Process for the preparation of tetraalkoxysilane

Abstract

A process for preparing a tetraalkoxysilane, the process comprising: a first step of the reaction of an alcohol with a silicon oxide and a second step of contacting an evaporated component of the reaction mixture obtained in the first step with a molecular sieve; where: the first step is carried out in a reactor whose temperature (T1) is controlled within the range 200°C < T1 < 300°C; the second step is carried out in a vessel whose temperature (T3) is controlled within the range 10°C ≤ T3 ≤ 150°C and which contains the molecular sieve provided therein; the vaporized component moves from the reactor to the vessel through an outward flow path whose temperature (T2) is controlled within the range 210°C ≤ T2 ≤ 300°C, where T2 > T1; a component that has been brought into contact with the molecular sieve in the second step moves from the vessel to the reactor through an inward flow path, the amount of alcohol used in the first step is one or more and 10,000 times or less, in terms of the amount of substance of the silicon oxide used, and the alcohol is an aliphatic alcohol or an aromatic alcohol, the first step is carried out at a pressure (P) of 0.1 MPa or more and 60 MPa or less, and the silicon oxide in the first step is silicon monoxide (SiO), silicon dioxide (SiO2) or is a composite oxide with another metal.

Description

TECHNICAL FIELD

[0001] The present invention relates to a process for producing a tetraalkoxysilane with high efficiency. More specifically, the present invention relates to a process for producing a tetraalkoxysilane using a molecular sieve. TECHNICAL BACKGROUND

[0002] Tetraalkoxysilanes are used as starting materials for the production of various types of silane compounds, organic silicone polymers, various types of silylating agents, colloidal silicon oxides, ceramics and the like.

[0003] Examples of conventionally known methods for industrially producing alkoxysilanes include a method in which natural silicon dioxide as a starting material is mixed with carbon, followed by reduction at a high temperature to obtain metallic silicon, the resulting metallic silicon is allowed to react with chlorine to obtain silicon tetrachloride, and the thus-obtained silicon tetrachloride is used as a starting material and allowed to react with an alcohol (see Patent Document 1). A production method in which metallic silicon is allowed to react directly with an alcohol is also known (see Patent Document 2).

[0004] However, both of these methods must involve a process for producing metallic silicon, which requires a high temperature, and therefore have problems in that they are poor in energy efficiency.

[0005] On the other hand, as a method for directly producing an alkoxysilane from silica, a method in which silica is reacted with an alkyl carbonate using an alkali metal element or an alkaline earth metal element as a catalyst to give an alkoxysilane is known (see Patent Documents 3 and 4). These methods are advantageous in terms of energy efficiency because the above-described metallic silicon is not used as a starting material. At the same time, however, these methods require the use of an alkyl carbonate, which is a relatively expensive compound, in a stoichiometric molar amount of at least twice that of silica, and are thus economically problematic as a method for industrially producing a tetraalkoxysilane.

[0006] The present inventors have found that it is possible to produce a tetramethoxysilane using methanol and a silicon oxide as starting materials, and developed a process capable of producing a tetramethoxysilane with a high yield by reacting methanol with a silicon oxide in the presence of carbon dioxide and removing water produced as a by-product using a molecular sieve (see Patent Document 5). LITERATURE LISTPATENT DOCUMENTS Patent Document 1: JP 62-114991 A Patent Document 2: US Patent No. 2473260 Patent Document 3: JP 2001-114786 A Patent Document 4: JP 3026371 B Patent Document 5: JP 2017-88498 A SUMMARY OF THE INVENTIONTechnical Problem

[0007] An object of the present invention is to provide a process capable of producing a tetraalkoxysilane with high energy efficiency and high yield. Solution to the problem

[0008] As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that it is possible to produce a tetraalkoxysilane with a high yield by connecting a reactor for reacting an alcohol with a silicon oxide and a container for bringing a vaporized component of the resulting reaction mixture into contact with a molecular sieve through an outward flow path and an inward flow path for moving the vaporized component between the reactor and the container, and further by controlling the temperature of the reactor, the temperature of the outward flow path, and the temperature of the container within respective specific ranges, thereby effectively removing water produced as a by-product.The present invention has been made on the basis of the above-described finding.

