Device and method for promoting methanation of carbon dioxide through laser scanning induced temperature oscillation

Abstract

The invention discloses a device and a method for promoting methanation of carbon dioxide through temperature oscillation induced by laser scanning. The device comprises a reactor, a laser and a galvanometer, a transparent cover plate is arranged at the top of the reactor, an air outlet is formed in the side surface, and an objective table is arranged in the reactor; a catalyst layer is arranged above the objective table; the catalyst layer is provided with a longitudinally-penetrating gas leading-in hole, a gas flow channel is arranged in the objective table, one end of the gas flow channel is communicated with the gas leading-in hole, and the other end of the gas flow channel is communicated with the gas inlet. Introducing mixed gas containing hydrogen and carbon dioxide into a gas inlet of the reactor, changing the irradiation position of a laser beam emitted by a laser through a galvanometer, and enabling the laser beam to periodically scan and irradiate the catalyst layer to obtain methane. The surface temperature distribution of the catalyst is dynamically regulated and controlled through laser scanning, so that the temperature of a catalytic active site is continuously switched between a high temperature and a low temperature, the thermodynamic limitation of a carbon dioxide methanation reaction can be effectively reduced, and an efficient and stable carbon dioxide methanation process is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide conversion, and particularly relates to a device and method for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation. Background Art

[0002] Carbon dioxide is a common greenhouse gas, and its large-scale emission has led to a significant greenhouse effect, having a profound impact on human life. The carbon dioxide methanation process converts carbon dioxide into methane with higher economic value, and has broad application prospects. The carbon dioxide methanation reaction (CO2 + 4H2 → CH4 + 2H2O, ΔH 298K = −165 kJ / mol) is a thermodynamically exothermic reaction. Too high temperature will inhibit the thermodynamic equilibrium of the conversion of carbon dioxide to methane; the reactant carbon dioxide (the bond energy of C=O is 806 kJ / mol) has chemical inertness, and its activation process on the catalyst surface requires a relatively high temperature to accelerate and complete. Traditional thermal catalysis usually provides a constant reaction temperature, and a constant temperature cannot simultaneously meet the carbon dioxide activation process and the low thermodynamic limitation conditions. If a non-equilibrium reaction temperature can be provided, the reaction may obtain a higher methane yield and methane selectivity than at a constant temperature.

[0003] Laser technology is a technology that uses lasers to process or detect specific targets and is considered one of the essential tools for human survival and development in an intelligent society. Researchers can utilize various characteristics of lasers, such as pulse effects, pressure effects, and thermal effects, to process specific targets. For example, "Laser-induced plasma and local temperature field for high-efficiency ammonia synthesis" (Tong Wu et al., NanoEnergy 116 (2023) 108855) reported the preparation of ammonia using hydrogen and nitrogen under the action of a laser. This method uses pulsed lasers to generate plasma from hydrogen and nitrogen, and then ammonia is prepared under the action of a catalyst. However, in addition to the pulse effect, lasers also have a thermal effect, that is, using the heat generated to process specific targets; however, due to the influence of their own characteristics, lasers can only generate local heat on a very small area. Therefore, lasers can only regulate the change of temperature on the spatial scale. When its heating mode is continuous heating, precise temperature regulation cannot be achieved at the time level, and temperature regulation at the time level can improve the utilization efficiency of catalytic sites and endow them with higher catalytic activity. However, there is currently no report that can simultaneously achieve the joint regulation of temperature in the time-space dimension. Therefore, it is necessary to explore technologies and equipment for achieving dual regulation of time-space temperature for catalytic reactions under mild conditions, improve the conversion rate of carbon dioxide, provide new ideas for the conversion of carbon dioxide, and be of great significance for the effective utilization of carbon dioxide. Summary of the Invention

[0004] Aiming at the above-mentioned prior art, the purpose of the present invention is to provide a device and method for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation. The present invention dynamically regulates the temperature distribution on the catalyst surface through periodic laser scanning, enabling the temperature of catalytic active sites to continuously switch between high / low temperatures. The instantaneous high temperature generated by laser irradiation promotes the activation process of carbon dioxide, and the rapid temperature drop after the laser is removed can effectively reduce the thermodynamic limitation of the carbon dioxide methanation reaction, realizing an efficient and stable carbon dioxide methanation process.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: In the first aspect of the present invention, there is provided an apparatus for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation, including a reactor, a laser and a galvanometer disposed above the reactor; a transparent cover plate is provided at the top of the reactor; an air outlet is provided on the side of the reactor; a carrier table is provided inside the reactor, and a catalyst layer is provided above the carrier table; gas inlet holes are provided in the catalyst layer, and the gas inlet holes longitudinally penetrate the catalyst layer; an air flow channel is provided inside the carrier table, one end of the air flow channel communicates with the gas inlet hole, and the other end of the air flow channel communicates with an air inlet.

