Preparation process of ultra-clean high-purity ammonium fluoride solution

Abstract

The invention provides a preparation process of an ultra-clean high-purity ammonium fluoride solution, and belongs to the technical field of preparation of electronic-grade chemicals. The microcapsule adsorbent is creatively introduced, various purification technologies are combined, the content of metal ions, particles and organic impurities in the ammonium fluoride solution is remarkably reduced, and the strict requirement of the semiconductor industry for high-purity chemicals is met. Wherein the hollow structure of the microcapsule adsorbent and the amide modified cyclodextrin have a synergistic effect, so that the microcapsule adsorbent is endowed with high specific surface area and strong adsorption capacity and has a strong adsorption effect on heavy metal ions and impurity particles, and the polyacrylate shell material enhances the stability of the microcapsule adsorbent in a strong acid / alkali environment. The traditional process has the problem of poor filtering effect and needs to use complex equipment (such as a centrifugal machine and an ultrafiltration device) for multi-step separation, while the method can achieve an efficient separation effect through conventional filtering operation, has the characteristics of high purification efficiency, convenience in separation, stable product quality and the like, and is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of electronic-grade chemicals or fluorine chemicals, and particularly relates to a preparation process of an ultra-clean high-purity ammonium fluoride solution. Background Art

[0002] Ammonium fluoride is an important inorganic compound with the chemical formula NH4F. It is usually white or colorless, transparent orthorhombic crystals, easily deliquescent and agglomerates in air, and is easily soluble in water. Ammonium fluoride is a versatile chemical that plays a key role in many industrial fields. For example, ammonium fluoride is an important material for glass etching, achieving the desired artistic or functional effects through specific chemical reactions. Due to its antibacterial properties, ammonium fluoride can be used as a preservative in certain chemical products and foods. Ammonium fluoride is also used in the field of metal surface treatment, such as anodizing of aluminum and its alloys to enhance corrosion resistance and wear resistance. As an additive in ceramic manufacturing, ammonium fluoride can improve the performance and structure of ceramics. In laboratories, ammonium fluoride is often used as an analytical reagent and is involved in various chemical analyses and experimental processes.

[0003] The above applications have relatively low purity requirements for ammonium fluoride. However, with the increasing demand from the electronics industry, its application in the semiconductor industry, in particular, is indispensable. As we all know, the semiconductor field has increasingly higher requirements for the purity of fine chemicals, and the demand for ultra-clean, high-purity ammonium fluoride is also increasing. The application of ammonium fluoride in the semiconductor field mainly includes: In the semiconductor manufacturing process, ammonium fluoride solution is used as a cleaning agent to help remove impurities and residues on the surface of silicon wafers. Etching agent: Ammonium fluoride solution is also used in the etching process in the semiconductor industry, especially for fine processing of material surfaces when manufacturing microelectronic devices. Impurity doping: During the doping process, ammonium fluoride may be used to introduce impurity atoms to change the electrical properties of semiconductors.

[0004] Common methods for preparing ammonium fluoride are as follows:

[0005] Direct neutralization method: Direct neutralization method is to prepare ammonium fluoride through the direct neutralization reaction of ammonia and hydrofluoric acid. This method is simple to operate, has a fast reaction, and is suitable for large-scale production.

[0006] Ion exchange method: By using ion exchange resins or other media, fluoride ions are exchanged for other cations to obtain ammonium fluoride. This method can produce a higher purity product, but the process is relatively complex and the cost is high.

[0007] Decomposition method: This method involves using albite, fluorite, and sulfuric acid to react at a certain temperature and pressure to produce ammonium fluoride. The advantage of this method is that it can treat some fluorine-containing minerals, but it requires precise control of the reaction conditions and ratios.

[0008] Each method has its own specific advantages and disadvantages. Choosing the right preparation method depends on the desired product quality, production scale, and cost-effectiveness. In practice, environmental protection, safety, and sustainability factors also need to be considered to ensure that the production process is both efficient and environmentally friendly.

