Carbon dioxide in-situ fixation hydrophobic membrane material and preparation method thereof

Abstract

The application provides a carbon dioxide in-situ fixing hydrophobic membrane material and a preparation method thereof. The prepared membrane material has a relatively rich nano-pore diameter on the surface, and allows carbon dioxide to permeate; and the middle part of the hydrophobic ceramic membrane material is in a hollow honeycomb shape, and the part is flowed through by a reaction liquid for in-situ fixing of carbon dioxide. The porous hydrophobic ceramic membrane material is first formed by high-temperature sintering once, and has a high yield; and then the ceramic membrane material is brushed by a hydrophobic material and is sintered at low temperature again, so that the ceramic membrane material has a strong hydrophobicity on the surface, and the hydrophobicity of the ceramic membrane tube almost does not change after multiple uses. The application has the advantages of novel method, simple implementation, hydrophobic modification by secondary low-temperature sintering on the basis of the hydrophilic ceramic membrane material at the beginning, reduced gas pressure required when the gas enters the membrane tube, enhanced mass transfer efficiency of the membrane tube, prolonged service life of the membrane tube, and reduced use cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrophobic ceramic membrane material preparation, and particularly relates to a hydrophobic ceramic membrane material for in-situ fixation of carbon dioxide in complex industrial waste gas and a preparation method thereof. BACKGROUND

[0002] Membrane separation technology is a high-efficiency pollution treatment method, and has many advantages such as convenient operation, low cost, energy saving, and system installation. According to the material classification, the membrane can be divided into organic polymer membrane and inorganic ceramic membrane. The organic polymer membrane has a high market share due to rich manufacturing materials, easy control of pore size, and large membrane module packing density. However, the organic polymer membrane is easily polluted by organic liquid due to similar chemical structure features of most organic pollutants, and has low heat stability and mechanical strength, resulting in low service life. The inorganic ceramic membrane has been widely studied in recent years due to high mechanical strength, good heat stability and chemical stability. However, the ceramic material is usually hydrophilic due to the influence of surface hydroxyl groups, which limits the application range of the porous ceramic membrane, such as membrane distillation, waste gas treatment and oil-water separation.

[0003] At present, the main methods for hydrophobic modification of the ceramic membrane include surface coating, surface spraying, surface chemical polymerization, surface grafting polymerization, surface radiation grafting, vacuum surface plating, and plasma surface polymerization. The solution grafting polymerization method uses the existence of hydroxyl groups (-OH) on the surface of the ceramic membrane, and selects fluorine-containing or chlorine-containing or amino-containing organic silane as a modifier. The organic silane is covalently connected to the substrate through grafting polymerization reaction to obtain a composite membrane. The modification method is simple and easy to implement in any laboratory, and can obtain a high-performance hydrophobic microporous membrane which can be used in the membrane distillation process. Meanwhile, the ceramic membrane itself also retains the advantages of high mechanical strength and narrow pore size distribution. SUMMARY

[0004] The main purpose of the present application is to provide a hydrophobic ceramic membrane material for in-situ fixation of carbon dioxide in complex industrial waste gas and a preparation method thereof, which can effectively solve the problem of large amount of carbon oxide emission caused by coal combustion, and efficiently fix the carbon dioxide in the atmosphere in-situ.

[0005] The technical scheme adopted by the present application is as follows: a carbon dioxide in-situ fixation hydrophobic membrane material, characterized in that the hydrophobic membrane material is a hydrophobic modified ceramic membrane material, the inside of which is a hollow honeycomb membrane tube structure, and the surface has nano micropores with a diameter of 50-200 nm; the ceramic honeycomb membrane tube has nano micropores in the inside, and the micropores are closely connected; after the hydrophobic modification of the ceramic membrane tube, the internal structure becomes smooth from rough, and the whole membrane tube has strong hydrophobicity with a contact angle of 130°-165°.

