Method and equipment for preparing nanoscale carbonyl iron powder

Abstract

According to the method for preparing the nanoscale carbonyl iron powder under the conditions of normal pressure and low temperature and the special integrated equipment for implementing the method, efficient cooling and nucleation of iron steam can be achieved by adopting a specially-designed micro-nano bubble generation device, and the nanoscale carbonyl iron powder which is narrow in particle size distribution, uniform in morphology and excellent in magnetic performance is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of nano material preparation, and in particular to a method for preparing nano-scale carbonyl iron powder by using micro-nano bubble technology under normal pressure and low temperature conditions and a special device thereof. Background Art

[0002] Carbonyl iron powder is a fine iron powder prepared by the decomposition of carbonyl compounds. It has high purity, high specific surface area and good magnetic properties. It has a wide range of applications in magnetic materials, biomedicine, catalysts, radar stealth absorbing materials, magnetic recording media, magnetic fluids, drug delivery and biosensors.

[0003] However, existing preparation methods such as chemical vapor deposition, pyrolysis, sol-gel, microemulsion and liquid phase reduction usually require high temperature, high pressure or special reaction environment, high equipment cost, high energy consumption and complex production process. Taking the process route of Dow Chemical Company as an example, its process is a two-step process of high-pressure synthesis and thermal decomposition. In the first step, sponge iron blocks are used as synthetic raw materials. First, they are ball-milled into powder and then reduced in a hydrogen atmosphere. Then they are transferred to a synthesis reactor, and then carbon monoxide gas is introduced into the reactor under pressure. At the same time, the reactor body is heated to produce a synthesis reaction to generate pentacarbonyl iron Fe(CO)5 and then cooled to liquid after reduced pressure; in the second step, the generated pentacarbonyl iron Fe(CO)5 is transferred to a vertical cylindrical pyrolysis furnace heated by gas spiral heating to heat it to decompose it and form iron nuclei to grow. After passivation treatment and gas-solid separation, carbonyl iron powder with the required technical performance is finally obtained. At present, the main domestic suppliers of industrial-grade carbonyl iron powder are Jiangsu Tianyi Ultrafine Metal Powder Co., Ltd., Jilin Zhuochuang Innovation Materials Co., Ltd. and Shaanxi Xinghua Chemical Co., Ltd. Their production processes are basically consistent with the process route of Dow Chemical in the United States in the patent, but the minimum particle size under the optimal conditions of this process is spherical carbonyl iron powder of about 5 microns.

[0004] Compared with micron-grade carbonyl iron powder, nano-grade carbonyl iron powder has the advantages of higher surface area, better dispersibility, better magnetic properties, better mechanical properties, and higher electrical and thermal conductivity. The research and development and industrial production of nano-grade carbonyl iron powder has gradually become a new development trend.

[0005] For example, Chinese patent CN105967242A disclosed by Jiangyou Hebao Nanomaterials Co., Ltd. claims that the average particle size of carbonyl iron powder can reach 50nm. However, the micro-nano carbonyl iron powder prepared by this method often has problems such as wide particle size distribution, uneven morphology, unstable magnetic properties, and easy oxidation and agglomeration, which limits its large-scale industrial production and application.

[0006] There is also a Chinese patent document CN204953905U that discloses a passivation device for preparing nano iron powder. After the compressed nitrogen is reduced in pressure, it enters a nitrogen buffer tank, passes through a nitrogen flowmeter, and enters a pentacarbonyl iron gasifier. The iron vapor enters a dilution tank along with the nitrogen gas flow, and enters a high-temperature reactor through a nozzle to undergo a pyrolysis reaction. The nano iron powder generated by the reaction enters a passivator to cool the nano iron powder. After the temperature drops below 30°C, compressed air is introduced to slowly oxidize the cooled iron powder. After the passivation treatment is completed, a (50-100) nm nano iron powder is generated. However, in this method, a high-pressure reactor is also required, and the main component of the generated nano iron powder is iron oxide, while the proportion of pentacarbonyl iron powder is very low.

[0007] Chinese patent document CN220549991U discloses a device for preparing nano carbonyl iron powder based on plasma CVD method, including a spherical reactor, a heater and an evaporation tank, etc., which effectively solves the problems of high activity, large specific surface area, easy disproportionation reaction and inability to mass produce in the process of nano carbonyl iron powder. This scheme uses high-frequency electron beam bombardment, and the carbonyl iron powder produced needs to be decomposed by ethanol catalysis. The process is complicated, and the generated carbonyl iron powder particles are limited by the control accuracy of electronic technology and the particle size is large, which is difficult to reach the nano level.

[0008] The prior art is in urgent need of a method and equipment for producing nano-scale carbonyl iron powder that has important practical significance and broad market prospects, is simple in process, has low energy consumption, is environmentally friendly and efficient, can accurately control the particle size and morphology of the product, and has stable product performance. Summary of the invention

[0009] In order to solve the problems existing in the prior art, the present invention provides a method for preparing nano-scale carbonyl iron powder under normal pressure and low temperature conditions and a special integrated equipment for implementing the above method. By adopting a specially designed micro-nano bubble generating device, efficient cooling and nucleation of iron vapor can be achieved, and nano-scale carbonyl iron powder with narrow particle size distribution, uniform morphology and excellent magnetic properties can be prepared.

[0010] According to one aspect of the present invention, the present invention first provides a method for preparing nanoscale carbonyl iron powder, characterized in that it comprises the following steps in sequence: Step 1: Raw material preparation: Add liquid iron pentacarbonyl into a normal pressure reactor equipped with a stirring device and a heat-insulating interlayer.

