Method for producing tetraalkoxysilane using alkyl carbonate, and composition containing tetraalkoxysilane

Abstract

The present invention addresses the problem of providing a method for producing an alkoxysilane, the method being less apt to be affected by the water contents of starting materials than conventional methods and making it possible to industrially produce the alkoxysilane through a low-temperature production process. Provided is a method for producing a tetraalkoxysilane which includes a step in which a dialkyl carbonate, silicon oxide, an alcohol, and a base catalyst are mixed to form a mixture.

Description

Method for producing tetraalkoxysilane using alkyl carbonate and composition containing tetraalkoxysilane

[0001] The present invention relates to a method for producing tetraalkoxysilanes using alkyl carbonates and compositions containing tetraalkoxysilanes.

[0002] Tetraalkoxysilanes are industrially important silicon compounds used in protective films, insulating and space-filling films between elements and wiring, etching-resistant films for forming holes and wiring patterns, insulating films between wiring layers and space-filling films for shielding, fixing, and absorbing impurities, crosslinking agents, etc. Furthermore, alkyl carbonates are environmentally friendly compounds that have recently been synthesized using carbon dioxide and alcohol as raw materials and are used as intermediates in the synthesis of diphenyl carbonate, a raw material for polycarbonate.

[0003] As a method for producing tetraalkoxysilane, for example, Non-Patent Document 1 discloses a production method in which dimethyl carbonate or diethyl carbonate is reacted with silica to synthesize tetramethoxysilane or tetraethoxysilane.

[0004] Furthermore, Patent Document 1 discloses a production method for synthesizing tetraethoxysilane from ethanol, silica, and carbon dioxide present in one reaction system.

[0005] Furthermore, Patent Document 2 discloses a production method for synthesizing tetraethoxysilane from ethanol, silica, and tetraethoxytitanium.

[0006] International Patent Publication No. 2015 / 170666 International Patent Publication No. 2015 / 170665

[0007] Chem. Mater. 1993, 5, 4, 442-447

[0008] However, the production method disclosed in Non-Patent Document 1 requires a high-temperature reaction at 400°C to obtain alkoxysilanes with a high yield. Furthermore, Patent Document 1 uses dimethoxypropane as a raw material, which generates by-products. Furthermore, Patent Document 2 adds tetraethoxytitanium, which makes it difficult to separate it from tetraethoxysilane. Therefore, conventional techniques have not been able to produce alkoxysilanes under low-temperature conditions suitable for industrial mass production. Furthermore, moisture accelerates the hydrolysis reaction of alkoxysilanes, reducing the yield, so conventional methods have required dehydration and drying processes for raw materials, etc.

[0009] Therefore, an object of the present invention is to provide a method for producing alkoxysilanes that is less affected by the moisture content of the raw materials than conventional methods and that can be produced industrially using a low-temperature production process.

[0010] That is, the present invention is as follows. [1] A method for producing tetraalkoxysilane, comprising a step of mixing a dialkyl carbonate, silicon oxide, an alcohol, and a base catalyst to obtain a mixture. [2] A method for producing tetraalkoxysilane according to the above item [1], wherein in the step, the mixture is heated at a temperature of 150°C or higher and 350°C or lower. [3] A method for producing tetraalkoxysilane according to the above item [1] or [2], wherein in the step, the mixture is refluxed at 10 MPa or lower. [4] A method for producing tetraalkoxysilane according to any of the above items [1] to [3], wherein the mass ratio of the alcohol to the dialkyl carbonate mixed in the step is 0.1 or higher and 15 or lower. [5] A method for producing tetraalkoxysilane according to any of the above items [1] to [4], wherein the molar ratio of the dialkyl carbonate to the silicon oxide mixed in the step is 0.01 or higher and 100 or lower. [6] The method for producing tetraalkoxysilane according to any one of [1] to [5] above, wherein the alcohol comprises an alcohol having 2 or more carbon atoms, and / or the dialkyl carbonate comprises a dialkyl carbonate in which each of the two alkyl chains has 2 or more carbon atoms. [7] The method for producing tetraalkoxysilane according to [3] above, wherein in the step, carbon dioxide is released from a vessel containing the mixture, and the pressure inside the vessel is maintained. [8] The method for producing tetraalkoxysilane according to any one of the above [1] to [7], wherein the step provides a composition comprising: (α) the tetraalkoxysilane; and (β) at least one compound selected from the group consisting of an ether represented by the following formula (1), an ester represented by the following formula (2), and an acetal represented by the following formula (3), wherein the content of the ether represented by the following formula (1), the ester represented by the following formula (2), or the acetal represented by the following formula (3), relative to the tetraalkoxysilane in the composition, is 0.001 ppm or more based on the peak area ratio in a gas chromatograph when the composition is analyzed by gas chromatography.

[0011]

[0012] (In the formula, R １ are the same or different and each represents a linear or branched alkyl group; R ２ represents a hydrogen atom or a linear or branched alkyl group.) [9] A composition comprising: (α) a tetraalkoxysilane; and (β) at least one compound selected from the group consisting of an ether represented by the following formula (1), an ester represented by the following formula (2), and an acetal represented by the following formula (3), wherein the content of the ether represented by the following formula (1), the ester represented by the following formula (2), or the acetal represented by the following formula (3) relative to the tetraalkoxysilane in the composition is 0.001 ppm or more based on the peak area ratio in a gas chromatograph when the composition is subjected to gas chromatography analysis.

[0013]

[0014] (In the formula, R １ are the same or different and each represents a linear or branched alkyl group; R ２represents a hydrogen atom or a linear or branched alkyl group.)

[10] The composition according to the above [9], wherein the content of the ether represented by the following formula (1), the ester represented by the following formula (2), or the acetal represented by the following formula (3) relative to the tetraalkoxysilane in the composition is 10% or less, based on the peak area ratio in a gas chromatograph when the composition is subjected to gas chromatography analysis.

[11] The composition according to the above [9] or

[10] , which contains all of the ether represented by the formula (1), the ester represented by the formula (2), and the acetal represented by the formula (3).

