JP3505744B2 - Method for producing alkoxysilane - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] Alkoxysilanes, especially trialkoxysilanes, are used in the fields of silane gas as a raw material for the production of silicon for semiconductors, composite materials and paints. It is an industrially important compound as a raw material for producing ring agents. The present invention relates to the rationalization of the production of trialkoxysilane. [0002] The trialkoxysilane referred to in the present invention is:
In the compound represented by the structural formula HSi (OR) ₃ , R is an alkyl group having 1 to 6 carbon atoms. The production method of trialkoxysilane is roughly classified into (1) a method in which trichlorosilane is reacted with an alcohol, and a method in which HSiCl ₃ + 3ROH → HSi (OR)
₃ + 3HCl (2) A method of reacting silicon and an alcohol with a cuprous chloride catalyst, [0005] The reaction products obtained by these methods are in the form of a mixture of trialkoxysilane, alcohol and various by-product alkoxysilanes. In addition, although the amount is small, in the case of (1), unreacted HSiCl ₃ and HCl by-produced, and in the case of (2), Cu
It also contains HCl generated by the decomposition of Cl. As a method for isolating trialkoxysilane from such a reaction product, generally, a distillation (rectification) method is used. However, the reaction product includes a metal such as stainless steel such as HSiCl ₃ or HCl. Since it contains a compound having a strong corrosive property to a material, there is a problem that an apparatus for separating and separating trialkoxysilane requires a high quality material. As a countermeasure against this corrosion, the present inventors have found a method in which the above-mentioned reaction product is brought into contact with an iron-based metal, and the form of chlorine is changed to an inert metal chloride such as iron chloride. . [0007] At this time, metal chlorides such as iron chloride are eluted into the reaction product of trialkoxysilane by contact with an iron-based metal. If alcohol is present in the object, it is dissolved. However, when a trialkoxysilane is fed to a distillation column to separate it by distillation from the reaction product, when the alcohol which is a low boiling component in the reaction product evaporates, the solubility of the chloride decreases, and the precipitation occurs. There is a problem of doing. The deposits adhere to the packing of the distillation column and cause problems such as blocking. In view of the above, the present inventors have studied a method for preventing the precipitation of metal chloride in a distillation column, and as a result, have found that a reaction product of trialkoxysilane has been obtained. was separated from the non-volatile metal chlorides by vaporizing the trialkoxysilane component through the evaporator prior to feeding to the distillation column of separation of trialkoxysilane, then feeds the door trialkoxysilane components leave the distillation column a vapor It has been found that by adopting this method, the precipitation of metal chloride in the distillation column can be effectively prevented, and the present invention has been achieved. That is, the present invention relates to a method for obtaining an alkoxysilane by reacting silicon or a silicon compound with an alcohol, wherein an alkoxysilane reaction product containing a chlorine compound is brought into contact with an iron-based metal, which is then heated. A method for producing an alkoxysilane, characterized in that a low-boiling component containing an alkoxysilane is vaporized and supplied to a distillation step. Hereinafter, the present invention will be described in detail. The trialkoxysilane reaction products to which the present invention is suitably applied are the following two types. A reaction product produced by the reaction of trichlorosilane and alcohol, having a trialkoxysilane content of 1 to 90% and an alcohol content of 1 to 90%, and having a chlorine concentration of 1 to 100,000 ppm. A reaction product produced by reacting with cuprous copper, a solution having a trialkoxysilane content of 1 to 90%, an alcohol content of 1 to 90%, and a chlorine concentration of 1 to 100,000 ppm. As a metal used when converting chlorine in a substance into a metal chloride having no corrosiveness to a metal material, iron or an alloy containing iron is cited, and preferably, chromium or stainless steel containing nickel is used. No. ## STR3 ## HSi (OR) ₃ + ROH → Si (OR)