[0006] Preferably, the galvanometer is directly above the cover plate; the cover plate is made of quartz; the cover plate is directly above the catalyst layer.

[0007] Preferably, the area of the cover plate is greater than or equal to the area of the catalyst layer; the galvanometer and the gas inlet hole are on the same central axis.

[0008] Preferably, the gas inlet hole is located at the center of the catalyst layer.

[0009] Preferably, the reactor is hermetically connected to the cover plate; the air outlets are evenly distributed on the side of the reactor.

[0010] In the second aspect of the present invention, there is provided a method for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation using the above apparatus, and the method is as follows: A mixed gas containing hydrogen and carbon dioxide is introduced into the air inlet of the reactor, the mixed gas enters the reactor through the air flow channel and the gas inlet hole, the laser emits a laser beam to the galvanometer, and the galvanometer changes the irradiation position of the laser beam to achieve periodic scanning irradiation of the catalyst layer through the cover plate, and the product gas collected at the air outlet is methane.

[0011] Preferably, in the mixed gas, the volume fraction ratio of hydrogen to carbon dioxide is 4:1; the gas hourly space velocity of the mixed gas is 50 - 250 L / g cat / h.

[0012] Preferably, the laser is emitted by a fiber laser with a wavelength of 1064 nm, the moving speed of the light spot is controlled by the galvanometer to be 10 - 500 mm / s, and the average output power of the laser is 5 - 20 W.

[0013] Preferably, the catalyst layer is obtained by physical mixing of nickel nanoparticles and cerium dioxide nanoparticles followed by powder pressing; the mass ratio of nickel nanoparticles to cerium dioxide nanoparticles is 1:5 - 2:1.

[0014] In the third aspect of the present invention, there is provided the application of the above method in any one of the following 1) - 3): 1) Improving the methane yield; 2) Improve the selectivity of methane; 3) Improve the conversion rate of carbon dioxide.

[0015] Advantages of the present invention: (1) The present invention utilizes the thermal effect generated by laser irradiation to generate a local temperature field on the catalyst surface, and realizes the periodic scanning of the laser beam through a galvanometer, so that the position of the local temperature field continuously moves, and then a forced and controllable temperature oscillation is generated at any catalytic site on the catalyst surface. The local high temperature generated by laser irradiation promotes the activation of carbon dioxide, and the temperature drop caused after the laser stops irradiation is beneficial to the subsequent intermediate hydrogenation reaction. The temperature oscillation induced by laser scanning effectively solves the thermodynamic conflict of carbon dioxide methanation through dual temperature regulation in time and space, improves the utilization efficiency of catalytic sites, significantly improves the yield of methane, and maintains a high methane selectivity.

[0016] (2) The catalyst used in the present invention does not require an additional cumbersome preparation process, and can be obtained only by uniformly mixing two raw materials, which greatly reduces the preparation cost of the catalyst and can be tableted.

[0017] (3) The central position of the catalyst used in the present invention has a pore structure, which serves as a gas inlet hole, enabling the reaction mixture gas to enter the reactor through the gas flow channel and the gas inlet hole. By designing the change of the pore structure of the catalyst, the gas flow direction is changed, so that the gas must pass through the catalyst to enter the reactor, increasing the contact between the gas and the catalyst.

