Adsorbent for removing metal impurities in octamethylcyclotetrasiloxane, preparation method thereof, and purification system and process

Abstract

The application provides an adsorbent for removing metal impurities in octamethylcyclotetrasiloxane, a preparation method of the adsorbent, and a purification system and process. The adsorbent takes activated silica gel as a carrier, and a catechol-type chelating functional group generated by the reaction of catechol with ethylenediamine and formaldehyde is grafted on the surface of the carrier. The adsorbent exhibits excellent adsorption capacity and selectivity to target metal ions. The preparation reaction condition of the adsorbent is mild, the repeatability is good, and the adsorbent is easy to produce on a large scale. The application also constructs an integrated octamethylcyclotetrasiloxane purification system. The system adopts a multi-stage series adsorption process, cooperates with inert atmosphere protection and online monitoring, and can stably remove Fe, Zn and other metal impurities in electronic-grade octamethylcyclotetrasiloxane to below 50 ppt at normal temperature and pressure, so as to meet the requirements of semiconductor and high-end silicone materials on the ultra-clean purity of raw materials.

Description

Technical Field

[0001] This invention relates to the field of purification technology for semiconductor organosilicon material precursors, and particularly to an adsorbent for removing metal impurities from octamethylcyclotetrasiloxane, its preparation method, purification system and process. Background Technology

[0002] Octamethylcyclotetrasiloxane has good electrical and thermal properties. In the semiconductor industry, it is used as a precursor for organosilicon materials to prepare semiconductor materials, optical fiber preforms, etc.

[0003] Electronic-grade octamethylcyclotetrasiloxane requires extremely high purity. In particular, trace metal impurities such as Fe, Zn, Na, Ca, and Cr can form deep-level defects even at very low concentrations, becoming carrier generation and recombination centers. This severely impacts device performance, significantly affecting the electrical performance and reliability of semiconductor devices, leading to increased leakage current, decreased oxide layer integrity, and a significant reduction in chip yield. Therefore, the metal impurity content of electronic-grade octamethylcyclotetrasiloxane must be strictly controlled at the ppt (parts per trillion) level.

[0004] my country has a wide range of sources for industrial-grade raw materials. Currently, processes for preparing high-purity octamethylcyclotetrasiloxane include batch distillation, complexation-distillation, crystallization-vacuum filtration, and metal removal agent purification. For example, Chinese patent CN103788124A, "A Purification Method for Electronic-Grade Octamethylcyclotetrasiloxane," uses 99% pure octamethylcyclotetrasiloxane as raw material. The process involves removing light components in a light component removal tower, adding the metal ligand tetramethoxyphenylphosphine to the reaction vessel of a heavy component removal tower, and then performing vacuum distillation under certain conditions. The resulting octamethylcyclotetrasiloxane has a purity of 99.99% and a metal impurity content of less than 5 ppb. This method produces high-quality products. However, it requires high equipment investment and the metal ligand is expensive, making industrial-scale production difficult. For example, Chinese patent CN111574551A, "Purification Process of Octamethylcyclotetrasiloxane," involves placing industrial octamethylcyclotetrasiloxane and an adsorbent into a distillation column, mixing them with a carrier gas, maintaining the column bottom temperature at approximately 170°C, and adsorbing for 1–10 hours. Through the adsorption reaction, metallic impurities in the octamethylcyclotetrasiloxane are removed. A first distillation purification separates the octamethylcyclotetrasiloxane from the adsorbent, removing organic impurities, water, and oxygen to obtain an intermediate product of octamethylcyclotetrasiloxane. A second distillation yields the high-purity product. This entire production process is energy-intensive, cumbersome, and unsuitable for mass production.

