Polysilicon high-boiler cracking method, cracking reactor, trichlorosilane-containing composition, recycling method and application of trichlorosilane

Abstract

The present application relates to a kind of polycrystalline silicon high-boiling cracking method, cracking reactor, the composition of trichlorosilane, the recycling method and application of trichlorosilane.It includes the following steps in the present application: in the reaction system including polycrystalline silicon high-boiling, composite organic catalyst and hydrogen chloride, under the continuous stirring, polycrystalline silicon high-boiling is cracked and treated, and cracking product is obtained;Wherein, composite organic catalyst includes 22wt%~31wt% of tri-n-butylamine, 68wt%~75wt% of tri-n-octylamine and 1wt%~3wt% of N, N-dimethyl aniline;Cracking product includes at least 35mol% of trichlorosilane.The polycrystalline silicon high-boiling is cracked and treated using composite organic catalyst, can effectively improve the single-pass conversion efficiency of high-boiling without increasing raw material input and operating cost, so that the proportion of trichlorosilane in the obtained cracking product is higher.

Description

Technical Field

[0001] This invention relates to the field of polycrystalline silicon high-boiling-point pyrolysis technology, and in particular to polycrystalline silicon high-boiling-point pyrolysis methods, pyrolysis reactors, trichlorosilane-containing compositions, trichlorosilane recycling methods and applications. Background Technology

[0002] Trichlorosilane is one of the main raw materials in the production of polysilicon. The quality of trichlorosilane has a significant impact on the quality, yield, and processing cost of polysilicon. Traditional technologies using the modified Siemens process generate large amounts of high-boiling-point polysilicon compounds, including significant amounts of hexachlorosilane and other high-boiling-point substances. Converting these high-boiling-point substances into trichlorosilane often requires complex processes and high energy consumption. Therefore, there is an urgent need to develop an efficient and low-cost method for cracking high-boiling-point polysilicon compounds. Summary of the Invention

[0003] Based on this, the purpose of this application includes providing a method for cracking high-boiling-point polycrystalline silicon, a cracking reactor, a trichlorosilane-containing composition, a method for recycling trichlorosilane, and its applications. This application uses a composite organic catalyst to crack high-boiling-point polycrystalline silicon, which can effectively improve the single-pass conversion efficiency of high-boiling-point substances. The resulting cracking products contain a high proportion of trichlorosilane without increasing raw material input or operating costs.

[0004] The first aspect of this application provides a method for pyrolyzing high-boiling polysilicon, comprising the following steps: pyrolyzing the high-boiling polysilicon in a reaction system comprising high-boiling polysilicon, a composite organic catalyst and hydrogen chloride under continuous stirring to obtain pyrolysis products;

[0005] The composite organic catalyst comprises, by weight percentage, 22 wt% to 31 wt% tri-n-butylamine, 68 wt% to 75 wt% tri-n-octylamine, and 1 wt% to 3 wt% N,N-dimethylaniline.

[0006] The pyrolysis products include at least 35 mol% trichlorosilane.

[0007] In some embodiments, the pyrolysis method satisfies one or more of the following conditions:

[0008] The mass ratio of tri-n-butylamine, tri-n-octylamine, and N,N-dimethylaniline in the composite organic catalyst is 1:(2.17–3.41):(0.03–0.14).

[0009] Based on molar percentage, the polycrystalline silicon high-boiling matter includes the following two components with a combined molar concentration of 96 mol% to 100 mol%: Si2Cl6 and Si2HCl5.

[0010] In some embodiments, the pyrolysis method satisfies one or more of the following conditions:

[0011] The molar concentration of the composite organic catalyst in the reaction system is 5 mol% to 65 mol%.

[0012] The pyrolysis treatment temperature is 60℃~180℃, and the pyrolysis treatment pressure is 0.1MPa~1MPa.

[0013] In some embodiments, the pyrolysis process is performed once or more, and the pyrolysis method satisfies one or more of the following conditions:

[0014] Based on molar percentage, the molar concentration of trichlorosilane in the pyrolysis products after one pyrolysis treatment is ≥35 mol%;

[0015] Based on molar percentage, the molar concentration of silicon tetrachloride in the pyrolysis products after one pyrolysis treatment is ≤65 mol%;

[0016] The single-pass conversion rate reached ≥95 mol after one pyrolysis treatment.

[0017] In some embodiments, the pyrolysis method includes the following steps:

[0018] In the presence of the composite organic catalyst, the high-boiling polycrystalline silicon was subjected to a first pyrolysis treatment under continuous stirring to obtain the first pyrolysis product.

[0019] At least a portion of the components in the i-th pyrolysis product is mixed with the polycrystalline silicon high-boiling material and subjected to the (i+1)-th pyrolysis treatment to obtain the (i+1)-th pyrolysis product; where i is an integer ≥ 1.

