阅读说明：本技术 新型硼酸功能化大孔树脂的制备以及在甜菊糖苷选择吸附中的应用 (Preparation of novel boric acid functionalized macroporous resin and application of novel boric acid functionalized macroporous resin in selective adsorption of stevioside ) 是由 王贺云 李�昊 吕银 魏忠 赵亚欣 贾茹 于 2020-12-07 设计创作，主要内容包括：本发明公开了一种甜菊糖苷选择性吸附材料的制备方法,涉及甜菊糖苷提纯技术领域。本发明包括以下步骤：通过悬浮聚合法制备丙烯酸酯类大孔树脂；通过引入引发剂BIBB,使丙烯酸酯类大孔树脂表面形成溴代活性位点,得到引发剂功能化树脂；将引发剂功能化树脂加入溶有硼酸功能化单体的聚合溶液中,在丙烯酸酯类大孔树脂表面的溴代活性位点进行接枝,得到甜菊糖苷选择性吸附材料。本发明通过范德华力和氢键作用力使在对甜菊糖苷具有较好的亲和力、较高吸附能力的树脂的成形,再利用硼酸对顺式二醇的特异性吸附力这一特点,在树脂表面进行硼酸位点接枝,从而有效增加树脂对甜菊糖的富集回收和分离能力。(The invention discloses a preparation method of a stevioside selective adsorption material, and relates to the technical field of stevioside purification. The invention comprises the following steps: preparing acrylic macroporous resin by a suspension polymerization method; forming a bromo-active site on the surface of the acrylic macroporous resin by introducing an initiator BIBB to obtain an initiator functionalized resin; adding the initiator functional resin into a polymerization solution dissolved with the boric acid functional monomer, and grafting the initiator functional resin on the bromo-active site on the surface of the acrylic macroporous resin to obtain the stevioside selective adsorption material. According to the invention, through Van der Waals force and hydrogen bond acting force, the resin with good affinity and high adsorption capacity to stevioside is formed, and then boric acid site grafting is carried out on the surface of the resin by utilizing the characteristic that the specific adsorption capacity of boric acid to cis-diol is utilized, so that the enrichment, recovery and separation capacity of the resin to stevioside is effectively increased.)

1. A preparation method of a stevioside selective adsorption material is characterized in that boric acid functionalized grafting modification is directly carried out by an atomic radical polymerization (ATRP) method on the basis of hydroxyl resin synthesis, and comprises the following steps:

step S01: preparing hydroxyl-containing acrylate macroporous resin by a suspension polymerization method;

step S02: introducing the acrylic macroporous resin into an initiator BIBB to form brominated active sites on the surface of the acrylic macroporous resin, so as to obtain initiator functionalized resin;

step S03: adding the initiator functional resin into a polymerization solution dissolved with the boric acid functional monomer, and grafting the initiator functional resin on the bromo-active site on the surface of the acrylic macroporous resin to obtain the stevioside selective adsorption material.

2. The method for preparing a steviol glycoside selective adsorption material according to claim 1, wherein in the step S01, the components of the acrylic macroporous resin comprise, by weight: 1.072 parts of acrylate, 1.072 parts of EGDMA-5.555 parts of acetate, 6.627 parts of acetate, 26.506 parts of AIBN-26.506 parts of HPMC-0.133 part of the mixture;

the preparation method of the acrylic macroporous resin comprises the following steps:

step SS 11: adding acrylate, GDMA, acetate, AIBN and HPMC into a reaction kettle in sequence, and stirring and dispersing the mixture evenly in purified water;

step SS 12: heating the reaction kettle to 65-80 ℃ to carry out suspension polymerization reaction for 9h to obtain a suspension polymerization reactant;

step SS 13: cooling the reaction kettle to normal temperature, cleaning the suspension polymerization reactant, and drying in vacuum to obtain the acrylic macroporous resin.

