Patent Application
20250066204
The present application claims priority to and the benefit of Korean Patent Application No. 10-2022-0128043 filed in the Korean Intellectual Property Office on Oct. 6, 2022, the entire contents of which are incorporated herein by reference.
The present application relates to a carbon dioxide reforming process.
As part of efforts to reduce greenhouse gases caused by global warming, much research is underway on carbon dioxide conversion technologies. A carbon dioxide reforming reaction, one of the carbon dioxide conversion technologies, is a technology to obtain a synthesis gas composed of hydrogen and carbon monoxide by reacting methane and carbon dioxide.
The synthesis gas is a material with high development value as a raw material for various downstream applications. As a method for industrially obtaining the synthesis gas (H2/CO), a reforming reaction of natural gas may be largely divided into a steam reforming process, a carbon dioxide (CO2) reforming process, a complex reforming process (steam & CO2 reforming process), a catalytic partial oxidation process, an autothermal reforming process, a tri-reforming process, such as the following Reaction Schemes 1 to 6, and the like.
CH4+H2O—3H2+CO ΔH=226 kJ/mol [Reaction Scheme 1]
CH4+CO2→2H2+2CO ΔH=261 KJ/mol [Reaction Scheme 2]
3CH4+CO2+2H2O→8H2+4CO ΔH=659 KJ/mol [Reaction Scheme 3]
CH4+0.5O2→2H2+CO ΔH=−44 KJ/mol [Reaction Scheme 4]
autothermal reforming: Reaction Scheme 1+Reaction Scheme 3 [Reaction Scheme 5]
tri-reforming: Reaction Scheme 1+Reaction Scheme 2+Reaction Scheme 3 [Reaction Scheme 6]
Among these, the carbon dioxide reforming process as shown in Reaction Scheme 2 is a method of producing a synthesis gas (syngas) through a catalytic reaction of carbon dioxide and methane without steam, and is also called a dry reforming process.
The dry reforming process or complex reforming process has an advantage in that it is advantageous for conversion into various carbon compounds, considering a proportion of hydrogenated carbon monoxide in the produced synthesis gas. In addition, the dry reforming process or complex reforming process is significant in that it uses carbon dioxide, a greenhouse gas, as a reactant.
Meanwhile, the dry reforming process or complex reforming process is an endothermic reaction and shows that the higher the temperature, the higher the conversion rate of carbon dioxide. However, in this process, there has been a problem of rapid carbon deposition on a surface of a commonly used nickel catalyst.
In order to solve this problem, a method of simultaneously supplying an excessive amount of steam (volume of hydrogen/volume of methane≥1) has been introduced, but problems such as an increase in required energy and a decrease in carbon dioxide conversion rate due to the supply of steam have occurred.
Therefore, there is a need to develop a method for suppressing carbon deposition on a catalyst used in the carbon dioxide reforming process without reducing the conversion rate of the carbon dioxide reforming process.
The present application has been made in an effort to provide a carbon dioxide reforming process.
An exemplary embodiment of the present application provides a carbon dioxide reforming process including: supplying a mixed raw material (feed) including carbon dioxide (CO2), methane (CH4) and hydrogen (H2) to a reactor; and causing the mixed raw material to contact a catalyst inside the reactor, wherein Equation 1 below is satisfied.
The carbon dioxide reforming process according to an exemplary embodiment of the present application has an advantage in that it is possible to suppress carbon deposition on a catalyst that may occur during the process, enabling a long-term stable operation.
In addition, the carbon dioxide reforming process has an advantage in that it is easy to adjust a ratio of H2 and CO, which is required in a post-stage process such as an oxo alcohol process that follows the carbon dioxide reforming process, to a desired ratio.
Hereinafter, the present specification will be described in more detail.
Throughout the present specification, when a member is referred to as being “on” another member, the member can be in direct contact with another member or an intervening member may also be present.
In the present specification, when a part is referred to as “including” a certain component, it means that the part can further include another component, not excluding another component, unless explicitly described to the contrary.
In the present specification, the “carbon dioxide reforming process” may also be expressed as “carbon dioxide reforming method” or “carbon dioxide reforming reaction.”
