Porous membrane photocatalytic reactor for methane selective oxidation and application thereof

Abstract

The invention discloses a porous membrane photocatalytic reactor for methane selective oxidation and application of the porous membrane photocatalytic reactor, and relates to the technical field of photocatalysis. The porous membrane photocatalytic reactor comprises a reactor body, the interior of the reactor body is hollow, a porous catalytic membrane is arranged in the reactor body, and the interior of the reactor body is divided into a gas chamber area on the left side and a liquid phase reaction area on the right side by the porous catalytic membrane; the porous catalytic membrane comprises a substrate membrane and an active substance loaded on the substrate membrane, one side surface of the substrate membrane of the porous catalytic membrane faces the gas chamber area, one side surface of the active substance faces the liquid phase reaction area, the substrate membrane is a PTFE (Polytetrafluoroethylene) membrane, and the active substance is Fe1 / NH2-UiO-66. By constructing a gas-membrane-liquid three-phase interface, not only can the mass transfer efficiency be improved, but also the reaction selectivity of the photocatalytic methane oxidation reaction can be improved, and the generation of by-products is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysis, and in particular to a porous membrane photocatalytic reactor for selective oxidation of methane and application thereof. Background Art

[0002] Methane is the main component of natural gas, with abundant global reserves, and is a potential important chemical raw material. Traditionally, the industrial method of converting methane into methanol mainly converts methane into synthesis gas through steam reforming reaction under high temperature and high pressure, and then the synthesis gas is used to produce methanol. This method consumes a lot of energy and operates under high temperature and high pressure conditions. Not only is the equipment complex and costly, but it is also accompanied by a large amount of carbon dioxide emissions, which has a negative impact on the environment. In addition, the traditional methane conversion process usually has low selectivity and is prone to generate by-products, resulting in overall low efficiency.

[0003] In recent years, the research on the selective oxidation of methane to methanol under mild conditions by photocatalytic technology has attracted widespread attention. This technology uses the electrons and holes generated by the catalyst under light conditions to activate the CH bonds of methane molecules, breaking the traditional high-energy thermodynamic limitations and allowing methane oxidation to be carried out at room temperature and pressure. However, the existing photocatalytic methane oxidation technology still has the following significant disadvantages: 1) Low catalyst activity: Existing photocatalytic systems usually rely on metal nanoparticles or clusters as co-catalysts. These catalysts have limited surface area and uneven distribution of active sites, resulting in low separation efficiency of photogenerated carriers, which in turn affects the reaction activity. In addition, these catalysts have low activation performance, insufficient adsorption and activation ability for methane molecules, and it is difficult to achieve efficient methane conversion. 2) Low interfacial mass transfer efficiency: Traditional photocatalytic reactions are mostly carried out at the solid-liquid interface, and the catalyst is immersed in an aqueous solution for reaction. However, the solubility of methane in water is extremely low, and gaseous methane molecules need to be dissolved in water first before they can diffuse to the catalyst surface for reaction. This inefficient mass transfer process severely limits the catalytic conversion efficiency of methane, resulting in a low reaction rate that is difficult to meet the needs of practical applications. 3) Poor product selectivity: The existing methane photocatalytic oxidation system easily produces by-products such as carbon monoxide and carbon dioxide during the reaction, making it difficult to achieve highly selective production of methanol. Due to the stable molecular structure of methane, it is easy to further oxidize to completely oxidized products after reaction activation, and the lack of effective reaction control strategies leads to poor reaction selectivity. The existence of these problems severely limits the promotion and development of photocatalytic methane conversion technology in practical applications.

[0004] In the prior art, CN115814858A discloses a method for preparing a MOF single-atom catalyst, wherein the method for preparing the MOF single-atom catalyst is as follows: dispersing the MOF material in a regulating solution, adding the metal soluble precursor solution, and reacting to obtain a MOF catalyst modified with a single atom M. The MOF material includes NH2-UiO-66, and the metal includes the transition metal Fe. The catalyst can be used for photocatalytic reactions. When the above catalyst is used for photocatalytic methane oxidation reaction, although the reaction activity can be increased, the reaction is still carried out at the solid-liquid interface. It can be seen that the above catalyst still cannot solve the problem of low interfacial mass transfer efficiency in photocatalytic methane oxidation.

