Photochemical reactor, method and system with total reflection characteristics

Abstract

The invention provides a photochemical reactor with a total reflection characteristic, a method and a system, and relates to the technical field of photochemistry. According to the invention, the light source is aligned with the direction of the reaction fluid, and the light energy is restrained in the reaction system by utilizing the total reflection condition, so that an optical waveguide structure which is propagated in order is formed, and the problem of serious loss caused by disordered light energy scattering, device wall absorption and transmission in the prior art is fundamentally solved. And due to the ordered and efficient utilization of light energy, the reaction rate is higher under the same light intensity, or higher light intensity can be used under the small pipe diameter, so that the reaction efficiency is greatly improved, and the reaction time is shortened. The structure of the reactor is only a simple tubular structure, no complex optical fiber coupling or nesting channel is needed, linear amplification can be achieved through simple series connection or parallel connection, and no obvious bad amplification effect exists. The two total reflection modes can be flexibly selected to adapt to reaction systems with different refractive indexes, the applicability is wide, the structure is simple, the energy consumption is low, and the requirements of green chemistry are met.

Description

Technical Field

[0001] This invention relates to the field of photochemical technology, and in particular to a photochemical reactor, method, and system with total internal reflection characteristics. Background Technology

[0002] Photochemical synthesis technology, due to its crucial role in green and low-carbon transformation, has become a cutting-edge field of focus for many countries worldwide. Photochemical reactions, reaction devices, and reaction processes are the key supports for photochemical technology. The form and efficiency of light utilization are the core differences between photoreactors and other energy-driven reaction methods such as thermocatalysis and electrocatalysis. Currently, there are many types of photochemical reaction devices. In terms of the spatial relationship between the light source and the reactor: when the light source (light-emitting part) is contained within the three-dimensional space of the reactor, it can be called a light source-embedded reactor; when the light source is not contained within the three-dimensional space of the reactor, it can be called a light source-external reactor. The form of material movement or flow does not affect the spatial relationship between the light source and the reactor, and the reactor types listed below all include continuous flow, intermittent flow, stirred mixing, and combinations thereof. Common forms of reactors with built-in light sources include: reaction vessels or reaction cylinders, reaction tubes + internal built-in light sources, with common internal light sources being mercury lamps with constant temperature water jackets and LED arrays; common forms of reactors with external light sources include: flat plate reactors + external light sources (such as array-type LED surface light sources), batch reactors with light windows + external light sources, tubular reactors + external end-face light sources, tubular reactors + external annular cylindrical irradiation light sources, overflow reactors + external light sources, reactors with a centrally placed light source (such as a medium-pressure mercury lamp) + multiple reactors with annular light source distribution, and reactors with a centrally placed reactor + multiple light sources distributed around the reactor, etc.

[0003] The following problems exist when these irradiation methods are used in conjunction with reactors: (1) The light energy utilization efficiency is low and there are many disordered losses. The duty cycle of the effective illumination area has an impact. For example, in a microchannel reactor, the reaction area accounts for about 50% of the illumination area, resulting in a significant waste of photons. Transmission, absorption, and reflection at the reaction window are also factors. When the concentration or thickness of reactants is insufficient, transmission is the main light loss. Absorption by the reaction vessel walls, such as in fluoroplastic coil reactors, exhibits extremely strong absorption by the vessel walls in the deep ultraviolet region. The absorption by non-effective reactants, such as the reaction solvent and reaction products, also affects the light energy utilization efficiency.

[0004] (2) The light distribution characteristics do not match the reactant distribution characteristics. An ideal photochemical reactor should be distributed as much as possible according to the conditions required for high-efficiency photochemical reactions. Currently, due to the absorption and loss of light energy by the reactor itself and the substances, the light energy in current photochemical reactors exhibits an exponential decay characteristic. The concentration of materials is significantly affected by the reaction intensity, mass transfer rate, and solution transport direction in different regions. In reality, the concentration of reactants is often lower in areas closer to strong light, indicating a mismatch between the two.

