WO2013019082A2 - Continuous production method for silicon tetrafluoride using silica and hydrogen fluoride - Google Patents

Abstract

The present invention relates to a continuous production method for silicon tetrafluoride (SiF₄) using silica (SiO₂) and hydrogen fluoride (HF), and, more specifically, relates to a continuous production method for silicon tetrafluoride, wherein silica and hydrogen fluoride (HF) are reacted by filling a bed reactor with crystalline or amorphous silica in the solid state and blowing hydrogen fluoride gas directly therein, such that it is possible to continuously produce silicon tetrafluoride in a high yield, and it is possible to use diverse forms of silica as raw materials and hence it is possible to ensure relatively economic operation.

Description

Continuous production method of silicon tetrafluoride using silica and hydrogen fluoride

The present invention relates to a continuous method for producing silicon tetrafluoride (SiF ₄ ) using silica (Siica, SiO ₂ ) and hydrogen fluoride (HF), and more particularly, to a solid crystalline or amorphous silica (crystalline or By filling an amorphous silica into a bed reactor and directly injecting hydrogen fluoride (HF) gas to react silica and hydrogen fluoride, silicon tetrafluoride can be continuously produced in high yield and various silica raw materials are used. It can operate more economically, and because it uses hydrogen fluoride (HF) gas directly as a starting reaction material, it is easier to control and process than the process of generating hydrogen fluoride gas from hydrogen fluoride source and using it for the next process. The present invention relates to a method for continuously manufacturing silicon tetrafluoride suitable for commercial mass production.

Silicon tetrafluoride (SiF ₄ ) is a semiconductor manufacturing method using fluorine doping reagent of quartz-based optical fiber, photomask material for semiconductor lithography, and chemical vapor deposition (CVD) for semiconductor manufacturing. It is used in industry, and its purity is becoming important because of high integration and high performance of electronic components. In recent years, as a precursor of monosilane (SiH ₄ , Monosilane), which is a basic raw material for manufacturing polysilicon for solar cells, the demand is increasing.

In the method for producing silicon tetrafluoride, a hydrofluoric acid (H ₂ SiF ₆ , Hexafluorosilicic acid) concentrate, which is usually produced as a by-product in the production of phosphoric acid, is prepared by dehydrothermal pyrolysis with sulfuric acid (WO 2005/030642 (H), hydrofluoric acid prepared from hydrofluoric acid, M ₂ SiF ₆ (M = Na, K) method of using hydrofluoric acid as a starting material, such as a method for producing by thermal decomposition reaction (US Pat. No. 2,615,872) Are known. However, these conventional methods thermally decompose hydrofluoric acid, which is generated as a by-product in the production of phosphoric acid, and there is a restriction to change or increase the phosphoric acid manufacturing process for scale-up of silicon tetrafluoride production.

U.S. Patent No. 6,770,253 proposes a method for producing silicon fluoride by reacting elemental silicon (Si) with hydrogen fluoride (HF), but the manufacturing cost is high because it uses expensive elemental silicon (Si). In order to remove SiHF ₃ produced as a reaction byproduct during the production of silicon fluoride, a separate facility for controlling the HF concentration in the reaction product or reacting with the metal at a high temperature is required. In addition, in order to separate the hydrogen produced as a reactant with silicon tetrafluoride, the process is complicated because it has to go through a distillation tower after manufacture.

U.S. Patent No. 4,382,071 proposes a method for producing silicon tetrafluoride by reacting crystalline or amorphous silica with hydrogen fluoride under sulfuric acid, but the process is very complicated because the reaction proceeds under sulfuric acid, especially in the case of crystalline silica sand hydrogen fluoride under sulfuric acid Reactivity with the gas is reduced, there is a disadvantage that there is a limit to the use of silica.

[Preceding technical literature]

<Patent Documents>

(Patent Document 1) International Patent Publication WO 2005/030642

(Patent Document 2) US Patent 2,615,872

(Patent Document 3) US Patent 6,770,253

(Patent Document 4) U.S. Patent 4,382,071

The present invention is to solve the above problems of the prior art, it is possible to continuously manufacture silicon tetrafluoride in high yield, and to use a variety of silica raw material can be operated more economically, starting hydrogen fluoride (HF) gas Because it is used directly as a reactant, hydrogen fluoride gas is generated from the hydrogen fluoride source, and it is easier to control the process than the process used for the next process, and the process can be simplified. It is a technical task to provide a continuous production method of silicon tetrafluoride suitable for commercial mass production by increasing the capacity.

