A method for preparing a modified titanium-silicon molecular sieve catalyst and a cyclic sulfate ester

Abstract

This invention provides a modified titanium-silicon molecular sieve catalyst and a method for preparing cyclic sulfates, belonging to the field of secondary battery technology. The method for preparing the modified titanium-silicon molecular sieve catalyst provided by this invention includes the following steps: doping and modifying the titanium-silicon molecular sieve with alumina, iron oxide, and nickel oxide. The method for preparing the modified titanium-silicon molecular sieve catalyst provided by this invention improves the catalytic performance and cycle performance of the catalyst molecular sieve, and can greatly reduce production costs. Using the modified titanium-silicon molecular sieve of this invention as a catalyst, the prepared cyclic sulfate has a purity of over 99.5%, a moisture content ≤50ppm, and an acid value ≤40ppm, making it well-suited for use as an additive in lithium-ion battery solid electrolyte interphase membranes and lithium-ion battery electrolytes.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a method for preparing a modified titanium-silicon molecular sieve catalyst and a cyclic sulfate ester. Background Technology

[0002] Cyclic sulfates, including vinyl sulfate, propylene sulfate, and butene sulfate, are novel additives that can be used in the solid electrolyte interphase film and electrolyte of lithium batteries. In particular, vinyl sulfate can effectively suppress the decline of the initial capacity of the battery, increase the initial discharge capacity, reduce the battery expansion after high temperature storage, improve the cycle number and charge-discharge performance of the battery, extend the cycle life of the battery, and have compatibility with high and low temperature performance. They have an important impact on the performance of lithium-ion batteries and have great market demand and development prospects.

[0003] Currently, the main method for preparing cyclic sulfates is to use cyclic sulfites as raw materials, which are then oxidized by an oxidizing agent to produce cyclic sulfates. The main oxidizing agents include sodium hypochlorite, sodium periodate, and hydrogen peroxide. When sodium hypochlorite is used as an oxidizing agent, the oxidation reaction is often incomplete, resulting in a large amount of sulfite residue that is difficult to remove and the product is difficult to purify and separate. When sodium periodate is used as an oxidizing agent, it is costly and difficult to recycle.

[0004] When hydrogen peroxide is used as an oxidant, cyclic sulfites can be directly converted into cyclic sulfates. No environmentally harmful substances are produced during the reaction, the conditions are mild, and the solvents and catalysts used can be recycled, saving production costs. However, this method requires titanium-silicon molecular sieves as catalysts, and acidic systems can damage the structure of titanium-silicon molecular sieves, leading to the loss of active titanium sites, reduced catalytic performance, and poor recycling performance, which in turn causes a decrease in product yield and purity. Summary of the Invention

[0005] To address the aforementioned problems, one objective of this invention is to provide a method for preparing a modified titanium-silicon molecular sieve catalyst, thereby improving the catalytic activity and cycle life of the molecular sieve.

[0006] The second objective of this invention is to provide a method for preparing cyclic sulfates, which utilizes the modified titanium silicate molecular sieve as a catalyst to improve the utilization rate of raw materials and the reaction conversion rate, thereby further improving the yield and purity of the cyclic sulfate product.

[0007] To achieve the above objectives, the technical solution for preparing the modified titanium-silicon molecular sieve catalyst of the present invention is as follows:

[0008] A method for preparing a modified titanium-silicon molecular sieve catalyst includes the following steps: modifying the titanium-silicon molecular sieve by doping it with alumina, iron oxide and nickel oxide.

[0009] The method for preparing modified titanium-silicon molecular sieve catalyst provided by the present invention involves doping and modifying titanium-silicon molecular sieves to form acid-resistant molecular sieves, avoiding damage to the structure of molecular sieves by acidic systems, which would lead to the loss of titanium at active sites. This improves the catalytic performance and recycling performance of titanium-silicon molecular sieves. The modified titanium-silicon molecular sieve provided by the present invention can be recycled multiple times, which can greatly reduce production costs and enhance market competitiveness.