[0020] A second aspect of this application provides a pyrolysis reactor, including a reaction vessel, a stirrer, and an insulation jacket;

[0021] The stirrer is installed at the center of the reactor and includes stirring blades and a stirring shaft; the heat insulation jacket is disposed on the outside of the reactor.

[0022] The pyrolysis process described in the first aspect is carried out in the reactor.

[0023] In some embodiments, the pyrolysis reactor satisfies one or more of the following conditions:

[0024] The high-boiling polycrystalline silicon compound is added to the reactor through feed inlet two at a rate of 320.5 L / min to 3205 L / min.

[0025] Hydrogen chloride is added to the reactor through the feed inlet three at a rate of 43 L / min to 475.5 L / min;

[0026] The pyrolysis products flow out of the reactor from the discharge port at a rate of 9.5 kg / min to 95 kg / min.

[0027] A third aspect of this application provides a trichlorosilane-containing composition, prepared according to the polycrystalline silicon high-boiling-point pyrolysis method described in the first aspect or obtained by performing the pyrolysis method using the pyrolysis reactor described in the second aspect.

[0028] A fourth aspect of this application provides a method for recycling trichlorosilane, comprising the following steps: using high-boiling polycrystalline silicon as raw material to perform the high-boiling polycrystalline silicon pyrolysis method described in the first aspect to obtain a recycled material containing trichlorosilane, or using the pyrolysis reactor described in the second aspect to perform the pyrolysis method to obtain the recycled material.

[0029] A fifth aspect of this application provides a method for synthesizing polycrystalline silicon, comprising the steps of at least one of the following methods:

[0030] The polycrystalline silicon high-boiling-point pyrolysis method as described in the first aspect;

[0031] A method for synthesizing polycrystalline silicon using the trichlorosilane-containing composition described in the third aspect as a raw material; and

[0032] The method for recycling trichlorosilane as described in the fourth aspect.

[0033] The polycrystalline silicon high-boiling-point cracking method provided in this application uses a composite organic catalyst containing appropriate relative amounts of tri-n-butylamine, tri-n-octylamine and N,N-dimethylaniline to crack polycrystalline silicon high-boiling-point substances. It can significantly improve the single-pass reaction efficiency of cracking under mild reaction conditions, and obtain cracking products with high silicon trichloride content and low tetrachlorosilane content. Moreover, the raw materials and operating costs of the reaction are low.

[0034] The pyrolysis reactor provided in this application is used for the pyrolysis process of high-boiling polysilicon, and can obtain pyrolysis products with high single-pass conversion rate without the introduction of cold hydrogenation equipment.

[0035] The trichlorosilane-containing composition provided in this application has a high trichlorosilane content, low impurity content, and low catalyst residue. It can be used to synthesize polycrystalline silicon through simple post-processing operations, such as without using a cold hydrogenation system.

[0036] The method for recycling trichlorosilane provided in this application has a simple overall process and a high single-pass conversion rate.

[0037] The polysilicon high-boiling-point cracking method, trichlorosilane-containing composition, and trichlorosilane recycling method provided in this application are suitable for polysilicon production. They can provide raw materials with high trichlorosilane content and low impurity content for polysilicon production, and the process is simple. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a reactor for the polycrystalline silicon high-boiling point cracking process in one embodiment of this application, wherein, reference numeral 1 is a reaction vessel, reference numeral 2 is a feed inlet 1, reference numeral 3 is a discharge outlet, reference numeral 4 is a feed inlet 2, reference numeral 5 is a feed inlet 3, reference numeral 6 is a stirrer, and reference numeral 7 is a variable frequency motor. Detailed Implementation

[0040] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0041] The implementation of the present invention will now be described in detail with reference to the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0043] the term

[0044] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0045] In this invention, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0046] In this invention, terms such as "further" and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0047] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0048] In this invention, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the distribution of selectable values ​​within a numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include numerical interval types such as percentage intervals, ratio intervals, and proportion intervals.

[0049] In this invention, the term "room temperature" generally refers to 4℃ to 35℃, and preferably 20℃ ± 5℃. In some embodiments of this invention, room temperature refers to 20℃ to 30℃.

[0050] In this invention, unless otherwise specified, the temperature parameters are allowed to be either constant temperature or vary within a certain temperature range. It should be understood that the constant temperature treatment allows temperature fluctuations within the precision range controlled by the instrument. Fluctuations are permitted within ranges such as ±5℃, ±4℃, ±3℃, ±2℃, and ±1℃.

[0051] There are two main processes for polysilicon production: the modified Siemens process and the silane fluidized bed process. The modified Siemens process is currently the primary method used in industrial production. In the modified Siemens process, trichlorosilane and hydrogen undergo reduction and thermal decomposition in a reduction reaction. The silicon generated during this process is deposited on the surface of a silicon core to form a polycrystalline silicon rod. Byproducts are also generated, including high-boiling-point disilicon and polysilicon compounds, i.e., high-boiling-point substances. At the current stage of technological development, the utilization of high-boiling-point substances is crucial for both economic efficiency and environmental protection in the production process. Therefore, reducing energy consumption and improving reaction efficiency are not only key to reducing polysilicon production costs, but also a direction and mission that enterprises need to continuously optimize for the comprehensive recycling and utilization of byproducts.

