Process of selectively hydrogenating gas mixture having high acetylene content

Abstract

To provide a method for producing ethylene in high yield by selective hydrogenation of a gas mixture containing high-concentration acetylene generated by a methane pyrolysis process.SOLUTION: There is disclosed a process for converting methane into value-added compounds, wherein a gas mixture containing high-concentration acetylene as well as hydrogen formed through methane pyrolysis (for example, non-oxidative coupling of methane) is selectively hydrogenated in the presence of a bimetallic supported catalyst to obtain ethylene from acetylene in the gas mixture, while unreacted methane and hydrogen are recovered as byproducts and / or additionally recycled.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a process for selectively hydrogenating a gas mixture having a high acetylene content. More specifically, the present disclosure relates to a process for selectively hydrogenating a gas mixture containing high concentrations of acetylene and hydrogen, formed by, for example, the thermal decomposition of methane (e.g., the non-oxidative coupling of methane), in the presence of a two-metal supported catalyst to produce ethylene from the acetylene in the gas mixture, while recovering and / or further recycling the unreacted methane and hydrogen as by-products, thereby converting the methane into highly-added compounds. [Background technology]

[0002] Methane is the most abundant compound in natural gas and contains twice the amount of carbon as any other known fossil fuel source. It has been reported that natural gas reserves are greater than coal and oil combined. As coal and oil become increasingly depleted, the utilization of natural gas has a significant impact on the global energy balance. Therefore, because natural gases, such as methane, are more abundant than petroleum resources, they have emerged as the most viable alternative raw material to replace petroleum as petroleum resources become depleted. As a result, active research is being conducted into technologies to convert methane into heavier, highly-added compounds, such as ethylene, benzene, naphtha, and fuel oil.

[0003] Direct and indirect conversion processes are known as methods for converting methane into heavier hydrocarbons. Indirect conversion processes primarily involve the production of synthesis gas through a steam reforming reaction, while direct conversion processes do not involve an intermediate step like synthesis gas production. Most currently commercialized methane conversion processes synthesize hydrocarbon compounds from synthesis gas produced by partial oxidation of methane. For example, the Fischer-Tropsch process produces hydrocarbons from synthesis gas using metal catalysts (Co, Fe). However, this indirect conversion technology requires multiple steps, has low reaction efficiency, and is expensive due to the high temperature and pressure operating environment, making it difficult to ensure economic viability in some regions.

[0004] As a result, direct conversion of methane without using synthesis gas has been proposed as an alternative. A representative example is the oxidative coupling of methane reaction, which produces C2+ hydrocarbons (e.g., C2 hydrocarbons such as ethane, ethylene, and / or acetylene, and aromatics such as benzene) (see, for example, Korean Patent Publication No. 2018-0113448). Another known direct conversion method for methane is the production of C2+ hydrocarbons using a non-oxidative route. However, the direct conversion method tends to produce by-products; oxidative conversion methods tend to produce carbon oxides (CO, CO2, etc.), and non-oxidative conversion methods tend to produce coke, which deactivates the catalyst.

[0005] Despite this, research is being conducted into methods to resolve issues such as coke formation while maintaining the advantages of direct conversion. In this regard, the present inventors have considered a method of increasing methane conversion while suppressing coke formation by adding hydrogen during methane pyrolysis and more precisely adjusting reaction conditions, such as the hydrogen-to-methane ratio, pyrolysis temperature, reaction pressure, and residence time. When methane pyrolysis is performed by adjusting reaction conditions to increase methane conversion while minimizing coke formation, acetylene is primarily produced as a C2 hydrocarbon. The gas phase product remaining after separating aromatic compounds such as benzene from the pyrolysis product contains a high concentration of acetylene. Furthermore, maximizing methane conversion during the pyrolysis reaction increases economic efficiency, but excessive coke formation can make the process unusable. Even when operating within an economical methane conversion range, the methane pyrolysis product inevitably contains hydrogen and unreacted methane. As described above, the acetylene concentration in the methane pyrolysis product obtained after aromatics separation is higher than that of methane pyrolysis products obtained using conventional technologies. Pyrolysis products containing such high acetylene concentrations can also be obtained by using a high-temperature plasma reactor and conducting the pyrolysis reaction under controlled reaction conditions to increase methane conversion while suppressing coke formation. However, the use of a plasma reactor has the disadvantage of being difficult to ensure economic viability. While platinum-supported catalysts and palladium-supported catalysts have been reported as acetylene conversion catalysts for hydrogenating acetylene to ethylene, the use of existing commercial catalysts on pyrolysis products containing high acetylene concentrations has limitations in terms of increasing acetylene conversion and ethylene selectivity. Furthermore, while the hydrogen and acetylene ratio is equivalent in conventional acetylene conversion processes, the hydrogen and acetylene ratio in the pyrolysis product is higher.