In order to achieve the above technical problem, the present invention is characterized by reacting silica and hydrogen fluoride by blowing gaseous hydrogen fluoride (HF) into a high-temperature bed reactor containing a solid silica (SiO ₂ , SiO ₂ ) source material. It provides a method for the continuous production of silicon tetrafluoride.

According to a preferred embodiment of the present invention, further comprising passing a gaseous mixture containing silicon tetrafluoride and water, produced by the reaction of the silica and hydrogen fluoride through a sulfuric acid scrubber (H ₂ SO ₄ scrubber) Provided is a continuous method for producing silicon tetrafluoride, characterized in that.

According to the present invention, when silicon tetrafluoride is continuously produced using a bed reactor, hydrogen tetrafluoride and silica can be efficiently reacted to maximize the amount converted to silicon tetrafluoride. minimizing the amount of, and a separate, not only does not require SiF ₄ and the water part reaction distillation equipment since sulfuric acid through the scrubber, except for four silicon fluoride from the reaction product of water and unreacted hydrogen fluoride (HF) that is efficiently removed The formation of H ₂ SiF ₆ and silica gel is prevented, so that the process can be safely operated from device corrosion without the problem of pipe blockage and yield reduction of SiF ₄ . In addition, various silica raw materials such as silica fume, cullet, diatomaceous earth, kaolin, fumed silica, fly ash, slag, activated earth, silica gel, quartz, silica sand and the like can be used to operate more economically.

1 is a schematic view of one embodiment of the configuration of a reaction facility for continuously performing a continuous silicon tetrafluoride production method according to the present invention.

Hereinafter, the present invention will be described in more detail.

In the silicon tetrafluoride production method of the present invention, silicon tetrafluoride is continuously produced through the reaction of hydrogen fluoride and silica sand of the following formula 1).

Formula 1) SiO₂+ 4HF (g) → SiF₄(g) + 2H₂O (g)

In the present invention, both crystalline and amorphous forms may be used as the silica source material. The silica source materials include silica fume, which is a microsilica particle collected by filtration through the production of silica sand, quartz, silicon iron and silicon metal from silica, Cullet, soft rock and soil made of harmful diatomaceous earth, diatomaceous earth, kaolinite and halosite are produced or broken in the glass manufacturing process. Flue fume produced from pyrolysis of Kaolin, Silicon Tetrachloride, and feldspar produced by chemical weathering with carbonic acid and water as main components. Fly ash, a coal ash collected from the gas dust collector, slag, the residue left after removing metal from the ore, and used as an adsorbent as a porous material. There may be mentioned active soil (clay Activated), silica gel (Silica gel) and the like.

In the method for producing silicon tetrafluoride of the present invention, the particle size of the silica source material may vary depending on the specific material, and is usually 10 to 5,000 μm, preferably 100 to 1,000 μm, more preferably 100 to 600 μm, even more preferred. Preferably it is 100-450 micrometers, More preferably, it is 100-300 micrometers. If the particle size of the silica source material is too smaller than the above range, a significant amount of silica in the reactor is entrained when hydrogen fluoride (HF) gas is introduced, which makes it difficult to operate efficiently and may cause process problems such as clogging of the pipe. It is not preferable because there is a problem that the silica sand reaction area per volume decreases and the STF conversion and productivity decrease.

