Xylose molecularly imprinted silica gel polymer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a xylose molecularly imprinted silica gel polymer as well as a preparation method and application thereof. The preparation method comprises the following steps: replacing chlorine atoms on polystyrene microspheres with nitrogen atoms of a functional monomer 3-pyridine boric acid to form modified microspheres, and then forming five-membered ring or six-membered ring boric acid ester from xylose and boric acid groups of 3-pyridine boric acid under a weakly alkaline condition. And covering the surface of the resin with a SiO2 imprinting layer, and finally washing off template molecule xylose by using an acidic solvent to obtain the xylose molecularly imprinted silica gel polymer. Xylose molecules can selectively enter a xylose cavity obtained through silica gel imprinting, boric acid groups and a cis-diol structure of xylose can form boric acid cyclic ester, and selective adsorption of xylose can be achieved through cooperation of the boric acid groups and the cis-diol structure.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a xylose molecularly imprinted silica gel polymer and a preparation method and application thereof. Background Art

[0002] Xylose is the most abundant pentose in the hemicellulose fraction of lignocellulosic biomass. It is stable, safe, and non-toxic, making it widely used in industries such as food, medicine, and feed. Its derivatives also have a huge market, such as in the preparation of a variety of high-value-added products such as xylitol, furfural, and xylonic acid. However, the production of xylose often requires the separation of xylose from complex hydrolysates. For example, the hydrolysate obtained by treating lignocellulosic biomass through methods such as dilute acid hydrolysis and autohydrolysis often contains impurities such as other sugars, acids, and phenols in addition to xylose. Efficient and selective xylose separation is crucial for improving the purity and quality of xylose, reducing production costs, and promoting its high-value utilization.

[0003] Molecular imprinting technology boasts characteristics such as predictability, recognition, and practicality. By selecting appropriate template molecules, functional monomers, and cross-linkers, molecularly imprinted polymers with high selectivity and affinity for specific target molecules can be prepared. Such polymers are able to specifically recognize and adsorb target molecules in complex mixtures. However, most current imprinted molecules for separating carbohydrates use borate as a functional group, utilizing the boric acid group to form a stable five- or six-membered ring borate ester with a cis-diol structure in a weakly alkaline environment to separate carbohydrates. However, lignocellulose hydrolysates are mostly acidic environments, so there is an urgent need for an imprinted molecule product that can adsorb xylose under weakly acidic conditions. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a method for preparing a xylose molecularly imprinted silica gel polymer.

[0005] The second technical problem to be solved by the present invention is to provide the application of the above polymer in the separation of sugar substances.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A method for preparing a xylose molecularly imprinted silica gel polymer comprises the following steps: using 3-pyridineboronic acid as a functional monomer to be grafted onto polystyrene microspheres to form modified microspheres; reacting a template molecule xylose with the boronic acid groups on the modified microspheres to form a stable five-membered ring lactone; then covering the microspheres with a SiO2 imprinting layer; and finally washing away the template molecule xylose with an acidic solvent to obtain the polymer.

[0008] The preparation method of the xylose molecularly imprinted silica gel polymer comprises the following steps:

[0009] (1) dissolving 3-pyridineboric acid in an organic solvent, adding polystyrene microspheres, and heating the mixture under nitrogen protection to obtain modified microspheres;

[0010] (2) dissolving the modified microspheres in an ammonium bicarbonate solution, adjusting the pH value to alkaline conditions, adding the template molecule xylose and reacting to obtain xylose-grafted modified microspheres;

[0011] (3) mixing the modified microspheres grafted with xylose with an ethanol solution of tetraethoxysilane, adding a catalyst for reaction, and filtering to obtain modified microspheres covered with a SiO2 imprinting layer;

[0012] (4) washing the modified microspheres covered with the SiO2 imprinting layer with an acidic solution to wash away the template molecule xylose, thereby obtaining a xylose molecular imprinted silica gel polymer.

