Chlorinated rare earth and preparation method and application thereof

Abstract

The application discloses a preparation method of chlorinated rare earth and application thereof, and belongs to the technical field of chlorinated rare earth preparation. The technical problems to be solved are long production period and low purity of the existing chlorinated rare earth. The technical solution points are that the preparation method comprises the following steps: S1, adding concentrated hydrochloric acid into rare earth raw materials to dissolve, so as to obtain a chlorinated rare earth solution; S2, concentrating the chlorinated rare earth solution to obtain a saturated chlorinated rare earth solution; S3, adding crystal seeds into the saturated chlorinated rare earth solution, and performing gradient cooling crystallization under an alternating magnetic field, so as to precipitate chlorinated rare earth crystals; and S4, drying the chlorinated rare earth crystals, so as to obtain anhydrous chlorinated rare earth.

Description

Technical Field

[0001] This invention belongs to the field of rare earth chloride preparation technology, specifically relating to a rare earth chloride, its preparation method, and its application. Background Technology

[0002] Rare earth chlorides are common raw materials in industrial production, also known as rare earth chlorides. Due to their catalytic activity and stability, rare earth chlorides are often used as catalysts in industrial production processes, and occasionally as raw materials for rare earth polishing powders and reactants for extracting rare earth elements.

[0003] In some chemical reactions, precise control of the amount of raw materials and auxiliary materials added is required, often necessitating that these materials exist in a fixed form. Rare earth chlorides generally contain multiple molecules of water of crystallization, thus exhibiting strong weathering and deliquescence, which can affect the amount added during use. Therefore, they are generally prepared as anhydrous chlorides for storage and use.

[0004] The main methods for preparing anhydrous rare earth chloride are as follows: (1) Anhydrous solvent method, that is, rare earth metals react with mercuric chloride in tetrahydrofuran (THF) solution to prepare anhydrous rare earth chloride; this method requires the use of toxic substances such as tetrahydrofuran and HgCl2, which seriously pollutes the environment and affects occupational health, and the subsequent processing is difficult. Moreover, the starting material of this method requires high-purity rare earth metals, which is not suitable for large-scale preparation; (2) Dehydration method of crystal water and rare earth chloride, that is, the water-containing crystalline rare earth chloride obtained by the process of dehydration concentration, cooling crystallization and artificial crushing of rare earth chloride solution is dehydrated under vacuum to obtain anhydrous rare earth chloride; The dehydration effect of this method is not good and the product purity is not high; (3) Ammonium chloride sublimation method is to convert rare earth oxides and ammonium chloride at 300℃-450℃ to convert rare earth oxides into rare earth chlorides; if there are +4 rare earth elements in the rare earth, such as CeO2, if anhydrous rare earth chloride is prepared by ammonium chloride sublimation method, redox reaction will occur during the reaction process, and it is difficult to obtain anhydrous rare earth chloride with high purity; (4) Rare earth oxide chlorination method, that is, chlorine gas is introduced into rare earth oxides. The product of this method is unstable and the chlorination temperature is as high as 1050℃-1100℃. During the chlorination process, chlorine gas at high temperature will seriously corrode the equipment and pose a great safety and environmental protection risk.

[0005] Relevant patent documents retrieved: Patent document CN104973617A (published on October 14, 2015) discloses a method for preparing anhydrous lanthanum chloride, comprising the following steps: 1. Dissolving lanthanum carbonate powder in dilute hydrochloric acid until the pH reaches 2-3, stirring for 1-5 hours; 2. Filtering to remove impurities; 3. Microfiltration of the solution to obtain a filtrate; 4. Evaporating and concentrating the filtrate; 5. Cooling the filtrate to 20°C on a crystallizing plate for natural crystallization for 12-24 hours; 6. Filtering the filtrate to obtain crystals, and then dehydrating the crystals in a centrifugal dehydrator for 20-60 minutes to obtain an intermediate product; 7. Placing the intermediate product in a non-oxidizing oven and heating it to 70°C, holding it at that temperature for 2 hours to obtain LaCl3·3H2O crystals; then heating it to 160°C and holding it at that temperature for 2 hours to obtain LaCl3·H2O crystals; finally heating it to 250°C and holding it at that temperature for 4 hours to obtain anhydrous lanthanum chloride. This invention features a simple and easily controllable reaction process, producing a clear and transparent product with low impurity content.