[0052] Through long-term research, the inventors of this application have discovered that the choice of catalyst in the reaction system plays a crucial role in the composition of the reaction products during the cracking reaction of high-boiling-point substances. When traditional catalysts are applied to the cracking process of high-boiling-point polycrystalline silicon, the trichlorosilane content in the resulting chlorosilane mixture is not high. More silicon tetrachloride needs to be returned to the cold hydrogenation system of the feedstock unit and reacted in a fluidized bed reactor to obtain trichlorosilane, which increases the energy consumption of the upstream and downstream systems and the catalyst consumption per unit.

[0053] In this application, a composite organic catalyst is used to crack polycrystalline silicon high-boiling-point substances, which can effectively improve the single-pass conversion efficiency of high-boiling-point substances. The resulting cracking products have a high proportion of trichlorosilane without increasing raw material input and operating costs.

[0054] The first aspect of this application provides a method for pyrolyzing high-boiling polysilicon, comprising the following steps: pyrolyzing the high-boiling polysilicon in a reaction system comprising high-boiling polysilicon, a composite organic catalyst and hydrogen chloride under continuous stirring to obtain pyrolysis products;

[0055] The pyrolysis products include at least 35 mol% trichlorosilane.

[0056] In some embodiments, the pyrolysis method includes the following steps: pyrolyzing the polycrystalline silicon high-boiling material in a reaction system comprising a polycrystalline silicon high-boiling material, a composite organic catalyst and hydrogen chloride under continuous stirring to obtain pyrolysis products;

[0057] The composite organic catalyst comprises, by weight percentage, 22 wt% to 31 wt% tri-n-butylamine, 68 wt% to 75 wt% tri-n-octylamine, and 1 wt% to 3 wt% N,N-dimethylaniline.

[0058] The pyrolysis products include at least 35 mol% trichlorosilane.

[0059] The polycrystalline silicon high-boiling-point cracking method provided in this application uses a composite organic catalyst containing appropriate relative amounts of tri-n-butylamine, tri-n-octylamine and N,N-dimethylaniline to crack polycrystalline silicon high-boiling-point substances. It can significantly improve the single-pass reaction efficiency of cracking under mild reaction conditions, and obtain cracking products with high silicon trichloride content and low tetrachlorosilane content. Moreover, the raw materials and operating costs of the reaction are low.

[0060] In some embodiments, in the pyrolysis method, the composite organic catalyst comprises 22wt% to 31wt% tri-n-butylamine by mass percentage, and may also be selected from any one or any two of the following mass percentages: 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, etc. If the percentage of tri-n-butylamine in the composite organic catalyst is too high, it may cause an increase in the silicon tetrachloride content in the product; if the percentage of tri-n-butylamine in the composite organic catalyst is too low, it may cause an increase in the entrainment in the gas phase outlet.

[0061] In some embodiments, in the pyrolysis method, the composite organic catalyst comprises 68wt% to 75wt% tri-n-octylamine, and may also be selected from any one or any two of the following mass percentages: 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, etc. If the percentage of tri-n-octylamine in the composite organic catalyst is too high, it may cause a decrease in the reaction rate; if the percentage of tri-n-octylamine in the composite organic catalyst is too low, it may cause an increase in the entrainment in the gas phase outlet.

[0062] In some embodiments, in the pyrolysis method, the composite organic catalyst comprises 1 wt% to 3 wt% N,N-dimethylaniline, calculated by mass percentage, and may also be selected from any one or any two mass percentages: 1 wt%, 2 wt%, 3 wt%, etc.; if the percentage of N,N-dimethylaniline in the composite organic catalyst is too high, the reaction rate may be difficult to control; if the percentage of N,N-dimethylaniline in the composite organic catalyst is too low, the reaction efficiency may be reduced.

[0063] In some embodiments, the mass ratio of tri-n-butylamine, tri-n-octylamine, and N,N-dimethylaniline in the composite organic catalyst is 1:(2.17–3.41):(0.03–0.14). A suitable mass ratio of tri-n-butylamine, tri-n-octylamine, and N,N-dimethylaniline in the composite organic catalyst helps improve the efficiency and reaction stability of the cracking treatment of high-boiling-point substances. If the mass ratio of tri-n-butylamine, tri-n-octylamine, and N,N-dimethylaniline in the composite organic catalyst is unbalanced, it may cause the cracking process of high-boiling-point substances to react too quickly, resulting in overheating and overpressure conditions, as well as safety and environmental hazards. It may also generate more by-products or reduce the safety of the reaction. In other cases, it may reduce the efficiency of the cracking process of high-boiling-point substances, and the molar percentage of trichlorosilane in the cracking products may be low, failing to meet production requirements.