[0018] (4) The present invention uses a low-power laser as the reaction source, with a simple device, a simple method, and low operating costs. Compared with traditional thermal catalytic equipment, it does not require high-temperature resistant and heat-insulating materials, does not require a high-pressure resistant chamber, and has high energy utilization efficiency, solving the problem of high energy consumption in traditional thermal catalysis. It is suitable for large-scale production. Description of the drawings

[0019] Figure 1 Schematic diagram of the device module for laser scanning-driven mobile-phase carbon dioxide methanation according to the present invention; wherein, 1 - laser, 2 - galvanometer, 3 - reactor, 4 - stage, 5 - catalyst layer, 6 - air inlet, 7 - air outlet, 8 - gas flow channel, 9 - gas inlet hole, 10 - cover plate; Figure 2 Schematic diagram of the gas flow direction in the device for laser scanning-driven mobile-phase carbon dioxide methanation according to the present invention; Figure 3 Temperature distribution diagram on the catalyst surface when the laser power is 5 W, the scanning path is circular, and the scanning rate is 100 mm / s; Figure 4It is a temperature fluctuation diagram of any point on the laser scanning path when the laser power is 5 W, the scanning path is circular, and the scanning speed is 100 mm / s. Figure 5 It is a schematic diagram of the reaction device of Comparative Example 4. Figure 6 It is a schematic diagram of the gas flow direction in the device when the inlet / outlet is distributed on both sides of the reactor. Figure 7 It is for the total energy efficiency and cost efficiency of laser-driven carbon dioxide methanation (5 W, circular path, scanning speed 100 mm / s) and thermal catalytic carbon dioxide methanation (450 °C) with the same mass of catalyst (30 mg) and gas flow rate of 50 L / g cat / h. In the figure, Laser catalysis refers to Example 1, and Thermal catalysis refers to Comparative Example 1. Detailed Description of the Invention

[0020] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0021] As introduced in the background art section, currently, the preparation of methane from hydrogen and carbon dioxide mainly uses biochemical methods or high-temperature heating methods. The equipment used in the biological method is relatively complex and the preparation cycle is long; the high-temperature heating in the chemical method requires a high amount of energy, but the preparation of methane from hydrogen and carbon dioxide is an exothermic reaction, and an increase in temperature will inhibit the thermodynamic equilibrium of the conversion of carbon dioxide to methane.

[0022] Based on this, the object of the present invention is to provide a device and method for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation. The present invention utilizes the thermal effect generated by laser irradiation to generate a local temperature field on the catalyst surface, and through a galvanometer, the laser beam is periodically scanned, so that the position of the local temperature field continuously moves, and then a forced and controllable temperature oscillation is generated at any catalytic site on the catalyst surface. The local high temperature generated by laser irradiation promotes the activation of carbon dioxide, and the temperature drop caused after the laser stops irradiation is beneficial to the subsequent hydrogenation reaction of the intermediate. The temperature oscillation induced by laser scanning effectively solves the thermodynamic conflict of carbon dioxide methanation through dual temperature regulation in time and space, improves the utilization efficiency of catalytic sites, significantly increases the methane yield, and maintains a high methane selectivity.

[0023] The present invention precisely regulates the heat generated by a laser in terms of both time and space to induce temperature oscillation, thereby promoting carbon dioxide methanation. 1. The laser emits a laser beam to a galvanometer scanner, and the galvanometer scanner changes the irradiation position of the laser beam to pass through a cover glass and irradiate a catalyst layer in a patterned periodic scan. This patterned periodic scan of the laser causes the position of the laser beam to continuously change, resulting in a rapid increase in temperature at the same position on the catalyst layer when irradiated by the laser and a rapid decrease when not irradiated by the laser, achieving temperature oscillation. Temperature oscillation can not only meet the activation process of carbon dioxide at a sufficient temperature but also avoid breaking the thermodynamic equilibrium, ultimately promoting carbon dioxide methanation. If the temperature during the reaction process remains high continuously, it is prone to trigger a side reaction, the reverse water-gas shift reaction: CO2 + H2 = CO + H2O, leading to the generation of a large amount of by-product CO. 2. The catalyst does not require an additional cumbersome preparation process, such as preparing a nickel / ceria composite material through complex chemical methods. It can be obtained simply by physically mixing two raw materials, greatly reducing the preparation cost of the catalyst, and can be tableted. Nickel and ceria play different roles in the method of promoting carbon dioxide methanation by laser scanning-induced temperature oscillation, and the appropriate ratio of the two can effectively drive the carbon dioxide methanation reaction with the assistance of the laser. After the catalyst is tableted, holes are drilled, enabling the reaction mixture gas to enter the reactor through an air flow channel and a gas inlet hole. By changing the direction of the gas flow through the holes drilled in the catalyst layer, the gas must pass through the catalyst to enter the reactor, increasing the contact between the gas and the catalyst. The above two aspects of the settings not only improve the conversion rate of raw materials but also reduce the occurrence of the side reaction, the reverse water-gas shift reaction: CO2 + H2 = CO + H2O, reduce the generation of CO, and improve the yield and selectivity of methane production. In addition, the setting of the laser scanning parameters in the present invention is very important. If the parameters are too high, the catalyst will be damaged; if the parameters are too low, it is not sufficient to cause temperature oscillation. In summary, the device and method of the present invention are both simple, with low operating costs. Compared with traditional thermal catalytic equipment, it does not require high-temperature resistant and heat-insulating materials, does not require a high-pressure resistant chamber, and has high energy utilization efficiency, solving the problem of high energy consumption of traditional thermal catalysis and being suitable for large-scale industrial production.

