Production system for producing silane gas by combining fixed bed reactor and reactive distillation column

Abstract

The utility model provides a production system for producing silane gas by combining a fixed bed reactor and a reactive distillation tower, and relates to the technical field of silane gas production. The production system for producing the silane gas by combining the fixed bed reactor and the reactive distillation column comprises the fixed bed reactor which is provided with a DCS (Distributed Control System) feed port and can be used for performing DCS disproportionation reaction to prepare a one-step disproportionated product; the primary separation tower is communicated with the fixed bed reactor and can be used for rectifying and separating a one-step disproportionated product, crude SiH4 is extracted from the tower top of the primary separation tower, and a chlorosilane mixture is extracted from the tower kettle of the primary separation tower; the second-stage separation tower is communicated with the first-stage separation tower and can be used for rectifying and separating the chlorosilane mixture, and a TCS mixture is extracted from a tower kettle of the second-stage separation tower; and the reactive distillation tower is communicated with the second-stage separation tower, is provided with a TCS feed port, can perform a TCS disproportionation reaction and rectify and separate a product, and crude SiH4 is extracted from the tower top of the reactive distillation tower. According to the utility model, not only can the conversion rate of the DCS total reaction process be improved, but also the silane gas productivity can be improved, and the operation energy consumption can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of silane gas production, in particular to a production system for producing silane gas by combining a fixed-bed reactor and a reactive distillation column. Background Technique

[0002] Silane, namely the compound of silicon and hydrogen, is the general term for a series of compounds, including (SiH4), (Si2H6) and some higher silicon hydrides, with the general formula SinH2n+2. Flexible and variable chemical reactions can be completed by using silane to produce silicon materials with high purity and high fineness (up to atomic size).

[0003] Methane silane, also known as silane tetrahydride, with the chemical formula SiH4, is the most common silane. Sometimes methane silane is simply referred to as silane. Methane silane can be used to manufacture high-purity polysilicon, monocrystalline silicon, microcrystalline silicon, amorphous silicon, silicon nitride, silicon oxide, hetero-silicon and various metal silicides. Because of its high purity and easy fine control, it has become the most important special gas in semiconductor microelectronics technology and cannot be replaced by other silicon sources. Methane silane is widely used in the microelectronics and optoelectronics industries, used in the manufacture of solar cells, flat panel displays, glass and other fields, and is an intermediate product for the global large-scale production of granular silicon so far.

[0004] The manufacturing processes of methane silane can be mainly divided into three types: magnesium silicide method, lithium aluminum hydride method and chlorosilane disproportionation method.

[0005] 1) The magnesium silicide method is the first industrial synthesis method of SiH4 developed abroad earlier. It contains relatively low metals. The crude silane adopts purification processes such as rectification or adsorption, complexation, absorption, etc. Its advantages are simple and mature process, wide raw material sources and low cost. Its disadvantages are high energy consumption for separating and recovering liquid ammonia, but the SiH4 yield is relatively low (the average yield is 80%).

[0006] 2) The lithium aluminum hydride method uses a strong reducing agent LiAlH4 in a solvent of dimethyl ether and tetrahydrofuran to generate SiH4 gas through a reduction reaction SiCl4 + LiAlH4 → SiH4 + LiCl + AlCl3. The raw materials LiAlH4 and SiCl4 used in this method are easy to obtain, but the raw materials have strong chemical activity, the reaction is violent, the danger is high, and it is difficult to control in the production process.

[0007] 3) The chlorosilane disproportionation method (i.e., the improved Siemens method) is to prepare chlorosilane by hydrogenation of chlorosilane and industrial silicon powder under the action of a catalyst, and then prepare silane through a secondary disproportionation reaction. It is simply called the "two-step" disproportionation process. The conversion rate of the first step of disproportionation is relatively low, and the conversion rate of the second step of disproportionation is high. The main reactions are:

[0008] SiCl4 + H2 + Si → SiHCl3, (hydrogenation reaction)

[0009] SiHCl3 → SiH2Cl2 + SiCl4, (the first disproportionation reaction)

[0010] SiH2Cl2 → SiH4 + SiHCl3. (the second disproportionation reaction)

[0011] The improved Siemens process is a widely used industrial production process with an annual output scale of up to 100,000 tons. It is also an ideal method for producing several silicon source gases (SiH4, SiH2Cl2, SiHCl3). All three silicon source gases can be widely used in the optoelectronics, microelectronics, and optical fiber manufacturing fields. The production process is mature, can be continuously produced, and the production process can be adjusted according to the usage of various silicon products. Therefore, the cost of manufacturing silane is low. In the SiHCl3 → SiH2Cl2 → SiH4 production chain, each step includes purification and separation, and the final product has a high purity. Therefore, this method has been widely used in large-scale silane production. It is used to prepare various microelectronic thin films and a series of silicon-containing substances such as single-crystalline silicon, polycrystalline silicon, amorphous silicon, metal silicides, silicon nitride, silicon carbide, and silicon oxide.

[0012] In the improved Siemens process, the main raw materials, intermediates, and products include: monochlorosilane, dichlorosilane, trichlorosilane, silicon tetrachloride, and silane. Among them, monochlorosilane (MCS) is an inorganic silicon compound with the chemical formula SiH3Cl and the English name: monochlorosilane, usually abbreviated as MCS. Currently, monochlorosilane is more used as an intermediate to synthesize compounds such as TSA and is widely used in the semiconductor chip industry and the solar energy industry. Dichlorosilane (DCS) is an inorganic silicon compound with the chemical formula SiH2Cl2 and the English name: dichlorosilane, usually abbreviated as DCS. DCS has a wide range of uses and is one of the commonly used special gases in the current integrated circuit industry and semiconductor chips. Trichlorosilane (TCS) is an inorganic silicon compound with the chemical formula SiHCl3 and the English name: trichlorosilane, usually abbreviated as TCS, mainly used to manufacture compounds. Silicon tetrachloride (STC), also known as tetrachlorosilane, is an inorganic silicon compound with the chemical formula SiCl4 and the English name: tetrachlorosilane, usually abbreviated as STC, mainly used to produce pure silicon, ethyl silicate, etc., and is also used to produce smoke agents.

