JPS6319220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst carrier consisting of whiskers.

Conventionally, granular pellets with a diameter of 3,000 microns or more and honeycomb-shaped refractories with a thickness of 200 microns or more have been used as carriers for catalysts, but these have a large heat capacity relative to the surface area of the carrier (there are many parts that do not come into contact with gas). ), it has drawbacks such as poor startability. Therefore, the present inventors first discovered that glass fiber has a diameter of 6 to 9 microns, has a large contact area with gas, and has a small heat capacity, so it has excellent starting properties. announced a catalyst using heat-resistant glass fibers containing more than 10% silica (Japanese Patent Publication No. 38264/1989); and also announced a method for forming a uniform catalyst film layer on the surface of this glass fiber (Japanese Patent Publication No. 38264/1989). 51-21629).

By the way, one of the glass fibers used as a carrier
The smaller the diameter of the book filament, the more the surface area per unit weight, while the heat capacity relative to the area in contact with the gas decreases. If this fact is approached to the limit, the activation energy on the surface of the catalyst will be transferred to the gas body without being carried away by the carrier, which will lower the starting temperature of the catalyst. This relationship, ie the effect of starting temperature (° C.) on carrier thickness (microns), is shown in FIG.

The present inventors focused on the above fact, and attempted to use particularly fine hair-like single crystal fibers, i.e., whiskers, as a catalyst carrier among needle-like crystals, with the intention of approaching the limit. .

Today, the production of whiskers is not limited to metals, but is also actively produced in refractories, such as alumina-based, silica-based, titania-based, etc. Among the titania-based whiskers, especially titania hydrate, titanic acid, etc. Barium, potassium titanate, etc. are known. Attempts to manufacture catalysts using these whiskers are not new today, but in reality, catalysts have been manufactured using whiskers, and the performance of the catalysts mentioned above, especially the start-up temperature, has been significantly improved. What has deteriorated has not appeared to this day. This is due to the fact that until now, no means has been established for uniformly coating the surface of whiskers, which are fine hair-like single crystal fibers, with catalyst components. That is, it is said that it is impossible to uniformly form the catalyst component on the surface of the whisker in the form of an extremely thin film using conventional means for coating the carrier with the catalyst component. This is because when the catalyst component-containing solution evaporates or concentrates, it moves from the surface of the carrier or aggregates on the surface, and furthermore, a bridging phenomenon occurs on the surface of the carrier. has been done.

The present inventors investigated the physical properties of these liquids, namely:
The above defects caused by surface tension and capillarity can be overcome by
It has been found that the above drawbacks can be overcome by introducing an esterification reaction into the catalyst solution and utilizing the gelling properties. This method of the present inventors basically uses the method of coating a catalyst component on a carrier, which the present inventors have previously announced. The outline of this method is to coat a carrier with an ester of a metal acid and an alcohol that is to be a catalyst component, apply the ester to the carrier surface while gelling it under heat, and then sinter it (specially (See Publication No. 51-21629).

The present inventors have further improved the method utilizing the above-mentioned gelling property as a method for uniformly coating the surface of a whisker carrier with a catalyst component.
In other words, the above technology of forming a catalyst layer with a thickness of about 0.4 microns on the surface of the carrier has been improved, and the thickness is 1/20.
The technology has been established to form a catalyst layer with a thickness of 0.02 microns on the surface of a whisker carrier.

With the establishment of this technology, the present invention has completed a catalyst carrier made of whiskers, which had been considered impossible until now. That is, the present invention has a diameter of 0.3
The gist of the present invention is a catalyst carrier for exhaust gas treatment, characterized in that it is formed by adhering submicron single crystal fibers (whiskers) to the surface of glass fibers or metal wires.

Whiskers that can be applied to the present invention are not limited and include all types of whiskers, including metal whiskers, but no matter what kind of whiskers are used, the whiskers themselves are extremely fine with a diameter of 0.3 microns or less. Because it is a single crystal fiber,
The range of applications in which it can be used as a catalyst in its current form is extremely narrow.

Therefore, in the present invention, whiskers are adhered to the surface of glass fiber or metal wire to form a catalyst carrier.

In the present invention, glass fiber or metal wire to which whiskers are bonded is formed into a cotton-like, felt-like, thread-like, cloth-like, or woven-like form.

