A multi-channel catalytic reaction device and a preparation method and use method thereof

Abstract

This application relates to the field of polluted gas treatment, specifically providing a multi-channel catalytic reaction device and its preparation and usage methods. The reaction device includes a light source, a tapered optical fiber, and a catalytic material layer. The catalytic material layer is disposed on the tapered surface of the tapered optical fiber. Light emitted from the light source enters the tapered optical fiber through a coupler. The tapered optical fiber is disposed in a reaction channel, with an inlet at one end and an outlet at the other. The reaction channel is a multi-channel reaction structure, comprising a substrate and multiple parallel extending channel units disposed within the substrate. Adjacent channel units are separated by partitions with connecting holes. Each channel unit contains a tapered optical fiber, and both ends of the multiple channel units are connected to the inlet and outlet, respectively. Through the combined effect of parallel channels and connecting holes, the device of this application can maintain high photocatalytic reaction efficiency under high throughput conditions, improving overall performance.

Description

Technical Field

[0001] This application relates to the field of polluted gas treatment, and more specifically, to a multi-channel catalytic reaction device and its preparation and use methods. Background Technology

[0002] Formaldehyde and other organic pollutants are characterized by high volatility, high toxicity, and long-lasting release. They are widely present in indoor decoration materials, furniture boards, and industrial waste gases, posing serious harm to the human respiratory and immune systems. Photocatalysis technology utilizes light to excite semiconductor catalytic materials to generate electron-hole pairs, thereby producing highly oxidizing reactive species such as ·OH and O2. - The system decomposes organic pollutants into carbon dioxide and water, thus achieving purification. The efficient decomposition of organic pollutants such as formaldehyde is of great significance for improving the performance of air purification devices and promoting their application in indoor air treatment and industrial waste gas treatment. Especially in the field of industrial waste gas treatment, the efficient purification of large quantities of polluting gases is required, which places high demands on the overall processing capacity of the device.

[0003] Existing photocatalytic formaldehyde purification devices typically incorporate a substrate structure loaded with a photocatalyst within the reaction chamber or flow channel. This substrate structure can be a flat plate, honeycomb, or porous support coated with the photocatalyst. As gas flows through the reaction zone, it comes into contact with the catalytic material and undergoes a photocatalytic reaction under illumination to decompose organic pollutants such as formaldehyde. To improve the decomposition efficiency of formaldehyde, current technologies often enhance the reaction by extending the gas residence time within the reaction zone, increasing the light intensity, increasing the catalyst loading, or expanding the reaction area. In gas-phase photocatalytic reaction systems, the catalytic reaction efficiency is closely related to the gas residence time within the reaction zone. To ensure a complete photocatalytic reaction, it is necessary to extend the contact time between the gas and the catalytic material surface, i.e., increase the gas residence time in the reaction channel. This allows organic pollutants to participate more fully in the photocatalytic reaction, improving the conversion rate per pass. However, extending the residence time means reducing the gas flow rate or the amount of gas processed per unit time, resulting in a lower throughput, which is not conducive to the high throughput requirements of practical applications. Conversely, if the flow rate or velocity of the introduced gas is increased to enhance the gas processing capacity and throughput of the device, the residence time of the gas in the reaction channel will be shortened, resulting in insufficient contact between the gas and the catalytic material. This leads to a decrease in the degree of photocatalytic reaction, thereby reducing the single-pass conversion rate of pollutants and even causing a decrease in overall purification efficiency.

[0004] In other words, there is a constraint between gas processing throughput and photocatalytic reaction efficiency. Increasing the throughput often comes at the cost of sacrificing reaction sufficiency, while increasing the reaction efficiency will reduce the processing capacity. This creates a contradiction that is difficult to balance, making it difficult to achieve efficient purification while ensuring high throughput. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a multi-channel catalytic reaction device. The device includes a light source, a tapered optical fiber, and a catalytic material layer. The catalytic material layer is disposed on the tapered surface of the tapered optical fiber. Light emitted from the light source enters the tapered optical fiber through a coupler. The tapered optical fiber is disposed in a reaction channel. One end of the reaction channel is provided with an inlet, and the other end is provided with an outlet. The reaction channel is a multi-channel reaction structure, which includes a substrate and a substrate cover plate. Multiple channel units extending side by side are disposed on the substrate. Adjacent channel units are separated by partitions, and the partitions are provided with connecting holes. Each channel unit is provided with a tapered optical fiber, and the two ends of the multiple channel units are respectively connected to the inlet and the outlet.

[0006] This application employs multiple parallel channel units with connecting holes between adjacent units, allowing gas to flow not only along the main flow direction within each channel but also creating lateral exchange flow between channels. Upon entering each channel unit, the gas forms a reaction region near the tapered region of the tapered optical fiber, where an evanescent field acts on a limited spatial area close to the fiber surface. During gas flow, formaldehyde molecules near the catalytic material surface are preferentially purified, creating a local concentration gradient and boundary layer thickening, leading to insufficient reactant supply to subsequent regions. The connecting holes introduce lateral exchange, continuously redistributing the gas between different channels, introducing unreacted gas into new catalytic regions while simultaneously carrying purified gas away from local reaction areas, thereby weakening boundary layer confinement and enhancing the diffusion flux of reactants to the catalytic surface. The parallel multi-channel configuration also improves the overall processing throughput, allowing the device to maintain a longer residence time while increasing the intensity of the photocatalytic reaction, balancing processing throughput and single-pass conversion rate, resolving the contradiction between the two, and improving processing capacity.