3. The method for preparing the stevioside selective adsorption material according to claim 1, wherein the boric acid functionalized grafting modification is directly performed by an atomic radical polymerization (ATRP) method on the basis of hydroxyl resin synthesis, and the method for forming the brominated active sites on the surface of the acrylate macroporous resin in the step S02 comprises the following steps:

step SS 21: pre-wetting the prepared acrylic macroporous resin in methanol for 10-15min to obtain pre-wetted macroporous resin;

step SS 22: soaking the pre-wet macroporous resin in water for 2 times, removing methanol, and drying the cleaned pre-wet macroporous resin in a vacuum drying oven to obtain macroporous resin to be reacted;

step SS 23: putting the macroporous resin to be reacted into a reaction solvent containing an initiator, and stirring for 24 hours at normal temperature to obtain initiator functionalized resin;

step SS 24: and thoroughly cleaning the initiator functionalized resin by using pure water.

4. The preparation method of the stevioside selective adsorption material according to claim 3, wherein the boric acid functionalized grafting modification is directly carried out by an atomic radical polymerization (ATRP) method on the basis of hydroxyl resin synthesis, the components of the reaction solution in the step SS23 comprise 2-bromoisobutyryl bromide, triethylamine and anhydrous tetrahydrofuran, and the weight ratio of the hydroxyl-containing macroporous resin, the 2-bromoisobutyryl bromide and the triethylamine is 4.39:2.3: 1.01.

5. The method according to claim 3, wherein the pure water is second-stage RO water or pure water having a purity higher than that of the second-stage RO water.

6. The method of claim 1, wherein the polymerization solution in step S03 comprises, by weight, 1.48 parts of 4-vinylphenylboronic acid, 1.48 parts of CuCl-0.00297 parts of 2-bipyridine-0.01024 parts of anhydrous methanol-31.64 parts of the polymerization solution;

the configuration method comprises the following steps: dissolving 4-vinylphenylboronic acid in absolute methanol, deoxidizing by circulating through a freezing pump for 3 times, and filling the vacuumized part with nitrogen after each vacuumizing; then uniformly stirring the treated anhydrous methanol solution dissolved with the 4-vinyl phenylboronic acid, CuCl and 2-bipyridyl in an oxygen-free environment to obtain a polymerization solution;

the method for grafting the bromo-active sites on the surface of the acrylic macroporous resin comprises the following steps:

step SS 31: under the room temperature and oxygen-free condition, the initiator functionalized resin is placed in the polymerization solution to react for 48 hours to obtain polymerization resin;

step SS 32: putting the obtained polymeric resin into a container filled with secondary RO water, stirring and cleaning for three times, wherein the first time is cleaned for 30 minutes at room temperature, the second time is cleaned for 60 minutes at 60 ℃, and the third time is cleaned for 30 minutes at room temperature;

step SS 33: and drying the washed polymeric resin at the temperature of 45 ℃ overnight to obtain the stevioside selective adsorption material.

Technical Field

The invention belongs to the technical field of stevioside purification, and particularly relates to a preparation method of a stevioside selective adsorption material.

Background

Stevioside is a mixture of several stevioside extracted from the leaves of stevia rebaudiana and is a natural sweetener, the sweetness of the stevioside is about 300 times that of cane sugar, and the stevioside has the advantages of high sweetness, low calorie, no toxicity, no side effect and the like, so the stevioside is popular among people, some artificially synthesized sweeteners are replaced in food additives, but the stevioside has bitter taste compared with the sweetness and the purity of cane sugar, the application effect is influenced to a certain extent, and the bitter taste needs to be removed.

Stevia glycosides are mixtures of eight diterpene glycosides, which are: stevioside (STV), steviolbioside (steviolbioside), Rebaudioside A (RA), Rebaudioside B (RB), Rebaudioside C (RC), Rebaudioside D (RD), Rebaudioside E (RE), dulcoside A (dulcoside A, Dul-A).

Wherein, STV and RA are main stevioside components in stevia rebaudiana Bertoni, which account for about 90 percent of the total stevioside content, and the taste of untreated stevioside is closer to that of stevioside and is far from that of cane sugar because the STV and RA account for more components. Therefore, the effective separation of STV from stevioside is an effective way to improve the mouthfeel of stevioside.

Currently, the effect of separating STV from stevioside is general, and therefore a material with higher separation efficiency is required.