[0009] In general, ammonium fluoride is prepared by numerous methods, each with its specific application scenarios and limitations. However, existing publicly available preparation processes still cannot meet the actual production demand for ultra-clean, high-purity ammonium fluoride, and the impurity content of the product cannot meet the requirements of high-grade, high-purity production and large-scale production. Summary of the Invention

[0010] The invention provides a preparation process of an ultra-clean high-purity ammonium fluoride solution, aiming to provide a new and efficient method for reducing the contents of metal ions, particles and organic impurities in the electronic-grade ammonium fluoride solution and improving the quality of the ammonium fluoride solution.

[0011] The present invention aims to overcome the deficiencies in the prior art and to provide a process for preparing an ultra-clean, high-purity ammonium fluoride solution. To achieve the above technical objectives, the present invention employs the following technical solutions:

[0012] A process for preparing an ultra-clean high-purity ammonium fluoride solution comprises the following steps:

[0013] (1) adding aqueous ammonia or liquid ammonia to a crude ammonium fluoride solution and reacting for 0.5-2 hours to obtain solution a;

[0014] (2) adding barium hydroxide solution to solution a; the introduced barium ions react with sulfate and fluorosilicate impurities in solution a to form a barium salt precipitate; react for 0.5-2 hours, filter, separate the barium salt precipitate, and the filtrate is ammonium fluoride solution b;

[0015] (3) adding a microcapsule adsorbent to the ammonium fluoride solution b, stirring the solution under magnetic stirring for equilibrium, and filtering the solution to obtain a filtrate c; the microcapsule adsorbent is a hollow microcapsule, the shell material of which is polyacrylate and the core material is amide-modified cyclodextrin;

[0016] (4) The filtrate c is heated and concentrated under vacuum. When crystallization begins, heating is stopped;

[0017] (5) transferring the solution d after crystallization in step (4) to a crystallizer for temperature-controlled crystallization, performing solid-liquid separation after the crystallization is completed, separating the ammonium fluoride filtrate, and obtaining ammonium fluoride crystals;

[0018] (6) The ammonium fluoride crystals are dried, dissolved in ultrapure water, and filtered through a 0.1 μm filter membrane to obtain an ultra-clean high-purity ammonium fluoride solution product.

[0019] Preferably, the mass concentration of the crude ammonium fluoride solution in step (1) is less than 20%.

[0020] Preferably, the amount of ammonia water or liquid ammonia added in step (1) is 20-100% excess relative to the amount of ammonium fluoride.

[0021] Preferably, the amount of the microcapsule adsorbent in step (3) is 0.1-5 g per 1 L of ammonium fluoride solution b.

[0022] Preferably, the core material in step (3) is an amide-modified cyclodextrin, and the amide is selected from dimethylamide, dipropylamide, and dibutylamide.

[0023] Preferably, the amide in step (3) is N,N-dibutyl dodecylamide.

[0024] Preferably, the vacuum degree in step (4) is -50kPa--30kPa.

[0025] Preferably, the temperature for heating and concentrating in step (4) is 25-100° C., and the time for heating and concentrating is 0.5-2 h.

[0026] Preferably, the temperature of the temperature-controlled crystallization in step (5) is controlled at -20-30°C.

[0027] Preferably, the temperature of the drying treatment in step (6) is 50-100°C.

[0028] Preferably, the concentration of the ultra-clean high-purity ammonium fluoride solution in step (6) is 40%.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects.

