Catalytic filter bag, preparation method and application thereof

Abstract

The present invention provides a catalytic filter bag, a preparation method and application thereof. The catalytic filter bag comprises: a flexible filter bag substrate and a modified molecular sieve catalyst, and the modified molecular sieve catalyst is fixed on the surface of the flexible filter bag substrate by a binder, wherein the modified molecular sieve catalyst comprises an H-type molecular sieve and an oxide of an active metal element loaded on the surface of the H-type molecular sieve, and the active metal element is selected from one or more of the metal elements in IB, IIB, VIIB or VIII. The catalytic filter bag can realize the integrated removal of dust and nitrogen oxides and shorten the process flow. It can be used at high or low temperatures, and has excellent low-temperature denitrification performance, a wide active temperature window and high nitrogen selectivity. In addition, the above-mentioned catalytic filter bag can be applied to flue gas purification and treatment in many fields, and has low production cost, simple operation method and easy industrial implementation.

Description

Technical Field

[0001] The present invention relates to the field of flue gas purification, and in particular to a catalytic filter bag, a preparation method and application thereof. Background Art

[0002] Modified molecular sieve catalysts have excellent low-temperature denitration performance, a wide active temperature window and good skeleton stability. They are currently the best option to replace the biotoxic vanadium-based metal oxide catalysts. There have been a lot of reports on the denitration performance of modified molecular sieves such as MFI (ZSM-5), BEA (Beta), and CHA (SSZ-13). The modified active components involved include Cu, Fe, Co, and Mn. In practical applications, molecular sieve catalysts need to be prepared from powders, which will bring about problems such as large molecular sieve catalyst usage, high cost, and difficult preparation.

[0003] In order to reduce the amount of catalyst used and save costs, studies have been conducted to make molecular sieve catalysts into slurry, and then evenly coat it on the surface of a rigid honeycomb ceramic carrier to form a monolithic catalyst with denitrification performance. The patent (CN202110030244.4) proposes a method for preparing a monolithic catalyst containing a molecular sieve coating slurry, wherein aluminum sol, molecular sieve catalyst and water are mixed and ball milled to obtain a coating slurry, and the slurry is directly coated on a cordierite honeycomb ceramic carrier to form a monolithic catalyst. In practical applications, the monolithic catalyst needs to be loaded into an independently operated denitrification unit. Therefore, the commonly used process for factory flue gas purification is "SNCR + semi-dry method + dry method (standby) + activated carbon injection + bag filter + SCR", in which the independent operation of the dust removal and denitrification multi-stage units will cause high costs, long processes, and large land occupation.

[0004] The method of in-situ synthesis or coating of molecular sieves on cordierite carriers is not suitable for flexible filter bags. The in-situ synthesis method cannot control the loading and thickness of the coating, and the quality of the resulting monolithic catalyst is unstable, making it difficult to industrialize. In addition, cordierite is a rigid carrier with strong adhesion after coating, and basically does not have problems such as pore plugging. However, for the filter bag materials required in short-process technology, pore plugging and pressure drop are issues that cannot be ignored. There are also related reports on coating catalysts on the surface of flexible filter materials, but the catalysts used are all metal oxide catalysts. The adhesion strength of the metal oxides loaded on the surface of the filter bag through the binder is insufficient, and there are problems such as severe powder loss, which greatly affects the use of catalytic filter bags.

[0005] In view of the above problems, it is necessary to provide a flexible catalytic filter bag material with low application cost, short process and high catalytic stability. Summary of the invention

[0006] The main purpose of the present invention is to provide a catalytic filter bag, a preparation method and application thereof, so as to solve the problems of high application cost, long process and large floor space of existing integral catalysts, and serious powder shedding of metal oxide catalysts in flexible filter materials, which greatly affects the catalytic effect of the catalytic filter bag.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a catalytic filter bag on the one hand, which comprises: a flexible filter bag substrate and a modified molecular sieve catalyst, and the modified molecular sieve catalyst is fixed on the surface of the flexible filter bag substrate by a binder, wherein the modified molecular sieve catalyst comprises an H-type molecular sieve and an oxide of an active metal element loaded on the surface of the H-type molecular sieve, and the active metal element is selected from one or more of the metal elements in IB, IIB, VIIB or VIII.

