Preparation method and application of PTFE catalytic filter material

Abstract

The application discloses a preparation method and application of PTFE catalytic filter material, and the preparation of the PTFE catalytic filter material comprises MnCeTi catalyst preparation, PTFE catalytic fiber preparation, heteropoly acid functionalization and needling. The three-dimensional flower-shaped spherical structure of the prepared PTFE catalytic filter material is used to optimize the mass transfer and conversion channel of pollutants, the intermetallic interaction of Mn, Ce and Ti is used to regulate the surface acid sites and active sites of the catalyst, the surface oxygen vacancies, acid sites and other characteristics are further optimized through the heteropoly acid functionalization, and the low-temperature catalytic dioxin performance of the PTFE catalytic filter material is effectively improved. Meanwhile, the heteropoly acid can form polyoxometalate on the surface of the catalyst, the adhesion strength of the catalyst and the filter material is strengthened, the loss problem of the catalyst in the use process is effectively relieved, and the prepared PTFE catalytic filter material has high efficiency and long-term use performance.

Description

Technical Field

[0001] This invention relates to the field of flue gas pollution control technology, specifically to a method for preparing and applying PTFE catalytic filter media. Background Technology

[0002] Waste incineration has become an important method for urban solid waste treatment. The pollutants generated during incineration, such as particulate matter, acid gases, nitrogen oxides (NOx), dioxins, volatile organic compounds (VOCs), and heavy metals, need to be treated using technologies such as bag filters, desulfurization and denitrification processes, and activated carbon adsorption. Currently, although flue gas treatment technologies are relatively mature, challenges remain, including balancing pollutant removal efficiency with cost, the risk of secondary pollution, and difficulties in the coordinated control of multiple pollutants. Furthermore, increasingly stringent environmental regulations and the challenges posed by the diversification of waste composition to the treatment of new pollutants place higher demands on existing technologies.

[0003] Catalytic filtration technology is a flue gas treatment method that combines filtration with catalytic reaction. By loading a catalyst onto the filter medium, it can not only efficiently remove particulate matter but also simultaneously decompose pollutants such as VOCs, NOx, and dioxins. The principle is that when flue gas passes through the filter material, particulate matter is intercepted, and gaseous pollutants react chemically with the catalyst, transforming into harmless substances. Currently, catalytic filtration technology is widely used in integrated dust removal and denitrification devices for waste incineration flue gas treatment, effectively reducing process steps and floor space requirements. However, this technology still faces challenges such as catalyst poisoning and deactivation, high initial investment, and decreased catalytic efficiency under high temperature and humidity conditions. Further optimization of catalyst performance and extension of service life are needed to improve its economic efficiency and stability.

[0004] To simultaneously remove particulate matter and harmful substances from flue gas, existing technologies often employ multi-layered filter media stacking to prepare catalytic filter media. Existing technology CN104226020B discloses a composite nanofilter media formed by stacking a dust-collecting layer, a buffer layer, a catalytic filtration layer, and a support layer, using electrospinning to prepare a fiber carrier, and then loading the active component. While this effectively imparts catalytic function to the filter material, the process is complex and the catalyst-gas contact time is short. Furthermore, existing technology CN101496974A discloses a method for preparing catalytic fibers by mixing the catalyst with polytetrafluoroethylene (PTFE) resin and then splitting the membrane, resulting in low porosity of the fibrous layer and low fiber yield. Existing technology CN103212245A uses an impregnation method to load the catalyst onto the filter media surface. Although this increases the catalyst-gas contact area, the catalyst is prone to detachment and has poor stability. This indicates a significant contradiction between existing technologies in improving catalytic efficiency and maintaining catalyst stability, making it difficult to simultaneously achieve high efficiency and long-term performance. Summary of the Invention

[0005] To address the problems existing in current catalytic filtration technologies, this invention provides a method for preparing PTFE catalytic filter media and its application. The catalytic filter media prepared using this method exhibits a higher bonding strength between the catalyst and the PTFE filter media, and can be used to remove harmful components such as particulate matter, volatile organic compounds (e.g., chlorobenzene), and dioxins from incineration flue gas.

