Industrial flue gas denitration filter bag and preparation method thereof

Abstract

The application discloses an industrial flue gas denitration filter bag and a preparation method thereof, and relates to the technical field of flue gas denitration. The industrial flue gas denitration filter bag comprises PTFE fibers, PPS fibers, PI fibers and PTFE loaded fibers. The PTFE loaded fibers are PTFE fiber layers loaded with modified molecular sieve catalysts; the modified molecular sieve catalysts are molecular sieves coated with modified nanorods as carriers, vanadium-titanium composite oxides as active catalytic components, and cerium-titanium composite oxides as catalytic components; and the modified nanorods are molybdenum-tungsten composite oxide modified cerium dioxide nanorods. The introduction of the modified molecular sieve catalysts prepared from raw materials such as cerium dioxide nanorods, lanthanum nitrate and molybdenum trioxide further improves the denitration capacity, ammonia escape prevention capacity, sulfur poisoning resistance, hydrothermal stability, working life and active temperature window. Therefore, the application has a wider application prospect.

Description

Technical Field

[0001] This invention relates to the field of flue gas denitrification technology, specifically to an industrial flue gas denitrification filter bag and its preparation method. Background Technology

[0002] Nitrogen oxides (NOx) are a major component of smog and acid rain, and their large-scale emissions pose a serious threat to human health. After the power industry achieved ultra-low emissions, non-power industries became the main source of NOx emissions and are currently the focus of denitrification control. NOx removal technologies are mainly divided into solid adsorption, plasma methods, wet scrubbing, catalytic decomposition, selective non-catalytic reduction (SNR), and selective catalytic reduction (SCR). The ammonia-selective catalytic reduction method utilizes ammonia as a reducing agent for selective catalytic reduction. This method is highly efficient and stable, and can achieve ultra-low NOx emissions from industrial flue gas. However, its application is limited due to the high catalyst operating temperature requirement and narrow operating temperature range.

[0003] To address the aforementioned issues, researchers have proposed a molecular sieve catalyst that exhibits high denitrification performance and a wide activity temperature window. However, in practical applications, the molecular sieve catalyst still suffers from poor hydrothermal stability, poor resistance to sulfur poisoning, and a relatively narrow activity temperature window. Therefore, the hydrothermal stability, sulfur poisoning resistance, and activity temperature window of existing catalysts used in flue gas denitrification filter bags still need improvement. Summary of the Invention

[0004] The purpose of this invention is to provide an industrial flue gas denitrification filter bag and its preparation method, thereby solving the following technical problems:

[0005] Existing catalysts for flue gas denitrification filter bags still suffer from poor hydrothermal stability, poor resistance to sulfur poisoning, and a narrow active temperature window.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] An industrial flue gas denitrification filter bag, characterized in that it comprises PTFE fiber, PPS fiber, PI fiber and PTFE-loaded fiber;

[0008] The PTFE-supported fiber is a PTFE fiber layer supporting a modified molecular sieve catalyst;

[0009] The modified molecular sieve catalyst uses a molecular sieve coated with modified nanorods as a support, vanadium-titanium composite oxide as the active catalytic component, and cerium-titanium composite oxide as the co-catalytic component.

[0010] The modified nanorods are cerium dioxide nanorods modified with molybdenum-tungsten composite oxide.

[0011] Preferably, the modified nanorods are prepared as follows:

[0012] Cerium dioxide nanorods and lanthanum nitrate were added to an aqueous solution of tetrapropylammonium hydroxide and stirred at 55-60℃ for 20-40 min. Then, molybdenum trioxide and tungsten trioxide were added and stirred at 55-60℃ for 1-2 h. The pH was then adjusted to 1 with a 65% nitric acid aqueous solution. The precipitate was separated by centrifugation and washed with deionized water 3-5 times. Finally, the precipitate was first dried under vacuum and then calcined at 450-550℃ for 1-2 h to obtain modified nanorods.

[0013] Preferably, the mass ratio of the tetrapropylammonium hydroxide aqueous solution, cerium dioxide nanorods, lanthanum nitrate, molybdenum trioxide, and tungsten trioxide is 200-300:8-12:0.4-0.6:0.8-2.3:0.7-2;

[0014] The mass fraction of the tetrapropylammonium hydroxide aqueous solution is 20%.

[0015] Preferably, the molecular sieve with the modified nanorods is prepared as follows:

[0016] Add MCM-41 molecular sieve and ZSM-5 molecular sieve to deionized water and stir for 20-30 min. Then add modified nanorods and stir for 1-2 h. Next, add sodium silicate aqueous solution at 85-90℃ at 1-3 g / min and stir until homogeneous. Adjust the pH to 6.5-7 with 0.1 mol / L hydrochloric acid, then add zirconium phosphate nanosheets and age at 85-90℃ for 2-4 h. After centrifugation, first vacuum dry the precipitate at 55-60℃, and then calcine at 300-350℃ for 3-5 h to obtain molecular sieve coated with modified nanorods.