The method for producing silicon tetrafluoride of the present invention is carried out continuously by introducing hydrogen fluoride gas into a bed reactor filled with a silica source material. At this time, the reaction type may be a fixed bed reaction, a fluidized bed reaction, or a mixture of both, but since the formation of silicon tetrafluoride is an exothermic reaction, a fluidized bed reaction capable of more efficient heat exchange than a fixed bed may be employed. It is desirable to drive as much as possible. In addition, the reaction can be controlled by adjusting the process conditions such as the flow rate of the hydrogen fluoride gas to be introduced. U.S. Patent No. 3,273,963 proposes a method of absorbing heat of reaction by spraying water or hydrofluoric acid aqueous solution into the reactor to control the heat of reaction between silica sand and hydrogen fluoride, but when the solution is sprayed into the reactor, water that is not completely vaporized There is a fear of forming silica gel by reacting with silicon tetrafluoride (Equation 3 below). Since the boiling point of hydrogen fluoride is 20 ° C., the hydrogen fluoride input line and the unit connected to the reactor operate at 20 ° C. or higher.

The reaction temperature inside the reactor is preferably 100 to 1,000 ° C, even more preferably 300 to 700 ° C, even more preferably 400 to 600 ° C. If the reaction temperature is less than 100 ℃, there may be a problem such as the generation of siloxane due to the reaction of the reaction product of water and silicon tetrafluoride, and if the reaction temperature is too high, the reverse reaction rather than the desired reaction is active and the silicon tetrafluoride produced Reaction with steam again returns to the silica sand and hydrogen fluoride, which is not preferred because the reaction conversion rate is lowered. U.S. Patent 3,273,963 limits the preferred reaction temperature of hydrogen fluoride and silica sand in a bed reactor to 450 [deg.] F. (232 [deg.] C.). This may be suitable for the purpose of converting hydrogen fluoride in the reaction product obtained by pyrolyzing hydrofluoric acid to silicon tetrafluoride, but is not preferable when only hydrogen fluoride is directly reacted with silica sand to continuously produce large amounts of silicon tetrafluoride.

There is no particular restriction on the reaction pressure, and the reaction may be carried out at normal pressure or higher and negative pressure conditions. According to one embodiment, the reaction pressure inside the reactor is preferably at atmospheric pressure (0 barG) to 30 barG, even more preferably at atmospheric pressure to 10 barG, even more preferably at atmospheric pressure to 5 barG. According to another embodiment, the reaction pressure inside the reactor may be negative pressure conditions, preferably from -3,000 mmH ₂ Og up to atmospheric pressure.

The flow rate of hydrogen fluoride gas is not particularly limited, but it should be able to satisfy the production amount of silicon tetrafluoride to be produced while increasing the yield of reaction as much as possible according to the reactor size. The feed flow rate of the hydrogen fluoride gas is preferably 0.5 to 40 cm / s, even more preferably 1.0 to 30 cm / s, even more preferably 1.0 to 20 cm / s at a linear velocity. If the input flow rate of the hydrogen fluoride gas is too lower than the above range, local hot spots are generated due to the reaction heat generated by the fixed bed reaction, making it difficult to operate for a long time and lowering the silicon tetrafluoride productivity with a small input amount. On the contrary, excessively high amount is not preferable because the amount of unreacted hydrogen fluoride increases and the entrainment of silica entrains, which makes it difficult to operate efficiently.

In the silicon tetrafluoride production method, the reaction products are silicon tetrafluoride and water, and other unreacted hydrogen fluoride is present in the gas produced as a result of the reaction. The generated gas is then cyclone and transported through a sulfuric acid scrubber to a storage tank. The role of the scrubber is to remove water and unreacted hydrogen fluoride contained in the reaction product gas and selectively move only silicon tetrafluoride to the storage tank while removing dust not removed by the cyclone. According to one embodiment of the invention, the operating temperature of the sulfuric acid scrubber is preferably between 10 ° C and 250 ° C, more preferably between 10 ° C and 100 ° C, even more preferably between 10 ° C and 60 ° C Is driven. In addition, the concentration of sulfuric acid is operated at a concentration condition of 60% or more, more preferably 80% or more. If the operation temperature of the sulfuric acid scrubber is too high, the hydrogen fluoride and water removal efficiency is lowered. If the sulfuric acid scrubber is too low, the sulfuric acid freezes as a solid rather than a liquid, making operation impossible. The concentration of sulfuric acid should be kept as high as possible and if it is too low, some of the silicon tetrafluoride will react with the water in the sulfuric acid, reducing the recovery of silicon tetrafluoride produced when passing through the sulfuric acid scrubber. The high temperature SiF ₄ , water vapor (H ₂ O) and a small amount of HF mixed gas from the reactor maintain a temperature above the dew point (preferably 100 ° C. or higher, eg 100 ° C. to 200 ° C.) from the reactor to sulfuric acid scrubbers. It is preferable to transfer the liquid, which may cause moisture to condense on the water vapor when the temperature is lower than the dew point. The water may react with SiF ₄ to generate H ₂ SiF ₆ or silica gel. This is because the cause of pipe blockage and loss of silicon tetrafluoride can be caused (Equations 2 and 3, respectively).