[0011] Step 2: Replace gas: introduce high-purity nitrogen (or inert gas) into the atmospheric pressure reactor at a flow rate of 2 times the reactor volume per minute for a period of time to replace the air in the reactor and ensure that the oxygen content is reduced to ≤0.5% (wt) to prevent the pentacarbonyl iron from reacting with oxygen and avoid safety hazards.

[0012] Step 3: heating decomposition: under the conditions of continuous introduction of high-purity nitrogen (or inert gas), ammonia and stirring at (300-600) rpm, the temperature in the autoclave is raised to (160-220)°C at a heating rate of (1-3)°C / min, so that the pentacarbonyl iron is slowly decomposed to generate carbon monoxide gas and iron vapor.

[0013] Step 4: Gas-liquid mixing: High-purity nitrogen (or inert gas) and ammonia are continuously introduced to generate a mixed gas of carbon monoxide and iron vapor from the gas outlet at the top of the atmospheric pressure reactor, and introduced into a micro-nano bubble generating device using a forced mixing method similar to a venturi tube for gas-liquid mixing.

[0014] Step 5: Cooling and nucleation: The micro-nano bubble generating device, the kerosene liquid storage device, the low-temperature cooling medium circulation system and the tail gas treatment system are started, and the nitrogen (or inert gas), ammonia and the generated carbon monoxide flow along the micro-nano bubble generating device and enter the tail gas treatment system from the top of the kerosene liquid storage device (in each embodiment of the present invention, it is exemplified as a liquid storage tank, so it is referred to as the liquid storage tank below), while the iron vapor is in the low-temperature kerosene or other cooling liquid medium (such as n-hexane, cyclohexane or anhydrous ethanol, etc.) with a temperature of (10-15) ° C in the liquid storage tank. The iron vapor is fully in contact with the low-temperature kerosene or other cooling liquid medium and forms micro-nano bubbles, so as to increase the gas-liquid contact area, thereby enhancing the solubility of the reaction gas in the liquid and the cooling effect, so as to quickly cool and nucleate, and form D in the liquid storage device connected to the micro-nano bubble generating device. 50 Nano-scale carbonyl iron powder with a median particle size of about 100nm. Therefore, the high specific surface area and special interface characteristics of micro-nano bubbles are used to promote uniform dispersion and rapid nucleation of iron vapor, thereby controlling the particle size and morphology of nano-scale carbonyl iron powder.

[0015] Step 6: Solid-liquid separation: Solid-liquid separation is performed by vacuum filtration, centrifugation or other appropriate methods. When a vacuum filter is used, a solvent-resistant microporous filter membrane with a pore size of (0.2-0.45) μm is used to achieve solid-liquid separation, and the nano-scale carbonyl iron powder in the liquid storage device is separated from the cooling medium. The filter medium is a solvent-resistant microporous filter membrane or other appropriate material to ensure separation efficiency and product purity.

[0016] Step 7: Washing and drying: Use anhydrous ethanol or organic solvents such as acetone and isopropanol to wash the filtered carbonyl iron powder to remove residual cooling medium and impurities. The number of washing times is (2 to 5) times, and the volume of solvent added each time is much larger than the volume of carbonyl iron powder, such as making its mass about (3 to 5) times the solid mass of carbonyl iron powder, and stirring for (10 to 20) minutes. Then dry in a vacuum drying oven at (60 to 80) ° C, the vacuum degree is (-0.08 to -0.1) MPa, and the drying time is (1 to 3) hours to obtain pure nano-scale carbonyl iron powder.

[0017] Step 8: Solvent recovery: The filtered cooling medium and washing solvent are treated by rectification or distillation to remove impurities and moisture, and then returned to the storage tank after cooling for recycling, thereby reducing resource consumption and environmental pollution.

[0018] According to the method described, the gas-liquid mixing method in step 4 is that the negative pressure generated at the throat of the venturi tube sucks the gas in and fully mixes it with kerosene.

[0019] According to the method described, the mixed gas-liquid volume flow ratio in step 4 is 1:6.

[0020] According to the method described, after heating in step 3, the temperature in the kettle is raised to (160-220)°C.

[0021] According to the method described, after heating in step 3, the temperature in the kettle is raised to 180°C.

[0022] According to the method, in step 3, heating is performed at a heating rate of (1-3)°C / min under stirring conditions of (300-600) rpm.

[0023] According to the method described, the low temperature in step 5 is (10-15)°C.

[0024] According to the method described, the low temperature in step 5 is 12°C.

[0025] According to the method described, the D 50 The median particle size is 155 nm, and the particle size distribution range is (25-826) nm, showing a single-peak narrow distribution and good particle size uniformity.

[0026] According to the method, the low temperature medium in step 5 is kerosene, n-hexane, cyclohexane or anhydrous ethanol. The optimum temperature is 12°C.

[0027] According to the method described, the pore size of the microporous filter membrane used in step 6 is (0.2-0.45) μm.

[0028] According to the method, the washing times in step 7 are (2 to 5) times, stirring is (10 to 20) minutes, and then drying is carried out in a vacuum drying oven at (60 to 80)°C, the vacuum degree is (-0.08 to -0.1) MPa, and the drying time is (1 to 3) hours.