In the present specification, “carbon dioxide (CO2)”, “methane (CH4)” and “hydrogen (H2)” may be supplied in the form of gas.
In the present specification, “methane (CH4)-hydrogen (H2) mixed gas” refers to a mixed gas of methane (CH4) and hydrogen (H2).
In the present specification, “final mixed gas” refers to a mixed gas that has completed mixing inside the mixer.
An exemplary embodiment of the present application provides a carbon dioxide reforming process including: supplying a mixed raw material (feed) including carbon dioxide (CO2), methane (CH4) and hydrogen (H2) to a reactor; and causing the mixed raw material to contact a catalyst inside the reactor, wherein Equation 1 below is satisfied.
The carbon dioxide reforming process according to the present application includes supplying a mixed raw material of carbon dioxide (CO2), methane (CH4) and hydrogen (H2) to a reactor, wherein a ratio of volumes of methane and hydrogen of the mixed raw material satisfies Equation 1 above, whereby it is possible to suppress carbon deposition on the catalyst that may occur during the process, enabling a long-term stable operation.
In the present specification, the carbon dioxide reforming process may also be expressed as a methane reforming process or a natural gas reforming process. In addition, the process may also be expressed as terms of method or reaction.
In an exemplary embodiment of the present application, the carbon dioxide reforming process may, more specifically, mean a dry process of carbon dioxide. In addition, the process may also be expressed as terms of method or reaction.
In an exemplary embodiment of the present application, a/b in Equation 1 may be 0.05<a/b≤0.3, and preferably 0.1≤a/b≤0.25. There are disadvantages in that if a/b is equal to or less than 0.05, it is difficult to exhibit the effect of suppressing carbon deposition on the catalyst by addition of hydrogen, and if a/b is larger than 0.3, occurrence of side reactions increases, and the yield of hydrogen is lowered.
In an exemplary embodiment of the present application, the step of causing the mixed raw material to contact the catalyst inside the reactor may be performed at a temperature ranging from 600° C. to 1,000° C., preferably 650° C. to 900° C., and most preferably 750° C. to 850° C. At temperatures below 600° C., the reforming reaction may not occur well, and at temperatures above 1,000° C., a reactor to withstand the high temperatures is required, which may increase process costs.
In an exemplary embodiment of the present application, the step of causing the mixed raw material to contact the catalyst inside the reactor may be performed at a pressure within the reactor ranging from 0 bar (g) to 20 bar (g), preferably 0 bar (g) to 10 bar (g), and more preferably 0 bar (g) to 5 bar (g). Here, bar (g) refers to a bar gauge pressure, and satisfies a relationship of Equation 3 below with a bar gauge absolute pressure expressed as bar (a).
In other words, a bar gauge pressure refers to a value obtained by adding an atmospheric pressure (standard condition: 1.013 bar) to a bar gauge absolute pressure.
In an exemplary embodiment of the present application, the step of supplying the mixed raw material (feed) to the reactor means supplying the mixed raw material in the form of gas, and a gas hourly space velocity (GHSV) may be 250 hr−1 to 3,000 hr−1, and preferably 500 hr−1 to 2,000 hr−1. In an exemplary embodiment of the present application, the catalyst may be a catalyst for carbon dioxide reformation.
In an exemplary embodiment of the present application, the catalyst may be nickel (Ni) or ruthenium (Ru) That is, the catalyst may be a catalyst including nickel or ruthenium, but is not limited thereto.
In an exemplary embodiment of the present application, the catalyst may be a perovskite-based catalyst containing nickel or ruthenium, but is not limited thereto.
That is, a catalyst commonly used in the carbon dioxide reforming process can be used as long as Equation 1 above and Equation 2 below of the present application can be satisfied. However, if the catalyst described above is satisfied, a more efficient carbon dioxide reforming process may be possible.
In an exemplary embodiment of the present application, the perovskite-based catalyst may be represented by the following Chemical Formula 1.
