Three-in-one coupling reinforced rare earth oxide preparation method and three-in-one coupling reinforced rare earth oxide preparation device

Abstract

The invention relates to the technical field of preparation of rare earth functional materials, and particularly discloses a preparation method and device of a trinity coupling reinforced rare earth oxide. The preparation device comprises an ultrasonic-microwave composite resonant cavity, a micro-channel reaction unit, an ultrasonic unit, a microwave heating unit, a pulse synchronous triggering module and a multi-parameter linkage closed-loop control module, and in-situ synchronous coupling of a micro-channel, ultrasonic and microwave in the cavity can be achieved. The preparation method is implemented based on the device, sequentially comprises five steps of raw material preparation, parameter presetting, coupling reaction, closed-loop regulation and control and product collection, and can realize time-space synchronous propulsion of precursor nucleation, agglomeration inhibition and in-situ crystallization. According to the device and the preparation method, the mass transfer efficiency in the rare earth oxide preparation process can be effectively improved, product particle aggregation is inhibited, the stability and the production efficiency of continuous production are improved, and the large-scale preparation requirements of high-end rare earth oxides are met.

Description

Technical Field

[0001] This application relates to the field of rare earth functional material preparation technology, and more specifically, it relates to a three-in-one coupled and strengthened rare earth oxide preparation method and apparatus. Background Technology

[0002] Rare earth oxides are indispensable core functional materials in high-end manufacturing fields such as electronics and information, catalysis and chemical engineering, new energy, and precision ceramics. The particle size uniformity, dispersibility, and crystal phase stability of their powders directly affect the overall performance of downstream application devices. Liquid-phase precipitation, with its strong process adaptability, controllable production costs, and ease of large-scale scaling, has become the mainstream process for the industrial preparation of rare earth oxides. To improve the mixing and mass transfer effect, inhibit particle agglomeration, and accelerate the crystallization process during precipitation, the industry often introduces microchannel, ultrasonic, and microwave technologies into the preparation process to optimize and improve product performance.

[0003] Currently, the application of the above technologies in the field of rare earth oxide preparation mostly adopts a combination of two types of fields, and generally uses a segmented series process route to advance each process step by step. It is difficult to achieve in-situ deep coupling of ultrasound, microwave and microchannel in the same cavity. The spatiotemporal separation between each process makes it impossible for the precursor nucleation, agglomeration suppression and in-situ crystallization processes to advance synchronously, which easily leads to poor mass transfer efficiency of the system and easy agglomeration of product particles. It is also difficult to ensure the stability and production efficiency of continuous production. This is a core technical problem that urgently needs to be solved in the industry. Summary of the Invention

[0004] To address the problem that existing technologies struggle to achieve in-situ deep coupling of ultrasound, microwave, and microchannel within the same cavity, leading to poor mass transfer efficiency, easy product agglomeration, and insufficient stability and efficiency in continuous production of rare earth oxides, this application provides a method and apparatus for preparing rare earth oxides with enhanced three-in-one coupling.

[0005] In a first aspect, this application provides a method for preparing a three-dimensional coupled and strengthened rare earth oxide, employing the following technical solution: A method for preparing rare earth oxides with three-in-one coupling enhancement is based on an in-situ coupled ultrasonic-microwave-microchannel co-cavity reactor. The reactor is an integrated device comprising a microchannel reaction unit, an ultrasonic unit, and a microwave heating unit within the same sealed cavity. The preparation method includes the following steps: S1. Raw material preparation: Prepare rare earth salt solution and precipitant separately; S2. Parameter preset: The operating parameters of the ultrasonic unit, microwave heating unit and feeding unit of the reactor are preset. The pulse period of the ultrasonic and microwave is set to be the same, and the microwave output power and ultrasonic power are matched according to the preset linear relationship. At the same time, the feed flow rate is set to regulate the material flow state in the microchannel reaction module. S3, Coupling Reaction: The prepared rare earth salt solution and precipitant are directly fed into the microchannel reaction module of the reactor through a dual plunger metering pump according to a preset molar ratio. The ultrasonic unit and microwave heating unit are activated simultaneously, so that the ultrasonic action, microwave action and the mixing reaction process in the microchannel reaction module are carried out in situ and synchronously in the same cavity. S4. Closed-loop control: Real-time detection of pH, temperature, conductivity and crystal nucleus size data of the reaction system through online sensors, and synchronous adjustment of the feed parameters of the two feed units, the operating parameters of the ultrasonic unit and the operating parameters of the microwave heating unit based on the detection data. S5. Product collection: The reaction slurry output from the reactor is subjected to solid-liquid separation, washing, drying and calcination to obtain rare earth oxide powder products.

[0006] By adopting the above technical solution, the three core processes of microchannel mixing, ultrasonic treatment, and microwave treatment are integrated into the same sealed cavity and implemented synchronously. With the pre-reaction dual-field parameter matching and preset, and the multi-parameter closed-loop dynamic control during the reaction, the spatiotemporal synchronous advancement of the three processes of precursor nucleus formation, agglomeration suppression, and in-situ crystallization is achieved. This avoids the secondary agglomeration and crystal form changes caused by environmental changes when transporting the nuclei between different units after formation, which is common in segmented processes. At the same time, the uniform nucleation environment brought about by microchannel mixing forms a continuous synergistic closed loop with the interface update of ultrasonic cavitation and the directional crystallization of microwaves, rather than a simple superposition of independent processes. This constructs a continuous preparation system that is suitable for the needs of large-scale production.

[0007] Preferably, in step S1, the concentration of the rare earth salt solution is controlled at 0.5-1 mol / L, the concentration of the precipitant is controlled at 0.75-1.5 mol / L, and the molar ratio of the precipitant to rare earth ions is set according to the type of precipitant. Specifically, the molar ratio of the oxalic acid and sodium carbonate precipitation system is 1.5-1.8:1, the molar ratio of the ammonium bicarbonate precipitation system is 3.0-3.6:1, and the molar ratio of the urea precipitation system is 3.0-10:1.

[0008] By adopting the above technical solution, the concentration of the rare earth salt solution is controlled at 0.5-1 mol / L, preferably 0.8-1 mol / L. This concentration is the standard output concentration of the extraction and impurity removal process in the rare earth hydrometallurgical industry. After the rare earth solution is extracted and impurity removed, it can be directly subjected to precipitation reaction after being adjusted to a suitable concentration, without the need for additional concentration or dilution, which greatly reduces the cost of industrial production. This concentration range can take into account both production efficiency and nucleation uniformity, avoiding insufficient nucleation efficiency and low product yield due to excessively low concentration, and also preventing local oversaturation and rapid agglomeration of crystal nuclei caused by excessively high concentration. Specific molar ratio ranges are set for different precipitant systems to perfectly match the stoichiometric ratios of the corresponding precipitation reactions: the theoretical stoichiometric ratio of oxalic acid, sodium carbonate, and rare earth ions is 1.5:1, and the range of 1.5-1.8:1 corresponds to a 5-20% excess of precipitant, which can ensure complete precipitation of rare earth ions while avoiding excessive precipitant residue that increases washing difficulty; the theoretical stoichiometric ratio of ammonium bicarbonate and rare earth ions is 3:1, and the range of 3.0-3.6:1 corresponds to a 5-20% excess of precipitant, which can adapt to the easy decomposition characteristics of ammonium bicarbonate, ensuring complete precipitation while avoiding side reactions; urea is a homogeneous precipitant, and the range of 3.0-10:1 can adapt to the hydrolysis kinetics of urea, ensuring stable pH changes in the system and achieving uniform nucleation; the above molar ratio ranges are all conventional and reasonable ranges for industrial production in the rare earth hydrometallurgical industry, which can take into account precipitation completeness, product purity, and industrial production costs, providing a uniform and stable precursor reaction basis for subsequent coupling reactions.

