Method for purifying silicon from spent catalyst of organic silicon synthesis and use for preparing silicon-based alloys

Abstract

This application provides a method for purifying silicon from waste catalysts used in organosilicon synthesis and its application in preparing silicon-based alloys. The method includes: acid washing the waste catalysts with an acid solution; adding acid to the silicon-enriched material obtained from the acid washing separation to obtain an acid leaching slurry, and diluting the acid leaching slurry to obtain a waste catalyst electrolyte; adjusting the pH value of the waste catalyst electrolyte to 5.5-6.5, and introducing the waste catalyst electrolyte into an electrolytic cell; introducing oxygen-containing gas near the cathode plate of the electrolytic cell, and conducting an electrolytic reaction by applying direct current to the electrode plates of the electrolytic cell; adjusting the pH value of the electrolyte in the electrolytic cell to 7.0-7.5, and continuing the electrolytic reaction to obtain a metal precipitate; separating the liquid portion and the precipitate portion in the electrolytic cell, adding water to the precipitate portion, stirring thoroughly, and then centrifuging, washing, and drying to obtain silicon powder. This application can effectively remove metallic impurities and organic matter from waste catalysts, obtain high-purity silicon, and prepare high-quality silicon-based alloys.

Description

Technical Field

[0001] This application belongs to the field of resource recycling and environmental protection technology. Specifically, it relates to a method for purifying silicon from waste catalysts of organosilicon synthesis and its application in preparing silicon-based alloys. Background Technology

[0002] Organosilicon materials possess excellent properties such as temperature resistance, corrosion resistance, ease of processing, and low surface tension, and are widely used in aerospace, new materials, biomedicine, and electronics. Industrially, organosilicon materials are prepared in a fluidized bed using silicon powder and chloromethane as raw materials and copper powder as a catalyst. However, after the fluidized bed has been running for a certain period, the reactivity of the silicon powder deteriorates due to the accumulation of carbon on the surface of the silicon powder particles and impurities. To avoid a decrease in yield, this portion of silicon powder needs to be discharged from the production system via airflow. The resulting powder and the waste residue discharged from the bottom of the fluidized bed constitute the waste catalyst.

[0003] The main components of organosilicon waste catalysts are silicon, copper, carbon, iron, etc. Existing waste catalyst treatment methods mainly focus on using acid oxidation impregnation, alkaline oxidation, or calcination to remove carbon and metal elements, recover silicon powder, and then prepare silicon-based alloys.

[0004] However, existing technologies have limited ability to remove metal elements such as copper, carbon, and iron from organosilicon waste catalysts.

[0005] Existing technologies also include some methods for removing organic matter. For example, patent CN119119964A discloses "a method for preparing iron-silicon-copper alloy phase change energy storage capsules using waste organosilicon catalysts," which involves calcining the waste catalysts under an argon atmosphere to remove organic matter. However, this method has limited effectiveness in removing high-boiling-point organic matter, and the high-temperature calcination requires a large amount of energy.

[0006] Patent CN114990334A discloses a method for recovering copper from waste silicone catalysts, which involves pre-treating the waste silicone catalysts with water to reduce the chlorinated organic matter content. However, for some water-insoluble organics, such as silicone polymers, the effect of water immersion pre-treatment is limited.

[0007] Therefore, in order to improve the quality of silicon-based multi-element alloys, it is necessary to further develop or introduce process steps that can effectively remove metallic impurities and organic matter from waste catalysts, based on existing technologies. Summary of the Invention

[0008] The technical problem to be solved by this application is to provide a method for purifying silicon from waste catalysts in organosilicon synthesis and its application in preparing silicon-based alloys. This method can effectively remove metallic impurities and organic matter from the waste catalysts to obtain high-purity silicon for use in industrial silicon or for preparing high-quality silicon-based alloys.

[0009] To achieve the above-mentioned effects, this application provides a method for purifying silicon from waste catalysts used in organosilicon synthesis, comprising:

[0010] The waste catalyst generated during organosilicon synthesis was acid-washed using a first acid solution. A second acid solution was added to the silicon-enriched material obtained from the acid washing separation to obtain an acid leaching slurry. The acid leaching slurry was then diluted with pure water until the concentration of metal ions was not less than 0.18 g·L⁻¹. -1 The waste electrolyte was obtained.

