Fluorides, processes for their preparation and use

Abstract

The application provides a fluoride and a preparation method and application thereof. The preparation method of the fluoride comprises the following steps: 1) preparing a precursor oxide; and 2) performing fluorination treatment on the precursor oxide in the step 1) to obtain the fluoride. The fluoride prepared by the application can be used in the synthesis of solid ion conductors, high-temperature coatings and catalysts and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of fluoride and its preparation method and use, especially it relates to the synthesis for solid ion conductor, high temperature coating and catalyst etc. BACKGROUND

[0002] The preparation method of fluoride includes common coprecipitation method, hydrothermal / solvothermal method, high-temperature solvothermal decomposition method, etc. in addition to mechanical mixing-high temperature synthesis method.

[0003] Coprecipitation method is an early synthesis method, and the general preparation steps are: under certain atmosphere conditions at high temperature, after mixing several liquid raw materials, a certain amount of precipitant is added to carry out chemical reaction, and after separation, washing and other processes, the precipitate is separated to obtain the required solid powder. When synthesizing nanocrystals using coprecipitation method, a suitable reagent needs to be added, which reacts with rare earth ions. On the one hand, it will affect the nucleation and growth of crystal grains, thereby realizing the size control of particles, and also improve the hydrophilic or hydrophobic degree of particles. Although this method can synthesize a large amount of materials, the temperature, ion concentration and pH value during the experiment need to be accurately controlled, and the addition of precipitant may cause local concentration to be too high, resulting in agglomeration or uneven composition. In addition, there are certain requirements for raw materials, and the hydrolysis conditions or precipitation conditions of each component should be the same or similar.

[0004] The preparation process of hydrothermal / solvothermal method: usually carried out in a high-pressure reaction kettle, which can provide high reaction pressure and sealed environment, using water / organic solvent as solvent, the raw materials are dissolved and then crystallized, and then treated by separation, washing and drying to obtain the material. The reaction conditions of hydrothermal / solvothermal method are mild: low reaction temperature; simple experimental operation; but the product will be affected by factors such as temperature, reaction time, pH value, etc. and needs to customize special reaction instruments, and the reaction process cannot be observed. The two processes are similar, and the main difference lies in the difference of reaction medium.

[0005] High-temperature solvothermal decomposition method is often used for rare earth fluoride nanomaterials. Organic or inorganic substances are usually dissolved in organic solvents, and nanomaterials are synthesized at high temperature under inert atmosphere. This method is suitable for synthesizing materials with relatively small particle size, uniform morphology and good dispersion. Water-sensitive nanofluoride is similar to the principle of hydrothermal method. However, the reaction conditions are harsh, the reaction process needs to be protected in anhydrous and oxygen-free inert atmosphere; the precursor is expensive and toxic; and the post-treatment is complex.

[0006] Up to now, the synthetic fluorides are mainly prepared by mechanical ball milling, co-precipitation, hydrothermal / solvothermal method, high-temperature solvothermal decomposition method and the like, but there are still the following problems: (1) poor uniformity of the constituent elements, which may cause poor performance and the like; (2) high cost of raw materials, toxicity or belonging to hazardous chemicals; (3) high energy cost (for example, high-energy ball milling, high temperature and high pressure and the like) is involved; (4) high-risk reagents such as hydrogen fluoride and ammonium fluoride need to be added in the reaction process; (5) some reaction conditions are harsh. SUMMARY

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] A preparation method of a fluoride, the preparation method specifically comprises:

[0009] 1) preparing a precursor oxide;

[0010] 2) performing fluorination treatment on the precursor oxide in step 1) to obtain the fluoride.

[0011] According to an embodiment of the present application, in step 1), the molecular formula of the precursor oxide is A n+1 B n O 3n+1 , wherein A is a first element, B is a metal element, and n is greater than or equal to 1, for example, n is equal to 2, or n is greater than or equal to 10 or greater than or equal to 100, for example, 1000, 10000.

[0012] According to an exemplary scheme of the present application, when n is greater than or equal to 100, the molecular formula of the precursor oxide is ABO3.

[0013] According to an embodiment of the present application, the first element A is selected from at least one of La, Pr, Nd, Gd, Sm and Sr. Exemplarily, the first element A is selected from La and Sr.

[0014] According to an embodiment of the present application, the metal element B is selected from at least one, two or three or more of Ni, Fe, Mn, Co, Cr, Al, Zn and Cu. Exemplarily, the metal element B is selected from Ni and Fe.

[0015] According to an embodiment of the present application, the molecular formula of the precursor oxide is, for example, La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4.

