Separation membrane for automobile exhaust pipe, preparation method of separation membrane and automobile exhaust pipe

Abstract

The invention belongs to the technical field of automobile exhaust emission, and particularly relates to a separation membrane for an automobile exhaust pipe, a preparation method of the separation membrane and the automobile exhaust pipe. The separation membrane for the automobile exhaust pipe is prepared by modifying the surface of an SSZ-23 molecular sieve membrane with a specific pore structure. According to the separation membrane for the automobile exhaust pipe, the pressure difference of the two sides of the membrane is used as pushing force, and the difference of the transmembrane permeation rates of different gas molecules is utilized, so that all pollutants discharged to an engine can be effectively separated; the separation efficiency is high, the cost is low, the membrane material is light, and vehicle light weight is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobile exhaust emissions, and particularly relates to a separation membrane for an automobile exhaust pipe, a preparation method thereof, and an automobile exhaust pipe. Background Art

[0002] Since the 1960s, with the continuous intensification of human activities and the rapid development of modern industry, environmental and energy problems have become increasingly prominent globally. The large emission of CO2 intensifies the greenhouse effect, leading to frequent global extreme climate phenomena, rising sea levels, and ecological system imbalance, seriously threatening the survival and development of mankind.

[0003] In the global transportation field, the number of vehicles exceeds one billion. Although the carbon emission per vehicle engine is relatively small, due to the extremely large number of vehicles, the overall carbon emission quantity is very large. In addition to implementing the strictest National VI emission standard limits for pollutants, China will also introduce equally strict fuel economy standards for passenger cars and commercial vehicles. Under the fuel economy standard restrictions, the specific conventional fuel consumption reduction solutions for passenger cars can be considered from the following aspects: reducing the tire rolling resistance coefficient, optimizing the wind resistance, lightening the vehicle body, optimizing the braking system drag, optimizing the powertrain, engine start-stop technology, and using electronic devices. In addition, to achieve low-carbon or zero-carbon emissions, choosing hybrid electric vehicles and pure electric vehicles has become the best solution. Regarding the separation and capture after vehicle carbon emissions, no relevant requirements and solutions have been proposed in the transportation industry. Therefore, to meet the increasingly strict carbon reduction requirements in the transportation industry, the present invention proposes a membrane separation technology for engine-emitted CO2 to solve the technical problem of CO2 separation in engine carbon emission capture control. Summary of the Invention

[0004] The purpose of the present invention is to provide a separation membrane for an automobile exhaust pipe, a preparation method thereof, and an automobile exhaust pipe; the automobile exhaust pipe solves the technical problem of CO2 separation in engine carbon emission capture control by adopting membrane separation technology.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a gas separation membrane for an automobile exhaust pipe is made by modifying the surface of an SSZ-23 molecular sieve membrane with a specific pore structure.

[0006] Further, the preparation method of the SSZ-23 molecular sieve membrane with a specific pore structure includes the following steps: S1. First, add a silicon source to water and stir, then add an aluminum source and stir, and then add a template agent and an alkali source and stir until completely dissolved to obtain a mixed solution; S2. Leave the mixed solution obtained in step S1 to age at room temperature for a period of time to allow the precursor to hydrolyze fully, obtaining an aged precursor solution. S3. Vertically place the substrate into a high-pressure autoclave lined with polytetrafluoroethylene, pour the aged precursor solution obtained in step S2 into it to submerge the substrate, then vertically fix the ceramic membrane in the high-pressure autoclave. After sealing the high-pressure autoclave, carry out a hydrothermal reaction under certain conditions. S4. After the hydrothermal reaction ends, take out the substrate, rinse it with deionized water, and dry it under certain conditions. Subsequently, put the dried membrane into a muffle furnace and calcine it under certain conditions to remove the template agent, thus obtaining the SSZ-23 molecular sieve membrane with a specific pore structure.

[0007] Further, in step S1, the silicon source is SiO2, the aluminum source is Al2O3, the template agent is N,N,N-trimethyl-1-adamantylammonium hydroxide, and the base source is NaOH; the mass ratio of SiO2, Al2O3, N,N,N-trimethyl-1-adamantylammonium hydroxide, NaOH, and water is 1:0.02:0.2:0.1:40. And / or, in step S3, the substrate uses a porous α-aluminum oxide substrate with a pore diameter of 100 - 200 nm; the ceramic membrane is a cordierite ceramic membrane; the conditions for the hydrothermal reaction are: carry out the hydrothermal reaction at 150 - 170 °C for 48 - 72 h. And / or, in step S4, the conditions for drying are: dry in an 80 °C oven for 6 hours; the calcination conditions are: heat to 550 °C at a heating rate of 1 °C / min and calcine for 6 hours.

[0008] Further, the gas separation membrane for the automobile exhaust pipe includes any one of an H2O separation membrane, an N2 / O2 / CO2 separation membrane, a CO2 separation membrane, and an N2 / O2 separation membrane.

