JP2013049625A - Methods for producing fine silicon carbide, fine silicon nitride, metal silicon and silicon chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing metal silicon which becomes a high functional material by utilizing the minute form and porous structure of diatomite particles.SOLUTION: In the method for producing the metal silicon, a carbon material, and a persistent organic chlorine compound or organic matter are mixed or absorbed in the pores of diatomite, the contact area of a carbon source with silicon dioxide is increased by heating it under an atmosphere of an inert gas, hydrogen gas, nitrogen gas, air or vacuum and then the metal silicon is efficiently produced. The organic matter is filled within the used filtration auxiliary agent of the diatomite.

Description

  The present invention relates to a method for producing fine silicon carbide, fine silicon nitride, metal silicon, and silicon chloride, utilizing the fine morphology and porous structure of diatomaceous earth particles.

Silica stone and silica sand, which are currently used as raw materials for silicon carbide and metal silicon, are composed of silicon dioxide mainly composed of covalent bonds, have a high melting point of 1,713 ° C., and require a lot of electric power for reduction. To do.
In addition, as shown in FIG. 2, in order to make the reaction efficient, it is necessary to add energy to pulverize the silica stone to an appropriate size and to add coke as a reducing agent.
On the other hand, diatomaceous earth is an aggregate of diatom fossils with a size of several tens of μm, and therefore has a large specific surface area and mainly contains amorphous silicon dioxide and metasilicic acid. There is an advantage. Furthermore, since it is processed into a powder or a granule in the process of commercialization, it does not need to be crushed again (FIG. 1).

Conventionally, it is known that filtration waste material discharged from the brewery's filtration process is subjected to activation treatment after granulation, carbonization, etc., if necessary, to obtain a filter medium having activated carbon adsorption capacity and diatomite humidity conditioning capacity. (See Patent Document 1).
In this known technique, filtered waste material from the filtration process of a beer factory is put into an electric furnace, and heated in a nitrogen gas atmosphere at 700 ° C. for 2 hours to carbonize organic matter. As a binder, 100 parts by weight of the carbide is used as a binder. After adding 10 parts by weight of starch and 15 parts by weight of water and kneading, the mixture is supplied to a granulator and granulated to an average particle size of 2 mm. The granulated product is 900 ° C. in a nitrogen gas atmosphere containing 35% of water vapor. The filter medium is produced by activating treatment for 2 hours.
In addition, diatomaceous earth from Akita Prefecture and carbon black are mixed, heated in an argon gas atmosphere at 1,450 ° C. for 1 hour to synthesize silicon carbide, heated in the atmosphere at 700 ° C. to remove residual carbon, It has also been proposed to perform discharge plasma sintering of silicon carbide powder at 1,500-1,800 ° C. and 50 MPa for 15-18 minutes (see Non-Patent Document 1).
In this method, carbon black, which is a simply mixed carbon source, reacts with SiO gas to form silicon carbide. Therefore, the particle size of silicon carbide becomes the same as the particle size of the mixed carbon source, and further finer And uniformity were demanded.

The former uses diatomaceous earth, but finally recycles the waste filter material as a filter material and heats and carbonizes it to add adsorption capacity, and produces silicon carbide, silicon nitride, metal silicon, and silicon chloride. It wasn't something to do.
In the latter method of mixing Akita Prefecture diatomaceous earth and carbon black, the mixed carbon and SiO gas generated from diatomaceous earth react to form silicon carbide, so the silicon carbide particle size is the mixed carbon source. It was the limit to be the same as the particle size of the material, and further refinement and uniformity were required.

JP 2003-251177 A

International Conference on Processing Materials for Properties (2nd) San Francisco Calif. Page.1081-1082 (2000)

  An object of the present invention is to provide a production method for producing fine silicon carbide, fine silicon nitride, metal silicon, and silicon chloride, which is a substance of a high-functional material, utilizing the fine form and porous structure of diatomaceous earth particles. .

