KR19990085368A - Method for producing tetraalkoxysilane - Google Patents

Abstract

The present invention relates to a method for producing tetraalkoxysilane, and more particularly, to a method of producing tetraalkoxysilane by reacting a lower alcohol with silicon, wherein a halide of copper or copper is used as a main catalyst, and cadmium or cadmium In the organic solvent is impregnated with a catalyst and a silicon (Silicone) by mixing one or more components selected from the group consisting of halides and halides of zinc or zinc in the main catalyst to prepare a silicon on which the catalyst is deposited, The present invention relates to a method for preparing a tetraalkoxysilane by activating it under a nitrogen atmosphere to produce a highly active contact material, and then supplying the contact material to a fluidized bed reactor to react with a lower alcohol. The method for producing a tetraalkoxysilane according to the present invention can greatly reduce the obstacles of the prior art, and ultimately increase the yield of the tetraalkoxysilane as a target compound.

Description

Method for producing tetraalkoxysilane

The present invention relates to a method for producing tetraraalkoxysilane of the present invention, and more particularly, a process called direct synthesis (Synthesis of Rochow) or a method of preparing organochlorinated silane. The present invention relates to a method for preparing a desired tetraalkoxysilane compound by reacting silicon with lower alcohol in the presence of a mixed catalyst of copper and other metal compounds.

In general, alkoxysilanes, especially tetraalkoxysilanes, are not only directly used in semiconductor wafer insulating films, semiconductor abrasives, etc., but also as raw materials for fumed silica, which is an essential additive in the production of silicone rubber for room temperature curing. It is widely used throughout.

Currently, the most widely used method for the production of alkoxysilanes is a method of preparing by reacting an alcohol with a silicon tetrachloride (SiCl ₄ ) represented by Scheme 1 below.

SiCl ₄ + 4 ROH ----- → Si (OR) ₄ + 4 HCl

However, the method requires a device of a special material to prevent corrosion in the production of hydrogen chloride by-produced, there is a disadvantage that a large cost is required for its removal and disposal.

In order to overcome this problem, a method as in Scheme 2 below has been proposed in which a tetraalkoxysilane is obtained by reacting a metal silicon powder with a lower alcohol using a copper catalyst.

Si + 4 ROH --- ^Cu- → Si (OR) ₄ + 2 H ₂

However, in the above Scheme 2, not only tetraalkoxysilane as a target compound but also trialkoxysilane (HSi (OR) ₃ ) and other silicone derivatives are produced together, and a disilane compound having a high molecular weight and a high boiling point. There is also a drawback that is generated. Therefore, the products obtained by the reaction can be obtained after the separation and purification process to obtain a high-purity final product for each component. Ultimately, in obtaining the tetraalkoxysilane which is the desired product, it is very important to set the reaction conditions so that the silane compound is generated as much as possible while reducing the trialkoxysilane having the highest amount of production in the above by-products.

In order to increase the production efficiency of tetraalkoxysilanes, a method of adding various additives in addition to copper or using other types of catalysts has already been disclosed. For example, a mixture of a copper catalyst and a special type of solvent is used to react in a liquid phase (US Pat. Nos. 4,289,889 and 4,762,939), or an alkali metal carbonate is used as a high pressure reaction catalyst (US Pat. No. 4,447,632) or A method of reacting in a liquid phase using an alkali metal or an alkali metal alkoxide as a catalyst and using a special type of solvent (US Pat. Nos. 4,211,717, 4,288,604, 4,752,647 and Japanese Patent Laid-Open No. 1-135788) and the like have been disclosed. .

The patents claim that by applying the above methods, the yield of tetraalkoxysilane synthesis by the direct synthesis method and the purity of the target compound can be improved. However, these methods are usually reactions in a liquid phase using a solvent. Therefore, in order to manufacture alkoxysilanes in a large capacity from an industrial point of view, a continuous production method is preferable, but these methods generally use a large amount of solvents, and thus they are usually operated in a batch reactor, thereby limiting the production of large capacity. In addition, the processes have at least one of the following problems.

First, the productivity of the reaction decreases due to the use of a large amount of solvent, and the solvent must be removed during or after the reaction. Second, the average weight ratio of the produced trialkoxysilane and tetraalkoxysilane (hereinafter referred to as Tr / Te) and the entire silane compound obtained The selectivity of the tetraalkoxysilane, which is evaluated by the molarity of the tetraalkoxysilane, is insufficient, and thirdly, it proceeds under high pressure to require a high pressure reaction vessel, and finally, many by-products, especially high boiling point silane compounds are produced.

