A time-resolved detection system for the dynamic evolution behavior of nanoparticles in an in-situ capture nucleation reactor

Abstract

This invention provides a time-resolved detection system for in-situ capture of the dynamic evolution of nanoparticles in a nucleation reactor, comprising a nucleation reactor, a light source, an in-situ flow cell, an optical fiber, a sampler, a fiber optic spectrometer, and signal control and acquisition devices. This invention captures nucleating particles in a high-speed shear field using a sampler connected to a flow cell. A time-resolved detection system with in-situ coupling to the nucleation reactor, employing a large-core optical fiber, a high-power light source, a fast acquisition rate CMOS detector, and a low integration time fiber optic spectrometer, is constructed to acquire the full spectrum (200-1200 nm) in hundreds of microseconds (<500 μs). This allows for the in-situ, real-time, and rapid capture of the evolution of nanoparticle size, coordination structure, and intermediate transition states during nucleation. This invention solves the problem of being unable to observe phase transitions, structural evolution, and instantaneous nucleation processes during nucleation, providing support for revealing the mechanism by which nucleation reactors can prepare nanomaterials with small and uniform particle sizes.

Description

Technical Field

[0001] This invention relates to a time-resolved detection system for in-situ capture of the coordination structure of nanoparticles and the dynamic evolution of intermediate species in a nucleation reactor. Background Technology

[0002] The application performance of nanomaterials largely depends on the initial nucleation process, which determines key parameters such as nanoparticle size, morphology, structure, and composition. However, due to the structure and poor micro-mixing effect of traditional stirred tank reactors, nucleation and crystal growth are asynchronous, resulting in large precipitate particle size and wide distribution, affecting product quality. In 2002, Academician Duan Xue's team at Beijing University of Chemical Technology first constructed a rotating liquid film reactor (Chem. Mater., 2002, 14, 4286-4291), which effectively promoted micro-mixing and mass transfer, facilitated the formation of a large number of crystal nuclei, and enabled them to rapidly detach from the reactor, achieving separation of the nucleation and crystallization processes. This allowed for the preparation of nanomaterials with uniform particle size distribution, but the nucleation mechanism remains unclear.

[0003] The nucleation process of nanomaterials typically occurs on extremely short timescales and involves complex chemical changes. Furthermore, the precipitation process for preparing nanomaterials is usually carried out in closed containers, making it difficult to rapidly and accurately capture transient processes such as phase transitions and crystallization, thus hindering the acquisition of effective nucleation information. Ultraviolet-visible absorption spectroscopy can utilize the varying degrees of absorption of ultraviolet and visible light by molecules or ions during valence electron transitions to obtain information such as material size and coordination structure. However, on a temporal scale, existing instruments can only achieve a time resolution of seconds for acquiring the full spectrum within a certain wavelength range. Therefore, upgrading the temporal resolution of structural characterization methods to the microsecond level is crucial for obtaining the evolutionary patterns of coordination structures and intermediate species, and for deeply analyzing and revealing the mechanisms of ultrafast reaction processes. Summary of the Invention

[0004] The purpose of this invention is to provide a time-resolved detection system for in-situ capture of the dynamic evolution behavior of nanoparticles in a rotating liquid film nucleation reactor, so as to solve the problem that the existing technology cannot monitor the dynamic evolution behavior of nanoparticles in a rotating liquid film reactor in real time and in situ, and realize high time-resolution observation of nanoparticle nucleation, growth and aggregation processes, so as to provide more comprehensive and accurate data support for the research and development of nanomaterials.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The time-resolved detection system for in-situ capture of the dynamic evolution behavior of nanoparticles in a rotating liquid film reactor, as described in this invention, includes: a rotating liquid film reactor, a light source, an in-situ flow cell, an optical fiber, a vacuum sampler, a fiber optic spectrometer, and a signal control and acquisition device.

[0007] The key feature is that a sampling port is axially positioned in the rotor-stator assembly of the rotating liquid film nucleation reactor and connected to an in-situ flow cell. The upper end of the in-situ flow cell is connected to a light source via optical fiber, and the lower end is connected to a fiber optic spectrometer, enabling the construction of in-situ spectra with a time resolution of hundreds of microseconds (<500 μs). Metal salt solutions and alkaline solutions are added to the rotating liquid film reactor for rapid nucleation. The nucleation slurry is captured at different stages in the high-speed shear zone using a vacuum sampler and then fed into the in-situ flow cell. High-speed acquisition yields time-resolved spectra with a time resolution of hundreds of microseconds (<500 μs), thereby capturing information on the changes in the coordination structure of nanoparticles during nucleation.