[0008] Furthermore, the H-type molecular sieve has one or more of the following topological structures: MFI, BEA, FAU, MOR, FER, CHA, LEV, AFX; the silicon-aluminum ratio of the H-type molecular sieve is 10 to 40, and the specific surface area is 250 to 800 m 2 / g; the active metal element is selected from one or more of the group consisting of copper, iron, cobalt, cerium and manganese; preferably, the loading amount of the active metal element is 2-5% in terms of weight percentage of the modified molecular sieve catalyst.

[0009] Furthermore, the particle size of the modified molecular sieve catalyst is 0.2 to 4 μm.

[0010] Furthermore, the flexible filter bag substrate is selected from one or more of the group consisting of polytetrafluoroethylene, polyimide, polyphenylene sulfide, glass fiber and basalt fiber.

[0011] Furthermore, the content of the modified molecular sieve catalyst is 20% to 40% based on the weight percentage of the catalytic filter bag.

[0012] The second aspect of the present application also provides a method for preparing the above-mentioned catalytic filter bag, comprising: preparing an H-type molecular sieve; impregnating and calcining the H-type molecular sieve in a salt solution of an active metal element to obtain a molecular sieve catalyst modified with the active metal element; mixing the molecular sieve catalyst modified with the active metal element, a binder and water to obtain a coating slurry; coating the above-mentioned coating slurry on the surface of a flexible filter bag substrate to obtain a semi-finished product; and performing a first calcination treatment on the semi-finished product to obtain a catalytic filter bag.

[0013] Furthermore, the temperature of the first calcination process is 240-270°C.

[0014] Furthermore, the process of preparing H-type molecular sieve includes: stirring the molecular sieve in a 0.1-0.2 mol / L NH4NO3 solution at 60-80°C for 4-6 hours to obtain an intermediate product; subjecting the intermediate product to a drying and a second calcination treatment process in sequence to obtain an H-type molecular sieve; preferably, the drying temperature is 90-110°C, and the temperature of the second calcination treatment is 500-550°C.

[0015] Furthermore, the coating slurry further comprises a diluent. Preferably, the diluent is selected from one or more of the group consisting of ethylene glycol, polyethylene glycol, propylene glycol and ethanol.

[0016] The third aspect of the present application also provides a catalytic filter bag or a catalytic filter bag prepared by the preparation method of the catalytic filter bag provided by the present application and its application in the field of flue gas purification.

[0017] By applying the technical solution of the present invention, the active metal elements have a strong catalytic effect on flue gas purification, and the above-mentioned active metal elements all belong to transition metal elements, which can have good binding force with the H-type molecular sieve catalyst. At the same time, the H-type molecular sieve is made of aluminosilicate material, so it can be stably compounded with the flexible filter bag substrate through a binder, thereby enhancing the coating strength, reducing the powder loss rate, and extending the service life. The catalytic filter bag provided in the present application can realize the integrated removal of dust and nitrogen oxides and shorten the process flow. At the same time, compared with the existing metal oxide catalysts, the catalytic filter bag provided in the present application can be used at high or low temperatures, and has excellent low-temperature denitrification performance, a wide active temperature window and high nitrogen selectivity. In addition, the above-mentioned catalytic filter bag can be applied to flue gas purification and treatment in many fields, and has low production cost, simple operation method, and is easy to implement industrially. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0019] As described in the background technology, the existing integral catalyst has the problems of high application cost, long process and large floor space, and the metal oxide type catalyst in the flexible filter material has the problem of serious powder shedding, which greatly affects the catalytic effect of the catalytic filter bag. In order to solve the above technical problems, the present application provides a catalytic filter bag, which comprises: a flexible filter bag substrate and a modified molecular sieve catalyst, and the modified molecular sieve catalyst is fixed on the flexible filter bag substrate by a binder, wherein the modified molecular sieve catalyst comprises an H-type molecular sieve and an oxide of an active metal element loaded on the surface of the H-type molecular sieve, and the active metal element is one or more metal elements selected from IB, IIB, VIIB or VIII.