[0006] This invention also provides a method for preparing the in-situ immobilized hydrophobic membrane material containing carbon dioxide, the preparation process being as follows:

[0007] (1) Sieve all the required raw materials through a sieve, mix them in proportion, and then pour them all into a V-type mixer for centralized mixing;

[0008] (2) The material obtained in step (1) is mixed with PVA solution and deionized water and stirred in a biaxial mixer to obtain dry-pressed preforms;

[0009] (3) After the dry-pressed blank is cooled, it is isostatically pressed in a honeycomb mold to obtain a membrane tube blank;

[0010] (4) Demold and dry the membrane tube preform obtained in step (3);

[0011] (5) Place the membrane tube preform obtained in step (4) into the burning boat, and fill the gap between the membrane tube preform and the burning boat with high-purity zirconium oxide sand.

[0012] (6) The membrane tube blank from step (5) and the firing boat are placed in a kiln and fired to obtain ceramic membrane material;

[0013] (7) Adjust the pH of the ceramic membrane material prepared in (6) to neutral, wash and dry it, and then soak it in the modified solution 3-5 times. After each soaking, bake it in an oven for 30 min-60 min. After the last baking, put the ceramic membrane tube into a low temperature kiln for firing. Heat it to 250-280℃ at a rate of 0.5-1.5℃ / min, and keep it at the highest temperature for 2-3 hours. Cool it to room temperature with the furnace to obtain the hydrophobic ceramic membrane material.

[0014] Furthermore, in step (1), the raw materials used include 75-77 wt% silicon carbide powder, 2-3 wt% powdered fly ash, 3-4 wt% silica fume, 1-3 wt% dextrin, 2-5 wt% carboxymethyl cellulose, 5-6 wt% kaolin, and 0.1-0.4 wt% tetraethyl ethylenediamine.

[0015] Furthermore, in step (1), the sieve particle size is 200-500 mesh, and the mixture is concentrated in a V-type mixer for 3-5 hours.

[0016] Further, in step (2), 5-8 wt% PVA solution is added; the mixture is stirred in a biaxial mixer for 3-5 hours.

[0017] Furthermore, in step (3), the dry-pressed blank is isostatically pressed in a honeycomb mold under a pressure of 35-50 MPa to obtain a membrane tube blank.

[0018] Furthermore, in step (4), the membrane tube preform is demembraned and then dried in a drying oven at 60-90℃ for 16-24 hours.

[0019] Further, in step (6), the membrane tube blank and the firing boat are placed in a kiln and heated to 1200-1250℃ at a rate of 0.5-1.5℃ / min, and kept at the highest temperature for 4-6 hours, and then cooled to room temperature with the furnace to obtain the ceramic membrane material.

[0020] Furthermore, in step (7), the modified solution used is prepared by mixing carbon fluoride, anhydrous ethanol, boric acid and deionized water in a mass ratio of 1:100 to 1:200 between the solutions of each substance and the deionized water.

[0021] Furthermore, the modified solution contains carbon fluoride, anhydrous ethanol, and boric acid in the following mass ratio: carbon fluoride (10-20%), anhydrous ethanol (30-40%), and boric acid (40-60%).

[0022] The hydrophobic membrane material for in-situ carbon dioxide fixation provided by this invention can be used for in-situ fixation of carbon dioxide in complex industrial waste gas. When carbon dioxide enters the membrane tube to react, the pressure inside the entire device is 0.01-0.05 MPa.

[0023] In this invention, dextrin is used as a pore-forming agent and carboxymethyl cellulose is used as an organic binding agent. The gap between the membrane preform and the sintering boat is filled with high-purity zirconium oxide sand to prevent expansion of the ceramic membrane material during sintering, which could lead to substandard product quality.

[0024] The modification solution used in this invention is prepared by mixing fluorinated carbon, anhydrous ethanol, boric acid, and deionized water in a certain proportion. The modification process of the membrane tube is essentially a secondary firing of the ceramic membrane tube, forming a highly hydrophobic layer on its surface. After modification with the solution, the internal structure of the ceramic membrane tube changes from rough to smooth, and the entire membrane tube exhibits strong hydrophobicity. By modifying the membrane tube to form a hydrophobic layer, its hydrophobic properties will not significantly decrease even after repeated use.

