KR19990084819A - Catalyst and method for producing nitrogen oxide and particulate matter discharged from diesel engine at the same time - Google Patents

Abstract

The present invention relates to a catalyst capable of simultaneously removing nitrogen oxide and particulate matter discharged from a diesel engine, and a method for preparing the same, wherein 1-XY: X: Y: 1 (X and Y are 0 to 1, and X + Y 0 to 1) molar ratio of La nitrate or its hydrate, Cs nitrate or its hydrate, Ce nitrate or its hydrate, and Co nitrate or its hydrate are mixed with nitric acid and dissolved in water to make a solution. And a lanthanoid of general formula La1-XMXCoO3, wherein X is 0 to 1 and M is Cs or Ce, and the lanthanoid-based perovskite catalyst is composed of drying and calcining. It is characterized by a perovskite catalyst.

Description

Catalyst and method for producing nitrogen oxide and particulate matter discharged from diesel engine at the same time

The present invention relates to a catalyst for simultaneously removing nitrogen oxide and particulate matter discharged from a diesel engine and a method of manufacturing the same, and more particularly, to a lanthanoid-based ferrophor for simultaneously removing nitrogen oxide and particulate matter discharged from a diesel engine. The present invention relates to a sky catalyst and a process for producing them by the nitric acid method.

Pollutants emitted from diesel engines include carbon monoxide, hydrocarbons, nitrogen oxides and particulate matter. Diesel engines operate with relatively sufficient air, so carbon monoxide and hydrocarbons are less problematic than gasoline vehicles. However, since nitrogen oxides (NOx) and particulate matter are a big problem as diesel vehicle pollutants, there is a need for effective treatment. For this treatment, combustion chamber improvement, fuel injection improvement, intake system improvement, and exhaust gas recirculation are used, but they are not yet recognized as a perfect technology. Nitrogen oxides cause serious environmental problems such as photochemical smog. Therefore, efforts to reduce nitrogen oxides in automobile exhaust gas have been steadily progressed. Known methods for treating nitrogen oxides include fuel denitrification, which preliminarily removes nitrogen compounds contained in the fuel using catalysts, combustion modifications for reducing them during combustion, and post-treatment for treating exhaust gases. Among them, the most researched in the world is a method of decomposing nitrogen oxide using a catalyst in the post-treatment method. Since the development of the three-way catalyst of gasoline cars, many studies have been conducted, and metal-substituted zeolite or metal oxide catalysts have been developed.

In addition, the present inventors have studied a catalyst for decomposing nitrogen oxides emitted from a diesel engine, and thus, a lanthanide-based perovskite catalyst having a large surface area and excellent catalytic activity and conversion rate of nitrogen oxides in a nitrogen oxide decomposition reaction was developed. It was published in Korean Patent Application No. 97-14017.

On the other hand, the particulate matter that is emitted a lot from the diesel engine is largely composed of Soluble Organic Fraction (SOF), soot and sulfide. Therefore, it is necessary to remove SOF, gaseous hydrocarbons, carbon monoxide and odor components which are mostly composed of hydrocarbons in the exhaust gas components. The technologies for purifying this exhaust gas largely include conversion to alternative fuel, high quality of diesel, improvement of engine performance and attachment of aftertreatment devices, which are complementary to each other.

Post-treatment technology is a technology that continuously removes pollutants contained in exhaust gas emitted from diesel engines under operating conditions. It is a filtration technology that filters and collects soot in exhaust gas with a filter and continuously collects particulate matter under operating conditions. It is divided into regeneration technology that burns and regenerates the filtration device. Among these post-treatment technologies, the filter trap method shows very high filtration efficiency, and therefore, active research is being conducted worldwide, and the development of actual vehicle experiment and commercialization stage is also being promoted. However, the particulate matter removing device of the filter trap method has problems such as complexity, durability and price of the control device.

On the other hand, catalytic converters for reducing particulate matter emitted from diesel vehicles using catalysts are not only harmful to particulate matter but also harmful to gaseous or particulate matter such as carbon monoxide, hydrocarbons, odorants, aldehydes, PAH, and nitro-PAH. Remove the material. In addition, the device structure is simple, the price is low, and the fuel consumption rate is relatively low, so it is not necessary to change the car of the car can be easily installed. Therefore, if only a catalyst having high activity is developed and used on a carrier, it is possible to solve the problems of complexity, difficulty and high cost of a regeneration system that require regeneration after filtering particulate matter such as a trap system.

The catalysts used to remove particulate matters to date are mainly metal oxides, and it is known that PbO, Co 3 O 4, V 2 O 5, MoO 3 and CuO exhibit good activity. In addition, as a noble metal catalyst, platinum, palladium and the like have been reported as excellent catalysts, and there have been reports that vanadium oxides that inhibit oxidation of sulfur dioxide, which is a side reaction, have been used as cocatalysts.

However, until now, practical use of a catalyst for simultaneously removing nitrogen oxide and particulate matter has not been achieved.

