RU2842998C1 - Method of producing organoalkoxy silanes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing organoalkoxysilanes. Disclosed is a method of producing organoalkoxysilanes by direct reaction of silicon with a simple symmetric or asymmetric ether, which involves reaction of technical crude silicon and an ether of general formula R¹OR², where R¹ and R² independently denote Me, Et, n-Pr, n-Bu, Ar, using copper catalyst in presence of promoting additives in vibrofluidized bed of grinding bodies at temperature of 100-300 °C. Method enables to obtain organoalkoxysilanes via direct synthesis without using carcinogenic organohalides and organic precursors susceptible to thermal decomposition with virtually complete conversion of silicon.

EFFECT: reducing the number of process steps and minimizing the total duration of the process, reducing power consumption and providing environmental friendliness of production.

8 cl, 2 dwg, 1 tbl, 18 ex

Description

Field of technology to which the invention relates

The invention relates to chemical technology, in particular to methods for producing organosilicon compounds, namely to methods for producing organoalkoxysilanes. Organoalkoxysilanes are important products from an industrial and commercial point of view, which are used in the production of binding agents for many industries, including the production of adhesives and sealants, coatings, plastics, fabrics, medical equipment, cosmetics, etc. The invention can be most effectively used in the chemical and pharmaceutical industries.

State of the art

The main industrial method for obtaining organoalkoxysilanes is the esterification of the corresponding chlorosilanes. The disadvantages of this method are the formation of a large amount of hydrochloric acid waste, a low yield of target alkoxysilanes, and the use of chlorosilanes as starting materials.

A method for producing methyldimethoxysilane by reacting metallic silicon and methanol in a flow reactor in the presence of copper(I) chloride catalyst and thiophene at a temperature of 280-450°C is known [Okamoto, M.; Abe, H.; Kusama, Y.; Suzuki, E.; Ono, Y. Direct Synthesis of Methyldimethoxysilane from Metallic Silicon and Methanol Using Copper(I) Chloride Catalyst. J. Organomet. Chem. 2000, 616 (1-2), 74-79. https://doi.org/10.1016/S0022-328X(00X)0543-X1. The method allows to obtain methyldimethoxysilane with a selectivity of 22% at a silicon conversion of 40%. The disadvantages of the method are: the need for preliminary treatment of silicon grains with hydrofluoric acid to remove the oxide film, preliminary heating of a mixture of silicon and copper chloride in a helium stream at a temperature of 450°C, and a lower demand for methyl compared to dimethyldimethoxysilane.

A method for producing ethyl dimethoxysilane by reacting metallic silicon with ethylene and methanol in the presence of copper (I) chloride in a high-pressure flow reactor is known [Okamoto, M.; Komai, J. I.; Uematsu, M.; Suzuki, E.; Ono, Y. Direct Synthesis of Alkyldialkoxysilanes by the Reaction of Silicon, Alcohol and Alkene Using a High-Pressure Row Reactor. J. Organomet. Chem. 2001, 619 (1-2), 235-240. https://doi.org/10.1016/S0022-328X(00)00681-1]. The method allows one to obtain ethyl dimethoxysilane with a selectivity of 33% at a silicon conversion of 60%. The disadvantages of the method are: the need for preliminary activation of silicon with hydrofluoric acid to remove the oxide film, treatment of the inner wall of the reactor with a layer of silicon oxide to prevent the formation of a copper alloy as a result of the reaction of stainless steel with copper and side reactions of reagents and/or products on stainless steel, treatment of the reaction products with ethylbenzene, low yield of the resulting alkoxysilane, lower demand for ethyldimethoxysilane compared to dimethyldimethoxysilane.

