Preparation method of 5N high-purity antimony

Abstract

A method for preparing 5N high-purity antimony includes the following steps: (1) using catalyst-grade Sb2O3 and polyester-grade ethylene glycol as raw materials, through high purification processes such as operation steps, filter material selection, process condition optimization, vacuum discharge, two primary filtrations and fine filtrations, and two crystallizations during the preparation of antimony glycolate, the obtained antimony glycolate meets the 5N standard; (2) mixing the 5N grade antimony glycolate with semiconductor-grade graphite powder as a supplementary reducing agent, and covering its surface with food-grade sodium carbonate, and reducing and melting under inert gas protection conditions to obtain 5N high-purity antimony with a total impurity content of <10ppm in one step. The process flow of this invention is simple, the process conditions are easy to control, the direct yield from antimony trioxide raw material to 5N high-purity antimony product is high, the cost is lower than other 5N high-purity antimony preparation processes, and it is more environmentally friendly.

Description

Technical Field

[0001] This invention relates to a method for preparing high-purity metallic antimony, and more particularly to a method for preparing 5N high-purity antimony. Background Technology

[0002] Antimony is a traditional advantageous resource for my country. my country is a major producer of primary and mid-range antimony products and a source of primary and mid-range antimony products—the raw materials for high-end antimony products (5N and above)—for developed Western countries. However, my country needs to import high-end antimony products of 5N grade and above (including 5N grade) for applications such as semiconductors and military industries, at prices several times to more than ten times higher than those from developed Western countries. With the rapid growth in demand for high-purity antimony of 5N and above in my country's semiconductor, defense, and military industries, especially the surge in demand in the new energy sector, a broad market prospect has been created for high-purity antimony of 5N grade and above.

[0003] Currently, the main methods for preparing high-purity antimony of grade 5N and above include two chlorination methods: oxidizing refined antimony with chlorine gas in a closed container to generate SbCl5 and SbCl3, and reacting Sb2O3 with HCl to generate SbCl3, followed by multi-stage distillation-H2 reduction smelting-vacuum distillation of the SbCl5 or SbCl3 solution; and a multi-stage vacuum distillation method using refined antimony as raw material.

[0004] The methods disclosed in CN 117965908B and CN 120555773 A both use ordinary antimony glycolate as raw material. The former directly reduces and melts the ordinary antimony glycolate product into 4N5 high-purity antimony, and then vacuum distills the 4N5 high-purity antimony to prepare 5N high-purity antimony; the latter first hydrolyzes the antimony glycolate to obtain Sb2O. 3， Sb₂O₃ is then reduced and smelted using a biomass reducing agent to obtain 4N antimony. This 4N antimony is then subjected to two-stage vacuum distillation to obtain 5N high-purity antimony. Both chlorination methods require extremely high-quality equipment. Both SbCl₅ and SbCl₃ are highly corrosive, and chlorine and hydrochloric acid pose significant environmental threats. Furthermore, the processes are lengthy, requiring substantial equipment investment and resulting in high costs. The multi-stage vacuum distillation method using refined antimony as raw material also suffers from low yields of 5N high-purity antimony, leading to high costs. Experimental studies have confirmed that the direct yield of 4N antimony from 3N antimony via vacuum distillation is approximately 60%, and the direct yield of 5N antimony from 4N antimony via vacuum distillation is approximately 40%. Although the two methods disclosed in CN 117965908 B and CN120555773 A have improved the cost and yield of 5N antimony products compared with the aforementioned methods, vacuum distillation is still required to convert 4N antimony to 5N antimony, which will significantly affect the final direct yield of 5N high-purity antimony. Furthermore, the method disclosed in CN 120555773 A also has environmental issues related to the treatment of wastewater from the hot hydrolysis of antimony glycol.

[0005] CN115305361A discloses a production process for high-purity antimony rods and antimony white, using 3N antimony oxide as raw material. The process route is: washing with dilute nitric acid - reacting with hydrochloric acid - obtaining antimony trioxide - hydrolysis - boiling deoxidation - 5N grade antimony trioxide - vacuum high-purity carbon reduction - vacuum distillation - Czochralski purification. However, this process also suffers from problems such as a lengthy process flow, difficulty in controlling process conditions, high equipment requirements, serious environmental pollution, the need for external addition of all reducing agents, and high production costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing 5N high-purity antimony with high product yield, simple process, low preparation cost, and environmental protection and safety.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows: A method for preparing 5N high-purity antimony, comprising the following steps:

