阅读说明：本技术 2-氨基-4-乙酰氨基苯甲醚的精制纯化方法 (Refining and purifying method of 2-amino-4-acetamino anisole ) 是由 黄昊飞 张琪 张文淑 孟华杰 尹磊 张建军 李连伟 李玉超 左村村 傅忠君 王鸣 于 2021-09-13 设计创作，主要内容包括：本发明属于染料提纯技术领域,具体涉及一种2-氨基-4-乙酰氨基苯甲醚的精制纯化方法。利用羰基化改性的氯甲基聚苯乙烯树脂对2-氨基-4-乙酰氨基苯甲醚的生产母液进行吸附,之后再用脱附剂进行脱附,将得到的脱附液干燥,得到高纯度、高收率的2-氨基-4-乙酰氨基苯甲醚产品。本发明相比较蒸干母液加水析出的方法能够有效提高产品的纯度,相比较重结晶的方法能够有效提高产品的收率。本发明能够有效提高产品纯度和收率,且树脂还可通过再生实现循环利用,避免高温回流等操作带来的高能耗,降低生产成本,减少废物排放。(The invention belongs to the technical field of dye purification, and particularly relates to a refining and purifying method of 2-amino-4-acetamino anisole. The production mother liquor of the 2-amino-4-acetamino anisole is absorbed by the carbonylation modified chloromethyl polystyrene resin, then desorbed by a desorption agent, and the desorption liquid is dried to obtain the 2-amino-4-acetamino anisole product with high purity and high yield. Compared with a method for evaporating mother liquor to dryness and adding water for precipitation, the method can effectively improve the purity of the product, and compared with a recrystallization method, the method can effectively improve the yield of the product. The invention can effectively improve the purity and yield of the product, and the resin can be recycled by regeneration, thereby avoiding high energy consumption caused by operations such as high-temperature reflux and the like, reducing the production cost and reducing the waste discharge.)

1. A refining and purifying method of 2-amino-4-acetamino anisole is characterized in that: the method comprises the steps of adsorbing a production mother liquor of 2-amino-4-acetamino anisole by using carbonylation modified chloromethyl polystyrene resin, desorbing by using a desorption agent, and drying the obtained desorption solution to obtain the 2-amino-4-acetamino anisole.

2. The purification process for refining 2-amino-4-acetamino anisole according to claim 1, characterized in that: the using amount ratio of the production mother liquor of the carbonylation modified chloromethyl polystyrene resin to the production mother liquor of the 2-amino-4-acetamino anisole is 160-170: 1, wherein the production mother liquor of the carbonylation modified chloromethyl polystyrene resin is counted by g, and the production mother liquor of the 2-amino-4-acetamino anisole is counted by L.

3. The purification process for refining 2-amino-4-acetamino anisole according to claim 1, characterized in that: the general formula of the carbonylation modified chloromethyl polystyrene resin is as follows:

in the formula:is divinylbenzene crosslinked styrene copolymer beads; r₁Is methyl, ethyl, tert-butyl, phenyl or benzyl; r₂Is sulfonic acid group, carboxyl group or hydroxyl group.

4. The purification process for refining 2-amino-4-acetamino anisole according to claim 3, characterized in that: the preparation method of the carbonylation modified chloromethyl polystyrene resin comprises the following steps: the chloromethyl polystyrene is placed in N, N-dimethylformamide for swelling, and then the ketone compound is added for reaction to prepare the methyl phenyl methyl methacrylate.

5. The purification process for refining 2-amino-4-acetamino anisole according to claim 4, characterized in that: the dosage ratio of the chloromethyl polystyrene to the ketone compound to the N, N-dimethylformamide is 1: 0.005-0.0075: 20-23, wherein the chloromethyl polystyrene is calculated by g, the ketone compound is calculated by mol, and the N, N-dimethylformamide is calculated by mL; the reaction temperature is 75-90 ℃, and the reaction time is 6-8 h.