In this way, the present invention uses whiskers as a practical catalyst carrier with a wide range of applications.

In order to uniformly coat the catalyst component on this carrier, a film-like catalyst layer is formed after adhering the whiskers to the surface of the glass fiber or metal wire in advance, or alternatively, after adhesion, the catalyst component is formed as described above. Either method can be adopted in the present invention, such as forming a film-like catalyst layer after that.

In the present invention, as a method for forming the catalyst component into a uniform film shape on the surface of the carrier, as described above, a method is adopted in which an esterification reaction is introduced into the catalyst component-containing solution and the gelling property is utilized. However, this means will be specifically explained in detail using reference examples and examples.

Reference Example 1 Add 10 parts of a 10 mol% magnesium acetate aqueous solution to 50 parts of an aqueous solution (weight ratio, same below) containing 20 mol% chromic acid, add 20 parts of propylene glycol to this mixed solution, and incubate for 1 hour. 100 parts of methanol, 200 parts of water, and 20 parts of a 0.1 mol % palladium chloride aqueous solution are added to 80 parts of the ester intermediate which has undergone the reaction and has become relatively stable, and is left to stand for 12 hours. 400 parts of this solution was applied by dip coating to 200 parts of potassium titanate whiskers (0.1 to 0.3 microns in diameter).
This is heated at 200°C for 2 hours to complete the esterification reaction. Next, ester decomposition is completed by baking at 600°C for 1 hour to form a uniform film of catalytic metal containing precious metals on the whisker surface, followed by activation treatment at 600°C for 1 hour in a reducing gas atmosphere containing hydrogen. I went to The catalyst produced in this way has a whisker surface with a diameter of 0.1 to 0.3 microns.
A uniform catalyst film layer with a thickness of 0.02 microns is formed.

FIG. 2C is a cross-sectional view of the catalyst thus produced. Note that A and B in Figure 2 are for reference only, and A is a case in which a uniform catalyst film layer of 0.4 microns in thickness is formed on the surface of a glass fiber carrier with a diameter of 6 microns. and
Catalyst B has a uniform catalyst film layer of 0.1 micron thickness formed on the surface of a ceramic short fiber carrier with a diameter of 1 micron. Both catalysts A and B carry out an esterification reaction in a catalyst component-containing solution. This product was manufactured using a method that utilizes gelling properties.

Reference Example 2 A potassium titanate whisker carrier with a diameter of 0.1 to 0.3 microns was used, the whiskers themselves were fired and formed into pellets with a diameter of 3 to 4 mm, and the surface of the whisker pellets was coated with the same method as in Reference Example 1. In this way, a uniform film-like catalyst layer was formed.

When this catalyst was placed in a cylinder with openings at both ends and lined with wire mesh, and applied to automobile pollution prevention measures (exhaust gas treatment in parking lots), the carbon monoxide concentration was
Air containing 1200ppm, SV value (space velocity) 10000
A purification rate of 91.4% was obtained under conditions where the gas was passed every hour and the processing gas temperature was 25°C.

Example Titanium oxide whisker (TiO ₂ 98.5%, fiber diameter 0.1
~0.3 micron) powder was mixed with an alumina sol aqueous solution, and this was applied by dip coating onto the surface of a glass fiber cloth (mesh equivalent to 14 mesh) formed from a filament with a diameter of 9 microns, and heated at 150°C for 2 hours and at 600°C.
After heat treatment for 1 hour, a uniform catalyst film mainly composed of platinum was formed as in Reference Example 1.

10 sheets of this catalyst cloth were stacked and used to treat the exhaust gas of a paint drying oven, and the inlet gas temperature was 82℃ and the hydrocarbon content was
1150ppm, residual air exhaust gas space velocity per hour
It was passed under the conditions of 10000, and a hydrocarbon removal rate of 94.7% was obtained.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between starting temperature (° C.) and support thickness (in microns). FIG. 2 is a cross-sectional view of a catalyst composed of three types of fiber carriers.

Claims (1)

[Claims] 1. A catalyst carrier for exhaust gas treatment, characterized in that it is made by bonding single crystal fibers (whiskers) with a diameter of 0.3 microns or less to the surface of glass fibers or metal wires.