JPS636483B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating residual silicon powder, and in particular to a method for producing halosilanes from residual silicon powder. Current industrial methods for producing organohalosilanes are well known and described in US Pat. No. 2,380,995. This patent describes the direct reaction of silicon particles with organohalides such as methyl chloride to make organochlorosilanes.
Copper particles are mixed with silicon particles, thereby forming a reactive mass or reactive contact mass.
When carried out industrially, this reaction is generally carried out in one of three types of equipment, such as a stirred bed reactor as described in Sellars US Pat. No. 2,449,821; No. 2,389,931; or a rotary kiln. Organotrichlorosilane and diorganodichlorosilane are the two basic products of the direct process reaction described above. Such compounds are described in U.S. Pat.
2258218 and 2258222 for the production of organopolysiloxane resins. Other products include U.S. Patent No. 2,469,888 and No.
No. 2,469,890 as well as organopolysiloxane elastomers as described in U.S. Pat. No. 2,448,756. Generally, it is preferable to produce diorganodichlorosilane from an industrial standpoint. This is because they are commonly utilized to make linear polysiloxane fluids and polymers used in the production of various room temperature curable silicone rubber compositions and thermoset rubber elastomers. At some stage in making organochlorosilanes by the direct process, the reactive mass or reactive catalytic mass containing silicon particles becomes less reactive and it is possible to replace the reactive catalytic mass. desirable. For example, waste silicon particles or less reactive silicon particles are removed from the reaction vessel, new silicon particles are inserted therein, and the reaction is then restarted.
The reactive contact mass has become less reactive or
When it has weakened and is replaced with a new batch of silicon, the less reactive or weakened contact mass is generally replaced by residual silicon, residual silicon powder,
Referred to as residual silicon-containing contact mass or residual contact mass, these terms are used interchangeably herein. The old solution to this problem was to discard the residual contact mass, however, there remained considerable reactive silicon in the residual contact mass, avoiding disposal problems and for economic reasons. Therefore, it is desirable to utilize at least some of the remaining silicon values in the remaining contact mass. The weight ratio of organotrichlorosilane (known as T) to diorganodichlorosilane (known as D) can be maintained at a desired level over a long period of time, thereby allowing the diorganodichlorosilane to Much research has been carried out in an effort to find a way to more fully utilize the residual silicon particles in the reactor used to carry out the direct synthesis of organochlorosilanes, resulting in maximum utilization of silicon particles to produce has been done. In the production of organochlorosilanes by the direct method of Lochiyo U.S. Pat. No. 2,380,995, triorganochlorosilane versus diorganochlorosilane (T/
The weight ratio of D) is approximately during the production of organochlorosilane.
0.1 is preferred, and preferably no more than about 0.35.
However, in most industrial manufacturing operations,
It has been found that this ratio is at a level of about 0.15 when starting the reactor with fresh material, but increases to a level of about 0.2 or higher after some time of reaction. One breakthrough in this field is the method disclosed by Dotson in US Pat. No. 3,133,109. Dotson describes that silicon particles can be utilized more completely and the amount of diorganodichlorosilane can be maximized by passing the particles used from a fluidized bed reactor into an external fluidized energy mill. As an alternative to an external flow energy mill, Dotson also passes spent silicon particles recycled from the reactor through multiple tuning fork jets placed at the base of the reactor, causing the particles to collide with each other or It is also described that the impact against a wall results in fragmentation of the particles. By using the Dotson method, the ratio can be kept near the desired 0.15 level and even below the 0.35 level for extended periods of time, yielding larger amounts of diorganic material from the same amount of silicon particles. It has been found that chlorosilane can be obtained. However, it has also been found that the Dotson process results in an underutilization of about 12-15% of the silicon that is introduced into the reactor and must be removed from the process as waste silicon. Such silicon was generally considered to be depleted or used up and therefore no longer available. This waste silicon,
Its use is desirable for economic reasons and to avoid the problems normally encountered in disposal. Further T/
It is even more desirable to find new methods that can utilize substantially all of the silicon values in the remaining silicon-containing contact mass after the D ratio increases to an undesirable level. U.S. Pat. No. 4,281,149 to Schied describes a method for treating silicon particles in such silicon reactor systems, thereby improving the usefulness of silicon metal particles. The Shaed method describes a method for treating silicon particles having an average diameter size of less than 40μ, polishing such particles to remove the surface coating thereon, and placing the polished particles in a reactor for further utilization. It can be returned. In U.S. Pat. No. 4,307,242, which is incorporated herein by reference, Surr and Ritzer disclose another method for recovering and recycling silicon fines in an organochlorosilane reactor system. The method published by Sarr and Ritzer involves grading direct contact mass by particle size, thereby identifying the most highly poisoned or impure (waste) mass.
The silicon particles are separated from relatively unpoisoned particles and only such unpoisoned particles are recycled, thereby improving the availability of the silicon. In this way, instead of discarding the entire mass of waste silicon fines from the direct process, only a small portion of the waste silicon fines needed at a given time is discarded. US Pat. No. 4,307,242 is directed to one or more mechanical cyclones to recover fine effluent powder (residual contact mass or residual silicon). This fine effluent powder is generally waste reaction mass from reactors that produce organotrichlorosilane and diorganodichlorosilane products. Crude T and D products are recovered from the top of the cyclone and these products may contain small amounts of very fine entrained particles therein. The remainder of the reaction mass is pneumatically treated in a mechanical cyclone and directed to a hopper for alternating placement. In any of the steps described by Surr and Ritzer, it is particularly desirable to obtain useful products from the relatively unpoisoned portion of the secondary cyclone fines obtained from the classification process of US Pat. No. 4,307,242. It is also desirable to obtain useful products from silicon and residual silicon-containing contact mass obtained from other sources. One such useful product that can be obtained from various reactions with silicon is trichlorosilane, designated herein as monohydrogen trichlorosilane (HSiCl ₃ ). During the synthesis of methylchlorosilane
A study of the effects of HCl was published in Voorhave's Organohalosilanes, Precursors to Silicones, No. 138, published by Elsbier in 1967.
