Environment-friendly low-temperature resistant water-resistant SCR denitration catalyst, preparation method and application thereof

Abstract

This invention relates to an environmentally friendly, low-temperature, water-resistant SCR denitrification catalyst, which is a MnOx-FeOx-MOx multi-metal oxide catalyst. The metal element M in the oxide MOx is selected from one or more of W, V, Cu, Mo, Ni, Sn, Sb, La, Ce, Co, Zr, Pr, Nd, and Pu; preferably one or more of W, V, Cu, Mo, Sn, La, Ce, Co, and Zr; and x is 1-4. This catalyst uses multi-metal oxides as the active component and can be prepared by a redox co-precipitation method with enhanced dispersion. The preparation method is simple, environmentally friendly, and easy to industrialize. Furthermore, the low-temperature denitrification and water-resistant properties of the catalyst are significantly improved, making it particularly suitable for low-temperature denitrification of high-water-content flue gas, such as that from natural gas, and it has broad industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of air pollution control technology, and more specifically, to an environmentally friendly low-temperature water-resistant SCR denitrification catalyst, its preparation method, and its application. Background Technology

[0002] Low-NOx combustion technology, which reduces NOx emissions by changing combustion conditions, can only reduce NOx emissions by about 50% at most. Therefore, it is necessary to use tail-end flue gas denitrification technology to further reduce NOx emissions.

[0003] Post-combustion flue gas denitrification technology refers to the reduction or decomposition of NOx in flue gas into N2 through various physical and chemical processes, or the removal of NOx by eliminating nitrogen-containing substances. Based on the state of the reaction system, flue gas denitrification technology can be broadly classified into two categories: dry (catalytic) and wet (absorption). Wet flue gas denitrification refers to various process technologies that utilize water or aqueous solutions of acids, alkalis, salts, and other substances to absorb NOx in waste gas, thereby purifying the waste gas. However, this technology has some insurmountable problems that limit its application value. Dry flue gas denitrification technologies mainly include selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), electron beam (EB), pulsed corona plasma (PCIPCP), SNRB (SOx-NOx-ROx-BOx) combined control process, combined denitrification and desulfurization technology (SNOx) process, solid absorption / regeneration method, etc. Compared with wet denitrification technology, dry denitrification technology is more efficient, requires less land, produces little or no harmful byproducts, and does not require a flue gas heating system. Therefore, most power plant boilers adopt dry flue gas denitrification technology, among which selective catalytic reduction (NH3-SCR) using vanadium-based catalysts is the most widely used. However, some problems still exist: First, vanadium-based catalysts have a wide effective activity temperature range. For commercially available V2O5-WO3 / TiO2 and V2O5-MoO3 / TiO2, under a stoichiometric ratio of NH3 / NO of 1:1... The optimal reaction temperature range is 380-420℃. When the temperature exceeds the upper limit of this range, the side reaction of NH3 oxidation occurs, generating N2O and NO, thus reducing the NO conversion rate. This necessitates that the denitrification device be installed in a suitable location within the flue gas duct. Secondly, V2O5, as an active component, is a highly toxic substance that can easily cause secondary pollution to humans and the environment. Thirdly, V2O5 readily oxidizes SO2 in the flue gas to SO3, which then reacts with NH3 to generate ammonium sulfate and ammonium bisulfate, leading to a decrease in catalyst activity and potential reactor blockage, posing safety hazards. In summary, the limitations of space and technology in retrofitting existing industrial plants result in complex engineering modifications and significant economic losses. Therefore, vigorously developing low-temperature SCR denitrification technology is essential.

[0004] Currently, low-temperature SCR denitrification catalysts mainly include carbon-based catalysts, molecular sieves, and manganese-based catalysts. Literature reports show that most low-temperature SCR denitrification catalysts operate at denitrification reaction temperatures between 80-250℃, and some exhibit excellent denitrification performance and N2 selectivity. However, a common problem is poor water resistance; when the water content in the flue gas reaches 10%, the catalyst performance significantly decreases. When dealing with high-water-content (15%-30%) flue gas from industrial applications such as those using natural gas as feedstock, the catalyst quickly deactivates. For example, manganese-based catalysts, even with single Mn oxides, exhibit good low-temperature denitrification performance, but their water resistance is poor. The denitrification performance of mixed metal oxides modified with multiple metal elements, such as Mn-Ce, Mn-Co, Mn-Fe, and Mn-Cu, has been extensively studied, showing improved SCR denitrification performance compared to single Mn oxides, but still some distance from industrial application.