[0005] Existing methods have limited separation efficiency for specific metal impurities (such as certain organometallic compounds) with boiling points close to or capable of forming weak complexes with octamethylcyclotetrasiloxane. Often, even after multiple distillations, the metal impurity content still cannot stably meet the requirements of the most advanced semiconductor processes. Summary of the Invention

[0006] This invention provides an adsorbent for removing metal impurities from octamethylcyclotetrasiloxane, its preparation method, and purification system and process to overcome the above-mentioned technical problems.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] An adsorbent for removing metallic impurities from octamethylcyclotetrasiloxane, wherein the adsorbent uses porous silica gel as a carrier and its surface is grafted with catechol-type chelating functional groups generated by the reaction of catechol with ethylenediamine and formaldehyde.

[0009] Furthermore, the adsorbent has an average particle size of 80-180 μm and a specific surface area of ​​400-700 m² / g.

[0010] Furthermore, the present invention also provides a method for preparing the adsorbent for removing metal impurities from octamethylcyclotetrasiloxane, comprising the following steps:

[0011] Step 1: Activate the porous silica gel by soaking it in sulfuric acid solution, then wash it with ultrapure water until neutral, and dry it under vacuum to obtain activated silica gel;

[0012] Step 2: Disperse the activated silica gel in anhydrous toluene, add excess catechol, ethylenediamine and formaldehyde, and stir continuously at 110±5 °C for 6~36 hours under an inert atmosphere.

[0013] Step 3: After the reaction is complete, cool to room temperature, wash thoroughly, and vacuum dry to obtain the target adsorbent.

[0014] Furthermore, the total mass of the catechol, ethylenediamine, and formaldehyde accounts for 10% to 100% of the total mass of the activated silica gel; wherein the mass ratio of the catechol, ethylenediamine, and formaldehyde is (2-5):1:(2-5).

[0015] Furthermore, the thorough washing involves sequentially washing with methanol, ethanol, and ultrapure water.

[0016] Furthermore, the present invention also provides a purification system using the adsorbent for removing metal impurities from octamethylcyclotetrasiloxane, comprising the adsorbent for removing metal impurities from octamethylcyclotetrasiloxane.

[0017] Furthermore, the purification system also includes an adsorption tank, which has a raw material inlet, a third product outlet, a first gas inlet, a first gas outlet, a first vacuum port, a first stirrer, and a first adsorption material outlet.

[0018] A backup adsorption tank, wherein the backup adsorption tank has a third product inlet, a fourth product outlet, a second gas inlet, a second gas outlet, a second vacuum suction port, a second adsorption material outlet, and a second stirrer;

[0019] Among them, the third product outlet and the third product inlet are connected; the first vacuum negative port and the second vacuum negative port are connected;

[0020] A filter container having a first product outlet, a fourth product inlet, a third gas inlet, a third gas outlet, and a third vacuum port;

[0021] The fourth product inlet and the fourth product outlet are connected;

[0022] A premium product storage tank, comprising a second product outlet, a fifth product inlet, a fourth gas inlet, a fourth gas outlet, and a fourth vacuum port;

[0023] Among them, the fifth product inlet and the first product outlet are connected; the fourth vacuum negative port and the third vacuum negative port are connected; and the passages of the fourth vacuum negative port and the third vacuum negative port are respectively connected to the first vacuum negative port and the second vacuum negative port.

[0024] The sample collection port is connected at one end to the passage formed by the third product outlet and the third product inlet, and at the other end to the passage formed by the fourth product inlet and the fourth product outlet.

[0025] A vacuum pump, which is connected to a third vacuum negative port.

[0026] Furthermore, the purification system using an adsorbent to remove metal impurities from octamethylcyclotetrasiloxane also includes an online monitoring device integrated with the equipment, the online monitoring device being configured to monitor the content of metal impurities in the purified octamethylcyclotetrasiloxane in real time.

[0027] Furthermore, the online monitoring device is a miniaturized online detection module based on inductively coupled plasma mass spectrometry, and its sample inlet is sealed to the product outlet pipeline of the adsorption device.

[0028] Furthermore, both the adsorption tank and the standby adsorption tank are filled with the adsorbent.

