Process for producing carbonyl iron powder from ferronickel pellets

Abstract

The application discloses a process method for producing carbonyl iron powder from nickel-iron particles in the technical field of metal powder metallurgy, and the method comprises the following steps: grinding and screening nickel-iron particles and then performing vacuum drying pretreatment; dispersing the pretreated nickel-iron particles in anhydrous ethanol, adding an organic-inorganic hybrid manganese sulfide ammonium molybdate composite activator to perform surface modification, and obtaining modified nickel-iron particles; loading the modified nickel-iron particles into a reaction kettle, introducing carbon monoxide gas, performing a carbonylation reaction by heating, stopping heating, waiting for the reaction kettle to cool down, introducing nitrogen gas for purging, and introducing mixed gas phase into a two-stage condenser system; the mixed gas phase is sequentially cooled by a first-stage cooling to obtain a liquid of iron pentacarbonyl, and then the liquid of iron pentacarbonyl is cooled by a second-stage cooling to obtain a liquid of nickel tetracarbonyl; the liquid of iron pentacarbonyl is gasified after being subjected to vacuum rectification, and then is injected into a thermal decomposition tower for decomposition, so that carbonyl iron powder is obtained. The process is simple, raw materials are easy to obtain, the carbonylation reaction efficiency can be effectively improved, and the product has high purity.

Description

Technical Field

[0001] This invention belongs to the field of metal powder metallurgy technology, specifically relating to a process method for producing carbonyl iron powder from nickel-iron particles. Background Technology

[0002] Carbonyl iron powder possesses excellent properties such as small particle size, high sphericity, and extremely high purity, and has wide applications in powder metallurgy, electromagnetic shielding, microwave absorbing materials, high-density alloys, and soft magnetic composite materials. Currently, the main industrial method for preparing carbonyl iron powder is the Maunder process, which uses sponge iron or iron filings as raw materials to generate pentacarbonyl iron in a high-pressure carbon monoxide atmosphere, followed by thermal decomposition to obtain carbonyl iron powder. In recent years, the technology of directly preparing carbonyl iron powder from nickel-iron particles has attracted attention because nickel-iron particles are widely available, have low cost, and can achieve preliminary separation of iron and nickel during the carbonylation process.

[0003] However, the carbonylation reaction using nickel-iron granules as raw material faces several technical bottlenecks. First, a dense oxide film easily forms on the surface of nickel-iron granules during long-term storage, severely hindering direct contact between carbon monoxide molecules and active metal sites, leading to a prolonged reaction induction period and a low initial reaction rate. Second, the nickel content in the nickel-iron alloy significantly affects the adsorption behavior of carbon monoxide: when the iron content is high, carbon monoxide readily dissociates and adsorbs on the alloy surface, which is beneficial for the carbonylation reaction; however, as the nickel content increases, the distribution of surface active sites changes, and the reaction selectivity decreases. Furthermore, conventional nickel-iron granules have a limited specific surface area and insufficient density of surface active sites, making it difficult to further improve the efficiency of the carbonylation reaction. This typically requires higher reaction pressure and longer reaction times, resulting in higher energy consumption and production costs.

[0004] To promote the carbonylation reaction, researchers have attempted to activate nickel-iron raw materials using sulfur-containing compounds. For example, by co-melting nickel-iron particles with sulfur powder and then atomizing and granulating, a nickel-iron melt with a low sulfur content can be prepared, which can then undergo a carbonylation reaction to obtain iron carbonyl products. However, the solubility of sulfur in the nickel-iron melt is limited and its uniform distribution is difficult to guarantee, leading to unstable activation effects. Other researchers have used hydrogen sulfide gas for sulfidation pretreatment of the nickel-iron particle surface, but this process requires strict control of sulfidation temperature and time, has a narrow operating window, and is highly toxic and corrosive, placing stringent demands on equipment. Recent studies have also explored the use of manganese-based phosphating coatings for surface modification of carbonyl iron powder, but this type of modification mainly targets the subsequent processing of the carbonyl iron powder product, rather than the pretreatment of the raw material. Therefore, developing a pretreatment method that can effectively activate the surface of nickel-iron particles, significantly improve the efficiency of the carbonylation reaction, and is easily industrialized is of significant practical importance for reducing the production cost of carbonyl iron powder, shortening the reaction cycle, and improving product quality. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a process for producing carbonyl iron powder from nickel-iron granules.

[0006] In a first aspect, the present invention provides a process for producing carbonyl iron powder from nickel-iron granules, comprising the following steps: S1. By weight, add 80-120 parts of nickel-iron particles into a ball mill and grind them under argon protection to obtain nickel-iron powder; sieve the nickel-iron powder to obtain sieved nickel-iron powder; vacuum dry the sieved nickel-iron powder under argon protection to obtain pretreated nickel-iron particles. S2. Add 80-120 parts of pretreated nickel-iron particles to 80-120 parts of anhydrous ethanol and disperse by ultrasonication to obtain a dispersion; disperse 3-8 parts of organic-inorganic hybrid manganese iron molybdate composite activator in 8-15 parts of anhydrous ethanol by ultrasonication to obtain a suspension; add the suspension dropwise to the dispersion and stir at room temperature; filter under vacuum to obtain a filter cake; wash the filter cake with anhydrous ethanol to obtain modified nickel-iron particles; dry the modified nickel-iron particles under vacuum to obtain dried modified nickel-iron particles; S3. Load 80-120 parts of dried modified nickel-iron granules into a reactor; introduce CO gas into the reactor to replace the air; after the gas replacement is completed, introduce 100-300 parts of CO gas into the reactor and heat to 174-176℃ to react; stop heating; wait for the reactor to cool down to 110-150℃; introduce nitrogen gas into the reactor for purging; introduce the mixed gas phase in the reactor into a two-stage condenser system to obtain the mixed gas phase introduced into the two-stage condenser system; S4. The mixed gas phase introduced into the two-stage condenser system is cooled at 50-60℃ to obtain pentacarbonyl iron liquid and uncondensed residual gas; then the uncondensed residual gas is cooled at -10-0℃ to obtain tetracarbonyl nickel liquid; the pentacarbonyl iron liquid is vaporized by vacuum distillation and sent to a vaporizer at 110-130℃, and then injected into a thermal decomposition tower for decomposition at 280-320℃.

