Efficient synthesis and decomposition process for preparing high-purity magnesium
By employing a catalytic-dynamic hydrogenation synthesis and a staged vacuum disproportionation purification and decomposition process, the problems of slow synthesis rate of magnesium hydride intermediates and poor coupling between decomposition and purification were solved, thus achieving high-efficiency, low-energy-consumption preparation of high-purity magnesium.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-28
- Publication Date
- 2026-04-14
AI Technical Summary
Existing technologies make it difficult to efficiently synthesize high-purity magnesium hydride intermediates, and the decomposition and purification processes of magnesium hydride are poorly coupled, resulting in low production efficiency and high energy consumption.
A catalytic-dynamic hydrogenation synthesis and staged vacuum disproportionation purification and decomposition process is adopted. By using a composite catalyst in a dynamic hydrogenation reactor for hydrogenation reaction, followed by staged decomposition and fractionation purification in a vacuum disproportionation furnace, the efficient synthesis and decomposition of magnesium hydride intermediates are achieved.
It significantly improves the synthesis rate and purity of magnesium hydride, simplifies the process, reduces energy consumption, and achieves efficient online separation through the difference in impurity vapor pressure, thereby improving production efficiency and equipment integration.
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Figure CN121847787A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic material synthesis and metallurgical engineering, specifically relating to an efficient synthesis and decomposition process for preparing high-purity magnesium. Background Technology
[0002] High-purity magnesium (≥99.99%) is a core raw material for high-end magnesium alloys, semiconductor sputtering targets, and high-value-added chemicals. The primary magnesium produced by traditional silicothermic reduction and electrolysis methods typically has a purity of 99.5%–99.8%, which is insufficient for high-end applications. Currently, industrial production of high-purity magnesium mainly relies on vacuum distillation, which involves vaporizing crude magnesium at temperatures above 1100°C under high vacuum, followed by condensation and purification. This method is extremely energy-intensive, requires complex equipment, struggles to separate impurities with similar vapor pressures to magnesium (such as zinc and cadmium), and limits production capacity.
[0003] As an important functional material, magnesium hydride is an excellent hydrogen storage medium and chemical reducing agent. In recent years, the route of purifying magnesium using magnesium hydride as an intermediate has attracted widespread attention. The principle is to use the difference in hydrogenation behavior between magnesium and impurity elements for preliminary separation, and then obtain relatively pure magnesium through the low-temperature decomposition of magnesium hydride. However, existing technologies have two major bottlenecks: First, the synthesis rate of magnesium hydride is slow and the cost is high. The traditional static autoclave hydrogenation method has a slow reaction rate and long cycle, and the product is prone to agglomeration and incomplete hydrogenation. While the "one-pot" mechanical ball milling hydrogenation technology borrowed from the field of hydrogen storage materials can achieve continuous production on a certain scale (such as a 150-ton / year demonstration line), the purity of its products (mostly 90-99%) and reactivity as a precursor for high-purity magnesium are still insufficient, and impurities introduced by the wear of the ball milling media are difficult to avoid. Second, the decomposition and purification of magnesium hydride have poor coupling. Existing processes typically treat the synthesis and decomposition of magnesium hydride as two separate unit operations. The decomposition process is mostly carried out at a single temperature, failing to fully utilize the difference in saturated vapor pressure between the magnesium vapor and impurity vapor generated during decomposition for real-time online separation. This results in low purification efficiency and requires complex refining steps in the subsequent process.
[0004] Therefore, it is of great significance to develop an integrated process that can efficiently synthesize high-quality magnesium hydride intermediates and deeply couple the decomposition and purification processes. Summary of the Invention
[0005] In view of the above problems, the present invention provides an efficient synthesis and decomposition process for preparing high-purity magnesium, which can efficiently synthesize high-quality magnesium hydride intermediates and achieve deep coupling of magnesium hydride intermediate decomposition and purification.
