JPS62140646A - Catalytic body for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To enhance the purification activity on both NO2 and CO by depositing a mixture of lanthanide oxide/palladium in 5-50wt. ratio on a ceramic porous body as the catalytic components to form the titled catalyst for purifying exhaust gas. CONSTITUTION:Lanthanide oxide and palladium are deposited as catalytic components on the ceramic porous body consisting of calcium aluminate, silicon dioxide, titanium dioxide, etc., to produce the catalytic body for purifying exhaust gas having 5-50wt. ratio of lanthanide oxide/palladium. When the mixing ratio of the lanthanide oxide is increased, the carbon monoxide purifying activity is deteriorated, since the surface of palladium is covered. However, high purification efficiency on both nitrogen dioxide and carbon monoxide can be obtained in 5-50 mixing ratio of lanthanide/palladium.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a catalyst body that purifies carbon monoxide, hydrocarbons, nitrogen dioxide, etc. contained in exhaust gas into more harmless substances.

Conventional technology Exhaust gas from combustion equipment such as oil, gas, and solid fuels contains substances that cause odors, such as hydrocarbons, and substances that are harmful to the human body, such as carbon oxide and nitrogen dioxide. In view of the living environment and the prevention of air pollution, there is a strong demand for combustion equipment that generates fewer harmful substances. As one method, a catalyst body in which palladium and lanthanide oxides are supported on a ceramic porous body made of lime aluminate, silicon dioxide, and titanium dioxide is installed in the combustion exhaust gas flow path, and carbon monoxide in the exhaust gas is There are ways to purify nitrogen dioxide.

Problems to be Solved by the Invention However, such catalysts have a problem in that their ability to purify carbon oxide and nitrogen dioxide decreases due to changes in the mixing ratio of palladium and lanthanide oxides.

The present invention aims to solve these problems and aims to improve the composition of the catalyst body.

Means to Solve the Problem In order to solve this problem, the present invention supports a ceramic porous body made of lime aluminate, silicon dioxide, titanium dioxide, etc. as a catalyst, and supports this lanthanide oxide and palladium. The oxide/palladium mixing ratio is in the range of 5 to 50 by weight.

Function: The nitrogen dioxide purification ability increases as the lanthanide oxide/palladium mixing ratio increases and approaches an equilibrium value. However, lanthanide oxides have almost no function as carbon monoxide purification catalysts. For this reason, when the mixing ratio of lanthanide oxide increases, the surface of palladium is covered, and the -carbon oxide purification ability decreases. If the mixing ratio of lanthanide oxide/palladium is 5 to 50, a high purification rate can be obtained for both nitrogen dioxide and carbon monoxide.

Example Embodiments of the present invention will be described in detail below with reference to the drawings.

Example 1 40M parts of lime aluminate, 4 parts by weight of silicon dioxide,
6 parts by weight of carboxymethyl cellulose as a molding aid is added to 20 parts by weight of titanium dioxide and mixed. A material obtained by adding and kneading 26 parts by weight of water to this mixed powder was extruded using a die, solidified, cured, and dried to obtain a porous ceramic carrier. By immersing this carrier in a mixed aqueous solution of palladium salt and cerium salt for 10 seconds, palladium was added to 0.1y per apparent volume of the carrier.
/fl was supported and heat treated at 1000'C.

Example 2 Palladium o, 1y7p, and cerium oxide o, 2y/fl were supported on the same carrier as in Example 1, and heat treated at 10oo'C.

Example 3 Palladium o, 1y/It and cerium oxide o, 5y/12 were supported on the same carrier as in Example 1, and heat treated at 1ooo'C.

Example 4 Palladium o, 1y/II, cerium oxide 1. oy/fl was supported and heat treated at 1000°C.

Example 5 Palladium OAy/It and cerium oxide 3. Of/β was supported and heat treated at 100O'C.

Example 6 The same carrier as in Example 1 was coated with palladium 0.1y/1. , cerium oxide5. oy/n was supported and subjected to 1000'Of heat treatment.

Example 7 Palladium o, 1y /λ and cerium oxide 7. were added to the same carrier as in Example 1. oy/f), supported, 1000'C
Heat treatment was performed.

Example 8 Palladium o, 1y/fl and cerium oxide 1o, 09t/J2 were supported on the same carrier as in Example 1, 1000'
Heat treatment was performed at C.

The above 8 types of catalyst bodies were prepared and heated to 300°C.
The carbon monoxide purification ability and nitrogen dioxide purification ability were measured. The measurement conditions are shown in Table 1, and the results are shown in the figure.

Table 1 Purification performance measurement conditions Nitrogen dioxide purification rate 1 increases as the mixing ratio of cerium oxide increases, but it hardly changes when the mixing ratio with palladium is 5 or more. On the other hand, the -carbon oxide purification rate 2 shows a nearly constant value when the mixing ratio with palladium is 60 degrees or less, but sharply decreases when it exceeds 5 degrees. In the case of nitrogen dioxide purification efficiency, both palladium and cerium oxide have nitrogen dioxide purification ability at low temperatures.

It is thought that when the two are mixed, the nitrogen dioxide purifying ability increases due to some synergistic effect. - Palladium has a catalytic ability to purify carbon oxide, but cerium oxide has almost no catalytic ability. Therefore, it is considered that when the mixing ratio of cerium oxide is 50 or more, the cerium oxide comes to cover the surface of the palladium particles, and the purification ability decreases rapidly.

The above was described for the system of palladium and cerium oxide, but a similar tendency was observed for the system of palladium and lanthanum oxide.

Effects of the Invention As described above, according to the present invention, by setting the mixing ratio of lanthanide oxide/palladium in the range of 5 to 50, a catalyst body having high purifying ability for both nitrogen dioxide and carbon monoxide can be obtained. It provides:

[Brief explanation of drawings]

The figure shows the nitrogen dioxide and carbon monoxide purification rates of catalyst bodies with different mixing ratios of cerium oxide and palladium. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] A catalyst body for exhaust gas purification in which a porous ceramic body supports lanthanide oxide and palladium as a catalyst, and the mixture ratio of lanthanide oxide/palladium is 5 to 50 by weight.