Method for preparing lithium heteropolyacid catalyst from waste electrolyte and application of lithium heteropolyacid catalyst

Abstract

The invention provides a method for preparing a lithium heteropolyacid catalyst by using a waste electrolyte and application of the method, and belongs to the technical field of catalysts, the lithium catalyst is extracted from the waste electrolyte, and organic components in the homologous waste electrolyte are catalyzed to synthesize a polyester product, so that the waste electrolyte is efficiently utilized, and the production cost is reduced. The purpose of saving resources is achieved; the five lithium heteropolyacid ionic liquid catalysts prepared by the invention have good activity on ester exchange reaction of ethylene carbonate and dimethyl succinate, the conversion rate is 86.43%, and the yield of the product PES is 75.17%; compared with common ionic liquid, the heteropolyacid ionic liquid has the characteristic of high melting point different from that of the common ionic liquid, and the heteropolyacid ionic liquid has the excellent characteristic of temperature control type reaction self-separation of high-temperature melting reaction-low-temperature solidification separation due to the performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a method for preparing a lithium-based heteropoly acid catalyst from waste electrolyte and application thereof. BACKGROUND

[0002] The global new energy automobile industry and other industries are developing rapidly under the background of low-carbon economy, which will drive the rapid development of the global lithium ion battery industry, and the number of scrap lithium batteries will also increase year by year. Therefore, the recycling and high-value utilization of waste lithium batteries are imperative.

[0003] The recycling process of waste lithium batteries can be divided into physical recycling and chemical recycling according to different principles, wherein the chemical recycling includes high-temperature metallurgy and hydrometallurgy. The physical recycling method can only recover part of the metal materials and lithium salt, and the efficiency is extremely low. In the high-temperature metallurgy and hydrometallurgy treatment process, if the electrolyte recovery treatment is not considered, it will bring great safety hidden danger to production and will also seriously pollute the environment.

[0004] The lithium ion battery is composed of a positive electrode, a negative electrode, an electrolyte and a separator, and the electrolyte is composed of carbonate and lithium salt. The carbonate solvent contained therein is easy to generate harmful small-molecule organic matters such as formaldehyde, methanol, acetaldehyde, ethanol and formic acid through chemical reactions such as hydrolysis, combustion and decomposition; the lithium salt containing fluorine (LiPF6) has strong toxicity; and the lithium salt in the electrolyte enters the environment and can generate fluorine-containing, arsenic-containing and phosphorus-containing compounds through chemical reactions such as hydrolysis, decomposition and combustion, causing fluorine pollution, arsenic pollution and phosphorus pollution. Therefore, the recycling of waste electrolyte has more important significance for safe production.

[0005] At present, the lithium salt in the waste lithium battery electrolyte is used to prepare a catalyst, the high-boiling organic matter in the waste lithium battery electrolyte is used as a reaction raw material, and polyethylene succinate (PES) is prepared through coupling reaction with a dibasic acid ester. PES is a biodegradable polymer material, which is easy to be decomposed and metabolized by microorganisms in the natural environment, and is finally converted into CO2 and H2O without pollution to the environment, and has important research significance. SUMMARY

[0006] The purpose of the present application is to provide a method for preparing a lithium-based heteropoly acid catalyst from waste electrolyte and application thereof. The lithium salt is extracted from the waste electrolyte, and a lithium-based heteropoly acid ionic liquid catalyst is synthesized to catalyze the preparation of degradable polyester PES from the carbonate in the homologous electrolyte, thereby providing a new idea for efficient recycling and high-value utilization of waste lithium battery electrolyte.

[0007] The purpose of the present application is achieved as follows:

[0008] A method for preparing a lithium-based heteropoly acid catalyst from waste electrolyte, and the specific steps are as follows:

[0009] Step 1: Distill the waste electrolyte under reduced pressure in a nitrogen environment to obtain a distillation component and a remaining component;

[0010] Step 2: Add an excess of sodium carbonate solid powder to the remaining component, stir for 10-40 min, and then perform suction filtration to obtain solid lithium carbonate;

[0011] Step 3: Place 0.12-0.15 mol of N-methylimidazole in a three-necked flask, and drop 0.1 mol of n-chlorobutane under condensation reflux conditions, with the reaction temperature controlled at 70-90°C. After 22-26 h of reaction, wash the reaction liquid with acetonitrile, spin and dry to obtain a light yellow intermediate A;

[0012] Step 4: Dissolve sodium molybdate in an appropriate amount of distilled water, heat to a slight boil, adjust the pH to 4-5, and then add lithium carbonate from Step 2 under condensation reflux. After 2 h of reaction, drop the complex metal salt, continue to react for 2 h after the drop is complete, and then add potassium chloride. A white precipitate is separated out, the insoluble matter is removed by filtration, and the product intermediate B is purified by adding anhydrous ethanol multiple times under an ice bath at about 0°C. After drying at 80°C for 5-8 h, a lithium-based vacancy Keggin-type heteropoly acid intermediate B with different coordination metals is obtained.

