Carbon dioxide cracking device and cracking method

Abstract

The invention relates to the technical field of carbon dioxide cracking, in particular to a carbon dioxide cracking device and method, and the cracking device is sequentially provided with a microwave discharge unit, a catalysis unit and a molten salt cracking unit from top to bottom; the microwave discharge unit comprises a shell, the shell is sequentially provided with a coaxial resonant cavity and a cylindrical resonant cavity from top to bottom, and a microwave generator is arranged on the side face of the cylindrical resonant cavity; the catalysis unit comprises a plasma cavity and a catalyst layer which are sequentially arranged from top to bottom; wherein the plasma cavity is communicated with the cylindrical resonant cavity; the fused salt cracking unit comprises a container communicated with the bottom of the catalyst layer, and a sealing plate for dividing the interior of the container into an upper space and a lower space is fixed in the container; a fused salt layer is arranged in the lower space, and the bottom end of the gas guide pipe is located in fused salt; the technology of synergistic microwave discharge, chemical catalysis, high-temperature molten salt catalytic cracking and the like is adopted, carbon dioxide can be efficiently converted into a nano carbon material with a high additional value, the reaction speed is high, the cracking effect is good, and the yield is high.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide cracking, and in particular to a carbon dioxide cracking device and a cracking method. Background Art

[0002] CO2 is the most important greenhouse gas. Carbon capture and utilization (CCUS) technology can effectively reduce the amount of CO2 emitted from industrial sources entering the atmosphere, thereby mitigating global warming and reducing the risks of extreme weather, sea level rise, and other environmental issues caused by climate change. It can also maintain ecosystem stability, protect biodiversity, and promote the health and sustainability of ecosystems. The development of CO2 capture and utilization technology will drive the transformation and upgrading of related industries. Traditional high-carbon emission sectors, such as energy, chemicals, and steel, can reduce carbon emission intensity through the adoption of CCUS, improving their competitiveness and sustainable development capabilities. It will also help foster the emergence of new industries and economic growth drivers. After capture, CO2 is converted into economically valuable products, such as chemicals, fuels, and building materials, achieving resource recycling, creating additional economic benefits for businesses, improving resource utilization efficiency, and reducing costs.

[0003] Currently, technologies related to the use of plasma to convert carbon dioxide include Mao Zongqiang et al. (CN215249587U), which uses H2 and carbon dioxide as reaction raw materials to catalytically produce methane, and then performs high-temperature cracking on the produced methane to produce hydrogen and solid carbon fuel. This method involves two processes: carbon dioxide methanation and methane cracking. The process is complex, the cost is high, and it is difficult to apply in industrial fields. Wu Angjian et al. (CN115364791A) uses photovoltaic power generation to drive low-temperature plasma to achieve the co-activation conversion of carbon dioxide and H2, but the carbon dioxide conversion rate is low. Zhao Songjian et al. (CN116588935A) uses low-temperature plasma coupled with bismuth-based MOF catalysts to reduce carbon dioxide, but the carbon dioxide conversion rate is low and the process is complex.

[0004] From the above, we can see that the current carbon dioxide cracking still has problems such as low efficiency and high cost.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a carbon dioxide cracking device and cracking method, which adopts the technologies of synergistic microwave discharge, chemical catalysis and high-temperature molten salt catalytic cracking, and can efficiently convert the greenhouse gas carbon dioxide into high-value-added nanocarbon materials with fast reaction speed, good cracking effect and high yield.

[0007] The first object of the present invention is to provide a carbon dioxide cracking device, which is provided with a microwave discharge unit, a catalytic unit and a molten salt cracking unit in order from top to bottom; The microwave discharge unit includes a shell, which is provided with a coaxial resonant cavity and a cylindrical resonant cavity from top to bottom, and a microwave generator is provided on the side of the cylindrical resonant cavity; The catalytic unit includes a plasma cavity and a catalyst layer arranged in sequence from top to bottom; wherein the plasma cavity is connected to the cylindrical resonant cavity; The molten salt cracking unit includes a container connected to the bottom of the catalyst layer, a sealing plate is fixed in the container to divide the interior of the container into an upper space and a lower space, and the upper space and the lower space are connected by a gas conduit; A molten salt layer is provided in the lower space, and the bottom end of the gas conduit is in the molten salt.

[0008] As a preferred solution of the present invention, the bottom of the coaxial resonant cavity is in the shape of a pointed probe.

[0009] As a preferred solution of the present invention, the axis of the coaxial resonant cavity is perpendicular to the axis of the cylindrical resonant cavity.

[0010] As a preferred embodiment of the present invention, the catalyst layer is based on nickel foam and loaded with 5-10% of at most two transition metals.

