A method for treating residues from the decanter of fluorinated ethylene carbonate

Abstract

The present invention discloses a method for treating the residue of a fluorinated ethylene carbonate deweighting kettle. A method for treating the residue of a fluorinated ethylene carbonate deweighting kettle includes the following steps: after adding a dispersant to a reaction vessel containing the deweighting kettle residue and stirring and dispersing it, the dispersant is selected from one or more of diatomaceous earth, silica gel, powdered molecular sieve, montmorillonite powder, and talc powder, and the mass ratio of the deweighting kettle residue to the dispersant is 100:7-25, and then the bottom material is separated, purified, and recycled through stepwise heating and reduced-pressure distillation or by adding an extraction solvent for extraction. The present invention fully extracts each component in the jelly-like deweighting kettle residue, thereby improving the recovery rates of the finished product and the solvent, reducing the generation of solid waste, reducing environmental pollution, having a simple process, and low treatment costs.

Description

Technical field:

[0001] The invention relates to the technical field of environmental protection and comprehensive treatment and utilization of chemical wastes, and in particular to a method for treating fluoroethylene carbonate deheavy still residue. Background technology:

[0002] Traditional electrolyte systems cannot meet the electrolyte requirements of high-capacity silicon negative electrode materials and lithium-rich manganese-based solid solution positive electrode materials, so it is necessary to develop a new and efficient lithium battery additive to improve the performance of the electrolyte. FEC (fluoroethylene carbonate) contains CF bonds and has a high electronegativity and strong electron-withdrawing ability. Adding FEC to the electrolyte can not only inhibit the decomposition of the electrolyte solvent, but also form a solid SEI film on the electrode surface, improve the cycle stability of lithium-ion batteries, thereby reducing battery impedance, improving battery low-temperature performance, and improving battery specific capacity and cycle performance.

[0003] At present, the treatment of fluoroethylene carbonate residues is mainly focused on the treatment of mixed salts. For example, patent CN112300111A discloses a method for treating fluoroethylene carbonate solid residues, including recovering solvents, recovering crude fluoroethylene carbonate, recovering by-product potassium chloride, etc. Patent ZL 201911027348.9 discloses a method for treating fluoroethylene carbonate solid waste, specifically recovering by-product potassium chloride after treating organic waste.

[0004] There are defects in the existing synthesis method of fluoroethylene carbonate. In the synthesis process of fluoroethylene carbonate, after solid-liquid separation, crude fluoroethylene carbonate, solvent, fluorinating agent, phase transfer catalyst and other organic impurities are entrained in the mother liquor. After vacuum distillation, the organic matter in the bottom of the kettle undergoes polymerization reaction, which will produce viscous jelly-like solid residues, with 5%-50% FEC residues, which seriously affects the output. At the same time, these kettle residues are difficult to handle, with complex composition, toxicity and harm, and great environmental damage, becoming a stumbling block to the sustainable development of enterprises. In the face of increasingly stringent environmental protection policies, the treatment and disposal of kettle residues has become an urgent problem to be solved. Summary of the invention:

[0005] The invention solves the problems existing in the prior art and provides a method for treating fluoroethylene carbonate de-heavy still residue. The invention can fully extract various components in the de-heavy still residue jelly sample, thereby improving the recovery rate of finished products and solvents, reducing the generation of solid waste and environmental pollution, and has a simple process and low treatment cost.

[0006] The object of the present invention is to provide a method for treating fluoroethylene carbonate de-weighting still residue, comprising the following steps: adding a dispersant to a reaction container containing the de-weighting still residue for stirring and dispersing, wherein the dispersant is selected from one or more of diatomaceous earth, silica gel, powdered molecular sieve, montmorillonite powder and talcum powder, and the mass ratio of the de-weighting still residue to the dispersant is 4-7:0.5-1; and then separating, purifying and recycling the bottom material by step-by-step temperature-raising and reduced-pressure distillation or by adding an extraction solvent for extraction.

