JP7646589B2 - Method for producing silicon monoxide - Google Patents

Description

The present invention relates to a method for producing silicon monoxide.

Conventionally well-known silicon monoxide (hereinafter, also referred to as "SiO") is produced by contacting metal silicon powder (hereinafter, also referred to as "Si" or "Si powder") with silica powder (hereinafter, also referred to as _SiO2 or _SiO2 powder), maintaining the temperature range of 1200°C or higher and close to 1500°C to react, and sublimating SiO. Such a solid-phase reaction sublimation method has been known for a long time, and many patent applications have been filed (Patent Document 1 to Patent Document 7). Since SiO does not have a liquid phase, it basically does not go through a liquid phase, but is directly sublimated by a contact reaction between powders to become SiO gas. The SiO gas is deposited on a deposition plate or the like, cooled, and solidified to become bulk SiO.

In order to generate SiO gas by this conventional method, it is necessary to increase the number of contact points between Si/ _SiO2 powders, and it is necessary to mix fine powders and granulate or compact them in some way to increase the number of contact points and promote the reaction.

In the conventional method, it is desirable to have a high reaction temperature, but if it is too high, metal silicon (Si) melts and it becomes difficult to retain the liquid. In order to increase the contact points between powders, it is effective to strongly pressurize the powders together, but there is a limit because both Si and _SiO2 are ceramics and do not deform. In order to increase the contact points between powders of Si powder and _SiO2 powder, it is effective to make each powder fine. However, to make fine powder of, for example, μm order, it requires equipment and energy costs, and if it is made too fine, the surface of the Si powder is easily oxidized and the risk of dust explosion increases, so there is a limit to the fineness. In other words, in the conventional solid-phase contact method, there is a limit to increasing the reaction temperature and increasing the powder contact points, so there is a limit to the SiO generation rate.

On the other hand, it is known that the process of obtaining metallic silicon Si by reducing SiO ₂ passes through SiO (Non-Patent Document 1). For example, it is believed that the reaction proceeds in the following order in a SiO ₂ reduction furnace in the order of elementary steps (1) to (3).
(1) SiO ₂ +C → SiO+CO
(2) SiO+C → Si+CO
(3) SiO ₂ +2C → Si+2CO

It would be desirable to stop the above-mentioned C reduction of _SiO2 at step (1) and extract only SiO. However, steps (1) to (3) occur continuously in the reduction furnace, and the generated SiO gas immediately undergoes reaction (2) in the molten metal, producing molten silicon. It is difficult to stop the process at step (1) and extract only SiO. In principle, it is conceivable to insert a high-temperature resistant pipe into the reduction furnace during step (1) to extract SiO gas, but this has not actually been done.

As such, no efficient method for producing SiO was known that surpassed the conventional solid-phase contact method.

On the other hand, methods for producing fine silica or composite oxides of fine SiO ₂ + other oxides by explosive combustion of Si and O ₂ are disclosed in the following prior art documents (Patent Documents 8 and 9).

For example, Patent Document 9 proposes "supplying metal silicon powder into an oxygen-containing air stream and burning it to form silicon dioxide powder having an average particle size of 0.01 to 10 μm," and a method for producing fine SiO ₂ powder is already known.

Furthermore, there are disclosures regarding the generation of SiO by explosive combustion or plasma jet, and the generation of _SiNx via SiO (Patent Documents 10 to 13).

JP 2001-220123 A JP 2001-220122 A JP 2001-220125 A JP 2002-373653 A Japanese Patent Application Publication No. 6-325765 JP 2015-149171 A International Publication No. WO2014/188851 Special Publication No. 7-61855 JP 2003-221218 A Special Publication No. 5-036363 Special Publication No. 4-079975 International Publication No. WO2015/015795 JP 2011-79724 A

Journal of the Japan Institute of Metals, Vol. 52, No. 10, 1988, pp. 945-953

From the above-mentioned prior art documents, it is known that _SiO2 is produced by a controlled explosive oxidation reaction of Si powder and _O2 gas. However, in order to produce silicon monoxide by these manufacturing methods, not only is a high temperature and high energy density environment such as plasma jet and high frequency heating required, but the explosive oxidation reaction occurs instantaneously, making it difficult to stop the reaction with silicon monoxide. Even if silicon monoxide could be produced, mass production would be costly, so this method has not yet been commercialized.

The present invention was made in consideration of the above problems, and aims to provide a highly productive method for producing silicon monoxide.

In order to achieve the above object, the present invention provides a method for producing silicon monoxide, which comprises: an operation A of supplying metallic silicon powder or a mixture of metallic silicon powder and SiOx (x≦2) powder to a combustion device using a first mixed fluid containing oxygen gas and an inert gas as a carrier; an operation B of supplying a flammable silicon compound fluid alone or a second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas to the combustion device; and an operation C of supplying a third mixed fluid containing a flammable gas, oxygen gas, and an inert gas to the combustion device to form a flame, and which is characterized in that the operations A, B, and C are performed simultaneously to produce silicon monoxide product.

In this method for producing silicon monoxide, silicon monoxide powder can be efficiently produced by an oxidation reaction in an air stream of metallic silicon powder or a mixture of metallic silicon powder and SiOx (x≦2) powder, which is much more productive than conventional solid-phase contact reaction methods. In addition, by adding a combustible silicon compound as a Si source (silicon atom source) in addition to metallic silicon powder or a mixture of metallic silicon powder and SiOx (x≦2) powder, a flame with high energy density can be formed, allowing uniform silicon monoxide to be produced.

At this time, it is preferable to further include an operation D of supplying a fourth mixed fluid containing oxygen gas and an inert gas to control oxygen diffusion into the metal silicon powder or the mixture of the metal silicon powder and SiOx (x≦2) powder, or an inert gas alone, and to simultaneously perform the operations A to C.

In this way, the generation of silicon monoxide powder can be controlled with even greater precision by using a gas to control oxygen diffusion into the silicon metal powder or into a mixture of silicon metal powder and SiOx (x≦2) powder.

In addition, in the silicon monoxide manufacturing method of the present invention, the first mixed fluid can be air.

In this way, by using air as a mixed gas, silicon monoxide can be produced at a lower cost.

In addition, in the method for producing silicon monoxide of the present invention, the flammable gas may be a flammable gas containing a hydrocarbon.

The flammable gas may also be a flammable gas containing hydrogen.