[0013] Step 5: Add intermediate B to a three-necked flask containing distilled water, stir and dissolve, then drop intermediate A into the three-necked flask. Immediately, a precipitate is separated out, which is filtered out, washed with distilled water, and then dried to obtain a lithium-based heteropoly acid ionic liquid catalyst.

[0014] Further, the distillation component in Step 1 is methyl ethyl carbonate (EMC) and dimethyl carbonate (DMC), which can be directly used as a finished product or as a chemical intermediate for synthesizing other compounds. After suction filtration in Step 2, the content of the EC component in the remaining component is determined to be more than 85%, and the rest is a small amount of low-boiling electrolyte and additives.

[0015] Further, the pressure of the reduced pressure distillation in Step 1 is -0.1 Mpa, the temperature is 120°C, and the distillation time is 2 h. The remaining component in Step 1 is ethylene carbonate (EC), lithium hexafluorophosphate (LiPF6), and additives, and lithium hexafluorophosphate (LiPF6) in the remaining component participates in the reaction in Step 2.

[0016] Further, the drop rate of n-chlorobutane in Step 2 is 10-100 mL / s;

[0017] The acetonitrile washing is performed 3-5 times;

[0018] The drying temperature is 70-90 DEG C, and the drying time is 5-8h.

[0019] Further, the coordination metal salt in step 4 is one of zinc salt, iron salt, copper salt, lead salt or titanium salt.

[0020] Further, the molar ratio of sodium molybdate, lithium carbonate and coordination metal salt in step 4 is 11:0.5:1;

[0021] The dropping speed of the coordination metal salt is 10-100mL / s;

[0022] The anhydrous ethanol is purified for 3-5 times.

[0023] Further, the molar ratio of intermediate A and intermediate B in step 5 is 5:1;

[0024] The dropping speed of the intermediate A is 10-100mL / s;

[0025] The drying temperature is 70-90 DEG C, and the drying time is 5-8h.

[0026] Further, the lithium-based heteropoly acid ionic liquid catalyst is at least one of Bmim9[Zn(H2O)LiMo 11 O 39 ], Bmim9[Fe II (H2O)LiMo 11 O 39 ], Bmim9[Cu(H2O)LiMo 11 O 39 ], Bmim7[Ti(H2O)LiMo 11 O 39 ], Bmim9[Pb(H2O)LiMo 11 O 39 ].

[0027] Further, the lithium-based heteropoly acid ionic liquid catalyst is used to catalyze the ester exchange reaction of ethylene carbonate (EC) and dimethyl succinate in the homologous waste electrolyte to synthesize polyethylene succinate (PES).

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1. The lithium-based catalyst is extracted from waste electrolyte, and the organic components in the homologous waste electrolyte are catalyzed to synthesize polyester products, thereby efficiently utilizing the waste electrolyte and achieving the purpose of saving resources.

[0030] 2. The 5 kinds of lithium heteropolyacid ionic liquid catalysts prepared by the present application have very good activity in the transesterification reaction of ethylene carbonate and dimethyl succinate (DMSu), the conversion rate is 86.43%, and the yield of product PES is 75.17%.

[0031] 3. The heteropolyacid ionic liquid prepared by the present application has the characteristic of high melting point which is different from that of general ionic liquid and does not have, and this performance makes it have the excellent characteristics of temperature control type reaction self-separation of "high temperature melting reaction-low temperature solidification separation". BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 It is the infrared spectrum of the intermediate A ([Bmim]Cl) in the present application;

[0034] Figure 2 It is the hydrogen nuclear magnetic spectrum of the intermediate A ([Bmim]Cl) in the present application;

[0035] Figure 3 It is the infrared spectrum of the intermediate B lithium heteropolyacid in the present application;

[0036] Figure 4 It is the infrared spectrum of the product lithium heteropolyacid ionic liquid catalyst in the present application;

[0037] Figure 5 It is the XRD spectrum of the product lithium heteropolyacid ionic liquid catalyst in the present application;

[0038] Figure 6 It is the thermogravimetric spectrum of the product lithium heteropolyacid ionic liquid catalyst in the present application;

[0039] Figure 7 It is the infrared spectrum of the polyester product PES in the present application. DETAILED DESCRIPTION

[0040] For the person skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the present application. If not specifically indicated, the technical means used in the embodiments is the conventional means familiar to the person skilled in the art.

[0041] The present application takes the waste electrolyte recovered by Suzhou Dingcheng New Energy Technology Co., Ltd. as raw material to recover lithium salt and organic matter in the electrolyte.

