A method for preparing bismuth trifluoride

Abstract

The present application relates to a kind of preparation method of bismuth trifluoride, belong to bismuth compound preparation technical field.The preparation method of bismuth trifluoride of the present application includes the following steps: bismuth-containing compound powder is hydrothermally reacted with hydrofluoric acid;The bismuth-containing compound is one or any combination of bismuth oxide, bismuth oxychloride, bismuth trichloride.The preparation method of bismuth trifluoride of the present application carries out hydrothermal reaction to bismuth oxide, bismuth oxychloride, bismuth trichloride and hydrofluoric acid, and the high temperature and high pressure generated by hydrothermal reaction are used to improve the reactivity, solve the problem that bismuth oxide, bismuth oxychloride and bismuth trichloride are not completely reacted with hydrofluoric acid under normal pressure, resulting in low yield and low purity, product can be obtained by one-step reaction.The preparation method of bismuth trifluoride of the present application is simple, and route is short, the solvent used is water, cost is low, yield is high, and it is economic and environmental protection.

Description

Technical Field

[0001] This invention relates to a method for preparing bismuth trifluoride, belonging to the field of bismuth compound preparation technology. Background Technology

[0002] Bismuth trifluoride is a white crystalline powder and a novel photocatalytic material. It has attracted much attention not only in the field of lithium-ion battery cathode materials but is also an important organofluorine reagent.

[0003] Currently, the main methods for synthesizing bismuth trifluoride are the gas-phase method and the liquid-phase method. The gas-phase method generally involves reacting fluorine gas with metallic bismuth powder. For example, Chinese invention patent CN111186856B discloses a method for preparing bismuth trifluoride by reacting fluorine gas with bismuth trichloride powder. The gas-phase process produces high-purity products, but the cost of fluorine gas is high. Traditional liquid-phase methods for preparing bismuth trifluoride often use fluorinating agents such as hydrofluoric acid to react with bismuth salt solutions such as bismuth nitrate and bismuth chloride. Compared to the gas-phase method, the raw material cost is lower, but the use of bismuth nitrate produces a large amount of nitric acid-containing wastewater that needs to be treated, increasing production costs. When using bismuth chloride, solid bismuth chloride and hydrofluoric acid cannot react directly under conventional reaction conditions. It is necessary to dissolve bismuth chloride in an alkaline solution to first convert it into bismuth oxychloride, then into bismuth oxide. The bismuth oxide then reacts with nitric acid to convert it into a bismuth salt solution, which then reacts with fluorinating agents such as hydrofluoric acid. This process is complex and involves many steps. In addition, bismuth trifluoride is prepared using a liquid-phase method with bismuth oxide as the bismuth source. For example, Chinese invention patent application CN115259219A discloses a method for preparing bismuth trifluoride. This method involves reacting bismuth oxide with hydrochloric acid to obtain a bismuth chloride solution, then reacting it with ammonia to prepare bismuth hydroxide, and finally fluorinating it with electronic-grade hydrofluoric acid to obtain the product. This method of preparing bismuth trifluoride generally requires multiple conversion steps, resulting in numerous steps and the generation of a large amount of wastewater containing ammonium chloride that needs to be treated, increasing the production cost of the product. Summary of the Invention

[0004] The purpose of this invention is to provide a simple and low-cost method for preparing bismuth trifluoride.

[0005] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0006] A method for preparing bismuth trifluoride includes the following steps: subjecting a bismuth-containing compound powder to a hydrothermal reaction with hydrofluoric acid; wherein the bismuth-containing compound is one or any combination of bismuth trioxide, bismuth oxychloride, and bismuth trichloride.

[0007] The method for preparing bismuth trifluoride of the present invention involves a hydrothermal reaction of bismuth-containing compounds such as bismuth trioxide, bismuth oxychloride, and bismuth trichloride with hydrofluoric acid. The high temperature and pressure generated by the hydrothermal reaction enhance the reactivity, thus solving the problem of low yield and low purity caused by incomplete reactions of bismuth trioxide, bismuth oxychloride, and bismuth trichloride with hydrofluoric acid under normal pressure. The product can be obtained in a single step. The method for preparing bismuth trifluoride of the present invention is simple, has a short route, uses water as the solvent, is low in cost, has a high yield, and is economical and environmentally friendly.

[0008] The chemical reactions that occur in the preparation method of bismuth trifluoride of the present invention are as follows:

[0009] Bi₂O₃ + 6HF = 2BiF₃ + 3H₂O

[0010] BiClO + 3HF = BiF3 + H2O + HCl

[0011] BiCl3 + 3HF = BiF3 + 3HCl

[0012] To increase the contact area between the bismuth-containing compound powder and hydrofluoric acid, the D50 particle size of the bismuth-containing compound powder is further defined as 50–150 nm. The particle size of the bismuth-containing solid can be reduced by grinding to increase surface energy, and pure-phase bismuth trifluoride crystals can be obtained after high-temperature, high-pressure fluorination with hydrofluoric acid.

