Functionalized polymer material for high-selectivity n-heptane adsorption separation and preparation method thereof

Abstract

The invention relates to the technical field of adsorption materials, in particular to a functional polymer material for high-selectivity n-heptane adsorption separation and a preparation method of the functional polymer material. During preparation, hydroxypropyl-beta-cyclodextrin is used as a core raw material, polymerizable double bonds are introduced through in-situ esterification, and then the functional polymer material is prepared from hydroxypropyl-beta-cyclodextrin, perfluorooctyl ethyl acrylate and divinyl benzene through an emulsion dispersion-emulsion polymerization process. According to the material, impurities are included in a hydrophobic cavity of modified hydroxypropyl-beta-cyclodextrin, and the hydrophobic synergistic effect of a perfluoro side chain is combined, so that the impurities are adsorbed, and a three-dimensional network constructed by divinyl benzene can fix functional sites and inhibit swelling of chain segments. The functionalized polymer material for high-selectivity n-heptane adsorption separation is high in n-heptane separation selectivity, excellent in solvent expansion resistance and long-term stable in functional sites, the preparation process does not need special monomers, conditions are mild, large-scale production is easy, and the functionalized polymer material can be efficiently applied to n-heptane purification in the fields of petrochemical engineering and the like.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials technology, and in particular to a functionalized polymer material for highly selective n-heptane adsorption and separation and its preparation method. Background Technology

[0002] n-Heptane, an important straight-chain alkane, is widely used in petrochemicals, fine chemicals, fuel preparation, and pharmaceutical intermediate synthesis. Its purity is particularly high (typically ≥99.5%), especially in applications such as high-standard gasoline blending, precision instrument cleaning, and chromatographic analysis solvents. In industrial production, n-heptane mainly originates from the C7 alkane fraction after petroleum refining. This fraction often contains isoalkanes such as 2-methylhexane and 3-methylhexane, as well as small amounts of impurities like toluene and ethanol. These impurities have similar boiling points and polarities to n-heptane, making efficient separation difficult using conventional distillation processes. Furthermore, distillation processes are energy-intensive and require significant equipment investment, failing to meet the demands for low-energy, high-purity separation. Therefore, developing efficient n-heptane adsorption and separation materials has become a research hotspot in the industry.

[0003] Currently, adsorption materials for the separation of n-heptane are mainly divided into three categories: The first category is traditional inorganic adsorption materials, such as molecular sieves and activated carbon. These rely on microporous sieving effects or surface physical adsorption to achieve separation. However, the pore size of molecular sieves is fixed, making it difficult to accurately match the molecular size of C7 isomeric impurities. Furthermore, they require operation under high temperature and high pressure conditions to maintain adsorption performance, resulting in significant energy consumption. Although activated carbon has a large specific surface area, it lacks specific adsorption sites on its surface, leading to low selectivity for n-heptane and isomeric impurities, which can easily result in insufficient purity of n-heptane after adsorption. The second category is conventional polymer adsorption materials, such as polystyrene-divinylbenzene resin and polyimide. These materials control the pore structure by adjusting the degree of crosslinking or by introducing hydrophobic groups to enhance the adsorption capacity for alkanes. However, due to the lack of precise recognition sites for C7 isomeric impurities, relying solely on pore sieving or single hydrophobic effects cannot effectively distinguish n-heptane from structurally similar impurities. The separation selectivity is generally low, and polymer segments are prone to swelling in alkane solvents, leading to pore deformation and rapid decay of adsorption performance. The third category is cyclodextrin-modified adsorbent materials. Cyclodextrin molecules possess a unique hydrophobic cavity structure, which theoretically allows for the inclusion of specific molecules through "size matching," thus making them suitable for alkane separation research. However, existing cyclodextrin-based materials mostly employ physical blending to introduce cyclodextrin into the polymer matrix. Since the cyclodextrin does not form a covalent bond with the polymer, it is easily lost with the solvent during the adsorption-desorption cycle, leading to a gradual reduction in functional sites. Furthermore, the unmodified hydrophobic cavity of the cyclodextrin only provides a single inclusion effect, lacking a synergistic adsorption mechanism, resulting in insufficient affinity for impurities. Additionally, the high water solubility of cyclodextrin molecules, readily dissolving in aqueous or polar solvents, further limits its stability in alkane systems.

[0004] Therefore, developing a n-heptane adsorption and separation material that combines high selectivity, strong resistance to expansion, stable functional sites, and simple preparation has become the key to overcoming the current technological bottlenecks. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a functionalized polymer material for highly selective n-heptane adsorption and separation and its preparation method.