[0010] To further improve the acid resistance of titanium-silicon molecular sieves in acidic systems and reduce damage to the molecular sieve structure, preferably, the total mass ratio of the alumina, iron oxide, and nickel oxide to the mass ratio of the titanium-silicon molecular sieve is 1:(2-4).

[0011] In order to make the molecular sieve doped with different oxides to synergistically improve the acid resistance, preferably, the mass ratio of alumina, iron oxide and nickel oxide is (1-3):(1-3):(1-3).

[0012] To facilitate the doping of alumina, iron oxide, and nickel oxide and improve the doping rate of the titanium-silicon molecular sieve, preferably, the alumina, iron oxide, and nickel oxide are nano-sized powders with a powder size of 100–700 nm; and the titanium-silicon molecular sieve has a particle size of 30–80 nm.

[0013] Preferably, the alumina, iron oxide, and nickel oxide are ball-milled to the nanoscale.

[0014] To achieve simple and efficient doping modification, preferably, the doping modification includes: mixing alumina, iron oxide, and nickel oxide with titanium-silicon molecular sieves in an organic solvent, followed by solvent removal and high-temperature calcination at 450–550°C. Preferably, the high-temperature calcination is carried out under an inert atmosphere.

[0015] To ensure uniform mixing and easy removal of raw materials, preferably, the organic solvent is selected from one or more of anhydrous methanol, ethanol, and propanol.

[0016] To successfully obtain the doped and modified molecular sieve, the high-temperature calcination time is preferably 4 to 6 hours.

[0017] To achieve the above objectives, the technical solution of the method for preparing cyclic sulfates of the present invention is as follows:

[0018] A method for preparing cyclic sulfates, using the modified titanium-silicon molecular sieve as a catalyst, specifically involves adding the cyclic sulfite and the modified titanium-silicon molecular sieve to an organic solvent, followed by adding hydrogen peroxide to induce an oxidation reaction, thereby obtaining the cyclic sulfate.

[0019] The method for preparing cyclic sulfates provided by this invention uses the modified titanium-silicon molecular sieve as a catalyst, which improves the utilization rate of raw materials and the reaction conversion rate, thereby increasing the yield and purity of the cyclic sulfate product. The purity of the cyclic sulfate is as high as 99.5% or more, the moisture content is ≤50ppm, and the acid value is ≤40ppm.

[0020] The method for preparing cyclic sulfates provided by this invention is mild, easy to control, uses readily available and inexpensive raw materials, has a simple process, is easy to operate, and has the potential for large-scale industrialization.

[0021] To ensure the molecular sieve, acting as a catalyst, fully exerts its catalytic effect and improves the oxidation reaction efficiency, preferably, the amount of modified titanium-silicon molecular sieve added is 10% to 50% of the mass of cyclic sulfite. More preferably, the amount of modified titanium-silicon molecular sieve added is 15% to 40% of the mass of cyclic sulfite. To ensure the cyclic sulfite is fully oxidized, preferably, the molar ratio of cyclic sulfite to hydrogen peroxide is 1:(1.2 to 2.5).

[0022] To ensure a full reaction between the cyclic sulfite and hydrogen peroxide, and to make the reaction mild and controllable, the hydrogen peroxide is preferably added dropwise. Before adding the hydrogen peroxide, the system temperature is lowered to -5℃ to 5℃. During the addition of hydrogen peroxide, the temperature is controlled at 0℃ to 30℃. After adding the hydrogen peroxide, the system is kept at 10℃ to 30℃ for 2 to 4 hours.

[0023] Preferably, the cyclic sulfate is one of vinyl sulfate, propylene sulfate, and butene sulfate.

[0024] To improve the purity of cyclic sulfates and reduce moisture content and acid value, preferably, the oxidation reaction is followed by two purification processes to obtain high-purity cyclic sulfates.

