Experimental device and method for adsorbing and removing carbon-containing chlorosilane in trichlorosilane

Abstract

The invention provides an experimental device and method for adsorbing and removing carbon-containing impurities in trichlorosilane. The experimental device comprises a nitrogen cylinder, a dryer, a feeding tank, an intermediate tank, a mass flow controller, an adsorption column, a sampler, a storage tank and a tail gas processor. After moisture of nitrogen is removed through a dryer, the nitrogen is used for pressurizing the device, a material in the feeding tank flows through an adsorption column through an intermediate tank under the action of pressure difference, methyl dichlorosilane in trichlorosilane is adsorbed and removed, the trichlorosilane is intermittently sampled from a sampler for analysis, and the remaining material enters a storage tank; the tail gas is emptied after being treated by the tail gas treater. According to the device, the methyl dichlorosilane can be adsorbed, meanwhile, materials are prevented from being in contact with moisture in air, more reliable experimental data are provided for industrial application, and corrosion to the device is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of chlorosilane separation, and particularly relates to an experimental device and method for adsorptively removing carbon-containing impurities in trichlorosilane. Background Technique

[0002] Polysilicon is the basic material for preparing photovoltaic cells. Along with the gradual evolution of photovoltaic cells from P-type cells with low conversion efficiency to N-type cells with higher conversion efficiency, the quality requirements for polysilicon are also getting higher and higher. Carbon impurities are an important factor in measuring the quality of polysilicon. They will exist in the form of interstitial atoms in solid solution or precipitation of silicon carbide, resulting in situations such as an increase in leakage current and a decrease in breakdown voltage of silicon devices, seriously affecting the photoelectric conversion efficiency and lifespan of the battery chips.

[0003] Currently, the improved Siemens method is the mainstream process for producing polysilicon. The process of producing polysilicon by the improved Siemens method mainly includes five steps: synthesis of trichlorosilane, purification of trichlorosilane, hydrogen reduction of trichlorosilane, recovery of tail gas, and hydrogenation separation of silicon tetrachloride. Among them, the synthesis of trichlorosilane uses metallurgical-grade silicon powder, hydrogen chloride, and silicon tetrachloride as raw materials, and reacts under the action of a catalyst in a synthesis furnace or a hydrogenation furnace to generate trichlorosilane. Due to the presence of a large number of impurities in industrial silicon, this process is the main source of carbon impurities in the polysilicon production process.

[0004] The carbon-containing impurities in chlorosilane are methylchlorosilane substances, mainly including: methyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, dimethyldichlorosilane, etc.; among them, the boiling point of methyldichlorosilane (41.9 °C) is relatively close to that of trichlorosilane (31.8 °C), and the relative volatility is only 1.16, making it difficult to completely remove it from trichlorosilane, and it will remain in the refined trichlorosilane material. The adsorption process is very suitable for removing methylchlorosilane with a boiling point similar to that of chlorosilane, but the selection of adsorbent and adsorption process parameters are all issues that need to be considered.

[0005] Patent CN109205627A discloses a device and method for adsorptively removing methylchlorosilane impurities to prepare high-purity trichlorosilane. According to the difference in the molecular size of methylchlorosilane monomers, adsorbents for directionally adsorbing different methylchlorosilanes are screened out, but it fails to clearly point out which adsorbent has the best effect.

[0006] Patent CN111115637A discloses a method and device for removing carbon-containing impurities in the production of high-purity chlorosilane. A resin-type adsorbent rich in amino groups and a platinum-based catalyst are filled in the adsorption device, effectively removing methylchlorosilane impurities and producing high-purity chlorosilane above 4N, but the implementation cost is high and the process is complex.

[0007] In order to further reduce the carbon content of trichlorosilane and achieve the preparation of electronic-grade polysilicon, the present invention proposes an experimental device and method for adsorptive removal of carbon-containing impurities in trichlorosilane, screens out adsorbents capable of efficiently separating methyldichlorosilane from trichlorosilane, and explores the process parameters of adsorption. Summary of the Invention

[0008]

Technical Problem to be Solved

[0009] Aiming at the deficiencies of the existing technology, the object of the present invention is to provide an experimental device and method for adsorptive removal of carbon-containing impurities in trichlorosilane, screen the existing adsorbents to achieve efficient separation of methyldichlorosilane from trichlorosilane, and obtain operating parameters to provide certain guidance for process scale-up. The present invention aims to avoid the contact of methyldichlorosilane and trichlorosilane with air through an experimental device and method for adsorptive removal of carbon-containing impurities in trichlorosilane, while obtaining more accurate experimental data and reducing the corrosion of the equipment by the materials.

