Composite catalyst and method for continuously synthesizing alkoxy silane

Abstract

The invention relates to a composite catalyst and a method for continuously synthesizing alkoxy silane, and belongs to the technical field of organic compound preparation. The composite catalyst comprises the following components: (1) an alkali metal compound; (2) a copper simple substance and / or a metal copper compound; the method comprises the following steps: preparing a material containing silicon powder, an initiator, a composite catalyst and alcohol, uniformly mixing, sequentially carrying out first-stage reaction, second-stage reaction and third-stage reaction, and rectifying to obtain alkoxy silane. According to the method, the silicon powder conversion rate reaches 99.5%, the product selectivity is greater than 99%, the reaction liquid is rectified to obtain the alkoxy silane with the purity greater than 99.99%, the alkoxy silane is continuously synthesized through the reaction, and the method is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a composite catalyst and a method for continuously synthesizing alkoxysilane, belonging to the technical field of organic chemical industry. Background Art

[0002] At present, there are four main production processes for tetramethoxysilane: 1) Silicon tetrachloride method, which uses silicon tetrachloride, a by-product of the polysilicon and organosilicon industries, as raw material, and undergoes an esterification reaction with methanol to produce tetramethoxysilane. The reaction produces a large amount of hydrochloric acid as a by-product, which is highly corrosive to equipment and pipelines. It is also prone to leakage, causing environmental pollution or personal injury; 2) Sodium fluorosilicate method, which uses sodium fluorosilicate, a by-product of the phosphate fertilizer industry, as raw material, and reacts with concentrated sulfuric acid to produce silicon fluoride, which then reacts with methanol to produce tetramethoxysilane. There is concentrated sulfuric acid, and hydrofluoric acid and sodium sulfate are by-products, which have high requirements for equipment and pipelines, and the product purification is difficult; 3) Alkoxysilane esterification method, using trimethoxysilane as raw material, a disproportionation reaction is carried out to obtain it, but the raw material of trimethoxysilane is expensive, and monosilane is extremely easy to burn, and the reaction is highly dangerous; 4) Silicon powder direct method, using silicon powder and methanol as raw materials, a direct reaction is carried out to produce tetramethoxysilane. This method does not introduce chlorine-containing compounds, has high reaction selectivity, and the product is easy to separate, becoming a research hotspot in recent years.

[0003] In recent years, domestic scholars have made important achievements in the direct synthesis of alkoxysilanes from silicon powder. For example, Chinese invention patent CN107216348A discloses a method for directly preparing tetramethoxysilane, and Chinese invention patent CN108640943A discloses a method for producing ethyl orthosilicate using silicon powder. However, the above studies have remained in the laboratory research stage, and it is difficult to achieve industrial scale-up. In addition, there are problems such as low raw material conversion rate and low product purity. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a composite catalyst and a method for preparing continuously synthesized alkoxysilane. The present invention continuously synthesizes alkoxysilane, and the reaction liquid is distilled to obtain alkoxysilane with a purity greater than 99.99%, which is suitable for industrial production.

[0005] The present invention provides a composite catalyst comprising the following components: (1) Alkali metal compounds; (2) Copper and / or metallic copper compounds.

[0006] Furthermore, the distribution ratio of each component is calculated based on metal atoms, and the atomic ratio of alkali metal to copper is 1:(0.1~5).

[0007] Furthermore, the distribution ratio of each component is calculated based on metal atoms, and the atomic ratio of alkali metal to copper is 1:(0.5~2).

[0008] Furthermore, the distribution ratio of each component is calculated based on metal atoms, and the atomic ratio of alkali metal to copper is 1:0.1, 1:0.2, 1:0.4, 1:0.8, 1:1, 1:1.5, 1:3, 1:4, 1:5, or any value between any two of the above points.

[0009] Furthermore, the alkali metal compound is selected from at least one of alkali metal oxides, alkoxides, and hydroxides; and the metallic copper compound is selected from at least one of copper salts and copper oxides.