[0009] Further, the preparation method of the H2O separation membrane includes the following steps: (1) Add 3-aminopropyltriethoxysilane in a volume ratio of 1 - 5% and dissolve it in absolute ethanol to obtain a silanized solution. (2) Add the SSZ-23 molecular sieve membrane with a specific pore structure into the silanized solution, stir at 60 - 80 °C for 6 - 12 h, then wash with absolute ethanol and dry to obtain a silanized molecular sieve. (3) Disperse nano-silica in deionized water and carry out ultrasonic treatment to obtain a nano-dispersion. Then add the alkylated molecular sieve into the nano-dispersion, stir evenly, and then obtain the material of the H2O separation membrane after drying and calcination. And / or, the method for preparing the N2 / O2 / CO2 separation membrane comprises the following steps: (1) Add 10-20 mg of graphene nanosheets or graphene oxide to 100 mL of absolute ethanol, and perform ultrasonic treatment to obtain a graphite nanodispersion; (2) Immerse the SSZ-23 molecular sieve membrane with a specific pore structure in the graphite nanodispersion. After impregnation at room temperature for 12-24 h, take out the membrane, rinse it with absolute ethanol, and then obtain the N2 / O2 / CO2 separation membrane after drying and calcination; And / or, the method for preparing the CO2 separation membrane comprises the following steps: (1) Add 3-aminopropyltriethoxysilane in a volume ratio of 1-5% and dissolve it in absolute ethanol to obtain a silylation solution; (2) Add the SSZ-23 molecular sieve membrane with a specific pore structure into the silylation solution, stir at 60-80 °C for 6-12 h, wash with absolute ethanol, and then dry to obtain the silylated molecular sieve; (3) Add 10-20 mg of graphene oxide to 100 mL of absolute ethanol, perform ultrasonic treatment, then add an amination reagent, and stir at 60 °C for 6 h to obtain a graphite nanodispersion; (4) Immerse the silylated molecular sieve in the graphite nanodispersion. After impregnation at room temperature for 12-24 h, take out the membrane, rinse it with absolute ethanol, and then obtain the CO2 separation membrane after drying and calcination; And / or, the method for preparing the N2 / O2 separation membrane comprises the following steps: (1) Add 10-20 mg of Na-Y zeolite to 100 mL of absolute ethanol, add 0.1-0.5 g of polyvinylpyrrolidone dispersant, and perform ultrasonic treatment to obtain a Na-Y zeolite dispersion; (2) Immerse the SSZ-23 molecular sieve membrane with a specific pore structure in the Na-Y zeolite dispersion. After impregnation at room temperature for 12-24 h, take out the membrane, rinse it with absolute ethanol, and then obtain the N2 / O2 separation membrane after drying and calcination.

[0010] In addition, the present invention also provides a gas separation membrane for an automobile exhaust pipe prepared by the above preparation method.

[0011] In addition, the present invention also provides an automobile exhaust pipe, which includes a main exhaust pipe connected to an automobile engine, an H2O exhaust pipe, a CO2 exhaust pipe, and an N2 / O2 exhaust pipe; the H2O exhaust pipe and the CO2 exhaust pipe are respectively communicated with the main exhaust pipe, the N2 / O2 exhaust pipe is arranged upstream of the exhaust port of the CO2 exhaust pipe and is communicated with the CO2 exhaust pipe; the exhaust ports of the H2O exhaust pipe, the CO2 exhaust pipe, and the N2 / O2 exhaust pipe are respectively communicated with the outside atmosphere; An H2O separation membrane is arranged at the connection between the H2O exhaust pipe and the main exhaust pipe, an N2 / O2 / CO2 separation membrane is arranged at the connection between the CO2 exhaust pipe and the main exhaust pipe, a CO2 separation membrane is arranged at the exhaust port of the CO2 exhaust pipe, and an N2 / O2 separation membrane is arranged at the connection between the N2 / O2 exhaust pipe and the CO2 exhaust pipe.

[0012] Further, the relationship between the diameter D1 of the main exhaust pipe, the diameter D2 of the H2O exhaust pipe, the diameter D3 of the CO2 exhaust pipe, and the diameter D4 of the N2 / O2 exhaust pipe is D1 > D2, D1 > D3, D3 > D2 > D4; The relationship between the diameter D2 of the H2O exhaust pipe and the diameter D3 of the CO2 exhaust pipe is calculated according to the following formula: or ; The relationship between the diameter D3 of the CO2 exhaust pipe and the diameter D4 of the N2 / O2 exhaust pipe is calculated according to the following formula: or ; In the formula, c N2 、c O2 、c H2O 、c CO2 are the concentrations of N2, O2, H2O, and CO2 respectively; m N2 、m O2 、m H2O 、m CO2 are the masses of N2, O2, H2O, and CO2 respectively.

