Hydrofluoric acid with low metal impurities and a method for its preparation
By combining plasma oxidation and modified chelating resin adsorption with a multi-effect coupled distillation process, the problem of deep removal of multivalent metal impurities in industrial hydrofluoric acid has been solved, achieving efficient, low-energy-consumption, and safe hydrofluoric acid preparation, which is suitable for microelectronics and semiconductor manufacturing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 安瑞森(宿迁)电子材料有限公司
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies are unable to effectively remove multivalent and broad-spectrum metallic impurities from industrial hydrofluoric acid, resulting in insufficient product purity that cannot meet the needs of high-end microelectronics and semiconductor manufacturing. Furthermore, traditional processes suffer from high energy consumption, significant equipment corrosion risks, and poor safety.
The process employs a combination of plasma oxidation and multi-stage modified chelating resin adsorption with multi-effect coupled distillation. By using plasma oxidation to convert low-valence metal impurities into high-valence states, and using modified chelating resin to construct a multi-active-site network, deep removal is achieved through multi-effect coupled distillation, enabling continuous and closed-loop production throughout the entire process.
It significantly improves the removal efficiency of multivalent metal impurities, reduces energy consumption, enhances product stability and safety, meets the requirements of nanoscale processes for ultra-high purity hydrofluoric acid, and possesses green and environmentally friendly characteristics.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of fine chemicals technology, specifically to a hydrofluoric acid with low metal impurities and its preparation method. Background Technology
[0002] Hydrofluoric acid, a key etching and cleaning agent in microelectronics, photovoltaics, and semiconductor manufacturing, requires high purity. The content of metallic impurities directly affects the conductivity and yield of chips and panels. Industrial-grade hydrofluoric acid is mostly prepared by reacting fluorite with sulfuric acid. However, the raw materials and production process easily introduce various metal ion impurities such as sodium, iron, aluminum, calcium, and lead, making it difficult to meet the ultra-clean requirements of high-end manufacturing scenarios. As semiconductor manufacturing processes iterate towards the nanoscale, traditional purification processes are no longer suitable for the low-metal impurity control standards of electronic-grade hydrofluoric acid, becoming a core bottleneck restricting the domestic production of high-end fluorochemicals.
[0003] Current industrial hydrofluoric acid purification methods primarily employ combinations of single distillation, conventional resin adsorption, or simple filtration, which have significant technological limitations. Conventional distillation struggles to deeply separate metal fluoride impurities with boiling points close to hydrogen fluoride, while resin adsorption is selective only for specific metal ions, failing to achieve simultaneous removal of multivalent and broad-spectrum metal impurities. These methods generally suffer from insufficient purification precision, low processing efficiency, high equipment corrosion risk, and high energy consumption, resulting in high residual metal impurities in the finished product and inconsistencies that fail to meet stringent industrial standards.
[0004] Furthermore, existing purification processes lack efficient coupling and synergistic design; each unit operates independently, heat is not fully recovered and utilized, resulting in poor overall economic efficiency. Ordinary filter materials have poor resistance to hydrogen fluoride corrosion, easily swelling, breaking, and causing secondary pollution, further reducing purification efficiency. Most processes cannot achieve continuous and closed-loop production, which not only increases safety hazards but also makes it difficult to stably produce ultra-high purity hydrofluoric acid with metal impurity content at the ppt level, failing to support the high-quality supply demands of the high-end electronics manufacturing industry for core consumables. Summary of the Invention
[0005] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing hydrofluoric acid with low metal impurities, comprising the following preparation steps: Step S1: Industrial anhydrous hydrogen fluoride is adsorbed and dried by passing it through a drying tower filled with molecular sieves, and then vaporized to obtain HF gas. Step S2: After mixing HF gas with oxygen, the mixture is introduced into a plasma reactor for plasma oxidation to obtain oxidized HF gas. Step S3: The oxidized HF gas is passed into a fixed bed adsorption tower filled with multi-stage modified chelating resin for adsorption, and HF gas after adsorption by multi-stage modified chelating resin is obtained. Step S4: The HF gas adsorbed by the multi-stage modified chelating resin is subjected to multi-effect coupled distillation to obtain HF gas after multi-effect coupled distillation. Step S5: Pass the HF gas after multi-effect coupled distillation into a falling film absorption tower and absorb it with ultrapure water to obtain hydrofluoric acid with low metal impurities.