[0013] In step (1), the organic solvent is N,N-dimethylformamide; the polystyrene microspheres are chloromethyl polystyrene resin; the particle size of the chloromethyl polystyrene resin is preferably 3 μm to 20 μm; the molar ratio of the polystyrene microspheres to 3-pyridineboronic acid is 1:1 to 1:1.5; the heating reaction has a reaction temperature of 50 to 100° C. (preferably 70° C.) and a reaction time of 24 to 72 h (preferably 48 h).

[0014] In step (2), the mass volume ratio of the modified microspheres to the ammonium bicarbonate solution is 1 g:130 mL to 1 g:160 mL (preferably 1 g:150 mL); the pH value is adjusted to 8 to 9 (preferably 8.5) under alkaline conditions using NaOH; the molar ratio of the modified microspheres to xylose is 1:1.2 to 1:1.5; the mixing reaction is a room temperature reaction, and the reaction time is 2 to 3 hours (preferably 3 hours).

[0015] In step (3), the concentration of the tetraethoxysilane ethanol solution is 0.1M to 1M; the mass ratio of the modified microspheres grafted with xylose to the tetraethoxysilane ethanol solution is 1:20 to 1:100; the catalyst is ammonia water, and the proportion of ammonia water in the total solution is 1% to 7%; the reaction is a room temperature reaction, and the reaction time is 1 to 2 hours (preferably 1 hour).

[0016] In step (4), the acidic solution is acetic acid with a pH of 2.3, sulfuric acid with a pH of 2.3, or hydrochloric acid with a pH of 2.3 (preferably acetic acid with a pH of 2.3); and the washing is immersion ultrasonic washing for 3 to 4 times (preferably 3 times), and each washing lasts for 5 to 20 minutes (preferably 30 minutes).

[0017] In some embodiments, the xylose molecularly imprinted silica gel polymer is prepared by replacing chlorine on chloromethyl polystyrene resin with 3-PBA, wherein the loading capacity of the chloromethyl polystyrene resin is 2-3 mmol / g and the loading capacity of 3-BPA is 0.4 mol / L-0.5 mol / L.

[0018] The xylose molecularly imprinted silica gel polymer prepared by the above preparation method is also within the protection scope of the present invention. Its structural diagram is shown in FIG. Figure 1 shown.

[0019] The application of the above xylose molecularly imprinted silica gel polymer in the separation of sugar substances also falls within the protection scope of the present invention.

[0020] The xylose molecularly imprinted silica polymer selectively adsorbs xylose under acidic conditions. Specifically, the xylose molecularly imprinted silica polymer has high selectivity and high adsorption capacity for xylose under acidic conditions, and can separate xylose in complex systems. Thus, this resin has the ability to efficiently and selectively separate xylose in complex systems such as cellulose acid hydrolysates.

[0021] The xylose molecularly imprinted silica gel polymer selectively adsorbs xylose from a mixed system of xylose and glucose under acidic conditions; preferably, the acidic conditions are acetic acid or sulfuric acid environments.

[0022] Compared with the prior art, the present invention has the following significant advantages:

[0023] 1. The xylose molecularly imprinted silica gel polymer provided by the present invention has a selective adsorption effect on xylose in acidic solution.

[0024] 2. The present invention is selective for xylose in an acidic xylose and glucose mixed solution and has little adsorption on glucose, thereby achieving the separation of xylose and glucose. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0026] Figure 1 The schematic diagram of the structure of the xylose molecularly imprinted silica gel polymer prepared by the preparation method of the present invention is shown in FIG. In which, PS represents chloromethyl polystyrene resin, Xly represents xylose, and 3-PBA represents 3-pyridine boronic acid.

[0027] Figure 2 This is the infrared spectrum of the xylose-imprinted silica gel polymer prepared in Examples 1 and 2.

[0028] Figure 3This is a diagram of the xylose separation performance of the xylose-imprinted silica gel polymer prepared in Examples 1 and 2.