[0013] Further, the thicknesses δ1 of the H2O separation membrane, δ2 of the N2 / O2 / CO2 separation membrane, δ3 of the CO2 separation membrane, and δ4 of the N2 / O2 separation membrane are all calculated according to the following formula: ; In the formula, △P is the pressure difference across the membrane; A is the membrane area; σ is the anti-tearing strength of the membrane; η is the permeability coefficient, and η = 0.95 - 1.

[0014] Furthermore, the pore size d1 of the H2O separation membrane is similar to the molecular dynamics diameter d N2 、The molecular dynamics diameter d of O2 O2 , the molecular dynamics diameter d of H2O H2O 、The molecular dynamics diameter d of CO2 CO2 The relationship is d N2 >d O2 >d CO2 >d1>d H2O ; And / or, the pore size d2 of the N2 / O2 / CO2 separation membrane is equal to the molecular dynamics diameter d N2 、The molecular dynamics diameter d of O2 O2 、The molecular dynamics diameter d of CO2 CO2 The relationship is d2>d N2 >d O2 >d CO2 ; And / or, the pore size d3 of the CO2 separation membrane is equal to the molecular dynamics diameter d N2 、The molecular dynamics diameter d of O2 O2 , the molecular dynamics diameter d of H2O H2O , the molecular dynamics diameter d of CO2 CO2 The relationship is d N2 >d O2 >d3>d CO2 >d H2O ; And / or, the pore size d4 of the N2 / O2 separation membrane is equal to the molecular dynamics diameter d N2 、The molecular dynamics diameter d of O2 O2 , the molecular dynamics diameter d of H2O H2O , the molecular dynamics diameter d of CO2 CO2 The relationship is d4>d N2 >d O2 >d CO2 >d H2O .

[0015] Compared with the closest existing technology, the technical solution provided by the present invention has the following excellent effects: (1) The separation membrane for automobile exhaust pipes of the present invention uses the pressure difference on both sides of the membrane as the driving force and utilizes the difference in the permeation rate of different gas molecules across the membrane to effectively separate the various pollutants emitted by the engine; the separation efficiency is high, the cost is low, and the membrane material is light, which is conducive to the lightweighting of vehicles.

[0016] (2) Through the technology of combining the specific structure of the automobile exhaust pipe of the present invention with the separation membrane, the technical problem of CO2 separation in the engine carbon emission capture control is solved; moreover, the structure is simple and suitable for application in the vehicle exhaust system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. Among them: Figure 1 is a schematic structural diagram of the automobile exhaust pipe of the present invention; Figure 2 is a pore structure diagram of a 7-membered ring pore channel parallel to the

[001] direction; Figure 3 is a pore structure diagram of a 9-membered ring pore channel parallel to the

[101] direction.

[0018] In the figure: 1 - main exhaust pipe; 2 - H2O exhaust pipe; 3 - CO2 exhaust pipe; 4 - N2 / O2 exhaust pipe; M1 - H2O separation membrane; M2 - N2 / O2 / CO2 separation membrane; M3 - CO2 separation membrane; M4 - N2 / O2 separation membrane; P1 - pressure inside the main exhaust pipe; P2 - ambient atmospheric pressure; P3 - pressure inside the corresponding exhaust pipe between M2 and M3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0020] In the description of the present invention, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate component. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0021] Unless otherwise stated, all scientific and technical terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. All patents and published publications referred to in the present invention are incorporated into the present invention by reference in their entirety.

[0022] Explanation of the technical terms related to the present invention is as follows: "9-membered ring and 7-membered ring": In the crystal structure, basic structural units such as silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons are connected by oxygen bridges to form rings with different numbers of members. The 9-membered ring and 7-membered ring refer to ring structures formed by connecting 9 and 7 tetrahedral structural units respectively; "

[001] direction": In crystallography,

[001] is a crystal orientation index indicating a specific direction of the crystal in three-dimensional space. The 7-membered ring pore channels are parallel to the

[001] direction, which means that the pore channels formed by the 7-membered rings extend along the direction indicated by

[001] in the crystal, that is, parallel to the c-axis in the crystal coordinate system; "

[101] direction": The 9-membered ring pore channels are parallel to the

[101] direction, which means that the pore channels formed by the 9-membered rings extend along the