[0009] More particularly, the present invention is as defined in the claims. Advantageous effects of the invention

[0010] According to the present invention, it is possible to produce a tetraalkoxysilane with a high yield. SHORT DESCRIPTION OF THE DRAWING Fig. 1 is a schematic diagram showing an apparatus that can be used in a process for producing a tetraalkoxysilane which is an embodiment of the present invention. DESCRIPTION OF THE EMBODIMENTS

[0011] The present invention will now be described with reference to specific examples. However, it should be noted that the present invention is not limited to the description given below, as long as it does not depart from the gist of the present invention, and can be carried out with appropriate modifications. <Verfahren zur Herstellung von Tetraalkoxysilan>

[0012] The process for producing a tetraalkoxysilane (hereinafter sometimes abbreviated as the "production process according to the present invention"), which is an embodiment of the present invention, is a process including a first step of reacting an alcohol with a silicon oxide (hereinafter sometimes abbreviated as the "first step"); and a second step of bringing a vaporized component of the reaction mixture obtained in the first step (hereinafter sometimes abbreviated as the "vaporized component") into contact with a molecular sieve (hereinafter sometimes abbreviated as the "second step").This method is characterized in that the first step is carried out in a reactor whose temperature (T1) is controlled within the range of 200 °C < T1 < 300 °C (hereinafter sometimes abbreviated as the "reactor"); the second step is carried out in a vessel whose temperature (T3) is controlled within the range of 10 °C ≤ T3 ≤ 150 °C and which encloses the molecular sieve provided therein (hereinafter sometimes abbreviated as the "vessel"); the vaporized component moves from the reactor to the vessel through an outward flow path whose temperature (T2) is controlled within the range of 210 °C ≤ T2 ≤ 300 °C; and a component that has been brought into contact with the molecular sieve in the second step moves from the vessel to the reactor through an inward flow path. In addition, the amount of alcohol used in the first step is one or more times and 10.000 times or less in terms of the amount of substance of the silicon oxide used, and the alcohol is an aliphatic alcohol or an aromatic alcohol. The first step is carried out at a pressure (P) of 0.1 MPa or more and 60 MPa or less, and the silicon oxide in the first step is silicon monoxide (SiO), silicon dioxide (SiO2), or a composite oxide with another metal.

[0013] The present inventors have found that it is possible to produce a tetraalkoxysilane with a high yield by connecting the reactor for reacting an alcohol with a silicon oxide (in the first step) and the container for bringing the vaporized component of the resulting reaction mixture into contact with a molecular sieve (in the second step) through the outward flow path and the inward flow path for moving the vaporized component between the reactor and the container, and further by controlling the temperature (T1) of the reactor, the temperature (T2) of the outward flow path, and the temperature (T3) of the container within the respective specific ranges described above.

[0014] The molecular sieve is used as a desiccant to remove water generated as a byproduct of the reaction between the alcohol and the silica. However, depending on the dehydration conditions, there are cases where the water cannot be sufficiently removed, possibly leading to a decrease in the yield of the resulting tetraalkoxysilane or the decomposition of the molecular sieve.The present inventors have made it clear that by controlling the temperature (T1) of the reactor, the temperature (T2) of the outward flow path, and the temperature (T3) of the container within the respective specific ranges described above, it is possible to improve the dehydration efficiency of the molecular sieve, the transport efficiency of the evaporated component, and the like, as well as to reduce the decomposition of the molecular sieve, and as a result, a tetraalkoxysilane can be produced efficiently and stably for a long period of time.