Sr1-xAxTi1-yByO3-δ [Chemical Formula 1]
In an exemplary embodiment of the present application, the catalyst may be a pellet-type catalyst, a ceramic support catalyst, or a porous metal structure catalyst. That is, an appropriate type of catalyst can be selected and used depending on environments in which the catalyst is used.
More specifically, in an exemplary embodiment of the present application, the catalyst includes a porous metal structure; a primary coating layer coated on the porous metal structure and including an inorganic oxide; and a perovskite-based compound coated on the primary coating layer and represented by Chemical Formula 1 above. A layer including the perovskite-based compound coated on the primary coating layer and represented by Chemical Formula 1 above may be referred to as a secondary coating layer.
In an exemplary embodiment of the present application, the primary coating layer may further include a perovskite-based compound represented by the following Chemical Formula 2.
SrTiO3 [Chemical Formula 2]
In an exemplary embodiment of the present application, the perovskite-based compound represented by Chemical Formula 2 is a compound without a catalyst component (i.e., it does not include A and/or B metals, compared to the structure of Chemical Formula 1), and the perovskite-based compound represented by Chemical Formula 1 above is a compound including a catalyst component (which means a metal corresponding to A and/or B in the structure of Chemical Formula 1), and they are different from each other. In an exemplary embodiment of the present application, the primary coating layer may include an inorganic oxide alone, or may simultaneously include a perovskite-based compound represented by Chemical Formula 2 and an inorganic oxide.
In an exemplary embodiment of the present application, the porous metal structure may be a metal foam including NiCrAlFe, NiCrAl, SiC, or α-Al2O3.
The porous metal structure is a structure having various shapes and has a small heat capacity and an excellent heat transfer ability, so it can be molded into a desired shape and used. The shape and size of the porous metal structure are not particularly limited, and a porosity of the porous metal structure may be 10% to 99%, 50% to 96%, or 85% to 96%. The pore size (cell size) of the porous metal structure may be 400 μm to 1,500 μm, or 450 μm to 1,400 μm. If the cell size of the porous metal structure is less than 400 μm, it may be difficult to coat a precursor solution, and if it exceeds 1,500 μm, it is undesirable because a surface area on which the catalyst can be coated is reduced, which may be disadvantageous in the process. The porous metal structure can be appropriately manufactured by one skilled in the art using methods known in the art, taking into account the material, cell size, porosity, and the like of the porous metal structure described above.
In an exemplary embodiment of the present application, the inorganic oxide may include one or more of TiO2, SiO2 and ZrO2.
In an exemplary embodiment of the present application, a total content of the perovskite-based compound represented by Chemical Formula 2 above and the inorganic oxide may be 1% by weight to 20% by weight or 1.5% by weight to 18% by weight based on a total weight of the porous metal structure. If the total content of the perovskite-based compound represented by Chemical Formula 2 above and the inorganic oxide exceeds 20% by weight, it is undesirable because the ability to coat the perovskite-based compound represented by Chemical Formula 1 above may be reduced and the activity of the catalyst compared to the volume of the porous metal structure may be lowered. In addition, if the total content of the perovskite-based compound represented by Chemical Formula 2 above and the inorganic oxide is less than 1% by weight, the content is so small that it may be difficult to obtain the effect of the primary coating layer.
In an exemplary embodiment of the present application, a weight ratio of the first coating layer to the second coating layer including the perovskite-based compound represented by Chemical Formula 1 above may be 1:1 to 1:20, or 1:1.1 to 1:15. If the weight ratio of the first coating layer to the second coating layer including the perovskite-based compound represented by Chemical Formula 1 above deviates from the above range, it is undesirable because the activity of the catalyst compared to the volume of the porous metal structure may be lowered.
In an exemplary embodiment of the present application, a content of the perovskite-based compound represented by Chemical Formula 1 above may be 3% by weight to 40% by weight, 6% by weight to 35% by weight, or 7% by weight to 30% by weight, based on a total weight of the catalyst. If the content of the perovskite-based compound represented by Chemical Formula 1 above is less than 3% by weight based on the total weight of the catalyst, it is not desirable because the reactivity may decrease due to the relatively small number of active sites on the surface of the catalyst. In addition, if the content of the perovskite-based compound represented by Chemical Formula 1 above exceeds 40% by weight based on the total weight of the catalyst, a relatively large amount of catalyst component compared to the porous metal structure is contained, so that it is difficult to maintain the pore structure and it is not easy to combine the catalyst component and the porous metal structure, resulting in a reduction in the practical benefit of the carbon dioxide reforming reaction. In an exemplary embodiment of the present application, the primary coating layer may be provided on an entire surface of the porous metal structure.
