Preparation method of tetramethoxysilane and application thereof

Abstract

The application discloses a preparation method of tetramethoxysilane and application of the tetramethoxysilane, and the preparation method comprises the following steps: S1, adding a suspended agent after impurity removal, silicon powder and a pretreatment catalyst into a reactor, controlling a reaction temperature to be 180-280 DEG C, introducing methanol from the bottom of the reactor, and stirring to obtain a crude product; and S2, rectifying the crude product at 90-120 DEG C to obtain the tetramethoxysilane. By using the suspended agent after impurity removal, the silicon powder, the pretreatment catalyst and the methanol are uniformly dispersed in the suspended agent and react, so that the reaction is more sufficient; the tetramethoxysilane prepared by using the method has extremely low chlorine content, the organic content of the product is greater than 99.99%, the total content of metal element impurities is less than 25 ppm, the total content of potassium, lithium and sodium is less than 2.5 ppm, is suitable for synthesizing high-purity quartz, and the product can be simultaneously applied to chemical vapor deposition and sol-gel method for producing high-purity quartz.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, specifically to a method for preparing tetramethoxysilane and its application. Background Technology

[0002] High-purity quartz is an irreplaceable fundamental material for the development of national strategic and pillar industries. It is an essential and irreplaceable functional material for high-tech industries such as semiconductor chips, solar photovoltaics, fiber optic communication, aerospace, precision optics, and special glass, making it a truly critical mineral resource. While quartz is widely distributed in nature, high-purity quartz is extremely rare. Currently, only the United States and India are recognized as suitable raw materials for high-purity quartz sand, and China's high-purity quartz sand is almost entirely dependent on imports. To address the shortage of high-purity quartz sand, break the foreign monopoly, and reduce dependence on natural quartz ore, the preparation of high-purity quartz using SiCl4 or other silicon compounds via chemical vapor deposition (CVD), sol-gel methods, and other techniques has gained increasingly widespread application in industrial production.

[0003] The sol-gel method (hydrothermal method) uses tetramethoxysilane, tetraethoxysilane, etc., as raw materials, which are hydrolyzed and crystallized into quartz crystals under high temperature and pressure. Chemical vapor deposition (CVD) uses high-purity SiCl4, SiH4, octamethylcyclotetrasiloxane (D4), tetramethoxysilane, etc., as raw materials, which are hydrolyzed in an oxyhydrogen flame to form silicon dioxide, which is then deposited onto the target surface and further melted to form quartz. Currently, domestic CVD methods mainly use high-purity SiCl4 as raw material. Because the raw material contains a large amount of chlorine, a large amount of hydrogen chloride gas is generated during the production process, which can corrode pipelines and equipment, and poses a risk of leakage, causing environmental pollution. Using SiCl4 as a raw material leads to a high chlorine concentration in the synthesized quartz glass, reducing its durability against ultraviolet light, and the presence of chlorine also reduces its spectral transmittance in the deep ultraviolet band.

[0004] In China, high-purity quartz is synthesized using octamethylcyclotetrasiloxane as a raw material. Octamethylcyclotetrasiloxane is liquid at room temperature, but its melting point is 17-18℃, and it easily solidifies at low temperatures; its boiling point is relatively high (>175℃), making it difficult to vaporize. Using octamethylcyclotetrasiloxane as a raw material requires a specialized conveying and vaporization system. High-purity quartz is also synthesized domestically using silane (SiH4), but SiH4 is extremely sensitive to oxygen and air, highly flammable, and a toxic gas, and its production is very limited. In summary, tetramethoxysilane is a relatively ideal raw material. It does not contain chlorine, is easy to vaporize and transport via pipeline, has a relatively large domestic production volume, and can be used simultaneously in CVD and sol-gel processes.

[0005] The traditional method for preparing tetramethoxysilane involves a direct liquid-phase reaction of silicon tetrachloride, a byproduct of polycrystalline silicon, with methanol. This method not only produces hydrogen chloride gas but also results in a high impurity content in the product, making it unsuitable for the high-purity quartz industry. Summary of the Invention

[0006] The main objective of this invention is to propose a method for preparing tetramethoxysilane and its application, aiming to solve the problem that existing methods for preparing tetramethoxysilane not only generate hydrogen chloride gas, but also produce products with high impurity content, making them unsuitable for the high-purity quartz industry.