[0013] Understandably, hydrofluoric acid is an aqueous solution of hydrogen fluoride gas, providing the solvent for the hydrothermal reaction. To further accelerate the reaction rate, the concentration of the hydrofluoric acid is further 20-50%.

[0014] Furthermore, the hydrothermal reaction temperature is 100–200°C, and the hydrothermal reaction time is 8–24 hours. The hydrothermal reaction is carried out in a hydrothermal synthesis reactor, the inner lining of which is made of polytetrafluoroethylene.

[0015] Further, the molar ratio of bismuth element in the bismuth-containing compound powder to hydrogen fluoride in hydrofluoric acid is 1:3.0 to 3.5. Further, when the bismuth-containing compound is bismuth trioxide, the molar ratio of the bismuth-containing compound to hydrogen fluoride in hydrofluoric acid is 1:6.0 to 6.5.

[0016] Furthermore, the rate of heating to the hydrothermal reaction temperature is 2–5 °C / min.

[0017] Furthermore, the method for preparing bismuth trifluoride further includes the following steps: after the hydrothermal reaction, cooling and solid-liquid separation are performed, followed by washing and drying of the solid obtained from the solid-liquid separation. Further, the cooling rate is 2–5 °C / min. When the bismuth-containing compound includes bismuth oxychloride and / or bismuth chloride powder, the liquid obtained from the solid-liquid separation is hydrochloric acid, which can be used to prepare anhydrous calcium chloride. The number of water washes is ≥3 times, and the volume of water used to obtain the solid corresponding to each 50g of fluorine-containing compound raw material is 40–60 mL. Attached Figure Description

[0018] Figure 1 The XRD pattern of bismuth trifluoride prepared in Example 1 of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0020] Example 1

[0021] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0022] 50g of bismuth trioxide powder with a D50 particle size of 50nm and 64.38g of 20% hydrofluoric acid were added to a 200mL hydrothermal reactor. The reactor was placed in a muffle furnace and heated to 100℃ at a rate of 2℃ / min, and the reaction was maintained at this temperature for 24h. The temperature was then lowered to room temperature at a rate of 2℃ / min. After filtration, the product was washed with water (3 times, 57mL of water each time) and dried to obtain 55.94g of pure bismuth trifluoride, with a yield of 98.1% and a purity of 99.91%. XRD analysis was performed, and the results are as follows: Figure 1 As shown.

[0023] Example 2

[0024] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0025] 50g of bismuth trioxide powder with a D50 particle size of 100nm and 46.5g of hydrofluoric acid with a mass fraction of 30% were added to a 200mL hydrothermal reactor. The hydrothermal reactor was placed in a muffle furnace and heated to 150℃ at a rate of 3℃ / min. The temperature was maintained for 12h, and then cooled to room temperature at a rate of 3℃ / min. After filtration, the product was washed with water (3 times, 57mL of water each time) and dried to obtain 56.51g of pure bismuth trifluoride, with a yield of 99% and a purity of 99.90%.

[0026] Example 3

[0027] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0028] 50g of bismuth trioxide powder with a D50 particle size of 150nm and 26.61g of hydrofluoric acid with a mass fraction of 50% were added to a 200mL hydrothermal reactor. The reactor was placed in a muffle furnace and heated to 200℃ at a rate of 5℃ / min, and the reaction was maintained at this temperature for 8h. Then, the temperature was lowered to room temperature at a rate of 5℃ / min. After filtration, the product was washed with water (3 times, 57mL of water each time) and dried to obtain 56.23g of pure bismuth trifluoride, with a yield of 98.5% and a purity of 99.89%.

[0029] Example 4

[0030] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0031] 50g of bismuth oxychloride powder with a D50 particle size of 50nm and 57.6g of hydrofluoric acid with a mass fraction of 20% were added to a 200mL hydrothermal reactor. The hydrothermal reactor was placed in a muffle furnace and heated to 100℃ at a rate of 2℃ / min. The temperature was maintained for 24h, and then cooled to room temperature at a rate of 2℃ / min. After filtration, the product was washed with water (3 times, 51mL of water each time) and dried to obtain 50.04g of pure bismuth trifluoride, with a yield of 98.0% and a purity of 99.85%.

[0032] Example 5

[0033] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0034] 50g of bismuth oxychloride powder with a D50 particle size of 100nm and 30.71g of hydrofluoric acid with a mass fraction of 40% were added to a 200mL hydrothermal reactor. The hydrothermal reactor was placed in a muffle furnace and heated to 150℃ at a rate of 3℃ / min. The temperature was maintained for 12h, and then cooled to room temperature at a rate of 3℃ / min. After filtration, the product was washed with water (3 times, 51mL of water each time) and dried to obtain 50.14g of pure bismuth trifluoride, with a yield of 98.2% and a purity of 99.87%.

