Refining method of pentaerythritol bicyclic sulfate

Abstract

The invention discloses a method for refining pentaerythritol bicyclic sulfate. The method comprises the following steps: 1, heating, stirring and washing a pentaerythritol bicyclic sulfate crude product to be refined by using a weak acid aqueous solution; 2, adding ethanol into the refining tank from the feeding hole, heating, stirring and washing; 3, adding pure water into the refining tank from the feeding hole, heating, stirring and washing; 4, introducing high-temperature nitrogen, taking away the residual solvent and moisture by high-temperature nitrogen flow, and discharging the residual solvent and moisture from a discharge pipe to finish drying; the device has the advantages that the integration of refining, filtering and drying can be realized, and the refining efficiency is greatly improved; meanwhile, various impurities in the crude product can be effectively removed, the pentaerythritol bicyclic sulfate with low acid value, low moisture, high purity and high refining yield is obtained, and the method is simple and convenient to operate and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium battery electrolyte additives and pharmaceutical intermediate synthesis technology, specifically to a purification method for pentaerythritol dicyclic sulfate. Background Technology

[0002] Lithium-ion batteries have become the preferred technology for current electronics, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and environmental friendliness. However, they also have drawbacks such as sensitivity to overcharging and over-discharging, and thermal runaway at high temperatures. To mitigate these shortcomings, electrolyte additives play a crucial role. Pentaerythritol dicyclic sulfate, as a novel battery electrolyte additive, has gradually gained widespread attention.

[0003] Pentaerythritol bicyclic sulfate can easily form a better SEI protective layer on the positive and negative electrode surfaces, inhibiting the oxidative decomposition of the electrolyte under high voltage, and improving the charge-discharge performance, cycle life and high-temperature stability of the battery. It is a lithium battery electrolyte additive with high commercial value, and has certain potential applications in the fields of organic synthesis and pharmaceutical intermediates, heat-resistant coatings, and special polymer additives.

[0004] Currently, the main synthetic route involves oxidizing pentaerythritol dicyclic sulfite to pentaerythritol dicyclic sulfate using sodium hypochlorite or hydrogen peroxide under the action of a catalyst. However, the presence of residual raw materials and incomplete oxidation during the catalytic oxidation reaction leads to increased impurity content in the target product and makes crude product purification difficult. Traditional purification processes are difficult, inefficient, and complex, thus requiring high-quality equipment and reagents.

[0005] Therefore, developing a purification method for pentaerythritol dicyclic sulfate that combines high purity, high purification yield, and low cost is of vital industrial value for the large-scale preparation of pentaerythritol dicyclic sulfate. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a purification method for pentaerythritol bicyclic sulfate, which has the advantages of efficiently removing impurities, obtaining high-purity and high-yield products, and is simple, continuous, and scalable, making it suitable for industrial production.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a refining method for pentaerythritol dicyclic sulfate, employing a refining apparatus, the refining apparatus comprising: a refining tank with a temperature control mechanism, a refining tank having an openable and closable inlet, a refining tank having an openable and closable outlet on the side wall at the lower end of the refining tank, a discharge pipe with a discharge control valve at the bottom of the refining tank, a stirring mechanism inside the refining tank, a sintering mesh inside the refining tank, the stirring mechanism being located above the sintering mesh, the outlet being located on one side of the top of the sintering mesh, and a nitrogen inlet with an inlet control valve on the refining tank; the refining tank also includes a scraping mechanism capable of scraping the material towards the outlet. The refining process includes: 1. Add the crude pentaerythritol dicyclic sulfate to be refined and a weak acid aqueous solution into the refining tank through the feed inlet; heat the material in the refining tank through the temperature control mechanism, stir through the stirring mechanism, and wash the crude pentaerythritol dicyclic sulfate with the weak acid aqueous solution. After washing, perform the filtration separation step. The filtration and separation steps include: opening the inlet control valve, introducing room temperature nitrogen from the nitrogen inlet, maintaining positive pressure in the refining tank, opening the discharge control valve, separating the liquid and solid through the sintering mesh, discharging the filtrate and gas from the discharge pipe, and retaining the solid on the sintering mesh, and then closing the inlet control valve and the discharge control valve. 2. Add ethanol into the refining tank through the feed inlet, heat and stir, and wash the solid particles with ethanol. After washing, perform the above-mentioned filtration and separation steps to discharge the ethanol. 3. Add pure water into the refining tank through the feed inlet, heat and stir, and wash the solid with pure water. After washing, perform the above-mentioned filtration and separation steps to drain the water. 4. Open the intake control valve to introduce high-temperature nitrogen gas, and open the exhaust control valve. The high-temperature nitrogen gas will carry away the residual solvent and moisture and be discharged from the exhaust pipe to complete the drying process. 5. A scraping mechanism is used to continuously scrape the dried material to the discharge port for discharge.

