 대 연료의 비율)가 14.7인 이론공연비 영역에서 높은 정화율을 나타내고 있는 촉매이다.Currently, three-way catalysts are known to purify the oxidation of HC (Hydrocarbons) and CO and the reduction of NOx as catalysts for exhaust gas purification of passenger car engines. These three-way catalysts are applied to honeycomb by γ-Al 2 O 3 . It is a catalyst that supports Pt, Pd, and Rh, and shows a high purification rate in a theoretical air fuel ratio range in which the air-fuel ratio of the engine (air to fuel ratio) is 14.7.
그러나, 상기 3원촉매는 연비와 배기가스 문제를 해결하기 위해 연구된 희박연소 엔진의 배기가스 정화용 촉매로는 사용할 수 없는 실정이다. 즉, 희박연소에서는 엔진의 공연비가 18~26까지 증가되어 과잉의 산소분위기가 되므로, HC와 CO는 산화반응에 의해 정화가 용이하지만 NOx는 산화분위기에서 환원시켜야 하므로 새로운 촉매계의 개발이 필요하다.However, the ternary catalyst cannot be used as a catalyst for purifying exhaust gases of lean burn engines studied to solve fuel consumption and exhaust gas problems. That is, in lean combustion, the air-fuel ratio of the engine is increased to 18 to 26, so the oxygen atmosphere is excessive. Therefore, HC and CO are easily purified by the oxidation reaction, but NOx must be reduced in the oxidation atmosphere, and thus a new catalyst system needs to be developed.
한편, 희박연소 엔진 뿐만 아니라 보일러 등의 산업용에서 발생되는 NOx의 건식처리 방법에 있어서, 환원제를 전혀 사용하지 않고 NOx를 N2로 직접 분해할 수 있는 직접분해 방법이 가장 바람직한 반응 경로이다. 이에 관한 촉매계는 실현되지 못하고 있다.On the other hand, in the dry treatment method of NOx generated not only in lean burn engines but also in industries such as boilers, a direct decomposition method capable of directly decomposing NOx to N 2 without using any reducing agent is the most preferable reaction route. The catalyst system related to this has not been realized.
이에 따라, NOx의 분해를 위해 HC를 환원제로 사용하는 새로운 촉매계가 제안되었는데, 그중 이와모토(Iwamoto) 등은 천이금속을 제올라이트에 이온교환시켜 NOx 분해를 위한 새로운 촉매를 개발하였다. 이러한 천이금속중 Cu가 이온교환된촉매에서 가장 높은 이온 교환율을 나타내었고, 촉매의 활성 및 HC의 가스 선택성은 제올라이트의 구리 이온 교환율이 높아짐에 따라 더욱 더 크게 나타난다고 보고하였다.Accordingly, a new catalyst system using HC as a reducing agent for the decomposition of NOx has been proposed. Among them, Iwamoto et al. Have developed a new catalyst for NOx decomposition by ion-exchanging a transition metal to zeolite. Among these transition metals, Cu showed the highest ion exchange rate in the ion-exchanged catalyst, and the activity of the catalyst and the gas selectivity of HC were reported to increase even more as the copper ion exchange rate of zeolite increased.
그러나, Cu가 이온교환된 제올라이트 촉매에서는 고온(350~450℃)에서의 활성은 우수하지만 과잉의 산소분위기, H2O 분위기 그리고 저온(200~250℃)에서의 활성 및 열적 내구성이 급격히 떨어지는 단점이 있었다. 즉, 다시 말해서 Cu가 이온교환된 Cu-제올라이트 촉매는 고온에서는 희박연소 분위기에서 배출되는 NO의 N2로의 활성은 우수하지만 저온에서와 과잉의 산소분위기 및 H2O 분위기에서는 NO정화율이 떨어지고, 내구성에 있어서도 급격한 감소를 나타내기 때문에 촉매의 상용화에 큰 걸림돌이 되는 문제점이 있었다. 또한, 상기 문제점을 해결하기 위해 제올라이트에 귀금속을 이온교환시키더라도 귀금속의 소결현상에 의해 귀금속의 입자가 커져 열적내구성이 떨어지는 단점이 있었다.However, Cu-ion-exchanged zeolite catalysts have excellent activity at high temperatures (350-450 ℃), but their activities and thermal durability drop rapidly in excess oxygen atmosphere, H 2 O atmosphere and low temperatures (200-250 ℃). There was this. In other words, the Cu-zeolite catalyst with Cu ion exchange is excellent in the activity of NO discharged from the lean-burning atmosphere to N 2 at high temperature, but the NO purification rate is low at low temperature and excessive oxygen atmosphere and H 2 O atmosphere, Since there is a sharp decrease in durability, there is a problem that a major obstacle to the commercialization of the catalyst. In addition, in order to solve the above problems, even when ionized precious metals to the zeolite, the sintering phenomenon of the precious metals causes the particles of the precious metals to increase, resulting in a poor thermal durability.