[0005] Therefore, it is of great significance to develop a porous membrane photocatalytic reactor that can be used for methane photocatalytic oxidation, and use the above device for methane photocatalytic oxidation reaction to improve catalytic activity, enhance mass transfer efficiency and optimize reaction selectivity. Summary of the invention

[0006] In view of the above-mentioned prior art, the purpose of the present invention is to provide a porous membrane photocatalytic reactor and its application, wherein the porous membrane photocatalytic reactor comprises a reactor body, the reactor body is hollow inside, a porous catalytic membrane is arranged inside the reactor body, and the porous catalytic membrane divides the inside of the reactor body into a gas chamber area on the left and a liquid phase reaction area on the right; the porous catalytic membrane comprises a substrate membrane and an active substance loaded on the substrate membrane, the substrate membrane side of the porous catalytic membrane faces the gas chamber area, and the active substance side faces the liquid phase reaction area, the substrate membrane is a PTEF film, and the active substance is Fe1 / NH2-UiO-66. When the porous membrane photocatalytic reactor of the present invention is used for photocatalytic methane oxidation reaction, a gas-membrane-liquid three-phase interface can be constructed to significantly improve the mass transfer efficiency, improve the reaction selectivity of the photocatalytic methane oxidation reaction, and reduce the generation of by-products. The technical solution of the present invention can achieve efficient conversion of methane under mild reaction conditions, and provides a new idea for the utilization of green energy and the synthesis of chemical fuels.

[0007] To achieve the above object, the present invention adopts the following technical solution: In a first aspect of the present invention, a porous membrane photocatalytic reactor is provided, comprising a reactor body, the reactor body is hollow inside, a porous catalytic membrane is arranged inside the reactor body, and the porous catalytic membrane divides the inside of the reactor body into a gas chamber area on the left and a liquid phase reaction area on the right; The porous catalytic membrane includes a substrate membrane and an active substance loaded on the substrate membrane. The substrate membrane side of the porous catalytic membrane faces the gas chamber area, and the active substance side faces the liquid phase reaction area. The substrate membrane is a PTEF film, and the active substance is Fe1 / NH2-UiO-66.

[0008] In the present invention, Fe1 is a single iron atom.

[0009] Preferably, an air inlet and an air outlet are provided on the reactor body, the air inlet is connected to the gas chamber area, and the air outlet is connected to the liquid phase reaction area; a flow meter is provided at the air inlet.

[0010] Preferably, a light-transmitting opening is provided on the right side wall of the reactor body, and the light-transmitting opening facilitates the light source to be taken into the composite porous membrane to realize the photocatalytic reaction.

[0011] Preferably, the reactor body is connected with a circulation device, and the circulation device keeps the temperature of the liquid phase reaction zone constant by circulating liquid.

[0012] Preferably, the porous catalytic membrane is prepared by the following method: (1) Dispersing defect-rich NH2-UiO-66 into water, adding ferric chloride solution to obtain a mixed solution, stirring the mixed solution and centrifuging it, collecting the solid after centrifugation, washing and drying it to obtain a powder, and annealing the powder in an inert atmosphere to obtain Fe1 / NH2-UiO-66 powder as an active material; (2) After mixing Fe1 / NH2-UiO-66 powder with Nafion solution, a precursor solution is obtained, and the precursor solution is deposited on one side of a polytetrafluoroethylene film by vacuum filtration. After drying and activation, a Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane is obtained.

[0013] Further preferably, in step (1), the defect-rich NH2-UiO-66 is prepared by the following method: placing NH2-UiO-66 under vacuum conditions and activating it at 150-180 °C for 12-24 h to obtain defect-rich NH2-UiO-66.

[0014] By subjecting NH2-UiO-66 to high-temperature dynamic vacuum activation, the acetic acid ligand was removed from the zirconium oxygen cluster, thereby introducing structural defects and obtaining defect-rich NH2-UiO-66. This defect site can significantly enhance the light absorption capacity of the MOF material and provide an anchoring site for the iron single-atom catalytic center.

