Device and method for producing hydrogen by decomposing water at low temperature through microwave-assisted catalyst

Abstract

The invention discloses a device and a method for producing hydrogen through low-temperature decomposition of water by a microwave-assisted catalyst. The device comprises a microwave source for providing adjustable microwave power, a microwave decomposition water reactor for heating catalyst decomposition water, a nitrogen or argon source for replacing air and cooling, a generator for supplying water vapor, a gas system for treating hydrogen and a temperature monitoring system. The reactor is cooperated with the catalyst, so that the reaction rate and the hydrogen production efficiency are improved, low-power operation is realized, and the power does not exceed 40W / g and is only 6.7% of that of a traditional method; the reduction temperature is as low as 400 DEG C, which is 26.7% of that of the traditional method; the cycle period is short, and the average cycle time is 300 s and is only 50% of that of a traditional method. Low-temperature hydrogen production is assisted by microwave internal heating, so that the reaction energy consumption is reduced, the dependence on high-temperature equipment is reduced, and the operation cost is reduced; hydrogen and oxygen generation can be directionally controlled by adjustable parameters, and products can be adjusted as required; the device is high in component collaboration, stable in operation, suitable for different microwave reaction cavities and capable of flexibly meeting the hydrogen production requirement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microwave decomposition of water to produce hydrogen, and particularly relates to a device and method for microwave-assisted catalyst low-temperature decomposition of water to produce hydrogen. BACKGROUND

[0002] The global energy system still relies on fossil fuels such as coal, oil and natural gas. According to data from the International Energy Agency (IEA), in the past few decades, fossil fuels have accounted for more than 80% of the global primary energy consumption structure. The depletion of fossil fuels and the requirement for carbon emission reduction make the development of new energy imminent. Hydrogen, as an ideal clean energy, has only water as its combustion product and does not produce any greenhouse gases and pollutants, and is zero-pollution to the environment, and is a key energy carrier for achieving carbon neutrality. The use of catalysts to decompose water to produce green hydrogen has the advantages of no secondary pollution, abundant resources and the ability to combine with renewable energy, and has good development prospects.

[0003] Currently, hydrogen production technologies mainly include electrolysis of water to produce hydrogen, reforming of fossil fuels to produce hydrogen, and photocatalytic production of hydrogen. However, these traditional hydrogen production methods have many shortcomings.

[0004] Therefore, it is of great practical significance to develop a green hydrogen production technology that is low in energy consumption, small in pollution and high in hydrogen production efficiency.

[0005] Solar-driven two-step thermochemical water splitting has become an attractive green hydrogen production method, which can greatly improve the collection and conversion efficiency of solar energy. In the two-step thermochemical process, in the high-temperature (1300-1500℃) thermal reduction step, the oxygen exchange material is first decomposed into low-valence metal oxide and oxygen, and then in the water decomposition step at a lower temperature (≥800℃), which is an exothermic process, the low-valence metal oxide is re-oxidized to the original state by water in the hydrogen production process.

[0006] Microwave-driven thermochemical water splitting is based on the fact that when materials with different dielectric constants are subjected to a microwave field at the interface, electric charges will accumulate and redistribute at the interface, forming an interfacial polarization. This interfacial polarization will consume microwave energy and convert it into heat energy. Microwave technology can preferentially heat the reactants through this dielectric loss. Compared with traditional thermal reactors, direct microwave heating can promote rapid heating and cooling, which can effectively combine with intermittently generated renewable electricity to produce green fuels on demand.

[0007] Professor J.M. Serra and Professor J.M. Catalá Civera published a paper entitled "Enhanced Hydrogen Production in Microwave-Driven Water-Splitting Redox Cycles by Engineering Ceria Properties". Although this research improved the single hydrogen production effect by changing the doping elements, it required a microwave power of 40-45 w / g for each reaction, which was high in energy consumption. Moreover, the process of switching water vapor in and out during oxidation and reduction was time-consuming and labor-intensive, which was not conducive to industrialization.

[0008] Professor Satoshi Horikoshi and his research team at Sophia University in Japan used water / ethanol mixed solution for energy-saving thermal chemical steam reforming reaction, and the results showed that the maximum hydrogen production rate was slightly higher than 80%. The micro high temperature field (hot spot) generated by microwaves on the surface of magnetite was estimated to be about 760°C. Using magnetite (Fe3O4) as a microwave absorption heating element, hydrogen was produced at a low temperature of 350°C, but the core defect was that the reaction system must be matched with water / ethanol mixed solution (ethanol accounted for 10%-90%), which relied on alcohol sacrificial agent and still produced carbon emissions. Hydrogen could not be produced in pure water, which limited its application in alcohol-free scenarios. Long-term use could cause catalyst deactivation due to the attachment of ethanol decomposition products, and the stability was insufficient.

[0009] Ghassan Chehade published "Hydrogen production by microwave based plasma dissociation of water". This paper used microwave plasma technology to directly dissociate water vapor to produce hydrogen, without the need for catalysts, but had high energy consumption and low purity problems: 900W high power input was required, and the energy efficiency was only 53.7%; the hydrogen concentration was only 2500-8000ppm (about 0.25%-0.8%), which needed additional separation and purification; and the plasma generation depended on tungsten electrodes, which were easily evaporated and lost due to high temperature. The electrodes need to be replaced after several experiments, which is high in maintenance cost and cannot be continuously and stably operated.