[0042] The present application provides a method for preparing lithium-based heteropoly acid catalyst by using waste electrolyte and application thereof, and the specific steps are as follows:

[0043] Step 1: The waste electrolyte is subjected to vacuum distillation under nitrogen environment to obtain a distillation component and a residual component;

[0044] Step 2: Excessive solid sodium carbonate powder is added to the residual component, and after stirring for 10-40 min, suction filtration is performed to obtain solid lithium carbonate;

[0045] Step 3: 0.12-0.15 mol of N-methyl imidazole is placed in a three-necked flask, 0.1 mol of n-butyl chloride is added dropwise under the condition of condensation reflux, the reaction temperature is controlled at 70-90 DEG C, and after reaction for 22-26 h, the reaction liquid is washed with acetonitrile, rotary evaporated and dried to obtain a light yellow intermediate A;

[0046] Step 4: Sodium molybdate is dissolved in appropriate distilled water, heated to micro-boiling, adjusted to pH 4-5, condensed and refluxed, and the lithium carbonate in step 2 is added, reacted for 2 h, then the coordination metal salt is added dropwise, after the dropwise addition is completed, the reaction is continued for 2 h, potassium chloride is further added, white precipitate is precipitated, the insoluble substance is removed by filtration, anhydrous ethanol is added for purification under ice bath at about 0 DEG C, the product intermediate B is precipitated, and after drying at 80 DEG C for 5-8 h, a lithium-based Keggin type heteropoly acid intermediate B with different coordination metals is obtained;

[0047] Step 5: The intermediate B is added to a three-necked flask containing distilled water, stirred and dissolved, then the intermediate A is added dropwise into the three-necked flask, immediately precipitate is precipitated, the precipitate is filtered out, washed with distilled water, and then dried to obtain a lithium-based heteropoly acid ionic liquid catalyst.

[0048] Optionally, the distillation components in step 1 are methyl ethyl carbonate (EMC) and dimethyl carbonate (DMC) as the finished product directly; the content of EC component in the remaining components measured after step 2 of filtration is more than 85%, and the rest is a small amount of low-boiling electrolyte and additives.

[0049] Optionally, the intermediate A in step 1 is 1-butyl-3-methylimidazolium chloride.

[0050] Optionally, the pressure of the reduced pressure distillation in step 1 is -0.1 Mpa, the temperature is 120℃, and the distillation time is 2h; the remaining components are ethylene carbonate (EC), lithium hexafluorophosphate (LiPF6) and additives, and lithium hexafluorophosphate (LiPF6) in the remaining components participates in the reaction in step 2.

[0051] Optionally, the rate of adding n-butyl chloride in step 2 is 10-100mL / s;

[0052] The acetonitrile washing is performed 3-5 times;

[0053] The drying temperature is 70-90℃, and the drying time is 5-8h.

[0054] Optionally, the complex metal salt in step 4 is one of zinc salt, iron salt, copper salt, lead salt or titanium salt.

[0055] Optionally, the molar ratio of sodium molybdate, lithium carbonate and complex metal salt in step 4 is 11:0.5:1;

[0056] The dropwise adding rate of the complex metal salt is 10-100mL / s;

[0057] The anhydrous ethanol is purified 3-5 times.

[0058] Optionally, the molar ratio of the intermediate A to the intermediate B in step 5 is 5:1;

[0059] The dropwise adding rate of the intermediate A is 10-100mL / s;

[0060] The drying temperature is 70-90℃, and the drying time is 5-8h.

[0061] Optionally, the lithium-based heteropoly acid ionic liquid catalyst is Bmim9[Zn(H2O)LiMo 11 O 39 ], Bmim9[Fe II (H2O)LiMo 11 O 39 ], Bmim9[Cu(H2O)LiMo 11 O 39]、Bmim7[Ti(H2O)LiMo 11 O 39 ]、Bmim9[Pb(H2O)LiMo 11 O 39 At least one of the following.

[0062] Optionally, the prepared lithium-based heteropolyacid ionic liquid catalyst is used to catalyze the transesterification reaction between ethylene carbonate (EC) and dimethyl succinate in the homologous waste electrolyte to synthesize polyethylene succinate (PES).

[0063] This invention involves vacuum distilling waste electrolyte under a nitrogen atmosphere to obtain distilled components and residual components. The distilled components are EMC (ethyl methyl carbonate) and DMC (dimethyl carbonate). The distillation temperature and time are optimal conditions obtained through experimental setup. These conditions may vary slightly with the amount of waste electrolyte being distilled to prevent the generation of toxic or harmful gases due to excessively high temperatures, thus obtaining pure distilled components. The residual components are ethylene carbonate (EC) and LiPF6, which are leached with sodium carbonate. The optimal amount of sodium carbonate was determined through experiments to achieve lithium recovery. The recovered components are then used to prepare polyester products. The yield and performance are studied, and the economic and environmental feasibility is analyzed.

[0064] This invention proposes five metal-substituted lithium-deficient Keggin-type heteropolyacid ionic liquid catalysts, their preparation methods, and applications. The aim is to form organic-inorganic hybrid materials—lithium-based heteropolyacid ionic liquids—by replacing the protons of heteropolyacids with the cations of ionic liquids through ion exchange. This assembly combines easily tunable and functionally designable organic ionic liquids with highly activated and easily designable inorganic heteropolyacids. This not only maintains the structural integrity and chemical properties of the cations and anions but also exhibits synergistic catalytic effects between metals and between metals and imidazole cations. Compared to traditional catalysts and ionic liquid catalysts, this catalyst, due to the presence of organic cations, allows Li+ to act as the main driving force for electron transfer during the reaction, attacking specific bond sites in the monomers through group transfer and hydrogen bonding. The organic cations, in turn, enhance the reaction activity through volume effects and electrostatic interactions. The coordination metal complexes further enhance the catalyst activity and accelerate the reaction process.