[0006] Patent document CN113336256A (publication date September 3, 2021) discloses a method for preparing anhydrous neodymium chloride, including the following steps: (1) dissolving neodymium oxide or neodymium carbonate in hydrochloric acid to prepare a saturated neodymium chloride solution, controlling the excess HCl to be less than 5% (g / g); (2) adjusting the HCl content in the saturated neodymium chloride solution in (1) to be greater than 25% (g / g), lowering it to the temperature before adjustment, and precipitating neodymium chloride crystals; (3) pre-dehydrating the neodymium chloride crystals obtained in (2) under microwave conditions to obtain anhydrous crude neodymium chloride; (4) mixing the anhydrous crude neodymium chloride obtained in (3) with ammonium chloride evenly, and drying at 200-320℃ for 2-6 hours to obtain anhydrous neodymium chloride. The invention features a simple and easy-to-operate process with very low material (ammonium chloride) consumption, a short preparation cycle, and produces anhydrous neodymium chloride with low moisture content, virtually no water-insoluble matter, and a rare earth element yield of over 99%.

[0007] Patent document CN114634198A (published on June 17, 2022) discloses a method for preparing high-purity anhydrous lanthanum chloride, comprising the following steps: S1, preparing a La2O3 solution; S2, preparing LaCl3·7H2O; S3, dehydrating LaCl3·7H2O; S4, post-treatment. This invention yields high-purity LaCl3, and the preparation method is simple, convenient to operate, and cost-effective.

[0008] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: The production cycle is long, and the relevant evidence is that the crystallization time during the preparation of CN104973617A is 12-24 hours, which leads to the long production cycle.

[0009] The purity is low. Relevant evidence includes: CN114634198A records that the product obtained in Example 2 had the highest lanthanum chloride purity, reaching 96%. CN113336256A records the preparation of anhydrous neodymium chloride with a neodymium chloride content greater than 99%. CN104973617A does not disclose purity data for the prepared anhydrous lanthanum chloride.

[0010] In summary, it is of great significance to develop a method for preparing rare earth chlorides with a short production cycle and high purity. Summary of the Invention

[0011] The purpose of this invention is to provide a method for preparing rare earth chloride and related technologies to solve the technical problems of long production cycle and low purity of existing rare earth chloride, or a combination thereof.

[0012] Terminology Explanation: Unless otherwise defined, all technical terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise stated, all patents, patent inventions, and publications cited in this document are incorporated herein by reference in their entirety. If multiple definitions exist for terms, the definition provided in this chapter shall prevail.

[0013] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0014] Definitions of standard chemical terms can be found in references such as "Zhang Yin, Wang Qingchun, et al. Rare Earth Materials Preparation Technology [M]. Chemical Industry Press, January 2015".

[0015] Unless otherwise stated, conventional methods within the scope of the art, such as ICP-MS purity testing and water solubility testing, shall be used.

[0016] Unless specifically defined herein, the use of all commercially available products herein employs standard techniques. For example, it may be carried out using the manufacturer's instructions for use with the kit, or in accordance with methods known in the art or the description of this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0017] The term "alternating electromagnetic field" used in this article refers to a physical field in which a periodic change in magnetic field strength is generated inside the reaction system by passing a low-frequency alternating current through an external electromagnetic coil of the crystallizer. The magnetic field strength is controlled at 0.15-0.4T, the alternating frequency is 5-25Hz, and it is continuously applied throughout the entire process of seed-induced crystallization.

[0018] The term "seed crystal" used in this article refers to fine particles of the same type of hydrated rare earth chloride that are completely matched with the crystal form and lattice structure of the target product. These particles are obtained by crushing and screening the previous batch of rare earth chloride crystals or by pre-precipitating them from saturated liquid. They serve as a heterogeneous nucleation substrate, inducing uniform deposition and growth of rare earth ions, reducing the critical supersaturation of the system, and shortening the crystallization cycle.

[0019] The term “gradient cooling crystallization” used in this article refers to a controlled cooling crystallization process with two-stage temperature control and staged temperature holding: first, the temperature is lowered to the medium temperature range at a relatively fast rate and the local supersaturation is released at a constant temperature, and then the temperature is lowered to the low temperature range to fill the crystallization. Unlike conventional one-time natural cooling, this process can stably control the crystal growth rate, reduce impurity encapsulation, and refine the grain size distribution.

