Method and apparatus for the synthesis of hexachlorodisilane

Abstract

The application relates to a method and device for synthesizing hexachloroethyldisilane, which comprises a quartz glass reactor, a ceramic substrate, a gas inlet pipe, a gas outlet pipe, a pair of polar opposite electric stages and a reactor box. The application uses trichlorosilane as an initial raw material, trichlorosilane is mixed with protective gas and enters the reactor, a catalytic reaction is carried out in the reactor, and then the reaction product is collected and used. The device can improve the conversion rate and product yield. The application uses trichlorosilane as a raw material for preparing hexachloroethyldisilane, which has important significance for reducing the production cost of hexachloroethyldisilane and breaking the monopoly of foreign enterprises. The application can be mass-produced based on the ionization discharge technology for synthesizing hexachloroethyldisilane.

Description

Technical Field

[0001] This invention relates to the field of hexachlorosilane production and application technology, specifically to a method and apparatus for synthesizing hexachlorosilane. Background Technology

[0002] Hexachlorosilane is a highly efficient deoxidizer and a raw material for producing silane. It can be used to produce amorphous silicon thin films, optical fiber raw materials, glass, MoSi2, etc. In the photovoltaic industry, Si2Cl6 has the highest adhesion among polycrystalline silicon residues. In thin film deposition processes, using hexachlorosilane, compared to using other silicon source gases (such as silane and dichlorosilane), results in lower deposition temperatures, faster film formation rates, and higher film uniformity. Currently, many advanced integrated circuit chip manufacturers have begun to widely use it.

[0003] Currently, domestic scholars have conducted extensive research on the preparation methods of hexachlorosilane. For example, Chinese patent CN112645337A discloses a method for preparing hexachlorosilane, in which silicon powder, silicon tetrachloride and catalyst are mixed evenly and reacted under microwave in a near-oxygen-free environment at a reaction temperature of 80℃~250℃ for more than 3 hours. After the microwave reaction is completed, the product is cooled to obtain a gas phase and a liquid phase. The liquid phase is filtered, and the filtrate is purified to obtain hexachlorosilane. However, the reaction conditions are quite harsh. Chinese patent CN115594183A discloses a method for preparing hexachlorosilane. First, the tail gas from an electronic-grade polycrystalline silicon production system is separated to obtain hydrogen and silicon tetrachloride. Then, the hydrogenated mixed gas from the electronic-grade polycrystalline silicon production system is distilled to obtain trichlorosilane. Next, silicon tetrachloride, hydrogen, trichlorosilane, and silicon are mixed and reacted to obtain a hexachlorosilane mixture. Finally, the hexachlorosilane mixture is separated to obtain electronic-grade hexachlorosilane. However, this reaction involves complex raw materials and numerous side reactions, making the removal of impurities from the product difficult. Chinese patent CN207918447U discloses a hexachlorosilane synthesis apparatus. This apparatus employs a multi-tiered layered structure within the reactor, with each layer containing a quartz-encased magnet. The magnets move, causing the material at the bottom to rise and better contact the reactant gas. This design also ensures the reactant gas is evenly distributed across each layer, improving material conversion and reducing byproduct formation. In summary, the preparation of hexachlorosilane faces challenges such as expensive raw materials, high production costs, a complex reaction process, demanding reaction conditions, complex products, difficult separation, and numerous side reactions. Therefore, the reaction equipment requires further improvement and enhancement. Summary of the Invention

[0004] In view of the problems in the preparation of hexachlorosilane in the prior art, such as expensive raw materials, high production costs, complicated reaction process, harsh reaction conditions, and complex products, the present invention provides a method and apparatus for the synthesis of hexachlorosilane.