[0007] To achieve the above objectives, this invention proposes a method for preparing tetramethoxysilane, comprising the following steps:

[0008] S1. Add the purified suspending agent, silica powder and pretreated catalyst to the reactor, control the reaction temperature at 180-280℃, introduce methanol from the bottom of the reactor and stir to obtain the crude product.

[0009] S2. The crude product is distilled at 90℃~120℃ to obtain tetramethoxysilane.

[0010] Optionally, in step S1, the mass ratio of the silicon powder to the pretreated catalyst is 100:1 to 10; and / or,

[0011] The mass ratio of the silicon powder to the purified suspending agent is 1:2 to 5.

[0012] Optionally, before step S1, the following steps are also included:

[0013] The tetramethoxysilane and the catalyst were mixed, stirred and heated to 25–50°C, kept at that temperature for 0.5–1 hour, and then filtered to obtain the pretreated catalyst.

[0014] Optionally, the mass ratio of the tetramethoxysilane to the catalyst is 10:1 to 5.

[0015] Optionally, the method for preparing the catalyst includes the following steps:

[0016] One or more copper-based catalysts are mixed and heated to 60–120°C for 8–12 hours to obtain the catalyst.

[0017] Optionally, the copper-based catalyst includes at least one of nano-copper powder, copper oxide, copper hydroxide, cuprous oxide, copper acetate, and diethyl copper phosphate.

[0018] Optionally, before step S1, the following steps are also included:

[0019] The suspending agent is heated to 200-260°C and stirred for 8-12 hours to evaporate the low-boiling substances in the suspending agent. Methanol is then introduced and stirring is continued for 4-8 hours to obtain the purified suspending agent.

[0020] Optionally, the mass ratio of methanol to the suspending agent is 0.5 to 5:100.

[0021] Optionally, the suspending agent includes at least one of dodecylbenzene, phenyl silicone oil, and bis(dodecylbenzene).

[0022] The present invention also proposes the application of the preparation method of tetramethoxysilane as described above in the synthesis of high-purity quartz.

[0023] In the technical solution provided by this invention, the impurity-removed suspending agent, silicon powder, and pretreated catalyst are mixed and then reacted directly with methanol. By using the impurity-removed suspending agent, the silicon powder, pretreated catalyst, and methanol are uniformly dispersed in the suspending agent and react, thus making the reaction more complete. In addition, the catalyst in this invention does not contain chlorine, and the tetramethoxysilane prepared by this method has extremely low chlorine content, and the organic content of the product is greater than 99.99%, and the total content of metal element impurities is less than 25 ppm, of which the total content of potassium, lithium, and sodium is less than 2.5 ppm. It is suitable for the synthesis of high-purity quartz. At the same time, this invention adopts a one-step direct preparation method, which is simple, suitable for industrial production, and in line with the future direction of chemical industry development. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The traditional method for preparing tetramethoxysilane involves a direct liquid-phase reaction of silicon tetrachloride, a byproduct of polycrystalline silicon, with methanol. This method not only produces hydrogen chloride gas but also results in a high impurity content in the product, making it unsuitable for the high-purity quartz industry.

[0026] In view of this, the present invention proposes a method for preparing tetramethoxysilane, aiming to provide a method for preparing tetramethoxysilane that does not produce hydrogen chloride gas and produces a product with low impurity content, which can be applied to the high-purity quartz industry.

[0027] This invention proposes a method for preparing tetramethoxysilane, comprising the following steps:

[0028] S1. Add the purified suspending agent, silica powder and pretreated catalyst to the reactor, control the reaction temperature at 180-280℃, introduce methanol from the bottom of the reactor and stir to obtain the crude product.

[0029] S2. The crude product is distilled at 90℃~120℃ to obtain tetramethoxysilane.

[0030] In the technical solution provided by this invention, the impurity-removed suspending agent, silicon powder, and pretreated catalyst are mixed and then reacted directly with methanol. By using the impurity-removed suspending agent, the silicon powder, pretreated catalyst, and methanol are uniformly dispersed in the suspending agent and react, thus making the reaction more complete. In addition, the catalyst in this invention does not contain chlorine, and the tetramethoxysilane prepared by this method has extremely low chlorine content, and the organic content of the product is greater than 99.99%, and the total content of metal element impurities is less than 25 ppm, of which the total content of potassium, lithium, and sodium is less than 2.5 ppm. It is suitable for the synthesis of high-purity quartz. At the same time, this invention adopts a one-step direct preparation method, which is simple, suitable for industrial production, and in line with the future direction of chemical industry development.

