CN106379902A - Preparation method of ultra-high-purity silicon tetrachloride - Google Patents

Abstract

The invention discloses a preparation method of ultra-high-purity silicon tetrachloride. The preparation method comprises the following steps: S1, continuously feeding high-purity silicon tetrachloride into the photochemical reactor under the action of nitrogen; S2, continuously feeding chlorine gas into the photochemical reactor under the condition of ultraviolet light to make the high-purity silicon tetrachloride The hydrogen-containing impurities in silicon chloride react with chlorine to obtain primary products; S3, the primary products are passed into the stripping tower from the upper part of the stripping tower, and nitrogen gas is fed from the bottom of the stripping tower to remove The unreacted chlorine in the primary product is obtained as a secondary product; and S4, the secondary product is sent to a silicon tetrachloride purification tower, and ultra-high-purity silicon tetrachloride is obtained after continuous light removal and weight removal. The optical fiber silicon tetrachloride prepared by this method has a purity of over 99.9999999%, and the infrared transmission index of related groups meets or even exceeds the high-purity silicon tetrachloride index of Merk Company, and meets the quality requirements of ultra-high-purity silicon tetrachloride .

Description

Preparation method of ultra-high purity silicon tetrachloride

technical field

The invention relates to the technical field of electronic materials, in particular to a method for preparing ultra-high-purity silicon tetrachloride.

Background technique

In the polysilicon production process, a large amount of silicon tetrachloride will be produced as a by-product, which can be used to prepare trichlorosilane and return to the polysilicon system, and can also be used to prepare many high value-added silicon industry chain products, such as fumed silica, optical fiber Preform and ethyl silicate, etc., among which fiber-grade silicon tetrachloride is one of the important raw materials for optical fiber preform.

With the launch of "fiber-to-copper" and "fiber-to-the-home" projects, triple play integration and 3G network construction projects, my country has become the world's most important optical fiber and cable market and the world's largest optical fiber and cable manufacturing country. However, the high-purity silicon tetrachloride used to prepare optical fiber preforms is heavily dependent on imports, which greatly restricts the development of my country's optical communication industry by foreign countries. The realization of its large-scale production will help solve the bottleneck problem of my country's optical communication industry.

The production process of optical fiber preform is divided into external deposition method and internal deposition method. According to different production processes, fiber-grade silicon tetrachloride can be divided into high-purity silicon tetrachloride (purity above 6N, that is, above 99.9999%) and ultra-high Pure silicon tetrachloride (purity 9N ~ 13N, that is, 99.9999999% ~ 99.99999999999%), the quality index of high-purity silicon tetrachloride products can be easily achieved through rectification purification or adsorption, and the product can be used for the preparation of optical fibers by extra-tube deposition Preform, while ultra-high-purity silicon tetrachloride has high quality requirements, and its separation difficulty lies in trace hydrogen-containing impurities. The product can be used in the preparation of optical fiber preforms by in-tube deposition and in the semiconductor industry. Table 1 shows some hydrogen-containing impurities in silicon tetrachloride and their boiling points. It can be found that the boiling points of hydrogen-containing impurities and silicon tetrachloride are very close, and it is difficult to remove hydrogen-containing impurities by conventional rectification processes.

Table 1 Boiling point table of silicon tetrachloride and some hydrogen-containing impurities

Contents of the invention

The invention aims to provide a method for preparing ultra-high-purity silicon tetrachloride, which is especially suitable for large-scale continuous production of ultra-high-purity silicon tetrachloride by polysilicon enterprises.

In order to achieve the above object, according to one aspect of the present invention, a method for preparing ultra-high purity silicon tetrachloride is provided. The preparation method comprises the following steps: S1, continuously feeding high-purity silicon tetrachloride into the photochemical reactor under the action of nitrogen; S2, continuously feeding chlorine gas into the photochemical reactor under the condition of ultraviolet light to make the high-purity silicon tetrachloride The hydrogen-containing impurities in silicon chloride react with chlorine to obtain primary products; S3, the primary products are passed into the stripping tower from the upper part of the stripping tower, and nitrogen gas is fed from the bottom of the stripping tower to remove The unreacted chlorine in the primary product is obtained as a secondary product; and S4, the secondary product is sent to a silicon tetrachloride purification tower, and ultra-high-purity silicon tetrachloride is obtained after continuous light removal and weight removal.