[0010] The present invention also provides a method for preparing the composite catalyst, which comprises mixing and stirring the components to obtain the composite catalyst.

[0011] The present invention also provides a method for continuously synthesizing alkoxysilanes, comprising preparing materials containing silicon powder, an initiator, a catalyst and an alcohol, mixing them uniformly, sequentially carrying out a primary reaction, a secondary reaction and a tertiary reaction, and distilling to obtain alkoxysilanes; the catalyst is selected from at least one of the above-mentioned composite catalysts.

[0012] Furthermore, the purity of the silicon powder is 99% and the particle size is 200-400 mesh.

[0013] Furthermore, the initiator is selected from at least one of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane.

[0014] Furthermore, the alcohol is methanol or ethanol.

[0015] Furthermore, the mass of the catalyst accounts for 0.1% to 5% of the mass of the silicon powder.

[0016] Furthermore, the mass of the catalyst accounts for 1% to 3% of the mass of the silicon powder.

[0017] Furthermore, the mass of the catalyst accounts for 0.1%, 0.2%, 0.5%, 2%, 2.5%, 3%, 4%, 4.5%, 5% of the mass of the silicon powder, or any value between any two of the above points.

[0018] Furthermore, the mass ratio of the silicon powder to the alcohol is 1:(4.5~9.5).

[0019] Furthermore, the mass ratio of the silicon powder to the alcohol is 1:(4.5~7).

[0020] Furthermore, the mass ratio of the silicon powder to the alcohol is 1:4.5, 1:5, 1:5.5, 1:6, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or any value between any two of the above points.

[0021] Furthermore, the mass of the initiator accounts for 0.1% to 1% of the mass of the alcohol.

[0022] Furthermore, the mass of the initiator accounts for 0.5% to 0.8% of the mass of the alcohol.

[0023] Furthermore, the mass of the initiator accounts for 0.1%, 0.2%, 0.4%, 0.6%, 0.7%, 1% of the mass of the alcohol, or any value between any two of the above points.

[0024] Furthermore, the temperature of the primary reaction is 100-135° C., the pressure is 2-6 MPa, and the time is 2-20 h.

[0025] Furthermore, the temperature of the secondary reaction is 130-170° C., the pressure is 2-6 MPa, and the time is 2-20 h.

[0026] Furthermore, the temperature of the tertiary reaction is 165-200° C., the pressure is 2-6 MPa, and the time is 2-20 h.

[0027] Furthermore, the feed rates of the primary reaction, the secondary reaction and the tertiary reaction are independently 5 to 50 mL / min.

[0028] Furthermore, the primary reaction, the secondary reaction and the tertiary reaction all use a high-pressure reactor, and the high-pressure reactor is provided with a stirring paddle, and the stirring paddle is a combination of a frame-type stirring paddle and a propeller-blade stirring paddle.

[0029] Furthermore, the conversion rate of the silicon powder is greater than 99.5%, the selectivity of the alkoxysilane is greater than 99%, and the purity is greater than 99.99%.

[0030] The present invention has the following beneficial effects: The preparation method of the present invention does not introduce chlorine or produce strong acid, resulting in an environmentally friendly production process. The reaction continuously synthesizes alkoxysilane, making it suitable for industrial production. The final silicon powder conversion rate of the present invention can reach 99.5%, with product selectivity exceeding 99%. After distillation of the reaction solution, alkoxysilane with a purity exceeding 99.99% is obtained, showing promising application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 1 is a process flow chart of the reaction system of the present invention.

[0032] Figure 2 This is a schematic diagram of the stirring paddle structure of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] The reagents and drugs used in the following examples can all be obtained from the market. The mesh size of the copper powder is 200 mesh, the mesh size of the silicon powder is 200 mesh, and the purity is 99%.