[0013] Gaseous silane is also known as silane gas. Currently, the processes for producing silane gas mainly include the disproportionation reaction of DCS or TCS based on the improved Siemens process to prepare silane gas. The process route is single and lacks flexibility. Moreover, in the process using DCS as the raw material, both DCS and silane gas are low-boiling substances, resulting in high energy consumption during the separation process. Additionally, DCS usually comes from the by-products and intermediate products of the improved Siemens process, and the yield of DCS in these by-products and intermediate products is relatively low. In the process using TCS as the raw material, it involves multiple steps of reactions, and they are reversible reactions, with a relatively low single-pass conversion rate of TCS. Summary of the Invention

[0014] The present invention aims to solve the problems in the prior art that the processes for producing silane gas mainly include the disproportionation reaction of DCS or TCS based on the improved Siemens process, with a single process route, high process energy consumption, and low conversion rate. The present invention provides a production system for producing silane gas by combining a fixed-bed reactor and a reactive distillation column, which can not only improve the conversion rate of the overall DCS reaction process, but also increase the production capacity of silane gas and reduce the operating energy consumption.

[0015] The technical solution adopted by the present invention is as follows:

[0016] A production system for producing silane gas by combining a fixed-bed reactor and a reactive distillation column, comprising:

[0017] A fixed-bed reactor, provided with a DCS feed port, capable of carrying out the DCS disproportionation reaction to obtain a primary disproportionation product;

[0018] A primary separation column, connected to the discharge end of the fixed-bed reactor, capable of rectifying and separating the primary disproportionation product. The top discharge end of the primary separation column is used to extract crude SiH4, and its bottom discharge end is used to extract a chlorosilane mixture;

[0019] A secondary separation column, connected to the bottom discharge end of the primary separation column, capable of rectifying and separating the chlorosilane mixture. The bottom discharge end of the secondary separation column is used to extract a TCS mixture; and

[0020] A reactive distillation column, connected to the bottom discharge end of the secondary separation column, provided with a TCS feed port, capable of carrying out the TCS disproportionation reaction and rectifying and separating the products. The top discharge end of the reactive distillation column is used to extract crude SiH4.

[0021] Furthermore, it further comprises a degassing column; the feed end of the degassing column is used to introduce DCS raw material, and its discharge end is connected to the DCS feed port of the fixed-bed reactor. The degassing column can carry out the light component removal and purification of the DCS raw material.

[0022] Furthermore, it further comprises:

[0023] An adsorption device, which is connected to the gas-phase pipelines at the output ends of the primary separation column and the reactive distillation column at the same time, and the adsorption device can adsorb and remove impurities from the crude SiH4 product in the gas phase; and

[0024] A purification column, which is connected to the liquid-phase pipelines at the output ends of the primary separation column and the reactive distillation column at the same time or connected to the discharge end of the adsorption device, and the purification column can rectify and remove the heavy components containing MCS and impurities in the crude SiH4.

[0025] Furthermore, the MCS discharge end of the purification column is connected to the feed end of the secondary separation column, and the liquid-phase mixture mainly composed of MCS taken out from the bottom of the purification column can be returned to the secondary separation column for rectification and separation.

[0026] Furthermore, a liquid-phase pipeline with an output end is arranged at the top of the secondary separation column for taking out the DCS mixture, and it is connected to the DCS feed port of the fixed-bed reactor, and the DCS mixture taken out from the top of the secondary separation column can be returned to the fixed-bed reactor for DCS disproportionation reaction.

[0027] The beneficial effects of the present utility model are as follows:

[0028] 1. The present utility model respectively uses a fixed-bed reactor and two-stage separation columns to carry out the disproportionation reaction and rectification separation of DCS. On the one hand, taking advantage of the characteristics of high disproportionation reaction conversion rate and low reverse reaction degree of DCS, energy consumption is saved through the fixed-bed reactor; on the other hand, according to the characteristic that the boiling points of DCS raw materials and products are close, the reaction space and the rectification space are separately arranged, reducing the DCS impurity content in the crude SiH4 product; at the same time, a reactive distillation column is used to carry out the reaction and rectification of TCS simultaneously, enabling the reversible TCS disproportionation reaction to proceed maximally in the forward direction, improving the conversion rate of TCS, thereby increasing the conversion rate in the total reaction process and reducing the operating energy consumption. The two disproportionation processes are coordinated and the fixed-bed reactor and reactive distillation are respectively selected to solve the problems of high energy consumption and low conversion rate in the existing silane gas production process;

[0029] 2. The present utility model also combines the process of preparing silane gas from DCS with the process of preparing silane gas from TCS, and continues to utilize the products of the DCS reaction in the TCS reaction, enabling the production method of the present utility model to adapt to the changes in the amounts of DCS and TCS, coordinating and cooperating with the improved Siemens process, enhancing the process flexibility and raw material adaptability, and solving the problem of the single process route in the existing technology where the processes for producing more silane gas mainly include the disproportionation reaction of DCS or TCS based on the improved Siemens process. Description of the Drawings

[0030] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0031] Figure 1 It is a flowchart of the production method of the embodiment of the present utility model;

[0032] Figure 2 It is a schematic structural diagram of the production system of the third embodiment of the present utility model.

