Method for efficiently removing methylchlorosilane impurities in trichlorosilane based on pt@zif-8 adsorbent

Abstract

This invention relates to a method for efficiently removing methylchlorosilane impurities from trichlorosilane using Pt@ZIF-8 adsorbent. The invention employs Pt@ZIF-8 adsorbent to simultaneously adsorb methyldichlorosilane and dimethylchlorosilane impurities, achieving a groundbreaking and efficient simultaneous removal of these two impurities. The process is simple, requires low equipment investment and energy consumption, and achieves a removal rate of up to 83% for methyldichlorosilane and up to 85% for dimethylchlorosilane. This single adsorbent can efficiently remove both methyldichlorosilane and dimethylchlorosilane simultaneously, effectively solving the problem of difficult removal of methylchlorosilane impurities from trichlorosilane. Furthermore, the adsorbent is easy to separate and can be reused through desorption under nitrogen, saving costs and demonstrating potential application value in the industrial field.

Description

Technical fields:

[0001] This invention relates to a method for efficiently removing methylchlorosilane impurities from trichlorosilane based on Pt@ZIF-8 adsorbent, belonging to the field of polycrystalline silicon technology. Background technology:

[0002] Trichlorosilane (SiHCl3, abbreviated as TCS) is a major raw material for the production of polycrystalline silicon and one of the main silicon source materials used in silicon epitaxial wafers in semiconductor chip manufacturing. Therefore, the control of impurities in trichlorosilane is of paramount importance. In the modified Siemens process, carbon impurities in trichlorosilane mainly originate from silicon powder and exist in the form of methylchlorosilanes. In particular, dimethylchlorosilane and methyldichlorosilane, whose boiling points are close to those of trichlorosilane, are difficult to remove. They easily deposit in the production of polycrystalline silicon and epitaxial wafers used as silicon sources, forming lattice point defects and thus affecting the performance of semiconductor materials.

[0003] In China, the main method for removing impurities from trichlorosilane is distillation. Multi-stage distillation can remove most impurities, but trace impurities in the distillation product cannot be completely removed through distillation purification. The total carbon in trichlorosilane mainly exists in the form of methylchlorosilanes. Since the boiling points of dimethylchlorosilane and methyldichlorosilane (34.7℃ and 41.9℃ respectively) are close to the boiling point of trichlorosilane (32℃), they easily form azeotropes. Therefore, ordinary distillation methods cannot deeply remove carbon-containing impurities from chlorosilanes. The accumulation of carbon-containing impurities in the system inevitably hinders the continuous improvement of product quality. To reduce the content of these methylchlorosilane impurities, distillation columns with very high theoretical plate numbers are required, along with a significant increase in the reflux ratio during operation. This necessitates increased fixed investment and operating costs, leading to a rise in the overall cost of polysilicon production.

[0004] Adsorption is a method that uses adsorbents to separate impurities from trichlorosilane, overcoming the difficulty of removing impurities with similar boiling points by distillation. General requirements for adsorbents include: 1) a large surface area; and 2) high surface activity. However, existing adsorbents have small surface areas and low specificity, exhibiting weak adsorption and removal capabilities for dimethylchlorosilane and methyldichlorosilane. For example, Chinese patent document CN111115637A discloses a method and apparatus for removing carbonaceous impurities in the production of high-purity chlorosilanes. The method includes the following steps: S1, removing high-boiling-point and low-boiling-point components from trichlorosilane raw material in a distillation unit to obtain distilled trichlorosilane; S2, feeding the distilled trichlorosilane into an adsorption unit to remove methylchlorosilane to obtain high-purity chlorosilane; wherein, the adsorption unit is filled with an amino-rich resin-type adsorbent and a platinum-based catalyst. The resin-type adsorbent has weak adsorption capacity and cannot efficiently remove dimethylchlorosilane and methyldichlorosilane, requiring the use of a platinum-based catalyst, which is costly and complex.

[0005] Therefore, designing a simple, low-cost, and efficient method for removing methylchlorosilane impurities from trichlorosilane is of great significance for industrial production.