[0029] Furthermore, the present invention also provides a purification method based on the purification system employing an adsorbent for removing metal impurities from octamethylcyclotetrasiloxane, comprising the following purification steps:

[0030] Step 1: Introduce high-purity nitrogen into the purification system to replace the oxygen atmosphere and ensure that the system is free of oxygen and water;

[0031] Step 2: The octamethylcyclotetrasiloxane raw material with a total metal impurity content of ppb is passed through an adsorption tank filled with the adsorbent and contacted at 20℃±5℃ for 12~14 hours.

[0032] Step 3: Use inductively coupled plasma mass spectrometry to analyze the Fe in the effluent. 3+ and Zn 2+ Content is monitored online;

[0033] Step 4: When Fe is detected 3+ or Zn 2+ When the content drops below 60 ppt, switch to the standby adsorption tank to continue adsorption; wait for Fe 3+ and Zn 2+ Once the content is below 20 ppt, the effluent is filtered through a precision filter, and the filtrate is collected to obtain electronic-grade octamethylcyclotetrasiloxane product.

[0034] Beneficial effects: 1. High selectivity: The catechol-functionalized adsorbent synthesized in this invention has high selectivity for Fe³⁺. + Zn² + Key metal ions have extremely strong chelating ability, enabling molecular-level recognition and capture, and can stably remove impurities to below 50 ppt, which is superior to traditional distillation and ordinary adsorbents.

[0035] 2. Low adsorption of main component: This adsorbent hardly adsorbs the main component of octamethylcyclotetrasiloxane, resulting in a high product yield and reduced product loss.

[0036] 3. No impurities are introduced: The preparation process is stable, the grafting rate is high, the functional groups are stable and not easy to fall off, and it will not cause secondary pollution to the octamethylcyclotetrasiloxane product.

[0037] 4. Enables industrialized production: The system provided by this invention can be directly connected to existing distillation systems as the final process, enabling continuous industrialized production. 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1This invention discloses an adsorbent for removing metal impurities from octamethylcyclotetrasiloxane, its preparation method, purification system, and a schematic diagram of the purification system in the process.

[0040] In the diagram: 1-Adsorption tank; 2-Spare adsorption tank; 3-Filter container; 4-Precipitated product storage tank; 5-Sample collection port; 6-Vacuum pump; 7-First adsorption material collection port; 8-Second adsorption material collection port; 9-First product outlet; 10-Second product outlet; 11-Raw material inlet; 12-Third product inlet; 13-Fourth product inlet; 14-Fifth product inlet; 15-Third product outlet; 16-Fourth product outlet; 17-First gas inlet; 18-Second gas inlet; 19-Third gas inlet; 20-Fourth gas inlet; 21-First gas outlet; 22-Second gas outlet; 23-Third gas outlet; 24-Fourth gas outlet; 25-First vacuum negative port; 26-Second vacuum negative port; 27-Third vacuum negative port; 28-Fourth vacuum negative port; 29-First stirrer; 30-Second stirrer. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] This embodiment provides an adsorbent for removing metallic impurities from octamethylcyclotetrasiloxane and its preparation method; the adsorbent uses activated silica gel as a carrier, and its surface is grafted with catechol-type chelating functional groups generated by the reaction of catechol with ethylenediamine and formaldehyde.

[0044] The adsorbent is prepared by the following method:

[0045] Step 1: Activate the porous silica gel by soaking it in sulfuric acid solution, then wash it with ultrapure water until neutral, and dry it under vacuum to obtain activated silica gel;

[0046] In this embodiment, 100g of porous silica gel with an average particle size of 80μm-120μm and a pore size of about 15nm was placed in 1L of 3% sulfuric acid solution and soaked and activated for 6 hours to obtain activated silica gel.