These gases can be used as the combustible gas in the silicon monoxide manufacturing method of the present invention.

The flammable silicon compound fluid is preferably a low molecular weight organic silicon compound selected from alkoxysilane, silane, alkylsilane, alkylsilanol, alkylcyclosilane, alkylsiloxane, alkylcyclosiloxane, silazane, and cyclosilazane, or a mixture thereof.

The silicon monoxide manufacturing method of the present invention can use fluids of these flammable silicon compounds.

In addition, in the present invention, it is preferable that the supply of metallic silicon powder or a mixture of metallic silicon powder and SiOx (x≦2) powder in the operation A and the supply of the flammable silicon compound fluid alone or a second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas in the operation B are mixed at the same location in the combustion device.

In this way, in the present invention, operation A and operation B can be performed in an integrated manner.

The method for producing silicon monoxide of the present invention can further include an operation E in which the silicon monoxide product produced by carrying out the operations A to C is heated at a temperature of 1100°C or higher and 1500°C or lower to extract the silicon monoxide contained in the product by sublimation.

When the silicon monoxide production method of the present invention produces a product in the form of a mixture with unreacted silicon and silicon dioxide (SiO ₂ ), which are components other than silicon monoxide, it is possible to extract only the silicon monoxide component by sublimation using this method, because the temperatures at which Si and SiO ₂ vaporize are much higher than that of silicon monoxide.

In the method for producing silicon monoxide of the present invention, silicon monoxide powder can be efficiently produced by oxidation reaction in an airflow fluid using metal silicon powder or a mixture of metal silicon powder and SiOx (x≦2) powder, which is highly productive compared to conventional solid-phase contact and liquid-solid-phase reaction methods, and a combustible silicon compound. In addition, a flame with high energy density can be formed by adding a combustible silicon compound as a Si source (silicon atom source) to metal silicon powder or a mixture of metal silicon powder and SiOx (x≦2) powder, and uniform silicon monoxide can be produced. The silicon monoxide produced by the method for producing silicon monoxide of the present invention can be used as an anode material for lithium-ion secondary batteries, in addition to glass and plastic coating applications and others. Such anode materials can also be widely used as high-capacity anode materials for mobile devices such as smartphones and smart watches, and batteries for electric vehicles. They are also suitable for applications such as deposition film agents with high gas barrier properties, and provide material properties with excellent cost performance.

FIG. 1 is a schematic cross-sectional view showing an example of a combustion apparatus that can be used in the method for producing silicon monoxide of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of a combustion apparatus that can be used in the method for producing silicon monoxide of the present invention. FIG. 2 is a schematic cross-sectional view showing yet another example of a combustion apparatus that can be used in the method for producing silicon monoxide of the present invention. FIG. 1 is a binary phase diagram of Si—O.

The following describes an embodiment of the present invention, but the present invention is not limited to this.

As mentioned above, there are limitations to the efficient production of silicon monoxide using the conventional solid-phase contact method and plasma jet method. Silicon monoxide is a very important material that is indispensable as a negative electrode material for future high performance lithium-ion secondary batteries, and its application fields are expected to expand. Therefore, there is a demand for an efficient (highly productive, low-cost) manufacturing method and a method for producing silicon monoxide that maintains a low disproportionation state.

The inventors have conducted extensive research in an attempt to provide a production method that is more productive and economical than the conventional solid-phase contact method, liquid-solid-phase contact method, and plasma jet method, and to provide silicon monoxide produced by this method with a low degree of disproportionation.

As a result, it was found that a highly productive method for producing silicon monoxide can be provided by simultaneously carrying out a combustible silicon compound having both a Si source and a high energy source, in addition to a mixture of metallic silicon powder or metallic silicon powder and SiOx (x _≦2) powder, and a combustible gas combustion reaction that further assists the energy source and ensures a high-temperature flame region, and controlling the O2 concentration in the flame. Furthermore, it was revealed that the addition of a combustible silicon compound to the Si source makes it less likely to be disproportionated than silicon monoxide synthesized by conventional solid-solid and solid-liquid reactions. Although the reason is not clear, it is believed that the method of the present invention is a method in which a part of the Si source exists in a liquid phase to a gas phase at room temperature, and therefore silicon monoxide that is more uniform than the conventional method can be produced.

The present invention is a method for producing silicon monoxide, which comprises an operation A of supplying metallic silicon powder or a mixture of metallic silicon powder and SiOx (x≦2) powder to a combustion device using a first mixed fluid containing oxygen gas and an inert gas as a carrier, an operation B of supplying a flammable silicon compound fluid alone or a second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas to the combustion device, and an operation C of supplying a third mixed fluid containing a flammable gas, oxygen gas, and an inert gas to the combustion device to form a flame, and is characterized in that the operations A, B, and C are carried out simultaneously to produce silicon monoxide product.

The method may further include an operation D of supplying a fourth mixed fluid containing oxygen gas and an inert gas to control oxygen diffusion into the metal silicon powder or into the mixture of metal silicon powder and SiOx (x≦2) powder, or supplying the inert gas alone, and may be performed simultaneously when performing operations A to C.

Figure 4 shows the binary phase diagram of Si-O. At Si:O = 1:1, the silicon monoxide (SiO) gas phase penetrates up to 1,860°C. In order to turn _SiO2 into a gas phase, it is necessary to raise the temperature to a temperature exceeding 2,860°C. In comparison, turning SiO into a gas phase can be achieved at a temperature 1,000°C lower, which is the lower limit temperature for generating the SiO gas phase. Therefore, it is sufficient to be able to raise the temperature above that temperature in an oxidizing atmosphere.

Figure 1 shows an example of a combustion device (combustion reaction device) that is important for realizing the silicon monoxide production method of the present invention. Of course, the combustion reaction device is not limited to the device shown in Figure 1, and any device that can control flame and combustion oxidation can be used to produce the silicon monoxide production method of the present invention.

The silicon monoxide manufacturing apparatus (combustion apparatus) 100 has a combustion vessel 10. A supply means 11 (illustrated as a supply means for metal silicon powder) for metal silicon powder or a mixture of metal silicon powder and SiOx (x≦2) powder and a first gas supply means 12 for supplying a first mixed fluid containing oxygen gas and an inert gas are connected to this combustion vessel 10 through a burner 13. In FIG. 1, the first gas supply means 12 shows a case where nitrogen gas ( _N2 gas) is added to air to make the first mixed fluid. In this case, the flow rate of the inert gas is adjusted by the added nitrogen gas together with the nitrogen and argon contained in the air. By these components, the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder as the raw material is supplied to the combustion apparatus 100 (inside the combustion vessel 10 of the combustion apparatus 100) with the first mixed fluid containing oxygen gas and an inert gas as a carrier.

