Production device and method of electronic grade silicon tetrachloride

Abstract

The application provides a production device and method of electronic-grade silicon tetrachloride, which comprises a pipeline mixer, a rectifying tower, a photochlorination device, and the like.

Description

Technical Field

[0001] This invention belongs to the field of electronic-grade silicon tetrachloride production technology, specifically relating to an apparatus and method for producing electronic-grade silicon tetrachloride. Background Technology

[0002] Electronic-grade silicon tetrachloride (STC) is used as a silicon source for semiconductor silicon epitaxy. It is a high-performance source material for low-temperature silicon deposition and can directly participate in metal etching. It also acts as a protective sidewall for polymer gas, increasing etching directionality. In waferless auto-cleaning (WAC) processes, STC is used as a precipitating polymer gas. Trace amounts of methylchlorosilanes such as methyldichlorosilane and methyltrichlorosilane in STC can negatively impact the etching morphology and must be removed.

[0003] Both domestically and internationally, crude silicon tetrachloride is generally produced by reacting industrial silicon powder with chlorine gas at high temperatures. During the synthesis of silicon tetrachloride, the presence of carbon in the silicon powder results in the presence of tens to hundreds of ppm of methylchlorosilanes, primarily methyldichlorosilane and methyltrichlorosilane. Silicon tetrachloride, as a byproduct of polycrystalline silicon production, also exhibits this problem. Under standard conditions, silicon tetrachloride has a boiling point of 57.6℃, methyldichlorosilane 41.9℃, and methyltrichlorosilane 66℃. Because the boiling points of silicon tetrachloride and methylchlorosilane are relatively close, traditional distillation methods are ineffective for separation, requiring numerous distillation columns and large reflux ratios, resulting in high energy consumption, poor efficiency, high cost, and an inability to effectively reduce the concentration to below 1 ppm.

[0004] Therefore, trace amounts of methylchlorosilane can be removed through photochlorination, converting it to chloromethylsilane, which has a boiling point above 110℃ and can be effectively removed by distillation. Currently, in the laboratory, photochlorination of methylchlorosilane in silicon tetrachloride can be carried out using a microchannel reactor, significantly reducing its content to less than 1 ppm. However, the product flow rate is low, with a maximum single-system flow rate of only about 10–50 kg / h, which cannot meet the needs of large-scale production. In large-scale production, some companies use stirred reactors for photochlorination. Considering safety issues, external light sources are used, resulting in low light intensity inside the reactor, low reaction efficiency, reaction time of several hours, large liquid holdup in the reactor, high risk, low chlorine utilization efficiency, the need for multiple reactors to operate in parallel, poor continuous operation, and a large initial investment.

[0005] Currently, domestic and foreign companies mainly use photochlorination and distillation methods to remove trace amounts of methylchlorosilane from silicon tetrachloride. However, existing silicon tetrachloride preparation technologies have the following drawbacks: distillation columns have poor removal efficiency for methylchlorosilane, complex processes, and high costs. Currently, photochlorination reactors with external light sources suffer from weak internal light intensity, low photochlorination efficiency, and long reaction times. Furthermore, considering continuous production, multiple reactors need to be connected in parallel, resulting in a large initial investment. Reactive distillation columns with reaction sections in the column body suffer from poor reactive distillation efficiency due to the large diameter of large-scale distillation columns, the rapid attenuation of ultraviolet light, and poor transmittance, preventing irradiation of the central part of the column. Due to the hazardous nature of silicon tetrachloride, reactors with built-in light sources pose significant safety hazards in actual operation. Microchannel reactors with good photochlorination effects have low throughput, which cannot meet the needs of industrial production, and the equipment is difficult to manufacture, with significant barriers to entry and high investment and maintenance costs. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, one embodiment of the present invention proposes a production apparatus for electronic-grade silicon tetrachloride. This solution integrates photochlorination reaction purification and distillation purification by setting a photochlorination device on the reflux pipe of the distillation column. Photochlorination is carried out in the reflux pipe of the distillation column, which can simultaneously realize reaction purification and distillation purification. The equipment is more centralized and the process is simpler.

[0008] Another embodiment of the present invention proposes a method for producing electronic-grade silicon tetrachloride. By photochlorinating methylchlorosilane to convert it into chloromethylsilane, the photochlorinated material is then fed back into a distillation column. Based on the principle that the boiling points of the materials are significantly different, it can effectively remove trace amounts of compounds such as methyldichlorosilane and methyltrichlorosilane that are difficult to remove by distillation. This method is highly targeted and effective.

[0009] According to an embodiment of the first aspect of the present invention, an apparatus for producing electronic-grade silicon tetrachloride is provided, comprising a pipeline mixer for premixing chlorine gas with silicon tetrachloride raw material within the pipeline mixer; a distillation column including a top outlet, a bottom outlet, and a feed inlet, a reflux inlet, and a product outlet disposed between the top outlet and the bottom outlet; the feed inlet of the distillation column is connected to the outlet of the pipeline mixer; the top outlet of the distillation column is connected to a reflux tank via a top condenser and a liquid discharge pipeline; the outlet of the reflux tank is connected to the reflux inlet via a discharge pipeline; and a photochlorination device including a plurality of sight glasses disposed on the liquid discharge pipeline and / or the discharge pipeline, and an ultraviolet light source disposed on one side outside the sight glasses.