Disclosure of Invention

The invention aims to provide a preparation method of a stevioside selective adsorption material, which solves the problem that the effect of separating STV from stevioside is limited in the prior art.

In order to solve the technical problems, the invention is realized by the following technical scheme:

the invention relates to a preparation method of a stevioside selective adsorption material, which comprises the following steps:

step S01: preparing hydroxyl-containing acrylate macroporous resin by a suspension polymerization method;

step S02: introducing the acrylic macroporous resin into an initiator BIBB to form brominated active sites on the surface of the acrylic macroporous resin, so as to obtain initiator functionalized resin;

step S03: adding the initiator functionalized resin into the polymerization solution, and grafting the initiator functionalized resin on the bromo-active sites on the surface of the acrylic macroporous resin to obtain the stevioside selective adsorption material.

Preferably, in step S01, the acrylic macroporous resin comprises the following components by weight: 1.072 parts of acrylates, 1.072 parts of GDMA-5.555 parts of ethyl acetate, 6.627 parts of ethyl acetate, 26.506 parts of AIBN-26.506 parts of HPMC-0.133 parts of the raw materials; wherein, the acrylate is a monomer, the EGDMA is a cross linker, the ethyl acetate is a pore-forming agent, the HPMC is a dispersant, and the AIBN is an initiator;

the preparation method of the acrylic macroporous resin comprises the following steps:

step SS 11: adding acrylate, GDMA, acetate, AIBN and HPMC into a reaction kettle in sequence, and stirring and dispersing the mixture evenly in purified water;

step SS 12: heating the reaction kettle to 65-80 ℃ to carry out suspension polymerization reaction for 9h to obtain a suspension polymerization reactant;

step SS 13: cooling the reaction kettle to normal temperature, cleaning the suspension polymerization reactant, and drying in vacuum to obtain the acrylic macroporous resin.

Preferably, in step S02, the method for forming the brominated active sites on the surface of the acrylic macroporous resin includes the following steps:

step SS 21: pre-wetting the prepared acrylic macroporous resin in methanol for 10-15min to obtain pre-wetted macroporous resin;

step SS 22: soaking the pre-wet macroporous resin in water for 2 times, removing methanol, and drying the cleaned pre-wet macroporous resin in a vacuum drying oven to obtain macroporous resin to be reacted;

step SS 23: putting the macroporous resin to be reacted into a reaction solvent, and stirring for 24 hours at normal temperature to obtain initiator functionalized resin;

step SS 24: and thoroughly cleaning the initiator functionalized resin by using pure water.

Preferably, the components of the reaction solution in the step SS23 comprise 2-bromoisobutyryl bromide, triethylamine and anhydrous tetrahydrofuran, and the weight ratio of the macroporous resin, the 2-bromoisobutyryl bromide and the triethylamine is 4.39:2.3: 1.01;

wherein the mass concentration of 2-bromoisobutyryl bromide is 10mmol/L, and the mass concentration of triethylamine is 10 mmol/L; reacting the 2-bromine isobutyryl bromide with carboxyl on the macroporous resin to be reacted to fix the bromine initiation group on the surface of the macroporous resin to be reacted.

Preferably, the pure water is second-grade RO water and pure water with the purity above.

Preferably, the polymerization solution in the step S03 includes, by weight group, 4-vinylphenylboronic acid-1.48 parts, CuCl-0.00297 parts, 2-bipyridine-0.01024 parts, and anhydrous methanol-31.64 parts; wherein, 4-vinyl phenylboronic acid is taken as a monomer, CuCl is taken as a catalyst, and 2-bipyridine and anhydrous methanol are taken as solvents;

the configuration method comprises the following steps: dissolving 4-vinylphenylboronic acid in absolute methanol, deoxidizing by circulating through a freezing pump for 3 times, and filling the vacuumized part with nitrogen after each vacuumizing; then uniformly stirring the treated anhydrous methanol solution dissolved with the 4-vinyl phenylboronic acid, CuCl and 2-bipyridyl in an oxygen-free environment to obtain a polymerization solution;

the method for grafting the bromo-active sites on the surface of the acrylic macroporous resin comprises the following steps:

step SS 31: under the room temperature and oxygen-free condition, the initiator functionalized resin is placed in the polymerization solution to react for 48 hours to obtain polymerization resin;

step SS 32: putting the obtained polymeric resin into a container filled with secondary RO water, stirring and cleaning for three times, wherein the first time is cleaned for 30 minutes at room temperature, the second time is cleaned for 60 minutes at 60 ℃, and the third time is cleaned for 30 minutes at room temperature;

step SS 33: and drying the washed polymeric resin at the temperature of 45 ℃ overnight to obtain the stevioside selective adsorption material.