[0065] This invention mainly designs and prepares five metal-substituted lithium-deficient Keggin-type heteropolyacid ionic liquid catalysts for the catalytic transesterification of ethylene carbonate extracted from waste electrolyte with dimethyl succinate to synthesize polyethylene succinate.

[0066] The specific embodiments of the present invention will be described in detail below:

[0067] Example 1

[0068] (1) Take 100 mL of waste electrolyte in a 250 mL three-necked distillation flask, connect the vacuum circulating water pump, check the air tightness of the device. Among them, the condenser is selected as a coiled condenser to improve the condensation efficiency; before starting, continuously introduce nitrogen into the distillation device for 5 min, open the vacuum circulating water pump, keep the pressure in the device at -0.1 MPa, use a heating jacket to keep the distillation temperature at 120°C, and distill for 2 h to obtain the distillation components and the remaining components.

[0069] (2) After stirring the remaining components in step (1) with 14 g of anhydrous sodium carbonate solid for 20 min, filter to obtain lithium carbonate, and dry;

[0070] (3) Preparation of intermediate A-imidazole ionic liquid

[0071] Weigh a certain amount of N-methyl imidazole into the reactor, slowly drop a certain amount of chloro-n-butane at a rate of 10-100 mL / s under condensation reflux conditions, control the reaction temperature at 70°C, after 26h of reaction, wash the reaction liquid with acetonitrile 4 times, spin to dryness at 70°C for 8h to obtain a light yellow intermediate A.

[0072] (4) Preparation of intermediate B-metal substituted lithium-based Keggin type heteropoly acid

[0073] Dissolve a certain amount of sodium molybdate in an appropriate amount of distilled water and heat to a slight boil, adjust the pH to 4, condense and reflux, and add a certain amount of lithium carbonate obtained in step (2), after 2h of reaction after dropwise addition, slowly drop a certain amount of ZnCl2 hydrochloric acid solution at a rate of 10-100 mL / s, continue to react for 2h after dropwise addition, add a certain amount of potassium chloride, and a white precipitate is precipitated, filter out the insoluble material, and add anhydrous ethanol at low temperature to purify repeatedly 3 times, precipitate the product intermediate B, and dry at 70°C for 8h to obtain lithium-based Keggin type heteropoly acid intermediate B with different coordination metals.

[0074] (5) Preparation of lithium-based heteropoly acid-Zn-ionic liquid catalyst

[0075] Add a certain amount of intermediate B to a three-necked flask containing distilled water, stir to dissolve, then slowly drop a certain amount of intermediate A into the three-necked flask at a rate of 10-100 ml / s, immediately precipitate, filter out the precipitate, wash with distilled water 3 times, and dry at 70°C for 8h to obtain the final product lithium-based heteropoly acid ionic liquid catalyst, denoted as Bmim9[Zn(H2O)LiMo 11 O 39 ]. The infrared spectrum is shown in Figure 4 .

[0076] (6) The composition and proportion of the remaining components are determined by gas chromatography. The EC component content of the remaining components is more than 90%, and only a small amount of low-boiling electrolyte and additives exist. The lithium-based heteropoly acid catalyst obtained in step (5) is used to catalyze the synthesis of polyester PES.

[0077] Example 2

[0078] (1) 100 mL of waste electrolyte was taken in a 250 mL three-neck distillation flask, and a vacuum circulating water pump was connected. The airtightness of the device was checked. The condenser was selected as a coiled condenser to improve the condensation efficiency. Nitrogen was continuously introduced into the distillation device before starting for 5 min. The vacuum circulating water pump was turned on, and the pressure in the device was maintained at -0.1 MPa. The distillation temperature was maintained at 130°C using a heating jacket, and the distillation time was 1.5 h. The distillation component and the remaining component were obtained.

[0079] (2) The remaining component in step (1) was mixed with 12 g of anhydrous sodium carbonate solid and stirred for 20 min. The lithium carbonate was obtained by suction filtration and dried.

[0080] (3) Preparation of intermediate A - imidazole ionic liquid

[0081] A certain amount of N-methyl imidazole was weighed into a reactor. A certain amount of chloro-n-butane was slowly added at a rate of 10-100 mL / s under condensation reflux conditions. The reaction temperature was controlled at 90°C. After 22 h of reaction, the reaction liquid was washed with acetonitrile for 5 times, and then rotary evaporated and dried at 90°C for 5 h to obtain a light yellow intermediate A.

