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

Abstract

The invention discloses an application and a method for producing trichlorosilane by taking photovoltaic cutting waste as a silicon tetrachloride cold hydrogenation raw material, and belongs to the technical field of comprehensive utilization of wastes and production of polycrystalline silicon raw materials, and the photovoltaic cutting waste is silicon chippings generated by cutting a photovoltaic raw material silicon wafer by a diamond wire. Specifically, the photovoltaic cutting waste and a copper chloride catalyst are mixed and ground according to the mass ratio of (5-200): 1 and then put into a reactor, then silicon tetrachloride steam and hydrogen are introduced into the reactor, and trichlorosilane can be obtained through a high-temperature catalytic reaction under normal pressure. The method realizes reutilization of photovoltaic cutting waste and silicon tetrachloride, turns waste into wealth, prepares a polycrystalline silicon production raw material, reduces the process cost, and has a good application prospect in the field of industrial manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of waste comprehensive utilization and polysilicon raw material production technology, specifically involving the application and method of using photovoltaic cutting waste as a raw material for cold hydrogenation of silicon tetrachloride to produce trichlorosilane. Background Technology

[0002] Photovoltaic cutting waste is generated during the wire cutting of crystalline silicon wafers. Direct discharge of photovoltaic cutting waste leads to serious resource waste and environmental pollution, and also poses safety hazards. However, photovoltaic cutting waste has high value-added recycling potential. For example, Chinese patent document CN115159453A discloses a method for producing hydrogen through hydrolysis of photovoltaic cutting silicon waste; Chinese patent document CN105112664A discloses a method for producing silicon-calcium alloys using photovoltaic industry cutting waste; and Chinese patent document CN114975959A discloses a method for preparing silicon / carbon composite anode materials using silicon from photovoltaic industry wire cutting waste. Achieving high-value utilization of photovoltaic cutting waste is of great significance for cost reduction, efficiency improvement, and environmental sustainable development in the photovoltaic industry.

[0003] Polycrystalline silicon is an indispensable core material for the micro-nano electronics and photovoltaic industries. Currently, the main polycrystalline silicon production method is the modified Siemens process, which uses trichlorosilane as a raw material and undergoes reduction deposition in a hydrogen atmosphere to obtain polycrystalline silicon. However, this method generates a large amount of silicon tetrachloride as a byproduct. Improper disposal of this silicon tetrachloride not only constitutes a serious waste of silicon-rich chemical resources but also poses a significant threat to the environment and human health. The current mainstream method for recovering silicon tetrachloride is to use it as a raw material to react with hydrogen (hydrogenation of silicon tetrachloride) to produce trichlorosilane, which is then reused as a raw material for polycrystalline silicon production. This recovery method can both recover and process large quantities of silicon tetrachloride and transform it back into a high-value chemical for polycrystalline silicon production, making it crucial for achieving resource recycling and sustainable development. For the above process, enterprises currently widely use a catalytic cold hydrogenation process (400~600 ℃) with added silicon powder for the hydrogen reduction of silicon tetrachloride. The reaction equation is 3SiCl4 + 2H2 + Si → 4SiHCl3. This indicates that silicon powder is a crucial raw material for the cold hydrogenation process of silicon tetrachloride. Currently, enterprises generally use metallurgical-grade silicon powder with relatively few impurities, which is expensive. Furthermore, metallurgical-grade silicon powder is large in size (hundreds of micrometers to millimeters), mainly in non-porous block form, resulting in low mixing with the catalyst during the reaction. This can easily cause agglomeration and bed imbalance in fluidized bed reactors, and also increases the difficulty of catalyst activation. If photovoltaic cutting waste can be used to replace traditional metallurgical-grade silicon powder as the silicon source, the raw material cost can be significantly reduced. Further coupling with a highly efficient catalytic system is expected to achieve efficient and low-cost synthesis of trichlorosilane, improving the overall economic efficiency of the process. Summary of the Invention

[0004] To address the issues of low mixing degree and high cost of silicon powder and catalyst in existing cold hydrogenation of silicon tetrachloride, this invention provides the application of photovoltaic cutting waste as a raw material for the cold hydrogenation of silicon tetrachloride to produce trichlorosilane.

