JPH05329334A - Catalyst for purifying exhaust gas and method for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To provide a novel catalyst having high activity in the removal reaction of NOx, CO and NH3 and to realize an exhaust gas purifying device having high function. CONSTITUTION:A catalyst for purifying exhaust gas consists of a first component having the reduction activity of NOx due to NH3 and a second component having activity forming NOx from NH3 and CO2 from CO. As the first component, a compsn. composed of oxide of one or more kinds of elements selected from Ti, V, W and Mo is used and, as the second component, a compsn. containing a salt of a noble metal selected from Pt, Pd and Rh or a moble metal preliminarily supported on a porous carrier such as geolite, alumina or silica is used. Exhaust gas containing NOx, CO and NH3 is purified by this catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst and an exhaust gas purifying method using the catalyst, and more particularly to nitrogen oxide (NOx), ammonia (NH ₃ ) or carbon monoxide (CO) contained in the exhaust gas. And a catalyst suitable for purifying an exhaust gas containing a) and a method for purifying an exhaust gas using the catalyst.

[0002]

2. Description of the Related Art NOx in smoke emitted from power plants, various factories, automobiles, etc. is a causative substance of photochemical smog and acid rain, and NH ₃ was used as a reducing agent as an effective removal method. Flue gas denitration method by selective catalytic reduction is widely used mainly in thermal power plants. As the catalyst, a titanium oxide (TiO ₂ ) based catalyst containing vanadium (V), molybdenum (Mo) or tungsten (W) as an active ingredient is used. Particularly, a catalyst containing vanadium as one of the active ingredients is not active. Not only is the cost high, but deterioration due to impurities contained in the exhaust gas is small, and it can be used even at a lower temperature. Therefore, it is the mainstream of the present denitration catalyst (Japanese Patent Laid-Open No. 50-128681).

Further, in order to cope with the recent increase in electric power demand, especially in summer, the construction of gas turbines or the construction of cogeneration systems using gas turbines is increasing mainly in central Tokyo. Since these facilities are often installed adjacent to artificially dense areas and the total amount of nitrogen oxides (NOx) is regulated, the amount of NOx in the exhaust gas discharged from the facilities is extremely low. It is desired to keep Therefore, methods such as increasing the catalyst filling amount and increasing the ammonia injection amount used as a reducing agent to operate the denitration device at a high denitration rate have been studied.

With the demand for such high-level denitration, it has become essential to reduce unreacted ammonia not used in the denitration reaction (hereinafter referred to as "leak ammonia") to the NOx level or less, thereby reducing the leak ammonia. Therefore, the installation of an ammonia decomposition catalyst in the downstream of the denitration catalyst is being considered. Research has also been conducted on catalysts for decomposing this leaked ammonia, and catalysts and the like having active components of copper (Cu), iron (Fe), etc., which are excellent in ammonia oxidation activity, are known (Japanese Patent Application Laid-Open No. 2004-242242). 52-43
767, etc.).

In addition to these NOx and NH ₃ , it has been desired to suppress CO contained in combustion exhaust gas to a low level, and in a gas turbine in the United States, a platinum (Pt) -based catalyst is already used in a denitration device. A method of installing NOx in the upstream and simultaneously oxidizing and removing CO contained in exhaust gas is widely practiced.

Further, it is desired to remove not only exhaust gas from the combustor but also CO and NH ₃ emitted from various factories to a very low level, and therefore NOx and NH ₃ are required.
The realization of catalysts and processes that remove ₃ and CO at the same time has become an important social issue.

[0007]

In the above-mentioned prior art, there is a problem that in order to remove NOx and CO in the exhaust gas at the same time, a plurality of stages of catalysts are required and the process becomes complicated. For example, in a denitration apparatus in which the amount of denitration catalyst is increased to operate the denitration apparatus at a high denitration rate and the amount of injected ammonia used as a reducing agent is increased, unreacted leaked ammonia increases. As shown by the solid line in FIG. 5, which shows the behavior of the NOx concentration and the leak ammonia concentration at the catalyst layer outlet when the denitration device is operated by changing the NH ₃ / NOx ratio, NH ₃ /
This is because if the NOx ratio is operated near 1, a high denitration rate can be obtained, but the NH ₃ / NOx ratio of leaked ammonia also suddenly increases from around 1. At this time, CO in the exhaust gas is not oxidized as shown by the solid line in FIG. 5 because the denitration device has no CO decomposing ability.