The method for producing fine silicon carbide according to the present invention is produced under an inert gas atmosphere by utilizing the fine form and porous structure of diatomaceous earth particles, increasing the contact area with the mixed or absorbed carbon source. is there.
In the present invention, the inert gas is generally argon gas and prevents carbon from reacting with oxygen in the air and being consumed for purposes other than the intended purpose.
The method for producing equal grain fine silicon nitride of the present invention uses a micro form of diatomaceous earth particles and a porous structure, increases the contact area with a mixed or absorbed carbon source, and is produced in a nitrogen gas or air atmosphere. It is a thing.
The method for producing metal silicon according to the present invention uses the micromorphology and porous structure of diatomaceous earth particles to increase the contact area with mixed or absorbed carbon sources (including persistent organic chlorine compounds) or organic matter. , Produced under an inert gas, hydrogen gas, air, or a vacuum atmosphere.
In the present invention, the hydrogen gas promotes the decomposition of the hardly decomposable organic chlorine compound, and further prevents the carbon from reacting with oxygen in the air and being consumed for purposes other than the intended purpose.
The method for producing silicon chloride according to the present invention is produced in a water-free atmosphere by utilizing the fine form and porous structure of diatomaceous earth particles, increasing the contact area with the mixed or absorbed chloride or chlorine source. It is.
In the present invention, the steamless atmosphere prevents decomposition of the generated silicon chloride.

The method for producing fine silicon carbide, fine silicon nitride, metal silicon, and silicon chloride of the present invention utilizes the fine form and porous structure of diatomaceous earth particles, and the reaction proceeds efficiently and consumes less power than before. There is an effect that can be produced.
In the case of metallic silicon and silicon chloride, used diatomaceous earth filter aid in the food industry can be used as a raw material, which has the effect of reducing the load on the landfill site.

It is a schematic explanatory drawing of the manufacturing apparatus used for the manufacturing method of the metal silicon of this invention. It is a schematic explanatory drawing of the manufacturing apparatus used for the manufacturing method of the conventional metal silicon.

A description will be given below based on an embodiment of a manufacturing method for producing fine silicon carbide, fine silicon nitride, metal silicon, and silicon chloride of the present invention.
Substances of high-functional materials such as fine silicon carbide, fine silicon nitride, metal silicon, and silicon chloride of the present invention are produced by taking advantage of the fine form and porous structure of diatomaceous earth particles.

The diatomaceous earth in the present invention is a sediment mainly composed of diatom-derived silicon dioxide, and usually crushed and dried diatomaceous earth is removed from sand and fine clay with a water tank. Accordingly, after heat treatment for several hours, washing with water is repeated, followed by dehydration and drying.
Preferably, it is heated at 800 ° C. or higher for several minutes to remove unnecessary organic substances and volatile components, so-called calcination, purified and homogenized can be used.
Diatomaceous earth once used for food filtration, filled with high-quality organic matter to the inside of its pores, has a wide contact area between silicon dioxide of diatomaceous earth and carbon constituting organic matter when producing metallic silicon Therefore, it is more preferable.

As the carbon source in the present invention, for fine silicon carbide and fine silicon nitride, carbon materials such as activated carbon and graphite powder carbon, fullerene and carbon nanotubes can be used, and these should be arranged in equal grains in advance. Accordingly, uniform grain fine silicon carbide and uniform grain fine silicon nitride can also be produced. For the production of metallic silicon and silicon chloride, in addition to the above carbon source, diatomaceous earth is used for filtration of objects mainly composed of food, etc., and then organic substances filled in the pores are also used. be able to.
In particular, when a carbon substance is further used in combination with diatomaceous earth once used for filtering food, the carbon source is uniformly and sufficiently filled inside the pores. In this case, it is only necessary to absorb and infiltrate carbon in colloidal solution from the outside of diatomaceous earth.
In this manner, after the carbon source is sufficiently sufficiently filled in the pores, the excess water is removed by heating at about 105 ° C., so that the sample can be prevented from scattering during the rapid heating.
Furthermore, it is preferable to perform carbonization treatment of the organic substance at about 500 ° C. in an oxygen-free atmosphere because the reaction proceeds smoothly.
As one of the carbon sources used for producing metal silicon, a hardly decomposable organochlorine compound represented by PCB may be used. Diatomaceous earth is also highly oil-absorbing and can easily be filled inside.
In the case of PCB, carbon and hydrogen constituting it act as a reducing agent, and chlorine is consumed during the purification of silicon, so that there is no problem. In addition, since PCB decomposition proceeds rapidly in a hydrogen atmosphere at 850 ° C. or higher, the decomposition treatment including by-products can be completely performed at a silicon dioxide reduction processing temperature of 1,750 ° C. or higher.