[0006] The technical solution adopted by this invention to solve its technical problem is:
[0007] A first aspect of the present invention provides an efficient synthesis and decomposition process for preparing high-purity magnesium, comprising the following steps:
[0008] S1. Catalytic-dynamic hydrogenation synthesis: The pretreated crude magnesium raw material is uniformly mixed with the composite catalyst and then fed into a dynamic hydrogenation reactor. Under a hydrogen atmosphere, the hydrogenation reaction is carried out for 2 to 12 hours at a pressure of 1.5~4.0 MPa and a temperature of 250~400℃. During the reaction, pneumatic fluidization or mechanical stirring is carried out to obtain magnesium hydride intermediate.
[0009] S2. Staged Vacuum Disproportionation Purification and Decomposition: The magnesium hydride intermediate obtained in step S1 is transferred to a vacuum disproportionation furnace, and vacuum is applied until the system pressure does not exceed 5 × 10⁻⁶. -2 Pa establishes a stable temperature gradient from a high-temperature zone to a low-temperature zone in the vacuum disproportionation furnace, causing the magnesium hydride intermediate to undergo disproportionation decomposition in the high-temperature zone. The generated magnesium vapor and hydrogen are fractionated and purified during the transfer to the low-temperature zone to obtain high-purity magnesium vapor. The temperature of the high-temperature zone is 380~450℃, and the temperature of the low-temperature zone is 300~350℃.
[0010] S3. Condensation and Collection: The high-purity magnesium vapor obtained in step S2 is guided to a low-temperature condensation chamber and condensed at a temperature of 50~280℃ under an inert atmosphere to collect the high-purity magnesium.
[0011] Further, in step S1, the pretreatment of the crude magnesium raw material includes surface cleaning, particle size control, and pre-composite with the composite catalyst; the composite catalyst is a complex formed by a transition metal halide supported on a porous carbon support, and its addition amount is 0.1~5.0% of the mass of the crude magnesium raw material; the transition metal halide is selected from at least one of TiF3, NbF5, and VCl3, and the porous carbon support is selected from at least one of activated carbon, carbon nanotubes, and graphene; the dynamic hydrogenation reaction device in step S1 is a stirred ball mill reactor, a fluidized bed reactor, or a rotary kiln with built-in crushing function. Before use, crude magnesium raw materials need to be pretreated. Pretreatment methods include surface cleaning to remove harmful layers from the surface of crude magnesium particles and expose fresh, highly reactive metallic magnesium surfaces; particle size control, which involves mechanically crushing or grinding the crude magnesium raw materials to a particle size range of 150~500μm under an inert atmosphere (nitrogen or argon) and mechanically stripping the oxide layer from the surface of the crude magnesium raw materials; and pretreatment methods also include using a composite catalyst (typically TiF3 / porous carbon) with highly catalytically active transition metal halides and porous carbon supports to pre-composite with the crude magnesium raw materials to improve their reactivity. This invention involves mixing pretreated crude magnesium raw material with a composite catalyst to ensure that the composite catalyst particles are highly dispersed on the surface of the raw material particles, and then adding the mixture into a dynamic hydrogenation reaction device (such as a high-pressure reactor with stirring and grinding media). Subsequently, the hydrogenation reaction is carried out under relatively mild pressure conditions (1.5~4.0MPa), temperature conditions (250~400℃), and a hydrogen atmosphere. During the reaction, pneumatic fluidization or mechanical stirring is carried out to obtain a highly active magnesium hydride intermediate. In this process, some impurities (such as Fe, Al, Si, etc.) are initially fixed in the hydrogenation step, forming unstable hydrides, which can initially separate some impurities in the crude magnesium raw material, so that the impurity content of the magnesium hydride intermediate is <500ppm; the composite catalyst (such as TiF3 / porous carbon, etc.) provides highly active sites, which can significantly reduce the energy barrier of hydrogen molecule dissociation and hydrogen atom diffusion in hydrogen gas; during the reaction, the dynamic mixing of continuous pneumatic fluidization or mechanical stirring (such as stirring, grinding) can break the dense film on the surface of the generated magnesium hydride in real time, continuously exposing fresh magnesium reaction interface, so that hydrogen gas can continuously penetrate, thereby achieving deep and rapid complete hydrogenation. The method provided by step S1 can achieve a hydrogenation rate of more than 98% in a short time (hydrogenation reaction time 2~12h), and the obtained magnesium hydride intermediate particles are small, highly active, and the impurity content (such as Fe, Cr, etc.) is significantly lower than that of pure mechanical ball milling. The main chemical reaction formula of step S1 is shown in the following formula (1):