[0030] The process flow and equipment adopted by the present invention have high output and stable product quality for producing ultra-clean high-purity ammonium fluoride solution, are convenient for industrial production, and are highly practical. The present invention creatively introduces a microcapsule adsorbent, and the microcapsule adsorbent is a hollow microcapsule, the shell material is polyacrylate, and the core material is amide-modified cyclodextrin. Among them, polyacrylate as a shell material can withstand the erosion of strong acid and strong alkaline environments, and plays a role in protecting the core material. The core material is amide-modified cyclodextrin, among which cyclodextrin is the most common cylindrical structure, which can form the form of an ultramicrocapsular compound. Since the surface of the cyclodextrin molecule contains many hydroxyl groups, it can form a strong adsorption effect on heavy metal ions and impurity particles; in addition, after amide modification, the introduction of amide molecules further strengthens the adsorption effect on heavy metal ions. The hollow structure of the microcapsule adsorbent has a large specific surface area and can also improve the adsorption effect of the adsorbent on impurities. As a result, the present invention does not require the use of complex equipment (such as centrifuges and ultrafiltration devices) and can efficiently perform separation through conventional filtration operations, avoiding the problem of poor filtration effect in traditional processes. It has the characteristics of high purification efficiency, convenient separation, stable product quality, etc., and is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0031] The following embodiments are merely examples of the present invention and do not constitute any limitation to the scope of implementation.

[0032] Example 1

[0033] The steps for preparing ultra-clean high-purity ammonium fluoride solution in this embodiment are as follows:

[0034] (1) adding aqueous ammonia to a crude ammonium fluoride solution, wherein the ammonia in the aqueous ammonia is in excess of 20% relative to the ammonium fluoride, and reacting for 0.5 h to obtain solution a;

[0035] (2) Adding barium hydroxide solution to solution a, 5 ml at a time, stirring for 1 minute, and observing whether the solution has precipitation. When no obvious precipitation is formed after adding the barium hydroxide solution, stop adding the solution, continue stirring for 0.5 hours, filter, separate the barium salt precipitate, and the filtrate is ammonium fluoride solution b;

[0036] (3) A hollow microcapsule adsorbent having a shell material of polyacrylate and a core material of cyclodextrin modified with N,N-dibutyl dodecylamide was added to the ammonium fluoride solution b at a ratio of 2 g of the hollow microcapsule adsorbent per 1 L of the ammonium fluoride solution b, magnetically stirred for 12 h, and filtered to obtain a filtrate c;

[0037] (4) Filtrate c was heated and concentrated under a vacuum of -40 kPa and a temperature of 65°C. Heating was stopped when crystallization of the filtrate began to occur, thereby obtaining solution d.

[0038] (5) transferring the solution d after crystallization in step (4) to a crystallizer for heat preservation and crystallization at a temperature of 30° C. After the crystallization is completed, solid-liquid separation is performed to obtain a filtrate and ammonium fluoride crystals;

[0039] (6) The ammonium fluoride crystals were dried at 80° C., dissolved in ultrapure water at a concentration of 40%, and filtered through a 0.1 μm filter membrane to obtain an ultra-clean high-purity ammonium fluoride solution product.

[0040] Example 2

[0041] The difference from Example 1 is that in step (3), the hollow microcapsule adsorbent is added at a ratio of 0.2 g of the hollow microcapsule adsorbent per 1 L of ammonium fluoride solution b.

[0042] Example 3

[0043] The difference from Example 1 is that in step (3), the hollow microcapsule adsorbent is added at a ratio of 4.5 g of the hollow microcapsule adsorbent per 1 L of ammonium fluoride solution b.

[0044] Comparative Example 1

[0045] The difference from Example 1 is that the adsorbent used is cyclodextrin modified with N,N-dibutyl dodecylamide, that is, only the core material of the adsorbent in Example 1 is used for adsorption.

[0046] The magnetic stirring time is 5 hours. When the time exceeds 5 hours, the viscosity of the solution increases, which means that the structure of cyclodextrin is destroyed.

[0047] Comparative Example 2

[0048] The difference from Example 1 is that the adsorbent used is polyacrylate, that is, only the shell material of the adsorbent in Example 1 is used for adsorption.

[0049] Comparative Example 3

[0050] The difference from Example 1 is that the shell material of the hollow microcapsule adsorbent used is polyacrylate, and the core material is cyclodextrin.

