Preparation method and application of PTFE catalytic filter material

Abstract

The invention discloses a preparation method and application of a PTFE catalytic filter material, the preparation of the PTFE catalytic filter material comprises the steps of MnCeTi catalyst preparation, PTFE catalytic fiber preparation, heteropoly acid functionalization and needling, and the prepared PTFE catalytic filter material optimizes a pollutant mass transfer and conversion channel by applying a three-dimensional flower-shaped spherical structure of the catalyst. Acidic sites and active sites on the surface of the catalyst are regulated and controlled by virtue of metal interaction of Mn, Ce and Ti, and the characteristics of surface oxygen vacancies, acidic sites and the like are further optimized by virtue of heteropoly acid functionalization, so that the low-temperature dioxin catalysis performance of the PTFE catalytic filter material is effectively improved. Meanwhile, the heteropolyacid can form polyoxometallate on the surface of the catalyst, the bonding strength of the catalyst and the filter material is enhanced, the problem of loss of the catalyst in the using process is effectively relieved, and the prepared PTFE catalytic filter material has high efficiency and long-term using performance.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas pollution control, and in particular to a preparation method and application of a PTFE catalytic filter material. Background Art

[0002] Waste incineration has become an important way to treat urban solid waste, but the environmental pollution caused by its flue gas emissions cannot be ignored. Pollutants such as particulate matter, acidic gases, nitrogen oxides (NOx), dioxins, volatile organic compounds (VOCs), heavy metals, etc. generated during the incineration process need to be treated through bag filters, desulfurization and denitrification processes, activated carbon adsorption and other technologies. At present, although the flue gas treatment technology is relatively mature, it still faces problems such as the balance between pollutant removal efficiency and cost, the risk of secondary pollution, and the difficulty of coordinated control of multiple pollutants. In addition, the increasingly stringent environmental protection regulations and the challenges of new pollutant treatment brought about by the diversification of garbage components also put higher demands on existing technologies.

[0003] Catalytic filtration technology is a flue gas treatment method that combines filtration with catalytic reaction. By loading the catalyst on the filter medium, it can not only efficiently remove particulate matter, but also decompose polluting gases such as VOCs, NOx and dioxins. The principle is that when the flue gas passes through the filter material, the particulate matter is intercepted, and the gaseous pollutants come into contact with the catalyst to undergo a chemical reaction and are converted into harmless substances. At present, catalytic filtration technology has been widely used in integrated dust removal and denitrification devices in waste incineration flue gas treatment, which can effectively reduce the process flow and reduce the floor space. However, this technology still has problems such as catalyst poisoning and deactivation, high initial investment, and decreased catalytic efficiency under high temperature and high humidity conditions. It is necessary to further optimize the catalyst performance and extend the service life to improve its economy and stability.

[0004] In order to achieve the simultaneous removal of particulate matter and harmful substances in flue gas, the prior art mostly adopts a multi-layer filter material stacking method to prepare catalytic filter material. The prior art CN104226020B discloses that a dust-facing layer, a buffer layer, a catalytic filter layer and a support layer are stacked to form a composite nano-filter material, a fiber carrier is prepared by an electrospinning method, and then the active component is loaded. Although the catalytic function is effectively imparted to the filter material, the process is complicated and the contact time between the catalyst and the gas is short. In addition, the prior art CN101496974A discloses a method for preparing catalytic fibers by mixing a catalyst with a polytetrafluoroethylene (PTFE) resin and then splitting the film, resulting in a low porosity of the fiberized layer and a low fiber yield. The prior art CN103212245A patent loads the catalyst to the surface of the filter material by an impregnation method. Although the contact area between the catalyst and the gas is increased, the catalyst is easy to fall off and has poor stability. This shows that there is an obvious contradiction between improving the catalytic efficiency and maintaining the stability of the catalyst in the prior art, and it is difficult to take into account both high efficiency and long-term performance. Summary of the invention

[0005] In view of the problems existing in the existing catalytic filtration technology, the present invention provides a preparation method and application of a PTFE catalytic filter material. The catalytic filter material prepared by the method of the present invention has a higher bonding strength between the catalyst and the PTFE filter material, and can be used to remove harmful components such as particulate matter, volatile organic matter (such as chlorobenzene), and dioxins in incineration flue gas.