2HF (aq) + SiF ₄ (g) → H ₂ SiF ₆ (aq)

3) SiF ₄ (g) + 2H ₂ O (l) → SiO ₂ (s, silica gel) + 4HF (g)

According to one embodiment of the present invention, a bed reactor (D) type reaction facility having a configuration as schematically shown in FIG. 1 is used as a reaction facility for continuously producing silicon tetrafluoride gas. Referring to FIG. 1, hydrogen fluoride (HF), which is a main raw material, is vaporized through a vaporizer in a storage tank A, and then introduced into a reactor using a mass flow controller (MFC) (1). ), The silica source material is initially added in a predetermined amount in the raw material input device (C), and then the amount that is lost as the reaction proceeds is introduced into the reactor using a separate device (2). The amount of the silica source material initially added to the reactor is not defined, but an excess of hydrogen fluoride added in consideration of the reaction efficiency is preferable. In addition, a hydrogen fluoride gas inlet at the bottom of the reactor may be provided with a distributor to uniformly and smoothly react the gas and the solid in the reactor to increase the reaction efficiency. Dust generated during the reaction is removed through a cyclone (E) as shown in Figure 1, water and unreacted hydrogen fluoride in the reaction product is completely removed through a sulfuric acid scrubber (F), Only silicon tetrafluoride is optionally transferred to the storage tank (G). Since water and hydrogen fluoride are removed through the sulfuric acid scrubber, silicon tetrafluoride is prevented from being changed to hydrogen silicate and silica gel, thereby eliminating silicon tetrafluoride. Since it is closely related to the concentration of sulfuric acid, the sulfuric acid concentration unit (H) can be placed and reused while maintaining the concentration of sulfuric acid in the sulfuric acid scrubber (F) above a certain level during operation.

 Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited by these examples.

[Examples 1 and 2]

Silicon tetrafluoride was continuously produced through a reaction process as shown in FIG. 1. The bed reactor (D) was heated to temperature using a resistive heating method, and the solid silica source material was fed to the top of the reactor. Initially a certain amount of silica source material was added first and then supplemented by the amount consumed as the reaction proceeds. Hydrogen fluoride is introduced into the bottom of the reactor, since the boiling point of hydrogen fluoride is 20 ° C, the hydrogen fluoride supply line and the mass flow controller (MFC) were operated while maintaining the temperature above the boiling point of hydrogen fluoride.

In Example 1, the silica sand was filled to a height of about 40 cm inside the reactor, and then the temperature inside the reactor was raised to 400 ° C. Hydrogen fluoride gas was introduced through the pipe 1 and the dispersion plate at a flow rate of about 3.5 cm / s based on the reactor. As soon as hydrogen fluoride was added, silicon tetrafluoride gas began to be generated, and the gas discharged through the pipe 3 was collected after passing through a sulfuric acid scrubber. The reaction gas passed through the sulfuric acid scrubber was confirmed to contain silicon tetrafluoride through GC-MS, FT-IR analysis, and the SiF4 reaction yield was obtained by reacting the produced silicon tetrafluoride with a trapping agent. After quantitative analysis by titration, it was calculated as the amount of silicon tetrafluoride compared to the amount of hydrogen fluoride input.

In Example 2, the reaction temperature conditions were changed as shown in Table 1 below. Except for the reaction temperature, the experiment was conducted in the same manner as in Example 1. The generated gas was confirmed by the same method as in Example 1.

It was confirmed that silicon tetrafluoride can be produced in high yield at a temperature of 400 ° C. or higher.