[0047] Step 2: Disperse the activated silica gel in anhydrous toluene, add catechol, ethylenediamine and formaldehyde, and stir continuously at 110±5 °C for 6 to 36 hours under an inert atmosphere; wherein the total amount of catechol, ethylenediamine and formaldehyde accounts for 10% to 100% of the total amount of activated silica gel, and the mass ratio of catechol, ethylenediamine and formaldehyde is (2-5):1:(2-5).

[0048] In this embodiment, 50g of activated silica gel was dispersed in 500mL of anhydrous toluene, and 12g of catechol (CAS: 120-80-9, manufacturer: Bailingwei Technology), 5g of ethylenediamine (CAS: 107-15-3, manufacturer: Nanjing Renheng Chemical Co., Ltd.), and 10g of formaldehyde (CAS: 50-00-0, manufacturer: Nantong Runfeng Petrochemical Co., Ltd.) were added in proportion. Under nitrogen protection, the mixture was continuously stirred at 110°C for 18 hours.

[0049] Step 3: After the reaction is complete, cool to room temperature, wash thoroughly, and vacuum dry to obtain the target adsorbent.

[0050] In this embodiment, after the reaction is completed, the mixture is cooled and washed 3 to 5 times each with methanol, ethanol, and ultrapure water, and then dried under vacuum at 100°C for 12 hours to obtain the target adsorbent A.

[0051] The functional group grafting capacity of adsorbent A was determined by titration to be 0.80 mmol / g.

[0052] In addition, unmodified commercial silicone was used as a control group.

[0053] Octamethylcyclotetrasiloxane raw material was used, with an Fe content of 924.85 ppb and a Zn content of 618.36 ppb. 20 g of adsorbent A and 20 g of ordinary commercial silica gel were weighed and added to 1000 ml of the above octamethylcyclotetrasiloxane raw material. The mixture was stirred at 20°C for 14 h for adsorption. The adsorbed octamethylcyclotetrasiloxane was then analyzed by ICP-MS.

[0054] The results are shown in Table 1:

[0055] Table 1: Comparison of Adsorption Performance

[0056]

[0057] The results show that the adsorbent prepared in this invention has a much higher adsorption capacity for target metal ions than ordinary silica gel.

[0058] Furthermore, to investigate the effect of functional group grafting amount on adsorption performance, following the preparation method of Example 1, four adsorbents with different grafting rates were prepared by changing the reaction time (6h, 12h, 18h, and 36h, respectively), and labeled as B1, B2, B3 (i.e., A in Example 1), and B4, respectively. Their grafting rates were determined by elemental analysis. Using the octamethylcyclotetrasiloxane raw material and testing method in Example 1, their effect on Fe³⁺ adsorption was determined. + The adsorption capacity of [the material] is shown in Table 2:

[0059] Table 2: Relationship between grafting rate and adsorption performance

[0060]

[0061] Conclusion: As shown in Table 2, the adsorbent has a good effect on Fe³⁺. + The adsorption capacity increases significantly with increasing grafting rate. When the reaction time reaches 18 hours and the grafting rate reaches 0.82 mmol / g, the adsorption capacity tends to saturate. Further extending the reaction time to 36 hours does not significantly increase either the grafting rate or the adsorption capacity. This indicates that the preferred reaction time range of the present invention is 12–36 hours, with the most preferred reaction time being 18 hours. At this time, high adsorption performance can be guaranteed while also considering production efficiency and economy. If the grafting rate is too low (e.g., B1), effective deep removal cannot be achieved.

[0062] Further, adsorbent A prepared in Example 1 was packed into a 1L round-bottom flask. Industrial-grade crude octamethylcyclotetrasiloxane (containing multiple metal ions such as Fe, Zn, Na, Ca, Cr, Ni, and Cu) was selected. Adsorption was carried out at 20 °C ± 0.5 °C for 14 hours with stirring. The metal ion content was analyzed by ICP-MS, and the removal rate of each metal ion was calculated. The results are shown in Table 3.

