Application and method of photovoltaic cutting waste as raw material for producing trichlorosilane by cold hydrogenation of silicon tetrachloride

Abstract

The application discloses application and method of photovoltaic cutting waste as raw material for cold hydrogenation of silicon tetrachloride to produce trichlorosilane, and belongs to the technical field of comprehensive utilization of waste and production of polysilicon raw material, wherein the photovoltaic cutting waste is silicon debris generated in the process of cutting photovoltaic raw material silicon wafer by diamond wire cutting. Specifically, the photovoltaic cutting waste is mixed with copper chloride catalyst at a mass ratio of 5-200:1, and then grinded and loaded into a reactor, and then silicon tetrachloride vapor and hydrogen are introduced into the reactor, so that trichlorosilane can be obtained through high-temperature catalytic reaction under normal pressure. The method can greatly improve the yield and selectivity of trichlorosilane, realizes the recycling of the photovoltaic cutting waste and silicon tetrachloride, changes waste into treasure, prepares polysilicon production raw material, reduces the process cost, and has a good application prospect in the industrial manufacturing field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste comprehensive utilization and polycrystalline silicon raw material production, and particularly relates to application and method of photovoltaic cutting waste as a raw material for cold hydrogenation of silicon tetrachloride to produce trichlorosilane. BACKGROUND

[0002] Photovoltaic cutting waste is a waste generated in the process of linear cutting of crystalline silicon wafers. Direct discharge of photovoltaic cutting waste will cause serious resource waste and environmental pollution, and also poses a safety hazard. Photovoltaic cutting waste has high-value recycling potential. For example, a method for hydrolysis of photovoltaic cutting silicon waste to produce hydrogen is disclosed in Chinese patent document CN115159453A, a method for producing silicon-calcium alloy using photovoltaic industry cutting waste is disclosed in Chinese patent document CN105112664A, and a method for preparing silicon / carbon composite negative electrode material using photovoltaic industry linear cutting waste silicon is disclosed in Chinese patent document CN114975959A. High-value utilization of photovoltaic cutting waste is of great significance to cost reduction and efficiency improvement of the photovoltaic industry and environmental sustainable development.

[0003] Polycrystalline silicon is an indispensable core basic material for micro-nano electronics and photovoltaic industries. The main production method of polycrystalline silicon at present is the modified Siemens method, i.e. a process of reducing and depositing polycrystalline silicon in a reducing furnace under a hydrogen atmosphere using trichlorosilane as a raw material. However, the production of polycrystalline silicon using this method produces a large amount of silicon tetrachloride as a byproduct. If the generated silicon tetrachloride is not properly treated, it not only represents a serious waste of silicon-rich chemical resources, but also poses a great threat to the environment and human health. The mainstream method for recycling silicon tetrachloride is to use it as a raw material to react with hydrogen gas (cold hydrogenation of silicon tetrachloride) to produce trichlorosilane, which is then reused as a raw material for the production of polycrystalline silicon. This recycling method not only recycles and disposes of a large amount of silicon tetrachloride, but also converts it back into a high-value chemical for the production of polycrystalline silicon, which is a key to realizing resource recycling and sustainable development. For the above process, enterprises currently widely use the catalytic cold hydrogenation process (400-600 ℃) with the addition of silicon powder to reduce silicon tetrachloride, and the reaction equation is 3SiCl4+ 2H2+ Si → 4SiHCl3. As can be seen from the equation, silicon powder is an important raw material for the cold hydrogenation process of silicon tetrachloride. The silicon powder currently used by enterprises is generally metallurgical-grade silicon powder with relatively few impurities, which is expensive, and the metallurgical-grade silicon powder is large in size (a few hundred microns to millimeters) and mainly in the form of non-porous blocks, which has a low degree of mixing with the catalyst in the reaction process, and can easily cause problems such as caking and uneven bed in the fluidized bed reactor, and also increases the difficulty of catalyst activation. If photovoltaic cutting waste is used to replace traditional metallurgical-grade silicon powder as a silicon source, the cost of raw materials can be significantly reduced; further coupled with an efficient catalytic system, it is expected to achieve efficient and low-cost synthesis of trichlorosilane and improve the overall economic efficiency of the process. SUMMARY

[0004] In order to solve the problems of low mixing degree and high cost of the existing silicon powder as a raw material for cold hydrogenation of silicon tetrachloride, the application of photovoltaic cutting waste as a raw material for producing trichlorosilane by cold hydrogenation of silicon tetrachloride is provided.