[0015] Further preferably, in step (1), the added amounts of defect-rich NH2-UiO-66, water and ferric chloride solution are (55-65) mg:45 mL:(2.5-3.5) mL.

[0016] Further preferably, in step (1), the concentration of the ferric chloride solution is 6-7 mM.

[0017] Further preferably, in step (1), the stirring treatment is: placing the mixed solution in a dark condition at 20-25° C. and stirring for 12 h.

[0018] Further preferably, in step (1), the inert atmosphere is an argon atmosphere, and the concentration of the argon atmosphere is 99.999%.

[0019] Further preferably, in step (1), the annealing temperature is 180-220° C., and the annealing time is 0.8-1.2 h.

[0020] Further preferably, in step (1), the loading amount of single iron atoms in Fe1 / NH2-UiO-66 is 1.5-3.0 wt%.

[0021] By controlling the iron loading in Fe1 / NH2-UiO-66, the uniform distribution and efficient catalytic activity of the iron single atom catalytic centers can be ensured.

[0022] Further preferably, in step (2), the material-liquid ratio of Fe1 / NH2-UiO-66 powder to Nafion solution is (12-13) g: (8.0-8.5) mL.

[0023] Further preferably, in step (2), the vacuum filtration time is 1-3 min.

[0024] Further preferably, in step (2), the activation temperature is 70-90°C and the activation time is 3-7h.

[0025] During the preparation process, after drying, it is placed in a high dynamic vacuum environment for further activation to ensure the cleanliness of the catalyst surface and the exposure of active sites.

[0026] Preferably, in step (2), in the Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane, the thickness of Fe1 / NH2-UiO-66 is 14-16 μm.

[0027] The second aspect of the present invention provides the use of the porous membrane photocatalytic reactor in photocatalytic methane oxidation.

[0028] Preferably, the specific steps of using the porous membrane photocatalytic reactor for photocatalytic methane oxidation are: Methane gas is introduced into the gas chamber through the air inlet, and then hydrogen peroxide solution is added to the liquid phase reaction area. A xenon light source is irradiated onto the porous catalytic membrane through the light-transmitting port. After the methane gas diffuses to the active material side of the porous catalytic membrane, a photocatalytic methane oxidation reaction is carried out under the action of xenon light.

[0029] Further preferably, the concentration of the methane gas is 99.999%, the gas flow rate of the methane gas is (110-130) mL / min, and the concentration of the hydrogen peroxide solution is 10 mol / L.

[0030] More preferably, the irradiation power of the xenon light source is 280-320W.

[0031] Further preferably, the time of the photocatalytic methane oxidation reaction is 3 hours.

[0032] Beneficial effects of the present invention: The present invention first activates NH2-UiO-66 to introduce structural defects to obtain defect-rich NH2-UiO-66, and then introduces a single-atom iron catalytic center into the above-mentioned defect-rich NH2-UiO-66, and after annealing, obtains Fe1 / NH2-UiO-66 powder as an active substance. The interaction between iron atoms and MOF substrates is optimized by defect engineering, which effectively improves the activation ability of the catalyst to methane molecules. At the same time, the catalyst designed by the present invention has highly dispersed active sites, which significantly improves the separation efficiency of photogenerated electrons and holes, thereby improving the overall activity of the catalytic reaction. Then, the above-mentioned active substance is combined with a polytetrafluoroethylene film by vacuum filtration to assemble a porous catalytic membrane with good air permeability. The above-mentioned porous catalytic membrane is used in a porous membrane photocatalytic reactor, so that the porous membrane photocatalytic reactor has a high-throughput gas-membrane-liquid interface structure, which effectively overcomes the low solubility and low diffusivity of methane in traditional solid-liquid systems. The design significantly improves the mass transfer rate of gaseous methane molecules in the reaction and improves the efficiency of the catalytic reaction.

