Application of ionic liquid functionalized super-crosslinked resin in nervonic acid adsorption

Abstract

The invention discloses an application of ionic liquid functionalized super-crosslinked resin in nervonic acid adsorption. The imidazole functionalized super-crosslinked resin HCl-M has high specific surface area and optimized pore size distribution, is matched with nervonic acid molecular size, remarkably improves the adsorption capacity and selectivity of nervonic acid, enhances the interaction force between the resin and nervonic acid through ionic liquid functional modification, and further improves the adsorption performance. The adsorption capacity of the imidazole functionalized super-crosslinked resin to nervonic acid is remarkably improved, and the adsorption process is controlled by multiple mechanisms such as screening action, hydrogen bond and pi-pi interaction and the like. The invention provides theoretical guidance and technical support for efficiently adsorbing nervonic acid from shiny-leaved yellowhorn oil, and has important application value.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials and neuraminic acid adsorption and separation, and in particular to the application of an ionic liquid functionalized super cross-linked resin in neuraminic acid adsorption. Background Art

[0002] In recent years, adsorption separation technology has gradually become a research hotspot for natural product separation due to its advantages such as high efficiency, environmental protection and simple operation. Hypercrosslinked polymers (HCPs) are a class of polymer materials with permanent microporous structures. Since Davankov first reported them, they have shown good application prospects in the field of adsorption separation due to their high specific surface area and adjustable pore structure. As a new type of environmentally friendly solvent, ionic liquids have shown excellent performance in a variety of separation and analysis methods. However, in the existing technology, commercial macroporous adsorption resins (such as WZK-1 and XHT-1) have problems such as low adsorption capacity, poor selectivity, mismatched pore size distribution, lack of multiple interaction forces, and limited research on pore structure regulation and functional modification when adsorbing neuraminic acid, which limits their application in actual production.

[0003] Nerve acid is an important monounsaturated fatty acid that has the dual effects of repairing damaged nerve fibers and promoting brain cell regeneration. It has important application value in infant brain development and Alzheimer's disease treatment. Xanthoceras sorbifolia oil is rich in nerve acid, but the existing technology lacks efficient separation and extraction methods for nerve acid, which restricts the large-scale application of nerve acid. Therefore, it is of great practical significance to develop a resin material with high adsorption capacity and high selectivity.

[0004] The ionic liquid functionalized super-crosslinked resin provided by the present invention significantly improves the adsorption capacity and selectivity for nervonic acid, and provides theoretical guidance and technical support for the efficient adsorption of nervonic acid from Xanthoceras sorbifolia oil. Summary of the invention

[0005] The purpose of the present invention is to provide an application of an ionic liquid functionalized super cross-linked resin in the adsorption of neuraminic acid.

[0006] 1. Preparation of resin Using chloromethylated polystyrene (labeled as CP, with a styrene-divinylbenzene skeleton) as raw material, using its abundant benzyl chloride groups, a Friedel-Crafts post-crosslinking reaction was carried out under the catalysis of anhydrous zinc chloride to prepare a hyper-crosslinked resin with a high specific surface area. The specific steps are as follows: (1) Resin pretreatment: soaking the CP resin in ethanol, washing and drying to obtain a pretreated CP resin; (2) Preparation of hyper-crosslinked resin: The pretreated CP resin was swollen in 1,2-dichloroethane, anhydrous zinc chloride was added to carry out Friedel-Crafts post-crosslinking reaction, and the hyper-crosslinked resin HCL-08 was obtained after washing, Soxhlet extraction and drying; The conditions of the Friedel-Crafts post-crosslinking reaction are as follows: the reaction temperature is 380-400 K, the reaction time is 8-12 h, the mass ratio of the pre-treated CP resin to anhydrous zinc chloride is 5:1-15:1, and after the swelling is completed, the stirring speed is adjusted to 30 rpm, and anhydrous zinc chloride is added quickly and heated at 1 K·min -1 The temperature was raised at a rate of 1.5 h and the sample was uniformly heated to 388 K for Friedel-Crafts post-crosslinking reaction.

