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A method for increasing the yield of 3,6-dichloro-2-hydroxybenzoic acid

A technology of hydroxybenzoic acid and dichlorophenol, applied in the directions of carboxylate preparation, organic chemistry, etc., can solve the problems of not taking into account phenol, long reaction time, unsatisfactory effect, etc., reducing the reaction time and improving the yield per pass , the effect of saving the reaction cost

Inactive Publication Date: 2011-12-28
EAST CHINA UNIV OF SCI & TECH +1
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  • Abstract
  • Description
  • Claims
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Problems solved by technology

[0013] In fact, although the existing technology is improving the dichlorosalicylic acid production process from different aspects, it does not take into account the carboxylation reaction to generate phenol
The usual treatment method is to dissolve the generated phenol in an organic solvent after the reaction is over, and recycle it as a raw material after separation and recovery, but the oil phase after recovery often contains tar components, and the effect of the re-reaction is also unsatisfactory; secondly, Kolbe -Schmitt reaction is a reversible reaction, and the formation of phenol also inhibits the forward reaction
Therefore industrially 3,6-dichloro-2-hydroxybenzoic acid can only reach 45% maximum single-pass yield after 16 hours of reaction time
In addition, the reaction time is longer, and the utilization rate of heat energy, one-time acid-base and catalyst is lower

Method used

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  • A method for increasing the yield of 3,6-dichloro-2-hydroxybenzoic acid
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  • A method for increasing the yield of 3,6-dichloro-2-hydroxybenzoic acid

Examples

Experimental program
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Effect test

Embodiment 1

[0037] Weigh 86g of 2,5-dichlorophenol (95%) in a 1000ml four-neck flask and dissolve in 34.3g of KOH (90%) and 28.27ml of H 2 O, then add 500ml of xylene as a solvent and mix evenly, heat up and dehydrate until almost no water is evaporated, take the potassium phenate suspension to measure the water, when the water is lower than 0.1%, it can be transferred to the autoclave, and the high-pressure reaction is turned on The inlet valve of the kettle is fed into CO 2 Remove the air in the autoclave, continue to ventilate for 10 minutes, and then heat the autoclave to raise the temperature, start stirring at the same time, and pass CO into the autoclave. 2 , Carry out a carboxylation reaction, the reaction temperature and pressure are controlled at 160°C and 8 MPa, and the reaction time is 4hr. After the carboxylation is completed, feed cooling water into the cooling pipe of the autoclave. When the system cools down to 100°C, add 50g of 40% KOH aqueous solution into...

Embodiment 2

[0039] Take 405g (95%) of 2,5-dichlorophenol, add KOH aqueous solution (176g KOH, 180ml H2O), and dehydrate in 500ml xylene solvent, the steps are the same as in Example 1. Then transfer to an autoclave for a carboxylation reaction, the reaction temperature is 140°C, the pressure is 6MPa, and the reaction time is 6h. After cooling, add KOH aqueous solution (90gKOH, 90mlH 2 O) carry out azeotropic dehydration, then add 70gNa 2 CO 3 The carboxylation reaction was carried out, and then CO was continuously introduced into the 2 Carry out the second carboxylation in 10 minutes, the second carboxylation conditions are also 140°C, 6MPa, and the reaction time is 6hr. After the secondary carboxylation reaction, 300ml of cooling water was introduced to reduce the temperature of the system to 100°C, stirred evenly, and the water phase was taken after layering, and then an aqueous hydrochloric acid solution with a mass fraction of 30% was added dropwise to the water p...

Embodiment 3

[0041] Weigh 86g of 2,5-dichlorophenol (95%) in a 1000ml four-necked flask and dissolve it in 34g of KOH (90%) and 25.5ml of H 2 In O, heat up and dehydrate in 300ml toluene until almost no water is evaporated, take a phenoxide suspension sample to measure the moisture, when the moisture is lower than 0.1%, it can be transferred to the autoclave, and the inlet valve of the autoclave is opened. Into CO 2 Remove the air in the autoclave, continue to ventilate for 10 minutes, and then heat the autoclave to raise the temperature, start stirring at the same time, and pass CO into the autoclave. 2 , Carry out a carboxylation reaction, the reaction temperature and pressure are controlled at 140°C and 6 MPa, and the reaction time is 6hr. After the carboxylation is completed, feed cooling water into the autoclave cooling pipe, then add 70g40% KOH aqueous solution in the still, and react while stirring until the dichlorophenol by-product is all converted into phenate. Th...

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Abstract

The invention belongs to a production technology of a dicamba intermediate, and relates to a method for preparing 3,6-dichloro-2-hydroxy benzoic acid by reacting 2,5-dichlorophenols salt with carbon dioxide in an organic solvent,the technology for increasing Kolbe-Schmitt carboxylation reaction yield by a secondary salt forming comprises the following steps: (1) preparing the raw material phenates and dehydrating; (2) performing a primary carboxylation reaction to the raw material phenates; (3) performing a salt forming and dehydration to by-product dichlorophenols; (4) carrying out a carboxylation reaction; (5) refining. Experiments show that the yield of 6-dichloro-2-hydroxybenzoic acid can reach 68.4%-70.5% after the secondary carboxylation, The method for increasing yield of 3,6-dichloro-2-hydroxybenzoic acid is capable of solving the unfavorable influence of dichlorophenols generated by the reaction, raising the reaction yield, minimizing the reaction time and saving the production cost.

Description

technical field [0001] The invention belongs to the production process of dicamba intermediates, and relates to a method of using 2,5-dichlorophenate and CO in an organic solvent 2 The key technology of reaction preparation 3,6-dichloro-2-hydroxybenzoic acid. Background technique [0002] 3,6-dichloro-2-hydroxybenzoic acid is 3,6-dichlorosalicylic acid, English name 3,6-Dichlorosalicylic Acid, structural formula: [0003] 水杨酸 [0004] 3,6-dichloro-2-hydroxybenzoic acid is an intermediate for the preparation of the pesticide herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid), and can also be used for the preparation of chemiluminescent agent intermediate 3, Organic chemicals such as 5,6-trichlorosalicylic acid. Dicamba (Banvel, dicamba), a kind of benzoic acid series herbicide firstly developed by American Bezier Chemical Company (now merged by Swiss Sandoz Company). With the prohibition and restricted use of chlorsulfuron-methyl and metsulfuron-methyl prepa...

Claims

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Application Information

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IPC IPC(8): C07C65/05C07C51/02
Inventor 程振民储消和颜星星余中宝蒋亦文陈明伟艾荣华
Owner EAST CHINA UNIV OF SCI & TECH
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