[101] direction. This direction is a specific direction in the plane determined by the a-axis and c-axis of the crystal, making a 45° angle with the a-axis and also a certain angle with the c-axis; "2.4Å×3.5Å": It is the pore size of the 7-membered ring pore channels, indicating that in the direction perpendicular to the 7-membered ring pore channels, the cross-sectional shape of the pore channels is approximately rectangular or elliptical, etc., and the dimensions in two perpendicular directions are 2.4Å and 3.5Å respectively, where Å (angstrom) is a unit of length, 1Å = 10 -10 meters; "3.7Å×5.3Å": It is the pore size of the 9-membered ring pore channels, indicating that on the cross-section perpendicular to the 9-membered ring pore channels themselves, the dimensions in two main directions are 3.7Å and 5.3Å respectively, which are larger than the pore size of the 7-membered ring pore channels; "The 7-membered ring pore channels are in the direction directly facing the air flow direction": It means that in the crystal structure, the axial direction of the pore channels formed by the 7-membered rings is parallel to the flow direction of the air flow, and the air flow can directly enter or pass through the pore channels along the direction of the 7-membered ring pore channels; "The 9-membered ring pore channels are in the direction directly facing the air flow direction": It means that in the crystal structure, for the pore channels formed by the ring structure connected by 9 tetrahedral structural units, their axial direction is parallel to the flow direction of the air flow, that is, the flow direction of the air flow is consistent with the extension direction of the 9-membered ring pore channels.

[0023] According to the first aspect of the present invention, a method for preparing a gas separation membrane for an automobile exhaust pipe is provided, which is made by modifying the surface of an SSZ-23 molecular sieve membrane with a specific pore structure. Among them, the SSZ-23 molecular sieve membrane is made by the specific preparation method of the present invention, and its specific pore structure includes 9-membered rings and 7-membered rings. The 7-membered ring pore channels are parallel to the

[001] direction (as Figure 2 shown), with a pore size of 2.4Å×3.5Å; the 9-membered ring pore channels are parallel to the

[101] direction (as Figure 3As shown in the figure, the pore size is 3.7 Å × 5.3 Å, and its preparation method is as follows: A porous α-aluminum oxide substrate with a pore size of 100 - 200 nm is used, and N, N, N-trimethyl-1-adamantylammonium hydroxide (TMAdaOH) is used as a template agent; a precursor solution is prepared according to SiO2:Al2O3:TMAdaOH:NaOH:H2O = 1:0.02:0.2:0.1:40. First, the silicon source (tetraethyl orthosilicate) is slowly added to deionized water and stirred for 30 minutes; then the aluminum source (aluminum nitrate) is added and stirring continues for 30 minutes; then the template agent (TMAdaOH) and the base source (NaOH) are added and stirred until completely dissolved. After that, the mixed solution is left to age at room temperature for 24 hours to allow the precursor to hydrolyze fully. The pretreated substrate is vertically placed into a polytetrafluoroethylene-lined autoclave, and then the aged precursor solution is poured into the autoclave to ensure that the substrate is completely immersed; then a cordierite membrane (whose outer surface is tightly wrapped with polytetrafluoroethylene tape so that zeolite crystals grow only on the inner surface of the tube) is vertically fixed in the autoclave, the autoclave is sealed, placed in an oven, and hydrothermally reacted at 150 - 170 °C for 48 - 72 hours. After the reaction is completed, it is naturally cooled to room temperature. The substrate is taken out, repeatedly rinsed with deionized water to remove unreacted particles on the surface, dried in an oven at 80 °C for 6 hours, and the dried membrane is placed in a muffle furnace and heated to 550 °C at a heating rate of 1 °C / min and calcined for 6 hours to remove the template agent (TMAdaOH), thus obtaining the SSZ-23 zeolite membrane with a specific pore structure.

[0024] Specifically, the cordierite ceramic membrane layer is prepared by the dip-coating method. 10 g of cordierite powder is added to 100 mL of deionized water, 0.5 - 1 g of polyvinylpyrrolidone dispersant and 0.5 - 1 g of polyvinyl alcohol binder are added, stirred and ultrasonically treated for 1 hour to ensure uniform dispersion of cordierite. The viscosity of the sol is adjusted to 10 - 50 mPa·s, the porous α-aluminum oxide substrate is vertically immersed in the cordierite precursor sol for 30 - 60 seconds, and then the substrate is vertically pulled out of the sol at a constant speed of 1 - 5 mm / s. The pulled substrate is left to stand at room temperature for 10 - 15 minutes to allow the solvent to volatilize and form a preliminary wet membrane; then the wet membrane is dried in an oven at 80 °C for 2 hours to remove the residual solvent, and then the dried membrane is placed in a muffle furnace and heated to 1200 - 1300 °C at a heating rate of 1 - 2 °C / min and held for 2 - 4 hours to form a dense cordierite ceramic membrane.

[0025] Based on the above solutions, the gas separation membrane for automobile exhaust pipes described in the present invention includes, but is not limited to, any one of the M1-H2O separation membrane (for separating H2O), M2-N2 / O2 / CO2 separation membrane (for separating N2, O2, and CO2), M3-CO2 separation membrane (for separating CO2), and M4-N2 / O2 separation membrane (for separating N2 and O2).

