An in-situ detection system for a rotating microliquid membrane reactor for monitoring the nucleation behavior of nanomaterials

Abstract

This invention relates to an in-situ detection system for a rotating microliquid film reactor (MFR) for monitoring the nucleation behavior of nanomaterials. The reactor comprises a rotor and a stator, with a stator base angle of 70-85°, a rotational speed of 500-5000 rpm, and a slit width of 10-500 μm to ensure that fluid passing through the slit does not undergo backmixing and to create a strong shear field. A micro-negative pressure sampler is fabricated to capture nucleating particles within the high-speed shear field and bring them into the visible observation area. A high-speed camera and microscope objective are connected in situ, thereby acquiring instantaneous images of the nucleation process at the nanoscale and capturing the transient evolution behavior of crystal nuclei. The construction of this rotating MFR in-situ detection system solves the problems of poor micro-mixing effects and uncontrollable nucleation and growth in traditional stirred tank reactors, leading to poor quality in large-scale preparations, and the inability to observe phase transitions and instantaneous nucleation processes in a closed reactor. The obtained hydrotalcite nucleation results enrich non-classical nucleation theories and provide guidance for the large-scale preparation of nanomaterials.

Description

Technical Field

[0001] This invention relates to an in-situ detection system for a rotating microfilm reactor. Specifically, it relates to an in-situ detection system for a rotating microfilm reactor that integrates high-speed photography and synchronous control technology for monitoring the nucleation and forced micro-mixing of nanomaterials. Background Technology

[0002] Inorganic nanomaterials are widely used in chemical, catalytic, agricultural, construction, and rubber and plastics processing industries, generating direct and indirect economic benefits in the hundreds of billions. One important method for preparing inorganic nanomaterials is precipitation reaction. However, due to the structure and poor micro-mixing effect of traditional stirred tank reactors, the nucleation and growth of inorganic nanomaterials are uncontrollable, resulting in poor quality in large-scale preparations and affecting the application performance of these materials. Furthermore, the precipitation process is usually carried out in a closed container in a darkroom manner, and the observation of the synthesized product is typically achieved through multiple "offline" steps such as cooling, washing, drying, and characterization. This makes it difficult to rapidly and accurately capture the instantaneous processes such as nucleation and phase transition during precipitation. Previously, the State Key Laboratory of Chemical Resource Effective Utilization at Beijing University of Chemical Technology invented a rotating liquid film reactor (CN102616749B) with forced micro-mixing for liquid-phase precipitation reactions. This reactor consists of a rotor and a stator. Due to the high supersaturation in the early stages of the precipitation reaction, a huge driving force is generated. After the reaction begins, a strong shear field is formed between the rotor and stator, effectively promoting micro-mixing and mass transfer. This allows for the continuous and rapid formation of a large number of crystal nuclei, which quickly detach from the reactor, achieving separation of the nucleation and crystallization processes. Consequently, the particle size of the generated precipitate is significantly reduced, and the particle size distribution range is narrowed, improving the precipitate's performance as a functional material. However, instantaneously capturing nucleated particles for in-situ characterization without disrupting the strong shear field remains a challenge.

[0003] Based on the design of a rotating liquid film reactor with forced micro-mixing, this work innovatively constructs an in-situ detection system for the rotating micro-liquid film reactor. While fully leveraging the effect of the confined space of the rotating liquid to enhance micro-mixing and achieve separation of nucleation and crystallization, sampling ports and viewing windows are selectively set on the side of the rotating liquid film reactor. A micro-negative pressure sampler is also created to capture nucleation particles. The system is connected in-situ to a visual system and a particle imaging system to capture the transient state of crystal nuclei, obtain instantaneous images of the nucleation process, and monitor the instantaneous evolution behavior of the liquid-solid and liquid-liquid interfaces. Summary of the Invention

[0004] The purpose of this invention is to provide an in-situ detection system for a rotating microliquid membrane reactor for monitoring the nucleation behavior of nanomaterials. This system not only separates the nucleation and crystallization processes, resulting in a significant reduction in the particle size and a narrowing of the particle size distribution range of the generated precipitate, but also allows for in-situ monitoring of the nucleation process, capturing transient nuclei, and establishing nucleation / crystallization kinetic equations.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] This invention relates to an in-situ detection system for a rotating microliquid membrane reactor for monitoring the nucleation behavior of nanomaterials, characterized in that...

