Preparation method for beryllium fluoride having high purity and uniform particle size

Abstract

The present invention relates to a preparation method for beryllium fluoride having high purity and uniform particle size, comprising the following steps: 1) dissolving a beryllium-containing starting material and tetrabutylammonium fluoride in hydrofluoric acid and cooling the mixture to form a beryllium-containing mixed solution; 2) adding ammonium fluoride to the beryllium-containing mixed solution in step 1) and heating and stirring the mixture to obtain a mixture; 3) heating and reacting the mixture; and 4) cooling the product and performing separation and purification on the cooled product to obtain the beryllium fluoride. In the present invention, the preparation temperature of the beryllium-containing solution is controlled, and tetrabutylammonium fluoride is added, thereby reducing the occurrence of side reactions in the system; in addition, by means of the change of the temperature of the mixed system, a high-temperature reaction is effectively initiated, improving reaction efficiency, and thus obtaining the beryllium fluoride having high purity and uniform particle size. The present invention exhibits convenient operation, simplified process, and significant technical advantages, and has popularization value.

Description

A method for preparing beryllium fluoride with high purity and uniform particle size Technical Field

[0001] This invention belongs to the field of beryllium fluoride preparation technology, specifically relating to a method for preparing beryllium fluoride with high purity and uniform particle size. Background Technology

[0002] Beryllium fluoride, with the chemical formula BeF2, is primarily used in the manufacture of beryllium alloys and is an important strategic nuclear energy material. High-purity beryllium fluoride is one of the main raw materials for preparing FLiBe molten salt for nuclear reactors. The United States, Russia, and other countries have a certain degree of technological advancement in beryllium fluoride preparation. Although my country's beryllium fluoride preparation technology has been developing for over a decade, technical bottlenecks remain in the preparation of high-purity or nuclear-grade beryllium fluoride, and there is limited involvement in the industrial production of high-purity beryllium fluoride.

[0003] CH345878A reacts beryllium oxide with ammonium bifluoride and a small amount of water. Beryllium fluoride readily combines with water to form beryllium fluoride tetrahydrate, which hydrolyzes upon heating. Therefore, the resulting beryllium fluoride requires high-temperature processing in the presence of salts, such as sodium chloride or magnesium fluoride, resulting in a complex and energy-intensive process. Existing technologies also involve dissolving beryllium-containing raw materials with ammonium fluoride in hydrofluoric acid and then evaporating at high temperatures to obtain beryllium fluoride powder. While this method can control hydrolysis side reactions to some extent, the fluoride oxide content remains around 0.5%. DE2147507C3 produces beryllium fluoride with an oxygen content below 0.02% under specific high-temperature inert gas conditions, but its stringent process environment is not conducive to large-scale production. Due to the large demand for beryllium fluoride and its high purity requirements in molten salt reactor construction, developing a novel high-purity beryllium fluoride preparation process is a pressing issue in this field. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies in preparing beryllium fluoride, such as low purity and uneven particle size, this invention proposes a method for preparing beryllium fluoride. In the preparation of the beryllium-containing mixture, tetrabutylammonium fluoride is added, which enhances the interaction between the beryllium-containing raw material and hydrofluoric acid, improving its solubility and uniformity, thereby contributing to the uniform particle size of the final beryllium fluoride product. Simultaneously, the addition of tetrabutylammonium fluoride also acts as a protective layer, reducing the probability of side reactions and improving the purity of the beryllium fluoride. Specifically, this invention provides the following technical solutions to address the above-mentioned technical problems:

[0005] A method for preparing beryllium fluoride with high purity and uniform particle size includes the following steps:

[0006] 1) Dissolve the beryllium-containing raw material and tetrabutylammonium fluoride in hydrofluoric acid, cool down, and form a beryllium-containing mixture;

[0007] 2) Add ammonium fluoride to the beryllium-containing mixture obtained in step 1), heat and stir to obtain a mixture;

[0008] 3) Heat the mixture to react;

[0009] 4) The product is cooled, separated, and purified to obtain beryllium fluoride.

[0010] Further, the temperature is lowered to 10-20°C as described in step 1).

[0011] The beryllium-containing raw material is selected from one or more of metallic beryllium, beryllium hydroxide, and beryllium oxide.

