Process for producing macroporous pseudo-boehmite through continuous flow and micro reaction

Abstract

The invention belongs to the field of inorganic material preparation, and provides a process for producing macroporous pseudo-boehmite through continuous flow and micro reaction, which comprises the following steps: respectively conveying an aluminum source solution, a precipitator solution and an additive solution to a micro mixer, and carrying out gas-liquid mixing to obtain a mixed solution; conveying the mixed solution into a microreactor for reaction to obtain a reaction product; and carrying out solid-liquid separation on the reaction product, washing and drying to obtain the pseudo-boehmite. By constructing a precise and controllable reaction system, continuous and intelligent control over the whole process of raw material mixing, crystallization growth and product aftertreatment is achieved, the product quality stability and the production efficiency are effectively improved, meanwhile, the production cost and the environmental influence are reduced, and the blank of the high-end macroporous pseudo-boehmite green manufacturing technology is filled.

Description

Technical Field

[0001] This invention belongs to the field of inorganic material preparation and relates to a continuous flow and micro-reaction process for producing macroporous pseudoboehmite. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Boehmite (AlOOH・nH2O, 0.05≤n≤0.8) possesses characteristics such as large pore volume, high specific surface area, and controllable pore size distribution, and is widely used in fine chemical synthesis, automotive exhaust purification, and petrochemical catalysis. Currently, the main industrial production methods for boehmite include the double-aluminum method, carbonization method, aluminum alkoxide hydrolysis method, and hydrothermal synthesis method. However, these methods are difficult to meet the requirements of efficient, environmentally friendly, and precisely controllable continuous production. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a continuous flow and micro-reaction process for producing macroporous pseudoboehmite. By constructing a precisely controllable reaction system, this invention achieves continuous and intelligent control of the entire process, from raw material mixing and crystal growth to product post-processing. This effectively improves product quality stability and production efficiency while reducing production costs and environmental impact, filling the gap in green manufacturing technology for high-end macroporous pseudoboehmite. In order to achieve the above object, the present invention adopts the following technical solutions: A first aspect of the present invention provides a continuous flow and micro-reaction process for producing macroporous pseudoboehmite, comprising: The aluminum source solution, precipitant solution, and additive solution are respectively fed to a micro mixer for gas-liquid mixing to obtain a mixed liquid. The mixture is fed into a microreactor for reaction to obtain the reaction product; The reaction product was separated into solid and liquid phases, washed, and dried to obtain boehmite.

[0005] In a second aspect, the present invention provides macroporous pseudoboehmite prepared by the above-described method.

[0006] The prepared macroporous pseudoboehmite has a pore size distribution of 20–100 nm, a specific surface area of ​​300–500 m² / g, and a purity of ≥99%.

[0007] Beneficial effects of the present invention (1) Significantly improved production efficiency: The continuous production mode increases the unit equipment capacity by 3 to 5 times and shortens the production cycle by more than 70%, effectively meeting the market's demand for large-scale and rapid production. (2) Excellent product performance: Through microscale reaction control, it achieves narrow pore size distribution (20-100 nm, CV < 8%), high specific surface area (300-500 m² / g), and purity of over 99%, which fully meets the application requirements of high-end catalyst carriers and other application scenarios; (3) Significant cost reduction: By using conventional industrial raw materials and combining continuous production to improve equipment utilization, energy consumption per unit product is reduced by 40%, production costs are reduced by 30%, and investment costs are reduced by 40%; (4) Green and environmentally friendly characteristics: No organic solvents are used in the production process, and the amount of wastewater generated is reduced by 60%. The near-zero emission of pollutants is achieved through clean production processes, which meets the requirements of sustainable development.

[0008] (5) The preparation method of the present invention is simple, practical and easy to promote. Detailed Implementation

[0009] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0010] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods in the art or product instructions. Similarly, unless otherwise specified, the test methods of this invention are performed in accordance with conventional methods in the art or industry-standard methods or practices. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0011] This invention provides a continuous flow and micro-reaction process for producing macroporous pseudoboehmite, comprising: The aluminum source solution, precipitant solution, and additive solution are respectively fed to a micro mixer for gas-liquid mixing to obtain a mixed liquid. The mixture is fed into a microreactor for reaction to obtain the reaction product; The reaction product was separated into solid and liquid phases, washed, and dried to obtain boehmite.

