Fly ash-based denitration catalyst and preparation method thereof

Abstract

The invention provides a fly ash-based denitration catalyst and a preparation method thereof, and the method comprises the following steps: 1) successively carrying out dissolution reaction and solid-liquid separation on raw materials comprising fly ash and a first acid solution to obtain a first solid phase and a first liquid phase; 2) sequentially performing activation reaction and solid-liquid separation on raw materials comprising the first solid phase and a first alkali solution to obtain a second solid phase and a second liquid phase; (3) roasting the second solid phase to obtain molten slag; 4) sequentially performing dissolution reaction and solid-liquid separation on raw materials comprising the slag and a second acid solution to obtain a third solid phase and a third liquid phase; and 5) sequentially carrying out activation reaction and solid-liquid separation on raw materials comprising the third solid phase, a second alkali solution and an oxidizing agent, and washing, drying and roasting the obtained solid phase to obtain the fly ash-based denitration catalyst. Through multi-step reaction, the characteristics of the fly ash are fully utilized, effective conversion and application of the fly ash are realized, and an efficient and environment-friendly catalyst preparation scheme is provided for the field of denitration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a fly ash-based denitration catalyst and a preparation method thereof. BACKGROUND

[0002] Fly ash is usually gray or dark gray, and is one of the largest industrial solid wastes currently discharged in China. The large accumulation of fly ash not only occupies land resources but also causes serious harm to the natural ecological environment. The chemical composition of fly ash is closely related to the composition of coal, and the main components are silicon dioxide, aluminum oxide, and diiron trioxide, calcium oxide, and unburned carbon, etc. Since fly ash contains a variety of useful elements (such as aluminum, silicon, etc.) in its chemical composition, fly ash is a very valuable resource. If the useful substances in fly ash can be effectively recovered, it can not only develop a circular economy and a conservation-oriented economy, but also reduce the damage to the natural ecological environment caused by mining.

[0003] In addition, in addition to waste fly ash, coal combustion also produces power plant flue gas particles, nitrogen oxides, carbon oxides, sulfur dioxide, etc. Nitrogen oxides (NOx) are one of the main pollutants in the atmosphere. Their large presence in the atmosphere not only directly harms the ecological environment and human health, but also reacts with other pollutants to form more harmful secondary pollution. In order to reduce emissions, research and development of NOx control technology has received widespread attention. Selective catalytic reduction (SCR) has become the mainstream denitration technology for coal-fired power plants due to its relatively mature technology and high NOx removal efficiency. If fly ash can be recycled and utilized, not only can the discharge of solid waste be reduced through the self-absorption of power plants, but also catalysts can be synthesized to supply the denitration system, which has high application value. SUMMARY

[0004] The purpose of the present application is to provide a fly ash-based denitration catalyst and a preparation method thereof, which can not only solve the problem of fly ash disposal and the environmental problems caused thereby, but also make full use of the silicon, aluminum, and iron resources in fly ash to prepare a denitration catalyst, and can be used for tail gas denitration in coal-fired power plants, achieving the effect of waste control.

[0005] In order to achieve one aspect of the above purpose, the present application adopts the following technical scheme:

[0006] In a first aspect, the present application provides a fly ash-based denitration catalyst and a preparation method thereof, comprising the following steps:

[0007] 1) sequentially performing a dissolution reaction and a solid-liquid separation on raw materials including fly ash and a first acid solution to obtain a first solid phase and a first liquid phase;

[0008] 2) sequentially performing an activation reaction and solid-liquid separation on the raw material comprising the first solid phase and the first alkali solution to obtain a second solid phase and a second liquid phase;

[0009] 3) performing calcination on the second solid phase to obtain a molten slag;

[0010] 4) sequentially performing a leaching reaction and solid-liquid separation on the raw material comprising the molten slag and the second acid solution to obtain a third solid phase and a third liquid phase;

[0011] 5) sequentially performing an activation reaction and solid-liquid separation on the raw material comprising the third solid phase and the second alkali solution and an oxidizing agent, and performing washing, drying and calcination on the obtained solid phase to obtain a fly ash-based denitration catalyst.

[0012] Further, in the fly ash, the content of Al is not less than 5%, the total content of Cu, Mn, Co and Ni is not less than 1500 mg / kg, the content of As is not higher than 0.5%, and the content of Fe is not less than 0.5%.

[0013] Further, the particle size of the fly ash is ≤100 mesh.