It is reported on page. Reactions have been reported using metallic grade silicon in the presence of copper catalysts at various molar ratios of methyl chloride to hydrogen chloride ranging from 6:1 to 1:6. However, all of these reactions were carried out at 300°C, and there are no reports of Voorhave's temperature selection effects. In U.S. Patent No. 2,488,487, Barry et al.
found an increase in the yield of "more valuable monoalkyl silicon halides" by the simultaneous introduction of hydrogen halides, e.g. Ta. Barry et al. 200-550
They found that mixtures of hydrogen chloride and raw methyl chloride produced increased yields of monomethyl silicon chloride, although reporting a temperature range of
There are no reports of any temperature selection effects or improved high yields of monohydrogen trihalosilanes. In a method for treating waste metal reaction mass from the direct production of organohalosilanes, U.S. Pat.
In No. 2803521, Nitsuchie et al.
reported that the reaction of methyl chloride and silicon, usually in the presence of copper or copper chloride, and often with HCl as an additional reaction component, is the best known and widely used industrial application of the direct method. are doing. According to Nitschie et al., this reaction can be performed using various methylchlorosilanes such as CH ₃ SiCl ₃
( _CH3 ) _{2SiCl2 , ( CH3} ) _3SiCl , and _CH3HSiCl2
give rise to However, Nitsuchie et al. dispersed the reaction mass in water or dilute hydrochloric acid and
The waste (residual) silicon-containing reaction mass is treated by contacting it with a chlorine source at temperatures of ~100°C. The silicon particles settle and separate from the supernatant, and the metal salts in the supernatant are precipitated, collected, and reused as new catalyst. Nitschie et al. do not teach the production of monohydrogentrichlorosilane from waste metal reaction mass, nor do they report temperature selection effects. Among the well-known uses of trichlorosilane is the hydrosilylation of trichlorosilane (monohydrogen trichlorosilane) to make organofunctional silanes, and the hydrosilylation of trichlorosilane (monohydrogen trichlorosilane) by Werner et al.
There are uses for trichlorosilane as a raw material in the production of ultra-pure silicon as discussed in British Patent Application No. GB 2028289 published in Japan. Recent developments in the semiconductor industry have created an ever-increasing demand for low-cost ultra-pure silicon for electronic devices, photovoltaic cells, solar cells, and the like. Werner et al. further show that trichlorosilane and silicon tetrachloride are made by the reaction of silicon and hydrogen chloride. Furthermore, in U.S. Patent No. 2380995, Rochiyo Compt.rend.
Volume 122, page 531 (1896) reports the reaction of silicon and hydrogen chloride as described by Comb, in which the reaction is carried out in an iron tube filled with silicon heated to 300-440°C. A mixture of about 80% trichlorosilane and 20% silicon tetrachloride is obtained through hydrogen chloride. It is therefore desirable to provide an alternative source for trichlorosilane, to provide an economical method of making trichlorosilane, and to provide a synthesis for making trichlorosilane that improves the yield of trichlorosilane. desired. It would also be desirable to provide an improved method for controlling residual silicon-containing contact mass obtained from the production of organohalosilanes by direct process reactions. The main object of the present invention is therefore to provide a method of utilizing the residual silicon obtained from the production of organochlorosilanes. Another object of the present invention is to provide a method for producing trichlorosilane from residual contact mass. Yet another object of the present invention is to provide a method for improving the amount of monohydrogen trihalosilanes (trihalosilanes) obtained from the reaction of alkyl halides with silicon in a direct metal catalytic process. Another object of the present invention is to provide a method for improving the yield of monohydrogentrichlorosilane (trichlorosilane) obtained from residual silicon-containing catalyzed mass obtained from the production of organochlorosilane by metal catalyzed direct reaction. It's about doing. Other objects and advantages of the invention will become apparent from the detailed description below. According to the present invention, monohydrogen trihalosilanes are produced from the residual silicon obtained from the production of organohalosilanes by a direct metal contact method, in which the residual silicon is simultaneously contacted with gaseous hydrogen halides and gaseous alkyl halides. and heating the residual silicon at a temperature below that at which substantial alkylation of the residual silicon occurs, thereby causing the residual silicon to react at said temperature to form a reaction product containing a monohydrogen trihalosilane. It consists of things. According to the present invention, there are strict restrictions on the selection of the temperature at which the residual silicon is heated; it must be a temperature that prevents or retards the alkylation of the residual silicon and promotes the hydrohalogenation of the residual silicon. Generally, the temperature at which hydrohalogenation of residual silicon occurs is from about 200°C to about 350°C. Temperature selectivity can alternatively be expressed as the temperature below which substantial alkylation of residual silicon occurs. According to at least some of the objects of the present invention, there is also provided a method for improving the amount of monohydrogen trihalosilanes obtained from the reaction of an alkyl halide with silicon in a direct metal catalyzed process, which comprises:
Contacting silicon simultaneously with a gaseous alkyl halide and a gaseous hydrogen halide to form a silicon-contacted mass, preventing or retarding alkylation of the silicon-contacted mass and producing hydrohalogenation of the silicon-contacted mass. About 200 to about 350 to tighten or promote