[0007] The process for producing carbonyl iron powder using nickel-iron particles in this invention is a complex metallurgical system integrating mechanochemistry, interfacial catalysis, gas-solid phase thermodynamic selectivity, and gas-liquid phase change separation. The process begins by adding nickel-iron particles to a ball mill and subjecting them to high-intensity grinding under argon protection. The intense mechanical impact and shearing action thoroughly peels away the dense passivated oxide film on the particle surface, exposing fresh metal crystal faces with extremely high surface energy, resulting in finely sized and clean nickel-iron powder. This powder is then sieved and vacuum-dried to remove trace amounts of moisture, yielding highly active pretreated nickel-iron particles. In the subsequent coating stage, the pretreated nickel-iron particles are mixed with anhydrous ethanol to form a dispersion. Utilizing the localized transient high energy generated by ultrasonic cavitation, the pre-dispersed organic-inorganic hybrid manganese iron molybdate composite activator suspension is uniformly and firmly added and anchored onto the clean metal particle surface. The filter cake was then obtained by vacuum filtration, washed with anhydrous ethanol, and vacuum dried. The resulting dried modified nickel-iron particles exhibited extremely high catalytic activity. In this state, the organic-inorganic hybrid manganese iron molybdate composite activator played a crucial dual role in physical anti-agglomeration and chemical catalysis: the organic ligands grafted onto its outer layer effectively blocked the secondary agglomeration of highly active metal particles under heating conditions by utilizing steric hindrance, ensuring the complete unobstructed gas-solid mass transfer channel; the composite multi-metal sulfide network in its core continuously released highly active free sulfur species, which in-situ penetrated and significantly weakened the metal bond energy on the nickel-iron lattice surface. At the same time, the multi-metal center, as an electron donor and acceptor platform, provided a large number of transition state sites for the chemical adsorption and enrichment of carbon monoxide molecules, greatly reducing the activation energy of the reaction system. After entering the core high-pressure carbonylation reaction stage, the dried modified nickel-iron granules are loaded into the reactor. First, carbon monoxide gas is introduced to replace the air. Then, under continuous carbon monoxide gas introduction and heating, gas molecules, catalytically induced by the activator, actively attack the empty orbitals of activated iron atoms in the nickel-iron lattice. Under a specific high-temperature thermodynamic window, carbon monoxide gas rapidly complexes with iron to generate volatile gaseous products, while nickel, due to the extremely reverse decomposition under these conditions, is highly selectively retained in the solid residue. After heating is stopped and the reactor cools to a safe temperature range, nitrogen gas is introduced into the reactor for purging. This gas-phase displacement mechanism cleverly removes the reactants required for the nickel side reaction at the source, safely exporting the mixed gas phase from the reactor to a two-stage condenser system. This gas phase utilizes the inherent difference in the physical boiling points of different metal carbonyl compounds to undergo a stepwise condensation phase transition. In the first stage, the high-temperature cooling promotes the liquefaction of the high-boiling-point components to obtain pentacarbonyl iron liquid and uncondensed residual gas. Subsequently, the uncondensed residual gas is deeply cooled at extremely low temperatures to obtain tetracarbonyl nickel liquid that escapes along with it, thus achieving precise cutting and purification of the gas-liquid multiphase system.Finally, the purified pentacarbonyl iron liquid was vaporized endothermally in a vaporizer via vacuum distillation and then entered a thermal decomposition tower where it underwent a violent homolytic decomposition reaction. The free iron atoms released by the instantaneous breakage of the coordination bonds rapidly collided and grew in the gas flow. In this crucial step of the thermal decomposition mechanism, the carrier gas in the thermal decomposition tower not only ensured the spatial dispersion of particle growth but also drastically reduced the partial pressure of carbon monoxide in the reaction microenvironment from a chemical kinetic perspective. This significantly weakened the catalytic ability of the nascent, highly active nano-iron powder surface for the disproportionation decomposition side reaction, thereby completely blocking the carburization pathway. Finally, carbonyl iron powder with regular morphology, intact crystal lattice, and high purity was collected through gas-solid separation.

[0008] According to a preferred embodiment of the present invention, in step S1, the temperature of vacuum drying is 118-122°C.

[0009] According to a preferred embodiment of the present invention, in step S2, the temperature of vacuum drying is 78-82°C.

[0010] According to a preferred embodiment of the present invention, in step S3, the reaction time at 174-176°C is 24-26 hours.

[0011] According to a preferred embodiment of the present invention, in step S4, the carrier gas in the pyrolysis tower is nitrogen.

[0012] According to a preferred embodiment of the present invention, the preparation steps of the organic-inorganic hybrid manganese iron molybdate composite activator include: A1. By weight, at room temperature, dissolve 5-10 parts of ammonium heptamolybdate tetrahydrate and 3-8 parts of ferrous ammonium sulfate hexahydrate together in 200-300 parts of deionized water and stir to obtain a mixed solution; dissolve 2-6 parts of manganese sulfate monohydrate in 80-120 parts of deionized water to obtain a manganese sulfate solution; add the manganese sulfate solution dropwise to the mixed solution and continue stirring; add 5-12 parts of citric acid and stir; then add 25-45 parts of anhydrous ethanol; adjust the pH to 4.8-5.2 to obtain a mixture; transfer the mixture to a constant temperature water bath at 58-62℃ for aging to obtain a precursor sol; A2. Transfer 310-500 parts of precursor sol to an evaporator and concentrate under reduced pressure at 54-56℃ to obtain a concentrated solution; dry the concentrated solution at 38-42℃ to obtain a wet gel; dry the wet gel under vacuum at 58-62℃ to obtain a dry gel; grind the dry gel to obtain a precursor powder. A3. Place 10-25 parts of precursor powder in a quartz boat of a tubular reactor and purge with nitrogen; heat to 198-202℃ and hold at that temperature; introduce a mixture of hydrogen sulfide and nitrogen and heat to 395-405℃ and hold at that temperature; stop introducing hydrogen sulfide and purge with nitrogen; then heat to 645-655℃ and hold at that temperature, cool to obtain the sulfide product; A4. Ball mill 8-18 parts of the sulfide product to obtain a ball-milled powder; disperse the ball-milled powder in a mixed solvent of 150-250 parts of anhydrous ethanol and deionized water, and sonicate; adjust the pH to 8.8-9.2 to obtain a suspension; add 2-4 parts of thiourea and 1.5-3 parts of triethylenetetramine to the suspension, and stir the reaction in a water bath at 38-42℃ to obtain a reaction mixture; centrifuge the reaction mixture to obtain a precipitate; wash the precipitate alternately with anhydrous ethanol and deionized water, and then vacuum dry at 78-82℃.

