Negative pressure purification method and device for electronic grade triethyl phosphate

Abstract

The invention discloses a negative pressure purification method and device for electronic grade triethyl phosphate, and the method comprises the following steps: S1, carrying out pretest on an equipment main body, a vacuum system, a heat conduction oil system, a cooling system and an instrument control instrument, and ensuring that all test indexes meet requirements; s2, opening a vacuum pump to vacuumize the vacuum buffer tank with condensation; meanwhile, refrigerant circulation of the vacuum condenser is started; s3, the raw materials are conveyed to the light component removal tower through a raw material feeding pump and a raw material feeding flow meter for controlling the feeding flow; s4, light component removal by a light component removal tower: when the content of light components at the bottom of a sample detection tower meets the requirements, conveying materials at the bottom of the light component removal tower to the heavy component removal tower through a heavy component removal tower feeding pump; s5, de-weighting by a de-weighting tower, and conveying the material to a product tank when the sampling is qualified; and S6, filtering to obtain an electronic-grade TEPO product. The boiling point of TEPO is reduced through negative pressure, and high-temperature decomposition is avoided; equipment is simplified through two-stage rectification (light component removal and heavy component removal); impurity introduction and material loss are reduced through nitrogen protection and vacuum condensation.

Description

Technical Field

[0001] This invention belongs to the field of electronic-grade triethyl phosphate production technology, specifically relating to a negative pressure purification process and dedicated equipment for electronic-grade triethyl phosphate (TEPO) used as a semiconductor BPSG thin film precursor. It is suitable for the purification and upgrading of industrial-grade TEPO to electronic-grade (purity ≥99.99%), and particularly relates to a negative pressure purification method and equipment for electronic-grade triethyl phosphate. Background Technology

[0002] In semiconductor manufacturing, borosilicate glass (BPSG) serves as both a pre-metal dielectric (PMD) and an inter-metal dielectric (MD), and its via-filling capability and planarization performance directly impact chip yield. The mainstream fabrication process for BPSG films is sub-atmospheric chemical vapor deposition (SACVD), and triethyl phosphate (TEPO) is the core precursor in SACVD, requiring extremely high purity (≥99.99%). Impurities (such as ethanol, diethyl phosphite, and diethyl butoxyphosphate) can increase the defect rate of BPSG films. Therefore, the purification technology of electronic-grade TEPO is a crucial step in the localization of semiconductor materials.

[0003] The existing technology has the following core problems:

[0004] Insufficient raw material purity and low localization rate: The purity of domestic industrial-grade TEPO (GB / T33106-2016) is only ≥99.5%, which cannot meet the needs of semiconductors; only two domestic companies, Guizhou Weidun Crystal Phosphorus and Apek, can produce electronic-grade TEPO, and the market mainly relies on foreign companies such as Versum Materials and Entegris, which restricts the localization of chips.

[0005] Existing purification processes have drawbacks: The published patent CN116251535 adopts a route of "first-stage distillation + extraction + second-stage distillation + third-stage distillation", which requires three distillation columns. The equipment cost is high (30% to 40% higher than that of this invention) and the operation is complex. Moreover, it does not solve the problem of high-temperature decomposition of TEPO. TEPO has a normal boiling point of 215℃, but it will decompose into diethyl phosphate at ≥200℃ (which is difficult to separate from TEPO). The bottom of the column will also generate viscous polyphosphoric acid, which will cause pipeline blockage, equipment shutdown and cleaning, and affect continuous production.

[0006] Risks of material loss and impurity introduction: The existing process does not use vacuum condensation recovery, and light components are easily discharged with the vacuum pump during negative pressure distillation, with a material loss rate of ≥3%; in addition, the raw material transportation is not isolated from air, which can easily introduce moisture (moisture ≥50ppm), affecting the insulation performance of the product.

[0007] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a negative pressure purification method and apparatus for electronic-grade triethyl phosphate. Summary of the Invention

[0008] The purpose of this invention is to provide a negative pressure purification method and apparatus for electronic-grade triethyl phosphate.