[0011] As a preferred embodiment of the present invention, the molten salt is one of NaCl and NaBr, and the molten salt contains 5-10 wt % of Cu-Bi or Ni-Bi alloy particles.

[0012] As a preferred embodiment of the present invention, the cracking device further comprises a separation unit and a collection unit, and the molten salt circulates between the separation unit and the container; Carbon dioxide is blown into the separation unit to make the nanocarbon in the molten salt flow to the collection unit, and the collection unit is used to separate the carbon dioxide and the nanocarbon.

[0013] As a preferred embodiment of the present invention, it further comprises an oxygen screening unit, and the gas in the lower space flows through the oxygen screening unit and then communicates with the coaxial resonant cavity; The oxygen screening unit includes a ceramic ion conductive membrane with a thickness of 20-30 μm and an oxygen permeability of 3-5 mL·cm -2 min -1 .

[0014] As a preferred embodiment of the present invention, the cracking device further comprises a heating unit, the heating unit comprises a storage tank 1 and a storage tank 2, and the molten salt flows in the storage tank 1, the storage tank 2 and the container; The heating unit further includes a heat collector and a photovoltaic module for supplying heat energy to the heat collector.

[0015] As a preferred solution of the present invention, a flow disturbance device is provided between the cylindrical resonant cavity and the plasma cavity.

[0016] The second object of the present invention is to provide a carbon dioxide cracking method, comprising: subjecting carbon dioxide to microwave discharge, chemical catalysis and molten salt heating treatment in sequence, so as to crack the carbon dioxide into nanocarbon and oxygen.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The cracking device of the present invention adopts the technology of synergistic microwave discharge, chemical catalysis and high-temperature molten salt catalytic cracking, which can efficiently convert greenhouse gas carbon dioxide into high-value-added nanocarbon materials with fast reaction speed, good cracking effect, high purity of nanocarbon and large output; (2) Combining microwave discharge primary carbon dioxide cracking, foam nickel catalytic carbon dioxide cracking and high-temperature molten salt deep cracking, effectively utilizing the active particles generated by microwave discharge to enhance the catalytic reduction of foam nickel, while promoting the cracking of high-temperature molten salt, to achieve complete, efficient and rapid cracking of carbon dioxide; (3) In the cracking device of the present invention, the O generated by the cracking of carbon dioxide by plasma is captured by the oxygen vacancies in the foam nickel catalyst, or the carbon dioxide is adsorbed by the foam nickel catalyst and the O migrates to the oxygen vacancies, thereby releasing oxygen and promoting the generation of CO. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a structural diagram of the separation unit, the air intake pump, and the collection unit; Figure 3 It is a structural diagram of the molten salt heating unit; Figure 4 1 is a schematic diagram of the structure of the spoiler; Markings in the accompanying drawings: 1. Carbon dioxide inlet; 2. Microwave discharge unit; 3. Coaxial resonant cavity; 4. Cylindrical resonant cavity; 5. Microwave generator; 6. Catalytic unit; 7. Turbine device; 8. Plasma cavity; 9. Catalyst layer; 10. Molten salt cracking unit; 11. Gas duct; 12. Sealing plate; 13. Molten salt layer; 14. Separation unit; 15. Circulation pump; 16. Valve; 17. Oxygen outlet; 18. Oxygen screening unit; 19. Air intake pump; 20. Molten salt inlet; 21. Molten salt outlet; 22. Collection unit; 23. Carbon dioxide outlet; 24. Storage tank one; 25. Collector; 26. Photovoltaic module; 27. Storage tank two. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0020] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0022] Example 1: Reference Figure 1 , this embodiment provides a carbon dioxide cracking device, which is provided with a microwave discharge unit 2, a catalytic unit 6 and a molten salt cracking unit 10 in sequence from top to bottom; The microwave discharge unit 2 includes a housing, on which a coaxial resonant cavity 3 and a cylindrical resonant cavity 4 are sequentially arranged from top to bottom, and a microwave generator 5 is arranged on the side of the cylindrical resonant cavity 4; More specifically, the top of the coaxial resonant cavity 3 is connected to a carbon dioxide inlet 1, and the housing is coaxially arranged with the coaxial resonant cavity 3. The cylindrical resonant cavity 4 is a hollow cylindrical structure, and a microwave generator 5 is installed on the side, which is connected to the coaxial resonant cavity 3 to form a discharge area. The power of the microwave generator 5 is 200-300W. The energy density in this power range is highly matched with the chemical bond energy of the CO2 molecule (about 750kJ / mol): below 200W, the electric field strength is insufficient to effectively ionize the CO2 molecules, resulting in a sharp drop in cracking efficiency; above 300W, it is easy to cause local overheating, resulting in energy waste and accelerated equipment loss. The catalytic unit 6 includes a plasma chamber 8 and a catalyst layer 9 arranged in sequence from top to bottom; the plasma chamber 8 is connected to the cylindrical resonant cavity 4; more specifically, the plasma chamber 8 is a conical structure with an insulation layer and a heating layer provided on the outside. The narrow upper end and wide lower end of the plasma chamber 8 can guide the airflow to gradually diffuse, expand the contact area between the gas and the catalyst layer 9, and at the same time extend the path of the airflow in the chamber, so that the CO2 can fully interact with the active sites on the catalyst surface; The molten salt cracking unit 10 includes a container connected to the bottom of the catalyst layer 9. A sealing plate 12 is fixed in the container to divide the interior of the container into an upper space and a lower space. The upper space and the lower space are connected by a gas conduit 11. More specifically, the gas conduit 11 is made of Al2O3, has a hollow structure, and an inner diameter of 1-3mm. Its bottom end extends 1-2cm into the high-temperature molten salt. There are multiple gas conduits 11, which are evenly arranged on the sealing plate 12. A molten salt layer 13 is provided in the lower space, and the bottom end of the gas conduit 11 is in the molten salt; The specific working process of this device is as follows: CO2 is injected from the carbon dioxide inlet 1 at the top of the coaxial resonant cavity 3 of the microwave discharge unit 2, and the microwave generator 5 excites the cylindrical resonant cavity 4 with a power of 200-300W to form a discharge area, so that the CO2 is initially cracked into active particles such as CO and O. The gas after microwave discharge enters the conical plasma cavity 8 (temperature 400-500℃) of the catalytic unit 6. Since the plasma cavity 8 is a conical structure, the airflow diffuses outward, reducing the gas flow rate, thereby extending the contact time with the catalyst layer 9. CO2 is further decomposed into CO and O2 under the catalytic action. The catalyzed gas enters the upper space of the molten salt cracking unit 10, and bubbles into the molten salt layer 13 at 700-800℃ through the Al2O3 gas duct 11. CO2 and CO are deeply cracked under the action of the high-temperature molten salt layer 13 to generate nanocarbon and O2, realizing efficient conversion of CO2.

