阅读说明：本技术 一种高纯四氟化硅的合成及纯化方法 (Synthesis and purification method of high-purity silicon tetrafluoride ) 是由 马建修 王新鹏 杜文东 张�杰 崔录芳 于 2019-06-20 设计创作，主要内容包括：本发明提出一种高纯四氟化硅的合成及纯化方法。一种高纯四氟化硅的合成及纯化方法,包括以下步骤：氟硅酸盐的预处理；氟硅酸盐经裂解反应制备四氟化硅粗料；在第一吸附工段脱除痕量水分及酸性气体；在第二吸附工段对氟硅醚进行脱除与阻聚控制；在精馏工段对轻组分和重组分进行分离；通过复杂精馏工段对恒沸物杂质进行分离。本发明提出的高纯四氟化硅的合成及纯化方法,其将加热裂解、吸附单元操作、精馏和复杂精馏科学组合,通过采用吸附单元脱除氟硅醚,通过常规精馏单元操作后增加复杂精馏工艺去除恒沸物。(The invention provides a method for synthesizing and purifying high-purity silicon tetrafluoride. A method for synthesizing and purifying high-purity silicon tetrafluoride comprises the following steps: pre-treating fluosilicate; carrying out cracking reaction on fluorosilicate to prepare a silicon tetrafluoride coarse material; removing trace moisture and acid gas in a first adsorption section; performing desorption and polymerization inhibition control on the fluorosilicone at a second adsorption section; separating light components and heavy components in a rectification section; and separating the azeotropic substance impurities through a complicated rectification working section. The synthesis and purification method of high-purity silicon tetrafluoride scientifically combines heating cracking, adsorption unit operation, rectification and complex rectification, adopts the adsorption unit to remove fluorosilicone, and adds a complex rectification process to remove azeotropic substances after the conventional rectification unit operation.)

1. A method for synthesizing and purifying high-purity silicon tetrafluoride is characterized by comprising the following steps:

and step S1: pre-treating fluosilicate;

and step S2: carrying out cracking reaction on fluorosilicate to prepare a silicon tetrafluoride coarse material;

and step S3: removing trace moisture and acid gas in a first adsorption section;

and step S4: performing desorption and polymerization inhibition control on the fluorosilicone at a second adsorption section;

and step S5: separating light components and heavy components in a rectification section;

and step S6: and separating the azeotropic substance impurities through a complicated rectification working section.

2. The method as claimed in claim 1, wherein the cracking reaction is performed under the conditions of pressure 0.02 ~ 0.1.1 MPa, temperature 300 ~ 500 ℃, reactor outlet operation flow rate 10-30 kg/h, reactor type rotary kiln reactor and volume 500-1000L in the step S2.

3. The method for synthesizing and purifying high-purity silicon tetrafluoride according to claim 1, wherein in the step of S4, the fluorosilicone ether is removed and polymerization inhibition controlled at the second adsorption stage by using a fluorinated resin prepared by coating a metal fluoride on the surface of a resin.

4. The method for synthesizing and purifying high-purity silicon tetrafluoride according to claim 3, wherein the metal fluoride is one of silver fluoride, cobalt fluoride, manganese fluoride, lead fluoride, aluminum fluoride, copper fluoride or magnesium fluoride, and the metal fluoride loading rate is 1 ~ 5 mmol/g.

5. The method as claimed in claim 4, wherein the resin is a porous cross-linked polystyrene resin having a specific surface area of 300 ~ 600m²/g。

6. The method for synthesizing and purifying high-purity silicon tetrafluoride according to claim 1, wherein in the step of S5, the rectifying section comprises a de-weighting tower and a de-weighting tower, the feeding amount of the de-weighting tower is 2 ~ 50kg/h, the tower pressure is 0.1 ~ 3.0.0 MPa, the tower top temperature is-80 ~ -10 ℃, the tower bottom temperature is-70 ~ -5 ℃, the feeding amount of the de-weighting tower is 2 ~ 50kg/h, the tower pressure is 0.1 ~ 4.0.0 MPa, the tower top temperature is-80 ~ 5 ℃, and the tower bottom temperature is-70 ~ 15 ℃.