[0006] To achieve the above objectives, the present invention provides a method for preparing a functionalized polymer material for highly selective n-heptane adsorption and separation, comprising the following steps:

[0007] (1) Under nitrogen protection, hydroxypropyl-β-cyclodextrin is added to deionized water, heated to 50-60℃ and stirred until dissolved, then acrylic acid and p-toluenesulfonic acid are added, heated to 70-90℃ and reacted for 3-4 hours to obtain an esterified solution. In this step, hydroxypropyl-β-cyclodextrin is fully dissolved in deionized water at 50-60℃, and the hydroxyl groups in its molecular structure are exposed. The added acrylic acid provides carboxyl groups, while p-toluenesulfonic acid, as a protonic acid catalyst, protonates the carboxyl groups of acrylic acid, enhances its electrophilicity, and promotes the esterification reaction between the carboxyl groups and the hydroxyl groups of hydroxypropyl-β-cyclodextrin to form ester bonds, ultimately generating modified hydroxypropyl-β-cyclodextrin with acrylate double bonds (C=C), providing active sites for subsequent polymerization reactions.

[0008] (2) Cool the esterification liquid to 40°C, add perfluorooctyl ethyl acrylate and polyvinyl alcohol aqueous solution, stir at 200-300 rpm and ultrasonically disperse for 40-50 min to obtain emulsion; In this step, the added perfluorooctyl ethyl acrylate is the oil phase monomer, and the 10wt% polyvinyl alcohol aqueous solution is the aqueous phase dispersant. The hydrophilic groups in the polyvinyl alcohol molecule interact with water, while the hydrophobic groups are adsorbed on the surface of the oil phase monomer to form an interfacial protective film. Through the synergistic effect of stirring at 200-300 rpm and ultrasonic dispersion at 300W and 40kHz, the oil phase agglomerates are broken and dispersed into tiny and uniform emulsion droplets, which are uniformly dispersed in the aqueous phase to form a stable oil-in-water emulsion, ensuring that the subsequent polymerization reaction can proceed synchronously and uniformly in each emulsion droplet;

[0009] (3) Under nitrogen protection, divinylbenzene and azobisisobutyronitrile were added to the emulsion, heated to 70-80℃, stirred for 6-8h, cooled to room temperature, filtered, and the solid was collected. After washing three times with deionized water and ethanol, it was dried, pulverized and passed through an 80-mesh sieve to obtain a functionalized polymer material for highly selective n-heptane adsorption and separation. This step is a free radical emulsion polymerization reaction. The core is to form a polymer material with both functional sites and a three-dimensional network structure. At a temperature of 70-80℃, azobisisobutyronitrile undergoes thermal decomposition to generate active free radicals. These free radicals will trigger free radical addition reactions of all monomers containing double bonds in the system to form linear polymer chains. Divinylbenzene, as a crosslinking agent, will have two double bonds in its molecule participate in the polymerization reactions of different polymer chains. Multiple linear chains are connected by covalent bonds to construct a three-dimensional network structure, thereby improving the structural stability and mechanical strength of the polymer.

[0010] Preferably, in (1), the weight ratio of hydroxypropyl-β-cyclodextrin and deionized water is 1:8-12.

[0011] Preferably, the molar ratio of hydroxypropyl-β-cyclodextrin, acrylic acid and p-toluenesulfonic acid in (1) is 1:3-5:0.03-0.07.

[0012] Preferably, in (2), the esterification solution, perfluorooctyl ethyl acrylate and polyvinyl alcohol aqueous solution are in a weight ratio of 1:0.15-0.2:0.15-0.25.

[0013] Preferably, the concentration of the polyvinyl alcohol aqueous solution in (2) is 10 wt%.

[0014] Preferably, the ultrasonic power in (2) is 300W and the frequency is 40kHz.

[0015] Preferably, in step (3), the emulsion, divinylbenzene and azobisisobutyronitrile are in a weight ratio of 1:0.003-0.005:0.001-0.003.

[0016] Preferably, the drying conditions in (3) are 65°C and -0.09 MPa.

[0017] Furthermore, the present invention also provides a functionalized polymer material for highly selective n-heptane adsorption and separation, which is prepared by the above-described method.

