Denitration catalyst with high sulfur resistance and water resistance and preparation method thereof

Abstract

The invention discloses a denitration catalyst with high sulfur resistance and water resistance and a preparation method thereof, the catalyst comprises a modified carrier and active components loaded on the modified carrier, the modified carrier comprises fly ash, titanium dioxide and iron powder, and the active components comprise vanadium oxide and tungsten oxide. The iron-modified fly ash partially replaces titanium dioxide to serve as a carrier of the catalyst, vanadium and tungsten active components are loaded, the obtained denitration catalyst shows excellent sulfur resistance and water resistance, meanwhile, the catalyst further has a wide active temperature window and high nitrogen selectivity, the preparation process is simple, operation is easy, cost is low, and the catalyst is suitable for industrial production. The method has high environmental value and economic value.

Description

Technical Field

[0001] This invention belongs to the field of industrial flue gas purification and treatment technology. Specifically, this invention relates to a high sulfur and water resistance denitrification catalyst and its preparation method. Background Technology

[0002] Coal-fired power plants are the main source of electricity supply in my country; however, nitrogen oxides (NOx) in coal-fired flue gas are a significant contributor to the problem. X It poses a great threat to human health and the environment. X If directly released into the atmosphere, NO will not only react with water vapor to produce nitric acid and nitrite, leading to acid rain; it will also combine with hydrocarbons in the atmosphere to form photochemical smog, posing a serious threat to soil, water sources, plants, and urban air quality; and it will further deteriorate air quality by forming particulate matter. Furthermore, for human health, NO... X It can irritate the respiratory tract, trigger respiratory diseases, and affect cardiovascular health; and NO X It may also damage the nervous system, affecting people's quality of life and long-term health. Therefore, the concentration of NO in the atmosphere... X The governance of this is of particular importance.

[0003] Ammonia selective catalytic reduction (NH3-SCR) technology is one of the most widely used flue gas denitrification technologies. This technology uses ammonia as a reducing agent and a catalyst to reduce NO3-. X Selective reduction produces nitrogen and water. Vanadium-based catalysts (V₂O₅-WO₃ / TiO₂, VWTi) are widely used in industry due to their excellent activity and stability. VWTi catalysts are obtained by supporting titanium dioxide (TiO₂) as a carrier, with the active components V₂O₅ and WO₃ loaded onto it. The proportion of titanium dioxide as the carrier is as high as 94-97 wt.%. However, the continuous increase in the price of titanium dioxide poses a challenge to the cost control of catalysts. Furthermore, commercial VWTi catalysts have a high operating temperature window (typically 300-400℃), requiring a high-dust arrangement for SCR. The disadvantage of this arrangement is that high concentrations of sulfur (SO₂) and water (H₂O) in the flue gas can cause catalyst poisoning and deactivation. Therefore, further reducing the cost of commercial VWTi catalysts and improving their sulfur and water resistance are important research directions.

[0004] Fly ash (CFA) is a waste product generated by coal-fired power plants with a very low reuse rate, necessitating the development of new utilization pathways. Current research includes some studies on the preparation of denitrification catalysts using fly ash. The most common approach involves synthesizing zeolite molecular sieves from fly ash and then loading them with active components. However, this route involves complex Si / Al ratio control, high-temperature acid-base activation, hydrothermal treatment, and subsequent purification steps, making it not only cumbersome but also resulting in limited yields. Furthermore, the use of strong acids and alkalis poses a potential environmental threat. Therefore, effectively combining fly ash, this waste product, with denitrification catalysts has become a focus of attention. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a highly sulfur- and water-resistant denitrification catalyst and its preparation method. This denitrification catalyst exhibits excellent sulfur and water resistance, a wide activity temperature window, high nitrogen selectivity, and low cost.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a highly sulfur- and water-resistant denitrification catalyst, the catalyst comprising a modified support and an active component supported on the modified support, the modified support comprising fly ash, titanium dioxide and iron powder, and the active component comprising vanadium oxide and tungsten oxide.

[0008] In some embodiments, the modified support accounts for 95.2-98.5% of the total mass of the catalyst; wherein the fly ash accounts for 30-66% of the total mass of the catalyst, the titanium dioxide accounts for 29-65% of the total mass of the catalyst, and the iron powder accounts for 0.5-7.0% of the total mass of the catalyst.

