A molecularly imprinted adsorbent, its preparation method and application

Abstract

This invention relates to the field of gas adsorbent materials technology, and discloses a molecularly imprinted adsorbent, its preparation method, and its application. The method includes: (1) mixing adsorbent raw materials with a solvent to obtain intermediate I; (2) spray-drying intermediate I to obtain polymer microspheres; (3) treating the polymer microspheres with supercritical carbon dioxide to obtain intermediate II; and (4) sequentially subjecting intermediate II to initiation treatment and gradient depressurization treatment to obtain the molecularly imprinted adsorbent. The molecularly imprinted adsorbent provided by this invention exhibits high selectivity and high adsorption efficiency for CO2 adsorption.

Description

Technical Field

[0001] This invention relates to the field of gas adsorbent materials technology, specifically to a molecularly imprinted adsorbent, its preparation method, and its application. Background Technology

[0002] In recent years, air pollution and the greenhouse effect caused by the massive emission of carbon dioxide (CO2) have posed a serious threat to the Earth's environment, on which humanity depends for survival. Therefore, the efficient and selective adsorption of CO2 from industrial waste gases, atmospheric mixtures, and other gas mixtures has gradually become a research hotspot.

[0003] Traditional adsorbents have limitations in adsorption selectivity and capacity, making it difficult to meet the growing environmental protection demands. Molecular imprinting (MIT), also known as template molecule technology, is a new technology developed through the interdisciplinary integration of polymer chemistry, biochemistry, chemical engineering, and materials science. MIT can prepare materials with specific recognition and efficient adsorption capabilities for specific target molecules, and this unique advantage has led to its wide application in environmental treatment and analysis.

[0004] Molecularly imprinted CO2 adsorbents are highly efficient adsorbents that selectively adsorb CO2, designed and prepared using molecular self-assembly based on the principles of molecular imprinting technology. They have advantages such as simple adsorbent preparation process, low energy consumption in the desorption process, and selective adsorption.

[0005] CN110743512A discloses a method for preparing a carbon dioxide molecularly imprinted adsorbent, characterized by the following steps: (1) taking sieved sunflower biomass, carbonizing it, and then activating it to obtain activated carbon for later use; (2) using the activated carbon from step (1) as a carrier, adding template molecules and functional monomers dissolved in a mixed solvent, then adding a crosslinking agent and an initiator, sealing the reaction in an inert atmosphere, separating the solid product in the reaction system, washing and drying it to obtain the carbon dioxide molecularly imprinted adsorbent. This method uses activated carbon as a carrier for molecular imprinting materials, providing a large specific surface area, which is beneficial for the loading of imprinted polymers and increases the number of adsorption sites. At the same time, the molecularly imprinted adsorbent prepared by this method has high carbon dioxide selectivity and adsorption efficiency. However, this method uses oxalic acid or oxalic acid as template molecules, and the adsorption rate and adsorption capacity of the obtained molecularly imprinted adsorbent for CO2 are relatively limited.

[0006] Therefore, developing a novel molecularly imprinted adsorbent with high selectivity and adsorption efficiency is of great significance for achieving efficient CO2 adsorption. Summary of the Invention

[0007] The purpose of this invention is to provide a molecularly imprinted adsorbent with high selectivity and high adsorption efficiency for CO2 adsorption.

[0008] To achieve the above objectives, the present invention provides a method for preparing a molecularly imprinted adsorbent, the method comprising:

[0009] (1) The adsorbent raw material is mixed with a solvent to obtain intermediate I; the adsorbent raw material contains a functional monomer, a crosslinking agent, an initiator and a linear polymer in a weight ratio of 1:0.2-0.6:0.02-0.15:0.8-2; the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and tetrahydrofuran;

[0010] (2) The intermediate I is spray-dried to obtain polymer microspheres;

[0011] (3) The polymer microspheres were subjected to supercritical carbon dioxide treatment to obtain intermediate II;

[0012] (4) The intermediate II is subjected to initiation treatment and gradient depressurization treatment in sequence to obtain the molecularly imprinted adsorbent; the conditions of the gradient depressurization treatment include: first depressurizing to 4-7 MPa and holding for 10-20 s, and then depressurizing to 0.1-0.12 MPa.