[0010]

Technical Solution

[0011] In order to achieve the above invention object, the present invention adopts the following technical solutions.

[0012] The present invention provides an experimental device for adsorptive removal of carbon-containing impurities in trichlorosilane, including a nitrogen cylinder, a dryer, a feeding tank, an intermediate tank, a mass flow controller, an adsorption column, a sampler, a storage tank and a tail gas processor; the dryer is used to remove moisture in nitrogen; the adsorption column is used to adsorb and remove methyldichlorosilane in trichlorosilane; the tail gas processor is used to absorb the chlorosilane mixed in the tail gas.

[0013] The outlet of the nitrogen cylinder is connected to the inlet of the dryer, the outlet of the dryer is respectively connected to the gas-phase inlets of the feeding tank, the intermediate tank and the adsorption column, the material outlet of the feeding tank is connected to the material inlet of the intermediate tank; the material outlet at the bottom of the intermediate tank is connected to the inlet of the mass flow controller, the outlet of the mass flow controller is connected to the liquid-phase inlet of the adsorption column; the liquid-phase outlet of the adsorption column is respectively connected to the inlets of the sampler and the storage tank, and the gas-phase outlets at the top of the intermediate tank, the gas-phase outlet at the top of the adsorption column and the gas-phase outlet at the top of the storage tank are connected to the inlet of the tail gas processor.

[0014] As a further supplementary description of the above technical solution, the dryer is a fixed-bed dryer, and a certain amount of calcium chloride or calcium sulfate is placed inside.

[0015] As a further supplementary description of the above technical solution, the feeding tank is detachable, made of polypropylene, and the pressure resistance range is 0.5 - 1.0 Mpa.

[0016] As a further supplementary description of the above technical solution, the intermediate tank is made of 316L, with a temperature range of 0 to 100 °C and a pressure resistance range of ≤0.6 Mpa.

[0017] As a further supplementary description of the above technical solution, the adsorption column is made of 316L, with a temperature range of 0 to 200 °C and a pressure resistance range of ≤1.0 Mpa.

[0018] As a further supplementary description of the above technical solution, the storage tank is made of 316L, with a temperature range of 0 to 100 °C and a pressure resistance range of ≤0.6 Mpa.

[0019] As a further supplementary description of the above technical solution, the tail gas processor is a two-stage absorption, and calcium oxide and water are added to the absorption device.

[0020] The operation method of the experimental device for adsorptive removal of carbon-containing impurities in trichlorosilane of the present invention is as follows:

[0021] Fill a certain amount of adsorbent in the adsorption column; after drying, nitrogen is used to pressurize the device through valve 2, keeping the pressure in the intermediate tank within the range of 0.02 to 0.05 Mpa, exhausting the air in the device to make the adsorbent in a dry nitrogen atmosphere; open valve 1, increase the pressure of the feeding tank, so that the material enters the intermediate tank through the pressure difference, avoiding the contact of the material with air; nitrogen is pressurized through valve 2 to make the pressure in the intermediate tank reach 0.1 to 0.5 Mpa, and the material flow rate into the adsorption column is adjusted by the mass flow controller. The material flows through the adsorption column from bottom to top to achieve the adsorption of methyl dichlorosilane; intermittently take a small amount of material from the sampling port for analysis to judge the adsorption effect of the adsorbent; after adsorption, open valve 3, adjust the temperature of the adsorption column, and desorb and regenerate the adsorbent; the tail gas is discharged after passing through the two-stage absorption device.

[0022] Further, in the above method, the selected adsorbent is one or a mixture of several of activated carbon, silica gel, molecular sieve, resin, metal-organic framework compound and its modified compound.

[0023] Further, in the above method, the flow rate of the material is controlled by the mass flow controller within the range of 1 to 10 g / min.

[0024] Further, in the above method, the adsorption temperature of the adsorption column is within the range of 10 to 50 °C.

[0025] Further, in the above method, GC-MS is used to detect the composition of the material in the sampler.

[0026] Further, in the above method, the desorption temperature of the adsorption column is within the range of 50 to 150 °C.

