A method for purifying chlorosilane by physical adsorption and coordination

Abstract

The present invention discloses a method for purifying chlorosilanes using physical adsorption and coordination, belonging to the technical field of silane purification. The method passes a crude liquid chlorosilane product through a fixed-bed absorption tower and, after treatment with modified activated carbon, obtains high-purity chlorosilane. By modifying the activated carbon, the modified activated carbon has improved mechanical properties, and the functional molecule Alizarin Red S is grafted onto the activated carbon via chemical bonds, effectively preventing the functional molecule from falling off during deep impurity removal treatment of the modified activated carbon, ensuring the long-term performance of the modified activated carbon, and improving the purity of the chlorosilane product.

Description

Technical Field

[0001] The present invention relates to the technical field of silane purification, and in particular to a method for purifying chlorosilane by utilizing physical adsorption and coordination. Background Art

[0002] With the rapid development of the new energy photovoltaic industry, polysilicon has become a strategic material for my country's nonferrous metals industry. The main production technologies for polysilicon are the modified Siemens process and the silane process. The modified Siemens process reacts industrial silicon powder with HCl to produce chlorosilane, which is then reduced and deposited in a reduction furnace filled with an H2 atmosphere to produce polysilicon. To improve raw material utilization and enhance environmental friendliness, the exhaust gases H2, SiHCl3, SiCl4, SiH2Cl2, and HCl from the reduction furnace are separated and recycled. The silane process involves introducing silane into a fluidized bed containing polysilicon seeds as fluidized particles, causing the silane to crack and deposit on the seeds, resulting in granular polysilicon.

[0003] Currently, domestic polysilicon companies produce polysilicon using a modified Siemens process. The primary impurities in the production process are silicon powder, including boron, phosphorus, and other metallic impurities such as iron, magnesium, and aluminum. These impurities significantly impact the quality of polysilicon. Existing technologies for purifying and refining chlorosilanes primarily rely on distillation. However, distillation towers are characterized by high investment costs, poor operational stability, significant energy consumption, unstable product quality, and poor practical operability. Metals such as iron, magnesium, and aluminum, as well as non-metallic ions such as boron and phosphorus, cannot be removed through distillation, severely impacting the performance of the polysilicon material. Therefore, there is a need for a method for purifying chlorosilanes using physical adsorption and coordination.

[0004] Chinese patent document CN105731465A discloses a method and apparatus for removing boron and phosphorus from a chlorosilane fixed bed using a chemical adsorption reaction method, comprising a heat exchanger, a fixed bed adsorption column, and a thermal oil circulation pump; the feed line at the bottom of the heat exchanger and the discharge line at the top of the heat exchanger are both connected to the bottom of the fixed bed, and the thermal oil circulation pump delivers heat transfer medium, thermal oil, to the fixed bed. Chlorosilane gas or liquid phase first enters the heat exchanger and then enters the chemical adsorption fixed bed, where an adsorbent loaded with a chemical complexing agent undergoes a chemical adsorption reaction on boron and phosphorus impurities, ultimately yielding high-purity chlorosilane. The adsorbent used in this invention is physically adsorbed by loading a chemical complexing agent. The chemical complexing agent is easily detached from the carrier, affecting its adsorption performance. In severe cases, it can also cause secondary contamination of the chlorosilane product, affecting the purity of the chlorosilane product. Summary of the Invention

[0005] The main purpose of the present invention is to propose a method for purifying chlorosilane by physical adsorption and coordination, wherein the crude liquid chlorosilane is passed into a fixed-bed absorption tower and treated with modified activated carbon to obtain high-purity chlorosilane.

[0006] To achieve the above object, the present invention proposes a method for purifying chlorosilane by physical adsorption and coordination, comprising the following steps:

[0007] The crude liquid chlorosilane is passed into a fixed-bed absorption tower filled with modified activated carbon. The crude liquid chlorosilane is contacted with the modified activated carbon for deep impurity removal and then discharged from the bottom of the tower to obtain purified liquid chlorosilane.

[0008] Preferably, the chlorosilane is at least one of dimethylmonochlorosilane, trimethylmonochlorosilane, methyldichlorosilane, trichlorosilane, methyltrichlorosilane, tetrachlorosilane, and dichlorodihydrosilane.

[0009] Preferably, the contact mode between the liquid phase crude chlorosilane and the modified activated carbon is countercurrent contact.