[0007] Furthermore, the diameter of the connecting hole near the inlet is smaller than that near the outlet. This smaller diameter near the inlet and larger diameter near the outlet gradually increases the lateral exchange intensity along the gas flow direction. In the early stages of gas entry into the channel, the formaldehyde concentration is high and the reaction driving force is strong, requiring a stable axial mainstream to ensure effective penetration of the upstream reaction zone. If the connecting hole is too large, it will cause premature lateral gas diversion, weakening the upstream catalytic utilization rate. As the gas flows along the channel, formaldehyde is gradually consumed, leading to reactant depletion and intermediate product accumulation in localized areas. Increasing the diameter of the connecting hole at this point enhances lateral exchange, redistributing the gas between different channels, introducing high-concentration gas into underreacted areas, diluting localized intermediate products, improving the utilization efficiency of the downstream reaction zone, and enhancing overall reaction uniformity and purification efficiency.

[0008] Furthermore, SiO2 rods are also disposed on the tapered surface of the tapered fiber. This SiO2 rod structure on the tapered surface of the fiber serves two purposes: First, it optically alters the local refractive index distribution, allowing the evanescent field to couple from the tapered fiber into the SiO2 rods, increasing the intensity of the emitted laser, expanding the effective optical field range, and improving the uniformity of light reception and the utilization rate of the optical field for the catalytic material. Second, as gas flows through the channel, the microscale rod-like structure introduces local disturbances, causing the fluid to form micro-vortices and turbulent flows around it, disrupting the original stable boundary layer, enhancing the intensity of convection and diffusion of gas on the catalytic material surface, and improving the transport efficiency of formaldehyde molecules to the catalytic active sites. Simultaneously, it strengthens the optical field distribution and mass transfer process, resulting in a more complete catalytic reaction, thereby further improving the overall purification efficiency.

[0009] Furthermore, the radial dimension of the channel unit is 500-1500 μm. Setting the radial dimension of the channel unit to 500-1500 μm ensures that the gas has a high specific surface area contact condition in the channel, while avoiding the problems of excessive pressure drop and reduced effective flow cross-section caused by an excessively small channel. At the same time, it ensures that the gas can form a stable flow around the optical fiber and effectively contact the catalytic region.

[0010] Furthermore, the tapered optical fiber is positioned at the center of the channel unit. This placement allows for a relatively symmetrical flow field distribution around the fiber as the gas flows through the channel. It ensures uniform gas contact with the catalytic material on the fiber surface across the channel cross-section, avoiding localized short-circuit flow and dead zones caused by biased placement, and improving the utilization rate of the catalytic region.

[0011] Furthermore, multi-channel reaction structures extend from both ends of the tapered optical fiber and are fixed and sealed by a sealing structure located at the substrate end. This sealing structure at the substrate end ensures the stable position of the tapered optical fiber within the channels and prevents gas leakage. The stable fiber position guarantees a stable evanescent field distribution, preventing uneven light field caused by fiber misalignment; simultaneously, the airtight structure ensures that all gas flows through the catalytic region rather than through a bypass, guaranteeing the stability of the purification effect.

[0012] Furthermore, the tapered fiber is obtained by tapering single-mode silica fiber or low-order multimode silica fiber. Using single-mode silica fiber or low-order multimode fiber ensures a stable mode distribution of light after tapering. Single-mode or low-order modes can form a uniform evanescent field distribution, avoiding the optical field inhomogeneity and local hotspots caused by higher-order modes, thereby improving the stability of the catalytic reaction.

[0013] Furthermore, the light source emits laser light with a wavelength of 350-380 nm. Using ultraviolet light with a wavelength of 350-380 nm matches the band gap of the photocatalytic material TiO2, allowing photon energy to effectively excite electron-hole pairs. This wavelength can efficiently generate active species with strong oxidizing capabilities, thereby increasing the oxidative decomposition rate of formaldehyde molecules and improving the efficiency of the catalytic reaction.

[0014] This application also proposes a method for preparing a multi-channel catalytic reaction device, the method comprising the following steps: S1, Prepare a matrix and form multiple channel units extending side by side, as well as inlet and outlet ports on the matrix. Adjacent channel units are separated by partitions, and connecting holes are provided on the partitions. S2, multiple optical fibers are heated and stretched to form tapered optical fibers, and photocatalytic materials are placed on the surface of the tapered region; S3, multiple tapered optical fibers are respectively inserted into each channel unit, the tapered optical fibers are arranged along the extension direction of the channel unit, and the tapered region is located in the channel unit; S4, to fix and seal the penetration point between the tapered optical fiber and the substrate; S5, A base cover plate is provided above the channel unit, and the base cover plate is bonded and sealed to the edge of the base; S6 connects the input ends of multiple tapered optical fibers to the output end of the coupler, and connects the input end of the coupler to the light source.

[0015] This application also proposes a method of using a multi-channel catalytic reaction device, the method comprising the following steps: S1, turn on the light source, so that the light emitted by the light source is coupled into multiple tapered optical fibers through the coupler, and an evanescent field is formed in the tapered region of the tapered optical fiber, which acts on the catalytic material on the surface of the tapered region; S2, the gas to be treated is introduced into the multi-channel reaction structure through the inlet. The gas enters multiple channel units and, upon contact with the catalytic material, a photocatalytic reaction occurs, decomposing the organic pollutants in the gas. S3, the gas flows to the other end of the multi-channel reaction structure and is discharged from the sample outlet.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This application constructs multiple parallel channel units with connecting holes between adjacent channel units, enabling lateral exchange between different channels while the gas flows along the main flow direction. After entering each channel, the gas forms a catalytic reaction region near the tapered region of the fiber optic cable, with the reaction mainly concentrated in a limited space near the fiber surface. Through the interconnected structure between channels, the gas undergoes continuous redistribution during flow, allowing reactants to be continuously supplied to each catalytic region, promoting the desorption of purified gas, thereby enhancing the mass transfer efficiency of the gas on the catalytic material surface and improving the photocatalytic reaction efficiency. Simultaneously, the multi-channel parallel structure improves the overall gas throughput, increasing the processing capacity while ensuring sufficient gas participation in the reaction. The device of this application can maintain high photocatalytic reaction efficiency under high throughput conditions, thus balancing processing capacity and purification effect, and improving overall performance. Attached Figure Description

[0017] Figure 1 A schematic diagram of the structure obtained in step S1 of the preparation method of a multi-channel catalytic reaction device provided by the present invention; Figure 2 A schematic diagram of the structure obtained in step S3 of the preparation method of a multi-channel catalytic reaction device provided by the present invention; Figure 3 This is a schematic diagram of the structure obtained in step S5 of the preparation method of a multi-channel catalytic reaction device provided by the present invention.