6. The purification process for refining 2-amino-4-acetamino anisole according to claim 4, characterized in that: the ketone compound has a general formula:

in the formula: r₁Is methyl, ethyl, tert-butyl, phenyl or benzyl; r₂Is sulfonic acid group, carboxyl group or hydroxyl group.

7. The purification process for refining 2-amino-4-acetamino anisole according to claim 1, characterized in that: the concentration of the 2-amino-4-acetamino anisole in the production mother liquor of the 2-amino-4-acetamino anisole is 125-130 g/L.

8. The purification process for refining 2-amino-4-acetamino anisole according to claim 1, characterized in that: during adsorption, the production mother liquor of 2-amino-4-acetamino anisole passes through the carbonylation modified chloromethyl polystyrene resin at the flow rate of 0.5-8 BV/h; the adsorption temperature is 10-40 ℃, and the adsorption time is 2-3 hours.

9. The purification process for refining 2-amino-4-acetamino anisole according to claim 1, characterized in that: the desorption agent is a mixed solution of hydrochloric acid, methanol and water, wherein the content of the hydrochloric acid is 1-10 wt.%, and the content of the methanol is 10-40 wt.%.

10. The purification process for refining 2-amino-4-acetamino anisole according to claim 1, characterized in that: during desorption, enabling a desorption agent to pass through the carbonylation modified chloromethyl polystyrene resin after adsorption at the flow rate of 0.5-8 BV/h; the desorption temperature is 10-40 ℃, the desorption time is 1-2 hours, and the drying is spray drying.

Technical Field

The invention belongs to the technical field of dye purification, and particularly relates to a refining and purifying method of 2-amino-4-acetamino anisole.

Background

The field of the chinese dye industry has continued to develop rapidly in recent years, and chinese dye production has been in the first place in the world, accounting for about sixty percent of the total share in the world, and is the most important country of production and supply of intermediates. The dye varieties which can be produced in China are about two thousand, the dye produced in daily routine production is as many as eight hundred, the annual output of the intermediate is as high as about forty-six thousand tons, and the intermediate has extremely important status in European and American markets due to the characteristics of excellent quality and low price, and at least thirty countries and regions are exported at present. 2-amino-4-acetamino anisole, a beige solid, with a melting point of 110 deg.C, slightly soluble in water, ethanol and acetone; the method is mainly used for producing disperse dye dark products, such as C.I disperse blue 79, C.I disperse blue 301, C.I disperse violet 58, disperse blue S-3GL, disperse blue HGL and the like, and is a dye intermediate with wide application.

The 2-amino-4-acetamido anisole is an important intermediate compound for synthesizing azo dyes and medicaments, and is mainly used for synthesizing 4-acetamido- (N, N-diethanolamino) anisole and preparing coupling components of a plurality of disperse dyes. At present, the synthesis of 2-amino-4-acetamino anisole is mainly divided into two methods, namely: the p-nitrochlorobenzene is etherified, reduced, acetylated, nitrated and reduced to obtain the 2-amino-4-acetamino anisole, and the specific reaction equation is as follows:

the second method comprises the following steps: the 2, 4-dinitrochlorobenzene is etherified, reduced and acetylated to obtain the 2-amino-4-acetamino anisole. The specific reaction equation is as follows:

the first method has the advantages of mature synthesis process, stable product yield and higher purity, but has the problems of overlong production process flow, more three wastes and the like, and is a process which is definitely eliminated or eliminated immediately by national industrial policies. Therefore, the main research at home and abroad at present mainly takes the method two as the main point.

