Preparation method of beryllium fluoride with high purity and uniform particle size

Abstract

The invention relates to a preparation method of beryllium fluoride with high purity and uniform particle size, which comprises the following steps: 1) dissolving a beryllium-containing raw material and tetrabutylammonium fluoride in hydrofluoric acid, and cooling to form a beryllium-containing mixed solution; (2) ammonium fluoride is added into the beryllium-containing mixed solution obtained in the step (1), heating and stirring are conducted, and a mixture is obtained; 3) heating the mixture for reaction; and 4) cooling, separating and purifying the product to obtain the beryllium fluoride. According to the method, the preparation temperature of the beryllium-containing solution is controlled, tetrabutylammonium fluoride is added, side reactions of a system are reduced, meanwhile, high-temperature reactions are effectively started through temperature changes of the mixed system, the reaction efficiency is improved, and therefore beryllium fluoride high in purity and uniform in particle size is obtained. The process is simplified, the technical advantages are obvious, and popularization value is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of beryllium fluoride preparation, and in particular relates to a method for preparing beryllium fluoride with high purity and uniform particle size. Background Art

[0002] Beryllium fluoride has the chemical formula of BeF2. It is mainly used to make beryllium alloys and is an important nuclear strategic energy material. High-purity beryllium fluoride is one of the main raw materials for preparing FLiBe molten salt for nuclear reactors. The United States and other countries have a certain leading position in the preparation process of beryllium fluoride. Although the preparation process of beryllium fluoride in my country has been developed for more than ten years, there are still technical bottlenecks in how to prepare high-purity or nuclear-grade beryllium fluoride, and there is little 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 is easily combined with water to form tetrahydrated beryllium fluoride, and tetrahydrated beryllium fluoride will hydrolyze when heated. Therefore, the formed beryllium fluoride needs to be obtained at high temperature in the presence of salt, such as sodium chloride or magnesium fluoride, and the process is complicated and the energy consumption is too high. The prior art also adopts dissolving the beryllium-containing raw material together with ammonium fluoride in hydrofluoric acid, and obtaining beryllium fluoride powder by high-temperature evaporation. Although the occurrence of hydrolysis side reactions can be controlled to a certain extent, the fluoride oxide content is still around 0.5%. DE2147507C3 prepares beryllium fluoride with an oxygen content of less than 0.02% under specific high-temperature inert gas conditions. Its harsh process environment is not conducive to the large-scale production of beryllium fluoride. Since the construction of molten salt reactors has a large demand for beryllium fluoride and high purity requirements, it is a problem to be solved in this field to develop a new high-purity beryllium fluoride preparation process. Summary of the invention

[0004] In order to overcome the defects of low purity and uneven particle size of beryllium fluoride prepared in the prior art, the present invention proposes a method for preparing beryllium fluoride. In the preparation process of the beryllium-containing mixed solution, tetrabutylammonium fluoride is added to improve the interaction between the beryllium-containing raw material and hydrofluoric acid, enhance its solubility and uniformity, thereby facilitating the uniform particle size of the final product beryllium fluoride; at the same time, the addition of tetrabutylammonium fluoride can also act as a protective layer, reduce the probability of side reactions, and improve the purity of beryllium fluoride. Specifically, the present invention provides the following technical solutions to solve the above technical problems:

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

[0006] 1) dissolving a beryllium-containing raw material and tetrabutylammonium fluoride in hydrofluoric acid, and cooling the solution to form a beryllium-containing mixed solution;

[0007] 2) adding ammonium fluoride to the beryllium-containing mixed solution in step 1), heating and stirring to obtain a mixture;

[0008] 3) heating the mixture to react;

[0009] 4) Cooling, separating and purifying the product to obtain the beryllium fluoride.

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

[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:tetrabutylammonium fluoride is 1:0.1.

