Exhaust gas treatment catalyst and exhaust gas treatment method

Abstract

To enhance catalytic performance even under fluctuation of exhaust gas components.SOLUTION: Provided is an exhaust gas treatment catalyst that promotes a reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, the exhaust gas treatment catalyst comprising titanium oxide as a main component and manganese as an active component, the manganese being, in terms of Mn2O3, 0.2 mass% or more and 1.0 mass% or less of the total amount.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an exhaust gas treatment catalyst and an exhaust gas treatment method for treating nitrogen oxides contained in exhaust gas. [Background technology]

[0002] Combustion plants, such as gas turbines and boilers, that burn fossil fuels such as natural gas, oil, and coal, as well as fuels such as biomass, are equipped with exhaust gas treatment devices that treat the exhaust gas generated by combustion.The exhaust gas treatment devices have denitration equipment that reduces nitrogen oxides contained in the exhaust gas.The denitration equipment supplies urea or ammonia to the exhaust gas, causing ammonia to react with nitrogen oxides, thereby reducing the nitrogen oxides.The denitration equipment is equipped with a catalyst that promotes the reaction between ammonia and nitrogen oxides.

[0003] Patent Document 1 describes a denitration catalyst (exhaust gas treatment catalyst) that removes nitrogen oxides in exhaust gases that have a NO2 / NO molar ratio of 1 or more, and that is made by adding 0.1 to 10 wt% of at least one of Cr, Cu, Mn, and Co, calculated as the oxide, to a catalyst made of TiO2-V2O5-WO3. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 04-18932 Summary of the Invention [Problem to be solved by the invention]

[0005] The catalyst described in Patent Document 1 can accelerate the reduction process of nitrogen oxides. Gas turbines, boilers, and other devices used for power generation may undergo variable load operation, adjusting the amount of power generated depending on the overall amount of power generated. When the load is varied, or when the device is operated at a low load, the components of the exhaust gas change depending on whether the device is operated at a load above a predetermined level. Therefore, there is a demand for improved catalyst performance even when the components of the exhaust gas fluctuate.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide an exhaust gas treatment catalyst and an exhaust gas treatment method that can improve the performance of the catalyst even when the components of the exhaust gas fluctuate. [Means for solving the problem]

[0007] In order to achieve the above object, the exhaust gas treatment catalyst of the present disclosure is an exhaust gas treatment catalyst that promotes the reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, and contains titanium oxide as a main component and manganese as an active component, in which the manganese accounts for 0.2 mass% or more and 1.0 mass% or less of the total amount in terms of Mn2O3.

[0008] The exhaust gas treatment method of the present disclosure also includes the steps of: introducing a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides; and promoting the reaction between the nitrogen oxides and ammonia using an exhaust gas treatment catalyst that contains titanium oxide as a main component and manganese as an active component, with the manganese being 1.0 mass% or less of the total amount. [Effects of the Invention]

[0009] According to the present disclosure, the performance of the catalyst can be improved even when the components of the exhaust gas vary. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a combustion plant to which the exhaust gas treatment catalyst of this embodiment is applied. [Figure 2]FIG. 2 is a graph showing the results of measuring the denitration performance. [Figure 3] FIG. 3 is a graph showing the results of measuring HCHO removal performance. [Figure 4] FIG. 4 is a graph showing the results of measuring the denitration performance. [Figure 5] FIG. 5 is a table showing the results of measuring the denitration performance. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0012] FIG. 1 is a schematic diagram showing a combustion plant to which the exhaust gas treatment catalyst of this embodiment is applied. The combustion plant to which the denitration equipment of this embodiment is applied is a gas turbine that rotates the turbine with combustion gas obtained by burning gaseous fuel in a combustion chamber. Note that in this embodiment, the combustion equipment is a gas turbine, but the combustion equipment is not particularly limited, and the denitration equipment can be used as a denitration equipment for various combustion equipment that combusts fuel and emits exhaust gas containing nitrogen oxides. For example, the combustion equipment may be a boiler that burns fuel with a combustion burner and is capable of recovering heat generated by this combustion. In addition, the denitration equipment can also be used as a treatment equipment for exhaust gas discharged from a multi-fuel combustion equipment that burns a mixture of coal, liquid fuel, and gaseous fuel as fuel. In addition, the denitration equipment can also be used as a treatment equipment for exhaust gas discharged from a combustion equipment that burns biomass or the like.

