Modified adsorption resin for high-impurity n-heptane raw material and purification method thereof

Abstract

The invention relates to the technical field of adsorption materials, in particular to modified adsorption resin for a high-impurity n-heptane raw material and a purification method of the modified adsorption resin. The resin is prepared from the following raw materials: polystyrene-divinylbenzene resin microspheres, chloromethyl ether, 1, 3, 5, 7-tetra (4-chloromethylphenyl) adamantane, 2-methylimidazole and the like. During preparation, polystyrene-divinylbenzene resin microspheres are subjected to chloromethylation to introduce active sites, adamantine crosslinking to construct rigid pore channels, and imidazolyl functionalization to introduce specific adsorption sites. During purification, dynamic adsorption is performed after pretreatment of two stages of adsorption columns, mild regeneration is performed by using an ethanol-acetone mixed solution, isoparaffin, aromatic hydrocarbon and oxygen-containing compounds can be synchronously removed, high-purity n-heptane is obtained, the resin regeneration performance is excellent, and the whole process is easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials technology, and in particular to a modified adsorption resin for high-impurity n-heptane feedstock and its purification method. Background Technology

[0002] n-Heptane, as an important nonpolar hydrocarbon solvent, plays an irreplaceable role in high-end fields such as electronic material cleaning, high-performance liquid chromatography analysis, pharmaceutical intermediate synthesis, and degreasing of precision instruments due to its stable chemical properties and excellent solubility. These applications have extremely high purity requirements for n-heptane, typically requiring a purity of 99.9% or higher, and some electronic-grade applications even require a purity of ≥99.95%. If trace impurities remain in the raw material, it may lead to serious problems such as short circuits in electronic components, chromatographic peak distortion, and substandard purity in pharmaceutical products, directly affecting the performance and quality of the final product.

[0003] However, the high-impurity n-heptane feedstock obtained in industrial production has a complex composition, mainly containing isoalkanes with similar carbon chain lengths (such as 2-methylhexane and 3-methylhexane), aromatics (such as benzene and toluene), and trace amounts of oxygen-containing compounds (such as ethanol and diethyl ether). These impurities have similar molecular structures to n-heptane and extremely small boiling point differences, making it difficult for conventional separation technologies to achieve efficient removal. For example, traditional distillation processes require high reflux ratios and multi-stage tower operation to initially enrich n-heptane, which not only consumes a lot of energy but also cannot completely separate isoalkanes and aromatics with similar boiling points. Simple physical adsorption (such as silica gel and ordinary activated carbon adsorption) lacks specific adsorption sites and has extremely low selectivity for impurities, easily adsorbing n-heptane simultaneously, leading to a significant decrease in product yield.

[0004] To address the technical bottlenecks in the preparation of high-purity n-heptane, various adsorption separation materials and processes have been developed in the existing technologies, but significant drawbacks remain: First, while molecular sieve materials (such as 5A molecular sieve) can separate n-isoalkanes through pore size sieving, the regeneration process requires high-temperature treatment (above 473K), resulting in high energy consumption and a tendency for framework collapse after long-term use. Furthermore, their adsorption capacity for aromatics and oxygen-containing compounds is extremely weak, requiring additional processes to achieve deep purification. Second, while metal-organic framework (MOF) materials (such as UiO-66 and Cu-BTC) possess high specific surface area and excellent adsorption selectivity, their synthesis requires expensive metal salts and organic ligands, demanding reaction conditions and difficult solvent recovery. The preparation cost is 10-20 times that of conventional adsorption materials, hindering large-scale industrial application. Third, conventional modified adsorption resins are mostly designed for wastewater treatment, lacking precise control over pore structure and exhibiting uneven distribution of active sites. Their synergistic adsorption capacity for multiple impurities in n-heptane is weak, resulting in low adsorption capacity and significant performance degradation after regeneration.

[0005] In summary, existing n-heptane purification technologies generally suffer from problems such as incomplete impurity removal, high energy consumption, high cost, and poor industrial feasibility. In particular, there is a lack of adsorption materials with both precise pore structure and specific adsorption sites, making it impossible to achieve simultaneous and efficient removal of isoalkanes, aromatics, and oxygen-containing compounds. Therefore, developing a modified adsorption resin material with controllable structure, stable performance, and low cost, along with a corresponding efficient purification process, is crucial to overcoming the technological bottleneck of large-scale production of high-purity n-heptane, and has significant industrial application value and practical significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a modified adsorption resin for high-impurity n-heptane feedstock and a purification method thereof.

