Process for extracting white oil in lithium battery diaphragm by ionic liquid and separating and recovering

Abstract

The application provides a process for extracting white oil in a lithium battery diaphragm by using an ionic liquid and separating and recovering the white oil, and belongs to the technical field of white oil separation and recovery processes.The PE diaphragm is subjected to multistage extraction by using an ionic liquid extractant, and the PE diaphragm is subjected to multistage water washing by using water, so that the oil content of the PE diaphragm can be reduced to <0.5%, and the residual extractant on the diaphragm can be reduced to <100ppm / m 2 The extractant can be efficiently recovered by performing separation and reverse osmosis treatment on the extractant and the water washing liquid, and the separated and recovered water can be recycled and meets the industrial wastewater discharge standard.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of white oil recovery and separation process, and particularly relates to a process for extracting and separating and recovering white oil in lithium battery diaphragm by using ionic liquid. BACKGROUND

[0002] Traditional lithium battery diaphragm extraction process uses dichloromethane or tetrachloroethylene as an extractant, which is not only toxic and irritating, but also has a certain impact on the environment. In this context, a new type of environmentally friendly extractant composed of ionic liquid has been developed, which is low-carbon, environmentally friendly, non-toxic, and has a higher flash point, and is more suitable for industrial production. It effectively solves the problem of energy and environmental protection.

[0003] However, the extraction, recovery and recycling process of ionic liquid extractant in lithium battery diaphragm extraction process has not been studied in the prior art. SUMMARY

[0004] The present application aims to provide a process for extracting and separating and recovering white oil in lithium battery diaphragm by using ionic liquid, to solve the technical problems of existing extractants being toxic and irritating, and not using ionic liquid as a diaphragm extractant.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a process for extracting and separating and recovering white oil in lithium battery diaphragm by using ionic liquid, comprising the following steps:

[0007] 1) using ionic liquid extractant to perform multi-stage extraction on PE diaphragm to obtain an extraction liquid;

[0008] 2) performing multi-stage water washing on the extracted PE diaphragm to obtain a water washing liquid; performing three times of RO reverse osmosis treatment on the water washing liquid to obtain purified water and a concentrated liquid;

[0009] 3) performing three-stage separation on the extraction liquid to obtain light-phase white oil and heavy-phase mixed liquid;

[0010] 4) combining the concentrated liquid and the mixed liquid obtained in step 3) to obtain mixed water liquid, and sequentially performing oil removal and short evaporation separation on the mixed water liquid to obtain water and ionic liquid extractant, respectively.

[0011] Further, in step 1), the temperature of multi-stage extraction is 30-70℃; the ionic liquid extractant comprises 7-14 parts of imidazole tetrafluoroborate, 10-18 parts of betaine salt, 22-30 parts of imidazole acetate, 13-20 parts of imidazole dicyanamide salt, 4-20 parts of imidazole ethyl sulfate salt, 4-8 parts of imidazole bisfluorosulfonylimide salt, 3-8 parts of bis-trifluorosulfonylimide salt, and 2-90 parts of alcohol ether mixture.

[0012] Further, the multi-stage extraction is 3-7 stage extraction, and the time of each stage extraction is 1-4 min.

[0013] Further, the liquid quantity of the ionic liquid extractant is 2-7 m 3 / h.

[0014] Further, in the step 2), the multi-stage water washing is 2-4 stage water washing, the water washing temperature is 30-70℃, the time of each stage water washing is 1-5 min, and the liquid quantity of the water washing liquid is 2-7 m 3 / h.

[0015] Further, in the step 3), the three-stage separation comprises: mixing the extraction liquid and 10-35% water in a separation device to perform first-stage separation to obtain light phase 1 and heavy phase 1; mixing the light phase 1 and 30-90% water in the separation device to perform second-stage separation to obtain light phase 2 and heavy phase 2; and mixing the light phase 2 and 30-90% water in the separation device to perform third-stage separation.

[0016] Further, in the step 4), in the short evaporation separation, the temperature is 30-80℃, and the pressure is 0--0.1 MPa.

[0017] Further, the concentration ratio of the RO reverse osmosis treatment is independently 30-80%

[0018] The present application has the following beneficial effects:

[0019] 1. From the aspect of energy saving, compared with the traditional dichloromethane process, the investment of rectification tower equipment is saved, and the energy consumption cost is reduced.