[0018] Icons: 1-Matrix; 2-Channel unit; 3-September; 4-Connecting hole; 5-Tapered optical fiber; 6-Catalyst material layer; 7-Inlet; 8-Outlet; 9-Matrix cover plate; 10-End cap. Detailed Implementation

[0019] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings. Example 1:

[0020] This invention provides a multi-channel catalytic reaction device, which includes a light source, a coupler, a tapered optical fiber 5, a catalytic material layer 6, and a multi-channel reaction structure. For example... Figures 1-3As shown, the multi-channel reaction structure includes a substrate 1 and a substrate cover plate 9. Multiple channel units 2 extending side-by-side are disposed on the substrate 1, forming a reaction space for gas flow. The substrate 1 can be made of quartz, glass, ceramic, silicon-based materials, metal-based materials, etc., making it easy to fabricate microchannels. If personnel are present during use, to prevent harm from ultraviolet light emission, the substrate 1 can be made of stainless steel or alumina ceramic to block ultraviolet light leakage. Multiple channel units 2 extending side-by-side are disposed within the substrate 1, each extending along the gas flow direction. The channel unit 2 is a linear microchannel, and its cross-section can be rectangular, square, circular, or elliptical. Preferably, the cross-sectional shape of the channel unit 2 is rectangular. This facilitates processing, allowing a regular straight-wall structure to be directly formed on the plate-like substrate 1 through processes such as photolithography-etching, laser processing, micro-milling, or molding. This results in high dimensional consistency, good batch processing capability, and easy alignment and encapsulation with the substrate cover plate 9, improving airtightness and structural stability. Furthermore, the rectangular channel has straight sidewalls and four corners, which helps to form local low-velocity zones and micro-scale disturbances at the corners during gas flow, enhancing near-wall mass transfer. At the same time, the overall flow field distribution is more uniform, allowing the gas to contact the catalyst material more fully within the cross-sectional area, thereby improving purification efficiency.

[0021] The radial dimension of channel unit 2 is 500-1500 μm, and all channel units 2 have the same size, which facilitates batch preparation. Adjacent channel units 2 are separated by partitions 3, which can be integrally formed from the substrate 1 and serve to separate the flow channels. Connecting holes 4 are provided on the partitions 3. The connecting holes 4 can be circular holes, oblong holes, slit holes, etc., preferably circular holes spaced along the channel extension direction. The circular holes have continuous and smooth boundaries, and the flow resistance in all directions is uniform. Under the action of pressure difference, the gas can stably form a near-axisymmetric jet that passes through the holes and diffuses into adjacent channels, thereby achieving more uniform and efficient lateral exchange. The center height of the connecting holes 4 is the same as that of the tapered optical fiber 5. The lateral jet formed by the perforated gas can directly reach the vicinity of the cone region, allowing formaldehyde molecules, oxygen, and moisture to be directly supplied to the main catalytic region, while simultaneously carrying away the reacted gases in a timely manner.

[0022] The inlet ends of multiple channel units 2 are connected to the sample inlet 7 located at one end of the multi-channel reaction structure, and the outlet ends are connected to the sample outlet 8 located at the other end, so as to realize the distribution and collection of the gas to be treated to each channel unit 2. Each channel unit 2 is provided with a tapered optical fiber 5, which is located at the center of the channel unit 2. The tapered optical fiber 5 is preferably formed by heating and stretching single-mode silica optical fiber or low-order multimode silica optical fiber. The silica material has good ultraviolet transmittance, thermal stability and processing stability. Single-mode or low-order multimode light transmission mode is conducive to forming a more stable and uniform evanescent field distribution in the tapered region. The tapered region of the tapered optical fiber 5 is located in the channel unit 2, and a catalyst material layer 6 is provided on the surface of the tapered region. The catalyst material layer 6 is a coating or particle layer of TiO2 or ZnO, which can be set by spraying or by in-situ growth.

[0023] The light emitted from the light source enters the tapered optical fiber 5 through a coupler. The coupler is a one-to-many fiber coupler, used to distribute the light output from a single light source to multiple tapered optical fibers 5, ensuring that incident light enters each channel unit 2. The light source is preferably a laser light source with a wavelength of 350-380nm. The two ends of the tapered optical fiber 5 respectively pass through the multi-channel reaction structure and are fixed and sealed by a sealing and fixing structure set at the end of the substrate 1. The sealing and fixing structure can be a sealant encapsulation structure, an elastic sealing sleeve, a glass brazing structure, or a resin sealing structure. On the one hand, it restricts the axial and radial displacement of the tapered optical fiber 5, keeps the position of the tapered region stable within the channel unit 2, and keeps the light field distribution and the position of the catalytic region stable. On the other hand, it prevents the gas to be treated from leaking from the optical fiber exiting part, ensuring that the gas passes through the catalytic reaction region and avoids leakage. To avoid the ultraviolet light emitted from the end of the tapered optical fiber 5 near the sample outlet 8 from causing harm to personnel in the surrounding environment, an end cap 10 is set at the exposed end of the tapered optical fiber 5 near the sample outlet 8. The end cap 10 is made of alumina ceramic, ultraviolet absorbing resin, black quartz composite material or metal light-shielding cap. The end cap 10 is fixedly sleeved on the outside of the end of the optical fiber to block or absorb ultraviolet light escaping from the end of the optical fiber.

