KR100429825B1 - Catalyst for purifying exhaust gas of automobil and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A catalyst for purifying automobile exhaust gas is provided which shows excellent activity for nitrogen oxides even in the low temperature range, and in which nitrogen oxide removing capacity is not rapidly lowered at a high temperature, and a method for manufacturing the same is provided. CONSTITUTION: The catalyst for purifying automobile exhaust gas comprises a support in which iron is supported onto porous material and a mixing mole ratio of the iron to the porous material is 1:10 to 1:20; and a precious metal supported onto the support. The method for manufacturing the catalyst for purifying automobile exhaust gas comprises a step (a) of preparing a support in which the porous material is impregnated with transition metal by drying and firing the agitated mixture after agitating porous material and iron hydrate in water; a step (b) of preparing solution 1 and solution 2 by respectively dissolving palladium salt and platinum complexes into polyol; a step (c) of supporting palladium and platinum onto the support by putting the support prepared in the step (a) into the solution 1 and the solution 2 prepared in the step (b); a step (d) of drying and milling the resulting material of the step (c); and a step (e) of heat treating the resulting material of the step (d).

Description

Catalyst for purifying exhaust gas of automobile and its manufacturing method {Catalyst for purifying exhaust gas of automobil and method for manufacturing the same}

The present invention relates to a catalyst for automobile exhaust gas purification and a method for manufacturing the same, and more particularly, to a catalyst having excellent purification ability for nitrogen oxide even in a low temperature range in which a diesel engine starts operation, and a method for manufacturing the same.

In recent years, there has been a growing concern about environmental protection along with concerns about environmental destruction. Environmental pollution can be roughly classified into air pollution, water pollution, and soil pollution.

In particular, the phenomenon due to air pollution includes the destruction of the ozone layer due to the use of hydrogen fluoride (CFC), and the global greenhouse effect due to carbon dioxide generated when using fossil fuels. In addition, sulfur oxides, nitrogen oxides, hydrocarbons, and the like emitted from various pollutant discharge facilities cause various diseases to animals and plants.

Since air pollution mainly comes from the combustion body, the magnitude of the damage is determined by the structure of the combustion facility, the method of operation, and external weather conditions. Representative combustion bodies include automobiles.

Unlike other air pollution emission facilities, cars emit pollutants while moving, and as the use of automobiles increases rapidly as living standards improve, the air pollution problem caused by cars becomes serious.

The composition and emissions of automobile exhaust are related to the engine's temperature, pressure and proportion of air. That is, by properly adjusting the air / fuel ratio of the engine, it is possible to increase the exhaust gas purification efficiency. Exhaust gas components and emissions also depend largely on the type of fuel source and purification equipment used.

For automobiles driven by spark ignition engines using gasoline as a fuel source, many exhaust gas removal technologies such as three-way catalysts have been developed, and emissions of pollutants by gasoline vehicles have been significantly reduced.

On the other hand, diesel engines using diesel as a fuel source have good thermal efficiency but emit large amounts of harmful pollutants, so developed countries strictly regulate their use. However, many diesel engines are still adopted in large countries such as trucks in many countries. Nevertheless, the technology for purifying the exhaust gas of diesel vehicles employing diesel engines is very low compared to gasoline automobiles. Therefore, the severity of air pollution on diesel vehicles is increasing, and the regulations on these are being tightened around the world, and the regulations are starting in Korea. Therefore, the development of exhaust gas purification equipment for diesel vehicles is urgently required. .

Exhaust gases of diesel vehicles include carbon monoxide, hydrocarbons, nitrogen oxides (NOX), sulfur oxides and particle matter. Among them, the particulate matter increases the photochemical smog phenomenon and the generation of suspended dust, which causes vision disturbances, and nitrogen oxides are combined with oxygen in the air under the action of sunlight to cause respiratory diseases, protein denaturation and fat in the body. Ozone is the cause of biochemical reactions such as peroxidation.

Therefore, it would be desirable if the particulate matter and the nitrogen oxide can be removed at the same time, but since the purification methods for them are mutually opposite to each other, it is impossible to remove them simultaneously with the current technology.