7. The method as claimed in claim 6, wherein in the step of S6, the complicated distillation section adopts a volume ratio of 4: 3: 3, extracting and rectifying the cyclohexane, the hexachlorobenzene and the m-phenylenediamine as extracting agents.

8. The method for synthesizing and purifying high-purity silicon tetrafluoride according to claim 6, wherein in the step of S6, the complicated distillation section comprises three removal columns connected in series, the feeding amount of the removal columns is 2 ~ 50kg/h, the column pressure is 0.2 ~ 4.0.0 MPa, the temperature at the top of the column is-80 ~ 5 ℃, and the temperature at the bottom of the column is-70 ~ 15 ℃.

9. The method for synthesizing and purifying high-purity silicon tetrafluoride according to claim 1, wherein the step S1 is carried out by vacuum-pumping fluorosilicate and heating at 100 ~ 200 ℃.

Technical Field

The invention relates to the fields of chemical engineering, separation engineering and electronic special gases, in particular to a method for synthesizing and purifying high-purity silicon tetrafluoride.

Background

Silicon tetrafluoride (SiF)₄) The compound of the tetrahalosilane family has the highest silicon atom proportion (about 27 percent), stable Si-F chemical bond energy (541.0 kJ/mol) and non-flammability and non-explosive characteristics. In the processing technology of high-depth wide-range and large-capacity silicon/silicon oxide and metal interlayer insulating layers in the new generation chip process, silicon tetrafluoride shows unique physical and chemical properties. Silicon tetrafluoride and N₂O、O₂、SiH₄And H₂The gases are used together to achieve the chemical deposition rate of 300-500 nm/min, and wide and thick SiO can be obtained within a limited time₂An insulating layer. In addition, silicon tetrafluoride can also be used as a main raw material for preparing high-purity quartz glass by using various epitaxial precipitation diffusion silicon sources such as silicon carbide, silicon nitride and the like, and optical fibers, and is a key component of a silicon-based semiconductor ion injection process in the optical fiber industry.

In 1771 Scheele et al successfully synthesized silicon tetrafluoride for the first time, specifically obtained by the reaction of hydrofluoric acid and silicon dioxide, and the reaction equation is as follows: SiO 2₂ + 4 HF = SiF₄ + 2 H₂And O. However, silica is chemically stable, has a large Si — O bond energy, requires a large amount of hydrogen fluoride, and the reaction temperature is often high, and this method is gradually eliminated due to the high cost of hydrogen fluoride.

The widely applied silicon tetrafluoride preparation method at present is a silicon dioxide fluorite sulfuric acid method, and the reaction equation is as follows: 2CaF₂+ 2H₂SO₄ + SiO₂ = 2CaSO₄ + SiF₄ + 2H₂And O. The method has the characteristics of easily available raw material sources, low cost and suitability for large-scale production, but mainly faces the problem that water is generated in a product, the water can react with silicon tetrafluoride to generate fluorosilicone ether impurities, and the reaction equation is as follows: 2SiF₄ + H₂O = (SiF₃)₂O + 2 HF. The fluorosilicone ether impurity has gel-like property, and is easy to flocculate and form polyfluorosilane- (SiF) with silicon tetrafluoride by continuous secondary growth₂O) n-, which easily causes the pipe fitting to be blocked, and threatens the safety and stability of production. On the other hand, the raw material fluorite has more impurities, the reaction cracking control difficulty is high, and the components in the produced silicon tetrafluoride coarse material are very complex.

The other preparation method of the silicon tetrafluoride is a cracking technology: mixing Na₂SiF₆Thermally cracking at high temperature to produce silicon tetrafluoride and sodium fluoride. The reaction equation is: na (Na)₂SiF₆ = SiF₄+ 2 NaF. The synthesis method has the characteristics of avoiding the use of concentrated sulfuric acid, not generating calcium sulfate slurry waste residue and further improving the safety and environmental protection. However, this method has some problems, such as numerous cracking reaction products, complex composition of different fluorine substituted silicide-forming azeotropes, low cracking conversion rate, and easy generation of fluorosilicones, polyfluorosilanes, and other impurities during the cracking process.