[0012] (Reaction 1)
[0013] Further, in step S2, the vacuum disproportionation furnace is a multi-temperature zone tubular furnace arranged horizontally or vertically; in step S2, the hydrogen gas discharged from the vacuum disproportionation furnace is treated with dust removal, drying, and purification to a purity of not less than 99.99% and a dew point not higher than -60°C, and then recovered and recycled for the hydrogenation reaction in step S1. This invention does not involve simple thermal decomposition in a uniform temperature field, but rather designs a vacuum disproportionation furnace with precisely controlled temperature gradients. The magnesium hydride intermediate is fed into the vacuum disproportionation furnace for reaction through a vacuum lock hopper. Based on the difference in saturated vapor pressure between impurities and magnesium vapor, staged sublimation separation between magnesium vapor and impurities is achieved during the migration of the mixed vapor from the high-temperature zone to the low-temperature zone. First, the magnesium hydride intermediate undergoes rapid disproportionation decomposition in the high-temperature zone (380~450℃), producing magnesium vapor and hydrogen gas. During this decomposition, various impurities (such as MgCl2 and some metallic impurities) are released or volatilized. Then, as the magnesium vapor and hydrogen gas generated from the decomposition of the magnesium hydride intermediate are transported to the low-temperature zone (300~350℃), high-boiling-point impurities (such as Fe, Al and their compounds) preferentially condense and precipitate in the slightly higher temperature zone and adhere to the furnace wall of the vacuum disproportionation furnace, while low-boiling-point impurities (such as alkali metals) condense and precipitate in the slightly lower temperature zone. The magnesium vapor, however, can migrate further to reach the even lower temperature zone, thus achieving the fractionation and purification of the target magnesium vapor, ultimately yielding high-purity magnesium vapor. The ultimate vacuum environment (system pressure not exceeding 5×10⁻⁶) is crucial. -2 Pa) can reduce the partial pressure of magnesium vapor, promote the decomposition reaction to the right; at the same time, it reduces the obstruction of other molecules to vapor transport, making it migrate in a near-molecular flow state; it can also eliminate the pollution of impurity gases such as oxygen. This step couples disproportionation decomposition, vapor transport and fractionation purification online and completes them simultaneously in the same vacuum disproportionation furnace, abandoning the traditional multi-step process of "decomposition-condensation-re-distillation", and efficiently completing the direct conversion and purification from magnesium hydride intermediate to high-purity magnesium vapor, significantly shortening the process flow and improving product purity, production efficiency and equipment integration. The main chemical reaction formula of step S2 is shown in the following formula (2):
[0014] (Reaction 2)
[0015] Further, in step S3, the low-temperature condensation chamber is equipped with a water-cooled or air-cooled jacket to control the condensation temperature. In this step, the high-purity magnesium vapor obtained in step S2 is guided to the low-temperature condensation chamber and condensed at a temperature of 50~280℃ under an inert atmosphere, collecting the high-purity magnesium. In this step, by precisely controlling the water-cooled or air-cooled jacket of the low-temperature condensation chamber, the condensation surface temperature of the chamber is controlled, thereby allowing for the directional collection of high-purity magnesium in different forms. If high-purity magnesium ingots are desired, the condensation surface temperature can be controlled below the melting point of magnesium (650℃) and above the recrystallization temperature (e.g., 200~400℃), allowing the high-purity magnesium vapor to slowly condense into a dense mass. If high-purity magnesium powder, as a precursor for plasma refining, is desired, the condensation surface temperature can be controlled at 50~150℃ for rapid cooling, causing the high-purity magnesium vapor to form dendritic or granular powder. This step is closely integrated with the preceding staged vacuum disproportionation purification and decomposition steps to ensure effective capture and morphology control of the high-purity magnesium vapor.