[0020] The above-mentioned active metal elements have a strong catalytic effect on flue gas purification, and the above-mentioned active metal elements all belong to transition metal elements, which can have good binding force with H-type molecular sieve catalysts. At the same time, the H-type molecular sieve is made of aluminosilicate material, so it can be stably compounded with the flexible filter bag substrate through a binder, thereby enhancing the coating strength, reducing the powder loss rate, and extending the service life. The catalytic filter bag provided in the present application can realize the integrated removal of dust and nitrogen oxides and shorten the process flow. At the same time, compared with the existing metal oxide catalysts, the catalytic filter bag provided in the present application can be used at high or low temperatures, and has excellent low-temperature denitrification performance, a wide active temperature window and high nitrogen selectivity. In addition, the above-mentioned catalytic filter bag can be applied to flue gas purification and treatment in many fields, and has low production costs, simple operation methods, and is easy to implement industrially.

[0021] In a preferred embodiment, the H-type molecular sieve has one or more of the following topological structures: MFI, BEA, FAU, MOR, FER, CHA, LEV, AFX; the silicon-aluminum ratio of the H-type molecular sieve is 10-40, and the specific surface area is 250-800m 2 / g. The use of the above-mentioned H-type molecular sieve to prepare the catalyst filter bag is conducive to further improving its catalytic effect. In a preferred embodiment, the active metal elements include but are not limited to one or more of the group consisting of copper, iron, cobalt, cerium and manganese. Compared with other transition metal elements, the above-mentioned elements have more excellent denitration catalytic performance and have better binding force with the above-mentioned H-type molecular sieve, which is conducive to further improving the catalytic performance of the above-mentioned catalytic filter bag.

[0022] In order to further improve the catalytic performance of the catalytic filter bag, in a preferred embodiment, the loading amount of the active metal element is 2-5% by weight percentage of the molecular sieve catalyst. Calculated based on the number of ion exchange sites, the loading amount is close to 100% ion exchange rate, that is, the active metal element exists in the form of ions.

[0023] In a preferred embodiment, the particle size of the modified molecular sieve catalyst is 0.2-4 μm. Compared with other ranges, limiting the particle size of the modified molecular sieve catalyst to the above range is conducive to further improving the catalytic effect of the catalytic filter bag.

[0024] In the above-mentioned catalytic filter bag, the flexible filter bag can be selected from substrates commonly used in the art. In a preferred embodiment, the flexible filter bag substrate includes but is not limited to one or more of the group consisting of polytetrafluoroethylene, polyimide, polyphenylene sulfide, glass fiber and basalt fiber.

[0025] The content of the modified molecular sieve catalyst in the catalytic filter bag affects the catalytic performance of the catalytic filter bag. In a preferred embodiment, the content of the modified molecular sieve catalyst is 20-40% by weight of the catalytic filter bag. The content of the modified molecular sieve catalyst includes but is not limited to the above range, and limiting it to the above range is conducive to further improving the catalytic performance of the catalytic filter bag.