[0027] Further, in the above method, trichlorosilane and methyldichlorosilane carried by the tail gas are successively absorbed by water and a 3-8% calcium hydroxide or sodium hydroxide solution, and then directly discharged. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0029] Figure 1 FIG. is the structure and flowchart of an experimental device for adsorptive removal of carbon-containing impurities in trichlorosilane according to the present invention, where: Ⅰ. nitrogen cylinder, Ⅱ. dryer, Ⅲ. feeding tank, Ⅳ. intermediate tank, Ⅴ. mass flow controller, Ⅵ. adsorption column, Ⅶ. sampler, Ⅷ. storage tank, Ⅸ. tail gas treatment device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation to the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0033] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are merely exemplary.

[0034] The terms "comprising", "including", "having", "containing", etc. used in this text are all open-ended terms, meaning including but not limited to.

[0035] The terms "first", "second", "Ⅰ", "Ⅱ", "Ⅲ", etc. are only used for differentiating descriptions and cannot be construed as indicating or implying relative importance. In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging vertically, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. The term "vertical" in the present invention is perpendicular to the ground direction.

[0036] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "arranged", "installed", "connected", and "joined" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] All raw materials used in the embodiments of the present invention are obtained by purchasing from the market.

[0038] The schematic diagram of the experimental device for adsorptive removal of carbon-containing impurities in trichlorosilane of the present invention is as Figure 1 shown, and it includes nitrogen cylinder Ⅰ, dryer Ⅱ, feeding tank Ⅲ, intermediate tank Ⅳ, mass flow controller Ⅴ, adsorption column Ⅵ, sampler Ⅶ, storage tank Ⅷ, and tail gas processor Ⅸ. The adsorption column is filled with a certain amount of adsorbent for removing methyldichlorosilane in trichlorosilane;

[0039] The adsorbent is one or a mixture of several of activated carbon, silica gel, molecular sieve, resin, metal-organic framework compound and its modified compound;

[0040] The operation method of the experimental device for adsorptive removal of carbon-containing impurities in trichlorosilane of the present invention is as follows:

[0041] Adsorption process: A certain amount of adsorbent is filled in adsorption column VI. After drying, nitrogen gas passes through valve 2 to pressurize the device, keeping the pressure in intermediate tank IV within the range of 0.02 - 0.05 Mpa, discharging the air in the device, and making the adsorbent in a dry nitrogen atmosphere; open valve 1, increase the pressure of charging tank III, and make the material enter intermediate tank IV through the pressure difference, avoiding the contact of the material with air; nitrogen gas is pressurized through valve 2 to make the pressure in equilibration kettle IV reach 0.1 - 0.5 Mpa, adjust the material flow rate into the adsorption column through mass flow controller V, and the material flows through adsorption column VI from bottom to top to achieve the adsorption of methyl dichlorosilane. Intermittently take a small amount of material from sampler VII for analysis using GC-MS;

[0042] Desorption process: After the adsorbent is saturated in adsorption, close valve 2 and stop feeding; open valve 3, adjust the temperature of adsorption column VI, and desorb and regenerate the adsorbent; the tail gas is discharged after passing through two-stage absorption device IX.

[0043] The technical solution of the present invention will be further described below through embodiments.

[0044] Example 1

[0045] Add a trichlorosilane mixed solution with a methyl dichlorosilane concentration of 0.2 wt% into charging tank III, and then enter the adsorption device at a flow rate of 2.5 g / min. Pass through adsorption column VI filled with 10 g of activated carbon. The particle size of the activated carbon is 0.6 - 0.8 mm, and the average pore diameter is The specific surface area is 300 - 400 m 2 / g. The pressure of adsorption column VI is 0.1 MPa, and the temperature is 20 °C.

[0046] Take a sample through sampler VII every 5 minutes, and analyze the content of methyl dichlorosilane in trichlorosilane by gas chromatography - mass spectrometry until the outlet concentration is close to the inlet concentration and then end the experiment. The analysis results are shown in Table 1.