In the silicon tetrafluoride synthesis section, the former carries out partial improvement on the process on the basis of the methods. For example, patent CN 108658081 a adopts a method of producing hydrogen fluoride and silicon tetrafluoride to be prepared by reacting sodium fluorosilicate with sulfuric acid, and repeatedly utilizes and integrates the generated hydrogen fluoride gas in many aspects, so that the hydrogen fluoride reacts with silicon dioxide to further react to obtain silicon tetrafluoride, and the method effectively utilizes hydrogen fluoride corrosive gas. Patent CN 105502410A mixes silicon-containing substance and fluorine-containing substance to react to obtain silicon tetrafluoride. According to the method, acidic and corrosive liquid substances are avoided, silicon-containing substances and fluorine-containing substances, particularly gaseous fluorine-containing substances are used for reacting to prepare the silicon tetrafluoride, less impurities are introduced, the purity of the product silicon tetrafluoride is high, less waste acid and waste residue can be generated, and the environmental pollution is less. CN 102897769 discloses a process for producing silicon tetrafluoride, which comprises the steps of stirring and heating raw materials of sodium fluosilicate, silicon dioxide powder and concentrated sulfuric acid to react at a certain temperature. CN 104843713 discloses a device for preparing silicon tetrafluoride by pyrolyzing sodium fluosilicate, which comprises the steps of washing and purifying sodium fluosilicate, then loading the sodium fluosilicate into a decomposition reaction kettle, heating and decomposing the sodium fluosilicate in a thin-layer static manner, collecting the obtained silicon tetrafluoride gas, condensing the silicon tetrafluoride gas by a heat exchanger and collecting the silicon tetrafluoride gas. The method for producing high-purity silicon tetrafluoride in the process of wet processing of phosphate ore by CN 102001666 collects fluorine-containing gas generated in the process of wet processing of phosphate ore; introducing the fluorine-containing gas into a reactor added with sulfuric acid and silicon dioxide to obtain a high-purity silicon tetrafluoride product. CN 104445074 is a method for preparing anhydrous hydrogen fluoride and co-producing silicon tetrafluoride by treating dilute fluosilicic acid by a solvent extraction method.

In a silicon tetrafluoride purification section, the traditional method is a rectification process at present, but silicon tetrafluoride still contains fluorosilicone ether and azeotrope impurities, and trace removal is difficult to realize. CN101774588 removes light and heavy component impurities by a conventional rectification method. CN 105347348A introduces silicon tetrafluoride, diluent gas and carbonyl fluoride into a water removal tower filled with filler, and the carbonyl fluoride contacts with water in the silicon tetrafluoride to react and remove water in the silicon tetrafluoride.

In order to reduce the production cost and improve the yield of the silicon tetrafluoride, although a large amount of work is also carried out domestically, the work cannot be really realized all the time. In summary, there are still deficiencies: 1. the silicon tetrafluoride reaction conversion rate is low; 2. the reaction selectivity is low, and the number of byproducts is large; 3. fluorosilicone in silicon tetrafluoride, although removed by adsorption, does not further achieve polymerization inhibition; 4. the impurities in the complex system of the azeotrope cannot be effectively removed.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention aims to provide a method for synthesizing and purifying high-purity silicon tetrafluoride, which scientifically combines pyrolysis, adsorption unit operation, rectification and complex rectification, removes fluorosilicone by adopting an adsorption unit, and removes azeotropic substances by adding a complex rectification process after the conventional rectification unit operation.

The technical problem to be solved by the invention is realized by adopting the following technical scheme.

The invention provides a method for synthesizing and purifying high-purity silicon tetrafluoride, which comprises the following steps:

and step S1: pre-treating fluosilicate;

and step S2: carrying out cracking reaction on fluorosilicate to prepare a silicon tetrafluoride coarse material;

and step S3: removing trace moisture and acid gas in a first adsorption section;

and step S4: performing desorption and polymerization inhibition control on the fluorosilicone at a second adsorption section;

and step S5: separating light components and heavy components in a rectification section;

and step S6: and separating the azeotropic substance impurities through a complicated rectification working section.

