JP3505745B2 - Method for separating trimethoxysilane - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a silane coupling agent used in the fields of silane gas, composite materials, paints, etc., which is a raw material for producing silicon for semiconductors. The present invention relates to a method for separating trimethoxysilane, which is an important compound. [0002] As a method for producing trimethoxysilane,
As shown in the following formula, a method of reacting silicon and methanol with a cuprous chloride catalyst is known. [0003] [0004] The reaction product obtained by this method is a mixture containing trimethoxysilane, methanol and by-produced tetramethoxysilane as main components and a polymer of methoxysilane. When trimethoxysilane is isolated from this reaction product, the boiling point of each component is methanol 64
Although the distillation method is considered because the temperature is 86 ° C., trimethoxysilane is 86 ° C., and tetramethoxysilane is 121 ° C., it cannot be separated because methanol and trimethoxysilane form an azeotrope in a weight ratio of 48:52. For this reason, an azeotropic distillation method for separating methanol and trimethoxysilane by adding a third component that forms an azeotrope with methanol (referred to as an “azeotropic agent”) to the reaction product is known. N-hexane or the like is used as a boiling agent. For example, when n-hexane is added to the reaction product, an azeotrope having a boiling point of 50 ° C. with a weight ratio of n-hexane to methanol of 74:26 is formed. That is, since the azeotropic point of methanol / n-hexane azeotrope 50 ° C. is lower than the azeotropic point of methanol / trimethoxysilane azeotrope 58 ° C., azeotropic composition of n-hexane with methanol is added. Then, distillation and separation of methanol / n-hexane azeotrope and trimethoxysilane can be performed. After removing the methanol, trimethoxysilane and tetramethoxysilane can be separated by ordinary distillation. This distillation method will be described with reference to FIG. The distillation column 10 is a separation column for methanol and trimethoxysilane, and feeds a reaction product of trimethoxysilane from one. Meanwhile, n-hexane as an azeotropic agent is fed from 4. The distillate of the distillation column 10 is an azeotrope of methanol and n-hexane. This distills at a temperature of 50 ° C., but when cooled to 42 ° C. or lower and left standing in a decanter, it separates into two phases, an upper phase rich in n-hexane and a lower phase rich in methanol. For this reason, the upper phase is n-hexane 4
For the distillation column 10. On the other hand, the lower phase is fed to the distillation column 11 through 5, and separated into a methanol / n-hexane azeotrope and methanol. The methanol / n-hexane azeotrope enters the decanter through 6 as a distillate. Methanol is obtained as bottoms 7. Distillation tower 10
Is a mixture of trimethoxysilane, tetramethoxysilane and other high-boiling substances. This is used for distillation column 12
To obtain trimethoxysilane as a distillate. The bottom liquid 9 is a mixture of tetramethoxysilane and a high-boiling substance. [0007] In the three distillation columns in FIG. 1, the maximum amount of the processing liquid is the distillation column 10, and the amount of the processing liquid and the number of stages in FIG. Since this greatly affects the cost of the entire equipment for isolating trimethoxysilane, it has been desired to reduce the amount of treatment liquid in the distillation column 10, that is, the separation column for methanol and trimethoxysilane. Means for Solving the Problems In view of the above facts, the present inventors have studied a method for reducing the amount of the processing solution in the distillation column 10 and found that the temperature in the decanter was set to 25 ° C. or less. As a result, it has been found that the purpose of increasing the concentration of n-hexane in the azeotropic agent returned to the distillation column 10 and reducing the amount of the treatment liquid can be achieved. That is, the present invention relates to an azeotropic distillation method in which n-hexane is used as an azeotropic agent to separate methanol from a liquid containing trimethoxysilane and methanol, wherein an azeotropic mixture of distilled n-hexane and methanol is heated at 25 ° C. or lower. A method for separating trimethoxysilane, which comprises separating n-hexane and methanol. Hereinafter, the present invention will be described in detail. The trimethoxysilane reaction product used as a distillation material in the present invention is, for example, a product obtained by reacting silicon and methanol with a cuprous chloride catalyst, and has a methanol content of 1 to 90% and a trimethoxysilane content of 1 to 1. 90%, tetramethoxysilane as other component and higher boiling point (121 ° C or higher)
And mixtures containing the compounds of formula (I). However, the present invention is not necessarily limited to the above-mentioned reaction products, but includes methanol and triethanol as components such as a mixture of trimethoxysilane and methanol produced by the reaction of trichlorosilane and methanol. A mixture containing methoxysilane can be similarly applied. The purity of n-hexane used as an azeotropic agent for methanol is 95%, preferably 97% or more. The number of theoretical plates of the distillation column (distillation column A in FIG. 1) used for azeotropic distillation of methanol is usually 3 to 50 plates, preferably 10 to 30 plates. In the present invention, the temperature of the decanter is set to 2
The temperature is set to 5 ° C or lower, preferably 10 ° C or lower. As is apparent from the mutual solubility curve of the binary system of methanol and n-hexane shown in FIG.
The concentration of methanol dissolved in hexane and returned to the distillation column 10 can be suppressed. For this reason the decanter temperature is 25 ° C
Or less, preferably kept at 10 ° C. or less. When the temperature exceeds 25 ° C., the concentration of methanol returned to the distillation column 10 together with n-hexane increases, and the separation efficiency decreases. If the temperature is too low, a problem of cooling cost occurs. Therefore, industrially, 0 to 25 ° C. is suitable, and it can be performed particularly efficiently at 0 to 10 ° C. 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 1 and 2] The flow rate of the distillation raw material 1 in the distillation column 10 of FIG. 1 was set to 100 kg / h, and the composition thereof was adjusted to methanol close to that of a typical trimethoxysilane reaction product. 28
% And trimethoxysilane 47%. On the other hand, the flow rate of the decanter upper phase 4 is 1 and 4
Of methanol and n-hexane in an azeotropic composition of 26: 7
Since it is uniquely determined to be 4, the flow rate of 4 is calculated from the methanol concentration of the upper phase at that time, assuming the decanter temperature from FIG. 1 + 4 flow rate to distillation column 1
Table 1 shows the relationship between the decanter temperature and the load of 0.
Shown in Comparative Example 1 Table 1 shows the results obtained in the same manner as in Example 1 except that the temperature of the decanter was changed to 40 ° C. [Table 1] According to the present invention, n-hexane as an azeotropic agent can be effectively separated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a distillation method used in the present invention. FIG. 2 is a diagram showing n-hexane-methanol mutual solubility. [Description of Signs] 1 Trimethoxysilane reaction product 2 Bottom liquid obtained by removing methanol from 1 3 Methanol / n-hexane azeotrope 4 Azeotropic agent which is the upper phase liquid (n-hexane rich liquid) of decanter 5 Lower phase liquid of decanter (methanol rich liquid) 6 Methanol / n-hexane azeotrope 7 Methanol 8 Trimethoxysilane 9 Tetramethoxysilane and other high-boiling substances 10 Azeotropic distillation column 11 for separating methanol 11 Methanol and n-hexane Separation distillation column 12 Distillation column for separating trimethoxysilane and tetramethoxysilane

Claims (1)

(57) [Claim 1] In an azeotropic distillation method in which n-hexane is used as an azeotropic agent to separate methanol from a liquid containing trimethoxysilane and methanol, the distilled n-hexane and A method for separating trimethoxysilane, comprising separating an azeotropic mixture of methanol into n-hexane and methanol at 25 ° C or lower.