JPS58172221A - Manufacture of chlorosilane by treating silicon - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention The present invention relates to silicon and residual silicon. The present invention relates to a method for processing powder, and more particularly to a method for producing chlorosilane from silicon and residual silicon powder.

Commercial methods of making organonorosilanes are well known and are described in Rochow, U.S. Pat.
It is stated in No. 5. Rochov et al. describe the direct reaction of an organic compound, such as methyl chloride, with silicon particles to produce organochlorosilanes. Such silicon particles are mixed with copper particles, thereby forming a reactive material or reactive contact material. In commercial practice, this reaction is generally carried out in one of three types and apparatuses: a stirred prototype reactor such as that described in 8ellers U.S. Pat. No. 2,449,821; Fluidized bed reactor as described in Re@d et al. US Pat. No. 2,589,951; or a rotary kiln.

Organotrichlorosilane and diorganodichlorosilane are the two basic products of the above direct reaction. Such compounds are described in U.S. Pat.
2.25 & 222 for the production of organopolysiloxane resins. Other products include U.S. Pat. No. 2,469.

No. 888 and U.S. Patent No. 2,469,89
0, as well as organopolysiloxane elastomers such as those described in U.S. Pat. No. 2,441,111,7,56. Generally, it is preferred to produce the diorganodichlorosilane commercially. This is because they are commonly utilized in the production of linear polysiloxane fluids and polymers used in the production of thermoset rubber elastomers and various types of room temperature vulcanizable silicone rubber compositions.

At a certain stage in the direct method of producing organochlorosilane, the reactivity of the reactive substance containing silicon particles or the reactive contact substance decreases, and it is therefore preferable to replace the reactive substance. Therefore, the old or less reactive silicon particles are removed from the reactor, new silicon particles are introduced, and the reaction is then restarted. When a reactive contact material becomes less reactive and is replaced by fresh silicon content, this less reactive contact material is generally combined with residual silicon, residual silicon powder, residual silicon-containing welding material, or residual contact material. Called. These terms can be used interchangeably here.

An early solution to this problem was to discard the residual contact material, but significant reactive silicon remains in the residual contact material, and for economic reasons and to avoid waste disposal problems, it was necessary to discard the residual contact material. Preferably, at least some of the remaining silicon value in the contact material is utilized.

Much work has been done to find ways to more fully utilize the residual silicon particles in the reactors used to carry out the direct synthesis of organochlorosilanes. the result,
Being able to maintain the weight ratio of organotrichlorosilane (designated T) to diorganodichlorosilane (designated D) at a desired level for an extended period of time ensures maximum utilization of silicon particles in the production of diorganodichlorosilane. I found it very cheerful. In the production of organochlorosilanes by the Rochhow direct method, the weight ratio of triorganochlorosilane to diorganodichlorosilane (T/D) should not exceed about α1, preferably about α55, during the production of chlorosilanes. However, in many commercial manufacturing operations, it has been found that when starting the reactor with fresh feed this ratio is at a level of about 115, but during the reaction period this increases to levels above a2. One improvement in this scope is disclosed in Dataon U.S. Pat. No. 31,331.
0? This is the method described in No. Dotson reveals that silicon particles can be more fully utilized and that the amount of diorganodichlorosilane can be maximized by passing the particles from a fluidized bed reactor to an external fluid energy mill. .

Apart from the external fluid energy mill, D Otson also passed the used silicon particles recycled from the reactor through a number of sonic jet nozzles located at the bottom of the reactor.
It is also mentioned that the particles are pulverized by impact with each other or with the reactor lid.

By utilizing the Dotson process, a larger amount of diorganodichlorosilane is obtained from the same amount of silicon particles, so that the above ratio can be kept near the desired level of α15 and below α55 for an extended period of time. I found out that it drips. However, it has been found that in the DOtllOn process, approximately 12-15% of the silicon introduced into the reactor is underutilized and must be removed from the process as waste silicon. It was generally believed that such silicon was exhausted and therefore could no longer be used. It is desirable to utilize this waste silicon to avoid the problems normally encountered in waste disposal and for economic reasons. Furthermore, it would be even more desirable to find a new method that can utilize substantially all of the silicon number in the residual silicon-containing contact material after the Te/p ratio rises to an undesirable level.