The combustion device 100 further includes second gas supply means 15a, 15b for supplying the flammable silicon compound fluid alone or a second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas to the combustion device 100 (inside the combustion vessel 10 of the combustion device 100). Figure 1 shows a case where TMOS (tetramethoxysilane) is supplied from the second gas supply means 15b, and _O2 and _N2 are supplied from the second gas supply means 15a. The case where the flammable silicon compound is supplied as a liquid will be described later.

The combustion device 100 further includes a third gas supply means 14 that supplies a third mixed fluid containing a combustible gas, oxygen gas, and an inert gas to the combustion device 100 (inside the combustion vessel 10 of the combustion device 100). Figure 1 shows a case where LPG and air are supplied as the third gas supply means 14.

The combustion device 100 may further include a fourth gas supply means for supplying the combustion device 100 (inside the combustion vessel 10 of the combustion device 100) with a fourth mixed fluid containing oxygen gas and an inert gas that controls oxygen diffusion into the metal silicon powder or the mixture of the metal silicon powder and SiOx (x≦2) powder, or with inert gas alone. The fourth gas supply means may also serve as a protective gas supply means for supplying a protective gas for the purpose of reducing radiant heat to the furnace wall, reducing the oxygen gas concentration in the furnace, cooling the product, etc. FIG. 1 shows a case in which a mixture of air and additional nitrogen gas is supplied as the fourth gas supply means 16, 17.

The combustion device 100 further includes a collection chamber 23 at the bottom for collecting the silicon monoxide powder 24 produced.

In the present invention, silicon monoxide can be produced using such a combustion device 100. That is, from the upper center of the combustion device 100, the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder is supplied from the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder by the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder supply means 11 and the first gas supply means 12 on the carrier gas flow consisting of the first mixed fluid (air and additional nitrogen gas in the example of FIG. 1) supplied from the first fluid supply means 12 (operation A). At this time, the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder can be, for example, about #200 mesh. Also, from the concentric outer or inner circumference, a flammable silicon compound fluid alone or a second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas is supplied from second fluid supply means 15a, 15b, and further from the concentric outer circumference, a third mixed fluid containing a flammable gas, oxygen gas, and an inert gas (in the example of FIG. 1, a flammable gas consisting of LPG, air, and additional nitrogen gas) is supplied from third fluid supply means 14.

As these are fed, they are ignited at the tip of the burner 13, forming a flame 21. In the flame 21, the metallic silicon powder or the mixture of metallic silicon powder and SiOx (x≦2) powder and flammable silicon compounds are oxidized, and the SiO gas is rapidly cooled and solidified at the bottom of the device to produce silicon monoxide powder (operation C).

Depending on the amount of metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder supplied, a fourth mixed gas containing oxygen gas and an inert gas (air and additional nitrogen gas in the case of Figure 1) is supplied as necessary (operation D). By simultaneously performing these operations A, B and C, or simultaneously performing operations A to D, the rate of silicon monoxide powder production by optimizing the oxygen atmosphere in the tank and in the flame and flame flow control are both achieved, resulting in stable production of silicon monoxide powder.

In the method for producing silicon monoxide of the present invention, operation C, in which a third mixed gas containing a combustible gas, oxygen gas, and an inert gas is supplied to a combustion device to form a flame, serves as a parallel heat source for oxidizing the metallic silicon powder or the mixture of metallic silicon powder and SiOx (x≦2) powder, and the combustible silicon compound.

In addition, operations A and B are performed in the same combustion device, in which the raw material metal silicon powder or a mixture of metal silicon powder and SiOx (x≦2) powder is supplied to the combustion device using a first mixed gas containing oxygen gas and an inert gas as a carrier, and a second mixed fluid containing a flammable silane compound alone or its oxygen gas and an inert gas. The temperature is raised to the SiO gas temperature range described above while adding the heat generated by oxidation of the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder and oxygen gas, and the heat generated by combustion of the flammable silicon compound, to generate silicon monoxide (SiO).

Each operation is explained in more detail below.

[Operation A]
Operation A is an operation of supplying metallic silicon powder or a mixture of metallic silicon powder and SiOx (x≦2) powder to a combustion device using a first mixed fluid containing oxygen gas and an inert gas as a carrier. The particles supplied in operation A may be metallic silicon powder alone or a mixture of metallic silicon powder and SiOx (x≦2) powder. In particular, when SiOx (x≦2) powder is added, the flow rate of the combustible gas or combustible silicon compound may be increased by an amount corresponding to the heating heat of the added SiOx (x≦2) powder.

As described above, in operation A, a mixture of metal silicon powder or metal silicon powder and SiOx (x≦2) powder is supplied to a combustion device using a first mixed fluid containing oxygen gas and an inert gas as a carrier. In operation A, a mixed fluid (first mixed fluid) of an inert gas other than the combustion-supporting _O2 gas is used as a carrier in order to control the oxidation reaction of the metal silicon powder or the powder mixture of metal silicon powder and SiOx (x≦2) powder. If the carrier gas is only the combustion-supporting _O2 gas, an explosive oxidation reaction may occur instantly, resulting in the production of _SiO2 . Therefore, the mixture fluid of the combustion-supporting _O2 gas and the inert gas is used to dilute the _O2 concentration and control the oxidation exothermic reaction rate, making it easier to produce SiO. In order to stop the reaction with SiO before it reaches _SiO2 production, it is necessary to prevent the oxygen concentration from exceeding the explosive limit of 10%. The first mixed fluid is preferably a mixed fluid of _O2 and _N2 , or a mixed fluid of _O2 and Ar, in which the ratio of the amounts of the components is controlled.

Also, an organic solvent may be used as part of the carrier for operation A. Furthermore, a flammable silicon compound or organic solvent such as alkoxysilane, silane, alkylsilane, alkylsilanol, alkylcyclosilane, alkylsiloxane, alkylcyclosiloxane, silazane, or cyclosilazane listed in operation B may be used as part of the carrier for operation A. In this case, operation A and operation B can be integrated as described below. This case is also included in the present invention. When using a flammable silicon compound, it is desirable to use a flammable silicon compound or organic solvent that is as volatile as possible in order to increase the combustion rate. In this way, a larger amount of heat can be secured compared to the case of a mixed gas carrier, and the flame can be made longer, so that the effect of increasing the generated SiO particles can be expected.