[0006] Furthermore, the preparation method of the multi-stage modified chelating resin is as follows: Step A1: Immerse the iminodiacetic acid chelating resin in dilute sulfuric acid, then wash it with deionized water to 6.5-7.5 to obtain the pretreated iminodiacetic acid chelating resin. Step A2: The pretreated iminodiacetic acid chelating resin is loaded into a glass column, and aluminum nitrate solution is circulated for 4-6 hours, then allowed to stand for 12-15 hours, and finally washed with deionized water to obtain Al-IDA resin. Step A3: Immerse Al-IDA resin in anhydrous ethanol and allow it to swell for 1.5-2.5 hours. Then add tetrabutyl titanate and stir the reaction at 50-60°C for 4-6 hours. After the reaction is complete, wash with anhydrous ethanol to obtain Ti-Al-IDA resin. Step A4: Add Ti-Al-IDA resin to anhydrous ethanol, add mercaptopropyltrimethoxysilane and polyethylenepolyamine, and reflux at 80℃-100℃ for 8h-10h under nitrogen protection. After the reaction is completed, filter, wash and dry to obtain multi-stage modified chelating resin.
[0007] Furthermore, in step A2, the flow rate of the circulating load is 2BV / h-4BV / h.
[0008] Furthermore, in the preparation process of the multi-stage modified chelating resin, the specific materials are as follows by weight: 90-100 parts of iminodiacetic acid chelating resin, 400-600 parts of aluminum nitrate solution, 5-12 parts of tetrabutyl titanate, 4-10 parts of mercaptopropyltrimethoxysilane, 2-6 parts of polyethylene polyamine, 200-300 parts of dilute sulfuric acid, and 700-1100 parts of anhydrous ethanol.
[0009] Furthermore, the aluminum nitrate solution is prepared as follows: aluminum nitrate nonahydrate is dissolved in deionized water to prepare an aluminum nitrate solution with a molar concentration of 0.5 mol / L-1.0 mol / L, and the pH value is adjusted to 2-3 with dilute nitric acid.
[0010] Furthermore, the mass fraction of the dilute sulfuric acid is 5%.
[0011] Furthermore, the molecular sieve in step S1 is a 5A type molecular sieve.
[0012] Furthermore, in step S1, the adsorption drying temperature is 15℃-20℃ and the pressure is 0.2MPa-0.4MPa.
[0013] Further, the vaporization process in step S1 is as follows: dried industrial anhydrous hydrogen fluoride is passed into a tubular ambient temperature vaporizer with a heating temperature of 25℃-30℃ to obtain HF gas.
[0014] Furthermore, in step S2, the volume ratio of oxygen to HF gas is 0.1-0.5:1; in step S2, the plasma reactor is a dielectric barrier discharge reactor with a discharge frequency of 50kHz and a power of 1kW-5kW.
[0015] Furthermore, in step S3, the adsorption temperature of the fixed-bed adsorption tower is 25-35℃, the pressure is 0.1MPa-0.3MPa, and the space velocity is 200-500h⁻¹. -1 .
[0016] Furthermore, in step S3, the height-to-diameter ratio of the fixed-bed adsorption tower is 3:1 to 5:1.
[0017] Further, the multi-effect coupled distillation in step S4 includes: First-stage distillation: at atmospheric pressure, with a top temperature of 20℃-25℃, to remove light component impurities; Secondary distillation: pressure 0.3MPa-0.4MPa, top temperature 50℃-60℃, to remove heavy component impurities; Furthermore, in step S5, the absorption temperature of the falling film absorption tower is 5℃-10℃.
[0018] Furthermore, in step S5, the HF gas purified by multi-effect coupled distillation is introduced into a falling film absorption tower and absorbed countercurrently with ultrapure water to obtain a hydrofluoric acid product with a mass fraction of 49% and low metal impurities.
[0019] On the other hand, the present invention provides a method for preparing hydrofluoric acid with low metal impurities, resulting in hydrofluoric acid with low metal impurities.
