Preparation method and application of PTFE composite filter material with denitration function

Abstract

The invention discloses a preparation method and application of a PTFE composite filter material with a denitration function, and belongs to the technical field of filter materials. A high-temperature-resistant PTFE polymer needled filter material is used as a base material, and polydopamine and MXene are adopted to carry out functional modification on the fiber surface of the filter material, so that the dispersion degree and the synergistic effect of a catalyst on the fiber surface are improved; the preparation method comprises the following steps: uniformly loading a manganese-cerium denitration catalyst precursor on the surface of a filter material fiber by virtue of an equivalent-volume impregnation method, then calcining to obtain an active component of the denitration catalyst, and finally impregnating in hydrogen peroxide to further activate the composite filter material, so that the low-temperature denitration activity of the composite filter material is improved. The PTFE composite filter material prepared by the invention has good denitration capability at low temperature, retains the original dust filtering effect in the preparation process, can meet the requirement of low-temperature denitration and dust removal integration in industrial tail gas, and effectively overcomes the defects of complexity, high treatment cost and the like of a tail flue gas purification system in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of filter materials, and specifically, relates to a preparation method and application of a PTFE composite filter material with denitrification function. Background Art

[0002] Nitrogen oxides (NO x ) and particulate matter are the main air pollutants emitted by coal-fired power plants, coking facilities and cement production units. They play a key role in the formation of photochemical smog, ozone layer depletion and the acceleration of global warming. The ammonia-based selective catalytic reduction technology (NH3-SCR) is one of the most advanced NO x emission reduction technologies. In the existing NH3-SCR technology system, Mn-based catalysts have the advantages of rich variable valence states, high electron mobility, high redox performance at low temperatures, low cost, low toxicity, environmental protection, etc. In addition, the doping of cerium elements can effectively improve the sulfur resistance of Mn-based catalysts. Therefore, the related research on manganese-cerium oxides as the active components of low-temperature SCR catalysts has received extensive attention from domestic and foreign scholars. However, the selection of related carriers mainly focuses on solid materials such as TiO2, Al2O3, activated carbon, etc. In addition, in traditional industrial flue gas treatment processes, denitrification and dust removal need to be carried out step by step, resulting in large equipment floor space and high resource consumption.

[0003] In recent years, the demand for industrial flue gas treatment has increased significantly. As the core material for flue gas purification, the technological iteration and function integration of dust removal filter materials have become the focus of the industry. Traditional filter materials mainly have a single dust removal function, while composite filter materials with denitrification function (i.e., directly loading denitrification catalysts on dust removal filter materials) have become a research hotspot because they can simplify the purification system and reduce costs.

[0004] At present, the preparation technologies of domestic denitrification-functional composite filter materials mostly involve first preparing catalysts and then loading them on filter materials through binders or some physical methods, such as patents: CN115337712A, CN115193160A, CN115155305A, CN116870586A, CN119215552A, etc.; this method will cause uneven dispersion of catalysts, large loading amounts, and easy blockage of the internal voids of filter materials, thus affecting air permeability, and the physical adhesion effect leads to insufficient firmness of the combination between catalysts and filter materials, and easy detachment of active components. In addition, there are some patents such as: CN106731226A, CN106334372A, CN118649704A, CN111359673A, which prepare denitrification-functional composite filter materials by in-situ growth of denitrification catalysts on filter material fibers. These methods also have problems such as insufficient firmness of catalyst loading, low low-temperature catalytic activity, and poor sulfur resistance of catalysts. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technologies mentioned in the above background art, the present invention provides a preparation method and application of a PTFE composite filter material with denitrification function. This preparation method not only prevents the loaded catalyst from clogging the fiber pores to retain the original dust filtration effect of the filter material, but also ensures very good bonding strength between the catalyst and the filter material, so that the catalyst will not fall off during the cleaning operation; the prepared composite filter material has good ability to remove nitrogen oxides at low temperature, can meet the requirements of integrated low-temperature denitrification and dust removal in industrial tail gas, and effectively overcomes the disadvantages such as the complexity and high treatment cost of the tail gas purification system in the existing technologies.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A preparation method of a PTFE composite filter material with denitrification function, using a high-temperature-resistant polytetrafluoroethylene (PTFE) polymer needle-punched filter material as a carrier. First, perform polydopamine surface functionalization modification on it, and then immerse it in MXene ink. Use electrostatic attraction to make the MXene lamellae evenly adsorbed on the surface of polydopamine to fully activate the originally inert PTFE fiber surface; then, use the equal-volume impregnation method to immerse the mixed solution prepared from manganese salt and cerium salt into the above composite filter material; finally, after the composite filter material is dried, calcined and activated, the PTFE composite filter material with denitrification function is obtained.

