JPS61117112A - Preparation of fluorochlorosilane - Google Patents

Abstract

PURPOSE:To prepare fluorochlorosilane with high energy efficiency and easy control of the amt. of introduced raw material resulting as a whole extremely high advantage as commercial preparation by allowing gaseous chlorine and gaseous SiF4 to react with metallic Si or Si alloy. CONSTITUTION:Metallic Si or Si alloy is used as a raw material. Suitable metallic Si is one obtd. by reducing generally available siliceous stone with carbon or one obtd. by crushing the above-described product from the siliceous stone and removing impurities deposited on the grain boundary by treating with an acid. Suitable Si alloy is generally available ferrosilicon, calcium silicon, or magnesium silicon, etc. Fluorochlorosilanes SiFnCl4-n (n=1,2,3) is obtd. by allowing gaseous chlorine and ¦SiF4 gas to react with the above described siliceous raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides fluorochlorosilanes 81. useful as intermediate raw materials for silicon compounds. F'nC14-n (n = 1,
2, 3) Regarding the manufacturing method.

[Prior art]

The following methods are known as methods for producing fluorochlorosilanes.

■ A method of partially fluorinating silicon tetrachloride using antimony trifluoride. For example, H, 8, Booth et al.

(, T.A.O., 8, 54-4750 (1932))
There is.

■ A method based on the reaction of hexafluoroxy2(131,F'.) with chlorine gas. For example, W, 0.13chum
bat al, (J, Mu, O, 8, 54-3943 (
1932)).

■ Redistribution reaction between silicon tetrachloride and silicon tetrafluoride
attribution) IC method. For example, LL
Anderaon (J, A, O, 572-2091 (
1950) ;I) or USF2,395,82
6 etc.

However, the method (2) has the drawbacks that the fluorinating agent, antimony trifluoride, has strong hygroscopicity and that it requires purification by sublimation to improve the purity of the antimony trifluoride, making it complicated to handle. ing. Method (2) involves a mild explosive reaction between hexafluorodisilane and chlorine gas, and is unsuitable for industrial scale production. Furthermore, it is difficult to obtain the raw material hexafluorodisilane, so this method cannot be said to be preferable. Among the three methods, method (2) in which silicon tetrachloride and silicon tetrafluoride are subjected to a redistribution reaction at 600 to 700° C. is considered to be suitable for industrial scale production.

[Problem that the invention seeks to solve]

However, silicon tetrachloride, one of the raw materials, is generally obtained by applying chlorine gas to a silicon alloy at about 400°C, and a considerable amount of thermal energy is required for the chlorination reaction. . Thermal energy for manufacturing this silicon tetrachloride raw material and thermal energy for carrying out the redistribution reaction at 600 to 700°C are required twice, and the loss of thermal energy is large. ing.

In addition, it is difficult to control the flow rate of silicon tetrachloride during the redistribution reaction, whether it is in a liquid state or in a gaseous state after being vaporized.

[Means for solving problems]

The inventors of the present invention have made intensive studies to eliminate the disadvantage of the method (2), and have found a method of carrying out a redistribution reaction at the same time as the silicon tetrachloride synthesis reaction, resulting in the present invention. That is, the present invention is a method for producing fluorochlorosilanes, which is characterized by causing chlorine gas and silicon tetrafluoride gas to act on metallic silicon or a silicon alloy.

According to the method of the present invention, it is only necessary to apply thermal energy during the production of fluorochlorosilanes, thereby eliminating the disadvantage of thermal energy loss. Furthermore, since both chlorine gas and silicon tetrafluoride gas are gaseous at room temperature, it is not difficult to control the flow rates, and the accuracy can be significantly improved.

The present invention will be explained in more detail below.

Metallic silicon or a silicon alloy is used as the S1 raw material for producing fluorochlorosilanes. As the metal silicon, one obtained by carbon reduction of general silica stone, or one obtained by crushing it and treating it with an acid to remove impurities precipitated at grain boundaries, etc. is used. Common silicon alloys include 7erosilicon (Fe-81) and calcium silicon (Oa-8i).
), magnesium silicon (Mg-81), etc. can be used.

As for the reaction format, any of fixed bed, fluidized bed, moving bed, etc. may be employed.

When using the S1 raw material, it is adjusted to an appropriate particle size range that matches the type of reaction. For example, in the case of a fixed bed, a range of about 1×1 m511 to 1 oxlofi is preferable. On the other hand, commercially available chlorine gas and silicon tetrafluoride gas can be used as they are. Also, crude gas before purification may be used, but chlorine gas must be thoroughly dehydrated before use6.
Ru.

Furthermore, an inert diluent gas such as nitrogen, helium, or argon may be flowed into the reaction system if necessary. Further, chlorine gas and silicon tetrafluoride gas may be introduced into the reaction system as a mixture, or may be introduced separately, or may be divided into a chlorination zone and a redistribution reaction zone.

In the case of using metallic silicon t-8i as a raw material, the nominal molar ratio MR of silicon tetrafluoride gas and chlorine gas (MR=SiF41014) is selected from the range of 0.05 to 5.

Fluorochlorosilane Si FnO14-n is monofluorotrichlorosilane 5iFn3 (n=1)
Boiling point: 12.2℃
5iF2012 (n=2) #-32,2tr
Trifluoromonochlorosilane 5iF3 (1 (n=3
) There are three types of p -70 and Op, but when the MR is increased, a rich mixed gas of 191F' is produced, and the MR
If i is made smaller, SiF'C! 1. A rich gas mixture is obtained. If the value is less than 0.05 or more than 5, it is not preferable because the yield of the reaction decreases.