[0013] In this invention, the preparation reaction mechanism of the organic-inorganic hybrid manganese ferromolybdate composite activator is based on multi-metal coordination chemistry and solid-phase sulfide crystal evolution. In the initial preparation stage, ammonium heptamolybdate tetrahydrate and ferrous ammonium sulfate hexahydrate are completely dissolved in deionized water to obtain a mixed solution. The metal cations undergo preliminary hydrolysis and hydration. Subsequently, a manganese sulfate solution prepared from manganese sulfate monohydrate and deionized water is added dropwise to ensure sufficient and uniform contact of the various metal elements. Then, citric acid is added. Its abundant carboxyl and hydroxyl groups can donate lone pairs of electrons to the empty orbitals of the metal ions, resulting in a strong polynuclear coordination complexation reaction. This not only prevents premature precipitation of metal ions during subsequent pH adjustment due to steric hindrance but also tightly links the various metal ions together at the microscopic molecular level. Subsequently, anhydrous ethanol was slowly added, significantly reducing the dielectric constant of the system. After adjusting the pH, a mixture was obtained, which promoted the transformation of hydroxyl bridges into more stable oxygen bridges through intermolecular dehydration condensation reactions of the metal complex. During aging, a highly homogeneous precursor sol was formed. The precursor sol was concentrated under reduced pressure to form a concentrated solution, and then gradually dried to form a wet gel and a dry gel. Finally, it was ground into precursor powder, completing a smooth transition from the liquid phase to a solid network framework. During the high-temperature calcination and sulfidation process, nitrogen gas was first introduced for purging and initial heating, promoting the pyrolysis and carbonization of the organic framework and creating extremely rich microporous channels inside the material. When the gas mixture of hydrogen sulfide and nitrogen was switched, hydrogen sulfide exhibited strong sulfidation and weak reduction properties, promoting a deep sulfur-oxygen replacement reaction of the metal-oxygen bonds in the precursor powder. This process guided the transition metal to transform into nanoscale metal sulfides. After calcination at higher temperatures, lattice rearrangement was promoted to form a stable solid solution structure, and the sulfidation product was obtained after cooling. Finally, the sulfide product was mechanically ball-milled to introduce a large number of highly active surface defects, resulting in a ball-milled powder. This powder was dispersed in a mixed solvent of anhydrous ethanol and deionized water to form a system, and thiourea and triethylenetetramine were added for reaction. These two ligands, utilizing their lone pairs of electrons, formed strong chemical coordination bonds with the unsaturated dangling bonds generated on the surface of the metal sulfide in the suspension due to mechanical breakage. After centrifugation, the corresponding precipitate of the reaction mixture was obtained and alternately washed and dried, ultimately constructing a dense molecular layer with specific catalytic activity outside the inorganic composite core, successfully synthesizing an organic-inorganic hybrid manganese iron molybdate composite activator.

[0014] According to a preferred embodiment of the present invention, in step A1, the time for aging the mixture in a constant temperature water bath at 58-62°C is 6-8 hours.

[0015] According to a preferred embodiment of the present invention, in step A2, the wet gel is vacuum dried at 58-62°C for 12-14 hours.

[0016] According to a preferred embodiment of the present invention, in step A3, the time for heating to 645-655°C and maintaining the temperature is 1-2 hours.

[0017] According to a preferred embodiment of the present invention, in step A4, the stirring reaction time in a water bath at 38-42°C is 2-4 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention proposes an organic-inorganic hybrid manganese iron molybdate composite activator and applies it to the surface modification of nickel-iron particles. This composite activator is prepared through a multi-step process including sol-gel, gradient temperature sulfidation, and surface organic ligand modification, and has nanoscale particle size, high specific surface area, and excellent thermal stability. After being loaded onto the surface of nickel-iron particles, it plays a multi-synergistic activation role in the carbonylation reaction: sulfur promotes the adsorption and dissociation of carbon monoxide, molybdenum provides additional coordination sites, manganese enhances the thermal stability of the coating, and surface organic ligands gradually release active species.

[0019] (2) This invention optimizes the overall process flow of carbonylation reaction and product separation. Regarding reaction conditions, the reaction temperature and pressure are rationally controlled to ensure selective carbonylation of iron, leaving the nickel bulk in the solid residue. Product separation employs a two-stage condenser system for gradient cooling, achieving efficient separation of iron-nickel carbonyl compounds. Simultaneously, after the reaction, the temperature is first lowered to an appropriate range before nitrogen purging, introducing all the mixed gas phase into the condensation system, effectively preventing the associated formation of tetracarbonyl nickel during cooling and avoiding the safety hazard of highly toxic substances. The pentacarbonyl iron liquid is completely vaporized after vacuum distillation and then injected into a thermal decomposition tower for decomposition. At the same time, nitrogen is used as a carrier gas to reduce the partial pressure of carbon monoxide, effectively suppressing the carbon deposition problem caused by the Budoal side reaction and ensuring product quality.

[0020] (3) The overall process of this invention is simple, the raw materials are readily available, and it is suitable for large-scale industrial production. Except for the organic-inorganic hybrid manganese iron molybdate composite activator, which needs to be prepared in-house, all raw materials are conventional commercial products, widely available and inexpensive. The equipment used are all standard equipment in the chemical and metallurgical fields, and no special customization is required. By adjusting the nickel-iron ratio of the raw materials and the reaction conditions, carbonyl iron powder products with different nickel contents and different particle sizes can be obtained. The products have high purity and can meet the needs of different application fields such as powder metallurgy, electromagnetic shielding, and soft magnetic materials. It has broad market application prospects and significant economic benefits. Detailed Implementation

[0021] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0022] Example 1 This embodiment provides a process for producing carbonyl iron powder from nickel-iron granules, including the following steps: S1. Using nickel-iron granules as raw material, weigh 80g and add it to the grinding jar of a planetary ball mill. Add stainless steel balls (ball-to-material ratio 5:1), seal, evacuate and fill with argon gas, and grind at 200rpm for 2h (stop and cool for 10min every 0.5h). The ground nickel-iron powder is then sieved through standard sieves of 40 mesh, 80 mesh and 120 mesh in sequence. Collect the nickel-iron powder that passes through the 80 mesh but is retained between the 120 mesh sieves. Place the sieved nickel-iron powder in a vacuum drying oven and dry it at 118℃ for 4h under argon protection (first evacuate to 0.09MPa, then fill with argon gas to atmospheric pressure, repeat three times) to remove the moisture and trace oxygen adsorbed on the powder surface, and obtain pretreated nickel-iron granules.

[0023] S2. Weigh 80g of pretreated nickel-iron particles and place them in a three-necked flask. Add 80g of anhydrous ethanol as a dispersion medium. Place the flask in an ultrasonic cell disruptor and ultrasonically disperse the particles for 15 minutes at 400W and 20kHz to ensure uniform dispersion. Separately, weigh 3g of an organic-inorganic hybrid manganese iron molybdate composite activator and add it to a beaker. Add 8g of anhydrous ethanol and ultrasonically disperse the particles for 10 minutes at 200W and 40kHz to form a uniform suspension. Transfer the activator suspension to a constant pressure dropping funnel and slowly add it dropwise at a rate of 2mL / min to the ethanol dispersion of nickel-iron particles. During the addition, use a mechanical stirrer at 30°C. The mixture was continuously stirred at 0 rpm while the three-necked flask was placed in an ice-water bath. The temperature of the reaction system was monitored with a thermometer to ensure that it did not exceed 25°C. After the addition was complete, the ice-water bath was removed, and the mixture was stirred at 300 rpm for 2 hours at room temperature. The coated nickel-iron particle mixture was transferred to a Buchner funnel and vacuum filtered (vacuum degree 0.08 MPa) using a vacuum pump. The filter cake was washed three times with 20 g of anhydrous ethanol (the filter cake was stirred with a glass rod each time to ensure thorough washing). The washed coated nickel-iron particles were spread evenly in a glass dish and placed in an 80°C vacuum drying oven at a vacuum degree of 0.095 MPa for 6 hours to obtain modified nickel-iron particles with a uniformly loaded activator on the surface.

