Synthesis method of high-purity anhydrous rare earth fluoride

Abstract

The invention discloses a synthesis method of high-purity anhydrous rare earth fluoride. The invention provides a synthesis method of rare earth fluoride, which comprises the following steps: reacting RE (LIGAND) 3 with a fluorinating reagent in an organic solvent to generate REF3; wherein RE is a rare earth element; and the LEGAND is a beta-diketone ligand. According to the synthesis method provided by the invention, the problems of severe reaction conditions and impurity introduction caused by easy corrosion in a traditional dry method and the problems of high oxygen content and difficult filtration caused in a wet water-containing system are avoided, and the rare earth fluoride with high purity, no water, low oxygen content and high crystallinity can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of chemical synthesis of rare earth fluorides, and particularly relates to a method for synthesizing high-purity anhydrous rare earth fluorides. Background Art

[0002] Rare earth elements (RE) are a general term for 17 chemical elements, including lanthanide elements in group IIIB of the periodic table, and closely related scandium and yttrium. As an important strategic resource, rare earths have excellent optical, electrical, magnetic and other physical properties. Fluorine has the characteristics of high electronegativity and small atomic radius. When combined with other atoms, it can be closer to the nucleus and form stronger chemical bonds, which makes metal fluoride (REF3) have lower phonon frequency than oxides, better stability and optical properties than chlorides, bromides and iodides, and plays an important role in the field of materials science. For example, as an ideal optical material, it is widely used in optical materials such as laser crystals, high-power laser fibers, optical coatings, as well as cutting-edge technology fields such as national defense, military industry, aerospace, etc. Generally, the application of these fields has very strict requirements on the purity of rare earth fluoride raw materials, and the key sensitive impurities (Fe, Co, Ni, Cu, RE, etc.) and oxygen content are required to be lower than ppm and 100 ppm respectively. This is because the energy loss of REF3 optical materials mainly comes from transition metals, rare earth element impurities and OH. - Ions produce absorption at specific wavelengths, so removing impurities is one of the key issues in obtaining low-loss optical materials.

[0003] Traditional methods for preparing rare earth fluorides mainly include dry and wet processes. The dry method uses rare earth compounds and fluorine-containing gases / fluorine-containing compounds as raw materials, and prepares products through gas-solid / solid-solid fluorination reactions under high temperature conditions (600-700°C). Due to the strong corrosiveness of fluorine-containing gas (HF), various impurities are easily introduced. The wet method is to add fluorides (such as hydrofluoric acid, ammonium bifluoride, etc.) to the rare earth compound solution for precipitation, and then wash and dry to obtain rare earth fluoride. This method has the disadvantages of difficult filtration and high oxygen content. These methods not only increase costs and operational difficulties, but also impose a burden on the environment. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a novel method for preparing high-purity anhydrous rare earth fluorides in view of the defects of the prior art. The present invention provides a method for synthesizing high-purity anhydrous rare earth fluorides. The synthesis method provided by the present invention avoids the harsh reaction conditions and the problem of easy corrosion and introduction of impurities in the traditional dry method, as well as the problems of high oxygen content and difficulty in filtration caused by the wet method aqueous system, and can obtain high-purity, anhydrous, low oxygen content, and high crystallinity rare earth fluorides.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The present invention provides a method for synthesizing rare earth fluorides, which comprises the following steps: in an organic solvent, RE(LIGAND)3 reacts with a fluorination agent to generate REF3;

[0007] Among them, RE is a rare earth element;

[0008] LEGAND is a β-diketone ligand;

[0009] The β-diketone ligand is ;

[0010] Among them, R 1 and R 2 are independently C1-C6 alkyl, a Substituted C1-C6 alkyl, C6-C 10 Aryl, one or more R b Substituted C6-C 10 Aryl, "a 5-12 membered heteroaryl group having 1, 2 or 3 heteroatoms selected from N, O and S" or "a 5-12 membered heteroaryl group having 1, 2 or 3 heteroatoms ... c Substituted "5-12 membered heteroaryl group having 1, 2 or 3 heteroatoms selected from N, O and S";

[0011] R a , R b and R c are independently halogen, -CN, OH and NH3.

[0012] In some embodiments, the RE(LIGAND)3 is a complex as shown in Formula I:

[0013]

[0014] Among them, RE, R 1 and R 2 Independently described in any embodiment of the present invention.

[0015] In some embodiments, the fluorination agent may be hydrofluoric acid, an ammonium salt of hydrofluoric acid, or a hydrofluoric acid organic base complex, such as ammonium fluoride, ammonium bifluoride, hydrogen fluoride-pyridine complex (PPHF, Euler reagent), or hydrogen fluoride, preferably ammonium bifluoride.

[0016] In some embodiments, the purity of the fluorination reagent is 99.99%-100%, for example 99.99%.