In particular, since oxygen and sulfur oxides contained in a large amount of pollutants emitted from diesel vehicles inhibit the purification of nitrogen oxides, it is difficult to improve the purification ability. In addition, most of the known nitrogen oxide removal system exhibits a maximum activity at a temperature of about 300 ° C., and thereafter, there is a disadvantage in that the activity rapidly decreases. Therefore, there is an increasing demand for a catalyst for automobile exhaust gas purification which improves catalytic activity at temperatures lower than 300 ° C. and does not cause a sharp drop in activity even at high temperatures.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a catalyst for automobile exhaust gas purification, which exhibits excellent activity against nitrogen oxides even in a low temperature range and does not sharply degrade nitrogen oxide removal capability at high temperatures.

In addition, another technical problem to be achieved by the present invention is to provide a method for producing a catalyst for the purification of automobile exhaust gas exhibits excellent activity against nitrogen oxides even in a low temperature range and does not rapidly decrease the ability to remove nitrogen oxides at high temperatures.

1 is a graph showing the activity of the catalyst for automobile exhaust purification according to the present invention compared with the activity of a conventional catalyst.

The technical problem of the present invention can be achieved by a carrier obtained by supporting a transition metal in a porous body, and a catalyst for automobile exhaust gas purification comprising a noble metal supported on the carrier.

In the catalyst for automobile exhaust gas purification of the present invention, the transition metal is iron, the porous body is alumina, zirconia, titanium dioxide, zeolite or mordenite, and the mixed molar ratio of the transition metal and the porous body is 1: 10-1: 20. The amount of the noble metal supported on the carrier is 1-1.5% by weight based on the total weight of the carrier, and a mixture of palladium and platinum is preferred as the noble metal.

Another technical problem of the present invention is to prepare a carrier having a transition metal impregnated into a porous body by (a) stirring the porous body and iron salt hydrate in water, and then drying and calcining; (b) dissolving palladium salts and platinum complexes in polyols, respectively, to prepare solution (1) and solution (2); (c) adding the carrier prepared in step (a) to the solutions (1) and (2) prepared in step (b) to support palladium and platinum on the carrier; (d) drying and grinding the product of step (c); And (e) it can be achieved by a method for producing a catalyst for automobile exhaust gas purification comprising the step of heat-treating the product of step (d).

In the method for preparing a catalyst for automobile exhaust gas purification of the present invention, the porous body is preferably alumina, zirconium, titanium dioxide, zeolite or mordenite, and the mixing ratio of the iron chloride and the porous body is 1: 10-1: 20. Is preferably. Preferably, the palladium content in the palladium salt solution and the platinum content in the platinum complex are 0.75-1% by weight and 0.25-0.5% by weight, respectively, based on the total weight of the carrier, and the polyol is ethylene glycol. Or propylene glycol is used. In addition, the step (e) is carried out for 2-5 hours at 400-600 ℃.

The catalyst for purifying automobile exhaust gas prepared according to the production method of the present invention is significantly improved in conversion of nitrogen oxide at a low temperature of 300 ° C. or lower as compared with the conventional catalyst, and does not drop rapidly in a high temperature of 300 ° C. or higher.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<Example>

132.22 g of ZrO 2 and 34.19 g of Fe (NO 3) 2 .9H 2 O were added to 0.2 L of water and stirred for 2 hours. Subsequently, water was evaporated, dried in an oven, and calcined at 500 ° C. for 2 hours to synthesize Fe-ZrO 2, a carrier including a transition metal and a porous body. Subsequently, a Pd (NO 3) 3 solution (containing 0.15 g of palladium) was dissolved in 6 ml of ethylene glycol to prepare an ethylene glycol solution of palladium, followed by Pt (NH 3) 4 Cl 2 .H 2 O (containing 0.05 g of platinum). It was dissolved in ml of ethylene glycol to prepare a solution of platinum ethylene glycol.