[Operation B]
As described above, in operation B, a flammable silicon compound fluid alone or a second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas is supplied to the combustion device. This operation is an operation of supplying a flammable silicon compound or a mixed fluid (second mixed fluid) of oxygen gas and an inert gas together with the flammable silicon compound, and supplying a supplementary raw material (sub raw material). This operation, combined with operation A, is a step of supplying raw material Si (silicon atom). In operation B, as in operation A, if only a flammable silicon compound and oxygen are supplied, the reaction may proceed violently and _SiO2 may be generated, so an inert gas is also mixed to control the exothermic oxidation reaction.

As the combustible silicon compound, one that is easily combustible is preferably selected, and low molecular weight organic silicon compounds selected from volatile, low boiling point alkoxysilanes, silanes, alkylsilanes, alkylsilanols, alkylcyclosilanes, alkylsiloxanes, alkylcyclosiloxanes, silazanes, cyclosilazanes, etc., or mixtures thereof, are preferable. In consideration of the combustion heat ratio, the appropriate selection can be made with consideration given to the operability and safety of the process.

[Integration of Operation A and Operation B]
The supply of metallic silicon powder or a mixture of metallic silicon powder and SiOx (x≦2) powder in operation A, and the supply of a combustible silicon compound fluid alone or a second mixed fluid containing the combustible silicon compound fluid, oxygen gas, and an inert gas in operation B can be carried out by mixing them at the same location in the combustion device.

For example, in addition to oxygen gas and inert gas, flammable silicon compounds such as alkoxysilane, silane, alkylsilane, alkylsilanol, alkylcyclosilane, alkylsiloxane, alkylcyclosiloxane, silazane, and cyclosilazane, or organic solvents may be used as carriers for operation A. In this case, it is desirable to use flammable silicon compounds that are as volatile as possible in order to increase the combustion rate. In this case, a larger amount of heat can be secured compared to the case of a mixed gas carrier, and the flame can be made longer, which is expected to have the effect of increasing the amount of SiO particles generated.

However, when a liquid flammable silicon compound is used, it becomes a slurry liquid when mixed with metallic silicon powder or a powder mixture of metallic silicon powder and SiOx (x≦2) powder, which tends to reduce operability and stability and increase equipment costs compared to supplying powder with a gas carrier, but can be selected depending on the required SiO properties.

It is also possible to form a supply device integrated with the metallic silicon powder described in operation A, or a powder mixture of metallic silicon powder and SiOx (x≦2) powder, a mixed slurry of combustible silicon compounds and organic solvents, or the ejector burner provided to the combustion device in operation A. In this case, too, it is preferable to select it because it is expected to increase the amount of heat and expand the flame vertically due to droplet combustion, which can contribute to increasing the particle size of the generated SiO particles. The advantage of seemingly integrating operations A and B is that it is possible to pursue completeness of combustion, and it is preferably used, but it goes without saying that in this case the stoichiometric ratio of Si/O must be controlled.

[Supplementary explanation for operation B]
In operation B, as described above, a single fluid of a combustible silicon compound (may be one or more types) or a second mixed fluid containing a fluid of the combustible silicon compound, oxygen gas, and an inert gas is supplied to the combustion device. This combustible silicon compound passes through while contacting and colliding with the metal silicon powder in the process of being oxidized in the combustion flame. The combustible silicon compound can be either a gas or a liquid at room temperature. The combustible silicon compound can be supplied in the form of a gas or fine droplets (atomized particles). The combustible silicon compound in operation B can be a mixture with the metal silicon powder of operation A, as described above. When the combustible silicon compound is supplied as a liquid, it is a mixture with metal silicon powder or SiOx (x≦2), so it may be supplied with a high-speed atomizer in order to reduce energy consumption until combustion. In this case, a mixing step can be selected in advance so that the metal silicon particles/SiOx (x≦2) particles are uniformly dispersed.

Various monomers and low molecular weight oligomers are preferably used for this flammable silicon compound. Silicone-based liquid polymers can also be used, but these polymer compounds are highly viscous and require a large amount of energy to be applied to disperse, vaporize, and ignite before they can burn, so it is preferable to use low molecular weight organic silicon compounds. In addition, it is also preferable that the flammable silicon compound used here is a flammable silicon compound that does not produce halides that may adversely affect the performance of the silicon monoxide produced, or solid or liquid oxides other than silicon monoxide after combustion.

Furthermore, it is preferable to use a compound that can secure combustion heat that can stabilize the combustion temperature of silicon monoxide in a flame.

The "combustion heat ratio" is an effective indicator for this. It represents the ratio of the heat of combustion reaction to SiO(g) when the heat of combustion in the complete combustion of the commonly known low molecular weight organic silicon compounds listed in Table 1 is taken as 1.0. This combustion heat ratio can be positioned as an indicator that can prevent a drastic drop in flame temperature when the oxygen concentration in the flame decreases. The larger this value is, the more resistant the flame that can be formed is to changes in oxygen concentration.

Below are examples of the heat of combustion when _SiO2 and SiO are the products after the silicon compounds in Table 1. Its usefulness can be understood by comparing it with the heat of combustion of combustible gases such as _CH4 and _H2 (see also Table 2).

The following chemical combustion reaction species are based on the gas state unless otherwise specified. Since SiO(g) is used as the standard, _SiO2 is usually treated as a solid, but here it is treated as a liquid that is thought to be in a state near 1860°C (2133K) where SiO(g) can exist. However, the standard enthalpy of formation ΔHf of _SiO2 (l) and _SiO2 (s) is such that in the state change from _SiO2 (s) to _SiO2 (l), whether _SiO2 (s) is crystal or glass, the heat of state change (heat of liquefaction) is extremely small, so there is no significant difference in the results even if _SiO2 (l) is considered to be SiO(s), and it can be considered as the combustion heat ratio with _SiO2 (s).