[0029] Figure 4 This is a graph showing the xylose separation performance of the non-imprinted silica gel polymer prepared in Example 3. DETAILED DESCRIPTION

[0030] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0031] Chloromethyl polystyrene microspheres (PS-CH2-Cl) used in the following examples were purchased from Tokyo Chemical Industry Development Co., Ltd. (Shanghai).

[0032] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0033] Embodiment 1:

[0034] The preparation steps of xylose molecularly imprinted silica polymer are as follows:

[0035] (1) Chloromethyl polystyrene resin grafted with 3-pyridineboronic acid

[0036] To a 150 mL three-necked flask, 40 mL of N,N-dimethylformamide, 1.48 g of 3-pyridineboronic acid, and 4.5 g of chloromethyl polystyrene resin (the molar ratio of chloromethyl polystyrene resin to 3-pyridineboronic acid was 1:1.2) were added sequentially. A spherical condenser was placed on the flask and nitrogen was introduced to protect the system. The reaction system was then heated to 70°C and reacted under magnetic stirring for 48 hours. After the reaction, the solid was filtered and washed with N,N-dimethylformamide three times for 10 minutes each. The mixture was then dried overnight under vacuum. 5.5 g of modified microspheres were obtained.

[0037] (2) Modified microspheres grafted with xylose

[0038] First, prepare 500 mL of ammonium bicarbonate solution and adjust the pH to 8.5 with NaOH. Add 2 g of the modified microspheres to a 500 mL three-necked flask, followed by 300 mL of the pH-adjusted ammonium bicarbonate solution. Finally, add 0.7 g of the template molecule, xylose. Seal the reaction system and stir at room temperature for 3 hours. After the reaction is complete, filter the solid and wash it three times with ammonium bicarbonate solution, each for 10 minutes. Allow to air-dry at room temperature to yield 2.22 g of xylose-grafted modified microspheres.

[0039] (3) Covering SiO2 imprinting layer

[0040] Prepare 40 mL of a 500 mmol tetraethoxysilane solution in ethanol and add it to two 150 mL three-necked flasks. Then, add 1 g of xylose-grafted modified microspheres to each flask, followed by 160 mL of ethanol and 15 mL of ammonia. Seal the reaction system and stir in parallel at room temperature for 50 and 60 minutes. After the reaction, filter and collect the two solids.

[0041] (4) Washing away the template molecule xylose

[0042] The two solids covered with the SiO2 imprinting layer were immersed and ultrasonically washed in an acetic acid solution with pH 2.3 for three times, each time for half an hour, to obtain two xylose imprinted silica gel polymers.

[0043] Example 2:

[0044] The preparation steps of xylose molecularly imprinted silica polymer are as follows:

[0045] (1) Chloromethyl polystyrene resin grafted with 3-pyridineboronic acid

[0046] To a 150 mL three-necked flask, 40 mL of N,N-dimethylformamide, 1.24 g of 3-pyridineboronic acid, and 4.13 g of chloromethyl polystyrene resin (the molar ratio of chloromethyl polystyrene resin to 3-pyridineboronic acid was 0.826:1) were added sequentially. A spherical condenser was placed on the flask and nitrogen was introduced to protect the system. The reaction system was then heated to 70°C and reacted under magnetic stirring for 48 hours. After the reaction, the solid was filtered and washed with N,N-dimethylformamide three times for 10 minutes each. The mixture was then dried overnight under vacuum. 5.1 g of modified microspheres were obtained.

[0047] (2) Modified microspheres grafted with xylose

[0048] First, prepare 500 mL of ammonium bicarbonate solution and adjust the pH to 8.5 with NaOH. Add 2 g of the modified microspheres to a 500 mL three-necked flask, followed by 300 mL of the pH-adjusted ammonium bicarbonate solution. Finally, add 0.6 g of the template molecule, xylose. Seal the reaction system and stir at room temperature for 3 hours. After the reaction is complete, filter the solid and wash it three times with ammonium bicarbonate solution, each for 10 minutes. Allow to dry at room temperature to yield 2.2 g of xylose-grafted modified microspheres.

