Method for purifying chlorosilane by utilizing physical adsorption and coordination

Abstract

The invention discloses a method for purifying chlorosilane by utilizing physical adsorption and coordination, and belongs to the technical field of silane purification. The method comprises the following steps: introducing a liquid-phase chlorosilane crude product into a fixed bed absorption tower, and treating the liquid-phase chlorosilane crude product with modified activated carbon to obtain high-purity chlorosilane. The activated carbon is modified, so that the modified activated carbon has better mechanical properties, and functional molecules alizarin red S are grafted on the activated carbon through chemical bonds, so that the functional molecules are effectively prevented from falling off in the deep impurity removal treatment process of the modified activated carbon, and the long-acting performance of the modified activated carbon is ensured; and the purity of the chlorosilane product is improved.

Description

Technical Field

[0001] The 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 metal industry. The main production technologies of polysilicon are the modified Siemens method and the silane method. The modified Siemens method reacts industrial silicon powder with HCl to produce chlorosilane, which is then oxidized in H 2 Polysilicon is obtained by reduction deposition in a reduction furnace with a low atmosphere. At the same time, in order to improve the utilization rate of raw materials and be environmentally friendly, the exhaust gas H 2 、SiHCl 3 、SiCl 4 、SiH 2 Cl 2 The silane method is to introduce silane into a fluidized bed with polycrystalline silicon seeds as fluidized particles, so that the silane is cracked and deposited on the seeds, thereby obtaining granular polycrystalline silicon.

[0003] At present, domestic polysilicon enterprises produce polysilicon by the modified Siemens method. The main impurities in the production process are silicon powder, including boron, phosphorus, and metal impurities such as iron, magnesium, and aluminum. These impurities have a huge impact on the quality of polysilicon. In the prior art, the purification and refining technology of chlorosilane is mainly distillation. However, the distillation tower has high investment cost, poor operating stability, huge energy consumption, unstable product quality, and poor practical operability. Metals such as iron, magnesium, and aluminum and non-metallic ions such as boron and phosphorus cannot be removed by distillation, which will have a serious impact on the performance of polysilicon materials. Therefore, it is necessary to provide a method for purifying chlorosilane using physical adsorption and coordination.

[0004] Chinese patent document CN105731465A discloses a method and equipment for removing boron and phosphorus by chemical adsorption reaction of chlorosilane fixed bed, including a heat exchanger, a fixed bed adsorption column and a heat transfer oil circulation pump; the feed pipeline at the bottom of the heat exchanger and the discharge pipeline at the top of the heat exchanger are both connected to the bottom of the fixed bed, and the heat transfer oil circulation pump transports the heat transfer medium to the fixed bed. Chlorosilane gas phase or liquid phase first enters the heat exchanger, and then enters the chemical adsorption fixed bed, and the adsorbent loaded with a chemical complexing agent performs a chemical adsorption reaction on boron and phosphorus impurities, and finally obtains high-purity chlorosilane. The adsorbent used in the invention is physically adsorbed by loading a chemical complexing agent. The chemical complexing agent is easy to fall off from the carrier and affects its adsorption performance. In severe cases, it will also cause secondary pollution to the chlorosilane product and affect 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 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 introduced 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 treatment and then discharged from the bottom of the tower to obtain purified liquid chlorosilane.

[0008] Preferably, the chlorosilane is at least one of dimethyl monochlorosilane, trimethyl monochlorosilane, methyl dichlorosilane, trichlorosilane, methyl trichlorosilane, tetrachlorosilane, and dichlorodihydrosilane.

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

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

[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 , 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 for reaction, and the solid is filtered and collected; 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 10-30h; the calcination temperature is 550-800°C, and the calcination time is 3-5h.

[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 crude liquid chlorosilane products, thereby effectively removing boron, phosphorus and metal impurities in the crude products; lanthanum oxide is introduced into the activated carbon, thereby improving the mechanical strength of the porous carbon and preventing it from being easily broken; on the other hand, phosphorus-containing impurities can be adsorbed, thereby improving the adsorption of the activated carbon; in addition, Alizarin Red S is grafted onto the activated carbon through chemical bonds, 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, thereby ensuring the long-term performance of the modified activated carbon; and improving the purity of the chlorosilane product.

[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 crude liquid chlorosilane. The modified activated carbon can remove impurities such as phosphorus and metals in the crude liquid chlorosilane by adsorption and coordination, which can significantly improve the purity of the liquid chlorosilane, and 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, and the cellulose becomes loose, which is conducive to the subsequent steps; then, a hydrothermal reaction is carried out with sodium carboxymethyl cellulose and lanthanum nitrate to generate lanthanum oxide in situ on the porous carbon. On the one hand, lanthanum oxide can improve the mechanical strength of the porous carbon and make it not easy to break. On the other hand, it can also resist phosphorus-containing impurities. Adsorption is beneficial to improve the removal effect of phosphorus; then amino groups are introduced on the surface of porous carbon, which is beneficial to react with the keto group on Alizarin Red S to form 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 activated carbon through chemical bonds, which has higher stability and effectively avoids the shedding of functional molecule Alizarin Red S during the deep impurity removal treatment of modified activated carbon, ensuring the long-term performance of modified activated carbon; the purity of chlorosilane products is improved. 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 dimethyl monochlorosilane by physical adsorption and coordination comprises the following steps:

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

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

[0026] 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; 72g of pretreated biomass, 9.2g of oxalic acid, 30g of lanthanum nitrate and 300mL of water were ultrasonically dispersed and hydrothermally reacted at 220°C for 20h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 700°C for 4h to obtain porous carbon; 50g of porous carbon was dispersed in 500mL of 50wt% ethanol aqueous solution, 8g of KH550 was added, and the reaction was heated at 50°C 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 Add 5 g of Alizarin Red S to N,N-dimethylformamide, ultrasonically disperse for 15 minutes, adjust the pH to 6 with 1 mol / L dilute hydrochloric acid, stir and react at 60°C for 5 hours. After the reaction is completed, cool and filter, collect the solid, wash and dry to obtain modified activated carbon.