[0020] The beneficial effects of this invention are: This invention achieves deep removal of multivalent and broad-spectrum metallic impurities from anhydrous hydrogen fluoride in industrial applications through the synergistic effect of plasma oxidation and multi-stage modified chelating resin adsorption, combined with a multi-effect coupled distillation process. Compared with traditional single distillation or ordinary resin adsorption processes, this invention, targeting the chemical characteristics of different valence metal ions, first utilizes plasma oxidation to convert low-valence metallic impurities (such as trivalent arsenic) into easily separable high-valence forms, significantly improving the removal efficiency of subsequent adsorption and distillation processes. Simultaneously, the multi-stage modified chelating resin, through aluminum loading, titanium loading, and functional group grafting modification, constructs a synergistic adsorption network with multiple active sites. This not only enhances the chelation ability for common metal ions such as aluminum, iron, and calcium, but also significantly improves the adsorption selectivity for specific toxic metallic impurities such as arsenic and lead, solving the industry problem of existing resins having limited adsorption selectivity and difficulty in simultaneously removing multiple elemental impurities.
[0021] This invention employs a multi-effect coupled distillation design to achieve cascaded heat utilization. The overhead vapor from the secondary distillation column serves as the heat source for the reboiler of the primary distillation column, significantly reducing the overall energy consumption of the process and overcoming the economic drawbacks of traditional distillation processes, such as high energy consumption and low heat utilization. Furthermore, the entire process achieves continuous and closed-loop production from raw material gasification, oxidation, adsorption, distillation, and absorption, effectively avoiding the risk of secondary contamination of the product by the external environment, while significantly improving the safety and controllability of the production process. The process parameters have a clear range and a wide operating window, facilitating industrial scale-up and batch-to-batch performance reproducibility, providing a reliable technical path for the stable and large-scale production of high-end electronic-grade hydrofluoric acid.
[0022] The hydrofluoric acid prepared by this invention has a low level of metal impurities, which can meet the stringent requirements of ultra-high purity chemical reagents in nanoscale processes and overcome the technical bottleneck of existing purification processes that cannot stably produce products with PPT-level metal impurity content. At the same time, this preparation method does not introduce new pollution sources and generates no high-risk solid or liquid waste, conforming to the concept of green and environmentally friendly production. It can be widely used in high-end manufacturing fields such as microelectronics, semiconductors, and photovoltaics, and has significant industrial value for the domestic substitution of ultra-high purity fluorine chemicals in my country. Detailed Implementation
[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0024] The iminodiacetic acid chelating resin used in this invention was purchased from Jining Tangyi Chemical Co., Ltd. Example 1
[0025] A method for preparing hydrofluoric acid with low metal impurities includes the following preparation steps: I. Preparation of Multi-stage Modified Chelating Resins Prepare the following materials by weight: 90 parts iminodiacetic acid chelating resin, 400 parts aluminum nitrate solution (prepared by dissolving aluminum nitrate nonahydrate in deionized water to a molar concentration of 0.5 mol / L, and adjusting the pH to 2 with 1.0% dilute nitric acid), 5 parts tetrabutyl titanate, 4 parts mercaptopropyltrimethoxysilane, 2 parts polyethylenepolyamine, 200 parts 5% dilute sulfuric acid, and 700 parts anhydrous ethanol. Step A1: Soak the iminodiacetic acid chelating resin in 5% dilute sulfuric acid for 2 hours. After taking it out, wash it 3 times with deionized water until the pH of the washing solution is 6.5 to obtain the pretreated iminodiacetic acid chelating resin. Step A2: The pretreated iminodiacetic acid chelating resin is loaded into a glass column. A closed-loop circulation method is used, with liquid entering from the bottom and exiting from the top and returning to the storage tank. The aluminum nitrate solution in the storage tank is passed into the glass column at a flow rate of 2 BV / h and the circulation load is maintained for 4 hours. During the circulation, the resin bed in the glass column is kept completely wetted and free of dry layers. After the circulation is completed, the inlet and return pipelines are closed, and the resin is allowed to stand in the glass column for 12 hours. After standing, the resin in the glass column is countercurrently washed 4 times with deionized water at a flow rate of 3 BV / h. The washing liquid is drained after each washing until the last washing liquid is tested by the chromium cyan S colorimetric method and no aluminum ions are detected. After draining the resin bed, Al-IDA resin is obtained. Step A3: Add Al-IDA resin to anhydrous ethanol (40% of the total mass of anhydrous ethanol) and swell at room temperature for 1.5 h. After swelling, add tetrabutyl titanate and react at 50 °C and stirring speed of 150 r / min for 4 h. After the reaction, wash twice with anhydrous ethanol to obtain Ti-Al-IDA resin. Step A4: Add Ti-Al-IDA resin to anhydrous ethanol (60% of the total mass of anhydrous ethanol), then add mercaptopropyltrimethoxysilane and polyethylenepolyamine. Under nitrogen protection, reflux at 80°C for 8 hours. After the reaction is complete, filter and wash three times with anhydrous ethanol. After washing, vacuum dry at -0.08 MPa and 45°C for 4 hours, and cool to room temperature to obtain multi-stage modified chelating resin.
