Method of photocatalytic reduction of co2, continuous flow reaction system and method of operating the same

Abstract

The application provides a method for photocatalytic reduction of CO2, a continuous flow reaction system and a running method thereof. The continuous flow reaction system comprises a feeding module, a photocatalytic reduction module and a reaction product detection module. The feeding module is connected to a vacuum tube reactor of the photocatalytic reduction module. A light source and a light reflector are arranged above the vacuum tube reactor, and a condenser is arranged below the vacuum tube reactor. The outlet end of the vacuum tube reactor is connected to a reaction product detection and analysis device and a gas collection device of the reaction product detection module. The method for photocatalytic reduction of CO2 is that, under the condition of light irradiation, the gaseous reactants continuously flow through the photothermal material and the photocatalyst in the reactor in sequence, exchange heat with the photothermal material first, and then flow to the photocatalyst to obtain the reaction product by catalytic reduction of CO2. The application integrates the low-energy-consumption heating effect and the high-efficiency heat storage capacity, and realizes the photocatalytic reduction of CO2 to prepare high-value chemicals under the condition of continuous flow reaction.

Description

[Technical Field]

[0001] This invention relates to the field of renewable energy technology, and in particular to a method for photothermal coupled catalytic reduction of CO2, a continuous flow reaction system and its operation method. [Background Technology]

[0002] The massive emissions of CO2 have exacerbated the global greenhouse effect, prompting many countries to set carbon reduction targets. Utilizing renewable energy sources such as solar power to catalytically convert CO2 into high-value fuels like methane and methanol can not only contribute to achieving carbon reduction targets but also help improve the energy structure. Photocatalytic reduction is a crucial technology for achieving efficient CO2 conversion, overcoming the high energy consumption problem of thermocatalytic conversion while effectively utilizing solar energy. Specifically, enhancing photocatalysis by increasing temperature to improve product yield, selectivity, and CO2 conversion rate is a clean, low-carbon, and efficient method that effectively addresses existing problems in photocatalytic CO2 reduction reactions. Therefore, increasing the temperature of the photocatalytic reaction zone and leveraging the unique characteristics of the reaction system to achieve temperature rise and heat storage in the reaction zone has significant theoretical research value and practical application value for promoting the large-scale high-value utilization of CO2.

[0003] Most existing research provides heat for photocatalytic reactions through external heating sources. For example, Chinese patent application CN114733458A discloses a photothermal composite catalytic multifunctional reaction system. This technology controls the reaction temperature through a programmed temperature-raising furnace that fixes the outer layer of the reaction vessel to achieve photothermal coupling under light source irradiation. However, this external heating source method has disadvantages such as high energy consumption and complex equipment. The powdered photocatalysts used in most current studies suffer from easy loss and difficulty in recovery. Preparing the powdered photocatalytic active components into a macroscopic monolithic catalyst can effectively solve this problem. Most existing photocatalytic systems are designed for the characteristics of powdered catalysts and are more suitable for long-term static reactions under closed conditions. To achieve a continuous flow reaction, the monolithic photocatalyst is placed inside a transparent quartz tube reactor. By matching the reactor diameter with the catalyst size, the reaction gas is ensured to flow through the entire volume of the catalyst. However, such reaction systems lack heating and insulation designs for the reaction area and cannot allow sunlight to fully irradiate the end of the monolithic catalyst away from the light source. [Summary of the Invention]

[0004] The purpose of this invention is to solve the problems in the prior art and to propose a photothermal coupled catalytic reduction method for CO2, a continuous flow reaction system and its operation method, which integrates low-energy heating effect with high-efficiency heat storage capacity to realize the photothermal coupled catalytic reduction of CO2 to produce high-value chemicals. It also realizes the maximum utilization of sunlight by the integral catalyst and the large-scale conversion of CO2 under continuous flow reaction conditions.

[0005] To achieve the above objectives, this invention proposes a photothermal coupled catalytic reduction method for CO2. Under light irradiation, the gaseous reactants flow continuously and sequentially through the photothermal material and photocatalyst in the reactor. The gaseous reactants exchange heat as they flow through the photothermal material, and then the heated gaseous reactants flow to the photocatalyst to catalytically reduce CO2 and obtain the reaction products.

[0006] Preferably, the photothermal material is carbon aerogel, and the preparation method of the carbon aerogel is as follows: biomass-based aerogel is prepared using biomass-based raw materials, and then the biomass-based aerogel is carbonized to obtain carbon aerogel. The amorphous carbon and a small amount of graphite carbon in the carbon aerogel help to improve the photothermal conversion performance.

[0007] Preferably, the carbon aerogel is modified with components that have a photothermal effect to improve spectral absorption rate and photothermal conversion performance.

[0008] Preferably, the biomass-based raw material is one or a mixture of cellulose and lignin.

[0009] Preferably, the photocatalyst is a monolithic photocatalyst, and the preparation method includes the following steps:

[0010] a. Preparation of aerogel carriers using biomass components;

[0011] b. Prepare biomass-based photocatalytic composite materials with highly dispersed active sites by combining metals or oxides with aerogel carriers;

[0012] c. Enhance the visible light response of biomass-based photocatalytic composite materials through photosensitive materials, metal and non-metal doping, and novel structural construction methods;

[0013] d. A monolithic photocatalyst is obtained by promoting the separation of photogenerated electrons and holes through metal-semiconductor coupling and semiconductor-semiconductor heterojunction methods.

