JP2009022928A - Nitrogen oxide decomposition catalyst, nitrogen oxide decomposition apparatus provided with the same, and nitrogen oxide decomposition method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a decomposition catalyst which can decompose nitrogen oxide simply at a low cost, a small-sized nitrogen oxide decomposition apparatus provided with the same, and a nitrogen oxide decomposition method using the same. <P>SOLUTION: The nitrogen oxide catalyst comprises a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component both of which are joined with each other to allow electrons to move between the catalyst components, and further are joined with each other with a proton-conductive solid electrolyte allowing protons to move between the catalyst components independently from the above joint, and decomposes nitrogen oxide in the presence of hydrogen. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a catalyst for decomposing nitrogen oxide (also referred to as “NOx”), which is harmful to the human body and causes photochemical smog and acid rain, a nitrogen oxide decomposing apparatus including the same, and a nitrogen oxide using the same It relates to a decomposition method. INDUSTRIAL APPLICABILITY The present invention can be suitably used for purifying nitrogen oxides in exhaust gas discharged into the atmosphere from internal combustion engines such as boilers, gasoline engines, and diesel engines, power generation plants, and industrial plants.

In recent years, nitrogen oxides in exhaust gas have been a problem from the viewpoint of protecting the global environment and preventing air pollution, and solutions have been studied.
However, since the exhaust gas contains excess oxygen (O ₂ ), it is extremely difficult to reduce the nitrogen oxides in the exhaust gas to nitrogen (N ₂ ) under such an oxygen-excess atmosphere.

Therefore, a catalyst method, a wet absorption method, an electron beam irradiation method, a plasma method, and the like have been proposed as a denitration technique for removing nitrogen oxides in exhaust gas.
The wet absorption method, the electron beam irradiation method, and the plasma method involve a large amount of energy consumption and post-treatment of the absorbing solution, and thus have a problem in cost.
On the other hand, the catalytic method is attracting attention as an inexpensive method that does not react with excess oxygen and consumes relatively little energy, and its research has been active year by year. In the catalytic method, nitrogen oxides are selectively decomposed in the presence of a reducing agent such as ammonia (NH ₃ ), hydrocarbon (HC), or hydrogen (H ₂ ).

In the catalyst method using ammonia as the reducing agent, a high nitrogen oxide removal rate of 80% or more is obtained using, for example, V ₂ O ₅ —TiO ₂ as the catalyst. For this reason, it is most frequently applied to the purification of nitrogen oxides in large fixed exhaust gas generation sources such as industrial plants. However, it is not easy to handle toxic ammonia, and it is extremely difficult to apply it to a small fixed exhaust gas generation source because the equipment is large in size and requires a high maintenance cost. In addition, the operating temperature (catalyst temperature) in this method is 300-400 degreeC.

In the catalytic method using a hydrocarbon as a reducing agent, for example, Cu-zeolite is used as a catalyst, and nitrogen oxide is decomposed by hydrocarbons such as propane (C ₃ H ₈ ) in the presence of oxygen. As low as 30%. In addition, the operating temperature in this method is 300-400 degreeC.

  In the catalytic method using hydrogen as a reducing agent, nitrogen oxides are decomposed by using, for example, alumina, silica, zeolite or the like carrying Pt as a catalyst (see, for example, JP-A-5-168856 (Patent Document 1)). ). However, this catalytic method has a slow reaction rate for the decomposition of nitrogen oxides in the presence of oxygen, requires a large amount of expensive noble metal catalyst, and cannot be said to have practical performance, and needs to be improved. is there. In addition, the operating temperature in this method is 150-300 degreeC.

A method of electrochemically decomposing nitrogen oxide using a solid electrolyte has also been proposed. For example, a zirconia-based oxygen ion conductive solid electrolyte (see Japanese Patent Application Laid-Open No. 2003-265926 (Patent Document 2)) and a proton conductive solid electrolyte (refer to Japanese Patent Application Laid-Open No. 7-136455 (Patent Document 3)). There is an example used.
However, these electrochemical methods require an external power source to energize both the anode and cathode electrodes provided on both sides of the solid electrolyte. In particular, in the former case, removal of the coexisting oxygen occurs preferentially, so that a large amount of energy is required for decomposition of the nitrogen oxides.

