RU2417228C1 - Method of producing alkoxysilanes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing alkoxysilanes of general formula Si(OR)₄, where R is an alkyl group. Disclosed is a method of producing alkoxysilanes by reacting aliphatic asymmetrical ethers of general formula R₁OR₂, where R₁=butyl, iso-butyl, tert-butyl, tert-amyl and R₂=methyl, ethyl, with finely dispersed silicon metal in gas-vapour phase in a closed reactor at temperature 200-270°C in the presence of copper monochloride as a catalyst, taken in amount of 10-20% of the weight of silicon metal.

EFFECT: improved method of producing alkoxy silanes, which enables to replace chlorosilanes and alcohols with aliphatic ethers, as well as increasing output of alkoxysilanes and purity of the end product.

1 cl, 9 ex

Description

The present invention relates to a method for producing silicic acid esters, namely alkoxysilanes of the general formula Si (OR) ₄ , where R is an alkyl group.

The invention can be most effectively used in the chemical industry for the modification of polymeric materials, for the synthesis of organosilicon products as starting compounds, and in mechanical engineering with precision casting as binders for foundry masses.

A known method of producing alkoxysilanes (Andrianov K.A. Methods of organoelemental chemistry. - M .: Nauka, 1968. p.174-187), which consists in the interaction of chlorosilane with alcohols and proceeding with the release of hydrogen chloride

SiCl ₄ +4 ROH → Si (OR) ₄ +4 HCl ^↑

Incomplete removal of hydrogen chloride from the reaction sphere leads to multiple side processes, which reduces the yield of the target product. To suppress side processes, the resulting hydrogen chloride is removed using dry nitrogen or a non-polar solvent.

A known method of producing alkoxysilanes (US Pat. France No. 1234828, class C07F 7/04, 1960), which consists in the interaction of organochlorosilanes with alcohols in the presence of 3-10% halocarbons, such as CCl ₄ , CHCl ₃ , as a solvent, followed by distillation of chlorosilane and hydrogen chloride. To increase the yield of the target product, the esterification of chlorosilanes with alcohol is carried out in the presence of organic solvents - chlorine derivatives of methane, ethane or ethylene with continuous distillation of the solvent (SU No. 717058, class C07F 7/18, 1976; SU. No. 1233802, class C07F 7/04, 1980).

A known method of producing alkoxysilanes (SU No. 148054, class C07F 7/04, 1961; SU No. 857140, class C07F 7/04, 1979) by the esterification of chlorosilane with ethyl alcohol, followed by desorption of hydrogen chloride in a thin film.

However, in all of the above methods for the production of alkoxysilanes due to the presence of hydrogen chloride in the reaction mixture, significant amounts of by-products are formed during the esterification of chlorosilanes.

The disadvantages of the known methods can also include obtaining the target product of insufficient quality (with a high content of residual HCl) and the need to remove organic solvents at the end of the process.

A known method of producing alkoxysilanes (US Pat. US No. 5527937, 556/470, 1996) by the interaction of silicon with alcohol in the presence of a copper-containing catalyst in a medium of high boiling solvent at a temperature of 100-350 ° C. The disadvantage of this method of producing alkoxysilanes is that in addition to the main reaction of the interaction of alcohols with metallic silicon, side reactions also occur, as a result of which dehydrocondensation forms water

2 ROH → ROR + H ₂ O

ROH + H ₂ → RH + H ₂ O

C ₂ H ₅ OH → C ₂ H ₄ + H ₂ O

Water generated in the reaction sphere hydrolyzes alkoxysilanes, resulting in the formation of by-products - oligo- and polyalkoxysiloxanes

(n + 1) Si (OR) ₄ + n H ₂ O → Si _{n + 1} O _n (OR) _{n + 3} + 2n ROH

In addition, the resulting water poisons the catalyst used in the reaction. As a result of these side processes, the yield of the target products, tetraalkoxysilanes, decreases markedly.

