阅读说明：本技术 一种具有层次孔结构的木质素基超交联聚合物及其制备方法和吸附应用 (Lignin-based hypercrosslinked polymer with hierarchical pore structure and preparation method and adsorption application thereof ) 是由 陈介南 刘娜 邵礼书 于 2020-07-09 设计创作，主要内容包括：本发明公开了一种木质素基超交联聚合物的制备方法及其吸附应用。其技术方案为：以木质素为原料,通过木质素接枝共聚及超交联聚合两步反应,制备出木质素基超交联聚合物,在第一步中,调节共聚中溶剂、接枝的单体、交联剂的类型和用量、共聚温度等,得到疏水可控的木质素基前体聚合物,第二步中,通过改变Friedel-Crafts反应中催化剂、温度等反应条件,可制备出比表面积高、层次孔结构的木质素基超交联聚合物,其对环境污染物吸附效果好,特别是放射性核素碘,去除率高,多次循环使用后仍能保持良好的吸附性能。该木质素基聚合物比表面积高,制备简单,绿色环保,在污染物吸附领域中具有广阔的应用前景。(The invention discloses a preparation method and adsorption application of a lignin-based hypercrosslinked polymer. The technical scheme is as follows: the method comprises the following steps of taking lignin as a raw material, preparing a lignin-based hypercrosslinked polymer through two steps of reactions of lignin graft copolymerization and hypercrosslinked polymerization, regulating the types and the dosage of a solvent, a grafted monomer, a crosslinking agent, copolymerization temperature and the like in copolymerization in the first step to obtain a lignin-based precursor polymer with controllable hydrophobicity, and changing the reaction conditions of a catalyst, the temperature and the like in Friedel-Crafts reaction in the second step to prepare the lignin-based hypercrosslinked polymer with high specific surface area and a hierarchical pore structure. The lignin-based polymer has the advantages of high specific surface area, simple preparation, environmental protection and wide application prospect in the field of pollutant adsorption.)

1. A preparation method of a lignin-based hypercrosslinked polymer with a hierarchical pore structure is characterized by comprising the following steps:

step (1): carrying out graft copolymerization on a solution containing lignin, aryl ethylene monomers, a cross-linking agent and an initiator to obtain a lignin precursor polymer; the aryl group of the aryl ethylene monomer is provided with a functional group which can carry out Friedel-crafts alkylation and/or Friedel-crafts acylation reaction;

step (2): carrying out Friedel-Crafts reaction in the lignin precursor polymer under the solid catalyst to obtain the lignin-based hypercrosslinked polymer with the hierarchical pore structure.

2. The method for preparing the lignin-based hypercrosslinked polymer having hierarchical pore structure according to claim 1, wherein the functional group in the arylethylene monomer is at least one of halogenated alkyl, acid halide, hydroxyalkyl, and vinyl;

the aryl in the arylethene monomer is five-membered heterocyclic aryl, six-membered heterocyclic aryl or phenyl, or fused ring aryl formed by the union of at least two aryl in the five-membered heterocyclic aryl, the six-membered heterocyclic aryl and the phenyl; preferably phenyl;

preferably, the aryl ethylene monomer is a monomer with a structural formula of formula 1;

said R₁～R₅Wherein at least one substituent is a haloalkyl group, an acid halide group, an alcoholic hydroxyl group, or a vinyl group;

more preferably, the arylvinyl monomer is at least one of p-chloromethylstyrene, vinylbenzyl alcohol and 4-ethylene-benzoyl chloride.

3. The method for preparing the lignin-based hypercrosslinked polymer with hierarchical pore structure according to claim 1, wherein the crosslinking agent is a diene monomer, preferably at least one of p-divinylbenzene, ethylene glycol dimethacrylate, 1, 4-butylene diacrylate and N, N-methylenebisacrylamide;

preferably, the initiator is at least one of azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide and tert-butyl peroxypivalate;

preferably, the solvent for the graft copolymerization reaction is at least one of ethyl acetate, dimethyl sulfoxide, ethanol and o-xylene glycol; wherein the mass ratio of the lignin to the solvent is 1: 10-1: 100.