[0014] In the preparation process of the beryllium-containing mixed solution, tetrabutylammonium fluoride is added to improve the interaction between the beryllium-containing raw material and hydrofluoric acid, and enhance its solubility; when the temperature is lowered to 5-15°C, the molecular movement of the system slows down, and a stable tetrabutylammonium fluoride "protective layer" is formed on the surface of the beryllium-containing raw material. In the subsequent process of HF and ammonium fluoride generating ammonium bifluoride, the reaction rate of the two in the system can be increased, playing a certain "placeholder" role, reducing the side reactions caused by the premature intervention of beryllium, and being conducive to the pre-or advanced formation of a stable beryllium fluoride hydrolysis inhibitor-ammonium bifluoride, effectively reducing the occurrence of beryllium fluoride hydrolysis reaction. Moreover, the organic ammonium fluoride is homologous to the ammonium fluoride evaporated from the solution in step 3), and can be converted into a more stable compound ammonium bifluoride under high temperature heating and the action of HF, without introducing unnecessary impurities into the system, simplifying the impurity removal step. In addition, since the introduction of organic ammonium fluoride improves the dissolution uniformity of the raw materials and effectively promotes the uniformity of the system, the particle size of the finally prepared beryllium fluoride is relatively uniform, and the technical advantages are obvious.

[0015] In addition, the inventors found that adding tetrabutylammonium fluoride is most appropriate. If a large molecular organic ammonium fluoride is used, the carbon chain of the substituent group may be large and the steric hindrance may be large, which may affect the solubility of the beryllium-containing system and the efficiency of the high-temperature heating reaction to generate the product beryllium fluoride. If a small molecular organic ammonium fluoride with a lower carbon number is used, there will be a risk of premature decomposition at high temperature and failure to control the progress of the forward reaction. At the same time, it is not conducive to fully protecting the beryllium-containing raw material, and the degree of suppressing the occurrence of side reactions is limited.

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

[0017] Furthermore, in step 2), after adding ammonium fluoride to the beryllium-containing mixed solution in step 1), the temperature is raised to 50-60° C. 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 min.

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

[0021] Ammonium fluoride will be converted into a more stable compound, ammonium bifluoride, in the presence of HF, which can inhibit the hydrolysis reaction of beryllium fluoride during the evaporation of the high-temperature solution, help reduce the content of beryllium oxyfluoride in the beryllium fluoride product, and improve the purity of beryllium fluoride.

[0022] The heating conditions in step 3) are: pressure 200-300 mmHg, temperature 200-300° C., 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 by-product beryllium oxyfluoride will significantly affect the purity, yield and performance of the target product beryllium fluoride, so it is necessary to minimize the occurrence of side reactions in the fluorination process.

[0025] In step 2) of the present invention, after the beryllium-containing solution is mixed with ammonium fluoride, before starting the high-temperature reaction, we take appropriate heating-stirring measures. In this process, the system is heated to 50-60°C, which optimizes the solubility and uniformity of each raw material in the system, avoids uneven local fluoride contact, and leads to side reactions caused by excessive local reaction rate during the rapid heating process in step 3), uneven reactions, and low overall reaction efficiency. In addition, the uniform bubbles generated during the heating and stirring process are conducive to the occurrence of multi-interface continuous phase reactions in the system during the subsequent high-temperature process. This reaction mechanism significantly improves the uniformity and effectiveness of the reaction, while reducing the probability of side reactions, thereby improving the overall reaction efficiency.

[0026] Moreover, before the high-temperature reaction in step 3), the mixture is first appropriately preheated. This not only utilizes the temperature change to fully transition the low-temperature solution in step 1) before the high-temperature reaction, 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 more controllable.

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

[0028] Beneficial effects of the present invention:

[0029] 1. The present invention utilizes tetrabutylammonium fluoride and temperature control to obtain a stable and uniform beryllium-containing mixed solution, thereby facilitating the subsequent high-temperature reaction, so that the prepared beryllium fluoride product has uniform particle size and improved purity; and in the high-temperature reaction process, tetrabutylammonium fluoride and ammonium fluoride can first form stable ammonium bifluoride, at which time the protected beryllium-containing raw material 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 inhibit the occurrence of beryllium fluoride hydrolysis to the greatest extent.

[0030] 2. The present invention performs temperature control intervention during the mixing process of the beryllium-containing mixed solution and ammonium fluoride to avoid the risk of excessive 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 reactions, thereby improving the reaction uniformity and reaction efficiency.

[0031] 3. The overall process of the present invention has low energy consumption, small amount of chemical reagents, simple process steps, convenient operation, and has wide promotion value, and is particularly suitable for the preparation of high-purity or nuclear-grade beryllium fluoride.

[0032] 4. The present invention does not require the addition of additional chemical reagents, simplifies the subsequent processing and impurity removal steps, and is suitable for industrial promotion and application. DETAILED DESCRIPTION

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions required for use in the embodiments are briefly introduced below. It should be understood that only certain embodiments of the present invention are shown below, and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related embodiments can be obtained based on these embodiments without paying creative work.