Liuwei, Zhou Jie Wen, Xuwangfu, Tang Chiyong, Liwenlan, Gao national spring, a synthesis process of 2-amino-4-acetamino anisole [ P ]. Zhejiang province: CN109608355A,2019-04-12 reports that 2, 4-dinitroanisole is used as a raw material, 2, 4-diaminoanisole is obtained by hydrogenation, 2-amino of 2, 4-diaminoanisole is complexed with an acidifying reagent, and then the 2-amino is subjected to acylation reaction with an acetylation reagent to obtain 2-amino-4-acetamino anisole, so that the generation of a 2, 4-diacetyl amino anisole byproduct is reduced. The final product is obtained by adding water into the acylation liquid, heating, filtering, removing impurities and drying after recovering methanol from the acylation liquid through reduced pressure distillation. The amino value of the product obtained by the method is 93%, the yield is 90%, and the purity is 99.8% by liquid chromatography detection.

A process for synthesizing 2-amino-4-acetamino anisole from 2, 4-dinitro chlorobenzene as raw material and methanol as solvent is disclosed in CN201711472007.3 P.2018-08-17; reducing 2, 4-dinitroanisole by using a sodium disulfide solution to obtain 2, 4-diaminophenyl ether; and finally, selectively acylating with acetic anhydride to obtain the 2-amino-4-acetamino anisole. The product is obtained by adding ice water, stirring and filtering, then washing once by using an ice water solution containing sodium hydrosulfite, and drying under reduced pressure. The purity of the 2-amino-4-acetamino anisole obtained in this patent was 95.8% and the yield was 93.5%.

CN 201310308426.9P 2014-01-22, reports that methanol is taken as a solvent, 2, 4-dinitroanisole is taken as a raw material, hydrogen is introduced under the condition of the existence of a catalyst to carry out catalytic hydrogenation reduction reaction, then solid-liquid separation is carried out, and the catalyst is recovered; adding acetic anhydride, performing acetylation reaction, recovering acetic acid through reduced pressure distillation, and cooling and crystallizing to obtain the 2-amino-4-acetamino anisole product. The patent does not mention the purification of the product, nor the purity and yield of the crystals.

In the second method reported at present, the main factor influencing the yield and purity of the product is the separation and purification of the 2-amino-4-acetamino anisole product. Therefore, it is required to provide a method capable of efficiently separating and purifying a 2-amino-4-acetamino anisole product and impurities such as acetic acid, a 2, 4-diacetyl aminobenzophenone by-product and the like in a reaction solution.

Disclosure of Invention

The invention aims to provide a refining and purifying method of 2-amino-4-acetamino anisole, which adopts carbonylation modified chloromethyl polystyrene resin to absorb the production mother liquor of 2-amino-4-acetamino anisole, and then realizes the refining and purification of 2-amino-4-acetamino anisole through desorption and drying, thereby improving the yield and purity of the product.

The technical scheme adopted by the invention for solving the technical problems is as follows:

according to the refining and purifying method of 2-amino-4-acetamino anisole, the production mother liquor of 2-amino-4-acetamino anisole is absorbed by carbonylation modified chloromethyl polystyrene resin, then desorbed by a desorption agent, and the obtained desorption liquid is dried to obtain the 2-amino-4-acetamino anisole.

Wherein:

the using amount ratio of the production mother liquor of the carbonylation modified chloromethyl polystyrene resin to the production mother liquor of the 2-amino-4-acetamino anisole is 160-170: 1, wherein the production mother liquor of the carbonylation modified chloromethyl polystyrene resin is counted by g, and the production mother liquor of the 2-amino-4-acetamino anisole is counted by L.

The general formula of the carbonylation modified chloromethyl polystyrene resin is as follows:

in the formula:is divinylbenzene crosslinked styrene copolymer beads; r₁Is methyl, ethyl, tert-butyl, phenyl or benzyl; r₂Is sulfonic acid group, carboxyl group or hydroxyl group.