[0025] More preferably, the two purification processes include crude purification and refining; the crude purification includes: filtering out the modified titanium-silicon molecular sieve after the oxidation reaction is completed, and obtaining crude cyclic sulfate after dehydration, concentration, low-temperature crystallization and drying; the refining process includes: dissolving the crude cyclic sulfate in a straight-chain carbonate solvent, and obtaining refined cyclic sulfate after dehydration, concentration, low-temperature crystallization and drying. Detailed Implementation

[0026] A method for preparing a modified titanium-silicon molecular sieve catalyst includes the following steps: modifying the titanium-silicon molecular sieve by doping it with alumina, iron oxide and nickel oxide.

[0027] In specific embodiments, the mass ratio of aluminum oxide, iron oxide, and nickel oxide is 1:1:1, 1:1:2, 1:1:3, 1:2:1, 1:2:2, 1:2:3, 1:3:1, 1:3:2, 1:3:3, 2:1:1, 2:1:2, 2:1:3, 2:2:1, 2:2:3, 2:3:1, 2:3:2, 2:3:3, 3:1:1, 3:1:2, 3:1:3, 3:2:1, 3:2:2, 3:2:3, 3:3:1, 3:3:2.

[0028] In a specific embodiment, the titanium-silicon molecular sieve is a TS-1 type molecular sieve.

[0029] A method for preparing cyclic sulfates, using the modified titanium-silicon molecular sieve as a catalyst, specifically involves adding the cyclic sulfite and the modified titanium-silicon molecular sieve to an organic solvent, followed by adding hydrogen peroxide to induce an oxidation reaction, thereby obtaining the cyclic sulfate.

[0030] In a specific embodiment, when the cyclic sulfate is vinyl sulfate, the cyclic sulfite is vinyl sulfite. The preparation method of the vinyl sulfite is as follows: thionyl chloride and ethylene glycol undergo a substitution reaction, followed by degassing and purification to obtain vinyl sulfite.

[0031] In a specific embodiment, the molar ratio of ethylene glycol to thionyl chloride is 1:1.01 to 1:1.3. More preferably, the molar ratio of ethylene glycol to thionyl chloride is 1:1.05 to 1:1.15.

[0032] In a specific embodiment, in order to improve the purity and yield of the intermediate vinyl sulfite, reduce the impact of neutralization, water washing and other operations on purity and yield, reduce the generation of impurities, and further improve the purity and yield of vinyl sulfite, the degassing and purification specifically involves: after the substitution reaction is completed, the reaction solution is degassed under vacuum, and purified by distillation under vacuum conditions to obtain high-purity vinyl sulfite.

[0033] In a specific embodiment, a portion of the hydrogen chloride gas in the substitution reaction product dissolves in the reaction solution. To further improve the removal rate of hydrogen chloride in the reaction solution, the vacuum degassing pressure is -0.1 to -0.08 MPa, and the time is 3 to 5 hours.

[0034] In a specific embodiment, in order to improve the purity of the distillation purification, the vacuum pressure during the distillation purification is -0.1MPa to -0.08MPa, and the temperature is 60-90℃.

[0035] In a specific embodiment, in order to fully react thionyl chloride and ethylene glycol and improve the utilization rate of raw materials, the substitution reaction is to add ethylene glycol dropwise to thionyl chloride. After the addition is completed, the temperature is raised to 25-40°C and kept at that temperature for 2-3 hours.

[0036] In a specific embodiment, the substitution reaction is carried out by adding ethylene glycol dropwise to thionyl chloride at room temperature for 2-3 hours.

[0037] In a specific embodiment, the purity of the vinyl sulfite product is above 99.5%, and the yield is above 95%.

[0038] In a specific implementation, the hydrogen peroxide used is commercially available hydrogen peroxide with a mass concentration of 25-35%.

[0039] In a specific embodiment, the organic solvent is dichloromethane, and the molar ratio of vinyl sulfite to dichloromethane is 1:5 to 1:15.