[0025] The hydrophobic membrane material for in-situ fixation of carbon dioxide provided by this invention, after hydrophobic modification, makes the micropores inside the membrane tube smooth instead of rough, and the contact angle of the entire membrane tube surface becomes 130°-165°. When carbon dioxide is fixed in situ inside the membrane tube, it can greatly increase the contact area between the reaction liquid and carbon dioxide, reduce the gas pressure of carbon dioxide entering the membrane tube to 0.01-0.05 MPa, and at the same time improve the mass transfer efficiency of carbon dioxide. Attached Figure Description

[0026] Figure 1This is a schematic flowchart of the preparation method according to an embodiment of the present invention.

[0027] Figure 2 The diagram shows a comparison of the contact angles of modified and unmodified ceramic membrane tubes in Case 1; a represents the unmodified ceramic membrane tube, and b represents the modified ceramic membrane tube.

[0028] Figure 3 The image shows a comparison of the surface microstructure of modified and unmodified ceramic membrane tubes in Case 1; a represents the unmodified ceramic membrane tube, and b represents the modified ceramic membrane tube. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be noted that the following embodiments are only used to describe the content of the invention and do not constitute a limitation on the scope of protection of the present invention.

[0030] The preparation process of the hydrophobically modified ceramic membrane material in the following examples is referenced in Appendix I. Figure 1 The comparison diagram of contact angles between modified and unmodified ceramic membrane tubes in the examples is attached. Figure 2 .

[0031] Explanation of relevant test index concepts in the embodiments:

[0032] Contact angle: The contact angle is an important parameter describing the interaction between a liquid and a solid surface. Specifically, the contact angle is the angle between a stationary liquid droplet formed on a solid surface and that surface. This angle is represented by the angle between the tangent at the interface of the liquid, solid, and gas phases and the solid surface.

[0033] Test method: 1. Place the solid sample on the sample stage; 2. Use a syringe to drop a drop of liquid onto the solid surface; 3. Use a camera to capture a side image of the droplet on the solid surface; 4. Use image analysis software to calculate the angle between the droplet and the solid surface.

[0034] CO2 in-situ fixation rate: The percentage of CO2 absorbed after entering the reaction device.

[0035]

[0036] x: CO2 in-situ fixation rate; b: CO2 reaction amount; a: CO2 injection rate. Example 1

[0037] The raw materials used to prepare the ceramic membrane material were sieved through a 200-mesh sieve. Then, they were mixed in a V-type mixer for 3-5 hours in the following proportions: 75-77 wt% silicon carbide powder, 2-3 wt% powdered fly ash, 3-4 wt% silica fume, 1 wt% dextrin, 2 wt% carboxymethyl cellulose, 5-6 wt% kaolin, and 0.1-0.4 wt% tetraethyl ethylenediamine. Then, 5-8 wt% PVA solution was added and the mixture was stirred in a biaxial mixer for 3-5 hours.

[0038] The dry-pressed preform prepared in a biaxial mixer is poured into a pre-prepared honeycomb mold and pressed. The honeycomb membrane tube preform is statically pressed under a pressure of 45 MPa, then demolded and dried in a 90℃ drying oven for 24 hours. After drying, the membrane tube preform is placed in a sintering boat for sintering. The gap between the sintering boat and the membrane tube preform is filled with high-purity zirconium oxide to prevent the membrane tube from expanding and cracking during sintering. When the membrane tube preform and the sintering boat are placed in the kiln for sintering, the temperature is gradually increased at a rate of 1℃ / min to 1200-1250℃. When the temperature reaches this range, it is maintained for 4 hours. After cooling to room temperature, the ceramic membrane material is demolded, and the nanopore diameter on its surface is about 200 nm.

[0039] The sintered ceramic membrane material is first soaked in a 1-2 mol / L NaOH solution for 30-60 min, then rinsed with distilled water for a period of time until the pH of the ceramic membrane material becomes neutral, and then the membrane tube is placed in an oven to dry. The dried ceramic membrane material is then soaked in a modification solution 3-5 times, and after each soaking, it is placed in an oven to bake for 30-60 min. After the last baking, the ceramic membrane tube is placed in a low-temperature kiln for firing, and the temperature is increased to 250-280℃ at a rate of 0.5-1.5 ℃ / min, and held at the highest temperature for 2-3 h. After cooling to room temperature with the furnace, a hydrophobic ceramic membrane material is obtained. The modification solution is prepared by mixing fluorinated carbon, anhydrous ethanol, boric acid (the mass ratio of the three is 10:30:60) and deionized water at a mass ratio of 1:200 between the solutions of each substance and the deionized water.