[0005] The specific technical solutions are as follows:

[0006] The application of photovoltaic cutting waste as a raw material for producing trichlorosilane by cold hydrogenation of silicon tetrachloride is as follows: the photovoltaic cutting waste is used as one of the raw materials, and the hydrogen reduction of silicon tetrachloride is carried out in the presence of copper chloride catalyst to obtain trichlorosilane.

[0007] Preferably, the photovoltaic cutting waste is silicon debris generated by diamond wire cutting of photovoltaic raw material silicon wafer.

[0008] Further preferably, the particle size of the photovoltaic cutting waste is 50 nm-20 μm, the content of silicon element in the photovoltaic cutting waste is ≥90%, the existence form of the silicon element is mainly silicon element, and a small amount of oxidized silicon, and the photovoltaic cutting waste also includes impurity elements Ca, Ni and Fe.

[0009] The photovoltaic cutting waste comes from the flaky or strip-shaped silicon debris generated by diamond wire cutting of photovoltaic raw material silicon wafer, and the size is mostly micron level (0.3~3 μm) or even nanometer level (50~150 nm), and the aggregate state is loose and porous, which is different from the blocky metallurgical grade silicon powder commonly used by enterprises. Compared with the metallurgical grade silicon powder used by enterprises, the micro-nano scale photovoltaic cutting waste has a larger specific surface area, is easier to mix with copper chloride catalyst powder and form more copper-silicon interfaces, thereby facilitating the rapid activation of the catalyst and the full reaction. Therefore, the photovoltaic cutting waste has great potential as a raw material for cold hydrogenation of silicon tetrachloride. In addition, the surface of the photovoltaic cutting waste has an oxidation layer (SiO2 layer), metal impurities (Al, Fe, Mg, Ni, etc.) and organic impurities, etc., and it is difficult to directly recycle and utilize as a silicon source for producing photovoltaic and integrated circuits. However, the present application directly uses the photovoltaic cutting waste as a raw material for producing trichlorosilane by cold hydrogenation of silicon tetrachloride without additional purification operation, which has high cost-effectiveness and provides a path for efficient recycling of photovoltaic cutting waste.

[0010] The application also provides a method for producing trichlorosilane by cold hydrogenation of silicon tetrachloride using photovoltaic cutting waste as a raw material, which comprises the following steps:

[0011] The photovoltaic cutting waste is mixed and ground with copper chloride catalyst at a mass ratio of 5~1000:1 (further 5~200:1), and then loaded into a reactor. Then, silicon tetrachloride vapor and hydrogen are introduced into the reactor, and trichlorosilane is obtained by high-temperature catalytic reaction under normal pressure (relative atmospheric pressure is 0 MPa).

[0012] Preferably, the copper chloride catalyst is CuCl or CuCl2.

[0013] Preferably, the reaction space velocity (total flow rate of silicon tetrachloride and hydrogen to catalyst mass ratio) is 2000-1000000 ml g 催化剂 -1 h -1 (further 20000-200000 ml g 催化剂 -1 h -1 ), the gas flow rate ratio of silicon tetrachloride vapor to hydrogen is 1:1-10.

[0014] Preferably, the high-temperature catalytic reaction conditions are temperature 300-600 ℃, further 400-600 ℃, and time ≥6h.

[0015] Optionally, the photovoltaic cutting waste and the copper chloride catalyst are mixed and ground at a mass ratio of 5-1000:1, then granulated to 40-60 meshes, and loaded into a reactor for high-temperature catalytic reaction.

[0016] Preferably, during the high-temperature catalytic reaction, the catalyst activation time is 0-6h (the catalyst activation time is significantly reduced compared with the prior art); after the high-temperature catalytic reaction under normal pressure reaches the stable period, the trichlorosilane yield is ≥20%, and the trichlorosilane selectivity is ≥90%. The system of the present application can theoretically achieve higher trichlorosilane yield under pressurized conditions.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] (1) The strategy of using photovoltaic cutting waste instead of metallurgical grade silicon powder used in industry as a silicon tetrachloride cold hydrogenation raw material provided by the present application can significantly improve the trichlorosilane yield and selectivity, wherein the trichlorosilane yield can be increased to 420% of the original, and the stable period selectivity can be increased by 12%.

