A polyphenylene sulfide-based composite catalytic filter material and a preparation method thereof

Abstract

The application discloses a polyphenylene sulfide-based composite catalytic filter material and a preparation method thereof, and belongs to the technical field of catalytic filter materials. The three-step modification strategy of "chloromethylation-MOF functional layer construction-catalyst loading" is adopted: firstly, chloromethyl active sites are introduced on the surface of PPS fibers through a Blanc reaction; then, a Co-MOF functional layer is grown in situ on the surface of the fibers through coordination; finally, a manganese-based metal oxide catalyst is loaded through a hydrothermal reaction, so that the composite catalytic filter material with a low-temperature denitration function is obtained. The composite catalytic filter material prepared by the application has a NO x conversion rate of more than 90% at 160-180 DEG C, has excellent low-temperature denitration activity, sulfur resistance and catalyst combination strength, and maintains good air permeability, thereby providing a new technical scheme for functional modification of polyphenylene sulfide filter material and integration of flue gas denitration and dust removal, and can be widely applied to the fields of industrial flue gas purification, such as coal-fired power plants and diesel vehicle tail gas.

Description

Technical Field

[0001] This invention belongs to the field of catalytic filter media technology, specifically, it relates to a polyphenylene sulfide-based composite catalytic filter media and its preparation method. Background Technology

[0002] Polyphenylene sulfide (PPS) fiber has become the most widely used filter material in high-temperature dust removal fields due to its excellent high-temperature resistance (long-term operating temperature up to 190℃), chemical corrosion resistance, and flame retardant properties. However, traditional PPS filter media only act as a physical barrier to intercept particulate matter and cannot effectively degrade gaseous pollutants in flue gas (such as nitrogen oxides). x Furthermore, its performance is prone to degradation due to chemical corrosion over long-term use.

[0003] To endow PPS filter media with catalytic function, researchers attempted to directly load denitrification catalysts onto the fiber surface. However, PPS molecules are regular in shape and highly crystalline, lacking polar functional groups on the surface, exhibiting typical hydrophobicity and chemical inertness. This leads to problems such as low bonding strength between the catalyst and the fiber substrate, uneven loading, and easy detachment, severely restricting the practical application of catalytic filter media.

[0004] In existing technologies, methods for surface modification of PPS mainly fall into two categories: physical modification and chemical modification. Physical modification (such as surface coating and plasma treatment) can improve surface activity to some extent, but it suffers from defects such as uneven coating and weak adhesion. Chemical modification (such as sulfonation and nitration) can introduce active functional groups, but the conditions are often harsh and can easily damage the fiber's bulk structure.

[0005] Chloromethylation is an effective method for introducing active chloromethyl groups (-CH2Cl), and the resulting chloromethyl groups can be further converted into various functional groups. However, existing chloromethylated PPS is mainly used in ion exchange resins or separation membranes, and there are no reports of its use in constructing MOF (metal-organic framework) functional layers and loading denitration catalysts. Furthermore, MOF materials exhibit unique advantages in catalysis due to their high specific surface area and designable pore structure, but research on using MOFs as a "bridging layer" between PPS filter media and denitration catalysts remains lacking.

[0006] Therefore, developing a mild and controllable method for functionalizing PPS filter media to construct a stable catalytic coating on the fiber surface and achieve synergistic effects of efficient dust removal and low-temperature denitrification is of great practical significance and industrial value. Summary of the Invention

[0007] The purpose of this invention is to provide a method for constructing a MOF functional layer on the surface of polyphenylene sulfide (PPS) filter media and for loading a low-temperature denitrification catalyst. This invention achieves high-strength bonding between the catalyst and the fiber substrate and efficient low-temperature denitrification performance by first introducing chloromethyl active sites onto the surface of PPS fibers, then growing a Co-MOF functional layer in situ, and finally loading a manganese-based metal catalyst.

