Rotary micro-liquid membrane reactor in-situ detection system for monitoring nucleation behavior of nano material

Abstract

The invention relates to a rotary micro-liquid membrane reactor in-situ detection system for monitoring the nucleation behavior of a nano material. The reactor comprises a rotor and a stator, the base angle of the stator is 70-85 degrees, the rotating speed of the stator is 500-5000 rpm, the width of a slit is 10-500 microns, it is guaranteed that fluid does not backmix when passing through the slit, and a strong shear field is formed. A micro-negative pressure sampler is manufactured to capture nucleation particles in a high-speed shear field to enter a visual observation area, and a high-speed camera and a microscope objective lens are connected in situ, so that an instantaneous image of a nucleation process is obtained in a nano-micro scale, and a transient evolution behavior of a crystal nucleus is captured in situ. The construction of the rotary micro-liquid membrane reactor in-situ detection system solves the problems that the large-scale preparation quality is poor due to the fact that a traditional stirred tank reactor is poor in structure and micro-mixing effect and uncontrollable in material nucleation and growth, and the instantaneous phase transformation and nucleation process cannot be observed due to the fact that the reactor is closed. The obtained hydrotalcite nucleation result enriches the non-classical nucleation theory, and provides guidance for large-scale preparation of nano materials.

Description

Technical Field

[0001] The present invention relates to an in-situ detection system for a rotating micro-liquid film reactor, and in particular to an in-situ detection system for a rotating micro-liquid film reactor for monitoring nano-material nucleation and forced micro-mixing, which integrates high-speed photography technology and synchronous control technology. Background Art

[0002] Inorganic nanomaterials are widely used in chemical industry, catalysis, agriculture, construction, rubber and plastic processing and other fields and industries, with direct and indirect economic benefits of hundreds of billions. Among them, the important method for preparing inorganic nanomaterials usually adopts precipitation reaction, but due to the poor structure and micro-mixing effect of traditional stirred tank reactor, the nucleation and growth of inorganic nanomaterials are uncontrollable, resulting in poor quality of large-scale preparation, affecting the application performance of inorganic nanomaterials. In addition, the precipitation process is usually carried out in a closed container in a dark box operation mode, and the observation of the synthetic product is usually realized by multi-step operations such as "off-line" cooling-washing-drying-characterization, resulting in a certain difficulty in rapidly and accurately capturing instantaneous processes such as nucleation and phase transition during the precipitation process. Previously, the State Key Laboratory of Effective Utilization of Chemical Resources of Beijing University of Chemical Technology invented a rotating liquid film reactor (CN102616749B) with forced micro-mixing effect that can be used for liquid phase precipitation reaction. The reactor consists of a rotor and a stator. Due to the high supersaturation in the initial stage of the precipitation reaction, a huge reaction driving force will be generated. After the reaction starts, a strong shear field is formed between the rotor and the stator, which effectively promotes micro-mixing and mass transfer, and can continuously and quickly form a large number of nuclei and quickly leave the reactor, realizing the separation of nucleation and crystallization processes, thereby greatly reducing the particle size of the generated precipitate and significantly narrowing the particle size distribution range, thereby improving the application performance of the precipitate as a functional material. However, it is still difficult to instantaneously capture nucleated particles for in-situ characterization without destroying the strong shear field.

[0003] Based on the design of a rotating liquid film reactor with forced micro-mixing, this work innovatively constructed an in-situ detection system for a rotating micro-liquid film reactor. While giving full play to the role of the rotating liquid in confined space to enhance micro-mixing and realize the separation of nucleation and crystallization, sampling ports and windows are selectively set on the side of the rotating liquid film reactor. An original micro-negative pressure sampler is created to capture nucleated particles, and the visual system and particle imaging system are connected in situ to capture the transient state of crystal nuclei, obtain instantaneous images of the nucleation process, and monitor the instantaneous evolution behavior of liquid-solid and liquid-liquid interfaces. Summary of the invention

[0004] The purpose of the present invention is to provide an in-situ detection system for a rotating micro-liquid film reactor for monitoring the nucleation behavior of nanomaterials. In addition to realizing the separation of the nucleation and crystallization processes, the system can significantly reduce the particle size of the generated precipitate and significantly narrow the particle size distribution range. In addition, the system can also monitor the nucleation process in situ, capture the transient state of the crystal nucleus, and establish the nucleation / crystallization kinetic equation.

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

[0006] The rotating micro-liquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials of the present invention is characterized in that:

[0007] The reactor is composed of a closed casing as a stator, and materials are added to the upper end of the stator according to a stoichiometric ratio. There is a rotatable rotor in the stator, and the rotor is connected to a motor; the rotation speed is 500-5000rpm, the slit width between the rotor and the stator is 10-500μm, and a shear field is formed between the rotor and the stator; a sampling port is set on one side of the stator side wall, and a sampler is made to capture nucleated particles in the shear field and enter a visible observation area; a viewing window is opened on the other side of one side of the stator side wall.