[0020] 2. From the aspect of environmental protection, dichloromethane is a 2A carcinogen, and the process method of the present application reduces the occupational health hazards and environmental pollution. DETAILED DESCRIPTION

[0021] The present application provides a process for extracting and recovering white oil in lithium battery diaphragm by using ionic liquid, which comprises the following steps:

[0022] 1) Multi-stage extraction of PE diaphragm by using ionic liquid extractant to obtain extraction liquid;

[0023] 2) Multi-stage water washing of the extracted PE diaphragm to obtain water washing liquid; and three times of RO reverse osmosis treatment of the water washing liquid to obtain purified water and concentrated liquid;

[0024] 3) Three-stage separation of the extraction liquid to obtain light phase white oil and heavy phase mixed liquid;

[0025] 4) combine the concentrated liquid and the mixed liquid obtained in step 3) to obtain a mixed water liquid, and sequentially remove oil and short-steam separate the mixed water liquid to obtain water and ionic liquid extractant respectively.

[0026] In the present application, in step 1), the temperature of multi-stage extraction is 30-70℃, preferably 40-60℃, and further preferably 45-55℃; the ionic liquid extractant comprises 7-14 parts of imidazole tetrafluoroborate, 10-18 parts of betaine salt, 22-30 parts of imidazole acetate, 13-20 parts of imidazole dicyanamide, 4-20 parts of imidazole ethyl sulfate, 4-8 parts of imidazole bisfluorosulfonylimide, 3-8 parts of bis-trifluorosulfonylimide, and 2-90 parts of alcohol-ether mixture.

[0027] In the present application, the ionic liquid extractant is the extractant disclosed in Chinese patent CN116351097B, and the preparation method refers to the method in Chinese patent CN116351097B.

[0028] In the present application, the imidazole tetrafluoroborate is one or a combination of 1-ethyl-3-methyl imidazole tetrafluoroborate and 1-butyl-3-methyl imidazole tetrafluoroborate; the imidazole acetate is one or a combination of 1-ethyl-3-methyl imidazole acetate and 1-butyl-3-methyl imidazole acetate.

[0029] In the present application, the betaine salt is one or a combination of malic acid betaine salt and tartaric acid betaine salt.

[0030] In the present application, the imidazole dicyanamide is one or a combination of 1-ethyl-3-methyl imidazole dicyanamide and 1-butyl-3-methyl imidazole dicyanamide; the imidazole ethyl sulfate is one or a combination of 1-ethyl-3-methyl imidazole ethyl sulfate and 1-butyl-3-methyl imidazole ethyl sulfate; the bisfluorosulfonylimide is one or a combination of 1-ethyl-3-methyl imidazole bisfluorosulfonylimide and 1-butyl-3-methyl imidazole bisfluorosulfonylimide.

[0031] In the present application, the bis-trifluorosulfonylimide is one or a combination of 1-ethyl-3-methyl imidazole bis-trifluorosulfonylimide, 1-butyl-3-methyl imidazole bis-trifluorosulfonylimide, and tributylmethylammonium bis-trifluorosulfonylimide.

[0032] In the present application, the alcohol-ether mixture is a combination of at least two of tripropylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol propyl ether, propylene glycol butyl ether, ethylene glycol phenyl ether, and propylene glycol phenyl ether.

[0033] In the present application, the multi-stage extraction is 3-7 stage extraction, preferably 4-6 stage extraction, and further preferably 5 stage extraction; the time for each stage of extraction is 1-4 min, preferably 2-3 min.

[0034] In the present application, the liquid feeding amount of the ionic liquid extractant is 2-7 m 3 / h, preferably 3-6 m 3 / h, and further preferably 4-5 m 3 / h.

[0035] In the present application, the multi-stage extraction can reduce the oil content of the PE separator to <0.5%.

[0036] In the present application, in step 2), the multi-stage water washing is 2-4 stage water washing, preferably 3 stage water washing; the water washing temperature is 30-70℃, preferably 40-60℃, and further preferably 45-55℃; the time for each stage of water washing is 1-5 min, preferably 2-4 min, and further preferably 3 min; the liquid feeding amount of the water washing liquid is 2-7 m 3 / h, preferably 3-6 m 3 / h, and further preferably 4-5 m 3 / h.

[0037] In the present application, the multi-stage water washing can reduce the residual ionic liquid extractant on the PE separator to <100 ppm / m 2 .