[0008] The objective of this invention can be achieved through the following technical solutions: A method for preparing a polyphenylene sulfide-based composite catalytic filter material employs a stepwise modification strategy of "chloromethylation-MOF functionalization-catalyst loading," specifically including the following steps: (1) Chloromethylation modification: After the polyphenylene sulfide filter material is soaked and swollen in a swelling agent, chloromethylation reagent and catalyst are added, and the Blanc reaction is carried out under hydrothermal conditions to introduce chloromethyl groups on the surface of polyphenylene sulfide fibers to obtain chloromethylated modified filter material; (2) MOF intermediate layer construction: The chloromethylated modified filter material obtained in step (1) was reacted sequentially with imidazole ligand solution and cobalt salt solution, through the nucleophilic substitution reaction of chloromethylated and imidazole ligands and Co 2+ Through coordination with imidazole, a Co-MOF interlayer is grown in situ on the fiber surface, resulting in Co-MOF modified filter media; (3) Catalyst loading: The Co-MOF modified filter material obtained in step (2) is placed in an aqueous solution containing potassium permanganate and subjected to hydrothermal reaction to grow manganese cobalt bimetallic oxide catalyst in situ on the fiber surface, thereby obtaining a composite catalytic filter material with low-temperature denitrification function.

[0009] Preferably, in step (1), the polyphenylene sulfide filter material is derived from industrial dust-collecting polyphenylene sulfide needle-punched felt, with a basis weight of 350-750 g / m³. 2 Between 1.5-2.5 mm in thickness and 150-200 L / dm³ in air permeability. 2 / min; and without any post-treatment, it can be used directly after washing and drying with water and ethanol.

[0010] Preferably, in step (1), the swelling agent is 1,2-dichloroethane, and its dosage is in a mass ratio of 20:1 to 40:1 with the filter material, and the swelling time is 1-24 hours; the chloromethylating agent is a mixture of trimethylchlorosilane and paraformaldehyde, and the catalyst is zinc chloride and acetic anhydride; the mass ratio of trimethylchlorosilane, paraformaldehyde, and zinc chloride to the filter material is independently (0.5-5):1, and the amount of acetic anhydride added is 0-10% of the solution mass; the filter material and the reaction solution are first stirred and reacted in a fume hood at 10-80℃ for 0.5-12h, and then transferred to a hydrothermal reactor for surface functionalization modification, the hydrothermal reaction temperature is 50-120℃, and the reaction time is 2-24 hours.

[0011] Preferably, in step (2), the imidazole ligand is dimethylimidazole, and the cobalt salt is cobalt nitrate or cobalt chloride, etc.; the mass ratio of dimethylimidazole to filter media and the mass ratio of cobalt salt to filter media are both (0.01-05):1; the chloromethylated filter media is first shaken and reacted in an ethanol aqueous solution of dimethylimidazole (a solution in which ethanol and water are mixed in any proportion) for 0.5-12 hours at a reaction temperature of 20-80℃, and then the cobalt salt solution is added and stirred and reacted at 20-80℃ for 1-24 hours.

[0012] Preferably, in step (3), the concentration of potassium permanganate solution is 0.01-0.2 mol / L, the hydrothermal reaction temperature is 90-180℃, and the reaction time is 2-24 hours. Additionally, cobalt salt can be added to the hydrothermal reaction solution for secondary doping, with the molar ratio of the doped cobalt salt to potassium permanganate being 0:1 to 1:1.

[0013] The polyphenylene sulfide-based composite catalytic filter material prepared by the present invention includes a polyphenylene sulfide fiber substrate, a Co-MOF interlayer coated on the fiber surface, and a manganese-based metal oxide catalyst supported on the interlayer.

[0014] The beneficial effects of this invention are: (1) The first three-step modification strategy of “chloromethylation-MOF functional layer-catalyst support”: existing technologies only modify PPS or directly support catalysts. This invention introduces active sites through chloromethylation, uses the MOF intermediate layer as a “molecular bridge”, and functionalizes the catalyst into a three-layer structure, thereby achieving a gradient and high-strength bond between the catalyst and the PPS substrate.

[0015] (2) The dual function of the MOF layer: On the one hand, Co-MOF is firmly bound to the active sites on the surface of chloromethylated PPS through coordination bonds; on the other hand, the porous structure and high specific surface area of ​​MOF provide abundant anchoring points and a larger contact area for the loading of manganese cobalt catalyst, which significantly improves the catalyst loading efficiency and dispersion uniformity.

[0016] (3) Excellent low-temperature denitrification activity: The composite catalytic filter material prepared by this invention can maintain a conversion rate of more than 90% in the temperature range of 160-180℃, breaking through the limitation of traditional vanadium-based catalysts requiring high-temperature activity of 300-400℃, and is particularly suitable for low-temperature denitrification of industrial flue gas.

