阅读说明：本技术 一种利用亚临界/超临界蒸汽热解法制备稀土氧化物的方法 (Method for preparing rare earth oxide by subcritical/supercritical steam pyrolysis method ) 是由 李玉虎 贺欣豪 刘志楼 马艳丽 陈金龙 李云 徐志峰 于 2020-05-21 设计创作，主要内容包括：本发明涉及一种利用亚临界/超临界蒸汽热解法制备稀土氧化物的方法,属于有色金属冶金领域。该方法以稀土氯化物为原料,通过干燥脱水-球磨活化后,使其在亚临界/超临界水蒸汽气氛中转化为相应的稀土氧化物。通过调控反应条件,获得粒度均一的超细稀土氧化物粉体。本发明具有工艺简单、绿色高效、且所得稀土氧化物品质高等优点,具有较好的产业化应用前景。(The invention relates to a method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method, belonging to the field of non-ferrous metallurgy. The method takes rare earth chloride as a raw material, and converts the rare earth chloride into corresponding rare earth oxide in subcritical/supercritical water vapor atmosphere after drying, dehydration and ball milling activation. By regulating and controlling the reaction conditions, the superfine rare earth oxide powder with uniform granularity is obtained. The method has the advantages of simple process, greenness, high efficiency, high quality of the obtained rare earth oxide and the like, and has good industrial application prospect.)

1. A method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method is characterized by comprising the following steps: heating and transforming the rare earth chloride crystal to obtain a transformed material; the chemical formula of the controlled transformation material is ReCl₃·xH₂O, wherein Re is a rare earth element, and x is more than 0.2 and less than 3;

and (3) placing the transformation material in a subcritical/supercritical steam atmosphere for carrying out gas-solid pyrolysis reaction, and discharging reaction tail gas in the reaction process to obtain the rare earth oxide.

2. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: the chemical formula of the rare earth chloride crystal is ReCl₃·yH₂O; y is 4-7 or less than 0.2;

preferably, the purity is greater than or equal to 98.5% and the amount of impurities does not exceed 100 ppm.

3. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: the temperature in the transformation treatment process is less than or equal to 180 ℃; preferably 100-180 ℃;

preferably, the transformation treatment process is carried out under a dry atmosphere;

preferably, the drying atmosphere is dry air.

4. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: the transformation material is subjected to mechanical activation treatment;

preferably, the mechanical activation treatment is ball milling treatment;

preferably, the particle size of the dope is not more than 45 μm.

5. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: the Re is at least one or a mixture of La, Ce, Y, Pr, Nd and Sm rare earth elements.

6. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 5, wherein: the temperature of the subcritical/supercritical steam atmosphere is 160-450 ℃, and the pressure is 2-25 Mpa;

preferably, the Re is La and/or Y; carrying out the gas-solid pyrolysis reaction under the atmosphere of supercritical steam;

preferably, the Re is at least one of Ce, Pr, Nd and Sm; carrying out the gas-solid pyrolysis reaction under a subcritical steam atmosphere;

preferably, the Re comprises La and/or Y and also comprises at least one of Ce, Pr, Nd and Sm; carrying out the gas-solid pyrolysis reaction under the atmosphere of supercritical steam;

preferably, the temperature of the supercritical steam atmosphere is 374.3-450 ℃, and the pressure is 22.1-25 Mpa;

preferably, the temperature of the subcritical steam atmosphere is 160-374.3 ℃, and the pressure is 2-22.1 MPa.

7. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: directly introducing subcritical/supercritical steam atmosphere into a pressure-resistant reactor filled with a transfer material, and maintaining the pressure and temperature required by the subcritical/supercritical steam atmosphere to carry out the gas-solid pyrolysis reaction;

or adding liquid water into a pressure-resistant reactor filled with a transfer material, heating under a closed condition to convert the liquid water into a subcritical/supercritical steam state, and carrying out the gas-solid pyrolysis reaction under the pressure and temperature required by maintaining a subcritical/supercritical steam atmosphere; preferably, the liquid water and the matrix are in different regions of the pressure-resistant reactor.

8. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: the subcritical/supercritical steam atmosphere is a single water vapor atmosphere; or a mixed atmosphere of water vapor and other gases, including: at least one of air, oxygen, nitrogen, and carbon dioxide.

9. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: in the gas-solid pyrolysis reaction process, the water in the subcritical/supercritical steam atmosphere is not lower than the theoretical amount of the complete reaction of the transformation material; preferably 1.5 to 3 times of the theoretical amount.

10. The method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method according to claim 1, wherein: after the gas-solid pyrolysis reaction, releasing pressure, and purging the reaction materials by adopting acid-free gas until no acid gas overflows; obtaining the rare earth oxide; and recovering the acid gas to obtain a hydrochloric acid byproduct.

Technical Field

The invention relates to a method for preparing rare earth oxide by using a subcritical/supercritical steam pyrolysis method, belonging to the field of non-ferrous metallurgy.

Technical Field

Rare earth materials are widely used in high and new technology industries such as new light sources, new energy sources, new magnetic sources, new materials and the like due to special physicochemical properties of the rare earth materials, and rare earth oxides are important components of the rare earth materials and have special properties of powder materials such as small-size effect, surface effect and the like, and also have the special optical properties, magnetic properties and other effects of the rare earth, so that the preparation and application of the rare earth materials are research hotspots in academia and industry.

The reported rare earth oxide methods mainly include a precipitation method, a sol-gel method, a hydrothermal method and a microemulsion method, wherein the precipitation method is most commonly researched and the application is most widely applied. The precipitation method takes alkaline solution such as sodium carbonate, sodium hydroxide, ammonia water and the like or oxalic acid solution as a precipitator, rare earth ions are precipitated into corresponding precursors under specific conditions, and then the precursors are dried and calcined to obtain rare earth oxides. The precipitation method has simple process technology, simple operation, low equipment requirement and relatively rich regulation and control means, thereby becoming a preferred method for preparing rare earth oxide. However, the precipitation method has some obvious disadvantages, such as long process flow and large amount of waste water, which causes great rare earth loss, because the precipitation method needs to perform the procedures of precipitation, washing, drying, calcining, classification and the like to prepare the rare earth oxide; secondly, the precipitation method needs to consume a large amount of precipitator, particularly the oxalic acid precipitation method has large investment and high cost; in addition, the introduction amount of impurities is large by a precipitation method, the particle size of the obtained rare earth oxide is coarse, the distribution is wide, and the product quality and the added value are not high.

In order to prepare high-quality rare earth oxide and solve the problems of large waste water amount and high production cost of the current rare earth oxide, a great deal of research is carried out by technical personnel, and some progress is made, such as preparation of rare earth oxide by adopting processes of a combustion method, a spray pyrolysis method and the like. The combustion method can prepare the rare earth oxide at a lower temperature (250-400 ℃), but needs expensive rare earth nitrate as a raw material; the spray pyrolysis method takes rare earth chloride solution as raw material, and the rare earth chloride solution is pyrolyzed into corresponding rare earth oxide in a high-temperature field (more than 1100 ℃). Although this process is theoretically highly feasible, the spraying process consumes a lot of energy for water evaporation, and it is particularly noteworthy that the economic value of the product obtained by this process is low due to the high chloride ion content of the product, so this process is still in research stage and cannot be applied industrially.

Therefore, no matter the currently and generally adopted precipitation method for preparing rare earth oxide, or new processes such as a combustion method, a spray pyrolysis method and the like, the method has a plurality of obvious defects, such as the precipitation method needs to consume expensive precipitant and generate a large amount of waste water, the obtained product has a relatively thick particle size, and the product quality is not high; the spray pyrolysis process has the disadvantages of high energy consumption, high chlorine content of the product and severe corrosion of equipment, and therefore, the development of a method for producing high-quality rare earth oxide with simple process and low cost is urgently needed in the industry.

Disclosure of Invention

In order to solve the defects of large product particle size, uneven distribution, high energy consumption, high chlorine content and the like caused by the high-temperature process involved in the preparation process of the conventional rare earth oxide preparation means, the invention aims to provide a method for preparing the rare earth oxide by using a subcritical/supercritical steam pyrolysis method, and aims to obtain the rare earth oxide with low chlorine, superfine property and high crystallinity at a lower temperature.

