JP2013014446A - Method for producing silicon tetrachloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which high purity silicon tetrachloride can be inexpensively produced using, as a raw material, decomposition residue obtained by heat treatment, chemical or biological treatment or the like of silica-containing plants.SOLUTION: Metallic silicon of 1.0-4.8 mm in nominal dimension of a JIS standard sieve is added to decomposition residue having a carbon to silica mass ratio of 0.2-2.0 obtained by heating silica-containing plants in an amount of 10-40 pts.mass relative to 100 pts.mass of silica in the decomposition residue and chlorination reaction is performed, whereby silicon tetrachloride can be produced with a high silica reaction rate without requiring excess energy supply from the outside.

Description

  The present invention relates to a method for efficiently producing silicon tetrachloride, which is widely used industrially as a raw material for semiconductors, solar cells, various silicon compounds, and the like, from bio-derived raw materials such as plants. In this way, high-purity silicon tetrachloride can be obtained.

Conventionally, as an industrial method for producing silicon tetrachloride, since the reaction can be carried out at a relatively low temperature of 300 ° C. or higher, a method of reacting metal silicon with hydrogen chloride has become the mainstream, which is the raw material. Industrial metal silicon is manufactured by carbon reduction of silica in an arc reduction furnace, and consumes a large amount of electric power for production. From the 1960s, instead of metal silicon, SiO ₂ (hereinafter referred to as silica) is used. Various methods for obtaining silicon tetrachloride using silicon as a silicon raw material have been studied. On the other hand, from the viewpoint of energy saving and resource saving, plant raw materials, especially rice husks and rice straw, are noted to contain a large amount of silica. Silica obtained by heat treatment such as carbonization and combustion of rice husks and rice straw. Research has also been made on methods for producing silicon tetrachloride using as a raw material a heating residue containing as a main component.

  Patent Document 1 discloses a method of reacting a mixture of a carbide of a silicic acid plant and a carbonaceous material exemplified by rice husk with chlorine at 400 to 1100 ° C. However, in Patent Document 2 filed at the same time by the same inventor and applicant as Patent Document 1, a method of reacting a mixture of a siliceous substance and a carbonaceous substance with chlorine is a reaction rate at 1000 ° C. or lower. However, it is also disclosed that a large apparatus has a problem of supplying heat. As a solution, Patent Documents 2 and 3 disclose a method in which a small amount of metallic silicon is added to a mixture of silica and a carbonaceous substance as an energy supplier and reacted with chlorine. Chlorination of metallic silicon gives silicon tetrachloride and generates a large heat of reaction. With this heat, it is possible to suppress the power cost for maintaining the high temperature by supplementing the temperature rise sensible heat and reaction endotherm necessary for the reaction of the mixture of silica and carbonaceous material with chlorine.

  Patent Document 2 describes a method in which metal silicon is used in combination when silicon tetrachloride is produced by reacting a siliceous substance and a carbonaceous substance with chlorine, but all of the solid raw materials have a particle size of 100 μm or less. It is disclosed that the fine particles are preferable. In all Examples of Patent Document 2, it is described that microsilica having a particle size of 100 μm or less, metal silicon, and coke powder are used as raw materials, and the reaction was performed while the reactor was heated and held from the outside. However, at this time, metal silicon was 100% reacted and consumed, whereas the reaction rate of microsilica was as low as 12.0 to 28.0%.

  In other words, when producing silicon tetrachloride by reacting a siliceous substance and a carbonaceous substance with chlorine, a method of utilizing the reaction heat of metal silicon in combination with metal silicon has been known. In addition, the reactor had to be heated as usual, and only the chlorination reaction of the metal silicon proceeded with priority, and the reaction rate of the siliceous substance was low and remained unreacted. There was a problem. If the fine silicic acid substance remains in the reactor, there is a problem that the treatment is time-consuming and the cost is greatly increased.

On the other hand, in Patent Document 3, the reaction is spontaneously continued at 1050 ° C. even when external heating is stopped, although the structure is almost the same as Patent Document 2, and the reaction rate is less than 95% based on the silica used. The examples from which are obtained are described. The difference from the example of Patent Document 2 is that rice husk ash was used instead of 100 μm or less of microsilica, that a cocoon having a specific surface area of 20 m ² / g was used instead of 100 μm or less of coke, and that of 100 μm or less. There is a description that metal silicon dust of less than 0.8 mm is used instead of metal silicon, and that the finest dust in the particle size range is most suitable for the purpose.

