Method foe manufacturing carbon material from raw material gas

Abstract

To provide an improved method for manufacturing carbon from carbon-containing raw material gas.SOLUTION: In a method for manufacturing carbon material from one or more carbon-containing raw material gases, one or more electrolytes are melted in a reaction chamber, a catalyst in an amount of 0.03 wt% to 0.5 wt% based on the total mass of the electrolyte is added at an addition rate of 16.7 ppm time-1 to 277.8 ppm time-1, one or more raw material gases are supplied to the molten electrolyte in the reaction chamber at a flow rate containing at least 4.2 standard cm3 min-1A-1 mass equivalent of CO2, and a direct current density in the range of 100 A m-2 to 20,000 A m-2 is supplied to one or more anodes and one or more cathodes.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure generally relates to the production of carbon materials, and more specifically to a method for producing carbon materials from a raw material gas.

Background Art

[0002] Carbon materials in various forms such as powders and dispersions are becoming increasingly important in the production of energy storage devices (e.g., supercapacitors, batteries, fuel cells, and other energy storage systems) due to their electrical and mechanical properties. Various methods and systems for producing carbon materials such as graphite, graphene, carbon nanotubes, carbon nanofibers, carbon nanospheres, or other carbon materials are known. One of the known methods is, for example, the chemical vapor deposition method (CVD method), which is the current industry standard for producing carbon nanotubes. The CVD method uses 800 MWh of energy to produce 1 ton of carbon nanotubes. Thus, the energy consumption for producing carbon materials is enormous, which makes the production cost very high. Therefore, it is necessary to reduce the energy consumption in the production of carbon materials. Furthermore, since the CVD method uses raw materials based on fossil fuels, it is harmful to the environment.

[0003] In US20220388847, Licht et al. proposed a method for synthesizing helical carbon nanostructures by an electrolysis reaction using a molten carbonate electrolyte and a carbon-containing input between the electrodes of a reaction vessel.

[0004] "Controlled Growth of Unusual Nanocarbon Allotropes by Molten Electrolysis of CO2" by Liu et al. in Catalysts 2022, 12, 125 relates to the same technology as above and further discloses the influence of different additives in the molten electrolyte on the form of the obtained nanocarbon.

[0005] In "Insights into carbon production by CO2 reduction in molten salt electrolysis in coaxial-type reactor", Laasonen et al. disclose a coaxial reactor used to reduce CO2 to carbon using various electrolytes without a catalyst for the purpose of studying the voltage-current characteristics of molten salt electrolysis of CO2.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] This application aims to provide an improved method for producing carbon from a carbon-containing raw material gas.

Means for Solving the Problems

[0009] The object of the present disclosure is to provide an efficient solution for manufacturing carbon materials. The object of the present disclosure is achieved by a method for manufacturing carbon materials from a raw material gas, as defined in the appended independent claims. Advantageous features are described in the appended dependent claims.

[0010] According to a preferred embodiment of the present disclosure, there is provided a method for manufacturing a carbon material, the method comprising the following steps: melting one or more electrolytes in a reaction chamber, and adding a catalyst in an amount of 0.03 wt% to 0.5 wt% based on the total mass of the electrolyte at a dosing rate of from 16.7 ppmh -1 to 277.8 ppmh -1 supplying at least 4.2 standard cm 3 min -1 A -1 mass equivalent of CO2-containing flow rate of one or more raw material gases, supplying a direct current density in the range of 100 A / m -2 to 20000 A / m -2 up to (preferably, a maximum of 6000 A / m -2 ) to one or more anodes and one or more cathodes. The advantage of the method according to the present disclosure is that the catalyst reaches the cathode in a more efficient and controlled manner, provides a carbon nanotube growth nucleation center, and results in a higher quality carbon nanotube morphology.

[0011] By this method, the annual production volume of carbon materials can be efficiently increased in tons, and at the same time, the amount of CO2 emitted can be reduced. In addition, this method enables the production of carbon materials in a controlled manner to achieve a form suitable for energy storage devices. The manufactured materials can be used for the production of carbonaceous powders, carbonaceous dispersions, carbon oxide powders, heteroatom-enriched powders, which are used in electric vehicle batteries, stationary energy storage (e.g., lithium-ion batteries, lithium iron phosphate batteries, sodium-ion batteries, lithium silicon batteries).

Mode for Carrying Out the Invention

[0012] The following detailed description shows embodiments of the present disclosure and ways in which they may be implemented.