[0035] The reaction system of the present invention is as follows Figure 1 As shown, it includes a first storage tank 1, a first reactor 2, a second reactor 3, a third reactor 4, a second storage tank 5, and a buffer tank 6 connected in sequence. A back pressure valve 7 is provided on the rear end pipeline of the buffer tank 6, and a discharge valve 8 is provided below the second storage tank 5; the reaction material enters from the top inlet of the first storage tank 1, is discharged from the top outlet of the first storage tank 1 after stirring, enters the top inlet of the first reactor 2, is discharged from the top outlet of the first reactor 2 after stirring reaction, enters the top inlet of the second reactor 3, is discharged from the top outlet of the second reactor 3 after stirring reaction, enters the top inlet of the third reactor 4, is discharged from the top outlet of the third reactor 4 after stirring reaction, enters the top inlet of the second storage tank 5, and after stirring, the reaction material is discharged from the bottom outlet of the second storage tank 5 through the discharge valve 8, enters the distillation tower after filtration, and the gas generated by the reaction passes through the buffer tank 6 and is discharged through the back pressure valve 7.

[0036] The first storage tank, the second storage tank, the first reactor, the second reactor and the third reactor involved in the embodiment of the present invention are all provided with stirring paddles, and the stirring paddles are matched with frame-type stirring paddles and propeller-type stirring paddles, and the structure is as follows: Figure 2 As shown, the stirring shaft of the stirring paddle is provided with two mutually perpendicular frame-type stirring blades, and propeller blades are symmetrically arranged inside the frame-type stirring blades with the stirring shaft as the center. The two stirring modes cooperate with each other to achieve the best mixing effect.

[0037] The effective volumes of the first reactor, the second reactor and the third reactor involved in the embodiment of the present invention are all 6L.

[0038] In the present invention, Silicon powder conversion rate = (initial silicon powder mass - remaining silicon powder mass) / initial silicon powder mass × 100%, Alkoxysilane selectivity = mass of alkoxysilane generated / (mass of alkoxysilane generated + mass of reaction impurities) × 100%, The purity of the alkoxysilane was measured using an Agilent 7820 chromatograph.

[0039] In the following examples, the conversion rate of silicon powder and the selectivity of the product were measured before distillation, and the purity of the product after distillation was greater than 99.99%. Example 1

[0040] 28 kg of silicon powder and 168 kg of methanol were weighed and mixed, followed by the addition of 0.84 kg of TMOS. A mixture of 0.14 kg of sodium hydroxide, 0.11 kg of sodium oxide, and 0.45 kg of copper powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 3 MPa. The nitrogen feed valve was opened and the feed flow rate was set to 18 mL / min (the residence time of the material in each reactor was 5.5 h). The feed reaction was initiated, and the temperatures of the first reactor, the second reactor, and the third reactor were set to 120°C, 140°C, and 165°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.5%, a product selectivity of 99.4%, and a product purity of 99.992%.

[0041] In this embodiment, the catalyst accounts for 2.5% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:1.02. Example 2

[0042] 28 kg of silicon powder and 210 kg of methanol were weighed and mixed, followed by the addition of 1.4 kg of TMOS. A mixture of 0.18 kg of sodium hydroxide, 0.14 kg of sodium oxide, and 0.29 kg of copper powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened and the nitrogen flow rate was set to 18 mL / min (the residence time of the material in each reactor was 5.5 h). The feed reaction was initiated, and the temperature of the first reactor was set to 135°C, the temperature of the second reactor to 155°C, and the temperature of the third reactor to 175°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.5%, a product selectivity of 99.2%, and a product purity of 99.992%.

[0043] In this embodiment, the catalyst accounts for 2.2% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:2. Example 3

[0044] 28 kg of silicon powder and 210 kg of methanol were weighed and mixed, followed by the addition of 1.4 kg of TMOS. A mixture of 0.17 kg of potassium hydroxide, 0.15 kg of potassium oxide, and 0.38 kg of copper powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened and the feed flow rate was set to 18 mL / min (the residence time of the material in each reactor was 5.5 h). The feed reaction was initiated, and the temperatures of the first reactor, the second reactor, and the third reactor were set to 135°C, 155°C, and 175°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.5%, a product selectivity of 99.4%, and a product purity of 99.993%.