[0034] Example 1

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

[0036] 1) dissolving 5 g of metallic beryllium and 14.5 g of tetrabutylammonium fluoride in 50 g of 40 wt% hydrofluoric acid, cooling to 10° C., to form a beryllium-containing mixed solution; wherein the molar ratio of beryllium to tetrabutylammonium fluoride is 1:0.1;

[0037] 2) adding 41 g of ammonium fluoride (the molar ratio of beryllium to fluorine is 1:2) to the beryllium-containing mixed solution in step 1), heating to 60° C., stirring for 30 min, to obtain a mixture;

[0038] 3) heating the mixture of step 2) at a pressure of 220 mmHg and a temperature of 260° C. for 2 h;

[0039] 4) The reaction product is 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 comprises the following steps:

[0042] 1) dissolving 5 g of beryllium oxide and 5.2 g of tetrabutylammonium fluoride in 50 g of 40 wt% hydrofluoric acid, cooling to 10° C., to form a beryllium-containing mixed solution; wherein the molar ratio of beryllium oxide to tetrabutylammonium fluoride is 1:0.1;

[0043] 2) adding 14.8 g of ammonium fluoride to the beryllium-containing mixed solution in step 1), heating to 50° C., and stirring for 20 min to obtain a mixture;

[0044] 3) heating the mixture of step 2) at a pressure of 250 mmHg and a temperature of 250° C. for 2 h;

[0045] 4) The reaction product is 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 comprises the following steps:

[0048] 1) dissolving 9 g of metallic beryllium and 26.1 g of tetrabutylammonium fluoride in 50 g of 40 wt% hydrofluoric acid, cooling to 20° C., to form a beryllium-containing mixed solution; wherein the molar ratio of beryllium to tetrabutylammonium fluoride is 1:0.1;

[0049] 2) adding 74 g of ammonium fluoride to the beryllium-containing mixed solution in step 1), heating to 60° C., and stirring for 10 min to obtain a mixture;

[0050] 3) heating the mixture of step 2) at a pressure of 240 mmHg and a temperature of 260° C. for 1.5 h;

[0051] 4) The reaction product is 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 comprises the following steps:

[0054] 1) dissolving 10 g of beryllium hydroxide and 6 g of tetrabutylammonium fluoride in 50 g of 40 wt% hydrofluoric acid, cooling to 15° C. to form a beryllium-containing mixed solution; wherein the molar ratio of beryllium hydroxide to tetrabutylammonium fluoride is 1:0.1;

[0055] 2) adding 17.2 g of ammonium fluoride to the beryllium-containing mixed solution in step 1), heating to 55° C., and stirring for 20 min to obtain a mixture;

[0056] 3) heating the mixture of step 2) at a pressure of 230 mmHg and a temperature of 250° C. for 2 h;

[0057] 4) The reaction product is 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 comprises the following steps:

[0060] 1) dissolving 5 g of beryllium oxide and 10.4 g of tetrabutylammonium fluoride in 50 g of 40 wt% hydrofluoric acid, cooling to 10° C., to form a beryllium-containing mixed solution; wherein the molar ratio of beryllium oxide to tetrabutylammonium fluoride is 1:0.2;

[0061] 2) adding 14.8 g of ammonium fluoride to the beryllium-containing mixed solution in step 1), heating to 50° C., and stirring for 20 min to obtain a mixture;

[0062] 3) heating the mixture of step 2) at a pressure of 250 mmHg and a temperature of 250° C. for 2 h;

[0063] 4) The reaction product is 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 comprises the following steps:

[0066] 1) dissolving 5 g of beryllium oxide and 15.6 g of tetrabutylammonium fluoride in 50 g of 30 wt% hydrofluoric acid, cooling to 12° C., to form a beryllium-containing mixed solution; wherein the molar ratio of beryllium oxide to tetrabutylammonium fluoride is 1:0.3;

[0067] 2) adding 14.8 g of ammonium fluoride to the beryllium-containing mixed solution in step 1), heating to 50° C., and stirring for 20 min to obtain a mixture;

[0068] 3) heating the mixture of step 2) at a pressure of 250 mmHg and a temperature of 250° C. for 2 h;