[0019] (2) The method of the present application can realize the recycling of photovoltaic cutting waste and silicon tetrachloride waste, turning waste into treasure, preparing polycrystalline silicon production raw materials, and reducing process cost; and the photovoltaic cutting waste does not need to be purified and can be directly applied, and the mixing degree of the photovoltaic cutting waste with the copper chloride catalyst is high, and it is not easy to form lumps and partial beds in the fluidized bed reactor, which can improve the catalyst activation speed. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 XRD patterns of photovoltaic cutting waste, metallurgical grade silicon powder and standard silicon (JCPDS 77-2108).

[0021] Figure 2For Example 1 and Comparative Example 1, the air velocity was 67680 ml g. 催化剂 -1 h -1 Comparison charts of the cold hydrogenation performance of silicon tetrachloride at different temperatures: A is a comparison chart of the yield of trichlorosilane, and B is a comparison chart of the selectivity of trichlorosilane.

[0022] Figure 3 For Example 2 and Comparative Example 2, the air velocity was 27072 ml g. 催化剂 -1 h -1 Comparison charts of the cold hydrogenation performance of silicon tetrachloride at different temperatures: A is a comparison chart of the yield of trichlorosilane, and B is a comparison chart of the selectivity of trichlorosilane.

[0023] Figure 4 For the repeatability verification experiment of Example 2, A is a comparison chart of trichlorosilane yield, and B is a comparison chart of trichlorosilane selectivity.

[0024] Figure 5 The images show SEM images of photovoltaic cutting waste and metallurgical grade silicon powder used in Example 3 and Comparative Example 3. A and B are SEM images of photovoltaic cutting waste, and C and D are SEM images of metallurgical grade silicon powder.

[0025] Figure 6 The images and elemental distribution diagrams of "photovoltaic cutting waste + CuCl2" and "metallurgical grade silicon powder + CuCl2" used in Example 3 and Comparative Example 3 are shown below. A is the SEM image of "photovoltaic cutting waste + CuCl2", B and C are the elemental scan diagrams of "photovoltaic cutting waste + CuCl2", D is the SEM image of "metallurgical grade silicon powder + CuCl2", and E and F are the elemental distribution diagrams of "metallurgical grade silicon powder + CuCl2".

[0026] Figure 7 For Example 3 and Comparative Example 3, the air velocity was 113364 ml g. 催化剂 -1 h -1 Comparison charts of the cold hydrogenation performance of silicon tetrachloride at different temperatures: A is a comparison chart of the yield of trichlorosilane, and B is a comparison chart of the selectivity of trichlorosilane.

[0027] Figure 8 The granulated and non-granulated samples in Example 3 were tested at a space velocity of 113364 ml g. 催化剂 -1 h -1 Comparison charts of the cold hydrogenation performance of silicon tetrachloride at different temperatures: A is a comparison chart of the yield of trichlorosilane, and B is a comparison chart of the selectivity of trichlorosilane. Detailed Implementation

[0028] In order to make the objects, features and advantages of the present application more apparent, specific embodiments will be described in detail below. In the following description, numerous specific details will be set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced in a variety of ways beyond those specifically described herein, and that the present application is not limited to the specific embodiments described below. The features of various embodiments of the present application can be combined, provided that they do not contradict each other, and the present application is not limited to the specific embodiments disclosed below.

[0029] The operation methods not specified in the following examples are generally carried out according to the conventional conditions or the conditions recommended by the manufacturers. The contents not described in detail in the specification belong to the prior art known to those skilled in the art. The experimental materials used in the following examples can be purchased from the conventional biochemical reagent companies, unless otherwise specified.