[0005] (3) If the photon path length relative to the distance it travels into and out of the substrate solution in the reactor is fixed or has too small a range of variation, the photon density will be difficult to adapt to changes in reactant concentration. Different reactions, even within the same reactor, will result in variations in the penetration depth due to differences in absorbance depending on the type of substrate. Similarly, at different stages of the same reaction, the absorbance will change as the reactant concentration progresses. According to the Lambert-Beer theorem, all of these situations will lead to changes in the optical path length. Furthermore, the penetration depth of photons into the substrate solution is not fixed but varies throughout the entire process of most reactions, especially in reactions with initially high concentrations and ultimately low concentrations, where the penetration depth varies significantly. Reactors with relatively fixed optical path lengths result in a fixed or very small variation in the penetration depth matching between light and reactants, making adaptive matching impossible based on material type and concentration changes. This is particularly evident in thin-layer, overflow, and microchannel continuous flow reactors. Their reactor shapes and material distribution patterns often result in the reaction solution being only millimeter- or sub-millimeter-sized in the direction of photon movement, inevitably leading to absorbance variations due to differences in substrate absorbance or concentration changes during the reaction, resulting in significant transmission losses.

[0006] For example, the total internal reflection characteristic of fluids in a pipe is utilized in a nested channel structure flow photoreactor. A laser is used as the light source, coupled and guided by an optical fiber. The fiber's output end extends into the cavity of the nested structure of the flow photoreactor. The angle of the emitted light satisfies total internal reflection at the sidewall of the outer channel. Multiple total internal reflections are performed using the medium within the channel as the light guide, achieving a light guiding method similar to that of an optical fiber. The liquid-core waveguide illumination method allows light to repeatedly pass through the inner channel in the longitudinal direction, maintaining strong and uniform illumination throughout the flow photoreactor, which can extend for several centimeters, thus increasing the effective illumination length for the photocatalytic organic reaction sample within the channel.

[0007] The aforementioned nested channels and fiber coupling complicate the device structure. Using a laser limits the selection of light sources with different wavelengths and their luminous efficacy. While the resulting uniform illumination is suitable for high-throughput testing and laboratory research, the very small diameter of the reaction channel restricts scale-up requirements. Furthermore, the narrow incident light coupling angle and repeated penetration of the outer isothermal liquid and inner container walls result in significant ineffective absorption. The device is also limited by the range and optical characteristics of the light source, the fiber optic cable and its coupling characteristics, and efficiency limitations due to losses in multiple spectral transmission regions of the outer liquid and inner container walls. Due to its device characteristics, particularly the end structure and annular gap features, it is prone to end losses and annular light transmission around the reaction zone that cannot be absorbed by the reaction solution, resulting in significant waste; the corresponding quantum yield in the literature is only 0.36%. Summary of the Invention

[0008] In view of this, one of the objectives of the present invention is to provide a photochemical reactor with total internal reflection characteristics, so as to solve the technical problems of existing photochemical reactors, such as low light energy utilization efficiency, numerous disordered losses, mismatch between light distribution characteristics and reactant distribution characteristics, and fixed reactor, making it difficult for light and reactants to adapt to each other.

[0009] The second objective of this invention is to provide a photochemical reaction method with total internal reflection characteristics.

[0010] The third objective of this invention is to provide a photochemical reaction system with total internal reflection characteristics.

[0011] To achieve one of the above objectives, the present invention provides a photochemical reactor with total internal reflection characteristics, comprising a reaction tube, wherein a light source is provided at one end of the reaction tube, and the main direction of the light source is consistent with the flow direction of the reaction fluid inside the reaction tube; When total internal reflection occurs on the inner surface of the reaction tube, the following conditions must be met:

[0012] Angle of incidence The refractive index of the region where the incident light is located. : Refractive index of the reactive fluid The refractive index of the reaction tube; Alternatively, when total internal reflection occurs on the outer surface of the reaction tube, the following conditions must be met:

[0013] Angle of incidence The refractive index of the region where the incident light is located. : Refractive index of the reactive fluid The refractive index of the reaction tube. : Refractive index of the region outside the reaction tube.

[0014] Optionally, one end of the reaction tube is a light-transmitting port, and the light source is disposed adjacent to the light-transmitting port.

[0015] Optionally, the light source includes, but is not limited to, a focused spot of light, such as a point, a circle, an ellipse, or a flat line.

[0016] Optionally, one end of the reaction tube is a liquid inlet, which is located in the tangential or diametrical direction of the reaction tube, and the opposite end of the liquid inlet is a liquid outlet, which is in the same direction as the light source.

[0017] Optionally, the reaction tubes include multiple tubes, which are arranged in series.

[0018] Optionally, the outer region of the reaction tube is the external region adjacent to the reaction tube, which may be a vacuum, filled with gas, or filled with a low-refractive-index liquid as needed.