  The specification of Patent Document 3 states that the chlorine used should be almost anhydrous (less than 10 ppm), but it is difficult to reduce the moisture of chlorine to 20 ppm or less unless special treatment is performed. It has been known. In addition, soot is also called carbon black, and is generally known as an ultrafine particle having a particle size of several tens of nanometers and high activity. Thus, the method of Patent Document 3 is a fine particle and has a large specific surface area. It can be considered that the reaction rate is increased by using raw materials or highly dehydrated chlorine. However, such raw materials and chlorine are expensive and difficult to obtain, and are not suitable for industrial production.

  In other words, a method of using metal silicon together in producing silicon tetrachloride by reacting a siliceous material and a carbonaceous material with chlorine is known, and a method of obtaining a high reaction rate using an expensive and special raw material. However, when ordinary industrial raw materials were used, the reaction rate of siliceous substances was not always good, and there was a problem that only metal silicon reacted. There has been a demand for a method for producing silicon tetrachloride which can provide a high reaction rate.

JP 58-55330 A JP 58-167419 A Special table 2009-542561 Japanese Patent Laid-Open No. 62-252311

  An object of the present invention is to provide a method capable of producing high-purity silicon tetrachloride at a low cost from a decomposition treatment residue obtained by subjecting a plant containing silica to heat treatment, chemical treatment, biological treatment, or the like as a raw material. It is.

(1) The present inventors added the nominal size of the JIS standard sieve to the decomposition treatment residue having a carbon / silica mass ratio of 0.2 to 2.0, which is obtained by decomposing a plant containing silica. Excess energy supply from outside by adding 10 to 40 parts by mass of metal silicon of 1.0 mm to 4.8 mm with 100 parts by mass of silica in the decomposition treatment residue. It was found that silicon tetrachloride can be produced with a high silica reaction rate.

The present invention also includes the inventions described in (2) to (5) below.
(2) The method for producing silicon tetrachloride according to the above (1), wherein a potassium compound as a reaction catalyst is used in an amount of 0.1 to 20 parts by mass with respect to 100 parts by mass of silica in the decomposition treatment residue. .
(3) The mixture of the decomposition treatment residue and metal silicon is granulated using a binder and reacted as a granulated product having a particle size range of 1.0 mm or more and 8.0 mm or less by a JIS standard sieve (1) ) Or the method for producing silicon tetrachloride according to (2).
(4) The method for producing silicon tetrachloride according to (3), wherein the reaction is continued by supplying a granulated product of the decomposition treatment residue and metal silicon to the reactor during the reaction.
(5) The granulated product of the decomposition treatment residue and metal silicon is supplied from the upper part of the vertical reactor, and the reaction is continued while extracting the reaction residue from the lower part. A method for producing silicon chloride.

  In the method for producing silicon tetrachloride according to the present invention, silicon tetrachloride can be produced at low cost by using a decomposition residue of a plant or the like that has conventionally been a waste as a raw material.

Hereinafter, the present invention will be described in detail. In the present invention, the decomposition treatment residue obtained by decomposing a plant containing silica is carbonization, combustion, chemical, biological, physical decomposition treatment of the plant containing silica. Means a substance containing carbides and incinerated ash, and preferably containing 20% by mass or more of silica. Examples of the plant containing silica include silicon-accumulating plants such as rice, wheat, corn, straw, and tokusa, and leaves, stems, rice husks, etc. are preferably used, and rice, wheat husks and rice are more preferable. Straw, wheat straw.

  The chemical decomposition treatment includes, for example, a hydrolysis treatment using an acid and an alkali, and the biological decomposition treatment includes, for example, a treatment such as saccharification and fermentation when producing bioethanol from a silicon-accumulated plant. In addition, the physical decomposition process includes processes such as shredding and crushing.

  There is no particular limitation on the method for carbonization or combustion, but the carbide can be obtained by heating a plant or the like in an atmosphere with less oxygen, preferably in the range of 300 ° C to 1200 ° C. Combustion ash is obtained by burning while supplying oxygen to plants and the like. In any case, the silica in the decomposition treatment residue obtained is amorphous and contains carbon and a trace amount of inorganic salt. In the case of carbide, if carbonization is performed so as to increase the carbon content, 20 to 40% of the decomposition treatment residue can be made carbon, so the amount of carbon in the decomposition treatment residue is controlled by heating conditions. Even in the case of incineration, the amount of carbon in the residue of the decomposition treatment can be controlled by controlling the amount of oxygen supplied and the combustion temperature. In the present invention, it is essential that the carbon content in the decomposition treatment residue is 0.2 to 2.0 in terms of the mass ratio of carbon / silica with respect to the silica content in the decomposition treatment residue. Yes, preferably 0.3 to 1.5, more preferably 0.4 to 1.0. In the production method of the present invention, when the mass ratio of carbon / silica in the decomposition treatment residue that is a raw material is within this range, the reactivity of silica increases, and the reaction proceeds efficiently and the raw material is not wasted. Can be consumed.