In the case of a device as shown in FIG. 6, in which the catalyst layer is made into two layers in order to reduce the leaked ammonia, the conventional denitration catalyst is installed in the upstream part, and the conventional ammonia decomposition catalyst is installed in the downstream part. Shows that the amount of leaked ammonia when the NH ₃ / NOx ratio is increased is certainly reduced as compared with FIG.
Due to the oxidative decomposition of NH _3, the NO generation reaction represented by the following formula (1) occurs simultaneously, and there is a problem that a high denitration rate cannot be obtained as shown by the solid line in FIG. 7. NH ₃ + 5 / 4O ₂ → NO + 3 / 2H ₂ O (1)

In this way, in the method of simply increasing the filling amount of the denitration catalyst and installing the ammonia decomposition catalyst for suppressing the leak of unreacted ammonia in the subsequent stage, the decomposition catalyst of NH ₃ produces NOx as a by-product. However, the NOx removal rate tends to decrease, and it is extremely difficult to control both NOx and NH ₃ to low levels depending on the amount of NH ₃ to be injected and the gas conditions.

On the other hand, in the example of arranging the CO oxidation catalyst in the preceding stage of the denitration catalyst to remove CO and NOx, in order to avoid the oxidation of NH _{3 by the} CO oxidation catalyst, the CO oxidation reactor is a denitration reactor. In addition to the above, the CO oxidation reaction and the NOx denitration reaction have different optimum reaction temperatures, which makes the system complicated and expensive.

In view of the social background described above, the object of the present invention is to eliminate the above-mentioned problems of the prior art.
Providing a new catalyst that is highly active in the x, CO, and NH ₃ removal reactions, (i) a denitrification device that hardly causes NH ₃ leakage (ii) an exhaust gas purification device that can remove both CO and NOx (iii) ) To realize a highly functional exhaust gas purification device such as a purification device that can turn NH ₃ into harmless nitrogen.

[0012]

The above object of the present invention is achieved by the following basic constitution. That is, in a catalyst for purifying exhaust gas, which comprises a first component having a reduction activity of nitrogen oxides by ammonia and a second component having an activity of producing nitrogen oxides from ammonia and an activity of producing carbon dioxide from carbon monoxide. is there.

The first component is titanium (Ti), vanadium (V), tungsten (W), molybdenum (M).
a composition comprising an oxide of one or more elements selected from o), and a salt of a noble metal selected from platinum (Pt), palladium (Pd), rhodium (Rh) or zeolite, alumina, silica as the second component. It is possible to use a composition containing the noble metal previously supported on a porous body such as.

More specifically, the following are used as the first component and the second component, and the concentration of the noble metal element is 100:
To achieve this by mixing both components so as to be in the range of 0 ppm or less, adding water and kneading, shaping into a plate shape, a honeycomb shape, or a granular shape by a known method, and then calcining at a predetermined temperature to obtain a catalyst. You can

(A) As the first component, Ti-V, Ti-
Denitrification activity by NH ₃ such as oxides of any combination of Mo, Ti-W, Ti-V-W or Ti-Mo-V or zeolites such as mordenite loaded with copper (Cu) or iron (Fe) by NH _3. The composition having is used.

As the second component (B), a composition in which a salt of a noble metal such as chloroplatinic acid, palladium nitrate, rhodium chloride or zeolite, porous silica or porous alumina is preliminarily supported by ion exchange impregnation or the like. For example, a composition having a function of oxidizing NO ₃ with oxygen to generate NOx is used. Further, it is desirable to use the mixture weight ratio of the second component and the first component in the range of 1/99 to 10/90.