In an exemplary embodiment of the present application, at least a portion of the surface of the catalyst may include a protrusion shape. The protrusion shape may be spherical, elliptical, or a combination thereof, but is not limited thereto.
In an exemplary embodiment of the present application, the primary coating layer including the inorganic oxide may serve to fix the perovskite-based compound (including the catalyst component) represented by Chemical Formula 1 above on the porous metal structure. In addition, the perovskite-based compound represented by Chemical Formula 1 above may be present in the form of protrusion on the primary coating layer, which can increase a reaction surface area of the catalyst to improve the performance of the carbon dioxide reforming reaction.
In addition, according to an exemplary embodiment of the present application, when the primary coating layer including the inorganic oxide and the perovskite-based compound represented by Chemical Formula 1 above are applied at the same time, a total amount of catalyst supported on the porous metal structure can be increased, as compared with a case where the catalyst particles are applied alone. In addition, according to an exemplary embodiment of the present application, when the primary coating layer including the inorganic oxide is applied, metals (Ni, Cr, etc.), which are main components of the porous metal structure, can be prevented from being exposed to a surface in the form of metal oxides (Nio, Cr2O3 etc.) under long-term operating conditions of high temperature (750° C. or higher), and the catalyst component ratio of Chemical Formula 1 or the catalyst phase change can be prevented, so that it is possible to improve the durability and performance of the catalyst.
In an exemplary embodiment of the present application, the method may further include preparing a mixed raw material (feed) including carbon dioxide (CO2), methane (CH4) and hydrogen (H2) for supplying to the reactor. In an exemplary embodiment of the present application, the step of preparing a mixed raw material (feed) including carbon dioxide (CO2), methane (CH4) and hydrogen (H2) for supplying to the reactor may include supplying carbon dioxide (CO2), natural gas and hydrogen (H2) to a mixer, respectively, or supplying carbon dioxide (CO2) and a mixed gas of methane (CH4)-hydrogen (H2) to a mixer, respectively; mixing the gases supplied to the mixer to produce a final mixed gas; and compressing the final mixed gas.
The carbon dioxide reforming process according to an exemplary embodiment of the present application may further include reforming the compressed final mixed gas to produce a synthesis gas including carbon monoxide (CO), hydrogen (H2), unreacted methane (CH4) and carbon dioxide (CO2). In an exemplary embodiment of the present application, the step of preparing the mixed raw material (feed) including carbon dioxide (CO2), methane (CH4) and hydrogen (H2) for supplying to the reactor may include supplying carbon dioxide (CO2), natural gas and hydrogen (H2) to a mixer, respectively; mixing the gases supplied to the mixer to produce a final mixed gas; and compressing the final mixed gas.
In this case as well, the carbon dioxide reforming process according to an exemplary embodiment of the present application may further include reforming the compressed final mixed gas to produce a synthesis gas including carbon monoxide (CO), hydrogen (H2), unreacted methane (CH4) and carbon dioxide (CO2).
In an exemplary embodiment of the present application, the step of preparing the mixed raw material (feed) including carbon dioxide (CO2), methane (CH4) and hydrogen (H2) for supplying to the reactor may include supplying carbon dioxide (CO2) and a mixed gas of methane (CH4)-hydrogen (H2) to a mixer, respectively; mixing the gases supplied to the mixer to produce a final mixed gas; and compressing the final mixed gas.
In this case, the carbon dioxide reforming process according to an exemplary embodiment of the present application may further include reforming the compressed final mixed gas to produce a synthesis gas including carbon monoxide (CO), hydrogen (H2), unreacted methane (CH4) and carbon dioxide (CO2).