[0030] In the examples and comparative examples, the photovoltaic cutting waste, metallurgical grade silicon powder and CuCl2 catalyst are all from enterprises, the metallurgical grade silicon powder is a commercially available product, and the photovoltaic cutting waste is silicon scrap waste generated during the cutting of silicon wafers by diamond wire saws in the process of preparing solar cells, mainly composed of micron and submicron silicon particles with a particle size range of 50 nm-20 μm. The main components of the photovoltaic cutting waste and the metallurgical grade silicon powder are both silicon Figure 1 ), the silicon content in the photovoltaic cutting waste is ≥90%, and the silicon content in the metallurgical grade silicon powder is ≥98%, and the main trace impurity elements contained in the photovoltaic cutting waste and the metallurgical grade silicon powder are shown in Table 1 and Table 2, respectively. The CuCl (AR) and SiCl4 (AR, 99.50%) used are purchased from China Pharmaceutical Group Co., Ltd. and Shanghai Aladdin Biochemical Technology Co., Ltd., respectively.

[0031] Table 1 Main impurity elements and contents contained in the photovoltaic cutting waste (ICP-MS test results)

[0032]

[0033] Note: The types and contents of impurity elements in this silicon powder are obtained by dissolving the silicon powder with aqua regia and then measuring the ICP-MS full spectrum of the obtained solution, and the mass fraction less than 0.0001% is not significant and is not included in the table.

[0034] Table 2 Main impurity elements and contents contained in the metallurgical grade silicon powder (ICP-MS test results)

[0035]

[0036] Note: The types and contents of impurity elements in the silicon powder were obtained by ICP-MS full spectrum of the solution obtained after the silicon powder was dissolved with aqua regia. Mass fractions less than 0.0001% are not significant and are not included in the table.

[0037] Example 1

[0038] (1) After the photovoltaic cutting waste and CuCl catalyst were mixed and ground at a mass ratio of 5:1 for 10 min, 100 mg was weighed into a quartz tube and placed in a flow phase reactor, then SiCl4vapor (3 ml / min) and H2(15.8 ml / min) were introduced into the reactor, and the above raw materials were converted into trichlorosilane by high-temperature and normal-pressure catalytic reaction (500°C, 22 h). The reaction product was monitored online by gas chromatography.

[0039] In this example, the photovoltaic cutting waste was used as the raw material for the cold hydrogenation of silicon tetrachloride, and the activation could be quickly achieved (A in Figure 2 , the activation time was 0 min, and the initial trichlorosilane yield could reach 10.8%, and the selectivity of trichlorosilane was 100% (B in Figure 2 ). As the reaction proceeded, the silicon powder was gradually consumed, and the trichlorosilane yield gradually decreased, but it was still much higher than that of Comparative Example 1. The results of integrating the trichlorosilane yield with respect to time showed that the yield of this example was increased by about 155% compared with Comparative Example 1. In this example, the selectivity of SiHCl3 remained unchanged as the reaction time was prolonged.

[0040] Example 2

[0041] (1) After the photovoltaic cutting waste and CuCl catalyst were mixed and ground at a mass ratio of 5:1 for 10 min, 100 mg was weighed into a quartz tube and placed in a flow phase reactor, then SiCl4vapor (3 ml / min) and H2(15.8 ml / min) were introduced into the reactor, and the above raw materials were converted into trichlorosilane by high-temperature and normal-pressure catalytic reaction (500°C, 22 h). The reaction product was monitored online by gas chromatography.

[0042] In this example, the photovoltaic cutting waste was used as the raw material for the cold hydrogenation of silicon tetrachloride, and the activation could be quickly achieved (A in Figure 3 , the activation time was 0 min, and the initial trichlorosilane yield could reach 15.9%, and the selectivity of trichlorosilane was 93.4% (B in Figure 3(B in the original text). As the reaction proceeds, the silicon powder is gradually consumed, and the yield of trichlorosilane gradually decreases, but it is still much higher than that of Comparative Example 2. The results of integrating the trichlorosilane yield with time show that the yield of this example is increased by approximately 420% compared to Comparative Example 2. In this example, the selectivity of trichlorosilane gradually increases slightly with the extension of reaction time, eventually approaching 100%, and the selectivity during the steady-state period is improved by approximately 12% compared to Comparative Example 2. In addition, repeatability verification was also performed in this example (…). Figure 4 That is, the same amount of sample was taken again and the catalytic experiment was carried out under the same conditions. The results showed that the repeatability was good.