[0006] In order to achieve the above object, the present invention adopts the following technical means: A preparation method and application of a PTFE catalytic filter material. First, a ternary MnCeTi catalyst is prepared by a redox method. Then the catalyst, a polytetrafluoroethylene resin, an auxiliary agent and an additive are mixed. The PTFE catalytic filter material is prepared by a film splitting method and surface functionalization modification of a heteropoly acid. The dust removal performance of the PTFE filter material is effectively retained, and the surface catalytic functional carrier is activated, showing excellent low-temperature removal performance of volatile organic compounds such as chlorobenzene, dioxins and particulate matter.

[0007] The present invention provides a method for preparing a PTFE catalytic filter material, which specifically comprises the following steps: (1) Preparation of MnCeTi catalyst The Mn metal precursor, the Ce metal precursor, the Ti metal precursor and the surfactant are uniformly mixed 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, reacted for 1-4 hours, and then dried at 80-105° C. for 24-48 hours, and finally calcined in a calcination atmosphere to obtain a ternary MnCeTi catalyst; (2) Preparation of PTFE catalytic fibers The MnCeTi catalyst, PTFE resin, auxiliary agent and additive are uniformly mixed in a mass ratio of (20-30):100:(20-30):(4-5), and aged for 12-48 h at 50-70°C to obtain a mixture, and then the mixture is taken out and extruded at a pressure of 3-5Mpa for preforming, and finally PTFE catalytic fibers are obtained through calendering, longitudinal drawing, slitting and curling steps; (3) Functionalization of heteropolyacids The PTFE catalytic fiber is placed in a heteropolyacid solution with a concentration of 0.1-2 mol / L, and then a hydrogen peroxide solution with a concentration of 0.1-2 mol / L is added dropwise to the heteropolyacid solution containing the fiber, stirred at room temperature for 1-5 h, then dried at 105°C, and finally a PTFE catalytic filter material is prepared by needle punching.

[0008] In some embodiments of the present invention, the molar ratio of the Mn metal precursor, the Ce metal precursor, the Ti metal precursor and the surfactant in step (1) is preferably 2:3:1:0.05.

[0009] In some embodiments of the present invention, the mass ratio of the MnCeTi catalyst, PTFE resin, auxiliary agent and additive in step (2) is preferably 30:100:26:5.

[0010] In some embodiments of the present invention, the concentration of the potassium permanganate solution in step (1) is 0.01-1 mol / L, and preferably, the concentration of the potassium permanganate solution is 0.15 mol / L.

[0011] In some embodiments of the present invention, the calcination atmosphere in step (1) is nitrogen or air. Preferably, the calcination atmosphere is nitrogen.

[0012] In some embodiments of the present invention, the calcination conditions in step (1) are: calcination at 300-600° C. for 2-6 h.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] In some embodiments of the present invention, the heteropoly acid in step (3) is one or more of silicotungstic acid, phosphotungstic acid, and silicomolybdic acid, and the concentration of the heteropoly acid solution is 0.1-2 mol / L; preferably, the heteropoly acid is silicotungstic acid, and the concentration is 0.3 mol / L.

[0017] The second aspect of the present invention provides a PTFE catalytic filter material prepared by the method described in the first aspect.

[0018] The third aspect of the present invention provides the use of the PTFE catalytic filter material prepared by the method described in the first aspect in the preparation of a product for removing dioxins, volatile organic compounds and particulate matter.