[0016] According to an embodiment of the present application, in step 1), the preparation method of the precursor oxide is a sol-gel method.

[0017] According to an embodiment of the present application, the sol-gel method specifically comprises the following method:

[0018] (A1) dissolving a salt of A and a metal salt in deionized water to obtain a mixed solution;

[0019] (A2) adding a complexing agent to the mixed solution of step (A1), stirring uniformly, then adding ammonia water to adjust the pH value to 7-9, and then heating in a water bath and drying to form a gel;

[0020] (A3) grinding and calcining the gel of step (A2) to obtain a precursor oxide.

[0021] According to an embodiment of the present application, in step (A1), the salt of A is selected from a nitrate of A or a chloride of A. Preferably, the first element A in the salt of A is selected from at least one of La, Pr, Nd, Gd, Sm, and Sr. Exemplarily, the salt of A is selected from at least one of La(NO3)3, Sr(NO3)2, SrCl2, and LaCl3.

[0022] According to an embodiment of the present application, in step (A1), the metal salt is selected from at least one of a nitrate of a metal, a chloride of a metal, and an acetate of a metal. Preferably, the metal element in the metal salt is selected from at least one, two, or three or more of Sr, Ni, Fe, Mn, Co, Cr, Al, Zn, and Cu. Further preferably, the metal element in the metal salt is selected from Ni and Fe.

[0023] Exemplarily, the metal salt is selected from one, two, or three or more of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, Mn(NO3)2·4H2O, Co(NO3)2·6H2O, Cr(NO3)2·9H2O, Cu(NO3)2, Al(NO3)3, Zn(NO3)2·6H2O, NiCl2, FeCl3, MnCl2, CoCl2, CrCl3·6H2O, CuCl2, AlCl3, ZnCl2, Fe(OH)(CH3COO)2, Co(CH3COO)2, Ni(CH3COO)2, and the like.

[0024] According to an embodiment of the present application, in step (A1), the molar ratio of the first element in the salt of A to the metal element in the metal salt is (n+1):n, n is greater than or equal to 1, for example, n is equal to 2, or n is greater than or equal to 10 or greater than or equal to 100, for example, 1000, 10000. Preferably, the molar ratio of the first element in the salt of A to the metal element in the metal salt is, for example, 2:1.

[0025] According to an embodiment of the present application, in step (A2), the molar ratio of the complexing agent to the sum of the first element in the salt of A and the metal element in the metal salt is 1:1-5, preferably 1:2.5.

[0026] According to an embodiment of the present application, in step (A2), the complexing agent is selected from one, two or more of glycine, glucose, hexamethylenetetramine, citric acid, ethylenediaminetetraacetic acid, oxalic acid and hexamethylene diisocyanate.

[0027] According to an embodiment of the present application, in step (A2), the water bath heating condition comprises: heating at a temperature not higher than 100°C for 1-10 hours under a sealed condition, for example, heating at 80°C for 5 hours.

[0028] According to an embodiment of the present application, in step (A2), the drying is performed at a temperature of 100-200°C for 10-20 hours, for example, at 180°C for 12 hours.

[0029] According to an embodiment of the present application, in step (A3), the calcination specifically comprises: low-temperature calcination, grinding and high-temperature calcination.

[0030] According to an embodiment of the present application, the low-temperature calcination is performed at a temperature of 200-400°C for 1-10 hours, for example, at 350°C for 5 hours.

[0031] According to an embodiment of the present application, the high-temperature calcination is performed at a temperature of 600-1100°C for 2-5 hours.

[0032] According to an embodiment of the present application, in step (A3), the grinding can be performed by a method known in the art, which is not specifically limited in the present application.

[0033] According to an embodiment of the present application, in step 2), the fluorination treatment specifically comprises:

[0034] (B1) mixing the precursor oxide with a fluorination agent to obtain a mixture;

[0035] (B2) subjecting the mixture of step (B1) to multi-stage calcination to obtain the fluoride.

[0036] According to an embodiment of the present application, in step (B1), the molar ratio of the fluorination agent to the precursor oxide is 1-5:1, for example, 3:1.