[0016] Furthermore, the magnesium hydride intermediate has a hydrogenation rate of not less than 98%, a total impurity element content of less than 500 ppm, and a particle size of 10-500 nm. The magnesium hydride intermediate prepared by this invention can be used to prepare high-purity magnesium metal, magnesium-based hydrogen storage materials, or as a chemical reducing agent.
[0017] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:
[0018] This invention combines catalytic-dynamic hydrogenation synthesis with staged vacuum disproportionation purification and decomposition, achieving efficient conversion from crude magnesium feedstock to high-purity magnesium in a single continuous process. The process significantly enhances the rate and depth of the hydrogenation reaction through the synergistic effect of catalysis and dynamic mixing. Simultaneously, it creatively integrates three key steps—disproportionation decomposition, magnesium vapor transport, and fractionation purification—within the same vacuum disproportionation furnace, achieving spatial coupling and continuous operation of the reaction and separation processes. This design not only greatly simplifies the process flow but also significantly improves production efficiency and equipment integration by synergistically combining high-temperature decomposition and gradient condensation, thereby increasing product purity. The entire process is dry, with no wastewater discharge, and achieves efficient purification and recycling of reaction byproduct hydrogen, reducing feedstock gas consumption and enhancing the greenness of the process. Compared to traditional distillation methods, this process significantly reduces energy consumption, and by flexibly adjusting condensation conditions, it can directly obtain lumpy or powdered magnesium products suitable for different downstream refining needs, demonstrating excellent process adaptability and application flexibility. Attached Figure Description
[0019] Figure 1 This is a process flow diagram of the efficient synthesis and decomposition process for preparing high-purity magnesium according to the present invention. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0021] The term "comprising" as used in this application is an open-ended inclusion, meaning "including but not limited to". The term "according to" means "at least in part according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment". Definitions of other terms will be given in the description below.
[0022] Example 1
[0023] This embodiment provides an efficient synthesis and decomposition process for preparing high-purity magnesium, the process flow of which is as follows: Figure 1 As shown, the specific steps include:
[0024] S1. Catalytic-Dynamic Hydrogenation Synthesis: 1 kg of 99.5% pure magnesium powder (particle size ~150 mesh) was mixed evenly with 20 g of a composite catalyst supported on 10 wt% TiF3 activated carbon in an argon glove box; the mixture was then loaded into a high-pressure stirred reactor equipped with a stirring paddle and zirconia grinding balls; after sealing, the reactor was purged with hydrogen three times, and hydrogen was introduced to an initial pressure of 2.0 MPa; stirring was started (200 rpm) and the temperature was raised to 320℃; during the reaction, the stirring paddle continuously ground the material with the grinding balls; after holding the reaction at the same temperature and pressure for 5 h, the mixture was cooled to room temperature to obtain a gray powdery magnesium hydride intermediate; sample analysis showed a hydrogenation rate of 98.7%;
[0025] S2. Staged Vacuum Disproportionation Purification and Decomposition: The above-mentioned magnesium hydride intermediate is loaded into a quartz boat and pushed into the high-temperature zone (set to 400°C) of a horizontal tubular vacuum decomposition furnace; a baffle is installed in the middle of the furnace tube, and the subsequent zone is maintained at 300°C; the system is evacuated to 1×10⁻⁶. -2 Pa; the temperature is increased to 400℃ at 10℃ / min and held for 2h; magnesium hydride decomposes, and magnesium vapor migrates to the low temperature region of 300℃ to obtain high-purity magnesium vapor;
[0026] S3. Condensation and Collection: The high-purity magnesium vapor obtained in step S2 is guided to the low-temperature condensation chamber and condensed on the inner wall of the water-cooled jacket condensation section at a temperature of about 50°C under the protection of an inert atmosphere. About 0.94 kg of silvery-white metallic magnesium condensate is collected, which is high-purity magnesium.
[0027] Results analysis: ICP-MS analysis showed that the purity of high-purity magnesium reached 99.93%, which was significantly improved compared to the purity of crude magnesium raw material (99.5%). Among them, the contents of typical catalytic impurity elements such as Fe and Ni were all below 20 ppm, proving that the staged vacuum disproportionation purification and decomposition process effectively separated impurities.
