CN114505084A - Pretreatment method of cuprous chloride catalyst - Google Patents

Abstract

The invention relates to the technical field of polycrystalline silicon production processes, in particular to a pretreatment method of a cuprous chloride catalyst. Cuprous chloride and Si silicon powder are filled in a tube elastic reactor, the partial pressure of the cuprous chloride is increased through a vacuum environment, the cuprous chloride is converted from a solid phase to a gas phase, the diffusion rate of the cuprous chloride is accelerated, and a uniformly dispersed copper silicon active center is formed; thereby accelerating the adsorption, deposition and reaction of cuprous chloride on the surface of silicon particles and reducing the deactivation caused by Cu sintering. The embodiment proves that the cold hydrogenation reaction of the silicon tetrachloride after the cuprous chloride and the Si silicon powder are pretreated can shorten the induction period, improve the catalytic efficiency of the silicon tetrachloride, improve the reaction efficiency of the cold hydrogenation and reduce the amount of copper impurities in a rear system. The method provided by the invention has the advantages of low requirement on equipment, simple preparation process, low energy consumption and obvious promotion on cold hydrogenation reaction effect.

Description

A kind of pretreatment method of cuprous chloride catalyst

technical field

The invention relates to the technical field of polysilicon production technology, in particular to a pretreatment method of a cuprous chloride catalyst.

Background technique

The modified Siemens method is the mainstream process for producing polysilicon. Its main disadvantage is that the hydrogenation efficiency of silicon tetrachloride in the exhaust gas recovery unit is low. For every 1t of polysilicon produced, the by-product exceeds 15t of silicon tetrachloride. Silicon tetrachloride is a highly toxic substance. To pollute the environment, my country stipulates that the recovery rate of silicon tetrachloride in the reduction exhaust gas of polysilicon production shall not be lower than 98.5%. The most effective measure is to convert silicon tetrachloride into trichlorosilane by hydrogenation in the polysilicon production process, and to recycle the silicon tetrachloride. At present, most domestic polysilicon hydrogenation methods use cold hydrogenation technology: SiCl ₄ +3Si+2H ₂ →4SiHCl ₃ , that is, under the action of catalyst, silicon powder, hydrogen and silicon tetrachloride will produce gas-solid “gas-solid” in the fluidized bed/fixed bed. -Solid" reaction. The reaction temperature is 400-600°C, the pressure is 1-4MPa, the molar feed ratio of hydrogen to silicon tetrachloride is 1-10, and the catalysts used are mostly copper-based catalysts.

Some studies believe that the active phase of the catalyst in the cold hydrogenation process is a copper-silicon compound. In the fluidized bed, the CuCl catalyst and the silicon particles are contacted and reduced, and the reaction generates SiCl ₄ and active free Cu. The irregular diffusion of Cu in the main body of the Si particles makes the "Cu-Si" compound discretely formed on the surface of the particles. When H ₂ and SiCl ₄ are introduced, the "Cu-Si" compound catalyzes the hydrogenation reaction of SiCl ₄ to generate HCl and SiHCl ₃ , and copper is continuously etched on the catalyst surface until the silicon reaction is complete. Therefore, accelerating the formation of "Cu-Si" compounds has become the focus of improving the reaction rate of cold hydrogenation. In the current industrial production, due to the low melting point of cuprous chloride and its easy volatilization loss, the copper catalyst is continuously lost. When using, cuprous chloride needs to be continuously added to the fluidized bed reactor, which causes an increase in production costs. So far, there is no good report on catalyst pretreatment method.

SUMMARY OF THE INVENTION

In view of the above technical problems, the present application provides a method for pretreatment of cuprous chloride catalyst. The invention effectively shortens the induction period of the catalyst in the cold hydrogenation process of silicon tetrachloride, accelerates the reaction between the solid-phase catalyst and the solid-phase silicon powder, and improves the catalytic efficiency of cuprous chloride.

The specific technical scheme of the present invention is as follows:

The invention provides a catalyst pretreatment method in the cold hydrogenation process of silicon tetrachloride. The pretreatment method comprises the following steps: putting CuCl and silicon powder into a closed reactor, and replacing the air in the closed reactor with an inert gas , heating and reacting for a period of time, and cooling to room temperature to complete the pretreatment process.

Further, the mass ratio of the CuCl to the silicon powder is 10:1-2.

Preferably, the reaction temperature of the heating reaction is 400-550° C., and the reaction time is 1-10 hours.

The silicon powder is acid-washed silicon powder.

Preferably, the closed reactor is a tube bomb reactor, and further, an air bag or a vacuum air pump is connected to the outlet of the tube bomb reactor.

Preferably, the inert gas is nitrogen or argon.

Further, the pretreatment process is in a vacuum state, and the degree of vacuum is -0.09Mpa.