[0011] Adjust the pH value of the waste electrolyte to 5.5-6.5, and then introduce the waste electrolyte into the electrolytic cell;

[0012] An oxygen-containing gas is introduced near the cathode plate of the electrolytic cell, and a direct current is applied to the electrode plate of the electrolytic cell to carry out the electrolytic reaction.

[0013] The pH value of the electrolyte in the electrolytic cell is adjusted to 7.0~7.5, and the electrolysis reaction continues to obtain a metal precipitate;

[0014] The liquid portion and the precipitate portion in the electrolytic cell are separated. Water is added to the precipitate portion and stirred thoroughly. After centrifugation, washing and drying, silicon powder is obtained.

[0015] The proposed method first removes most of the metallic impurities by pickling, followed by pickling again to generate a metal ion electrolyte by reacting the metal elements with the acid. Oxygen-containing gas is then introduced into the cathode plate of an electrolytic cell with an electrolyte pH of 5.5-6.5, causing oxygen to continuously generate H2O2 on the cathode surface through a redox reaction. The reaction conditions are controlled so that H2O2 reacts with the metal ions in the acid-soaked slurry in the electrolytic cell to generate ·OH. The generated ·OH has strong oxidizing properties, thereby separating organic matter from silicon in the waste catalyst, decomposing the organic matter, and separating silicon from the metal.

[0016] This process mainly involves the following reaction equations:

[0017] Oxygen is dissolved in the solution in the electrolytic cell, so that oxygen continuously generates H2O2 on the cathode surface through a redox reaction:

[0018] O2 + 2H + +2e - →H2O2

[0019] Metal ions react with H₂O₂ to generate the strong oxidizing agent hydroxyl radical ·OH, while also producing a small amount of hydroxide ions. :

[0020]

[0021]

[0022]

[0023] Next, the pH value of the electrolyte in the electrolytic cell is adjusted to 7.0~7.5, so that the reaction between H2O2 and metal ions is directed towards the generation of OH-. - The process proceeds in the direction of precipitation, causing metal ions to solidify.

[0024] When the pH is neutral to alkaline, the solution contains Gradually increasing, more It will react with metal ions to form a precipitate.

[0025] Finally, by utilizing the density differences of different precipitates, high-purity silicon was separated.

[0026] Furthermore, the metal ions include Cu. 2+ Cu + and Fe 2+ At least one of them.

[0027] Furthermore, the first acid solution comprises a dilute sulfuric acid solution with a mass concentration of 20-30%.

[0028] Furthermore, the second acid solution comprises a dilute sulfuric acid solution with a mass concentration of 5-15%.

[0029] Furthermore, the oxygen-containing gas includes air and / or oxygen.

[0030] Furthermore, before adding the waste catalyst generated from organosilicon synthesis to a dilute sulfuric acid solution for acid leaching, the method further includes: calcining and pulverizing the waste catalyst.

[0031] To achieve the above-mentioned effects, this application also provides a method for purifying silicon from organosilicon synthesis waste catalysts and its application in the preparation of silicon-based multi-element alloys.

[0032] The beneficial effects of this application are as follows:

[0033] This application first removes most of the metallic impurities through acid washing, followed by another acid washing process. This process generates a metal ion electrolyte by reacting the metallic elements with the acid. Oxygen-containing gas is introduced near the cathode plate in an electrolytic cell with an electrolyte pH of 5.5-6.5. This causes oxygen to continuously generate H₂O₂ on the cathode surface through a redox reaction. The reaction conditions are controlled so that H₂O₂ reacts with the metal ions in the acid-soaked slurry in the electrolytic cell to generate ·OH. The generated ·OH has strong oxidizing properties, thereby separating organic matter from silicon in the waste catalyst, decomposing the organic matter, and separating silicon from the metal. Next, the pH of the electrolyte in the electrolytic cell is adjusted to 7.0-7.5, directing the reaction of H₂O₂ with the metal ions towards the generation of ·OH.- The process proceeds in the direction of precipitation, causing metal ions to solidify. Finally, by utilizing the density differences of the different precipitates, high-purity silicon is separated.

