JPS5889950A - Production of honeycomb catalyst having improved thermal shock resistance - Google Patents

Abstract

PURPOSE:To improve thermal shock resistance markedly, by coating water soluble org. polymer compds. on a honeycomb carrier prior to coating of almina. CONSTITUTION:Org. polymer compds of >=200mol.wt., and <=500cp viscosity (e.g.; wheat flour, potatoes, gloiopeltis glue, soybean casein, gum arabic, methyl cellulose, polyacrylic acid) are coated on the surface of a honeycomb carrier. Thereafter, a catalyst component is deposited thereon and is calcined. The coating of the org. polymer compds. on the honeycomb catalyst is accomplished by immersing the honeycomb catalyst in an aq. soln. of the water soluble org. polymer compds. Taking-out the carrier from the soln. after immersion, blowing away the excess soln. in air flow and drying the same at an ordinary temp. or <=200 deg.C.

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a honeycomb catalyst. Review
The present invention relates to a method for manufacturing a ceramic one-nicum catalyst having an integrated structure with improved thermal resistance and shock resistance. In general, honeycomb fibers have a monolithic structure on which a catalyst component mainly consists of activated alumina, platinum group metals such as platinum, palladium, and rhodium, and copper, copper, etc.
Transition gold such as nickel, cobalt, iron, etc. or its hemide;
Catalyst components containing rare earth elements such as cerium and lanthanum are included as necessary. This honeycomb touch is widely used for the υF air gas in the internal combustion engine of the automobile, for the 0ization treatment of At1-1 nitrogen oxides, and for general industrial purposes, such as the pleasant odor treatment of waste gas. has been done. Among these, especially when used in automobiles, the temperature K of the catalyst used changes from moment to moment depending on the operating conditions. By the way, when the honeycomb structure is 1 m long, the coefficient of thermal expansion is variable between the Cera Z honeycomb carrier and the catalyst component supported on the phase body, and distortion tends to occur between the phase body and the catalyst component. As a result, honeycomb catalysts develop cracks during the intense m&change cycle.