[0010] CN117623219A discloses a microwave-induced high-efficiency low-temperature water cracking hydrogen production system, which uses microwave electromagnetic energy to induce high-efficiency low-temperature water cracking of solid oxides to produce hydrogen. However, the solid oxide reduction reaction requires continuous heating for 900±200 seconds. Even at reaction temperatures below 400℃, the total heating and reaction cycle is still too long, resulting in low energy transfer efficiency to the reaction system. Furthermore, the system integrates complex components such as a phased array antenna, electromagnetic shielding structure, and waste heat recovery pipelines, leading to a large overall size and complex structure. This makes miniaturization difficult and unsuitable for small-scale, space-constrained hydrogen production scenarios, limiting its application scope.

[0011] CN110155941A discloses a microwave-heated hydrogen production system, method, and application based on a thermochemical cycle. This patent requires continuous microwave heating of 500-800W for 180-200 seconds to reach a reaction temperature above 1500℃, resulting in high energy input, high energy consumption per unit time, and a prolonged heating phase, leading to low overall hydrogen production efficiency. Metal oxide reduction requires an ultra-high temperature environment of at least 1500℃, placing extremely high demands on equipment materials. After heating, the temperature needs to be cooled from above 1500℃ to 800-900℃, a lengthy cooling process. Furthermore, after introducing superheated steam, an additional 300-600 seconds of reaction time is required for hydrogen production. The entire cycle from heating start-up to final hydrogen production exceeds 500 seconds. While loading the catalyst onto silicon carbide ceramic foam increases the surface area, the ultra-high temperature of 1500℃ easily causes the porous structure of the ceramic foam to collapse and age, compromising the catalyst's loading stability and thus affecting its recyclability. Summary of the Invention

[0012] This invention provides an apparatus and method for low-temperature water splitting with microwave-assisted catalyst to produce hydrogen, thereby overcoming the above-mentioned problems.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows: The present invention provides an apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst, comprising a microwave source for providing stable, continuously adjustable microwave power; A microwave water splitting reactor is used to catalytically split water by heating an internal catalyst and producing gas. A gas source is used to introduce gas into the microwave water splitting reactor to replace the air inside the reactor and to lower the temperature of the catalyst. The gas source is nitrogen or argon.

[0014] A steam generator is used to provide stable reactants for the microwave water splitting reaction to produce hydrogen. A gas dehydration, detection and collection system is used for the detection and collection of hydrogen produced by a microwave water splitting reactor. A temperature monitoring system is used to monitor the real-time temperature of the reaction inside the microwave water splitting reactor.

[0015] Furthermore, the microwave source is connected to the microwave water splitting reactor via a coaxial cable, the gas source and the steam generator are respectively connected to the microwave water splitting reactor via pipelines, the gas dehydration, detection and collection system is connected to the microwave water splitting reactor via pipelines, and the outlet of the gas dehydration, detection and collection system is connected to the gas collector via two branches, one branch is connected to the oxygen collection system and the other branch is connected to the hydrogen collection system.

[0016] Furthermore, the microwave water splitting reactor includes a coaxial waveguide converter, a microwave reaction cavity, and a circulator, a coupler, and a three-pin mixer arranged sequentially from the microwave source to the microwave reaction cavity. The microwave reaction cavity is a resonant single-mode microwave reaction cavity or a standing wave multimode microwave reaction cavity. When the microwave reaction cavity is a resonant single-mode microwave reaction cavity, the side of the microwave source closest to the resonant single-mode microwave reaction cavity is connected to the circulator, and the side of the three-pin tuner furthest from the microwave source is connected to the coaxial waveguide converter. The resonant single-mode microwave reaction cavity is connected to the side of the coaxial waveguide converter furthest from the three-pin tuner via a coaxial cable. When the microwave reaction cavity is a standing wave multimode microwave reaction cavity, the microwave source is connected to the coaxial waveguide converter via a coaxial cable, and the circulator is connected to the side of the coaxial waveguide converter away from the microwave source; the standing wave multimode microwave reaction cavity is connected to the side of the three-pin tuner away from the coupler. The microwave reaction cavity has a built-in catalyst assembly. The bottom of the catalyst assembly has an air inlet for connecting to the gas source, and the top of the catalyst assembly has an air outlet for connecting to the gas dehydration, detection and collection system. The catalyst assembly also has a water vapor inlet for connecting to the water vapor generator. The temperature monitoring system is located outside the microwave reaction cavity to detect the temperature of the microwave catalytic reaction inside the microwave reaction cavity.

[0017] Furthermore, the catalyst is a metal oxide that has a microwave absorption effect and can undergo thermochemical cycling.

[0018] Furthermore, the catalyst is a cerium-based metal oxide or a perovskite oxide; The chemical formula of the cerium-based metal oxide is Co / Ce. m Me 1-m O 2-δ ; Me is selected from any one of the elements La, Gd, Nd, Er, and Yb; the range of m is 0.85 ≤ m ≤ 0.95.

[0019] Furthermore, the catalyst assembly includes a quartz tube, quartz wool, a sealing joint, and the catalyst. The quartz tube is fixed inside the microwave reaction cavity. The interior of the quartz tube is filled with and secured with two sections of quartz wool spaced apart vertically. The catalyst is fixed between the two sections of quartz wool. The sealing joint is provided at both the top and bottom of the quartz tube. The air inlet is located on the sealing joint at the top of the quartz tube, and the air outlet is located on the sealing joint at the bottom of the quartz tube. The water vapor inlet is located on the sealing joint at the bottom of the quartz tube.