Closest to the present invention and adopted as a prototype is a method of producing tetraalkoxysilanes by the interaction of crushed silicon with alcohol in a high boiling solvent in the presence of a copper-containing catalyst at an elevated temperature to obtain trialkoxysilane and its subsequent dehydrocondensation in the presence of calcium oxide or hydroxide as a catalyst (RU No. 2320666 Cl. C07F 7/04, 2005).

The disadvantage of this method is the formation of a significant amount of water, which leads to the formation of a large number of hydrolysis products, and, therefore, a decrease in the yield of the target product - tetraalkoxysilane. In addition, the presence of an additional stage of processing the reaction products formed in the first stage with calcium oxide or hydroxide, although it leads to an increase in the yield of alkoxysilanes, nevertheless significantly complicates the technology and apparatus design of the process. The disadvantages of this method also include the use of a high boiling solvent, which is difficult to separate from the target product.

The objective of the invention is to provide an improved method for producing alkoxysilanes with the aim of expanding the raw material base of the starting compounds, namely the replacement of chlorosilanes and alcohols with simple aliphatic asymmetric ethers, increasing the yield of alkoxysilanes and increasing the purity of the target product.

The solution of this problem is achieved by the interaction of simple aliphatic asymmetric ethers of the general formula R ₁ OR ₂ , where R ₁ = butyl, isobutyl, tert-butyl, tert-amyl and R ₂ = methyl, ethyl, with finely divided metallic silicon in the presence of a copper-containing catalyst when heated in the vapor-gas phase in a closed reactor at a temperature of 200-270 ° C, moreover, copper monochloride taken in an amount of 10-20% by weight of silicon metal is used as a catalyst.

At a lower temperature (below 200 ° C), the process is ineffective, the conversion sharply decreases and the content of the initial asymmetric dialkyl ether R ₁ OR ₂ in the reaction products increases. At a higher temperature (above 280 ° C), the contribution of pyrolytic processes sharply increases, as a result of which the yield of the target product decreases.

In the interaction of asymmetric ethers with metallic silicon in the presence of less than 10% copper monochloride by weight of silicon, a sharp decrease in the conversion and an increase in the content of the initial ether in the reaction products are also observed.

The invention is illustrated by the following examples.

Example 1

A 50 ml steel autoclave is charged with 2.5 g of a mixture containing 80% powdered silicon metal and 20% powdered copper monochloride Cu ₂ Cl ₂ as a reaction catalyst, then 20.0 g of tert-butyl methyl ether are added, after which the autoclave is sealed and heated with stirring at a temperature of 220 ° C for 8 hours. At the end of the reaction, the gaseous reaction products containing isobutylene and hydrogen are vented with a valve. The composition of the liquid reaction products was analyzed by chromatography and NMR spectroscopy. According to the results of the analysis, the liquid reaction products are tetramethoxysilane (yield 65.2%), which is mixed with unreacted tert-butyl methyl ether (28.1%) and methanol (4.4%).

Example 2

Similarly to the above example, after loading all the components, the autoclave is heated with stirring at a temperature of 270 ° C for 8 hours. At the end of the reaction, gaseous reaction products containing isobutylene and hydrogen are vented. The liquid reaction products are tetramethoxysilane (yield 94.2%), which is mixed with unreacted tert-butyl methyl ether (2.3%) and methanol (1.8%).

Example 3

Similarly to the above example, 2.5 g of a mixture containing 80% powdered silicon metal and 20% Cu ₂ Cl ₂ monochloride were loaded into the autoclave, 20.0 g of butyl methyl ether were added and the autoclave was heated with stirring at a temperature of 270 ° C for 8 hours. At the end of the reaction, gaseous reaction products containing butylene and hydrogen are vented. The liquid reaction products are tetramethoxysilane (yield 93.3%) mixed with unreacted butyl methyl ether (2.6%) and methanol (2.8%).