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It has been pointed out that if it grows gradually, the catalyst itself may break into two or more pieces in the case of the innermost cavity, which may cause problems in use. If a honeycomb catalyst is installed near the engine outlet, the exhaust temperature will be high, and the operating temperature difference will be large, so the physical mt of the honeycomb catalyst will be
Thermal shock resistance is especially strongly required in le,%. The object of the present invention is to provide a method for producing a ceramic honeycomb M medium that fully satisfies this goal. As a result of careful efforts to satisfy this objective, the Ministry of Honjitsu and colleagues found that coating a water-soluble polymeric monomer compound before leaving an alumina coating on the Ni-Cam phase would cause vibrations and exhaust gas flow. It has been found that thermal shock resistance can be significantly improved without causing practical problems such as peeling of the catalyst coating layer from the cam catalyst, and without having any negative impact on the activity of the catalyst. Heading: We were able to complete the present invention. To further explain the object of the present invention, the conventional method V (in which the honeycomb and the mutual contact tIi on it are
(Since the coefficient of thermal expansion is narrow, it is likely to be affected by rapid changes in intensity during use.) In honeycomb, a catalyst component such as alumina having a different thermal expansion coefficient is infiltrated into the pores of the honeycomb phase body, so there is a tendency for the occurrence of cracks to occur due to the difference in the thermal expansion coefficient between the two. In this practical example, the generation of w-type cracks, which is considered to be due to the MK of the coefficient of thermal expansion of the honeycomb phase and the supporting catalyst component, is suppressed by 11η above f''l; coated on the surface of
If a catalyst component is added on top of it and fired, the pre-coated polymeric organic compound will burn and disappear.)
Since a gap equivalent to a thin film is externally created between the 5v portion of the catalyst and the supported catalyst, the generation of distortion due to the difference in thermal expansion can be alleviated. According to the method of the present invention, the desired level of thermal shock resistance can be determined by changing the amount of coating on the polymer fixture to be coated first, that is, by changing the thickness of the coating film. I can do things. The polymer compound used in the present invention is desirably water-soluble for handling purposes. The molecular weight of the polymer compound used is preferably 200 or more, particularly preferably 500 or more. The viscosity used is determined by its viscosity, preferably below 500 Cp (centiboise), preferably below 200 ep, particularly preferably below 10 ep.
It is less than 0 ep. After being coated and dried, the polymer monomer compound used in the present invention forms a so-called film, and has an affinity with the aqueous medium containing the core catalyst component, except for the next operation, which is to separate and support the catalyst. It is desirable to have something that maintains the sexiness to a certain extent. More specifically preferred water-soluble polymeric MW compounds include, for example, various starches (wheat, corn, potato, tapioca), funose, soybean casein, and natural gums such as gum arabic and gum tragacanth. , glue casein, various flu starch powders,
Starch conductor, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, various polyvinyl esters, polyacrylic alcohol and its derivatives, maleic acid copolymers-1, such as vinyl acetate anhydride maleic copolymer, styrene maleic Examples include copolymers, which can be used alone or in a mixture of two or more. Preferably, various polyvinyl alcohols, polyacrylic noodles, and derivatives thereof are included in the rut%, taking into consideration the properties and ease of use of the catalyst afterward. [Dose of the above monomolecular compound is Jf in aqueous solution]
(Anything between 1.5 and SO volume can be used.) The coating method for the ceramic honeycomb pentate bodies involves immersing the honeycomb carrier in the above-mentioned water bathing product molecular organic compound water bathing solution at normal pressure, reduced pressure, (Any pressurized state is fine), take it out, for example, blow off the excess bath liquid in an air stream, and keep it under normal IM or Fi 200℃, that is, the water-soluble polymeric refrigerant compound will not be deformed due to burning etc. The ceramic used in the present invention is dried at a high temperature or, if necessary, is directly subjected to the next catalyst-supporting operation.After coating with the water-soluble polymeric organic compound, the catalyst-supporting step is carried out by a conventional method. Any commonly used vine carrier can be used as the honeycomb carrier, and heat-resistant ceramics such as cordierite, mullite, α-alumina, and zircon are particularly preferred. -Welfare is not limited to these examples.Example 1 51% aqueous solution of completely saponified polyvinyl rutile alcohol (PVA105 manufactured by Kuraray ■) with a molecular weight of t500],
300 cells/square inch to make a diameter of 90m1m
A cordierite ceramic honeycomb (average pore size 4 microns) with a length of 11 Oq/m was completely immersed in the above solution for 2 minutes, taken out, blown off the excess solution in an air stream, and heated at 120 °C for about 5 minutes. time dried m lk,
k *The company was criticized for increasing the amount of electricity by about IF. The sample was immersed in 1.0 t of water for 2 minutes, taken out in the same manner as above, blown off excess slurry in an air stream, dried at 120°C, and then fired at 700°C. This chilled coating process was repeated twice (9 times), and about 509 alumina was mixed. After that, 1.4 the above alumina-supported carrier is immersed in oil,
After 1 hour, it was taken out, dried at 120°C, and then calcined at 700°C to obtain a finished catalyst. Example 2 Saponified polyvinyl alcohol (slurry ■fiPVA217) with molecules 1i1706 and about 80% weight 4
A completed catalyst was obtained in the same manner as in Example 1 except that an aqueous solution was used. Example 3 A complete catalyst was obtained in the same manner as in Example 1, except that a 3 weight 4A solution of completely saponified polyvinyl alcohol (Kuraray@Yo pvA1t7) having a molecular weight of 1700 was used. Example 4 SX of polyacrylic butylammonium with an e molecular weight of about 4000
A completed catalyst was obtained using the same procedure as in Example 1 except for the aqueous solution. Example 5 A completed catalyst was obtained in the same manner as in Example 1 except that 5 g of 8 inches of corn star and 111% water bath solution was used. Comparative Example 1 A finished catalyst was obtained in the same manner as in Example 1 except that the coating treatment was not performed using the method of Example 1. Example 6 Polyvinyl alcohol with a molecular weight of 1700 and completely saponified (slurry
The same cordierite support as in Example 1 was coated with a 3-weight aqueous solution of VA117), and activated alumina 7509 with a specific surface of about 100 g"/f was coated with 7600C containing 25 f of buty-aluminum nitrate. Step 11 was placed in a water bath and wet-pulverized at 16:1'11 using a porcelain ball mill.
- immersed in alumina for 2 minutes, blown off excess slurry in a stream of air, dried at 120°C, then calcined at 500°C to incorporate about 709 alumina, then 0.4
1 t of catalyst solution prepared by mixing platinum chloride containing 7 F of platinum and an aqueous solution of palladium chloride containing (+, 23 F of palladium) was heated to about 50°C, and the alumina co-supported carrier was evaporated to 30 Fg. A portion was taken out, dried at 120°C, and then reduced and sintered at 500°C for 1 hour in a nitrogen stream containing 5 volumes of hydrogen to obtain a completely defeated catalyst. Example 7 Polyvinyl having a molecular weight of 500 and completely saponified A completed catalyst was obtained in the same manner as in Example 6, except that a 1011-volume water bath liquid of Chirukoru (PVA105 manufactured by Kuraray Axis Co., Ltd.) was used. A completed catalyst was obtained in the same manner as in Example 8. The thermal shock resistance test of each catalyst obtained in Examples 1 to 7 and Comparative Example 1.2 was carried out as follows.