  Chemical decomposition treatment, biological decomposition treatment, physical decomposition treatment, carbonization or combustion treatment can also be performed in combination, and when combined treatment is performed after all combined decomposition treatments are performed. It is called the decomposition treatment residue in the invention, and is used as a standard for determining the amount of silica, carbon and the like. Among the combinations of the decomposition treatments, those including a biological decomposition treatment and carbonization or combustion treatment are preferable because a decomposition treatment residue having high energy and advantageous reactivity can be obtained. Further preferred is a decomposition treatment residue obtained by performing carbonization treatment after biological decomposition treatment.

  Before subjecting the decomposition treatment residue to the chlorination reaction, a carbon compound can be added to adjust the mass ratio of carbon / silica. Any carbon compound may be added as long as it contains carbon. Preferable carbon content added to the decomposition treatment residue is activated carbon, petroleum coke, coal or the like. A carbon compound can be added before the decomposition treatment. However, the decomposition treatment residue in the present invention is obtained by decomposition treatment of a plant containing silica, and the amount of carbon added in addition thereto is the mass ratio of carbon / silica of the decomposition treatment residue. Not included in the rules.

  In addition, the determination method of the silica content in the decomposition treatment residue is a method in which the decomposition treatment residue is subjected to wet chemical decomposition and the silicon content is measured by a spectroscopic method such as ICP. In addition, a method called CHN elemental analysis, which is measured from the amount of carbon dioxide generated when thermally decomposed in oxygen, can be used, and quantitative analysis can also be performed by fluorescent X-ray analysis in a solid state. When it is measured after adding metallic silicon, it becomes difficult to distinguish between silica and metallic silicon, so decompose the non-added material under the same conditions, measure the silica content and carbon content, and add afterwards. For the metallic silicon and carbon compounds, the compounding amount may be excluded as a concentration contribution. In saccharification residues and carbides of plants called silicon-accumulated plants, carbon and silica occupy most of the components. For example, in thermogravimetric analysis called TG / DTA which measures weight change by heating in air or nitrogen As a simple measurement method, there is no large error even if the weight difference decreased during heating up to 1000 ° C in air and nitrogen, and the weight remaining after heating in air at 1000 ° C is silica. Can be used.

  In the present invention, as a method for carbonizing or burning a plant containing silica or its decomposition product to obtain a decomposition treatment residue, a known method can be used, and the carbide and combustion ash may be a cyclone, a bag filter, It can be collected by a known method such as an electric dust collector, and the exhaust heat of incineration can be used for various purposes.

  In the present invention, a reaction catalyst can be added in order to improve the reactivity between silica and chlorine in the decomposition treatment residue. Preferred as the reaction catalyst is a potassium compound. Examples of the potassium compound include potassium carbonate, potassium chloride, potassium hydrogen carbonate, potassium hydroxide, potassium nitrate, potassium sulfate, potassium acetate, potassium oxalate, and potassium formate. . Of these, potassium chloride is particularly preferred.

  The addition ratio in the case of using a potassium compound is 0.1-20 mass parts as a potassium amount with respect to 100 mass parts of silica in a decomposition-processing residue, Preferably it is the range of 0.5-15 mass parts. If the amount added is small, there is no effect, and if it is too large, the amount remaining as a residue after the reaction increases, which is not advantageous.

  In the present invention, in order to obtain a higher reaction rate of silica by the reaction of silica and chlorine in the decomposition residue, metal silicon having a nominal size of JIS standard sieve of 1.0 mm to 4.8 mm is used. It is essential. As for the particle size of the decomposition treatment residue, the finer the particles, the higher the reaction activity, which is preferable. However, since it is difficult to make the particles finer, it is preferably 0.1 μm or more and 500 μm or less, more preferably 0. 5 μm or more and 100 μm or less.

  Any method may be used as a method for obtaining metallic silicon having the above particle diameter and the decomposition treatment residue, but there are no particular limitations on the equipment used for fine grinding, for example, jet mill, pin mill, ball mill, crusher, etc. Using an apparatus, it can be carried out dry or under wet conditions in the presence of a solvent.

  In general, the particle size of the fine particles is measured by measuring the diameter of the enlarged particles with a device such as a microscope or an electron microscope, or by various measuring devices such as a laser particle size distribution meter or a Coulter counter. However, there are differences in the values obtained by the measurement principle. In addition, it is a simple method to define the particle size distribution using a standard sieve, but even when other methods are used, the definitions can be interchanged by associating the measurement values using standard particles. In addition, even after it has become a granulated product of the decomposition residue and metal silicon, use an analytical electron microscope or EPMA (electron beam microanalyzer) to determine which component is the particle being observed. The particle size can also be measured by fractionation.