In order to solve the above problems, the present inventors have conducted a series of studies. 1) The average selectivity for tetraalkoxysilane and the initial selectivity increased at the beginning of the reaction are maintained to the maximum until the catalyst system is finally deactivated. 2) Ultimately, the yield of tetraalkoxysilane should be maximized by increasing the conversion rate of silicon as a raw material, and 3) high active materials as raw material silicon and catalysts are prepared beforehand and continuously supplied to a fluidized bed reactor for fluidization. In order to prevent the separation of silicon and catalyst and the loss of the catalyst in the process, it was necessary to develop a process capable of continuous manufacturing to increase the reaction rate of alkoxysilane and selectivity to tetraalkoxysilane.

In order to satisfy these requirements, the present inventors have conducted extensive research and found that the type and amount of additives constituting the catalyst system are the key factors that influence the selectivity and yield of the tetraalkoxysilane. Based on this, a series of studies have been carried out to use a catalyst system in which one or more catalysts selected from the group consisting of zinc (or halides of zinc) and cadmium (or halides of cadmium) are already mixed with the proposed copper catalyst system. Thus, it was found that the selectivity and yield of tetraalkoxysilanes were increased, and the present invention was completed based on this.

Accordingly, an object of the present invention is to provide a method for producing tetraalkoxysilane using a catalyst system which does not cause the above problems or can be minimized.

The method of the present invention for achieving the above object is a method of producing tetraalkoxysilane by reacting a lower alcohol to silicon, the main catalyst is a halide of copper or copper, halides of cadmium or cadmium and zinc or zinc After impregnating an organic solvent with a catalyst component and silicon mixed with one or more components selected from the group consisting of halides in the main catalyst, the organic solvent is removed to prepare silicon having the catalyst component deposited thereon, and nitrogen atmosphere It is activated under the following conditions to prepare a highly active contact material, which is then fed to a fluidized bed reactor to react with lower alcohol.

Looking at the present invention in more detail as follows.

As described above, in the method for producing tetraalkoxysilane by reacting lower alcohol with silicon, the type and amount of additives constituting the catalyst system are key factors that influence the selectivity and yield of the tetraalkoxysilane. Accordingly, in the present invention, a catalyst system in which one or more catalysts selected from the group consisting of zinc (or halides of zinc) and cadmium (or halides of cadmium) is mixed with the copper catalyst system already proposed.

In other words, in the method for producing tetraalkoxysilane according to the present invention, in the production of tetraalkoxysilane by reacting lower alcohol with silicon, the composition of the catalyst used is mainly copper or halide of copper, and cadmium or cadmium One or more components selected from the group consisting of halides of halides and halides of zinc or zinc were prepared in the main catalyst to prepare tetraalkoxysilanes.

According to the present invention, a catalyst-based material comprising copper or a copper halide as a main catalyst and one or more components selected from the group consisting of cadmium or cadmium halides and zinc or zinc halides mixed in the main catalyst Is added to silicon as a raw material, and mixed in an organic solvent selected from the group consisting of methanol, ethanol, propanol, butanol, normal nucleic acid, acetone, and ether, and then mixed well, and a predetermined temperature and pressure (for example, 80 to 100 ° C. and 10 torr) to remove the organic solvent. By removing the organic solvent, it is possible to obtain silicon in which copper and additives are uniformly deposited. The reason for using the organic solvent is to uniformly mix the metal or metal chloride components, which are components of the catalyst system, and the raw material, silicon.

In the case of copper or copper halides, the content of pure copper in copper or copper halides is preferably 1 to 20 parts by weight based on 100 parts by weight of silicon content. At this time, when the content of the pure copper is less than 1 part by weight, the reaction rate is significantly lowered. When it exceeds 20 parts by weight, the effect of increasing the reaction rate is slowed while the amount of waste copper to be treated after the reaction is increased. In the case of cadmium or a halide of cadmium, the content of pure cadmium is preferably about 0.001 to 2.0 parts by weight based on 100 parts by weight of pure copper. At this time, when the content of the pure cadmium is less than 0.001 parts by weight, the effect of the addition of cadmium, that is, the effect of maintaining high selectivity to the target compound for a long time is hardly seen, and when it exceeds 2.0 parts by weight, the side reaction is promoted to increase the boiling point D. Silane compounds are produced. In the case of zinc or a halide of zinc, the content of pure zinc is preferably about 0.1 to 20 parts by weight relative to 100 parts by weight of pure copper. At this time, when the content of the pure zinc is less than 0.1 parts by weight, there is almost no effect of adding zinc, that is, suppressing the production of trialkoxysilane, and when the content is more than 20 parts by weight, a reverse action of increasing the amount of trialkoxysilane appears. .