[0019] Optionally, the reaction fluid includes, but is not limited to, a homogeneous system or a solution system containing particulate matter or microbubbles.

[0020] To achieve the second objective mentioned above, the present invention provides a photochemical reaction method using a photochemical reactor with total internal reflection characteristics as described above, comprising the following steps: Step 1: Using fluid transport measures, the reaction fluid is transported to the inlet of the photochemical reactor at a preset flow rate and the reaction tube is filled; Step 2: The incident light enters the reaction tube through the light-transmitting port at a preset angle on the end face of the reaction tube, and the main direction of the light is consistent with the main flow direction of the reaction fluid. Step 3: When the refractive index of the reaction fluid is greater than that of the reaction tube, total internal reflection can be formed on the inner wall of the reaction tube filled with liquid, and light propagates in the reaction fluid; Alternatively, when the refractive index of the reaction fluid is smaller than that of the reaction tube, total internal reflection can be formed on the outer wall of the transparent reaction tube in the low refractive index state of the outside, and the light propagates within the tube wall, which is dominated by the reaction fluid. Step 4: The reaction fluid is transported in the total reflection structure, while photons propagate in the reaction fluid. The two interact fully to complete the photochemical reaction, and the products are discharged from the outlet of the reaction tube. Step 5: Maintain the reaction temperature within the set range by precooling or preheating the reaction fluid and controlling the temperature of the reaction tube wall to ensure the reaction effect.

[0021] To achieve the third objective mentioned above, the present invention provides a photochemical reaction system with total internal reflection characteristics, including any of the above-mentioned photochemical reactors with total internal reflection characteristics, and further including a mixing tank and a product collection tank, wherein the mixing tank is connected to the inlet of the photochemical reactor, and the outlet of the photochemical reactor is connected to the product collection tank.

[0022] Optionally, the outer wall of the photochemical reactor includes a temperature control structure.

[0023] The photochemical reactor, method, and system with total internal reflection characteristics provided by this invention have the following technical effects: By aligning the light source with the reaction fluid and utilizing total internal reflection to confine the light energy within the reaction system, an ordered optical waveguide structure is formed. This fundamentally solves the severe loss problems caused by disordered light scattering, absorption by the container walls, and transmission in existing technologies, significantly improving light energy utilization. The ordered and efficient utilization of light energy allows for faster reaction rates at the same light intensity, or the use of higher light intensity in smaller tube diameters, thereby greatly improving reaction efficiency and shortening reaction time.

[0024] Furthermore, the reactor structure of this invention is a simple tubular structure, requiring no complex fiber optic coupling or nested channels. Linear scale-up can be achieved through simple series or parallel connections without significant adverse scale-up effects. Two total internal reflection modes can be flexibly selected to adapt to reaction systems with different refractive indices, making it widely applicable. Its simple structure and low energy consumption meet the requirements of green chemistry. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a preferred embodiment of the photochemical reactor with total internal reflection characteristics of the inner surface of the reaction tube according to the present invention; Figure 2 yes Figure 1 Schematic diagram of total internal reflection at the interface inside the reaction tube; Figure 3 This is a schematic diagram of a preferred embodiment of the photochemical reactor with total internal reflection characteristics of the outer surface of the reaction tube according to the present invention; Figure 4 yes Figure 3 Schematic diagram of total internal reflection at the outer interface of the intermediate reaction tube; Figure 5 It contains Figure 1 or Figure 3 Schematic diagram of the photochemical reaction system in the photochemical reactor; Figure 6 This is a schematic flowchart of a preferred embodiment of the photochemical reaction method with total internal reflection characteristics according to the present invention.

[0027] in, Figures 1-6 : 10. Mixing tank; 20. Fluid transfer pump; 30. Photochemical reactor; 31. Reaction tube; 311. Inlet; 312. Outlet; 32. Light source; 33. Temperature control structure; 40. Product collection tank; 50. Reaction fluid; 60. Incident light; 61. Reflected light; 70. External medium. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] A preferred embodiment of the present invention provides a photochemical reactor with total internal reflection characteristics. The reactor has a simple structure and can efficiently confine light energy inside the reaction fluid, thereby significantly improving the light energy utilization efficiency and reaction rate.