따라서, 본 발명의 목적은 상술한 문제점을 해결할 수 있는 질소산화물 정화용 촉매의 제조방법을 제공하는데 있다.Accordingly, it is an object of the present invention to provide a method for preparing a catalyst for purifying nitrogen oxides which can solve the above problems.
상기 목적을 달성하기 위한 본 발명의 방법은 Ca를 제올라이트에 이온교환시킨 다음, 상기 Ca-제올라이트에 Pt, Pd, Ir 및 Rh로 이루어진 군으로 부터 선택된 하나 또는 그 이상의 귀금속성분을 첨가시키는 것으로 이루어진다.The method of the present invention for achieving the above object consists in ion exchange of Ca to zeolite, and then adding one or more precious metal components selected from the group consisting of Pt, Pd, Ir and Rh to the Ca-zeolite.
이하 본 발명을 첨부된 도면을 참조하여 좀 더 구체적으로 살펴보면 다음과 같다.Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.
본 발명에서는 종래의 문제점을 해결하기 위하여, 먼저 제올라이트에 귀금속 성분중 저온에서의 산화 및 환원 활성력이 뛰어난 Pt, Pd, Ir 및 Rh로 이루어진 군으로 부터 선택된 하나 또는 그 이상의 귀금속을 이온교환시키기 전에 Ca를 이온교환시킨 후 상기 귀금속을 이온교환시킨다. 그 이유는 촉매의 저온에서의 활성과 장기간의 신뢰성을 주기 위한 것으로서, 상기 귀금속에 앞서 Ca를 먼저 이온교환시킨 후, 귀금속을 이온교환시키면 제올라이트의 세경내에 이온교환된 귀금속이 작은 입자크기로 세경내에 위치하므로써 귀금속의 분산도를 높여 촉매의 활성을 향상시킬 수 있다. 또한, 세경내에 위치한 귀금속은 장기간 사용시 귀금속이 세경내에서 세경밖으로 이동하여 장기신뢰성이 떨어지는데, 이러한 귀금속의 운동성을 억제시켜 초기와 동일한 입자크기를 유지하므로서 열적 내구성을 향상시키기 때문이다.In the present invention, in order to solve the conventional problems, first, before ion-exchanging one or more precious metals selected from the group consisting of Pt, Pd, Ir, and Rh excellent in oxidation and reduction activity at low temperatures among the precious metal components in the zeolite The precious metal is ion exchanged after Ca ion exchange. The reason for this is to give long-term reliability and low-temperature activity of the catalyst. If Ca is ion-exchanged prior to the noble metal and then ion-exchanged, the noble metal that is ion-exchanged within the fine diameter of the zeolite has a fine particle size Positioning can improve the activity of the catalyst by increasing the dispersion of precious metals. In addition, the precious metal located in the narrow diameter of the long-term reliability of the precious metal is moved out of the narrow diameter in the long-term use, because the long-term reliability is reduced, because it maintains the same particle size as the initial to improve the thermal durability.
한편, 상기 Ca의 이온 교환량은 제올라이트에 대해 0.5~4.5중량%의 범위가 바람직한데, 0.5중량% 이하이면 효과가 없고, 4.5중량% 이상이면 촉매활성을 저하시키는 문제점이 있으며, 상기 귀금속의 담지량은 Ca-제올라이트 양에 대하여 0.5~3.5중량%가 바람직하데, 0.5중량% 이하이면 활성에 문제가 있으며, 3.5중량% 이상이면 활성은 증가하나 제조비용이 상승되는 문제점이 있다.On the other hand, the ion exchange amount of Ca is preferably in the range of 0.5 to 4.5% by weight relative to the zeolite, but if it is 0.5% by weight or less, there is no effect, and if it is 4.5% by weight or more, there is a problem of lowering the catalytic activity. 0.5 to 3.5% by weight relative to the amount of silver Ca-zeolite is preferable, 0.5% by weight or less has a problem in activity, 3.5% by weight or more there is a problem that the activity is increased but the manufacturing cost is increased.