[0014] Further, in step 1), the first acid solution is a strong acid selected from one or more of sulfuric acid and nitric acid, and the concentration range is 0.05-1 mol / L.

[0015] Further, the liquid-solid ratio (ml / g) of the first acid solution to the fly ash is 2:1 or more, preferably 2:1-10:1, the leaching reaction temperature range is 50-80℃, and the reaction time range is 2h-6h.

[0016] Further, in step 2), the first alkali solution is selected from one or more of sodium hydroxide and potassium hydroxide, and the concentration range is 5%-20%; and / or,

[0017] Further, the liquid-solid ratio (ml / g) of the first alkali solution to the first solid phase is 5:1 or more, preferably 5:1-40:1, the activation reaction temperature range is 90-200℃, and the reaction time range is 30min or more, preferably 30-60min.

[0018] Further, in step 3), the calcination conditions include a temperature range of 400-600℃ and a time range of 0.5h or more, 1-3h.

[0019] Further, in step 4), the second acid solution is one or more of organic weak acids, preferably oxalic acid, and the concentration range is 0.05mol / L or more, preferably 0.05-2mol / L.

[0020] Further, in step 4), the liquid-solid ratio (ml / g) of the second acid solution to the slag is greater than 5:1, preferably 5:1-40:1, the temperature of the leaching reaction is 30-90℃, and the reaction time is greater than 30 min, preferably 30-60 min.

[0021] Further, in step 5), the second base solution is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water, and the concentration is 0.2%-10%.

[0022] Further, in step 5), the liquid-solid ratio (ml / g) of the second base solution to the third solid phase is greater than 5:1, preferably 5:1-40:1, the temperature of the activation reaction is 60-100℃, and the reaction time is 30-240 min.

[0023] Further, in step 5), the oxidant is H2O2, the concentration is commercially available 20%-30%, and the amount of the oxidant added is 2%-10% of the base solution.

[0024] Further, in step 5), the drying conditions include a temperature of 60-90℃ and a time of 30 min-120 min, the calcination conditions include a temperature of 400-650℃ and a time of greater than 2 h, preferably 2-12 h, and the washing includes using a mixed solution of a weak acid and an organic solution.

[0025] Further, the method further comprises washing the third solid phase before the activation reaction in step 5), and the washing preferably includes using a weak acid or a mixed solution of a weak acid and an organic solution, the weak acid is preferably oxalic acid, the organic solution is a water-miscible solution, the volume ratio of the weak acid to the organic solution is 1:10-10:1, the washing temperature is 60-90℃, and the washing time is greater than 30 min.

[0026] In a second aspect, the application provides a fly ash-based denitration catalyst prepared by the above method.

[0027] In the application, the liquid-solid ratio is the ratio of the volume of the liquid to the mass of the solid (ml / g).

[0028] Compared with the prior art, the application has the following advantages:

[0029] The application provides a preparation method of a fly ash-based denitration catalyst. The method first performs a leaching reaction on fly ash and a first acid solution, and the reaction time is not less than a certain time length, the leaching reaction aims to promote the separation of harmful heavy metals and the repair of pore diameter and the activation of part of metals, to obtain a first solid phase. Then, an activation reaction is performed on the first solid phase and a first alkali solution to activate silicon, and then calcination is performed to obtain a slag, and then a leaching reaction is performed on the slag and a second acid solution to obtain a third solid phase. An activation reaction is performed on the third solid phase, a second alkali solution and an oxidizing agent to realize activation and oxidation, and at the same time, the effects of removing As and activating Si and Al are achieved. Finally, the obtained solid phase is washed to improve the surface acidic sites, dried and calcined to obtain the fly ash-based denitration catalyst. The preparation method fully utilizes the catalytically active metals and silicon-aluminum characteristics in the fly ash through multiple reactions, realizes effective conversion and application of the fly ash, and is expected to provide an efficient and environmentally friendly catalyst preparation scheme for the field of denitration.

[0030] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0031] The specific embodiments of the present application are described in detail below. It should be understood that the following examples are only used to more clearly illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Various changes, modifications, replacements and variations made by those skilled in the art to the examples without departing from the principles and purposes of the present application shall be included in the protection scope of the present application.

[0032] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. These ranges and values should be construed as being approximate. For numeric values, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to obtain one or more new numeric ranges, which should be considered as being specifically disclosed herein.