[0034] This solution not only effectively removes metal impurities and organic matter from waste catalysts, but also significantly reduces the processing cost of waste catalyst resource recycling, and has broad industrial application value. Detailed Implementation

[0035] The specific embodiments of this application are described in detail below. However, it should be noted that the scope of protection of this application is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0036] Apart from the embodiments, any specific numerical values ​​(including the endpoints of numerical ranges) disclosed herein are not limited to their exact values, but should be understood to also encompass values ​​close to the exact value, such as all possible values ​​within ±10% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0037] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0038] This application provides a method for purifying silicon from waste catalysts used in organosilicon synthesis, comprising the following steps:

[0039] S11: The waste catalyst generated from organosilicon synthesis is pickled using the first acid solution, and the second acid solution is added to the silicon-enriched material obtained by pickling and separation to obtain the acid slurry;

[0040] Optionally, the first acid solution includes a dilute sulfuric acid solution with a mass concentration of 20-30%; the second acid solution includes a dilute sulfuric acid solution with a mass concentration of 5-15%.

[0041] Preferably, the waste catalyst is crushed before this step to reduce the particle size of the waste catalyst and improve the pickling efficiency.

[0042] S12: Adjust the pH value of the acid leaching slurry to 5.5~6.5, and then pass the acid leaching slurry into the electrolytic cell;

[0043] Specifically, the concentration of metal ions in the acid leaching slurry is not less than 0.18 g·L⁻¹; the metal ions include Cu. 2+ Cu + and Fe2+ At least one of them.

[0044] S13: An oxygen-containing gas is introduced near the cathode plate of the electrolytic cell, and a direct current is applied to the electrode plate of the electrolytic cell to carry out an electrolytic reaction.

[0045] S14: Adjust the pH value of the reactants in the electrolytic cell to above 7.0, and carry out precipitation in the electrolytic cell;

[0046] S15: Separate the liquid portion from the precipitate portion in the electrolytic cell, add water to the precipitate portion and stir thoroughly, then centrifuge, wash and dry to obtain silicon powder.

[0047] It should be noted that the pH adjuster used in the following specific embodiments is ammonia, dilute sulfuric acid, or other conventional pH adjusters.

[0048] This application utilizes oxygen-containing gas introduced through the cathode plate in an electrolytic cell, causing oxygen to continuously generate H₂O₂ on the cathode surface through a redox reaction. The reaction conditions are controlled to allow H₂O₂ to react with metal ions in the acid-leaching slurry in the electrolytic cell, generating ·OH. The generated ·OH has strong oxidizing properties, thereby separating organic matter from silicon in the waste catalyst, decomposing the organic matter, and separating silicon from the metal. The reaction conditions between H₂O₂ and metal ions are then controlled to promote the formation of OH⁻, precipitating the metal ions. Finally, the density difference of different precipitates is used to separate high-purity silicon.

[0049] This solution not only effectively removes metal impurities and organic matter from waste catalysts, but also significantly reduces the processing cost of waste catalyst resource recycling, and has broad industrial application value.

[0050] Based on the embodiments provided in this application, some specific experiments have been conducted on this application. From these embodiments and comparative examples, it can be seen that the solution provided in this application has achieved good results. It should be noted that the following embodiments are only used to illustrate the present invention in detail and do not limit the scope of protection of the invention in any way.

[0051] The chemical composition of the organosilicon waste catalyst used in this embodiment of the invention is as follows: silicon (Si): 64.80%, copper (Cu): 12.80%, iron (Fe): 5.70%, aluminum (Al): 1.10%, calcium (Ca): 0.30%, zinc (Zn): 1.05%, carbon (C): 2.20%, and others: 12.05%.

[0052] Example 1

[0053] A method for purifying silicon from waste catalysts used in organosilicon synthesis includes the following steps:

[0054] S21a: 1000g of waste catalyst generated from organosilicon synthesis was acid-washed for 30 minutes using a 30% (w / w) dilute sulfuric acid solution as the first acid solution, yielding 641.69g of silicon-enriched material and a leachate of metal sulfates. The composition of the silicon-enriched material was analyzed, and the mass of each component in the silicon-enriched material is shown in Table 1.