₄ + H ₂ [0013] The reaction product is brought into contact with the iron-based metal by a method in which an iron-based metal plate is immersed in the reaction product, or a method in which the iron-based metal powder is converted into a reaction product using a reaction tank equipped with a stirrer. Various industrial operations for contacting solid and liquid, such as a method of suspending, are generally considered. Among them, a fixed bed flow system in which a reaction product is continuously flowed through a packed bed of iron-based metal particles is preferable. . Next, a method of isolating trialkoxysilane from the reaction product obtained by subjecting the contained chlorine to a metal chloride treatment by distillation will be described. The boiling points of the components in the reaction product are from low boiling point to alcohol, trialkoxysilane,
Other by-product alkoxysilanes are obtained in this order. If rectification is performed in this order, trialkoxysilane is obtained as the second distillate component. However, in general, alcohol and trialkoxysilane are azeotropic, and therefore, when the alcohol and trialkoxysilane are separated by distillation, azeotropic distillation by adding a third component (JP-A-55-11538) or extractive distillation (JP-A-55-11538). 61-65889, JP-A-2-91
No. 079). 2 to 50 theoretical plates required for distillation,
Preferably, 10 to 20 stages are suitable. Next, a method for vaporizing a trialkoxysilane component in a reaction product of trialkoxysilane will be described. When the trialkoxysilane is vaporized, the coexisting low-boiling (or azeotropic) alcohol is vaporized together with the entire amount. At this time, the metal chloride dissolved in the reaction product precipitates. In order to increase the vaporization rate of trialkoxysilane, a component having a higher boiling point is also partially vaporized. As a device used for vaporization, a vapor heating type evaporator with a heating tube is suitable.However, since the metal chloride precipitates during evaporation, the liquid surface of the heat transfer surface is scraped off with a scraping plate. Film-type evaporators are preferred. The temperature of the heating medium used in the evaporator is preferably low, in order to suppress the reaction between the alcohol and trialkoxysilane, and is not higher than the boiling point of trialkoxysilane plus 100 ° C., preferably 50 ° C. The vapor of the trialkoxysilane component thus vaporized can be directly fed to a distillation column for separating alcohol and trialkoxysilane. Next, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited by the following examples unless it exceeds the gist of the present invention. EXAMPLES [Production of trialkoxysilane] An example of producing trimethoxysilane will be described. 1053 g of metal silicon powder (98% purity), 18.6 g of cuprous chloride and 2050 ml of dodecylbenzene were placed in a 5-liter metal reactor (SUS304) equipped with a distilling column having a condenser, a thermometer and a methanol inlet tube and equipped with a stirrer. Was charged. Then
The mixture was heated, and when the internal solution temperature reached 220 ° C., methanol was fed into the reactor at a rate of 1500 ml / h from the inlet tube and reacted at 220 ° C. for 6 hours. At that time, components evaporated from the reactor were condensed by a condenser to obtain a distillate (reaction product) having a total amount of 8600 g. As a result of analysis by gas chromatography, this solution was found to contain 2410 g (28% by weight) of methanol, 3870 g (45% by weight) of trimethoxysilane,
It contained 460 g (17% by weight). Further, as a result of analyzing the chlorine content and the metal component, HCl 147p
pm, FeCl ₂ 20.9 ppm, CrCl ₃ 6.1p
pm, NiCl ₂ 2.2 ppm. Metal components such as Fe are eluted from the reactor. Next, an example of treatment in which the reaction product is brought into contact with a stainless steel material to convert HCl into metal is described. SUS3
04 1mm diameter x 2mm length cut wire 5N
It was immersed in nitric acid for 12 hours, and then sufficiently washed with water and dried to remove iron oxide and water. This has an inner diameter of 26 mm and a length of 10
A 00 mm glass column was packed for a length of 800 mm (filling amount: 2200 g) to obtain a fixed bed reactor. In the reactor, the above-mentioned trimethoxysilane reaction product was added to 70
The solution was fed from the bottom at a flow rate of ml / min, and the liquid overflowing from the top was collected in a glass container. As a result of analyzing the recovered liquid, 201.5 ppm of FeCl ₂ ,