[0015] It is noted that the definition of the term including the "first step" and the "second step" encompasses not only an embodiment in which the first step and the second step occur separately, but also an embodiment in which the first step and the second step occur simultaneously. (First step)

[0016] The first step is a step of reacting an alcohol with a silicon oxide. The type of alcohol to be used is not particularly limited, and the alcohol can be selected as appropriate depending on the desired tetraalkoxysilane to be produced. For example, tetramethoxysilane can be produced using methanol as the alcohol, and tetraethoxysilane can be produced using ethanol as the alcohol.

[0017] The alcohol is either an aliphatic alcohol or an aromatic alcohol, and the hydrocarbon group in the alcohol may have any of a branched structure, a cyclic structure, a carbon-carbon unsaturated bond, and the like.

[0018] The number of carbon atoms in the alcohol is usually one or more, and preferably two or more, and at the same time preferably 15 or less, more preferably 10 or less, and even more preferably 8 or less.

[0019] Specific examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, benzyl alcohol, and phenol. Of these, ethanol is preferred. In a process using a conventional metallic silicon, the use of an alcohol containing a larger number of carbon atoms tends to result in a decrease in the yield of the resulting tetraalkoxysilane. However, the use of the production method according to the present invention makes it possible to produce a tetraalkoxysilane with a high yield.

[0020] The amount of the alcohol to be used is one time or more, preferably five times or more, and more preferably 10 times or more, and at the same time 10,000 times or less, preferably 5,000 times or less, and more preferably 3,000 times or less, with respect to the amount of substance of the silicon oxide used.

[0021] The first step is a step of reacting an alcohol with a silicon oxide. As used herein, silicon oxide refers to a compound containing a silicon atom (Si) and an oxygen atom (O) as its main constituent elements. Specifically, the silicon oxide is silicon monoxide (SiO), silicon dioxide (SiO2), or a composite oxide with another metal, such as zeolite.

[0022] Specific examples of silica include natural minerals such as quartzite, silica sand, diatomaceous earth, and quartz; burnt ash from silicon-containing plants; volcanic ash; silicates; silica gels derived from silica sols; fumed silica; silica-alumina; and zeolites.

[0023] The first step is carried out in a reactor whose temperature (T1) is controlled within the range of 200 °C < T1 < 300 °C. The temperature (T1) is preferably 205 °C or higher, and more preferably 210 °C or higher. In the case of using ethanol as an alcohol starting material, the temperature (T1) is even more preferably 240 °C or higher, and at the same time, the temperature (T1) is preferably 280 °C or lower, and more preferably 260 °C or lower. When the temperature (T1) is within the above-described range, a tetraalkoxysilane can be produced with a higher yield.

[0024] The temperature (T1) can be controlled by heating the outer surface of the reactor using a heater or the like; circulating constant temperature water or constant temperature oil around the outer surface of the reactor; or the like.

[0025] The first step is preferably carried out in the presence of an alkali metal compound and / or an alkaline earth metal compound. When the first step is carried out in the presence of an alkali metal compound and / or an alkaline earth metal compound, the cleavage of a silicon-oxygen bond in the silicon oxide is facilitated, thereby enabling the production of a tetraalkoxysilane with a higher yield.

[0026] Examples of the alkali metal and alkaline earth metal in the alkali metal compound and the alkaline earth metal compound include lithium (Li), sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), and cesium (Cs). Examples of counterions include hydroxides, halides, oxides, carbonates, bicarbonates, alkoxides, silicates, aluminates, phosphates, organic acid salts, sulfates, and nitrates. Of these, hydroxides, halides, carbonates, and bicarbonates are preferred, and alkali metal hydroxides, alkali metal halides, alkali metal carbonates, and alkali metal bicarbonates are more preferred.

[0027] 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 can be used not only as one type, but also in combination with two or more types.

[0028] The total amount of the alkali metal compound and the alkaline earth metal compound is usually 0.0001 mol or more, preferably 0.001 mol or more, and at the same time, usually 20 mol or less, preferably 10 mol or less, with respect to 1 mol of the silicon oxide (in the case of silicon dioxide). When the total amount is within the above-described range, a tetraalkoxysilane can be produced with a higher yield.

