阅读说明：本技术 三氟羧草醚的制备工艺 (Preparation process of acifluorfen ) 是由 陈伟 谢丹 于 2020-07-27 设计创作，主要内容包括：本发明涉及除草剂技术领域,公开了一种三氟羧草醚的制备工艺,包括步骤：以3,4-二氯三氟甲苯为原料合成3-[2-氯-4-(三氟甲基)苯氧基]苯甲酸、以浓硫酸和浓硝酸为混酸进行硝化反应得到三氟羧草醚。本发明生产工艺中直接将萃取后的3-[2-氯-4-(三氟甲基)苯氧基]苯甲酸溶液输送至硝化釜进行硝化反应,工艺更加简单,能有效加快生产进度和提高收率,而且本发明工艺中硝化反应的温度为40℃左右,反应时间较短,可以避免高温以及反应时间过长带来的杂质偏多的问题,同时也能节省时间成本,具有反应条件温和、收率高的特点。(The invention relates to the technical field of herbicides, and discloses a preparation process of acifluorfen, which comprises the following steps: 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid is synthesized by taking 3, 4-dichlorotrifluorotoluene as a raw material, and concentrated sulfuric acid and concentrated nitric acid are taken as mixed acid to carry out nitration reaction to obtain acifluorfen. In the production process, the extracted 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid solution is directly conveyed to a nitration kettle for nitration reaction, the process is simpler, the production progress can be effectively accelerated, and the yield can be improved.)

1. The preparation process of acifluorfen is characterized by comprising the following steps:

(1) preparing mixed acid: uniformly mixing concentrated nitric acid and concentrated sulfuric acid according to the volume ratio of 1:1.5-2.5 to obtain mixed acid for later use;

(2) preparation of 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid: adding DMSO and water into a reaction device, then adding m-hydroxymethyl benzoic acid and sodium hydroxide, stirring, heating and dehydrating until the water content in the system is reduced to a set value, adding 3, 4-dichlorotrifluorotoluene and potassium carbonate, raising the temperature of the reaction system to 135-150 ℃, carrying out heat preservation reaction for 1-2h, removing the solvent, then slowly adding water into the reaction device, adjusting the pH value of the system to 1-2, and extracting to obtain a 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid solution;

(3) nitration reaction: transferring the 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid solution obtained in the step (2) to a nitration device, dehydrating, cooling to 38-42 ℃, adding acetic anhydride, cooling to 15-20 ℃, slowly dropwise adding mixed acid, reacting at 24-28 ℃ after dropwise adding is finished until the raw materials completely react, standing for layering, and separating to remove lower-layer waste acid to obtain a acifluorfen crude product;

(4) refining: and adding water into the crude product of acifluorfen, washing, standing for layering, adding water into the lower layer solution obtained by separation, washing, distilling at normal pressure to recover dichloroethane, stirring, discharging, filtering to obtain a wet product, and drying to obtain a finished product.

2. The process according to claim 1, wherein the molar ratio of 3, 4-dichlorotrifluorotoluene, m-hydroxymethylbenzoic acid and sodium hydroxide in step (2) is 1:2-2.5: 4-5.

3. The process for preparing acifluorfen according to claim 1, wherein the dehydration at elevated temperature in step (2) further comprises: adding DMSO (dimethyl sulfoxide) after the system becomes viscous, wherein the volume of the added DMSO is 70-80% of that of the initially added DMSO, and then steaming until the water content of the system is less than or equal to 0.2%; the solvent used in the extraction is dichloroethane.

4. The process of claim 1, wherein the molar ratio of the potassium carbonate to the 3, 4-dichlorotrifluorotoluene is 3.5-3.7: 100.

5. The process for preparing acifluorfen according to claim 1, wherein the temperature is reduced after the dehydration in the step (3) is carried out until the water content in the system is less than or equal to 0.2%; the molar ratio of the acetic anhydride to the 3, 4-dichlorotrifluorotoluene is 1.9-2.5.

6. The process of claim 1, wherein the molar ratio of the concentrated nitric acid to the 3, 4-dichlorotrifluorotoluene is 3.0 to 3.2; the concentration of the concentrated nitric acid in the nitration reaction system is 80-96%.

7. The process according to claim 1, wherein the drop rate of the mixed acid in step (3) is 2-3L/min.

8. The process for preparing acifluorfen according to claim 1, wherein the wet product is dried at 45-55 ℃ for 5-6 hours to obtain the final product.

Technical Field

The invention relates to the technical field of herbicides, and in particular relates to a preparation process of acifluorfen.

Background

Acifluorfen (5- (2-chloro-2, 2, 2-trifluoro-p-tolyloxy) -2-nitrobenzoic acid, CAS:50594-66-6) is a contact-killing type selective postemergence herbicide, can be absorbed by weed stems and leaves, and has the characteristics of difficult root absorption and easy microbial decomposition in soil. The acifluorfen is safe to the growth of soybeans, is mainly used as a herbicide for controlling broadleaf weeds, and is suitable for removing weeds in soybean fields, including amaranth deironi, amaranth, ragweed, brassica, chenopodium album, watermelons, melons, stramonium, petunia, brassicaceae, rubiaceae, polygonum hydropiper, polygonum bingzhou, scarlet and the like. Acifluorfen has a better preventing or inhibiting effect on the green bristlegrass, millet, wild sorghum, endive and aralia elata in a specific period. However, the existing industrial production of acifluorfen has the problems of harsh reaction conditions, low yield and high production cost.