[0024] After the gas to be treated enters through the inlet 7, it is distributed into multiple parallel channel units 2. Within each channel unit 2, it flows along the catalytic material layer 6 on the surface of the tapered optical fiber 5 and undergoes a catalytic reaction under illumination. Simultaneously, lateral exchange occurs between adjacent channels through the connecting holes 4, redistributing the gas in different channels. This improves both the overall throughput and the replenishment state of reactants on the catalytic material surface, as well as the uniformity of the reaction. The multi-channel parallel structure is beneficial for increasing the throughput per unit time. The centrally located tapered optical fiber 5, the appropriate channel size, stable ultraviolet excitation, and the lateral exchange between channels work together to maintain good mass transfer efficiency and photocatalytic reaction intensity under high throughput conditions, thereby enhancing the overall purification effect.

[0025] Furthermore, the inlet pipe is designed with a tapering structure that gradually narrows along the gas flow direction to create a throttling zone before entering the sample inlet 7. The upstream inner diameter of the inlet pipe can be 4-8 mm, gradually narrowing to 1.5-3 mm near the sample inlet 7. In the tapering section, the gas velocity increases and the local pressure decreases, resulting in a temperature drop caused by the Joule-Thomson effect, thus slightly lowering the temperature of the gas entering the reaction zone; throttling of air or formaldehyde-containing gas can produce a cooling effect. Since photocatalysis is exothermic, lower temperatures are beneficial for the adsorption stability of organic pollutants such as formaldehyde on the catalytic material surface, increasing the enrichment of reactants on the catalytic surface and reducing the desorption disturbance of some intermediate products, making the photocatalytic oxidation process more complete. The tapering throttling also avoids violent eddies and excessive pressure drops, allowing the gas to enter each channel unit 2 more smoothly, thus facilitating uniform subsequent reactions.

[0026] Furthermore, to increase the humidity of the introduced gas, a gas washing bottle can be connected in series in the gas inlet pipe upstream of inlet 7. The gas to be treated is first introduced into the gas washing bottle containing deionized water, and after bubbling, it carries water vapor before entering the multi-channel reaction structure. Increased moisture content facilitates the generation of active species during the photocatalytic reaction. Specifically, the vacancies generated by the catalytic material under ultraviolet light irradiation can react with adsorbed water or hydroxyl groups to generate strong oxidizing free radicals such as ·OH, accelerating the oxidative decomposition of organic pollutants such as formaldehyde, and improving the reactivity of the catalytic surface and the overall purification efficiency. Example 2:

[0027] Based on Example 1, the diameter of the connecting hole 4 near the inlet 7 is smaller than that of the connecting hole 4 near the outlet 8. The diameter of the connecting hole 4 gradually increases from the inlet 7 to the outlet 8, with the diameter of the front connecting hole 4 being 50-120 μm, the middle connecting hole 4 being 100-180 μm, and the rear connecting hole 4 near the outlet 8 being 150-300 μm. The diameter of the connecting hole 4 is between 50-300 μm, which ensures effective lateral exchange while avoiding flow runaway; if the diameter is too small, the gas resistance is high, the lateral exchange is insufficient, and it is difficult to achieve effective redistribution between channels; if the diameter is too large, it is easy to form an excessively strong lateral jet, generating short-circuit flow, weakening the axial mainstream stability, and reducing the overall residence time and reaction sufficiency.

[0028] Furthermore, the distance between adjacent connecting holes 4 gradually decreases from the inlet 7 side to the outlet 8 side. Specifically, the spacing between adjacent connecting holes 4 at the front end is 1.0-2.5 mm, in the middle is 0.6-1.5 mm, and at the rear end is 0.3-0.5 mm. In this way, in the front-end region, after the gas initially enters the channel unit 2, the overall flow momentum is large and the mainstream direction is clear. At this time, using a smaller aperture and a larger spacing allows only a small amount of gas to pass through the partition wall 3 under the action of pressure difference, forming a weaker, discrete transverse microjet. This avoids excessive transverse diversion before the mainstream has fully passed through the front-end catalytic region, ensuring that the front-end gas still mainly flows axially, and the gas preferentially contacts the front-end catalytic material. As the gas flows along the channel, the gas velocity distribution, concentration distribution, and local pressure difference gradually change. The later region requires stronger inter-channel exchange to promote the redistribution of gas in different channels; therefore, a larger aperture and a smaller spacing are used. Larger apertures increase the amount of lateral gas that can pass through a unit channel, resulting in stronger lateral jets and deeper penetration after the perforated gas enters adjacent channels. Smaller aperture spacing allows multiple adjacent lateral jets to more easily overlap in adjacent channels, creating a more continuous disturbance zone near the wall and around the optical fiber. This leads to more frequent lateral renewal of the gas, which originally flowed in axial layers, enhancing component exchange near the catalytic surface in adjacent channels. In other words, the fine and sparse connecting holes 4 at the front end result in a localized pulsed lateral exchange, achieving moderate coupling without disrupting mainstream penetration; the coarse and dense connecting holes 4 at the rear end result in a continuous, superimposed lateral exchange, continuously driving gas migration across channels and diffusion within adjacent channels at multiple locations. This distribution pattern—sparse at the front and dense at the rear, small at the front and large at the rear—maintains good mainstream contact characteristics at the front end, while enhancing lateral replenishment and disturbance renewal at the rear end. This matches the flow requirements and reaction requirements of different regions along the process, ultimately improving the overall purification effect.