[0010] Preferably, the deep impurity removal time is 1-2 hours.

[0011] Preferably, the deep impurity removal treatment conditions are a temperature of 20-40°C and a liquid space velocity of 0.5-1.5h -1 , the pressure is 0.01-0.1MPa.

[0012] Preferably, the preparation method of the modified activated carbon is as follows:

[0013] The biomass raw material is dried and crushed, and then added to a sodium hydroxide aqueous solution for immersion. After the immersion is completed, the solid is filtered and collected. The solid is washed and dried to obtain a pretreated biomass; the pretreated biomass, oxalic acid, lanthanum nitrate, and water are ultrasonically dispersed and then hydrothermally reacted. After the reaction is completed, the solid is filtered and collected, washed, dried, and calcined to obtain porous carbon; the porous carbon is dispersed in an ethanol aqueous solution, KH550 is added, heated to react, and the solid is filtered to collect the solid; under a nitrogen atmosphere, the solid is dispersed in N,N-dimethylformamide, Alizarin Red S is added, the pH is adjusted to weak acidity after ultrasonic dispersion, and the reaction is heated. After the reaction is completed, the modified activated carbon is obtained by cooling, filtering, washing, and drying.

[0014] Preferably, the biochar raw material is at least one of peanut shells, rice husks, corn stalks, coconut shells, animal excrement, and tree branches.

[0015] Preferably, the mass ratio of the pretreated biomass, oxalic acid, and lanthanum nitrate is 10-15:1-2:4-6; the hydrothermal reaction temperature is 180-250° C., and the hydrothermal reaction time is 10-30 hours; the calcination temperature is 550-800° C., and the calcination time is 3-5 hours.

[0016] Preferably, the mass ratio of the porous carbon, KH550, and Alizarin Red S is 20-30:3-5:2-3.

[0017] The present invention uses modified activated carbon to perform deep treatment on a crude liquid chlorosilane product, thereby effectively removing boron, phosphorus and metal impurities in the crude product. Lanthanum oxide is introduced into the activated carbon, thereby improving the mechanical strength of the porous carbon and preventing it from breaking. Furthermore, the invention can adsorb phosphorus-containing impurities and improve the adsorption capacity of the activated carbon. Furthermore, Alizarin Red S is grafted onto the activated carbon through a chemical bond, thereby having higher stability, effectively avoiding the shedding of the functional molecule Alizarin Red S during the deep impurity removal treatment of the modified activated carbon, and ensuring the long-term performance of the modified activated carbon. The purity of the chlorosilane product is also improved.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present application uses modified activated carbon to deeply remove impurities from the crude liquid chlorosilane product. The modified activated carbon can remove impurities such as phosphorus and metals in the crude liquid chlorosilane product by adsorption and coordination, which can significantly improve the purity of the liquid chlorosilane. It has the effects of low equipment investment, high adsorption efficiency, and safe and stable continuous production.

[0020] (2) The preparation of the modified activated carbon of the present invention is firstly to pre-treat the biomass raw material with sodium hydroxide to remove a large amount of impurities on the surface of the biomass raw material, expose more active groups, and at the same time destroy the hydrogen bonds between the cellulose molecules inside the biomass, so that the distance between the molecules is increased, the cellulose becomes loose, and it is conducive to the subsequent steps; then it is hydrothermally reacted with sodium carboxymethyl cellulose and lanthanum nitrate to generate lanthanum oxide in situ on the porous carbon. Lanthanum oxide can improve the mechanical strength of the porous carbon and is not easy to break. On the other hand, it can also resist phosphorus-containing impurities. Adsorption is carried out, which is beneficial to improving the removal effect of phosphorus; then amino groups are introduced into the surface of porous carbon, which is beneficial to react with the ketone group on Alizarin Red S to form a Schiff base. The Schiff base works synergistically with the hydroxyl and sulfonic acid groups on Alizarin Red S to further improve the treatment effect of modified activated carbon on phosphorus, boron and metal impurities in crude chlorosilane. Alizarin Red S is grafted onto the activated carbon through chemical bonds, which has higher stability and effectively avoids the shedding of the functional molecule Alizarin Red S during the deep impurity removal treatment of the modified activated carbon, ensuring the long-term performance of the modified activated carbon; and improving the purity of the chlorosilane product. DETAILED DESCRIPTION

[0021] To avoid redundancy, the items used in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0022] Example 1

[0023] A method for purifying dimethylchlorosilane by physical adsorption and coordination comprises the following steps:

[0024] The crude dimethylchlorosilane in the liquid phase is passed into a fixed-bed absorption tower filled with modified activated carbon. The crude dimethylchlorosilane in the liquid phase is subjected to a deep impurity removal treatment by countercurrent contact with the modified activated carbon, and then discharged from the bottom of the tower to obtain purified dimethylchlorosilane. The deep impurity removal time is 1.5 hours. The deep impurity removal treatment conditions are a temperature of 30°C and a liquid space velocity of 1 hour. -1 ;The pressure is 0.05MPa.