[0006] Metal-organic frameworks (MOFs) are organic-inorganic hybrid materials with intramolecular pores, formed by the self-assembly of organic ligands and metal ions or clusters through coordination bonds. Due to their unique and excellent surface properties, such as high specific surface area and tunable porosity, MOFs have been widely explored in the field of adsorption and separation. Among them, the zeolite imidazolate framework-8 (ZIF-8) is a metal-organic framework with a large specific surface area and good thermal and chemical stability. It possesses a sodium zeolite-like topology and combines the advantages of both metal-organic frameworks and natural zeolites. Summary of the Invention:

[0007] To address the shortcomings of existing technologies, this invention provides a method for efficiently removing methylchlorosilane impurities from trichlorosilane based on Pt@ZIF-8 adsorbent. Compared with traditional distillation processes that employ high theoretical plate numbers and high reflux ratios, this invention uses Pt@ZIF-8 adsorbent to adsorb and remove carbonaceous impurities of methylchlorosilane from trichlorosilane. The process is simple, with low equipment investment and low energy consumption. It achieves a removal rate of up to 83% for methyldichlorosilane and up to 85% for dimethylchlorosilane. One adsorbent can simultaneously and efficiently remove methyldichlorosilane and dimethylchlorosilane, eliminating the need for separate directional adsorbents for methyldichlorosilane and dimethylchlorosilane, effectively solving the problem of difficult removal of methylchlorosilane impurities from trichlorosilane.

[0008] This invention is achieved through the following technical solution:

[0009] A method for efficiently removing methylchlorosilane impurities from trichlorosilane based on Pt@ZIF-8 adsorbent, the method comprising the following steps:

[0010] Add Pt@ZIF-8 adsorbent to trichlorosilane solution, seal, and shake in ice-water bath for 2-6 hours to achieve efficient removal of methylchlorosilane impurities from trichlorosilane;

[0011] The Pt@ZIF-8 adsorbent is prepared by the following method:

[0012] (1) Dissolve zinc nitrate hydrate and dimethylimidazole in methanol, stir and react at room temperature. After the reaction is complete, centrifuge, wash and vacuum dry the mixed solution to obtain solid powder A.

[0013] (2) Solid powder A was calcined under an inert atmosphere to obtain ZIF-8;

[0014] (3) Dissolve polyvinylpyrrolidone (PVP) in methanol with stirring to obtain solution A;

[0015] (4) Chloroplatinic acid hexahydrate was dissolved in ultrapure water under stirring to obtain solution B;

[0016] (5) Add solution B dropwise to solution A, heat under reflux, remove solvent by rotary evaporation, wash to remove free PVP, and obtain stable Pt NPs;

[0017] (6) Disperse the ZIF-8 powder from step (2) into an organic solvent to obtain solution C;

[0018] (7) Disperse the Pt NPs from step (5) into an organic solvent, then add them dropwise to solution C, stir the reaction at room temperature, centrifuge, wash, filter, and vacuum dry to obtain solid powder B;

[0019] (8) Solid powder B was calcined under an inert atmosphere to obtain Pt@ZIF-8 adsorbent.

[0020] According to a preferred embodiment of the present invention, the mass-to-volume ratio of the Pt@ZIF-8 adsorbent to the trichlorosilane solution is (4-10):(10-30), in g / mL.

[0021] According to a preferred embodiment of the present invention, the ice-water bath oscillation time is 3 hours.

[0022] According to a preferred embodiment of the present invention, in step (1), the molar ratio of zinc nitrate hydrate to dimethylimidazole is 1:(7-9);

[0023] According to a preferred embodiment of the present invention, in step (1), the mass ratio of dimethylimidazole to methanol is (0.1-0.5):1.

[0024] According to a preferred embodiment of the present invention, in step (1), the reaction time is 3-8 hours.

[0025] According to a preferred embodiment of the present invention, in step (2), the calcination temperature is 300-500℃.

[0026] According to a preferred embodiment of the present invention, in step (2), the calcination time is 2-6 hours.

[0027] According to a preferred embodiment of the present invention, in step (3), the mass-to-volume ratio of polyvinylpyrrolidone to methanol is (10-20):(200-300), unit, g / mL.