[0045] In this embodiment, the catalyst accounts for 2.5% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:1. Example 4

[0046] 28 kg of silicon powder and 210 kg of methanol were weighed and mixed, followed by the addition of 1.4 kg of TMOS. A mixture of 0.19 kg of sodium oxide, 0.32 kg of sodium methoxide, and 0.38 kg of copper powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened and the feed flow rate was set to 25 mL / min (the residence time of the material in each reactor was 4 h). The feed reaction was initiated, and the temperatures of the first reactor, the second reactor, and the third reactor were set to 135°C, 155°C, and 175°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.5%, a product selectivity of 99.2%, and a product purity of 99.995%.

[0047] In this embodiment, the catalyst accounts for 3.2% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:0.5. Example 5

[0048] 28 kg of silicon powder and 210 kg of methanol were weighed and mixed, followed by the addition of 1.4 kg of TMOS. A mixture of 0.08 kg of sodium oxide, 0.13 kg of sodium methoxide, and 0.75 kg of copper powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened, and the material flow rate was set to 25 mL / min (the residence time of the material in each reactor was 4 h). The feed reaction was initiated, and the temperature of the first reactor was set to 135°C, the temperature of the second reactor to 155°C, and the temperature of the third reactor to 175°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.5%, a product selectivity of 99%, and a product purity of 99.992%.

[0049] In this embodiment, the catalyst accounts for 3.4% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:2. Example 6

[0050] 28 kg of silicon powder and 210 kg of methanol were weighed and mixed, followed by the addition of 1.4 kg of TMOS. A mixture of 0.54 kg of sodium methoxide, 0.31 kg of copper powder, and 0.4 kg of copper oxide powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened, and the material flow rate was set to 25 mL / min (the residence time of the material in each reactor was 4 h). The feed reaction was initiated, and the temperature of the first reactor was set to 135°C, the temperature of the second reactor to 155°C, and the temperature of the third reactor to 175°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.5%, a product selectivity of 99.2%, and a product purity of 99.992%.

[0051] In this embodiment, the catalyst accounts for 4.5% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:1. Example 7

[0052] 28 kg of silicon powder and 210 kg of methanol were weighed and mixed, followed by the addition of 1.4 kg of TMOS. A mixture of 0.56 kg of potassium methoxide and 0.31 kg of copper oxide powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened, and the material flow rate was set to 25 mL / min (the material residence time in each reactor was 4 h). The feed reaction was initiated, and the temperature of the first reactor was set to 135°C, the temperature of the second reactor to 155°C, and the temperature of the third reactor to 175°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.6%, a product selectivity of 99.0%, and a product purity of 99.995%.

[0053] In this embodiment, the catalyst accounts for 3.1% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:0.5. Example 8

[0054] 28 kg of silicon powder and 301 kg of ethanol were weighed, mixed, and 1.4 kg of TEOS was added. A mixture of 0.08 kg of sodium oxide, 0.13 kg of sodium methoxide, and 0.75 kg of copper powder was prepared and added to the mixture, which was then added to a storage tank with stirring. Stirring was started, and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks, and after nitrogen replacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened. The flow rate of the material was set to 25 mL / min (the residence time of the material in each reaction was 4 h). The feeding reaction was started, and the temperature of the first reactor was set to 135 ° C. The temperature of the second reactor was 170 ° C. The temperature of the third reactor was 180 ° C. After the reaction was completed, the reaction system was depressurized and the material was discharged. The material entered the distillation tower for distillation to recover excess ethanol and purify TEOS. The conversion rate of silicon powder in the final reaction material was detected to be 99.5%, the selectivity of the product was 99.0%, and the purity of the product was 99.992%.