[0026] II. Preparation of Hydrofluoric Acid with Low Metal Impurities Step S1: Industrial anhydrous hydrogen fluoride is passed into a drying tower filled with 5A molecular sieve and adsorbed and dried at a temperature of 15℃ and a pressure of 0.2MPa; the dried industrial anhydrous hydrogen fluoride is then passed into a tubular ambient air vaporizer with a heating temperature of 25℃ and vaporized to obtain HF gas. Step S2: Mix HF gas and oxygen at a volume ratio of 0.1:1 until homogeneous. After mixing, pass the mixture into a dielectric barrier discharge reactor for plasma oxidation. Control the reactor discharge frequency at 50kHz, power at 1kW, electrode spacing at 5mm, and gas residence time at 0.5s. After the reaction is complete, oxidized HF gas is obtained. Step S3: The oxidized HF gas is passed into a fixed-bed adsorption tower packed with the above-mentioned multi-stage modified chelating resin; the control conditions are: adsorption temperature 25℃, pressure 0.1MPa, space velocity 200h / h. -1 The fixed-bed adsorption tower has a height-to-diameter ratio of 3:1, and after adsorption, HF gas is obtained after adsorption by multi-stage modified chelating resin. Step S4: The adsorbed HF gas is subjected to multi-effect coupled distillation: the first-stage distillation is carried out at atmospheric pressure and the top temperature is 20°C to remove light component impurities; the second-stage distillation is carried out at a pressure of 0.3MPa and the top temperature is 50°C to remove heavy component impurities; the top vapor of the second-stage distillation column is used as the heat source of the bottom of the first-stage distillation column to achieve heat coupling and obtain HF gas after multi-effect coupled distillation. Step S5: The HF gas after multi-effect coupled distillation is introduced into the falling film absorption tower, and the absorption temperature is controlled at 5℃. Ultrapure water with a conductivity ≤0.055μS / cm is used to conduct countercurrent contact absorption with HF gas at a gas-liquid ratio of 1:1.2 (volume ratio). The density of the absorbent is monitored in real time by an online density meter, and the ultrapure water feed flow rate and HF gas feed flow rate are adjusted accordingly to control the mass fraction of the absorbent at 49%, thereby obtaining a hydrofluoric acid product with low metal impurities. Example 2
[0027] A method for preparing hydrofluoric acid with low metal impurities includes the following preparation steps: I. Preparation of Multi-stage Modified Chelating Resins Materials prepared by weight: 95 parts iminodiacetic acid chelating resin, 500 parts aluminum nitrate solution (aluminum nitrate nonahydrate is dissolved in deionized water to prepare an aluminum nitrate solution with a molar concentration of 0.8 mol / L, and the pH value is adjusted to 2.5 with 1.0% dilute nitric acid), 8.5 parts tetrabutyl titanate, 7 parts mercaptopropyltrimethoxysilane, 4 parts polyethylene polyamine, 250 parts 5% dilute sulfuric acid, and 900 parts anhydrous ethanol. Step A1: Soak the iminodiacetic acid chelating resin in 5% dilute sulfuric acid for 2.5 hours. After soaking, wash it with deionized water 4 times until the pH of the washing solution is 7.0 to obtain the pretreated iminodiacetic acid chelating resin. Step A2: The pretreated iminodiacetic acid chelating resin is loaded into a glass column. A closed-loop circulation method is used, with liquid entering from the bottom and exiting from the top and returning to the storage tank. The aluminum nitrate solution in the storage tank is passed into the glass column at a flow rate of 3 BV / h and the circulation load is maintained for 5 hours. During the circulation, the resin bed in the glass column is kept completely wetted and free of dry layers. After the circulation is completed, the inlet and return pipelines are closed, and the resin is allowed to stand in the glass column for 13.5 hours. After standing, the resin in the glass column is countercurrently washed 4 times with deionized water at a flow rate of 3 BV / h. The washing liquid is drained after each washing until the last washing liquid is tested by the chromium cyanine S colorimetric method and no aluminum ions are detected. After draining the resin bed, Al-IDA resin is obtained. Step A3: Add Al-IDA resin to anhydrous ethanol (40% of the total mass of anhydrous ethanol), swell at room temperature for 2 hours, add tetrabutyl titanate after swelling, and react at 55°C and stirring speed of 200 r / min for 5 hours. After the reaction, wash three times with anhydrous ethanol to obtain Ti-Al-IDA resin. Step A4: Add Ti-Al-IDA resin to anhydrous ethanol (60% of the total mass of anhydrous ethanol), then add mercaptopropyltrimethoxysilane and polyethylenepolyamine. Under nitrogen protection, reflux at 90°C for 9 hours. After the reaction is complete, filter and wash four times with anhydrous ethanol. After washing, vacuum dry at -0.07 MPa and 52.5°C for 6 hours, and cool to room temperature to obtain multi-stage modified chelating resin.
