A preparation and purification system and method for rare earth fluoride

Abstract

The present invention provides a preparation and purification system and method for rare earth fluorides, which includes a reaction unit, a dehydration and deoxygenation unit, and a first distillation tower connected in sequence, wherein the reactant solid phase outlet of the reaction unit is connected to the first feed port of the dehydration and deoxygenation unit; the dehydration and deoxygenation unit is provided with a product outlet and a hydrogen fluoride outlet, and the hydrogen fluoride outlet is connected to the feed port of the first distillation tower; the top gas phase outlet of the first distillation tower is connected to the second feed port of the dehydration and deoxygenation unit, and the bottom outlet of the first distillation tower is connected to a feed port of the reaction unit; the first distillation tower is used to separate hydrogen fluoride and water from the gas exiting the hydrogen fluoride outlet of the dehydration and deoxygenation unit, and the obtained gas phase mixture is refluxed to the dehydration and deoxygenation unit through the top gas phase outlet of the first distillation tower, and the obtained liquid phase mixture is refluxed to the reaction unit through the bottom outlet of the first distillation tower. The method of the present invention has the advantages of higher deoxygenation degree and high resource utilization.

Description

Technical Field

[0001] The present invention particularly relates to a system and method for preparing and purifying rare earth fluorides. Background Art

[0002] Low-oxygen, high-purity rare earth fluorides can be used to manufacture laser crystals with high luminescence efficiency and low phonon noise. There are 17 rare earth elements, including the lanthanides—lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), as well as two closely related elements to the lanthanides: yttrium (Y) and scandium (Sc). Rare earth elements can be combined with fluorine to form binary and ternary rare earth fluorides, such as the binary rare earth fluorides EuF3, ErF3, and SmF3, and the ternary rare earth fluorides NaYF4, NaNdF4, and NaDyF4.

[0003] There are two common methods for preparing anhydrous rare earth fluorides: dry and wet processes. The dry process typically involves directly fluorinating rare earth oxides in high-temperature hydrogen fluoride gas, or mixing rare earth oxides with solid ammonium bifluoride and then heating them for fluorination. The wet process typically involves adding hydrofluoric acid or a fluoride salt to a rare earth solution to produce a fluoride precipitate, which is then dried and vacuum-dehydrated to produce anhydrous fluorides.

[0004] Wet processes are generally simple to operate, but the oxygen content of the product is relatively high, typically not less than 3000 ppm. Patent CN1059320A discloses a method for preparing anhydrous niobium pentafluoride or tantalum pentafluoride, which involves contacting the raw materials with an excess of anhydrous hydrogen fluoride for a sufficient period of time. The contact is carried out in the presence of an effective amount of a dehydrating agent that reacts with the generated water. The dehydrating agent can be selected from phosgene, thionyl chloride, or sulfuryl chloride. The patent does not disclose specific data on the oxygen content of the product.

[0005] The products produced by the dry and wet processes currently available in the existing technology usually do not have a deep enough deoxidation depth, which limits the output power of the laser crystal. In addition, in order to achieve deep deoxidation, the existing technology generally uses an excessive amount of fluorinating agent, or a fluorinating agent combined with an excessive amount of dehydrating agent. This strategy does not fully consider the resource utilization and environmental protection issues brought about by the excessive use of toxic and harmful fluorinating agents and dehydrating agents. This problem is particularly prominent in large-scale production.

[0006] Therefore, there is an urgent need for a process for preparing rare earth fluorides that has a deep deoxidation depth, high resource utilization of fluorinating agents, and is green and environmentally friendly. Summary of the Invention

[0007] To overcome technical deficiencies in the prior art of rare earth fluoride preparation and purification, such as insufficient deoxygenation depth, the inability to repeatedly recycle fluorinating agents, and environmental hazards, the present invention provides a system and method for preparing and purifying rare earth fluorides. The method has the advantages of higher deoxygenation levels, high resource utilization, and environmental safety.

[0008] The present invention solves the above technical problems through the following technical solutions.

[0009] A system for preparing and purifying rare earth fluorides comprises a reaction device, a dehydration and deoxygenation device and a first distillation tower connected in sequence.

[0010] The reactant solid phase outlet of the reaction device is connected to the first feed inlet of the dehydration and deoxygenation device; the dehydration and deoxygenation device is provided with a product outlet and a hydrogen fluoride outlet, and the hydrogen fluoride outlet is connected to the feed inlet of the first distillation tower; the top gas phase outlet of the first distillation tower is connected to the second feed inlet of the dehydration and deoxygenation device, and the bottom outlet of the first distillation tower is connected to a feed inlet of the reaction device;

[0011] The reaction device is used for the rare earth compound containing oxygen element to undergo fluorination reaction with hydrofluoric acid;

[0012] The dehydration and deoxygenation device is used to react the solid product of the fluorination reaction with anhydrous hydrogen fluoride;

[0013] The first distillation tower is used to separate hydrogen fluoride and water in the material coming out of the hydrogen fluoride outlet of the dehydration and deoxygenation device, and reflux the obtained gaseous mixture into the dehydration and deoxygenation device through the gaseous phase outlet at the top of the first distillation tower, and reflux the obtained liquid phase mixture into the reaction device through the bottom outlet of the first distillation tower.