[0019] Beneficial Effects of the Invention Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a MnCeTi catalyst, which is used as the catalytic active component of a catalytic filter material, and the metal-metal interaction between Mn, Ce and Ti is used to achieve the regulation of surface characteristics such as surface acid sites, active sites and oxygen vacancies. The large specific surface area and three-dimensional flower-like spherical structure of the MnCeTi catalyst are used to improve the low-temperature catalytic activity of the catalytic filter material for volatile organic compounds such as chlorobenzene and dioxins. 90 The lowest temperature can reach below 200℃.

[0020] (2) The catalytic filter material of the present invention uses polyoxometalate formed by oxidizing heteropolyacid to strengthen the bonding strength between the catalyst and the filter cloth, optimize the catalytic performance of the MnCeTi catalyst on the filter material surface, and make the catalytic filter material have application prospects in harsh industrial flue gas environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a preparation flow chart of PTFE catalytic filter material; Figure 2 This is a SEM image of the MnCeTi catalyst prepared in Example 1 of the present invention; wherein a is the catalyst prepared in Example 3, and b is the catalyst prepared in Comparative Example 2; Figure 3 The SEM images of the MnCeTi catalysts prepared in Examples 3 and 4 of the present invention; wherein a is the catalyst prepared in Example 4, and b is the catalyst prepared in Example 5; Figure 4 This is an EPR diagram of the PTFE catalytic filter material prepared in Example 1 of the present invention; Figure 5 The catalytic performance diagram of the PTFE catalytic filter material prepared in Example 1 of the present invention in catalyzing the degradation of actual dioxins is shown. DETAILED DESCRIPTION

[0022] The following examples are used to demonstrate preferred embodiments of the present invention. It will be appreciated by those skilled in the art that the techniques disclosed in the following examples represent techniques discovered by the inventors that can be used to implement the present invention and therefore can be considered as preferred embodiments of the present invention. However, it will be appreciated by those skilled in the art based on this specification that many modifications may be made to the specific embodiments disclosed herein and still achieve the same or similar results without departing from the spirit or scope of the present invention.

[0023] The present invention discloses a preparation method and application of a PTFE catalytic filter material, which can be used to control volatile organic matter, particulate matter and dioxin in incineration flue gas. The specific preparation steps are as follows: Figure 1 As shown below: the ternary MnCeTi catalyst is prepared by the redox method, then the catalyst, polytetrafluoroethylene resin, auxiliary agent and additive are mixed, the catalytic fiber is prepared by the film splitting method and heteropoly acid functionalization, and finally the PTFE catalytic filter material is prepared by needle punching.

[0024] Example 1 The specific preparation steps of the PTFE catalytic filter material of this embodiment are as follows: (1) Preparation of MnCeTi catalyst Manganese nitrate, cerium nitrate, titanium sulfate and hexadecyltrimethylammonium bromide were mixed in a molar ratio of 2:3:1:0.05, and then 0.15 mol / L potassium permanganate solution was added dropwise, reacted for 2 h, then dried at 105 °C for 24 h, and finally calcined at 300 °C for 4 h under a nitrogen atmosphere to obtain a ternary MnCeTi catalyst. Figure 2 As shown in a, the MnCeTi catalyst presents a three-dimensional flower-like spherical shape; (2) Preparation of PTFE catalytic fibers MnCeTi catalyst, PTFE resin, white oil and silane coupling agent (KH570) were mixed uniformly in a mass ratio of 10:100:26:5, and aged at 60°C for 24 h to obtain a mixture, and then the mixture was taken out and extruded at a pressure of 5 MPa for preforming, and finally PTFE catalytic fibers were obtained through calendering, longitudinal drawing, slitting and curling steps. (3) Functionalization of heteropolyacids The PTFE catalytic fiber was placed in a 0.3 mol / L silicotungstic acid solution of a certain concentration, and then a 0.1 mol / L hydrogen peroxide solution was added dropwise into the silicotungstic acid solution containing the fiber, stirred at room temperature for 2 h, and then dried at 105 °C. Finally, the PTFE catalytic filter material was prepared by needle punching.