[0012] In step 1), the molar ratio of beryllium-containing raw material to tetrabutylammonium fluoride is 1:(0.1-0.3).

[0013] In one embodiment of the present invention, the molar ratio of beryllium to tetrabutylammonium fluoride is 1:0.1.

[0014] In the preparation of the beryllium-containing mixture, this invention adds tetrabutylammonium fluoride, which enhances the interaction between the beryllium-containing raw material and hydrofluoric acid, thereby increasing its solubility. When the temperature drops to 5-15℃, the molecular motion of the system slows down, and a stable tetrabutylammonium fluoride "protective layer" forms on the surface of the beryllium-containing raw material. In the subsequent process of HF and ammonium fluoride generating ammonium bifluoride, this layer can increase the reaction rate of the two components in the system, playing a certain "site-occupying" role and reducing the side reactions caused by premature beryllium intervention. This facilitates the early or pre-formation of a stable beryllium fluoride hydrolysis inhibitor—ammonium bifluoride—effectively reducing the occurrence of beryllium fluoride hydrolysis. Moreover, the organofluorine ammonium is homologous to the ammonium fluoride evaporated from the solution in step 3). Under high-temperature heating and the action of HF, it can be converted into the more stable compound ammonium bifluoride, without introducing additional impurities into the system, simplifying the impurity removal steps. Furthermore, the introduction of organic ammonium fluoride improves the uniformity of raw material dissolution and effectively promotes the homogeneity of the system, resulting in a more uniform particle size of the final beryllium fluoride, demonstrating significant technological advantages.

[0015] Furthermore, the inventors discovered that adding tetrabutylammonium fluoride is most suitable. If large molecular weight organofluorine ammonium fluoride is used, the large number of carbon chains of the substituent groups may result in large steric hindrance, which may affect the solubility of the beryllium-containing system and the efficiency of the beryllium fluoride product generated by high-temperature heating reaction. If small molecular weight organofluorine ammonium fluoride with a lower carbon number is used, there is a risk of premature decomposition at high temperature, which is not conducive to controlling the forward reaction process. At the same time, it is not conducive to fully protecting the beryllium-containing raw materials and has a limited degree of suppression of side reactions.

[0016] Further, in step 1), the concentration of hydrofluoric acid is 30-40 wt%, and the mass ratio of beryllium-containing raw material to hydrofluoric acid is 1:(1-5), for example, 1:3-4.

[0017] Further, in step 2), after adding ammonium fluoride to the beryllium-containing mixture from step 1), the temperature is raised to 50-60℃ and stirred for 10-30 minutes;

[0018] In one embodiment of the present invention, the temperature is raised to 60°C and stirred for 20 minutes.

[0019] In step 2), the amount of ammonium fluoride added is such that the molar ratio of beryllium-containing raw material to ammonium fluoride is 1:(1.9-2.1).

[0020] In one embodiment of the present invention, the molar ratio of beryllium-containing raw material to ammonium fluoride is 1:2.

[0021] Ammonium fluoride transforms into the more stable compound ammonium hydrogen fluoride in the presence of HF. During the high-temperature solution evaporation process, it can inhibit the hydrolysis reaction of beryllium fluoride, which helps to reduce the content of beryllium oxyfluoride in beryllium fluoride products and improve the purity of beryllium fluoride.

[0022] The heating conditions described in step 3) are: pressure 200-300 mmHg, temperature 200-300℃, and time 1-4 h.

[0023] In one embodiment of the present invention, the reaction pressure is 220 mmHg, the temperature is 260°C, and the time is 2 h.

[0024] In the prior art, the presence of the byproduct beryllium fluoride significantly affects the purity, yield, and performance of the target product beryllium fluoride. Therefore, it is necessary to minimize the occurrence of side reactions in the fluorination process.

[0025] In step 2) of this invention, after mixing the beryllium-containing solution with ammonium fluoride, appropriate heating and stirring measures were taken before initiating the high-temperature reaction. This process raised the system temperature to 50-60°C, optimizing the solubility and uniformity of the raw materials within the system. This avoided uneven local fluoride contact, preventing problems such as excessively rapid local reaction rates, side reactions, uneven reaction, and low overall reaction efficiency during the rapid heating process in step 3). Furthermore, the uniform bubbles generated during the heating and stirring process facilitated the occurrence of multi-interface continuous phase reactions in the subsequent high-temperature process. This reaction mechanism significantly improved the uniformity and effectiveness of the reaction, while reducing the probability of side reactions, thereby enhancing the overall reaction efficiency.