[0007] The reactor consists of a closed casing as the stator, with materials added to the upper end of the stator according to the stoichiometric ratio. Inside the stator is a rotatable rotor connected to a motor. The rotational speed is 500–5000 rpm, and the slit width between the rotor and the stator is 10–500 μm, forming a shear field between them. A sampling port is set on one side of the stator sidewall, and a sampler is used to capture nucleated particles in the shear field and bring them into the visible observation area. A viewing window is opened on the other side of the stator sidewall.

[0008] A high-speed camera is installed in the visible observation area or through the viewing window, recording at a speed of 10,000 to 12,000 frames per second. The high-speed camera is connected to a microscope lens with a magnification of 10x to 50x. A light source is installed on the opposite side of the high-speed camera. The high-speed camera is connected to a computer.

[0009] The stator's internal cavity is a frustum of a cone with a narrow top and wide bottom, its cross-section being trapezoidal with a base angle of 70-85°. The stator height is 60-80mm, and the stator height Δh can be moved up and down to adjust the slit width. The rotor's structure matches the stator's, and to ensure it remains parallel to the sides when adjusting the gap, a hole is provided at its axial center for connecting to the motor shaft, allowing it to rotate at high speed under the motor's drive after being connected to the electrodes.

[0010] The highest sampling port is 3 cm away from the top of the stator, and the adjacent sampling ports are spaced 0.6 cm apart.

[0011] The visible observation area is composed of two glass plates stacked in parallel with a thickness of 1-3 mm, and there are micro-scale channels of different shapes and diameters with different diameters of 50-100 μm between the two glass plates; the glass material is one of polydimethylsiloxane, borosilicate, polystyrene, and polyurethane.

[0012] The visual observation area is equipped with a vertical lifting platform, which is used to adjust the height of the visual observation area.

[0013] The light source is an LED white light source, an LED red light source, an LED green light source, or a pulsed laser light source.

[0014] The nanomaterials include hydrotalcite, oxides, hydroxides, boehmite, or barium sulfate.

[0015] The beneficial effects of this invention are as follows: Starting from the basic process of preparing metal hydroxides by precipitation, this invention simulates the fluid mixing process of a rotating liquid film reactor using computational fluid dynamics (CFD). The rotating liquid film reactor features a truncated conical stator with a base angle of 70-85°, a rotation speed of 500-5000 rpm, and a slit width of 10-500 μm, ensuring that backmixing does not occur as the fluid passes through the slit and creating a strong shear field between the rotor and stator. A micro-negative pressure sampler is fabricated to capture nucleating particles within the high-speed shear field and bring them into the visible observation area. A high-speed camera and microscope objective are coupled in situ, thereby capturing the transient evolution behavior of crystal nuclei at the nanoscale. The construction of the in-situ detection system for the rotating micro-liquid film reactor solves the problems of poor micro-mixing effect and uncontrollable nucleation and growth in traditional stirred tank reactors, leading to poor quality in large-scale preparations, and the inability to observe phase transitions and instantaneous nucleation processes in a closed reactor. The obtained hydrotalcite nucleation results enrich non-classical nucleation theory and provide guidance for the large-scale preparation of nanomaterials. Attached Figure Description

[0016] Figure 1 This is a block diagram of the overall structure of an in-situ detection system for a rotating microliquid membrane reactor used to monitor the nucleation behavior of nanomaterials.

[0017] Figure 2 This is a visual observation area for the rotor-stator three-dimensional design and in-situ connection.

[0018] Figure 3 This is a schematic diagram of the rotor-stator slit gap, where Δh is the height the stator rises.

[0019] Figure 4 This is a schematic diagram showing eight sampling ports and viewing windows set at 0.6 cm intervals on the side of the reactor, 3 cm from the top of the stator, as shown in Example 1.

[0020] Figure 5 This is a schematic diagram of the connection between the macro lens and the objective lens of the high-speed camera in Example 1.