[0013] An apparatus suitable for practicing the present invention includes a reaction chamber adapted to contain one or more electrolytes selected from at least one alkali electrolyte or one or more alkaline earth electrolytes, one or more anodes arranged in a three-dimensional structure, one or more cathodes, a power source for supplying current to the one or more anodes and the one or more cathodes, a heating unit configured to heat the reaction chamber to melt the one or more electrolytes, and a gas supply unit configured to supply one or more source gases to the molten electrolyte within the reaction chamber.

[0014] However, those skilled in the art will understand that any suitable conventional apparatus may be used.

[0015] The apparatus may be a modular apparatus composed of two or more devices that function in a system for producing carbon materials from one or more source gases. The apparatus can be connected to a factory or production network that discharges source gases.

[0016] The reaction chamber of the apparatus is adapted to contain one or more electrolytes selected from at least one alkali electrolyte or one or more alkaline earth electrolytes and may have a circular or square cross-section. The reaction chamber is made of nickel alloy and may optionally be coated with NiCoCrAl[Ta, Hf, Si]Y, an alumina (Al2O3) coating for improving corrosion resistance, or a ceramic tile such as alumina (Al2O3).

[0017] According to the method of the present disclosure, the reaction chamber is used for electrolysis, purification, and functionalization with heteroatoms. The reaction chamber includes a metal container adapted to contain an electrolyte medium (consisting of one or a combination of lithium, potassium, sodium carbonate, or halides, or any mixture thereof). In particular, the reaction chamber is adapted to contain one or more electrolytes including at least one alkali electrolyte or one or more alkaline earth electrolytes. According to an embodiment, the one or more electrolytes include carbonate electrolytes from 90% to 100%. The carbonate electrolyte is selected to be at least one of Na2CO3, Li2CO3, K2CO3, BaCO3, CaCO3.

[0018] According to an embodiment of the present disclosure, the one or more electrolytes further include at least one catalyst selected from Fe2O3, Li2O, LiOH, NiO, ZnO, Cr2O3, Ni, or others. The amount of Fe2O3, Li2O, LiOH, NiO, ZnO, Cr2O3, Ni in the electrolyte is from 0.03 wt% to 10 wt% (preferably from 0.03 wt% to 0.5 wt%). The structure of the carbon material particles can be controlled by the catalyst. For example, Fe2O3 makes it possible to obtain linear or mainly intertwined carbon nanotubes. It is further possible to generate nucleation centers by adding a metal oxide, such as Fe2O3 (preferably 0.1 wt%), to the electrolyte in a continuously controlled linear dosage form throughout the synthesis process. Optionally, the reaction chamber includes a nickel metal alloy. The advantage of a reaction chamber including a nickel metal alloy is that low impurity levels and a uniform carbon form can be achieved.

[0019] A power source for supplying current to one or more anodes and one or more cathodes is adapted to supply a current of 12000 - 24000 amperes (A) to the device. For example, 4000 A. According to an embodiment of the present disclosure, the supplied direct current density is from 100 A m -2 to 20000 (preferably 6000) A m -2It is within the range up to. For example, when using a direct current (DC) power source or a rectifier, the positive (+) terminal is connected to one or more anodes, and the negative (-) terminal is connected to one or more cathodes. A high current density and a low voltage can slow down the growth of the carbon material, and thus improve the structure of the carbon material. As the power source, renewable energy such as sunlight, wind power, and hydraulic power can be used.

[0020] In an embodiment of the present disclosure, the heating unit is configured to heat one or more electrolytes in the reaction chamber to a temperature ranging from 400°C to 900°C. In the case of a lithium carbonate electrolyte, the preferred range is from 730°C to 800°C. The heating unit may be one or more insulated industrial ovens for heating the reaction chamber. By the heating unit, a molten salt can be obtained in the reaction chamber. The reaction chamber may be heated to, for example, 770°C to melt the electrolyte (e.g., lithium carbonate).

[0021] The gas supply unit for supplying one or more raw material gases to the molten electrolyte in the reaction chamber is configured to continuously supply the gas while the device is operating. The gas supply unit may be provided with means for uniformly diffusing the raw material gas in the electrolyte. Such means for diffusing the raw material gas may be a pipe for the raw material gas disposed in the reaction chamber. Optionally, the gas supply unit includes electrolyte mixing means for uniformly diffusing CO2 gas in the electrolyte. By the electrolyte mixing means, the gas can be uniformly dissolved and dispersed in the electrolyte. If the mass transfer in the reactor is slow, a concentration gradient of the oxide occurs, and the corrosion of the anode is accelerated. The electrolyte mixing means may be an S-shaped tube having pores and may be disposed in the electrolyte of the reaction chamber. When the raw material gas is pumped through the S-shaped tube in the electrolyte, bubbling of the raw material gas in the electrolyte occurs, enabling mixing of the electrolyte.