[0029] Furthermore, upper and lower rows of connecting holes are also provided on the upper and lower sides of the connecting hole 4, arranged symmetrically in two rows along the height direction of the channel unit 2. After the gas passing through the upper and lower rows of connecting holes enters the adjacent channel, it forms upper and lower transverse jets near the tapered region of the tapered fiber 5, respectively, and superimposes in the central reaction region. The aperture of the upper and lower rows of connecting holes is 100-300μm, which is approximately the same as the aperture of the middle and rear section of the middle connecting hole 4, so as to balance the exchange intensity on the upper and lower sides. The spacing between the upper and lower rows of connecting holes is 0.8-1.0mm, so that a continuous disturbance band is formed between adjacent upper row jets, between adjacent lower row jets, and between the upper and lower rows of jets within a short distance. In this way, the upper jet drives the low-velocity gas near the upper wall of the channel to renew it towards the center, while the lower jet drives the low-velocity gas near the lower wall of the channel to renew it towards the center. The superposition of the velocity and pressure fields of the two jets near the tapered optical fiber 5 disperses the previously stratified flow within the rectangular channel cross-section, ensuring more thorough component exchange and gas renewal in both the central reaction zone and the upper and lower near-wall regions. The symmetrical upper and lower connecting holes expand the cross-sectional area covered by the lateral exchange and can form an enveloping disturbance through bilateral coupling, more effectively weakening the boundary layer constraint near the cone region, improving the transport efficiency of organic pollutants such as formaldehyde to the surface of the catalytic material, and further enhancing the overall purification effect. Example 3:

[0030] Based on Example 1, the tapered surface of the tapered fiber 5 is further provided with SiO2 rods. The diameter of the SiO2 rods is 5-10 μm and the length is 100-250 μm. The SiO2 rods are inclined relative to the axis of the tapered fiber 5. Preferably, the axial direction of the SiO2 rods forms an acute angle with the direction of the airflow velocity, that is, the free end of the SiO2 rods is closer to the direction of the sample outlet 8, and the inclination direction of multiple SiO2 rods is consistent. The SiO2 rods are microscale guiding-scattering units arranged on the surface of the tapered region. SiO2 has high light transmittance and stable refractive index, and is the same material as the fiber core. After the evanescent field propagates to the root of the SiO2 rod, it can couple the light field into the SiO2 rod. This allows the local evanescent light field close to the fiber surface to be extended to the area around the rod and between the rods, thereby increasing the effective light-receiving volume and improving the capture and utilization of the light field by the catalytic material layer 6. Since the SiO2 rods are made of the same material as the fiber, it is also beneficial to reduce interface transmission loss. As gas flows along the inclined SiO2 rod, a local pressure difference is created between the windward and leeward sides of the rod, generating micro-scale flow around the rod, wake disturbances, and periodic pulsations. This continuously disturbs and renews the near-wall layer gas close to the catalytic material surface. When the free end of the SiO2 rod faces the sample outlet 8, the mainstream gas, after passing over the rod, more easily forms an attached disturbance zone extending downstream along the surface of the conical region. This avoids excessively obstructing the mainstream flow and increasing the pressure drop, as is the case with an obtuse-angled arrangement, while continuously weakening the boundary layer thickness near the catalytic surface and enhancing the transport of formaldehyde, oxygen, and moisture to the catalytic active sites. The aforementioned local pressure difference drives the SiO2 rod to produce micro-amplitude vibrations, which periodically disturb the gas layer near the catalytic material surface, continuously breaking down the boundary layer and enhancing the mass transfer of formaldehyde, oxygen, and moisture to the active sites. Simultaneously, the vibration helps accelerate the desorption of intermediate products and the re-adsorption of new reactants, preventing localized accumulation on the surface and thus improving overall purification efficiency. Furthermore, multiple SiO2 rods can be arranged in a spiral, staggered, or partitioned array along the circumference of the conical region. Preferably, adjacent SiO2 rods are staggered in the axial direction and spaced apart in the circumferential direction to avoid the rods blocking the light field or forming a continuous flow obstruction zone. When the gas flows through, it forms micro-tails with different directions and superimposes on each other, thereby increasing the disturbance intensity within the cross section and thus improving the overall photocatalytic purification effect.

[0031] In the preparation process, firstly, the tapered region of the tapered optical fiber 5 is subjected to surface cleaning and activation treatment. It is then ultrasonically cleaned with ethanol and deionized water for 5-10 minutes each, followed by low-power oxygen plasma treatment for 30-120 seconds to remove organic contaminants and increase the surface hydroxyl density. Subsequently, a firmly bonded SiO2 microstructure layer is formed on the surface of the tapered region. Specifically, a sol-gel coating method is used, with tetraethoxysilane as the silicon source, ethanol as the solvent, and ammonia and deionized water as hydrolysis components. The volume ratio of tetraethoxysilane:ethanol:water:ammonia is 1:(8-15):(1-4):(0.2-1). The tapered region of the tapered optical fiber 5 is dipped or sprayed with the coating and then dried at 60-100℃ for 10-30 minutes, followed by heat treatment at 150-300℃ for 30-120 minutes to obtain a dense SiO2 microstructure layer. Then, rod-shaped protrusions are oriented and etched using a mask, preserving only localized areas to form a small number of spaced, tilted long rod structures. The resulting SiO2 rods have a diameter of 5-10 μm and a length of 100-250 μm, with an axial spacing of 500 μm-2000 μm between adjacent rods, arranged circumferentially to avoid mutual obstruction or the formation of continuous flow-blocking bands. The resulting SiO2 rods provide good flow guidance and micro-vibration control. Example 4:

[0032] This application also proposes a method for preparing a multi-channel catalytic reaction device, the method comprising the following steps: S1, prepare a substrate 1, and form multiple channel units 2 extending side by side on the substrate 1, as well as an inlet 7 and an outlet 8. Adjacent channel units 2 are separated by partitions 3, and connecting holes 4 are provided on the partitions 3, such as... Figure 1 As shown.