[0028] Example 2: Catalyst Optimization
[0029] The experimental conditions were the same as in Example 1, except that the composite catalyst in step S1 was replaced with 15g of NbF5 / carbon nanotube composite material, the hydrogenation reaction pressure was increased to 2.8MPa, the reaction temperature was 300℃, and the reaction time was shortened to 3.5h.
[0030] Results analysis: The hydrogenation rate of the magnesium hydride intermediate was 99.1%; the high-purity magnesium obtained after decomposition had a purity of 99.94%, and the yield was slightly higher than that in Example 1, indicating that the NbF5 / CNT catalyst system has better catalytic performance.
[0031] Example 3: Refining the decomposition temperature gradient
[0032] The experimental conditions were the same as in Example 1, except that the temperature zones of the vacuum disproportionation furnace in step S2 were set as follows: high temperature zone 420℃, medium temperature zone 350℃, and low temperature zone 250℃. Magnesium hydride decomposes at 420℃, which is expected to be more conducive to the separation of medium- and high-boiling-point impurities.
[0033] Results analysis: A small amount of grayish-white condensate (enriched with Al and Ca) was observed on the inner wall of the furnace tube in the medium temperature zone of 350℃. The purity of high-purity magnesium collected below 250℃ increased to 99.95%. This indicates that a finer temperature gradient is beneficial for the segmented collection of impurities and improves the purity of the main product.
[0034] Example 4: Preparation of high-purity magnesium powder
[0035] The experimental conditions were the same as in Example 1, except that the condensation conditions in step S3 were adjusted: a quench chamber filled with high-purity argon was connected to the outlet of the vacuum disproportionation furnace, and a rotating condenser drum cooled by liquid nitrogen (surface temperature -80°C) was installed inside the chamber.
[0036] Results: High-purity magnesium vapor rapidly condenses on an extremely cold surface to obtain loose, porous dendritic magnesium powder with a wide particle size distribution (0.1~10μm). This powder has a large specific surface area and high activity, making it very suitable as a high-quality raw material for subsequent plasma refining to prepare nano-magnesium powder.
[0037] Example 5: Simulated Semi-continuous Scale-up Experiment
[0038] This embodiment simulates a scaled-up process flow, using a small rotary kiln with built-in lifting plates to simulate continuous dynamic hydrogenation, with a processing capacity of 5 kg / batch. The specific steps include:
[0039] S1. Catalytic-dynamic hydrogenation synthesis: In a rotary kiln, crude magnesium feedstock and composite catalyst react at 320℃ and 2.5 MPa hydrogen pressure for 4 hours;
[0040] S2. Staged vacuum disproportionation purification and decomposition: Magnesium hydride intermediates are continuously fed into a vertical multi-temperature zone vacuum decomposition furnace for decomposition from top to bottom;
[0041] S3. Condensation and Collection: The hydrogen produced by decomposition is purified by dust removal and low-temperature adsorption, then mixed with the replenished hydrogen and recompressed and fed back to the rotary kiln as reaction gas.
[0042] Results analysis: The system operated stably with a hydrogen recycling rate exceeding 85%; batch product consistency was good, and the average purity of crude magnesium remained stable at 99.94% ± 0.01%; verifying the feasibility of continuous operation and material recycling of this process.
[0043] Test method:
[0044] (1) The purity of the product was tested by inductively coupled plasma mass spectrometry (ICP-MS);
[0045] (2) The hydrogenation rate of magnesium hydride intermediates was tested by gravimetric method (hydrogen absorption weight gain) / XRD phase quantitative analysis method;
[0046] (3) The decomposition initiation temperature was determined by differential scanning calorimetry (DSC);
[0047] (4) Hydrogen storage capacity was tested using the pressure-composition-isotherm method;
[0048] (5) Test the hydrogen recovery rate using a gas flow meter.