[0033] The present invention constructs highly dispersed single-atom catalytic centers and an optimized gas-membrane-liquid reaction interface. On the one hand, it can achieve efficient control of the selective oxidation of methane to methanol and avoid the formation of by-products, thereby improving the selectivity and yield of the target product. On the other hand, it can also improve the catalyst activity and solve the problem of low interfacial mass transfer efficiency in the photocatalytic methane oxidation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 : Schematic diagram of the structure of the porous membrane photocatalytic reactor provided in Example 3; Figure 2 : A schematic diagram of the coordination between the porous membrane photocatalytic reactor and the circulation device provided in Example 3; Figure 3 : Schematic diagram of preparing porous catalytic membrane by vacuum filtration; Figure 4 : Schematic diagram of photocatalytic methane oxidation reaction on porous catalytic membrane; Figure 5: Scanning electron microscope image and transmission electron microscope image of Fe1 / NH2-UiO-66 prepared in Example 1; wherein, a is a scanning electron microscope image of Fe1 / NH2-UiO-66; b is a scanning transmission electron microscope combined with energy spectrum element distribution image of Fe1 / NH2-UiO-66; c is a spherical aberration corrected transmission electron microscope image of Fe1 / NH2-UiO-66; Figure 6 : Scanning electron microscope image and EDS analysis image of the cross section of the Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane prepared in Example 2; wherein a is a scanning electron microscope image of the cross section; b is an EDS analysis image; Figure 7 : Performance comparison diagram of different reactors in Experimental Example 1, wherein a is a graph showing the change of methane yield with reaction time; b is a graph showing the change of methane conversion with reaction time; Figure 8 : Effect of different catalysts and different reactors on methanol production in Experimental Example 2; Fig. 9 : Cycle performance diagram in Test Example 2; Among them, 1. Reactor body; 2. Porous catalytic membrane; 11. Gas chamber area; 12. Liquid phase reaction area; 13. Air inlet; 14. Air outlet; 15. Light transmission port; 3. Circulation device. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0036] In the prior art, the activity of photocatalysts is limited by the limited distribution of active sites on their surfaces and the low efficiency of photogenerated carrier separation. The methane mass transfer efficiency in the existing solid-liquid photocatalytic system is low, and methane is easily further oxidized into by-products during the photocatalytic reaction, making it difficult to achieve highly selective production of methanol.

[0037] Based on this, the present invention provides a porous membrane photocatalytic reactor, including a reactor body, the interior of the reactor body is hollow, and a porous catalytic membrane is arranged inside the reactor body, and the porous catalytic membrane divides the interior of the reactor body into a gas chamber area on the left and a liquid phase reaction area on the right; the porous catalytic membrane includes a substrate membrane and an active substance loaded on the substrate membrane, the substrate membrane side of the porous catalytic membrane faces the gas chamber area, and the active substance side of the porous catalytic membrane faces the liquid phase reaction area, the substrate membrane is a PTEF film, and the active substance is Fe1 / NH2-UiO-66.

[0038] The porous catalytic membrane includes a substrate membrane and an active substance loaded on the substrate membrane, wherein the substrate membrane is a PTEF film, and the active substance is Fe1 / NH2-UiO-66. On the one hand, NH2-Uio-66 is selected as a catalyst carrier, and defects are introduced by activating it to broaden its visible light absorption range, and iron single-atom catalytic centers are anchored at its nodes. This design not only improves the catalyst's absorption efficiency of photons, but also optimizes the electronic structure of iron single atoms through metal-carrier interactions, thereby enhancing its ability to activate methane molecules. Compared with traditional systems that use metal nanoparticles or clusters as catalytic sites, the iron single atoms used in the present invention have higher atomic utilization and significantly improved catalytic activity. Through this optimized design, the present invention can achieve efficient photocatalytic oxidation of methane under mild conditions, and the reaction activity is improved by several orders of magnitude compared with traditional systems. On the other hand, the active component of Fe1 / NH2-UiO-66 is fixed on the PTEF film by suction filtration, such as Figure 3 As shown, the prepared catalytic membrane has a high-flux pore structure, which enables methane gas to pass through the pores in the membrane at a high flow rate, significantly improving the diffusion and mass transfer efficiency of gaseous reactants, thereby accelerating the reaction rate, while maintaining efficient catalytic performance, it also has excellent mechanical stability and chemical stability. Compared with traditional powder catalysts, membrane catalysts are not easy to agglomerate or lose during use, and can maintain high activity and stability in long-term continuous reactions. This makes the present invention have high operability and durability in practical applications, and is suitable for large-scale production and application. In addition, the present invention effectively regulates the partial oxidation process of methane by introducing iron single-atom active centers in the catalyst design and combining the efficient mass transfer capacity of the porous membrane, significantly improving the selective generation of methanol, and significantly reducing the amount of by-products. Therefore, the present invention not only improves the reaction selectivity, but also significantly improves the purity of the product, achieving the effect of energy saving and consumption reduction and reducing environmental pollution.