[0008] (1) Preparation of 5N grade antimony glycol ester: The raw material catalyst grade antimony trioxide and polyester grade ethylene glycol (EG) are added to the reflux reactor, vacuum is drawn, and heating is carried out for vacuum reflux reaction; after the reaction is completed, the temperature is raised and the mixture is slowly stirred to clarify, and a clear reaction solution is obtained; the obtained clear reaction solution is cooled down, and then subjected to two-stage filtration by vacuum discharge method, the filtrate is sent to the crystallization reactor for cooling and crystallization, and then centrifuged and filtered to obtain 4N grade crystalline antimony glycol ester with total impurities <15ppm;

[0009] The 4N grade crystalline antimony glycol ester prepared above was added to a refining kettle and dissolved by heating to obtain a polyester grade ethylene glycol solution of 4N grade crystalline antimony glycol ester. The obtained solution was cooled and then subjected to two-stage filtration (primary filtration and fine filtration) by vacuum discharge. The filtrate was sent to a crystallization kettle for cooling and recrystallization, and then centrifuged and filtered to obtain a crystalline 5N grade antimony glycol ester product with total impurities <10ppm, which meets the requirements for the impurity content of 5N high-purity antimony.

[0010] (2) Preparation of 5N high-purity antimony: The crystalline 5N grade antimony glycol ester obtained in step (1) is mixed with semiconductor grade graphite powder as a supplementary reducing agent. After stirring evenly, the mixture is placed in an alumina crucible. A layer of food-grade sodium carbonate, which has the functions of removing arsenic and selenium and slag formation, is then covered on the surface of the mixture. The alumina crucible is then placed in a vacuum medium-frequency melting furnace, a vacuum is drawn, and inert gas is injected simultaneously from the top and bottom of the furnace. Under the protection of inert gas and the action of stirring, the temperature is raised to carry out the reduction reaction melting. After the reduction reaction melting is completed, the gas supply to the bottom of the furnace is stopped. Then, under the protection of inert gas at the top of the furnace, the mixture is kept at a constant temperature for clarification, and then the slag is skimmed off. Inert gas is then continued to be supplied from the top of the furnace for protection, and the mixture is cooled to room temperature to obtain 5N high-purity antimony ingots. Then, the gas supply is stopped, the antimony ingots are taken out and rinsed with pure water and dried to obtain the 5N high-purity antimony product.

[0011] The reaction equation for the vacuum reflux reaction between Sb₂O₃ and ethylene glycol is as follows:

[0012] Sb₂O₃ + 3C₂H₆O₂ Sb2(OCHCH2O)3 + 3H2O

[0013] The media used for both primary and fine filtration are composed of layers of activated carbon fiber fabric (cloth or felt) and a membrane-type composite needle-punched filter felt containing polytetrafluoroethylene (PTFE) resin. The primary filtration medium consists of three layers: PTFE (polytetrafluoroethylene) – 3mm activated carbon fiber fabric (cloth or felt) – PTFE (polytetrafluoroethylene). The fine filtration medium consists of five layers: PTFE (polytetrafluoroethylene) filter cloth – 3mm thick carbon fiber felt – PTFE (polytetrafluoroethylene) filter cloth – 5mm thick carbon fiber felt – PTFE (polytetrafluoroethylene) filter cloth. The filtration media system is resistant to damp heat temperatures exceeding 300℃, and is resistant to acids, alkalis, and organic solvents. It has a three-dimensional microporous structure, resulting in low filtration resistance and easy peeling of the filter cake layer, enabling miniaturization of the adsorption device and thinning of the adsorption layer.

[0014] The specific surface area of ​​the activated carbon fiber fabric—cloth or felt—is 900-2500 m². 2 With a porosity of ≥ 90% and a pore size of approximately 20 Å, more than 90% of its pores are micropores. It can rapidly and effectively trap ultrafine particles and effectively remove heavy metals from water, especially showing strong adsorption capacity for heavy metals such as As, Pb, Fe, Cu, Se, Bi, Te, Ni, Mn, Sn, and Ag. The single-component equilibrium adsorption capacity is between 0.080 and 0.175 mmol / g.

[0015] Studies have shown that, under conditions below 160℃, the oxides of various heavy metals and other harmful impurities in Sb₂O₃, such as As, Pb, Fe, Cu, Se, Bi, Te, Ni, Mn, Sn, Ag, and Si, mostly do not undergo esterification with ethylene glycol and instead remain suspended as particles in the ethylene glycol antimony ester solution. However, a few compounds, such as tellurium oxide, copper oxide, and silver oxide, are reduced to small metal particles and precipitate at the reaction temperature of ethylene glycol antimony ester, and are separated from the ethylene glycol antimony ester solution through primary and secondary filtration.

[0016] The reduction reaction melting mechanism in the medium-frequency melting furnace is as follows:

[0017] Sb2(OCH2CH2O)3 Sb₂O₃ + 3HOCH₂CH₂OH

[0018] Sb₂O₃ + C Sb+CO

[0019] Sb₂O₃ + C Sb + CO2

[0020] At 200–250 °C, antimony glycol ester begins to release ethylene glycol, accompanied by the formation of Sb2O3. At >800 °C and in an inert atmosphere (such as N2), the ethylene glycol is completely carbonized and, together with semiconductor-grade graphite powder, acts as a reducing agent to reduce Sb2O3 to metallic antimony (Sb).