  When the decomposition treatment residue and potassium compound are used in combination, it is preferably used after mixing, and more preferably, after adding a solvent such as water and mixing, pulverization, pulverization and use are performed. It is also preferable to mix in advance before processing. The reason for pre-mixing is that the efficiency of the chlorination reaction of silica in the decomposition treatment residue is improved. For mixing, it is possible to use a mixer such as a ribbon mixer or a Henschel mixer that is difficult to share, but more preferable is a mixer that shares a particle such as a ball mill or a crusher. It has the effect of increasing the reaction efficiency.

  Metallic silicon for general industrial use can be used as metallic silicon. It is desirable to use metal silicon having a particle size range of 1.0 to 4.8 mm, preferably 2.0 to 3.4 mm. In general, metal silicon has been produced by a method of collecting powder by pulverization and classification, and many methods are known for classification, such as airflow classification and classification simultaneously with pulverization. The particle size is preferably determined by a classification method having a sieving function for cutting oversized and undersized particles, and more preferably metal silicon having a distribution close to the normal distribution from the center particle size. The particle size distribution of the metallic silicon obtained by various classification methods can be specified by, for example, sieving with a standard sieve defined in JIS Z8801-1982, or the particle size range can be defined by an enlargement method such as an optical microscope. Can be measured and confirmed. In the present invention, the nominal size of the JIS standard sieve is used as the particle size range. That is, particles that are on a sieve having a nominal size of 2.0 mm and that are under the sieve having a nominal size of 3.4 mm are referred to as particles having a particle size of 2.0 to 3.4 mm. The JIS nominal size is specified to the second decimal place, such as 3.35 mm and 4.75 mm, but in the present invention, it is called 3.4 mm, 4.8 mm, etc. for simplicity.

  Metallic silicon particles with a particle size smaller than 1 mm have a large surface area and high reactivity, so that metal silicon consumes more chlorine, and the silica in the decomposition residue can consume relatively less chlorine. Since the rate is lowered and the metal silicon is consumed in a short time, the temperature in the reactor tends to decrease thereafter. On the other hand, when the particle size is larger than 4.8 mm, since the surface area is small and the reactivity is low, a sufficient reaction temperature cannot be obtained only by reaction heat, and the reaction rate of silica may not increase.

  The metal silicon used in the present invention is required to have a particle size range of 1 mm or more and 4.8 mm or less. However, if any particles other than this numerical range are included, it cannot be implemented. The present invention can be carried out even if the excessive and excessively small metal silicon particles other than are preferably contained in an amount of 10% by mass or less, more preferably 5% by mass or less of the entire metal silicon.

  The amount of metal silicon used is in the range of 10 to 40 parts by mass, preferably in the range of 15 to 35 parts by mass with respect to 100 parts by mass of silica in the decomposition treatment residue. When the amount used is small, the heating value is small and the reaction temperature is insufficient, so that external heating is required. On the other hand, when the amount is large, the calorific value is large and the reaction temperature becomes unnecessarily high. Considering the energy required for the production of metal silicon, the use of metal silicon more than necessary does not meet the purpose of energy saving.

  When the raw material containing the decomposition treatment residue and metal silicon is molded into a granulated product, a binder can be preferably used. The reason is that granulation can be performed efficiently and pulverization during the conveyance of the granulated product can be prevented. Examples of the binder include water, polyethylene glycol, starch, gelatin, molasses, cellulose, water glass, and silica sol.

  When mixing the raw material containing the decomposition treatment residue and metal silicon, the constituent components may be mixed as they are, but when the decomposition treatment residue and the potassium compound are used in combination, the decomposition treatment residue and the potassium compound are used. Is preferably mixed well and then pulverized, and then granulated with metal silicon.

  When the raw material containing the decomposition treatment residue and the metal silicon is granulated, the smaller the particle size of the granulated particles, the more easily it reacts with chlorine, but it cannot fall below the lower limit of the particle size of the metal silicon. Accordingly, the nominal size of the JIS standard sieve is preferably 1.0 mm or more and 8.0 mm or less, that is, on the sieve of the JIS standard sieve having a nominal size of 1.0 mm, and has a particle size range that is below the sieve of 8.0 mm. Is. More preferably, it is 2.0 mm or more and 4.8 mm or less.