The carbon dioxide reforming process according to an exemplary embodiment of the present application may further include supplying the synthesis gas to the reactor; and causing the synthesis gas to contact the catalyst. For a supply rate in the step of supplying the synthesis gas to the reactor and a temperature and a pressure at which the step of causing the synthesis gas to contact the catalyst are performed, a supply rate condition in the step of supplying the mixed raw material to the reactor and temperature and pressure conditions at which the step of causing the mixed raw material to contact the catalyst are performed may be applied, respectively.
In an exemplary embodiment of the present application, the step of reforming the compressed final mixed gas to produce a synthesis gas including carbon monoxide (CO), hydrogen (H2), unreacted methane (CH4) and carbon dioxide (CO2) may include adding steam to the compressed final mixed gas; and reforming the compressed final mixed gas to which the steam has been added to produce a synthesis gas including carbon monoxide (CO), hydrogen (H2), unreacted methane (CH4) and carbon dioxide (CO2).
In an exemplary embodiment of the present application, the mixed raw material (feed) may further include steam, and the mixed raw material may satisfy Equation 2 below.
In an exemplary embodiment of the present application, the mixed raw material (feed) may include carbon dioxide (CO2), methane (CH4), hydrogen (H2) and steam, and may satisfy Equation 2 above.
In an exemplary embodiment of the present application, c/b in Equation 2 above may be 0.1≤c/b≤0.3, preferably 0.1≤c/b≤0.22, and more preferably 0.1≤c/b≤0.2. When c/b is larger than 0.3, there is a disadvantage in that a carbon dioxide conversion rate is lowered and the energy cost for generating steam increases.
The carbon dioxide reforming process according to an exemplary embodiment of the present application may include preparing a mixed raw material (feed) including carbon dioxide (CO2), methane (CH4), hydrogen (H2) and steam for supplying to the reactor.
In an exemplary embodiment of the present application, the step of preparing the mixed raw material (feed) including carbon dioxide (CO2), methane (CH4), hydrogen (H2) and steam for supplying to the reactor may include supplying the mixed raw material to a mixer; mixing the mixed raw material supplied to the mixer to produce a final mixed gas; and compressing the final mixed gas.
In this case as well, the carbon dioxide reforming process according to an exemplary embodiment of the present application may further include reforming the compressed final mixed gas to produce a synthesis gas including carbon monoxide (CO), hydrogen (H2), unreacted methane (CH4), steam, and carbon dioxide (CO2).
In this case, the above description can be applied, except that the synthesis gas is produced by reforming the mixed raw material further including steam.
An exemplary embodiment of the present invention provides a carbon dioxide reforming process including: supplying a mixed raw material (feed) including carbon dioxide (CO2), methane (CH4), hydrogen (H2), and steam to a reactor; and causing the mixed raw material to contact a catalyst inside the reactor, wherein the Equations 1 and 2 are satisfied.
More specifically, an exemplary embodiment of the present application provides a carbon dioxide reforming process including: supplying carbon dioxide (CO2), natural gas and hydrogen (H2) to a mixer, respectively, or supplying carbon dioxide (CO2) and a mixed gas of methane (CH4)-hydrogen (H2) to a mixer, respectively; adding steam to the mixer and then mixing the gases supplied to the mixer to produce a final mixed gas; compressing the final mixed gas; adding steam to the compressed final mixed gas; reforming the compressed final mixed gas to which the steam has been added to produce a synthesis gas including carbon monoxide (CO), hydrogen (H2), steam, unreacted methane (CH4) and carbon dioxide (CO2); supplying the synthesis gas to a reactor; and causing the synthesis gas to contact a catalyst inside the reactor, wherein Equation 1 and Equation 2 above are satisfied.
In the present specification, the final mixed gas may refer to a mixed raw material.
In this case, the above description is applied as description of the mixed raw material, the mixed gas, the mixer, the reactor, the mixed raw material catalyst, the synthesis gas, and the like.