본 발명에 따른 NOx 촉매 제조방법의 바람직한 일 실시예에 따르면, Na-모데나이트(Na-mordenite)를 Ca 수용액에 첨가시켜 약 40~70℃의 온도에서 교반에 의해 Ca 이온교환시킨 후, 이를 여과시킨다. 여과된 습식 케이크(Wet cake)를 탈이온수(DI-water)와 함께 용기에 넣고 교반에 의해 표면에 잔존하는 Ca 이온이 제거될 수 있도록 세척 및 여과를 약 3~5회 실시한 후 100~120℃의 온도범위에서12~24시간 건조시킨다.According to a preferred embodiment of the method for preparing a NOx catalyst according to the present invention, Na-mordenite is added to an aqueous solution of Ca, and then subjected to Ca ion exchange by stirring at a temperature of about 40 to 70 ° C., followed by filtration thereof. Let's do it. Put the filtered wet cake into the container with DI water and wash and filter about 3 ~ 5 times to remove the Ca ions remaining on the surface by stirring. Dry for 12 to 24 hours in the temperature range of.
건조된 Ca-모데나이트 분말은 귀금속, 예를 들어 Pd의 이온교환을 위해 Pd(NH3)4(NO3)4(Tetraaminepalladium(II)nitrate) 수용액을 사용하여 교반시켜 이온교환시킨다. 이온교환후 여과시킨 습식 케이크는 교반에 의해 세척 및 여과를 3~5회 실시한 후 약 100~120℃의 온도범위에서 다시 12~24시간 건조시킨다. 상기 건조된 분말은 400~500℃의 온도에서 약 2-5시간 공기중에서 열처리시킨다. 열처리시킨 분말은 환원분위기하의 300 - 400℃의 온도에서 약 2시간동안 재열처리시켜 본 발명에 따른 NOx 정화용 촉매를 제조하였다.The dried Ca-mordenite powder is ion exchanged by stirring using an aqueous solution of Pd (NH 3 ) 4 (NO 3 ) 4 (Tetraaminepalladium (II) nitrate) for ion exchange of precious metals such as Pd. The wet cake filtered after ion exchange was washed and stirred three to five times by stirring, and then dried again for 12 to 24 hours at a temperature range of about 100 to 120 ° C. The dried powder is heat-treated in air for about 2-5 hours at a temperature of 400 ~ 500 ℃. The heat-treated powder was reheated at a temperature of 300-400 ° C. for about 2 hours under a reducing atmosphere to prepare a catalyst for NOx purification according to the present invention.
이하 실시예 및 비교예를 통하여 본 발명을 좀 더 구체적으로 살펴보지만, 하기 예에 본 발명의 범주가 한정되는 것은 아니다.Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples.
실시예 1Example 1
Na-모데나이트 15g을 1mol의 Ca 수용액 1000㎖에 첨가하여 약 50℃의 온도에서 약 15시간 동안 교반에 의하여 Ca를 이온교환시킨 후, 이를 여과시켰다. 상기 1mol의 Ca 수용액은 칼슘 아세테이트 모노하이드레이트((CH3COO)2Ca ·H2O) 158.17g을 1ℓ의 탈이온수(DI-water)에 녹여 제조하였다. 상기 여과된 습식 케이크를 탈이온수와 함께 비이커에 넣고 교반에 의해 표면에 잔존하는 Ca 이온이 제거될 수 있도록 세척 및 여과를 3∼5회 실시한 후 100∼120℃의 온도범위에서 약 15시간 동안 건조시켰다. 그 결과, 3 중량%의 Ca가 담지된(이온교환된) Ca-모데나이트가 제조되었다. 건조된 Ca-모데나이트 분말은 0.1mol의 Pd(NH3)4(NO3)4수용액에 혼합한 후,교반시켜 Pd를 이온교환시켰다. 상기 Pd(NH3)4(NO3)4수용액은 Pd(NH3)4(NO3)440.5g을 1ℓ의 탈이온수에 녹여 제조되었다. 이온교환 후 여과시킨 습식 케이크는 교반에 의한 세척 및 여과를 3∼5회 실시한 후 약 100∼120℃의 온도범위에서 다시 약 15시간 동안 건조시켰다. 상기 건조된 분말은 400∼500℃의 온도에서 약 2-5시간 동안 공기 중에서 열처리시켰다. 