Quenching crystallization reaction system and application thereof in clean preparation of layered composite metal hydroxide

Abstract

The invention provides a quenching crystallization reaction system for preparing layered composite metal hydroxides and a corresponding preparation method, a high-pressure cooling distributor is additionally arranged between a reaction kettle and a collecting tank, and the high-pressure cooling distributor comprises a cavity and a quenching device which are communicated with each other; and a low-temperature cooling medium enters the cavity from the quenching device, is in direct contact with the high-temperature reaction slurry and rapidly cools the high-temperature reaction slurry, so that the layered composite metal hydroxide with the surface defect active site can be obtained. According to the invention, a cooling liquid system consistent with hydrotalcite reaction slurry is adopted, construction of defect active sites is realized for hydrotalcite through a quenching type cooling mode under the condition of not introducing impurities, the product performance can be effectively improved, the equipment requirement is low, the process is simple, the cost is effectively reduced, and the method is suitable for industrial production. And meanwhile, the impurity ion introduction problem caused by acid-base solvent etching and the like is also avoided, the process cleanliness is guaranteed, and the method is very suitable for industrial implementation.

Description

Technical Field

[0001] This invention belongs to the field of inorganic functional material preparation technology, and specifically relates to a quenching crystallization reaction system and a method for preparing layered composite metal hydroxides using the same. Background Technology

[0002] Layered double hydroxides (LDHs), also known as hydrotalcite, are a typical anionic layered material with the chemical formula [M]. 2+1-x M 3+x (OH)2]A n- x / n ·mH2O, where M 2+ M 3+ They are divalent and trivalent metal cations, respectively, A n- For interlayer anions, x is M 3+ The mole fraction of ions, where m is the amount of water of crystallization. LDHs have rich tunability; by designing and preparing their structures in a targeted manner, functional materials with different properties can be designed and constructed, such as high-efficiency smoke suppressants, chlorine absorbers, ultra-stable mineralizing materials, and catalytic materials. They have wide applications in plastic additives, environmental protection, and industrial catalysis, with broad industry coverage and large demand.

[0003] In recent years, a series of studies have found that material defect sites can serve as reactive sites to significantly improve material performance. Hydrotalcite, as a functional nanomaterial, can be used to enhance its application performance in areas such as smoke suppression, catalysis, and ion adsorption by constructing and precisely controlling defect structures within it. Traditional methods for constructing surface defect active sites in nanomaterials such as hydrotalcite often employ chemical methods like acid-base etching and hydrogen reduction, as well as physical methods such as high-energy ion irradiation and ball milling. However, these methods all have several drawbacks: acid-base etching requires the introduction of solvents such as acids or alkalis into the reaction vessel to treat the surface, which can easily introduce new impurity ions, necessitating washing to remove them. This process generates wastewater, leading to a lengthy process, increased costs, and failure to meet environmental protection requirements. Hydrogen reduction methods often require the use of reducing gases such as hydrogen at high temperatures to treat solid powders, which can easily cause powder agglomeration. Furthermore, the use of hydrogen places high demands on equipment safety. Ball milling also tends to cause powder agglomeration and exhibits poor stability. High-energy ion irradiation methods have high equipment requirements and are difficult to scale up for production. Therefore, improving methods for constructing surface defects in materials while ensuring reaction effectiveness, enhancing safety, and reducing costs has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0004] To improve production efficiency and cleanliness, and to enable rapid and controllable preparation of layered composite metal hydroxides with abundant surface defect structures and active sites, and to facilitate large-scale production, this invention provides a quenching crystallization reaction system and its application in the clean preparation of layered composite metal hydroxides.

[0005] This invention provides a quenching crystallization reaction system for preparing layered composite metal hydroxides, comprising a reaction vessel for preparing a slurry and a collection tank for collecting the slurry, wherein a high-pressure cooling distributor is connected between the reaction vessel and the collection tank. The high-pressure cooling distributor includes a cavity and a quenching device for injecting cooling medium into the cavity. The cavity is connected to the reactor and the collection tank, and is used to contain the slurry from the reactor and output the slurry after being quenched by the quenching device to the collection tank; The quenching device includes one or more nozzles communicating with a cavity and a delivery channel for conveying a cooling medium to the nozzles; the nozzles are used to spray the cooling medium into the cavity to quench the slurry, and the cooling medium has the same composition as the reaction medium in the reactor; the cavity is also used to convey the slurry cooled by the cooling medium to the collection tank.