C. and heating the silicon-contacted mass at the selected temperature, thus reacting the silicon with the gaseous alkyl halide and the gaseous hydrogen halide at the selected temperature to form an improved monohydrogen trihalosilane. The process consists of producing a high yield. By supplying gaseous hydrogen chloride and gaseous methyl chloride to the residual silicon, the alkylation reaction between silicon and methyl chloride is inhibited when the reaction is carried out at the selected low temperature. was proved by the method of the present invention. Although there is some discrepancy in the silicon utilization by using the process of the present invention compared to the silicon utilization of the reaction between gaseous hydrogen chloride and metallic quality silicon in the absence of methyl chloride, The process of the present invention remains desirable where a source of methyl chloride is readily available. However, it has been demonstrated that silicon utilization is increased in the process of the present invention over the actual silicon utilization when methyl chloride is used in the absence of hydrogen chloride. It has been found that not only monohydrogen trichlorosilane but also silicon tetrachloride can be produced along with various methyltrichlorosilanes. However, by selecting a reduced operating temperature, suppression of the formation of methylchlorosilane by suppression of alkylation is achieved while promoting the hydrochlorination reaction to form monohydrogentrichlorosilane. The present invention discloses that when silicon, particularly the residual silicon obtained from the production of organohalosilanes by direct metal contact method, is reacted with gaseous alkyl halides in the presence of gaseous hydrogen halide, monohydrogen trihalosilane (HSiX ₃ ) ( X is halogen). Conventional reactions have been substantial alkylation reactions of residual silicon resulting in the production of alkyl silicon halides with only small amounts of hydrohalogenation. In accordance with at least some objects of the present invention, by controlling the temperature, i.e., by conducting the reaction at a lower selected temperature, the yield of monohydrogen trihalosilanes is substantially improved, and in certain embodiments. In this case, the product is primarily monohydrogen trihalosilane. In order to achieve improved yields of monohydrogen trihalosilanes, there are strict controls on temperature selection, with the remaining silicon being heated below the temperature at which substantial alkylation of the remaining silicon occurs. The primary alkyl halide silicon products resulting from silicon alkylation are described in Barry et al.
No. 2488487 and U.S. Patent No. 2803521 to Nitsuchie et al.
clearly indicated in the number. The results of alkylation and hydrohalogenation by contacting metallic quality silicon with methyl chloride and hydrogen chloride in various ratios at constant temperature are also shown in the above-mentioned paper by Woerheve. The examples and explanations of Barry et al. show that without temperature selection, alkylation of silicon is the predominant reaction when methyl chloride and hydrogen chloride are brought into contact with silicon in the presence of a metal catalyst at elevated temperatures. be able to.
describe various methylchlorosilanes obtained from the reaction of methyl chloride and silicon at 200-500°C in the presence of hydrogen chloride and copper as added reaction components. According to the method of the present invention, the alkylation reaction is suppressed, prevented or delayed, while the hydrohalogenation reaction is accelerated by careful selection and control of the reaction temperature. Woolhave showed that this phenomenon could also be produced by varying the molar ratio of methyl chloride to hydrogen chloride while maintaining a constant temperature of 300°C. For example, by increasing the amount of hydrogen chloride, Woolhave showed that the amount of various methylchlorosilanes decreased, but the amount of trichlorosilane in the product increased. When methyl chloride is used as the gaseous alkyl halide and hydrogen chloride is used as the gaseous hydrogen halide, and when the reaction is carried out by a direct method using a suitable catalyst such as copper, the products are generally Silicon chloride (SiCl ₄ ), monohydrogen trichlorosilane (otherwise referred to herein as trichlorosilane) (HSiCl ₃ ), methylhydrogen dichlorosilane (CH ₃ HSiCl ₂ ), methyltrichlorosilane (CH ₃ SiCl ₃ ), dimethyl dichlorosilane It contains a remainder consisting of several _{components including chlorosilane ((CH3)2SiCl2), trimethylchlorosilane ((CH3)3SiCl ) and generally hexachlorodisilane} ( _Cl3Si -SiCl3 ₎ and various siloxanes. The remainder is generally designated as the high-boiling fraction and contains components with boiling points greater than 70°C. As stated above, according to the process of the present invention and in preferred embodiments where the gaseous alkyl halide is methyl chloride and the gaseous hydrogen halide is hydrogen chloride, the desired product is monohydrogen trichlorosilane. In a preferred embodiment of the process of the invention, the silicon is a residual silicon-containing contact mass obtained from the direct synthesis or production of organochlorosilanes using a metal catalyst during the reaction, for example. In the method of the present invention, the residual silicon is a waste contact mass from a direct method using a metal catalyst and thus contains a metal catalyst, or the metal catalyst is a metal catalyst present in the silicon contact mass. Metal catalyst may be added to the silicon contact mass when this is not possible or when it is desired to make up for insufficient metal catalyst in the remaining contact mass. Generally, according to the invention, the residual silicon-containing contact mass may contain other auxiliaries and additives added during the direct process reaction, or additives and auxiliaries that do not interfere with the process of the invention. It may be added to accelerate the hydrohalogenation reaction or for other suitable purposes. Direct synthesis or production of organosilanes is described above and in US Pat. No. 2,380,995.