[0007] To achieve the above objectives, this invention provides a modified adsorption resin for high-impurity n-heptane feedstock, comprising the following raw materials in parts by weight: polystyrene-divinylbenzene resin microspheres: 90-110 parts; chloromethyl ether: 200-300 parts; anhydrous zinc chloride: 15-25 parts; 1,3,5,7-tetra(4-chloromethylphenyl)adamantane: 10-20 parts; anhydrous aluminum trichloride: 5-8 parts; 2-methylimidazole: 15-25 parts;

[0008] The preparation method of the 1,3,5,7-tetra(4-chloromethylphenyl)adamantane is as follows:

[0009] Under nitrogen protection, dichloroethane was added to a dry reaction vessel, followed by 1,3,5,7-tetraphenyladamantane. After stirring until completely dissolved, anhydrous aluminum trichloride was added, and stirring continued for 20-30 minutes to activate the reaction. The temperature was raised to 30-40°C, and chloromethyl ether was added. The reaction was stirred for 6-8 hours. After the reaction was complete, deionized water was added to quench the reaction. The product was then washed successively with 5 wt% sodium carbonate solution and deionized water. The solvent was removed by rotary evaporation. The crude product was recrystallized from methanol to obtain 1,3,5,7-tetra(4-chloromethylphenyl)adamantane. The chemical reaction equation is as follows: The product was characterized by ¹H NMR. This reaction is essentially a Lewis acid-catalyzed Friedel-Crafts electrophilic substitution reaction, carried out entirely under a nitrogen atmosphere to avoid interference with reaction selectivity by oxygen. Anhydrous aluminum trichloride coordinates with chloromethyl ether, causing the C-Cl bond in the chloromethyl ether to polarize and break, generating the strongly electrophilic chloromethyl cation (CH₂Cl₂). + ) and [AlCl4] - The anions, specifically the chloromethyl cations, preferentially attack the para positions (where steric hindrance is minimal and electron cloud density is relatively high) of each benzene ring in 1,3,5,7-tetraphenyladamantane, combining with the π electron cloud of the benzene ring to form unstable σ-complexes, subsequently [AlCl4]. -The anion abstracts a proton from an adjacent carbon atom in the σ-complex, restoring the aromaticity of the benzene ring, and finally introduces a chloromethyl group at the para position of each benzene ring to generate 1,3,5,7-tetra(4-chloromethylphenyl)adamantane.

[0010] Preferably, the BET specific surface area of ​​the polystyrene-divinylbenzene resin microspheres is 800 m². 2 / g.

[0011] Preferably, in the method for preparing 1,3,5,7-tetraphenyladamantane, the molar ratio of 1,3,5,7-tetraphenyladamantane, chloromethyl ether, and anhydrous aluminum trichloride is 1:8-12:0.6-1.

[0012] Preferably, in the preparation method of 1,3,5,7-tetraphenyladamantane, the weight ratio of 1,3,5,7-tetraphenyladamantane and dichloroethane is 1:8-12.

[0013] Furthermore, the present invention also provides a method for preparing a modified adsorption resin for high-impurity n-heptane feedstock, comprising the following steps:

[0014] (1) Polystyrene-divinylbenzene resin microspheres were added to dichloroethane, heated to 50-60℃, stirred and swollen for 8-12 hours, cooled to 30-35℃, anhydrous zinc chloride was added, stirred and activated for 30-60 minutes, then chloromethyl ether was added, heated to 45-55℃, stirred and reacted for 16-20 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain chloromethylated resin, washed three times with 5wt% hydrochloric acid solution and then washed with deionized water until neutral, and dried to obtain chloromethylated intermediate. This step is a Friedel-Crafts electrophilic substitution reaction, the core of which is to introduce chloromethyl active sites into polystyrene-divinylbenzene resin microspheres. Dichloroethane permeates the resin skeleton to fully open the pores, facilitating the diffusion of subsequent reagents to contact the active sites of the benzene ring; anhydrous zinc chloride acts as a Lewis acid to activate chloromethyl ether, causing it to undergo polarization cleavage to generate chloromethyl cations. The chloromethyl cations directionally attack the active sites of the benzene ring in the resin, and undergo electrophilic substitution to graft chloromethyl onto the benzene ring;

[0015] (2) The chloromethylated intermediate was added to toluene, heated to 60-80℃ and stirred to swell for 12-18h. Then, 1,3,5,7-tetra(4-chloromethylphenyl)adamantane and anhydrous aluminum trichloride were added. After purging with nitrogen to replace the air, the mixture was stirred at 80-100℃ for 16-24h. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain resin particles. The particles were washed three times with 5wt% hydrochloric acid solution and then washed with deionized water until neutral to obtain adamantane crosslinked modified resin. This reaction belongs to the Friedel-Crafts electrophilic substitution crosslinking reaction, which constructs a three-dimensional network structure of resin through a rigid framework. The chloromethylation intermediate is added to toluene, which acts as a good solvent to further open the resin channels, allowing 1,3,5,7-tetra(4-chloromethylphenyl)adamantane (crosslinking agent) and anhydrous aluminum trichloride to penetrate deep into the resin. The anhydrous aluminum trichloride catalyzes the chloromethyl groups on the crosslinking agent and the chloromethylation intermediate, causing them to generate chloromethyl cations. The cations generated at the four chloromethyl sites in the crosslinking agent molecule will undergo electrophilic substitution reactions with the benzene rings of different resin molecules (or different segments of the same resin molecule). With adamantane as a rigid node, the scattered resin segments are connected by covalent bonds to form a three-dimensional crosslinking network of "resin chain-adamantane-resin chain", thereby controlling the resin channel size.