[0008] Furthermore, in the aforementioned method for refining pentaerythritol dicyclic sulfate, a discharge pipe is connected to a condenser, the condenser's drain port is connected to a recovery tank, the condenser's exhaust port is connected to a nitrogen buffer tank, the nitrogen buffer tank is connected to a nitrogen heater and a reflux pipe, the nitrogen buffer tank is equipped with a nitrogen input pipe connected to a nitrogen source, the nitrogen heater's input end is equipped with a heating control valve, and the reflux pipe's input end is equipped with a reflux control valve; the output ends of the nitrogen heater and the reflux pipe are both connected to a circulating fan, and the circulating fan's outlet is connected to an intake control valve on the nitrogen inlet via an intake pipe, the nitrogen inlet being located at the top of the refining tank.

[0009] Furthermore, in the aforementioned method for refining pentaerythritol dicyclic sulfate, the filtration and separation step includes: opening the discharge control valve, the reflux control valve, and the inlet control valve; nitrogen in the nitrogen buffer tank enters the refining tank through the reflux pipe, the circulating fan, the inlet pipe, and the nitrogen inlet; the nitrogen pressure in the refining tank is maintained at 0.4 MPa; nitrogen and liquid pass through the sintered mesh into the condenser; the solid remains at the top of the sintered mesh; the liquid in the condenser flows into the recovery tank; the nitrogen in the condenser enters the nitrogen buffer tank; the nitrogen in the nitrogen buffer tank returns to the refining tank through the reflux pipe, the circulating fan, the inlet pipe, and the nitrogen inlet; this cycle continues until the liquid is completely drained; the nitrogen in the circulation pipeline is stored in the nitrogen buffer tank.

[0010] Furthermore, in the aforementioned method for refining pentaerythritol dicyclic sulfate, in the fourth refining step, the temperature of the high-temperature nitrogen gas is 110°C, and the nitrogen pressure is maintained at 0.1 MPa. The nitrogen gas in the nitrogen buffer tank enters the refining tank through the nitrogen heater, circulating fan, inlet pipe, and nitrogen inlet. The nitrogen gas and liquid pass through the sintering mesh and enter the condenser, while the solid remains on top of the sintering mesh. The liquid in the condenser flows into the recovery tank, and the nitrogen gas in the condenser enters the nitrogen buffer tank. The nitrogen gas in the nitrogen buffer tank flows back into the refining tank through the nitrogen heater, circulating fan, inlet pipe, and nitrogen inlet, continuously circulating until drying is completed.

[0011] Furthermore, in the aforementioned method for refining pentaerythritol dicyclic sulfate, the stirring mechanism includes: a stirring shaft disposed within a refining tank, a stirring paddle disposed on the stirring shaft, the upper end of the stirring shaft extending out of the refining tank, the upper end of the stirring shaft being driven by an explosion-proof motor, under the drive of the explosion-proof motor the stirring shaft can rotate within the refining tank; the scraping mechanism includes: an S-shaped scraper disposed at the bottom of the stirring shaft, the S-shaped scraper being located at the top of the sintering mesh, the scraper being able to scrape the material at the top of the sintering mesh toward the discharge port.

[0012] Furthermore, in the aforementioned method for refining pentaerythritol dicyclic sulfate, the structure of the temperature control mechanism includes: the tank body of the refining tank adopts a jacketed structure, and the refining tank is provided with a heat source inlet and a heat source outlet connected to the inside of the jacketed layer. The heat source inlet is located at the lower end of the refining tank, and the heat source outlet is located at the upper end of the refining tank. The heating medium enters the jacketed layer from the heat source inlet and then flows out from the heat source outlet.