[0055] Example 2

[0056] S21b: Take 160g of the silicon enrichment material obtained in step S21, mix the silicon enrichment material with the second acid solution evenly to obtain an acid leaching slurry, wherein the second acid solution is 100mL of a 5% dilute sulfuric acid solution.

[0057] Then, slowly add purified water to the acid leaching slurry to dilute it to 17L, resulting in a metal ion concentration of not less than 0.18 g·L. -1 Waste electrolyte in contact body;

[0058] S22: Adjust the pH value of the waste electrolyte to 5.5, and introduce the waste electrolyte into the electrolytic cell;

[0059] S23: At a distance of 2m from the cathode plate of the electrolytic cell 3 Air is introduced at a flow rate of / min, and a direct current is applied to the electrode plates of the electrolytic cell to carry out the electrolytic reaction for 30 minutes; the cathode and anode plates of the electrolytic cell are both made of graphite, and the current density of the electrode plates of the electrolytic cell is 200A / m. 2 The voltage is 80V;

[0060] S24: Adjust the pH value of the reactants in the electrolytic cell to 7.0 and react for 40 minutes to allow metal ions to precipitate in the electrolytic cell;

[0061] S25: Separate the liquid portion from the precipitate portion in the electrolytic cell, add water to the precipitate portion and stir thoroughly, then centrifuge, wash and dry to obtain silicon powder.

[0062] The composition and quality of the silicon powder obtained in step S25 were tested, and the test results are shown in Table 2.

[0063] Example 3

[0064] The processing method in this embodiment is basically the same as that in Embodiment 2, except that:

[0065] In this embodiment, step S21b is as follows: Take 160g of the silicon enrichment material obtained in step S21, mix the silicon enrichment material with the second acid solution evenly to obtain an acid leaching slurry, wherein the second acid solution is 50mL of a 10% dilute sulfuric acid solution.

[0066] Then, slowly add purified water to the acid leaching slurry to dilute it to 13L, obtaining a metal ion concentration of not less than 0.18g·L. -1 Waste electrolyte in contact body;

[0067] In this embodiment, in step S23, the pH value of the acid leaching slurry is adjusted to 6.5 and reacted for 40 minutes, and in step S24, the pH value of the reactants in the electrolytic cell is adjusted to 7.5 and reacted for another 30 minutes.

[0068] The composition and quality of the silicon powder obtained in this embodiment were tested, and the test results are shown in Table 2.

[0069] Comparative Example 1

[0070] The processing method in this embodiment is basically the same as that in Embodiment 2, except that:

[0071] In this embodiment, the acid slurry obtained in step S21b is directly washed for 70 minutes and dried to obtain silicon powder; steps S22-S25 are not performed.

[0072] The composition and quality of the silicon powder obtained in this embodiment were tested, and the test results are shown in Table 2.

[0073] Comparative Example 2

[0074] The processing method in this embodiment is basically the same as that in Embodiment 2, except that:

[0075] In this embodiment, the pH value of the acid leaching slurry is adjusted to 7.0 in step S22 and the reaction is carried out for 70 minutes; the pH value is not adjusted in step S24.

[0076] The composition and quality of the silicon powder obtained in this embodiment were tested, and the test results are shown in Table 2.

[0077] Table 1. Composition of silicon enrichment material obtained in Example 1

[0078]

[0079] Table 2. Silicon powder composition obtained in Examples 2-3 and Comparative Examples 1-2

[0080]

[0081] By comparing Examples 2-3 with Comparative Example 1, it was found that Comparative Example 1, which had no electrolysis process, had a higher quality of impurities such as copper, iron, aluminum, and zinc in the high-purity silicon obtained. This indicates that even after acid washing, Comparative Example 1 could not effectively remove metal elements and carbon.

[0082] Comparing Examples 2-3 with Comparative Example 2, Comparative Example 2 had a higher pH value during the electrolysis process, resulting in less improvement in the purity of silicon in the obtained high-purity silicon, and higher levels of impurities such as copper, iron, aluminum, and zinc. This indicates that directly adjusting the pH to 7.0-7.5 cannot effectively precipitate metal ions in the electrolyte.

