Method for producing chlorosilanes

Abstract

In the production of chlorosilanes by the chlorination reaction of metal silicon, in order to prevent the deposition of scale on the inner wall of the upstream portion of a heat exchanger provided in the transfer path of the reaction gas to a distillation column and to enable the stable production of chlorosilanes, metal silicon is used that has a zirconium content (Zr%) of 35 mass ppm or less in elemental terms and a mass ratio (Ti% / Zr%) of the titanium content (Ti%) to the zirconium content (Zr%) of 8.0 or more.

Description

[Technical Field]

[0001] The present invention relates to a novel method for producing chlorosilanes, and more particularly to a method for stably producing chlorosilanes by the chlorination reaction of metal silicon. [Background technology]

[0002] Chlorosilanes used in the production of high-purity polysilicon, as typified by the Siemens process, are produced by purifying chlorosilanes obtained by the chlorination reaction of metal silicon. For example, a common method is to supply metal silicon powder and hydrogen chloride to a fluidized bed in a reactor and produce trichlorosilane by the chlorination reaction of metal silicon. Another known method is to supply metal silicon powder, tetrachlorosilane, and, if necessary, hydrogen to a fluidized bed and produce trichlorosilane by the chlorination reaction of metal silicon.

[0003] This reaction is expressed as follows: It is known that the reactions of the following formulas (1) and (2) occur at reaction temperatures of 300 to 360°C, and the reaction of the following formula (3) occurs at temperatures of 500 to 550°C.

[0004] [ka]

[0005] The metallic silicon used as the raw material is generally silicon powder with a relatively high degree of refinement, which is called metallurgical grade. A specific method for producing such metallic silicon of metallurgical grade is to use a silicon raw material, typically silica, and charcoal, coke, coal, wood chips, or the like as a reducing agent, fill a mixture of these as a raw material layer in an arc furnace, and heat it at a high temperature of 2000 to 2500°C to reduce the silica (see Non-Patent Document 1).

[0006] The purity of the metallurgical-grade metallic silicon is typically about 99% by mass in terms of elements. Specifically, the silicon content is 98.5 to 99.4% by mass in terms of elements, preferably 99.0 to 99.4%, and further includes metal impurities such as Fe, Ca, Al, Mn, Ni, Zr, Zn, and Ti (Patent Documents 1 and 2). According to Patent Document 2, for example, the amounts of metal impurities include 2300 to 3600 ppm by mass for iron, 1400 to 1600 ppm by mass for aluminum, less than 10 ppm by mass to 11 ppm by mass for zirconium, and 0.013 to 0.021 ppm by mass for titanium. It is known that metallic silicon used in the production of chlorosilanes contains zirconium and titanium, but only a small amount of titanium relative to zirconium has been known (Tables 1 and 2 of Patent Document 2).

[0007] By producing chlorosilanes using such metallurgical-grade metallic silicon, the target chlorosilanes can be obtained with high reactivity. However, in the purification process of the obtained chlorosilanes, when the reaction liquid is distilled, a considerable amount of scale is deposited on the inner walls of the distillation column and the subsequent tanks, piping, and other equipment, causing blockage of the equipment. Analysis has revealed that the scale deposited in the distillation column and subsequent equipment is mainly aluminum chloride, and that this scale is generated when the aluminum component of the metal impurities contained in the metallurgical-grade metallic silicon is chlorinated during the trichlorosilane production reaction (Patent Document 3

[0005] ).

[0008] As a countermeasure against the deposition of scale made of aluminum chloride, the deposited scale is extracted from the bottom of the distillation column.In addition, it has been proposed to provide a sodium chloride-packed column in the transfer path to the distillation column for the reaction gas discharged from the chlorination reactor, and to remove the aluminum chloride by double chlorination therein (Patent Document 4). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-534930 [Patent Document 2] Special Publication No. 2013-535399 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-010648 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-256197 [Non-patent literature]

[0010] [Non-Patent Document 1] Industrial Heating, Vol. 46, No. 3 (2009), pp. 1-11, "Current Status and Issues of Small Arc Furnaces" Summary of the Invention [Problem to be solved by the invention]

[0011] The above-mentioned measures against aluminum chloride deposition effectively alleviate the problem of scale deposition on the inner walls of the equipment downstream of the distillation column. However, from the viewpoint of industrially stable operation, the prevention of scale deposition is still insufficient, and in particular, scale deposition can occur locally in the transfer path of the reaction gas to the distillation column, which is unsatisfactory.