4. The method for preparing the lignin-based hypercrosslinked polymer with the hierarchical pore structure as claimed in claim 1, wherein the mass ratio of the lignin, the aryl ethylene monomer, the cross-linking agent and the initiator is 1-5: 1-20: 1-10: 0.2-0.8.

5. The method for preparing the lignin-based hypercrosslinked polymer with hierarchical pore structure according to claim 1, wherein in step (1), the graft copolymerization temperature is 60-90 ℃ and the time is preferably 6-24 h.

6. The method for preparing the hierarchical pore structure lignin-based hypercrosslinked polymer according to claim 1, wherein the solid catalyst is a lewis acid catalyst; preferably AlCl₃、FeCl₃、TiCl₄、ZnCl₂At least one of;

preferably, the mass ratio of the solid catalyst to the precursor polymer is 1: 5-2: 1.

7. The method for preparing the lignin-based hypercrosslinked polymer with hierarchical pore structure as claimed in claim 1, wherein the solvent in the Friedel-Crafts reaction process is at least one of 1, 2-dichloroethane, 1, 2-dichloromethane and nitrobenzene; wherein the mass ratio of the precursor polymer to the solvent is preferably 1:5 to 1: 20.

8. The method for preparing the lignin-based hypercrosslinked polymer with the hierarchical pore structure as claimed in claim 1, wherein Friedel-Crafts reaction temperature is 40-85 ℃ and time is preferably 3-12 h.

9. The lignin-based hypercrosslinked polymer with hierarchical pore structure prepared by the preparation method of any one of claims 1 to 8, characterized in that it has hierarchical pore structure of micropores, mesopores and macropores;

preferably, the content of micropores is 15-35%; the content of mesopores is 50-75%; the content of macropores is 5-10%;

the specific surface area is 450-1800 m²(ii)/g; oxygen content: 10 to 25 atm.%.

10. The application of the lignin-based hypercrosslinked polymer with the hierarchical pore structure prepared by the preparation method of any one of claims 1 to 8 is characterized in that the lignin-based hypercrosslinked polymer is used as an adsorbing material for removing harmful substances in the environment;

the harmful substances are small molecular pollutants, preferably at least one of radioactive nuclides, heavy metal ions and organic dyes; more preferably, it is a compound that emits iodine vapor and iodine.

Technical Field

The invention belongs to the technical field of biomass resource utilization and biomass materials, and particularly relates to a preparation method and adsorption application of a lignin-based super-crosslinked polymer.

Background

Currently, the common adsorbents are mainly activated carbon, silver-exchanged zeolites, aerogels, Metal Organic Frameworks (MOFs), and Porous Organic Polymers (POPs). POPs have been increasingly studied by global scientists as a new class of hot porous materials in recent years. However, most POPs often use complex monomers, expensive catalysts, or harsh chemical reaction conditions during the preparation process, which increase the development cost of the materials, limit the industrial production of the materials, and limit the large-scale application of the materials. Therefore, developing a new organic porous material for environmental pollution adsorption with green and low cost, and studying adsorption behavior and cyclic regeneration performance under various conditions are one of the important tasks of current pollutant treatment.

Lignin is the most abundant aromatic natural high molecular compound on earth. However, only 5% of the lignin is effectively utilized and mostly considered as waste and burned to produce energy, which not only results in a huge waste of resources but also results in a serious pollution of the environment. The lignin is an amorphous three-dimensional reticular high molecular compound formed by connecting phenylpropane structural units through carbon-carbon bonds and ether bonds, and contains various active functional groups, so that the lignin becomes an attractive macromolecule in a biomass-based material. In particular, in the last decade, researchers have made extensive efforts to develop lignin-based porous organic polymer (LPOPs) adsorbent materials, and many work have demonstrated that LPOPs have strong adsorption properties for organic pollutants, heavy metals, gases, etc., and have low cost and environmental compatibility, demonstrating great potential as adsorbents. However, compared with the advanced commercial adsorbents such as activated carbon, zeolite, ion exchange resin, etc., the adsorption performance of the existing LPOPs adsorbents still needs to be improved.