[0026] The binder in the catalytic filter bag can be of the type commonly used in the art. In the first preferred embodiment, the binder includes a silane coupling agent, a first tackifier and an emulsifier. Preferably, the silane coupling agent includes but is not limited to one or more of the group consisting of methyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxy(ethyl)silane, KH-550, γ-glycidyloxypropyltrimethoxysilane and γ-(methacryloyloxy)propyltrimethoxysilane; the first tackifier includes but is not limited to one or more of the group consisting of sodium polyacrylate, sodium alginate and sesbania powder; the emulsifier includes but is not limited to one or more of the group consisting of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate and hexadecyltrimethylammonium bromide. In the second preferred embodiment, the binder is an inorganic sol, preferably an aluminum sol and / or a silica sol. In the third preferred embodiment, the binder includes a second tackifier, a stabilizer and a foaming agent, preferably, the second tackifier includes one or more of the group consisting of polytetrafluoroethylene solution, polyethylene glycol and hydroxyethyl cellulose. The above-mentioned adhesives have good bonding properties in a wide temperature range, and have good bonding properties with the modified molecular sieve and the flexible filter bag substrate. The selection of the above-mentioned adhesives is beneficial to further improve the bonding force between the modified molecular sieve catalyst and the flexible filter bag substrate, thereby helping to further reduce the probability of the modified molecular sieve catalyst falling off, thereby improving the catalytic performance of the catalyst.

[0027] In a preferred embodiment, the coating slurry further comprises a diluent. Adding the diluent can adjust the viscosity of the coating slurry, thereby being beneficial to improving the coating performance of the coating slurry and improving the uniformity of the coating. Preferably, the diluent includes but is not limited to one or more of the group consisting of ethylene glycol, polyethylene glycol, propylene glycol and ethanol.

[0028] Another aspect of the present application also provides a method for preparing the above-mentioned catalytic filter bag, comprising: preparing an H-type molecular sieve; impregnating and calcining the H-type molecular sieve in a salt solution of an active metal element to obtain a molecular sieve catalyst modified with the active metal element; mixing the molecular sieve catalyst modified with the active metal element, a binder and water to obtain a coating slurry; coating the above-mentioned coating slurry on the surface of a flexible filter bag substrate to obtain a semi-finished product; and performing a first calcination treatment on the semi-finished product to obtain a catalytic filter bag.

[0029] The present invention provides a method for preparing a flexible catalytic filter bag coated with a molecular sieve catalyst, and conducts design research around the coating preparation method thereof, focusing on constructing a molecular sieve catalytic filter bag for integrated dust removal and denitrification, thereby reducing costs and shortening the process flow.

[0030] The catalyst filter bag prepared by the above preparation method has the following advantages: ① excellent low-temperature denitrification performance, a wider active temperature window and higher nitrogen selectivity; ② high load strength and low powder loss rate; ③ flexible materials do not have the disadvantage of poor shock resistance of rigid materials; ④ realize integrated denitrification and dust removal, shorten the process flow and reduce costs.

[0031] In a preferred embodiment, the temperature of the first calcination process is 240-270° C. The temperature of the first calcination process includes but is not limited to the above range, and limiting it within the above range is beneficial to further reduce impurities in the catalyst filter bag, improve structural stability, and thus further improve its catalytic performance.

[0032] In a preferred embodiment, the process of preparing the H-type molecular sieve comprises: stirring the molecular sieve in a 0.1-0.2 mol / L NH4NO3 solution at 60°C-80°C for 4h-6h to obtain an intermediate product; and subjecting the intermediate product to a drying and calcination process in sequence to obtain the H-type molecular sieve. The molecular sieves of different topological structures (silicon-aluminum ratio (10-40): 1) that can be used in the preparation of the H-type molecular sieve include but are not limited to MFI, BEA, FAU, MOR, FER, CHA, LEV, AFX and other configurations. Then, the active metal elements are loaded by ion exchange to prepare the modified molecular sieve catalyst.

[0033] In a preferred embodiment, the temperature of the drying process is 90-110°C, and the temperature of the second calcination process is 500-550°C, such as 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, or a range formed by any two of the above values.

[0034] Another aspect of the present application also provides an application of the above-mentioned catalytic filter bag or the catalytic filter bag prepared by the preparation method of the above-mentioned catalytic filter bag in the field of flue gas purification. Compared with the existing metal oxide catalysts, the catalytic filter bag provided by the present application can be used at high or low temperatures, and has excellent low-temperature denitrification performance, a wide active temperature window and high nitrogen selectivity. In addition, the above-mentioned catalytic filter bag can be applied to flue gas purification in many fields, and has low production cost, simple operation method, and is easy to implement industrially.

