1. The preparation method of the selective absorbing material is characterized by dissolving vinyl imidazolium ionic liquid, polymerizable sodium salt and a cross-linking agent in a solvent, heating to 70-100 ℃ under the protection of nitrogen, adding an initiator azobisisobutyronitrile, stirring for reaction for 6-24 hours, and after the reaction is finished, carrying out acidification or/and washing and drying post-treatment to obtain the selective absorbing material; wherein:

the molar ratio of the vinyl imidazolium ionic liquid to the polymerizable sodium salt is 1: 0.2-5;

the molar ratio of the vinyl imidazolium ionic liquid to the cross-linking agent is 1: 0.05-0.5;

the mass of the solvent is 2-5 times of the total mass of the vinyl imidazolium ionic liquid, the polymerizable sodium salt and the cross-linking agent;

the mass of the initiator AIBN is 1-10% of the total mass of the vinyl ionic liquid, the polymerizable sodium salt and the cross-linking agent.

2. The method for preparing the selective absorbing material according to claim 1, wherein the vinylimidazolium ionic liquid is a 1-vinyl-3- (3-sulfopropyl) imidazolium inner salt having a chemical structure shown in formula (I), a 1-vinyl-3-hydroxyethylimidazolium chloride salt having a chemical structure shown in formula (II), a 1-vinyl-3- (1, 2-dihydroxypropyl) imidazolium chloride salt having a chemical structure shown in formula (III), a 1-vinyl-3-ethyleneglycol-imidazolium chloride salt having a chemical structure shown in formula (IV) or a 1-vinyl-3-triethyleneglycol-imidazolium chloride salt having a chemical structure shown in formula (V);

3. the method of claim 1, wherein the polymerizable sodium salt is sodium acrylate, sodium 4-vinylbenzoate, or sodium 4-vinylbenzenesulfonate.

4. The method for preparing the selective absorbing material according to claim 1, wherein the cross-linking agent is divinylbenzene, ethylene glycol dimethacrylate, N '-methylenebisacrylamide, 3' - (hexane-1, 6-diyl) bis (1-vinyl-3-imidazolium) dibromide having a chemical structure represented by formula (VI), 3'- (octane-1, 8-diyl) bis (1-vinyl-3-imidazolium) dibromide having a chemical structure represented by formula (VII), or 3,3' - (triethylene glycol-based) bis (1-vinyl-3-imidazolium) dibromide having a chemical structure represented by formula (VIII);

5. the method for producing a selective absorbing material according to claim 1, wherein the solvent is selected from water, methanol, N-dimethylformamide, a water/methanol mixed solvent, or a water/N, N-dimethylformamide mixed solvent.

6. A selective absorbing material made by the method of claim 1.

7. Use of the selective absorbing material according to claim 6 for selective absorption in a mixed solvent.

8. The use according to claim 7, wherein a water/solvent mixed solvent prepared from an equimolar amount of water and a solvent or a formamide/solvent mixed solvent prepared from an equimolar amount of formamide and a solvent is added to a sealed bottle, the dried selective absorbing material is added to the sealed bottle containing the mixed solvent, and stirred at room temperature for 6 hours and left to stand for 3 hours, and then the selective absorbing material sufficiently absorbed in the mixed solvent is separated from the sealed bottle, the mixed solvent absorbed on the surface is removed, and then the mixed solvent absorbed by the selective absorbing material is quantitatively analyzed by a gas chromatograph and a Karl Fischer moisture meter.

9. The use according to claim 7, wherein the solvent of the water/solvent mixed solvent or formamide/solvent mixed solvent is selected from methanol, ethanol, acetonitrile, acetone, tetrahydrofuran, DMF or dimethyl sulfoxide.