열처리시킨 분말은 환원분위기하의 300-400℃의 온도에서 약 2시간 동안 재열처리시켜 본 발명에 따른 NOx 정화용 촉매(Pd가 0.5 중량% 담지된 Ca-Pd-모데나이트)를 제조하였다.15 g of Na-mordenite was added to 1000 ml of 1 mol of aqueous Ca solution to ion exchange Ca by stirring at a temperature of about 50 ° C. for about 15 hours, followed by filtration. The 1 mol Ca aqueous solution was prepared by dissolving 158.17 g of calcium acetate monohydrate ((CH 3 COO) 2 Ca.H 2 O) in 1 L of DI water. The filtered wet cake was placed in a beaker with deionized water and washed and filtered three to five times to remove Ca ions remaining on the surface by stirring, followed by drying in a temperature range of 100 to 120 ° C. for about 15 hours. I was. As a result, Ca-mordenite supported (ion exchanged) of 3% by weight of Ca was prepared. The dried Ca-mordenite powder was mixed with 0.1 mol of Pd (NH 3 ) 4 (NO 3 ) 4 aqueous solution, followed by stirring to ion exchange Pd. The Pd (NH 3 ) 4 (NO 3 ) 4 aqueous solution was prepared by dissolving 40.5 g of Pd (NH 3 ) 4 (NO 3 ) 4 in 1 L of deionized water. The wet cake filtered after ion exchange was washed with stirring and subjected to filtration three to five times, and then dried again for about 15 hours at a temperature range of about 100 to 120 ° C. The dried powder was heat-treated in air at a temperature of 400-500 ° C. for about 2-5 hours. The heat-treated powder was reheated at a temperature of 300-400 ° C. under a reducing atmosphere for about 2 hours to prepare a catalyst for purifying NOx according to the present invention (Ca-Pd-mordenite carrying 0.5 wt% of Pd).
한편, Na-ZSM-5 담체를 1mol의 Cu 수용액에 첨가하여 Na-ZSM-5에 Cu를 이온교환시켰고, 이때 pH는 NH4OH 용액을 사용하여 적정하였다. 상기 1mol의 Cu 수용액은 (CH3COO)2Cu(Copper(II) acetate) 181.64g을 1ℓ의 탈이온수에 녹여 제조하였다. 상기와 같이 이온교환시킨 후 세척, 건조된 분말은 약 550℃의 온도에서 3시간 동안 열처리시켰다(3 중량%의 Cu가 담지된 Cu-ZSM-5). 열처리된 분말은 고정상 반응기(Fixed-bed flow reactor)를 이용하여 온도 변화에 따른 활성을 측정하였다(도 1 참조). 그리고, 열적 내구성을 측정하기 위해서 촉매를 700℃의 온도에서 6시간 동안 열처리하여 숙성시킨 후(내구성 실험 후) 활성 측정과 동일한 방법으로 측정하였다(도 1 참조). 또한, Ca-Pd-모데나이트에 대하여도 동일한 방법으로 열적내구성 측정 전, 후의 촉매 활성 및 정화율의 변화를 측정하였다(도 2 참조).On the other hand, Na-ZSM-5 carrier was added to 1 mol of aqueous Cu solution to ion-exchange Cu to Na-ZSM-5, and the pH was titrated using NH 4 OH solution. The 1 mol aqueous solution of Cu was prepared by dissolving 181.64 g of (CH 3 COO) 2 Cu (Copper (II) acetate) in 1 L of deionized water. After the ion exchange as described above, the washed and dried powder was heat-treated at a temperature of about 550 ° C. for 3 hours (Cu-ZSM-5 loaded with 3% by weight of Cu). The heat-treated powder was measured for activity according to temperature change by using a fixed-bed flow reactor (see FIG. 1). Then, in order to measure the thermal durability, the catalyst was aged by heat treatment at a temperature of 700 ° C. for 6 hours (after durability experiments), and then measured in the same manner as in the activity measurement (see FIG. 1). In addition, for Ca-Pd- mordenite, the change of the catalyst activity and the purification rate before and after thermal durability measurement was measured by the same method (refer FIG. 2).
상기 촉매활성 측정에 사용된 가스조성 및 조건은 다음과 같다.Gas composition and conditions used for the catalytic activity measurement are as follows.
