A method for purifying 1,3,6-hexanetricarbonitrile, an electrolyte additive, and applications

Abstract

This invention provides a method for purifying 1,3,6-hexanetrionitrile, an electrolyte additive, and its applications. The purification method includes: step S1, adding a monomer containing a sulfonic acid group and a catalyst to crude 1,3,6-hexanetrionitrile and heating the reaction; step S2, washing and distilling the reaction product to obtain pure 1,3,6-hexanetrionitrile; the monomer containing the sulfonic acid group in step S1 contains unsaturated bonds. The purification method of this invention is simple and mild, consumes little energy, and yields a product with high purity and low color, maintaining stable color during long-term storage, meeting the requirements for high-quality electronic-grade products.

Description

Technical Field

[0001] This invention relates to the field of materials processing technology, and more specifically, to a method for purifying 1,3,6-hexanetrionitrile, an electrolyte additive, and its application. Background Technology

[0002] 1,3,6-Hexanetrionitrile (HTCN) is primarily used as an electrolyte additive in high-performance lithium-ion batteries, especially in batteries employing high-voltage cathodes (such as nickel-rich layered oxides) and silicon-based anodes. Electrolytes based on traditional carbonates with HTCN additions of 1-3 wt% can promote the formation of a more stable and effective electrode-electrolyte interface, inhibit electrolyte decomposition, and improve electrode material stability, thereby enhancing battery performance. Its advantages include better cycle stability, higher capacity retention, and stronger rate performance, particularly under high voltage and high temperature conditions. HTCN also exhibits similar positive effects in sodium-ion and zinc-ion batteries.

[0003] The mainstream industrial route for preparing 1,3,6-hexanetrionitrile uses adiponitrile and acrylonitrile as raw materials, followed by purification after reaction to obtain the product. Specific details can be found in patents such as CN117534591B, US6790976B2, and KR20220051913A. As an electrolyte additive for high-voltage lithium-ion batteries, 1,3,6-hexanetrionitrile must meet stringent quality requirements. Its core quality requirements lie in high purity and low color, ensuring the formation of a stable protective film on the electrode surface and avoiding the introduction of side reactions.

[0004] Existing technologies disclose many purification methods for 1,3,6-hexanetrionitrile, mainly including: 1) filtering, concentrating, and distilling the reaction product, and collecting the fraction (see patents CN116947695A, CN114621116A, CN113891877A, CN1341589A, CN118955326A). In this method, repeated distillation consumes a lot of energy, has a low yield, and the color of the distilled product changes significantly with storage time; 2) adsorption with activated carbon (see patent CN108). 033900A, CN119661401A: Activated carbon adsorption can only adsorb a small amount of pigment substances, and its effect on improving purity is limited; 3) Washing with saturated salt water, see patent CN115784927A: Washing can only remove some water-soluble substances, and has little effect on removing organic impurities and color, and requires an additional dehydration step; 4) Adding a strong oxidant for reaction and filtration, see patent CN104387291A: Using a strong oxidant poses a great production risk, and the color of the resulting product is not ideal.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a purification method, electrolyte additive, and application of 1,3,6-hexanetrionitrile. This purification method is simple and mild, consumes little energy, and produces a product with high purity and low color. Furthermore, the color remains stable during long-term storage, meeting the requirements for high-quality electronic grade products.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A method for purifying 1,3,6-hexanetrionitrile includes the following steps: Step S1: Add a monomer containing a sulfonic acid group and a catalyst to the crude 1,3,6-hexanetrionitrile and heat to react; Step S2: Wash and distill the reaction product to obtain pure 1,3,6-hexanetrionitrile; The monomer containing sulfonic acid groups in step S1 contains unsaturated bonds.

[0008] Furthermore, the unsaturated bond is a carbon-carbon double bond; The sulfonic acid group-containing monomer has the following structural formula: , Wherein, R1 includes at least one of a hydrocarbon group and an amide group; R2 is one of H and C1~C3 alkyl groups.

[0009] Furthermore, R1 includes at least one of alkyl, aromatic, and amide groups.