[0025] The preparation method of the modified activated carbon is as follows:

[0026] 100 g of biomass raw material (a mixture of rice husk and coconut shell in a mass ratio of 2:3) was dried, crushed and passed through an 80-mesh sieve, then added to a 1 mol / L sodium hydroxide aqueous solution and immersed for 2 h. After the immersion was completed, the solid was filtered and collected. The solid was washed and dried to obtain a pretreated biomass; 72 g of pretreated biomass, 9.2 g of oxalic acid, 30 g of lanthanum nitrate and 300 mL of water were ultrasonically dispersed and hydrothermally reacted at 220 ° C for 20 h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 700 ° C for 4 h to obtain porous carbon; 50 g of porous carbon was dispersed in 500 mL of 50 wt% ethanol aqueous solution, 8 g of KH550 was added, and the mixture was heated at 50 ° C for 4 h. After the reaction was completed, the solid was cooled and filtered to collect the solid; under a nitrogen atmosphere, the solid was dispersed in 400 mL 5 g of Alizarin Red S was added to N,N-dimethylformamide, ultrasonically dispersed for 15 min, the pH was adjusted to 6 with 1 mol / L dilute hydrochloric acid, and stirred at 60°C for 5 h. After the reaction was completed, the mixture was cooled and filtered, and the solids were collected, washed, and dried to obtain modified activated carbon.

[0027] Example 2

[0028] A method for purifying dimethylchlorosilane by physical adsorption and coordination comprises the following steps:

[0029] The crude dimethylchlorosilane in liquid phase is passed into a fixed-bed absorption tower filled with modified activated carbon. The crude dimethylchlorosilane in liquid phase and the modified activated carbon are subjected to a deep impurity removal treatment by countercurrent contact and then discharged from the bottom of the tower to obtain purified dimethylchlorosilane. The deep impurity removal time is 1 hour. The deep impurity removal treatment conditions are a temperature of 40°C and a liquid space velocity of 1.5h. -1 ;The pressure is 0.1MPa.

[0030] The preparation method of the modified activated carbon is as follows:

[0031] 100g of biomass raw material (a mixture of rice husk and coconut shell in a mass ratio of 2:3) was dried, crushed and passed through an 80-mesh sieve, then added to a 1mol / L sodium hydroxide aqueous solution and immersed for 2h. After the immersion was completed, the solid was filtered and collected. The solid was washed and dried to obtain a pretreated biomass; 60g of pretreated biomass, 6g of oxalic acid, 24g of lanthanum nitrate and 300mL of water were ultrasonically dispersed and hydrothermally reacted at 180℃ for 30h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 500℃ for 5h to obtain porous carbon; 40g of porous carbon was dispersed in 500mL of 50wt% ethanol aqueous solution, 6g of KH550 was added, and the mixture was heated at 50℃ for 4h. After the reaction was completed, the solid was cooled and filtered to collect the solid; under a nitrogen atmosphere, the solid was dispersed in 400mL 4 g of Alizarin Red S was added to N,N-dimethylformamide, ultrasonically dispersed for 15 min, the pH was adjusted to 6 with 1 mol / L dilute hydrochloric acid, and stirred at 60°C for 5 h. After the reaction was completed, the mixture was cooled and filtered, and the solids were collected, washed, and dried to obtain modified activated carbon.

[0032] Example 3

[0033] A method for purifying dimethylchlorosilane by physical adsorption and coordination comprises the following steps:

[0034] The crude dimethylchlorosilane in liquid phase is passed into a fixed-bed absorption tower filled with modified activated carbon. The crude dimethylchlorosilane in liquid phase and the modified activated carbon are subjected to a deep impurity removal treatment by countercurrent contact and then discharged from the bottom of the tower to obtain purified dimethylchlorosilane. The deep impurity removal time is 2 hours. The deep impurity removal treatment conditions are a temperature of 20°C and a liquid space velocity of 0.5 h -1 ;The pressure is 0.01MPa.