[0029] The present invention also provides an integrated device for implementing the above method, comprising a normal pressure reactor 1, a micro-nano bubble generating device 2, a heating circulation device 3, a cooling circulation device 4, a solid-liquid separation device 5, a vacuum drying oven 6, a liquid storage device 7, an exhaust gas treatment system 8, a nitrogen (or inert gas) generating device 9 and an ammonia generating device 10, wherein high-purity nitrogen (or inert gas) and ammonia are continuously introduced into the normal pressure reactor 1 through the nitrogen (or inert gas) generating device 9 and the ammonia generating device 10, the normal pressure reactor 1 is equipped with a stirring device 11 for stirring, and a heat-insulating interlayer 12 for circulating a heating medium and ensuring a uniform temperature in the reactor, the heating circulation device 3 includes a mold temperature controller for maintaining a stable temperature, a first circulation pump for thermal circulation and a second circulation pump for controlling the temperature. A temperature controller, the cooling circulation device 4 includes a cooler, a liquid storage tank for storing a cooling medium, a second circulation pump for a thermal cycle and a second temperature controller for controlling the temperature, the solid-liquid separation device 5 includes a vacuum filter, a centrifuge, and a washing device, and the drying equipment includes a vacuum drying box 6, wherein the atmospheric pressure reactor 1 is connected to the circulation inlet and outlet 341 and 342 of the heating circulation device 3, the gas outlet 13 of the atmospheric pressure reactor 1 is connected to the inlet 21 of the micro-nano bubble generating device 2, the outlet of the micro-nano bubble generating device 2 is connected to the inlet of the liquid storage device 7, the liquid outlet 72 of the liquid storage device 7 is connected to the inlet 54 of the solid-liquid separation device 5, the outlet 55 of the solid-liquid separation device 5 is connected to the inlet 61 of the vacuum drying box 6, and the collection pipeline of the tail gas treatment system 8 is connected to the gas outlet 71 of the liquid storage device 7.

[0030] According to the equipment, the cooling medium of the cooling circulation device 4 can be pure water.

[0031] According to the equipment, the atmospheric pressure reactor 1 is equipped with a stirring device: including a paddle-type, anchor-type or ribbon-type stirrer driven by a variable frequency speed regulating motor, and the stirring speed is adjustable.

[0032] According to the equipment, the pore size of the microporous filter membrane used in the solid-liquid separation device 5 is (0.2-0.45) μm.

[0033] According to the equipment, the heat transfer medium of the heating circulation device 3 can be selected from mineral oil-based heat transfer oil or silicone oil-based heat transfer oil.

[0034] According to the equipment, the micro-nano bubble generating device 2 is a structure similar to a venturi tube, an ultrasonic atomizer, a static mixer, a jet mixer or a high shear mixer.

[0035] According to the equipment, the atmospheric pressure reactor and the liquid storage device are made of 316L stainless steel, glass lining or ceramic material, and the inner wall is provided with a corrosion-resistant lining coating of PTFE or enamel.

[0036] According to the equipment, the tail gas treatment system includes a tail gas collection pipeline, a carbon monoxide treatment device, a safety valve and a gas detection instrument. The escaped gas is collected and treated to prevent environmental pollution and safety hazards.

[0037] According to the equipment, the tail gas treatment system uses a catalytic oxidation device or an activated carbon adsorption tower to convert or adsorb carbon monoxide.

[0038] According to the present invention, it can be widely used in the field of nano material preparation, and is particularly suitable for large-scale preparation of high-quality nano-scale carbonyl iron powder to meet the needs of the following fields: 1. Magnetic materials: used to manufacture high-performance soft magnetic materials, magnetic recording media, magnetic fluids, etc., to improve the efficiency and performance of electronic devices.

[0039] 2. Biomedicine: As magnetic resonance imaging (MRI) contrast agent, drug delivery carrier, tumor thermal therapy material, biosensor, etc., it has good biocompatibility and magnetic response characteristics.

[0040] 3. Catalyst: As a catalyst or carrier, it is used in organic synthesis, chemical reaction processes and environmental management to improve reaction efficiency and selectivity.

[0041] 4. Radar stealth absorbing materials: used to manufacture electromagnetic shielding materials and stealth materials, used in national defense, aerospace and communications fields to prevent electromagnetic interference.

[0042] 5. Other fields: such as energy storage, sensors, nanocomposites, etc., have broad application prospects.

[0043] According to the present invention, compared with the existing technology, the beneficial effects of this technical solution are as follows: 1. Simple process and low energy consumption: The whole process is carried out under normal pressure and low temperature conditions, without the need for high temperature and high pressure equipment, which reduces equipment investment and operating costs. The innovative micro-nano bubble technology is used to achieve efficient cooling and nucleation of iron vapor, thereby improving production efficiency.

[0044] 2. Excellent product performance: Due to the low temperature, large gas-liquid interface, high nucleation rate, and suppressed particle growth, nano-scale carbonyl iron powder with narrow particle size distribution and uniform morphology is finally formed. The prepared nano-scale carbonyl iron powder has small particle size (average particle size of about 100 nm), narrow particle size distribution (10nm to 1000nm), uniform morphology, and excellent magnetic properties (high saturation magnetization and low coercive force), meeting the needs of high-end applications.

[0045] 3. Green and environmentally friendly: No harmful by-products are produced during the production process, and the tail gas is effectively treated (such as catalytic oxidation and adsorption) to meet environmental protection requirements. Solvents (such as kerosene and anhydrous ethanol) can be recycled, reducing resource consumption and environmental pollution.

[0046] 4. Suitable for industrial-scale production: The equipment has a simple structure, is easy to operate and maintain, and is suitable for large-scale industrial production.

[0047] 5. Wide application: The parameters are highly controllable. By adjusting the stirring speed, heating rate, gas-liquid ratio, cooling medium type and temperature, the particle size and morphology of the product can be accurately controlled to meet the needs of different application fields.

[0048] In general, compared with the prior art, the present invention has the advantages of low cost, environmental protection, high efficiency, narrow particle size distribution, uniform morphology, stable magnetic properties, etc. It is an ideal production equipment and method for nano-scale carbonyl iron powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The present invention is a schematic diagram of an integrated device for preparing nano-scale carbonyl iron powder according to a method for preparing nano-scale carbonyl iron powder according to a specific embodiment of the present invention.

[0050] Figure 2 The figure shows the particle size distribution of an iron powder product prepared by a method for preparing nano-scale carbonyl iron powder according to a specific embodiment of the present invention.

