JPS6227041A - Production of catalytic body for cleaning up of waste gas - Google Patents

Abstract

PURPOSE:To simultaneously clean up CO and NO2 in a waste gas at 300-900 deg.C by melting and uniting a catalyst component down to 100mum depth from the surface of a carrier contg. a lanthanide oxide thereby depositing said component on the carrier. CONSTITUTION:The catalyst mixture composed of platinum or palladium and lanthanide oxide is deposited on the carrier such as honeycomb type porous ceramic carrier molded of calcium aluminate, silicon dioxide, titanium dioxide, etc. down to about 100mum depth from the surface thereof. The carrier is then subjected to a heat treatment in a 300-1,100 deg.C temp. range by which the catalyst melted and united with the carrier and deposited catalyst for cleaning up of the waste gas is produced. The harmful materials in the waste gas are efficiently cleaned up by installing such catalyst into the waste gas flow passage of a combustion apparatus.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is installed in an exhaust gas flow path from a combustion equipment using oil, gas, solid fuel, etc. as fuel, and is used to remove carbon monoxide and hydrocarbons contained in the exhaust gas. The present invention also relates to a method for producing a catalyst body that purifies nitrogen dioxide and the like into harmless substances, and provides a catalyst body that is easy to manufacture and has excellent purification efficiency.

Conventional technology Exhaust gas from fuel devices using oil, gas, solid fuel, etc. as fuel contains odor-causing substances such as hydrocarbons,
- Contains substances that are harmful to the human body, such as carbon oxide and nitrogen dioxide, and there is a strong demand for combustion equipment that generates less of these harmful substances from the perspective of housing environments and air pollution prevention. One of the methods is to install a catalyst supporting manganese dioxide in the combustion exhaust gas flow path to oxidize and purify carbon monoxide and hydrocarbons in the exhaust gas.
This is proposed in Publication No. 831 and the like. However, these usage methods do not mention nitrogen dioxide.

Furthermore, a three-way catalyst is used to simultaneously purify nitrogen oxides such as carbon monoxide, hydrocarbons, and nitrogen dioxide in automobile exhaust gas. However, the special public service
As seen in Publication No. 66, etc., these catalyst bodies are 12
A catalyst layer made of fine powder of aluminum or silica supporting platinum, rhodium, etc. is applied to the surface of a cordierite substrate sintered at a temperature of 00° C. or higher. Furthermore, these three-way catalysts usually require an oxygen concentration of 1 g or less, and combustion conditions must be strictly controlled.

Problems to be Solved by the Invention In this way, carbon monoxide, which is contained in exhaust gas with a relatively high oxygen concentration of 6 to 15%, as in combustion equipment that uses oil, gas, solid fuel, etc. as fuel, With conventional techniques, it has been difficult to purify substances harmful to the human body, such as hydrocarbons and nitrogen dioxide, at the same time and with high efficiency using a catalyst body based on an inexpensive manufacturing method.

The present invention aims to solve such conventional problems.

To solve the problem, the present invention provides a method of applying platinum or palladium to a depth of about 100 μm from the surface of a carrier, such as a porous ceramic carrier made of lime aluminate, silicon dioxide, or titanium dioxide. This is a method for producing a catalyst body in which a mixed catalyst of lanthanide oxides is supported and heat treated in a temperature range of 300 to 1100°C, thereby melting and integrating the support and the supported catalyst. By installing such a catalyst body according to the present invention in the exhaust gas flow path of a combustion device, harmful substances in the exhaust gas can be efficiently purified.

Function: It is widely known that platinum metals such as platinum and palladium oxidize and purify carbon monoxide (Go) and hydrocarbons (HC) under conditions of 300'C or higher. The reaction is expressed by the following formula % Formula % On the other hand, nitrogen oxides in the combustion exhaust gas are nitrogen monoxide (No),
Mainly nitrogen dioxide (N02), with some N2O5, N
2o etc. are included. Of these, the most harmful to the human body is N.
The reduction of O□ is the biggest problem in preventing air pollution. The inventors focused on No. 2 and No. 2, and investigated the nitrogen oxide purification characteristics of various catalyst compositions. For this study, we considered the following equilibrium reaction as the oxidation and reduction characteristics of nitrogen oxides.

■ No + 1 /202: No2-・----(3)
■ Generally, No. and No.2 in exhaust gas from oil-burning equipment
The ratio is about 10/1 to 7/1, and the 02 concentration is 1
It is around 0%. Now, the exhaust gas from the combustor (NOx 0
゜=7/1. o2 concentration IQ%) No-NO2-
Considering the equilibrium relationship of the 02 system, the equilibrium curve shown in FIG. 6 is obtained.

That is, at temperatures above about 660° C., the reaction of formula (3) proceeds in the direction (2), and below that temperature, the reaction proceeds in the direction (2). Therefore, the present invention was discovered as a result of searching for a catalyst composition that would have a slow propagation speed in the direction (2) at low temperatures and a large propagation speed in the (2) direction at high temperatures.

Example Hereinafter, the details of the present invention will be explained with reference to Examples.

Catalyst A - 40 parts by weight of lime aluminate, 4 parts by weight of silicon dioxide
0 parts by weight, 20 parts by weight of titanium dioxide, 20% by weight of water based on the powder was added... Platinum was added to 0.1 parts by immersing the carrier formed into a nicomb shape in an aqueous platinum salt solution for 1 Q seconds.
t/l (amount of platinum per apparent volume of carrier) supported and heat treated at 10 oo'c.

Catalyst B - By immersing the same carrier as catalyst A in a palladium salt aqueous solution for 10 seconds, palladium was added to 0.1 f.
/(l) and heat treated at 1000°C.