The present invention is also achieved by the following constitution. That is, exhaust gas purification using the catalyst as a catalyst for decomposing nitrogen oxides and carbon monoxide in the exhaust gas and decomposing unreacted ammonia among ammonia injected into the exhaust gas as a reducing agent for the nitrogen oxides. Method, or by installing the catalyst in the downstream of the denitration catalyst for catalytic reduction removal of nitrogen oxides in the exhaust gas containing carbon monoxide, nitrogen oxides and ammonia, the unreacted ammonia and one This is a method for purifying exhaust gas by decomposing and removing carbon oxide.

[0018]

FIG. 1 shows a model of pores of the catalyst according to the present invention. The structure is such that there are micropores formed by porous materials such as zeolite in the macropores formed by the denitration catalyst component (first component), and the precious metal element-containing component (second component) is supported in the micropores. It is in a state of

With such a structure, ammonia, which is easily adsorbed by the denitration catalyst component, is selectively adsorbed by the denitration catalyst component at the entrance of the macropore, and NO is diffused as shown in FIG.
It reacts with x and is consumed. Therefore, it does not reach the noble metal element-containing component (second component) in the micropore, which has a large diffusion resistance, and exhibits the same high NOx removal rate as in the case of a normal denitration catalyst.

On the other hand, when the NOx decreases and the adsorbed ammonia is not consumed, the ammonia diffuses into the micropores and reaches the second component. Further, in the case of the exhaust gas containing only ammonia, the above (1) ) And the oxygen oxidation reaction represented by the following equation (2) proceed. NH ₃ + 5 / 4O ₂ → NO + 3 / 2H ₂ O (1) NO + NH ₃ + 1 / 4O ₂ → N ₂ + 3 / 2H ₂ O (2) That is, NO generated by the equation (1) is obtained from the micropore as shown in FIG. During the process of diffusing out of the catalyst into the macropores, it collides with the ammonia adsorbed on the inner surface of the macropores and is reduced to nitrogen by the denitration reaction of the formula (2). As described above, when the catalyst of the present invention is used in the denitration apparatus using NH ₃ as a reducing agent, NO is not produced and the denitration rate does not decrease. Further, at this time, even if NH ₃ is excessively added, it is a great feature that ammonia leaked from the catalyst layer can be reduced.

When the catalyst of the present invention is used for purifying ammonia-containing exhaust gas, it can oxidize and decompose NH ₃ into N ₂ very efficiently, and various odor control devices can be realized. Not only that, but CO contained in the exhaust gas has the property of easily diffusing in the catalyst pores.
As shown in formula (3)
Oxidized to O ₂ . CO + 1 / 2O ₂ → CO ₂ (3) For this reason, this catalyst not only denitrates but also contains C contained in exhaust gas.
Another major feature is that exhaust gas can be purified by oxidative decomposition of O.

As shown above, the catalyst according to the present invention is
When NO _x is present, it acts in the same way as a normal denitration catalyst, and when NO x is consumed and ammonia becomes excessive, the catalytic action of the noble metal element-containing component (second component) and the denitration catalyst component of ammonia It is a novel three-way catalyst capable of decomposing ammonia into nitrogen by the concerted action of the (first component), and at the same time removing CO as well.
Therefore, when the catalyst of the present invention is used alone,
It is possible to suppress the amount of leaked ammonia as shown by the solid line in FIG. 5 which is caused by increasing the NH ₃ / NO ratio, which is a problem in the prior art, to an extremely low value as shown by the broken line in the figure, and at the same time remove CO.

If the catalyst according to the present invention is installed in the downstream portion of the two-layer reactor shown in FIG. 6 (a normal denitration catalyst is installed in the upstream portion) and used for oxidative decomposition of leaked ammonia, N
Since no Ox is generated, a high denitration rate can be obtained as shown by the broken line in the figure without the deterioration of the denitrification rate as shown by the solid line in FIG. Can also be reduced. Further, in this case as well, it goes without saying that CO in the exhaust gas can be removed at the same time. Further, if the catalyst of the present invention is used for removing NH ₃ -containing exhaust gas (for example, exhaust gas from a diazo copying machine), NH ₃ can be oxidized and decomposed into N ₂ extremely efficiently.