[0010] Further, the sulfonic acid-containing monomer includes at least one of sodium propylene sulfonate, sodium methpropylene sulfonate, sodium styrene sulfonate, sodium p-methacrylamide benzene sulfonate, and sodium 2-acrylamido-2-methylpropane sulfonate.

[0011] Furthermore, the amount of the sulfonic acid-containing monomer used in step S1 accounts for 0.1% to 10% of the weight of the crude 1,3,6-hexanetrionitrile.

[0012] Further, the catalyst in step S1 includes at least one of azobisisobutyronitrile, ammonium persulfate, potassium persulfate, sodium persulfate, nickel(II) dichloride (tri(ethylenediamine)) and palladium(II) triphenylphosphine acetate.

[0013] Further, the amount of catalyst used in step S1 is 0.1% to 0.5% of the weight of the crude 1,3,6-hexanetrionitrile; Furthermore, in step S1, the reaction heating temperature is 30~80℃, and the reaction time is 2~12h.

[0014] Furthermore, the detergent used in the washing process in step S2 includes at least one of pure water and saline solution with a concentration of 1-10% wt.

[0015] Furthermore, the amount of detergent used accounts for 20% to 50% of the weight of the crude 1,3,6-hexanetrionitrile.

[0016] Furthermore, during the distillation process in step S2, the oil temperature is 170~220℃ and the distillation pressure is 5~30Pa. The light component obtained by distillation is pure 1,3,6-hexanetrionitrile.

[0017] Furthermore, in step S2, the washing process first adds an organic solvent, then adds a detergent and stirs to separate the aqueous phase.

[0018] Furthermore, the mass ratio of the organic solvent to the detergent is 8:1 to 2:1.

[0019] Furthermore, the distillation process in step S2 includes: performing a first distillation on the washed organic phase to obtain a first heavy component, and performing a second distillation on the first heavy component to obtain a second light component, which is pure 1,3,6-hexanetrionitrile.

[0020] Furthermore, the oil temperature during the first distillation is 170~185℃ and the distillation pressure is 5~30Pa; the oil temperature during the second distillation is 195~220℃ and the distillation pressure is 5~30Pa.

[0021] Furthermore, in step S2, the organic phase is subjected to vacuum distillation at a controlled temperature of 50-60°C before the distillation process, and concentrated to an organic solvent content of <0.1wt%.

[0022] Furthermore, the organic solvent includes at least one of dichloroethane, dichloropropane, and chlorobenzene.

[0023] An electrolyte additive comprising pure 1,3,6-hexanetrionitrile obtained by the above purification method.

[0024] Applications of the 1,3,6-hexanetrionitrile obtained by the above purification method, or the electrolyte additives mentioned above, in lithium-ion batteries, sodium-ion batteries, and zinc-ion batteries.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention involves adding a monomer containing a sulfonic acid group to crude 1,3,6-hexanetrionitrile and carrying out a catalytic reaction to convert olefinic substances into sulfonates that are easy to remove or separate. After washing and distillation, high-quality pure 1,3,6-hexanetrionitrile can be obtained, and its color remains stable during long-term storage, meeting the requirements of electronic-grade chemicals. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 The images show a color comparison of the 1,3,6-hexanetrionitrile obtained in Example 4 and Comparative Example 1 after storage at 25°C for 60 days. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0029] A method for purifying 1,3,6-hexanetrionitrile includes the following steps: Step S1: Add a monomer containing a sulfonic acid group and a catalyst to the crude 1,3,6-hexanetrionitrile and heat to react; Step S2: Wash and distill the reaction product to obtain pure 1,3,6-hexanetrionitrile.

[0030] Acrylonitrile, the raw material used in the production of 1,3,6-hexanetrionitrile, is prone to oxidative decomposition and self-polymerization during the production and storage processes, generating dimers and polymers, which also change its color. Freshly prepared high-purity 1,3,6-hexanetrionitrile is often colorless and transparent or pale yellow, but its color changes significantly with prolonged storage.

[0031] The inventors discovered that acrylonitrile, its dimers and polymers are the main causes of color changes in 1,3,6-hexanetrionitrile during storage. Products obtained through multiple distillations have lower color values, while trace amounts of acrylonitrile gradually react during long-term storage, leading to color changes.