[0021] Using the above technical solution, the direct yield of 5N high-purity antimony is several times higher than that of vacuum distillation. The process is simple, the process conditions are easy to control, and the cost is lower and more environmentally friendly than other 5N high-purity antimony preparation processes.

[0022] Furthermore, in the catalyst-grade antimony trioxide, the antimony content (Sb₂O₃) is ≥99.85%, the total impurities are <150ppm, and the particle size is 0.75~1.1μm; in the polyester-grade ethylene glycol, the impurity limit is <1ppm.

[0023] Furthermore, in step (1), the mass ratio of antimony (Sb) to polyester-grade ethylene glycol (EG) in the catalyst-grade antimony trioxide is 0.07~0.10, preferably 0.08~0.09.

[0024] Furthermore, in step (1), the temperature of the vacuum reflux reaction (i.e., the synthesis reaction of antimony glycol) is 135-150°C, preferably 140-145°C.

[0025] Furthermore, in step (1), the vacuum reflux reaction (ethylene glycol antimony ester synthesis reaction) takes 4 to 8 hours, preferably 4.5 to 6.5 hours.

[0026] Appropriately lowering the reaction temperature and extending the reaction time can significantly reduce the participation of heavy metals and other harmful impurities in the reaction, reduce the probability of various impurities entering the ethylene glycol antimony ester solution in a combined state, and improve the purity of the ethylene glycol antimony ester solution.

[0027] Furthermore, in step (1), the negative pressure condition of the vacuum reflux reaction (ethylene glycol antimony ester synthesis reaction) is 0.055 MPa to 0.095 MPa; preferably 0.065 to 0.09 MPa.

[0028] Furthermore, in step (1), during the process of heating and slow stirring to clarify, the temperature is controlled at 140-155℃, preferably 145-150℃.

[0029] Furthermore, in step (1), the stirring speed of the slow stirring is 5-10 r / min, preferably 6-8 r / min.

[0030] Furthermore, in step (1), the time for heating and slow stirring to clarify is 35-90 min, preferably 40-60 min.

[0031] Further, in step (1), the antimony glycolate reaction solution is cooled to 115-140°C, preferably 120-130°C, and then filtered.

[0032] Furthermore, in step (1), the crystallization temperature of the ethylene glycol antimony ester filtrate is <30℃, and the crystallization time is 3-8h, preferably 4-6h.

[0033] Furthermore, in step (1), during the refining of the 4N grade crystalline antimony glycol ester, the mass ratio of antimony glycol ester to the solvent polyester grade ethylene glycol (EG) is 1 / 1.3 to 2.0, preferably 1 / 1.5 to 1.8.

[0034] Furthermore, in step (1), the 4N-grade crystalline antimony glycolate is refined at a dissolution temperature of 100–120°C, preferably 110–120°C.

[0035] Furthermore, in step (1), the 4N grade crystalline antimony glycolate is purified, and the dissolution time is 60-90 min, preferably 60-80 min.

[0036] Furthermore, in step (1), during the initial filtration and fine filtration processes, the vacuum pressure is 0.07 MPa - 0.09 MPa, preferably 0.085 MPa. Excessive pressure can cause fine impurities to pass through the filter; insufficient pressure will affect the filtration speed.

[0037] Furthermore, in step (2), the mass ratio of the 5N grade antimony glycolate to the covering flux, food-grade sodium carbonate, and the supplementary reducing agent, semiconductor-grade graphite powder, is 1:0.12~0.18:0.05~0.10, preferably 1:0.14~0.16:0.06~0.08.

[0038] Furthermore, in step (2), the temperature of the reduction smelting is 800~1200℃, preferably 1000~1200℃.

[0039] Furthermore, in step (2), the isothermal reaction time for the reduction smelting is 3-6 hours, preferably 4-5 hours.

[0040] Furthermore, in step (2), the vacuuming refers to evacuating to a vacuum level of 10~60 Pa; preferably 30~50 Pa.

[0041] Furthermore, in step (2), the temperature for constant temperature clarification under inert gas protection is 800~1300℃, preferably 1000~1200℃; the time is 1.5~2.5h, preferably 2.0h.

[0042] Furthermore, the inert gas is nitrogen (N2).

[0043] The purity of 4N grade antimony glycol semi-finished products, 5N grade antimony glycol products, and the final 5N high-purity antimony product was detected using inductively coupled plasma mass spectrometry (ICP-MS).

