Method for high-selectivity synthesis of ethylene sulfate from ethylene sulfite

Abstract

The invention discloses a method for high-selectivity synthesis of ethylene sulfate from ethylene sulfite. An organosilane functional group is introduced to the surface of a TS-1 molecular sieve, the hydrophilic and hydrophobic degree of TS-1 is regulated and controlled, water is effectively prevented from being enriched around TS-1, and DTD hydrolysis side reaction is reduced, so that the stability and oxidation performance of the catalyst are improved, and the dispersity of TS-1 in a system is improved. The TS-1 treated by octadecyl trichlorosilane has moderate-strength hydrophobicity, so that the adsorption of substrates ES and H2O2 on the surface of the catalyst can be ensured, the aggregation of H2O molecules on the surface can be reduced, and the hydrolysis of DTD on the surface of the catalyst is inhibited. When the modified TS-1 molecular sieve catalyzes an ES oxidation reaction, DTD selectivity can reach 95% or above, and the modified TS-1 molecular sieve has good stability and reusability. The method is simple to operate, low in cost and suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic synthesis, and particularly relates to a method for highly selectively synthesizing vinylene sulfate from ethylene sulfite. Background Art

[0002] As a new type of film-forming additive for the solid electrolyte interface membrane (SEI) of lithium-ion batteries, vinylene sulfate (DTD) has been proven to be an effective strategy for regulating the properties of the SEI film on the battery electrode surface. At the same time, DTD can inhibit battery swelling, reduce battery impedance, and improve low-temperature discharge performance. Patents CN 115215834 B and CN 114210351 B use a catalytic oxidation system composed of RuCl3 as a catalyst and NaClO as an oxidant to convert ethylene sulfite (ES) into DTD. This route has a mature process and is also the mainstream route in the industry at present. However, due to the relatively high cost of the catalyst and the large amount of chloride ions in the waste liquid generated by the reaction, it does not conform to the development concept of green environmental protection. Therefore, it is necessary to find a new synthesis route.

[0003] At present, the catalytic oxidation system composed of titanium silicalite (TS-1) and H2O2 has received extensive attention due to its excellent oxidation performance. Patent CN 10942271 A uses the TS-1 / H2O2 catalytic oxidation system, with dichloromethane as a solvent, to oxidize ethylene sulfite in a batch reaction, but the yield is only 44%. Patents CN 118955461 A and CN116425715 B respectively adopt a fixed-bed reactor for the continuous synthesis of vinylene sulfate. Under the optimal reaction conditions, the selectivity of DTD reaches 88%. The literature (Ind. Eng. Chem. Res., 2024, 63(35): 15448-15457) reports that in a microreactor loaded with TS-1, using H2O2 as an oxidant and acetone as a solvent, a yield of 89.3% of vinylene sulfate is obtained. Although this scheme realizes the rapid separation of vinylene sulfate and water and inhibits the hydrolysis of DTD to a certain extent, the use of acetone increases the risk of the reaction and the difficulty of catalyst recovery. In current research, there is no report on suppressing the hydrolysis of DTD by regulating the catalyst structure. In order to inhibit the hydrolysis of DTD, the surface of TS-1 can be hydrophobically modified. However, in the ES oxidation reaction, both the raw material ES and the oxidant H2O2 are hydrophilic reagents. Therefore, when modifying the catalyst, it is necessary to regulate the degree of hydrophobicity and select a suitable hydrophobic group to ensure that the selectivity of DTD is improved without affecting the oxidation performance of ES. Summary of the Invention

[0004] In view of the limitations of the above-mentioned prior art, the present invention prepares a dual-functional catalyst with both oxidation and hydrophobicity. By regulating the hydrophilicity and hydrophobicity of TS-1, side reactions between DTD and water are inhibited, and the destruction of titanium active centers in the catalyst by hydrophilic solutions is avoided.