US Pat. No. 4,281,149 to 8hade shows a method for processing silicon particles in such a silicon reactor system, thereby improving the utility of silicon metal particles. The 5hade process generally processes silicon particles with an average diameter of less than 40 microns, then polishes such particles to remove the surface coating on the particles, and then returns the polished particles to the reactor for further utilization. There are many ways in which it can be done.

U.S. Patent No. 4,302, which is cited here as a cited document.
No. 42, 5hah and Rltger
presents another method for recovering and recycling silicon particulates in an organochlorosilane reaction system. The method described therein classifies the direct contact material by particle size and in doing so classifies the most severely damaged or contaminated (
This book consists of methods for separating spent silicon particles from relatively flat silicon particles and recycling only such intact particles to improve the usefulness of the silicon. Therefore, instead of discarding all the spent silicon particulates from the direct process, only a small amount of used silicon particulates need to be disposed of at any given time. U.S. Patent No. 4,307,242
No. 3, the effluent fines (residual contact material or residual silicon) are collected in one or more patterned cyclones.

This effluent fines is generally spent reactant from reactors that produce organotrichlorosilane and diorganodichlorosilane products. The T and D crude products are collected from the top of the cyclone. These products may contain submicron particles entrapped therein. The remaining reactants are treated with air in a mechanical cyclone and placed in a receiving hopper for further disposal. It is preferred to obtain the useful product from the second cyclone fines obtained from the classification process of 8hah and R1tm@r at any stage described, especially from any other source. It is highly desirable to obtain useful products from the resulting silicon residue and residual silicon-containing contact material.

One such useful product obtained from various reactions with silicon is trichlorosilane (HBi 01.). A well-known use of trichlorosilane is the hydrosilation reaction of trichlorosilane to form organofunctional silanes, and the English-Japanese patent application GB 2 of Woerner et al., published March 5, 1980.
The use of trichlorosilane as a raw material for the production of ultrapure silicon as discussed in No. 289-02A.

Woernet et al. show that trichlorosilane and silicon tetrachloride are made by the reaction of silicon and hydrogen chloride. Additionally, US patent tic 2. s s
In the o, q q s issue, Rochow said that a mixture of about 80% trichlorosilane and about 20% silicon tetrachloride was
Com is said to be obtained by passing hydrogen chloride through an iron tube filled with silicon heated to 30°C to 440°C.
bes is f:! empt, rend.

122.531 (1896), reported the reaction between hydrogen chloride and silicon. It would thus be desirable to provide additional sources of trichlorosilane, to provide an economical process for making trichlorosilane, and to provide a process for the synthesis of trichlorosilane in which the yield of trichlorosilane is improved. ing.

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a method for utilizing residual silicon obtained from the production of organochlorosilanes.

Another object of the invention is to provide an improved process for obtaining trichlorosilane from silicon.

Another object of the present invention is to provide a method for producing trichlorosilane from residual silicon powder.

Other objects and advantages of the invention will become apparent from the detailed description below.

In accordance with the purposes of the present invention, trichlorosilane is prepared by contacting silicon with an anhydrous chlorine source selected from the group consisting of hydrogen chloride, chlorine and mixtures thereof in the presence of silicon tetrachloride vapor at elevated temperatures. □It is built. Silicon may be derived from any source so long as it is in a form suitable for contacting the chlorine source and silicon tetrachloride vapor at elevated temperatures.

In accordance with at least some of the objects of the present invention, the residual silicon or residual silicon-containing contact material is an anhydrous chlorine source selected from the group consisting of hydrogen chloride, chlorine, and mixtures thereof;
A method is described for producing trichlorosilane from residual silicon obtained from the direct production of organochlorosilanes or from residual silicon-containing contact materials, which comprises contacting in the presence of silicon tetrachloride vapor at elevated temperatures.

Generally, silicon tetrachloride vapor is utilized as a carrier gas and is also a fluidizing medium for granular or powdered silicon or a silicon-containing source or contact material. To produce trichlorosilane, hydrogen chloride gas and/or
Alternatively, chlorine gas may be mixed with a silicon tetrachloride carrier gas. In the method of the invention, the external source of silicon tetrachloride is hydrogen chloride gas.

Alternatively, it is important to supply it to the reactor type together with chlorine gas. By external source is meant a source other than the products obtained during the reaction.