[0009] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0010] The negative pressure purification method for electronic-grade triethyl phosphate includes the following steps:

[0011] S1: Conduct pre-testing of the main body of the purification unit, vacuum system, heat transfer oil system, cooling system and instrumentation to ensure that all test indicators meet the requirements;

[0012] S2: Turn on the vacuum pump to evacuate the vacuum buffer tank with condenser, and control the pressure inside the tank to ≤-0.1MPa; at the same time, start the refrigerant circulation of the vacuum condenser to stabilize the refrigerant temperature at -20℃~-30℃.

[0013] S3: The raw material is transported to the light-weight material removal tower by means of a raw material feed pump and a raw material feed flow meter, with the feed flow rate controlled at 0.6-0.9 kg / h;

[0014] S4: When the liquid level in the bottom of the light component removal tower reaches 1 / 3 to 2 / 3, stabilize the vacuum in the tower at -0.085 to -0.095 MPa; heat the bottom of the tower to maintain the temperature at 126 to 150℃; control the temperature of the top condenser at 60 to 80℃; after total reflux for 12 to 24 hours, take a sample to test the content of light components at the bottom of the tower. When the requirements are met, use the feed pump of the heavy component removal tower to transport the bottom material of the light component removal tower to the heavy component removal tower.

[0015] S5: When the liquid level in the bottom of the deweighting tower reaches 1 / 3 to 2 / 3, stabilize the vacuum degree in the tower at -0.085 to -0.095 MPa; maintain the bottom temperature at 126 to 150℃; control the temperature of the top condenser at 60 to 80℃; after total reflux for 12 to 24 hours, take samples to test the triethyl phosphate content. When the content is ≥99.99%, moisture <20ppm, chloride ion <50ppb, and metal ion impurity content is less than 0.0000005%, reflux and control the outflow rate according to the reflux ratio to transport the material to the product tank;

[0016] S6: Stop feeding when the liquid level in the product tank reaches 2 / 3 to 3 / 4, open the product circulation pipeline, and circulate the product through the circulation filter until the particle size of the product meets the requirements; finally, perform nitrogen protection filling to obtain electronic grade TEPO product.

[0017] Preferably, the negative pressure purification method for electronic-grade triethyl phosphate may specifically include the following steps:

[0018] S1: Conduct pre-testing of the main body of the purification unit, vacuum system, heat transfer oil system, cooling system, and instrumentation to ensure that all test indicators meet the requirements (air tightness: pressure drop ≤ 0.001 MPa after pressurizing to 0.6 MPa and holding for 12 hours; vacuum degree: pressure rise ≤ 0.002 MPa after evacuating to -0.1 MPa and holding for 12 hours; instrument accuracy ±0.5%).

[0019] S2: Turn on the vacuum pump to evacuate the vacuum buffer tank with condenser, and control the pressure inside the tank to ≤-0.1MPa; at the same time, start the refrigerant circulation of the vacuum condenser to stabilize the refrigerant temperature at -20℃~-30℃.

[0020] S3: Introduce 0.05–0.1 bar of nitrogen gas into the sealed raw material container containing industrial-grade TEPO (purity ≥99.5%) through the gas phase port of the raw material injector to maintain a slight positive pressure inside the container to isolate air and moisture; open the vent valve of the raw material container to prevent overpressure, and transport the raw material to the light-weight removal tower by means of a raw material feed pump (corrosion-resistant diaphragm pump) and a raw material feed flow meter (high-precision electromagnetic flow meter, accuracy ±0.5%FS) with the feed flow rate controlled at 0.6–0.9 kg / h;

[0021] S4: When the liquid level in the bottom of the light component removal tower reaches 1 / 3 to 2 / 3, stabilize the vacuum in the tower at -0.085 to -0.095 MPa using the light component removal tower pressure controller; turn on the first heat engine (heat transfer oil heater, temperature control accuracy ±1℃) to heat the tower bottom, maintaining the tower bottom temperature at 126 to 150℃; turn on the first integrated cooling and heating unit at the top of the light component removal tower (temperature control accuracy ±2℃) to control the temperature of the top condenser at 60 to 80℃; after 12-24 hours of total reflux, take samples to test the content of light components (ethanol, water, diethyl phosphite) at the bottom of the tower. When the requirements of ethanol ≤10ppm, water ≤15ppm, and diethyl phosphite ≤5ppm are met, transport the material from the bottom of the light component removal tower to the heavy component removal tower using the feed pump of the heavy component removal tower.

