JP6934683B2 - Method for producing tetraalkoxysilane using calcium oxide - Google Patents

Description

The present invention relates to a highly efficient method for producing tetraalkoxysilane, and more particularly to a method for producing tetraalkoxysilane using calcium oxide.

Tetraalkoxysilane is used as a raw material for producing various silane compounds, organic silicone polymers, various silylating agents, colloidal silica, ceramics and the like.
As a conventionally known industrial production method of alkoxysilanes, for example, natural silicon dioxide is used as a starting material, mixed with carbon and reduced at a high temperature to obtain metallic silicon, which is used as chlorine. A method of reacting silicon tetrachloride obtained by reaction with alcohol as a raw material is known (see Patent Document 1). A production method in which metallic silicon and alcohol are directly reacted is also known (see Patent Document 2).
However, all of these methods need to go through a process of producing metallic silicon, which requires a high temperature, and have a problem of poor energy efficiency.
On the other hand, as a method for directly producing alkoxysilane from silica, a method for producing alkoxysilane by reacting silica with an alkyl carbonate using an alkali metal element or an alkaline earth metal element as a catalyst is known (Patent Document 3). 4). Since these methods do not use the above-mentioned metallic silicon as a raw material, they are advantageous in terms of energy efficiency, but at least twice the molar amount of alkyl carbonate, which is a relatively expensive compound, is added to silica as a stoichiometry. There is an economic problem as an industrial production method of tetraalkoxysilane.
The present inventors have found that tetramethoxysilane can be produced from methanol and silicon oxide as raw materials, react methanol and silicon oxide in the presence of carbon dioxide, and remove by-produced water using a molecular sieve. We have developed a method for obtaining tetramethoxysilane in high yield (see Patent Document 5).

Japanese Unexamined Patent Publication No. 62-114991 U.S. Pat. No. 2,473,260 Japanese Unexamined Patent Publication No. 2001-114786 Japanese Patent No. 3026371 JP-A-2017-88498

An object of the present invention is to provide a method capable of producing tetraalkoxysilane in an energy-saving manner and in a high yield.

As a result of diligent studies to solve the above problems, the present inventors have obtained tetraalkoxysilane by reacting alcohol with silicon oxide to produce tetraalkoxysilane in the presence of calcium oxide. The present invention has been completed by finding that it can be produced in a high yield.

That is, the present invention is as follows.
<1> A method for producing tetraalkoxysilane, which comprises a reaction step of reacting alcohol with silicon oxide to produce tetraalkoxysilane.
A method for producing tetraalkoxysilane, wherein the reaction step is carried out in the presence of calcium oxide.
<2> The method for producing tetraalkoxysilane according to <1>, wherein the reaction step is further carried out in the presence of an alkali metal compound and / or an alkaline earth metal compound other than calcium oxide.
<3> The amount of calcium oxide used in the reaction step is an amount such that the amount of substance of calcium atom of calcium oxide / the amount of substance of silicon atom of silicon oxide is 1 to 50, according to <1> or <2>. Method for producing tetraalkoxysilane.

According to the present invention, tetraalkoxysilane can be produced in high yield.

It is a conceptual diagram of an example of the apparatus which can be used in the manufacturing method of the tetraalkoxysilane of this invention. It is a conceptual diagram of an example of the apparatus which can be used in the manufacturing method of the tetraalkoxysilane of this invention. It is a conceptual diagram of an example of the apparatus which can be used in the manufacturing method of the tetraalkoxysilane of this invention.

In explaining the present invention, specific examples will be given, but the contents are not limited to the following as long as the gist of the present invention is not deviated, and the present invention can be appropriately modified.

<Manufacturing method of tetraalkoxysilane>
The method for producing tetraalkoxysilane (hereinafter, may be abbreviated as "the production method of the present invention"), which is one aspect of the present invention, is a reaction step (hereinafter, referred to as "method for producing tetraalkoxysilane") in which alcohol and silicon oxide are reacted to produce tetraalkoxysilane. , It may be abbreviated as "reaction step"), and is characterized in that the reaction step is carried out in the presence of calcium oxide.
The present inventors have found that tetraalkoxysilane can be produced in high yield by carrying out a reaction of reacting alcohol with silicon oxide to produce tetraalkoxysilane in the presence of calcium oxide. ..
Calcium oxide is considered to play a role as a dehydrating agent that removes water produced by the reaction of alcohol and silicon oxide, and the reverse reaction is suppressed by removing water, so that tetraalkoxysilane is highly yielded. It is considered that it can be manufactured at a rate. In addition, the calcium oxide used in the reaction reacts with water and changes to calcium hydroxide, but since calcium hydroxide can be easily regenerated into calcium oxide, it can be reused and is industrial. It can be said that it is very suitable for.
Hereinafter, the conditions of "alcohol", "silicon oxide", "reaction step" and the like will be described in detail.

