JPS5810135B2 - High Gas Jiyou Kayoshiyoku Baitai - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid catalyst used for purifying exhaust gas, particularly carbon monoxide and hydrocarbons, and provides an inexpensive catalyst with excellent wear resistance and long life.

Conventional catalyst bodies for exhaust gas purification are mostly produced by using alumina balls or glass fibers as a carrier, impregnating the carrier with a water-soluble catalytic metal salt, and depositing the catalyst on the carrier by thermal decomposition.

Catalyst bodies obtained by such conventional methods are not only uneconomical because the alumina or glass fiber supports are expensive, but also have poor wear resistance due to vibrations because it is extremely difficult to impregnate the catalyst into the support. It has drawbacks such as being weak and therefore having a short catalyst life and poor heat resistance.

The present invention aims to eliminate the above-mentioned conventional drawbacks and provide a catalyst body that has excellent exhaust gas purification ability, is inexpensive, and has constant quality.

That is, the present invention converts manganese dioxide into lime silicate (mca
This is a catalyst body for exhaust gas purification characterized by being bonded and solidified using the following method.

To manufacture this catalyst body, a mixture of manganese dioxide and lime silicate is wet-mixed by adding enough water to form it, and after being formed, it has a hardness sufficient to maintain its shape. A suitable method is to perform primary curing to achieve the following, and then add moisture to completely cure and solidify.

As the binder, any lime silicate commercially available as Portland cement can be used.

As the main catalyst, electrolytic manganese dioxide obtained by electrolyzing an aqueous solution of manganese salt is used.
Naturally produced manganese dioxide ore and chemically treated manganese dioxide may be used.

However, from the viewpoint of uniformity of catalyst performance, it is preferable to use electrolytic manganese dioxide.

The pH value of manganese dioxide is also very important, and a suitable pH value ranges from 4.0 to 8.0 when measured with 20% NH4Cl.

The reason for this is that the lime content (Cab) as a binder reacts with the acid in electrolytic manganese dioxide, which affects the binding force of the binder, and the pH value of manganese dioxide is 4.
If it is less than 0, the bonding force becomes weak.

Since the particle size of manganese dioxide affects the active surface of the catalyst and the mechanical strength of the molded article, it is suitable that the average particle size is in the range of 3 to 30 microns.

Next, regarding the co-catalyst, one of the purposes of the present invention is to obtain an inexpensive catalyst body, so cheap manganese dioxide is selected as the main catalyst, and silicate lime as a binder also serves as a co-catalyst. .

However, it is also possible to add other promoters to further improve the carbon monoxide purification ability at low temperatures and to improve the carbon monoxide conversion rate.

NiO, CuO as promoters. V2O5, Co3 o,
1 pbo 1 TiO2, etc. can be arbitrarily selected and added depending on the purpose.

Table 1 shows preferred blending ratios (weight ratios) of materials used in the present invention.

Lime silicate as a binder may not be impossible to manufacture even if it is less than 10% by weight, but the mechanical strength of the molded product will be weakened.
Approximately 80% by weight is preferable.

The amount of water required for molding is too large, and molding becomes difficult.

If the amount is too small, cracks will occur in the molded product, and molding will become difficult.

The optimum value for moisture is set with the most emphasis on moldability.

Since this moisture content at the optimum value for molding is insufficient as bound water during curing, water is added again during complete curing.

Therefore, the water content in Table 1 means the amount from the viewpoint of moldability.

Next, the present invention will be explained in more detail with reference to Examples.

Table 2 shows examples of formulations using Portland cement and manganese dioxide, and those using copper oxide as a co-catalyst.

After thoroughly dry-mixing the mixtures in the proportions shown in Table 2, excluding water, water is added and wet-mixing is performed.

Thereafter, a rod-shaped molded product with a diameter of 3 to 5 mm is obtained using an extrusion molding machine.

Only the surfaces of the molded products are dried to prevent them from bonding to each other.

Thereafter, primary curing is performed by leaving the molded article until it has a certain degree of mechanical strength.

After that, since the moisture shown in Table 2 is still insufficient for complete curing, complete curing is performed by sprinkling with water or in water, hot water, or steam.

The solid catalyst thus obtained is extremely effective in purifying exhaust gas.

Note that the reactions in which manganese dioxide is used to purify exhaust gas to cause carbon monoxide to react with carbon dioxide gas, and reactions in which hydrocarbons react with water and carbon dioxide gas are all exothermic reactions, so the temperature rises.

Furthermore, as will be described later, when used for purifying automobile exhaust gas, etc., it will be exposed to high temperatures.

Manganese dioxide undergoes the following thermal transformation due to such heat.

260℃ 650℃ 950℃CMnO2
→ β-Mn02 → Ct-Mn2O3 → Mn3O4 M
It is also possible to use n2O3 and Mn3O4 as raw materials, but these are basic oxides and are chemically more unstable than MnO2, and the bond strength will be weak unless the ratio of 1 binder is increased.

2 Expensive as a raw material, 3 Mn 02. It is advantageous to use manganese dioxide because the catalyst performance is more stable and the life is longer when it is transformed during use.

In order to test the catalytic activity of the catalyst body thus obtained, a test was conducted using a JARI type (Japan Automobile Research Institute) gas phase contact type apparatus.

As the test conditions, a gas of 5% carbon monoxide and residual nitrogen was used at a flow rate of 21/min, and at the same time, dry air was fed at a flow rate of 0.51/min.
Using 5 g of the above-mentioned catalyst fed at a flow rate of /min, the catalytic ability was tested by a gas phase contact heating method.

Table 3 shows actually measured values when carbon monoxide was converted to carbon dioxide at a catalyst temperature of 500°C.

The upper part was measured based on the test method for automobile exhaust gas, but the same catalyst and about 11 of the above catalysts were installed 5 cm above the flame of a convection type kerosene stove, and the catalyst for converting carbon monoxide to carbon dioxide. When the performance was measured, it was 55 ppm without a catalyst, but when passed through a catalyst, it was 5 to 8 ppm.
m.

The above catalyst can be used to purify carbon monoxide and hydrocarbons in combustion gas from various oil stoves, various gas combustion appliances, various engines, etc. into carbon dioxide gas and water by changing the granulation method or molding method of the catalyst body. Can be used.

Since the catalyst body for exhaust gas purification of the present invention is made by bonding and solidifying manganese dioxide with silicate lime as described above, it is possible to easily obtain a catalyst body having a desired shape and composition.

Therefore, it is suitable for mass production of catalyst bodies in desired shapes such as granular or honeycomb structures depending on the application.

Furthermore, since it uses silicate lime as a binder, it is extremely economical, and has features such as, for example, even if the surface is worn away, the next exposed part has a constant composition, so the gas purification ability is always constant.

Claims (1)

[Claims] 1. A catalyst for exhaust gas purification characterized by manganese dioxide bound and solidified with lime silicate.