[0028] According to a preferred embodiment of the present invention, in step (4), the mass-to-volume ratio of chloroplatinic acid hexahydrate to ultrapure water is 1:(200-400), unit: g / mL.

[0029] According to a preferred embodiment of the present invention, in step (5), the volume ratio of solution B to solution A is 1:(8-10).

[0030] According to a preferred embodiment of the present invention, in step (5), the heating reflux time is 2-6 hours.

[0031] According to a preferred embodiment of the present invention, in step (6), the mass-to-volume ratio of ZIF-8 powder to organic solvent is (5-20):(150-250), unit, g / mL.

[0032] According to a preferred embodiment of the present invention, in step (7), the mass-to-volume ratio of Pt NPs to organic solvent is 1:(40-100), unit, g / mL.

[0033] According to a preferred embodiment of the present invention, in step (7), the mass ratio of Pt NPs to ZIF-8 is (0.1-1):1.

[0034] According to a preferred embodiment of the present invention, in steps (1) and (7), the vacuum drying temperature is 30-60°C and the vacuum drying time is 8-10 hours.

[0035] According to a preferred embodiment of the present invention, in steps (2) and (8), the inert atmosphere is nitrogen or argon, the calcination temperature is 200-500℃, and the calcination time is 2-4 hours.

[0036] According to a preferred embodiment of the present invention, in steps (6) and (7), the organic solvent is methanol or DMF.

[0037] The technical features and beneficial effects of this invention are as follows:

[0038] 1. This invention utilizes Pt@ZIF-8 adsorbent to simultaneously adsorb methyldichlorosilane and dimethylchlorosilane impurities, achieving a groundbreaking and efficient removal of both impurities. The process is simple, with low equipment investment and low energy consumption. The removal rate for methyldichlorosilane is as high as 83%, and for dimethylchlorosilane, it is as high as 85%. One adsorbent can simultaneously and efficiently remove methyldichlorosilane and dimethylchlorosilane. Furthermore, the adsorbent of this invention is easy to separate and can be reused through desorption under nitrogen, saving costs and demonstrating potential application value in the industrial field.

[0039] 2. This invention utilizes the large surface area, surface activity, and complexing properties of Pt@ZIF-8 adsorbent to remove methylchlorosilane impurities in the trichlorosilane system through an adsorption process. The synergistic effect of ZIF-8 and Pt in the adsorbent greatly improves the removal rate of methyldichlorosilane and dimethylchlorosilane impurities, and significantly improves the purity of trichlorosilane.

[0040] 3. The Pt@ZIF-8 adsorbent of this invention efficiently removes carbon-containing impurities in the trichlorosilane system, which can meet the production requirements of electronic-grade polycrystalline silicon.

[0041] 4. The Pt@ZIF-8 adsorbent of the present invention is first calcined under an inert atmosphere to obtain ZIF-8. ZIF-8 is mixed with stable PtNPs, dried, and then calcined to obtain Pt@ZIF-8 adsorbent with excellent adsorption performance. Calcination under an inert atmosphere allows Pt to be uniformly and firmly loaded on ZIF-8. When the Pt loading is 0.5%, the removal rate of carbon-containing impurities in the trichlorosilane system reaches the optimal level. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0043] Furthermore, unless otherwise specified, the methods described in the following embodiments are all conventional methods; and unless otherwise specified, the materials, reagents, etc., can be obtained commercially.

[0044] Trichlorosilane solution is liquid trichlorosilane containing unqualified carbon impurities after multi-stage distillation.

[0045] Example 1

[0046] Synthesis of 0.1-Pt@ZIF-8 adsorbent:

[0047] (1) Weigh 29.75g of zinc nitrate hydrate and 65.68g of dimethylimidazole, dissolve them in 250ml of methanol, stir the reaction at room temperature for 5 hours, and after the reaction is completed, centrifuge, wash, and vacuum dry at 50℃ for 8 hours to obtain solid powder A;

[0048] (2) Solid powder A was calcined at 350°C for 2 hours under nitrogen to obtain sample ZIF-8;

[0049] (3) Weigh 13.3g of PVP (polyvinylpyrrolidone) and dissolve it in 250ml of methanol with stirring to obtain solution A;

[0050] (4) Weigh 1g of chloroplatinic acid hexahydrate and dissolve it in 300ml of ultrapure water with stirring to obtain solution B;

[0051] (5) Take 30 ml of solution B and add it dropwise to solution A. After heating and refluxing for 3 hours, remove most of the solvent by rotary evaporation. After washing with DMF several times to remove free PVP, stable Pt NPs are obtained.