[0017] (4) Excellent sulfur resistance and self-recovery properties: The conversion rate decreases by no more than 20 percentage points in the presence of sulfur dioxide, and it exhibits self-recovery properties, indicating that the manganese-cobalt composite structure effectively slows down the poisoning of the active center by sulfate.

[0018] (5) High catalyst bonding strength: After three cycles of 10 min ultrasonic treatment, the catalyst loading decreased by no more than 2%, proving that the bonding force between the catalyst and the fiber substrate is significantly better than that of the direct loading method through the dual anchoring effect of chloromethylation and MOF functional layer.

[0019] (6) Good air permeability: The pressure drop of the modified filter material is only slightly higher than that of the original PPS, indicating that the modification method of the present invention does not cause serious blockage of the pores between fibers, and retains the good gas permeability and dust removal performance of the filter material. Attached Figure Description

[0020] The invention will now be further described with reference to the accompanying drawings.

[0021] Figure 1 This is a diagram of a self-made tubular SCR reactor used in the catalytic filter media activity test.

[0022] In the diagram: 1. Gas source; 2. Pressure reducing valve; 3. Flow meter; 4. Mixer; 5. Air preheater; 6. Heating and catalytic reactor; 7. Test sample; 8. Flue gas analyzer.

[0023] Figure 2 This is a SEM image of the polyphenylene sulfide-based composite catalytic filter material prepared in Example 1 of the present invention.

[0024] Figure 3 This is a comparison chart of the pressure drop of the original polyphenylene sulfide filter material and the composite catalytic filter material of Example 3 of the present invention at different space velocities.

[0025] Figure 4 This is a test diagram of the robustness of the composite catalytic filter material in Example 3 of the present invention. Detailed Implementation

[0026] The technical solutions 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 The diagram shows a self-made tubular SCR reactor device used to test the activity of the catalytic filter material in the following embodiment. It includes a gas source 1, a pressure reducing valve 2, and a flow meter 3 connected in sequence. The flow meter 3 is connected to the 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 the test sample 7 is placed inside the heating and catalytic reactor 6.

[0028] Example 1

[0029] Step 1: Chloromethylation modification of PPS filter media 0.8 g of PPS filter media and 40 mL of 1,2-dichloroethane were added to a beaker and allowed to swell at room temperature for 12 hours. Then, 1.44 g of paraformaldehyde, 3.5 mL of trimethylchlorosilane, 3 g of zinc chloride, and 2 mL of acetic anhydride were added. The filter media and reaction solution were first stirred and reacted in a fume hood at 60 °C for 1 h, and then transferred to a hydrothermal reactor for surface functionalization modification at 90 °C for 4 hours. After the reaction, the mixture was decanted, and the resulting filter media was washed sequentially with ethanol, hydrochloric acid solution, and deionized water to remove residual catalyst and unreacted monomers. The resulting chloromethylated filter media was then vacuum dried.

[0030] Step 2: Preparation of Co-MOF functionalized modified filter media The chloromethylated modified filter material obtained in step 1 was added to a mixed solution of 0.2 g dimethylimidazole and water and ethanol (volume ratio 1:1) and shaken for 4 hours at a reaction temperature of 50°C. Then, a cobalt salt solution was added and stirred at 25°C for 12 hours. After the reaction was completed, the sample was taken out, washed with water and ethanol in sequence, and dried to obtain Co-MOF functionalized modified filter material.

[0031] Step 3: Supporting the manganese-based catalyst The Co-MOF functionalized modified filter material obtained in step 2 was placed in 40 mL of 0.05 mol / L potassium permanganate solution for hydrothermal reaction at 160℃ for 12 hours. After the reaction, the sample was cooled overnight, removed, washed sequentially with water and ethanol, and dried. The final microstructure of the composite catalytic filter material is shown in the figure. Figure 2 As shown.

[0032] Example 2

[0033] The process is basically the same as in Example 1, except that in step 3, the Co-MOF functionalized modified filter material is subjected to a hydrothermal reaction with a mixed solution of potassium permanganate and cobalt nitrate, wherein the molar ratio of Mn:Co is 1:1.

[0034] Example 3

[0035] The process is basically the same as in Example 1, except that in step 3, the Co-MOF functionalized modified filter material is subjected to a hydrothermal reaction in a mixed solution of potassium permanganate and cobalt nitrate, wherein the Mn:Co molar ratio is 3:1.