[0026] Moreover, before the high-temperature reaction in step 3), the mixture is preheated appropriately. This not only allows the low-temperature solution in step 1) to be fully transitioned before the high-temperature reaction by utilizing temperature changes, which is beneficial to the stability of the precursor system, but also enhances the timing of starting and controlling the high-temperature reaction, making the entire chemical reaction highly controllable.

[0027] Further, the reaction product in step 4) is cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention utilizes tetrabutylammonium fluoride and temperature control to obtain a stable and uniform beryllium-containing mixture, which facilitates subsequent high-temperature reactions, resulting in uniform particle size and improved purity of the prepared beryllium fluoride product. Moreover, during the high-temperature reaction, tetrabutylammonium fluoride and ammonium fluoride can first form stable ammonium bifluoride. At this time, the protected beryllium-containing raw materials will not undergo side reactions due to premature participation, and a more stable beryllium fluoride hydrolysis inhibitor NH4HF2 can be formed in advance, which can suppress the occurrence of beryllium fluoride hydrolysis to the greatest extent.

[0030] 2. In the mixing process of beryllium-containing mixture and ammonium fluoride, the present invention incorporates temperature control intervention to avoid risks such as excessively rapid local contact reaction during the heating process; in addition, pre-stirring not only improves the uniformity of mixing, but also provides a multi-interface continuous phase reaction basis for subsequent high-temperature reaction, thereby improving reaction uniformity and reaction efficiency.

[0031] 3. The present invention has low overall energy consumption, low chemical reagent consumption, simple process steps, and convenient operation, and has wide application value, especially suitable for the preparation of high purity or nuclear grade beryllium fluoride.

[0032] 4. This invention does not require the addition of additional chemical reagents, which simplifies the subsequent processing and impurity removal steps, making it suitable for industrial-scale promotion and application. Detailed Implementation

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions used in the embodiments will be briefly introduced below. It should be understood that only some embodiments of the present invention are shown below, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related embodiments can be obtained based on these embodiments without creative effort.

[0034] Example 1

[0035] A method for preparing beryllium fluoride with high purity and uniform particle size includes the following steps:

[0036] 1) Dissolve 5g of metallic beryllium and 14.5g of tetrabutylammonium fluoride in 50g of 40wt% hydrofluoric acid, and cool to 10℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium to tetrabutylammonium fluoride is 1:0.1;

[0037] 2) Add 41g of ammonium fluoride (molar ratio of beryllium to fluorine is 1:2) to the beryllium-containing mixture obtained in step 1), heat to 60°C, and stir for 30 minutes to obtain the mixture;

[0038] 3) The mixture from step 2) was heated at a pressure of 220 mmHg and a temperature of 260 °C for 2 hours.

[0039] 4) The reaction product was cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0040] Example 2

[0041] A method for preparing beryllium fluoride with high purity and uniform particle size includes the following steps:

[0042] 1) Dissolve 5g of beryllium oxide and 5.2g of tetrabutylammonium fluoride in 50g of 40wt% hydrofluoric acid and cool to 10℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium oxide to tetrabutylammonium fluoride is 1:0.1;

[0043] 2) Add 14.8g of ammonium fluoride to the beryllium-containing mixture obtained in step 1), heat to 50°C, and stir for 20 minutes to obtain the mixture;

[0044] 3) The mixture from step 2) was heated and reacted at a pressure of 250 mmHg and a temperature of 250 °C for 2 hours;

[0045] 4) The reaction product was cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0046] Example 3

[0047] A method for preparing beryllium fluoride with high purity and uniform particle size includes the following steps:

[0048] 1) Dissolve 9g of metallic beryllium and 26.1g of tetrabutylammonium fluoride in 50g of 40wt% hydrofluoric acid, and cool to 20℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium to tetrabutylammonium fluoride is 1:0.1;

[0049] 2) Add 74g of ammonium fluoride to the beryllium-containing mixture obtained in step 1), heat to 60°C, and stir for 10 minutes to obtain the mixture;

[0050] 3) The mixture from step 2) was heated at a pressure of 240 mmHg and a temperature of 260 °C for 1.5 h.