Preferably, the cracking reaction conditions are that the pressure is 0.02 ~ 0.1.1 MPa, the temperature is 300 ~ 500 ℃, the operation flow of the outlet of the reactor is 10-30 kg/h, and the volume of the reactor is 500-1000L.

Preferably, the fluorosilicone is removed and polymerization inhibition is controlled in the second adsorption section by using a fluorinated resin, and the fluorinated resin is prepared by coating metal fluoride on the surface of the resin.

Preferably, the metal fluoride is one of silver fluoride, cobalt fluoride, manganese fluoride, lead fluoride, aluminum fluoride, copper fluoride or magnesium fluoride, and the metal fluoride loading rate is 1 ~ 5 mmol/g.

Preferably, the resin is porous polystyrene cross-linked resin with the specific surface area of 300 ~ 600m²/g。

Preferably, the rectification section comprises a heavy component removal tower and a light component removal tower, the feeding amount of the heavy component removal tower is 2 ~ 50kg/h, the tower pressure is 0.1 ~ 3.0.0 MPa, the tower top temperature is-80 ~ -10 ℃, the tower bottom temperature is-70 ~ -5 ℃, the feeding amount of the light component removal tower is 2 ~ 50kg/h, the tower pressure is 0.1 ~ 4.0.0 MPa, the tower top temperature is-80 ~ 5 ℃, and the tower bottom temperature is-70 ~ 15 ℃.

Preferably, the complex rectification section adopts a volume ratio of 4: 3: 3, extracting and rectifying the cyclohexane, the hexachlorobenzene and the m-phenylenediamine as extracting agents.

Preferably, the complex rectification section comprises three removal towers connected in series, wherein the feeding amount of the removal towers is 2 ~ 50kg/h, the tower pressure is 0.2 ~ 4.0.0 MPa, the tower top temperature is-80 ~ 5 ℃, and the tower bottom temperature is-70 ~ 15 ℃.

Preferably, the S1 step is to vacuumize the fluorosilicate while heating at 100 ~ 200 deg.C.

The method for synthesizing and purifying the high-purity silicon tetrafluoride has the beneficial effects that:

(1) a negative pressure process is adopted in the cracking reaction, when silicon tetrafluoride is produced, the silicon tetrafluoride can be pumped away quickly, and the conversion rate and selectivity of cracking are improved.

(2) The adsorption unit is adopted to remove the fluorosilicone ether, and the polymerization problem of the fluorosilicone ether is solved through the polymerization inhibitor.

(3) Aiming at the difficulty in removing the azeotrope, a complex rectification process system is added after the conventional rectification unit is adopted for operation.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The synthesis and purification method of high purity silicon tetrafluoride according to the embodiment of the present invention will be described in detail below.

The embodiment of the invention provides a method for synthesizing and purifying high-purity silicon tetrafluoride, which comprises the following steps:

and step S1: pre-treating fluosilicate;

further, in the preferred embodiment of the invention, the fluorosilicate is vacuumized and heated at 100 ~ 200 ℃, the moisture in the fluorosilicate can be effectively removed through the vacuumization and the heating, and the normal operation of the cracking reaction is ensured by removing the moisture and the oxygen in the air.

And step S2: carrying out cracking reaction on fluorosilicate to prepare a silicon tetrafluoride coarse material; the crude silicon tetrafluoride material with complex components, including light components and heavy component impurities, is obtained by cracking. Wherein the light component impurities comprise H₂、CO、CO₂、O₂、SiF₃H、SiF₂H、SiFH₃、SiH₄And the like. Heavy component impurities including HF, Si₂F₆O、Si₂F₆、Si₃F₈、SiF₃Cl、SiF₂Cl₂And the like.

Furthermore, in the preferred embodiment of the present invention, the cracking reaction conditions are 0.02 ~ 0.1.1 MPa, 300 ~ 500 ℃, 10-30 kg/h of reactor outlet operation flow rate, and 500-1000L of reactor volume, and the cracking reaction is a gap operation, under which better cracking can be achieved.