[0035] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0036] Example 1

[0037] (1) Preparation of modified molecular sieves

[0038] According to the CHA configuration with a silicon-aluminum ratio of 10 (SSZ-13, Tianjin Nanhua Catalyst Co., Ltd., model NKF-13, silicon-aluminum ratio (SiO2 / Al2O3) is 10-30, relative crystallinity ≥90, specific surface area ≥600m 2 / g) molecular sieve, prepare 0.2mol / L copper acetate solution, ensure that the Cu loading of the modified molecular sieve is about 2wt%. Specifically: place SSZ-13 molecular sieve in 0.1mol / L NH4NO3 solution, stir at 80℃ for 6h and then centrifuge, repeat the above operation three times, dry at 100℃ for 3h, calcine at 500℃ for 3h to obtain H-type SSZ-13 molecular sieve sample, mix the obtained H-type SSZ-13 molecular sieve sample with 0.2mol / L copper acetate solution, stir at 80℃ for 8h, dry at 100℃ for 3h, calcine at 550℃ for 5h to obtain copper-modified SSZ-13 molecular sieve sample, the particle size is 2-4μm powder.

[0039] (2) Preparation of coating slurry

[0040] 10g of copper-modified SSZ-13 molecular sieve powder (20%), 8g of 5wt% polytetrafluoroethylene solution (16%), 2g of 0.05wt% hydroxyethyl cellulose solution (4%), and 0.6g of polyethylene glycol (1.2%) (Aladdin reagent, P103724, Mn~4000) were put into 29.4g of water and mixed and stirred at 800r / min for 5h to obtain a coating slurry.

[0041] (3) Selection of flexible filter bag substrate

[0042] The flexible filter bag substrate was made of high temperature resistant basalt fiber (Yangzhou Qingshan Environmental Protection Technology Co., Ltd., basalt needle felt). Before coating, the filter material was treated in a vacuum drying oven at 100°C for 3 hours.

[0043] (4) Preparation of catalytic filter bags

[0044] The basalt fiber filter bag treated in step 3 is immersed in the coating slurry prepared in step (2), and is allowed to stand for 5 minutes. After being taken out, the residual liquid is blown off with hot air, and the bag is placed in a muffle furnace at 270°C and baked for 10 minutes. The impregnation process is repeated to ensure that the loading amount of the obtained catalytic filter bag is about 30%.

[0045] Example 2

[0046] Compared with Example 1, the only difference is that the type of molecular sieve used in this example is different. Specifically, the preparation steps of the modified molecular sieve are as follows:

[0047] According to the MFI configuration with a silicon-aluminum ratio of 10 (ZSM-5, Tianjin Nanhua Catalyst Co., Ltd., model NKF-5-21FXH, silicon-aluminum ratio (SiO2 / Al2O3) of 21, relative crystallinity ≥95, specific surface area ≥352m 2 / g)) molecular sieve, prepare 0.2mol / L copper acetate solution, and ensure that the Cu loading of the modified molecular sieve is about 2%. Specifically: place the ZSM-5 molecular sieve in 0.1mol / L NH4NO3 solution, stir at 80℃ for 6h and then centrifuge, repeat the above operation three times, dry at 100℃ for 3h, calcine at 500℃ for 3h to obtain H-type ZSM-5 molecular sieve sample, mix the obtained H-type ZSM-5 molecular sieve sample with 0.2mol / L copper acetate solution, stir at 80℃ for 8h, dry at 100℃ for 3h, calcine at 550℃ for 5h to obtain copper-modified ZSM-5 molecular sieve sample, and sieve the sample to obtain powder with a particle size of 0.2 to 0.6μm.