[0020] The term "saturated rare earth chloride solution" used in this article refers to the rare earth chloride mother liquor in which the solute dissolves to equilibrium at the corresponding temperature after being vacuum concentrated to remove free water, and no solid precipitates out; the system has sufficient hydrochloric acid concentration to inhibit premature hydrolysis of rare earth ions and provide a stable liquid phase environment for magnetic field-seed crystallization synergistic crystallization.

[0021] As used in this article, "concentration" refers to a process that uses physical or chemical methods to remove solvents (such as water) from materials, thereby increasing the concentration of active ingredients and reducing their volume. Conventional concentration methods in this field include vacuum concentration, spray concentration, and vacuum distillation.

[0022] The term "drying" as used in this article refers to the conventional operation of removing moisture from liquid mixtures or solid components to obtain dried products, including but not limited to vacuum freeze drying, low-temperature drying, spray drying, and hot air drying.

[0023] All numerical values ​​or expressions relating to component amounts, process conditions, etc., used in this invention should be understood to be modified by “about” in all cases.

[0024] As used herein, the term "about" refers to a quantity or range of values ​​that is an approximation within experimental variability (or within statistical experimental error). In this invention, the term "about" should have the meaning of being within 10%, preferably within 5%, of a specified value or range.

[0025] Unless otherwise specified, the temperature mentioned in this invention is room temperature (20-25℃), the solvent is water, and the percentage (%) is a mass percentage.

[0026] To achieve the above technical solution, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing rare earth chloride, comprising the following steps: S1. Add concentrated hydrochloric acid to the rare earth raw material to dissolve it, and obtain a rare earth chloride solution; S2. Concentrate the rare earth chloride solution to obtain a saturated rare earth chloride solution; S3. Add seed crystals to a saturated rare earth chloride solution and perform gradient cooling crystallization under an alternating magnetic field to precipitate rare earth chloride crystals. S4. Dry the rare earth chloride crystals to obtain anhydrous rare earth chloride.

[0027] In some implementations, the rare earth raw material mentioned in step S1 includes rare earth oxides or rare earth carbonates.

[0028] Preferably, the rare earth element includes lanthanum, neodymium, or cerium.

[0029] In some implementations, the mass fraction of the concentrated hydrochloric acid in step S1 is 30%-36%; for example, the mass fraction can be selected as 30%, 31%, 32%, 33%, 34%, 35%, 36%, or a range derived therefrom.

[0030] In some implementations, the mass ratio of the rare earth raw material to concentrated hydrochloric acid in step S1 is 1:2.5-4; for example, the mass ratio can be selected as 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4.0, or a range derived therefrom.

[0031] In some embodiments, the dissolution in step S1 is performed by stirring at 90-100°C for 10-30 minutes; for example, the dissolution temperature can be selected from 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, or a range derived therefrom; the stirring time can be selected from 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, or a range derived therefrom.

[0032] In some implementations, the dissolution described in step S1 is performed by stirring at 90-95°C for 15-25 minutes.

[0033] In some embodiments, the concentration in step S2 is vacuum concentration. Preferably, the vacuum concentration is a vacuum degree of -0.07 to -0.09 MPa and a temperature of 75-85°C; for example, the vacuum degree can be selected as -0.07 MPa, -0.08 MPa, -0.09 MPa, or a range derived therefrom, and the temperature can be selected as 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, or a range derived therefrom.

[0034] In some embodiments, the amount of seed crystals added in step S3 is 0.1%-1% of the mass of the rare earth chloride saturated solution; for example, the amount of seed crystals added is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% of the mass of the rare earth chloride saturated solution, or a range derived therefrom.

[0035] In some embodiments, the amount of seed crystals added in step S3 is 0.3%-0.8% of the mass of the rare earth chloride saturated solution.

[0036] In some implementations, the intensity of the alternating magnetic field in step S3 is 0.15-0.35T, and the frequency is 5-20Hz; for example, the intensity can be selected from 0.15T, 0.16T, 0.17T, 0.18T, 0.19T, 0.20T, 0.21T, 0.22T, 0.23T, 0.24T, 0.25T, 0.06T, 0.27T, 0.28T, 0.29T, 0.30T, 0.31T, 0.32T, 0.33T, 0.34T, 0.35T, or a range derived therefrom; the frequency can be selected from 5Hz, 6Hz, 7Hz, 8Hz, 9Hz, 10Hz, 11Hz, 12Hz, 13Hz, 14Hz, 15Hz, 16Hz, 17Hz, 18Hz, 19Hz, 20Hz, or a range derived therefrom.