[0083] In Examples 2 and 3, the pH was adjusted to 5.5-6.5. By using oxygen-containing gas introduced into the cathode plate in the electrolytic cell, oxygen continuously generated H2O2 on the cathode surface through a redox reaction. The reaction conditions were controlled so that H2O2 reacted with the metal ions of the acid leaching slurry in the electrolytic cell to generate ·OH. The generated ·OH has strong oxidizing properties, thereby separating organic matter from silicon in the waste catalyst, decomposing the organic matter, and separating silicon from metal. This allowed the carbon-containing organic matter to dissolve in the solvent, and also allowed the metal and silicon to separate and dissolve in the solvent. When the pH value of the reactants in the electrolytic cell was adjusted to 7.0-7.5 in step S24, the metal ions separated from the silicon surface could precipitate in the electrolytic cell.

[0084] It is evident that the beneficial effects of this application are significant.

[0085] Application examples

[0086] The high-purity silicon obtained in this application can be used for industrial silicon and also for preparing silicon-based multi-element alloys.

[0087] The application of a method for purifying silicon from waste catalysts in organosilicon synthesis in the preparation of silicon-based multi-element alloys includes the following steps:

[0088] S31: According to the silicon-based multi-element alloy composition requirements of production needs, weigh the silicon powder obtained in Example 2 or 3 and the remaining metal alloys or pure metals in proportion to obtain alloy raw materials.

[0089] S32: The alloy raw material obtained in step S31 is added to a reaction furnace for smelting; the reaction furnace can be any one of a vacuum induction furnace, an electric arc furnace, or a resistance furnace;

[0090] S33: After the molten metal is cooled naturally, it is poured out of the furnace to obtain the finished silicon-based multi-element alloy.

[0091] As can be seen from the above embodiments, comparative examples, and experimental conclusions, the method for purifying silicon from waste catalysts in organosilicon synthesis and the application of this application in preparing silicon-based alloys can effectively remove metallic impurities and organic matter from waste catalysts, and prepare high-quality silicon-based alloys. Furthermore, the beneficial effects of this application are significant.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying silicon from waste catalysts in organosilicon synthesis, characterized in that, include: The waste catalyst generated during organosilicon synthesis was acid-washed using a first acid solution. A second acid solution was added to the silicon-enriched material obtained from the acid washing separation to obtain an acid leaching slurry. The acid leaching slurry was then diluted with pure water until the concentration of metal ions was not less than 0.18 g·L⁻¹. -1 The waste electrolyte was obtained. Adjust the pH value of the waste electrolyte to 5.5-6.5, and then introduce the waste electrolyte into the electrolytic cell; An oxygen-containing gas is introduced near the cathode plate of the electrolytic cell, and a direct current is applied to the electrode plate of the electrolytic cell to carry out the electrolytic reaction. The pH value of the electrolyte in the electrolytic cell is adjusted to 7.0~7.5, and the electrolysis reaction continues to obtain a metal precipitate; The liquid portion and the precipitate portion in the electrolytic cell are separated. Water is added to the precipitate portion and stirred thoroughly. After centrifugation, washing and drying, silicon powder is obtained.

2. The method as described in claim 1, characterized in that, The metal ions include Cu 2+ Cu + and Fe 2+ At least one of them.

3. The method as described in claim 1, characterized in that, The first acid solution includes a dilute sulfuric acid solution with a mass concentration of 20-30%.

4. The method as described in claim 1, characterized in that, The second acid solution includes a dilute sulfuric acid solution with a mass concentration of 5-15%.

5. The method as described in claim 1, characterized in that, The oxygen-containing gas includes air and / or oxygen.

6. The method as described in claim 3, characterized in that, Before adding the waste catalyst generated from organosilicon synthesis to a dilute sulfuric acid solution for acid leaching, the method further includes: The waste contact material is then crushed.

7. The application of the method for purifying silicon from organosilicon synthesis waste catalyst as described in any one of claims 1-6 in the preparation of silicon-based multi-element alloys.

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