[0044] Compared with existing technologies, the present invention has the following beneficial effects: (1) By selecting catalyst-grade antimony trioxide and polyester-grade ethylene glycol to produce 5N-grade antimony glycol, and then using the 5N-grade antimony glycol ester as a raw material, a one-step production of 5N high-purity antimony is achieved; the preparation process of 5N high-purity antimony is simplified; (2) Through the optimization of the selection of antimony trioxide, ethylene glycol raw materials, and raw and auxiliary materials such as graphite powder and sodium carbonate, as well as filter media materials and process conditions, the production of 4N and 5N-grade antimony glycol esters with simpler operation steps, higher efficiency, and lower cost is achieved, providing a superior method for one-step production of 5N high-purity antimony. Raw material basis; (3) The filtration of the antimony glycol synthesis reaction solution and the ethylene glycol solution of antimony glycol is carried out by vacuum discharge, so that more than 90% of heavy metals and other harmful impurities are deposited in the bottom residue of the reactor after separate treatment, which greatly reduces the possibility of these impurity elements passing through the filter and reduces the adsorption load of the filter medium carbon fiber felt; (4) The direct yield of 5N high-purity antimony products is increased several times (from 40%-60% of the existing technology to more than 80%), which greatly reduces the preparation cost of 5N high-purity antimony and avoids the shortcomings of the direct yield of 5N high-purity antimony products being greatly reduced due to multiple vacuum distillations. Detailed Implementation

[0045] The present invention will be further illustrated by the following examples.

[0046] The raw materials used in the following embodiments of the present invention are as follows: catalyst-grade antimony trioxide is produced by Xikuangshan Shanxing Antimony Industry Co., Ltd. under the Shanxing brand; polyester-grade ethylene glycol (EG) is produced by Yangzi Petrochemical Co., Ltd.; and semiconductor-grade graphite powder is produced by Qingdao Huashichuang Co., Ltd. All other materials were obtained through conventional commercial channels.

[0047] The filter media used for primary and secondary filtration in each embodiment are composed of layers of activated carbon fiber fabric (cloth or felt) and a membrane-type composite needle-punched filter felt containing polytetrafluoroethylene (PTFE) resin. The primary filtration media consists of three layers: PTFE (polytetrafluoroethylene) – 3mm activated carbon fiber fabric (cloth or felt) – PTFE (polytetrafluoroethylene). The secondary filtration media consists of five layers: PTFE (polytetrafluoroethylene) filter cloth – 3mm thick carbon fiber felt – PTFE (polytetrafluoroethylene) filter cloth – 5mm thick carbon fiber felt – PTFE (polytetrafluoroethylene) filter cloth. The filter media system is resistant to damp heat temperatures above 300℃, and is resistant to acids, alkalis, and organic solvents. It has a three-dimensional microporous structure, low filtration resistance, and easy-to-remove filter cake layer, which allows for miniaturization of the adsorption device and thinner adsorption layers.

[0048] The average specific surface area of ​​the activated carbon fiber fabric—cloth or felt—is 1500 m². 2 With a porosity of ≥ 90% and an average pore size of approximately 20 Å, more than 90% of its pores are micropores. It can rapidly and effectively trap ultrafine particles and effectively remove heavy metal particles from solutions. In particular, it has a strong adsorption capacity for heavy metals such as As, Pb, Fe, Cu, Se, Bi, Te, Ni, Mn, Sn, and Ag. The single-component equilibrium adsorption capacity is approximately 0.125 mmol / g.

[0049] The purity and impurities of the intermediate products 4N grade antimony glycolate, 5N grade antimony glycolate, and the final 5N high-purity antimony in each embodiment were detected by inductively coupled plasma mass spectrometry (ICP-MS).

[0050] Example 1

[0051] (1) Preparation of 5N grade antimony glycolate

[0052] In a 50L reactor equipped with a reflux device, 41.0 kg of polyester-grade ethylene glycol (EG) and 3.7 kg of catalyst-grade antimony trioxide (99.87% purity) were added at a ratio of Sb / EG = 0.09. The reaction was carried out under reflux for 5 hours at a fixed heating temperature of 140℃ and a vacuum of 0.085 MPa. After the reaction was completed, the temperature was raised to 145℃, the stirring speed was adjusted to 6 r / min, and the mixture was clarified for 60 minutes. Then, the temperature was lowered to 125℃, and the antimony glycol reaction solution was filtered twice under a vacuum discharge method, first by primary filtration and then by fine filtration. The filtrate was sent to a crystallization vessel for cooling and crystallization. The crystallization temperature was controlled at 28℃, and the crystallization time was 6 hours. The solution was then centrifuged and filtered (the mother liquor was returned to the reactor for recycling. After 5 cycles, it was distilled to remove impurities and then returned to the reactor). 5.2 kg of solid 4N grade crystalline antimony glycol ester was obtained. The product was sampled, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 1.