[0014] In the present invention, preferably, the rare earth fluoride preparation and purification system further comprises a first top condenser, and the top gas phase outlet of the first distillation tower is connected to the first top condenser and the dehydration and deoxygenation device in sequence.

[0015] In the present invention, preferably, the rare earth fluoride preparation and purification system further comprises a second distillation system connected to the reaction device, wherein the second distillation system comprises a second distillation tower, or two or more second distillation towers connected in series;

[0016] The feed port of the first second distillation tower is connected to the non-solid phase outlet of the reaction device, and the bottom liquid phase outlet of the last second distillation tower is connected to another feed port of the reaction device. The second distillation tower is used to separate hydrogen fluoride and water in the material flowing out of the non-solid phase outlet of the reaction device, and the obtained azeotropic hydrofluoric acid flows out from the bottom liquid phase outlet of the second distillation tower and refluxes to the reaction device through another feed port of the reaction device.

[0017] The second distillation system preferably further includes a second top condenser, which is connected to the top gas phase outlet of the second distillation tower, and is used to condense water coming out of the top gas phase outlet of the second distillation tower.

[0018] The number of plates of the second distillation tower is preferably 6-20, for example 14.

[0019] Wherein, the second distillation tower is preferably a plate tower.

[0020] The feed inlet of the second distillation tower is preferably located at the 3rd to 10th tray, for example, the 6th tray.

[0021] In a preferred embodiment of the present invention, the rare earth fluoride preparation and purification system includes a second distillation system connected to the reaction device, the second distillation system includes a second distillation tower and a second top condenser; the feed port of the second distillation tower is connected to the non-solid phase outlet of the reaction device, and the bottom liquid phase outlet of the second distillation system is connected to another feed port of the reaction device.

[0022] In another preferred embodiment of the present invention, the rare earth fluoride preparation and purification system includes a second distillation system connected to the reaction device, the second distillation system includes two second distillation towers connected in series, and two second top condensers respectively connected to the two second distillation towers; the feed port of the first second distillation tower is connected to the non-solid phase outlet of the reaction device, and the bottom liquid phase outlet of the second second distillation system is connected to another feed port of the reaction device.

[0023] In the present invention, preferably, the preparation and purification system of rare earth fluorides also includes a dehydration device, and the top gas phase outlet of the first distillation tower, the dehydration device and the second feed port of the dehydration and deoxygenation device are connected in sequence; the dehydration device is used to further remove water from the gas phase mixture discharged from the top gas phase outlet of the first distillation tower, and reflux the material obtained after the water removal to the dehydration and deoxygenation device.

[0024] The dewatering device is preferably an electrolysis device for electrolyzing water in the gaseous mixture exiting the gaseous discharge port at the top of the first distillation tower. Preferably, the gaseous discharge port at the top of the first distillation tower, the first overhead condenser, and the dewatering device are sequentially connected. The gaseous mixture exiting the gaseous discharge port at the top of the first distillation tower is condensed into a liquid by the first overhead condenser and then enters the electrolysis device for water removal.

[0025] In the present invention, preferably, the number of plates of the first distillation tower is 3-8, for example, 5.

[0026] In the present invention, preferably, the first distillation tower is a plate tower.

[0027] In the present invention, preferably, the feed inlet of the first distillation tower is located at the 2nd to 4th tray, for example, at the 2nd tray.

[0028] In the present invention, the reaction device can be a conventional reaction device in the art, such as a batch or continuous solid-liquid reactor;

[0029] In the present invention, preferably, the structure type of the reaction device is a tank reactor, and the tank reactor preferably comprises a stirring device.

[0030] In the present invention, the dehydration and deoxygenation device can be a conventional dehydration and deoxygenation device in the art, such as a batch or continuous solid-liquid reactor.

[0031] In the present invention, preferably, the structure type of the dehydration and deoxygenation device is a tank reactor, and the tank reactor preferably includes a stirring device.

