A system and method for trimethylchlorosilane production

Abstract

The present application relates to a kind of trimethylchlorosilane preparation system, including sequentially connected: feed unit, preheating unit, reaction unit and light removal unit;Feed unit, including hydrogen chloride purification device and tetramethylsilane mixture storage tank;Preheating unit: preheating unit includes preheater;Raw material tetramethylsilane mixture and hydrogen chloride gas are preheated after preheating unit and enter reaction unit;Reaction unit: including fixed bed reactor, raw material is reacted in reaction unit after preheating, and product is obtained;Light removal unit: including light removal tower, reaction product enters light removal tower, and the mixture containing target product trimethylchlorosilane of light component removal is obtained by rectification, separation.The present application is not consumed on the basis of other organosilicon monomer, utilizes the hydrogen chloride gas generated by methylchlorosilane hydrolysis TMS comprehensive utilization, is converted into trimethylchlorosilane, and trimethylchlorosilane content in product reaches 93% or more.

Description

Technical Field

[0001] This invention belongs to the field of methylchlorosilane preparation technology, and relates to a new process and method for preparing trimethylchlorosilane in the field of organosilicon. Background Technology

[0002] Methylchlorosilane is a crucial monomer in the production of organosilicon materials, accounting for over 90% of all organosilicon monomers used in the organosilicon industry. Currently, large-scale industrial production of methylchlorosilane employs a "direct method" synthesis process, which involves the direct reaction of chloromethane and metallic silicon under heating and with a copper catalyst. Due to the numerous reaction products obtained by the "direct method," distillation separation is necessary to obtain the desired dimethyldichlorosilane, trimethylchlorosilane, monomethyltrichlorosilane, low-boiling fractions (hereinafter referred to as "tetramethylsilane mixture"), and high-boiling fractions. Trimethylchlorosilane accounts for approximately 1% to 3% of the total products. It can be used to produce organosilicon polymers and as an intermediate in organosilicon synthesis reactions. It can also be used as a raw material for polymer end-capping agents, desiccants, dehydrators, high-temperature adhesives, and resins, making it a widely used organosilicon monomer.

[0003] In addition, the tetramethylsilane mixture accounts for approximately 0.5% to 1.5% of the total product, of which tetramethylsilane (hereinafter referred to as "TMS") accounts for approximately 30% to 50%. High-purity TMS (content ≥99% wt) can be used as a nuclear magnetic resonance reference reagent, a foaming agent, and a fuel additive. However, the boiling points of TMS are very close to those of other components in the low-boiling-point fraction. Purification by distillation requires very high theoretical plate numbers and operating pressures, resulting in high energy consumption and numerous safety measures, which is very unfavorable for industrial production. Therefore, the common practice of most companies is to convert the tetramethylsilane mixture, monomethyltrichlorosilane, and trimethylchlorosilane, or high-boiling-point substances or azeotropes, into dimethyldichlorosilane through disproportionation. For example, CN113831362A describes the disproportionation reaction of a mixture of tetramethylsilane, monomethyltrichlorosilane, and trimethylchlorosilane to obtain dimethyldichlorosilane. The content of dimethyldichlorosilane in the finished product is about 80% to 90%, but this process consumes important organosilicon monomers, such as monomethyltrichlorosilane and trimethylchlorosilane.

[0004] This invention proposes a new process and method for preparing trimethylchlorosilane from a mixture of tetramethylsilanes. The purpose of this invention is to utilize the hydrogen chloride gas generated by the hydrolysis of methylchlorosilanes after purification and comprehensive utilization of TMS to convert it into the trimethylchlorosilane we need, without consuming other organosilicon monomers. The trimethylchlorosilane content in the product reaches more than 93%. Summary of the Invention

[0005] The present invention provides a system for preparing trimethylchlorosilane, comprising, in sequence: a feeding unit, a preheating unit, a reaction unit, and a light-weight removal unit.

[0006] 1. Feeding unit, including hydrogen chloride purification device and tetramethylsilane mixture storage tank.

[0007] The raw material hydrogen chloride gas comes from purification unit 1, and the tetramethylsilane mixture comes from TMS storage tank 2;

[0008] Specifically, the hydrogen chloride gas in the purification device is produced by the hydrolysis of methylchlorosilane and water. After being dehydrated and deoiled, the hydrogen chloride gas is sent to the purification device, which then further dehydrates and deoils the hydrogen chloride gas.

[0009] The tetramethylsilane mixture refers to the low-boiling-point fraction or tetramethylsilane mixture produced during the "direct method" synthesis of organosilicon monomers.