[0082] (4) Preparation of intermediate B - metal-substituted lithium-based lacunary Keggin-type heteropoly acid

[0083] A certain amount of sodium molybdate was dissolved in an appropriate amount of distilled water and heated to a slight boil. The pH was adjusted to 5. Condensation reflux was performed and a certain amount of lithium carbonate obtained in step (2) was added. After the addition was completed, the reaction was continued for 2 h. A certain amount of FeSO4 aqueous solution was slowly added at a rate of 10-100 mL / s. After the addition was completed, the reaction was continued for 2 h. A certain amount of potassium chloride was added, and a white precipitate was precipitated. The insoluble material was removed by filtration. Anhydrous ethanol was added at low temperature and purified repeatedly for 3 times. The product intermediate B was precipitated. The titanium-based lacunary Keggin-type heteropoly acid intermediate B with different coordination metals was obtained by drying at 90°C for 5 h.

[0084] (5) Preparation of lithium-based heteropoly acid - Fe II ionic liquid catalyst

[0085] A certain amount of intermediate B was added to a three-neck flask containing distilled water, stirred and dissolved, and then a certain amount of intermediate A was slowly added dropwise to the three-neck flask at a rate of 10-100 ml / s, and immediately precipitates were separated out, the precipitates were filtered and washed with distilled water for 3 times, and dried at 90°C for 5h to obtain the final product lithium-based heteropoly acid ionic liquid catalyst, denoted as Bmim9[Fe II (H2O)LiMo 11 O 39 ]. The infrared spectrum is shown in Figure 4

[0086] (6) The composition and proportion of the remaining components were determined by gas chromatography, and the content of EC component in the remaining components was more than 90%, only a small amount of low-boiling electrolyte and additives were present, and the lithium-based heteropoly acid catalyst obtained in step (5) was used to catalyze the synthesis of polyester PES.

[0087] Example 3

[0088] (1) 100 mL of waste electrolyte was taken in a 250 mL three-neck distillation flask, a vacuum circulating water pump was connected, and the device was checked for air tightness. The condenser was selected as a snake-shaped condenser to improve the condensation efficiency; before starting, nitrogen was continuously introduced into the distillation device for 5 min, the vacuum circulating water pump was turned on, the pressure in the device was maintained at -0.1 MPa, the distillation temperature was maintained at 120°C using a heating jacket, and the distillation time was 1.5 h to obtain a distillation component and a remaining component.

[0089] (2) The remaining component in step (1) was mixed with 10 g of anhydrous sodium carbonate solid and stirred for 20 min, then filtered to obtain lithium carbonate, which was dried;

[0090] (3) Preparation of intermediate A - imidazole ionic liquid

[0091] A certain amount of N-methyl imidazole was weighed into a reactor, and a certain amount of chloro-n-butane was slowly added dropwise at a rate of 10-100 mL / s under condensation reflux conditions, and the reaction temperature was controlled at 80°C. After 24h of reaction, the reaction liquid was washed with acetonitrile for 3 times, and then rotary evaporated and dried at 80°C for 6h to obtain a light yellow intermediate A.

[0092] (4) Preparation of intermediate B - metal-substituted lithium-based vacancy Keggin-type heteropoly acid

[0093] ​A certain amount of sodium molybdate was dissolved in a certain amount of distilled water and heated to a slight boil, the pH was adjusted to 5, and a certain amount of Li2CO3 obtained in step (2) was added under reflux. After 2 hours of reaction, a certain amount of CuSO4 aqueous solution was slowly added at a rate of 10-100 mL / s. After 2 hours of reaction after the dropwise addition was completed, a certain amount of potassium chloride was added, and white precipitate was separated out. The insoluble matter was removed by filtration, and the product intermediate B was separated out by repeatedly purifying the product intermediate B at low temperature for 3 times. The product intermediate B was dried at 80°C for 8 hours to obtain a lithium-based Keggin-type heteropoly acid intermediate B with different coordination metals.

[0094] (5) Preparation of lithium-based heteropoly acid-Cu-ion liquid catalyst

[0095] A certain amount of intermediate B was added to a three-necked flask containing distilled water, and stirred and dissolved. Then a certain amount of intermediate A was slowly added to the three-necked flask at a rate of 10-100 ml / s, and precipitate was immediately separated out. The precipitate was filtered out, washed with distilled water for 3 times, and dried at 80°C for 6 hours to obtain the final product lithium-based heteropoly acid ion liquid catalyst, which was recorded as Bmim9[Cu(H2O)LiMo 11 O 39 ]. The infrared spectrum is shown in Figure 4 .

[0096] (6) The composition and proportion of the remaining components were determined by gas chromatography. The content of EC component was more than 90%, and a small amount of low-boiling-point electrolyte and additives were present. The lithium-based heteropoly acid catalyst obtained in step (5) was used to catalyze the synthesis of polyester PES.

[0097] Example 4

[0098] Example 4 was basically the same as the steps of Example 3. The coordination metal atom salt in (2) in Example 3 was replaced by lead acetate aqueous solution instead of ZnCl2 hydrochloric acid aqueous solution to obtain a lithium-based heteropoly acid ion liquid catalyst, which was recorded as Bmim9[Pb(H2O)LiMo 11 O 39 ]. The infrared spectrum is shown in Figure 4 .

