JPH064132B2 - Integrated catalyst carrier for exhaust gas purification - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an integrated catalyst carrier for use in detoxification of hydrocarbon (HC), carbon monoxide (CO), and nitric oxide (NO _x ). In particular, the present invention relates to a catalyst carrier used for purifying automobile exhaust gas and stationary engine exhaust gas.

[Prior Art] There are various types of monolithic structured carriers (materials, shapes, and manufacturing methods), but generally they are cordierite-made and rectangular cell monoliths manufactured by Corning Incorporated and Nippon Insulators Co., Ltd. Carriers are often used. Since this cordierite monolithic carrier has a very small specific surface area of about 1 m ² / g, it cannot be dispersed on the surface of the carrier even if it carries a catalytic metal such as a noble metal. As a result, only a catalyst having poor initial performance and durability is obtained, and it is not practical to use it as a carrier as it is. Therefore, in order to solve the above-mentioned drawbacks, conventionally, an active alumina coating is formed on the monolith carrier to increase the specific surface area to improve the dispersibility of the catalyst metal and improve the performance.

Conventionally, the activated alumina used for this alumina coating is
As shown in Japanese Examined Patent Publication No. 56-27295, about 50 m ²
It has a specific surface area of / g or more and generally refers to activated alumina species excluding α, θ-alumina. further,
After that, as disclosed in JP-A-54-148187, a structure in which δ-alumina is mainly contained and χ, γ, κ, θ, ρ-alumina is partly disclosed, and JP-A-58-58 is also shown.
Japanese Patent No. 30333 discloses a method for producing a catalyst carrier by firing α-alumina and alumina sol at 1000 ° C or lower. Alumina sol exhibits an amorphous form when fired at 1000 ° C. or less, so according to this production method, the alumina coating has an α-
The X-ray-diffraction result of only alumina is shown.

[Problems to be Solved by the Invention] Since the upper limit of the catalyst inlet gas temperature is around 800 ° C, the required performance of the conventional automobile exhaust gas purifying catalyst is that the catalyst has thermal durability up to 800 ° C. there were. However, since the recent movement of the catalyst mounting position to the upstream portion of the exhaust pipe and the use at high speed are emphasized, the upper limit of the catalyst inlet gas temperature rises to around 900 ° C., and the catalyst temperature is 1000 ° C. It is thought that the temperature is around ℃. As a result, high-temperature durability, which has not been so much emphasized in the past, has recently become particularly problematic. Therefore, the catalyst according to the prior art has insufficient high temperature durability. To infer the reason for this, Japanese Patent Publication No.
In the activated alumina species disclosed in JP-A-54-148187 and JP-A-54-148187, the crystal undergoes transformation at a high temperature of 1000 ° C., and in the new state, the catalyst metal is supported in a highly dispersed state. Therefore, it is considered that the sintering of the catalytic metal is promoted as a result. Also, JP-A-5
In the invention of 8-30333, 100
Since α-alumina whose crystal does not transform even at 0 ° C is used, it is considered to be good in that respect, but originally, α-alumina having a low specific surface area of 1 m ² / g or less
Since the catalyst metal is supported, the catalyst metal is not supported in high dispersion and the performance is considered to be insufficient.

[Means for Solving Problems] As a result of intensive studies to solve the problems of the above-mentioned conventional techniques, the present inventors have found that the exhaust gas-purifying catalyst is superior in high temperature durability to conventional catalysts. We have succeeded in providing a catalyst carrier that can be obtained.

That is, the integrated catalyst carrier for exhaust gas purification according to the present invention comprises activated alumina having an alumina coat on a substrate for supporting a catalytic metal, which contains α-alumina and θ-alumina, which can be identified by X-ray diffraction, and δ-alumina, γ-
It is a mixture containing at least one selected from alumina, κ-alumina, χ-alumina and ρ-alumina.

In this invention, the monolith carrier used as the substrate is
Cordierite, mullite, etc., and the base material preferably has a triangular, square, or corrugated cell structure.

As the catalyst metal supported on the catalyst carrier of the present invention, it is preferable to use at least one of platinum, palladium and rhodium.