Background

Methanol, ethanol, THF and the like are very important chemical basic raw materials and organic solvents. In the Chemical production process, a large amount of mixed waste liquid containing methanol/ethanol/THF and the like and water is often generated (Journal of Chemical & Engineering Data,2012,57, 3309-. In the contemporary society of increasingly urgent environmental protection and resource shortage, if the water and organic solvent in the mixed waste liquid can be separated and recovered simply and effectively, the environmental protection can be realized, and the resource utilization of the waste can be realized, so that the method has very important significance.

methanol/ethanol/THF and the like and water are in a homogeneous azeotrope state at normal temperature, and thus separation and recovery thereof are very difficult. Industrially, rectification techniques and membrane separation techniques are commonly employed to treat these low boiling point homogeneous azeotropes. The distillation Technology needs special distillation technologies such as azeotropic distillation, pressure swing distillation, extractive distillation, etc., which not only has great process difficulty but also has high energy consumption (Computers and Chemical Engineering,2016,89, 204-) (Separation and Purification Technology,2015,156, 336-) (Separation and Purification Technology,2014,122, 73-77). The membrane separation technology is also a widely used separation and recovery technology, but the membrane technology has small treatment capacity, long time and easy membrane pollution (applied chemical industry, 2013,42, 532-. The development of rectification technology and membrane separation technology is restricted by the existence of the problems.

The adsorption is a separation and recovery method which is simple to operate, efficient and convenient. However, some conventional adsorbents such as molecular sieves, silica gel, activated carbon, activated alumina and the like have the problems of small adsorption capacity, high desorption difficulty, complex adsorbent regeneration and the like.

Disclosure of Invention

The invention aims to provide a selective absorbing material and a preparation method and application thereof. The selective absorbing material is prepared by taking vinyl imidazolium ionic liquid, polymerizable sodium salt and a cross-linking agent as raw materials and carrying out free radical polymerization and post-treatment. The selective absorption material can be rapidly absorbed in solvents such as water, formamide, ethylene glycol, methanol, DMSO, ethanol, DMF and the like, and has good chemical and cyclic stability. Based on the characteristic of different absorption capacities in the solvent, the selective absorption material is applied to the selective absorption of the homogeneous mixed solvent, and the material is found to have excellent selective absorption performance. In a series of water/solvent mixed solvent systems, the selective absorption material can absorb water with high selectivity, and the mole percentage content of the water in the absorbed mixed solvent can reach 97.6 percent at most. In addition, the high selective absorption capacity of the prepared selective absorption material for water is basically kept unchanged in the process of 5 times of circulation.

The specific technical scheme for realizing the purpose of the invention is as follows:

a preparation method of selective absorption material is characterized in that: dissolving vinyl imidazolium ionic liquid, polymerizable sodium salt and a crosslinking agent in a solvent, heating to 70-100 ℃ under the protection of nitrogen, adding an initiator Azobisisobutyronitrile (AIBN), stirring and reacting for 6-24 hours, and after the reaction is finished, carrying out acidification or/and washing and drying post-treatment to obtain the selective absorbing material; wherein:

the vinyl imidazolium ionic liquid is 1-vinyl-3- (3-sulfopropyl) imidazolium inner salt, the chemical structure of which is shown as formula (I), 1-vinyl-3-hydroxyethyl imidazolium chloride, the chemical structure of which is shown as formula (II), 1-vinyl-3- (1, 2-dihydroxypropyl) imidazolium chloride, the chemical structure of which is shown as formula (III), and 1-vinyl-3-diethylene glycol imidazolium chloride, the chemical structure of which is shown as formula (IV) or 1-vinyl-3-triethylene glycol imidazolium chloride, the chemical structure of which is shown as formula (V);

the polymerizable sodium salt is sodium acrylate, 4-vinyl sodium benzoate or 4-vinyl sodium benzene sulfonate.

The crosslinking agent is Divinylbenzene (DVB), Ethylene Glycol Dimethacrylate (EGDMA), N '-Methylenebisacrylamide (MBA), 3' - (hexane-1, 6-diyl) bis (1-vinyl-3-imidazolium) dibromide salt, the chemical structure of which is shown as a formula (VI), and 3,3'- (octane-1, 8-diyl) bis (1-vinyl-3-imidazolium) dibromide salt, the chemical structure of which is shown as a formula (VII) or 3,3' - (triethylene glycol) bis (1-vinyl-3-imidazolium) dibromide salt, the chemical structure of which is shown as a formula (VIII);

the solvent of the invention is selected from water, methanol, N-Dimethylformamide (DMF), a water/methanol mixed solvent or a water/DMF mixed solvent.