[0013] Furthermore, in the aforementioned method for refining pentaerythritol bicyclic sulfate, the temperature of the heating medium within the jacket layer is maintained at 30°C to 60°C during the first, second, and third refining steps.

[0014] Furthermore, in the aforementioned method for refining pentaerythritol bicyclic sulfate, the pore size of the sintered mesh is 1–20 μm.

[0015] Furthermore, in the aforementioned method for refining pentaerythritol bicyclic sulfate, in the first step of refining, the weak acid in the weak acid aqueous solution is carbonic acid or acetic acid, the mass ratio of the weak acid to water in the weak acid aqueous solution is 1:5 to 15, the mass ratio of crude pentaerythritol bicyclic sulfate to the weak acid aqueous solution is 1:2 to 5, and the washing time is 2 to 4 hours.

[0016] Furthermore, in the aforementioned method for purifying pentaerythritol bicyclic sulfate, in the second purification step, the mass ratio of crude pentaerythritol bicyclic sulfate to ethanol is 1:1 to 4.

[0017] Furthermore, in the aforementioned method for purifying pentaerythritol dicyclic sulfate, in the third purification step, the mass ratio of crude pentaerythritol dicyclic sulfate to pure water is 1:1 to 5.

[0018] The advantages of this invention are: it provides a purification method for pentaerythritol bicyclic sulfate, employing multiple solvent washing within a single purification tank to effectively remove impurities from the crude product. This method integrates purification, filtration, and drying, offering convenience and speed, significantly improving purification efficiency and product quality. The resulting product has low acid value, low moisture content, high purity, and high purification yield. Circulating nitrogen pressure enhances material filtration, and heated nitrogen is used to dry the solids within the purification tank. Nitrogen gas flow drying achieves efficient heat and mass transfer, rapidly removing acid and moisture from the solids, avoiding common problems in static drying such as clumping and uneven heating. It also removes residual solvents, acids, and moisture, reducing the risk of product hydrolysis, thereby greatly improving purification yield and purity, making it suitable for industrial production. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the refining apparatus used in the refining method of pentaerythritol bicyclic sulfate according to the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of the stirring paddle and S-shaped scraper in the refining device. Detailed Implementation

[0021] The purification method of pentaerythritol bicyclic sulfate according to the present invention will be described in detail below through specific embodiments.

[0022] First, let's introduce the refining apparatus. For example... Figure 1 , Figure 2As shown, the specific structure of the refining device includes: a refining tank 1 with a temperature control mechanism; a closable feed inlet 11 on the refining tank 1; a closable discharge outlet 12 on the side wall at the lower end of the refining tank 1; and a discharge pipe 13 with a discharge control valve 131 at the bottom of the refining tank 1. A stirring mechanism 2 is installed inside the refining tank 1, and a sintered mesh 3 for solid-liquid separation is fixedly installed inside the refining tank 1. The stirring mechanism 2 is located above the sintered mesh 3, and the discharge outlet 12 is located on one side of the top of the sintered mesh 3. A nitrogen inlet 14 with an air intake control valve 141 is also provided on the refining tank 1. A scraping mechanism that can scrape the material towards the discharge outlet 12 is also provided inside the refining tank 1.

[0023] In this embodiment, the discharge pipe 13 is connected to the condenser 4, the drain port of the condenser is connected to the recovery tank 5, and the exhaust port of the condenser 4 is connected to a nitrogen buffer tank 8. The nitrogen buffer tank 8 is connected to the nitrogen heater 6 and the return pipe 7, respectively. A nitrogen input pipe 81 connected to a nitrogen source is provided on the nitrogen buffer tank 8. A heating control valve 61 is provided at the input end of the nitrogen heater 6, and a return control valve 71 is provided at the input end of the return pipe 7. The output ends of the nitrogen heater 6 and the return pipe 7 are both connected to the circulating fan 9. The outlet of the circulating fan 9 is connected to the intake control valve 141 on the nitrogen inlet 14 through the intake pipe 142. The nitrogen inlet 14 is located at the top of the refining tank 1.

[0024] In this embodiment, the stirring mechanism includes: a stirring shaft 21 disposed inside the refining tank 1, a stirring paddle 22 disposed on the stirring shaft 21, the upper end of the stirring shaft 21 extending out of the refining tank 1, and the upper end of the stirring shaft 21 being driven by an explosion-proof motor 23. Under the drive of the explosion-proof motor 23, the stirring shaft 21 can drive the stirring paddle 22 to rotate inside the refining tank 1.