[0018] Preferably, the mechanism of action of the functionalized polymer material for highly selective n-heptane adsorption and separation in this invention is as follows:

[0019] In this invention, in-situ esterified hydroxypropyl-β-cyclodextrin is the core functional unit for selective impurity recognition. Its molecular structure retains the unique hydrophobic cavity characteristic of hydroxypropyl-β-cyclodextrin. The inner diameter of this cavity matches the kinetic diameter of isomeric alkane impurities such as 2-methylhexane, enabling precise encapsulation of impurity molecules within the cavity through van der Waals forces and hydrophobic interactions. Heptane molecules, due to their regular carbon chain structure and slightly smaller kinetic diameter, cannot form stable inclusion complexes within the cavity and can easily penetrate the material. For alkane impurities with significantly different carbon chain lengths (such as hexane and octane), the molecular size mismatch with the cavity makes it difficult to form stable inclusion complexes. This cavity encapsulation effect based on "impurity size matching - heptane steric repulsion" is the core foundation for the material's high selective separation of heptane.

[0020] Perfluorooctyl ethyl acrylate, as a modifying monomer, primarily plays a synergistic role in enhancing the hydrophobic properties of impurities in the material, further improving its adsorption capacity and selectivity. Its fluorinated side chains possess strong hydrophobicity, enabling the creation of hydrophobic microenvironments on the polymer material surface and within its pores. When nonpolar impurity molecules such as 2-methylhexane approach the material, in addition to the inclusion effect of the cyclodextrin cavity, the hydrophobic groups of the fluorinated side chains form additional hydrophobic interactions with the impurity molecules. This dual effect of "cavity inclusion + hydrophobic adsorption" significantly enhances the material's adsorption affinity for impurities, thereby increasing the impurity adsorption capacity. Simultaneously, the rigid fluorocarbon chain structure inhibits the swelling of polymer segments in the alkane system, preventing deformation of the cyclodextrin cavity or blockage of the n-heptane penetration channel due to segment swelling, ensuring the material's selective adsorption of impurities and efficient release stability of n-heptane during long-term use.

[0021] The three-dimensional network structure formed by divinylbenzene crosslinking is the structural basis for ensuring the stable performance of the material. On the one hand, the three-dimensional crosslinked network tightly connects the linear polymer chains formed by modified hydroxypropyl-β-cyclodextrin and perfluorooctyl ethyl acrylate through covalent bonds, fixing the spatial positions of the hydrophobic cavities of cyclodextrin and the fluorine-rich hydrophobic groups. This prevents the displacement or loss of impurity adsorption sites during the adsorption-desorption cycle, ensuring the long-term stability of the material's recognition and adsorption performance for impurities. On the other hand, the three-dimensional crosslinked structure can also regulate the pore size distribution of the material, forming a pore size suitable for the rapid diffusion of n-heptane molecules. This ensures that n-heptane molecules can efficiently penetrate the material, improving separation efficiency, and can also further intercept some larger impurity agglomerates through pore sieving, thus enhancing separation selectivity. In addition, the stable three-dimensional structure also improves the mechanical strength of the material. The 80-mesh granular form formed after drying and pulverization is convenient for filling in actual separation equipment, ensuring sufficient contact between the gas and liquid phases and maximizing the separation efficiency of the material.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention utilizes an in-situ esterification reaction to form stable ester bonds between hydroxypropyl-β-cyclodextrin and acrylic acid, successfully introducing polymerizable double bonds. This ensures that the cyclodextrin is covalently anchored in the polymer network, and its hydrophobic cavities can precisely match the molecular size of C7 isomeric impurities such as 2-methylhexane, achieving specific inclusion. Simultaneously, the fluorine-rich side chains introduced by perfluorooctyl ethyl acrylate construct a hydrophobic microenvironment, forming a dual "inclusion-hydrophobic" effect with the cyclodextrin cavities, enhancing the adsorption affinity for impurities. Compared to existing materials that rely solely on single-channel sieving or physical adsorption, this invention significantly improves the selective adsorption capacity for impurities, effectively releasing n-heptane and meeting the requirement of n-heptane purity ≥99.5% in industrial applications.

[0024] 2. In this invention, divinylbenzene forms a three-dimensional rigid network through a cross-linking reaction, immobilizing modified hydroxypropyl-β-cyclodextrin and perfluorooctyl ethyl acrylate with strong covalent bonds, thus restricting the free movement of polymer chain segments. Simultaneously, the fluorine-rich side chains of perfluorooctyl ethyl acrylate exhibit a rigid rod-like structure with strong intermolecular forces, further suppressing chain swelling in alkane systems. This avoids the problems of pore deformation and functional site shift caused by chain swelling in existing polymer materials. Even after long-term immersion in n-heptane, the material's volume expansion rate remains low, and the separation performance shows only slight degradation, making it suitable for continuous industrial separation operations.