[0005] The specific technical solution adopted is as follows: The application of photovoltaic cutting waste as a raw material for the cold hydrogenation of silicon tetrachloride to produce trichlorosilane involves using photovoltaic cutting waste as one of the raw materials to perform hydrogen reduction of silicon tetrachloride in the presence of a copper chloride catalyst to obtain trichlorosilane.

[0006] Preferably, the photovoltaic cutting waste is silicon debris generated from diamond wire cutting of photovoltaic raw material silicon wafers.

[0007] Further preferably, the particle size range of photovoltaic cutting waste is 50 nm-20 μm, the silicon content in the photovoltaic cutting waste is ≥90%, the silicon exists mainly in the form of elemental silicon, and also includes a small amount of oxidized silicon, and the photovoltaic cutting waste also includes impurity elements Ca, Ni and Fe.

[0008] Photovoltaic cutting waste originates from the sheet-like or strip-like silicon fragments generated during diamond wire cutting of photovoltaic raw material silicon wafers. These fragments are mostly micrometer-sized (0.3~3 μm) or even nanometer-sized (50~150 nm), exhibiting a loose and porous aggregated state, unlike the bulk metallurgical-grade silicon powder commonly used by enterprises. Compared to the metallurgical-grade silicon powder used by enterprises, the micro-nano-scale photovoltaic cutting waste has a larger specific surface area, making it easier to mix thoroughly with copper chloride catalyst powder and form more copper-silicon interfaces, thus facilitating rapid catalyst activation and complete reaction. Therefore, photovoltaic cutting waste has great potential as a raw material for the cold hydrogenation of silicon tetrachloride. Furthermore, the surface of photovoltaic cutting waste contains an oxide layer (SiO2 layer), metallic impurities (Al, Fe, Mg, Ni, etc.), and organic impurities, making it difficult to directly recycle and reuse as a silicon source for photovoltaic and integrated circuit production. This invention, however, does not involve additional purification operations, directly using photovoltaic cutting waste as a raw material for the cold hydrogenation of silicon tetrachloride to produce trichlorosilane, offering high cost-effectiveness and providing a highly efficient path for the recycling and reuse of photovoltaic cutting waste.

[0009] This invention also provides a method for producing trichlorosilane from photovoltaic cutting waste as a cold hydrogenation feedstock for silicon tetrachloride, comprising the following steps: Photovoltaic cutting waste and copper chloride catalyst are mixed and ground at a mass ratio of 5~1000:1 (further 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 at atmospheric pressure (0 MPa relative to atmospheric pressure).

[0010] Preferably, the copper chloride catalyst is CuCl or CuCl2.

[0011] Preferably, the reaction space velocity (the ratio of the total flow rate of silicon tetrachloride to hydrogen to the mass of the catalyst) is 2000~1000000 ml g. 催化剂 -1 h -1 (further, 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.

[0012] Preferably, the conditions for the high-temperature catalytic reaction are a temperature of 300~600 ℃, more preferably 400~600 ℃, and a time of ≥6h.

[0013] Optionally, photovoltaic cutting waste and copper chloride catalyst are mixed and ground at a mass ratio of 5~1000:1, granulated to 40~60 mesh, and then loaded into a reactor for high-temperature catalytic reaction.

[0014] Preferably, during the high-temperature catalytic reaction, the catalyst activation time is 0-6 h (significantly reduced compared to existing technologies); after the high-temperature catalytic reaction reaches a stable period under normal pressure, the trichlorosilane yield is ≥20%, and the trichlorosilane selectivity is ≥90%. Theoretically, the system of this invention can achieve a higher trichlorosilane yield under pressurized conditions.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The strategy of using photovoltaic cutting waste instead of industrial metallurgical grade silicon powder as raw material for cold hydrogenation of silicon tetrachloride provided by the present invention can significantly improve the yield and selectivity of trichlorosilane, wherein the yield of trichlorosilane can be increased to 420% of the original, and the selectivity during the stabilization period can be increased by 12%.

