CN103708470B - SiF 4preparation method - Google Patents

Abstract

The invention relates to the field of chemical engineering, in particular to a method for preparing SiF ₄ . The preparation method of SiF ₄ comprises the following steps: mixing silicon-containing mineral raw materials or silicon-containing metal oxides with fluoride to obtain a mixture; reacting the mixture to obtain gaseous SiF ₄ . The preparation method of SiF ₄ provided by the present invention is much cheaper than traditional raw materials (concentrated sulfuric acid and fluorite powder or anhydrous hydrofluoric acid), thereby reducing the preparation cost of SiF ₄ .

Description

The preparation method of SiF4

technical field

The invention relates to the field of chemical engineering, in particular to a method for preparing SiF ₄ .

Background technique

Silicon tetrafluoride (SiF ₄ ) is an important basic chemical product. SiF ₄ can be used as etchant for silicon nitride and tantalum silicide, P-type dopant, epitaxial deposition diffusion silicon source, etc. It can also be used to prepare electronic grade silane or silicon. SiF ₄ is a synthetic material of organosilicon compounds, used in the manufacture of fluorosilicic acid and silicon fluoride, as a hardener for cement and artificial marble, and also used in plasma etching, solar cells, copier photosensitive cylinders, amorphous silicon film formation and chemical vapor deposition, etc. SiF ₄ is also the raw material of high-purity quartz glass for optical fiber. In addition, SiF ₄ is also widely used in the preparation of fluorosilicic acid and aluminum fluoride, chemical analysis, fluorinating agent, oil well drilling, magnesium alloy casting, catalyst, fumigant, hardener for cement and artificial marble, etc. Therefore, SiF ₄ has a large market demand space.

_In related technology, the preparation of SiF mainly has following methods: sulfuric acid method and hydrofluoric acid method; Concentrated sulfuric acid reacts to prepare silicon tetrafluoride; hydrofluoric acid method is to prepare silicon tetrafluoride by mixing silicon powder and anhydrous hydrofluoric acid under high temperature conditions.

However, in the above two methods, the first method needs to consume a large amount of concentrated sulfuric acid and fluorite powder; the price of anhydrous hydrofluoric acid used in the second method is high; therefore, in the related art, the preparation of SiF ₄ The method has the disadvantage of high cost.

Contents of the invention

The object of the present invention is to provide a kind of preparation method of SiF ₄ , to solve above-mentioned problem.

_A kind of SiF4 preparation method is provided in the embodiment of the present invention, comprises the following steps:

Mixing silicon-containing mineral raw materials or silicon-containing metal oxides with fluoride to obtain a mixture;

The mixture is reacted to obtain gaseous SiF4 _.

The preparation method of the SiF ₄ provided by the present invention is to obtain gaseous SiF ₄ by reacting a mixture of silicon-containing mineral raw materials or silicon-containing metal oxides and fluorides.

In the process of preparing SiF ₄ in this method, the raw materials used are silicon-containing mineral raw materials or silicon-containing metal oxides and fluorides, and the raw materials are cheaper than traditional raw materials (concentrated sulfuric acid and fluorite powder or anhydrous hydrofluoric acid) Many, thereby reducing the preparation cost of SiF ₄ .

Description of drawings

Fig. ₁ shows the flow chart of the preparation method of SiF that the embodiment of the present invention 1 provides;

Fig. ₂ shows the flow chart of the preparation method of SiF that the embodiment of the present invention 2 provides;

Fig. 3 shows the flow chart of the preparation method of SiF ₄ provided by the embodiment of the present invention 3;

Fig. ₄ shows the flow chart of the preparation method of SiF provided by the embodiment of the present invention 4;

Fig. 5 shows a flowchart of the preparation method of SiF ₄ provided by Example 5 of the present invention.

detailed description

The present invention will be described in further detail below through specific implementation examples and in conjunction with the accompanying drawings.

A kind of SiF provided by the invention _The preparation method comprises the following steps:

Step 101: mixing silicon-containing mineral raw materials or silicon-containing metal oxides with fluoride to obtain a mixture;

After the silicon-containing mineral raw material or silicon-containing metal oxide is mixed with the fluoride, a mixture to be reacted is obtained for subsequent preparation operations.

Step 102: reacting the mixture to obtain gaseous SiF ₄ ;

After the mixture is obtained, gaseous SiF ₄ is obtained by reacting the mixture.