[0020] Furthermore, a first valve is installed on the pipeline connecting the gas source and the steam generator to the microwave water decomposition reactor to control the on / off state of the inert gas and the on / off state of the steam in the pipeline, respectively. The outlet of the gas dehydration, detection and collection system is equipped with a second valve, which can control the on / off state of the two branches.

[0021] In another aspect, the present invention provides a method for producing hydrogen from water at low temperature using a microwave-assisted catalyst using the aforementioned microwave-assisted catalyst water splitting apparatus, the method comprising the following steps: (1) Fill the quartz tube with quartz wool, fill the quartz tube with catalyst, fill the quartz wool to fix the catalyst, and seal the joint tightly. (2) Place the quartz tube into the microwave reaction cavity of the microwave reaction system, connect the gas source and the gas dehydration, detection and collection system, check the air tightness of the catalyst assembly, and after there is no leakage, purge nitrogen or argon into the quartz tube. After keeping the quartz tube and pipeline full of nitrogen or argon, turn on the steam generator to pump steam into the quartz tube at a set rate. (3) Turn on the microwave source and input microwaves into the reaction chamber. After the catalyst absorbs the microwaves, it begins to heat up. The temperature monitoring system monitors the temperature change of the catalyst in the microwave reaction chamber in real time. (4) After the set reaction temperature is reached, the microwave input is turned off. The reaction products enter the gas dehydration, detection and collection system and pass through the dehydration device and online analysis device of the gas dehydration, detection and collection system in sequence. Finally, the gaseous products hydrogen and oxygen are collected in the collection device. The opening and closing of the first valve is adjusted according to the product analysis of the gas analysis system to regulate the gas source and the flow of reactants. The number of times the catalyst is cyclically reacted is adjusted by switching the opening and closing of the second valve to regulate the type of gaseous products.

[0022] Furthermore, in step (2), the flow rate of the nitrogen or argon gas used for purging is 10-500 mL / min, and the flow rate of the water vapor is 1%-5% of the flow rate of the nitrogen or argon gas.

[0023] Furthermore, the ratio of microwave power of the microwave source to the mass of the catalyst is 25-40 W / g, the microwave heating time is 10-120 s, and the reaction temperature is 380-600℃; after the reaction temperature reaches the set value, the time from turning off the microwave source to turning it on again is 50-150 s.

[0024] The beneficial effects of this invention are: (1) The device for low-temperature water splitting to produce hydrogen disclosed in this invention uses microwave-assisted catalyst. The microwave water splitting reactor and the catalyst work together to improve the water splitting reaction rate and hydrogen production efficiency, shorten the hydrogen production cycle, and achieve high hydrogen production efficiency under low temperature, low power and short hydrogen production cycle conditions. Compared with other microwave hydrogen production methods, it achieves low power (≤40W / g, which is 6.7% of the traditional method), minimum reduction temperature of 400℃ (which is 26.7% of the traditional method), and average single cycle of 300s (which is 50% of the traditional method). (2) This device provides stable and continuously adjustable microwave power by means of a microwave source. Combined with the internal heating characteristics of microwave, it can achieve hydrogen production by water decomposition under relatively mild low temperature conditions, which greatly reduces reaction energy consumption, reduces dependence on high temperature equipment, and reduces operating costs. (3) This device can directionally adjust the generation process of hydrogen and oxygen by adjusting microwave parameters and reaction conditions of thermochemical cycle, and can flexibly adjust the product output according to needs. (4) The components of this device are highly coordinated, the operation is stable and reliable, and it is compatible with different microwave reaction cavity types, which can flexibly meet the hydrogen production needs. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a microwave-assisted catalyst low-temperature water splitting device for hydrogen production disclosed in an embodiment of the present invention. Figure 1 (The microwave reaction cavity is a standing wave multimode microwave reaction cavity.) Figure 2 This is a schematic diagram of a microwave-assisted catalyst low-temperature water splitting device for hydrogen production disclosed in an embodiment of the present invention. Figure 2(The microwave reaction cavity is a resonant single-mode microwave reaction cavity.) Figure 3 This is a schematic diagram of the structure of a microwave-assisted catalyst low-temperature water splitting reactor for hydrogen production, as disclosed in an embodiment of the present invention. Figure 1 (The microwave reaction cavity is a resonant single-mode microwave reaction cavity.) Figure 4 This is a schematic diagram of the structure of a microwave-assisted catalyst low-temperature water splitting reactor for hydrogen production, as disclosed in an embodiment of the present invention. Figure 2 (The microwave reaction cavity is a standing wave multimode microwave reaction cavity.) Figure 5 This is a schematic diagram of the catalyst assembly of a microwave-assisted catalyst low-temperature water splitting hydrogen production device disclosed in an embodiment of the present invention. Figure 6 This is a comparison chart of hydrogen production in a single cycle for Examples 1-10 of the present invention; Figure 7 The reaction temperature and cycle time of Example 1 of this invention (catalyst is 1M%Co / Ce) 0.9 La 0.1 O 2-δ ) Result figure.