And step S3: removing trace moisture and acid gas in a first adsorption section; trace moisture and acid gas are removed through the first adsorption section, and pure products are obtained subsequently.

And step S4: performing desorption and polymerization inhibition control on the fluorosilicone at a second adsorption section;

further, in the preferred embodiment of the present invention, the fluorosilicone is removed and polymerization inhibition is controlled in the second adsorption section by using a fluorinated resin prepared by coating a metal fluoride on the surface of the resin. In the production and purification of high-purity electronic grade silicon tetrafluoride, fluorosilicone ether impurities are easily generated, and the impurities can be even repolymerized with silicon tetrafluoride to generate fluorosilicone ether high polymer. The fluorosilicone polymer can be rapidly aggregated into particles from the colloid, so that the pipeline and the adsorbent are easily blocked, and safety accidents occur, thereby having an important effect on the removal and polymerization inhibition control of the fluorosilicone.

Further, in the preferred embodiment of the present invention, the metal fluoride is one of silver fluoride, cobalt fluoride, manganese fluoride, lead fluoride, aluminum fluoride, copper fluoride or magnesium fluoride, and the loading rate of the metal fluoride is 1 ~ 5 mmol/g.

Further, in the preferred embodiment of the present invention, the resin is a porous cross-linked polystyrene resin with a specific surface area of 300 ~ 600m²(ii) in terms of/g. The adoption of a larger specific surface area can not only increase the loading capacity of the metal fluoride, but also improve the adsorption effect.

And step S5: separating light components and heavy components in a rectification section; the crude silicon tetrafluoride material prepared by the cracking, the first adsorption section and the second adsorption section comprises light components and heavy component impurities. Wherein the light component impurities comprise H₂、CO、CO₂、O₂、SiF₃H、SiF₂H、SiFH₃、SiH₄And the like. Heavy component impurities including HF, Si₂F₆O、Si₂F₆、Si₃F₈、SiF₃Cl、SiF₂Cl₂And the like. Light component impurities and heavy component impurities which can not form the azeotrope are respectively separated by using a common rectification method in a rectification section.

Further, in the preferred embodiment of the invention, the rectification section comprises a heavy component removal tower and a light component removal tower, the feeding amount of the heavy component removal tower is 2 ~ 50kg/h, the tower pressure is 0.1 ~ 3.0.0 MPa, the tower top temperature is-80 ~ -10 ℃, the tower bottom temperature is-70 ~ -5 ℃, the feeding amount of the light component removal tower is 2 ~ 50kg/h, the tower pressure is 0.1 ~ 4.0.0 MPa, the tower top temperature is-80 ~ 5 ℃, and the tower bottom temperature is-70 ~ 15 ℃, so that most of heavy component and light component impurities can be separated by the heavy component removal tower and the light component removal tower.

And step S6: and separating the azeotropic substance impurities through a complicated rectification working section. After the rectification working section, the composition of the azeotropic substance is SiF₄、SiF₃H、SiF₂H₂、SiFH₃、SiF₃Cl and SiF₂Cl₂. These substances have different boiling points but become azeotropic substances. The separation can not be carried out by adopting the conventional rectification, and the separation is carried out by adopting the complex rectification.

Further, in the preferred embodiment of the present invention, the complex rectification section employs a volume ratio of 4: 3: 3, extracting and rectifying the cyclohexane, the hexachlorobenzene and the m-phenylenediamine as extracting agents. The extractant can separate the azeotrope.

Further, in the preferred embodiment of the invention, the complex rectification section comprises three removal towers connected in series, the feeding amount of the removal towers is 2 ~ 50kg/h, the tower pressure is 0.2 ~ 4.0.0 MPa, the tower top temperature is-80 ~ 5 ℃, and the tower bottom temperature is-70 ~ 15 ℃, so that the purity of the product can be effectively improved through the series work of the three removal towers.

The features and properties of the present invention are described in further detail below with reference to examples.