The invention can be carried out without further treatment of the residual silicon-containing contact mass left after the direct synthesis of, for example, US Pat. No. 2,380,995. However, in a preferred embodiment, the residual silicon-containing contact mass is removed from poisoning the hydrohalogenation reaction by, for example, comminution, separation, treatment with agents to dissolve or extract non-reactive materials, etc. Further processing to remove any interfering residual contact mass. In one preferred embodiment, the residual silicon-containing contact mass obtained from the direct synthesis may be treated as described in Sur and Ritzer, US Pat. No. 4,307,242. According to this method (this U.S. patent is incorporated herein by reference), a "flow-contacted mass powder" is produced.
Alternatively, the silicon-containing contact mass, referred to as "silicon fine powder", is sent to an aerodynamic centrifugal grader. Such a classifier is a device capable of classifying cyclone fines into discrete fractions according to particle size.
In the most common case, the relatively coarse fines are recycled to the organochlorosilane reactor and the finest fraction is discarded. However, according to US Pat. No. 4,307,242, the so-called finest fraction primarily contains the highest percentage of non-silicon impurities, and a decision must be made as to whether to discard or recycle the size fraction. In a method for purifying silicon metal contact mass from a direct organohalosilane reactor system according to U.S. Pat. No. 4,307,242, a portion of the reactor contact mass is analyzed for particle size distribution and the analyzed contact mass is into a relatively pure first fraction and a relatively impure second fraction, and the first and second fractions are separated. The fine silicon powder or effluent contact agglomerate powder is collected in a secondary cyclone, passed through a receiver hopper, then passed through a transfer hopper, and then the fine silicon powder is preferably passed through a pneumatic or centrifugal grader. Pass through a mechanical grading machine. These fine powders are defined herein as silicon fine powders collected from secondary cyclones used to separate waste silicon fine powders obtained from direct process production of organochlorosilanes. In a preferred embodiment of the invention, a relatively pure graded secondary cyclone fine powder is contacted simultaneously with a gaseous hydrogen halide such as hydrogen chloride and a gaseous alkyl halide such as methyl chloride, at a temperature that selecting a temperature from about 200 to about 350°C that prevents or retards alkylation of the mass and promotes hydrohalogenation of the remaining silicon-containing contact mass, and heating the remaining silicon-containing contact mass at the selected temperature; and thereby react silicon with gaseous alkyl halides and gaseous hydrogen halides at selected temperatures to produce improved yields of monohydrogen trihalosilanes. In another embodiment, the residual silicon source is finely divided particles of silicon from the method and apparatus described in Dotson, US Pat. No. 3,133,109, which is incorporated herein by reference. In this patent, silicon-containing particles from a fluidized bed reactor are passed through an external fluid energy mill or they are passed through a number of ultrasonic jets placed at the bottom of the reactor, resulting in mutual collision of the particles or The silicon particles are crushed as a result of impact with the wall. Any remaining silicon-containing contact mass that has been pulverized by crushing individual particles of the silicon-containing mixture, eg, from compaction, impact, abrasion, grinding, etc., can be used in the process of the invention. In some cases, fresh silicon powder, which has never been used in the method described above, can be used as the silicon source. For example, finely divided silicon, which preferably does not contain contaminants that could cause contamination of the final product, can be used in the process of the invention in combination with a suitable catalyst, such as those well known to those skilled in the art. The size of the residual silicon particles that can be used in the process of the invention is not strictly limited; the residual silicon can be in any finely divided form, and for best results the silicon in the reactor is generally about 20 μm. with average particle diameters ranging from ~200μ. silicon particles at least
Preferably, 25% by weight has an actual diameter in the range of about 20μ to about 200μ. As previously mentioned, various types of residual silicon alloys, or corresponding mixtures of residual silicon and metals, may be used in the method of the invention. Examples of silicon alloys or mixtures that may be used include calcium-silicon alloys, calcium-manganese-silicon alloys, manganese-zirconium-silicon alloys, iron-silicon alloys, titanium-silicon alloys, zirconium-silicon alloys, copper-silicon alloys. , including homogeneous mixtures of silicon and copper, nickel, tin, or silver, etc. Although there are no limitations as to the equipment that may carry out the process of the present invention, the equipment is capable of suitably contacting the residual silicon with the alkyl halide and the hydrogen halide and is maintained at the selected temperature for the hydrohalogenation reaction. It must also be a device that can be controlled. The reactor or reaction chamber may be of any suitable size or shape and does not interfere with the reaction with the reaction components and products and/or by-products;
Preferably, it is made from a material that does not corrode. The equipment must be capable of heating the silicon-containing contact mass to the critical temperature or range of temperatures mentioned above. The process according to the invention can be carried out continuously, intermittently or batchwise. Any suitable prior art is available to implement this method. One way to carry out the process of the invention is to mix halogen with hydrogen halide on or in a fixed bed of residual silicon kept at a selected temperature that retards or prevents alkylation and promotes hydrohalogenation. It consists of conducting an alkyl compound. Alternatively, it can be carried out by simultaneously passing the alkyl halide and hydrogen halide vapors through a rotating, externally heated tumbler containing residual silicon while maintaining the heated tumbler at a selected temperature. Yet another method of carrying out the method of the invention is:
It consists of preheating the vapor mixture before contacting the residual silicon to a selected temperature that promotes hydrohalogenation and inhibits alkylation. There are no strict restrictions on the introduction of gases and/or vapors into the reaction chamber; the hydrogen halide gas and the alkyl halide gas or vapor may be mixed before being introduced into the reaction chamber or vessel, or they may be separated. may be introduced into the reaction chamber or container at any time. Conventional metering and/or metering equipment may be used to provide the appropriate ratio of gases in the reaction chamber or vessel. It is also within the scope of the invention to supply multiple streams of gas into the reactor. In one preferred embodiment, the process is carried out by forming a fluidized bed of the residual silicon or silicon and contacting it with a suitable gas or steam while maintaining the residual silicon in the form of a fluidized bed. Various embodiments for maintaining a fluidized bed of residual silicon can be used, including the use of gas or vapor velocities sufficient to maintain the residual silicon in a fluidized state within the reactor. This can be accomplished by injecting the alkyl halide and/or hydrogen halide into the particulate residual silicon at a rate suitable to fluidize the particulate material.