From this table, the ΔHr (298) of the substances exemplified below is as follows:
Si(OCH ₃ ) ₄ +5.5O ₂ → SiO+4CO ₂ +6H ₂ O
ΔHr(298)=-1946kJ/mol
( _CH3 ) _3SiOSi ( _CH3 ) ₃ [HMDS]+ _11O2
→ 2SiO+ _6CO2 + _9H2O
ΔHr(298)=-3923kJ/mol
{(CH ₃ ) ₂ SiO} ₄ [OMCTS:D4]+16O ₂
→ 4SiO+ _8CO2 + _12H2O
ΔHr (298) = -5172kJ/mol

In contrast, in the case of combustible gases such as methane and propane, and Si(l),
CH ₄ +2O ₂ → CO ₂ +2H ₂ O
ΔHr(298)=-802kJ/mol
C ₃ H ₈ +5O ₂ → 3CO ₂ +4H ₂ O
ΔHr (298) = -2044kJ/mol
Si(l)+0.5O ₂ → SiO
ΔHr(298)=-149kJ/mol
(See Table 2), and combustible silicon compounds not only have a great advantage in terms of the combustion heat of combustible gas, but can also be used as a silicon source. Therefore, as the silicon source, metal silicon powder, a mixture of metal silicon powder and SiOx (x≦2), or a combustible silicon compound can be selected, and the selection can be made taking into consideration the economical efficiency and the performance required for the silicon monoxide to be produced.

However, in the present invention, by selecting both metallic silicon/SiOx (x≦2) and a "combustible silicon compound" as the Si source, it has surprisingly become clear that the silicon monoxide produced is less prone to disproportionation than silicon monoxide obtained by solid-phase or liquid-solid-phase reactions.

The conditions for synthesizing silicon monoxide from combustible silicon compounds can be found by adjusting the relationship between the amount of heat generated and the partial pressure of oxygen in the flame.

The combustible silicon compound used in operation B is mainly used to maintain the flame temperature, and since it is a heat source having a Si source, it is necessary to constantly adjust the blending with other Si sources (metallic silicon powder, etc.). Therefore, the amount of the combustible silicon compound can be set subordinately. Operation B is an important operation for reacting the Si source with _O2 gas in the flame to produce more uniform silicon monoxide. In operation B, it is desirable to adjust the balance between the Si source, the supporting gas, and the inert gas to make the flame as long and large as possible, and to produce silicon monoxide while controlling the oxidation reaction of Si in the flame as slowly as possible.

When using a flammable silicon compound that is liquid at room temperature, the burning speed can be slower than with a gas, so even if it is a mixture with metallic silicon powder or SiOx (x≦2) as in operation (A), the effect of lengthening the flame can be expected. In that case, the amount of oxyhydrogen flame or flammable gas can be adjusted to optimize it.

The combustible silicon compound used in the present invention can be appropriately selected taking this explanation into consideration, and is not particularly limited. For example, low molecular weight organic silicon compounds such as the alkoxysilanes listed above can be used alone or in mixtures thereof.

[Operation C]
As described above, the operation C is an operation of supplying a third mixed fluid containing a combustible gas, oxygen gas (combustion-supporting _O2 gas), and an inert gas to a combustion device to form a flame. This operation is the third heat supply step for converting a mixture of metal silicon powder or metal silicon powder and SiOx (x≦2) powder into silicon monoxide. At this time, it is preferable to adjust the amount of heat in the operation C. For example, when the mixed fluid (first mixed fluid and second mixed fluid) in the operation A or B is air or a nitrogen-rich gas, there is often a shortage of _O2 for SiO generation, so it is preferable to adjust the amount of heat with a mixed fluid (third mixed fluid) of a combustible gas and oxygen gas (combustion-supporting _O2 gas) in the operation C. Furthermore, in the same way as in the operations A and B, an inert gas is also added in the operation C to adjust and control the SiO generation rate. The inert gas here may be nitrogen, argon, or the like contained in air.

The combustible gas may be a hydrocarbon gas such as _CH4 or LPG (liquefied natural gas). Of course, the usable hydrocarbon gas is not limited to these. As the combustible gas here, hydrocarbons such as methane, ethane, propane, acetylene, and propylene are preferable because they can provide sufficient combustion heat, but are not limited to these. The combustible gas may be hydrogen (hereinafter sometimes written as _H2 ) or a mixed fluid of _H2 and a hydrocarbon. The shape of the flame, such as the amount of heat generated and the flame length, may be determined by determining the ratio so as to be suitable for silicon monoxide generation.

Operation C is an essential step for forming a flame and reacting, in the flame, the metallic silicon powder or the mixture of the metallic silicon powder and the SiOx (x≦2) powder, the first mixed fluid (supplied in operation A), and the combustible silicon compound (supplied in operation B) with _O2 gas to stably produce silicon monoxide.

In operation C, as in operation B, the flame is made as large and long as possible, and silicon is oxidized in the flame as slowly and controlled as possible to produce silicon monoxide. It is preferable to carry out the reaction between the silicon component and oxygen gas under conditions that produce silicon monoxide powder.

That is, it is necessary to control the _O2 concentration in the flame to within the silicon monoxide generation range to carry out the oxidation reaction. As described above, the oxidation reaction is controlled by adjusting the ratio between the amount of Si raw material supplied to the combustion device and the amount of oxygen gas (the total amount of oxygen gas contained in the first mixed fluid, the second mixed fluid, and the third mixed fluid). Furthermore, it is preferable to control the oxidation reaction by optimizing the mixture ratio and type of combustible gas (hydrocarbon gas, _H2 , etc.), and the mixture ratio of combustible gas, oxygen gas (combustion supporting gas), and inert gas. That is, the appropriate _O2 amount in the flame changes depending on the Si source supply amount, the type of combustible gas, the flow rate, etc., so these generation conditions can be adjusted experimentally.

[Supplementary explanation for operation C]
Such operation C is an operation for supplying a mixed gas of a combustible gas, a combustion-supporting oxygen gas, and an inert gas to a combustion device to auxiliary form a flame, and serves as a heat source for complementing the Si source oxidation region.

To this, operation A is performed on the same combustion device, in which metal silicon powder or a mixture of metal silicon powder and SiOx (x≦2) powder is supplied to the combustion device using a first mixed fluid containing oxygen gas and an inert gas as a carrier, and silicon monoxide is generated by raising the temperature to the above-mentioned SiO gas temperature range while also adding the oxidation heat of the Si source containing a combustible silicon compound and oxygen gas in operation B. The reason why a mixed gas containing an inert gas other than oxygen gas is used as a carrier in operation A is to control the oxidation reaction of Si. If the carrier gas is only oxygen gas, an explosive oxidation reaction may occur instantly, resulting in the generation of _SiO2 .