[0017] In some embodiments, the organic solvent can be selected from one or more of alcohol solvents, amide solvents, nitrile solvents, ether solvents, ester solvents, aromatic hydrocarbons, halogenated aromatic hydrocarbon solvents, alkyl solvents and halogenated alkane solvents, preferably one or more of ethanol, toluene, chlorobenzene, ethyl acetate, chloroform, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, 1,2-dichloroethane, diethyl ether and acetonitrile, more preferably chlorobenzene.

[0018] In some embodiments, the reaction temperature is 120°C-140°C, preferably 129°C.

[0019] In some embodiments, the RE 3+ For La 3+ , Y 3+ 、Ce 3+ , Pr 3+ 、Nd 3+ , Gd 3+ 、Ho 3+ 、Tm 3+ 、Lu 3+ , Tb 3+ 、Eu 3+ , Er 3+ 、Sm 3+ 、Dy 3+ or Yb 3+ .

[0020] In some embodiments, the REF3 includes lanthanum fluoride (LaF3), yttrium fluoride (YF3), cerium fluoride (CeF3), praseodymium fluoride (PrF3), neodymium fluoride (NdF3), gadolinium fluoride (GdF3), holmium fluoride (HoF3), thulium fluoride (TmF3), lutetium fluoride (LuF3), terbium fluoride (TbF3), europium fluoride (EuF3), erbium fluoride (ErF3), samarium fluoride (SmF3), dysprosium fluoride (DyF3) or ytterbium fluoride (YbF3), preferably yttrium fluoride, lanthanum fluoride, terbium fluoride, dysprosium fluoride, ytterbium fluoride, gadolinium fluoride, thulium fluoride or europium fluoride.

[0021] In some embodiments, the RE(LIGAND)3 is purified anhydrous RE(LIGAND)3.

[0022] In some embodiments, the molar ratio of the RE(LIGAND)3 to the fluorination agent is 1:(1-5), preferably 1:1.5.

[0023] In some embodiments, the molar volume ratio of the RE(LIGAND)3 to the organic solvent is 1:(6-10) mmoL / mL, preferably 1:8 mmoL / mL.

[0024] In some embodiments, the reaction further comprises the following post-treatment step: after the reaction is completed, the reaction solution is washed, filtered and dried to obtain REF3.

[0025] The washing may be performed with conventional solvents in the art, preferably with halogenated alkane solvents, such as dichloromethane.

[0026] In some embodiments, the drying temperature is 200°C-500°C, for example, 240°C, 280°C, 290°C, 300°C, 320°C, 380°C or 390°C.

[0027] In some embodiments, the drying may be vacuum drying, normal pressure drying or inert gas drying, preferably vacuum drying.

[0028] In some embodiments, R 1 and R 2 are independently C1-C6 alkyl, a Substituted C1-C6 alkyl, C6-C 10 Aryl or "a 5- to 12-membered heteroaryl group wherein the heteroatom is selected from 1, 2 or 3 of N, O and S and the number of the heteroatoms is 1, 2 or 3".

[0029] In some embodiments, each of the C1-C6 alkyl groups is independently methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl, preferably methyl.

[0030] In some embodiments, each of the C6-C 10 Aryl is independently phenyl or naphthyl, preferably phenyl.

[0031] In some embodiments, in each of the 5-12 membered heteroaryl groups, the heteroatom is S, and / or the number of the heteroatom is 1.

[0032] In some embodiments, the halogen is F, Cl, Br or I.

[0033] In some embodiments, R 1 for ,methyl, or -CF3.

[0034] In some embodiments, R 2 for ,methyl, or -CF3.

[0035] In some embodiments, R 1 and R 2 same.

[0036] In some embodiments, R 1 and R2 Not the same.

[0037] In some embodiments, the β-diketone ligand is , , , , , or ; Preferred , or .

[0038] In some embodiments, the purity of REF3 is 99.991%-99.995%, such as 99.991%, 99.992%, 99.993% or 99.995%.

[0039] In some embodiments, the oxygen content of REF3 is 320-470 ppm, for example, 320 ppm, 330 ppm, 340 ppm, 360 ppm, 430 ppm, 450 ppm or 470 ppm.

[0040] In some embodiments, the RE(LIGAND)3 is anhydrous RE(LIGAND)3 obtained by recrystallization.

[0041] In some embodiments, the recrystallization comprises the following steps: mixing the raw material RE(LIGAND)3 with a solvent, crystallizing, and drying to obtain the RE(LIGAND)3.

[0042] In some embodiments, in the recrystallization, the raw material RE(LIGAND)3 is RE(LIGAND)3 containing crystal water.