[0040] In a specific implementation, the hydrogen peroxide is added over a period of 2 to 4 hours.

[0041] In a specific embodiment, after the oxidation reaction is completed, the process involves two purification steps, including crude purification and refining. In the crude purification, anhydrous magnesium sulfate is used as the dehydrating agent, added at 1-3% of the system solution weight. Concentration involves concentrating dichloromethane to 50-80% of its added amount. In the refining process, the linear carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The amount of linear carbonate added is 2-4 times the crude weight of the cyclic sulfate. 4A molecular sieve is used as the dehydrating agent, added at 1-3% of the solution weight. Concentration involves concentrating the linear carbonate to 40-70% of its added amount. The low-temperature crystallization temperature in both the crude and refining processes is -20 to 0°C. Drying is performed using vacuum drying at a vacuum degree of -0.1 MPa to -0.08 MPa, a temperature of 45-50°C, and a time of 2-5 hours.

[0042] In a specific embodiment, the linear carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0043] The embodiments of the present invention will be further described below with reference to specific examples. Unless otherwise specified, the chemical reagents involved in the following examples are all commercially available conventional products.

[0044] I. Specific Examples of the Preparation Method of the Modified Titanium-Silicon Molecular Sieve Catalyst of the Present Invention

[0045] Example 1

[0046] The preparation method of the modified titanium-silicon molecular sieve catalyst in this embodiment includes the following steps:

[0047] Take 5g of alumina, 2.5g of iron oxide, and 2.5g of nickel oxide (mass ratio 2:1:1), ball mill to nanoscale (300-700nm), and then mix them thoroughly with 20g of titanium silicate molecular sieve TS-1 in anhydrous methanol. After removing the methanol by heating, calcine at 500℃ for 5h under an inert atmosphere to obtain 30g of modified TS-1, which is the modified titanium silicate molecular sieve catalyst.

[0048] Example 2

[0049] The preparation method of the modified titanium-silicon molecular sieve catalyst in this embodiment includes the following steps:

[0050] Take 2g of alumina, 1.33g of iron oxide, and 0.67g of nickel oxide (mass ratio 3:2:1), ball mill to nanoscale (200-600nm), and then mix them thoroughly with 16g of titanium silicate molecular sieve TS-1 in anhydrous ethanol. After removing the ethanol by heating, calcine at 520℃ for 4h under an inert atmosphere to obtain 20g of modified TS-1, which is the modified titanium silicate molecular sieve catalyst.

[0051] Example 3

[0052] The preparation method of the modified titanium-silicon molecular sieve catalyst in this embodiment includes the following steps:

[0053] Take 1.67g of alumina, 3.33g of iron oxide, and 5g of nickel oxide (mass ratio 1:2:3), ball mill to nanoscale (300-700nm), and then mix them thoroughly with 30g of titanium silicate molecular sieve TS-1 in anhydrous propanol. After removing the propanol by heating, calcine at 450°C for 6 hours under an inert atmosphere to obtain 40g of modified TS-1, which is the modified titanium silicate molecular sieve catalyst.

[0054] II. Specific Examples of the Preparation Method of the Cyclic Sulfate of the Present Invention

[0055] Example 4

[0056] This embodiment uses the modified titanium-silicon molecular sieve obtained in Example 1 as a catalyst to prepare vinyl sulfate, including the following steps:

[0057] 1) Synthesis of vinyl sulfite: 131g (1.1mol) thionyl chloride was added to the reaction vessel at room temperature, and 62g (1mol) ethylene glycol was added dropwise over 2 hours. After the addition was completed, the temperature was raised to 35℃ and kept at that temperature for 2 hours. After the reaction was completed, the reaction solution was evacuated and degassed at a vacuum of -0.08MPa for 3 hours. Then, the solution was purified by distillation at 70℃ under a vacuum of -0.09MPa to obtain 104g vinyl sulfite.