In the process of preparing SiF ₄ in this method, the raw materials used are silicon-containing mineral raw materials or silicon-containing metal oxides and fluorides, and the raw materials are cheaper than traditional raw materials (concentrated sulfuric acid and fluorite powder or anhydrous hydrofluoric acid) Many, thereby reducing the preparation cost of SiF ₄ .

In addition, the method for preparing SiF ₄ provided by the present invention has fewer process steps and simple operation, and mixed oxides can also be obtained during the reaction process, thereby increasing the added value in the preparation process.

In order to make the preparation method of SiF ₄ in Example 1 of the present invention be better applied and more effectively applied to the process of preparing high-purity SiF ₄ , all the above-mentioned processes can also be carried out in accordance with the following steps, which are now described in detail Elaboration and explanation:

Step 201: mixing silicon-containing mineral raw materials or silicon-containing metal oxides with fluoride to obtain a mixture;

In step 201, in order to facilitate the mixing operation, the silicon-containing mineral raw materials or silicon-containing metal oxides are in the form of granules or powders. Generally speaking, the silicon-containing mineral raw materials include bauxite, fly ash, iron ore or Silicon-containing oxides; silicon-containing metal oxides include granular SiO ₂ with a particle size of 95-500 mesh; the above-mentioned types of substances have high silicon content, which in turn is beneficial to increase the production of SiF ₄ . In addition, in order to facilitate the reaction process, the fluoride in the above embodiments may preferably be: HF solution with a mass concentration of 25-40%, NH ₄ F, NH ₄ HF ₂ , CaF ₂ , NaF or AlF ₃ .

And in order to make the above-mentioned mixture of silicon-containing mineral raw materials or silicon-containing metal oxides and fluorides react as completely as possible, preferably, the weight percentage of fluorides in the mixture is 20%-80%.

In addition, the above-mentioned silicon-containing mineral raw materials or silicon-containing metal oxides and fluorides can be mixed as uniformly as possible when forming a mixture; preferably, the particle size of the silicon-containing mineral raw materials is less than 7 mm; NH ₄ F, NH ₄ HF _2. The particle size of CaF ₂ , NaF or AlF ₃ is less than 7mm.

Step 202: reacting the mixture to obtain gaseous SiF ₄ ;

In the process of reacting the mixture, preferably, when the fluoride includes NH ₄ F, NH ₄ HF ₂ , CaF ₂ , NaF or AlF ₃ , the specific steps of the reaction can be: put the mixture at a high temperature of 600°C-1300°C Calcining for 3 hours to 15 hours, to obtain gaseous SiF ₄ ; by calcination at high temperature, the mixture is easy to react, and calcining in the above-mentioned predetermined temperature range for a predetermined time will fully react and form a large amount of gaseous SiF ₄ . At the same time, preferably, in the process of reacting the mixture, the reaction is selected in an air atmosphere, and the mixture is reacted in an air atmosphere, which is beneficial to increase the output of gaseous SiF ₄ .

In addition, when the fluoride includes HF solution with a mass concentration of 25-40%, the specific steps of the reaction can be: react the mixture at 100°C-200°C for 3 hours-15 hours to obtain gaseous SiF ₄ with a mass concentration of 25-40%. 40% HF solution can fully react with silicon-containing mineral raw materials or silicon-containing metal oxides at 100°C-200°C to form gaseous SiF ₄ .

In this embodiment, during the reaction process of silicon-containing mineral raw materials or silicon-containing metal oxides and fluorides, the chemical reactions that occur are as follows:

M _x O _y nSiO ₂ +AF _z →M _x O _y +A ₂ O _z +SiF ₄ ↑

In addition, in this embodiment, in order to obtain high-purity SiF ₄ , after the step of reacting the mixture to obtain gaseous SiF ₄ , it also includes: gas-liquid separation, concentrated sulfuric acid drying, molecular sieve adsorption and condensation purification of gaseous SiF 4 Finally, SiF ₄ gas with a purity of 99%-99.9% is obtained.

In addition, on the basis of the above steps, the present invention also provides the following specific embodiments: Please refer to Figure 1-Figure 5:

Example 1: Preparation of high-purity SiF ₄ with fly ash and NH ₄ F as raw materials

Step 301: uniformly mixing fly ash (Al ₂ O ₃ ·nSiO ₂ ) and NH ₄ F with particle sizes less than 7mm to obtain a mixture;

Wherein, NH ₄ F accounts for 30% by weight of the mixture;

Step 302: calcining the mixture at a high temperature of 600° C. for 3 hours to obtain gaseous SiF ₄ ;

Step 303: Purify the gaseous SiF ₄ through gas-liquid separation, drying with concentrated sulfuric acid, molecular sieve adsorption and condensation to obtain SiF ₄ gas with a purity of 99.0%.