[0043] In some embodiments, in the recrystallization, the solvent can be selected from one or more of amide solvents, urea solvents, ketone solvents, alcohol solvents and aromatic hydrocarbon solvents; preferably one or more of N,N dimethylformamide, N,N dimethylacetamide, tetramethyl urea, N-methylpyrrolidone, 1,3 dimethyl 2-imidazolidinone, ethylene glycol, 1,3-propylene glycol and toluene, more preferably toluene or N,N dimethylformamide.

[0044] In some embodiments, in the recrystallization, the mixing is followed by heating to dissolve.

[0045] In some embodiments, in the recrystallization, the crystallization is cooling crystallization, such as cooling to room temperature crystallization.

[0046] In some embodiments, in the recrystallization, the mass volume ratio of the raw material RE(LIGAND)3 to the solvent is (0.2-0.5) g / mL, preferably 0.2 g / mL.

[0047] In some embodiments, during the recrystallization, the temperature of the heating for dissolution is 100°C-120°C, preferably 110°C.

[0048] In some embodiments, during the recrystallization, the drying temperature is 150°C-300°C, such as 180°C, 200°C, 210°C, 230°C, 240°C or 270°C.

[0049] In some embodiments, the synthesis method of the rare earth fluoride further includes a preparation method of RE(LIGAND)3, which comprises the following steps: in an organic solvent, in the presence of a base, a β-diketone compound reacts with a rare earth inorganic salt to generate RE(LIGAND)3; the β-diketone compound is a compound as shown in Formula II:

[0050] ;

[0051] Among them, R 1 and R 2 As described in any scheme of the present invention.

[0052] In some embodiments, the β-diketone compound may be dibenzoylmethane, benzoyl acetone, thenoyl trifluoroacetone, trifluoroacetylacetone, hexafluoroacetylacetone, benzoyl trifluoroacetone or acetylacetone, preferably dibenzoylmethane, acetylacetone or thenoyl trifluoroacetone, more preferably dibenzoylmethane.

[0053] In some embodiments, the rare earth inorganic salt may be a nitrate of a rare earth element, a halide of a rare earth element, a carbonate of a rare earth element, or a hydrate thereof (referring to a nitrate of a rare earth element, a halide of a rare earth element, or a carbonate of a rare earth element), such as lanthanum nitrate, yttrium nitrate, terbium chloride, dysprosium nitrate, ytterbium carbonate, gadolinium nitrate, thulium nitrate, or europium nitrate, or a hydrate thereof (referring to lanthanum nitrate, yttrium nitrate, terbium chloride, dysprosium nitrate, ytterbium carbonate, gadolinium nitrate, thulium nitrate, and europium nitrate), preferably lanthanum nitrate hexahydrate, yttrium nitrate hexahydrate, terbium chloride hexahydrate, dysprosium nitrate hexahydrate, ytterbium carbonate hexahydrate, gadolinium nitrate hexahydrate, thulium nitrate hexahydrate, or europium nitrate hexahydrate.

[0054] In some embodiments, the base is an inorganic base, such as potassium hydroxide, sodium hydroxide or magnesium hydroxide, preferably potassium hydroxide.

[0055] In some embodiments, in the method for preparing RE(LIGAND)3, the organic solvent is an alcohol solvent, preferably ethanol.

[0056] In some embodiments, the molar ratio of the β-diketone compound to the base is 1:(0.5-5), preferably 1:1.

[0057] In some embodiments, the molar ratio of the β-diketone compound to the rare earth inorganic salt is (1-5):1, preferably 3:1.

[0058] In some embodiments, in the method for preparing RE(LIGAND)3, the molar volume ratio of the β-diketone compound to the organic solvent is (1-2) mmoL / mL, preferably 1.2 mmoL / mL.

[0059] In some embodiments, in the method for preparing RE(LIGAND)3, the reaction temperature is 70°C-90°C, preferably 80°C.

[0060] In some embodiments, in the method for preparing RE(LIGAND)3, the reaction comprises the following reaction steps: at 70°C-90°C, ethanol and β-diketone compounds are mixed, and then alkali and rare earth inorganic salts are added in sequence to react and generate RE(LIGAND)3.

[0061] In some embodiments, in the preparation method of RE(LIGAND)3, the reaction also includes post-reaction treatment, which includes the following reaction steps: after the reaction is completed, the reaction solution is filtered, dried, a halogenated alkane solvent is added, filtered, and dried to obtain a complex as shown in Formula II.

[0062] In some embodiments, the drying temperature may be 80°C-100°C, preferably 90°C.

[0063] In some embodiments, the halogenated alkane solvent is, for example, dichloromethane.

[0064] In some embodiments, the drying is performed by spin drying, for example, preferably spin drying using a rotary evaporator.

[0065] In some embodiments, the preparation method of RE(LIGAND)3 further comprises the recrystallization step described in any embodiment of the present invention.