[0006] Furthermore, the products of methane pyrolysis contain a considerable amount of hydrogen, which has a high energy efficiency per unit mass and produces only water upon combustion without producing any other harmful by-products. Due to these advantageous properties, hydrogen has become increasingly valuable as a clean energy source in recent years. If the hydrogen formed as a by-product of the dehydrogenation reaction during the methane pyrolysis process could be effectively recovered, it would be advantageous in terms of improving the economic efficiency of the entire process.

[0007] Therefore, a selective hydrogenation catalyst capable of maximizing the yield of ethylene from methane pyrolysis products, which have a high acetylene content and therefore contain almost no ethylene compared to conventional techniques produced by non-oxidative coupling of methane, and a method for enhancing the utilization of hydrogen in the pyrolysis reaction products are required. Summary of the Invention [Problem to be solved by the invention]

[0008] One embodiment of the present disclosure provides a method for producing ethylene in high yield by selective hydrogenation of a gas mixture containing high concentrations of acetylene produced by a methane pyrolysis process.

[0009] Another embodiment of the present disclosure provides a method for effectively recovering or utilizing hydrogen in addition to ethylene from the product of the pyrolysis of methane. [Means for solving the problem]

[0010] According to a first aspect of the present disclosure, a) providing a gas mixture containing at least 2 mol% acetylene, at least 50 mol% hydrogen, and up to 48 mol% methane; b) hydrogenating the gas mixture in the presence of a hydrogenation catalyst having a first metal (M1) having hydrogenation activity and a second metal (M2) having the function of inducing selective hydrogenation supported on a porous support to form a hydrogenation product having an increased ethylene concentration compared to the gas mixture; and c) separating and recovering ethylene and hydrogen from the hydrogenation product; Including, wherein the first metal (M1) is at least one selected from the group consisting of Pd, Pt, Rh, Ir, Ni, and Co, and the second metal (M2) is at least one selected from the group consisting of Cu, Ag, Au, Zn, Ga, and Sn, The contents of the first metal (M1) and the second metal (M2) in the hydrogenation catalyst are in the ranges of 0.15 to 2% by weight and 0.8 to 30% by weight, respectively; and A selective hydrogenation method is provided that satisfies Equation 1 below: [Number 1]

number

[0011] In the above formula, W M1 is the weight percent of the first metal in the hydrogenation catalyst, and W M2 is the weight percent of the second metal in the hydrogenation catalyst.

[0012] According to an exemplary embodiment, the gas mixture may contain 3-10 mol % acetylene, 52-75 mol % hydrogen, and 18-45 mol % methane.

[0013] According to an exemplary embodiment, the gas mixture may further contain C2 hydrocarbons other than acetylene, the concentration of which may be less than 1 mol %.

[0014] According to an exemplary embodiment, the gas mixture may further contain at least one selected from the group consisting of C3 to C5 hydrocarbons, the concentration of which may be less than 1 mol %.

[0015] According to an exemplary embodiment, said step b) may be carried out without a separate external hydrogen supply.

[0016] According to an exemplary embodiment, the first metal (M1) may have a hydrogen adsorption energy in the range of -4 to -2 eV, and the second metal (M2) may have a hydrogen adsorption energy in the range of -1 to 0 eV.

[0017] According to an exemplary embodiment, the first metal (M1) and the second metal (M2) in the hydrogenation catalyst may be palladium (Pd) and copper (Cu), respectively.

[0018] According to an exemplary embodiment, the porous support in the hydrogenation catalyst may be at least one selected from the group consisting of alumina, silica, carbon, zirconia, titania, ceria, and silicon carbide.