[0016] (3) Add the adamantane crosslinked modified resin to N,N-dimethylformamide, then add 2-methylimidazole, and stir the reaction at 95-110℃ for 20-28h. After the reaction is complete, filter to obtain resin particles, wash with deionized water until neutral, wash three times with anhydrous ethanol, and dry to obtain the modified adsorption resin for high-impurity n-heptane raw material. This reaction is a nucleophilic substitution reaction, the core of which is to introduce specific adsorption sites into the crosslinked resin. Add the adamantane crosslinked modified resin to N,N-dimethylformamide (DMF). DMF, as a polar aprotic solvent, can dissolve 2-methylimidazole and further swell the crosslinked resin, allowing the imidazole molecules to penetrate deep into the resin pores and contact the chloromethyl active sites remaining after the crosslinking reaction. The nitrogen atom on the imidazole ring in the 2-methylimidazole molecule has a strong nucleophilicity due to the lone pair of electrons. It will directionally attack the partially positively charged carbon atom in the chloromethyl group of the resin, causing a nucleophilic substitution reaction, breaking the C-Cl bond, and releasing the chlorine atom to form Cl. - The imidazole ring is covalently linked to the resin skeleton through the -CH2- group, thereby achieving the grafting of the imidazole group.

[0017] Preferably, in (1), the polystyrene-divinylbenzene resin microspheres and dichloroethane are in a weight ratio of 5-10.

[0018] Preferably, in step (2), the chloromethylation intermediate and toluene are in a weight ratio of 1:8-10.

[0019] Preferably, in (3), the adamantane crosslinked modified resin and N,N-dimethylformamide are in a weight ratio of 1:8-10.

[0020] Furthermore, the present invention also provides a method for purifying high-impurity n-heptane feedstock using a modified adsorption resin, comprising the following steps:

[0021] S1. Column packing: The modified adsorption resin for high-impurity n-heptane feedstock is wet-packed into the primary and secondary adsorption columns. Anhydrous ethanol is used to replace the water in the resin pores, and then n-heptane is used to replace the anhydrous ethanol, thus completing the pretreatment of the adsorption columns.

[0022] S2. Adsorption purification: The high-impurity n-heptane raw material to be treated is fed from the top of the primary adsorption column, and the feed flow rate is controlled at 1-3 BV / h. Dynamic adsorption is carried out at a temperature of 20-40℃. The effluent is collected from the bottom of the adsorption column to obtain preliminarily purified n-heptane.

[0023] S3. Deep purification: The pre-purified n-heptane is passed through a two-stage adsorption column, and the flow rate is controlled at 2-4 BV / h. Secondary adsorption is carried out at a temperature of 25-35℃. The effluent is collected to obtain high-purity n-heptane product.

[0024] S4. Resin regeneration: The saturated resin is regenerated with a mixture of anhydrous ethanol and acetone in a volume ratio of 1:1-3. The desorption flow rate is 1-2 BV / h. After desorption, the resin is rinsed with n-heptane until the effluent is colorless, and then it can be reused.

[0025] Preferably, the aspect ratio of the primary and secondary adsorption columns is 5-10:1, and the amount of the anhydrous ethanol and acetone mixture is 3-5 times the volume of the adsorption column.

[0026] More preferably, the aspect ratio of the primary and secondary adsorption columns is 8:1, and the amount of the anhydrous ethanol and acetone mixture is 4 times the volume of the adsorption column.

[0027] Preferably, the resin saturated with adsorption in S4 is regenerated using a mixture of anhydrous ethanol and acetone in a volume ratio of 1:2.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention constructs a resin structure with both rigid channels and specific adsorption sites through a three-step modification process: "chloromethylation-adamantane crosslinking-imidazolium functionalization". The cuboethane skeleton of adamantane forms precise channels, which can efficiently screen isoparaffins through steric hindrance. The imidazolium groups specifically adsorb aromatics through π-π stacking interactions, while removing oxygen-containing compounds through dipole-dipole interactions, achieving simultaneous and deep removal of multiple impurities. This eliminates the need for multi-step separation processes and meets the stringent requirements for impurity residues in high-purity n-heptane, solving the problems of poor selectivity and incomplete removal of complex impurities in existing materials.

[0030] 2. The three-dimensional rigid network formed by the crosslinking of adamantane in this invention exhibits high mechanical strength and strong structural stability, making it less prone to pore collapse or dimensional deformation due to solvent swelling during the adsorption-regeneration cycle. The imidazole groups are firmly connected to the resin skeleton via covalent bonds, preventing functional group detachment or decomposition during desorption. Regeneration utilizes a mild ethanol-acetone mixture for desorption, eliminating the need for high-temperature treatment, significantly reducing regeneration energy consumption, and ensuring stable adsorption performance of the resin even after long-term use, thus extending material lifespan and reducing replacement costs and waste generation.

[0031] 3. The raw materials used in the resin preparation process of this invention are readily available, the reaction conditions are mild, and no special high-pressure or extreme environment equipment is required. The purification process adopts a two-stage adsorption column series design, which is compact and allows for easy control of parameters such as feed and desorption flow rates and temperature. Furthermore, the desorbent can be recovered and recycled through simple distillation, reducing raw material consumption. The overall process requires low equipment investment, is easy to operate, and has controllable costs, effectively solving the problems of complex preparation, high cost, and difficulty in large-scale application of existing high-end adsorption materials.