[0066] In some embodiments, the recrystallization solvent is as described in any embodiment of the present invention.

[0067] The present invention also provides a method for preparing a rare earth complex, which comprises the following steps: in an organic solvent, in the presence of the base, reacting the β-diketone compound with the rare earth inorganic salt to generate the RE(LIGAND)3;

[0068] Wherein, the preparation conditions of RE(LIGAND)3 are as described in any scheme of the present invention.

[0069] The present invention also provides RE(LIGAND)3 as described in any scheme of the present invention, wherein the RE(LIGAND)3 is anhydrous and has a purity of 99.99%-100.00%, for example, 99.99%. Preferably, the RE(LIGAND)3 is prepared by the method as described in any scheme of the present invention.

[0070] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0071] The reagents and raw materials used in the present invention are commercially available.

[0072] The positive and progressive effects of the present invention are:

[0073] (1) The present invention synthesizes and prepares a high-purity anhydrous rare earth complex precursor in an organic system, and then fluorinates it in an organic system to prepare a high-purity anhydrous rare earth fluoride; thereby avoiding the harsh reaction conditions and the problem of easy corrosion and introduction of impurities in the traditional dry method, as well as the high oxygen content and difficulty in filtration caused by the wet method aqueous system;

[0074] (2) The preparation method of the present invention can obtain rare earth fluorides with high purity, anhydrous, low oxygen content and high crystallinity. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 This is the XRD characterization diagram of the high-purity lanthanum fluoride obtained in Example 1;

[0076] Figure 2 This is the XRD characterization diagram of the high-purity yttrium fluoride obtained in Example 2. DETAILED DESCRIPTION

[0077] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0078] Example 1: Preparation of lanthanum fluoride

[0079]

[0080] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (43.3 g) of lanthanum nitrate hexahydrate after complete dissolution; keep the temperature and continue heating and stirring for 5 hours, then filter, dry the solid product at 90°C, add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the by-product potassium nitrate). The filtrate is dried by rotary evaporator to obtain 78.3 g of diphenylpropanedione lanthanum hydrate (yield: 92.3%). The elemental analysis results are C64.1%, H4.45%, O15.2%. The rare earth complex containing crystal water is added to toluene (1g / 5mL), heated at 110°C until completely dissolved, and the heating is stopped after complete dissolution, and the mixture is gradually cooled to room temperature along with the heating system, and allowed to stand overnight to obtain yellow crystals, which are filtered and dried to obtain the product. The solid product after recrystallization is dried at high temperature in a vacuum at 210°C to remove the crystal water.

[0081] The high-purity rare earth complex 50 mmol (40.4 g) (purity ≥ 99.99%) obtained after drying was reacted with high-purity ammonium fluoride (purity ≥ 99.99%) 75 mmol (4.3 g) in chlorobenzene (400 mL) at 129°C. The reaction was completed, washed with dichloromethane and filtered, and dried at 280°C under vacuum to obtain 10.2 g of high-purity anhydrous lanthanum fluoride (yield: 96%) (XRD characterization results are shown in Figure 1 ), purity 99.992%, oxygen content 320 ppm.

[0082] Example 2: Preparation of yttrium fluoride

[0083] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (38.3 g) of yttrium nitrate hexahydrate after complete dissolution; continue heating and stirring for 5 hours and filter, dry the solid product at 90°C and add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the by-product potassium nitrate). The filtrate is dried by rotary evaporator to obtain 77.2 g of diphenylpropanedione yttrium hydrate (yield: 97.2%). The elemental analysis results are C68.2%, H4.69%, O16.12%. The rare earth complex containing crystal water is added to toluene (1g / 5mL), heated at 110°C until completely dissolved, and the heating is stopped after complete dissolution, and the mixture is gradually cooled to room temperature along with the heating system, and allowed to stand overnight to obtain yellow crystals, which are filtered and dried to obtain the product. The solid product after recrystallization is dried at high temperature in a vacuum at 230°C to remove the crystal water.

[0084] The high-purity rare earth complex 50 mmol (37.9 g) (purity ≥ 99.99%) obtained after drying was reacted with high-purity ammonium fluoride (purity ≥ 99.99%) 75 mmol (4.3 g) in chlorobenzene (400 mL) at 129°C. The reaction was completed, washed with dichloromethane and filtered, and dried at 380°C under vacuum to obtain 7.0 g of high-purity anhydrous yttrium fluoride (yield: 95.9%) (XRD characterization results are shown in Figure 2 ), purity 99.995%, oxygen content 360ppm.