It is known from the properties of rare earth chlorides that decomposition reactions can occur under high temperature heating, but the product is not a single compound, usually a mixture of rare earth oxychloride and oxide. In order to intensify the decomposition reaction, it is most effective to increase the reaction temperature. However, the experimental results show that after the calcination temperature is increased to 1200-1500 ℃, the decomposition of the rare earth chloride can be promoted remarkably, but the content of chloride ions in the product is still higher. Moreover, as the temperature increases, the resulting product is strongly agglomerated and has a large particle size. Based on this, the inventors have intensively studied and provided the following improved schemes:

a method for preparing rare earth oxide by subcritical/supercritical steam pyrolysis comprises heating and transforming rare earth chloride crystal to obtain transformed material; the chemical formula of the controlled transformation material is ReCl₃·xH₂O, wherein Re is a rare earth element, and x is more than 0.2 and less than 3;

and (3) placing the transformation material in a subcritical/supercritical steam atmosphere for carrying out gas-solid pyrolysis reaction, discharging reaction tail gas in the reaction process, preparing rare earth oxide, and obtaining hydrochloric acid by-products.

The invention innovatively discovers that the rare earth chloride is subjected to transformation treatment, the transformed rare earth chloride crystalline state is strictly controlled, and the rare earth chloride is reacted under subcritical/supercritical steam by matching with an innovative fluidized gas-solid reaction mode under subcritical/supercritical steam atmosphere, so that deep pyrolysis can be realized at a lower temperature, the product phase can be effectively controlled, a product with a single oxide phase can be obtained, the agglomeration problem of the product can be favorably improved, the particle size of the product can be reduced, the particle size distribution uniformity can be improved, and the chlorine content of the product can be reduced.

In order to solve the problems of rare earth oxide in terms of crystal phase purity, chlorine content, product morphology and the like, the inventor carries out a large number of verification tests and finds that: firstly, the structural characteristics of the raw materials have very obvious influence on the gas-solid pyrolysis reaction effect, and the most suitable decomposed rare earth chloride is the rare earth chloride (Recl) containing specific crystal water₃·xH₂O, x is more than 0.2 and less than 3), and when the water of crystallization of the rare earth chloride is higher or lower, the decomposition is not favorable. Secondly, the gas-solid reaction is innovatively carried out under the atmosphere condition of subcritical/supercritical steam, which is more beneficial to the decomposition of the rare earth chloride and can realize the complete decomposition of the rare earth chloride at lower temperature. Thirdly, the method comprises the following steps: further the gas-solid reaction mode under the subcritical/supercritical steam atmosphere and the deviceThe combination of the transformation crystalline state control technology can generate synergistic effect, and is helpful for further improving the phase purity of the product, improving the form of the product and reducing the chlorine content of the product. The method has simple process and low cost, and can produce high-quality rare earth oxide with high efficiency.

In the invention, the rare earth chloride crystal comes from a rare earth strip liquor concentration and crystallization process, the purity is more than or equal to 98.5 percent, and the impurity dosage is not more than 100 ppm.

In the invention, the chemical formula of the rare earth chloride crystal is ReCl₃·yH₂O; y is 4 to 7 or y is less than 0.2.

The technical scheme of the invention is suitable for preparing the oxide of any rare earth element.

Preferably, Re is at least one or a mixture of La, Ce, Y, Pr, Nd, Sm and other rare earth elements.

Preferably, the temperature during the transformation treatment is less than or equal to 180 ℃; preferably 100 to 180 ℃.

Preferably, the transformation process is carried out under a dry atmosphere.

Preferably, the drying atmosphere is dry air.

The transformation material is subjected to mechanical activation treatment. Preferably, the mechanical activation treatment is a ball milling treatment. Preferably, the particle size of the transfer material is not more than 45 μm (mesh number is 325 mesh or more). Researches find that under the mechanical activation, the particle size is further controlled, the preparation effect of the gas-solid reaction is further improved, the single rare earth oxide phase is further obtained, the product form is improved, and the chlorine content of the product is reduced.

In the invention, the temperature of the subcritical/supercritical steam atmosphere is 160-450 ℃, and the pressure is 2-25 Mpa.

Preferably, the temperature of the supercritical steam atmosphere is 374.3-450 ℃, and the pressure is 22.1-25 MPa.

Preferably, the temperature of the subcritical steam atmosphere is 160-374.3 ℃, and the pressure is 2-22.1 MPa.

In the invention, the steam atmosphere in the reaction process can be regulated and controlled according to the types of the rare earth elements, which is beneficial to further preparation.