[0022] According to an embodiment of the present disclosure, the one or more source gases include at least one of exhaust gas or industrial gas containing one or more of CO, CO2, or CH4. By using source gases such as exhaust gas, industrial exhaust gas, and other waste gases containing CO2, environmental damage can be reduced. For example, CO2 may be industrial waste CO2 or exhaust CO2 from heavy industrial emission sources, and according to the present disclosure, it is used as a raw material for manufacturing carbon materials.

[0023] This method can be implemented by an apparatus including a heating unit (e.g., a furnace), a reaction chamber, one or more anodes arranged in a three-dimensional structure, a gas supply unit, and a power source.

[0024] An electrode and an electrolyte (e.g., lithium carbonate, potassium carbonate, sodium carbonate, lithium halide, potassium halide, sodium halide, or any mixture thereof, etc.) are inserted into the reaction chamber. When the electrode is connected to a power source and an electric current is supplied to the electrode, the electrolysis process is initiated. The power source supplies electrons to the electrode to split the electrolyte into solid carbon and dissolved alkali metal oxide. The current input at that time ranges from 12000 - 24000 A, and the direct current density ranges from 100 A m -2 to 20000 A m -2 up to. The direct current of the positive (+) terminal of the power source is connected to the anode, and the negative (-) terminal is connected to one or more cathodes. The specific current density used per cathode surface area is, for example, 0.08 A cm -3 - 0.16 A cm -3 is.

[0025] The electrode and the electrolyte are ideally heated at a temperature from 450°C to 850°C. Lithium carbonate is preferably used as the electrolyte. The heating unit is heated to 770°C to melt the electrolyte, and an iron(III) oxide Fe2O3 catalyst (at 0.1 wt%) is added to the electrolyte salt to generate nucleation centers.

[0026] The oxide anions move to one or more anodes where they are oxidized to gaseous oxygen. At the same time, the electrolyte readily absorbs CO2. The electrochemical process is initiated by applying an electric potential to the molten electrolyte and the electrodes. In this process, CO2 molecules are separated into C and O2. Oxygen is generated and optionally discharged from the reaction chamber by a ventilation system. At the same time, carbon is collected at one or more cathodes of the electrodes.

[0027] The concentrated CO2 is bubbled through an S-shaped gas supply unit installed near the bottom of the reaction chamber and having holes in the bottom side of the tube. The flow rate of CO2 should preferably be at least 4.2 standard cm 3 min -1 A -1 per minute.

[0028] The maximum flow rate is limited by bubbling. If the bubbling is too intense, the contact area between the electrolyte and the electrodes decreases. When a current is supplied to the electrodes, the electrolysis process begins. Carbon is transformed from Li2CO3 into a carbon material such as multi-walled carbon nanotubes (MWCNT) and deposits on the cathodes.

[0029] This process is a four-electron reduction. This conversion also produces Li2O and O2 gas, which are released in a bubbly form from the molten electrolyte. On the other hand, the generated Li2O immediately reacts with the incoming CO2 to produce Li2CO3 in order to play a role in carbon capture. Therefore, this process depends on CO2 and electrical energy, and these are the only consumables in this process.

[0030] At the beginning of the process, the electrolyte containing additives is melted by a heating unit in which the reaction chamber is placed. After the electrolyte is in a molten state, the flow of CO2 is turned on by a mass flow controller (MFC), and the electrodes are lowered into the molten electrolyte. Then, the current from the power source is turned on, and the electrolytic electrochemical conversion process is initiated. MWCNT is deposited on the cathodes at about 0.12 g A -1 h -1It grows at the speed of

[0031] This method may further include a step of adding an additive to the electrolyte, for example, an electrolyte dopant additive containing dopant heteroatoms such as N, S, B, Fe, Mn, Co, Ni, Zn, P, Cu, Cr, Ti, etc. By adding such an additive, metal oxides that act as catalysts can be included in the electrolyte in a controlled amount instead of impurities from the electrodes.