[0033] As analyzed in the background art of the present application, in order to solve the problems of fly ash dumping and the environmental problems caused thereby, and to make full use of the resources of silicon, aluminum, iron and the like in fly ash, the present application provides a fly ash-based denitration catalyst and a preparation method thereof, which comprises the following steps:

[0034] 1) sequentially performing a leaching reaction and solid-liquid separation on raw materials comprising fly ash and a first acid solution to obtain a first solid phase and a first liquid phase;

[0035] 2) sequentially performing an activation reaction and solid-liquid separation on raw materials comprising the first solid phase and a first alkali solution to obtain a second solid phase and a second liquid phase;

[0036] 3) calcining the second solid phase to obtain a slag;

[0037] 4) sequentially performing a leaching reaction and a solid-liquid separation on the raw material comprising the slag and the second acid solution to obtain a third solid phase and a third liquid phase;

[0038] 5) sequentially performing an activation reaction and a solid-liquid separation on the raw material comprising the third solid phase and the second base solution and an oxidizing agent, washing, drying and calcining the obtained solid phase to obtain a fly ash-based denitration catalyst.

[0039] In the present application, the first solid phase comprises the main components of the tailings and the fly ash, the first liquid phase comprises the removed heavy metals and the acid solution, the second solid phase comprises the components such as silicon after the removal of the main heavy metals, the second liquid phase comprises part of the heavy metals and the alkali solution, the third solid phase comprises the components such as silicon after the removal of the main heavy metals, and the third liquid phase comprises the residual acid and alkali.

[0040] The main reaction route in the present application is the first acid leaching reaction-the first base activation reaction-calcination-the second acid leaching reaction-the second base activation reaction, which can fully remove the heavy metals in the above order, and if the above order is not followed, the metal removal will be insufficient, and the residual metal will be unstable.

[0041] In some embodiments, the fly ash has an Al content of not less than 5%, a total Cu, Mn, Co and Ni content of not less than 1500 mg / kg, an As content of not more than 0.5%, and an Fe content of not less than 0.5%. The advantages of selecting the fly ash with the above component contents are that the residual metals (Al, Cu, Mn, Co, Ni and Fe) can be fully utilized to play a role in denitration, external active components are avoided, and the effect of As and the like on denitration is avoided.

[0042] In some embodiments, the particle size of the fly ash is ≤100 mesh. The advantage of selecting this particle size is that it is convenient for mixing and subsequent reactions. Exemplarily, the fly ash is subjected to screening and ball milling operations to meet the above particle size requirement.

[0043] In some embodiments, in step 1), the first acid solution is a strong acid selected from one or more of sulfuric acid and nitric acid, and the concentration range is 0.05-1 mol / L.

[0044] In some embodiments, the liquid-solid ratio (ml / g) of the first acid solution to the fly ash is 2:1 or more, preferably 2:1-10:1, the leaching reaction temperature is 50-80℃, and the reaction time is 2h-6h.

[0045] In step 1), the first acid leaching reaction is preferably performed under the above conditions, which can separate the harmful heavy metals and repair the pore size.

[0046] In some embodiments, in step 2), the first alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, with a concentration ranging from 5% to 20%; and / or,

[0047] In some embodiments, the liquid-solid ratio (ml / g) of the first alkaline solution to the first solid phase in step 2) is greater than 5:1, preferably ranging from 5:1 to 40:1, the activation reaction temperature ranges from 90 to 200°C, and the reaction time is greater than 30 minutes, preferably ranging from 30 to 60 minutes.

[0048] In step 2), the first alkaline activation reaction is preferably carried out under the above conditions, which can activate silicon to promote the stability of subsequent materials.

[0049] In some embodiments, in step 3), the calcination conditions include a temperature ranging from 400 to 600°C, a time greater than 0.5h, 1 to 3h, and exemplarily 450°C, 2.5h, 500°C, 2h, 550°C, 1.5h, etc. The calcination is preferably carried out under the above conditions, which can remove moisture and stabilize active components.

[0050] In some embodiments, in step 4), the second acid solution is one or more of organic weak acids, preferably oxalic acid, with a concentration greater than 0.05 mol / L, preferably ranging from 0.05 to 2 mol / L.

[0051] In some embodiments, in step 4), the liquid-solid ratio (ml / g) of the second acid solution to the molten slag is greater than 5:1, preferably ranging from 5:1 to 40:1, the dissolution reaction temperature ranges from 30 to 90°C, and the reaction time is greater than 30 minutes, preferably ranging from 30 to 60 minutes.

[0052] In step 4), the second acid dissolution reaction is preferably carried out under the above conditions, which can increase the acidic sites and promote the stable complexation of silicon to active metals.