[0005] Composite oxide catalysts are mostly prepared through physical mixing, co-precipitation, impregnation, sol-gel methods, etc. Impregnation is easily affected by element diffusion, and co-precipitation is easily affected by factors such as the precipitation rate of metal precursors, resulting in non-uniform metal oxides. The composite oxides prepared by the sol-gel method are uniform and the strength is controllable, but the process is complex and difficult to industrialize. The catalytic performance of metal oxide catalysts is greatly affected by factors such as the type of active component, the interaction of active components, the specific surface area of ​​the catalyst, the valence state distribution of metal elements, surface oxygen species, surface acidity, particle dispersion of active species, particle size and distribution.

[0006] The water resistance of low-temperature SCR denitrification catalysts has become a bottleneck for catalyst life and industrial application, and further research and improvement are needed. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention proposes an environmentally friendly low-temperature water-resistant SCR denitrification catalyst. Specifically, it relates to an environmentally friendly low-temperature water-resistant SCR denitrification catalyst, its preparation method, and its application.

[0008] Based on detailed research, this invention provides an environmentally friendly low-temperature water-resistant SCR denitrification catalyst and its preparation method. The catalyst uses multi-metal oxides as active components and can be prepared by a redox co-precipitation method with enhanced dispersion. Experimental results show that the preparation method is simple, environmentally friendly, and easy to industrialize. The low-temperature denitrification and water resistance performance of the catalyst are significantly improved, making it particularly suitable for low-temperature denitrification of high-water-content flue gas such as natural gas, and it has broad industrial application prospects.

[0009] One objective of this invention is to provide an environmentally friendly, low-temperature, water-resistant SCR denitrification catalyst, which is a MnOx-FeOx-MOx multi-metal oxide catalyst. The catalyst comprises MnOx, FeOx, and MOx. The metal element M of the oxide MOx is selected from one or more of W, V, Cu, Mo, Ni, Sn, Sb, La, Ce, Co, Zr, Pr, Nd, and Pu. Preferably, it is selected from one or more of W, V, Cu, Mo, Sn, La, Ce, Co, and Zr.

[0010] Where x ranges from 1 to 4.

[0011] in,

[0012] In the MnOx-FeOx-MOx multi-element metal oxide catalyst, the molar ratio of element Mn, Fe and metal element M can be (100-0.1):(100-0.1):1; preferably (80-0.1):(50-0.1):1. More preferably (60-0.5):(30-0.1):1, even more preferably (25-0.5):(15-0.1):1, and even more preferably (1-10):(1-10):1.

[0013] The second objective of this invention is to provide a method for preparing the environmentally friendly low-temperature water-resistant SCR denitrification catalyst as described in the first objective of this invention. Specifically, the catalyst is prepared by a redox coprecipitation method; preferably, the catalyst active component precursor is prepared by a redox coprecipitation method with enhanced dispersion.

[0014] Specifically, the preparation method of the environmentally friendly low-temperature water-resistant SCR denitrification catalyst may include the following steps:

[0015] (1) The active component soluble metal salt is dissolved in water to prepare a mixed salt solution, preferably the total concentration of the mixed salt solution is 0.05 to 3.0 mol / L; the active component soluble metal salt includes soluble manganese salt, soluble iron salt and soluble M metal salt;

[0016] (2) Add the peroxide solution to the mixed salt solution and stir;

[0017] (3) Add the dispersant to the mixed salt solution and stir; preferably, the dispersant is selected from at least one of polyethylene oxide, polyvinyl alcohol, polyacrylic acid, ammonium sulfate, polyethylene glycol, alkylphenol polyoxyethylene ether, etc.

[0018] (4) Prepare an alkaline solution by dissolving the alkali in water;

[0019] (5) The mixed salt solution is mixed with an alkaline solution to form a precipitate, which is then aged, washed, and dried to obtain the catalyst precursor.

[0020] (6) The catalyst precursor is calcined to obtain the catalyst;

[0021] Steps (2) and (3) can exist alone or simultaneously.

[0022] in,

[0023] The soluble manganese salt may be selected from at least one of manganese nitrate, manganese acetate, manganese sulfate, etc.; and / or,

[0024] The soluble iron salt may be selected from at least one of ferric chloride, ferric nitrate, ferric acetate, etc.; and / or,

[0025] The soluble M metal salt, wherein M can be selected from one or more of W, V, Cu, Mo, Ni, Sn, Sb, La, Ce, Co, Zr, Pr, Nd, Pu, etc., and is preferably one or more of W, V, Cu, Mo, Sn, La, Ce, Co, Zr.