In the process of the present invention, the residual silicon-containing contact material obtained as second particulates from the cyclone separator is treated with an anhydrous chlorine source in the presence of added silicon tetrachloride vapor to produce organohalosilanes directly. Residual silicon-containing contact material resulting from production was converted to trichlorosilane. As explained above, the silicon tetrachloride vapor stream may contain hydrogen chloride gas and/or F3t-fJ gas, or separate streams of silicon tetrachloride and hydrogen chloride gas and/or chlorine gas may be added to the reactor or It may also be introduced into the reaction chamber. Furthermore, silicon tetrachloride is an inherent by-product in the direct synthesis of trichlorosilane and is therefore an ideal carrier gas for the process of the present invention and subsequent recycling. External silicon tetrachloride used in the process of the invention can also be collected and recycled. When the trichlorosilane product, which generally has a boiling point of about 51.5°C, is recovered, silicon tetrachloride, which generally has a boiling point of about 57.6°C, is also recovered.

For example, when they are collected by condensation methods, they generally condense at the same time and form a mixture. This mixture can be distilled or subjected to another separation process to separate the trichlorosilane from the silicon tetrachloride, which is then stored and recycled or converted into silicon tetrachloride for the process of the invention. can be immediately recycled as an external source of The silicon tetrachloride by-product mentioned above, dichlorosilane (HxS
i04), monochlorosilane (a3s i(!t)
, high boilers such as hexachlorodisilane (Ots8
By-products of the reaction are also formed during the reaction, including 1-810ts), and these by-products can also be separated and recovered, if desired, by conventional separation and recovery methods.

The present invention relates to a process for the preparation of trichlorosilane, which comprises contacting silicon with hydrogen chloride and/or chlorine at elevated temperatures in the presence of an external source of silicon tetrachloride. As used herein, silicon may be in any suitable form, and in a preferred embodiment, silicon is residual silicon obtained from the direct synthesis or production of organochlorosilanes.

The silicon may be in any finely divided form, and for optimum results the silicon in the reactor generally has an average particle size in the range of about 20 to about 2 oo microns. At least 25% by weight of the silicon particles have an actual diameter of about 20 to about 20
A range of 0 microns is preferred.

If residual silicon is used, for example a residual silicon-containing contact material obtained in the direct synthesis or production of organochlorosilanes, the residual contact material may contain other auxiliaries and other auxiliaries previously added to the elemental silicon for the production of organochlorosilanes. Additives may also be included. Direct synthesis or production of organosilanes is described in US Pat. No. 2,38 to Rochow.
G, No. 995. The present invention, for example,
After the direct synthesis of ochow, the remaining residual contact material may be carried out without further processing; however, in a preferred embodiment, the contact material may be further processed to remove some of the auxiliaries and additives. They do not contaminate the trichlorosilane (nstcz@) product. To this end, in preferred embodiments, various conventional methods are applied to the residual silicon-containing material before carrying out the method of the invention. For example, Elh
U.S. Pat. No. 4.ah and R1tg8r. '507,2
42, in which the silicon-containing contact material, referred to as effluent contact material powder', or alternatively referred to as 1 silicon grains', is subjected to an aerodynamic or centrifugal classifier. Such a classifier is a device that can classify and separate cyclone fine particles according to particle size.

The most common method involves recycling the relatively coarse particulates into the organochlorosilane reactor and discarding the finest portion. However, 5hah and Rltzer
According to the authors, the so-called finest fraction contains by far the highest proportion of non-silicon impurities, and decisions must be made regarding which grain sizes to discard and which grain sizes to recycle.

Accordingly, in the 8hah and R1t2er method for purifying silicon metal contact material from a direct organohalosilane reactor system, a portion of the reactor contact material is analyzed for particle size distribution; Sort into one part and a relatively impure second part: and separate the first and second parts. The silicon fine particles are collected in a second cyclone and sent to a receiving hopper and then to a transfer hopper and from there to a mechanical classifier, preferably an aerodynamic or centrifugal classifier. In a preferred embodiment of the invention, the second cyclone particulate is supplied with a suitable anhydrous chlorine source, such as hydrogen chloride,
Chlorine and mixtures thereof are contacted at an elevated temperature in the presence of an external source of silicon tetrachloride.