Compared with the prior art, the beneficial effects of the present invention are:

In the invention, the mixed cuprous chloride and Si silicon powder are loaded into the tube bomb reactor, and the vacuum pump is used to evacuate during the heating process. In the gas phase, the diffusion rate of cuprous chloride is accelerated, and a uniformly dispersed copper-silicon active center is formed. Thus, the adsorption, deposition and reaction of cuprous chloride on the surface of silicon particles are accelerated and the deactivation caused by Cu sintering is reduced. At the same time, the products such as gas generated by the reaction can also be discharged in time to promote the forward progress of the reaction, that is, the formation of the copper-silicon active phase. After the pretreatment is completed, the reaction product containing the copper-silicon compound is directly put into the fixed bed to carry out the cold hydrogenation reaction of silicon tetrachloride. It is confirmed by the examples that the pretreatment of cuprous chloride and Si silicon powder can not only shorten the induction period, improve the catalytic efficiency of silicon tetrachloride, and then improve the reaction efficiency of cold hydrogenation, but also can reduce the amount of copper impurities in the post-system. . The method provided by the invention has low requirements on equipment, simple preparation process, low energy consumption, and obviously promotes the effect of cold hydrogenation reaction.

Description of drawings

Figure 1 is a schematic diagram of a tube bomb reactor; in the figure, (1) lined with quartz glass, (2) graphite gasket, (3) flange, (4) pressure gauge, (5) needle valve, (6) tee Valve, (7) first outlet, (8) second outlet.

Figure 2 is a comparison diagram of the conversion ratios without pretreatment and after catalyst pretreatment in Examples 2-4.

Detailed ways

The present invention will be further described below in conjunction with the embodiments: those skilled in the art can learn from the contents of this paper and appropriately improve the process parameters to achieve. It should be particularly pointed out that all similar substitutions and modifications are obvious to those skilled in the art, and they are deemed to be included in the present invention. The method and application of the present invention have been described through the preferred embodiments, and it is obvious that relevant persons can make changes or appropriate changes and combinations of the methods and applications described herein without departing from the content, spirit and scope of the present invention to achieve and Apply the technology of the present invention. The experimental methods with no specific conditions indicated in the examples are all in accordance with conventional conditions; the reagents and biological materials used can be obtained from commercial sources unless otherwise specified.

Comparative Example 1:

8 g of the acid-washed silicon powder and 1.6 g of cuprous chloride (CuCl) were weighed, fully mixed, and then filled into a fixed-bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4 :1. It was determined that the conversion rate of silicon tetrachloride after the reaction was completed was 14.61%.

Example 1:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, place it in a closed reactor, and replace it with nitrogen several times to ensure that there is no air inside. Then, the temperature was raised to 450°C at a heating rate of 10°C/min, and the temperature was kept constant for 3 hours. The reaction system was closed during the whole reaction process. After the reaction was completed, the pressure was gradually increased to 4 atm (standard atmospheric pressure). After cooling to room temperature, 9.6 g of the treated silicon powder was weighed and filled into a fixed-bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4 :1. It was determined that the conversion rate of silicon tetrachloride after the reaction was completed was 14.17%.

Example 2:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, put it in the tube bomb reactor, pass nitrogen gas, and replace it several times to ensure that there is no air inside. is normal pressure. The temperature was raised to 450°C at a heating rate of 10°C/min, and the temperature was kept constant for 3h. After cooling to room temperature, 9.6 g of the treated silicon powder was weighed and filled into a fixed-bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 15.48%.

Figure 1 is a schematic diagram of a tube bomb reactor; as shown in Figure 1, the tube bomb reactor includes (1) lined with quartz glass, (2) graphite gasket, (3) flange, (4) pressure gauge, (5) ) needle valve, (6) three-way valve; the three-way valve (6) includes a first outlet (7) connected to a steel cylinder for replacing the gas in the tube bomb reactor, and a second outlet (7) connected to an air bag or a vacuum pump 8).

Example 3:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, put it in the tube bomb reactor, pass nitrogen, and replace it several times to ensure that there is no air inside. The outlet of the tube bomb reactor is connected to a vacuum pump for vacuuming. -0.09MPa. The temperature was raised to 450°C at a heating rate of 10°C/min, kept at a constant temperature for 3 hours, and then cooled to room temperature. 9.6 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 21.15%.

Example 4:

Mix 1g of CuCl and 10g of acid-washed Si powder thoroughly, put it in the tube bomb reactor, pass nitrogen, and replace it several times to ensure that there is no air inside. The outlet of the tube bomb reactor is connected to a vacuum pump for vacuuming. -0.09MPa. The temperature was raised to 450°C at a heating rate of 10°C/min, kept at a constant temperature for 3 hours, and then cooled to room temperature. 8.8 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 19.14%.

Figure 2 is a comparison chart of the conversion ratios without pretreatment and after catalyst pretreatment in Examples 2 to 4; it can be seen from Figure 2 that the conversion ratio of silicon tetrachloride increases significantly after the catalyst is pretreated, and the catalyst is carried out in a vacuum state. The conversion rate after pretreatment increased to about 20%.