[0010] Generally, tetramethylsilane mixtures (i.e., low-boiling fractions) are mixtures with boiling points below 40°C, and their main components are (CH3)4Si, CH3HSiCl2, (CH3)2SiHCl and small amounts of silicon tetrachloride and other compounds.

[0011] The tetramethylsilane mixture accounts for approximately 0.5% to 1.5% of the total product, of which the tetramethylsilane (hereinafter referred to as "TMS") content is approximately 30% to 50%. However, the boiling points of TMS are very close to those of other components in the low-boiling-point fraction, and the distillation energy consumption and cost required for its purification are very high.

[0012] This invention utilizes the hydrogen chloride gas generated by the hydrolysis of methylchlorosilane to comprehensively utilize TMS and convert it into the target product trimethylchlorosilane. The trimethylchlorosilane content in the product can reach more than 80% (even more than 93%), which can reduce the loss of other organosilicon monomers and improve the utilization rate of low-boiling-point fractions.

[0013] Preferably, the mixture of raw materials, hydrogen chloride and tetramethylsilane, must be purged with high-purity nitrogen at least three times before being fed into the system.

[0014] 2. Preheating unit: The raw material tetramethylsilane mixture and hydrogen chloride gas are preheated in a certain proportion and flow rate before entering the reaction unit.

[0015] The present invention controls the ratio of a tetramethylsilane mixture (calculated as tetramethylsilane) to hydrogen chloride gas. Specifically, the mass ratio of hydrogen chloride to tetramethylsilane is 0.2 to 1.25, preferably 0.4 to 1.0.

[0016] The preheating unit includes a preheater; the preheater temperature is 30-50℃.

[0017] The preheater can preheat and mix the raw material hydrogen chloride gas and methylchlorosilane mixture before entering the reaction unit, improving reaction efficiency. At the same time, the preheater can also be used to exchange heat with the products of the reaction unit. After passing through the recooler, the products enter the intermediate buffer storage tank, which can make full use of the heat of the raw materials and products, greatly reducing energy consumption and making it suitable for industrial promotion.

[0018] Furthermore, it was found that controlling the preheating temperature of the raw materials separately can further improve the purity and proportion of trimethylchlorosilane in the product.

[0019] Preferably, the preheating unit includes a multi-stage preheater, namely preheater I and preheater II.

[0020] Preheater I controls the preheating temperature of the raw material hydrogen chloride, and the temperature range of preheater I is 40-50℃.

[0021] Preheater II controls the preheating temperature of the raw material tetramethylsilane mixture, and the temperature range of preheater II is 32-45℃.

[0022] More preferably, the temperature of preheater I is higher than the temperature of preheater II. For example, the temperature of preheater I is 5-10°C higher than the temperature of preheater II.

[0023] Tetramethylsilane mixtures are derived from the tetramethylsilane mixture produced during the "direct method" synthesis of organosilicon monomers. They are multi-component mixtures containing TMS. When preheated, during contact with HCl preheated at a higher temperature, the smaller hydrogen chloride molecules, due to their higher temperature and faster molecular motion, can quickly contact or disperse around the TMS in the tetramethylsilane mixture. This reduces the probability of hydrogen chloride contacting other components in the mixture and causing side reactions, thereby improving the reaction efficiency of the raw material hydrogen chloride and enhancing the selectivity of the chemical reaction.

[0024] 3. Reaction Unit: Includes a fixed-bed reactor, in which preheated raw materials undergo the following reaction to obtain products.

[0025] (CH3)4Si + HCl → (CH3)3SiCl + CH4

[0026] 1) The fixed-bed reactor is selected from either a continuous fixed-bed reactor or an intermittent fixed-bed reactor.

[0027] The fixed-bed reactor is selected from vertical fixed-bed reactors, batch reactors, or distillation column reactors, with vertical fixed-bed reactors being preferred.

[0028] Specifically, the fixed bed reactor can be a DN50 vertical tube or batch fixed bed reactor based on a continuous process, or a batch reactor under batch process conditions, or a distillation column reactor in which the catalyst is integrated on a tray or packing. Vertical tube fixed bed reactors are preferred.

[0029] Preferably, the reactor is a multi-tube fixed-bed reactor.

[0030] The upper, middle, and lower sections of the fixed-bed reactor are filled with inert ceramic balls, catalyst, and inert ceramic balls, respectively. The packing height of each layer of inert ceramic balls is approximately 1.2-1.8 times the packing height of the catalyst. The catalyst packing amount is determined by the residence time and the tetramethylsilane mixture feed pump.