Another preferred source of residual silicon is finely divided particles of silicon obtained from the method and apparatus described in DOtliOn US Pat. No. 4,131,099, which is incorporated by reference. DotsOn passes the silicon-containing use particles from the fluidized bed reactor through an external fluid energy mill or passes them through a number of sonic jets at the bottom of the reactor to pulverize the particles.

Alternatively, particles are crushed by impact between silicon particles or by impact of silicon particles against the reactor wall. In this way, K, compression, impact,
Any residual silicon-reactive material that has been crushed, ground, or disintegrated by breaking up the individual particles of the silicon-containing mixture, such as by grinding, may be used in the process of the present invention.

As mentioned above, the silicon source may be a new silicon powder that has not yet been used in the manner described above. Thus, any finely divided silicon, preferably finely divided silicon that is free of any contaminants that could cause contamination of the final product, such as trichlorosilane, may be used in the process of the present invention.

There are no restrictions on the equipment for carrying out the method of the present invention, but the electrical production must be such that silicon can be sufficiently brought into contact with an anhydrous chlorine source at high temperature in the presence of silicon tetrachloride. No. The reactor or reaction chamber may be of any suitable size or shape and is preferably made of a material that will not be corroded by or react with the reactants and products and/or by-products. The apparatus heats silicon and a silicon-containing contact material at a suitable elevated temperature sufficient to effect a reaction between the silicon and a source of chlorine in the presence of an external source of silicon tetrachloride to produce a trichoprosilane. You must be able to express yourself. In one preferred embodiment, the method is carried out by forming a fluidized bed, and the silicon is contacted with an anhydrous chlorine source and silicon tetrachloride while the silicon remains in the fluidized bed. There are various examples for maintaining a fluidized bed of silicon, including ensuring that the gas or vapor velocity is sufficient to maintain the silicon in a fluidized state within the reactor. This is preferably carried out by injecting silicon tetrachloride as a carrier, ie as a fluidizing medium, into the granular silicon. Of course, other conventional fluidization means can also keep the silicon bed in a fluidized state.
It is also within the scope of the present invention to utilize a combination of methods to simultaneously contact the anhydrous chlorine source in the presence of silicon tetrachloride and to maintain the silicon bed in a fluidized state.

The use of inert gases, such as nitrogen, to fluidize silicon powder or residual silicon-containing contact materials or to assist other fluidization means, although generally not preferred because of the need for powerful evacuation means. I can do it. A conventional fluidized bed reactor is disclosed in U.S. Pat. No. 2.589.9 S1 by R@el et al.
It is stated in the number. Alternative means of contacting silicon with an anhydrous chlorine source and silicon tetrachloride include in a stirred prototype reactor as described in 8.110rs U.S. Pat. No. 2.449.821, or in a conventional rotary kiln. . The means for heating the silicon bed within the reactor may be any conventional means, and internal and external heating sources, including gas and/or steam heating, may be used in the process of the present invention. Examples of conventional means of heating beds contained therein are presented in the above-mentioned documents.

The high temperature at which the reaction mixture of silicon or silicon-containing contact material, anhydrous chlorine source, and silicon tetrachloride is heated is limited, as long as the temperature is sufficient to produce trichlorosilane product from the reaction mixture. Not done. Generally, temperatures of about 30°C to about 350°C are suitable for the production of trichlorosilane from the reactants.

Any anhydrous chlorine source may be used in the process of the present invention, so long as it is possible to produce trichlorosilane from the reaction between silicon used with an external source such as silicon tetrachloride and chlorine in an anhydrous chlorine source. . Preferred sources of anhydrous chlorine are hydrogen chloride gas, chlorine gas, and mixtures thereof. The amount of chlorine source need only be sufficient to form trichlorosilane from the silicon contact material. Of course, the reaction rate is proportional to the amount of chlorine source present in the reaction mixture;
And silicon tetrachloride acts as their dilution medium.

The amount of chlorine source required by the desired reaction rate in the particular reaction system or reactor utilized in the production of trichlorosilane can be determined by one skilled in the art. In certain preferred embodiments, the chlorine source is about 1α
0 mol% to about 990 mol%, in other words, silicon tetrachloride is about 1.0 mol% to about 9n of the silicon tetrachloride-chlorine source.
o mol%. In the most preferred embodiment, the silicon tetrachloride to hydrogen chloride gas ratio is about 1.5:
1 to about 2.6:1. Hydrogen chloride gas and/or chlorine gas may be any conventional gas source provided in commercial applications.