[0032] In the purification method of 1,3,6-hexanetrionitrile of the present invention, acrylonitrile, acrylonitrile dimers and polymers in the crude product are removed by catalytic reaction, followed by washing and distillation to obtain a high-quality electronic-grade pure 1,3,6-hexanetrionitrile product. The product exhibits stable color during long-term storage, meeting the requirements of electronic-grade chemicals.

[0033] In some embodiments, the monomer containing sulfonic acid groups in step S1 contains unsaturated bonds, which are carbon-carbon double bonds; the double bonds in acrylonitrile, acrylonitrile dimers, and polymers in the crude product react with the double bonds in the monomer containing sulfonic acid groups, and the reaction products can be easily removed or separated.

[0034] The sulfonic acid group-containing monomer has the following structural formula: , Wherein, R1 includes at least one of a hydrocarbon group and an amide group; R2 is one of H and C1~C3 alkyl groups.

[0035] Furthermore, R1 includes at least one of alkyl, aromatic, and amide groups.

[0036] The equations for the double bond addition polymerization reactions of acrylonitrile monomers, acrylonitrile dimers, and monomers containing sulfonic acid groups are as follows: .

[0037] Further, the sulfonic acid-containing monomer includes at least one of sodium propylene sulfonate, sodium methpropylene sulfonate, sodium styrene sulfonate, sodium p-methacrylamide benzene sulfonate, and sodium 2-acrylamido-2-methylpropane sulfonate.

[0038] In some embodiments, the amount of the sulfonic acid group-containing monomer used in step S1 is 0.1% to 10% of the weight of the crude 1,3,6-hexanetrionitrile (including but not limited to 0.1%, 0.5%, 1%, 2%, 5%, 6%, 8%, and 10%).

[0039] The monomer containing sulfonic acid groups described in this invention undergoes a double bond addition polymerization reaction with acrylonitrile, acrylonitrile dimers, and polymers in the crude product under catalysis, converting olefinic substances (acrylonitrile, acrylonitrile dimers, and polymers) into sulfonates (with sodium sulfonate groups in the side chain to increase water solubility) that are easy to remove or separate, including soluble small molecule sulfonates and insoluble large molecule sulfonates.

[0040] Among them, small molecule sulfonates are water-soluble (small molecular weight, small proportion of organic part) and are removed by subsequent washing; large molecule sulfonates are poorly water-soluble (large quantity, large proportion of organic part, and water solubility will be correspondingly weakened), which may lead to insufficient removal by the washing step, and since the boiling points of salts are very high, they need to be further removed by subsequent distillation. In some embodiments, the catalyst mentioned in step S1 includes at least one of azobisisobutyronitrile, ammonium persulfate, potassium persulfate, sodium persulfate, tri(ethylenediamine)nickel(II) dichloride, and palladium(II) triphenylphosphine acetate.

[0041] In some embodiments, the amount of catalyst used in step S1 is 0.1% to 0.5% of the weight of the crude 1,3,6-hexanetrionitrile (including but not limited to 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%).

[0042] In some embodiments, the reaction heating temperature in step S1 is 30~80℃, including but not limited to 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, and the reaction time is 2~12h, including but not limited to 2h, 4h, 5h, 6h, 8h, 10h, 12h.

[0043] Furthermore, the detergent used in the washing process in step S2 includes at least one of pure water and saline solution with a concentration of 1-10%wt (the saline solution concentration includes, but is not limited to, 1%wt, 2%wt, 3%wt, 5%wt, 6%wt, 8%wt, and 10%wt).

[0044] Furthermore, the amount of detergent used accounts for 20% to 50% of the weight of the crude 1,3,6-hexanetrionitrile (including but not limited to 20%, 25%, 30%, 35%, 40%, 45%, and 50%).

[0045] This invention can remove excess sulfonic acid group-containing monomers (which are water-soluble) as impurities through a washing process, and can also remove soluble small molecule sulfonates generated by the reaction of sulfonic acid group-containing monomers with acrylonitrile, acrylonitrile dimers and polymers as impurities.