[0053] The obtained 4N-grade crystalline antimony glycol ester and solvent ethylene glycol were added to a 50L refining vessel at a weight ratio of 1:1.8 (antimony glycol ester to ethylene glycol (EG)). The solution was dissolved at 110℃ for 80 minutes to obtain a 4N-grade crystalline antimony glycol ester ethylene glycol solution. The solution was then subjected to two filtrations (primary and secondary filtrations) using a vacuum top-discharge method. The filtrate was sent to a crystallization vessel for cooling and recrystallization at 28℃ for 6 hours. After recrystallization, the solution was centrifuged and filtered to obtain 5.08 kg of solid 5N-grade crystalline antimony glycol ester. The mother liquor was recycled five times and then distilled to remove impurities before reuse. Samples of the 5N-grade crystalline antimony glycol ester were taken, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 1.

[0054] (2) Preparation of 5N high-purity antimony

[0055] Take the above steps 1 kg of the obtained 5N grade crystalline antimony glycolate product was mixed evenly with 80 g of semiconductor grade graphite powder and placed in an alumina crucible. Then, 150 g of food-grade sodium carbonate was evenly covered on top of the mixture. The alumina crucible was then placed in a vacuum induction furnace, and the vacuum was evacuated to a negative pressure of 40 Pa. Inert gas N2 was slowly injected simultaneously from the top and bottom of the furnace. Under the protection of inert gas N2 and the action of stirring, the temperature was rapidly increased. When the temperature reached 1000℃, it was kept constant for 4 hours for reduction reaction melting. After the reduction reaction melting was completed, the gas flow at the bottom of the furnace was stopped. Under the protection of N2 gas in the upper part of the reaction liquid, the mixture was kept constant at 1000℃ for clarification for 2 hours, and then the slag was skimmed off. After skimming off the slag, N2 gas was continued to flow from the top of the furnace. The mixture was cooled to room temperature under the protection of N2 gas to obtain 5N high-purity antimony ingots. The ingots were taken out, rinsed with pure water, and dried to obtain 470.9 g of 5N high-purity antimony product. Samples were taken and sent for testing. The results of elemental analysis of antimony and impurities are shown in Table 1.

[0056] Table 1: Elemental Analysis Results of Antimony and Impurities

[0057]

[0058] Note: Direct yield from 5N grade antimony glycolate to 5N high-purity antimony: 81.6%

[0059] Example 2

[0060] (1) Preparation of 5N grade antimony glycolate

[0061] In a 50L reactor equipped with a reflux device, 40 kg of polyester-grade ethylene glycol and 4.1 kg of catalyst-grade antimony trioxide were added at a ratio of Sb / EG = 0.085 in the raw material antimony trioxide (99.89%). The reaction was refluxed for 4.5 h at a fixed heating temperature of 145℃ and a vacuum of 0.09 MPa. After the reaction was completed, the temperature was raised to 150℃, the stirring speed was adjusted to 8 r / min, and the mixture was clarified for 45 min. The temperature was then lowered to 120℃, and the antimony glycol reaction solution was filtered twice, first by primary filtration and then by fine filtration, under a negative pressure of 0.8 MPa using a vacuum discharge method. The filtrate was sent to a crystallization vessel for cooling and crystallization. The crystallization temperature was controlled at 26℃, and the crystallization time was 5.5 h. After centrifugation and filtration, the mother liquor was returned to the reactor for recycling. After five cycles, the mother liquor was distilled to remove impurities and then returned to the reactor for reuse. The solid was 5.8 kg of 4N grade crystalline antimony glycolate. Samples were taken, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 2.

[0062] The 4N-grade crystalline antimony glycol ester obtained above was added to a 50L refining kettle at a mass ratio of 1:1.6 of antimony glycol ester to solvent ethylene glycol (EG). The antimony glycol ester was dissolved at 120℃ for 70 minutes. Then, the ethylene glycol solution of antimony glycol ester was subjected to two filtrations—primary filtration and fine filtration—using a vacuum discharge method. The filtrate was sent to a crystallization kettle for cooling and recrystallization at 26℃ for 6 hours. After centrifugation and filtration, 5.65 kg of 5N-grade crystalline antimony glycol ester product was obtained. The mother liquor was returned to the circulation system and, after five cycles, was distilled to remove impurities before reuse. Samples of the 5N-grade crystalline antimony glycol ester product were taken, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 2.