[0051] Figure 3 The present invention is directed to a scanning electron microscope image of an iron powder product prepared by a method for preparing nano-scale carbonyl iron powder according to a specific embodiment of the present invention.

[0052] Figure 4 for Figure 1 A schematic diagram of a normal-pressure reactor of an integrated device for preparing nano-scale carbonyl iron powder is shown.

[0053] Figure 5 for Figure 1 A schematic diagram of a micro-nano bubble generating device of an integrated device for preparing nano-scale carbonyl iron powder is shown.

[0054] Figure numerals: 1-normal pressure reactor; 11-stirring device; 12-insulating interlayer; 13-reactor outlet; 2-micro-nano bubble generating device; 21-micro-nano bubble generating device air inlet; 22-micro-nano bubble generating device liquid inlet; 23-gas-liquid forced mixer (Venturi tube); 24-micro-nano bubble generating device gas-liquid outlet; 3-heating circulation device; 341, 342-circulation inlet and outlet; 4-cooling circulation device; 5-solid-liquid separation device; 54-solid-liquid separation device inlet; 55-solid-liquid separation device outlet; 6-vacuum drying oven; 61-vacuum drying oven inlet; 7-kerosene liquid storage device; 71-gas outlet of liquid storage device 7; 72-liquid outlet of liquid storage device 7; 8-tail gas treatment system; 9-nitrogen (or inert gas) generating device; 10-ammonia generating device; 1001-solid-liquid separation pump. DETAILED DESCRIPTION

[0055] The present invention will be described in detail below in combination with specific embodiments with reference to the accompanying drawings. Those skilled in the art will appreciate that the description is exemplary and the present invention is not limited to the specific embodiments.

[0056] Figure 1 The present invention is a schematic diagram of an integrated device for preparing nano-scale carbonyl iron powder according to a method for preparing nano-scale carbonyl iron powder according to a specific embodiment of the present invention.

[0057] like Figure 1As shown, an integrated device for preparing nano-scale carbonyl iron powder comprises a normal pressure reactor 1, a micro-nano bubble generator 2, a heating circulation device 3, a cooling circulation device 4, a solid-liquid separation device 5, a vacuum drying oven 6, a liquid storage device 7, an exhaust gas treatment system 8, a nitrogen (or inert gas) generator 9 and an ammonia generator 10, wherein high-purity nitrogen (or inert gas) is continuously introduced into the normal pressure reactor 1 through the nitrogen (or inert gas) generator 9, and high-purity ammonia is continuously introduced into the normal pressure reactor 1 through the ammonia generator 10, and the normal pressure reactor 1 is equipped with a stirring device 11 for stirring and a heating medium 12 for heating. The atmospheric pressure reactor 1 is connected to the circulation inlet and outlet 341 and 342 of the heating circulation device 3, the gas outlet 13 of the atmospheric pressure reactor 1 is connected to the inlet 21 of the micro-nano bubble generating device 2, the outlet of the micro-nano bubble generating device 2 is connected to the inlet of the kerosene liquid storage device 7, the liquid outlet 71 of the kerosene liquid storage device 7 is connected to the inlet 54 of the solid-liquid separation device 5, a solid-liquid separation pump 1001 is arranged near the inlet 54 of the solid-liquid separation device, the outlet 55 of the solid-liquid separation device 5 is connected to the inlet 61 of the vacuum drying box 6, and the collection pipeline of the tail gas treatment system 8 is connected to the gas outlet 72 of the liquid storage device 7. The nitrogen (or inert gas) generating device 9 is used to continuously introduce nitrogen (or inert gas) into the atmospheric pressure reactor 1. The ammonia generating device 10 is used to continuously introduce ammonia into the atmospheric pressure reactor 1.

[0058] The liquid storage device 7 is similar to the atmospheric pressure reactor 1 except for its shape. The reactor body of the liquid storage device 7 is made of 316L stainless steel, glass-lined or ceramic material, and the inner wall is provided with a corrosion-resistant lining of PTFE or enamel coating, equipped with a stirring device and a thermal insulation interlayer, and is used for the storage of low-temperature kerosene or other cooling liquid media.

[0059] The tail gas treatment system 8 includes: a tail gas collection pipeline: connected to the gas outlet 71 of the kerosene liquid storage device 7, and made of PTFE or other corrosion-resistant materials.

[0060] Carbon monoxide treatment device: Use catalytic oxidation device or activated carbon adsorption tower to convert or adsorb carbon monoxide.

[0061] Safety valve and testing instruments: Equipped with pressure safety valve, carbon monoxide detection alarm device and oxygen analyzer to ensure system safety.

[0062] The tail gas treatment system 8 is used to collect, enrich and treat the escaped nitrogen and carbon monoxide gases to prevent environmental pollution and safety hazards.

[0063] It should be noted that, during the preparation process, various safety and environmental protection measures are preferably designed to prevent unexpected accidents, such as: Equipment anti-corrosion: The inner wall of key equipment is covered with PTFE lining or corrosion-resistant materials such as glass lining and ceramics to prevent corrosive media from eroding the equipment and extend the service life of the equipment.

[0064] Gas detection: Install carbon monoxide and oxygen detection alarm devices and pressure sensors to monitor the working environment and equipment operating status in real time to ensure the safety of operators.

[0065] Explosion-proof design: The equipment complies with explosion-proof standards, and electrical equipment adopts explosion-proof type to eliminate the risks of sparks and static electricity.

[0066] Emergency Plan: Develop a detailed emergency plan and equip yourself with necessary safety protection equipment and facilities, such as fire extinguishers, first aid kits, protective clothing, etc.

[0067] Tail gas treatment: Tail gas is treated by catalytic oxidation or adsorption to ensure that emissions meet environmental protection requirements and reduce impact on the environment.