[0099] Example 5

[0100] Example 5 was basically the same as the steps of Example 3. The coordination metal atom salt in (2) in Example 3 was replaced by TiCl4 hydrochloric acid aqueous solution instead of ZnCl2 hydrochloric acid aqueous solution to obtain a lithium-based heteropoly acid ion liquid catalyst, which was recorded as Bmim7[Ti(H2O)LiMo 11 O 39 ]. The infrared spectrum is shown in Figure 4 .

[0101] Example 6

[0102] The method for synthesizing polyester PES product is as follows:

[0103] The remaining components, dimethyl succinate (DMSu) 43.84 g (0.3 mol) and the remaining part of ethylene carbonate (EC) 44.04 g (0.5 mol) after distillation of the waste electrolyte, are weighed and mixed into a three-necked flask with a distillation device. The lithium-containing heteropoly acid ionic liquid catalyst 0.87 g, which is 1% of the total mass of the reactants, is added under N2 protection. The reaction system is stirred and heated to 120-150°C. After 3-5 h of reaction, the reaction liquid is subjected to re-reduced pressure distillation. The reaction system is stirred and heated to 180-200°C. After 2-4 h of reaction, it is cooled to 50°C and taken out. The product purity is detected by a gas chromatograph, and the conversion rate, selectivity and yield are calculated.

[0104] Five lithium-containing heteropoly acid ionic liquid catalysts prepared in Examples 1-5 are used to catalyze the synthesis of polyethylene succinate (PES) by ester exchange of DMSu and EC. Under the same conditions, the common heteropoly acid K6[Fe(H2O)FeMo 11 O 39 ] and the common ionic liquid [Bmim]Cl catalyst are used for comparison.

[0105] Table 1 Evaluation results of the catalytic performance of Examples 1-6

[0106]

[0107]

[0108] As can be seen from the data in the table, under the same reaction conditions, the common heteropoly acid K6[Fe(H2O)FeMo 11 O 39 ] and the common ionic liquid [Bmim]Cl catalyst have certain catalytic activity, but their reaction rate is slow and the reaction period is long, which is quite different from the heteropoly acid ionic liquid. Through experiments, it is found that the catalytic activity of the common heteropoly acid and the common ionic liquid in the ester exchange reaction process is not ideal, and there are problems such as low conversion rate, low yield and poor selectivity. In order to further solve the problem of lack of active sites in the traditional catalyst and improve the yield of the ester exchange reaction, we focus on the heteropoly acid ionic liquid catalyzing the ester exchange reaction based on the advantage of strong designability of ionic liquid and heteropoly acid. According to the above table, Bmim7[Ti(H2O)LiMo 11 O 39The catalytic performance was the best, with a conversion rate of 86.43% for DMSu and a PES yield of 75.17%. The catalytic activities of the other heteropolyacid ionic liquids with different coordination metals were in the following order: Ti > Fe > Pb > Zn > Cu.

[0109] The infrared spectrum of intermediate A (1-butyl-3-methylimidazolium chloride) is as follows: Figure 1 As shown, the proton NMR spectra of intermediate A (1-butyl-3-methylimidazolium chloride) are as follows: Figure 2 As shown, the infrared spectrum of intermediate B is as follows: Figure 3 As shown, the infrared spectrum of the heteropolyacid ionic liquid catalyst product is as follows: Figure 4 As shown, the XRD pattern is as follows Figure 5 As shown, the thermogravimetric spectrum is as follows: Figure 6 As shown. The infrared spectrum of the polyester product is as follows. Figure 7 As shown.

[0110] Figure 1 Mid-infrared spectrum shows 2917 cm⁻¹ -1 It is the CH stretching vibration peak of the -CH3 group on the substituent, 2849 cm⁻¹. -1 It is the stretching absorption peak of -CH2 on the substituent, 1466 cm⁻¹ -1 It is the stretching vibration peak of C=N on the imidazole ring, 1165 cm⁻¹ -1 It is the CH bending vibration peak in the imidazole ring, 3417 cm⁻¹ -1 The peaks are impurities caused by a small amount of water. This indicates that the compound is an imidazole ionic liquid containing a butyl chain, and its structure is highly consistent with that of 1-butyl-3-methylimidazolium chloride ([Bmim]Cl).

[0111] Figure 2 Hydrogen NMR spectroscopy revealed chemical shifts: δ 0.95 corresponds to the hydrogen atom of the -CH3 group on the butyl side chain; δ 1.34 corresponds to the -CH2 hydrogen atom attached to the CH3 group on the butyl side chain; δ 1.78 corresponds to the hydrogen atom of the -CH2 group in the middle of the butyl side chain; δ 4.14 corresponds to the H atom in the CH3 group on the methyl side chain attached to the N group on the imidazole ring; δ 7.50 and 7.79 correspond to the hydrogen atoms corresponding to CH=CH on the imidazole ring; and δ 9.5 corresponds to the hydrogen atoms of the CH group attached to two N groups on the ring. The figure indicates that the synthesized ionic liquid is the target ionic liquid [Bmim]Cl.