[0047] Table 1 Concentration ratio of inlet and outlet of the adsorption device in Example 1

[0048] Time / min <![CDATA[Inlet / Outlet Concentration Ratio (C / C 0 )]]> 5 0.0034 10 0.0052 15 0.0157 20 0.0339 25 0.1813 30 0.6787 35 0.8787 40 0.9100 45 0.9113 50 0.9030 55 0.9400 60 0.9670

[0049] Example 2

[0050] Add a trichlorosilane mixed solution with a methyl dichlorosilane concentration of 0.2 wt% into charging tank III, and then enter the adsorption device at a flow rate of 2.5 g / min. Pass through adsorption column VI filled with 10 g of activated silica gel. The particle size of the silica gel is 0.4 - 0.6 mm, and the average pore diameter is The specific surface area is 450 - 650 m 2 / g. The pressure of adsorption column VI is 0.1 MPa, and the temperature is 20 °C.

[0051] Samples were taken once every 5 minutes through Sampler VII, and the content of methyldichlorosilane in trichlorosilane was analyzed by gas chromatography-mass spectrometry until the outlet concentration was close to the inlet concentration, and then the experiment was terminated. The analysis results are shown in Table 2.

[0052] Table 2 Concentration ratio of inlet and outlet of the adsorption device in Example 2

[0053]

[0054]

[0055] Example 3

[0056] A trichlorosilane mixed solution with a methyldichlorosilane concentration of 0.2 wt% was added to Feeding Tank III, and then it entered the adsorption device at a flow rate of 5 g / min, passing through Adsorption Column VI filled with 10 g of activated silica gel. The particle size of the silica gel was 0.4 - 0.6 mm, and the average pore diameter was The specific surface area was 450 - 650 m 2 / g. The pressure of Adsorption Column VI was 0.1 MPa and the temperature was 20 °C.

[0057] Samples were taken once every 5 minutes through Sampler VII, and the content of methyldichlorosilane in trichlorosilane was analyzed by gas chromatography-mass spectrometry until the outlet concentration was close to the inlet concentration, and then the experiment was terminated. The analysis results are shown in Table 3.

[0058] Table 3 Concentration ratio of inlet and outlet of the adsorption device in Example 3

[0059] Time / min <![CDATA[Inlet / Outlet Concentration Ratio (C / C 0 )]]> 5 0.0000 10 0.0008 15 0.0025 20 0.0038 25 0.0071 30 0.1288 35 0.7296 40 0.8946 45 0.9371 50 0.9504 55 0.9558 60 0.9613

[0060] Example 4

[0061] A trichlorosilane mixed solution with a methyldichlorosilane concentration of 0.2 wt% was added to Feeding Tank III, and then it entered the adsorption device at a flow rate of 2.5 g / min, passing through Adsorption Column VI filled with 10 g of activated silica gel. The particle size of the silica gel was 0.4 - 0.6 mm, and the average pore diameter was The specific surface area was 450 - 650 m 2 / g. The pressure of Adsorption Column VI was 0.1 MPa and the temperature was 10 °C.

[0062] Samples were taken once every 5 minutes through Sampler VII, and the content of methyldichlorosilane in trichlorosilane was analyzed by gas chromatography-mass spectrometry until the outlet concentration was close to the inlet concentration, and then the experiment was terminated. The analysis results are shown in Table 4.

[0063] Table 4 Concentration ratio of inlet and outlet of the adsorption device in Example 4

[0064] Time / min <![CDATA[Inlet / Outlet concentration ratio (C / C 0 )]]> 5 0.0000 10 0.0000 15 0.0008 20 0.0017 25 0.0033 30 0.0363 35 0.2171 40 0.4338 45 0.7454 50 0.8408 55 0.8867 60 0.9104

[0065] From the results of Example 1 and Example 2, it can be found that for the same material, the breakthrough time of silica gel is longer than that of activated carbon, and the adsorption capacity is also greater than that of activated carbon, indicating that silica gel is more suitable for removing methyldichlorosilane from trichlorosilane. From the results of Example 2, Example 3 and Example 4, it can be found that the flow rate and temperature will affect the adsorption effect of silica gel. Generally speaking, the smaller the flow rate and the lower the temperature, the better the adsorption performance of silica gel. In summary, when using the experimental device and method for adsorptive removal of carbon-containing impurities in trichlorosilane, the corrosion of the equipment by the material can be reduced, and more accurate data can be obtained, providing certain guidance for industrial applications.

[0066] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An experimental device for adsorbing and removing carbon-containing impurities from trichlorosilane, characterized in that: The experimental device comprises a nitrogen bottle (I), a dryer (II), a feed tank (III), an intermediate tank (IV), a mass flow controller (V), an adsorption column (VI), a sampler (VII), a storage tank (VIII) and an exhaust gas processor (IX); the dryer (II) is used to remove moisture from nitrogen; the adsorption column (VI) is used to adsorb and remove methyldichlorosilane from trichlorosilane; and the exhaust gas processor (IX) is used to absorb chlorosilane mixed in the exhaust gas.