Preferably, Re is La and/or Y; the gas-solid pyrolysis reaction is carried out under the atmosphere of supercritical steam.

Preferably, the Re is at least one of Ce, Pr, Nd and Sm; the gas-solid pyrolysis reaction is carried out under a subcritical steam atmosphere.

Preferably, the Re comprises La and/or Y and also comprises at least one of Ce, Pr, Nd and Sm; the gas-solid pyrolysis reaction is carried out under the atmosphere of supercritical steam.

In the present invention, the subcritical/supercritical steam atmosphere required for the reaction can be established and maintained by the existing method. For example, the pressure-resistant reactor is heated to maintain or establish the temperature required for the high-pressure subcritical/supercritical steam atmosphere. Furthermore, the required pressure of the subcritical/supercritical steam atmosphere may be maintained by passing a high pressure subcritical/supercritical steam atmosphere and optionally other atmospheres. The other atmosphere may be at least one of air, oxygen, nitrogen and carbon dioxide. That is, the subcritical/supercritical steam atmosphere is a single water vapor atmosphere; or a mixed atmosphere of water vapor and other gases, including: at least one of air, oxygen, nitrogen, and carbon dioxide.

Preferably, in the invention, the gas-solid pyrolysis reaction can be carried out by directly introducing a subcritical/supercritical steam atmosphere into a pressure-resistant reactor filled with a transfer material and maintaining the pressure and the temperature required by the subcritical/supercritical steam atmosphere.

Or adding liquid water into a pressure-resistant reactor filled with a transfer material, heating under a closed condition to convert the liquid water into a subcritical/supercritical steam state, and carrying out the gas-solid pyrolysis reaction under the pressure and temperature required by maintaining a subcritical/supercritical steam atmosphere; preferably, the liquid water and the matrix are in different regions of the pressure-resistant reactor.

Preferably, the temperature in the gas-solid pyrolysis reaction process is controlled to be 160-450 ℃, and the pressure is controlled to be 2-25 MPa.

Preferably, during the gas-solid pyrolysis reaction, the water in the subcritical/supercritical steam atmosphere is not less than the theoretical amount for completely reacting the transformation material; preferably 1.5 to 3 times of the theoretical amount.

In the present invention, during the reaction, off-gas during the reaction is continuously or intermittently discharged, and HCl is mixed in water vapor and discharged from the reaction system.

In the invention, after the reaction process reaches the required pressure and temperature of the high-pressure subcritical/supercritical steam, the pressure and temperature can be maintained by adopting the conventional method, and the continuous or discontinuous discharge of the reaction tail gas is synchronously realized during the period. For example, in the present invention, a back pressure valve may be used to maintain a desired pressure and temperature and to exhaust reaction off-gas.

Preferably, after the gas-solid pyrolysis reaction, pressure is released, reaction tail gas is collected, and acid-free gas is adopted to purge the reaction materials until no acid gas overflows; obtaining the rare earth oxide; and recovering the acid gas to obtain a hydrochloric acid byproduct.

A further preferred method of the invention comprises the steps of:

first, a rare earth chloride crystal (Recl)₃·yH₂O, y is 5 to 7 or less than 0.2) and converting the rare earth chloride with specific crystal water (Recl)₃·xH₂O, 0.2 < x < 3) content.

Then, the dried rare earth chloride is ball-milled and crushed so that the maximum particle size is less than 45 μm.

And finally, adding the ground rare earth chloride into a high-pressure reactor, heating and enabling the rare earth chloride to be in a subcritical/supercritical steam atmosphere, maintaining the rare earth chloride to be in a critical state or a subcritical state for reaction for a certain time, and transferring reaction tail gas in the reaction process and after the reaction, thus obtaining the corresponding rare earth oxide. After the reaction tail gas is cooled and absorbed, hydrochloric acid by-products can be obtained.

The method of the invention can prepare the composite rare earth oxide besides the single rare earth oxide.

Principles and advantages

The method adopts specific transformation treatment and accurately controls the transformed crystalline state to ensure that the method is favorable for the decomposition reaction of the rare earth chloride; then, the decomposition reaction of the rare earth chloride is carried out in the subcritical/supercritical water vapor atmosphere, and the reaction activity of the rare earth chloride is ensured and the progress of the decomposition reaction is promoted. Through the work, the defects of long process flow, large wastewater quantity, high energy consumption and high cost of the traditional process are thoroughly eliminated, and the high-efficiency decomposition of the rare earth chloride and the preparation of the high-quality rare earth oxide are realized.