[0012] More specifically, a cooling heat exchanger for liquefying the high-temperature reaction gas is provided midway along the transfer path of the reaction gas distillation column. The high-temperature reaction gas is typically cooled and liquefied to 10 to 40°C here. During this process, scale locally precipitates on the upstream wall surface of the heat exchanger into which the gas flows. (Hereinafter, the upstream wall surface of the heat exchanger refers to the upper wall surface into which the gas flows.) In particular, when a shell-and-tube heat exchanger is used as this cooling heat exchanger from the viewpoint of good cooling efficiency, a large amount of scale precipitates on a fixing perforated plate to which the inlet end of the reaction gas of each cooling tube disposed in the heat exchanger is connected, which can cause a problem of clogging the small-diameter opening at the end of the cooling tube.

[0013] In view of the above, when producing chlorosilanes by the chlorination reaction of metal silicon, it has been an important issue to prevent the deposition of scale on the inner wall of the upstream portion of a heat exchanger provided in a transfer path for the reaction gas to a distillation column, thereby enabling the stable production of chlorosilanes. [Means for solving the problem]

[0014] In view of the above problems, the present inventors have conducted extensive research into measures to suppress scale deposition on the inner wall of the upstream portion of the heat exchanger provided in the reaction gas transfer path. As a result, they have found that the scale deposited at this location has a specific composition containing zirconium. Based on this finding, they have found that the deposition can be significantly prevented by using metallic silicon with low contents of zirconium and titanium within specific ranges, and have completed the present invention.

[0015] That is, the present invention provides a method for producing chlorosilanes by the chlorination reaction of metal silicon, comprising the steps of: The method for producing chlorosilanes is characterized in that the metal silicon used has a zirconium content (Zr%) of 35 mass ppm or less in elemental terms and a mass ratio (Ti% / Zr%) of the titanium content (Ti%) to the zirconium content (Zr%) of 8.0 or more. [Effects of the Invention]

[0016] According to the present invention, by using metallic silicon having a zirconium content within a specific range and a titanium to zirconium mass ratio within a specific range, it is possible to significantly reduce the deposition of scale on the inner wall of the upstream portion of a heat exchanger when a reaction gas of chlorosilanes produced by the chlorination reaction is transferred to a distillation column. As a result, the cooling efficiency of the heat exchanger can be maintained at a high level, enabling the stable production of chlorosilanes. Furthermore, when the heat exchanger is a shell-and-tube heat exchanger, it is possible to prevent blockage of the end openings of each cooling tube connected to the perforated plate for fixing the inlet side of the reaction gas, enabling the stable production of chlorosilanes, which is extremely useful industrially. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a representative flow diagram for producing chlorosilanes by the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the present invention, any known method for chlorinating metal silicon can be used to produce chlorosilanes without any restrictions. Such chlorination reactions are generally carried out using a fluidized bed reactor.

[0019] For example, a method for producing chlorosilanes can be mentioned, in which the metal silicon and hydrogen chloride are supplied to a fluidized bed of a fluidized bed reactor to carry out a chlorination reaction of the metal silicon. In the present invention, chlorosilanes include dichlorosilane, trichlorosilane, tetrachlorosilane, etc., and the present invention is particularly preferably a method for producing trichlorosilane.

[0020] As the hydrogen chloride, various industrially available hydrogen chlorides can be used. Furthermore, the amounts of silicon metal and hydrogen chloride supplied are in a ratio that allows chlorination, and known conditions can be adopted without particular limitation as long as the silicon metal and hydrogen chloride can be supplied at a flow rate that allows the formation of a fluidized bed.

[0021] The reaction temperature is determined appropriately taking into consideration the material and capacity of the reaction apparatus, the catalyst, etc., but is generally set in the range of 200 to 500°C, preferably 250 to 450°C.

[0022] Another method for producing chlorosilanes is to supply metallic silicon powder, tetrachlorosilane, and hydrogen together with a catalyst such as copper silicide to a fluidized bed to carry out a chlorination reaction of the metallic silicon.