[0031] 2) Catalyst

[0032] The catalyst used in this invention is a Lewis acid type solid or powder catalyst. The catalyst is spherical, cylindrical, strip-shaped or powdered. The catalyst includes, but is not limited to, γ-Al2O3, AlCl3, molecular sieve, zeolite or γ-Al2O3 supported active component AlCl3.

[0033] More preferably, the catalyst is γ-Al2O3 supported AlCl3+MgCl2, with Mg as a catalyst promoter, wherein the molar ratio of Al:Mg is 1:(0.05-0.5), and Mg, as a promoter, forms a bifunctional metal active center with Al, thereby activating more catalytic sites.

[0034] The γ-Al2O3-supported AlCl3+MgCl2 catalyst can be obtained by conventional impregnation method, which is a simple preparation method.

[0035] By combining supported catalysts with active components, a multi-stage catalyst structure can be formed, optimizing the mechanical strength of the catalyst and improving the efficiency and selectivity of the catalytic reaction.

[0036] 3) Duration of stay

[0037] The residence time in this invention is measured using tetramethylsilane TMS, and the residence time is 0.5 min to 90 min, preferably 50 min to 70 min.

[0038] 4) Reaction temperature

[0039] The reaction temperature of this invention is 55℃~280℃, preferably 90℃~140℃.

[0040] 5) Fixed bed reaction pressure

[0041] The reaction pressure of this invention is 0.01 MPa.g to 0.8 MPa.g, preferably 10 kPa.g to 50 kPa.g.

[0042] In the reaction unit, a preheated tetramethylsilane mixture and hydrogen chloride gas react in a fixed-bed reactor under the conditions of a catalyst, a specific temperature, and a residence time to obtain the reaction products.

[0043] The reaction principle is as follows:

[0044] (CH3)4Si + HCl → (CH3)3SiCl + CH4

[0045] The reaction unit also includes a recooler and an intermediate buffer tank. The reaction products obtained from the fixed-bed reactor exchange heat with the raw materials through the preheater of the preheating unit, and then enter the intermediate buffer tank through the recooler. Further, the reaction products enter the light-duty removal unit through the intermediate buffer tank.

[0046] When a multi-stage preheater is used to preheat the raw materials to different temperatures, the reaction products exchange heat with the raw materials through preheater II (preheating tetramethylsilane mixture) in the preheating unit, and then enter the intermediate buffer storage tank through the recooler.

[0047] 4. Remove the light unit

[0048] The light-removal unit includes a light-removal tower, where the reaction product enters the light-removal tower for distillation and separation to obtain a mixture containing the target product trimethylchlorosilane after light removal.

[0049] The operating conditions of the light-weight removal tower are as follows: tower operating pressure: 0.1 MPa.g to 0.4 MPa.g, preferably 0.2 MPa.g; tower top temperature: 40-60℃; tower reflux ratio: 15-25, preferably 20.

[0050] After separation by the light phase distillation column, the liquid product containing trimethylchlorosilane in the bottom of the column is sent to the reaction product collection tank; the gaseous material at the top of the column is cooled and the unreacted liquid light component containing TMS is collected at a certain reflux ratio, and the liquid material at the top of the column is sent to the TMS storage tank to form a TMS cycle, reducing the amount of additional raw materials used and improving the raw material utilization rate; the non-condensable gas containing methane at the top of the column is sent to incineration to achieve comprehensive product collection.

[0051] Secondly, the present invention provides a method for preparing trimethylchlorosilane, comprising the following steps:

[0052] (1) Feed: Raw material 1, hydrogen chloride gas, comes from the purification unit, and raw material 2, tetramethylsilane mixture, comes from the tetramethylsilane mixture produced during the "direct method" synthesis of organosilicon monomers;

[0053] Preferably, the mixture of raw materials, hydrogen chloride and tetramethylsilane, must be purged with high-purity nitrogen at least three times before being fed into the system.

[0054] (2) Preheating and mixing: The tetramethylsilane mixture and hydrogen chloride gas are preheated in a preheater at a certain ratio and flow rate before entering the fixed bed reactor;

[0055] The mass ratio of hydrogen chloride to tetramethylsilane is 0.2 to 1.25, preferably 0.4 to 1.0.

[0056] The temperature of the preheater is 30-50℃.

[0057] Preferably, a multi-stage preheater is used to preheat the mixture of hydrogen chloride and tetramethylsilane separately.

[0058] Among them, the preheater I controls the preheating temperature of the raw material hydrogen chloride, and the temperature range of the preheater I is 40-50℃.

[0059] Preheater II controls the preheating temperature of the raw material tetramethylsilane mixture, and the temperature range of preheater II is 32-45℃.