The optimum rate of gas and/or steam can be determined by one skilled in the art and will depend on various operating conditions. When using a stirred bed reactor or when using a rotary kiln, the gas velocity or flow rate can be less than or equal to the minimum velocity required to fluidize the silicon in the reactor, and the hydrogen halide and The theoretical amount of alkyl halide can be more accurately reflected. Other conventional fluidization means may be used to maintain the bed of residual silicon in a fluidized state while in contact with the alkyl halide and hydrogen halide;
It is also within the scope of the present invention to utilize a combination of means for maintaining the bed of residual silicon in a fluidized state.
Inert gases such as nitrogen may be used to fluidize the remaining silicon-containing contact mass or to supplement other means of fluidization, although this is generally undesirable due to the need for strong venting means.
A typical fluidized bed reactor is the U.S. patent of Reed et al.
Described in No. 2389931. Other means for contacting the gaseous material with the residual silicon include a stirred bed reactor such as that described in Seller US Pat. No. 2,449,821 or a conventional rotary kiln. The means for heating the bed of residual silicon in the reactor and maintaining the bed of residual silicon at a selected temperature that promotes the hydrohalogenation reaction and inhibits the alkylation reaction may be any conventional means. Well, both internal and external sources of cooling and/or heating, including gas and/or steam heating, can be used in the method of the invention. The aforementioned documents provide examples of conventional means for heating beds contained therein. In a preferred embodiment of the invention the alkyl halide is methyl chloride (CH ₃ Cl). Alkyl halides that can generally be used in the process of the invention include those having the general formula CnH2o _+1X , where X is halogen and n is an integer from 1 to 4. Alkyl groups having 1 to 4 carbon atoms can be straight-chain or straight-branched. Halogen can be chlorine, bromine, iodine or fluorine. In the process of the invention, a single alkyl halide may be used during the reaction,
Alternatively, mixtures of alkyl halides may be used. A preferred hydrogen halide that can be used in the process of the invention is hydrogen chloride. However, in various embodiments, hydrogen bromide, hydrogen iodide or hydrogen fluoride can be used as the hydrogen halide. It is also possible to use mixtures of hydrogen halides in the process of the invention. There are no strict restrictions on the amounts or proportions of hydrogen halides and alkyl halides used in the process of the invention. Usually vaporized alkyl halide 1
For parts by volume, from 0.5 to 20 parts by volume of hydrogen halide are used, but if desired hydrogen halide can be used in larger or smaller proportions. In certain embodiments, the molar ratio of alkyl halide to hydrogen halide is about 6:1.
~about 1:6. However, in certain preferred embodiments, the molar ratio of alkyl halide to hydrogen halide ranges from about 3:1 to about 1:3. In one preferred embodiment of the invention, when the alkyl halide is methyl chloride and the hydrogen halide is hydrogen chloride, the molar ratio of methyl chloride to hydrogen chloride is about 3:1. As mentioned above, it was reported by Woerhave that as the amount of hydrogen chloride increases, the amount of trichlorosilane increases in the reaction of silicon with methyl chloride and hydrogen chloride at a temperature of 300°C in the presence of a copper catalyst. ing. The rate of gas or vapor flow in the process of the invention is not strictly limited, but in a preferred embodiment is controlled to result in a consumption of about 0.5 or more of the alkyl halide in a single pass through the bed of residual silicon. . Since it is sometimes difficult to achieve high conversions in a single pass, a significant portion, e.g., about 0.5 to about 0.8 of the vapor exiting the bed, is then transferred into the bed to cause further consumption of the alkyl halide. can be recirculated. Such vapor recirculation has the additional advantage of making the temperature throughout the reaction zone more nearly uniform and tends to cause the reaction to occur throughout a large portion of the residual silicon-containing bed rather than locally in the bed. While operating in this manner, a portion of the vapors exiting the residual silicon bed, ie exiting the reactor, may be removed from the reaction system and cooled to condense the products therein. The operation may be continued until the silicon in the remaining silicon is consumed to a desired point. As previously mentioned, a batch process is also possible; in some cases the reactor can be initially charged with the alkyl halide and hydrogen halide and maintained at the desired selected temperature until the reaction is complete. Completion or substantial completion of the reaction can be readily determined by product analysis as detailed below. As mentioned above, the reaction temperature of the residual silicon with the alkyl halide and hydrogen halide is subject to strict regulations and must be selective in order to achieve the desired hydrohalogenation of the silicon. The residual silicon contact mass, i.e., the residual silicon in the presence of hydrogen halides and alkyl halides, is between about 200°C and about 350°C depending on process variables.
selectively heated at a temperature in the range of . Therefore, in order to achieve an improved yield of monohydrogentrihalosilanes by the process of the invention, the remaining silicon-contacted mass is
Heating in the presence of gaseous hydrogen halide and gaseous alkyl halide at a temperature below that at which substantial alkylation of the silicon occurs or is promoted. Generally, in the production of monohydrogen trichlorosilane, residual silicon is used at a temperature below the temperature at which substantial alkylation of the residual silicon occurs and at a temperature at which substantial hydrohalogenation of the silicon occurs.