[0025] like Figure 2 As shown, the scraping mechanism includes an S-shaped scraper 24 located at the bottom of the stirring shaft 21, which is situated at the top of the sintered mesh 3. The S-shaped scraper 24 scrapes the material on the top of the sintered mesh 3 towards the discharge port 12. The pore size of the sintered mesh is 1–20 μm. In the following refining embodiment, the pore size of the sintered mesh is 10 μm.

[0026] In this embodiment, the temperature control mechanism includes: the tank body of the refining tank 1 adopts a jacketed structure; the refining tank 1 is provided with a heat source inlet 101 and a heat source outlet 102 connected to the interior of the jacket; the heat source inlet 101 is located at the lower end of the refining tank, and the heat source outlet 102 is located at the upper end of the refining tank; the heating medium enters the jacket from the heat source inlet 101 and then flows out from the heat source outlet 102. The heating medium can be water or heat transfer oil. The temperature of the heating medium inside the jacket is maintained at 30℃~60℃.

[0027] The crude pentaerythritol dicyclic sulfate to be purified in the following examples is obtained by catalytic oxidation of the raw material pentaerythritol dicyclic sulfite with ruthenium trichloride and sodium hypochlorite. The crude product contains impurities such as raw materials, intermediates, salts, and by-reaction products.

[0028] Example 1: The inlet control valve 141 and the outlet control valve 131 are closed, and the outlet 12 is in the closed state. An aqueous acetic acid solution (acetic acid to water mass ratio of 1:5) and the crude pentaerythritol dicyclic sulfate to be purified are added to the refining tank 1 through the inlet 11. The mass ratio of the crude pentaerythritol dicyclic sulfate to the aqueous acetic acid solution is 1:5. The stirring mechanism is turned on, and 50 mL of acetic acid solution is introduced into the jacket layer. o C water, stir for 2 hours.

[0029] Open the discharge control valve 131, the return control valve 71, and the intake control valve 141. Room temperature nitrogen is introduced into the nitrogen buffer tank 8 via the nitrogen input pipe 81. The nitrogen in the nitrogen buffer tank 8 flows back to the refining tank 1 via the return pipe 7, the circulating fan 9, the intake pipe 142, and the nitrogen inlet 14. The nitrogen pressure in the refining tank 1 is maintained at 0.4 MPa. Nitrogen and liquid pass through the sintering mesh 3 and enter the condenser 4, while the solid remains at the top of the sintering mesh 3. The liquid in the condenser 4 flows into the recovery tank 5, and the nitrogen in the condenser 4 enters the nitrogen buffer tank 8. The nitrogen in the nitrogen buffer tank 8 flows back to the refining tank 1 via the return pipe 7, the circulating fan 9, the intake pipe 142, and the nitrogen inlet 14, continuously circulating until the liquid is completely drained. The nitrogen in the circulating pipeline is stored in the nitrogen buffer tank 8.

[0030] Close the emission control valve 131 and the intake control valve 141, and add ethanol into the refining tank 1 through the feed inlet 11. The mass ratio of crude pentaerythritol dicyclic sulfate to ethanol is 1:1. Continue to circulate 50 ppm of ethanol through the jacket. o C water, heat and stir for 2 hours.

[0031] Open the discharge control valve 131, intake control valve 141, and reflux control valve 71. Nitrogen in the nitrogen buffer tank 8 enters the refining tank 1 through the reflux pipe 7, circulating fan 9, intake pipe 142, and nitrogen inlet 14. The nitrogen pressure in the refining tank 1 is maintained at 0.4 MPa. Nitrogen and liquid pass through the sintering mesh 3 and enter the condenser 4, while solids remain on top of the sintering mesh 3. The liquid in the condenser 4 flows into the recovery tank. The nitrogen in the condenser 4 enters the nitrogen buffer tank 8. The nitrogen in the nitrogen buffer tank 8 flows back to the refining tank 1 through the reflux pipe 7, circulating fan 9, intake pipe 142, and nitrogen inlet 14. The nitrogen continues to circulate until the liquid is completely drained. The nitrogen in the circulation pipeline is stored in the nitrogen buffer tank 8.

