JPS589690B2 - Treatment method for exhaust gas containing carbon monoxide - Google Patents

Description

[Detailed Description of the Invention] This invention deals with carbon monoxide (CO) contained in various exhaust gases.
The present invention relates to a method for treating exhaust gas by oxidizing CO2 to harmless carbon dioxide (CO2).

In catalytic reactions, the activity and life of the catalyst are always a problem, but pressure loss due to the shape of the catalyst is also a major problem.

In particular, when a large amount of gas is treated at normal pressure, as in the case of exhaust gas treatment, there is a high possibility that the pressure loss will be large, leading to an increase in the power consumption of the blower and the like, resulting in an increase in operating costs.

In order to solve this problem of pressure loss, ceramic honeycomb carriers have been developed and are now being used in place of conventional granular carriers.

However, this carrier has a strength disadvantage in that it is easily damaged, and is not suitable for large-scale treatment such as exhaust gas treatment.

In view of the above points, the present inventors have developed a CO oxidation catalyst that does not cause the problem of pressure loss and has excellent strength and strength, and has completed the present invention.

That is, the present invention provides an exhaust gas treatment method for catalytically detoxifying carbon monoxide in the exhaust gas, in which a steel material having a predetermined shape such as a ring shape, a honeycomb shape, or a plate shape is treated with aluminum.
The steel material with the plated surface is heat treated to diffuse Al into the steel material, the steel material having an AI diffusion surface layer is subjected to AI elution treatment with an AI soluble solution to make the surface layer porous, and this steel material is oxidized. Then, the catalyst base material obtained in this way was heated with H2Pt which had been adjusted to be slightly alkaline with Ba(OH)2.
The catalyst base material is made to contain Pt by immersion in a Cl6 aqueous solution,
This is a method for treating CO-containing exhaust gas, which is characterized by drying a PT-containing catalyst base material to produce a CO oxidation catalyst, and using this catalyst to carry out a catalytic reaction of exhaust gas.

In the above, the reason why a steel material having a predetermined shape such as a ring shape, a honeycomb shape, or a plate shape is used is that the steel material has high strength and there is little risk of pressure loss occurring even when processing a large amount of exhaust gas.

Further, as the steel material, stainless steel, carbon steel, pure iron, etc. are used, but the material is not limited to these.

M-plating treatment of steel materials is performed by a method such as a hot-dip plating method, a diffusion-penetration plating method, a vacuum evaporation plating method, a thermal spraying method, or the like.

In particular, the hot-dip plating method is preferred because it is the simplest and most economical in terms of operation.

Heat treatment of steel materials whose surfaces are plated with AI is done at the melting point of AI (
660°C or higher, preferably about 800°C, for several minutes to several hours, preferably about 1 hour.

The Al elution treatment is performed by immersing the steel in an AI-soluble solution or by spraying the Al-soluble solution onto the alloy layer of the steel material.

As the AI-soluble solution, an aqueous solution of an alkali metal hydroxide, an alkali metal carbonate, an alkaline earth metal hydroxide, a mineral acid, etc., is used.

This AI elution makes the surface layer of the steel material porous.

The oxidation treatment of the steel material whose surface layer has been made porous is preferably carried out under mild conditions.

There are no particular limitations on the treatment temperature, treatment time, or oxygen concentration, but usually the oxygen concentration is 0.1 to 2 at room temperature to 400°C.
The treatment is carried out for 0.1 to 2 hours in an atmosphere containing 1% by volume.

In this way, the base material of the catalyst in this invention is formed.

The immersion treatment of the catalyst base material in the H2PtCl6 aqueous solution
Adjusted to weak alkalinity with (OH)2 aqueous solution and PtO
．． It is preferable to use an aqueous H2ptCl6 solution containing 01 to 1.0% by weight.

The preferred peak value for weak alkalinity is 8-10.

The immersion time is preferably 10 minutes to 1 hour.

This dipping treatment causes the catalyst base material to contain Pt.

After soaking, the pi-containing catalyst substrate was extracted from the solution and
Dry at 0°C or slightly higher temperature.

The catalyst thus obtained was PtO. 0 0 01~1.0
Including weight %.

Since Ba(OH)2 is a substance that is relatively insoluble in water, it is usually used as a healthy aqueous solution.

For example, to adjust the H2PtCl6 aqueous solution to weak alkalinity, prepare an H2PtCl6 aqueous solution with a concentration 10 to 15 times that of the H2PiCl6 aqueous solution to be finally prepared.
This is done by adding a saturated aqueous solution of Ba(OH)2 to make the aqueous solution weakly alkaline, and then adding a predetermined amount of water.