[0068] Solvent recovery: Cooling medium and washing solvent are recycled after treatment, reducing resource consumption and production costs and reducing environmental pollution.

[0069] For the sake of simplicity and convenience, all the following embodiments are described by taking the introduction of nitrogen as an example. Those skilled in the art will appreciate that, alternatively, an inert gas may be used instead of nitrogen.

[0070] The preparation process is described in detail below.

[0071] First, raw materials are prepared: liquid iron pentacarbonyl is added into a normal pressure reactor 1 equipped with a stirring device 11 and a heat-insulating interlayer 12 .

[0072] Then: Replace gas: introduce high-purity nitrogen generated by the nitrogen generator 9 into the atmospheric pressure reactor 1 at a flow rate of 2 times the reactor volume per minute, and continue to introduce it for a period of time to replace the air in the reactor, ensuring that the oxygen content in the atmospheric pressure reactor 1 drops to ≤0.5% (wt) to prevent the pentacarbonyl iron from reacting with oxygen and avoid safety hazards.

[0073] Next: heating decomposition: under the condition of continuous introduction of high-purity nitrogen and ammonia and stirring at (300-600) rpm of the stirring device 11, the temperature in the kettle is raised to (160-220)°C at a heating rate of (1-3)°C / min using the heating circulation device 3, so that the pentacarbonyl iron is slowly decomposed to generate carbon monoxide gas and iron vapor.

[0074] Further: gas-liquid mixing: high-purity nitrogen and ammonia are continuously introduced to introduce the mixed gas of carbon monoxide and iron vapor generated in the atmospheric pressure reactor 1 from the gas outlet 13 at the top of the atmospheric pressure reactor 1 into the micro-nano bubble generating device 2 using a forced mixing method similar to a venturi tube to perform gas-liquid mixing.

[0075] Then: cooling and nucleation: start the micro-nano bubble generating device 2, the kerosene liquid storage device 7, the low-temperature cooling medium circulation system 4, and the tail gas treatment system 8, the nitrogen, ammonia and the generated carbon monoxide flow along the micro-nano bubble generating device 2, and enter the tail gas treatment system 8 from the top of the kerosene liquid storage device 7 through the gas outlet 71, while the iron vapor is in the low-temperature kerosene or other cooling liquid medium (in one embodiment, n-hexane, cyclohexane or anhydrous ethanol, etc.) with a temperature of (10-15) ° C in the liquid storage tank 7, and fully contacts with the low-temperature kerosene or other cooling liquid medium to form micro-nano bubbles, so as to increase the gas-liquid contact area and thus enhance the solubility of the reaction gas in the liquid and the cooling effect, so as to quickly cool and nucleate, and form D in the liquid storage device 7 connected to the micro-nano bubble generating device 2. 50 Nano-scale carbonyl iron powder with a median particle size of about 100nm. Therefore, the high specific surface area and special interface characteristics of micro-nano bubbles are used to promote uniform dispersion and rapid nucleation of iron vapor, thereby controlling the particle size and morphology of nano-scale carbonyl iron powder.

[0076] Further: Solid-liquid separation: The solid-liquid product formed in the liquid storage device 7 is subjected to vacuum filtration, centrifugation or other appropriate methods (in a preferred embodiment, extraction) by the solid-liquid separation device 5 to perform solid-liquid separation. When a vacuum filter is used, a solvent-resistant microporous filter membrane with a pore size of (0.2-0.45) μm is used to achieve solid-liquid separation, and the nano-scale carbonyl iron powder in the liquid storage device 7 is separated from the cooling medium. The filter medium is selected from a solvent-resistant microporous filter membrane or other appropriate materials (such as activated carbon) to ensure separation efficiency and product purity.

[0077] Finally: washing and drying: use anhydrous ethanol or acetone, isopropanol and other organic solvents to wash the filtered carbonyl iron powder to remove the residual cooling medium and impurities. The washing times are (2 to 5) times, and the volume of the solvent added each time is much larger than the volume of the carbonyl iron powder, such as making its mass about (3 to 5) times the solid mass of the carbonyl iron powder, and stirring for (10 to 20) minutes. Then dry in a vacuum drying oven 6 at (60 to 80) ° C, the vacuum degree is (-0.08 to -0.1) MPa, and the drying time is (1 to 3) hours to obtain pure nano-scale carbonyl iron powder.

[0078] In addition, in order to save costs and protect the environment, a solvent recovery step can be further included: the filtered cooling medium and washing solvent are subjected to rectification or distillation to remove impurities and moisture, and then returned to the liquid storage tank 7 after cooling for recycling, thereby reducing resource consumption and environmental pollution.

[0079] In a preferred embodiment, the gas-liquid mixing method is that the negative pressure generated at the throat of the venturi tube sucks the gas in and fully mixes it with the kerosene.

[0080] In a preferred embodiment, the mixed gas-liquid volume flow ratio is 1:6.

[0081] In a preferred embodiment, after heating, the temperature inside the normal temperature reactor 1 is raised to (160-220)° C. More preferably, after heating, the temperature inside the reactor is raised to 180° C.

[0082] In a preferred embodiment, the heating is carried out at a heating rate of (1-3)° C. / min under stirring conditions of (300-600) rpm.

[0083] In a preferred embodiment, the low temperature is (10-15)°C. More preferably, the low temperature is 12°C.

[0084] In the present invention, the low-temperature medium is kerosene, n-hexane, cyclohexane or anhydrous ethanol.

[0085] In a preferred embodiment, the pore size of the microporous filter membrane used is (0.2-0.45) μm.

[0086] In a preferred embodiment, the washing times are (2 to 5) times, stirring is (10 to 20) minutes, and then drying is carried out in a vacuum drying oven at (60 to 80)°C, the vacuum degree is (-0.08 to -0.1) MPa, and the drying time is (1 to 3) hours.