[0058] 2) Synthesis of vinyl sulfate: 104g (0.96mol) of vinyl sulfite obtained in step 1) and 30g of modified TS-1 obtained in Example 1 were added to 982g of dichloromethane (11.55mol). After cooling to -5℃, 170g (1.5mol) of 30% hydrogen peroxide was added dropwise over 2 hours at a controlled temperature of 10-25℃. After the addition was completed, the mixture was kept at 10-25℃ for 3 hours. After the reaction was completed, TS-1 was filtered out for recycling. After separating the aqueous phase from the filtrate, the solution was dehydrated, concentrated, crystallized at low temperature, and dried to obtain 113g of crude vinyl sulfate. In a glove box under inert gas protection, the 113g of crude vinyl sulfate was dissolved in 240g of dimethyl carbonate. After dehydration, concentration, crystallization at low temperature, and drying, 109g of vinyl sulfate was obtained.

[0059] Example 5

[0060] This embodiment uses the modified titanium-silicon molecular sieve obtained in Example 2 as a catalyst to prepare vinyl sulfate, including the following steps:

[0061] 1) Synthesis of vinyl sulfite: 125g (1.05mol) thionyl chloride was added to a reaction vessel at room temperature, and 62g (1mol) ethylene glycol was added dropwise over 2 hours. After the addition was completed, the temperature was raised to 30℃ and kept at that temperature for 2 hours. After the reaction was completed, the reaction solution was evacuated and degassed at a vacuum of -0.08MPa for 4 hours. Then, the solution was purified by distillation at 65℃ under a vacuum of -0.08MPa to obtain 105g vinyl sulfite.

[0062] 2) Synthesis of vinyl sulfate: 105g (0.97mol) of vinyl sulfite obtained in step 1) and 20g of modified TS-1 obtained in Example 2 were added to 826g of dichloromethane (9.72mol). After cooling to 5℃, 242g (2.13mol) of 30% hydrogen peroxide was added dropwise over 3 hours at a controlled temperature of 10-20℃. After the addition was completed, the mixture was kept at 10-20℃ for 4 hours. After the reaction was completed, TS-1 was filtered out for recycling. After separating the aqueous phase from the filtrate, the solution was dehydrated, concentrated, crystallized at low temperature, and dried to obtain 114g of crude vinyl sulfate. In a glove box under inert gas protection, 114g of crude vinyl sulfate was dissolved in 400g of diethyl carbonate. After dehydration, concentration, crystallization at low temperature, and drying, 110g of vinyl sulfate was obtained.

[0063] Example 6

[0064] This embodiment uses the modified titanium-silicon molecular sieve obtained in Example 3 as a catalyst to prepare ethylene sulfate, including the following steps:

[0065] 1) Synthesis of vinyl sulfite: 133g (1.12mol) of thionyl chloride was added to a reaction vessel at room temperature, and 62g (1mol) of ethylene glycol was added dropwise over 3 hours. After the addition was completed, the temperature was raised to 35℃ and kept at that temperature for 2 hours. After the reaction was completed, the reaction solution was evacuated and degassed under a vacuum of -0.08MPa for 5 hours. Then, under a vacuum of -0.08MPa, the solution was purified by distillation at 80℃ to obtain 105.6g of vinyl sulfite.

[0066] 2) Synthesis of vinyl sulfate: 105.6 g (0.978 mol) of vinyl sulfite obtained in step 1) and 40 g of modified TS-1 obtained in Example 3 were added to 1200 g of dichloromethane (14.12 mol). After cooling to 0 °C, 227 g (2 mol) of 30% hydrogen peroxide was added dropwise over 3 h at a controlled temperature of 15-30 °C. After the addition was complete, the mixture was kept at 15-30 °C for 2.5 h. After the reaction was completed, TS-1 was filtered out for recycling. After separating the aqueous phase from the filtrate, the solution was dehydrated, concentrated, crystallized at low temperature, and dried to obtain 116 g of crude vinyl sulfate. In a glove box under inert gas protection, 116 g of crude vinyl sulfate was dissolved in 280 g of methyl ethyl carbonate. After dehydration, concentration, crystallization at low temperature, and drying, 111.4 g of vinyl sulfate was obtained.