[0060] More preferably, the temperature of preheater I is higher than the temperature of preheater II. For example, the temperature of preheater I is 5-10°C higher than the temperature of preheater II.

[0061] Tetramethylsilane mixtures are derived from the direct synthesis of organosilicon monomers. They are multi-component mixtures containing TMS. When preheated and in contact with HCl at a higher temperature, the smaller hydrogen chloride molecules, due to their higher temperature and faster molecular motion, can quickly contact or disperse around the TMS in the tetramethylsilane mixture. This reduces the probability of hydrogen chloride contacting other components in the mixture and causing side reactions, thereby improving the reaction efficiency of the raw material hydrogen chloride and enhancing the selectivity of the chemical reaction.

[0062] (3) Reaction: The preheated tetramethylsilane mixture and hydrogen chloride gas raw material react in a fixed bed reactor in the presence of a catalyst to obtain the reaction product; the product enters the preheater to exchange heat with the raw material, passes through the recooler, and is then fed into the intermediate buffer storage tank.

[0063] The reaction principle is as follows:

[0064] (CH3)4Si + HCl → (CH3)3SiCl + CH4

[0065] The catalyst used in this invention is a Lewis acid type solid or powder catalyst. The catalyst is spherical, cylindrical, strip-shaped or powdered. The catalyst includes, but is not limited to, γ-Al2O3, AlCl3, molecular sieve, zeolite or γ-Al2O3 supported catalyst, preferably zeolite or γ-Al2O3 supported active component AlCl3.

[0066] More preferably, the catalyst is a γ-Al₂O₃ supported dual-active component AlCl₃+MgCl₂, wherein the molar ratio of Al:Mg is 1:(0.1-0.5), and Mg acts as a promoter to form bifunctional metal active centers with Al, thereby activating more catalytic sites. The loading of the single-active component or dual-active component is 10-40 wt%.

[0067] The γ-Al2O3-supported AlCl3+MgCl2 catalyst can be obtained by conventional impregnation method, which is a simple preparation method.

[0068] By combining supported catalysts with active components, a multi-stage catalyst structure can be formed, optimizing the mechanical strength of the catalyst, improving the efficiency and selectivity of the catalytic reaction, and resulting in higher product purity.

[0069] The residence time in the reactor of the present invention is measured by tetramethylsilane (TMS) and is 0.5 min to 90 min, preferably 50 min to 70 min.

[0070] The reaction temperature of this invention is 55℃~280℃, preferably 90℃~140℃.

[0071] The fixed-bed reaction pressure of the present invention is 0.01 MPa.g to 0.8 MPa.g, preferably 10 kPa.g to 50 kPa.g.

[0072] (4) Light phase separation: The product enters the light phase separation tower through the intermediate buffer tank. After distillation separation, the liquid product containing trimethylchlorosilane in the bottom of the tower is sent to the reaction product collection tank for collection. The gaseous material at the top of the tower is cooled and the unreacted liquid material containing TMS is collected at a certain reflux ratio. The liquid material collected at the top of the tower is sent to the TMS storage tank to form a TMS cycle and improve the raw material utilization rate. The non-condensable gas containing methane at the top of the tower is sent to the incinerator.

[0073] The operating conditions of the light-weight removal tower are as follows: tower operating pressure: 0.1 MPa.g~0.4 MPa.g; tower top temperature: 40-60℃; tower reflux ratio: 15~25.

[0074] To implement the method of the present invention, the apparatus of the process of the present invention includes an HCl gas purification device 1, a tetramethylsilane mixture stored in a TMS storage tank 2, a preheater 3 for heat exchange of raw materials and reaction products, a fixed-bed reactor 4, a recooler 5, an intermediate buffer storage tank for reaction products 6, a light-weight removal tower 7, a light-weight removal tower condenser 8, and a reaction product collection tank 9.

[0075] The beneficial effects of this invention are:

[0076] 1) This invention utilizes the hydrogen chloride gas generated by the hydrolysis of methylchlorosilane to comprehensively utilize TMS and convert it into the target product trimethylchlorosilane. The trimethylchlorosilane content in the product reaches more than 80%, reducing the loss of other organosilicon monomers such as monomethyltrichlorosilane and trimethylchlorosilane, and improving the utilization rate of low-boiling-point fractions.

[0077] 2) By setting a preheater in the preheating unit, the present invention can preheat and mix the raw material hydrogen chloride gas and methylchlorosilane mixture before entering the reaction unit, thereby improving the reaction efficiency. At the same time, the preheater is used to exchange heat with the products of the reaction unit and then enter the intermediate buffer storage tank through the recooler. This can make full use of the heat of the reaction raw materials and products, reduce energy consumption, and is suitable for industrial promotion.