[0016] (2) The method of the present invention can realize the reuse of photovoltaic cutting waste and silicon tetrachloride, turning waste into treasure, and preparing raw materials for polycrystalline silicon production, thereby reducing process costs. Moreover, photovoltaic cutting waste can be used directly without purification. It has a high degree of mixing with copper chloride catalyst, and is not easy to agglomerate or deviate in the fluidized bed reactor, which can improve the activation rate of the catalyst. Attached Figure Description

[0017] Figure 1 XRD patterns of photovoltaic cutting waste, metallurgical grade silicon powder, and standard silicon (JCPDS 77-2108).

[0018] Figure 2 For 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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".

[0023] 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.

[0024] 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

[0025] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0026] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0027] In the examples and comparative examples, the photovoltaic cutting waste, metallurgical-grade silicon powder, and CuCl2 catalyst were all sourced from the company. The metallurgical-grade silicon powder was a commercially available product. The photovoltaic cutting waste was silicon debris generated during the diamond wire saw cutting of silicon wafers in the process of manufacturing solar cells, mainly composed of micron- and submicron-sized silicon particles with a particle size range of 50 nm-20 μm. The main component of both the photovoltaic cutting waste and the metallurgical-grade silicon powder was silicon (…). Figure 1 The silicon content in photovoltaic cutting waste is ≥90%, and the silicon exists in the form of elemental silicon and a small amount of silicon oxide (generated by oxidation). The silicon content in metallurgical grade silicon powder is ≥98%. The main trace impurity elements contained in photovoltaic cutting waste and metallurgical grade silicon powder are shown in Table 1 and Table 2, respectively. The CuCl (AR) and SiCl4 (AR, 99.50%) used were purchased from China National Pharmaceutical Group Co., Ltd. and Shanghai Aladdin Biochemical Technology Co., Ltd., respectively.

[0028] Table 1. Main impurity elements and their contents in photovoltaic cutting waste (ICP-MS test results)

[0029] Note: The types and contents of impurity elements in this silicon powder are obtained by measuring the full spectrum of the solution after dissolving the silicon powder in aqua regia. Mass fractions below 0.0001% are not significant and are not included in this table.

[0030] Table 2. Main impurity elements and their contents in metallurgical grade silicon powder (ICP-MS test results)

[0031] Note: The types and contents of impurity elements in this silicon powder are obtained by measuring the full spectrum of the solution after dissolving the silicon powder in aqua regia. Mass fractions below 0.0001% are not significant and are not included in this table.

[0032] Example 1 (1) Photovoltaic cutting waste and CuCl catalyst were mixed and ground at a mass ratio of 5:1 for 10 min. 100 mg of the mixture was weighed, placed into a quartz tube, and then placed in a mobile phase reactor. SiCl4 vapor (3 ml / min) and H2 (15.8 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℃, 22 h). The reaction products were monitored online by gas chromatography.

[0033] This embodiment uses photovoltaic cutting waste as a raw material for cold hydrogenation of silicon tetrachloride, which can quickly activate ( Figure 2 In option A), the activation time is 0 minutes, the initial trichlorosilane yield can reach 10.8%, and the trichlorosilane selectivity is 100%. Figure 2 (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 1. The results of integrating the yield of trichlorosilane over time show that the yield of this example is increased by about 155% compared with Comparative Example 1. In this example, the selectivity of SiHCl3 remains unchanged as the reaction time increases.

[0034] Example 2

[0035] (1) Photovoltaic cutting waste and CuCl catalyst were mixed and ground at a mass ratio of 5:1 for 10 min. 250 mg of the mixture was weighed, placed into a quartz tube, and then placed in a mobile phase reactor. SiCl4 vapor (3 ml / min) and H2 (15.8 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℃, 22 h). The reaction products were monitored online by gas chromatography.

[0036] This embodiment uses photovoltaic cutting waste as a raw material for SiCl4 cold hydrogenation, which can quickly activate ( Figure 3 (A) The activation time is 0 minutes, the initial trichlorosilane yield can reach 15.9%, and the trichlorosilane selectivity is 93.4%. 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.

[0037] Example 3

[0038] (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.

[0039] 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.