[12] The composition according to the above-mentioned

[11] , wherein the content ratio of the ester represented by the formula (2) to the ether represented by the formula (1) in the composition is 0.5 to 2.0 based on the peak area intensity ratio in a gas chromatograph when the composition is subjected to gas chromatography analysis, and the content ratio of the acetal represented by the formula (3) to the ether represented by the formula (1) in the composition is 0.5 to 2.0 based on the peak area ratio in a gas chromatograph when the composition is subjected to gas chromatography analysis.

[0015] According to the present invention, it is possible to provide a method for producing alkoxysilanes that can be produced industrially using a low-temperature production process that is less affected by the moisture content of the raw materials than conventional methods.

[0016] The present invention will be described in detail below. Note that the present invention is not limited to the following embodiments (present embodiments) and can be practiced in various modifications within the scope of the gist thereof. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage.

[0017] [Method for Producing Tetraalkoxysilane] The method for producing tetraalkoxysilane of this embodiment is a method including a step of mixing an alcohol, a dialkyl carbonate, silicon oxide, and a base catalyst to form a mixture (hereinafter referred to as the "reaction step"). By forming a mixture of the dialkyl carbonate, silicon oxide, alcohol, and base catalyst, a reaction between the dialkyl carbonate and silicon oxide proceeds. By creating a state in which the alcohol and dialkyl carbonate coexist, the alcohol improves the compatibility between the base catalyst, silicon oxide, and the alkyl carbonate, which has high reactivity, making it possible to carry out the reaction at a low temperature.

[0018] The coexistence of alcohol and carbonate allows the alkoxylation reaction to proceed without the need for special dehydration or drying processes for the raw materials. Generally, alkoxysilanes are known to have a tendency to hydrolyze, and it is believed that the product alkoxysilane will hydrolyze if water is present in the system. However, the present inventors have found that in a reaction system in which alcohol and carbonate coexist, there is almost no difference in the yield of alkoxysilane between the use of dehydrated raw materials and the use of non-dehydrated raw materials. Although the reason for this is unclear, it is assumed that the carbonate acts as a sacrificial agent for moisture, thereby suppressing the hydrolysis of the alkoxysilane.

[0019] The weight of water contained in a mixture obtained by mixing an alcohol, a dialkyl carbonate, silicon oxide, and a base catalyst (particularly, an alcohol and a dialkyl carbonate) is 0.001 g / mol or more, 0.003 g / mol or more, 0.005 g / mol or more, 0.007 g / mol or more, 0.01 g / mol or more, 0.03 g / mol or more, 0.05 g / mol or more, 0.07 g / mol or more, 0.1 g / mol or more, based on the number of moles of silicon oxide in the mixture. The water content may be 0.2 g / mol or more, 0.3 g / mol or more, 0.4 g / mol or more, 0.5 g / mol or more, 0.6 g / mol or more, 0.7 g / mol or more, 0.8 g / mol or more, 0.9 g / mol or more, 1.0 g / mol or more, 1.1 g / mol or more, 1.2 g / mol or more, 1.3 g / mol or more, 1.4 g / mol or more, or 1.5 g / mol or more, and the upper limit is not particularly limited, but may be, for example, 20 g / mol or less. The weight of water contained in the mixture can be measured and calculated based on the Karl Fischer measurement method.

[0020] In the reaction step, it is preferable to heat the mixture. In the reaction step, the lower limit of the heating temperature (reaction temperature) for the mixture is preferably 150°C or higher, more preferably 180°C or higher, even more preferably 200°C or higher, and particularly preferably 240°C or higher, from the viewpoint of the reaction rate. In terms of the upper limit of the heating temperature (reaction temperature) for the mixture, from the viewpoint of a decrease in yield due to the occurrence of side reactions, it is preferably 350°C or lower, more preferably 300°C or lower, and particularly preferably 290°C or lower.

[0021] In the reaction step, the time (reaction time) for which the mixture is heated within the heating temperature (reaction temperature) range is, for example, 1 hour or more, preferably 6 hours or more, and more preferably 12 hours or more, and for example, 96 hours or less, preferably 48 hours or less, and more preferably 24 hours or less.

[0022] The internal temperature of the mixture is preferably 140°C or higher, more preferably 170°C or higher, even more preferably 190°C or higher, and particularly preferably 220°C or higher, and the upper limit is preferably 340°C or lower, more preferably 290°C or lower, and particularly preferably 280°C or lower.

[0023] In the reaction step, it is preferable to apply pressure to the mixture. In the reaction step, the upper limit of the pressure on the mixture (pressure during the reaction) is preferably 10 MPa or less, more preferably 7 MPa or less, even more preferably 5 MPa or less, and particularly preferably 3 MPa or less, from the viewpoint of allowing the reaction to proceed at low pressure. In view of the boiling points of the alcohol and dialkyl carbonate used as raw materials, the lower limit of the pressure on the mixture (pressure during the reaction) is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and particularly preferably 0.5 MPa or more.

[0024] The mixture is preferably refluxed, for example, within the above pressure range. Refluxing refers to the process of cooling and liquefying the vaporized components of the mixture by contacting them with a cooling means and returning them to the mixture. The method of bringing the vaporized components of the mixture into contact with the cooling means during refluxing is not particularly limited and can be selected appropriately depending on the purpose. For example, a method using a known cooling device used for refluxing and equipped with a cooling means can be used. The cooling device is not particularly limited, but for example, a double-tube heat exchanger with a thin tube inside a thick tube to form two flow paths can be used. Such a heat exchanger is used by passing a refrigerant (cooling chiller) through one flow path as the cooling means, and passing the vaporized components of the mixture through the other flow path. The heat exchanger may be made of glass or stainless steel.

[0025] The temperature of the cooling means during reflux is preferably lower than the reaction temperature, for example, 290°C or lower, preferably 200°C or lower, more preferably 100°C or lower, and for example, -60°C or higher, preferably -20°C or higher. Within the above range, the reaction can be carried out without excessively increasing the internal pressure due to vaporized alcohol. Furthermore, refluxing suppresses the production of by-products derived from carbonates and alcohols, further improving the yield of alkoxysilanes.