[0023] In the above method, the supply amounts of metal silicon, tetrachlorosilane, and hydrogen are in a ratio that allows chlorination, and known conditions can be used without particular limitation as long as the metal silicon, tetrachlorosilane, and hydrogen can be supplied at a rate that allows the formation of a fluidized bed. The reaction temperature in the reaction is appropriately determined taking into consideration the material and capacity of the reactor, the catalyst, etc., but is generally set in the range of 400 to 700°C, preferably 450 to 600°C.

[0024] In the present invention, the metallurgical silicon used is preferably of the purity of metallurgical grade described above. Usually, a silicon raw material, typically silica, and a reducing agent, such as charcoal, coke, coal, or wood chips, are used, and a mixture of these is filled into an arc furnace as a raw material layer and heated at a high temperature of 2000 to 2500°C to reduce the silica, thereby obtaining the metallurgical silicon used. The reduction produces large lumps with a mass of about 1000 to 2000 kg, but for the production of chlorosilanes, it is preferable to crush these lumps and use metallurgical silicon of a size suitable for the reaction.

[0025] As mentioned above, since the production of chlorosilanes is usually carried out in a fluidized bed system, the metallic silicon is required to have a size that can be fluidized in the fluidized bed. Metallic silicon having an average particle size of 150 to 400 μm, particularly 180 to 300 μm, is preferred. The average particle size of the metallic silicon can be measured according to the method described in the Examples. By setting the average particle size of the metallic silicon within the above range, a stable fluidized bed can be obtained, which is preferable.

[0026] In the method for producing chlorosilanes of the present invention, the metallic silicon used as the raw material has a zirconium content (Zr%) of 35 mass ppm or less, preferably 25 mass ppm or less, and more preferably 25 mass ppm or less, calculated as the element. Furthermore, the metallic silicon used has a mass ratio (Ti% / Zr%) of the titanium content (Ti%) to the zirconium content (Zr%) of 8.0 or more, preferably 9.0 or more, and even more preferably 9.0 or more. By using metallic silicon with a low zirconium content and a particularly high titanium-to-zirconium mass ratio as the reaction raw material, it is possible to effectively reduce the deposition of scale on the inner wall of the heat exchanger provided in the transfer path to the distillation column. Furthermore, in the method for producing chlorosilanes of the present invention, the metallic silicon used as the raw material has a zirconium content (Zr%) of preferably 1 mass ppm or more, more preferably 5 mass ppm or more, and even more preferably 15 mass ppm or more, calculated as the element. Such metallic silicon containing a certain amount of zirconium or more can be easily purified for producing the metallic silicon, and is therefore easily available as a reaction raw material. Furthermore, the metallic silicon used has a low mass ratio (Ti% / Zr%) of the titanium content (Ti%) to the zirconium content (Zr%), preferably 30.0 or less, more preferably 20.0 or less, and even more preferably 15.0 or less. By using metallic silicon with this low mass ratio as a reaction raw material, the titanium impurity content in the reaction gas liquefaction product is reduced.

[0027] That is, according to the investigations of the present inventors, the composition of the scale deposited on the inner wall of the upstream part of the heat exchanger in the reaction gas transfer path is different from the aluminum chloride that constitutes the scale deposited on the inner wall of the equipment downstream of the distillation column, and contains only a trace amount of aluminum (usually 0.3 mass% or less). On the other hand, the composition of the scale deposited on the inner wall of the upstream part of the heat exchanger is analyzed to have a unique composition, with a characteristically high zirconium content of 30 to 40 mass%. Therefore, the amount of scale deposited on the inner wall of the upstream part of the heat exchanger can be reduced to a certain extent effectively by using metallic silicon with a zirconium content as low as possible.

[0028] However, even then, there is a natural limit to how much the zirconium content of the metallic silicon can be reduced, and in fact, even if commercially available metallic silicon having the lowest zirconium content is used as the reaction raw material, the suppression of scale deposition on the inner wall of the upstream portion of the heat exchanger is still not satisfactory. Under these circumstances, if the metallic silicon used not only has a low zirconium content as described above, but also has a titanium content that is higher than the zirconium content by a specific range, an excellent effect of significantly improving the effect of suppressing scale deposition on the inner wall of the heat exchanger can be achieved.

