RU2299213C1 - Method for preparing alkoxysilanes - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for synthesis of alkoxysilanes. Invention describes a method for synthesis of alkoxysilanes of the general formula: R'_nSi(OR)_m wherein n = 0-3; m = 1-4 and n + m = 4. Method involves reaction of chlorosilanes of the general formula: R'_nSiCl_m wherein R' means hydrogen atom (H), CH₃, C₂H₄, C₂H or C₆H₆ with alcohols of the general formula: ROH wherein R means (C₂-C₈)-alkyl or (C₂-C₈)-aryl. Chlorosilane solution in an inert volatile nonpolar solvent is added to boiling alcohol solution in the same solvent at temperature 75-95°C, solvent is distilled off and evolving dry hydrogen chloride is captured. Method provides increasing yield, simplified process and decreasing time during the reaction carrying out.

EFFECT: improved method of synthesis.

6 cl, 1 tbl, 11 ex

Description

The invention relates to a method for producing alkoxysilanes by reacting the corresponding chlorosilanes and alcohols.

Chlorinated silanes, for example dimethyldichlorosilane, are the main feedstock for a variety of organosilicon products. An important intermediate in their conversion to rubbers and varnishes are alkoxysilanes obtained by the reaction of chlorosilanes with alcohols. Upon receipt of alkoxysilanes, significant amounts of by-products are formed: ethers, chloralkanes, condensed siloxanes. Their formation requires the use of excess alcohol to complete the reaction. The reaction of alkoxysilanes with hydrogen chloride is reversible [1, p. 107], therefore, the quick and effective removal of hydrogen chloride from the reaction zone allows one to significantly intensify the process and increase the yield of the target product. To accelerate the removal of HCl can be an inert gas current. It is especially effective to feed an inert gas into the reaction zone countercurrent to a mixture of chlorosilane and alcohol [2].

In practice, HCl binding with bases is often used. So methylphenyldimethoxysilane is obtained from methylphenyldichlorosilane and anhydrous methanol, linking HCl with urea. During the reaction in toluene, urea hydrochloride dissolves in excess alcohol, forming a layer immiscible with a toluene solution of methylphenyl dimethoxysilane [1, p. 108]. Upon receipt of aromatic esters, dimethylformamide is used as a catalyst [1, p. 112]. Tertiary amines, for example pyridine, are effective for HCl binding [3, p. 189]. When carrying out the reaction, well-dried alcohol taken with a 10% excess is used, and the liberated pyridine hydrochloride is filtered off [4].

Closest to the proposed is a method for the synthesis of alkoxysilanes from chlorosilanes and alcohols by heating and distillation [5]. In a 12 L flask equipped with a dropping funnel and condensation system from a ball reflux condenser and a refrigerator cooled with a dry ice-acetone mixture, a mixture of 3.82 kg of dimethyldichlorosilane (DMDCS) and 0.33 kg of methyltrichlorosilane, to which 5 are added over 8 hours, are added. 8 kg of butanol, after which the reaction mixture is heated to 90 ° C to distill off the HCl. Distilled at atmospheric pressure, collecting four fractions: A) T _bale 184-190 ° C - 4.05 kg (crude dimethyldibutoxysilane 67% conversion of the original DMDC); B) T _bale 190-217 ° C - 0.17 kg; C) T _bale 217-240 ° C - 0.53 kg; D) T _bale 240-325 ° C - 0.61 kg; VAT residue 0.22 kg

The reaction uses an excess of butanol in an amount of 26.1%.

The disadvantages of the known methods of obtaining are multi-stage process, the presence of difficult to separate by-products, the cost of additional reagents, the inability to simultaneously obtain dry high purity hydrogen chloride.

The aim of the present invention is to develop a highly efficient method for producing alkoxysilanes, allowing the process to be carried out at a high speed, to efficiently consume reagents and to obtain additionally high purity hydrogen chloride suitable for hydrochlorination without further purification.

This goal is achieved by carrying out the alkoxylation of chlorosilanes in a boiling inert organic solvent having a boiling point of 75-95 ° C, for example, in carbon tetrachloride (CFC) or benzene. The solvent is used repeatedly, freeing from the HCl contained in it by distillation.