[0005] The technical solution of the present invention is as follows: One aspect is the provision of an apparatus for synthesizing hexachlorosilane: It includes a quartz glass reactor, a ceramic substrate, an inlet pipe, an outlet pipe, a pair of electrodes with opposite polarities, and a reactor box; An inlet pipe and an outlet pipe are installed on the reactor box. The inlet pipe is connected to one side of the quartz glass reactor, and the outlet pipe is connected to the other side of the quartz glass reactor. The quartz glass reactor is located inside the reactor box, and its two ends are electrically connected to electrodes. A ceramic substrate is placed inside the quartz glass reactor, parallel to it. The ceramic substrate is made of alumina and has a honeycomb cross-section. The ceramic substrate serves two purposes: first, it acts as a catalyst carrier, providing a framework, increasing the contact area, accelerating the reaction rate, and improving the conversion rate and product yield; second, it provides high-temperature resistance, preventing catalyst pulverization. On the other hand, a method for preparing hexachlorosilane using the apparatus for synthesizing hexachlorosilane provided by the present invention is as follows: A mixture of trichlorosilane gas and protective gas enters the reactor through the inlet pipe, where a catalytic reaction takes place in a quartz glass reactor, and the reaction products are then collected through the outlet pipe. Preferably, the purity of the trichlorosilane gas is 99%~99.9%, the protective gas is helium or argon, the volume ratio of the trichlorosilane gas to the protective gas is 10:1, and the flow rate of the mixture of trichlorosilane gas and protective gas is 500~800 mL / min. Preferably, the conditions for the catalytic reaction are a discharge frequency of 5 Hz to 20 Hz, a reaction pressure of 0.05 MPa to 0.1 MPa, and a reaction temperature of 180 to 240 °C. Preferably, the catalyst used in the catalytic reaction is a chromium-based catalyst, and the amount of catalyst used is 0.5~0.8L, which is suitable for the device of the present invention. The preparation method is as follows: aluminum salt is dispersed in water, followed by the addition of chromium salt to obtain a reaction mixture, and the solid obtained by filtering the mixture is dried to obtain a chromium-based catalyst; Preferably, the aluminum salt is any one of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, and aluminum sulfide, the mass ratio of the aluminum salt to water is 1:10, the chromium salt is chromium hydroxide, the mass ratio of the chromium salt to the aluminum salt is 0.9~0.99:0.01~0.1, the reaction temperature is 35~78℃, the stirring time is 30~50min, the pH is 7~8, the drying temperature is 400~550℃, and the drying time is 10~20h.

[0006] The beneficial effects of this invention are as follows: (1) The device of the present invention adds ceramic substrate to the quartz glass reactor. Firstly, it serves as a catalyst carrier, plays the role of a skeleton, increases the contact area, accelerates the reaction rate, and improves the conversion rate and product yield. Secondly, it can play a role in resisting high temperature and avoid catalyst pulverization. (2) The present invention uses trichlorosilane as the raw material for preparing hexachlorosilane. The raw material is simple and inexpensive, which is of great significance for reducing the production cost of hexachlorosilane and breaking the monopoly of foreign companies. The purity of the trichlorosilane raw material is 99%~99.9%, which improves the conversion rate of the raw material and the yield of the product, and avoids the influence of too many impurities on the yield of the product. (3) The present invention is based on strong electric field ionization discharge technology as the synthesis process, and the discharge frequency used is controlled within 5Hz~20Hz. Within this frequency range, the reaction yield is high, and it is energy-saving and environmentally friendly. (4) The chromium-based catalyst used in this invention is heat-resistant, has a simple preparation process, and has a good catalytic effect. Attached Figure Description

[0007] Figure 1 The diagram shows the reaction apparatus of this application: 1. Electrode a; 2. Outlet pipe; 3. Reactor box; 4. Quartz glass reactor; 5. Ceramic base; 6. Electrode b; 7. Inlet pipe. Detailed Implementation