The type of alcohol used in the reaction step is not particularly limited, and can be appropriately selected depending on the tetraalkoxysilane intended for production. For example, if methanol is used as the alcohol, tetramethoxysilane can be produced, and if ethanol is used, tetraethoxysilane can be produced.
The alcohol may be either an aliphatic alcohol or an aromatic alcohol, and the hydrocarbon group in the alcohol may have a branched structure, a cyclic structure, a carbon-carbon unsaturated bond, or the like.
The number of carbon atoms of the alcohol is usually 1 or more, preferably 2 or more, preferably 15 or less, more preferably 10 or less, still more preferably 8 or less, and the number of carbon atoms in the case of an aromatic alcohol is usually 6. That is all.
Specific alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, benzyl alcohol, phenol and the like. Be done.
The amount of alcohol used is usually 1 time or more, preferably 5 times or more, more preferably 10 times or more, usually 10000 times or less, preferably 5000 times or less, more preferably with respect to the amount of substance of silicon oxide. Is less than 3000 times.

Silicon oxide used in the reaction step means a compound containing a silicon atom (Si) and an oxygen atom (O) as main constituent elements, such as silicon monoxide (SiO), silicon dioxide (SiO ₂ ), or zeolite. It may be a composite oxide with another metal.
Specific examples of silicon oxide include natural minerals such as siliceous stone, silica sand, diatomaceous earth, and quartz, calcined ash of silicon-containing plants, volcanic ash, silicates, silica gel derived from silica sol, fumed silica, silica alumina, and zeolite. And so on.

The reaction step is characterized by being carried out in the presence of calcium oxide, and the amount of calcium oxide used in the reaction step is the amount of substance of calcium atom of calcium oxide / the amount of substance of silicon atom of silicon oxide (Ca / Si). ) Is usually 1 to 50, preferably 2 or more, more preferably 3 or more, preferably 30 or less, and more preferably 10 or less. Within the above range, tetraalkoxysilane can be produced in a higher yield.

The reaction step is preferably carried out in the presence of an alkali metal compound and / or an alkaline earth metal compound other than calcium oxide. In the presence of an alkali metal compound or an alkaline earth metal compound other than calcium oxide, the cleavage of the silicon-oxygen bond of silicon oxide is promoted, and tetraalkoxysilane can be produced in a higher yield.
Examples of alkali metals and alkaline earth metals in alkaline earth metal compounds other than alkali metal compounds and calcium oxide include lithium (Li), sodium (Na), magnesium (Mg), potassium (K), cesium (Cs) and the like. Can be mentioned. Examples of counter ions include hydroxides, halides, oxides, carbonates, hydrogen carbonates, alkoxides, silicates, aluminates, phosphates, organic acid salts, sulfates, nitrates and the like. .. Among them, hydroxides, halides, carbonates and hydrogen carbonates are preferable, and alkali metal hydroxides, alkali metal halides, alkali metal carbonates and alkali metal hydrogen carbonates are more preferable.
Specific alkali metal compounds and alkaline earth metal compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium fluoride, and potassium fluoride. , Cesium hydroxide and the like. The alkali metal compound and the alkaline earth metal compound other than calcium oxide may be used not only in one type but also in combination of two or more types.
The total amount of the alkali metal compound and the alkaline earth metal compound other than calcium oxide used is usually 0 mol or more, preferably 0.001 mol or more, and usually 20 mol or less, preferably 20 mol or less, relative to 1 mol of silicon oxide (in the case of silicon dioxide). Is 10 mol or less. Within the above range, tetraalkoxysilane can be produced in a higher yield.

The reaction conditions in the reaction step are not particularly limited and can be appropriately selected depending on the intended purpose.
The reaction temperature in the reaction step is usually 100 ° C. or higher, preferably 130 ° C. or higher, more preferably 150 ° C. or higher, and usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower.
The reaction pressure in the reaction step is usually 0.1 MPa or more, preferably 0.3 MPa or more, more preferably 0.5 MPa or more, and usually 20 MPa or less, preferably 10 MPa or less, more preferably 8 MPa or less. The type of gas used as the gas phase in the reaction step includes an inert gas such as nitrogen gas and argon gas, and may be a mixed gas of two or more types.
When a batch reactor is used, the reaction time of the reaction step is usually 1 minute or more, preferably 5 minutes or more, more preferably 19 minutes or more, usually 10 hours or less, preferably 5 hours or less, more preferably 1 hour. It is as follows. When a continuous tube reactor is used, the reaction time of the reaction step is usually 10 minutes or more, preferably 30 minutes or more, more preferably 60 minutes or more, usually 24 hours or less, preferably 8 hours or less, and more. It is preferably 6 hours or less.
Within the above range, tetraalkoxysilane can be produced in a higher yield.