Heat in the presence of methyl chloride and hydrogen chloride at a temperature of 200 to about 350°C. Substantial hydrohalogenation is generally considered to be reached when about 15% by weight of the product is monohydrogen trihalosilane as determined by gas chromatography. Generally, alkylation is considered to have substantially occurred when the distribution of organohalosilanes in the product totals greater than about 70% by weight as determined by gas chromatography. For example, in improving the amount of monohydrogentrihalosilane in the reaction product between silicon and alkyl halides and hydrogen halides in the residual silicon contact mass, the temperature is between about 200 and about 350°C. the silicon contact mass is heated at a selected temperature to convert the silicon into gaseous alkyl halides and Reaction with hydrogen halides results in improved yields of monohydrogen trihalosilanes. Temperature selectivity can be readily determined in product analysis by monitoring the product stream, gas recycle flow, gas in the reaction chamber, etc. by gas chromatography or similar means for determining the composition of the gas. This inherent flow or chamber monitoring may be intermittent or continuous and may be performed with conventional equipment and methods well known to those skilled in the art. When an alkylation reaction occurs and organohalosilanes appear in undesired amounts, i.e., substantial amounts in the monitored stream or chamber, they inhibit the alkylation of silicon in the remaining silicon mass and hydrogen halide. Lower the temperature to promote oxidation. Furthermore, in some cases it may be necessary to suppress the temperature within a range that suppresses alkylation and promotes hydrohalogenation. For example, when the reaction becomes exothermic after its initiation, it is desirable to control the temperature within a range that suppresses silicon alkylation and promotes silicon hydrohalogenation. This can also be determined by monitoring the flow and/or gas in the room as described above and taking appropriate action to provide normal cooling and/or to stop heating to maintain the selected temperature. You can take it. In view of the foregoing, the selected temperature may also include a temperature range within which the alkylation reaction is suppressed and the hydrohalogenation reaction is promoted. Certain variables that effect the reaction between silicon and alkyl halides and hydrogen halides in the residual silicon contact mass include the particular alkyl and hydrogen halides used as starting materials and the conditions under which the reactions are conducted. Examples include contact time of reaction components, amount of silicon, particle size, etc. Furthermore, the rate constants will differ for each reaction and under changing conditions, and this will have an effect on temperature selection; however, as a practical matter, temperature selection can be determined by monitoring the product gas as described above. Most easily determined for reaction conditions, reaction components, and reactor equipment. The reaction is usually carried out at atmospheric pressure, but lower pressures or very high pressures, such as as high as 2000 lbs/in ² , can be used. Optionally diluents such as carbon dioxide, carbon monoxide, silicon tetrachloride,
Nitrogen and various other inert gases may also be added. The products formed by the process of this invention can be collected and separated using conventional equipment and methods. For example, the products from the reactions of the present invention can be suitably collected and the monohydric trichlorosilane separated therefrom by any suitable method. One method of collection is condensation in a conventional condenser cooled to about -20°C with a suitable coolant, such as a methanol-based coolant. This is monohydrogen trichlorosilane,
The silicon tetrahalides, organohalosilanes and other by-products and residues are condensed. They can be suitably collected and then separated by any suitable separation method, including fractional distillation. It is desirable to carry out the process under anhydrous conditions to prevent the formation of hydrolysis byproducts and other undesirable byproducts that generally reduce the yield of monohydrogen trihalosilanes. Accordingly, in preferred embodiments, steps may be taken to exclude moisture from the apparatus and reaction components. The following examples are illustrative of the invention and are not intended to limit the scope of the invention. As a reactor, a 2.54 cm (1 in.) of stainless steel, 45.7 cm (18 in.) long and 2.54 cm (1 in.) in diameter, equipped with a motor-driven discontinuous helical stirrer and a special flange end plug for bed stirring. ) An electrically heated stirred bed reactor was used. The tube section was divided into an upper reaction zone and a lower reaction zone, and each reaction zone was equipped with an independent heater for maintaining the desired temperature set. The reactor shell or tubes were well insulated to prevent heat loss and fluctuations. Inlets were provided at the bottom of the tube for supplying gas and/or vapor sources, ie alkyl halides and hydrogen halides. An outlet was provided at the top of the tube and a suitable condenser was provided for collection of liquid trichlorosilane product and by-products and for venting of gas. Appropriate glass and plastic fittings and tubing were used to minimize the corrosive effects of the reactant gases. For these examples the reactions were carried out in batches. The residual silicon-containing contact mass used in the following examples consisted of secondary cyclone fine powder previously described in the manner described in U.S. Pat. No. 4,307,242. The residual silicon secondary cyclone fine powder was analyzed and found to be approximately