[0025] 3. This invention utilizes a synergistic process of in-situ esterification and emulsion polymerization, enabling all functional units to be covalently bonded to the polymer matrix: hydroxypropyl-β-cyclodextrin is grafted via ester bonds, and perfluorooctyl ethyl acrylate and divinylbenzene are incorporated into the network via double bond polymerization, eliminating physically dispersed functional components. Compared to the problem of functional units easily being lost with solvents in existing cyclodextrin-based materials, the material of this invention does not detach or shift from the cyclodextrin cavities and fluorinated hydrophobic groups during multiple adsorption-desorption cycles. The impurity adsorption capacity and selectivity remain stable, significantly extending the material's service life and reducing replacement costs in industrial applications.

[0026] 4. This invention directly uses industrially available hydroxypropyl-β-cyclodextrin as a raw material, introducing polymerizable groups in one step through in-situ esterification, eliminating the need for prior synthesis of dedicated cyclodextrin derivative monomers and simplifying the raw material preparation process. The emulsion polymerization process utilizes conventional equipment such as a four-necked flask and a constant-temperature water bath, allowing for easy control of ultrasonic dispersion and stirring operations. The reaction conditions are mild, requiring no high temperature, high pressure, or special catalysts. Compared to existing processes that rely on complex monomer synthesis and specialized reaction equipment, this invention offers lower preparation costs, simpler operation, and rapid large-scale production, facilitating the industrial promotion of n-heptane separation technology. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] Example 1: A specific preparation method of a functionalized polymer material for highly selective n-heptane adsorption and separation, comprising the following steps:

[0029] (1) Under nitrogen protection, 1 kg of hydroxypropyl-β-cyclodextrin was added to 8 kg of deionized water, heated to 50°C and stirred until dissolved, 140.24 g of acrylic acid and 3.35 g of p-toluenesulfonic acid were added, heated to 70°C and reacted for 3 h to obtain esterified solution;

[0030] (2) Cool 9 kg of esterified liquid to 40 °C, add 1.35 kg of perfluorooctyl ethyl acrylate and 1.35 kg of 10 wt% polyvinyl alcohol aqueous solution, stir at 200 rpm and ultrasonically disperse at 300 W power and 40 kHz frequency for 40 min to obtain emulsion.

[0031] (3) Under nitrogen protection, 35.1 g of divinylbenzene and 11.7 g of azobisisobutyronitrile were added to 11.7 kg of emulsion, the temperature was raised to 70 °C, the mixture was stirred for 6 h, cooled to room temperature, filtered, the solid was collected, washed three times each with deionized water and ethanol, dried at 65 °C and -0.09 MPa, and pulverized through an 80-mesh sieve to obtain a functionalized polymer material for highly selective n-heptane adsorption and separation.

[0032] Example 2: A specific preparation method of a functionalized polymer material for highly selective n-heptane adsorption and separation, comprising the following steps:

[0033] (1) Under nitrogen protection, 1 kg of hydroxypropyl-β-cyclodextrin was added to 10 kg of deionized water, heated to 55 °C and stirred until dissolved, 186.98 g of acrylic acid and 5.59 g of p-toluenesulfonic acid were added, the temperature was raised to 80 °C and the reaction was carried out for 3.5 h to obtain the esterified solution.

[0034] (2) Cool 11.19 kg of esterified liquid to 40 °C, add 1.9 kg of perfluorooctyl ethyl acrylate and 2.24 kg of 10 wt% polyvinyl alcohol aqueous solution, stir at 250 rpm and ultrasonically disperse at 300 W power and 40 kHz frequency for 45 min to obtain emulsion.

[0035] (3) Under nitrogen protection, 60g of divinylbenzene and 30g of azobisisobutyronitrile were added to 15kg of emulsion, the temperature was raised to 75℃, the mixture was stirred for 7h, cooled to room temperature, filtered, the solid was collected, washed three times each with deionized water and ethanol, dried at 65℃ and -0.09MPa, and pulverized through an 80-mesh sieve to obtain a functionalized polymer material for highly selective n-heptane adsorption and separation.

[0036] Example 3: A specific preparation method of a functionalized polymer material for highly selective n-heptane adsorption and separation, comprising the following steps:

[0037] (1) Under nitrogen protection, 1 kg of hydroxypropyl-β-cyclodextrin was added to 12 kg of deionized water, heated to 60 °C and stirred until dissolved, 233.73 g of acrylic acid and 7.82 g of p-toluenesulfonic acid were added, heated to 90 °C and reacted for 4 h to obtain esterified solution;

[0038] (2) Cool 13.2 kg of esterified liquid to 40 °C, add 2.64 kg of perfluorooctyl ethyl acrylate and 3.3 kg of 10 wt% polyvinyl alcohol aqueous solution, stir at 300 rpm and ultrasonically disperse at 300 W power and 40 kHz frequency for 40-50 min to obtain emulsion.