  Furthermore, in the electrochemical method, the operating temperatures of the solid electrolyte that exhibits oxygen ion conductivity and proton conductivity are 600 to 1000 ° C. and 300 to 1000 ° C., respectively. Therefore, the exhaust gas other than the exhaust gas such as a diesel engine in a lower temperature range than this temperature range needs to be heated by an external heater or the like, that is, a large amount of energy is input, resulting in low energy efficiency.

  Further, in the electrochemical method, exhaust gas is circulated only on one surface of the solid electrolyte in the electrode / solid electrolyte / electrode three-layer structure, so that the decomposition efficiency of nitrogen oxide per unit volume is low, and the large capacity A decomposition reactor is required, and it is difficult to control the thickness of each layer in the formation of a three-layer structure, which requires a complicated manufacturing process of the reactor, and its practical use is difficult.

  The operating temperature in the above prior art method for decomposing nitrogen oxides is higher than the exhaust gas temperature of 200 to 400 ° C. and the exhaust muffler inlet temperature of 150 to 200 ° C. There is the actual situation that the nitrogen oxides of the can not be decomposed. Therefore, a method capable of decomposing nitrogen oxides at a lower temperature is strongly desired.

JP-A-5-168856 JP 2003-265926 A Japanese Patent Laid-Open No. 7-136455

As described above, useful nitrogen oxide purification (decomposition) technology has not been established for small fixed exhaust gas generation sources such as household combustors and mobile exhaust gas generation sources such as automobiles.
Accordingly, it is an object of the present invention to provide a decomposition catalyst that can decompose nitrogen oxides easily and at low cost, a small-sized nitrogen oxide decomposition apparatus including the decomposition catalyst, and a nitrogen oxide decomposition method using the decomposition catalyst. And

  As a result of intensive studies to solve the above problems, the present inventor has joined the hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component so that electrons and protons can move separately. The present inventors have found that a catalyst capable of efficiently decomposing nitrogen oxides in the presence of hydrogen has led to the completion of the present invention.

  Thus, according to the present invention, the oxidation catalyst component of hydrogen and the reduction catalyst component of nitrogen oxide are joined so that electrons can move between the two catalyst components, and separately between the two catalyst components. There is provided a nitrogen oxide decomposition catalyst for decomposing nitrogen oxides in the presence of hydrogen, wherein the catalyst is bonded with a proton conductive solid electrolyte capable of transferring protons.

In addition, according to the present invention, a catalyst part including the above-described nitrogen oxide decomposition catalyst, an inlet flue for introducing exhaust gas into the catalyst part, and an outlet flue for discharging the exhaust gas treated in the catalyst part An apparatus for decomposing nitrogen oxides is provided.
Furthermore, according to the present invention, there is provided a method for decomposing nitrogen oxides, characterized in that exhaust gas is treated with the above-described nitrogen oxide decomposition catalyst to decompose nitrogen oxides in the exhaust gas. .

ADVANTAGE OF THE INVENTION According to this invention, the decomposition catalyst which can decompose | disassemble nitrogen oxide easily and at low cost, the small-sized nitrogen oxide decomposition | disassembly apparatus provided with the same, and the decomposition | disassembly method of nitrogen oxide using the said decomposition catalyst can be provided. It is extremely useful in industry.
In particular, according to the present invention, nitrogen oxides can be efficiently decomposed at a low temperature of 200 ° C. or less without the need for an external power source, and the decomposition of nitrogen oxides can be achieved more than a method using only a noble metal such as Pt. Since the efficiency is high and the amount of noble metal used can be reduced, the cost can be reduced.