Accordingly, an object of the present invention is to provide a catalyst capable of simultaneously removing nitrogen oxide and particulate matter discharged from a diesel engine.

Another object of the present invention is to provide a method for preparing a catalyst capable of simultaneously removing nitrogen oxide and particulate matter discharged from a diesel engine with high efficiency.

The above object of the present invention is 1-XY: X: Y: 1 (X and Y is 0 to 1, X + Y is 0 to 1) molar ratio La nitrate or its hydrate, Cs nitrate or its hydrate, Ce nitrate Alternatively, the hydrate and Co nitrate or its hydrate are mixed with nitric acid to dissolve in water to form a solution, and the base is adjusted to weakly acidic pH to prepare a lanthanoid-based perovskite catalyst comprising drying and calcining. Is achieved by the method.

Another object of the present invention is achieved by a lanthanoid-based perovskite catalyst of general formula La1-X-YCsXCeYCoO3 wherein X and Y are 0 to 1 and X + Y is 0 to 1 prepared by the above method.

Hereinafter, the present invention will be described in detail.

Lanthanoid-based perovskite catalysts are conventionally prepared by the solid phase reaction method or by the citric acid method. However, since the lanthanoid-based perovskite catalyst prepared by this method had a small surface area, in the present invention, the surface area of the lanthanoid-based perovskite catalyst was increased by about 50 times as compared to that produced by the solid phase reaction method. Due to the increase of the surface area, the activity increased in the decomposition of nitrogen oxides and the oxidation of particulate matter. In addition, when the A site (Site) of the lanthanoid-based perovskite catalyst was replaced with an alkali metal, it was confirmed that the reaction activity was greatly increased. In addition, in the case of the catalyst prepared by the solid-phase method, most of the activity only at a high temperature of 400 ℃ or more, but the catalyst prepared by the present invention showed a high activity at 250-400 ℃.

Nitrate of each metal constituting the catalyst, its hydrate, and nitric acid are mixed and dissolved in water, and then a pH such as aqueous ammonia is added to adjust the pH to weak acidity, and then dried sufficiently in a drier at high temperature to be porous. The lanthanoid-based perovskite catalyst of the present invention is prepared by pulverizing and pulverizing the powder to change the temperature over three steps.

The decomposition reaction of nitrogen oxides and the oxidation reaction of particulate matter according to the present invention are preferably carried out at atmospheric pressure and at a wide range of temperatures. This is because the actual exhaust gas temperature shows several temperatures depending on the operating conditions. In addition, the concentration of nitrogen oxide, the concentration of hydrocarbon as a reducing agent, the concentration of oxygen, and the concentration of water vapor, etc. were also selected to preserve the concentration range of the actual exhaust gas. In addition, the space velocity was selected to preserve the concentration range of the actual exhaust gas. The space velocity was also adjusted to the conditions of the actual emissions.

In other words, at a pressure of atmospheric pressure and a temperature range of 200-700 ° C., preferably 250-400 ° C., the concentration of nitrogen oxide is 0-2000 ppm and the concentration of hydrocarbon, which is a reducing agent, is 0-2000 ppm, and the reducing agent is ethane, propane, Hydrocarbons such as propylene were used, and the concentration of oxygen was 0-20%, the concentration of water 0-20%, the concentration of sulfur dioxide 0-2000ppm, and the space velocity 10,000-10,000hr-1.

In addition, in order to be used as a catalyst for removing nitrogen oxides and particulate matter in the exhaust gas, a stable state must be maintained for a long time. That is, since the activity must be maintained even when traveling more than 20,000 km, the catalyst activity test was also carried out for a long time in the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

6.6691g of La (NO3) 3.6H2O, 2.1931g of Ce (NO3) 3.6H2O, 1.0828g of CsNO3, 7.5007g of Co (NO3) 2.6H2O were mixed with 6.7g of 1N nitric acid and dissolved in 100cc of ultrapure water to make a solution. It was slowly added dropwise to ammonia water diluted to%. The whole solution was stirred well to adjust the pH to 4.0. Dry at a temperature of 150 ° C. in a drier to make porous and pulverized. A catalyst powder was prepared by calcination at 200 ° C. for 30 minutes, 350 ° C. for 30 minutes, and 600 ° C. for 12 hours. The surface area of this catalyst was 25 m 2 / g.

This catalyst is placed together with particulate matter in a reactor of a fixed bed reactor, and the concentration of 600 ppm of nitrogen oxides, 1000 ppm of propane, 4% of oxygen, 5% of water, and sulfur dioxide in the temperature range of 200-400 ° C. After the concentration of 1000ppm and the space velocity of the reaction at 30,000hr-1 at atmospheric pressure, the product was analyzed by nitrogen oxide analyzer and gas chromatography. The analysis results are shown in Table 1.

In addition, to test the stability of the catalyst over a long period of time, the reaction temperature is 300 ° C, the nitrogen oxide concentration is 600 ppm, the propane concentration is 1000 ppm, the oxygen concentration is 4%, the water concentration is 5%, the sulfur dioxide concentration is 1000 ppm, and the space velocity. After 48 hours at 30,000hr-1 the product was analyzed by nitrogen oxide analyzer and gas chromatography. The conversion rate of nitrogen oxide was 31.8% and the removal rate of particulate matter was 45.6%.