[0087] In a preferred embodiment, the cooling medium may also be pure water.

[0088] In a preferred embodiment, the stirring device 11 equipped in the atmospheric pressure reactor 1 may include a paddle-type, anchor-type or ribbon-type stirrer driven by a variable frequency speed regulating motor, and the stirring speed is adjustable.

[0089] In a preferred embodiment, the heat transfer medium used in the heating circulation device 3 to heat the atmospheric pressure reactor 1 to a temperature above the set temperature can be selected from mineral oil-based heat transfer oil or silicone oil-based heat transfer oil.

[0090] In a preferred embodiment, the micro-nano bubble generating device 2 is a structure similar to a venturi tube, including an ultrasonic atomizer, a static mixer, a jet mixer or a high shear mixer.

[0091] In a preferred embodiment, the atmospheric pressure reactor 1 and the liquid storage device 7 are made of 316L stainless steel, glass lining or ceramic material, and the inner wall is provided with a corrosion-resistant lining coating of PTFE or enamel.

[0092] In a preferred embodiment, the tail gas treatment system includes a tail gas collection pipeline, a carbon monoxide treatment device, a safety valve and a gas detection instrument to collect and treat the escaped gas to prevent environmental pollution and safety hazards.

[0093] In a preferred embodiment, the tail gas treatment system uses a catalytic oxidation device or an activated carbon adsorption tower to convert or adsorb carbon monoxide.

[0094] The heating circulation device 3, the cooling circulation device 4, and the filtering and drying equipment are described in detail below.

[0095] In a preferred embodiment, the heating circulation device 3 comprises: Heater (temperature mold machine, not shown): Use plate heat exchanger, spiral tube heat exchanger or other high-efficiency heat exchange equipment to increase the medium temperature.

[0096] Liquid storage tank (not shown): used to store the solid-liquid products after cooling, made of 316L stainless steel lined with PTFE or other corrosion-resistant materials.

[0097] First circulation pump: adjusts the circulation flow rate of the heat transfer medium to ensure a stable liquid supply.

[0098] First temperature controller: The heat transfer medium can be selected from mineral oil-based heat transfer oil or silicone oil-based heat transfer oil, which can accurately ensure that the temperature is maintained at (160-220)°C, preferably 180°C, to provide a stable heating environment.

[0099] In a preferred embodiment, the cooling circulation device 4 comprises: Cooler (not shown): Use plate heat exchanger, spiral tube heat exchanger or other high-efficiency heat exchange equipment to reduce the temperature of the cooling medium.

[0100] The second liquid storage tank (not shown): used to store the cooled medium, made of 316L stainless steel lined with PTFE or other corrosion-resistant materials.

[0101] Second circulation pump (not shown): adjusts the circulation flow rate of the cooling medium to ensure a stable liquid supply.

[0102] The second temperature controller (not shown): provides a stable cooling environment and accurately controls the temperature of the cooling medium at (10-15)°C, with the optimum being 12°C. Pure water can be used as the cooling medium.

[0103] The cooling circulation device 4 provides a low-temperature cooling medium for the micro-nano bubble generating device, ensuring that the iron vapor is rapidly cooled and nucleated therein.

[0104] In a preferred embodiment, the filtering and drying equipment comprises a solid-liquid separation device 5 and a drying device, wherein the solid-liquid separation device 5 comprises a vacuum filter and a centrifuge. A solid-liquid separation pump 1001 is installed near the inlet and outlet of the solid-liquid separation device 5.

[0105] Filter medium: solvent-resistant microporous filter membrane with a pore size of (0.2~0.45) μm.

[0106] Material: The equipment material should be solvent-resistant and corrosion-resistant, lined with PTFE or made of stainless steel.

[0107] Washing device: Washing device using anhydrous ethanol or other organic solvents, made of stainless steel lined with PTFE.

[0108] The drying equipment includes a vacuum drying box 6, which is used for separation, washing and drying of carbonyl iron powder and cooling medium to ensure the purity and quality of the product.

[0109] Temperature control: The temperature is set at (60~80)℃.

[0110] Vacuum degree: (-0.08~-0.1) MPa.

[0111] Material: Stainless steel lined with PTFE or other corrosion resistant materials.

[0112] Figure 2 The figure shows the particle size distribution of an iron powder product prepared by a method for preparing nano-scale carbonyl iron powder according to a specific embodiment of the present invention. Figure 3 This is a scanning electron microscope image.

[0113] like Figure 2 As shown in the figure, the D of nano-scale carbonyl iron powder was measured by tracking analyzer ZetaView. 50 The median particle size is 155 nm, and the particle size distribution range is (25-826) nm, showing a single-peak narrow distribution and good particle size uniformity.

[0114] like Figure 3 As shown, the morphology was observed using a scanning electron microscope (SEM). The particles were mainly spherical, with a small amount of ellipsoidal, smooth surface, no obvious defects or roughness, good particle dispersion, and no obvious agglomeration.

[0115] Figure 4 for Figure 1 A schematic diagram of a normal-pressure reactor of an integrated device for preparing nano-scale carbonyl iron powder is shown.

[0116] like Figure 4As shown, the atmospheric pressure reactor 1 structurally comprises: Kettle body: cylindrical, made of 316L stainless steel, glass-lined or ceramic materials, with PTFE, glass-lined or enamel corrosion-resistant lining coating on the inner wall to prevent corrosive media from eroding the equipment and extend the service life of the equipment.

[0117] Stirring device 11: equipped with a paddle, anchor or ribbon stirrer driven by a variable frequency speed regulating motor, with adjustable stirring speed.

[0118] Insulation interlayer 12: used for circulation of heating medium to ensure uniform temperature in the kettle.