2. The experimental device for adsorbing and removing carbon-containing impurities from trichlorosilane according to claim 1, characterized in that: The outlet of the nitrogen bottle (I) is connected to the inlet of the dryer (II), the outlet of the dryer (II) is respectively connected to the gas phase inlets of the feeding tank (III), the intermediate tank (IV) and the adsorption column (VI), and the material outlet of the feeding tank (III) is connected to the material inlet of the intermediate tank (IV); the material outlet at the bottom of the intermediate tank (IV) is connected to the inlet of the mass flow controller (V), and the outlet of the mass flow controller (V) is connected to the liquid phase inlet of the adsorption column (VI); the liquid phase outlet of the adsorption column (VI) is respectively connected to the inlet of the sampler (VII) and the storage tank (VIII), and the gas phase outlet at the top of the intermediate tank (IV), the gas phase outlet at the top of the adsorption column (VI), and the gas phase outlet at the top of the storage tank (VIII) are connected to the inlet of the tail gas processor (IX).

3. The experimental device for adsorbing and removing carbon-containing impurities from trichlorosilane according to claim 1, characterized in that: The dryer (II) is a fixed bed dryer, in which a certain amount of calcium chloride or calcium sulfate is placed.

4. The experimental device for removing carbon-containing impurities from trichlorosilane by adsorption according to claim 1, characterized in that: The feeding tank (III) is detachable, made of polypropylene, and has a pressure resistance range of 0.5 to 1.0 MPa.

5. The experimental device for removing carbon-containing impurities from trichlorosilane by adsorption according to claim 1, characterized in that: The temperature range of the adsorption column (VI) is 0-200°C, and the pressure range is ≤1.0Mpa.

6. The experimental device for adsorbing and removing carbon-containing impurities from trichlorosilane according to claim 1, characterized in that: The tail gas processor (IX) is a two-stage absorption device, the absorbent of the first stage is water, and the absorbent of the second stage is 3-8% calcium hydroxide or sodium hydroxide solution.

7. A method for removing carbon-containing impurities from trichlorosilane by adsorption, characterized in that: An experimental device for removing carbon-containing impurities from trichlorosilane by adsorption according to any one of claims 1 to 6 comprises the following steps: Step 1. Fill a certain amount of adsorbent into the adsorption column (VI); Step 2. The dried nitrogen is passed through valve (2) to pressurize the device, the pressure of the intermediate tank (IV) is maintained within the range of 0.02 to 0.05 MPa, and the air in the device is exhausted to place the adsorbent in a dry nitrogen atmosphere; Step 3. Open valve (1) to increase the pressure of the feed tank (III), so that the material enters the intermediate tank (IV) through the pressure difference, avoiding contact between the material and the air; Step 4. Nitrogen is pressurized through valve (2) to make the pressure in the intermediate tank (IV) reach 0.1-0.5 MPa, and the material flow rate into the adsorption column is adjusted by the mass flow controller (V). The material flows through the adsorption column from bottom to top to achieve the adsorption of methyldichlorosilane; a small amount of material is intermittently taken out from the sampler (VII) for analysis to determine the adsorption effect of the adsorbent; Step 5. After the adsorption is completed, open the valve (3), adjust the temperature of the adsorption column (VI), and desorb and regenerate the adsorbent; Step 6. The tail gas passes through a two-stage absorption device (IX) and is then discharged.

8. The method for removing carbon-containing impurities from trichlorosilane by adsorption according to claim 7, characterized in that: In step 1, the selected adsorbent is one or a mixture of several of activated carbon, silica gel, molecular sieve, resin, metal organic framework compound and modified compounds thereof.

9. The method for removing carbon-containing impurities from trichlorosilane by adsorption according to claim 7, characterized in that: In step 4, the mass flow controller (V) controls the flow rate of the material in the range of 1 to 10 g / min; the adsorption temperature of the adsorption column (VI) is in the range of 10 to 50°C.

10. The method for removing carbon-containing impurities from trichlorosilane by adsorption according to claim 7, characterized in that: In step 5, the temperature during desorption is in the range of 50 to 150°C.

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