Here, if an aqueous H2Ptel6 solution that has not been weakly alkalized with Ba(OH)2 is used, the aqueous solution is strongly acidic (pFI direct 1 to 2), which would lead to corrosion of the catalyst base material, which would not be appropriate.

Furthermore, when aqueous ammonia is used instead of Ba(OH)2 as a pH adjuster, a suspension is already formed at pH=3 to 4, and a yellow precipitate is formed.

Therefore, ammonia water cannot be used.

Furthermore, when caustic potash is used, no precipitation occurs, but almost no CO oxidation activity is observed in the finished catalyst.

Therefore, caustic potash is also not preferred.

A CO-containing exhaust gas is passed through the catalyst thus obtained.

As a result, pressure loss is reduced and Co
Complete oxidation of can be achieved.

Furthermore, even when sulfur dioxide (S02) coexists in the exhaust gas, the catalyst is not poisoned by it and exhibits stable activity, and has only a small activity against the oxidation of SO2 to sulfuric anhydride (SO3). Not shown.

Then, Ba (O
H)2 does not have any negative effect on the activity of the CO oxidation catalyst, and the resulting catalyst still has high activity.

Moreover, since the catalyst base material is made of steel, its thermal conductivity is significantly higher than that of conventional ceramic catalysts.

Therefore, when this catalyst is used, the generated reaction heat can be easily removed even in a significantly exothermic reaction such as the oxidation reaction of CO.

Example 1 Manufacture of catalyst Stainless steel SUS 304 (J
A plate made by IS) was immersed in a molten aluminum bath at 700°C for 5 minutes, and then the plate that came out of the bath was heat-treated at 800°C in an electric furnace.

After cooling, the plate was immersed in a 10% NaOH aqueous solution at 80° C. for 3 hours, taken out from the solution, and washed with water.

Furthermore, in an air stream consisting of 2% by volume oxygen and the balance nitrogen, 1%
It was left at 00°C for 1 hour, and then left at 200°C for 1 hour in an air stream consisting of 10% by volume of oxygen and the balance nitrogen.
Finally, the plate was left to stand in air at 300° C. for 1 hour to oxidize the plate to form a catalyst base material.

On the other hand, 1% of H2PtC7I6 aqueous solution containing Ptl by weight was added.
0d was prepared, and a saturated aqueous solution of Ba(OH)2 was added dropwise thereto to adjust the temperature to 8-9.

Then, water was added to adjust the immersion treatment liquid so that the total amount was 1001 d.

This solution did not form any precipitate even if it was left for one day and night.

Therefore, the previously formed catalyst base material was immersed in this solution for 1 hour at room temperature, and after the treated product was taken out of the solution, it was heated to 110°C for 1 hour.
After drying for several hours, a catalyst was obtained.

Activity test For the catalyst thus obtained, CO oxidation rate and SO
The J conversion rate was measured.

First, the quartz flow-through reactor used in this test will be explained.

In Fig. 1, 1 is a quartz reaction tube with an inner diameter of 30+ m;
It is set inside a circular electric furnace.

2 is a lower horizontal plate made of quartz having a large number of ventilation holes 3; 4 is an upper horizontal plate made of quartz; 5 is a pair of left and right vertical plates made of quartz provided over the pair of upper and lower horizontal plates 2 and 4; A large number of protrusions 6 are provided to support the plate-shaped catalyst.

The gap 7 between the pair of vertical quartz plates 5 is open upward, and the plate-shaped catalyst is filled from there.

8 is a thermometer protection tube. First, the cavity 7 of the reactor
was charged with catalyst A, and then the reaction temperature was changed from 250°C to 450°C using a circular electric furnace, and the prepared exhaust gas for testing having the composition ratio shown in Table 1 was heated at 1.2 l/min based on the dry state. The CO oxidation rate and SO2 oxidation rate were determined by the following equations when flowing into the reaction tube at a flow rate of (S.T.P.).

The test results are shown in Figure 2.

Example 2 Following the operation in Example 1, gas was passed at 450° C. for 2 hours, and then the operation was performed again under the same conditions as in Example 1 to measure the CO oxidation rate and the S02 oxidation rate.

The results are shown in Figure 2. Example 3 Following the operation in Example 2, gas was further passed at 450° C. for 2 hours, and the CO oxidation rate was measured in the same manner as in Example 1.