[0009] In some embodiments, the active component accounts for 1.5 to 4.8% of the total mass of the catalyst; wherein the vanadium oxide accounts for 0.7 to 1.6% of the total mass of the catalyst, and the tungsten oxide accounts for 0.8 to 3.2% of the total mass of the catalyst.

[0010] In some embodiments, the modified carrier is prepared by a method comprising the following steps: Step a: Mix fly ash with acetic acid solution and perform wet ball milling to obtain acid-treated fly ash; Step b: Wash, dry and sieve the acid-treated fly ash to obtain pretreated fly ash; Step c: Mix the pretreated fly ash with iron powder and titanium dioxide, and perform dry ball milling to obtain the modified carrier.

[0011] In some embodiments, in step a, the concentration of the acetic acid solution is 0.5~2 mol / L; And / or, the wet ball milling speed is 140~200 r / min, and the ball milling time is 2~5 h.

[0012] In some embodiments, in step b, the drying temperature is 100~120℃ and the drying time is 3~8h; And / or, the sieve used for sieving has a mesh size of 80 to 120.

[0013] In some embodiments, in step c, the rotation speed of the dry ball mill is 120~200 r / min, and the ball milling time is 2~5 h.

[0014] Secondly, embodiments of the present invention also provide a method for preparing a high sulfur and water-resistant denitrification catalyst as described in the first aspect, comprising the following steps: (1) Place ammonium metatungstate, ammonium metavanadate, and anhydrous oxalic acid in water, stir to dissolve, and obtain an active component solution; (2) Immerse the modified carrier in the solution of the active component, stir evenly, let stand, and then let it air dry naturally; (3) The sample dried in step (2) is calcined to obtain the high sulfur and water resistance denitrification catalyst.

[0015] In some embodiments, the settling time in step (2) is 1 to 2 hours.

[0016] In some embodiments, in step (3), the heating rate of the calcination treatment is 3~7℃ / min, the calcination temperature is 500~550℃, and the calcination time is 1.5~5h.

[0017] The advantages and beneficial effects of the embodiments of the present invention are as follows: (1) The denitrification catalyst in the embodiments of the present invention has high denitrification activity and excellent sulfur and water resistance, as well as a wide activity temperature window and a wide range of applications.

[0018] (2) In this embodiment of the invention, solid waste fly ash is used to partially replace titanium dioxide (TiO2) as a catalyst carrier, which can not only significantly reduce the production cost of denitrification agent, but also provide a new idea for the high-value utilization of fly ash.

[0019] (3) The denitrification catalyst in the embodiments of the present invention has a simple preparation process, is easy to scale up for production, and has practical application value. Attached Figure Description

[0020] Figure 1This is a process flow diagram of the preparation method of the high sulfur and water resistance denitrification catalyst according to an embodiment of the present invention.

[0021] Figure 2 The graphs show the denitrification performance of the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention and a conventional commercial denitrification catalyst.

[0022] Figure 3 The figures show the sulfur and water resistance test results of the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention, the denitrification catalysts prepared in Comparative Examples 1-2, and traditional commercial denitrification catalysts.

[0023] Figure 4 The graph shows the N2 selectivity and NH3 conversion of the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention.

[0024] Figure 5 The images show SEM images of the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention, the denitrification catalyst prepared in Comparative Example 1, and fly ash.

[0025] Figure 6 This is an elemental distribution diagram of the VWTi / CFA-Fe catalyst prepared in Example 1 of the present invention.

[0026] Figure 7 The image shows the pore size distribution of the VWTi / CFA-Fe catalyst and fly ash prepared in Example 1 of this invention.

[0027] Figure 8 Thermogravimetric analysis (TGA) results of the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention after being poisoned by SO2.

[0028] Figure 9 The image shows the NO-TPD test results of the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention before and after SO2 poisoning. Detailed Implementation

[0029] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] In this invention, when a value is described as a range, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as specific numerical values ​​falling within that range, regardless of whether specific numerical values ​​or specific subranges are explicitly specified.

[0031] In this invention, the terms “comprising” and “including” and their various variations mean that other elements or wholes may be included but are not specifically described.