[0025] Example 2 The steps for preparing the catalytic filter material of this embodiment are the same as those of Embodiment 1, except that the mixing ratio of the MnCeTi catalyst, PTFE resin, white oil and silane coupling agent (KH570) in step (2) is adjusted to a mass ratio of 20:100:26:5.

[0026] Example 3 The steps for preparing the catalytic filter material of this embodiment are the same as those of Embodiment 1, except that the mixing ratio of the MnCeTi catalyst, PTFE resin, white oil and silane coupling agent (KH570) in step (2) is adjusted to a mass ratio of 30:100:26:5.

[0027] Example 4 The steps for preparing the catalytic filter material in this embodiment are the same as those in embodiment 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. Figure 3 As shown in a.

[0028] Example 5 The steps for preparing the catalytic filter material in this embodiment are the same as those in embodiment 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. Figure 3 As shown in b.

[0029] Example 6 The steps for preparing the catalytic filter material in this embodiment are the same as those in Embodiment 3, except that the silicotungstic acid solution in step (3) is adjusted to a silicomolybdic acid solution.

[0030] Example 7 The steps for preparing the catalytic filter material in this embodiment are the same as those in Embodiment 3, except that the silicotungstic acid solution in step (3) is adjusted to a phosphotungstic acid solution.

[0031] Comparative Example 1 The steps for preparing the catalytic filter material in this embodiment are the same as those in Embodiment 3, except that the silicotungstic acid solution in step (3) is adjusted to an aqueous solution.

[0032] Comparative Example 2 The steps for preparing the catalytic filter material in this embodiment are the same as those in embodiment 3, except that the cerium nitrate in step (1) is replaced with cerium acetate. The SEM image of the catalyst is as follows: Figure 2 As shown in b.

[0033] Performance Exploration (1) Taking chlorobenzene as the model pollutant, the PTFE catalytic filter materials prepared in Examples 1-7 and Comparative Examples 1-2 were selected for particulate matter removal test and catalytic performance evaluation. The catalytic performance test conditions were as follows: total flow rate was 500 mL / min, oxygen volume fraction was 11%, catalytic fiber mass was 1 g, and chlorobenzene was 100 ppm. The particulate matter removal test showed that the above filter materials could achieve 99.9% particulate matter removal below 240°C. The catalytic performance evaluation results are shown in Table 1 below.

[0034] Table 1 Chlorobenzene catalytic performance of PTFE catalytic filter material

[0035] It can be seen from Examples 1-3 in Table 1 that as the catalyst content increases, the catalytic performance of the prepared PTFE catalytic filter material also increases, and the low-temperature catalytic performance of the catalyst is significantly improved. The PTFE catalytic filter material prepared in Example 3 has the highest catalyst loading, and its T 90 The temperature is below 200℃.

[0036] It can be seen from Examples 3-5 in Table 1 that the catalytic performance of the PTFE catalytic filter material prepared with a high surfactant content is reduced, and its low-temperature catalytic performance is also poor. The reason is that the surfactant can affect the structure of the catalyst. A higher surfactant content will destroy the catalyst structure and miniaturize the catalyst particles. Figure 3 As shown, this further affects the catalytic performance of the PTFE catalytic filter material.

[0037] It can be seen from Example 3 and Comparative Example 2 in Table 1 that the metal precursor has a great influence on the catalyst structure, thereby affecting the catalytic performance of the PTFE catalytic filter material. This can be mainly attributed to the three-dimensional flower-like spherical structure having a higher specific surface area and pore volume, which effectively promotes the mass transfer and conversion of dioxin pollutants.

[0038] Depend on Figure 3 It can be seen that heteropolyacid functionalization can effectively increase the oxygen vacancies on the surface of the catalytic filter material, and the oxygen vacancy content is ranked as follows: Example 3> Example 7> Example 6> Comparative Example 1, which is consistent with the catalytic performance of the PTFE catalytic filter materials prepared in Example 1, Example 6, Example 7 and Comparative Example 1.