The molar ratio of the vinyl imidazolium ionic liquid to the polymerizable sodium salt is 1: 0.2-5.

The molar ratio of the vinyl imidazolium ionic liquid to the cross-linking agent is 1: 0.05-0.5.

The mass of the solvent is 2-5 times of the total mass of the vinyl imidazolium ionic liquid, the polymerizable sodium salt and the cross-linking agent.

The mass of the initiator AIBN is 1-10% of the total mass of the vinyl imidazolium ionic liquid, the polymerizable sodium salt and the cross-linking agent.

The selective absorption material is applied to selective absorption in a mixed solvent, and is characterized in that: adding a water/solvent mixed solvent prepared from water and a solvent in an equimolar amount or adding a formamide/solvent mixed solvent prepared from formamide and a solvent in an equimolar amount into a sealed bottle, adding a dried selective absorption material into the sealed bottle filled with the mixed solvent, stirring at room temperature for 6 hours, standing for 3 hours, separating the selective absorption material fully absorbed in the mixed solvent from the sealed bottle, removing the mixed solvent absorbed on the surface, and quantitatively analyzing the mixed solvent absorbed by the selective absorption material by a gas chromatograph and a Karl Fischer moisture tester; wherein:

the solvent in the water/solvent mixed solvent or formamide/solvent mixed solvent is selected from methanol, ethanol, acetonitrile, acetone, Tetrahydrofuran (THF), DMF or dimethyl sulfoxide (DMSO).

The invention has the following advantages: (1) the preparation method is simple, the selective absorbing material can be obtained by simple free radical polymerization, and the high specific surface area is not needed like a molecular sieve, activated carbon and the like; (2) the absorption capacity is large, and the selective absorption material can absorb several times or even dozens of times of the mixed solvent of the self weight; (3) the absorption rate is high, and the selective absorption material can achieve full absorption within minutes or tens of minutes; (4) the absorption selectivity is high, and the selective absorption material can absorb a certain solvent with high selectivity; when the water-soluble organic compound is absorbed in a water/solvent mixed solvent, the molar percentage of the water in the absorbed mixed solvent can reach 97.6 percent at most; (5) the cycle stability is good, and the selective absorption capacity of the selective absorption material to the solvent is basically kept unchanged in the process of 5 cycles.

Drawings

FIG. 1 is a graph of the absorption rate of selective absorption material A in water and formamide in example 3 of the present invention;

FIG. 2 is a diagram showing the state of the selective absorbing material A in a water/methanol mixed solvent in example 4 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following specific examples, but the present invention is not limited to the following examples. Variations and advantages that may occur to those skilled in the art may be incorporated into the invention without departing from the spirit and scope of the inventive concept, and the scope of the appended claims is intended to be protected. The procedures, conditions, reagents, experimental methods and the like for carrying out the present invention are general knowledge and common general knowledge in the art except for the contents specifically mentioned below, and the present invention is not particularly limited.

Example 1: preparation of Selective absorbent Material A

1.58 g of 1-vinyl-3- (3-sulfopropyl) imidazolium inner salt, 0.50 g of sodium p-styrenesulfonate and 0.12 g of 3,3' - (triethylene glycol) bis (1-vinyl-3-imidazolium) dibromide salt are dissolved in 5 ml of deionized water, added into a 50 ml two-neck flask, heated to 80 ℃ under the protection of nitrogen, immediately added with 0.11 g of initiator AIBN, and then continuously stirred for reaction for 24 hours. After the reaction was completed, the resulting crosslinked polymer was dispersed in a 1 mol/l aqueous sulfuric acid solution and stirred at room temperature for 24 hours. After stirring, washing the mixture for multiple times by using deionized water, methanol and acetone, and drying the mixture for 24 hours in vacuum at the temperature of 60 ℃ to obtain the target selective absorbing material, which is named as A, wherein the yield of the material reaches 86%.

