JPS58167484A - Method for producing porous ceramic molded body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a porous ceramic molded body used as a catalyst carrier, a trapper for diesel particulate collate, and the like. A ceramic honeycomb structure having a large number of honeycomb-shaped cells is known as a porous ceramic molded body used as a carrier for supporting a catalyst such as platinum or palladium for purifying exhaust gas.

This kind of ceramic molded body not only has a large number of cells, but also the partition walls that form the cells are porous.Furthermore, because the molded body is used in a place where it comes into direct contact with exhaust gas, it has excellent heat resistance. Impact resistance and strength are required. The present invention provides a porous ceramic molded body with improved thermal shock resistance and strength.

In the present invention, it has been discovered that by coating the surface of a conventional cordierite porous ceramic molded body with powder containing lithium oxide, the thermal shock resistance and strength of the entire ceramic molded body can be improved by making it porous. I have completed the present invention.

That is, the 1J method for manufacturing the porous ceramic molded body of the present invention is similar to the conventional method, by molding and firing a mixed powder containing 7 gnesia, alumina, and silica, synthetic cola 1 lye] to 1H powder, or 2 kinds of powder to produce cordierai 1- The second step is to coat the surface of the culm and the obtained molded body material with a compound containing lithium.

＼1go, which becomes cordierite composition by firing here,
Δl 203, S i 02 Gold powder 1
．． t, chemical composition is Mg014 ω%, △l 2033
It refers to a mixed powder of kaolin, talc, aluminium (alumina, aluminum hydroxide, etc.), etc., with a chemical composition centered around 5% by weight and 51% by weight of 5iOz. Such a mixed powder reacts during firing and becomes a ceramic whose main component is diilite or cordierite.

Synthetic cordierite powder is MgO, Aft○3, S
It is heated from i 02 to form gelite ceramic, which is then powdered. Synthesis with these mixed powders]
-DiI-LyI powder can be used alone or in combination with each other.
C is also good. In addition, M(l O, A
Components other than 12O5 and St 02 may also be included.

The first step of the present invention is to mold and fire the above-mentioned raw material composition in the same manner as conventional methods to form a porous ceramic molded body material. That is, each raw material powder constituting the composition has a particle size ranging from submicron to several tens of microns, and a binder such as methylcellulose and a liquid such as water are added and kneaded using a kneader such as a kneader to prepare an extrusion material. . This extruded material is extruded into a honeycomb shape using a vacuum extruder. The extruded molded product is dried under heat. then 1
370° C. to 1450° C.) for 3 to 20 hours and sintered while producing cordierite to produce a porous ceramic molded body material. J5, molding is not limited to extrusion molding; a relatively large amount of liquid is added to the raw material composition powder to prepare a paste, and this paste is introduced into a plastic porous body (2), and after (2) As it dries,
It is also possible to decompose and remove the plastic to create a porous molded body similar to a plastic foam, which is then fired to produce a porous ceramic molded body material.

The shape of the porous ceramic molded material is not limited to the external shape, such as a honeycomb shape obtained by extrusion molding or a bubble-like cell shape.

Any lithium compound may be used as long as it becomes lithium oxide when heated, such as f-ram hydroxide, lithium nitrate, halides, or composite oxides such as magnezi N, which is a component of cordierite, alumina, and silica. But it's okay. Examples of composite oxides include lithium silicate. The coating acid for lithium oxide was 1 to 10 parts by weight of lithium oxide based on 100 parts by weight of Coke 1948, which is the material of the molded body, and 10 parts of cordierite as a mixed oxide of lithium oxide and silica, magnesia, alumina, etc.
5 to 25 parts by weight is suitable for 0 parts by weight.

The second step of the present invention, in which the surface of the molded body material is coated with a compound containing lithium, involves dissolving water-soluble lithium hydroxide and sulfur salt in water, and immersing the molded body material in this aqueous solution. This can be achieved by applying an aqueous solution to the surface and then drying it. Another method is to use a slurry in which fine powder such as richer is dispersed in a liquid, immerse the molded body material in the slurry, and coat the surface with an oxide containing richer. Note that it is preferable that the compound such as char coated on the surface of the molded body material be fired at a temperature of 600 to 1300°C, more preferably 800 to 1200°C. This firing is not always necessary. When used as a catalyst carrier, etc., it is heated with exhaust gas and can be expected to have the same effect as actually being fired. In this way, a molded body made of a porous ceramic molded body material coated with an oxide containing lithium has a strength 1.5 times that of a porous molded body without a coating layer, and a thermal shock resistance of about 600°C. temperature increases to 700-800°C.

The porous rhenomic molded body obtained by the production method of the present invention is obtained by coating the molded body with a catalyst support layer of γ-alumina, etc., and then contacting it with an aqueous solution containing white Φ etc. to support the catalyst. 111 gas purification device. It can also be used as a trapper that collects fine powder γ in exhaust gas. In this case, no catalyst support layer or catalyst is required. This will be explained below using examples.