[0008] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0009] Example 1

[0010] Appendix Figure 1 The apparatus diagram for this reaction is shown in this embodiment. This embodiment provides an apparatus for synthesizing hexachlorosilane. The apparatus for synthesizing hexachlorosilane includes a quartz glass reactor 4, a ceramic substrate 5, an inlet pipe 7, an outlet pipe 2, a pair of electrodes with opposite polarities, and a reactor box 3, wherein the pair of electrodes with opposite polarities are a and b. The reactor box 3 primarily serves as heat insulation and electrical insulation. It is equipped with an inlet pipe 7 and an outlet pipe 2. The inlet pipe 7 connects to one side of the quartz glass reactor 4, and the outlet pipe 2 connects to the other side. The quartz glass reactor 4 is located inside the reactor box 3. A pair of electrodes 1 and 6 with opposite polarities are connected to both ends of the quartz glass reactor 4. A ceramic substrate 5 is placed parallel to the quartz glass reactor 4 inside the reactor box 3. The ceramic substrate 5 is made of alumina and has a honeycomb cross-section. The ceramic substrate 5 serves two purposes: firstly, it acts as a catalyst carrier, providing a framework, increasing the contact area, accelerating the reaction rate, and improving the conversion rate and product yield; secondly, it provides high-temperature resistance, preventing catalyst pulverization.

[0011] Examples 2-6

[0012] Based on the apparatus for synthesizing hexachlorosilane provided in Example 1, Examples 2-6 aim to provide a method for synthesizing hexachlorosilane. As shown in Tables 1 and 2, the main technical difference between Examples 2-6 lies in the different technical parameters, with Example 2 serving as an example for illustration.

[0013] Example 2 provides a method for synthesizing hexachlorosilane, comprising the following steps: S1. Mix aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate or aluminum sulfide with water at a mass ratio of 1:1~5, then add chromium hydroxide, controlling the mass ratio of aluminum salt to chromium hydroxide to be 0.01~0.1:0.9~0.99, set the reaction temperature to 35~78℃, the stirring time to 30~50min, and the pH value to 7~8. Filter the obtained liquid mixture, and dry the obtained solid at a drying temperature of 400~550℃ for 10~20h.

[0014] S2. Trichlorosilane gas and protective gas are mixed at a ratio of 10:1 and introduced into the reactor. The gas flow rate is set at 500~800 mL / min, the discharge frequency is 5Hz~20Hz, the reaction pressure is 0.05MPa~0.1MPa, and the reaction temperature is 180~240℃. The honeycomb structure of the ceramic substrate 5 in the reactor is pre-filled with 0.5~0.8L of the catalyst prepared in S1. Under these conditions, some of the Si-H bonds of trichlorosilane are opened to generate SiCl3 free radicals. The SiCl3 free radicals combine with each other to form Si-Si bonds, thereby forming the product hexachlorosilane.

[0015] Table 1 Example 2 Aluminum chloride 0.01:0.99 35 30 7 Example 3 Aluminum sulfate 0.03:0.96 45 35 7.5 Example 4 Aluminum nitrate 0.05:0.93 55 40 7.5 Example 5 Aluminum silicate 0.07:0.91 65 45 7.5 Example 6 Aluminum Sulfide 0.1:0.9 78 50 8 Table 2 Example 2 500 5 0.05~0.1 180~200 Example 3 550 10 0.05~0.1 180~200 Example 4 600 15 0.05~0.1 200~220 Example 5 700 15 0.05~0.1 200~220 Example 6 800 20 0.05~0.1 220~240 It should be noted that the trichlorosilane raw material gas used in Examples 2 to 6 above has a purity of 99.9%.

[0016] Comparative Example 1 Based on Example 6, the main technical difference between Example 1 and the Example 6 is that the purity of chloroform is 90%.

[0017] Comparative Example 2 Based on Example 6, the main technical feature that distinguishes Example 2 from the comparative example is that the discharge frequency is 25Hz.

[0018] Comparative Example 1 Based on Example 6, the main distinguishing feature of Comparative Example 1 is that no ceramic substrate (5) is placed in the reactor.

[0019] Product yield calculation The yields of the synthesized products in the above embodiments, comparative embodiments, and comparative examples were calculated, as shown in Table 3.