[0038] In the present application, in step 3), the steps of the three-stage separation are: mixing the extract liquid and 10-35% water in a separation device to perform first stage separation, to obtain light phase 1 and heavy phase 1; mixing the light phase 1 and 30-90% water in a separation device to perform second stage separation, to obtain light phase 2 and heavy phase 2; and mixing the light phase 2 and 30-90% water in a separation device to perform third stage separation.

[0039] Preferably, the steps of the three-stage separation are: mixing the extract liquid and 20-25% water in a separation device to perform first stage separation, to obtain light phase 1 and heavy phase 1; mixing the light phase 1 and 40-80% water in a separation device to perform second stage separation, to obtain light phase 2 and heavy phase 2; and mixing the light phase 2 and 40-80% water in a separation device to perform third stage separation.

[0040] Further preferably, the steps of the three-stage separation are: mixing the extract liquid and 23% water in a separation device to perform first stage separation, to obtain light phase 1 and heavy phase 1; mixing the light phase 1 and 50-60% water in a separation device to perform second stage separation, to obtain light phase 2 and heavy phase 2; and mixing the light phase 2 and 50-60% water in a separation device to perform third stage separation.

[0041] In the present application, in step 4), the temperature in the short distillation separation is 30-80℃, preferably 40-70℃, and further preferably 50-60℃; and the pressure is 0- -0.1 MPa, preferably -0.1 MPa.

[0042] In the present application, the short distillation separation is short path distillation, which is a device commonly used for separating liquid mixtures, and is a distillation process carried out under vacuum, which is based on the boiling point difference between liquid components, and is effectively separated in a short distillation path. The process of the present application separates the mixture of ionic liquid and water by short distillation to realize recycling and reduce wastewater discharge. Short path distillation utilizes the different boiling points of different components (ionic liquid and water), evaporates the liquid mixture by heating, and then condenses and collects the steam (water) to separate the ionic liquid and water, and recycle the water and ionic liquid to reduce the discharge of wastewater.

[0043] The short path distillation process includes four processes: pretreatment, heating, separation and collection. The mixed liquid is heated to a set temperature (30-80℃) to evaporate. As the liquid is heated, the component with higher volatility (water) begins to evaporate and form steam. The steam is cooled by a condenser to convert it into a liquid, which is collected by a collection device for recycling. The short path distillation is equipped with a vacuum system, which reduces the operating pressure to significantly reduce the boiling point of the product. The short path rectification has the characteristics of short residence time of the product, high process evaporation pressure, and can obtain pure and safe product, the content of the extractant in the water is less than 100 ppm, the operation process is simple, and the equipment demand is less.

[0044] In the present application, the concentration ratio of the RO reverse osmosis treatment is independently 30-80%, preferably 40-70%, and further preferably 50-60%.

[0045] In the present application, the COD value of water is reduced to below 500 ppm after three times of RO reverse osmosis treatment of specific ionic liquid, and the filtered water is reused, aiming to maximize the recovery and reuse of RO concentrate and reduce wastewater discharge.

[0046] The principle of RO reverse osmosis treatment: RO membrane is a kind of reverse osmosis membrane, which is a kind of high-efficiency water treatment technology. Through high-pressure treatment of water, water molecules are filtered through the microporous structure of RO membrane, and ionic liquid is refluxed for concentration treatment. Concentration can improve the concentration of ionic liquid, reduce the amount of treatment and discharge, and reduce the treatment cost. The COD value of the treated water is less than 200 ppm, which fully meets the industrial discharge standard.

[0047] The RO reverse osmosis treatment device selects a filter membrane with a specific size, and the suspended particles and high molecular organic matters in the low-concentration ionic liquid are intercepted on the surface of the filter membrane, so that the low-concentration ionic liquid passes through the membrane hole, thereby realizing the filtration and separation of impurities and further prolonging the service life of the RO membrane in subsequent operation. A certain operating pressure is required for subsequent RO membrane to push the low-concentration ionic liquid through the filter membrane pores, thereby increasing the water permeation rate. The water after three times of RO membrane treatment can be recycled to production as required to meet the production demand.

[0048] In the present application, the purified water obtained by the RO reverse osmosis treatment can be recycled to the water washing step.

[0049] The technical solutions provided by the present application will be described in detail below in combination with the embodiments, but they should not be understood as limitations to the scope of protection of the present application.

