Process for preparing methyl silicate by silicon powder method

Abstract

The invention provides a process for preparing methyl silicate by a silicon powder method, and belongs to the technical field of organic synthesis. The process comprises the following steps: firstly, adding copper abietate into silicon powder under the action of protective gas flow, activating by adopting plasma, and reacting for 20-30 minutes to obtain a silicon powder-copper abietate mixture; and adding a substrate methyl silicate into the obtained silicon powder-copper abietate mixture, stirring, heating to 90-120 DEG C, dropwise adding methanol, continuously reacting for 20-30 minutes after adding, and distilling to obtain the methyl silicate. The process is short in reaction time and low in reaction temperature, the reaction rate of methanol and silicon can be effectively increased, and the utilization rate of copper is increased.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a process for preparing methyl silicate by a silicon powder method. Background Art

[0002] At present, the main methods for industrial mass production of methyl silicate are the silicon tetrachloride method and the silicon powder method. The silicon tetrachloride method is a classic method for preparing tetramethyl silicate, in which silicon tetrachloride and methanol react at room temperature and pressure to generate tetramethyl silicate and a large amount of hydrochloric acid gas. However, this method has the disadvantages of high process raw material consumption, long production cycle, low yield, unstable product quality, and large environmental pollution caused by the HCl gas generated by the reaction. The silicon powder method uses silicon powder as raw material, adds catalytic materials to react with methanol gas, and is more environmentally friendly and cleaner than the silicon tetrachloride method to prepare methyl silicate, and is gradually favored by people. However, due to the common reason that the catalytic material activity is not high in the process of preparing methyl silicate by the silicon powder method, the reaction conversion rate is not high, the reaction rate is slow, and other problems, which restrict the development of efficient and green production technology of methyl silicate.

[0003] The main reactions of the silicon tetrachloride method are as follows:

[0004] SiCl4+CH3OH=Cl3Si-OCH3+HCl (1)

[0005] Cl3Si-OCH3+CH3OH=Cl2Si-(OCH3)2+HCl (2)

[0006] Cl2Si-(OCH3)2+CH3OH=ClSi-(OCH3)3+HCl (3)

[0007] Cl2Si-(OCH3)3+CH3OH=Si-(OCH3)4+HCl (4)

[0008] The overall reaction is:

[0009] SiCl4+4CH3OH=Si-(OCH3)4+4HCl (5)

[0010] The main reactions of the silicon powder method are as follows:

[0011]

[0012] It can be seen from the reaction that the silicon tetrachloride method will produce a large amount of HCl. During the reaction, a large amount of HCl will inhibit the forward reaction in step (4) and will also aggravate the occurrence of side reactions. In addition, studies have found that excess methanol in the reaction system will react with the by-product HCl to generate CH3OCl and water. The water generated by this side reaction will cause methyl silicate to hydrolyze to generate methyl silicate polymers, which is also the main reason affecting the yield of methyl silicate. Therefore, during this method, the HCl generated by the reaction needs to be discharged from the system in a timely manner to inhibit the occurrence of side reactions. In addition, due to the corrosiveness of HCl to the reaction materials, the anti-corrosion cost of the reaction materials is also increased, and the requirements for the reaction materials and processes are more stringent than the direct method.

[0013] Therefore, the silicon powder method is an important method for enterprises to produce methyl silicate and upgrade their industry in the future. However, the existing silicon powder method for preparing methyl silicate involves a catalyst and silicon powder pretreatment process, where the catalyst and silicon powder are pretreated before reacting with methanol. This pretreatment process is often a macroscopic mixing, resulting in a very limited contact area, low gas-solid catalytic reaction efficiency, high catalyst consumption, and high cost, so it cannot be applied on a large scale.

[0014] Chinese patent CN117186137A discloses a method for preparing tetramethyl silicate, wherein silicon powder, methanol and alkali metal carbonate are added to a reactor, reacted for 160 min to 200 min at a temperature of 150 to 190°C and a pressure of 2 MPa to 3 MPa, and tetramethyl silicate is obtained by separation and purification after the reaction. Although this method improves the yield of tetramethyl silicate, the reaction must be carried out under high temperature and high pressure conditions, and the reaction time is too long. Summary of the invention

[0015] The invention provides a process for preparing methyl silicate by a silicon powder method, the process has a short reaction time and can be carried out at normal pressure and relatively low temperature. The process uses copper rosinate as a catalyst and adopts low-temperature plasma PECVD technology to activate silicon powder and form atomic-level distribution of copper elements on the surface of silicon powder, thereby effectively increasing the reaction rate of methanol and silicon and improving the utilization rate of copper.