[0023] In some embodiments of the present invention, reference Figure 1 , the bottom of the coaxial resonant cavity 3 is in the shape of a pointed probe; more specifically, the bottom of the coaxial resonant cavity 3 is in the shape of a pointed probe because the tip discharge principle is used to form a strong electric field concentration area, which significantly reduces the ionization threshold of CO2 molecules under a microwave power of 200-300W, making it easier to excite plasma.

[0024] In some embodiments of the present invention, reference Figure 1 The axis of the coaxial resonant cavity 3 is perpendicular to the axis of the cylindrical resonant cavity 4; more specifically, the coaxial resonant cavity 3 is arranged vertically and the cylindrical resonant cavity 4 is arranged horizontally. After CO2 is vertically injected from the top of the vertical coaxial resonant cavity 3, it enters the horizontal cylindrical resonant cavity 4 through the bottom tip probe. At this time, the vertical airflow and the horizontal microwave field form a right-angle interaction, forcing the gas to perform a spiral motion in the cylindrical resonant cavity 4, significantly extending the actual path of the gas in the discharge area and prolonging the residence time; at the same time, the microwave forms a transverse standing wave in the horizontal cavity, which is superimposed with the vertical electric field gradient to excite a stable elliptical discharge area around the tip probe, greatly increasing the collision frequency of CO2 molecules and plasma, improving the initial cracking rate, and providing a high concentration of active particles for the subsequent catalytic unit 6.

[0025] In some embodiments of the present invention, the catalyst layer 9 is based on nickel foam and is loaded with 5-10% of at most two transition metals; for example, the transition metals are Cu, Fe, Mn, etc. The unique three-dimensional porous network structure of nickel foam can provide abundant surface adsorption sites, and its interconnected pore structure can promote the diffusion and retention of CO2 gas inside the catalyst, so that the gas molecules are in full contact with the transition metals. The introduction of transition metals can change the charge distribution of CO2 molecules through the electron orbital hybridization effect, weakening the strength of their intramolecular chemical bonds, and limiting the number of transition metals to at most two avoids complex interactions between multiple components, ensuring efficient utilization of catalytic active sites.