[0033] In this embodiment, the substrate 1 is made of a quartz block substrate. Quartz material has good mechanical strength, dimensional stability, corrosion resistance, and low organic gas adsorption characteristics, making it suitable as a substrate for a multi-channel reaction structure. Specifically, a plate-shaped quartz substrate with a thickness of 3-5 mm is used, and multiple parallel channel units 2 are formed in the middle of its upper surface. Each channel unit 2 is arranged in the same direction, with a rectangular cross-section and a radial dimension of 500-1500 μm. A partition wall 3 is retained between each channel unit 2, integrally formed with the substrate 1, to separate adjacent channel units 2 and provide processing areas for subsequent connecting holes 4. The two sides of the channel unit 2 are not completely connected to retain a solid side area for subsequent insertion of tapered optical fibers 5 and formation of a sealed fixing structure. Simultaneously, a manifold is processed at both ends of the substrate 1, so that the inlet ends of multiple channel units 2 are connected to the sample inlet area on one side, and the outlet ends are connected to the sample outlet area on the other side. It can be formed using processes such as micro-milling, ultrasonic machining, laser etching, or wet etching. For quartz materials, a combination of laser etching and fine finishing is used to balance processing accuracy and efficiency. This embodiment uses a frequency-triple-harmonic Nd:YAG laser with a wavelength of 355nm, a single-pulse energy of 10-200μJ, and an average power of 1-10W. The high photon energy and good absorption properties of quartz enable high-precision laser etching of quartz materials.

[0034] The connecting holes 4 on the partition walls 3 between adjacent channel units 2 can be further formed by laser drilling, micro-drilling, or local etching. Preferably, the connecting holes 4 are directly machined from the planar direction at the corresponding positions on the partition walls 3 using a micro-milling cutter, micro-drill, or ultrasonic machining head. To improve processing efficiency, the connecting holes 4 can also be laser-machined in the planar direction, and then the connecting holes 4 on the outer sides of the channel units 2 on both sides are melted or bonded to seal them. Finally, sample inlets 7 and sample outlets 8, which communicate with multiple channel units 2, are respectively provided at both ends of the substrate 1. The sample inlets 7 and sample outlets 8 are tubular channel structures, and the materials can be quartz tubes, glass tubes, stainless steel microtubes, or polytetrafluoroethylene tubes. The tubular connectors are aligned with the openings at both ends of the substrate 1 and fixed to the substrate 1 by means of corrosion-resistant sealant bonding, hot-melt connection, glass brazing, or mechanical compression sealing. Through the above processing methods, an integrated multi-channel reaction structure is formed on the same quartz substrate 1.

[0035] S2, multiple optical fibers are heated and stretched to form tapered optical fiber 5, and a photocatalytic material is placed on the surface of the tapered region.

[0036] First, fiber segments of a predetermined length are cut from single-mode or low-order multimode silica fibers, which can be 1.5-2 times the length of the multichannel reaction structure. Then, the coating layer in a localized area of ​​the middle section of each fiber is removed, exposing the silica fiber body. The two ends of the fiber after coating removal are fixed to a tapering device. The exposed middle section is heated using an oxyhydrogen flame, carbon dioxide laser, or resistance wire heating method, while simultaneously controlling the two ends to stretch in opposite directions, thereby forming a tapered fiber 5 with a reduced diameter in the middle. Preferably, the tapered section length is 0.5-1.5 cm. After tapering, the tapered section is cleaned with ethanol and deionized water and dried to remove processing residues. Then, a photocatalytic material layer 6 is deposited on the surface of the tapered section. In this embodiment, TiO2 is used as an example, and the photocatalytic material layer 6 is preferably formed by spraying. Specifically, nano-TiO2 powder is dispersed in ethanol or isopropanol to prepare a spraying suspension with a concentration of 1-20 mg / mL. A small amount of binder can be added to improve adhesion. Subsequently, the suspension is uniformly sprayed onto the surface of the conical region using a micro-spraying device. After spraying, it is dried at 60-100℃ for 10-30 minutes, followed by heat treatment at 150-300℃ for 30-120 minutes to improve the adhesion strength between the catalyst material layer 6 and the fiber surface. The above spraying-drying process can be repeated as needed. In addition to spraying, hydrothermal growth, sol-gel deposition, or chemical deposition can also be used to form the catalyst material layer 6 on the surface of the conical region. It should be noted that when SiO2 rods are also placed on the surface of the conical region, the SiO2 rod structure should be prepared on the surface of the conical region first, and then the catalyst material layer 6 should be placed on its surface or in the interstitial region to ensure that the SiO2 rods are in full contact with the conical region of the tapered optical fiber 5, so as to ensure that the light field extracted from the conical region can be effectively transmitted to the SiO2 rods and the surrounding catalyst region.

[0037] S3, multiple tapered optical fibers 5 are respectively threaded into each channel unit 2. The tapered optical fibers 5 are arranged along the extension direction of the channel unit 2, and the tapered region is located in the channel unit 2, such as... Figure 2 As shown.