[0027] In the picture: 1. Microwave source; 2. Microwave water splitting reactor; 21. Coaxial waveguide converter; 22. Microwave reaction cavity; 23. Circulator; 24. Coupler; 25. Three-pin mixer; 26. Catalyst assembly; 261. Quartz tube; 262. Quartz wool; 263. Sealing joint; 264. Catalyst; 3. Gas source; 4. Gas dehydration, detection and collection system; 41. Dehydration device; 42. Online analysis device; 43. Collection device; 5. Temperature monitoring system; 6. Piping; 7. Steam generator; 8. Oxygen collection system; 9. Hydrogen collection system. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The principle involved in this invention: This invention provides a water splitting technology for hydrogen production at low reaction temperatures and low power, achieving precise control and reducing energy consumption.

[0030] Based on the thermochemical cycle theory, metal oxides undergo a reduction reaction after absorbing microwaves, and an oxidation reaction occurs after the microwaves are turned off. The thermochemical cycle reaction involves the following steps: 1. Effects of microwave energy Microwaves, as a type of high-frequency electromagnetic wave, possess excellent penetrability, enabling them to penetrate deep into the reaction system and interact with the molecules involved in the thermochemical cycle. During the thermochemical cycle, microwave energy is absorbed by the molecules and subsequently converted into their kinetic and internal energy, raising the system temperature and providing the necessary energy for subsequent thermochemical reactions, thus driving chemical changes in water molecules and other circulating substances.

[0031] 2. Activation of substances in thermochemical cycles Under the continuous action of microwave energy, specific substances involved in thermochemical cycles (such as metal oxides) are activated. Microwave energy intensifies the atomic or molecular motion of these substances, significantly enhancing their chemical activity and creating conditions for subsequent reactions with water molecules.

[0032] 3. The reaction process of water decomposition After the microwave is turned off, the system temperature decreases, and the reduced low-valence metal oxide still exhibits high chemical activity. At this point, it comes into contact with water, and the H₂ in the water... + The metal gains electrons from the lower-valence metal and is reduced to hydrogen atoms. These hydrogen atoms then combine to form H2 molecules and are released. Simultaneously, the lower-valence metal loses electrons and is oxidized to an initial higher-valence metal oxide, thus completing the regeneration of the metal oxide and achieving a thermochemical cycle. The transfer of electrons between the metal and hydrogen in the water is crucial in this process, driving the generation of hydrogen and the oxidative regeneration of the metal oxide.

[0033] 4. Recycling and product separation After one water splitting reaction is completed, the substances involved in the thermochemical cycle are regenerated, allowing them to participate in the next round of water splitting and thus achieving recycling. The hydrogen and oxygen produced in the reaction are generated at different reaction stages; therefore, they can be separated by controlling the valves in the gas collection system to obtain high-purity hydrogen and oxygen products.

[0034] The thermochemical cycle theory under microwave conditions utilizes the high-frequency electromagnetic field of microwaves to cause high-frequency vibration and frictional heat generation in metal oxide molecules, achieving internal heating and rapid temperature rise. This also reduces the activation energy of the reaction, making it more efficient than traditional external heating. This technology offers advantages such as cleanliness, environmental friendliness, energy saving, and emission reduction, and can be applied to multiple fields.

[0035] like Figures 1-5 The apparatus shown in this embodiment is a microwave-assisted catalyst for low-temperature water splitting to produce hydrogen, comprising: Microwave source 1 is used to provide stable and continuously adjustable microwave power; Microwave water splitting reactor 2 is used to split water by heating the catalyst 264 inside it and produce gas; Gas source 3 is used to introduce gas into microwave water splitting reactor 2 to replace the air in microwave water splitting reactor 2 and to reduce the temperature of catalyst 264 in microwave water splitting reactor 2; the gas source is nitrogen or argon.

[0036] Steam generator 7 is used to provide stable reactants (steam) for microwave water splitting to produce hydrogen. Gas dehydration, detection and collection system 4 is used to detect and collect hydrogen produced by microwave water splitting reactor 2; Temperature monitoring system 5 is used to monitor the real-time temperature of the reaction inside microwave water splitting reactor 2.

[0037] Preferably, the microwave source 1 is connected to the microwave water splitting reactor 2 via a coaxial cable, the gas source and the steam generator are respectively connected to the microwave water splitting reactor 2 via pipelines 6, the gas dehydration, detection and collection system 4 is connected to the microwave water splitting reactor 2 via pipelines, and the outlet of the gas dehydration, detection and collection system 4 is connected to a gas collector via two branches, one branch is connected to an oxygen collection system 8, and the other branch is connected to a hydrogen collection system 9. The coaxial cable connection between the microwave source and the microwave water splitting reactor ensures stable microwave energy transmission, reduces transmission loss, improves microwave-catalyst coupling efficiency, and guarantees system stability and reliability. The gas source and steam generator are independently connected to the reactor via pipelines, enabling precise delivery and independent control of the replacement gas and reactants, ensuring a clean reaction atmosphere and stable material supply. A branch of the gas dehydration, detection, and collection system connects to the oxygen-hydrogen collection system, enabling efficient product dehydration, precise detection, and oxygen-hydrogen separation and collection, avoiding safety hazards from mixed product storage, and improving the purity and collection flexibility of hydrogen and oxygen products. The overall connection method is simple and reasonable, with clear material and energy transmission paths, ensuring continuous and stable operation of the device and improving the controllability and practicality of the hydrogen production process.