  When water is present in the raw material for carrying out the present invention, there are problems such as blockage of piping due to silica produced by hydrolysis of silicon tetrachloride and a decrease in the yield of silicon tetrachloride. Therefore, it is preferable to use the raw material containing metal silicon and the decomposition treatment residue after heat dehydration before reacting with chlorine. Examples of the heat dehydration method include dehydration by heating at 150 to 900 ° C. for about 0.5 to 24 hours in air, vacuum, or an inert gas atmosphere such as argon, helium, and nitrogen. More preferably, it is 400-600 degreeC.

  Moreover, this heat dehydration process may serve as carbonization or a combustion process. In other words, once a plant has been subjected to chemical decomposition treatment, biological decomposition treatment, physical decomposition treatment, carbonization or combustion treatment, etc., it is subjected to each step of pulverization, mixing, granulation, etc., and then this heat dehydration treatment is performed. This is efficient because the carbonization process and the heat dehydration process can be performed at the same time. When the heat dehydration treatment also serves as the carbonization treatment, a method of heating at 150 to 900 ° C. for about 0.5 to 24 hours in an inert gas atmosphere such as argon, helium, nitrogen, etc. can be exemplified, and more preferably 400 to 600. ° C.

  The reaction with chlorine may be carried out in a fixed bed, a fluidized bed, a moving bed or the like as long as the mixture containing the decomposition treatment residue and metal silicon can be sufficiently brought into contact with chlorine. Chlorine preferably having a purity of 98% by mass or more may be used as it is, or diluted with an inert gas such as argon, helium or nitrogen. The pressure in the reactor can also be set arbitrarily.

  The temperature at which the reaction with chlorine is started is preferably 300 to 500 ° C. As a method of raising the temperature of the mixture containing the decomposition residue and metal silicon, it may be preheated and then added to the reactor, or a preheated gas may be flowed into the reactor to raise the temperature. .

  Once the reaction is started, heat of reaction is generated by the chlorination reaction of metal silicon, and if the reactor is kept warm and insulated with a heat insulating material, the reaction can be carried out without requiring heat supply to the reactor from the outside. Can continue. The heat insulating material is not particularly limited as long as it is generally a heat insulating material that can be heat-resistant at a high temperature, and for example, ceramic wool or quartz fiber wool can be used.

  The reaction may be performed in a batch operation, but it is preferable to perform the reaction in a continuous operation in which the supply of the raw material and the discharge of the reacted residue are performed intermittently. The reason is that the utilization efficiency of thermal energy and the reaction rate of silica are increased.

  After the reaction is completed, unreacted silica, or a potassium compound when a potassium compound is used, remains in the reactor as a reaction residue. They can be discharged, for example, by an opening / closing mechanism such as a ball valve that can be opened and closed at predetermined time intervals from an outlet installed at the bottom of the reactor. For discharging, it is preferable to provide the reactor with a mechanism capable of applying vibration to the entire reactor or a part of the reactor. The discharged reaction residue can be reused by mixing it with a fresh decomposition residue instead of the catalyst. In that case, it is preferable to supply to a reactor from the inlet installed in the reactor upper part.

<Action>
In the present invention, the highest effect is obtained by covering the metal silicon having a sieving particle size of 1 mm or more and 4.8 mm or less with a mixture of the decomposition treatment residue and the potassium compound as a coating layer. It is a form of a granulated product having a particle size of 0.0 mm or more and 8.0 mm or less. In this case, since the chlorine passing through the coating layer causes an exothermic reaction on the surface of the metal silicon, the interface between the metal silicon and the coating layer becomes high temperature, and further, the silica in the decomposition treatment residue is rapidly chlorinated by the catalytic action of the potassium compound. React with. And since the granulated product keeps its form until it almost reacts, the gas flow between the particles is good, but when it almost reacts, it becomes a slightly fine reaction residue. Spills from between. For this reason, even if it does not use the special apparatus for continuation, a new granulated material is added from the upper part of the reactor, and the reaction residue is easily extracted from the lower part of the reactor to carry out the continuous reaction easily for a long time. be able to.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to this embodiment. Unless otherwise specified,% is mass%. For the granulated material containing metallic silicon and metallic silicon, particles sieved by a standard sieve defined in JISZ8801-1982 were used. “Less than 0.3 mm” means below a sieve with a nominal size of 0.3 mm, and “greater than 4.8 mm” means above a standard sieve with a nominal size of 4.75 mm.

