A preparation method of tetraalkoxysilane

Abstract

The present invention provides a method for preparing tetraalkoxysilane, belonging to the technical field of organic chemistry. The method comprises the following steps: (1) subjecting alcohol and carbon dioxide to a dehydration reaction under the action of a catalyst; and (2) reacting the system in step (1) with nano-silicon oxide, centrifuging, and drying the filtrate to obtain tetraalkoxysilane. The present invention prepares a catalyst with a high specific surface area and high reactivity, greatly improving the catalytic activity of the catalyst, thereby enabling efficient, mild, and high-yield preparation of tetraalkoxysilane.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemistry, and in particular to a method for preparing tetraalkoxysilane. Background Art

[0002] Tetraalkoxysilane is used as a raw material for producing various silane compounds, organosilicone polymers, various silylating agents, colloidal silica, ceramics, and the like.

[0003] As a conventionally known industrial method for producing alkoxysilanes, the following method is known: natural silicon dioxide is used as a starting material, mixed with carbon, and reduced at high temperature to obtain metallic silicon, which is then reacted with chlorine to produce silicon tetrachloride, which is then reacted with alcohol (see Patent Document 1). In addition, a production method is also known in which metallic silicon is directly reacted with alcohol (see Patent Documents 2 and 3).

[0004] However, these methods all require a high-temperature metal silicon manufacturing process and have a problem of poor energy efficiency.

[0005] On the other hand, as a method for directly manufacturing alkoxysilanes from silicon dioxide, there are known methods for manufacturing alkoxysilanes by reacting silicon dioxide with alkyl carbonate using alkali metal elements or alkaline earth metal elements as catalysts (see Patent Documents 4 and 5). These methods are advantageous in terms of energy efficiency because they do not use the above-mentioned metallic silicon as a raw material. On the other hand, they require a stoichiometric amount of at least 2 times the molar amount of the silicon dioxide to be charged into a more expensive compound, namely alkyl carbonate, which presents economic problems as an industrial method for producing tetraalkoxysilanes.

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 62-114991

[0008] Patent Document 2: U.S. Patent No. 2,473,260

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2000-178283

[0010] Patent Document 4: Japanese Patent Application Laid-Open No. 2001-114786

[0011] Patent Document 5: Japanese Patent No. 3026371. Summary of the Invention

[0012] The present invention aims to provide a method for preparing tetraalkoxysilane, which is simple and greatly improves the catalytic activity of the catalyst, thereby enabling the tetraalkoxysilane to be prepared efficiently, mildly and in high yield.

[0013] The technical solution of the present invention is achieved as follows:

[0014] The present invention provides a method for preparing tetraalkoxysilane, comprising the following steps:

[0015] (1) dehydrating alcohol and carbon dioxide under the action of a catalyst;

[0016] (2) reacting the system in step (1) with nano-silicon oxide, centrifuging, and drying the filtrate to obtain tetraalkoxysilane.

[0017] As a further improvement of the present invention, the catalyst is an Al / Ti deposited UiO-66 catalyst.

[0018] As a further improvement of the present invention, the preparation method of the catalyst is as follows:

[0019] S1. Preparation of UiO-66-NH2: Zirconium tetrachloride and 2-aminoterephthalic acid were added to a DMF solution, hydrothermally reacted, centrifuged, washed, and dried to obtain UiO-66-NH2;

[0020] S2. Preparation of sol: Aluminum isopropoxide and tetrabutyl titanate were dissolved in ethanol, water was added, and stirred to form a sol;

[0021] S3. Preparation of catalyst: UiO-66-NH2 was added to the sol, dispersed evenly by ultrasonication, dried, ball-milled, and calcined to obtain the catalyst.

[0022] As a further improvement of the present invention, the molar ratio of zirconium tetrachloride to 2-aminoterephthalic acid in step S1 is 1:0.5-1.5.

[0023] As a further improvement of the present invention, the temperature of the hydrothermal reaction in step S1 is 120-140° C., and the time is 20-24 hours.

[0024] As a further improvement of the present invention, the mass ratio of aluminum isopropoxide, tetrabutyl titanate, ethanol and water in step S2 is 10-12:7-10:100-120:10-15.

[0025] As a further improvement of the present invention, the mass ratio of UiO-66-NH2 to sol in step S3 is 10:12-15.