[0016] The technical solution of the present invention is as follows:

[0017] The present invention provides a process for preparing methyl silicate by a silicon powder method, comprising the following steps:

[0018] (1) adding copper rosinate to silicon powder under the action of protective gas flow, using plasma activation, and reacting for 20-30 minutes to obtain a silicon powder-copper rosinate mixture;

[0019] (2) Adding substrate methyl silicate to the silicon powder-copper rosinate mixture obtained in step (1), stirring, heating to 90-120° C., then dropping methanol, continuing the reaction for 20-30 minutes after the addition, and distilling to obtain methyl silicate.

[0020] In one specific embodiment, the protective gas in step (1) is nitrogen.

[0021] In one specific embodiment, in step (1), the rate of adding copper rosinate is 10 to 30 g / min.

[0022] In a specific embodiment, in step (1), the plasma activation is low temperature plasma enhanced chemical vapor deposition activation.

[0023] In a specific embodiment, the mass ratio of silicon powder, copper rosinate and methanol is 10:1-3:50-70.

[0024] In one specific embodiment, in step (2), the rate of methanol dripping is 2 to 3 g / min.

[0025] In one specific embodiment, in step (2), the mass ratio of the substrate methyl silicate to the silica powder-copper rosinate mixture is 2 to 5:1.

[0026] In one embodiment, in step (2), the distillation temperature is 110-140°C.

[0027] In one embodiment, step (2) is performed in a reflux device.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention adopts copper rosinate as a copper source and adopts low-temperature plasma PECVD technology to activate silicon powder and form atomic-level distribution of copper elements on the surface of silicon powder, thereby effectively increasing the reaction rate of methanol and silicon and improving the utilization rate of copper. DETAILED DESCRIPTION

[0030] The present invention provides a process for preparing methyl silicate by a silicon powder method, comprising the following steps:

[0031] (1) adding copper rosinate to silicon powder under the action of protective gas flow, using plasma activation, and reacting for 20-30 minutes to obtain a silicon powder-copper rosinate mixture;

[0032] (2) Adding substrate methyl silicate to the silicon powder-copper rosinate mixture obtained in step (1), stirring, heating to 90-120° C., then dropping methanol, continuing the reaction for 20-30 minutes after the addition, and distilling to obtain methyl silicate.

[0033] The process for preparing methyl silicate by silicon powder method of the present invention uses copper rosinate as a catalyst and adopts low-temperature plasma PECVD technology to activate silicon powder and form atomic-level distribution of copper element on the surface of silicon powder, thereby effectively increasing the reaction rate of methanol and silicon and improving the utilization rate of copper. Moreover, the process has a short reaction time and can be carried out at normal pressure and relatively low temperature.

[0034] In the present invention, the catalyst is solid, and direct dropwise addition of methanol will result in uneven solid-liquid mixing. Therefore, the target product and the catalyst are first mixed to form a suspension, and when methanol is added dropwise, the catalyst is more thoroughly contacted and reacts faster, and no new substances are introduced in this process.

[0035] In one specific embodiment, the protective gas in step (1) is nitrogen.

[0036] In one specific embodiment, in step (1), the rate of adding copper rosinate is 10 to 30 g / min.

[0037] In a specific embodiment, in step (1), the plasma activation is low temperature plasma enhanced chemical vapor deposition activation.

[0038] Low-temperature plasma enhanced chemical vapor deposition activation is PECVD activation. A large amount of energy is released during the low-temperature plasma discharge process. The copper in copper rosinate is excited to produce copper ions or copper atoms, which are deposited on the surface of silicon powder, making the copper evenly distributed on the surface of silicon powder.

[0039] In a specific embodiment, the mass ratio of silicon powder, copper rosinate and methanol is 10:1-3:50-70.