Silicon tetrachloride from an external source may also be from any suitable source. Silicon tetrachloride is an inherent by-product of the direct synthesis of trichlorosilane, and any silicon tetrachloride formed as a by-product of the reactions of the present invention is collected and recycled as an external source of silicon tetrachloride in the present invention. I can get it back. Therefore,
This is ideal for use as a carrier gas, which can then be recycled from the reactor for further use in the process of the invention. Silicon tetrachloride from external sources can also be collected and recycled for further use. Thus, when collecting the trichlorosilane product, silicon tetrachloride can be collected both from external sources and as a by-product. One way to collect it is with a methanol-based coolant, which is about -2
By condensing in a conventional condenser cooled to 0°C. This condenses the product, silicon tetrachloride and most by-products. These can be appropriately collected and separated by any suitable separation method, including truncated distillation.

Anhydrous chlorine sources, such as hydrogen chloride gas and/or chlorine gas, and silicon tetrachloride can be brought into contact with the silicon in a suitable manner and the gas(es) or vapors are introduced into the reaction chamber in which the reaction is carried out. Any suitable gas velocity that supplies the gas may be used. In preferred embodiments where silicon tetrachloride vapor is the silicon fluidizing medium, the gas velocity is sufficient to maintain the silicon bed in a fluidized state. Generally, the silicon tetrachloride gas velocity is about 5 to about 15 times the flow rate of the particular silicon contact material.

The optimum rate of gas and/or steam can be determined by one skilled in the art and is based on various operating conditions. When using a stirred reactor or when using a rotary kiln, the gas velocity spanning flow rate can be lower than the minimum rate required to fluidize the silicon in the reactor.

When using silicon tetrachloride gas or vapor with an anhydrous source, in a preferred embodiment, hydrogen chloride gas and/or chlorine gas are co-fed to the reaction chamber with the silicon tetrachloride stream. However, separate streams of gas into the reactor,
It is also within the scope of the invention to feed multiple streams of gas to the reactor and combinations thereof. Silicon tetrachloride is not only a byproduct of the direct production process for organochlorosilanes, but it is also collected, separated, and recycled to the reactor for contacting the silicon with an anhydrous chlorine source in the presence of silicon tetrachloride. The use of silicon tetrachloride is advantageous in the process of the present invention because of its ease of preparation. Thus, in accordance with at least some of the objects of the present invention, silicon tetrachloride is used as a diluent for the chlorine source and/or as a carrier gas and/or as a fluidizing medium, and when silicon tetrachloride is used in the present method. Significant improvements have been recognized. The trichlorosilane product is also collected by any suitable means, such as the use of a condenser and subsequent distillation.

Generally, it is preferred to carry out the process of the present invention under anhydrous conditions to prevent the formation of hydrolysis by-products and other undesirable by-products that reduce the yield of trichlorosilane. Accordingly, preferred embodiments may employ steps to remove moisture from the system and reactants. The following examples illustrate the invention and do not limit its scope: Electric motor six-drive discontinuous helix with special flanged end plug and bed agitation; A 1 inch (2.54 ex) stirred bed reactor made of stainless steel consisting of 2.54 cm diameter and 45.7 cm (18 inch) long tubing with a stirrer was used as the reactor. The tube section was divided into upper and lower reaction zones and each reaction zone was fitted with an independent heater to maintain each zone at the desired temperature. The reactor barrel or tube was well insulated to prevent heat loss. Inlets were made at the bottom of the tube for supplying sources of gas and/or steam, ie for supplying silicon tetrachloride and chlorine sources. An outlet was made at the top of the tube and provided with a suitable condenser for collecting the liquid trichlorosilane product and by-products and a suitable vent chamber for degassing. Using suitable glass and plastic fittings and tubing,
Corrosion effects caused by reactive gases were minimized.