Disclosure of Invention

The invention provides a preparation process of acifluorfen with high yield and high production efficiency.

The invention provides a preparation process of acifluorfen, which comprises the following steps:

(1) preparing mixed acid: uniformly mixing concentrated nitric acid and concentrated sulfuric acid according to the volume ratio of 1:1.5-2.5 to obtain mixed acid for later use;

(2) preparation of 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid: adding DMSO and water into a reaction device, then adding m-hydroxymethyl benzoic acid and sodium hydroxide, stirring, heating for dehydration until the water content in the system is reduced to a set value, adding 3, 4-dichlorotrifluorotoluene and potassium carbonate, raising the temperature of the reaction system to 135-150 ℃, carrying out heat preservation reaction for 1-2h, removing the solvent, then slowly adding water into the reaction device, adjusting the pH value of the system to 1-2, and extracting to obtain a 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid solution;

(3) nitration reaction: transferring the 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid solution obtained in the step (2) to a nitration device, dehydrating, cooling to 38-42 ℃, adding acetic anhydride, cooling to 15-20 ℃, slowly dropwise adding mixed acid, reacting at 24-28 ℃ after dropwise adding is finished until the raw materials completely react, standing for layering, and separating to remove lower-layer waste acid to obtain a acifluorfen crude product;

(4) refining: and adding water into the crude product of acifluorfen, washing, standing for layering, adding water into the lower layer solution obtained by separation, washing, distilling at normal pressure to recover dichloroethane, stirring, discharging, filtering to obtain a wet product, and drying to obtain a finished product.

The preparation process of the invention is divided into nitration reaction for preparing 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid and 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid. In the preparation process of the 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid, dimethyl sulfoxide is used as a solvent, so that the solvent recovery cost is lower, the process is simpler, and the use of toluene as the solvent is avoided, so that the consumption of nitric acid in the nitration stage of residual toluene is avoided, and impurities are avoided.

In addition, in the production process, the extracted 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid solution is directly conveyed to a nitration kettle for nitration reaction, the process is simpler, the production progress can be effectively accelerated, and the yield can be improved. In addition, the temperature of the nitration reaction is about 40 ℃, the reaction time is short, the problem of excessive impurities caused by high temperature and overlong reaction time can be avoided, and the time cost can be saved.

In some preferred embodiments, the molar ratio of 3, 4-dichlorotrifluorotoluene, m-hydroxymethylbenzoic acid, sodium hydroxide in step (2) is from 1:2 to 2.5:4 to 5.

In some preferred embodiments, the dewatering at elevated temperature in step (2) further comprises: adding DMSO (dimethyl sulfoxide) after the system becomes viscous, wherein the volume of the added DMSO is 70-80% of that of the initially added DMSO, and then steaming until the water content of the system is less than or equal to 0.2%.

Specifically, the solvent used in the extraction is dichloroethane. The invention takes the mixed acid of sulfuric acid and nitric acid as a nitrating agent, strictly controls the moisture in the system, and takes a small amount of acetic anhydride as a dehydrating agent, thereby ensuring that the moisture is basically below 0.01 percent, and the invention has relatively lower cost and safer reaction.

In some preferred embodiments, the molar ratio of the potassium carbonate to the 3, 4-dichlorotrifluorotoluene is from 3.5 to 3.7: 100.

In some preferred embodiments, the temperature is reduced after the dehydration in the step (3) is carried out until the moisture content of the system is less than or equal to 0.2%; the molar ratio of the acetic anhydride to the 3, 4-dichlorotrifluorotoluene is 1.9-2.5.

In some preferred embodiments, the molar ratio of the concentrated nitric acid to the 3, 4-dichlorotrifluorotoluene is from 3.0 to 3.2.

The concentration of the concentrated nitric acid in the nitration reaction system is 80-96%; particularly preferably 95% to 96%.

In some preferred embodiments, the dropping speed of the mixed acid in the step (3) is 2-3L/min.

In some preferred embodiments, the wet product is dried at 45-55 ℃ for 5-6h to obtain the finished product.

The invention has the beneficial effects that:

the invention provides a preparation process of acifluorfen, which has the characteristics of mild reaction conditions, high yield and high reaction efficiency. In the process of the present invention, 84% to 86% of the 3- [ 2-chloro-4- (trifluoromethyl) phenoxy ] benzoic acid is converted to a 2-nitro substituent and 3% to 4% is converted to a 6-nitro substituent.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.

The invention provides a preparation process of acifluorfen, and test materials used in the embodiment of the invention are purchased from a conventional biochemical reagent store unless specified otherwise.