It goes without saying that the catalyst of the present invention is characterized by the constitution of the catalyst as described above, and any preparation method can be adopted as long as it can realize such a structure. However, a better catalyst can be obtained by using the following method. Of the catalyst components,
As the first component, various types as described above can be used, but a more excellent catalyst can be obtained by using the following method. Among the catalyst components, the first component may be any of the various components described above, and particularly Ti-V, Ti-V-Mo, T
Good results are obtained when an oxide catalyst composed of an element such as i-WV is used. These are salts such as vanadium, molybdenum, and oxygenates of tungsten added to a slurry of hydrous titanium oxide such as metatitanic acid, and made into a paste while evaporating water using a heating kneader, and after drying at 400 ° C. To 700 ° C., and optionally pulverized.

The addition of the second component may be carried out by a method in which the above-mentioned soluble salts of the noble metal are dissolved in water and kneaded with the powder of the first component and supported in the micropores of the first component. It is advisable to prepare a porous microporous material such as zeolite, silica, or alumina supported by ion exchange or kneading in advance and add it to the first component. Zeolite used for the second component is mordenite,
Zeolites selected from clinoptilolite, erionite, Y-type zeolite, and the like, which are hydrogen-substituted, sodium-type, and calcium-type can be used. Also,
As silica and alumina, those having a surface area of 100 m ² / g to 500 m ² / g obtained by firing a hydrous oxide at a low temperature are used. These particles have a particle size of about 1 to 10 μm, and can also be used after being crushed to the extent that the structure of zeolite or the like is not destroyed.

The noble metal is immersed in an aqueous solution in which the noble metal is dissolved in the form of its chloride, nitrate or ammine complex for ion exchange, or it is evaporated to dryness together with the aqueous solution, and 0.01 wt% to 0.1 wt% of the noble metal is added. The supported powder is obtained and used as the second component. The obtained first and second components have a second component / first component weight ratio (hereinafter, second component / first component ratio) of 20/80 to 0.5 / 99.5, preferably 10/9.
The mixture is mixed in the range of 0 to 1/99, water, an inorganic binder, a molding aid, an inorganic fiber, and other well-known moldability improvers are added to the mixture, and the mixture is kneaded by a kneader to form a paste catalyst mixture. The obtained paste-like catalyst is an inorganic fiber mesh substrate,
It is applied to a metal substrate or the like that has been roughened by thermal spraying or the like and formed into a plate-shaped catalyst, or formed into a columnar shape or a honeycomb shape by an extrusion molding machine.

The second component / first component ratio is particularly important in the present invention, and when the second component / first component ratio is larger than the above range, NOx is produced and the denitrification rate is lowered,
If it is small, there is a problem that the decomposition rate of ammonia cannot be increased. In particular, within the above range, zeolite, silica, alumina or the like having a large amount of supported precious metal is selected so that the second component / first component ratio is small, and the supported amount of the precious metal of the entire catalyst exceeds 0 ppm. 1000p
Up to pm, preferably in the range 10 to 100 ppm gives good results. As shown in the model of FIG. 1, this is because the micropores formed by the second component are sparsely present in the macropores formed by the first component, and NH ₃ is selectively adsorbed on the first component to cause denitration reaction. This is to make it easier to use.

Further, by reducing the amount of noble metal, in addition to the economical effect that the catalyst unit price can be lowered, there is also an effect that the denitration reaction and the oxidation reaction of ammonia are easily separated depending on the presence or absence of NO. Furthermore, when used with a single catalyst, the second component / first component ratio is selected to be small, and when used in a two-layer type reactor as shown in FIG. 6, the second component / first component is used. The higher the ratio and the higher the precious metal content, the easier it is to obtain good results.