[0048] Example 3

[0049] Compared with Example 1, the only difference is that the type of molecular sieve used in this example is different. Specifically, the preparation steps of the modified molecular sieve are as follows:

[0050] According to the BEA configuration with a silicon-aluminum ratio of 10 (Beta, Tianjin Nanhua Catalyst Co., Ltd., model NKF-6-25YYH, silicon-aluminum ratio (SiO2 / Al2O3) is 26, relative crystallinity ≥95, specific surface area ≥650m 2 / g) molecular sieve, prepare 0.2mol / L copper acetate solution, ensure that the Cu loading of the modified molecular sieve is about 2%. Specifically: place the Beta molecular sieve in 0.12mol / NH4NO3 solution, stir at 80℃ for 6h and then centrifuge, repeat the above operation three times, dry at 100℃ for 3h, calcine at 500℃ for 3h to obtain H-type Beta molecular sieve sample, mix the obtained H-type Beta molecular sieve sample with 0.2mol / L copper acetate solution, stir at 80℃ for 8h, dry at 100℃ for 3h, calcine at 550℃ for 5h to obtain copper-modified Beta molecular sieve sample, sieve the sample to obtain powder with a particle size of 0.2-0.4μm.

[0051] Example 4

[0052] Compared with Example 1, the only difference is that the type of active component in this example is different. Specifically, the active component in the modified molecular sieve is Mn, and the loading amount is about 2 wt%.

[0053] Example 5

[0054] Compared with Example 1, the only difference is that the coating slurry composition in this embodiment is different. Specifically, the coating slurry preparation includes:

[0055] 10g copper-modified SSZ-13 molecular sieve powder (20%), 1g silane coupling agent KH-550 (2%), 0.5g sodium polyacrylate (1%), 2g sodium dodecyl sulfate (4%), and 1g polyethylene glycol (2%) (Aladdin reagent, P103724, Mn~4000) were put into 35.5g water and mixed and stirred at 800r / min for 5h to obtain a coating slurry.

[0056] Example 6

[0057] Compared with Example 1, the only difference is that the composition of the coating slurry in this embodiment is different. Specifically, the coating slurry preparation includes: 10g of copper-modified SSZ-13 molecular sieve powder (20%), 10g of silica sol (16%) (McLean reagent, S888350, silicon dioxide content: 29%~31%), and 1g of polyethylene glycol (2%) (Aladdin reagent, P103724, Mn~4000) are put into 29g of water and mixed and stirred at 800r / min for 5h to obtain a coating slurry.

[0058] Example 7

[0059] Compared with Example 1, the only difference is that the coating slurry composition in this embodiment is different. Specifically, the coating slurry preparation includes:

[0060] 20g of copper-modified SSZ-13 molecular sieve powder (40%), 8g of 5wt% polytetrafluoroethylene solution (16%), 2g of 0.05wt% hydroxyethyl cellulose solution (4%), and 0.6g of polyethylene glycol (1.2%) (Aladdin reagent, P103724, Mn~4000) were put into 19.4g of water and mixed and stirred at 800r / min for 5h to obtain a coating slurry.

[0061] Example 8

[0062] Compared with Example 1, the only difference is that the material of the flexible filter bag in this embodiment is different. Specifically, the flexible filter bag base material is made of polytetrafluoroethylene (PTFE) material with strong acid and alkali resistance (Blue Sky Environmental Protection Technology Co., Ltd., PTFE needle-punched felt).

[0063] Example 9

[0064] Compared with Example 1, the only difference is that the material of the flexible filter bag in this embodiment is different. Specifically, the flexible filter bag base material is glass fiber (Yangzhou Qingshan Environmental Protection Technology Co., Ltd., glass fiber needle-punched felt).

[0065] Example 10

[0066] Compared with Example 1, the only difference is that the preparation method of the catalytic filter bag in this embodiment is different. Specifically, the preparation of the catalytic filter bag includes: loading the coating slurry into a high-pressure spray gun, spraying the basalt fiber filter bag treated in step (3), blowing off the residual liquid with hot air after spraying, placing it in a muffle furnace at 270°C for calcining for 10 minutes, and repeating the spraying process to ensure that the mounting amount of the obtained catalytic filter bag is about 30%.