The reaction is carried out by feeding a solution of chlorosilane in an inert volatile non-polar solvent to a boiling alcohol solution in the same solvent in a reactor equipped with a reflux condenser and a device for effectively mixing the reaction mixture. The rate of addition of chlorosilane depends on the efficiency of the device for receiving hydrogen chloride, which, for example, can be liquefied by cooling the receiver with liquid nitrogen or a mixture of dry ice with a slightly boiling solvent, which provides the temperature necessary for liquefaction (less than -86 ° C). The released hydrogen chloride is then transferred to other consumers, for example, to produce trichlorosilane. After supplying the entire amount of chlorosilane, the organic solvent begins to distill off while continuing to capture the released HCl. The product containing alkoxysilanes remaining after distillation of the solvent is dispersed or used as such, since the content of impurities in it is insignificant. When using carbon tetrachloride as a solvent, introduced in an amount equal to the weight of the starting reagents in the mixture remaining after its distillation, the HCl content does not exceed 0.01%.

A distilled solvent was placed in a reactor liberated from alkoxysilanes, heated under reflux until the evolution of HCl dissolved in it ceased, and distilled. A distilled solvent containing less than 0.001% HCl is reused to produce alkoxysilanes.

Favorable for the effective implementation of the process is the use of excess stoichiometric amounts of alcohol. Excess alcohol is distilled off with the organic solvent and is also reused.

As alcohols, primary or secondary aliphatic alcohols, as well as phenols, can be used. The method is limitedly suitable for producing methyl esters, since methanol has a too low boiling point.

This method can be used to obtain other esters by the reaction of halides with alcohols, for example, to obtain esters of carboxylic acids or acids containing phosphorus.

The following are examples of specific implementations of the proposed method of obtaining.

Example 1. A mixture of 117.6 g of distilled CHC and 38.7 g (0.3 M) of distilled DMDHS was added dropwise at room temperature to 88.8 g (1.2 M) of dry butanol-1. The reaction mixture was heated for 2 hours at 88 ° C and the solvent was distilled off (fraction 67-113 ° C, weight - 105.3 g). In the cube, 90.1 g of liquid remained (n _D ^20.5 = 1.4052), from which after two consecutive distillations 52 g (84.9% of the theoretically possible amount) of dimethyldibutoxysilane (T _bp 185-195 ° С, n _D ^20.5 = 1.4061, found,%: Si 13.08; C 58.58; H 11.58; calculated,%: Si 13.73; C 58.82; H 11.76). Additionally, during distillation in vacuo, 5 g of tetramethyl-1,3-di-n-butoxydisiloxane and 2.4 g of a bottom residue that were not identified were isolated.

The regenerated solvent contained 105.6 g of CFCs (loss of 12 g of CFCs removed by the flow of HCl) and 37.5 g of butanol.

29.1 g (100%) of hydrogen chloride also evolved.

Comparison with the prototype shows that the introduction of carbon tetrachloride into the reaction mixture allowed a more than four-fold reduction in the reaction time, the yield of the target product increased from 67% to almost 85%, and the proportion of by-products formed correspondingly fell. The regenerated solvent and butanol are reused.

Example 2. In a three-necked flask equipped with a stirrer, dropping funnel and reflux condenser, the upper part of which is connected by a silicone hose to a trap for gaseous components cooled by liquid nitrogen, 88.8 g (1.2 M) of butanol-1 are placed and an equal weight the number of CHU. Turn on heating and stirring.

77.4 g (0.6 mol) of DMDHS and an equal amount of CFC are placed in a dropping funnel. Shake the funnel to mix the components and add the resulting solution in a three-necked flask in 25 minutes. Instillation begins when the contents of the flask begin to boil.

Replace the reflux condenser with a drop-down one, and the solvents are distilled off at a vapor temperature of 40-112 ° C. Distillation yield 136.4 g.

The remainder contains 125.4 g of liquid, upon distillation of which an additional 13.8 g of CFC and butanol are obtained, 99.7 g (81.4% of the theoretically possible amount) of dimethyldibutoxysilane having a T _boiling point of 186-196 ° C (basic 193 ° C) ), n _D ²¹ = 1.4055, as well as 11.9 g of a mixture of tetramethyl-1,3-di-n-butoxydisiloxane and other high-boiling products.

