A method for dehydration with a dehydrating agent and assisted catalytic synthesis of alkoxysilanes

Abstract

This invention relates to a method for dehydration using a dehydrating agent and for the catalytic synthesis of alkoxysilanes. An appropriate amount of silicon source is added to excess alcohol, heated to 150-160°C, and stirred for 0.5-1 hour. After nitrogen purging, the mixture is cooled to room temperature. Under nitrogen protection, a catalyst and a dehydrating agent are rapidly added, and the reaction is carried out under a nitrogen atmosphere. After the reaction is complete, the mixture is filtered. The filtrate is then purged with nitrogen and distilled under reduced pressure to remove unreacted alcohol. The distillation residue is added to an organic solvent, stirred, and filtered. The solvent is removed by distillation under reduced pressure to obtain alkoxysilanes. This method utilizes widely available raw materials, has low cost, low energy consumption, and is environmentally friendly.

Description

Technical Field

[0001] This invention relates to the synthesis of alkoxysilanes, particularly the synthesis of tetranonyl orthosilicate and tetradecyl orthosilicate. Background Technology

[0002] The preparation of organoalkoxysilanes mainly involves two methods: chlorosilane alcoholysis and direct reaction of lower aliphatic alcohols with elemental silicon. Both methods use elemental silicon as the starting point, resulting in high raw material costs, high energy consumption, and severe pollution. This invention uses diatomaceous earth and silicic acid as silicon sources to prepare organoalkoxysilanes. Diatomaceous earth is abundant in nature, inexpensive, and readily available; silicic acid is produced by the reaction of silicates with acids, a simple and inexpensive process that is readily available in large quantities. The main mineral component of diatomaceous earth is opal (SiO2·nH2O), a standard aggregate hydrogel mineral formed by the partial dehydration of hydrated silica gel, generally referred to as a hydrated colloidal mineral or colloidal mineral. Its silica is amorphous and highly reactive. However, due to the high amount of bound water in opal, a significant amount of water is generated during the reaction, and the bound water within the opal becomes free water, affecting the reaction process. Silicic acid (H2SiO3) is a glassy, ​​colorless, transparent, amorphous particle, but it also generates two molecules of water during the reaction, affecting the reaction process.

[0003] Therefore, this invention provides a method for directly synthesizing alkoxysilanes from diatomaceous earth and silicic acid using alcohols. By selecting suitable catalysts and dehydrating agents, and directly using internal dehydration methods within the system, the water generated during the reaction is promptly reacted away. Calcium hydroxide, formed by the reaction of calcium oxide with the water generated during the process, is a strong base and can assist in catalyzing the reaction between the silicon source and the alcohol. This method is highly effective in assisting the reaction of diatomaceous earth and silicic acid, which produces a significant amount of water during the reaction process, with alcohols. Furthermore, the dehydrating agent used is inexpensive, readily available, and environmentally friendly. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for dehydration using a dehydrating agent and assisted catalytic synthesis of alkoxysilanes. The method includes the following steps: adding an appropriate amount of silicon source to excess alcohol, heating to 150-160 °C, maintaining the temperature and stirring for 0.5-1 hour, purging with nitrogen, cooling to room temperature, rapidly adding a catalyst and dehydrating agent under nitrogen protection, and carrying out the reaction under a nitrogen atmosphere. After the reaction is complete, filtering is performed, and the filtrate is purged with nitrogen and then distilled under reduced pressure to remove unreacted alcohol. The distillation residue is added to an organic solvent, stirred, and then filtered. The filtrate is then distilled under reduced pressure to remove the solvent, yielding alkoxysilanes.

[0005] In the above scheme, the silicon source is diatomaceous earth or silica.

[0006] In the above scheme, the alcohol is n-nonanol or n-decanol.

[0007] In the above scheme, the catalyst is anhydrous magnesium chloride or anhydrous aluminum chloride.

[0008] In the above scheme, the dehydrating agent is calcium oxide, and the molar ratio of silicon source to calcium oxide is 1:1~3.