[0064] In some embodiments, in the pyrolysis method, the mass ratio of tri-n-butylamine to tri-n-octylamine in the composite organic catalyst is 1:(2.17–3.41), and can be further selected from any one of the following mass ratios or a range consisting of any two mass ratios: 1:2.17, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 3.41, etc. A suitable mass ratio of tri-n-butylamine to tri-n-octylamine in the composite organic catalyst contributes to the stability of the pyrolysis treatment of high-boiling-point substances. If the mass ratio of tri-n-butylamine to tri-n-octylamine in the composite organic catalyst is too high, it may lead to an increase in the silicon tetrachloride content in the product; if the mass ratio of tri-n-butylamine to tri-n-octylamine in the composite organic catalyst is too low, it may lead to an increase in the entrainment in the gas phase outlet and a decrease in the reaction rate.

[0065] In some embodiments, in the pyrolysis method, the mass ratio of tri-n-butylamine to N,N-dimethylaniline in the composite organic catalyst is 1:(0.03-0.14), and can be further selected from any one of the following mass ratios or a range consisting of any two mass ratios: 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, etc. A suitable mass ratio of tri-n-butylamine to N,N-dimethylaniline in the composite organic catalyst contributes to the reaction efficiency of the pyrolysis treatment of high-boiling-point substances. If the mass ratio of tri-n-butylamine to N,N-dimethylaniline in the composite organic catalyst is too high, it may cause a decrease in reaction efficiency; if the mass ratio of tri-n-butylamine to N,N-dimethylaniline in the composite organic catalyst is too low, it may lead to difficulty in controlling the reaction efficiency.

[0066] In this application, unless otherwise specified, high-boiling-point polysilicon compounds refer to high-boiling-point disilicon and polysilicon compounds, i.e., high-boiling-point compounds, in the polysilicon production process, including Si2Cl6, Si2HCl5, Si2H2Cl4, Si3Cl8 and Si3Cl8O, etc., among which Si2Cl6 and Si2HCl5 have the highest content.

[0067] In some embodiments, in the pyrolysis method, the high-boiling polycrystalline silicon comprises, by molar percentage, 68-70 mol% Si₂Cl₆, 28-30 mol% Si₂HCl₅, and 2 mol% other components; more specifically, it may be 69 mol% Si₂Cl₆, 29 mol% Si₂HCl₅, and 2 mol% other components. In this application, unless otherwise specified, the other components in the high-boiling polycrystalline silicon refer to Si₂H₂Cl₄, Si₃Cl₈, and Si₃Cl₈O.

[0068] In some embodiments, in the pyrolysis method, the polycrystalline silicon high-boiling matter, based on molar percentage, includes two components with a combined molar concentration of 96-100 mol% as follows: Si2Cl6 and Si2HCl5, and may also be selected from any one molar percentage or any range of two molar percentages: 96 mol%, 97 mol%, 98 mol%, 99 mol%, 100 mol%, etc.

[0069] In some embodiments, in the pyrolysis method, the high-boiling polycrystalline silicon comprises 68-70 mol% Si2Cl6 by molar percentage, and the Si2Cl6 in the high-boiling polycrystalline silicon can be selected from any one or any two molar percentages of the following: 68 mol%, 68.1 mol%, 68.2 mol%, 68.3 mol%, 68.4 mol%, 68.5 mol%, 68.6 mol%, 68.7 mol%, 68.8 mol%, 68.9 mol%, 69 mol%, 69.1 mol%, 69.2 mol%, 69.3 mol%, 69.4 mol%, 69.5 mol%, 69.6 mol%, 69.7 mol%, 69.8 mol%, 69.9 mol%, and 70 mol%.

[0070] In some embodiments, in the pyrolysis method, the high-boiling polycrystalline silicon comprises 28-30 mol% Si₂HCl₅ by molar percentage, wherein the Si₂HCl₅ in the high-boiling polycrystalline silicon can be selected from any one or any two molar percentages of the following: 28 mol%, 28.1 mol%, 28.2 mol%, 28.3 mol%, 28.4 mol%, 28.5 mol%, 28.6 mol%, 28.7 mol%, 28.8 mol%, 28.9 mol%, 29 mol%, 29.1 mol%, 29.2 mol%, 29.3 mol%, 29.4 mol%, 29.5 mol%, 29.6 mol%, 29.7 mol%, 29.8 mol%, 29.9 mol%, and 30 mol%.

[0071] By adjusting the ratio of the composite organic catalyst, further optimization of other process parameters in the reaction system can help improve the single-pass conversion efficiency of high-boiling-point substances and the proportion of trichlorosilane in the cracking products. This can improve the single-pass reaction efficiency of the system without increasing raw material input and operating costs. The improved single-pass conversion efficiency can yield more trichlorosilane, the raw material required for industrial production, thereby helping to reduce the operating cost of the high-boiling-point substance treatment system and reduce the production load of downstream units.