[0009] Preferably, in step S1, the rare earth salt solution is prepared using one of a single rare earth nitrate, a single rare earth chloride, a mixed rare earth nitrate, or a mixed rare earth chloride, and the precipitant is prepared using one or more of oxalic acid, ammonium bicarbonate, sodium carbonate, and urea.

[0010] By adopting the above technical solution, rare earth salt solution can be prepared by dissolving the corresponding rare earth oxides in hydrochloric acid or nitric acid, or by directly using the rare earth salt solution after extraction and impurity removal. The selected rare earth solution and precipitant are mixed in a microchannel under a three-in-one coupled turbulent environment, avoiding local concentration unevenness and providing a stable ionic environment for uniform nucleation. The precipitant can quickly undergo a quantitative precipitation reaction with rare earth ions, playing a role in generating stable precursor crystal nuclei. The selected precipitants all have good dielectric loss characteristics in a microwave field, which can realize bulk heating of precursor particles, replacing the traditional external heating method and greatly improving crystallization efficiency. Preferably, in step S2, the feed flow rate is set to make the Reynolds number of the material in the microchannel reaction module 2000-8000, the pulse frequency of the ultrasonic unit is set to 10-50kHz, and the pulse duty cycle is set to 30-70%.

[0011] By adopting the above technical solution, the Reynolds number is controlled within this range, which can form fully developed turbulence in the microchannel reaction module. The secondary flow generated by the bend in the flow channel enhances the interphase mass transfer and achieves millisecond-level molecular mixing. The above operating parameters can be adaptively adjusted according to the actual production scale and material system.

[0012] Preferably, in step S2, the pulse frequency and pulse duty cycle of the microwave heating unit are set to be the same as those of the ultrasonic unit, and the peak time of the ultrasonic pulse and the peak time of the microwave electric field are made to coincide in time sequence through the pulse synchronization trigger module; the linear matching relationship between the microwave output power and the ultrasonic power is that the microwave output power increases linearly with the increase of the ultrasonic power.

[0013] By adopting the above technical solution, the timing of the pulse peak times coincides, allowing the superheated microbubbles generated by microwave heating to violently collapse during the negative pressure phase of ultrasonic cavitation. The resulting microjets further enhance mass transfer, and the local hot spots generated by the collapse can assist in precursor crystallization, achieving mutual reinforcement of the dual-field effect. The microwave power is linearly matched with the ultrasonic power, ensuring that the microwave heating intensity is synchronously adapted while the ultrasonic cavitation effect is enhanced, avoiding the system temperature fluctuation caused by the accelerated thermal boundary layer renewal after the cavitation effect is enhanced, and maintaining the stability of the reaction environment.

[0014] Preferably, in step S2, the residence time of the material in the microchannel reaction module is controlled by adjusting the feed flow rate so that the residence time is an integer multiple of the pulse period of the ultrasonic unit and the pulse period of the microwave unit.

[0015] By adopting the above technical solution, the residence time of the material in the microchannel reaction module can be controlled by precisely adjusting the feed flow rate, making it an integer multiple match with the pulse period of ultrasound and microwave. This ensures that throughout the entire process of material flow in the microchannel reaction module, each micro-element volume of material can experience the same number of ultrasonic cavitation cycles and microwave resonance cycles. This avoids the problem of insufficient coupling caused by material flowing through the channel during the pulse interval, ensuring that all material from the feed end to the discharge end can obtain a uniform coupling effect, resulting in a narrower particle size distribution and a more uniform crystal phase structure in the final product.

[0016] Preferably, in step S3, the temperature of the reaction is controlled to be 60-180℃ by microwave selective heating, and the heating rate of the system is matched with the ultrasonic power boosting rate during the reaction; the heating rate of the system and the ultrasonic power boosting rate are linearly positively correlated.

[0017] By adopting the above technical solutions, the optimal temperature range for rare earth liquid-phase precipitation reaction is 60℃, which ensures the stable progress of the precipitation reaction and avoids decomposition of the precipitant or side reactions caused by excessively high temperatures. Utilizing the selective heating characteristics of microwaves on polar molecules, precursor particles and polar water molecules can be heated preferentially. Under the condition of a relatively low overall system temperature, in-situ dehydration and crystal phase reconstruction of the precursor particle surface can be achieved, and crystallization can be completed without subsequent high-temperature calcination, significantly reducing heat treatment energy consumption. The linear matching of the heating rate and the ultrasonic power enhancement rate allows the ultrasonic cavitation anti-agglomeration effect to be synchronously enhanced with the crystallization process throughout the entire process of crystal nucleation and crystal phase reconstruction. It continuously blocks the agglomeration bridging between particles at the critical stage of grain growth, achieving agglomeration suppression throughout the entire process of nucleation, growth, and crystallization, avoiding the problem of rapid particle agglomeration during the crystallization stage in traditional processes.

[0018] Preferably, in step S5, the linkage adjustment is as follows: when the precursor crystal nucleus particle size is detected online to be larger than the particle size threshold, the ultrasonic power and microchannel feed flow rate are increased simultaneously, and the microwave output power and pulse frequency are adjusted accordingly; when the pH value of the system deviates from the range, the flow ratio of the two feeds and the microwave heating temperature are adjusted simultaneously, and the pulse duty cycle of the ultrasonic wave is adjusted accordingly; the particle size threshold is 50-200nm, and the pH value range is set according to the system type as follows: oxalic acid precipitation system 1.5-2.0, ammonium bicarbonate precipitation system 6-7, sodium carbonate precipitation system 6-7, urea mineralization system 5.5-6.

[0019] By adopting the above technical solution, when the crystal nucleus size exceeds the threshold, multiple parameters can be adjusted simultaneously. This enhances the ultrasonic anti-agglomeration effect while shortening the material residence time by increasing the feed flow rate, preventing excessive crystal nucleus growth. Simultaneously, the microwave power is adjusted to maintain a stable crystallization environment, avoiding reaction environment imbalance caused by single-parameter adjustments. Specific pH control ranges are set for different reaction systems. For the oxalic acid precipitation system, the pH range is set to 1.5-2.0 to prevent oxalate hydrolysis and ensure uniform and stable rare earth oxalate precipitation. For the ammonium bicarbonate precipitation system, the pH range is set to 6-7, within which rare earth can be efficiently precipitated, avoiding the formation of basic rare earth carbonate impurities and ensuring the uniformity of the precursor crystal phase. For sodium carbonate precipitation… The pH range of the precipitation system is set to 6-7 to ensure the completeness and purity of rare earth carbonate precipitation, avoid the formation of basic rare earth carbonate at excessively high pH, ​​and reduce the co-precipitation of impurities. The pH range of the urea mineralization system is set to 5.5-6 to adapt to the hydrolysis rate of urea and achieve stable pH changes in the system, providing a stable alkaline environment for in-situ crystallization of the precursor. When the pH value of the system deviates from the preset range of the corresponding system, the flow ratio of the two feeds and the microwave heating temperature are adjusted simultaneously, and the pulse duty cycle of the ultrasonic wave is adjusted accordingly. This can quickly stabilize the precipitation reaction equilibrium of the system, adapt to the changed nucleation environment, ensure that the reaction system is always in the optimal coupling reaction state, and achieve continuous and precise control of grain morphology and particle size.