[0052] (6) Disperse 10g of ZIF-8 into 200ml of DMF to obtain a ZIF-8 solution;

[0053] (7) Take 1g of Pt NPs and disperse it in 50ml of DMF. Add it dropwise to the solution of ZIF-8. Stir for a certain time at room temperature, centrifuge, wash, filter, and vacuum dry at 50℃ for 8 hours to obtain solid powder B.

[0054] (8) Solid powder B was calcined at 250°C under a nitrogen atmosphere for 2 hours to obtain 0.1-Pt@ZIF-8 adsorbent.

[0055] The synthesized adsorbent 0.1-Pt@ZIF-8 was used for the adsorption and removal of methylchlorosilane impurities in trichlorosilane, as follows:

[0056] Before adsorption, the adsorbent was dried at 150°C for 4 hours.

[0057] 5 g of 0.1-Pt@ZIF-8 adsorbent was weighed and added to 20 mL of trichlorosilane solution. The solution containing the adsorbent was sealed in a 100 mL round-bottom flask and then shaken in an ice-water bath at a constant temperature for 3 hours. After adsorption equilibrium was reached, the mixed solution was centrifuged at room temperature, and the supernatant was analyzed by GC-MS. The results showed that the adsorbent removed 77% of methyldichlorosilane and 79% of dimethylchlorosilane.

[0058] The separated solid material was dried under nitrogen purging, and then calcined at 200°C for 1 hour under an argon atmosphere for thermal desorption. The treated sample was then subjected to adsorption of methylchlorosilane impurities in trichlorosilane using the same method. After adsorption, the methylchlorosilane impurities in trichlorosilane were detected. The results showed that the adsorbent had a removal rate of 72% for methyldichlorosilane and a removal rate of 76% for dimethylchlorosilane, indicating that the adsorbent of the present invention has good reusability.

[0059] Example 2

[0060] Synthesis of 0.3-Pt@ZIF-8 adsorbent:

[0061] (1) Weigh 29.75g of zinc nitrate hydrate and 65.68g of dimethylimidazole, dissolve them in 250ml of methanol, stir the reaction at room temperature for 6 hours, and after the reaction is completed, centrifuge, wash, and vacuum dry at 50℃ for 8 hours to obtain solid powder A;

[0062] (2) Solid powder A was calcined at 250°C for 2 hours under nitrogen to obtain sample ZIF-8;

[0063] (3) Weigh 13.3g of PVP (polyvinylpyrrolidone) and dissolve it in 250ml of methanol with stirring to obtain solution A;

[0064] (4) Weigh 1g of chloroplatinic acid hexahydrate and dissolve it in 300ml of ultrapure water with stirring to obtain solution B;

[0065] (5) Take 30 ml of the above solution B and add it dropwise to solution A. After heating and refluxing for 3 hours, remove most of the solvent by rotary evaporation. After washing with DMF several times to remove free PVP, stable Pt NPs are obtained.

[0066] (6) Disperse 10g of ZIF-8 into 200ml of DMF to obtain a ZIF-8 solution;

[0067] (7) Take 3g of Pt NPs and disperse it in 50ml of DMF. Add it dropwise to the above ZIF-8 solution and stir for a certain time at room temperature. After centrifugation, washing, filtration, and vacuum drying at 50℃ for 8 hours, solid powder B is obtained.

[0068] (8) Solid powder B was calcined at 300°C under a nitrogen atmosphere for 2 hours to obtain 0.3-Pt@ZIF-8 adsorbent.

[0069] The synthesized adsorbent 0.3-Pt@ZIF-8 was used for the adsorption and removal of methylchlorosilane impurities in trichlorosilane, as follows:

[0070] Before adsorption, the adsorbent was dried at 150°C for 4 hours.