[0007] (3) Preparation of imidazole functional super cross-linked adsorption resin: HCL-08 resin was swelled in N,N-dimethylformamide, and NaOH and imidazole were added to carry out imidazole functionalization reaction. After washing, Soxhlet extraction and drying, imidazole functional super cross-linked resin HCL-M was obtained; The amount of imidazole added is 5% to 25% of the mass of the CP resin; the mass ratio of NaOH to HCL-08 resin is 1:1 to 1:3; the imidazole functionalization reaction is carried out at 340 to 350 K for 8 to 12 hours; Different doses of imidazole were added for reaction to obtain imidazole functionalized super cross-linked resin HCL-M series. When the imidazole addition amount was 5%, 10%, 15%, 20% and 25% of the mass of CP resin, different imidazole functionalized super cross-linked adsorption resins HCL-M02, HCL-M04, HCL-M06, HCL-M08 and HCL-M10 were obtained.

[0008] 2. Resin structure characterization The specific surface area and pore structure of the polymeric adsorbent were determined by the Brunauer-Emmett-Teller (BET) method using nitrogen as the adsorbate under liquid nitrogen environment (77 K) using an ASAP 2020 rapid specific surface area / pore analyzer.

[0009] The physical and chemical properties of WZK-1, XHT-1, CP, HCL-08 and HCL-M series resins are shown in Tables 1 and 2. As can be seen from the table, compared with the macroporous adsorption resins WZK-1 and XHT-1, the hypercrosslinked resins HCL-08 and HCL-M08 have relatively high specific surface areas, and the micropores contribute more to the specific surface area of ​​the hypercrosslinked resins.

[0010] According to the principle reported in the literature that "when the pore size of the adsorbent is 2-6 times the size of the adsorbate, it is most conducive to adsorption", the pore structure distribution of the resin was modified. Therefore, the size of the resin we use to adsorb nervonic acid should be between 2.8 and 8.4 nm. Using CP (chloromethylated polystyrene) as a precursor, its average pore size is 21.53nm, which belongs to the mesoporous range. It is first hyper-cross-linked to obtain the HCL series of resins, among which HCL-08 has the best adsorption performance. Then it is functionalized to obtain the imidazole-modified hyper-cross-linked adsorption resin HCL-M series, among which HCL-M08 has the best adsorption performance. As shown in Table 2, the average pore size of HCL-M08 resin is 3.60 nm, which is just the pore size suitable for adsorbing nervonic acid.

[0011] The nitrogen adsorption / desorption isotherms of WZK-1, XHT-1, CP, HCL-08 and HCL-M08 at 77 K are shown in Figure 2 (a). The CP isotherm type characteristics are not particularly obvious, but it also has a certain degree of adsorption hysteresis loop. The HCL-08 and HCL-M08 isotherms also have a certain degree of adsorption hysteresis loop. When the relative pressure is less than 0.1, the nitrogen adsorption amount increases rapidly, and the increase is significantly greater than that of WZK-1 and XHT-1, indicating that it contains rich microporous structures; when the relative pressure is between 0.1 and 0.9, the nitrogen adsorption amount gradually increases, indicating that the mesopore content is less than the micropore content; when the relative pressure is greater than 0.9, the nitrogen adsorption amount increases slightly, indicating that the HCL-08 and HCL-M08 structures may contain a small amount of macroporous structures.

[0012] The pore size distribution of WZK-1, XHT-1, CP, HCL-08 and HCL-M08 at 77 K is shown in Figure 2 (b) From Figure 2 (b) It can be seen that the pore size distributions of CP, WZK-1 and XHT-1 are quite different, while the pore size distributions of HCL-08 and HCL-M08 are basically the same. Both mesopores and micropores exist in the four adsorbents WZK-1, XHT-1, HCL-08 and HCL-M08. The nitrogen adsorption amount of CP increases steadily with the increase of relative pressure, indicating that there is no microporous structure in CP. It can be clearly seen from the pore size distribution diagram that HCL-08 and HCL-M08 resins are typical microporous adsorbents containing mesopores and macropores (2–100nm), while WZK-1 and XHT-1 are mesoporous macroporous adsorbents containing a small amount of micropores, which is consistent with the conclusions in Tables 1 and 2.