[0022] S5: When the liquid level in the bottom of the deweighting tower reaches 1 / 3 to 2 / 3, stabilize the vacuum in the tower at -0.085 to -0.095 MPa using the deweighting tower pressure controller; turn on the second heat engine to heat the bottom of the tower and maintain the bottom temperature at 126 to 150°C; turn on the second integrated cooling and heating unit at the top of the deweighting tower and control the temperature of the condenser at the top of the tower at 60 to 80°C; after total reflux for 12-24 hours, take a sample to test the content of the heavy component butoxydiethyl phosphate at the top of the tower. When the content of triethyl phosphate is ≥99.99%, moisture is <20 ppm, chloride ion is <50 ppb, and the content of metal ion impurities is less than 0.0000005%, reflux is started and the outflow rate is controlled according to the reflux ratio to transport the material to the product tank;

[0023] S6: Stop feeding when the liquid level in the product tank reaches 2 / 3 to 3 / 4, open the product circulation pipeline, and circulate the product through the circulation filter (filtration accuracy 0.1μm) until the particle size of the product meets the requirements; finally, perform nitrogen protection filling to obtain electronic grade TEPO product.

[0024] In one or more embodiments of the present invention, the pre-test in step S1 is selected from air tightness test and / or vacuum pressure holding test and / or heat transfer oil circulation smoothness test and / or cooling system cooling rate test and / or instrument and control accuracy calibration test.

[0025] In one or more embodiments of the present invention, the pre-test criteria in step S1 include:

[0026] Air tightness test: The system is pressurized to 0.6 MPa and held for 12 hours; the pressure drop is ≤0.001 MPa; and / or

[0027] Vacuum pressure holding test: The system is evacuated to -0.1MPa and held for 12 hours; the pressure rise is ≤0.002MPa; and / or

[0028] Heat transfer oil circulation smoothness test: The heat transfer oil circulation flow rate reaches the design value of 5-10 L / min, with no blockage, and the circulation flow rate fluctuation is ≤±5%; and / or

[0029] Cooling system cooling rate test: time to drop from room temperature to -30℃ ≤ 30min, cooling rate ≥ 5℃ / min; and / or

[0030] Instrument and control accuracy calibration test: pressure gauge accuracy ±0.001MPa, thermometer accuracy ±0.5℃, flow meter accuracy ±0.5%FS.

[0031] In one or more embodiments of the present invention, the reflux ratio during reflux in step S3 is 80:4 to 100:4.

[0032] In one or more embodiments of the present invention, the reflux ratio in step S3 is 80:4, at which point the product purity (≥99.995%) and the output (≥0.75Kg / h) reach equilibrium.

[0033] In one or more embodiments of the present invention, the raw material is fed in step S3 under inert gas protection. The inert gas can be nitrogen, argon, helium, etc.

[0034] In one or more embodiments of the present invention, the raw material feed flow rate is 0.8 kg / h during step S3, at which point the device capacity and product purity reach a balance.

[0035] In one or more embodiments of the present invention, the vacuum degree inside the column in step S4 and / or S5 is -0.095 MPa, and the temperature of the column bottom is 126°C. Preferably, the vacuum degree inside the column in steps S4 and S5 is -0.095 MPa, and the temperature of the column bottom is 126°C, at which point the TEPO decomposition rate is ≤0.01%.

[0036] In one or more embodiments of the present invention, the electronic-grade triethyl phosphate negative pressure purification device for implementing the method includes a raw material supply unit, a light distillation unit, a heavy distillation unit, a vacuum condensation unit, and a product processing unit.