[0017] Preferably, the mass ratio of the deionized water, MCM-41 molecular sieve, ZSM-5 molecular sieve, modified nanorods, sodium silicate aqueous solution, and zirconium phosphate nanosheets is 500-600: 50-60: 50-60: 5-6: 100-120: 0.5-0.6.

[0018] The sodium silicate aqueous solution contains 10% silicon dioxide by mass.

[0019] Preferably, the modified molecular sieve catalyst is prepared by the following method:

[0020] A1: Add citric acid to deionized water and stir at 55-60℃ for 10-20 min. Then add vanadium dioxide and titanium dioxide 1 and stir at 55-60℃ for 30-60 min. Then add cerium dioxide, titanium dioxide 2, and carbon quantum dots and ultrasonically disperse for 40-60 min to obtain the precursor solution.

[0021] A2: The molecular sieve coated with modified nanorods is immersed in a precursor solution, stirred at 85-90℃ for 10-12h and then centrifuged. The precipitate is first vacuum dried at 55-60℃, then calcined at 500-600℃ for 3-5h, and finally crushed and ground to an average particle size of 100-300nm to obtain the modified molecular sieve catalyst.

[0022] Preferably, the mass ratio of deionized water, citric acid, vanadium dioxide, titanium dioxide 1, cerium dioxide, titanium dioxide 2, and carbon quantum dots in A1 is 1150-1380: 230-276: 16.5-19.8: 16-19.2: 34.4-41.3: 16-19.2: 0.1-0.12;

[0023] The mass ratio of the molecular sieve to the precursor solution for coating the modified nanorods described in A2 is 11.5-14:1463-1755.

[0024] Preferably, the PTFE-supported fiber is prepared by the following method:

[0025] B1: Add ammonium chloride to deionized water and stir for 20-30 min, then add methyl acrylate and stir for 30-60 min, then add modified molecular sieve catalyst and perform ultrasonic dispersion at 400-450 W and 20-25 kHz for 30-60 min. After filtration with a filter membrane with a pore size of 0.40-0.45 μm, the catalyst composite solution is obtained.

[0026] B2: Spray the catalyst composite liquid onto the PTFE fibers that have been split into strands and sinter at 300-320℃ for 4-5 hours. After cooling to 20-40℃, rinse with deionized water 5-7 times and vacuum dry at 75-80℃ to obtain PTFE-loaded fibers.

[0027] Preferably, the mass ratio of deionized water, ammonium chloride, methyl acrylate, and modified molecular sieve catalyst in B1 is 1-1.2:0.25-0.3:4-4.8:10-12;

[0028] The mass ratio of the PTFE fiber to the catalyst composite liquid described in B2 is 500-1000:2-5.

[0029] A method for preparing an industrial flue gas denitrification filter bag includes the following steps:

[0030] After the PTFE fibers, PPS fibers, PI fibers and PTFE loaded fibers are mixed evenly and needle-punched into felt, they are then reinforced by hydroentangling, cut and sewn to obtain industrial flue gas denitrification filter bags.

[0031] The mass ratio of the PTFE fiber, PPS fiber, PI fiber, and PTFE-loaded fiber is 50-100:30-60:10-20:10-20.

[0032] The beneficial effects of this invention are:

[0033] This invention provides an industrial flue gas denitrification filter bag and its preparation method. The invention effectively improves the denitrification capacity, ammonia escape prevention capacity, sulfur poisoning resistance, hydrothermal stability, service life, and expands the active temperature window of the industrial flue gas denitrification filter bag through the following methods.