[0029] Reaction conditions other than the temperature (T1) in the first step are not particularly limited and can be selected as appropriate depending on the purpose.

[0030] The first step is carried out at a pressure (P) of 0.1 MPa or more, preferably 1.0 MPa or more, and more preferably 2.8 MPa or more, and at the same time 60 MPa or less, preferably 30 MPa or less, and more preferably 20 MPa or less.

[0031] When the pressure (P) is within the range described above, a tetraalkoxysilane can be produced with a higher yield. (Second step)

[0032] The second step is a step of bringing a vaporized component of the reaction mixture obtained in the first step into contact with a molecular sieve. The molecular sieve is not particularly limited, and any material can be used as long as the material functions as a sieve for molecules and exhibits a dehydrating effect by absorbing water into its pores. Porous type A and type X zeolites, such as 3A, 4A, 5A, and 13X, can be preferably used. Of these, the molecular sieve is more preferably 3A and 4A, and particularly preferably 3A. When a 3A molecular sieve is used, it is possible to selectively remove water, and a tetraalkoxysilane can be produced with a higher yield.

[0033] The second step is carried out in a container whose temperature (T3) is controlled within the range of 10 °C ≤ T3 ≤ 150 °C and which encloses the molecular sieve provided therein. The temperature (T3) is preferably 30 °C or higher, and more preferably 40 °C or higher, and at the same time, preferably 80 °C or lower, and more preferably 60 °C or lower. When the temperature (T3) is within the above-described range, a tetraalkoxysilane can be produced with a higher yield.

[0034] The temperature (T3) can be controlled by heating the outer surface of the container using a heater or the like; using the heat in the first step; circulating constant temperature water or constant temperature oil around the outer surface of the container; or the like.

[0035] The device to be used in the manufacturing method according to the present invention may, for example, be the device described in Fig. 1. A specific description will be given below with reference to the device shown in Fig. 1 shown.

[0036] A device 101 that is in Fig.1 has a configuration including a reactor 106 in which the first step is performed; a container 107 enclosing a molecular sieve 105 provided therein and in which the second step is performed; an outward flow path 108 for allowing a vaporized component 104 to move from the reactor 106 to the container 107; and an inward flow path 109 for allowing a component that has been brought into contact with the molecular sieve 105 to move from the container 107 to the reactor 106. An alcohol 102, a silicon oxide 103, an alkali metal compound, and the like are introduced into the reactor 106, and the temperature (T1) is controlled within the range of 200°C < T1 < 300°C. In this manner, the first step is performed.The vaporized component 104 of the reaction mixture obtained in the first step is then introduced into the vessel 107 through the outward flow path 108, and a component that was brought into contact with the molecular sieve 105 in the second step moves back into the reactor 106 through the inward flow path 109. The temperature (T3) is controlled within the range of 10 °C ≤ T3 ≤ 150 °C, and the vaporized component 104 is brought into contact with the molecular sieve 105 in the vessel 107. In this way, the second step is carried out.Due to the difference between the temperature (T1) and the temperature (T3) and as a result of the temperature (T2) of the outward flow path 108 being controlled within the range of 210 °C ≤ T2 ≤ 300 °C, the vaporized component 104 efficiently moves from the reactor 106 to the vessel 107, and a component that has been brought into contact with the molecular sieve 105 efficiently moves from the vessel 107 to the reactor 106 without the use of a carrier gas, a compressor, or the like due to the difference in temperature and / or the difference in pressure within the reaction system.

[0037] The temperature (T2) is 210°C or higher, and at the same time, preferably 290°C or lower, and more preferably 280°C or lower. When the temperature (T2) is within the above-described range, the evaporated component and the like can move more efficiently. The temperature (T2) is a higher temperature than the temperature (T1). The temperature (T2) is preferably within the range of (T1) ± 50°C, and more preferably within the range of (T1) ± 35°C. From the viewpoint of improving the yield, the temperature (T2) is preferably higher than the temperature (T1). The temperatures (T1) and (T2) are set so that T2 > T1, so that energy saving and an improvement in yield are achieved as a result of a decrease in the temperature (T1).