[0053] In some embodiments, in step 5), the second alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia, with a concentration ranging from 0.2% to 10%.

[0054] In some embodiments, in step 5), the liquid-solid ratio (ml / g) of the second alkaline solution to the third solid phase is greater than 5:1, preferably ranging from 5:1 to 40:1, the activation reaction temperature ranges from 60 to 100°C, and the reaction time ranges from 30 to 240 minutes.

[0055] In step 5), the second alkaline activation reaction is preferably carried out under the above conditions, which can remove As and activate Si and Al.

[0056] In some embodiments, in step 5), the oxidant is H2O2, the concentration range is 20%-30% of commercially available, and the volume of the added oxidant accounts for 2%-10% of the volume of the second alkali solution. The effect of simultaneously adding the oxidant in the second alkali activation reaction is to promote the oxidation of As to a high valence state, thereby effectively removing.

[0057] In some embodiments, in step 5), the drying conditions include: the temperature range is 60-90℃, and the time range is 30min-120min; the calcination conditions include: the temperature range is 400-650℃, and the time range is 2h or more, preferably 2-12h; the washing includes: washing with a mixed solution of a weak acid and an organic solution.

[0058] In some embodiments, the method further comprises: washing the third solid phase after washing, and then performing the activation reaction in step 5); preferably, the washing includes: washing with a weak acid or washing with a mixed solution of a weak acid and an organic solution; the weak acid is preferably oxalic acid, the organic solution is a water-miscible solution, the volume ratio of the weak acid and the organic solution is 1:10-10:1, the washing temperature is 60-90min, and the washing time is 30min or more.

[0059] In the present application, the solid-liquid separation can be performed in a conventional manner in the art, such as filtration, centrifugal separation, etc.

[0060] In the present application, the types of the first acid solution and the second acid solution can be different, the first acid solution is mainly used for separating heavy metals, and the second acid solution is used for alkalization and then acidification; the concentrations of the first alkali solution and the second alkali solution can be different, for example, the concentration of the second alkali solution is lower than that of the first alkali solution, the first alkali solution is used for removing part of the residual heavy metals, activating the tailings and fly ash, and removing silicon and aluminum, and the second alkali solution is mainly used for removing As and improving the microstructure.

[0061] In a second aspect, the present application provides a fly ash-based denitration catalyst prepared by the above method. The present application uses solid waste as a catalyst, uses the residual metals in fly ash for activation and uses them as active components to prepare the catalyst, and at the same time, the activation of silicon and aluminum during the preparation process improves the overall activity.

[0062] The technical solutions of the present application will be further described in detail below in combination with embodiments.

[0063] I. Test method:

[0064] The test method or reference standard of the performance index is as follows:

[0065] Metal content: ICP test

[0066] Denitrification efficiency: Test the nitrogen oxide denitrification rate of the denitrification catalyst at different temperatures: The test method is to take a small sample of the denitrification catalyst and pass a simulated gas to evaluate the activity. The composition of the simulated gas is similar to that of industrial boiler exhaust, and its composition is as follows: 500ppm of NO, 400ppm of NH3, 10.00% of O2, 12% of water, and the rest is nitrogen. The simulated gas is passed into the denitrification reactor for reaction. The concentration of nitrogen oxides in the flue gas before and after the reaction is analyzed using a 42i-HL flue gas analyzer, and then the denitrification rate of the denitrification catalyst at a specific temperature is calculated. The calculation method of the denitrification rate is: η = (ab) / a × 100%, where the concentration of nitrogen oxides in the flue gas before the reaction is a, the concentration of nitrogen oxides in the flue gas after the reaction is b, and the denitrification rate of the denitrification catalyst is η.

[0067] Specific surface area: DeNOx catalysts and products were tested using a fully automatic nitrogen adsorption and desorption instrument (Mike 2020).

[0068] 2. Source of raw materials:

[0069] Select fly ash from a thermal power plant in Inner Mongolia

[0070] Example 1

[0071] The fly ash indicators are as follows: by mass percentage, Al2O3 content is 5.22%, the total content of Cu, Mn, Co and Ni is 3478 mg / kg, the As content is 63 mg / kg, and the Fe content is 0.64%.