In addition, in an exemplary embodiment of the present application, the mixed raw material may use a by-product gas, which is a by-product generated in an NCC (Naphtha Cracking Center) decomposition process. The by-product gas may include methane (CH4) and hydrogen (H2). Additionally, a ratio of volumes of methane (CH4) and hydrogen (H2) in the by-product gas may satisfy Equation 1 above. Additionally, the by-product gas can be used by adding steam, and Equation 2 above can be satisfied.
The carbon dioxide reforming process according to the present application is to supply the mixed raw material into the reactor or to supply synthesis gas reformed from the mixed raw material, where the ratio of volumes of methane and hydrogen of the mixed raw material satisfies Equation 1 above and the ratio of volumes of methane and steam of the mixed raw material satisfies Equation 2 above, so carbon deposition on the catalyst that may occur during the process can be suppressed more efficiently, enabling a long-term stable operation.
In an exemplary embodiment of the present application, the step of reforming the compressed gas refers to reforming hydrocarbon-based fuel to produce hydrogen and carbon monoxide. This is expressed as synthesis gas.
In an exemplary embodiment of the present application, the step of reforming the compressed gas may use steam reforming, but is not limited thereto.
In the present specification, the natural gas refers to a substance including methane as a main component and sulfur and C2 to C3 hydrocarbon components.
In an exemplary embodiment of the present application, the step of supplying carbon dioxide (CO2), natural gas and hydrogen (H2) to the mixer, respectively, includes supplying the natural gas and the hydrogen (H2) to desulfurization system; removing sulfur components of the natural gas from the desulfurization system; and supplying the carbon dioxide (CO2), the natural gas from which the sulfur components have been removed, and the hydrogen to the mixer, respectively.
In an exemplary embodiment of the present application, the step of supplying the carbon dioxide (CO2), natural gas and hydrogen (H2) to the mixer, respectively, further includes pre-reforming C2 to C3 hydrocarbon components of the natural gas to a C1 hydrocarbon component before reforming the compressed gas.
In this case, a volume of hydrogen and a volume of methane in the mixed raw material satisfy Equation 1, and a volume of steam and a volume of methane in the mixed raw material satisfy Equation 2.
The reformed mixed raw material is cooled through a second heat exchanger 2 and then supplied to a reactor 40. In this case, a quench tower may be used as the reactor 40. In the reactor 40, a synthesis gas of H2 and CO is produced as a product, so that the carbon dioxide reforming process is ultimately completed. Thereafter, condensate water is removed from the reactor 40, and the generated synthesis gas product of H2 and CO can be cooled. The cooled synthesis gas product of H2 and CO is compressed to an appropriate pressure in a second compressor 21 and then supplied for a downstream process.
In this case, the condensate water can be recycled as cooling water through a pump 50 of
In addition, in the case of
However, when the natural gas is used as a raw material as shown in
In addition, unlike the process of
In general, natural gas contains not only sulfur components that can poison the catalyst and C1 hydrocarbons, but also C2 to C3 hydrocarbon components. Therefore, if natural gas is directly supplied to the reformer, the catalyst may be poisoned by the sulfur components, and more coke is produced due to the C2 to C3 hydrocarbon components. Therefore, when natural gas (methane) and hydrogen are supplied separately as shown in
For reference, in the present specification, “Cn” means “n carbon atoms.” In other words, C3 means that there are 3 carbon atoms.
After decomposing the C2 to C3 hydrocarbon components of the mixed raw material into methane in the pre-reformer, fuel reforming is performed in the reformer 30 as described above to produce the mixed raw material.
After the reforming is completed and the mixed raw material is produced, the synthesis gas is cooled through the second heat exchanger 2 and then supplied to the reactor 40, like
In this case as well, condensate water can be recycled as cooling water through the pump 50 of
Examples of the downstream process (post-stage process) include an oxo alcohol process, but the present invention is not limited thereto, and various processes can be applied depending on the composition of the produced mixed gas. In other words, the downstream process to be applied may be different depending on purposes and conditions of the process.
In other words, the carbon dioxide reforming process according to the present application can suppress coke production in the catalyst used in the carbon dioxide reforming process (dry reforming process) by introducing a certain amount (small amount) of hydrogen and/or steam, and can be used in various downstream processes.
