Electrochemical Synthesis Of 4-Amino-3,6-Dichloropicolinic Acid And Electro-Fenton Process Of Mother Liquor

4-Amino-3,6-dichloropicolinic acid?4-N-3,6-DCP?is a kind of pyridine carboxylic acid herbicide with high efficiency and low toxicity.At present,Chinese patents report a method for the electrochemical synthesis of 4-N-3,6-DCP with4-amino-3,5,6-trichloropicolinic acid?4-N-3,5,6-TCP?.However,the following problems still remain to be solved:the p H of catholyte is unstable,the alkali consumption is large,and the amount of waste salt generated is large.The first part of this article proposes a method of recovering mother liquor as anolyte after product extraction to improve the above problems.We explored the feasibility of the mother liquor recovery method and optimized parameters such as temperature,current density,and substrate concentration.At the same time,we conducted industrial simulations,including substrate concentration amplification and electrode stability investigation.The results are as follows:Electrolysis uses constant current electrolysis and activated silver as the working electrode.The mother liquor is adjusted to p H 1.16.Repeated experiments found that the yield obtained by the mother liquor recovery method is greater than 89%,which is close to the original method.The conversion rate of 4-N-3,5,6-TCP is 100%.When the initial p H of cathode liquid increased from 11.7 to 13.0,the yield increased by nearly 3%.Used a DSA electrode instead of graphite in anode,the anolyte conductivity dropped to 0.88S·m^-1 after two electrolysis.When the reaction temperature is 30°C,the current density is 74 A·m^-2,and the catholyte composition is 0.2 M 4-N-3,6-DCP+0.2 M Na OH aqueous solution,4-N-3,5,6-TCP can synthesize 4-N-3,6-DCP with high selectivity.4-N-3,6-DCP can still be synthesized with high selectivity by increasing the substrate concentration to 0.6 M,and the activated silver electrode shows good dechlorination stability after repeated electrolysis.In the second part of this paper,the method of using electro-Fenton by gas diffusion electrode is proposed for the treatment of waste liquid after electrolysis.We have studied the Electro-Fenton reaction with 4-N-3,6-DCP as the substrate.At the same time,we optimized the reaction parameters for the preparation of H₂O₂ using gas diffusion electrodes.We used a diaphragm electrolyzer with a gas chamber instead of the traditional H-type electrolytic cell.Gas diffusion electrode prepared by the ultrasonic sprayer is used to replace the traditional electrode.The results are as follows:Cabot XC-72 and monoatomic cobalt have similar selectivity to H₂O₂.When the reaction temperature is 30°C,the catalyst loading is 2 mg·cm^-2,the current density is 13.3 m A·cm^-2,and the stirring speed is 800 rpm,the selectivity of H₂O₂prepared by gas diffusion electrode is the best.The solution containing 4-N-3,6-DCP is completely degraded after Electro-Fenton treatment.When the concentration of substrate is 10 m M,current density is 26.7 m A·cm^-2,and initial concentration of Fe²⁺is 0.5 m M,the degradation rate of 4-N-3,6-DCP is the fastest.The third part of this article is the design of 4-N-3,6-DCP with an annual output of 1,000 tons.The plate-frame electrolytic cell was used instead of the H-type electrolytic cell.At the same time,the industrial electrolytic reactor was designed and the relevant process route was also drawn up.In addition,we have conducted an economic feasibility analysis,including designing the production organization plan,calculation of fixed and mobile costs,and economic accounting.The results show that the annual profit of industrial production is about 19.271 million yuan.