[0026] Furthermore, the temperature of the plasma chamber 8 is at 400-500°C; the temperature of the plasma chamber 8 is controlled at 400-500°C, which can not only activate the active sites on the catalyst surface through thermal energy and enhance the chemical adsorption and dissociation ability of CO2, but also avoid excessively high temperature causing metal particle agglomeration and inactivation or a significant increase in energy consumption. The synergistic effect of the two enables the catalyst to efficiently promote the conversion of CO2 into CO, O2 and nanocarbon precursors in a suitable thermodynamic environment, thereby improving the overall cracking efficiency.

[0027] In some embodiments of the present invention, the molten salt is one of NaCl and NaBr, and the molten salt contains 5-10wt% of Cu-Bi or Ni-Bi alloy particles, wherein the alloy particles have a particle size of 50-100 mesh and the molten salt temperature is 700-800°C; more specifically, NaCl or NaBr is selected as the molten salt because their melting points are 801°C and 747°C, respectively, and they are in a molten state at 700-800°C, which can uniformly transfer heat through high thermal conductivity and provide an ion conduction environment; 5-10wt% of Cu-Bi or Ni-Bi alloy particles (particle size 50-100 mesh) are added, and the Bi component can reduce the surface tension of the molten salt, promote bubble breakage and gas diffusion, and Cu / Ni provides catalytic active sites to form a liquid catalytic interface at high temperature, which cooperates with the molten salt to enhance the deep cracking of CO2 and CO.

[0028] In some embodiments of the present invention, reference Figure 1 and Figure 2 The cracking device also includes a separation unit 14 and a collection unit 22. The molten salt circulates between the separation unit 14 and the container. More specifically, the separation unit 14 is a storage tank. The molten salt inlet 20 is provided at the top of the separation unit 14. An air intake pump 19 is provided on the side of the separation unit 14. The air intake pump 19 is used to blow high-pressure carbon dioxide into the separation unit 14. Since the density of nanocarbon is generally less than that of molten salt and molten metal, the nanocarbon will be separated from the molten salt layer 13 and located above the molten salt layer 13. The molten salt in the separation unit 14 is pumped into the container by a circulation pump 15, and the flow rate is controlled by a valve 16. Blowing carbon dioxide into the separation unit 14 causes the nanocarbon in the molten salt to flow with it to the collection unit 22, which is used to separate carbon dioxide and nanocarbon. More specifically, the collection unit 22 is a bag filter. The specific operation process of the separation unit 14 and the collection unit 22 is as follows: the molten salt carries the generated nanocarbon into the separation unit 14 from the molten salt inlet 20 at the top. Since the density of the nanocarbon is less than that of the molten salt and the molten metal, it naturally floats to the top of the molten salt layer 13; at this time, the air intake pump 19 on the side blows high-pressure CO2 into the separation unit 14, and the air flow drives the nanocarbon floating on the surface to move, and then transports it to the collection unit 22 through the pipeline; in the collection unit 22, the porous structure of the bag intercepts the solid nanocarbon, and the CO2 gas is discharged through the carbon dioxide outlet 23 and can be recycled, thereby realizing efficient separation of nanocarbon from molten salt and gas, and the molten salt returns to the container for recycling through the molten salt outlet 21 of the separation unit 14. The whole process uses density difference and air flow to drive to achieve continuous collection of nanocarbon and recycling regeneration of molten salt.

[0029] In some embodiments of the present invention, reference Figure 1 , further comprising an oxygen screening unit 18, wherein the gas in the lower space flows through the oxygen screening unit 18 and is connected to the coaxial resonant cavity 3; the gas in the lower space is connected to the coaxial resonant cavity 3 after oxygen is screened out, and can re-participate in the plasma discharge process or circulate to the reaction system as an oxidant, on the one hand, improving the utilization rate of oxygen resources and reducing emissions, and on the other hand, maintaining the balance of gas components in the system through closed-loop airflow, enhancing the continuous and efficient CO2 cracking reaction, and preventing other gas impurities from interfering with the catalytic path, ultimately achieving the coordinated optimization of nanocarbon generation and gas circulation; The oxygen screening unit 18 includes a ceramic ion conductive membrane with a thickness of 20-30 μm and an oxygen permeability of 3-5 mL·cm -2 min -1 More specifically, the ceramic ion conductive membrane utilizes the oxygen ion conductive properties at high temperature to selectively allow O2 molecules to achieve directional migration through lattice defects, thereby separating the O2 generated by the reaction from the mixed gas, and the separated oxygen is discharged from the oxygen screening unit 18 through the oxygen outlet 17.