[0024] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0025] Note: The selectivity (S CH4 ) of methane in the present invention is calculated by the following formula: (1); Where CH 4 out is the volume of methane in the gas flowing out of the reactor, and CO out is the volume of carbon monoxide in the gas flowing out of the reactor.

[0026] The conversion rate (X CO2) The calculation formula is as follows: (2); Where CO 2 in is the volume of carbon dioxide entering the reactor, and CO 2 out is the volume of carbon dioxide flowing out of the reactor. Ar in is the volume of argon entering the reactor, and Ar out is the volume of argon flowing out of the reactor. Argon (Ar) is an inert gas and does not participate in the catalytic reaction. Adding argon as an internal standard can calibrate the volume change of the gas before and after the reaction.

[0027] The calculation formula for the yield is as follows: (3); Where GHSV is the gas hourly space velocity (mL g −1 h −1 ), C CO2 in is the concentration of carbon dioxide entering the reactor (%), X CO2 is the carbon dioxide conversion rate (the calculated value of formula (2)), S CH4 is the selectivity of methane in the product (the calculated value of formula (1)), and V m is the molar volume at a specific temperature (under the conditions of 0 °C and 101 kPa, 22.4 L mol −1 ).

[0028] The test materials used in the examples of the present invention are all conventional test materials in the art and can be obtained through commercial channels.

[0029] Example 1: Preparation of methane by laser (1) The device for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation is as Figure 1 shown. The reaction device includes a reactor 3, a laser 1 and a galvanometer 2 arranged above the reactor 3; a transparent cover plate 10 is provided at the top of the reactor 3; an air outlet 7 is provided on the side of the reactor 3; a carrier table 4 is provided inside the reactor, and a catalyst layer 5 is provided above the carrier table 4; a gas inlet hole 9 is provided in the catalyst layer 5, and the gas inlet hole 9 longitudinally penetrates the catalyst layer 5; an air flow channel 8 is provided inside the carrier table 4, one end of the air flow channel 8 is communicated with the gas inlet hole 9, and the other end of the air flow channel 8 is communicated with the air inlet 6.

[0030] The galvanometer 2 is located directly above the cover glass 10; the cover glass 10 is made of quartz; the cover glass 10 is located directly above the catalyst layer 5. The area of the cover glass 10 is greater than or equal to the area of the catalyst layer 5; the galvanometer 2 and the gas inlet hole 9 are on the same central axis. The gas inlet hole 9 is located at the center of the catalyst layer 5. The reactor 3 is hermetically connected to the cover glass 10; the gas outlet 7 is evenly distributed on the side of the reactor 3.

[0031] (2)Catalyst preparation: Physically mix nickel nanoparticles and cerium dioxide nanoparticles (particle size 50 - 200 nm) at a mass ratio of 1.5:1. Use a tablet press (Hefei Kejing, YLJ-24T) to press 30 mg of the mixed powder into a circular thin sheet (thickness about 0.25 mm), and drill a circular hole with a diameter of 1 mm at the center of the catalyst.

[0032] (3)Place the catalyst horizontally on the carrier stage inside the reactor, connect the gas inlet hole on the catalyst to the gas flow channel of the carrier stage, place the cover glass on the top of the reactor and seal it to make the inside of the reactor airtight.

[0033] (4)Pass flowing argon into the inlet of the reactor to clean the reactor for ten minutes.

[0034] (5)Pass a mixed gas of hydrogen, carbon dioxide and argon into the inlet of the reactor. The volume fraction of hydrogen is 76%, the volume fraction of carbon dioxide is 19%, and the volume fraction of argon is 5%. The gas flow rate is controlled at 50 L / g cat / h.