Contains 2.1% carbon, 3.8% copper, 2.7% iron, 1.7% aluminum, 1.0% zinc, 69.0% silicon, and residual chlorine, hydrogen and traces of other elements. Was. The indicated amount of secondary cyclone powder was placed in the stirred bed reactor described above. The reaction zone temperature was maintained at the selected temperature throughout the experiment. Methyl chloride and/or anhydrous hydrogen chloride were metered into the reaction zone by a linear mass flow meter at the rates indicated in each example. The reaction was carried out at three temperatures: 300°C, 250°C and 200°C. Prior to reaction studies, the reactor internal temperature profile was established using a thermocouple probe with nitrogen flow. Temperature control settings were measured using this method. Under reaction conditions, reactor external temperature (both reaction zone and upper zone)
was continuously monitored. Methyl chloride reaction component streams were standardized using a Rotameter linear mass flowmeter during the series. Hydrogen chloride co-feedstock was achieved using a linear mass flowmeter with appropriate correction factors. The reaction rate was determined by the recovery of crude product per unit time. The methylchlorosilane crude (crude fraction) was corrected or normalized for unreacted methyl chloride based on gas chromatographic analysis. Silicon utilization was calculated by subtracting the silicon consumed to form product from the initial silicon concentration as determined by the alkaline fusion method of contact mass samples. For this reason, it is advisable to use appropriate silicon analysis. Crude product distribution was determined by gas chromatography. The residue or high boiling fraction content was also determined by gas chromatography. For comparative total material yields at various temperatures using methyl chloride, hydrogen chloride or mixed methyl chloride/hydrogen chloride, the contact mass was reacted until consumed, ie, no additional crude product formation. Example 1 A 50g sample of the above-mentioned secondary cyclone fine powder was placed in the above-mentioned reactor, and anhydrous hydrogen chloride was added at 100SCCM.
was fed into the reactor. The reactor was maintained at normal pressure.
Heated at 300°C. Analyzing the product as described above,
Approximately 76% of the silicon in the secondary cyclone powder was converted to product, of which 94.4% consisted of trichlorosilane and silicon tetrachloride. About 4.6% by weight of the effluent was considered high boiling residue, ie, it had a boiling point above 70°C, about half of which was hexachlorodisilane. The results are shown in Tables 1 and 2 below for comparison. Example 2 All reaction conditions and quantities were the same in this example as in Example 1, except that the stirred bed reactor was maintained at 250°C at atmospheric pressure. The analytical data of this example are shown in Tables 1 and 2. Example 3 The reaction conditions and quantities were the same in this example as in Example 1, except that the stirred bed reactor was kept at 200°C at atmospheric pressure. Data for this example are shown in Tables 1 and 2. Example 4 Residual silicon secondary cyclone fine powder from the same batch as in each of the above Examples was prepared as described in Examples 1 to 3 above using a methyl chloride gas feed at normal pressure and 300° C. as in Example 1 above. The reaction was carried out in the same stirred bed reactor. In this example, anhydrous hydrogen chloride was not used. A silicon utilization of approximately 36% was achieved, approximately 92% of the effluent consisted of methyltrichlorosilane and dimethyldichlorosilane, 2.6% by weight of the product was high boiling residue, of which approximately 85% was
The weight percent was 1,1,2-trichlorotrimethyldisilane and 1,1,2,2-tetrachlorodimethyldisilane. Data for this example are shown in Tables 1 and 2. Example 5 Except that the reaction was carried out at normal pressure 250°C.
Another identical sample of secondary cyclone fine powder was processed by the method of Example 4. Data from this example is shown in Tables 1 and 2. Example 6 50.0 g of residual silicon secondary cyclone fine powder taken from the same batch as in each of the above examples was treated with methyl chloride gas in such a way that the total molar amount of gas processed per unit time was the same as that in each of the above examples. and anhydrous hydrogen chloride gas in the same reaction vessel at normal pressure and 300°C. Gas was metered to achieve a 3:1 molar ratio of methyl chloride to hydrogen chloride distribution. Overall silicon utilization of approximately 64% was achieved.
Approximately 22% by weight of the effluent was the sum of silicon tetrachloride and trichlorosilane; approximately 59% by weight of the effluent
was the sum of methyltrichlorosilane and dimethyldichlorosilane, with the remainder consisting primarily of about 12% by weight methylmonohydrogendichlorosilane, about 2.5% by weight trimethylchlorosilane and about 3.1% by weight residue and dimethylmonohydrogenchlorosilane. . The data of this example are shown in Tables 1 and 2.
Shown below. Example 7 The reaction conditions and amounts were the same as in Example 6 above, except that the reaction temperature was 250°C at normal pressure. The overall silicon utilization was 50%. The data for this example are shown in Tables 1 and 2, which show that silicon utilization to the desired products trichlorosilane and silicon tetrachloride was approximately doubled by lowering the reaction temperature, i.e., 300°C. This shows that the temperature was 13.2% at 250°C and 25.5% at 250°C. Example 8 In this example, the reaction conditions and quantities were the same as in Examples 6 and 7, except that a reaction temperature of 200°C was used. Overall silicon utilization is 31%
It was hot. Data for this example are shown in Tables 1 and 2.