[0032] In one embodiment, one or more source gases are bubbled through the molten electrolyte in the reaction chamber. The bubbled gas can be mixed in the molten electrolyte and be led to the electrodes.

[0033] Therefore, the method according to the embodiments of the present disclosure manufactures carbon materials such as carbon nanotubes (CNT), carbon nanospirals, carbon nanospheres, carbon nanofibers (CNF), carbon nanoflakes, multi-walled carbon nanotubes (MWCNT), and oxidized multi-walled carbon nanotubes (OMWCNT).

[0034] Additional aspects, advantages, features, and objectives of the present disclosure will become apparent from the detailed description of exemplary embodiments interpreted in connection with the drawings and the appended claims that follow.

Brief Description of the Drawings

[0035] Similar to the detailed description of the following exemplary embodiments, the above summary is better understood when read in conjunction with the accompanying drawings. For the purpose of explaining the present disclosure, an exemplary configuration of an embodiment of the present disclosure is shown in the drawings with reference to the following figures:

Figure 1

Figure 2

Figure 3

[0036] Referring to FIG. 1, a block scheme is shown that depicts an embodiment of an apparatus for manufacturing a carbon material from one or more source gases according to the present disclosure. Apparatus 100 includes a reaction chamber 120, a power supply 160, a heating unit 170, and a gas supply unit 180.

[0037] Referring to FIG. 2, a schematic view of an embodiment of an apparatus according to the present disclosure is shown. Apparatus 100 includes a heating unit 170 having a drain 123 and a reaction chamber 120 insertable into the heating unit 170, the reaction chamber 120 including a drain passage 125 and a gas supply unit 180. The apparatus 100 also includes an electrode interface having a first frame 128 with a socket for anode attachment and a second frame 130 with a cathode socket for cathode attachment, a sheet anode 140 adapted to be attachable to the socket of the first frame 128 and arranged in a three-dimensional structure, a plurality of cathodes 150 adapted to be attachable to the socket of the second frame 130, and a furnace cover 132.

[0038] The gas supply unit 180 is disposed within the reaction chamber 120. The anode 140, attached to the first frame 128 and arranged in a three-dimensional structure, is insertable into a container of one or more electrolytes, and when the anode 140 arranged in the three-dimensional structure is inserted into the reaction chamber 120, the pipeline of the gas supply unit 180 is disposed within the reaction chamber 120. The plurality of cathodes 150 attached to the second frame 130 are insertable into the reaction chamber 120.

[0039] Referring to Fig. 3A, SEM images of the form of carbon nanotubes obtained by the bulk catalyst addition method and mixed with carbon black are shown. Fig. 3B shows SEM images of the form of carbon nanotubes obtained by the controlled catalyst addition method of the present invention and mixed with carbon black.

Example

[0040] The carbon nano-material was synthesized in an Inconel 600 container and securely placed in a stainless-steel safety container. The Inconel 600 container was filled with high-purity Li2CO3 (>99%) added with 0.1 wt% Fe2O3 (purity ≧96%, Sigma Aldrich, Germany). The anode of Inconel 600 and the cathode of Monel 400 were placed about 1 - 2 cm above the bottom of the reactor. Electrolysis was initiated by applying a direct current electrical program determined by accurate cathode surface area measurement. A controllable power supply was used to adjust the supply current over time. Pressurized CO2 (>98% purity) was introduced to the bottom of the molten salt at a constant flow rate (4.2 standard cm 3 min -1 A -1 mass equivalent) maintained by a mass flow controller. The synthesis time was set to 18 hours.

[0041] After the reaction, the carbon product was removed from the cathode. The recovered material was subjected to electrolyte desalting including a washing step using 10 M HCl to remove excess electrolyte and metal impurities. The subsequent steps were neutralization by water washing, vacuum filtration, and oven drying at 60°C for 12 hours.

[0042] The results are shown in Fig. 3A.

[0043] In another experiment, the carbon nano-material was synthesized in an Inconel 600 container and securely placed in a stainless-steel safety container. The Inconel 600 container was filled with high-purity Li2CO3 (>99%). The electrolyte was melted overnight to ensure uniformity and complete water removal.