[0035] (6)Use a 1064 nm fiber laser to emit a laser beam, and control the laser beam to scan on the surface of the catalyst through a galvanometer. Set the laser equipment parameters as power 5 W, the scanning path as circular, and the scanning speed as 100 mm / s for laser-driven carbon dioxide methanation.

[0036] (7)Collect the gas generated by the reaction through the gas outlet, and analyze the methane yield and selectivity, etc. through gas chromatography.

[0037] At a gas hourly space velocity of 50 L / g cat / h and a laser scanning speed of 100 mm / s, the laser spot acts quickly on the surface of the catalyst. The temperature at the laser irradiation position rises rapidly, and the temperature in this area drops rapidly after the laser moves away. Eventually, a temperature field with a high-temperature area and an annular low-temperature area is formed on the surface of the catalyst ( Figure 2 ). The gas flows out of the central hole of the catalyst, passes through the temperature field formed by the laser, and then flows out of the reactor ( Figure 3). Since the scanning speed of the laser beam (100 mm / s) far exceeds the flow rate of the gas in the reactor (about 2 mm / s), the reaction gas passes through the heated / cooled catalyst multiple times ( Figure 4 ), and the carbon dioxide methanation reaction occurs.

[0038] Comparative Example 1: Preparation of methane by thermal catalysis According to the thermal catalysis carbon dioxide methanation performance test method reported in the literature "Eu 3+ doping-promoted Ni-CeO2 interaction for efficient low-temperature CO2 methanation" (Zhihe Zhang et al., Applied Catalysis B: Environmental 317 (2022) 121800): Place 30 mg of the catalyst sample in a fixed-bed quartz tube (inner diameter 6 mm). The reaction gas is a mixed gas of hydrogen and carbon dioxide. The volume fraction of hydrogen is 80%, and the volume fraction of carbon dioxide is 20%. The gas flow rate in the quartz tube is 50 L / g cat / h, and the thermal catalysis performance is tested at 450 °C. Collect the gas generated by the reaction through the outlet, and analyze the methane yield and selectivity by gas chromatography. At a constant temperature, it is not possible to simultaneously facilitate the activation of carbon dioxide and the hydrogenation reaction, so the methane yield is relatively low.

[0039] Comparative Example 2: Preparation of methane by laser with a low scanning speed The difference from Example 1 is that the scanning speed of the laser is 1 mm / s. At this scanning speed, the laser cannot form an effective temperature oscillation on the catalyst surface, which results in too high a temperature in the locally irradiated area, and the reverse water-gas shift reaction occurs, generating a large amount of carbon monoxide, while the temperature in the non-irradiated area is too low to effectively carry out the catalytic reaction, ultimately resulting in a low methane yield and selectivity.

[0040] Comparative Example 3: Preparation of methane by laser with a high scanning speed The difference from Example 1 is that the scanning speed of the laser is 3000 mm / s. At this scanning speed, the action time of the laser on the catalyst surface is too short to produce an obvious heating / cooling process, and the formed local temperature field has no obvious temperature fluctuation, resulting in a relatively low methane yield.

[0041] Comparative Example 4 The difference from Example 1 is that the reaction device is different. As Figure 5 shown, there is no hole in the center of the catalyst, and an inlet is provided at one end of the side of the reactor, and an outlet is provided at the other end. Methane is finally prepared.

[0042] As Figure 6 shown, the thermal catalytic carbon dioxide methanation reaction carried out in a fixed bed in Comparative Example 1 (reaction temperature: 450 °C, catalyst dosage: 30 mg, gas flow rate: 50 L / g cat / h) was compared with the laser catalytic carbon dioxide methanation reaction in Example 1. In addition, the methane yields, selectivities, etc. of Comparative Examples 2 to 4 were also compared. It can be seen that the method of Example 1 can obtain more methane with higher purity. In Comparative Example 1, the catalyst was in a temperature field with uniform and constant temperature distribution, and the CO2 activation process and hydrogenation process could not be taken into account at the same time, resulting in low CO2 methanation activity. In Comparative Example 2, the moving speed of the laser on the catalyst surface was too slow, and the formed temperature field was basically the same as that formed by the fixed laser. The too-high local temperature led to the occurrence of the reverse water-gas shift reaction, reducing the CH4 yield and selectivity. In Comparative Example 3, the moving speed of the laser on the catalyst surface was too fast, and it was unable to effectively form temperature oscillations on the catalyst surface. However, compared with Comparative Example 2, the distribution of the temperature field was changed, and the high-temperature area formed by the laser was reduced. Therefore, the measured CH4 yield and selectivity were better than those in Comparative Example 2. According to actual detection, the yield and selectivity of Comparative Example 3 were also higher than those of Comparative Example 1. In Comparative Example 4, the reaction gas flowed through the laser scanning area in a left-in and right-out manner. Compared with Example 1, the contact between the gas and the laser-induced temperature oscillation area was not sufficient enough, so the CH4 yield was lower than that in Example 1.