[0008] The rotating liquid film reactor structure described is referenced from patent CN202411657126.6. This rotating liquid film reactor consists of a closed casing serving as the stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. The internal cavity of the stator is a truncated cone with a narrow top and wide bottom structure. Its top diameter is 42.3 mm, its bottom diameter is 51.5 mm, its height is 75 mm, and its cross-section is trapezoidal with a base angle of 85°. The stator contains a rotatable frustum-shaped rotor, forming a slit between it and the stator. The slit width is adjustable from 10 to 500 μm. A motor is connected to the rotor to drive it to rotate, with a speed adjustable from 500 to 5000 rpm. At a certain speed and slit width, a strong shear field is formed between the rotor and the stator. Because the rotor is a frustum-shaped rotor with a smaller top and a larger bottom, the centrifugal force gradually increases from top to bottom. As the centrifugal force increases, the instability of the fluid increases, making it easier to form Taylor vortices. This increases the chances of collision and mixing between fluid micro-elements, allowing the reactants to come into more complete contact and mix. Therefore, sampling ports are set at 6 mm intervals, 30 mm axially from the top of the stator in the "rotor-stator assembly", for a total of 8 sampling ports to cover the entire flow field.

[0009] The dynamic evolution of the nucleation process of the nanoparticles ends in the region below the location of sampling port 8.

[0010] The in-situ flow cell inlet is located at the top of the in-situ flow cell, and the outlet is located at the bottom of the in-situ flow cell, which can stabilize the flow of the nucleating slurry and reduce bubble interference. The in-situ flow cell material has a light transmittance of >92% and is one of borosilicate glass, quartz glass, or polymethyl methacrylate. Each end of the in-situ flow cell is provided with a convex lens, the two convex lenses have a focal length of 20mm and a light aperture of 10mm, forming a symmetrical light path. The light inlet end has a collimation function, and the light outlet end converges and couples.

[0011] The connecting optical fiber has a core diameter of 400-600μm and a transmission wavelength of 200-1200nm; the light source is one of xenon lamp, deuterium lamp, deuterium halogen lamp, or halogen lamp, with a power of 40-400W.

[0012] The fiber optic spectrometer described above features a CMOS detector with an integration time of <300μs. It also employs a high-speed random access memory as its storage medium, allowing for the simultaneous storage of 50,000 spectra. This fast read / write speed enables the fiber optic spectrometer to acquire data at its maximum acquisition speed, improving its acquisition efficiency and achieving time-resolved spectra acquisition at the microsecond (<500μs) level.

[0013] The molar concentration ratio of the metal salt solution and the alkaline solution is 1 / 1-3, and the concentration of the nucleating slurry is 0.005-0.01 mol / L to avoid affecting signal detection. The flow rate of the nucleating slurry captured at different stages of the high-speed shear field entering the in-situ flow cell is 50-80 mL / min, thereby avoiding the interference of bubble interference with the detection signal in the flow cell.

[0014] The application of the time-resolved detection system is characterized by in-situ capture of the coordination structure, particle size, and dynamic evolution behavior of reaction intermediates of nanoparticles in a rotating liquid film reactor. The nanoparticles include, but are not limited to, hydrotalcite, oxides, hydroxides, boehmite, and barium sulfate.

[0015] The beneficial effects of this invention are as follows: By constructing a time-resolved detection system and using a fiber optic spectrometer with a CMOS detector, this invention improves the spectral acquisition speed, increasing the time resolution of the full spectrum acquisition in the 200-1200nm acquisition band to the level of hundreds of microseconds (<500μs). Subsequently, the constructed time-resolved detection system is coupled with a rotating liquid film reactor, and the dynamic changes of the rapid nucleation process of hydrotalcite in the rotating liquid film reactor are captured in situ at a time resolution of hundreds of microseconds (<500μs). This allows for the analysis of the evolution trend of the coordination structure of reactants and intermediate species in the nucleation process of hydrotalcite in different shear regions within the rotating liquid film reactor, laying the foundation for a deeper understanding of the nucleation mechanism of nanoparticles and the derivation of the nucleation mechanism. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a time-resolved spectroscopic detection system for a rotating liquid film reactor used to monitor the nucleation process of nanomaterials.