[0006] To achieve the above objectives, the present invention employs the following technical means:

[0007] A method for preparing and applying PTFE catalytic filter media is disclosed. First, a ternary MnCeTi catalyst is prepared by redox method. Then, the catalyst, polytetrafluoroethylene resin, additives and auxiliaries are mixed and PTFE catalytic filter media is prepared by membrane splitting method and surface functionalization modification of heteropoly acids. This method effectively retains the dust removal performance of PTFE filter material and activates the surface catalytic functional carrier, exhibiting excellent performance in removing volatile organic compounds such as chlorobenzene, dioxins and particulate matter at low temperature.

[0008] The present invention provides a method for preparing PTFE catalytic filter media, specifically including the following steps:

[0009] (1) Preparation of MnCeTi catalyst

[0010] Mn metal precursor, Ce metal precursor, Ti metal precursor and surfactant are mixed evenly in a molar ratio of (2-3):(2-3):(1-2):(0.05-0.1), and then a certain concentration of potassium permanganate solution is added dropwise. The reaction is carried out for 1-4 hours, followed by drying at 80-105℃ for 24-48 hours, and finally calcined in a calcining atmosphere to obtain the ternary MnCeTi catalyst.

[0011] (2) Preparation of PTFE catalytic fibers

[0012] MnCeTi catalyst, PTFE resin, additives and auxiliaries are mixed evenly in a mass ratio of (20-30):100:(20-30):(4-5), and aged at 50-70℃ for 12-48 h to obtain a mixture. Then, the mixture is taken out and extruded under a pressure of 3-5 MPa to preform it. Finally, PTFE catalytic fibers are obtained through calendering, longitudinal stretching, slitting and curling steps.

[0013] (3) Functionalization of heteropolyacids

[0014] PTFE catalytic fibers were placed in a heteropoly acid solution with a concentration of 0.1-2 mol / L, and then hydrogen peroxide solution with a concentration of 0.1-2 mol / L was added dropwise to the heteropoly acid solution containing the fibers. The mixture was stirred at room temperature for 1-5 h, then dried at 105 °C, and finally the PTFE catalytic filter material was prepared by needle punching.

[0015] In some embodiments of the present invention, the molar ratio of Mn metal precursor, Ce metal precursor, Ti metal precursor and surfactant in step (1) is preferably 2:3:1:0.05.

[0016] In some embodiments of the present invention, the mass ratio of the MnCeTi catalyst, PTFE resin, additives and auxiliaries in step (2) is preferably 30:100:26:5.

[0017] In some embodiments of the present invention, the concentration of potassium permanganate solution in step (1) is 0.01~1 mol / L, preferably, the concentration of potassium permanganate solution is 0.15 mol / L.

[0018] In some embodiments of the present invention, the calcination atmosphere in step (1) is nitrogen or air, preferably nitrogen.

[0019] In some embodiments of the present invention, the calcination conditions in step (1) are: calcination at 300-600℃ for 2-6 h.

[0020] In some embodiments of the present invention, in step (1), the Mn metal precursor is one or more of manganese acetate, manganese nitrate, manganese sulfate, and manganese carbonate; the Ce metal precursor is one or more of cerium acetate, cerium nitrate, cerium sulfate, and cerium carbonate; the Ti metal precursor can be one or more of titanium sulfate, sodium titanate, and potassium titanate; the surfactant is one or more of quaternary ammonium salts, alkylamine salts, alkyl sulfonates, and lecithin; preferably, the Mn metal precursor is a nitrate, the Ce metal precursor is cerium nitrate, the Ti metal precursor is titanium sulfate, and the surfactant is hexadecyltrimethylammonium bromide.

[0021] In some embodiments of the present invention, the auxiliary agent in step (2) is one or more of white oil, aviation kerosene, liquid paraffin, naphtha or petroleum ether; the additive is a silane coupling agent KH570 or KA1003; preferably, the auxiliary agent is white oil and the additive is KH570.

[0022] In some embodiments of the present invention, the temperature of the stretching zone during longitudinal stretching in step (2) is 120-350°C; preferably, the temperature of the stretching zone is 300°C.

[0023] In some embodiments of the present invention, the heteropoly acid in step (3) is one or more of silicotungstic acid, phosphotungstic acid, and silicotomolybdic acid, and the concentration of the heteropoly acid solution is 0.1-2 mol / L; preferably, silicotungstic acid is selected as the heteropoly acid, and the concentration is 0.3 mol / L.