[Function] The activated alumina of the catalyst carrier of the present invention contains α-alumina and θ-alumina, and contains at least one of δ-alumina, γ-alumina, κ-alumina, χ-alumina and ρ-alumina. It is a mixture containing.

Since the catalyst carrier of the present invention has a sufficient specific surface area, the catalyst metal is supported in a sufficiently high dispersion, thereby providing a high-performance catalyst. Moreover, even when used under high temperature, the influence of the crystal modification of alumina on the catalyst metal is small, and therefore it is considered that a catalyst having sufficient durability can be provided.

In the catalyst carrier of the present invention, one of δ, γ, κ, χ, ρ-alumina, which is an activated alumina having a specific surface area of 50 m ² / g or more, is sufficiently present, and therefore, α having a low specific surface area or Even if θ-alumina is present, a catalyst carrier having a sufficient specific surface area (about 30 m ² / g or more) can be obtained, and a noble metal can be supported on the carrier in a sufficiently high dispersion. Furthermore, at high temperature, since the α- or θ-alumina, in which the precious metal is hardly supported, is contained, the influence of the transformation of alumina on the precious metal is small, and since the precious metal is supported in a highly dispersed state, the It is considered that the catalyst can provide a catalyst having sufficient durability and a small grain growth.

Example 1 1 kg of activated alumina powder having an average particle size of 15μ and a specific surface area of about 100 m ² / g and alumina powder obtained by firing this powder at 1200 ° C. for 3 hours (having a specific surface area of 5 m ² / g or less) 1 kg, and 120 g of aluminum nitrate nonahydrate,
580 g of ion-exchanged water and 1400 g of alumina sol (trade name AS-200) manufactured by Nissan Chemical Co., Ltd. were mixed and stirred for 3 hours or more with a LaPoster manufactured by Yamato to prepare a slurry. The slurry had a pH of 4.1 and a viscosity of 320 c.ps as measured by a Brookfield viscometer.

Next, a honeycomb-shaped monolithic carrier (diameter 93 mm, length 100 mm, volume 0.679, manufactured by Nippon Insulators Co., Ltd.) formed of a cylindrical cordierite having 400 cells / inch ² was immersed in water to sufficiently absorb water. It was taken out and the water remaining in the cell was blown with an air stream. This water-absorbed carrier was immersed in the previously prepared slurry for 15 minutes and then taken out, and the excess slurry in the cell was blown with an air stream. In this way, the carrier with the slurry attached,
After drying for 5 hours, 700 ° C in air using an electric furnace
After baking for 1 hour, 68 g of coating film was formed on the carrier. The coating operation was repeated to form a total of 135 g of coating film on the carrier to obtain a catalyst carrier.
When the coating of this carrier is scraped off and this is X-ray diffracted,
γ, θ, δ and α-alumina were detected.

Next, this catalyst carrier was immersed in an aqueous solution of platinum ammine to adsorb the catalytic metal platinum, and then 80
Drying with warm air at ℃ for 1 hour, then further drying at 250 ℃ for 1 hour, and then immersing the catalyst carrier in the rhodium chloride aqueous solution to adsorb the catalyst metal rhodium on the catalyst carrier, then heat at 80 ℃. Air drying was performed to obtain catalyst A. Quantitative analysis of the amount of precious metal in this catalyst showed that platinum was 1.0 g / -catalyst,
Rhodium was 0.1 g / -catalyst.

Example 2 1 kg of activated alumina powder having an average particle size of 16 μ and a specific surface area of about 50 m ² / g, 1200 kg of 1200 ° C. calcined alumina powder (specific surface area of 5 m ² / g or less) used in Example 1, and aluminum nitrate 9 120 g of hydrate and 530 g of deionized water
Alumina sol (trade name AS-200) manufactured by Nissan Chemical Co., Ltd. 140
0 g was mixed and stirred with a Yamato-type Laposterer for 3 hours or more to prepare a slurry. This slurry has a pH of 4.1,
The viscosity was 280 c.ps with a Brookfield viscometer.

Using the slurry thus prepared, a coating film was formed on the monolith carrier in the same manner as in Example 1 to obtain a catalyst carrier. When the coating was subjected to X-ray diffraction, θ, δ and α-alumina were detected.