Further, in S1 and S3, the dew point of nitrogen is not lower than -90°C.

Further, in S2, the purity of chlorine gas is not lower than 99.999%.

Further, in S2, the volume ratio of chlorine gas to high-purity silicon tetrachloride is 1˜10:1.

Further, in S3, the temperature of nitrogen is 120-200° C., and the volume ratio of nitrogen to primary product is 1-10:1.

Further, the silicon tetrachloride purification tower is composed of a lightness removal purification tower and a weight removal purification tower, wherein the reflux ratio of the lightness removal purification tower is 100-200, and the reflux ratio of the weight removal purification tower is 10-20.

Further, the light removal and purification tower and the weight removal and purification tower are packed towers, and the packing of the packed tower includes one or more of corrugated metal mesh packing BX, corrugated metal mesh packing CY and corrugated metal plate packing.

Further, the light removal and purification tower and the weight removal and purification tower are made of 316L stainless steel, and the operating pressure at the top of the tower is 0.2-0.5 MPa.

Further, the high-purity silicon tetrachloride is silicon tetrachloride obtained after polysilicon reduction tail gas and hydrogenation condensate are purified.

Further, the photochemical reactor is a microchannel reaction device made of quartz, the diameter of the reaction channel is in the order of microns, the reaction temperature is 20-60° C., and the reaction pressure is 0.3-1 MPa.

Applying the technical scheme of the present invention, a method combining light chlorination and rectification purification is adopted, wherein the hydrogen-containing impurities generate high-boiling chlorides through the photochlorination reaction, and then effectively remove the chlorides through rectification, so as to achieve separation The role of purification. The optical fiber silicon tetrachloride prepared by this method has a purity of more than 99.9999999%, and the infrared transmission index of related groups meets or even exceeds the high-purity silicon tetrachloride index of Merk Company, and meets the quality requirements of ultra-high purity silicon tetrachloride .

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

Fig. 1 shows a schematic flow chart of a method for preparing ultra-high-purity silicon tetrachloride according to Example 1 of the present invention.

detailed description

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

According to a typical embodiment of the present invention, a method for preparing ultra-high-purity silicon tetrachloride is provided. The method comprises the following steps: S1, continuously feeding high-purity silicon tetrachloride into the photochemical reactor under the action of nitrogen; S2, continuously feeding chlorine gas into the photochemical reactor under the condition of ultraviolet light to make the high-purity silicon tetrachloride The hydrogen-containing impurities in the silicon dioxide react with chlorine to obtain the primary product; S3, the primary product is passed into the stripping tower from the upper part of the stripping tower, and the nitrogen gas is fed from the bottom of the stripping tower to remove the primary product. The unreacted chlorine in the product is obtained as a secondary product; and S4, the secondary product is sent to a silicon tetrachloride purification tower, and after continuous light removal and weight removal, ultra-high-purity silicon tetrachloride is obtained.

The invention prepares ultra-high-purity silicon tetrachloride through the combination of light chlorination and rectification purification.

The principle of the photochemical reaction is: Cl ₂ dissociates into two active chlorine radicals under the irradiation of ultraviolet light:

Cl ₂ →2Cl ⁽ 1)

The photolyzed chlorine radicals can cause dehydrochlorination of hydrogen-containing impurities, and the process is as follows (2), (3):

(CH ₃ ) ₃ SiCl+2Cl +2e-→C ₃ H ₈ ^ClSiCl +HCl (2)

(CH ₃ ) ₃ BCl ₂ +2Cl +2e-→C ₃ H ₈ ^ClBCl ₂ +HCl (3)

The boiling point of the reacted chloride is much higher than that of silicon tetrachloride, which can be removed by rectification and purification.