【Ta. That is, each sample was placed on a stand made of a 15 mm mullite plate, placed in an electric furnace set at each temperature for 30 minutes, and after 30 minutes, taken out to room temperature along with the stand, and left to cool for 30 minutes. do. This series of heating and cooling was repeated three times, and if no obvious cracking occurred in the catalyst, the temperature of the electric furnace was increased by 50° C. and the same test as above was repeated. The results obtained are as shown in Table 1 below. According to Table 1, each example according to the present invention has a ratio of
It turns out that this is better than the example. Practical Example 9 The peeling degree of each catalyst obtained in Practical Examples 1 to 7p and Comparative Examples 1 and 2 was tested as follows. That is, each of the above samples was cut with a cutter to a diameter and height of 25 mm.
After cutting into 4 pieces and thoroughly drying at 150°C, each sample was suspended in the center of a 5000C torbeaker containing 4500C wood and held for 20 minutes while generating 200W of blade power from an ultrasonic oscillator. All of the filtrate powder scattered in the separated water was calcined at 500°C with 2% filtration. The degree of peeling was calculated using the following formula. The results obtained are shown in Table 2 below. Table 2 Example 1 0.12 Weight 2 0.11# 30.14# 40.15# 50.15# Comparative example 10, 13 1 Example 60.10# t 7 0.12# Comparative example 20.
14# According to Table 2, there was no difference in peelability between each Example and each Comparative Example. Example 10 Examples 1 to 7 and Ratio 1# The activity test of each catalyst obtained in Example 1 and 2 was conducted as follows. That is, each of the above samples was cut with a cutter into a diameter of 33 cm and a length of 76 cm.
■ Cut it to h multi converter and put it in 4ki 11i2
,0OOCC engine with catalyst inlet temperature of 750℃
100 hours space 77100,000hr-1 air fuel ratio]
Bench delivery test at 5,5'! J! provided. Samples before and after durability test at intermediate speed &100,000hr' air fuel ratio 1
5.5, the catalyst activity was evaluated as the purification rate of hydrocarbon (HC) and -oxycarbon (CO), and the results are shown in Table 3. No difference in activity was found.

Claims (2)

[Claims] (1) In the manufacturing method of ceramics/two-cam touch wrinkles having an integral structure, a water-bathable polymeric organic compound film is previously formed on the honeycomb phase body before the catalyst component is added thereto.
A method for producing a Cera-containing Tsukuno Nikam catalyst with improved thermal shock resistance, characterized by: (2) The method according to claim (1), wherein the water bathing polymeric organic compound is polyvinyl alcohol.