[0119] Sealing design: A corrosion-resistant sealing ring (such as PTFE gasket) is used to seal the kettle cover and the kettle body to prevent gas leakage.

[0120] Inlet and outlet: A gas outlet 13 is provided at the top, and a raw material inlet and a discharge port (not shown) are provided at the bottom to facilitate the addition of materials and the extraction of gas.

[0121] Iron pentacarbonyl is thermally decomposed in the atmospheric pressure reactor 1 to generate carbon monoxide gas and iron vapor.

[0122] Figure 5 for Figure 1 A schematic diagram of a micro-nano bubble generating device 2 of an integrated device for preparing nano-scale carbonyl iron powder is shown.

[0123] like Figure 5 As shown, the structure adopts a structure similar to that of a Venturi tube. Figure 5 The part marked as 23 is a gas-liquid forced mixer, which adopts a venturi tube structure. In another preferred embodiment of the present invention, it can also be an ultrasonic atomizer, a static mixer, a jet mixer, a high shear mixer, and other mixing devices capable of generating micro-nano bubbles. For specific details, please refer to another patent CN115318118A of the applicant, which is introduced into this article by reference.

[0124] Venturi tube: includes an inlet 21, a throat 23 and an outlet 24. The inlet and outlet are designed to be gradually contracted and expanded to ensure a smooth transition of the fluid.

[0125] The gas inlet is set at the throat and is made of corrosion-resistant materials to prevent medium corrosion.

[0126] Material: The main body is made of 316L stainless steel, the inner wall is lined with PTFE, and the key parts can be made of corrosion-resistant alloys or polymer materials.

[0127] In the micro-nano bubble generating device 2, the high-speed flowing cooling medium generates negative pressure or shear force in the throat or specific structure, sucking in the gas and fully mixing it with the cooling medium to form micro-nano bubbles, thereby increasing the gas-liquid contact area and enhancing the solubility of the reaction gas in the liquid and the cooling effect. Example 1

[0128] Liquid pentacarbonyl iron was added to a 5L atmospheric pressure reactor with a PTFE lining on the inner wall. The reactor thickness was 5mm. The stirring device of the reactor was started at a stirring speed of 100 rpm. High-purity nitrogen and ammonia were continuously introduced into the reactor at a flow rate of 10L / min for 15min. The oxygen content in the reactor was detected using an oxygen analyzer to ensure that it dropped to ≤0.5%. The stirring speed was increased to 500 rpm, the high-temperature heating medium circulation system was started, and the temperature in the reactor was raised to 160℃ at a heating rate of 2℃ / min. The generated gas escaped from the gas outlet at the top of the reactor and entered the micro-nano bubble generator. The low-temperature cooling medium circulation system, the micro-nano bubble generator and the liquid storage tank were started, and nitrogen, ammonia and carbon monoxide entered the exhaust gas treatment system from the top of the liquid storage tank. Kerosene was used as the cooling medium with a temperature of 12℃ and a flow rate of 20 mL / s. The throat diameter of the venturi tube was 5mm, the mixed gas was fully mixed with kerosene, and the flow ratio of gas to liquid was adjusted to 1:6.

[0129] The kerosene suspension containing nano-scale carbonyl iron powder in the liquid storage device is passed through a vacuum filter, and a solvent-resistant microporous filter membrane with a pore size of 0.45 μm is used to achieve solid-liquid separation. The filter cake is then washed three times with anhydrous ethanol. The washed carbonyl iron powder is then placed in a vacuum drying oven at 60°C and a vacuum degree of -0.09 Mpa for 1 hour and then sealed and stored. Example 2

[0130] Liquid pentacarbonyl iron was added to a 5L atmospheric pressure reactor with a PTFE lining on the inner wall. The reactor thickness was 5mm. The stirring device of the reactor was started at a stirring speed of 300 rpm. High-purity nitrogen and ammonia were continuously introduced into the reactor at a flow rate of 10L / min for 15min. The oxygen content in the reactor was detected using an oxygen analyzer to ensure that it dropped to ≤0.5%. The stirring speed was increased to 500 rpm, the high-temperature heating medium circulation system was started, and the temperature in the reactor was raised to 180℃ at a heating rate of 2℃ / min. The generated gas escaped from the gas outlet at the top of the reactor and entered the micro-nano bubble generator. The low-temperature cooling medium circulation system, the micro-nano bubble generator and the liquid storage tank were started, and nitrogen, ammonia and carbon monoxide entered the exhaust gas treatment system from the top of the liquid storage tank. Kerosene was used as the cooling medium with a temperature of 10℃ and a flow rate of 20 mL / s. The throat diameter of the venturi tube was 10mm, the mixed gas was fully mixed with kerosene, and the flow ratio of gas to liquid was adjusted to 1:6.

[0131] The kerosene suspension containing nano-scale carbonyl iron powder in the liquid storage device is passed through a vacuum filter, and a solvent-resistant microporous filter membrane with a pore size of 0.35 μm is used to achieve solid-liquid separation. The filter cake is then washed three times with anhydrous ethanol. The washed carbonyl iron powder is then placed in a vacuum drying oven at 60°C and a vacuum degree of -0.09 Mpa for 2 hours and then sealed and stored. Example 3

[0132] Liquid pentacarbonyl iron was added to a 5L atmospheric pressure reactor with a PTFE lining on the inner wall. The reactor thickness was 5mm. The stirring device of the reactor was started at a stirring speed of 300 rpm. High-purity nitrogen and ammonia were continuously introduced into the reactor at a flow rate of 10L / min for 15min. The oxygen content in the reactor was detected using an oxygen analyzer to ensure that it dropped to ≤0.5%. The stirring speed was increased to 500 rpm, the high-temperature heating medium circulation system was started, and the temperature in the reactor was raised to 120℃ at a heating rate of 2℃ / min. The generated gas escaped from the gas outlet at the top of the reactor and entered the micro-nano bubble generator. The low-temperature cooling medium circulation system, the micro-nano bubble generator and the liquid storage tank were started, and nitrogen, ammonia and carbon monoxide entered the exhaust gas treatment system from the top of the liquid storage tank. Kerosene was used as the cooling medium with a temperature of 10℃ and a flow rate of 20 mL / s. The throat diameter of the venturi tube was 5mm, the mixed gas was fully mixed with kerosene, and the flow ratio of gas to liquid was adjusted to 1:6.