Applying the technical scheme of the present invention, a method combining light chlorination and rectification purification is adopted, wherein the hydrogen-containing impurities generate high-boiling chlorides through the photochlorination reaction, and then effectively remove the chlorides through rectification, so as to achieve separation The role of purification. The optical fiber silicon tetrachloride prepared by this method has a purity of more than 9N (99.9999999%), and the infrared transmission index of related groups meets or even exceeds the high-purity silicon tetrachloride index of Merk Company, reaching ultra-high purity silicon tetrachloride. Silicon quality requirements.

Preferably, in S1 and S3, the dew point of nitrogen is not lower than -90°C. At this time, the oxygen content and water content in nitrogen are both at ppb level, which will not affect the quality of silicon tetrachloride products.

Preferably, in S2, the purity of chlorine gas is not lower than 99.999%.

According to a typical implementation of the present invention, in S2, the volume ratio of chlorine gas to high-purity silicon tetrachloride is 1-10:1, thereby ensuring that the raw materials in silicon tetrachloride are fully in contact with chlorine gas.

According to a typical implementation of the present invention, in S3, the temperature of nitrogen is 120-200° C., and the volume ratio of nitrogen to primary product is 1-10:1, thereby significantly separating unreacted chlorine.

Preferably, the silicon tetrachloride purification tower is composed of a lightness removal purification tower and a weight removal purification tower, wherein the reflux ratio of the lightness removal purification tower is 100-200, and the reflux ratio of the weight removal purification tower is 10-20. An appropriate reflux ratio can ensure the purity of the product silicon tetrachloride without affecting the processing capacity of the purification tower. In other words, if the reflux ratio is too small, the gas-liquid mass transfer will be poor, and the purity of silicon tetrachloride will not meet the production requirements; if the reflux ratio is too large, the production capacity of the purification tower will decrease, thereby increasing energy consumption.

According to a typical embodiment of the present invention, the light removal and purification tower and the weight removal and purification tower are packed towers, and the packing includes one or more of metal mesh corrugated packing BX, metal mesh corrugated packing CY and metal plate corrugated packing .

Preferably, the light removal and purification tower and the weight removal and purification tower are made of 316L stainless steel, and the operating pressure at the top of the tower is 0.2-0.5 MPa, thereby significantly improving the efficiency of the purification tower.

According to a typical embodiment of the present invention, the high-purity silicon tetrachloride is silicon tetrachloride obtained after polysilicon reduction tail gas and hydrogenation condensate are purified.

Preferably, the photochemical reactor is a microchannel reaction device made of quartz, the diameter of the reaction channel is in the order of microns, the reaction temperature is 20-60° C., and the reaction pressure is 0.3-1 MPa, thus the reaction speed can be significantly accelerated.

The beneficial effects of the present invention will be further described below in conjunction with examples.

Example 1

As shown in Figure 1, the ultra-high-purity silicon tetrachloride production process of the present embodiment comprises the following steps:

S1, the purity is more than 99.9999%, that is, high-purity silicon tetrachloride raw material, which contains trace impurities such as trichlorosilane, methylchlorosilane and borophosphorus, and uses high-purity nitrogen to send the raw material silicon tetrachloride into the photochemical reaction device , the dew point of the high-purity nitrogen is not lower than -90°C.

S2, after sending the high-purity silicon tetrachloride raw material into the photochemical reaction device, under the condition of ultraviolet light, a certain amount of high-purity chlorine gas is passed into the photochemical reactor. In this method, the liquid material of high-purity silicon tetrachloride is fed first, and then the gas material of high-purity chlorine is fed. Among them, the photochemical reactor is composed of a microchannel reactor, an ultraviolet light source and heat exchange equipment. The raw materials of high-purity silicon tetrachloride and high-purity chlorine flow laminarly in the microchannel reaction device, and an ultraviolet light source is placed outside the microchannel reaction device. Trichlorosilane and hydrogen-containing impurities in the raw material silicon tetrachloride react with high-purity chlorine gas under ultraviolet light irradiation and release heat, and the temperature in the reaction device is kept constant by heat exchange equipment.

S3, the primary product at the outlet of the photochemical reactor enters from the upper part of the stripping tower, a certain amount and temperature of high-purity nitrogen enters from the bottom of the stripping tower, and the unreacted chlorine in the outlet product of the photochemical reactor is discharged from the high-purity nitrogen After the tower is lifted, it enters the tail gas treatment system for treatment.