[0014] Preferably, in step a, one or more of nitrogen, cerium, and zirconium are used to in-situ dope the biomass component raw material during the preparation of the aerogel carrier, thereby increasing the surface alkalinity and oxygen vacancy concentration and promoting the adsorption and activation of CO2.

[0015] Preferably, in step b, the metal or oxide is Au or Cu. xOne or more of O, ZnO, and TiO2 are used to bond Au and Cu through hydrothermal processes, atomic layer deposition, impregnation, etc. x Biomass-based photocatalytic composite materials with highly dispersed active sites are prepared by combining metals or oxides such as O, ZnO, and TiO2 with an aerogel support.

[0016] Compared to the commonly used method of coupling photocatalysts and photothermal materials to prepare a single monolithic photothermal catalytic material, the photothermal coupled catalytic reduction method for CO2 proposed in this invention prepares the photothermal material and photocatalyst separately, which has the following advantages:

[0017] 1. The synthesis steps are simpler, and photocatalytic materials can be prepared independently without the need to add photothermal materials.

[0018] 2. The lifespan of photothermal conversion materials is not affected by photocatalytic materials, and the lifespan will be extended.

[0019] 3. The main function of photothermal materials is to convert sunlight into heat. Their role is photothermal conversion, heat storage, and heat transfer. The materials themselves have almost no photocatalytic reduction performance for CO2. In the overall photothermal catalytic material, the photothermal material with photothermal effect will cover some of the reactive sites of the photocatalyst, resulting in a decrease in conversion efficiency.

[0020] 4. In this invention, the photothermal material and photocatalytic material are separated. The temperature of the reaction zone can be controlled by adjusting the photothermal material, which can be used to study the photocatalytic conversion performance at the target temperature and the influence of heat and mass transfer processes on the catalytic reaction. In contrast, the photothermal catalytic material causes the temperature of the reaction zone to rise rapidly, which is not conducive to temperature control.

[0021] This invention also proposes a continuous flow reaction system for photothermal coupled catalytic reduction of CO2, comprising a feeding module, a photothermal coupled flow reaction module, and a reaction product detection module; the feeding module includes a gas supply device and a first gas path, the gas supply device being connected to the vacuum tube reactor of the photothermal coupled flow reaction module through the first gas path; the photothermal coupled flow reaction module includes a vacuum tube reactor, a light source for providing illumination, a light reflector for reflecting reflected light back to the vacuum tube reactor, and a concentrator for reflecting transmitted light and unabsorbed light back to the vacuum tube reactor; the reaction product detection module includes a second gas path, a reaction product detection and analysis device, and a gas collection device, the outlet end of the vacuum tube reactor of the photothermal coupled flow reaction module being connected to the second gas path and then connected to the reaction product detection and analysis device and the gas collection device respectively.

[0022] Preferably, the first gas path includes a main gas path connected to the outlet of the gas supply device, and a water container and a gas mixer connected sequentially to the outlet of the main gas path. The outlet of the gas mixer is connected to a gas preheater, a first heat-tracing gas path, a vortex flow meter, and then connected to the vacuum tube reactor of the photothermal coupled flow reaction module. The second gas path is a second heat-tracing gas path. Both the first and second heat-tracing gas paths are electrically heated gas paths, using a method of fixing electric heating tape to the gas path pipelines. The gas preheater is connected to the vacuum tube reactor, and the vacuum tube reactor is connected to the gas chromatograph, respectively, to prevent gaseous reactants and reaction products from cooling and condensing inside the pipeline, which would affect the accuracy of the experiment.

[0023] Preferably, the first gas path further includes a first gas path branch and a second gas path branch connected to the outlet end of the main gas path. The first gas path branch and the second gas path branch are respectively connected to a water container and a steam generator and then connected to a gas mixer.

[0024] Preferably, a photocatalyst is placed inside the vacuum tube reactor.

[0025] Preferably, the front section of the vacuum tube reactor facing the air inlet is filled with photothermal material, and the rear section at the other end is filled with photocatalyst.

[0026] Preferably, a first pressure reducing valve, a safety valve, a pressure gauge, a second pressure reducing valve, a mass flow meter, and a ball valve are sequentially arranged along the main gas path in the direction of gaseous reactant flow.

[0027] Preferably, a pressure sensor and a temperature sensor for measuring the pressure and temperature of the gaseous reactants are also connected between the vortex flowmeter and the vacuum tube reactor.

[0028] Preferably, the water container stores deionized water to provide water for the catalytic reduction reaction of CO2.

[0029] Preferably, the gas supply device is a gas cylinder, which is placed in an explosion-proof cabinet.

[0030] Preferably, the vacuum tube reactor is a transparent quartz glass tube with a vacuum insulation layer, and a sealing ring is provided at the air inlet and air outlet to ensure airtightness.

[0031] Preferably, the photothermal coupled flow reaction module further includes a reactor support, a drive mechanism, and a motor. The vacuum tube reactor is rotatably mounted on the reactor support. The motor is connected to the vacuum tube reactor via the drive mechanism, which provides rotational power to the vacuum tube reactor, allowing incident light to be uniformly radiated onto every side of the photocatalyst and photothermal material.