[0034] (1) In the modified molecular sieve catalyst of this invention, cerium dioxide itself has excellent oxygen storage / release capacity and a large number of acidic sites, which can enhance the denitrification capacity. Lanthanum doping forms a cerium-lanthanum solid solution, which increases the surface oxygen vacancy concentration through lattice distortion and improves redox activity; at the same time, the addition of lanthanum can inhibit the growth of cerium dioxide grains, maintain a high specific surface area, and increase the number of active sites. The introduction of molybdenum and tungsten can form a cerium-molybdenum / tungsten composite oxide and increase the number of surface acidic sites, promoting the adsorption and activation of ammonia; the d-orbital electronic characteristics of molybdenum / tungsten can also regulate the electronic structure of cerium dioxide and accelerate NO. x The adsorption and conversion of nitrogen, combined with the oxygen storage capacity of cerium, improves the denitrification efficiency across the entire temperature range. The composite framework of MCM-41 and ZSM-5 molecular sieves provides abundant mesoporous-microporous hierarchical channels, significantly increasing the specific surface area and enabling NO to be absorbed more readily. x The reactants, such as NH3, are in full contact with the active sites, improving catalytic efficiency. The sodium silicate and zirconium phosphate in the surface coating layer can also adjust surface acidity and optimize the NH3-SCR reaction pathway. The modified molecular sieve catalyst also combines the core denitrification activity of the vanadium-titanium system, the oxygen storage / release capacity of cerium dioxide, and the electron transport promoting effect of carbon quantum dots; among them, vanadium pentoxide, as the main active phase in the SCR reaction, effectively inhibits NO3-NO3 reaction in the mid-temperature range. x Reduction has a highly efficient catalytic effect; cerium dioxide accelerates the migration of oxygen species through the valence state cycle of trivalent cerium / tetravalent cerium, thereby improving low-temperature activity; the high conductivity of carbon quantum dots can optimize charge transfer efficiency and enhance reaction kinetics.

[0035] (2) The lanthanum-doped solid solution in the modified molecular sieve catalyst of the present invention can improve the lattice stability of cerium dioxide, inhibit grain growth at high temperature, and avoid a sharp decrease in specific surface area; during calcination, the silica coating layer forms an amorphous or microcrystalline structure, which encapsulates the active components and can reduce the erosion of the cerium dioxide lattice by water vapor; molybdenum / tungsten oxide will form an inert coating layer or solid solution on the surface of cerium dioxide, further blocking the erosion of the active sites of cerium dioxide by water vapor and reducing the activity decay caused by high temperature hydrolysis; the layered structure of zirconium phosphate nanosheets can also act as a "molecular scaffold" to inhibit high temperature sintering; the silicon-aluminum skeleton of ZSM-5 molecular sieve is not easy to collapse under hydrothermal conditions, maintaining the stability of the pore structure, while the mesoporous structure of MCM-41 combined with the silica coating layer can block water vapor penetration through the "physical barrier" effect and delay the hydrolytic deactivation of the active sites.

[0036] (3) In the modified molecular sieve catalyst of this invention, the binding ability of hexavalent molybdenum / tungsten to sulfur dioxide is weaker than that of tetravalent cerium. It can preferentially adsorb silica to form stable but reversible sulfate, avoiding irreversible occupation of cerium sites and sulfidation of vanadium pentoxide. The acidic sites of molybdenum / tungsten oxide can promote sulfate decomposition and reduce its deposition on the catalyst surface. The d electrons of molybdenum / tungsten participate in the redox cycle of cerium dioxide, which can weaken the chemical adsorption intensity of sulfur dioxide at cerium sites and reduce the generation of irreversible sulfur species. Molybdenum / tungsten oxide can consume sulfur dioxide through the "lattice oxygen" mechanism, reducing the probability of its oxidation to sulfur trioxide and inhibiting the deposition of sulfate at active sites. At the same time, it and zirconium phosphate can also adjust the distribution of acidic sites in the catalyst, reducing the probability of ammonia reacting with sulfur dioxide to form ammonium bisulfate. The silica coating layer can reduce the direct contact between sulfur dioxide and cerium dioxide through physical barrier. The molecular sieve coating can prevent sulfur dioxide in flue gas from diffusing into the internal active sites, while the strong oxidizing ability of cerium dioxide can oxidize some sulfur dioxide into sulfur trioxide, which is then adsorbed through the formation of sulfate by surface hydroxyl groups, thus avoiding direct poisoning of the active sites.

[0037] (4) The modification of lanthanum / molybdenum / tungsten in the modified molecular sieve catalyst of this invention inhibits high-temperature sintering. The oxygen vacancy migration rate of the cerium dioxide-lanthanum oxide solid solution is fast, which can promote the oxidation of nitric oxide to nitrogen dioxide at low temperature and accelerate the "fast SCR" reaction. The interfacial electron transfer between molybdenum / tungsten oxide and cerium dioxide can reduce the reaction activation energy and broaden the lower limit of low-temperature activity. At the same time, molybdenum / tungsten oxide can maintain stable acidic sites and redox capabilities at high temperatures, avoiding a decrease in high-temperature denitrification efficiency. The synergistic effect of lanthanum / molybdenum / tungsten and cerium dioxide can achieve a wide temperature range of "low-temperature activation-medium-high temperature high efficiency" to adapt to industrial flue gas temperature fluctuations. The molecular sieve framework and silica coating layer can further inhibit the sintering of cerium dioxide at high temperatures. The oxygen vacancy defects of cerium dioxide and the surface functional groups of carbon quantum dots can promote the activation and adsorption of ammonia at low temperatures, thus significantly reducing the lower limit of the active temperature. The introduction of lanthanum / molybdenum / tungsten also inhibits the phase transformation and sintering of vanadium pentoxide at high temperatures. Combined with the high-temperature resistant framework of molecular sieves, the upper limit of the active temperature is extended to 500℃.