[0026] In the reaction step, it is preferable to release carbon dioxide from a vessel containing the mixture and maintain the pressure inside the vessel. As a method for maintaining the pressure inside the vessel, for example, a method using a pressure-maintaining valve (back pressure valve) can be used. By maintaining a constant pressure inside the vessel while refluxing the vaporized components of the mixture to contact a cooling means, it is possible to prevent the raw materials, alcohol and dialkyl carbonate, from being liquefied by cooling and released outside the system together with carbon dioxide, and it is possible to selectively release carbon dioxide generated inside the vessel.

[0027] In the production process, the internal pressure may be reduced using a pressure-maintaining valve to carry out the reaction under a constant pressure. When the target product is produced while cooling the reaction heat with a condenser, generally, liquefiable components of the gas generated in the reactor are condensed in the condenser, and then the unliquefied gas is discharged through the pressure-maintaining valve. However, in the present embodiment, since carbon dioxide, which is difficult to liquefy, is generated, the position of the pressure-maintaining valve in the reactor and condenser connected at the same pressure is not limited. The gas released from the pressure-maintaining valve during venting can also be separated and / or recovered using a cooling trap, a seal pot, a scrubber, an adsorption tower containing an adsorbent, or the like.

[0028] When refluxing the mixture, the vaporized components of the mixture may be dehydrated. As a dehydration method, a method of contacting a dehydration means with the vaporized components of the mixture may be used. As the dehydration means, for example, an adsorbent such as molecular sieves or zeolite may be used. When the heat exchanger described above is used as the cooling device, a method may be used in which a refrigerant (cooling chiller) flows through one flow path and the vaporized components flow through the other flow path filled with a dehydration means.

[0029] In one embodiment, from the viewpoint of purification and separation of the reaction product, the alcohol is preferably an alcohol having 1 to 8 carbon atoms, more preferably an alcohol having 1 to 4 carbon atoms, or more preferably an alcohol having 2 or more carbon atoms, more preferably an alcohol having 2 to 6 carbon atoms, even more preferably an alcohol having 2 to 5 carbon atoms, and particularly preferably an alcohol having 2 to 4 carbon atoms. Specific alcohols include methanol, ethanol, n-propanol, isopropanol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. In particular, from the viewpoint of being able to proceed with the reaction at low pressure, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butyl alcohol are preferred, and isobutyl alcohol is preferred from the viewpoint of purification and separation of the reaction product. Since there is a possibility that a very small amount of alcohol may react with silica to produce an alkoxysilane bond, it is preferable to make the carbon chain of the alcohol and the carbon chain of the carbonate the same in order to improve the yield of the obtained alkoxysilane.

[0030] In one embodiment, from the viewpoint of purification and separation of the reaction product, the dialkyl carbonate is preferably a dialkyl carbonate in which each of the two alkyl chains of the dialkyl carbonate has 1 to 8 carbon atoms, more preferably a dialkyl carbonate in which each of the two alkyl chains has 1 to 4 carbon atoms, or preferably a dialkyl carbonate in which each of the two alkyl chains has 2 or more carbon atoms, more preferably a dialkyl carbonate in which each of the two alkyl chains has 2 to 6 carbon atoms, even more preferably a dialkyl carbonate in which each of the two alkyl chains has 2 to 5 carbon atoms, and particularly preferably a dialkyl carbonate in which each of the two alkyl chains has 2 to 4 carbon atoms. Specific examples of the dialkyl carbonate include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, di-n-butyl carbonate, diisobutyl carbonate, di-sec-butyl carbonate, and di-tert-butyl carbonate. In particular, from the viewpoint of allowing the reaction to proceed at low pressure, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, di-n-butyl carbonate, diisobutyl carbonate, di-sec-butyl carbonate, and di-tert-butyl carbonate are preferred, and from the viewpoint of purification and separation of the reaction product, diisobutyl carbonate is preferred. Furthermore, the chain lengths of the two carbon chains of the dialkyl carbonate may be different, but when it is desired to produce a single alkoxysilane with good yield, it is preferable that the chain lengths are the same.

[0031] Silicon oxide refers to a compound containing silicon atoms (Si) and oxygen atoms (O) as the main constituent elements, and includes silicon monoxide (SiO), silicon dioxide (SiO ２ ), or a composite oxide with other metals such as zeolite. Specific examples of silicon oxide include natural minerals such as silica stone, silica sand, diatomaceous earth, and quartz, as well as burned ash of silicon-containing plants, volcanic ash, silicates, silica gel derived from silica sol, fumed silica, silica alumina, and zeolite.

[0032] Regarding the ratio of dialkyl carbonate and silicon oxide mixed in the reaction step, from the viewpoint of enabling the reaction of tetraalkoxysilane at low temperature and pressure, the molar ratio of dialkyl carbonate / silicon oxide is preferably 0.001 or more, more preferably 0.01 or more, and even more preferably 0.1 or more. Furthermore, from the viewpoint of improving the yield of tetraalkoxysilane, the molar ratio of dialkyl carbonate / silicon oxide is preferably 100 or less, more preferably 50 or less, and even more preferably 10 or less, and from the viewpoint of the yield per charged amount, it is preferably 5 or less.

[0033] Regarding the ratio of the base catalyst and silicon oxide mixed in the reaction step, from the viewpoint of improving the yield of tetraalkoxysilane, the molar ratio of base catalyst / silicon oxide is preferably 0.001 or more, more preferably 0.01 or more, and particularly preferably 0.1 or more. Furthermore, from the viewpoint of improving the yield per charged amount of tetraalkoxysilane, the molar ratio of base catalyst / silicon oxide is preferably 100 or less, more preferably 10 or less, even more preferably 5 or less, and particularly preferably 1 or less.