[0085] Table 1 Impurity content in high-purity LaF3 and YF3 (“-” means the element is below the detection limit of 1.0 ppm)

[0086]

[0087] Example 3 Preparation of Terbium Fluoride

[0088] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (26.5 g) of terbium chloride hexahydrate after it is completely dissolved; continue heating and stirring for 5 hours and filter, dry the solid product at 90°C and add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the by-product potassium nitrate). The filtrate is dried by rotary evaporator to obtain 79.5 g of the product diphenylpropanedione terbium hydrate (yield: 92%). The rare earth complex containing crystal water is added to toluene (1 g / 5 mL), heated at 110°C until completely dissolved, and stopped heating after complete dissolution. The heating system is gradually cooled to room temperature, and it is left to stand overnight to obtain yellow crystals. The product can be obtained by filtering and drying. The solid product after recrystallization was dried under high temperature vacuum at 180°C to remove crystal water.

[0089] The high-purity rare earth complex 50 mmol (41.4 g) (purity ≥ 99.99%) obtained after drying was reacted with high-purity ammonium fluoride (purity ≥ 99.99%) 75 mmol (4.3 g) in chlorobenzene (400 mL) at 129°C. The reaction was complete, and the mixture was washed with dichloromethane and filtered. After drying at 290°C under vacuum conditions, 10.0 g (yield: 92.6%) of high-purity anhydrous terbium fluoride was obtained with a purity of 99.993% and an oxygen content of 430 ppm.

[0090] Example 4 Preparation of Dysprosium Fluoride

[0091] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (34.5 g) of dysprosium nitrate hexahydrate after complete dissolution; continue heating and stirring for 5 hours and filter, dry the solid product at 90°C and add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the by-product potassium nitrate). The filtrate is dried by rotary evaporator to obtain 81.3 g of diphenylpropanedione dysprosium hydrate (yield: 93.5%). The rare earth complex containing crystal water is added to toluene (1 g / 5 mL), heated at 110°C until completely dissolved, and stopped heating after complete dissolution. The mixture is gradually cooled to room temperature with the heating system, and left to stand overnight to obtain yellow crystals. The product can be obtained by filtering and drying. The solid product after recrystallization was dried under high temperature vacuum at 240°C to remove crystal water.

[0092] The high-purity rare earth complex 50 mmol (41.7 g) (purity ≥ 99.99%) obtained after drying was reacted with 75 mmol (4.3 g) of high-purity ammonium fluoride (purity ≥ 99.99%) in chlorobenzene (400 mL) at 129°C. The reaction was completed, and the mixture was washed with dichloromethane and filtered. After drying at 320°C under vacuum conditions, 10.4 g (yield: 94.8%) of high-purity anhydrous dysprosium fluoride was obtained with a purity of 99.991% and an oxygen content of 450 ppm.

[0093] Example 5 Preparation of Ytterbium Fluoride

[0094] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (59.8 g) of ytterbium carbonate hexahydrate after complete dissolution; continue heating and stirring for 5 hours and filter, dry the solid product at 90°C and add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the by-product potassium nitrate). The filtrate is dried by rotary evaporator to obtain 83.1 g of diphenylpropanedione ytterbium hydrate (yield: 94.5%). The rare earth complex containing crystal water is added to toluene (1 g / 5 mL), heated at 110°C until completely dissolved, and the heating is stopped after complete dissolution. The heating system is gradually cooled to room temperature, and it is allowed to stand overnight to obtain yellow crystals. The product can be obtained by filtering and drying. The solid product after recrystallization was dried under high temperature vacuum at 270°C to remove crystal water.

[0095] The high-purity rare earth complex 50mmol (42.2g) (purity ≥99.99%) obtained after drying was reacted with high-purity ammonium fluoride (purity ≥99.99%) 75mmol (4.3g) in chlorobenzene (400mL) at 129°C. The reaction was complete, and the mixture was washed with dichloromethane and filtered. After drying at 390°C under vacuum conditions, 11.2g (yield: 97%) of high-purity anhydrous ytterbium fluoride was obtained with a purity of 99.993% and an oxygen content of 330ppm.

[0096] Example 6 Preparation of Gadolinium Fluoride

[0097] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (45.1 g) of gadolinium nitrate hexahydrate after complete dissolution; continue heating and stirring for 5 hours and filter, dry the solid product at 90°C and add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the by-product potassium nitrate). The filtrate is dried by rotary evaporator to obtain 80.8 g of diphenylpropanedione gadolinium hydrate (yield: 93.7%). The rare earth complex containing crystal water is added to toluene (1 g / 5 mL), heated at 110°C until completely dissolved, and stopped heating after complete dissolution. The heating system is gradually cooled to room temperature, and left to stand overnight to obtain yellow crystals. The product can be obtained by filtering and drying. The solid product after recrystallization was dried under high temperature vacuum at 210°C to remove crystal water.