  The nitrogen oxide decomposition catalyst for decomposing nitrogen oxides in the presence of hydrogen of the present invention is such that the hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component can transfer electrons between the two catalyst components. In addition to the joining, the joining is performed with a proton conductive solid electrolyte capable of transferring protons between both catalyst components.

Although the decomposition mechanism of the nitrogen oxide of the present invention is not clear, it is presumed to be due to the reaction process shown in the following formula.
Anode: 2H ₂ → 4H ⁺ + 4e ^{−
Cathode: 2NO + 4H + + 4e -} → N 2 + 2H 2 O
That is, the oxidation catalyst component of hydrogen acts as an anode to protonate hydrogen, and the generated protons pass through a proton conductive solid electrolyte, and the generated electrons pass through a support made of a conductive material, or directly It is assumed that the nitrogen oxides acting as the cathode move to the reduction catalyst component and reduce the adsorbed nitrogen oxides.

  The hydrogen oxidation catalyst component used in the present invention is preferably at least one metal selected from platinum group metals of Pt, Ru, Rh, Pd and Ir, or a compound thereof.

  The reduction catalyst component of nitrogen oxide used in the present invention is at least one metal selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Cd, Sn, Pb and Zn or a compound thereof Is preferred.

The weight ratio of the hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component used in the present invention is appropriately set depending on the concentration and temperature of the exhaust gas containing the nitrogen oxide to be treated and other conditions. Usually, the reduction catalyst component of nitrogen oxide is preferably 1 to 500 parts by weight, particularly preferably 5 to 200 parts by weight, based on 1 part by weight of the hydrogen oxidation catalyst component.
When the nitrogen oxide reduction catalyst component is less than 1 part by weight with respect to 1 part by weight of the hydrogen oxidation catalyst component, the nitrogen oxide removal rate may decrease. On the other hand, when the reduction catalyst component of nitrogen oxide exceeds 500 parts by weight, the apparatus provided with the decomposition catalyst may be enlarged.

The proton conductive solid electrolyte used in the present invention includes a fluororesin proton conductive solid polymer (for example, perfluorosulfonic acid polymer) and a hydrocarbon proton conductive solid polymer, and a barium cerium system. It is preferably at least one selected from barium zirconium, calcium cerium, calcium zirconium, zirconium strontium and cerium strontium perovskite oxides.
Examples of the fluororesin proton conductive solid polymer include perfluorosulfonic acid polymer (manufactured by DuPont, Nafion (registered trademark)), and examples of the hydrocarbon solid polymer include sulfonated polyimide. Can be mentioned.
Among these, a fluororesin-based proton conductive solid polymer is particularly preferable from the viewpoint of decomposition activity at low temperatures.

In the nitrogen oxide decomposition catalyst of the present invention, (1) the hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component are dispersed on the same plane of the support made of a conductive material, or (2 It is preferable that the hydrogen oxidation catalyst component is dispersedly arranged on the conductive nitrogen oxide reduction catalyst component and joined so that electrons can move between the two catalyst components.
1 and 2 are schematic cross-sectional views showing the main structure of a nitrogen oxide decomposition catalyst according to the present invention having the arrangement forms (1) and (2), respectively. In the figure, 1 is a hydrogen oxidation catalyst component, 2 is a nitrogen oxide reduction catalyst component, 2 (4) is a conductive nitrogen oxide reduction catalyst component, 3 is a proton conductive solid electrolyte, and 4 is conductive. A support made of a substance is shown.

  The support (carrier) made of a conductive material used in the present invention is not particularly limited as long as it functions as an electrical connection member. Specific examples include carbon carriers such as carbon black, acetylene black, activated carbon, and amorphous carbon.

Arrangement form (1)
As a method for dispersing and supporting (supporting) a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component on the same plane of a support (support) made of a conductive material, a known method such as an impregnation method or a precipitation method is used. Is mentioned. In general, an impregnation method in which a carrier is impregnated with a solution obtained by dissolving a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component in a solvent is particularly preferable.