[0019] According to an illustrative embodiment, the hydrogenation catalyst may be prepared by a method including the step of preparing a precursor solid by impregnating a support with a solution of a composite precursor, which is a combination of a precursor of a first metal (M1) and a precursor of a second metal (M2), by spraying.

[0020] According to an illustrative embodiment, the method for preparing the hydrogenation catalyst may further include reducing the precursor of the first metal (M1) and the precursor of the second metal (M2) in the precursor solid in a reducing atmosphere at a temperature of 200 to 400°C. [Effects of the Invention]

[0021] A method for producing ethylene and hydrogen from a gas mixture according to an embodiment of the present disclosure can produce ethylene in a high yield by selectively hydrogenating acetylene in the gas mixture in the presence of a supported bimetallic catalyst, taking into account the composition of a product containing a relatively high concentration of acetylene during methane pyrolysis depending on the reaction conditions. The hydrogen in the gas mixture can be recovered and used to create high-value-added products. Furthermore, by utilizing the hydrogen as a hydrogen source required for the selective acetylene hydrogenation reaction, the need for a separate external hydrogen supply can be eliminated. Furthermore, when methane and / or hydrogen in the hydrogenation product are recycled to a preceding methane pyrolysis reaction, the methane conversion rate during the methane pyrolysis reaction can be increased while suppressing coke formation. Furthermore, the selectivity for acetylene in particular can be increased, enabling the formation of a gas mixture in which acetylene accounts for the majority of C2 hydrocarbons in the methane pyrolysis product. Thus, the method according to this embodiment provides advantages particularly advantageous for commercialization, such as the ability to improve the overall efficiency of a high methane conversion platform by combining the selective hydrogenation process with the upstream and downstream processes. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram of a process for producing ethylene by combining a methane pyrolysis process and an acetylene hydrogenation process. [Figure 2] FIG. 1 is a diagram schematically illustrating the structure of an apparatus used in the examples. [Figure 3] 1 is a graph showing methane conversion calculated under different operating conditions (temperature, operating pressure, hydrogen / methane volume ratio, and residence time) (each graph is plotted as the logarithm of the reaction pressure (0.1 to 10 atmospheres) versus residence time (sec)). [Figure 4] 1 is a graph showing the calculated yields of C2 hydrocarbons and benzene under various operating conditions. [Figure 5]5A, 5B, 5C, 5D, and 5E show the simulation results of the selectivity plots for C2 + CH6, C2 (FIG. 5A, D, and G), C2 (FIG. 5B, E, and H), and CH6 (FIG. 5C, F, and I) versus methane conversion, respectively, for a temperature of 1200°C and a residence time of 1 to 5 seconds, with different reaction pressures and hydrogen supply. (Here, H2 / CH4 = 0, 1 to 10 bar for (FIG. 5A, B, and C); H2 / CH4 = 1, 0.1 to 10 bar for (FIG. 5D, E, and F); and H2 / CH4 = 1, 0 to 0.5 bar for (FIG. 5G, H, and I).) [Figure 6] A is a graph showing methane conversion versus time on stream (TOS) for different pyrolysis conditions, and B is a graph showing average product selectivity for different pyrolysis conditions. [Figure 7] 1 is a graph showing selected conversions vs. selectivity for <C hydrocarbons under different conditions (black squares represent H2 / CH4 = 0 and atmospheric pressure conditions, blue triangles represent H2 / CH4 = 1 and atmospheric pressure conditions, red circles represent H2 / CH4 = 1 and below atmospheric pressure conditions, contour lines correspond to yields, and each point represents the average of an individual experiment). [Figure 8] Graph A shows the yield of hydrocarbons produced by methane pyrolysis and hydrogenation using a PdCu catalyst (pyrolysis conditions: 1235°C, 0.5 bar, H / CH = 1 and GHSV = 1415 hr-1; hydrogenation conditions: 100°C, 0.5 bar, WHSV = 4 L / g hr), and graph B shows the calculated ethylene selectivity for each of the PdCu, PdAg, and PdAu catalysts (the temperature for the catalytic reactor is varied to adjust the acetylene conversion). DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention can be achieved by the following description. The following description should be understood as describing a preferred embodiment of the present invention, and the present invention is not necessarily limited thereto. It should also be understood that the accompanying drawings are for the purpose of aiding understanding, and are not intended to limit the present invention.