[0024] S3. Load 80g of dried modified nickel-iron granules into a high-pressure reactor (design pressure 25MPa, material 316L stainless steel), filling it to approximately 45% of the reactor's volume. Seal the reactor and connect the CO gas pipeline. Perform three pressurization-depressurization operations with high-purity CO gas to replace the air inside the reactor: first, open the inlet valve to purge CO to 0.5MPa, close the inlet valve, maintain the pressure for 5 minutes, then open the exhaust valve to depressurize to atmospheric pressure. Repeat this process three times. After gas replacement, close the exhaust valve, open the inlet valve to introduce CO gas into the reactor to an initial pressure of 4.0MPa, and then close the inlet valve. Start the heating device, set the heating rate to 3℃ / min, and raise the temperature inside the reactor to 174℃. As the temperature rises, the pressure inside the reactor increases. Adjust the pressure using the pressure reducing valve to maintain the pressure inside the reactor at 8.0MPa. When the temperature inside the reactor stabilizes at 174℃ and the pressure stabilizes at 8.5MPa... Timing begins at a certain time. During the reaction, CO gas is continuously supplied via a mass flow meter to maintain a constant pressure inside the reactor at a flow rate of approximately 1.0 L / min. The back pressure valve automatically vents to maintain stable pressure. The reaction continues for 24 hours. Every 2 hours, samples are taken from the gas phase outlet of the reactor through a needle valve, and the gas composition is analyzed using a gas chromatograph to monitor the concentration changes of iron pentacarbonyl and nickel tetracarbonyl. When the concentration of iron pentacarbonyl in the gas phase no longer increases in two consecutive samplings (2-hour intervals), heating is stopped, and the CO inlet valve is closed. After the reactor cools naturally to 110°C (monitored by a thermometer on the reactor wall), the nitrogen inlet valve is opened, and high-purity nitrogen is introduced at a flow rate of 1.0 L / min for purging. At the same time, the pipeline valve leading to the two-stage condenser system is opened, and all the mixed gas phase in the reactor (containing residual CO, iron pentacarbonyl vapor, and trace amounts of nickel tetracarbonyl vapor) is introduced into the two-stage condenser system.

[0025] S4. The two-stage condenser system consists of two serpentine condensers connected in series. The first-stage condenser uses 50°C warm water as the circulating cooling medium (controlled by a constant temperature water bath), and the second-stage condenser uses -10°C chilled brine as the circulating cooling medium (controlled by a low-temperature constant temperature bath). The mixed gas phase from the reactor first enters the first-stage condenser, where high-boiling-point iron pentacarbonyl (boiling point 103°C) condenses into a yellow to reddish-brown transparent liquid, which is collected in a receiving flask. The uncondensed remaining gas (mainly containing CO and trace amounts of nickel tetracarbonyl) continues to enter the second-stage condenser, where nickel tetracarbonyl (boiling point 43°C) condenses into a colorless to pale yellow liquid, which is collected separately. The collected iron pentacarbonyl liquid is transferred to a vacuum distillation apparatus for purification under conditions of 50°C and a vacuum of 0.09 MPa, and the distillate is collected. The purified iron pentacarbonyl liquid is continuously pumped into the vaporizer (tube) at a liquid equivalent rate of 0.5 L / h using a micro-pump. A vaporizer (10mm inner diameter, 50cm length, with an external electric heating element) is used to completely vaporize ferric pentacarbonyl into steam. The ferric pentacarbonyl steam is mixed with high-purity nitrogen carrier gas (2L / min flow rate) and continuously injected into a pyrolysis tower (vertical tube furnace, 50mm inner diameter, 100cm length, filled with quartz packing). The temperature of the pyrolysis tower is controlled at 280℃, where ferric pentacarbonyl undergoes a decomposition reaction to produce iron powder and CO gas. The carbonyl iron powder generated by decomposition enters a cyclone separator (inlet velocity 15m / s) with the airflow, and the solid powder is collected in a hopper. The exhaust gas is adsorbed by activated carbon before being discharged. The collected carbonyl iron powder is a gray-black spherical powder.

[0026] Preparation of organic-inorganic hybrid manganese ferromolybdate composite activator: A1. At room temperature, add 5g of ammonium heptamolybdate tetrahydrate and 3g of ferrous ammonium sulfate hexahydrate to 200g of deionized water and stir at 300rpm for 15min until completely dissolved to obtain a pale green transparent solution. Separately, dissolve 2g of manganese sulfate monohydrate in 80g of deionized water and stir at 300rpm for 5min until completely dissolved to obtain a manganese sulfate solution. Slowly add this manganese sulfate solution dropwise to the above mixed solution of ammonium heptamolybdate and ferrous ammonium sulfate at a rate of 0.5mL / s, maintaining the solution temperature at 30℃ during the addition (using a constant temperature water bath). After the addition is complete, continue stirring at 300rpm for 60 minutes. min; then add 5g citric acid and stir for 10min until completely dissolved. Citric acid acts as a chelating agent to form a stable heteropolynuclear complex with metal ions. Subsequently, measure 25g anhydrous ethanol and slowly add it at a rate of 2mL / min to reduce the dielectric constant of the solution. Add 1mol / L sodium hydroxide solution dropwise while monitoring with a pH meter with an accuracy of ±0.01 to precisely adjust the pH of the mixed solution to 4.8. Transfer the above mixed solution to a 60℃ constant temperature water bath and age it for 6h with stirring at 350rpm. The solution color gradually changes from light green to dark brown, yielding the molybdenum-iron-manganese ternary heteropolyacid complex precursor sol.

[0027] A2. Transfer 310g of the precursor sol to a rotary evaporator, set the water bath temperature to 54℃ and the vacuum degree to 0.08MPa, and concentrate under reduced pressure at a rotation speed of 60rpm until the solution volume is reduced to one-third of the original volume. At this point, the solution viscosity increases significantly and exhibits semi-fluid gel characteristics. Pour the concentrated solution into a 15cm diameter polytetrafluoroethylene petri dish and place it in a 40℃ constant temperature drying oven with a relative humidity of 50%. Let it stand for 48 hours to allow the sol to transform into a wet gel through a condensation reaction. During the standing process, saturated water is introduced into the drying oven every 8 hours. Steam for 5 minutes to maintain the moisture of the microenvironment on the gel surface and prevent cracking; when the wet gel is a dark brown, semi-transparent block and has no obvious flow when touched with a glass rod, it indicates that gelation is complete; transfer the wet gel to a 60℃ vacuum drying oven, set the vacuum degree to 0.09MPa, and dry for 12 hours to remove the residual free water and some bound water in the gel network, obtaining a structurally complete composite gel block; place the dry gel block in an agate mortar and grind manually for 10 minutes, then pass it through a 100-mesh standard sieve to obtain a gel precursor powder with a particle size of less than 100 mesh.