Disclosure of Invention

The invention aims to provide a preparation method of a lignin-based hypercrosslinked polymer, and aims to prepare the lignin-based hypercrosslinked polymer with a hierarchical pore structure and high specific surface area.

The second purpose of the invention is to provide the lignin-based hypercrosslinked polymer prepared by the preparation method.

The third purpose of the invention is to provide the application of the lignin-based hypercrosslinked polymer prepared by the preparation method.

A preparation method of a lignin-based hypercrosslinked polymer with a hierarchical pore structure comprises the following steps:

step (1): carrying out graft copolymerization on a solution containing lignin, aryl ethylene monomers, a cross-linking agent and an initiator to obtain a lignin precursor polymer; the aryl group of the aryl ethylene monomer is provided with a functional group which can carry out Friedel-crafts alkylation and/or Friedel-crafts acylation reaction;

step (2): and (3) carrying out Friedel-Crafts reaction in the lignin precursor polymer under a solid catalyst (Friedel-Crafts solid catalyst) to obtain the lignin-based hypercrosslinked polymer with the hierarchical pore structure.

The lignin-based polymer has rich pore structures, but the lignin-based polymer mainly has a macroporous and mesoporous structure, and the lignin-based polymer with a hierarchical pore structure containing micropores is not available. In order to fill the technical blank, the invention innovatively adopts the functionalized aryl ethylene monomer and lignin to carry out crosslinking copolymerization in advance, carries out functionalized modification on the precursor polymer while realizing crosslinking copolymerization, creatively carries out aromatic ring crosslinking in the structure on the basis of the Friedel-Crafts reaction idea, and constructs a rigid crosslinking bridge in situ in the polymer structure, thus regulating and controlling the microstructure, the orientation of active groups and the hydrophilic performance of the polymer and obtaining the material with a hierarchical pore structure. The research of the invention finds that the method can improve the physical and chemical properties of the polymer in the aspect of adsorption.

In the invention, lignin and the aryl ethylene monomer bridged with the Friedel-crafts reaction functional group are subjected to crosslinking reaction in advance, and the key point for successfully realizing the construction of the lignin-based polymer hierarchical pore structure and improving the adsorption performance is matched with the subsequent in-situ Friedel-crafts reaction in the polymer structure.

In the present invention, the functional group in the arylethylene monomer is at least one of a halogenated alkyl group, an acid halide group, a hydroxyalkyl group and a vinyl group.

The aryl in the arylethene monomer is five-membered heterocyclic aryl, six-membered heterocyclic aryl or phenyl, or fused ring aryl formed by the union of at least two aryl in the five-membered heterocyclic aryl, the six-membered heterocyclic aryl and the phenyl; preferably phenyl.

Preferably, the aryl ethylene monomer is a monomer with a structural formula of formula 1;

said R₁～R₅In (b), at least one substituent is a haloalkyl group, an acid halide group, an alcoholic hydroxyl group, or a vinyl group.

The haloalkyl group is, for example, a halomethyl group, a haloethyl group, etc.; the halogen is chlorine or bromine. Examples of the hydroxyalkyl group include a hydroxymethyl group and a hydroxyethyl group. The acyl group is, for example, a haloformyl group.

Preferably, R₁～R₅Wherein at least one substituent is a haloalkyl group, an acid halide group, an alcoholic hydroxyl group, or a vinyl group; the remaining substituents are H, haloalkyl, acid halide, alcoholic hydroxyl or vinyl; even more preferably, R is₁～R₅Wherein one substituent is a haloalkyl group, an acid halide group, an alcoholic hydroxyl group or a vinyl group; the other substituent is H.