[0032] The present invention provides a method for preparing and purifying rare earth fluorides, which uses the above-mentioned system for preparing and purifying rare earth fluorides and comprises the following steps:

[0033] S1. Fluorination reaction of a rare earth compound containing oxygen with hydrofluoric acid in the reaction device;

[0034] S2, the solid product of the fluorination reaction enters the dehydration and deoxygenation device to react with anhydrous hydrogen fluoride;

[0035] S3, the reacted material (mainly water-containing hydrogen fluoride) of step S2 enters the first distillation tower from the hydrogen fluoride outlet of the dehydration and deoxygenation device for distillation separation to separate hydrogen fluoride and water;

[0036] The gaseous mixture obtained by the distillation separation is refluxed to the dehydration and deoxygenation device through the top gaseous phase outlet of the first distillation tower for reacting with the solid product of the fluorination reaction; the liquid mixture obtained by the distillation separation is refluxed to the reaction device through the bottom outlet of the first distillation tower for fluorination reaction with the rare earth compound containing oxygen element.

[0037] In the present invention, preferably, the method for preparing and purifying rare earth fluorides further comprises the following steps:

[0038] S21, the non-solid phase product (mainly hydrofluoric acid) after the fluorination reaction enters the second distillation tower through the feed port of the second distillation tower for distillation separation to separate hydrogen fluoride and water;

[0039] The azeotropic hydrofluoric acid obtained by the distillation separation is refluxed from the bottom liquid phase outlet of the second distillation tower to the reaction device for fluorination reaction with the rare earth compound containing oxygen element; wherein steps S21 and S2 are performed in no particular order.

[0040] The temperature of the top of the second distillation tower is preferably 100-200°C, more preferably 100-120°C, for example 101°C or 108°C.

[0041] The temperature of the bottom of the second distillation tower is preferably 100-200°C, more preferably 100-120°C, for example 118°C or 112°C.

[0042] The reflux ratio of the second distillation tower is preferably 4 to 9, for example, 6.5 or 6. When the rare earth fluoride preparation and purification system further includes a second top condenser, the condensation temperature of the second top condenser is preferably 20 to 40°C, for example, 30°C.

[0043] In the present invention, preferably, step S3 further comprises: the reacted material of step S2 enters the first distillation tower from the hydrogen fluoride outlet of the dehydration and deoxygenation device for distillation separation, and then enters the dehydration device for further water removal;

[0044] The gaseous mixture obtained by the distillation separation enters the dehydration device through the gaseous discharge port at the top of the first distillation tower for further water removal, and the material obtained after the water removal is refluxed to the dehydration and deoxygenation device for reacting with the solid product of the fluorination reaction; the liquid mixture obtained by the distillation separation is refluxed to the reaction device through the bottom outlet of the first distillation tower for fluorination reaction with the rare earth compound containing oxygen element.

[0045] More preferably, the reacted material in step S2 enters the first distillation tower from the hydrogen fluoride outlet of the dehydration and deoxygenation device for distillation separation, and then enters the dehydration device through the first top condenser for further water removal.

[0046] Those skilled in the art know that the boiling point of anhydrous hydrogen fluoride is 20°C.

[0047] In the present invention, the temperature of the fluorination reaction is generally less than 20°C, preferably -10°C to 20°C, for example 10°C.

[0048] In the present invention, the pressure of the fluorination reaction is generally normal pressure.

[0049] In the present invention, the temperature of the dehydration and deoxygenation device may be less than 20°C, preferably -10°C to 20°C, for example 10°C.

[0050] In the present invention, the operating pressure of the dehydration and deoxygenation device is generally atmospheric pressure.

[0051] In the present invention, the temperature of the top of the first distillation tower is preferably 10-120°C, more preferably 10-30°C, for example 21°C.

[0052] In the present invention, the temperature of the bottom of the first distillation tower is preferably 10-120°C, more preferably 10-30°C, for example 22°C.

[0053] In the present invention, the reflux ratio of the first distillation tower is preferably 10 to 15, for example, 12.5.

[0054] In the present invention, the rare earth compound containing oxygen can be selected from conventional rare earth compounds containing oxygen in the art, and is preferably selected from oxides, hydroxides, carbonates or oxalates containing one or more rare earth elements.

[0055] In the present invention, the rare earth element of the rare earth compound containing oxygen element can be selected from the conventional rare earth elements in the art, preferably including one or more of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), yttrium (Y) and scandium (Sc); more preferably including one or more of lanthanum, cerium, neodymium, yttrium and scandium.

[0056] Among them, the rare earth compound containing oxygen element preferably includes one or more of cerium oxide (CeO2), lanthanum oxide (La2O3), lanthanum hydroxide (La(OH)3), neodymium carbonate (Nd2(CO3)3), yttrium carbonate (Y2(CO3)3), scandium oxalate (Sc2(C2O4)3) and lanthanum oxalate (La2(C2O4)3). Those skilled in the art know that CeO2 reacts with hydrofluoric acid to obtain CeF4, and La2O3 reacts with hydrofluoric acid to obtain LaF3; for rare earth hydroxides, for example, La(OH)3 reacts with hydrofluoric acid to produce LaF3; for rare earth carbonates and oxalates, for example, Nd2(CO3)3, Y2(CO3)3, Sc2(C2O4)3 and La2(C2O4)3 react with hydrofluoric acid to produce corresponding rare earth fluorides.