[0026] As a further improvement of the present invention, the ball milling time in step S3 is 1-3 hours, and the calcination temperature is 400-500° C. and the calcination time is 1-3 hours.

[0027] As a further improvement of the present invention, a dehydrating agent is added in the dehydration reaction, and the added amount is 10-15 wt% of the total mass of the system.

[0028] As a further improvement of the present invention, the dehydrating agent is selected from magnesium sulfate or calcium chloride.

[0029] The present invention has the following beneficial effects:

[0030] The present invention prepares a high-surface-weight, highly reactive catalyst using a zirconium-based metal-organic framework as a support. This support significantly increases the loading capacity for aluminum and titanium, while also providing excellent catalytic performance for the reaction due to the zirconium base. The catalyst further deposits aluminum oxide and titanium oxide through a sol-gel reaction, significantly enhancing its catalytic activity. This allows for the efficient, mild, and high-yield preparation of tetraalkoxysilanes. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] Preparation Example 1 Preparation of catalyst

[0033] The following steps are involved:

[0034] S1. Preparation of UiO-66-NH2: 10 mmol of zirconium tetrachloride and 5 mmol of 2-aminoterephthalic acid were added to 200 mL of DMF solution, hydrothermally reacted at 120°C for 20 h, centrifuged, washed, and dried to obtain UiO-66-NH2;

[0035] S2. Preparation of sol: 1 g of aluminum isopropoxide and 0.7 g of tetrabutyl titanate were dissolved in 10 g of ethanol, 1 g of water was added, and stirred for 30 min to form a sol;

[0036] S3. Preparation of catalyst: 1 g UiO-66-NH2 was added to 1.2 g sol, ultrasonically dispersed at 1000 W for 10 min, dried, ball-milled for 1 h, and calcined at 400 ° C for 1 h to obtain the catalyst.

[0037] Preparation Example 2 Preparation of catalyst

[0038] The following steps are involved:

[0039] S1. Preparation of UiO-66-NH2: 10 mmol of zirconium tetrachloride and 15 mmol of 2-aminoterephthalic acid were added to 200 mL of DMF solution, hydrothermally reacted at 140°C for 24 h, centrifuged, washed, and dried to obtain UiO-66-NH2;

[0040] S2. Preparation of sol: 1.2 g of aluminum isopropoxide and 1 g of tetrabutyl titanate were dissolved in 12 g of ethanol, 1.5 g of water was added, and stirred for 30 min to form a sol;

[0041] S3. Preparation of catalyst: 1 g UiO-66-NH2 was added to 1.5 g sol, ultrasonically dispersed at 1000 W for 10 min, dried, ball-milled for 3 h, and calcined at 500 ° C for 3 h to obtain the catalyst.

[0042] Preparation Example 3 Preparation of catalyst

[0043] The following steps are involved:

[0044] S1. Preparation of UiO-66-NH2: 10 mmol of zirconium tetrachloride and 10 mmol of 2-aminoterephthalic acid were added to 200 mL of DMF solution, and the mixture was hydrothermally reacted at 130°C for 22 h. The mixture was centrifuged, washed, and dried to obtain UiO-66-NH2.

[0045] S2. Preparation of sol: 1.1 g of aluminum isopropoxide and 0.85 g of tetrabutyl titanate were dissolved in 11 g of ethanol, 1.2 g of water was added, and stirred for 30 min to form a sol;

[0046] S3. Preparation of catalyst: 1 g UiO-66-NH2 was added to 1.35 g sol, ultrasonically dispersed at 1000 W for 10 min, dried, ball-milled for 2 h, and calcined at 450 ° C for 2 h to obtain the catalyst.

[0047] Test Example 1

[0048] The specific surface areas of the catalysts prepared in Preparation Examples 1-3 were measured using a 3-FLEX 3500 multi-station high-throughput gas adsorption instrument. The results are shown in Table 1.

[0049] Table 1

[0050] Group <![CDATA[Specific surface area (m 2 / g)]]> Example 1 667.8 Example 2 671.1 Example 3 675.2

[0051] It can be seen from the above table that the catalysts prepared in Preparation Examples 1-3 of the present invention have a relatively high specific surface area.

[0052] Example 1

[0053] This embodiment provides a method for preparing tetraalkoxysilane, comprising the following steps:

[0054] (1) 3 g of methanol and carbon dioxide were subjected to a dehydration reaction in the presence of the catalyst prepared in Preparation Example 1. The carbon dioxide pressure was 1 MPa, and the amount of the catalyst added was 2 wt % of the ethanol. Magnesium sulfate was added to the dehydration reaction in an amount of 10 wt % of the total mass of the system.