[0039] (3) Under nitrogen protection, 95.5g of divinylbenzene and 57.3g of azobisisobutyronitrile were added to 19.1kg of emulsion, the temperature was raised to 80℃, the mixture was stirred for 8h, cooled to room temperature, filtered, the solid was collected, washed three times each with deionized water and ethanol, dried at 65℃ and -0.09MPa, and pulverized through an 80-mesh sieve to obtain a functionalized polymer material for highly selective n-heptane adsorption and separation.

[0040] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that step (1) is omitted. Hydroxypropyl-β-cyclodextrin is added to deionized water, heated and stirred until dissolved, and then perfluorooctyl ethyl acrylate and 10wt% polyvinyl alcohol aqueous solution are added.

[0041] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that perfluorooctyl ethyl acrylate is not added.

[0042] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that divinylbenzene is replaced with ethylene glycol dimethacrylate.

[0043] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that ultrasonic dispersion is omitted in step (2).

[0044] Performance testing:

[0045] 1. Selectivity test for n-heptane adsorption: Take 0.5g of each of the functionalized polymer materials of Examples 1-3 and Comparative Examples 1-4, and place them in stoppered conical flasks. Add 50mL of a simulated industrial mixing system (n-heptane mass fraction 95%, impurities are 3% 2-methylhexane, 1% n-hexane, and 1% n-octane). After sealing, place the flasks in a constant temperature water bath shaker and shake at 25℃ and 150r / min until adsorption equilibrium is reached (equilibrium is determined when the difference in impurity concentration between two consecutive samples is ≤0.01%). After equilibrium, take the supernatant and use a gas chromatograph to detect the concentration of each component. Calculate the selectivity coefficient of the material for n-heptane relative to each impurity based on the changes in the concentration of each component before and after adsorption, the solution volume, and the mass of the material (selectivity coefficient = impurity adsorption amount / n-heptane adsorption amount). The experimental results are shown in Table 1.

[0046] 2. Saturated adsorption capacity test: Accurately weigh 0.5 g each of the functionalized polymer materials of Examples 1-3 and Comparative Examples 1-4, place them in a 50 mL stoppered conical flask, add 50 mL of simulated industrial mixing system (95% n-heptane mass fraction, impurities are 3% 2-methylhexane, 1% n-hexane, and 1% n-octane), seal the flask, and place it in a 30℃ constant temperature water bath shaker. Shake at 150 r / min for 24 h until equilibrium is reached. After adsorption equilibrium, the mass change of the sample before and after adsorption is measured by gravimetric method, and the saturated adsorption capacity is calculated (adsorption capacity = (mass of sample after adsorption - mass of sample before adsorption) / mass of sample before adsorption). The experimental results are shown in Table 1.

[0047] 3. Solvent Swelling Resistance Test: Weigh 1.0 g (accurate to 0.001 g) of each of the functionalized polymer materials of Examples 1-3 and Comparative Examples 1-4, place them in a 10 mL graduated centrifuge tube, record the initial volume of the sample, add 8 mL of n-heptane, seal and soak at 25 °C for 72 h. During this period, observe and record the change in sample volume every 12 h. After soaking, centrifuge (3000 r / min, 5 min), remove the supernatant, measure the volume of the sample after swelling, and calculate the volume swelling rate (swelling rate = (swelled volume - initial volume) / initial volume × 100%). The experimental results are shown in Table 1.

[0048] 4. Regeneration Performance Test: 10g each of the functionalized polymer materials from Examples 1-3 and Comparative Examples 1-4 were selected and wet-packed into an adsorption column with an inner diameter of 1cm and a height of 8cm. A simulated industrial mixing system (same as the selectivity test) was introduced, and dynamic adsorption was performed at 30℃ with a flow rate of 2BV / h until breakthrough (the 2-methylhexane content in the effluent reached 5% of the content in the raw material). Subsequently, an ethanol-acetone mixture with a volume ratio of 1:2 was used as the desorbent, and desorption and regeneration were performed at 25℃ with a flow rate of 1.5BV / h. After desorption, the effluent was washed with n-heptane until it was colorless. The above adsorption-regeneration cycle was repeated 5 times. After each cycle, the selectivity coefficient of the sample to n-heptane was tested, and the selectivity coefficient retention rate after 5 cycles was calculated. The experimental results are shown in Table 1.