[0057] The present invention provides a rare earth fluoride, which is prepared by the above-mentioned preparation and purification method of rare earth fluoride, wherein the oxygen content of the rare earth fluoride is less than 30 ppm, for example, 29 ppm, 25 ppm, 22 ppm, 24 ppm, 27 ppm, 28 ppm or 8 ppm.

[0058] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0059] The reagents and raw materials used in the present invention are commercially available.

[0060] The positive progress effect of the present invention is:

[0061] The rare earth fluoride preparation and purification system of the present invention comprises a reaction device, a dehydration and deoxygenation device, and a first distillation tower connected in sequence and the specific connection relationship between them. The rare earth fluoride produced by the system has a low oxygen content (can be below 30 ppm), hydrogen fluoride can be recycled, waste liquid discharge is small, and the waste liquid has low acidity and low fluorine content (the HF content of the waste liquid in Example 3 can be ≤1.5wt%), which is beneficial to environmental protection, high resource utilization, and green and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a process flow chart of the rare earth fluoride preparation and purification system of Example 1.

[0063] Figure 2 This is a process flow chart of the rare earth fluoride preparation and purification system of Example 2.

[0064] Figure 3 This is a process flow chart of the rare earth fluoride preparation and purification system of Example 3.

[0065] Description of reference numerals:

[0066] Reaction device 1

[0067] Dehydration and deoxygenation device 2

[0068] First distillation tower 3

[0069] Second distillation tower 4

[0070] Electrolysis device 5 DETAILED DESCRIPTION

[0071] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples without specifying specific conditions were performed according to conventional methods and conditions, or selected according to the product specifications.

[0072] The oxygen content in zirconium fluoride was tested using the method of Example 1 in Chinese Patent Application No. 201410184920.3. The instrument used for the test was an oxygen analyzer model RO600 produced by LECO.

[0073] Example 1

[0074] This embodiment 1 provides a system for preparing and purifying rare earth fluorides, such as Figure 1 As shown, the rare earth fluoride separation system includes a reaction unit 1, a dehydration and deoxygenation unit 2, a first distillation tower 3, and a first top condenser. The reaction unit 1, the dehydration and deoxygenation unit 2, and the first distillation tower 3 are connected in sequence. The reactant solid phase outlet of the reaction unit 1 is connected to the first feed inlet of the dehydration and deoxygenation unit 2. The dehydration and deoxygenation unit 2 is provided with a product outlet and a hydrogen fluoride outlet, and the hydrogen fluoride outlet is connected to the feed inlet of the first distillation tower 3. The top gas phase outlet of the first distillation tower 3 and the first top condenser are connected to the second feed inlet of the dehydration and deoxygenation unit 2. The bottom outlet of the first distillation tower 3 is connected to a feed inlet of the reaction unit 1.

[0075] The reaction device 1 is used to react a rare earth compound containing oxygen with hydrofluoric acid for a fluorination reaction; the dehydration and deoxygenation device 2 is used to react a solid product of the fluorination reaction with anhydrous hydrogen fluoride; the first distillation tower 3 is used to separate hydrogen fluoride and water from the material discharged from the hydrogen fluoride outlet of the dehydration and deoxygenation device 2, and to reflux the obtained gaseous mixture into the dehydration and deoxygenation device 2 through the top gaseous phase outlet of the first distillation tower 3 and the first top condenser in sequence, and to reflux the obtained liquid phase mixture into the reaction device 1 through the bottom outlet of the first distillation tower 3.

[0076] The first distillation tower 3 has five plates.

[0077] The first distillation tower 3 is a plate tower.

[0078] The feed inlet of the first distillation tower 3 is located at the second tower plate.

[0079] The reaction apparatus 1 is a batch-type tank reactor including a stirring device. The inner lining material of the reaction apparatus 1 is PTFE and the capacity is 3 liters.

[0080] Dehydration and deoxygenation unit 2 is a batch-type kettle solid-liquid reactor with a stirring device. The structure of dehydration and deoxygenation unit 2 is a kettle reactor, which includes a stirring device. The inner lining material of reaction unit 1 is PTFE and the capacity is 3 liters.

[0081] Example 2

[0082] This embodiment 2 provides a preparation and purification system for rare earth fluoride, which, compared with the system in embodiment 1, further includes a second distillation system, which includes a second distillation tower 4 and a second tower top condenser. Figure 2 shown.