Examples of the solution in which the hydrogen oxidation catalyst component is dissolved in a solvent include hexachloroplatinic (IV) acid hexahydrate, dinitrodiammineplatinum (II) nitric acid solution and the like in the case of Pt.
Examples of the solution obtained by dissolving the nitrogen oxide reduction catalyst component in a solvent include nickel chloride aqueous solution, nickel sulfate aqueous solution, nickel nitrate aqueous solution and the like in the case of Ni.

  In addition, a reducing agent such as sodium borohydride or alcohol such as ethyl alcohol is added to these solutions in order to deposit a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component on the support. Of these, ethyl alcohol is particularly preferred from the viewpoint of industrial availability and easy handling. Further, hydrogen gas may be used as a reducing agent.

Arrangement form (2)
Examples of the method for dispersing (supporting) the hydrogen oxidation catalyst component on the conductive nitrogen oxide reduction catalyst component include, for example, a hydrogen oxidation catalyst component and a proton conductive solid electrolyte solution or a mixed solution of a slurry. And a method of coating on a reduction catalyst component of nitrogen oxide having conductivity.
Examples of the shape of the conductive nitrogen oxide reduction catalyst component to be coated include a plate shape, a pellet shape, a honeycomb shape, a porous shape, and the like. Among these, pressure loss during exhaust gas circulation is included. A metal porous body integrally formed with a metal component material of a reduction catalyst component of nitrogen oxide having conductivity at low points is preferable.
Further, the hydrogen oxidation catalyst component may be a single metal component material, or the metal component material may be supported on a conductive support such as a carbon carrier.

  The nitrogen oxide decomposition apparatus according to the present invention exhausts the exhaust gas treated in the catalyst section including the catalyst section including the nitrogen oxide decomposition catalyst of the present invention, an inlet flue for introducing exhaust gas into the catalyst section, and the catalyst section. An exit flue is provided.

  3 and 4 are schematic views showing the main configuration of the nitrogen oxide decomposing apparatus of the present invention. In the figure, 11 is a decomposition device, 12 is an inlet flue, 13 is an outlet flue, 14 is a catalyst unit, 15 is a hydrogen gas injection device, E is exhaust gas, H is hydrogen gas, and arrows indicate gas flow.

  When decomposing nitrogen oxides in actual exhaust gas according to the present invention, it is preferable that the catalyst portion is formed of the nitrogen oxide decomposing catalyst of the present invention in a three-dimensional structure. Examples of the forming method include coating.

  FIG. 5 is a schematic cross-sectional view showing the main configuration of the catalyst portion of the three-dimensional structure used in the nitrogen oxide decomposition apparatus of the present invention. In the figure, 5 is a three-dimensional structure (honeycomb carrier), 6 is a cell (gas flow space), 7 is a lattice, 8 is a carrier layer, and 9 is a catalyst (see FIG. 1).

Examples of the three-dimensional structure include pellets and honeycomb carriers, and an integrally formed honeycomb carrier is preferable from the viewpoint of low pressure loss when exhaust gas flows.
Examples of the honeycomb carrier include a monolith honeycomb carrier such as a ceramic honeycomb carrier and a metal honeycomb carrier.
Examples of the ceramic honeycomb carrier include honeycomb carriers made of cordierite, mullite, α-alumina, zirconia, titania, silicon carbide and the like, and among these, cordierite honeycomb carriers are particularly preferable in terms of light weight. .
Examples of the metal honeycomb carrier include an integral structure made of an oxidation-resistant heat-resistant metal such as stainless steel and Fe—Cr—Al alloy.

The shape and size of the lattices (cells) in the honeycomb carrier are not particularly limited as long as the exhaust gas flow containing nitrogen oxides can be efficiently brought into contact with the catalyst part. What is necessary is just to set suitably.
The number of cells in the honeycomb carrier is usually about 100 to 400 cells / (25.4 mm) ² (100 to 400 cpsi).

