Preparation method of flue gas denitration catalyst substrate

Abstract

The application discloses a preparation method of a flue gas denitration catalyst matrix, and comprises the following steps: (1) mixing water, fermentation bacteria, flour and sesbania powder, and mixing and kneading the mixture into a plastic body; (2) sealing and storing the plastic body for a certain period of time, mixing and kneading the plastic body again, forming the plastic body into a honeycomb-shaped forming body, and then performing hydrothermal treatment under a closed condition, drying and calcining to obtain the honeycomb-shaped matrix. The flue gas denitration catalyst matrix prepared by the method has a low specific surface area, contains developed large-size through channels, has a high compressive strength, and waste agents can be conveniently regenerated by acid pickling or directly incinerated, so that environmental pollution caused by landfill is avoided.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment and relates to a method for preparing a flue gas denitrification catalyst matrix. Background Technology

[0002] In the field of waste gas treatment, such as flue gas denitrification and catalytic combustion, honeycomb ceramic materials are generally used as the substrate, coated with an alumina coating. However, ceramic materials have high density and heavy weight, making them inconvenient to load and unload. At the same time, the waste filter media is difficult to treat and recycle, and direct landfilling would cause serious environmental pollution.

[0003] Current research on carbon materials mainly focuses on adsorption, separation, and catalysis, utilizing their high specific surface area, controllable pore structure, and good physicochemical stability. However, research on carbon materials with low specific surface area, large-sized interconnected channels, and high compressive strength is relatively limited. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a flue gas denitrification catalyst matrix. The flue gas denitrification catalyst matrix prepared by this method has a low specific surface area, contains well-developed large-sized through channels, and has high compressive strength. Waste catalysts can be easily regenerated by acid washing or directly incinerated, avoiding environmental pollution caused by landfilling.

[0005] The preparation method of the flue gas denitrification catalyst matrix of the present invention includes the following: (1) mixing water, fermentation bacteria, flour and guar gum powder and kneading them into a plastic body; (2) sealing and storing the plastic body for a certain period of time, kneading the plastic body again, and molding it into a honeycomb-shaped body, and then hydrothermally treating it under sealed conditions, drying and calcining it to obtain a honeycomb-shaped matrix.

[0006] In the method of the present invention, the fermenting bacteria in step (1) are various bacterial microorganisms that can react with starch and generate carbon dioxide, including yeast or various modified yeasts.

[0007] In the method of the present invention, the amount of fermentation bacteria used in step (1) is 0.1wt%-5wt% of the flour mass.

[0008] In the method of the present invention, the flour in step (1) includes glutinous rice flour, ordinary wheat flour and durum wheat flour. Based on the flour quality, the glutinous rice flour is 10%-45%, the ordinary wheat flour is 50%-80%, and the durum wheat flour is 5%-15%.

[0009] In the method of the present invention, the glutinous rice flour in step (1) is a commercially available product with a particle size greater than 100 mesh, preferably 200-500 mesh.

[0010] In the method of the present invention, the ordinary wheat flour mentioned in step (1) is a commercially available product with a particle size greater than 100 mesh, preferably 200-500 mesh.

[0011] In the method of the present invention, the durum wheat flour mentioned in step (1) is a high-density hard wheat flour, which is a commercially available product with a particle size greater than 200 mesh, preferably 500-1000 mesh.

[0012] In the method of the present invention, the mass of water used in step (1) is 20%-60% of the mass of flour.

[0013] In the method of the present invention, the mass of guar gum powder in step (1) is 1%-3% of the mass of flour.

[0014] In the method of the present invention, the fermentation bacteria described in step (1) are pre-dispersed in water at 2-5 times their weight, and then added to the mixture of flour and guar gum powder.

[0015] In the method of the present invention, step (1) is further preferably glutinous rice flour is heated with water to form a gelatin, and then mixed with other materials.

[0016] Step (1) The conditions for gelatinizing glutinous rice flour are: disperse glutinous rice flour into water with a weight of 2-10 times its own weight, heat it to 58-95℃ while stirring, and keep it for 5-30 minutes.

[0017] In the method of the present invention, the temperature for sealing and storing the plastic body in step (1) is 25-45℃, and the storage time is 0.2-5 hours.

[0018] In the method of the present invention, the conditions for re-mixing in step (2) are: mixing time of 10-60 minutes, ambient temperature of room temperature, generally 10-40℃.