[0037] Compared with existing technologies, the electronic-grade triethyl phosphate (TEPO) negative pressure purification method and apparatus of the present invention uses negative pressure control to lower the boiling point of TEPO to 126-150°C, combined with precise pressure / temperature control and vacuum condensation recovery, to finally obtain electronic-grade TEPO with a purity ≥99.99%, impurities meeting standards, and particle size meeting requirements. Compared with existing technologies, this process reduces equipment costs by 30%-40%, energy consumption by 20%-25%, and material loss rate ≤0.5%, making it suitable for the large-scale production of semiconductor BPSG thin film precursors. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the negative pressure purification process of electronic-grade triethyl phosphate in one embodiment of the present invention;

[0040] Figure 2 This is a graph showing the detection data of the sample after negative pressure purification of electronic-grade triethyl phosphate in Example 1 of the present invention, where the metal ion impurity content is in ppb.

[0041] Explanation of key figure labels:

[0042] 1-Sealed raw material tank, 2-Raw material injector, 3-Raw material feed pump, 4-Raw material feed flow meter, 5-Light weight removal tower, 6-Light weight removal tower pressure controller, 7-First heat engine, 8-First integrated heating and cooling unit, 9-Heavy weight removal tower feed pump, 10-Heavy weight removal tower feed flow meter, 11-Heavy weight removal tower, 12-Heavy weight removal tower pressure controller, 13-Second heat engine, 14-Second integrated heating and cooling unit, 15-Vacuum buffer tank with condensation, 16-Vacuum pump, 17-Product tank, 18-Circulation filter. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments disclosed herein. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0044] The implementation of this invention mainly employs the following equipment configuration, and all of the following embodiments can be adopted:

[0045] The raw material supply unit includes a sealed raw material tank (volume 500-1000L), a raw material injector, a raw material feed pump (corrosion-resistant diaphragm pump, flow rate 0.5-1.0Kg / h), and a raw material feed flow meter (electromagnetic type, accuracy ±0.5%FS). The gas phase port of the raw material injector is connected to a nitrogen source (purity ≥99.999%), and the liquid phase port is connected in sequence to the raw material feed pump and the raw material feed flow meter before being connected to the light weight removal tower.

[0046] The light-weight distillation unit includes a light-weight removal column (packed column, inner diameter 50-100mm, packing height 2-3m, packing is stainless steel corrugated packing), a light-weight removal column pressure controller (accuracy ±0.001MPa), a first heat engine (thermal oil heater, power 5-10kW), and a first integrated heating and cooling unit (cooling capacity 3-5kW). A condenser (heat exchange area 0.5-1.0㎡) is installed at the top of the light-weight removal column, and a first pressure gauge and a first thermometer are installed at the bottom of the column. The heavy-weight distillation unit includes a heavy-weight removal column (structure same as the light-weight removal column), a heavy-weight removal column pressure controller (accuracy ±0.001MPa), a second heat engine (same as the first heat engine), and a second integrated heating and cooling unit (same as the first integrated heating and cooling unit). The bottom of the light-weight removal column is connected to the heavy-weight removal column through a heavy-weight removal column feed pump (same as the raw material feed pump) and a heavy-weight removal column feed flow meter (same as the raw material feed flow meter). A condenser (same as the light-weight removal column) is installed at the top of the heavy-weight removal column, and a second pressure gauge and a second thermometer are installed at the bottom of the column.

[0047] The vacuum condensation unit includes a vacuum buffer tank with condensation (volume 0.5-1m³) and a vacuum pump (rotary vane vacuum pump, pumping speed 5-10L / s). The buffer tank is equipped with a vacuum condenser (heat exchange area 0.3-0.5m²), and the vacuum condenser is connected to a refrigerant system (ethylene glycol aqueous solution, temperature -20℃ to -30℃).

[0048] The product processing unit includes a product tank (volume 200-500L, stainless steel) and a circulation filter (filter element precision 0.1μm, flow rate 1-2L / min), with the circulation filter located on the circulation pipeline of the product tank.

[0049] Example 1

[0050] Equipment: The aforementioned apparatus is used, wherein: the inner diameter of the light / heavy removal tower is 80mm, the packing height is 2.5m; the raw material tank volume is 800L; and the vacuum pump pumping speed is 8L / s.