Examples of the coating method include the following methods (a) to (c), but are not limited to these methods as long as they do not contradict the gist of the present invention.
(A) A mixed solution of a support carrying a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component is impregnated in an inorganic oxide, dried, and calcined as necessary. Water or the like is added to the obtained powder and wet pulverized to form a slurry, which is applied to a three-dimensional structure, dried, and fired as necessary.
(B) Water or the like is added to the inorganic oxide and wet pulverized to form a slurry, which is applied to the three-dimensional structure, dried, and fired as necessary. The obtained three-dimensional structure is impregnated with a mixed solution of a support carrying a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component, dried, and calcined as necessary.
(C) An inorganic oxide is partially impregnated with a mixed solution of a support carrying a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component, dried, and calcined as necessary. Water or the like is added to the obtained powder and wet pulverized to form a slurry, which is applied to a three-dimensional structure, dried, and fired as necessary. The obtained three-dimensional structure is impregnated with the rest of the mixed solution of the support on which the hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component are supported, dried, and calcined as necessary.

  Examples of the inorganic oxide used for coating include alumina, silica, titania, magnesia, zirconia, and among these, alumina is particularly preferable from the viewpoint of miniaturization. In the methods (a) to (c), an inorganic oxide is used. However, if the catalyst part is coated on the three-dimensional structure, the inorganic oxide may not be used.

Next, a proton conductive solid electrolyte is disposed between the catalyst components so that the hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component can move protons between the catalyst components.
Specifically, a proton conductive solid electrolyte solution or slurry as described above is applied to a three-dimensional structure coated with a support carrying a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component and dried. And firing as necessary.

  In the above method, the proton conductive solid electrolyte was formed in the final step, but the formation procedure is not particularly limited as long as it does not contradict the gist of the present invention. For example, a support carrying a hydrogen oxidation catalyst component and a nitrogen oxide reduction catalyst component impregnated with a solution or slurry of a proton conductive solid electrolyte, dried, and calcined as necessary, has a three-dimensional structure. It may be coated on the body.

The inlet flue in the nitrogen oxide decomposition apparatus of the present invention is a small fixed exhaust gas generation source such as an internal combustion engine such as a boiler, a gasoline engine, or a diesel engine, a power generation plant, an industrial plant, or a household combustor. The exhaust gas is connected to a moving exhaust gas generation source such as an automobile and introduced into the catalyst unit.
The outlet flue discharges the exhaust gas treated in the catalyst portion, that is, the residual gas after decomposing nitrogen oxides, to the outside of the decomposition apparatus.

  As long as these inlet flues and outlet flues are capable of efficiently introducing an exhaust gas flow into the catalyst unit and exhausting the exhaust gas treated in the catalyst unit out of the decomposition device, respectively. There is no particular limitation, and the material and shape may be set as appropriate depending on the processing capacity of nitrogen oxides.

  The nitrogen oxide decomposition method of the present invention is characterized in that exhaust gas is treated with the nitrogen oxide decomposition catalyst of the present invention using hydrogen as a reducing agent to decompose the nitrogen oxide in the exhaust gas.

  The exhaust gas is not particularly limited as long as it contains a nitrogen oxide as described above. For example, the exhaust gas is introduced into the atmosphere from an internal combustion engine such as a boiler, a gasoline engine, a diesel engine, a power generation plant, an industrial plant, or the like. Exhaust gas emitted into the atmosphere from a small fixed exhaust gas generation source such as a household combustor or a mobile exhaust gas generation source such as an automobile.

In the method of the present invention, hydrogen is used as a reducing agent.
Exhaust gas to be treated was burned with a fuel that was steam reformed or a fuel that was burned with a fuel that was reformed by a water gas shift reaction of carbon monoxide, etc., with an excess of fuel (rich) than the normal air-fuel ratio When an appropriate amount of hydrogen is contained together with nitrogen oxides such as gas, only the exhaust gas may be treated by the method of the present invention.
However, when the exhaust gas to be treated does not contain an appropriate amount of hydrogen together with nitrogen oxides, hydrogen may be injected as a reducing agent into the exhaust gas before treatment.