[0006] Furthermore, the quenching device includes multiple conveying channels, each of which is connected to multiple nozzles; And / or, the cavity is a cylindrical body, and the outer surface of the cylinder is uniformly provided with multiple conveying channels and multiple nozzles communicating with each conveying channel. Optionally, the length-to-diameter ratio of the cylinder is 1-10.

[0007] Furthermore, the nozzles connected along the same conveying channel are arranged axially along the cylinder; And / or, each nozzle protrudes 1-5 cm into the cavity wall; And / or, the nozzle is an anti-clogging atomizing nozzle.

[0008] Furthermore, the cooling medium is selected from one or two of water, ethanol, and ethylene glycol, preferably water.

[0009] Furthermore, a heat exchanger is connected between the reactor and the high-pressure cooling distributor to pre-cool the high-temperature reaction slurry. When the slurry reaction temperature is too high (e.g., above 150°C), it is cooled by 10-20°C before entering the high-pressure cooling distributor, thereby protecting the equipment.

[0010] Preferably, the high-pressure cooling distributor 3 is a sealed pressure-resistant cylinder that can withstand pressures of 0~3MPa. The cylinder diameter is 1~50 times the diameter of the reactor outlet pipe, preferably 5~20 times; the cylinder length-to-diameter ratio is 1-10.

[0011] Preferably, the high-pressure cooling distributor 3 is made of stainless steel and can withstand pressures of 0~2.0MPa, with a cylinder diameter of 40cm and a length of 80cm.

[0012] Preferably, the high-pressure cooling distributor 3 is made of nickel-based alloy and can withstand pressures of 0~2.5MPa, with a cylinder diameter of 30cm and a length of 90cm.

[0013] Preferably, the high-pressure cooling distributor 3 is made of Hastelloy alloy, which can withstand pressures of 0~2.0MPa, and has a cylinder diameter of 50cm and a length of 100cm.

[0014] Another aspect of the present invention provides a method for preparing layered composite metal hydroxides, which utilizes the above-described quenching crystallization reaction system. The method includes the following steps: A. Using M1 2+ Hydroxides and M1 2+ At least one of the oxides and M2 3+ Hydroxides and M2 3+ At least one of the oxides, according to M1 2+ With M2 3+ The mixture is prepared in a molar ratio of 1:1 to 1:4, and a reaction medium is added to adjust the solid content to 10% to 50%. After pretreatment in a sand mill, the slurry is transferred to the reaction vessel. M1 2+ Selected from Mg 2+ Zn 2+ Ca 2+ Ni 2+ One or two of them, the M2 3+ Selected from Al 3+ Cr 3+ One or two of them; B. The slurry is heated and stirred in a reactor at a stirring speed of 50~500 rpm and a temperature of 80~200℃. After reaching the reaction temperature, it is pressurized or the interlayer guest material is added before heating. C. After the reaction is completed, the reacted slurry is transported to the cavity of the high-pressure cooling distributor, and at the same time, the high-pressure cooling medium is transported to the cavity through the quenching device to rapidly cool the slurry to 20~60℃. The pressure of the cooling medium is 0.1~1.7MPa and the temperature is 5~30℃. D. The cooled slurry is transported to the collection tank, and the slurry is pressure filtered and dried to obtain a layered composite metal hydroxide with surface defect active sites.

[0015] Furthermore, the pressurization treatment method is as follows: CO2 gas is continuously introduced into the slurry at a pressure of 0.1~1.6 MPa, and the reaction is carried out for 1~12 hours.

[0016] Furthermore, the method for the guest intercalation reaction is as follows: according to M2 3+ / A n- Acid H is added to the slurry in a molar ratio of n. n A n Or metal salt M 2n A3, reaction time 1-12 hours, where A n- Selected from Cl - CO3 2- H2BO3 - Any one of them.

[0017] Further, in step C, the cooling medium is selected from one or two of water, ethanol, and ethylene glycol, preferably water.

[0018] Furthermore, in step C, before conveying the reacted slurry to the high-pressure cooling distributor, the following operation is also included: passing the reacted slurry through a heat exchanger to reduce the temperature of the slurry by 10~20°C.