[0051] Purity test of the ammonium fluoride solution products obtained in each embodiment and comparative example:

[0052] Metal ion mass fractions were determined using an inductively coupled plasma mass spectrometer (ICP-MS). A 5g sample was weighed to the nearest 0.01g and slowly placed into a 50mL volumetric flask containing a small amount of ultrapure water. The sample was cooled to room temperature, diluted to the mark with water, and shaken well. The signal intensity of each element in the sample was measured under the same analytical conditions as the standard solution series, and a blank test was performed simultaneously. The mass fractions of aluminum, arsenic, barium, boron, cadmium, calcium, chromium, cobalt, copper, gold, iron, lead, magnesium, manganese, nickel, silver, tin, titanium, vanadium, and zinc were determined, and the total concentration of the twenty metal ions was calculated.

[0053] The particle concentration was measured using a laser liquid particle counter.

[0054] The total concentration of organic impurities (acetaldehyde, 2-butenal, 2-ethyl-2-butenal) was quantitatively determined by GC-MS analysis (gas chromatography mass spectrometry).

[0055] The test results are shown in Table 1 below:

[0056] Table 1 Purity test results of examples and comparative examples

[0057]

[0058] The above embodiments and test data are only some applications and implementation methods of the present invention and do not limit the scope of protection of the present invention. Through the above description, any person skilled in the art can see that the present invention is innovatively created by adopting novel ideas and means and has obvious practicality and creativity.

Claims

1. A process for preparing an ultra-clean high-purity ammonium fluoride solution, comprising the following steps: (1) adding aqueous ammonia or liquid ammonia to a crude ammonium fluoride solution and reacting for 0.5-2 hours to obtain solution a; (2) adding barium hydroxide solution to solution a, reacting for 0.5-2 hours, filtering to separate the barium salt precipitate, and the filtrate is ammonium fluoride solution b; (3) adding a microcapsule adsorbent to the ammonium fluoride solution b, stirring the solution under magnetic stirring for equilibrium, and filtering the solution to obtain a filtrate c; the microcapsule adsorbent is a hollow microcapsule, the shell material of which is polyacrylate and the core material is amide-modified cyclodextrin; (4) The filtrate c is heated and concentrated under vacuum. When crystallization begins, heating is stopped; (5) transferring the solution d after crystallization in step (4) to a crystallizer for temperature-controlled crystallization, performing solid-liquid separation after the crystallization is completed, separating the ammonium fluoride filtrate, and obtaining ammonium fluoride crystals; (6) The ammonium fluoride crystals are dried, dissolved in ultrapure water, and filtered through a 0.1 μm filter membrane to obtain an ultra-clean high-purity ammonium fluoride solution product.

2. The preparation process according to claim 1, wherein: The mass concentration of the crude ammonium fluoride solution in step (1) is less than 20%.

3. The preparation process according to claim 1, wherein: The amount of ammonia water or liquid ammonia added in step (1) is 20-100% excess relative to the amount of ammonium fluoride.

4. The preparation process according to claim 1, wherein: The amount of the microcapsule adsorbent used in step (3) is 0.1-5 g per 1 L of ammonium fluoride solution b.

5. The preparation process according to claim 1, wherein: The core material in step (3) is an amide-modified cyclodextrin, wherein the amide is selected from dimethylamide, dipropylamide, and dibutylamide.

6. The preparation process according to claim 5, characterized in that: The amide described in step (3) is N,N-dibutyl dodecylamide.

7. The preparation process according to claim 1, characterized in that: The vacuum degree in step (4) is -50kPa to -30kPa.

8. The preparation process according to claim 1, characterized in that: The temperature for heating and concentrating in step (4) is 25-100° C., and the time for heating and concentrating is 0.5-2 h.

9. The preparation process according to claim 1, characterized in that: The temperature of the temperature-controlled crystallization in step (5) is controlled at -20-30°C.

10. The preparation process according to claim 1, characterized in that: The temperature of the drying treatment in step (6) is 50-100°C.

11. The preparation process according to claim 1, characterized in that: The concentration of the ultra-clean high-purity ammonium fluoride solution in step (6) is 40%.

Images