[0028] II. Preparation of Hydrofluoric Acid with Low Metal Impurities Step S1: Industrial anhydrous hydrogen fluoride is passed into a drying tower filled with 5A molecular sieve and adsorbed and dried at a temperature of 17.5℃ and a pressure of 0.3MPa; the dried industrial anhydrous hydrogen fluoride is then passed into a tubular ambient air vaporizer with a heating temperature of 27.5℃ and vaporized to obtain HF gas. Step S2: Mix HF gas and oxygen at a volume ratio of 0.3:1 until homogeneous. After mixing, pass the mixture into a dielectric barrier discharge reactor for plasma oxidation. Control the reactor discharge frequency at 50kHz, power at 3kW, electrode spacing at 7.5mm, and gas residence time at 0.75s. After the reaction is complete, oxidized HF gas is obtained. Step S3: The oxidized HF gas is passed into a fixed-bed adsorption tower packed with the above-mentioned multi-stage modified chelating resin; the control conditions are: adsorption temperature 30℃, pressure 0.2MPa, and space velocity 350h. -1 The fixed-bed adsorption tower has a height-to-diameter ratio of 4:1, and after adsorption, HF gas is obtained after adsorption by multi-stage modified chelating resin. Step S4: The adsorbed HF gas is subjected to multi-effect coupled distillation: the first-stage distillation is carried out at atmospheric pressure and the top temperature is 22.5℃ to remove light component impurities; the second-stage distillation is carried out at a pressure of 0.35MPa and the top temperature is 55℃ to remove heavy component impurities; the top vapor of the second-stage distillation column is used as the heat source of the bottom of the first-stage distillation column to achieve heat coupling and obtain HF gas after multi-effect coupled distillation. Step S5: Pass the HF gas after multi-effect coupled distillation into the falling film absorber, and control the absorption temperature to [temperature value missing]. Ultrapure water with a conductivity ≤0.055μS / cm was used to absorb HF gas in a countercurrent manner at a gas-liquid ratio of 1:1.3 (volume ratio). The density of the absorbent was monitored in real time by an online density meter, and the flow rates of the ultrapure water and HF gas were adjusted accordingly to control the mass fraction of the absorbent at 49%, thus obtaining a hydrofluoric acid product with low metal impurities. Example 3
[0029] A method for preparing hydrofluoric acid with low metal impurities includes the following preparation steps: I. Preparation of Multi-stage Modified Chelating Resins Prepare the following materials by weight: 100 parts iminodiacetic acid chelating resin, 600 parts aluminum nitrate solution (prepared by dissolving aluminum nitrate nonahydrate in deionized water to a molar concentration of 1.0 mol / L, and adjusting the pH to 3 with 1.0% dilute nitric acid), 12 parts tetrabutyl titanate, 10 parts mercaptopropyltrimethoxysilane, 6 parts polyethylene polyamine, 300 parts 5% dilute sulfuric acid, and 1100 parts anhydrous ethanol. Step A1: Soak the iminodiacetic acid chelating resin in 5% dilute sulfuric acid for 3 hours. After taking it out, wash it 5 times with deionized water until the pH of the washing solution is 7.5 to obtain the pretreated iminodiacetic acid chelating resin. Step A2: The pretreated iminodiacetic acid chelating resin is loaded into a glass column. A closed-loop circulation method is used, with liquid entering from the bottom and exiting from the top and returning to the storage tank. The aluminum nitrate solution in the storage tank is passed into the glass column at a flow rate of 4 BV / h and the circulation load is maintained for 6 hours. During the circulation, the resin bed in the glass column is kept completely wetted and free of dry layers. After the circulation is completed, the inlet and return pipelines are closed, and the resin is allowed to stand in the glass column for 15 hours. After standing, the resin in the glass column is countercurrently washed 4 times with deionized water at a flow rate of 4 BV / h. The washing liquid is drained after each washing until