[0031] Furthermore, in step S1, the mass ratio of silicon powder to the pretreated catalyst is 100:1 to 10; the mass ratio of silicon powder to the purified suspending agent is 1:2 to 5. By controlling the silicon powder and the pretreated catalyst within this range, the catalytic reaction can be fully completed without waste of raw materials. By controlling the silicon powder and the purified suspending agent within the range of this invention, the silicon powder can be completely dispersed in the suspending agent, which is beneficial to subsequent reactions.

[0032] In one embodiment of the present invention, prior to step S1, a pretreatment of the catalyst is further included, comprising the following steps:

[0033] S11. Mix tetramethoxysilane and catalyst, stir and heat to 25-50°C, keep warm for 0.5-1 hour, filter to obtain pretreated catalyst.

[0034] The tetramethoxysilane is a high-purity tetramethoxysilane, preferably the high-purity tetramethoxysilane prepared in this invention. After pretreatment of the catalyst, no dust is generated, the catalyst adsorption is significantly improved, the affinity between the catalyst and silicon powder is enhanced, and the utilization rate of the catalyst is improved. At the same time, by using the tetramethoxysilane prepared in this invention to treat the catalyst, the product of this invention can be further used as a raw material for repeated recycling without further removal, thus saving resources.

[0035] Preferably, the mass ratio of the tetramethoxysilane to the catalyst is 10:1 to 5. In this embodiment, by controlling the tetramethoxysilane and the catalyst within this range, the catalyst can be fully treated, and the tetramethoxysilane prepared by this invention can be used for pretreatment, making full use of resources.

[0036] Furthermore, the method for preparing the catalyst includes the following steps:

[0037] S10. Mix one or more copper-based catalysts, heat to 60-120°C, and heat for 8-12 hours to obtain the catalyst.

[0038] The catalyst used in this invention is a copper-based catalyst that does not contain chlorine. The tetramethoxysilane prepared by this method has an extremely low chlorine content, and the tetramethoxysilane prepared by this method also has an extremely low chlorine content when used to synthesize high-purity quartz.

[0039] Preferably, the copper-based catalyst comprises at least one of nano-copper powder, copper oxide, copper hydroxide, cuprous oxide, copper acetate, and diethylcopper phosphate. That is, the catalyst can be any one or a mixture of two or more of nano-copper powder, copper oxide, copper hydroxide, cuprous oxide, copper acetate, and diethylcopper phosphate. These catalysts are all chlorine-free and suitable for the catalytic reaction of silicon powder with methanol. In a preferred embodiment, the copper-based catalyst is selected from one or more of nano-copper powder, cuprous oxide, copper hydroxide, and copper oxide.

[0040] Furthermore, prior to step S1, the following steps are also included:

[0041] S12. Heat the suspending agent to 200-260°C and stir for 8-12 hours to evaporate the low-boiling substances in the suspending agent. Then, introduce methanol and continue stirring for 4-8 hours to obtain the purified suspending agent.

[0042] This suspension purification process uses methanol vaporization to remove residual impurities from the suspension, while also removing substances that can form an azeotropic reaction with tetramethoxysilane. The tetramethoxysilane prepared by this method has a high organic content, and the high-purity quartz prepared in this way has almost no residual carbon and no black spots. In addition, the small amount of methanol remaining after this purification process does not need to be removed and can be used for subsequent reactions.

[0043] Preferably, the mass ratio of methanol to the suspending agent is 0.5 to 5:100. Controlling the mass ratio of methanol to the suspending agent within this range can completely remove the impurities remaining in the suspending agent without wasting resources.

[0044] The suspending agent includes at least one of dodecylbenzene, phenyl silicone oil, and bis-dodecylbenzene. That is, the suspending agent can be any one of dodecylbenzene, phenyl silicone oil, and bis-dodecylbenzene, or a mixture of two of them, or a mixture of the three. All of the above suspending agents can fully suspend the reaction raw materials of the present invention in the suspending agent.

[0045] Preferably, in step S2, the pressure of the crude tetramethoxysilane distillation is -0.098 MPa, the reflux ratio is 1 to 10, the distillation equipment is made of fully lined polytetrafluoroethylene, and the packing is polytetrafluoroethylene Pall rings. Under these distillation conditions, the tetramethoxysilane can be fully purified to obtain high-purity tetramethoxysilane.