[0012] Flow rate affects the mixing effect and mixing time of the physical components. Therefore, this invention studies the flow rate of each component in the micro mixer. In some embodiments, the flow rates of the aluminum source solution, precipitant solution and additive solution are all 10-300 mL / min to obtain a better mixing effect and shorten the mixing time.

[0013] The micron-level channel size affects the mixing efficiency, mixing uniformity, and mass and heat transfer effect of the micro mixer. Therefore, this invention studies the micron-level channel size of the micro mixer. In some embodiments, the micron-level channel size of the micro mixer is 50 to 500 μm to obtain better mixing efficiency, mixing uniformity, and mass and heat transfer effect.

[0014] Changes in temperature and pressure can affect the flowability and mixing efficiency of materials in a micro mixer. Therefore, this invention studies the conditions for gas-liquid mixing. In some embodiments, the gas-liquid mixing conditions are: reaction temperature 20-40°C, pressure 0.1-0.4 MPa, residence time 5-10 min, and final reaction pH value 9-11, in order to obtain a better gas-liquid mixing effect.

[0015] Different aluminum sources can affect the reaction efficiency, pore size distribution, specific surface area, and purity of macroporous boehmite. Therefore, this invention has studied aluminum sources. In some embodiments, the aluminum source solution is selected from one of aluminum nitrate, aluminum sulfate, and aluminum chloride solutions, or a refined sodium aluminate solution from the Bayer process (sintering process) alumina process, in order to obtain better reaction efficiency, pore size distribution, specific surface area, and higher purity.

[0016] Different precipitants can affect the reaction efficiency, pore size distribution, specific surface area, and purity of macroporous boehmite. Therefore, this invention has studied precipitants. In some embodiments, the precipitant is ammonia, sodium hydroxide, or sodium bicarbonate to obtain better reaction efficiency, pore size distribution, specific surface area, and higher purity.

[0017] Different additives can affect the pore size distribution and specific surface area of ​​macroporous boehmite. Therefore, this invention has studied additives. In some embodiments, the additives are polyethylene glycol or polyvinyl alcohol, so as to optimize the pore size distribution and specific surface area of ​​macroporous boehmite by using the polymer as a structure directing agent.

[0018] Channel size affects the mixing efficiency, mixing uniformity, and mass and heat transfer effect of microreactors. Therefore, this invention studies the channel size of microreactors. In some embodiments, the channel size of the microreactor is 50-500 μm to obtain better mixing efficiency, mixing uniformity, and mass and heat transfer effect.

[0019] Changes in temperature and pressure can affect reaction efficiency and product purity. Therefore, this invention has studied the reaction conditions. In some embodiments, the reaction temperature is 80-90°C, the pressure is 0.1-0.4 MPa, and the reaction time is 60-120 min to obtain better reaction efficiency and product purity.

[0020] More specifically, including: (1) Raw material pretreatment: Soluble aluminum salts such as aluminum nitrate, aluminum sulfate, or aluminum chloride are selected as aluminum sources, ammonia, sodium hydroxide, or sodium carbonate are used as precipitants, and high molecular weight polymers such as polyethylene glycol and polyvinyl alcohol are used as structure directing agents, and solutions of uniform concentration are prepared respectively. Alternatively, the sodium aluminate purification solution of deep desilication in the Bayer process (sintering process) alumina process is used, and the proportion of each raw material is strictly controlled by a precision metering system to ensure the stoichiometric accuracy of the reaction system. (2) Microscale mixing reaction: A high-precision metering pump is used to deliver the aluminum source solution (sodium aluminate solution), precipitant solution (carbon dioxide gas), and additive solution to the micro mixer at a set flow rate (10-300 mL / min). The micro mixer is designed based on the principle of enhanced mass transfer through microchannels. The micron-level channel size (50-500 μm) enables uniform gas-liquid mixing of reactants within milliseconds. At the same time, the reaction temperature is controlled at 20-40℃, the pressure at 0.1-0.4 MPa, the residence time at 5-10 min, and the final reaction pH value is controlled at 9-11 to ensure rapid initiation and completion of the reaction.