[0049] Performance verification:
[0050] (1) Demonstration of hydrogenation rate: The hydrogenation rate was measured by gravimetric method to be ≥98%, and the reaction time was shortened to 2~4h. This is because the supported nanocatalyst (such as TiF3 / porous carbon) provides high active sites, and the dynamic mixing of the dynamic hydrogenation reaction device (such as fluidized bed with internal breakage) continuously updates the surface of magnesium particles, preventing the dense layer on the surface of hydride magnesium from being wrapped, thus minimizing the hydrogen diffusion resistance. The two work together to accelerate the reaction rate of hydrogenation reaction.
[0051] (2) Purity and initial decomposition temperature of high-purity, high-activity magnesium hydride intermediates: The total impurity content of magnesium hydride intermediates was <500ppm as measured by ICP-MS. This is due to two aspects of purification: First, some impurities (such as Al, Si, etc.) do not form stable hydrides under hydrogenation conditions, thus achieving initial separation; second, this process avoids wear impurities such as iron and chromium introduced by traditional high-energy ball milling. The initial decomposition temperature of magnesium hydride intermediates was found to be as low as about 200℃ as measured by DSC. The low decomposition temperature is due to the "high-activity state" of magnesium hydride intermediates: the induction of composite catalysts and the fine grains and numerous defects of magnesium hydride intermediates produced by dynamic synthesis jointly reduce the energy barrier of the decomposition reaction, which is conducive to the low-temperature decomposition of magnesium hydride intermediates.
[0052] (3) High-efficiency decomposition and simultaneous purification: The purity of high-purity magnesium was measured to be ≥99.95% by ICP-MS, which fully demonstrates the advantages of integrating the three key steps of disproportionation decomposition, magnesium vapor transport and fractionation purification into the same vacuum disproportionation furnace. The precise temperature gradient between the high-temperature zone and the low-temperature zone is established in the vacuum disproportionation furnace, which not only drives the decomposition of magnesium hydride, but also utilizes the difference in saturated vapor pressure between magnesium vapor and different impurity vapors to achieve gradient condensation separation during the migration process.
[0053] (4) Comprehensive techno-economic analysis: The product performance and cost of the preparation process of this invention are significantly better than those of the existing technical routes, as shown in Table 1:
[0054] Compared to other technologies, the synthesis rate of magnesium hydride in this invention is increased by 2-3 times, and the decomposition activity of magnesium hydride intermediates is significantly improved (the starting temperature is reduced by about 80°C), laying the foundation for continuous and low-energy operation of the entire process.
[0055] This invention integrates three key steps—disproportionation decomposition, magnesium vapor transport, and fractionation purification—into a single vacuum disproportionation furnace, achieving spatial coupling and continuous operation of the reaction and separation processes. During decomposition, the difference in saturated vapor pressure between impurities and the main product removes most impurities, increasing the purity of the produced high-purity magnesium to over 99.95%, significantly reducing subsequent refining costs.
[0056] The hydrogen recycling rate of this invention is ≥85%, which significantly reduces the cost of raw material gas.
[0057] Table 1 Comparison between the present invention and traditional methods
[0058] Comparison Projects Traditional vacuum distillation method (for producing high-purity magnesium) <![CDATA["One-pot" mechanical hydrogenation (for the production of MgH2 for hydrogen storage)]]> <![CDATA[The present invention (MgH2 intermediate for producing high-purity magnesium)]]> Core Technology Physical phase transition (melting-vaporization-condensation) Mechanically assisted hydrogenation (Target: Hydrogen storage materials) Catalysis-dynamic hydrogenation + staged decomposition and purification (target: high-purity magnesium precursor) Key conditions >1100℃, high vacuum Ball milling at room temperature to 400℃ under medium and high pressure for extended periods. Hydrogenation occurs at around 300℃, decomposition at around 400℃, under medium vacuum. Product Form High-purity magnesium ingots / powder Magnesium hydride powder (purity 90-99%) Highly active magnesium hydride intermediate → High-purity crude magnesium ingots / powder Impurity control Ineffective against impurities with similar vapor pressures, and susceptible to equipment contamination. Ball milling introduces impurities such as Fe and Cr, limiting purity. Preliminary hydrogenation separation + gradient decomposition and online fractionation for targeted impurity removal Energy consumption level Extremely high (maintaining high temperature and high vacuum) Medium (mechanical energy + thermal energy) Low (medium temperature reaction, coupled purification and energy saving) Hydrogen utilization Not involved Single use or simple recycling Highly efficient purification and closed-loop circulation, with a utilization rate >85%. Economic evaluation Large equipment investment and extremely high operating costs Suitable for large-scale production of hydrogen storage materials, but with limited contribution to improving purity. The investment and operating costs are far lower than those of the vacuum method, providing a low-cost precursor for the preparation of high-purity magnesium, making it highly economical.