[0072] Unless otherwise specified in this application, single-pass conversion rate refers to the cracking treatment of polycrystalline silicon high-boiling-point material in a reaction system including polycrystalline silicon high-boiling-point material, composite organic catalyst and hydrogen chloride, under continuous stirring; during the treatment process, there can be material inflow and outflow and necessary gas flow to reasonably control temperature and pressure; the outflowing material is a product with a low boiling point, including trichlorosilane and silicon tetrachloride, and the outflowing material can also enter a distillation column for separation.

[0073] In some embodiments, in the pyrolysis method, the molar concentration of the composite organic catalyst in the reaction system is 5 mol% to 65 mol%, further 20 mol% to 65 mol%, and even further 30 mol% to 65 mol%. It can also be selected from any one or any two molar concentrations within a range: 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, and 65 mol%. A suitable molar concentration of the composite organic catalyst in the reaction system is beneficial for improving the efficiency of pyrolysis treatment of high-boiling-point substances and preparing pyrolysis products with a high molar percentage of trichlorosilane. If the molar concentration of the composite organic catalyst in the reaction system is too high, it may cause a decrease in the trichlorosilane content; if the molar concentration of the composite organic catalyst in the reaction system is too low, it may cause an increase in the silicon tetrachloride content.

[0074] In some embodiments, the pyrolysis treatment temperature is 60℃ to 180℃, and can also be selected from any one or any two of the following temperatures: 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, etc.

[0075] In some embodiments, the pyrolysis treatment pressure of 0.1 MPa to 1 MPa in the pyrolysis method can also be selected from any one or any two of the following pressures: 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc.

[0076] In some embodiments, in the pyrolysis method, the molar concentration of trichlorosilane (SiHCl3) in the pyrolysis products after one pyrolysis treatment is ≥35 mol%, further 35 mol% to 65 mol%, and may also be selected from any one or any two molar percentages: 35 mol%, 35.31 mol%, 35.53 mol%, 35.66 mol%, 37.28 mol%, 38.65 mol%, 40 mol%, 42.89 mol%, 47.92 mol%, 45 mol%, 50 mol%, 52.51 mol%, 55 mol%, 56.75 mol%, 58.27 mol%, 59.83 mol%, 60 mol%, 60.37 mol%, 60.77 mol%, 61.24 mol%, 65 mol%, etc.

[0077] In some embodiments, in the pyrolysis method, the molar concentration of silicon tetrachloride (SiCl4) in the pyrolysis products after one pyrolysis treatment is ≤65 mol%, further 35 mol% to 65 mol%, and may also be selected from any one or any two molar percentages: 35 mol%, 36.97 mol%, 37.25 mol%, 37.66 mol%, 38.26 mol%, 39.77 mol%, 40 mol%, 41.29 mol%, 45 mol%, 45.65 mol%, 50 mol%, 50.22 mol%, 55 mol%, 55.57 mol%, 59.57 mol%, 60 mol%, 61.29 mol%, 62.89 mol%, 62.98 mol%, 63.11 mol%, 65 mol%, etc.

[0078] In some embodiments, in the pyrolysis method, the sum of Si2H2Cl4, Si3Cl8, and Si3Cl8O in the pyrolysis products after one pyrolysis treatment, based on molar percentage, is 0 mol% to 2 mol%, further 1 mol% to 2 mol%, and even further 1.4 mol% to 2 mol%. It can also be selected from any of the following molar percentages or any range of two molar percentages: 1 mol%, 1.1 mol%, 1.2 mol%, 1.3 mol%, 1.4 mol%, 1.43 mol%, 1.45 mol%, 1.49 mol%, 1.54 mol%, 1.58 mol%, 1.78 mol%, 1.79 mol%, 1.84 mol%, 1.86 mol%, 1.91 mol%, 1.96 mol%, 1.96 mol%, 1.97 mol%, 1.98 mol%, and 2 mol%, etc.

[0079] In some embodiments, the pyrolysis method achieves a single-pass conversion rate of ≥95% in a single pyrolysis process, which can also be selected from any of the following conversion rate values ​​or a range consisting of any two conversion rate values: 95%, 96%, 97%, 98%, etc.

[0080] Unless otherwise specified in this application, primary pyrolysis treatment refers to mixing the raw materials for the pyrolysis reaction, including high-boiling polycrystalline silicon, composite organic catalyst and hydrogen chloride, in a reactor and reacting them under continuous stirring and suitable temperature, pressure and other conditions; during this treatment process, there may be inflow and outflow of materials and necessary gas flow to reasonably control temperature and pressure.