[0072] First, the fly ash is ball-milled and sieved to below 100 mesh, and then nitric acid is added for reaction at a reaction temperature of 60°C, a nitric acid concentration of 0.5 mol / L, a liquid-solid ratio of 6:1, and a reaction time of 4 hours. The first solid phase and the first liquid phase are filtered. The first solid phase is then mixed with a 20% sodium hydroxide solution for activation reaction for 1 hour. The reaction temperature is 110°C and the liquid-solid ratio is 7:1. The second solid phase and the second liquid phase are filtered. The second solid phase is roasted at 500°C for 30 minutes to obtain slag. The slag is mixed with 0.5 mol / L oxalic acid for reaction for 1 hour. The reaction temperature is 60°C and the liquid-solid ratio is 6:1. The third solid phase and the third liquid phase are filtered. The third solid phase is mixed with a 5% sodium hydroxide solution and commercially available 30% hydrogen peroxide for activation reaction for 1 hour. The reaction temperature is 80°C and the liquid-solid ratio is 7:1. The amount of hydrogen peroxide added is 3% of the volume of the sodium hydroxide solution. The product is then filtered, washed, dried and roasted.

[0073] Example 2

[0074] The difference from Example 1 is that some reaction temperatures and reaction times are different, specifically: the first acid reaction temperature is 80°C, the reaction time is 2h, the first alkali activation temperature is 200°C, the reaction time is 30min, the second acid reaction temperature is 90°C, the reaction time is 30min, and the second alkali activation temperature is 100°C, and the reaction time is 2h.

[0075] Example 3

[0076] The difference from Example 1 is that some reaction temperatures and reaction times are different, specifically: the first acid reaction temperature is 50°C, the reaction time is 6 hours, the first alkali activation temperature is 90°C, the reaction time is 60 minutes, the second acid reaction temperature is 30°C, the reaction time is 60 minutes, and the second alkali activation temperature is 60°C, and the reaction time is 4 hours.

[0077] Example 4

[0078] The difference from Example 1 is that some concentration conditions are different, specifically: the first acid solution is 1 mol / L nitric acid, the first alkaline solution is 15% sodium hydroxide solution, the second acid solution is 1 mol / L oxalic acid, and the second alkaline solution is 10% sodium hydroxide solution.

[0079] Example 5

[0080] The difference from Example 1 is that some concentration conditions are different, specifically: the first acid solution is 0.05 mol / L sulfuric acid, the first alkaline solution is 5% sodium hydroxide solution, the second acid solution is 0.05 mol / L oxalic acid, and the second alkaline solution is 0.2% sodium hydroxide solution.

[0081] Example 6

[0082] The difference from Example 1 is that some liquid-solid ratios are different, specifically: the liquid-solid ratio of the first acid reaction is 10:1, the liquid-solid ratio of the first alkali activation is 10:1, the liquid-solid ratio of the second acid reaction is 10:1, the liquid-solid ratio of the second alkali activation is 10:1, and the amount of hydrogen peroxide added is 10% of the volume of the second alkali solution.

[0083] Example 7

[0084] The difference from Example 1 is that some liquid-solid ratios are different, specifically: the liquid-solid ratio of the first acid reaction is 2:1, the liquid-solid ratio of the first alkali activation is 5:1, the liquid-solid ratio of the second acid reaction is 5:1, the liquid-solid ratio of the second alkali activation is 5:1, and the amount of hydrogen peroxide added is 2% of the volume of the second alkali solution.

[0085] Example 8

[0086] The difference from Example 1 is that the first acid solution and the second acid solution are the same, both containing 0.5 mol / L nitric acid.

[0087] Comparative Example 1

[0088] Without the first acid reaction and the first base reaction, the rest is the same as Example 1.

[0089] Comparative Example 2

[0090] Without the second acid reaction and the second base reaction, the rest is the same as Example 2.

[0091] Comparative Example 3

[0092] Without the intermediate calcination, the rest is the same as Example 1.

[0093] Comparative Example 4

[0094] The order of acid reaction and base reaction is changed, and the specific order is: first base activation reaction-first acid dissolution reaction-second base activation reaction-second acid dissolution reaction, and the rest is the same as Example 1.

[0095] The performance of the catalyst product obtained in the examples and comparative examples of the present application is shown in Table 1 below.

[0096] Table 1

[0097]

[0098] Although the content of the present application has been described in detail through the above preferred examples, it should be recognized that the above description should not be considered as a limitation of the present application. Those skilled in the art can understand that some modifications or adjustments can be made to the present application under the teaching of the present specification. These modifications or adjustments should also be within the scope defined by the claims of the present application.