[0020] Table 3

[0021] As can be seen from Examples 2-6, the main technical differences between Examples 2-6 are the different process parameters and the types of catalysts. As can be seen from Table 3, the yields of hexachlorosilane synthesized in Examples 2-6 are not significantly different. Among them, the data obtained using the process parameters of Example 4 are the best. This may be because the reaction device, catalyst and corresponding process parameter range provided by the present invention are more reasonable, resulting in a higher yield of synthesized hexachlorosilane.

[0022] Based on Example 6, Comparative Example 1, and Table 3, it can be seen that the product yield obtained in Comparative Example 1 is relatively low. This may be because the purity of the reaction product raw material trichlorosilane is lower than that in Example 6, and impurities in the reaction product or the generation of other byproducts by the catalytic reaction directly lead to a reduction in the content of hexachlorosilane.

[0023] Based on Example 6, Comparative Example 1, Comparative Example 2, and Table 3, it can be seen that the product yield of Comparative Example 2 is lower than that of Example 6 but higher than that of Comparative Example 1. This indirectly reflects that the purity of the raw material trichlorosilane has a significant impact on the final product yield. Meanwhile, the product yield of Comparative Example 2 is lower than that of Example 6. This may be because the ionization energy generated at the higher discharge frequency leads to the breakage of more Si-Cl bonds, producing free radicals unrelated to the reaction product. Even the Si-Si bonds in the synthesized product are broken under the action of high ionization energy, resulting in more by-reaction products, a more complex reaction, and a lower yield of the product hexachlorosilane.

[0024] Based on Example 6, Comparative Example 1, Comparative Example 2, Comparative Example 1, and Table 3, it can be seen that the product yield of Comparative Example 1 is much lower than that of Example 6, Comparative Example 1, and Comparative Example 2. This may be because the reaction device used in Comparative Example 1 does not have a ceramic substrate, so the reaction raw material trichlorosilane cannot fully contact the catalyst. As the product is directly discharged, the yield of the reaction product is directly reduced. This also reflects that the ceramic substrate of the device of the present invention can greatly increase the contact area of ​​the reaction raw material with the catalyst, improve the catalytic reaction efficiency, and increase the yield of the reaction product.

[0025] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for synthesizing hexachlorosilane, characterized in that: A mixture of trichlorosilane gas and protective gas is introduced into a quartz glass reactor. Under the action of a chromium-based catalyst, a catalytic reaction is carried out in the quartz glass reactor. The catalytic reaction is carried out under the conditions of electric field ionization discharge, and then the reaction products are collected. The conditions for the catalytic reaction are a discharge frequency of 5 Hz to 20 Hz, a reaction pressure of 0.05 MPa to 0.1 MPa, and a reaction temperature of 180 to 240 °C.

2. The method for synthesizing hexachlorosilane according to claim 1, characterized in that: The trichlorosilane gas has a purity of 99% to 99.9%, the protective gas is helium or argon, the volume ratio of the trichlorosilane gas to the protective gas is 10:1, and the flow rate of the mixed gas composed of the trichlorosilane gas and the protective gas is 500 to 800 mL / min.

3. The method for synthesizing hexachlorosilane according to claim 1, characterized in that: The amount of the catalyst used is 0.5~0.8L; its preparation method is as follows: aluminum salt is dispersed in water, then chromium salt is added to obtain a reaction mixture, and the solid obtained by filtering the mixture is dried to obtain a chromium-based catalyst.

4. The method for synthesizing hexachlorosilane according to claim 3, characterized in that: The aluminum salt is any one of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, and aluminum sulfide. The mass ratio of the aluminum salt to water is 1:

10. The chromium salt is chromium hydroxide. The mass ratio of the chromium salt to the aluminum salt is 0.9~0.99:0.01~0.

1. The reaction temperature in the catalyst preparation method is 35~78℃, the pH is 7~8, the drying temperature is 400~550℃, and the drying time is 10~20h.

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