[0009] The heat preservation reaction temperature is 210 ℃~250 ℃, and the heat preservation reaction time is 4-12 h.

[0010] First, the mixture of silicon source and alcohol is heated to initially decompose the silicon source into water, reducing the amount of water released during the reaction. The alkoxy radicals (-OR) released from the alcohol at high temperature react with the silicon source under the action of a catalyst to produce alkoxysilanes. The reaction is accompanied by the generation of water as a byproduct. Calcium oxide absorbs water to form calcium hydroxide. Calcium hydroxide provides an alkaline environment, promoting the generation of alkoxy radicals (-OR). The alkoxy radicals react with the silicon source to form alkoxysilanes.

[0011] The beneficial effects of this invention are as follows: 1) This invention uses inexpensive silicon sources such as diatomaceous earth, reducing production costs; 2) This invention directly uses diatomaceous earth and silicic acid as silicon sources, avoiding the process of reducing silicon dioxide to elemental silicon and preparing silicon dioxide. The reaction process is short, energy consumption is low, and it is environmentally friendly. Attached Figure Description

[0012] Figure 1 The infrared spectrum of tetranonyl orthosilicate prepared in Example 1 is shown.

[0013] Figure 2 The infrared spectrum of tetradecyl orthosilicate prepared in Example 7 is shown. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below.

[0015] Example 1

[0016] 1.95 g of silicic acid was added to excess n-nonyl alcohol, stirred and heated to 155 °C, and maintained at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.95 g of anhydrous magnesium chloride and 1 g of calcium oxide were quickly added. After nitrogen purging, the mixture was reacted at 220 °C for 4 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 140 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to ethanol and stirred for 1 hour, then filtered. The ethanol was removed by rotary evaporation of the filtrate at 60 °C to obtain oily tetranonyl orthosilicate, with a yield of 63.2%. Its infrared spectrum is shown below. Figure 1 As shown, 1455cm -1 The peak at 2924 cm⁻¹ represents the bending vibration of the methylene group. -1The peak at 2957 cm⁻¹ represents the asymmetric stretching vibration of the methylene group. -1 The peak at 2854 cm⁻¹ represents the asymmetric stretching vibration of the methyl group. -1 The peak at 1087 cm⁻¹ represents the symmetric stretching vibration of the methylene group. -1 and 880 cm -1 The peak value for the stretching vibration of Si-OC is 1043 cm⁻¹. -1 The peak at this location represents the stretching vibration of CO.

[0017] Example 2

[0018] 1.90 g of silicic acid was added to excess n-nonyl alcohol, stirred and heated to 150 °C, and maintained at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.98 g of anhydrous magnesium chloride and 1.2 g of calcium oxide were quickly added. After nitrogen purging, the mixture was reacted at 217 °C for 5 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. The filtrate was then purged with nitrogen and distilled under reduced pressure at 140 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to methanol and stirred for 1 hour, then filtered. The filtrate was then rotary evaporated at 40 °C to remove methanol, yielding oily tetranonyl orthosilicate with a yield of 66.1%.

[0019] Example 3

[0020] 1.64 g of diatomaceous earth was added to excess n-nonyl alcohol, stirred and heated to 155 °C, and kept at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 1.01 g of anhydrous magnesium chloride and 1.6 g of calcium oxide were quickly added. After nitrogen purging, the mixture was kept at 218 °C for 5 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 150 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to isopropanol and stirred for 1 hour, then filtered. The isopropanol was removed by rotary evaporation at 80 °C to obtain oily tetranonyl orthosilicate, with a yield of 61.3%.

[0021] Example 4

[0022] 1.7 g of diatomaceous earth was added to excess n-nonyl alcohol, stirred and heated to 155 °C, and kept at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.96 g of anhydrous magnesium chloride and 2 g of calcium oxide were quickly added. After nitrogen purging, the mixture was kept at 222 °C for 5 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 140 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to ethanol and stirred for 1 hour, then filtered. The ethanol was removed by rotary evaporation of the filtrate at 60 °C to obtain oily tetranonyl orthosilicate, with a yield of 59.8%.