[0067] Embodiment 11

[0068] Compared with Example 1, the only difference is that the preparation methods of the coating slurry and the catalytic filter bag in this embodiment are different. Specifically,

[0069] (1) The preparation of modified molecular sieve is the same as that in Example 1.

[0070] (2) Preparation of coating slurry

[0071] ① Molecular sieve catalyst dispersion: Disperse 10g of copper-modified SSZ-13 molecular sieve powder in 50ml of ethanol;

[0072] ② Binder slurry: 15g 5wt% polytetrafluoroethylene solution (15%), 5g 0.05wt% hydroxyethyl cellulose solution (5%), 1g polyethylene glycol (1%), put into 79g water and mix and stir at 800r / min for 5h to obtain coating slurry.

[0073] (3) The selection of flexible filter bag substrate is the same as that in Example 1.

[0074] (4) Preparation of catalytic filter bags

[0075] The basalt fiber filter bag treated in step (3) is immersed in a 2% molecular sieve catalyst dispersion, allowed to stand for 5 minutes, ultrasonicated for 20 minutes, taken out and placed in a 100°C oven for drying for 2 hours, and the impregnation process is repeated to control the molecular sieve catalyst hanging amount to be about 20%. Subsequently, the filter bag coated with the molecular sieve is immersed in a 2% binder slurry, allowed to stand for 5 minutes, taken out and blown off the residual liquid with hot air, and placed in a 280°C muffle furnace for calcination for 10 minutes. The impregnation process is repeated to ensure that the mounting amount of the obtained catalytic filter bag is about 30%.

[0076] Example 12

[0077] Compared with Example 1, the only difference is that the molecular sieve is SSZ-13 (manufacturer is Tianjin Nanhua Catalyst Co., Ltd., model is NKF-13, silicon-aluminum ratio is 15:1).

[0078] Example 13

[0079] Compared with Example 1, the only difference is that the molecular sieve is SSZ-13 (manufacturer is Tianjin Nanhua Catalyst Co., Ltd., model is NKF-13, silicon-aluminum ratio is 20:1).

[0080] Embodiment 14

[0081] Compared with Example 1, the only difference is that the molecular sieve is SSZ-13 (manufacturer is Tianjin Nanhua Catalyst Co., Ltd., model is NKF-13, silicon-aluminum ratio is 30:1).

[0082] Embodiment 15

[0083] Compared with Example 1, the only difference is that the particle size of the modified molecular sieve catalyst is 20 μm.

[0084] Comparative Example 1

[0085] The difference from Example 3 is that the catalyst powder loaded is a metal oxide (VW / Ti catalyst), and a catalytic filter bag loaded with a metal oxide catalyst is finally obtained.

[0086] The denitrification performance of the catalysts obtained in Examples 1 to 15 and Comparative Example 1 was tested, and the test method was as follows: the denitrification performance and SO2 resistance experiment of the catalytic filter material were tested (200 ppm SO2 was introduced for reaction for 10 hours) at 230°C, a gas velocity of 0.8 m / min, 500 ppm NO, 600 ppm NH3, and 8% O2.

[0087] The test results are shown in Table 1.

[0088] Table 1

[0089] <![CDATA[NO removal x Rate, %]]> <![CDATA[SO2 resistance experiment, %]]> Example 1 88 85 Example 2 50 30 Example 3 47 22 Example 4 95 68 Example 5 81 75 Example 6 86 82 Example 7 92 88 Example 8 83 77 Example 9 87 82 Example 10 75 68 Embodiment 11 90 86 Example 12 82 77 Embodiment 13 75 69 Embodiment 14 50 40 Embodiment 15 55 40 Comparative Example 1 15 8