[0028] Example 2 The difference between this embodiment and Embodiment 1 is that this embodiment provides a process method for producing carbonyl iron powder from nickel-iron granules, including the following steps: S1. Add 100g of nickel-iron particles to a planetary ball mill, using stainless steel balls as the grinding medium (ball-to-material ratio 5:1), and grind at 200rpm for 2 hours under argon protection. The ground nickel-iron powder is then sieved through standard sieves of 40 mesh, 80 mesh, and 120 mesh, collecting the powder that passes through the 80 mesh but is retained between the 120 mesh sieves. The sieved nickel-iron powder is then transferred to a vacuum drying oven under argon protection and dried at 120℃ and 0.09MPa for 4 hours to obtain pretreated nickel-iron particles.

[0029] S2. Weigh 100g of pretreated nickel-iron particles and place them in a three-necked flask. Add 100g of anhydrous ethanol as a dispersion medium and ultrasonically disperse them for 15min using an ultrasonic cell disruptor (power 400W, frequency 20kHz). Separately weigh 5.5g of organic-inorganic hybrid manganese iron molybdate composite activator and ultrasonically disperse it in 11.5g of anhydrous ethanol for 10min to form a uniform suspension. Then, slowly add this suspension dropwise to the ethanol dispersion of nickel-iron particles at a rate of 2mL / min. During the dropwise addition, continuously stir with a mechanical stirrer at 300rpm while placing the flask in an ice-water bath to control the temperature to not exceed 25℃. After the dropwise addition is complete, continue stirring at room temperature for 2h. Separate the coated nickel-iron particles using a vacuum filtration device. Wash the filter cake three times with 35g of anhydrous ethanol. Dry the washed coated nickel-iron particles in a vacuum drying oven at 80℃ (vacuum degree 0.095MPa) for 6h to obtain the dried modified nickel-iron particles.

[0030] S3. 100g of dried modified nickel-iron granules are loaded into a high-pressure reactor, filling 40-50% of the reactor volume. After sealing the reactor, high-purity CO gas is used to pressurize and depressurize the reactor three times to replace the air inside. Each pressurization is performed to 0.5MPa, held for 5 minutes, and then depressurized to atmospheric pressure. After gas replacement, 200g of high-purity CO gas is introduced into the reactor to an initial pressure of 4.0MPa. The heating device is started to raise the temperature inside the reactor to 175℃ at a heating rate of 3℃ / min. The pressure inside the reactor is maintained at 8.5MPa by adjusting the pressure reducing valve. Within the specified range; timing begins when the temperature inside the reactor stabilizes at 175℃ and the pressure stabilizes at 8.5MPa. During the reaction, CO gas is continuously introduced to replenish the consumption, and the pressure inside the reactor is automatically maintained at around 8.5MPa through the back pressure valve; the reaction continues for 25 hours, during which samples are taken from the gas phase outlet of the reactor every 2 hours for gas chromatography analysis; when the concentration of iron pentacarbonyl in the gas phase no longer increases in two consecutive samplings, heating and gas introduction are stopped; after the reactor cools down to 130℃, high-purity nitrogen is introduced into the reactor for purging; the mixed gas phase in the reactor is then introduced into a two-stage condenser system.

[0031] S4. The mixed gas phase introduced into the two-stage condenser system is cooled at 55°C to obtain pentacarbonyl iron liquid and uncondensed residual gas; then the uncondensed residual gas is cooled at -5°C to obtain tetracarbonyl nickel liquid; the pentacarbonyl iron liquid is purified by vacuum distillation and then sent to a vaporizer at 120°C for vaporization, and then continuously injected into the pyrolysis tower at a liquid equivalent rate of 0.5 L / h. The temperature inside the pyrolysis tower is controlled at 300°C, and the carrier gas is high-purity nitrogen (flow rate 2 L / min); the carbonyl iron powder generated by decomposition is collected by a cyclone separator.

[0032] Preparation of organic-inorganic hybrid manganese ferromolybdate composite activator: A1. Under room temperature conditions, 7.5 g of ammonium heptamolybdate tetrahydrate and 5.5 g of ferrous ammonium sulfate hexahydrate were weighed and dissolved together in 250 g of deionized water, and a mixed solution was obtained by stirring at 300 rpm. 4 g of manganese sulfate monohydrate was weighed and dissolved in 100 g of deionized water to obtain a manganese sulfate solution. This manganese sulfate solution was added dropwise to the above mixed solution at a rate of 0.5 mL / s, and the solution temperature was maintained at 30 °C. Stirring was continued for 60 min. 8.5 g of citric acid was added and stirred until completely dissolved. Then, 35 g of anhydrous ethanol was slowly added. The pH was adjusted to 5.0 using 1 mol / L sodium hydroxide solution. The above mixture was transferred to a 60 °C constant temperature water bath and aged for 7 h to obtain the precursor sol.

[0033] A2. Transfer 405g of precursor sol to a rotary evaporator and concentrate it to one-third of its original volume under reduced pressure at 55℃ and a vacuum of 0.08MPa to obtain a concentrated solution. Pour the concentrated solution into a polytetrafluoroethylene petri dish and place it in a constant temperature drying oven at 40℃ and a relative humidity of 50% for 48 hours. Every 8 hours, saturated water vapor is introduced into the drying oven for 5 minutes. When the wet gel becomes a dark brown semi-transparent block, dry it in a vacuum drying oven at 60℃ for 13 hours to obtain a dry gel. Grind this gel block in an agate mortar until the particle size is less than 100 mesh to obtain the precursor powder.

[0034] A3. Place 17.5g of precursor powder in a quartz boat of a tubular reactor and purge with high-purity nitrogen for 30min. Then, under continuous nitrogen purging, raise the temperature to 200℃ at 3℃ / min and hold for 2h. Next, introduce a mixture of hydrogen sulfide and nitrogen (volume ratio 1:4, flow rate 80mL / min) and raise the temperature to 400℃ at a rate of 2℃ / min, hold for 3h. Stop the introduction of hydrogen sulfide and purge with high-purity nitrogen. Then raise the temperature to 650℃ at 5℃ / min and hold for 1.5h. After cooling, obtain the sulfide product.

[0035] A4. After cooling 13g of the sulfidation product, it was placed in a planetary ball mill and milled for 4h at 300rpm under argon protection using ZrO2 balls as the grinding medium (ball-to-material ratio 10:1). The milled powder was then dispersed in 200g of a 1:1 mixture of anhydrous ethanol and deionized water under ultrasonic assistance (power 200W, frequency 40kHz, time 30min). The pH of the system was adjusted to 9.0 with 1mol / L sodium hydroxide solution to obtain a suspension. 3g of thiourea and 2.25g of triethylenetetramine were added to the suspension, and the mixture was stirred in a 40℃ water bath for 3h. The suspension was centrifuged at 12000rpm, and the precipitate was washed three times alternately with anhydrous ethanol and deionized water. Then, it was dried in a vacuum drying oven at 80℃ for 24h to obtain an organic-inorganic hybrid manganese iron molybdate composite activator.