[0024] The terms used in this specification can be defined as follows:

[0025] "Coke" can refer to hydrocarbons having a low hydrogen content, specifically, solid-phase carbonaceous residue by-products.

[0026] "Coupling" can refer narrowly to a chemical reaction in which two identical molecules react to form a larger molecule.

[0027] "Methane Coupling" refers to the process of converting methane into C2 hydrocarbons (e.g., ethane, ethylene, acetylene, etc.) as well as hydrocarbons with a higher carbon number (C 2+ ) (e.g., benzene, naphthalene, etc.) and the like.

[0028] "Pyrolysis" can refer to a reaction in which hydrocarbons are decomposed upon exposure to heat or the like, even without the addition of oxygen or oxygen-containing reactants, and in this disclosure can include reactions in which heat is applied to convert a compound into one or more other substances.

[0029] "Heterogeneous catalyst" refers to a catalyst that exists in a different phase from the reactants during a catalytic reaction, e.g., a catalyst that is not dissolved in the reaction medium. For a reaction to occur, at least one reactant must diffuse and adsorb onto the surface of the heterogeneous catalyst, and after the reaction, the product must desorb from the surface of the heterogeneous catalyst.

[0030] "Support" can refer to a material (typically a solid phase material) having a high specific surface area to which catalytically active components are attached.

[0031] "Hydrogenation" can refer to a reaction that increases the hydrogen content of a compound by chemically adding hydrogen to at least a portion of the compound by contacting the compound with a catalyst in the presence of a supply of hydrogen.

[0032] The term "impregnation" refers to a method of preparing a catalyst by impregnating a support with a solution containing a catalyst precursor, followed by drying and / or calcination (or reduction) as necessary.

[0033] "Conversion" can refer to the number of moles converted to a compound other than the source material per mole of the source material.

[0034] "Selectivity" can refer to the number of moles of target product per mole of feed converted.

[0035] According to one embodiment of the present disclosure, there is provided a process for selectively converting acetylene into ethylene by hydrogenating a gas mixture. Such a gas mixture may typically be a methane pyrolysis product, specifically a gas mixture remaining after separating C6 or higher hydrocarbons, particularly aromatic hydrocarbons, from the methane pyrolysis product. Therefore, the gas mixture may be substantially free of aromatic hydrocarbons such as benzene, toluene, naphthalene, etc.

[0036] According to one specific example, the gas mixture used as the feedstock for the hydrogenation reaction may contain a higher concentration of acetylene than existing methane pyrolysis products. Such a gas mixture containing a high concentration of acetylene is achieved by adjusting the pyrolysis reaction conditions (e.g., temperature, pressure, residence time) to increase the methane conversion rate while minimizing coke formation during the pyrolysis process, particularly when the pyrolysis reaction is carried out under hydrogenation. A gas mixture having such a composition can be obtained from non-oxidative pyrolysis products of methane (specifically, non-oxidative coupling products of methane), plasma pyrolysis (or coupling) products of methane, or a combination thereof. In particular, the gas mixture applicable to this specific example is typically derived from a pyrolysis reaction of methane that does not use oxygen (specifically, non-oxidative pyrolysis), and therefore is substantially free of carbon monoxide, carbon dioxide, and the like.

[0037] According to one specific example, the concentration of acetylene in the gas mixture may be at least about 2 mol%, specifically about 3 to 10 mol%, more specifically about 4 to 8 mol%. The above-mentioned acetylene concentration is distinct from existing methane pyrolysis reaction products, which have an acetylene concentration of less than about 2 mol% (more specifically about 0.5 to 1 mol%) and a relatively high concentration of C2 hydrocarbons other than acetylene, such as ethane and ethylene.

[0038] Meanwhile, the gas mixture may further contain hydrogen formed as a by-product by the C—C coupling reaction of the methane pyrolysis reaction, and / or hydrogen supplied with or reacted with methane for the purpose of increasing the conversion rate and suppressing coke formation during methane pyrolysis, as described below. For example, the gas mixture may contain at least about 50 mol%, specifically about 52-75 mol%, and more specifically about 60-65 mol% hydrogen. Furthermore, the gas mixture typically contains methane that was not converted in the pyrolysis reaction (i.e., unreacted methane), and in this case, the methane concentration may be up to about 48 mol%, specifically about 18-45 mol%, and more specifically about 28-35 mol% methane.