The amount of hydrogen in the exhaust gas may be appropriately set depending on the concentration of nitrogen oxides, the temperature of the exhaust gas, and other conditions. Usually, the hydrogen concentration in the exhaust gas is less than 4% of the lower explosion limit, It may be in the range of 1 to 100 times the nitrogen oxide.
Therefore, when the amount of hydrogen in the exhaust gas is less than 1 times that of nitrogen oxides, the reducing gas is used as a reducing agent in the exhaust gas before treatment in order to improve the decomposition efficiency in terms of the size and cost of the decomposition apparatus Hydrogen may be injected.
That is, as shown in FIG. 4, the decomposition apparatus may be accompanied by a hydrogen gas injection device 15 that injects a hydrogen-containing gas between the inlet flue 12 and the catalyst unit 14.
Here, the hydrogen-containing gas means a mixed gas obtained by diluting the hydrogen gas with a nitrogen gas, an inert gas (for example, helium, argon) or the like in addition to the hydrogen gas.

  Hydrogen gas injection devices are, for example, hydrogen storage facilities such as cylinders and tanks, hydrogen generators that generate hydrogen by reforming city gas or methanol using a catalyst, water or steam electricity using proton conductive solid electrolyte What is necessary is just to provide the hydrogen generator which produces | generates hydrogen by decomposition | disassembly.

  What is necessary is just to set suitably the introduction amount of the exhaust gas containing hydrogen gas to a catalyst part with the processing capacity of the nitrogen oxide of a catalyst part.

  The method of the present invention has a low reaction activity with oxygen coexisting with nitrogen oxides in the exhaust gas, and the operating temperature is preferably in a low-temperature atmosphere of 200 ° C. or less, particularly preferably 50 to 100 ° C.

  The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1
A catalyst part having a support structure composed of a hydrogen oxidation catalyst component, a nitrogen oxide reduction catalyst component, and a conductive material as shown in FIG. 1 was prepared.
To 300 g of dinitrodiamine platinum (II) nitric acid solution containing 1.5 wt% of Pt, 10 g of carbon black (made by Lion Corporation, trade name: Ketjen Black EC-600JD) as a support made of a conductive material is added. And mixed with stirring. To the obtained mixed solution, 100 ml of ethyl alcohol was added as a reducing agent, and the mixture was stirred and mixed at about the boiling point (78 ° C.) of ethyl alcohol for about 5 hours. Next, the obtained mixed solution was filtered, dried at 60 ° C., and a hydrogen oxidation catalyst component (Pt) was supported on a support (carbon) made of a conductive material.

  Next, 5 g of the obtained Pt-supported carbon was added to 30 g of nickel chloride solution containing 8 wt% Ni and mixed with stirring. 100 ml of ethyl alcohol was added to the obtained mixed solution, and the mixture was stirred and mixed at the boiling point (78 ° C.) of ethyl alcohol for about 5 hours. Next, the obtained mixed solution is filtered, dried at 60 ° C., and a nitrogen oxide reduction catalyst component (Ni) is formed on a support (carbon) made of a conductive material in the same manner as the hydrogen oxidation catalyst component (Pt). ) Was supported. The weight ratio of the hydrogen oxidation catalyst component (Pt) to the nitrogen oxide reduction catalyst component (Ni) on the support was 1: 5.

A support (carbon) 2 g, 2 g of alumina, and 5 g of water on which a hydrogen oxidation catalyst component (Pt) and a nitrogen oxide reduction catalyst component (Ni) are dispersedly supported are placed in a magnetic ball mill, and stirred for 1 hour to mix the slurry. Obtained. The obtained slurry was applied to a cordierite honeycomb carrier, excess slurry was blown off with an air stream, dried at 130 ° C. for 2 hours, and further fired at 400 ° C. for 1 hour to obtain a honeycomb carrier. The honeycomb carrier had 400 cells / (25.4 mm) ² (400 cpsi) and a volume of 4.8 cm ³ .
Next, a solution containing 5 wt% of a perfluorosulfonic acid polymer (manufactured by DuPont, Nafion (registered trademark): proton conductive solid electrolyte) is applied to the obtained honeycomb carrier, and an excess solution is applied by an air flow. The catalyst part which decomposes | disassembles nitrogen oxide was obtained by blowing off and drying at 100 degreeC for 1 hour.

