Photochemical reactor, method and system with total reflection properties

Abstract

The application provides a photochemical reactor, method and system with total reflection characteristics, and relates to the technical field of photochemistry.The application aligns a light source with the direction of a reaction fluid, and uses total reflection conditions to constrain light energy in a reaction system, thereby forming an orderly propagating optical waveguide structure, and fundamentally solving the problem of serious loss caused by disordered scattering of light energy, wall absorption and transmission in the prior art.Orderly and efficient use of light energy enables faster reaction rate under the same light intensity, or higher light intensity can be used under small pipe diameter, thereby greatly improving reaction efficiency and shortening reaction time.The reactor structure of the application is only a simple pipe structure, and does not need complex optical fiber coupling or nested channels, and linear amplification can be realized through simple series connection or parallel connection without obvious adverse amplification effect.Two total reflection modes can be flexibly selected to adapt to reaction systems with different refractive indexes, are widely applicable, and have simple structure and low energy consumption, and meet the requirements of green chemistry.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photochemistry, in particular to a photochemical reactor with total reflection characteristics, a method and a system. BACKGROUND

[0002] Photochemical synthesis technology has become a global frontier field due to its key role in green low-carbon transformation. Photochemical reaction, reaction device and reaction process are the key support of photochemical technology, and the form and efficiency of light utilization are the core difference between photochemical reactors and other energy-driven reaction forms such as thermal catalysis and electrocatalysis. At present, there are many forms of photochemical reaction devices. From the spatial position relationship between the light source and the reactor: when the light source (light emitting part) is contained in the three-dimensional space of the reactor, it can be called a light source built-in reactor; when the light source is not contained in 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 position relationship between the light source and the reactor, and the following examples of these reactor forms include continuous flow, intermittent flow, stirring and their combination. Common forms of light source built-in reactor include: reaction kettle or reaction cylinder, reaction tube + internal built-in light source, internal light source commonly has mercury lamp with constant temperature water jacket, LED array; common forms of light source external reactor include: flat plate reactor + external light source (such as array type LED surface light source), kettle type reactor with light window + external light source, pipe type reactor + end surface external light source, pipe type reactor + external ring cylindrical surface irradiation light source, overflow type reactor + external light source, middle placed light source (such as medium pressure mercury lamp) + ring light source distributed multiple reactors, middle placed reactor + ring reactor distributed multiple light sources, etc.

[0003] When the current irradiation forms are combined with the reactor, the following problems exist:

[0004] (1) Low light energy utilization efficiency, with many disordered losses

[0005] The duty cycle of the effective light irradiation area, specifically, the reaction area of the microchannel reactor accounts for about 50% of the irradiation area, causing a great waste of photons; the transmission, absorption and reflection of the reaction window, when the reactant concentration or thickness is insufficient, the transmission is the main loss of light; the absorption of the wall of the reaction container, such as fluoroplastic coil type reactor, which has a strong container wall absorption in deep ultraviolet; the absorption of non-effective reactants, such as the absorption of reaction solvents, reaction products and other light photons, which affects the light energy utilization efficiency.

[0006] (2) Light distribution characteristics do not match the distribution characteristics of the reactants

[0007] The ideal photochemical reactor should be as much as possible to meet the distribution of the various elements required by the high-efficiency photo-reaction. The current photochemical reactor shows exponential decay characteristics of light energy due to the reactor itself and the absorption and loss of the material, and the material concentration is obviously affected by the reaction strength in different areas, the mass transfer speed, the solution transportation direction, etc. In actual situations, the concentration of reactants is low near the strong light area, and the two are not matched.

[0008] (3) The photon optical path is fixed or the variation range is too small relative to the distance of penetrating into and out of the substrate solution in the reactor, and the photon density and the concentration of the reactants are difficult to adapt to changes

[0009] Different reactions, the same reactor, and different reaction substrates will change the penetration depth due to the difference in absorbance; different stages of the same reaction, because the concentration of the reactants changes with the progress of the reaction, the absorbance will also change. According to the Lambert-Beer law, the above situations will all lead to changes in the optical path, and further, the penetration depth of photons into the reaction substrate solution is not determined in the complete process of most reactions, but changes, especially in the initial high concentration and the final low concentration reaction, the penetration depth of photons into the reaction substrate solution changes greatly. The penetration depth of photons into the reaction substrate solution is fixed or changes very little, and cannot adapt to the changes in the concentration of the material according to the material type and the concentration change process. Thin layer, overflow, and micro-channel continuous flow reactors are particularly obvious, their reactor shape and material distribution shape often lead to only millimeter or even sub-millimeter of reaction solution in the direction of photon motion, which will inevitably lead to greater transmission loss due to the absorbance changes of different reaction substrate types or the absorbance changes of the reaction process.