[0020] Secondly, this application provides a three-in-one coupled and strengthened rare earth oxide preparation apparatus, which adopts the following technical solution: A three-in-one coupled and strengthened rare earth oxide preparation apparatus includes a pressure shell. A control module is disposed on the upper surface of the pressure shell. A first microwave heating unit, a first ultrasonic unit, and a support block are fixedly connected to the inner wall of the pressure shell. A support plate is fixedly connected to the lower surface of the support block. A microchannel reaction module is disposed on the lower surface of the support plate. A second microwave heating unit and a second ultrasonic unit are fixedly connected to the inside of the support plate. A feed inlet is opened at one end of the microchannel reaction module, and a discharge outlet is opened at the other end. A dual-plunger metering pump is fixedly connected to the outer wall of the microchannel reaction module. The outer wall of the microchannel reaction module is fixedly connected to the inside of the support plate and the pressure shell.

[0021] By adopting the above technical solution, the pressure-bearing shell serves as the overall sealing and pressure-bearing structure, providing a stable and sealed reaction space for each internal functional unit, isolating the external environment from interference with the coupling field within the cavity, thereby ensuring the pressure stability and field effect uniformity of the reaction system. The pressure-bearing shell is filled with deionized water as the ultrasonic transmission medium, which significantly reduces the attenuation loss of ultrasonic energy in air, improves the uniformity and intensity of the ultrasonic cavitation effect, and ensures that the precursor crystal nuclei throughout the flow channel are subjected to uniform ultrasonic action. The control module centrally regulates and links the operating parameters of the entire system, receiving real-time detection data from various sensors and outputting corresponding control commands, thus achieving precise and controllable control of the entire reaction process. The support blocks and support plates provide layered positioning and precise limiting, accurately fixing the microchannel reaction module, the second microwave heating unit, and the second ultrasonic unit to the preset positions at the center of the cavity, thereby ensuring the alignment accuracy of each functional unit with the microchannel flow channel. The first microwave heating unit and the second microwave heating unit form a symmetrical microchannel... The wave-emission structure, combined with the microwave-reflecting layer on the inner wall of the pressure-bearing shell, forms a uniform single-mode microwave resonant field across the entire flow channel, achieving uniform heating of the entire flow channel of the microchannel reaction module without dead angles. A symmetrical ultrasonic emission structure is formed by the first and second ultrasonic units. The first ultrasonic unit is positioned directly opposite the bend in the flow channel of the microchannel reaction module, while the second ultrasonic units are alternately arranged in the gaps between the flow channels, achieving ultrasonic cavitation that covers the entire fluid flow channel and precisely targets and inhibits crystal agglomeration. The microchannel reaction module uses rare earth salt solution. The system provides a closed mixing reaction space with the precipitant solution, and the serpentine flow channel structure enhances the turbulent mixing effect, thereby achieving millisecond-level molecular-level uniform mixing of the two feed solutions. The dual-plunger metering pump enables precise synchronous feeding of the two feed solutions, allowing for precise control of the feed rate and flow ratio, thus achieving stable regulation of the Reynolds number and residence time of the materials within the microchannel reaction module. The continuous entry and exit of the feed solutions through the inlet and outlet ensures the continuous operation of the reaction system, thereby meeting the needs of large-scale continuous production.

[0022] Preferably, the first microwave heating unit and the second microwave heating unit are used to form a uniform microwave resonant field covering the entire flow channel of the microchannel reaction module, forming a coupling enhancement zone that spatially overlaps with the ultrasonic field; the first ultrasonic unit and the second ultrasonic unit are used to form a uniform ultrasonic focusing field covering the entire flow channel of the microchannel reaction module, used to simultaneously suppress precursor crystal nuclei agglomeration; the control module is used to synchronously regulate the operating parameters of the first microwave heating unit, the second microwave heating unit, the first ultrasonic unit, and the second ultrasonic unit, as well as the feed parameters of the dual-plunger metering pump, to achieve synchronous pulse timing of the dual fields and multi-parameter linkage closed-loop control of the entire reaction process.

[0023] By adopting the above technical solution, the symmetrical arrangement of the first and second microwave heating units forms a uniform microwave resonant field covering the entire flow channel of the microchannel reaction module. This field forms a coupling enhancement zone that completely overlaps with the ultrasonic field, thereby achieving deep spatial coupling between the microwave heating effect and the ultrasonic cavitation effect, avoiding the problem of local reaction differences caused by uneven field strength distribution. Furthermore, the symmetrical arrangement of the first and second ultrasonic units forms a uniform ultrasonic focusing field covering the entire flow channel of the microchannel reaction module. During the entire process of precursor crystallization via microwave heating, the cavitation effect simultaneously suppresses crystal growth. Nuclear aggregation is achieved, thus realizing the simultaneous advancement of precursor nucleation, aggregation inhibition, and in-situ crystallization in space and time, solving the pain point of easy particle aggregation in the crystallization process of traditional processes. By synchronously regulating the operating parameters of the first microwave heating unit, the second microwave heating unit, the first ultrasonic unit, and the second ultrasonic unit, as well as the feed parameters of the dual-plunger metering pump, the pulse timing of ultrasonic and microwave can be precisely controlled and synchronized. At the same time, the parameters of each unit are adjusted in linkage according to the real-time status of the reaction system, thereby achieving the effect of multi-parameter linkage closed-loop control of the entire reaction process, ensuring the uniformity and stability of product performance in continuous production.

[0024] In summary, this application has the following beneficial effects: 1. This application adopts an ultrasonic-microwave-microchannel three-in-one co-cavity in-situ coupled reactor, which integrates three core units into the same sealed cavity to carry out the reaction synchronously, realizing the spatiotemporal synchronous advancement of precursor nucleation, aggregation inhibition and in-situ crystallization. It is different from the existing two-field synergy and segmented series process, and breaks through the technical limitations of low mass transfer efficiency and easy product aggregation in traditional processes, thereby improving the stability and efficiency of continuous production.

[0025] 2. In this application, the preferred coupling method is to have the peak timing of ultrasonic and microwave pulses coincide, the power is linearly matched, and the material residence time is adapted to an integer multiple of the dual-field pulse period. Because the various operating parameters form a precise synergistic matching relationship, the ultrasonic cavitation and microwave heating effects reinforce each other, ensuring the synergistic stability of the entire reaction process and improving the overall uniformity of the reaction process.

[0026] 3. The method of this application, through online multi-parameter synchronous linkage closed-loop control, adjusts the operating parameters of feed, ultrasound, and microwave synchronously based on real-time detected data of pH value, temperature, conductivity, and crystal nucleus size. Therefore, it achieves precise control of precursor crystal morphology and particle size, and improves product uniformity and reaction process controllability.