[0046] In some embodiments, in step S2, the washing process first adds an organic solvent, then adds a detergent, stirs to separate the aqueous phase, and then distills the organic phase.

[0047] Furthermore, the mass ratio of the organic solvent to the detergent is 8:1 to 2:1 (including but not limited to 8:1, 6:1, 5:1, 4:1, 2:1).

[0048] Furthermore, the organic solvent includes at least one of dichloroethane, dichloropropane, and chlorobenzene.

[0049] In some embodiments, the oil temperature during step S2 distillation is 170~220℃ (including but not limited to 170℃, 180℃, 190℃, 200℃, 210℃, 220℃), and the distillation pressure is 5~30Pa (including but not limited to 5Pa, 10Pa, 15Pa, 20Pa, 25Pa, 30Pa). The light component obtained by distillation is pure 1,3,6-hexanetrionitrile.

[0050] In some embodiments, the distillation process in step S2 includes: performing a primary distillation using a molecular distillation apparatus to obtain a primary heavy component (removing impurities with a boiling point lower than that of the purified product), and performing a secondary distillation on the primary heavy component using a thin-film distillation apparatus (removing impurities with a boiling point higher than that of the purified product and insoluble macromolecular sulfonates, the boiling point of which is usually higher than that of the purified product), and the resulting secondary light component is pure 1,3,6-hexanetrionitrile.

[0051] Furthermore, the oil temperature during the first distillation is 170~185℃ (including but not limited to 170℃, 175℃, 180℃, 185℃), and the distillation pressure is 5~30Pa (including but not limited to 5Pa, 10Pa, 15Pa, 20Pa, 25Pa, 30Pa).

[0052] Furthermore, the oil temperature for the secondary distillation is 195~220℃ (including but not limited to 195℃, 200℃, 205℃, 210℃, 215℃, 220℃), and the distillation pressure is 5~30Pa (including but not limited to 5Pa, 10Pa, 15Pa, 20Pa, 25Pa, 30Pa).

[0053] In some embodiments, before the distillation process in step S2, the organic phase is subjected to vacuum distillation at a controlled temperature of 50~60°C (including but not limited to 50°C, 52°C, 55°C, 56°C, 58°C, and 60°C) to concentrate the organic solvent concentration to <0.1wt%.

[0054] An electrolyte additive comprising pure 1,3,6-hexanetrionitrile obtained by the above purification method.

[0055] The application of the 1,3,6-hexanetrionitrile obtained by the above purification method and the above electrolyte additive in the preparation of lithium-ion batteries, sodium-ion batteries and zinc-ion batteries.

[0056] In this invention, GC detection refers to gas chromatography (GC) detection.

[0057] Example 1 A method for purifying 1,3,6-hexanetrionitrile includes the following steps: 1. Add 300g of commercially available light yellow liquid 1,3,6-hexanetrionitrile (crude product GC test purity 98.5%, color >100APHA) to a reaction flask, then add 15g of sodium methylpropenesulfonate and 0.3g of potassium persulfate, heat to 45℃ and keep warm for 4 hours. 2. After the reaction is complete, the system is cooled to 25°C. 600g of dichloroethane is added to the reaction system, followed by 100g of pure water. The mixture is stirred for 30 minutes, and the aqueous phase is separated. 3. The organic phase was subjected to vacuum distillation at a controlled temperature of 55°C and concentrated until the solvent dichloroethane was <0.1wt% (GC detection). 4. After concentration, a single distillation was performed using a molecular distillation apparatus at an oil temperature of 170℃ and a pressure of 7Pa. The distillation yielded 291g of the single heavy component (GC purity: 99.1%). 5. The primary heavy component was subjected to secondary distillation using a thin-film distillation apparatus at an oil temperature of 195℃ and a pressure of 6Pa. 275g of a nearly colorless secondary light component was obtained, namely pure 1,3,6-hexanetrionitrile (GC purity: 99.7%, color 10 APHA, water content 45ppm), with a total yield of 91.6%. After storage at 25℃ for 2 months, the color was 10 APHA.