[0040] The modified ceramic membrane material obtained has nanopores inside, and the micropores are tightly connected. The contact angle was measured to be approximately 138°. When used for in-situ fixation of carbon dioxide in complex industrial waste gas, the reaction pressure was approximately 0.05 MPa, and the in-situ fixation rate of carbon dioxide was 97.1%. The results compared with those of the unmodified ceramic membrane material are shown in Table 1, and the contact angle comparison diagram is shown in the figure. Figure 2 As shown.

[0041] To further analyze the changes in the microstructure of the ceramic membrane tube caused by the modified solution, we conducted contact angle tests on the membrane tube. Figure 3The figures show a comparison of the surface microstructure of modified and unmodified ceramic membrane tubes; a represents the unmodified ceramic membrane tube, and b represents the modified ceramic membrane tube. As can be seen from the figures, the surface structure of the modified ceramic membrane tube becomes significantly smoother, and its contact angle is also significantly increased, indicating a significant enhancement in hydrophobicity.

[0042] Table 1

[0043] . Example 2

[0044] The raw materials used to prepare the ceramic membrane material were sieved through a 200-mesh sieve. Then, they were mixed in a V-type mixer for 3-5 hours in the following proportions: silicon carbide powder 75-77 wt%, powdered fly ash 2-3 wt%, silica powder 3-4 wt%, dextrin 1 wt%, carboxymethyl cellulose 3 wt%, kaolin 5-6 wt%, and tetraethyl ethylenediamine 0.1-0.4 wt%. Then, 5-8 wt% PVA solution was added and the mixture was stirred in a biaxial mixer for 3-5 hours.

[0045] The dry-pressed preform prepared in a biaxial mixer is poured into a pre-prepared honeycomb mold and pressed. The honeycomb membrane tube preform is statically pressed under a pressure of 45 MPa, then demolded and dried in a 90℃ drying oven for 24 hours. After drying, the membrane tube preform is placed in a sintering boat for sintering. The gap between the sintering boat and the membrane tube preform is filled with high-purity zirconium oxide to prevent the membrane tube from expanding and cracking during sintering. When the membrane tube preform and the sintering boat are placed in the kiln for sintering, the temperature is gradually increased at a rate of 1℃ / min to 1200-1250℃. When the temperature reaches this range, it is maintained for 4 hours. After cooling to room temperature, the ceramic membrane material is demolded, and the nanopore diameter on its surface is about 160 nm.

[0046] The sintered ceramic membrane material is first soaked in a 1-2 mol / L NaOH solution for 30-60 min, then rinsed with distilled water for a period of time until the pH of the ceramic membrane material becomes neutral, and then the membrane tube is placed in an oven to dry. The dried ceramic membrane material is then soaked in a modification solution 3-5 times, and after each soaking, it is placed in an oven to bake for 30-60 min. After the last baking, the ceramic membrane tube is placed in a low-temperature kiln for firing, and the temperature is increased to 250-280℃ at a rate of 0.5-1.5℃ / min, and held at the highest temperature for 2-3 h. After cooling to room temperature in the furnace, a hydrophobic ceramic membrane material is obtained. The modification solution is prepared by mixing fluorinated carbon, anhydrous ethanol, boric acid (the mass ratio of the three is 20:40:40), and deionized water at a mass ratio of 1:200 between each substance solution and deionized water.

[0047] The modified ceramic membrane material has nanopores inside, and the micropores are closely connected. The contact angle was measured to be about 146.6°. When used for in-situ fixation of carbon dioxide in complex industrial waste gas, the reaction pressure was about 0.047 MPa, and the in-situ fixation rate of carbon dioxide was 98.5%. The results compared with those of the unmodified ceramic membrane material are shown in Table 2.