[0030] The following will be combined with the appendix Figure 1-6 Provide a detailed description. Figure 5 The overall architecture of the photochemical reaction system involved in this invention is shown, while Figure 1 and 2 The working principle of total internal reflection using an inner surface, as described in a preferred embodiment of the present invention, is illustrated in detail. Figure 3 and Figure 4 The working principle of total internal reflection of the outer surface used in a preferred embodiment of the present invention is shown in detail.

[0031] In this embodiment, the photochemical reactor 30 is the core component of the entire reaction system, which mainly includes a reaction tube 31 and a light source 32 disposed at one end of the reaction tube 31.

[0032] Specifically, for example, reaction tube 31 is a quartz glass tube with an inner diameter of 2 mm and a length of 1 meter. It is understood that quartz glass is chosen because of its good chemical stability and transmittance to specific wavelengths of light, and its refractive index n at the wavelength of the light source used in this embodiment... p It is approximately 1.46.

[0033] The reaction tube 31 has an inlet 311 and an outlet 312 located at its two ends, respectively, for the entry and exit of the reaction fluid. Accordingly, the flow path of the reaction fluid in the tube is along the axial direction of the reaction tube 31 from the inlet 311 to the outlet 312.

[0034] The light source 32 is located at one end of the liquid inlet 311 of the reaction tube 31, and its light-emitting surface is close to the end face of the reaction tube 31. In order to achieve efficient light coupling, this end face of the reaction tube 31 is optically polished to form a light-transmitting port.

[0035] As an optional implementation, the light source 32 may include one or more light-emitting diodes, laser diodes, or other types of light sources.

[0036] It should be noted that the main direction of the light source 32, that is, the direction of the central axis of its emitted beam, is consistent with the flow direction of the reaction fluid in the reaction tube 31. This unidirectional arrangement ensures that the light energy can propagate over long distances along the flow path of the reaction fluid, achieving synergy between the optical path and the reaction process. That is, by utilizing the reaction fluid and the incident photons, a positive match is formed between the photon density and the concentration of the reaction fluid, avoiding a reverse or lateral match between the two.

[0037] The key to this implementation is that it achieves total internal reflection of light on the inner wall of the reaction tube 31.

[0038] Its physical principle is as follows Figure 2 As shown (n) w (Refractive index of the light-transmitting aperture, offset during calculation). Total internal reflection occurs when light travels from an optically denser medium to an optically less dense medium at an angle of incidence greater than the critical angle. In this embodiment, the components of the reactive fluid 50 are carefully selected to achieve an overall refractive index n. r The refractive index n of the material of reaction tube 31 is greater than that of reaction tube 31. p .

[0039] Accordingly, in order to ensure that most of the incident light rays 60 can be confined to propagate in the reactive fluid 50, another condition must be met, namely, the numerical aperture NA of the incident light beam must be smaller than the maximum receiving numerical aperture determined by the difference in refractive indices of the two media.

[0040] The formula for the maximum numerical aperture is as follows:

[0041] Angle of incidence The refractive index of the region where the incident light is located. : Refractive index of the reactive fluid : The refractive index of the pipe.

[0042] During the operation of this embodiment, you can refer to Figure 6 The flowchart shown.

[0043] First, in step S101, a pre-prepared reaction fluid 50 is pumped into the reaction tube 311 through a fluid transfer pump 20 (e.g., a peristaltic pump) until the reaction fluid 50 completely fills the entire reaction tube 31.

[0044] Subsequently, in step S102, the light source 32 is activated and operated to emit incident light 60, which enters from the light-transmitting end face of the reaction tube 31. Since the main body direction of the light source 32 is consistent with the fluid flow direction, the light beam will enter the reaction fluid 50 along the tube axis.

[0045] After the beam enters, the core reaction phase S103 begins. This is because n is simultaneously satisfied. r >n p Under the condition that NA is less than the maximum receiving numerical aperture, the incident light 60 entering the reactive fluid 50 undergoes total internal reflection when it reaches the interface between the reactive fluid 50 and the inner wall of the reaction tube 31, forming reflected light 61. The light energy is completely reflected back into the reactive fluid 50 without penetrating the tube wall and causing energy loss. These reflected light 61 continue to propagate forward, gradually weakening, and then reach the opposite inner wall interface again for total internal reflection. This process repeats, and the light energy is efficiently confined in the "liquid core" waveguide composed of the reactive fluid 50, just like in an optical fiber, and travels in a zigzag pattern along the length of the reaction tube 31. During this process, the reactive fluid 50 flows stably in the tube at a set flow rate (e.g., 10 ml per minute), allowing the reactant molecules in the fluid to interact continuously and fully with the photons confined in the same space and propagating over long distances, thereby efficiently carrying out the photochemical reaction.