[0010] The electronic-grade silicon tetrachloride production apparatus of the present invention, by installing a pipeline mixer before the reactive distillation column, allows chlorine gas and silicon tetrachloride raw material to be premixed before entering the distillation column. Once the premixed material enters the distillation column, the column itself enables further uniform mixing of chlorine gas and silicon tetrachloride raw material during the distillation process. Since photochlorination devices are installed on both the liquid outlet and discharge outlet of the reflux tank, the methylchlorosilane contained in the low-boiling point condensed at the top of the distillation column can achieve a complete photochlorination reaction under the assistance of an ultraviolet lamp irradiation microscope. Therefore, this scheme achieves a good organic integration of photochlorination devices, eliminating the need for additional equipment; it can be implemented by modifying the existing distillation column equipment. The equipment principle of this scheme is simple, easy to manufacture and maintain, and has low initial investment and maintenance costs.

[0011] In some embodiments, a chlorine recovery device is further included, which includes a chlorine recovery condenser. The tail gas inlet of the chlorine recovery condenser is connected to the tail gas outlet of the tower top condenser. The chlorine recovery condenser is used to condense a portion of the substances in the tail gas into a liquid recoverable. The liquid recoverable is a mixture containing silicon tetrachloride and chlorine. The condensate outlet of the chlorine recovery condenser is connected to a reflux tank.

[0012] This solution utilizes a chlorine recovery device installed at the tail gas outlet of the overhead condenser to recover unreacted chlorine, thereby improving chlorine utilization efficiency and reducing chlorine consumption and production costs. The solution also connects a chlorine recovery condenser to the outlet of the uncondensed gas in the overhead condenser. Through heat exchange with a lower-temperature refrigerant, the incompletely liquefied chlorine and silicon tetrachloride in the overhead condenser are further liquefied. The liquefied material is then piped back into the reflux tank and ultimately returned to the distillation column, maximizing material recovery and utilization, thus reducing costs.

[0013] In some embodiments, the exhaust gas outlet of the chlorine recovery condenser is connected to the alkaline washing treatment unit.

[0014] Since some hydrogen chloride gas in the non-condensable gas is condensed at the condensation temperature of the chlorine recovery condenser, an alkaline scrubbing treatment unit is set up here to effectively absorb the hydrogen chloride gas and ensure it meets the required standards before it is released into the air, in order to avoid direct emission into the atmosphere.

[0015] In some embodiments, the diameter of the sight glass is Φ100mm~200mm, the thickness is 10mm~20mm, and the number of sight glasses is 10~30.

[0016] In some embodiments, each ultraviolet light source has 50 to 200 LEDs, which are evenly distributed on a light-emitting surface of Φ50mm to Φ150mm. The power of a single LED is 2W to 3W. The wavelength of the light source is 200nm to 405nm. The distance between the ultraviolet light source and the viewing mirror is less than 10cm.

[0017] According to a second aspect of the present invention, a method for producing electronic-grade silicon tetrachloride comprises the following steps:

[0018] Step 1: The mixture of chlorine and silicon tetrachloride feedstock, after premixing in a pipeline mixer, is fed into the feed inlet of the distillation column;

[0019] Step 2: The mixture of chlorine and silicon tetrachloride feedstock is purified by distillation in a distillation column. The low-boiling point at the top of the column contains chlorine, silicon tetrachloride and methylchlorosilane. The low-boiling point at the top of the column is condensed by the top condenser to form a liquid low-boiling point.

[0020] Step 3: The chlorine and methylchlorosilane contained in the liquid low-boiling product obtained in Step 2 undergo photochlorination reaction under the action of the photochlorination device on the liquid outlet pipe and / or discharge pipe, thereby converting methylchlorosilane into chloromethylsilane.

[0021] Step 4: The low-boiling-point substances after the photochlorination reaction in Step 3 enter the distillation column through the reflux port for distillation and purification. Chloromethylsilane is separated and discharged from the bottom of the column along with the high-boiling-point substances.

[0022] In this scheme, the photochlorination reaction is taken as an example of the methyltrichlorosilane reaction, and the reaction formula is as follows:

[0023] Main reaction: CH3SiCl3 + Cl2 → ClCH2SiCl3 + HCl

[0024] Side reaction: CH3SiCl3 + 2Cl2 → Cl2CHSiCl3 + 2HCl

[0025] CH3SiCl3+3Cl2→Cl3CSiCl3+3HCl

[0026] According to the silicon tetrachloride production method described in this scheme, the materials are first pre-mixed using a pipeline mixer, and then the uniformity of the mixture of chlorine and silicon tetrachloride is greatly improved through gas-liquid exchange in a distillation column. Ultraviolet light irradiation is added to the reflux pipeline. By using LED light sources, increasing the density of LED beads, reducing the distance between the light source and the reactor, and reducing the diameter of the reaction section, gas-liquid miscibility is avoided, effectively preventing ultraviolet light attenuation and significantly increasing the light intensity of the photo-reaction section of the reaction device, thus significantly improving the photochlorination efficiency. After photochlorination, trace impurities of methylchlorosilane are converted to chloromethylsilane, making it easier to separate from silicon tetrachloride during further distillation. The efficient photochlorination reaction effectively removes methylchlorosilane, saving multiple distillation columns, shortening the process flow, and conserving a significant amount of hot water and circulating water, resulting in significant energy savings and consumption reduction. The content of methyldichlorosilane and methyltrichlorosilane in the product is significantly reduced, improving product quality and increasing added value. This method achieves efficient removal of trace methylchlorosilane from silicon tetrachloride and enables large-scale production.

[0027] Preferably, in step two, the uncondensed gas from the low-boiling-point substances at the top of the column, after condensation in the top condenser, enters the chlorine recovery condenser for secondary condensation via heat exchange with a lower-temperature refrigerant, thus forming a liquid mixture of chlorine and silicon tetrachloride. The uncondensed gas after heat exchange in the chlorine recovery condenser is then sent to the alkaline washing unit for tail gas absorption treatment. This process recovers and reuses the incompletely reacted chlorine, improving chlorine utilization, and also recovers and reuses the incompletely condensed silicon tetrachloride, saving production costs. Absorption of hydrogen chloride in the uncondensed gas reduces air pollution.

[0028] Preferably, the mass flow rate ratio of silicon tetrachloride to chlorine gas is 1000:1 to 4000:1.

[0029] Preferably, the feed flow rate of the distillation column is 1000 kg / h to 2000 kg / h, the reflux feed ratio is 5:1 to 10:1, the operating pressure of the distillation column is 90 kPa to 110 kPa, and the top temperature is 77℃ to 83℃. By increasing the throughput of the reaction section, efficient and continuous production can be achieved, greatly improving production efficiency.

[0030] Preferably, in step three, the material temperature inside the reflux tank and the photochlorination unit is 50°C to 70°C, and the pressure inside the reflux tank is equal to the pressure in the distillation column.

[0031] Beneficial effects

[0032] Firstly, this invention incorporates a pipeline mixer, which premixes chlorine gas with silicon tetrachloride feedstock before introducing it into the distillation column. Firstly, the distillation column itself ensures further uniform mixing of chlorine gas and silicon tetrachloride feedstock during the distillation process. Secondly, because photochlorination devices are installed on both the liquid outlet and discharge pipe of the reflux tank, the methylchlorosilane contained in the low-boiling material condensed at the top of the distillation column undergoes a complete photochlorination reaction under the assistance of an ultraviolet lamp sight glass, generating high-boiling-point chloromethylsilane. When the material in the discharge pipe re-enters the distillation column through the reflux port, the high-boiling-point chloromethylsilane generated by photochlorination gradually separates from the silicon tetrachloride and enters the high-boiling-point material, thus being gradually separated and discharged from the column bottom outlet. This solution achieves simultaneous distillation purification and photochlorination reactions through the cooperation of the photochlorination devices on the distillation column and reflux pipe. The equipment principle of this solution is simple, easy to manufacture and maintain, and has low initial investment and maintenance costs.

[0033] Secondly, this solution optimizes the production process. By combining it with the aforementioned production equipment with a specific structure, firstly, by integrating photochlorination and distillation for impurity removal, photochlorination is performed in the reflux pipe of the distillation column, simultaneously achieving both reaction and distillation impurity removal. This results in more centralized equipment and a simpler process. Secondly, by shortening the reaction section diameter, avoiding gas-liquid miscibility, using a single-wavelength UV lamp, increasing UV lamp power, and polishing the inner wall of the reaction section, various elements of the photochlorination reaction are enhanced, significantly improving photochlorination efficiency. Thirdly, through efficient photochlorination, methylchlorosilane is effectively removed, saving multiple distillation columns, shortening the process flow, and conserving significant amounts of hot water and circulating water, resulting in significant energy savings and reduced consumption. Finally, unreacted chlorine gas is recovered and reused, improving chlorine utilization. This solution achieves efficient removal of trace amounts of methylchlorosilane from silicon tetrachloride and enables large-scale production. The content of methyldichlorosilane and methyltrichlorosilane in the product is significantly reduced, improving product quality and increasing its added value to some extent. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the production apparatus of the present invention;

[0036] Figure 2 The sight glass layout in the photochlorination pipeline of this invention Figure 1;

[0037] Figure 3 The sight glass layout in the photochlorination pipeline of this invention Figure 2 ;

[0038] The diagram is labeled as follows: 1. Distillation column, 2. Pipeline mixer, 3. Top condenser, 4. Chlorine recovery condenser, 5. Reflux tank, 6. High boiling point storage tank, 7. Product tank, 8. Ultraviolet light source, 9. Liquid discharge pipe, 10. Discharge pipe, 11. Chlorine gas source, 12. Silicon tetrachloride feed source, 13. Reflux port, 14. Discharge pipe, 15. Alkali washing treatment unit, 16. Sight glass, 17. Ultraviolet lamp light source. Detailed Implementation

[0039] The present invention will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0040] It should be noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," or "the," and similar words used in the specification and claims of this patent application do not express a limitation of quantity, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the elements or objects preceding "comprising" encompass the elements or objects listed following "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same function.