[0017] Figure 2 This is a design drawing of the stator cross-section of a rotating liquid film reactor, where the base angle is 85°.

[0018] Figure 3 This is a schematic diagram of the rotor-stator slit gap in a rotating liquid film reactor.

[0019] Figure 4 A schematic diagram showing eight sampling ports spaced 6 mm apart, located 30 mm from the top of the stator on the side of the rotating liquid film reactor.

[0020] Figure 5 Microsecond time-resolved ultraviolet-visible spectra obtained from different sampling ports.

[0021] Figure 6 The UV-Vis spectrum of sampling port 1 was obtained by testing with a halogen light source with a trial power of 400W as described in Example 8.

[0022] Figure 7 The image shows the UV-Vis spectrum of sampling port 1 obtained using an optical fiber with a core diameter of 50 μm, as described in Comparative Example 1.

[0023] Figure 8 The UV-Vis spectrum of sampling port 1 was obtained when the flow rate of the nucleating slurry into the flow cell was increased to 80 mL / min as described in Comparative Example 2.

[0024] List of components and accompanying drawings:

[0025] 1. Halogen light source; 2. In-situ flow cell; 3. Convex lens; 4. Vacuum sampler; 5. Sampling port; 6. Fiber optic spectrometer; 7. Rotating liquid film reactor; 8. Computer. Detailed Implementation

[0026] Example 1

[0027] like Figure 1 This invention discloses a time-resolved detection system for in-situ capture of the dynamic evolution of nanoparticles in a nucleation reactor. The nucleation reactor has a closed casing, and the stator cavity is a truncated cone with a narrow top and wide bottom, its cross-section being trapezoidal with a base angle of 85°. Materials can be added to the upper end of the stator according to a stoichiometric ratio. A rotatable frustum-shaped rotor is located inside the stator, with a motor connected below it. A strong shear field is formed between the rotor and the stator. Eight sampling ports are set at 6mm intervals, 30mm axially from the top of the stator in the "rotor-stator assembly," and are in-situ connected to an in-situ flow cell made of quartz glass. The upper end of the in-situ flow cell is connected to a 40W halogen light source via a 600μm core optical fiber with a transmission band of 200-1200nm, and the lower end is connected to a fiber optic spectrometer with a CMOS detector having an integration time of 220μs.

[0028] The above-mentioned rotating liquid film reactor time-resolved spectroscopic detection system for monitoring the nucleation process of nanomaterials was applied to the preparation of cobalt-based layered double hydroxides. The specific operation is as follows:

[0029] Co(Cl)2 and Al(Cl)3 were reacted according to Co 2+ / Al 3+ A mixed chloride solution is prepared with a molar ratio of 2, wherein [Co] 2+ ] = 0.02 mol / L; according to [n(Co 2+)+n(Al 3+ A NaOH solution was prepared with a NaOH content of 1:2 (NaOH / NaOH). The mixed salt and alkali solutions were simultaneously injected into a rotating liquid film reactor for rapid nucleation. The nucleation rotation speed was 1000 rpm, the slit width between the rotor and stator was 200 μm, and the nucleation slurry concentration was 0.005 mol / L. The nucleation slurry was sampled through a vacuum sampler at sampling port 1 in the high-speed shear zone and then introduced into the in-situ flow cell at a flow rate of 50 mL / min. A UV-Vis spectrum with a time resolution of 435 μs was obtained using high-speed acquisition.

[0030] from Figure 5 As can be seen, the nucleating slurry obtained from sampling port 1 only showed the presence of substances belonging to [a specific group] at a wavelength of 490-530 nm. 4 T 1g (P)→ 4 T 1g (F), 4 T2g→ 4 T 1g (F) Transformation of v3(O) h The characteristic vibration peaks were observed, but the typical lamellar structure characteristic peaks (460 nm) of LDH had not yet appeared, indicating that Co... 2+ Initial and OH - Coordination forms [Co(OH)6] 4- It has an octahedral structure, but it is not related to [Al(OH)6]. 3- Stacked together to form a layer of hydrotalcite.

[0031] Example 2

[0032] The experiment was conducted under the same conditions and parameters as in Example 1. Nucleating slurry was obtained from sampling port 2 in the high-speed shear zone using a vacuum sampler and then entered into the in-situ flow cell.