[0039] In addition, the present invention uses a porous catalyst membrane to divide the reactor body into a gas chamber area on the left and a liquid phase reaction area on the right, and ensures that the substrate membrane side of the porous catalyst membrane faces the gas chamber area and the active material side faces the liquid phase reaction area. Based on this, when the porous membrane photocatalytic reactor is used for photocatalytic methane oxidation, Figure 4 As shown. A high-throughput gas-membrane-liquid three-phase reaction interface is constructed in the reactor. Methane gas diffuses through the pores of the catalytic membrane to the active material side of the catalytic membrane. At this time, the hydrogen peroxide solution in the liquid phase reaction zone and the methane gas contact the active material, successfully constructing a gas-membrane-liquid three-phase reaction interface. Then, under the action of the light source, the catalyst is excited to perform a photocatalytic oxidation reaction. The efficient mass transfer performance of the gas-membrane-liquid three-phase interface effectively overcomes the limitation of low mass transfer efficiency of gaseous reactants in traditional solid-liquid reaction systems, ensuring the high efficiency and stability of the reaction.

[0040] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0041] The experimental materials used in the embodiments of the present invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0042] Example 1: Preparation method of Fe1 / NH2-UiO-66 NH2-UiO-66 was placed in vacuum and activated at 150℃ for 24 h to obtain defect-rich NH2-UiO-66; 60 mg of defect-rich NH2-UiO-66 powder was dispersed in 45 mL of ultrapure water, and 3 mL of 6.17 mM ferric chloride solution was added under vigorous stirring to obtain a mixed solution; The mixed solution was stirred at 25°C in the dark for 12 hours, and centrifuged. The solid after centrifugation was collected, washed with distilled water, and dried to obtain a powder. The powder was placed in an argon atmosphere with a purity of 99.999% and annealed at 200°C for 1 hour to obtain Fe1 / NH2-UiO-66 powder, wherein the loading amount of iron in Fe1 / NH2-UiO-66 was 3.0wt%.

[0043] The Fe1 / NH2-UiO-66 powder prepared in this example was characterized by the structure. Figure 5 As shown. Figure 5 It can be seen from a that the Fe1 / NH2-UiO-66 powder is in regular granular shape with uniform particle size. Figure 5 b It can be seen that the Fe atoms in Fe1 / NH2-UiO-66 powder are evenly distributed on the surface and inside of NH2-UiO-66. Figure 5 c It can be seen that the bright-spotted signals represent Fe atoms, and Fe atoms are evenly distributed in the lattice of NH2-UiO-66.

[0044] Example 2: Preparation method of Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane The Fe1 / NH2-UiO-66 powder prepared in Example 1 was mixed with the Nafion solution at a ratio of 7.5 mg:8.15 mL to obtain a precursor solution, and the precursor solution was deposited on one side of the polytetrafluoroethylene film by vacuum filtration for 2 min. Figure 3 As shown, after drying, the Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane was obtained by activation at 80°C for 4 h. The thickness of Fe1 / NH2-UiO-66 in the porous catalytic membrane was 15 μm.

[0045] The structural characterization of the Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane prepared in this example is as follows Figure 6 As shown. Figure 6 It can be seen that the Fe1 / NH2-UiO-66 active material and the PTFE film are separated by a clear boundary. It can be seen that the Fe1 / NH2-UiO-66 active material is successfully embedded on one side of the PTFE film using vacuum filtration technology.

