Preparation method of refined impurity-removing liquid-phase chlorosilane adsorbent

Abstract

The invention discloses a preparation method of a refined impurity-removing liquid-phase chlorosilane adsorbent, and relates to the field of preparation of adsorbents, and the preparation method comprises the following steps: by taking activated carbon as a precursor, carrying out oxidation modification on the surface of the activated carbon for a period of time by taking a nitric acid solution as an oxidizing agent in an ultrasonic environment; after filtering, drying for a certain time at a certain temperature to serve as a carrier of the adsorbent; the preparation method comprises the following steps: dispersing an organic active component in a solvent to prepare a dipping solution with a certain concentration, mixing and dipping a carrier and the dipping solution for a period of time according to a certain solid-to-liquid ratio, filtering to obtain an adsorbent precursor, and drying the adsorbent precursor at a certain temperature for a period of time to obtain the liquid-phase chlorosilane refining impurity-removing adsorbent. According to the preparation method of the refined impurity-removing liquid-phase chlorosilane adsorbent, equipment required by preparation is low in investment, the adsorption efficiency is high, safe and stable continuous production can be realized, the purity of chlorosilane can be effectively improved, and the quality of subsequent polycrystalline silicon products can be improved.

Description

Technical Field

[0001] The present invention relates to the field of preparation of adsorbents, and particularly to a method for preparing a refined and impurity-removed liquid-phase chlorosilane adsorbent. Background Art

[0002] Polysilicon is the direct raw material for producing monocrystalline silicon, and is the electronic information basic material for contemporary semiconductor devices such as artificial intelligence, automatic control, information processing, and optoelectronic conversion, with a wide range of application fields. The impurity content in polysilicon will directly affect the solar photoelectric conversion efficiency, and high-purity polysilicon is an important material for solar photovoltaic new energy.

[0003] The methods for producing polysilicon include chemical methods and physical methods, represented by the improved Siemens method and the physical method respectively, and there are also other purification processes generated by improving, optimizing, and adjusting some links. The chemical purification methods mainly include the Siemens method (vapor deposition reaction method), silane thermal decomposition method, and fluidized bed method, while the physical purification methods mainly include zone melting purification method (FZ), Czochralski method (CZ), and directional solidification polysilicon ingot method (casting method). Currently, the improved Siemens method is mainly used. In the improved Siemens method, hydrogen chloride and industrial silicon powder are synthesized into trichlorosilane at a certain temperature, and then the trichlorosilane is separated and rectified for purification. The purified trichlorosilane undergoes a vapor deposition reaction in a hydrogen (99.9999% purity) reduction furnace to produce high-purity polysilicon. In this process, due to the purity of silicon powder and hydrogen chloride, the impurity content of trichlorosilane is high, and the purity of the polysilicon obtained by subsequent reduction is not high, which cannot meet the requirements of solar-grade polysilicon, let alone the requirements of electronic-grade polysilicon. Therefore, it is necessary to improve the purity of trichlorosilane. Although its purity can reach 99.9% after multi-stage rectification, trace impurities will affect the quality of subsequent products. Its impurities are mainly boron and phosphorus compounds with boiling points very close to those of silicon tetrachloride and trichlorosilane. If the boron and phosphorus compounds are controlled to the ppb level, about 55 - 70 theoretical plates of the rectification column will be required, and at this time, a large amount of steam, cold substances, electric energy, etc. will be consumed by equipment such as heat exchangers, storage tanks, and motors.

[0004] In the existing technical solutions for removing impurities from silicon chloride, CN201010257626.2 and CN200910052693.8 disclose a process for removing trace phosphorus and boron by fully contacting trichlorosilane with a moist inert gas and performing local hydrolysis; CN109292780A discloses a process for removing impurities and purifying chlorosilane by reaction. An oxidizing inorganic salt is loaded on the surface of a porous silicate, and the hydrogen-containing boron compound with reducibility in the chlorosilane is oxidized into a boronic alcohol compound. The boiling point of the alcohol compound itself is increased, and the high-boiling substances are removed through a rectification column; CN113402640A discloses an adsorption resin for removing impurities from chlorosilane and a preparation method thereof. The chlorinated beads are swollen in an organic solvent and then reacted with reactants to obtain an initial product; the reactants contain polyamine, and the initial product contains tertiary amine; the initial product is reacted with an optimization reagent to convert the tertiary amine into a secondary amine, obtaining the adsorption resin. In the adsorption resin prepared by this preparation method, the tertiary amine has been converted into a secondary amine, so that the disproportionation effect of chlorosilane can be inhibited and the impurity removal adsorption rate can be improved. 200810180270.X invention discloses a method for removing boron and phosphorus ion impurities from chlorosilane with a resin. The removal rate of trace boron and phosphorus impurities is more than 95%, but the specific name of the resin is not disclosed. CN101913610A discloses a method for removing boron impurities from trichlorosilane. Activated carbon is added to trichlorosilane, mixed evenly, allowed to stand, and filtered to obtain trichlorosilane from which boron impurities have been removed.