[0038] (5) In the modified molecular sieve catalyst of this invention, the acidic sites of ZSM-5 molecular sieve and modified cerium dioxide work synergistically to allow ammonia to exist in the form of "coordination adsorption" rather than "strong chemisorption," which ensures both reactivity and avoids escape caused by excessive ammonia adsorption. The weak acidity of zirconium phosphate can further regulate the site strength and reduce ammonia retention. The mesoporous structure of MCM-41 can also accelerate ammonia diffusion and avoid incomplete reaction caused by excessively high local concentration, thereby reducing the ammonia escape rate. The presence of carbon quantum dots accelerates the rate-controlling step of the NH3-SCR reaction, allowing ammonia to react completely at a lower temperature and reducing the escape rate.

[0039] (6) In the modified molecular sieve catalyst of this invention, the silica coating layer forms a "rigid network" with the molecular sieve framework, which enhances the mechanical strength of the catalyst and reduces the shedding of active components during the needle punching and hydroentangling processes of the filter bag. The doping of lanthanum / molybdenum / tungsten improves the thermal stability of cerium dioxide and delays high-temperature sintering deactivation; the zirconium phosphate and silica layer can capture some sulfur species through "reversible adsorption". When oxygen and ammonia are present in the flue gas, some sulfates can be reduced or decomposed, restoring some activity and thus extending the effective working life of the catalyst. Carbon quantum dots can also inhibit the polymerization of polycyclic aromatic hydrocarbons and reduce carbon deposition. The mesoporous structure of MCM-41 is not easily blocked by flue gas dust, and the hydrophobicity of the surface-modified catalyst is improved, reducing the adhesion of water vapor and dust and extending the regeneration cycle.

[0040] Therefore, the industrial flue gas denitrification filter bag prepared by this invention has excellent denitrification ability, ammonia escape prevention ability, sulfur poisoning resistance, hydrothermal stability, service life and an extremely wide active temperature window, as well as a wider range of application prospects. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention:

[0043] Cerium dioxide nanorods were purchased from Hubei Xinhongli Chemical Co., Ltd., with a length of 10-40 nm and a diameter of 5-10 nm; MCM-41 molecular sieves (pore size: 1.5-10 nm) were purchased from Dalian Zeer Catalytic Materials Co., Ltd.; ZSM-5 molecular sieves (pore size: 0.55-0.6 nm) were purchased from Dalian Zeer Catalytic Materials Co., Ltd.

[0044] Example 1: A method for preparing an industrial flue gas denitrification filter bag is as follows:

[0045] S1: Add 8g of cerium dioxide nanorods and 0.4g of lanthanum nitrate to 200g of 20% tetrapropylammonium hydroxide aqueous solution and stir at 500r / min for 20min at 55℃. Then add 0.8g of molybdenum trioxide and 0.7g of tungsten trioxide and stir at 55℃ for 1h. Then adjust the pH to 1 with 65% nitric acid aqueous solution. Centrifuge and wash the precipitate three times with deionized water. Finally, vacuum dry at 55℃ and calcine at 450℃ for 1h to obtain modified nanorods.

[0046] S2: Add 50g of MCM-41 molecular sieve and 50g of ZSM-5 molecular sieve to 500mL of deionized water and stir at 300r / min for 20min. Then add 5g of modified nanorods and stir for 1h. Then add 100g of sodium silicate aqueous solution with a silica mass fraction of 10% at 85℃ at 1g / min and stir evenly. Adjust the pH to 6.5 with 0.1mol / L hydrochloric acid and add 0.5g of zirconium phosphate nanosheets and age at 85℃ for 2h. After centrifugation, first vacuum dry the precipitate at 55℃ and then calcine at 300℃ for 3h to obtain molecular sieve coated with modified nanorods.

[0047] S3: Add 230g of citric acid to 1150mL of deionized water and stir at 55℃ for 10min. Then add 16.5g of vanadium dioxide and 16g of titanium dioxide and stir at 55℃ for 30min. Then add 34.4g of cerium dioxide, 16g of titanium dioxide and 0.1g of carbon quantum dots and sonicate for 40min to obtain the precursor solution.

[0048] S4: 11.5g of molecular sieve coated with modified nanorods was immersed in 1463g of precursor solution, stirred at 85℃ for 10h and then centrifuged. The precipitate was first vacuum dried at 55℃, then calcined at 500℃ for 3h, and finally crushed and ground to an average particle size of 100nm to obtain the modified molecular sieve catalyst.