[0024] A second aspect of the present invention provides a PTFE catalytic filter media prepared by the method described in the first aspect.

[0025] A third aspect of the invention provides the use of PTFE catalytic filter media prepared by the method of the first aspect in the preparation of products for the removal of dioxins, volatile organic compounds and particulate matter.

[0026] Beneficial effects of the present invention

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) This invention provides a MnCeTi catalyst, which is used as the catalytic active component of the catalytic filter media. The surface characteristics, such as acidic sites, active sites, and oxygen vacancies, are regulated by the intermetallic interactions of Mn, Ce, and Ti. The large specific surface area and three-dimensional flower-like spherical structure of the MnCeTi catalyst are applied to improve the low-temperature catalytic activity of the catalytic filter media for volatile organic compounds chlorobenzene and dioxins. 90 The temperature can drop to below 200℃.

[0029] (2) The catalytic filter material of the present invention strengthens the adhesion strength between the catalyst and the filter cloth by forming polyoxometalates from oxidized heteropolyacids, optimizes the catalytic performance of the MnCeTi catalyst on the surface of the filter material, and makes the catalytic filter material applicable in harsh industrial flue gas environments. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation process of PTFE catalytic filter media.

[0031] Figure 2 SEM images of the MnCeTi catalyst prepared in Example 1 of this invention are shown; where a is the catalyst prepared in Example 3 and b is the catalyst prepared in Comparative Example 2.

[0032] Figure 3 SEM images of the MnCeTi catalysts prepared in Examples 3 and 4 of this invention are shown; where a is the catalyst prepared in Example 4 and b is the catalyst prepared in Example 5.

[0033] Figure 4 The EPR diagram of the PTFE catalytic filter material prepared in Example 1 of this invention;

[0034] Figure 5 The diagram shows the catalytic performance of the PTFE catalytic filter material prepared in Example 1 of this invention in the catalytic degradation of actual dioxins. Detailed Implementation

[0035] The following examples are used to illustrate preferred embodiments of the invention. Those skilled in the art will understand that the techniques disclosed in the examples represent techniques discovered by the inventors that can be used to implement the invention, and therefore can be considered preferred embodiments for implementing the invention. However, those skilled in the art should understand from this specification that many modifications can be made to the specific embodiments disclosed herein, still yielding the same or similar results, without departing from the spirit or scope of the invention.

[0036] This invention discloses a method for preparing PTFE catalytic filter media and its application. This catalytic filter media can be used for controlling volatile organic compounds, particulate matter, and dioxins in incineration flue gas. The specific preparation steps are as follows: Figure 1 As shown below: A ternary MnCeTi catalyst was prepared by redox method. Then, the catalyst, polytetrafluoroethylene resin, additives and auxiliaries were mixed and catalytic fibers were prepared by membrane splitting method and heteropoly acid functionalization. Finally, PTFE catalytic filter material was prepared by needle punching.

[0037] Example 1

[0038] The specific preparation steps of the PTFE catalytic filter material in this embodiment are as follows:

[0039] (1) Preparation of MnCeTi catalyst

[0040] Manganese nitrate, cerium nitrate, titanium sulfate, and hexadecyltrimethylammonium bromide were mixed in a molar ratio of 2:3:1:0.05, and then a 0.15 mol / L potassium permanganate solution was added dropwise. The reaction was allowed to proceed for 2 h, followed by drying at 105 °C for 24 h, and finally calcined at 300 °C for 4 h under a nitrogen atmosphere to obtain the ternary MnCeTi catalyst. Figure 2 As shown in a, the MnCeTi catalyst exhibits a three-dimensional flower-like spherical shape;

[0041] (2) Preparation of PTFE catalytic fibers

[0042] MnCeTi catalyst, PTFE resin, white oil and silane coupling agent (KH570) were mixed evenly in a mass ratio of 10:100:26:5 and aged at 60℃ for 24 h to obtain a mixture. The mixture was then taken out and extruded under a pressure of 5 MPa to preform it. Finally, PTFE catalytic fibers were obtained through calendering, longitudinal stretching, slitting and crimping steps.