[0013] The combustion plant 10 of this embodiment has a fuel supply unit 12, an air supply unit 14, a combustion device 20, a flue 30, and a denitration equipment 40. The combustion plant 10 may also include a heat exchanger that exchanges heat with the exhaust gas discharged from the combustion device 20, and an exhaust gas treatment device other than the denitration equipment 40. The fuel supply unit 12 supplies fuel, such as LNG or shale gas, to the combustion device 20. The air supply unit 14 supplies air to the combustion device 20.

[0014] The combustion device 20 is a gas turbine. The combustion device 20 has a combustor, a compressor, and a turbine, with the compressor and turbine connected by a shaft. The combustion device 20 compresses air supplied from the air supply unit 14 using the compressor, mixes the compressed air with fuel supplied from the fuel supply unit 12, and combusts the air in the combustor to generate high-temperature, high-pressure combustion gas. The combustion device 20 uses the energy of the combustion gas to rotate the turbine, and exhaust gas that rotates the turbine is discharged.

[0015] The flue 30 is connected to the combustion equipment 20, and the exhaust gas that has passed through the turbine of the combustion equipment 20 flows into the flue 30.

[0016] The denitration equipment 40 removes and reduces nitrogen oxides in the exhaust gas by supplying a reducing agent, such as ammonia or urea water, into the flue 30 and passing the exhaust gas to which the reducing agent has been supplied through a selective catalytic reduction catalyst that promotes a reaction between the nitrogen oxides and the reducing agent. The denitration equipment 40 includes a reducing agent supply device 42, a first denitration catalyst layer 50, and a second denitration catalyst layer 52. The denitration equipment 40 may further include a control device that measures the ammonia concentration, etc., and controls the amount of the reducing agent supplied.

[0017] The reducing agent supply device 42 has a reducing agent storage unit 42a and an injection unit 42b. The reducing agent storage unit 42a is a tank that stores a reducing agent. Examples of the reducing agent that can be used include ammonia water, gaseous ammonia, and urea water. The injection unit 42b is connected to the reducing agent storage unit 42a and has a supply port disposed inside the flue 30. The reducing agent supply device 42 supplies the reducing agent from the reducing agent storage unit 42a to the injection unit 42b, and discharges (injects) the reducing agent from the supply port of the injection unit 42b disposed inside the flue 40, thereby supplying the reducing agent into the flue 30. The reducing agent supplied from the reducing agent supply device 42 moves together with the exhaust gas and diffuses within the path through which the exhaust gas flows.

[0018] The first denitration catalyst layer 50 is disposed downstream of the reducing agent supply device 42 in the flow direction of the exhaust gas. The first denitration catalyst layer 50 has a catalyst and a support mechanism for fixing the catalyst to the flue 30. The shape of the catalyst is not particularly limited, and may be either a plate shape or a honeycomb shape. The components of the catalyst will be described later. The support mechanism may be any mechanism capable of supporting the catalyst, and the structure is not particularly limited.

[0019] The second Denitration catalyst layer 52 is disposed downstream of the first Denitration catalyst layer 50 in the flow direction of the exhaust gas. The second Denitration catalyst layer 52 has a catalyst and a support mechanism that fixes the catalyst to the flue 30. The second Denitration catalyst layer 52 is similar to the first Denitration catalyst layer 50 except for its location.

[0020] In the denitration equipment 40, a reducing agent supply device 42 supplies a reducing agent to the flue 30, and the exhaust gas mixed with the reducing agent passes through a first denitration catalyst layer 50 and a second denitration catalyst layer 52. The denitration equipment 40 removes nitrogen oxides from the exhaust gas by promoting a reaction between the nitrogen oxides and the reducing agent in the first denitration catalyst layer 50 and the second denitration catalyst layer 52. Although the denitration equipment 40 of this embodiment has two denitration catalyst layers, the total number is not particularly limited, and may be three or more layers or one layer. The denitration equipment 40 may also have a rectification layer upstream of the denitration catalyst layers.

[0021] Next, the catalysts of the first denitration catalyst layer 50 and the second denitration catalyst layer 52, that is, the exhaust gas treatment catalyst of this embodiment, will be described. The exhaust gas treatment catalyst contains titanium oxide as a main component and manganese as an active component. The amount of manganese (Mn) added to the exhaust gas treatment catalyst is 1.0 mass % (wt. %) or less in terms of Mn2O3 relative to the total amount of the catalyst.