[0026] In step (2), the molar ratio of the peroxide to the total moles of manganese, iron, and M in the mixed salt solution can be (15-0):1; preferably (10-0.1):1 (for example, it can be 15, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.8, 0.5, 0.3, 0.2, 0.1 or any value between the above values ​​or a range between any two of the above values); the amounts of peroxide and dispersant used in steps (2) and (3) are not both 0;

[0027] In step (3), the amount of dispersant added is 0 to 12% of the total molar number of manganese, iron, and M in the mixed salt solution, preferably 0.01% to 10% (for example, it can be 0.01, 0.02, 0.03, 0.05, 0.07, 0.096, 1.0, 1.2, 1.4, 1.6, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, 12, 14 or any value between the above values ​​or a range between any two of the above values); in steps (2) and (3), the amount of peroxide and dispersant used is not 0 at the same time.

[0028] In step (4), the alkali is preferably selected from one or more of sodium hydroxide, sodium carbonate, ammonia, ammonium carbonate, ammonium bicarbonate, and urea; preferably, the concentration of the alkali solution is 0.1–3.0 mol / L; and / or,

[0029] In step (5), the pH value at which the precipitate forms is 7–11; the precipitation temperature is preferably 30–90°C; the drying temperature is preferably 80–120°C; and / or,

[0030] In step (6), the preferred roasting temperature is 300-800℃ and the roasting time is 4-12h.

[0031] The molar ratio of elements Mn, Fe and M in the catalyst precursor can be (100-0.1):(100-0.1):1; preferably (80-0.1):(50-0.1):1, more preferably (60-0.5):(30-0.1):1, even more preferably (25-0.5):(15-0.1):1, and even more preferably (1-10):(1-10):1.

[0032] In some preferred embodiments of the present invention

[0033] The peroxide solution can be a conventional hydrogen peroxide solution, such as a commercially available product like 30% hydrogen peroxide.

[0034] The third objective of this invention is to provide an environmentally friendly low-temperature water-resistant SCR denitrification catalyst prepared by the preparation method described in the second objective of this invention.

[0035] The environmentally friendly low-temperature water-resistant SCR denitrification catalyst described in one objective of this invention or the environmentally friendly low-temperature water-resistant SCR denitrification catalyst prepared by the preparation method described in another objective of this invention has a water content of 5-25%, a flue gas temperature of 120-300℃, and good denitrification performance and denitrification stability.

[0036] The fourth objective of this invention is to provide the application of the environmentally friendly low-temperature water-resistant SCR denitrification catalyst described in the first objective of this invention or the environmentally friendly low-temperature water-resistant SCR denitrification catalyst prepared by the preparation method described in the second objective of this invention.

[0037] The essential difference between this invention and the prior art lies in the fact that the redox coprecipitation method results in a composite oxide catalyst with superior specific surface area, metal element valence state distribution, surface oxygen species, oxide particle dispersion, particle size and distribution, thereby ensuring the synergistic effect of several active components. This gives the catalyst excellent low-temperature denitrification performance, good water resistance, and good stability. Attached Figure Description

[0038] Figure 1 The graph shows the trend of NO conversion (%) over time for the catalysts of Examples 1-5 and Comparative Examples 1-3. Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0040] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] Raw material source:

[0042] 50% manganese nitrate aqueous solution, Xilong Scientific Co., Ltd.

[0043] Ferric nitrate nonahydrate, Xilong Scientific Co., Ltd.

[0044] Lanthanum nitrate hexahydrate, Xilong Scientific Co., Ltd.

[0045] Ammonium heptamolybdate tetrahydrate, Xilong Scientific Co., Ltd.

[0046] Anhydrous sodium carbonate, Xilong Scientific Co., Ltd.

[0047] 30% hydrogen peroxide, Xilong Scientific Co., Ltd.

[0048] 65% Nitric Acid, Xilong Scientific Co., Ltd.

[0049] Anhydrous tin tetrachloride, Xilong Scientific Co., Ltd.;

[0050] Cerium nitrate hexahydrate, Xilong Scientific Co., Ltd.

[0051] Copper nitrate trihydrate, Xilong Scientific Co., Ltd.

[0052] Polyethylene glycol 6000, Xilong Scientific Co., Ltd.;

[0053] OP-10, Xilong Scientific Co., Ltd.;

[0054] Graphite, Sinopharm Chemical Reagent Co., Ltd.