the last washing liquid is tested by the chromium cyanine S colorimetric method and no aluminum ions are detected. After draining the resin bed, Al-IDA resin is obtained. Step A3: Add Al-IDA resin to anhydrous ethanol (40% of the total mass of anhydrous ethanol) and allow it to swell at room temperature for 2.5 h. After swelling, add tetrabutyl titanate and react at 60 °C and stirring speed of 250 r / min for 6 h. After the reaction, wash with anhydrous ethanol 4 times to obtain Ti-Al-IDA resin. Step A4: Add Ti-Al-IDA resin to anhydrous ethanol (60% of the total mass of anhydrous ethanol), then add mercaptopropyltrimethoxysilane and polyethylenepolyamine. Under nitrogen protection, reflux at 100°C for 10 h. After the reaction is complete, filter and wash 5 times with anhydrous ethanol. After washing, vacuum dry at -0.06 MPa and 60°C for 8 h, and cool to room temperature to obtain multi-stage modified chelating resin.
[0030] II. Preparation of Hydrofluoric Acid with Low Metal Impurities Step S1: Industrial anhydrous hydrogen fluoride is passed into a drying tower filled with 5A molecular sieve and adsorbed and dried at a temperature of 20℃ and a pressure of 0.4MPa; the dried industrial anhydrous hydrogen fluoride is then passed into a tubular ambient air vaporizer with a heating temperature of 30℃ and vaporized to obtain HF gas. Step S2: Mix HF gas and oxygen at a volume ratio of 0.5:1 until homogeneous. After mixing, pass the mixture into a dielectric barrier discharge reactor for plasma oxidation. Control the reactor discharge frequency at 50kHz, power at 5kW, electrode spacing at 10mm, and gas residence time at 1.0s. After the reaction is complete, oxidized HF gas is obtained. Step S3: The oxidized HF gas is passed into a fixed-bed adsorption tower packed with the above-mentioned multi-stage modified chelating resin; the control conditions are: adsorption temperature 35℃, pressure 0.3MPa, and space velocity 500h. -1 The fixed-bed adsorption tower has a height-to-diameter ratio of 5:1, and after adsorption, HF gas is obtained after adsorption by multi-stage modified chelating resin. Step S4: The adsorbed HF gas is subjected to multi-effect coupled distillation: the first-stage distillation is carried out at atmospheric pressure with a top temperature of 25°C to remove light component impurities; the second-stage distillation is carried out at a pressure of 0.4 MPa with a top temperature of 60°C to remove heavy component impurities; the top vapor of the second-stage distillation column is used as the heat source of the bottom of the first-stage distillation column to achieve heat coupling and obtain the HF gas after multi-effect coupled distillation. Step S5: Pass the HF gas after multi-effect coupled distillation into the falling film absorber, and control the absorption temperature to [temperature value missing]. Ultrapure water with a conductivity ≤0.055μS / cm was used to absorb HF gas in a countercurrent manner at a gas-liquid ratio of 1:1.5 (volume ratio). The density of the absorbent was monitored in real time by an online density meter, and the flow rates of the ultrapure water and HF gas were adjusted accordingly to control the mass fraction of the absorbent at 49%, thus obtaining a hydrofluoric acid product with low metal impurities.
[0031] Comparative Example 1 Compared with Example 1, in step S3, the "multi-stage modified chelating resin" was replaced with "Ti-Al-IDA resin"; the remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, hydrofluoric acid with low metal impurities was obtained.
[0032] Comparative Example 2 Compared with Example 1, in step S3, "multi-stage modified chelating resin" was replaced with "Al-IDA resin"; the remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, hydrofluoric acid with low metal impurities was obtained.
[0033] Comparative Example 3 Compared with Example 1, in step S3, the "multi-stage modified chelating resin" was replaced with "iminodiacetic acid chelating resin"; the remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, hydrofluoric acid with low metal impurities was obtained.