[0039] According to a particular embodiment, the gas mixture may contain about 4-7 mole percent acetylene, about 62-64 mole percent hydrogen, and about 30-33 mole percent methane.

[0040] According to exemplary embodiments, the gas mixture may further contain C2 hydrocarbons other than acetylene, and such C2 hydrocarbons may be ethane and / or ethylene. The concentration of C2 hydrocarbons other than acetylene may be, for example, less than about 1 mol%, specifically less than about 0.75 mol%, and more specifically less than about 0.5 mol%. According to certain embodiments, the concentration of ethylene in the gas mixture may be, for example, less than about 1 mol%, specifically less than about 0.75 mol%, and more specifically less than about 0.5 mol%.

[0041] According to an exemplary embodiment, the gas mixture may further contain hydrocarbons, such as C3 to C5 hydrocarbons, that were not removed during the aromatics separation process from the methane pyrolysis product. Such hydrocarbons may be present at a concentration typically less than about 1 mol %, specifically less than about 0.75 mol %, and more specifically less than about 0.5 mol %.

[0042] According to one embodiment, the acetylene in the gas mixture may be converted to ethylene by selective hydrogenation using a catalyst. It is noteworthy that the hydrogen required for the acetylene hydrogenation reaction can be directly utilized without the need for a separate hydrogen supply. While external hydrogen supplementation is not completely eliminated to achieve a hydrogen partial pressure suitable for effective acetylene hydrogenation, the amount of hydrogen added can be significantly reduced. In this regard, the H / C H molar ratio in the reaction product suitable for selective hydrogenation of acetylene to ethylene may be adjusted, for example, within a range of about 5 to 35, specifically about 8 to 30, more specifically about 9 to 20, and particularly about 10 to 15.

[0043] The hydrogenation reaction may be carried out in the presence of a catalyst. The catalyst must be active enough to increase both the acetylene conversion rate and the selectivity for ethylene when used with a gas mixture containing a higher acetylene concentration than typical pyrolysis products. To this end, in this example, the hydrogenation reaction is carried out in the presence of a heterogeneous catalyst in which at least two metals, specifically, a first metal (M1) with hydrogenation activity and a second metal (M2) with the function of inducing selective hydrogenation, are supported on a porous support. These metal functions can be quantified by the H adatom adsorption energy calculated using Density Functional Theory (DFT). The first metal (M1) exhibits a hydrogen adsorption energy in the range of approximately -4 to -2 eV, and the second metal (M2) exhibits a hydrogen adsorption energy in the range of -1 to 0 eV.

[0044] For example, the first metal (M1) may be at least one selected from the group consisting of Pd, Pt, Rh, Ir, Ni, and Co, specifically Pd. The second metal (M2) may be at least one selected from the group consisting of Cu, Ag, Au, Zn, Ga, and Sn, specifically Cu. In a specific embodiment, the combination of metals supported on the support may be Pd and Cu, the reason for which may be explained by the alloying effect. The hydrogenation catalyst used in this embodiment is a catalyst containing two active metal components, and the first metal (particularly Pd) and the second metal (particularly Cu) may be in a crystalline state, in the form of an alloy, or in a form supported in intimate contact with each other. Alternatively, the first metal (M1) may exist in a monoatomic form, and the second metal (M2) may exist in the form of nanoparticles.

[0045] In an illustrative embodiment, the size of the active metal (or each of the first metal and the second metal) in the hydrogenation catalyst may be, for example, about 100 nm or less, specifically about 10 to 70 nm, more specifically about 20 to 50 nm.

[0046] According to one specific example, the content of the first metal (M1) in the hydrogenation catalyst may be, for example, about 0.15 to 2 wt%, specifically about 0.2 to 1 wt%, and more specifically about 0.21 to 0.5 wt%. The content of the first metal is a factor that affects selective hydrogenation activity and selectivity, so it may be advantageous to determine it within the aforementioned range. Furthermore, the content of the second metal (M2) may be, for example, about 0.8 to 30 wt%, specifically about 1 to 10 wt%, and more specifically about 1.5 to 5 wt%. If the content of the second metal is too high or too low, the activity may be insufficient or a hydrogenation phenomenon other than selective hydrogenation may be induced, so it may be determined within the aforementioned range.