[0033] from Figure 5 As can be seen from the data, the nucleating slurry obtained from sampling port 2 has a v3(O) value at 490-530 nm. h The characteristic vibrational peaks of [Co(OH)6] are significantly enhanced, indicating that... 4- The number of octahedral cells gradually increases.

[0034] Example 3

[0035] The experiment was conducted under the same conditions and parameters as in Example 1. Nucleating slurry was obtained from sampling port 3 in the high-speed shear zone using a vacuum sampler and then entered into the in-situ flow cell.

[0036] from Figure 5 As can be seen from the data, the nucleating slurry obtained from sampling port 3 has a v3(O) value at 490-530 nm. hThe characteristic vibrational peaks continued to intensify, and new characteristic peaks appeared at 580 nm and 640 nm, which were attributed to Co[(OH)]. x (H2O) δ ] |x-2| intermediate transition state and 4 A 2g (F)→ 4 T 1g (F) Transformation of ν3(T) d The characteristic vibrational peaks of [Co(OH)4] are due to the instability of the intermediate transition state, which readily decomposes into H2O to form tetrahedral coordinated [Co(OH)4]. 2- Furthermore, a shoulder peak appears at 460 nm, indicating that [Co(OH)6] 4- Octahedron and [Al(OH)6] 3- Octahedral cells begin to stack.

[0037] Example 4

[0038] The experiment was conducted under the same conditions and parameters as in Example 1. Nucleating slurry was obtained from sampling port 4 in the high-speed shear zone using a vacuum sampler and then entered into the in-situ flow cell.

[0039] from Figure 5 As can be seen, the intensity of the characteristic peaks in the nucleating slurry obtained from sampling port 4 at 490-530nm, 580nm, 640nm and 460nm increases slowly.

[0040] Example 5

[0041] The experiment was conducted under the same conditions and parameters as in Example 1. Nucleating slurry was obtained from sampling port 6 in the high-speed shear zone using a vacuum sampler and then introduced into the in-situ flow cell.

[0042] from Figure 5 As can be seen, the nucleating slurry obtained from sampling port 6 showed significantly enhanced intensity of characteristic peaks at 490-530nm, 580nm, 640nm, and 460nm.

[0043] Example 6

[0044] The experiment was conducted under the same conditions and parameters as in Example 1. Nucleating slurry was obtained from sampling port 8 in the high-speed shear zone using a vacuum sampler and then entered into the in-situ flow cell.

[0045] from Figure 5 As can be seen from the data, the intensity of the characteristic peaks of the intermediate transition state of the nucleating slurry obtained from sampling port 8 decreased at 580 nm and 640 nm, while the intensity of the characteristic peaks at 490-530 nm and 460 nm continued to increase. This indicates that the intermediate transition state gradually transformed at this time, forming an LDH layer of Co-Al octahedral cells.

[0046] Example 7

[0047] The experiment was conducted under the same conditions and parameters as in Example 1. Nucleating slurry was obtained from the bottom outlet using a vacuum sampler and then entered into the in-situ flow cell.

[0048] from Figure 5 As can be seen from the data, the characteristic peaks of the intermediate transition state at 580 nm and 640 nm of the nucleation slurry obtained from the bottom completely disappeared, while the characteristic peak intensities at 490-530 nm and 460 nm reached their highest levels, indicating the formation of the characteristic layered structure of CoAl-LDH.

[0049] Example 8

[0050] The experiment was conducted under the same conditions and parameters as in Example 1. A halogen light source with a power of 400W was connected to an optical fiber with a core diameter of 600μm and a transmission band of 200-1200nm to improve the detection sensitivity. The lower end was connected to an optical fiber spectrometer with a CMOS detector with an integration time of 220μs.

[0051] The rotating liquid film reactor time-resolved spectroscopy detection system for monitoring the nucleation process of nanomaterials described above was applied to the preparation of cobalt-based hydrotalcite, and the specific operation was the same as in Example 1.

[0052] Compared to Figure 5 The spectrum obtained from port 1 was obtained using a 400W halogen light source. Figure 6 The signal-to-noise ratio was significantly improved, and the peak positions were the same, with only the values ​​at 490-530 nm belonging to the range. 4 T 1g (P)→ 4 T 1g (F), 4 T 2g → 4 T 1g (F) Transformation of ν3(O) h Characteristic vibration peaks indicate that Co 2+ First with OH - Coordination forms the growth unit [Co(OH)6] with an octahedral structure. 4- And it is not related to [Al(OH)6] 3- Stacked together to form a layer.