[0032] Preferably, the photothermal coupling flow reaction module further includes a reaction test platform, the light source is adjustablely mounted on the reaction test platform, and the installation position can be adjusted as needed; the light reflector is adjustablely mounted on the reaction test platform, and the installation angle can be adjusted as needed.

[0033] Preferably, the reaction product detection and analysis device includes a data acquisition and analysis system and a gas chromatograph. A back pressure valve is provided in the second gas path. The outlet end of the back pressure valve is connected to a third gas path branch and a fourth gas path branch. The third gas path branch is connected to a one-way valve and then connected to a gas collection device. The fourth gas path branch is connected to the gas chromatograph. The outlet end of the gas chromatograph is connected to a tail gas treatment device.

[0034] This invention also proposes a method for operating a continuous flow reaction system for photothermal coupled catalytic reduction of CO2, comprising the following steps:

[0035] S1. The gaseous reactants flow out from the gas supply device and output water-containing gaseous reactants through the first gas path. The gaseous reactants enter the vacuum tube reactor through the gas preheater, the first heat tracing gas path and the vortex flow meter. The vacuum tube reactor contains photothermal materials and photocatalysts in sequence along the flow direction of the gaseous reactants, or only photocatalysts.

[0036] S2. Under the illumination of the light source, the gaseous reactants heated to the target temperature by the gas preheater or photothermal material flow to the photocatalyst to undergo a photothermal coupled catalytic reaction, and carry out a continuous catalytic conversion reaction at the set target flow rate;

[0037] S3. The reaction products obtained in the vacuum tube reactor are collected by the gas collection device or detected online by a gas chromatograph after passing through the second gas path. After detection, the reaction products are collected by the tail gas treatment device.

[0038] Preferably, when the temperature of the gas preheater is set to room temperature, a photothermal material is placed in the front section of the vacuum tube reactor facing the gas inlet, and a photocatalyst is placed in the rear section of the other end. The photothermal material first converts the light from the light source into heat to heat the gaseous reactants, and then the photocatalyst performs a photothermal coupling catalytic reaction on the heated gaseous reactants.

[0039] Preferably, only a photocatalyst is placed inside the vacuum tube reactor. The gaseous reactants are first heated by a gas preheater, and then the heated gaseous reactants undergo a photothermal coupled catalytic reaction through the photocatalyst.

[0040] Preferably, in step S1, after the gaseous reactants flow out of the gas supply device, they are divided into two gas paths via the first gas path: in the first gas path branch, the gaseous reactants flow through the water container and then enter the gas mixer; in the second gas path branch, the gaseous reactants and the water vapor generated by the steam generator enter the gas mixer together; one of the water container or the steam generator is turned on to output the water-containing gaseous reactants from the first gas path branch or the second gas path branch.

[0041] Traditional heat-assisted photocatalytic static reactions often employ external heating methods, such as water bath heating or reactant preheating; the reactor is typically a single-layer quartz glass or stainless steel vessel; and the reactants are allowed to stand for several hours after entering the reactor. Compared to traditional externally heated heat-assisted photocatalytic static reactions, the photothermal coupled catalytic reduction of CO2 continuous flow reaction system and its operation method proposed in this invention have the following advantages:

[0042] 1. By utilizing the photothermal effect of the pre-heated photothermal material in the reactor and simulating highly uniform solar spots with a light source, the temperature of the reaction zone is increased by heating the reactants, thus avoiding the energy consumption of an external heating source. Photothermal coupling catalytic reaction can be achieved using only solar energy (light source).

[0043] 2. By matching the dimensions of the integrated photocatalyst, photothermal material and vacuum tube reactor, and by using a flow meter and gas mixer to adjust the flow rate of gaseous reactants, catalytic reaction under continuous CO2 flow conditions was achieved, which can significantly reduce the static reaction time.

[0044] 3. Compared to traditional quartz reactors, vacuum tube reactors reduce heat loss through a vacuum layer to ensure a higher temperature in the reaction zone.

[0045] 4. The vacuum tube reactor is rotated by a motor, so that the photothermal material and the monolithic photocatalyst are fully and uniformly irradiated by sunlight, which enhances the photothermal conversion performance of the photothermal material and stimulates more reactive sites of the monolithic photocatalyst.

[0046] 5. By using concentrators and light reflectors to perform secondary reflection of both reflected and unabsorbed light, the utilization rate of the solar spectrum is maximized.

[0047] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. [Attached Image Description]

[0048] Figure 1 This is a schematic diagram of the structure of a continuous flow reaction system for photothermal coupled catalytic reduction of CO2 according to the present invention;

[0049] The attached diagram is labeled as follows: 1 Explosion-proof cabinet; 2 Gas cylinder; 3 Pressure reducing valve; 4 Safety valve; 5 Pressure gauge; 6 Mass flow meter; 7 Ball valve; 8 Water container; 9 Gas mixer; 10 Steam generator; 11 Gas preheater; 121 First heating gas path; 122 Second gas path; 13 Vortex flow meter; 14 Pressure sensor; 15 Temperature sensor; 16 Reaction test bench; 17 Light source; 18 Reactor support; 19 Sealing ring; 20 Vacuum tube reactor; 21 Concentrator; 22 Light reflector; 23 Drive mechanism; 24 Motor; 25 Back pressure valve; 26 Check valve; 27 Gas collection device; 28 Data acquisition and analysis system; 29 Gas chromatograph; 30 Tail gas treatment device.