[0010] For example, a flow photochemical reactor with a nested channel structure is used to take advantage of the total reflection characteristics of the pipeline fluid. The light source used is a laser, which is coupled with an optical fiber and conducted. The optical fiber emits end into the cavity of the nested structure of the flow photochemical reactor, and the angle of the emitted light satisfies the total reflection of the light on the side wall of the outer channel. The light is transmitted multiple times by total reflection with the medium in the channel as the light guide medium, realizing the light guide method similar to the optical fiber. The liquid core waveguide light irradiation method makes the light repeatedly penetrate the inner channel in the longitudinal direction, which can maintain strong and uniform light irradiation in a flow photochemical reactor as long as several centimeters, and improve the effective light irradiation length of the organic reaction sample in the channel.

[0011] The nested channel and fiber coupling make the device structure complex; the use of laser restricts the selection of light source of different wavelengths and light efficiency; the formed uniform light irradiation is suitable for high flux testing, laboratory research, and reaction flow channel diameter range, and the diameter is very small, which restricts the amplification demand. In addition, the incident light coupling angle is relatively narrow, and a large amount of invalid absorption occurs when the light repeatedly penetrates the outer layer of constant temperature liquid and the inner layer of device wall; the selection range and optical properties of the light source are limited, the optical fiber and its coupling properties are limited, the loss efficiency of the multiple spectral transmission intervals of the outer liquid and the inner wall of the device is limited; due to the device characteristics, especially the end structure and the annular gap characteristics, end loss is easily formed, and the annular light conduction around the reaction area cannot be absorbed by the reaction solution, causing great waste, and the corresponding quantum yield in the literature is only 0.36%. SUMMARY

[0012] Therefore, one of the purposes of the present application is to provide a photochemical reactor with total reflection characteristics to solve the technical problems of low light energy utilization efficiency, numerous disordered losses, mismatch between light distribution characteristics and reactant distribution characteristics, and reactor fixation in the prior art, and the difficulty of self-adaptation of light and reactants.

[0013] The second purpose of the present application is to provide a photochemical reaction method with total reflection characteristics.

[0014] The third purpose of the present application is to provide a photochemical reaction system with total reflection characteristics.

[0015] In order to achieve one of the above purposes, the present application provides a photochemical reactor with total reflection characteristics, comprising a reaction tube, one end of the reaction tube is provided with a light source, the main body direction of the light source is consistent with the flow direction of the reaction fluid in the reaction tube.

[0016] When total reflection occurs on the inner surface of the reaction tube, the following conditions need to be met:

[0017]

[0018] : incident angle, : refractive index of the region where the incident light is located, : refractive index of the reaction fluid, : refractive index of the reaction tube;

[0019] Or when total reflection occurs on the outer surface of the reaction tube, the following conditions need to be met:

[0020]

[0021] : incident angle, : refractive index of the region where the incident light is located, : refractive index of the reaction fluid, : refractive index of the reaction tube, : refractive index of the region outside the reaction tube.

[0022] Optionally, one end of the reaction tube is a light-transmitting port, and the light source is arranged immediately adjacent to the light-transmitting port.

[0023] Optionally, the light source includes, but is not limited to, a light spot focused by a point, a circle, an ellipse, or a flat line.

[0024] Optionally, one end of the reaction tube is a liquid inlet port, the liquid inlet port is located in a tangential direction or a diameter direction of the reaction tube, an opposite end of the liquid inlet port is a liquid outlet port, and the liquid inlet port is in the same direction as the light source.

[0025] Optionally, the reaction tube includes a plurality of reaction tubes, and the plurality of reaction tubes are arranged in series.

[0026] Optionally, the region outside the reaction tube is an external region adjacent to the reaction tube, and the region can be vacuum, filled with gas, or filled with a liquid with a low refractive index, as needed.