[0049] 5. Dynamic Adsorption Breakthrough Performance Test: 1 kg each of the functionalized polymer materials from Examples 1-3 and Comparative Examples 1-4 were wet-packed into an adsorption column with an aspect ratio of 8:1. Anhydrous ethanol was used to replace the water in the resin pores, followed by pretreatment with n-heptane to replace the anhydrous ethanol. A simulated industrial mixing system (same as the selectivity test) was continuously fed at a flow rate of 2 BV / h and 30°C. The effluent from the adsorption column was collected every 1 hour, and the content of 2-methylhexane in the effluent was detected using gas chromatography. Breakthrough was defined as when the 2-methylhexane content in the effluent reached 5% of the content in the raw material. The total throughput from the start of feeding to breakthrough was recorded. The experimental results are shown in Table 1.

[0050] Table 1 Performance Test Results

[0051]

[0052]

[0053] Performance Analysis:

[0054] In summary, Examples 1-3 were all prepared through a complete "in-situ esterification-emulsification dispersion-emulsion polymerization" process. The impurity recognition sites of modified hydroxypropyl-β-cyclodextrin, the hydrophobic synergistic groups of perfluorooctyl ethyl acrylate, and the three-dimensional rigid network constructed by divinylbenzene formed a highly efficient synergistic effect, which significantly outperformed Comparative Examples 1-4 in terms of n-heptane adsorption selectivity, saturated adsorption capacity, anti-solvent swelling performance, regeneration performance, and dynamic adsorption penetration performance. Among them, Example 2 had the best overall performance.

[0055] The high selectivity of Example 2 is due to the following reasons: First, in the in-situ esterification reaction, p-toluenesulfonic acid precisely protonates the carboxyl group of acrylic acid, enhancing its electrophilicity and efficiently forming ester bonds with the hydroxyl groups of hydroxypropyl-β-cyclodextrin. This successfully grafts the acrylate double bonds onto the cyclodextrin molecule, which are then stably anchored to the polymer network via covalent bonds during subsequent polymerization, resulting in a uniform distribution of hydrophobic cavities in the cyclodextrin, allowing for precise inclusion of impurities. Second, the fluorine-rich side chain of perfluorooctyl ethyl acrylate is incorporated into the network through polymerization, forming a dual effect of "inclusion + hydrophobicity" with the cyclodextrin cavities, thus strengthening the adsorption affinity for impurities. Third, the two vinyl groups of divinylbenzene are crosslinked with different polymer chains to construct a rigid three-dimensional network, fixing the spatial position of the cyclodextrin cavities and preventing site shifts during impurity inclusion. In contrast, Comparative Example 1 omits the in-situ esterification reaction. In the chemical process, hydroxypropyl-β-cyclodextrin lacks ester-linked double bonds and cannot be covalently grafted onto the polymer network. It can only be physically dispersed, and the cyclodextrin cavity is easily lost, resulting in very few impurity recognition sites and a selectivity far lower than that of Example 2. Comparative Example 2 did not add perfluorooctyl ethyl acrylate, lacking the hydrophobic synergistic effect of the fluorinated side chains. It relies solely on the single inclusion effect of the cyclodextrin cavity, resulting in weak adsorption affinity for impurities and a selectivity lower than that of Example 2. Comparative Example 3 used ethylene glycol dimethacrylate instead of divinylbenzene, and the network formed by its crosslinking was not rigid enough. The cyclodextrin cavity was easily deformed due to chain segment movement and could not stably encapsulate impurities, resulting in a selectivity lower than that of Example 2. Comparative Example 4 omitted ultrasonic dispersion, resulting in the aggregation of oil phase monomers, leading to uneven distribution of fluorinated side chains and cyclodextrin cavities, with some areas lacking effective adsorption sites, resulting in a selectivity lower than that of Example 2.