[0037] According to an embodiment of the present application, in step (B2), the fluorinating agent is at least one selected from the group consisting of hydrogen fluoride, carbon tetrafluoride, fluorine gas, boron trifluoride, tetrafluoroethylene, hexafluoroethane, hexafluoropropylene, octafluoropropane, perfluorobutene, octafluorocyclobutane, perfluorobutane, tetrafluorobutane, hexafluoroethane, nitrogen trifluoride, tetrafluoro-hydrazine, phosphorus trifluoride, phosphorus pentafluoride, arsenic trifluoride, arsenic pentafluoride, dioxygen difluoride, sulfur tetrafluoride, chlorine pentafluoride, chlorine trifluoride, bromine trifluoride, bromine pentafluoride, iodine pentafluoride, sulfur hexafluoride, methyl fluoride, difluorotetrafluoroethane, trifluorotetrafluoroethane, fluoroethylene, ethyl fluoride, 1,1-difluoroethylene, 1,1-difluoroethane, trifluoroethane, trichlorofluoromethane, difluorodichlorotetrafluoroethane, chlorotrifluoromethane, difluorotetrachloroethane, chlorotrifluoroethylene, trifluorotrichloroethane, 1,2-dichlorotetrafluoroethane, pentafluorochloroethane, difluorodibromomethane, trifluorobromomethane, bromotrifluoroethylene, 1,2-dibromotetrafluoroethane, hydroxyl fluoride, hexafluoroacetone, monofluorosilane, difluorosilane, trifluorosilane, sulfonyl fluoride, chloroperoxyfluoride, dichlorofluoromethane, chlorodifluoromethane, chlorodifluoroethylene, 1,1-difluoro-1-chloroethane, difluoro-chloro-monobromomethane, polyvinylidene fluoride, polytetrafluoroethylene.

[0038] According to an embodiment of the present application, in step (B2), the activation temperature is 300-600°C; the reaction time is 3-24h, for example 10h, 12h, 15h, 20h.

[0039] According to an embodiment of the present application, in step (B2), the multi-stage calcination includes: a first calcination, a second calcination. Preferably, before the first calcination and / or the second calcination, grinding is optionally performed.

[0040] According to an embodiment of the present application, the first calcination is performed at 200-400°C for 10-20h, for example at 300°C for 14h.

[0041] According to an embodiment of the present application, the second calcination is performed at 400-450°C for 3-14h.

[0042] The present application also provides a fluoride obtained by the above preparation method.

[0043] According to an embodiment of the present application, the fluoride is obtained by fluorination treatment of a precursor oxide.

[0044] According to an embodiment of the present application, the fluoride refers to the number of O elements in the precursor oxide being replaced is at least greater than 0, for example 1, 2, 3 or 4; when n=1, for example the number of O elements being replaced is at least greater than 0, for example 1 or 3, 4.

[0045] According to an embodiment of the present application, the molecular formula of the precursor oxide is An+1 B n O 3n+1 wherein A is a first element, B is a metal element, and n is greater than or equal to 1, for example n is equal to 2, or n is greater than or equal to 10 or greater than or equal to 100, for example 1000, 10000.

[0046] According to an exemplary aspect of the present application, when n is greater than or equal to 100, the molecular formula of the precursor oxide is ABO3.

[0047] According to an embodiment of the present application, the first element A is selected from at least one of La, Pr, Nd, Gd, Sm, Sr.

[0048] According to an embodiment of the present application, the metal element B is selected from at least one, two or three or more of Ni, Fe, Mn, Co, Cr, Al, Zn, Cu.

[0049] According to an embodiment of the present application, the molecular formula of the precursor oxide is, for example, La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4.

[0050] The present application also provides the use of the above-mentioned fluoride, for example, for the synthesis of solid ionic conductors, high-temperature coatings and catalysts.

[0051] Advantages

[0052] The present application provides a brand new method for preparing fluoride, the prepared fluoride can be doped by adjusting other elements, the preparation method of the present application involves few high-energy synthesis steps, and the process is easy to control, the synthesis temperature is low, the constituent elements are more uniform, and the problems such as poor performance caused by uneven composition are avoided. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is the XRD pattern of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4and fluoride prepared in Example 1;

[0054] Figure 2a is the mapping pattern of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4prepared in Example 1;

[0055] Figure 2b is the mapping pattern of fluoride prepared in Example 1;

[0056] Figure 3 is an impedance spectrum of the fluoride prepared in Example 1;

[0057] Figure 4 is an XRD pattern of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4 and the fluoride after fluorination with different amounts of PVDF;

[0058] Figure 5 is an XRD pattern of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3 and the fluoride after fluorination thereof. DETAILED DESCRIPTION

[0059] The technical solutions of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustratively used to explain and describe the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0060] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0061] Example 1

[0062] (1) Preparation of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4 precursor oxide

[0063] First step: weigh 1.9501 g of La(NO3)3, 0.8467 g of Sr(NO3)2, 0.8725 g of Ni(NO3)2·6H2O, and 0.8081 g of Fe(NO3)3·9H2O, and add them to 150 mL of water. Stir to dissolve at room temperature to obtain solution I;