[0041] To address the technical problem that conventional distillation and photochlorination methods cannot deeply remove methylchlorosilane impurities, this invention proposes the following solution.

[0042] In a typical embodiment of the present invention, the production apparatus for electronic-grade silicon tetrachloride includes a distillation column 1, a pipe mixer 2 installed on the feed inlet pipe of the distillation column 1, a top condenser 3 installed at the top outlet of the distillation column 1, and the liquid phase outlet of the top condenser 3 connected to a reflux pipe. The reflux pipe includes a liquid discharge pipe 9 installed at the feed inlet of the reflux tank 5 and a discharge pipe 10 installed at the discharge outlet of the reflux tank 5. Photochlorination devices are installed on both the liquid discharge pipe 9 and / or the discharge pipe 10. Preferably, photochlorination devices are installed on both the liquid discharge pipe 9 and the discharge pipe 10 to achieve better photochlorination effect. The material passing through the discharge pipe 10 will return to the distillation column 1 to achieve effective separation of the converted chloromethylsilane from silicon tetrachloride. This apparatus integrates the photochlorination device and the distillation column 1 to achieve efficient removal of trace amounts of methylchlorosilane from silicon tetrachloride.

[0043] In this design, a pipeline mixer 2 is specifically installed to pre-mix the materials entering distillation column 1. The pipeline mixer 2 is connected to the outlet of chlorine gas source 11 and the feed inlet of silicon tetrachloride source 12. The pipeline mixer 2 enables efficient pre-mixing of chlorine and silicon tetrachloride before they enter distillation column 1. In this design, the pipeline mixer 2 is a static pipeline mixer made of stainless steel, preferably 304 stainless steel. The silicon tetrachloride inlet and the mixed liquid outlet of the static pipeline mixer are both 1.5-inch pipes with flange connections, while the chlorine inlet is a 1 / 2-inch pipe. Chlorine is transported from chlorine gas source 11 to the pipeline mixer 2 using a 1 / 2-inch double-layer EP pipeline, and chlorine metering is achieved using a gaseous MFC.

[0044] In one embodiment of the present invention, the distillation column 1 includes a top outlet, a bottom outlet, a feed inlet, a reflux inlet, and a product outlet, wherein the feed inlet, reflux inlet, and product outlet are located between the top outlet and the bottom outlet, and the product outlet is located between the reflux inlet and the top outlet. The feed inlet of the distillation column 1 is connected to the outlet of the pipeline mixer 2, and the chlorine and silicon tetrachloride material mixed by the pipeline mixer 2 is introduced into the distillation column 1 for distillation treatment. This part of the material contains chlorine, silicon tetrachloride, and trace amounts of methylchlorosilane contained in the silicon tetrachloride raw material. During the distillation process in the distillation column 1, the silicon tetrachloride raw material and chlorine are further fully mixed and gradually enter the low-boiling part, and are discharged through the top outlet and condensed into liquid phase material.

[0045] In this design, the top outlet of the column is connected to the top condenser 3. The low-boiling-point substances at the top of the column exchange heat with the condensing medium inside the shell of the condenser 3 via the tube side, gradually condensing into a liquid phase. The condensing medium is water. The low-boiling-point substances in the liquid phase include silicon tetrachloride, trace amounts of methylchlorosilane, and chlorine. A liquid phase outlet is located at the lower bottom of the connecting head at the end of the tube side, while an outlet for uncondensed gas is located at the top of the connecting head. The liquid phase outlet returns to the reflux port via a reflux pipe and ultimately enters the distillation column 1 for a circulating distillation process. The low-boiling-point inlet side of the top condenser 3 is higher than the outlet side, creating a slope that facilitates the collection and discharge of condensate.

[0046] In this design, a reflux tank 5 is installed on the reflux pipeline. The inlet of the reflux tank 5 is connected to the liquid outlet of the end cap of the condenser 3 at the top of the column via a liquid discharge pipeline 9. The outlet of the reflux tank 5 is ultimately returned to the distillation column 1 via a discharge pipeline 10 and the reflux port. The product outlet is located between the top outlet and the reflux port. One end of the product discharge pipeline 14 is connected to the liquid collector inside the distillation column 1, and the other end is connected to the product tank 7, used to discharge the distilled product into the product tank 7 through the product discharge pipeline 14.