[0026] M1-H2O separation membrane material: The 7-membered ring pore direction of the SSZ-23 zeolite membrane is facing the gas flow direction. On this direction, it is modified with nano-silica to form a hydrophilic surface layer for H2O, and the 7-membered ring pores are modified by the silanization method to make its pore diameter d < 3.3 Å < dCO2; the specific preparation method is as follows: Using the silanization method, 3-aminopropyltriethoxysilane (APTES) is used as the silanization reagent to modify the 7-membered ring pores. First, APTES is dissolved in absolute ethanol at a volume ratio of 1-5%, then the dried SSZ-23 is added to the silanization solution, and stirred at 60-80 °C for 6-12 hours, then washed 3 times with absolute ethanol to remove the unreacted silanization reagent, and dried at 80 °C for 6 hours. Then, nano-silica is dispersed in deionized water at a concentration of 1 wt.%, ultrasonically treated for 30 minutes, then the silanized SSZ-23 is added to the dispersion, stirred for 2-4 hours, dried at 80 °C for 6 hours, and finally calcined at 300 °C for 2 hours to enhance the binding force.

[0027] M2-N2 / O2 / CO2 separation membrane material: The 9-membered ring pore direction of the SSZ-23 zeolite membrane is facing the gas flow direction. On this direction, it is modified with graphite nano-materials to form a hydrophobic surface layer for H2O, and its pore diameter d > 3.7 Å > d N2 ; the specific preparation method is as follows: Using octadecyltrimethoxysilane (ODTMS) as the silanization reagent, first, graphene nanosheets or graphene oxide (10-20 mg) are added to absolute ethanol (100 mL), ultrasonically treated for 1 hour to ensure the uniform dispersion of the graphite nano-materials, then the SSZ-23 membrane is immersed in the graphite nano-material dispersion, impregnated at room temperature for 12-24 hours to make the graphite nano-materials uniformly adhere to the membrane surface, then the membrane is taken out, rinsed with absolute ethanol to remove the unadhered graphite nano-materials, and dried in an 80 °C oven for 6 hours, and finally the membrane is calcined at 300 °C for 2 hours to enhance the binding of the graphite nano-materials to the zeolite.

[0028] M3-CO2 separation membrane material: The 9-membered ring pore direction of the SSZ-23 zeolite membrane is facing the gas flow direction. On this direction, it is modified with graphene nano-materials to form a CO2-philic surface layer, and the 9-membered ring pores are modified by the silanization method to make its pore diameter d < 3.4 Å < d O2; The specific preparation method is as follows: The 9-membered ring channels are modified with 3-aminopropyltriethoxysilane (APTES) as the silylating agent. First, APTES is dissolved in absolute ethanol at a volume ratio of 1-5%, and then the dried SSZ-23 is added to the silylation solution. Stir at 60-80 °C for 6-12 hours to ensure that APTES reacts with the hydroxyl groups on the surface of the molecular sieve to form covalent bonds. Then wash with absolute ethanol three times to remove the unreacted silylating agent, and dry at 80 °C for 6 hours. Next, graphene oxide (10-20 mg) is added to absolute ethanol (100 mL), and ultrasonic treatment is carried out for 1 hour to ensure uniform dispersion of graphene. Then the dispersion is mixed with an amino-functionalized reagent (such as ethylenediamine) at a ratio of 1:10 and stirred at 60 °C for 6 hours for surface modification. After that, the silylation-modified SSZ-23 membrane is immersed in the graphene nanomaterial dispersion and impregnated at room temperature for 12-24 hours to make graphene uniformly adhere to the membrane surface and inside the pores. Then the membrane is taken out, rinsed with absolute ethanol to remove the unadhered graphene, and dried in an oven at 80 °C for 6 hours. Finally, the membrane is calcined at 300 °C for 2 hours to enhance the binding between graphene and the molecular sieve.

[0029] M4-N2 / O2 separation membrane material: The 9-membered ring channels of the SSZ-23 molecular sieve membrane are oriented perpendicular to the gas flow direction. In this direction, the cationic zeolite Na-Y is used to modify the surface layer to be hydrophilic to O2 and N2, so that the pore diameter d > 3.7 Å > d N2 ; The specific preparation method is as follows: First, Na-Y zeolite (10-20 mg) is added to deionized water (100 mL), and 0.1-0.5 g of polyvinylpyrrolidone dispersant is added. Ultrasonic treatment is carried out for 1 hour to ensure uniform dispersion of Na-Y zeolite. Then the SSZ-23 membrane is immersed in the Na-Y zeolite dispersion and impregnated at room temperature for 12-24 hours to make Na-Y zeolite uniformly adhere to the membrane surface and inside the pores. Then the membrane is taken out from the dispersion, rinsed with deionized water to remove the unadhered Na-Y zeolite, and then dried in an oven at 80 °C for 6 hours. Finally, the membrane is calcined at 300 °C for 2 hours to enhance the binding between Na-Y zeolite and the molecular sieve.

[0030] According to the second aspect of the present invention, there is provided a gas separation membrane for an automobile exhaust pipe prepared by the above preparation method.