(Example 2)
A catalyst part having a structure of a hydrogen oxidation catalyst component and a conductive nitrogen oxide reduction catalyst component as shown in FIG. 2 was produced.
1 g of a solution containing 5 wt% of a perfluorosulfonic acid polymer as a proton conductive solid electrolyte and 8 g of water are added to 0.5 g of commercially available 50 wt% Pt-supported carbon (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product number: TEC10E50E), A slurry was obtained by stirring and mixing. A metal porous body containing Ni as a main composition (Celmet (registered trademark), manufactured by Sumitomo Electric Industries, Ltd.) is immersed in the obtained slurry, and the slurry is attached to the metal porous body, and then excess slurry is added by an air flow. The catalyst part which decomposes | disassembles nitrogen oxide was obtained by blowing off and drying at 100 degreeC for 1 hour. The weight ratio of the hydrogen oxidation catalyst component (Pt) to the conductive nitrogen oxide reduction catalyst component (Ni) was 1: 150.

(Comparative example)
A catalyst part for decomposing nitrogen oxides in the same manner as in Example 2 except that a 5 wt% polyvinyl alcohol solution is used instead of a solution containing 5 wt% perfluorosulfonic acid polymer as a proton conductive solid electrolyte. Got. The weight ratio of the hydrogen oxidation catalyst component (Pt) to the conductive nitrogen oxide reduction catalyst component (Ni) was 1: 150.

(Performance evaluation test)
The catalyst parts obtained in Examples 1 and 2 and Comparative Example 1 were each attached to a stationary flow reactor, and a simulated gas having a gas composition assuming exhaust gas from the following diesel engine was flown for 10 hours under the flow conditions below. The nitrogen oxide concentration before and after the treatment was measured every hour, and the removal rate was calculated.
The obtained results are shown in FIG. 6 (●: Example 1, ▲: Example 2, Comparative Example: ×).

Gas composition NOx: 200ppm
O ₂ : 19%
H ₂ : 0.2%
N ₂ : balance
SV (space velocity): 10,000 Hr ⁻¹
Reactor temperature: 80 ° C

The nitrogen oxide concentration before and after the treatment was measured using a NOx-O ₂ measuring device for combustion exhaust gas (manufactured by Shimadzu Corporation, model: NOA-7000).
The removal rate of nitrogen oxides (NOx) was calculated by the following formula.
NOx removal rate (%)
= [(NOx concentration before treatment) − (NOx concentration after treatment)] / (NOx concentration before treatment) × 100

  From the result of FIG. 6, the catalyst part containing the nitrogen oxide decomposition catalyst of the present invention, that is, “the hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component are dispersed on the same plane of the support made of a conductive material. Of the nitrogen oxide formed by joining the catalyst components such that electrons can move between the two catalyst components, and joined by a proton conductive solid electrolyte capable of transferring protons between the two catalyst components separately from the junction. Example 1 using "catalyst portion including cracking catalyst" and "the oxidation catalyst component of hydrogen is dispersedly disposed on the reduction catalyst component of conductive nitrogen oxide so that electrons can move between the two catalyst components." Of Example 2 using a "catalyst portion comprising a decomposition catalyst for nitrogen oxides joined to a proton conductive solid electrolyte which is joined to the catalyst component and is joined with a proton conductive solid electrolyte capable of transferring protons between both catalyst components separately from the joining" The oxide removal rate is A 5.5 to 7 times of Comparative Example using the catalyst unit "consisting of reduction catalyst component of the oxidation catalyst component and nitrogen oxides-containing found to have a removal effect superior nitrogen oxides.