[0064] Second step: while stirring solution I, add 4.3840 g of ethylenediaminetetraacetic acid and 4.3234 g of citric acid to it. After stirring uniformly, add ammonia water dropwise to adjust the pH value to 7-9 to obtain solution II;

[0065] Third step: seal solution II and place it in a water bath at 80°C for stirring for 5 h;

[0066] Fourth step: take out solution II from the third step, do not seal it, and transfer it to an oven in a fume hood. Dry it at 180°C overnight to form a gel;

[0067] Fifth step: The gel was taken out and ground in a mortar and pestle and calcined in a muffle furnace at 350°C for 5h to obtain precursor III.

[0068] Sixth step: Precursor III was taken out, ground again, and then calcined in a muffle furnace at 600-1100°C for 2-5h to obtain La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4perovskite precursor oxide.

[0069] (2) Fluorination of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4to produce fluoride:

[0070] First step: 0.2000g of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4and 0.1089g of PVDF (molecular weight 64, calculated as monomer CH2CF2) were weighed and mixed and ground to obtain precursor mixture IV.

[0071] Second step: Precursor mixture IV was placed in a muffle furnace and calcined at 300°C for 14h to obtain precursor V.

[0072] Third step: Precursor V was taken out and ground and placed in a muffle furnace and calcined at 400-450°C for 3-14h to obtain fluorinated fluoride.

[0073] As Figure 1 is the XRD pattern of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4and fluorinated fluoride prepared in Example 1, it can be seen that La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4has been completely fluorinated. As Fig. 2 is the EDX pattern of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4before and after fluorination prepared in Example 1, it can be seen that the La, Sr, Ni, Fe elements in the fluoride are more evenly distributed, and the F element is completely in it and is evenly distributed. From Figure 3 it can be seen that the conductivity of the fluoride is calculated to be 3.76 x 10- 5 Scm -1 .

[0074] Example 2

[0075] fluorinated La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4:

[0076] Step 1 : Take four portions of 0.2000 g of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4 prepared in Example 1 and mix grind with 0.0197 g, 0.0377 g, 0.0734 g, 0.1089 g, 0.1447 g of PVDF (molecular weight of 64) respectively to obtain precursor I.

[0077] Step 2: Put the precursor I in a muffle furnace and calcine at 300 °C for 14 h to obtain precursor II.

[0078] Step 3: Take out and grind the precursor II and put it in a muffle furnace and calcine at 450 °C for 3 h to obtain fluorides of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4 with different degrees of fluorination as shown in Table 1.

[0079] Table 1 Fluorides of Example 2

[0080] PVDF / g Theoretical fluorination degree 0.0197g F substitution of 0.5 O 0.0377g F substitution of 1 O 0.0734g F substitution of 2 O 0.1089g F substitution of 3 O 0.1447g F substitution of all 4 O

[0081] As Figure 4 La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4 prepared in Example 2 and fluorides obtained after fluorination with different amounts of PVDF.

[0082] Example 3

[0083] fluorinated La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4:

[0084] Step 1 : Take four portions of 0.2000 g of La 1.2 Sr 0.8 Ni 0.6 Fe 0.4O4, and mixed and ground with 0.015 g, 0.035 g, 0.075 g, 0.15 g PTFE (molecular weight 64) respectively to obtain precursor I;

[0085] Second step: the precursor I was placed in a muffle furnace and calcined at 300°C for 14 h to obtain precursor II.

[0086] Third step: the precursor II was taken out and ground, and placed in a muffle furnace and calcined at 450°C for 3 h to obtain La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4, as shown in Table 2.

[0087] Table 2 Fluorides of Example 3

[0088] PTFE / g Theoretical fluorination degree 0.015g F substitution of 0.5 O 0.035g F substitution of 1.25 O 0.075g F substitution of 2.7 O 0.15g F substitution of all 4 O

[0089] Example 4

[0090] (1) La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3 precursor oxide preparation

[0091] First step: 0.9754 g La(NO3)3, 0.4236 g Sr(NO3)2, 0.2903 g Co(NO3)2·6H2O and 1.6151 g Fe(NO3)3·9H2O were weighed into 100 mL water, and dissolved by stirring at room temperature to obtain solution I;

[0092] Second step: 2.9236 g ethylenediaminetetraacetic acid and 2.8828 g citric acid were added to solution I under stirring, and after stirring uniformly, ammonia water was added dropwise to adjust the pH value to 7-9 to obtain solution II;

[0093] Third step: solution II was sealed and placed in a water bath at 80°C and stirred for 5 h;

[0094] Fourth step: solution II of the third step was taken out, not sealed, and transferred to an oven in a fume hood and dried at 180°C overnight to form a gel;

[0095] Fifth step: the gel was taken out, ground in a mortar, and calcined in a muffle furnace at 350°C for 5 h to obtain precursor III.