[0036] Example 4

[0037] The reaction was basically the same as in Example 1, except that: in step 1, 1 g of paraformaldehyde, 1 mL of trimethylchlorosilane, 1 g of zinc chloride, and 0.5 mL of acetic anhydride were added, the hydrothermal reaction temperature was 80 °C, and the reaction time was 8 h; in step 2, the amount of dimethylimidazole was 0.5 g, the reaction temperature was 25 °C, and the reaction time was 12 h; in step 3, the Co-MOF functionalized modified filter material was added to a mixed solution of potassium permanganate and cobalt nitrate for hydrothermal reaction, wherein the Mn:Co molar ratio was 1:1, the hydrothermal reaction temperature was 120 °C, and the reaction time was 10 h.

[0038] Example 5

[0039] The reaction was basically the same as in Example 1, except that: in step 1, acetic anhydride was not added, the hydrothermal reaction temperature was 90°C, and the reaction time was 12 h; in step 2, the amount of dimethylimidazole was 0.05 g, the reaction temperature was 50°C, and the reaction time was 4 h; in step 3, the Co-MOF functionalized modified filter material was subjected to a hydrothermal reaction with a mixed solution of potassium permanganate and cobalt nitrate, wherein the Mn:Co molar ratio was 1:1, the hydrothermal reaction temperature was 120°C, and the reaction time was 12 h.

[0040] Comparative Example 1 It is basically the same as Example 1, except that the step of Co-MOF functionalization modification of filter material in step 2 is not performed.

[0041] Comparative Example 2 It is basically the same as Example 1, except that the step of chloromethylation modification of PPS filter media in step 1 is not performed.

[0042] Denitrification and sulfur resistance tests The denitrification activity of the catalytic filter media prepared in the above examples and comparative examples was tested under the following conditions: NO and NH3 volume fractions were both 0.05%, O2 volume fraction was 5%, the remainder was N2, and the gas flow rate was 300 mL·min. -1 After the airflow stabilized for 30 minutes, NO levels before and after the reaction were measured using a flue gas analyzer (AFRISO, M60x). x Concentration, calculate NO x Conversion rate was tested at 160℃ and 180℃.

[0043] The sulfur resistance test was also conducted in Figure 1 The denitrification test was conducted in a self-made tubular SCR reactor. After 10 minutes of reaction at 180°C, 100 ppm SO2 was introduced into the reaction atmosphere to examine the sulfur resistance of the composite catalytic filter material. The SO2 was turned off after 100 minutes of reaction, and the activity recovery was observed.

[0044] The relevant test results are shown in the table below: Comparative analysis of the examples and comparative examples reveals that chloromethylation and the construction of the MOF functional layer have an indispensable synergistic relationship. Chloromethylation solves the fundamental problem of chemical inertness on the PPS surface, providing covalent anchoring sites for MOF growth; the MOF layer expands the limited anchoring sites into a three-dimensional network, providing a high-density nucleation site and coordination-locking environment for the catalyst. The synergistic effect of these two processes achieves high catalyst loading, high binding strength, and high catalytic activity. These three elements form a complete technical chain of "layer-by-layer anchoring, gradient transition, and synergistic enhancement," constituting the core innovation of this invention that distinguishes it from existing technologies.

[0045] Breathability test At airspeeds of 24,000–96,000 h -1 The pressure drop changes of the original PPS filter media and the composite catalytic filter media of Example 3 were tested within the specified range. The results are as follows: Figure 3 As shown, the two pressure drop curves almost overlap, indicating that the air permeability of the modified filter material was not significantly affected, and the good gas permeability of the original PPS was retained.

[0046] Strength test The composite catalytic filter media of Example 3 was subjected to three rounds of aqueous phase circulating ultrasonic treatment, each lasting 10 minutes. The catalyst loading was calculated after each ultrasonic treatment. The results are as follows: Figure 4 As shown, the catalyst loading decreased sequentially to 14.31%, 13.34%, and 13.17%, and then tended to stabilize. This indicates that the catalyst is firmly bonded to the fiber substrate and has good erosion resistance.