[0029] The reason for this is not entirely clear, but the present inventors speculate that the following effect may be responsible. That is, for most metal impurities contained in metal silicon, including the aluminum, zirconium, and even titanium, these metal species are chlorinated to form chlorides during the reaction to produce chlorosilanes such as trichlorosilane. Among such metal chlorides, the melting point of aluminum chloride (aluminum chloride), the main component of the metal impurities, is 192°C. While this is a fairly high melting point, it is significantly lower than the high reaction temperature of the chlorination reaction of metal silicon that produces the chlorosilanes. Therefore, in the upstream portion of the heat exchanger on the transfer path to the distillation column, into which the high-temperature reaction gas produced in the chlorination reaction flows, precipitation of aluminum chloride is prevented from becoming very active. On the other hand, since the melting point of the zirconium chloride (zirconium tetrachloride) is higher than 400°C, it is thought that it has already solidified in the reaction gas that has flowed into the upstream part of the heat exchanger, and that when it is exposed to the temperature drop at the initial stage of cooling, it selectively adheres to the inner wall surface in the upstream part of the heat exchanger and forms scale.

[0030] Under these circumstances, when titanium is contained in the metal silicon in the above-mentioned specific amount, the melting point of the titanium chloride (titanium tetrachloride) is as low as −25° C., and furthermore, the boiling point is as low as 136.4° C., so it is thought that these will liquefy in the upstream portion of the heat exchanger that cools and liquefies the high-temperature reaction gas to 10 to 40° C. This titanium chloride liquid has good affinity with the zirconium chloride solid and effectively reduces its adhesion to the inner wall surface of the device, thereby presumably achieving the remarkable effect of inhibiting scale deposition on the inner wall of the heat exchanger as described above.

[0031] When metallic silicon containing the specific amount of titanium is used as the reaction raw material, the reaction liquid is cooled and condensed in a heat exchanger and transferred to distillation column 5 shown in FIG. 1, and contains titanium chloride in proportion to the titanium content in the reaction raw material. However, most of the titanium chloride can be easily removed by being discharged into the high boiling point fractions through distillation separation in distillation column 5.

[0032] Here, if the zirconium content (Zr%) of the metallic silicon used as the raw material exceeds 35 ppm by mass, the deposition of scale on the inner wall of the upstream part of the heat exchanger increases significantly. Moreover, such metallic silicon with a zirconium content (Zr%) of less than 1 ppm by mass requires a high degree of refinement and is difficult to obtain.

[0033] Furthermore, when the mass ratio (Ti% / Zr%) of the titanium content (Zr%) of the metallic silicon used to the zirconium content (Zr%) is 8.0 or less, the deposition of scale on the inner wall of the upstream part of the heat exchanger increases significantly. Moreover, when this value exceeds 30.0, the content of titanium impurities in the reaction gas liquefaction product becomes excessively high.

[0034] In metal silicon, when the titanium content satisfies the specification of the mass ratio (Ti% / Zr%) to the zirconium content (Zr%) as described above, the titanium content, expressed in elemental mass, is generally 10 ppm by mass or more and 600 ppm by mass or less, more preferably 10 ppm by mass or more and 400 ppm by mass or less, and even more preferably 10 ppm by mass or more and 300 ppm by mass or less.

[0035] Although metallurgical-grade metallic silicon is highly pure as described above, it still contains various metallic impurities, and the specific contents of each metal species vary within a certain range depending on the degree of purification of the silicon raw material and the purification method of the obtained metallic silicon. The zirconium and titanium contents specified in the present invention are also within the ranges of variation of each metallic impurity in such metallurgical-grade metallic silicon, and metallic silicon satisfying these relationships as specified above can be produced by those skilled in the art by adjusting the selection of the silicon raw material and the degree of purification applied. In fact, even among commercially available metallic silicon products, there are small proportions of products that satisfy the specified zirconium and titanium contents, and these can be selected by analyzing and identifying them.

[0036] As mentioned above, aluminum in metallic silicon is not a major component of the scale that deposits on the inner wall of the upstream portion of the heat exchanger, and reducing its content does not significantly affect the effects of the present invention. However, a lower content is more preferable, and taking into consideration the effective prevention of scale deposition made of aluminum chloride in the distillation step and subsequent steps, it is desirable to use silicon metal having an aluminum content of preferably 50 ppm by mass or more and 3000 ppm by mass or less, more preferably 1400 ppm by mass or more and 1600 ppm by mass or less, calculated as the element.