[0005] In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions: A method for highly selectively synthesizing ethylene sulfate from ethylene sulfite, comprising the following steps: (1) Catalyst preparation: An organosilicon coupling agent and TS-1 are uniformly dispersed in a solvent, stirred and reacted at room temperature for a certain time, then centrifuged, washed and dried to obtain a catalyst; (2) Synthesis of ethylene sulfate: Weigh a certain amount of catalyst, ethylene sulfite, and an organic solvent into a jacketed reactor. When the reaction temperature rises to the specified temperature, add H2O2 dropwise to the reaction system and react for a certain time.

[0006] The organosilicon coupling agent in the above step (1) is one or more of trimethylchlorosilane, trimethoxy(propyl)silane, phenyltrimethoxysilane, hexamethyldisiloxane, cetyltrimethoxysilane, octadecyltrichlorosilane.

[0007] In the above step (1), the mass ratio of the amount of the organosilicon coupling agent to TS-1 is 0.1:1 to 2:1, and the reaction time is 12 h - 48 h.

[0008] The solvent used to disperse TS-1 and the organosilicon coupling agent in the above step (1) is any one or more of toluene, water, methanol, ethanol, and acetonitrile.

[0009] The organic solvent in the above step (2) includes any one of dimethyl carbonate, methanol, acetonitrile, dichloromethane, and N,N-dimethylformamide.

[0010] In the above step (2), the dosage ratio of the catalyst, ethylene sulfite, and the organic solvent is 0.25 g:1 g:25 mL.

[0011] The reaction temperature in the above step (2) is 25 - 55 o °C, and the reaction time is 2 h - 6 h.

[0012] The addition amount of H2O2 in the above step (2) is 1.12 mL.

[0013] The advantages of the present invention are as follows: The present invention uses an organosilicon coupling agent to modify TS-1. The modified catalyst can inhibit the enrichment of water molecules in the system on the surface of TS-1. During long-term operation, it can also maintain the high dispersion of TS-1, effectively inhibit the hydrolysis of DTD on the surface of TS-1, realize the highly selective synthesis of DTD, and improve the catalytic performance. When the reaction time is 5 h, ES is almost completely converted, and the selectivity of vinyl sulfate increases from 80% to over 95%. As the reaction time is extended, the selectivity of DTD shows no obvious fluctuation. This invention effectively inhibits the hydrolysis of DTD and at the same time ensures the stable dispersion of TS-1 during long-term operation. Description of the Drawings

[0014] Figure 1 It is the cyclic stability diagram of TS-1 modified by octadecyltrichlorosilane in Example 1.

[0015] Figure 2 It is the infrared spectrum diagram of the catalyst in Example 1.

[0016] Figure 3 It is the test diagram of the contact angle between TS-1 modified by different organosilicon coupling agents and water in Example 2. (A) TS-1, (B) trimethylchlorosilane, (C) hexamethyldisiloxane, (D) octadecyltrichlorosilane.

[0017] Figure 4 It is the time-dependent reaction diagram of the modified TS-1 in Example 6. Detailed Embodiments

[0019] In order to illustrate the technical problems to be solved, technical solutions and beneficial effects of the present invention, the present invention will be further described in detail below with specific examples. Without special instructions, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment and reagents used can be obtained through commercial channels.

[0020] The inventors found that the main reason for the low selectivity of vinyl sulfate (DTD) is that the presence of hydroxyl silicon (Si-OH) and hydroxyl titanium (Ti-OH) on the surface of TS-1 reduces its hydrophobic performance, and there is an enrichment effect on the water in the system in the pore structure around the Ti sites during the reaction, resulting in product hydrolysis; at the same time, when the reaction runs for a long time, TS-1 will agglomerate and adhere to the inner wall of the reactor, and the mass transfer is subject to resistance, which may cause the catalyst to deactivate. Based on the above findings, the inventors proposed a method for improving the performance of TS-1 in oxidizing ES by inhibiting the hydrolysis of DTD.

[0021] The present invention will be further described below through specific embodiments.