[0047] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method for preparing a polyphenylene sulfide-based composite catalytic filter material, characterized in that, Includes the following steps: (1) Chloromethylation modification: After the polyphenylene sulfide filter material is soaked and swollen in a swelling agent, chloromethylation reagent and catalyst are added to carry out the Blanc reaction, and chloromethyl groups are introduced on the surface of the polyphenylene sulfide fiber to obtain chloromethylated modified filter material; (2) MOF intermediate layer construction: The chloromethylated modified filter material obtained in step (1) was reacted sequentially with imidazole ligand solution and cobalt salt solution, through the nucleophilic substitution reaction of chloromethylated and imidazole ligands and Co 2+ Through coordination with imidazole, a Co-MOF interlayer is grown in situ on the fiber surface, resulting in Co-MOF modified filter media; (3) Catalyst loading: The Co-MOF modified filter material obtained in step (2) is placed in an aqueous solution containing potassium permanganate and subjected to hydrothermal reaction to grow manganese cobalt bimetallic oxide catalyst in situ on the fiber surface, thereby obtaining a composite catalytic filter material with low-temperature denitrification function.

2. The method for preparing a polyphenylene sulfide-based composite catalytic filter material according to claim 1, characterized in that, The polyphenylene sulfide filter material mentioned in step (1) is polyphenylene sulfide needle-punched felt with a basis weight of 350-750 g / m³. 2 The thickness is 1.5-2.5 mm, and the air permeability is 150-200 L / dm. 2 / min.

3. The method for preparing a polyphenylene sulfide-based composite catalytic filter material according to claim 1, characterized in that, The swelling agent in step (1) is 1,2-dichloroethane, and its mass ratio with the filter media is 20:1 to 40:1, with a swelling time of 1-24 hours; the chloromethylation reagent is a mixture of trimethylchlorosilane and paraformaldehyde, and the catalyst is zinc chloride and acetic anhydride; the mass ratio of trimethylchlorosilane, paraformaldehyde, and zinc chloride with the filter media is independently (0.5-5):1, and the amount of acetic anhydride added is 0-10% of the solution mass.

4. The method for preparing a polyphenylene sulfide-based composite catalytic filter material according to claim 1, characterized in that, The conditions for the Blanc reaction in step (1) are: first, stir the reaction at 10-80℃ for 0.5-12 hours, and then transfer it to a hydrothermal reactor and react at 50-120℃ for 2-24 hours.

5. The method for preparing a polyphenylene sulfide-based composite catalytic filter material according to claim 1, characterized in that, The imidazole ligand in step (2) is dimethylimidazole, and the cobalt salt is cobalt nitrate or cobalt chloride; the mass ratio of dimethylimidazole to filter media and the mass ratio of cobalt salt to filter media are both (0.01-0.5):

1.

6. The method for preparing a polyphenylene sulfide-based composite catalytic filter material according to claim 1, characterized in that, The reaction conditions described in step (2) are as follows: the chloromethylated filter material is first reacted with a dimethylimidazole aqueous solution in an ethanol solution at 20-80°C for 0.5-12 hours with shaking, and then a cobalt salt solution is added and the mixture is stirred at 20-80°C for 1-24 hours.

7. The method for preparing a polyphenylene sulfide-based composite catalytic filter material according to claim 1, characterized in that, The concentration of the potassium permanganate solution in step (3) is 0.01-0.2 mol / L, the hydrothermal reaction temperature is 90-180℃, and the reaction time is 2-24 hours.

8. The method for preparing a polyphenylene sulfide-based composite catalytic filter material according to claim 1, characterized in that, In step (3), cobalt salt is added to the hydrothermal reaction solution for secondary doping, and the molar ratio of the doped cobalt salt to potassium permanganate is 0:1 to 1:

1.

9. A polyphenylene sulfide-based composite catalytic filter material, characterized in that, The product is prepared by the method according to any one of claims 1-8, comprising a polyphenylene sulfide fiber substrate, a Co-MOF interlayer coated on the fiber surface, and a manganese cobalt bimetallic oxide catalyst supported on the interlayer.

10. The polyphenylene sulfide-based composite catalytic filter material according to claim 9, characterized in that, The composite catalytic filter material has a conversion rate of >90% for ammonia oxides in the temperature range of 160-180℃. After three cycles of 10-minute ultrasonic treatments, the catalyst loading decreases by no more than 2%, and the conversion rate decreases by no more than 20% in the presence of sulfur dioxide.

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