[0049] S5: Add 0.25g of ammonium chloride to 1mL of deionized water and stir for 20min. Then add 4g of methyl acrylate and stir for 30min. Then add 10g of modified molecular sieve catalyst and perform ultrasonic dispersion at 400W and 20kHz for 30min. After filtration with a filter membrane with a pore size of 0.40μm, the catalyst composite solution is obtained.

[0050] S6: Spray 2g of catalyst composite liquid onto 500g of PTFE fibers that have been split into strands and sinter at 300℃ for 4h. After cooling to 20℃, rinse with deionized water 5 times and vacuum dry at 75℃ to obtain PTFE supported fibers.

[0051] S7: Mix 50g of PTFE fiber, 30g of PPS fiber, 10g of PI fiber and 10g of PTFE loaded fiber evenly, then needle punch them into felt, and then reinforce them with hydroentanglement, cut and sew them to obtain industrial flue gas denitrification filter bags.

[0052] Example 2: A method for preparing an industrial flue gas denitrification filter bag is as follows:

[0053] S1: 10g of cerium dioxide nanorods and 0.5g of lanthanum nitrate were added to 250g of a 20% (w / w) tetrapropylammonium hydroxide aqueous solution and stirred at 650r / min for 30min at 58℃. Then, 1.5g of molybdenum trioxide and 1.4g of tungsten trioxide were added and stirred at 58℃ for 1.5h. The pH was then adjusted to 1 with a 65% (w / w) nitric acid aqueous solution. The precipitate was separated by centrifugation and washed four times with deionized water. Finally, the precipitate was first vacuum dried at 58℃ and then calcined at 500℃ for 1.5h to obtain modified nanorods.

[0054] S2: Add 55g of MCM-41 molecular sieve and 55g of ZSM-5 molecular sieve to 550mL of deionized water and stir at 350r / min for 25min. Then add 5.5g of modified nanorods and stir for 1.5h. Then add 110g of sodium silicate aqueous solution with a silica mass fraction of 10% at 88℃ at 2g / min and stir evenly. Adjust the pH to 6.8 with 0.1mol / L hydrochloric acid and add 0.55g of zirconium phosphate nanosheets and age at 88℃ for 3h. After centrifugation, first vacuum dry the precipitate at 58℃ and then calcine at 325℃ for 4h to obtain molecular sieve coated with modified nanorods.

[0055] S3: Add 253g of citric acid to 1265mL of deionized water and stir at 58℃ for 15min. Then add 17.9g of vanadium dioxide and 17.6g of titanium dioxide and stir at 58℃ for 45min. Then add 37.5g of cerium dioxide, 17.6g of titanium dioxide and 0.11g of carbon quantum dots and sonicate for 50min to obtain the precursor solution.

[0056] S4: 12.8g of molecular sieve coated with modified nanorods was immersed in 1609g of precursor solution, stirred at 88℃ for 11h and then centrifuged. The precipitate was first vacuum dried at 58℃, then calcined at 550℃ for 4h, and finally crushed and ground to an average particle size of 200nm to obtain the modified molecular sieve catalyst.

[0057] S5: Add 0.28g of ammonium chloride to 1.1mL of deionized water and stir for 25min. Then add 4.4g of methyl acrylate and stir for 45min. Then add 11g of modified molecular sieve catalyst and perform ultrasonic dispersion at 430W and 23kHz for 45min. After filtration with a filter membrane with a pore size of 0.45μm, the catalyst composite solution is obtained.

[0058] S6: Spray 3.5g of catalyst composite liquid onto 750g of PTFE fibers that have been split into strands and sinter at 310℃ for 4.5h. After cooling to 30℃, rinse with deionized water 6 times and vacuum dry at 78℃ to obtain PTFE supported fibers.

[0059] S7: 75g of PTFE fiber, 45g of PPS fiber, 15g of PI fiber and 15g of PTFE loaded fiber are mixed evenly and then needle-punched into felt. After being reinforced by hydroentangling, cut and sewn, an industrial flue gas denitrification filter bag is obtained.

[0060] Example 3: A method for preparing an industrial flue gas denitrification filter bag is as follows:

[0061] S1: 12g of cerium dioxide nanorods and 0.6g of lanthanum nitrate were added to 300g of a 20% (w / w) tetrapropylammonium hydroxide aqueous solution and stirred at 800r / min for 40min at 60℃. Then, 2.3g of molybdenum trioxide and 2g of tungsten trioxide were added and stirred at 60℃ for 2h. The pH was then adjusted to 1 with a 65% (w / w) nitric acid aqueous solution. The precipitate was separated by centrifugation and washed 5 times with deionized water. Finally, the precipitate was first vacuum dried at 60℃ and then calcined at 550℃ for 2h to obtain modified nanorods.