[0021] Figure 6 The nucleation behavior captured in Example 1. Detailed Implementation

[0022] Example 1

[0023] like Figure 1The rotating microliquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials is shown. It consists of a closed casing with a truncated cone-shaped structure (narrower at the top, wider at the bottom) and a base angle of 85° as the stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. Inside the stator is a rotatable conical rotor connected to a motor. At a rotational speed of 1500 rpm and a slit width of 200 μm, a strong shear field is formed between the rotor and stator. Eight sampling ports are set at 0.6 cm intervals, 3 cm axially from the top of the stator in the "rotor-stator assembly." A micro-negative pressure sampler is used to capture nucleating particles in the high-speed shear field, allowing them to enter a 2 mm thick, polydimethylsiloxane glass channel with a 50 μm diameter cross-shaped observation area. The height of this area is adjusted by a vertical lifting platform. A viewing window 2 with a diameter of 10 mm and a thickness of 1 mm is opened on the other side of the "rotor-stator assembly." A high-speed camera (recording speed of 12,000 frames per second) with a coupling microscope objective lens (10x) is connected in situ to both types of visual observation areas. An LED white light source is provided on the opposite side of the high-speed camera. It is further connected to a computer to drive the high-speed camera and the rotating liquid film reactor to work simultaneously.

[0024] The above-mentioned in-situ detection system for monitoring the nucleation behavior of nanomaterials using a rotating microliquid membrane reactor was applied to the preparation of cobalt-based LDHs. The specific operation is as follows:

[0025] Co(NO3)2 and Al(NO3)3 were mixed according to Co 2+ / Al 3+ A nitrate mixed solution is prepared with a molar ratio of 2, wherein [M 2+ ] = 1.2 mol / L; according to n(NaOH) / [n(Co 2+ )+n(Al 3+ A NaOH solution was prepared at a ratio of 1.8. The mixed salt and alkali solutions were simultaneously injected into a rotating liquid film reactor for rapid nucleation. Nucleated particles were captured in the high-speed shear field and brought into the visible observation area through the first sampling port on the side of the reactor, located from the top of the stator. High-speed cameras recording at 12,000 frames per second captured images in situ, allowing observation of the formation of bubbles in the nucleation slurry. Different regions with abundant and scarce solutes were observed within the bubbles. Phase separation resulted in the formation of solute-rich regions, leading to the generation of amorphous aggregates with a particle size of ~1 μm. These results indicate that cobalt-based LDHs conform to the two-step nucleation theory.

[0026] Example 2

[0027] like Figure 1The rotating microliquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials is shown. It consists of a closed casing with a truncated cone-shaped structure (narrower at the top, wider at the bottom) and a base angle of 85° as the stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. Inside the stator is a rotatable conical rotor connected to a motor. At a rotational speed of 1500 rpm and a slit width of 200 μm, a strong shear field is formed between the rotor and stator. Eight sampling ports are set at 0.6 cm intervals, 3 cm axially from the top of the stator in the "rotor-stator assembly." A micro-negative pressure sampler is used to capture nucleating particles in the high-speed shear field, allowing them to enter a 2 mm thick, polydimethylsiloxane glass channel with a 50 μm diameter cross-shaped observation area. The height of this area is adjusted by a vertical lifting platform. A viewing window 2 with a diameter of 10 mm and a thickness of 1 mm is opened on the other side of the "rotor-stator assembly." A high-speed camera (recording speed of 12,000 frames per second) with a coupling microscope objective lens (10x) is connected in situ to both types of visual observation areas. An LED white light source is provided on the opposite side of the high-speed camera. It is further connected to a computer to drive the high-speed camera and the rotating liquid film reactor to work simultaneously.

[0028] The above-mentioned in-situ detection system for monitoring the nucleation behavior of nanomaterials using a rotating microliquid membrane reactor was applied to the preparation of cobalt-based LDHs. The specific operation is as follows:

[0029] Co(NO3)2 and Al(NO3)3 were mixed according to Co 2+ / Al 3+ A nitrate mixed solution is prepared with a molar ratio of 2, wherein [M 2+ ] = 1.2 mol / L; according to n(NaOH) / [n(Co 2+ )+n(Al 3+ A NaOH solution was prepared at a ratio of 1.8. The mixed salt and alkali solutions were simultaneously injected into a rotating liquid film reactor for rapid nucleation. Nucleated particles were captured in the visible observation area through a micro-negative pressure sampler at the sixth sampling port on the side of the reactor from the top of the stator, within a high-speed shear field. Nucleated particles with a diameter >1 μm could be observed in situ using a high-speed camera. The results indicate that with prolonged reaction time, amorphous aggregates further crystallize to form ordered nucleated particles.