[0023] Example 5

[0024] 1.80 g of diatomaceous earth was added to excess n-nonyl alcohol, stirred and heated to 155 °C, and kept at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.99 g of anhydrous magnesium chloride and 1.3 g of calcium oxide were quickly added. After nitrogen purging, the mixture was kept at 220 °C for 6 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 145 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to ethanol and stirred for 1 hour, then filtered. The filtrate was rotary evaporated at 60 °C to remove the ethanol, yielding oily tetranonyl orthosilicate with a yield of 60.2%.

[0025] Example 6

[0026] 2.00 g of silicic acid was added to excess n-nonyl alcohol, stirred and heated to 155 °C, and maintained at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.95 g of anhydrous magnesium chloride and 1.6 g of calcium oxide were quickly added. After nitrogen purging, the mixture was reacted at 218 °C for 6 hours under a carbon dioxide atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 140 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to isopropanol and stirred for 1 hour, then filtered. The isopropanol was removed by rotary evaporation of the filtrate at 80 °C to obtain oily tetranonyl orthosilicate, with a yield of 66.7%.

[0027] Example 7

[0028] 1.80 g of diatomaceous earth was added to excess n-decanol, stirred and heated to 153 °C, and kept at this temperature for 0.5 hours. Nitrogen was applied three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.95 g of anhydrous magnesium chloride and 1 g of calcium oxide were quickly added. After nitrogen purging, the reaction was maintained at 235 °C for 6 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 160 °C to remove unreacted n-decanol. The distilled n-decanol was collected and recycled. The residue was added to ethanol and stirred for 1 hour, then filtered. The ethanol was removed by rotary evaporation at 60 °C to obtain an oily tetradecyl orthosilicate. Cooling to 25 °C and solidifying yielded a waxy solid, with a yield of 58.9%. Its infrared spectrum is shown below. Figure 2 As shown, its infrared spectrum is as follows Figure 2 As shown, 1468 cm -1 The peak at 2916 cm⁻¹ represents the methylene bending vibration. -1 The peak at 2954 cm⁻¹ represents the asymmetric stretching vibration of the methylene group. -1 The peak at 2850 cm⁻¹ represents the asymmetric stretching vibration of methyl groups. -1 The peak at 1089 cm⁻¹ represents the methylene symmetric stretching vibration. -1 and 881 cm -1The peak at 1048 cm⁻¹ represents the stretching vibration of Si-OC. -1 The peak at this point corresponds to the CO stretching vibration. This confirms that the product is tetradecyl orthosilicate.

[0029] Example 8

[0030] 2.01 g of silicic acid was added to excess n-decanol, stirred and heated to 153 °C, and kept at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and cooled to 25 °C. Under nitrogen protection, 0.01 g of anhydrous magnesium chloride and 2.00 g of calcium oxide were rapidly added. After nitrogen purging, the mixture was reacted at 240 °C for 6 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 170 °C to remove unreacted n-decanol. The distilled n-decanol was collected and recycled. The residue was added to methanol and stirred for 1 hour, then filtered. The filtrate was rotary evaporated at 45 °C to remove methanol, yielding an oily tetradecyl orthosilicate. Upon cooling to 25 °C, the solid solid solidified, yielding a yield of 68.1%.

[0031] Example 9

[0032] 1.91 g of silicic acid was added to excess n-decanol, stirred and heated to 153 °C, and kept at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times and cooled to 25 °C. Under nitrogen protection, 0.98 g of anhydrous magnesium chloride and 1.10 g of calcium oxide were rapidly added, and the reaction was maintained at 230 °C for 6 hours under a nitrogen atmosphere. The mixture was then cooled to 40 °C and filtered. After purging with nitrogen, the filtrate was distilled under reduced pressure at 160 °C to remove unreacted n-decanol. The distilled n-decanol was collected and recycled. The residue was added to isopropanol and stirred for 1 hour, then filtered. The isopropanol was removed by rotary evaporation at 80 °C to obtain an oily tetradecyl orthosilicate. Cooling to 25 °C solidified the solid to obtain a waxy substance with a yield of 65.5%.