[0046] Finally, in step S104, the fully reacted fluid flows out from the outlet 312 at the other end of the reaction tube 31 and is collected in the product collection tank 40 for subsequent analysis and purification.

[0047] The solution provided in this embodiment effectively confines light energy within the fluid region where the reaction occurs, with almost no energy loss due to penetration or absorption by the tube wall. It also avoids the significant scattering and transmission losses found in traditional externally irradiated reactors. Compared to using a traditional externally irradiated tubular reactor at the same light power and reactant concentration, this embodiment achieves a reaction conversion rate increase of over 50%, thereby significantly improving energy efficiency and production efficiency.

[0048] As a preferred embodiment, a structural enhancement scheme for extending the reaction pathway and reaction time is also provided, namely a series photochemical reactor. This approach is particularly suitable for photochemical reaction systems with slow reaction rates or requiring high conversion rates.

[0049] Understandably, in this series structure, only one light source 32 needs to be set at the very front of the entire series structure, that is, at the inlet end of the uppermost reaction tube 31, without having to equip each subsequent reaction tube with an independent light source, thereby simplifying the system structure and reducing costs.

[0050] As a preferred embodiment, such as Figure 3 and Figure 4 As shown, this embodiment demonstrates another operating mode of the photochemical reactor: the external surface total internal reflection mode. This mode is particularly suitable for situations where the refractive index of the reaction fluid is lower than that of the reaction tube material, such as in aqueous reaction systems.

[0051] The following will focus on combining Figure 3 and Figure 4 (n) w The refractive index of the light-transmitting aperture (which is offset during calculation) is used to explain the structure of the photochemical reactor 30 and its working principle of total internal reflection on its outer surface. In this embodiment, the material selection for the reaction tube 31 is crucial. Here, a reaction tube 31 made of high-refractive-index glass (e.g., F2 Schott glass) with a refractive index n at a specific wavelength is selected. p Up to 1.62.

[0052] The reaction fluid 50 processed in this embodiment is an aqueous photocatalytic reaction system, whose main solvent is water, hence its overall refractive index n r It is approximately 1.33. Clearly, at this point, n... r <n p This does not meet the total internal reflection condition of the inner surface in the above embodiments.

[0053] To achieve total internal reflection confinement, this embodiment suspends and fixes the reaction tube 31 in the air. Air serves as the external medium 70 outside the reaction tube 31, with a refractive index n. o It is approximately 1.0. Thus, n is formed. p (1.62)>n r (1.33) and n p (1.62)>n o The refractive index gradient relationship (1.0) creates conditions for achieving total internal reflection on the outer surface.

[0054] The incident numerical aperture NA of the light source 32 is configured to satisfy the condition of total internal reflection at the outer surface, that is, NA must be smaller than the maximum receiving numerical aperture determined by the refractive index difference between the reaction tube 31 and the external medium 70.

[0055] The formula for the maximum numerical aperture is as follows:

[0056] Angle of incidence The refractive index of the region where the incident light is located. : Refractive index of the reactive fluid The refractive index of the pipe, : Refractive index of the outer region of the pipe.

[0057] In addition, to precisely control the reaction temperature, a jacketed temperature control structure 33 can be fitted onto the outer wall of the reaction tube 31. The temperature control structure 33 has a circulation channel inside, through which circulating water from a constant temperature water bath can be introduced, thereby precisely maintaining the temperature of the reaction tube 31 at, for example, 25 degrees Celsius.

[0058] The complete workflow of this implementation method is as follows, and can also be referred to... Figure 6 Method flowchart: Before the formal reaction begins, a pretreatment step can be set up, in which various raw materials (such as catalysts, substrates, etc.) required for the reaction are thoroughly stirred and mixed with water solvent in the mixing tank 10 to form a uniform reaction fluid 50.

[0059] Subsequently, in step S101, the fluid delivery pump 20 is started to pump the uniformly mixed reaction fluid 50 into the inlet 311 of the reaction tube 31.

[0060] Subsequently, in step S102, the light source 32 is activated so that the light emitted by it enters from the end face of the reaction tube 31.