[0037] In some implementations, the intensity of the alternating magnetic field in step S3 is 0.2-0.3T and the frequency is 10-15Hz.

[0038] In some implementations, the gradient cooling crystallization in step S3 is as follows: cooling to 50-60°C at a rate of 3-5°C / min and holding for 15-20 min; cooling to 30-40°C at a rate of 1-3°C / min and holding for 20-40 min.

[0039] In some implementations, the gradient cooling crystallization in step S3 is as follows: cooling to 55°C at a rate of 4°C / min and holding for 17 min; cooling to 35°C at a rate of 2°C / min and holding for 30 min.

[0040] In some implementations, the drying in step S4 is as follows: after microwave pre-drying of rare earth chloride crystals, ammonium chloride is added and mixed for further drying.

[0041] Preferably, the microwave pre-drying conditions are: microwave power 500-800W, temperature 75-85℃, and time 10-20min; for example, the microwave power can be selected as 500W, 550W, 600W, 650W, 700W, 750W, 800W, or a range derived therefrom; the temperature can be selected as 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, or a range derived therefrom; and the time can be selected as 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, 20min, or a range derived therefrom.

[0042] Preferably, the amount of ammonium chloride added is 40%-80% of the mass of the rare earth chloride crystals; for example, the amount of ammonium chloride added is 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or a range derived thereof, of the mass of the rare earth chloride crystals.

[0043] Preferably, the mixing and drying conditions are: holding at 220-250℃ for 4-6 hours; for example, the holding temperature can be selected from 220℃, 221℃, 222℃, 223℃, 224℃, 225℃, 226℃, 227℃, 228℃, 229℃, 230℃, 231℃, 232℃, 233℃, 234℃, 235℃, 236℃, 237℃, 238℃, 239℃, 240℃, 241℃, 242℃, 243℃, 2... The temperature ranges are 44℃, 245℃, 246℃, 247℃, 248℃, 249℃, 250℃, or a range derived thereof; the heat preservation time can be selected as 4.0h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h, 5.0h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, 5.6h, 5.7h, 5.8h, 5.9h, 6.0h, or a range derived thereof.

[0044] Secondly, the present invention provides: rare earth chloride prepared by the above preparation method.

[0045] In some embodiments, the rare earth chloride is at least one of anhydrous lanthanum chloride, anhydrous neodymium chloride, or anhydrous cerium chloride.

[0046] Thirdly, the present invention provides the application of rare earth chlorides prepared by the above preparation method in industrial production.

[0047] The applications include: as catalysts or catalyst precursors in petrochemical, exhaust gas treatment, and organic synthesis reactions; as raw materials for preparing high-precision optical and semiconductor rare earth polishing powders; as molten salt electrolytic electrolytes for the production of metallic lanthanum, neodymium, cerium, and rare earth permanent magnets and hydrogen storage alloys; used in the preparation of piezoelectric electronic ceramics and LED fluorescent luminescent materials; as metallurgical additives for wet rare earth extraction and separation and rare earth recovery from wastewater; and added to plastics and rubber polymers as anti-aging and UV shielding modifiers.

[0048] Based on further solutions to the technical problems of the present invention, or simultaneous solutions to multiple technical problems, the preferred solution in the technical solution provided in the first aspect of the present invention includes: The first preferred option is an alternating magnetic field with an intensity of 0.15-0.35T and a frequency of 5-20Hz. This technical solution, while addressing the issues of shortening the crystallization cycle, improving product purity, and enhancing water solubility, further strengthens the effects of improving product purification and water solubility.

[0049] The second preferred method is gradient cooling crystallization: cooling to 50-60℃ at a rate of 3-5℃ / min and holding for 15-20 min; then cooling to 30-40℃ at a rate of 1-3℃ / min and holding for 20-40 min. This technical solution, while addressing the issues of shortening the crystallization cycle, improving product purity, and enhancing water solubility, further strengthens the effects of improving product purification and water solubility.

[0050] Examples 1-3 of this invention at least support the protection scope of the preparation method of rare earth chloride.