S4, secondary products without chlorine are discharged from the bottom of the stripping tower and enter the silicon tetrachloride purification tower. The silicon tetrachloride purification tower is composed of two towers. After the reaction product is continuously lightened and heavy removed by the silicon tetrachloride purification tower, the chloride, boron and phosphorus impurities are discharged from the high and low boiling, and the purified silicon tetrachloride has a purity of up to 9N. Above, meet the quality requirements of ultra-high purity silicon tetrachloride.

The specific conditions of this embodiment are as follows:

Using the ultra-high-purity silicon tetrachloride production process according to the present invention, the production of ultra-high-purity silicon tetrachloride is carried out using the flow chart shown in FIG. 1 .

The purity of the raw material silicon tetrachloride is above 99.9999%, and the silicon tetrachloride after polysilicon reduction tail gas and hydrogenation condensate purification can meet the requirements. The dew point temperature of high-purity nitrogen is not lower than -90°C, and the purity of high-purity chlorine is not lower than 99.999%.

The photochemical reactor is a quartz microchannel reaction device, the diameter of the reaction channel is micron, the reaction temperature is 30°C, the reaction pressure is 0.4MPa, the volume ratio of high-purity chlorine gas and raw material silicon tetrachloride is 10:1, and the light source can use high pressure UV mercury lamp or cold light source UV lamp. The heat exchange medium is heat conduction oil, which is used to cool the photochemical reaction device and maintain the reaction temperature in the reactor.

The product of the photochemical reactor contains unreacted chlorine, which needs to be taken out with high-purity nitrogen after passing through the stripping tower. The temperature of high-purity nitrogen is 120°C, and the volume ratio of the reaction product is 10:1.

The chlorine-free product is passed into the silicon tetrachloride purification tower. The silicon tetrachloride purification tower is made of 316L material. The inside of the tower and the internal parts of the tower are all electropolished. It can be cooled by circulating water, and the tower kettle can be heated by hot water. The purification tower is composed of two towers, and after the low boilers and high boilers are continuously discharged through the light removal tower and the weight removal tower, the product purity can reach more than 9N.

The stripping tower and the silicon tetrachloride purification tower can be plate towers or packed towers, preferably packed towers. The packing includes, but not limited to, one or more of corrugated wire mesh packing BX, corrugated wire mesh packing CY and corrugated metal plate packing. The reflux ratio of the ultra-high-purity silicon tetrachloride light removal and purification tower is 100, and the reflux ratio of the heavy removal and purification tower is 10.

The purified product needs to enter the ultra-high-purity silicon tetrachloride for storage tank, the storage tank is made of 316L material, and the interior is electropolished. When the product tank is full or idle, it needs to be pressurized with high-purity nitrogen to 0.1-0.2MPa for protection.

After 15 days of stable operation, the product in the product storage tank was sampled and analyzed.

Analysis method: The infrared transmittance of hydrogen-containing impurity groups was analyzed by Fourier transform infrared analyzer, and the analysis results are shown in Table 1. After comparing the analysis results with the standards of Merck, Germany, it can be obtained that the product in the storage tank can meet the quality requirements of ultra-high-purity SiCl ₄ .

Table 1

Wavenumber(cm ^-1 ) group Merck Standard (%) Example 1 (%) 3666 SiCl ₃ OH >90 99.54 3100～3020 -CH >99 99.91 2970～2925 -CH >95 99.86 2860～2830 HCl >95 99.93 2338 CO ₂ >95 >99 2295 Si(NCO) ₄ >97 >99.02 2257 SiHCl ₃ >99 >99 2023 Si(CH ₃ )Cl ₃ >99 >99 1540 Si ₂ OCl ₆ >99 >99

Example 2

Processing step is with embodiment 1, and concrete condition is as follows:

The purity of the raw material silicon tetrachloride is above 99.9999%, and the silicon tetrachloride after polysilicon reduction tail gas and hydrogenation condensate purification can meet the requirements. The dew point temperature of high-purity nitrogen is not lower than -90°C, and the purity of high-purity chlorine is not lower than 99.999%.