[0019] The beneficial effects of this invention are as follows: Based on the structural characteristics of LDHs products and the "dissolution-precipitation" balance in the LDHs crystal reaction process, this invention provides a quenching crystallization reaction system. A high-pressure cooling distributor is added to the outlet of the reactor. After the LDHs crystallization reaction is completed, the reaction slurry enters the high-pressure cooling distributor and is rapidly sprayed with a low-temperature cooling medium to "quench" the LDHs crystals formed by the high-temperature reaction. The reaction slurry is rapidly cooled, the "dissolution-precipitation" on the LDHs surface is destroyed, the precipitation process at the liquid-solid interface becomes supersaturated, and the surface atomic arrangement becomes highly disordered, thereby constructing a large number of defective active sites, which significantly improves the performance of LDHs products. This reactor, by using a cooling liquid system consistent with the hydrotalcite reaction slurry, achieves the construction of defective active sites in the material through quenching-type cooling without introducing impurities. It can effectively improve product performance and shorten the cooling time by more than half. The equipment requirements are low, the process is simple, thus effectively reducing costs. It also avoids the introduction of impurity ions caused by acid and alkali solvent etching, ensuring the cleanliness of the process, and is very suitable for industrial implementation. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, and these illustrative examples are not intended to limit the embodiments. The term "illustrative" as used herein means "serving as an example, embodiment, or illustration." Any embodiment illustrated herein as "illustrative" is not necessarily to be construed as superior to or better than other embodiments.

[0021] Figure 1 A schematic diagram of the quenching and crystallization reaction system for preparing layered composite metal hydroxides provided by the present invention, wherein: 1. Reactor; 2. Heat exchanger; 3. High-pressure cooling distributor; 4. Collection tank; 5. Automatic pressure balancing valve; Figure 2 This is a schematic diagram of the external structure of the high-pressure cooling distributor in the quenching crystallization reaction system provided by the present invention, wherein: 31. Inlet; 32. Outlet; 33. Cylinder; 34. Nozzle; 35. Conveying channel; Figure 3 A cross-sectional view along the axial direction of the high-pressure cooling distributor in the quenching crystallization reaction system provided by the present invention; Figure 4 A cross-sectional view of the high-pressure cooling distributor in the quenching crystallization reaction system provided by the present invention along the radial direction; Figure 5 This is the XRD pattern of the layered composite metal hydroxide prepared in Example 3; Figure 6 This is a TEM image of the layered composite metal hydroxide prepared in Example 3; Figure 7 The XRD pattern of the layered composite metal hydroxide prepared in Comparative Example 1 is shown. Figure 8 This is a TEM image of the layered composite metal hydroxide prepared in Comparative Example 1. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprising of," etc., will be understood to include the stated elements or components, and does not exclude other elements or other components.

[0023] Furthermore, to better illustrate the present invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In some embodiments, materials, elements, methods, and means well known to those skilled in the art are not described in detail in order to highlight the spirit of the invention.

[0024] The reactor and collection tank used in the following embodiments are not limited to any particular model or brand, as long as they meet the following parameters: reactor, volume 30L, working pressure 0~2.5MPa, working temperature 0~200℃; collection tank, volume 100L, working pressure 0~0.3MPa, working temperature 0~100℃. The top of the collection tank is equipped with a conventional automatic pressure balancing valve with a maximum pressure of 0.3MPa, used to regulate the pressure inside the collection tank.

[0025] Example 1 A quenching crystallization reaction system for preparing layered composite metal hydroxides, such as Figures 1-4 As shown, the system includes a reactor 1 for preparing a slurry and a collection tank 4 for collecting the slurry. A high-pressure cooling distributor 3 connects the reactor 1 and the collection tank 4. The high-pressure cooling distributor includes a cavity and a quenching device for injecting cooling medium into the cavity. The cavity is a cylindrical body 33, connected to the slurry outlet of the reactor 1 and the slurry inlet of the collection tank 4 through inlets 31 and outlets 32 at both ends, respectively. It is used to contain the slurry from the reactor 1 and output the slurry quenched by the quenching device to the collection tank 4. The quenching device includes one or more nozzles 34 connected to the cylinder 33 and a conveying channel 35 for conveying the cooling medium to the nozzles 34. The nozzles 34 are used to spray the cooling medium into the cylinder 33 to quench the slurry. The cooling medium has the same composition as the reaction medium in the reactor 1. The cavity is also used to convey the slurry cooled by the cooling medium to the collection tank 4. An automatic pressure balancing valve 5 is provided at the top of the collection tank 4, with a maximum pressure of 0.3 MPa, for regulating the pressure inside the collection tank 4. After filtering and drying the slurry in collection tank 4, a layered composite metal hydroxide with surface defect active sites is obtained.