[0034] Regarding the ratio of the alcohol and dialkyl carbonate mixed in the reaction step, from the viewpoint of enabling the reaction of tetraalkoxysilane at low temperature and pressure, the mass ratio of alcohol / dialkyl carbonate is preferably 0.01 or more, more preferably 0.05 or more, and from the viewpoint of yield, it is particularly preferred that it be 0.1 or more. Also, from the viewpoint of enabling the reaction of tetraalkoxysilane at low temperature and pressure, the mass ratio of alcohol / dialkyl carbonate is preferably 100 or less, more preferably 15 or less, and from the viewpoint of yield per charged amount, it is particularly preferred that it be 10 or less.

[0035] The base catalyst is preferably an alkali metal compound and / or an alkaline earth metal compound. The presence of an alkali metal compound or an alkaline earth metal compound promotes the cleavage of the silicon-oxygen bond in silicon oxide, allowing for the production of tetramethoxysilane in a higher yield.

[0036] Examples of the alkali metals and alkaline earth metals in the alkali metal compounds and alkaline earth metal compounds include lithium (Li), sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), and cesium (Cs). Examples of counter ions include hydroxides, halides, oxides, carbonates, bicarbonates, alkoxides, silicates, aluminates, phosphates, organic acid salts, sulfates, and nitrates. Among these, hydroxides, halides, carbonates, and bicarbonates are preferred, with alkali metal hydroxides, alkali metal halides, alkali metal carbonates, and alkali metal bicarbonates being more preferred. Specific examples of alkali metal compounds and alkaline earth metal compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium fluoride, potassium fluoride, and cesium fluoride. The alkali metal compounds and alkaline earth metal compounds may be used singly or in combination of two or more.

[0037] The total amount of the alkali metal compound and alkaline earth metal compound used is, for example, 0.1 mol or more, preferably 0.5 mol or more, and for example, 100 mol or less, preferably 20 mol or less, per mol of silicon oxide (in the case of silicon dioxide), from the viewpoint of accelerating the reaction between the alcohol, the dialkyl carbonate, and the silicon oxide.

[0038] In the reaction step, the reactor, operating procedure, reaction conditions, etc. for reacting the alcohol, dialkyl carbonate, silicon oxide, and base catalyst are not particularly limited and can be appropriately selected depending on the purpose. The reactor is preferably a pressure-resistant reactor such as an autoclave. For example, the operating procedure may include a method in which the alcohol, alkyl carbonate, silicon oxide, base, etc. are charged into the reactor and the reactor is heated to the reaction temperature.

[0039] After the reaction in the reaction step has progressed, any one or more of the dialkyl carbonate, silicon oxide, alcohol, and base catalyst, or other components may be re-supplied to the mixture to further promote the reaction between the dialkyl carbonate and silicon oxide. The process for producing alkoxysilanes, which includes the reaction step, can be carried out as either a batch process or a continuous process.

[0040] In the method for producing tetraalkoxysilane of this embodiment, when an alcohol represented by the following formula (B) and a dialkyl carbonate represented by the following formula (C) are used as raw materials, a tetraalkoxysilane represented by the following formula (A) is produced.

[0041]

[0042] (In the formula, R １ are the same or different and each represents a linear or branched alkyl group.

[0043] In the method for producing tetraalkoxysilane of this embodiment, R of the alcohol represented by formula (B) used as a raw material is １ and the two R of the dialkyl carbonate represented by formula (C) used as the raw material １ If all R are the same, then all R １ is the raw material R １ On the other hand, the R of the alcohol represented by formula (B) used as the raw material is converted into a tetraalkoxysilane represented by formula (A). １ and the two R of the dialkyl carbonate represented by formula (C) used as the raw material １ If all R １ A mixture containing tetraalkoxysilanes of formula (A) is produced in which the tetraalkoxysilanes are not all the same.

[0044] In the method for producing tetraalkoxysilane of this embodiment, in addition to the tetraalkoxysilane represented by formula (A), at least one compound selected from the group consisting of an ether represented by formula (1), an ester represented by formula (2), and an acetal represented by formula (3) below tends to be produced due to a side reaction of the raw material alcohol or alkyl carbonate.

[0045]

[0046] (In the formula, R １ are the same or different and each represents a linear or branched alkyl group; R ２ represents a hydrogen atom or a linear or branched alkyl group.

[0047] Therefore, in one embodiment of the method for producing a tetraalkoxysilane of the present embodiment, a mixture (composition) containing: (α) the tetraalkoxysilane; and (β) at least one compound selected from the group consisting of an ether represented by formula (1), an ester represented by formula (2), and an acetal represented by formula (3) is obtained in the reaction step.

[0048] The present embodiment also provides a mixture (composition) containing: (α) the tetraalkoxysilane; and (β) at least one compound selected from the group consisting of an ether represented by formula (1), an ester represented by formula (2), and an acetal represented by formula (3).

[0049] In one embodiment of the method for producing tetraalkoxysilane of the present embodiment, R １ and the two R of the dialkyl carbonate represented by formula (C) used as the raw material １ If all are the same, then the two R １ is the raw material R １ Ethers represented by the same formula (1) as １ is the raw material R １ and an ester represented by the same formula (2) as １ is the raw material R １ On the other hand, at least one compound selected from the group consisting of acetals represented by the same formula (3) as those of the alcohol represented by formula (B) used as a raw material is produced. １ and the two R of the dialkyl carbonate represented by formula (C) used as the raw material １ If all R １Ethers represented by formula (1) in which R １ are not all the same, and R １ In this case, at least one compound selected from the group consisting of acetals represented by formula (3), wherein

[0050] In one embodiment of the method for producing tetraalkoxysilane of the present embodiment, when, for example, ethanol and diethyl carbonate are used as raw materials, tetraethoxysilane (formula (1-A) below) is produced as the tetraalkoxysilane, and at least one compound selected from the group consisting of diethyl ether (formula (1-1) below) as the ether, ethyl acetate (formula (1-2) below) as the ester, and 1,1-diethoxyethane (formula (1-3) below) as the acetal is produced.