Compared with the prior art, the invention has the following advantages:

(1) the technical scheme of the invention can obtain the rare earth oxide single phase at a lower temperature, and can improve the form of the product, thereby being beneficial to reducing the content of chlorine; researches show that the particle size of the rare earth oxide obtained by the method can be controlled within the range of 0.1-2m, TREO is more than 99.9 percent, and the chlorine content is not more than 50 ppm.

(2) The invention has short process flow, low production cost and easy realization of industrialization.

(3) The invention does not use chemical agents, does not introduce new impurities and has low chlorine content of products.

(4) The rare earth oxide product obtained by the invention has high quality, fine granularity, uniform granularity distribution and higher added value.

(5) The invention is environment-friendly, does not produce waste gas, waste water and waste residue, and can produce hydrochloric acid products as by-products.

Drawings

FIG. 1 is a schematic view of the reactor structure of the present invention

FIGS. 2 and 3 are SEM photographs of products obtained in example 1 and comparative example 1, respectively;

as can be seen from FIGS. 2 and 3, the product particles obtained in example 1 are in a sphere-like shape and have a particle size of approximately 0.1-0.3 μm, while the product particles obtained in comparative example 1 are in an irregular shape and have a particle size of significantly larger than 10 μm, which fully proves the superiority of the subcritical/supercritical atmosphere in preparing high-quality ultrafine rare earth oxide powder.

Detailed Description

The following examples are intended to further illustrate the present disclosure, but not to limit the scope of the invention as claimed.

In the invention, the rare earth chloride is transformed and then placed in a high-pressure reactor, and supercritical or subcritical water vapor is continuously introduced into the high-pressure reactor, or liquid water is added into the high-pressure reactor and heated to be transformed into the supercritical or subcritical water vapor. And when the pressure and the temperature of the reaction system meet the requirements, maintaining the temperature and the pressure of the system through a back pressure valve (during which the reaction tail gas (HCl) is continuously or discontinuously transferred out of the reaction system), and carrying out the gas-solid reaction. And after the reaction is finished, releasing the pressure to normal pressure, purging the reaction system and the product by acid-free gas until the acid-free gas is discharged, and recovering to obtain the rare earth oxide.

The particle sizes of the products of the following examples, unless otherwise stated, refer to the D50 particle size.

Example 1:

4.5Kg of lanthanum chloride crystals (LaCl)₃·6H₂O, water content 7.3%) in a hot air drying oven, performing transformation treatment at 160 deg.C for 4 hr, grinding, and sieving with 325 mesh rotary vibration sieve. Lanthanum chloride (LaCl) under the sieve₃·2.3H₂O) was charged into a high-pressure reactor, and high-pressure steam (steam pressure: 25MPa), starting heating, and heating to 380 ℃. After the target temperature is reached, the pressure in the reactor is maintained to be 23MPa through a back pressure valve, and the reaction is carried out for 48min under heat preservation. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing, and obtaining the product La₂O₃The particle size was 0.22 μm (D50), and the chlorine content was 37 ppm.

Comparative example 1:

the only difference from example 1 is that supercritical water vapor was not introduced. A sample was taken and analyzed, and the resulting product was predominantly LaOCl, having a particle size of 16.46 μm and a chlorine content of 14560 ppm.

Comparative example 1 differs from example 1 in that: in example 1, the supercritical steam of 25MPa is used, and the reaction pressure is maintained at 23MPa, while in comparative example 1, the supercritical steam atmosphere is not used in the reaction process, but the effect of the supercritical steam atmosphere is greatly different, and the product obtained in comparative example 1 is mainly lanthanum oxychloride, the chlorine content is 14560ppm, and the particle size is coarse.