Example 2: testing of the absorption Capacity of Selective absorbent Material A in a Single solvent

About 50 mg of dry selective absorbing material a was added to a sealed bottle containing 10 ml of solvent. Standing at room temperature for 24 hours to allow the selective absorbing material A to achieve sufficient absorption. The selective absorbing material a which sufficiently absorbed the solvent was separated from the sealed bottle, and the solvent absorbed on the surface was sucked off with filter paper and immediately weighed. The absorption capacity of the selective absorption material a in a single solvent is calculated by the following equation:

wherein m is_{Dry matter}Represents the mass of the dry selective absorbing material a; m is_{Suction device}Represents the mass of the selective absorbing material a after sufficiently absorbing the solvent.

The absorption capacities of the selective absorption material a in different solvents are shown in table 1.

Table 1 absorption capacity of selective absorption material a in different solvents

The results in table 1 show that the prepared selective absorbing material a can not only absorb the solvent, but also have different absorbing abilities for different solvents.

Example 3: absorption Rate test of Selective absorbent Material A in Water and formamide

In this example, the absorption capacity Q of the selective absorbing material a for water and formamide, i.e., the absorption rate, was measured at different times; see fig. 1. The results in fig. 1 show that the selective absorbing material a only took 5 minutes and 15 minutes to reach a sufficient absorption state in water and formamide. This indicates that the selective absorbing material a prepared has the ability to rapidly absorb the solvent.

Example 4: selective absorption Material A Selective absorption Capacity test in Mixed solvent

The selective absorption capability test of the selective absorption material A in a water/methanol mixed solvent is taken as an example. In a sealed bottle, a water/methanol mixed solvent prepared from 0.2 mol of water and 0.2 mol of methanol was added. About 50 mg of the dried selective absorbing material A was added to the sealed bottle and stirred at room temperature for 6 hours, and then left to stand for 3 hours. The state of the selective absorbing material A in a water/methanol mixed solvent; see fig. 2. The selective absorbing material a sufficiently absorbed in the mixed solvent was separated from the sealed bottle, and the mixed solvent absorbed on the surface was removed by blotting with filter paper. The molar percentage content of water and methanol in the mixed solvent absorbed by the selective absorbing material a was quantitatively analyzed by a gas chromatograph and a karl fischer moisture meter.

The results of the selective absorption capacity of the selective absorption material a in a series of water/solvent mixed solvents and formamide/solvent mixed solvents are shown in table 2.

TABLE 2 Selective absorption Capacity of Selective absorbing Material A in Water/solvent Mixed solvent and formamide/solvent Mixed solvent

The results in table 2 show that the selective absorbing material a has excellent selective absorbing ability. When the composite material is absorbed in a series of water/solvent mixed solvents or formamide/solvent mixed solvents, the absorbed mixed solvents can contain water or formamide with the mol percentage of 97.6 or 94.6 percent at most.

Example 5: cyclic stability of Selective absorbent Material A

The cycle stability of the selective absorbing material a and the reproducibility of the selective absorbing performance were evaluated by 5 consecutive selective absorbing tests in a water/methanol mixed solvent. After each selective absorption capacity test, the selective absorption material A is recovered by acetone deswelling, centrifugal separation, acetone washing and vacuum drying, and then enters the next selective absorption capacity test. The results of the recycling performance of selective absorbing material a in a water/methanol mixed solvent are shown in table 3.

TABLE 3 Recycling Performance of Selective absorbing Material A in Water/methanol Mixed solvent

Number of cycles	1	2	3	4	5
						Molar percentage of Water (%)	72.5	73.8	70.7	71.4	70.0
Molar percentage of methanol (%)	27.5	26.2	29.3	28.6	30.0

The results in table 3 show that the selective absorbing material a has good cycling stability and the selective absorbing capacity has good reproducibility.