Preparation method of high-purity silicon tetrafluoride

Abstract

The invention relates to the technical field of fluoride preparation, in particular to a preparation method of high-purity silicon tetrafluoride, which comprises the following steps: step 1, preparing a fluosilicic acid solution and magnesium oxide, and carrying out mixed reaction on the fluosilicic acid solution and the magnesium oxide; 2, reacting to generate a magnesium fluosilicate solution, and crystallizing the solution; step 3, carrying out dehydration treatment on the crystallized crystal; step 4, calcining the dehydrated crystal; and 5, purifying the silicon tetrafluoride gas obtained by calcining, and collecting the purified silicon tetrafluoride gas. The preparation method comprises the following steps: mixing a fluosilicic acid solution and magnesium oxide for reaction to generate a magnesium fluosilicate solution, crystallizing the solution, dehydrating crystallized crystals, removing attached water and crystal water, centrifugally separating to obtain dry magnesium fluosilicate crystals, and properly calcining the magnesium fluosilicate crystals to obtain the magnesium fluosilicate. And the silicon tetrafluoride gas is purified and then collected, so that high-purity silicon tetrafluoride is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of fluoride preparation, in particular to a method for preparing high-purity silicon tetrafluoride. Background Art

[0002] Silicon fluoride is widely used in the electronics and semiconductor industries. It is an important raw material for the preparation of silane, crystalline silicon, optical fiber, etc. It can also be used to prepare cement and marble hardeners, etc. It has broad application prospects in the microelectronics industry, especially silicon tetrafluoride, which is mainly used as a material for the production of polysilicon and then wafers.

[0003] Currently, silicon tetrafluoride is mostly prepared by mixing multiple substances, which has a complex composition. The produced silicon tetrafluoride gas contains more impurities, which affects the purity of silicon tetrafluoride. Therefore, it is necessary to provide a method for preparing high-purity silicon tetrafluoride. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a method for preparing high-purity silicon tetrafluoride, which has the advantages of high purity and less impurities, and solves the above-mentioned problems.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing high-purity silicon tetrafluoride comprises the following steps:

[0009] Step 1: prepare a fluorosilicic acid solution and magnesium oxide, and mix them for reaction;

[0010] Step 2: reacting to generate a magnesium fluorosilicate solution, and subjecting the solution to a crystallization treatment;

[0011] Step 3: Dehydrating the crystals after crystallization;

[0012] Step 4: calcining the dehydrated crystals;

[0013] Step 5: The silicon tetrafluoride gas obtained by calcination is collected after purification.

[0014] Preferably, in the step 1, the fluorosilicic acid solution and magnesium oxide are pre-proportioned and reacted for 10-60 minutes. After the two react, they are filtered to obtain a magnesium fluorosilicate solution, and then the solution is concentrated and crystallized to obtain magnesium fluorosilicate crystals. This step utilizes the chemical reaction characteristics of fluorosilicic acid and magnesium oxide to react them to generate magnesium fluorosilicate, and then converts it into a crystalline form by concentration and crystallization for subsequent operations.

[0015] Preferably, the crystallization treatment of the magnesium fluorosilicate solution in step 2 comprises the following steps:

[0016] S1. The filtered magnesium fluorosilicate solution is injected into a vacuum concentration system;

[0017] S2. In a cooling crystallization tank, the concentrated solution is cooled and crystallized, and then filtered to obtain magnesium fluorosilicate crystals. The filtrate obtained by filtration is returned to prepare a saturated magnesium fluorosilicate solution.

[0018] Preferably, the magnesium fluorosilicate crystals obtained in step 3 are agitated with an air flow at 25 to 55° C. for 1 to 3 hours to remove attached water and crystal water.

[0019] Preferably, the magnesium fluorosilicate crystals are freed of attached water and crystal water and then centrifuged to obtain dry magnesium fluorosilicate crystals.