[0078] 3) This invention controls the preheating temperature of the raw materials separately to further improve the purity and proportion of trimethylchlorosilane in the product. During the contact between the tetramethylsilane mixture and HCl preheated at a higher temperature, the hydrogen chloride temperature is also higher, enabling it to quickly contact or disperse around the TMS of the tetramethylsilane mixture. This reduces the probability of hydrogen chloride contacting other components and undergoing side reactions, improves the reaction efficiency of the hydrogen chloride raw material, and enhances the selectivity of the chemical reaction.

[0079] 4) This invention selects a suitable Lewis acid catalyst and uses alumina to support aluminum chloride and magnesium chloride to form a dual-structure catalyst. This not only increases the number of active sites and active centers of the catalyst, improves the catalytic reaction efficiency and the purity of the product trimethylchlorosilane, but also further improves the mechanical strength and service life of the catalyst by using the alumina support. Attached Figure Description

[0080] Figure 1 This is a structural diagram and process route diagram of the system for preparing trimethylchlorosilane in Example 1. Detailed Implementation

[0081] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0082] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0083] The system of the present invention is initially in a nitrogen-sealed state of 10 kPa.g, and the device temperature is at room temperature. Before feeding materials, it must be purged with high-purity nitrogen at least 3 times.

[0084] Example 1

[0085] This embodiment provides a trimethylchlorosilane preparation system, comprising, in sequence, a feeding unit, a preheating unit, a reaction unit, and a light-weight removal unit. The feeding unit includes a hydrogen chloride purification device and a tetramethylsilane mixture storage tank. The raw material hydrogen chloride gas originates from the purification device 1, and the tetramethylsilane mixture originates from the TMS storage tank 2. Both the raw materials, hydrogen chloride and tetramethylsilane mixture, must be purged with high-purity nitrogen at least three times before being fed into the system.

[0086] The preheating unit includes a preheater 3. The raw material tetramethylsilane mixture and hydrogen chloride gas are preheated in the preheating unit at a certain ratio and flow rate before entering the reaction unit.

[0087] The reaction unit includes a fixed-bed reactor 4, a recooler 5, and an intermediate buffer tank 6 for reaction products. The upper, middle, and lower sections of the fixed-bed reactor 4 are filled with inert ceramic balls, catalyst, and inert ceramic balls, respectively. The packing height of each layer of inert ceramic balls is 1.5 times the packing height of the catalyst, and the catalyst packing amount is determined by the residence time and the tetramethylsilane mixture feed pump.

[0088] The reaction products obtained from the fixed-bed reactor 4 exchange heat with the raw materials through the preheater 3 of the preheating unit, and then enter the intermediate buffer tank 6 through the recooler 5; further, the reaction products enter the light-duty removal unit through the intermediate buffer tank 6.

[0089] The light component removal unit includes a light component removal tower 7. The reaction products enter the light component removal tower for distillation, removing the light components from the mixture containing the target product trimethylchlorosilane. After distillation separation in the light component removal tower, the liquid product containing trimethylchlorosilane at the bottom of the tower goes to the reaction product collection tank 9; the gaseous material at the top of the tower passes through the light component removal tower condenser 8 and is then collected at a certain reflux ratio as an unreacted liquid material containing TMS, which goes to the TMS storage tank 2; the non-condensable gas containing methane at the top of the tower is incinerated.

[0090] This embodiment also provides a method for preparing trimethylchlorosilane, which is carried out using the system described in this embodiment, and includes the following steps:

[0091] (1) Feeding: The raw material hydrogen chloride gas comes from purification device 1, and the raw material tetramethylsilane mixture comes from the tetramethylsilane mixture TMS storage tank 2 generated during the direct synthesis of organosilicon monomers.

[0092] (2) Preheating and mixing: The mass ratio of hydrogen chloride to tetramethylsilane is 0.954. After being preheated to 40°C by preheater 3, it enters the fixed bed reactor.

[0093] (3) Reaction: The preheated tetramethylsilane mixture and hydrogen chloride gas raw material react in a fixed bed reactor 4 in the presence of a catalyst to obtain the reaction product; the product enters the preheater 3 to exchange heat with the raw material, passes through the recooler 5, and is then fed into the intermediate buffer storage tank 6.