[0047] Meanwhile, in an exemplary embodiment, the first metal (M1) and the second metal (M2) may be combined in a predetermined ratio taking into consideration the properties of each metal. In this regard, the hydrogenation catalyst may satisfy the following formula 1 (ICP-OES analysis standard): [Number 1]

number

[0048] In the above formula, W M1 is the weight percent of the first metal in the hydrogenation catalyst, and W M2 is the weight percent of the second metal in the hydrogenation catalyst.

[0049] According to an exemplary embodiment,

number

[0050] On the other hand, the support for supporting the two kinds of metals (first and second metals) may be at least one selected from the group consisting of alumina, silica, carbon, zirconia, titania, ceria, and silicon carbide. Specifically, alumina, more specifically gamma-alumina, can be used.

[0051] According to an exemplary embodiment, the support may be a porous support, and the porosity of the support may be adjusted so that reactants or products do not remain within the support for an excessively long period of time upon diffusion.

[0052] In this connection, the support may exhibit the following exemplary properties:

[0053] - Specific surface area (BET): at least approximately 300m 2 / g, specifically about 400 to 700m 2 / g, more specifically, about 500-600m 2 / g, - Pore volume: at least about 0.5cm 3 / g, specifically about 0.75 to 2 cm 3 / g, more specifically, about 1 to 1.5 cm 3 / g, and - Average pore size: about 50-200 Å, specifically about 70-180 Å, more specifically about 100-150 Å.

[0054] According to exemplary embodiments, the support may be prepared in various shapes known in the art, in addition to powder form. Examples include spherical (including hollow), cylindrical (including hollow), granular, tablet, ring, saddle, star, honeycomb, pellet, trilobe, and quatrolobe shapes. To prepare a support of a specific shape, methods known in the art, such as molding, extrusion, spray drying, pelletizing, and oil dropping, can be used, but these methods are merely exemplary. The average size of the support having the above exemplary shapes may be, for example, about 1 to 5 mm, specifically about 1.5 to 3 mm, and more specifically about 2 to 2.75 mm, but these methods are merely exemplary.

[0055] According to an exemplary embodiment, the hydrogenation catalyst may be prepared by a supporting method known in the art, such as impregnation, deposition, ion-exchange, or deposition-precipitation. Specifically, the impregnation method, more specifically, the incipient wetness impregnation method or the modified incipient wetness impregnation method may be applied.

[0056] In a specific example, the catalyst can be prepared by impregnation. For this purpose, the metal can be used in the form of a precursor, specifically a metal compound, more specifically a metal salt, a complex, or the like. The metal can be selected from those that are soluble in the medium (specifically, an aqueous medium) used in preparing the impregnation solution. For example, when the first active metal is palladium, the precursor can be an organic or inorganic acid salt, a complex, a hydroxide, a halide, a combination thereof, or the like. For example, the palladium precursor can be at least one selected from palladium acetate, palladium chloride, palladium nitrate, ammonium palladium nitrate, palladium sulfate, palladium carbonate, palladium hydroxide, palladium halide, and hydrates thereof, but this can be understood as an example. More typically, ammonium palladium nitrate can be used as the precursor. On the other hand, when the second metal is copper, the precursor can be at least one selected from copper hydroxide phosphate, copper nitrate, copper sulfate, copper acetate, copper formate, copper (II) chloride, copper iodide, and the like, and more typically, copper nitrate can be used.

[0057] According to an illustrative embodiment, the first metal precursor and the second metal precursor can be added sequentially or simultaneously to a medium to prepare the impregnation solution. The total concentration of the active metal precursors (first metal precursor and second metal precursor) in the impregnation solution can be adjusted, for example, to about 0.01-2 μM, specifically about 0.1-1 μM, and more specifically about 0.25-0.75 μM, taking into account the amount of the first and second metals supported in the final catalyst and the ratio of the first metal to the second metal. Additionally, the pH of the solution containing the first and second metal precursors can be adjusted, for example, to about 1-3, specifically about 1.2-2, and more specifically about 1.3-1.5, to effectively disperse the metal precursors in the support. To this end, an acid component known in the art can be added to the impregnation solution. Examples of such acid components include at least one selected from nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, etc.

