Carbon dioxide separation membrane as well as preparation method and application thereof

Abstract

The invention relates to a carbon dioxide separation membrane as well as a preparation method and application thereof. The carbon dioxide separation membrane is prepared from cucurbit [7] uril CB [7] and a dual-network hydrogel polymer matrix, the dual-network hydrogel polymer matrix is formed by carrying out ultraviolet polymerization on a first network monomer and a second network monomer; the first network monomer is 2-acrylamide-2-methyl propane sulfonic acid (AMPS); and the second network monomer is N, N-dimethylacrylamide DMAAm (N, N-dimethylacrylamide). The CB [7] inherent nanopore channel and an additional channel formed by the CB [7] and a polymer chain interface cooperatively construct an efficient CO2 transmission path, and meanwhile, the CO2 permeability and CO2 / CH4 selectivity of the membrane are improved; the separation membrane is simple in preparation method and stable in performance, and has a wide application prospect in the field of carbon dioxide separation such as biogas upgrading.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane technology, and specifically relates to a carbon dioxide separation membrane, its preparation method, and its application. Background Technology

[0002] With the increasing demand for renewable energy, biogas derived from organic waste has attracted much attention as an important transitional energy source. However, biogas typically contains 30-45% carbon dioxide by volume, which not only reduces its calorific value but also causes corrosion of pipelines, thus necessitating efficient upgrading technologies. Among numerous gas separation technologies, membrane separation has been widely studied due to its advantages such as low energy consumption, simple operation, and environmental friendliness.

[0003] Currently, commercially available gas separation membranes are mainly polymer membranes. However, the overall performance of these polymer membranes is limited by the inherent trade-off between permeability and selectivity (i.e., the Robeson upper limit), making it difficult to meet the application requirements of high-end gas separation scenarios. To overcome these performance bottlenecks, mixed matrix membranes (MMMs) have been proposed and gradually developed. Their core is to organically combine the excellent processing and molding properties of polymer matrices with the unique molecular sieving characteristics of inorganic or porous fillers, thereby achieving a synergistic improvement in membrane material performance. Currently, commonly used fillers in the preparation of mixed matrix membranes include zeolites, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). However, most existing mixed matrix membranes generally suffer from technical problems during preparation and application, such as uneven dispersion of fillers in the polymer matrix, poor compatibility between fillers and the polymer matrix, and the tendency for non-selective defects to form at the interface. These issues make it difficult to further optimize the separation performance of mixed matrix membranes, severely restricting their large-scale promotion and practical application.

[0004] Cucurbituril (CB[n]) is a class of organic macrocyclic molecules with rigid cavities and large port diameters. It exhibits a specific adsorption affinity for CO2 molecules, mainly due to the dipole-quadrupole interaction between the port carbonyl group and CO2. In particular, CB[7] has good water solubility, which is conducive to achieving uniform dispersion in hydrophilic polymer matrices. If it can be introduced into a suitable polymer matrix as a functional filler, it is expected to construct an efficient and defect-free CO2 transport channel and prepare a separation membrane with excellent performance. However, there are currently few studies on the application of CB[7] in gas separation membranes, especially for CO2 / CH4 separation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a carbon dioxide separation membrane, its preparation method and application, which effectively solves the problems of filler agglomeration and interface defects in traditional mixed matrix membranes.

[0006] The present invention provides a carbon dioxide separation membrane, which is prepared by cucurbita[7]urea CB[7] and a dual-network hydrogel polymer matrix; the dual-network hydrogel polymer matrix is ​​formed by ultraviolet light polymerization of a first network monomer and a second network monomer; the first network monomer is 2-acrylamide-2-methylpropanesulfonic acid AMPS; the second network monomer is N,N-dimethylacrylamide DMAAm.

[0007] Preferably, the dual-network hydrogel polymer matrix is ​​a PAMPS / PDMAAm hydrogel.

[0008] Preferably, the loading of CB[7] is 10-30 mg / mL.