Detailed Implementation Methods

[0050] This invention discloses a method for photothermal coupled catalytic reduction of CO2. Under light irradiation, gaseous reactants flow continuously and sequentially through photothermal materials and photocatalysts in a reactor. The gaseous reactants exchange heat as they flow through the photothermal materials, and then the heated gaseous reactants flow to the photocatalyst to catalytically reduce CO2 to obtain reaction products.

[0051] Examples of photothermal coupled catalytic reduction of CO2 are as follows:

[0052] Photothermal material preparation: Priority is given to biomass-based raw materials with potential photothermal effects that facilitate the construction of a three-dimensional framework structure, such as cellulose and lignin. After preparing biomass-based aerogels, they are carbonized in a tube furnace. The amorphous carbon and a small amount of graphitic carbon in the resulting carbon aerogels contribute to improved photothermal conversion performance. Heat transfer performance is enhanced by optimizing the raw material composition ratio, carbonization conditions, and pore structure. Subsequently, photothermal components such as Cu and MXene are modified into the aerogel structure to improve spectral absorption and photothermal conversion performance.

[0053] Photocatalyst preparation: Biomass components such as chitosan are preferentially selected as raw materials, as they can withstand certain temperatures and are conducive to preparing photocatalyst aerogel supports with high light transmittance. In-situ doping with nitrogen, cerium, and zirconium is performed during the preparation process to increase surface alkalinity and oxygen vacancy concentration, promoting CO2 adsorption and activation. Subsequently, Au and Cu are incorporated through hydrothermal processes, atomic layer deposition, and impregnation. x Biomass-based photocatalytic composite materials with highly dispersed active sites are prepared by combining metals or oxides such as O, ZnO, and TiO2 with aerogel supports. These composites are then used to generate photosensitive materials (such as zinc phthalocyanine doped materials) and metal ions (such as Au). 3+Doping with TiO2, using non-metals (such as N-doped TiO2), and employing novel structural construction methods (such as unique porous structures) can enhance the visible light response of biomass-based photocatalytic composite materials. Furthermore, methods such as metal-semiconductor coupling (e.g., TiO2 / Ag) and semiconductor-semiconductor heterojunctions (e.g., TiO2 / CdS) can promote the separation of photogenerated electrons and holes, ultimately yielding monolithic bio-based aerogel composite photocatalysts, or simply monolithic photocatalysts. During the preparation process, the light transmittance of the photocatalytic aerogel can be controlled by adjusting the size and distribution of nanoparticles, altering freeze-dry processing, changing crosslinking conditions, and restricting polymer chain mobility, thereby achieving a balance between transmittance and absorbance.

[0054] Among them, photothermal materials and photocatalysts exist in the form of macroscopic monolithic aerogels, with biomass as the raw material for the aerogel skeleton.

[0055] Catalytic methods:

[0056] Step 1. The heat storage capacity of photothermal materials and the effect of heat and mass transfer behavior of the reaction medium on the temperature increase of the post-photocatalyst.

[0057] Under standard sunlight / light source irradiation conditions, the reaction medium flows sequentially through the photothermal material (carbon aerogel) and the photocatalyst (monolithic aerogel photocatalyst) within the reactor. Under simulated sunlight irradiation, the photothermal material absorbs the incident light and converts it into heat. As the reaction medium flows through the porous structure of the photothermal material, it exchanges heat with the material. Subsequently, the heated reaction medium flows towards the photocatalyst.

[0058] Step 2. Continuous catalytic conversion mechanism of CO2 in a composite system of photothermal materials and photocatalysts.

[0059] The reaction medium flows from the gas cylinder at a target flow rate into the reactor for reaction, and the reaction products are then directly analyzed by a gas chromatograph. This process is continuous flow and continuous reaction, not a static reaction. Under simulated sunlight irradiation, the photocatalyst is excited to generate photoelectrons and holes. When the heated reaction medium flows into the porous structure of the photocatalyst, it is first adsorbed onto the aerogel surface, and then combines with the photogenerated electrons and holes, undergoing a reduction-oxidation reaction. Specifically, the reducing medium (H2 or H2O), acting as a hydrogen source, combines with holes to undergo oxidation; the reactant CO2 combines with electrons and hydrogen to undergo reduction, generating reaction products. Finally, the reaction products are analyzed in real time by a gas chromatograph. Because the reaction medium is heated to a higher temperature, more reactants are activated during the reaction, the migration rate of photogenerated electrons and holes is accelerated, the recombination rate is reduced, and the photocatalytic efficiency is improved.

[0060] The present invention also discloses a continuous flow reaction system for photothermal coupled catalytic reduction of CO2, comprising a feeding module, a photothermal coupled flow reaction module, and a reaction product detection module; the feeding module includes a gas supply device 2 and a first gas path, the gas supply device 2 being connected to the vacuum tube reactor 20 of the photothermal coupled flow reaction module through the first gas path; the photothermal coupled flow reaction module includes the vacuum tube reactor 20, a light source 17 disposed above the vacuum tube reactor 20, a light reflector 22, and a concentrator 21 disposed below the vacuum tube reactor 20; the reaction product detection module includes a second gas path 122, a reaction product detection and analysis device, and a gas collection device, the outlet end of the vacuum tube reactor 20 of the photothermal coupled flow reaction module being connected to the second gas path 122 and then connected to the reaction product detection and analysis device and the gas collection device respectively.