[0056] The microscopic mechanism behind the high saturated adsorption capacity in Example 2 is as follows: On the one hand, the optimal molar ratio of acrylic acid reacts with hydroxypropyl-β-cyclodextrin, resulting in a moderate number of acrylate double bonds grafted onto the cyclodextrin molecules. This leads to the formation of high-density cross-linking points with divinylbenzene and perfluorooctyl ethyl acrylate during subsequent polymerization, significantly increasing the cyclodextrin cavity density. On the other hand, the esterification temperature of 80°C avoids insufficient ester bond formation due to low temperatures or hydrolysis due to high temperatures, ensuring that each cyclodextrin molecule can serve as an effective adsorption site. Simultaneously, the fluorine-rich side chains of perfluorooctyl ethyl acrylate, through hydrophobic interactions, can assist in the adsorption of trace impurities not encapsulated by the cyclodextrin, further enhancing the total adsorption capacity. Compared to Example 2, Comparative Example 1, lacking an esterification reaction, The cyclodextrin in Comparative Example 2 lacked double bonds and could not anchor itself in the polymer network, resulting in significant loss during washing. This resulted in very few impurity adsorption sites and a saturated adsorption capacity far lower than in Example 2. Comparative Example 2 lacked the auxiliary adsorption effect of fluorinated side chains, relying solely on cyclodextrin cavities for adsorption, thus reducing the total number of adsorption sites and resulting in a saturated adsorption capacity lower than in Example 2. The flexible crosslinking agent in Comparative Example 3 loosened the network structure, causing some cyclodextrin cavities to be compressed and deformed, preventing proper encapsulation of impurities and reducing effective adsorption sites, leading to a saturated adsorption capacity lower than in Example 2. Comparative Example 4, due to the lack of ultrasonic dispersion, experienced oil phase agglomeration, causing fluorinated side chains to concentrate in localized areas, leaving no auxiliary adsorption sites in other areas. Furthermore, the cyclodextrin cavities were unevenly distributed, with some areas having vacant sites, resulting in a saturated adsorption capacity lower than in Example 2.

[0057] The excellent anti-solvent swelling performance of Example 2 is due to the following microscopic factors: First, the fluorine-rich side chains of perfluorooctyl ethyl acrylate possess extremely strong intermolecular forces, and the high electronegativity of fluorine atoms gives the side chains a rigid rod-like structure, which can inhibit the free movement of polymer segments in n-heptane and reduce segment swelling. Second, the high crosslinking density of divinylbenzene tightly connects the linear polymer chains through covalent bonds, forming a dense three-dimensional network that restricts the diffusion of chain segments into the solvent. Third, the high conversion rate of the in-situ esterification reaction ensures the stability of the connection between cyclodextrin and the polymer network, preventing cyclodextrin from falling off due to segment swelling, and further maintaining the integrity of the network structure. In comparison, Comparative Example 1 has no... In the esterification reaction, cyclodextrin was not grafted, and the polymer network was formed by only a small amount of monomer crosslinking, resulting in a loose structure. The chain segments easily swelled in n-heptane, and the expansion rate was much higher than that of Example 2. Comparative Example 2 did not contain perfluorooctyl ethyl acrylate, and lacked the constraint of rigid fluorinated side chains. The polymer chain segments had a high degree of freedom, a large degree of swelling, and an expansion rate higher than that of Example 2. In Comparative Example 3, ethylene glycol dimethacrylate was a flexible crosslinking agent. The network bond energy formed by its crosslinking was low, and the chain segments were easily stretched, resulting in a swelling degree higher than that of Example 2. In Comparative Example 4, ultrasonic dispersion was omitted, and the agglomeration of the oil phase led to uneven distribution of fluorinated side chains. Some areas lacked rigid side chain constraints, resulting in a high degree of chain segment swelling and an expansion rate higher than that of Example 2.

[0058] The stable regeneration performance of Example 2 is due to the following reasons: First, the rigid three-dimensional network formed by divinylbenzene crosslinking fixes the modified hydroxypropyl-β-cyclodextrin and perfluorooctyl ethyl acrylate through strong covalent bonds. During the regeneration process (ethanol-acetone desorption + n-heptane rinsing), functional sites will not be lost due to solvent immersion. Second, the inclusion effect between the cyclodextrin cavity and impurities is a physical effect (van der Waals forces + hydrophobic interaction). The desorbent can effectively disrupt this effect, and the cyclodextrin molecules are stably grafted through ester bonds. After desorption, the cavity structure remains unchanged and can still re-encapsulate impurities. Third, the hydrophobic groups of the fluorine-rich side chains are chemically stable and will not undergo hydrolysis or oxidation during the regeneration process, and the hydrophobic synergistic effect continues. Compared with Example 2, In Comparative Example 1, the cyclodextrin was not grafted and was only physically dispersed. During regeneration, it was easily lost with the desorbent, and the number of functional sites decreased successively, resulting in a much lower selective retention rate than in Example 2. In Comparative Example 2, there were no fluorine-rich side chains, and the cyclodextrin cavity relied solely on a single inclusion effect to adsorb impurities. After desorption, some cavities deformed due to chain segment swelling and could not recover their original size, resulting in a lower selective retention rate than in Example 2. In Comparative Example 3, the flexible cross-linked network was prone to shrinkage during regeneration due to solvent immersion, leading to compression and deformation of the cyclodextrin cavity, a decrease in impurity inclusion ability, and a lower selective retention rate than in Example 2. In Comparative Example 4, the functional sites were unevenly distributed, and during regeneration, local areas were prone to site aggregation due to solvent erosion, resulting in a decrease in adsorption selectivity and a lower retention rate than in Example 2.