[0021] (3) Controlled aging reaction process: The mixture enters the microreactor (channel size 50-500 μm), and the reaction temperature is maintained at 80-90℃ and the pressure at 0.1-0.4 MPa by a precision temperature control system, with a reaction time of 60-120 min. The efficient heat and mass transfer characteristics of the microreactor enable the high uniformity of temperature and concentration in the reaction system, promoting the directional growth of pseudoboehmite crystals and forming the target macroporous structure. (4) Refined post-processing: The reaction products are separated into solid and liquid by centrifugation or membrane filtration. The solid products are washed in multiple stages of countercurrent to remove impurity ions, and then vacuum dried at 80-120℃ for 4-8 hours to finally obtain high-performance macroporous pseudoboehmite products. The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0022] Example 1 (1) Raw material preparation: Weigh 200g of aluminum nitrate (AlNO3) and dissolve it in 1000mL of deionized water to obtain an aluminum source solution; measure 600mL of 25% ammonia water and dilute it to 1000mL to obtain a precipitant solution; weigh 10g of polyethylene glycol and dissolve it in 200mL of deionized water to obtain an additive solution. (2) Continuous flow reaction: The aluminum source solution, precipitant solution (ammonia) and additive solution from step (1) are pumped into a micro mixer at flow rates of 100 mL / min, 60 mL / min and 20 mL / min, respectively. The mixing temperature is 30℃, the pressure is 0.2 MPa and the residence time is 5 min to obtain a mixture. The mixture is then pumped into a microreactor and reacted for 7 min at 30℃ and 0.2 MPa. (3) Post-processing: The product obtained in step (2) was centrifuged, the solid was washed with water three times, and then dried at 100℃ for 6 h. The obtained product has a pore size distribution of 25-80 nm, a specific surface area of ​​450 m² / g, and a purity of 99.2% macroporous boehmite. Example 2 (1) Raw material preparation: Take 2200ml of crude liquid from sintering method, add an appropriate amount of lime (the molar ratio of lime CaO to SiO2 is 1.1 to 1.7) and stir to mix. In the reaction vessel, keep it at 150℃ for 2h to carry out deep desilication and decolorization. Then, separate the solid and liquid to obtain 2000ml of pure sodium aluminate solution with a silicon index (A / S) ≥700. (2) Continuous flow reaction: Sodium aluminate solution (flow rate 200 mL / min) and carbon dioxide gas (flow rate 30 mL / min) were pumped into a micro mixer and mixed for 1 min at 25℃ and 0.1 MPa; then pumped into a microreactor and reacted for 9 min at 30℃ and 0.1 MPa. The final reaction pH was controlled at 10. (3) Post-processing: After filtering and separating the product obtained in step (2), the solid was washed with water 4 times and dried at 120℃ for 4 hours. The product has a pore size distribution of 30-90 nm, a specific surface area of ​​500 m² / g, and a purity of 99.3%.

[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A continuous flow and micro-reaction process for producing macroporous pseudoboehmite, characterized in that, include: The aluminum source solution, precipitant solution, and additive solution are respectively fed to a micro mixer for gas-liquid mixing to obtain a mixed liquid. The mixture is fed into a microreactor for reaction to obtain the reaction product; The reaction product was separated into solid and liquid phases, washed, and dried to obtain boehmite.

2. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The flow rates of the aluminum source solution, precipitant solution, and additive solution are all 10–300 mL / min.

3. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The micro-channel size of the micro-mixer is 50–500 μm.

4. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The conditions for gas-liquid mixing are: reaction temperature 20-40℃, pressure 0.1-0.4 MPa, residence time 5-10 min, and final reaction pH value 9-11.

5. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The aluminum source solution is selected from one of aluminum nitrate, aluminum sulfate, and aluminum chloride solutions, or a refined sodium aluminate solution from the Bayer process (sintering process) alumina process.

6. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The precipitant is ammonia, sodium hydroxide, or sodium carbonate.

7. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The additive is polyethylene glycol or polyvinyl alcohol.

8. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The channel size of the microreactor is 50–500 μm.

9. The process for producing macroporous pseudoboehmite using continuous flow and microreaction as described in claim 1, characterized in that, The reaction temperature is 80–90℃, the pressure is 0.1–0.4 MPa, and the reaction time is 60–120 min.

10. Macroporous pseudoboehmite prepared by the method according to any one of claims 1-9.