[0043] Compared with the methane yield (42 mmol / g / h) and selectivity (95%) of the thermal catalytic system in Comparative Example 1, the laser catalytic carbon dioxide methanation in Example 1 achieved a higher methane yield (331 mmol / g / h) and selectivity (98%). In addition, energy efficiency is also one of the key indicators of different carbon dioxide methanation catalytic systems, as Figure 7 shown. Compared with thermal catalysis (reaction temperature: 450 °C, catalyst dosage and gas hourly space velocity used were the same as those in the laser catalytic system of Example 1) and Comparative Example 1, the laser catalytic carbon dioxide methanation in Example 1 had higher energy efficiency (1.81×10 3 kJ / mmol) and more economical power cost efficiency (7.05 kWh / mmol), showing practical application prospects. In addition, from the perspective of production application, the price of industrial medium-power lasers is less than ten thousand US dollars, with high automation, easy adjustment, stable laser output performance, and long working life, generally up to more than one hundred thousand hours.

[0044] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A device for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation, characterized in that, It includes a reactor, a laser and a galvanometer scanner arranged above the reactor; a transparent cover plate is provided at the top of the reactor; an air outlet is provided on the side of the reactor; a stage is provided inside the reactor, and a catalyst layer is provided above the stage; gas inlet holes are provided in the catalyst layer, and the gas inlet holes longitudinally penetrate the catalyst layer; an air flow channel is provided inside the stage, one end of the air flow channel communicates with the gas inlet hole, and the other end of the air flow channel communicates with the air inlet.

2. The device according to claim 1, characterized in that, The galvanometer scanner is directly above the cover plate; the cover plate is made of quartz; the cover plate is directly above the catalyst layer.

3. The device according to claim 2, characterized in that, The area of the cover plate is greater than or equal to the area of the catalyst layer; the galvanometer scanner and the gas inlet hole are on the same central axis.

4. The device according to claim 3, wherein The gas inlet hole is located at the center of the catalyst layer.

5. The device according to claim 1, characterized in that, The reactor is hermetically connected to the cover plate; the air outlets are evenly distributed on the side of the reactor.

6. A method for promoting carbon dioxide methanation by laser scanning-induced temperature oscillation using the device according to claims 1 to 5, characterized in that, The method is as follows: A mixed gas containing hydrogen and carbon dioxide is introduced into the air inlet of the reactor. The mixed gas enters the reactor through the air flow channel and the gas inlet hole. The laser emits a laser beam to the galvanometer scanner. The galvanometer scanner changes the irradiation position of the laser beam and realizes periodic scanning and irradiation of the catalyst layer through the cover plate. The product gas is collected at the air outlet, which is methane.

7. The method according to claim 6, characterized in that, In the mixed gas, the volume fraction ratio of hydrogen to carbon dioxide is 4:1; the gas hourly space velocity of the mixed gas is 50 to 250 L / g cat / h.

8. The method according to claim 6, wherein The laser is emitted by a fiber laser with a wavelength of 1064 nm. The moving speed of the light spot is controlled by the galvanometer scanner to be 10 - 500 mm / s, and the average output power of the laser is 5 - 20 W.

9. The method according to claim 6, wherein The catalyst layer is obtained by powder pressing after physical mixing of nickel nanoparticles and cerium dioxide nanoparticles; the mass ratio of nickel nanoparticles to cerium dioxide nanoparticles is 1:5 - 2:

1.

10. Application of the method according to any one of claims 6 - 9 in any one of the following 1) - 3): 1) Improving the yield of methane; 2) Improving the selectivity of methane; 3) Improving the conversion rate of carbon dioxide.

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