[0032] In this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0033] In a first aspect, embodiments of the present invention provide a highly sulfur- and water-resistant denitrification catalyst, the catalyst comprising a modified support and an active component supported on the modified support, the modified support comprising fly ash, titanium dioxide and iron powder, and the active component comprising vanadium oxide and tungsten oxide.

[0034] In some embodiments, the modified support accounts for 95.2% to 98.5% of the total mass of the catalyst; wherein the fly ash accounts for 30% to 66% of the total mass of the catalyst, the titanium dioxide accounts for 29% to 65% of the total mass of the catalyst, and the iron powder accounts for 0.5% to 7.0% of the total mass of the catalyst. Using fly ash, a solid waste material, to partially replace titanium dioxide as the support for the denitrification catalyst, with the fly ash accounting for 30% to 66 wt.%, can significantly reduce the manufacturing cost of the catalyst, lowering its cost by 21% to 50%.

[0035] In some embodiments, the active component accounts for 1.5 to 4.8% of the total mass of the catalyst; wherein the vanadium oxide accounts for 0.7 to 2.0% of the total mass of the catalyst, and the tungsten oxide accounts for 0.8 to 3.2% of the total mass of the catalyst.

[0036] In some embodiments, the modified carrier is prepared by a method comprising the following steps: Step a: Mix fly ash with acetic acid solution and perform wet ball milling to obtain acid-treated fly ash; Step b: Wash, dry and sieve the acid-treated fly ash to obtain pretreated fly ash; Step c: Mix the pretreated fly ash with iron powder and titanium dioxide, and perform dry ball milling to obtain the modified carrier.

[0037] In some embodiments, in step a, the concentration of the acetic acid solution is 0.5~2 mol / L. By using acetic acid solution to acid treat fly ash, alkaline substances and other soluble pollutants on the surface of fly ash can be dissolved, achieving a cleaning effect and improving the purity of the fly ash carrier, thus preventing these pollutants from clogging active sites or causing side reactions during the SCR process. Furthermore, the inventors have found that if the concentration of the acetic acid solution is too high, in addition to the dissolution of target impurities, the active framework (such as aluminosilicates) in the fly ash will also be excessively dissolved by the strong acid, leading to a decrease in the specific surface area of ​​the fly ash and collapse of the pores. However, if the concentration of the acetic acid solution is too low, impurities will not be completely removed, and poisons such as CaO, MgO, and free alkali metals will remain, clogging the pores, neutralizing the acidic sites on the surface, and reacting with SO2 to generate sulfates in the SCR reaction, accelerating catalyst deactivation. Therefore, it is advantageous to control the concentration of the acetic acid solution in the range of 0.5~2 mol / L in the embodiments of the present invention. And / or, the wet ball milling speed is 140~200 r / min, and the ball milling time is 2~5 h.

[0038] In some embodiments, in step b, the drying temperature is 100~120℃ and the drying time is 3~8h; And / or, the sieve used for sieving has a mesh size of 80 to 120. If the mesh size of the sieve is too large, the fly ash particle size will be too small, making it very easy to agglomerate. It will be difficult to disperse evenly in the subsequent ball milling or impregnation process, which will lead to uneven distribution of active components. However, if the mesh size of the sieve is too small, the fly ash particle size will be too coarse, the specific surface area will be significantly reduced, the available active surface will be limited, resulting in low loading or sparse distribution of active components and insufficient number of active sites per unit mass of catalyst.

[0039] In some embodiments, in step c, the rotation speed of the dry ball mill is 120~200 r / min, and the ball milling time is 2~5 h.

[0040] This invention utilizes fly ash as a carrier, which not only provides a large specific surface area but also successfully retains its internal microporous structure after loading the active components. This significantly enhances the catalyst's pore complexity and specific surface area, effectively promoting the full exposure of active sites on the catalyst surface and further improving its activity. Furthermore, the catalyst surface has a high content of acid sites, exhibiting strong adsorption capacity for NH3 and NO, while its adsorption of SO2 is relatively weak. This selective adsorption characteristic not only improves denitrification efficiency but also significantly enhances the catalyst's sulfur resistance. In the presence of SO2, the catalyst can adsorb more NO. XIn addition, SO2 also promotes the reaction of NH3 at Lewis acid sites, generating more NO2 and completely consuming it, thus triggering a "fast SCR" reaction, demonstrating its excellent sulfur resistance.