The reactor, operating procedure, reaction conditions, etc. for reacting the alcohol with silicon oxide in the reaction step are not particularly limited, and can be appropriately selected depending on the intended purpose.
Examples of the reactor include a batch reactor (see FIG. 1A), a continuous tube reactor (see FIGS. 1B and 1C), and the like. The batch reactor is preferably a pressure resistant reactor such as an autoclave. Further, the continuous tube reactor is preferably a fluidized bed reactor or a fixed bed reactor.
As for the operation procedure, for example, when a batch reactor is used, alcohol, silicon oxide, calcium oxide, an alkali metal compound, etc. are charged into the reactor, the inside of the reaction vessel is swept with a gas used as a gas phase, and then the reaction vessel is filled with gas. There is a method of sealing and heating to the reaction temperature. The filling pressure of the gas at 25 ° C. is preferably 0.1 to 10 MPa. Within the above range, tetraalkoxysilane can be produced in a higher yield.
Further, when a continuous tube type reactor is used, there is a method in which the reaction vessel is heated to the reaction temperature and then a mixture containing alcohol, silicon oxide, calcium oxide, an alkali metal compound and the like is continuously charged into the reaction vessel ( See FIG. 1B.). A carrier gas may be used to add silicon oxide, calcium oxide, an alkali metal compound, or the like. As the carrier gas, an inert gas such as nitrogen gas or argon gas can be used. The carrier gas supply rate and the like can be appropriately selected according to the size of the reactor, reaction conditions and the like.
When a continuous tube reactor is used, for example, a mixture containing silicon oxide, calcium oxide, an alkali metal compound, etc. is filled in a predetermined position of the reactor, the reactor is heated to the reaction temperature, and then alcohol is continuously added. (See FIG. 1C). In this case, carrier gas may or may not be used. As the carrier gas, an inert gas such as nitrogen gas or argon gas can be used. The supply rate of alcohol and the like can be appropriately selected according to the size of the reactor, reaction conditions and the like. As reaction conditions, for example, the pressure in the tubular reactor is 0.1 to 1.0 MPa (absolute pressure), and the raw material alcohol is fed at a flow rate of 0.01 to 1.000 mL / min for 10 minutes to 24 hours. To do. The continuous tube reactor may be made by oneself or a commercially available product may be used. Examples of commercially available products include Flow Reactor (FFX-1000G) manufactured by Tokyo Rika Kikai Co., Ltd. and KeyChem (registered trademark) -Integral manufactured by YMC Co., Ltd.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention can be appropriately modified as long as it does not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limited by the specific examples shown below.

<Example 1>
Silicon dioxide (Wako Pure Chemical Industries, Ltd. Wako Gel 60N 63-212 μm) 4.5 mmol, potassium hydroxide 0.45 mmol, ethanol 24 g, calcium oxide in a 30 mL volume SUS autoclave (manufactured by Pressure-Resistant Glass Industry Co., Ltd.) containing a mechanical stirrer. (Wako Pure Chemical Industries, Ltd. special grade) 18 mmol was added, and the mixture was sealed. Then, the inside of the autoclave was heated to a reaction temperature of 180 ° C. while stirring at 1200 rpm, and the reaction was carried out for 30 minutes. After cooling, the reaction mixture was analyzed by gas chromatography (Shimadzu GC-2014 ATF / SPL). The yield of tetraethoxysilane based on silicon dioxide was 72%. The results are shown in Table 1.

<Example 2>
Tetraethoxysilane was produced by the same procedure as in Example 1 except that calcium oxide was set to 13.5 mmol with respect to the reaction conditions of Example 1. The yield of tetraethoxysilane based on silicon dioxide was 71%. The results are shown in Table 1.

<Example 3>
Tetraethoxysilane was produced by the same procedure as in Example 1 except that calcium oxide was set to 9.0 mmol with respect to the reaction conditions of Example 1. The yield of tetraethoxysilane based on silicon dioxide was 52%. The results are shown in Table 1.

<Example 4>
Tetraethoxysilane was produced by the same procedure as in Example 1 except that calcium oxide was 4.5 mmol with respect to the reaction conditions of Example 1. The yield of tetraethoxysilane based on silicon dioxide was 33%. The results are shown in Table 1.

<Example 5>
Tetraethoxysilane was produced by the same operation as in Example 1 except that silicon dioxide was 9.0 mmol, calcium oxide was 45 mmol, the reaction temperature was 195 ° C., and the time was 20 minutes with respect to the reaction conditions of Example 1. went. The yield of tetraethoxysilane based on silicon dioxide was 62%. The results are shown in Table 1.