[0112] Figure 3 In this context, 'a' represents K9[Zn(H2O)LiMo. 11 O 39 b is K9[Fe II (H2O)LiMo 11 O 39 ]; c is K9[Cu(H2O)LiMo 11 O 39] ; d is K9[Pb(H20)LiMo 11 O 39 ] ; e is K7[Ti(H20)LiMo 11 O 39 ] ; the strong peak at 918 cm -1 is attributed to the Mo=0 terminal oxygen stretching vibration, and the peaks at 890 cm -1 and 828 cm -1 correspond to the asymmetric and symmetric Mo-O-Mo bridge oxygen vibrations, respectively, confirming the Keggin-type [Mo 11 O 39 ] skeleton; the broad peak at 3411 cm -1 and the medium strong peak at 1614 cm -1 indicate the presence of coordinated water (O-H stretching and H-O-H bending), and the doping of metals causes the Mo-O vibration to shift to 650-600 cm -1 (the medium strong peak), and the overall spectral characteristics are consistent with the structure of heteropoly acids.

[0113] Figure 4 Medium a is Bmim9[Zn(H20)LiMo 11 O 39 ] ; b is Bmim9[Fe II (H20)LiMo 11 O 39 ] ; c is Bmim9[Cu(H20)LiMo 11 O 39 ] ; d is Bmim9[Pb(H20)LiMo 11 O 39 ] ; e is Bmim7[Ti(H20)LiMo 11 O 39 ] ; the five lithium-based heteropoly acid ionic liquid catalysts all exhibit strong Keggin heteropoly acid structure characteristic peaks in the 700-1200 cm-1 region, indicating that the lithium-based heteropoly acid ionic liquid Keggin-type characteristic structure is well preserved. The characteristic absorption peaks of -CH3 appear at 3140 cm-1, the characteristic absorption peaks of -CH2- appear at 3075 cm -1 , and the stretching vibration of -CH2- on the benzene ring side chain can be observed near 2960 cm -1 , the absorption peaks at 3420 cm -1 and 1562 cm -1 are the O-H bond stretching vibration and H-O-H bond bending vibration of water molecules in the heteropoly acid, respectively, indicating the presence of bound water or crystallization water in the heteropoly acid.

[0114] Figure 5XRD spectra of lithium-based heteropoly acid ionic liquid; a is Bmim9[Zn(H2O)LiMo 11 O 39 ]; b is Bmim9[Fe II (H2O)LiMo 11 O 39 ]; c is Bmim9[Cu(H2O)LiMo 11 O 39 ]; d is Bmim9[Pb(H2O)LiMo 11 O 39 ]; e is Bmim7[Ti(H2O)LiMo 11 O 39 ]; from the figure, the diffraction characteristic peaks of imidazole appear at 14.42°, 16.75°, 23.14°, 26.05°, the diffraction characteristic peaks of heteropoly acid appear at 23.14°, 26.05°, 25.18° and 31.15°, which shows that the Keggin structure is not destroyed. In addition, the characteristic peaks of MoO6 appear at 23.14° and 26.05°, the characteristic diffraction peaks of TiO4 appear at 25.18° and 31.15°, which shows that the catalyst Bmim7[Ti(H2O)LiMo 11 O 39 ] is the target product.

[0115] Figure 6 TG curve of lithium-based heteropoly acid ionic liquid; from the figure, the starting temperature of thermal decomposition of the catalyst is about 310°C, while the temperature of the catalytic reaction is 180-200°C. This shows that the thermal stability of the catalyst is very good, which meets the temperature requirements of the catalytic reaction.

[0116] Figure 7 Infrared spectra of polyester product PES, PES-1, PES-2, PES-3, PES-4 and PES-5 correspond to the infrared spectra of PES products synthesized in Examples 1-5 above, respectively. According to the spectrum analysis, the wave number 3451cm -1 is the stretching vibration absorption peak of hydroxyl (-OH); the wave number 2955cm -1 , 1386cm -1 is the stretching and bending methylene (-CH2) peak; the wave number 1726cm -1 is the carbonyl (-OCH2CH2O-) absorption peak; the wave number 1220cm -1 , 1146cm -1 , 1044cm -1 is the carbon oxygen (C-O) stretching vibration peak. Through the above structure analysis, it is shown that the product is the target product PES, and the structure is correct.

[0117] The application relates to a preparation method and application of a waste electrolyte-based lithium-based heteropoly acid ionic liquid catalyst and the lithium-based heteropoly acid ionic liquid catalyst, the structure of the catalyst comprising a metal-substituted lithium-based vacancy Keggin type heteropoly acid anion and an imidazole organic cation, forming an organic-inorganic functional hybrid material. The preparation method comprises the following steps: preparation of an intermediate A imidazole ionic liquid; preparation of an intermediate B metal-substituted lithium-based vacancy Keggin type heteropoly acid; and preparation of the lithium-based heteropoly acid ionic liquid catalyst.