When using a silicon alloy as the S1 raw material, for example, in the case of 7-erosilicon, Fe01g is produced as a by-product, so the molar ratio MR of silicon tetrafluoride gas and chlorine gas charged to the reaction system should naturally be smaller than in the case of metallic silicon. There is a need.

Although the flow rates of chlorine gas and silicon tetrafluoride gas vary depending on the type of reaction, they must be allowed sufficient contact time with the S1 raw material. The reaction temperature is preferably in the range of 180 to 1000°C, at which the chlorination reaction of the S1 raw material proceeds, and more preferably in the range of 350 to 800°C. Below 180℃, the chlorination rate of S1 raw material is too slow, and below 100℃
Even if the temperature is higher than that, no special benefit can be obtained by increasing the temperature.

In the conventional redistribution reaction of silicon tetrachloride and silicon tetrafluoride, one reaction at a relatively high temperature was necessary to obtain a sufficient yield, but in the method of the present invention, although the reason is not clear, , sufficient yields can be obtained at lower temperatures. The generated gas A discharged from the reaction system contains a small amount of silicon tetrachloride gas and unreacted silicon tetrafluoride gas as well as the above three types of fluorochloroheptanaranes. In order to collect only fluorochlorosilanes, first use high boiling point silicon tetrachloride gas (boiling point 57°C).
Pass through a cold trap at 0 to -20°C to remove. Next, the fluorochlorosilanes are collected through a cold trap at -80 to -110°C. Finally, low boiling point silicon tetrafluoride gas (boiling point -95°C) is collected in a -196°C cold trap.

The collected fluorochloro7ranes are subjected to distillation operations such as low temperature distillation or pressure distillation F) 5iFC1s, 5iy
IC1! It can be isolated as well as 5iFsC1.

An example of a reaction formula for simultaneous chlorination and redistribution reaction is 81+201! + 5iF4- 28iF, (U1
(Sf31 + 2012+3SiF, -481F
, 01 (2)3Si+601. +5iF4-4S
iFO1, (31 can be considered.

The present invention is illustrated by examples in the arrows.

Example 1 Particle size 2 x 2 - 5 in a quartz tube with an inner diameter of 34φ and a length of 550 m
A sufficient amount of metal silicon of approximately 5W was filled at 450F for the reaction. This quartz tube was set in a tube furnace, and the temperature was raised while flowing Sihelium from the inlet side, and after almost completely purging air and moisture inside the tube, the temperature of the tube furnace was set at 700°C. Next, dry chlorine gas 8000/min as raw material gas
A mixed gas of 40 Co/min of silicon tetrafluoride gas and 20007 ffdn of helium for dilution was e-charged on the inlet side, and chlorination reaction and redistribution reaction were performed simultaneously. (Corresponding to MR-8iF4101.=0.5) Of the quartz tube outlet gas, silicon tetrachloride gas was collected in a trap at -10°C, and fluorochlorosilanes were collected in a trap at -100°C. Unreacted silicon tetrafluoride gas is 1196
It was collected in a trap at ℃. The reaction time was 2 hours, and after stopping the charging of the raw material gas, helium was added at 100 QC to sufficiently trap the gas remaining in the quartz tube.
/In1n for 2 hours. After the reaction, -100℃
The fluorochlorosilanes collected in the trap were vaporized in a separate vacuum container, and the resulting fluorochlorosilanes were measured to be 43.07.9 The amount of silicon tetrafluoride and chlorine gas in the raw material gas was The yield based on the total amount including the amount converted to silicon tetrachloride was 80%. Further, as a result of analyzing the vaporized mixed gas by gas chromatography, the average composition was found to be SiF4 trace.

Example 2 A reaction was carried out in the same manner as in Example 1 except that MR'i was 0.35 and the temperature of the tube furnace was 500°C.

That is, dry chlorine gas 88.9 honey n1 as raw material gas
Silicon tetrafluoride gas 31. Icc/In1n, Helium 20
When a mixed gas of Cq/min was charged to the inlet side and reacted, the fluorochloro 7-ranes produced were 41
．． 3791, the yield was 78. Further, as a result of analyzing the vaporized mixed gas by gas chromatography, the average composition was found to be SiF4 trace.

Example 3 Using 7erosilicon (day 1; 90%) adjusted to particle size zxzm ~ 5X5■, dry chlorine gas 800C/m1ns
Example 1 except that the silicon tetrafluoride gas was used at 3000/min.
A similar reaction was carried out. As a result, the yield after 2 hours of reaction was 82 cm. Further, as a result of analysis by gas t-cass chromatography, the average composition was found to be SiF4 trace.

〔Effect of the invention〕

According to the present invention, it is possible to easily obtain fluorochloroheptadranes by acting chlorine gas and silicon tetrafluoride gas on metallic silicon or a silicon alloy, and the energy efficiency is good, and the amount of raw materials introduced can be easily controlled. Therefore, fluorochlorosilanes can be obtained in a very industrially advantageous manner.

Claims (1)

[Claims] Fluorochlorosilanes SiFnCl_4_-_n (n=1, 2
, 3) manufacturing method.