[0033] Reference numerals: 100 - degassing tower, 101 - condenser, 103 - reboiler;

[0034] 200 - primary separation tower;

[0035] 300 - secondary separation tower;

[0036] 400 - purification tower, 401 - first SiH4 discharge end, 402 - second SiH4 discharge end, 403 - MCS discharge end;

[0037] 500 - fixed bed reactor, 510 - DCS feed port;

[0038] 600 - reactive distillation column, 610 - TCS feed port, 620 - catalyst reaction section, 630 - rectification section, 640 - stripping section;

[0039] 700 - adsorption device;

[0040] 810 - first booster pump, 820 - second booster pump, 830 - compressor, 840 - third booster pump. Detailed embodiments

[0041] In the description of the present utility model, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present utility model.

[0042] The following disclosure provides many different embodiments or examples for implementing different structures of the present utility model. To simplify the disclosure of the present utility model, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present utility model.

[0043] The embodiments of the utility model will be described in detail below with reference to the accompanying drawings.

[0044] Embodiment 1

[0045] Currently, the processes for producing more silane gas mainly include the disproportionation reaction of DCS or TCS based on the improved Siemens process to produce silane gas. The process route is single and the flexibility is not strong. Moreover, in the process using DCS as the raw material, both DCS and silane gas are low-boiling substances, and the energy consumption is high during the separation process. And DCS usually comes from the by-products and intermediate products of the improved Siemens process, and the yield of DCS in these by-products and intermediate products is low. In the process using TCS as the raw material, it involves multiple steps of reactions and is a reversible reaction, and the single-pass conversion rate of TCS is low.

[0046] Please refer to Figure 1 - Figure 2 , this embodiment provides a method for producing silane gas by combining a fixed-bed reactor and a reactive distillation column. By combining and utilizing the by-products DCS and TCS produced in the improved Siemens process to produce silane gas, the original silane gas production mode is changed, the process flexibility and raw material adaptability are enhanced. At the same time, not only can the total reaction process conversion rate of DCS be improved, but also the silane gas production capacity can be increased and the operation energy consumption can be reduced. As Figure 1 shown in, the method for producing silane gas by combining the fixed-bed reactor and the reactive distillation column mainly includes the following steps:

[0047] S10. Using DCS raw material, enter the fixed-bed reactor 500 through the DCS feed port 510, and carry out the DCS disproportionation reaction in the fixed-bed reactor 500 to obtain the primary disproportionation product. Among them, the main component of the DCS raw material is the by-product DCS of the improved Siemens process, which enables the method for producing silane gas by combining the fixed-bed reactor and the reactive distillation column in this embodiment to be used for treating the surplus and inconvenient-to-treat by-product DCS of the improved Siemens process. The fixed-bed reactor 500 feeds in a bottom-up manner, the DCS feed port 510 is arranged at its bottom, and the inside of the fixed-bed reactor 500 is filled with a catalyst to form a fixed-bed layer. The reactants can pass through the fixed-bed layer in a continuous flow manner, while the catalyst in the fixed-bed layer remains stationary for catalysis. The main reaction formula of the DCS disproportionation reaction is:

[0048] SiH2Cl2 → SiH4 + SiHCl3;

[0049] During the reaction process, the temperature in the fixed-bed reactor 500 is preferably maintained at 30°C to 80°C, and the pressure is preferably maintained at 20 to 35 bar. The one-step disproportionation products mainly include SiH4, TCS, as well as MCS generated by side reactions and unreacted DCS, etc.

[0050] S20. The one-step disproportionation products obtained in S10 are rectified and separated in the primary separation column 200. Crude SiH4 is taken out from the top of the column, and the chlorosilane mixture is taken out from the bottom of the column. Among them, the primary separation column 200 mainly conducts the rectification and separation of the one-step disproportionation products, and is mainly used to separate the crude SiH4 product. During the rectification process, the temperature in the primary separation column 200 is preferably maintained at -35°C to -15°C, and the pressure is preferably maintained at 20 to 30 bar. The main component of the crude SiH4 taken out from the top of the column is SiH4 with a relatively high purity, and it contains a trace amount of MCS. Since the disproportionation reaction is carried out in the fixed-bed reactor 500 and the rectification separation is carried out in the primary separation column 200, it avoids the mixing of a large amount of DCS raw materials in the crude SiH4 and saves the energy consumption of rectification separation; the main components of the chlorosilane mixture taken out from the bottom of the column are MCS, DCS, TCS, and a trace amount of STC.

[0051] S30. The chlorosilane mixture taken out from the bottom of the column in S20 is rectified and separated in the secondary separation column 300. The DCS mixture is taken out from the top of the column, and the TCS mixture is taken out from the bottom of the column. Among them, the secondary separation column 300 mainly conducts the rectification and separation of the chlorosilane mixture, and is mainly used to separate the TCS mixture for subsequent TCS disproportionation reaction. During the rectification process, the temperature in the secondary separation column 300 is preferably maintained at 40°C to 70°C, and the pressure is preferably maintained at 5 to 10 bar. The main components of the DCS mixture taken out from the top of the column are DCS and MCS, etc.; the main components of the chlorosilane mixture taken out from the bottom of the column are TCS and a trace amount of STC.