Next, in the same manner as in Example 1, the catalyst metals platinum and rhodium were adsorbed on this catalyst carrier to obtain catalyst B. The amount of platinum and the amount of rhodium were 1.0 g, which was the same as in Example 1 as a result of the analysis.
It was Pt / -catalyst and 0.1 gRh / -catalyst.

Example 3 Alumina (trade name KHA 46) manufactured by Sumitomo Aluminum Smelting Co., Ltd.
Was finely pulverized with a vibro mill manufactured by Yasukawa Seisakusho, and activated alumina powder with an average particle diameter of 12μ (this specific surface area is about 12
1 kg, which was 0 m ² / g) and 1200 used in Example 1.
℃ calcined alumina powder (specific surface area 5 m ² / g or less) 1
_kg , 120 g of aluminum nitrate nonahydrate, 580 g of ion-exchanged water, alumina sol (trade name AS-200) 1400
g was mixed and stirred with a Yamato lab stirrer for 3 hours or more to prepare a slurry. This slurry has a pH of 4.5 and a viscosity of 4
It was 10 c.ps. Using the slurry thus prepared, a coating film was formed on the monolith carrier in the same manner as in Example 1 to obtain a catalyst carrier. X-ray diffraction of this coating detected κ, χ, ρ, θ, δ, α-alumina.

Next, in the same manner as in Example 1, the catalyst metals platinum and rhodium were adsorbed on this catalyst carrier to obtain catalyst C. As a result of the quantitative analysis, the amounts of platinum and rhodium were the same as in Example 1.

Example 4 400 g of activated alumina powder having an average particle diameter of 15 μm and a specific surface area of about 100 m ² / g, and 1,600 g of 1200 ° C. calcined alumina powder used in Example 1 (specific surface area of 5 m ² / g or less)
120 g of aluminum nitrate nonahydrate, 580 g of ion-exchanged water, and alumina sol (trade name AS-200) 1400
g was mixed and stirred with a Yamato Lab Stirrer for 3 hours or more to prepare a slurry. This slurry had a pH of 4.2 and a viscosity of 265 c.ps as measured by a Brookfield viscometer. Using the slurry thus prepared, a coating film was formed on the monolith carrier in the same manner as in Example 1 to obtain a catalyst carrier. When the coating was subjected to X-ray diffraction, γ, θ, δ and α-alumina were detected as in Example 1. Next, in the same manner as in Example 1, the catalyst metals platinum and rhodium were adsorbed on the catalyst carrier,
Catalyst D was obtained. As a result of the quantitative analysis, the amounts of platinum and rhodium were the same as in Example 1.

Comparative Example 1 2 kg of activated alumina powder having an average particle diameter of 15 μ and a specific surface area of about 100 m ² / g, and 120 g of aluminum nitrate nonahydrate
And 580 g of ion-exchanged water and alumina sol (trade name AS
-200) and 1400 g were mixed and stirred with a Yamato Lab Stirrer for 3 hours or more to prepare a slurry. This slurry has a pH
At 4.0 the viscosity was 300 c.ps on a B type viscometer. Using the slurry thus prepared, a coating film was formed on the monolith carrier in the same manner as in Example 1 to obtain a catalyst carrier. When this coating was subjected to X-ray diffraction, only γ-alumina was detected.

Next, as in Example 1, 1.0 g / -catalyst of catalytic metal and 0.1 g / -rhodium of rhodium were adsorbed on the catalyst carrier to obtain catalyst E.

Comparative Example 2 2 kg of activated alumina powder having an average particle diameter of 16 μ and a specific surface area of 50 m ² / g, and 120 g of aluminum nitrate nonahydrate,
530g of deionized water and alumina sol (trade name AS-20
0) 1400 g was mixed and stirred in the same manner as in Example 1 to prepare a slurry. Using this slurry, a coating film was formed on the monolith carrier in the same manner as in Example 1 to obtain a catalyst carrier. X-ray diffraction of the coating of this carrier results in θ, δ-
Alumina was detected. Then, platinum was added to 1.
Catalyst F was obtained by adsorbing 0 g / -catalyst and rhodium on 0.1 g / -catalyst and a catalyst carrier.