The preparation method of the carbonylation modified chloromethyl polystyrene resin comprises the following steps: the chloromethyl polystyrene is placed in N, N-dimethylformamide for swelling, and then the ketone compound is added for reaction to prepare the methyl phenyl methyl methacrylate. The dosage ratio of the chloromethyl polystyrene to the ketone compound to the N, N-dimethylformamide is 1: 0.005-0.0075: 20-23, wherein the chloromethyl polystyrene accounts for g, the ketone compound accounts for mol, and the N, N-dimethylformamide accounts for mL; the reaction temperature is 75-90 ℃, and the reaction time is 6-8 h.

The ketone compound has a general formula:

in the formula: r₁Is methyl, ethyl, tert-butyl, phenyl or benzyl; r₂Is sulfonic acid group, carboxyl group or hydroxyl group.

Carbonyl group in carbonylation-modified chloromethyl polystyrene resin can react with 2-amino-4-acetamidoAnd (3) reacting amino in the anisole to generate Schiff base, and separating the product from the mother liquor. And R is₁The more complex the group structure, the more the product is desorbed from the resin, R₂The groups can improve the hydrophilicity of the resin and are beneficial to the hydrolysis of Schiff base during desorption.

Specifically, the preparation method of the carbonylation modified chloromethyl polystyrene resin comprises the following steps: adding 10g of chloromethyl polystyrene (CMPS) with chlorine content of about 0.05mol and 200-230 mL of N, N-Dimethylformamide (DMF) into a 250mL three-neck flask, swelling the CMPS for 6-12 h, adding 0.05-0.075 mol of ketone compound and 0.05-0.06 mol of anhydrous K₂CO₃And 0.05-0.06 mol of KI, introducing nitrogen for protection, reacting at the temperature of 75-90 ℃ for 6-8 h, and performing suction filtration after the reaction is finished. Taking 2-sulfonic acid-4-hydroxyacetophenone modified chloromethyl polystyrene resin as an example, the preparation process is as follows:

the concentration of the 2-amino-4-acetamino anisole in the production mother liquor of the 2-amino-4-acetamino anisole is 125-130 g/L; the method for obtaining the production mother liquor of the 2-amino-4-acetamino anisole is as follows:

taking 2, 4-dinitrochlorobenzene as a raw material, taking methanol as a solvent, and adding sodium methoxide to carry out etherification reaction to prepare 2, 4-dinitroanisole; then adding 2, 4-dinitroanisole into a methanol solvent, adding 5% Pd/C as a catalyst, and introducing hydrogen for reaction to obtain 2, 4-diaminoanisole; and finally, adding the 2, 4-diaminoanisole into acetic anhydride for selective acylation to obtain the production mother liquor of the 2-amino-4-acetamino anisole. The mother liquor contains impurities such as 2-amino-4-acetamino anisole product, 2, 4-diacetyl aminobenzyl ether with two acylated amino groups, acetic acid and the like.

During adsorption, the production mother liquor of the 2-amino-4-acetamino anisole passes through the carbonylation modified chloromethyl polystyrene resin at the flow rate of 0.5-8 BV/h.

The adsorption temperature is 10-40 ℃, and the adsorption time is 2-3 hours.

The desorption agent is a mixed solution of hydrochloric acid, methanol and water, wherein the content of the hydrochloric acid is 1-10 wt.%, and the content of the methanol is 10-40 wt.%.

And during desorption, enabling a desorption agent to pass through the carbonylation modified chloromethyl polystyrene resin after adsorption at the flow rate of 0.5-8 BV/h.

The desorption temperature is 10-40 ℃, and the desorption time is 1-2 hours; the drying is spray drying.