[0009] The present invention also provides a method for preparing a carbon dioxide separation membrane, comprising the following steps:

[0010] (1) Dissolve the first network monomer, crosslinking agent, photoinitiator and CB[7] in deionized water and sonicate to form a uniform first network precursor solution;

[0011] (2) The first network precursor solution is injected into a mold and polymerized under ultraviolet light to form a first network hydrogel;

[0012] (3) The first network hydrogel is immersed in an aqueous solution containing the second network monomer, photoinitiator and swelling inhibitor; then the hydrogel after immersion equilibrium is placed under ultraviolet light to irradiate and polymerize to form a double network structure, thus obtaining a carbon dioxide separation membrane.

[0013] Preferably, the crosslinking agent in step (1) is N,N'-methylenebisacrylamide (MBAA); and the photoinitiator is 2-oxoglutaric acid (OA).

[0014] Preferably, the mass ratio of the first network monomer, crosslinking agent, photoinitiator and CB[7] in step (1) is 1-2g:0.01-0.05g:0.0001-0.001g:0.05-0.15g.

[0015] Preferably, the photoinitiator in step (3) is 2-oxoglutaric acid (OA); the swelling inhibitor is sodium chloride, in order to prevent the first network hydrogel film from rupturing.

[0016] Preferably, the mass ratio of the second network monomer, photoinitiator and swelling inhibitor in step (3) is 30-40g:0.01-0.1g:1-5g.

[0017] Preferably, the ultraviolet light wavelength in steps (2) and (3) is 365 nm, and the irradiation time is 1-5 h.

[0018] The present invention also provides an application of a carbon dioxide separation membrane in gas separation, particularly in the separation of carbon dioxide from methane-containing gases (such as biogas). Preferably, the separation process is carried out under anhydrous conditions.

[0019] The carbon dioxide separation membrane provided by this invention adopts a composite technology of CB[7] and dual-network hydrogel. CB[7] is a macrocyclic molecule with rigid cavity and water solubility. With its specific adsorption affinity for CO2 and inherent nanopores, it serves as a functional filler for efficient CO2 transport channels. The preferred polymer matrix is ​​a PAMPS / PDMAAm dual-network hydrogel formed by ultraviolet light polymerization. Through screening the amount of CB[7] added and optimizing the preparation process, the dispersion state of CB[7] in the gel matrix and the microenvironment within the membrane can be precisely controlled, thereby synergistically improving the CO2 transport efficiency and sieving capacity, and preparing a separation membrane with high CO2 permeability and high CO2 / CH4 selectivity.

[0020] Beneficial effects

[0021] (1) This invention utilizes the water solubility of CB[7] and uses in-situ ultraviolet light polymerization to uniformly fix it in a double network hydrogel matrix, which effectively avoids the common problems of filler agglomeration and interface defects in traditional mixed matrix membranes, and ensures the compactness and uniformity of the membrane structure.

[0022] (2) The inherent nanoscale pores of CB[7] molecules can serve as efficient CO2 molecule transport channels; at the same time, the interface region between CB[7] and the polymer chain forms an additional CO2 affinity transport path; the selective adsorption capacity of CB[7] for CO2 further enhances the transport selectivity of CO2 relative to CH4.

[0023] (3) The introduction of CB[7] increases the water holding capacity of the hydrogel membrane, while water molecules, as plasticizers, can increase the polymer chain spacing, reduce the transport resistance of CO2, and form a water-mediated transport-promoting mechanism, thereby synergistically improving the permeation flux and selectivity of CO2.

[0024] (4) Experiments show that the CO2 permeability of the carbon dioxide separation membrane prepared by the present invention can reach more than 927 Barrer and the CO2 / CH4 selectivity can reach more than 81.5, which exceeds the Robeson upper limit in 2019. It also has excellent long-term operational stability and pressure tolerance, showing great application potential in carbon capture fields such as biogas upgrading. Attached Figure Description

[0025] Figure 1 This is the reaction equation for the first network hydrogel of the present invention.

[0026] Figure 2 The images in the middle are SEM images of the heat-dried and freeze-dried sections of the PAMPS / PDMAAm membrane and the PAMPS / PDMAAm / CB[7]-30 mg / ml membrane in the examples.