[0027] Optionally, the reaction fluid includes, but is not limited to, a homogeneous system or a solution system containing particles or micro-bubbles.

[0028] To achieve the second purpose, the present application provides a photochemical reaction method using the photochemical reactor with total reflection characteristics as described in any one of the above.

[0029] Step 1: using fluid delivery measures, the reaction fluid is delivered to the liquid inlet port of the photochemical reactor at a preset flow rate, and the reaction tube is filled;

[0030] Step 2: the incident light is incident to the reaction tube through the light-transmitting port at the end face of the reaction tube at a preset angle, and the main direction of the light is consistent with the main flow direction of the reaction fluid;

[0031] Step 3: when the refractive index of the reaction fluid is greater than that of the reaction tube, total reflection can be formed on the inner wall surface of the reaction tube filled with the liquid, and the light propagates in the reaction fluid;

[0032] or when the refractive index of the reaction fluid is smaller than that of the reaction tube, total reflection can be formed on the outer wall surface of the transparent reaction tube in a low-refractive-index state outside, and the light propagates in the reaction fluid containing the tube wall;

[0033] Step 4: the reaction fluid is transported in the total reflection structure, and the photons propagate in the reaction fluid, the two fully interact with each other, the photochemical reaction is completed, and the product is discharged from the liquid outlet port of the reaction tube;

[0034] Step five: maintain the reaction temperature in the set range by pre-cooling or pre-heating the reaction fluid and adjusting the temperature of the reaction tube wall, to ensure the reaction effect.

[0035] To achieve the third of the above purposes, the present application provides a photochemical reaction system with total reflection characteristics, comprising the photochemical reactor with total reflection characteristics as described above, and further comprising a mixing tank and a product collection tank, the mixing tank being in communication with the liquid inlet of the photochemical reactor, and the liquid outlet of the photochemical reactor being in communication with the product collection tank.

[0036] Optionally, the outer wall of the photochemical reactor comprises a temperature control structure.

[0037] The photochemical reactor, method and system with total reflection characteristics provided by the present application have the following technical effects:

[0038] By aligning the light source with the direction of the reaction fluid and using total reflection conditions to confine the light energy in the reaction system, an orderly propagating optical waveguide structure is formed, which fundamentally solves the problem of serious loss caused by disordered scattering of light energy, wall absorption and transmission in the prior art, and significantly improves the light energy utilization rate. The orderly and efficient use of light energy makes the reaction rate faster under the same light intensity, or higher light intensity can be used under small pipe diameter, thereby greatly improving the reaction efficiency and shortening the reaction time.

[0039] In addition, the reactor structure of the present application is only a simple pipe structure, without complex optical fiber coupling or nested channels, and linear amplification can be achieved by simple series or parallel connection without obvious adverse amplification effect. Two total reflection modes can be flexibly selected to adapt to reaction systems with different refractive indices, have wide applicability, and have simple structure and low energy consumption, meeting the requirements of green chemistry. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the description of the embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0041] Figure 1 is a structure schematic diagram of a preferred embodiment of the photochemical reactor with total reflection characteristics of the inner surface of the reaction tube of the present application;

[0042] Figure 2 is Figure 1 is a schematic diagram of the total reflection of the inner interface of the reaction tube in

[0043] Figure 3is a structural schematic diagram of a preferred embodiment of the photochemical reactor with total reflection characteristics of the outer surface of the reaction tube according to the present application;

[0044] Figure 4 is Figure 3 is a schematic diagram of the total reflection of the outer interface of the reaction tube;

[0045] Figure 5 is a preferred embodiment of the photochemical reaction system of the photochemical reactor according to the present application; Figure 1 or Figure 3 is a structural schematic diagram of the photochemical reaction system of the photochemical reactor according to the present application;

[0046] Figure 6 is a flow schematic diagram of a preferred embodiment of the photochemical reaction method with total reflection characteristics according to the present application.

[0047] wherein, Figures 1-6 :

[0048] 10, mixing tank; 20, fluid delivery pump; 30, photochemical reactor; 31, reaction tube; 311, liquid inlet; 312, liquid 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 DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0050] A preferred embodiment of the present application provides a photochemical reactor with total reflection characteristics, which 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.