[0046] This invention also proposes a method for preparing tetramethoxysilane and its application in the synthesis of high-purity quartz. The tetramethoxysilane prepared using the technical solution of this invention has an organic content greater than 99.99% and a total metal element impurity content of less than 25 ppm, of which the total content of potassium, lithium, and sodium is less than 2.5 ppm. The tetramethoxysilane prepared using the technical solution of this invention can be used for the preparation of high-purity quartz, and this product can be used simultaneously in the production of high-purity quartz by chemical vapor deposition and sol-gel methods.

[0047] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0048] Example 1

[0049] A method for preparing a tetramethoxysilane includes the following steps:

[0050] (1) Add phenyl silicone oil to the reactor, heat to 200℃, and stir for 8 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 0.5% of the weight of the suspending agent.

[0051] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 25°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 10:1.

[0052] The catalyst is prepared by mixing 50 parts by mass of nano-copper powder and 50 parts by mass of copper hydroxide using a high-speed disperser; then placing the mixture in a kiln and heating it to 60°C for 8 hours.

[0053] (3) Phenyl silicone oil after impurity removal, silicon powder and pretreated catalyst are added into the reactor respectively. The reaction temperature is controlled at 180°C. Methanol is introduced from the bottom of the reactor. Under stirring conditions, all materials are evenly dispersed in the suspension and reacted to finally obtain crude tetramethoxysilane.

[0054] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 90°C, a pressure of -0.098 MPa, and a reflux ratio of 2. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, which can be used to synthesize high-purity quartz.

[0055] Example 2

[0056] A method for preparing a tetramethoxysilane includes the following steps:

[0057] (1) Add dodecylbenzene to the reactor, heat to 220°C, and stir for 10 hours. Continue heating, introduce methanol, stir for 6 hours, and then cool to room temperature. The amount of methanol introduced is 1% of the weight of the suspending agent.

[0058] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.8 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0059] The catalyst is prepared by mixing 50 parts by mass of nano-copper powder and 50 parts by mass of copper hydroxide using a high-speed disperser; then placing the mixture in a kiln, heating it to 80°C, and drying it for 10 hours.

[0060] (3) Add the purified dodecylbenzene, silicon powder and pretreated catalyst into the reactor, control the reaction temperature at 200°C, and introduce methanol from the bottom of the reactor. Under stirring conditions, all materials are evenly dispersed in the suspension and reacted to finally obtain crude tetramethoxysilane.

[0061] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 100℃, a pressure of -0.098MPa, and a reflux ratio of 4. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, and this product can be used to synthesize high-purity quartz.

[0062] Example 3

[0063] A method for preparing a tetramethoxysilane includes the following steps:

[0064] (1) Add didodecylbenzene to the reactor, heat to 260°C, and stir for 12 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 5% of the weight of the suspending agent.

[0065] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0066] The catalyst is prepared by mixing 50 parts by mass of nano-copper powder and 50 parts by mass of copper hydroxide using a high-speed disperser; then placing the mixture in a kiln, heating it to 120°C, and drying it for 12 hours.

[0067] (3) Add impurity-removed dodecylbenzene, silicon powder and pretreated catalyst into the reactor, control the reaction temperature at 280°C, introduce methanol from the bottom of the reactor, and under stirring conditions, make all materials uniformly dispersed in the suspension and react to finally obtain crude tetramethoxysilane.

[0068] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 120℃, a pressure of -0.098MPa, and a reflux ratio of 4. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, and this product can be used to synthesize high-purity quartz.

[0069] Example 4

[0070] A method for preparing a tetramethoxysilane includes the following steps:

[0071] (1) Add phenyl silicone oil to the reactor, heat to 240°C, and stir for 8 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 1% of the weight of the suspending agent.

[0072] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0073] The catalyst is prepared by mixing 50 parts by mass of copper oxide and 50 parts by mass of nano-copper powder using a high-speed disperser; then placing the mixture in a kiln and heating it to 120°C for 8 hours.

[0074] (3) Phenyl silicone oil, silicon powder and pretreated catalyst were added into the reactor after impurity removal. The reaction temperature was controlled at 200°C. Methanol was introduced from the bottom of the reactor. Under stirring conditions, all materials were evenly dispersed in the suspension and reacted to finally obtain crude tetramethoxysilane.

[0075] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 100℃, a pressure of -0.098MPa, and a reflux ratio of 2. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, which can be used to synthesize high-purity quartz.

[0076] Example 5

[0077] A method for preparing a tetramethoxysilane includes the following steps:

[0078] (1) Add dodecylbenzene to the reactor, heat to 240°C, and stir for 12 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 1% of the weight of the suspending agent.