[0052] S40. Using the TCS raw material and the TCS mixture taken out from the bottom of the column in S30, they enter the reactive distillation column 600 through the TCS feed port 610, and the TCS disproportionation reaction is carried out together in the reactive distillation column 600, and the products are rectified and separated. Crude SiH4 is taken out from the top of the column, and the STC by-product is taken out from the bottom of the column. Among them, the main component of the TCS raw material is the intermediate product TCS of the improved Siemens process, enabling the method for producing silane gas in this embodiment to provide a new way for the intermediate product TCS of the improved Siemens process in silane gas production; the TCS mixture is derived from the by-product of S30, making full use of this part of the by-product. At the same time, a catalyst reaction section 620 is provided inside the reactive distillation column 600. The catalyst filled in the catalyst reaction section 620 can not only promote the occurrence of the disproportionation reaction but also be used as a packing in the distillation column to provide a place for mass transfer and heat transfer of the gas and liquid phases inside the column, achieving the effect of component separation. The main reaction formula of the TCS disproportionation reaction is:

[0053] SiHCl3 → SiH2Cl2 + SiCl4, (the first disproportionation reaction)

[0054] SiH2Cl2 → SiH4 + SiHCl3. (the second disproportionation reaction)

[0055] During the reaction process, the temperature inside the reactive distillation column 600 is preferably maintained at -100°C to -50°C, and the pressure is preferably maintained at 1 to 7 bar. The products of the two-step disproportionation mainly include SiH4, STC, and MCS generated by side reactions. After component separation, crude SiH4 is withdrawn from the top of the column. The main component of the crude SiH4 product is also high-purity SiH4, with a trace amount of MCS; the STC by-product is withdrawn from the bottom of the column and can be returned to the improved Siemens process production system as a raw material for the production of chlorosilanes. Moreover, the withdrawal from the top and bottom of the reactive distillation column 600 is carried out simultaneously during the reaction process, and the products SiH4 and STC during the reaction process can be timely removed from the system from the top and bottom of the column, which is conducive to the forward progress of the TCS disproportionation reaction, thereby achieving the effect of improving its conversion rate.

[0056] In summary, in this embodiment, the method for producing silane gas by combining a fixed-bed reactor and a reactive distillation column uses a fixed-bed reactor 500 and a two-stage separation column to carry out the disproportionation reaction and rectification separation of DCS. On the one hand, taking advantage of the characteristics of high conversion rate and low degree of reverse reaction of the DCS disproportionation reaction, energy consumption is saved through the fixed-bed reactor 500; on the other hand, according to the characteristic that the boiling points of the DCS raw material and the product are close, the reaction space and the rectification space are separately arranged, reducing the content of DCS impurities in the crude SiH4 product; at the same time, the reactive distillation column 600 is used to carry out the reaction and rectification of TCS simultaneously, enabling the reversible TCS disproportionation reaction to proceed forward to the maximum extent, improving the conversion rate of TCS, thereby increasing the conversion rate in the total reaction process and reducing the operating energy consumption, solving the problems of high energy consumption and low conversion rate in the existing silane gas production process.

[0057] At the same time, in this embodiment, the process of preparing silane gas from DCS is combined with the process of preparing silane gas from TCS, and the products of the DCS reaction are continuously utilized in the TCS reaction, enabling the production method of this embodiment to adapt to changes in the amounts of DCS and TCS, coordinating with the improved Siemens process, enhancing the process flexibility and raw material adaptability, and solving the problem of the single process route in the existing silane gas processes, which mainly include the disproportionation reaction of DCS or TCS based on the improved Siemens process to prepare silane gas.

[0058] Such as Figure 1As shown, in order to reduce the hydrogen and light component impurities that are easily contained in the DCS raw material, the S10 step of this embodiment further includes: before the DCS raw material enters the fixed-bed reactor 500, it is first introduced into the degassing tower 100 to analyze the dissolved hydrogen, remove the light component impurities and hydrogen, and finally be withdrawn from the bottom of the tower and enter the fixed-bed reactor 500. Among them, the degassing tower 100 analyzes the hydrogen dissolved inside the raw material mainly composed of DCS, removes the light component impurities and hydrogen through rectification separation, and discharges them in the state of non-condensable gas from the gas-phase pipeline of the condenser 101 at the top of the tower; the purified raw material mainly composed of DCS is withdrawn from the bottom of the tower in the liquid phase and then enters the subsequent catalytic disproportionation reaction, so as to avoid the contamination of the catalytic disproportionation reaction product by light component impurities and hydrogen and affect the product quality. In addition, in the S10 step, the temperature for removing light components and impurities in the degassing tower 100 is preferably maintained at 15°C to 50°C, and the pressure is preferably maintained at 2 to 7 bar.

[0059] At the same time, in this embodiment, the crude SiH4 products extracted in the S20 and S40 steps can be withdrawn in the gas phase through the gas-phase pipelines at the tops of the primary separation tower 200 and the reactive distillation tower 600; they can also be withdrawn in the liquid phase through the liquid-phase pipelines of the condensers 101 at the tops of the primary separation tower 200 and the reactive distillation tower 600, and after being condensed by the condenser 101. In order to reduce impurities and improve the purity of the crude SiH4 product, the method for producing silane gas in this embodiment further includes the following steps:

[0060] S50. Adsorb and remove impurities from the gaseous crude SiH4 product containing a small amount of MCS extracted in S20 and S40 through the adsorption device 700, and then rectify and purify it through the purification tower 400. A high-purity SiH4 gas-phase product or liquid-phase product is withdrawn from the upper part of the purification tower 400, and a liquid-phase mixture mainly composed of MCS and impurities is withdrawn from the bottom of the purification tower 400. Among them, the adsorption device 700 is filled with an adsorbent (such as adsorption resin or activated carbon), which can remove B, P and metal impurities. The purification tower 400 is used to remove the heavy components and impurities containing MCS in the gaseous crude SiH4 product. In the S50 step, the rectification and purification temperature is preferably maintained at -50°C to -15°C, and the pressure is preferably maintained at 20 to 30 bar.