The absorption and desorption reaction processes of the carbonylation modified chloromethyl polystyrene resin and the 2-amino-4-acetamino anisole in the mother liquor are as follows (taking the 2-sulfonic acid-4-hydroxyacetophenone modified chloromethyl polystyrene resin as an example):

the invention has the following beneficial effects:

according to the invention, amino in 2-amino-4-acetamino anisole is taken as a nucleophilic reagent, a pair of lone electrons is contained on a nitrogen atom, the carbonyl in the carbonylation modified chloromethyl polystyrene resin can be attacked, the carbon atom with positive charge in the carbonyl completes nucleophilic addition reaction to form an intermediate compound consisting of alpha-hydroxylamine, and the compound is further dehydrated to form Schiff base. Utilization of amino group in 2-amino-4-acetamino anisole to react with R in carbonylation modified chloromethyl polystyrene resin₁The carbonyl group connected with the group forms a Schiff base structure, so that the carbonyl group is adsorbed on the resin, and the separation of the 2-amino-4-acetamino anisole from the mother liquor is realized, while the byproducts and other impurities can not be combined with the resin and are remained in the mother liquor. Then, the mixed solution of hydrochloric acid, methanol and water is used as a desorption agent, the Schiff base structure undergoes hydrolysis reaction under the catalytic action of the desorption agent, and R in the resin₂The group can improve the hydrophilicity of the resin, thereby improving the hydrolysis efficiency of Schiff base, and the 2-amino-4-acetamino anisole is desorbed from the resin, and the 2-amino-4-acetamino anisoleDissolving ether in the desorption agent, and spray-drying the desorption solution to obtain the high-purity 2-amino-4-acetamino anisole. The desorbed resin is washed by water and can be recycled.

R introduced into carbonylation modified chloromethyl polystyrene resin₂The group is an electron-withdrawing group, so that the electropositivity of a carbon atom in the carbonyl group can be improved, and the nucleophilic addition reaction of the 2-amino-4-acetamino anisole and the carbonyl group in the adsorption process is facilitated to form a Schiff base structure. In the process of analysis, when the water content is high, the Schiff base can be rapidly hydrolyzed under the catalysis of acid, and R is₂The group can improve the hydrophilicity of the resin, is beneficial to the water molecules to enter the resin, and can promote the hydrolysis of Schiff base.

Compared with a method for evaporating mother liquor to dryness and adding water for precipitation, the method can effectively improve the purity of the product, and compared with a recrystallization method, the method can effectively improve the yield of the product. The invention can effectively improve the purity and yield of the product, and the resin can be recycled by regeneration, thereby avoiding high energy consumption caused by operations such as high-temperature reflux and the like, reducing the production cost and reducing the waste discharge.

Detailed Description

The present invention is further described below with reference to examples.

Example 1

In a 250mL three-necked flask, 10g of Chloromethylpolystyrene (CMPS) having a chlorine content of about 0.05mol and 200mL of N, N-Dimethylformamide (DMF) were charged to swell the CMPS for 8 hours, and then 0.05mol of 2-sulfonic acid-4-hydroxyacetophenone and 0.05mol of anhydrous K were added₂CO₃And 0.05mol of KI, introducing nitrogen for protection, reacting for 6 hours at the temperature of 80 ℃, and performing suction filtration after the reaction is finished to obtain the carbonylation modified chloromethyl polystyrene resin, wherein the structural formula is as follows:

whereinIs divinylbenzene crosslinked styrene copolymer beads.

Accurately weighing 500g (with the purity of 99%) of 2, 4-dinitrochlorobenzene, putting the 2, 4-dinitrochlorobenzene into a container, adding 3L of methanol as a solvent, heating to 60 ℃, adding sodium methoxide with the molar ratio of 1:1.05 to the 2, 4-dinitrochlorobenzene, reacting for 15 minutes, cooling, and filtering to obtain 2, 4-dinitroanisole; putting 2, 4-dinitroanisole into a high-pressure kettle, adding 2L of methanol as a solvent, 62g of 5% Pd/C catalyst, introducing 1.2MPa of hydrogen to react at 65 ℃, and ending the reaction after the pressure stops and does not decrease to obtain 2, 4-diaminoanisole; putting 2, 4-diaminoanisole into a container under the protection of nitrogen, adding hydrochloric acid with the molar ratio of 2, 4-diaminoanisole being 1:1 for acidification, then adding acetic anhydride with the molar ratio of 2, 4-diaminoanisole being 1:1, carrying out selective acylation reaction at 0 ℃, and finishing the reaction after 30 minutes to obtain the production mother liquor of 2-amino-4-acetamino anisole, wherein the concentration of 2-amino-4-acetamino anisole is 127.4 g/L.