Example 2:

4.8Kg of cerium chloride crystals (CeCl)₃·7H₂O, water content 8.1%) in a hot air drying oven, performing transformation treatment at 135 deg.C for 8 hr, grinding, and sieving with 325 mesh rotary vibration sieve. Passing the sieved cerium chloride (CeCl)₃·1.7H₂O) is charged into the high-pressure reactor, the high-pressure reactor is closed, and high-pressure steam (steam pressure: 11MPa), starting heating, and heating to 260 ℃. And after the target temperature is reached, continuously introducing oxygen into the reactor, maintaining the pressure in the reactor to be 8.2MPa through a back pressure valve, and carrying out heat preservation reaction for 55 min. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing to obtain a product CeO₂The particle size was 0.46. mu.m, and the chlorine content was 23 ppm.

Comparative example 2:

compared with example 2, the difference is mainly that the rare earth chloride is not transformed to the required conditions, specifically:

4.8Kg of cerium chloride crystals (CeCl)₃·7H₂O, water content 8.1%) in a hot air drying oven, transforming at 135 deg.C for 2 hr, and grinding. Grinding to obtain cerium chloride (CeCl)₃·4.8H₂O) is filled into the high-pressure reactor, the high-pressure reactor is closed, and high-pressure steam (steam pressure is: 11MPa), starting heating, and heating to 260 ℃. And after the target temperature is reached, continuously introducing oxygen into the reactor, maintaining the pressure in the reactor to be 8.2MPa through a back pressure valve, and carrying out heat preservation reaction for 55 min. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing to obtain a product CeO₂And CeOCl with a particle size of 4.86 μm and a chlorine content of 3825 ppm.

In comparative example 2 and example 2, it can be seen that the purity of the crystal phase and the chlorine content of the product are remarkably deteriorated when the transformation is not performed to the extent required by the present invention and the particle size of the transformed material is not as required.

Example 3:

different functional zones are arranged in a reaction chamber of the high-pressure reactor and are divided into a heating zone (volatilization zone) and a reaction zone; wherein, the volatilization area is provided with water; the decomposing area is provided with a molding material.

The preparation process comprises the following steps:

5.2Kg of yttrium chloride crystals (YCl)₃·6H₂O, water content 6.7%) in a hot air drying oven, performing transformation treatment at 175 deg.C for 5 hr, grinding, and sieving with 325 mesh rotary vibration sieve. Sieving yttrium chloride (YCl)₃·0.4H₂O) is loaded into a reaction zone of the high-pressure reactor, 0.6kg of high-purity water heating zone is added into the high-pressure reactor (the temperature of the heating zone is 110-. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing, and obtaining a product Y₂O₃The particle size was 0.17 μm, and the chlorine content was 26 ppm.

Comparative example 3:

5.2Kg of yttrium chloride crystals (YCl)₃·6H₂O, water content 6.7%) in a hot air drying oven, performing transformation treatment at 175 deg.C for 5 hr, grinding, and sieving with 325 mesh rotary vibration sieve. Sieving yttrium chloride (YCl)₃·0.4H₂O) is filled into a reaction zone of a high-pressure reactor, 0.6kg of high-purity water heating zone is added into the high-pressure reactor, then the high-pressure reactor is closed, the heating is started, the temperature is increased to 285 ℃, the pressure in the reactor is maintained to be 6.9MPa through a back pressure valve, and the heat preservation reaction is carried out for 65 min. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing, and obtaining a product Y₂Cl₄Mixture of O and YClO, free of Y₂O₃And (4) generating.

Comparative example 3 differs from example 3 in that: the reaction temperature and pressure for pyrolysis of yttrium chloride in example 3 were 375 deg.c and 22.1MPa, respectively, while the reaction temperature and pressure for comparative example 3 were 285 deg.c and 6.9MPa, respectively. Although both were subjected to transformation, the reaction temperature and pressure were so low in comparative example 3 that the pyrolysis reaction could not be completely carried out and only mesophase yttrium oxychloride of yttrium chloride pyrolysis could be obtained.

Example 4:

4.5Kg of praseodymium chloride crystals (PrCl) were added₃·7H₂O, water content 8.6%) in a hot air drying oven, performing transformation treatment at 145 deg.C for 8h, grinding, and sieving with 325 mesh rotary vibration sieve. Praseodymium chloride (PrCl) under the sieve₃·1.8H₂O) is charged into the high-pressure reactor, the high-pressure reactor is then closed, and high-pressure steam (steam pressure: 15MPa), starting heating, raising the temperature to 320 ℃, maintaining the pressure in the reactor to be 12MPa through a back pressure valve, and carrying out heat preservation reaction for 50 min. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction is finished, the introduction of the water vapor and the heating are stopped. After the pressure relief is finished, continuously introducing air until no acid gas exists, and opening the reaction vesselAnd (4) reaction product is collected. Sampling and analyzing, and obtaining Pr serving as a product₂O₃The particle size was 0.62. mu.m, and the chlorine content was 37 ppm.