[0096] Sixth step: the precursor III was taken out, ground again, and then calcined in a muffle furnace at 600-1100°C for 2-5 h to obtain La 0.6 Sr0.4 Co 0.2 Fe 0.8 O3 of perovskite type precursor oxide.

[0097] (2) Fluorination treatment of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3 to prepare fluoride:

[0098] First step: weigh 0.0991g La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4, 0.0862g PVDF (molecular weight is 64), mix and grind to obtain precursor mixture IV.

[0099] Second step: put the precursor mixture IV into a muffle furnace, calcine at 300°C for 14h to obtain precursor V.

[0100] Third step: take out and grind the precursor V, put it into a muffle furnace, calcine at 400-450°C for 3-14h to obtain fluorinated fluoride.

[0101] As Figure 5 La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3 prepared in Example 4 and its fluorinated fluoride, thus it can be known that La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3 has been completely fluorinated.

[0102] In the present application, complete fluorination refers to that the number of O elements in the precursor oxide which are replaced is at least 3n+1; when n=1, for example, the number of O elements which are replaced is at least 4.

[0103] The above has described the exemplary embodiments of the present application. However, the protection scope of the present application is not limited to the above-mentioned embodiments. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for the production of fluorides, characterized in that, The preparation method specifically comprises the following steps: 1) preparing a precursor oxide; the molecular formula of the precursor oxide is La 1.2 Sr 0.8 Ni 0.6 Fe 0.4 O4 or La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3; The preparation method of the precursor oxide is a sol-gel method; the sol-gel method specifically comprises the following method: (A1) dissolving a salt of A and a metal salt in deionized water to obtain a mixed solution; A is La and Sr; the metal in the metal salt is selected from Ni and Fe, or Co and Fe; (A2) adding a complexing agent to the mixed solution of step (A1), stirring uniformly, then adding ammonia water to adjust the pH value to 7-9, and then performing water bath heating and drying to form a gel; (A3) grinding and calcining the gel of step (A2) to obtain the precursor oxide; 2) performing fluorination treatment on the precursor oxide in step 1), and the fluorination treatment specifically comprises the following steps: (B1) mixing the precursor oxide with a fluorination agent to obtain a mixture; the molar ratio of the fluorination agent to the precursor oxide is 1-5:1; the fluorination agent is selected from at least one of polyvinylidene fluoride and polytetrafluoroethylene; (B2) performing multi-stage calcination on the mixture of step (B1) to obtain the fluoride.

2. The production method according to claim 1, characterized by, In step (A1), the salt of A is selected from a nitrate of A or a chloride of A.

3. The preparation method according to claim 1, characterized in that, In step (A1), the metal salt is selected from at least one of a nitrate of the metal, a chloride of the metal, and an acetate of the metal.

4. The production method according to claim 1, characterized by, In step (A2), the molar ratio of the complexing agent to the sum of the first element in the salt of A and the metal element in the metal salt is 1:1-5. In step (A2), the complexing agent is selected from one of glycine, glucose, hexamethylenetetramine, citric acid, ethylenediaminetetraacetic acid, oxalic acid, and hexamethylene diisocyanate.

5. The preparation method according to claim 1, characterized in that, In step (A2), the water bath heating conditions include: heating at not higher than 100℃ for 1-10 hours under a sealed condition. In step (A2), the drying refers to drying at 100-200℃ for 10-20 hours.

6. The method of claim 1, wherein, In step (A3), the calcination specifically comprises low-temperature calcination, grinding, and high-temperature calcination.

7. The production method according to claim 6, characterized by, The low-temperature calcination refers to calcination at 200-400℃ for 1-10 hours. The high-temperature calcination conditions include: the temperature of the high-temperature calcination is 600-1100℃; and the time of the high-temperature calcination is 2-5 hours.

8. The method of claim 1, wherein, In step (B2), the multi-stage calcination includes first calcination and second calcination; and grinding is further performed before the first calcination and / or the second calcination.

9. The production method according to claim 8, characterized by, The first calcination conditions include: calcination at 200-400℃ for 10-20 hours; The second calcination conditions include: calcination at 400-450℃ for 3-14 hours.

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