[0032] 4. The modified resin specifically designed in this invention can simultaneously address the three main impurities commonly found in high-impurity n-heptane: isoalkanes, aromatics, and oxygen-containing compounds. It eliminates the need to adjust process parameters or change adsorption materials for different impurity types, making it suitable for purifying n-heptane feedstocks with varying impurity contents. The purified product can meet the high-purity n-heptane requirements of various high-end fields such as electronic cleaning, chromatographic analysis, and pharmaceutical synthesis, avoiding the limitations of existing technologies in terms of narrow adaptability to raw material impurity composition and restricted application scenarios, thus enhancing the practical value and promotion potential of the technology. Attached Figure Description

[0033] Figure 1 The 1H NMR spectrum of 1,3,5,7-tetra(4-chloromethylphenyl)adamantane prepared in Example 2 of this invention. Detailed Implementation

[0034] 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.

[0035] Preparation Example 1: A specific method for preparing 1,3,5,7-tetra(4-chloromethylphenyl)adamantane includes the following steps:

[0036] Under nitrogen protection, 80 g of dichloroethane was added to a dry reaction vessel, followed by 10 g of 1,3,5,7-tetraphenyladamantane. After stirring until completely dissolved, 1.82 g of anhydrous aluminum trichloride was added, and stirring was continued for 20 min to activate the reaction. The temperature was raised to 30 °C, and 14.62 g of chloromethyl ether was added. The reaction was stirred for 6 h. After the reaction was completed, deionized water was added to quench the reaction. The product was then washed successively with 5 wt% sodium carbonate solution and deionized water. The solvent was removed by rotary evaporation. The crude product was recrystallized from methanol to obtain 1,3,5,7-tetra(4-chloromethylphenyl)adamantane.

[0037] Preparation Example 2: A specific method for preparing 1,3,5,7-tetra(4-chloromethylphenyl)adamantane, including the following steps:

[0038] Under nitrogen protection, 100 g of dichloroethane was added to a dry reaction vessel, followed by 10 g of 1,3,5,7-tetraphenyladamantane. After stirring until completely dissolved, 2.42 g of anhydrous aluminum trichloride was added, and stirring was continued for 25 min to activate the reaction. The temperature was raised to 35 °C, and 18.27 g of chloromethyl ether was added. The reaction was stirred for 7 h. After the reaction was completed, deionized water was added to quench the reaction. The product was then washed successively with 5 wt% sodium carbonate solution and deionized water. The solvent was removed by rotary evaporation. The crude product was recrystallized from methanol to obtain 1,3,5,7-tetra(4-chloromethylphenyl)adamantane.

[0039] Preparation Example 3: A specific method for preparing 1,3,5,7-tetra(4-chloromethylphenyl)adamantane, including the following steps:

[0040] Under nitrogen protection, 120 g of dichloroethane was added to a dry reaction vessel, followed by 10 g of 1,3,5,7-tetraphenyladamantane. After stirring until completely dissolved, 3.03 g of anhydrous aluminum trichloride was added, and stirring was continued for 30 min to activate the reaction. The temperature was raised to 40 °C, and 21.93 g of chloromethyl ether was added. The reaction was stirred for 8 h. After the reaction was completed, deionized water was added to quench the reaction. The product was then washed successively with 5 wt% sodium carbonate solution and deionized water. The solvent was removed by rotary evaporation. The crude product was recrystallized from methanol to obtain 1,3,5,7-tetra(4-chloromethylphenyl)adamantane.

[0041] Example 1: A specific preparation method of a modified adsorption resin for high-impurity n-heptane feedstock, comprising the following steps:

[0042] (1) 900g of polystyrene-divinylbenzene resin microspheres were added to 4.5kg of dichloroethane, heated to 50℃, stirred and swollen for 8h, cooled to 30℃, 150g of anhydrous zinc chloride was added, stirred and activated for 30min, then 2kg of chloromethyl ether was added, heated to 45℃, stirred and reacted for 16h, after the reaction was completed, cooled to room temperature, filtered to obtain chloromethylated resin, washed 3 times with 5wt% hydrochloric acid solution and washed with deionized water until neutral, and dried to obtain chloromethylated intermediate;

[0043] (2) 900g of chloromethylated intermediate was added to 7.2kg of toluene, heated to 60℃ and stirred for 12h to swell. 100g of 1,3,5,7-tetra(4-chloromethylphenyl)adamantane prepared according to Preparation Example 1 and 50g of anhydrous aluminum trichloride were added. After purging with nitrogen to replace the air, the mixture was stirred at 80℃ for 16h. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain resin particles, and washed three times with 5wt% hydrochloric acid solution and then washed with deionized water until neutral to obtain adamantane crosslinked modified resin.

[0044] (3) 900g of adamantane crosslinked modified resin was added to 7.2kg of N,N-dimethylformamide, and then 150g of 2-methylimidazole was added. The mixture was stirred at 95℃ for 20h. After the reaction was completed, the resin particles were filtered and washed with deionized water until neutral, and then washed three times with anhydrous ethanol. After drying, the modified adsorption resin for high-impurity n-heptane raw material was obtained.