[0034] Comparative Example 4 Compared with Example 1, this comparative example omits step S2 plasma oxidation, and HF gas is directly introduced into a fixed-bed adsorption tower filled with multi-stage modified chelating resin for adsorption; the remaining steps and parameters are the same, and will not be repeated in this comparative example, and finally hydrofluoric acid with low metal impurities is obtained.
[0035] The performance of hydrofluoric acid with low metal impurities prepared in Examples 1-3 and hydrofluoric acid with low metal impurities prepared in Comparative Examples 1-4 was tested, and the results are recorded in Table 1.
[0036] Test method: Referring to the HG / T 4509-2013 standard "Industrial High Purity Hydrofluoric Acid", the total acidity (calculated as HF), fluorosilicic acid, chloride, nitrate, phosphate and sulfate of the hydrofluoric acid prepared in Examples 1-3 and Comparative Examples 1-4 were determined.
[0037] The contents of trace impurity elements (aluminum, arsenic, iron, copper, nickel, lead, calcium, magnesium, and zinc) in the hydrofluoric acid prepared in Examples 1-3 and Comparative Examples 1-4 were determined by inductively coupled plasma mass spectrometry (ICP-MS) according to the method specified in T / CNIA 0118-2021 "Determination of Trace Impurity Element Content in High-Purity Hydrofluoric Acid for Electronic Industry".
[0038] Table 1: Hydrofluoric Acid Detection Results As shown in Table 1, the low-metal-impurity hydrofluoric acid prepared in Examples 1-3 of this invention exhibits excellent comprehensive performance in terms of metal impurity removal and anion control, which is significantly better than that of Comparative Examples 1-4.
[0039] Data from Example 1 and Comparative Example 1 show that: Comparative Example 1 replaced the "multi-stage modified chelating resin" with "Ti-Al-IDA resin" without grafting modification with mercaptopropyltrimethoxysilane and polyethylenepolyamine. Due to the lack of synergistic chelation between thiol and amino functional groups, the resin's adsorption selectivity for specific metal ions (especially arsenic, lead, etc.) decreased, resulting in a significant increase in the content of metal impurities such as arsenic and iron in hydrofluoric acid, and a significant increase in residual fluorosilicic acid. The overall purification effect was significantly worse than that of Example 1.
[0040] Data from Example 1 and Comparative Example 2 show that in Comparative Example 2, the "multi-stage modified chelating resin" was replaced with "Al-IDA resin," and no tetrabutyl titanate loading modification was performed. Due to the lack of the synergistic complexing effect of titanium, the resin's ability to capture anionic impurities and multivalent metals was insufficient, resulting in a significant increase in the residual aluminum and other metals in hydrofluoric acid compared to Example 1. At the same time, the content of anionic impurities such as sulfate and phosphate also increased significantly, confirming the key role of titanium loading in improving the overall adsorption performance of the resin.
[0041] Data from Example 1 and Comparative Example 3 show that replacing the "multi-stage modified chelating resin" with "iminodiacetic acid chelating resin" in Comparative Example 3 significantly reduced its adsorption capacity and affinity for metal ions. Detection data indicates that the content of metal impurities such as aluminum, iron, and calcium in hydrofluoric acid increased compared to Example 1, and the residual fluorosilicic acid also increased significantly. The purity of hydrofluoric acid no longer meets the requirements for electronic-grade applications, fully demonstrating that aluminum and titanium loading are indispensable for achieving the goal of low metal impurities.
[0042] As shown by the data from Example 1 and Comparative Example 4, Comparative Example 4 omitted the plasma oxidation process in step S2. Due to the lack of a strong oxidizing environment, the raw materials exist in low valence states (such as As). 3+ Metal impurities are difficult to effectively convert into easily adsorbed or volatile forms, leading to a decrease in the removal efficiency of adsorption and distillation processes. Test results showed that the arsenic content in Comparative Example 4 was worse than in Example 1, and the residues of iron, copper, and other metals also increased to varying degrees, indicating that plasma oxidation technology plays an irreplaceable role in the deep removal of metal impurities in specific valence states.
[0043] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.