[0040] In one specific embodiment, in step (2), the rate of methanol dripping is 2 to 3 g / min.

[0041] In one specific embodiment, in step (2), the mass ratio of the substrate methyl silicate to the silica powder-copper rosinate mixture is 2 to 5:1.

[0042] In one embodiment, in step (2), the distillation temperature is 110-140°C.

[0043] Distillation temperature refers to the temperature of the vapor at the top of the still.

[0044] Distillation is to collect the distillate in sections according to the distillation temperature. The boiling point of methyl silicate is 121-122°C, the boiling point of methanol is 64.7°C, and the boiling point of methyl silicate polymer is >200°C. The distillate with a boiling point of 121-122°C is a product with a higher purity. Of course, in order to further improve the purity of the product, multiple distillations or rectification can be used.

[0045] In one embodiment, step (2) is performed in a reflux device.

[0046] The present invention is further described below with specific examples, but the embodiments of the present invention are not limited thereto.

[0047] Example 1

[0048] 10g of dry silicon powder was added into the low-temperature plasma PECVD activation reactor, the activation reactor device was turned on, 2g of catalyst copper rosinate powder was weighed, and slowly released into the activation reactor under the action of nitrogen gas flow. The catalyst addition time was 5s. After the catalyst was released, the reaction was continued for 25min. After the mixed reactor was cooled, a silicon powder-copper rosinate mixture was obtained.

[0049] Add the silicon powder-copper rosinate mixture into a 250mL three-necked flask, add 35g of substrate methyl silicate, connect the reflux device, start stirring, wait until the solid powder fully forms a suspension, turn on the heating to 90°C, and slowly add 55g of methanol at a methanol drop rate of 2.5g / min for 22min. After the addition is completed, continue the reaction for 25min, and then distill (the top temperature of the distillation kettle is 120°C, and stop after the top temperature exceeds 120°C. At this time, the bottom temperature of the kettle is 175°C.) to obtain 87.1g of methyl silicate product, and after suction filtration and drying at the bottom of the kettle, 2.43g of solid residue is obtained, of which 0.43g of unreacted silicon powder remains.

[0050] Example 2

[0051] 10g of dry silicon powder was added into the low-temperature plasma PECVD activation reactor, the activation reactor device was turned on, 1g of catalyst copper rosinate powder was weighed, and slowly released into the activation reactor under the action of nitrogen gas flow. The catalyst addition time was 3s. After the catalyst was released, the reaction was continued for 25min. After the mixed reactor was cooled, a silicon powder-copper rosinate mixture was obtained.

[0052] Add the silicon powder-copper rosinate mixture into a 250mL three-necked flask, add 35g of substrate methyl silicate, connect the reflux device, start stirring, wait until the solid powder fully forms a suspension, turn on the heating to 90°C, and slowly add 55g of methanol at a methanol drop rate of 2.5g / min for 22min. After the addition is completed, continue the reaction for 25min, and then distill (the top temperature of the distillation kettle is 120°C, and stop after the top temperature exceeds 120°C. At this time, the bottom temperature of the kettle is 175°C) to obtain 86.2g of methyl silicate product. After filtering and drying the bottom of the kettle, 1.51g of solid residue is obtained, of which 0.51g of unreacted silicon powder remains.

[0053] Example 3

[0054] 10g of dry silicon powder was added into the low-temperature plasma PECVD activation reactor, the activation reactor device was turned on, 2g of catalyst copper rosinate powder was weighed, and slowly released into the activation reactor under the action of nitrogen gas flow. The catalyst addition time was 5s. After the catalyst was released, the reaction was continued for 25min. After the mixed reactor was cooled, a silicon powder-copper rosinate mixture was obtained.

[0055] Add the silicon powder-copper rosinate mixture into a 250mL three-necked flask, add 35g of substrate methyl silicate, connect the reflux device, start stirring, wait until the solid powder fully forms a suspension, turn on the heating to 100°C, and slowly add 55g of methanol at a methanol drop rate of 2.5g / min for 22min. After the addition is completed, continue the reaction for 25min, and then distill (the top temperature of the distillation kettle is 120°C, and stop after the top temperature exceeds 120°C. At this time, the bottom temperature of the kettle is 175°C) to obtain 87.3g of methyl silicate product. After filtration and drying at the bottom of the kettle, 2.41g of solid residue is obtained, of which 0.41g of unreacted silicon powder remains.