[0019] In the method of the present invention, in the hydrothermal treatment described in step (2), the water does not come into direct contact with the honeycomb molded body, the hydrothermal temperature is 100-200℃, the time is 0.5-5 hours, and the pressure is the self-generated pressure under closed conditions.

[0020] In the method of the present invention, the drying conditions in step (2) are: drying at 60-200℃ for 1-48 hours, preferably drying at 100-150℃ for 3-24 hours.

[0021] In the method of this invention, the calcination conditions in step (2) are as follows: calcination at 250-350°C for 2-5 hours under an inert atmosphere, followed by calcination at 750-950°C for 1-5 hours. The inert atmosphere is nitrogen and / or an inert gas, and the inert gas is one or more of helium, neon, argon, or xenon.

[0022] The flue gas denitrification catalyst matrix prepared by the method of this invention has the following properties: it has an integral honeycomb structure with honeycomb pores of 2-8 mm in size; the pore walls have large channels with a size of 100-1000 μm; and its specific surface area is less than 25 m². 2 / g, compressive strength is 10-20MPa.

[0023] The present invention also provides a flue gas denitrification catalyst support, which is an alumina coating or a silicon-aluminum composite oxide coating loaded on the above-mentioned flue gas denitrification catalyst substrate, wherein the coating content is 5% to 20% by the mass of the substrate.

[0024] This invention utilizes the reaction of fermenting bacteria with starch to generate carbon dioxide. The proteins in wheat flour possess extensibility and can form a three-dimensional network, sealing the carbon dioxide within the plastic body. The carbon dioxide then flows and forms three-dimensional pores within the plastic body. Wheat flour particles absorb water and swell upon contact with water, forming a three-dimensional interwoven structure with the proteins. Through two kneading processes, this three-dimensional structure becomes more stable and dense. Hydrothermal fumigation hardens the starch and proteins, fixing the shape of the plastic body. The incorporated glutinous rice flour, generally with a high proportion of branched-chain starch, acts as a binder after gelatinization, further enhancing the strength of the molded body. Simultaneously, it is converted into carbonaceous matter during the carbonization process. Attached Figure Description

[0025] Figure 1 The image shows a scanning electron microscope (SEM) image of the flue gas denitrification catalyst matrix prepared in Example 1. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments. The dimensions of the honeycomb channels were measured using vernier calipers, and the compressive strength was tested according to the method described in "Test Methods for Properties of Porous Ceramics GB / T 1964-1996". The microstructure and macropore morphology were observed and measured using a scanning electron microscope, and the specific surface area was tested using the BET method.

[0027] Example 1

[0028] Mix 100g of glutinous rice flour (120 mesh) with 135g of water at 80℃ and gelatinize for 30 minutes. Disperse 5g of yeast in 20g of water, mix with 7g of guar gum powder, 500g of ordinary wheat flour (200 mesh), and 35g of durum powder (300 mesh), then add the gelatinized glutinous rice flour and mix well, kneading into a pliable shape. Seal and store at 35℃ for 2 hours, then knead again at room temperature for 15 minutes, and then extrude into a honeycomb structure. Steam the honeycomb structure at 150℃ for 2 hours, cool, and then dry at 120℃ for 24 hours. Place it in a tube furnace under nitrogen protection, raise the temperature to 300℃ and hold for 3 hours, then raise the temperature to 800℃ and hold for 3 hours. After cooling, obtain matrix A.

[0029] The matrix has a compressive strength of 10.6 MPa, square honeycomb cells with a diameter of 2 mm and a distribution density of 4 cells / cm³. 2 Scanning electron microscopy revealed that the particles possessed large-sized interconnected channels ranging from 168 to 1000 μm, with a honeycomb pore surface area of ​​12.2 cm². 2 / g.

[0030] Example 2

[0031] Mix 120g of glutinous rice flour (300 mesh) with 150g of water at 80℃ until gelatinized and maintain for 30 minutes. Disperse 5g of yeast in 20g of water, mix with 7g of guar gum powder, 500g of ordinary wheat flour (200 mesh), and 50g of durum powder (300 mesh), then add the gelatinized glutinous rice flour and mix well, kneading into a pliable shape. Seal and store at 70℃ for 2 hours, then knead again at room temperature for 30 minutes, and then extrude into a honeycomb structure. Steam the honeycomb structure at 150℃ for 2 hours, cool, and then dry at 120℃ for 24 hours. Place it in a tube furnace under nitrogen protection, raise the temperature to 300℃ and maintain for 3 hours, then raise the temperature to 900℃ and maintain for 3 hours. After cooling, obtain matrix B.