[0051] Raw materials: Industrial grade TEPO, purity 99.5%, impurity content: ethanol 500ppm, diethyl phosphite 300ppm, diethyl butoxyphosphate 200ppm, moisture 100ppm;

[0052] Process parameters:

[0053] S3: Feed flow rate 0.8 kg / h, nitrogen pressure 0.08 bar;

[0054] S4: Vacuum degree of light component removal tower -0.095MPa, tower bottom temperature 126℃, condenser temperature 70℃, total reflux for 24h;

[0055] S5: Vacuum degree of the deweight removal tower -0.095MPa, tower bottom temperature 126℃, condenser temperature 70℃, reflux ratio 80:4, total reflux 24h;

[0056] S6: Circulating filter for 3 hours;

[0057] Test results:

[0058] Product purity: 99.9962% (gas chromatography, detection accuracy ±0.0005%).

[0059] Impurity content: ethanol 3.2 ppm, diethyl phosphite 2.1 ppm, diethyl butoxyphosphate 1.8 ppm, water 8.5 ppm;

[0060] After 72 hours of continuous operation: tower pressure fluctuation ±0.001MPa, temperature fluctuation ±0.5℃, and no decomposition products were generated.

[0061] Example 2

[0062] The only difference from Example 1 is that the reflux ratio in S5 is 100:2;

[0063] Test results:

[0064] Product purity: 99.9985%;

[0065] Production rate: 0.55 kg / h;

[0066] Conclusion: A high reflux ratio improves purity but reduces output, making it suitable for scenarios requiring high purity.

[0067] Example 3

[0068] The only difference from Example 1 is that the vacuum degree in S4 and S5 is -0.085MPa and the reboiler temperature is 150°C.

[0069] Test results:

[0070] Product purity: 99.9921%;

[0071] Production rate: 0.78 kg / h;

[0072] Conclusion: Lower negative pressure increases production output, but purity decreases slightly, making it suitable for production-priority scenarios.

[0073] Example 4

[0074] The only difference from Example 1 is that the reflux ratio in S5 is 100:4;

[0075] Test results:

[0076] Product purity: 99.9975%;

[0077] Extraction rate: 0.45 kg / h;

[0078] Conclusion: A high reflux ratio improves purity but reduces output, making it suitable for scenarios requiring high purity.

[0079] Example 5

[0080] The only difference from Example 1 is that the feed flow rate is 0.6 kg / h;

[0081] Test results:

[0082] Product purity: 99.9977%;

[0083] Extraction rate: 0.33 kg / h;

[0084] Conclusion: Reducing the feed rate can improve purity, but it significantly reduces the output.

[0085] Example 6

[0086] The only difference from Example 1 is that the feed flow rate is 0.9 kg / h;

[0087] Test results:

[0088] Product purity: 99.9940%;

[0089] Production rate: 0.48 kg / h;

[0090] Conclusion: Increasing the feed rate affects purity, but significantly improves the output.

[0091] Comparative Example 1

[0092] Equipment: 3 distillation columns (same structure as the light-light product removal column in Example 1) + extraction column;

[0093] Raw materials: Same as in Example 1;

[0094] Process: First-stage distillation (atmospheric pressure, bottom of column 210℃) → Extraction (water as extractant) → Second-stage distillation (negative pressure -0.08MPa, 180℃) → Third-stage distillation (negative pressure -0.09MPa, 160℃).

[0095] Test results:

[0096] Product purity: 99.9915%;

[0097] Equipment cost: 35% higher than Example 1;

[0098] Unit energy consumption: 22% higher than Example 1;

[0099] Processing time: 18% longer than Example 1.

[0100] Comparative Example 2

[0101] Difference from Example 1: The vacuum buffer tank with condensation is removed, and the vacuum pump is directly connected to the light-weight removal tower / heavy-weight removal tower;

[0102] Test results:

[0103] Material loss rate: 3.2% (0.4% in Example 1);

[0104] Product purity: 99.9908% (loss of light components leads to decreased separation efficiency).

[0105] Comparative Example 3

[0106] Difference from Example 1: In S3, nitrogen is not introduced into the raw material tank; the material is fed directly.

[0107] Test results:

[0108] Product moisture content: 52.3 ppm (8.5 ppm in Example 1);

[0109] Product insulation resistance: 15% lower than Example 1 (moisture caused a decrease in insulation performance).