[0043] Example 3

[0044] (1) Photovoltaic cutting waste and CuCl2 catalyst were mixed and ground at a mass ratio of 200:1 for 10 min. 1000 mg of the mixture was weighed, placed in a quartz tube, and then placed in a mobile phase reactor. SiCl4 vapor (1.5 ml / min) and H2 (7.9 ml / min) were then introduced into the reactor. The above raw materials were converted into trichlorosilane through a high-temperature and atmospheric-pressure catalytic reaction (500 °C, 85 h). The reaction products were monitored online by gas chromatography.

[0045] This embodiment uses photovoltaic cutting waste as a raw material for SiCl4 cold hydrogenation and employs CuCl2 as a catalyst for the reaction. The photovoltaic cutting waste is relatively small in size ( Figure 5 (AB in the image) can be uniformly mixed with CuCl2 catalyst (see the characterization diagram of the mixture and grinding of photovoltaic cutting waste and CuCl2 catalyst for details). Figure 6 (AC). The results show that after a relatively short activation period (~6 h), the hydrogenation yield of silicon tetrachloride rapidly increases to ~20% and can be stably produced for at least 75 h. Figure 7 In the case of A), the selectivity of trichlorosilane during the stable period is approximately 96%. Figure 7 (B in the example). The yield of trichlorosilane during the stabilization period in this embodiment (~20%) is about 4 to 5 times that of Comparative Example 3 (4%~5%), and the selectivity of trichlorosilane during the stabilization period is also improved compared to Comparative Example 3.

[0046] Meanwhile, this embodiment also prepared a set of granulated samples, that is, the mixture of photovoltaic cutting waste and CuCl2 was granulated to 40~60 mesh and tested under the same conditions as above. The results showed that the activation period of the granulated sample was slightly longer than that of the ungranulated sample (from ~6h to ~20h), but the trichlorosilane yield of the granulated sample during the stable period was not much different from that of the ungranulated sample. Figure 8 In A). The selectivity of SiHCl3 was slightly lower than that of the ungranulated sample ( Figure 8 (B in the middle).

[0047] Comparative Example 1

[0048] (1) Metallurgical grade silicon powder and CuCl catalyst were mixed and ground for 10 min at a mass ratio of 5:1. 100 mg of the mixture was loaded into a quartz tube and placed in a flow reactor. SiCl4 vapor (3 ml / min) and H2 (15.8 ml / min) were then introduced into the reactor. The raw materials were converted into trichlorosilane by high-temperature and atmospheric pressure catalytic reaction (500°C, 22 h). The reaction products were monitored online by gas chromatography.

[0049] This comparative example used metallurgical grade silicon powder as the SiCl4 cold hydrogenation raw material. The other experimental procedures and parameters were the same as in Example 1. The initial activity of the catalyst was low (A in Table 1), and the initial trichlorosilane yield was only about 2.7%. The selectivity of trichlorosilane was 100% (B in Table 1). As the reaction progressed, the silicon powder was gradually consumed, and the trichlorosilane yield gradually decreased. The selectivity of trichlorosilane remained unchanged. Figure 2 Figure 2 This comparative example used metallurgical grade silicon powder as the SiCl4 cold hydrogenation raw material. The other experimental procedures and parameters were the same as in Example 1. The initial activity of the catalyst was low (A in Table 1), and the initial trichlorosilane yield was only about 2.7%. The selectivity of trichlorosilane was 100% (B in Table 1). As the reaction progressed, the silicon powder was gradually consumed, and the trichlorosilane yield gradually decreased. The selectivity of trichlorosilane remained unchanged.

[0050] Comparative Example 2

[0051] (1) Metallurgical grade silicon powder and CuCl catalyst were mixed and ground for 10 min at a mass ratio of 5:1. 250 mg of the mixture was loaded into a quartz tube and placed in a flow reactor. SiCl4 vapor (3 ml / min) and H2 (15.8 ml / min) were then introduced into the reactor. The raw materials were converted into trichlorosilane by high-temperature and atmospheric pressure catalytic reaction (500°C, 22 h). The reaction products were monitored online by gas chromatography.