3L of the above production mother liquor of 2-amino-4-acetamino anisole was circulated from top to bottom at a flow rate of 1BV/h through an adsorption column containing 500g of the above carbonylation-modified chloromethyl polystyrene resin at 20 ℃ to complete adsorption by circulating for 2h, thereby effecting separation of 2-amino-4-acetamino anisole from by-products, after which the resin was taken out. Using a mixed solution of hydrochloric acid, methanol and water (the content of hydrochloric acid is 6 wt.%, the content of methanol is 40 wt.%) as a desorption agent, enabling 3L of the desorption agent to pass through the carbonylation modified chloromethyl polystyrene resin after adsorption at the flow rate of 1BV/h at 20 ℃, circularly flowing for 1h to complete desorption, desorbing 2-amino-4-acetamino anisole on the resin in the desorption agent, and performing spray drying to obtain 374.11g of 2-amino-4-acetamino anisole, wherein the purity is 99.2%, and the yield is 97.1%; and then the desorption agent is recycled, and the resin is dried and recycled.

Example 2

A production mother liquor of 2-amino-4-acetamidoanisole was prepared in accordance with the procedure in example 1, wherein the concentration of 2-amino-4-acetamidoanisole was 125.5 g/L.

3L of a production mother liquor of 2-amino-4-acetamino anisole was circulated from top to bottom at a flow rate of 4BV/h through an adsorption column packed with 500g of the carbonylation modified chloromethyl polystyrene resin of example 1, the adsorption was completed by circulating flow for 3h to effect separation of 2-amino-4-acetamino anisole and by-products, after which the resin was taken out. Using a mixed solution of hydrochloric acid, methanol and water (the content of hydrochloric acid is 5 wt.%, the content of methanol is 20 wt.%) as a desorption agent, enabling 3L of the desorption agent to pass through the carbonylation modified chloromethyl polystyrene resin after adsorption at the flow rate of 4BV/h at 35 ℃, circularly flowing for 1h to complete desorption, desorbing 2-amino-4-acetamino anisole on the resin in the desorption agent, and performing spray drying to obtain 373.45g of 2-amino-4-acetamino anisole, wherein the purity is 98.9%, and the yield is 98.1%; and then the desorption agent is recycled, and the resin is dried and recycled.

Example 3

A production mother liquor of 2-amino-4-acetamidoanisole was prepared in accordance with the procedure in example 1, wherein the concentration of 2-amino-4-acetamidoanisole was 129.5 g/L.

3L of a production mother liquor of 2-amino-4-acetamino anisole was circulated from top to bottom at a flow rate of 8BV/h through an adsorption column packed with 500g of the carbonylation modified chloromethyl polystyrene resin of example 1, and adsorption was completed by circulating flow for 2.5h to effect separation of 2-amino-4-acetamino anisole and by-products, after which the resin was taken out. Using a mixed solution of hydrochloric acid, methanol and water (the content of hydrochloric acid is 5 wt.%, the content of methanol is 30 wt.%) as a desorption agent, enabling 3L of the desorption agent to pass through the carbonylation modified chloromethyl polystyrene resin after adsorption at the flow rate of 8BV/h at 25 ℃, circularly flowing for 1.5h to complete desorption, desorbing 2-amino-4-acetamino anisole on the resin in the desorption agent, and performing spray drying to obtain 387.31g of 2-amino-4-acetamino anisole, wherein the purity is 98.2%, and the yield is 97.9%; and then the desorption agent is recycled, and the resin is dried and recycled.