[0094] The reaction principle is as follows:

[0095] (CH3)4Si + HCl → (CH3)3SiCl + CH4

[0096] In the fixed-bed reactor, the residence time was 60 min, the reaction temperature was 140℃, the fixed-bed reaction pressure was 40 kPa·g, the catalyst was γ-Al2O3 supported AlCl3, and the active component loading was 20%.

[0097] (4) Light weight separation: The product enters the light weight separation tower 7 via an intermediate buffer tank. The operating pressure of the light weight separation tower is 0.2 MPa.g, and the top temperature of the light weight separation tower is 45℃. After distillation separation, the liquid phase product containing trimethylchlorosilane in the bottom product of the tower is sent to the reaction product collection tank 9 for collection; the gaseous material at the top of the tower is cooled and collected at a reflux ratio R=20 to the unreacted liquid phase material containing TMS. The liquid phase material collected at the top of the tower is sent to the TMS storage tank 2, and the non-condensable gas containing methane at the top of the tower is sent for incineration.

[0098] Two hours after the product was collected from the light-light removal tower 7, a sample was taken for gas chromatography analysis, which showed that the content of trimethylchlorosilane in the liquid product at the bottom of the tower was 93.5%.

[0099] Example 2

[0100] This embodiment provides a preparation system for trimethylsilane, identical to that of Example 1. Additionally, this embodiment provides a method for preparing trimethylchlorosilane, differing from Example 1 only in the catalyst. Using the same catalyst loading, the catalyst is γ-Al₂O₃ supported on AlCl₃ and MgCl₂, prepared using a conventional impregnation method, with an Al:Mg molar ratio of 1:0.1; the dual-active component loading is 20%. All other steps are the same as in Example 1.

[0101] Two hours after the product was collected from the light-light removal tower 7, a sample was taken for gas chromatography analysis, which showed that the content of trimethylchlorosilane in the liquid product at the bottom of the tower was 94.0%.

[0102] Example 3

[0103] The preparation system was the same as in Example 1, except that the mass ratio of hydrogen chloride to tetramethylsilane was adjusted to 0.4 during the preparation of trimethylchlorosilane. Two hours after the product was collected from the bottom of the light-light removal tower, a sample was taken for gas chromatography analysis, revealing a trimethylchlorosilane content of 82.2% in the liquid product from the bottom of the tower.

[0104] Example 4

[0105] The preparation system was the same as in Example 1, except that the mass ratio of hydrogen chloride to tetramethylsilane was 1.244, the reaction residence time was 90 min, and the reaction temperature was 180 °C during the preparation of trimethylchlorosilane. Two hours after the product was collected from the bottom of the light-light removal tower, a sample was taken for gas chromatography analysis, revealing a trimethylchlorosilane content of 73.8% in the liquid product from the bottom of the tower.

[0106] Example 5

[0107] The preparation system was the same as in Example 1, except that the temperature of the fixed-bed reactor was 240°C during the preparation of trimethylchlorosilane. Two hours after the product was collected from the bottom of the light-light removal column, a sample was taken for gas chromatography analysis, revealing a trimethylchlorosilane content of 86.9% in the liquid product.

[0108] Example 6

[0109] The preparation system was the same as in Example 1, except that the temperature of the fixed-bed reactor was 80°C during the preparation of trimethylchlorosilane. Two hours after the product was collected from the bottom of the light-light removal column, a sample was taken for gas chromatography analysis, revealing a trimethylchlorosilane content of 79.2% in the liquid product.

[0110] Example 7 (Preheating unit adopts multi-stage preheater)

[0111] This embodiment provides a system for preparing trimethylsilane, comprising, in sequence, a feeding unit, a preheating unit, a reaction unit, and a light-weight removal unit. The feeding unit and light-weight removal unit are the same as in Embodiment 1, the only difference being the preheating unit and the reaction unit.

[0112] The preheating unit includes preheater I and preheater II, which are respectively installed on the feed lines of the mixture of hydrogen chloride and tetramethylsilane. Preheater I controls the preheating temperature of the hydrogen chloride to 40°C. Preheater II controls the preheating temperature of the tetramethylsilane mixture to 45°C. The raw materials are preheated to different temperatures before entering the reaction unit.

[0113] The reaction unit includes a fixed-bed reactor 4, a recooler 5, and an intermediate buffer tank 6 for reaction products. The upper, middle, and lower sections of the fixed-bed reactor 4 are filled with inert ceramic balls, catalyst, and inert ceramic balls, respectively. The packing height of each layer of inert ceramic balls is 1.5 times the packing height of the catalyst, and the catalyst packing amount is determined by the residence time and the tetramethylsilane mixture feed pump.