[0081] In this application, unless otherwise specified, the conversion rate is defined as the molar percentage of high-boiling polycrystalline silicon converted into low-boiling trichlorosilane and silicon tetrachloride, and is calculated as follows: Conversion rate = (M... 三氯氢硅 +M 四氯化硅 ) / M 多晶硅高沸物 M 三氯氢硅 and M 四氯化硅 and M 多晶硅高沸物 These represent the molar amounts of trichlorosilane and silicon tetrachloride generated during the pyrolysis reaction (or, in continuous reactions, the molar amounts of high-boiling polycrystalline silicon consumed). The single-pass conversion rate is defined as described above, representing the conversion rate during a single pyrolysis process, i.e., the conversion rate without subsequent separation processes to return components other than the target product to the pyrolysis system.

[0082] In some embodiments, the pyrolysis method includes the following steps:

[0083] S100: In the system where the composite organic catalyst is present, the high-boiling polycrystalline silicon is subjected to a first pyrolysis treatment under continuous stirring to obtain a first pyrolysis product;

[0084] S200: At least a portion of the components in the i-th pyrolysis product is mixed with the polycrystalline silicon high-boiling material and subjected to the (i+1)-th pyrolysis treatment to obtain the (i+1)-th pyrolysis product; where i is an integer ≥1.

[0085] In some implementations, the cumulative amount method includes the following step before step S200:

[0086] S120: Separate the low-boiling-point components from the first pyrolysis product, while retaining the other components in the first pyrolysis product in the reaction system; the low-boiling-point components include trichlorosilane and silicon tetrachloride. Understandably, the low-boiling-point components may also be separated in a distillation column.

[0087] A second aspect of this application provides a pyrolysis reactor, characterized in that it includes a reaction vessel, a stirrer, and a thermal insulation jacket;

[0088] The stirrer is installed at the center of the reactor and includes stirring blades and a stirring shaft; the heat insulation jacket is disposed on the outside of the reactor.

[0089] The reactor is provided with a feed inlet 1, a feed inlet 2 and a discharge outlet at the top, and a feed inlet 3 at the bottom;

[0090] The pyrolysis process described in the first aspect is carried out in the reactor.

[0091] The pyrolysis reactor provided in this application is used for the pyrolysis process of high-boiling polysilicon, and can obtain pyrolysis products with high single-pass conversion rate without the introduction of cold hydrogenation equipment.

[0092] In some embodiments, the pyrolysis method includes the following steps: introducing a composite organic catalyst, high-boiling polycrystalline silicon, and hydrogen chloride into a reactor 1 through inlet 2, inlet 4, and inlet 5, respectively; stirring with a stirrer 6 driven by a variable frequency motor 7 to distribute the raw materials; continuously stirring at a temperature of 60–180°C and a pressure of 0.1–1 MPa; and after pyrolysis treatment, separating and recovering the pyrolysis products (including silicon tetrachloride, trichlorosilane, dichlorosilane, etc.) through outlet 3 into a downstream system.

[0093] In some embodiments, during the pyrolysis process, high-boiling polycrystalline silicon is added to the reactor through feed inlet two at a rate of 320.5 L / min to 3205.1 L / min.

[0094] In some embodiments, during the pyrolysis process, hydrogen chloride is added to the reactor from the feed inlet three at a rate of 43.2 L / min to 475.5 L / min.

[0095] In some embodiments, during the pyrolysis process, the pyrolysis products flow out of the reactor from the discharge port at a rate of 9.5 kg / min to 95.1 kg / min.

[0096] A third aspect of this application provides a trichlorosilane-containing composition, prepared according to the polycrystalline silicon high-boiling-point pyrolysis method described in the first aspect or obtained by processing the pyrolysis method using the pyrolysis reactor described in the second aspect.

[0097] The trichlorosilane-containing composition provided in this application has a high trichlorosilane content, low impurity content, and low catalyst residue. It can obtain a high-content trichlorosilane suitable for the synthesis of polycrystalline silicon through simple post-processing operations, such as without using a cold hydrogenation system.

[0098] A fourth aspect of this application provides a method for recycling trichlorosilane, comprising the following steps: using high-boiling polycrystalline silicon as raw material to perform the high-boiling polycrystalline silicon pyrolysis method described in the first aspect to obtain a recycled material containing trichlorosilane, or processing it using the pyrolysis reactor described in the second aspect to obtain the recycled material.

[0099] The method for recycling trichlorosilane provided in this application has a simple overall process and a high single-pass conversion rate.

[0100] A fifth aspect of this application provides a method for synthesizing polycrystalline silicon, comprising the steps of at least one of the following methods:

[0101] The polycrystalline silicon high-boiling-point pyrolysis method as described in the first aspect;

[0102] A method for synthesizing polycrystalline silicon using the trichlorosilane-containing composition described in the third aspect as a raw material; and

[0103] The method for recycling trichlorosilane as described in the fourth aspect.

[0104] The polysilicon high-boiling-point cracking method, trichlorosilane-containing composition, and trichlorosilane recycling method provided in this application are suitable for polysilicon production. They can provide raw materials with high trichlorosilane content and low impurity content for polysilicon production, and the process is simple.

[0105] To facilitate understanding and implementation of the present invention, the following more specific and detailed embodiments and comparative examples that are easier to implement are provided for reference.