Example 4

A carbonylation-modified chloromethyl polystyrene resin, the structural formula of which is shown below, was prepared according to the method in example 1, changing 2-sulfonic acid-4-hydroxyacetophenone in example 1 to 2-carboxy-4-hydroxyacetophenone:

whereinIs divinylbenzene crosslinked styrene copolymer beads.

The carbonylation-modified chloromethyl polystyrene resin was used for the purification of 3L of a production mother liquor of 2-amino-4-acetamino anisole (mass concentration of 2-amino-4-acetamino anisole was 127.4g/L), and the procedure was the same as in example 1, whereby 381.03g of the product, 2-amino-4-acetamino anisole, was obtained with a purity of 97.8% and a yield of 97.5%.

Example 5

The carbonylation-modified chloromethyl polystyrene resin, the structural formula of which is shown below, was prepared according to the method in example 1, changing 2-sulfonic acid-4-hydroxyacetophenone in example 1 to 2, 4-dihydroxypropiophenone:

whereinIs divinylbenzene crosslinked styrene copolymer beads.

The carbonylation-modified chloromethyl polystyrene resin was used for the purification of 3L of a production mother liquor of 2-amino-4-acetamino anisole (mass concentration of 2-amino-4-acetamino anisole was 127.4g/L), and the procedure was the same as in example 1, whereby 379.47g of the product, 2-amino-4-acetamino anisole, was obtained with a purity of 97.9% and a yield of 97.2%.

Example 6

A carbonylation-modified chloromethylphenylstyrene resin having the following structural formula was prepared by the method of example 1, except that 2-sulfonic acid-4-hydroxyacetophenone in example 1 was changed to 1- (2-sulfonic acid-4-hydroxycyclohexyl) -ethanone:

whereinIs divinylbenzene crosslinked styrene copolymer beads.

The carbonylation-modified chloromethyl polystyrene resin was used for the purification of 3L of a production mother liquor of 2-amino-4-acetamino anisole (mass concentration of 2-amino-4-acetamino anisole was 127.4g/L), and the procedure was the same as in example 1, whereby 379.09g of the product, 2-amino-4-acetamino anisole, was obtained with a purity of 98.2% and a yield of 97.4%.

Comparative example 1

3L of the production mother liquor of 2-amino-4-acetamino anisole from example 1 was distilled under reduced pressure to remove the methanol solvent, and then 50mL of methanol was added for recrystallization, heated to 55 ℃ and then a small amount of water was added, and when the solution became cloudy, the temperature was further raised to 66 ℃ and the mixture was refluxed for 20 minutes. After the recrystallization is finished, a small amount of 2-amino-4-acetamino anisole is added as seed crystal to promote the precipitation, and after cooling, the product 376.54g is obtained by suction filtration, the purity is 94.6%, and the yield is 93.2%.

Comparative example 2

3L of the production mother liquor of 2-amino-4-acetamino anisole in example 1 was distilled under reduced pressure to remove the methanol solvent, and then 100mL of water was added to conduct a recrystallization operation, heated to 75 ℃ and refluxed for 20 minutes. Slowly cooling after recrystallization is finished, adding a small amount of 2-amino-4-acetamino anisole as seed crystal to promote precipitation, and after cooling, carrying out suction filtration to obtain 379.39g of product with the purity of 95.2% and the yield of 94.5%.

Comparative example 3

3L of the production mother liquor of 2-amino-4-acetamino anisole from example 1 was distilled off under reduced pressure to remove the methanol solvent, then 100mL of ice water was added thereto, stirred and filtered, then washed once with an ice water solution containing sodium dithionite, and further dried under reduced pressure to obtain 369.80g of a product with a purity of 95.6% and a yield of 92.5%.

As can be seen from the comparison of example 1 with comparative examples 1 to 3, the present invention, compared with the prior art recrystallization method, adopts carbonylation modified chloromethyl polystyrene resin to purify the production mother liquor of 2-amino-4-acetamino anisole, and obviously improves the yield and purity of the product 2-amino-4-acetamino anisole.