[0027] 4. The device of this application, through the ultrasonic-microwave composite resonant cavity and the special adapter microchannel structure, makes the ultrasonic reflection focusing area and the microwave standing wave antinode area spatially coincide, and the microchannel flow channel and the dual-field action end are precisely aligned, thus maximizing the efficiency of the three-field coupling effect, strengthening the mixing mass transfer and crystal phase reconstruction process, and improving the coupling enhancement effect of the device. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation process of a three-in-one coupled enhanced rare earth oxide provided in this application; Figure 2 This is a main diagram of a three-in-one coupled and strengthened rare earth oxide preparation apparatus provided in this application; Figure 3 This is a schematic diagram of the support block of a three-in-one coupled and strengthened rare earth oxide preparation apparatus provided in this application. Figure 4 This is a schematic diagram of the first microwave heating unit of a three-in-one coupled and strengthened rare earth oxide preparation apparatus provided in this application. Figure 5 This is a schematic diagram of the second microwave heating unit of a three-in-one coupled and strengthened rare earth oxide preparation apparatus provided in this application. Figure 6 This is a schematic diagram of the first ultrasonic unit of a three-in-one coupled and strengthened rare earth oxide preparation apparatus provided in this application. Figure 7 This is a schematic diagram of a microchannel reaction module of a three-in-one coupled enhanced rare earth oxide preparation apparatus provided in this application.

[0029] The components include: 1. Pressure-bearing shell; 2. Control module; 3. First microwave heating unit; 4. First ultrasonic unit; 5. Support block; 6. Support plate; 7. Second microwave heating unit; 8. Second ultrasonic unit; 9. Microchannel reaction module; 10. Feed inlet; 11. Dual plunger metering pump; and 12. Discharge outlet. Detailed Implementation

[0030] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0031] Technical Concept: In the field of rare earth oxide liquid-phase precipitation preparation, existing technologies mostly combine microchannels, ultrasound, and microwave technologies in a two-field synergy and segmented series manner, making it difficult to achieve deep coupling and synergistic effects among the three. The reasons for this are twofold: First, each process is completed step-by-step within different units, resulting in spatiotemporal fragmentation in precursor nucleation, agglomeration suppression, and in-situ crystallization processes. Crystal nuclei are prone to secondary agglomeration and crystal form changes during inter-unit transport. Second, the operating parameters of each unit are set independently, failing to form a suitable synergistic matching relationship, thus failing to leverage the synergistic effect of multi-field coupling. Ultimately, this leads to poor mass transfer efficiency, poor product dispersion, and difficulty in ensuring the stability of continuous production.

[0032] This technical solution first constructs an in-situ coupled reactor integrating ultrasound, microwave, and microchannel into a single sealed cavity, achieving spatiotemporal synchronization of the core reaction process. Then, through pulse timing overlap, power linear matching, and adaptation of residence time to pulse period, deep synergy of the dual-field effect is achieved. Simultaneously, multi-parameter synchronous linkage closed-loop control adapts to the dynamic changes of the reaction system, achieving deep coupling of the three components from both device structure and process design perspectives, thus solving the core problems of existing technologies.

[0033] Example 1: This example provides a method for preparing a three-dimensional coupled and strengthened rare earth oxide, which is implemented based on a three-dimensional coupled and strengthened rare earth oxide preparation apparatus. The preparation method includes the following steps: S1. Raw material preparation: Prepare rare earth salt solution and precipitant separately; In a closed environment at room temperature, lanthanum nitrate was added to deionized nitric acid in a first stirred tank and stirred at 300 r / min for 20 min until completely dissolved. The mixture was then filtered to remove insoluble impurities, resulting in a rare earth salt solution with a concentration controlled at 0.70 mol / L. In a second stirred tank, oxalic acid was added to deionized water and stirred at 200 r / min for 15 min until completely dissolved, resulting in a precipitant solution with a concentration controlled at 1.0 mol / L. The molar ratio of oxalic acid precipitant to rare earth lanthanum ions in lanthanum nitrate was controlled at 1.5-1.8:1, where 1.5:1 is the theoretical stoichiometric ratio.

[0034] S2. Parameter preset: The operating parameters of the ultrasonic unit, microwave heating unit and feeding unit of the reactor are preset. The pulse period of the ultrasonic and microwave is set to be the same, and the microwave output power and ultrasonic power are matched according to the preset linear relationship. At the same time, the feed flow rate is set to regulate the material flow state in the microchannel reaction module. Specifically, the feed flow rates of the two precision feed pumps were set according to actual conditions to ensure a Reynolds number of 5000 for the material within the microchannel reaction module, forming a stable turbulent state and guaranteeing millisecond-level uniform mixing. The pulse frequency of the ultrasonic unit was set to 30kHz, and the pulse duty cycle to 50%. The pulse frequency and pulse duty cycle of the microwave heating unit were set exactly the same as those of the ultrasonic unit, and the peak times of the ultrasonic pulses and the microwave electric field were synchronized in time through a pulse synchronization trigger module, with a timing deviation not exceeding 100ns. The basic ultrasonic power Ps was set to 275W, and the linear matching relationship between the microwave output power and the ultrasonic power was set as follows: microwave output power... The power increases linearly with the increase of ultrasonic power, and the specific matching formula is P=5×Ps+200, corresponding to a basic microwave output power of 1575W. The residence time of the material in the microchannel reaction module is controlled by adjusting the feed flow rate, so that the residence time is an integer multiple of the pulse period of the ultrasonic unit and the pulse period of the microwave unit. The ultrasonic pulse period T1≈33.3μs and the microwave resonance period T2≈0.408ns. The feed flow rate is adjusted so that the residence time of the material in the microchannel reaction module is t=0.999s, which is 30,000 times T1 and 2450,000,000 times T2, which fully meets the integer multiple matching requirement.

[0035] S3. Coupling Reaction: The prepared rare earth salt solution and precipitant are directly and synchronously fed into the microchannel reaction module of the reactor via a dual-plunger metering pump according to a preset molar ratio. The ultrasonic unit and microwave heating unit are simultaneously activated, so that the ultrasonic action, microwave action, and the mixing reaction process within the microchannel reaction module occur synchronously in situ within the same cavity. In this process, the system reaction temperature is controlled at 120℃ by microwave selective heating. During the reaction, the system heating rate is matched with the ultrasonic power boosting rate, which are linearly positively correlated. The specific matching formula is v=0.1×ΔPs+5. In this embodiment, the ultrasonic power boosting rate ΔPs=50W / min is set, corresponding to a system heating rate of 10℃ / min. The system is heated from room temperature to 120℃ at a uniform rate of 10℃ / min, and the heating rate and ultrasonic power boosting rate are kept synchronously matched throughout the process. After the two liquid streams come into initial contact at the Y-shaped feed port of the microchannel, molecular-level uniform mixing and lanthanum oxalate precursor crystal nuclei are completed within 50ms. Simultaneously, the crystal nuclei are suppressed by the ultrasonic cavitation effect and the fluid boundary layer is renewed. Simultaneously, the precursor is aged, dehydrated, and reconstructed in situ by microwave selective heating. The three processes are completed completely synchronously in the same cavity without any temporal or spatial separation.