[0005] The technical features of the above inventions have the following disadvantages: When trichlorosilane is in full contact with a moist inert gas, local hydrolysis cannot occur. At the same time, the water content is not easy to control. Excessive local water will cause the hydrolysis of chlorosilane to form sediments and block the equipment pipeline, posing a safety hazard; by filling the reactor with inorganic metal oxides to oxidize the reducing substances, but the reaction degree is uncontrollable, and the shed metal impurities will further affect the total impurity content of polysilicon; while using functional groups grafted on the resin to complex and adsorb impurities, although the impurity removal efficiency can be improved, the specific surface area of the resin is low, the pressure drop is large, and the formation of high-boiling substances cannot be removed in time, which will lead to production safety accidents. At present, flash explosions have occurred in several resin adsorption devices; directly filling microsphere activated carbon into the adsorption tank can reduce the impurity content in chlorosilane, but it cannot be continuously produced, the production efficiency is low, and the microsphere particles are easy to break during the desorption and adsorption process, affecting the quality of subsequent products. Summary of the Invention

[0006] The main purpose of the present invention is to provide a preparation method for a refined impurity-removing liquid-phase chlorosilane adsorbent, which can effectively solve the problems in the background technology.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A preparation method for a refined impurity-removing liquid-phase chlorosilane adsorbent includes the following operating steps: S1: Prepare the raw materials for preparation, including activated carbon, oxidant, and organic active components. S2: Prepare the adsorbent carrier. Using activated carbon as the precursor, oxidize the surface of the activated carbon with an oxidant for a certain period of time in an ultrasonic environment. After the oxidation modification is completed, take it out and filter it. After filtration, dry it at a certain temperature and for a certain time to obtain the adsorbent carrier. S3: Prepare the refined impurity-removing adsorbent by impregnation. Disperse the organic active components in a solvent to prepare an impregnation solution with a certain concentration, and mix and impregnate the carrier and the impregnation solution at a certain solid-liquid ratio for a certain period of time. Then filter it to obtain the adsorbent precursor, and then dry it at a certain temperature to obtain the liquid-phase chlorosilane refined impurity-removing adsorbent.

[0008] Preferably, the activated carbon is one of columnar activated carbon, granular activated carbon, and spherical activated carbon. The activated carbon is preferably coconut shell granular activated carbon with a mesh size of 12 - 30. The strength of the coconut shell granular activated carbon should be greater than 98%, the ash content should be less than 1%, the specific surface area should be greater than 1350 m 2 / g, and the acetic acid adsorption capacity should be 480 - 620 mg / g. The oxidant is a nitric acid solution, and the concentration of the nitric acid solution is 30 - 50%.

[0009] Preferably, the ultrasonic environment refers to an environment with a frequency range of 2*10 6 ~10 9 Hz.

[0010] Preferably, the time for oxidation modification is 3 - 5 hours. The oxidation modification means adding a certain amount of basic groups to the surface of the activated carbon, including amino group, imide group, lactam group, amide-like group, and pyridine-like group.

[0011] Preferably, the drying at a certain temperature and for a certain time is a drying temperature of 110 - 130°C and a drying time of 4 - 6 hours.

[0012] Preferably, the organic active component is one or more of propionamide, ammonium pyrrolidine dithiocarbamate, p-hydroxyazobenzene, triethylamine, triphenylmethyl chloride, diphenylmethyl chloride, ethylenediamine, (β-naphthyl)-amide of thioglycolic acid, and β-lactam, and the concentration of the organic active component is 3 - 10%.

[0013] Preferably, the solvent is one of methanol, ethanol, petroleum ether, dichloromethane, ether, and ethyl acetate.

[0014] Preferably, the solid-liquid ratio of the carrier to the impregnation solution is 1:2 - 1:5 by volume ratio.

[0015] Preferably, the time for mixed impregnation is 4 - 6 hours.