[0098] 50mmol (43.1g) of the dried rare earth complex salt (purity ≥99.99%) and 75mmol (4.3g) of high-purity ammonium fluoride (purity ≥99.99%) were reacted in chlorobenzene (400mL) at 129°C. The reaction was completed, washed with dichloromethane and filtered, and dried at 240°C under vacuum conditions to obtain 10.4g (yield: 97%) of high-purity anhydrous gadolinium fluoride with a purity of 99.991% and an oxygen content of 430ppm.

[0099] Example 7 Preparation of Thulium Fluoride

[0100] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (46.3 g) of thulium nitrate hexahydrate after complete dissolution; continue heating and stirring for 5 hours and filter, dry the solid product at 90°C and add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the by-product potassium nitrate). The filtrate is dried by rotary evaporator to obtain 82.3 g of the product diphenylpropanedione thulium hydrate (yield: 94.2%). The rare earth complex containing crystal water is added to toluene (1 g / 5 mL), heated at 110°C until completely dissolved, and the heating is stopped after complete dissolution. The heating system is gradually cooled to room temperature, and it is allowed to stand overnight to obtain yellow crystals. The product can be obtained by filtering and drying. The solid product after recrystallization was dried under high temperature vacuum at 180°C to remove crystal water.

[0101] 50mmol (43.7g) of the dried rare earth complex salt (purity ≥99.99%) and 75mmol (4.3g) of high-purity ammonium fluoride (purity ≥99.99%) were reacted in chlorobenzene (400mL) at 129°C. The reaction was completed, and the mixture was washed with dichloromethane and filtered. The mixture was dried at 390°C under vacuum to obtain 10.7g of high-purity anhydrous thulium fluoride (yield: 95%) with a purity of 99.992% and an oxygen content of 470ppm.

[0102] Example 8 Preparation of Europium Fluoride

[0103] In a 500 mL round-bottom flask, add 250 mL of ethanol and heat and stir to 80°C, then add 300 mmol (67.3 g) of dibenzoylmethane (DBM); add 300 mmol (16.8 g) of KOH under heating and stirring conditions to react, and add 100 mmol (44.6 g) of europium nitrate hexahydrate after complete dissolution; continue heating and stirring for 5 hours and filter, dry the solid product at 90°C and add it to dichloromethane, stir and dissolve, and filter to remove the residue (the residue is the byproduct potassium nitrate). The filtrate is dried by rotary evaporator to obtain 78 g of diphenylpropanedione europium hydrate (yield: 91%). The rare earth complex containing crystal water is added to toluene (1 g / 5 mL), heated at 110°C until completely dissolved, and stopped heating after complete dissolution. The heating system is gradually cooled to room temperature, and left to stand overnight to obtain yellow crystals. The product can be obtained by filtering and drying. The solid product after recrystallization was dried under high temperature vacuum at 200°C to remove crystal water.

[0104] The dried rare earth complex salt 50mmol (42.9g) (purity ≥99.99%) and high-purity ammonium fluoride (purity ≥99.99%) 75mmol (4.3g) were reacted in chlorobenzene (400mL) at 129°C. The reaction was completed, washed with dichloromethane and filtered, and dried at 300°C under vacuum conditions to obtain 10.1g (yield: 97%) of high-purity anhydrous europium fluoride with a purity of 99.995% and an oxygen content of 340ppm.

[0105] Example 9 Preparation of lanthanum fluoride

[0106] The specific operation was the same as that in Example 1, except that 300 mmol (67.3 g) of dibenzoylmethane (DBM) was replaced with 300 mmol (30.0 g) of acetylacetone (Hacac), and the recrystallization solvent was changed to N,N-dimethylformamide. The yield of lanthanum fluoride obtained was 94% (44.4 g).

[0107] Example 10 Preparation of lanthanum fluoride

[0108] The specific operation was the same as that in Example 1, except that 300 mmol (67.3 g) of dibenzoylmethane (DBM) was replaced with 300 mmol (66.7 g) of thenoyltrifluoroacetone (TTFA), and the recrystallization solvent was changed to N,N-dimethylformamide. The yield of lanthanum fluoride obtained was 95% (79.6 g).

[0109] Comparative Example 1

[0110] The specific operation is the same as that in Example 1, except that the recrystallization step is not performed, and the purity of the obtained product is lower than 99.91%, which cannot meet the requirements of the crystal raw material.

[0111] Comparative Example 2

[0112] The specific operation is the same as that in Example 1, except that the complex is not heated to remove crystal water after drying, and the oxygen content of the obtained product is 4000 ppm, which cannot meet the requirements of the crystal raw material.