[0020] Preferably, the calcination process in step 4 is divided into three stages: S1. slowly heating to 200° C. to completely dry the magnesium fluorosilicate;

[0021] S2. Continue to heat up to 300°C and start to produce silicon tetrafluoride;

[0022] S3. Finally, the temperature is raised to 500°C, at which point magnesium fluorosilicate undergoes intense thermal decomposition to generate silicon tetrafluoride.

[0023] Preferably, the silicon tetrafluoride gas obtained in step five is collected by a receiver inserted into liquid nitrogen, the first receiver is placed in dry ice acetone to receive the generated impurities such as fluorosilicic acid and hydrogen fluoride, and the second receiver is inserted into liquid nitrogen to receive pure silicon tetrafluoride gas. The collected silicon tetrafluoride gas needs to be further purified to ensure that its purity reaches more than 98%.

[0024] (III) Beneficial effects

[0025] Compared with the prior art, the present invention provides a method for preparing high-purity silicon tetrafluoride, which has the following beneficial effects:

[0026] 1. The present invention performs a mixed reaction of a fluorosilicic acid solution and magnesium oxide to generate a magnesium fluorosilicate solution, and performs a crystallization treatment on the solution. The crystals after crystallization are dehydrated to remove attached water and crystallization water, and dried magnesium fluorosilicate crystals are obtained by centrifugal separation. Silicon tetrafluoride gas is generated by appropriately calcining the silicon tetrafluoride gas, which is collected after purification to obtain high-purity silicon tetrafluoride.

[0027] 2. In the present invention, silicon tetrafluoride gas is collected by a receiver inserted into liquid nitrogen. The first receiver is placed in dry ice acetone to receive the generated impurities such as fluorosilicic acid and hydrogen fluoride. The second receiver is inserted into liquid nitrogen to receive pure silicon tetrafluoride gas. The collected silicon tetrafluoride gas needs to be further purified to ensure that its purity reaches more than 98%. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention relates to a method for preparing high-purity silicon tetrafluoride, comprising the following steps:

[0030] Step 1: prepare a fluorosilicic acid solution and magnesium oxide, and mix them for reaction;

[0031] Fluorosilicic acid solution and magnesium oxide are reacted for 10-60 minutes according to a pre-proportioned mixture. After the two react, the magnesium fluorosilicate solution is filtered to obtain a magnesium fluorosilicate solution, and then the solution is concentrated and crystallized to obtain magnesium fluorosilicate crystals. This step utilizes the chemical reaction characteristics of fluosilicic acid and magnesium oxide to react to generate magnesium fluorosilicate, and then converts it into a crystalline form by concentrated crystallization for subsequent operations;

[0032] Step 2: reacting to generate a magnesium fluorosilicate solution, and subjecting the solution to a crystallization treatment;

[0033] The crystallization process of magnesium fluorosilicate solution comprises the following steps:

[0034] S1. The filtered magnesium fluorosilicate solution is injected into a vacuum concentration system;

[0035] S2. In a cooling crystallization tank, the concentrated solution is cooled and crystallized, and then filtered to obtain magnesium fluorosilicate crystals, and the filtrate obtained by filtration is returned for the preparation of a saturated solution of magnesium fluorosilicate;

[0036] Step 3: Dehydrating the crystals after crystallization;

[0037] The obtained magnesium fluorosilicate crystals are agitated with an air flow at 25 to 55° C. for 1 to 3 hours to remove attached water and crystal water, and dried magnesium fluorosilicate crystals are obtained by centrifugal separation;

[0038] Step 4: calcining the dehydrated crystals;

[0039] The calcination process is divided into three stages: S1. Slowly raise the temperature to 200°C to completely dry the magnesium fluorosilicate;

[0040] S2. Continue to heat up to 300°C and start to produce silicon tetrafluoride;

[0041] S3. Finally, the temperature is raised to 500°C, at which time magnesium fluorosilicate undergoes intense thermal decomposition to generate silicon tetrafluoride;

[0042] During the entire calcination process, temperature control is crucial. Too high a temperature may lead to side reactions, while too low a temperature may not completely decompose magnesium fluorosilicate.