[0022] By setting the manganese content within the above range, the exhaust gas treatment catalyst can maintain catalytic activity under NO2-rich conditions, thereby increasing denitration performance, and can also maintain catalytic activity under conditions where high concentrations of HCHO (formaldehyde) coexist, thereby increasing denitration performance.

[0023] Furthermore, the exhaust gas treatment catalyst preferably contains vanadium, tungsten, or the like as an active component. That is, the exhaust gas treatment catalyst is preferably a binary TiO2-WO3 catalyst, TiO2-V2O5 catalyst, or a ternary TiO2-V2O5-WO3 catalyst, and the amount of manganese (Mn) added is preferably 1.0 mass% (wt.%) or less in terms of Mn2O3 relative to the total amount of the catalyst. The exhaust gas treatment catalyst may also contain molybdenum (Mo) as an active component. That is, the exhaust gas treatment catalyst may be a TiO2-MoO3 catalyst, a TiO2-V2O5-MoO3 catalyst, or the like.

[0024] The following describes the catalyst components used in the experimental examples and comparative examples.

[0025] (Experimental Example 1) The exhaust gas treatment catalyst of Experimental Example 1 contains, in mass % relative to the total amount, 79.8 mass % TiO2, 2.6 mass % V2O5, 6.2 mass % WO3, 0 mass % Mn2O3, and 0.45 mass % SO3. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, the catalyst does not contain chromium, copper, or cobalt as active components. Here, "free of target components" means that the amount is below the unavoidable impurity amount.

[0026] (Experimental Example 2) The exhaust gas treatment catalyst of Experimental Example 2 contains, by mass % relative to the total amount, 60 mass % or more of TiO2 (main component, though not measured), 4.8 mass % of V2O5, 5.3 mass % of WO3, 0.22 mass % of Mn2O3, and 0.27 mass % of SO3. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, the catalyst does not contain chromium, copper, or cobalt as active components.

[0027] (Experimental Example 3) The exhaust gas treatment catalyst of Experimental Example 3 contains, by mass % relative to the total amount, 60 mass % or more of TiO2 (main component, though not measured), 2.4 mass % of V2O5, 7.9 mass % of WO3, 0.23 mass % of Mn2O3, and 0.35 mass % of SO3. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, the catalyst does not contain chromium, copper, or cobalt as active components.

[0028] (Experimental Example 4) The exhaust gas treatment catalyst of Experimental Example 4 contains, in mass % relative to the total amount, 78.1 mass % TiO2, 2.5 mass % V2O5, 5.3 mass % WO3, 0.53 mass % Mn2O3, and 1.1 mass % SO3. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, the catalyst does not contain chromium, copper, or cobalt as active ingredients.

[0029] (Experimental Example 5) The exhaust gas treatment catalyst of Experimental Example 5 contains, in mass % relative to the total amount, 80.0 mass % TiO2, 2.4 mass % V2O5, 4.1 mass % WO3, 0.94 mass % Mn2O3, and 0.78 mass % SO3. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, the catalyst does not contain chromium, copper, or cobalt as active ingredients.

[0030] (Comparative Example 1) The exhaust gas treatment catalyst of Comparative Example 1 contains, in mass % relative to the total amount, 60 mass % or more of TiO2 (main component, though not measured), 2.4 mass % of V2O5, 5.2 mass % of WO3, 2.9 mass % of Mn2O3, and 0.57 mass % of SO3. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, chromium, copper, and cobalt are not included as active components.

[0031] (Comparative Example 2) The exhaust gas treatment catalyst of Comparative Example 2 contains, in mass % relative to the total amount, 60 mass % or more of TiO2 (main component, though not measured), 2.3 mass % of V2O5, 5.0 mass % of WO3, 4.6 mass % of Mn2O3, and 0.67 mass % of SO3. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, chromium, copper, and cobalt are not included as active components.