[0062] S2: Add 60g of MCM-41 molecular sieve and 60g of ZSM-5 molecular sieve to 600mL of deionized water and stir at 400r / min for 30min. Then add 6g of modified nanorods and stir for 2h. Then add 120g of sodium silicate aqueous solution with a silica mass fraction of 10% at 3g / min at 90℃ and stir evenly. Adjust the pH to 7 with 0.1mol / L hydrochloric acid and add 0.6g of zirconium phosphate nanosheets. Age at 90℃ for 4h. After centrifugation, first dry the precipitate under vacuum at 60℃, and then calcine at 350℃ for 5h to obtain molecular sieve coated with modified nanorods.

[0063] S3: Add 276g of citric acid to 1380mL of deionized water and stir at 60℃ for 20min. Then add 19.8g of vanadium dioxide and 19.2g of titanium dioxide and stir at 60℃ for 60min. Then add 41.3g of cerium dioxide, 19.2g of titanium dioxide and 0.12g of carbon quantum dots and sonicate for 60min to obtain the precursor solution.

[0064] S4: 14g of molecular sieve coated with modified nanorods was immersed in 1755g of precursor solution, stirred at 90℃ for 12h and then centrifuged. The precipitate was first vacuum dried at 60℃, then calcined at 600℃ for 5h, and finally crushed and ground to an average particle size of 300nm to obtain the modified molecular sieve catalyst.

[0065] S5: Add 0.3g of ammonium chloride to 1.2mL of deionized water and stir for 30min. Then add 4.8g of methyl acrylate and stir for 60min. Then add 12g of modified molecular sieve catalyst and perform ultrasonic dispersion at 450W and 25kHz for 60min. After filtration with a filter membrane with a pore size of 0.45μm, the catalyst composite solution is obtained.

[0066] S6: Spray 5g of catalyst composite liquid onto 1000g of PTFE fibers that have been split into strands and sinter at 320℃ for 5h. After cooling to 40℃, rinse with deionized water 7 times and vacuum dry at 80℃ to obtain PTFE supported fibers.

[0067] S7: Mix 100g of PTFE fiber, 60g of PPS fiber, 20g of PI fiber and 20g of PTFE loaded fiber evenly, then needle punch them into felt, and then reinforce them with hydroentanglement, cut and sew them to obtain industrial flue gas denitrification filter bags.

[0068] Comparative Example 1:

[0069] Compared with Example 1, this comparative example only did not add "lanthanum nitrate" in the preparation process of S1. All other steps and parameters were the same, and will not be repeated here. The final product was an industrial flue gas denitrification filter bag.

[0070] Comparative Example 2:

[0071] Compared with Example 1, this comparative example only did not add "molybdenum trioxide and tungsten trioxide" in the preparation process of S1. All other steps and parameters were the same, and will not be repeated here. The final product is an industrial flue gas denitrification filter bag.

[0072] Comparative Example 3:

[0073] Compared with Example 1, this comparative example only replaces the "MCM-41 molecular sieve" added in the preparation process of S2 with "ZSM-5 molecular sieve". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, an industrial flue gas denitrification filter bag is obtained.

[0074] Comparative Example 4:

[0075] Compared with Example 1, this comparative example only replaces the "ZSM-5 molecular sieve" added in the preparation process of S2 with "MCM-41 molecular sieve". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, an industrial flue gas denitrification filter bag is obtained.

[0076] Comparative Example 5:

[0077] Compared with Example 1, this comparative example only did not add "modified nanorods" in the preparation process of S2. All other steps and parameters were the same, and will not be repeated here. The final product was an industrial flue gas denitrification filter bag.

[0078] Comparative Example 6:

[0079] Compared with Example 1, this comparative example only did not add "zirconium phosphate nanosheets" in the preparation process of S2. All other steps and parameters were the same, and will not be repeated here. The final product was an industrial flue gas denitrification filter bag.

[0080] Comparative Example 7:

[0081] Compared with Example 1, this comparative example only omits the addition of "cerium dioxide and titanium dioxide" in the preparation process of S3. All other steps and parameters are the same, and will not be repeated here. The final product is an industrial flue gas denitrification filter bag.

[0082] Comparative Example 8:

[0083] Compared with Example 1, this comparative example only did not add "carbon quantum dots" in the preparation process of S3. All other steps and parameters were the same, and will not be repeated here. The final product is an industrial flue gas denitrification filter bag.