[0037] In the present invention, the content of metal impurities contained in the metallic silicon is a value measured by dissolving the metallic silicon in nitric acid and then filtering the resultant filtrate, and introducing the filtrate into an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0038] A typical process flow for carrying out the above-described method for producing chlorosilanes of the present invention is shown in Figure 1. In the production process shown in Figure 1, trichlorosilane is produced by supplying metal silicon and hydrogen chloride to the fluidized bed of a fluidized bed reactor in the reaction step, and carrying out a chlorination reaction of the metal silicon. That is, metal silicon is supplied to fluidized bed reactor 1 through metal silicon powder inlet channel 2, and hydrogen chloride is supplied through hydrogen chloride supply pipe 3, and the chlorination reaction is carried out within fluidized bed reactor 1. The reaction gas (at a temperature of 320°C or higher) produced in fluidized bed reactor 1 is discharged from the top of the reactor into transfer pipe 4 and sent to distillation column 5.

[0039] A filter 6 that removes fine silicon metal powder contained in the reaction gas is provided in the middle of this transfer piping 4. A portion of the transfer piping 4 upstream of the filter 6 is a double pipe, and the filter 6 removes fine silicon metal powder from the reaction gas.

[0040] A cooling heat exchanger 7 is provided in the transfer pipe 4 downstream of the filter 6, and the reaction gas is cooled there to 10 to 40°C, preferably 20 to 30°C, liquefied, and sent to the distillation column 5. As the heat exchanger 7, a shell-and-tube heat exchanger is generally preferably used to increase the heat transfer area, but a plate type, finned tube type, or the like can also be used. As explained above, in the heat exchanger 7, a peculiar scale mainly composed of zirconium is deposited on its upstream wall surface, particularly, in the case of the shell-and-tube type heat exchanger, on the stationary perforated plate located on the reaction gas inlet side and on the wall surface of the cooling tube end opening thereto. However, according to the present invention, the amount of deposition is significantly suppressed.

[0041] When a shell-and-tube type heat exchanger is used as the heat exchanger 7, a suitable mode is to shower a liquid containing chlorosilanes such as trichlorosilane and tetrachlorosilane onto the perforated fixing plate, which allows a liquid film of the chlorosilanes to be formed on the wall surface of the perforated fixing plate, thereby making it possible to more effectively suppress the deposition of scale.

[0042] The reaction liquid that has passed through the heat exchanger 7 is distilled in the distillation column 5, and a purified gas containing trichlorosilane is recovered from the upper purified gas recovery pipe 8. In addition, high boiling points containing aluminum chloride, titanium tetrachloride, etc. are discharged from the bottom of the column to the high boiling point discharge pipe 9. [Example]

[0043] Examples are given below to explain the present invention in more detail, but the present invention is not limited to these examples. In the examples and comparative examples, the content of each metal impurity in the metallic silicon, the content of silicon, the average particle size of the metallic silicon, and the composition analysis of scale were carried out by the following methods.

[0044] 1) [Content of each metal impurity in metallurgical silicon] 0.5 g of metallic silicon was weighed into a 50 ml Teflon (registered trademark) beaker. 30 ml of 7N-HNO3 was added, and then HF (50 mass%) was gradually added to decompose the sample. After decomposition, the sample liquid was placed on a hot plate and heated at 140°C for 2 hours, then at 160°C for 1 hour, and then the hot plate temperature was adjusted to 140°C until a small amount of residual liquid remained. After heating, 2 ml of HCl (35 mass%) was added as a recovery reagent to the residual liquid, and 5 ml of pure water was added, followed by heating at 140°C for 5 minutes. The beaker was removed from the hot plate and allowed to cool to room temperature.

[0045] The sample liquid in the beaker was filtered into a 100 ml polyethylene measuring flask using a polyethylene funnel and filter paper, and then the volume was increased to 100 ml with pure water. This liquid was introduced into an Optima 8300 (trade name; manufactured by PerkinElmer Co., Ltd.), a two-wave sequential inductively coupled plasma optical emission spectrometry (ICP-OES) analyzer, and analyzed.