[0027] Figure 3 The transmittance of the PAMPS / PDMAAm membrane and the PAMPS / PDMAAm / CB[7]-x mg / ml membrane in the examples is shown.

[0028] Figure 4 The infrared spectra of the PAMPS / PDMAAm membrane and the PAMPS / PDMAAm / CB[7]-x mg / ml membrane in the examples are shown.

[0029] Figure 5 This is a schematic diagram of a gas separation device.

[0030] Figure 6 The figure shows the CO2 / CH4 separation performance of the PAMPS / PDMAAm / CB[7]-x mg / ml membrane in the example. Detailed Implementation

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] Example 1

[0033] This embodiment provides a method for preparing a carbon dioxide separation membrane, including the following steps:

[0034] (1) such as Figure 1 As shown, the first network precursor solution was prepared by dissolving 1.03625 g of AMPS in 5 mL of deionized water, followed by adding 0.03083 g of crosslinking agent MBAA and 0.0007 g of photoinitiator OA; then adding CB[7] (x=0,0.05, 0.10, 0.15 g, i.e., the concentration of CB[7] is 0, 10, 20, 30 mg / mL) to the above solution and sonicating for 30 min to completely dissolve and disperse it.

[0035] (2) The first network precursor solution was injected into a mold composed of two glass plates and irradiated under 365 nm ultraviolet light for 3 h to complete the polymerization of the first network hydrogel film.

[0036] (3) The obtained first network hydrogel was immersed in an aqueous solution containing 396.5 mg / mL of the second network monomer DMAAm, 0.58 mg / mL of the photoinitiator OA and 29.2 mg / mL of NaCl for 3 h; NaCl was used to inhibit the excessive swelling of the first network in the monomer solution.

[0037] (4) The hydrogel after equilibrium was irradiated again under 365 nm ultraviolet light for 3 h to form a double network structure, and finally carbon dioxide separation membranes were obtained, which were named PAMPS / PDMAAm membrane, PAMPS / PDMAAm / CB[7]-10 mg / ml membrane, PAMPS / PDMAAm / CB[7]-20 mg / ml membrane and PAMPS / PDMAAm / CB[7]-30 mg / ml membrane respectively.

[0038] Example 2

[0039] The carbon dioxide separation membrane prepared in Example 1 was characterized as follows.

[0040] (1) Morphological observation (SEM): The morphology of this carbon dioxide separation membrane was characterized by observation on a JEOL JSM-7600F field emission scanning electron microscope, such as... Figure 2 As shown, the results indicate that the carbon dioxide separation membrane maintains a dense structure and CB[7] does not exhibit agglomeration.

[0041] (2) Transmittance: The transmittance of this carbon dioxide separation membrane was tested using a Hitachi UV-3010 ultraviolet-visible spectroscopy system in Japan. Figure 3 As shown, the results show that the transmittance of the carbon dioxide separation membrane in the visible light region increases, and CB[7] has good compatibility with the dual-network hydrogel polymer matrix.

[0042] (3) Chemical structure: The chemical structure of this carbon dioxide separation membrane was determined using Shimadzu IRAffinity-1S Fourier transform infrared spectroscopy, such as... Figure 4 As shown, the result is at 1739 cm. -1 The characteristic carbonyl peak of CB[7] appeared at the point, confirming that CB[7] has been successfully introduced into the carbon dioxide separation membrane.

[0043] Example 3

[0044] Performance testing of carbon dioxide separation membranes:

[0045] Simulated biogas is produced by using a CO2 / CH4 mixture (volume ratio 3:7) and passing it through a gas separation device. Figure 5The composition of the permeated gas was analyzed using a gas chromatograph (Agilent 8860) to evaluate the performance of the carbon dioxide separation membrane prepared in Example 1. The feed pressure was 75 cmHg, pure nitrogen was used as the scavenging gas, and the volumetric flow rate was 20 mL / min. The process was carried out at 20°C under anhydrous conditions.