[0051]

[0052] In one embodiment of the method for producing tetraalkoxysilane of the present embodiment, when, for example, n-propanol and di-n-propyl carbonate are used as raw materials, tetrapropoxysilane (formula (2-A) below) is produced as the tetraalkoxysilane, and at least one compound selected from the group consisting of dipropyl ether (formula (2-1) below) as the ether, propyl propionate (formula (2-2) below) as the ester, and 1,1-dipropoxypropane (formula (2-3) below) as the acetal is produced.

[0053]

[0054] In one embodiment of the method for producing tetraalkoxysilane of the present embodiment, when isopropanol and diisopropyl carbonate, for example, are used as raw materials, tetraisopropylsilane (formula (3-A) below) is produced as the tetraalkoxysilane, and at least one compound selected from the group consisting of diisopropyl ether (formula (3-1) below) as the ether and 2,2-diisopropoxypropane (formula (3-3) below) as the acetal is produced.

[0055]

[0056] In one embodiment of the method for producing tetraalkoxysilane of the present embodiment, when, for example, n-butanol and di-n-butyl carbonate are used as raw materials, tetrabutylsilane (formula (4-A) below) is produced as the tetraalkoxysilane, and at least one compound selected from the group consisting of dibutyl ether (formula (4-1) below) as the ether, butyl butyrate (formula (4-2) below) as the ester, and 1,1-dibutoxybutane (formula (4-3) below) as the acetal is produced.

[0057]

[0058] In one embodiment of the method for producing tetraalkoxysilane of the present embodiment, when isobutanol and diisobutyl carbonate, for example, are used as raw materials, tetraisobutylsilane (formula (5-A) below) is produced as the tetraalkoxysilane, and at least one compound selected from the group consisting of diisobutyl ether (formula (5-1) below) as the ether, isobutyl isobutyrate (formula (5-2) below) as the ester, and 1,1-diisobutoxy-2-methylpropane (formula (5-3) below) as the acetal is produced.

[0059]

[0060] The content ratio of the ether represented by formula (1), the ester represented by formula (2), or the acetal represented by formula (3) relative to the tetraalkoxysilane in the mixture (composition) obtained in the reaction step (before the purification step) is 0.001 ppm or more, based on the peak area ratio in a gas chromatograph when the mixture (composition) is subjected to gas chromatography analysis.

[0061] The content ratio of the ether represented by formula (1), the ester represented by formula (2), or the acetal represented by formula (3) relative to the tetraalkoxysilane in the mixture (composition) obtained in the reaction step (before the purification step) varies depending on the reaction conditions, but in a preferred specific embodiment, based on the peak area ratio in a gas chromatograph when gas chromatography analysis of the mixture (composition) is performed, the content is 0.001 ppm or more, 0.01 ppm or more, 0.1 ppm or more, 1 ppm or more, 0.001% or more (10 ppm or more), 0.01% or more, 0.1% or more, 1% or more, 2% or more, 3% or more, 4% or more, or 5% or more, and the upper limit is 20% or less, 18% or less, 16% or less, 14% or less, 12% or less, 10% or less, 9% or less, 8% or less, or 7% or less.

[0062] The total content of the ether represented by formula (1), the ester represented by formula (2), and the acetal represented by formula (3) relative to the tetraalkoxysilane in the mixture (composition) (before the purification step) obtained in the reaction step varies depending on the reaction conditions, but in a preferred specific embodiment, based on the peak area ratio in a gas chromatograph when the mixture (composition) is analyzed by gas chromatography, the total content is 0.001 ppm or more, 0.01 ppm or more, 0.1 ppm or more, 1 ppm or more, 0.001% or more (10 ppm or more), 0.01% or more, 0.1% or more, 1% or more, 5% or more, 10% or more, 13% or more, or 15% or more, and the upper limit is 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, or 20% or less.

[0063] In a preferred specific embodiment, the mixture (composition) obtained in the reaction step (before the purification step) preferably contains at least two of the ether represented by formula (1), the ester represented by formula (2), and the acetal represented by formula (3), and more preferably contains all of the ether represented by formula (1), the ester represented by formula (2), and the acetal represented by formula (3).

[0064] In a preferred specific embodiment, the content ratio of the ester represented by formula (2) to the ether represented by formula (1) in the mixture (composition) obtained in the reaction step (before the purification step) is 0.01 or more, 0.05 or more, 0.1 or more, 0.3 or more, or 0.5 or more, based on the area intensity ratio of a gas chromatograph when gas chromatography analysis of the mixture (composition) is performed, while the upper limit side is 10.0 or less, 5.0 or less, 4.0 or less, 3.0 or less, or 2.0 or less.

[0065] In a preferred specific embodiment, the content ratio of the acetal represented by formula (3) to the ether represented by formula (1) in the mixture (composition) obtained in the reaction step (before the purification step) is 0.01 or more, 0.05 or more, 0.1 or more, 0.3 or more, or 0.5 or more, based on the peak area ratio in a gas chromatograph when the mixture (composition) is subjected to gas chromatography analysis, while the upper limit side is 10.0 or less, 5.0 or less, 4.0 or less, 3.0 or less, or 2.0 or less.

[0066] The method for producing tetraalkoxysilane according to this embodiment may include, in addition to the reaction step, a step of purifying tetraalkoxysilane from the mixture obtained after the reaction step (hereinafter referred to as the "purification step"). The method for purifying tetraalkoxysilane in the purification step is not particularly limited, but examples thereof include distillation. The purification step can achieve a purity of tetraalkoxysilane of preferably 95% or more, more preferably 98% or more, and particularly preferably 99% or more. After the reaction step, a residue containing at least one of dialkyl carbonate, silicon oxide, alcohol, and base catalyst may be recovered in the purification step and reused in the reaction step.

[0067] The content of the ether represented by formula (1), the ester represented by formula (2), or the acetal represented by formula (3) relative to the tetraalkoxysilane in the mixture (composition) after the purification step (e.g., distillation) varies depending on the purification method. In a preferred specific embodiment, the content is 0.001 ppm or more, 0.01 ppm or more, 0.1 ppm or more, 1 ppm or more, 0.001% or more (10 ppm or more), 0.01% or more, 0.1% or more, or 1% or more, based on the peak area ratio in a gas chromatograph when the mixture (composition) is analyzed by gas chromatography. In contrast, the upper limit is 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1.0% or less, 0.5% or less, 0.1% or less, or 0.01% or less.