[0041] Furthermore, the embodiments of the present invention also improve the electron transfer characteristics of the catalyst surface and enhance the activity of the SCR reaction through the strong interaction between the added Fe and the V active component in the catalyst. In addition, V 5+ Fe 3+ The increased proportion of surface active oxygen enhances the catalyst's redox ability, promotes the oxidation of NO to NO2, further drives the "fast SCR" reaction, and greatly shortens the reaction path.

[0042] Secondly, such as Figure 1 As shown in the embodiments of the present invention, a method for preparing a high sulfur and water-resistant denitrification catalyst as described in the first aspect is also proposed, comprising the following steps: (1) Place ammonium metatungstate, ammonium metavanadate, and anhydrous oxalic acid in water, stir to dissolve, and obtain an active component solution; (2) Immerse the modified carrier in the solution of the active component, stir evenly, let stand, and then let it air dry naturally; (3) The sample dried in step (2) is calcined to obtain the high sulfur and water resistance denitrification catalyst.

[0043] In some embodiments, the settling time in step (2) is 1 to 2 hours.

[0044] In some embodiments, in step (3), the heating rate of the calcination treatment is 3~7℃ / min, the calcination temperature is 500~550℃, and the calcination time is 1.5~5h. Furthermore, the inventors have found that excessively high calcination temperatures or prolonged calcination times can lead to a series of negative effects: TiO2 in the support transforms from a high-specific-surface-area anatase phase to a low-activity rutile phase, reducing the structural stability and active site anchoring ability of the support; the aluminosilicate skeleton in fly ash may sinter, causing the mesoporous structure to collapse and increasing diffusion resistance; simultaneously, the generated active component V2O5 may partially volatilize at excessively high temperatures, resulting in the loss of active components; V2O5 and WO3 particles migrate and aggregate, increasing crystal size, significantly decreasing specific surface area, and reducing the number of active sites; Fe species may sinter, weakening their synergistic effect with V and W; strong heat causes dehydration of surface Brønsted acid sites, covering Lewis acid sites, and reducing NH3 adsorption capacity. However, if the calcination temperature is too low or the calcination time is too short, a series of problems will occur: precursors such as ammonium metavanadate and ammonium metatungstate will not be completely converted into active component oxides; V2O5 and WO3 crystallize insufficiently, and although the dispersion is high, the active centers are not fully formed, resulting in low redox cycle efficiency; Fe species cannot be fully integrated into the support surface, limiting the improvement of resistance to SO2 / H2O; and acid sites are not fully formed, resulting in low NH3 adsorption capacity, affecting the initiation of the SCR reaction and low-temperature activity. Therefore, it is advantageous to control the calcination temperature and calcination time within the above-mentioned range in the embodiments of the present invention.

[0045] The following are non-limiting embodiments and comparative examples of the present invention. It should be noted that the schemes in the comparative examples are not prior art, but are only set up for comparison with the schemes in the embodiments, and are not intended to limit the present invention. Unless otherwise stated, all raw materials used in the embodiments and comparative examples are conventional commercially available products, or can be prepared by known methods; and the experimental methods in the embodiments that do not specify specific conditions are conventional methods and conditions well known in the art.

[0046] Example 1 This embodiment provides a method for preparing a highly sulfur- and water-resistant denitrification catalyst, comprising the following steps: (1) Preparation of modified carrier Step a: Add 100g of fly ash and 100mL of acetic acid solution (1mol / L) to a ball mill jar, and wet mill at 150r / min for 3h to obtain acid-treated fly ash; Step b: Wash the acid-treated fly ash twice with deionized water, then dry it in an oven at 105°C for 4 hours. Then, sieve the dried fly ash through an 80-120 mesh screen to remove large particles. After that, seal it in a sealed bag for later use to obtain pretreated fly ash. Step c: Take 4.75g of pretreated fly ash, 0.25g of iron powder and 2.5g of titanium dioxide, place them in a ball mill jar, and dry grind them at 150r / min for 3h to obtain the modified carrier, denoted as Ti / CFA-Fe.