[0046] Example 3: A porous membrane photocatalytic reactor like Figure 1 and Figure 2 As shown, the porous membrane photocatalytic reactor comprises a reactor body 1, the reactor body 1 is hollow inside, a porous catalytic membrane 2 is arranged inside the reactor body 1, and the porous catalytic membrane 2 divides the inside of the reactor body 1 into a gas chamber area 11 on the left and a liquid phase reaction area 12 on the right; The porous catalytic membrane 2 includes a substrate membrane and an active substance loaded on the substrate membrane. The substrate membrane side of the porous catalytic membrane 2 faces the gas chamber area 11, and the active substance side faces the liquid phase reaction area 12. The substrate membrane is a PTEF film, and the active substance is Fe1 / NH2-UiO-66. The reactor body 1 is provided with an air inlet 13 and an air outlet 14, the air inlet 13 is connected to the gas chamber area 11, and the air outlet 14 is connected to the liquid phase reaction area 12; a flow meter is provided at the air inlet 13, and a light-transmitting port 15 is provided on the right side wall of the reactor body 1, and the light-transmitting port 15 facilitates the light source to be taken into the composite porous membrane 2 to realize the photocatalytic reaction. The reactor body 1 is also connected with a circulation device 3, and the circulation device 3 keeps the temperature of the liquid phase reaction area 12 constant by circulating the liquid Example 4: Photocatalytic methane oxidation method The porous membrane photocatalytic reactor in Example 3 was used to carry out photocatalytic methane oxidation reaction. The specific steps are as follows: The methane gas with a purity of 99.9999% was introduced into the gas chamber area 11 through the gas inlet 13, and the gas flow rate of the methane gas was controlled by a flow meter to be 120 mL min -1 , then add 10 mol / L hydrogen peroxide solution into the liquid phase reaction zone 12, turn on the xenon lamp, control its power to 300 W, and irradiate it onto the Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane 2 through the light-transmitting hole 15, wait for the methane gas to diffuse through the Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane 2 to the liquid phase reaction zone 12, and contact with the hydrogen peroxide solution in the liquid phase reaction zone 12, and then be excited by the xenon light source and catalyzed by Fe1 / NH2-UiO-66, and then undergo photocatalytic methane oxidation reaction for 3 hours to obtain methanol.

[0047] Comparative Example 1: The Fe1 / NH2-UiO-66 prepared in Example 1 was placed in a 10 mol / L hydrogen peroxide solution, and then a gas with a purity of 99.999% and a flow rate of 120 mL min -1 Methanol gas is introduced into the hydrogen peroxide solution, and a xenon lamp with a power of 300 W is turned on. Under the catalytic action of Fe1 / NH2-UiO-66, photocatalytic methane oxidation reaction is carried out for 3 hours after excitation by the xenon light source to obtain methanol.

[0048] Comparative Example 2: The difference between this comparative example and Example 4 is that the active material on the porous catalytic membrane in the porous membrane photocatalytic reactor is Fe1 / TiO2.

[0049] The preparation method of Fe1 / TiO2 is as follows: weigh 60 mg TiO2 (Acros, 99.8%) powder and completely disperse it in 45 mL ultrapure water to obtain a dispersion; then, under vigorous stirring, inject 3 mL of 6.17 mmol / L FeCl3 solution into the above dispersion by syringe pump to obtain a mixture, stir the mixture at a speed of 700 rpm for 12 hours at room temperature and dark conditions, centrifuge it at a speed of 7000 rpm for 5 minutes, collect the product after centrifugation, wash it once with ultrapure water, and dry it in a vacuum oven at room temperature to obtain a powder; place the powder in a quartz boat and put it into a tube furnace, pass an argon atmosphere with a purity of 99.999%, wherein the gas flow rate of the argon atmosphere is 60 sccm, heat it to 200°C at a heating rate of 5°C / min, keep it warm and heat it for 1 hour, and after the system is naturally cooled, Fe1 / TiO2 is obtained.

[0050] Comparative Example 3: Fe / TiO2 was used as a catalyst in a 10 mol / L hydrogen peroxide solution, and then a gas with a purity of 99.999% and a flow rate of 120 mL min -1 Methanol gas is introduced into the hydrogen peroxide solution, and a xenon lamp with a power of 300 W is turned on. Under the catalytic action of Fe / TiO2 and excitation by the xenon light source, photocatalytic methane oxidation reaction is carried out for 3 hours to obtain methanol.