[0047] In a typical embodiment of the present invention, photochlorination devices are respectively installed on the liquid discharge pipe 9 and the discharge pipe 10 of the reflux tank 5. The photochlorination devices include sight glasses 16 installed on the liquid discharge pipe 9 and the discharge pipe 10. Specifically, quartz sight glasses are evenly distributed on the liquid discharge pipe 9 and the discharge pipe 10 of the reflux tank 5, that is, a set of quartz sight glasses is installed at intervals. The sight glasses 16 are arranged in pairs opposite each other. In order to ensure uniform and sufficient ultraviolet light irradiation, the center line of each pair of quartz sight glasses is deflected from the center line of the adjacent pair of sight glasses 16 by a certain angle α, such as 45°, 60°, 90°, etc., as shown in the figure as 60°. Of course, it is not limited to the above-mentioned deflection direction, so that the direction of ultraviolet light irradiated by each pair of adjacent sight glasses 16 is different, thereby achieving a more uniform light reflection effect in the pipe. The spacing between adjacent sight glasses along the length of the pipe is 400-500mm between the centers of two sight glasses 16. Since adjacent sets of sight glasses have a deflection angle, the center-to-center spacing between two sets of adjacent sight glasses in this scheme refers to the distance along the axial direction of the pipe where they are installed. The total length of the pipe with sight glasses is 4-5m. The ultraviolet light transmittance of the quartz sight glasses is 85%-95%, the diameter of the quartz sight glasses is Φ100mm-200mm, and the thickness is 10mm-20mm. The total number of sight glasses 16 installed on the liquid discharge pipe 9 and the discharge pipe 10 is 10-30. As the number of sight glasses increases, the overall length of the photochlorination reaction sight glass pipe is extended, and the photochlorination efficiency is improved. The number of lamps in the ultraviolet lamp light source 17 is 50-200, evenly distributed on the luminous surface of Φ50mm-Φ150mm, and the power of a single lamp is 2W-3W. The distance between the ultraviolet lamp light source 17 and the sight glass 16 should be less than 10cm, preferably less than 5cm. The ultraviolet light enters the pipe through the sight glass 16 and is reflected inside the pipe, thereby providing conditions for the photochlorination reaction.

[0048] This scheme recovers and reuses unreacted chlorine gas, improving chlorine utilization and avoiding material loss. A chlorine recovery device is connected to the gas phase outlet of the top condenser 3 of the distillation column 1. The chlorine recovery section is located at the rear end of the top condenser 3 of the distillation column 1 to recover silicon tetrachloride and unreacted chlorine gas in the tail gas of the column, while HCl and other tail gases are discharged. The chlorine recovery device includes a chlorine recovery condenser 4. Gaseous substances that fail to condense in the top condenser 3 can enter the chlorine recovery condenser 4 for further condensation. The chlorine recovery condenser 4 adopts a shell-and-tube heat exchanger. A refrigerant is introduced into its shell side, and the tail gas of the column enters the tube side. The condensed silicon tetrachloride and chlorine mixture is returned to the reflux tank 5. The inlet side of the chlorine recovery condenser 4 is higher than the outlet side, thus forming a certain slope, which is conducive to the collection and discharge of condensate. The refrigerant used is R22, R23 or R410a, and the refrigerant temperature is controlled at -35℃ to -55℃. At this temperature, silicon tetrachloride and chlorine can condense, while HCl will not condense. The non-condensable HCl gas is then absorbed by the tail gas through the alkaline scrubbing unit.

[0049] The present invention also provides a method for producing electronic grade silicon tetrachloride, the specific steps of which are as follows: Step 1: The mixture of chlorine gas and silicon tetrachloride raw material after premixing in pipeline mixer 2 is fed into the feed inlet of distillation column 1;

[0050] In this invention, considering that the raw material of silicon tetrachloride has a significant impact on the subsequent impurity removal process, in order to reduce the consumption of chlorine, the silicon tetrachloride raw material used needs to be controlled to contain -CH, -SiH impurity components such as dichlorosilane, trichlorosilane, and methylchlorosilane. This can significantly reduce the amount of chlorine consumed in the impurity removal reaction.

[0051] To increase the removal efficiency of methyldichlorosilane and methyltrichlorosilane, this scheme requires controlling the content of -SiH impurities such as dichlorosilane and trichlorosilane in the raw materials; the silicon tetrachloride content should be ≥99.9%, dichlorosilane ≤0.001%, and trichlorosilane ≤0.001%. Because trichlorosilane and dichlorosilane preferentially react with chlorine, the content of these two substances must be controlled. The reaction formulas for trichlorosilane and dichlorosilane with chlorine are as follows:

[0052] SiHCl3 + Cl2 → SiCl4 + HCl

[0053] SiH₂Cl₂ + 2Cl₂ → SiCl₄ + 2HCl

[0054] In this invention, the silicon tetrachloride raw material contains methyl dichlorosilane ≤100ppm and methyl trichlorosilane ≤500ppm; preferably methyl dichlorosilane ≤50ppm and methyl trichlorosilane ≤200ppm; more preferably methyl dichlorosilane ≤30ppm and methyl trichlorosilane ≤100ppm.

[0055] To minimize the introduction of impurities, chlorine gas with a purity of 3N or higher is selected, preferably 5N or higher, thus effectively reducing the introduction of impurity components in the chlorine gas. The chlorine gas is stored in steel cylinders, and the outlet pressure of the gas cylinders is controlled at 3 bar to 6 bar, preferably 4 bar to 5 bar. In this scheme, the chlorine gas is introduced continuously in the gas phase.