[0056] Comparative Example 1

[0057] 10g of dry silicon powder was added into the low-temperature plasma PECVD activation reactor, the activation reactor device was turned on, 2g of catalyst copper and copper oxide (Cu-CuO-Cu2O, the mass ratio of the three was 1:1.25:2.25) powder were weighed, and slowly released into the activation reactor under the action of nitrogen flow. The catalyst addition time was 5s. After the catalyst was released, the reaction was continued for 25min. After the mixed reactor was cooled, a silicon powder-copper mixture was obtained.

[0058] Add the silicon powder-copper mixture into a 250mL three-necked flask, add 35g of substrate methyl silicate, connect the reflux device, start stirring, wait until the solid powder fully forms a suspension, turn on the heating to 90°C, and slowly add 55g of methanol at a methanol drop rate of 2.5g / min for 22min. After the addition is completed, continue the reaction for 25min, and then distill (the top temperature of the distillation kettle is 120°C, and stop after the top temperature exceeds 120°C. At this time, the bottom temperature of the kettle is 175°C) to obtain 82.5g of methyl silicate product. After filtration and drying at the bottom of the kettle, 3.21g of solid residue is obtained, of which 1.21g of unreacted silicon powder remains.

[0059] Comparative Example 2

[0060] Add 10g of dry silicon powder to a 250mL three-necked flask, add 2g of catalyst copper and copper oxide powder (Cu-CuO-Cu2O, the mass ratio of the three is 1:1.25:2.25), start stirring to mix the silicon powder and the catalyst for 10 minutes, then add 35g of substrate methyl silicate, connect the reflux device, start stirring, wait until the solid powder fully forms a suspension, start heating and raise the temperature to 90°C, start to slowly drop 55g of methanol, the methanol drop rate is 2.5g / min, and the time is 22min. After the dropwise addition is completed, continue to react for 25min, then distill (the top temperature of the distillation kettle is 120°C, and stop after the top temperature exceeds 120°C. At this time, the bottom temperature of the kettle is 175°C) to obtain 77.3g of methyl silicate product, and after suction filtration and drying at the bottom of the kettle, 4.04g of solid residue is obtained, of which 2.04g of unreacted silicon powder remains.

[0061]

[0062] Methyl silicate content: directly determined by gas chromatography.

[0063] Methyl silicate yield (w%): m0 is the amount of silicon powder added, g; m1 is the mass of methyl silicate obtained by the reaction, g; ω is the content of methyl silicate obtained by the reaction, %; M is the relative molecular mass of methyl silicate.

[0064] Silicon powder conversion rate (x%): m0 is the amount of silicon powder added, g; m2 is the amount of unreacted remaining silicon powder, g.

[0065] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A process for preparing methyl silicate by a silicon powder method, characterized in that: The steps include: (1) adding copper rosinate to silicon powder under the action of protective gas flow, using plasma activation, and reacting for 20 to 30 minutes to obtain a silicon powder-copper rosinate mixture; (2) Adding substrate methyl silicate to the silicon powder-copper rosinate mixture obtained in step (1), stirring, heating to 90-120° C., then dropping methanol, continuing the reaction for 20-30 minutes after the addition, and distilling to obtain methyl silicate.

2. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: In step (1), the protective gas is nitrogen.

3. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: In step (1), the rate of adding copper rosinate is 10 to 30 g / min.

4. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: In step (1), the plasma activation is low temperature plasma enhanced chemical vapor deposition activation.

5. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: The mass ratio of silicon powder, copper rosinate and methanol is 10:1-3:50-70.

6. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: In step (2), the rate of methanol dripping is 2 to 3 g / min.

7. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: In step (2), the mass ratio of the substrate methyl silicate to the silica powder-copper rosinate mixture is 2 to 5:

1.

8. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: In step (2), the distillation temperature is 110-140°C.

9. The process for preparing methyl silicate by the silicon powder method according to claim 1, characterized in that: Step (2) is carried out in a reflux device.

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