[0114] The reaction products obtained from the fixed-bed reactor 4 exchange heat with the raw materials through the preheater II of the preheating unit, and then enter the intermediate buffer tank 6 through the recooler 5; further, the reaction products enter the light-duty removal unit through the intermediate buffer tank 6.

[0115] The preparation of trimethylchlorosilane using the system described in this embodiment includes the following steps:

[0116] (1) Feeding: The raw material hydrogen chloride gas comes from purification device 1, and the raw material tetramethylsilane mixture comes from the tetramethylsilane mixture TMS storage tank 2 generated during the direct synthesis of organosilicon monomers.

[0117] (2) Preheating and mixing: Hydrogen chloride is preheated to 40°C by preheater I; the tetramethylsilane mixture is preheated to 45°C by preheater II and then enters the fixed bed reactor; the mass ratio of hydrogen chloride to tetramethylsilane is 0.954.

[0118] (3) Reaction: The preheated tetramethylsilane mixture and hydrogen chloride gas raw material react in the fixed bed reactor 4 in the presence of a catalyst to obtain the reaction product; the product enters the preheater II to exchange heat with the raw material, passes through the recooler 5, and is then fed into the intermediate buffer storage tank 6.

[0119] The reaction principle is as follows:

[0120] (CH3)4Si + HCl → (CH3)3SiCl + CH4

[0121] In the fixed-bed reactor, the residence time was 60 min, the reaction temperature was 140℃, the fixed-bed reaction pressure was 40 kPa·g, the catalyst was γ-Al2O3 supported AlCl3, and the active component loading was 20%.

[0122] (4) Separation of light components: The operation is the same as in Example 1.

[0123] Two hours after the product was collected from the light-light removal tower 7, a sample was taken for gas chromatography analysis, which showed that the content of trimethylchlorosilane in the liquid product at the bottom of the tower was 95.70%.

[0124] Example 8

[0125] The preparation system is the same as in Example 7, with preheater I and preheater II used to preheat the raw material mixture of hydrogen chloride and tetramethylsilane, respectively.

[0126] The preparation method is the same as in Example 7, except that: hydrogen chloride is preheated to 38°C by preheater I; the tetramethylsilane mixture is preheated to 44°C by preheater II before entering the fixed-bed reactor.

[0127] Two hours after the product was collected from the light-light removal tower 7, a sample was taken for gas chromatography analysis, which showed that the trimethylchlorosilane content in the liquid product at the bottom of the tower was 96.20%.

[0128] Example 9

[0129] The preparation system is the same as in Example 7, with preheater I and preheater II used to preheat the raw material mixture of hydrogen chloride and tetramethylsilane, respectively.

[0130] The preparation method is the same as in Example 7, except that: hydrogen chloride is preheated to 38°C by preheater I; the tetramethylsilane mixture is preheated to 41°C by preheater II before entering the fixed-bed reactor.

[0131] Two hours after the product was collected from the light-light removal tower 7, a sample was taken for gas chromatography analysis, which showed that the content of trimethylchlorosilane in the liquid product at the bottom of the tower was 94.4%.

[0132] Example 10 (Multi-stage preheating + multiple catalysts)

[0133] The preparation system is the same as in Example 7, with preheater I and preheater II used to preheat the raw material mixture of hydrogen chloride and tetramethylsilane, respectively.

[0134] The preparation method is the same as in Example 7, except that the catalyst is different. Based on the same catalyst loading, the catalyst is γ-Al2O3 loaded with AlCl3 and MgCl2. The catalyst is prepared by conventional impregnation method, with an Al:Mg molar ratio of 1:0.1 and a dual active component loading of 20%.

[0135] Two hours after the product was collected from the light-light removal tower 7, a sample was taken for gas chromatography analysis, which showed that the content of trimethylchlorosilane in the liquid product at the bottom of the tower was 97.9%.

[0136] Comparative Example 1 (without a preheating unit)

[0137] This comparative example provides a system for preparing trimethylsilane, comprising, in sequence, a feeding unit, a reaction unit, and a light-weight removal unit. The feeding unit is the same as that in Example 1.

[0138] The reaction unit includes a fixed-bed reactor 4, a recooler 5, and an intermediate buffer tank 6 for reaction products. The upper, middle, and lower sections of the fixed-bed reactor 4 are filled with inert ceramic balls, catalyst, and inert ceramic balls, respectively. The packing height of each layer of inert ceramic balls is 1.5 times the packing height of the catalyst, and the catalyst packing amount is determined by the residence time and the tetramethylsilane mixture feed pump.