[0071] 5 g of 0.3-Pt@ZIF-8 adsorbent was weighed and added to 20 mL of trichlorosilane solution. The solution containing the adsorbent was sealed in a 100 mL round-bottom flask and then shaken in an ice-water bath at a constant temperature for 3 hours. After adsorption equilibrium was reached, the mixture was centrifuged at room temperature, and the supernatant was analyzed by GC-MS. The results showed that the adsorbent removed 79% of methyldichlorosilane and 80% of dimethylchlorosilane.

[0072] The separated solid material was dried under nitrogen purging, and then calcined at 200°C for 1 hour under an argon atmosphere for thermal desorption. The treated sample was then subjected to adsorption of methylchlorosilane impurities in trichlorosilane using the same method. After adsorption, the methylchlorosilane impurities in trichlorosilane were detected. The results showed that the adsorbent had a removal rate of 73% for methyldichlorosilane and a removal rate of 75% for dimethylchlorosilane, indicating that the adsorbent of the present invention has good reusability.

[0073] Example 3

[0074] Synthesis of 0.5-Pt@ZIF-8 adsorbent:

[0075] (1) Weigh 29.75g of zinc nitrate hydrate and 65.68g of dimethylimidazole, dissolve them in 250ml of methanol, stir the reaction at room temperature for 4 hours, and after the reaction is completed, centrifuge, wash, and vacuum dry at 40℃ for 8 hours to obtain solid powder A;

[0076] (2) Solid powder A was calcined at 200°C for 2 hours under nitrogen to obtain sample ZIF-8;

[0077] (3) Weigh 13.3g of PVP (polyvinylpyrrolidone) and dissolve it in 250ml of methanol with stirring to obtain solution A;

[0078] (4) Weigh 1g of chloroplatinic acid hexahydrate and dissolve it in 300ml of ultrapure water with stirring to obtain solution B;

[0079] (5) Take 30 ml of the above solution B and add it dropwise to solution A. After heating and refluxing for 3 hours, remove most of the solvent by rotary evaporation. After washing with DMF several times to remove free PVP, stable Pt NPs are obtained.

[0080] (6) Disperse 10g of ZIF-8 into 200ml of DMF to obtain a ZIF-8 solution;

[0081] (7) Take 5g of Pt NPs and disperse it in 50ml of DMF. Add it dropwise to the above ZIF-8 solution. Stir for a certain time at room temperature, centrifuge, wash, filter, and vacuum dry at 40℃ for 10 hours to obtain solid powder B.

[0082] (8) The above solid powder B was calcined at 400°C under an argon atmosphere for 2 hours to obtain 0.5-Pt@ZIF-8 adsorbent.

[0083] The synthesized adsorbent 0.5-Pt@ZIF-8 was used for the adsorption and removal of methylchlorosilane impurities in trichlorosilane, as follows:

[0084] Before adsorption, the adsorbent was dried at 150°C for 4 hours.

[0085] 5 g of 0.5-Pt@ZIF-8 adsorbent was weighed and added to 20 mL of trichlorosilane solution. The solution containing the adsorbent was sealed in a 100 mL round-bottom flask and then shaken in an ice-water bath at a constant temperature for 3 hours. After adsorption equilibrium was reached, the mixed solution was centrifuged at room temperature, and the supernatant was analyzed by GC-MS. The results showed that the adsorbent removed 83% of methyldichlorosilane and 85% of dimethylchlorosilane.

[0086] The separated solid material was dried under nitrogen purging, and then calcined at 200°C for 1 hour under an argon atmosphere for thermal desorption. The treated sample was then subjected to adsorption of methylchlorosilane impurities in trichlorosilane using the same method. After adsorption, the methylchlorosilane impurities in trichlorosilane were detected. The results showed that the adsorbent had a removal rate of 79% for methyldichlorosilane and a removal rate of 81% for dimethylchlorosilane, indicating that the adsorbent of the present invention has good reusability.