[0027] Example 2

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

[0029] The crude liquid dimethyl monochlorosilane is passed into a fixed bed absorption tower filled with modified activated carbon, and the crude liquid dimethyl monochlorosilane and the modified activated carbon are subjected to deep impurity removal treatment by countercurrent contact and then discharged from the bottom of the tower to obtain purified dimethyl monochlorosilane; 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°C for 30h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 500°C 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 reaction was heated at 50°C 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 Add 4 g of Alizarin Red S to N,N-dimethylformamide, ultrasonically disperse for 15 minutes, adjust the pH to 6 with 1 mol / L dilute hydrochloric acid, stir and react at 60°C for 5 hours. After the reaction is completed, cool and filter, collect the solid, wash and dry to obtain modified activated carbon.

[0032] Example 3

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

[0034] The crude liquid dimethyl monochlorosilane is passed into a fixed bed absorption tower filled with modified activated carbon, and the crude liquid dimethyl monochlorosilane and the modified activated carbon are subjected to deep impurity removal treatment by countercurrent contact and then discharged from the bottom of the tower to obtain purified dimethyl monochlorosilane; 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] 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; 90g of pretreated biomass, 12g of oxalic acid, 36g of lanthanum nitrate and 400mL of water were ultrasonically dispersed and hydrothermally reacted at 250°C for 10h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 800°C for 3h to obtain porous carbon; 60g of porous carbon was dispersed in 500mL of 50wt% ethanol aqueous solution, 10g of KH550 was added, and the reaction was heated at 50°C 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 Add 6 g of Alizarin Red S to N,N-dimethylformamide, ultrasonically disperse for 15 minutes, adjust the pH to 6 with 1 mol / L dilute hydrochloric acid, stir and react at 60°C for 5 hours. After the reaction is completed, cool and filter, collect the solid, wash and dry to obtain modified activated carbon.

[0037] Comparative Example 1

[0038] A method for purifying dimethyl monochlorosilane 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 liquid dimethyl monochlorosilane is passed into a fixed bed absorption tower filled with modified activated carbon, and the crude liquid dimethyl monochlorosilane and the modified activated carbon are subjected to deep impurity removal treatment by countercurrent contact and then discharged from the bottom of the tower to obtain purified dimethyl monochlorosilane; 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 1h -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 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 the 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 dimethyl monochlorosilane by physical adsorption and coordination is similar to Example 1, except that lanthanum nitrate is not added to the modified activated carbon, and specifically comprises the following steps:

[0044] The crude liquid dimethyl monochlorosilane is passed into a fixed bed absorption tower filled with modified activated carbon, and the crude liquid dimethyl monochlorosilane and the modified activated carbon are subjected to deep impurity removal treatment by countercurrent contact and then discharged from the bottom of the tower to obtain purified dimethyl monochlorosilane; 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 1h -1 ; The pressure is 0.05MPa.

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

[0046] 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; 72g of pretreated biomass, 9.2g of oxalic acid and 300mL of water were ultrasonically dispersed and hydrothermally reacted at 220℃ for 20h. After the reaction was completed, the solid was filtered and collected, washed and dried, and calcined at 700℃ for 4h to obtain porous carbon; 50g of porous carbon was dispersed in 500mL of 50wt% ethanol aqueous solution, 8g of KH550 was added, and the reaction 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 Add 5 g of Alizarin Red S to N,N-dimethylformamide, ultrasonically disperse for 15 minutes, adjust the pH to 6 with 1 mol / L dilute hydrochloric acid, stir and react at 60°C for 5 hours. After the reaction is completed, cool and filter, collect the solid, wash and dry to obtain modified activated carbon.

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

[0048] Table 1 Dimethylchlorosilane purity test results

[0049]

[0050] Compressive strength test: Use a vernier caliper to measure the length of the modified activated carbon particles after drying in Example 1 and Comparative Example 2, then place the activated carbon in a particle strength tester, apply pressure, record the instantaneous pressure value when the modified activated carbon is crushed, and calculate the average force value per unit length of a specified number of modified activated carbons 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 only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection 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 introduced 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 treatment and then discharged from the bottom of the tower to obtain purified liquid chlorosilane.

2. The method according to claim 1, characterized in that: The chlorosilane is at least one of dimethyl monochlorosilane, trimethyl monochlorosilane, methyl dichlorosilane, trichlorosilane, methyl trichlorosilane, tetrachlorosilane and dichlorodihydrosilane.

3. The method according to claim 1, characterized in that: The contact mode between the liquid phase crude chlorosilane and the modified activated carbon is countercurrent contact.

4. The method according to claim 1, characterized in that: The deep impurity removal time is 1-2h.

5. The method according to claim 1, characterized in that 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, characterized in that 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 a pretreated biomass; The pretreated biomass, oxalic acid, lanthanum nitrate and water are ultrasonically dispersed and then subjected to hydrothermal reaction. After the reaction is completed, 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, heated for reaction, and the solid is filtered and collected; 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.

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

8. The method according to claim 6, characterized in that: The hydrothermal reaction temperature is 180-250° C., and the hydrothermal reaction time is 10-30 hours.

9. The method according to claim 6, characterized in that: The calcination temperature is 550-800° C., and the calcination time is 3-5 hours.

10. The method according to claim 6, 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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