[0083] Among them, the feed port of the second distillation tower 4 is connected to the non-solid phase outlet of the reaction unit 1, and the bottom liquid phase outlet of the second distillation tower 4 is connected to another feed port of the reaction unit 1. The second distillation tower 4 is used to separate hydrogen fluoride and water in the material coming out of the non-solid phase outlet of the reaction unit 1, and the obtained azeotropic hydrofluoric acid is discharged from the bottom liquid phase outlet of the second distillation tower 4 and refluxed to the reaction unit 1 through another feed port of the reaction unit 1. The azeotropic hydrofluoric acid is an azeotropic mixture of hydrogen fluoride and water; the second top condenser is used to condense water coming out of the top gas phase outlet of the second distillation tower 4.

[0084] The second distillation tower 4 has 14 plates.

[0085] Wherein, the second distillation tower 4 is a plate tower.

[0086] The feed inlet of the second distillation tower 4 is located at the 7th tower plate.

[0087] This embodiment 2 provides a method for preparing and purifying rare earth fluorides, which uses the above rare earth fluoride preparation and purification system and includes the following steps:

[0088] S1. A rare earth compound containing oxygen (La2O3, 4N purity, Shanghai test) and hydrofluoric acid undergo fluorination reaction in reaction device 1; wherein, 100 g of solid rare earth compound containing oxygen, the mass concentration of hydrofluoric acid is 40%, and the volume is 2 liters; the water content of hydrofluoric acid is continuously monitored. After 17 hours, it is found that the fluctuation for 1 hour is less than 0.1%, and the fluorination reaction is completed.

[0089] S2. The solid product of the fluorination reaction enters dehydration and deoxygenation device 2 to react with anhydrous hydrogen fluoride. The volume of anhydrous hydrogen fluoride added is 2 liters, and the concentration is 5N (99.999%). The water content of the anhydrous hydrogen fluoride in dehydration and deoxygenation device 2 is continuously monitored. After 21 hours, it is found that the water content is less than 30 ppm for 1 hour continuously, indicating that the dehydration and deoxygenation reaction is complete.

[0090] S21, the material after the fluorination reaction enters the second distillation tower 4 from the non-solid phase outlet of the reaction unit 1 (mainly hydrofluoric acid) through the feed port of the second distillation tower 4 for distillation separation to separate hydrogen fluoride and water;

[0091] The azeotropic hydrofluoric acid obtained by distillation separation is refluxed from the bottom liquid phase outlet of the second distillation tower 4 to the reaction device 1 for fluorination reaction with the rare earth compound containing oxygen element; the water obtained by distillation separation is discharged from the top gas phase outlet of the second distillation tower 4 and then condensed by the second top condenser;

[0092] Herein, steps S21 and S2 are performed simultaneously.

[0093] S3, the material after the reaction in step S2 (including anhydrous hydrogen fluoride containing impurity water) enters the first distillation tower 3 for distillation separation to separate hydrogen fluoride and water;

[0094] The gaseous mixture obtained by distillation separation is refluxed to the dehydration and deoxygenation device 2 through the top gas phase outlet of the first distillation tower 3 and the first top condenser in sequence for reaction with the solid product of the fluorination reaction; the liquid mixture obtained by distillation separation is refluxed to the reaction device 1 through the bottom outlet of the first distillation tower 3 for fluorination reaction with the rare earth compound containing oxygen element.

[0095] The temperature at the top of the second distillation tower 4 was 101°C.

[0096] The temperature at the bottom of the second distillation tower 4 was 118°C.

[0097] The condensation temperature of the second top condenser of the second distillation tower 4 is 30°C.

[0098] The reaction temperature of the fluorination reaction is 10° C. All the hydrofluoric acid is transferred to the second distillation tower 4 , and all the solid products in the reaction device 1 are transferred to the dehydration and deoxygenation device 2 .

[0099] The pressure of the fluorination reaction is normal pressure.

[0100] The temperature of the dehydration and deoxygenation device 2 is 10°C.

[0101] The operating pressure of the dehydration and deoxygenation device 2 is normal pressure.

[0102] The temperature of the top of the first distillation tower 3 was 21° C. The condensation temperature of the first top condenser was 19° C.

[0103] The temperature at the bottom of the first distillation tower 3 is 22° C. The final rare earth fluoride after dehydration and deoxygenation is obtained from the product outlet of the dehydration and deoxygenation device 2 .

[0104] The method for monitoring the water content of anhydrous hydrogen fluoride used in Example 2 is the tunable semiconductor laser absorption spectroscopy (TDLAS) method.

[0105] The oxygen content of the rare earth fluoride prepared by the preparation and purification method of rare earth fluoride in Example 2 is 29 ppm.