More preferably, the arylvinyl monomer is at least one of p-chloromethylstyrene, vinylbenzyl alcohol and 4-ethylene-benzoyl chloride.

In the present invention, the crosslinking agent and the initiator may be those known in the art.

Preferably, the cross-linking agent is at least one of diene monomer, p-divinylbenzene, ethylene glycol dimethacrylate, 1, 4-butylene diacrylate and N, N-methylenebisacrylamide.

Preferably, the initiator is at least one of azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide and tert-butyl peroxypivalate.

In the step (1), the hydrophobic controllable lignin-based precursor polymer can be obtained by adjusting the type and the amount of a solvent, a grafted monomer, a crosslinking agent, the copolymerization temperature and the like in copolymerization.

Preferably, the solvent for the graft copolymerization reaction is at least one of ethyl acetate, dimethyl sulfoxide, ethanol and o-xylene glycol; wherein the mass ratio of the lignin to the solvent is not required, and is, for example, 1:10 to 1: 100.

Preferably, the mass ratio of the lignin, the aryl ethylene monomer, the cross-linking agent and the initiator is 1-5: 1-20: 1-10: 0.2-0.8.

More preferably, the weight ratio of the lignin to the arylethene monomer is 1-3: 5-15.

In the step (1), the graft copolymerization temperature is 60-90 ℃, and the time is preferably 6-24 h.

In the invention, based on the crosslinking copolymerization, a functional group of Friedel-crafts reaction is modified in situ in the molecular structure of the polymer, and the subsequent Friedel-crafts reaction is further matched to realize rigid connection in the molecular of the polymer, improve the structure of the polymer and the orientation of an active group, and finally improve the performance of the material in the adsorption aspect, such as the adsorption rate and the cycling stability of the material.

Preferably, the solid catalyst is a lewis acid catalyst; preferably AlCl₃、FeCl₃、TiCl₄、ZnCl₂At least one of (1).

Preferably, the mass ratio of the solid catalyst to the precursor polymer is 1: 5-2: 1.

Preferably, the solvent in the Friedel-Crafts reaction process is at least one of 1, 2-dichloroethane, 1, 2-dichloromethane and nitrobenzene; wherein the mass ratio of the precursor polymer to the solvent is preferably 1:5 to 1: 20.

Preferably, the Friedel-Crafts reaction temperature is 40-85 ℃, and the time is preferably 3-12 h.

The invention relates to a preparation method of a preferable lignin-based hypercrosslinked polymer with a hierarchical pore structure, which is characterized in that organic lignin is fully dissolved in an organic solvent, then a proper amount of cross-linking agent, aryl ethylene monomer and initiator are added for polymerization to obtain a lignin-based precursor polymer with adjustable and controllable hydrophobic property, and Friedel-Crafts reaction is carried out to form the lignin-based hypercrosslinked polymer with the hierarchical pore structure, and the lignin-based hypercrosslinked polymer is used as an adsorbent to capture pollutants such as radioactive iodine and the like in the environment. The specific operation steps are as follows:

(1) dissolving lignin with different mass in an organic solvent, fully dissolving the lignin in the organic solvent through ultrasonic treatment, and filtering through a 0.45um filter membrane to obtain a lignin organic solution.

The mass ratio of the lignin to the solvent is 1: 10-1: 100, and preferably 1: 30.

The organic solvent is ethyl acetate, acetone and dimethyl sulfoxide, and ethyl acetate is preferred.

(2) And (2) adding a proper amount of aryl ethylene monomer, a cross-linking agent and an initiator into the lignin organic solution obtained in the step (1), and reacting in a nitrogen environment to obtain the controllable hydrophobic lignin-based precursor polymer.