[0051] The present application will be described in detail below with reference to the accompanying drawings. Figures 1-6 The present application will be described in detail below with reference to the accompanying drawings. Figure 5 The overall architecture of the photochemical reaction system involved in the present application is shown, and Figure 1 and 2 detailedly shows the working principle of the inner surface total reflection adopted by a preferred embodiment of the present application, and Figure 3 and Figure 4 detailedly shows the working principle of the outer surface total reflection adopted by a preferred embodiment of the present application.

[0052] In the present embodiment, the photochemical reactor 30 is the core component constituting the entire reaction system, which mainly includes a reaction tube 31 and a light source 32 arranged at one end of the reaction tube 31.

[0053] Specifically, for example, the reaction tube 31 is a quartz glass tube with an inner diameter of 2 mm and a length of 1 m. It can be understood that quartz glass is selected because of its good chemical stability and transmittance to specific wavelengths of light, and its refractive index n p is about 1.46 at the wavelength of the light source used in the present embodiment.

[0054] The reaction tube 31 has a liquid inlet 311 and a liquid outlet 312 at its two ends, respectively, to realize 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 liquid inlet 311 to the liquid outlet 312.

[0055] The light source 32 is arranged at the liquid inlet 311 end of the reaction tube 31, and its light emitting surface is adjacent to the end surface of the reaction tube 31. In order to realize efficient light coupling, the end surface of the reaction tube 31 is polished to form a light transmission port.

[0056] As an optional implementation, the light source 32 can include one or more light-emitting diodes, laser diodes or other types of light sources.

[0057] It should be noted that the main direction of the light source 32, i.e. the direction of its central axis of the emitted light beam, is consistent with the flow direction of the reaction fluid in the reaction tube 31. This co-directional arrangement ensures that the light energy can propagate along the flow path of the reaction fluid for a long distance, realizing the coordination of the optical path and the reaction process, i.e. using the reaction fluid and the incident photons to form a positive matching of the photon density and the reaction fluid concentration, avoiding the reverse or lateral matching of the two.

[0058] The key of the present embodiment is to realize the total reflection of light on the inner wall surface of the reaction tube 31.

[0059] The physical principle is shown in Figure 2 (n w : refractive index of light transmission port, which is offset in the calculation process), when light is emitted from a light-dense medium to a light-lean medium and the incident angle is greater than the critical angle, total reflection will occur. In the present embodiment, by carefully selecting the components of the reaction fluid 50, the overall refractive index n r is greater than the refractive index n p of the material of the reaction tube 31.

[0060] Accordingly, to ensure that most of the incident light rays 60 can be confined in the reaction fluid 50, another condition must be met, i.e. the numerical aperture NA of the incident light beam must be less than the maximum acceptance numerical aperture determined by the difference of the refractive indices of the two media.

[0061] The maximum numerical aperture is given by the following formula:

[0062]

[0063] : the incident angle, : the refractive index of the region where the incident light is located, : the refractive index of the reaction fluid, : the refractive index of the pipe.

[0064] In the working process of the present embodiment, reference can be made to the flow chart shown in FIG. 1. Figure 6

[0065] First, in step S101, the pre-prepared reaction fluid 50 is pumped into the inlet port 311 of the reaction tube 31 by the fluid delivery pump 20 (e.g. a peristaltic pump) until the reaction fluid 50 completely fills the entire reaction tube 31.

[0066] Subsequently, in step S102, the light source 32 is started and operated to emit incident light rays 60 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.

[0067] After the light beam enters, the core reaction stage S103 begins. Since the conditions of n r >n p and NA being less than the maximum acceptance numerical aperture are met at the same time, the incident light rays 60 entering the reaction fluid 50 will undergo total reflection when propagating to the interface between the reaction fluid 50 and the inner wall of the reaction tube 31, forming reflected light rays 61. The light energy is completely reflected back into the reaction fluid 50 without penetrating into the pipe wall to cause energy loss. These reflected light rays 61 continue to propagate forward and gradually weaken, reaching the opposite inner wall interface again and undergoing total reflection. This process is repeated, and the light energy is efficiently confined in the "liquid core" waveguide formed by the reaction fluid 50 and advances in the length direction of the reaction tube 31 in a zigzag manner. In this process, the reaction fluid 50 flows stably in the tube at a set flow rate (e.g. 10 milliliters per minute), so that the reactant molecules in the fluid and the photons confined in the same space and propagating over a long distance continuously and sufficiently interact with each other, thereby efficiently performing photochemical reactions.