[0061] Further, in this embodiment, the first gas path includes a main gas path connected to the outlet end of the gas supply device 2, and a first gas path branch and a second gas path branch connected to the outlet end of the main gas path. The first gas path branch and the second gas path branch are respectively connected to the water container 8 and the steam generator 10, and then connected to the gas mixer 9. The outlet end of the gas mixer 9 is connected to the gas preheater 11, the first heat tracing gas path 121, and the vortex flow meter 13, and then connected to the vacuum tube reactor 20 of the photothermal coupling flow reaction module. Furthermore, along the flow direction of the gaseous reactants, a first pressure reducing valve 31, a safety valve 4, a pressure gauge 5, a second pressure reducing valve 32, a mass flow meter 6, and a ball valve 7 are sequentially arranged on the main gas path. A pressure sensor 14 and a temperature sensor 15 for measuring the pressure and temperature of the gaseous reactants are also connected between the vortex flow meter 13 and the vacuum tube reactor 20. The gas supply device 2 is a gas cylinder placed in the explosion-proof cabinet 1.

[0062] The gaseous reactants flow out from the gas supply device 2 and pass sequentially through the first pressure reducing valve 31, safety valve 4, pressure gauge 5, second pressure reducing valve 32, mass flow meter 6, and ball valve 7, before splitting into two gas paths: In the first gas path branch, the gaseous reactants flow through the water container 8 and then into the gas mixer 9. The water container 8 stores deionized water to provide water for the catalytic reduction reaction of CO2. In the second gas path branch, the gaseous reactants and the water vapor generated by the steam generator 10 enter the gas mixer 9 together. The water-containing gaseous reactants pass through the gas preheater 11, the first heat-traced gas path 121, and the vortex flow meter 13 before entering the vacuum tube reactor 20. The pressure and temperature of the gaseous reactants are measured by the pressure sensor 14 and the temperature sensor 15. Both the first heating gas path 121 and the second gas path 122 are electrically heated gas paths. The gaseous reactants flow out from the gas preheater 11, pass through the first heating gas path 121, and enter the vacuum tube reactor 20. Subsequently, the reaction products are collected by the gas collecting device 27 through the second gas path 122, or detected online by the gas chromatograph 29.

[0063] Furthermore, in this embodiment, the vacuum tube reactor 20 is a transparent quartz glass tube with a vacuum insulation layer, and sealing rings 19 are respectively provided at the air inlet and the air outlet to ensure airtightness.

[0064] Furthermore, in this embodiment, the photothermal coupled flow reaction module also includes a reactor support 18, a drive mechanism 23, and a motor 24. The vacuum tube reactor 20 is rotatably mounted on the reactor support 18. The motor 24 is connected to the vacuum tube reactor 20 via the drive mechanism 23. The drive mechanism 23 provides rotational power to the vacuum tube reactor 20, which allows the photothermal material and photocatalyst to be irradiated by simulated sunlight over the largest possible area.

[0065] Furthermore, in this embodiment, the photothermal coupling flow reaction module also includes a reaction test platform 16. The light source 17 is adjustablely mounted on the reaction test platform 16, and the light source 17 can move left and right, up and down, and forward and backward via a moving track on the reaction test platform 16. The light source 17 is a xenon lamp equipped with an AM 1.5G filter, and the power of the xenon lamp is 1000W. Optical filters that can transmit different wavelengths are provided according to experimental requirements; the side length of the light spot is no greater than 300mm, the uniformity within the irradiated area is greater than 90%, and the light intensity is 0.5-2 sun. The light intensity can be adjusted by the current and lifting height of the light source. The concentrator 21 is a secondary parabolic concentrator, fixed on the reaction test platform 16 and located directly below the vacuum tube reactor 20. After the light emitted by the light source 17 reaches the vacuum tube reactor 20, the transmitted and unabsorbed light is focused by the concentrator 21 and reflected back to the vacuum tube reactor 20. The light reflector 22 is installed at an adjustable angle on the reaction test platform 16, located directly above the right side of the vacuum tube reactor 20. The placement angle can be changed according to the experimental requirements to reflect the light reflected by the photocatalyst back to the photothermal material of the vacuum tube reactor 20, thereby improving the utilization rate of the full spectrum of sunlight.

[0066] Further, in this embodiment, the reaction product detection and analysis device includes a data acquisition and analysis system 28 and a gas chromatograph 29. A back pressure valve 25 is provided on the second gas path 122. The outlet end of the back pressure valve 25 is connected to a third gas path branch and a fourth gas path branch. The third gas path branch is connected to a one-way valve 26 and then to a gas collection device 27. The fourth gas path branch is connected to the gas chromatograph 29, and the outlet end of the gas chromatograph 29 is connected to a tail gas treatment device 30. The reaction products are divided into two gas paths after passing through the back pressure valve 25: the third gas path branch and the fourth gas path branch. There are two detection methods: in the third gas path branch, the reaction products are collected by the gas collection device 27 after passing through the one-way valve 26; in the fourth gas path branch, the reaction products are detected online in real time by the gas chromatograph 29. The detection data is collected and analyzed by the data acquisition and analysis system 28, and finally, the reaction products enter the tail gas treatment device 30. The gas chromatograph 29 performs qualitative and quantitative real-time detection of the reaction products of the continuous flow reaction using a thermal conductivity detector and a flame ionization detector.