[0036] Example 3 The difference between this embodiment and Embodiment 1 is that this embodiment provides a process method for producing carbonyl iron powder from nickel-iron granules, including the following steps: S1. Add 120g of nickel-iron particles to a planetary ball mill, using stainless steel balls as the grinding medium (ball-to-material ratio 5:1), and grind at 200rpm for 2 hours under argon protection. The ground nickel-iron powder is then sieved through standard sieves of 40 mesh, 80 mesh, and 120 mesh, collecting the powder that passes through the 80 mesh but is retained between the 120 mesh sieves. The sieved nickel-iron powder is then transferred to a vacuum drying oven under argon protection and dried at 122℃ and a vacuum of 0.09MPa for 4 hours to obtain pretreated nickel-iron particles.

[0037] S2. Weigh 120g of pretreated nickel-iron particles and place them in a three-necked flask. Add 120g of anhydrous ethanol as a dispersion medium and ultrasonically disperse them for 15min using an ultrasonic cell disruptor (power 400W, frequency 20kHz). Separately weigh 8g of the above-mentioned organic-inorganic hybrid manganese iron molybdate composite activator and ultrasonically disperse it in 15g of anhydrous ethanol for 10min to form a uniform suspension. Then, slowly add this suspension dropwise to the ethanol dispersion of nickel-iron particles at a rate of 2mL / min. During the dropwise addition, continuously stir with a mechanical stirrer at 300rpm while placing the flask in an ice-water bath to control the temperature to not exceed 25℃. After the dropwise addition is complete, continue stirring at room temperature for 2h. Separate the coated nickel-iron particles using a vacuum filtration device. Wash the filter cake three times with 50g of anhydrous ethanol. Dry the washed coated nickel-iron particles in a vacuum drying oven at 82℃ (vacuum degree 0.095MPa) for 6h to obtain modified nickel-iron particles with a uniformly loaded activator on the surface.

[0038] S3. 120g of dried modified nickel-iron granules are loaded into a high-pressure reactor (design pressure 25MPa, material 316L stainless steel), filling 50% of the reactor volume. After sealing the reactor, high-purity CO gas is used to pressurize and depressurize the reactor three times to replace the air inside. Each pressurization is increased to 0.5MPa, held for 5 minutes, and then depressurized to atmospheric pressure. After the gas replacement is completed, 300g of high-purity CO gas is introduced into the reactor to an initial pressure of 4.0MPa. The heating device is started to raise the temperature inside the reactor to 176℃ at a heating rate of 3℃ / min. The temperature inside the reactor is maintained by adjusting the pressure reducing valve. The pressure was maintained within the range of 9.0 MPa. Timing began when the temperature inside the reactor stabilized at 176℃ and the pressure stabilized at 8.5 MPa. During the reaction, CO gas was continuously introduced to replenish the consumption, and the pressure inside the reactor was automatically maintained at around 8.5 MPa through the back pressure valve. The reaction continued for 26 hours, during which samples were taken from the gas phase outlet of the reactor every 2 hours for gas chromatography analysis. When the concentration of iron pentacarbonyl in the gas phase no longer increased in two consecutive samplings, heating and gas supply were stopped. After the reactor cooled to 150℃, high-purity nitrogen gas was introduced into the reactor for purging. The mixed gas phase inside the reactor was then introduced into a two-stage condenser system.

[0039] S4. The mixed gas phase introduced into the two-stage condenser system is cooled at 60°C to obtain pentacarbonyl iron liquid and uncondensed residual gas; then the uncondensed residual gas is cooled at 0°C to obtain tetracarbonyl nickel liquid; the pentacarbonyl iron liquid is purified by vacuum distillation and then sent to a vaporizer at 130°C for vaporization, and then continuously injected into the pyrolysis tower at a liquid equivalent rate of 0.5 L / h. The temperature inside the pyrolysis tower is controlled at 320°C, and the carrier gas is high-purity nitrogen (flow rate 2 L / min); the carbonyl iron powder generated by decomposition is collected by a cyclone separator.

[0040] Preparation of organic-inorganic hybrid manganese ferromolybdate composite activator: A1. Under room temperature conditions, 10g of ammonium heptamolybdate tetrahydrate and 8g of ferrous ammonium sulfate hexahydrate were weighed and dissolved together in 300g of deionized water, and a mixed solution was obtained by stirring at 300rpm. 6g of manganese sulfate monohydrate was weighed and dissolved in 120g of deionized water to obtain a manganese sulfate solution. This manganese sulfate solution was added dropwise to the above mixed solution at a rate of 0.5mL / s, and the solution temperature was maintained at 30℃. Stirring was continued for 60min. 12g of citric acid was added and stirred until completely dissolved. Then, 45g of anhydrous ethanol was slowly added. The pH was adjusted to 5.2 using 1mol / L sodium hydroxide solution. The above mixture was transferred to a 62℃ constant temperature water bath and aged for 8h to obtain the precursor sol.

[0041] A2. Transfer 500g of precursor sol to a rotary evaporator and concentrate it to one-third of its original volume under reduced pressure at 56℃ and a vacuum of 0.08MPa to obtain a concentrated solution. Pour the concentrated solution into a polytetrafluoroethylene petri dish and place it in a constant temperature drying oven at 42℃ and a relative humidity of 50% for 48 hours. Every 8 hours, saturated water vapor is introduced into the drying oven for 5 minutes. When the wet gel becomes a dark brown semi-transparent block, dry it in a vacuum drying oven at 62℃ for 14 hours to obtain a dry gel. Grind this gel block in an agate mortar until the particle size is less than 100 mesh to obtain the precursor powder.

[0042] A3. Place 25g of precursor powder in a quartz boat of a tubular reactor and purge with high-purity nitrogen for 30min. Then, under continuous nitrogen purging, raise the temperature to 202℃ at 3℃ / min and hold for 2h. Next, introduce a mixture of hydrogen sulfide and nitrogen (volume ratio 1:4, flow rate 80mL / min) and raise the temperature to 405℃ at a rate of 2℃ / min, hold for 3h. Stop introducing hydrogen sulfide and purge with high-purity nitrogen. Then raise the temperature to 655℃ at 5℃ / min and hold for 2h. After cooling, obtain the sulfide product.

[0043] A4. After cooling 18g of the sulfidation product, it was placed in a planetary ball mill and milled for 4h at 300rpm under argon protection using ZrO2 balls as the grinding medium (ball-to-material ratio 10:1). The milled powder was then dispersed in 250g of a 1:1 mixture of anhydrous ethanol and deionized water under ultrasonic assistance (power 200W, frequency 40kHz, time 30min). The pH of the system was adjusted to 9.2 with 1mol / L sodium hydroxide solution to obtain a suspension. 4g of thiourea and 3g of triethylenetetramine were added to the suspension, and the mixture was stirred in a 42℃ water bath for 4h. The suspension was centrifuged at 12000rpm, and the precipitate was washed three times alternately with anhydrous ethanol and deionized water. Then, it was dried in a vacuum drying oven at 82℃ for 24h to obtain an organic-inorganic hybrid manganese iron molybdate composite activator.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that the organic-inorganic hybrid manganese iron molybdate composite activator is not used. The remaining steps are the same as in Example 1.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that an equal mass of sulfur powder is used instead of the organic-inorganic hybrid manganese iron molybdate composite activator. The remaining steps are the same as in Example 1.