[0045] Example 2: A specific preparation method of a modified adsorption resin for high-impurity n-heptane feedstock, comprising the following steps:

[0046] (1) 1 kg of polystyrene-divinylbenzene resin microspheres were added to 8 kg of dichloroethane, heated to 55 °C, stirred and swollen for 10 h, cooled to 32 °C, 200 g of anhydrous zinc chloride was added, stirred and activated for 45 min, then 2.5 kg of chloromethyl ether was added, heated to 50 °C, stirred and reacted for 18 h, after the reaction was completed, cooled to room temperature, filtered to obtain chloromethylated resin, washed 3 times with 5 wt% hydrochloric acid solution and washed with deionized water until neutral, and dried to obtain chloromethylated intermediate;

[0047] (2) 1 kg of chloromethylated intermediate was added to 9 kg of toluene, heated to 70 °C and stirred to swell for 15 h, 150 g of 1,3,5,7-tetra(4-chloromethylphenyl)adamantane prepared according to Preparation Example 2 and 65 g of anhydrous aluminum trichloride were added, nitrogen gas was introduced to replace the air, and the reaction was stirred at 90 °C for 20 h. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain resin particles, and washed three times with 5 wt% hydrochloric acid solution and then washed with deionized water until neutral to obtain adamantane crosslinked modified resin.

[0048] (3) Add 1 kg of adamantane crosslinked modified resin to 9 kg of N,N-dimethylformamide, then add 200 g of 2-methylimidazole, stir and react at 105 °C for 24 h. After the reaction is completed, filter to obtain resin particles, wash with deionized water until neutral, wash with anhydrous ethanol 3 times, and dry to obtain modified adsorption resin for high impurity n-heptane raw material.

[0049] Example 3: A specific preparation method of a modified adsorption resin for high-impurity n-heptane feedstock, comprising the following steps:

[0050] (1) 1.1 kg of polystyrene-divinylbenzene resin microspheres were added to 11 kg of dichloroethane, heated to 60 °C, stirred and swollen for 12 h, cooled to 35 °C, 250 g of anhydrous zinc chloride was added, stirred and activated for 60 min, then 3 kg of chloromethyl ether was added, heated to 55 °C, stirred and reacted for 20 h, after the reaction was completed, cooled to room temperature, filtered to obtain chloromethylated resin, washed 3 times with 5 wt% hydrochloric acid solution and washed with deionized water until neutral, and dried to obtain chloromethylated intermediate;

[0051] (2) 1.1 kg of chloromethylated intermediate was added to 11 kg of toluene, heated to 80 °C and stirred to swell for 18 h, 200 g of 1,3,5,7-tetra(4-chloromethylphenyl)adamantane prepared according to Preparation Example 3 and 80 g of anhydrous aluminum trichloride were added, nitrogen gas was introduced to replace the air, and the reaction was stirred at 100 °C for 24 h; after the reaction was completed, the mixture was cooled to room temperature, filtered to obtain resin particles, and washed three times with 5 wt% hydrochloric acid solution and then washed with deionized water until neutral to obtain adamantane crosslinked modified resin;

[0052] (3) 1.1 kg of adamantane crosslinked modified resin was added to 11 kg of N,N-dimethylformamide, and then 250 g of 2-methylimidazole was added. The mixture was stirred at 110 °C for 28 h. After the reaction was completed, the resin particles were filtered and washed with deionized water until neutral, and then washed three times with anhydrous ethanol. After drying, the modified adsorption resin for high-impurity n-heptane raw material was obtained.

[0053] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that step (1) is omitted and the styrene-divinylbenzene resin microspheres are not modified by chloromethylation.

[0054] Comparative Example 2: The difference between the comparative example and Example 2 is that step (2) is omitted and 1,3,5,7-tetra(4-chloromethylphenyl)adamantane is not added.

[0055] Comparative Example 3: The difference between Comparative Example 2 and Example 2 is that step (3) is omitted and 2-methylimidazole is not added.

[0056] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that styrene-divinylbenzene resin microspheres were directly used as the modified adsorption resin for high-impurity n-heptane raw material.

[0057] Performance testing:

[0058] Following the purification method for high-impurity n-heptane feedstock, the modified adsorption resins prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. The high-impurity n-heptane used contained 3% isoalkanes, 1.2% toluene, and 0.1% ethanol. The specific steps included:

[0059] S1. Column packing: The modified adsorption resin for high-impurity n-heptane feedstock is wet-packed into the primary and secondary adsorption columns. Anhydrous ethanol is used to replace the water in the resin pores, and then n-heptane is used to replace the anhydrous ethanol, thus completing the pretreatment of the adsorption columns.

[0060] S2. Adsorption purification: The high-impurity n-heptane raw material to be treated is fed from the top of the primary adsorption column, and the feed flow rate is controlled at 2 BV / h. Dynamic adsorption is carried out at a temperature of 30℃. The effluent is collected from the bottom of the adsorption column to obtain preliminarily purified n-heptane.

[0061] S3. Deep purification: The pre-purified n-heptane is passed through a two-stage adsorption column at a flow rate of 3 BV / h and a temperature of 30℃ for secondary adsorption. The effluent is collected to obtain high-purity n-heptane product.