[0067] Example 7

[0068] This embodiment uses the modified titanium-silicon molecular sieve obtained in Example 1 as a catalyst to prepare propylene sulfate, including the following steps:

[0069] 1) Synthesis of propylene sulfite: 131 g (1.1 mol) of thionyl chloride was added to a reaction vessel at room temperature, and 76 g (1 mol) of 1,3-propanediol was added dropwise over 2 hours. After the addition was completed, the temperature was raised to 35°C and held for 2 hours. After the reaction was completed, the reaction solution was evacuated and degassed at a vacuum of -0.08 MPa for 4 hours. Then, the solution was purified by distillation at 80°C under a vacuum of -0.09 MPa to obtain 117 g of propylene sulfite.

[0070] 2) Synthesis of propylene sulfate: 117g (0.96mol) of propylene sulfite obtained in step 1) and 30g of modified TS-1 obtained in Example 1 were added to 850g of dichloromethane (10mol). After cooling to -5℃, 217g (1.92mol) of 30% hydrogen peroxide was added dropwise over 2 hours at a controlled temperature of 10-25℃. After the addition was completed, the mixture was kept at 10-25℃ for 3 hours. After the reaction was completed, TS-1 was filtered out for recycling. After separating the aqueous phase from the filtrate, the solution was dehydrated, concentrated, crystallized at low temperature, and dried to obtain 126g of crude propylene sulfate. In a glove box under inert gas protection, 126g of crude propylene sulfate was dissolved in 250g of dimethyl carbonate. After dehydration, concentration, crystallization at low temperature, and drying, 121g of propylene sulfate was obtained.

[0071] Example 8

[0072] This embodiment uses the modified titanium-silicon molecular sieve obtained in Example 1 as a catalyst to prepare butene sulfate, including the following steps:

[0073] 1) Synthesis of butene sulfite: 127 g (1.07 mol) of thionyl chloride was added to a reaction vessel at room temperature, and 90 g (1 mol) of 1,4-butanediol was added dropwise over 2 h. After the addition was completed, the temperature was raised to 35 °C and held for 2 h. After the reaction was completed, the reaction solution was evacuated and degassed at a vacuum of -0.08 MPa for 5 h. Then, the solution was purified by distillation at 90 °C under a vacuum of -0.09 MPa to obtain 131 g of butene sulfite.

[0074] 2) Synthesis of butenyl sulfate: 131g (0.965mol) of butenyl sulfite obtained in step 1) and 30g of modified TS-1 obtained in Example 1 were added to 1020g of dichloromethane (12mol). After cooling to -5℃, 219g (1.93mol) of 30% hydrogen peroxide was added dropwise over 2 hours at a controlled temperature of 10-25℃. After the addition was completed, the mixture was kept at 10-25℃ for 3 hours. After the reaction was completed, TS-1 was filtered out for recycling. After separating the aqueous phase from the filtrate, the product was dehydrated, concentrated, crystallized at low temperature, and dried to obtain 139.5g of crude butenyl sulfate. In a glove box under inert gas protection, 139.5g of crude butenyl sulfate was dissolved in 300g of dimethyl carbonate. After dehydration, concentration, crystallization at low temperature, and drying, 134g of butenyl sulfate was obtained.