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

[0070] Comparative Example 1

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

[0072] 2) heating the mixed solution of step 1) at a pressure of 220 mmHg and a temperature of 260° C. for 2 h;

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

[0074] Comparative Example 2

[0075] 1) dissolving 5 g of metallic beryllium and 14.5 g of tetrabutylammonium fluoride in 50 g of 40 wt% hydrofluoric acid to form a beryllium-containing mixed solution 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) dissolving 5 g of metallic beryllium and 10.3 g of tetraethylammonium fluoride in 50 g of 40 wt% hydrofluoric acid, cooling to 10° C. to form a beryllium-containing mixed solution; 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 5 g of metallic beryllium and 17.6 g of tetrapentylammonium fluoride (CAS registration number 69468-58-2) in 50 ml of 40% hydrofluoric acid, cool to 10° C., to form a beryllium-containing mixed solution; wherein the molar ratio of beryllium to tetrapentylammonium fluoride is 1:0.1;

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

[0083] Test example:

[0084] The particle sizes of the beryllium fluoride powders D10, D50 and D90 obtained in each embodiment and comparative example were detected by sedimentation method, and the span value (span) was obtained according to formula (I); at the same time, the products were chemically analyzed to calculate the yield, purity and oxygen content of the beryllium fluoride products in each embodiment and comparative example. The results are shown in Table 1.

[0085]

[0086] Table 1

[0087]

[0088]

[0089] It can be seen from Examples 1-6 and Comparative Example 1 that the present invention improves the uniformity of the system by adding tetrabutylammonium fluoride, coordinating the preparation temperature of the beryllium-containing solution, controlling the reaction process, etc., which has a positive and important role in particle size control, and the particle size span is relatively low (below 1.5), which can simplify subsequent post-processing processes such as screening; on the other hand, it reduces the probability of side reactions, and the oxygen content in the product is reduced (below 290 ppm), thereby improving the purity of the product beryllium fluoride (higher than 99.6%).

[0090] It can be seen from Example 1 and Comparative Example 2 that the beryllium-containing mixed solution in Example 1 is in a low temperature state and is easy to keep the molecular motion slow, and the beryllium-containing raw material is stably protected by tetrabutylammonium fluoride, so that in the subsequent heating high-temperature reaction process, it is conducive to the early generation of ammonium bifluoride, and the hydrolysis side reaction process of the product beryllium fluoride can be effectively inhibited, so that the oxygen content in the product is reduced and the purity of beryllium fluoride is improved.

[0091] It can be seen from Example 1 and Comparative Examples 3 and 4 that the use of tetrabutylammonium fluoride has a certain influence on the dissolution uniformity and the generation of ammonium bifluoride, a side reaction inhibitor; the tetraethylammonium fluoride in Comparative Example 3 has a shorter molecular chain segment and cannot effectively protect the beryllium-containing compound, so 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 subsequent high-temperature reaction uniformity, so there are more side reaction products and a higher oxygen content, and the reaction efficiency is low, and the product yield is reduced.

[0092] In summary, the present invention controls the preparation temperature of the beryllium-containing solution and adds tetrabutylammonium fluoride to reduce the occurrence of side reactions in the system, and at the same time utilizes the change in the temperature of the mixed system to effectively transition to a high-temperature reaction, thereby improving the reaction efficiency, thereby obtaining high-purity (oxygen content is less than 300ppm) beryllium fluoride with uniform particle size. The present invention is easy to operate, has a simplified process, and has obvious technical advantages.

Claims

1. A method for preparing beryllium fluoride with high purity and uniform particle size, characterized in that: The steps include: 1) dissolving a beryllium-containing raw material and tetrabutylammonium fluoride in hydrofluoric acid, and cooling the solution to form a beryllium-containing mixed solution; 2) adding ammonium fluoride to the beryllium-containing mixed solution in step 1), heating and stirring to obtain a mixture; 3) heating the mixture to react; 4) Cooling, separating and purifying the product to obtain the beryllium fluoride.

2. The preparation method according to claim 1, characterized in that: Step 1) is cooled to 10-20°C.

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 volume ratio of the beryllium-containing raw material to the hydrofluoric acid is 1:(1-5).

7. The preparation method according to claim 1, characterized in that: In step 2), the temperature is raised to 50-60° C. and stirred for 10-30 min.

8. The preparation method according to claim 1, characterized in that: In step 2), the molar ratio of the 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° C., 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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