[0013] A second aspect of the present invention provides a molecularly imprinted adsorbent prepared by the method described in the first aspect above.

[0014] A third aspect of the present invention provides the application of the molecularly imprinted adsorbent described in the second aspect above in the field of CO2 adsorption.

[0015] This invention uses functional monomers, crosslinking agents, initiators, and linear polymers in a weight ratio of 1:0.2-0.6:0.02-0.15:0.8-2 as raw materials for the adsorbent. These materials are first mixed with a solvent, and the resulting mixture is then spray-dried to prepare polymer microspheres. These microspheres are then treated with supercritical carbon dioxide, fully utilizing the triple action of supercritical carbon dioxide as a swelling agent, template molecule, and foaming agent to prepare the molecularly imprinted adsorbent described in this invention. First, the polymer microspheres swell in supercritical carbon dioxide, allowing carbon dioxide molecules to penetrate the interior of the microspheres and contact the functional monomers. The carbon dioxide molecules act as template molecules, completing self-assembly with the functional monomers to form stable molecularly imprinted sites. Second, after energy initiation, the resulting mixture allows the functional monomers to crosslink and copolymerize with the crosslinking agent. Finally, under the specific conditions of this invention, gradient depressurization causes a phase change in the supercritical carbon dioxide, resulting in foaming inside the polymer microspheres. Simultaneously, carbon dioxide molecules are removed from the polymer microspheres, thus obtaining the molecularly imprinted adsorbent with a hierarchical porous structure described in this invention.

[0016] Through the above technical solution, the present invention also has at least the following beneficial effects:

[0017] (1) The molecularly imprinted adsorbent provided by the present invention has a hierarchical porous structure, and its large specific surface area significantly improves the adsorption capacity and adsorption rate of carbon dioxide.

[0018] (2) The molecularly imprinted adsorbent provided by the present invention can adjust its pore structure according to actual application to meet the needs of different application scenarios.

[0019] (3) The molecularly imprinted adsorbent provided by the present invention uses supercritical CO2 as a template molecule and has a high adsorption selectivity for carbon dioxide, which is of great significance for mitigating the greenhouse effect and achieving carbon emission reduction targets. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation process of the molecularly imprinted adsorbent provided by the present invention. Detailed Implementation

[0021] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0022] As previously described, a first aspect of the present invention provides a method for preparing a molecularly imprinted adsorbent, the method comprising:

[0023] (1) The adsorbent raw material is mixed with a solvent to obtain intermediate I; the adsorbent raw material contains a functional monomer, a crosslinking agent, an initiator and a linear polymer in a weight ratio of 1:0.2-0.6:0.02-0.15:0.8-2; the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and tetrahydrofuran;

[0024] (2) The intermediate I is spray-dried to obtain polymer microspheres;

[0025] (3) The polymer microspheres were subjected to supercritical carbon dioxide treatment to obtain intermediate II;

[0026] (4) The intermediate II is subjected to initiation treatment and gradient depressurization treatment in sequence to obtain the molecularly imprinted adsorbent; the conditions of the gradient depressurization treatment include: first depressurizing to 4-7 MPa and holding for 10-20 s, and then depressurizing to 0.1-0.12 MPa.

[0027] Preferably, in step (1), the functional monomer is selected from at least one of acrylamide, methacrylamide and N,N-dimethylacrylamide.

[0028] Preferably, in step (1), the crosslinking agent is selected from dimethyl propylene glycol ester and / or N,N'-methylenebisacrylamide.

[0029] Preferably, in step (1), the initiator is selected from azobisisobutyronitrile and / or benzophenone.

[0030] Preferably, in step (1), the linear polymer is selected from polyvinylidene fluoride and / or polyacrylonitrile.

[0031] More preferably, in step (1), the weight ratio of the adsorbent raw material to the solvent is 1:2.5-4.