[0029]

The present invention will be described in detail below with reference to examples. Example 1 Slurry of metatitanate (TiO ₂ content: 30 wt%, S
O ₄ content: 8 wt%) 67 kg of ammonium paratungstate _{((NH 4) 10 H 10} · W 12 O 46 · 6H 2 O)
3.59 kg and ammonium metavanadate 1.29 kg
Were added and kneaded while evaporating water using a heating kneader to obtain a paste having a water content of about 36%. This was extruded into a column of 3 mmφ, granulated, dried by a fluidized drier, and then calcined in the air at 550 ° C. for 2 hours. The obtained granules were pulverized with a hammer mill so that the particle size of 1 μm was 60% or more, to obtain a denitration catalyst powder as the first component. The composition at this time is V / W / Ti = 4/5/91 (atomic ratio).

On the other hand, chloroplatinic acid (H ₂ [PtC1 ₆ ] .6
The H ₂ O) 0.665 g is dissolved in a 1 liter of water, Si / Al atomic ratio of about 21, addition of H-type mordenite 500g having an average particle size of about 10 [mu] m, the Pt evaporated to dryness on a sand bath Carried. This was dried at 180 ° C. for 2 hours and then baked in air at 500 ° C. for 2 hours to obtain 0.05 wt% Pt-
Mordenite was prepared and used as the second component.

Separately from this, a twisted yarn composed of 1400 E-glass fibers having a fiber diameter of 9 μm and having a roughness of 10 yarns / inch is plain woven into a net-like material having 40% titania and 20% silica sol.
Impregnate a slurry of polyvinyl alcohol 1%, 15
A catalyst base material was obtained by drying at 0 ° C. to provide rigidity.

To 20 kg of the first component and 408 g of the second component, 5.3 kg of silica / alumina type inorganic fiber and 17 kg of water were added and kneaded with a kneader to obtain a catalyst paste. The paste catalyst mixture prepared was placed between two sheets of the catalyst substrate, and the catalyst was pressure-bonded between the stitches and the surface of the substrate by passing through a pressure roller to obtain a plate catalyst having a thickness of about 1 mm. .. The obtained catalyst was dried at 180 ° C. for 2 hours and then dried in air at 50
It was calcined at 0 ° C. for 2 hours. The second component / first component ratio of the first component and the second component in this catalyst was 2/98, and the Pt content was 10 ppm excluding the catalyst substrate and the inorganic fiber.

Comparative Example 1 A catalyst was prepared in the same manner as in Example 1 except that the second component was not added. Comparative Example 2 A catalyst was obtained by using titania (manufactured by Ishihara Sangyo Co., Ltd., trade name: CR50) produced by a chlorine method in place of the first component of Example 1. Test Example 1 The catalysts of Example 1 and Comparative Examples 1 and 2 were mixed with a width of 20
mm 3 × 100 mm, cut into 3 reactors at 3 mm intervals, and denitration rate and unreacted ammonia and CO oxidation at the reactor outlet when the amount of ammonia was changed under the conditions shown in Table 1. The rate was measured. The obtained results are shown in FIG.

[0034]

As shown in FIG. 8, the catalyst of Example 1 is C
Despite a high O oxidation rate, the denitration rate when the ammonia injection amount was increased and the NH ₃ / NO ratio was increased was equivalent to that of the denitration catalyst component alone of Comparative Example 1, and the ammonia at the reactor outlet was The concentration is as low as a few ppm. On the other hand, Comparative Example 1 hardly oxidizes CO and NH ₃ /
As the NO ratio increases, high concentrations of ammonia are detected at the reactor outlet. On the other hand, in the case of the titania containing the second component of Comparative Example 2 and having no denitration activity, the CO oxidation rate was high and the NH ₃ concentration at the reactor outlet was low, but a large amount of NOx was produced and the denitration rate was negative. Became. The decomposition rate of CO at this time was high as shown in the figure.