[0013] 3. Adsorption of neuraminic acid 1. Calculation of the molecular size of neuraminic acid Gaussian 09D01 software was used to optimize the molecular configuration of neuraminic acid by quantum chemical theoretical calculation based on density functional theory and Hartree-Fock method. Figure 1 The geometric structure parameters can be obtained by calculation, as shown in Table 3. The molar volume of nervonic acid molecule is 1429.78 cm 3 ·mol -1 , it can be calculated that the molecular size of neuraminic acid is 1.40 nm.

[0014] 2. Adsorption kinetics experiments Take 1.0 g (dry weight) of each of the five resins and 100 mL of nervonic acid solution (0.25 mg mL -1 ) was added to a 250 mL stoppered conical flask and oscillated in a thermostatic oscillator at 298.15±1 K for 12 h (100 rpm). Then, samples were taken at different time intervals during the adsorption process and their contents were determined by HPLC until the content of nervonic acid in the solution remained unchanged. The adsorption capacity of different resins for nervonic acid at different time points was calculated to investigate the adsorption kinetics of nervonic acid on different resins.

[0015] Depend on Figure 3 It can be seen that the adsorption capacity of nervonic acid on WZK-1, XHT-1, CP, HCL-08 and HCL-M08 increases with the increase of adsorption time until the adsorption reaches equilibrium. The adsorption capacity of nervonic acid on super-crosslinked resins HCL-M08 and HCL-08 is significantly higher than that on commercial macroporous resins WZK-1 and XHT-1. As shown in Tables 1 and 2, the average pore sizes of WZK-1, XHT-1, HCL-08 and HCL-M08 are 7.63 nm, 7.52 nm, 3.86 nm and 3.60 nm, respectively. It can be calculated from Tables 1 and 2 that the micropore specific surface areas of WZK-1 and XHT-1 account for 2.68% and 3.09% of their total specific surface areas, respectively, while the micropore specific surface areas of HCL-08 and HCL-M08 account for 56.65% and 59.89% of their total specific surface areas, respectively. Increasing the proportion of micropores can significantly increase the specific surface area of ​​the adsorbent, thereby providing more active adsorption sites for the adsorbate, which helps to improve the overall adsorption capacity.

[0016] In order to better analyze all the kinetic data and explain the adsorption mechanism of WZK-1, XHT-1, CP, HCL-08 and HCL-M08, the intraparticle diffusion model and micropore diffusion model were used to fit the experimental data and study the diffusion behavior of the adsorbed substances during the adsorption process on the resin surface.q t and t 1 / 2 The control mechanism of the adsorption process can be determined by the relationship curve: when the obtained graph presents a single linear relationship, it indicates that the adsorption process is mainly dominated by the intra-particle diffusion; if the curve presents multiple linear segments, it indicates that the adsorption process is jointly regulated by a multi-stage mechanism.

[0017] The adsorption kinetics data were fitted using the intraparticle diffusion model. The fitting results are shown in Figure 4 As shown. Figure 4 It can be seen that the intraparticle diffusion curve consists of a straight line passing through the origin, a straight line not passing through the origin, and a platform, which correspond to the three stages of diffusion from macropores to mesopores to micropores, respectively. This indicates that the adsorption process of nervonic acid on HCL-M08 is controlled by both intraparticle diffusion and external diffusion.

[0018] like Figure 5 As shown in the figure, the micropore diffusion model was used to fit the adsorption kinetics experimental data, and the linear correlation coefficient ( R 2 ) and the micropore diffusion coefficient ( D c ) are shown in Table 4. As can be seen from Table 4, for HCL-08 and HCL-M08, R 2 >0.99, the micropore diffusion model can well describe the adsorption process of nervonic acid on HCL-08 and HCL-M08, indicating that there are a considerable number of micropores in the pore structure of HCL-08 and HCL-M08. However, the adsorption of nervonic acid on the three preferred resins WZK-1, XHT-1 and CP cannot be well fitted by the micropore diffusion model. This also shows that the three resins WZK-1, XHT-1 and CP are mesoporous macroporous adsorbents, while HCL-08 and HCL-M08 are microporous polymeric adsorbents. This result is also consistent with the average pore size data of the adsorbents in Table 1.