[0032] Close the discharge control valve 131 and the intake control valve 141, and add pure water into the refining tank 1 through the feed inlet 11. The mass ratio of pentaerythritol dicyclic sulfate crude product to pure water is 1:3. Continue to circulate 50 ppm of pure water through the jacket layer. o C water, heat and stir for 3 hours.

[0033] Open the discharge control valve 131, intake control valve 141, and reflux control valve 71. Nitrogen in the nitrogen buffer tank 8 enters the refining tank 1 through the reflux pipe 7, circulating fan 9, intake pipe 142, and nitrogen inlet 14. The nitrogen pressure in the refining tank 1 is maintained at 0.4 MPa. Nitrogen and liquid pass through the sintering mesh 3 and enter the condenser 4, while solids remain on top of the sintering mesh 3. The liquid in the condenser 4 flows into the recovery tank. The nitrogen in the condenser 4 enters the nitrogen buffer tank 8. The nitrogen in the nitrogen buffer tank 8 flows back to the refining tank 1 through the reflux pipe 7, circulating fan 9, intake pipe 142, and nitrogen inlet 14. The nitrogen continues to circulate until the liquid is completely drained. The nitrogen in the circulation pipeline is stored in the nitrogen buffer tank 8.

[0034] With the reflux control valve 71 closed and the heating control valve 61 opened, the nitrogen in the nitrogen buffer tank 8 is heated to 110°C by the nitrogen heater 6. o C, then enters the refining tank 1 through the circulating fan 9, inlet pipe 142, and nitrogen inlet 14, where the pressure is maintained at 0.1 MPa. Nitrogen continuously circulates and stirs. During stirring, the solid is dried by high-temperature nitrogen, which carries residual solvent, acid, and moisture to condenser 4 for condensation. The liquid produced in condenser 4 enters the recovery tank 5, and the nitrogen in condenser 4 is heated to 110°C through nitrogen buffer tank 8 and nitrogen heater 6. o C, and then flows back to the refining tank 1 through the circulating fan 9, the air inlet pipe 142, and the nitrogen inlet 14, thus continuously circulating.

[0035] After drying, the discharge port 12 is opened, and the solid is pushed to the discharge port 12 for output under the rotation of the S-shaped scraper 24, thus obtaining the pentaerythritol dicyclic sulfate product.

[0036] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 99.5%, a moisture content of 61 ppm, an acid value (based on HF) of 101 ppm, and a final purification yield of 94.8%.

[0037] Example 2: The only difference between this example and Example 1 is that the temperature of the heating medium introduced into the jacket layer is 60°C. o C, the mass ratio of acetic acid to water is 1:9, the mass ratio of crude pentaerythritol bicyclic sulfate to ethanol is 1:2, and the mass ratio of crude pentaerythritol bicyclic sulfate to pure water is 1:2.

[0038] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 99.7%, a water content of 43 ppm, an acid value (based on HF) of 65 ppm, and a final purification yield of 98.7%.

[0039] Example 3: The only difference between this example and Example 2 is that the mass ratio of acetic acid to water is 1:15.

[0040] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 99.1%, a water content of 60 ppm, an acid value (based on HF) of 88 ppm, and a final purified yield of 98.4%.

[0041] Example 4: The only difference between this example and Example 1 is that the temperature of the heat transfer medium introduced into the jacket layer is 80°C. o C.

[0042] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 90.4%, a water content of 153 ppm, an acid value (based on HF) of 248 ppm, and a final purified yield of 80.4%.

[0043] Example 5: The only difference between this example and Example 2 is that the mass ratio of crude pentaerythritol bicyclic sulfate to the weak acid aqueous solution is 1:2.

[0044] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 97.6%, a water content of 67 ppm, an acid value (based on HF) of 83 ppm, and a final purification yield of 98.8%.

[0045] Example 6: The only difference between this example and Example 2 is that the temperature of the heat transfer medium introduced into the jacket layer is 30°C. o C.

[0046] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 94.5%, a water content of 114 ppm, an acid value (based on HF) of 104 ppm, and a final purification yield of 98.5%.

[0047] Example 7: The only difference between this example and Example 2 is that the mass ratio of crude pentaerythritol bicyclic sulfate to ethanol is 1:4.