A method for producing methylmethoxysilanes from metallic silicon and dimethyl carbonate in the presence of copper(I) chloride by adding tin chloride (SnCl ₂ ) in a fixed-bed reactor at a temperature of 350°C is known [Patent US11319335 B2 (2022)]. The method allows for producing dimethyldimethoxysilane with a selectivity of 56-62%. The disadvantages of the method are: the need for preliminary preparation of the silicon-copper contact mass by heating at 400°C in a hydrogen atmosphere for its activation, as well as the decomposition of dimethyl carbonate under the reaction conditions, which leads to a significant decrease in the productivity of the process and the appearance of a large number of by-products.

A method is known for producing organoalkoxysilanes by reacting metallic silicon with a dialkyl ether in the presence of catalytic amounts of chlorine- or bromine-containing compounds (metal halides, hydrogen halides, halosilanes and siloxanes, organohalides) in an autoclave at a temperature of 200 to 300°C [US 4088669 A, 1978]. The method makes it possible to produce organoalkoxysilanes, specifically methylmethoxysilanes, with a selectivity for dimethyldimethoxysilane of 13-64%. The disadvantages of the method are: the need for preliminary activation of silicon in the presence of copper powder in a hexane solution, a low reaction rate, and the presence of halogen-containing impurities in the reaction products.

A method for producing methylmethoxysilanes by reacting metallic silicon with dimethyl ether (DME) and carbon dioxide (CO ₂ ) in the presence of copper(I) chloride (CuCl) with the addition of tin chloride (SnCl ₂ ) at a temperature of 150-400 ° C is known [US 20210292346 A1, 2021]. The method allows to obtain methylmethoxysilanes, specifically dimethyldimethoxysilane (Me ₂ Si(OMe) ₂ ) with a selectivity of 52 mol.%, methyltrimethoxysilane (MeSi(OMe) ₃ ) with a selectivity of 26 mol.%, tetramethoxysilane (TMOS) with a selectivity of 13 mol.%, the formation of linear dimethylsiloxanes (9 mol.%) is also observed. The conversion of Me ₂ O is 0.1 mol.%. The disadvantages of the method are: the need for preliminary preparation of the contact mass by heating at 400°C in a hydrogen atmosphere for its activation, the use of _CO2 , which leads to a decrease in the reaction rate and a decrease in the productivity of the process, limitations on the loading of promoting additives, which leads to low values of conversion of DME and silicon.

The common disadvantages of the known methods for obtaining organoalkoxysilanes are: low yield of the final products obtained, multi-stage processes, including preliminary preparation of silicon using aggressive reagents such as HF and activation of the silicon-copper contact mass, carried out at high temperatures, low productivity of the processes.

An alternative to the above-mentioned methods for obtaining organoalkoxysilanes are mechanochemical, chlorine-free, environmentally friendly synthesis methods, which make it possible to abandon the mass use of chlorosilanes and create opportunities for the production of silicones at any chemical plant.

The prior art discloses methods for the mechanochemical synthesis of tri- and tetraalkoxysilanes, including the interaction of metallic silicon with an aliphatic alcohol containing 1 to 4 carbon atoms at a temperature of 200-300°C in the presence of a copper-containing catalyst or using grinding media made of copper or a copper-containing alloy, which are carried out in a vibrofluidized bed of grinding media with an oscillation acceleration of 26.6 to 985.9 m/s [RU Patent 2628299, IPC C07F 7/02, C07F 7/04, Bulletin 23, 2017; RU Patent 2801799, IPC C07F 7/04, C07F 7/18, Bulletin 23, 2023]. During the grinding process, silicon is mechanically activated, i.e. its transfer to a reactive state due to the destruction of the silicon oxide film, multiple increase and renewal of its specific surface. Simultaneously with the grinding process, the alcohol vapors entering the reactor interact with the mechanically activated silicon, resulting in the formation of alkoxysilanes. The alkoxysilane vapors are removed from the reactor, condensed in the refrigerator, and the finished product enters the receiver.

The disadvantage of these methods is that they do not allow the production of organoalkoxysilanes, which are more valuable and in-demand products compared to alkoxysilanes.

The current technical problem is the elimination of the above-mentioned shortcomings of known technical solutions and the development of a technological method for obtaining organoalkoxysilanes to create an environmentally friendly large-tonnage production.