[0047] (2) Preparation of denitration catalyst Step d: Add 0.21g ammonium metatungstate, 0.20g ammonium metavanadate, and 0.5g anhydrous oxalic acid to 20mL of deionized water and stir until all solid particles are completely dissolved to obtain the active component solution. Step e: Immerse the modified carrier in the active component solution, stir evenly, and let it stand for 1 hour. Then pour it into a plastic flat-bottomed petri dish and spread it out to air dry naturally. Step f: Place the dried sample in a muffle furnace for calcination. Set the heating rate to 5℃ / min, the calcination temperature to 510℃, and the calcination time to 2h. After calcination, wait for the temperature of the muffle furnace to drop to room temperature, and then take out the sample to obtain the high sulfur and water resistance denitrification catalyst, denoted as VWTi / CFA-Fe.

[0048] Example 2 The preparation method of the high sulfur and water resistance denitrification catalyst in this embodiment is basically the same as that in Example 1, except that in step c of this embodiment, the mass of the pretreated fly ash is 4.7g and the mass of the iron powder is 0.3g.

[0049] Example 3 The preparation method of the high sulfur and water resistance denitrification catalyst in this embodiment is basically the same as that in Example 1, except that: in step a, the volume of acetic acid solution is 150 mL; in step c, the mass of pretreated fly ash is 4.625 g and the mass of iron powder is 0.375 g; in step d, the mass of ammonium metatungstate is 0.23 g and the mass of ammonium metavanadate is 0.21 g.

[0050] Example 4 The preparation method of the high sulfur and water resistance denitrification catalyst in this embodiment is basically the same as that in Example 1, except that: in step a of this embodiment, the concentration of acetic acid solution is 1.5 mol / L; in step c, the mass of pretreated fly ash is 4.8 g and the mass of iron powder is 0.2 g.

[0051] Example 5 The preparation method of the high sulfur and water resistance denitrification catalyst in this embodiment is basically the same as that in Example 1, except that in step c of this embodiment, the mass of the pretreated fly ash is 4.5g and the mass of the iron powder is 0.5g.

[0052] Comparative Example 1 The preparation method of the denitrification catalyst in this comparative example is basically the same as that in Example 1, except that in step c of this comparative example, the raw materials do not contain iron powder, but only 5g of pretreated fly ash and 2g of titanium dioxide.

[0053] Comparative Example 2 The preparation method of the denitrification catalyst in this comparative example is basically the same as that in Example 1, except that in step c of this comparative example, the raw materials do not contain titanium dioxide, but only 6.75g of pretreated fly ash and 0.25g of iron powder.

[0054] The denitrification performance of the high sulfur and water resistant denitrification catalyst (i.e., VWTi / CFA-Fe catalyst) prepared in Example 1 of this invention and the traditional commercial denitrification catalyst (the denitrification catalyst used in Unit #1 of Xiamen Huaxia Power Company) were tested, and the results are as follows: Figure 2 As shown. From Figure 2 As can be seen from the data, in the simulated flue gas with 1000ppm NO + 1000ppm NH3 + 5% O2 and a space velocity of 30,000 h⁻¹, -1 Under the same conditions, compared with the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention, the traditional commercial denitrification catalyst has poor denitrification activity at low temperatures, with a performance gap of more than 10% compared with the VWTi / CFA-Fe catalyst prepared in Example 1; and its denitrification efficiency at 350℃ is only 87.6%, while the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention has a denitrification performance of more than 90% at 330~450℃, showing excellent denitrification performance.