[0067] Example 1

[0068] First, debug each component of the reaction system to ensure that it is functioning properly. Then, place the integral photocatalyst, matching the dimensions of the vacuum tube reactor 20, into the reactor, and then proceed as follows... Figure 1 The components are assembled sequentially into a complete reaction system. Depending on the experimental requirements, either water container 8 or steam generator 10 is selected as the water supply device. The parameters of gas mixer 9, flow meters (mass flow meter 6, vortex flow meter 13), and motor 24 are set to their target values. The temperature of gas preheater 11 is set to room temperature. Gas chromatograph 29 is turned on. Then, the gas path switch and the power switches of each component are turned on, inert gas is input, and the operation of each component is monitored to ensure proper functioning. The gas path of the entire reaction system is tested for smoothness and leaks. If the system is normal, the gas type and ratio are switched, and the required gaseous reactants are input. When the gas components detected by gas chromatograph 24 match the set gas type and ratio, the experiment begins.

[0069] Move light source 17 directly above the photocatalyst, turn it on, and adjust the spot size and intensity to the required experimental values. Adjust condenser 21 so that it is directly below vacuum tube reactor 20 to reflect unabsorbed incident light back to the photocatalyst. After the reactants are thoroughly mixed in gas mixer 9, they enter vacuum tube reactor 20 for a 5-hour static photocatalytic reaction. Samples are taken every 30 minutes after the reaction begins and analyzed by gas chromatograph 29. The temperature inside vacuum tube reactor 20 is monitored in real time using an infrared thermal imager during the reaction.

[0070] Example 2

[0071] This invention provides a continuous flow reaction system for photothermal coupled catalytic reduction of CO2, and its application method in the continuous flow reaction of photothermal coupled catalytic CO2 under the condition of heating with a gas preheater is as follows:

[0072] First, debug each component of the reaction system to ensure that it is functioning properly. Then, place the integral photocatalyst, matching the dimensions of the vacuum tube reactor 20, into the reactor, and then proceed as follows... Figure 1 The components are assembled sequentially into a complete reaction system. Depending on the experimental requirements, either the water container 8 or the steam generator 10 is selected as the water supply device. The parameters of the gas mixer 9, flow meters (mass flow meter 6, vortex flow meter 13), and motor 24 are set to their target values. The temperature of the gas preheater 11 is set to the required experimental temperature, and the power of the first heating gas path 121 is set to its target value. The gas chromatograph 29 is then turned on. Subsequently, the gas path switch and the power switches of each component are turned on, inert gas is input, and the operation of each component is monitored to ensure normal function. The gas path of the entire reaction system is tested for smoothness and leaks. If the system is normal, the gas type and ratio are switched, and the required gaseous reactants are input. When the gas components detected by the gas chromatograph 24 are the same as the gas type and ratio set for the experiment, the experiment begins.

[0073] Move light source 17 directly above the photocatalyst, turn on light source 17, and adjust the spot size and light intensity to the required values ​​for the experiment. Adjust the condenser 21 so that it is directly below the vacuum tube reactor 20 to reflect unabsorbed incident light back to the photocatalyst. After the gaseous reactants flow out from the gas supply device 2, they obtain the water required for the reaction through the water container 8 or steam generator 10, and then are thoroughly mixed in the gas mixer 9 before entering the gas preheater 11. After the gaseous reactants are heated to the target temperature, they enter the vacuum tube reactor 20 through the first heated gas path 121, where the heated gaseous reactants undergo a photothermal coupled catalytic reduction reaction at the photocatalyst. After the reaction begins, the reaction products enter the gas chromatograph 29 for real-time detection through the second gas path 122. The data is collected and analyzed by the data acquisition and analysis system 28, and then the reaction products enter the tail gas treatment device 30 for collection and treatment. During the reaction, the temperature of the vacuum tube reactor 20 is monitored in real time using an infrared thermal imager.

[0074] Example 3

[0075] This invention provides a photothermal coupled catalytic reduction CO2 continuous flow reaction system, and its application method in the photothermal coupled catalytic CO2 continuous flow reaction under conditions of only light source irradiation, as detailed below:

[0076] First, debug each component of the reaction system to ensure normal operation. Then, place the photothermal material and integral photocatalyst, matching the dimensions of the vacuum tube reactor 20, into the reactor, and then proceed as follows... Figure 1 The components are assembled sequentially into a complete reaction system. Depending on the experimental requirements, either water container 8 or steam generator 10 is selected as the water supply device. The parameters of gas mixer 9, flow meters (mass flow meter 6, vortex flow meter 13), and motor 24 are set to their target values. The temperature of gas preheater 11 is set to room temperature, and the power of the first heating gas path 121 is set to its target value. The gas chromatograph 29 is turned on. Then, the gas path switch and the power switches of each component are turned on, inert gas is input, and the operation of each component is monitored to ensure proper functioning. The gas path of the entire reaction system is tested for smoothness and leaks. If the system is normal, the gas type and ratio are switched, and the required gaseous reactants are input. When the gas components detected by gas chromatograph 24 match the set gas type and ratio, the experiment begins.