[0050] The preparation method of the ionic liquid extractant used in the embodiments of the present application is as follows:

[0051] 14 kg of imidazole tetrafluoroborate (1-butyl-3-methyl imidazole tetrafluoroborate), 18 kg of betaine salt (10 kg of betaine tartrate, 8 kg of betaine malate), 22 kg of imidazole acetate (1-butyl-3-methyl imidazole acetate), 20 kg of imidazole dicyanamide salt (1-butyl-3-imidazole dicyanamide salt), 9 kg of imidazole ethyl sulfate salt (1-ethyl-3-methyl imidazole ethyl sulfate salt), 4 kg of imidazole bisfluorosulfonylimide salt (1-ethyl-3-methyl imidazole bisfluorosulfonylimide salt), 8 kg of bis-trifluorosulfonylimide salt (1-ethyl-3-methyl imidazole bis-trifluorosulfonylimide salt), and 5 kg of alcohol ether mixture (1 kg of ethylene glycol butyl ether, 2 kg of dipropylene glycol propyl ether, and 2 kg of propylene glycol phenyl ether). The imidazole tetrafluoroborate, imidazole bisfluorosulfonylimide salt, imidazole ethyl sulfate salt, and betaine salt are sequentially added to a reaction kettle, heated to 45°C, and stirred for 1 h, and then the imidazole acetate, alcohol ether mixture, imidazole dicyanamide salt, and bis-trifluorosulfonylimide salt are added, heated to 55°C, and stirred for 35 min to obtain a mixture; the mixture is filtered, and the filtrate is the extractant for ultra-high molecular weight PE fibers and membranes in the present embodiment.

[0052] Example 1

[0053] The lithium battery PE membrane is extracted three times with the ionic liquid extractant at a temperature of 50°C and a liquid feeding rate of 5 m 3 / h, and each extraction time is 4 min to obtain an extracted liquid;

[0054] The extracted PE membrane is washed with water three times at a temperature of 50°C, and the water feeding amount is 4 m 3 / h, the water washing time is 3 min, the water washing liquid is obtained, the water washing liquid is treated by RO reverse osmosis for three times, the concentration ratio is 50% each time, the concentrated liquid and purified water are obtained, and the purified water is recycled to the water washing step;

[0055] The extraction liquid is subjected to three-stage separation: the extraction liquid and 30% water are mixed in a separation device for first-stage separation to obtain light phase 1 and heavy phase 1; the light phase 1 and 50% water are mixed in a separation device for second-stage separation to obtain light phase 2 and heavy phase 2; the light phase 2 and 80% water are mixed in a separation device for third-stage separation, and the heavy phase mixture is collected, and the light phase is white oil;

[0056] The concentrated liquid and the heavy phase mixture are combined to obtain mixed water liquid, and the mixed water liquid is sequentially subjected to oil removal and short evaporation separation to obtain water and ionic liquid extractant, the short evaporation separation temperature is 50 DEG C, and the separation pressure is -0.1 MPa.

[0057] Example 2

[0058] The PE separator of lithium battery is subjected to three-stage extraction by using ionic liquid extractant at a temperature of 60 DEG C and a liquid feeding rate of 5 m 3 / h, the extraction time is 4 min each time, and the extraction liquid is obtained;

[0059] The PE separator after extraction is subjected to three-stage water washing at a temperature of 50 DEG C and a liquid feeding rate of 4 m 3 / h, the water washing time is 3 min, the water washing liquid is obtained, the water washing liquid is treated by RO reverse osmosis for three times, the concentration ratio is 60% each time, the concentrated liquid and purified water are obtained, and the purified water is recycled to the water washing step;

[0060] The extraction liquid is subjected to three-stage separation: the extraction liquid and 25% water are mixed in a separation device for first-stage separation to obtain light phase 1 and heavy phase 1; the light phase 1 and 60% water are mixed in a separation device for second-stage separation to obtain light phase 2 and heavy phase 2; the light phase 2 and 90% water are mixed in a separation device for third-stage separation, and the heavy phase mixture is collected, and the light phase is white oil;

[0061] The concentrated liquid and the heavy phase mixture are combined to obtain mixed water liquid, and the mixed water liquid is sequentially subjected to oil removal and short evaporation separation to obtain water and ionic liquid extractant, the short evaporation separation temperature is 50 DEG C, and the separation pressure is -0.1 MPa.