[0055] The sulfur and water resistance properties of the high sulfur and water resistant denitrification catalyst prepared in Example 1 of this invention, the denitrification catalysts prepared in Comparative Examples 1-2, and traditional commercial denitrification catalysts were tested. The test results are as follows: Figure 3 As shown. From Figure 3As can be seen, the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention maintained a denitrification efficiency of over 90% after introducing 500ppm SO2 and 10% H2O. In contrast, the denitrification catalyst prepared in Comparative Example 1 (without Fe modification of fly ash) showed a denitrification efficiency that decreased from 93% to 65% after introducing 500ppm SO2 and 10% H2O, a decrease of 28%, demonstrating that the addition of iron powder can effectively improve the sulfur and water resistance of the denitrification catalyst. The denitrification catalyst prepared in Comparative Example 2 (using only fly ash as a catalyst support without TiO2) showed a denitrification performance of only 60% under the same conditions, a decrease of about 35% compared to Example 1. This proves that TiO2 is not merely a support material similar to fly ash; it plays a crucial role in effectively connecting the active component with the fly ash support. Therefore, fly ash cannot be completely replaced by TiO2 to reduce catalyst costs. Traditional commercial denitrification catalysts, after introducing 500ppm SO2 and 10% H2O, showed a denitrification efficiency that decreased from 93% to 65%, a decrease of 28%, demonstrating that the addition of iron powder can effectively improve the sulfur and water resistance of the denitrification catalyst. After H2O was introduced, the denitrification efficiency decreased by about 8%, dropping to less than 80%. Furthermore, after an 8-hour sulfur and water resistance test, when the introduction of SO2 and H2O was stopped, the denitrification performance only recovered to 84.8%, failing to fully recover. This indicates that the loss of catalytic activity of traditional commercial denitrification catalysts under the influence of SO2 and H2O is somewhat irreversible.

[0056] The NH3 conversion rate and N2 selectivity of the high sulfur and water resistant denitrification catalyst prepared in Example 1 of this invention were tested, and the results are as follows: Figure 4 As shown. From Figure 4 As can be seen from the above, the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention exhibits an NH3 conversion rate exceeding 80% at 210℃, and the NH3 conversion rate remains stably at 100% when the temperature rises to 330℃ and above. Simultaneously, within the temperature range of 90-240℃, the N2 selectivity of this VWTi / CFA-Fe catalyst remains at 100%, while at higher temperatures, the N2 selectivity only decreases to approximately 97%, demonstrating that the catalyst possesses high N2 selectivity and exhibits minimal over-oxidation of NH3 into the byproduct N2O.

[0057] The morphology of the high sulfur and water resistant denitrification catalyst prepared in Example 1 of this invention, the denitrification catalyst prepared in Comparative Example 1, and untreated fly ash (CFA) were characterized, and the results are as follows: Figure 5 As shown. From Figure 5As can be seen, the denitrification catalyst prepared in Comparative Example 1 has a larger particle size and may have agglomerated. In contrast, the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention has a more irregular particle morphology and a significantly smaller particle size compared to Comparative Example 1 and the original fly ash. This can increase the exposed area of ​​active sites, promote the loading and dispersion of active components, and further prove that adding iron powder can partially alleviate the agglomeration trend of active components.

[0058] The surface elemental distribution of the high sulfur and water resistance denitrification catalyst prepared in Example 1 of this invention was characterized, and the results are as follows: Figure 6 As shown. From Figure 6 As can be seen from the above, the distribution of V, W and Fe elements in the VWTi / CFA-Fe catalyst prepared in Example 1 of this invention is very uniform, which confirms that the active components have been successfully and uniformly loaded onto the support.

[0059] The pore size distribution of the high sulfur and water resistance denitrification catalyst prepared in Example 1 of this invention and untreated fly ash (CFA) was characterized, and the results are as follows: Figure 7 As shown. From Figure 7 As can be seen, the denitrification catalyst prepared by Fe modification of fly ash retains some of the microporous structure of the original fly ash, while also exhibiting a rich 4-6 nm mesoporous structure. The extensive and abundant pore network increases the effective contact area between the reactant gas and the catalyst interface, improves the specific surface area of ​​the catalyst, and promotes the full exposure of surface active sites, thereby improving the activity of the catalyst.

[0060] Furthermore, to demonstrate the sulfur resistance of the denitrification catalyst in the embodiments of the present invention, the VWTi / CFA-Fe catalyst prepared in Example 1 was also subjected to SO2 poisoning, and thermogravimetric analysis (TG) was performed on the poisoned catalyst to evaluate the sulfur species deposition behavior on the catalyst surface after SO2 poisoning. The results are as follows: Figure 8 As shown. Typically, the thermal weight loss process of SO2 poisoning samples can be divided into two stages: the first stage (below 200℃) is mainly caused by water evaporation; the second stage (above 200℃) is mainly due to the decomposition of ammonium bisulfate (NH4HSO4), ammonium sulfate ((NH4)2SO4), and metal sulfides. However, from... Figure 8 As can be seen, the VWTi / CFA-Fe catalyst prepared in Example 1, after SO2 poisoning, has a mass loss of less than 1% at temperatures above 200°C, which is almost negligible. This fully demonstrates that the catalyst has excellent sulfur resistance.