Claims

1. A method for preparing a fly ash-based denitrification catalyst, characterized in that: The steps include: 1) subjecting the raw materials including fly ash and the first acid solution to a dissolution reaction and solid-liquid separation in sequence to obtain a first solid phase and a first liquid phase; 2) subjecting the raw materials including the first solid phase and the first alkaline solution to activation reaction and solid-liquid separation in sequence to obtain a second solid phase and a second liquid phase; 3) calcining the second solid phase to obtain slag; 4) subjecting the raw materials including the slag and the second acid solution to a dissolution reaction and solid-liquid separation in sequence to obtain a third solid phase and a third liquid phase; 5) The raw materials including the third solid phase, the second alkaline solution and the oxidant are sequentially subjected to activation reaction and solid-liquid separation, and the obtained solid phase is washed, dried and calcined to obtain a fly ash-based denitrification catalyst.

2. The method for preparing the fly ash-based denitration catalyst according to claim 1, wherein: Taking the mass of fly ash as 100%, the fly ash has the following contents: Al content is not less than 5%, the total content of Cu, Mn, Co and Ni is not less than 1500 mg / kg, As content is not higher than 0.5%, and Fe content is not less than 0.5%; preferably, the particle size of the fly ash is ≤100 mesh.

3. The method for preparing the fly ash-based denitration catalyst according to claim 1 or 2, characterized in that: In step 1), the first acid solution is a strong acid selected from one or more of sulfuric acid and nitric acid, with a concentration range of 0.05-1 mol / L; and / or, In step 1), the liquid-solid ratio of the first acid solution to the fly ash is in the range of 2:1 or more, preferably 2:1-10:1, the dissolution reaction temperature is in the range of 50-80°C, and the reaction time is in the range of 2h-6h.

4. The method for preparing the fly ash-based denitration catalyst according to any one of claims 1 to 3, characterized in that: In step 2), the first alkaline solution is selected from one or more of sodium hydroxide and potassium hydroxide, with a concentration range of 5%-20%; and / or, In step 2), the liquid-solid ratio of the first alkaline solution to the first solid phase is in the range of 5:1 or more, preferably 5:1-40:1, the activation reaction temperature is in the range of 90-200° C., and the reaction time is in the range of 30 min or more, preferably 30-60 min.

5. The method for preparing the fly ash-based denitration catalyst according to any one of claims 1 to 4, characterized in that: In step 3), the calcination conditions include: a temperature range of 400-600° C., and a time range of more than 0.5 h and 1-3 h.

6. The method for preparing the fly ash-based denitration catalyst according to any one of claims 1 to 5, characterized in that: In step 4), one or more of the organic weak acids in the second acid solution, preferably oxalic acid, has a concentration range of 0.05 mol / L or more, preferably 0.05-2 mol / L; and / or, In step 4), the liquid-solid ratio of the second acid solution to the slag is in the range of 5:1 or more, preferably 5:1-40:1, the dissolution reaction temperature is in the range of 30-90°C, and the reaction time is in the range of 30 min or more, preferably 30-60 min.

7. The method for preparing the fly ash-based denitration catalyst according to any one of claims 1 to 6, characterized in that: In step 5), the second alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water, with a concentration ranging from 0.2% to 10%; and / or, In step 5), the liquid-solid ratio of the second alkaline solution to the third solid phase is in the range of 5:1 or more, preferably 5:1-40:1, the activation reaction temperature is in the range of 60-100° C., and the reaction time is in the range of 30-240 min; and / or, In step 5), the oxidant is H2O2, the concentration range of which is commercially available at 20%-30%, and the amount of the oxidant added accounts for 2%-10% of the alkaline solution.

8. The method for preparing the fly ash-based denitration catalyst according to any one of claims 1 to 7, characterized in that: In step 5), the drying conditions include: temperature range 60-90°C, time range 30min-120min; the roasting conditions include: temperature range 400-650°C, time range more than 2h, preferably 2-12h; the washing conditions include: washing with a mixed solution of weak acid and organic solvent.

9. The method for preparing a fly ash-based denitration catalyst according to any one of claims 1 to 8, characterized in that: The method further comprises: washing the third solid phase and then performing the activation reaction described in step 5); Preferably, the washing includes: washing with a weak acid or washing with a mixed solution of a weak acid and an organic solution; the weak acid is preferably oxalic acid, the organic solution is a solution miscible with water, the volume ratio of the weak acid to the organic solution is 1:10-10:1, the washing temperature is 60-90min, and the washing time is more than 30min.

10. A fly ash-based denitration catalyst prepared by the method according to any one of claims 1 to 9.

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