[0084] Comparative Example 9:

[0085] Compared with Example 1, this comparative example only omits the addition of "cerium dioxide, titanium dioxide and carbon quantum dots" in the preparation process of S3. All other steps and parameters are the same, and will not be repeated here. The final product is an industrial flue gas denitrification filter bag.

[0086] Performance testing:

[0087] Determination of the active temperature window:

[0088] Referring to GB / T 38219-2019 "Technical Specification for Testing Flue Gas Denitrification Catalysts", simulated flue gas was prepared (NO concentration 500ppm, NH3 concentration 500ppm, SO2 concentration 500ppm, O2 5%, H2O 10%, dust content 30g / m³). 3 (N2 is the balance gas), its total gas flow rate is 2 L / min, and its space velocity is 10000 h⁻¹. -1 Using a quartz tube with an inner diameter of 50 mm, the temperature was increased from 100 °C to 550 °C in steps of 25 °C. After stabilizing at each temperature point for 30 min, samples were taken. The inlet and outlet NO concentrations at each temperature point were measured and the corresponding denitrification efficiency was calculated. The lowest and highest temperatures corresponding to a denitrification efficiency of ≥80% were used as the window boundaries. The active temperature window (°C) of the industrial flue gas denitrification filter bags prepared in Examples 1-3 and Comparative Examples 1-9 of this invention were determined according to the above method. The measurement results are shown in Table 1.

[0089] Determination of ammonia slip rate, sulfur conversion rate, and denitrification efficiency:

[0090] Referring to GB / T 38219-2019 "Technical Specification for Testing Flue Gas Denitrification Catalysts", the reactor temperature was adjusted to 125℃ and stabilized for 30 minutes. Then, simulated flue gas (NO concentration 500ppm, NH3 concentration 500ppm, SO2 concentration 500ppm, O2 5%, H2O 10%, dust content 30g / m³) was introduced. 3 (N2 is the balance gas), its total gas flow rate is 2 L / min, and its space velocity is 10000 h⁻¹. -1 After 4 hours of continuous operation, sampling began to detect the NO concentration at the inlet and outlet and calculate the corresponding denitrification efficiency. Simultaneously, NH3 escape rate (chemiluminescence method, HJ 533-2009) and SO2 / SO3 conversion rate (ion chromatography, GB / T 38219-2019) were monitored. The denitrification efficiency (%), ammonia escape rate (ppm), and sulfur conversion rate (%) of the industrial flue gas denitrification filter bags prepared in Examples 1-3 and Comparative Examples 1-9 of this invention were determined according to the above method. The results are shown in Table 1.

[0091] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-9

[0092]

[0093] Determination of sulfur poisoning resistance:

[0094] Referring to the sulfur resistance test method in GB / T 38219-2019 "Technical Specification for Testing Flue Gas Denitrification Catalysts", the denitrification efficiency reduction rate (%) of the industrial flue gas denitrification filter bags prepared in Examples 1-3 and Comparative Examples 1-9 of this invention after continuous operation at 125℃ for 100h was determined using the simulated flue gas used for the above test. The test results are shown in Table 2.

[0095] Determination of hydrothermal stability:

[0096] Referring to the hydrothermal aging method of honeycomb catalyst in GB / T 31587-2015 "Honeycomb Flue Gas Denitrification Catalyst", the retention rate (%) of denitrification efficiency of the industrial flue gas denitrification filter bags prepared in Examples 1-3 and Comparative Examples 1-9 of this invention after continuous treatment at 125℃ for 100h was determined using the simulated flue gas used for the above test. The test results are shown in Table 2.

[0097] Determination of working life:

[0098] Referring to the sulfur resistance test method in GB / T 38219-2019 "Technical Specification for Testing Flue Gas Denitrification Catalysts", the denitrification efficiency retention rate (%) of the industrial flue gas denitrification filter bags prepared in Examples 1-3 and Comparative Examples 1-9 of this invention after continuous treatment at 400℃ for 5000h was determined using the simulated flue gas used for the above test. The test results are shown in Table 2.

[0099] Table 2: Resistance test results of Examples 1-3 and Comparative Examples 1-9

[0100]

[0101] Data Analysis:

[0102] As can be seen from Tables 1 and 2, the industrial flue gas denitrification filter bags prepared in the embodiments of the present invention have excellent denitrification ability, ammonia escape prevention ability, sulfur poisoning resistance, hydrothermal stability, working life and an extremely wide active temperature window of 125-500℃.