The silicon carbide is impregnated with colloidal solution powdered carbon such as activated carbon or graphite, or carbon material such as fullerene or carbon nanotubes in diatomaceous earth or calcined diatomaceous earth, and after drying, 1,400 in an inert gas atmosphere. Obtained by heating to ˜1,600 ° C. The carbon source reacts with silicon in the grain boundaries and pores of diatomaceous earth particles innumerable in diatomaceous earth, and extremely fine and uniform fine silicon carbide is synthesized while maintaining the shape of the carbon source.
Further, by aligning the carbon source with a uniform grain size, it is possible to produce a uniform silicon carbide fine grain.

The silicon nitride is synthesized by changing the atmosphere during the reaction to nitrogen gas or air. That is, impregnated diatomaceous earth or calcined diatomaceous earth is impregnated with powdered carbon such as activated carbon or graphite, carbon materials such as fullerene and carbon nanotubes in colloidal solution, and after drying, in a nitrogen gas or air atmosphere, 1, 400-1 , Heated to 600 ° C.
As in the case of silicon carbide, uniform grain fine silicon nitride can be produced by aligning the grain size of the carbon source to equal grains in advance.

The metal silicon is filled with carbon sources such as activated carbon and graphite, persistent organic chlorine compounds typified by PCB, or organic substances in countless diatomaceous earth grain boundaries and pores. It is produced by increasing the contact area between silicon dioxide and diatomaceous earth and increasing the reaction efficiency.
In addition, diatomaceous earth is composed of amorphous silicon dioxide and metasilicic acid, so it has a lower melting point than silica or silica, which is the usual raw material for metallic silicon, and can be reduced to metallic silicon with less energy consumption. (FIG. 1).
In the case of metal silicon production, by raising the temperature to 1,700 to 1,900 ° C. in a short time, the amount of silicon carbide produced at the same time can be suppressed, and metal silicon can be obtained with high yield.
When the organic substance filled in the diatomaceous earth pores is used as a carbon source, it is preferably carbonized at about 500 ° C. in an oxygen-free atmosphere in order to cause a smooth reaction.
When a hardly decomposable organochlorine compound is used as the reducing agent, it is necessary to prevent evaporation from diatomaceous earth in a vacuum atmosphere or in the heating process for safety. This is solved by utilizing the oil absorption and heat insulation properties of diatomaceous earth.
Diatomaceous earth is molded into a container shape, and paraffin as a reducing agent is impregnated with a heating apparatus using electromagnetic waves (microwaves). Since diatomaceous earth transmits electromagnetic waves, diatomaceous earth with high heat insulation can be heated evenly by adopting heating by this, and paraffin can be absorbed efficiently.
Refractory organochlorine compound is absorbed into diatomaceous earth and placed in a diatomaceous earth container that has been molded and impregnated with paraffin. Finally, the container is closed with a lid made of diatomaceous earth impregnated with paraffin, and melted paraffin is filled in the gap between the lids and sealed. Thereby, even if a vacuum is pulled, evaporation of a hardly decomposable organochlorine compound can be prevented.
Furthermore, by filling another diatomaceous earth around the diatomaceous earth container, the heat insulation property of the diatomaceous earth container does not raise the temperature above the melting point of paraffin even in the heating process up to 850 ° C. . Above 850 ° C., even if the hardly decomposable organochlorine compound evaporates, the decomposition temperature has already been exceeded, so there is no problem.