[0026] In this embodiment, the high-pressure cooling distributor 3 is made of stainless steel and can withstand pressures of 0~2.5MPa. The cylinder diameter is 40cm and the length is 80cm. To ensure sufficient contact between the cooling medium and the high-temperature slurry, multiple conveying channels 35 and multiple nozzles 34 connected to each conveying channel are evenly arranged on the outer surface of the cylinder 33. Each group of nozzles 34 is arranged evenly along the length of the cylinder 33, and the conveying channels 35 extend along the length of the cylinder 33 and are evenly arranged, allowing the cooling medium to be evenly injected into the cylinder 33 along the slurry flow direction. The nozzles 34 are conventional anti-clogging atomizing nozzles, further ensuring the cooling medium is evenly integrated into the high-temperature slurry. Each nozzle protrudes 1~5cm into the inner wall of the cavity.

[0027] Example 2 A quenching crystallization reaction system for preparing layered composite metal hydroxides is improved based on Example 1 as follows: a heat exchanger 2 is connected between the reaction vessel 1 and the high-pressure cooling distributor 3 to pre-cool the high-temperature reaction slurry. When the slurry reaction temperature is too high (e.g., above 150°C), it is cooled by 10-20°C before entering the high-pressure cooling distributor, thereby protecting the equipment. The heat exchanger used in this example has a heat exchange area of ​​1 m².

[0028] Example 3 A method for preparing layered composite metal hydroxides, using the quenching crystallization reaction system of Example 2, comprises the following steps: A. Mix Mg(OH)2 and Al(OH)3 according to Mg 2+ / Al 3+ Mix them in a molar ratio of 2:1, weigh 2 kg, add them to 8 kg of deionized water to prepare a suspension with a solid content of 20% and stir evenly. After pretreatment in a sand mill, adjust the solid content to 10% again and transfer the slurry into reactor 1. B. The slurry was heated and stirred in reactor 1 at a stirring speed of 300 rpm and a temperature of 160°C; then pressurized by continuously introducing CO2 gas at a pressure of 0.7 MPa for 6 hours and then stopping the gas supply. C. The reacted slurry is fed into the cylinder 33 of the high-pressure cooling distributor 3 through the heat exchanger 2 at a flow rate of 0.5 L / min. Cooling water at 5 °C is injected into the conveying channel 35 at a pressure of 0.5 MPa and a flow rate of 1.5 L / min, and further injected into the cylinder 33 through the nozzle 34 to directly contact the slurry, thereby rapidly cooling the slurry. The cooling time is 20 min. When the slurry flows out of the high-pressure cooling distributor 3, the temperature drops to 35.3 °C, and the quenching operation is completed. D. Adjust the automatic pressure balancing valve 5 to 0.1 MPa, and transport the cooled slurry to the collection tank 4. After pressure filtration, dry the slurry at 70℃ for 8 hours to obtain Mg4Al2(OH) rich in surface defect active sites. 12 CO3·4H2O layered composite metal hydroxide.

[0029] The crystal structure of the obtained product was characterized using X-ray powder diffraction, and the XRD pattern is shown below. Figure 5As shown in the figure, characteristic diffraction peaks (003), (006), and (009) of Mg2Al-CO3-LDHs appear at 2θ = 11.7°, 23.4°, and 34.5°. These peaks are low and broad, indicating poor crystal structure integrity. The sample morphology was observed using transmission electron microscopy (TEM), and the TEM images are shown below. Figure 6 As shown in the figure, the prepared sample exhibits a high degree of lattice fringing disorder, and its ordered structure is disrupted. This confirms the successful preparation of Mg4Al2(OH) with abundant surface defect active sites in this embodiment. 12 CO3·4H2O layered complex metal hydroxide Example 4 A method for preparing layered composite metal hydroxides, using the quenching crystallization reaction system of Example 2, comprises the following steps: A. Mix ZnO, Mg(OH)2, and Al(OH)3 according to Zn... 2+ :Mg 2+ :Al 3+ Mix them in a molar ratio of 1:3:2, weigh 1.5 kg, add them to 8.5 kg of deionized water to prepare a suspension with a solid content of 15% and stir evenly. After pretreatment in a sand mill, adjust the solid content to 10% again and transfer the slurry into reactor 1. B. The slurry was heated and stirred in reactor 1 at a stirring speed of 300 rpm and a temperature of 140°C; then pressurized by continuously introducing CO2 gas at a pressure of 0.5 MPa for 4 hours and then stopping the gas supply. C. The reacted slurry is fed into the cylinder 33 of the high-pressure cooling distributor 3 through the heat exchanger 2 at a flow rate of 0.8 L / min. Cooling water at 10 ℃ is injected into the conveying channel 35 at a pressure of 0.3 MPa and a flow rate of 2.5 L / min, and further injected into the cylinder 33 through the nozzle 34 to directly contact the slurry, thereby rapidly cooling the slurry. The cooling time is 30 min. When the slurry flows out of the high-pressure cooling distributor 3, the temperature drops to 32.3 ℃, and the quenching operation is completed. D. Adjust the automatic pressure balancing valve 5 to 0.1 MPa, and transport the cooled slurry to the collection tank 4. After pressure filtration, the slurry is dried at 70°C for 6 hours. The product is examined by XRD and TEM, confirming that Zn3Mg1Al2(OH) with surface defect active sites was successfully prepared in this embodiment. 12 CO3·4H2O layered composite metal hydroxide.