[0022] Example 1 A method for highly selective synthesis of ethylene sulfate from vinylene sulfite, comprising the following steps: Weigh 0.16 g of different kinds of organosilicon coupling agents (trimethylchlorosilane, hexamethyldisiloxane, cetyltrimethoxysilane, octadecyltrichlorosilane), disperse them in a test tube containing 10 mL of toluene, and mix well by ultrasonic treatment. The resulting solution is denoted as Solution 1; weigh 0.8 g of titanium silicalite molecular sieve (TS-1) into 10 mL of toluene, stir evenly, then pour Solution 1 into it. After sealing and stirring at room temperature for 24 h, pour it into a centrifuge tube, and wash it 3 times with ethanol and deionized water respectively until the toluene is completely removed, and dry it overnight in an oven at 80 o °C to obtain the catalyst.

[0023] Weigh 0.25 g of the above catalyst, 1 g of vinylene sulfite, and 25 mL of dimethyl carbonate, disperse them into a jacketed reactor. When the temperature in the reactor rises to 35 o °C, inject 1.12 mL of H2O2 into the reaction system through an injection pump. After the dropping is completed, react for 2 h. The resulting liquid is filtered through an organic filter membrane and then subjected to gas phase analysis. The results are shown in Table 1. Combining infrared spectroscopy and contact analysis shows that the long carbon chain organosilicon coupling agent can effectively achieve grafting with TS-1, adjust the wettability of TS-1, inhibit the enrichment of water on the surface of TS-1, and improve the DTD selectivity.

[0024] Table 1 Figure 1 It is the cyclic stability diagram of TS-1 modified by octadecyltrichlorosilane. The results show that after the reaction, the catalyst is centrifugally washed with ethanol until there is no reaction liquid residue on the surface, and then dried in a vacuum drying oven at 60 °C for 10 h, and directly put into the next round of reaction without any activation treatment. Select 2 h of reaction time as the benchmark period for cyclic stability test. After 5 cycles, the catalytic activity basically remains unchanged, showing good cyclic stability, and the DTD selectivity is maintained at 94%.

[0025] Figure 2 It is the infrared spectrogram of the catalysts modified by different kinds of organosilicon coupling agents. The results show that the TS-1 modified by the organosilicon coupling agent still maintains the MFI topological structure. From the partial enlarged view with wave numbers in 2700 cm -1 ~3000 cm -1 It can be observed that two peaks appear at about 2858 cm -1 and 2926 cm -1 respectively. They are respectively attributed to the stretching vibration peak of -(CH2) n and the asymmetric stretching vibration peak of -CH3. These peaks prove the existence of hydrophobic organic alkyl groups on the surface of TS-1.

[0026] Figure 3 Contact angle tests of TS-1 with water after modification by different organosilane coupling agents were carried out. The results showed that when the carbon chain length increased from C3 to C18, the hydrophobicity increased. This could be attributed to the increase in the carbon chain length, which led to an increase in the proportion of the non-polar part (C-H), and thus enhanced the hydrophobicity of the overall TS-1-C. When TS-1 was modified with hexamethyldisiloxane (TS-1-HMDS), the contact angle of the catalyst with water changed from 22º before modification to 11º, and the hydrophilic ability increased instead. This might be due to the oxidation reaction during the modification process of hexamethyldisiloxane, generating hydrophilic groups (such as silanols). Combining the evaluation results of this catalyst, it was shown that hydrophilic TS-1 was not conducive to the formation of DTD.

[0027] Example 2 A method for highly selective synthesis of ethylene sulfate from ethylene sulfite, comprising the following steps: Using the best-performing octadecyltrichlorosilane in Example 1 as a modifying reagent, 0.16 g of octadecyltrichlorosilane was respectively dispersed in test tubes containing 10 mL of different solvents (toluene, methanol, acetonitrile), and ultrasonically mixed evenly. The resulting solution was denoted as Solution 1. 0.8 g of TS-1 was weighed and dissolved in 10 mL of the same different solvents (toluene, methanol, acetonitrile). After stirring evenly, Solution 1 was poured into it. After sealing and stirring at room temperature for 24 h, it was poured into a centrifuge tube and washed 3 times with ethanol and deionized water respectively until the solvent was completely removed, and then dried overnight in an oven at 80 o °C to obtain the catalyst.