[0087] Example 4

[0088] Synthesis of 0.9-Pt@ZIF-8 adsorbent:

[0089] (1) Weigh 29.75g of zinc nitrate hydrate and 65.68g of dimethylimidazole, dissolve them in 250ml of methanol, stir the reaction at room temperature for 7 hours, and after the reaction is completed, centrifuge, wash, and vacuum dry at 40℃ for 8 hours to obtain solid powder A;

[0090] (2) Solid powder A was calcined at 300°C for 2 hours under nitrogen to obtain sample ZIF-8;

[0091] (3) Weigh 13.3g of PVP (polyvinylpyrrolidone) and dissolve it in 250ml of methanol with stirring to obtain solution A;

[0092] (4) Weigh 1g of chloroplatinic acid hexahydrate and dissolve it in 300ml of ultrapure water with stirring to obtain solution B;

[0093] (5) Take 30 ml of the above solution B and add it dropwise to solution A. After heating and refluxing for 3 hours, remove most of the solvent by rotary evaporation. After washing with DMF several times to remove free PVP, stable Pt NPs are obtained.

[0094] (6) Disperse 10g of ZIF-8 into 200ml of DMF to obtain a ZIF-8 solution;

[0095] (7) Take 9g of Pt NPs and disperse it in 50ml of DMF. Add it dropwise to the above ZIF-8 solution and stir for a certain time at room temperature. After centrifugation, washing, filtration, and vacuum drying at 40℃ for 10 hours, solid powder B is obtained.

[0096] (8) Solid powder B was calcined at 350°C under an argon atmosphere for 2 hours to obtain 0.9-Pt@ZIF-8 adsorbent.

[0097] The synthesized adsorbent 0.9-Pt@ZIF-8 was used for the adsorption and removal of methylchlorosilane impurities in trichlorosilane, as follows:

[0098] Before adsorption, the adsorbent was dried at 150°C for 4 hours.

[0099] 5 g of 0.9-Pt@ZIF-8 adsorbent was weighed and added to 20 mL of trichlorosilane solution. The solution containing the adsorbent was sealed in a 100 mL round-bottom flask and then shaken in an ice-water bath at a constant temperature for 3 hours. After adsorption equilibrium was reached, the mixed solution was centrifuged at room temperature, and the supernatant was analyzed by GC-MS. The results showed that the adsorbent removed 81% of methyldichlorosilane and 83% of dimethylchlorosilane.

[0100] The separated solid material was dried under nitrogen purging, and then calcined at 200°C for 1 hour under an argon atmosphere for thermal desorption. The treated sample was then subjected to adsorption of methylchlorosilane impurities in trichlorosilane using the same method. After adsorption, the methylchlorosilane impurities in trichlorosilane were detected. The results showed that the adsorbent had a removal rate of 73% for methyldichlorosilane and a removal rate of 75% for dimethylchlorosilane, indicating that the adsorbent of the present invention has good reusability.

[0101] Comparative Example 1

[0102] Synthesis of Air-0.5-Pt@ZIF-8 adsorbent:

[0103] (1) Weigh 29.75g of zinc nitrate hydrate and 65.68g of dimethylimidazole, dissolve them in 250ml of methanol, stir the reaction at room temperature for 5 hours, and after the reaction is completed, centrifuge, wash, and vacuum dry at 40℃ for 8 hours to obtain solid powder A;

[0104] (2) Solid powder A was calcined in air at 400°C for 2 hours to obtain sample ZIF-8;

[0105] (3) Weigh 13.3g of PVP (polyvinylpyrrolidone) and dissolve it in 250ml of methanol with stirring to obtain solution A;

[0106] (4) Weigh 1g of chloroplatinic acid hexahydrate and dissolve it in 300ml of ultrapure water with stirring to obtain solution B;

[0107] (5) Take 30 ml of the above solution B and add it dropwise to solution A. After heating and refluxing for 3 hours, remove most of the solvent by rotary evaporation. After washing with DMF several times to remove free PVP, stable Pt NPs are obtained.

[0108] (6) Disperse 10g of ZIF-8 into 200ml of DMF to obtain a ZIF-8 solution;

[0109] (7) Take 5g of Pt NPs and disperse it in 50ml of DMF. Add it dropwise to the above ZIF-8 solution. Stir for a certain time at room temperature, centrifuge, wash, filter, and vacuum dry at 40℃ for 10 hours to obtain solid powder B.