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

[0009] The internal cavity of the stator is a truncated cone with a narrow upper and wide lower structure, and its cross section is a trapezoidal shape with a bottom angle of 70-85°. The stator height is 60-80 mm, and the stator height Δh can be moved up and down to adjust the slit width; the rotor is consistent with the stator structure, and in order to keep the sides parallel when adjusting the gap, a hole that can be connected to the motor shaft is set at its axial center, so that after connecting with the electrode, it can rotate at high speed under the drive of the motor.

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

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

[0012] The visual observation area is provided with a vertical lifting platform, and the height of the visual observation area is adjusted by the vertical lifting platform.

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

[0014] The nano material includes hydrotalcite, oxide, hydroxide, pseudo-boehmite or barium sulfate.

[0015] Beneficial effects of the present invention: Starting from the basic process of preparing metal hydroxides by precipitation method, the present invention simulates the fluid mixing process of the rotating liquid film reactor by computational fluid dynamics (CFD), so that the bottom angle of the truncated cone stator of the rotating liquid film reactor is 70-85°, the rotation speed is 500-5000rpm, and the slit width is 10-500μm, so as to ensure that the fluid does not mix back when passing through the slit, and form a strong shear field between the rotor and the stator. By making a micro-negative pressure sampler, the nucleated particles are captured in the high-speed shear field and enter the visual observation area, and the high-speed camera and the microscope objective are coupled in situ, so as to capture the transient evolution behavior of the crystal nucleus in situ at the nano-micro scale. The construction of the in-situ detection system of the rotating micro-liquid film reactor solves the problems of poor structure and microscopic mixing effect of the traditional stirred tank reactor, uncontrollable nucleation and growth of the material, resulting in poor quality of large-scale preparation, and the difficulty that the reactor is closed and the phase transition and the transient process of nucleation cannot be observed. The obtained hydrotalcite nucleation results enrich the non-classical nucleation theory and provide guidance for the large-scale preparation of nanomaterials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figure is a block diagram of the overall structure of an in-situ detection system of a rotating micro-liquid film reactor for monitoring the nucleation behavior of nanomaterials.

[0017] Figure 2 Visual observation area for the rotor-stator stereogram and in-situ connection.

[0018] Figure 3 Schematic diagram of the rotor-stator gap, where Δh is the height of the stator rise.

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

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

[0021] Figure 6 The nucleation behavior captured in Example 1. DETAILED DESCRIPTION

[0022] Example 1

[0023] like Figure 1The present invention discloses an in-situ detection system for a rotating micro-liquid membrane reactor for monitoring the nucleation behavior of nano-materials. The system comprises a closed casing, a truncated cone with a narrow upper and wide lower structure and a bottom angle of 85° as a stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. A rotatable conical rotor is arranged in the stator, and a motor is connected to the lower end of the stator. At a rotation speed of 1500 rpm and a slit width of 200 μm, a strong shear field is formed between the rotor and the stator. Eight sampling ports are arranged at intervals of 0.6 cm at a distance of 3 cm from the top of the stator in the axial direction of the "rotor-stator group". A micro-negative pressure sampler is made to capture nucleated particles in the high-speed shear field and enter a cross-shaped visual observation area with a thickness of 2 mm, a polydimethylsiloxane glass composition, and a channel diameter of 50 μm. The height of the cross-shaped visual observation 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 group". A high-speed camera (recording speed 12,000 frames per second) coupled to a microscope objective (10x) is connected in situ to the two types of visual observation areas, and 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 rotating micro-liquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials was applied to the preparation of cobalt-based LDHs. The specific operation is as follows:

[0025] Will Co(NO 3 ) 2 and Al(NO 3 ) 3 According to Co 2+ / Al 3+ The molar ratio is 2, and a nitrate mixed solution is prepared, wherein [M 2+ ]=1.2mol / L; according to n(NaOH) / [n(Co 2+ )+n(Al 3+ )]=1.8 to prepare NaOH solution. The mixed salt solution and alkaline solution were injected into the rotating liquid film reactor at the same time for rapid nucleation. The nucleated particles were captured by a micro-negative pressure sampler in the high-speed shear field through the first sampling port on the side of the reactor away from the top of the stator and entered the visual observation area. The formation of bubbles in the nucleation slurry can be observed in situ by shooting with a high-speed camera at a recording speed of 12,000 frames per second. Different areas with rich and poor solutes were observed in the bubbles. After phase separation, solute-rich areas were formed, and then amorphous aggregates were produced with a particle size of ~1μm. The results show that cobalt-based LDHs conform to the two-step nucleation theory.