[0007] Preferably, the de-weighted still residue refers to the still residue obtained by de-weighting the filtrate after the synthesis of fluoroethylene carbonate. The de-weighted still residue provided by the present invention is similar to jelly.

[0008] Preferably, the stirring rate of adding the dispersant for stirring is 150-350 rpm, and the stirring time is 0.3-0.5 h. More preferably, the stirring rate of adding the dispersant for stirring is 180-300 rpm.

[0009] Preferably, the specific steps of separating, purifying and recycling the bottom material by step-by-step temperature increase and reduced pressure distillation are as follows: the dispersed bottom material of the kettle is subjected to reduced pressure distillation by step-by-step temperature increase, kettle residue and crude fluoroethylene carbonate are obtained after the distillation, the kettle residue is taken and added with an organic solvent, and the content of fluoroethylene carbonate is detected until the mass of fluoroethylene carbonate in the kettle residue is less than 1% of the mass of fluoroethylene carbonate in the kettle residue before dispersion, and the addition of organic solvent is stopped, the incineration residue obtained by incineration of the kettle residue treated with organic solvent is washed with water, filtered, dried, crushed and sieved, and then thrown into a reaction container filled with de-heavy kettle residue to serve as a dispersant for recycling, and the crude fluoroethylene carbonate is transferred to a distillation de-light kettle, and purified to obtain high-purity fluoroethylene carbonate (with a purity of more than 99.95%).

[0010] More preferably, the stepwise temperature increase is performed slowly at a rate of 1°C per minute, and the pressure of the vacuum distillation is -0.1-0.5 MPa. The stepwise temperature increase is performed from 60°C to 150°C for vacuum distillation, and the distillation time is 3 hours.

[0011] Preferably, the organic solvent is selected from one or more of ethyl acetate, methyl acetate, ethyl formate, butyl formate, butyl acetate, acetonitrile, propionitrile, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0012] Preferably, the specific steps of extracting the bottom material with an extraction solvent to separate, purify and recycle the bottom material are: adding an extraction solvent to the dispersed bottom material of the kettle for extraction, centrifuging the organic phase after extraction for solid-liquid separation, adding an organic solvent to the solid phase after solid-liquid separation, and testing the content of fluoroethylene carbonate until the mass of fluoroethylene carbonate in the solid phase sample is less than 1% of the mass of fluoroethylene carbonate in the solid phase sample before dispersion, stopping the addition of organic solvent, washing the solid phase sample after organic solvent treatment with water, filtering, drying, crushing and sieving, and then throwing it into a reaction container filled with deweighting kettle residue to act as a dispersant for recycling, and transferring the liquid phase after solid-liquid separation to a distillation kettle, and purifying to obtain high-purity fluoroethylene carbonate and high-purity extraction solvent.

[0013] Further preferably, the extraction solvent is selected from one or more of diethyl ether, isopropyl ether, methyl tert-ether, anisole, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, tetrahydrofuran, 1,4-dioxane, dichloromethane, chloroform, and 1,2-dichloroethane.

[0014] Preferably, the mass ratio of the extraction solvent to the dispersant is 5 to 10:1.

[0015] More preferably, the organic solvent is selected from one or more of ethyl acetate, methyl acetate, ethyl formate, butyl formate, butyl acetate, acetonitrile, propionitrile, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The present invention adopts one or more of non-toxic and environmentally friendly materials such as diatomaceous earth, silica gel, powdered molecular sieve, montmorillonite powder, and talcum powder as dispersants; after the viscous and difficult-to-separate heavy slag at the bottom of the kettle is dispersed with the dispersant, the material at the bottom of the kettle is easy to clean, shortening the time for cleaning the tower kettle.

[0018] 2. The present invention directly puts the dispersant into the kettle, which is simple to operate; after being treated with the dispersant, the material is easy to distill out with less loss, and the residual amount of fluoroethylene carbonate after distillation is less than 0.1%, which is cleaner and more thorough than direct distillation.