[0063] Table 3: Removal efficiency (%) for different metal ions

[0064]

[0065] Conclusion: As shown in Table 3, the adsorbent prepared in this invention is effective against transition metal ions, especially Fe³⁺. + Zn² + Cu² + Cr³ + Ni² + It exhibits extremely high removal rates (>99%), and is effective against alkali metal and alkaline earth metal ions (Na+). + Ca² +The removal rate of catechol is relatively low. This demonstrates that the catechol functional group has excellent selective adsorption capacity for transition metal ions that readily form stable complexes, precisely targeting the most lethal harmful metal impurities in semiconductor processes and achieving accurate removal.

[0066] Furthermore, the above-mentioned adsorbent is regenerated. The regeneration process is as follows: first, it is soaked and washed with 0.5 mol / L dilute hydrochloric acid solution for 4 hours to desorb the metal ions attached to the surface; then, it is washed with ultrapure water until neutral; and finally, it is vacuum dried at 80°C for 12 hours.

[0067] The regenerated adsorbent was added back into a 1000 ml round-bottom flask, and adsorption tests were performed under identical conditions. This adsorption-regeneration cycle was repeated five times, and the Fe³⁺ concentration in octamethylcyclotetrasiloxane was recorded after each cycle. + The content of [ ] is shown in Table 4.

[0068] Table 4: Effect of regeneration number on adsorption performance

[0069]

[0070] Conclusion: As shown in Table 4, after 5 adsorption-regeneration cycles, the adsorbent described in this invention effectively removes Fe³⁺. + The adsorption capacity remains good, indicating that the adsorbent has excellent chemical stability and reusability. Its regeneration method is simple and effective, significantly reducing the production cost of electronic-grade octamethylcyclotetrasiloxane and possessing extremely high industrial application value.

[0071] Furthermore, this embodiment describes the adsorbent of the present invention for the adsorption of Fe³⁺ in octamethylcyclotetrasiloxane. + and Zn² + The dynamic penetration capacity of metal ions was tested. The test procedure is as follows:

[0072] Raw material: The octamethylcyclotetrasiloxane raw material described in this embodiment is used.

[0073] Column packing: Weigh 20g of the adsorbent described in this invention and pack it into a glass column with an inner diameter of 10mm and a length of 300mm, with a bed height of about 180mm.

[0074] Adsorption: Octamethylcyclotetrasiloxane was pumped from bottom to top at a constant flow rate of 10 mL / min ± 0.2 mL / min under constant temperature conditions of 20℃ ± 0.5℃. Each 250 mL of effluent was collected as a sample, and a total of 6 samples were collected.

[0075] Detection: Fe³⁺ in each sample was determined by ICP-MS. + Zn² + The residual amounts are shown in Table 5.

[0076] Table 5: Adsorption Depth Test Results

[0077]

[0078] Experiments show that when the cumulative treatment volume reaches 1000 mL, the Fe³⁺ in the effluent... + The initial concentration exceeding 50 ppt can be considered the adsorption breakthrough point. Therefore, under the conditions of this embodiment, the maximum processing capacity of 20 g of adsorbent for octamethylcyclotetrasiloxane is at least 1000 mL, corresponding to a solid-liquid mass ratio of approximately 1:500. Under other preferred conditions, for other octamethylcyclotetrasiloxane feedstocks, the ratio of adsorbent dosage to processing capacity can be adjusted within the range of 1:400-1:600 ​​while maintaining the same breakthrough capacity.

[0079] Example 2

[0080] like Figure 1 As shown, this embodiment provides a purification system for removing metal impurities from octamethylcyclotetrasiloxane using an adsorbent, comprising:

[0081] Adsorption tank 1, the adsorption tank having a raw material inlet 11, a third product outlet 15, a first gas inlet 17, a first gas outlet 21, a first vacuum suction port 25, a first stirrer 29 and a first adsorption material outlet 7;

[0082] The backup adsorption tank 2 has a third product inlet 12, a fourth product outlet 16, a second gas inlet 18, a second gas outlet 22, a second vacuum suction port 26, a second adsorption material outlet 8, and a second stirrer 30.