[0008] Specifically, it includes the following steps:

[0009] (1) Take a piece of cleaned PTFE filter material, immerse it in ethanol once and then immerse it in an alkaline aqueous solution of dopamine, stir for a period of time at a certain temperature, then take it out and dry it to uniformly coat a polydopamine functional layer on the surface of the filter material fibers;

[0010] (2) Prepare MXene ink by chemically etching the ternary layered carbide Ti3AlC2 with a fluorine-containing solution, and then immerse the polydopamine-modified filter material obtained in step (1) into the above ink. After standing for a period of time, take out the filter material and dry it;

[0011] (3) According to the amount of solution that the PTFE filter material can adsorb at one time, use the equal-volume impregnation method to immerse the filter material obtained in step (2) in a certain amount of mixed solution of manganese salt and cerium salt, stand for a period of time, and place it in an oven to dry, so that the metal salts are dispersed and deposited on the surface of the modified fiber filter material;

[0012] (4) Place the dried PTFE filter material obtained in step (3) in a muffle furnace and calcine it for a period of time at a temperature lower than the highest service temperature of the PTFE filter material to fully decompose the metal salts on it;

[0013] (5) Finally, take out the filter material in step (4), put it into a hydrogen peroxide solution with a certain concentration for activation treatment, and finally wash and dry it to obtain the PTFE composite filter material with denitrification function.

[0014] In the above preparation method: the air permeability of the PTFE filter material in step (1) is between 20 - 200 L / dm 2 ·min, the thickness is between 0.5 and 3 mm, and the gram weight is between 100 and 1000 g / m 2 , and it has the properties of being resistant to strong acids, strong alkalis, and high temperatures of at least 260 °C.

[0015] In the above preparation method: the concentration of dopamine in step (1) is 0.1 - 10 g / L; the alkaline aqueous solution is prepared from one or more compounds among sodium hydroxide, potassium hydroxide, ammonia water, or tris(hydroxymethyl)aminomethane, and the pH is between 8 - 10.

[0016] In the above preparation method: the concentration of MXene ink in step (2) is 0 - 10 g / L, the pH value of the solution is 6 - 8, the static impregnation time is 0.5 - 48 h, the drying temperature is between 30 - 120 °C, and the drying duration is 0.5 - 48 h.

[0017] In the above preparation method: the manganese salt in step (3) is selected from one or more of manganese nitrate, manganese chloride, manganese sulfate, and manganese acetate, the cerium salt is selected from one or more of cerium nitrate, cerium chloride, cerium sulfate, and cerium acetate, and its mixed solution is prepared from deionized water and ethanol in any proportion; the molar ratio of the manganese salt to the cerium salt is between 1:0 - 1:3, and the total mass ratio of the manganese salt and the cerium salt to the filter material is controlled between 0.01:1 - 3:1; the equal - volume impregnation time is 0.5 - 48 h, the drying temperature is between 30 - 120 °C, and the drying duration is 0.5 - 48 h.

[0018] In the above preparation method: the calcination temperature in step (4) is between 200 - 260 °C, and the calcination duration is 0.5 - 12 h.

[0019] In the above preparation method: the activation process in step (5) is to oxidize the composite filter material in a hydrogen peroxide solution with a mass concentration of 0.1% - 30% for 0.5 - 48 h; the drying temperature is between 60 - 120 °C, and the drying duration is 0.5 - 48 h.

[0020] Another object of the present invention is to provide the application of the PTFE composite filter material prepared by the above - mentioned preparation method in the integrated low - temperature denitrification and dust removal of industrial tail gas.

[0021] The beneficial effects of the present invention:

[0022] 1. The PTFE composite filter media prepared by the present invention combines the dual functions of dust removal and low-temperature denitration, simplifies the originally complex post-treatment method of industrial tail gas, greatly saves the floor space and cost of industrial tail gas treatment, and has strong economic practicability. At the same time, by using the method of equal-volume impregnation, the loading amount of the catalyst can be effectively regulated. The activation treatment of hydrogen peroxide can further improve the low-temperature activity of the catalyst, making the preparation method simple and easy to implement, and enabling large-scale industrial production.