[0046] The main tests cover the following aspects:

[0047] (1) Gas permeability: The gas permeability of the membrane material is tested by common gas permeation method, and CO2 and CH4 are measured to evaluate the membrane flux.

[0048] The permeability coefficient P of gas i i (Unit: barrer, 1 barrer = 10) -10 cm 3 (STP)cm / (cm) 2 The ·s·cmHg) is calculated using formula (Ⅰ):

[0049] (I)

[0050] Among them, Q i (Unit: cm) 3 (STP) / s) is the volumetric flow rate, l (unit: cm) is the membrane thickness, and ΔP i (Unit: cmHg) is the partial pressure difference of gas i, A (unit: cm 2 () is the effective membrane area.

[0051] Experimental results are as follows Figure 6 As shown, specifically, at a pressure of 75 cmHg, the CO2 permeability coefficient after the mixed gas permeates the PAMPS / PDMAAm / CB [7]-30 mg / mL membrane is 927.2 Barrer.

[0052] (2) Selectivity: The separation selectivity of the membrane for CO2 / CH4 was determined, and the separation selectivity factor was calculated. The selectivity factor (αi / j) of the CO2 / CH4 pair was calculated using formula (II):

[0053] (II)

[0054] Experimental results are as follows Figure 6 As shown, specifically, at a pressure of 75 cmHg, the CO2 / CH4 selectivity factor was 81.5 after the mixed gas permeated the PAMPS / PDMAAm / CB [7]-30 mg / mL membrane.

[0055] The experimental results above show that the membrane of the present invention has excellent selectivity for carbon dioxide.

Claims

1. A carbon dioxide separation membrane, characterized in that, The carbon dioxide separation membrane is prepared from cucurbit[7]urea CB[7] and a dual-network hydrogel polymer matrix; the dual-network hydrogel polymer matrix is ​​formed by ultraviolet light polymerization of a first network monomer and a second network monomer; the first network monomer is 2-acrylamide-2-methylpropanesulfonic acid AMPS; the second network monomer is N,N-dimethylacrylamide DMAAm.

2. The carbon dioxide separation membrane according to claim 1, characterized in that, The dual-network hydrogel polymer matrix is ​​PAMPS / PDMAAm hydrogel.

3. A carbon dioxide separation membrane according to claim 1, characterized in that, The loading of CB[7] is 10-30 mg / mL.

4. A method for preparing a carbon dioxide separation membrane as described in claim 1, characterized in that, Includes the following steps: (1) Dissolve the first network monomer, crosslinking agent, photoinitiator and CB[7] in deionized water and sonicate to form a uniform first network precursor solution; (2) The first network precursor solution is injected into a mold and polymerized under ultraviolet light to form a first network hydrogel; (3) The first network hydrogel is immersed in an aqueous solution containing the second network monomer, photoinitiator and swelling inhibitor; then the hydrogel after immersion equilibrium is placed under ultraviolet light to irradiate and polymerize to form a double network structure, thus obtaining a carbon dioxide separation membrane.

5. The preparation method according to claim 4, characterized in that, The crosslinking agent in step (1) is N,N'-methylenebisacrylamide (MBAA); the photoinitiator is 2-oxoglutaric acid (OA).

6. The preparation method according to claim 4, characterized in that, The mass ratio of the first network monomer, crosslinking agent, photoinitiator and CB[7] in step (1) is 1-2g:0.01-0.05g:0.0001-0.001g:0.05-0.15g.

7. The preparation method according to claim 4, characterized in that, The photoinitiator in step (3) is 2-oxoglutaric acid (OA); the swelling inhibitor is sodium chloride.

8. The preparation method according to claim 4, characterized in that, The mass ratio of the second network monomer, photoinitiator and swelling inhibitor in step (3) is 30-40g:0.01-0.1g:1-5g.

9. The preparation method according to claim 4, characterized in that, The ultraviolet light wavelength in steps (2) and (3) is 365 nm, and the irradiation time is 1-5 h.

10. An application of the carbon dioxide separation membrane as described in claim 1 in gas separation.

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