[0049] (3) Covering SiO2 imprinting layer

[0050] First, 0.1 mL of tetraethoxysilane and 0.2 mL of tetraethoxysilane solution were mixed with 40 mL of ethanol to create two pre-coagulation solutions. These solutions were then added to two 150 mL three-necked flasks. One gram of xylose-grafted modified microspheres was added to each flask, followed by 160 mL of ethanol. The sealed reaction system was stirred at room temperature for 60 minutes. After the reaction was complete, the solid was filtered.

[0051] (4) Washing away the template molecule xylose

[0052] The imprinted layer solid covered with SiO2 was soaked and ultrasonically washed in an acetic acid solution with pH 2.3 for 3 times, each time for half an hour, to obtain a xylose imprinted silica gel polymer.

[0053] Example 3:

[0054] This embodiment is the same as embodiment 1, except that the operation of grafting xylose onto the modified microspheres in step (2) is deleted, that is, the modified microspheres obtained in step (1) are directly subjected to the operation of covering the SiO2 imprinting layer in step (3).

[0055] Example 4:

[0056] Take 600 mg of each imprinted silica gel polymer obtained in Example 1 to Example 2, divide them equally into 3 groups, with two parallel groups in each group, and add them into 25 mL conical flasks respectively. Add glucose solution (10 mL, 2 g / L) to the first group; add xylose solution (10 mL, 2 g / L) to the second group; add a mixed solution of glucose (10 mL, 2 g / L) and xylose (10 mL, 2 g / L) to the third group. All three solutions are prepared using ammonium bicarbonate solution with a pH of 8.5. Then shake at room temperature and 150 rpm for 6 hours. Determine the concentrations of xylose and glucose in the supernatant after shaking, as well as the concentrations of glucose and xylose in the initial feed solution (see Table 1). Finally, calculate the adsorption amount of xylose and glucose by the imprinted silica gel polymer (see Figure 3 ) and separation factor (2.39).

[0057] The calculation formula of adsorption amount:

[0058] Where Co is the initial concentration of sugar in the feed solution, Ce is the final concentration of sugar in the feed solution, V is the volume of the adsorbed feed solution, and m is the mass of the adsorption medium.

[0059] The calculation formula of separation factor is:

[0060] Where Qx is the final adsorption amount of xylose on the medium, Qg is the final adsorption amount of glucose on the medium; Cx is the final concentration of xylose in the supernatant, and Cg is the final concentration of glucose in the supernatant.

[0061] The calculation formulas for adsorption capacity and separation factor in the following examples are the same.

[0062] Table 1

[0063]

[0064] Example 5:

[0065] (1) The xylose-imprinted silica gel polymer, chloromethyl polystyrene resin and modified microspheres prepared in Examples 1 and 2 were subjected to infrared detection, respectively. The results were as follows: Figure 2 As shown. Figure 2 Let's take a look at 3390cm -1 The absorption peak of -OH is 1305cm -1 It is the characteristic infrared absorption peak of BO. According to the above two infrared absorption peaks, it can be judged that 3-pyridine boronic acid has been successfully connected. And because the infrared absorption peaks of xylose imprinted silica gel polymer at 50min and 60min are at 1070cm -1 The absorption of xylose was attributed to the stretching vibration of Si-O. Therefore, the successful synthesis of xylose-imprinted silica gel polymer can be judged.

[0066] (2) The loading amount of PS@3-pyridineboronic acid prepared in Examples 1 and 2 was calculated according to the following formula, and the grafting rate of 3-PBA was calculated based on the loading amount, as shown in Table 2:

[0067] PS@3-PBA loading: LA = [(W2-W1) / 122.93] / W1

[0068] Boric acid group grafting rate formula:

[0069] In the above formula, W1 and W2 are the mass of the resin before and after the reaction, respectively; 122.93 is the relative molecular mass of 3-pyridineboronic acid; and 0.002 is the chlorine loading amount in the chloromethyl polystyrene resin.