[0030] Example 3

[0031] like Figure 1The rotating microliquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials is shown. It consists of a closed casing with a truncated cone-shaped structure (narrower at the top, wider at the bottom) and a base angle of 85° as the stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. Inside the stator is a rotatable conical rotor connected to a motor. At a rotational speed of 1500 rpm and a slit width of 200 μm, a strong shear field is formed between the rotor and stator. Eight sampling ports are set at 0.6 cm intervals, 3 cm axially from the top of the stator in the "rotor-stator assembly." A micro-negative pressure sampler is used to capture nucleating particles in the high-speed shear field, allowing them to enter a 2 mm thick, polydimethylsiloxane glass channel with a 50 μm diameter cross-shaped observation area. The height of this area is adjusted by a vertical lifting platform. A viewing window 2 with a diameter of 10 mm and a thickness of 1 mm is opened on the other side of the "rotor-stator assembly." A high-speed camera (recording speed of 12,000 frames per second) with a coupling microscope objective lens (10x) is connected in situ to both types of visual observation areas. An LED white light source is provided on the opposite side of the high-speed camera. It is further connected to a computer to drive the high-speed camera and the rotating liquid film reactor to work simultaneously.

[0032] The above-mentioned in-situ detection system for monitoring the nucleation behavior of nanomaterials using a rotating microliquid membrane reactor was applied to the preparation of cobalt-based LDHs. The specific operation is as follows:

[0033] Co(NO3)2 and Al(NO3)3 were mixed according to Co 2+ / Al 3+ A nitrate mixed solution is prepared with a molar ratio of 2, wherein [M 2+ ] = 1.2 mol / L; according to n(NaOH) / [n(Co 2+ )+n(Al 3+ A NaOH solution was prepared at a ratio of 1.8. The mixed salt solution and alkali solution were simultaneously injected into a rotating liquid film reactor for rapid nucleation. Nucleated particles with a diameter of ~10 μm were observed in situ through a viewing window using a high-speed camera. The results showed that secondary nucleation of the nucleated particles occurred with the extension of reaction time.

Claims

1. An in-situ detection system for a rotating microliquid membrane reactor for monitoring the nucleation behavior of nanomaterials, characterized in that, The reactor consists of a closed casing serving as the stator. Materials are added to the upper end of the stator according to a stoichiometric ratio. Inside the stator is a rotatable rotor connected to a motor. The rotational speed is 500~5000 rpm. The slit width between the rotor and the stator is 10~500 μm, creating a shear field between them. A sampling port is set on one side of the stator sidewall, and a micro-negative pressure sampler captures nucleated particles within the shear field, allowing them to enter the visible observation area. A viewing window is opened on the other side of the stator sidewall. A high-speed camera is installed in the visible observation area or through the viewing window, recording at a speed of 10,000 to 12,000 frames per second. The high-speed camera is connected to a microscope lens with a magnification of 10x to 50x. A light source is installed on the opposite side of the high-speed camera. The high-speed camera is connected to a computer. The stator's internal cavity is a frustum of a cone with a narrow top and wide bottom, and its cross-section is trapezoidal with a base angle of 70-85 degrees. o The stator height is 60-80 mm, and the stator height ∆h can be moved up and down to adjust the slit width. The rotor is matched with the stator structure. In order to keep it parallel to the side when adjusting the gap, a hole is provided in its axial center to connect to the motor shaft so that it can be connected to the electrode and rotate at high speed under the drive of the motor.

2. The system according to claim 1, characterized in that, Multiple sampling ports are set up, with the highest sampling port 3 cm away from the top of the stator, and adjacent sampling ports spaced 0.6 cm apart.

3. The system according to claim 1, characterized in that, The visible observation area consists of two glass plates stacked in parallel with a thickness of 1-3 mm, and there are microscale channels of different shapes and diameters with a diameter of 50-100 μm between the two glass plates. The glass material is one of polydimethylsiloxane, borosilicate, polystyrene, and polyurethane.

4. The system according to claim 1, characterized in that, The visual observation area is equipped with a vertical lifting platform, which is used to adjust the height of the visual observation area.

5. The system according to claim 1, characterized in that, The light source is an LED white light source, an LED red light source, an LED green light source, or a pulsed laser light source.

6. The system according to claim 1, characterized in that, The nanomaterials include hydrotalcite, oxides, hydroxides, boehmite, or barium sulfate.

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