[0035] The preparation method of the modified activated carbon is as follows:

[0036] 100 g of biomass raw material (a mixture of rice husk and coconut shell in a mass ratio of 2:3) was dried, crushed and passed through an 80-mesh sieve, then added to a 1 mol / L sodium hydroxide aqueous solution and immersed for 2 h. After the immersion was completed, the solid was filtered and collected. The solid was washed and dried to obtain a pretreated biomass; 90 g of pretreated biomass, 12 g of oxalic acid, 36 g of lanthanum nitrate and 400 mL of water were ultrasonically dispersed and hydrothermally reacted at 250 ° C for 10 h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 800 ° C for 3 h to obtain porous carbon; 60 g of porous carbon was dispersed in 500 mL of 50 wt% ethanol aqueous solution, 10 g of KH550 was added, and the mixture was heated at 50 ° C for 4 h. After the reaction was completed, the solid was cooled and filtered to collect the solid; under a nitrogen atmosphere, the solid was dispersed in 400 mL 6 g of Alizarin Red S was added to N,N-dimethylformamide, and ultrasonic dispersion was performed for 15 min. The pH was adjusted to 6 with 1 mol / L dilute hydrochloric acid, and the mixture was stirred at 60°C for 5 h. After the reaction was completed, the mixture was cooled and filtered, and the solid matter was collected, washed, and dried to obtain modified activated carbon.

[0037] Comparative Example 1

[0038] A method for purifying dimethylmonochlorosilane by physical adsorption and coordination is similar to Example 1, except that the modified activated carbon is porous carbon, and specifically comprises the following steps:

[0039] The crude dimethylchlorosilane in the liquid phase is passed into a fixed-bed absorption tower filled with modified activated carbon. The crude dimethylchlorosilane in the liquid phase is subjected to a deep impurity removal treatment by countercurrent contact with the modified activated carbon, and then discharged from the bottom of the tower to obtain purified dimethylchlorosilane. The deep impurity removal time is 1.5 hours. The deep impurity removal treatment conditions are a temperature of 30°C and a liquid space velocity of 1 hour. -1 ;The pressure is 0.05MPa.

[0040] The preparation method of the modified activated carbon is as follows:

[0041] 100 g of biomass raw material (a mixture of rice husks and coconut shells in a mass ratio of 2:3) was dried, crushed, and passed through an 80-mesh sieve. It was then added to a 1 mol / L sodium hydroxide aqueous solution and immersed for 2 h. After the immersion was completed, the solid was filtered and collected. The solid was washed and dried to obtain pretreated biomass. 72 g of pretreated biomass, 9.2 g of oxalic acid, 30 g of lanthanum nitrate, and 300 mL of water were ultrasonically dispersed and hydrothermally reacted at 220°C for 20 h. After the reaction was completed, it was filtered, the solid was collected, washed, and dried, and calcined at 700°C for 4 h to obtain porous carbon; that is, modified activated carbon.

[0042] Comparative Example 2

[0043] A method for purifying dimethylmonochlorosilane by physical adsorption and coordination is similar to Example 1, except that lanthanum nitrate is not added to the modified activated carbon. The method specifically comprises the following steps:

[0044] The crude dimethylchlorosilane in the liquid phase is passed into a fixed-bed absorption tower filled with modified activated carbon. The crude dimethylchlorosilane in the liquid phase is subjected to a deep impurity removal treatment by countercurrent contact with the modified activated carbon, and then discharged from the bottom of the tower to obtain purified dimethylchlorosilane. The deep impurity removal time is 1.5 hours. The deep impurity removal treatment conditions are a temperature of 30°C and a liquid space velocity of 1 hour. -1 ;The pressure is 0.05MPa.