[0048] Table 2

[0049] . Example 3

[0050] The raw materials used to prepare the ceramic membrane material were sieved through a 400-mesh sieve. Then, they were mixed in a V-type mixer for 3-5 hours in the following proportions: silicon carbide powder 75-77 wt%, powdered fly ash 2-3 wt%, silica powder 3-4 wt%, dextrin 2 wt%, carboxymethyl cellulose 3.5 wt%, kaolin 5-6 wt%, and tetraethyl ethylenediamine 0.1-0.4 wt%. Then, 5-8 wt% PVA solution was added and the mixture was stirred in a biaxial mixer for 3-5 hours.

[0051] The dry-pressed preform prepared in a biaxial mixer is poured into a pre-prepared honeycomb mold and pressed. The honeycomb membrane tube preform is statically pressed under a pressure of 45 MPa, then demolded and dried in a 90℃ drying oven for 24 hours. After drying, the membrane tube preform is placed in a sintering boat for sintering. The gap between the sintering boat and the membrane tube preform is filled with high-purity zirconium oxide to prevent the membrane tube from expanding and cracking during sintering. When the membrane tube preform and the sintering boat are placed in the kiln for sintering, the temperature is gradually increased at a rate of 1℃ / min to 1200-1250℃. When the temperature reaches this range, it is maintained for 4 hours. After cooling to room temperature, the ceramic membrane material is demolded, and the nanopore diameter on its surface is about 110 nm.

[0052] The sintered ceramic membrane material is first soaked in a 1-2 mol / L NaOH solution for 30-60 min, then rinsed with distilled water for a period of time until the pH of the ceramic membrane material becomes neutral, and then the membrane tube is placed in an oven to dry. The dried ceramic membrane material is then soaked in a modification solution 3-5 times, and after each soaking, it is placed in an oven to bake for 30-60 min. After the last baking, the ceramic membrane tube is placed in a low-temperature furnace for firing, and the temperature is increased to 250-280℃ at a rate of 0.5-1.5℃ / min, and held at the highest temperature for 2-3 h. After cooling to room temperature with the furnace, a hydrophobic ceramic membrane material is obtained. The modification solution is prepared by mixing fluorinated carbon, anhydrous ethanol, boric acid (the mass ratio of the three is 15:35:50) and deionized water at a mass ratio of 1:150 between each substance solution and deionized water.

[0053] The modified ceramic membrane material has nanopores inside, and the micropores are closely connected. The contact angle was measured to be about 153.2°. When used for in-situ fixation of carbon dioxide in complex industrial waste gas, the reaction pressure is about 0.03 MPa, and the in-situ fixation rate of carbon dioxide is 98.9%. The results are compared with those of the unmodified ceramic membrane material in Table 3.

[0054] Table 3

[0055] . Example 4

[0056] The raw materials used to prepare the ceramic membrane material were sieved through a 400-mesh sieve. Then, they were mixed in a V-type mixer for 3-5 hours in the following proportions: silicon carbide powder 75-77 wt%, powdered fly ash 2-3 wt%, silica powder 3-4 wt%, dextrin 2 wt%, carboxymethyl cellulose 4 wt%, kaolin 5-6 wt%, and tetraethyl ethylenediamine 0.1-0.4 wt%. Then, 5-8 wt% PVA solution was added and the mixture was stirred in a biaxial mixer for 3-5 hours.

[0057] The dry-pressed preform prepared in a biaxial mixer is poured into a pre-prepared honeycomb mold and pressed. The honeycomb membrane tube preform is statically pressed under a pressure of 45 MPa, then demolded and dried in a 90℃ drying oven for 24 hours. After drying, the membrane tube preform is placed in a sintering boat for sintering. The gap between the sintering boat and the membrane tube preform is filled with high-purity zirconium oxide to prevent the membrane tube from expanding and cracking during sintering. When the membrane tube preform and the sintering boat are placed in the kiln for sintering, the temperature is gradually increased at a rate of 1℃ / min to 1200-1250℃. When the temperature reaches this range, it is maintained for 4 hours. After cooling to room temperature, the ceramic membrane material is demolded, and the nanopore diameter on its surface is about 80 nm.