The monomer is p-chloromethyl styrene and vinyl benzyl alcohol, preferably p-chloromethyl styrene.

The crosslinking agent is p-divinylbenzene, ethylene glycol dimethacrylate, 1, 4-butylene diacrylate, N-methylenebisacrylamide, preferably p-divinylbenzene.

The mass ratio of the lignin to the monomer and the cross-linking agent is 3:1: 1-1: 20:10, and preferably 1:7: 2.

The reaction temperature range is 60-90 ℃, and the reaction time range is 6-24h, preferably 80 ℃ and 8-12 h.

(3) Swelling the lignin-based precursor polymer obtained in the step (2) in a solvent overnight, heating to 40-45 ℃, adding a catalyst, stirring for dissolving, heating to 60-80 ℃ for reaction, and stopping the reaction by using 40-50 (v/v)% ethanol and an aqueous solution to obtain the lignin-based hypercrosslinked polymer.

The lignin-based precursor polymer solvent is 1, 2-dichloroethane, 1, 2-dichloromethane, nitrobenzene, preferably 1, 2-dichloroethane.

The mass ratio of the lignin-based precursor polymer to the solvent is 1: 5-1: 20, preferably 1: 10.

The catalyst is AlCl₃,FeCl₃,TiCl₄,ZnCl₂Equal Lewis acid, the mass ratio of the catalyst dosage to the precursor polymer is 1: 5-2: 1, and preferably the catalyst FeCl₃And the amount of the catalyst is 1: 1.

The reaction temperature range is 40-85 ℃, and the reaction time range is 3-12 h.

The invention also provides the lignin-based hypercrosslinked polymer with the hierarchical pore structure, which is prepared by the preparation method and has the hierarchical pore structures of micropores, mesopores and macropores.

Preferably, the content of micropores is 15-35%; the content of mesopores is 50-75%; the content of macropores is 5-10%;

the specific surface area is 450-1800 m²(ii)/g; oxygen content: 10 to 25 atm.%.

The invention also provides application of the lignin-based hypercrosslinked polymer with the hierarchical pore structure prepared by the preparation method, and the lignin-based hypercrosslinked polymer is used as an adsorption material for removing harmful components in the environment. For example, adsorbing dissolved harmful components in a body of water, or adsorbing volatile harmful components in a gas.

The harmful substances are small molecular pollutants, preferably at least one of radioactive nuclides, heavy metal ions and organic dyes; more preferably, it is a compound that emits iodine vapor and iodine.

Advantageous effects

According to the preparation method and the environment-friendly application of the lignin-based hypercrosslinked polymer, the hydrophobic controllable lignin-based precursor polymer prepared by grafting copolymerization and hypercrosslinked polymerization reaction of organic lignin and the special functionalized monomer can better adapt to variable environmental conditions; then carrying out in-situ Friedel-Crafts reaction in a polymer structure by utilizing a functional group pre-modified by a precursor polymer, constructing a rigid connecting bridge in situ, and regulating and controlling the orientation of an active group, so that the lignin-based hypercrosslinked polymer with high specific surface area and hierarchical pore structure can be prepared; researches show that the polymer obtained by the preparation method can synergistically improve the adsorption effect of environmental pollutants in various aspects such as physics, chemistry and the like. For example, the material has an adsorption rate of 257 wt% on radioactive waste pollutant iodine, is easy to desorb, has a removal rate of 99%, and can be regenerated and recycled; the preparation method is simple, mild in condition, green and environment-friendly, has the advantages of reducing cost and environmental compatibility, and can realize resource and high-value utilization of industrial waste lignin.

The material prepared by the invention has good chemical and physical stability, and also has excellent cycling stability on the premise of having excellent adsorption performance.