[0051] Among them, the preparation method of Fe1 / TiO2 is the same as that of Comparative Example 2.

[0052] Test Example 1: The amount of methanol generated and the amount of methane gas reduced at different reaction times in the photocatalytic methane oxidation reaction in Example 4 and Comparative Example 1 were counted, and the methanol yield and methane conversion rate were calculated. The results are as follows: Figure 7 shown.

[0053] Depend on Figure 7It can be seen that under the same illumination conditions, the novel gas-membrane-liquid mode of the present invention exhibits higher methane conversion rate and methanol selectivity. Specifically, when the porous membrane photocatalytic reactor of the present invention is used for photocatalytic methane oxidation reaction, when the gas-membrane-liquid mode is constructed, when the reaction is carried out for 3 h, the methanol yield is 5.59 mmol / g cat The conversion rate of methane was 63.2%, while in Comparative Example 1, the traditional solid-liquid mode was used. When the reaction was carried out for 3 h, the methanol yield was 1.03 mmol / g cat , the conversion rate of methane is 11.6%. In addition, the yield of methanol gradually decreases with time, which may be due to the gradual consumption of hydrogen peroxide and the gradual decrease in concentration as the reaction proceeds.

[0054] It can be seen that the traditional solid-liquid mode has low mass transfer efficiency of gaseous reactants due to the low solubility of methane in water and the coverage of water on the catalyst surface, thus limiting the overall reaction activity. In contrast, the new gas-membrane-liquid mode significantly improves the mass transfer efficiency of methane gas through the optimized three-phase interface design, reduces the shielding effect of water on the catalytic sites, and thus greatly improves the reaction performance. This comparison chart fully demonstrates the superiority of the present invention in interface and device design.

[0055] Test Example 2: The methane production during the photocatalytic methane oxidation reaction in Example 4 and Comparative Examples 1-3 was recorded, and the methane yield was calculated. The results are as follows: Figure 8 shown.

[0056] TiO2 is used as a commercial photocatalyst, on which single iron atoms are loaded to form a Fe1 / TiO2 catalyst. The difference between the Fe1 / TiO2 catalyst and the catalyst in the present invention is that the Fe1 / TiO2 catalyst has a non-porous structure, while the Fe1 / NH2-UiO-66 catalyst in the present invention has a rich open pore structure.

[0057] Depend on Figure 8 It can be seen that when the photocatalytic reactor of the present invention is used for photocatalytic reaction, when Fe1 / NH2-UiO-66 is used as the active material of the catalytic membrane, the methanol yield is 0.34 mmol / (g cat ·h), when Fe1 / TiO2 is used as the active material of the catalytic membrane, the methanol production is 0.11 mmol / (g cat ·h). When the traditional solid-liquid reaction interface is used for photocatalytic reaction, the methanol yield is 0.14mmol / (g cat ·h), when Fe1 / TiO2 is used as the active material of the catalytic membrane, the methanol production is 0.01 mmol / (g cath). It can be seen that the present invention can significantly improve the reaction yield by using Fe1 / NH2-UiO-66 as the active material of the porous catalytic membrane in combination with the porous membrane photocatalytic reactor of the present invention.

[0058] Test Example 3: Long cycle test The porous film photocatalytic reactor in Example 3 was used to carry out the photocatalytic methane oxidation reaction, and the specific reaction steps and parameters were the same as those in Example 4. During the reaction, the reaction time was controlled to be 3 hours. After the reaction was completed, the porous catalyst membrane was taken out, the surface was rinsed with ultrapure water, and it was placed in an 80°C oven for drying for 1 hour. The dried porous catalyst membrane was placed inside the reactor body 1, and the methane gas and hydrogen peroxide solution of the catalytic system were renewed. The photocatalytic methane oxidation reaction was carried out again. The test was repeated 7 times. The results are as follows. Fig. 9 shown.

[0059] Depend on Fig. 9 It can be seen that after repeating the experiment 7 times, the methanol production increased from 5.59 mmol / g cat Reduced to 5.46 mmol / g cat , only decreased by 2.3%, and the yield of formic acid increased from 0.33 mmol / g cat Reduced to 0.31 mmol / g cat , which only decreased by 6.0%. It can be seen that the porous membrane photocatalytic reactor prepared by the present invention has good long-cycle stability.