[0062] S4. Resin regeneration: The saturated resin is regenerated with a mixture of anhydrous ethanol and acetone in a volume ratio of 1:2. The desorption flow rate is 1.5 BV / h. After desorption, the resin is rinsed with n-heptane until the effluent is colorless, and then it can be reused.

[0063] 1. Purification effect test: The contents of isoalkanes, toluene and ethanol in the high-purity n-heptane product eluted from the secondary adsorption column were detected by gas chromatography-FID, and the purity of high-purity n-heptane was recorded. The experimental results are shown in Table 1.

[0064] 2. Static Adsorption Capacity Test: Accurately weigh 0.5 g of each resin sample from Examples 1-3 and Comparative Examples 1-4, place them in stoppered conical flasks, add 50 mL of the aforementioned high-impurity n-heptane, seal, and place in a constant temperature water bath shaker (temperature 30℃, rotation speed 150 r / min) until adsorption equilibrium is reached (24 h; impurity content is detected by periodic sampling; equilibrium is determined when the deviation between two consecutive detection results is ≤0.01%). After equilibrium, take the supernatant and detect the concentration of each impurity using a gas chromatograph. Based on the changes in impurity concentration before and after adsorption, solution volume, and mass of modified adsorption resin, calculate the static adsorption capacity of the modified adsorption resin for isoparaffins, toluene, and ethanol. The experimental results are shown in Table 1.

[0065] 3. Resin regeneration performance test: The modified adsorption resins prepared in Examples 1-3 and Comparative Examples 1-4 were regenerated according to the purification method of high-impurity n-heptane raw material. After adsorption saturation, the adsorption-regeneration cycle was performed 5 times. The purity of high-purity n-heptane flowing out of the secondary adsorption column after 5 cycles was tested. The experimental results are shown in Table 1.

[0066] 4. Dynamic adsorption breakthrough performance test: Take 1L of each of the resins from Examples 1-3 and Comparative Examples 1-4 and pack them into a single adsorption column (length-to-diameter ratio 8:1). After pretreatment according to the purification method, high-impurity n-heptane is continuously fed at a flow rate of 2BV / h and 30℃. The effluent from the adsorption column is taken every 1h, and the toluene content in the effluent is detected by gas chromatography. When the toluene content in the effluent reaches 5% of the toluene content in the raw material, it is determined to be adsorption breakthrough. Record the total throughput from the start of feeding to breakthrough. The experimental results are shown in Table 1.

[0067] Table 1 Performance Test Results

[0068]

[0069]

[0070] Performance Analysis:

[0071] As can be seen from the experimental data in Table 1, the modified adsorption resins prepared by the present invention in Examples 1-3 are significantly better than the comparative examples in terms of n-heptane purification effect, static adsorption capacity, resin regeneration performance and dynamic adsorption breakthrough performance. Among them, Example 2 has the best overall performance.

[0072] Example 2 showed excellent purification results, which may be because the polystyrene-divinylbenzene resin microspheres underwent chloromethylation, grafting -C H2Cl active sites onto the benzene ring, providing sufficient and uniformly distributed reaction sites for subsequent crosslinking and functionalization. Secondly, 1,3,5,7-tetra(4-chloromethylphenyl)adamantane was crosslinked with the resin benzene ring via anhydrous aluminum trichloride-catalyzed Friedel-Crafts electrophilic substitution reaction. The rigid cubane skeleton of adamantane constructed a three-dimensional crosslinking network, precisely controlling the pore size to achieve a high degree of matching with the diameter of isoparaffin molecules, enabling efficient sieving of isoparaffins through steric hindrance. Finally, 2-methylimidazole was grafted onto the residual -C via a nucleophilic substitution reaction. At the H2Cl site, the aromatic structure of the imidazole ring forms a π-π stacking interaction with toluene, and the lone pair electrons of the nitrogen atom in the imidazole ring form a dipole-dipole interaction with ethanol. Simultaneously, trace amounts of other impurities (such as trace alkenes and low-carbon alkanes) are trapped by the rigid pores, ultimately achieving deep impurity removal and high purity of n-heptane. Comparison with the comparative examples: Comparative Example 1, due to the omission of the chloromethylation step, has resin without -C... The active sites in H2Cl prevent effective adamantane crosslinking and imidazole functionalization. There are no rigid sieving channels or specific adsorption sites, so impurities cannot be retained or adsorbed. Therefore, the impurity residue is much higher than in Example 2, and the purity of n-heptane is much lower than in Example 2. In Comparative Example 2, because the adamantane crosslinking step was omitted, the resin channels have a flexible, disordered structure, making it impossible to sieve isoalkanes through steric hindrance. The residue of isoalkanes is significantly higher than in Example 2. In Comparative Example 3, because the imidazole functionalization step was omitted, there is a lack of π-π stacking and dipole-dipole interaction sites. Toluene and ethanol cannot be specifically adsorbed, and their residues are significantly higher than in Example 2. Comparative Example 4 uses the original resin directly, which lacks active sites, rigid channels, and specific adsorption sites. All impurities cannot be effectively removed, resulting in the highest impurity residue and the lowest purity of n-heptane.