[0032] (Measurement conditions) For the above catalyst, the first measurement was performed with a composition of NOx = 47 ppm, NO2 / NO x =0.85, NH3 = 54 ppm, HCHO = 179 ppm, O2 = 15.1%, H2O = 6.5%, CO2 = 4%, the remainder N2. The exhaust gas was at a temperature of 294°C and had a volumetric flow rate of AV 21 Nm 3 / m 2 The exhaust gas was supplied to each catalyst at a rate of 1 / hr, and the amounts of nitrogen oxides and HCHO after passing through the catalyst were measured, and the denitration rate, which is the rate of reduction of nitrogen oxides before and after the catalyst, and the HCHO removal rate, which is the rate of reduction of HCHO before and after the catalyst, were calculated. In Comparative Example 2, the exhaust gas was in an ammonia-rich state with NH3 = 142 ppm and HCHO = 200 ppm.

[0033] The second measurement was conducted with a composition of NOx = 47 ppm, NO2 / NO x =0.85, NH3=54ppm, HCHO=0ppm, O2=15.1%, H2O=6.5%, CO2=4%, the remainder is N2, and the exhaust gas does not contain formaldehyde. The temperature is 294°C, and the treated gas flow rate per catalyst gas contact area is AV21Nm 3 / m 2 The nitrogen oxide amount after passing through the catalyst was measured, and the denitration rate, which is the reduction rate of nitrogen oxide before and after the catalyst, was calculated.

[0034] The measurement results are shown in Figures 2 to 5. Figure 2 is a graph showing the results of measuring denitration performance. Figure 3 is a graph showing the results of measuring HCHO removal performance. Figure 4 is a graph showing the results of measuring denitration performance. Figure 5 is a table showing the results of measuring denitration performance.

[0035] Figure 2 is a plot of the relationship between the denitration rate (%) and the Mn2O3 proportion (mass%) for each experimental example and each comparative example measured in the first measurement (HCHO = 179 ppm). In Figure 2, the horizontal axis represents the Mn2O3 proportion (mass%) and the vertical axis represents the denitration rate (%).

[0036] Figure 3 is a plot of the relationship between the HCHO removal rate (%) and the Mn2O3 proportion (mass%) for each experimental example and each comparative example measured in the first measurement (HCHO = 179 ppm). In Figure 3, the horizontal axis represents the Mn2O3 proportion (mass%), and the vertical axis represents the HCHO removal rate.

[0037] Figure 4 is a plot of the relationship between the denitration rate (%) and the Mn2O3 proportion (mass%) for each experimental example and each comparative example measured in the second measurement (HCHO = 0 ppm). In Figure 4, the horizontal axis represents the Mn2O3 proportion (mass%) and the vertical axis represents the denitration rate (%).

[0038] FIG. 5 is a table summarizing the catalyst components of the experimental examples and comparative examples, the denitration rate and HCHO removal rate of the first measurement, and the denitration rate of the second measurement.

[0039] The exhaust gas treatment catalyst has titanium oxide as its main component and contains manganese as an active component. By adding 1.0 mass% (wt.%) or less of manganese (Mn) converted into Mn2O3 relative to the total amount of catalyst, it is possible to remove a high percentage of nitrogen oxides from exhaust gases containing a large amount of nitrogen dioxide, regardless of the presence or absence of HCHO, as shown in Figures 2 and 4. Furthermore, the exhaust gas treatment catalyst has titanium oxide as its main component and contains manganese as an active component. By adding 1.0 mass% (wt.%) or less of manganese (Mn) converted into Mn2O3 relative to the total amount of catalyst, it is possible to remove a high percentage of HCHO, as shown in Figure 3.

[0040] In other words, if the Mn2O3 content of an exhaust gas treatment catalyst exceeds 1.0 mass% of the total catalyst, the denitration performance will decrease in an environment where nitrogen oxides in exhaust gases containing a lot of nitrogen dioxide and HCHO coexist, but by keeping it within the range of the present application, the denitration performance can be maintained. Also, by reducing the manganese content, the proportion of titanium oxide, which is the main component, can be relatively increased, thereby further improving the functionality of the catalyst.