Silicon chloride liquefies carbon sources such as activated carbon and graphite (reducing agent for silicon dioxide) and chlorides such as sodium chloride and potassium chloride (chlorine source for chlorination of silicon) in the grain boundaries and pores of diatomaceous earth particles. Then, it can be produced more efficiently than the conventional method by adding chlorine gas as necessary at a high temperature of 900 to 1,400 ° C. and reacting it in a non-water vapor atmosphere.
The liquefaction mode at this time is a fine powder colloidal solution such as activated carbon or graphite in the case of a carbon source, and an aqueous solution or colloidal solution in the case of a chloride or chlorine source.
The high-salt-containing waste diatomaceous earth used for soy sauce filtration and the like already contains food-derived organic matter and sodium chloride, and can be used as it is as a raw material for silicon chloride.
The atmosphere may be any of inert gas, hydrogen gas, chlorine gas, or a mixture of these gases as long as it does not contain water vapor in order to prevent decomposition of the generated silicon chloride.

  Furthermore, by using it for the filtration of foods mainly composed of organic matter, a used diatomaceous earth filter aid whose pores are filled with organic matter, and a colloidal solution of carbon sources such as activated carbon and graphite. Mixing, carbonizing at about 500 ° C. in an inert gas or vacuum atmosphere, and then heating at about 1,400 to 1,500 ° C. in an inert gas atmosphere to produce silicon carbide You can also.

Example 1
A used diatomaceous earth filter aid used in the sugar refining process was prepared. The spent diatomaceous earth filter aid is almost completely filled with high-quality organic matter into the pores. The graphite was uniformly mixed at a weight ratio of 1: 1 to 1: 4 and dried at 105 ° C. These mixtures were carbonized by heating at 500 ° C. in an argon gas atmosphere using an infrared gold image furnace (MR-39H / D ULVAC-RIKO, Inc.).

  The carbonized spent diatomaceous earth filter aid was further heated to 1,500 ° C. at 200 ° C. per hour to produce silicon carbide. After removing excess carbon from the product by firing at 960 ° C., as a result of identification with a powder X-ray diffraction apparatus and a scanning electron microscope, dietary fibers and additions filled in diatomaceous earth in all samples We succeeded in synthesizing fine and uniform silicon carbide with the same shape as the graphite particles.

Example 2
The carbonized spent diatomaceous earth filter aid is heated up to 1,750 ° C. as quickly as possible at the maximum output of an infrared gold image furnace (MR-39H / D ULVAC-RIKO) (amount of silicon carbide produced simultaneously) In order to reduce this, metal silicon was produced. The product was identified using a powder X-ray diffraction apparatus. As a result, although it was a mixture of silicon carbide and glass, metal silicon was successfully produced.

Example 3
A sealed container for using a hardly decomposable organochlorine compound as a reducing agent was made. Diatomaceous earth can be freely molded with a simple press, so after making the diatomaceous earth container, it was impregnated with paraffin. Usually, diatomaceous earth has high heat insulation and is not easy to heat, but when it is heated using electromagnetic waves in a commercially available microwave oven in contact with a diatomaceous earth container and paraffin, the inside of the diatomaceous earth pores is uniform. The paraffin was absorbed in Diatomaceous earth can be heated uniformly from the inside through electromagnetic waves (microwaves), so that melted paraffin can be filled to every corner.

Silicon carbide can be used not only as a general abrasive, but also for purification of nucleic acids and proteins, structural materials for fusion reactors, and the like.
On the other hand, metallic silicon is a raw material for alternative silicon-based polymer materials in preparation for the depletion of petroleum resources. Silicon chloride is liquid at room temperature, can be easily purified, and can be used as a raw material for high-purity metallic silicon used for semiconductors and solar cells.

Claims (3)

  Metallic silicon characterized by mixing or absorbing a carbon substance, a hardly decomposable organochlorine compound or an organic substance inside the pores of diatomaceous earth, and heating in an inert gas, hydrogen gas, nitrogen gas, air or vacuum atmosphere Manufacturing method.   The method for producing metal silicon according to claim 1, wherein the organic substance is an organic substance filled in a used diatomaceous earth filter aid.   Form diatomaceous earth into a container, impregnate paraffin while heating with electromagnetic waves to make a diatomaceous earth molded container, and heat the diatomaceous earth mixed or absorbed with refractory organochlorine compounds in this diatomaceous earth molded container A method for producing metal silicon, which is characterized.

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