[0061] After the light beam enters, the photochemical reaction stage of step S103 begins. For example... Figure 3 As shown, the incident light 60 first passes through the reaction fluid 50 with a lower refractive index and enters the wall of the reaction tube 31 with a higher refractive index. When the light propagates to the interface between the outer wall of the reaction tube 31 and the external air (external medium 70), since the light is traveling from the optically denser medium (tube wall) to the optically less dense medium (air) and the numerical aperture condition for total internal reflection is met, the light will undergo total internal reflection at this interface, forming reflected light 61, which is then reflected back into the tube wall.

[0062] Then, the light passes through the tube wall, enters the internal reactive fluid 50, exits the fluid to reach the opposite tube wall, and undergoes total internal reflection again at the outer wall surface. In this way, the light energy is effectively confined in the composite waveguide structure formed by the tube wall of the reaction tube 31 and the internal reactive fluid 50, and propagates along the axial direction.

[0063] Throughout the reaction process, step S105 is carried out continuously, that is, the temperature control structure 33 continuously adjusts the reaction temperature through circulating water to keep it constant at 25 degrees Celsius, so as to ensure the stability and selectivity of the reaction.

[0064] Finally, in step S104, the liquid that has completed the reaction flows out from the outlet 312 of the reaction tube 31 and enters the product collection tank 40, completing one continuous flow production cycle.

[0065] This implementation method solves the technical problem of confining light energy using the principle of total internal reflection in low-refractive-index reaction systems such as aqueous phases. By adopting an external surface total internal reflection mode, efficient and orderly propagation of light energy is also achieved. The entire system integrates upstream, midstream, and downstream units, has a high degree of automation, and allows for precise control of reaction conditions (such as flow rate, light intensity, and temperature). It provides a complete and highly practical technical solution for achieving stable and efficient continuous photochemical synthesis.

[0066] In summary, the technical solution of this invention is not only applicable to homogeneous liquid reactions, but can also be efficiently applied to solid-liquid heterogeneous catalytic reactions. Even in systems containing a large number of scattering particles (as long as the conditions for total internal reflection are not disrupted or severely damaged, such as when the size is much smaller than the wavelength of light, or the number is small), the waveguide effect of total internal reflection can still effectively confine light energy within the reaction region, achieving uniform activation of the catalyst, thereby significantly improving the reaction rate of photocatalytic degradation or synthesis.

[0067] The technical solution of the present invention will be described in detail below with reference to specific embodiments 1 and 2.

[0068] Example 1: Preparation of m-methylbenzoic acid compounds from m-xylene derivatives (using total internal reflection from the inner wall surface) Implementation steps: Construction of the photochemical reactor: Fluoroplastic tube (inner diameter 10 mm, length 5 cm) was selected, with inlet and outlet ports 312 at both ends, and corresponding light windows were set. The outside of the fluoroplastic tube (refractive index 1.35) was the air environment (refractive index 1.000). The light source was a 420 nm high-power UV-LED (light power 20 W, irradiated on one side of the reactor).

[0069] Reaction parameters: reactant was xylene saturated with oxygen at 0.3 MPa (refractive index approximately 1.496), catalyst was tribromopyridine compound (1%), solution flow rate was 50.0 mL / min, and residence time was 6 s.

[0070] Because the reaction consumes oxygen and requires heat exchange, it needs to be carried out in multiple stages (10 stages) in series and in a cyclical manner.

[0071] Results: Xylene conversion rate was 85%, and the selectivity of the product m-methylbenzoic acid was 80%.

[0072] Calculation of refractive index: That is, NA=0.5<0.645, which satisfies the condition of total internal reflection of the inner wall surface.

[0073] Compared with other photochemical methods: by improving efficiency and increasing light irradiance, the reaction time is shortened by more than 5 times; the photon yield reaches 20.4%, an increase of about 76%.

[0074] Example 2: Preparation of ε-caprolactam from cyclohexanone oxime rearrangement induced by ultraviolet light (using total internal reflection from the outer wall surface) Implementation steps: Construction of the photochemical reactor: A quartz glass tube (inner diameter 8 mm, length 6 cm) was selected, with inlet and outlet ports 312 at both ends, and corresponding light windows were set. The outside of the quartz tube (refractive index 1.475) was an air environment (refractive index 1.000). The light source was a 365 nm high-power UV-LED (light power 10W×2, emission half angle 30°, irradiating the end faces of both ends of the reactor).