[0079] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0080] The catalyst is prepared by mixing 50 parts by mass of copper oxide and 50 parts by mass of nano-copper powder using a high-speed disperser; then placing the mixture in a kiln and heating it to 100°C for 8 hours.

[0081] (3) Add the purified dodecylbenzene, silicon powder and pretreated catalyst into the reactor, control the reaction temperature at 200°C, and introduce methanol from the bottom of the reactor. Under stirring conditions, all materials are evenly dispersed in the suspension and reacted to finally obtain crude tetramethoxysilane.

[0082] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 100℃, a pressure of -0.098MPa, and a reflux ratio of 6. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, and this product can be used to synthesize high-purity quartz.

[0083] Example 6

[0084] A method for preparing a tetramethoxysilane includes the following steps:

[0085] (1) Add didodecylbenzene to the reactor, heat to 240°C, and stir for 12 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 1% of the weight of the suspending agent.

[0086] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0087] The catalyst is prepared by mixing 50 parts by mass of copper oxide and 50 parts by mass of nano-copper powder using a high-speed disperser; then placing the mixture in a kiln, heating it to 100°C, and drying it for 8 hours.

[0088] (3) Add impurity-removed dodecylbenzene, silicon powder and pretreated catalyst into the reactor, control the reaction temperature at 200°C, introduce methanol from the bottom of the reactor, and under stirring conditions, make all materials uniformly dispersed in the suspension and react to finally obtain crude tetramethoxysilane.

[0089] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 100℃, a pressure of -0.098MPa, and a reflux ratio of 6. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, and this product can be used to synthesize high-purity quartz.

[0090] Example 7

[0091] A method for preparing a tetramethoxysilane includes the following steps:

[0092] (1) Add phenyl silicone oil to the reactor, heat to 260°C, and stir for 12 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 1% of the weight of the suspending agent.

[0093] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0094] The catalyst is prepared by mixing 50 parts by mass of cuprous oxide and 50 parts by mass of copper oxide using a high-speed disperser; then placing the mixture in a kiln and heating it to 80°C for 8 hours.

[0095] (3) Phenyl silicone oil, silicon powder and pretreated catalyst were added into the reactor after impurity removal. The reaction temperature was controlled at 200°C. Methanol was introduced from the bottom of the reactor. Under stirring conditions, all materials were evenly dispersed in the suspension and reacted to finally obtain crude tetramethoxysilane.

[0096] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 100℃, a pressure of -0.098MPa, and a reflux ratio of 8. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, and this product can be used to synthesize high-purity quartz.

[0097] Example 8

[0098] A method for preparing a tetramethoxysilane includes the following steps:

[0099] (1) Add dodecylbenzene to the reactor, heat to 260°C, and stir for 12 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 1% of the weight of the suspending agent.

[0100] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0101] The catalyst is prepared by mixing 50 parts by mass of cuprous oxide and 50 parts by mass of copper oxide using a high-speed disperser; then placing the mixture in a kiln and heating it to 80°C for 8 hours.

[0102] (3) Add the purified dodecylbenzene, silicon powder and pretreated catalyst into the reactor, control the reaction temperature at 200°C, and introduce methanol from the bottom of the reactor. Under stirring conditions, all materials are evenly dispersed in the suspension and reacted to finally obtain crude tetramethoxysilane.

[0103] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 100℃, a pressure of -0.098MPa, and a reflux ratio of 8. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, and this product can be used to synthesize high-purity quartz.

[0104] Example 9

[0105] A method for preparing a tetramethoxysilane includes the following steps:

[0106] (1) Add didodecylbenzene to the reactor, heat to 260°C, and stir for 12 hours. Continue heating, introduce methanol, stir for 8 hours, and then cool to room temperature. The amount of methanol introduced is 1% of the weight of the suspending agent.

[0107] (2) Tetramethoxysilane and catalyst are added and mixed in a reactor, stirred and heated to 30°C, kept at that temperature for 0.5 hours, and the catalyst is filtered out. The mass ratio of tetramethoxysilane to catalyst is 3:1.

[0108] The catalyst is prepared by mixing 50 parts by mass of cuprous oxide and 50 parts by mass of copper oxide using a high-speed disperser; then placing the mixture in a kiln and heating it to 80°C for 8 hours.