[0046] Comparative Example 3 The difference between this comparative example and Example 1 is that a manganese- and molybdenum-free modifier is used instead of the organic-inorganic hybrid manganese sulfide iron molybdate composite activator. Specifically, it is prepared according to the preparation method of the organic-inorganic hybrid manganese sulfide iron molybdate composite activator in Example 1, but without the addition of ammonium heptamolybdate tetrahydrate and manganese sulfate monohydrate.

[0047] In accordance with national and industry standard testing specifications, a series of standardized tests were conducted on the process methods for producing carbonyl iron powder from nickel iron particles described in Examples 1-3 and Comparative Examples 1-3.

[0048] Determination of pentacarbonyl iron yield: Quantitative analysis of the mixed gas at the gas phase outlet of the reaction vessel was performed using gas chromatography. Samples were taken every 2 hours using a gas chromatograph equipped with a thermal conductivity detector. The chromatographic column was an HP-PLOT Q capillary column (30 m in length, 0.32 mm in inner diameter, and 10 μm in film thickness). High-purity helium was used as the carrier gas at a flow rate of 2.0 mL / min. The column temperature program was as follows: initial temperature 40℃, held for 5 min, then increased to 200℃ at a rate of 10℃ / min and held for 5 min. The injection port temperature was 150℃, and the detector temperature was 200℃. The injection volume was 1 mL, and quantification was performed using the external standard method. The pentacarbonyl iron yield was calculated as the percentage of the actual mass (g) of the condensed and collected pentacarbonyl iron liquid after the reaction to the theoretical maximum mass (calculated based on the iron content in the nickel-iron particles, in g).

[0049] Reaction time determination: Timing started when the temperature inside the reactor of Examples 1-3 and Comparative Examples 1-3 stabilized at the target reaction temperature, and stopped when gas chromatography showed that the concentration of iron pentacarbonyl no longer increased in two consecutive samplings (2 hours apart). The length of this time period was recorded in hours.

[0050] Purity determination of carbonyl iron powder: The content of metal elements such as iron, nickel, molybdenum, and manganese was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), the carbon content was determined by high-frequency infrared carbon-sulfur analysis, and the oxygen and nitrogen contents were determined by an oxygen-nitrogen analyzer. 0.5 g of sample was weighed and placed in a polytetrafluoroethylene digestion vessel, 10 mL of aqua regia was added, the vessel was capped, and digestion was carried out on a 120℃ hot plate for 2 h. The volume was then cooled and brought to 100 mL. The metal element content was determined using an ICP-AES spectrometer (RF power 1300 W, nebulizing gas flow rate 0.8 L / min, auxiliary gas flow rate 0.2 L / min, cooling gas flow rate 12 L / min). Separately, 0.5 g of sample was weighed and placed in a ceramic crucible, 1.5 g of tungsten-tin granules were added, and the carbon content was determined using a high-frequency infrared carbon-sulfur analyzer. Finally, 0.1 g of sample was weighed and the oxygen and nitrogen contents were determined using an oxygen-nitrogen analyzer. The purity (%) of carbonyl iron powder is calculated by subtracting the sum of the mass fractions of all impurity elements (Ni, Mo, Mn, C, O, N, etc.) from 100%.

[0051] Carbon content determination: High-frequency infrared carbon-sulfur analysis was used. 0.5g of carbonyl iron powder sample was weighed and placed in a ceramic crucible, with 1.5g of tungsten tin granules added as flux. The crucible was placed in a high-frequency infrared carbon-sulfur analyzer, and the sample was burned by high-frequency heating (2.2kW power, 20MHz frequency) under an oxygen atmosphere (purity ≥99.5%, flow rate 3L / min). The infrared detector measured the released carbon dioxide signal, and the instrument automatically calculated the carbon mass fraction in wt%.

[0052] Average particle size D 50 Determination: Laser particle size analysis was used. 0.1 g of carbonyl iron powder sample was added to 50 mL of anhydrous ethanol and ultrasonically dispersed for 3 min (power 200 W, frequency 40 kHz). The particle size was measured using a laser particle size analyzer (measurement range 0.01-3500 μm), with the particle refractive index set to 2.42, absorbance to 0.1, and the refractive index of the dispersion medium (anhydrous ethanol) to 1.36. Three measurements were taken, and the average value was recorded. The median particle size D in the volume distribution was recorded. 50 The unit is μm.

[0053] Determination of nickel tetracarbonyl formation rate: Nickel tetracarbonyl liquid was collected from the second-stage receiving flask of the two-stage condenser. Its mass was weighed using an analytical balance, and its purity was confirmed by gas chromatography-mass spectrometry (characteristic ion peak of nickel tetracarbonyl, m / z 170). The nickel tetracarbonyl formation rate (%) was calculated as the percentage of the actual mass (g) of the collected nickel tetracarbonyl liquid from condensation to the theoretical maximum mass (g) of nickel tetracarbonyl corresponding to the nickel content in the nickel-iron granules.

[0054] The performance test data above are shown in Table 1.

[0055] Table 1 Performance Test Results

[0056] As can be seen from the above, Examples 1-3 significantly solved the following technical problems compared to Comparative Examples 1-3: First, the pentacarbonyl iron yields of Examples 1-3 reached 72.3%, 85.6%, and 91.2%, respectively, while those of Comparative Examples 1-3 were only 48.7%, 62.4%, and 68.1%. This indicates that the present invention effectively improves the carbonylation reaction activity of nickel-iron particles and significantly increases the yield of the target product through surface modification with an organic-inorganic hybrid manganese iron molybdate composite activator.

[0057] Secondly, the reaction times of Examples 1-3 were shortened to 26h, 22h and 20h respectively, while those of Comparative Examples 1-3 were as long as 38h, 32h and 28h, indicating that the organic-inorganic hybrid manganese iron molybdate composite activator significantly accelerated the reaction rate and reduced the production cycle and energy consumption.

[0058] Third, the carbonyl iron powder obtained in Examples 1-3 has a purity of up to 99.2%, 99.6% and 99.8%, while the purity of Comparative Examples 1-3 is only 97.5%, 98.3% and 98.7%, which proves that the process of the present invention effectively reduces impurity residue and improves product quality.

[0059] Fourth, the carbon content of Examples 1-3 was as low as 0.42wt%, 0.28wt%, and 0.19wt%, respectively, which was much lower than that of Comparative Examples 1-3 (0.85wt%, 0.63wt%, and 0.55wt%). This indicates that the process design of high-temperature nitrogen purging and carrier gas dilution of CO partial pressure successfully suppressed the carburization problem caused by the Budoal side reaction catalyzed by nascent iron powder.