[0023] 2. The surface of the filter media fiber is functionalized and modified by using polydopamine and MXene ink, which not only provides active sites for the anchoring and dispersion of the catalyst, making it disperse evenly and bind firmly on the filter media fiber, but also the doping of MXene improves the dispersion degree, loading amount and synergistic effect of the catalyst on the fiber surface. Its unique physical and chemical properties and structure enable strong correlation effects to be established between it and the active components of the denitration catalyst, and thus it has better low-temperature denitration activity and sulfur resistance. Brief Description of the Drawings

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 It is a diagram of a self-made tubular SCR reactor device for the activity test of the composite filter media.

[0026] Figure 2 It is a scanning electron microscope image of the composite filter media of Example 1 of the present invention.

[0027] Figure 3 It is an anti-sulfur effect diagram of the composite filter media of Example 1 of the present invention under the atmosphere conditions of 180°C and 100 ppm SO2.

[0028] In the figure: 1. Gas source; 2. Pressure reducing valve; 3. Flowmeter; 4. Mixer; 5. Air preheater; 6. Heating and catalytic reactor; 7. Test sample; 8. Flue gas analyzer. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Such as Figure 1As shown in the figure, it is a self-made tubular SCR reactor device diagram, including a gas source 1, a pressure reducing valve 2 and a flow meter 3 connected in sequence. The flow meter 3 is connected to a heating and catalytic reactor 6 through a mixer 4 and an air preheater 5. The heating and catalytic reactor 6 is directly connected to a flue gas analyzer 8, and a test sample 7 is placed in the heating and catalytic reactor 6.

[0031] In the following examples, the MXene ink was prepared by the following steps: Weigh 2 g of lithium fluoride and add it to a polytetrafluoroethylene reaction kettle containing a mixed solution of 31 mL of concentrated hydrochloric acid and 9 mL of deionized water. After stirring for 15 min, slowly add 2 g of Ti3AlC2 and continue to stir and react at 40 °C for 24 h. Then, the obtained product was centrifugally washed with 1 mol / L hydrochloric acid solution for several times until the pH > 6, and the MXene ink could be obtained. Its concentration can be adjusted according to the degree of dilution.

[0032] The activity evaluation of the composite filter material was completed on a self-made tubular SCR reactor. The structural schematic diagram is as Figure 1 shown. The composite filter material (test sample 7) was placed at the middle position of the heating and catalytic reactor 6. The experimental tubular resistance furnace was used to control the test temperature of the sample, and the flow meter 3 controlled the flow rate of each gas. The composition of the gas simulated the composition in flue gas, that is, NO was 500 ppm, NH3 was 500 ppm, O2 accounted for 5%, and the rest was N2. The total gas flow rate was 300 mL / min. The gas was mixed evenly through the mixer 4 before entering the tubular resistance furnace and then preheated to a certain temperature through the air preheater 5. The experimental test temperature range was 100 - 180 °C. The flue gas analyzer 8 was used to measure the composition and content of the inlet and outlet gases in the tubular resistance furnace. Each test point needed to be tested after the temperature was stable for at least 10 min. The denitrification activity of the composite filter material was calculated from the concentrations of nitrogen oxides (NOx) at the inlet and outlet, as shown in the following formula:

[0033]