[0061] In addition, in order to make full use of the by-products of the production method of this embodiment, the method for producing silane gas in this embodiment further includes the following steps:

[0062] S60. Return the liquid-phase mixture with the main component of MCS taken from the bottom of the column in S50 to the secondary separation column 300 in S30 for rectification separation. After the return, the liquid-phase mixture can continue to participate in the rectification separation and subsequent processes according to the production process flow, so as to make full use of MCS in the by-products for disproportionation reaction to prepare silane gas. Additionally, when the re-addition in S60 is not carried out or an emergency occurs due to abnormal production system, the mixture with the main component of MCS taken from the liquid-phase in S50 can be transported to the flare for combustion treatment to eliminate potential safety hazards.

[0063] S70. Return the DCS mixture with the main components of DCS and MCS taken from the top of the column in S30 to the fixed-bed reactor 500 in S10 for DCS disproportionation reaction. After the return, the DCS mixture can continue to participate in the disproportionation reaction and subsequent processes according to the production process flow, so as to make full use of DCS and MCS in the by-products and intermediate products for disproportionation reaction to prepare silane gas.

[0064] Example 2

[0065] In the above-mentioned examples, the crude SiH4 product taken out in steps S20 and S40 can be taken out in the gas phase through the gas-phase pipeline at the top of the first separation column 200 and the reactive distillation column 600; it can also be taken out in the liquid phase through the liquid-phase pipeline of the condenser 101 at the top of the first separation column 200 and the reactive distillation column 600, and after being condensed by the condenser, in order to reduce impurities and improve the purity of the crude SiH4 product, another production method is proposed in the second example.

[0066] Please refer to Figure 1 、 Figure 2 The difference between the second example and the first example is that the crude SiH4 product of SiH4 and MCS taken out in S20 and S40 is the liquid-phase product after condensation and liquefaction. The method for producing silane gas by combining the fixed-bed reactor and the reactive distillation column in the second example uses the following steps to replace step S50 in the above-mentioned examples:

[0067] S52. Rectify and purify the liquid-phase crude SiH4 product taken out in S20 and S40, take out the high-purity SiH4 gas-phase product or liquid-phase product from the top of the purification column 400, and take out the liquid-phase mixture with the main component of MCS from the bottom of the purification column 400. This step can directly carry out rectification and purification, take out the high-purity SiH4 gas-phase product or liquid-phase product, and take out the liquid-phase mixture with the main component of MCS.

[0068] Example 3

[0069] Please refer to Figure 2, on the basis of the production methods in the above embodiments, the third embodiment provides a production system for producing silane gas by combining a fixed-bed reactor and a reactive distillation column based on these production methods. The production system for producing silane gas by combining the fixed-bed reactor and the reactive distillation column can simultaneously utilize DCS and TCS by-products from the improved Siemens process to produce silane gas, change the original silane gas production mode, enhance process flexibility and raw material adaptability, and can improve the conversion rate in the overall reaction process while reducing operating energy consumption. The production system for producing silane gas by combining the fixed-bed reactor and the reactive distillation column mainly includes: a fixed-bed reactor 500, a primary separation column 200, a secondary separation column 300, a reactive distillation column 600, etc.

[0070] As Figure 2 shown, the fixed-bed reactor 500 is a reaction device for DCS raw materials, provided with a DCS feed inlet 510, capable of introducing DCS raw materials to carry out DCS disproportionation reaction to obtain a one-step disproportionation product. Among them, the main component of the DCS raw material is the by-product DCS of the improved Siemens process, enabling the production system for producing silane gas by combining the fixed-bed reactor and the reactive distillation column in this embodiment to be used for treating the surplus and inconveniently treated by-product DCS of the improved Siemens process. The fixed-bed reactor 500 feeds in a bottom-up manner, and the DCS feed inlet 510 is arranged at its bottom. The inside of the fixed-bed reactor 500 is filled with a catalyst to form a fixed-bed layer. The reactants can pass through the fixed-bed layer in a continuous flow manner, while the catalyst in the fixed-bed layer remains stationary for catalysis. The main reaction formula of the DCS disproportionation reaction is:

[0071] SiH2Cl2 → SiH4 + SiHCl3;

[0072] During the reaction process, the temperature in the fixed-bed reactor 500 is preferably maintained at 30 °C to 80 °C, and the pressure is preferably maintained at 20 to 35 bar. The one-step disproportionation product mainly includes SiH4, TCS, as well as MCS and DCS generated by side reactions, etc.

[0073] The primary separation column 200 is a separation device for the products of one-step disproportionation. The primary separation column 200 is connected to the discharge end of the fixed-bed reactor 500 and can rectify and separate the products of one-step disproportionation. The top discharge end of the primary separation column 200 is used to extract crude SiH4, and its bottom discharge end is used to extract the chlorosilane mixture. Among them, the primary separation column 200 is mainly used to separate the crude SiH4 product. During the rectification process, the temperature inside the primary separation column 200 is preferably maintained at -35°C to -15°C, and the pressure is preferably maintained at 20 to 30 bar. The main component of the crude SiH4 extracted from the top of the column is SiH4 with a relatively high purity, and it contains a small amount of MCS. Since the disproportionation reaction takes place in the fixed-bed reactor 500 and the rectification separation takes place in the primary separation column 200, it is avoided that a large amount of DCS raw materials are mixed into the crude SiH4, and the energy consumption of rectification separation is saved. The main components of the chlorosilane mixture extracted from the bottom of the column are MCS, DCS, TCS, and a small amount of STC. Moreover, a condenser 101 is provided at the top of the primary separation column 200. The top discharge end of the column is divided into a gas-phase pipeline and a liquid-phase pipeline. The gas-phase pipeline is connected to the top of the primary separation column 200 and is used to extract the gaseous crude SiH4; the liquid-phase pipeline is connected to the condenser 101 at the top of the primary separation column 200 and is used to extract the liquid-phase crude SiH4; another part of the liquid phase in the condenser 101 flows back into the top of the column to achieve the rectification separation of components and reach the required separation effect. At the same time, a reboiler 103 is provided below the bottom of the primary separation column 200. The reboiler 103 provides heat for the primary separation column 200. After the liquid-phase material at the bottom of the column enters the reboiler 103, it is heated and vaporized and then returns to the bottom of the column to provide sufficient gas-phase material flow inside the column, thereby achieving the rectification separation of components.