[0056] In this invention, the mass flow rate ratio of silicon tetrachloride to chlorine is 1000:1 to 4000:1, preferably 1000:1 to 2000:1. If there are many impurity components, the amount of chlorine introduced can be increased, and vice versa.

[0057] Step 2: The mixture of chlorine and silicon tetrachloride feedstock is purified by distillation in distillation column 1. The low-boiling-point product at the top of the column contains chlorine, silicon tetrachloride and methylchlorosilane. After being condensed by the top condenser 3, the low-boiling-point product is partially condensed to form a liquid low-boiling-point product.

[0058] In this scheme, the feed flow rate of distillation column 1 is 1000 kg / h to 2000 kg / h, and the reflux feed ratio is 5:1 to 10:1. It can be understood that the reflux feed ratio refers to the ratio of the reflux flow rate to the feed flow rate, and the ratio of the high-boiling-point product output of distillation column 1 to the feed flow rate is 5% to 10%. The operating pressure of distillation column 1 is 90 kPa to 110 kPa, and the top temperature is 77℃ to 83℃. The packing of distillation column 1 is structured wire mesh packing made of 304 stainless steel, and the theoretical number of plates is 50 to 100.

[0059] Step 3: The chlorine and methylchlorosilane contained in the liquid low-boiling product obtained in Step 2 undergo photochlorination reaction in the photochlorination unit on the liquid outlet pipe 9 before reflux tank 5 and the discharge pipe 10 after reflux tank 5, thereby converting it into chloromethylsilane.

[0060] The reflux tank 5 and the material it discharges at a temperature of 50-70℃ have an internal pressure equal to the tower pressure. This limitation is intended to determine the reaction temperature and pressure for photochlorination. In this design, the volume of reflux tank 5 is 2m³. 3 ~5m 3 The material used is 304 stainless steel. For example, in the following embodiments of this solution, a 4m³ reflux tank is used. 3 The reflux tank 5's liquid outlet pipe 9 and discharge pipe 10 are made of DN150~DN300mm 304 stainless steel, and the interior is preferably electrolytically polished with a roughness of 0.3-0.5um. In the following embodiments of this scheme, the roughness is 0.4um. The polished inner wall of the pipe can increase the reflection of ultraviolet light and improve the photochlorination efficiency.

[0061] In one embodiment of this scheme, the light source of the photochlorination reaction device is selected as an LED light source with a wavelength of 200nm to 405nm. The single wavelength band and the reduction of useless ultraviolet light generation compared with the high-pressure mercury lamp increase efficiency and reduce energy consumption.

[0062] In this embodiment, considering that the intensity of the light source plays a decisive role in the photochlorination reaction and is crucial to the entire process, an ultraviolet light intensity of 50 mW / cm² is selected as the light source to increase the photochlorination efficiency. 2 ~300mW / cm 2 200mW / cm is preferred 2 ~300mW / cm 2 Ultraviolet light photons have high energy, and the intensity of ultraviolet light decreases significantly with increasing distance.

[0063] Step 4: The low-boiling-point material after the photochlorination reaction in Step 3 enters the distillation column 1 through the reflux port for further purification. Chloromethylsilane enters the high-boiling-point material at the bottom of the column and is separated and discharged from the bottom outlet. In the initial state of the reaction system, full reflux regulation is used to ensure that all the low-boiling-point material returns to the distillation column 1. After the system is running stably, a portion of it will enter the product tank 7 through the product pipeline.

[0064] By optimizing the production process, this invention provides a highly efficient process route for removing trace amounts of methylchlorosilane from silicon tetrachloride. This invention significantly improves production capacity, enabling large-scale continuous production. The process achieves high impurity removal efficiency through the integration of photochlorination and distillation columns. The streamlined process and improved impurity removal efficiency result in significant cost savings.

[0065] The following description is based on specific embodiments:

[0066] Example 1

[0067] Step 1: The mixture of chlorine and silicon tetrachloride raw materials, after premixing in pipeline mixer 2, is fed into the feed inlet of distillation column 1; silicon tetrachloride raw materials and chlorine are mixed in pipeline mixer, with silicon tetrachloride flow rate of 1000 kg / h, silicon tetrachloride to chlorine mass flow rate ratio of 1000:1, and chlorine flow rate of 1 kg / h.

[0068] Step 2: The mixture of chlorine and silicon tetrachloride feedstock is purified by distillation in distillation column 1. The low-boiling point at the top of the column contains chlorine, silicon tetrachloride, and methylchlorosilane. The low-boiling point at the top of the column is condensed by the top condenser 3 to form a liquid low-boiling point. The packing of the photochlorination reactive distillation column is a structured wire mesh packing made of 304 stainless steel, with 80 trays, a feed flow rate of 1000 kg / h, and a reflux feed ratio of 8:1. The high-boiling point of the reactive distillation column is 50 kg / h. The operating pressure of the reactive distillation column is 100 kPa, and the top temperature is 83℃.