[0106] Example 3

[0107] Example 3 provides a system for preparing and purifying rare earth fluorides, such as Figure 3 As shown, the difference between this system and the system of Example 2 is that the system further includes an electrolysis device 5, wherein the top gas phase outlet of the first distillation tower 3, the first top condenser, the electrolysis device 5, and the second feed inlet of the dehydration and deoxygenation device 2 are connected in sequence. The gas phase mixture discharged from the top gas phase outlet of the first distillation tower 3 is condensed by the first top condenser and then enters the electrolysis device 5 for further water removal. The material obtained after water removal is refluxed to the dehydration and deoxygenation device 2.

[0108] The method for preparing and purifying rare earth fluorides of Example 3 differs from the method of Example 2 in that step S3 further includes: the gas after the reaction in step S2 enters the first distillation tower 3 for distillation separation, is condensed by the first tower top condenser, and then enters the electrolysis device 5 for further water removal; the electrolysis voltage of the electrolysis device 5 is 3.5V.

[0109] Among them, the gaseous mixture obtained by distillation separation is condensed by the first top condenser after passing through the top gas phase outlet of the first distillation tower 3 and enters the electrolysis device 5 for further water removal. The material obtained after water removal is refluxed to the dehydration and deoxygenation device 2 for reaction with the solid product of the fluorination reaction; the liquid mixture obtained by distillation separation is refluxed to the reaction device 1 through the bottom outlet of the first distillation tower 3 for fluorination reaction with the rare earth compound containing oxygen element.

[0110] The reaction time of Example 3 was shorter. After 15 hours, it was found that the water content was less than 30 ppm for 1 hour continuously, and the fluorination reaction was completed.

[0111] The oxygen content of the rare earth fluoride prepared by the preparation and purification method of rare earth fluoride in Example 3 is 8 ppm.

[0112] Example 4

[0113] Example 4 provides a system for preparing and purifying rare earth fluorides. This system differs from the system of Example 2 in that the second distillation system comprises two second distillation towers 4 and a second overhead condenser connected in series. The feed inlet of the first second distillation tower 4 is connected to the non-solid phase outlet of the reaction unit 1, the bottom liquid phase outlet of the first second distillation tower 4 is connected to the feed inlet of the second second distillation tower 4, and the bottom liquid phase outlet of the second second distillation tower 4 is connected to another feed inlet of the reaction unit 1. The first second distillation tower 4 has seven trays, and the feed inlet is located on the third tray.

[0114] The second second distillation tower 4 has 7 plates, and the feed inlet is located at the third plate.

[0115] Example 4 provides a method for preparing and purifying rare earth fluorides, which differs from the method in Example 2 in that the temperature at the top of the first second distillation tower 4 is 108°C, the temperature at the bottom of the tower is 118°C, and the reflux ratio is 6.

[0116] The temperature of the top of the second second distillation tower 4 was 100° C., the temperature of the bottom was 112° C., and the reflux ratio was 6.5.

[0117] The oxygen content of the rare earth fluoride prepared by the preparation and purification method of rare earth fluoride in Example 4 is 28 ppm.

[0118] Examples 5-11

[0119] Examples 5-11 all employed the same rare earth fluoride preparation and purification system as Example 2. The preparation and purification methods of the rare earth fluorides of Examples 5-11 differed from those of Example 2 only in the use of different oxygen-containing rare earth compound raw materials, fluorination reaction times, and dehydration and deoxygenation reaction times. The raw materials, fluorination reaction times, dehydration and deoxygenation reaction times, products, and oxygen contents of the products of Examples 5-11 are shown in Table 1 below.

[0120] Table 1. Reaction conditions and reaction results of Examples 5-11

[0121]

Claims

1. A system for preparing and purifying rare earth fluorides, characterized in that: It includes a reaction device, a dehydration and deoxygenation device and a first distillation tower connected in sequence. The reactant solid phase outlet of the reaction device is connected to the first feed inlet of the dehydration and deoxygenation device; the dehydration and deoxygenation device is provided with a product outlet and a hydrogen fluoride outlet, and the hydrogen fluoride outlet is connected to the feed inlet of the first distillation tower; the top gas phase outlet of the first distillation tower is connected to the second feed inlet of the dehydration and deoxygenation device, and the bottom outlet of the first distillation tower is connected to a feed inlet of the reaction device; The reaction device is used for the rare earth compound containing oxygen element to undergo fluorination reaction with hydrofluoric acid; The dehydration and deoxygenation device is used to react the solid product of the fluorination reaction with anhydrous hydrogen fluoride; The first distillation tower is used to separate hydrogen fluoride and water in the material coming out of the hydrogen fluoride outlet of the dehydration and deoxygenation device, and reflux the obtained gaseous mixture into the dehydration and deoxygenation device through the gaseous phase outlet at the top of the first distillation tower, and reflux the obtained liquid phase mixture into the reaction device through the bottom outlet of the first distillation tower.