[0034] Example 1

[0035] After immersing the cleaned circular PTFE filter material with a mass of 1.1782 g in an ethanol solution, it was immediately added to a 2 g / L dopamine alkaline solution. The pH value was adjusted to about 8.5 by tris(hydroxymethyl)aminomethane and stirred at room temperature for 12 h. Then it was taken out, rinsed thoroughly with deionized water and ethanol, and vacuum dried at 60 °C for 12 h. The dried filter material was immersed again in freshly prepared MXene ink with a concentration of about 1 g / L and a pH of about 6.5, left standing for 12 h, then taken out and washed, and vacuum dried at 60 °C for 12 h. Take 2 mL of a uniform mixed solution containing 0.38 mL of manganese nitrate aqueous solution and 0.1502 g of cerium nitrate (the molar ratio of manganese salt to cerium salt is 1:0.2, and the total amount of manganese salt and cerium salt to the mass of the filter material is 0.38:1) to completely wet the modified PTFE filter material, and let it stand at room temperature for 12 h. Then it was placed in an oven and dried at 110 °C for 2 h. Finally, the dried filter material was placed in a muffle furnace and calcined at 250 °C for 2 h. After cooling, the composite filter material was taken out, placed in a 10% hydrogen peroxide solution for activation treatment for 1 h, then washed and dried at 110 °C for 12 h to obtain the PTFE composite filter material loaded with manganese-cerium denitration catalyst. When measured with a German M60x flue gas analyzer, the denitration rate was 82.6% at a reaction temperature of 160 °C; the denitration rate was 91.5% at a reaction temperature of 180 °C; as Figure 2 shown is the scanning electron microscope image of the composite filter material of this example.

[0036] Example Two

[0037] After immersing the cleaned circular PTFE filter material with a mass of 1.1718 g in an ethanol solution, it was immediately added to a 2 g / L dopamine alkaline solution. The pH value was adjusted to about 9 by tris(hydroxymethyl)aminomethane and stirred at room temperature for 18 h. Then it was taken out, rinsed thoroughly with deionized water and ethanol, and vacuum dried at 80 °C for 16 h. The dried filter material was immersed again in freshly prepared MXene ink with a concentration of about 1 g / L and a pH of about 6.5, left standing for 12 h, then taken out and washed, and vacuum dried at 80 °C for 12 h. Take 2 mL of a uniform mixed solution containing 0.25 mL of manganese nitrate aqueous solution and 0.3030 g of cerium nitrate (the molar ratio of manganese salt to cerium salt is 1:0.54, and the total amount of manganese salt and cerium salt to the mass of the filter material is 0.42:1) to completely wet the modified PTFE filter material, and let it stand at room temperature for 12 h. Then it was placed in an oven and dried at 110 °C for 4 h. Finally, the dried filter material was placed in a muffle furnace and calcined at 250 °C for 2 h. After cooling, the composite filter material was taken out, placed in a 1% hydrogen peroxide solution for activation treatment for 1 h, then washed and dried at 110 °C for 12 h to obtain the PTFE composite filter material loaded with manganese-cerium denitration catalyst. When measured with a German M60x flue gas analyzer, the denitration rate was 72.8% at a reaction temperature of 160 °C; the denitration rate was 76.6% at a reaction temperature of 180 °C.

[0038] Example 3

[0039] After immersing the cleaned circular PTFE filter material with a mass of 1.2189 g in an ethanol solution, immediately add it to a 2 g / L dopamine alkaline solution, adjust the pH value to about 9 with ammonia water, stir at room temperature for 18 h, then take it out, rinse it clean with deionized water and ethanol, and vacuum dry it at 80 °C for 16 h; Immerse the dried filter material again in about 2 g / L freshly prepared MXene ink with a pH of about 6.5, let it stand for 12 h, then take it out and wash it, and vacuum dry it at 80 °C for 12 h. Take 2 mL of an aqueous solution containing 0.5 mL of manganese nitrate (the mass ratio of the manganese salt to the filter material is 0.32:1) to completely soak the modified PTFE filter material, let it stand at room temperature for 12 h, then place it in an oven and dry it at 110 °C for 4 h, and finally place the dried filter material in a muffle furnace and calcine it at 250 °C for 2 h. After cooling, take out the composite filter material, put it into a 10% hydrogen peroxide solution for activation treatment for 1 h, then wash it and dry it at 110 °C for 12 h to obtain a PTFE composite filter material loaded with a pure manganese oxide denitration catalyst. When measured with a German M60x flue gas analyzer, the denitration rate is 75.1% at a reaction temperature of 160 °C; the denitration rate is 80.8% at a reaction temperature of 180 °C.