[0038] The temperature (T2) can be controlled by heating the outer surface of the container using a heater or the like; using the heat in the first step; circulating constant temperature water or constant temperature oil around the outer surface of the container; or the like.

[0039] The temperature of the inward flow path is the same as the temperature (T3) and is usually 10 °C or higher, preferably 40 °C or higher, and more preferably 60 °C or higher, and at the same time usually 150 °C or lower, preferably 100 °C or lower, and more preferably 80 °C or lower.

[0040] The second step is a step of bringing the vaporized component of the reaction mixture obtained in the first step into contact with a molecular sieve, and the reaction mixture preferably does not contain a compound for conducting azeotropic distillation (hereinafter sometimes abbreviated to "compound for azeotropic distillation") and the like. Since the reaction mixture containing an alcohol and water produced as a by-product may be an azeotropic mixture, the addition of a compound for azeotropic distillation, such as benzene or xylene, may also be considered. However, in the production method according to the present invention, it is possible to produce a tetraalkoxysilane with a high yield without using a compound for azeotropic distillation.Furthermore, the use of an azeotropic distillation compound may interfere with the purification of the resulting tetraalkoxysilane to a high purity, and it is preferred that the reaction mixture does not contain an azeotropic distillation compound. EXAMPLES

[0041] The present invention will now be described more specifically with reference to examples. However, the present invention can be modified as appropriate, as long as the gist of the present invention is not deviated from. Accordingly, the scope of the present invention should not be construed as limited by the specific examples described below. <Beispiel 1>

[0042] With the upper part of a 200 mL autoclave (manufactured by Nitto Koatsu Co., Ltd.) made of SUS 316 and equipped with a mechanical stirrer, a tube made of SUS 316 and having an inner diameter of 4.6 mm, which tube was used as the outward flow path (corresponding to the part considered as 108 in Fig. 1) is to be used to make the vaporized component of the reaction mixture move therethrough and is configured to be heated with a band heater, as well as a tube made of SUS 316 and having an inner diameter of 4.6 mm, the tube being used as the inward flow path (corresponding to the part indicated as 109 in Fig.1) to be used to move a component brought into contact with the molecular sieve through. The temperature (T2) in the outward flow path piping was maintained at 249 °C during the reaction. A 30 mL portable reactor (manufactured by Taiatsu Techno Corporation) made of SUS and containing 25 g of molecular sieve 3A (in the form of 2 mm beads, manufactured by Merck KGaA) was further connected to these piping. Constant-temperature water was circulated around the exterior of the portable reactor so that the temperature (T3) of the molecular sieve portion inside the portable reactor was maintained at 53 °C. An amount of 0.9 g of silica (Wako Gel 60N, from 63 to 212 µm; manufactured by Wako Pure Chemical Industries, Ltd.), 80 g of ethanol and 0.008 g of potassium hydroxide were introduced into the autoclave.Subsequently, argon gas was introduced from a gas cylinder at a temperature of 25 °C to fill the autoclave so that the pressure therein was 0.75 MPa, as indicated by a pressure gauge (PGC-50M-MG10; manufactured by Swagelok Company). The autoclave was then kept under stirring for 10 minutes and sealed. Afterward, the autoclave was heated to 240 °C (T1) while stirring the interior of the autoclave at 500 rpm, and the reaction was allowed to proceed for six hours. The yield of the resulting tetraethoxysilane, based on silica, was 72.5%. The reaction results are shown in Table 1. <Beispiel 2 (Referenzbeispiel)>

[0043] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the temperature T2 in the outgoing piping was set to 231 °C and the temperature T3 of the molecular sieve part was set to 52 °C. The yield of the resulting tetraethoxysilane, based on silica, was 72.2%. The reaction results are shown in Table 1. <Beispiel 3 (Referenzbeispiel)>