[0061] Meanwhile, the VWTi / CFA-Fe catalyst in Example 1 after SO2 poisoning was tested for NO-TPD (nitric oxide temperature-programmed desorption), and the results are as follows. Figure 9 As shown. From Figure 9 As can be seen, the adsorption capacity of NO by the SO2-poisoned catalyst increases significantly, and the NO desorption temperature shifts towards higher temperatures. This indicates that the SO2-poisoned catalyst exhibits more stable NO adsorption, resulting in a higher adsorption capacity for NO. X Species are difficult to desorb at lower temperatures, which is conducive to the denitrification reaction proceeding according to the Langmuir-Hinshelwood (LH) mechanism.

[0062] This invention uses fly ash solid waste as a carrier and mixes it with added iron powder and a small amount of titanium dioxide by ball milling to precisely control the Fe content in the fly ash and achieve Fe modification of the fly ash. Then, vanadium and tungsten active components are loaded by impregnation to prepare VWTi / CFA-Fe denitrification catalyst, which can significantly improve the denitrification activity and sulfur and water resistance of the catalyst, so that it can maintain a high denitrification efficiency under harsh conditions.

[0063] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A highly sulfur- and water-resistant denitrification catalyst, characterized in that, The catalyst comprises a modified support and an active component supported on the modified support. The modified support comprises fly ash, titanium dioxide, and iron powder, and the active component comprises vanadium oxide and tungsten oxide.

2. The high sulfur and water resistance denitrification catalyst according to claim 1, characterized in that, The modified support accounts for 95.2-98.5% of the total mass of the catalyst; wherein, the fly ash accounts for 30-66% of the total mass of the catalyst, the titanium dioxide accounts for 29-65% of the total mass of the catalyst, and the iron powder accounts for 0.5-7.0% of the total mass of the catalyst.

3. The high sulfur and water resistance denitrification catalyst according to claim 1, characterized in that, The active component accounts for 1.5 to 4.8% of the total mass of the catalyst; wherein the vanadium oxide accounts for 0.7 to 2.0% of the total mass of the catalyst, and the tungsten oxide accounts for 0.8 to 3.2% of the total mass of the catalyst.

4. The high sulfur and water resistance denitrification catalyst according to claim 1 or 2, characterized in that, The modified carrier is prepared by a method comprising the following steps: Step a: Mix fly ash with acetic acid solution and perform wet ball milling to obtain acid-treated fly ash; Step b: Wash, dry and sieve the acid-treated fly ash to obtain pretreated fly ash; Step c: Mix the pretreated fly ash with iron powder and titanium dioxide, and perform dry ball milling to obtain the modified carrier.

5. The high sulfur and water resistance denitrification catalyst according to claim 4, characterized in that, In step a, the concentration of the acetic acid solution is 0.5~2 mol / L; And / or, the wet ball milling speed is 140~200 r / min, and the ball milling time is 2~5 h.

6. The high sulfur and water resistance denitrification catalyst according to claim 4, characterized in that, In step b, the drying temperature is 100~120℃ and the drying time is 3~8h; And / or, the sieve used for sieving has a mesh size of 80 to 120.

7. The high sulfur and water resistance denitrification catalyst according to claim 4, characterized in that, In step c, the rotation speed of the dry ball mill is 120~200 r / min, and the milling time is 2~5 h.

8. A method for preparing a high sulfur and water-resistant denitrification catalyst as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Place ammonium metatungstate, ammonium metavanadate, and anhydrous oxalic acid in water, stir to dissolve, and obtain an active component solution; (2) Immerse the modified carrier in the solution of the active component, stir evenly, let stand, and then let it air dry naturally; (3) The sample dried in step (2) is calcined to obtain the high sulfur and water resistance denitrification catalyst.

9. The preparation method of the high sulfur and water resistance denitrification catalyst according to claim 8, characterized in that, In step (2), the settling time is 1 to 2 hours.

10. The preparation method of the high sulfur and water resistance denitrification catalyst according to claim 8, characterized in that, In step (3), the heating rate of the calcination treatment is 3~7℃ / min, the calcination temperature is 500~550℃, and the calcination time is 1.5~5h.

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