[0040] Example 4

[0041] After immersing the cleaned circular PTFE filter material with a mass of 1.0893 g in an ethanol solution, immediately add it to a 4 g / L dopamine alkaline solution, adjust the pH value to about 8.5 with tris(hydroxymethyl)aminomethane, stir at room temperature for 18 h, then take it out, rinse it clean with deionized water and ethanol, and vacuum dry it at 60 °C for 10 h; Immerse the dried filter material again in about 1 g / L freshly prepared MXene ink with a pH of about 6.5, let it stand for 12 h, then take it out and wash it, and vacuum dry it at 80 °C for 12 h. Take 2 mL of a uniformly mixed solution containing 0.46 mL of manganese nitrate aqueous solution and 0.1836 g of cerium nitrate (the molar ratio of the manganese salt to the cerium salt is 1:0.2, and the total mass ratio of the manganese salt and the cerium salt to the filter material is 0.46:1) to completely soak the modified PTFE filter material, let it stand at room temperature for 12 h, then place it in an oven and dry it at 80 °C for 6 h, and finally place the dried filter material in a muffle furnace and calcine it at 230 °C for 4 h. After cooling, take out the composite filter material, put it into a 5% hydrogen peroxide solution for activation treatment for 2 h, then wash it and dry it at 110 °C for 12 h to obtain a PTFE composite filter material loaded with a manganese-cerium denitration catalyst. When measured with a German M60x flue gas analyzer, the denitration rate is 82.5% at a reaction temperature of 160 °C; the denitration rate is 85% at a reaction temperature of 180 °C.

[0042] Example 5

[0043] After immersing a cleaned circular PTFE filter material with a mass of 1.1267 g in an ethanol solution, it was immediately added to a 4 g / L dopamine alkaline solution. The pH value was adjusted to about 8.5 by ammonia water, and it was stirred at room temperature for 16 h. Then, after taking it out, it was rinsed clean with deionized water and ethanol, and vacuum dried at 60 °C for 6 h; the dried filter material was immersed again in a freshly prepared MXene ink with a concentration of about 2 g / L and a pH of about 7, left standing for 12 h, then taken out and washed, and vacuum dried at 80 °C for 12 h. Take 2 mL of a uniformly mixed solution containing 0.23 mL of manganese nitrate aqueous solution and 0.7232 g of cerium nitrate (the molar ratio of manganese salt to cerium salt is 1:

[0044] 1.6, and the total amount of manganese salt and cerium salt to the mass of the filter material is 0.8:1) to completely soak the modified PTFE filter material, and left standing at room temperature for 6 h, then placed in an oven and dried at 80 °C for 12 h. Finally, the dried filter material was placed in a muffle furnace and calcined at 220 °C for 4 h. After cooling, the composite filter material was taken out, put into a 20% hydrogen peroxide solution for activation treatment for 2 h, then washed and dried at 110 °C for 12 h, and the PTFE composite filter material loaded with manganese-cerium denitration catalyst was obtained. When measured with a German M60x flue gas analyzer, the denitration rate was 64.5% at a reaction temperature of 160 °C; the denitration rate was 69.6% at a reaction temperature of 180 °C.

[0045] Example Six

[0046] After immersing a cleaned circular PTFE filter material with a mass of 1.0343 g in an ethanol solution, it was immediately added to a 1 g / L dopamine alkaline solution. The pH value was adjusted to about 8.5 by tris(hydroxymethyl)aminomethane, and it was stirred at room temperature for 18 h. Then, after taking it out, it was rinsed clean with deionized water and ethanol, and vacuum dried at 60 °C for 10 h; the dried filter material was immersed again in a freshly prepared MXene ink with a concentration of about 0.5 g / L and a pH of about 7, left standing for 12 h, then taken out and washed, and vacuum dried at 80 °C for 12 h. Take 2 mL of a uniformly mixed solution containing 0.92 mL of manganese nitrate aqueous solution and 0.3634 g of cerium acetate (the molar ratio of manganese salt to cerium salt is 1:0.27, and the total amount of manganese salt and cerium salt to the mass of the filter material is 1.03:1) to completely soak the modified PTFE filter material, and left standing at room temperature for 12 h, then placed in an oven and dried at 80 °C for 6 h. Finally, the dried filter material was placed in a muffle furnace and calcined at 230 °C for 4 h. After cooling, the composite filter material was taken out, put into a 10% hydrogen peroxide solution for activation treatment for 2 h, then washed and dried at 110 °C for 12 h, and the PTFE composite filter material loaded with manganese-cerium denitration catalyst was obtained. When measured with a German M60x flue gas analyzer, the denitration rate was 84.6% at a reaction temperature of 160 °C; the denitration rate was 88.2% at a reaction temperature of 180 °C.