[0044] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the temperature T2 in the outgoing piping was set to 209 °C and the temperature T3 of the molecular sieve part was set to 58 °C. The yield of the resulting tetraethoxysilane, based on silica, was 66.2%. The reaction results are shown in Table 1. <Beispiel 4>

[0045] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the reaction temperature T1 was set to 260 °C, the temperature T2 in the outgoing piping was set to 264 °C, and the temperature T3 of the molecular sieve part was set to 66.1 °C. The yield of the resulting tetraethoxysilane, based on silica, was 78.6%. The reaction results are shown in Table 1. <Beispiel 5>

[0046] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the reaction temperature T1 was set to 280 °C, the temperature T2 in the outgoing piping was set to 284 °C, and the temperature T3 of the molecular sieve part was set to 57.4 °C. The yield of the resulting tetraethoxysilane, based on silica, was 80.7%. The reaction results are shown in Table 1. <Beispiel 6>

[0047] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that 1.8 g of silica was used, 0.16 g of potassium hydroxide was used, and 90 g of molecular sieve 3A (charged into a 100 mL portable reactor made of SUS) was used under the reaction conditions of Example 1. The yield of the resulting tetraethoxysilane, based on silica, was 79.1%. The reaction results are shown in Table 1. <Beispiel 7>

[0048] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, 1.8 g of silica was used, 0.16 g of potassium hydroxide was used, and 90 g of Molecular Sieve 4A (in the form of 2 mm beads, manufactured by Merck KGaA) (filled in a 100 mL portable reactor made of SUS) was used as the molecular sieve. The yield of the resulting tetraethoxysilane based on silica was 55.2%. The reaction results are shown in Table 1. <Beispiel 8>

[0049] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that 1.8 g of silica was used in the reaction conditions of Example 1, 0.17 g of potassium fluoride was used instead of potassium hydroxide as the alkali metal compound to be added, and 90 g of molecular sieve 3A (charged into a 100 mL portable reactor made of SUS) was used. The yield of the resulting tetraethoxysilane based on silica was 91.7%. The reaction results are shown in Table 1. <Beispiel 9>

[0050] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that 1.8 g of silica was used in the reaction conditions of Example 1, 0.21 g of potassium carbonate was used instead of potassium hydroxide as the alkali metal compound to be added, and 90 g of molecular sieve 3A (charged into a 100 mL portable reactor made of SUS) was used. The yield of the resulting tetraethoxysilane based on silica was 79.6%. The reaction results are shown in Table 1. <Beispiel 10>

[0051] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that 1.8 g of silica was used in the reaction conditions of Example 1, 0.12 g of sodium hydroxide was used instead of potassium hydroxide as the alkali metal compound to be added, and 90 g of molecular sieve 3A (charged into a 100 mL portable reactor made of SUS) was used. The yield of the resulting tetraethoxysilane based on silica was 72.8%. The reaction results are shown in Table 1. <Beispiel 11>

[0052] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that 1.8 g of silica was used in the reaction conditions of Example 1, 0.11 g of sodium carbonate was used instead of potassium hydroxide as the alkali metal compound to be added, and 90 g of molecular sieve 3A (charged into a 100 mL portable reactor made of SUS) was used. The yield of the resulting tetraethoxysilane based on silica was 79.4%. The reaction results are shown in Table 1. <Beispiel 12>

[0053] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that 1.8 g of silica was used in the reaction conditions of Example 1, 0.49 g of calcium carbonate was used instead of potassium hydroxide as the alkali metal compound to be added, and 90 g of molecular sieve 3A (charged into a 100 mL portable reactor made of SUS) was used. The yield of the resulting tetraethoxysilane based on silica was 84.1%. The reaction results are shown in Table 1. <Beispiel 13>