Table 1

EXAMPLES 3-9

Instead of silica sand of Examples 1 and 2, silica fume, diatomaceous earth, kaolin, fumed silica, fly ash, silica gel and silica (silica gel) and quartz ( Quartz) is applied. In addition to the raw material, the reaction temperature was performed at 400 ° C., and other conditions were performed in the same manner as in Example 1. The generated gas was confirmed in the same manner as in Example 1 after 12 hours of reaction. As a result, it was confirmed that hydrogen fluoride and various kinds of silica source materials reacted smoothly under the conditions of the present invention.

TABLE 2

Example 10

In Example 10, the silica sand filled in the reactor was changed to 20 cm under the same conditions as in Example 1, and hydrogen fluoride gas was introduced through the pipe 1 and the dispersion plate at a flow rate of 10.3 cm / s based on the reactor. Increasing the flow rate of hydrogen fluoride gas facilitated the fluidization of the silica sand particles, thereby maintaining a more stable temperature in the reactor.

TABLE 3

Example 11

Example 11 was performed by increasing the reactor internal pressure from 0 barG to 2 barG under the same conditions as in Example 1. As a result, productivity was improved by increasing the actual hydrogen fluoride input amount due to the pressure increase effect, while maintaining the yield at an appropriate level.

Table 4

[Examples 12-13]

In Examples 12 and 13, the size of the silica sand was tested under the same conditions as in Example 1, and as the size of the silica sand decreased, the contact time with hydrogen fluoride increased and thus the yield increased.

Table 5

[Description of the code]

A: hydrogen fluoride storage tank

B: Hydrogen Fluoride Input Control (MFC)

C: solid silica source material input device

D: bed reactor

E: cyclone

F: sulfuric acid scrubber

G: Silicon tetrafluoride storage tank

H: sulfuric acid concentration unit

1: hydrogen fluoride input pipe

2: silica injection piping

3: Silicon tetrafluoride, water and hydrogen fluoride mixed gas discharge piping

4: Dust-free silicon tetrafluoride, water and hydrogen fluoride mixed gas discharge pipe

5: silicon tetrafluoride discharge piping

6: dilute sulfuric acid drainage pipe including hydrogen fluoride and water

Claims (11)

1. A method for the continuous production of silicon tetrafluoride, comprising reacting silica and hydrogen fluoride by blowing gaseous hydrogen fluoride (HF) into a high temperature bed reactor containing a solid silica (SiO ₂ ) source material.
2. The method of claim 1, further comprising passing a gaseous mixture containing silicon fluoride and water through a H ₂ SO ₄ scrubber produced by the reaction of the silica with hydrogen fluoride. Process for Continuous Production of Silicon Fluoride.
3. The method of claim 1, wherein the reaction form of silica and hydrogen fluoride is a fixed bed reaction, a fluidized bed reaction, or a mixture of both.
4. The method of claim 1, wherein the silica source material is silica sand, silica fume, cullet, diatomaceous earth, kaolin, fumed silica, fly ash (Fly ash, slag, slag, activated clay, silica gel, silica (Quartz) and a method for the continuous production of silicon tetrafluoride, characterized in that selected from the group consisting of.
5. The method of claim 1, wherein the reaction temperature of the silica and hydrogen fluoride is 100 ~ 1,000 ℃ method of producing silicon tetrafluoride.
6. The method of claim 1, wherein the reaction pressure between the silica and hydrogen fluoride is from normal pressure to 30 barG.
7. The method of claim 1, wherein the reaction pressure of the silica and hydrogen fluoride is a negative pressure from -3,000 mmH ₂ Og to normal pressure.
8. The method of claim 1 wherein the particle size of the solid silica source material is 10-5,000 μm.
9. The method of claim 1, wherein the flow rate of the hydrogen fluoride gas in the reactor is a linear velocity of 0.5 to 30 cm / s.
10. The method for producing silicon tetrafluoride according to claim 2, wherein an operating temperature of the sulfuric acid scrubber is 10 to 250 ° C.
11. 3. The process for producing silicon tetrafluoride according to claim 2, wherein the gaseous mixture containing silicon fluoride and water is transferred from the reactor to the sulfuric acid scrubber at a temperature above the dew point.

Images