<Example 1>
The slurry-like saccharification / fermentation residue discharged during the production of bioethanol from domestic rice straw is solid-liquid separated by centrifugation, then the same amount of deionized water is added to the solid, and then centrifuged again The solid content was washed with water, and the solid content was dried at 140 ° C. to obtain a dry solid content. To 110 g of dry solids, add 5.9 g of potassium chloride (potassium amount is 3.1 g), add deionized water 2.0 times the weight of solids, add zirconia balls, and add ball mill For 60 hours. The dried product obtained by drying the pulverized slurry at 140 ° C. for 2 hours was pulverized again. To 116 g of the powder after dry pulverization, metal silicon having a particle size of 2.0 to 3.4 mm is added to 10.5 g, and a 1.2 mass% starch water / methanol mixed solution (water: methanol = 50 as a binder). 10% (mass%: 50 mass%) is added to form a granulated product with a rolling granulator, and the particle size is obtained by collecting the sieve under a JIS standard sieve having a nominal size of 2.0 mm and under a sieve of 4.8 mm. The granulated product was 2.0 to 4.8 mm. Oversized and undersized granulated materials were crushed and again made into granules with a rolling granulator, and this operation was repeated until there were almost no oversized and undersized granulated materials. The yield based on the charge was 99% by mass or more. This was dried at 500 ° C. for 6 hours under a nitrogen flow, and carbonized and heat-dehydrated to obtain a granulated decomposition residue 75.8 g. From the result of heating to 1000 ° C. in air and nitrogen by TG / DTA analysis, the amount of carbon in the granulated product was calculated to be 19.2 g, and the amount of metal silicon added from the heating residue at 1000 ° C. in air was 10. Excluding 5 g, the amount of silica was calculated to be 40.1 g, and the mass ratio of carbon / silica was determined to be 0.48. Moreover, the addition amount of potassium chloride with respect to 100 mass parts of silica was computed with 7.6 mass parts as potassium. In Example 1, the amount of metal silicon added to 100 parts by mass of silica in the decomposition treatment residue was calculated to be 26.2 parts by mass.

  The granulated residue 75.8 g was filled in a 200 ml quartz reactor, and quartz fiber wool was wound around the reactor so as to have a thickness of 1.0 cm as a heat insulating material. It was inserted into a crucible heater with a lower opening with good thermal insulation, and quartz fiber wool was packed in the gap with the heater. The reactor was heated from outside while flowing nitrogen through the opening at the bottom of the reactor, and the reactor internal temperature was raised to 420 ° C. After the temperature rise, external heating and nitrogen were stopped, and the reaction was carried out by circulating chlorine at 400 ml / min. The internal temperature rose to 1140 ° C. and then gradually decreased. When the internal temperature dropped below 800 ° C, the circulation of chlorine was stopped. The circulation time of chlorine at that time was 1.0 hour.

  The product gas from the upper part of the reactor was collected by cooling with a refrigerant to obtain 139 g of silicon tetrachloride. In addition, the reacted residue in the reactor is put into water and stirred, and the solid content that settles first due to the difference in specific gravity is recovered as metal silicon, and dried to measure the weight as the amount of residual metal silicon. The reaction rate of metallic silicon was determined. On the other hand, the reaction rate of silica was calculated by subtracting the amount of silicon tetrachloride derived from metal silicon from the total amount of silicon tetrachloride and calculating the difference as the amount of silicon tetrachloride derived from silica. The reaction rate of metal silicon was 96.4%, and the reaction rate of silica was 67.9%.

<Example 2>
A ball mill was used for 60 hours in the same manner as in Example 1 except that 12.1 g of petroleum raw coke was added to 110 g of dry solids. Granulation, carbonization, and heat dehydration treatment were performed on 128 g of the pulverized and dried powder in the same manner as in Example 1 to obtain 87.4 g of granulated decomposition residue. The mass ratio of carbon / silica in the granulated product was 0.77.
The granulated decomposition residue was charged into a 200 ml quartz reactor and reacted under the same conditions as in Example 1. The internal temperature at that time rose to 1060 ° C. The yield of silicon tetrachloride was 134 g, and the chlorine circulation time was 1.3 hours. The reaction rate of metal silicon was 97.4%, and the reaction rate of silica was 63.6%.

<Example 3>
In the same manner as in Example 1 until the dried product obtained by drying the pulverized slurry at 140 ° C. is pulverized, the obtained dried product is heated at 500 ° C. for 6 hours under nitrogen flow, and carbonized and heated. With respect to 65.3 g of the decomposition treatment residue obtained by the dehydration treatment, 10.5 g of metal silicon having a particle size of 2.0 to 3.4 mm (26.2 parts by mass with respect to 100 parts by mass of silica) is obtained. The mixture was physically well mixed with a tabletop mixer (Oster blender), and the mixture was charged in a 200 ml quartz reactor without being granulated and reacted under the same conditions as in Example 1. The internal temperature at that time rose to 1010 ° C. The chlorine circulation time was 1.0 hour. The reaction rate of metal silicon was 87.0%, and the reaction rate of silica content was 54.6%.