[0118] The application is characterized in that the lithium source of the catalyst is extracted and recovered from waste electrolyte, and the raw material for catalysis is an organic matter part of a homologous electrolyte for synthesizing polyester, without affecting the activity and selectivity of the catalyst. Compared with a traditional catalyst for synthesizing polyester, the catalyst Li + As the main driving force of electron transfer, the organic cation attacks specific bond sites in monomers through group transfer and hydrogen bonding, the organic cation enhances the reactivity through volume effect and electrostatic effect, and the coordination metal complex further improves the activity of the catalyst, and promotes the reaction process. The application provides a new idea and a new way for recycling and high-value utilization of waste electrode liquid.

[0119] The above is only a specific embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method for preparing lithium-based heteropolyacid catalysts using waste electrolyte, characterized in that, The specific steps are as follows: Step 1: The waste electrolyte is subjected to vacuum distillation under nitrogen atmosphere to obtain distilled components and residual components; Step 2: Add excess sodium carbonate solid powder to the remaining components, stir for 10-40 minutes, and then filter to obtain solid lithium carbonate; Step 3: Place 0.12-0.15 mol of N-methylimidazole in a three-necked flask, add 0.1 mol of n-chlorobutane dropwise under reflux condensation, control the reaction temperature at 70-90℃, and react for 22-26 h. Then wash the reaction solution with acetonitrile, rotary evaporate and dry to obtain light yellow intermediate A. Step 4: Dissolve sodium molybdate in an appropriate amount of distilled water, heat to a gentle boil, adjust the pH to 4-5, reflux and add lithium carbonate from Step 2, react for 2 hours, then add the coordination metal salt dropwise. After the addition is complete, continue the reaction for 2 hours, then add potassium chloride. A white precipitate will form. Filter to remove insoluble matter, and purify by adding anhydrous ethanol multiple times in an ice bath at around 0°C. The precipitated product intermediate B is dried at 80°C for 5-8 hours to obtain lithium-based vacant Keggin-type heteropolyacid intermediate B vacant metal heteropolyacid with different coordination metals. Step 5: Add intermediate B to a three-necked flask containing distilled water, stir to dissolve, and then add intermediate A dropwise to the three-necked flask. A precipitate will immediately form. Filter out the precipitate, wash it with distilled water, and then dry it to obtain a lithium-based heteropolyacid ionic liquid catalyst.

2. The method for preparing catalysts and polyester products based on waste electrolyte according to claim 1, characterized in that, The distillation components in step 1 are ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), which can be used directly as the finished product or as chemical intermediates for the synthesis of other compounds; the remaining components measured after filtration in step 2 contain more than 85% EC components, with the remainder being small amounts of low-boiling-point electrolyte and additives.

3. The method for preparing catalysts and polyester products based on waste electrolyte according to claim 1, characterized in that, The pressure of vacuum distillation in step 1 is -0.1 MPa, the temperature is 120°C, and the distillation time is 2 hours. The remaining components in step 1 are ethylene carbonate (EC), lithium hexafluorophosphate (LiPF6), and additives. The lithium hexafluorophosphate (LiPF6) in the remaining components participates in the reaction in step 2.

4. The method for preparing catalysts and polyester products based on waste electrolyte according to claim 1, characterized in that, The rate at which chlorobutane is added in step 2 is 10-100 mL / s; The washing with acetonitrile is performed 3-5 times; The drying temperature is 70-90℃, and the drying time is 5-8 hours.

5. The method for preparing catalysts and polyester products based on waste electrolyte according to claim 1, characterized in that, The coordination metal salt mentioned in step 4 is one of zinc salt, iron salt, copper salt, lead salt, or titanium salt.

6. The method for preparing catalysts and polyester products based on waste electrolyte according to claim 1, characterized in that, The molar ratio of sodium molybdate, lithium carbonate, and coordination metal salt in step 4 is 11:0.5:1; The dropping rate of the coordinated metal salt is 10-100 mL / s; The anhydrous ethanol is purified 3-5 times.

7. The method for preparing catalysts and polyester products based on waste electrolyte according to claim 1, characterized in that, The molar ratio of intermediate A to intermediate B in step 5 is 5:1; The dropping rate of intermediate A is 10-100 mL / s; The drying temperature is 70-90℃, and the drying time is 5-8 hours.

8. The method for preparing catalysts and polyester products based on waste electrolyte according to claim 1, characterized in that, The lithium-based heteropolyacid ionic liquid catalyst is Bmim9[Zn(H2O)LiMo 11 O 39 ]、Bmim9[Fe II (H2O)LiMo 11 O 39 ]、Bmim9[Cu(H2O)LiMo 11 O 39 ]、Bmim7[Ti(H2O)LiMo 11 O 39 ]、Bmim9[Pb(H2O)LiMo 11 O 39 At least one of the following.

9. An application of a lithium-based heteropolyacid ionic liquid catalyst prepared by the method described in claim 1, characterized in that, Using the prepared lithium-based heteropolyacid ionic liquid catalyst, ethylene carbonate (EC) and dimethyl succinate in homologous waste electrolyte were catalyzed to undergo transesterification reaction to synthesize polyethylene succinate (PES).

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