【table】

【table】

[Table] From the above data, it can be seen that the residual silicon secondary cyclone fine powder and hydrogen chloride react easily at 300°C, 250°C and 200°C to mainly generate trichlorosilane and silicon tetrachloride. At comparable temperatures, the reaction with hydrogen chloride (200
The reaction with methyl chloride (even at 10°C) gives rise to considerably higher silicon utilisation, as opposed to the reaction with methyl chloride. 300℃ to 250
Although lowering the temperature to 30°F had no effect on overall silicon utilization by reactions using exclusively methyl chloride or hydrogen chloride, there was a significant selectivity difference in the low-temperature methyl chloride reaction, i.e., a sharp There was a decrease in overall batch E/F, decreased methylmonohydrogendichlorosilane formation, and increased residue formation. Co-feeding of the reaction components, as represented by a 3:1 molar ratio of methyl chloride to hydrogen chloride, changed the results as follows. (a) At 250°C, the overall silicon utilization was lower than the 100% hydrogen chloride method but greater than the 100% methyl chloride method. (b) At 300°C, the overall silicon utilization was comparable to a 100% hydrogen chloride feeding reaction. (c) At 300°C, the mixed feed methyl chloride versus hydrogen chloride is
It resulted in higher silicon utilization to form methylchlorosilane than 100% methyl chloride reaction at the same temperature. (d) The reaction at 200°C sharply suppressed the alkylation reaction, i.e. the reaction between methyl chloride and silicon, but led to a reduction in overall silica utilization. (e) The inclusion of hydrogen chloride causes a significant increase in the E/F of the methylchlorosilane product. (f) Residue formation increases as reaction temperature decreases. It is clear from the above data that at the selected low temperatures hydrogen chloride and methyl chloride react with the silicon-copper mixture to form trichlorosilane and silicon tetrachloride. In accordance with at least some objects of the present invention, the method provides trichlorosilane in substantial amounts by a hydrochlorination reaction conducted under selected temperature conditions that suppress the alkylation reaction between methyl chloride and silicon. Proved that it can be manufactured. By varying the reaction temperature and careful control of temperature, increased yields of trichlorosilane and silicon tetrachloride were achieved. Furthermore, a reaction in which the raw materials are fed together, that is, a reaction in which both hydrogen chloride and methyl chloride are fed in the presence of silicon at a low temperature in the range of about 200 to about 300°C, leads to the hydrochlorination of silicon. On the other hand, the ability to selectively inhibit the methylchlorosilane reaction, ie the alkylation reaction, was clearly demonstrated. Although this method was not carried out using fresh silicon, the method of the present invention is applicable to such applications, and it is possible to convert fresh silicon into a material that suppresses alkylation of silicon and produces hydrogen halogenation of silicon. The reaction can be performed with gaseous alkyl halides and gaseous hydrogen halides at selected temperatures between 200 and about 350°C, thereby resulting in improved yields of monohydrogen trihalosilanes. Although this invention has been described in particular detail with respect to certain preferred embodiments, it will be appreciated that modifications may be made within the scope of the invention.

Claims (1)

[Claims] 1. A method for producing monohydrogentrihalosilane from residual silicon obtained from the production of organohalosilane by a direct metal contact method, in which the residual silicon is removed at a temperature lower than the temperature at which substantial alkylation of the residual silicon occurs. The remaining silicon is simultaneously brought into contact with gaseous hydrogen halide and gaseous alkyl halide while heating, and the remaining silicon is thus reacted at the above temperature to produce a reaction product containing monohydrogen trihalosilane. how to. 2. The method of claim 1, wherein gaseous hydrogen halide and gaseous alkyl halide are contacted with a fluidized bed of residual silicon. 3 Gaseous alkyl halide with 1 to 1 carbon atoms
4. The method of claim 1, wherein the alkyl group is selected from the group consisting of chloride, bromide, iodide, or fluoride of an alkyl group having 4. 4. The method according to claim 1, wherein the gaseous hydrogen halide is selected from the group consisting of hydrogen chloride, hydrogen bromide, hydrogen iodide and hydrogen fluoride. 5. The method according to claim 1 or 2, wherein the gaseous hydrogen halide is hydrogen chloride, the gaseous alkyl halide is methyl chloride, and the monohydrogen trihalosilane is monohydrogen trichlorosilane. 6. The method of claim 1, wherein the molar ratio of alkyl halide to hydrogen halide is in the range 6:1 to 1:6. 7. The method according to claim 1 or 2, wherein the residual silicon is selectively heated at a temperature of 200°C to 350°C. 8. The method of claim 1, comprising collecting the reaction product and separating the monohydrogen trihalosilane therefrom. 9. Feed gaseous methyl chloride and gaseous hydrogen chloride to a fluidized bed of residual silicon at a molar ratio of methyl chloride to hydrogen chloride ranging from 6:1 to 1:6, and heat the fluidized bed of residual silicon to 200-300°C. , but below the temperature at which substantial alkylation of the residual silicon occurs to produce a product containing substantial amounts of monohydrogen trihalosilane and silicon tetrachloride. A method for producing monohydrogentrichlorosilane from residual silicon obtained from the production of organochlorosilane by a direct metal contact method. 10 Molar ratio of methyl chloride to hydrogen chloride is 3:1 ~
10. The method of claim 9, wherein the ratio is 1:3. 11. The method of claim 9, wherein the residual silicon comprises silicon fines collected from a secondary cyclone used to separate waste silicon fines obtained from the metal-catalyzed direct production of organochlorosilanes. 12 Claim 9 comprising collecting the product and separating the monohydrogen trihalosilane therefrom.
The method described in section. 13. Claim 9, wherein the molar ratio of methyl chloride to hydrogen chloride is 3:1, the temperature is 200-250°C, and the main product is monohydrogen trichlorosilane.
The method described in section.