[0030] In some embodiments of the present invention, reference Figure 3 The cracking device further includes a heating unit, which includes a storage tank 1 24 and a storage tank 2 27. The molten salt flows in the storage tank 1 24, the storage tank 2 27 and the container. In order to circulate the molten salt in the above components, a pump is provided at an appropriate position to drive the molten salt to flow; The heating unit further includes a heat collector 25 and a photovoltaic assembly 26 for supplying heat energy to the heat collector 25; The photovoltaic module 26 converts solar energy into electrical energy, providing power or direct heat for the collector 25. The collector 25 efficiently captures solar energy through photothermal conversion and transfers it to molten salt, forming a green energy chain. On the one hand, it uses the high specific heat capacity of molten salt to store excess thermal energy, solve the problem of intermittent solar energy, and ensure the system's all-weather operation; on the other hand, it avoids the high energy consumption of traditional electric heating or fossil fuel heating, thereby reducing costs.

[0031] In some embodiments of the present invention, reference Figure 1 and Figure 4 A turbulent flow device 7 is provided between the cylindrical resonant cavity 4 and the plasma cavity 8; more specifically, the turbulent flow device 7 is a plurality of inclined blades evenly distributed on the top of the plasma cavity 8, with an inclination angle of 15-30 degrees. The inclined blades guide the airflow to form a rotation, so that the gas entering the plasma cavity 8 from the cylindrical resonant cavity 4 changes its flow direction, forming a spiral path in the cavity, prolonging the contact time between the gas and the catalyst layer 9, and at the same time expanding the contact area between the gas and solid phases, ensuring that gas molecules such as CO2 fully interact with the active sites on the catalyst surface, and enhancing the conversion effect of the catalytic unit 6 on CO2.

[0032] Example 2: A carbon dioxide cracking method, using the cracking device in Example 1, comprises: subjecting carbon dioxide to microwave discharge, chemical catalysis and molten salt heating treatment in sequence, so as to crack the carbon dioxide into nanocarbon and oxygen.

[0033] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A carbon dioxide cracking device, characterized in that: The cracking device is provided with a microwave discharge unit, a catalytic unit and a molten salt cracking unit in sequence from top to bottom; The microwave discharge unit includes a shell, wherein the shell is provided with a coaxial resonant cavity and a cylindrical resonant cavity in sequence from top to bottom, and a microwave generator is provided on the side of the cylindrical resonant cavity; The catalytic unit includes a plasma cavity and a catalyst layer arranged in sequence from top to bottom; wherein the plasma cavity is connected to the cylindrical resonant cavity; The molten salt cracking unit includes a container connected to the bottom of the catalyst layer, a sealing plate is fixed in the container to divide the interior of the container into an upper space and a lower space, and the upper space and the lower space are connected by a gas conduit; A molten salt layer is provided in the lower space, and the bottom end of the gas conduit is located in the molten salt.

2. The carbon dioxide cracking device according to claim 1, characterized in that: The bottom of the coaxial resonant cavity is in the shape of a pointed probe.

3. The carbon dioxide cracking device according to claim 1, characterized in that: The axis of the coaxial resonant cavity is perpendicular to the axis of the cylindrical resonant cavity.

4. The carbon dioxide cracking device according to claim 1, characterized in that: The catalyst layer is based on nickel foam and loaded with 5-10% of at most two transition metals.

5. The carbon dioxide cracking device according to claim 1, characterized in that: The molten salt is one of NaCl and NaBr, and the molten salt contains 5-10 wt % of Cu-Bi or Ni-Bi alloy particles.

6. The carbon dioxide cracking device according to claim 1, characterized in that: The cracking device further comprises a separation unit and a collection unit, and the molten salt circulates between the separation unit and the container; Carbon dioxide is blown into the separation unit to make the nano-carbon in the molten salt flow to the collection unit, and the collection unit is used to separate the carbon dioxide and the nano-carbon.

7. The carbon dioxide cracking device according to claim 1, characterized in that: It also includes an oxygen screening unit, and the gas in the lower space flows through the oxygen screening unit and then communicates with the coaxial resonant cavity; The oxygen screening unit includes a ceramic ion-conducting membrane.

8. The carbon dioxide cracking device according to claim 1, characterized in that: The cracking device further includes a heating unit, the heating unit includes a storage tank 1 and a storage tank 2, and the molten salt flows in the storage tank 1, the storage tank 2 and the container; The heating unit further comprises a heat collector and a photovoltaic component for supplying heat energy to the heat collector.

9. The carbon dioxide cracking device according to claim 1, characterized in that: A flow disturbance device is provided between the cylindrical resonant cavity and the plasma cavity.

10. A carbon dioxide cracking method, characterized in that: include: The carbon dioxide is treated by microwave discharge, chemical catalysis and molten salt heating in succession to decompose it into nanocarbon and oxygen.

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