Silicon in which the copper and the additives are uniformly deposited is placed in a fluidized bed reactor, and the raw material is dried while flowing nitrogen at 210 to 240 ° C. Then, by raising the temperature and reacting the catalyst with silicon at 300 to 320 ° C., the silicon tetrahalide is released to obtain a “contact material” in which the metal catalyst is chemically deposited on the silicon particles, and the contact material is cooled to room temperature. Stored under nitrogen atmosphere.

The contact material thus prepared was placed in a reactor maintained at 370 to 390 ° C and reacted with a lower alcohol vaporized in a vaporizer at 160 to 300 ° C to prepare tetraalkoxysilane. The lower alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol and tertiary butanol. Reactor types that can be used in the present invention are suitable agitated reactors, comparative semi-fluid bed reactors, fixed bed reactors or agitated fluid bed reactors. In addition, when preparing the tetraalkoxy silane, the reaction rate is greatly reduced if the reactor temperature is less than 160 ℃, a problem that a large number of side reactions proceed if the temperature exceeds 300 ℃. The reactor temperature is preferably 180 to 260 ° C.

In addition, the activated contact material can be continuously supplied to the fluidized bed reactor as well as batchwise to produce alkoxysilanes continuously. By continuously supplying the activated contact material to the fluidized bed reactor, it was confirmed that the reaction rate was also increased by maintaining the concentration of the raw materials and the catalysts constant due to the loss of the catalyst in the fluidized bed. When the fluidized bed reactor is continuously operated in this way, it is possible to keep the rate of tetraalkoxysilane produced by intermittently removing the residue of the reactant used in the reaction, which is generated for a long time, almost for a long time, resulting in high productivity. Will have

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Example 1

40 g of silicon, 4.36 g of cuprous chloride (the net content of copper is 7 parts by weight based on 100 parts by weight of silicon), 0.29 g of zinc chloride (5 parts by weight of 100 parts by weight of copper) are added to 50 ml of acetone and mixed well. , Acetone was removed by drying under the condition of 90 ° C./10 torr to obtain silicon in which copper and additives were uniformly deposited. The silicon was placed in a tubular fluidized bed reactor having an inner diameter of 3.5 cm and a length of 60 cm provided with a double spiral stirring blade, and dried at 230 ° C. under nitrogen flow. When tetrachloride is reacted with silicon at 310 ° C, silane tetrachloride is produced. Upon completion of the reaction, the catalyst was heated to 380 ° C. to activate the catalyst for 3 hours, methanol was slowly injected into the bottom of the reactor, and evaporated to react at 200 ° C. The injection flow rate of methanol was 9.0 g per hour and the total reaction time was 20 hours. The purity (gas chromatography) of the tetramethoxysilane in the silane obtained at this time was 99.7% at the moment, average 94.7%, and the production ratio (Tr / Te) of trimethoxysilane and tetramethoxysilane was 0.035. In addition, the conversion of silicon was about 92% based on the amount of silicon remaining, and the yield of tetramethoxysilane was 86.2%.

Example 2

In the method described in Example 1, 40 g of silicon, 6.23 g of cuprous chloride (the net content of copper is 10 parts by weight based on silicon), 0.834 g of zinc chloride (10 parts by weight of copper) and 0.040 g of cadmium chloride (copper 0.6 parts by weight) was added to 50 ml of normal nucleic acid and mixed well, followed by drying under the condition of 90 ° C / 10 torr to remove normal nucleic acid to obtain silicon in which copper and additives were uniformly deposited. The catalyst was prepared and activated in the same manner using the same reactor as described in Example 1 and then activated. Ethanol was slowly injected into the bottom of the reactor and evaporated to react at 240 ° C. The injection flow rate of ethanol was 9.0 g per hour, and the total reaction time was 18 hours. The purity (gas chromatography) in the obtained silane was 87.0% of tetraethoxysilane, 1.4% of triethoxysilane, and 11.7% of unreacted ethanol, and the production ratio of triethoxysilane and tetraethoxysilane (Tr / Te ) Was 0.016. In addition, the conversion of silicon was about 87% based on the amount of silicon remaining, and the yield of tetramethoxysilane was 81.6%.

Example 3

Metallic silicon powder (average particle size 200㎛) 280g, cuprous chloride 30.5g (copper content is 7 parts by weight of silicon), zinc chloride 2.03g (5 parts by weight of copper), cadmium chloride 0.28g (copper 0.6 parts by weight) was added to 200 ml of methanol, mixed well, and dried under conditions of 90 ° C / 10 torr to remove methanol. Methanol was volatilized to obtain silicon in which copper and additives were uniformly deposited. When the silicon is placed in a fluidized bed reactor, nitrogen is flowed, and the temperature is increased to react copper chloride and silicon at 310 ° C. to release silane tetrachloride, thereby obtaining a “contact material” in which a metal catalyst is chemically deposited on silicon particles.