[0046] 2) [Silicon content in metallic silicon] 3 to 10 g of metallic silicon was collected in a mortar. The collected silicon was ground with a pestle. The obtained powder sample was placed on a sample stage dedicated to fluorescent X-rays, and the silicon content was measured using an X-ray fluorescence analyzer (manufactured by Rigaku Corporation, product name: "ZSX Primus II").

[0047] 3) [Average particle size of metallic silicon] <Collection method> Approximately 1 kg of metallic silicon was collected from a 1-ton flexible container and placed in a glass container. After thorough stirring, the amount required for the following analysis was collected. <Analysis method> Approximately 100 g of the metal silicon powder was classified using a vibrating sieve machine having multiple sieves, and the cumulative diameter when the cumulative sum of each fraction, starting from the smallest fraction, reached 50 mass % was taken as the average particle size (median diameter). The vibrating sieve machine used was a vibrating sieve machine equipped with stacked sieves conforming to the test sieves specified in JIS Z 8801-1, with nominal mesh sizes of 500 μm, 355 μm, 250 μm, 212 μm, 150 μm, 106 μm, and 45 μm.

[0048] 4) [Method for analyzing the composition of scale deposited on the upstream inner wall of a heat exchanger] <Collection method> The heat exchanger 7 installed in the transfer pipe 4 was disassembled, and about 5 g of scale adhering to the upper surface of the fixing perforated plate on the inlet side of the reaction gas in the shell-and-tube heat exchanger was collected in a glass bottle and subjected to the following analysis. <Analysis method> 2.0 to 5.0 g of the scale sample was accurately weighed into a 50 ml Teflon (registered trademark) beaker, and 30 ml of pure water was added. Filter paper was placed in a polyethylene funnel, and the sample liquid in the beaker was filtered. Pure water was added to the filtrate using a 100 ml polyethylene measuring flask to make the total volume 100 ml to obtain a sample liquid. The obtained sample liquid was diluted with pure water according to the concentration of the target element to be measured, and these liquids were introduced into an ICP-OES device (Optima 8300 (trade name; manufactured by PerkinElmer Co., Ltd.) and analyzed.

[0049] Examples 1 to 3, Comparative Examples 1 and 2 Trichlorosilane was produced according to the production process shown in Figure 1. The metal silicon powder used had the silicon content and metal impurity content (zirconium content, titanium content, and aluminum content) shown in Table 1 below, and an average particle size of 250 μm.

[0050] [Table 1]

[0051] 1, the heat exchanger 7 was of a shell-and-tube type, and was equipped with 110 cooling tubes (25 mm in diameter). The shell-and-tube heat exchanger 7 was configured such that a liquid containing chlorosilanes was showered onto a fixed perforated plate located on the inlet side of the reaction gas.

[0052] The metal silicon powder and hydrogen chloride were supplied to the fluidized bed reactor 1, and a chlorination reaction was carried out at a reaction temperature of 350°C. A reaction gas containing 85% by volume of trichlorosilane and 15% by volume of tetrachlorosilane was introduced at 500 m 3 The reaction gas was discharged into the transfer pipe 4 at a production rate of 1000 kJ / hour. The reaction gas flowed through the transfer pipe 4 and into the heat exchanger 7, and was condensed into a reaction liquid at 20°C and transferred to the distillation column 5.

[0053] After the chlorination reaction was continued for 8,000 hours, the reaction was stopped, the heat exchanger 7 was disassembled, and the openings at the inlet end of the reaction gas of the cooling tube were observed. The openings completely blocked by the deposition of scale were evaluated as blocked, and the number of such openings was counted. The blockage rate was calculated using the following formula: Blockage rate (%) = Number of blocked tubes / Total number of tubes × 100 was determined and is shown in Table 2. However, in Comparative Example 1, the differential pressure of the heat exchanger 7 increased after about 3000 hours, making operation impossible, and the clogging rate at that time is recorded.

[0054] [Table 2]

[0055] Furthermore, in each of the Examples and Comparative Examples, a composition analysis of the precipitated scale revealed that the zirconium content [wt %] was 30 to 40 mass %.

[0056] Preferred embodiments of the invention are described below.