Therefore, the mixed gas containing oxygen gas and inert gas is used to dilute the oxygen concentration and control the rate of the exothermic oxidation reaction, making it easier to generate SiO. In order to stop the reaction at SiO before it reaches _SiO2 generation, it is necessary to ensure that the oxygen concentration does not exceed the explosion limit of 10% in the flame. As the mixed gas, it is preferable to use air, a mixed gas of oxygen and nitrogen, a mixed gas of oxygen and Ar, or the like, with the amount ratio controlled.

Operation C is a process in which a mixed gas containing a combustible gas, oxygen gas, and an inert gas is supplied to maintain and assist in the formation of a flame and high temperatures. This process serves as an auxiliary heat supply process to convert silicon into silicon monoxide.

When the mixed gas in operation A is air, there is a shortage of oxygen for silicon monoxide production, so the main heat supply is carried out in operation B, in which one or more combustible silicon compounds are selected from a group and a mixed gas of at least this compound with oxygen gas is supplied to the combustion device, and furthermore, in this operation C, the heat supply is supplementally adjusted with a mixed gas of combustible gas and oxygen gas. Furthermore, in order to adjust and control the SiO production rate in the same way as in operation A, an inert gas is added. The inert gas may be the nitrogen contained in air, or it may be nitrogen with a concentration of about 90 to 95% generated by a nitrogen PSA (pressure swing adsorption type nitrogen gas generator) or the like.

The combustible gas in operation C may be a hydrocarbon gas such as _CH4 or LPG, and of course the hydrocarbon gas is not limited to these. The combustible gas may also be hydrogen or a mixed gas of hydrogen and a hydrocarbon. Operation C is a step that auxiliary forms a flame, and since it is a heat source without a Si source, its amount can be set independently, and is necessary for reacting the Si source and oxygen gas in the flame to produce more uniform silicon monoxide. In this step, as in operation B, it is desirable to make the size of the flame as long and large as possible, and to controllably oxidize the metallic silicon powder in the flame as slowly as possible to produce silicon monoxide.

Therefore, controlling the oxidation reaction by optimizing the ratio and type of combustible gas and hydrogen, and the mixture ratio of combustible gas, combustion supporting gas, and inert gas, is an important control, just like the adjustments in operation B.

Naturally, the mixed gas ratio of combustible silicon compounds and combustible gases in operations B and C must be optimized according to the amount of metal silicon powder supplied, but this may not be compatible with the optimization of the flame. In the case of flame optimization, the flame is made as long as possible, and the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder is dropped into the flame while controlled oxidation is performed to generate SiO, but there are cases where the flame length, temperature distribution, and oxygen amount control are not compatible. In such a case, as described later, the oxidation rate in operations B and C can be controlled by operation D, which supplies a mixed gas containing oxygen and an inert gas or an inert gas alone to control the oxygen diffusion into the metal silicon powder or the mixture of metal silicon powder and SiOx (x≦2) powder. When the amount of metal silicon powder supplied is small, the amount of oxygen required is naturally small. In that case, if the amount of oxygen gas in operation C is reduced, the flame cannot be optimized. Therefore, in operation B, 100% flammable silicon compounds or oxygen-nitrogen mixed fluid containing them are used to maintain the flame within an adjustable range, and in operation D, a mixed gas containing oxygen and an inert gas is supplied with the ratio adjusted to the oxygen-reducing side.

Conversely, when the supply of metallic silicon powder is large, it is possible to choose whether to increase operation B or operation C. In that case, the ratio of the mixed gas containing oxygen and an inert gas in operation D described below can be adjusted to increase oxygen.

[Operation D]
As described above, it is preferable to optimize the supply ratio of the fourth mixed fluid in operation D according to the amount of the metallic silicon powder or the mixture of metallic silicon powder and SiOx (x≦2) powder and the combustible silicon compound to be supplied. However, there are cases where such optimization of the supply ratio and optimization of the flame are not compatible. In other words, flame optimization is to make the flame as long as possible. In the present invention, the metallic silicon powder or the mixture of metallic silicon powder and SiOx (x≦2) powder is dropped into the flame together with the combustible silicon compound, etc., and oxidation is controlled to generate SiO, but there are cases where the flame length, temperature distribution, and oxygen amount control are not compatible.

In this case, the oxidation rate in the operations A, B, and C can be finally finely adjusted and controlled by the operation D of supplying a fourth mixed fluid containing oxygen gas and an inert gas, or an inert gas, which controls the oxygen diffusion into the metal silicon powder or the mixture of the metal silicon powder and the SiOx (x≦2) powder. Specifically, the method for producing silicon monoxide of the present invention can further include an operation D of supplying a fourth mixed fluid containing oxygen gas and an inert gas, or an inert gas alone, to the combustion device in order to control the oxygen diffusion into the metal silicon powder or the mixture of the metal silicon powder and the SiOx (x≦2) powder. When the supply amount of the metal silicon powder or the mixture of the metal silicon powder and the SiOx (x≦2) powder and the combustible silicon compound is small, the amount of _O2 required for oxidation (combustion) can be naturally small. In this case, if the amount of the combustion-supporting _O2 gas in the operation D is reduced, the flame cannot be optimized. Therefore, the mixed gas in operation C is adjusted to maintain the flame within the adjustment range, and the _O2 /inert gas ratio is adjusted to the _O2 -less side (low _O2 content) in operation D. When the supply of metallic silicon powder and combustible silicon compounds is large, the opposite is true, and the _O2 /inert gas ratio in operation D is adjusted to the _O2 -rich side (high _O2 content).

The supply of protective gas from the fourth gas supply means 16, 17, etc. shown in FIG. 1 is also part of operation D, which supplies a fourth mixed fluid containing oxygen gas and an inert gas, or an inert gas alone, to control oxygen diffusion into the metal silicon powder, or into the metal silicon powder and the SiOx (x≦2) powder.

The present invention makes it possible to efficiently produce silicon monoxide by an oxidation reaction in an air stream between silicon powder and a combustible silicon compound, which is highly productive compared to conventional solid-phase contact reaction methods. In particular, it makes it possible to efficiently produce low-disproportionation silicon monoxide anode material, making it possible to obtain a silicon monoxide material suitable as an anode material for LIBs (lithium ion batteries). The silicon monoxide produced by the production method of the present invention can be used as an anode material for lithium ion secondary batteries, in addition to being used for glass and plastic coatings and other purposes. Furthermore, it can be widely used as a high-capacity anode material for mobile devices such as smartphones and smart watches, and batteries for electric vehicles.