[0032] The matrix has a compressive strength of 13.5 MPa, a diameter of 2 mm for the circular pores, and a distribution density of 4 pores / cm³. 2 Scanning electron microscopy revealed that the particles possess large-sized interconnected channels ranging from 120 to 790 μm, with a honeycomb pore specific surface area of ​​10.8 cm². 2 / g.

[0033] Example 3

[0034] 100g of glutinous rice flour (300 mesh) was mixed with 130g of water at 80℃ and gelatinized for 30 minutes. 8g of yeast was dispersed in 20g of water and mixed with 10g of guar gum powder, 500g of ordinary wheat flour (200 mesh), and 100g of durum wheat flour (300 mesh). The gelatinized glutinous rice flour was then added, and the mixture was stirred until smooth and kneaded into a malleable mass. The mixture was sealed and stored at 30℃ for 5 hours, then kneaded again at room temperature for 60 minutes. The resulting mass was then extruded into a honeycomb structure. The honeycomb structure was hydrothermally steamed at 130℃ for 3 hours, cooled, and then dried at 120℃ for 24 hours. It was then placed in a tube furnace under nitrogen protection, heated to 300℃ and held for 3 hours, then heated to 950℃ and held for 3 hours. After cooling, matrix C was obtained.

[0035] The matrix has a compressive strength of 17.3 MPa, a square honeycomb cell side length of 1 mm, and a distribution density of 5 cells / cm². 2 Scanning electron microscopy revealed that the particles possess large-sized interconnected channels ranging from 105 to 745 μm, with a honeycomb pore specific surface area of ​​9.7 cm². 2 / g.

[0036] Comparative Example 1

[0037] Similar to Example 1, except that wheat flour is not added, the hardening effect is not good, and the final shaped particles are difficult to form a relatively regular honeycomb matrix.

[0038] Comparative Example 2

[0039] Same as Example 1, except that steaming is not performed. The final molded particles are difficult to form a relatively regular honeycomb matrix.

[0040] Comparative Example 3

[0041] Similar to Example 1, except that it was directly extruded after being sealed and stored. The final molded particles were relatively loose and difficult to form a regular honeycomb matrix.

[0042] Comparative Example 4

[0043] Similar to Example 1, except that the calcination process involves a single-stage calcination, where the temperature is directly raised to 800°C and held for 3 hours. This material has a lower carbon conversion rate, still contains polymeric organic matter, and the final formed particles are relatively loose.

[0044] Example 4

[0045] Preparation of coating slurry: 20 g of boehmite was added to 150 mL of deionized water, and 7 g of concentrated nitric acid was added dropwise while stirring. After stirring for a certain period of time, the mixture was heated to 80 °C, and nitric acid was added dropwise until the gel was completely dissolved. The pH of the solution was controlled at 2-5, and the mixture was aged for 24 hours to obtain a transparent aluminum sol with an alumina content of 8 wt%.

[0046] The substrates A, B, and C were subjected to coating loading processes to obtain carriers A, B, and C, respectively. The loading process was as follows: immersion in the coating slurry for 20 minutes, removal, blowing off residual liquid, drying at 110°C for 9 hours, and then treating in air at 550°C for 3 hours to obtain the carriers with the loaded coating. The specific properties are shown in Table 1.

[0047] Table 1. Sample weight gain ratio and results of ultrasonic coating peeling.

[0048] serial number Example 1 Example 2 Example 3 Weight gain percentage, % 13.6 13.2 13.8 Ultrasonic shedding rate, % 2.4 1.9 2.2

[0049] Wherein, the weight gain ratio = (weight after calcination - original weight of the matrix) / original weight of the matrix × 100%

[0050] The coating adhesion was evaluated by ultrasonic vibration test. The sample was placed in an ultrasonic cleaner (KQ-250D, power 150W, frequency 100kHz) with water as the medium and the peeling rate was calculated after 30 minutes of ultrasonic cleaning.

[0051] The ultrasonic peeling rate is calculated as follows: (Coating weight - Weight after ultrasonic oscillation) / Coating weight × 100%.

[0052] The data above show that the coating loading of the samples in Examples 1-3 increased by more than 10%, indicating that the matrix prepared by the method of the present invention can meet the requirements of the flue gas denitrification catalyst support.