[0039] (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 was 500 mL / min, oxygen volume fraction was 11%, and catalytic fiber mass was 1 g. During the experimental operation, PCDD / Fs in the reaction tail gas were absorbed by the XAD-2 resin and the two-stage series toluene solution. The results are shown in Figure 5 shown.

[0040] There are 136 isomers of dioxins, which can be divided into PCDDs and PCDFs, and the general name of the two is PCDD / Fs. The toxic equivalent I-TEQ can be obtained by calculating the 17 toxic dioxins.

[0041] In the figure, Re is the removal rate. The whole column shown in vermilion is the removal rate of 17 toxic dioxins, and the whole column shown in purple is the removal rate of 136 dioxins. De represents the degradation rate. The whole column shown in yellow is the degradation rate of 17 toxic dioxins, and the whole column shown in blue is the degradation rate of 136 dioxins.

[0042] The results showed that the removal rate of PCDD / Fs in 17 toxic dioxins by PTFE catalytic filter material was 86.5%, and the degradation rate was 61.1%; the removal rate of toxic equivalent was 92.3%, and the degradation rate was 85.5%. The removal rate of PCDD / Fs in 136 dioxins by PTFE catalytic filter material was 83.7%, and the degradation rate was 55.2%.

[0043] (3) The catalyst content and loss of the catalytic filter materials 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.

[0044] Table 2 Changes in catalyst content of catalytic filter media

[0045] Through Example 3 and Comparative Example 1, it can be seen that heteropolyacid functionalization can effectively increase the bonding strength of the catalyst to PTFE and reduce the loss of the catalyst.

[0046] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field may make some substitutions and improvements to some technical features therein according to the disclosed technical content without departing from the principles of the present invention. These substitutions and improvements should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing a PTFE catalytic filter material, characterized in that: The steps include: (1) Preparation of MnCeTi catalyst The Mn metal precursor, the Ce metal precursor, the Ti metal precursor and the surfactant are uniformly mixed in a molar ratio of (2-3): (2-3): (1-2): (0.05-0.1), and a potassium permanganate solution is added dropwise, reacted for 1-4 h, then dried at 80-105° C. for 24-48 h, and finally calcined in a calcination atmosphere to obtain a ternary MnCeTi catalyst; (2) Preparation of PTFE catalytic fibers The MnCeTi catalyst, PTFE resin, auxiliary agent and additive are uniformly mixed in a mass ratio of (20-30):100:(20-30):(4-5), and aged for 12-48 h at 50-70°C to obtain a mixture, and then the mixture is taken out and extruded at a pressure of 3-5 MPa for preforming, and finally PTFE catalytic fibers are obtained through calendering, longitudinal drawing, slitting and curling steps; (3) Functionalization of heteropolyacids The PTFE catalytic fiber is placed in a 0.1-2 mol / L heteropoly acid solution, a 0.1-2 mol / L hydrogen peroxide solution is added dropwise to the heteropoly acid solution containing the fiber, stirred at room temperature for 1-5 h, then dried at 105°C, and finally needle-punched to obtain a PTFE catalytic filter material.

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

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

4. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that: 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 is one or more of titanium sulfate, sodium titanate, and potassium titanate; and the surfactant is one or more of quaternary ammonium salts, alkylamine salts, alkyl sulfonates, and lecithin.

5. 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°C for 2-6 h.

6. 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; and the additive is one of the silane coupling agents KH570 or KA1003.

7. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that: The temperature of the stretching zone during longitudinal stretching is 120-350°C.

8. The method for preparing a PTFE catalytic filter material according to claim 1, characterized in that: In step (3), the heteropoly acid is one or more of silicotungstic acid, phosphotungstic acid and silicomolybdic acid.

9. A PTFE catalytic filter material prepared according to the method according to any one of claims 1 to 8.

10. Use of the PTFE catalytic filter material prepared by the method according to any one of claims 1 to 8 in preparing products for removing dioxins, volatile organic compounds and particulate matter.

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