[0083] Among them, the third product outlet 15 and the third product inlet 12 are connected; the first vacuum negative port 25 and the second vacuum negative port 26 are connected;

[0084] The filter container 3 has a first product outlet 9, a fourth product inlet 13, a third gas inlet 19, a third gas outlet 23 and a third vacuum port 27.

[0085] Among them, the fourth product inlet 13 and the fourth product outlet 16 are connected;

[0086] The premium product storage tank 4 includes a second product outlet 10, a fifth product inlet 14, a fourth gas inlet 20, a fourth gas outlet 24, and a fourth vacuum port 28.

[0087] Among them, the fifth product inlet 14 and the first product outlet 9 are connected; the fourth vacuum negative port 28 and the third vacuum negative port 27 are connected; and the passages of the fourth vacuum negative port 28 and the third vacuum negative port 27 are respectively connected to the first vacuum negative port 25 and the second vacuum negative port 26.

[0088] The sample collection port 5 is connected at one end to the passage formed by the third product outlet 15 and the third product inlet 12, and at the other end to the passage formed by the fourth product inlet 13 and the fourth product outlet 16.

[0089] Vacuum pump 6, which is connected to the third vacuum port 27.

[0090] The purification system has the following process steps:

[0091] First, the adsorbent A prepared in Example 1 is filled into adsorption tank 1 and standby adsorption tank 2. Temperature regulating devices are respectively provided on the outer walls of adsorption tank 1 and standby adsorption tank 2, and the adsorption temperature is set at 20 ℃ ± 0.5 ℃.

[0092] The octamethylcyclotetrasiloxane raw material mentioned in Example 1 was introduced into the adsorption tank 1 through the raw material inlet 11, and the sample solution was periodically taken for ICP-MS elemental analysis.

[0093] When the online monitoring system detected Fe in the octamethylcyclotetrasiloxane feedstock 3+ or Zn 2+ When the content is less than 60 ppt; open the third product inlet 12, pump the octamethylcyclotetrasiloxane raw material into the standby adsorption tank 2, and periodically take sample solutions for ICP-MS elemental analysis.

[0094] When the online monitoring system detected Fe in the octamethylcyclotetrasiloxane feedstock 3+ or Zn 2+ When the content is below 20 ppt, open the fourth product outlet 16 and the fourth product inlet 13 to pump the product into the filter container 3 for filtration.

[0095] The filtrate enters the refined product storage tank 4 through the first product outlet 9 and the fifth product inlet 14 to obtain electronic-grade octamethylcyclotetrasiloxane product.

[0096] In this embodiment, Fe in the first 20 sample solutions 3+ Zn 2+ The content of all impurities was below 10 ppt, and the content of other metallic impurities (Na, Ca, Cr, etc.) was also significantly reduced, far exceeding the electronic grade standard. The yield of octamethylcyclotetrasiloxane exceeded 99.7%.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adsorbent for removing metal impurities from octamethylcyclotetrasiloxane, characterized in that: The adsorbent takes activated silica gel as a carrier, and a catechol type chelating functional group generated by the reaction of catechol, ethylenediamine and formaldehyde is grafted on the surface of the carrier; wherein the adsorbent can reduce the content of Fe 3+ and Zn 2+ to 20 ppt or less to obtain an electronic grade octamethylcyclotetrasiloxane product.

2. The adsorbent for removing metal impurities from octamethylcyclotetrasiloxane according to claim 1, characterized in that: The adsorbent has an average particle size of 80-180 μm and a specific surface area of ​​400-700 m² / g.