[0110] (8) Solid powder B was calcined at 350°C under an argon atmosphere for a certain time to obtain Air-0.5-Pt@ZIF-8 adsorbent.

[0111] The adsorbent Air-0.5-Pt@ZIF-8 synthesized in Comparative Example 1 was used for the adsorption and removal of methylchlorosilane impurities in trichlorosilane, as follows:

[0112] Before adsorption, the adsorbent was dried at 150°C for 4 hours.

[0113] 5g of Air-0.5-Pt@ZIF-8 adsorbent was weighed and added to 20ml of trichlorosilane solution. The solution containing the adsorbent was sealed in a 100mL round-bottom flask and then shaken in an ice-water bath at a constant temperature for 3 hours. After adsorption equilibrium, the mixed solution was frozen and centrifuged, and the supernatant was analyzed by GC-MS. The results showed that the adsorbent removed 60% of methyldichlorosilane and 68% of dimethylchlorosilane.

[0114] The separated solid material was dried under nitrogen purging, and then calcined at 300°C for 2 hours under argon atmosphere for thermal desorption. The treated sample was then subjected to adsorption of methylchlorosilane impurities in trichlorosilane using the same method. After adsorption, the methylchlorosilane impurities in trichlorosilane were detected. The results showed that the adsorbent had a removal rate of 55% for methyldichlorosilane and a removal rate of 58% for dimethylchlorosilane.

[0115] The comparative example obtained by calcining ZIF-8 in an air atmosphere showed a much lower removal rate of methylchlorosilane impurities than that of the present invention, which is attributed to the small pore size of ZIF-8 obtained by calcination in an air atmosphere.

[0116] Comparative Example 2

[0117] Synthesis of Air-1.0-Pt@ZIF-8 adsorbent:

[0118] (1) Weigh 29.75g of zinc nitrate hydrate and 65.68g of dimethylimidazole, dissolve them in 250ml of methanol, stir the reaction at room temperature for 5 hours, and after the reaction is completed, centrifuge, wash, and vacuum dry at 50℃ for 8 hours to obtain solid powder A;

[0119] (2) Solid powder A was calcined in air at 350°C for 2 hours to obtain sample ZIF-8;

[0120] (3) Weigh 13.3g of PVP (polyvinylpyrrolidone) and dissolve it in 250ml of methanol with stirring to obtain solution A;

[0121] (4) Weigh 1g of chloroplatinic acid hexahydrate and dissolve it in 300ml of ultrapure water with stirring to obtain solution B;

[0122] (5) Take 30 ml of the above solution B and add it dropwise to solution A. After heating and refluxing for 3 hours, remove most of the solvent by rotary evaporation. After washing with DMF several times to remove free PVP, stable Pt NPs are obtained.

[0123] (6) Disperse 10g of ZIF-8 into 200ml of DMF to obtain a ZIF-8 solution;

[0124] (7) Take 10g of Pt NPs and disperse it in 50ml of DMF. Add it dropwise to the above ZIF-8 solution and stir for a certain time at room temperature. After centrifugation, washing, filtration, and vacuum drying at 40℃ for 10 hours, solid powder B is obtained.

[0125] (8) Solid powder B was calcined at 300°C under a nitrogen atmosphere for a certain time to obtain Air-1.0-Pt@ZIF-8 adsorbent.

[0126] The adsorbent Air-1.0-Pt@ZIF-8 synthesized in Comparative Example 2 was used for the adsorption and removal of methylchlorosilane impurities in trichlorosilane, as follows:

[0127] Before adsorption, the adsorbent was dried at 150°C for 4 hours.

[0128] 5g of Air-1.0-Pt@ZIF-8 adsorbent was weighed and added to 20ml of trichlorosilane solution. All solutions containing the adsorbent were sealed in a 100mL round-bottom flask and then shaken in an ice-water bath at a constant temperature for 3 hours. After adsorption equilibrium, the mixed solution was centrifuged at room temperature, and the supernatant was analyzed by GC-MS. The results showed that the adsorbent removed 60% of methyldichlorosilane and 65% of dimethylchlorosilane.