The photochemical reactor is a quartz microchannel reaction device, the diameter of the reaction channel is micron, the reaction temperature is 20°C, the reaction pressure is 0.3MPa, the volume ratio of high-purity chlorine gas and raw material silicon tetrachloride is 1:1, and the light source can use high pressure UV mercury lamp or cold light source UV lamp. The heat exchange medium is heat conduction oil, which is used to cool the photochemical reaction device and maintain the reaction temperature in the reactor.

The product of the photochemical reactor contains unreacted chlorine, which needs to be taken out with high-purity nitrogen after passing through the stripping tower. The temperature of high-purity nitrogen is 120 ° C, and the volume ratio of the reaction product is 1:1.

The chlorine-free product is passed into the silicon tetrachloride purification tower. The silicon tetrachloride purification tower is made of 316L material. The inside of the tower and the internal parts of the tower are all electropolished. It can be cooled by circulating water, and the tower kettle can be heated by hot water. The purification tower is composed of two towers, and after the low boilers and high boilers are continuously discharged through the light removal tower and the weight removal tower, the product purity can reach more than 9N.

The stripper and the silicon tetrachloride purification tower can use packed towers, and the packing includes but not limited to one or more of corrugated metal mesh packing BX, corrugated metal mesh packing CY and corrugated metal plate packing. The reflux ratio of the ultra-high-purity silicon tetrachloride light removal and purification tower is 100, and the reflux ratio of the heavy removal and purification tower is 10.

The purified product needs to enter the ultra-high-purity silicon tetrachloride for storage tank, the storage tank is made of 316L material, and the interior is electropolished. When the product tank is full or idle, it needs to be pressurized with high-purity nitrogen to 0.1-0.2MPa for protection.

After 15 days of stable operation, the product in the product storage tank was sampled and analyzed.

Analysis method: Fourier transform infrared analyzer is used to analyze the infrared transmittance of hydrogen-containing impurity groups, and the analysis results are shown in Table 2. After comparing the analysis results with the standards of Merck, Germany, it can be obtained that the product in the storage tank can meet the quality requirements of ultra-high-purity SiCl ₄ .

Table 2

Wavenumber(cm ^-1 ) group Merck Standard (%) Example 2 (%) 3666 SiCl ₃ OH >90 99.68 3100～3020 -CH >99 99.59 2970～2925 -CH >95 97.71 2860～2830 HCl >95 97.91 2338 CO ₂ >95 96.86 2295 Si(NCO) ₄ >97 >99 2257 SiHCl ₃ >99 >99 2023 Si(CH ₃ )Cl ₃ >99 >99 1540 Si ₂ OCl ₆ >99 >99

Example 3

Processing step is with embodiment 1, and concrete condition is as follows:

The purity of the raw material silicon tetrachloride is above 99.9999%, and the silicon tetrachloride after polysilicon reduction tail gas and hydrogenation condensate purification can meet the requirements. The dew point temperature of high-purity nitrogen is not lower than -90°C, and the purity of high-purity chlorine is not lower than 99.999%.

The photochemical reactor is a micro-channel reaction device made of quartz material, the diameter of the reaction channel is micron, the reaction temperature is 60°C, the reaction pressure is 1MPa, the volume ratio of high-purity chlorine gas and raw material silicon tetrachloride is 10:1, and the light source can be high-pressure ultraviolet light. Mercury lamp or cold light source UV lamp. The heat exchange medium is heat conduction oil, which is used to cool the photochemical reaction device and maintain the reaction temperature in the reactor.

The product of the photochemical reactor contains unreacted chlorine, which needs to be taken out with high-purity nitrogen after passing through the stripping tower. The temperature of high-purity nitrogen is 200 ° C, and the volume ratio of the reaction product is 10:1.

The chlorine-free product is passed into the silicon tetrachloride purification tower. The silicon tetrachloride purification tower is made of 316L material. The inside of the tower and the internal parts of the tower are all electropolished. It can be cooled by circulating water, and the tower kettle can be heated by hot water. The purification tower is composed of two towers, and after the low boilers and high boilers are continuously discharged through the light removal tower and the weight removal tower, the product purity can reach more than 9N.