Claims

1. A method for preparing a flue gas denitrification catalyst matrix, characterized in that... The following contents are included: (1) Mix water, fermentation bacteria, flour and sesame powder and knead them into a plastic body; (2) After sealing and storing the plastic body for a certain period of time, knead the plastic body again and shape it into a honeycomb-shaped body. Then, under sealed conditions, perform hydrothermal treatment, dry and bake to obtain a honeycomb matrix. The flour mentioned in step (1) includes glutinous rice flour, ordinary wheat flour and durum wheat flour. Based on the flour quality, glutinous rice flour accounts for 10%-45%, ordinary wheat flour accounts for 50%-80%, and durum wheat flour accounts for 5%-15%. The calcination conditions described in step (2) are: calcination at 250-350℃ for 2-5 hours under an inert atmosphere, followed by calcination at 750-950℃ for 1-5 hours. The flue gas denitrification catalyst matrix has an integral honeycomb structure with honeycomb pores ranging from 2 to 8 mm in size; the pore walls have large channels with a size of 100-1000 μm; and the specific surface area is less than 25 m². 2 / g, compressive strength is 10-20MPa.

2. The method according to claim 1, characterized in that: The fermenting bacteria mentioned in step (1) are various bacteria and microorganisms that can react with starch and generate carbon dioxide.

3. The method according to claim 2, characterized in that: The fermentation bacteria mentioned in step (1) are yeast or various modified yeasts.

4. The method according to claim 1, characterized in that: The amount of fermentation bacteria used in step (1) is 0.1wt%-5wt% of the flour mass.

5. The method according to claim 1, characterized in that: The glutinous rice flour in step (1) has a particle size greater than 100 mesh.

6. The method according to claim 5, characterized in that: The glutinous rice flour in step (1) has a particle size of 200-500 mesh.

7. The method according to claim 1, characterized in that: The ordinary wheat flour in step (1) has a particle size greater than 100 mesh.

8. The method according to claim 7, characterized in that: The ordinary wheat flour mentioned in step (1) has a particle size of 200-500 mesh.

9. The method according to claim 1, characterized in that: The durum wheat flour in step (1) has a particle size greater than 200 mesh.

10. The method according to claim 9, characterized in that: The durum wheat flour in step (1) has a particle size of 500-1000 mesh.

11. The method according to claim 1, characterized in that: The water used in step (1) should be 20%-60% of the flour mass.

12. The method according to claim 1, characterized in that: The amount of guar gum powder mentioned in step (1) is 1%-3% of the flour weight.

13. The method according to claim 1, characterized in that: The fermentation bacteria described in step (1) are pre-dispersed in water at 2-5 times their weight, and then added to the mixture of flour and guar gum powder.

14. The method according to claim 1, characterized in that: Step (1) Glutinous rice flour is preheated with water to form a gelatin, and then mixed with other materials.

15. The method according to claim 14, characterized in that: Step (1) The conditions for gelatinizing glutinous rice flour are: disperse glutinous rice flour into water with a weight of 2-10 times its own weight, heat it to 58-95℃ while stirring, and keep it for 5-30 minutes.

16. The method according to claim 1, characterized in that: In step (1), the temperature for sealing and storing the plastic body is 25-45℃, and the storage time is 0.2-5 hours.

17. The method according to claim 1, characterized in that: The conditions for re-mixing in step (2) are: mixing time of 10-60 minutes and ambient temperature of 10-40℃.

18. The method according to claim 1, characterized in that: In step (2), the hydrothermal treatment does not involve direct contact between water and the honeycomb-shaped molded body. The hydrothermal temperature is 100-200℃, the time is 0.5-5 hours, and the pressure is the self-generated pressure under sealed conditions.

19. The method according to claim 1, characterized in that: The drying conditions described in step (2) are: drying at 60-200℃ for 1-48 hours.

20. The method according to claim 19, characterized in that: The drying conditions described in step (2) are: drying at 100-150℃ for 3-24 hours.

21. The method according to claim 1, characterized in that: The inert atmosphere mentioned in step (2) is nitrogen and / or an inert gas, wherein the inert gas is one or more of helium, neon, argon or xenon.

22. A flue gas denitrification catalyst matrix prepared by the method according to any one of claims 1 to 21, characterized in that: It features an integral honeycomb structure with honeycomb cells ranging from 2 to 8 mm in size; the cell walls have large pores with a size of 100-1000 μm; and the specific surface area is less than 25 m². 2 / g, compressive strength is 10-20MPa.

23. A catalyst support for flue gas denitrification, characterized in that: The carrier is an alumina coating or a silicon-aluminum composite oxide coating supported on a flue gas denitrification catalyst substrate prepared by any of the methods described in claims 1 to 17, wherein the coating content is 5% to 20% by the mass of the substrate.

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