[0038] The tapered optical fibers 5 obtained in step S2 are sequentially threaded into the multiple channel units 2 processed in step S1. Specifically, the tapered optical fibers 5 can be sequentially threaded into the corresponding channel unit 2 through the fiber-threading holes (or fiber-threading grooves for ease of placement, which are then sealed with material after the fiber is inserted) on one side of the substrate 1, and arranged along the extension direction of the channel unit 2, so that each channel unit 2 contains one tapered optical fiber 5. During assembly, ensure that the tapered region of each tapered optical fiber 5 is located in the main center position of the corresponding channel unit 2, so that the gas can form a relatively uniform flow field around the tapered region and fully contact the catalyst material layer 6. For multiple optical fibers, the positioning can be adjusted sequentially to make the position of the tapered region of each tapered optical fiber 5 approximately consistent, thereby improving the consistency of the reaction conditions in each channel unit 2.

[0039] S4, fix and seal the insertion part between the tapered optical fiber 5 and the substrate 1.

[0040] The portions of the tapered optical fibers 5 that exit the substrate 1 are fixed and sealed to ensure the stability of each tapered optical fiber 5 within the channel unit 2 and to prevent leakage of the gas to be treated. Specifically, the fiber insertion holes can be filled with UV-curable adhesive, low-shrinkage epoxy resin, chemically resistant silicone sealant, or miniature elastic sealing sleeves, and the sealing material should cover the gap between the tapered optical fiber 5 and the hole wall of the substrate 1. After filling, the sealing material is cured, for example, by UV curing or heat curing, to fix the tapered optical fibers 5 in both the axial and radial directions. In this way, on the one hand, the tapered optical fibers 5 can be prevented from shifting due to airflow impact, assembly stress, or subsequent connection operations, ensuring that the tapered area remains in the corresponding position; on the other hand, it can ensure that the gas mainly flows along the inside of the channel unit 2, avoiding bypass leakage from the fiber insertion points, thereby improving reaction efficiency and device operational stability.

[0041] S5, a base cover plate 9 is provided above the channel unit 2, and the base cover plate 9 is bonded and sealed to the edge of the base 1, such as... Figure 3 As shown.

[0042] A substrate cover plate 9 is installed above the substrate 1 after fiber optic assembly and partial fixation to seal each channel unit 2 and form a complete gas reaction channel. The substrate cover plate 9 is made of quartz or glass. If ultraviolet light leakage needs to be prevented, materials that do not transmit ultraviolet light, such as stainless steel, can be used. Its size is slightly larger than the outer contour of the channel processing area on the substrate 1 to cover all channel units 2, partitions 3, and other areas. A corrosion-resistant sealant, low-volatile epoxy adhesive, or ultraviolet-curing adhesive is uniformly applied to the contact area between the edge of the substrate cover plate 9 and the edge of the substrate 1. The substrate cover plate 9 is then adhered to the upper surface of the substrate 1, pressed tightly, and cured to form a sealed connection. If necessary, thermosetting bonding, anodic bonding, or glass brazing can also be used to improve the sealing performance.

[0043] S6, connect the input ends of multiple tapered optical fibers 5 to the output end of the coupler respectively, and connect the input end of the coupler to the light source.

[0044] The input ends of multiple tapered optical fibers 5 are connected to the multiple output ends of a coupler, which is a one-to-many fiber coupler. Connection methods include fusion splicing, mechanical connectors, or precision coupling sleeves. To reduce insertion loss and improve long-term stability, fiber fusion splicing can be used. Specifically, the input ends of the tapered optical fibers 5 and the output ends of the coupler are first cut and cleaned, and then precise core alignment and splicing are completed using a fiber fusion splicer. The input end of the coupler is then connected to the output fiber of the light source, also using fusion splicing or a standard fiber optic connector. In this way, the light emitted from the light source is distributed by the coupler and enters the multiple tapered optical fibers 5, causing ultraviolet light to be emitted from the tapered region of each channel unit 2, irradiating the catalytic material and photocatalytically decomposing pollutants such as formaldehyde in the air. Example 5:

[0045] This application also proposes a method of using a multi-channel catalytic reaction device, the method comprising the following steps: S1, turn on the light source, so that the light emitted by the light source is coupled into multiple tapered optical fibers 5 through the coupler, and an evanescent field is formed in the tapered region of the tapered optical fiber 5, which acts on the catalytic material on the surface of the tapered region.

[0046] First, the light source is turned on, and the laser emits ultraviolet light with a wavelength of 350-380nm. After being distributed by the coupler, the light enters multiple tapered optical fibers 5 and is transmitted to the tapered region of each fiber 5. To ensure stable laser output power, wavelength, and coupling state, a preheating and stabilization process is performed after the laser is turned on, with a stabilization time of 30-60 seconds. The stability is determined by detecting whether the fluctuation of optical power at the input end of the coupler or the output end of each branch remains within 5%; alternatively, the normal operation of the light source can be confirmed by monitoring the laser's operating indicator signal, the output power meter, or the reference light intensity signal after coupling. After the output stabilizes, the ultraviolet light forms an evanescent field in the tapered region of the tapered fiber 5 and directly acts on the catalytic material layer 6 on the surface of the tapered region, thus keeping the catalytic material continuously activated and providing stable optical field conditions for the photocatalytic reaction after the gas to be treated enters. This method of stabilizing before gas introduction avoids fluctuations in reaction conditions in each channel due to unstable laser output at the beginning of laser operation, thereby improving the stability of the multi-channel reaction.

[0047] S2, the gas to be treated is introduced into the multi-channel reaction structure through the inlet 7. The gas enters multiple channel units 2 respectively, and when it comes into contact with the catalytic material, a photocatalytic reaction is generated to decompose the organic pollutants in the gas.

[0048] Before introducing the gas to be treated, clean air, nitrogen, or other inert gas are purged into the multi-channel reaction structure for 10-120 seconds. Pre-purging removes residual impurities, dust, or residual gas from previous experiments, ensuring the catalytic surface is in a clean and reproducible initial state. Simultaneously, pre-purging helps verify the airtightness of the apparatus and the smooth flow in each channel, thereby improving the stability and repeatability of subsequent reaction results.