8hah and R1tit@r U.S. Patent No. 4.507
．． 9, the residual silicon-containing contact material consisting of the second cyclone fine particles 5a, Of obtained from the method described in No. 242,
into the stirred bed reactor system described above. The temperature of the reaction zone was maintained at approximately 250° C. during the experiment. Anhydrous hydrogen chloride through a linear flow meter at 2.45 ?/hr. (hourly rL06
The input rate of silicon tetrachloride, which was supplied to the reaction zone at a constant rate of 7 mol), varied, but was 14.7 to 2 q, a per hour.
tC was maintained at about 0.09 to about 0.17 kph). Therefore, the silicon tetrachloride to hydrogen chloride ratio (mol) Fi was maintained in the range of about 1.3 to about 'L6. The gray heater-evaporator two-part zone was ensured to be transported lightly to the contact storage floor area. Trichlorosilane (as1cz3) was initially retained in the reaction effluent by gas chromatographic analysis.

Thus, in accordance with at least some of the objects of the present invention, trichlorosilane was prepared from residual silicon powder recovered from the production of organochlorosilane by a direct process.

Anhydrous hydrogen chloride was added to the silicon tetrachloride vapor; the hydrogen chloride in the resulting silicon tetrachloride vapor was passed through a bed of residual silicon powder to form the reaction mixture; and the reaction mixture was heated at an elevated temperature [,
A method has been described for treating residual silicon powder recovered from the production of organochlorosilane by a direct process by forming trichlorosilane.

Although the present invention has been described in detail with reference to particularly preferred embodiments, it is to be understood that modifications may be made within the spirit and scope of the invention.

Claims (9)

[Claims] (1) A method for producing trichlorosilane comprising contacting silicon with an anhydrous chlorine source selected from the group consisting of hydrogen chloride, chlorine and mixtures thereof in the presence of silicon tetrachloride at high temperature. (2) The method of claim 1, wherein the silicon is a powder and the chlorine source and silicon tetrachloride are contacted with a fluidized bed of silicon powder. (3) The method of claim (1), wherein the silicon is a powder and the chlorine source and silicon tetrachloride are contacted with a stirred bed of silicon powder. (4) The method according to claim (1), wherein silicon tetrachloride is a carrier for the chlorine source. (5) The method according to claim (1), wherein silicon tetrachloride is a silicon fluid medium. (6) The method according to claim (1), wherein the temperature is about 50°C to about 550°C. (7) Silicon tetrachloride is about 1.0 to 1.0 of silicon tetrachloride-chlorine source
The method of claim 1, wherein the amount is about 910 mol%. 8. The method of claim 1, further comprising collecting the trichlorosilane product and silicon tetrachloride and separating the trichlorosilane and silicon tetrachloride. (9) further comprising collecting the trichlorosilane product and silicon tetrachloride, separating the trichlorosilane and silicon tetrachloride, and recycling the silicon tetrachloride;
A method according to claim (1). Ql Production of organochlorosila/ by contacting residual silicon with an anhydrous chlorine source selected from the group consisting of hydrogen chloride, chlorine and mixtures thereof in the presence of silicon tetrachloride at elevated temperature A method for producing trichlorosilane from residual silicon obtained from. 42. The method of claim 41, wherein the silicon is a powder and the chlorine source and silicon tetrachloride are contacted with a fluidized bed of silicon powder. Method described. αD further comprising collecting the dichlorosilane product and silicon tetrachloride and separating the trichlorosilane and silicon tetrachloride. A method according to claim 2, comprising: collecting, separating trichlorosilane and silicon tetrachloride, and recycling silicon tetrachloride. a! From the group recovered from the production of organochlorosilane. adding a selected anhydrous chlorine source to the silicon tetrachloride vapor; (b) passing the resulting chlorine source in the silicon tetrachloride through a bed of residual silicon powder to form a reaction mixture; and (C) heating the reaction mixture at an elevated temperature. and forming trichlorosilane. ■ A method according to claim αl, wherein the reaction mixture is heated at about 30° C. to about 350° C. Qυ Further, trichlorosilane is The method according to claim α9, which further comprises recovering the residual silicon powder. - The method according to claim 01, which further comprises forming a fluidized bed of the residual silicon powder. Fluidized by the velocity of silicon tetrachloride vapor,
A method according to claim 1. The method of claim 11 further comprising: forming a stirred bed of residual silicon powder; further collecting the trichlorosilane product and silicon tetrachloride; 19. The method of claim 19, further comprising: collecting the trichlorosilane product and silicon tetrachloride; separating the trichlorosilane and silicon tetrachloride; A method according to claim 0, comprising recycling the .