[0068] According to the method for producing tetraalkoxysilane of this embodiment, tetraalkoxysilane can be produced in a high yield using a low-temperature production process. The yield of tetraalkoxysilane can be preferably 10% or more, more preferably 30% or more, even more preferably 40% or more, and particularly preferably 50% or more, based on the amount of tetraalkoxysilane charged.

[0069] The present invention will be explained in more detail below with reference to examples and comparative examples, but modifications can be made as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0070] Example 1: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g (16.6 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries), 1.02 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries), and 10.15 g (58.3 mmol) of diisobutyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 0.1) at room temperature. The autoclave was cooled by a -5°C chiller and cooled to 14 cm. ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 240°C, and the pressure was 2.2 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 15%. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.57 g / mol based on the number of moles of silicon dioxide.

[0071] Example 2: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g (16.6 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries), 10.24 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries), and 10.15 g (58.3 mmol) of diisobutyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 1.0) at room temperature. The autoclave had an internal volume of 14 cm and was cooled by a -5°C chiller. ３SUS piping was connected. The autoclave was then stirred at 150 rpm while the reaction was carried out for 12 hours in an oil bath heated to 260°C. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 236°C, and the pressure was 2.2 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation, GC-2030) to calculate the yield using the absolute calibration curve method. The yield of tetraisobutoxysilane based on silicon dioxide was 61%. The content ratios of ether, ester, and acetal relative to the tetraalkoxysilane in the reaction mixture were calculated from the gas chromatographic peak area ratios based on the analysis results of the reaction mixture by gas chromatography (Shimadzu Corporation, GC-2030). The proportions of ether, ester, and acetal, based on the peak area ratio in gas chromatography, were 5.4%, 5.7%, and 6.6%, respectively, relative to the tetraalkoxysilane. The reaction solution was distilled to obtain a target product with a purity of 99% or more relative to the tetraalkoxysilane (manufactured by Kojundo Chemical Laboratory, product name SIR05LB) used as a standard. The proportions of ether, ester, and acetal relative to the tetraalkoxysilane in the target product were calculated as the peak area ratio in gas chromatography from the results of gas chromatography analysis (Shimadzu Corporation "GC-2030"). The proportions of ether, ester, and acetal, based on the peak area ratio in gas chromatography, were 10 ppm, 0.19%, and 1.1%, respectively, relative to the tetraalkoxysilane. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.67 g / mol based on the number of moles of silicon dioxide.

[0072] Example 3: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 0.10 g (16.6 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries), 15.36 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries), and 1.015 g (58.3 mmol) of diisobutyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 10.0, weight of alcohol / weight of dialkyl carbonate = 15) at room temperature. The autoclave was cooled by a -5°C chiller and cooled to 14 cm. ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 236°C, and the pressure was 2.7 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 65%. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.26 g / mol based on the number of moles of silicon dioxide.

[0073] Example 4: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g (16.6 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries), 10.24 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries), and 10.15 g (58.3 mmol) of diisobutyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 1.0) at room temperature. The autoclave was cooled to -5 ° C. by a chiller and cooled to 14 cm 3 . ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 210°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 200°C, and the pressure was 1.1 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 15%. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.70 g / mol based on the number of moles of silicon dioxide.

[0074] Example 5: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g (16.6 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries), 10.24 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries), and 10.15 g (58.3 mmol) of diisobutyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 1.0) at room temperature. The autoclave was cooled by a -5 ° C. chiller and had a capacity of 14 cm 3 . ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 290°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 270°C and the pressure was 4.0 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 60%. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.70 g / mol based on the number of moles of silicon dioxide.

[0075] Example 6: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 0.10 g (1.7 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide, 2.50 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries), and 9.90 g (83.8 mmol) of diethyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 50, moles of base / moles of silicon oxide = 10, weight of alcohol / weight of dialkyl carbonate = 0.25) at room temperature. The autoclave was cooled by a -5°C chiller and had a capacity of 14 cm. ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 255°C, and the pressure was 1.9 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation, GC-2030) and the yield was calculated using the absolute calibration curve method. The yield of tetraethoxysilane based on silicon dioxide was 98%. Furthermore, the total weight of water contained in the raw material reagents of ethanol and diethyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 1.59 g / mol based on the number of moles of silicon dioxide.

[0076] Example 7: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g (16.6 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide, 4.03 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries), and 16.03 g (136 mmol) of diethyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 8.2, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 0.25) at room temperature. The autoclave was cooled by a -5°C chiller and had a capacity of 14 cm. ３ SUS piping was connected. The autoclave was then stirred at 150 rpm while the reaction was carried out for 12 hours in an oil bath heated to 260°C. The surface temperature of the SUS piping was 10-20°C. At the end of the reaction, the internal temperature of the reactor was 251°C, and the pressure was 1.9 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation, GC-2030) using the absolute calibration curve method to calculate the yield. The yield of tetraethoxysilane based on silicon dioxide was 60%. The reaction solution was distilled to obtain the target product with a purity of 99% or more relative to the tetraethoxysilane (manufactured by Kojundo Chemical Laboratory, product name SIR02LB) used as a standard. Furthermore, the total weight of water contained in the raw material reagents of ethanol and diethyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.26 g / mol based on the number of moles of silicon dioxide.

[0077] Example 8 A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g of potassium hydroxide, 1.73 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries), and 6.88 g of diethyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 0.25) at room temperature. The autoclave was cooled by a -5°C chiller and cooled to 14 cm. ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours to react. At the end of the reaction, the internal temperature of the reactor was 224°C and the pressure was 0.5 MPa. The surface temperature of the SUS piping was 10 to 20°C. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraethoxysilane based on silicon dioxide was 51%. Furthermore, the total weight of water contained in the raw material reagents of ethanol and diethyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.11 g / mol based on the number of moles of silicon dioxide.