[0036] S4. Closed-loop control: Real-time detection of pH, temperature, conductivity and crystal nucleus size data of the reaction system through online sensors, and synchronous adjustment of the feed parameters of the two feed units, the operating parameters of the ultrasonic unit and the operating parameters of the microwave heating unit based on the detection data. The linkage adjustment method is as follows: the online crystal nucleus size sensor collects precursor crystal nucleus size data every 2 seconds, and when the online sensor detects precursor crystal nucleus D... 50 When the particle size exceeds the preset 125nm particle size threshold, the system automatically and synchronously increases the ultrasonic power and microchannel feed flow rate, and adjusts the microwave output power and pulse frequency accordingly according to the linear matching formula. The online pH sensor collects system pH data every 1 second. When the system pH value deviates from the preset 1.8-2.0 range, the system automatically and synchronously adjusts the flow ratio of the two feeds and the microwave heating temperature, and adjusts the ultrasonic pulse duty cycle accordingly. Temperature and conductivity sensors monitor the system status in real time. When the data fluctuates, the microwave power and feed flow rate are adjusted synchronously to maintain the stability of the reaction system.

[0037] S5. Product collection: The reaction slurry output from the reactor is subjected to solid-liquid separation, washing and drying to obtain rare earth oxide powder products. The reaction slurry flows continuously from the reactor outlet and enters a horizontal spiral sedimentation centrifuge for continuous centrifugal filtration. The centrifugal speed is controlled at 3000 r / min, and solid-liquid separation is performed to obtain lanthanum oxalate precursor filter cake. The filter cake is first washed three times with deionized water and then washed twice with anhydrous ethanol until the conductivity of the washing filtrate is less than 10 μS / cm and the pH value is neutral. After washing, the filter cake is placed in a vacuum drying oven and dried at 90℃ and -0.09MPa vacuum for 4 hours. After drying, the precursor is placed in a muffle furnace and calcined at 900℃ for 2 hours. After natural cooling to room temperature, it is lightly ground and dispersed to obtain lanthanum oxide powder product.

[0038] Example 2: This example provides a method for preparing a three-dimensional coupled and strengthened rare earth oxide, which is implemented based on a three-dimensional coupled and strengthened rare earth oxide preparation apparatus. The preparation method includes the following steps: S1. Raw material preparation: Prepare rare earth salt solution and precipitant separately; In the first stirred tank, cerium chloride was added to hydrochloric acid and stirred at 250 r / min for 25 min until completely dissolved, under a closed environment at room temperature. Insoluble impurities were removed by filtration to obtain a rare earth salt solution with a concentration controlled at 0.5 mol / L. In the second stirred tank, ammonium bicarbonate was added to deionized water and stirred at 200 r / min for 15 min until completely dissolved to obtain a precipitant solution with a concentration controlled at 0.75 mol / L. The molar ratio of ammonium bicarbonate precipitant to rare earth cerium ions in cerium chloride was controlled at 3.0-3.6:1, where 3:1 is the theoretical stoichiometric ratio.

[0039] S2. Parameter preset: The operating parameters of the ultrasonic unit, microwave heating unit and feeding unit of the reactor are preset. The pulse period of the ultrasonic and microwave is set to be the same, and the microwave output power and ultrasonic power are matched according to the preset linear relationship. At the same time, the feed flow rate is set to regulate the material flow state in the microchannel reaction module. Specifically, the feed flow rates of the two precision feed pumps are set according to actual conditions to ensure a Reynolds number of 2000 for the material within the microchannel reaction module, forming a stable turbulent state and guaranteeing millisecond-level uniform mixing. The pulse frequency of the ultrasonic unit is set to 10kHz, and the pulse duty cycle to 30%. The pulse frequency and pulse duty cycle of the microwave heating unit are exactly the same as those of the ultrasonic unit, and the peak times of the ultrasonic pulses and the microwave electric field are time-sequentially synchronized through a pulse synchronization trigger module, with a timing deviation not exceeding 100ns. The basic ultrasonic power Ps is set to 50W, and the linear matching relationship between the microwave output power and the ultrasonic power is as follows: microwave output power... The output power increases linearly with the increase of ultrasonic power, and the specific matching formula is P=5×Ps+200, corresponding to a basic microwave output power of 450W. The residence time of the material in the microchannel reaction module is controlled by adjusting the feed flow rate, so that the residence time is an integer multiple of the pulse period of the ultrasonic unit and the pulse period of the microwave unit. The ultrasonic pulse period T1=100μs and the microwave resonance period T2≈0.408ns. The feed flow rate is adjusted so that the residence time of the material in the microchannel reaction module is t=1.0s, which is 10000 times T1 and 2450000000 times T2, which fully meets the integer multiple matching requirement.

[0040] S3, Coupling Reaction: The prepared rare earth salt solution and precipitant are directly fed into the microchannel reaction module of the reactor through a dual plunger metering pump according to a preset molar ratio. The ultrasonic unit and microwave heating unit are activated simultaneously, so that the ultrasonic action, microwave action and the mixing reaction process in the microchannel reaction module are carried out in situ and synchronously in the same cavity. In this process, the system reaction temperature is controlled at 60℃ by microwave selective heating. During the reaction, the system heating rate is matched with the ultrasonic power boosting rate, which are linearly positively correlated. The specific matching formula is v=0.1×ΔPs+5. In this embodiment, the ultrasonic power boosting rate ΔPs=20W / min is set, corresponding to a system heating rate of 7℃ / min. The system is heated from room temperature to 60℃ at a uniform rate of 7℃ / min, and the heating rate and ultrasonic power boosting rate are kept synchronously matched throughout the process. After the two liquids come into initial contact at the Y-shaped feed port of the microchannel, molecular-level uniform mixing and cerium carbonate precursor crystal nuclei are completed within 100ms. Simultaneously, the crystal nuclei agglomeration is suppressed and the fluid boundary layer is renewed through ultrasonic cavitation effect. Simultaneously, the precursor is aged, dehydrated, and reconstructed in situ through microwave selective heating. The three processes are completed completely synchronously in the same cavity without any temporal or spatial separation.

[0041] S4. Closed-loop control: Real-time detection of pH, temperature, conductivity and crystal nucleus size data of the reaction system through online sensors, and synchronous adjustment of the feed parameters of the two feed units, the operating parameters of the ultrasonic unit and the operating parameters of the microwave heating unit based on the detection data. The linkage adjustment method is as follows: the online crystal nucleus size sensor collects precursor crystal nucleus size data every 2 seconds, and when the online sensor detects precursor crystal nucleus D... 50 When the particle size exceeds the preset 50nm particle size threshold, the system automatically and synchronously increases the ultrasonic power and microchannel feed flow rate, and adjusts the microwave output power and pulse frequency accordingly according to the linear matching formula. The online pH sensor collects system pH data every 1 second. When the system pH value deviates from the preset 6.5-6.8 range, the system automatically and synchronously adjusts the flow ratio of the two feeds and the microwave heating temperature, and adjusts the ultrasonic pulse duty cycle accordingly. Temperature and conductivity sensors monitor the system status in real time. When the data fluctuates, the microwave power and feed flow rate are adjusted synchronously to maintain the stability of the reaction system.

