CN116282041A - Method for preparing silicon tetrafluoride from fluorine-containing silicon slag - Google Patents
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- 239000002893 slag Substances 0.000 title claims abstract description 73
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 61
- 239000010703 silicon Substances 0.000 title claims abstract description 61
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 title claims abstract description 54
- 229910052731 fluorine Inorganic materials 0.000 title claims abstract description 54
- 239000011737 fluorine Substances 0.000 title claims abstract description 54
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 39
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 37
- 239000007789 gas Substances 0.000 claims abstract description 19
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 17
- 239000003513 alkali Substances 0.000 claims abstract description 15
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 14
- 150000002221 fluorine Chemical class 0.000 claims abstract description 13
- 239000002253 acid Substances 0.000 claims abstract description 11
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 11
- 238000001035 drying Methods 0.000 claims abstract description 10
- 229910000040 hydrogen fluoride Inorganic materials 0.000 claims abstract description 10
- 238000006386 neutralization reaction Methods 0.000 claims abstract description 10
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- 238000001914 filtration Methods 0.000 claims abstract description 8
- 239000002994 raw material Substances 0.000 claims abstract description 8
- 239000000706 filtrate Substances 0.000 claims abstract description 7
- 230000003472 neutralizing effect Effects 0.000 claims abstract description 7
- 239000008247 solid mixture Substances 0.000 claims abstract description 4
- 239000006227 byproduct Substances 0.000 claims abstract description 3
- 239000007788 liquid Substances 0.000 claims abstract description 3
- 238000004064 recycling Methods 0.000 claims abstract description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 16
- 229910052786 argon Inorganic materials 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 238000005273 aeration Methods 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 238000010907 mechanical stirring Methods 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 238000002791 soaking Methods 0.000 claims description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims 1
- 239000001301 oxygen Substances 0.000 claims 1
- 229910052760 oxygen Inorganic materials 0.000 claims 1
- 239000002699 waste material Substances 0.000 abstract description 7
- 150000001875 compounds Chemical class 0.000 abstract description 2
- 238000003912 environmental pollution Methods 0.000 abstract description 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 24
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 18
- 229910000029 sodium carbonate Inorganic materials 0.000 description 9
- 239000000047 product Substances 0.000 description 8
- 239000011734 sodium Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 4
- 229940104869 fluorosilicate Drugs 0.000 description 3
- 239000002367 phosphate rock Substances 0.000 description 3
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 3
- 238000000197 pyrolysis Methods 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 2
- 239000004115 Sodium Silicate Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011775 sodium fluoride Substances 0.000 description 2
- 235000013024 sodium fluoride Nutrition 0.000 description 2
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 2
- 229910052911 sodium silicate Inorganic materials 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 229910008284 Si—F Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 239000011532 electronic conductor Substances 0.000 description 1
- 239000012776 electronic material Substances 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 150000004673 fluoride salts Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 238000006053 organic reaction Methods 0.000 description 1
- 239000003504 photosensitizing agent Substances 0.000 description 1
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910021332 silicide Inorganic materials 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 235000019795 sodium metasilicate Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/08—Compounds containing halogen
- C01B33/107—Halogenated silanes
- C01B33/10705—Tetrafluoride
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/186—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof from or via fluosilicic acid or salts thereof by a wet process
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
A method for preparing silicon tetrafluoride from fluorine-containing silicon slag relates to a compound of fluorine and silicon, in particular to a method for preparing silicon tetrafluoride gas from fluorine-containing silicon slag. The invention aims to provide a method for preparing silicon tetrafluoride by using fluorine-containing silicon slag, which takes fluorine-containing silicon slag as a raw material, effectively utilizes fluorine and silicon elements in the waste slag, realizes high-value utilization of the waste slag, and avoids environmental pollution and land occupation caused by stacking. The method comprises the following specific steps: (1) neutralizing fluorine-containing silicon slag with alkali liquor; (2) Filtering, wherein the filtrate is used for preparing alkali liquor and recycling fluorine-containing silica slag for neutralization; drying the filter residue to obtain modified fluorine-containing silicon slag; (3) And (3) heating and decomposing the modified fluorine-containing silicon slag in vacuum or inert atmosphere to obtain silicon tetrafluoride gas, and collecting to obtain silicon tetrafluoride liquid or compressed gas, wherein the byproduct is decomposed slag mainly containing active silicon dioxide. The method is suitable for enterprises which extract silicon tetrafluoride from solid mixtures which mainly contain silicon dioxide and contain fluosilicic acid and hydrogen fluoride.