[0038] Preferably, the microwave water splitting reactor 2 includes a coaxial waveguide converter 21, a microwave reaction cavity 22, and a circulator 23, a coupler 24, and a three-pin mixer 25 arranged sequentially from the microwave source 1 to the microwave reaction cavity 22. The microwave reaction cavity 22 is a resonant single-mode microwave reaction cavity or a standing wave multimode microwave reaction cavity. When the microwave reaction cavity 22 is a resonant single-mode microwave reaction cavity, the side of the microwave source 1 closest to the resonant single-mode microwave reaction cavity is connected to the circulator 23, and the side of the three-pin tuner 25 furthest from the microwave source 1 is connected to the coaxial waveguide converter 21. The resonant single-mode microwave reaction cavity is connected to the side of the coaxial waveguide converter 21 furthest from the three-pin tuner 25 via a coaxial cable. The circulator 23 is used for unidirectional transmission of microwaves output from the microwave source 1, blocking reflected waves to protect the microwave source 1. The coupler 24 is used to monitor the transmission power and reflected power of the microwaves transmitted through the circulator 23. The three-pin tuner 25 is used to adjust the impedance matching of the microwaves transmitted through the coupler 24 to reduce microwave loss. The coaxial waveguide converter 21 is used to convert waveguide transmission mode microwaves to coaxial transmission mode, adapting the coaxial cable and the reaction cavity impedance to ensure efficient microwave coupling. When the microwave reactive cavity 22 is a standing wave multimode microwave reactive cavity, the microwave source 1 is connected to the coaxial waveguide converter 21 via a coaxial cable, and the circulator 23 is connected to the side of the coaxial waveguide converter 21 away from the microwave source 1; the standing wave multimode microwave reactive cavity is connected to the side of the three-pin tuner 25 away from the coupler 24; the coaxial waveguide converter 21 is used to convert the coaxial transmission mode microwave output from the microwave source 1 into waveguide transmission mode and adapt it to the subsequent link impedance; the circulator 23 is used to unidirectionally transmit the microwave output from the coaxial waveguide converter 21, while blocking reflected waves to protect the microwave source 1; the coupler 24 is used to monitor the transmission power and reflected power of the microwave transmitted through the circulator 23; the three-pin tuner 25 is used to adjust the impedance matching of the microwave transmitted through the coupler 24 to improve the coupling efficiency between the microwave and the reactive cavity. Both connection configurations can better improve the coupling efficiency between the microwave and the reactive cavity.

[0039] The microwave reaction cavity 22 has a built-in catalyst assembly 26. The catalyst assembly 26 has an air inlet at the bottom for connection with the gas source, an air outlet at the top for connection with the gas dehydration, detection and collection system 4, and a water vapor inlet on the catalyst assembly 26 for connection with the water vapor generator. The temperature monitoring system 5 is located outside the microwave reaction cavity 22 to detect the microwave catalytic reaction temperature inside the microwave reaction cavity 22. The microwave transmission components are arranged sequentially in a specific direction to achieve unidirectional microwave transmission, power monitoring, and precise impedance matching, reducing microwave loss and protecting the microwave source, ensuring efficient and stable energy transmission. The two reaction cavities are adapted to different connection forms. The resonant single-mode cavity can concentrate the electric field to improve coupling efficiency. Its single-mode transmission characteristics can ensure that microwave energy is accurately applied to the reaction area and reduce ineffective energy consumption. The design of the standing wave multimode microwave cavity optimizes the electric field distribution, making the microwave energy uniformly distributed in the reactor, avoiding the hot spot problem existing in traditional multimode microwave cavities, and improving the uniformity and stability of the reaction. The multi-interface design of the catalyst assembly enables independent delivery of gas source and water vapor and directional product export, ensuring a clean reaction atmosphere and continuous material supply. The temperature monitoring system is located outside the reaction cavity to accurately detect the temperature inside the cavity in real time, which facilitates the control of the reaction process and further improves the controllability and reliability of the hydrogen production process.

[0040] Preferably, the catalyst 264 is a metal oxide with microwave absorption effect and thermochemical cycling capability. It can efficiently absorb microwave energy and quickly convert it into heat energy, accurately adapt to microwave-assisted reaction conditions, improve microwave energy utilization and reduce energy consumption. It can also stably participate in water splitting reaction through thermochemical cycling and be recycled, reducing catalyst loss and replacement costs. At the same time, it enhances catalytic activity under low temperature conditions, ensuring efficient and continuous hydrogen production reaction.

[0041] Preferably, the catalyst 264 is a cerium-based metal oxide or a perovskite oxide; The chemical formula of the cerium-based metal oxide is Co / Ce. m Me 1-m O 2-δ ; Me is selected from any one of the elements La, Gd, Nd, Er, and Yb; m ranges from 0.85 to 0.95; cerium-based metal oxides or perovskite oxides are selected as catalysts to adapt to microwave-assisted low-temperature hydrogen production conditions; cerium-based metal oxides, through element doping and Co modification, can effectively control the oxygen vacancy content, enhance microwave absorption performance and catalytic activity, and can also efficiently participate in water splitting reactions and be recycled, reducing catalyst loss and ensuring efficient and stable hydrogen production reactions.

