Preparation method of tetraalkoxysilane

Abstract

The invention provides a preparation method of tetraalkoxysilane, and belongs to the technical field of organic chemistry. Comprising the following steps: (1) carrying out a dehydration reaction on alcohol and carbon dioxide under the action of a catalyst; and (2) reacting the system in the step (1) with nano silicon oxide, centrifuging, and drying the filtrate to obtain the tetraalkoxysilane. The catalyst with high specific surface area and high reaction activity is prepared, and the catalytic activity of the catalyst is greatly improved, so that the tetraalkoxysilane can be efficiently and mildly prepared with high yield.

Description

Technical Field

[0001] The 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, and then the metallic silicon is reacted with chlorine to produce silicon tetrachloride, which is then reacted with alcohol (see Patent Document 1). In addition, a production method in which metallic silicon is directly reacted with alcohol is also known (see Patent Documents 2 and 3).

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

[0005] On the other hand, as a method for directly manufacturing alkoxysilanes from silicon dioxide, it is known that a method for manufacturing alkoxysilanes by reacting silicon dioxide with alkyl carbonate using an alkali metal element or an alkaline earth metal element as a catalyst is known (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, but on the other hand, they require a stoichiometric amount of at least 2 times the molar amount of silicon dioxide to be charged into a more expensive compound, namely alkyl carbonate, which, as an industrial method for manufacturing tetraalkoxysilanes, has economic problems.

[0006] Patent Literature

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

[0008] Patent Document 2: U.S. Patent No. 2473260

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

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

[0011] Patent document 5: Japanese Patent No. 3026371. Summary of the invention

[0012] The purpose of the present invention is to provide a method for preparing tetraalkoxysilane. The preparation method is simple and greatly improves the catalytic activity of the catalyst, so that the tetraalkoxysilane can be prepared efficiently, mildly and with high yield.

[0013] The technical solution of the present invention is achieved in this way:

[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: adding zirconium tetrachloride and 2-aminoterephthalic acid into DMF solution, hydrothermal reaction, centrifugation, washing, and drying 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 h.

[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 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 10-15wt% 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 catalyst with high specific surface area and high reaction activity, using a zirconium-based metal organic framework as a carrier. On the one hand, the carrier greatly increases the loading amount of aluminum and titanium, and on the other hand, the zirconium group can also have good catalytic performance for the reaction. The catalyst of the present invention further deposits aluminum oxide and titanium oxide through a sol-gel reaction, greatly improving the catalytic activity of the catalyst, so that tetraalkoxysilane can be prepared efficiently, mildly and with high yield. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 zirconium tetrachloride and 5 mmol 2-aminoterephthalic acid were added to 200 mL DMF solution, and the mixture was 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 zirconium tetrachloride and 15 mmol 2-aminoterephthalic acid were added to 200 mL DMF solution, and 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 zirconium tetrachloride and 10 mmol 2-aminoterephthalic acid were added to 200 mL DMF solution, and the mixture was hydrothermally reacted at 130° C. for 22 h, 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 to 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 under the action of the catalyst prepared in Preparation Example 1, the pressure of the carbon dioxide was 1 MPa, the amount of the catalyst added was 2 wt % of the ethanol, and magnesium sulfate was added in the dehydration reaction, and the amount added was 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 hours, 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 under the action of the catalyst prepared in Preparation Example 2, the pressure of the carbon dioxide was 1 MPa, the amount of the catalyst added was 2 wt % of the ethanol, and magnesium sulfate was added in the dehydration reaction, and the amount added was 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 under the action of the catalyst prepared in Preparation Example 3, the pressure of the carbon dioxide was 1 MPa, the amount of the catalyst added was 2 wt% of the ethanol, and calcium chloride was added in the dehydration reaction, and the amount added was 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] It can be seen from the above table that 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 principle of the present invention should be included in the protection scope 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.

2. The preparation method according to claim 1, characterized in that: The catalyst is an Al / Ti deposited UiO-66 catalyst.

3. The preparation method according to claim 2, characterized in that: The preparation method of the catalyst is as follows: S1. Preparation of UiO-66-NH2: adding zirconium tetrachloride and 2-aminoterephthalic acid into DMF solution, hydrothermal reaction, centrifugation, washing, and drying 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.

4. The preparation method according to claim 3, characterized in that: The molar ratio of zirconium tetrachloride to 2-aminoterephthalic acid in step S1 is 1:0.5-1.

5.

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

6. The preparation method according to claim 3, 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.

7. The preparation method according to claim 3, characterized in that: The mass ratio of UiO-66-NH2 to sol in step S3 is 10:12-15.

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

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

10. The preparation method according to claim 9, characterized in that: The dehydrating agent is selected from magnesium sulfate or calcium chloride.