Description
Technical Field
The invention relates to a compound of fluorine and silicon, in particular to silicon tetrafluoride, and particularly relates to a method for preparing silicon tetrafluoride gas by utilizing fluorine-containing silicon slag.
Background
Silicon tetrafluoride is an important raw material in the electronic and semiconductor industries, and is mainly used as an etchant for tantalum silicide, silicon nitride and the like, a P-type dopant and an epitaxial deposition diffusion silicon source; due toHydrolysis of silicon tetrafluoride in a high temperature flame can produce a heat sink SiO with a high specific surface area 2 The method can also be used for manufacturing high-purity quartz glass for optical fibers; silicon tetrafluoride is an important component of ion implantation methods employed in the manufacture of silicon-based semiconductor devices in semiconductor manufacturing techniques; in addition, silicon tetrafluoride is also widely used in the production of cement, electronic materials, solar cell elements, photocopier photosensitive drums, very large scale integrated circuits, and the like. With the development of laser in organic reaction, it can also be used as photosensitizer and the like.
The existing production method of silicon tetrafluoride mainly comprises the following steps: sulfuric acid process, hydrofluoric acid process, si-F 2 Direct synthesis, fluorosilicate pyrolysis, and the like. The sulfuric acid method and the hydrofluoric acid method are used for preparing the silicon tetrafluoride to produce more impurity gas components, and the subsequent separation difficulty is high. Si-F 2 The direct synthesis method needs to prepare by reacting fluorine gas and simple substance silicon, and has high cost and high risk. The fluorosilicate pyrolysis method has high energy consumption and high requirements on the sealing performance of equipment at high temperature. Overall silicon tetrafluoride is costly to produce and therefore the price of the product is relatively high.
95% of fluorine elements on the earth are associated with phosphorite, so that phosphorite gradually becomes a main raw material for preparing fluorine. The preparation of hydrogen fluoride by the reaction of concentrated sulfuric acid with fluosilicic acid is the mainstream method for preparing hydrogen fluoride from phosphorite. However, this process produces a fluorosilicate residue based on activated silica, containing hydrogen fluoride and fluorosilicic acid. The waste residue is acidic and corrosive due to the hydrogen fluoride and the fluosilicic acid, and the comprehensive utilization of the waste residue is difficult. The patent CN106829983A reacts the fluorine-containing silicon slag with sodium carbonate at high temperature to obtain sodium silicate with modulus between 2 and 3, the patent CN105883836A reacts the fluorine-containing silicon slag with sodium hydroxide to prepare sodium metasilicate and co-produce sodium fluoride, the patent CN105036144A reacts the fluorine-containing silicon slag with sodium hydroxide to prepare high-dispersion white carbon black, and the methods can process the fluorine-containing silicon slag into products with a certain application prospect. However, the fluorine-containing silica slag cannot be applied in a large amount due to the factors of high preparation cost, low added value of products and the like, and the comprehensive utilization rate is low.
Compared with common industrial products, the silicon tetrafluoride product has high added value, is prepared by taking fluorine-containing silicon slag as a raw material, can improve the utilization rate of waste slag, and realizes high-value utilization.
Disclosure of Invention
The invention aims to provide a method for preparing silicon tetrafluoride by using fluorine-containing silicon slag, which takes fluorine-containing silicon slag as a raw material, effectively utilizes fluorine and silicon elements in waste slag, realizes high-value utilization of the waste slag, and avoids environmental pollution and land occupation caused by stacking.