Subsequently, 0.75 Pd 0.25 Pt / Fe-ZrO 2 supported with platinum and palladium was prepared by gradually adding platinum ethylene glycol solution and palladium ethylene glycol solution to 20 g of the carrier (Fe-ZrO 2) prepared as described above. . The product was put into an oven at 80 ° C. and dried, then ground in a mortar and put into an electric furnace to be powdered by heat treatment at 500 ° C. for 2 hours. The powder was made into pellets, and then only those with a size of about 1-2 mm were selected using a sieve. 2 ml of the pellet-type catalyst prepared as described above was placed in a reactor, and catalytic activity of nitrogen oxide was measured. The exhaust gas composition and reaction conditions in the measurement are as follows:

NO: 500 ppm, C3H6: 800 ppm, O2: 8%, CO2: 14%, CO: 0.2%, SO2: 200 ppm

Reaction temperature: 200-600 ℃

Space velocity: 40,000 h-1.

The catalytic activity measurement results are shown in the graph of FIG. 1 (a).

Comparative Example

A catalyst of 0.75 Pd 0.25 Pt / ZrO 2 was prepared in the same manner as in Example 1, except that zirconia (ZrO 2) was used as the carrier. The catalyst thus prepared was subjected to the same drying, grinding and heat treatment processes as in Example 1 to form a powder, which was then pelletized. Catalytic activity for this pellet type catalyst was carried out under the same exhaust gas composition and reaction conditions as those in Example 1. The results are shown in Figure 1 (b).

As can be seen from the results of FIG. 1, the conventional catalyst (b) having a noble metal supported on a conventional catalyst shows high nitrogen oxide conversion at a temperature of about 300 ° C., but has a low conversion rate at a low temperature of less than 300 ° C., and conversely, 300 ° C. It was found that the conversion rate dropped sharply at temperatures exceeding. In contrast, the catalyst (a) of the present invention using a carrier containing a transition metal not only shows a relatively high nitrogen oxide conversion even at low temperatures but also does not show a sharp decrease in the conversion even at high temperatures.

The catalyst for automobile exhaust gas purification according to the present invention has a higher catalytic activity than a conventional automobile exhaust gas catalyst at a low temperature of 300 ° C. or lower, and shows a relatively even distribution of catalytic activity without a sharp decrease in activity at high temperatures. As can be seen from this, the catalyst of the present invention exhibits the effect of greatly improving the catalytic activity as a whole compared to the conventional catalyst.

Claims (11)

A carrier having iron supported on the porous body and having a mixed molar ratio of iron and the porous body of 1:10 to 1:20; And Catalyst for purification of automobile exhaust gas comprising a noble metal supported on the carrier The catalyst for purifying automobile exhaust gas according to claim 1, wherein the porous body is alumina, zirconia, titanium dioxide, zeolite or mordenite. The catalyst for purification of automobile exhaust gas according to claim 1, wherein the noble metal is a mixture of palladium and platinum. The catalyst for purifying automobile exhaust gas according to claim 1, wherein the content of the noble metal is 1 to 1.5% by weight based on the total weight of the carrier. (a) stirring the porous body and the iron salt hydrate in water, and then drying and calcining to prepare a carrier impregnated with the transition metal in the porous body; (b) dissolving palladium salts and platinum complexes in polyols, respectively, to prepare solution (1) and solution (2); (c) adding the carrier prepared in step (a) to the solutions (1) and (2) prepared in step (b) to support palladium and platinum on the carrier; (d) drying and grinding the product of step (c); And (e) a method for producing a catalyst for automobile exhaust gas purification, comprising the step of heat-treating the resultant of step (d). The method for producing a catalyst for automobile exhaust gas conversion according to claim 5, wherein the porous body is alumina, zirconium, titanium dioxide, zeolite or mordenite. The method according to claim 5, wherein the mixing molar ratio of the iron chloride and the porous body is 1: 10-1: 20. The method for producing a catalyst for automobile exhaust gas purification according to claim 5, wherein the palladium content in the palladium salt solution is 0.75-1% by weight based on the total weight of the carrier. 6. The method of claim 5, wherein the platinum content in the platinum complex is 0.25-0.5% by weight based on the total weight of the carrier. The method of claim 5, wherein the polyol is ethylene glycol or propylene glycol. The method of claim 5, wherein the step (e) is carried out at 400-600 ° C for 2-5 hours.