[0041] If NH3 is added for denitration to exhaust gas containing high concentrations of HCHO, the NH3 and HCHO will react on the catalyst, causing the following reaction to occur, generating by-products and resulting in a shortage of NH3 required for the denitration reaction. NH3+HCHO+(1 / 2)·O2→HCONH2+H2O

[0042] In the exhaust gas treatment catalyst of the present disclosure, by adjusting the manganese content to 1.0 mass % in terms of Mn2O3 relative to the total amount of the catalyst, the promotion of the above reaction can be suppressed, and a significant decrease in the denitrification rate in the presence of HCHO can be suppressed. NH3+HCHO+(1 / 2)·O2→HCONH2+H2O While suppressing the reaction of nitrogen oxides and ammonia, 4NO+4NH3+O2→4N2+6H2O NO + NO2 + 2NH3 → 2N2 + 3H2O 6NO2+8NH3→NO+CO+H2O and the reaction of nitrogen oxides with formaldehyde. HCHO+NO2→NO+CO+H2O and the formaldehyde removal reaction HCHO+O2→CO2,CO+H2O It can activate the air and remove a high percentage of nitrogen oxides and formaldehyde, a VOC.

[0043] In addition, as in this embodiment, the exhaust gas treatment catalyst is xis 0.5 or more and the HCHO concentration is equal to or greater than the NO2 concentration. For example, when the natural gas-fired gas turbine of this embodiment is used for power generation, it will be operated at a low load by adjusting the output during times when solar power generation is high. Since the natural gas-fired gas turbine is operated at a low load that was not anticipated at the time of construction, it is not possible to perform combustion under suitable combustion conditions, and the NO2 / NO x However, when the ratio of nitrogen oxides to HCHO is 0.5 or more, HCHO may be generated. Even when exhaust gas is generated under such conditions, the exhaust gas treatment method using the exhaust gas treatment catalyst of the present embodiment can remove nitrogen oxides at a high rate, and can remove both nitrogen oxides and HCHO at a high rate.

[0044] Furthermore, the exhaust gas treatment catalyst of the present disclosure can achieve a nitrogen oxide removal rate comparable to that of the comparative example even when no HCHO is contained, that is, even when combustion is performed under favorable conditions in a natural gas-fired gas turbine. In other words, the exhaust gas treatment method using the exhaust gas treatment catalyst of the present disclosure can achieve a high NO2 / NO x is 0.5 or more and the HCHO concentration varies from the NO2 concentration or more to the HCHO concentration not being present, a high denitrification rate can be maintained, and even if HCHO is generated, it can be suitably removed.

[0045] Here, the exhaust gas treatment catalyst preferably contains titanium oxide in an amount of 60 mass % or more, more preferably 70 mass % or more, calculated as TiO2. It is preferable to use TiO2 as the titanium oxide. By keeping the titanium oxide content of the main component within the above range, the denitrification rate can be increased.

[0046] The exhaust gas treatment catalyst preferably contains manganese in an amount of 0.2 mass % or more and 1.0 mass % or less of the total amount, calculated as Mn2O3. By containing manganese, the exhaust gas treatment catalyst can increase the denitrification rate.

[0047] The exhaust gas treatment catalyst preferably contains at least one of tungsten oxide and vanadium oxide as an active component, which can increase the denitrification rate. The exhaust gas treatment catalyst may also contain molybdenum as an active component.

[0048] In the exhaust gas treatment catalyst, the vanadium oxide content, calculated as V2O5, is preferably 0.1% by mass to 10% by mass, more preferably 2% by mass to 5% by mass, of the total amount, which can increase the denitrification rate.

[0049] In the exhaust gas treatment catalyst, the tungsten oxide content is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 4% by mass or more and 8% by mass or less, in terms of WO3, of the total amount, which can increase the denitrification rate.

[0050] The exhaust gas treatment catalyst preferably further contains sulfur trioxide in an amount of 0.1 wt% to 2% of the total amount, and more preferably 0.2 wt% to 2% of the total amount, which can increase the denitrification rate.

[0051] It is preferable that the exhaust gas treatment catalyst does not contain chromium, copper, or cobalt as an active component, which simplifies the catalyst configuration and prevents a decrease in the proportion of the main component.

[0052] [Effects of this embodiment] The present disclosure has the following features, but is not limited to the following. (1) An exhaust gas treatment catalyst that promotes the reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, and that contains titanium oxide as the main component and manganese as the active component, with the manganese being 0.2% by mass or more and 1.0% by mass or less of the total amount, calculated as Mn2O3. This allows exhaust gas treatment with a high denitrification rate whether or not formaldehyde is present, and also allows formaldehyde to be treated.

[0053] (2) The exhaust gas treatment catalyst according to (1), wherein the titanium oxide is 60 mass % or more of the total amount in terms of TiO2, thereby making it possible to increase the denitrification rate.