The technical principle of the method is that alkali liquor is used for neutralizing the fluorine-containing silicon slag, fluosilicic acid in the fluorine-containing silicon slag generates fluosilicate, the fluosilicate in the slag is heated and decomposed into fluoride salt and silicon tetrafluoride by high-temperature heating, and the industrial grade silicon tetrafluoride product is obtained after cooling and collecting. Taking sodium hydroxide solution and sodium carbonate solution as examples, when the sodium hydroxide solution and the sodium carbonate solution are respectively mixed with the fluorine-containing silicon slag, fluosilicic acid in the fluorine-containing silicon slag respectively reacts as follows to generate sodium fluosilicate:
H 2 SiF 6 +2NaOH→Na 2 SiF 6 +H 2 O (1)
H 2 SiF 6 +Na 2 CO 3 →Na 2 SiF 6 +H 2 O+CO 2 ↑ (2)
the neutralized product contains water, and direct pyrolysis can lead to side reactions. Therefore, the method adopts the steps of filtering firstly, and the filtrate is reused for preparing alkali liquor; drying filter residues, then decomposing at high temperature, and decomposing sodium fluosilicate in the neutralized and dried fluorine-containing silicon residues to generate silicon tetrafluoride and sodium fluoride:
Na 2 SiF 6 →2NaF+SiF 4 ↑ (3)
after collecting silicon tetrafluoride in the product, the rest solid is powder with porous active silica as main component, and may be used as stuffing, building material, etc.
The method for preparing silicon tetrafluoride from the fluorine-containing silicon slag provided by the inventor comprises the following specific steps:
(1) Neutralizing the fluorine-containing silicon slag with alkali liquor;
(2) Filtering the fluorine-containing silicon slag neutralized by alkali liquor, and using the filtrate for preparing alkali liquor and recycling the alkali liquor for neutralizing the fluorine-containing silicon slag; drying the filter residue to obtain modified fluorine-containing silicon slag;
(3) And (3) heating and decomposing the modified fluorine-containing silicon slag in vacuum or inert atmosphere to obtain silicon tetrafluoride gas, cooling and collecting the silicon tetrafluoride gas to obtain silicon tetrafluoride liquid or compressed gas, and obtaining the decomposed slag mainly containing active silicon dioxide.
The alkali liquor used in the step (1) is one or a mixture of more than two of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution and calcium hydroxide emulsion, and the mass fraction of the alkali liquor is 2-60%.
In the neutralization process in the step (1), the neutralization efficiency is improved by standing and soaking or by stirring methods such as mechanical stirring or aeration; the neutralization is carried out until the pH value is 7.0-8.0.
And (3) drying the filter residues in the step (2) at the temperature of 100-300 ℃ and with the water content of less than 0.1%.
The inert atmosphere in the step (3) is anhydrous, anaerobic nitrogen, argon or helium atmosphere; the heating temperature is controlled between 450 ℃ and 900 ℃.
The inventors point out: the fluorine-containing silicon slag is a solid mixture mainly comprising silicon dioxide, fluosilicic acid and hydrogen fluoride, and comprises byproducts when the fluosilicic acid or the fluosilicate is used as a raw material and concentrated sulfuric acid is adopted for producing anhydrous hydrogen fluoride in a contact way.
From the industrial application point of view, the inventor of the invention develops a method for preparing silicon tetrafluoride from fluorine-containing silicon slag, and realizes the high-value and resource utilization of industrial waste slag. The method is suitable for extracting the silicon tetrafluoride from a solid mixture which is mainly silicon dioxide and contains fluosilicic acid and hydrogen fluoride.
Drawings
FIG. 1 is a process flow diagram of the method of the present invention.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to be limiting.
Example 1:
(1) 1000g of fluorine-containing silicon slag is taken, 10% sodium hydroxide solution is added under continuous stirring, and the mixture is neutralized to pH value of 7.5;
(2) Filtering the fluorine-containing silicon slag neutralized by sodium hydroxide solution, and drying filter residues at 120 ℃ until the water content is lower than 0.1% to obtain modified fluorine-containing silicon slag; the filtrate is used for preparing sodium hydroxide solution and is recycled for neutralization of fluorine-containing silicon slag;
(3) And (3) vacuumizing the modified fluorine-containing silicon slag in a closed reaction kettle, then injecting high-purity argon, vacuumizing, repeatedly injecting argon and vacuumizing for 3 times, heating for 1h at the temperature of 650 ℃ and the vacuum degree of-85 Pa, decomposing to obtain silicon tetrafluoride gas, cooling and collecting 50g of the silicon tetrafluoride gas, and obtaining the decomposed slag mainly comprising active silicon dioxide.