[0019] 3. The material evaporated by the dispersant of the present invention is clear and transparent in color and has few impurities.

[0020] 4. The present invention reduces the organic content in the kettle residue after the crude fluoroethylene carbonate is distilled off to the minimum, and incineration is more environmentally friendly at this time. After the kettle residue is incinerated, a very small amount of salt therein is dissolved and removed by washing, and the remaining residue can be reused after drying, which is more economical and environmentally friendly and suitable for industrial production.

[0021] 5. The present invention breaks the conventional understanding of the application fields of products such as diatomaceous earth, silica gel, powdered molecular sieve, montmorillonite powder, talcum powder, etc., and also provides a new solution for the treatment of kettle residues.

[0022] 6. The treatment of the de-weighting still residue proposed in the present invention is to first disperse it with a dispersant and then extract it, rather than directly adding an extraction solvent to the de-weighting still residue. This method can improve the extraction efficiency and reduce the amount of extraction solvent used. Specific implementation method:

[0023] The following examples are provided to further illustrate the present invention, rather than to limit the present invention.

[0024] Unless otherwise defined, all technical terms used hereinafter are the same as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the experimental materials and reagents herein are conventional commercial products in the art. In the following examples, the purity of the high-purity fluoroethylene carbonate obtained by purification reaches more than 99.95%.

[0025] Example 1

[0026] 7 kg of silica gel is added to a dispersion reaction kettle containing 100 kg of de-heavy kettle residue and stirred at a stirring rate of 300 rpm. After stirring for 0.3 h, the temperature is increased stepwise from 60° C. to 150° C. for reduced pressure distillation. The distillation time is 3 h and the pressure of the reduced pressure distillation is 0.3 MPa. After the distillation, kettle residue and crude fluoroethylene carbonate are obtained. After the distillation, the kettle residue is extracted with ethyl acetate. After detection, the amount of fluoroethylene carbonate in the kettle residue is less than 1% of the amount of fluoroethylene carbonate in the kettle residue before dispersion. The addition of ethyl acetate is stopped, and the remaining kettle residue is incinerated in an incinerator. The remaining incineration residue after incineration is washed with water, dried, crushed, sieved, and then thrown into the dispersion reaction kettle for recycling as a dispersant. The crude fluoroethylene carbonate is transferred to a distillation de-light kettle and purified to obtain high-purity fluoroethylene carbonate.

[0027] Example 2

[0028] 25 kg of diatomaceous earth is added to a dispersion reaction kettle containing 100 kg of de-heavy kettle residue, and the mixture is stirred at a stirring rate of 180 rpm. After stirring for 0.5 h, the temperature is raised in a stepwise manner from 60° C. to 150° C. for vacuum distillation. The distillation time is 3 h, and the pressure of the vacuum distillation is 0.5 MPa. After the distillation, kettle residue and crude fluoroethylene carbonate are obtained. After the distillation, the kettle residue is extracted with dimethyl carbonate. After detection, the amount of fluoroethylene carbonate in the kettle residue is less than 1% of the amount of fluoroethylene carbonate in the kettle residue before dispersion. The addition of dimethyl carbonate is stopped, and the remaining kettle residue is incinerated in an incinerator. The remaining incineration residue after incineration is washed with water, dried, crushed, sieved, and then thrown into the dispersion reaction kettle for recycling as a dispersant. The crude fluoroethylene carbonate is transferred to a distillation de-light kettle and purified to obtain high-purity fluoroethylene carbonate.

[0029] Comparative Example 1

[0030] 100 kg of deweighting kettle residue was directly added into the dispersion reactor for stirring at a rate of 180 rpm. After stirring for 0.5 h, the temperature was increased stepwise from 90°C to 150°C. The distillation time was 3 h. After the distillation, kettle residue and a small amount of mixed solution were obtained. After testing, the content of fluoroethylene carbonate was less than 5%, and the purification effect was not achieved.