2. The system for preparing and purifying rare earth fluorides according to claim 1, wherein: The rare earth fluoride preparation and purification system further includes a second distillation system connected to the reaction device, wherein the second distillation system includes a second distillation tower, or two or more second distillation towers connected in series; The feed port of the first second distillation tower is connected to the non-solid phase outlet of the reaction device, and the bottom liquid phase outlet of the last second distillation tower is connected to another feed port of the reaction device. The second distillation tower is used to separate hydrogen fluoride and water in the material flowing out of the non-solid phase outlet of the reaction device, and the obtained azeotropic hydrofluoric acid flows out from the bottom liquid phase outlet of the second distillation tower and refluxes to the reaction device through another feed port of the reaction device.

3. The system for preparing and purifying rare earth fluorides according to claim 2, wherein: The second distillation tower has 6 to 20 plates.

4. The system for preparing and purifying rare earth fluorides according to claim 3, wherein: The second distillation tower has 14 plates.

5. The system for preparing and purifying rare earth fluorides according to claim 2, wherein: The second distillation tower is a plate tower.

6. The system for preparing and purifying rare earth fluorides according to claim 2, wherein: The feed inlet of the second distillation tower is located at the 3rd to 10th trays.

7. The system for preparing and purifying rare earth fluorides according to claim 6, wherein: The feed inlet of the second distillation tower is at the sixth tray.

8. The system for preparing and purifying rare earth fluorides according to claim 1, wherein: The rare earth fluoride preparation and purification system also includes a dehydration device, wherein the top gas phase outlet of the first distillation tower, the dehydration device and the second feed port of the dehydration and deoxygenation device are connected in sequence; the dehydration device is used to further remove water from the gas phase mixture discharged from the top gas phase outlet of the first distillation tower, and reflux the material obtained after the water removal to the dehydration and deoxygenation device.

9. The system for preparing and purifying rare earth fluorides according to claim 8, wherein: The water removal device is an electrolysis device, which is used to electrolyze water in the gas phase mixture discharged from the gas phase discharge port at the top of the first distillation tower.

10. The system for preparing and purifying rare earth fluorides according to claim 1, wherein: The number of plates of the first distillation tower is 3-8; And / or, the first distillation tower is a plate tower; And / or, the top of the first distillation tower is connected to the first top condenser, and the top gas phase discharge port of the first distillation tower is connected to the first top condenser and the dehydration and deoxygenation device in sequence; And / or, the feed inlet of the first distillation tower is located at the 2nd to 4th tower plates.

11. The system for preparing and purifying rare earth fluorides according to claim 10, wherein: The first distillation tower has 5 plates.

12. The system for preparing and purifying rare earth fluorides according to claim 10, wherein: The feed inlet of the first distillation tower is located at the second tower plate.

13. The system for preparing and purifying rare earth fluorides according to claim 1, wherein: The reaction device is a batch or continuous solid-liquid reactor; And / or, the structure type of the reaction device is a kettle reactor; And / or, the dehydration and deoxygenation device is a batch or continuous solid-liquid reactor; And / or, the dehydration and deoxygenation device is a kettle reactor.

14. The system for preparing and purifying rare earth fluorides according to claim 13, wherein: The structure type of the reaction device is a tank reactor, and the tank reactor comprises a stirring device.

15. The system for preparing and purifying rare earth fluorides according to claim 13, wherein: The dehydration and deoxygenation device has a structure of a tank reactor, and the tank reactor comprises a stirring device.

16. A method for preparing and purifying rare earth fluorides, characterized in that: The method adopts the rare earth fluoride preparation and purification system according to any one of claims 1 to 15, comprising the following steps: S1. Fluorination reaction of a rare earth compound containing oxygen with hydrofluoric acid in the reaction device; S2, the solid product of the fluorination reaction enters the dehydration and deoxygenation device to react with anhydrous hydrogen fluoride; S3, the reacted material of step S2 enters the first distillation tower from the hydrogen fluoride outlet of the dehydration and deoxygenation device for distillation separation to separate hydrogen fluoride and water; The gaseous mixture obtained by the distillation separation is refluxed to the dehydration and deoxygenation device through the top gaseous phase outlet of the first distillation tower for reacting with the solid product of the fluorination reaction; the liquid mixture obtained by the distillation separation is refluxed to the reaction device through the bottom outlet of the first distillation tower for fluorination reaction with the rare earth compound containing oxygen element.

17. The method for preparing and purifying rare earth fluorides according to claim 16, wherein: The method for preparing and purifying rare earth fluorides further comprises the following steps: S21, the non-solid phase product after the fluorination reaction enters the second distillation tower through the feed port of the second distillation tower for distillation separation to separate hydrogen fluoride and water; The azeotropic hydrofluoric acid obtained by the distillation separation is refluxed from the bottom liquid phase outlet of the second distillation tower to the reaction device for fluorination reaction with the rare earth compound containing oxygen element; wherein steps S21 and S2 are performed in no particular order.