[0042] Preferably, the catalyst assembly 26 includes a quartz tube 261, quartz wool 262, a sealing joint 263, and the catalyst 264. The quartz tube is fixed inside the microwave reaction chamber 22. The quartz tube is filled with and secured with two sections of quartz wool spaced apart vertically. The catalyst is fixed between the two sections of quartz wool. The sealing joint is provided at both the top and bottom of the quartz tube. The air inlet is located on the sealing joint at the top of the quartz tube, and the air outlet is located on the sealing joint at the bottom of the quartz tube. The water vapor inlet is located on the sealing joint at the bottom of the quartz tube. The catalyst assembly uses a quartz tube adapted to microwave conditions, which is high-temperature resistant and does not interfere with the microwave field distribution, ensuring a stable microwave catalytic environment. Two sections of quartz wool stabilize and limit the catalyst, preventing catalyst loss while ensuring smooth airflow and improving the contact efficiency between water vapor, gas source, and catalyst. Sealed joints effectively ensure the assembly's airtightness, preventing gas leakage and ensuring a clean reaction atmosphere and safe operation. The interface layout is reasonable, enabling orderly delivery of gas source and water vapor and directional product output. This assembly has a simple and reliable structure, low cost, and is suitable for the continuous and stable operation requirements of microwave-assisted low-temperature hydrogen production.

[0043] Preferably, a first valve is installed on the pipeline connecting the gas source and the steam generator to the microwave water decomposition reactor 2 to control the flow of inert gas and steam in the pipeline, respectively. The outlet of the gas dehydration, detection, and collection system 4 is equipped with a second valve, which can control the on / off state of the two branches. The valves on the pipelines enable independent on / off control of inert gas and water vapor, allowing for precise switching of material supply during the reaction stage and ensuring controllable reaction progress. The outlet branch valves can flexibly regulate the separation and collection of oxygen and hydrogen products, preventing product co-existence from causing safety hazards and improving the safety and flexibility of product collection. The design of each valve allows for precise control of material transmission at each stage of the device, enhancing the controllability and reliability of the device operation.

[0044] A method for producing hydrogen from water at low temperature using a microwave-assisted catalyst using the aforementioned microwave-assisted catalyst water splitting apparatus, the method comprising the following steps: (1) Fill the quartz tube with quartz wool, fill the quartz tube with catalyst, fill the quartz wool to fix the catalyst, and seal the joint tightly. (2) Place the quartz tube into the microwave reaction cavity 22 of the microwave reaction system, connect the gas source (inlet system) and the gas dehydration, detection and collection system 4 (outlet system), check the airtightness of the catalyst assembly 26, and after confirming that there is no leakage, purge nitrogen or argon into the quartz tube. After keeping the quartz tube and pipeline full of nitrogen or argon, turn on the steam generator to pump steam into the quartz tube at a set rate. The flow rate of the purging nitrogen or argon is 10-500 mL / min, and the flow rate of the steam is 1%-5% of the flow rate of the nitrogen or argon.

[0045] (3) Turn on microwave source 1 and input microwaves into the reaction chamber. After the catalyst absorbs the microwaves, it begins to heat up. The temperature monitoring system 5 monitors the temperature change of the catalyst in the microwave reaction chamber 22 in real time. The temperature monitoring system is an infrared thermometer, which is set outside the quartz tube at the position corresponding to the catalyst. The ratio of microwave power of microwave source 1 to the mass of the catalyst is 25-40W / g, the microwave heating time is 10-120s, and the reaction temperature is 380-600℃. After the reaction temperature reaches the set value, the time from turning off microwave source 1 to turning it on again is 50-150s. The purge flow rate and the appropriate water vapor flow rate ratio can achieve precise material ratio supply. The optimized setting of parameters such as microwave power to catalyst mass ratio, heating time, and reaction temperature, combined with the natural cooling interval after the microwave is turned off, not only enhances the microwave absorption and catalytic activity of the catalyst and ensures the hydrogen production effect, but also avoids overheating and deactivation and reduces energy consumption.

[0046] (4) After the set reaction temperature is reached, the microwave input is turned off, and the reaction products enter the gas dehydration, detection and collection system 4 and pass through the dehydration device 41 (the dehydration device is a condenser) and the online analysis device 42 (the online analysis device can be an online gas chromatograph, GC, used to detect the type of products, gas concentration and other data) in sequence. Finally, the gaseous products hydrogen and oxygen are passed into the collection device 43 and collected. The opening and closing of the first valve is adjusted according to the product analysis of the gas analysis system to regulate the gas source and the flow of reactants, and the number of times the catalyst is circulated is adjusted by switching the opening and closing of the second valve to regulate the type of gaseous products (the product analysis includes the product type and product content, the product type is the hydrogen (H2) and oxygen (O2) generated by the reaction; the product content is the volume fraction or molar concentration of hydrogen and oxygen).

[0047] This device is also equipped with conventional devices such as temperature sensors and pressure sensors to measure conventional data such as temperature and pressure. At the same time, this device can be equipped with a controller to intelligently control the various components of the device and analyze the detected product data to determine whether it meets the standard value and then adjust the components accordingly. The temperature sensors, pressure sensors and controllers mentioned are all conventional settings and are not the inventive points of this solution. Therefore, more specific detection principles, equipment control and analysis and judgment logic will not be described in this document.

[0048] Example 1 The microwave reaction cavity is a multimode microwave reaction cavity, with a microwave frequency of 2.45 GHz and a microwave power of 30 W / g catalyst. In this embodiment, a microwave-coupled catalyst of 1 M% Co / Ce is used. m La1-m O 2-δ Hydrogen is produced by the water splitting reaction (m is 0.9, δ represents the natural number of non-stoichiometric vacancies of oxygen).