[0030] Example 5 A method for preparing layered composite metal hydroxides, using the quenching crystallization reaction system of Example 2, comprises the following steps: A. Mix Mg(OH)2 and Al(OH)3 according to Mg 2+ / Al 3+ Mix them in a molar ratio of 2:1, weigh 2 kg, add them to 8 kg of deionized water to prepare a suspension with a solid content of 20% and stir evenly. After pretreatment in a sand mill, adjust the solid content to 8% again and transfer the slurry into reactor 1. B. The slurry was heated and stirred in reactor 1 at a stirring speed of 500 rpm and a temperature of 150°C; then pressurized by continuously introducing CO2 gas at a pressure of 0.65 MPa for 8 hours and then stopping the gas supply. C. The reacted slurry is fed into the cylinder 33 of the high-pressure cooling distributor 3 through the heat exchanger 2 at a flow rate of 1 L / min. Cooling water at 8 °C is injected into the conveying channel 35 at a pressure of 0.4 MPa and a flow rate of 5 L / min. The cooling time is 35 min. The water is then injected into the cylinder 33 through the nozzle 34 to directly contact the slurry and rapidly cool it down. When the slurry flows out of the high-pressure cooling distributor 3, the temperature drops to 25.6 °C, and the quenching operation is completed. D. Adjust the automatic pressure balancing valve 5 to 0.2 MPa, and transport the cooled slurry to the collection tank 4. After pressure filtration, the slurry is dried at 70°C for 6 hours. The product is examined by XRD and TEM, confirming that Mg6Al2(OH) with abundant surface defect active sites was successfully prepared in this embodiment. 14 CO3·4H2O layered composite metal hydroxide.

[0031] Comparative Example 1 A method for preparing layered composite metal hydroxides, using the same reaction vessel, heat exchanger, and collection tank as in Example 2 (but without using a high-pressure cooling distributor), comprises the following steps: A. Mix Mg(OH)2 and Al(OH)3 according to Mg 2+ / Al 3+ Mix them in a molar ratio of 2:1, weigh 2 kg, add them to 8 kg of deionized water to prepare a suspension with a solid content of 20% and stir evenly. After pretreatment in a sand mill, adjust the solid content to 10% again and transfer the slurry into the reaction vessel. B. The slurry was heated and stirred in reactor 1 at a stirring speed of 300 rpm and a temperature of 160°C; then pressurized by continuously introducing CO2 gas at a pressure of 0.7 MPa for 6 hours and then stopping the gas supply. C. Stop heating and cool the slurry to 35°C through the outer jacket of the reactor for 2 hours; D. The cooled slurry is transferred to collection tank 4, filtered by pressure, and then dried at 70℃ for 8 hours to obtain Mg4Al2(OH).12 CO3·4H2O layered composite metal hydroxide.

[0032] The crystal structure of the product was determined using X-ray powder diffraction, and the morphology of the sample was observed using transmission electron microscopy (TEM). The XRD patterns and TEM images are shown below. Figure 7 and Figure 8 As shown in the figure, the XRD pattern of the LDHs product prepared by conventional cooling in the reactor in Comparative Example 1 shows that the peaks of each characteristic diffraction peak are high and narrow, indicating that the crystal structure of the product is highly intact; the lattice fringes of the sample in the TEM image are regular, which also indicates that the prepared product has a good crystal structure and no obvious defects.