[0047] Comparative Example 1

[0048] After immersing a cleaned circular PTFE filter material with a mass of 1.1467 g into an ethanol solution, immediately add it to a 2 g / L dopamine alkaline solution, adjust the pH value to about 8.5 with tris(hydroxymethyl)aminomethane, and stir at room temperature for 12 h. Then take it out, rinse it thoroughly with deionized water and ethanol, and vacuum dry it at 60 °C for 12 h; Immerse the dried filter material again into about 1 g / L freshly prepared MXene ink with a pH of about 6.5, let it stand for 12 h, then take it out and wash it, and vacuum dry it at 60 °C for 12 h. Take 2 mL of a uniform mixed solution containing 0.38 mL of manganese nitrate aqueous solution and 0.14982 g of cerium nitrate (the molar ratio of manganese salt to cerium salt is 1:0.2, and the total amount of manganese salt and cerium salt to the mass of the filter material is 0.38:1) to completely soak the modified PTFE filter material, and let it stand at room temperature for 12 h, then place it in an oven and dry it at 110 °C for 2 h. Finally, place the dried filter material in a muffle furnace and calcine it at 250 °C for 2 h.

[0049] A PTFE composite filter material loaded with a manganese-cerium denitration catalyst is obtained. When measured with a German M60x flue gas analyzer, the denitration rate is 76.6% at a reaction temperature of 160 °C; the denitration rate is 85.8% at a reaction temperature of 180 °C.

[0050] Comparative Example 2

[0051] After immersing a cleaned circular PTFE filter material with a mass of 1.3889 g into an ethanol solution, immediately add it to a 2 g / L dopamine alkaline solution, adjust the pH value to about 9 with ammonia water, and stir at room temperature for 18 h. Then take it out, rinse it thoroughly with deionized water and ethanol, and vacuum dry it at 80 °C for 16 h; Take 2 mL of an aqueous solution containing 0.5 mL of manganese nitrate (the mass ratio of manganese salt to the filter material is 0.28:1) to completely soak the modified PTFE filter material, and let it stand at room temperature for 12 h. Then place it in an oven and dry it at 110 °C for 4 h. Finally, place the dried filter material in a muffle furnace and calcine it at 250 °C for 2 h. After cooling, take out the composite filter material and put it into a 10% hydrogen peroxide solution for activation treatment for 1 h, then wash it and dry it at 110 °C for 12 h, and a PTFE composite filter material loaded with a pure manganese oxide denitration catalyst is obtained. When measured with a German M60x flue gas analyzer, the denitration rate is 71.1% at a reaction temperature of 160 °C; the denitration rate is 71.5% at a reaction temperature of 180 °C.

[0052] During the implementation of the examples, it was found that the main factors affecting the low-temperature denitrification performance of the PTFE composite filter material of the present invention include the molar ratio of metal ions in the manganese-cerium mixed solution, the mass ratio of metal salt to filter material, and whether to impregnate MXene ink and perform hydrogen peroxide activation, etc. The Mn / Ce molar ratio of manganese salt and cerium salt in the mixed solution has a great influence on the number and structural form of the surface active sites of the catalyst, and thus affects its low-temperature denitrification activity. It can be found from Comparative Example 1 that the composite filter material was not activated by hydrogen peroxide, and its low-temperature denitrification activity was about 6% worse than that of Example 1. In Comparative Example 2, MXene impregnation was not carried out, and its denitrification effect also became worse compared with Example 3. This is mainly because after MXene is adsorbed on the surface of the polydopamine-modified fiber, it will improve the dispersion degree, loading amount and synergistic effect of the catalyst on the fiber surface, and thus enhance the low-temperature denitrification effect of the composite filter material.

[0053] In addition, we also carried out a sulfur resistance test on Example 1 with the best effect, and the results are as Figure 3 shown. The composite filter material shows better sulfur resistance and recovery ability than most denitrification and dust removal filter materials under the atmosphere conditions of 180 °C and 100 ppm SO2.

[0054] The above specific implementation part specifically introduces the analysis method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and idea of the present invention, rather than a limitation on the relevant content. Without departing from the principle of the present invention, those skilled in the art can also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications should also fall within the protection scope of the present invention.