The contact was heated to 380 ° C. for at least 3 hours to obtain an “activated contact” which was cooled to room temperature and stored under nitrogen atmosphere until the reaction was complete. 60 g of the contact material was put in a tubular fluidized bed reactor having an inner diameter of 3.5 cm and a length of 60 cm, and methanol was slowly injected at an amount of 9.0 g per hour into a preheater installed at the bottom of the reactor and evaporated at 180 ° C. to be fed to the bottom of the fluidized bed reactor. When 15 g of contact material was added every 5 hours and the reaction was continued for a total of 72 hours, 1,095 g of methoxysilane, a product, was continuously obtained.

The methoxysilane obtained at this time was analyzed by gas chromatography, and the results were tetramethoxysilane 94.1%, trimethoxysilane 3.0%, methyltrimethoxysilane 0.1%, and high boiling point disilanes 2,8%. Accordingly, the production ratio (Tr / Te) of trimethoxysilane and tetramethoxysilane was 0.032, and the silicon consumption was about 86.2%.

Comparative Example 1

U.S. Patent 4,762,939

In a 100 ml four-necked flask equipped with a mechanical stirrer and a multi-stage distillation machine, 50 g of silicon, 202 g of mixed solvent (101 g of Therminol and Kemamine), and 5 g of cuprous chloride were added to each other, followed by heating.

The temperature of the reactor was heated to 226 ° C. while flowing nitrogen, and the product was distilled through a distillator while methanol was injected into the metering pump. The purity of the tetramethoxysilane in the silane obtained at this time was up to 87.9% at an instant and an average purity of 44.1%, and the rest were trimethoxysilane, unreacted methanol, a reaction solvent and a high boiling point silane compound.

The production ratio (Tr / Te) of trimethoxysilane and tetramethoxysilane ranged from 0.001 to 2.10, depending on the type and amount of reaction solvent used. The conversion of silicon ranged from 81.3% to 39.7%, depending on the type of reaction solvent, the amount used and the amount of silicon injected.

The purity of the tetramethoxysilane prepared according to Examples 1 to 3 and Comparative Example 1, the production ratio (Tr / Te) and silicon consumption of trimethoxysilane and tetramethoxysilane are shown in Table 1 below.

Item Tetramethoxysilane purity Tr / Te Silicon consumption rate Moment best Average Moment Average Example 1 99.7% 94.7% 0.01 0.035 92.0% Example 2 - 87.0% - 0.016 87.0% Example 3 - 94.1% - 0.032 86.2% Comparative Example 1 87.9% 44.1% 0.001 to 2.10 0.19 Maximum: 81.3% Minimum: 39.7%

Tr / Te: Lower value means smaller amount of by-products of trialkoxysilane.

As can be seen from Table 1, the present invention can greatly reduce the obstacles of the prior art in the production of tetraalkoxysilane and ultimately increase the yield of the tetraalkoxysilane of the target compound. Therefore, it is possible to apply to more economical and competitive tetraalkoxysilane production technology.

Claims (9)

In the method for producing tetraalkoxysilane by reacting silicon with lower alcohol, one or more selected from the group consisting of halides of cadmium or cadmium and halides of zinc or zinc as a main catalyst, After impregnating the catalyst component and silicon mixed with the above components in the main catalyst in an organic solvent, the organic solvent is removed to prepare a silicon in which the catalyst component is deposited, and activated in a nitrogen atmosphere to prepare a highly active contact material. Next, the method for producing a tetraalkoxysilane, characterized in that for supplying the contact material to the reactor to react with lower alcohol at 160 ~ 300 ℃. The method of claim 1, wherein the reactor is a stirred or non-fluidized fluidized bed reactor, a fixed bed reactor or a batch reactor. The method for producing tetraalkoxysilane according to claim 1, wherein the reaction proceeds batchwise or continuously. The method of claim 1, wherein the reaction temperature is 180 to 260 ° C. The method of claim 1, wherein the organic solvent is one selected from the group consisting of methanol, ethanol, propanol, butanol, normal nucleic acid, acetone and ether. The method of claim 1, wherein the lower alcohol is one selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol and tertiary butanol. The method for producing tetraalkoxysilane according to claim 1, wherein the content of pure copper contained in the copper or a halide of copper is 1.0 to 20.0 parts by weight based on 100 parts by weight of silicon. The method of claim 1, wherein the content of pure cadmium in the cadmium or cadmium halide is 0.001 to 2.0 parts by weight based on 100 parts by weight of pure copper. The method of claim 1, wherein the content of pure zinc contained in the zinc or the halide of zinc is 0.1 to 20.0 parts by weight based on 100 parts by weight of pure copper.