[0032] Particularly preferably, in step (1), the mixing conditions include: a temperature of 25-35°C and a time of 4-8 hours.

[0033] In step (1) of the present invention, there are no special requirements for the mixing speed, as long as the adsorbent raw materials are mixed evenly. For example, the mixing speed can be 500-2000 rpm.

[0034] According to a preferred embodiment, in step (2), the conditions for the spray drying process include: an air inlet temperature of 110-130°C, an air outlet temperature of 80-90°C, and a feed rate of 4-6 mL / min.

[0035] According to a more preferred embodiment, in step (3), the conditions for supercritical carbon dioxide treatment include: a pressure of 8-12 MPa, a temperature of 35-45°C, and a time of 2-6 h. The inventors of this invention have discovered that, under this preferred condition, the molecularly imprinted adsorbent prepared according to this invention exhibits a higher carbon dioxide adsorption efficiency.

[0036] According to a preferred embodiment, in step (4), the initiation treatment is photoinitiation treatment and / or thermal initiation treatment; the conditions for photoinitiation treatment include: wavelength of 360-380nm and time of 0.5-2h; the conditions for thermal initiation treatment include: temperature of 60-70℃ and time of 6-30h.

[0037] Preferably, in step (4), the pressure relief rate of the gradient pressure relief process is 1-2 MPa / min.

[0038] According to a particularly preferred embodiment, the preparation process of the molecularly imprinted adsorbent is as follows: Figure 1 As shown, specifically:

[0039] (1) The functional monomers, crosslinking agents, initiators, and linear polymers in a weight ratio of 1:0.2-0.6:0.02-0.15:0.8-2 are mixed with a solvent and stirred at 25-35℃ for 4-8 hours to obtain intermediate I (i.e. Figure 1 (mixed solutions);

[0040] (2) The intermediate I is spray-dried (i.e. granulated) to obtain polymer microspheres; the conditions for spray drying include: inlet temperature of 110-130℃, outlet temperature of 80-90℃, and feed rate of 4-6 mL / min.

[0041] (3) The polymer microspheres are placed in a high-pressure reactor and swollen under supercritical carbon dioxide conditions to obtain intermediate II; the specific conditions of the swelling treatment include: pressure of 8-12 MPa, temperature of 35-45℃, and time of 2-6 h.

[0042] (4) The intermediate II is subjected to initiation treatment and gradient depressurization treatment in sequence to obtain the molecularly imprinted adsorbent; the initiation treatment can be selected from photoinitiation treatment and / or thermal initiation treatment. After the initiation treatment, the functional monomer in intermediate II undergoes cross-linking copolymerization with the cross-linking agent; the conditions for photoinitiation treatment include: wavelength of 360-380nm and time of 0.5-2h; the conditions for thermal initiation treatment include: temperature of 60-70℃ and time of 6-30h; the conditions for gradient depressurization treatment include: first depressurizing to 4-7MPa and holding for 10-20s, and then depressurizing to 0.1-0.12MPa.

[0043] As previously stated, a second aspect of the present invention provides a molecularly imprinted adsorbent prepared by the method described in the first aspect.

[0044] Preferably, the molecularly imprinted adsorbent has a hierarchical porous structure.

[0045] According to a preferred embodiment, the distribution of pores of different sizes in the multi-level pore structure is as follows: the number of micro-mesopores with a channel diameter in the range of 0.1-5 μm accounts for 10-20% of the total number of pores, the number of mesopores with a channel diameter in the range of 5-10 μm accounts for 30-45% of the total number of pores, and the number of pores with a channel diameter of more than 10 μm accounts for 35-60% of the total number of pores.

[0046] As previously stated, a third aspect of the present invention provides the application of the molecularly imprinted adsorbent described in the second aspect above in the field of CO2 adsorption.

[0047] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all instruments and raw materials used are commercially available products.

[0048] Example 1

[0049] (1) Weigh 4g acrylamide, 1.5g dimethyl propylene glycol, 0.1g azobisisobutyronitrile and 5.5g polyvinylidene fluoride, add them to 30mL of N,N-dimethylformamide solution, and stir and mix at 1000rpm for 5h at 30℃ to obtain intermediate I.