Claims

1. A method for synthesizing rare earth fluorides, characterized in that: The method comprises the following steps: in an organic solvent, RE(LIGAND)3 reacts with a fluorination agent to generate REF3; Among them, RE is a rare earth element; LEGAND is a β-diketone ligand; The β-diketone ligand is ; Among them, R 1 and R 2 are independently C1-C6 alkyl, a Substituted C1-C6 alkyl, C6-C 10 Aryl, one or more R b Substituted C6-C 10 Aryl, "a 5-12 membered heteroaryl group having 1, 2 or 3 heteroatoms selected from N, O and S" or "a 5-12 membered heteroaryl group having 1, 2 or 3 heteroatoms ... c Substituted "5-12 membered heteroaryl group having 1, 2 or 3 heteroatoms selected from N, O and S"; R a , R b and R c are independently halogen.

2. The synthesis method according to claim 1, characterized in that It meets one or more of the following conditions: (1) The RE(LIGAND)3 is a complex as shown in Formula I: Among them, RE, R 1 and R 2 Independently as claimed in claim 1; (2)RE 3+ is La 3+ , Y 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Gd 3+ , Ho 3+ , Tm 3+ , Lu 3+ , Tb 3+ , Eu 3+ , Er 3+ , Sm 3+ , Dy 3+ or Yb 3+ .

3. The synthesis method according to claim 2, characterized in that It meets one or more of the following conditions: (1) The fluorination agent is hydrofluoric acid, an ammonium salt of hydrofluoric acid or a hydrofluoric acid organic base complex, such as ammonium fluoride, ammonium bifluoride, hydrogen fluoride-pyridine complex or hydrogen fluoride, preferably ammonium bifluoride; (2) The purity of the fluorination agent is 99.99%-100%, for example 99.99%; (3) The organic solvent is selected from one or more of alcohol solvents, amide solvents, nitrile solvents, ether solvents, ester solvents, aromatic hydrocarbons, halogenated aromatic hydrocarbon solvents, alkyl solvents and halogenated alkane solvents, preferably one or more of ethanol, toluene, chlorobenzene, ethyl acetate, chloroform, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, 1,2-dichloroethane, diethyl ether and acetonitrile, more preferably chlorobenzene; (4) The reaction temperature is 120°C-140°C, preferably 129°C; (5) the RE(LIGAND)3 is anhydrous; (6) The REF3 comprises lanthanum fluoride, yttrium fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, gadolinium fluoride, holmium fluoride, thulium fluoride, lutetium fluoride, terbium fluoride, europium fluoride, erbium fluoride, samarium fluoride, dysprosium fluoride or ytterbium fluoride, preferably yttrium fluoride, lanthanum fluoride, terbium fluoride, dysprosium fluoride, ytterbium fluoride, gadolinium fluoride, thulium fluoride or europium fluoride; (7) The purity of REF3 is 99.991%-99.995%, for example, 99.991%, 99.992%, 99.993% or 99.995%; (8) The oxygen content of REF3 is 320-470 ppm, for example, 320 ppm, 330 ppm, 340 ppm, 360 ppm, 430 ppm, 450 ppm or 470 ppm; (9) The molar ratio of the RE(LIGAND)3 to the fluorination agent is 1:(1-5), preferably 1:1.5; (10) The molar volume ratio of the RE(LIGAND)3 to the organic solvent is 1:(6-10) mmoL / mL, preferably 1:8 mmoL / mL; (11) The reaction further comprises the following post-treatment step: after the reaction is completed, the reaction solution is washed, filtered and dried to obtain REF3; preferably, the washing solvent is a halogenated alkane solvent, such as dichloromethane; more preferably, the drying temperature is 200°C-500°C, such as 240°C, 280°C, 290°C, 300°C, 320°C, 380°C or 390°C; the drying is, for example, vacuum drying, normal pressure drying or inert gas drying, and another example is vacuum drying.

4. The synthesis method according to claim 2, characterized in that It meets one or more of the following conditions: (1) R 1 and R 2 are independently C1-C6 alkyl, a Substituted C1-C6 alkyl, C6-C 10 Aryl or "a 5-12 membered heteroaryl group having 1, 2 or 3 heteroatoms selected from N, O and S"; (2) Each of the C1-C6 alkyl groups is independently methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl, preferably methyl; (3) Each of the C6-C 10 Aryl is independently phenyl or naphthyl, preferably phenyl; (4) In each of the “5-12 membered heteroaryl”, the heteroatom is S, and / or the number of the heteroatom is 1; (5) The halogen is F, Cl, Br or I.

5. The synthesis method according to claim 2, characterized in that It meets one or more of the following conditions: (1) R 1 for ,methyl, or -CF3; (2) R 2 for ,methyl, or -CF3; (3) R 1 and R 2 same; (4) R 1 and R 2 Not the same; (5) β-diketone ligands are , , , , , or ; Preferred , or .