[0074] The secondary separation tower 300 is a separation device for the chlorosilane mixture withdrawn from the bottom of the primary separation tower 200. The secondary separation tower 300 is connected to the bottom discharge end of the primary separation tower 200, and can rectify and separate the chlorosilane mixture. The top discharge end of the secondary separation tower 300 is used to withdraw the DCS mixture, and its bottom discharge end is used to withdraw the TCS mixture. Among them, the secondary separation tower 300 is mainly used to separate the TCS mixture for subsequent TCS disproportionation reaction. During the rectification process, the temperature in the secondary separation tower 300 is preferably maintained at 40°C to 70°C, and the pressure is preferably maintained at 5 to 10 bar. The main components of the DCS mixture withdrawn from the top of the tower are DCS, MCS, etc.; the main components of the chlorosilane mixture withdrawn from the bottom of the tower are TCS and a small amount of STC. Also, a condenser 101 is provided at the top of the secondary separation tower 300, but only a liquid-phase pipeline is provided at the top discharge end. The liquid-phase pipeline is connected to the condenser 101 at the top of the secondary separation tower 300 for withdrawing the liquid-phase DCS mixture; another part of the liquid phase in the condenser 101 flows back into the top of the tower to achieve rectification separation of components and reach the required separation effect. At the same time, a reboiler 103 is also provided below the bottom of the secondary separation tower 300. The reboiler 103 provides heat for the secondary separation tower 300. After the liquid-phase material at the bottom of the tower enters the reboiler 103, it is heated and vaporized and then returns to the bottom of the tower to provide sufficient gas-phase logistics in the tower, thereby achieving rectification separation of components.

[0075] The reactive distillation column 600 is a device that organically combines a reactor and a distillation column still into one. The reactive distillation column 600 is both a reaction device for TCS and a rectification separation device for TCS. At the same time, the reactive distillation column 600 is connected to the bottom discharge end of the secondary separation tower 300, and the TCS mixture can be introduced, and a TCS feed port 610 is provided through which the TCS raw material can be introduced. Also, the reactive distillation column 600 can perform a TCS disproportionation reaction using TCS as a raw material and rectify and separate the products. The top discharge end of the reactive distillation column 600 is used to withdraw crude SiH4, and its bottom discharge end is used to withdraw the STC by-product. Among them, the main component of the TCS raw material is the intermediate product TCS of the improved Siemens process, enabling the production system that combines the fixed-bed reactor and the reactive distillation column to produce silane gas in this embodiment to provide a new use for the intermediate product TCS of the improved Siemens process in silane gas production; the TCS mixture is from the output end of the secondary separation tower 300, enabling full utilization of this part of the by-product. At the same time, a catalyst reaction section 620, a rectification section 630, and a stripping section 640 are provided inside the reactive distillation column 600. The catalyst filled in the catalyst reaction section 620 can not only promote the occurrence of the disproportionation reaction but also be used as a packing in the distillation column to provide a place for mass transfer and heat transfer of the gas and liquid phases in the tower, achieving the effect of component separation. The main reaction formula of the TCS disproportionation reaction is:

[0076] SiHCl3 → SiH2Cl2 + SiCl4, (the first disproportionation reaction)

[0077] SiH2Cl2 → SiH4 + SiHCl3. (the second disproportionation reaction)

[0078] During the reaction process, the temperature inside the reactive distillation column 600 is preferably maintained at -100°C to -50°C, and the pressure is preferably maintained at 1 to 7 bar. The products of the two-step disproportionation mainly include SiH4, STC, and MCS generated by side reactions, etc. The rectifying section 630 is arranged above the catalyst reaction section 620. The rectifying section 630 is equipped with a rectifier (tray or packing). Under the condition of constant pressure, the gas mixture moving upward after the reaction in the catalyst reaction section 620 is purified and separated by temperature control. The main component of the gas mixture to be treated is SiH4, but it also contains a small amount of MCS, etc. The rectifying section 630 is mainly used to remove the heavy components in SiH4, liquefy and reflux them, while the crude SiH4 containing a trace amount of MCS enters the top of the tower in a gaseous state. The stripping section 640 is arranged below the catalyst reaction section 620. The stripping section 640 is equipped with a stripper (tray or packing). Under the condition of constant pressure, the liquid mixture moving downward after the reaction in the catalyst reaction section 620 is purified and separated by temperature control. The main components of the liquid mixture to be treated are STC, unreacted TCS, and a small amount of DCS, etc. The stripping section 640 is mainly used to evaporate and lift the unreacted TCS and a small amount of DCS to the upper section of the reactive distillation column 600 to continue to participate in the reaction, while STC enters the bottom of the tower in a liquid state. After the component separation, crude SiH4 is withdrawn from the top of the tower. The main component of the crude SiH4 product is also high-purity SiH4, with a trace amount of MCS; the STC by-product is withdrawn from the bottom of the tower and can be returned to the improved Siemens process production system as a raw material for the production of chlorosilanes. Moreover, the withdrawal from the top and bottom of the reactive distillation column 600 is carried out simultaneously during the reaction process. The products SiH4 and STC in the reaction process are timely removed from the system from the top and bottom of the tower, which is beneficial to the forward progress of the TCS disproportionation reaction, thereby achieving the effect of improving its conversion rate. In addition, a condenser 101 is also arranged at the top of the reactive distillation column 600. The top discharge end of the column is divided into a gas-phase pipeline and a liquid-phase pipeline. The gas-phase pipeline is connected to the top of the reactive distillation column 600 for withdrawing gaseous crude SiH4; the liquid-phase pipeline is connected to the condenser 101 at the top of the reactive distillation column 600 for withdrawing liquid crude SiH4; another part of the liquid phase in the condenser 101 flows back into the top of the tower to achieve the rectifying separation of components and reach the required separation effect. At the same time, a reboiler 103 is also arranged below the bottom of the reactive distillation column 600. The reboiler 103 provides heat for the reactive distillation column 600. After the liquid-phase material at the bottom of the tower enters the reboiler 103, it is heated and vaporized and then returned to the bottom of the tower to provide sufficient gas-phase logistics in the tower, thereby achieving the rectifying separation of components.