[0052] This comparative example used metallurgical grade silicon powder as the SiCl4 cold hydrogenation raw material. The other experimental procedures and parameters were the same as in Example 2. The initial activity of the catalyst was low (A in Table 2), and the initial trichlorosilane yield was only about 4.9%. The selectivity of trichlorosilane was 93.9% (B in Table 2). As the reaction progressed, the silicon powder was gradually consumed, and the SiHCl3 yield gradually decreased. The SiHCl3 yield increased briefly around 10 h and then decreased rapidly. The selectivity of trichlorosilane also showed a downward trend overall. Figure 3 Figure 3 This comparative example used metallurgical grade silicon powder as the SiCl4 cold hydrogenation raw material. The other experimental procedures and parameters were the same as in Example 2. The initial activity of the catalyst was low (A in Table 2), and the initial trichlorosilane yield was only about 4.9%. The selectivity of trichlorosilane was 93.9% (B in Table 2). As the reaction progressed, the silicon powder was gradually consumed, and the SiHCl3 yield gradually decreased. The SiHCl3 yield increased briefly around 10 h and then decreased rapidly. The selectivity of trichlorosilane also showed a downward trend overall.

[0053] Comparative Example 3

[0054] (1) Metallurgical grade silicon powder and CuCl2 catalyst were mixed and ground for 10 min at a mass ratio of 200:1. 1000 mg of the mixture was loaded into a quartz tube and placed in a flow reactor. SiCl4 vapor (1.5 ml / min) and H2 (7.9 ml / min) were then introduced into the reactor. The raw materials were converted into trichlorosilane by high-temperature and atmospheric pressure catalytic reaction (500°C, 77 h). The reaction products were monitored online by gas chromatography.

[0055] ​​This comparative example uses metallurgical-grade silicon powder as the raw material for cold hydrogenation of SiCl4. Other experimental procedures and parameters are the same as in Example 3. The metallurgical-grade silicon powder used by the company has a larger particle size (…). Figure 5 The CD in the mixture was not uniformly mixed with the CuCl2 catalyst. Figure 6 The results showed that after a relatively long activation period (~25 h), the yield slowly increased to 4%~5%. Figure 7 In the case of A), the selectivity of SiHCl3 during the stable period is approximately 94%. Figure 7 Example B), with performance significantly worse than Example 3.

[0056] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing trichlorosilane from photovoltaic cutting waste as a cold hydrogenation feedstock for silicon tetrachloride, characterized in that, Includes the following steps: Photovoltaic cutting waste and copper chloride catalyst are mixed and ground at a mass ratio of 5~200:1, and then loaded into a reactor. Silicon tetrachloride vapor and hydrogen are then introduced into the reactor, and trichlorosilane is obtained through a high-temperature catalytic reaction under normal pressure. Photovoltaic cutting waste is silicon debris generated from diamond wire cutting of photovoltaic raw material silicon wafers. It is aggregated in a loose and porous state. The particle size range of photovoltaic cutting waste is 50 nm-20 μm. The silicon content in photovoltaic cutting waste is ≥90%. The silicon exists mainly in the form of elemental silicon, and also includes a small amount of oxidized silicon. Photovoltaic cutting waste also includes impurity elements Ca, Ni and Fe. During the high-temperature catalytic reaction, the catalyst activation time is 0-6 h.

2. The method according to claim 1, characterized in that, The copper chloride catalyst is CuCl or CuCl2.

3. The method according to claim 1, characterized in that, The reaction space velocity is 20,000~200,000 ml / g. 催化剂 -1 h -1 The gas flow rate ratio of silicon tetrachloride vapor to hydrogen is 1:1~10.

4. The method according to claim 1, characterized in that, The conditions for high-temperature catalytic reaction are a temperature of 300~600 ℃ and a time of ≥6 h.

5. The method according to claim 1, characterized in that, Photovoltaic cutting waste and copper chloride catalyst are mixed and ground at a mass ratio of 5~200:1, granulated to 40~60 mesh, and then loaded into a reactor for high-temperature catalytic reaction.

6. The method according to claim 1, characterized in that, After the high-temperature catalytic reaction under normal pressure reaches the steady-state period, the yield of trichlorosilane is ≥20% and the selectivity of trichlorosilane is ≥90%.

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