[0031] According to the third aspect of the present invention, there is provided an automobile exhaust pipe, which uses the above gas separation membrane for an automobile exhaust pipe, and the specific structure is as Figure 1As shown in the figure: it includes the main exhaust pipe 1 connected to the vehicle engine, the H2O exhaust pipe 2, the CO2 exhaust pipe 3, and the N2 / O2 exhaust pipe 4; the H2O exhaust pipe 2 and the CO2 exhaust pipe 3 are respectively communicated with the main exhaust pipe 1, the N2 / O2 exhaust pipe 4 is arranged upstream of the exhaust port of the CO2 exhaust pipe 3 and is communicated with the CO2 exhaust pipe 3; the exhaust ports of the H2O exhaust pipe 2, the CO2 exhaust pipe 3, and the N2 / O2 exhaust pipe 4 are respectively communicated with the outside atmosphere; It should be noted that the purpose of the present invention is to separate CO2 from the exhaust mixture. Compared with the existing method of directly adsorbing and separating CO2 from the exhaust mixture using an adsorbent, it helps the adsorbent to adsorb and utilize CO2. If considering the adsorption and utilization of CO2, a conventional adsorption device needs to be connected.

[0032] An M1-H2O separation membrane is provided at the connection between the H2O exhaust pipe 2 and the main exhaust pipe 1, an M2-N2 / O2 / CO2 separation membrane is provided at the connection between the CO2 exhaust pipe 3 and the main exhaust pipe 1, an M3-CO2 separation membrane is provided at the exhaust port of the CO2 exhaust pipe 3, and an M4-N2 / O2 separation membrane is provided at the connection between the N2 / O2 exhaust pipe 4 and the CO2 exhaust pipe 3.

[0033] In the present invention, let the exhaust component concentration be represented by c, the exhaust component mass be represented by m, and the exhaust velocity be represented by v The concentrations corresponding to N2, O2, H2O, and CO2 are respectively represented as: c , quality 、c N2 、c O2 、c H2O 、c CO2 , and the masses are respectively represented as: m N2 、m O2 、m H2O 、m CO2 . The relationship between D1, D2, D3, and D4 is: D1>D2, D1>D3, D3>D2>D4.

[0034] The relationship between D2 and D3 is designed according to the following formula: Or .

[0035] The relationship between D3 and D4 is designed according to the following formula: Or .

[0036] δ1, δ2, δ3, and δ4 are respectively the thicknesses of the separation membranes M1, M2, M3, and M4 in the engine exhaust pipe. δ1, δ2, δ3, and δ4 are all calculated according to the following formula: ; ΔP is the pressure difference across the membrane, determined according to the exhaust performance requirements of the engine; A is the membrane area, , D is determined according to the exhaust pipe diameter and in accordance with the design requirements of the exhaust pipe; σ is the anti-tear strength of the membrane, evaluated by three-point anti-tear test or four-point anti-tear test; η is the permeability coefficient, η = 0.95 - 1 (obtained by experimentally measuring the exhaust component concentrations on both sides of the membrane according to the formula of membrane thickness δ).

[0037] All membranes are separation membranes made of nanomaterials. Under the action of pressure difference and molecular polarity, the separation of CO2 is achieved. The pore diameter of the separation membrane is represented by d, and the molecular dynamic diameters of N2, O2, H2O, and CO2 are respectively expressed as: d N2 , d O2 , d CO2 , d H2O , N2, O2, and CO2 are non-polar molecules, and H2O is a polar molecule. From the molecular properties: d N2 > d O2 > d CO2 > d H2O .

[0038] The membrane layer material for M1 to separate H2O should satisfy: d N2 > d O2 > d CO2 > d > d H2O ; The membrane layer material for M2 to separate N2, O2, and CO2 should satisfy: d > d N2 > d O2 > d CO2 ; The membrane layer material for M3 to separate CO2 should satisfy: d N2 > d O2 > d > d CO2 > d H2O ; The membrane layer material for M4 to separate O2 and N2 should satisfy: d > d N2 > d O2 > d CO2 > d H2O ; Separation of N2, O2, H2O, and CO2: M1 separates H2O: d > d H2O ; H2O has an adhesion force F1 and surface tension f 1: F1 > f 1; The pressure difference ΔP across the membrane satisfies: ΔP = P1 - P2 > 0; H2O passes through the membrane. d N2 > d O2 > d CO2>d, N2, O2, and CO2 cannot pass through the membrane.

[0039] M2 separates N2, O2, and CO2: ΔP = P1 - P3 > 0; d > d N2 >d O2 >d CO2 , N2, O2, H2O, and CO2 can all pass through the membrane. However, H2O has an adhesion force F2 and surface tension on the surface of the membrane f 2: F2 < f 2; preventing H2O from passing through the membrane.

