JPH04293544A - Catalyst composition - Google Patents

Abstract

PURPOSE:To provide a catalyst composition generating no lowering catalytic activity even in a reducible atmosphere at high temp. of 200 deg.C or higher and excellent in durability. CONSTITUTION:A catalyst composition consists of a perovskite type multicomponent oxide wherein iron is contained in a part of the B-site of a chemical formula ABO3, rare earth metal oxide, at least one oxide among zirconium oxide and aluminum oxide and at least one noble metal and has excellent durability shown by Fig 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst composition that converts hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) into water, carbon dioxide and nitrogen through an oxidation or reduction reaction.

0002

[Prior Art] Conventional catalyst compositions of this type include those consisting of rare earth element oxides, perovskite-type composite oxides, and palladium (Japanese Patent Application Laid-open No. 156349/1983), and those consisting of perovskite-type composite oxides and palladium. There is a catalyst in which palladium or other noble metal is supported as a catalyst component on the surface of a catalyst made of an oxygen storage rare earth oxide (Japanese Patent Application Laid-Open No. 162948/1983).

0003

[Problems to be Solved by the Invention] However, when the above-mentioned conventional catalyst composition is used for a long time in a reducing atmosphere at a high temperature of 200°C or higher, noble metals such as palladium may cause grain growth or perovskite-type composite oxides may occur. There was a problem that the durability was poor, such as the catalytic activity gradually decreasing due to diffusion inside the catalyst.

The object of the present invention is to solve the above problems and provide a catalyst composition with excellent durability.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention consists of a perovskite-type composite oxide containing iron in a part of the B site of the chemical formula ABO3 and a rare earth oxide, and is composed of a rare earth oxide and a perovskite-type composite oxide containing iron in a part of the B site of the chemical formula ABO3. one of them
It consists of one or more oxides and one or more noble metals.

[0006]

[Function] With the above structure, the present invention suppresses noble metal grain growth and diffusion into the perovskite composite oxide even in a reducing atmosphere at a high temperature of 200° C. or higher.

[0007]

[Examples] Examples of the present invention will be described below.

The chemical formula is La0.9 Ce0.1 Co0
．． 100g of 98Fe0.02 perovskite complex oxide powder, 80g of cerium oxide (CeO2) powder
A slurry was prepared by mixing and stirring 20 g of zirconium oxide (ZrO2) powder, 50 g of alumina sol (nitric acid acidity, solid content 1/10), 0.9 g of palladium nitrate, and 150 g of water.

In the slurry, 400 cells/(inch)2 of cordierite (2Mg0.5S) with a grid-like cross section are added.
A honeycomb carrier made of (iO2 .2Al2O3) was immersed, pulled up, and then the excess slurry was blown away by air flow.

[0010] Thereafter, the carrier was dried at 200°C for 1 hour,
A catalyst body supporting the catalyst composition of this example was prepared by firing at 650° C. for 1 hour.

[0011] The structure of the catalyst body after calcination is as follows: catalyst composition 24
% by weight, the carrier is 76% by weight, the perovskite type composite oxide in the catalyst composition is 48.6% by weight, cerium oxide is 38.9% by weight, zirconium oxide is 9.9% by weight,
Aluminum oxide is 2.4% by weight, palladium is 0.2%
% by weight.

[0012] As a comparative example, La0.9 does not contain iron.
A catalyst body was prepared in which a catalyst composition comprising a perovskite-type composite oxide of Ce0.1CoO3, cerium oxide, zirconium oxide, aluminum oxide, and palladium was supported.

[0013] The two types of catalyst bodies produced above were compared in terms of initial characteristics of catalyst performance and durability.

The test conditions were as follows, and the test results are shown in Table 1. Catalyst performance test conditions (1) Gas composition (volume basis): A reaction gas consisting of 1% NO, 1% CO, and 98% helium was used. (2) Space velocity: 12500/Hr (3) Measuring method: The reaction was carried out using a fixed bed flow system, and the conversion rate of NO to N2 was determined by gas chromatography. The reaction temperature is 300°C.

The measurement results are shown in Table 1.

[0016]

[Table 1]

From the same table, it is clear that the durability of the catalyst body using the catalyst composition of this example is superior to that of the comparative example.

Next, the changes in catalytic performance over time of the above two types of catalyst bodies were measured, and the results shown in FIG. 1 were obtained.

From the figure, the catalyst body using the catalyst composition of this example showed excellent durability. The test conditions at this time were as follows.

[0020] The catalyst body was placed in an electric furnace maintained at 900°C and treated in an air atmosphere to examine changes in activity. (1) Gas composition (volume basis): NO 1%, CO 1%, helium 98% (2) Space velocity: 12500/Hr (3) Measurement method: Reaction was carried out using a fixed bed flow system, and NO nitrogen was measured by gas chromatography. The conversion rate was calculated. The reaction temperature is 300°C.

[0021] In the examples, the case where palladium was used as the noble metal was explained, but similar effects could be obtained by using platinum or rhodium in part or in whole in addition to palladium.

[0022]

Effects of the Invention As explained above, the catalyst composition of the present invention is composed of a perovskite-type composite oxide containing iron in a part of the B site of the chemical formula ABO3 and a rare earth oxide, and one or more noble metals, the initial activity is improved, and even at high temperatures of 200°C or higher and in a reducing atmosphere, noble metal grain growth and perovskite composite oxides are prevented. Since it suppresses diffusion inside, it has excellent durability.

[Brief explanation of drawings]

[Figure 1] Comparison diagram of durability of catalyst performance between an example of the present invention and a comparative example

Claims (2)

[Claims] Claim 1: A perovskite-type composite oxide containing iron in a part of the B site of the chemical formula ABO3, and a rare earth oxide, comprising an oxide of one or more of zirconium oxide and aluminum oxide, and an oxide of one or more of noble metals. A catalyst composition consisting of one or more types. 2. The catalyst composition according to claim 1, wherein the iron content is 0.1% to 5% by weight of the B site.