[0055] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0056] Example 1

[0057] Weigh 23.3g of 50wt% manganese nitrate solution, 29.6g of ferric nitrate nonahydrate, and 2.2g of ammonium heptamolybdate, and add them to 300ml of deionized water to prepare a mixed salt solution. Add 2.3g of 30% hydrogen peroxide to the mixed salt solution and stir vigorously. Then add 73.8g of anhydrous sodium carbonate to 450ml of deionized water to prepare an alkaline solution. Drop the alkaline solution into the mixed salt solution at a rate of 80-120ml / min, stirring constantly to precipitate the initial product until the pH reaches 9.0. Maintain the precipitation reaction temperature at 60℃. Then age the precipitate at 60℃ with stirring for 1 hour, followed by filtration and washing with water to obtain a black filter cake. Dry the cake at 110℃ until the moisture content is 5%, then grind it, add graphite to compress it into tablets, and calcine it in a muffle furnace at 350℃ for 4 hours. Crush the tablets to obtain 40-60 mesh particles for denitrification activity evaluation, and label them as MnFeMo-O.

[0058] Example 2

[0059] Weigh 58.2g of 50wt% manganese nitrate solution, 32.5g of ferric nitrate nonahydrate, 10.9g of ammonium heptamolybdate, and 8.5g of cerium nitrate hexahydrate and add them to 300ml of deionized water to prepare a mixed salt solution. Add 5.6g of 30% hydrogen peroxide and 8.1g of polyethylene glycol 6000 to the mixed salt solution and mix thoroughly and vigorously. Then add 73.8g of anhydrous sodium carbonate to 450ml of deionized water to prepare an alkaline solution. The alkaline solution was added dropwise to the mixed salt solution at a rate of 80-120 ml / min, and the initial product was precipitated by continuous stirring until the pH reached 9.0. The precipitation reaction temperature was maintained at 60℃. The precipitated product was then aged for 1 hour with stirring at 60℃. After filtration and washing with water, a black filter cake was obtained. The cake was dried at 110℃ until the moisture content was 5%. It was then ground, graphite tablets were added, and the cake was calcined in a muffle furnace at 350℃ for 4 hours. The 40-60 mesh particles were then pulverized for denitrification activity evaluation and denoted as MnFeCeMo-OD.

[0060] Example 3

[0061] Weigh 29.1g of 50wt% manganese nitrate solution, 32.5g of ferric nitrate nonahydrate, and 2.1g of copper nitrate trihydrate, and add them to 300ml of deionized water to prepare a mixed salt solution. Add 5.6g of 30% hydrogen peroxide to the mixed salt solution and stir vigorously. Then add 85.3g of anhydrous sodium carbonate to 400ml of deionized water to prepare an alkaline solution. Drop the mixed salt solution into the alkaline solution at a rate of 80-120ml / min, stirring constantly to precipitate the initial product until the pH reaches 9.0. Maintain the precipitation reaction temperature at 60℃. Then age the precipitate at 60℃ with stirring for 1 hour, followed by filtration and washing with water to obtain a black filter cake. Dry the cake at 110℃ until the moisture content is 5%, then grind it, add graphite to compress it into tablets, and calcine it in a muffle furnace at 350℃ for 4 hours. Crush the tablets to obtain 40-60 mesh particles for denitrification activity evaluation, and label them as MnFeCu-O.

[0062] Example 4

[0063] Weigh 46.6g of 50wt% manganese nitrate solution, 35.5g of ferric nitrate nonahydrate, 5.1g of cerium nitrate hexahydrate, and 4.6g of tin tetrachloride, and add them to 300ml of deionized water to prepare a mixed salt solution. Add 4.5g of 30% hydrogen peroxide and 15.8g of OP-10 to the mixed salt solution and mix thoroughly and vigorously. Then add 124.4g of anhydrous sodium carbonate to 780ml of deionized water to prepare an alkaline solution. The alkaline solution was added dropwise to the mixed salt solution at a rate of 80-120 ml / min, and the initial product was precipitated by continuous stirring until the pH reached 9.0. The precipitation reaction temperature was maintained at 60℃. The precipitated product was then aged for 1 hour with stirring at 60℃. After filtration and washing with water, a black filter cake was obtained. The cake was dried at 110℃ until the moisture content was 5%. It was then ground, graphite tablets were added, and the cake was calcined in a muffle furnace at 350℃ for 4 hours. The 40-60 mesh particles were then pulverized for denitrification activity evaluation and denoted as MnFeCeSn-OD.