In an exemplary embodiment of the present application, the catalyst may be applied to a dry reforming process, a steam reforming process, a carbon dioxide (CO2) reforming process, a catalytic partial oxidation process, an autothermal reforming process, a tri-reforming process or a mixed reforming process, and the method of the carbon dioxide reforming process to be applied is not particularly limited.
In an exemplary embodiment of the present application, the method may further include filling the reactor with the catalyst according to the present application before causing the mixed raw material to contact the catalyst inside the reactor; and subjecting the reactor filled with the catalyst to reduction condition of H2/N2.
In an exemplary embodiment of the present application, the step of subjecting the reactor filled with the catalyst to reduction condition of H2/N2 may include subjecting the reactor filled with the catalyst to reduction at temperatures ranging from 700° C. to 800° C. for 1 to 2 hours under condition of H2/N2.
In an exemplary embodiment of the present application, the condition of H2/N2 refers to a volume ratio of a volume of hydrogen (H2) to a volume of nitrogen (N2), and H2/N2 may satisfy 5% to 12%, and preferably 10%.
Below, Examples will be described in detail for specifically describing the present application. However, the Examples according to the present application may be modified in other forms, and the scope of the present application is not construed as being limited to the Examples described in detail below. The Examples of the present application are provided to more completely explain the present application to one skilled in the art.
A fixed bed reaction system was introduced in order to perform a carbon dioxide reforming reaction, more specifically a dry reforming reaction of carbon dioxide.
In the fixed bed reaction system, an Inconel reactor (inner diameter=½ inch, length=50 cm) was used, as the catalyst, a catalyst where a porous metal structure was coated with the material (B=Ni) represented by Chemical Formula 1, that is, a Ni catalyst (about 2 g) was filled, a reduction process was performed at 800° C. for 1 to 2 hours under conditions of 10% H2/N2, and then a catalytic reaction was carried out for 60 hours at a reaction temperature condition of 700° C. and a reaction pressure condition of 0 bar (g) while supplying a mixed raw material including carbon dioxide (CO2), methane (CH4) and hydrogen (H2) with satisfying gas hourly space velocity (GHSV)=1,500 hr−1 (based on CH4).
In this case, the ratio of the volume of hydrogen to the volume of methane in the mixed raw material (hereinafter, H2/CH4) was 0.25.
The catalytic reactions of Examples 2 to 6 and Comparative Examples 1 to 4 were performed in the same manner as in Example 1, except that the condition of H2/CH4, the reaction temperature condition, and the reaction pressure condition were set as shown in Table 1 below.
That is, in Comparative Examples 1 to 4, the catalytic reaction was carried out under conditions where hydrogen was not included in the mixed raw material.
That is, the ranges of conditions for Examples 1 to 6 and Comparative Examples 1 to 4 in Table 1 below are as follows (excluding content of hydrogen).
After completion of each reaction of Examples 1 to 6 and Comparative Examples 1 to 4, a reaction conversion rate after 60 hours of reaction was calculated by analyzing the composition of the produced gas using gas chromatography (GC), and is shown in Table 1 below. In addition, the ratio (hereinafter referred to as H2/CO) of the volume of hydrogen to the volume of carbon monoxide after completion of the reaction was also obtained.
The conversion rate was obtained by Equation 4 below, and the GC analysis conditions were as follows. In relation to Table 1 below, in Equation 4 below, i is CH4 or CO2 means.
(Fi=flow rate of i)
In addition, after completion of the reaction, a ratio of a reaction (reverse water gas shift (RWGS) reaction that is an opposite of a water gas shift (WGS) reaction) where carbon monoxide and steam in the synthesis gas react to produce hydrogen and carbon dioxide was calculated through Equation 5 below.
A coke generation rate was also calculated using Equation 6 below.
The result values are shown in Table 1 below.
As can be seen in Table 1 above, it could be confirmed that a ratio of when H2/CH4 in the mixed raw material satisfies Equation 1 according to the present application, appropriate levels of CH4 and CO2 conversion rates were exhibited and the coke generation rate was low under the same reaction temperature and reaction pressure conditions. That is, when comparing Example 1 and Comparative Example 1, it could be confirmed that the coke generation rate in Example 1 was lower.