As can be seen from these results, the catalyst according to the present embodiment has the same high denitration rate as the ordinary denitration catalyst when the NH ₃ / NO ratio is low, due to the cooperative action of the first component and the second component as described above. When NOx is consumed in the denitration reaction, it is an extremely excellent catalyst that can reduce excess ammonia without producing NOx, and at the same time decompose and remove CO.

Examples 2 and 3 Instead of the H-type mordenite in Example 1, fine silica powder (manufactured by Tomita Pharmaceutical Co., Ltd., trade name: Microcomputer F) (Example 2) and γ-alumina powder (manufactured by Sumitomo Chemical Co., Ltd.) Was used to prepare a second component in the same manner, and a catalyst was prepared using the second component and the first component in Example 1 and the second component / first component ratio of 2/98.

Example 4 A catalyst was prepared in the same manner as in Example 2 except that 833 ml of an aqueous chloroplatinic acid solution (Pt concentration: 1.2 mg / ml) was used instead of the second component in Example 2. Example 5 In place of ammonium paratungstate in the first component preparation method of Example 2, ammonium paramolybdate ((N
Other using _{H 4) 6 · Mo 7 O} 24 · 4H 2 O) was the catalyst prepared in the same manner.

Examples 6 and 7 The chloroplatinic acid used in Example 2 was replaced with palladium nitrate (Pd).
(NO ₃ ) ₃ ) (Example 6) and rhodium nitrate (Rh
(NO ₃ ) ₃ ) (Example 7) was used instead of the nitric acid solution to prepare mordenite having a palladium or rhodium loading of 0.05 wt%. This was added to the first component in the same manner as in the case of Pt-mordenite to prepare a catalyst.

Examples 8 to 10 The second component / first component ratio in Example 2 was changed from 2/98 to 0.5 / 99.5, 1/9, 2/8, and other similar catalysts were used. Prepared. Examples 11 to 13 The second component was prepared by changing the addition amount of chloroplatinic acid in Example 2 to 2.66 g, and using this, the catalyst was used in the same second component / first component ratio as in Examples 8 to 10. Was prepared.

Comparative Example 3 A catalyst was prepared by using the first component alone without adding the second component in Example 5. Comparative Examples 4 to 7 Using the same titania as used in Comparative Example 3 except that the first component in Examples 2, 3, 6 and 7 was replaced, a catalyst was prepared.

Test Example 2 With respect to the catalysts of Examples 1 to 13 and Comparative Examples 1 to 7, under the conditions of Table 2, the denitration rate, the unreacted ammonia decomposition rate and C
The O removal rate was measured. The obtained results are summarized in Tables 3 and 4. The decomposition rate of unreacted ammonia was calculated by the following equation. Ammonia decomposition ratio (%) = {/ (inlet NH ₃ concentration - - Consumption NH ₃ concentration in the reaction NH ₃ concentration at the outlet) (inlet NH ₃ concentration - Consumption NH ₃ concentration in the denitrification reaction)} × 100

[0043]

[0044]

[Table 3]

[0045]

[Table 4]

As can be seen from Tables 3 and 4, the catalysts of the examples of the present invention showed higher denitration rate, decomposition rate of ammonia and CO oxidation rate than those of the comparative examples. It can be seen that it is an excellent catalyst capable of simultaneously removing CO and oxidizing CO while preventing leakage of unreacted ammonia.

Test Example 3 Catalyst 2 of Experimental Examples 1 to 13 and Comparative Examples 1 to 7
The NO under the above conditions was set to 0 ppm, and the decomposition rate of ammonia and the concentration of NOx produced as a by-product in the absence of NO were measured. The obtained results are summarized in Tables 5 and 6. The decomposition rate of ammonia was calculated by the following formula. Ammonia decomposition ratio (%) = {(reactor inlet NH ₃ concentration -
NH ₃ concentration at reactor outlet) / NH ₃ concentration at reactor inlet} × 10
0

[0048]

[Table 5]

[0049]

[Table 6]

Further, as is clear from Tables 5 and 6, the catalysts of the examples of the present invention have higher decomposition rates of ammonia than those of the comparative examples, and are excellent in that NOx is not generated by decomposition of ammonia. It turns out that it is a catalyst.

