A method for preparing di-tert-butoxydiacetoxysilane

Abstract

This invention relates to a method for synthesizing di-tert-butoxydiacetoxysilane, belonging to the field of silane crosslinking agent synthesis. The preparation method is a two-step process: acylation of silicon tetrachloride with acetic acid to obtain tetraacetoxysilane, followed by esterification with tert-butanol to generate the product di-tert-butoxydiacetoxysilane. This invention avoids the use of acetic anhydride, greatly improving atom utilization, simplifying the process, and reducing production costs. The use of a seed crystal precipitation process significantly shortens the induction period, accelerates the precipitation rate of the tetraacetoxysilane intermediate, and improves production efficiency. Furthermore, the crystal precipitation process carries away a large amount of acidic gas, avoiding the formation of polymers. In addition, the timely removal of byproducts generated in the system during the later stages of the esterification reaction promotes the forward reaction, greatly improving the product yield and purity.

Description

Technical Field

[0001] This invention belongs to the field of silane crosslinking agent synthesis, specifically relating to a method for preparing di-tert-butoxydiacetoxysilane. Background Technology

[0002] Di-tert-butoxydiacetoxysilane is a core component used in the production of deacidified silicone sealants. It is a small-volume, high-value-added specialty silicone product.

[0003] Currently, there are two main methods for synthesizing di-tert-butoxydiacetoxysilanes: the acetic anhydride method and the acetic acid method. The reaction of organochlorosilanes with acetic anhydride is the most commonly used method for the industrial production of organoacyloxysilanes. However, this method has drawbacks such as low utilization of acetic anhydride, large consumption, the generation of a large amount of the byproduct acetyl chloride, poor atom economy, and high price of acetic anhydride, resulting in high production costs. In contrast, the acetic acid method can significantly reduce production costs and improve atom utilization. However, the existing acetic acid method suffers from severe polymerization and poor product quality because the byproduct hydrogen chloride cannot be removed from the reaction system in a timely manner. Patent CN108586511A discloses a method for preparing di-tert-butoxydiacetoxysilanes using silicon tetrachloride, acetic acid, and tert-butanol as raw materials, but this process suffers from low product purity and a large amount of dimers and polymers generated by crosslinking. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a method for preparing di-tert-butoxydiacetoxysilane.

[0005] A method for preparing a di-tert-butoxydiacetoxysilane includes the following steps:

[0006] (A) Nitrogen purging reaction system, while the tail gas is connected to the gas scrubbing system;

[0007] (B) Tetraacetoxysilane seed crystals, inert solvent, silicon tetrachloride and acetic acid were added sequentially and reacted. After the reaction was completed, the tetraacetoxysilane intermediate was obtained by vacuum distillation at the reaction temperature.

[0008] (C) Tert-butanol is added to the tetraacetoxysilane intermediate obtained in step (B) to carry out the reaction. After the reaction reaches equilibrium, the reaction is carried out under normal pressure in a water separation reflux system to obtain the di-tert-butoxydiacetoxysilane product.

[0009] Preferably, in step (B), the amount of tetraacetoxysilane seed crystals added is 0%-3.0% of the molar amount of silicon tetrachloride.

[0010] Preferably, in step (B), the inert solvent is n-pentane, n-hexane, cyclohexane, or n-heptane, and the amount added is 10%-45% of the total mass of silicon tetrachloride and acetic acid.

[0011] Preferably, in step (B), the molar ratio of silicon tetrachloride to acetic acid is 1:(4.1-5.0).

[0012] Preferably, in step (B), the reaction temperature is 80-120℃ and the reaction time is 3-6h.

[0013] Preferably, in step (C), the molar ratio of the tetraacetoxysilane intermediate to tert-butanol is 1:(2-3).

[0014] Preferably, in step (C), the reaction conditions are: temperature of 25-60℃, reaction time of 2-5h, and after the reaction is completed, the product is obtained by reflux reaction in a water separation reflux system for 1-3h.

[0015] The beneficial effects of this invention are as follows:

[0016] (1) The seed crystal precipitation process can shorten the induction period and accelerate the precipitation rate of tetraacetoxysilane intermediate. Without seed crystals, the precipitation time is 1.5-3 hours, while with seed crystals, solid can be precipitated in 30-50 minutes, which can shorten the reaction cycle and improve production efficiency.

[0017] (2) By adopting the seed crystal precipitation process, the solid tetraacetoxysilane is precipitated and effectively removes a large amount of HCl gas from the system, promoting the forward reaction and improving the product yield and purity.

[0018] (3) Adding an appropriate amount of inert solvent can effectively remove a large amount of HCl gas from the system and improve product quality.

[0019] (4) The transesterification reaction is a reversible reaction. After the reaction reaches equilibrium, the acetic acid produced by the reaction is removed by water separation and reflux, which promotes the reaction to move in the forward direction, reduces the amount of tert-butanol used, and improves the purity and yield of the product. Detailed implementation method:

[0020] The present invention will be further described below with reference to specific embodiments. However, the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0021] Example 1

[0022] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0023] 1) The reaction system was purged with nitrogen while the reaction raw materials were added, sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0024] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1), react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0025] Example 2

[0026] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0027] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.2% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0028] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0029] Example 3

[0030] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0031] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0032] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0033] Example 4

[0034] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0035] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 1.0% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0036] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0037] Example 5

[0038] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0039] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 3.0% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0040] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0041] Example 6

[0042] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0043] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% n-pentane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0044] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0045] Example 7

[0046] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0047] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% n-hexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0048] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0049] Example 8

[0050] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0051] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% n-heptane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0052] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0053] Example 9

[0054] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0055] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 1% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0056] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0057] Example 10

[0058] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0059] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 4% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0060] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0061] Example 11

[0062] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0063] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.1), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0064] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0065] Example 12

[0066] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0067] 1) The reaction system was purged with nitrogen while the reaction raw materials were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:5.0), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0068] 2) Add tert-butanol (tetraacetoxysilane: tert-butanol = 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then reflux in a water separation reflux system for 2 hours. Separate the acetic acid generated during the reaction to obtain the di-tert-butoxydiacetoxysilane product.