[0068] ​Finally, in step S104, the fully reacted fluid flows out of 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.

[0069] With the scheme provided by the present embodiment, the light energy is effectively confined within the fluid region where the reaction takes place, with little loss due to penetration or absorption by the tube wall, while avoiding the large scattering and transmission losses in conventional external-illumination tube reactors. Compared with a conventional external-illumination tube reactor under the same light power and reactant concentration, the reaction conversion rate of the present embodiment can be improved by more than 50%, thereby significantly improving the energy efficiency and production efficiency.

[0070] As a preferred embodiment, a structure enhancement scheme for extending the reaction path and reaction time is also provided, i.e. a series-connected photochemical reactor. This mode is particularly suitable for photochemical reaction systems with slow reaction rates or high conversion requirements.

[0071] It can be understood that in this series-connected structure, the light source 32 only needs to be provided at the front end of the entire series-connected structure, i.e. at the inlet end of the uppermost reaction tube 31, without the need to provide an independent light source for each subsequent reaction tube, thereby simplifying the system structure and reducing the cost.

[0072] As a preferred embodiment, as shown in Figure 3 and Figure 4 , the present embodiment demonstrates another working mode of the photochemical reactor, i.e. the external surface total reflection mode. This mode is particularly suitable for cases where the refractive index of the reaction fluid is lower than that of the reaction tube material, for example in aqueous phase reaction systems.

[0073] The structure of the photochemical reactor 30 and the working principle of its external surface total reflection will be described below in detail with reference to Figure 3 and Figure 4 (n w : refractive index of the light-transmitting port, which is cancelled in the calculation process), in the present embodiment, the material of the reaction tube 31 is crucial. Here, a reaction tube 31 made of high-refractive-index glass (e.g. F2 Schott glass) is selected, which has a refractive index n p as high as 1.62 at a specific wavelength.

[0074] The reaction fluid 50 processed by the present embodiment is an aqueous phase photochemical reaction system, whose main solvent is water, and thus its overall refractive index n r is about 1.33. Obviously, in this case, n r <n p , which does not satisfy the internal surface total reflection condition in the above embodiment.

[0075] In order to achieve total reflection constraints of light, the present embodiment suspends the reaction tube 31 in the air. The air as the external medium 70 outside the reaction tube 31 has a refractive index n o of about 1.0. Thus, a refractive index gradient relationship of n p (1.62) > n r (1.33) and n p (1.62) > n o (1.0) is formed, thereby creating conditions for achieving total reflection of the outer surface.

[0076] The numerical aperture NA of the light source 32 is configured to satisfy the condition of total reflection of the outer surface, that is, NA must be less than the maximum receiving numerical aperture determined by the refractive index difference of the reaction tube 31 and the external medium 70.

[0077] The maximum numerical aperture formula is as follows:

[0078]

[0079] : the incident angle, : the refractive index of the region where the incident light is located, : the refractive index of the reaction fluid, : the refractive index of the pipe, : the refractive index of the region outside the pipe.

[0080] In addition, in order to accurately control the reaction temperature, the outer wall of the reaction tube 31 can also be sleeved with a jacket type temperature control structure 33. The temperature control structure 33 is provided with a circulating channel inside, and circulating water from a constant temperature water bath can be introduced, so that the temperature of the reaction tube 31 is accurately maintained at, for example, 25 degrees Celsius.

[0081] The complete workflow of the present embodiment is as follows, and can also refer to the method flowchart of Figure 6 :

[0082] Before the formal reaction starts, a pretreatment step can be set, that is, in the mixing tank 10, various raw materials required for the reaction (such as catalysts, substrates, etc.) are fully stirred and mixed with the aqueous solvent to form a uniform reaction fluid 50.

[0083] Subsequently, in step S101, the fluid delivery pump 20 is started to pump the uniformly mixed reaction fluid 50 from the liquid inlet 311 of the reaction tube 31.

[0084] Then, in step S102, the light source 32 is started to emit light from the end face of the reaction tube 31.