In this example, the chemical reaction that takes place is as follows:

SiO ₂ +4NH ₄ F→SiF ₄ ↑+4NH ₃ ↑+2H ₂ O

Embodiment 2: take coarse particle SiO ₂ and CaF ₂ as raw material to prepare high-purity SiF ₄

Step 401: uniformly mixing granular SiO ₂ with a particle size of 95-500 mesh and CaF ₂ with a particle size of less than 7 mm to obtain a mixture;

Wherein, CaF _The weight percent that accounts for mixture is 40%;

Step 402: calcining the mixture at a high temperature of 1100° C. for 2 hours to obtain gaseous SiF ₄ ;

Step 403: Purify the gaseous SiF ₄ through gas-liquid separation, drying with concentrated sulfuric acid, molecular sieve adsorption and condensation to obtain SiF ₄ gas with a purity of 99.9%.

In this example, the chemical reaction that takes place is as follows:

SiO ₂ +2CaF ₂ →SiF ₄ ↑+2CaO

Example 3: Preparation of high-purity SiF ₄ using bauxite (Al ₂ O ₃ ·mTiO ₂ ·nSiO ₂ ) and AlF ₃ as raw materials

Step 501: uniformly mixing bauxite (Al ₂ O ₃ ·mTiO ₂ ·nSiO ₂ ) with a particle size of less than 7mm and AlF ₃ to obtain a mixture;

Wherein, AlF _The weight percent that accounts for mixture is 50%;

Step 502: calcining the mixture at a high temperature of 1300° C. for 15 hours to obtain gaseous SiF ₄ ;

Step 503: Purify the gaseous SiF ₄ through gas-liquid separation, drying with concentrated sulfuric acid, molecular sieve adsorption and condensation to obtain SiF ₄ gas with a purity of 99.9%.

In this example, the chemical reaction that takes place is as follows:

3SiO ₂ +4AlF ₃ 3H ₂ O→2Al ₂ O ₃ +3SiF ₄ ↑+12H ₂ O

Example 4: Preparation of high-purity SiF ₄ using coarse-grained SiO ₂ and NH ₄ HF ₂ as raw materials

Step 601: uniformly mixing coarse-grained SiO ₂ with particle sizes less than 7 mm and NH ₄ HF ₂ to obtain a mixture;

Wherein, NH HF ₂ accounts for 60% by weight of the mixture _;

Step 602: calcining the mixture at a high temperature of 700° C. for 5 hours to obtain gaseous SiF ₄ ;

Step 603: Purify the gaseous SiF ₄ through gas-liquid separation, drying with concentrated sulfuric acid, molecular sieve adsorption and condensation to obtain SiF ₄ gas with a purity of 99.3%.

In this example, the chemical reaction that takes place is as follows:

SiO ₂ +2NH ₄ HF ₂ →SiF ₄ ↑+2NH ₃ ↑+2H ₂ O

Example 5: Preparation of high-purity SiF ₄ with iron ore and NaF as raw materials

Step 701: uniformly mixing iron ore with a particle size less than 7 mm and NaF to obtain a mixture;

Wherein, NaF accounts for the weight percentage of mixture and is 40%;

Step 702: calcining the mixture at a high temperature of 900° C. for 5 hours to obtain gaseous SiF ₄ ;

Step 703: Purify the gaseous SiF ₄ through gas-liquid separation, drying with concentrated sulfuric acid, molecular sieve adsorption and condensation to obtain SiF ₄ gas with a purity of 99.5%.

SiO ₂ +4NaF+2H ₂ O→SiF ₄ ↑+4NaOH

In all the above _- mentioned embodiments, the steps to obtain SiF gas with a purity of 99%-99.9% after gas _- liquid separation, concentrated sulfuric acid drying, molecular sieve adsorption and condensation purification are as follows:

S1: Separating gaseous SiF ₄ from gas and liquid and drying concentrated sulfuric acid in sequence to obtain gaseous SiF ₄ with water vapor and/or ammonia removed;

Through gas-liquid separation and concentrated sulfuric acid drying, the water vapor or ammonia generated in the entire reaction system can be removed, and then the gaseous SiF ₄ with water vapor and/or ammonia removed can be obtained;

S2: Adsorb the gaseous SiF ₄ that removes water vapor or ammonia through molecular sieves to obtain gaseous SiF ₄ that removes particulate impurities and acid gases;