[0044] The anode of Inconel 600 and the cathode of Monel 400 were placed approximately 1 - 2 cm above the bottom of the reactor. Electrolysis was initiated by applying a direct current electrical program determined by accurate cathode surface area measurement. A controllable power supply was used to adjust the supply current over time. Pressurized CO2 (>98% purity) was introduced at a constant flow rate (4.2 standard cm 3 min -1 A -1 mass equivalent) to the bottom of the molten salt. One hour prior to the start of electrolytic synthesis, the controlled addition of Fe2O3 was initiated at a constant rate of 52.6 ppm h -1 and continued until reaching a total catalyst amount of 0.1 wt% of the total molten electrolyte mass by the end of the synthesis. The synthesis time was set to 18 hours.

[0045] After the reaction, the carbon product was removed from the cathode. The recovered material was subjected to electrolyte desalination including a washing step with 10 M HCl to remove excess electrolyte and metal impurities. Subsequent steps were neutralization by water washing, vacuum filtration, and oven drying at 60 °C for 12 hours.

[0046] The results are shown in Figure 3B.

[0047] As can be seen from the results of the SEM images of the first experiment (Figure 3A), when the catalyst was added in bulk all at once, the final form of the carbon product was not well-defined multi-walled carbon nanotubes (MWCNTs). Rather, a mixture of spherical carbon (carbon black [CB] / nano-onions) began to grow slightly, resulting in a low-grade mixture of CB / MWCNTs. This is because most of the Fe2O3 catalyst fell to the bottom of the reaction vessel. This was detectable even with slight stirring of the molten electrolyte mixture with an alumina rod, indicating that the viscosity was high at the bottom of the mixture. When the catalyst fell to the bottom, Fe2O3 could no longer reach the cathode efficiently and no longer functioned as a nucleation center for carbon nanotube growth.

[0048] The results of the SEM images in Figure 3B, by the controlled addition method of the second experiment, demonstrate that carbon products with a clearer MWCNT morphology can be obtained by adding the Fe2O3 catalyst in a controlled and constant manner throughout the synthesis process.

[0049] The appropriate range determined to reach a total Fe2O3 addition of 0.03 wt% - 0.5 wt% from the total electrolyte mass in the reaction vessel by the end of the 18-hour synthesis is from 16.7 ppm -1 to 277.8 ppm -1 at that time. If the concentration of the Fe2O3 catalyst becomes too high, the morphology of the final carbon product will change back to low-grade carbon.

Claims

Claim 1 A method for producing a carbon material from one or more carbon-containing feed gases, the method comprising the following steps: (a) melting one or more electrolytes in a reaction chamber; (b) A step of adding a catalyst to the molten electrolyte, wherein the catalyst is added at a dosing rate of from 16.7 ppm to 277.8 ppm based on the total mass of the electrolyte in an amount of from 0.03 wt% to 0.5 wt% of the total mass of the electrolyte. -1 to 277.8 ppm -1 at a dosing rate of. (c) At least 4.2 standard cm 3 min -1 A -1 Mass equivalent CO 2 A step of adding one or more raw material gases to the electrolyte obtained by melting the raw material gases at a flow rate of (d) Supplying a direct current density in the range from 100 A m -2 to 20000 A m -2 to one or more anodes and one or more cathodes in contact with the molten electrolyte. Claim 2 wherein the catalyst is Fe 2 O 3 , Li 2 O, LiOH, NiO, ZnO, Cr 2 O 3 , Ni, or any combination thereof, the method according to claim 1. Claim 3 wherein the catalyst is Fe 2 O 3 The method according to claim 1 or 2 Claim 4 The method according to claim 1 or 2, wherein the electrolyte contains a carbonate group. Claim 5 wherein the electrolyte is Na 2 CO 3 、 Li 2 CO 3 、 K 2 CO 3 、 BaCO 3 、 CaCO 3 or any combination thereof, the method according to claim 1 or 2. Claim 6 wherein the electrolyte is Li 2 CO 3 The method according to claim 1 or 2, comprising. Claim 7 The method according to claim 1 or 2, wherein the one or more electrolytes are heated to a temperature from 400°C to 900°C. Claim 8 The method according to claim 1 or 2, wherein the one or more electrolytes contain from 90% to 100% of an electrolyte containing a carbonate group. Claim 9 wherein the raw material gas is CO 2 , CH 4 and the method according to claim 1 or 2, which is one or a combination of COs. Claim 10 wherein the raw material gas is CO 2 The method according to claim 1 or 2 Claim 11 The method according to claim 1 or 2, further comprising removing the carbon material from the one or more cathodes. Claim 12 The method according to claim 1 or 2, wherein the one or more feed gases are bubbled into the molten electrolyte. Claim 13 The method according to claim 1 or 2, wherein the administration rate is substantially linear.

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