[0063] (2) Preparation of 5N high-purity antimony

[0064] Take 1 kg of the above-mentioned 5N grade crystalline antimony glycolate product and mix it evenly with 75 g of semiconductor grade graphite powder. Place the mixture in an alumina crucible, and then evenly cover the surface of the mixture with 160 g of food-grade sodium carbonate. Place the alumina crucible in a vacuum induction furnace, evacuate it to a negative pressure of 40 Pa, and then slowly inject inert gas N2 from the top and bottom of the furnace. Under the action of inert gas N2 and stirring, the temperature is rapidly increased. When the temperature reaches 1100℃, it is kept at a constant temperature for 4 hours for reduction reaction melting. After the reduction reaction melting is completed, the gas flow at the bottom of the furnace is stopped, and the mixture is kept at a constant temperature of 1100℃ for clarification under the protection of N2 in the upper part for 2 hours. After skimming off the slag, N2 gas is continuously supplied from the top of the furnace for protection and cooled to room temperature to obtain 5N high-purity antimony ingots. These ingots are taken out, rinsed with pure water, and dried to obtain 469.3 g of 5N high-purity antimony product. Samples are sent for testing. The results of antimony and impurity elemental analysis are shown in Table 2.

[0065] Table 2: Elemental Analysis Results of Antimony and Impurities

[0066]

[0067] Note: The direct yield from 5N grade antimony glycol to 5N high-purity antimony is 81.3%.

[0068] Example 3:

[0069] (1) Preparation of 5N grade antimony glycolate

[0070] In a 50L reactor equipped with a reflux device, 41 kg of polyester-grade ethylene glycol and 4.3 kg of catalyst-grade antimony trioxide were added according to the ratio of Sb / EG in the raw material antimony trioxide (99.92%) of 0.088. The reaction was refluxed for 5 hours under a fixed heating temperature of 145℃ and a vacuum degree of 0.08 MPa. After the reaction was completed, the temperature was raised to 150℃, the stirring speed was adjusted to 6 r / min, and the mixture was clarified for 50 minutes. The temperature was then lowered to 120℃, and the antimony glycol reaction solution was subjected to two-stage filtration (primary filtration and fine filtration) under a vacuum discharge method under a negative pressure of 0.8 MPa. The filtrate was sent to a crystallization kettle for cooling and crystallization. The crystallization temperature was controlled at 26℃, and the crystallization time was 5.5 hours. After centrifugation and filtration, the mother liquor was returned to the reactor for recycling (after 4-5 cycles, it was distilled to remove impurities and then returned to the reactor), yielding 6.2 kg of 4N-grade crystalline antimony glycol product. Samples were taken, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 3.

[0071] The above-mentioned 4N grade crystalline antimony glycol was added to a 50L refining kettle at a mass ratio of antimony glycol to solvent ethylene glycol (EG) of 1:1.7. The antimony glycol was dissolved at 115℃ for 70 min. Then, the ethylene glycol solution of antimony glycol was filtered twice by primary and fine filtration using a vacuum discharge method. The filtrate was sent to a crystallization kettle for cooling and recrystallization at a controlled temperature of 26℃ for 6 h. After recrystallization, the product was centrifuged and filtered to obtain 6.06 kg of 5N grade crystalline antimony glycol (the mother liquor was recycled and reused after 5 cycles of recycling and distillation). Samples were taken, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 3.

[0072] (2) Preparation of 5N high-purity antimony

[0073] Take 1 kg of the above-mentioned 5N grade crystalline antimony glycolate product and mix it evenly with 70 g of semiconductor grade graphite powder. Place the mixture in an alumina crucible, and then evenly cover the surface of the mixture with 140 g of food-grade sodium carbonate. Place the alumina crucible in a vacuum induction furnace, evacuate it to a negative pressure of 40 Pa, and then slowly inject inert gas N2 from the top and bottom of the furnace. Under the protection of inert gas N2 and with stirring, raise the temperature to 1200℃ and hold it at that temperature for 4 hours for reduction reaction melting. After the reduction reaction melting is completed, stop the gas flow from the bottom of the furnace. Under the protection of N2 gas at the top of the furnace and at a constant temperature of 1200℃ for clarification, the clarification time is 2 hours. Then skim off the slag, continue to circulate N2 gas from the top of the furnace and cool to room temperature to obtain 5N high-purity antimony ingots. Take them out, rinse them with pure water, and dry them to obtain 470.4 g of 5N high-purity antimony product. Samples were sent for testing, and the results of antimony and impurity element analysis are shown in Table 3.

[0074] Table 3: Elemental Analysis Results of Antimony and Impurities

[0075]

[0076] Note: Direct yield from 5N grade antimony glycol to 5N high-purity antimony: 81.52%.