[0059] In summary, this invention provides a novel, efficient, and green process focused on the synthesis and conversion of magnesium hydride intermediates. It is not only an innovation in magnesium hydride preparation technology but also opens up a new, low-energy-consumption, low-cost raw material route for the high-purity magnesium smelting industry, possessing significant industrial application value.
[0060] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
Claims
1. A highly efficient synthesis and decomposition process for preparing high-purity magnesium, characterized in that, Includes the following steps: S1. Catalytic-dynamic hydrogenation synthesis: The pretreated crude magnesium raw material is uniformly mixed with the composite catalyst and then fed into a dynamic hydrogenation reactor. Under a hydrogen atmosphere, the hydrogenation reaction is carried out for 2 to 12 hours at a pressure of 1.5~4.0 MPa and a temperature of 250~400℃. During the reaction, pneumatic fluidization or mechanical stirring is carried out to obtain magnesium hydride intermediate. S2. Staged Vacuum Disproportionation Purification and Decomposition: The magnesium hydride intermediate obtained in step S1 is transferred to a vacuum disproportionation furnace, and vacuum is applied until the system pressure does not exceed 5 × 10⁻⁶. -2 Pa establishes a stable temperature gradient from a high-temperature zone to a low-temperature zone in the vacuum disproportionation furnace, causing the magnesium hydride intermediate to undergo disproportionation decomposition in the high-temperature zone. The generated magnesium vapor and hydrogen are fractionated and purified during the transfer to the low-temperature zone to obtain high-purity magnesium vapor. The temperature of the high-temperature zone is 380~450℃, and the temperature of the low-temperature zone is 300~350℃. S3. Condensation and Collection: The high-purity magnesium vapor obtained in step S2 is guided to a low-temperature condensation chamber and condensed at a temperature of 50~280℃ under an inert atmosphere to collect the high-purity magnesium.
2. The efficient synthesis and decomposition process according to claim 1, characterized in that, In step S1, the pretreatment of the crude magnesium raw material includes surface cleaning, particle size control, and pre-composite with the composite catalyst.
3. The efficient synthesis and decomposition process according to claim 1, characterized in that, In step S1, the composite catalyst is a composite formed by supporting a transition metal halide on a porous carbon support, and its addition amount is 0.1~5.0% of the mass of the crude magnesium raw material; the transition metal halide is selected from at least one of TiF3, NbF5, and VCl3, and the porous carbon support is selected from at least one of activated carbon, carbon nanotubes, and graphene.
4. The efficient synthesis and decomposition process according to claim 1, characterized in that, The dynamic hydrogenation reaction device in step S1 is a stirred ball mill reactor, a fluidized bed reactor, or a rotary kiln with built-in crushing function.
5. The efficient synthesis and decomposition process according to claim 1, characterized in that, In step S2, the vacuum disproportionation furnace is a multi-temperature zone tube furnace arranged horizontally or vertically.
6. The efficient synthesis and decomposition process according to claim 1, characterized in that, In step S2, the hydrogen gas discharged from the vacuum disproportionation furnace is treated with dust removal, drying and purification to a purity of not less than 99.99% and a dew point of not more than -60°C, and then recovered and recycled for the hydrogenation reaction in step S1.
7. The efficient synthesis and decomposition process according to claim 1, characterized in that, In step S3, the low-temperature condensation chamber is equipped with a water-cooled or air-cooled jacket to control the condensation temperature.
8. The efficient synthesis and decomposition process according to claim 1, characterized in that, The hydrogenation rate of the magnesium hydride intermediate is not less than 98%, the total content of impurity elements is less than 500 ppm, and its particle size is 10~500 nm.