Claims

1. A preparation method of a PTFE composite filter material with denitrification function, characterized in that, Using a PTFE polymer needle-punched filter material as the carrier, first perform polydopamine surface functionalization modification on it, then immerse it in MXene ink, and use electrostatic attraction to evenly adsorb MXene laminates on the surface of polydopamine to fully activate the originally inert surface of PTFE fibers; then, use the equal-volume impregnation method to immerse a mixed solution prepared from manganese salt and cerium salt into the above composite filter material; finally, after the composite filter material is dried, calcined and activated, a PTFE composite filter material with denitrification function is obtained.

2. The preparation method of a PTFE composite filter material with denitrification function according to claim 1, characterized in that, It includes the following steps: (1) Take a piece of cleaned PTFE filter material, immerse it in ethanol once and then immerse it in an alkaline aqueous solution of dopamine, stir for a period of time at a certain temperature, then take it out and dry it to evenly coat a polydopamine functional layer on the surface of the filter material fibers; (2) Prepare MXene ink by chemically etching the ternary layered carbide Ti3AlC2 with a fluorine-containing solution, then immerse the polydopamine-modified filter material obtained in step (1) into the above ink, after standing for a period of time, take out the filter material and dry it; (3) According to the amount of solution that the PTFE filter material can adsorb at one time, use the equal-volume impregnation method to immerse the filter material obtained in step (2) in a certain amount of mixed solution of manganese salt and cerium salt, stand for a period of time, and place it in an oven to dry, so that the metal salts are dispersed and deposited on the surface of the modified fiber filter material; (4) Place the dried PTFE filter material obtained in step (3) in a muffle furnace and calcine it for a period of time at a temperature lower than the maximum service temperature of the PTFE filter material to fully decompose the metal salts on it; (5) Finally, take out the filter material in step (4), put it into a hydrogen peroxide aqueous solution with a certain concentration for activation treatment, and finally wash and dry it to obtain a PTFE composite filter material with denitrification function.

3. The preparation method of a PTFE composite filter material with denitrification function according to claim 2, characterized in that, The air permeability of the PTFE filter material in step (1) is between 20 - 200 L / dm 2 ·min, the thickness is between 0.5 and 3 mm, and the grammage is between 100 and 1000 g / m 2 It can withstand high temperatures of 260 °C.

4. The preparation method of a PTFE composite filter material with denitrification function according to claim 2, characterized in that, The dopamine concentration in step (1) is 0.1-10 g / L; the alkaline aqueous solution is prepared from one or more compounds among sodium hydroxide, potassium hydroxide, ammonia water or tris(hydroxymethyl)aminomethane, and the pH is between 8-10.

5. The preparation method of a PTFE composite filter material with denitrification function according to claim 2, characterized in that, The MXene ink concentration in step (2) is 0-10 g / L, the pH value of the solution is 6-8, the standing impregnation time is 0.5-48 h, the drying temperature is between 30-120 °C, and the drying duration is 0.5-48 h.

6. The preparation method of a PTFE composite filter material with denitrification function according to claim 2, characterized in that, The manganese salt in step (3) is selected from one or more of manganese nitrate, manganese chloride, manganese sulfate and manganese acetate, and the cerium salt is selected from one or more of cerium nitrate, cerium chloride, cerium sulfate and cerium acetate; the molar ratio of manganese salt and cerium salt is between 1:0-1:3, and the mass ratio of the total amount of manganese salt and cerium salt to the filter material is controlled between 0.01:1-3:1; the equal-volume impregnation time is 0.5-48 h, the drying temperature is between 30-120 °C, and the drying duration is 0.5-48 h.

7. The preparation method of a PTFE composite filter material with denitrification function according to claim 2, characterized in that, The calcination temperature in step (4) is between 200-260 °C, and the calcination duration is 0.5-12 h.

8. The preparation method of a PTFE composite filter material with denitrification function according to claim 2, characterized in that, The activation process in step (5) is to oxidize the composite filter material in hydrogen peroxide aqueous solution with a mass concentration of 0.1%-30% for 0.5-48 h; the drying temperature is between 60-120 °C, and the drying duration is 0.5-48 h.

9. Application of the PTFE composite filter material prepared by the preparation method according to any one of claims 1-8 in integrated low-temperature denitrification and dust removal of industrial tail gas.

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