[0106] The following description, in conjunction with the accompanying drawings, further illustrates the concept, specific examples, and technical effects of the present invention to provide a full understanding of the invention. These descriptions are provided solely to aid in explaining the invention and should not be construed as limiting the scope of the claims.

[0107] Unless otherwise specified, the raw materials used in the following experiments can be purchased from the market.

[0108] Example 1

[0109] Figure 1 The reactor is for the polycrystalline silicon high-boiling-point cracking process in Example 1.

[0110] Based on weight percentage, the composite organic catalyst (27 wt% tri-n-octylamine, 71 wt% tri-n-butylamine, and 2 wt% N,N-dimethylaniline, equivalent to a mass ratio of 1:2.62:0.08 for tri-n-butylamine, tri-n-octylamine, and N,N-dimethylaniline) enters reactor 1 through inlet 2. Polycrystalline silicon high-boiling-point catalyst (composed of 69 mol% Si₂Cl₆, 29 mol% Si₂HCl₅, and 2 mol% other components) enters reactor 1 through inlet 4 at a rate of 320.5 L / min to 3205.1 L / min. Chlorination... Hydrogen is fed into reactor 1 through inlet 5 at a rate of 43.2 L / min to 475.5 L / min according to a certain ratio. The molar concentration of the composite organic catalyst in the reaction system is 5%. The reaction is carried out at a temperature range of 60 to 180°C and a pressure of 0.1 to 1 MPa. During the reaction, the mixture is stirred and distributed by stirrer 6 to improve the mixing effect of liquid and gas. The cracking products obtained from the reaction (silicon tetrachloride, trichlorosilane, dichlorosilane, etc.) are fed into the downstream system for separation and recovery through outlet 3 at a rate of 9.5 kg / min to 95.1 kg / min.

[0111] The pyrolysis products drawn from outlet 3 were found to contain 61.24 mol% silicon tetrachloride, 36.97 mol% trichlorosilane, and 1.79 mol% other components (see Table 1).

[0112] The components in the pyrolysis products were detected using GC-MS (gas chromatography-mass spectrometry).

[0113] Examples 2-14

[0114] The pyrolysis treatment steps in Examples 2 to 14 are basically the same as those in Example 1, except that the molar concentration of the composite organic catalyst in the reaction system is different, which are 8 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, and 65 mol%, respectively. The composition of the pyrolysis products can be found in Table 1.

[0115] Table 1. Catalyst concentration and cracking product composition in Examples 1-14

[0116]

[0117] Therefore, it can be seen that the trichlorosilane content in the pyrolysis products in Examples 1-14 ranges from 36.97 to 63.11 mol%, which is significantly higher than the trichlorosilane content in the products obtained after a single-pass pyrolysis reaction of high-boiling substances in conventional technologies. During the initial increase of catalyst concentration, the molar percentage of trichlorosilane in the reaction products increases slightly; when the catalyst concentration reaches 10 mol%, the trichlorosilane content in the reaction products continues to increase with further increases in catalyst concentration; when the catalyst concentration reaches 55 mol%, further increases in catalyst concentration do not significantly alter the molar percentage of trichlorosilane in the reaction products. It can be seen that when the catalyst concentration is approximately 55 mol%, the high-boiling-point conversion efficiency is highest, resulting in the highest trichlorosilane content in the obtained products, achieving optimal reaction efficiency and product yield.

[0118] Comparative Example 1:

[0119] The pyrolysis treatment steps in Comparative Example 1 are basically the same as those in Example 12, except that the composition of the composite catalyst is different. The catalyst in Comparative Example 1, based on weight percentage, is a composite organic catalyst (tri-n-octylamine 34.1 wt%, tri-n-butylamine 63.1 wt%, N,N-dimethylaniline 2.7 wt%, equivalent to a mass ratio of tri-n-butylamine, tri-n-octylamine and N,N-dimethylaniline of 1:1.85:0.08). The composition of the pyrolysis products obtained can be found in Table 2.

[0120] Comparative Example 2:

[0121] The pyrolysis treatment steps in Comparative Example 2 are basically the same as those in Example 12, except that the composition of the composite catalyst is different. The catalyst in Comparative Example 2, by weight percentage, is a composite organic catalyst (tri-n-octylamine 26.4 wt%, tri-n-butylamine 69 wt%, N,N-dimethylaniline 4.5 wt%, which is equivalent to a mass ratio of tri-n-butylamine, tri-n-octylamine and N,N-dimethylaniline of 1:2.62:0.17). The composition of the pyrolysis products obtained can be found in Table 2.