[0040] M3 separates CO2: ΔP = P3 - P2 > 0; CO2 has an adhesion force F3 and surface tension on the surface of the membrane f 3: F3 > f 3; d > d CO2 ; CO2 can pass through the membrane. d N2 >d O2 >d, N2 and O2 cannot pass through the membrane.

[0041] M4 separates O2 and N2: ΔP = P3 - P2 > 0; d > d N2 >d O2 ; N2, O2, H2O, and CO2 can all pass through the membrane. However, CO2 has an adhesion force F4 and surface tension on the surface of the membrane f 4: F4 < f 4; preventing CO2 from passing through the membrane.

[0042] Finally, N2 is separated from O2, H2O, and CO2 through three different exhaust ports. The automotive exhaust pipe of the present invention, through the technology of combining its specific structure with the separation membrane, solves the technical problem of CO2 separation in engine carbon emission capture control; moreover, it has a simple structure and is suitable for application in vehicle exhaust systems.

[0043] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a gas separation membrane for an automobile exhaust pipe, characterized in that, It is made by modifying the surface of an SSZ-23 molecular sieve membrane with a specific pore structure.

2. The preparation method according to claim 1, wherein The preparation method of the SSZ-23 molecular sieve membrane with a specific pore structure includes the following steps: S1. First, add a silicon source to water and stir, then add an aluminum source and stir, and then add a template agent and an alkali source and stir until completely dissolved to obtain a mixed solution; S2. Let the mixed solution obtained in step S1 stand and age at room temperature for a period of time to fully hydrolyze the precursor, obtaining an aged precursor solution; S3. Vertically place the substrate into a high-pressure autoclave lined with polytetrafluoroethylene, pour the aged precursor solution obtained in step S2 and immerse the substrate, then vertically fix the ceramic membrane in the high-pressure autoclave. After sealing the high-pressure autoclave, carry out a hydrothermal reaction under certain conditions; S4. After the hydrothermal reaction is completed, take out the substrate, rinse it with deionized water, and dry it under certain conditions; then put the dried membrane into a muffle furnace and calcine it under certain conditions to remove the template agent, obtaining the SSZ-23 molecular sieve membrane with a specific pore structure.

3. The preparation method according to claim 2, wherein In step S1, the silicon source is SiO2, the aluminum source is Al2O3, the template agent is N,N,N-trimethyl-1-adamantylammonium hydroxide, and the alkali source is NaOH; the mass ratio of SiO2, Al2O3, N,N,N-trimethyl-1-adamantylammonium hydroxide, NaOH, and water is 1:0.02:0.2:0.1:40; And / or, in step S3, the substrate uses a porous α-aluminum oxide substrate with a pore diameter of 100-200 nm; the ceramic membrane is a cordierite ceramic membrane; the conditions of the hydrothermal reaction are: hydrothermal reaction at 150-170 °C for 48-72 h; And / or, in step S4, the drying conditions are: drying in an 80 °C oven for 6 hours; the calcination conditions are: heating to 550 °C at a heating rate of 1 °C / min and calcining for 6 hours.

4. The preparation method according to claim 1, characterized in that, The gas separation membrane for the automobile exhaust pipe includes any one of an H2O separation membrane, an N2 / O2 / CO2 separation membrane, a CO2 separation membrane, and an N2 / O2 separation membrane.

5. The preparation method according to claim 4, characterized in that, The preparation method of the H2O separation membrane includes the following steps: (1) Add 3-aminopropyltriethoxysilane in a volume ratio of 1-5% and dissolve it in absolute ethanol to obtain a silanized solution; (2) Add the SSZ-23 molecular sieve membrane with a specific pore structure to the silanized solution, stir at 60-80 °C for 6-12 h, wash with absolute ethanol, and then dry to obtain a silanized molecular sieve; (3) Disperse nano-silica in deionized water and perform ultrasonic treatment to obtain a nano-dispersion liquid. Then add the alkylated molecular sieve to the nano-dispersion liquid, stir evenly, and then obtain the material of the H2O separation membrane after drying and calcination; And / or, the preparation method of the N2 / O2 / CO2 separation membrane includes the following steps: (1) Add 10-20 mg of graphene nanosheets or graphene oxide to 100 mL of absolute ethanol and perform ultrasonic treatment to obtain a graphite nano-dispersion liquid; (2) Immerse the SSZ-23 molecular sieve membrane with a specific pore structure in the graphite nano-dispersion liquid. After impregnation at room temperature for 12 - 24 h, take out the membrane, rinse it with absolute ethanol, and then obtain the N2 / O2 / CO2 separation membrane after drying and calcination; And / or, the preparation method of the CO2 separation membrane includes the following steps: (1) Add 3-aminopropyltriethoxysilane in a volume ratio of 1 - 5% and dissolve it in absolute ethanol to obtain a silanization solution; (2) Add the SSZ-23 molecular sieve membrane with a specific pore structure into the silanization solution, stir at 60 - 80 °C for 6 - 12 h, wash it with absolute ethanol, and then dry it to obtain the silanized molecular sieve; (3) Add 10 - 20 mg of graphene oxide to 100 mL of absolute ethanol, perform ultrasonic treatment, then add an amination reagent, and stir at 60 °C for 6 h to obtain a graphite nano-dispersion liquid; (4) Immerse the silanized molecular sieve in the graphite nano-dispersion liquid. After impregnation at room temperature for 12 - 24 h, take out the membrane, rinse it with absolute ethanol, and then obtain the CO2 separation membrane after drying and calcination; And / or, the preparation method of the N2 / O2 separation membrane includes the following steps: (1) Add 10 - 20 mg of Na-Y zeolite to 100 mL of absolute ethanol, add 0.1 - 0.5 g of polyvinylpyrrolidone dispersant, and perform ultrasonic treatment to obtain a Na-Y zeolite dispersion liquid; (2) Immerse the SSZ-23 molecular sieve membrane with a specific pore structure in the Na-Y zeolite dispersion liquid. After impregnation at room temperature for 12 - 24 h, take out the membrane, rinse it with absolute ethanol, and then obtain the N2 / O2 separation membrane after drying and calcination.