[0042] S5. Product collection: The reaction slurry output from the reactor is subjected to solid-liquid separation, washing and drying to obtain rare earth oxide powder products. The reaction slurry flows continuously from the reactor outlet and enters a horizontal spiral sedimentation centrifuge for continuous centrifugal filtration. The centrifugal speed is controlled at 3000 r / min, and solid-liquid separation is performed to obtain cerium carbonate precursor filter cake. The filter cake is first washed three times with deionized water and then washed twice with anhydrous ethanol until the conductivity of the washing filtrate is less than 10 μS / cm and the pH value is neutral. After washing, the filter cake is placed in a vacuum drying oven and dried at 60℃ and -0.09 MPa vacuum for 6 hours. After drying, the precursor is placed in a muffle furnace and calcined at 850℃ for 3 hours. After natural cooling to room temperature, it is lightly ground and dispersed to obtain cerium oxide powder product.

[0043] Example 3: This example provides a method for preparing a three-dimensional coupled and strengthened rare earth oxide, which is implemented based on a three-dimensional coupled and strengthened rare earth oxide preparation apparatus. The preparation method includes the following steps: S1. Raw material preparation: Prepare rare earth salt solution and precipitant separately; In the process, under a closed environment at room temperature, equimolar amounts of lanthanum nitrate and yttrium nitrate are mixed and added to nitric acid in a first stirred tank and stirred at 350 rpm for 30 minutes until completely dissolved. The mixture is then filtered to remove insoluble impurities, yielding a mixed rare earth salt solution with a concentration controlled at 1 mol / L. In a second stirred tank, urea is added to deionized water and stirred at 250 rpm for 20 minutes until completely dissolved, yielding a precipitant with a concentration controlled at 1.5 mol / L. The molar ratio of urea to the total rare earth ions in the mixed rare earth salt is controlled at 3.0-10:1. Here, 1.5:1 is the theoretical stoichiometric ratio. The theoretical stoichiometric ratio for urea precipitation of rare earths is 1:1. However, in actual operation, to ensure high yield and product performance, the actual dosage is usually several times or even tens of times the theoretical value. This ratio can be adjusted adaptively according to the actual reaction temperature and hydrolysis rate.

[0044] S2. Parameter preset: The operating parameters of the ultrasonic unit, microwave heating unit and feeding unit of the reactor are preset. The pulse period of the ultrasonic and microwave is set to be the same, and the microwave output power and ultrasonic power are matched according to the preset linear relationship. At the same time, the feed flow rate is set to regulate the material flow state in the microchannel reaction module. Specifically, the feed flow rates of the two precision feed pumps were set according to actual conditions to achieve a Reynolds number of 8000 for the material within the microchannel reaction module, creating a highly turbulent state and ensuring ultra-fast and uniform mixing. The pulse frequency of the ultrasonic unit was set to 50kHz, and the pulse duty cycle to 70%. The pulse frequency and pulse duty cycle of the microwave heating unit were identical to those of the ultrasonic unit, and the peak times of the ultrasonic pulses and the microwave electric field were synchronized in time through a pulse synchronization trigger module, with a timing deviation not exceeding 100ns. The basic ultrasonic power Ps was set to 500W, and the linear matching relationship between the microwave output power and the ultrasonic power was [missing information - likely a parameter]. The output power increases linearly with the increase of ultrasonic power, and the specific matching formula is P=5×Ps+200, corresponding to a basic microwave output power of 2700W. The residence time of the material in the microchannel reaction module is controlled by adjusting the feed flow rate, so that the residence time is an integer multiple of the pulse period of the ultrasonic unit and the pulse period of the microwave unit. The ultrasonic pulse period T1=20μs and the microwave resonance period T2≈0.408ns. The feed flow rate is adjusted so that the residence time of the material in the microchannel reaction module is t=1.0s, which is 50,000 times T1 and 2450,000,000 times T2, which fully meets the integer multiple matching requirement.

[0045] S3, Coupling Reaction: The prepared rare earth salt solution and precipitant are directly fed into the microchannel reaction module of the reactor through a dual plunger metering pump according to a preset molar ratio. The ultrasonic unit and microwave heating unit are activated simultaneously, so that the ultrasonic action, microwave action and the mixing reaction process in the microchannel reaction module are carried out in situ and synchronously in the same cavity. In this process, the system reaction temperature is controlled at 180℃ by microwave selective heating. During the reaction, the system heating rate is matched with the ultrasonic power boosting rate, which are linearly positively correlated. The specific matching formula is v=0.1×ΔPs+5. In this embodiment, the ultrasonic power boosting rate ΔPs=100W / min is set, corresponding to a system heating rate of 15℃ / min. The system is heated from room temperature to 180℃ at a uniform rate of 15℃ / min, and the heating rate and ultrasonic power boosting rate are kept synchronously matched throughout the process. After the two liquids come into initial contact at the Y-shaped feed port of the microchannel, molecular-level uniform mixing and rare earth hydroxide precursor crystal nuclei are completed within 1ms. Simultaneously, the crystal nuclei agglomeration is suppressed and the fluid boundary layer is renewed through ultrasonic cavitation effect. Simultaneously, the precursor is aged, dehydrated, and reconstructed in situ through microwave selective heating. The three processes are completed completely synchronously in the same cavity without any temporal or spatial separation.

[0046] S4. Closed-loop control: Real-time detection of pH, temperature, conductivity and crystal nucleus size data of the reaction system through online sensors, and synchronous adjustment of the feed parameters of the two feed units, the operating parameters of the ultrasonic unit and the operating parameters of the microwave heating unit based on the detection data. The linkage adjustment method is as follows: the online crystal nucleus size sensor collects precursor crystal nucleus size data every 2 seconds, and when the online sensor detects precursor crystal nucleus D... 50 When the particle size exceeds the preset 200nm particle size threshold, the system automatically and synchronously increases the ultrasonic power and microchannel feed flow rate, and adjusts the microwave output power and pulse frequency accordingly according to the linear matching formula. The online pH sensor collects system pH data every 1 second. When the system pH value deviates from the preset 5.6-5.8 range, the system automatically and synchronously adjusts the flow ratio of the two feeds and the microwave heating temperature, and adjusts the ultrasonic pulse duty cycle accordingly. Temperature and conductivity sensors monitor the system status in real time. When the data fluctuates, the microwave power and feed flow rate are adjusted synchronously to maintain the stability of the reaction system.

[0047] S5. Product collection: The reaction slurry output from the reactor is subjected to solid-liquid separation, washing and drying to obtain rare earth oxide powder products. The reaction slurry flows continuously from the reactor outlet and enters a horizontal spiral sedimentation centrifuge for continuous centrifugal filtration. The centrifugal speed is controlled at 3000 r / min, and solid-liquid separation is performed to obtain a rare earth precursor filter cake. The filter cake is first washed three times with deionized water and then washed twice with anhydrous ethanol until the conductivity of the washing filtrate is less than 10 μS / cm and the pH value is neutral. After washing, the filter cake is placed in a vacuum drying oven and dried at 120℃ and -0.09MPa vacuum for 2 hours. After drying, the precursor is placed in a muffle furnace and calcined at 1000℃ for 2 hours. After natural cooling to room temperature, it is lightly ground and dispersed to obtain lanthanum-yttrium composite rare earth oxide powder product.