[0058] Example 2 A method for purifying 1,3,6-hexanetrionitrile includes the following steps: 1. Add 300g of commercially available light yellow liquid 1,3,6-hexanetrionitrile (crude product with GC purity of 98.5% and color >100 APHA) to a reaction flask, then add 15g of sodium methylpropenesulfonate and 0.5g of tri(ethylenediamine)nickel(II) dichloride, heat to 60℃ and keep the temperature for 8 hours. 2. After the reaction is complete, the system is cooled to 26°C. 600g of dichloroethane is added to the reaction system, followed by 150g of pure water. The mixture is stirred for 30 minutes, and the aqueous phase is separated. 3. The organic phase was subjected to vacuum distillation at a controlled temperature of 58°C and concentrated until the solvent dichloroethane was <0.1wt% (GC detection). 4. After concentration, a single distillation was performed using a molecular distillation apparatus at an oil temperature of 170℃ and a pressure of 7Pa. The distillation yielded 289g of the single heavy component (GC purity: 99.2%). 5. The primary heavy component was subjected to secondary distillation using a thin-film distillation apparatus at an oil temperature of 195℃ and a pressure of 6Pa. 278g of a nearly colorless secondary light component was obtained, namely pure 1,3,6-hexanetrionitrile (GC purity: 99.6%, color 15 APHA, water content 58ppm), with a total yield of 92.7%. After storage at 25℃ for 2 months, the color was 15 APHA.

[0059] Example 3 A method for purifying 1,3,6-hexanetrionitrile includes the following steps: 1. Add 300g of commercially available light yellow liquid 1,3,6-hexanetrionitrile (crude product with GC purity of 98.5% and color >100APHA) to a reaction flask, then add 25g of sodium p-methacrylamide benzenesulfonate and 1.5g of ammonium persulfate, heat to 65℃ and keep the temperature for 10 hours. 2. After the reaction is complete, the system is cooled to 26°C. 600g of dichloroethane is added to the reaction system, followed by 150g of pure water. The mixture is stirred for 30 minutes, and the aqueous phase is separated. 3. The organic phase was subjected to vacuum distillation at a controlled temperature of 56°C and concentrated until the solvent dichloroethane was <0.1wt% (GC detection). 4. After concentration, a single distillation was performed using a molecular distillation apparatus at an oil temperature of 170℃ and a pressure of 7Pa. The distillation yielded 288g of the single heavy component (GC purity: 99.2%). 5. The primary heavy component was subjected to secondary distillation using a thin-film distillation apparatus at an oil temperature of 195℃ and a pressure of 6Pa. 277g of a nearly colorless secondary light component was obtained, namely pure 1,3,6-hexanetrionitrile (GC purity: 99.55%, color 15 APHA, water content 56ppm), with a total yield of 92.3%. After storage at 25℃ for 2 months, the color was 15 APHA.

[0060] Example 4 A method for purifying 1,3,6-hexanetrionitrile includes the following steps: 1. Add 300g of commercially available light yellow liquid 1,3,6-hexanetrionitrile (crude product with GC purity of 98.5% and color >100 APHA) to a reaction flask, then add 30g of sodium 2-acrylamido-2-methylpropanesulfonate and 0.3g of palladium(II) triphenylphosphine acetate, heat to 70℃ and keep the temperature for 10 hours. 2. After the reaction is complete, the system is cooled to 25°C. 600g of dichloroethane is added to the reaction system, followed by 150g of pure water. The mixture is stirred for 30 minutes, and the aqueous phase is separated. 3. The organic phase was concentrated by vacuum distillation at 55°C until the solvent dichloroethane was <0.1wt% (GC detection). 4. After concentration, a single distillation was performed using a molecular distillation apparatus at an oil temperature of 170℃ and a pressure of 8Pa. The distillation yielded 292g of the single heavy component (GC purity: 99.3%). 5. The primary heavy component was subjected to secondary distillation using a thin-film distillation apparatus at an oil temperature of 195℃ and a pressure of 6Pa. 276g of a nearly colorless secondary light component was obtained, namely pure 1,3,6-hexanetrionitrile (GC purity: 99.6%, color 20 APHA, water content 47ppm), with a total yield of 92.0%. After storage at 25℃ for 2 months, the color was 20 APHA.