[0055] In this embodiment, the catalyst accounts for 3.32% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:2. Example 9

[0056] 28 kg of silicon powder and 310 kg of methanol were weighed and mixed, followed by the addition of 1.4 kg of TMOS. A mixture of 0.56 kg of sodium ethoxide and 0.52 kg of copper powder was prepared and added to the mixture, which was then placed in a stirred tank. Agitation was initiated and the stirring speed was set to 15 Hz. The entire reaction system was pressure tested for leaks and, after nitrogen displacement, the pressure was set to 4 MPa. The nitrogen feed valve was opened, and the material flow rate was set to 25 mL / min (the material residence time in each reactor was 4 hours). The feed reaction was initiated, and the temperature of the first reactor was set to 135°C, the temperature of the second reactor to 155°C, and the temperature of the third reactor to 175°C. After the reaction was completed, the reaction system was depressurized and the material was discharged to a distillation tower for distillation to recover excess methanol and purify TMOS. The final reaction mass showed a silicon powder conversion of 99.6%, a product selectivity of 99.0%, and a product purity of 99.995%.

[0057] In this embodiment, the catalyst accounts for 3.85% of the mass of the silicon powder; the atomic ratio of the alkali metal and copper atoms is 1:1.

[0058] While particular aspects of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications may be made without departing from the spirit and scope of the invention. It is therefore intended that the appended claims cover all such changes and modifications as fall within the scope of the invention.

Claims

1. A composite catalyst, characterized in that: The composite catalyst comprises the following components: (1) Alkali metal compounds; (2) Copper and / or metallic copper compounds.

2. The composite catalyst according to claim 1, characterized in that The distribution ratio of each component is calculated based on metal atoms, and the atomic ratio of alkali metal to copper is 1:(0.1-5), preferably 1:(0.5-2).

3. The composite catalyst according to claim 1 or 2, characterized in that The alkali metal compound is selected from at least one of alkali metal oxides, alkoxides, and hydroxides; and the metallic copper compound is selected from at least one of copper salts and copper oxides.

4. A method for preparing the composite catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises mixing and stirring the components to obtain the composite catalyst.

5. A method for continuously synthesizing alkoxysilane, characterized in that: Prepare materials containing silicon powder, initiator, catalyst and alcohol, mix them evenly, carry out primary reaction, secondary reaction and tertiary reaction in sequence, and distill to obtain alkoxysilane; The catalyst is selected from at least one of the composite catalysts according to any one of claims 1 to 3.

6. The method according to claim 5, characterized in that The purity of the silicon powder is 99% and the particle size is 200-400 mesh; And / or, the initiator is selected from at least one of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane; And / or, the alcohol is methanol or ethanol.

7. The method according to claim 5 or 6, characterized in that The mass of the catalyst accounts for 0.1% to 5% of the mass of the silicon powder, preferably 1% to 3%; And / or, the mass ratio of the silicon powder to the alcohol is 1:(4.5-9.5), preferably 1:(4.5-7); And / or, the mass of the initiator accounts for 0.1% to 1% of the mass of the alcohol, preferably 0.5% to 0.8%.

8. The method according to any one of claims 5 to 7, characterized in that The temperature of the first-stage reaction is 100-135°C, the pressure is 2-6 MPa, and the time is 2-20 hours; And / or, the temperature of the secondary reaction is 130-170° C., the pressure is 2-6 MPa, and the time is 2-20 h; And / or, the temperature of the tertiary reaction is 165-200° C., the pressure is 2-6 MPa, and the time is 2-20 h; And / or, the feed rates of the primary reaction, the secondary reaction and the tertiary reaction are independently 5 to 50 mL / min.

9. The method according to any one of claims 5 to 8, characterized in that The primary reaction, the secondary reaction and the tertiary reaction all adopt a high-pressure reactor, and the high-pressure reactor is provided with a stirring paddle, and the stirring paddle adopts a combination of a frame-type stirring paddle and a propeller-blade-type stirring paddle.

10. The method according to any one of claims 5 to 9, characterized in that The conversion rate of the silicon powder is greater than 99.5%, the selectivity of the alkoxysilane is greater than 99%, and the purity is greater than 99.99%.

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