The results are also shown in FIG.

Example 4 10 d of H2PtCd6 aqueous solution containing 3% by weight of Pi was prepared, and a saturated aqueous solution of Ba(OH)2 was added dropwise thereto.
I adjusted the river to 8-9.

Then, water was added so that the total amount was 100 rrLl to prepare an immersion treatment liquid.

The catalyst base material formed in Example 1 was immersed in this solution for 1 hour, and after the treated product was taken out of the solution, it was dried at 110° C. for 1 hour to obtain a catalyst.

Regarding this catalyst, the CO oxidation rate and the S02 oxidation rate were measured in the same manner as in Example 1.

The results are shown in Figure 3.

Example 5 The procedure of the example was followed by gassing at 450° C. for 2 hours, followed by the same operation as in Example 1 with CO oxidation rate and SO
The oxidation rate was measured.

The results are shown in Figure 3.

Example 6 Following the operation in Example 5, gas was further passed at 450° C. for 2 hours, and then the CO oxidation rate, SQ, and oxidation rate were measured in the same manner as in Example 1.

The results are also shown in FIG.

Comparative Example 1 H2P containing 1% by weight of Pt as pti-containing immersion treatment liquid
Using the tCl6 aqueous solution as it was without adjusting the pH, other operations were performed in the same manner as in Example 1 to obtain a catalyst, and then the CO oxidation rate, SQ, and oxidation rate of this catalyst were measured in the same manner as in Example 1. .

The results are shown in Figure 4.

Comparative Example 2 Following the operation in Comparative Example 1, gas was passed at 450° C. for 2 hours, and then the CO oxidation rate and the So2 oxidation rate were measured in the same manner as in Example 1.

The results are also shown in FIG.

Comparative Example 3 KO was used instead of Ba(OH)2 aqueous solution as a pH adjuster.
Using an H aqueous solution, other operations were performed in the same manner as in Example 1 to obtain a catalyst, and then the CO oxidation rate and S02 oxidation rate of this catalyst were measured in the same manner as in Example 1.

The results are shown in Figure 5. Comparative Example 4 Following the operation in Example 3, gas was passed at 450° C. for 2 hours, and then the CO oxidation rate and the S02 oxidation rate were measured in the same manner as in Example 1.

The results are also shown in FIG.

Comparative Example 5 Using NaOH aqueous solution instead of B a (OH ) 2 aqueous solution as a PH adjuster, other operations were performed in the same manner as in Example 1 to obtain a catalyst, and then this catalyst was subjected to the same operations as in Example 1. The CO oxidation rate and the So2 oxidation rate were measured.

The results are shown in Figure 6. As can be seen from a comparison between FIGS. 2 and 3 and FIGS. 4, 5, and 6, according to the method of the present invention, Co in the exhaust gas can be efficiently oxidized. Even if SO2 coexists, oxidation of SO2 can be suppressed as much as possible.

Moreover, since the catalyst has excellent SO2 resistance, it can be used stably and continuously for a long period of time.

[Brief explanation of drawings]

Figure 1 is a cutaway perspective view showing the reaction device for activity testing;
From Figure 6 Figure 1 is a graph showing the relationship between reaction temperature and oxidation rate for each catalyst, and Figure 2 is a graph showing the relationship between the reaction temperature and oxidation rate for each catalyst.
Figure 3 shows the catalysts of Examples 4, 5 and 6, Figure 4 shows the catalysts of Comparative Examples 1 and 2, and Figure 5 shows the catalysts of Comparative Examples 3 and 4.
and FIG. 6 relates to the catalyst of Comparative Example 5, respectively.

Claims (1)

[Claims] 1. In an exhaust gas treatment method that oxidizes and detoxifies carbon monoxide in exhaust gas, a steel material having a predetermined shape such as a ring shape, a honeycomb shape, or a plate shape is aluminum-plated, and the steel material with the plated surface is heat-treated. diffuse aluminum into the steel material, treat the steel material with an aluminum diffused surface layer with an aluminum soluble solution to make the surface layer porous, and oxidize the steel material,
The catalyst base thus obtained is immersed in a chloroplatinic acid aqueous solution adjusted to be weakly alkaline with barium hydroxide to make the catalyst base contain platinum, and the platinum-containing catalyst base is dried to become a carbon monoxide oxidation catalyst. A method for treating exhaust gas containing carbon monoxide, which comprises producing a catalyst and carrying out a catalytic reaction of exhaust gas using this catalyst.