The invention has the following beneficial effects:

according to the invention, through Van der Waals force and hydrogen bond acting force, the resin with good affinity and high adsorption capacity to stevioside is formed, and then boric acid site grafting is carried out on the surface of the resin by utilizing the characteristic of specific adsorption capacity of boric acid to cis-diol, so that the enrichment recovery and separation capacity of the resin to stevioside is effectively increased, high selectivity is realized on the basis of ensuring high adsorption quantity, and the separation and purification effects of stevioside are improved.

Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of the ATRP grafting process of hydroxyl-containing acrylate resin according to the present invention;

fig. 2 is a graph of infrared absorption spectrum test performed on the steviol glycoside selective adsorbent material of the present invention.

Fig. 3 is an XPS test chart performed on the steviol glycoside selective adsorbent material of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, the present invention is a method for preparing a selective steviol glycoside adsorption material, which includes the following steps:

step S01: preparing acrylic macroporous resin by a suspension polymerization method;

step S02: introducing the acrylic macroporous resin into an initiator BIBB to form brominated active sites on the surface of the acrylic macroporous resin, so as to obtain initiator functionalized resin;

step S03: adding the initiator functionalized resin into the polymerization solution, and grafting the initiator functionalized resin on the bromo-active sites on the surface of the acrylic macroporous resin to obtain the stevioside selective adsorption material.

Preferably, in step S01, the acrylic macroporous resin comprises the following components by weight: 1.072 parts of acrylates, 1.072 parts of GDMA-5.555 parts of ethyl acetate, 6.627 parts of ethyl acetate, 26.506 parts of AIBN-26.506 parts of HPMC-0.133 parts of the raw materials; wherein, acrylic ester is a monomer, GDMA is a cross-linking agent, ethyl acetate is a pore-forming agent, HPMC is a dispersing agent, and AIBN is an initiator;

the preparation method of the acrylic macroporous resin comprises the following steps:

step SS 11: adding acrylate, GDMA, acetate, AIBN and HPMC into a reaction kettle in sequence, and stirring and dispersing the mixture evenly in purified water;

step SS 12: heating the reaction kettle to 65-80 ℃ to carry out suspension polymerization reaction for 9h to obtain a suspension polymerization reactant;

step SS 13: cooling the reaction kettle to normal temperature, cleaning the suspension polymerization reactant, and drying in vacuum to obtain the acrylic macroporous resin.

Preferably, in step S02, the method for forming the brominated active sites on the surface of the acrylic macroporous resin comprises the following steps:

step SS 21: pre-wetting the prepared acrylic macroporous resin in methanol for 10-15min to obtain pre-wetted macroporous resin;

step SS 22: soaking the pre-wet macroporous resin in water for 2 times, removing methanol, and drying the cleaned pre-wet macroporous resin in a vacuum drying oven to obtain macroporous resin to be reacted;

step SS 23: putting the macroporous resin to be reacted into a reaction solvent, and stirring for 24 hours at normal temperature to obtain initiator functionalized resin;

step SS 24: and thoroughly cleaning the initiator functionalized resin by using pure water.

Preferably, the components of the reaction solution in step SS23 include 2-bromoisobutyryl bromide, triethylamine and anhydrous tetrahydrofuran, and the weight ratio of the macroporous resin, the 2-bromoisobutyryl bromide and the triethylamine is 4.39:2.3: 1.01;

wherein the mass concentration of 2-bromoisobutyryl bromide is 10mmol/L, and the mass concentration of triethylamine is 10 mmol/L; reacting the 2-bromine isobutyryl bromide with carboxyl on the macroporous resin to be reacted to fix the bromine initiation group on the surface of the macroporous resin to be reacted.