[0060] Fifth, the average particle size D of the carbonyl iron powder in Examples 1-3 50 The particle sizes were 4.8 μm, 3.9 μm, and 3.2 μm, while those of Comparative Examples 1-3 were 6.5 μm, 5.7 μm, and 5.1 μm, indicating that the process conditions of the present invention are favorable for obtaining finer and more uniformly distributed spherical particles.

[0061] Sixth, the tetracarbonyl nickel formation rates in Examples 1-3 were only 0.15%, 0.09%, and 0.06%, respectively, while those in Comparative Examples 1-3 were as high as 0.52%, 0.38%, and 0.28%. This demonstrates that the nitrogen purging operation when the reactor is cooled to 110-150°C effectively cuts off the thermodynamic pathway of the carbonylation reaction between nickel and residual CO during the cooling stage, greatly reducing the associated risk of highly toxic tetracarbonyl nickel and improving production safety.

[0062] Seventh, in summary, this invention comprehensively solves the key technical problems of low carbonylation reaction efficiency, poor product quality, and significant safety hazards in the prior art from multiple dimensions such as yield, reaction rate, product purity, carbon content, particle size control, and by-product suppression.

Claims

1. A process for producing carbonyl iron powder from nickel-iron granules, characterized in that, Includes the following steps: S1. By weight, add 80-120 parts of nickel-iron particles into a ball mill and grind them under argon protection to obtain nickel-iron powder; sieve the nickel-iron powder to obtain sieved nickel-iron powder; vacuum dry the sieved nickel-iron powder under argon protection to obtain pretreated nickel-iron particles. S2. Add 80-120 parts of pretreated nickel-iron particles to 80-120 parts of anhydrous ethanol and disperse by ultrasonication to obtain a dispersion; disperse 3-8 parts of organic-inorganic hybrid manganese iron molybdate composite activator in 8-15 parts of anhydrous ethanol by ultrasonication to obtain a suspension; add the suspension dropwise to the dispersion and stir at room temperature; filter under vacuum to obtain a filter cake; wash the filter cake with anhydrous ethanol to obtain modified nickel-iron particles; dry the modified nickel-iron particles under vacuum to obtain dried modified nickel-iron particles; S3. Load 80-120 parts of dried modified nickel-iron granules into a reactor; introduce CO gas into the reactor to replace the air; after the gas replacement is completed, introduce 100-300 parts of CO gas into the reactor and heat to 174-176℃ to react; stop heating; wait for the reactor to cool down to 110-150℃; introduce nitrogen gas into the reactor for purging; introduce the mixed gas phase in the reactor into a two-stage condenser system to obtain the mixed gas phase introduced into the two-stage condenser system; S4. The mixed gas phase introduced into the two-stage condenser system is cooled at 50-60℃ to obtain pentacarbonyl iron liquid and uncondensed residual gas; then the uncondensed residual gas is cooled at -10-0℃ to obtain tetracarbonyl nickel liquid; the pentacarbonyl iron liquid is vaporized by vacuum distillation and sent to a vaporizer at 110-130℃, and then injected into a thermal decomposition tower for decomposition at 280-320℃.

2. The process for producing carbonyl iron powder from nickel-iron granules according to claim 1, characterized in that, In step S1, the vacuum drying temperature is 118-122℃.

3. The process for producing carbonyl iron powder from nickel-iron granules according to claim 1, characterized in that, In step S2, the vacuum drying temperature is 78-82℃.

4. The process for producing carbonyl iron powder from nickel-iron granules according to claim 1, characterized in that, In step S3, the reaction time is 24-26 hours after the temperature is raised to 174-176℃.

5. The process for producing carbonyl iron powder from nickel-iron granules according to claim 1, characterized in that, In step S4, the carrier gas in the pyrolysis tower is nitrogen.

6. The process for producing carbonyl iron powder from nickel-iron granules according to any one of claims 1-5, characterized in that, The preparation steps of the organic-inorganic hybrid manganese ferromolybdate composite activator include: A1. By weight, at room temperature, dissolve 5-10 parts of ammonium heptamolybdate tetrahydrate and 3-8 parts of ferrous ammonium sulfate hexahydrate together in 200-300 parts of deionized water and stir to obtain a mixed solution; dissolve 2-6 parts of manganese sulfate monohydrate in 80-120 parts of deionized water to obtain a manganese sulfate solution; add the manganese sulfate solution dropwise to the mixed solution and continue stirring; add 5-12 parts of citric acid and stir; then add 25-45 parts of anhydrous ethanol; adjust the pH to 4.8-5.2 to obtain a mixture; transfer the mixture to a constant temperature water bath at 58-62℃ for aging to obtain a precursor sol; A2. Transfer 310-500 parts of precursor sol to an evaporator and concentrate under reduced pressure at 54-56℃ to obtain a concentrated solution; dry the concentrated solution at 38-42℃ to obtain a wet gel; dry the wet gel under vacuum at 58-62℃ to obtain a dry gel; grind the dry gel to obtain a precursor powder. A3. Place 10-25 parts of precursor powder in a quartz boat of a tubular reactor and purge with nitrogen; heat to 198-202℃ and hold at that temperature; introduce a mixture of hydrogen sulfide and nitrogen and heat to 395-405℃ and hold at that temperature; stop introducing hydrogen sulfide and purge with nitrogen; then heat to 645-655℃ and hold at that temperature, cool to obtain the sulfide product; A4. Ball mill 8-18 parts of the sulfide product to obtain a ball-milled powder; disperse the ball-milled powder in a mixed solvent of 150-250 parts of anhydrous ethanol and deionized water, and sonicate; adjust the pH to 8.8-9.2 to obtain a suspension; add 2-4 parts of thiourea and 1.5-3 parts of triethylenetetramine to the suspension, and stir the reaction in a water bath at 38-42℃ to obtain a reaction mixture; centrifuge the reaction mixture to obtain a precipitate; wash the precipitate alternately with anhydrous ethanol and deionized water, and then vacuum dry at 78-82℃.

7. The process for producing carbonyl iron powder from nickel-iron granules according to claim 6, characterized in that, In step A1, the mixture is transferred to a constant temperature water bath at 58-62℃ for aging for 6-8 hours.

8. The process for producing carbonyl iron powder from nickel-iron granules according to claim 6, characterized in that, In step A2, the wet gel is vacuum dried at 58-62℃ for 12-14 hours.

9. The process for producing carbonyl iron powder from nickel-iron granules according to claim 6, characterized in that, In step A3, the time to raise the temperature to 645-655℃ and maintain the constant temperature is 1-2 hours.

10. The process for producing carbonyl iron powder from nickel-iron granules according to claim 6, characterized in that, In step A4, the reaction is stirred in a water bath at 38-42℃ for 2-4 hours.

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