[0078] Example 9 A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 4.00 g of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 3.92 g of potassium hydroxide, 2.01 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries), and 8.01 g of diethyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 1.0, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 0.25) at room temperature. The autoclave was cooled to -5°C by a chiller and cooled to 14 cm3. ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours to react. At the end of the reaction, the internal temperature of the reactor was 225°C and the pressure was 0.4 MPa. The surface temperature of the SUS piping was 10 to 20°C. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraethoxysilane based on silicon dioxide was 25%. Furthermore, the total weight of water contained in the raw material reagents of ethanol and diethyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.032 g / mol based on the number of moles of silicon dioxide.

[0079] Example 10: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g of potassium hydroxide, 1.52 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries), and 6.07 g of ethyl methyl carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.) at room temperature (number of moles of dialkyl carbonate / number of moles of silicon oxide = 3.5, number of moles of base / number of moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 0.25). The autoclave was cooled to -5 ° C. by a chiller and cooled to 14 cm 3 . ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 224°C, and the pressure was 0.5 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraethoxysilane based on silicon dioxide was 25%. Furthermore, the total weight of water contained in the raw material reagents of ethanol and ethyl methyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.073 g / mol based on the number of moles of silicon dioxide.

[0080] Example 11 A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g of potassium hydroxide, 10.24 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries), and 10.15 g of diisobutyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, alcohol weight / weight of dialkyl carbonate = 1.0) at room temperature. The autoclave was cooled by a -5 ° C. chiller and cooled to 14 cm 3 . ３ A stainless steel pipe was connected to the autoclave, and a pressure-maintaining valve (manufactured by TESCOM) set to 1 MPa was attached to the end of the stainless steel pipe. The autoclave was then stirred at 150 rpm while the reaction was carried out for 12 hours in an oil bath heated to 260°C. The surface temperature of the stainless steel pipe was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 240°C, and the pressure was 1.0 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 47%. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.70 g / mol based on the number of moles of silicon dioxide.

[0081] [Example 12] A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g (16.6 mmol) of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g (16.6 mmol) of potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries), 10.24 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries), and 10.15 g (58.3 mmol) of diisobutyl carbonate (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 1.0) at room temperature. The autoclave was cooled by a -5 ° C. chiller and cooled to 14 cm 3 . ３ A stainless steel pipe filled with molecular sieves 3A (manufactured by Wako Pure Chemical Industries, Ltd.) was connected. The autoclave was then stirred at 150 rpm while the reaction was carried out for 12 hours in an oil bath heated to 260°C. The surface temperature of the stainless steel pipe was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 250°C, and the pressure was 2.1 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation, GC-2030) using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 61%. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.70 g / mol based on the number of moles of silicon dioxide.

[0082] Example 13: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g (16.6 mmol) of silicon dioxide (Wakogel® C-500HG, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 0.93 g (16.6 mmol) of potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 10.24 g of isobutyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 10.15 g (58.3 mmol) of diisobutyl carbonate at room temperature (moles of dialkyl carbonate / moles of silicon oxide = 3.5, moles of base / moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 1.0). The autoclave was stirred at 150 rpm and reacted for 12 hours in an oil bath heated to 260°C. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 254°C, and the pressure was 2.6 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation, GC-2030) using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 31%. Furthermore, the total weight of water contained in the raw material reagents of isobutyl alcohol and diisobutyl carbonate used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.70 g / mol based on the number of moles of silicon dioxide.

[0083] Comparative Example 1: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g of potassium hydroxide, and 20 g of diisobutyl carbonate at room temperature (number of moles of dialkyl carbonate / number of moles of silicon oxide = 3.5, number of moles of base / number of moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 0). The autoclave was cooled to -5°C by a chiller and cooled to 14 cm. ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 250°C and the pressure was 0.5 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was less than 0.1%. No ethers, esters, or acetals were detected in the reaction solution. Furthermore, the weight of water contained in the diisobutyl carbonate raw material reagent used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.56 g / mol based on the number of moles of silicon dioxide.

[0084] Comparative Example 2: A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g of potassium hydroxide, and 20 g of diisobutyl alcohol at room temperature (number of moles of dialkyl carbonate / number of moles of silicon oxide = 0, number of moles of base / number of moles of silicon oxide = 1.0). The autoclave was cooled to -5°C by a chiller and cooled to 14 cm. ３ SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 200°C, and the pressure was 1.0 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was less than 0.1%. No ethers, esters, or acetals were detected in the reaction solution. The weight of water contained in the raw material reagent of isobutyl alcohol used above was calculated based on the amount charged from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.14 g / mol based on the number of moles of silicon dioxide.

[0085] Comparative Example 3: 1.00 g of silicon dioxide (Wakogel® C-500HG, Fujifilm Wako Pure Chemical Industries, Ltd.), 0.93 g of potassium hydroxide, and 20 g of diisobutyl alcohol were added to a 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and titanium stirring blades (manufactured by Nitto Koatsu) at room temperature (moles of dialkyl carbonate / moles of silicon oxide = 0, moles of base / moles of silicon oxide = 1.0). The autoclave was then stirred at 150 rpm in an oil bath heated to 260°C for 12 hours to react. At the end of the reaction, the internal temperature of the reactor was 213°C, and the pressure was 1.5 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was 1%. The weight of water contained in the raw material reagent of isobutyl alcohol used above was calculated based on the amount charged from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.14 g / mol based on the number of moles of silicon dioxide.

[0086] [Comparative Example 4] A 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) was charged with 1.00 g of silicon dioxide (manufactured by Fujifilm Wako Pure Chemical Industries, Wakogel (registered trademark) C-500HG), 0.93 g of potassium hydroxide, and 6.88 g of diethyl carbonate at room temperature (number of moles of dialkyl carbonate / number of moles of silicon oxide = 3.5, number of moles of base / number of moles of silicon oxide = 1.0, weight of alcohol / weight of dialkyl carbonate = 0). The autoclave was cooled to -5°C by a chiller and cooled to 14 cm. ３SUS piping was connected. Thereafter, the autoclave was stirred at 150 rpm while being placed in an oil bath heated to 260°C for 12 hours for reaction. The surface temperature of the SUS piping was 10 to 20°C. At the end of the reaction, the internal temperature of the reactor was 250°C and the pressure was 0.5 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using the absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was less than 0.1%. Furthermore, the weight of water contained in the diethyl carbonate raw material reagent used above was calculated based on the charged amounts from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm's "899 Coulometer," catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K," anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"), and the weight of water was found to be 0.090 g / mol based on the number of moles of silicon dioxide.