[0049] Then, the gas to be treated is introduced into the multi-channel reaction structure through the inlet 7. After entering the confluence areas at both ends of the substrate 1 through the inlet 7, the gas is distributed into multiple parallel channel units 2 and flows along the extension direction of each channel unit 2. The gas flow rate in the main pipeline before entering the inlet 7 is 10-500 mL / min (expressed as volumetric flow rate), which can be equivalently converted according to the number of channels. After entering each channel unit 2, the gas contacts the catalyst material layer 6 near the tapered region of the tapered optical fiber 5 and undergoes a photocatalytic oxidation reaction under evanescent field excitation to decompose organic pollutants such as formaldehyde. Since the gas can also be laterally exchanged through the connecting holes 4 on the partition walls 3 between adjacent channel units 2 while flowing in the channels, the reactants can be continuously redistributed among multiple channels, thereby enhancing the gas renewal along the process and the mass transfer efficiency of the catalytic surface.

[0050] Furthermore, to enhance the reaction efficiency, the gas to be treated was set to an adjustable flow rate input, employing pulsed flow rate changes. The flow rate was periodically increased by 10%-50% from a baseline before returning to the original rate. Under constant flow conditions, the gas more easily forms a stable stratified flow and boundary layer within the channel. The periodic flow rate changes continuously disrupt this stable flow, constantly perturbing and renewing the gas layer near the catalyst surface. This enhances the transport of formaldehyde, oxygen, and moisture to the catalyst surface, while also facilitating the timely removal of reaction intermediates from the local area. The pulsed flow creates a stronger renewal effect during the flow rate increase phase and maintains a longer local residence time during the flow rate decrease phase, thus balancing enhanced mass transfer and reaction sufficiency.

[0051] S3, the gas flows to the other end of the multi-channel reaction structure and is discharged from the sample outlet 8.

[0052] After undergoing photocatalytic reactions within each channel unit 2, the gas to be treated is collected in the confluence area at the other end of the multi-channel reaction structure and finally discharged from the sample outlet 8. The discharged gas can either directly enter the surrounding environment or be discharged through a pipeline.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-channel catalytic reaction apparatus, the apparatus comprising a light source, a tapered optical fiber, and a catalytic material layer, wherein the catalytic material layer is disposed on the tapered surface of the tapered region of the tapered optical fiber, light emitted from the light source enters the tapered optical fiber through a coupler, the tapered optical fiber is disposed in a reaction channel, one end of the reaction channel is provided with an inlet, and the other end is provided with an outlet, characterized in that: The reaction channel is a multi-channel reaction structure, which includes a substrate and a substrate cover plate. Multiple channel units extending side by side are provided on the substrate. Adjacent channel units are separated by partitions, and the partitions are provided with connecting holes. Each channel unit is provided with a tapered optical fiber. The two ends of the multiple channel units are respectively connected to the sample inlet and the sample outlet.

2. The multi-channel catalytic reaction device according to claim 1, characterized in that: The diameter of the connecting hole on the side closer to the inlet is smaller than the diameter of the connecting hole on the side closer to the outlet.

3. The multi-channel catalytic reaction device according to claim 2, characterized in that: The tapered fiber is further provided with SiO2 rods on the tapered region surface.

4. The multi-channel catalytic reaction device according to claim 3, characterized in that: The radial dimension of the channel unit is 500-1500 μm.

5. The multi-channel catalytic reaction device according to claim 4, characterized in that: The tapered optical fiber is positioned at the center of the channel unit.

6. The multi-channel catalytic reaction device according to claim 5, characterized in that: The two ends of the tapered optical fiber pass through the multi-channel reaction structure and are fixed and sealed by a sealing and fixing structure set at the end of the substrate.

7. The multi-channel catalytic reaction apparatus according to claim 6, characterized in that: The tapered optical fiber is obtained by tapering a single-mode silica fiber or a low-order multimode silica fiber.

8. The multi-channel catalytic reaction apparatus according to claim 7, characterized in that: The wavelength of the laser emitted by the light source is 350-380nm.

9. A method for preparing a multi-channel catalytic reaction device, characterized in that, The preparation method includes the following steps: S1, Prepare a substrate and form multiple channel units extending side by side, as well as an inlet and an outlet on the substrate. Adjacent channel units are separated by partitions, and connecting holes are provided on the partitions. S2, multiple optical fibers are heated and stretched to form tapered optical fibers, and photocatalytic materials are placed on the surface of the tapered region; S3, the tapered optical fibers are respectively threaded into each of the channel units, the tapered optical fibers are arranged along the extension direction of the channel unit, and the tapered region is located in the channel unit; S4, fix and seal the penetration portion between the tapered optical fiber and the substrate; S5, a base cover plate is provided above the channel unit, and the base cover plate is bonded and sealed to the edge of the base; S6, connect the input ends of the multiple tapered optical fibers to the output end of the coupler respectively, and connect the input end of the coupler to the light source.

10. A method of using a multi-channel catalytic reaction device, characterized in that, The method of use includes the following steps: S1, turn on the light source, so that the light emitted by the light source is coupled into multiple tapered optical fibers through the coupler, and an evanescent field is formed in the tapered region of the tapered optical fiber, which acts on the catalytic material on the surface of the tapered region; S2, the gas to be treated is introduced into the multi-channel reaction structure through the inlet. The gas enters multiple channel units and, upon contact with the catalytic material, a photocatalytic reaction occurs, decomposing the organic pollutants in the gas. S3, the gas flows to the other end of the multi-channel reaction structure and is discharged from the sample outlet.

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