[0059] The high total throughput of dynamic adsorption in Example 2 is likely due to the following reasons: First, ultrasonic dispersion causes the oil phase monomers to form uniform micro-emulsion droplets, resulting in a uniform distribution of polymer channels after polymerization, allowing for rapid penetration of n-heptane and efficient contact of impurities with the cyclodextrin cavities within the channels. Second, the three-dimensional network formed by divinylbenzene crosslinking has controllable pore size, preventing impurities from being directly penetrated without adsorption due to excessively large pore sizes, or hindering mass transfer of n-heptane due to excessively small pore sizes. Third, the high-density cyclodextrin cavities can continuously adsorb impurities, extending the penetration time of the adsorption column and thus increasing the total throughput. In contrast, the cyclodextrin in Comparative Example 1 was not grafted. In Comparative Example 2, there were no effective adsorption sites within the pores, and impurities rapidly penetrated the adsorption column, resulting in a total throughput far lower than in Example 2. Comparative Example 2 lacked fluorine-rich side chains, leading to a slow adsorption rate of impurities within the pores and a short residence time for impurities, making them prone to premature penetration; the total throughput was also lower than in Example 2. In Comparative Example 3, the flexible crosslinking agent resulted in uneven pore size, with impurities directly penetrating in large-pore areas and hindering heptane mass transfer in small-pore areas; the total throughput was lower than in Example 2. In Comparative Example 4, ultrasonic dispersion was omitted, resulting in localized blockages or voids in the pores due to oil phase agglomeration. Blocked areas experienced slow heptane mass transfer, while voided areas showed no impurity adsorption; the total throughput was lower than in Example 2.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a functionalized polymer material for highly selective n-heptane adsorption and separation, characterized in that, Includes the following steps: (1) Under nitrogen protection, hydroxypropyl-β-cyclodextrin was added to deionized water, heated to 50-60℃ and stirred until dissolved, acrylic acid and p-toluenesulfonic acid were added, the temperature was raised to 70-90℃ and the reaction was carried out for 3-4 hours to obtain esterified solution; (2) Cool the esterification solution to 40°C, add perfluorooctyl ethyl acrylate and polyvinyl alcohol aqueous solution, stir at 200-300 rpm and ultrasonically disperse for 40-50 min to obtain emulsion; (3) Under nitrogen protection, add divinylbenzene and azobisisobutyronitrile to the emulsion, heat to 70-80℃, stir for 6-8h, cool to room temperature, filter, collect the solid, wash three times with deionized water and ethanol, dry, pulverize and pass through an 80-mesh sieve to obtain a functionalized polymer material for highly selective n-heptane adsorption and separation.

2. The method for preparing the functionalized polymer material for highly selective n-heptane adsorption and separation according to claim 1, characterized in that, In (1), the hydroxypropyl-β-cyclodextrin and deionized water are in a weight ratio of 1:8-12.

3. The method for preparing the functionalized polymer material for highly selective n-heptane adsorption and separation according to claim 1, characterized in that, In (1), the molar ratio of hydroxypropyl-β-cyclodextrin, acrylic acid and p-toluenesulfonic acid is 1:3-5:0.03-0.

07.

4. The method for preparing the functionalized polymer material for highly selective n-heptane adsorption and separation according to claim 1, characterized in that, In (2), the esterification solution, perfluorooctyl ethyl acrylate and polyvinyl alcohol aqueous solution are in a weight ratio of 1:0.15-0.2:0.15-0.

25.

5. The method for preparing the functionalized polymer material for highly selective n-heptane adsorption and separation according to claim 1, characterized in that, The concentration of the polyvinyl alcohol aqueous solution in (2) is 10 wt%.

6. The method for preparing the functionalized polymer material for highly selective n-heptane adsorption and separation according to claim 1, characterized in that, The ultrasonic power in (2) is 300W and the frequency is 40kHz.

7. The method for preparing the functionalized polymer material for highly selective n-heptane adsorption and separation according to claim 1, characterized in that, In (3), the emulsion, divinylbenzene and azobisisobutyronitrile are in a weight ratio of 1:0.003-0.005:0.001-0.

003.

8. The method for preparing the functionalized polymer material for highly selective n-heptane adsorption and separation according to claim 1, characterized in that, The drying conditions in (3) are 65°C and -0.09 MPa.

9. A functionalized polymer material for highly selective n-heptane adsorption and separation, prepared by the method described in any one of claims 1-8.

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