[0085] After the light beam is incident, it enters the photochemical reaction stage of step S103. As Figure 3As shown, the incident light ray 60 first passes through the reaction fluid 50 of lower refractive index, and enters the reaction tube 31 wall of higher refractive index. When the light ray propagates to the interface between the reaction tube 31 outer wall and the external air (external medium 70), since the light is emitted from the optically dense medium (tube wall) to the optically sparse medium (air), and the numerical aperture condition of total reflection is satisfied, the light ray will be totally reflected at this interface to form a reflected light ray 61, and is reflected back into the tube wall.

[0086] Then, the light ray passes through the tube wall, enters the internal reaction fluid 50, and then passes out of the fluid to the opposite tube wall, and again totally reflects at the outer wall surface. In this way, the light energy is effectively confined in the composite waveguide structure composed of the reaction tube 31 tube wall and the internal reaction fluid 50, and propagates axially.

[0087] Throughout the reaction process, step S105 is continuously performed, i.e., the temperature control structure 33 continuously adjusts the reaction temperature by circulating water, so that the reaction temperature is kept constant at 25 degrees Celsius, to ensure the stability and selectivity of the reaction.

[0088] Finally, in step S104, the liquid after the reaction is completed flows out of the liquid outlet 312 of the reaction tube 31, and enters the product collection tank 40, to complete a continuous flow production cycle.

[0089] The present embodiment solves the technical problem that the low refractive index reaction system such as an aqueous phase is difficult to confine light energy by using the total reflection principle. By using the external surface total reflection mode, efficient and orderly propagation of light energy is also achieved. The entire system integrates upstream, midstream and downstream units, has high automation degree, and the reaction conditions (such as flow rate, light intensity, temperature) are accurately controllable, thereby providing a complete and highly practical technical solution for realizing stable and efficient continuous flow photochemical synthesis.

[0090] In summary, the technical solution of the present application is not only suitable for homogeneous liquid reactions, but also can be efficiently applied to solid-liquid heterogeneous catalytic reactions. Even in a system containing a large number of scattering particles (as long as the condition of total reflection is not destroyed or not seriously destroyed, such as the size being much smaller than the light wave length, or the number being small), the waveguide effect of total reflection can still effectively confine the light energy in the reaction region, realize uniform activation of the catalyst, and further significantly improve the reaction rate of photocatalytic degradation or synthesis.

[0091] The technical solution of the present application will be described in detail below in combination with specific examples 1 and 2.

[0092] Example 1: Preparation of m-toluic acid compounds from m-xylene (using inner wall surface total reflection)

[0093] Implementation steps:

[0094] Photochemical reactor construction: Fluoroplastic pipe (inner diameter 10 mm, length 5 cm) was selected, and inlet and outlet ports 312 were arranged at both ends, and corresponding light windows were arranged. The fluoroplastic pipe (refractive index 1.35) was surrounded by an air environment (refractive index 1.000); the light source was a 420 nm high-power UV-LED (light power 20 W, and the single side end face of the reactor was irradiated).

[0095] Reaction parameters: The reactant was 0.3 MPa oxygen-saturated xylene (refractive index about 1.496), the catalyst was a tribromopyridine compound (1%), the solution flow rate was 50.0 mL / min, and the residence time was 6 s.

[0096] Due to the consumption of oxygen and heat exchange in the reaction, multi-stage (10 stages) series and circulation reactions were required.

[0097] Results: The conversion rate of xylene was 85%, and the selectivity of the product m-toluic acid was 80%.

[0098] Calculation of refractive index: That is, NA = 0.5 < 0.645, which meets the total reflection condition of the inner wall surface.

[0099] Comparison with other photochemical methods: The reaction time was shortened by more than 5 times by improving the efficiency and increasing the light irradiance; the photo quantum yield reached 20.4%, which was increased by about 76%.

[0100] Example 2: UV-induced rearrangement of cyclohexanone oxime to prepare ε-caprolactam (using total reflection of the outer wall surface)

[0101] Implementation steps:

[0102] Photochemical reactor construction: A quartz glass tube (inner diameter 8 mm, length 6 cm) was selected, and inlet and outlet ports 312 were arranged at both ends, and corresponding light windows were arranged. The quartz tube (refractive index 1.475) was surrounded by an air environment (refractive index 1.000); the light source was a 365 nm high-power UV-LED (light power 10 W x 2, light-emitting half-angle 30°, and the end faces of both ends of the reactor were irradiated.