[0051] The technical feature "preparation method of rare earth chloride" is summarized from the foregoing explanation and / or the common feature steps S1, S2, S3, and S4 in Examples 1-3. Therefore, those skilled in the art can reasonably infer that the above-mentioned technical features, their subordinate concepts, their substantially equivalent technical means, and technical means that can be replaced by conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of this invention. For example, replacing the drying method with freeze drying, vacuum drying, etc., while keeping other technical features unchanged, still falls within the protection scope of this invention.

[0052] In this invention, embodiments 1-3 at least support a protection range with an alternating magnetic field strength of 0.15-0.35T and a frequency of 5-20Hz.

[0053] The technical feature "the intensity of the alternating magnetic field is 0.15-0.35T, and the frequency is 5-20Hz" is derived from the foregoing explanation and / or the specific intensity and frequency of the alternating magnetic field in the common feature step S3 of Examples 1-3. Therefore, those skilled in the art can reasonably infer that the above-mentioned technical features, their subordinate concepts, their substantially equivalent technical means, and technical means that can be replaced by conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of this invention. For example, replacing 0.15-0.35T with 0.2T, 0.3T, etc., or replacing 5-20Hz with 10Hz, 15Hz, etc., while keeping other technical features unchanged, still falls within the protection scope of this invention.

[0054] In this invention, Examples 1-3 at least support gradient cooling crystallization within the following protection ranges: cooling to 50-60°C at a rate of 3-5°C / min and holding for 15-20min; cooling to 30-40°C at a rate of 1-3°C / min and holding for 20-40min.

[0055] The technical feature "gradient cooling crystallization is as follows: cooling to 50-60℃ at a rate of 3-5℃ / min and holding for 15-20min; cooling to 30-40℃ at a rate of 1-3℃ / min and holding for 20-40min" is summarized from the foregoing explanation and / or the specific parameters of gradient cooling crystallization in step S3 of Examples 1-3, such as cooling rate, temperature, and holding time. Therefore, those skilled in the art can reasonably infer that the above-mentioned technical features, their subordinate concepts, their substantially equivalent technical means, and technical means that can be replaced by conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of this invention. For example, replacing 3-5℃ / min with 3.2℃ / min or 4.8℃ / min while keeping other technical features unchanged still falls within the protection scope of this invention.

[0056] The beneficial effects of this invention are as follows: Compared with existing technologies, this invention uses a synergistic system of alternating magnetic field coupled gradient cooling crystallization combined with microwave pre-dehydration and ammonium chloride composite drying to simultaneously solve the core defects of traditional solutions such as long production cycle, low product purity, and easy deliquescence and hydrolysis. It has outstanding advantages in crystallization efficiency, product purity, and water solubility.

[0057] 1. This invention uses alternating magnetic field coupled gradient cooling crystallization, which shortens the crystallization time from the traditional 12-24h to within 1h.

[0058] 2. The present invention produces anhydrous rare earth chloride with a purity of ≥99.99%, which is far superior to the purity level of products disclosed in existing literature. It eliminates the need for additional recrystallization and acid washing secondary purification processes, thus solving the core defect of low purity of finished products from the source of crystallization.

[0059] 3. This invention uses magnetic field control to obtain crystals with regular morphology and uniform particle size, and the product has superior resistance to deliquescence compared to rare earth chloride crystals.

[0060] 4. In addition, the process parameters of this invention are easy to control, the process is simple, it is suitable for large-scale production, the process temperature is mild throughout, chlorine and heavy metal toxic reagents are not used, the equipment corrosion is small, it is environmentally friendly and safe, and the energy consumption and labor production costs are lower.

[0061] 5. The high-purity, low-water finished product prepared by this invention is suitable for a variety of high-end applications such as molten salt electrolysis, catalysis, polishing powder, luminescent materials, and polymer modification, and can effectively improve the performance of downstream end products.

[0062] Furthermore, based on the present invention: 1. Based on the comparison between Example 1 and Comparative Examples 1-4, even if any changes are made to the alternating magnetic field, the magnetic field strength deviating from the 0.15-0.35T range, or the gradient cooling rate not being within the specified range, the product purity will decrease significantly even if the other process conditions are completely consistent with Example 1. Hydrolysis defects such as dissolution and turbidity will appear in most groups. This shows that the combination of alternating magnetic field with specific parameters and gradient cooling crystallization technology in this invention achieves a synergistic effect that cannot be achieved by a single process. The overall performance after combination is far superior to the simple sum of the effects of using each technology individually. Detailed Implementation

[0063] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0064] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0065] The rare earth raw material used in this invention is lanthanum oxide (99.99% purity) and the seed crystal is lanthanum chloride heptahydrate (99.999%), both of which are sourced from Inner Mongolia Zhongke Mengxi New Materials Co., Ltd.