[0016] Preferably, the drying at a certain temperature is specifically a drying temperature of 80 - 110°C and a drying time of 8 - 12 hours.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses modified activated carbon as an adsorbent carrier for the first time. The basic groups such as amino groups, imido groups, lactam groups, amide-like groups, and pyridine-like groups added to the surface of the activated carbon after modification will contribute to the adsorption and removal of electron-deficient compound impurities; at the same time, the pore size of the activated carbon after oxidation modification is enlarged, and the larger pore size is more conducive to the full contact between the impurities in the chlorosilane and the adsorbent, which can effectively improve the adsorption efficiency of the adsorbent; At the same time, it not only has good adsorption capacity for boron and phosphorus compounds, but also has good adsorption performance for other metal impurities. Different from distillation columns and other adsorbents, the present invention requires less equipment investment, has high adsorption efficiency, can be continuously produced safely and stably, can effectively improve the purity of chlorosilane, improve the quality of subsequent polysilicon products, meet the needs of solar grade, and even semiconductor grade. Specific embodiments

[0018] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0019] The present invention relates to a preparation method of a refined and impurity-removed liquid-phase chlorosilane adsorbent, which includes the following steps: S1: Prepare raw materials for preparation, including activated carbon, oxidant, and organic active components; The activated carbon is one of columnar activated carbon, granular activated carbon, and spherical activated carbon. The activated carbon is preferably coconut shell granular activated carbon with a mesh size of 12 - 30. The strength of the coconut shell granular activated carbon needs to be greater than 98%, the ash content is less than 1%, the specific surface area is greater than 1350 m 2 / g, and the acetic acid adsorption capacity is 480 - 620 mg / g. The oxidant is a nitric acid solution, and the concentration of the nitric acid solution is 30 - 50%.

[0020] S2: Prepare an adsorbent carrier, using activated carbon as a precursor, in a frequency range of 2*10 6 ~10 9The surface of activated carbon is oxidatively modified with an oxidant in an ultrasonic environment of 2×107 Hz for 3-5 hours. The oxidative modification is to increase a certain amount of basic groups on the surface of activated carbon, including amino groups, imide groups, lactam groups, amide-like groups, and pyridine-like groups. After the oxidative modification is completed, it is taken out and filtered, and then dried at 110-130°C for 4-6 hours to be used as the carrier of the adsorbent.

[0021] S3: Prepare the refined impurity removal adsorbent by the impregnation method. Disperse the organic active components in a solvent to prepare an impregnation solution with a certain concentration. The organic active components are one or more of propionamide, ammonium pyrrolidine dithiocarbamate, p-hydroxyazobenzene, triethylamine, triphenylmethyl chloride, diphenylmethyl chloride, ethylenediamine, (β-naphthyl)-amide of thioglycolic acid, and β-lactam. The concentration of the organic active components is 3-10%, and the solvent is one of methanol, ethanol, petroleum ether, dichloromethane, ether, and ethyl acetate. The carrier and the impregnation solution are mixed and impregnated for 4-6 hours at a solid-liquid ratio of 1:2 to 1:5. Then it is filtered to obtain the adsorbent precursor, and after drying at a drying temperature of 80-110°C for 8-12 hours, the liquid-phase chlorosilane refined impurity removal adsorbent can be prepared. Specific Example 1: A method for preparing a refined impurity removal liquid-phase chlorosilane adsorbent, specifically using activated carbon as a precursor, oxidatively modifying the surface of activated carbon with a nitric acid solution as an oxidant in an ultrasonic environment for a period of time, filtering, and then drying at a certain temperature and time to be used as the carrier of the adsorbent; dispersing the organic active components in a solvent to prepare an impregnation solution with a certain concentration, and mixing and impregnating the carrier and the impregnation solution at a certain solid-liquid ratio for a period of time, filtering to obtain the adsorbent precursor, and drying and drying at a certain temperature for a period of time to prepare the liquid-phase chlorosilane refined impurity removal adsorbent.

[0023] In this example, preferably 12-30 mesh coconut shell granular activated carbon is used, with a strength of 99.3%, an ash content of 0.8%, a specific surface area of 1400 m2 / g, and an acetic acid adsorption capacity of 580 mg / g.

[0024] The ultrasonic environment preferably used in this example means a frequency of 2×107 Hz.

[0025] The nitric acid solution preferably used in this example means a nitric acid solution with a concentration of 30%.

[0026] The preferably oxidative modification time in this example is 2 hours.