[0031] Comparative Example 2

[0032] 100 kg of deweighting kettle residue was directly added into the dispersion reactor for stirring at a rate of 180 rpm. After stirring for 0.5 h, the temperature was increased stepwise from 50°C to 150°C for reduced pressure distillation. The distillation time was 5 h. After the distillation, kettle residue and crude fluoroethylene carbonate were obtained. After the distillation, a sample of the kettle residue was taken and extracted with acetonitrile. After testing, the content of fluoroethylene carbonate in the kettle residue was still 5%-15%. Due to the high content of organic matter, direct incineration is harmful to the environment, so the hazardous waste transfer process is adopted.

[0033] Comparing Example 2, Comparative Example 1 and Comparative Example 2, after adding the dispersant, Example 2 can completely purify the solvent and 95%-99.5% of fluoroethylene carbonate in the kettle residue, and the residue is directly sent to the incinerator, which is convenient to handle and saves costs; while Comparative Examples 1 and Comparative Examples 2 use direct distillation and reduced pressure distillation to purify only 5%-85% of the incidental ethylene carbonate in the kettle residue. The kettle residue has high viscosity, is difficult to stir, and has a difficult handling process. The later residue handling is relatively difficult and the handling cost is high.

[0034] Example 3

[0035] 12 kg of powdered molecular sieves were added to a dispersion reactor containing 100 kg of deweighting kettle residue and stirred at a stirring rate of 240 rpm. After stirring for 0.4 h, 100 kg of methyl tertiary ether, an extraction solvent, was added to the dispersion reactor for extraction, and the mixture was transferred to a centrifuge for solid-liquid separation to obtain a solid phase and a liquid phase. A solid phase sample was added with acetonitrile to detect the content of fluoroethylene carbonate until the amount of fluoroethylene carbonate in the solid phase sample was less than 1% of the amount of fluoroethylene carbonate in the solid phase sample before dispersion. The addition of acetonitrile was stopped, and the solid phase sample was washed with water, filtered, dried, crushed, sieved, and then thrown into the dispersion reactor for recycling as a dispersant. The liquid phase was transferred to a distillation kettle and purified to obtain high-purity fluoroethylene carbonate and high-purity methyl tertiary ether, an extraction solvent.

[0036] Comparative Example 3

[0037] To a dispersed reaction kettle containing 100 kg of deweighting kettle residue, 100 kg of methyl tert-ether as an extraction solvent was added for extraction at a rotation speed of 240 rpm. After stirring for 0.4 h, the mixture was transferred to a centrifuge for solid-liquid separation to obtain a solid phase and a liquid phase. A solid phase sample was added with acetonitrile to detect the content of fluoroethylene carbonate. The results showed that 25% of the fluoroethylene carbonate was not extracted and 8% of the extraction solvent remained.

[0038] Comparing Example 3 with Comparative Example 3, when treating the same amount of de-weighting still residue, Example 3 first disperses with a dispersant and then extracts, rather than directly adding an extraction solvent to the de-weighting still residue, which can greatly improve the extraction efficiency, reduce the amount of extraction solvent used, and reduce the processing cost.

[0039] Example 4

[0040] Add 20 kg of powdered molecular sieves to a dispersion reactor containing 100 kg of deweighting kettle residue and stir at a stirring rate of 240 rpm. After stirring for 0.5 h, add 100 kg of extraction solvent isopropyl ether to the dispersion reactor for extraction, transfer to a centrifuge for solid-liquid separation to obtain a solid phase and a liquid phase, take a solid phase sample and add dimethyl carbonate to detect the content of fluoroethylene carbonate until the amount of fluoroethylene carbonate in the solid phase sample is less than 1% of the amount of fluoroethylene carbonate in the solid phase sample before dispersion, stop adding dimethyl carbonate, wash the solid phase sample with water, filter, dry, crush and sieve it, and then throw it into the dispersion reactor to serve as a dispersant for recycling, and transfer the liquid phase to a distillation kettle for purification to obtain high-purity fluoroethylene carbonate and high-purity extraction solvent isopropyl ether.