<Example 4>
The same procedure as in Example 1 was performed except that potassium chloride was not added, and the granulated decomposition residue was charged into a 200 ml quartz reactor and reacted under the same conditions as in Example 1. The internal temperature at that time rose to 1050 ° C. The chlorine circulation time was 0.9 hours, the reaction rate of metal silicon was 83.4%, and the reaction rate of silica was 54.1%.

<Example 5>
A 200 ml quartz reactor was charged with 114 g of the granulated decomposition residue prepared in the same manner as in Example 1, and the reaction was started under the same conditions and method as in Example 1. After 1.0 hour from the start, 265 g of granulated material is fed from the top of the reactor at a feed rate of 26.5 g in 30 minutes, and accordingly, the reacted residue after 2.0 hours from the start, Discharge from the bottom of the reactor at a discharge rate of 6.5 g in 30 minutes. When the internal temperature dropped below 800 ° C, the circulation of chlorine was stopped. The chlorine circulation time was 6.0 hours, the reaction rate of metallic silicon was 99.0%, and the reaction rate of silica in the decomposition treatment residue was 71.6%. In the continuous reaction performed while supplying the granulated product, a silica reaction rate superior to the batch reaction was obtained.

<Comparative Example 1>
The reaction was carried out under the same conditions as in Example 4 except that the particle size of metal silicon was smaller than 0.3 mm. The internal temperature at that time rose to 1090 ° C. The circulation time of chlorine was 0.9 hours, the reaction rate of metal silicon obtained by calculation was 95.9%, and the reaction rate of silica was 30.7%.

<Comparative example 2>
The reaction was carried out under the same conditions as in Example 1 except that the particle size of metal silicon was smaller than 0.3 mm. The internal temperature at that time rose to 1100 ° C. The reaction time was 0.9 hours, the reaction rate of metal silicon was 96.3%, and the reaction rate of silica was 31.4%.

<Comparative Example 3>
The reaction was carried out under the same conditions as in Example 1 except that the particle size of the metal silicon was larger than 4.8 mm and the particle size of the granulated product was 4.8 to 8.0 mm. The internal temperature at that time rose to 860 ° C. The reaction time was 0.7 hours, the reaction rate of metal silicon was 83.8%, and the reaction rate of silica was 33.9%.

<Comparative example 4>
A metal having a particle size of 2.0 to 3.4 mm is used in the same manner as in Example 1 until the dried product obtained by drying the pulverized slurry at 140 ° C. is used in the same manner as in Example 1. The reaction was carried out in the same manner as in Example 1 except that silicon was added to 1.2 g. The reaction was started by raising the reactor internal temperature to 420 ° C., but the reactor internal temperature only increased to 830 ° C., and the reaction was terminated because it dropped below 800 ° C. in 0.1 hour. The reaction rate of metallic silicon was 34.0%, and the reaction rate of silica in the decomposition treatment residue was 4.3%. In addition, the addition amount of the metal silicon with respect to 100 mass parts of silica in the granulated decomposition treatment residue was calculated with 3.0 mass parts.

<Comparative Example 5>
A metal having a particle size of 2.0 to 3.4 mm is used in the same manner as in Example 1 until the dried product obtained by drying the pulverized slurry at 140 ° C. is used in the same manner as in Example 1. The reaction was conducted in the same manner as in Example 1 except that silicon was added to 20.1 g. The reaction was started by raising the reactor internal temperature to 420 ° C, but the reactor internal temperature rapidly increased and was observed to rise even when the temperature exceeded 1250 ° C. did. The reaction rate of metallic silicon and silica in the decomposition treatment residue was not measured. In addition, the addition amount of the metal silicon with respect to 100 mass parts of silica in the granulated decomposition processing residue was computed with 50.0 mass parts.