[0049] Place 3g of catalyst into a quartz tube with an inner diameter of 13mm, and fix the catalyst inside the quartz tube with quartz wool. Place the quartz tube in a microwave reaction chamber, and purge nitrogen gas at a flow rate of 60mL / min for 2 minutes. Expel the air from the tube and check for airtightness, keeping the tube filled with nitrogen. After the air is completely expelled, purge water vapor at a flow rate of 5% nitrogen. Open the branch valve of the oxygen collection system. Turn on the microwave power supply. After the catalyst absorbs the microwave, it begins to heat up. Monitor the catalyst temperature change in real time using an infrared thermometer at the axial section of the quartz tube. After reaching the set reaction temperature of 500℃ in about 10 seconds, turn off the microwave. During the reaction, after the oxygen has been collected, close the branch valve of the oxygen collection system and open the branch valve of the hydrogen collection system until the hydrogen has been collected.

[0050] Example 2 The difference between this embodiment and Embodiment 1 is that in this embodiment, the microwave power is adjusted to 32W / g catalyst.

[0051] Example 3 The difference between this embodiment and Embodiment 1 is that in this embodiment, the microwave power is adjusted to 34 W / g catalyst.

[0052] Example 4 The difference between this embodiment and Embodiment 1 is that in this embodiment, the water vapor flow rate is adjusted to 1% nitrogen.

[0053] Example 5 The difference between this embodiment and Embodiment 1 is that in this embodiment, the water vapor flow rate is adjusted to 3% nitrogen.

[0054] Example 6 The difference between this embodiment and Embodiment 1 is that in this embodiment, the nitrogen flow rate is adjusted to 100 mL / min.

[0055] Example 7 The difference between this embodiment and Embodiment 1 is that in this embodiment, the set temperature is adjusted to 400°C.

[0056] Example 8 The difference between this embodiment and Embodiment 1 is that in this embodiment, the set temperature is adjusted to 600°C.

[0057] Example 9 The difference between this embodiment and Embodiment 1 is that the amount of catalyst used is reduced to 1g in this embodiment.

[0058] Example 10 The difference between this embodiment and Embodiment 1 is that the amount of catalyst used is reduced to 2g in this embodiment.

[0059] like Figure 6 The figure shown is a comparison of hydrogen production in a single cycle of this device under the conditions of Examples 1-10 of the present invention. Figure 6 It can be seen that different process parameters have a significant impact on the hydrogen production per cycle. Increasing the microwave power (Examples 1-3) can improve the hydrogen production, with Example 3 (34W / g catalyst) achieving the highest hydrogen production of 220.1 mL / cycle. The water vapor flow rate is preferably 5% of the nitrogen flow rate (Examples 1-3), while decreasing the flow rate (Examples 4-5) will reduce the hydrogen production. The hydrogen production effect at a reaction temperature of 500℃ (Example 1) is better than that at 400℃ (Example 7) and 600℃ (Example 8). Excessive nitrogen flow rate (Example 6) and reduced catalyst dosage (Examples 9-10) will both reduce the hydrogen production. This indicates that the device has better hydrogen production performance under the parameter combination of 34W / g catalyst power, 500℃, 5% water vapor flow rate, 60 mL / min nitrogen flow rate, and 3g catalyst dosage.

[0060] Figure 7 The reaction temperature and cycle time results for Example 1 of the present invention are derived from... Figure 7 As can be seen, in Example 1, the reaction temperature rises rapidly after the microwave is turned on, with a minimum reduction temperature of only 400°C, which is only 26.7% of that of the traditional method, significantly lowering the reaction temperature threshold. The average cycle time (including the microwave start-stop phase) is 300 seconds, which is only 50% of that of the traditional method, resulting in a significant improvement in cycle efficiency. Simultaneously, the hydrogen flow rate fluctuates regularly with the microwave start-stop, synchronized with temperature changes, demonstrating good adaptability between the reaction process and microwave control. This further highlights the advantages of this device and method in terms of cooling and efficiency improvement.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst, characterized in that, include A microwave source (1) is used to provide stable and continuously adjustable microwave power; A microwave water splitting reactor (2) is used to catalytically split water by heating a catalyst (264) inside it and to produce gas; Gas source (3) is used to introduce gas into microwave water splitting reactor (2) to replace the air in microwave water splitting reactor (2) and to reduce the temperature of catalyst (264) in microwave water splitting reactor (2); A steam generator (7) is used to provide stable reactants for the microwave water splitting reaction to produce hydrogen; A gas dehydration, detection and collection system (4) is used to detect and collect hydrogen produced by the microwave water splitting reactor (2); Temperature monitoring system (5) is used to monitor the real-time temperature of the reaction inside the microwave water splitting reactor (2).

2. The apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst according to claim 1, characterized in that, The microwave source (1) is connected to the microwave water decomposition reactor (2) via a coaxial cable. The gas source and the steam generator are connected to the microwave water decomposition reactor (2) via pipes (6). The gas dehydration, detection and collection system (4) is connected to the microwave water decomposition reactor (2) via pipes. The outlet of the gas dehydration, detection and collection system (4) is connected to the gas collector via two branches. One branch is connected to the oxygen collection system (8), and the other branch is connected to the hydrogen collection system (9).