[0057] [1] When producing chlorosilanes by the chlorination reaction of metal silicon, The method for producing chlorosilanes is characterized in that the metal silicon used has a zirconium content (Zr%) of 35 mass ppm or less in elemental terms and a mass ratio (Ti% / Zr%) of a titanium content (Ti%) to the zirconium content (Zr%) of 8.0 or more.

[0058] [2] The method for producing chlorosilanes according to [1], wherein the metal silicon is used, in which the mass ratio (Ti% / Zr%) of the titanium content (Ti%) to the zirconium content (Zr%) is 30.0 or less.

[0059] [3] The method for producing chlorosilanes according to [1] or [2], wherein the metallic silicon has a zirconium content (Zr%) of 1 mass ppm or more in elemental terms.

[0060] [4] The method for producing chlorosilanes according to any one of [1] to [3], wherein the titanium content (Ti%) in the metal silicon is 10 ppm by mass or more and 600 ppm by mass or less in terms of element.

[0061] [5] The method for producing chlorosilanes according to any one of [1] to [4], wherein the chlorination reaction of metal silicon is a reaction between metal silicon and hydrogen chloride to produce trichlorosilane.

[0062] [6] The method for producing chlorosilanes according to any one of [1] to [5], wherein the average particle size of the metallic silicon is 150 to 400 μm.

[0063] [7] The method for producing chlorosilanes according to any one of [1] to [6], wherein the reaction gas obtained by the chlorination reaction of metal silicon is transferred to a distillation column and purified, and a heat exchanger for cooling and liquefying the reaction gas is provided in the transfer path to the distillation column.

[0064] [8] The method for producing chlorosilanes according to [7], wherein the heat exchanger cools and liquefies the reaction gas to 10 to 40°C.

[0065] [9] The method for producing chlorosilanes according to [7] or [8], wherein the heat exchanger is a shell-and-tube heat exchanger.

[0066]

[10] When producing chlorosilanes by the chlorination reaction of metal silicon, A method for producing chlorosilanes, characterized in that the metal silicon used has a zirconium content (Zr%) of 1 ppm by mass or more and 35 ppm by mass or less in elemental terms, and a mass ratio (Ti% / Zr%) of a titanium content (Ti%) to the zirconium content (Zr%) of 8.0 or more and 30.0 or less. [Explanation of symbols]

[0067] 1. Fluidized bed reactor 2: Metal silicon powder introduction channel 3: Hydrogen chloride supply pipe 4. Transfer piping 5. Distillation tower 6; Filter 7; Heat exchanger 8. Purified gas recovery pipe 9; High boiling point discharge pipe

Claims

1. When producing chlorosilanes by the chlorination reaction of metal silicon, As the metallic silicon, metallic silicon is used in which the zirconium content (Zr%) is 35 mass ppm or less in elemental terms and the mass ratio (Ti% / Zr%) of the titanium content (Ti%) to the zirconium content (Zr%) is 8.0 or more, a reaction gas obtained by the chlorination reaction of the metal silicon is transferred to a distillation column and purified, and a heat exchanger for cooling and liquefying the reaction gas is provided in the transfer path to the distillation column; 2. A method for producing chlorosilanes, wherein the heat exchanger is a shell-and-tube heat exchanger.

2. 2. The method for producing chlorosilanes according to claim 1, wherein the metal silicon used has a mass ratio (Ti% / Zr%) of the titanium content (Ti%) to the zirconium content (Zr%) of 30.0 or less.

3. 3. The method for producing chlorosilanes according to claim 1, wherein the metal silicon has a zirconium content (Zr %) of 1 ppm by mass or more in terms of elemental value.

4. 3. The method for producing chlorosilanes according to claim 1, wherein the titanium content (Ti%) in the metal silicon is 10 ppm by mass or more and 600 ppm by mass or less in terms of element.

5. 3. The method for producing chlorosilanes according to claim 1, wherein the chlorination reaction of metal silicon is a reaction of metal silicon with hydrogen chloride to produce trichlorosilane.

6. 3. The method for producing chlorosilanes according to claim 1, wherein the average particle size of the metallic silicon is 150 to 400 μm.

7. 3. The method for producing chlorosilanes according to claim 1, wherein the heat exchanger cools and liquefies the reaction gas to a temperature of 10 to 40°C.

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