[Operation E]
According to the method for producing silicon monoxide of the present invention, silicon monoxide can be produced with good productivity by the above-mentioned method, but depending on the conditions, the product may be obtained as a mixture with unreacted Si and SiO ₂ , which are components other than silicon monoxide. In that case, the method may further include an operation E in which the silicon monoxide product produced by carrying out operations A to C (of course, operation D may also be carried out) is heated at a temperature of 1100°C or higher and 1500°C or lower to sublimate and extract the silicon monoxide contained in the product. By heating the product at a temperature of 1100°C or higher and 1500°C or lower, the SiO contained in the product can be sublimated and extracted. Since the temperature at which Si and SiO ₂ vaporize is much higher than that of SiO, only the SiO component can be sublimated and extracted by such a method.

The present invention will be described in more detail below with examples and comparative examples, but the present invention is not limited to these examples.

[Example 1]
Silicon monoxide was produced according to the production method of the present invention using a combustion apparatus (combustion reaction apparatus) 100 shown in Figure 1. The combustible silicon compound used in operation B was tetramethoxysilane Si( _OCH3 ) ₄ (hereinafter referred to as TMOS), and the combustible gas used in operation C was LPG. _{The O2} gas and the inert gas were air, and the third mixed gas used in operation C was air (i.e., a mixed gas containing oxygen gas and containing nitrogen and argon as inert gases).

First, as the second mixed fluid in the step B, TMOS was vaporized by an evaporator and supplied at 5.69 kg/hr and air for TMOS combustion was supplied at 24.13 Nm ³ /hr, and ignited by the burner 13 (operation B).

Next, as the first mixed fluid, 2.50 kg/hr of metallic silicon powder was supplied from metallic silicon powder supply means 11, and this metallic silicon powder was supplied on a carrier gas ( _O2 concentration 8 vol% standard) mixed with air and additional _N2 gas at 1.01 ^Nm3 /hr and Ar at 0.86 ^Nm3 /hr supplied from first gas supply means 12 (operation A).

On the outer periphery of the second mixed fluid, 1.00 Nm ³ /hr of LPG gas and 26.67 Nm ³ /hr of air were mixed from the third gas supply means (burner) 14 and combusted (operation C).

An air + _N2 air flow curtain was supplied to the combustion vessel 10 from fourth gas supply means 16, 17 in two stages at a rate of 2.5 ^Nm3 /hr in order to control the air flow and flame inside the furnace, to reduce radiant heat to the furnace wall, to maintain a low oxygen concentration inside the furnace, and for cooling purposes.

This was also part of run C (third mixed fluid) in which the air: _N2 ratio was varied and controlled for flame control, thereby controlling the oxygen concentration in the furnace (also run D).

By carrying out the above operations A, B, C and D, silicon monoxide powder was produced at about 5.55 kg/hr while controlling the amount of _O2 in the combustion flame 21.

In this example, about 97.0% of the silicon monoxide powder 24 produced in the collection chamber 23 was recovered. The pressure inside the furnace was kept reduced in the range of 0 to 2000 Pa. Powder XRD and XPS analysis of the produced silicon monoxide powder 24 confirmed that it was amorphous SiO.

[Example 2]
Silicon monoxide was produced using the silicon monoxide production apparatus 200 shown in FIG. 2. The configuration of the silicon monoxide production apparatus 200 in FIG. 2 is basically the same as that in FIG. 1, except that _H2 gas (third mixed gas) is supplied from the third gas supply means 14. Other configurations with the same reference numerals are the same as those in FIG. 1. In operation C, instead of the flammable hydrocarbon gas (LPG) in Example 1, _H2 gas and a stoichiometric amount of _O2 gas were supplied from the third gas supply means 14 to serve as the main heat source. In addition, the flame was mainly controlled in operation C, but air was made to be able to be introduced while being mixed with the above _H2 (however, in this example, the amount of air introduced was adjusted to zero as described later), and the amount of oxygen in the flame was adjusted.

In this embodiment, the protective gas is air + _N2 (however, the amount of nitrogen is adjusted depending on the adhesion state to the furnace wall and the cooling state), and the amount of oxygen in the tank (inside the combustion vessel 10) is further adjusted and controlled.

The supply rate of metal silicon powder from the metal silicon powder supply means 11 was 2.50 kg/hr, the same as in Example 1, and the amount of the accompanying carrier gas was the same as in Example 1 (operation A). Tetramethoxysilane Si( _OCH3 ) ₄ (hereinafter referred to as TMOS) was vaporized by an evaporator and supplied at a rate of 5.69 kg/hr (operation B). In addition, _H2 gas was introduced from the third gas supply means 14 at 8.45 ^Nm3 /hr, and air and oxygen gas were introduced from the same third gas supply means 14 at an initial speed of up to 100 m/sec from a nozzle with a flow rate of _O2 gas supplied from the PSA device of 4.86 ^Nm3 /hr, to form a _H2 / _O2 hydrolysis flame (operation C). The protective gas in operation D was _N2 gas with an _O2 concentration of 5%, which was fed from two locations at a rate of 2.2 ^Nm3 /hr to adjust the amount of oxygen in the tank (inside the combustion vessel 10). The silicon monoxide powder produced was also collected in the collection chamber 23 and its characteristics were examined. When the silicon monoxide powder obtained was analyzed by XRD and XPS, it was confirmed that it was amorphous SiO with no Si peak and only broad reflection.

[Example 3]
Silicon monoxide was produced using a silicon monoxide production apparatus 300 shown in Fig. 3. The configuration of the silicon monoxide production apparatus 300 in Fig. 3 is substantially the same as that in Fig. 1, but the means 11, 12 for supplying the second mixed fluid (a flammable silane compound alone or a second mixed fluid containing oxygen gas and an inert gas) and the first mixed fluid are integrated. Another difference is that hexamethyldisiloxane HMDS: (CH ₃ ) ₃ SiOSi (CH ₃ ) ₃ is supplied from the second mixed fluid supply means 35b, and dry air (Dry-Air) is supplied from the supply means 35a forming the two-fluid nozzle. In addition, dry air and nitrogen supplied from the PSA device are supplied as the protective gas supply means 36a, 36b, 37a, and 37b. Other configurations with the same reference numerals are the same as those in Fig. 1.