6. The synthesis method according to claim 2, characterized in that The RE(LIGAND)3 is anhydrous RE(LIGAND)3 obtained by recrystallization; Preferably, the recrystallization comprises the following steps: mixing the raw material RE(LIGAND)3 with a solvent, crystallizing, and drying to obtain the RE(LIGAND)3; Wherein, the raw material RE(LIGAND)3 is preferably RE(LIGAND)3 containing crystal water; More preferably, the recrystallization satisfies one or more of the following conditions: (1) The solvent is selected from one or more of amide solvents, urea solvents, ketone solvents, alcohol solvents and aromatic hydrocarbon solvents; preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, ethylene glycol, 1,3-propylene glycol and toluene, more preferably toluene or N,N-dimethylformamide; (2) heating and dissolving after mixing; the temperature of heating and dissolving is preferably 100°C-120°C, more preferably 110°C; (3) The crystallization is cooling crystallization, for example, cooling to room temperature crystallization; (4) The mass volume ratio of the raw material RE(LIGAND)3 to the solvent is (0.2-0.5) g / mL, preferably 0.2 g / mL; (5) The drying temperature is 150°C-300°C, for example, 180°C, 200°C, 210°C, 230°C, 240°C or 270°C.

7. The synthesis method according to claim 1, characterized in that The synthetic method of the rare earth fluoride also includes a preparation method of RE(LIGAND)3, which comprises the following steps: in an organic solvent, in the presence of a base, a β-diketone compound reacts with a rare earth inorganic salt to generate RE(LIGAND)3; the β-diketone compound is a compound as shown in Formula II: ； Among them, R 1 and R 2 As claimed in claim 1; Preferably, the preparation method of RE(LIGAND)3 satisfies one or more of the following conditions: (1) The β-diketone compound is dibenzoylmethane, benzoyl acetone, thenoyl trifluoroacetone, trifluoroacetylacetone, hexafluoroacetylacetone, benzoyl trifluoroacetone or acetylacetone, preferably dibenzoylmethane, acetylacetone or thenoyl trifluoroacetone, more preferably dibenzoylmethane; (2) The rare earth inorganic salt is a nitrate of a rare earth element, a halide of a rare earth element, a carbonate of a rare earth element or a hydrate thereof, such as lanthanum nitrate, yttrium nitrate, terbium chloride, dysprosium nitrate, ytterbium carbonate, gadolinium nitrate, thulium nitrate or europium nitrate or a hydrate thereof, preferably lanthanum nitrate hexahydrate, yttrium nitrate hexahydrate, terbium chloride hexahydrate, dysprosium nitrate hexahydrate, ytterbium carbonate hexahydrate, gadolinium nitrate hexahydrate, thulium nitrate hexahydrate or europium nitrate hexahydrate; (3) The base is an inorganic base, such as potassium hydroxide, sodium hydroxide or magnesium hydroxide, preferably potassium hydroxide; (4) The organic solvent is an alcohol solvent, preferably ethanol; (5) The molar ratio of the β-diketone compound to the base is 1:(0.5-5), preferably 1:1; (6) The molar ratio of the β-diketone compound to the rare earth inorganic salt is (1-5):1, preferably 3:1; (7) The molar volume ratio of the β-diketone compound to the organic solvent is (1-2) mmoL / mL, preferably 1.2 mmoL / mL; (8) The reaction temperature is 70°C-90°C, preferably 80°C; (9) The reaction comprises the following steps: mixing ethanol and a β-diketone compound at 70°C-90°C, and then adding a base and a rare earth inorganic salt to react and generate RE(LIGAND)3.

8. The synthesis method according to claim 7, characterized in that The preparation method of RE(LIGAND)3 further comprises the following post-treatment steps: after the reaction is completed, the reaction solution is filtered, dried, a halogenated alkane solvent is added, filtered, and dried to obtain a complex as shown in Formula II; Preferably, the preparation method of RE(LIGAND)3 further comprises recrystallization as claimed in claim 6; Preferably, the post-processing step satisfies one or more of the following conditions: (1) In the post-treatment, the drying temperature is 80°C-100°C, preferably 90°C; (2) In the post-treatment, the halogenated alkane solvent is dichloromethane; (3) In the post-treatment, the drying is performed by spin drying, preferably by using a rotary evaporator.

9. A method for preparing a rare earth complex, characterized in that: The method comprises the following steps: in an organic solvent, in the presence of a base, a β-diketone compound reacts with a rare earth inorganic salt to generate RE (LIGAND) 3; Wherein, the preparation conditions of RE(LIGAND)3 are as described in claim 7 or 8.

10. A RE(LIGAND)3 as claimed in any one of claims 1 to 9, characterized in that: The RE(LIGAND)3 is anhydrous and has a purity of 99.99%-100.00%, such as 99.99%; preferably, the RE(LIGAND)3 is prepared by the method according to any one of claims 7-9.

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