[0077] Example 4:

[0078] (1) Preparation of 5N grade antimony glycolate

[0079] In a 50L reactor equipped with a reflux device, 41 kg of polyester-grade ethylene glycol and 3.95 kg of catalyst-grade antimony trioxide were added to the raw material antimony trioxide (purity 99.91%) at a ratio of Sb / EG = 0.08. The reaction was carried out under reflux for 5.5 h at a fixed heating temperature of 140℃ and a vacuum degree of 0.088 MPa. After the reaction was completed, the temperature was raised to 145℃, the stirring speed was adjusted to 6 r / min, and the mixture was clarified for 40 min. The temperature was then lowered to 120℃, and the antimony glycol ester reaction solution was subjected to two-stage filtration (primary filtration and fine filtration) under a negative pressure of 0.8 MPa using a vacuum discharge method. The filtrate was sent to a crystallization kettle for cooling and crystallization. The crystallization temperature was controlled at 28℃, and the crystallization time was 6 h. After crystallization, the solution was centrifuged and filtered (the mother liquor was returned to the reactor for recycling, and after 4 cycles, it was distilled to remove impurities before being returned to the reactor). 5.57 kg of 4N-grade crystalline antimony glycol ester was obtained. Samples were taken, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 4.

[0080] The above-mentioned 4N grade crystalline antimony glycol was added to a 50L refining reactor at a mass ratio of 1:1.6 of antimony glycol to solvent ethylene glycol (EG). The antimony glycol was dissolved at 110℃ for 75 minutes. After complete dissolution, the ethylene glycol solution of antimony glycol was subjected to two filtrations—primary filtration and fine filtration—using a vacuum discharge method. The filtrate was sent to a crystallization reactor for cooling and recrystallization at 20℃ for 5 hours. After crystallization, the solution was centrifuged and filtered to obtain 5.45 kg of 5N grade crystalline antimony glycol product (the mother liquor was returned to the reactor for reuse, and after five cycles of distillation to remove impurities, it was reused). Samples were taken, dried, and sent for testing. The results of antimony and impurity elemental analysis are shown in Table 4.

[0081] (2) Preparation of 5N high-purity antimony

[0082] Take 1 kg of the above-mentioned 5N grade crystalline antimony glycolate product and mix it evenly with 65 g of semiconductor grade graphite powder. Place the mixture in an alumina crucible, and then evenly cover the surface of the mixture with 155 g of food-grade sodium carbonate. Place the alumina crucible in a vacuum induction furnace, evacuate it to a negative pressure of 40 Pa, and then slowly inject inert gas N2 from the top and bottom of the furnace. Under the protection of inert gas N2 and with stirring, rapidly heat the mixture to 1150℃ and hold it at that temperature for 4 hours for reduction reaction melting. After the reduction reaction melting is completed, clarify the mixture at 1150℃ under the protection of N2 from the top of the furnace for 2 hours. Then skim off the slag, continue to circulate N2 from the top of the furnace for protection, and cool to room temperature to obtain 5N high-purity antimony ingots. Remove the ingots, rinse them with pure water, and dry them to obtain 468.2 g of 5N high-purity antimony product. Samples were sent for testing, and the results of antimony and impurity element analysis are shown in Table 4.

[0083] Table 4: Elemental Analysis Results of Antimony and Impurities

[0084]

[0085] Note: Direct yield from 5N grade antimony glycolate to 5N high-purity antimony: 81.1%.

[0086] The above-described Examples 1-4 demonstrate that the present invention has the following beneficial effects: (1) Using 5N grade antimony glycol ester as raw material, 5N high-purity antimony can be produced in one step; the process flow for producing 5N high-purity antimony is simplified; (2) In the present invention, step (1) achieves the production of 5N grade antimony glycol ester that meets the requirements for preparing 5N grade high-purity antimony raw materials by optimizing the selection of antimony trioxide, ethylene glycol raw materials, and auxiliary materials such as graphite powder and sodium carbonate, as well as the filter media materials, and optimizing the operation steps and process conditions, thus providing a suitable raw material for the one-step production of 5N high-purity antimony (there is currently no 5N grade antimony glycol ester suitable for the preparation of 5N high-purity antimony available on the market); (3) Antimony glycol ester synthesis reaction solution and antimony glycol ester ethylene glycol solution. The filtration process employs a vacuum top discharge method, which separates over 90% of heavy metals and other harmful impurities from the raw materials (see Tables 1-4 for details) and deposits them in the bottom residue of the reactor. This significantly reduces the possibility of these impurity elements passing through the filter and reduces the adsorption load on the carbon fiber felt filter medium. (4) The direct yield of 5N high-purity antimony products is increased several times: the direct yield of existing technologies is approximately 40-60%, while the yield of this invention is as high as over 80% (the yields of the four embodiments are 81.6%, 81.3%, 81.52%, and 81.1%, respectively). This significantly reduces the preparation cost of 5N high-purity antimony and avoids the significant reduction in the direct yield of 5N high-purity antimony products caused by multiple vacuum distillations.