[0054] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, 1.8 g of silica was used, 90 g of methanol was used as the alcohol to be used, 0.16 g of potassium hydroxide was used, 90 g of molecular sieve 3A (charged in a 100 mL portable reactor made of SUS) was used, the reaction temperature T1 was set to 230 °C, the temperature T2 in the outgoing piping was set to 240 °C, and the temperature T3 of the molecular sieve part was set to 60.0 °C. The yield of the resulting tetramethoxysilane based on silica was 51.0%. The reaction results are shown in Table 1. <Beispiel 14>

[0055] A tetraalkoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, 1.8 g of silica was used, 90 g of 1-propanol was used as the alcohol to be used, 0.16 g of potassium hydroxide was used, 90 g of molecular sieve 3A (charged in a 100 mL portable reactor made of SUS) was used, the reaction temperature T1 was set to 210 °C, the temperature T2 in the outgoing piping was set to 210 °C, and the temperature T3 of the molecular sieve part was set to 60.0 °C. The yield of the resulting tetrapropoxysilane based on silica was 78.7%. The reaction results are shown in Table 1. <Bezugsbeispiel 1>

[0056] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the temperature T2 in the outgoing piping was set to 246°C, 0 g of molecular sieve was used, and the temperature T3 of the molecular sieve part (internal temperature of the empty container) was set to 65°C. The yield of the resulting tetraethoxysilane, based on silica, was 20.6%. The reaction results are shown in Table 1. <Vergleichsbeispiel 1>

[0057] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the temperature T2 in the outgoing piping was set to 187°C and the temperature T3 of the molecular sieve part was set to 37°C. The yield of the resulting tetraethoxysilane, based on silica, was 20.0%. The reaction results are shown in Table 1. <Vergleichsbeispiel 2>

[0058] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the reaction temperature T1 was set to 180 °C, the temperature T2 in the outgoing piping was set to 264 °C, and the temperature T3 of the molecular sieve part was set to 41 °C. The yield of the resulting tetraethoxysilane, based on silica, was 16.0%. The reaction results are shown in Table 1. <Vergleichsbeispiel 3>

[0059] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the reaction temperature T1 was set to 200 °C, the temperature T2 in the outgoing piping was set to 325 °C, and the temperature T3 of the molecular sieve part was set to 24 °C. The yield of the resulting tetraethoxysilane, based on silica, was 34.2%. The reaction results are shown in Table 1. <Vergleichsbeispiel 4>

[0060] A tetraethoxysilane was prepared in the same manner as in Example 1, except that in the reaction conditions of Example 1, the temperature T2 in the outgoing piping was set to 360 °C and the temperature T3 of the molecular sieve part was set to 151.4 °C. The yield of the resulting tetraethoxysilane, based on silica, was 49.9%. The reaction results are shown in Table 1. Table 1 T1 [°C] T2 [°C] T3 [°C] P [MPa] Molecular sieve Alkali metal compound / alkaline earth metal compound alcohol Yield [%] type [g] type [g] Example 1 240 249 53 5,7 3A 25 KOH 0,008 EtOH 72,5 Example 2 240 231 52 5,8 3A 25 KOH 0,008 EtOH 72,2 Example 3 240 209 58 5,8 3A 25 KOH 0,008 EtOH 66,2 Example 4 260 264 66,1 8,3 3A 25 KOH 0,008 EtOH 78,6 Example 5 280 284 57,4 10,3 3A 25 KOH 0,008 EtOH 80,7 Example 6 240 249 53 5,7 3A 90 KOH 0,16 EtOH 79,1 Example 7 240 249 53 5,7 4A 90 KOH 0,16 EtOH 55,2 Example 8 240 249 53 5,7 3A 90 KF 0,17 EtOH 91,7 Example 9 240 249 53 5,7 3A 90 K2CO3 0,21 EtOH 79,6 Example 10 240 249 53 5,7 3A 90 NaOH 0,12 EtOH 72,8 Example 11 240 249 53 5,7 3A 90 Na2CO3 0,11 EtOH 79,4 Example 12 240 249 53 5,7 3A 90 Cs2CO3 0,49 EtOH 84,1 Example 13 230 240 60 6,7 3A 90 KOH 0,16 MeOH 51,0 Example 14 210 210 60 1,5 3A 90 KOH 0,16 1-ProOH 78,7 Reference example 1 240 246 65 5,9 3A 0 KOH 0,008 EtOH 20,6 Comparison example 1 240 187 37 5,7 3A 25 KOH 0,008 EtOH 20,0 Comparison example 2 180 264 41 1,78 3A 25 KOH 0,008 EtOH 16,0 Comparison example 3 200 325 24 2,7 3A 25 KOH 0,008 EtOH 34,2 Comparison example 4 240 360 151,4 5,9 3A 25 KOH 0,008 EtOH 49,9