[0139] The raw materials enter the fixed-bed reactor 4, and the resulting reaction products enter the intermediate buffer tank 6 through the recooler 5; further, the reaction products enter the light-duty removal unit through the intermediate buffer tank 6.

[0140] The light removal unit is the same as in Example 1.

[0141] This comparative example also provides a method for preparing trimethylchlorosilane, which is carried out using the above-described system and includes the following steps:

[0142] (1) Feeding: The raw material hydrogen chloride gas comes from purification device 1, and the raw material tetramethylsilane mixture comes from the tetramethylsilane mixture TMS storage tank 2 generated during the direct synthesis of organosilicon monomers.

[0143] (2) Preheating and mixing: The mass ratio of hydrogen chloride to tetramethylsilane is 0.954. After being preheated to 40°C by preheater 3, it enters the fixed bed reactor.

[0144] (3) Reaction: Tetramethylsilane mixture and hydrogen chloride gas feedstock enter fixed bed reactor 4 and react in the presence of catalyst to obtain reaction products; after passing through recooler 5, the products are fed into intermediate buffer tank 6.

[0145] The reaction principle is as follows:

[0146] (CH3)4Si + HCl → (CH3)3SiCl + CH4

[0147] In the fixed-bed reactor, the mass ratio of hydrogen chloride to tetramethylsilane was 0.954, the residence time was 60 min, the reaction temperature was 140℃, the fixed-bed reaction pressure was 40 kPa·g, the catalyst was γ-Al2O3 supported AlCl3, and the active component loading was 20%.

[0148] (4) Light separation: Same as in Example 1.

[0149] Two hours after the product was collected from the light-removal tower 7, a sample was taken for gas chromatography analysis, which showed that the content of trimethylchlorosilane in the liquid product at the bottom of the tower was 64.5%.

[0150] Table 1

[0151]

[0152]

[0153] Those skilled in the art should understand that the above embodiments are merely for illustrating this disclosure and are not intended to limit the scope of this application. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of this invention.

Claims

1. A method for preparing trimethylchlorosilane, comprising the following steps: (1) Feed: Raw material 1 hydrogen chloride gas comes from the purification unit, the hydrogen chloride in the purification unit comes from the methylchlorosilane hydrolysis unit, and raw material 2 tetramethylsilane mixture comes from the tetramethylsilane mixture generated during the "direct method" synthesis of organosilicon monomers; (2) Preheating and mixing: The tetramethylsilane mixture and hydrogen chloride gas are preheated in a preheater at a certain ratio and flow rate before entering the fixed bed reactor; the temperature of the preheater is 30-45℃; (3) Reaction: The preheated tetramethylsilane mixture and hydrogen chloride gas raw material react in a fixed bed reactor in the presence of a catalyst to obtain the reaction product; the product enters the preheater to exchange heat with the raw material, passes through the recooler, and is then fed into the intermediate buffer storage tank. (4) Light component separation: The product enters the light component separation tower through the intermediate buffer tank. After distillation separation, the liquid product containing trimethylchlorosilane in the bottom of the tower is sent to the reaction product collection tank for collection. The gaseous material at the top of the tower is cooled and the unreacted liquid light component containing TMS is collected at a certain reflux ratio. The liquid material collected at the top of the tower is sent to the TMS storage tank, and the non-condensable gas containing methane at the top of the tower is sent to the incinerator. Step (3) uses Lewis acid type solid or powder catalyst. The catalyst is spherical, cylindrical, strip or powder. The catalyst is γ-Al2O3 supported with dual active components AlCl3+MgCl2, where the molar ratio of Al:Mg is 1:(0.1-0.5) and the loading of the active components of the catalyst is 5wt%~40wt%.

2. The method according to claim 1, characterized in that, Step (2) uses a multi-stage preheater, with preheater I and sub-preheater II preheating the raw material mixture of hydrogen chloride and tetramethylsilane, respectively; The temperature range of the preheater I is 40-50℃. The temperature range of preheater II is 32-45℃. Furthermore, the temperature of preheater I is higher than that of preheater II.

3. The method according to claim 1, characterized in that, The temperature of preheater I is 5-8℃ higher than that of preheater II.

4. The method according to claim 1, characterized in that, The fixed-bed reaction pressure was 10 kPa·g to 50 kPa·g; the reaction temperature was 90℃ to 140℃; and the residence time in the reactor was measured in tetramethylsilane TMS and was 50 min to 70 min.

5. The method according to claim 1, characterized in that, The operating conditions for the light-weight removal tower are as follows: tower operating pressure: 0.1 MPa.g~0.4 MPa.g; tower top temperature: 40-60℃; tower reflux ratio: 15~25.

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