[0103] Reaction parameters: The reactant was cyclohexanone oxime (0.5 M acetonitrile solution), the refractive index was about 1.35, the solution flow rate was 3.5 mL / min, and the residence time was 45 s.

[0104] Post-processing: The effluent was directly concentrated and recrystallized with hexane.

[0105] Results: The yield of the product ε-caprolactam was 95% (HPLC purity > 99%).

[0106] Calculation of refractive index: That is, NA=0.5<0.907, satisfying the total reflection condition of the outer wall surface.

[0107] Compared with other photochemical methods: the reaction time is shortened by more than 6 times by improving the efficiency and increasing the light irradiance; the photo quantum yield reaches 45.4%, which is increased by about 30%.

[0108] In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0109] In the description of the present application, it should also be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0110] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A photochemical reactor having total reflection characteristics, characterized by comprising: The reaction tube is provided with a light source at one end, and the main direction of the light source is consistent with the flow direction of the reaction fluid in the reaction tube. When total reflection occurs on the inner surface of the reaction tube, the following condition must be met: NA: numerical aperture of the incident light beam, : angle of incidence, : refractive index of the region in which the incident light is located, : refractive index of the reaction fluid, : refractive index of the reaction tube; When total reflection occurs on the outer surface of the reaction tube, the following condition must be met: NA: Numerical aperture of the incident light beam, : Incident angle, : Refractive index of the region where the incident light is located, : Refractive index of the reaction fluid, : Refractive index of the reaction tube, : Refractive index of the region outside the reaction tube.

2. The photochemical reactor with total 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 arranged adjacent to the light-transmitting port.

3. The photochemical reactor with total reflection characteristics according to claim 1, characterized in that, The light source is a point or a circular or elliptical or flat line focused light spot.

4. The photochemical reactor with total 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 direction or the diameter direction of the reaction tube, and the opposite end of the liquid inlet is a liquid outlet, and the liquid inlet and the light source are in the same direction.

5. The photochemical reactor with total reflection properties according to claim 4, characterized in that, The reaction tube includes a plurality of tubes arranged in series.

6. The photochemical reactor with total reflection characteristics according to claim 1, characterized in that, The outer area of the reaction tube is the outer area adjacent to the reaction tube, which is in a vacuum state or filled with gas or filled with a liquid with low refractive index.

7. The photochemical reactor with total reflection characteristics according to claim 1, characterized in that, The reaction fluid is a homogeneous system or a solution system containing particles or micro-bubbles.

8. A photochemical reaction method using the photochemical reactor having total reflection characteristics according to any one of claims 1 to 7, characterized by, The method comprises the following steps: Step 1: using fluid conveying measures, the reaction fluid is conveyed to the liquid inlet of the photochemical reactor at a preset flow rate, and the reaction tube is filled; Step 2: incident light is incident to the reaction tube through the light-transmitting port at the end face of the reaction tube at a preset angle, 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 reflection can be formed on the inner wall of the reaction tube filled with liquid, and the light propagates in the reaction fluid; Or when the refractive index of the reaction fluid is smaller than that of the reaction tube, total reflection can be formed on the outer wall of the transparent reaction tube in the low refractive state, and the light propagates in the reaction fluid containing the tube wall; Step 4: the reaction fluid is transported in the total reflection structure, and the photons propagate in the reaction fluid, and the two fully interact to complete the photochemical reaction, and the product is discharged from the liquid outlet of the reaction tube; Step 5: by pre-cooling or pre-heating the reaction fluid and adjusting the temperature of the reaction tube wall, the reaction temperature is maintained in a set range to ensure the reaction effect.

9. A photochemical reaction system having total reflection characteristics, characterized by comprising: The photochemical reactor with total reflection characteristics according to any one of claims 1-7 further comprises a mixing tank and a product collection tank, the mixing tank is in communication with the liquid inlet of the photochemical reactor, and the liquid outlet of the photochemical reactor is in communication with the product collection tank.

10. The photochemical reaction system having total reflection characteristics according to claim 9, wherein, The outer wall of the photochemical reactor comprises a temperature control structure.

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