JPS606701B2 - Method for manufacturing oxidation catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an oxidation catalyst that maintains high activity.

Conventionally, alumina,
When preparing a clean carrier with a high surface area by attaching fine particles such as silica or silica/alumina, these base carriers are soaked in alumina sol, silica sol, etc., and then calcined 2 to prepare the base carrier. Catalysts are prepared by supporting active substances.

The oxidation catalyst obtained by such a conventional method consists of alumina, silica, and silica attached to a base carrier.

The adhesion strength of fine particles such as alumina is not sufficient2, and they are easily peeled off due to vibration, friction, etc. The peeling phenomenon causes a loss of the noble metal active substance in addition to a decrease in activity due to deterioration of the noble metal active substance, leading to a decrease in the activity ability.

Furthermore, since the noble metal active substance is generally supported in a larger amount on the fine particles of alumina, silica, silica/alumina, etc. attached to the base carrier than on the base carrier, there is a remarkable tendency for the activity to decrease. Silane compounds have long been known to act as intermediaries between organic materials, and the inventors have discovered that these silane compounds also have an excellent effect as intermediaries between inorganic materials. We have discovered and developed a method for producing durable catalysts by utilizing this effect in catalyst preparation.

That is, the method for producing an oxidation catalyst of the present invention has the following characteristics. First, a honeycomb carrier made of cordierite or mullite, or a Q alumina pellet carrier is mixed with water or an organic solvent using a silane compound containing one kind of alkoxy group or silanol group in the molecule and the other one containing a vinyl group, epoxy group, methacrylic group, or amino group. The porous material is immersed in a solution dissolved in the material, air-dried, and then immersed in a sol of the porous material or a suspension of fine particles to attach the porous material. Next, a porous carrier having a high surface area is obtained by drying and firing in a conventional manner. Next, this carrier is immersed in a solution of an active noble metal, such as a solution of chloroplatinic acid or palladium chloride, to support the active noble metal, and the noble metal is then activated by a conventional method to obtain a catalyst. The present invention will be explained in detail below using Examples and Comparative Examples.

Example 1 ■ Cordierite honeycomb carrier 200 x 3 sides N-8
(aminoethyl)y-aminop.

Add pyrutrimethoxysilane to a 0.5% aqueous solution of 2N(CH2)2NH(C ratio)3Si(OCH3)3 at room temperature for 30 minutes.
Soak for 2 minutes, then take out and air dry at room temperature for 2 hours. In this way, a base carrier treated with a silane compound is obtained. Next ■
The base support obtained above is immersed in a 1% suspension of fine particles of activated alumina (y-alumina) of 37 microns or less in water.

After soaking the bond for 1 hour at room temperature while thoroughly observing it, take it out 110
Dry at 0 for 2 hours and then bake at 500o for 3 hours. A porous carrier is thereby obtained. Next, (1) immerse this porous body in a 1% palladium chloride solution for 1 hour at room temperature. After taking it out from the solution and draining off excess palladium chloride, it was dried at 12,000 for 2 hours, and then transferred to a calcining furnace and calcined at 500°C for 3 hours under air circulation to obtain a catalyst. Example 2 ■ Cordierite honeycomb carrier 200 x 3 sides N-B
(aminoethyl)aminopropylmethyldimethoxysilane2N(CH2)2NH(CH2)3Si(OC
H3) 2" Soaked in 0.5% water CH3 solution at room temperature for 30 minutes, taken out and soaked in 2" at room temperature.
Air dry for an hour.

In this way, a base carrier treated with a silane compound is obtained. Next, the base carrier is immersed in a sol containing 5% alumina, which is an alumina hydrate produced from aluminum**nium nitrate and aqueous ammonia. After soaking at room temperature for 1 hour, take out
Dry at 1000C for 2 hours, and then bake at 50000C for 3 hours. A porous compact is thereby obtained. Next, (1) this porous carrier is immersed in a 0.5% chloroplatinic acid solution for 1 hour at room temperature. After taking it out of the solution and draining off the platinum chloride solution that had adhered to it, it was dried at 120° C. for 2 hours, and then transferred to a calcining furnace and calcined at 60,000 for 3 hours under air circulation to obtain a catalyst. Comparative Example 1 ■ Activated alumina (y-alumina) is crushed into fine particles of 37 microns or less and suspended in water to make a 1% suspension.

A cordierite honeycomb carrier of 200×3 lengths was soaked in this solution for 1 hour at room temperature. Next, it was dried at 110oC for 2 hours and further calcined at 500qo for 3 hours to obtain a carrier. Next, (2) this carrier was immersed in a 1% palladium chloride solution for 1 hour in the same manner as in Example 1, and the same treatment was carried out to obtain a catalyst. Comparative Example 2 ① In the same manner as in Example 2, a 20×30 cordierite honeycomb carrier was immersed in a sol of alumina hydrate produced from aluminum nitrate and aqueous ammonia at room temperature for 1 hour.

After bonding, it was dried at 11,000°C for 3 hours, and further fired at 500°C for 3 hours to obtain a carrier. Next, ■ this carrier was soaked in a 0.5% chloroplatinic acid solution for 1 hour in the same manner as in Example 2,
Thereafter, the same treatment was carried out to obtain a catalyst. In order to examine the effect of the silane compound treatment on the adhesion of activated alumina obtained in the above examples, a test was conducted to measure the amount of loss of deposited alumina using a shaking tester.

The samples used in this test were those before the active metal component was supported in each of the Examples and Comparative Examples. The results are shown in Table 1. Table 1 The loss rate of alumina was calculated using the following formula.

(Weight before test - Weight after test) x 100/(Weight of vehicle before test - Weight of base carrier) = Alumina loss rate Next, the oxidation activity of the catalysts obtained in Examples and Comparative Examples was investigated.

This activity test was carried out by filling the prepared catalyst into a quartz glass reaction tube with a diameter of about 2 square meters, and flowing a mixed gas containing carbon monoxide and propane to determine the respective conversion rates. The conversion rate was calculated by measuring the gas concentration before and after the reaction. Table 2 shows the reaction gas.
The gas hourly space velocity (SV) was 20,000 hr-1, and the reaction temperature was determined by the gas temperature before the catalyst layer entrance. Table 2 Table 3 shows the results of the activity tests performed on the prepared product and the product after shaking with a shaking tester.

In the column below each temperature, the left column shows the conversion rate of -carbon oxide, and the right column shows the conversion rate of propane. Left side: Carbon monoxide conversion rate Right side: As is clear from the shaking test results and the activity test results, which exceed the propane conversion rate, the silane compound treatment by the method of the present invention improves the adhesion of the porous carrier. It has a remarkable effect on increasing strength.

Claims (1)

[Claims] 1. In a method for producing an oxidation catalyst in which fine particles such as alumina, silica, or silica/alumina are attached to the surface of a base carrier such as a cordierite honeycomb, a mullite honeycomb, or an α-alumina pellet, and an active precious metal is supported on the base carrier, the above-mentioned base carrier is When attaching fine particles such as alumina, silica, or silica-alumina to the surface of a carrier, the base carrier is immersed in advance in a solution of a silane compound having an alkoxy group and an amino group in water or an organic solvent, and then air-dried. A method for producing a featured oxidation catalyst.