KR100250817B1 - Preparation of catalyst body containing pt,pd or rh for automotive exhaust gas - Google Patents

Abstract

PURPOSE: Provided is a catalytic converter containing Pt, Pd, and Rd for purifying automobile flue gas, which has improved thermal resistance, durability, and has competitiveness in cost. CONSTITUTION: The catalytic converter is manufactured by impregnating Al2O3 with Pt, Rh, Pd at the ratio of 0.5-3:12-15:0.5-3; blending and milling; adding Ce-Zr oxides to prepare washcoat slurry (solid content: 30-50%) having rare earth metal content of up to 10g/L; washcoating the slurry on the surface of a honeycomb monolith: drying the honeycomb monolith in the temperature range of 100 to 150deg.C; and then sintering it in the temperature range of 400 to 600deg.C.

Description

Method for producing catalyst body for automobile exhaust gas purification containing platinum, palladium or rhodium

The present invention relates to a method for preparing a catalyst for automobile exhaust gas purification comprising the step of impregnating a noble metal such as platinum, palladium and rhodium on a support and then coating the carrier.

Cars, which began mass production at Ford Corp. in the early 20th century, exploded and became an indispensable vehicle for now. As the use of such vehicles increases, traffic increases, traffic congestion, damage caused by various traffic accidents and vibrations, and serious air pollution due to exhaust gases are emerging as important social problems.

Gases emitted from automobiles are divided into exhaust gas, blow-by-gas and evaporative gas. Exhaust gas is a gas which is discharged from the exhaust pipe to the atmosphere after the fuel is combusted in a cylinder, becomes a gas of high temperature and high pressure, and expands, and it is water vapor and carbon dioxide (CO ₂ ). And other hazardous substances such as carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NO _X ). Among the components in the exhaust gas, carbon monoxide, unburned hydrocarbons, and nitrogen oxides, which are called three-way gas, cause very serious environmental pollution, and studies are being actively conducted to reduce such substances. That is, research is being conducted to develop automobiles in which exhaust gas is not generated at all, but there are still many difficulties in commercialization in terms of efficiency. On the other hand, the research to reduce the generation of harmful exhaust gas by improving the shape, operating conditions and operating conditions of each engine in the existing vehicle continues. In addition, research has been conducted to reduce the emission of these harmful components by decomposing the exhaust gas into a catalyst, and these efforts have a considerable effect and are currently applied to various vehicles.

Catalysts are usefully applied in many fields, including exhaust gas treatment of internal combustion engines such as engines of automobiles and other gasoline fuels. Emission standards for these pollutants are set by the government, and new vehicles must meet these standards. In order to meet these standards, a so-called catalytic converter containing a suitable catalyst is installed in the exhaust pipe of the internal combustion engine to promote decomposition of unburned hydrocarbons, oxidation of carbon monoxide and reduction of nitrogen oxides. Catalytic converters are largely classified into functional catalytic converters and three-way catalytic converters. First, the oxidation catalyst converter attaches extremely thin noble metals such as palladium or palladium + platinum, which catalyzes the surface of granular alumina called catalyst pellets, and makes carbon monoxide and unburned hydrocarbons in the exhaust gas into carbon dioxide and water vapor. Meanwhile, the three-way catalytic converter uses precious metals such as platinum + rhodium or platinum + rhodium + palladium to catalyze carbon monoxide, unburned hydrocarbons and nitrogen oxides in the exhaust gas at the same time. It is used a lot.

Many efforts have been made to economically produce catalysts with good activity and long lifetimes for converting the above unburned hydrocarbons, carbon monoxide and nitrogen oxides into carbon dioxide, water and nitrogen. In three-way conversion catalysts, the ratio of air to fuel that is typically introduced in the engine where the exhaust gas is not treated must be substantially exceeded as a narrow deviation in the stoichiometric amount to achieve an optimal redox reaction at substantially the same time. Do. In order to promote ternary conversion, catalysts consisting of one or more noble metals dispersed on a high surface area support are well known in the art. The support may be composed of a monolithic carrier and a high surface area alumina coating filled on a carrier substrate with a honeycomb refractory ceramic, as is well known in the art. The alumina support is preferably supported on a carrier substrate, such as a honeycomb substrate, in which a plurality of microgas flow paths are spread throughout. In order to easily coat such a micropath, a slurry of extremely fine activated alumina particles called washcoat is made and then applied to a substrate.

In automobile exhaust gas purification catalysts requiring heat resistance and durability, catalysts containing precious metals such as platinum, palladium or rhodium have been actively studied and applied to automobiles produced. These catalysts containing noble metals were impregnated with noble metals, such as platinum, palladium or rhodium, respectively, and then slurried and multi-coated to the carrier so that each noble metal component was evenly dispersed to have high heat resistance and high durability.

However, since the expensive precious metals such as platinum, palladium or rhodium are impregnated into the support and then slurried to coat the carrier in multiple layers, the production cost of the catalyst is increased.

Accordingly, the inventors of the present invention continue to solve the above problems, while maintaining the heat resistance and durability required for the catalyst for automobile exhaust gas purification, the performance of the catalyst is improved, and the production cost of the excellent catalyst can be reduced The manufacturing method was developed to complete the present invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing a catalyst for purification of automobile exhaust gas containing precious metals such as platinum, palladium or rhodium, which has heat resistance and durability, improves the performance of the catalyst, and reduces manufacturing costs.