[0079] In summary, in this embodiment, the production system for producing silane gas by combining a fixed-bed reactor and a reactive distillation column uses a fixed-bed reactor 500 and a two-stage separation column to carry out the disproportionation reaction and rectification separation of DCS respectively. On the one hand, taking advantage of the characteristics of high conversion rate of the disproportionation reaction of DCS and low degree of reverse reaction, energy consumption is saved through the fixed-bed reactor 500. On the other hand, according to the characteristic that the boiling points of the DCS raw material and the product are close, the reaction space and the rectification space are separately arranged, reducing the content of DCS impurities in the crude SiH4 product. At the same time, the reactive distillation column 600 is used to carry out the reaction and rectification of TCS simultaneously, enabling the reversible disproportionation reaction of TCS to proceed forward to the greatest extent, improving the conversion rate of TCS, thereby increasing the conversion rate in the overall reaction process and reducing the operating energy consumption. The two disproportionation processes are coordinated and the fixed-bed reactor and reactive distillation are respectively selected to solve the problems of high energy consumption and low conversion rate in the prior art silane gas production process.

[0080] As Figure 2 shown in the figure, in order to reduce the hydrogen and light component impurities easily carried in the DCS raw material, the production system for producing silane gas by combining a fixed-bed reactor and a reactive distillation column in this embodiment further includes a degassing column 100. The feed end of the degassing column 100 is used to introduce the DCS raw material, and the discharge end of the degassing column 100 is connected to the DCS feed port 510 of the fixed-bed reactor 500. The degassing column 100 is mainly used for light component removal and purification, to analyze the hydrogen dissolved in the DCS raw material, remove light component impurities and hydrogen, and finally take out from the bottom of the column and enter the fixed-bed reactor 500. Moreover, a condenser 101 is also provided at the top of the degassing column 100, but only a gas phase pipeline is provided at the discharge end of the top of the column. The gas phase pipeline is connected to the condenser 101 at the top of the degassing column 100, for discharging light component impurities in the state of non-condensable gas. The condenser 101 mainly provides liquid reflux for the top of the degassing column 100. By providing the liquid reflux for gas-liquid contact, mass transfer and heat transfer in the degassing column 100, the effect of purifying and removing impurities from the DCS raw material is achieved. At the same time, a reboiler 103 is also provided below the bottom of the degassing column 100. The reboiler 103 is used to provide heat source for the degassing column 100 and provide gas phase logistics in the column, facilitating the analysis of hydrogen and light component impurities dissolved in the liquid phase, and ensuring the quality of the material taken out from the bottom of the column. In addition, during the working process, the temperature for light component removal and impurity removal in the degassing column 100 is preferably maintained at 15°C to 50°C, and the pressure is preferably maintained at 2 to 7 bar.

[0081] Meanwhile, in this embodiment, the crude SiH4 products extracted from the primary separation column 200 and the reactive distillation column 600 can be extracted in the gas phase through the gas-phase pipelines at the tops of the primary separation column 200 and the reactive distillation column 600; they can also be extracted in the liquid phase through the liquid-phase pipelines of the condensers 101 at the tops of the primary separation column 200 and the reactive distillation column 600, and are in the liquid phase after being condensed by the condensers. In order to reduce impurities and improve the purity of the SiH4 products, the production system for producing silane gas by combining the fixed-bed reactor and the reactive distillation column in this embodiment further includes an adsorption device 700, a purification column 400, etc.

[0082] The adsorption device 700 is simultaneously connected to the gas-phase pipelines at the output ends of the tops of the primary separation column 200 and the reactive distillation column 600, and can introduce the gas-phase crude SiH4 products. The adsorption device 700 is filled with adsorbents, mainly including adsorption resins or activated carbon, etc., and can adsorb and remove impurities from the gas-phase crude SiH4 products, adsorbing and removing solid particle impurities in the gas-phase crude SiH4, mainly including B, P, and metal impurities, etc.

[0083] The purification column 400 is simultaneously connected to the liquid-phase pipelines at the output ends of the tops of the primary separation column 200 and the reactive distillation column 600, as well as the discharge end of the adsorption device 700, and is used for rectifying and removing the heavy components and impurities containing MCS in the crude SiH4. According to the product requirements, the purification column 400 can be switched to be connected to the liquid-phase pipelines at the output ends of the tops of the primary separation column 200 and the reactive distillation column 600 to directly introduce the liquid-phase crude SiH4; or be connected to the adsorption device 700 to introduce the gas-phase crude SiH4 after adsorption and impurity removal. Moreover, the purification column 400 has a first SiH4 discharge end 401, a second SiH4 discharge end 402, an MCS discharge end 403, etc. Among them, the first SiH4 discharge end 401 is connected to the liquid-phase pipeline of the condenser 101 at the top of the purification column 400 and is used for extracting the high-purity SiH4 in the liquid phase; the condenser 101 is used to liquefy the gas-phase SiH4 product at the top of the column. Through the liquid-phase pipeline of the condenser 101, part of the liquid flows back into the top of the column, and the other part is extracted as the SiH4 product in the liquid phase. The second SiH4 discharge end 402 is connected to the side of the purification column 400 and can be used to extract the high-purity SiH4 product in the gas phase when needed. At the same time, the MCS discharge end 403 is connected to the liquid-phase connection pipe between the bottom of the purification column 400 and the reboiler 103 below the bottom of the column and is used for extracting the heavy components and impurities containing MCS in the liquid phase. In addition, when in use, the temperature inside the purification column 400 is preferably maintained at -50°C to -15°C, and the pressure is preferably maintained at 20 to 30 bar.