Comparative Example 3 Activated alumina powder obtained by finely pulverizing the alumina (trade name KHA-46) used in Example 3 (having an average particle diameter of 12 μ and a specific surface area of 12).
0 m ² / g) 2 kg and aluminum nitrate nonahydrate 120 g
And 580 g of ion-exchanged water and alumina sol (trade name AS
-200) and 1400 g were mixed and stirred in the same manner as in Example 1 to prepare a slurry. Using this slurry, a coating film was formed on the monolith carrier in the same manner as in Example 1 to obtain a catalyst carrier. X-ray diffraction of the coating of this carrier gives κ, χ,
ρ-alumina was detected. Then, platinum was adsorbed on 1.0 g / -catalyst and rhodium on 0.1 g / -catalyst in the same manner as in Example 1 to obtain a catalyst G.

Comparative Example 4 ² kg of alumina powder (specific surface area of 5 m ² / g or less) obtained by firing activated alumina powder having an average particle diameter of 15 μ and a specific surface area of about 100 m ² / g for 3 hours at 1200 ° C. and 120 g of aluminum nitrate nonahydrate. Then, 580 g of ion-exchanged water and 1400 g of alumina sol (trade name AS-200) were mixed and stirred in the same manner as in Example 1 to prepare a slurry.

Using this slurry, a coating film was formed on the monolith carrier in the same manner as in Example 1 to obtain a catalyst carrier. When the coating film of this carrier was subjected to X-ray diffraction, θ, α-alumina was detected. Next, platinum was adsorbed on 1.0 g / -catalyst and rhodium on 0.1 g / -catalyst in the same manner as in Example 1 to obtain a catalyst H.

Catalyst A obtained in Examples 1 to 4 and Comparative Examples 1 to 4 above
.About.H, the types of raw material alumina and the form of alumina in the coating are summarized in Table 1.

Example 5 and Comparative Example 5 In Example 1 and Comparative Example 1, each of the obtained catalyst carriers was immersed in an aqueous solution of palladium chloride, and further subjected to reduction treatment with sodium borohydride, and then an aqueous solution of platinum ammine and rhodium chloride. Immerse in an aqueous solution to add 0.5g each of platinum, palladium and rhodium to the catalyst carrier.
/ -Catalyst, 0.5 g / -catalyst, 0.1 g / -catalyst was adsorbed to obtain a catalyst.

Example 6 and Comparative Example 6 Each of the catalyst carriers obtained in Example 1 and Comparative Example 1 was
After being immersed in an aqueous solution of palladium chloride and further subjected to a reduction treatment with sodium borohydride, it is immersed in an aqueous solution of rhodium chloride to adsorb palladium and rhodium on the catalyst carrier at 1.0 g / -catalyst and 0.1 g / -catalyst, respectively. A catalyst was obtained.

Catalyst durability performance evaluation test results The durability test conditions are as follows: engine speed of 3800cc, engine speed 3300rpm, boost 100mmHg, catalyst inlet gas temperature 890 ° C, air-fuel ratio (A / F) 14.5, catalyst exposed to exhaust gas for 50 hours. Is the condition. In this way, the evaluation of the performance of a durable catalyst was carried out on an engine with a displacement of 1600 cc, a rotation speed of 2600 rpm, a boost of 360 mmHg,
Exhaust gas is passed through the catalyst after endurance under the conditions of catalyst inlet gas temperature of 460 ° C and A / F of 14.5, and hydrocarbon (HC), carbon monoxide (C
It was performed by calculating the purification rate for O) and nitrogen oxides (NOx). The results are shown in Table 2.

[Effects of the Invention] As is clear from the above results, the catalyst carrier of the present invention exhibits very excellent catalytic performance in high temperature durability as compared with the conventional catalyst carrier carrying the same catalyst metal. be able to.

Claims (1)

[Claims] 1. The activated alumina contained in the coating layer on the substrate comprises α-alumina and θ-alumina, and δ
An integrated catalyst carrier for exhaust gas purification, which comprises a mixture containing at least one selected from alumina, γ-alumina, κ-alumina, χ-alumina and ρ-alumina.