[0043] Step 5: The silicon tetrafluoride gas obtained by calcination is collected after purification;

[0044] The silicon tetrafluoride gas obtained in step five is collected by inserting a receiver into liquid nitrogen. The first receiver is placed in dry ice acetone to receive the generated impurities such as fluorosilicic acid and hydrogen fluoride. The second receiver is inserted into liquid nitrogen to receive pure silicon tetrafluoride gas. The collected silicon tetrafluoride gas needs to be further purified to ensure that its purity reaches more than 98%. Silicon tetrafluoride is a toxic gas. Safety protection should be paid attention to during operation to avoid leakage and inhalation.

[0045] The beneficial effects of the present invention are as follows: the present invention performs a mixed reaction of a fluorosilicic acid solution and magnesium oxide to generate a magnesium fluorosilicate solution, and then concentrates and crystallizes the solution to obtain magnesium fluorosilicate crystals. This step utilizes the chemical reaction characteristics of fluorosilicic acid and magnesium oxide to react to generate magnesium fluorosilicate, and then converts the magnesium fluorosilicate into a crystalline form by means of concentration and crystallization for subsequent operation. The crystals after crystallization are dehydrated to remove attached water and crystallization water, and dried magnesium fluorosilicate crystals are obtained by centrifugal separation. Silicon tetrafluoride gas is generated by appropriately calcining the silicon tetrafluoride gas, and the silicon tetrafluoride gas is collected after purification to obtain high-purity silicon tetrafluoride.

[0046] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-purity silicon tetrafluoride, characterized in that: The following steps are involved: Step 1: prepare a fluorosilicic acid solution and magnesium oxide, and mix them for reaction; Step 2: reacting to generate a magnesium fluorosilicate solution, and subjecting the solution to a crystallization treatment; Step 3: Dehydrating the crystals after crystallization; Step 4: calcining the dehydrated crystals; Step 5: The silicon tetrafluoride gas obtained by calcination is collected after purification.

2. A method for preparing high-purity silicon tetrafluoride according to claim 1, characterized in that: In the step 1, the fluorosilicic acid solution and magnesium oxide are mixed according to a pre-proportion and reacted for 10-60 minutes. After the two react, they are filtered to obtain a magnesium fluorosilicate solution.

3. A method for preparing high-purity silicon tetrafluoride according to claim 1, characterized in that: The crystallization treatment of the magnesium fluorosilicate solution in step 2 comprises the following steps: S1. The filtered magnesium fluorosilicate solution is pumped into a vacuum concentration system; S2. In a cooling crystallization tank, the concentrated solution is cooled and crystallized, and then filtered to obtain magnesium fluorosilicate crystals.

4. The method for preparing high-purity silicon tetrafluoride according to claim 1, characterized in that: In the step 3, the obtained magnesium fluorosilicate crystals are agitated with an air flow at 25 to 55° C. for 1 to 3 hours to remove attached water and crystal water.

5. A method for preparing high-purity silicon tetrafluoride according to claim 4, characterized in that: The magnesium fluorosilicate crystals are freed of attached water and crystal water and then centrifuged to obtain dry magnesium fluorosilicate crystals.

6. A method for preparing high-purity silicon tetrafluoride according to claim 1, characterized in that: The calcination process in step 4 is divided into three stages: S1. slowly heating to 200° C. to completely dry the magnesium fluorosilicate; S2. Continue to heat up to 300°C and start to produce silicon tetrafluoride; S3. Finally, the temperature is raised to 500°C, at which point magnesium fluorosilicate undergoes intense thermal decomposition to generate silicon tetrafluoride.

7. The method for preparing high-purity silicon tetrafluoride according to claim 1, characterized in that: The silicon tetrafluoride gas obtained in step five is collected by a receiver inserted into liquid nitrogen, the first receiver is placed in dry ice acetone to receive the generated impurities such as fluorosilicic acid and hydrogen fluoride, and the second receiver is inserted into liquid nitrogen to receive pure silicon tetrafluoride gas.