[0073] The microscopic reasons for the high static adsorption capacity in Example 2 are as follows: The rigid pores formed by the cross-linking of adamantane are not only suitable for the purification of high-impurity n-heptane, but also have a large internal surface area, allowing for efficient physical retention of isoparaffin molecules. Simultaneously, the hydrophobic properties of the pore walls enhance the interaction with isoparaffins, resulting in a high adsorption capacity for isoparaffins. The imidazole groups are firmly grafted onto the pore surface via covalent bonds, and each imidazole ring can form a stable π-π stacking interaction with toluene molecules, resulting in a high density of adsorption sites and sufficient contact, thus leading to a high toluene adsorption capacity. The polarity of the nitrogen atom in the imidazole ring forms a strong dipole-dipole interaction with the hydroxyl group of the ethanol molecule, and this interaction is not affected by the pore structure, resulting in fast adsorption kinetics and a high saturation adsorption capacity, thus leading to a high ethanol adsorption capacity. Comparison with the comparative examples: Comparative Example 1 lacks chloromethylation, leading to the absence of active sites; adamantane cannot cross-link to form rigid pores, and imidazole... The first example, Comparative Example 2, lacked imidazole group cross-linking, resulting in neither the ability to screen isoparaffins nor specific adsorption sites for toluene and ethanol. The adsorption capacity of all impurities was significantly lower than in Example 2. Comparative Example 3, lacking imidazole group functionalization, lacked π-π and dipole-dipole interaction sites, resulting in significantly lower adsorption capacities for toluene and ethanol than in Example 2. Although imidazole cross-linking resulted in relatively high adsorption capacity for isoparaffins, the disordered pores led to insufficient contact at adsorption sites, resulting in lower adsorption capacities than in Example 2. Comparative Example 4, being the original resin, lacked rigid pores and specific adsorption sites, resulting in a small pore surface area and the lowest adsorption capacity for all impurities.

[0074] The excellent regeneration performance of Example 2 is due to the following: the rigid three-dimensional cross-linked network of adamantane possesses extremely high mechanical strength and structural stability. During the "adsorption-regeneration" cycle, the pores are not prone to collapse or dimensional deformation due to solvent swelling, maintaining precise sieving dimensions. Simultaneously, the imidazole groups are covalently connected to the resin skeleton, preventing functional group detachment or decomposition during desorption, resulting in high adsorption site retention. Furthermore, the active sites formed by chloromethylation and the chemical bonds formed by subsequent cross-linking and functionalization exhibit strong stability. After regeneration, the overall structure and functional group distribution of the resin remain almost unchanged, thus maintaining a high level of n-heptane purity after regeneration. Comparison with other comparative examples: Comparative Example 1: None Chloromethylation results in the absence of effective cross-linking and functionalization, leading to a loose resin structure. During regeneration, the resin is prone to skeletal collapse due to solvent swelling, resulting in a lack of stable adsorption sites. Consequently, the purity after regeneration is significantly lower than that of Example 2. Comparative Example 2 lacks adamantane cross-linking, resulting in a flexible pore structure. During regeneration, the resin is prone to dimensional deformation due to solvent action, leading to a significant decrease in sieving capacity. Consequently, the purity after regeneration is significantly lower than that of Example 2. Comparative Example 3 lacks imidazole functionalization. Although the pore structure is stable, the adsorption sites are already scarce, resulting in poor recovery of adsorption capacity after regeneration and a purity lower than that of Example 2. Comparative Example 4's original resin lacks a cross-linked structure, making it prone to particle breakage or structural loosening during regeneration. This leads to the fastest decline in adsorption capacity and the lowest purity after regeneration.

[0075] The microscopic reason for the good dynamic adsorption breakthrough performance in Example 2 is that the rigid pores ensure uniform flow velocity and no local dead volume when the high-impurity n-heptane feedstock flows in the adsorption column. Impurity molecules can fully contact the sieving sites and functional group adsorption sites in the pores, avoiding local rapid breakthrough caused by pore blockage or uneven flow velocity. At the same time, the high density and uniform distribution of adsorption sites can continuously retain or adsorb impurities until all sites are saturated before breakthrough occurs, resulting in a high total throughput. In comparison with the comparative examples: Comparative Example 1 has very few adsorption sites, and impurity molecules quickly occupy the limited sites before breakthrough occurs, resulting in a total throughput far lower than that of Example 2; Comparative Example 2, due to the lack of adamantane crosslinking, cannot be sieved for isoalkanes, and isoalkanes molecules quickly pass through the pores and breakthrough occurs, resulting in a total throughput significantly lower than that of Example 2; Comparative Example 3, due to the lack of imidazole functionalization, cannot be adsorbed for toluene and ethanol, and both breakthrough occur rapidly, resulting in a total throughput lower than that of Example 2; Comparative Example 4 has no effective adsorption and sieving sites, and impurity molecules pass through the adsorption column almost unimpeded, resulting in the fastest breakthrough and the lowest total throughput.