[0028] Weigh 0.25 g of the above catalyst, 1 g of ethylene sulfite, and 25 mL of dimethyl carbonate and disperse them into a jacketed reactor. When the temperature in the reactor rises to 35 o °C, 1.12 mL of H2O2 is injected into the reaction system through a syringe pump. After the dropping is completed, the reaction is carried out for 2 h. The resulting liquid is filtered through an organic filter membrane and then subjected to gas phase analysis. The results are shown in Table 2.

[0029] Table 2 Example 3 A method for highly selective synthesis of ethylene sulfate from ethylene sulfite, comprising the following steps: Weigh different masses of octadecyltrichlorosilane (OTS) (m(OTS):m(TS - 1) are 0.1, 0.2, 0.3, 0.4, 0.5 respectively), disperse them in a test tube containing 10 mL of toluene, and mix well by ultrasonic treatment. The resulting solution is denoted as Solution 1. Weigh 0.8 g of titanium silicalite (TS - 1) into 10 mL of toluene, stir well, then pour Solution 1 into it. After sealing and stirring at room temperature for 24 h, pour it into a centrifuge tube, and wash it 3 times with ethanol and deionized water respectively until the toluene is completely removed, and dry it overnight in an oven at 80 o °C to obtain the catalyst.

[0030] Weigh 0.25 g of the above catalyst, 1 g of vinylene sulfite, and 25 mL of dimethyl carbonate, disperse them into a jacketed reactor. When the temperature in the reactor rises to 35 o °C, inject 1.12 mL of H2O2 into the reaction system through a syringe pump. After the addition is complete, react for 4 h. The resulting liquid is filtered through an organic filter membrane and then subjected to gas phase analysis. The results are shown in Table 3.

[0031] Table 3 Example 4 A method for highly selectively synthesizing ethylene sulfate from vinylene sulfite, comprising the following steps: Weigh 0.16 g of octadecyltrichlorosilane and disperse it in a test tube containing 10 mL of toluene, and mix well by ultrasonic treatment. The resulting solution is denoted as Solution 1. Weigh 0.8 g of TS - 1 into 10 mL of toluene, stir well, then pour Solution 1 into it. After sealing and stirring at room temperature for 6 h, pour it into a centrifuge tube, and wash it 3 times with ethanol and deionized water respectively until the toluene is completely removed, and dry it overnight in an oven at 80 o °C.

[0032] Weigh 0.25 g of the above catalyst, 1 g of vinylene sulfite, and 25 mL of dimethyl carbonate, disperse them into a jacketed reactor. When the temperature in the reactor rises to 35 o °C, inject 1.12 mL of H2O2 into the reaction system through a syringe pump. After the addition is complete, react for 2 h. The resulting liquid is filtered through an organic filter membrane and then subjected to gas phase analysis to obtain an ES conversion rate of 88% and a DTD selectivity of 85%.

[0033] Example 5 Weigh 0.16 g of octadecyltrichlorosilane and disperse it in a test tube containing 10 mL of toluene. Ultrasonically mix it evenly. The resulting solution is denoted as Solution 1. Weigh 0.8 g of TS-1 into 10 mL of toluene, stir evenly, then pour Solution 1 into it. After sealing and stirring at room temperature for 24 h, pour it into a centrifuge tube and wash it 3 times with ethanol and deionized water respectively until the toluene is completely removed, and dry it overnight in an oven at 80 o °C.

[0034] Weigh 0.25 g of the above catalyst, 1 g of vinylene sulfite, and 25 mL of different solvents (dimethyl carbonate, acetonitrile, dichloromethane, methanol, N,N-dimethylformamide) and disperse them into a jacketed reactor. When the temperature in the reactor rises to 35 o °C, inject 1.12 mL of H2O2 into the reaction system through a syringe pump. After the dropping is complete, react for 2 h. The resulting liquid is filtered through an organic filter membrane and then subjected to gas phase analysis. The results are shown in Table 4.