[0035] Example 6

[0036] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0037] 50g of bismuth oxychloride powder with a D50 particle size of 150nm and 44.79g of hydrofluoric acid with a mass fraction of 30% were added to a 200mL hydrothermal reactor. The reactor was placed in a muffle furnace and heated to 200℃ at a rate of 5℃ / min, and the reaction was maintained at this temperature for 8h. Then, the temperature was lowered to room temperature at a rate of 5℃ / min. After filtration, the product was washed with water (3 times, 51mL of water each time) and dried to obtain 50.6g of pure bismuth trifluoride, with a yield of 99.1% and a purity of 99.89%.

[0038] Example 7

[0039] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0040] 50g of bismuth chloride powder with a D50 particle size of 50nm and 31.7g of hydrofluoric acid with a mass fraction of 30% were added to a 200mL hydrothermal reactor. The reactor was placed in a muffle furnace and heated to 100℃ at a rate of 5℃ / min, and the reaction was maintained at this temperature for 24h. Then, the temperature was lowered to room temperature at a rate of 5℃ / min. After filtration, the product was washed with water (3 times, 42mL of water each time) and dried to obtain 41.57g of pure bismuth trifluoride, with a yield of 98.6% and a purity of 99.88%.

[0041] Example 8

[0042] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0043] 50g of bismuth chloride powder with a D50 particle size of 100nm and 22.19g of hydrofluoric acid with a mass fraction of 50% were added to a 200mL hydrothermal reactor. The reactor was placed in a muffle furnace and heated to 150℃ at a rate of 3℃ / min, and the reaction was maintained at this temperature for 12h. Then, the temperature was lowered to room temperature at a rate of 3℃ / min. After filtration, the product was washed with water (3 times, 42mL of water each time) and dried to obtain 41.65g of pure bismuth trifluoride, with a yield of 98.8% and a purity of 99.86%.

[0044] Example 9

[0045] The method for preparing bismuth trifluoride in this embodiment includes the following steps:

[0046] 50g of bismuth chloride powder with a D50 particle size of 150nm and 50.7g of hydrofluoric acid with a mass fraction of 20% were added to a 200mL hydrothermal reactor. The reactor was placed in a muffle furnace and heated to 200℃ at a rate of 2℃ / min, and the reaction was maintained at this temperature for 8h. Then, the temperature was lowered to room temperature at a rate of 2℃ / min. After filtration, the product was washed with water (3 times, 42mL of water each time) and dried to obtain 41.31g of pure bismuth trifluoride, with a yield of 98.0% and a purity of 99.92%.

[0047] Comparative Example 1

[0048] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0049] 50g of bismuth trioxide powder with a D50 particle size of 50nm and 64.38g of hydrofluoric acid with a mass fraction of 20% were added to a PFA flask. The PFA flask was placed in a water bath and heated to 40℃ at a rate of 2℃ / min. The temperature was maintained for 24h, and then cooled to room temperature at a rate of 2℃ / min. After filtration, the product was washed with water (3 times, 57mL of water each time) and dried to obtain 34.25g of bismuth trifluoride product, with a yield of 60% and a purity of 91.1%.

[0050] Comparative Example 2

[0051] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0052] 50g of bismuth trioxide powder with a D50 particle size of 100nm and 46.5g of hydrofluoric acid with a mass fraction of 30% were added to a PFA flask. The PFA flask was placed in a water bath and heated to 50℃ at a rate of 3℃ / min. The temperature was maintained for 12h, and then cooled to room temperature at a rate of 3℃ / min. After filtration, the product was washed with water (3 times, 57mL of water each time) and dried to obtain 28.54g of bismuth trifluoride product, with a yield of 50% and a purity of 90.2%.

[0053] Comparative Example 3

[0054] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0055] 50g of bismuth trioxide powder with a D50 particle size of 150nm and 26.61g of 50% hydrofluoric acid were added to a PFA flask. The PFA flask was placed in a water bath and heated to 60℃ at a rate of 5℃ / min. The temperature was maintained for 8h, and then cooled to room temperature at a rate of 5℃ / min. After filtration, the product was washed with water (3 times, 57mL of water each time) and dried to obtain 25.69g of bismuth trifluoride product, with a yield of 45% and a purity of 89.3%.

[0056] Comparative Example 4

[0057] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0058] 50g of bismuth oxychloride powder with a D50 particle size of 50nm and 57.6g of 20% hydrofluoric acid were added to a PFA flask. The PFA flask was placed in a water bath and heated to 40℃ at a rate of 2℃ / min. The temperature was maintained for 24h, and then cooled to room temperature at a rate of 2℃ / min. After filtration, the product was washed with water (3 times, 51mL of water each time) and dried to obtain 29.36g of pure bismuth trifluoride, with a yield of 57.5% and a purity of 91.5%.