Example 5:

the reaction apparatus was the same as in example 3

5.6Kg of neodymium chloride crystals (NdCl)₃·6H₂O, water content 9.1%) in a hot air drying oven, performing transformation treatment at 160 deg.C for 4 hr, grinding, and sieving with 325 mesh rotary vibration sieve. The neodymium chloride (NdCl) under the sieve is separated₃·2.7H₂O) is filled into a reaction zone of a high-pressure reactor, 0.5kg of high-purity water is added into the heating zone, then the high-pressure reactor is closed, the heating is started, compressed air is introduced after the temperature is raised to 275 ℃, the pressure in the reactor is maintained to be 9MPa through a back pressure valve, and the reaction is carried out for 70min under heat preservation. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of compressed air and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing, and obtaining Nd product₂O₃The particle size was 1.17 μm, and the chlorine content was 29 ppm.

Example 6:

4.4Kg of samarium chloride crystals (SmCl)₃·6H₂O, water content 8.4%) in hot air drying oven, performing transformation treatment at 155 deg.C for 6 hr, grinding, and sieving with 325 mesh rotary vibration sieve. Samarium chloride (SmCl) under the sieve₃·2.1H₂O) is charged into the high-pressure reactor, the high-pressure reactor is then closed, and high-pressure steam (steam pressure: 10MPa), starting heating, raising the temperature to 280 ℃, maintaining the pressure in the reactor to be 7MPa through a back pressure valve, and carrying out heat preservation reaction for 80 min. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing to obtain Sm₂O₃The particle size was 1.54 μm, and the chlorine content was 41 ppm.

Example 7:

3.0Kg of praseodymium chloride (3 kgPrCl) was weighed out separately₃·7H₂O, water content 7.3%) and 3.0kg of neodymium chloride (3kg of NdCl)₃·6H₂O, water content 5.2%), mixing them together, hot air drying at 170 deg.C for 4 hr, grinding, and sieving with 325-mesh rotary vibrating sieve. Mix (Recl) under sieve₃·0.9H₂O) is charged into the high-pressure reactor, the high-pressure reactor is closed, and high-pressure steam (steam pressure: 15MPa), starting heating, raising the temperature to 280 ℃, maintaining the pressure in the reactor to be 10MPa through a back pressure valve, and carrying out heat preservation reaction for 55 min. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. The sample was analyzed, and the obtained product was a lanthanum cerium composite oxide having a particle size of 0.84 μm and a chlorine content of 37 ppm.

Example 8:

the reaction apparatus was the same as in example 3.

3.5Kg of cerium chloride (3Kg of CeCl) was weighed out separately₃·6H₂O, water content 8.3%) and 2kg of lanthanum chloride (3kg of LaCl)₃·7H₂O, 6.2 percent of water content), mixing the crystal substances in a mixer, placing the mixture in a hot air drying box, carrying out transformation treatment at 150 ℃ for 6 hours, then grinding the mixture, and sieving the ground mixture by using a 325-mesh rotary vibration sieve. Mix (Recl) under sieve₃·1.7H₂O) was charged into a high-pressure reactor, and then 0.3kg of high-purity water was added to the high-pressure reactor, followed by turning on the heating and raising the temperature to 330 ℃. And after the target temperature is reached, continuously introducing air into the reactor, maintaining the pressure in the reactor to be 18MPa through a back pressure valve, and carrying out heat preservation reaction for 45 min. Discharging HCl tail gas generated during the reaction, and introducing the tail gas into an absorption tower for scrubbing treatment to obtain a hydrochloric acid byproduct. After the reaction was completed, the introduction of water vapor and heating were stopped. And after pressure relief is finished, continuously introducing air until no acid gas exists, starting the reactor, and collecting reaction products. Sampling and analyzing to obtain a product of lanthanum and cerium complexThe particle size of the double oxide was 0.72. mu.m, and the chlorine content was 32 ppm.