The objective of the present invention is to develop an effective, environmentally friendly method for obtaining organoalkoxysilanes, which allows for a reduction in the overall time of its implementation, eliminating the use of aggressive reagents, solvents and organohalides, which could become promising for the creation of industrial production.

Disclosure of the essence of the invention

The technical result, which the claimed invention is aimed at achieving, consists in reducing the number of stages of the process and minimizing the total time of its implementation, reducing energy consumption and ensuring environmentally friendly production.

The technical result is achieved by the declared method of obtaining

organoalkoxysilanes of the general formula R ¹ _(4-a) Si(OR ² ) _a , where R ¹ and R ² independently denote Me, Et, n-Pr, n-Bu, Ar, the index a denotes an integer from 1 to 4, by direct synthesis from silicon and a symmetrical or asymmetrical ether of the general formula R ¹ OR ² , where R ¹ and R ² independently denote Me, Et, n-Pr, n-Bu, Ar, including mechanical activation of silicon in the presence of a copper-containing catalyst and promoting additives in a vibratory fluidized bed of grinding bodies with a diameter of 1-20 mm and subsequent interaction of activated silicon with ether vapors at 100-300°C, which leads to the formation of organoalkoxysilanes.

The simple ether used is a symmetrical ether selected from the group including dimethyl, diethyl, dipropyl, dibutyl, diphenyl ether, or an unsymmetrical ether selected from the group including methyl ethyl, methyl propyl, methyl phenyl ether.

Copper (I) salts (halides, nitrate, sulfate), copper (II) salts (halides, nitrate, sulfate), copper (I) oxide, copper (II) oxide, copper powder, mixtures of two or more copper compounds in an amount of 0.1-20 wt.% are used as a copper catalyst.

The following are used as promoting additives: zinc (Zn), zinc compounds, tin (Sn), tin compounds, mercury (Hg), mercury compounds, aluminum (Al), aluminum compounds, phosphorus (P), phosphorus compounds, arsenic (As), arsenic compounds, antimony (Sb), antimony compounds, mixtures of two or more compounds in an amount of 0.1 - 20,000 ppm. The method uses grinding bodies made of materials such as zirconium oxide, stainless steel, brass, tungsten carbide, silicon nitride.

The claimed method for the direct synthesis of organoalkoxysilanes is carried out in a reactor comprising a working chamber equipped with grinding bodies made of copper or a copper-containing alloy, an electric heater, process pipes and mounted on a vibration drive or similar [RU Patent No. 2671732, Bulletin No. 31, 2018; RU Patent No. 2752507, Bulletin No. 22, 2021]. The reactor is loaded with an initial sample of silicon, grinding bodies, a copper-containing catalyst, promoting additives and ether. The working chamber is heated in the temperature range of 100-300 °C and the reactor vibration drive is turned on with an oscillation acceleration of 26.6 to 985.9 m/s ² . Under the action of vibrations, the grinding bodies pass into a vibroboiling state, due to which the grinding and mechanical activation of silicon occurs, i.e. its transfer into a reactive state due to the destruction of the oxide film, multiple increase and renewal of its specific surface. Activated silicon enters into interaction with ether, and direct synthesis of organoalkoxysilanes occurs within 50-300 min. After the specified time, the mixture is cooled to room temperature. Liquid reaction products are analyzed by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), IR spectroscopy, NMR spectroscopy. The contact mass is analyzed by powder X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS).