[0077] Move the light source 17 directly above the photothermal material and photocatalyst, turn on the light source 17, and adjust the spot size and light intensity to the required values ​​for the experiment. Adjust the concentrator 21 so that it is directly below the vacuum tube reactor 20 so that the unabsorbed incident light is reflected a second time to the photothermal material and photocatalyst. Adjust the angle of the light reflector 22 so that it can reflect the light reflected by the photocatalyst a second time to the photothermal material, thereby improving the utilization rate of the solar spectrum. After the gaseous reactants flow out from the gas supply device 2, they obtain the water required for the reaction through the water container 8 or the steam generator 10, and then mix them thoroughly in the gas mixer 9 before entering the vacuum tube reactor 20 through the first heated gas path 121. The gaseous reactants are first heated at the high temperature of the photothermal material, and then flow to the photocatalyst for photothermal coupling catalytic reaction. After the reaction begins, the reaction products enter the gas chromatograph 29 for real-time detection through the first heated gas path 122. The data is collected and analyzed by the data acquisition and analysis system 28, and then the products enter the tail gas treatment device 30 for collection and treatment. The temperature of the vacuum tube reactor 20 was monitored in real time using an infrared thermal imager during the reaction.

[0078] This invention also discloses a method for operating the above-mentioned photothermal coupled catalytic reduction of CO2 continuous flow reaction system, comprising the following steps:

[0079] S1. The gaseous reactants flow out from the gas supply device 2 and are divided into two gas paths via the first gas path: in the first gas path branch, the gaseous reactants flow through the water container 8 and then enter the gas mixer 9; in the second gas path branch, the gaseous reactants and the water vapor generated by the steam generator 10 enter the gas mixer 9 together; select to open one of the water container 8 or the steam generator 10, so that the gaseous reactants containing water output from the first gas path branch or the second gas path branch enter the vacuum tube reactor 20 through the gas preheater 11, the first heat tracing gas path 121 and the vortex flow meter 13. The vacuum tube reactor 20 contains photothermal materials and photocatalysts in sequence along the flow direction of the gaseous reactants, or only photocatalysts are placed.

[0080] S2. Under the irradiation of the light source 17, the gaseous reactants heated to the target temperature by the gas preheater 11 or photothermal material flow to the photocatalyst to undergo a photothermal coupled catalytic reaction, and carry out a continuous catalytic conversion reaction at the set target flow rate.

[0081] S3. The reaction products obtained from the reaction in the vacuum tube reactor 20 are collected by the gas collection device 27 or detected online by the gas chromatograph 29 after passing through the second gas path 122. After detection, the reaction products are collected by the tail gas treatment device 30.

[0082] Operating Method 1: The gaseous reactants are heated using a gas preheater 11 to increase the temperature during photocatalysis. At this time, the vacuum tube reactor 20 contains only the photocatalyst, without any photothermal material. The photocatalyst is an integral photocatalyst.

[0083] First, adjust the parameters of the flow meters (mass flow meter 6, vortex flow meter 13), gas mixer 9, gas preheater 11, first heat tracing gas path 121, second gas path 122, motor 24 and other equipment to the target values. Place the photocatalyst at the rear of the vacuum tube reactor 20 and connect each device to ensure that the continuous flow reaction system for photothermal coupled catalytic reduction of CO2 has good airtightness and that all components are operating normally.

[0084] Next, adjust the input gas reactant ratio to the target value, turn on the gas chromatograph 29 to detect the outflowing gas, and wait for the gas composition in the detection result to be consistent with the target value. Then turn on the light source 17 and adjust its position and power so that the incident light irradiates the photocatalyst in the vacuum tube reactor 20.

[0085] The gaseous reactants obtain the necessary moisture for the reaction through water container 8, are uniformly mixed by gas mixer 9, and then enter gas preheater 11 to be heated to the target temperature before flowing into vacuum tube reactor 20. Under simulated sunlight irradiation by light source 17, the heated gaseous reactants undergo a thermally assisted photocatalytic reaction at the photocatalyst, and the catalytic conversion reaction proceeds continuously at a set target flow rate. The reaction products enter gas chromatograph 29 through second gas path 122 for detection.

[0086] Operating Method 2: The gas preheater 11 is set to room temperature, and carbon aerogel is used as the photothermal material. At this time, the photothermal material is placed in the front section of the vacuum tube reactor 20, and the photocatalyst is placed in the rear section.

[0087] First, adjust the parameters of the flow meter, gas mixer 9, first heating gas path 121, second gas path 122, motor 24, and other equipment to the target values, and adjust the temperature of the gas preheater 11 to room temperature. Place the photothermal material in the front section of the vacuum tube reactor 20 and the photocatalyst in the rear section of the vacuum tube reactor 20, and connect all the equipment to ensure that the continuous flow reaction system for photothermal coupled catalytic reduction of CO2 has good airtightness and that all components are operating normally.

[0088] Next, the input gas reactant ratio is adjusted to the target value, and the gas chromatograph 29 is turned on to detect the outflowing gas. Once the gas composition in the detection result is consistent with the target value, the light source 17 is turned on and its position and power are adjusted so that the incident light irradiates the photothermal material and photocatalyst in the vacuum tube reactor 20.