Example 2:
(1) 1000g of fluorine-containing silicon slag is taken, 10% sodium carbonate solution is added under continuous stirring, and the mixture is neutralized to pH value of 7.8;
(2) Filtering the fluorine-containing silicon slag neutralized by the sodium carbonate solution, and drying filter residues at 180 ℃ until the water content is lower than 0.1% to obtain modified fluorine-containing silicon slag; the filtrate is used for preparing sodium carbonate solution and is recycled for neutralization of fluorine-containing silicon slag;
(3) And (3) vacuumizing the modified fluorine-containing silicon slag in a closed reaction kettle, then injecting high-purity argon, vacuumizing, repeatedly injecting argon and vacuumizing for 3 times, heating for 50min at the vacuum degree of-90 Pa and the temperature of 750 ℃, decomposing to obtain silicon tetrafluoride gas, cooling and collecting 51g of the silicon tetrafluoride gas, and obtaining the decomposed slag mainly comprising active silicon dioxide.
Example 3:
(1) 1000g of fluorine-containing silicon slag is taken, 10% potassium hydroxide solution is added under continuous stirring, and the mixture is neutralized to pH value of 7.6;
(2) Filtering the fluorine-containing silicon slag neutralized by the sodium carbonate solution, and drying filter residues at 200 ℃ until the water content is lower than 0.1% to obtain modified fluorine-containing silicon slag; the filtrate is used for preparing sodium carbonate solution and is recycled for neutralization of fluorine-containing silicon slag;
(3) And (3) vacuumizing the modified fluorine-containing silicon slag in a closed reaction kettle, then injecting high-purity argon, vacuumizing, repeatedly injecting argon and vacuumizing for 3 times, heating for 30min at the vacuum degree of-96 Pa and the temperature of 800 ℃ to decompose the modified fluorine-containing silicon slag to obtain silicon tetrafluoride gas, and cooling and collecting 52g of the silicon tetrafluoride gas to obtain the decomposed slag mainly comprising active silicon dioxide.
Claims (5)
1. The method for preparing silicon tetrafluoride by using fluorine-containing silicon slag as a raw material is characterized by comprising the following steps of: neutralizing the fluorine-containing silicon slag with alkali liquor, filtering, drying the filter residue, and decomposing the filter residue at high temperature to obtain silicon tetrafluoride gas and active silicon dioxide; the method comprises the following specific steps:
(1) Neutralizing the fluorine-containing silicon slag with alkali liquor;
(2) Filtering the fluorine-containing silicon slag neutralized by alkali liquor, and using the filtrate for preparing alkali liquor and recycling the alkali liquor for neutralizing the fluorine-containing silicon slag; drying the filter residue to obtain modified fluorine-containing silicon slag;
(3) And (3) heating and decomposing the modified fluorine-containing silicon slag in vacuum or inert atmosphere to obtain silicon tetrafluoride gas, cooling and collecting the silicon tetrafluoride gas to obtain silicon tetrafluoride liquid or compressed gas, and obtaining the decomposed slag mainly containing active silicon dioxide.
2. The method for preparing silicon tetrafluoride from the fluorine-containing silicon slag according to claim 1, wherein the neutralization process in the step (1) is standing soaking or stirring methods such as mechanical stirring or aeration to improve the neutralization efficiency; the neutralization is carried out until the pH value is 7.0-8.0.
3. The method for preparing silicon tetrafluoride from fluorine-containing silica slag according to claim 1, wherein the temperature of the drying of the filter slag in the step (2) is controlled to be 100-300 ℃ and the water content is lower than 0.1%.
4. The method for preparing silicon tetrafluoride from fluorine-containing silica slag according to claim 1, characterized in that the inert atmosphere in the method step (3) is a nitrogen, argon or helium atmosphere free of water and oxygen; the heating temperature is controlled between 450 ℃ and 900 ℃.
5. The method for preparing silicon tetrafluoride from fluorine-containing silica slag according to claim 1, wherein: the fluorine-containing silicon slag is a solid mixture mainly comprising silicon dioxide, fluosilicic acid and hydrogen fluoride, and comprises byproducts when the fluosilicic acid or the fluosilicate is used as a raw material and concentrated sulfuric acid is adopted to contact and produce anhydrous hydrogen fluoride.
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