Example 1 51% by weight of silica, 35% by weight of alumina, 1% by weight of magneja
Talc, fluorinium hydroxide, clay, etc. are blended to give a 4% concentration of talcum, 5 parts by weight of water and 20 parts by weight of a starch paste solution with 80% water are added to 100 parts by weight of this mixture, and the mixture is kneaded. The mixture was sufficiently kneaded using a vacuum extrusion molding machine to produce a honeycomb-shaped extrusion molded body. After that, after sufficiently drying, 1430
A cordierite ceramic molded body was produced by firing at ℃ for 3 hours. This molded body material was immersed in a lithium silicate aqueous solution containing 2.2% by weight of lithium oxide and 20% by weight of silica for 20 minutes, dried by flaming, and then fired at 1200°C for 2 hours to produce the present invention. A porous ceramic molded body was obtained.

Next, this porous ceramic molded body is immersed in a slurry containing γ-alumina powder to form a γ-alumina catalyst support layer by a conventional method, and then platinum is supported as a catalyst to become a catalyst for purifying automobile exhaust gas. A converter (hereinafter referred to as monolith catalyst) was obtained. In addition, several copies of the same product were manufactured for later tests.

The hydrostatic strength of this monolithic catalyst was measured as follows. In this method, first, aluminum plates with a thickness of 2Qmm and having the same outer diameter are placed on both end faces of a monorif catalyst, a urethane sheet with a thickness of In+m is wrapped around the sides, and then these are placed in a rubber chicove with a thickness of 1ml and 1l. Insert and close both ends of the rubber tube to prevent water from entering. Next, it is placed in water inside a hydraulic container, the container is sealed, and water pressure is applied. The water pressure increases and the monolithic catalyst breaks down at a certain water pressure.

The hydrostatic strength at this point of fracture is defined as the hydrostatic strength. The hydrostatic strength of the monolithic catalyst in this example was approximately 65 Kg/'cm''C on average for four pieces. From the damaged converter, the weight of lithium oxide per 100,000 parts of ]-silite was determined. The amount of lithium oxide was 1.4 parts by weight.Next, a heat l! (1) First, put the test object in a 600℃ oven for 20 minutes, then take it out and let it return to room temperature for 6 minutes.
Five cycles of thermal shock were performed, one cycle being 0 minutes of exposure. After this, the test object is examined to see if there are any cracks, and if no cracks are found, the same thermal shock is applied for five more cycles in a heating furnace heated to 100°C. The maximum temperature of the heating furnace that did not cause any cracks was the index of thermal shock resistance. The thermal shock resistance of the monolithic catalyst of this example was 80° C. for all four tested samples.

In addition, a catalytic action test of the monolithic catalyst of this example was carried out in an actual engine, and its exhaust gas purification effect was investigated. As a result, it was confirmed that there was no difference in catalytic action from conventional monolith catalysts.

For reference, only the step of immersing the molded body material in the lithium silicate aqueous solution was omitted in the above example.
A monolithic catalyst was manufactured in the same manner as in the example.

The hydrostatic strength of this monolithic catalyst is 43Kp/cm2 (
Example 2 In Example 1, the molded body material was immersed in an aqueous solution of lithium silicone, and after drying, the firing temperature was increased to 600°C. A monolithic catalyst was produced in the same manner as in Example 1 except that the temperature was changed to .degree.

The hydrostatic strength of the monolithic catalyst in this example is 51KO/C
D+” (average value of 4), thermal shock resistance is 600 for each
It was ℃.

Example 3 A monolithic catalyst was produced in the same manner as in Example 1, except that the molded body material was immersed in an aqueous lithium silicate solution, and after drying, the firing temperature was 1000°C.

Monolithic catalyst of this example still water 11 strength 19 LJL
62K Q/cm2 (average value of 4 pieces), thermal shock resistance (3 pieces at 700°C and 1 piece at 800°C).

patent applicant ! ~Yota Automobile Industry Co., Ltd. agent Patent attorney Hiroshi Okawa

Claims (4)

[Claims] (1) A porous ceramic molded body material is formed by molding and firing one or two types of synthetic cordierite powder, a mixed powder containing silica, alumina, and silica, which is converted into a cone 1 lye 1 by firing. 1. An rG method for producing a porous ceramic molded body, comprising the steps of: making a porous ceramic molded body; and coating the surface of the molded body material with a small amount of a compound containing lithium. (2) The manufacturing method according to claim 1, wherein the molded body material is coated with a lithium-containing compound and then fired at 600 to 1,300°C to obtain a 47I fineness. (3) The method of coating the surface of the molded body material with a lithium-containing compound is to dissolve a water-soluble lithium compound in water, immerse the molded body material in the aqueous solution, and apply the lithium-containing aqueous solution to the surface of the molded body material. The ¥J structure 15 method according to claim 1, which is achieved by. (4) The manufacturing method according to claim 3, wherein the water-soluble lithium compound is lithium hydroxide, lithium silicate, lithium chloride, or lithium nitrate.