18. The method for preparing and purifying rare earth fluorides according to claim 17, wherein: The temperature of the top of the second distillation tower is 100-200°C.

19. The method for preparing and purifying rare earth fluorides according to claim 18, wherein: The temperature of the top of the second distillation tower is 100-120°C.

20. The method for preparing and purifying rare earth fluorides according to claim 19, wherein: The temperature of the top of the second distillation tower is 101°C or 108°C.

21. The method for preparing and purifying rare earth fluorides according to claim 17, wherein: The temperature of the bottom of the second distillation tower is 100-200°C.

22. The method for preparing and purifying rare earth fluorides according to claim 21, wherein: The temperature of the bottom of the second distillation tower is 100-120°C.

23. The method for preparing and purifying rare earth fluorides according to claim 22, wherein: The temperature of the bottom of the second distillation tower is 118°C or 112°C.

24. The method for preparing and purifying rare earth fluorides according to claim 17, wherein: The reflux ratio of the second distillation tower is 4-9.

25. The method for preparing and purifying rare earth fluorides according to claim 24, wherein: The reflux ratio of the second distillation tower is 6.5 or 6.

26. The method for preparing and purifying rare earth fluorides according to claim 17, wherein: When the rare earth fluoride preparation and purification system further comprises a second top condenser, the condensation temperature of the second top condenser is 20-40°C.

27. The method for preparing and purifying rare earth fluorides according to claim 26, wherein: When the rare earth fluoride preparation and purification system further includes a second top condenser, the condensation temperature of the second top condenser is 30°C.

28. The method for preparing and purifying rare earth fluorides according to claim 16, wherein: Step S3 further includes: the reacted material of step S2 enters the first distillation tower from the hydrogen fluoride outlet of the dehydration and deoxygenation device for distillation separation, and then enters the dehydration device for further water removal; The gaseous mixture obtained by the distillation separation enters the dehydration device through the gaseous discharge port at the top of the first distillation tower for further water removal, and the material obtained after the water removal is refluxed to the dehydration and deoxygenation device for reacting with the solid product of the fluorination reaction; the liquid mixture obtained by the distillation separation is refluxed to the reaction device through the bottom outlet of the first distillation tower for fluorination reaction with the rare earth compound containing oxygen element.

29. The method for preparing and purifying rare earth fluorides according to claim 16, wherein: The temperature of the fluorination reaction is less than 20°C; and / or, the temperature of the dehydration and deoxygenation device is less than 20° C.; and / or, the temperature of the top of the first distillation tower is 10° C.-120° C.; and / or, the temperature of the bottom of the first distillation tower is 10° C.-120° C.; and / or, the reflux ratio of the first distillation tower is 10-15; And / or, the rare earth compound containing oxygen is an oxide, hydroxide, carbonate or oxalate containing one or more rare earth elements; And / or, the rare earth element of the rare earth compound containing oxygen element includes one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium.

30. The method for preparing and purifying rare earth fluorides according to claim 29, wherein: The temperature of the fluorination reaction is -10°C to 20°C.

31. The method for preparing and purifying rare earth fluorides according to claim 30, wherein: The temperature of the fluorination reaction is 10°C.

32. The method for preparing and purifying rare earth fluorides according to claim 29, wherein: The temperature of the dehydration and deoxygenation device is -10°C-20°C.

33. The method for preparing and purifying rare earth fluorides according to claim 32, wherein: The temperature of the dehydration and deoxygenation device is 10°C.

34. The method for preparing and purifying rare earth fluorides according to claim 29, wherein: The temperature of the top of the first distillation tower is 10°C-30°C.

35. The method for preparing and purifying rare earth fluorides according to claim 34, wherein: The temperature of the top of the first distillation tower was 21°C.

36. The method for preparing and purifying rare earth fluorides according to claim 29, wherein: The temperature of the bottom of the first distillation tower is 10°C-30°C.

37. The method for preparing and purifying rare earth fluorides according to claim 36, wherein: The temperature of the bottom of the first distillation tower was 22°C.

38. The method for preparing and purifying rare earth fluorides according to claim 29, wherein: The reflux ratio of the first distillation tower is 12.

5.

39. The method for preparing and purifying rare earth fluorides according to claim 29, wherein: The rare earth element of the rare earth compound containing oxygen element includes one or more of lanthanum, cerium, neodymium, yttrium and scandium.

40. The method for preparing and purifying rare earth fluorides according to claim 29, wherein: The rare earth element of the rare earth compound containing oxygen element includes one or more of cerium oxide, lanthanum oxide, lanthanum hydroxide, neodymium carbonate, yttrium carbonate, scandium oxalate and lanthanum oxalate.

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