[0110] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0111] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A negative pressure purification method for electronic-grade triethyl phosphate, comprising the following steps: S1: Conduct pre-testing of the main body of the purification unit, vacuum system, heat transfer oil system, cooling system and instrumentation to ensure that all test indicators meet the requirements; S2: Turn on the vacuum pump to evacuate the vacuum buffer tank with condenser, and control the pressure inside the tank to ≤-0.1MPa; at the same time, start the refrigerant circulation of the vacuum condenser to stabilize the refrigerant temperature at -20℃~-30℃. S3: The raw material is transported to the light-weight material removal tower by means of a raw material feed pump and a raw material feed flow meter, with the feed flow rate controlled at 0.6-0.9 kg / h; S4: When the liquid level in the bottom of the light component removal tower reaches 1 / 3 to 2 / 3, stabilize the vacuum in the tower at -0.085 to -0.095 MPa; heat the bottom of the tower to maintain the temperature at 126 to 150℃; control the temperature of the top condenser at 60 to 80℃; after total reflux for 12 to 24 hours, take a sample to test the content of light components at the bottom of the tower. When the requirements are met, use the feed pump of the heavy component removal tower to transport the bottom material of the light component removal tower to the heavy component removal tower. S5: When the liquid level in the bottom of the deweighting tower reaches 1 / 3 to 2 / 3, stabilize the vacuum degree in the tower at -0.085 to -0.095 MPa; maintain the bottom temperature at 126 to 150℃; control the temperature of the top condenser at 60 to 80℃; after total reflux for 12 to 24 hours, take samples to test the triethyl phosphate content ≥99.99%, moisture <20ppm, chloride ion <50ppb, and metal ion impurity content <0.0000005%. Reflux the material and control the outflow rate according to the reflux ratio to transport the material to the product tank. S6: Stop feeding when the liquid level in the product tank reaches 2 / 3 to 3 / 4, open the product circulation pipeline, and circulate the product through the circulation filter until the particle size of the product meets the requirements; finally, perform nitrogen protection filling to obtain electronic grade TEPO product.

2. The method according to claim 1, characterized in that, The pre-tests mentioned in step S1 are selected from air tightness test and / or vacuum pressure holding test and / or heat transfer oil circulation smoothness test and / or cooling system cooling rate test and / or instrument and control accuracy calibration test.

3. The method according to claim 2, characterized in that, The pre-test criteria mentioned in step S1 include: Air tightness test: The system is pressurized to 0.6 MPa and held for 12 hours; the pressure drop is ≤0.001 MPa; and / or Vacuum pressure holding test: The system is evacuated to -0.1MPa and held for 12 hours; the pressure rise is ≤0.002MPa; and / or Heat transfer oil circulation smoothness test: The heat transfer oil circulation flow rate reaches the design value of 5-10 L / min, with no blockage, and the circulation flow rate fluctuation is ≤±5%; and / or Cooling system cooling rate test: time to drop from room temperature to -30℃ ≤ 30min, cooling rate ≥ 5℃ / min; and / or Instrument and control accuracy calibration test: pressure gauge accuracy ±0.001MPa, thermometer accuracy ±0.5℃, flow meter accuracy ±0.5%FS.

4. The method according to claim 1, characterized in that, The reflux ratio during reflux in step S3 is 80:4 to 100:

4.

5. The method according to claim 4, characterized in that, The reflux ratio mentioned in step S3 is 80:

4.

6. The method according to claim 1, characterized in that, In step S3, the raw material is fed in an inert gas for protection.

7. The method according to claim 6, characterized in that, In step S3, the raw material feed flow rate is 0.8 kg / h.

8. The method according to claim 1, characterized in that, The vacuum level inside the column in steps S4 and / or S5 is -0.095 MPa, and the temperature of the column bottom is 126°C.

9. An electronic-grade triethyl phosphate negative pressure purification apparatus for implementing the method of any one of claims 1 to 5, comprising a raw material supply unit, a light distillation unit, a heavy distillation unit, a vacuum condensation unit, and a product processing unit.

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