[0051]

EFFECT OF THE INVENTION By using the catalyst of the present invention alone, the outflow of unreacted ammonia when operating the denitration device at a high NH ₃ / NOx ratio can be made extremely low, and the oxidative decomposition of contained CO can be reduced. Can be done at the same time.

If the catalyst of the present invention is installed in the downstream of another highly active denitration catalyst and is used for decomposing unreacted ammonia (leak ammonia), unreacted ammonia will flow out due to imbalance in the injection amount of ammonia. In addition to eliminating CO2, CO that is harmful to the human body can be removed, and the multi-functional exhaust gas treatment process of the denitration device desired in the suburbs of the city can be realized.

Further, the catalyst of the present invention functions as a denitration catalyst in the presence of NOx, and as an ammonia decomposition catalyst in the absence of NOx. In addition, NOx is less likely to be generated by the decomposition of ammonia, so that the amount of the catalyst used can be significantly reduced as compared with the case where the denitration catalyst and the conventional ammonia decomposition catalyst are formed in two layers.

[Brief description of drawings]

FIG. 1 is a schematic view of a catalyst cross section for showing characteristics of the catalyst according to the present invention.

FIG. 2 is a conceptual diagram showing the action of the catalyst of the present invention.

FIG. 3 is a conceptual diagram showing the action of the catalyst of the present invention.

FIG. 4 is a conceptual diagram showing the action of the catalyst of the present invention.

FIG. 5 is a diagram showing the behavior of NOx and unreacted ammonia at the outlet of the denitration device using the conventional catalyst and the catalyst of the present invention.

FIG. 6 is a configuration diagram when a denitration catalyst and an ammonia decomposition catalyst are used in two layers.

FIG. 7 is a diagram showing a problem when a denitration catalyst and an ammonia decomposition catalyst are used in two layers.

FIG. 8 C of catalysts of Example 1 and Comparative Examples 1 and 2
It is a figure which compared O decomposition performance, denitration performance, and unreacted ammonia.

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[Procedure amendment]

[Submission date] December 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction content]

[0049]

[Table 6]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B01J 35/02 P 7821-4G (72) Inventor Ikuhisa Hamada 3 36 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Co., Ltd. Kure Laboratory (72) Inventor Hayato Morita 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory

Claims (6)

[Claims] 1. A first component having a reduction activity of nitrogen oxides with ammonia, and a second component having an activity of producing nitrogen oxides from ammonia and an activity of producing carbon dioxide from carbon monoxide. A catalyst for purifying exhaust gas. 2. A composition comprising an oxide of one or more elements selected from titanium, vanadium, tungsten and molybdenum as a first component, salts of noble metals selected from platinum, palladium and rhodium or zeolite, alumina, silica and the like. 2. The exhaust gas purifying catalyst according to claim 1, comprising a composition containing the noble metal-containing composition previously supported on the porous body as a second component. 3. The noble metal content of the catalyst is 1000 ppm.
The exhaust gas purifying catalyst according to claim 2, which is in the following range. 4. The mixing weight ratio of the second component and the first component is 1 /
The exhaust gas purifying catalyst according to claim 1, 2 or 3, wherein the catalyst is in a range of 99 to 10/90. 5. A catalyst for decomposing nitrogen oxides and carbon monoxide in exhaust gas and decomposing unreacted ammonia among ammonia injected into exhaust gas as a reducing agent for the nitrogen oxides. An exhaust gas purification method comprising using the catalyst according to any one of 1 to 4. 6. The catalyst according to any one of claims 1 to 4 in a downstream portion of a denitration catalyst for catalytically reducing nitrogen oxides in exhaust gas containing carbon monoxide, nitrogen oxides and ammonia. A method for purifying exhaust gas, which is installed and decomposes and removes unreacted ammonia and carbon monoxide in the exhaust gas.