[0070] Table 2

[0071]

[0072] Comparative Example 1:

[0073] The non-imprinted silica gel polymer obtained in Example 3 was also subjected to the same experimental steps as in Example 4 to measure the adsorption capacity of xylose and glucose by the non-imprinted silica gel polymer (see Figure 4 ) and the separation factor for xylose and glucose (0.96).

[0074] Table 3

[0075]

[0076] The present invention provides a xylose molecularly imprinted silica gel polymer, its preparation method, and its application. There are many methods and approaches to implement this technical solution. The above is only a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A method for preparing a xylose molecularly imprinted silica gel polymer, characterized in that: 3-Pyridineboronic acid is grafted onto polystyrene microspheres as a functional monomer to form modified microspheres. Then, the template molecule xylose reacts with the boronic acid groups on the modified microspheres to form a stable five-membered ring lactone. Then, a SiO2 imprinting layer is covered, and finally, the template molecule xylose is washed away with an acidic solvent to obtain the product.

2. The preparation method according to claim 1, characterized in that The following steps are involved: (1) dissolving 3-pyridineboric acid in an organic solvent, adding polystyrene microspheres, and heating the mixture under nitrogen protection to obtain modified microspheres; (2) dissolving the modified microspheres in an ammonium bicarbonate solution, adjusting the pH value to alkaline conditions, adding the template molecule xylose and reacting to obtain xylose-grafted modified microspheres; (3) mixing the modified microspheres grafted with xylose with an ethanol solution of tetraethoxysilane, adding a catalyst for reaction, and filtering to obtain modified microspheres covered with a SiO2 imprinting layer; (4) washing the modified microspheres covered with the SiO2 imprinting layer with an acidic solution to wash away the template molecule xylose, thereby obtaining a xylose molecular imprinted silica gel polymer.

3. The preparation method according to claim 2, characterized in that In step (1), the organic solvent is N,N-dimethylformamide; the polystyrene microspheres are chloromethyl polystyrene resin; the molar ratio of the polystyrene microspheres to 3-pyridineboric acid is 1:1 to 1:1.5; the heating reaction has a reaction temperature of 50 to 100° C. and a reaction time of 24 to 72 hours.

4. The preparation method according to claim 2, characterized in that In step (2), the mass volume ratio of the modified microspheres to the ammonium bicarbonate solution is 1 g:130 mL to 1 g:160 mL; the pH value is adjusted to 8 to 9 under alkaline conditions using NaOH; the molar ratio of the modified microspheres to xylose is 1:1.2 to 1:1.5; the mixing reaction is carried out at room temperature, and the reaction time is 2 to 3 hours.

5. The preparation method according to claim 2, characterized in that In step (3), the concentration of the tetraethoxysilane ethanol solution is 0.1M to 1M; the mass ratio of the modified microspheres grafted with xylose to the tetraethoxysilane ethanol solution is 1:20 to 1:100; the catalyst is ammonia water, and the proportion of ammonia water in the total solution is 1% to 7%; the reaction is a room temperature reaction, and the reaction time is 1 to 2 hours.

6. The preparation method according to claim 2, characterized in that In step (4), the acidic solution is acetic acid with a pH of 2.3, sulfuric acid with a pH of 2.3, or hydrochloric acid with a pH of 2.3; and the washing is immersion ultrasonic washing for 3 to 4 times, with each washing lasting 5 to 20 minutes.

7. The xylose molecularly imprinted silica polymer prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the xylose molecularly imprinted silica gel polymer according to claim 7 in the separation of carbohydrates.

9. The use according to claim 8, characterized in that The xylose molecularly imprinted silica gel polymer selectively adsorbs xylose under acidic conditions.

10. The use according to claim 9, characterized in that The xylose molecularly imprinted silica gel polymer selectively adsorbs xylose from a mixed system of xylose and glucose under acidic conditions; preferably, the acidic conditions are acetic acid or sulfuric acid environments.

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