[0043] (3) Functionalization of heteropolyacids

[0044] PTFE catalytic fibers were placed in a 0.3 mol / L silicotungstic acid solution of a certain concentration, and then 0.1 mol / L hydrogen peroxide solution was added dropwise to the silicotungstic acid solution containing the fibers. The mixture was stirred at room temperature for 2 h, then dried at 105 °C, and finally PTFE catalytic filter media was prepared by needle punching.

[0045] Example 2

[0046] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 1, except that the mixing ratio of MnCeTi catalyst, PTFE resin, white oil and silane coupling agent (KH570) in step (2) is adjusted to 20:100:26:5 by mass.

[0047] Example 3

[0048] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 1, except that the mixing ratio of MnCeTi catalyst, PTFE resin, white oil and silane coupling agent (KH570) in step (2) is adjusted to 30:100:26:5 by mass.

[0049] Example 4

[0050] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 3, except that the molar ratio of manganese nitrate, cerium nitrate, titanium sulfate, and hexadecyltrimethylammonium bromide in step (1) is adjusted to 2:3:1:0.1. The catalyst morphology is as follows: Figure 3 As shown in a.

[0051] Example 5

[0052] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 3, except that the molar ratio of manganese nitrate, cerium nitrate, titanium sulfate, and hexadecyltrimethylammonium bromide in step (1) is adjusted to 2:3:1:0.15. The catalyst morphology is as follows: Figure 3 As shown in b.

[0053] Example 6

[0054] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 3, except that the silicotungstic acid solution in step (3) is changed to a silicotungstic acid solution.

[0055] Example 7

[0056] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 3, except that the silicotungstic acid solution in step (3) is changed to phosphotungstic acid solution.

[0057] Comparative Example 1

[0058] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 3, except that the silicotungstic acid solution in step (3) is adjusted to an aqueous solution.

[0059] Comparative Example 2

[0060] The preparation steps of the catalytic filter material in this embodiment are the same as those in Example 3, except that: cerium nitrate in step (1) is replaced with cerium acetate, and the SEM image of the catalyst is shown below. Figure 2 As shown in b.

[0061] Performance Investigation

[0062] (1) Using chlorobenzene as a model pollutant, PTFE catalytic filter media prepared in Examples 1-7 and Comparative Examples 1-2 were selected for particulate matter removal tests and catalytic performance evaluation. The catalytic performance testing conditions were as follows: total flow rate of 500 mL / min, oxygen volume fraction of 11%, catalytic fiber mass of 1 g, and chlorobenzene concentration of 100 ppm. The particulate matter removal test showed that the above filter media could achieve 99.9% particulate matter removal at temperatures below 240℃. The catalytic performance evaluation results are shown in Table 1 below.

[0063] Table 1 Chlorobenzene catalytic performance of PTFE catalytic filter media

[0064]

[0065] As shown in Tables 1-3, the catalytic performance of the prepared PTFE catalytic filter media increases with the increase of catalyst content, and the low-temperature catalytic performance of the catalyst is significantly improved. The PTFE catalytic filter media prepared in Example 3 has the highest catalyst loading and its T 90 Temperature below 200℃.

[0066] As shown in Examples 3-5 of Table 1, the catalytic performance of PTFE catalytic filter media prepared with high surfactant content is reduced, and its low-temperature catalytic performance is also worse. This is because surfactants can affect the catalyst structure; higher surfactant content can damage the catalyst structure and cause the catalyst particles to become smaller. Figure 3 As shown, this in turn affects the catalytic performance of PTFE catalytic filter media.

[0067] As shown in Table 1, Example 3 and Comparative Example 2, the metal precursor has a significant impact on the catalyst structure, thereby affecting the catalytic performance of the PTFE catalytic filter media. This can mainly be attributed to the fact that the three-dimensional flower-like spherical structure has a higher specific surface area and pore volume, effectively promoting the mass transfer and conversion of dioxin pollutants.

[0068] Depend on Figure 3 It can be seen that heteropoly acid functionalization can effectively increase the oxygen vacancies on the surface of the catalytic filter material. The oxygen vacancy content is ranked as follows: Example 3 > Example 7 > Example 6 > Comparative Example 1. This is consistent with the catalytic performance of the PTFE catalytic filter materials prepared in Examples 1, 6, 7 and Comparative Example 1.