[0035] Table 4 Example 6 A method for highly selectively synthesizing ethylene sulfate from vinylene sulfite, comprising the following steps: Weigh 0.16 g of octadecyltrichlorosilane and disperse it in a test tube containing 10 mL of toluene. Ultrasonically mix it evenly. The resulting solution is denoted as Solution 1. Weigh 0.8 g of TS-1 into 10 mL of toluene, stir evenly, then pour Solution 1 into it. After sealing and stirring at room temperature for 24 h, pour it into a centrifuge tube and wash it 3 times with ethanol and deionized water respectively until the toluene is completely removed, and dry it overnight in an oven at 80 o °C, denoted as TS-1-OTS.

[0036] Weigh 0.25 g of the above catalyst, 1 g of vinylene sulfite, and 25 mL of dimethyl carbonate and disperse them into a jacketed reactor. When the temperature in the reactor rises to 35 o °C, inject 1.12 mL of H2O2 into the reaction system through a syringe pump. After the dropping is complete, react for different times (1 h - 8 h). The resulting liquid is filtered through an organic filter membrane and then subjected to gas phase analysis. The results are as Figure 4 shown. After reacting for 5 h, the conversion rate of ES reaches 99%, and the selectivity of DTD is 95%. This shows that even after the catalyst has been running for a long time, it still maintains good stability and to a certain extent inhibits the occurrence of the hydrolysis side reaction of DTD.

[0037] In summary, the present invention regulates the surface hydrophobicity of TS-1 by a post-treatment method, which can inhibit the enrichment of water molecules around TS-1, effectively avoid the hydrolysis of DTD on the surface of TS-1, improve the selectivity of DTD, and the conversion rate of ES is not affected. At the same time, the modified catalyst can still maintain good dispersibility after long-term operation, improve the service life of the catalyst, and the catalyst has good industrial application prospects.

[0038] As described above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A method for highly selectively synthesizing ethylene sulfate from vinylene sulfite, characterized in that, It includes the following steps: (1) Catalyst preparation: Uniformly disperse the organosilicon coupling agent and TS-1 into a solvent, stir and react at room temperature for a certain period of time, then carry out centrifugal washing and drying to obtain the catalyst; (2) Synthesis of vinyl sulfate: Weigh a certain amount of catalyst, vinyl sulfite, and organic solvent into a jacketed reactor. When the reaction temperature rises to the specified temperature, add H2O2 dropwise to the reaction system and react for a certain period of time.

2. The method according to claim 1, wherein: In step (1), the organosilicon coupling agent is one or more of trimethylchlorosilane, trimethoxy(propyl)silane, phenyltrimethoxysilane, hexamethyldisiloxane, cetyltrimethoxysilane, octadecyltrichlorosilane.

3. The method according to claim 1, wherein: In step (1), the mass ratio of the amount of the organosilicon coupling agent used to the mass of TS-1 is 0.1:1 to 2:1, and the reaction time is 12 h - 48 h.

4. The method according to claim 1, characterized in that: In step (1), the solvent used to disperse TS-1 and the organosilicon coupling agent is any one or more of toluene, water, methanol, ethanol, and acetonitrile.

5. The method according to claim 1, characterized in that: In step (2), the organic solvent includes any one of dimethyl carbonate, methanol, acetonitrile, dichloromethane, and N,N-dimethylformamide.

6. The method according to claim 1, characterized in that: In step (2), the dosage ratio of the catalyst, vinyl sulfite, and organic solvent is 0.25 g:1 g:25 mL.

7. The method according to claim 1, characterized in that: The reaction temperature described in step (2) is 25~55 o °C, and the reaction time is 2 h~6 h.

8. The method according to claim 1, characterized in that: In step (2), the addition amount of H2O2 is 1.12 mL.

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