[0064] Example 5

[0065] Weigh 52.4g of 50wt% manganese nitrate solution, 23.7g of ferric nitrate nonahydrate, and 5.7g of tin tetrachloride, and add them to 300ml of deionized water to prepare a mixed salt solution. Add 15.8g of polyethylene glycol 6000 to the mixed salt solution and stir vigorously. Then, add 120.0g of anhydrous sodium carbonate to 750ml of deionized water to prepare an alkaline solution. Drop the alkaline solution into the mixed salt solution at a rate of 80-120ml / min, stirring continuously to precipitate the initial product until the pH reaches 9.0. Maintain the precipitation reaction temperature at 60℃. Then, age the precipitate at 60℃ with stirring for 1 hour. After filtration and washing with water, a black filter cake is obtained. Dry the cake at 110℃ until the moisture content is 5%, then grind it, add graphite to compress it into tablets, and calcine it in a muffle furnace at 350℃ for 4 hours. Powder the tablets to obtain 40-60 mesh particles for denitrification activity evaluation, denoted as MnFeSn-D.

[0066] Comparative Example 1

[0067] Weigh 58.2g of 50wt% manganese nitrate solution, 32.5g of ferric nitrate nonahydrate, 10.9g of ammonium heptamolybdate, and 8.5g of cerium nitrate hexahydrate and add them to 300ml of deionized water to prepare a mixed salt solution. Then, add 73.8g of anhydrous sodium carbonate to 450ml of deionized water to prepare an alkaline solution. Add the alkaline solution dropwise to the mixed salt solution at a rate of 80-120ml / min, stirring continuously to precipitate the initial product until the pH reaches 9.0. Maintain the precipitation reaction temperature at 60℃, then age the precipitate at 60℃ with stirring for 1 hour. After filtration and washing with water, a black filter cake is obtained, dried at 110℃ to a moisture content of 5%, then ground, and graphite is added to compress the cake. The cake is then calcined in a muffle furnace at 350℃ for 4 hours, pulverized, and 40-60 mesh particles are collected for denitrification activity evaluation, denoted as MnFeCeMo.

[0068] Comparative Example 2

[0069] Weigh 48.5g of 50wt% manganese nitrate solution and 49.3g of ferric nitrate nonahydrate, add them to 300ml of deionized water to prepare a mixed salt solution. Add 4.7g of 30% hydrogen peroxide and 16.5g of OP-10 to the mixed salt solution and mix thoroughly and vigorously. Then add 135.8g of anhydrous sodium carbonate to 850ml of deionized water to prepare an alkaline solution. Drop the alkaline solution into the mixed salt solution at a rate of 80-120ml / min, stirring continuously to precipitate the initial product until the pH reaches 9.0. Maintain the precipitation reaction temperature at 60℃. Then age the precipitate at 60℃ with stirring for 1 hour. After filtration and washing with water, a black filter cake is obtained. Dry the cake at 110℃ until the moisture content is 5%, then grind it, add graphite to compress it into tablets, and calcine it in a muffle furnace at 350℃ for 4 hours. Powder the cake to obtain 40-60 mesh particles for denitrification activity evaluation, denoted as MnFe-OD.

[0070] Comparative Example 3 prepared a Mn(0.4)Fe(0.08)Sn(0.3)CeOx catalyst according to the formulation and method provided in Example 4 of Patent CN101879452A.

[0071] Catalyst performance evaluation

[0072] Catalyst denitrification activity evaluation: The simulated flue gas composition was 120 ppm NO, 120 ppm NH3, 3% O2, 17.5% H2O, with the remainder being N2. The evaluation temperature was 150–300℃, and the space velocity was 20,000 h⁻¹. -1 The specific NO conversion rates are shown in Table 1.

[0073] Table 1 NO conversion rate (%) at different reaction temperatures

[0074]

[0075] Catalyst stability study: The simulated flue gas composition was 120 ppm NO, 120 ppm NH3, 3% O2, 17.5% H2O, with the remainder being N2. The evaluation temperature was 210℃, and the space velocity was 20000 h⁻¹. -1 The NO conversion rate of the catalyst after 100 h is shown in the figure. Figure 1 As shown.

[0076] As can be seen from the evaluation results in Table 1, despite a water content as high as 17.5% in the flue gas, the catalyst still maintained a high NO conversion rate, demonstrating good denitrification performance and water resistance. Figure 1 Data on the change in NO conversion rate of the catalyst with reaction time show that, with the extension of reaction time, the catalyst of this invention can still maintain a high NO conversion rate, while the NO conversion rate of the comparative catalyst shows a significant decreasing trend. The catalyst of this invention exhibits good reaction stability.