Catalyst C - By immersing the same carrier as Catalyst A in a mixed aqueous solution of platinum salt and cerium salt for 1 Q seconds, platinum and cerium oxides were 0.15'/(lrl, o9/
1 supported and heat treated at 1000°C.

Catalyst Body - By immersing the same carrier as Catalyst A for 10 seconds in a mixed aqueous solution of palladium salt and cerium salt, palladium and cerium oxides were added to a concentration of 0.1% each. ,Q,
1.0? /(l) and heat treated at 10oo'C.

Catalyst E - The same carrier as catalyst A is a palladium salt.

By immersing it in a mixed aqueous solution of cerium salt and lanthanum salt for 10 seconds, hepalladium, cerium oxide, and lanthanum oxide were extracted with o and 1? /(1.

0.5? /l, o, s? /l supported, 1o
Heat treated at oo'C.

The above six types of catalyst bodies were prepared, and carbon monoxide (Co) and nitrogen dioxide (N
The purification effect of O2) was measured. That is, from the waste inlet portion 1 to No. 2. N0202. N2 or CQ, 02. N2
A mixed gas of
o Total 6 determines whether NO or Co in the gas exiting from the outlet.
Measure the concentration. Co purification rate is SV 80000H,
The experiment was carried out under the conditions of an inlet Co concentration of 50 ppm and an inlet 02 concentration of 10%. The results are shown in FIG. Also, No2 purification rate measurement is 5v8oooOH-1, inlet NO concentration 70p
pm, Muro No2 concentration 10ppm, inlet 02 concentration 10%
(7) Conducted under conditions. The results are shown in FIG.

As is clear from Figures 4 and 2, for Co, 3
At 00°C or higher, the total melting medium showed a purification rate of 00°C or higher.

Regarding No2, any catalyst has an extremely large effect on NO2 purification at temperatures above about 660°C. On the other hand, below 560°C, catalysts A and B tend to increase No2, while catalysts C and B tend to increase No2.
D and E have a purifying effect. The reason why catalyst bodies C, D, and E have No2 purification effect at low temperature is thought to be because the cerium oxide supported at the same time has the function of promoting the reaction in the direction of the previous formula (3) at low temperature. It will be done.

Lanthanum oxide is also thought to have a similar effect. The following description will mainly focus on catalyst bodies containing cerium oxide.

caused by Therefore, the larger the surface area of the catalyst, the greater its purification effect. The porous carrier in the present invention is
It has many pores through which gas can easily diffuse, providing a convenient field for catalytic reactions.

However, if the catalyst is attached only to the surface of the carrier, there will be insufficient reaction space, and conversely, if the catalyst is attached too deep from the surface, gas diffusion will be difficult and the catalyst will be wasted. Therefore, we prepared samples with the same catalyst composition as the catalyst body, but by controlling the catalyst concentration and immersion time, we changed the distribution of the supported catalyst in the depth direction from the surface of the carrier. The horizontal axis is the depth showing the average value of the catalyst concentration distribution by X-ray microanalyzer analysis, and the No.
Figure 1 shows the purification rate plotted on the vertical axis. That is, if the catalyst is present within 100 μm from the carrier surface,
Shows high No2 purification rate. The six types of catalyst bodies in the examples shown above were all produced so that the catalyst was supported within 100 μm from the surface of the carrier.

Further, in order to carry out the purification effect for a long period of time, it is necessary that the catalyst does not fall off from the carrier and that the two are firmly fused and integrated. This is accomplished by impregnating the carrier with the catalyst liquid and then heat-treating it at a temperature in the range of 300 to 1100°C to remove water contained in the carrier, additives during molding, and the like. It is difficult to completely remove additives during molding only by heat treatment at 3°C or lower. In addition, when the heat treatment is carried out at a temperature exceeding 110'C, the carrier and the catalyst melt violently, making it difficult to obtain good purification properties.

Effects of the Invention As described above, a catalyst body in which a mixed catalyst consisting of platinum or palladium and a lanthanide oxide is supported at a depth of about 100 μm from the surface of a porous carrier is easy to manufacture, and has no exhaust gas. When used for purification, it is possible to simultaneously purify Co and N02 in the entire temperature range of 300 to 900°C.

[Brief explanation of the drawing]

Figure 1 is a graph showing the No. 2 purification rate of samples with different catalyst distributions in the depth direction, Figure 2 is a graph showing the No. 2 purification rate of each catalyst body, and Figure 3 is a simulation device for measuring the exhaust gas purification effect. FIG. 4 is a graph showing the Co purification rate, and FIG. 5 is a graph showing the NO2 change rate curve obtained from the equilibrium relationship of the No-NO2-02 system. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
ward surface force uno;fj-se (P) Fig. 2, 7L L ('') Fig. 3 Fig. 4; A &('')

Claims (3)

[Claims] (1) A method for producing a catalyst body comprising a catalyst and a porous carrier for purifying exhaust gas from combustion equipment using oil, gas, solid fuel, etc. as fuel, the catalyst having at least a lanthanide oxide, A method for producing a catalyst for exhaust gas purification, characterized in that the catalyst is fused and integrated with a carrier and supported at a depth of 100 μm from the surface of the carrier. (2) The carrier is a honeycomb-shaped ceramic porous body made of lime aluminate, silicon dioxide, and titanium dioxide, and the catalyst is a mixed catalyst of platinum or palladium and cerium oxide. A method for producing a catalyst body for exhaust gas purification according to item 1. (3) The catalyst body for exhaust gas purification according to claim 1, wherein the catalyst body is heat-treated in a temperature range of 300 to 1100°C in order to melt and integrate the catalyst and the porous carrier. manufacturing method.