[0051] 4) The reaction product was cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0052] Example 4

[0053] A method for preparing beryllium fluoride with high purity and uniform particle size includes the following steps:

[0054] 1) Dissolve 10g of beryllium hydroxide and 6g of tetrabutylammonium fluoride in 50g of 40wt% hydrofluoric acid and cool to 15℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium hydroxide to tetrabutylammonium fluoride is 1:0.1;

[0055] 2) Add 17.2g of ammonium fluoride to the beryllium-containing mixture obtained in step 1), heat to 55°C, and stir for 20 minutes to obtain the mixture;

[0056] 3) The mixture from step 2) was heated at a pressure of 230 mmHg and a temperature of 250 °C for 2 hours.

[0057] 4) The reaction product was cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0058] Example 5

[0059] A method for preparing beryllium fluoride with high purity and uniform particle size includes the following steps:

[0060] 1) Dissolve 5g of beryllium oxide and 10.4g of tetrabutylammonium fluoride in 50g of 40wt% hydrofluoric acid and cool to 10℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium oxide to tetrabutylammonium fluoride is 1:0.2;

[0061] 2) Add 14.8g of ammonium fluoride to the beryllium-containing mixture obtained in step 1), heat to 50°C, and stir for 20 minutes to obtain the mixture;

[0062] 3) The mixture from step 2) was heated and reacted at a pressure of 250 mmHg and a temperature of 250 °C for 2 hours;

[0063] 4) The reaction product was cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0064] Example 6

[0065] A method for preparing beryllium fluoride with high purity and uniform particle size includes the following steps:

[0066] 1) Dissolve 5g of beryllium oxide and 15.6g of tetrabutylammonium fluoride in 50g of 30wt% hydrofluoric acid, and cool to 12℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium oxide to tetrabutylammonium fluoride is 1:0.3;

[0067] 2) Add 14.8g of ammonium fluoride to the beryllium-containing mixture obtained in step 1), heat to 50°C, and stir for 20 minutes to obtain the mixture;

[0068] 3) The mixture from step 2) was heated and reacted at a pressure of 250 mmHg and a temperature of 250 °C for 2 hours;

[0069] 4) The reaction product was cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0070] Comparative Example 1

[0071] 1) Dissolve 5g of metallic beryllium and 43g of ammonium fluoride (the molar ratio of beryllium to fluorine is 1:2.1) in 50g of 40wt% hydrofluoric acid;

[0072] 2) The mixed solution from step 1) was heated and reacted at a pressure of 220 mmHg and a temperature of 260 °C for 2 hours;

[0073] 3) The reaction product was cooled, precipitated with ethanol, and centrifuged to obtain beryllium fluoride powder.

[0074] Comparative Example 2

[0075] 1) Dissolve 5g of metallic beryllium and 14.5g of tetrabutylammonium fluoride in 50g of 40wt% hydrofluoric acid to form a beryllium-containing mixture at room temperature; wherein the molar ratio of beryllium to tetrabutylammonium fluoride is 1:0.1;

[0076] Steps 2)-4) are the same as in Example 1.

[0077] Comparative Example 3

[0078] 1) Dissolve 5g of metallic beryllium and 10.3g of tetraethylammonium fluoride in 50g of 40wt% hydrofluoric acid, and cool to 10℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium to tetraethylammonium fluoride is 1:0.1;

[0079] Steps 2)-4) are the same as in Example 1.

[0080] Comparative Example 4

[0081] 1) Dissolve 5g of metallic beryllium and 17.6g of tetrapentyl ammonium fluoride (CAS registration number 69468-58-2) in 50ml of 40% hydrofluoric acid and cool to 10℃ to form a beryllium-containing mixture; wherein the molar ratio of beryllium to tetrapentyl ammonium fluoride is 1:0.1;

[0082] Steps 2)-4) are the same as in Example 1.

[0083] Example of detection:

[0084] The particle size of beryllium fluoride powders D10, D50 and D90 obtained in each example and comparative example was determined by sedimentation method, and the span value was obtained according to formula (I); at the same time, chemical analysis was performed on the products, and the yield, purity and oxygen content of beryllium fluoride products in each example and comparative example were calculated. The results are shown in Table 1.