[0069] Example 13

[0070] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0071] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0072] 2) Add tert-butanol (the ratio of tetraacetoxysilane to tert-butanol is 1:2) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then distill under reduced pressure at 100℃ for 30 minutes to obtain the di-tert-butoxydiacetoxysilane product.

[0073] Example 14

[0074] A method for synthesizing di-tert-butoxydiacetoxysilane comprises the following steps:

[0075] 1) The reaction system was purged with nitrogen while the reactants were added sequentially: silicon tetrachloride, acetic acid (molar ratio of silicon tetrachloride to acetic acid 1:4.5), 0.5% tetraacetoxysilane crystals (based on the molar amount of silicon tetrachloride), and 2% cyclohexane (based on the mass of silicon tetrachloride and acetic acid). The reaction was carried out at 100°C for 3 hours, and the precipitation time of the tetraacetoxysilane intermediate was observed and recorded during the reaction. After the reaction was completed, tetraacetoxysilane was obtained by vacuum distillation at this temperature.

[0076] 2) Add tert-butanol (the ratio of tetraacetoxysilane to tert-butanol is 1:2.5) to the intermediate obtained in step 1, react at room temperature for 2 hours, and then distill under reduced pressure at 100℃ for 30 minutes to obtain the di-tert-butoxydiacetoxysilane product.

[0077] To verify the impact of the formulation and process of this invention on the invention's effectiveness, comparative experiments were conducted on various process parameters, and the following results were obtained, as shown in Table 1:

[0078] Table 1

[0079]

[0080]

[0081] As shown in Table 1, the seed crystal precipitation process employed in this invention not only effectively increases the precipitation rate of tetraacetoxysilane intermediates and improves product production efficiency, but also significantly improves the yield and purity of the final product. Specifically, adding 0.5% seed crystals (based on the molar amount of silicon tetrachloride) to 1 mol of di-tert-butoxysilane diacetoxysilane product is sufficient to meet product quality standards. Adding an appropriate proportion of inert solvent effectively removes a large amount of HCl gas from the system, reducing polymer formation and improving product quality. Adding 2% cyclohexane yields the best effect (based on the combined mass of silicon tetrachloride and acetic acid). Furthermore, the transesterification reaction employs a simultaneous reaction and extraction process, driving the reaction forward and significantly reducing the amount of tert-butanol used, while simultaneously improving the yield and purity of the final product. Comparing Examples 2 and 3, it is evident that crystals promote precipitation, but too few crystals will dissolve in acetic acid, hindering precipitation; only a concentration of 0.5% is sufficient to achieve the desired precipitation effect. Examples 9 and 10 show that the amount of hydrogen chloride removed was insufficient, resulting in low purity. Increasing the inert solvent to 4% and 2% yielded similar results. Examples 13 and 14 show that separating byproducts during the reaction in the second step is beneficial for improving conversion rate and reducing the amount of tert-butanol used.

[0082] The above description is only a preferred embodiment of the present invention, but not every embodiment contains only one independent technical solution. Any equivalent substitutions or changes made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the protection scope of the present invention.

Claims

1. A method for preparing di-tert-butoxydiacetoxysilane, characterized in that, Includes the following steps: (A) The reaction system is purged with nitrogen, and the tail gas is connected to the gas scrubbing system. (B) Add tetraacetoxysilane seed crystals, inert solvent, silicon tetrachloride and acetic acid sequentially. After the reaction is completed, distill under reduced pressure at the reaction temperature to obtain the tetraacetoxysilane intermediate. The amount of tetraacetoxysilane seed crystals added is 0.5%-3.0% of the molar amount of silicon tetrachloride. The inert solvent is cyclohexane, and the amount added is 2% or 4% of the total mass of silicon tetrachloride and acetic acid. (C) Tert-butanol is added to the tetraacetoxysilane intermediate obtained in step (B) to carry out the reaction. After the reaction reaches equilibrium, the reaction is carried out under normal pressure in a water separation reflux system to obtain the di-tert-butoxydiacetoxysilane product.

2. The method for preparing di-tert-butoxydiacetoxysilane according to claim 1, characterized in that, In step (B), the molar ratio of silicon tetrachloride to acetic acid is 1:(4.1-5.0).

3. The method for preparing di-tert-butoxydiacetoxysilane according to claim 1, characterized in that, In step (B), the reaction temperature is 80-120℃ and the reaction time is 3-6h.

4. The method for preparing di-tert-butoxydiacetoxysilane according to claim 1, characterized in that, In step (C), the molar ratio of tetraacetoxysilane intermediate to tert-butanol is 1:(2-3).

5. The method for preparing di-tert-butoxydiacetoxysilane according to claim 1, characterized in that, In step (C), the reaction conditions are: temperature 25-60℃, reaction time 2-5h, after the reaction is completed, reflux reaction in the water separation reflux system for 1-3h to obtain di-tert-butoxydiacetoxysilane product.

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