[0109] (3) Add impurity-removed dodecylbenzene, silicon powder and pretreated catalyst into the reactor, control the reaction temperature at 200°C, introduce methanol from the bottom of the reactor, and under stirring conditions, make all materials uniformly dispersed in the suspension and react to finally obtain crude tetramethoxysilane.

[0110] (4) The crude tetramethoxysilane is subjected to further distillation at a distillation temperature of 100℃, a pressure of -0.098MPa, and a reflux ratio of 8. The distillation equipment is made of polytetrafluoroethylene with a full inner lining and the packing material is polytetrafluoroethylene Pall rings. Tetramethoxysilane is obtained, and this product can be used to synthesize high-purity quartz.

[0111] Comparative Example 1

[0112] Without adding the suspending agent after impurity removal in step (1), the other steps are the same as in Example 1, and tetramethoxysilane is prepared.

[0113] Comparative Example 2

[0114] In step (1), a common suspending agent is added, and the other steps are the same as in Example 1, to prepare tetramethoxysilane.

[0115] Comparative Example 3

[0116] In step (1), a common catalyst was added, and the other steps were the same as in Example 1, to prepare tetramethoxysilane.

[0117] Comparative Example 4

[0118] In step (1), silicon powder is replaced with silicon tetrachloride, and the other steps are the same as in Example 1 to prepare tetramethoxysilane.

[0119] Test methods and results

[0120] The tetramethoxysilanes prepared in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in the table below.

[0121] Table 1 Performance tests of the prepared tetramethoxysilane

[0122]

[0123]

[0124] The comparison between Comparative Example 1 and Example 1 shows that without the addition of a suspending agent after impurity removal, the organic content of the obtained tetramethoxysilane is low and the reaction is not sufficient. The comparison between Comparative Examples 2 and 3 and Example 1 shows that the reaction between the suspending agent without impurity removal and the pretreated catalyst is not sufficient and the impurity content is high. The comparison between Comparative Example 4 and Example 1 shows that no hydrogen chloride is generated in the process of preparing tetramethoxysilane by the present invention, and the obtained product does not contain chlorine.

[0125] In summary, the method for preparing tetramethoxysilane provided by this invention, after catalyst pretreatment, does not generate dust, significantly improves catalyst adsorption, enhances the affinity between the catalyst and silicon powder, and improves catalyst utilization. The catalyst is chlorine-free, resulting in tetramethoxysilane with extremely low chlorine content, which is also extremely low for synthesizing high-purity quartz. The suspension impurity removal process removes substances that can form azeotropes with tetramethoxysilane, leading to tetramethoxysilane with high organic content. The resulting high-purity quartz has almost no residual carbon and no black spots.

[0126] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing tetramethoxysilane, characterized in that, Includes the following steps: S1. Add the purified suspending agent, silica powder and pretreated catalyst to the reactor, control the reaction temperature at 180~280℃, introduce methanol from the bottom of the reactor and stir to obtain crude product; S2. The crude product is distilled at 90℃~120℃ to obtain tetramethoxysilane; Before step S1, the following steps are also included: Tetramethoxysilane and the catalyst were mixed, stirred and heated to 25-50°C, kept at that temperature for 0.5-1 hour, and then filtered to obtain the pretreated catalyst. Before step S1, the following steps are also included: The suspending agent is heated to 200~260℃ and stirred for 8~12h to evaporate the low-boiling substances in the suspending agent. Methanol is then introduced and stirring is continued for 4~8h to obtain the purified suspending agent. The method for preparing the catalyst includes the following steps: One or more copper-based catalysts are mixed and heated to 60-120°C for 8-12 hours to obtain the catalyst. The copper-based catalyst includes at least one of the following: nano-copper powder, copper oxide, copper hydroxide, cuprous oxide, copper acetate, and diethyl copper phosphate. The suspending agent includes at least one of dodecylbenzene, phenyl silicone oil, and bis(dodecylbenzene).

2. The method for preparing tetramethoxysilane according to claim 1, characterized in that, In step S1, the mass ratio of the silicon powder to the pretreated catalyst is 100:1~10; and / or, The mass ratio of the silicon powder to the purified suspending agent is 1:2~5.

3. The method for preparing tetramethoxysilane according to claim 1, characterized in that, The mass ratio of the tetramethoxysilane to the catalyst is 10:1~5.

4. The method for preparing tetramethoxysilane according to claim 1, characterized in that, The mass ratio of methanol to the suspending agent is 0.5~5:

100.

5. The application of the method for preparing tetramethoxysilane according to any one of claims 1 to 4 in the synthesis of high-purity quartz.

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