[0058] The sintered ceramic membrane material is first soaked in a 1-2 mol / L NaOH solution for 30-60 min, then rinsed with distilled water for a period of time until the pH of the ceramic membrane material becomes neutral, and then the membrane tube is placed in an oven to dry. The dried ceramic membrane material is then soaked in a modification solution 3-5 times, and after each soaking, it is placed in an oven to bake for 30-60 min. After the last baking, the ceramic membrane tube is placed in a low-temperature kiln for firing, and the temperature is increased to 250-280℃ at a rate of 0.5-1.5℃ / min, and held at the highest temperature for 2-3 h. After cooling to room temperature with the furnace, a hydrophobic ceramic membrane material is obtained. The modification solution is prepared by mixing fluorinated carbon, anhydrous ethanol, boric acid (the mass ratio of the three is 10:40:50) and deionized water at a mass ratio of 1:150 between the solutions of each substance and the deionized water.

[0059] The modified ceramic membrane material has nanopores inside, and the micropores are closely connected. The contact angle was measured to be about 156.2°. When used for in-situ fixation of carbon dioxide in complex industrial waste gas, the reaction pressure was about 0.021 MPa, and the in-situ fixation rate of carbon dioxide was 98.9%. The results compared with those of the unmodified ceramic membrane material are shown in Table 4.

[0060] Table 4

[0061] . Example 5

[0062] The raw materials used to prepare the ceramic membrane material were sieved through a 500-mesh sieve. Then, they were mixed in a V-type mixer for 3-5 hours in the following proportions: silicon carbide powder 75-77 wt%, powdered fly ash 2-3 wt%, silica powder 3-4 wt%, dextrin 3 wt%, carboxymethyl cellulose 4 wt%, kaolin 5-6 wt%, and tetraethyl ethylenediamine 0.1-0.4 wt%. Then, 5-8 wt% PVA solution was added and the mixture was stirred in a biaxial mixer for 3-5 hours.

[0063] The dry-pressed preform prepared in a biaxial mixer is poured into a pre-prepared honeycomb mold and pressed. The honeycomb membrane tube preform is statically pressed under a pressure of 45 MPa, then demolded and dried in a 90℃ drying oven for 24 hours. After drying, the membrane tube preform is placed in a sintering boat for sintering. The gap between the sintering boat and the membrane tube preform is filled with high-purity zirconium oxide to prevent the membrane tube from expanding and cracking during sintering. When the membrane tube preform and the sintering boat are placed in the kiln for sintering, the temperature is gradually increased at a rate of 1℃ / min to 1200-1250℃. When the temperature reaches this range, it is maintained for 4 hours. After cooling to room temperature, the ceramic membrane material is demolded, and the nanopore diameter on its surface is about 60 nm.

[0064] The sintered ceramic membrane material is first soaked in a 1-2 mol / L NaOH solution for 30-60 min, then rinsed with distilled water for a period of time until the pH of the ceramic membrane material becomes neutral, and then the membrane tube is placed in an oven to dry. The dried ceramic membrane material is then soaked in a modification solution 3-5 times, and after each soaking, it is placed in an oven to bake for 30-60 min. After the last baking, the ceramic membrane tube is placed in a low-temperature furnace for firing, and the temperature is increased to 250-280℃ at a rate of 0.5-1.5℃ / min, and held at the highest temperature for 2-3 h. After cooling to room temperature in the furnace, a hydrophobic ceramic membrane material is obtained. The modification solution is prepared by mixing fluorinated carbon, anhydrous ethanol, boric acid (the mass ratio of the three is 15:40:45) and deionized water at a mass ratio of 1:100 between the solutions of each substance and the deionized water.

[0065] The modified ceramic membrane material has nanopores inside, and the micropores are closely connected. The contact angle was measured to be about 158.1°. When used for in-situ fixation of carbon dioxide in complex industrial waste gas, the reaction pressure is about 0.015 MPa, and the in-situ fixation rate of carbon dioxide is 99.2%. The results are compared with those of the unmodified ceramic membrane material in Table 5.