[0084] Moreover, to make full use of the by-products of the production system of this embodiment, in the production system for producing silane gas by combining a fixed-bed reactor and a reactive distillation column in this embodiment, the MCS discharge end 403 of the purification column 400 is connected to the feed end of the secondary separation column 300, and the liquid-phase mixture mainly composed of MCS taken from the bottom of the purification column 400 can be returned to the secondary separation column 300 for addition and rectification separation. After the return, it continues to participate in rectification separation and subsequent processes according to the production process flow, so as to make full use of MCS in the by-products for disproportionation reaction to prepare silane gas. In addition, when no re-addition is carried out or an emergency occurs due to the abnormality of the production system, the purification column 400 is also connected to the flare tail gas treatment equipment, and the liquid-phase mixture mainly composed of MCS taken from the liquid phase of the purification column 400 can be transported to the flare for combustion treatment to eliminate potential safety hazards. At the same time, the liquid-phase pipeline at the top output end of the secondary separation column 300 is connected to the feed end of the degassing column 100 and the DCS feed port 510 of the fixed-bed reactor 500, and the DCS mixture mainly composed of DCS and MCS taken from the top of the secondary separation column 300 can be returned to the fixed-bed reactor 500 for addition to the DCS disproportionation reaction. After the return, it continues to participate in the disproportionation reaction and subsequent processes according to the production process flow, so as to make full use of DCS and MCS in the by-products for disproportionation reaction to prepare silane gas.

[0085] In addition, in this embodiment, a first booster pump 810 is further provided on the connecting pipeline between the discharge end of the degassing column 100 and the DCS feed port 510 of the fixed-bed reactor 500; a second booster pump 820 is provided on the connecting pipeline between the liquid-phase pipeline at the top output end of the secondary separation column 300 and the DCS feed port 510 of the fixed-bed reactor 500; a compressor 830 is provided on the connecting pipeline between the gas-phase pipeline at the top output end of the reactive distillation column 600 and the feed end of the adsorption device 700; a third booster pump 840 is provided on the connecting pipeline between the liquid-phase pipeline at the top output end of the reactive distillation column 600 and the feed end of the purification column 400. The compressor and the booster pump are both used to enable the material to overcome the pressure difference and be able to enter from a low-pressure device into a high-pressure device.

[0086] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A production system for producing silane gas by combining a fixed bed reactor with a reactive distillation tower, characterized in that: Include: The fixed bed reactor (500) is provided with a DCS feed port (510) and is capable of performing a DCS disproportionation reaction to produce a one-step disproportionation product; A primary separation tower (200) is connected to the discharge end of the fixed bed reactor (500) and is capable of distilling and separating the first-step disproportionation product, and the top discharge end of the primary separation tower (200) is used to produce crude SiH4, and the bottom discharge end thereof is used to produce a chlorosilane mixture; A secondary separation tower (300) is connected to the bottom discharge end of the primary separation tower (200), capable of rectifying and separating the chlorosilane mixture, and the bottom discharge end of the secondary separation tower (300) is used to extract the TCS mixture; and The reaction distillation tower (600) is connected to the bottom discharge end of the secondary separation tower (300) and is provided with a TCS feed port (610), capable of performing TCS disproportionation reaction and separating the product by distillation. The top discharge end of the reaction distillation tower (600) is used to extract crude SiH4.

2. The production system for producing silane gas by combining a fixed bed reactor with a reactive distillation tower as claimed in claim 1, characterized in that: It also comprises a degassing tower (100); the feed end of the degassing tower (100) is used to introduce DCS raw materials, and the discharge end thereof is connected to the DCS feed port (510) of the fixed bed reactor (500); the degassing tower (100) can be used to remove light and purify the DCS raw materials.

3. The production system for producing silane gas by combining a fixed bed reactor with a reactive distillation tower as claimed in claim 1, characterized in that: Also includes: An adsorption device (700) is connected to the gas phase pipelines at the top output ends of the first separation tower (200) and the reactive distillation tower (600), and the adsorption device (700) can perform adsorption and impurity removal of the crude SiH4 product in the gas phase; and The purification tower (400) is connected to the liquid phase pipeline at the top output end of the first separation tower (200) and the reaction distillation tower (600) or is connected to the discharge end of the adsorption device (700). The purification tower (400) can distill and remove heavy components and impurities including MCS in the crude SiH4.

4. The production system for producing silane gas by combining a fixed bed reactor with a reactive distillation tower as claimed in claim 3, characterized in that: The MCS discharge end (403) of the purification tower (400) is connected to the feed end of the secondary separation tower (300), so that the liquid mixture with MCS as the main component extracted from the bottom of the purification tower (400) can be returned to the secondary separation tower (300) for distillation separation.

5. The production system for producing silane gas by combining a fixed bed reactor with a reactive distillation tower as claimed in claim 1, characterized in that: The top of the secondary separation tower (300) is provided with a liquid phase pipeline at the output end for extracting a DCS mixture and connected to a DCS feed port (510) of the fixed bed reactor (500). The DCS mixture extracted from the top of the secondary separation tower (300) can be returned to the fixed bed reactor (500) for adding DCS to the disproportionation reaction.

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