[0069] Step 3: The chlorine and methylchlorosilane contained in the liquid low-boiling product obtained in Step 2 undergo a photochlorination reaction under the action of photochlorination devices on the lower liquid pipe 9 and the discharge pipe 10, thereby converting methylchlorosilane into chloromethylsilane. The inner diameter of the lower liquid pipe 9 and the discharge pipe 10 is 219 mm, and the inner wall roughness is 0.4 μm. There are a total of 20 quartz sight glasses, i.e., 10 pairs. The center distance between two adjacent pairs of sight glasses is 400 mm, and the deflection angle between the center lines of two adjacent pairs of sight glasses is 60 degrees. The sight glasses have a diameter of 150 mm and a thickness of 20 mm. The ultraviolet light transmittance of the quartz sight glasses is 90%. The total power of the ultraviolet lamps is 300 W, with 120 lamp beads distributed at a diameter of 150 mm. The ultraviolet lamp wavelength is 365 nm. The distance between the ultraviolet lamps and the sight glasses is 4 cm. The average light intensity at this location is measured to be 200 mW / cm². 2 The temperature of the photochlorination reaction section is controlled at 65℃, and the pressure of the photochlorination reaction section is the same as the operating pressure inside the distillation column.

[0070] Step 4: The low-boiling-point substances after the photochlorination reaction in Step 3 enter the distillation column 1 through the reflux port for distillation purification. Chloromethylsilane is separated and discharged from the bottom of the column along with the high-boiling-point substances through the column bottom outlet. The purified product is discharged into the product tank 7 through the product discharge pipe 14.

[0071] according to Figure 1 The process flow is as follows: the content of methyldichlorosilane and methyltrichlorosilane in silicon tetrachloride raw material and product purified by photochlorination reaction distillation column is shown in the table below. In each embodiment of this scheme, the content of dichlorosilane and trichlorosilane is detected by GC, and the content of methyldichlorosilane and methyltrichlorosilane is detected by GC-MS.

[0072] Table 1 Example 1

[0073]

[0074] As can be seen from Table 1, after the photochlorination reaction, the detection limit of methyldichlorosilane was lower than 0.01 ppm, and the content of methyltrichlorosilane decreased significantly, down to 0.01 ppm, resulting in a significant improvement in product quality.

[0075] Examples 2-4

[0076] The conditions were the same as in Example 1, except that the light intensity was changed to 20 mW / cm². 2 100mW / cm 2 280mW / cm 2 .

[0077] Table 2 Examples 2-4

[0078]

[0079] Compared to Example 1, only the light source intensity was reduced. As shown in Table 2, the photochlorination efficiency decreased significantly after the light source intensity was reduced, resulting in a significant increase in the content of methyltrichlorosilane and methyldichlorosilane in the distillation product. After increasing the light intensity, the content of methyldichlorosilane and methyltrichlorosilane was both below 0.01 ppm. Therefore, the intensity of ultraviolet light has a significant impact on the efficiency of the photochlorination reaction.

[0080] Examples 5 and 6

[0081] Similar to other conditions in Example 1, the chlorine flow rate in the reactive distillation column of Example 1 was changed to 200 g / h and 2000 g / h.

[0082] Table 3 Examples 5 and 6

[0083]

[0084] Compared with Example 1, only the chlorine gas flow rate was reduced. As can be seen from Table 3, the photochlorination efficiency decreased significantly after the chlorine gas flow rate was reduced, resulting in an increase in impurity components in the distillation product. Therefore, to ensure a high photochlorination efficiency, a sufficient chlorine gas supply must be guaranteed.

[0085] Examples 7 and 8

[0086] Similar to Example 1, the content of methylchlorosilane in the raw materials of Example 1 was adjusted, and the specific data are shown in Table 4.

[0087] Table 4 Examples 7 and 8

[0088]

[0089]

[0090] Compared to Example 1, Examples 7 and 8 only adjusted the content of methylchlorosilane in the raw materials. As shown in Table 4, in the photochlorination section, when the content of methyldichlorosilane and methyltrichlorosilane in the material is high, the reaction efficiency decreases; when the content of these components is low, the reaction efficiency increases significantly. Reducing the content of methyldichlorosilane and methyltrichlorosilane in the silicon tetrachloride raw material can significantly reduce the amount of chlorine used and improve the removal efficiency.

[0091] Examples 9 and 10

[0092] Similar to Example 1, the contents of dichlorosilane, trichlorosilane and methylchlorosilane in the raw materials of Example 1 were increased, as detailed in Table 5.