[0076] 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 modified adsorption resin for high-impurity n-heptane feedstock, characterized in that, The raw materials include the following parts by weight: polystyrene-divinylbenzene resin microspheres: 90-110 parts; chloromethyl ether: 200-300 parts; Anhydrous zinc chloride: 15-25 parts; 1,3,5,7-tetra(4-chloromethylphenyl)adamantane: 10-20 parts; Anhydrous aluminum trichloride: 5-8 parts; 2-methylimidazole: 15-25 parts; The preparation method of the 1,3,5,7-tetra(4-chloromethylphenyl)adamantane is as follows: Under nitrogen protection, dichloroethane was added to a dry reaction vessel, followed by 1,3,5,7-tetraphenyladamantane. After stirring until completely dissolved, anhydrous aluminum trichloride was added, and stirring was continued for 20-30 min to activate the mixture. The temperature was raised to 30-40℃, chloromethyl ether was added, and the reaction was stirred for 6-8 h. After the reaction was completed, deionized water was added to quench the reaction. The mixture was then washed successively with 5 wt% sodium carbonate solution and deionized water. The solvent was removed by rotary evaporation. The crude product was recrystallized from methanol to obtain 1,3,5,7-tetra(4-chloromethylphenyl)adamantane.

2. The modified adsorption resin for high-impurity n-heptane feedstock according to claim 1, characterized in that, The polystyrene-divinylbenzene resin microspheres have a BET specific surface area of ​​800 m². 2 / g.

3. The modified adsorption resin for high-impurity n-heptane feedstock according to claim 1, characterized in that, In the preparation method of 1,3,5,7-tetraphenyladamantane, the molar ratio of 1,3,5,7-tetraphenyladamantane, chloromethyl ether, and anhydrous aluminum trichloride is 1:8-12:0.6-1.

4. The modified adsorption resin for high-impurity n-heptane feedstock according to claim 1, characterized in that, In the preparation method of 1,3,5,7-tetraphenyladamantane, the weight ratio of 1,3,5,7-tetraphenyladamantane and dichloroethane is 1:8-12.

5. The method for preparing the modified adsorption resin for high-impurity n-heptane feedstock according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Add polystyrene-divinylbenzene resin microspheres to dichloroethane, heat to 50-60℃, stir and swell for 8-12h, cool to 30-35℃, add anhydrous zinc chloride, stir and activate for 30-60min, then add chloromethyl ether, heat to 45-55℃, stir and react for 16-20h, after the reaction is completed, cool to room temperature, filter to obtain chloromethylated resin, wash 3 times with 5wt% hydrochloric acid solution and wash with deionized water until neutral, and dry to obtain chloromethylated intermediate; (2) The chloromethylated intermediate was added to toluene, heated to 60-80℃ and stirred to swell for 12-18h. Then, 1,3,5,7-tetra(4-chloromethylphenyl)adamantane and anhydrous aluminum trichloride were added. After purging the air with nitrogen, the mixture was stirred at 80-100℃ for 16-24h. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain resin particles. The particles were washed three times with 5wt% hydrochloric acid solution and then washed with deionized water until neutral to obtain adamantane crosslinked modified resin. (3) Add the adamantane crosslinked modified resin to N,N-dimethylformamide, then add 2-methylimidazole, stir and react at 95-110℃ for 20-28h. After the reaction is completed, filter to obtain resin particles, wash with deionized water until neutral, wash with anhydrous ethanol 3 times, and dry to obtain modified adsorption resin for high impurity n-heptane raw material.

6. The method for preparing the modified adsorption resin for high-impurity n-heptane feedstock according to claim 5, characterized in that, In (1), the polystyrene-divinylbenzene resin microspheres and dichloroethane are in a weight ratio of 5-10.

7. The method for preparing the modified adsorption resin for high-impurity n-heptane feedstock according to claim 5, characterized in that, In (2), the chloromethylation intermediate and toluene are in a weight ratio of 1:8-10.

8. The method for preparing the modified adsorption resin for high-impurity n-heptane feedstock according to claim 5, characterized in that, In (3), the adamantane crosslinked modified resin and N,N-dimethylformamide are in a weight ratio of 1:8-10.

9. The method for purifying high-impurity n-heptane feedstock using a modified adsorption resin according to claim 1, characterized in that, Includes the following steps: S1. Column packing: The modified adsorption resin for high-impurity n-heptane feedstock is wet-packed into the primary and secondary adsorption columns. Anhydrous ethanol is used to replace the water in the resin pores, and then n-heptane is used to replace the anhydrous ethanol, thus completing the pretreatment of the adsorption columns. S2. Adsorption purification: The high-impurity n-heptane raw material to be treated is fed from the top of the primary adsorption column, and the feed flow rate is controlled at 1-3 BV / h. Dynamic adsorption is carried out at a temperature of 20-40℃. The effluent is collected from the bottom of the adsorption column to obtain preliminarily purified n-heptane. S3. Deep purification: The pre-purified n-heptane is passed through a two-stage adsorption column, and the flow rate is controlled at 2-4 BV / h. Secondary adsorption is carried out at a temperature of 25-35℃. The effluent is collected to obtain high-purity n-heptane product. S4. Resin regeneration: The saturated resin is regenerated with a mixture of anhydrous ethanol and acetone in a volume ratio of 1:1-3. The desorption flow rate is 1-2 BV / h. After desorption, the resin is rinsed with n-heptane until the effluent is colorless, and then it can be reused.

10. The method for purifying high-impurity n-heptane feedstock using a modified adsorption resin according to claim 9, characterized in that, The aspect ratio of the primary and secondary adsorption columns is 5-10:1.

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