Claims
1. A method for preparing hydrofluoric acid with low metal impurities, characterized in that, The preparation steps include the following: Step S1: Industrial anhydrous hydrogen fluoride is adsorbed and dried by passing it through a drying tower filled with molecular sieves, and then vaporized to obtain HF gas. Step S2: After mixing HF gas with oxygen, the mixture is introduced into a plasma reactor for plasma oxidation to obtain oxidized HF gas. Step S3: The oxidized HF gas is passed into a fixed bed adsorption tower filled with multi-stage modified chelating resin for adsorption, and HF gas after adsorption by multi-stage modified chelating resin is obtained. Step S4: The HF gas adsorbed by the multi-stage modified chelating resin is subjected to multi-effect coupled distillation to obtain HF gas after multi-effect coupled distillation. Step S5: Pass the HF gas after multi-effect coupled distillation into a falling film absorption tower and absorb it with ultrapure water to obtain hydrofluoric acid with low metal impurities.
2. The method for preparing hydrofluoric acid with low metal impurities according to claim 1, characterized in that, The preparation method of the multi-stage modified chelating resin is as follows: Step A1: Immerse the iminodiacetic acid chelating resin in dilute sulfuric acid, then wash it with deionized water to 6.5-7.5 to obtain the pretreated iminodiacetic acid chelating resin. Step A2: The pretreated iminodiacetic acid chelating resin is packed into a glass column, and aluminum nitrate solution is circulated for 4-6 hours. After standing for 12-15 hours, it is washed with deionized water to obtain Al-IDA resin. Step A3: Immerse Al-IDA resin in anhydrous ethanol and allow it to swell for 1.5-2.5 hours. Then add tetrabutyl titanate and stir the reaction at 50-60°C for 4-6 hours. After the reaction is complete, wash with anhydrous ethanol to obtain Ti-Al-IDA resin. Step A4: Add Ti-Al-IDA resin to anhydrous ethanol, add mercaptopropyltrimethoxysilane and polyethylenepolyamine, and reflux at 80℃-100℃ for 8h-10h under nitrogen protection. After the reaction is completed, filter, wash and dry to obtain multi-stage modified chelating resin.
3. The method for preparing hydrofluoric acid with low metal impurities according to claim 2, characterized in that, In the preparation process of the multi-stage modified chelating resin, the specific materials are as follows by weight: 90-100 parts of iminodiacetic acid chelating resin, 400-600 parts of aluminum nitrate solution, 5-12 parts of tetrabutyl titanate, 4-10 parts of mercaptopropyltrimethoxysilane, 2-6 parts of polyethylene polyamine, 200-300 parts of dilute sulfuric acid, and 700-1100 parts of anhydrous ethanol.
4. The method for preparing hydrofluoric acid with low metal impurities according to claim 2, characterized in that, The method for preparing the aluminum nitrate solution is as follows: dissolve aluminum nitrate nonahydrate in deionized water to prepare an aluminum nitrate solution with a molar concentration of 0.5 mol / L-1.0 mol / L, and adjust the pH value to 2-3 with dilute nitric acid.
5. The method for preparing hydrofluoric acid with low metal impurities according to claim 1, characterized in that, The molecular sieve used in step S1 is a 5A type molecular sieve.
6. The method for preparing hydrofluoric acid with low metal impurities according to claim 1, characterized in that, In step S2, the volume ratio of oxygen to HF gas is 0.1-0.5:1; in step S2, the plasma reactor is a dielectric barrier discharge reactor with a discharge frequency of 50kHz and a power of 1kW-5kW.
7. The method for preparing hydrofluoric acid with low metal impurities according to claim 1, characterized in that, In step S3, the fixed-bed adsorption tower has an adsorption temperature of 25-35℃, a pressure of 0.1MPa-0.3MPa, and a space velocity of 200h⁻¹. -1 -500h -1 .
8. The method for preparing hydrofluoric acid with low metal impurities according to claim 1, characterized in that, The multi-effect coupled distillation in step S4 includes: First-stage distillation: at atmospheric pressure, with a top temperature of 20℃-25℃, to remove light component impurities; Secondary distillation: pressure 0.3MPa-0.4MPa, top temperature 50℃-60℃, to remove heavy component impurities.
9. The method for preparing hydrofluoric acid with low metal impurities according to claim 1, characterized in that, The absorption temperature of the falling film absorption tower in step S5 is 5℃-10℃.
10. Hydrofluoric acid with low metal impurities prepared by the method for preparing hydrofluoric acid with low metal impurities according to any one of claims 1-9.