The method according to the invention makes it possible to obtain organoalkoxysilanes of the general formula R ¹ _(4-a) Si(OR ² ) _a , where R ¹ and R ² independently denote Me, Et, n-Pr, n-Bu, Ar, the index a denotes an integer from 1 to 4. Examples of organoalkoxysilanes obtained by the present method include dimethyldiethoxysilane (Me ₂ Si(OEt) ₂ ), trimethylmethoxysilane (Me ₃ SiOMe), diethyldimethoxysilane (Et ₂ Si(OMe) ₂ ), dimethyldimethoxysilane (Me ₂ Si(OMe) ₂ ), methyltrimethoxysilane (MeSi(OMe) ₃ ), tetramethoxysilane (TMOS) and combinations of two or more of Me ₂ Si(OEt) ₂ , Me ₃ SiOMe, Et ₂ Si(OMe) ₂ , Me ₂ Si(OMe) ₂ , MeSi(OMe) ₃ and TMOS.

The advantages of the claimed method are: the absence of the stage of purification of technical silicon from the oxide film in the presence of hydrofluoric acid, the exclusion of the process of preliminary preparation of the contact mass at high temperatures in a hydrogen atmosphere. The use of mechanical activation allows to significantly reduce the reaction temperature and increase the process rate. The method allows to use a high concentration of the promoter, which is of decisive importance for the activation of ether molecules. Simple ethers are chlorine-free analogues of alkyl chlorides, which allows to carry out the direct synthesis of organoalkoxysilanes without the use of carcinogenic organohalides and organic precursors prone to thermal destruction. The claimed method makes it possible to obtain organoalkoxysilanes with high selectivity for diorganodialkoxysilane with almost complete conversion of silicon.

Brief description of the drawings

Fig. 1 shows a chromatogram (GC) of the product mixture obtained in Example 1. The products were assigned in accordance with the GC-MS method. Based on the chromatogram, the obtained methylmethoxysilanes were identified and the selectivity of their formation was determined.

Fig. 2 shows diffraction patterns of samples of the contact mass used in Example 1, taken after 20, 60, 120 and 240 min of simultaneous heating and vibration of the reaction mixture. Figure 2 demonstrates 100% conversion of silicon upon completion of the reaction (Example 1).

The technical result is achieved by a combination of all essential features of the invention. The results obtained are presented in the table. The invention is illustrated by the examples of its implementation given below.

As a result of searching for analogues of the claimed invention in patent and scientific and technical sources of information, it was not possible to find an analogue characterized by features identical to all essential features of the claimed method.

Implementation of the invention:

Example 1

Silicon KR-1 technical (particle size 1-1.5 mm, 1 g, 36 mmol), copper(I) chloride (0.2 g), Zn powder (0.02 g), Sn powder (0.03 g) and grinding media (balls with a diameter of 1 - 20 mm (ZrO ₂ (stabilized Y ₂ O ₃ )) 14 pcs., 38.38 g) are loaded into the working chamber and filled with dimethyl ether (3.3 g) while cooling using an INFLOW mass flow meter (Bronkhorst, Netherlands). After that, the vibration drive and electric heater are turned on. The reaction is carried out at a temperature of 250 °C. After 240 min of simultaneous heating and vibration, the mixture is cooled to room temperature. Liquid reaction products are analyzed by GC, GC-MS, NMR, IR. The contact mass (CM) is separated from the products and examined by powder X-ray diffraction. The results of the study are presented in the table.

Example 2

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, Zn powder, Sn powder and grinding media, but the reaction temperature is 100°C. The reaction time is 300 min. The results are presented in the table.

Example 3

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, Zn powder, Sn powder and grinding media, but the reaction temperature is 290°C. The reaction time is 70 min. The results are presented in the table.

Example 4

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, Sn powder and grinding media, but without using Zn powder. The results are presented in the table.

Example 5

Direct synthesis of ethylethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, Sn powder, Zn powder and grinding media, but using diethyl ether (5.3 g) and at a temperature of 220°C. The silicon conversion was 40%, the product mixture consisted of tetraethoxysilane, ethyltriethoxysilane and siloxanes. The results are presented in the table.

Example 6

Direct synthesis of dimethyldiphenoxysilane is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, Sn powder, Zn powder and grinding media, but using anisole (7.7 g) at a temperature of 290°C. The silicon conversion was 80-90%, resulting in a mixture of methylphenoxysilanes and their derivatives. The results are presented in the table.