[0019] 3. Adsorption isotherm experiment In order to better describe the adsorption process, the present invention investigated the equilibrium adsorption isotherms of nervonic acid on five resins, WZK-1, XHT-1, CP, HCL-08 and HCL-M08, at 298, 308 and 318 K. The specific experimental process is as follows: 100 mL of nervonic acid solution of different concentrations and 1.0 g of pretreated resin (by dry weight) were added to a 250 mL stoppered conical flask, and the flask was oscillated at a constant temperature of 298K for 12 h (100 rpm). The adsorption residue was taken out, and the content of nervonic acid in the adsorption residue was determined by HPLC, and the corresponding adsorption capacity was calculated.

[0020] Figure 6 The adsorption isotherms of five adsorption resins, WZK-1, XHT-1, CP, HCL-08 and HCL-M08, at 298 K were compared. The Langmuir and Freundlich isotherm models were used to fit the adsorption isotherm data, and the relevant fitting parameters are shown in Table 5. The experimental results show that the Langmuir isotherm model shows a good fitting effect on the isotherm data of the two adsorbents WZK-1 and XHT-1; in contrast, the Freundlich isotherm model is more suitable for the isotherm fitting of the three adsorbents CP, HCL-08 and HCL-M08. This phenomenon reveals that there are significant differences in the adsorption characteristics of the five polymeric adsorbents. From a theoretical perspective, the Langmuir model is based on the monolayer adsorption hypothesis and believes that there are a limited number of uniform adsorption sites on the adsorbent surface. Therefore, the adsorption process of WZK-1 and XHT-1 on nervonic acid may conform to the monolayer adsorption mechanism. The adsorption process of CP, HCL-08 and HCL-M08 on neuraminic acid may conform to the multilayer adsorption mechanism.

[0021] like Figure 7 As shown in Figure , the equilibrium adsorption isotherms of HCL-M08 were studied at 288, 298, and 308 K. Figure 7 It can be seen that the adsorption capacity increases with the increase of concentration, and high temperature is more conducive to adsorption, indicating that adsorption is an endothermic process.

[0022] 4. Adsorption mechanism Macroporous adsorption resin is a separation material that combines the principles of sieving and adsorption. The sieving performance relies on the mesh holes with a certain pore size inside the resin, which presents a certain selectivity according to the size of its molecular volume, thereby achieving the purpose of separating the target compound; the adsorption performance mainly relies on its internal porous structure and specific surface area, and uses weak interactions such as hydrophobic forces and van der Waals forces in molecules to adsorb the target compound. Figure 8 Figure 1 is a schematic diagram of the interaction force between HCL-M08 and neuraminic acid. Figure 8 It can be seen that the adsorption of nervonic acid by imidazole-modified hyper-crosslinked adsorption resin HCL-M08 is controlled by multiple mechanisms such as sieving, hydrogen bonding, π-π interaction, etc. The large adsorption capacity of HCL-M08 for nervonic acid is the result of the synergistic effect of these forces.

[0023] Beneficial effects of the present invention: (1) Imidazole functionalized hypercrosslinked resin HCL-M has a high specific surface area and optimized pore size distribution. The BET specific surface area of ​​HCL-M08 is 802.95 m² / g, and the micropore specific surface area accounts for 59.89% of the total specific surface area. The average pore size is 3.60 nm, which matches the molecular size of nervonic acid, significantly improving the adsorption capacity and selectivity of nervonic acid. The polarity matching between HCL-M08 and nervonic acid, and the matching of the average pore size of HCL-M08 with the molecular size of nervonic acid are critical for adsorption.

[0024] (2) The imidazole-functionalized hyper-cross-linked resin was functionalized with ionic liquid to enhance the interaction between the resin and neuraminic acid, further improving the adsorption performance.