[0061] The color of the pure 1,3,6-hexanetrionitrile obtained in Example 4 after storage at 25°C for 60 days is as follows: Figure 1 As shown.

[0062] Comparative Example 1 A method for purifying 1,3,6-hexanetrionitrile includes the following steps: 1. 300g of commercially available light yellow liquid 1,3,6-hexanetrionitrile (crude product with GC purity of 98.5% and color >100 APHA) was distilled using a molecular distillation apparatus at an oil temperature of 170℃ and a pressure of 6Pa, yielding 293g of heavy fraction (GC: 98.9%). 2. The primary heavy component was subjected to secondary distillation using a thin-film distillation apparatus at an oil temperature of 195℃ and a pressure of 7Pa. 281g of a nearly colorless secondary light component was obtained, namely pure 1,3,6-hexanetrionitrile (GC purity: 99.4%, color 20 APHA, water content 45ppm), with a total yield of 93.7%. After storage at 25℃ and 45℃ for 2 months, the color reached 100 APHA in both cases.

[0063] The color of the pure 1,3,6-hexanetrionitrile obtained in Comparative Example 1 after storage at 25°C for 60 days is as follows: Figure 1 As shown.

[0064] Experimental example: I. The pure 1,3,6-hexanetrionitrile obtained in Examples 1-4 and Comparative Example 1 were subjected to colorimetric testing using the platinum-cobalt colorimetric method. 1. Instruments and equipment Colorimetric tubes: 50mL; Colorimetric tube rack; Pipette: 10.00 mL.

[0065] 2. Reagents Platinum-cobalt standard stock solution: 500 degrees Celsius; Pure water: Deionized water with a resistivity (at 25°C) of not less than 18 megohms·cm.

[0066] 3. Preparation of color standard solution Using a pipette, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00, 6.00, 7.00 and 10.00 mL of color standard solution were transferred to colorimetric tubes, respectively. The solutions were then diluted to the mark with ultrapure water to obtain color values ​​of 5, 10, 20, 30, 40, 50, 60, 70 and 100 degrees.

[0067] 4. Sample solution preparation The samples were directly compared by colorimetry.

[0068] 5. Testing Fill the colorimetric tube with the sample solution, fill it to the 50mL mark, and then compare the colorimetric value with the standard colorimetric solution already filled to the 50mL mark of the colorimetric tube to obtain the colorimetric value of this product.

[0069] Note: If the color of the product solution is too high, the solution can be diluted by a certain factor, and then compared with the standard solution. The result can be multiplied by the dilution factor to obtain the color of the product.

[0070] II. The water content of the pure 1,3,6-hexanetrionitrile obtained in Examples 1-4 and Comparative Example 1 was tested using the following methods: 1. Instruments and equipment Coulometric moisture analyzer: Wantong 831 or equivalent testing equipment; Glove box: Moisture content ≤0.1ppm.

[0071] 2. Main reagents Karl Fischer reagent: Tianjin Saifure CO2 coulometric Karl Fischer reagent or equivalent reagent.

[0072] 3. Measurement The reaction should be carried out in a glove box. Weigh 0.5g of sample (accurate to 0.0001g), call the measurement program, input the sample weight, and read the numerical result directly after completion. Take the arithmetic mean of two parallel measurements as the final result.

[0073] III. Long-term storage stability test of the pure 1,3,6-hexanetrionitrile products obtained in Examples 1-4 and Comparative Example 1: The prepared pure 1,3,6-hexanetrionitrile products were stored at 25°C and 45°C for 10 days, 30 days and 60 days, respectively, and then the colorimetric properties were tested.

[0074] The test data of the pure 1,3,6-hexanetrionitrile obtained in Examples 1-4 and Comparative Example 1 of this invention are shown in Table 1.

[0075] Table 1. Water content, color, and color data after storage of the pure 1,3,6-hexanetrionitrile obtained in Examples 1-4 and Comparative Example 1.