[0027] The preferably drying temperature and time in this example mean 110°C and 5 hours.

[0028] The preferably organic active components in this example mean triethylamine and diphenylmethyl chloride.

[0029] The preferred solvent in this embodiment refers to dichloromethane.

[0030] The preferred concentration in this embodiment refers to a solution with a concentration of 5% prepared by mixing triethylamine and diphenylchloromethane in a ratio of 1:1.

[0031] The preferred solid-liquid ratio in this embodiment refers to a volume ratio of 1:2.

[0032] The preferred impregnation time in this embodiment refers to 4 hours of impregnation.

[0033] The preferred drying temperature and time in this embodiment refer to 80°C and 10 hours; After cooling, a refined and impurity-removed adsorbent for liquid-phase chlorosilane is obtained. Specific Example 2: A method for preparing a refined and impurity-removed adsorbent for liquid-phase chlorosilane. Specifically, using activated carbon as a precursor, in an ultrasonic environment, nitric acid solution is used as an oxidant to perform oxidation modification on the surface of activated carbon for a certain period of time. After filtration, it is dried at a certain temperature and time to obtain a carrier for the adsorbent; the organic active components are dispersed in a solvent to prepare an impregnation solution with a certain concentration, and the carrier and the impregnation solution are mixed and impregnated for a period of time at a certain solid-liquid ratio. After filtration, the adsorbent precursor is dried at a certain temperature for a certain period of time to obtain a refined and impurity-removed adsorbent for liquid-phase chlorosilane.

[0035] The preferred material in this embodiment is coconut shell granular activated carbon with a mesh size of 12 - 30, a strength of 99%, an ash content of 0.8%, a specific surface area of 1500 m2 / g, and an acetic acid adsorption capacity of 600 mg / g.

[0036] The preferred ultrasonic environment in this embodiment refers to a frequency of 2*107 Hz.

[0037] The preferred nitric acid solution in this embodiment refers to a nitric acid solution with a concentration of 35%.

[0038] The preferred oxidation modification time in this embodiment is 3 hours.

[0039] The preferred drying temperature and time in this embodiment refer to 110°C and 5 hours.

[0040] The preferred organic active components in this embodiment refer to propionamide and diphenylchloromethane.

[0041] The preferred solvent in this embodiment refers to dichloromethane.

[0042] The preferred concentration in this embodiment refers to a solution with a concentration of 5% prepared by mixing propionamide and diphenylchloromethane in a ratio of 1:1.

[0043] The preferred solid-liquid ratio in this embodiment refers to a volume ratio of 1:3.

[0044] The preferred impregnation time in this embodiment refers to impregnation for 4 hours.

[0045] The preferred drying temperature and time in this embodiment refer to 90 °C and 10 hours; After cooling, a refined impurity-removing adsorbent for liquid-phase chlorosilane is obtained. Specific Embodiment Three: A method for preparing a refined impurity-removing adsorbent for liquid-phase chlorosilane. Specifically, activated carbon is used as a precursor, and in an ultrasonic environment, a nitric acid solution is used as an oxidant to perform oxidative modification on the surface of the activated carbon for a certain period of time. After filtration, it is dried at a certain temperature and time to obtain a carrier for the adsorbent; the organic active component is dispersed in a solvent to prepare an impregnation solution with a certain concentration, and the carrier and the impregnation solution are mixed and impregnated for a certain period of time at a certain solid-liquid ratio. After filtration, the adsorbent precursor is dried at a certain temperature for a certain period of time to obtain a refined impurity-removing adsorbent for liquid-phase chlorosilane.

[0047] The preferred activated carbon in this embodiment is 12-30 mesh coconut shell granular activated carbon with a strength of 98.5%, an ash content of 0.5%, a specific surface area of 1600 m2 / g, and an acetic acid adsorption capacity of 620 mg / g.

[0048] The preferred ultrasonic environment in this embodiment refers to a frequency of 2*107 Hz.

[0049] The preferred nitric acid solution in this embodiment refers to a nitric acid solution with a concentration of 40%.

[0050] The preferred oxidation modification time in this embodiment is 3 hours.

[0051] The preferred drying temperature and time in this embodiment refer to 110 °C and 5 hours.

[0052] The preferred organic active components in this embodiment refer to propionamide and diphenylchloromethane.

[0053] The preferred solvent in this embodiment refers to dichloromethane.

[0054] The preferred concentration in this embodiment refers to a solution prepared by mixing propionamide and diphenylchloromethane in a 1:1 ratio to a concentration of 5%.