Example 7

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, and grinding media, but using Al powder in an amount of 0.02 g and grinding media made of brass in an amount of 14 pcs. The results are presented in the table.

Example 8

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, but using powder P in the amount of 0.02 g and grinding bodies made of stainless steel in the amount of 14 pcs. The results are presented in the table.

Example 9

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, and grinding media, but using Sb powder in an amount of 5000 ppm. The results are presented in the table.

Example 10

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, but using Ca powder in the amount of 0.02 g and grinding bodies made of tungsten carbide in the amount of 14 pcs. The results are presented in the table.

Example 11

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, grinding media, but using Fe powder in an amount of 0.01 g. The results are presented in the table.

Example 12

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, grinding media, but using Hg powder in an amount of 0.01 g. The results are presented in the table.

Example 13

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, but using Cr powder in the amount of 0.01 g and grinding bodies made of silicon nitride in the amount of 14 pcs. The results are presented in the table.

Example 14

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, grinding media, but using Mn powder in an amount of 0.01 g. The results are presented in the table.

Example 15

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, and grinding media, but using Co powder in an amount of 5000 ppm. The results are presented in the table.

Example 16

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, and grinding media, but using Pd powder in an amount of 5000 ppm. The results are presented in the table.

Example 17

Direct synthesis of methylmethoxysilanes is carried out in the same way as described in Example 1, with the same amount of silicon, copper(I) chloride, but using grinding bodies made of tin-coated stainless steel in the amount of 14 pieces without adding promoting additives. The results are presented in the table.

Example 18

Direct synthesis of methylmethoxysilanes is carried out with the same amount of silicon, copper(I) chloride, Zn powder, Sn powder and grinding bodies as in Example 1, but in a semi-continuous reactor with a vibrating fluidized bed. DME was fed into a reactor heated to 250°C with a volumetric flow rate of 250 ml/min. The resulting methylmethoxysilanes and unreacted DME were condensed in a receiver cooled to -25°C. The reaction time was 300 min. The results are presented in the table.

Claims (8)

1. A method for producing organoalkoxysilanes of the general formula R ¹ _(4-a) Si(OR ² ) _a , where R ¹ and R ² independently denote Me, Et, n-Pr, n-Bu, Ar, the index a denotes an integer from 1 to 4, by direct synthesis from silicon and a symmetrical or asymmetrical ether of the general formula R ¹ OR ² , where R ¹ and R ² independently denote Me, Et, n-Pr, n-Bu, Ar, comprising mechanical activation of silicon in the presence of a copper-containing catalyst and promoting additives in a vibratory fluidized bed of grinding bodies with a diameter of 1-20 mm and subsequent interaction of activated silicon with ether vapors at 100-300°C to form organoalkoxysilanes. 2. The method according to claim 1, characterized in that the simple ether is a symmetrical ether selected from the group including dimethyl, diethyl, dipropyl, dibutyl, and diphenyl ether. 3. The method according to claim 1, characterized in that the simple ether is an unsymmetrical ether selected from the group including methyl ethyl, methyl propyl, and methyl phenyl ether. 4. The method according to claim 1, characterized in that the copper-containing catalyst is copper powder. 5. The method according to claim 1, characterized in that the copper-containing catalyst is copper oxide or a copper salt. 6. The method according to claim 1, characterized in that the promoting additives are compounds of zinc (Zn), tin (Sn), aluminum (Al), phosphorus (P), antimony (Sb), calcium (Ca), iron (Fe), mercury (Hg), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), palladium (Pd), a mixture of two or more compounds of Zn, Sn, Al, P, Sb, Ca, Fe, Hg, Cr, Mn, Co, Ni, Pd. 7. The method according to item 1, characterized in that the grinding bodies are made of materials such as zirconium oxide, stainless steel, brass, tungsten carbide, silicon nitride. 8. The method according to item 1, characterized in that the promoting additives are applied to grinding bodies made of stainless steel.

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