<Comparative Example 6>
Ash produced when domestic rice husks were burned in a forced air supply incinerator was used as the residue of the decomposition process. As a result of examining the weight loss by heating to 1000 ° C. in air and nitrogen by TG / DTA analysis, silica in rice husk ash was 96.0% by mass, carbon was 4.0% by mass, The mass ratio of carbon / silica in the decomposition treatment residue was 0.04. Therefore, 17.6 g of raw coke and 5.9 g of potassium chloride (3.1 g as the amount of potassium) are added to 41.8 g of rice husk ash, and deionized water 2.0 times the weight of the solid content. Was added, and zirconia balls were added and pulverized with a ball mill for 60 hours. The dried product obtained by drying the pulverized slurry at 140 ° C. for 2 hours was pulverized again. To 65.3 g of the powder after dry pulverization, metal silicon having a particle size of 2.0 to 3.4 mm is added to 10.5 g, and a 1.2 mass% starch water / methanol mixed solution (water: methanol as a binder). = 50% by mass: 50% by mass), and granulated with a tumbling granulator, and collected on a sieve with a nominal size of 2.0 mm of JIS standard sieve and 4.8 mm below the sieve. A granulated product was obtained. Oversized and undersized granulated materials were crushed and again made into granules with a rolling granulator, and this operation was repeated until there were almost no oversized and undersized granulated materials. The yield based on the charge was 99 wt% or more. This was dried at 140 ° C. for 2 hours under nitrogen flow. The mass ratio of carbon / silica of the granulated decomposition residue was 0.48.
The granulated decomposition residue 75.8 g was charged into a 200 ml quartz reactor and reacted under the same conditions as in Example 1. The temperature rose to 1010 ° C. The chlorine circulation time was 1.0 hour. The reaction rate of metal silicon was 87.3%, and the reaction rate of silica content was 49.7%.
Table 1 shows the reaction results of Examples 1 to 5 and Comparative Examples 1 to 6. In Table 1, the carbon / silica ratio of Example 2 and Comparative Example 6 is a number including post-added carbon.

  Comparing Example 1 and Comparative Example 6, when the carbon / silica mass ratio is out of the range of 0.2 or more and 2.0 or less, the decomposition treatment residue with a small amount of carbon is the same as the amount by post-addition. In the comparative example 6 which added carbon which becomes, it turned out that only the silica reaction rate inferior to Example 1 is obtained. This is because the decomposition treatment maintains a high degree of dispersion with the carbon / silica coexisting at the cell molecular level of the original plant, so the silica is higher than the one with the same amount of carbon added after the addition. It can be understood that the reaction rate can be given. As a result, it can be considered that this reason is supported by the fact that in Example 2 in which carbon was further added to the decomposition treatment residue of Example 1, the silica reaction rate was rather lowered.

  Example 1 and Example 3 have the same particle size range of the added metal silicon, but compared to Example 3 in which granulation was not performed, Example 1 in which granulation was performed also had a metal silicon reaction rate. As a result, the reaction rate of silica was also high. This is probably because the drift of chlorine gas hardly occurs between the granulated particles, the contact efficiency between metal silicon and chlorine is improved, and the reaction rate of metal silicon is increased. At the same time, the reaction heat generated on the surface of the metal silicon is increased and the reaction time is increased, so that the silica is chlorinated at a high temperature for a long time, and the reaction rate of the silica is increased.

  The results of Comparative Examples 4 and 5 indicate that if there is too much metal silicon, it will run out of control, and if it is too little, only metal silicon will react and the reaction rate of silica will be unexpectedly low. Indicated. From this, the amount of metal silicon used in the present invention has an important meaning, and if used in an appropriate range, the reaction proceeds autonomously, and the reaction rate of silica in the decomposition treatment residue is expected to increase. It seems to show that it has an effect that cannot be done.

The method for producing silicon tetrachloride of the present invention is industrially feasible, and since the reaction rate of silica is high, cheaper silicon tetrachloride can be supplied to the market.

Claims (5)

  In a decomposition treatment residue having a carbon / silica mass ratio of 0.2 or more and 2.0 or less obtained by decomposing a plant containing silica, a nominal size of a JIS standard sieve is 1.0 mm or more and 4.8 mm or less. A method for producing silicon tetrachloride, wherein 10 to 40 parts by mass of the metal silicon is added to 100 parts by mass of silica in the residue of the decomposition treatment, and a chlorination reaction is performed.   The manufacturing method of the silicon tetrachloride of Claim 1 which uses 0.1-20 mass parts of potassium compounds as a reaction catalyst with respect to 100 mass parts of the silica in a decomposition process residue.   The mixture of the decomposition treatment residue and metal silicon is granulated using a binder, and reacted as a granulated product having a particle size range of 1.0 mm or more and 8.0 mm or less by a JIS standard sieve. A method for producing silicon tetrachloride as described.   The method for producing silicon tetrachloride according to claim 3, wherein the reaction is continued by supplying a granulated product of the decomposition treatment residue and metal silicon to the reactor during the reaction.   The production of silicon tetrachloride according to claim 4, wherein the granulated product of the decomposition treatment residue and metal silicon is supplied from the upper part of the vertical reactor and the reaction is continued while extracting the reaction residue from the lower part. Method.