[0066] Example 1 A method for preparing rare earth chloride The steps are as follows: S1. Add 32% concentrated hydrochloric acid to lanthanum oxide at a mass ratio of 1:3, stir and dissolve at 95°C for 20 min, filter, and obtain rare earth chloride solution. S2. Vacuum concentration of rare earth chloride solution (vacuum degree -0.08MPa, temperature 80℃) to obtain saturated rare earth chloride solution; S3. Add seed crystals to the saturated rare earth chloride solution. The amount of seed crystals added is 0.5% of the mass of the saturated rare earth chloride solution. Perform gradient cooling crystallization under an alternating magnetic field (0.25T, frequency 10Hz). Cool down to 55℃ at a rate of 4℃ / min and hold for 17min. Then cool down to 35℃ at a rate of 2℃ / min and hold for 30min to precipitate lanthanum chloride crystals. S4. After microwave pre-removal (microwave power 600W, temperature 80℃, time 15min) and drying of rare earth chloride crystals, ammonium chloride (60% of the mass of lanthanum chloride crystals) is added, and the mixture is dried at 240℃ for 5h to obtain anhydrous lanthanum chloride.

[0067] Example 2 A method for preparing rare earth chloride The steps are as follows: S1. Add 30% concentrated hydrochloric acid to lanthanum oxide at a mass ratio of 1:4, stir and dissolve at 90°C for 10 min, filter, and obtain rare earth chloride solution. S2. Vacuum concentration of rare earth chloride solution (vacuum degree -0.07MPa, temperature 85℃) to obtain saturated rare earth chloride solution; S3. Add seed crystals to the saturated rare earth chloride solution. The amount of seed crystals added is 0.3% of the mass of the saturated rare earth chloride solution. Perform gradient cooling crystallization under an alternating magnetic field (0.3T, frequency 20Hz). Cool down to 60℃ at a rate of 5℃ / min and hold for 15min. Then cool down to 40℃ at a rate of 3℃ / min and hold for 20min to precipitate lanthanum chloride crystals. S4. After microwave pre-removal (microwave power 500W, temperature 75℃, time 20min) and drying of rare earth chloride crystals, ammonium chloride (40% of the mass of lanthanum chloride crystals) is added, and the mixture is dried at 220℃ for 6h to obtain anhydrous lanthanum chloride.

[0068] Example 3 A method for preparing rare earth chloride The steps are as follows: S1. Add 36% concentrated hydrochloric acid to lanthanum oxide at a mass ratio of 1:2.5, stir and dissolve at 100°C for 30 min, filter, and obtain rare earth chloride solution. S2. Vacuum concentration of rare earth chloride solution (vacuum degree -0.09MPa, temperature 75℃) to obtain saturated rare earth chloride solution; S3. Add seed crystals to the saturated rare earth chloride solution. The amount of seed crystals added is 0.8% of the mass of the saturated rare earth chloride solution. Perform gradient cooling crystallization under an alternating magnetic field (0.15T, frequency 5Hz). Cool down to 50℃ at a rate of 3℃ / min and hold for 20min. Then cool down to 30℃ at a rate of 1℃ / min and hold for 40min to precipitate lanthanum chloride crystals. S4. After microwave pre-removal (microwave power 800W, temperature 85℃, time 10min) of rare earth chloride crystals, ammonium chloride (80% of the mass of lanthanum chloride crystals) is added, and the mixture is dried at 250℃ for 4h to obtain anhydrous lanthanum chloride.

[0069] Comparative Example 1 The difference between this comparative example and Example 1 is that the alternating magnetic field is replaced by stirring at 300 rpm.

[0070] Everything else is the same as in Example 1.

[0071] Comparative Example 2 The difference between this comparative example and Example 1 is that the alternating magnetic field is 0.4T and the frequency is 10Hz.

[0072] Everything else is the same as in Example 1.

[0073] Comparative Example 3 The difference between this comparative example and Example 1 is that the alternating magnetic field is 0.1T and the frequency is 10Hz.