[0025] (3) Excellent adsorption kinetics and multilayer adsorption mechanism: The adsorption capacity of HCL-M08 is 65.59 mg / g, and the adsorption rate is fast, which is suitable for industrial application. The intraparticle diffusion model shows that the adsorption process is controlled by both intraparticle diffusion and external diffusion. The Freundlich isotherm model has the best fitting effect on the adsorption data of HCL-M08 (R²=0.9955). The adsorption capacity increases with increasing temperature, indicating that the adsorption process is an endothermic reaction.

[0026] (4) Adsorption by synergistic action of multiple interaction forces: The interactions between HCL-M08 and neuraminic acid include sieving, hydrogen bonding, and π-π interactions. The synergistic action of multiple forces further improves the adsorption performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The molecular configuration of neuraminic acid optimized by Hartree-Fock method using Gaussian 09D01 software; Figure 2 (a) N2 adsorption / desorption isotherms of WZK-1, XHT-1, CP, HCL-08 and HCL-M08; Figure 2 (b) Pore size distribution of WZK-1, XHT-1, CP, HCL-08 and HCL-M08; Figure 3 Adsorption kinetics curves of WZK-1, XHT-1, CP, HCL-08 and HCL-M08; Figure 4 Linear fitting of intraparticle diffusion model for WZK-1, XHT-1, CP, HCL-08 and HCL-M08; Figure 5 Linear fitting of micropore diffusion model for WZK-1, XHT-1, CP, HCL-08 and HCL-M08; Figure 6 Adsorption isotherms (298K) of nervonic acid on five resins: WZK-1, XHT-1, CP, HCL-08 and HCL-M08; Figure 7 Adsorption isotherm of nervonic acid on HCL-M08; Figure 8 Schematic diagram of the adsorption mechanism of neuraminic acid on HCL-M08. DETAILED DESCRIPTION

[0028] The present invention is further described below through specific implementation modes.

[0029] The instruments and reagents used in the present invention are as follows: Instruments: Shimadzu Prominence LC-20A high performance liquid chromatography system (Shimadzu Corporation, Japan), equipped with SPD-M20A diode array detector, LC-20AT quaternary pump and SIL-20AC autosampler; ASAP 2020 specific surface area and pore analyzer (Micromeritics Instrument Corp., USA); KQ-250DE ultrasonic cleaning equipment (Kunshan Ultrasonic Instrument Co., Ltd., China); DZF-6050 vacuum drying oven (Yingyu Yuhua Instrument Factory, Gongyi City, China); ZFD-5090 drying oven (Shanghai Zhicheng Analytical Instrument Manufacturing Co., Ltd., China); MP200A electronic balance (Shanghai Jingke Balance Factory, China); SHA-B constant temperature water bath oscillator (Jiangsu Jintan Zhengji Instrument Co., Ltd., China); Spring-R10 pure water preparation system (Rui Sijie Scientific Instrument Co., Ltd., China); DF-101S magnetic stirring heater (Zhengzhou Great Wall Science and Technology Industry and Trade Co., Ltd., China); HD2015W electric stirrer (Shanghai Si Le Instrument Co., Ltd., China).

[0030] Reagents: Neural acid standard (purity ≥ 99.0%, Aladdin Biochemical Technology Co., Ltd., Shanghai, China); chromatographic grade acetonitrile (Tianjin Chemical Reagent Co., Ltd., China); chromatographic grade methanol and tetrahydrofuran (Aladdin Biochemical Technology Co., Ltd., Shanghai, China); laboratory-made deionized water; analytical grade glacial acetic acid (Shandong Yuwang Chemical Co., Ltd., China). Example

[0031] 1. Resin pretreatment Weigh 50 g of CP resin, place it in a stoppered conical flask, add 250 mL of ethanol and soak it for 24 h, filter, discard the filtrate, wash the resin repeatedly with ethanol until no white turbidity appears when 3 times the volume of water is added to the washing liquid, then wash it with distilled water until there is no alcohol smell, and vacuum dry it at 313 K for 6 h to obtain the pretreated CP resin.