[0066] Table 5

[0067] . Example 6

[0068] The raw materials used to prepare the ceramic membrane material are sieved through a 500-mesh sieve. Then, they are mixed in a V-type mixer for 3-5 hours in the following proportions: 75-77 wt% silicon carbide powder, 2-3 wt% powdered fly ash, 3-4 wt% silica fume, 3 wt% dextrin, 5 wt% carboxymethyl cellulose, 5-6 wt% kaolin, and 0.1-0.4 wt% tetraethyl ethylenediamine. Then, 5-8 wt% PVA solution is added and the mixture is stirred in a biaxial mixer for 3-5 hours.

[0069] The dry-pressed preform prepared in a biaxial mixer is poured into a pre-prepared honeycomb mold and pressed. The honeycomb membrane tube preform is statically pressed into shape under a pressure of 45 MPa. After demolding, it is placed in a 90℃ drying oven for 24 hours. After drying, the membrane tube preform is placed in a sintering boat for sintering. The gap between the sintering boat and the membrane tube preform is filled with high-purity zirconium oxide. The purpose of filling is to prevent the membrane tube from expanding and cracking during sintering. When the membrane tube preform and the sintering boat are placed in the kiln for sintering, the temperature is gradually increased at a rate of 1℃ / min to 1200-1250℃. When the temperature reaches this temperature range, it is maintained at this temperature for 4 hours. After cooling to room temperature, the ceramic membrane material is demolded, and the pore size of the nanopores on its surface is about 50 nm.

[0070] The sintered ceramic membrane material is first soaked in a 1-2 mol / L NaOH solution for 30-60 min, then rinsed with distilled water for a period of time until the pH of the ceramic membrane material becomes neutral. The membrane tube is then placed in an oven to dry. The dried ceramic membrane material is then soaked in a modification solution 3-5 times, and after each soaking, it is baked in an oven for 30-60 min. After the final baking, the ceramic membrane tube is placed in a low-temperature kiln for firing, and the temperature is increased to 250-280℃ at a rate of 0.5-1.5℃ / min, and held at the highest temperature for 2-3 h. The membrane tube is then cooled to room temperature with the furnace to obtain a hydrophobic ceramic membrane material. The modification solution is prepared by mixing fluorinated carbon, anhydrous ethanol, boric acid, and deionized water in a mass ratio of 1:100 between the solutions of each substance and the deionized water.

[0071] The modified ceramic membrane material has nanopores inside, and the micropores are closely connected. The contact angle was measured to be about 159.6°. When used for in-situ fixation of carbon dioxide in complex industrial waste gas, the reaction pressure is about 0.01 MPa, and the in-situ fixation rate of carbon dioxide is 99.2%. The results are compared with those of the unmodified ceramic membrane material in Table 6.

[0072] Table 6

[0073] .

[0074] Based on a comparison of different implementation examples, the beneficial results of this invention can be seen:

[0075] 1. After hydrophobic modification, the contact angle of the entire membrane tube surface is greatly increased. This allows the contact area between the reaction liquid and carbon dioxide to be increased significantly when carbon dioxide is fixed in situ inside the membrane tube, thereby reducing the reaction pressure of carbon dioxide and improving the mass transfer efficiency of carbon dioxide.

[0076] 2. As the particle size of the raw materials decreases and the content of dextrin and carboxymethyl cellulose increases, the surface and internal nanopore size of the ceramic membrane tube becomes smaller.

[0077] 3. Gradually increasing the mass ratio of carbon fluoride, anhydrous ethanol, boric acid, and deionized water in the modified solution helps to increase the hydrophobicity of the modified ceramic membrane tube, reduce the pressure during the reaction, improve the in-situ fixation rate of CO2 reaction, extend the service life of the membrane tube, and reduce the cost of use.