[0129] The separated solid material was dried under nitrogen purging, and then calcined at 300°C for 2 hours under argon atmosphere for thermal desorption. The treated sample was then subjected to adsorption of methylchlorosilane impurities in trichlorosilane using the same method. After adsorption, the methylchlorosilane impurities in trichlorosilane were detected. The results showed that the adsorbent had a removal rate of 52% for methyldichlorosilane and a removal rate of 53% for dimethylchlorosilane.

[0130] The comparative example obtained by calcining ZIF-8 in an air atmosphere showed a much lower removal rate of methylchlorosilane impurities than that of the present invention, which is attributed to the small pore size of ZIF-8 obtained by calcination in an air atmosphere.

Claims

1. A method for efficiently removing methylchlorosilane impurities from trichlorosilane based on Pt@ZIF-8 adsorbent, the method comprising the following steps: Pt@ZIF-8 adsorbent was added to a trichlorosilane solution, sealed, and shaken in an ice-water bath for 3 hours to achieve efficient removal of methylchlorosilane impurities from trichlorosilane. The mass-to-volume ratio of Pt@ZIF-8 adsorbent to trichlorosilane solution was (4-10):(10-30), unit: g / mL. The removal rate of methyldichlorosilane was as high as 83%, and the removal rate of dimethylchlorosilane was as high as 85%. One adsorbent can simultaneously and efficiently remove methyldichlorosilane and dimethylchlorosilane. Furthermore, the adsorbent is easy to separate and can be reused by desorption under nitrogen. The Pt@ZIF-8 adsorbent is prepared by the following method: (1) Dissolve zinc nitrate hydrate and dimethylimidazole in methanol, stir and react at room temperature. After the reaction is complete, centrifuge, wash and vacuum dry the mixed solution to obtain solid powder A. (2) Solid powder A is calcined in an inert atmosphere at a temperature of 300-500℃ for 2-6 hours to obtain ZIF-8; (3) Dissolve polyvinylpyrrolidone (PVP) in methanol with stirring to obtain solution A; (4) Chloroplatinic acid hexahydrate was dissolved in ultrapure water under stirring to obtain solution B; (5) Add solution B dropwise to solution A, heat under reflux, remove solvent by rotary evaporation, wash to remove free PVP, and obtain stable Pt NPs; the volume ratio of solution B to solution A is 1:(8-10), and the heating under reflux time is 2-6 hours; (6) Disperse the ZIF-8 powder from step (2) into an organic solvent to obtain solution C; the mass-to-volume ratio of ZIF-8 powder to organic solvent is (5-20):(150-250), unit: g / mL. (7) Disperse the Pt NPs from step (5) into an organic solvent, then add it dropwise to solution C. Stir the reaction at room temperature, centrifuge, wash, filter, and vacuum dry to obtain solid powder B; the mass-to-volume ratio of Pt NPs to organic solvent is 1:(40-100), unit, g / mL. In step (7), the mass ratio of Pt NPs to ZIF-8 is (0.1-1):

1. (8) Solid powder B was calcined under an inert atmosphere to obtain Pt@ZIF-8 adsorbent.

2. The method according to claim 1, characterized in that, In step (1), the molar ratio of zinc nitrate hydrate to dimethylimidazole is 1:(7-9), the mass ratio of dimethylimidazole to methanol is (0.1-0.5):1, and the reaction time is 3-8 hours.

3. The method according to claim 1, characterized in that, In step (3), the mass-to-volume ratio of polyvinylpyrrolidone to methanol is (10-20):(200-300), unit: g / mL.

4. The method according to claim 1, characterized in that, In step (4), the mass-to-volume ratio of chloroplatinic acid hexahydrate to ultrapure water is 1:(200-400), unit: g / mL.

5. The method according to claim 1, characterized in that, In steps (1) and (7), the vacuum drying temperature is 30-60℃, and the vacuum drying time is 8-10 hours. In steps (2) and (8), the inert atmosphere is nitrogen or argon, the calcination temperature is 200-500℃, and the calcination time is 2-4 hours. In steps (6) and (7), the organic solvent is methanol or DMF.