[0062] Example 3

[0063] The PE separator of lithium battery is subjected to three-stage extraction by using ionic liquid extractant at a temperature of 50 DEG C and a liquid feeding rate of 5 m 3 / h, the extraction time is 4 min each time, and the extraction liquid is obtained;

[0064] The PE separator after extraction is washed with water for three times at a temperature of 50℃, the water inlet quantity is 4m 3 / h, each time of water washing is 3min, to obtain a water washing liquid, the water washing liquid is treated by three times of RO reverse osmosis, each time of concentration ratio is 75%, to obtain a concentrated liquid and purified water, the obtained purified water is recycled to the water washing step;

[0065] The extraction liquid is separated for three times: the extraction liquid and 30% water are mixed in a separation device to carry out first separation, to obtain a light phase 1 and a heavy phase 1; the light phase 1 and 50% water are mixed in a separation device to carry out second separation, to obtain a light phase 2 and a heavy phase 2; the light phase 2 and 80% water are mixed in a separation device to carry out third separation, to collect a heavy phase mixture, and the light phase is white oil;

[0066] The concentrated liquid and the heavy phase mixture are combined to obtain a mixed water liquid, the mixed water liquid is sequentially subjected to oil removal and short evaporation separation, to separate water and ionic liquid extractant, the short evaporation separation temperature is 60℃, and the separation pressure is-0.1MPa.

[0067] The PE separators after extraction and the PE separators after water washing in examples 1-3 are detected, and the results are shown in the following table 1.

[0068] Table 1: Oil content and extractant residue detection on PE separator

[0069] Item Original oil content / % Oil content after treatment / % extractant residual (ppm / m 2 )]]> Example 1 70 0.2 68 Example 2 75 0.4 85 Example 3 74 0.3 70

[0070] It can be seen from the above examples that the present application provides a process for extracting white oil in lithium battery separator by ionic liquid and separation and recovery. Through the process method of the present application, the oil content of PE separator can be reduced to <0.5%, and the extractant residue on the separator can be reduced to <100ppm / m 2 .

[0071] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A process for extracting and separating white oil from lithium battery separators using ionic liquids, characterized in that, Includes the following steps: 1) The PE membrane was subjected to multi-stage extraction using an ionic liquid extractant to obtain the extract; 2) The extracted PE membrane is subjected to multi-stage water washing to obtain a washing solution; The washing solution was subjected to three RO reverse osmosis treatments to obtain purified water and concentrate. 3) The extract was subjected to three-stage separation to obtain a mixture of light-phase white oil and heavy-phase liquid; 4) Combine the concentrate and the mixture obtained in step 3) to obtain a mixed aqueous solution. After sequentially removing oil and separating by short evaporation, water and ionic liquid extractant are obtained respectively. In step 3), the three-stage separation process is as follows: the extract and 10-35% water are mixed in a separation device for primary separation to obtain light phase 1 and heavy phase 1; light phase 1 and 30-90% water are mixed in a separation device for secondary separation to obtain light phase 2 and heavy phase 2; light phase 2 and 30-90% water are mixed in a separation device for tertiary separation. The concentration ratio of the RO reverse osmosis treatment is 30-80% independently.

2. The process for extracting and separating / recovering white oil from lithium battery separators using ionic liquids according to claim 1, characterized in that, In step 1), the temperature of the multi-stage extraction is 30~70℃; the ionic liquid extractant contains 7~14 parts imidazole tetrafluoroborate, 10~18 parts betaine salt, 22~30 parts imidazole acetate, 13~20 parts imidazole dinitrileamine salt, 4~20 parts imidazole ethyl sulfate salt, 4~8 parts imidazole difluorosulfonyl imide salt, 3~8 parts ditrifluorosulfonyl imide salt and 2~90 parts alcohol ether mixture.

3. The process for extracting and separating / recovering white oil from lithium battery separators using ionic liquids according to claim 1 or 2, characterized in that, The multi-stage extraction consists of 3 to 7 stages, with each stage lasting 1 to 4 minutes.

4. The process for extracting and separating / recovering white oil from lithium battery separators using ionic liquids according to claim 1 or 2, characterized in that, The influent flow rate of the ionic liquid extractant is 2-7 ml. 3 / h.

5. The process for extracting and separating / recovering white oil from lithium battery separators using ionic liquids according to claim 4, characterized in that, In step 2), the multi-stage water washing consists of 2 to 4 stages, with a washing temperature of 30 to 70°C, a washing time of 1 to 5 minutes for each stage, and a water washing solution flow rate of 2 to 7 ml. 3 / h.

6. The process for extracting and separating / recovering white oil from lithium battery separators using ionic liquids according to claim 5, characterized in that, In step 4), during the short-distillation separation, the temperature is 30~80℃ and the pressure is 0~-0.1MPa.