[0033] It is evident that Comparative Example 1, which did not use a high-pressure cooling distributor for rapid cooling, could not prepare layered composite metal hydroxides rich in surface defect active sites.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A quenching crystallization reaction system for preparing layered composite metal hydroxides, comprising a reaction vessel for preparing a slurry and a collection tank for collecting the slurry, characterized in that, A high-pressure cooling distributor is connected between the reaction vessel and the collection tank. The high-pressure cooling distributor includes a cavity and a quenching device for injecting cooling medium into the cavity. The cavity is connected to the reactor and the collection tank, and is used to contain the slurry from the reactor and output the slurry after being quenched by the quenching device to the collection tank; The quenching device includes one or more nozzles communicating with a cavity and a delivery channel for conveying a cooling medium to the nozzles; the nozzles are used to spray the cooling medium into the cavity to quench the slurry, and the cooling medium has the same composition as the reaction medium in the reactor; the cavity is also used to convey the slurry cooled by the cooling medium to the collection tank.

2. The quenching and crystallization reaction system for preparing layered composite metal hydroxides according to claim 1, characterized in that, The quenching device includes multiple conveying channels, each of which is connected to multiple nozzles; And / or, the cavity is a cylindrical body, and the outer surface of the cylinder is uniformly provided with multiple conveying channels and multiple nozzles communicating with each conveying channel. Optionally, the length-to-diameter ratio of the cylinder is 1-10.

3. The quenching and crystallization reaction system for preparing layered composite metal hydroxides according to claim 2, characterized in that, The nozzles connected by the same conveying channel are arranged along the axial direction of the cylinder; And / or, each nozzle protrudes 1-5 cm into the cavity wall; And / or, the nozzle is an anti-clogging atomizing nozzle.

4. The quenching crystallization reaction system for preparing layered composite metal hydroxides according to any one of claims 1 to 3, characterized in that, The cooling medium is selected from one or two of water, ethanol and ethylene glycol, and the pressure of the cooling medium is 0.1~1.7MPa and the temperature is 5~30℃.

5. The quenching crystallization reaction system for preparing layered composite metal hydroxides according to claim 1, characterized in that, A heat exchanger is connected between the reactor and the high-pressure cooling distributor.

6. A method for preparing layered composite metal hydroxides, characterized in that, The preparation is carried out using the quenching crystallization reaction system described in claim 1, and the method includes the following steps: A. Using M1 2+ Hydroxides and M1 2+ At least one of the oxides and M2 3+ Hydroxides and M2 3+ At least one of the oxides, according to M1 2+ With M2 3+ The mixture is prepared in a molar ratio of 1:1 to 1:4, and a reaction medium is added to adjust the solid content to 10% to 50%. After pretreatment in a sand mill, the slurry is transferred to the reaction vessel. M1 2+ Selected from Mg 2+ Zn 2+ Ca 2+ Ni 2+ One or two of them, the M2 3+ Selected from Al 3+ Cr 3+ One or two of them; B. The slurry is heated and stirred in a reactor at a stirring speed of 50~500 rpm and a temperature of 80~200℃. After reaching the reaction temperature, it is subjected to pressure treatment or guest intercalation reaction. C. After the reaction is completed, the reacted slurry is transported to the cavity of the high-pressure cooling distributor, and at the same time, the high-pressure cooling medium is transported to the cavity through the quenching device to rapidly cool the slurry to 20~60℃. The pressure of the cooling medium is 0.1~1.7MPa and the temperature is 5~30℃. D. The cooled slurry is transported to the collection tank, and the slurry is pressure filtered and dried to obtain a layered composite metal hydroxide with surface defect active sites.

7. The method for preparing layered composite metal hydroxides according to claim 6, characterized in that, The pressurization process is as follows: CO2 gas is continuously introduced into the slurry at a pressure of 0.1~1.6 MPa, and the reaction is carried out for 1~12 hours.

8. The method for preparing layered composite metal hydroxides according to claim 6, characterized in that, The method for the guest intercalation reaction is as follows: according to M2 3+ / A n- Acid H is added to the slurry in a molar ratio of n. n A n Or metal salt M 2n A3, reaction time 1-12 hours, where A n- Selected from Cl - CO3 2- H2BO3 - Any one of them.

9. The method for preparing layered composite metal hydroxides according to any one of claims 6 to 8, characterized in that, In step C, the cooling medium is selected from one or two of water, ethanol, and ethylene glycol.

10. The method for preparing layered composite metal hydroxides according to any one of claims 6, characterized in that, In step C, before the reacted slurry is conveyed to the high-pressure cooling distributor, the following operation is also included: passing the reacted slurry through a heat exchanger to reduce the temperature of the slurry by 10~20°C.

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