Drawings

FIG. 1 is a flow chart of the preparation;

FIG. 2 is a diagram of a preparation mechanism, wherein a black ball is Lignin;

FIG. 3 is a two-dimensional nuclear magnetic assay Organolignin (OL) building block map;

FIG. 4 is a graph of IR spectra measurements of lignin (OL), lignin-based precursor polymer (OLCP in FIG. 4 refers to OLCP2), and lignin-based hypercrosslinked polymer (OLHCP in FIG. 4 refers to OLHCP2) of example 1;

FIG. 5 is an electron microscope and contact angle measurement chart of the hydrophobic controllable lignin-based graft copolymer of examples 1-3 and comparative example 1; wherein, from left to right, the first plot is OLCP0 with a contact angle of 144.3 °; the second plot is OLCP1 with a contact angle of 117.5 °; the third plot is OLCP2 with a contact angle of 109.2 °; the fourth plot is OLCP3 with a contact angle of 105.1 °.

FIG. 6 is a nitrogen adsorption-desorption isotherm of a lignin-based hypercrosslinked polymer;

FIG. 7 shows measurement of iodine adsorption performance by Organic Lignin (OL), lignin-based hypercrosslinked polymers (OLHCP) with different contents of organic lignin, and dealkalized lignin hypercrosslinked polymers (ALHCP);

FIG. 8 is a graph of desorption experiment of iodine in ethanol by lignin-based hypercrosslinked polymer;

FIG. 9 shows measurement of iodine adsorption performance of lignin-based hypercrosslinked polymers in recycling;

FIG. 10 is a graph of the stability of lignin-based hypercrosslinked polymers in strong acids, strong bases and organic solvents.

Detailed Description

The following examples are intended to further illustrate the invention without limiting it.

Extraction and molecular weight determination and characterization of alkali lignin, acid lignin, organic lignin, and molten salt lignin:

extracting lignin from residues of the fermentation production of ethanol from acid exploded poplar by using an alkali extraction and acid precipitation method, an ethanol solvent extraction method, a Klason method and a molten salt method respectively, wherein products are marked as alkali lignin, acid lignin, organic lignin and molten salt lignin respectively. The molecular weight and the distribution range thereof were measured as shown in table 1, and the molecular weight of the organic lignin was relatively large and the distribution range was relatively concentrated. In addition, the structural units of the organic lignin are completely preserved by two-dimensional nuclear magnetism determination as shown in figure 3.

TABLE 1 comparison of molecular weight and distribution of lignin extracted by different methods

Lignin extraction	Alkali lignin	Acid lignin	Organic lignin	Molten salt lignin
					Average molecular weight (Mv)	597	638	729	680
Coefficient of distribution	1.438	1.494	1.380	1.473

And (3) lignin solubility determination:

lignin (dealkalized) (commercial grade, available from Merland) was prepared in a similar manner to alkali lignin, and solubility measurements of organic lignin (Table 1: ethanol solvent extraction) and sodium lignosulfonate (commercial grade, available from Merland) were made. 0.1g of dealkalized lignin, organic lignin and sodium lignosulphonate are respectively dissolved in 10mL of solvents such as water, ethanol, ethyl acetate, n-hexane, dimethyl sulfoxide and the like. The dealkalized lignin is only dissolved in dimethyl sulfoxide and is not dissolved in solvents such as ethanol, ethyl acetate, n-hexane and the like; the organic lignin is insoluble in water and soluble in most organic solvents; sodium lignosulfonate is soluble only in water and insoluble in organic solvents.

Lignin adsorption Performance measurement

The adsorption effect of dealkalized lignin, organic lignin (table 1) and lignosulfonate on iodine was determined. Respectively putting 20mg of dealkalized lignin, organic lignin and lignosulfonate into an open glass vial, putting the vial into a 250mL iodine measuring flask filled with saturated iodine, heating to 75 ℃, and measuring the weight change after 24 hours. It was found that the adsorption effect of alkali lignin on iodine was 0, the adsorption performance of organic lignin was 148 wt% (fig. 7), and the adsorption effect could not be determined by absorption of a large amount of water by lignosulfonate.