[0060] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A porous membrane photocatalytic reactor, characterized in that: The reactor body comprises a reactor body, the interior of the reactor body is hollow, a porous catalytic membrane is arranged inside the reactor body, and the porous catalytic membrane divides the interior of the reactor body into a gas chamber area on the left and a liquid phase reaction area on the right; The porous catalytic membrane includes a substrate membrane and an active substance loaded on the substrate membrane. The substrate membrane side of the porous catalytic membrane faces the gas chamber area, and the active substance side faces the liquid phase reaction area. The substrate membrane is a PTEF film, and the active substance is Fe1 / NH2-UiO-66.

2. The porous membrane photocatalytic reactor according to claim 1, characterized in that: The reactor body is provided with an air inlet and an air outlet, the air inlet is connected to the gas chamber area, and the air outlet is connected to the liquid phase reaction area; a flow meter is provided at the air inlet; a light-transmitting port is provided on the right side wall of the reactor body; and a circulation device is also connected to the reactor body.

3. The porous membrane photocatalytic reactor according to claim 1, characterized in that: The porous catalytic membrane is prepared by the following method: (1) Dispersing defect-rich NH2-UiO-66 in water, and then adding ferric chloride solution to obtain a mixed solution; stirring the mixed solution and then centrifuging it, collecting the solid after centrifugation, washing, and drying it to obtain a powder; annealing the powder in an inert atmosphere to obtain Fe1 / NH2-UiO-66 powder as an active material; (2) After mixing Fe1 / NH2-UiO-66 powder with Nafion solution, a precursor solution is obtained; the precursor solution is deposited on one side of a polytetrafluoroethylene film by vacuum filtration, and then activated after drying to obtain a Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane.

4. The porous membrane photocatalytic reactor according to claim 3, characterized in that: In step (1), defect-rich NH2-UiO-66 is prepared by the following method: NH2-UiO-66 is placed under vacuum conditions and activated at 150-180° C. for 12-24 hours to obtain defect-rich NH2-UiO-66.

5. The porous membrane photocatalytic reactor according to claim 3, characterized in that: The added amounts of defect-rich NH2-UiO-66, water and ferric chloride solution are (55-65) mg:45 mL:(2.5-3.5) mL; the concentration of the ferric chloride solution is 6-7 mM.

6. The porous film photocatalytic reactor according to claim 3, characterized in that: In step (1), the inert atmosphere is an argon atmosphere, the concentration of the argon atmosphere is 99.999%, the annealing temperature is 180-220° C., and the annealing time is 0.8-1.2 h; the loading amount of single iron atoms in Fe1 / NH2-UiO-66 is 1.5-3.0 wt%.

7. The porous film photocatalytic reactor according to claim 3, characterized in that: In step (2), the material-liquid ratio of Fe1 / NH2-UiO-66 powder to Nafion solution is (12-13) mg: (8.0-8.5) mL; the activation temperature is 70-90°C, and the activation time is 3-7 h; in the Fe1 / NH2-UiO-66 / PTFE porous catalytic membrane, the thickness of Fe1 / NH2-UiO-66 is 14-16 μm.

8. Use of the porous membrane photocatalytic reactor according to any one of claims 1 to 7 in photocatalytic methane oxidation.

9. Use of the porous membrane photocatalytic reactor according to claim 8 in photocatalytic methane oxidation, characterized in that: The specific steps are: Methane gas is introduced into the gas chamber area, and then hydrogen peroxide solution is added to the liquid phase reaction area. A xenon light source is irradiated onto the porous catalytic membrane through the light transmission port. When the methane gas diffuses to the active material side of the porous catalytic membrane, photocatalytic methane oxidation reaction can be carried out under the action of xenon light.

10. Use of the porous membrane photocatalytic reactor according to claim 9 in photocatalytic methane oxidation, characterized in that: The irradiation power of the xenon light source is 280-320W, and the time of the photocatalytic methane oxidation reaction is 3h.

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