[0075] Reaction parameters: The reactant is cyclohexanone oxime (0.5 M acetonitrile solution), with a refractive index of approximately 1.35, a flow rate of 3.5 mL / min, and a residence time of 45 s.

[0076] Post-treatment: The effluent was directly concentrated and recrystallized from hexane.

[0077] Results: The yield of the product ε-caprolactam was 95% (HPLC purity > 99%).

[0078] Calculation of refractive index: That is, NA=0.5<0.907, which satisfies the condition of total internal reflection of the outer wall surface.

[0079] Compared with other photochemical methods: by improving efficiency and increasing light irradiance, the reaction time is shortened by more than 6 times; the photon yield reaches 45.4%, an increase of about 30%.

[0080] In the description of this invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0081] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A photochemical reactor with total internal reflection characteristics, characterized in that, It includes a reaction tube, one end of which is equipped with a light source, the main direction of which is consistent with the flow direction of the reaction fluid inside the reaction tube; When total internal reflection occurs on the inner surface of the reaction tube, the following conditions must be met: Angle of incidence The refractive index of the region where the incident light is located. : Refractive index of the reactive fluid : The refractive index of the reaction tube; Alternatively, when total internal reflection occurs on the outer surface of the reaction tube, the following conditions must be met: Angle of incidence The refractive index of the region where the incident light is located. : Refractive index of the reactive fluid The refractive index of the reaction tube. : Refractive index of the region outside the reaction tube.

2. The photochemical reactor with total internal reflection characteristics according to claim 1, characterized in that, One end of the reaction tube is a light-transmitting port, and the light source is positioned adjacent to the light-transmitting port.

3. The photochemical reactor with total internal reflection characteristics according to claim 1, characterized in that, The light source includes, but is not limited to, light spots focused from points, circles, ellipses, or flat lines.

4. The photochemical reactor with total internal reflection characteristics according to claim 1, characterized in that, One end of the reaction tube is a liquid inlet, which is located in the tangential or diametrical direction of the reaction tube. The opposite end of the liquid inlet is a liquid outlet, and the liquid inlet is in the same direction as the light source.

5. The photochemical reactor with total internal reflection characteristics according to claim 4, characterized in that, The reaction tubes consist of multiple tubes, which are connected in series.

6. The photochemical reactor with total internal reflection characteristics according to claim 1, characterized in that, The outer region of the reaction tube is the external region adjacent to the reaction tube, which may be a vacuum, filled with gas, or filled with a low-refractive-index liquid as needed.

7. The photochemical reactor with total internal reflection characteristics according to claim 1, characterized in that, The reaction fluid includes, but is not limited to, homogeneous systems or solution systems containing particulate matter or microbubbles.

8. A photochemical reaction method using a photochemical reactor with total internal reflection characteristics as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Using fluid transport measures, the reaction fluid is transported to the inlet of the photochemical reactor at a preset flow rate and the reaction tube is filled; Step 2: The incident light enters the reaction tube through the light-transmitting port at a preset angle on the end face of the reaction tube, and the main direction of the light is consistent with the main flow direction of the reaction fluid. Step 3: When the refractive index of the reaction fluid is greater than that of the reaction tube, total internal reflection can be formed on the inner wall of the reaction tube filled with liquid, and light propagates in the reaction fluid; Alternatively, when the refractive index of the reaction fluid is smaller than that of the reaction tube, total internal reflection can be formed on the outer wall of the transparent reaction tube in the low refractive index state of the outside, and the light propagates within the tube wall, which is dominated by the reaction fluid. Step 4: The reaction fluid is transported in the total reflection structure, while photons propagate in the reaction fluid. The two interact fully to complete the photochemical reaction, and the products are discharged from the outlet of the reaction tube. Step 5: Maintain the reaction temperature within the set range by precooling or preheating the reaction fluid and controlling the temperature of the reaction tube wall to ensure the reaction effect.

9. A photochemical reaction system with total internal reflection characteristics, characterized in that, The photochemical reactor with total reflection characteristics as described in any one of claims 1-7 further includes a mixing tank and a product collection tank, wherein the mixing tank is connected to the inlet of the photochemical reactor and the outlet of the photochemical reactor is connected to the product collection tank.

10. The photochemical reaction system with total internal reflection characteristics according to claim 9, characterized in that, The outer wall of the photochemical reactor includes a temperature control structure.

Images