It is a schematic cross section which shows the main structures (arrangement form (1)) of the decomposition catalyst of the nitrogen oxide of this invention. It is a schematic cross section which shows the main structures (arrangement form (2)) of the decomposition | disassembly catalyst of the nitrogen oxide of this invention. It is a schematic diagram which shows the main structures of the decomposition | disassembly apparatus of the nitrogen oxide of this invention. It is a schematic diagram which shows the main structures of the decomposition | disassembly apparatus of the nitrogen oxide of this invention. It is a schematic cross section which shows the main structures of the catalyst part of the three-dimensional structure in the decomposition | disassembly apparatus of the nitrogen oxide of this invention. It is a figure which shows the relationship between the elapsed time (time) and the NOx removal rate (%) in the decomposition | disassembly method of the nitrogen oxide of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrogen oxidation catalyst component 2 Nitrogen oxide reduction catalyst component 2 (4) Conductive nitrogen oxide reduction catalyst component 3 Proton conductive solid electrolyte 4 Support comprising conductive material

5 Three-dimensional structure (honeycomb carrier)
6 cells (gas flow space)
7 Lattice 8 Support layer 9 Catalyst

DESCRIPTION OF SYMBOLS 11 Decomposition apparatus 12 Inlet flue 13 Outlet flue 14 Catalyst part 15 Hydrogen gas injection apparatus E Exhaust gas H Hydrogen gas

Claims (9)

  Proton conductivity in which an oxidation catalyst component of hydrogen and a reduction catalyst component of nitrogen oxide are joined so that electrons can move between the two catalyst components, and protons can move between the two catalyst components separately from the junction. A nitrogen oxide decomposition catalyst for decomposing nitrogen oxides in the presence of hydrogen, characterized by being bonded with a conductive solid electrolyte.   2. The nitrogen oxide decomposition catalyst according to claim 1, wherein the hydrogen oxidation catalyst component is at least one metal selected from platinum group metals of Pt, Ru, Rh, Pd and Ir, or a compound thereof.   2. The reduction catalyst component of the nitrogen oxide is at least one metal selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Cd, Sn, Pb and Zn or a compound thereof. Or the nitrogen oxide decomposition catalyst according to 2;   The proton conductive solid electrolyte is a fluororesin-based or hydrocarbon-based proton conductive solid polymer, and a perovskite type of barium cerium, barium zirconium, calcium cerium, calcium zirconium, zirconium strontium and cerium strontium The decomposition catalyst for nitrogen oxide according to any one of claims 1 to 3, which is at least one selected from oxides.   The decomposition catalyst for nitrogen oxides according to any one of claims 1 to 4, wherein the reduction catalyst component for nitrogen oxides is 1 to 500 parts by weight with respect to 1 part by weight of the oxidation catalyst component for hydrogen.   The hydrogen oxidation catalyst component and the nitrogen oxide reduction catalyst component are dispersed on the same plane of a support made of a conductive material, or the hydrogen oxidation catalyst component has conductivity. The nitrogen oxide decomposition catalyst according to any one of claims 1 to 5, wherein the catalyst is dispersedly disposed on a reduction catalyst component of the product and joined so that electrons can move between the two catalyst components.   A catalyst part including the nitrogen oxide decomposition catalyst according to any one of claims 1 to 6, an inlet flue for introducing exhaust gas into the catalyst part, and the exhaust gas treated in the catalyst part are discharged. An apparatus for decomposing nitrogen oxides, comprising an exit flue.   The nitrogen oxide decomposition apparatus according to claim 7, further comprising a hydrogen gas injection device that injects a hydrogen-containing gas between the inlet flue and the catalyst unit.   Nitrogen oxidation, characterized in that exhaust gas is treated with a nitrogen oxide decomposition catalyst according to any one of claims 1 to 6 using hydrogen as a reducing agent to decompose nitrogen oxide in the exhaust gas. Decomposition method.

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