[0089] The gaseous reactants obtain the necessary water for the reaction through water container 8, are uniformly mixed by gas mixer 9, and then flow into vacuum tube reactor 20. Under simulated sunlight irradiation by light source 17, the gaseous reactants are heated at the photothermal material. The heating temperature of the gaseous reactants is controlled by adjusting the structure and spatial configuration of the photothermal material. The gaseous reactants heated to the target temperature flow to the photocatalyst to undergo a photothermal coupled catalytic reaction, and the catalytic conversion reaction proceeds continuously at a set target flow rate. The reaction products enter the gas chromatograph 29 through the second gas path 122 for detection.

[0090] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. A method of operating a continuous flow reaction system for photocatalytic reduction of CO2, characterized in that: The continuous flow reaction system includes a feeding module, a photothermal coupled flow reaction module, and a reaction product detection module; The feeding module includes a gas supply device (2) and a first gas path. The gas supply device (2) is connected to the vacuum tube reactor (20) of the photothermal coupling flow reaction module through the first gas path. The photothermal coupled flow reaction module includes a vacuum tube reactor (20), a light source (17) for providing illumination, a light reflector (22) for reflecting reflected light back to the vacuum tube reactor (20), and a concentrator (21) for reflecting transmitted light and unabsorbed light back to the vacuum tube reactor (20). The reaction product detection module includes a second gas path (122), a reaction product detection and analysis device, and a gas collection device. After the outlet end of the vacuum tube reactor (20) of the photothermal coupled flow reaction module is connected to the second gas path (122), it is connected to the reaction product detection and analysis device and the gas collection device respectively. The first gas path includes a main gas path connected to the outlet end of the gas supply device (2), and a water container (8) and a gas mixer (9) connected in sequence to the outlet end of the main gas path. The outlet end of the gas mixer (9) is connected to a gas preheater (11), a first heat tracing gas path (121), a vortex flow meter (13), and then connected to the vacuum tube reactor (20) of the photothermal coupling flow reaction module. The first gas path also includes a first gas path branch and a second gas path branch connected to the outlet end of the main gas path. The first gas path branch and the second gas path branch are respectively connected to the water container (8) and the steam generator (10) and then connected to the gas mixer (9). Either the water container (8) or the steam generator (10) is selected as the water supply device. The reaction product detection and analysis device includes a data acquisition and analysis system (28) and a gas chromatograph (29). A back pressure valve (25) is provided on the second gas path (122). The outlet end of the back pressure valve (25) is connected to the third gas path branch and the fourth gas path branch. The third gas path branch is connected to a one-way valve (26) and then connected to a gas collection device (27). The fourth gas path branch is connected to the gas chromatograph (29). The outlet end of the gas chromatograph (29) is connected to a tail gas treatment device (30). The operation method includes the following steps: S1. The gaseous reactant flows out from the gas supply device (2), and outputs the water-containing gaseous reactant through the first gas path. The gaseous reactant enters the vacuum tube reactor (20) through the gas preheater (11), the first heat tracing gas path (121) and the vortex flow meter (13). Photothermal materials and photocatalysts are placed sequentially in the vacuum tube reactor (20) along the gaseous reactant flow direction. S2. Under the irradiation of the light source (17), the gaseous reactants heated by the photothermal material flow to the photocatalyst to undergo a photothermal coupling catalytic reaction, and carry out a continuous catalytic conversion reaction at the set target flow rate. The catalytic reaction catalytically reduces CO2 to obtain the reaction products. S3. The reaction products obtained from the reaction in the vacuum tube reactor (20) are collected by the gas collection device (27) or detected online by the gas chromatograph (29) after passing through the second gas path (122). After detection, the reaction products are collected by the tail gas treatment device (30).

2. The operating method of the continuous flow reaction system for photothermal coupled catalytic reduction of CO2 as described in claim 1, characterized in that: The temperature of the gas preheater (11) is set to room temperature. Photothermal material is placed in the front part of the vacuum tube reactor (20) facing the gas inlet, and photocatalyst is placed in the rear part of the other end. The light of the light source (17) is first converted into heat by the photothermal material to heat the gas reactants. Then, the heated gas reactants are subjected to photothermal coupling catalytic reaction by the photocatalyst.

3. The method of operating a continuous flow reaction system for the photocatalytic reduction of CO2 by a thermo-optical coupling according to claim 1, characterized in that: The photothermal material is carbon aerogel, and the preparation method of the carbon aerogel is as follows: biomass-based aerogel is prepared using biomass-based raw materials, and then the biomass-based aerogel is carbonized to obtain carbon aerogel. The carbon aerogel is modified with components that have a photothermal effect. The photocatalyst is a monolithic photocatalyst, and its preparation method includes the following steps: a. Aerogel carriers are prepared using biomass components as raw materials, and one or more of nitrogen, cerium, and zirconium are used to dope the biomass components in situ during the preparation of the aerogel carriers. b. Prepare biomass-based photocatalytic composite materials with highly dispersed active sites by combining metals or oxides with aerogel carriers; c. Enhance the visible light response of biomass-based photocatalytic composite materials by doping with photosensitive materials, metal ions, or non-metals; d. Promoting the separation of photogenerated electrons and holes through metal-semiconductor coupling or semiconductor-semiconductor heterojunction methods to obtain monolithic photocatalysts.

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