[0085] Table 1

[0086] As can be seen from Examples 1-6 and Comparative Example 1, the present invention, by adding tetrabutylammonium fluoride and controlling the preparation temperature and reaction process of the beryllium-containing solution, improves the uniformity of the system, which has a positive significance and important role in particle size control. The particle size span is low (below 1.5), which simplifies the subsequent sieving and other post-processing procedures. On the other hand, it reduces the probability of side reactions and reduces the oxygen content in the product (below 290 ppm), thereby improving the purity of the beryllium fluoride product (higher than 99.6%).

[0087] As can be seen from Example 1 and Comparative Example 2, the beryllium-containing mixture in Example 1 is in a low-temperature state, which makes it easier to maintain the slow molecular motion. The beryllium-containing raw material is stabilized and protected by tetrabutylammonium fluoride, which facilitates the early formation of ammonium hydrogen fluoride in the subsequent high-temperature heating reaction process. This can effectively suppress the hydrolysis side reaction of beryllium fluoride in the product, thereby reducing the oxygen content in the product and improving the purity of beryllium fluoride.

[0088] As can be seen from Examples 1 and Comparative Examples 3 and 4, the use of tetrabutylammonium fluoride has a certain impact on the uniformity of dissolution and the formation of the side reaction inhibitor, ammonium hydrogen fluoride. The tetraethylammonium fluoride in Comparative Example 3 has a shorter molecular chain segment, which cannot effectively protect the beryllium-containing compound. Therefore, the effect of inhibiting the hydrolysis of beryllium fluoride is slowed down, the content of by-products increases, and the oxygen content in the system increases. The tetrapentylammonium fluoride in Comparative Example 4 may have a longer molecular chain segment and greater steric hindrance, which is not conducive to dissolution or uniform occurrence of subsequent high-temperature reactions. Therefore, there are more side reaction products, the oxygen content is also higher, and the reaction efficiency is low, resulting in a lower product yield.

[0089] In summary, this invention controls the preparation temperature of the beryllium-containing solution and adds tetrabutylammonium fluoride to reduce side reactions in the system. Simultaneously, it utilizes temperature changes in the mixed system to effectively transition to a high-temperature reaction, improving reaction efficiency and thus obtaining high-purity (oxygen content below 300 ppm) beryllium fluoride with uniform particle size. This invention is convenient to operate, has a simplified process, and offers significant technical advantages.

Claims

1. A method for preparing beryllium fluoride with high purity and uniform particle size, characterized in that, Includes the following steps: 1) Dissolve the beryllium-containing raw material and tetrabutylammonium fluoride in hydrofluoric acid, cool down, and form a beryllium-containing mixture; 2) Add ammonium fluoride to the beryllium-containing mixture obtained in step 1), heat and stir to obtain a mixture; 3) Heat the mixture to react; 4) The product is cooled, separated, and purified to obtain beryllium fluoride.

2. The preparation method according to claim 1, characterized in that, The temperature is lowered to 10-20℃ as described in step 1).

3. The preparation method according to claim 1, characterized in that, In step 1), the beryllium-containing raw material is selected from one or more of metallic beryllium, beryllium hydroxide, and beryllium oxide.

4. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of beryllium-containing raw material to tetrabutylammonium fluoride is 1:(0.1-0.3).

5. The preparation method according to claim 1, characterized in that, In step 1), the concentration of hydrofluoric acid is 30-40 wt%.

6. The preparation method according to claim 1, characterized in that, In step 1), the mass-to-volume ratio of beryllium-containing raw material to hydrofluoric acid is 1:(1-5).

7. The preparation method according to claim 1, characterized in that, In step 2), heat to 50-60℃ and stir for 10-30 minutes.

8. The preparation method according to claim 1, characterized in that, In step 2), the molar ratio of beryllium-containing raw material to ammonium fluoride is 1:(1.9-2.1).

9. The preparation method according to claim 1, characterized in that, In step 3), the heating conditions are: pressure 200-300 mmHg, temperature 200-300℃, and time 1-4 h.

10. The preparation method according to claim 1, characterized in that, In step 4), the product is cooled to room temperature, precipitated with ethanol, and centrifuged to obtain beryllium fluoride.

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