[0122] Table 2. Catalyst concentration and cracking product composition in Comparative Examples 1–2

[0123]

[0124] The composition of the pyrolysis products after the pyrolysis reactions of Comparative Examples 1, 2, and Example 12 shows that, when the catalyst concentration is the same, the pyrolysis products obtained using the composite organic catalyst in Example 12 have a higher content of trichlorosilane. The content of trichlorosilane in the pyrolysis products of Comparative Example 1 is lower than the corresponding content in Example 12. This may be because the proportion of tri-n-octylamine in the composite catalyst of Comparative Example 1 is lower, and the content of the three components in the composite organic catalyst is unbalanced, thus affecting the efficient pyrolysis of high-boiling polycrystalline silicon and resulting in pyrolysis products with a higher trichlorosilane content.

[0125] The trichlorosilane content in the pyrolysis products of Comparative Example 2 was lower than that in Example 12. This may be because the composite catalyst in Comparative Example 2 had a higher N,N-dimethylaniline content, and the composition of the three components in the composite organic catalyst was unbalanced, thus affecting the efficient pyrolysis of high-boiling polysilicon and resulting in pyrolysis products with a higher trichlorosilane content. Furthermore, a higher N,N-dimethylaniline content in the composite organic catalyst leads to a more vigorous pyrolysis reaction, requiring more sophisticated cooling and subsequent processing, and may also reduce the catalyst's lifespan.

[0126] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

[0127] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0128] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for pyrolyzing high-boiling-point polycrystalline silicon, characterized in that, Includes the following steps: In a reaction system comprising high-boiling polycrystalline silicon, a composite organic catalyst, and hydrogen chloride, the high-boiling polycrystalline silicon is subjected to pyrolysis under continuous stirring to obtain pyrolysis products. The composite organic catalyst comprises, by weight percentage, 22 wt% to 31 wt% tri-n-butylamine, 68 wt% to 75 wt% tri-n-octylamine, and 1 wt% to 3 wt% N,N-dimethylaniline. The pyrolysis products include at least 35 mol% trichlorosilane.

2. The pyrolysis method according to claim 1, characterized in that, One or more of the following conditions must be met: The mass ratio of tri-n-butylamine, tri-n-octylamine, and N,N-dimethylaniline in the composite organic catalyst is 1:(2.17–3.41):(0.03–0.14). Based on molar percentage, the polycrystalline silicon high-boiling material includes the following two components with a combined molar percentage of 96 mol% to 100 mol%: Si2Cl6 and Si2HCl5.

3. The pyrolysis method according to claim 1, characterized in that, One or more of the following conditions must be met: The composite organic catalyst has a molar percentage of 5 mol% to 65 mol% in the reaction system. The pyrolysis treatment temperature is 60℃~180℃, and the pyrolysis treatment pressure is 0.1MPa~1MPa.

4. The pyrolysis method according to claim 1, characterized in that, The pyrolysis process is performed once or multiple times, and the pyrolysis method satisfies one or more of the following conditions: Based on molar percentage, the molar percentage of trichlorosilane in the pyrolysis products after one pyrolysis treatment is ≥35 mol%; Based on molar percentage, the molar percentage of silicon tetrachloride in the pyrolysis products after one pyrolysis treatment is ≤65 mol%; The single-pass conversion rate achieved after one pyrolysis treatment is ≥95 mol.

5. The pyrolysis method according to claim 1, characterized in that, Includes the following steps: In the presence of the composite organic catalyst, the high-boiling polycrystalline silicon was subjected to a first pyrolysis treatment under continuous stirring to obtain the first pyrolysis product. At least a portion of the components in the i-th pyrolysis product is mixed with the polycrystalline silicon high-boiling material and subjected to the (i+1)-th pyrolysis treatment to obtain the (i+1)-th pyrolysis product; where i is an integer ≥ 1.

6. The pyrolysis method according to any one of claims 1 to 5, characterized in that, The pyrolysis process is carried out using a pyrolysis reactor, which includes a reaction vessel, a stirrer, and an insulation jacket. The stirrer is installed at the center of the reactor and includes stirring blades and a stirring shaft; the heat insulation jacket is disposed on the outside of the reactor. The reactor has a feed inlet 1, a feed inlet 2 and a discharge outlet at the top, and a feed inlet 3 at the bottom.

7. The pyrolysis method according to claim 6, characterized in that, One or more of the following conditions must be met: The high-boiling polycrystalline silicon compound is added to the reactor through feed inlet two at a rate of 320.5 L / min to 3205.1 L / min. Hydrogen chloride is added to the reactor through the feed inlet three at a rate of 43.2 L / min to 475.5 L / min; The pyrolysis products flow out of the reactor from the discharge port at a rate of 9.5 kg / min to 95.1 kg / min.

8. A method for recycling trichlorosilane, characterized in that, The method includes the following steps: using high-boiling polycrystalline silicon as raw material, the method for cracking high-boiling polycrystalline silicon according to any one of claims 1 to 7 is used to obtain a recycled material containing trichlorosilane.

9. A method for synthesizing polycrystalline silicon, characterized in that, The steps include at least one of the following methods: The method for pyrolyzing high-boiling polycrystalline silicon according to any one of claims 1 to 7; The method for recycling trichlorosilane as described in claim 8.

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