3. A method for preparing an adsorbent for removing metal impurities from octamethylcyclotetrasiloxane as described in any one of claims 1-2, characterized in that: Includes the following steps: Step 1: Immerse the porous silica gel in sulfuric acid solution to activate it, then wash it with ultrapure water until neutral, and dry it under vacuum to obtain activated silica gel; Step 2: Disperse the activated silica gel in anhydrous toluene, add catechol, ethylenediamine and formaldehyde, and stir continuously at 110±5 °C under an inert atmosphere for 18~36 hours; Step 3: After the reaction is complete, cool to room temperature, wash thoroughly, and vacuum dry to obtain the target adsorbent; The total amount of catechol, ethylenediamine and formaldehyde accounts for 10% to 100% of the total mass of the activated silica gel; wherein the mass ratio of catechol, ethylenediamine and formaldehyde is (2-5):1:(2-5); The thorough washing process involves sequentially washing with methanol, ethanol, and ultrapure water.

4. A purification system, characterized in that: Includes the adsorbent for removing metal impurities from octamethylcyclotetrasiloxane as described in claim 1 or 2.

5. The purification system according to claim 4, characterized in that: include: The adsorption tank (1) has a raw material inlet (11), a third product outlet (15), a first gas inlet (17), a first gas outlet (21), a first vacuum suction port (25), a first stirrer (29), and a first adsorption material outlet (7). The backup adsorption tank (2) has a third product inlet (12), a fourth product outlet (16), a second gas inlet (18), a second gas outlet (22), a second vacuum suction port (26), a second adsorption material outlet (8), and a second stirrer (30). The third product outlet (15) and the third product inlet (12) are connected; the first vacuum suction port (25) and the second vacuum suction port (26) are connected; both the adsorption tank (1) and the standby adsorption tank (2) are filled with the adsorbent. The filter container (3) has a first product outlet (9), a fourth product inlet (13), a third gas inlet (19), a third gas outlet (23) and a third vacuum port (27). Among them, the fourth product inlet (13) and the fourth product outlet (16) are connected; The premium storage tank (4) includes a second product outlet (10), a fifth product inlet (14), a fourth gas inlet (20), a fourth gas outlet (24), and a fourth vacuum port (28). Among them, the fifth product inlet (14) and the first product outlet (9) are connected; the fourth vacuum negative port (28) and the third vacuum negative port (27) are connected; and the passages of the fourth vacuum negative port (28) and the third vacuum negative port (27) are respectively connected to the first vacuum negative port (25) and the second vacuum negative port (26); The sample collection port (5) is connected at one end to the passage formed by the third product outlet (15) and the third product inlet (12), and at the other end to the passage formed by the fourth product inlet (13) and the fourth product outlet (16). Vacuum pump (6), which is connected to the third vacuum port (27).

6. The purification system according to claim 5, characterized in that, It also includes an online monitoring device configured to monitor in real time the content of metal impurities in the purified octamethylcyclotetrasiloxane.

7. The purification system according to claim 6, characterized in that: The online monitoring device is a detection device based on inductively coupled plasma mass spectrometry, and its sample inlet is connected to the product outlet pipeline of the adsorption equipment.

8. A purification process based on the purification system as described in claim 7, characterized in that: The process includes the following steps: Step 1: Introduce high-purity nitrogen into the purification system to replace the oxygen atmosphere and ensure that the system is free of oxygen and water; Step 2: The octamethylcyclotetrasiloxane raw material with a total metal impurity content of ppb is passed through an adsorption tank filled with the adsorbent and contacted at 20℃±5℃ for 12~14 hours. Step three: Fe and Zn content in effluent was monitored on-line by inductively coupled plasma mass spectrometry 3+ 2+ ​​ Step four: when the Fe 3+ or Zn 2+ content is reduced to below 60 ppt, switch to the standby adsorption tank for continuous adsorption; after the Fe 3+ and Zn 2+ contents are below 20 ppt, filter the effluent through a precision filter, collect the filtrate, and obtain the electronic-grade octamethylcyclotetrasiloxane product.

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