6. A gas separation membrane for an automobile exhaust pipe prepared by the preparation method according to any one of claims 1 - 5.

7. An automobile exhaust pipe, characterized in that, It includes a main exhaust pipe connecting to an automobile engine, an H2O exhaust pipe, a CO2 exhaust pipe, and an N2 / O2 exhaust pipe; the H2O exhaust pipe and the CO2 exhaust pipe are respectively communicated with the main exhaust pipe, the N2 / O2 exhaust pipe is arranged upstream of the exhaust port of the CO2 exhaust pipe and is communicated with the CO2 exhaust pipe; the exhaust ports of the H2O exhaust pipe, the CO2 exhaust pipe, and the N2 / O2 exhaust pipe are respectively communicated with the outside atmosphere; An H2O separation membrane is arranged at the connection between the H2O exhaust pipe and the main exhaust pipe, an N2 / O2 / CO2 separation membrane is arranged at the connection between the CO2 exhaust pipe and the main exhaust pipe, a CO2 separation membrane is arranged at the exhaust port of the CO2 exhaust pipe, and an N2 / O2 separation membrane is arranged at the connection between the N2 / O2 exhaust pipe and the CO2 exhaust pipe.

8. The automotive exhaust pipe according to claim 7, wherein, The relationship between the diameter D1 of the main exhaust pipe, the diameter D2 of the H2O exhaust pipe, the diameter D3 of the CO2 exhaust pipe, and the diameter D4 of the N2 / O2 exhaust pipe is D1 > D2, D1 > D3, D3 > D2 > D4; The relationship between the diameter D2 of the H2O exhaust pipe and the diameter D3 of the CO2 exhaust pipe is calculated according to the following formula: or ; The relationship between the diameter D3 of the CO2 exhaust pipe and the diameter D4 of the N2 / O2 exhaust pipe is calculated according to the following formula: or ; Where c N2 , c O2 , c H2O , c CO2 are the concentrations of N2, O2, H2O, and CO2 respectively; m N2 , m O2 , m H2O , m CO2 are the masses of N2, O2, H2O, and CO2 respectively.

9. The motor vehicle exhaust pipe according to claim 7, characterized in that, The thicknesses δ1 of the H2O separation membrane, δ2 of the N2 / O2 / CO2 separation membrane, δ3 of the CO2 separation membrane, and δ4 of the N2 / O2 separation membrane are all calculated according to the following formula: ； In the formula, △P is the pressure difference across the membrane; A is the membrane area; σ is the breaking strength of the membrane; η is the permeability coefficient, where η = 0.95 - 1.

10. The automotive exhaust pipe according to claim 7, characterized in that, The relationship between the pore diameter d1 of the H2O separation membrane and the molecular dynamic diameters dN2 of N2, dO2 of O2, dH2O of H2O, and dCO2 of CO2 is dN2 > dO2 > dCO2 > d1 > dH2O; And / or, the pore diameter d2 of the N2 / O2 / CO2 separation membrane and the molecular dynamic diameters d N2 of N2, d O2 of O2, and d CO2 of CO2 satisfy the relationship: d2 > d N2 > d O2 > d CO2 ; and / or, the pore diameter d3 of the CO2 separation membrane and the molecular dynamic diameters d N2 of N2, d O2 of O2, d H2O of H2O, d CO2 of CO2 satisfy the relationship d N2 > d O2 > d3 > d CO2 > d H2O ; and / or, the pore diameter d4 of the N2 / O2 separation membrane and the molecular dynamic diameters d N2 of N2, d O2 of O2, d H2O of H2O, d CO2 of CO2 satisfy the relationship d4 > d N2 > d O2 > d CO2 > d H2O .

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