[0093] Table 5 Examples 9 and 10

[0094]

[0095]

[0096] Compared with Example 1, the content of dichlorosilane, trichlorosilane and methylchlorosilane in the silicon tetrachloride raw materials in Examples 9 and 10 increased significantly. The excessive -CH and -SiH impurity components resulted in poor photochlorination effect and a significant decrease in product quality. Conversely, the material with lower -CH and -SiH impurity components showed a significant improvement in product quality after the photochlorination reaction. Therefore, the control of raw material quality is crucial.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A production apparatus for electronic-grade silicon tetrachloride, characterized in that: include: A pipeline mixer is used to premix chlorine gas with silicon tetrachloride raw material within the pipeline mixer. A distillation column includes a top outlet, a bottom outlet, and a feed inlet, a reflux inlet, and a product outlet located between the top outlet and the bottom outlet. The feed inlet of the distillation column is connected to the outlet of a pipeline mixer, used to feed the mixture of chlorine and silicon tetrachloride feedstocks, which have been premixed in the pipeline mixer, into the feed inlet of the distillation column. The mixture of chlorine and silicon tetrachloride feedstocks is then purified by distillation within the distillation column, where the low-boiling-point substances at the top of the column are condensed into liquid low-boiling-point substances by a top condenser. The top outlet of the distillation column is connected to a reflux tank via the top condenser and a liquid outlet pipe. The outlet of the reflux tank is connected to the reflux inlet via a discharge pipe. The product outlet is located between the reflux inlet and the top outlet. The photochlorination device includes several sight glasses installed in the liquid outlet and / or discharge pipe, and an ultraviolet lamp source installed on the outside of the sight glasses. The distance between the ultraviolet lamp source and the sight glasses is less than 10 cm. The ultraviolet light passes through the sight glasses and enters the pipe, where it is reflected, providing conditions for the photochlorination reaction. The photochlorination device is used to carry out the photochlorination reaction of chlorine and methylchlorosilane contained in the liquid phase low-boiling substances in the reflux pipe of the distillation column under the action of the photochlorination device in the liquid outlet and / or discharge pipe, thereby converting methylchlorosilane into chloromethylsilane. After the photochlorination reaction, the low-boiling substances enter the distillation column through the reflux port for distillation purification, wherein the chloromethylsilane is separated and discharged from the bottom of the column along with the high-boiling substances.

2. The production apparatus for electronic-grade silicon tetrachloride according to claim 1, characterized in that: It also includes a chlorine recovery device, which includes a chlorine recovery condenser. The tail gas inlet of the chlorine recovery condenser is connected to the tail gas outlet of the tower top condenser. The chlorine recovery condenser is used to condense some substances in the tail gas into liquid recoverables. The liquid recoverables are a mixture containing silicon tetrachloride and chlorine. The condensate outlet of the chlorine recovery condenser is connected to a reflux tank.

3. The production apparatus for electronic-grade silicon tetrachloride according to claim 2, characterized in that: The tail gas outlet of the chlorine recovery condenser is connected to the alkaline washing treatment unit.

4. The production apparatus for electronic-grade silicon tetrachloride according to claim 1, characterized in that: The diameter of the sight glass is Φ100mm~200mm, the thickness is 10mm~20mm, and the number of sight glasses is 10~30.

5. The production apparatus for electronic-grade silicon tetrachloride according to claim 1, characterized in that: Each ultraviolet light source has 50 to 200 LED beads, evenly distributed on a light-emitting surface of Φ50mm to Φ150mm, with a power of 2W to 3W per LED bead; the light source wavelength is 200nm to 405nm; and the distance between the ultraviolet light source and the viewing mirror is less than 10cm.

6. A production method using the production apparatus for electronic-grade silicon tetrachloride according to any one of claims 1-5, characterized in that: The specific steps are as follows: Step 1: The mixture of chlorine and silicon tetrachloride feedstock, after premixing in a pipeline mixer, is fed into the feed inlet of the distillation column; Step 2: The mixture of chlorine and silicon tetrachloride feedstock is purified by distillation in a distillation column. The low-boiling point at the top of the column contains chlorine, silicon tetrachloride and methylchlorosilane. The low-boiling point at the top of the column is condensed by the top condenser to form a liquid low-boiling point. Step 3: The chlorine and methylchlorosilane contained in the liquid low-boiling product obtained in Step 2 undergo photochlorination reaction under the action of the photochlorination device on the liquid outlet pipe and / or discharge pipe, thereby converting methylchlorosilane into chloromethylsilane. Step 4: The low-boiling-point substances after the photochlorination reaction in Step 3 enter the distillation column through the reflux port for distillation and purification. Chloromethylsilane is separated and discharged from the bottom of the column along with the high-boiling-point substances.

7. The production method according to claim 6, characterized in that: In step two, some of the uncondensed gas after the low-boiling-point substances at the top of the tower are condensed by the top condenser enters the chlorine recovery condenser for secondary condensation through refrigerant heat exchange, thereby forming a liquid mixture of chlorine and silicon tetrachloride. The uncondensed gas after heat exchange in the chlorine recovery condenser is sent to the alkaline washing treatment unit for tail gas absorption treatment.

8. The production method according to claim 6, characterized in that: The mass flow rate ratio of silicon tetrachloride to chlorine gas is 1000:1 to 4000:

1.

9. The production method according to claim 6, characterized in that: The feed flow rate of the distillation column is 1000 kg / h to 2000 kg / h, and the reflux feed ratio is 5:1 to 10:1; the operating pressure of the distillation column is 90 kPa to 110 kPa, and the top temperature is 77℃ to 83℃.

10. The production method according to claim 6, characterized in that: In step three, the material temperature inside the reflux tank and photochlorination unit is 50℃~70℃.

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