[0055] (2) Add 1 g of nano-silicon oxide (average particle size of 200 nm) to the system in step (1), heat to 245° C., stir and react for 24 h, centrifuge, and dry the filtrate to obtain tetraalkoxysilane.

[0056] Example 2

[0057] This embodiment provides a method for preparing tetraalkoxysilane, comprising the following steps:

[0058] (1) 3 g of methanol and carbon dioxide were subjected to a dehydration reaction in the presence of the catalyst prepared in Preparation Example 2. The carbon dioxide pressure was 1 MPa, and the amount of the catalyst added was 2 wt % of the ethanol. Magnesium sulfate was added to the dehydration reaction in an amount of 15 wt % of the total mass of the system.

[0059] (2) Add 1 g of nano-silicon oxide (average particle size of 200 nm) to the system in step (1), heat to 245° C., stir and react for 24 h, centrifuge, and dry the filtrate to obtain tetraalkoxysilane.

[0060] Example 3

[0061] This embodiment provides a method for preparing tetraalkoxysilane, comprising the following steps:

[0062] (1) 3 g of methanol and carbon dioxide were subjected to a dehydration reaction in the presence of the catalyst prepared in Preparation Example 3. The carbon dioxide pressure was 1 MPa, and the amount of the catalyst added was 2 wt % of the ethanol. Calcium chloride was added to the dehydration reaction in an amount of 12 wt % of the total mass of the system.

[0063] (2) Add 1 g of nano-silicon oxide (average particle size of 200 nm) to the system in step (1), heat to 245° C., stir and react for 24 h, centrifuge, and dry the filtrate to obtain tetraalkoxysilane.

[0064] Comparative Example 1

[0065] Test Example 2 was conducted using the method of Example 2 in the method for producing tetraalkoxysilane of Patent 201580024399X.

[0066] The reactions in Examples 1-3 of the present invention were evaluated, and the results are shown in Table 2.

[0067] Table 2

[0068] Group Yield (%) Example 1 96 Example 2 95 Example 3 97 Comparative Example 1 89

[0069] As can be seen from the above table, the yield of tetraalkoxysilane prepared by the method in Examples 1-3 of the present invention is relatively high.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing tetraalkoxysilane, characterized in that: The following steps are involved: (1) dehydrating alcohol and carbon dioxide under the action of a catalyst; (2) reacting the system in step (1) with nano-silicon oxide, centrifuging, and drying the filtrate to obtain tetraalkoxysilane; The catalyst is an Al / Ti deposited UiO-66 catalyst; The preparation method of the catalyst is as follows: S1. Preparation of UiO-66-NH2: Zirconium tetrachloride and 2-aminoterephthalic acid were added to a DMF solution, hydrothermally reacted, centrifuged, washed, and dried to obtain UiO-66-NH2; S2. Preparation of sol: Aluminum isopropoxide and tetrabutyl titanate were dissolved in ethanol, water was added, and stirred to form a sol; S3. Preparation of catalyst: UiO-66-NH2 was added to the sol, dispersed evenly by ultrasonication, dried, ball-milled, and calcined to obtain the catalyst.

2. The preparation method according to claim 1, characterized in that The molar ratio of zirconium tetrachloride to 2-aminoterephthalic acid in step S1 is 1:0.5-1.

5.

3. The preparation method according to claim 1, characterized in that The temperature of the hydrothermal reaction in step S1 is 120-140° C., and the time is 20-24 hours.

4. The preparation method according to claim 1, characterized in that The mass ratio of aluminum isopropoxide, tetrabutyl titanate, ethanol and water in step S2 is 10-12:7-10:100-120:10-15.

5. The preparation method according to claim 1, characterized in that The mass ratio of UiO-66-NH2 to sol in step S3 is 10:12-15.

6. The preparation method according to claim 1, characterized in that The ball milling time in step S3 is 1-3 hours, and the calcination temperature is 400-500° C. and the calcination time is 1-3 hours.

7. The preparation method according to claim 1, characterized in that The dehydrating agent is added in the dehydration reaction, and the amount added is 10-15 wt% of the total mass of the system.

8. The preparation method according to claim 7, characterized in that The dehydrating agent is selected from magnesium sulfate or calcium chloride.