[0045] The preparation method of the modified activated carbon is as follows:

[0046] 100 g of biomass raw material (a mixture of rice husk and coconut shell in a mass ratio of 2:3) was dried, crushed and passed through an 80-mesh sieve, then added to a 1 mol / L sodium hydroxide aqueous solution and immersed for 2 h. After the immersion was completed, the solid was filtered and collected. The solid was washed and dried to obtain a pretreated biomass; 72 g of pretreated biomass, 9.2 g of oxalic acid and 300 mL of water were ultrasonically dispersed and hydrothermally reacted at 220 ° C for 20 h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 700 ° C for 4 h to obtain porous carbon; 50 g of porous carbon was dispersed in 500 mL of 50 wt% ethanol aqueous solution, 8 g of KH550 was added, and the mixture was heated at 50 ° C for 4 h. After the reaction was completed, the solid was cooled and filtered to collect the solid; under a nitrogen atmosphere, the solid was dispersed in 400 mL 5 g of Alizarin Red S was added to N,N-dimethylformamide, ultrasonically dispersed for 15 min, the pH was adjusted to 6 with 1 mol / L dilute hydrochloric acid, and stirred at 60°C for 5 h. After the reaction was completed, the mixture was cooled and filtered, and the solids were collected, washed, and dried to obtain modified activated carbon.

[0047] The dimethyl monochlorosilane prepared in Example 1 and Comparative Examples 1-2 was subjected to purity tests. The test results are shown in Table 1:

[0048] Table 1 Dimethylchlorosilane purity test results

[0049]

[0050] Compressive Strength Test: The length of the modified activated carbon particles after drying in Example 1 and Comparative Example 2 was measured with a vernier caliper. The activated carbon was then placed in a particle strength tester, pressure was applied, and the instantaneous pressure value when the modified activated carbon was crushed was recorded. The average force per unit length of a specified amount of modified activated carbon was calculated as the strength value. The test results are shown in Table 2:

[0051] Table 2 Compressive strength test results of modified activated carbon

[0052] Compressive strength (N / cm) Example 1 145.3 Comparative Example 2 105.6

[0053] It can be seen from the experimental data in Table 1 and Table 2 that the modified activated carbon prepared in the present invention has good mechanical properties and has a good removal effect on phosphorus, boron and metal impurities in chlorosilane, thereby improving the purity of chlorosilane.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of the present invention.

Claims

1. A method for purifying chlorosilane by physical adsorption and coordination, characterized in that: The steps include: The crude liquid chlorosilane is passed into a fixed-bed absorption tower filled with modified activated carbon, the crude liquid chlorosilane is contacted with the modified activated carbon for deep impurity removal, and then discharged from the bottom of the tower to obtain purified liquid chlorosilane; The preparation method of the modified activated carbon is as follows: The biomass raw material is dried and crushed, and then added to a sodium hydroxide aqueous solution for immersion. After the immersion is completed, the solid matter is filtered and collected, and the solid matter is washed and dried to obtain pretreated biomass; The pretreated biomass, oxalic acid, lanthanum nitrate and water are ultrasonically dispersed and then subjected to a hydrothermal reaction. After the reaction is completed, the mixture is filtered, and the solid is collected, washed, dried and calcined to obtain porous carbon. The porous carbon is dispersed in an ethanol aqueous solution, KH550 is added, the mixture is heated for reaction, and the solid is collected by filtration. Under a nitrogen atmosphere, the solid is dispersed in N,N-dimethylformamide, Alizarin Red S is added, the pH is adjusted to a weak acidic state after ultrasonic dispersion, the mixture is heated for reaction, and after the reaction is completed, the mixture is cooled, filtered, washed and dried to obtain modified activated carbon.

2. The method according to claim 1, wherein: The chlorosilane is at least one of dimethylmonochlorosilane, trimethylmonochlorosilane, methyldichlorosilane, trichlorosilane, methyltrichlorosilane, tetrachlorosilane, and dichlorodihydrosilane.

3. The method according to claim 1, wherein: The contact mode of the liquid phase crude chlorosilane and the modified activated carbon is countercurrent contact.

4. The method according to claim 1, wherein: The deep impurity removal time is 1-2 hours.

5. The method according to claim 1, wherein The deep impurity removal treatment conditions are a temperature of 20-40°C and a liquid space velocity of 0.5-1.5h -1 , the pressure is 0.01-0.1MPa.

6. The method according to claim 1, wherein: The mass ratio of the pretreated biomass, oxalic acid and lanthanum nitrate is 10-15:1-2:4-6.

7. The method according to claim 1, wherein: The hydrothermal reaction temperature is 180-250° C., and the hydrothermal reaction time is 10-30 hours.

8. The method according to claim 1, wherein: The calcination temperature is 550-800° C., and the calcination time is 3-5 hours.

9. The method according to claim 1, characterized in that The mass ratio of the porous carbon, KH550 and Alizarin Red S is 20-30:3-5:2-3.

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