[0048] Comparative Example 1: The only difference between this comparative example and Example 1 is that the three-in-one co-cavity coupled reactor is cancelled and replaced with an existing conventional segmented series reaction system. Specifically, a microchannel premixing unit, an ultrasonic treatment vessel, and a microwave heat treatment vessel are connected in sequence. The three units operate independently and act in stages. The flow parameters and feed flow rate of the microchannel premixing unit are completely consistent with those of Example 1. The ultrasonic power, frequency, and total action time of the ultrasonic treatment vessel are completely consistent with those of Example 1. The microwave power, temperature, and heating rate of the microwave heat treatment vessel are completely consistent with those of Example 1. The total reaction time is exactly the same as that of Example 1. All other raw materials, proportions, and process parameters are completely consistent with those of Example 1.

[0049] Comparative Example 2: The only difference between this comparative example and Example 1 is that the microchannel reaction unit is removed and replaced with a conventional stirred reactor of equal volume. The same ultrasonic and microwave effects with the same parameters as in Example 1 are applied synchronously throughout the reaction. All other raw materials, proportions, power, temperature, reaction time, etc. are completely consistent with Example 1.

[0050] Comparative Example 3: The only difference between this comparative example and Example 1 is that the control logic of the pulse synchronization trigger module is adjusted so that the peak time of the ultrasonic pulse and the peak time of the microwave electric field are completely staggered. The ultrasonic peak is located in the first 1 / 4 segment of the pulse period, and the microwave peak is located in the last 1 / 4 segment of the pulse period. Only the pulse period and duty cycle of the two are kept the same. All other raw materials, proportions, equipment, process parameters and operating steps are completely consistent with Example 1.

[0051] Comparative Example 4: The only difference between this comparative example and Example 1 is that the linear matching relationship between the system heating rate and the ultrasonic power increase rate is cancelled. The ultrasonic power is increased to 275W at the beginning of the reaction and remains unchanged throughout the process. The system heating rate is still fixed at 10℃ / min and uniformly heated to 120℃. All other raw materials, proportions, equipment, process parameters, and operating steps are completely consistent with Example 1.

[0052] Comparative Example 5: The only difference between this comparative example and Example 1 is that the multi-parameter synchronous linkage closed-loop control logic is cancelled and replaced with single-parameter independent adjustment. When the precursor crystal nucleus particle size is detected to exceed the threshold, only the ultrasonic power is increased, and the feed flow rate and microwave parameters are not adjusted. When the pH value is detected to deviate from the range, only the flow ratio of the two feeds is adjusted, and the microwave temperature and ultrasonic parameters are not adjusted. All other raw materials, ratios, equipment, process parameters, and operating steps are completely consistent with Example 1.

[0053] I. Specific Surface Area Detection of Rare Earth Oxide Powders. Test Standard: GB / T19587-2004 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method". According to the above standard, a fully automated specific surface area and porosity analyzer was used to test the lanthanum oxide powder prepared in Example 1, the cerium oxide powder prepared in Example 2, the lanthanum-yttrium composite rare earth oxide powder prepared in Example 3, and the rare earth oxide powders obtained in Comparative Examples 1-5. Before the test, all powder samples were degassed under vacuum at 200℃ for 4 hours. After degassed, nitrogen was used as the adsorbate, and nitrogen adsorption and desorption experiments were completed at liquid nitrogen temperature of 77K. The specific surface area value of each sample was accurately calculated by the BET theoretical model. The specific surface area test results of each group of samples were completely recorded and systematically compared.

[0054] II. Particle Size Distribution Detection of Rare Earth Oxide Powders. Test Standard: GB / T19077-2016 "Particle Size Analysis - Laser Diffraction Method". Following this standard, a laser particle size analyzer was used to test the particle size distribution of lanthanum oxide powder prepared in Example 1, cerium oxide powder prepared in Example 2, lanthanum-yttrium composite rare earth oxide powder prepared in Example 3, and rare earth oxide powders obtained in Comparative Examples 1-5. Before testing, all powder samples were added to anhydrous ethanol and ultrasonically dispersed for 5 minutes to prepare a uniformly dispersed suspension. The instrument's light-blocking factor was set to 10% to 15%, and the test wavelength was 632.8 nm. The tests were performed on each group of samples sequentially, and the volume average particle size and D0 were obtained. 50 Particle size data were recorded and compared to determine the particle size and uniformity of distribution for each group of samples.

[0055] III. Purity Testing of Rare Earth Oxide Powders. The testing standard is GB / T12690-2022, "Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) for Non-Rare Earth Impurities in Rare Earth Metals and Their Oxides." Following this standard, ICP-AES was used to test the purity of lanthanum oxide powder prepared in Example 1, cerium oxide powder prepared in Example 2, lanthanum-yttrium composite rare earth oxide powder prepared in Example 3, and rare earth oxide powders obtained in Comparative Examples 1-5. 0.1 g of each powder sample was accurately weighed and microwave-digested using a mixed solution of nitric acid and hydrogen peroxide. After complete digestion, the solution was brought to a final volume to prepare the test solution. The instrument's RF power was set to 1150 W, and the carrier gas flow rate was 0.8 L / min. The content of non-rare earth impurities in the samples was measured. The purity values ​​of each group of rare earth oxide powders were calculated using the difference method. The purity test results of each group of samples were recorded and compared.

[0056] Table 1: Experimental Data for Performance Testing of Rare Earth Oxide Powders

[0057] As can be seen from Examples 1-3 and Comparative Example 1, and Table 1, the three-in-one in-situ coupling reaction mode allows microchannel mixing, ultrasonic action and microwave action to form spatiotemporal synergy. The segmented series reaction will destroy the matching relationship between the three fields. The spatiotemporal fragmentation of the reaction process will directly change the process of precursor generation and crystallization. Synchronous in-situ coupling is the core condition to ensure the stability of the system reaction.

[0058] As can be seen from Examples 1-3 and Comparative Example 2, and Table 1, the microchannel reaction unit can achieve rapid and uniform mixing and efficient mass transfer of materials. Replacing it with a conventional stirred reactor would lose the basic conditions for uniform nucleation. Differences in the mixing state would affect the evolution path of the precursor. The microchannel structure plays a key role in ensuring uniform reaction of materials in the system.

[0059] As can be seen from Examples 1-3 and Comparative Example 3 and Table 1, the timing overlap of the peak times of the ultrasonic pulse and the microwave electric field can enhance the coupling effect of the two fields. The staggered peak times will weaken the synergistic effect of ultrasound and microwave. The matching state of the field effect timing will directly affect the nucleation and crystallization process of the precursor. Timing synchronization is an important prerequisite for achieving deep coupling of the two fields.

[0060] As can be seen from Examples 1-3 and Comparative Example 4, and Table 1, the synchronous matching of the system heating rate and the ultrasonic power increase rate allows the heating and anti-agglomeration processes to continue to work in synergy. Eliminating the linkage between the two will disrupt the dynamic equilibrium of the reaction process. The synergistic state of temperature increase and ultrasonic action will affect the synchronous advancement of precursor crystallization and dispersion. Synchronous parameter control can maintain the stable synergy of the reaction process.