<Example 6>
With respect to the reaction conditions of Example 1, the alcohol was changed from ethanol to 24 g of methanol, silicon dioxide was 9.0 mmol, calcium oxide was 27 mmol, the reaction temperature was 220 ° C., and the time was 45 minutes. Tetramethoxysilane was produced by the same operation. The yield of tetramethoxysilane based on silicon dioxide was 43%. The results are shown in Table 1.

<Example 7>
Silicon dioxide (Wako Pure Chemical Industries, Ltd. Wakogel 60N 63-212 μm) 1.1 mmol was added to a solution of 0.11 mmol of potassium hydroxide in 5 mL of ethanol and mixed, and then ethanol was distilled off under reduced pressure to obtain silicon dioxide. And potassium hydroxide were prepared. To this mixture, 4.4 mmol of calcium oxide (Wako Pure Chemical Industries, Ltd.) was further added, and the mixture was filled in a SUS316 tube having an inner diameter of 4.6 mm. This tube is connected to a flow reactor (FFX-1000G) manufactured by Tokyo Rika Kikai, and while heating to 200 ° C., the pressure inside the tube is 0.8 MPa, and ethanol is sent at a flow rate of 0.025 mL / min for 6 hours. As a result, tetraethoxysilane was produced with the apparatus configuration of FIG. 1C type. When the solution was recovered downstream of the flow reactor and the amount of tetraethoxysilane produced was determined, the yield of tetraethoxysilane based on silicon dioxide was 73%. The results are shown in Table 1.

<Example 8>
Tetramethoxysilane was produced in the same manner as in Example 7 except that the amount of calcium oxide used was 5.5 mmol and the alcohol to be fed was methanol with respect to the reaction conditions of Example 7. The yield of tetramethoxysilane based on silicon dioxide was 54%. The results are shown in Table 1.

<Comparative example 1>
Tetraethoxysilane was produced in the same manner as in Example 1 except that calcium oxide was not added to the reaction conditions of Example 1. The yield of tetraethoxysilane based on silicon dioxide was 6%. The results are shown in Table 1.

<Comparative example 2>
Tetramethoxysilane was produced in the same manner as in Example 6 except that calcium oxide was not added to the reaction conditions of Example 6. The yield of tetraethoxysilane based on silicon dioxide was 4%. The results are shown in Table 1.

<Comparative example 3>
Tetraethoxysilane was produced by the same flow reactor operation as in Example 7 except that calcium oxide was not added to the reaction conditions of Example 7. The yield of tetraethoxysilane based on silicon dioxide was 3%. The results are shown in Table 1.

<Comparative example 4>
Tetramethoxysilane was produced by the same flow reactor operation as in Example 8 except that calcium oxide was not added to the reaction conditions of Example 8. The yield of tetramethoxysilane based on silicon dioxide was 13%. The results are shown in Table 1.

This application is based on a Japanese patent application filed on December 27, 2017 (Japanese Patent Application No. 2017-252112), the contents of which are incorporated herein by reference.

According to the production method of the present invention, tetraalkoxysilane used as a raw material for producing various silane compounds, organic silicone polymers, various silylating agents, colloidal silica, ceramics and the like can be produced with high efficiency.

101a, 101b, 101c Equipment that can be used in the production method of the present invention 102 Alcohol 103 Mixtures of silicon oxide, calcium oxide, alkali metal compounds, etc. 104 Mixtures of alcohol, silicon oxide, calcium oxide, alkali metal compounds, etc. 105 Tetraalkoxy Silane

Claims (3)

A method for producing tetraalkoxysilane, which comprises a reaction step of reacting alcohol with silicon oxide to produce tetraalkoxysilane (excluding those carried out in the presence of carbon dioxide).
The reaction step is carried out in the presence of calcium oxide .
The reaction step is carried out by continuously charging the alcohol into a continuous tube reactor filled with the mixture containing silicon oxide and calcium oxide.
In the reaction step, the reaction temperature is 200 ° C. or lower, and the pressure in the continuous tube reactor is 0.1 to 1.0 MPa (absolute pressure).
The silicon oxide, wherein the silicon dioxide (SiO ₂₎ der Rukoto method of tetraalkoxysilane. In the reaction step, the mixture further comprises an alkali metal compound and / or alkaline earth metal compounds other than calcium oxide, method for producing a tetraalkoxysilane according to claim 1. The tetraalkoxysilane according to claim 1 or 2, wherein the amount of calcium oxide used in the reaction step is an amount such that the amount of substance of calcium atom of calcium oxide / the amount of substance of silicon atom of silicon oxide is 1 to 50. Production method.

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