In operation C, instead of the flammable hydrocarbon gas (LPG) in Example 1, _H2 gas and a stoichiometric amount of _O2 gas were supplied from the third gas supply means 14 as a supplementary heat source. In addition, the flame was mainly controlled in operation C, but air could be introduced while being mixed with the above _H2 (however, in this example, the amount of air introduced was adjusted to zero as described below), and the amount of oxygen in the flame was adjusted.

In this embodiment, the protective gas is air + _N2 (however, the amount of nitrogen is adjusted depending on the adhesion state to the furnace wall and the cooling state), and the amount of oxygen in the tank (inside the combustion vessel 10) is further adjusted and controlled.

The supply rate of metal silicon powder from the metal silicon powder supply means 11 was 2.50 kg/hr, the same as in Example 1, and the amount of accompanying carrier gas was the same as in Example 1 (Operation A).

Operation B was carried out from an atomizer nozzle that was formed by forming a two-fluid nozzle in the ejector of Operation A. That is, hexamethyldisiloxane (HMDS): ( _CH3 ) _3SiOSi ( _CH3 ) ₃ liquid was supplied at a rate of 3.04 Kg/hr, while dry air was supplied at 24.13 ^Nm3 /hr to form HMDS microparticles (Operation B).

_H2 gas at 8.40 ^Nm3 /hr was introduced from the third supply means 14, and air and oxygen gas were introduced from the same third supply means 14 as _O2 gas at 4.83 ^Nm3 /hr supplied from the PSA device through a coaxial burner at an initial velocity of up to 100 m/sec from a nozzle to form a _H2 / _O2 hydrolysis flame (operation C).

The protective gas in operation D was dry air flowing from two locations (36a, 36b) at 2.2 ^Nm3 /hr, and 95% _N2 gas flowing from two locations (37a, 37b) at 0.5 ^Nm3 /hr to further strengthen cooling, to adjust the amount of oxygen in the tank (combustion vessel 10). The silicon monoxide powder produced was also collected in the collection chamber 23, and its characteristics were examined. The silicon monoxide powder obtained was analyzed by XRD and XPS, and it was confirmed that it was amorphous SiO with no Si peak and only broad reflection.

[Comparative Example 1]
Operation B in the apparatus of Example 1 shown in FIG. 1 was not carried out, and the flammable silane compound alone or the second mixed fluid containing oxygen gas and an inert gas was not supplied.

Metallic silicon powder containing a supplemental Si source was supplied at 3.55 Kg/hr from the first gas supply means 12 in operation A, and further, this metallic powder was supplied together with 1.44 Nm3/hr of a carrier gas ( _O2 concentration 8 vol% standard) mixed with air and additional _N2 gas, and ^{1.22 Nm3} /hr of Ar from the first gas supply means 12. Since operation B was not performed, a third mixed gas LPG of ^{1.8 Nm3} /hr and air of 49.93 Nm3/hr were mixed and combusted from the third gas supply means 14 in order to supplement the amount of heat.

Other than the first, second and third supply means and the supply fluid conditions, the same procedure was followed as in Example 1, and 5.3 kg/hr of gray powder was obtained. However, when the product was analyzed by XRD and XPS, a slight Si peak was observed, and about 20% of the bonds derived from _SiO2 were observed. Although a flame with the same amount of heat supply was formed, it was not possible to obtain silicon monoxide powder equivalent to that of Examples 1 to 3.

The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.

10... Combustion vessel,
11...Means for supplying metal silicon powder or a mixture of metal silicon powder and SiOx (x≦2) powder,
12...first gas supply means,
13... burner (first, second, third mixed fluid supply device),
14...Third gas supply means (burner),
15a, 15b...second fluid supply means (burner),
16, 17...fourth gas supply means,
21...Flame,
23...Collection chamber,
24...produced silicon monoxide powder,
100, 200, 300...Silicon monoxide manufacturing equipment (combustion equipment).

Claims (8)

1. A method for producing silicon monoxide, comprising the steps of:
An operation A of supplying a metal silicon powder or a mixture of a metal silicon powder and a SiOx (x≦2) powder to a combustion device using a first mixed fluid containing oxygen gas and an inert gas as a carrier;
An operation B of supplying a flammable silicon compound fluid alone or a second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas to the combustion device;
and an operation C of supplying a third mixed fluid containing a combustible gas, an oxygen gas, and an inert gas to the combustion device to form a flame;
A method for producing silicon monoxide, comprising simultaneously carrying out the above-mentioned operations A, B and C to produce a silicon monoxide product. The method further includes an operation D of supplying a fourth mixed fluid containing oxygen gas and an inert gas for controlling oxygen diffusion into the metal silicon powder or the mixture of the metal silicon powder and SiOx (x≦2) powder, or an inert gas alone;
2. The method for producing silicon monoxide according to claim 1, wherein the operation D is simultaneously carried out when the operations A to C are carried out. The method for producing silicon monoxide according to claim 1 or 2, characterized in that the first mixed fluid is air. The method for producing silicon monoxide according to any one of claims 1 to 3, characterized in that the flammable gas is a flammable gas containing a hydrocarbon. The method for producing silicon monoxide according to any one of claims 1 to 4, characterized in that the flammable gas is a flammable gas containing hydrogen. The method for producing silicon monoxide according to any one of claims 1 to 5, characterized in that the flammable silicon compound fluid is a low molecular weight organic silicon compound selected from alkoxysilane, silane, alkylsilane, alkylsilanol, alkylcyclosilane, alkylsiloxane, alkylcyclosiloxane, silazane, and cyclosilazane, or a mixture thereof. In the above step A, supplying a silicon metal powder or a mixture of a silicon metal powder and a SiOx (x≦2) powder;
In the operation B, the supply of the flammable silicon compound fluid alone or the second mixed fluid containing the flammable silicon compound fluid, oxygen gas, and an inert gas is
7. The method for producing silicon monoxide according to claim 1, wherein the mixture is mixed in the same place in the combustion device. The method for producing silicon monoxide according to any one of claims 1 to 7, further comprising an operation E in which the silicon monoxide product produced by carrying out the operations A to C is heated at a temperature of 1100°C or higher and 1500°C or lower to sublimate and extract the silicon monoxide contained in the product.

Images