[0041] The description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for treating the residue of a fluorinated ethylene carbonate stripping still, characterized in that, it comprises the following steps: after adding a dispersant to a reaction vessel containing the residue of the stripping still and stirring to disperse, the dispersant is selected from one or more of diatomaceous earth, silica gel, powdered molecular sieve, montmorillonite powder and talc powder, and the mass ratio of the residue of the stripping still to the dispersant is 100:7-25, and then the bottom material is separated, purified and recycled through stepwise temperature-raising and pressure-reducing distillation or by adding an extraction solvent for extraction.

2. The treatment method according to claim 1, characterized in that, the residue of the stripping still refers to the residue obtained after filtration of the filtrate after fluorinated ethylene carbonate synthesis and stripping treatment.

3. The treatment method according to claim 1, characterized in that, the stirring rate for adding the dispersant and stirring is 150-350 rpm, and the stirring time is 0.3-0.5 h.

4. The treatment method according to claim 1, characterized in that, the specific steps for separating, purifying and recycling the bottom material through stepwise temperature-raising and pressure-reducing distillation are: subjecting the well-dispersed bottom material at the bottom of the kettle to pressure-reducing distillation through stepwise temperature-raising. After the distillation is completed, kettle slag and crude fluorinated ethylene carbonate are obtained. Add an organic solvent to the kettle slag for detection of the content of fluorinated ethylene carbonate until the mass of fluorinated ethylene carbonate in the kettle slag is less than 1% of the mass of fluorinated ethylene carbonate in the kettle slag before dispersion, stop adding the organic solvent. The incineration slag obtained after incinerating the kettle slag treated with the organic solvent is washed with water, filtered, dried, pulverized, sieved and then thrown into the reaction vessel containing the residue of the stripping still to be used as a dispersant in a cycle. The crude fluorinated ethylene carbonate is transferred to a rectifying and de-lighting kettle and purified to obtain high-purity fluorinated ethylene carbonate.

5. The treatment method according to claim 4, characterized in that, the stepwise temperature-raising is carried out by slowly raising the temperature at a rate of 1 °C per minute, and the pressure of the pressure-reducing distillation is -0.1-0.5 Mpa.

6. The treatment method according to claim 4, characterized in that, the organic solvent is selected from one or more of ethyl acetate, methyl acetate, ethyl formate, butyl formate, butyl acetate, acetonitrile, propionitrile, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

7. The treatment method according to claim 1, characterized in that, the specific steps for separating, purifying and recycling the bottom material by extraction with an extraction solvent are: adding an extraction solvent to the well-dispersed bottom material at the bottom of the kettle for extraction. The organic phase after extraction is centrifuged for solid-liquid separation. Add an organic solvent to the solid phase after solid-liquid separation for detection of the content of fluorinated ethylene carbonate until the mass of fluorinated ethylene carbonate in the solid phase sample is less than 1% of the mass of fluorinated ethylene carbonate in the solid phase sample before dispersion, stop adding the organic solvent. The solid phase sample treated with the organic solvent is washed with water, filtered, dried, pulverized, sieved and then thrown into the reaction vessel containing the residue of the stripping still to be used as a dispersant in a cycle. The liquid phase after solid-liquid separation is transferred to a rectifying kettle and purified to obtain high-purity fluorinated ethylene carbonate and high-purity extraction solvent.

8. The treatment method according to claim 7, characterized in that, The extraction solvent selected is one or more of diethyl ether, isopropyl ether, methyl tert-butyl ether, anisole, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, tetrahydrofuran, 1,4-dioxane, dichloromethane, chloroform, 1,2-dichloroethane.

9. According to the treatment method described in claim 7, characterized in that, the mass ratio of the extraction solvent to the dispersant is 5 to 10:

1.

10. According to the treatment method described in claim 7, characterized in that, the organic solvent selected is one or more of ethyl acetate, methyl acetate, ethyl formate, butyl formate, butyl acetate, acetonitrile, propionitrile, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.