가스조정: NO 500ppm, 프로필렌 1500ppm, O25%, H2O 5%, CO 1000ppmGas Adjustment: NO 500ppm, Propylene 1500ppm, O 2 5%, H 2 O 5%, CO 1000ppm
반응온도: 200∼600℃Reaction temperature: 200-600 ℃
배기가스 통과량(space velocity): 10,000/hrSpace velocity of exhaust gas: 10,000 / hr
비교예 1Comparative Example 1
실시예 1에서 Ca를 이온교환시키지 않고, Pd만을 이온교환시킨 것(즉, Na-모데나이트 15g을 0.1mol의 Pd(NH3)4(NO3)4수용액에 혼합하여 이온교환시킴)을 제외하고는 동일하게 촉매를 제조하였다(0.5 중량%의 Pd가 담지된 Pd-모데나이트). 그 다음, 상기 실시예 1과 같이 열적 내구성 측정 전, 후의 촉매활성 및 정화율의 변화를 측정하여 도 2에 도시하였다.Except for ion exchange of only Pd without ion exchange of Ca in Example 1 (i.e., 15 g of Na-mordenite was mixed with 0.1 mol of Pd (NH 3 ) 4 (NO 3 ) 4 aqueous solution to ion exchange). A catalyst was prepared in the same manner (Pd-mordenite carrying 0.5 wt% of Pd). Then, as shown in FIG. 2, changes in catalytic activity and purification rate before and after thermal durability measurement were measured as in Example 1.
도 1의 온도에 따른 Cu-ZSM-5 촉매 정화율은 촉매의 숙성(aging) 전, 후 모두 400∼500℃에서 가장 높은 촉매 정화율을 나타내고 있다. Ca-모데나이트에 Pd를 이온교환시킨 Ca-Pd-모데나이트는 도 2에서 알 수 있는 바와 같이, Pd-모데나이트보다 촉매 정화율에서 높은 특성을 나타내고, 약 300℃에서 가장 높은 촉매 정화율을 나타내고 있다.Cu-ZSM-5 catalyst purification rate according to the temperature of Figure 1 shows the highest catalyst purification rate at 400 ~ 500 ℃ both before and after aging (catalyst) of the catalyst. As can be seen in FIG. 2, Ca-Pd-mordenite having Pd ion-exchanged with Ca-mordenite exhibits higher characteristics in catalytic purification than Pd-mordenite and exhibits the highest catalytic purification at about 300 ° C. It is shown.
따라서, 본 발명에서는 귀금속 이온교환 이전에 Ca을 먼저 이온교환시켜 귀금속의 입자크기가 작아지고, 제올라이트 세경 내에 이온교환된 귀금속의 분산성이 향상되었고, 제올라이트의 세경 내에 위치한 귀금속은 장기간 사용 시 귀금속이 세경 내에서 세경 밖으로 이동하여 장기 신뢰성이 떨어지는데 이러한 귀금속의 운동성을 억제시켜 귀금속의 교반현상에 의한 과대 입자로의 성장을 억제시켜 초기와 동일한 입자크기를 유지함으로써 장기 신뢰성을 향상시킨다.Therefore, in the present invention, the particle size of the noble metal is reduced by ion-exchanging Ca first before the noble metal ion exchange, and the dispersibility of the ion-exchanged noble metal in the zeolite narrow diameter is improved. Long-term reliability is reduced by moving out of the narrow diameter, and the long-term reliability is reduced. By suppressing the motility of the precious metal to suppress the growth of the excessive metal due to the stirring phenomenon, the long-term reliability is improved by maintaining the same particle size.
제 1도는 종래의 Cu-제올라이트 촉매 및 상기 촉매의 내구성 실험후의 온도에 따른 촉매정화율의 변화를 나타낸 그래프이고,1 is a graph showing the change of the catalyst purification rate according to the temperature after the durability test of the conventional Cu-zeolite catalyst and the catalyst,
제 2도는 종래의 Pd-제올라이트 촉매 및 상기 촉매의 내구성 실험후의 온도에 따른 촉매정화율과 본 발명에 따른 Ca 및 Pd-제올라이트 촉매 및 상기 촉매의 내구성 실험후의 온도에 따른 촉매정화율의 변화를 나타낸 그래프이다.FIG. 2 shows the catalytic purification rate according to the temperature after the durability test of the conventional Pd-zeolite catalyst and the catalyst and the change of the catalyst purification rate according to the temperature after the durability test of the Ca and Pd-zeolite catalyst and the catalyst according to the present invention. It is a graph.
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