3. The apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst according to claim 2, characterized in that, The microwave water splitting reactor (2) includes a coaxial waveguide converter (21), a microwave reaction cavity (22), and a circulator (23), a coupler (24), and a three-pin mixer (25) arranged sequentially from the microwave source (1) to the microwave reaction cavity (22). The microwave reaction cavity (22) is a resonant single-mode microwave reaction cavity or a standing wave multimode microwave reaction cavity; When the microwave reaction cavity (22) is a resonant single-mode microwave reaction cavity, the microwave source (1) is connected to the circulator (23) on the side close to the resonant single-mode microwave reaction cavity, and the three-pin tuner (25) is connected to the coaxial waveguide converter (21) on the side away from the microwave source (1). The resonant single-mode microwave reaction cavity is connected to the side of the coaxial waveguide converter (21) away from the three-pin tuner (25) via a coaxial cable. When the microwave reaction cavity (22) is a standing wave multimode microwave reaction cavity, the microwave source (1) is connected to the coaxial waveguide converter (21) via a coaxial cable, and the circulator (23) is connected to the side of the coaxial waveguide converter (21) away from the microwave source (1); the standing wave multimode microwave reaction cavity is connected to the side of the three-pin tuner (25) away from the coupler (24); The microwave reaction cavity (22) has a built-in catalyst assembly (26). The bottom of the catalyst assembly (26) is provided with an air inlet for connecting to the gas source. The top of the catalyst assembly (26) is provided with an air outlet for connecting to the gas dehydration, detection and collection system (4). The catalyst assembly (26) is also provided with a steam inlet for connecting to the steam generator. The temperature monitoring system (5) is located outside the microwave reaction cavity (22) to detect the microwave catalytic reaction temperature inside the microwave reaction cavity (22).

4. The apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst according to claim 1, characterized in that, The catalyst (264) is a metal oxide that has a microwave absorption effect and can undergo thermochemical cycling.

5. The apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst according to claim 4, characterized in that, The catalyst (264) is a cerium-based metal oxide or a perovskite oxide; The chemical formula of the cerium-based metal oxide is Co / Ce. m Me 1-m O 2-δ ; Me is selected from any one of the elements La, Gd, Nd, Er, and Yb; the range of m is 0.85 ≤ m ≤ 0.

95.

6. The apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst according to claim 3, characterized in that, The catalyst assembly (26) includes a quartz tube (261), quartz wool (262), a sealing joint (263), and the catalyst (264). The quartz tube is fixed inside the microwave reaction cavity (22). The quartz tube is filled with two sections of quartz wool spaced apart vertically. The catalyst is fixed between the two sections of quartz wool. The sealing joint is provided at the top and bottom of the quartz tube. The air inlet is located on the sealing joint at the top of the quartz tube, and the air outlet is located on the sealing joint at the bottom of the quartz tube. The water vapor inlet is located on the sealing joint at the bottom of the quartz tube.

7. The apparatus for low-temperature water splitting to produce hydrogen using a microwave-assisted catalyst according to claim 2, characterized in that, The first valve installed on the pipeline connecting the gas source (3) and the steam generator (7) to the microwave water decomposition reactor (2) is used to control the flow of inert gas and steam in the pipeline respectively. The outlet of the gas dehydration, detection and collection system (4) is provided with a second valve, which can control the on / off state of the two branches.

8. A method for producing hydrogen from water by low-temperature microwave-assisted catalyst using the apparatus for low-temperature water splitting with a microwave-assisted catalyst as described in claim 6, characterized in that, The method includes the following steps: (1) Fill the quartz tube with quartz wool, fill the quartz tube with catalyst, fill the quartz wool to fix the catalyst, and seal the joint tightly. (2) Place the quartz tube into the microwave reaction cavity (22) of the microwave reaction system, connect the gas source and the gas dehydration, detection and collection system (4), check the air tightness of the catalyst assembly (26), and after there is no leakage, purge nitrogen or argon into the quartz tube. After keeping the quartz tube and pipeline full of nitrogen or argon, turn on the steam generator to pump steam into the quartz tube at a set rate. (3) Turn on the microwave source (1) and input microwaves into the reaction chamber. After the catalyst absorbs the microwaves, it begins to heat up. The temperature monitoring system (5) monitors the temperature change of the catalyst in the microwave reaction chamber (22) in real time. (4) After the set reaction temperature is reached, the microwave input is turned off, and the reaction products enter the gas dehydration, detection and collection system (4) and pass through the dehydration device (41) and online analysis device (42) of the gas dehydration, detection and collection system (4) in sequence. Finally, the gaseous products hydrogen and oxygen are collected in the collection device (43). The opening and closing of the first valve is adjusted according to the product analysis of the gas analysis system to regulate the gas source and the flow of reactants, and the number of times the catalyst is cyclically reacted is adjusted by switching the opening and closing of the second valve to regulate the type of gaseous products.

9. The method for producing hydrogen from water by low-temperature microwave-assisted catalyst decomposition according to claim 8, characterized in that, In step (2), the flow rate of nitrogen or argon gas during purging is 10-500 mL / min, and the flow rate of water vapor is 1%-5% of the flow rate of nitrogen or argon gas.

10. The method for producing hydrogen from water by low-temperature microwave-assisted catalyst decomposition according to claim 8, characterized in that, The microwave power of the microwave source (1) is 25-40W / g in ratio to the mass of the catalyst, the microwave heating time is 10-120s, and the reaction temperature is 380-600℃. After the reaction temperature reaches the set value, the time from turning off the microwave source (1) to turning it on again is 50-150s.

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