[0032] 2. Preparation of Resin ① Preparation of hypercrosslinked resin: Take 20 g of pretreated CP resin and place it in a 250 mL round-bottom flask. Add 120 mL of 1,2-dichloroethane at room temperature and allow it to swell for 24 h. Then, adjust the stirring speed to 30 rpm and quickly add 2 g of anhydrous zinc chloride. -1 The reaction mixture was uniformly heated to 388 K within 1.5 h at a heating rate of 1.5 h, and an oil bath reaction was carried out at this temperature for 10 h. After the reaction was completed, the reaction solution was poured out and washed with 95% ethanol containing 1% (W / W) hydrochloric acid and pure water in turn to remove residual nitrobenzene and zinc chloride. Then, Soxhlet extraction was carried out for 10 h with 300 mL of 95% ethanol as the solvent, and finally vacuum dried for 12 h at 313 K and a pressure below 10 mm Hg. The resulting hypercrosslinked resin was labeled HCL-08.

[0033] ② Preparation of imidazole functional group super cross-linked adsorption resin: Weigh 10 g of HCL-08 resin, place it in a three-necked round-bottom flask, add 135 mL of N, N-dimethylformamide to swell for 12 h, add 5 g of NaOH, add different doses (0.5 g, 1.0 g, 1.5 g, 2.0 g, 2.5 g) of imidazole (5%, 10%, 15%, 20%, 25% of CP mass, respectively), and react in an oil bath at 343 K for 10 h. After the experiment, the reaction mixture was first filtered and separated, and then the resin was washed alternately with ethanol and distilled water until the pH value of the washing liquid reached neutral. Then, the resin was extracted with 95% ethanol by Soxhlet extraction for 12 hours, and finally vacuum dried at 313 K for 12 h to obtain different imidazole functionalized hyper-crosslinked adsorption resins HCL-M02, HCL-M04, HCL-M06, HCL-M08, and HCL-M10. The adsorption capacity of HCL-M08 is 65.59 mg / g.

Claims

1. Application of an ionic liquid functionalized hypercrosslinked resin in the adsorption of neuraminic acid, characterized in that: The resin is prepared by the following steps: (1) Resin pretreatment: soaking the CP resin in ethanol, washing and drying to obtain a pretreated CP resin; (2) Preparation of hyper-crosslinked resin: The pretreated CP resin was swollen in 1,2-dichloroethane, anhydrous zinc chloride was added to carry out Friedel-Crafts post-crosslinking reaction, and the hyper-crosslinked resin HCL-08 was obtained after washing, Soxhlet extraction and drying; (3) Preparation of imidazole functionalized super cross-linked adsorption resin: HCL-08 resin was swollen in N,N-dimethylformamide, and NaOH and imidazole were added to carry out imidazole functionalization reaction. After washing, Soxhlet extraction and drying, imidazole functionalized super cross-linked resin HCL-M was obtained.

2. The use according to claim 1, characterized in that: The conditions of the Friedel-Crafts post-crosslinking reaction are: reaction temperature of 380-400 K, reaction time of 8-12 h.

3. The use according to claim 1, characterized in that: The mass ratio of the pretreated CP resin to anhydrous zinc chloride is 5:1 to 15:

1.

4. The use according to claim 1, characterized in that: The amount of imidazole added is 5% to 25% of the mass of the CP resin.

5. The use according to claim 1, characterized in that: The imidazole functionalization reaction is carried out at 340-350K for 8-12 h.

6. The use according to claim 1, characterized in that: The specific surface area of ​​the imidazole functionalized super cross-linked resin HCL-M is 617.66-949.57 m² / g, and the average pore size is 3.60-4.05 nm.

7. The use according to claim 1, characterized in that The adsorption capacity of the resin for nervonic acid is 65.59 mg / g.

8. The use according to claim 1, characterized in that: The adsorption process of the resin on nervonic acid is controlled by multiple mechanisms including sieving, hydrogen bonding and π-π interaction.

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