[0054] (3) The exhaust gas treatment catalyst according to (1) or (2), which contains at least one of tungsten oxide and vanadium oxide as an active component.

[0055] (4) The exhaust gas treatment catalyst according to (3), wherein the vanadium oxide is 0.1 mass % or more and 10 mass % or less of the total amount in terms of V2O5, thereby making it possible to increase the denitrification rate.

[0056] (5) The exhaust gas treatment catalyst according to (3) or (4), wherein the tungsten oxide is 0.1% by mass or more and 20% by mass or less of the total amount in terms of WO3, thereby making it possible to increase the denitrification rate.

[0057] (6) The exhaust gas treatment catalyst according to any one of (1) to (5), further containing sulfur trioxide in an amount of 0.1 wt % to 2% of the total amount, thereby making it possible to increase the denitrification rate.

[0058] (7) The exhaust gas treatment catalyst according to any one of (1) to (6), which does not contain chromium, copper, or cobalt as an active component, thereby enabling a high denitrification rate.

[0059] (8) NO2 / NO of the exhaust gas to be treated x The exhaust gas treatment catalyst according to any one of (1) to (7), wherein the ratio is 0.5 or more and the catalyst can be suitably treated even when the concentration of HCHO is equal to or higher than the concentration of NO2. This makes it possible to increase the denitrification rate.

[0060] (9) A method for treating exhaust gas, comprising the steps of: introducing a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides; and promoting the reaction between nitrogen oxides and ammonia with an exhaust gas treatment catalyst containing titanium oxide as a main component and manganese as an active component, the manganese being 1.0 mass% or less of the total amount.

[0061] (10) The exhaust gas is NO2 / NO x is 0.5 or more, and the condition varies from a condition where the concentration of HCHO is equal to or higher than the concentration of NO2 to a condition where no HCHO is contained. [Explanation of symbols]

[0062] 10 Combustion Plant 12 Fuel supply section 14 Air supply section 20 Combustion equipment 30 Flue (exhaust gas passage) 42 Reducing agent supply device 50 1st denitrification catalyst layer 52 2nd denitrification catalyst layer

Claims

1. An exhaust gas treatment catalyst that promotes a reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, The main component is titanium oxide, and manganese as an active ingredient, Manganese is Mn ２ O ３ The exhaust gas treatment catalyst has a total amount of 0.2 mass % or more and 1.0 mass % or less, calculated as a percentage of the total amount of the exhaust gas treatment catalyst.

2. The titanium oxide is TiO ２ The exhaust gas treatment catalyst according to claim 1, wherein the catalyst content is 60 mass % or more of the total amount of the catalyst.

3. 2. The exhaust gas treatment catalyst according to claim 1, comprising at least one of tungsten oxide and vanadium oxide as an active component.

4. Vanadium oxide is V ２ O ５ The exhaust gas treatment catalyst according to claim 3, wherein the amount of the catalyst is 0.1 mass % or more and 10 mass % or less of the total amount of the catalyst.

5. Tungsten oxide is WO ３ The exhaust gas treatment catalyst according to claim 3, wherein the amount of the catalyst is 0.1 mass % or more and 20 mass % or less of the total amount of the catalyst.

6. 2. The exhaust gas treatment catalyst according to claim 1, further comprising sulfur trioxide in an amount of 0.1 wt % or more and 2 wt % or less of the total amount.

7. 2. The exhaust gas treatment catalyst according to claim 1, which does not contain chromium, copper, or cobalt as an active component.

8. NO in the exhaust gas to be treated ２ / NO ｘ is 0.5 or more, and the concentration of HCHO is NO ２ The exhaust gas treatment catalyst according to any one of claims 1 to 7, wherein the concentration is equal to or higher than that of the catalyst.

9. A step in which a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides flows in; and promoting the reaction of nitrogen oxides with ammonia using an exhaust gas treatment catalyst containing titanium oxide as a main component and manganese as an active component, the manganese content of which is 1.0 mass% or less of the total amount.

10. The exhaust gas is NO ２ / NO ｘ is 0.5 or more, and the concentration of HCHO is NO ２ The exhaust gas treatment method according to claim 9, wherein the conditions vary from a concentration of HCHO or more to a concentration of no HCHO.

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