[0059] Comparative Example 5

[0060] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0061] 50g of bismuth oxychloride powder with a D50 particle size of 100nm and 30.71g of hydrofluoric acid with a mass fraction of 40% were added to a PFA flask. The PFA flask was placed in a water bath and heated to 50℃ at a rate of 3℃ / min. The temperature was maintained for 12h, and then cooled to room temperature at a rate of 3℃ / min. After filtration, the sample was washed with water (3 times, 51mL of water each time) and dried to obtain 26.70g of pure bismuth trifluoride, with a yield of 52.3% and a purity of 89.87%.

[0062] Comparative Example 6

[0063] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0064] 50g of bismuth oxychloride powder with a D50 particle size of 150nm and 44.79g of 30% hydrofluoric acid were added to a PFA flask. The PFA flask was placed in a water bath and heated to 60℃ at a rate of 5℃ / min. The temperature was maintained for 8h, and then cooled to room temperature at a rate of 5℃ / min. After filtration, the product was washed with water (3 times, 51mL of water each time) and dried to obtain 28.13g of pure bismuth trifluoride, with a yield of 55.1% and a purity of 89.89%.

[0065] Comparative Example 7

[0066] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0067] 50g of bismuth chloride powder with a D50 particle size of 50nm and 31.7g of hydrofluoric acid with a mass fraction of 30% were added to a PFA flask. The PFA flask was placed in a water bath and heated to 40℃ at a rate of 5℃ / min. The temperature was maintained for 24h, and then cooled to room temperature at a rate of 5℃ / min. No solid product was obtained.

[0068] Comparative Example 8

[0069] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0070] 50g of bismuth chloride powder with a D50 particle size of 100nm and 22.19g of hydrofluoric acid with a mass fraction of 50% were added to a PFA flask. The PFA flask was placed in a water bath and heated to 50℃ at a rate of 3℃ / min. The temperature was maintained for 12h, and then cooled to room temperature at a rate of 3℃ / min. No solid product was obtained.

[0071] Comparative Example 9

[0072] The preparation method of bismuth trifluoride in this comparative example includes the following steps:

[0073] 50g of bismuth chloride powder with a D50 particle size of 150nm and 50.7g of hydrofluoric acid with a mass fraction of 20% were added to a PFA flask. The PFA flask was placed in a water bath and heated to 60℃ at a rate of 2℃ / min. The temperature was maintained for 8h, and then cooled to room temperature at a rate of 2℃ / min. No solid product was obtained.

Claims

1. A method for preparing bismuth trifluoride, characterized in that: Includes the following steps: The bismuth-containing compound powder is subjected to a hydrothermal reaction with hydrofluoric acid at 100-200°C for 8-24 hours; the bismuth-containing compound is one or any combination of bismuth trioxide, bismuth oxychloride, and bismuth trichloride, and the molar ratio of bismuth element in the bismuth-containing compound powder to hydrogen fluoride in the hydrofluoric acid is 1:3.0-3.

5.

2. The method for preparing bismuth trifluoride according to claim 1, characterized in that: The particle size of the bismuth-containing compound powder is 50~150 nm.

3. The method for preparing bismuth trifluoride according to claim 1, characterized in that: The concentration of the hydrofluoric acid is 20-50%.

4. The method for preparing bismuth trifluoride according to claim 1, characterized in that: When the bismuth-containing compound is bismuth trioxide, the molar ratio of the bismuth-containing compound to hydrogen fluoride in hydrofluoric acid is 1:6.0~6.

5.

5. The method for preparing bismuth trifluoride according to claim 2, characterized in that: When the bismuth-containing compound is bismuth trioxide, the molar ratio of the bismuth-containing compound to hydrogen fluoride in hydrofluoric acid is 1:6.0~6.

5.

6. The method for preparing bismuth trifluoride according to claim 3, characterized in that: When the bismuth-containing compound is bismuth trioxide, the molar ratio of the bismuth-containing compound to hydrogen fluoride in hydrofluoric acid is 1:6.0~6.

5.

7. The method for preparing bismuth trifluoride according to any one of claims 1 to 3, characterized in that: The rate of heating to the hydrothermal reaction temperature is 2~5℃ / min.

8. The method for preparing bismuth trifluoride according to any one of claims 1 to 3, characterized in that: It also includes the following steps: After the hydrothermal reaction is completed, the temperature is lowered and the solid and liquid are separated. The solid obtained from the solid-liquid separation is then washed with water and dried.

9. The method for preparing bismuth trifluoride according to claim 8, characterized in that: The cooling rate is 2~5℃ / min.

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