[0077] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0078] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. An environmentally friendly low-temperature water-resistant SCR denitrification catalyst, which is a MnOx-FeOx-MOx multi-metal oxide catalyst; The metal element M in the oxide MOx is selected from Mo and Sn, or from Sn and Ce; In the MnOx-FeOx-MOx multi-metal oxide catalyst, the molar ratio of element Mn, Fe and metal element M is (1~10):(1~10):1; in, x is between 1 and 4; The aforementioned environmentally friendly low-temperature water-resistant SCR denitrification catalyst is prepared by a method comprising the following steps: (1) Prepare a mixed salt solution by dissolving the soluble metal salt of the active component in water; the soluble metal salt of the active component includes soluble manganese salt, soluble iron salt, and soluble M metal salt; (2) Add the peroxide solution to the mixed salt solution and stir; (3) Add the dispersant to the mixed salt solution and stir; the dispersant is selected from at least one of polyethylene oxide, polyvinyl alcohol, polyethylene glycol, alkylphenol polyoxyethylene ether, and polyacrylic acid; (4) Prepare an alkaline solution by dissolving the alkali in water; (5) The mixed salt solution is mixed with an alkaline solution to form a precipitate, which is then aged, washed, and dried to obtain the catalyst precursor; (6) The catalyst precursor is calcined to obtain the catalyst; In step (2), the molar ratio of the peroxide to the total molars of manganese, iron, and M in the mixed salt solution is (10~0.1):1; in step (3), the amount of dispersant added is 0.01%~10% of the total molars of manganese, iron, and M in the mixed salt solution.

2. A method for preparing the environmentally friendly low-temperature water-resistant SCR denitrification catalyst as described in claim 1, characterized in that... Includes the following steps: (1) Prepare a mixed salt solution by dissolving the soluble metal salt of the active component in water; the soluble metal salt of the active component includes soluble manganese salt, soluble iron salt, and soluble M metal salt; (2) Add the peroxide solution to the mixed salt solution and stir; (3) Add the dispersant to the mixed salt solution and stir; (4) Prepare an alkaline solution by dissolving the alkali in water; (5) The mixed salt solution is mixed with an alkaline solution to form a precipitate, which is then aged, washed, and dried to obtain the catalyst precursor; (6) The catalyst precursor is calcined to obtain the catalyst.

3. The preparation method of the environmentally friendly low-temperature water-resistant SCR denitrification catalyst according to claim 2, characterized in that: The soluble manganese salt is selected from at least one of manganese nitrate, manganese acetate, and manganese sulfate; and / or, The soluble iron salt is selected from at least one of ferric chloride, ferric nitrate, and ferric acetate.

4. The preparation method of the environmentally friendly low-temperature water-resistant SCR denitrification catalyst according to claim 2, characterized in that: In step (1), the total concentration of the mixed salt solution is between 0.05 and 3.0 mol / L.

5. The preparation method of the environmentally friendly low-temperature water-resistant SCR denitrification catalyst according to claim 2, characterized in that: In step (4), the alkali is selected from one or more of sodium hydroxide, sodium carbonate, ammonia, ammonium carbonate, ammonium bicarbonate, and urea; and / or, In step (5), the pH value at which the precipitate forms is 7-11; and / or, In step (6), the roasting temperature is 300~800℃; the roasting time is 4~12h.

6. The preparation method of the environmentally friendly low-temperature water-resistant SCR denitrification catalyst according to claim 2, characterized in that: In step (4), the concentration of the alkaline solution is 0.1~3.0 mol / L; and / or, In step (5), the precipitation temperature is 30~90℃; the drying temperature is 80~120℃.

7. An environmentally friendly low-temperature water-resistant SCR denitrification catalyst prepared by the preparation method according to any one of claims 2 to 6.

8. The application of the environmentally friendly low-temperature water-resistant SCR denitrification catalyst according to claim 1 or the environmentally friendly low-temperature water-resistant SCR denitrification catalyst prepared by any one of claims 2 to 6.

9. The application according to claim 8 is for the application in low-temperature denitrification of flue gas with high water content using natural gas as feedstock.

10. The application according to claim 9, characterized in that: The flue gas temperature of the high water content flue gas is in the range of 120~300℃, and / or, The water content of the high-moisture flue gas is 5-25 vol.%.

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