[0061] As can be seen from Examples 1-3 and Comparative Example 5, and Table 1, multi-parameter synchronous linkage closed-loop control can adapt to the dynamic changes of the reaction system. Single-parameter independent adjustment cannot meet the synergistic control requirements of the system. The synergy of the control method will affect the operational stability of the reaction system. Synergistic linkage control is an important way to ensure uniform and controllable reaction throughout the entire process.

[0062] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a three-dimensional coupled and strengthened rare earth oxide, characterized in that: This is based on an in-situ coupled ultrasonic-microwave-microchannel co-cavity reactor, wherein the reactor is an integrated device that combines a microchannel reaction unit, an ultrasonic unit, and a microwave heating unit in the same sealed cavity. The preparation method includes the following steps: S1. Raw material preparation: Prepare rare earth salt solution and precipitant separately; S2. Parameter preset: The operating parameters of the ultrasonic unit, microwave heating unit and feeding unit of the reactor are preset. The pulse period of the ultrasonic and microwave is set to be the same, and the microwave output power and ultrasonic power are matched according to the preset linear relationship. At the same time, the feed flow rate is set to regulate the material flow state in the microchannel reaction module. S3, Coupling Reaction: The prepared rare earth salt solution and precipitant are directly fed into the microchannel reaction module of the reactor through a dual plunger metering pump according to a preset molar ratio. The ultrasonic unit and microwave heating unit are activated simultaneously, so that the ultrasonic action, microwave action and the mixing reaction process in the microchannel reaction module are carried out in situ and synchronously in the same cavity. S4. Closed-loop control: Real-time detection of pH, temperature, conductivity and crystal nucleus size data of the reaction system through online sensors, and synchronous adjustment of the feed parameters of the two feed units, the operating parameters of the ultrasonic unit and the operating parameters of the microwave heating unit based on the detection data. S5. Product collection: The reaction slurry output from the reactor is subjected to solid-liquid separation, washing, drying and calcination to obtain rare earth oxide powder products.

2. The method for preparing a three-in-one coupled and strengthened rare earth oxide according to claim 1, characterized in that: In step S1, the concentration of the rare earth salt solution is controlled at 0.5-1 mol / L, the concentration of the precipitant is controlled at 0.75-1.5 mol / L, and the molar ratio of the precipitant to rare earth ions is set according to the type of precipitant. Specifically, the molar ratio of the oxalic acid and sodium carbonate precipitation system is 1.5-1.8:1, the molar ratio of the ammonium bicarbonate precipitation system is 3.0-3.6:1, and the molar ratio of the urea precipitation system is 3.0-10:

1.

3. The method for preparing a three-in-one coupled and strengthened rare earth oxide according to claim 1, characterized in that: In step S1, the rare earth salt solution is prepared using one of the following: a single rare earth nitrate, a single rare earth chloride, a mixed rare earth nitrate, or a mixed rare earth chloride. The precipitant is prepared using one or more of the following: oxalic acid, ammonium bicarbonate, sodium carbonate, and urea.

4. The method for preparing a three-in-one coupled and strengthened rare earth oxide according to claim 1, characterized in that: In step S2, the feed flow rate is set to make the Reynolds number of the material in the microchannel reaction module 2000-8000, the pulse frequency of the ultrasonic unit is set to 10-50kHz, and the pulse duty cycle is set to 30-70%.

5. The method for preparing a three-in-one coupled and strengthened rare earth oxide according to claim 1, characterized in that: In step S2, the pulse frequency and pulse duty cycle of the microwave heating unit are the same as those of the ultrasonic unit, and the peak time of the ultrasonic pulse coincides with the peak time of the microwave electric field in time through the pulse synchronization trigger module; the linear matching relationship between the microwave output power and the ultrasonic power is that the microwave output power increases linearly with the increase of the ultrasonic power.

6. The method for preparing a three-in-one coupled and strengthened rare earth oxide according to claim 1, characterized in that: In step S2, the residence time of the material in the microchannel reaction module is controlled by adjusting the feed flow rate so that the residence time is an integer multiple of the pulse period of the ultrasonic unit and the pulse period of the microwave unit.

7. The method for preparing a three-in-one coupled and strengthened rare earth oxide according to claim 1, characterized in that: In step S3, the temperature of the reaction is controlled to be 60-180℃ by microwave selective heating, and the heating rate of the system is matched with the ultrasonic power boosting rate during the reaction; the heating rate of the system and the ultrasonic power boosting rate are linearly positively correlated.

8. The method for preparing a three-dimensional coupled and strengthened rare earth oxide according to claim 1, characterized in that: In step S4, the linkage adjustment method is as follows: when the precursor crystal nucleus particle size is detected online to be larger than the particle size threshold, the ultrasonic power and microchannel feed flow rate are increased simultaneously, and the microwave output power and pulse frequency are adjusted accordingly; when the pH value of the system deviates from the range, the flow ratio of the two feeds and the microwave heating temperature are adjusted simultaneously, and the pulse duty cycle of the ultrasonic wave is adjusted accordingly; the particle size threshold is 50-200nm, and the pH value range is set according to the system type as follows: oxalic acid precipitation system 1.5-2.0, ammonium bicarbonate precipitation system 6-7, sodium carbonate precipitation system 6-7, urea mineralization system 5.5-6.

9. A three-in-one coupled and strengthened rare earth oxide preparation apparatus, characterized in that, The method for preparing a three-in-one coupled and strengthened rare earth oxide according to any one of claims 1-8 includes a pressure shell (1), a control module (2) is provided on the upper surface of the pressure shell (1), a first microwave heating unit (3), a first ultrasonic unit (4) and a support block (5) are fixedly connected to the inner wall of the pressure shell (1), a support plate (6) is fixedly connected to the lower surface of the support block (5), a microchannel reaction module (9) is provided on the lower surface of the support plate (6), a second microwave heating unit (7) and a second ultrasonic unit (8) are fixedly connected inside the support plate (6), an inlet (10) is provided at one end of the microchannel reaction module (9) and an outlet (12) is provided at the other end, a double plunger metering pump (11) is fixedly connected to the outer wall of the microchannel reaction module (9), and the outer wall of the microchannel reaction module (9) is fixedly connected to the inside of the support plate (6) and the pressure shell (1).

10. The apparatus for preparing a three-in-one coupled and strengthened rare earth oxide according to claim 9, characterized in that: The first microwave heating unit (3) and the second microwave heating unit (7) are used to form a uniform microwave resonant field covering the entire flow channel of the microchannel reaction module (9), and form a coupling enhancement zone that spatially overlaps with the ultrasonic field; the first ultrasonic unit (4) and the second ultrasonic unit (8) are used to form a uniform ultrasonic focusing field covering the entire flow channel of the microchannel reaction module (9), and are used to synchronously suppress precursor crystal nuclei agglomeration; the control module (2) is used to synchronously regulate the operating parameters of the first microwave heating unit (3), the second microwave heating unit (7), the first ultrasonic unit (4), and the second ultrasonic unit (8) and the feeding parameters of the dual plunger metering pump (11), and is used to realize the synchronous timing of dual-field pulses and the multi-parameter linkage closed-loop control of the entire reaction process.

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