Claims

1. A method for preparing a hydrophobic membrane material with in-situ immobilized carbon dioxide, characterized in that: The preparation process is as follows: (1) The required raw materials are sieved through a sieve, mixed in proportion, and then poured into a V-type mixer for centralized mixing; the raw materials used are 75-77wt% silicon carbide powder, 2-3wt% powdered fly ash, 3-4wt% silica fume, 1-3wt% dextrin, 2-5wt% carboxymethyl cellulose, 5-6wt% kaolin, and 0.1-0.4wt% tetraethyl ethylenediamine; (2) The material obtained in step (1) is mixed with PVA solution and deionized water and stirred in a biaxial mixer to obtain dry-pressed preforms; (3) After the dry-pressed blank is cooled, it is isostatically pressed in a honeycomb mold to obtain a membrane tube blank; (4) Demold and dry the membrane tube preform obtained in step (3); (5) Place the membrane tube preform obtained in step (4) into the burning boat, and fill the gap between the membrane tube preform and the burning boat with high-purity zirconium oxide sand. (6) The membrane tube blank from step (5) and the firing boat are placed in a kiln and fired to obtain ceramic membrane material; (7) Adjust the pH of the ceramic membrane material prepared in (6) to neutral, wash and dry it, and then soak it in the modified solution 3-5 times. After each soaking, bake it in an oven for 30 min-60 min. After the last baking, put the ceramic membrane tube into a low temperature kiln for firing. Heat it to 250-280℃ at a rate of 0.5-1.5℃ / min, and keep it at the highest temperature for 2-3 hours. Cool it to room temperature with the furnace to obtain the hydrophobic ceramic membrane material. The modified solution used is a mixture of fluorinated carbon, anhydrous ethanol, boric acid and deionized water in a mass ratio of 1:100-1:200 between each substance solution and deionized water.

2. The method for preparing the in-situ immobilized hydrophobic membrane material of carbon dioxide according to claim 1, characterized in that: In step (1), the sieve particle size is 200-500 mesh, and the mixture is concentrated in a V-type mixer for 3-5 hours.

3. The method for preparing the in-situ carbon dioxide immobilized hydrophobic membrane material according to claim 1, characterized in that: In step (2), add 5-8 wt% PVA solution; stir in a biaxial mixer for 3-5 hours.

4. The method for preparing the in-situ immobilized hydrophobic membrane material of carbon dioxide according to claim 1, characterized in that: In step (3), the dry-pressed blank is isostatically pressed in a honeycomb mold under a pressure of 35-50 MPa to obtain a membrane tube blank.

5. The method for preparing the in-situ immobilized hydrophobic membrane material of carbon dioxide according to claim 1, characterized in that: In step (4), the membrane tube preform is demembraned and then dried in a drying oven at 60-90℃ for 16-24 hours.

6. The method for preparing the in-situ immobilized hydrophobic membrane material of carbon dioxide according to claim 1, characterized in that: In step (6), the membrane tube blank and the firing boat are placed in a kiln and heated to 1200-1250℃ at a rate of 0.5-1.5℃ / min, and kept at the highest temperature for 4-6 hours. The ceramic membrane material is then cooled to room temperature with the furnace.

7. The method for preparing the in-situ immobilized hydrophobic membrane material of carbon dioxide according to claim 1, characterized in that: In step (7), the modified solution of carbon fluoride, anhydrous ethanol and boric acid is in the following mass ratio: (10-20%): (30-40%): (40-60%).

8. The in-situ immobilized hydrophobic membrane material for carbon dioxide prepared by the preparation method according to any one of claims 1-7, characterized in that... The hydrophobic membrane material is a hydrophobically modified ceramic membrane material with a hollow honeycomb membrane tube structure inside and nanopores on the surface with a diameter of 50-200 nm. The honeycomb membrane tube ceramic body has nanopores inside, and the micropores are tightly connected. After hydrophobic modification, the internal structure of the ceramic membrane tube changes from rough to smooth, and the entire membrane tube has strong hydrophobicity with a contact angle of 130°-165°.

9. The in-situ carbon dioxide immobilized hydrophobic membrane material according to claim 8, characterized in that: Used for in-situ fixation of carbon dioxide in complex industrial waste gases, the pressure inside the entire device is 0.01-0.05 MPa when carbon dioxide enters the membrane tube for reaction.

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