[0053] Comparative Example 1

[0054] The experiment was conducted under the same conditions and parameters as in Example 1. A halogen light source with a power of 40W was connected to an optical fiber with a core diameter of 50μm and a transmission band of 200-1200nm. The nucleating slurry was obtained at port 1 of the high-speed shearing zone through a vacuum sampler and entered into the in-situ flow cell.

[0055] from Figure 7As can be seen, the spectrum obtained using an optical fiber with a core diameter of 50μm did not show obvious characteristic peaks due to the small light flux.

[0056] Comparative Example 2

[0057] The experiment was conducted under the same conditions and parameters as in Example 1. Nucleating slurry was obtained at sampling port 1 using a vacuum sampler and entered into the in-situ flow cell at a flow rate of 80 mL / min.

[0058] from Figure 8 As can be seen, when the flow rate of the nucleating slurry entering the in-situ flow cell was increased to 80 mL / min, no obvious characteristic peaks appeared due to significant bubble interference.

Claims

1. A time-resolved detection system for capturing the dynamic evolution behavior of nanoparticles in an in-situ nucleation reactor, characterized in that... include: Rotating liquid film reactor, light source, in-situ flow cell, optical fiber, vacuum sampler, fiber optic spectrometer, signal control and acquisition device; A sampling port is set up in a rotating liquid film reactor and connected to an in-situ flow cell. The upper end of the in-situ flow cell is connected to a light source via an optical fiber, and the lower end is connected to a fiber optic spectrometer to achieve the construction of a time-resolved in-situ spectrum of <500μs. Metal salt solution and alkaline solution are added to the rotating liquid film reactor for nucleation. The nucleation slurry is captured by a vacuum sampler and enters the in-situ flow cell. The time-resolved spectrum of <500μs is obtained by acquisition, thereby capturing the information on the coordination structure changes of nanoparticles during the nucleation process. A convex lens is set at each end of the in-situ flow cell to form a symmetrical optical path. This rotating liquid film reactor consists of a closed casing as the stator. Materials can be added to the upper end of the stator according to a stoichiometric ratio. The internal cavity of the stator is a truncated, hollow cone with a narrow top and wide bottom structure. Its top diameter is 42.3 mm, bottom diameter is 51.5 mm, height is 75 mm, and cross-section is trapezoidal with a base angle of 85°. Inside the stator is a rotatable frustum-shaped rotor, forming a slit with the stator. The slit adjustment range is 10-500 μm. A motor is connected below the rotor to drive its rotation, with a speed adjustment range of 500-5000 rpm. Sampling ports are set at 6 mm intervals, 30 mm from the top of the stator, for a total of 8 sampling ports to cover the entire flow field. The dynamic evolution of the nucleation process of the nanoparticles ends in the region below the location of sampling port 8.

2. The system according to claim 1, characterized in that: The in-situ flow cell inlet is located at the top of the in-situ flow cell, and the outlet is located at the bottom of the in-situ flow cell.

3. The system according to claim 1, characterized in that: The in-situ flow cell material has a light transmittance of >92% and is one of borosilicate glass, quartz glass, or polymethyl methacrylate.

4. The system according to claim 1, characterized in that: The focal length of the convex lens is set to 20mm, and the aperture is set to 10mm.

5. The system according to claim 1, characterized in that: The connecting optical fiber has a core diameter of 400-600μm and a transmission wavelength of 200-1200nm; the light source is one of xenon lamp, deuterium lamp, deuterium halogen lamp, or halogen lamp, with a power of 40-400W.

6. The system according to claim 1, characterized in that: The fiber optic spectrometer described above has a CMOS detector with an integration time of <300μs.

7. The system according to claim 1, characterized in that: The fiber optic spectrometer uses a high-speed random access memory as its storage medium, which can store more than 50,000 spectra at a time.

8. The system according to claim 1, characterized in that: The molar concentration ratio of the metal salt solution and the alkaline solution is 1 / 1-3, the concentration of the nucleating slurry is 0.005-0.01 mol / L, and the flow rate of the nucleating slurry entering the in-situ flow cell is 50-80 mL / min.

9. The system according to claim 1, characterized in that: The application of the time-resolved detection system is characterized by in-situ capture of the coordination structure, particle size, and dynamic evolution behavior of reaction intermediates of nanoparticles in a rotating liquid film reactor. The nanoparticles include hydrotalcite, oxides, hydroxides, boehmite, barium sulfate, etc.

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