[0050] (2) The intermediate I was transferred to a spray dryer, the inlet temperature was set to 120°C, the outlet temperature was set to 80°C, and the feed rate was set to 5 mL / min to obtain polymer microspheres.

[0051] (3) The polymer microspheres were placed in a high-pressure reactor and supercritical carbon dioxide was introduced. The reactor was kept at a pressure of 10 MPa and a temperature of 40 °C for 5 hours to obtain intermediate II.

[0052] (4) The high-pressure reactor is placed at 60°C and the intermediate II is subjected to initiation treatment for 24 hours. Then, the gradient depressurization treatment is started. Specifically, the pressure is adjusted to 6MPa at a depressurization rate of 1.5MPa / min for the first time and held for 10s. Then, the pressure is reduced to 0.1MPa at the same depressurization rate to obtain molecularly imprinted adsorbent-I.

[0053] Example 2

[0054] (1) Weigh 4.5g acrylamide, 2.0g dimethyl propylene glycol, 0.2g benzophenone and 6g polyacrylonitrile, add them to 35mL of N,N-dimethylacetamide, and stir and mix at 1500rpm at 35℃ for 4h to obtain intermediate I.

[0055] (2) The intermediate I was transferred to a spray dryer, the inlet temperature was set to 130°C, the outlet temperature was set to 85°C, and the feed rate was set to 6 mL / min to obtain polymer microspheres.

[0056] (3) The polymer microspheres were placed in a high-pressure reactor and supercritical carbon dioxide was introduced. The reactor was kept at a pressure of 12 MPa and a temperature of 45 °C for 6 hours to obtain intermediate II.

[0057] (4) The intermediate II was subjected to an initiation treatment under light with a wavelength of 365nm for 1h, and then a gradient depressurization treatment was started. Specifically, the pressure was adjusted to 7MPa for the first time, maintained for 10s, and then the pressure was reduced to 0.1MPa for the second time to obtain molecularly imprinted adsorbent-II.

[0058] Example 3

[0059] This embodiment uses a method similar to that of Example 1, except that in step (3), after introducing supercritical carbon dioxide, the conditions for supercritical carbon dioxide treatment are adjusted to: pressure of 7.5 MPa and temperature of 32°C for 6 hours to obtain intermediate II. The remaining operations are the same as in Example 1 to prepare molecularly imprinted adsorbent-III.

[0060] Comparative Example 1

[0061] This comparative example was conducted using a method similar to that of Example 1. The difference was that in step (3), supercritical carbon dioxide was not introduced. Instead, the polymer microspheres were directly placed in a high-pressure reactor, nitrogen gas was introduced, and the conditions of 10 MPa and 40°C were maintained for 5 hours to obtain intermediate II. The remaining operations were the same as in Example 1 to prepare the molecularly imprinted adsorbent-DI.

[0062] Comparative Example 2

[0063] This comparative example was carried out using a method similar to that of Example 1. The difference is that in step (4), the product after initiation treatment was subjected to a one-step depressurization treatment. Specifically, the high-pressure reactor was placed at 60°C and the intermediate II was subjected to initiation treatment for 24 hours. Then, the depressurization treatment was started, and the pressure was directly depressurized to 0.1 MPa at a depressurization rate of 1.5 MPa / min to obtain the molecularly imprinted adsorbent-DII.

[0064] Comparative Example 3

[0065] This comparative example was carried out using a method similar to that of Example 1. The difference was that in step (1), the amount of linear polymer polyvinylidene fluoride was adjusted to 8.5 g. The remaining steps and conditions were the same as in Example 1, and molecularly imprinted adsorbent-DIII was obtained.

[0066] Comparative Example 4

[0067] This comparative example was carried out using a method similar to that of Example 1. The difference is that in step (4), the conditions of the gradient depressurization process were adjusted as follows: the pressure was adjusted to 3 MPa at a depressurization rate of 1.5 MPa / min, held for 10 s, and then the pressure was reduced to 0.1 MPa at the same depressurization rate to obtain the molecularly imprinted adsorbent-DIV.