Preferably, the pure water is second-grade RO water and pure water of the above purity.

Preferably, the polymerization solution in step S03 includes, in terms of weight group, 4-vinylphenylboronic acid-1.48 parts, CuCl-0.00297 parts, 2-bipyridine-0.01024 parts, and anhydrous methanol-31.64 parts; wherein, 4-vinyl phenylboronic acid is taken as a monomer, CuCl is taken as a catalyst, and 2-bipyridine and anhydrous methanol are taken as solvents;

the configuration method comprises the following steps: dissolving 4-vinylphenylboronic acid in absolute methanol, deoxidizing by circulating through a freezing pump for 3 times, and filling the vacuumized part with nitrogen after each vacuumizing; then uniformly stirring the treated anhydrous methanol solution dissolved with the 4-vinyl phenylboronic acid, CuCl and 2-bipyridyl in an oxygen-free environment to obtain a polymerization solution;

the method for grafting the bromo-active sites on the surface of the acrylic macroporous resin comprises the following steps:

step SS 31: under the room temperature and oxygen-free condition, the initiator functionalized resin is placed in the polymerization solution to react for 48 hours to obtain polymerization resin;

step SS 32: putting the obtained polymeric resin into a container filled with secondary RO water, stirring and cleaning for three times, wherein the first time is cleaned for 30 minutes at room temperature, the second time is cleaned for 60 minutes at 60 ℃, and the third time is cleaned for 30 minutes at room temperature;

step SS 33: and drying the washed polymeric resin at the temperature of 45 ℃ overnight to obtain the stevioside selective adsorption material.

The first embodiment is as follows:

the embodiment provides application of the stevioside selective adsorption material in adsorption of stevioside.

Weighing 0.1g of stevioside selective adsorption material, placing the stevioside selective adsorption material into an erlenmeyer flask, then transferring 50ml of prepared stevioside solution (STV: RA ═ 1:1) with the concentration of 6g/L, adding the stevioside solution into the erlenmeyer flask, sealing the erlenmeyer flask, placing the erlenmeyer flask into a constant-temperature oscillation box, oscillating at the constant temperature of 30 ℃, and calculating the equilibrium adsorption quantity Qe of stevioside according to the following formula:

wherein Qe is the equilibrium adsorption capacity of the selective adsorption material to stevioside, and the unit is mg/g; v is the volume of the stevioside solution in mL; c₀Is the initial concentration of the stevioside solution in g/L; ct is the concentration of stevioside in the supernatant after adsorption equilibrium, and the unit is g/L; and m is the mass of the composite adsorbing material PMAA/PAS and the unit is g.

The selectivity a for STV versus RA in steviol glycosides was calculated by the formula:

wherein a is the selectivity of the resin to STV, Q_STV，Q_RAAdsorption amounts of STV and RA, respectivelyIn units of mg/g, C in solution_STV,C_RAThe concentrations of STV and RA in the adsorbed solution are respectively in mg/ml.

In the application, the optimal adsorption temperature is 30 ℃, the adsorption pH is 9, the maximum adsorption capacity is 75.23mg/g, the highest selectivity is 10.42, and the boric acid functionalized resin has stronger selective adsorption capacity on stevioside.

Example two:

as shown in FIG. 2, the IR spectra of the original hydroxyl-containing acrylic resin and the grafted resin microspheres obtained in this example show that 1350cm in the spectrum of the boric acid functionalized grafted resin^-1A new B-O bond characteristic absorption peak appears, which proves that VPBA is successfully grafted to the surface of the acrylate resin;

as shown in figure 3, XPS test is carried out on grafted acrylate resins with different particle sizes, and the test result shows that the highest grafting amount of boron can reach 6.36%, so that the stevioside selective adsorption material prepared by the method provided by the invention is helpful for improving the enrichment, recovery and separation capacity of stevioside, has higher selectivity on the basis of ensuring higher adsorption amount, and has better effect in the separation and purification of stevioside.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.