[0069] (2) The PTFE catalytic filter material prepared in Example 3 was selected for actual dioxin catalytic performance evaluation. The test conditions were as follows: total flow rate of 500 mL / min, oxygen volume fraction of 11%, and catalytic fiber mass of 1 g. During the experiment, PCDD / Fs in the reaction tail gas were absorbed by XAD-2 resin and two-stage toluene solution connected in series. The results are as follows: Figure 5 As shown.

[0070] Dioxins have 136 isomers, which can be divided into PCDDs and PCDFs, and the two are collectively referred to as PCDD / Fs; the toxicity equivalent I-TEQ can be obtained by calculating 17 toxic dioxins.

[0071] In the figure, Re represents the removal rate. The red column represents the removal rate of 17 toxic dioxins, and the purple column represents the removal rate of 136 dioxins. De represents the degradation rate. The yellow column represents the degradation rate of 17 toxic dioxins, and the blue column represents the degradation rate of 136 dioxins.

[0072] The results showed that the PTFE catalytic filter media achieved a removal rate of 86.5% for PCDD / Fs from 17 types of toxic dioxins, with a degradation rate of 61.1%; the toxicity equivalent removal rate was 92.3%, and the degradation rate was 85.5%. For 136 types of dioxins, the PTFE catalytic filter media achieved a removal rate of 83.7% for PCDD / Fs, with degradation rates of 55.2%.

[0073] (3) The catalyst content and loss of the catalytic filter media prepared in Example 3 and Comparative Example 1 were calculated by the weight of the filter cloth before and after use. The test results are shown in Table 2.

[0074] Table 2. Changes in catalyst content of catalytic filter media

[0075]

[0076] Through Example 3 and Comparative Example 1, it can be seen that heteropolyacid functionalization can effectively increase the adhesion strength of the catalyst to PTFE and reduce catalyst loss.

[0077] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and improvements to some technical features without departing from the principles of this invention. Such substitutions and improvements should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing PTFE catalytic filter media, characterized in that, Includes the following steps: (1) Preparation of MnCeTi catalyst Mn metal precursor, Ce metal precursor, Ti metal precursor and surfactant are mixed evenly in a molar ratio of (2-3):(2-3):(1-2):(0.05-0.1), and potassium permanganate solution is added dropwise. The reaction is carried out for 1-4 h, followed by drying at 80-105℃ for 24-48 h, and finally calcined in a calcining atmosphere to obtain the ternary MnCeTi catalyst. (2) Preparation of PTFE catalytic fibers MnCeTi catalyst, PTFE resin, additives and auxiliaries are mixed evenly in a mass ratio of 30:100:26:5 and aged at 50-70℃ for 12-48 h to obtain a mixture. The mixture is then taken out and extruded under a pressure of 3-5 MPa to preform it. Finally, PTFE catalytic fibers are obtained through calendering, longitudinal stretching, slitting and curling steps. (3) Functionalization of heteropolyacids PTFE catalytic fibers were placed in a heteropoly acid solution with a concentration of 0.1-2 mol / L. Hydrogen peroxide solution with a concentration of 0.1-2 mol / L was added dropwise to the heteropoly acid solution containing the fibers. The mixture was stirred at room temperature for 1-5 h, then dried at 105℃, and finally needle-punched to obtain PTFE catalytic filter media. The Mn metal precursor is manganese nitrate; the Ce metal precursor is cerium nitrate; the Ti metal precursor is titanium sulfate; the surfactant is hexadecyltrimethylammonium bromide; and the heteropoly acid is silicotungstic acid.

2. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that, In step (1), the concentration of potassium permanganate solution is 0.01~1 mol / L.

3. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that, In step (1), the calcination atmosphere is nitrogen or air.

4. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that, The calcination conditions in step (1) are: calcination at 300-600℃ for 2-6 hours.

5. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that, In step (2), the auxiliary agent is one or more of white oil, aviation kerosene, liquid paraffin, naphtha, and petroleum ether; the additive is one of silane coupling agents KH570 or KA1003.

6. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that, The temperature in the tensile zone during longitudinal tension is 120-350℃.

7. A PTFE catalytic filter media prepared by the method according to any one of claims 1-6.

8. The use of the PTFE catalytic filter media prepared by the method of any one of claims 1-6 in the removal of dioxins, volatile organic compounds and particulate matter.

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