Molecular sieve adsorption can remove the acid gas contained in the gaseous SiF ₄ and the particulate impurities mixed in the reaction system;

S3: Low-temperature condensation of the gaseous SiF ₄ that removes particulate impurities and acid gases to obtain a SiF ₄ liquid with a purity of 99%-99.9%;

Specifically, the temperature of cryogenic condensation is preferably: -70°C - 60°C, SiF ₄ gas will be transformed into liquid at this temperature, and the gas that has not been completely removed in the previous operation still exists in the form of gaseous phase at this temperature , SiF ₄ liquid with a purity of 99%-99.9% can be easily obtained through low-temperature condensation operation.

S4: vaporize the SiF ₄ liquid to obtain a SiF ₄ gas with a purity of 99%-99.9%.

By gasifying the obtained SiF ₄ liquid, and then obtaining SiF ₄ gas with a purity of 99%-99.9%, the preparation of high-purity SiF ₄ gas is realized.

In addition, in the above steps, the used concentrated sulfuric acid can be recycled, for example, the concentrated sulfuric acid containing hydrogen fluoride can be distilled in an evaporator, and then concentrated to the required concentration for further purification.

Table 1 shows the above-mentioned five embodiments in the preparation of SiF gas Parameters and the data of each embodiment yield in the process of gas, please refer to Table ₁ :

The data comparison table of each embodiment of table 1

It can be seen from Table 1 that the method for preparing SiF ₄ provided by the embodiments of the present invention has effects such as low cost, high quality, high yield, and high purity.

To sum up, the method for preparing SiF ₄ provided by the present invention has the effects of less process steps, simple operation and low cost. And by controlling the gaseous SiF ₄ through gas-liquid separation, concentrated sulfuric acid drying, molecular sieve adsorption and condensation purification to obtain SiF ₄ gas with a purity of 99%-99.9%, and all the above operations can be realized through existing equipment .

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. a SiF ₄preparation method, it is characterized in that, comprise the following steps:

Siliceous mineral raw material or siliceous metal oxide are mixed with fluorochemical, obtains mixture;

Described fluorochemical comprises NH ₄f, NH ₄hF ₂, CaF ₂, NaF or AlF ₃;

Reacted by described mixture, described mixture, 600 DEG C of-1300 DEG C of high-temperature calcinations 3 hours-15 hours, obtains gaseous state SiF ₄;

By described gaseous state SiF ₄the SiF that purity is 99%-99.9% is obtained after being purified by gas-liquid separation, vitriol oil drying, molecular sieve adsorption and condensation ₄gas.

2. SiF according to claim 1 ₄preparation method, it is characterized in that, described, siliceous mineral raw material is mixed with fluorochemical, obtain in the step of mixture:

The weight percentage that described fluorochemical accounts for described mixture is 20%-80%.

3. SiF according to claim 2 ₄preparation method, it is characterized in that, described siliceous mineral raw material comprises bauxitic clay, flyash, iron ore or oxide containing silicon;

It is 95-500 object particulate state SiO that described siliceous metal oxide comprises particle diameter ₂.

4. SiF according to claim 3 ₄preparation method, it is characterized in that, described siliceous mineral raw material is the particle or Powdered that particle diameter is less than 7 millimeters;

Described NH ₄f, NH ₄hF ₂, CaF ₂, NaF or AlF ₃particle diameter be all less than 7 millimeters.

5. the SiF according to any one of claim 1-4 ₄preparation method, it is characterized in that, described by described gaseous state SiF ₄the SiF that purity is 99%-99.9% is obtained after being purified by gas-liquid separation, vitriol oil drying, molecular sieve adsorption and condensation ₄step in, specifically comprise:

By described gaseous state SiF ₄carry out gas-liquid separation and vitriol oil drying successively, obtain the gaseous state SiF removing water vapour and/or ammonia ₄;

By the gaseous state SiF of described removal water vapour or ammonia ₄by molecular sieve adsorption, obtain the gaseous state SiF removing granule foreign and sour gas ₄;

By the gaseous state SiF of described removal granule foreign and sour gas ₄carry out cryogenic condensation, obtain the SiF that purity is 99%-99.9% ₄liquid;

By described SiF ₄liquid gasification, obtains the SiF that purity is 99%-99.9% ₄gas.

6. SiF according to claim 5 ₄preparation method, it is characterized in that, the temperature of described cryogenic condensation is-70 DEG C--60 DEG C.