₃ 50.3 ppm, NiCl ₂ 25.6 ppm, HC
l was 1 ppm or less. On the other hand, the concentrations of methanol, trimethoxysilane and tetramethoxysilane did not change. Using this recovered liquid (hereinafter referred to as “raw material”), experiments described in Examples and Comparative Examples were performed next. Example 1 Distillation for separating methanol and trimethoxysilane in a raw material was performed, and the presence or absence of metal chloride precipitation in a distillation column was examined. Methanol (boiling point: 64 ° C.) and trimethoxysilane (boiling point: 86 ° C.) form a minimum azeotropic mixture in a ratio of 48:52 (azeotropic point: 58 ° C.) and cannot be separated by distillation as it is. For this reason, distillation was performed by adding n-hexane to the raw material as an azeotropic agent. n-hexane (boiling point 69
C) and methanol at a ratio of 74:26 to form a minimum azeotrope having an azeotropic point of 50 ° C. Since the azeotropic point of methanol and trimethoxysilane is lower than the azeotropic point of 58 ° C, distillation in the presence of n-hexane results in n The azeotrope of hexane and methanol first distills off. This makes it possible to separate methanol and trimethoxysilane. The distillation was performed in the apparatus shown in FIG. The material of this device is made of glass and ethylene tetrafluoride. The distillation column 5 in the figure uses an Oldershaw type (made by Shibata Scientific Co., Ltd.) fractionating tube (inner diameter 32 mm) that performs gas-liquid contact with a perforated plate having a diameter of about 1 mm. From the 25th stage to the 26th stage. Hereinafter, description will be given along the line in FIG. In the tank 1, 3000 g of the above-mentioned raw material and the amount of n-hexane which is azeotropic with respect to 840 g of methanol in the raw material are set to 1.
2870 g of n-hexane, which is twice as much, was charged and sufficiently mixed with a stirrer, and this was used as a raw material for distillation. This distillation raw material was fed to the wet wall type evaporator No. 3 using the pump 2 at a flow rate of 300 g / hr, and the generated steam was fed to the distillation column 5. The reflux ratio was adjusted to 1.5 using the reflux unit 7, and further, the amount of the distillate was adjusted to 180 g / h of the total amount of methanol in the distillation raw material and n-hexane azeotropic with it.
The temperature of the heat medium (silicon oil) of the reboiler 6 was adjusted. On the other hand, the bottom liquid of 6 was continuously extracted using an extraction valve 11 that opens and closes intermittently, and was retained in a receiver 10. When the distillation became sufficiently steady, the distillate and the bottoms were taken and analyzed for composition by gas chromatography. This distillation operation could be performed without any problem for 18 hours. Eighteen hours later, a liquid containing needle-like crystals remained in the receiver 4 of the distiller, and the crystals were filtered and analyzed. As a result, FeCl ₂ was the main component. [Table 1] Comparative Example 1 In FIG. 1, the evaporator 3 was removed, and the distillation material 1 was fed directly to the distillation column 5 in a liquid state by using the pump 2, and the other conditions were the same as in the example. Operating, the same distillation was performed. As a result, a flooding phenomenon in which the liquid phase did not drop at the 26th stage after 5 hours occurred. The distillation was interrupted, and the fractionation tube No. 5 was disassembled to examine the 26th stage. As a result, the pores of the perforated plate were closed with brown solids. When the solid was taken and analyzed, Fe, Cr and Ni were detected. In the production of alkoxysilane, the precipitation of metal chloride in the distillation column can be effectively prevented.

[Brief description of the drawings] FIG. 1 shows an example of a distillation apparatus used in the present invention. [Explanation of symbols] 1 distillation material tank, 5 distillation tower, 8 Condenser of distillate steam

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Claims (1)

(57) [Claim 1] A method for obtaining alkoxysilane by reacting silicon or a silicon compound with an alcohol,
A method for producing an alkoxysilane, comprising contacting an alkoxysilane reaction product containing a chlorine compound with an iron-based metal, followed by heating to vaporize a low-boiling component containing the alkoxysilane and supplying it to a distillation step. Method.