The stripper and the silicon tetrachloride purification tower can use packed towers, and the packing includes but not limited to one or more of corrugated metal mesh packing BX, corrugated metal mesh packing CY and corrugated metal plate packing. The reflux ratio of the ultra-high-purity silicon tetrachloride light removal and purification tower is 200, and the reflux ratio of the heavy removal and purification tower is 20.

The purified product needs to enter the ultra-high-purity silicon tetrachloride for storage tank, the storage tank is made of 316L material, and the interior is electropolished. When the product tank is full or idle, it needs to be pressurized with high-purity nitrogen to 0.1-0.2MPa for protection.

After 15 days of stable operation, the product in the product storage tank was sampled and analyzed.

Analysis method: Fourier transform infrared analyzer is used to analyze the infrared transmittance of hydrogen-containing impurity groups, and the analysis results are shown in Table 3. After comparing the analysis results with the standards of Merck, Germany, it can be obtained that the product in the storage tank can meet the quality requirements of ultra-high-purity SiCl ₄ .

table 3

From the above description, it can be seen that the above-mentioned embodiments of the present invention have achieved the following technical effects:

1) The silicon tetrachloride prepared according to the embodiment can meet the quality requirements of ultra-high purity silicon tetrachloride.

2) The method provided by the invention has a relatively wide application range, and qualified products can be obtained under low temperature and low pressure conditions.

3) Among the above-mentioned examples, the product quality of Example 1 is the best, indicating that there is an optimum process parameter in this method.

The ultra-high-purity silicon tetrachloride production process according to this embodiment has the advantages of high purity silicon tetrachloride, low energy consumption, and no tail gas pollution.

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 (10)

1. a kind of preparation method of ultra-pure Silicon chloride. is it is characterised in that comprise the following steps：

S1, high purity silicon tetrachloride is continuously passed through in photochemical reactor under nitrogen effect；

S2, under ultraviolet irradiation condition, is continuously passed through chlorine into described photochemical reactor, makes in described high purity silicon tetrachloride Hydrogen containing foreign and chlorine there is optical chlorinating reaction, obtain primary product；

S3, described primary product are passed through in described stripper from the top of stripper, and nitrogen leads to from the bottom of described stripper Enter, obtain secondary products to remove unreacted chlorine in described primary product；And

S4, described secondary products is sent into Silicon chloride. purifying column, after continuously taking off light and de- weight, obtains described ultra-pure four Silicon chloride.

2. preparation method according to claim 1 is not it is characterised in that in described S1 and S3, the dew point of described nitrogen is low In -90 DEG C.

3. preparation method according to claim 1 is it is characterised in that in described S2, the purity of described chlorine is not less than 99.999%.

4. preparation method according to claim 1 is it is characterised in that in described S2, described chlorine and described high-purity tetrachloro The volume ratio of SiClx is 1～10:1.

5. preparation method according to claim 1 is it is characterised in that in described S3, and the temperature of described nitrogen is 120～ 200 DEG C, described nitrogen is 1～10 with the volume ratio of described primary product:1.

6. preparation method according to claim 1 it is characterised in that described Silicon chloride. purifying column by de- light purifying column and De- repurified tower composition, wherein, the described reflux ratio taking off light purifying column is 100～200, and the reflux ratio of described de- repurified tower is 10～20.

7. preparation method according to claim 6 is it is characterised in that described de- light purifying column and described de- repurified tower are Packed tower, the filler of described filler tower includes corrugated wire gauze packing BX, corrugated wire gauze packing CY and metallic plate ripple One or more of filler.

8. preparation method according to claim 6 is it is characterised in that described de- light purifying column and described de- repurified tower are 316L stainless steel, tower top operating pressure is 0.2～0.5MPa.

9. preparation method according to claim 1 is it is characterised in that described high purity silicon tetrachloride is polycrystalline silicon reduction exhaust And the Silicon chloride. obtaining after hydrogenation condensation material purification.

10. preparation method according to claim 1 is it is characterised in that described photochemical reactor is the micro- of quartz material Pathway reaction device, a diameter of micron order of reaction channel, reaction temperature is 20～60 DEG C, reaction pressure 0.3～1MPa.