[0133] The kerosene suspension containing nano-scale carbonyl iron powder in the liquid storage device is passed through a vacuum filter, and a solvent-resistant microporous filter membrane with a pore size of 0.2 μm is used to achieve solid-liquid separation. The filter cake is then washed three times with anhydrous ethanol. The washed carbonyl iron powder is then placed in a vacuum drying oven at 60°C and a vacuum degree of -0.09 Mpa for 1 hour and then sealed and stored.

[0134] The performance of the products prepared in Examples 1 to 3 was tested Measurement method: Determination by ZetaView nanoparticle tracking analyzer.

[0135] D 50 The median particle size is 155 nm, the particle size distribution range is (25-826) nm, showing a single peak narrow distribution, and the particle size uniformity is good ( Figure 2 ).

[0136] Observation method: Scanning electron microscope (SEM) was used for morphology observation.

[0137] Morphological characteristics: The particles are mainly spherical, with a small amount of ellipsoidal, smooth surface, no obvious defects or roughness, good particle dispersion, no obvious agglomeration ( Figure 3 ).

[0138] The present invention has been described in detail above with reference to specific embodiments. Those skilled in the art will appreciate that the description is illustrative only and that various changes and modifications may be made thereto. As long as they do not depart from the purpose and spirit of the present invention, these changes and modifications shall fall within the scope of protection of the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A method for preparing nano-scale carbonyl iron powder, comprising the following steps in sequence: Step 1: Raw material preparation: Add liquid iron pentacarbonyl into a normal pressure reactor; Step 2: Replace gas: introduce high-purity nitrogen or inert gas into the reactor at a flow rate of 2 times the reactor volume per minute for a period of time to replace the air in the reactor and ensure that the oxygen content drops to ≤0.5%; Step 3: Heating and decomposing: heating the reactor under continuous introduction of high-purity nitrogen or inert gas, ammonia and stirring conditions to raise the temperature in the reactor, so that the pentacarbonyl iron slowly decomposes to generate carbon monoxide gas and iron vapor; Step 4: gas-liquid mixing: high-purity nitrogen and ammonia are continuously introduced to generate a mixed gas of carbon monoxide and iron vapor from the gas outlet at the top of the atmospheric pressure reactor, and introduced into the micro-nano bubble generating device for gas-liquid mixing; Step 5: Cooling and nucleation: The micro-nano bubble generator, the kerosene liquid storage device, the low-temperature cooling medium circulation system, and the tail gas treatment system are started, and the nitrogen, ammonia, and the generated carbon monoxide flow along the micro-nano bubble generator and enter the tail gas treatment system from the top of the kerosene liquid storage device, while the iron vapor is rapidly cooled and nucleated in the cooling medium in the liquid storage tank to form nano-scale carbonyl iron powder; Step 6: solid-liquid separation: separating the formed nano-scale carbonyl iron powder from the cooling medium; Step 7: Washing and drying: Use an organic solvent to wash the filtered carbonyl iron powder to remove residual cooling medium and impurities to obtain pure nano-scale carbonyl iron powder.

2. The method according to claim 1, characterized in that The gas-liquid mixing method is that the negative pressure generated at the throat of the venturi tube sucks the gas and fully mixes it with the kerosene.

3. The method according to claim 2, characterized in that The mixed gas-liquid volume flow ratio in step 5 is 1:

6.

4. The method according to any one of claims 1 to 3, characterized in that Nano-scale carbonyl iron powder was measured by tracking analyzer ZetaView 50 The median particle size is 155 nm, and the particle size distribution range is (25-826) nm, showing a single-peak narrow distribution and uniform particle size.

5. The method according to claim 1, characterized in that The low-temperature medium is kerosene, n-hexane, cyclohexane or anhydrous ethanol.

6. An integrated device for preparing nano-scale carbonyl iron powder by the method according to any one of claims 1 to 5, comprising a normal pressure reactor, a micro-nano bubble generating device, a heating circulation device, a cooling circulation device, a solid-liquid separation device, a vacuum drying oven, and a liquid storage device, wherein: The atmospheric pressure reactor is connected to the circulation inlet and outlet of the heating circulation device, the gas outlet of the atmospheric pressure reactor is connected to the inlet of the micro-nano bubble generating device, the outlet of the micro-nano bubble generating device is connected to the inlet of the liquid storage device, the liquid outlet of the liquid storage device is connected to the inlet of the solid-liquid separation device, and the outlet of the solid-liquid separation device is connected to the inlet of the vacuum drying box.

7. The device according to claim 6, characterized in that Pure water is selected as the cooling medium.

8. The device according to claim 6, characterized in that The pore size of the microporous filter membrane used in the solid-liquid separation device is (0.2-0.45) μm.

9. The device according to claim 6, characterized in that The atmospheric pressure reactor and the liquid storage device are both made of 316L stainless steel, glass lining or ceramic materials, and the inner walls are both provided with a corrosion-resistant lining coating of PTFE or enamel.

10. The device according to any one of claims 6 to 9, characterized in that It also includes an exhaust gas treatment system, which includes an exhaust gas collection pipeline, a carbon monoxide treatment device, a safety valve and a gas detection instrument.

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