[0087] Comparative Example 5: 1.00 g of silicon dioxide (Wakogel® C-500HG, Fujifilm Wako Pure Chemical Industries, Ltd.), 0.93 g of potassium hydroxide, and 6.043 g of ethanol were added to a 100 mL titanium autoclave (manufactured by Nitto Koatsu) equipped with two paddles and a titanium stirring blade (manufactured by Nitto Koatsu) at room temperature (moles of dialkyl carbonate / moles of silicon oxide = 0, moles of base / moles of silicon oxide = 1.0). A stainless steel pipe running a -5°C chiller was connected to the autoclave. The contents were then stirred at 150 rpm in an oil bath heated to 260°C and reacted for 12 hours. The surface temperature of the stainless steel pipe was 10-20°C. At the end of the reaction, the internal temperature of the reactor was 248°C, and the pressure was 0.9 MPa. The reaction mixture was analyzed by gas chromatography (Shimadzu Corporation "GC-2030") using an absolute calibration curve method to calculate the yield. The yield of tetraisobutoxysilane based on silicon dioxide was less than 0.1%. In addition, the weight of water contained in the raw ethanol reagent used above was calculated based on the amount charged from the measurement results using a Karl Fischer trace moisture analyzer (Metrohm "899 Coulometer", catholyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat CG-K", anolyte: Honeywell-Fluka (registered trademark) "HYDRANAL (registered trademark) Coulomat AK"). The weight of water was calculated based on the number of moles of silicon dioxide and was 0.022 g / mol.

[0088] The evaluation results obtained in the examples and comparative examples are shown in Table 1.

[0089]

[0090] From the above results, it can be seen that alkoxysilanes can be produced in high yields by mixing dialkyl carbonate, silicon oxide, alcohol and a base catalyst and reacting the mixture.

[0091] This application claims priority to Japanese Patent Application No. 2024-083841 filed on May 23, 2024, the entire contents of which are deemed to be part of the disclosure of this application and are incorporated herein by reference.

Claims

1. A method for producing tetraalkoxysilanes, comprising the step of combining dialkyl carbonate, silicon oxide, alcohol, and a base catalyst to form a mixture.

2. The method for producing tetraalkoxysilane according to claim 1, wherein in the step, the mixture is heated at a temperature of 150°C or higher and 350°C or lower.

3. The method for producing tetraalkoxysilane according to claim 1 or 2, wherein in the step, the mixture is refluxed at 10 MPa or less.

4. The method for producing tetraalkoxysilane according to claim 1 or 2, wherein the mass ratio of the alcohol to the dialkyl carbonate mixed in the step is 0.1 or more and 15 or less.

5. The method for producing tetraalkoxysilane according to claim 1 or 2, wherein the molar ratio of the dialkyl carbonate to the silicon oxide mixed in the step is 0.01 or more and 100 or less.

6. The method for producing tetraalkoxysilane according to claim 1 or 2, wherein the alcohol comprises an alcohol having two or more carbon atoms, and / or the dialkyl carbonate comprises a dialkyl carbonate in which each of the two alkyl chains has two or more carbon atoms.

7. The method for producing tetraalkoxysilane according to claim 3, wherein in the step, carbon dioxide is released from a vessel containing the mixture, and the pressure within the vessel is maintained.

8. A method for producing tetraalkoxysilane according to claim 1 or 2, wherein the step obtains a composition comprising: (α) the tetraalkoxysilane; and (β) at least one compound selected from the group consisting of an ether represented by the following formula (1), an ester represented by the following formula (2), and an acetal represented by the following formula (3), wherein the content of the ether represented by the following formula (1), the ester represented by the following formula (2), or the acetal represented by the following formula (3) relative to the tetraalkoxysilane in the composition is 0.001 ppm or more based on the peak area ratio in a gas chromatograph when the composition is subjected to gas chromatography analysis. (In the formula, R １ are the same or different and each represents a linear or branched alkyl group; R ２ represents a hydrogen atom or a linear or branched alkyl group.

9. A composition comprising (α) a tetraalkoxysilane, and (β) at least one compound selected from the group consisting of an ether represented by the following formula (1), an ester represented by the following formula (2), and an acetal represented by the following formula (3), wherein the content of the ether represented by the following formula (1), the ester represented by the following formula (2), or the acetal represented by the following formula (3) relative to the tetraalkoxysilane in the composition is 0.001 ppm or more based on the peak area ratio in a gas chromatograph when the composition is analyzed by gas chromatography. (In the formula, R １ are the same or different and each represents a linear or branched alkyl group; R ２ represents a hydrogen atom or a linear or branched alkyl group.

10. The composition according to claim 9, wherein the content of the ether represented by the following formula (1), the ester represented by the following formula (2), or the acetal represented by the following formula (3) relative to the tetraalkoxysilane in the composition is 10% or less, based on the peak area ratio in the gas chromatograph when the composition is subjected to gas chromatography analysis.

11. The composition according to claim 9 or 10, comprising all of the ether represented by formula (1), the ester represented by formula (2), and the acetal represented by formula (3).

12. The composition according to claim 11, wherein the content ratio of the ester represented by formula (2) to the ether represented by formula (1) in the composition is 0.5 to 2.0 based on the gas chromatograph area intensity ratio when the composition is subjected to gas chromatography analysis, and the content ratio of the acetal represented by formula (3) to the ether represented by formula (1) in the composition is 0.5 to 2.0 based on the gas chromatograph peak area ratio when the composition is subjected to gas chromatography analysis.

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