Through comparisons of the other Examples and Comparative Examples, it could be confirmed that a more stable operation was possible over a long period of time than using, as fuel, methane not mixed with hydrogen under the same conditions.
In addition, it could be confirmed that the ratio of reverse water gas shift (RWGS) reaction and the ratio of H2/CO could be changed by adjusting the ratio of H2/CH4. This means that the ratio of H2 and CO necessary for downstream processes following the carbon dioxide reforming process can be easily adjusted according to a purpose of each process.
In Comparative Example 5 in which the ratio of H2/CH4 in the mixed raw material exceeded 0.3, the upper limit of Equation 1 above according to the present application, it could be confirmed that the value of RWGS exceeded 18. If the value of RWGS exceeds 18, a problem that the yield deteriorates may occur.
That is, when the ratio of H2/CH4 in the mixed raw material satisfies Equation 1 according to the present application, there is an advantage in that it is possible to lower the coke generation rate while increasing the yield of the carbon dioxide reforming process.
A mixed raw material including carbon dioxide (CO2), methane (CH4), steam, and hydrogen (H2) was added with steam and then reformed to produce synthetic gas. In this case, the synthesis gas produced so that the ratio (hereinafter, steam/CH4) of the volume of steam to the volume of methane in the mixed raw material satisfied 0.1 and the ratio (hereinafter, H2/CH4) of the volume of hydrogen to the volume of methane in the mixed raw material satisfied 0.1.
Then, the catalytic reaction of Example 7 was performed in the same manner as in Example 1, except for undergoing reaction with the catalyst under the reaction temperature and reaction pressure conditions shown in Table 2 below.
The catalytic reactions of Examples 8 and 9 and Comparative Example 7 were performed in the same manner as in Example 7, except that the condition of steam/CH4, the condition H2/CH4, the reaction temperature condition, and the reaction pressure condition of the mixed raw material were set as shown in Table 2 below.
That is, in Comparative Example 7, the catalytic reaction was carried out under conditions where hydrogen was not included in the mixed raw material and only steam was partially included.
After completion of each reaction of Examples 7 to 9 and Comparative Example 7, a reaction conversion rate after 60 hours of reaction was calculated by analyzing the composition of the produced gas using gas chromatography (GC), and is shown in Table 2 below. In addition, the ratio (hereinafter referred to as H2/CO) of the volume of hydrogen to the volume of carbon monoxide after completion of the reaction was also obtained.
Additionally, the coke generation rate was also calculated.
The result values are shown in Table 2 below.
In this case, the conversion rate and the coke generation rate were calculated using Equations 4 to 6 above.
As can be seen in Table 2 above, it could be confirmed that when the ratio of H2/CH4 in the mixed raw material satisfies Equation 1 according to the present application and the ratio of steam/CH4 satisfies Equation 2 according to the present application, appropriate levels of CH4 and CO2 conversion rates were exhibited, and the coke generation rate was low under the same reaction temperature and reaction pressure conditions. In other words, it could be confirmed that a more stable operation was possible over a long period of time than using, as fuel, methane not mixed with hydrogen under the same conditions.
In addition, it could be confirmed that the ratio of H2/CO could also be changed by adjusting the ratio of steam/CH4. This means that the ratio of H2 and CO necessary for downstream processes following the carbon dioxide reforming process can be easily adjusted according to a purpose of each process.
Additionally, when compared to Example 5 in Table 1 above with the same ratio of H2/CH4, reaction temperature condition, and reaction pressure condition, it could be confirmed that if the ratio of H2/CH4 in the mixed raw material satisfies Equation 1 according to the present application and the ratio of steam/CH4 satisfies Equation 2 according to the present application, the appropriate CH4 conversion rate and CH conversion rate were exhibited and the coke generation rate was lower.
In other words, it could be confirmed that when a certain amount (small amount) of steam is included in the mixed raw material, a more stable operation is possible over a long period of time.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0128043 | Oct 2022 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2023/014480 | 9/22/2023 | WO |