[0075] III. Comparative Example

[0076] Comparative Example (Synthesis of Ethylene Sulfate using Unmodified Titanium-Silica Molecular Sieves as Catalysts)

[0077] This comparative example uses unmodified titanium silicate molecular sieve as a catalyst to prepare vinyl sulfate, including the following steps:

[0078] 1) Synthesis of vinyl sulfite: 133g (1.12mol) of thionyl chloride was added to a reaction vessel at room temperature, and 62g (1mol) of ethylene glycol was added dropwise over 3 hours. After the addition was completed, the temperature was raised to 35℃ and kept at that temperature for 2 hours. After the reaction was completed, the reaction solution was evacuated and degassed under a vacuum of -0.08MPa for 5 hours. Then, under a vacuum of -0.08MPa, the solution was purified by distillation at 80℃ to obtain 105.6g of vinyl sulfite.

[0079] 2) Synthesis of vinyl sulfate: 105.6 g (0.978 mol) of vinyl sulfite obtained in step 1) and 30 g of titanium silicate molecular sieve TS-1 were added to 1200 g of dichloromethane (14.12 mol). After cooling to 0℃, 227 g (2 mol) of 30% hydrogen peroxide was added dropwise over 3 hours at a controlled temperature of 15-30℃. After the addition was complete, the mixture was kept at 15-30℃ for 2.5 hours. After the reaction was completed, TS-1 was filtered out for recycling. After separating the aqueous phase from the filtrate, the product was dehydrated, concentrated, crystallized at low temperature, and dried to obtain 114.6 g of crude vinyl sulfate. In a glove box under inert gas protection, 114.6 g of crude vinyl sulfate was dissolved in 280 g of methyl ethyl carbonate. After dehydration, concentration, crystallization at low temperature, and drying, 109.8 g of vinyl sulfate was obtained.

[0080] IV. Experimental Examples

[0081] Experimental Example 1

[0082] The purity of the vinyl sulfite and cyclic sulfates obtained in Examples 4-6 was tested by gas chromatography, and the yield of vinyl sulfite was calculated. The moisture content of the cyclic sulfates obtained in Examples 4-8 was tested by Karl Fischer coulometric titration. The acid value of the cyclic sulfates obtained in Examples 4-8 was tested by potentiometric titration.

[0083] The purity and yield of the vinyl sulfite obtained in Examples 4-6 are shown in Table 1.

[0084] Table 1. Purity and yield of vinyl sulfite in Examples 4-6

[0085] product purity / % Yield / % Example 4 vinyl sulfite 99.67 96.6 Example 5 vinyl sulfite 99.75 97.2 Example 6 vinyl sulfite 99.78 97.8

[0086] As can be seen from Table 1, the vinyl sulfite obtained by this invention has high purity and high yield, with a purity of over 99.5% and a yield of over 96%. This indicates that vacuum degassing and vacuum distillation purification during the preparation of vinyl sulfite avoids operations such as neutralization and water washing, greatly improving the purity and yield of vinyl sulfite. In addition, the improved purity and yield of vinyl sulfite further reduce its impact as an intermediate on subsequent processes, which is beneficial to improving the purity and yield of vinyl sulfate in the later stages.

[0087] The purity, moisture content, and acid value of the cyclic sulfates obtained in Examples 4-8 are shown in Table 2.

[0088] Table 2. Purity, moisture content, and acid value of the cyclic sulfates in Examples 4-8

[0089] product purity / % Yield / % Moisture content / ppm Acid value / ppm Example 4 vinyl sulfate 99.71 91.50 35 30 Example 5 vinyl sulfate 99.68 91.45 40 32 Example 6 vinyl sulfate 99.74 91.80 37 29 Example 7 propylene sulfate 99.66 91.33 42 34 Example 8 Butene sulfate 99.64 91.35 45 33

[0090] As can be seen from Table 2, the cyclic sulfate ester obtained by this invention has a purity of over 99.5%, a moisture content of ≤50ppm, and an acid value of ≤40ppm, and can be well used as an additive for the solid electrolyte interphase membrane and lithium battery electrolyte.