[0055] The preferred solid-liquid ratio in this embodiment refers to a volume ratio of 1:3.

[0056] The preferred impregnation time in this embodiment refers to impregnation for 4 hours.

[0057] The preferred drying temperature and time in this embodiment refer to 90 °C and 10 hours; After cooling, a refined impurity-removing adsorbent for liquid-phase chlorosilane is obtained.

[0058] Based on Embodiments 1-3, the performance of the prepared liquid-phase chlorosilane refining and impurity-removing adsorbent was detected. The following is the detection table: The performance of the liquid-phase chlorosilane refining and impurity-removing adsorbent prepared in the present invention was compared with the adsorbents of the prior art. The adsorbents of the prior art are denoted as the original adsorbents I and II. The following is the comparison table: As can be seen from the above, the performance of the liquid-phase chlorosilane refining and impurity-removing adsorbent prepared in this application is relatively high.

[0059] In the present invention, modified activated carbon is used as the adsorbent carrier for the first time. The basic groups such as amino groups, imide groups, lactam groups, amide-like groups, and pyridine-like groups added to the surface of the modified activated carbon will contribute to the adsorption and removal of electron-deficient compound impurities. At the same time, the pore size of the activated carbon after oxidation modification has been enlarged, and the larger pore size is more conducive to the full contact between the impurities in the chlorosilane and the adsorbent, which can effectively improve the adsorption efficiency of the adsorbent. At the same time, it not only has good adsorption capacity for boron and phosphorus compounds, but also has good adsorption performance for other metal impurities. Different from distillation columns and other adsorbents, the equipment required for the preparation of the present invention has less investment, high adsorption efficiency, and can be continuously produced safely and stably. It can effectively improve the purity of chlorosilane, enhance the quality of subsequent polysilicon products, and meet the needs of solar grade, and even semiconductor grade.

[0060] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirits of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent, characterized in that: The steps include: S1: preparing raw materials for preparation, including activated carbon, oxidant, and organic active components; S2: preparing an adsorbent carrier, using activated carbon as a precursor, and using an oxidant to oxidize the surface of the activated carbon in an ultrasonic environment for a period of time. After the oxidation modification is completed, the activated carbon is taken out and filtered, and then dried at a certain temperature and time as an adsorbent carrier; S3: Prepare a refined impurity-removing adsorbent by an impregnation method, disperse the organic active component in a solvent to prepare an impregnation solution of a certain concentration, and mix the carrier and the impregnation solution at a certain solid-liquid ratio and impregnate for a period of time, then filter it to obtain an adsorbent precursor, and then dry it at a certain temperature to obtain a liquid chlorosilane refined impurity-removing adsorbent.

2. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The activated carbon is one of columnar activated carbon, granular activated carbon and spherical activated carbon. The activated carbon is preferably 12-30 mesh coconut shell granular activated carbon. The strength of the coconut shell granular activated carbon must be greater than 98%, the ash content must be less than 1%, and the specific surface area must be greater than 1350m 2 / g, acetic acid adsorption capacity 480-620mg / g, the oxidant is nitric acid solution, and the concentration of the nitric acid solution is 30-50%.

3. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The ultrasonic environment refers to a frequency range of 2*10 6 ~10 9 Hz environment.

4. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The oxidation modification time is 3-5 hours. The oxidation modification refers to adding a certain amount of basic groups on the surface of the activated carbon, including amino, imido, lactam, amide and pyridine groups.

5. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The drying at a certain temperature and time is a drying temperature of 110-130° C. and a drying time of 4-6 hours.

6. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The organic active component is one or more of propionamide, ammonium pyrrolidine dithiocarboxylate, p-hydroxyazobenzene, triethylamine, triphenylmethane chloride, diphenylmethane chloride, ethylenediamine, thioglycolic acid (β-naphthyl)-amide, and β-lactam, and the concentration of the organic active component is 3-10%.

7. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The solvent is one of methanol, ethanol, petroleum ether, dichloromethane, ether and ethyl acetate.

8. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The solid-to-liquid ratio of the carrier to the impregnation solution is 1:2 to 1:5 by volume.

9. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The mixed impregnation time is 4-6 hours.

10. The method for preparing a refined and impurity-removing liquid-phase chlorosilane adsorbent according to claim 1, characterized in that: The drying at a certain temperature is specifically a drying temperature of 80-110° C. and a drying time of 8-12 hours.

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