[0076] As shown in Table 1, the 1,3,6-hexanetrionitrile purified by the process of this invention exhibits significantly improved color stability, indicating that the substances causing discoloration (acrylonitrile, acrylonitrile dimers and polymers) in the material system were effectively removed after purification.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying 1,3,6-hexanetrionitrile, characterized in that, Includes the following steps: Step S1: Add a monomer containing a sulfonic acid group and a catalyst to the crude 1,3,6-hexanetrionitrile and heat to react; Step S2: Wash and distill the reaction product to obtain pure 1,3,6-hexanetrionitrile; The monomer containing sulfonic acid groups in step S1 contains unsaturated bonds.

2. The purification method for 1,3,6-hexanetrionitrile according to claim 1, characterized in that, The unsaturated bond is a carbon-carbon double bond; The sulfonic acid group-containing monomer has the following structural formula: ， Wherein, R1 includes at least one of a hydrocarbon group and an amide group; R2 is one of H and C1~C3 alkyl groups.

3. The purification method for 1,3,6-hexanetrionitrile according to claim 2, characterized in that, It should include at least one of the following technical features: (1) R1 includes at least one of alkyl, aromatic, and amide groups; (2) The monomer containing sulfonic acid group includes at least one of sodium propylene sulfonate, sodium methpropylene sulfonate, sodium styrene sulfonate, sodium p-methacrylamide benzene sulfonate, and sodium 2-acrylamido-2-methylpropane sulfonate; (3) The amount of the sulfonic acid group-containing monomer used in step S1 is 0.1% to 10% of the weight of the crude 1,3,6-hexanetrionitrile; (4) The catalyst mentioned in step S1 includes at least one of azobisisobutyronitrile, ammonium persulfate, potassium persulfate, sodium persulfate, nickel(II) dichloride (tri(ethylenediamine)) and palladium(II) triphenylphosphine acetate; (5) The amount of catalyst used in step S1 is 0.1% to 0.5% of the weight of the crude 1,3,6-hexanetrionitrile; (6) The reaction heating temperature in step S1 is 30~80℃ and the reaction time is 2~12h.

4. The purification method for 1,3,6-hexanetrionitrile according to claim 1, characterized in that, It should include at least one of the following technical features: (1) The detergent used in the washing process in step S2 includes at least one of pure water and salt water with a concentration of 1-10%wt; (2) The amount of the detergent used accounts for 20% to 50% of the weight of the crude 1,3,6-hexanetrionitrile; (3) During the distillation process in step S2, the oil temperature is 170~220℃ and the distillation pressure is 5~30Pa. The light component obtained by distillation is pure 1,3,6-hexanetrionitrile.

5. The purification method for 1,3,6-hexanetrionitrile according to claim 4, characterized in that, In step S2, the washing process involves first adding an organic solvent, then adding a detergent and stirring to separate the aqueous phase; the mass ratio of the organic solvent to the detergent is 8:1 to 2:

1.

6. The purification method for 1,3,6-hexanetrionitrile according to claim 5, characterized in that, The distillation process in step S2 includes: performing a first distillation on the washed organic phase to obtain a first heavy component, and performing a second distillation on the first heavy component to obtain a second light component, which is pure 1,3,6-hexanetrionitrile.

7. The purification method for 1,3,6-hexanetrionitrile according to claim 6, characterized in that, The oil temperature for the first distillation is 170~185℃ and the distillation pressure is 5~30Pa; the oil temperature for the second distillation is 195~220℃ and the distillation pressure is 5~30Pa.

8. The purification method for 1,3,6-hexanetrionitrile according to claim 6, characterized in that, It should include at least one of the following technical features: (1) Before the distillation process in step S2, the organic phase is subjected to vacuum distillation at a controlled temperature of 50~60℃ to concentrate it to an organic solvent content of <0.1wt%; (2) The organic solvent includes at least one of dichloroethane, dichloropropane, and chlorobenzene.

9. An electrolyte additive, characterized in that, The purified 1,3,6-hexanetrionitrile obtained by the purification method according to any one of claims 1 to 8.

10. The application of the 1,3,6-hexanetrionitrile purified by any one of claims 1 to 8, or the electrolyte additive as described in claim 9, in lithium-ion batteries, sodium-ion batteries, and zinc-ion batteries.

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