Example 4

Similarly to the above example, 2.5 g of a mixture containing 80% powdered silicon metal and 20% Cu ₂ Cl ₂ monochloride were charged into an autoclave, 20.0 g of butyl ethyl ether were added and the autoclave was heated with stirring at a temperature of 270 ° C for 8 hours. At the end of the reaction, gaseous reaction products containing butylene and hydrogen are vented. The liquid reaction products are tetraethoxysilane (90.2% yield), which is mixed with unreacted butyl ethyl ether (4.6%) and ethanol (3.8%).

Example 5

Similarly to the above example, 2.5 g of a mixture containing 80% powdered silicon metal and 20% Cu ₂ Cl copper chloride were charged into an autoclave, 20.0 g of tert-amyl methyl ether was added and the autoclave was heated with stirring at a temperature of 270 ° C for 8 hours . At the end of the reaction, the gaseous reaction products are vented. The liquid reaction products are tetramethoxysilane (yield 92.6%), in a mixture with unreacted tert-amyl methyl ether (3.2%) and methanol (2.3%).

Example 6

Similarly to the above example, 2.5 g of a mixture containing 90% powdered silicon metal and 10% Cu ₂ Cl copper chloride were charged into an autoclave, 20.0 g of tert-butyl methyl ether was added, and the autoclave was heated with stirring at a temperature of 270 ° C. for 8 hours . At the end of the reaction, the gaseous reaction products are vented. The liquid reaction products are tetramethoxysilane (87.4% yield), which is mixed with unreacted tert-butyl methyl ether (9.3%) and methanol (2.1%).

Example 7

Similarly to the above example, 2.5 g of a mixture containing 80% powdered silicon metal and 20% Cu ₂ Cl ₂ monochloride were charged into an autoclave, 20.0 g of tert-butyl methyl ether was added and the autoclave was heated with stirring at a temperature of 190 ° C for 8 hours. At the end of the reaction, gaseous reaction products containing butylene and hydrogen are vented. The liquid reaction products are tetraethoxysilane (yield 35.2%), in a mixture with unreacted tert-butyl methyl ether (52.1%) and methanol

(9.4%),

Example 8

Similarly to the above example, after loading all the components, the autoclave is heated with stirring at a temperature of 300 ° C for 8 hours. At the end of the reaction, the gaseous reaction products containing isobutylene, hydrogen and other gases are vented. The yield of liquid reaction products is sharply reduced due to pyrolytic processes.

Example 9

Similarly to the above example, 2.5 g of a mixture containing 95% of powdered silicon metal and 5% of Cu ₂ Cl ₂ monochloride are charged into an autoclave, 20.0 g of tert-butyl methyl ether are added and the autoclave is heated with stirring at a temperature of 270 ° C for 8 hours. At the end of the reaction, the gaseous reaction products are vented. The liquid reaction products are tetramethoxysilane (61.6% yield), in a mixture with unreacted tert-butyl methyl ether (28.1%) and methanol (7.8%).

The technical and economic result of this invention is the expansion of the raw material base of the starting compounds, namely the replacement of chlorosilanes and alcohols with simple aliphatic asymmetric ethers, an increase in the yield of alkoxysilanes (in the prototype 60-70%, 90-95% obtained) and an increase in the purity of the target product compared to prototype due to the absence of alkoxysilane hydride.

Claims (1)

The method of producing alkoxysilanes by the interaction of simple aliphatic asymmetric esters of the general formula R ₁ OR ₂ , where R ₁ - butyl, isobutyl, tert-butyl, tert-amyl and R ₂ = methyl, ethyl, with finely divided metallic silicon in the presence of a copper-containing catalyst when heated, characterized the fact that the process is carried out in the vapor-gas phase in a closed reactor at a temperature of 200-270 ° C, and copper monochloride taken in an amount of 10-20% by weight of silicon metal is used as a catalyst.