[0090] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: the active metal elements have a strong catalytic effect on flue gas purification, and the above active metal elements are all transition metal elements that can have good binding force with the H-type molecular sieve catalyst. At the same time, the H-type molecular sieve is made of aluminosilicate material, so it can be stably compounded with the flexible filter bag substrate through a binder, thereby enhancing the coating strength, reducing the powder loss rate, and extending the service life. The catalytic filter bag provided in the present application can realize the integrated removal of dust and nitrogen oxides and shorten the process flow. At the same time, compared with the existing metal oxide catalysts, the catalytic filter bag provided in the present application can be used at high or low temperatures, and has excellent low-temperature denitrification performance, a wide active temperature window and high nitrogen selectivity. In addition, the above-mentioned catalytic filter bag can be applied to flue gas purification and treatment in many fields, and has low production cost, simple operation method, and is easy to implement industrially.

[0091] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A catalytic filter bag, characterized in that: The catalytic filter bag comprises: a flexible filter bag substrate and a modified molecular sieve catalyst, and the modified molecular sieve catalyst is fixed on the surface of the flexible filter bag substrate by a binder, wherein the modified molecular sieve catalyst comprises an H-type molecular sieve and an oxide of an active metal element loaded on the surface of the H-type molecular sieve; The flexible filter bag substrate is selected from one or more of the group consisting of polytetrafluoroethylene, polyimide, polyphenylene sulfide, glass fiber and basalt fiber; The H-type molecular sieve has a silicon-aluminum ratio of 10 to 40 and a specific surface area of ​​250 to 800 m 2 / g; The active metal element is selected from one or more of the group consisting of copper, iron, cobalt, cerium and manganese; Calculated by weight percentage of the catalytic filter bag, the content of the modified molecular sieve catalyst is 20% to 40%.

2. The catalytic filter bag according to claim 1, characterized in that: The H-type molecular sieve has one or more of the following topological structures: MFI, BEA, FAU, MOR, FER, CHA, LEV, AFX.

3. The catalytic filter bag according to claim 2, characterized in that: Calculated by weight percentage of the modified molecular sieve catalyst, the loading amount of the active metal element is 2-5%.

4. The catalytic filter bag according to any one of claims 1 to 3, characterized in that: The particle size of the modified molecular sieve catalyst is 0.2-4 μm.

5. A method for preparing a catalytic filter bag according to any one of claims 1 to 4, characterized in that: The preparation method of the catalytic filter bag comprises: Preparation of H-type molecular sieve; The H-type molecular sieve is impregnated in a salt solution of an active metal element and calcined to obtain a molecular sieve catalyst modified with an active metal element; Mixing the active metal element-modified molecular sieve catalyst, a binder and water to prepare a coating slurry; Coating the coating slurry on the surface of the flexible filter bag substrate to obtain a semi-finished product; The semi-finished product is subjected to a first calcination treatment to obtain the catalytic filter bag.

6. The method for preparing a catalytic filter bag according to claim 5, characterized in that: The temperature of the first calcination treatment is 240-270°C.

7. The method for preparing a catalytic filter bag according to claim 5, characterized in that: The process for preparing H-type molecular sieve comprises: The molecular sieve is stirred in a 0.1-0.2 mol / L NH4NO3 solution at 60-80°C for 4-6 hours to obtain an intermediate product; The intermediate product is subjected to drying and a second calcination treatment in sequence to obtain the H-type molecular sieve.

8. The method for preparing a catalytic filter bag according to claim 7, characterized in that: The drying temperature is 90-110°C, and the second calcination temperature is 500-550°C.

9. The method for preparing a catalytic filter bag according to claim 5, characterized in that: The coating slurry also includes a diluent.

10. The method for preparing a catalytic filter bag according to claim 9, characterized in that: The diluent is selected from one or more of the group consisting of ethylene glycol, polyethylene glycol, propylene glycol and ethanol.

11. Use of the catalytic filter bag according to any one of claims 1 to 4 or the catalytic filter bag prepared by the preparation method of the catalytic filter bag according to any one of claims 6 to 10 in the field of flue gas purification.