Example 2

6.6691g of La (NO3) 3.6H2O, 4.3862g of Ce (NO3) 3.6H2O, and 7.5007g of Co (NO3) 2.6H2O were mixed with 6.7g of 1N nitric acid, dissolved in 100cc of ultrapure water, and diluted to 10%. It was slowly added dropwise to ammonia water. The whole solution was stirred well to adjust the pH to 4.0. Dry at a temperature of 150 ° C. in a drier to make porous and pulverized. A catalyst powder was prepared by calcination at 200 ° C. for 30 minutes, 350 ° C. for 30 minutes, and 600 ° C. for 12 hours. The surface area of this catalyst was 20 m 2 / g.

This catalyst is placed together with particulate matter in a reactor of a fixed bed reactor, and the concentration of 600 ppm of nitrogen oxides, 1000 ppm of propane, 4% of oxygen, 5% of water, and sulfur dioxide in the temperature range of 200-400 ° C. After the concentration of 1000ppm and the space velocity of the reaction at 30,000hr-1 at atmospheric pressure, the product was analyzed by nitrogen oxide analyzer and gas chromatography. The analysis results are shown in Table 1.

In addition, to test the stability of the catalyst over a long period of time, the reaction temperature is 300 ° C, the nitrogen oxide concentration is 600 ppm, the propane concentration is 1000 ppm, the oxygen concentration is 4%, the water concentration is 5%, the sulfur dioxide concentration is 1000 ppm, and the space velocity. After 48 hours at 30,000hr-1 the product was analyzed by nitrogen oxide analyzer and gas chromatography. The conversion rate of nitrogen oxide was 58.0% and the removal rate of particulate matter was 34.1%.

Example 3

11.1601g of La (NO3) 3.6H2O and 7.5007g of Co (NO3) 2.6H2O were mixed with 6.7g of 1N nitric acid, dissolved in 100cc of ultrapure water to make a solution, and slowly added dropwise to ammonia water diluted to 10%. The whole solution was stirred well to adjust the pH to 4.0. Dry at a temperature of 150 ° C. in a drier to make porous and pulverized. A catalyst powder was prepared by calcination at 200 ° C. for 30 minutes, 350 ° C. for 30 minutes, and 600 ° C. for 12 hours.

After the catalyst was put together with the particulate matter in the reactor of the fixed bed reactor, 600 ppm of nitrogen oxide, 1000 ppm of propane, 4% of oxygen, and 5% of water in the temperature range of 200-700 ° C. After atmospheric pressure reaction at a concentration of 1000 ppm of sulfur dioxide and a space velocity of 30,000 hr-1, the product was analyzed by nitrogen oxide analyzer and gas chromatography. The analysis results are shown in Table 1.

Reaction temperature Conversion rate Example 1 Example 2 Example 3 Nitrogen oxide Particulate matter Nitrogen oxide Particulate matter Nitrogen oxide Particulate matter 200 0 0 0 0 0 0 220 62.4 8.4 47.2 1.7 10.2 0.3 240 86.1 11.2 59.8 1.8 24.5 0.5 260 71.6 14.3 78.9 4.3 43.4 0.9 280 63.5 21.8 65.3 12.5 53.2 1.7 300 32.2 46.2 58.7 34.7 41.6 3.5 340 14.8 75.5 30.1 76.9 27.1 16.0 360 10.2 97.0 14.7 93.4 10.2 34.0 400 8.5 100.0 11.2 98.9 8.9 57.5

As can be seen in Table 1, the catalyst of the present invention has a large surface area compared to the catalyst prepared by the conventional solid phase reaction method, it can be seen that the conversion of nitrogen oxides and the removal efficiency of particulate matter is excellent. In addition, when one or more of Cs nitrate or its hydrate and Ce nitrate or its hydrate are included in the manufacturing process, especially when two metal raw materials are included at the same time, the conversion rate of nitrogen oxide and removal efficiency of particulate matter are most excellent. It was.

As described above, the lanthanoid-based perovskite catalyst of the present invention is an excellent catalyst that can efficiently remove nitrogen oxide and particulate matter discharged from a diesel engine at the same time and does not change its activity even in long-term use.

Claims (2)

1-XY: X: Y: 1 (X and Y are 0 to 1, X + Y is 0 to 1) molar ratio La nitrate or its hydrate, Cs nitrate or its hydrate, Ce nitrate or its hydrate, and Co nitrate Or mixing the hydrate with nitric acid to dissolve in water to form a solution, adding a base to adjust the pH to weakly acidic, and then drying and calcining the lanthanoid perovskite catalyst. X and Y prepared by the method of claim 1 is 0 to 1, X + Y is 0 to 1 Lanthanoid-based perovskite catalyst of the general formula La1-X-YCsXCeYCoO3.