Claims

1. A method for preparing 5N high-purity antimony, characterized in that, Includes the following steps: (1) Preparation of 5N grade antimony glycol ester: The raw material catalyst grade antimony trioxide and polyester grade ethylene glycol (EG) are added to the reflux reactor, vacuum is drawn, and heating is carried out for vacuum reflux reaction; after the reaction is completed, the temperature is raised and the mixture is slowly stirred to clarify, and a clear reaction solution is obtained; the obtained clear reaction solution is cooled down, and then subjected to two-stage filtration by vacuum discharge method, the filtrate is sent to the crystallization reactor for cooling and crystallization, and then centrifuged and filtered to obtain 4N grade crystalline antimony glycol ester with total impurities <15ppm; The 4N grade crystalline antimony glycol ester prepared above was added to a refining kettle and dissolved by heating to obtain a polyester grade ethylene glycol solution of 4N grade crystalline antimony glycol ester. The obtained solution was cooled and then subjected to two-stage filtration (primary filtration and fine filtration) by vacuum discharge. The filtrate was sent to a crystallization kettle for cooling and recrystallization, and then centrifuged and filtered to obtain a crystalline 5N grade antimony glycol ester product with total impurities <10ppm, which meets the requirements for the impurity content of 5N high-purity antimony. (2) Preparation of 5N high-purity antimony: The crystalline 5N grade antimony glycol ester obtained in step (1) is mixed with semiconductor grade graphite powder as a supplementary reducing agent. After stirring evenly, the mixture is placed in an alumina crucible. A layer of food-grade sodium carbonate, which has the functions of removing arsenic and selenium and slag formation, is then covered on the surface of the mixture. The alumina crucible is then placed in a vacuum medium-frequency melting furnace, a vacuum is drawn, and inert gas is injected simultaneously from the top and bottom of the furnace. Under the protection of inert gas and the action of stirring, the temperature is raised to carry out the reduction reaction melting. After the reduction reaction melting is completed, the gas supply to the bottom of the furnace is stopped. Under the protection of inert gas at the top of the furnace, the mixture is kept at a constant temperature for clarification, and then the slag is skimmed off. Then, inert gas is continued to be supplied from the top of the furnace for protection, and the mixture is cooled to room temperature to obtain 5N high-purity antimony ingots. Then, the gas supply is stopped, the antimony ingots are taken out and rinsed with pure water and dried to obtain the 5N high-purity antimony product.

2. The method for preparing 5N high-purity antimony according to claim 1, characterized in that, In step (1), the antimony content (Sb₂O₃) in the catalyst-grade antimony trioxide is ≥99.85%, the total impurity content is <150ppm, and the particle size is 0.75~1.1μm; the impurity limit value in the polyester-grade ethylene glycol is <1ppm; and the mass ratio of antimony to polyester-grade ethylene glycol in the catalyst-grade antimony trioxide is 0.07~0.

10.

3. The method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, In step (1), the temperature of the vacuum reflux reaction is 135-150°C, preferably 140-145°C; the reaction time is 4-8 hours, preferably 4.5-6.5 hours.

4. A method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, The negative pressure conditions for the vacuum reflux reaction are 0.055 MPa to 0.095 MPa, preferably 0.065 to 0.09 MPa.

5. A method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, In step (1), during the heating and slow stirring clarification, the temperature is controlled at 140-155℃, preferably 145-150℃; the stirring speed is 5-10 r / min, preferably 6-8 r / min; and the heating and slow stirring clarification time is 35-90 min, preferably 40-60 min.

6. A method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, In step (1), the antimony glycolate reaction solution is cooled to 115-140°C, preferably 120-130°C, and then filtered.

7. A method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, In step (1), the crystallization temperature of the ethylene glycol antimony ester filtrate is <30℃, and the crystallization time is 3-8h, preferably 4-6h.

8. A method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, In step (1), during the refining of the 4N-grade crystalline antimony glycol, the mass ratio of antimony glycol to polyester-grade ethylene glycol is 1 / 1.3–2.0, preferably 1 / 1.5–1.8; the dissolution temperature of antimony glycol is 100–120°C, preferably 110–120°C; the dissolution time is 60–90 min, preferably 60–80 min; during the initial and fine filtration processes, the vacuum pressure is 0.07 MPa–0.09 MPa, preferably 0.085 MPa.

9. A method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, In step (2), the mass ratio of the 5N grade antimony glycolate to the covering flux, food-grade sodium carbonate, and the supplementary reducing agent, semiconductor-grade graphite powder, is 1:0.12~0.18:0.05~0.10; the reduction melting temperature is 800~1300℃, preferably 1000~1200℃; the isothermal reaction time for the reduction melting is 3~6h; and the vacuuming refers to evacuating to a vacuum degree of 10~60Pa.

10. A method for preparing 5N high-purity antimony according to claim 1 or 2, characterized in that, In step (2), the temperature for constant temperature clarification under inert gas protection is 800~1300℃, preferably 1000~1200℃; the time for constant temperature clarification is 1.5~2.5h, preferably 2h.

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