A method for preparing transition metal fluorides under high temperature and high pressure

Abstract

This invention relates to a high-temperature, high-pressure preparation method for transition metal fluorides, belonging to the technical field of high-temperature, high-pressure synthesis methods. A transition metal oxide and ammonium hydrogen fluoride are mixed in a molar ratio of 1:5, encapsulated in a silver tube, and then placed in a high-temperature, high-pressure apparatus. The mixture is pressurized to 120–200 MPa, heated to 200–450°C, and held at that temperature and pressure for 2 hours. After the reaction is complete, the mixture is naturally cooled to room temperature. The reaction product is then filtered, washed, and dried to obtain the transition metal fluoride. This invention utilizes inexpensive and readily available raw materials, a simple synthesis process, a short reaction cycle, low energy consumption, and is environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the technical field of high-temperature and high-pressure synthesis methods, specifically relating to a method for directly preparing transition metal fluorides using transition metal oxides and ammonium hydrogen fluoride as raw materials. Background Technology

[0002] The unique structure and composition of transition metal fluorides endow them with distinctive optical, electrical, magnetic, and catalytic properties, making them widely used in solar converters, solid potassium-ion battery electrode materials, magnetic materials, capacitor materials, and catalysts.

[0003] There are many methods for synthesizing transition metal fluorides. Traditional methods involve toxic raw materials and organic additives, or have high requirements for reaction vessels, complex reaction steps, and inevitably produce waste that pollutes the environment. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a method for preparing transition metal fluorides under high temperature and high pressure. The specific technical solution is as follows:

[0005] A high-temperature and high-pressure preparation method for transition metal fluorides involves using transition metal oxides and ammonium bifluoride as raw materials, followed by mixing, high-temperature and high-pressure synthesis, annealing, and depressurization. The operation steps are as follows: the transition metal oxides and ammonium bifluoride are mixed in a molar ratio of 1:5, sealed in a silver tube, and then placed in a high-temperature and high-pressure reactor. The pressure is increased to 120-200 MPa, and the temperature is raised to 200-450℃ and maintained at the pressure for 4 hours. After the reaction is completed, the reactor is cooled to room temperature. The reaction product is filtered and washed 2-3 times with deionized water, and then dried in an oven at 60℃ to obtain the transition metal fluoride.

[0006] Preferably, the reaction pressure in the high-temperature and high-pressure reactor is 175 MPa and the reaction temperature is 300 °C.

[0007] Preferably, the transition metal fluoride is KMnF3 and the transition metal oxide is potassium permanganate.

[0008] Beneficial effects:

[0009] This invention provides a method for synthesizing transition metal fluorides using high temperature and high pressure. The raw materials used in the preparation method are inexpensive and readily available, the synthesis process is novel, the reaction cycle is short, the energy consumption is low, and it is environmentally friendly. Attached Figure Description

[0010] Figure 1 This is an X-ray diffraction pattern of the material in Example 1.

[0011] Figure 2 This is an X-ray diffraction pattern of the material in Example 2.

[0012] Figure 3 This is an X-ray diffraction pattern of the material in Example 3.

[0013] Figure 4 This is an X-ray diffraction pattern of the material in Example 4.

[0014] Figure 5 This is an X-ray diffraction pattern of the material in Example 5. Detailed Implementation

[0015] Example 1

[0016] Potassium permanganate (Alpha Co., Ltd., CAS: 7722-64-7; purity 99.5%) and ammonium bifluoride (Aladdin Co., Ltd., CAS: 1341-49-7; purity 98%) were weighed at a molar ratio of 1:5. The weighed powder was placed in an agate mortar with a diameter of 50 mm and mixed for 10 min. The mixed precursor was placed in a LECO high-temperature and high-pressure hydrothermal reactor (HR-1B-2 type) and reacted at 120 MPa and 200℃ for 4 h. After the reaction, the reactor was cooled to room temperature, and the reaction product was filtered, washed 2-3 times with deionized water, and then dried in an oven at 60℃ to obtain the KMnF3 sample. The XRD results of the material are shown in [Figure number missing]. Figure 1 .

[0017] Example 2

[0018] Repeat Example 1 to prepare the precursor. The mixed precursor was then placed in an environment of 175 MPa and 300 °C for 4 hours. KMnF3 material was obtained. The XRD results of the material are shown below. Figure 2 .

[0019] Example 3

[0020] The precursor was prepared in the same manner as in Example 1, and the mixed precursor was placed in an environment of 200 MPa and 450℃ for 4 hours. High-purity KMnF3 material was obtained. The XRD results of the material are shown below. Figure 3 .

[0021] Example 4

[0022] The precursor was prepared in the same manner as in Example 1, but the reaction time was changed. The mixed precursor was then placed in an environment of 120 MPa and 200 °C for 2 h. KMnF3 material was obtained. The XRD results of the material are shown below. Figure 4 .

[0023] Example 5

[0024] The precursor was prepared in the same manner as in Example 1, but the reaction temperature was changed. The mixed precursor was placed in an environment of 100 MPa and 150 °C for 4 h. KMnF3 material was obtained. The XRD results of the material are shown below. Figure 5 .

[0025] The above content demonstrates the preparation of transition metal fluorides using a high-temperature, high-pressure method. Examples 1, 2, and 3 show that the minimum reaction temperature and shortest reaction time for preparing this sample are 200°C and 4 hours, respectively. Example 4 describes the reaction at 200°C for 2 hours. Figure 4 It can be seen that the sample purity is insufficient, and the X-ray diffraction pattern contains many impurity peaks. Figure 5 The X-ray diffraction pattern is obtained after reacting at 150℃ for 4 hours, which shows that the crystallinity of the sample is insufficient.

Claims

1. A high-temperature and high-pressure preparation method for transition metal fluorides, comprising using transition metal oxides and ammonium bifluoride as raw materials, and a process of mixing, high-temperature and high-pressure synthesis, annealing, and depressurization; the operation steps are as follows: the transition metal oxides and ammonium bifluoride are mixed in a molar ratio of 1:5, sealed in a silver tube, and then placed in a high-temperature and high-pressure reactor and pressurized to 120-200 MPa, heated to 200-450 ℃ and held at the temperature and pressure for 4 h. After the reaction is completed, the reactor is cooled to room temperature, the reaction product is filtered and washed 2-3 times with deionized water, and then dried in an oven at 60 ℃ to obtain the transition metal fluoride; wherein the transition metal fluoride is KMnF3, and the transition metal oxide is potassium permanganate.

2. The high-temperature and high-pressure preparation method for transition metal fluorides according to claim 1, characterized in that, The reaction pressure in the high-temperature and high-pressure reactor is 175 MPa, and the reaction temperature is 300 ℃.

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