[0048] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 99.7%, a water content of 71 ppm, an acid value (based on HF) of 68 ppm, and a final purification yield of 96.8%.

[0049] Example 8: The only difference between this example and Example 2 is that the mass ratio of crude pentaerythritol bicyclic sulfate to pure water is 1:5.

[0050] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 99.7%, a water content of 89 ppm, an acid value (based on HF) of 58 ppm, and a final purification yield of 97.3%.

[0051] Example 9: The only difference between this example and Example 2 is that the washing time with the weak acid aqueous solution is 4 hours.

[0052] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 99.6%, a water content of 63 ppm, an acid value (based on HF) of 97 ppm, and a final purification yield of 95.1%.

[0053] Example 10: The only difference between this example and Example 2 is that the weak acid used is carbonic acid.

[0054] Gas chromatography analysis showed that pentaerythritol bicyclic sulfate had a purity of 99.5%, a water content of 66 ppm, an acid value (based on HF) of 95 ppm, and a final purification yield of 98.5%.

[0055] As can be seen from the above embodiments, this invention provides a purification method for pentaerythritol bicyclic sulfate. Multiple solvent washing is used in a single purification tank to effectively remove impurities from the crude product, achieving integrated purification, filtration, and drying. This method is convenient and fast, significantly improving purification efficiency and product quality, resulting in a product with low acid value, low moisture content, high purity, and high purification yield. Pressurized nitrogen circulation enhances material filtration, and heated nitrogen is used to dry the solids in the tank, removing residual solvents, acids, and moisture, reducing the risk of product hydrolysis, thereby greatly improving purification yield and purity, making it suitable for industrial production.

Claims

1. A method for purifying pentaerythritol bicyclic sulfate, characterized in that: The refining device includes: a refining tank with a temperature control mechanism; an openable and closable inlet on the refining tank; an openable and closable outlet on the side wall at the lower end of the refining tank; a discharge pipe with a discharge control valve at the bottom of the refining tank; a stirring mechanism inside the refining tank; a sintering mesh inside the refining tank; the stirring mechanism located above the sintering mesh; the outlet located on one side of the top of the sintering mesh; a nitrogen inlet with an air intake control valve on the refining tank; and a scraping mechanism inside the refining tank that scrapes the material toward the outlet. The refining process includes:

1. Add the crude pentaerythritol dicyclic sulfate to be refined and a weak acid aqueous solution into the refining tank through the feed inlet; heat the material in the refining tank through the temperature control mechanism, stir through the stirring mechanism, and wash the crude pentaerythritol dicyclic sulfate with the weak acid aqueous solution. After washing, perform the filtration separation step. The filtration and separation steps include: opening the inlet control valve, introducing room temperature nitrogen from the nitrogen inlet, maintaining positive pressure in the refining tank, opening the discharge control valve, separating the liquid and solid through the sintering mesh, discharging the filtrate and gas from the discharge pipe, and retaining the solid on the sintering mesh, and then closing the inlet control valve and the discharge control valve.

2. Add ethanol into the refining tank through the feed inlet, heat and stir, and wash the solid particles with ethanol. After washing, perform the above-mentioned filtration and separation steps to discharge the ethanol.

3. Add pure water into the refining tank through the feed inlet, heat and stir, and wash the solid with pure water. After washing, perform the above-mentioned filtration and separation steps to drain the water.

4. Open the intake control valve to introduce high-temperature nitrogen gas, and open the exhaust control valve. The high-temperature nitrogen gas will carry away the residual solvent and moisture and be discharged from the exhaust pipe to complete the drying process.

5. A scraping mechanism is used to continuously scrape the dried material to the discharge port for discharge.

2. The purification method for pentaerythritol bicyclic sulfate according to claim 1, characterized in that: The discharge pipe is connected to the condenser, the condenser's drain port is connected to the recovery tank, the condenser's exhaust port is connected to a nitrogen buffer tank, the nitrogen buffer tank is connected to a nitrogen heater and a reflux pipe, the nitrogen buffer tank is equipped with a nitrogen input pipe connected to a nitrogen source, the nitrogen heater's input end is equipped with a heating control valve, and the reflux pipe's input end is equipped with a reflux control valve; the output ends of the nitrogen heater and the reflux pipe are both connected to a circulating fan, and the circulating fan's outlet is connected to an intake control valve on the nitrogen inlet through an intake pipe, the nitrogen inlet being located at the top of the refining tank.