[0040] 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).

[0041] Comparative Example 1 (1) Metallurgical grade silicon powder and CuCl catalyst were mixed and ground at a mass ratio of 5:1 for 10 min. 100 mg of the mixture was weighed, placed into a quartz tube, and then placed in a mobile phase reactor. SiCl4 vapor (3 ml / min) and H2 (15.8 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℃, 22 h). The reaction products were monitored online by gas chromatography.

[0042] This comparative example used metallurgical-grade silicon powder as the SiCl4 cold hydrogenation feedstock. Other experimental steps and parameters were the same as in Example 1. The catalyst had a lower initial activity. Figure 2 In option A), the initial yield of trichlorosilane was only about 2.7%, and the selectivity of trichlorosilane was 100%. Figure 2 (B in the text). As the reaction proceeds, the silicon powder is gradually consumed, the yield of trichlorosilane gradually decreases, while the selectivity of trichlorosilane remains unchanged.

[0043] Comparative Example 2 (1) Metallurgical grade silicon powder and CuCl catalyst were mixed and ground at a mass ratio of 5:1 for 10 min. 250 mg of the mixture was weighed, placed into a quartz tube, and then placed in a mobile phase reactor. SiCl4 vapor (3 ml / min) and H2 (15.8 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℃, 22 h). The reaction products were monitored online by gas chromatography.

[0044] This comparative example used metallurgical-grade silicon powder as the SiCl4 cold hydrogenation feedstock. Other experimental procedures and parameters were the same as in Example 2. The catalyst had a lower initial activity. Figure 3 In option A), the initial yield of trichlorosilane was only about 4.9%, and the selectivity of trichlorosilane was 93.9%. Figure 3 (B in the text). As the reaction proceeds, the silicon powder is gradually consumed, and the yield of SiHCl3 gradually decreases. After a brief increase of about 10 hours, it rapidly decreases, and the overall selectivity of trichlorosilane also shows a downward trend.

[0045] Comparative Example 3 (1) Metallurgical grade silicon powder 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 into 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, 77 h). The reaction products were monitored online by gas chromatography.

[0046] 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.

[0047] 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. The application of photovoltaic cutting waste as a raw material for the cold hydrogenation of silicon tetrachloride to produce trichlorosilane, characterized in that, Using photovoltaic cutting waste as one of the raw materials, silicon tetrachloride was reduced by hydrogen in the presence of a copper chloride catalyst to obtain trichlorosilane.

2. The application according to claim 1, characterized in that, Photovoltaic cutting waste refers to silicon debris generated from diamond wire cutting of photovoltaic raw material silicon wafers.

3. The application according to claim 1, characterized in that, The particle size range of photovoltaic cutting waste is 50 nm-20 μm. The silicon content in photovoltaic cutting waste is ≥90%. The silicon mainly exists in the form of elemental silicon, and also includes a small amount of oxidized silicon. Photovoltaic cutting waste also contains impurity elements Ca, Ni and Fe.

4. A method for producing trichlorosilane from photovoltaic cutting waste as a cold hydrogenation feedstock for silicon tetrachloride, characterized in that, The following steps are involved: Photovoltaic cutting waste and copper chloride catalyst are mixed and ground at a mass ratio of 5~1000:1, 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.

5. The method according to claim 4, characterized in that, The copper chloride catalyst is CuCl or CuCl2.

6. The method according to claim 4, characterized in that, The reaction space velocity is 2000~1000000 ml g 催化剂 -1 h -1 The gas flow rate ratio of silicon tetrachloride vapor to hydrogen is 1:1~10.

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

8. The method according to claim 4, characterized in that, Photovoltaic cutting waste and copper chloride catalyst are mixed and ground at a mass ratio of 5~1000:1, granulated to 40~60 mesh, and then loaded into a reactor for high-temperature catalytic reaction.

9. The method according to claim 4, characterized in that, During the high-temperature catalytic reaction, the catalyst activation time is 0-6 h; after the high-temperature catalytic reaction reaches the steady-state period under normal pressure, the yield of trichlorosilane is ≥20% and the selectivity of trichlorosilane is ≥90%.

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