Example 5:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, place it in a tube bomb reactor, and replace it with nitrogen several times to ensure that there is no air inside. The temperature was raised to 400°C at a heating rate of 10°C/min, and the temperature was kept constant for 3 hours. The whole process was evacuated by a vacuum pump, and the vacuum degree was -0.09MPa. 9.6 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 20.61%.

Example 6:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, place it in a tube bomb reactor, and replace it with nitrogen several times to ensure that there is no air inside. The temperature was raised to 500°C at a heating rate of 10°C/min, and the temperature was kept constant for 3 hours. The whole process was evacuated by a vacuum pump, and the vacuum degree was -0.09MPa. 9.6 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 19.66%.

Example 7:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, place it in a closed reactor, and replace it with nitrogen several times to ensure that there is no air inside. The temperature was raised to 550°C at a heating rate of 10°C/min, and the temperature was kept constant for 3 hours. The whole process was evacuated by a vacuum pump, and the vacuum degree was -0.09MPa. 9.6 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 22.70%.

Example 8:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, place it in a closed reactor, and replace it with argon several times to ensure that there is no air inside. The temperature was raised to 550°C at a heating rate of 10°C/min, and the temperature was kept constant for 1 h. The whole process was evacuated by a vacuum pump, and the vacuum degree was -0.09MPa. 9.6 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, in a nitrogen atmosphere, the temperature is raised to 500°C at a heating rate of 10°C/min, the reaction pressure is normal pressure, the flow rate of hydrogen is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 19.88%.

Example 9:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, place it in a closed reactor, and replace it with argon several times to ensure that there is no air inside. The temperature was raised to 550°C at a heating rate of 10°C/min, and the temperature was kept constant for 5h. The whole process was evacuated by a vacuum pump, and the vacuum degree was -0.09MPa. 9.6 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 21.07%.

Example 10:

Mix 2g of CuCl and 10g of acid-washed Si powder thoroughly, place it in a closed reactor, and replace it with argon several times to ensure that there is no air inside. The temperature was raised to 550°C at a heating rate of 10°C/min, and the temperature was kept constant for 10h. The whole process was evacuated by a vacuum pump, and the vacuum degree was -0.09MPa. 9.6 g of the treated silicon powder was weighed and filled into a fixed bed reactor for cold hydrogenation reaction. The reaction conditions are: after nitrogen purging, the temperature is raised to 500°C at a heating rate of 10°C/min in a nitrogen atmosphere, the reaction pressure is normal pressure, the hydrogen flow rate is 200mL/min, and the molar ratio of hydrogen to silicon tetrachloride is 4: 1. The conversion rate of silicon tetrachloride is 21.35%.

Table 1. Comparison of the effects of pretreatment methods on cold hydrogenation

It can be seen from Table 1 that the catalytic efficiency of silicon tetrachloride can be improved by pre-processing silicon powder and cuprous chloride and then performing cold hydrogenation reaction of silicon tetrachloride, thereby improving the reaction efficiency of cold hydrogenation. This is because the pretreatment reaction increases the partial pressure of cuprous chloride, which transforms it from solid phase to gas phase, accelerates the diffusion rate of cuprous chloride, and forms uniformly dispersed copper-silicon active centers. Moreover, the pretreatment reaction accelerates the adsorption, deposition and reaction of cuprous chloride on the surface of silicon particles, and reduces the deactivation caused by Cu sintering. At the same time, products such as gas generated by the reaction can also be discharged in time to promote the forward progress of the reaction.

The series of detailed descriptions listed above are only specific descriptions for the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Changes should all be included within the protection scope of the present invention.

Claims (8)

1. the pretreatment method of catalyst in a silicon tetrachloride cold hydrogenation process, is characterized in that, described pretreatment method comprises: CuCl and silicon powder are put into closed reactor, and inert gas replaces closed reactor In the air, the temperature is raised and heated for a period of time, and then cooled to room temperature to complete the pretreatment process. 2 . The pretreatment method according to claim 1 , wherein the mass ratio of the CuCl to the silicon powder is 10:1-2. 3 . 3 . The pretreatment method according to claim 1 , wherein the reaction temperature of the heating reaction is 400-550° C., and the reaction time is 1-10 hours. 4 . 4 . The pretreatment method according to claim 1 , wherein the silicon powder is acid-washed silicon powder. 5 . 5. The pretreatment method according to claim 1, wherein the closed reactor is a tube bomb reactor. 6 . The pretreatment method according to claim 5 , wherein an air bag or a vacuum air pump is connected to the outlet of the tube bomb reactor. 7 . 7. The pretreatment method according to claim 1, wherein the inert gas is nitrogen or argon. 8. The pretreatment method according to claim 1, wherein the pretreatment process is in a vacuum state, and the degree of vacuum is -0.09Mpa.

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