[0061] This application is based on Japanese patent application (Japanese Patent Application No. 2017-252118) filed on December 27, 2017, the contents of which are incorporated herein by reference. INDUSTRIAL APPLICABILITY

[0062] The production method according to the present invention enables highly efficient production of a tetraalkoxysilane used as a starting material for producing various kinds of silane compounds, organic silicone polymers, various kinds of silylating agents, colloidal silicon oxides, ceramics and the like. List of reference symbols 101 Device that can be used in the manufacturing method according to the present invention 102 Alcohol 103 Silicon oxide 104 evaporated component of the reaction mixture 105 molecular sieve 106 reactor to carry out the first step 107 Containers for carrying out the second step 108 outward flow path to allow the vaporized component of the reaction mixture to move through 109 inward flow path to allow a component that has been brought into contact with the molecular sieve to move through 110 connecting part connecting between the container for performing the second step and the outward flow path

Claims

[1] A process for preparing a tetraalkoxysilane, the process comprising: a first step of the reaction of an alcohol with a silicon oxide and a second step of contacting an evaporated component of the reaction mixture obtained in the first step with a molecular sieve; where: the first step is carried out in a reactor whose temperature (T1) is controlled within the range 200°C < T1 < 300°C; the second step is carried out in a vessel whose temperature (T3) is controlled within the range 10°C ≤ T3 ≤ 150°C and which contains the molecular sieve provided therein; the vaporized component moves from the reactor to the vessel through an outward flow path whose temperature (T2) is controlled within the range 210°C ≤ T2 ≤ 300°C, where T2 > T1; a component that has been brought into contact with the molecular sieve in the second step moves from the vessel to the reactor through an inward flow path, the amount of alcohol used in the first step is one or more and 10,000 times or less, in terms of the amount of substance of the silicon oxide used, and the alcohol is an aliphatic alcohol or an aromatic alcohol, the first step is carried out at a pressure (P) of 0.1 MPa or more and 60 MPa or less, and the silicon oxide in the first step is silicon monoxide (SiO), silicon dioxide (SiO2) or is a composite oxide with another metal. [2] The process for producing a tetraalkoxysilane according to claim 1, wherein the first step is carried out in the presence of an alkali metal compound and / or an alkaline earth metal compound. [3] The process for producing a tetraalkoxysilane according to claim 2, wherein the alkali metal compound is at least one selected from the group consisting of an alkali metal hydroxide, an alkali metal halide, an alkali metal carbonate, and an alkali metal bicarbonate. [4] The process for producing a tetraalkoxysilane according to any one of claims 1 to 3, wherein the reaction mixture does not comprise a compound for conducting azeotropic distillation. [5] The process for producing a tetraalkoxysilane according to any one of claims 2 to 4, wherein the alkali metal compound and / or alkaline earth metal compound is at least one selected from the group consisting of 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. [6] The process for producing a tetraalkoxysilane according to any one of claims 1 to 5, wherein the molecular sieve is type 3A zeolite or type 4A zeolite. [7] The process for producing a tetraalkoxysilane according to any one of claims 1 to 6, wherein the alcohol is an alcohol having 1 to 10 carbon atoms.

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