3. The purification method for pentaerythritol bicyclic sulfate according to claim 2, characterized in that: The filtration and separation steps include: opening the discharge control valve, the reflux control valve, and the inlet control valve; nitrogen in the nitrogen buffer tank enters the refining tank through the reflux pipe, the circulating fan, the inlet pipe, and the nitrogen inlet; the nitrogen pressure in the refining tank is maintained at 0.4 MPa; nitrogen and liquid pass through the sintering mesh and enter the condenser; solids remain on top of the sintering mesh; liquid in the condenser flows into the recovery tank; nitrogen in the condenser enters the nitrogen buffer tank; nitrogen in the nitrogen buffer tank returns to the refining tank through the reflux pipe, the circulating fan, the inlet pipe, and the nitrogen inlet; this cycle continues until the liquid is completely drained; and nitrogen in the circulation pipeline is stored in the nitrogen buffer tank.

4. The purification method for pentaerythritol bicyclic sulfate according to claim 2, characterized in that: In the fourth refining step, the temperature of the high-temperature nitrogen is 110℃, and the nitrogen pressure is maintained at 0.1 MPa. The nitrogen in the nitrogen buffer tank enters the refining tank through the nitrogen heater, circulating fan, air inlet pipe, and nitrogen inlet. The nitrogen and liquid pass through the sintering mesh and enter the condenser, while the solid remains on top of the sintering mesh. The liquid in the condenser flows into the recovery tank, and the nitrogen in the condenser enters the nitrogen buffer tank. The nitrogen in the nitrogen buffer tank flows back into the refining tank through the nitrogen heater, circulating fan, air inlet pipe, and nitrogen inlet, continuously circulating until drying is complete.

5. The purification method for pentaerythritol bicyclic sulfate according to claim 1, characterized in that: The stirring mechanism includes: a stirring shaft installed inside the refining tank, a stirring paddle installed on the stirring shaft, the upper end of the stirring shaft extending out of the refining tank, the upper end of the stirring shaft being driven by an explosion-proof motor, under the drive of the explosion-proof motor the stirring shaft can rotate inside the refining tank; the scraping mechanism includes: an S-shaped scraper installed at the bottom of the stirring shaft, the S-shaped scraper being located at the top of the sintering mesh, the scraper being able to scrape the material on the top of the sintering mesh toward the discharge port.

6. The purification method for pentaerythritol bicyclic sulfate according to claim 1, characterized in that: The structure of the temperature control mechanism includes: the tank body of the refining tank adopts a jacketed structure, and the refining tank is provided with a heat source inlet and a heat source outlet that are connected to the inside of the jacketed layer. The heat source inlet is located at the lower end of the refining tank, and the heat source outlet is located at the upper end of the refining tank. The heating medium enters the jacketed layer from the heat source inlet and then flows out from the heat source outlet.

7. The purification method for pentaerythritol bicyclic sulfate according to claim 6, characterized in that: In the first, second, and third refining steps, the temperature of the heating medium inside the jacket layer is maintained at 30℃~60℃.

8. The purification method for pentaerythritol bicyclic sulfate according to claim 1, characterized in that: The pore size of the sintered mesh in the sintered mesh is 1 to 20 μm.

9. The purification method for pentaerythritol bicyclic sulfate according to claim 1, characterized in that: In the first step of refining, the weak acid in the weak acid aqueous solution is carbonic acid or acetic acid, and the mass ratio of the weak acid to water in the weak acid aqueous solution is 1:5 to 15. The mass ratio of the crude pentaerythritol bicyclic sulfate to the weak acid aqueous solution is 1:2 to 5, and the washing time is 2 to 4 hours.

10. The purification method for pentaerythritol bicyclic sulfate according to claim 1, characterized in that: In the second refining step, the mass ratio of crude pentaerythritol bicyclic sulfate to ethanol is 1:1 to 4.

11. The purification method for pentaerythritol bicyclic sulfate according to claim 1, characterized in that: In the third refining step, the mass ratio of crude pentaerythritol bicyclic sulfate to pure water is 1:1 to 5.

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