In order to achieve the above object, the present invention provides a method for producing a catalyst for automobile exhaust gas purification containing noble metals such as platinum, palladium or rhodium.

Hereinafter, the present invention will be described in detail.

The production method of the present invention consists of a process of impregnating a noble metal such as platinum, palladium or rhodium into a support, followed by mixing, milling to prepare a washcoat, coating the carrier, drying and firing.

First, the platinum solution, the rhodium solution and the palladium solution are impregnated in alumina (Al ₂ O ₃ ), which is a support, respectively, and then mixed.

Next, the mixed support is wet milled to obtain a washcoat slurry. At this time, 90% or more of the entire powder component is distributed to a particle size of 9 μm or less, and it is preferable to mill so that the content of solid content is 45 to 50%. In addition, rare earth oxides and alkali metal oxides are added during wet milling, and cerium (Ce) -zirconium (Zr) composite oxides are preferably added to the slurry obtained by wet milling.

The washcoat slurry prepared through the above process is coated on the catalyst carrier of the honeycomb structure. At this time, it is preferable to coat the slurry having a noble metal concentration of up to 10 g / l using up to 2.0 l, platinum; Palladium; The content ratio of rhodium is preferably adjusted to be 0.5 to 3:12 to 15 to 0.5 to 3. It is also preferred to single coat or double coat the washcoat slurry onto the catalyst pellets, more preferably to single coat.

The coated carrier is dried and sintered to produce a catalyst body. At this time, it is preferable to dry the carrier coated with a washcoat slurry containing precious metals such as platinum, palladium and rhodium at 100 to 150 ° C and then sinter at 400 to 600 ° C.

Hereinafter, the catalyst body for automobile exhaust gas purification of this invention is demonstrated in detail by an Example. However, these Examples are only for illustrating the present invention and the present invention is not limited by the Examples.

Example 1

The platinum solution, rhodium solution and palladium solution were impregnated into alumina as a support, followed by wet milling using a ball-mill for 14 hours. The particle size distribution was 8 µm, and the content of platinum: palladium: rhodium A washcoat slurry (solid content: 45-50%) with a ratio of 1: 14: 1 and a concentration of 3.6 g / L was prepared, 1 L of this slurry was coated on a catalyst dim-die, dried at 130 ° C., and then 500 Sintered at a temperature of ℃ to prepare a catalyst body.

Example 2

1 L of the washcoat slurry prepared in the same manner as in Example 1 was coated on the catalyst carrier, dried at 130 ° C., and then sintered at a temperature of 550 ° C. to prepare a catalyst body.

On the other hand, the catalyst of the following Comparative Example was prepared in order to compare with the catalyst of the above Example.

Comparative Example

The platinum solution and the rhodium solution were impregnated with alumina as a support, followed by wet milling with a ball-mill for 14 hours, and the washcoat had a particle size distribution of 9 μm or less, a platinum: rhodium content of 5: 1, and a concentration of 2.0 g / l. A slurry (solid content: 30-50%) was prepared, and 1 liter of this slurry was coated on the catalyst carrier in duplicate, dried at 130 ° C., and sintered at a temperature of 550 ° C. to prepare a catalyst body.

Experimental Example

Measurement of the heat resistance and durability of the catalyst

Aging of the catalyst body obtained in the above Examples and Comparative Examples for 140 hours at 950 ℃ and 100 hours at 1100 ℃, respectively, oxidation of three-way gas (hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxides (NO _X )) And the reduction properties were measured and the results are shown in Table 1 below.

TABLE 1a

Aging at 950 ° C. for 140 hours

TABLE 1b

Aging at 1100 ° C. for 100 hours

In addition, after the catalytic converter made of the catalyst bodies of the above examples and the comparative examples was mounted on an actual vehicle, a FTP (federal test procedure) test (aging the engine to correspond to 100,000 miles of driving) was performed to perform three-way gas [ Hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxides (NO _X )] were measured for oxidation and reduction properties, the results are shown in Table 2 below.

TABLE 2

FTP test (significant engine aging for 100,000 miles of driving)

As described above, the catalyst body produced through the production method of the present invention has a greater property of oxidizing and reducing ternary gas into harmless nitrogen gas or carbon dioxide, and has higher heat resistance and durability than conventional catalyst bodies. In addition, the production cost is excellent catalyst body that is reduced by 10 to 15% compared to the existing catalyst body, it can be usefully used to prepare a catalyst for automobile exhaust gas purification.

Claims (2)

In the method for preparing a catalyst for automobile exhaust gas purification containing platinum (Pt), rhodium (Rh) or palladium (Pd), platinum, rhodium and palladium having a content ratio of 0.5 to 3:12 to 15 to 0.5 to 3, respectively After impregnating the support, mixing and milling, a cerium (Ce) -zirconium (Zr) composite oxide was further added to prepare a washcoat slurry (solid content: 30 to 50%) having a noble metal concentration of up to 10 g / l. After manufacturing, the washcoat slurry is coated with a single layer or a double layer on a carrier up to 2 L, dried, and then fired. The method of claim 1, wherein in the process of mixing and milling the support impregnated with platinum, rhodium, or palladium, a rare earth oxide or an alkali metal oxide is added.