[0074] Everything else is the same as in Example 1.

[0075] Comparative Example 4 The difference between this comparative example and Example 1 is that the crystallization gradient is different.

[0076] Specifically: cool down to 55℃ at a rate of 1℃ / min and hold for 17min; cool down to 35℃ at a rate of 3℃ / min and hold for 35min.

[0077] Everything else is the same as in Example 1.

[0078] Detection Example 1 Purity: The purity of anhydrous lanthanum chloride was determined according to the ICP-MS method in GB / T 30903-2026.

[0079] Water solubility test: Take 50g of sample and add it to 100mL of 80℃ pure water, shake to mix. Observe whether the solution is clear and transparent and free of visible precipitate.

[0080] The properties of the anhydrous lanthanum chloride prepared in each embodiment and comparative example are shown in Table 1.

[0081] Table 1

[0082] Note: √ indicates that the solution is clear and transparent with no visible precipitate; × indicates that the solution is turbid or has precipitate.

[0083] Verification of technical effectiveness and / or analysis of technical problem solving Experimental results show that, in Examples 1-3 of the present invention, the purity of anhydrous lanthanum chloride can reach 99.993%-99.999%, and the aqueous solution is clear and free of precipitate.

[0084] As shown in Comparative Examples 1-4, during the crystallization process, removing the alternating magnetic field, deviating the magnetic field strength from the 0.15-0.35T range, or altering the gradient cooling program all significantly reduced product purity, with most samples exhibiting hydrolysis turbidity after dissolution. This indicates that relying solely on seed crystals or gradient cooling cannot control the orderly precipitation of rare earth ions. Fine crystals easily adsorb and encapsulate impurities from the mother liquor, making it difficult to prepare anhydrous rare earth chlorides with ultra-high purity (above 99.993%). This invention employs a specific alternating magnetic field and gradient cooling in synergy, which reduces the amount of impurities entrained during the crystallization stage. The subsequent microwave and ammonium chloride combined drying inhibits the formation of dehydration and hydrolysis byproducts. The entire process is interconnected and inseparable, synergistically achieving multiple beneficial effects, including a significantly shortened crystallization cycle, ultra-high product purity, and excellent water solubility.

[0085] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing rare earth chloride, characterized in that, Includes the following steps: S1. Add concentrated hydrochloric acid to the rare earth raw material to dissolve it, and obtain a rare earth chloride solution; S2. Concentrate the rare earth chloride solution to obtain a saturated rare earth chloride solution; S3. Add seed crystals to a saturated rare earth chloride solution and perform gradient cooling crystallization under an alternating magnetic field to precipitate rare earth chloride crystals. S4. Dry the rare earth chloride crystals to obtain anhydrous rare earth chloride.

2. The preparation method according to claim 1, characterized in that, The rare earth raw materials mentioned in step S1 include rare earth oxides or rare earth carbonates.

3. The preparation method according to claim 1, characterized in that, The amount of seed crystals added in step S3 is 0.1%-1% of the mass of the rare earth chloride saturated solution.

4. The preparation method according to claim 1, characterized in that, The intensity of the alternating magnetic field in step S3 is 0.15-0.35T, and the frequency is 5-20Hz.

5. The preparation method according to claim 1, characterized in that, The gradient cooling crystallization described in step S3 is as follows: cooling to 50-60℃ at a rate of 3-5℃ / min and holding for 15-20min; cooling to 30-40℃ at a rate of 1-3℃ / min and holding for 20-40min.

6. The preparation method according to claim 1, characterized in that, The drying process described in step S4 involves microwave pre-drying of rare earth chloride crystals followed by mixing and drying with ammonium chloride.

7. The preparation method according to claim 6, characterized in that, The microwave pre-drying conditions are: microwave power 500-800W, temperature 75-85℃, and time 10-20min. The amount of ammonium chloride added is 40%-80% of the mass of the rare earth chloride crystals; The conditions for mixing and drying are: heat preservation at 220-250℃ for 4-6 hours.

8. Rare earth chloride prepared by the preparation method according to any one of claims 1-7.

9. The rare earth chloride according to claim 8, characterized in that, The rare earth chloride is at least one of anhydrous lanthanum chloride, anhydrous neodymium chloride, or anhydrous cerium chloride.

10. The application of rare earth chloride prepared by the preparation method according to any one of claims 1-7 in industrial production.

Images