[0033] Example 10

[0034] 1.71 g of diatomaceous earth was added to excess n-decanol, stirred and heated to 153 °C, and kept at this temperature for 0.5 hours. Nitrogen was purged three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.96 g of anhydrous magnesium chloride and 1.00 g of calcium oxide were quickly added. After nitrogen purging, the reaction was maintained at 235 °C for 5 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 160 °C to remove unreacted n-decanol. The distilled n-decanol was collected and recycled. The residue was added to ethanol and stirred for 1 hour, then filtered. The ethanol was removed by rotary evaporation at 60 °C to obtain an oily tetradecyl orthosilicate. Cooling to 25 °C solidified to obtain a waxy solid, with a yield of 58.1%.

[0035] Example 11

[0036] 1.75 g of diatomaceous earth was added to excess n-decanol, stirred and heated to 153 °C, and kept at this temperature for 0.5 hours. Nitrogen was purged three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.95 g of anhydrous magnesium chloride and 1.20 g of calcium oxide were quickly added. After nitrogen purging, the reaction was maintained at 230 °C for 5 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 165 °C to remove unreacted n-decanol. The distilled n-decanol was collected and recycled. The residue was added to methanol and stirred for 1 hour, then filtered. The filtrate was rotary evaporated at 50 °C to remove methanol, yielding an oily tetradecyl orthosilicate. Cooling to 25 °C solidified the solid to obtain a waxy substance with a yield of 59.6%.

[0037] Comparative Example 1

[0038] 1.92 g of silicic acid was added to excess n-nonyl alcohol, stirred and heated to 153 °C, and maintained at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.99 g of anhydrous magnesium chloride was quickly added. After nitrogen purging, the mixture was reacted at 217 °C for 5 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. After nitrogen purging, the filtrate was distilled under reduced pressure at 140 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to methanol and stirred for 1 hour, then filtered. The filtrate was rotary evaporated at 40 °C to remove methanol, yielding oily tetranonyl orthosilicate with a yield of 5.5%.

[0039] Comparative Example 2

[0040] 1.65 g of diatomaceous earth was added to excess n-nonyl alcohol, stirred and heated to 153 °C, and kept at this temperature for 0.5 hours. The mixture was then purged with nitrogen three times, and the temperature was lowered to 25 °C. Under nitrogen protection, 0.98 g of anhydrous magnesium chloride was quickly added. After nitrogen purging, the mixture was kept at 217 °C for 5 hours under a nitrogen atmosphere, and then cooled to 40 °C and filtered. The filtrate was then purged with nitrogen and distilled under reduced pressure at 140 °C to remove unreacted n-nonyl alcohol. The distilled n-nonyl alcohol was collected and recycled. The residue was added to methanol and stirred for 1 hour, then filtered. The filtrate was then rotary evaporated at 40 °C to remove methanol, yielding oily tetranonyl orthosilicate with a yield of 3.1%.

Claims

1. A method for dehydration with a dehydrating agent and assisted catalytic synthesis of alkoxysilanes, characterized in that, The process includes the following steps: Add an appropriate amount of silicon source to excess alcohol, heat to 150-160 °C, stir for 0.5-1 hour, purge with nitrogen, cool to room temperature, rapidly add catalyst and dehydrating agent under nitrogen protection, heat to react under nitrogen atmosphere, filter after reaction, purge with nitrogen and then distill under reduced pressure to remove unreacted alcohol, add organic solvent to the distillation residue, stir and filter, distill under reduced pressure to remove solvent, and obtain alkoxysilane. The alcohol is n-nonanol or n-decanol, the dehydrating agent is calcium oxide, and the molar ratio of silicon source to calcium oxide is 1:1~3. The reaction temperature is 210 °C~250 °C, the reaction time is 4-12 h, and the catalyst is anhydrous magnesium chloride or anhydrous aluminum chloride.

2. The method for dehydration with a dehydrating agent and assisted catalytic synthesis of alkoxysilanes according to claim 1, characterized in that, The silicon source is diatomaceous earth or silica.

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