[0103] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. An industrial flue gas denitrification filter bag, characterized in that, Including PTFE fiber, PPS fiber, PI fiber, and PTFE-loaded fiber; The PTFE-supported fiber is a PTFE fiber layer supporting a modified molecular sieve catalyst; The modified molecular sieve catalyst uses a molecular sieve coated with modified nanorods as a support, vanadium-titanium composite oxide as the active catalytic component, and cerium-titanium composite oxide as the co-catalytic component. The modified nanorods are cerium dioxide nanorods modified with molybdenum-tungsten composite oxide; The modified nanorods are prepared as follows: Cerium dioxide nanorods and lanthanum nitrate were added to an aqueous solution of tetrapropylammonium hydroxide and stirred at 55-60°C. Then molybdenum trioxide and tungsten trioxide were added and stirred at 55-60°C for 1-2 hours. The pH was then adjusted to 1, centrifuged, and the precipitate was washed. Finally, the precipitate was dried under vacuum and then calcined at 450-550°C for 1-2 hours to obtain modified nanorods. The preparation method of the molecular sieve with the modified nanorod coating is as follows: Add MCM-41 molecular sieve and ZSM-5 molecular sieve to deionized water and stir well. Then add modified nanorods and stir for 1-2 hours. Then add sodium silicate aqueous solution at 85-90℃ and stir well. Adjust the pH to 6.5-7 and add zirconium phosphate nanosheets. Age at 85-90℃ for 2-4 hours. After centrifugation, first vacuum dry the precipitate and then calcine at 300-350℃ for 3-5 hours to obtain molecular sieve coated with modified nanorods. The modified molecular sieve catalyst is prepared as follows: A1: Add citric acid to deionized water and stir at 55-60℃. Then add vanadium dioxide and titanium dioxide 1 and stir at 55-60℃. Then add cerium dioxide, titanium dioxide 2, and carbon quantum dots and ultrasonically disperse for 40-60 min to obtain the precursor solution. A2: The molecular sieve coated with modified nanorods is immersed in a precursor solution, stirred at 85-90℃ for 10-12h and then centrifuged. The precipitate is first vacuum dried, then calcined at 500-600℃ for 3-5h, and finally crushed and ground to obtain the modified molecular sieve catalyst.

2. The industrial flue gas denitrification filter bag according to claim 1, characterized in that, The mass ratio of the tetrapropylammonium hydroxide aqueous solution, cerium dioxide nanorods, lanthanum nitrate, molybdenum trioxide, and tungsten trioxide is 200-300:8-12:0.4-0.6:0.8-2.3:0.7-2. The mass fraction of the tetrapropylammonium hydroxide aqueous solution is 20%.

3. The industrial flue gas denitrification filter bag according to claim 1, characterized in that, The mass ratio of the deionized water, MCM-41 molecular sieve, ZSM-5 molecular sieve, modified nanorods, sodium silicate aqueous solution, and zirconium phosphate nanosheets is 500-600: 50-60: 50-60: 5-6: 100-120: 0.5-0.

6. The sodium silicate aqueous solution contains 10% silicon dioxide by mass.

4. The industrial flue gas denitrification filter bag according to claim 1, characterized in that, The mass ratio of deionized water, citric acid, vanadium dioxide, titanium dioxide 1, cerium dioxide, titanium dioxide 2, and carbon quantum dots in A1 is 1150-1380:230-276:16.5-19.8:16-19.2:34.4-41.3:16-19.2:0.1-0.12; The mass ratio of the molecular sieve to the precursor solution for coating the modified nanorods described in A2 is 11.5-14:1463-1755.

5. The industrial flue gas denitrification filter bag according to claim 1, characterized in that, The method for preparing the PTFE-supported fiber is as follows: B1: Add ammonium chloride to deionized water and stir well, then add methyl acrylate and stir well, then add modified molecular sieve catalyst and ultrasonically disperse for 30-60 minutes, and filter to obtain catalyst composite solution; B2: Spray the catalyst composite liquid onto the PTFE fibers that have been split into strands and sinter them at 300-320℃ for 4-5 hours. After cooling, rinse and vacuum dry to obtain PTFE-loaded fibers.

6. The industrial flue gas denitrification filter bag according to claim 5, characterized in that, The mass ratio of deionized water, ammonium chloride, methyl acrylate, and modified molecular sieve catalyst in B1 is 1-1.2:0.25-0.3:4-4.8:10-12; The mass ratio of the PTFE fiber to the catalyst composite liquid described in B2 is 500-1000:2-5.

7. A method for preparing an industrial flue gas denitrification filter bag according to any one of claims 1-6, characterized in that, Includes the following steps: After the PTFE fibers, PPS fibers, PI fibers and PTFE loaded fibers are mixed evenly and needle-punched into felt, they are then reinforced by hydroentangling, cut and sewn to obtain industrial flue gas denitrification filter bags. The mass ratio of the PTFE fiber, PPS fiber, PI fiber, and PTFE-loaded fiber is 50-100:30-60:10-20:10-20.

Images