HCl yield 43.8 g (100%).

Using the above detailed procedures, alkoxysilanes R ′ _n Si (OR) _m are prepared and are presented in the table.

Table Example Chlorosilane Alcohol OH / Cl moles Solvent Output R ' _n Si (OR) _m one (CH ₃ ) ₂ SiCl ₂ C ₄ H ₉ OH 2 CCl ₄ 85% 2 (CH ₃ ) ₂ SiCl ₂ C ₄ H ₉ OH one CCl ₄ 81% 3 (CH ₃ ) ₂ SiCl ₂ C ₈ H ₁₇ OH one CCl ₄ 79% four (CH ₃ ) ₂ SiCl ₂ H (CF ₂ ) ₄ CH ₂ OH one CCl ₄ 80% 5 (CH ₃ ) ₂ SiCl ₂ C ₆ H ₅ OH one CCl ₄ 96% 6 (CH ₃ ) ₂ SiCl ₂ iso-C ₃ H ₇ OH 2 CCl ₄ 63% 7 (CH ₃ ) ₂ SiCl ₂ C ₄ H ₉ OH 2 Benzene 70% 8 CH ₃ SiCl ₃ C ₄ H ₉ OH one CCl ₄ 65% 9 CH ₂ = CHSiCl ₃ C ₄ H ₉ OH one CCl ₄ 68% 10 C ₂ H ₅ SiCl ₃ C ₄ H ₉ OH one CCl ₄ 71% eleven (C ₆ H ₅ ) ₂ SiCl ₂ C ₄ H ₉ OH one CCl ₄ 91%

The above examples do not exhaust the options for possible substituents R and R 'that are part of the chlorosilane or alcohol. As the alcohol, polyols, for example ethylene glycol, glycerin or hydroquinone, amino alcohols, for example triethanolamine, or other substituents, can be used. The reaction can also be carried out using mixtures of chlorosilanes or alcohols.

Information sources

1. Khananashvili L.M., Andrianov K.A. Technology of organoelement monomers and polymers. - M.: Chemistry, 1983.- 415 p.

2. Lebedev E.N., Dubrovskaya G.A., Kleschevnikova S.I. and other patent of the Russian Federation No. 2203282, IPC C07F 7/04 from 12.24.2001,

3. Andrianov K.A. Organoelemental chemistry methods. Silicon. - M .: Nauka, 1968 .-- 700 p., P. 189.

4. Andrianov K.A., Gornets L.V., DAN USSR 101, 259 (1955).

5. Saner R.O. Derivatives of methylchlorosilanes. III. n-Butyl Ethers. JACS 68, No. 1, 138-139 (1946).

Claims (6)

1. A process for preparing alkoxysilanes of the general formula _{R 'n Si (OR) m} n = 0-3, m = 1-4, and n + m = 4, the reaction of chlorosilanes of the general formula R' _n SiCl _m, where R '= H, CH ₃ , C ₂ H ₄ , C ₂ H ₅ or C ₆ H ₅ , with alcohols of the general formula ROH, where R = alkyl C ₂ -C ₈ or aryl, characterized in that, in order to increase the yield and simplify the process, a solution of chlorosilane in an inert volatile non-polar solvent is added to a boiling alcohol solution in the same solvent at a temperature of 75-95 ° C and the solvent is distilled off, trapping the released dry hydrogen chloride. 2. The method of producing alkoxysilanes according to claim 1, in which 1 mol of ROH alcohol is taken per 1 g / chlorine atom of chlorosilane R ' _n SiCl _m . 3. The method of producing alkoxysilanes according to claim 1, in which hydrocarbons or chlorohydrocarbons with a boiling point of 75-95 ° C are used as an inert volatile non-polar solvent. 4. The method of producing alkoxysilanes according to claim 1, in which carbon tetrachloride is used as an inert volatile non-polar solvent. 5. The method of producing alkoxysilanes according to claim 1, in which benzene is used as an inert volatile non-polar solvent. 6. The method of producing alkoxysilanes according to claim 1, in which the inert solvent is mixed with reagents in a ratio of 1: 1.