[0068] Test Case

[0069] The CO2 adsorption performance of the molecularly imprinted adsorbents prepared in the above examples was tested, specifically as follows:

[0070] In this test example, a fully automated physical adsorption instrument was used to determine the CO2 adsorption capacity. Each molecularly imprinted adsorbent was heated in a degassing station to remove residual moisture and gas, thus activating the sample. The sample was then contacted with CO2 gas, and the measurement was performed at 25°C and 0.1 MPa. An adsorption equilibrium experiment was used to determine the CO2 / N2 separation factor, under the following conditions: 25°C and 0.1 MPa.

[0071] The test results are shown in Table 1.

[0072] Table 1

[0073] <![CDATA[CO2 adsorption capacity (mmol / g)]]> Separation factor Molecularly imprinted adsorbent-I 19.5 90 Molecularly Imprinted Adsorbent-II 18.8 85 Molecularly Imprinted Adsorbent-III 14.5 75 Molecularly imprinted adsorbent-DI 6.2 42 Molecularly Imprinted Adsorbent - DII 5.8 63 Molecularly Imprinted Adsorbent-DIII 6.5 65 Molecularly imprinted adsorbent - DIV 7.2 70

[0074] As can be seen from the results in Table 1, the molecularly imprinted adsorbent prepared by the present invention has significantly better performance in terms of CO2 adsorption selectivity and adsorption capacity, demonstrating its excellent carbon dioxide adsorption performance.

[0075] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a molecularly imprinted adsorbent, characterized in that, The method includes: (1) The adsorbent raw material is mixed with a solvent to obtain intermediate I; the adsorbent raw material contains a functional monomer, a crosslinking agent, an initiator and a linear polymer in a weight ratio of 1:0.2-0.6:0.02-0.15:0.8-2; the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and tetrahydrofuran; (2) The intermediate I is spray-dried to obtain polymer microspheres; (3) The polymer microspheres were subjected to supercritical carbon dioxide treatment to obtain intermediate II; (4) The intermediate II is subjected to initiation treatment and gradient depressurization treatment in sequence to obtain the molecularly imprinted adsorbent; the conditions of the gradient depressurization treatment include: first depressurizing to 4-7 MPa and holding for 10-20 s, and then depressurizing to 0.1-0.12 MPa.

2. The method according to claim 1, wherein, In step (1), the functional monomer is selected from at least one of acrylamide, methacrylamide, and N,N-dimethylacrylamide; And / or, the crosslinking agent is selected from dimethyl propylene glycol ester and / or N,N'-methylenebisacrylamide.

3. The method according to claim 1, wherein, In step (1), the initiator is selected from azobisisobutyronitrile and / or benzophenone; And / or, the linear polymer is selected from polyvinylidene fluoride and / or polyacrylonitrile.

4. The method according to claim 1, wherein, In step (1), the weight ratio of the adsorbent raw material to the solvent is 1:2.5-4.

5. The method according to claim 1, wherein, In step (2), the conditions for the spray drying process include: an air inlet temperature of 110-130℃, an air outlet temperature of 80-90℃, and a feed rate of 4-6 mL / min.

6. The method according to claim 1, wherein, In step (3), the conditions for supercritical carbon dioxide treatment include: pressure of 8-12 MPa, temperature of 35-45℃, and time of 2-6 h.

7. The method according to claim 1, wherein, In step (4), the initiation treatment is a photoinitiation treatment and / or a thermal initiation treatment; The conditions for the photoinitiation treatment include: wavelength of 360-380 nm and time of 0.5-2 h; The conditions for the thermal initiation treatment include: a temperature of 60-70℃ and a time of 6-30h.

8. A molecularly imprinted adsorbent prepared by the method according to any one of claims 1-7.

9. The molecularly imprinted adsorbent according to claim 8, wherein, The molecularly imprinted adsorbent has a hierarchical porous structure.

10. The application of the molecularly imprinted adsorbent according to claim 8 or 9 in the field of CO2 adsorption.

Images