[0091] Experiment Example 2

[0092] This experimental example demonstrates the cyclic performance test of a modified titanium-silicon molecular sieve catalyst. The modified titanium-silicon molecular sieve and the unmodified titanium-silicon molecular sieve provided by this invention were used as catalysts to complete the preparation of vinyl sulfate. After filtration, the obtained titanium-silicon molecular sieve was washed, dried, and then used as a catalyst for recycling to prepare vinyl sulfate. The purity and yield of vinyl sulfate after different cycles were tested to characterize its cyclic performance.

[0093] Table 3 Comparison of the cycling performance of titanium-silicon molecular sieve catalysts in the synthesis of ethylene sulfate.

[0094]

[0095]

[0096] As can be seen from the test results in Table 3, with the increase of the number of cycles, the yield and purity of ethylene sulfate prepared by the modified titanium-silicon molecular sieve provided by the present invention are both high, with a yield of over 90% and a purity of over 99.5%, which are much higher than those of the unmodified titanium-silicon molecular sieve. This indicates that the silicon-titanium molecular sieve of the present invention has good stability and excellent cycling performance in the system.

[0097] The above description is merely an embodiment of the present invention and is not intended to limit the technical solutions described herein. Any modifications or equivalent substitutions made based on the content of this specification should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a modified titanium-silicon molecular sieve catalyst, characterized in that, Includes the following steps: A titanium-silicon molecular sieve is modified by doping with alumina, iron oxide, and nickel oxide; the total mass ratio of alumina, iron oxide, and nickel oxide to the mass of the titanium-silicon molecular sieve is 1:(2~4); the titanium-silicon molecular sieve is a TS-1 type molecular sieve; the mass ratio of alumina, iron oxide, and nickel oxide is (1~3):(1~3):(1~3); the doping modification includes: mixing alumina, iron oxide, and nickel oxide with the titanium-silicon molecular sieve in an organic solvent, removing the solvent, and then calcining at a high temperature of 450~550℃.

2. The preparation method of the modified titanium-silicon molecular sieve catalyst as described in claim 1, characterized in that, The mass ratio of aluminum oxide, iron oxide and nickel oxide is (1~3):(1~2):(1~3).

3. The method for preparing the modified titanium-silicon molecular sieve catalyst as described in claim 1, characterized in that, The alumina, iron oxide, and nickel oxide are nano-sized powders with a particle size of 100~700nm; the titanium-silicon molecular sieve has a particle size of 30~80nm.

4. The method for preparing the modified titanium-silicon molecular sieve catalyst according to any one of claims 1-3, characterized in that, The doping modification includes: mixing alumina, iron oxide, and nickel oxide with titanium-silicon molecular sieves in an organic solvent, and then calcining the mixture at a high temperature of 450~520℃ after solvent removal.

5. The method for preparing the modified titanium-silicon molecular sieve catalyst as described in claim 4, characterized in that, The high-temperature calcination time is 4~6 hours.

6. A method for preparing a cyclic sulfate ester, characterized in that, Using the modified titanium-silicon molecular sieve according to any one of claims 1-5 as a catalyst, the specific method is as follows: adding the cyclic sulfite and the modified titanium-silicon molecular sieve into an organic solvent, and then adding hydrogen peroxide to undergo an oxidation reaction to obtain the cyclic sulfite.

7. The method for preparing cyclic sulfates as described in claim 6, characterized in that, The amount of modified titanium-silicon molecular sieve added is 10% to 50% of the mass of cyclic sulfite; the molar ratio of cyclic sulfite to hydrogen peroxide is 1:(1.2~2.5).

8. The method for preparing cyclic sulfates as described in claim 6, characterized in that, The hydrogen peroxide is added dropwise. Before adding hydrogen peroxide, the system temperature is lowered to -5℃ to 5℃. During the addition of hydrogen peroxide, the temperature is controlled at 0℃ to 30℃. After adding hydrogen peroxide, the system is kept at 10℃ to 30℃ for 2 to 4 hours.

9. The method for preparing cyclic sulfates as described in claim 6, characterized in that, The cyclic sulfate ester is one of vinyl sulfate, propylene sulfate, and butene sulfate.

Images