[0026] Example 2

[0027] like Figure 1The present invention discloses an in-situ detection system for a rotating micro-liquid membrane reactor for monitoring the nucleation behavior of nano-materials. The system comprises a closed casing, a truncated cone with a narrow upper and wide lower structure and a bottom angle of 85° as a stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. A rotatable conical rotor is arranged in the stator, and a motor is connected to the lower end of the stator. At a rotation speed of 1500 rpm and a slit width of 200 μm, a strong shear field is formed between the rotor and the stator. Eight sampling ports are arranged at intervals of 0.6 cm at a distance of 3 cm from the top of the stator in the axial direction of the "rotor-stator group". A micro-negative pressure sampler is made to capture nucleated particles in the high-speed shear field and enter a cross-shaped visual observation area with a thickness of 2 mm, a polydimethylsiloxane glass composition, and a channel diameter of 50 μm. The height of the cross-shaped visual observation 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 group". A high-speed camera (recording speed 12,000 frames per second) coupled to a microscope objective (10x) is connected in situ to the two types of visual observation areas, and 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 rotating micro-liquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials was applied to the preparation of cobalt-based LDHs. The specific operation is as follows:

[0029] Will Co(NO 3 ) 2 and Al(NO 3 ) 3 According to Co 2+ / Al 3+ The molar ratio is 2, and a nitrate mixed solution is prepared, wherein [M 2+ ]=1.2mol / L; according to n(NaOH) / [n(Co 2+ )+n(Al 3+ )]=1.8 to prepare NaOH solution. The mixed salt solution and alkaline solution were injected into the rotating liquid film reactor at the same time for rapid nucleation. The nucleated particles were captured by a micro-negative pressure sampler in the high-speed shear field through the sixth sampling port at the side of the reactor away from the top of the stator and entered the visual observation area. The nucleated particles with a particle size of >1μm can be observed in situ by high-speed camera photography. The results show that with the extension of reaction time, the amorphous aggregates further crystallize to form orderly arranged nucleated particles.

[0030] Example 3

[0031] like Figure 1The present invention discloses an in-situ detection system for a rotating micro-liquid membrane reactor for monitoring the nucleation behavior of nano-materials. The system comprises a closed casing, a truncated cone with a narrow upper and wide lower structure and a bottom angle of 85° as a stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. A rotatable conical rotor is arranged in the stator, and a motor is connected to the lower end of the stator. At a rotation speed of 1500 rpm and a slit width of 200 μm, a strong shear field is formed between the rotor and the stator. Eight sampling ports are arranged at intervals of 0.6 cm at a distance of 3 cm from the top of the stator in the axial direction of the "rotor-stator group". A micro-negative pressure sampler is made to capture nucleated particles in the high-speed shear field and enter a cross-shaped visual observation area with a thickness of 2 mm, a polydimethylsiloxane glass composition, and a channel diameter of 50 μm. The height of the cross-shaped visual observation 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 group". A high-speed camera (recording speed 12,000 frames per second) coupled to a microscope objective (10x) is connected in situ to the two types of visual observation areas, and 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 rotating micro-liquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials was applied to the preparation of cobalt-based LDHs. The specific operation is as follows:

[0033] Will Co(NO 3 ) 2 and Al(NO 3 ) 3 According to Co 2+ / Al 3+ The molar ratio is 2, and a nitrate mixed solution is prepared, wherein [M 2+ ]=1.2mol / L; according to n(NaOH) / [n(Co 2+ )+n(Al 3+ )]=1.8. The mixed salt solution and the alkaline solution were simultaneously injected into the rotating liquid film reactor for rapid nucleation. The nucleated particles with a particle size of ~10μm were observed in situ by taking pictures with a high-speed camera through the viewing window. The results showed that as the reaction time increased, the nucleated particles underwent secondary nucleation.

Claims

1. A rotating micro-liquid membrane reactor in-situ detection system for monitoring the nucleation behavior of nanomaterials, characterized in that: The reactor is composed of a closed casing as a stator, materials are added to the upper end of the stator according to a stoichiometric ratio, a rotatable rotor is arranged inside the stator, and the rotor is connected to a motor; the rotation speed is 500-5000rpm, the slit width between the rotor and the stator is 10-500μm, and a shear field is formed between the rotor and the stator; a sampling port is arranged on one side of the stator side wall, and a sampler is made to capture nucleated particles in the shear field and enter a visual observation area; a viewing window is opened on the other side of one side of the stator side wall; A high-speed camera is arranged in the visible observation area or the open viewing window, with a recording speed of 10,000 to 12,000 frames per second, and the high-speed camera is connected to a microscope lens with a magnification of 10 to 50 times; a light source is arranged on the opposite side of the high-speed camera; and the high-speed camera is connected to a computer; The internal cavity of the stator is a truncated cone with a narrow upper and wide lower structure, and its cross-section is a trapezoidal shape with a trapezoidal bottom angle designed to be 70-85°; the stator height is 60-80 mm, and the stator height Δh can be moved up and down to adjust the slit width; the rotor is consistent with the stator structure, and in order to keep the sides parallel when adjusting the gap, a hole that can be connected to the motor shaft is set at its axial center so that it can rotate at high speed driven by the motor after connecting with the electrode.

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

3. The system according to claim 1, characterized in that The visual observation area is composed of two pieces of glass with a thickness of 1-3 mm stacked in parallel, and there are micro-scale channels of different shapes with different diameters of 50-100 μm between the two pieces of glass; 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 provided with a vertical lifting platform, and the height of the visual observation area is adjusted by the vertical lifting platform.

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 pulse laser light source.

6. The system according to claim 1, characterized in that The nano material includes hydrotalcite, oxide, hydroxide, pseudo-boehmite or barium sulfate.

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