[0058] The impregnation process is not limited to a specific method as long as the metal precursor solution (i.e., a composite precursor solution of the first and second metals) can be sufficiently contacted within the pores of the support. For example, the metal precursor solution can be contacted or impregnated by a spray method to produce a precursor solid. Alternatively, the support can be immersed in the metal precursor solution, for example, at about 15 to 80°C (specifically, about 20 to 50°C, more specifically, room temperature) for about 0.5 to 3 hours (specifically, about 1 to 2 hours). However, these conditions should be understood as exemplary.

[0059] As described above, after the active metal is impregnated into the support, a drying process can be performed, for example, in an oxygen-containing atmosphere (e.g., air). The drying temperature can be, for example, about 60 to 150°C, specifically about 70 to 100°C, but is not limited thereto. The drying time can be, for example, about 3 to 24 hours, specifically about 6 to 12 hours. The drying process can allow the metal precursor to adhere more tightly to the support. As a result, the active metal precursor can be coated on the support, and can have, for example, a core-cell structure.

[0060] After the solid material having the first and second metal precursors attached to the support is obtained as described above, the metal components can be converted to reduced or elemental forms by a reduction treatment. While calcination or heat treatment prior to reduction is not precluded, specifically, the precursor solid material can be reduced without a calcination treatment.

[0061] The reduction treatment can be carried out using hydrogen alone or in an inert gas (e.g., N, He, Ar, etc.). The reduction treatment can be carried out at a temperature ranging from about 200 to 400°C, specifically about 220 to 380°C, and more specifically about 250 to 350°C. The heating rate can be set at a rate of about 3 to 10°C / min, specifically about 4 to 8°C / min, and more specifically about 5 to 7°C / min. The reduction treatment time is not particularly limited, but can be adjusted within a range of about 0.5 to 24 hours, specifically about 1 to 12 hours. For example, when the reduction gas is diluted with an inert gas, the reduction gas concentration can be in a range of about 5 to 20% by volume. The pressure during the reduction treatment can be in a range of about atmospheric pressure to 10 bar (mainly atmospheric pressure).

[0062] According to one embodiment, a gas mixture containing a high concentration of acetylene is hydrotreated in the presence of the catalyst. At this time, the hydrotreatment temperature may be determined within a range of room temperature to 250°C, specifically about 40 to 200°C, more specifically about 50 to 150°C. The hydrotreatment pressure may be determined within a range of, for example, about 0.2 to 1 bar, specifically about 0.3 to 0.8 bar, more specifically about 0.4 to 0.7 bar.

[0063] According to an exemplary embodiment, the hydrogenation process may be carried out in a batch or continuous mode, with the continuous mode being preferred from the viewpoint of operational economy. In this case, the reactor is not particularly limited, and may be, for example, a gas-phase fixed-bed reactor, a fluidized-bed reactor, or the like, with a fixed-bed reactor being advantageous. The gas hourly space velocity (GHSV) is determined by comprehensively considering the productivity of ethylene and the conversion rate using catalytic contact. If the GHSV is too low, productivity may decrease, while if it is too high, contact with the catalyst may be insufficient. For this reason, the space velocity is, for example, about 1 to 15 L / g. cat ·hr -1 , specifically about 2 to 10 L / g cat ·hr -1 , more specifically about 3-5 L / g cat ·hr-1 may be adjusted in the range of

[0064] According to illustrative embodiments, the conversion of acetylene in the feed gas mixture may be, for example, at least about 95%, specifically at least about 97.5%, and more specifically in the range of about 99-99.9%, and the selectivity to ethylene may be, for example, at least about 95%, specifically at least about 97.5%, and more specifically in the range of about 99-99.9%, although it should be understood that these numerical ranges are provided for illustrative purposes only.

[0065] The product of the completed hydrogenation reaction can be separated or purified using a combination of means known in the art (e.g., distillation, PSA, etc.) to recover ethylene and hydrogen. However, the hydrogenated product may still contain methane and hydrogen that were retained during the hydrogenation reaction, and a portion of the methane and hydrogen can be recycled during the separation process. In this case, methane and hydrogen can be recycled individually or in the form of a mixed gas. For example, methane and hydrogen can be recycled in the form of a mixed gas and supplied to the thermal cracking reactor together with a fresh methane-containing feedstock (or a combination of the mixed gas and hydrogen), and the CH4 / H2 molar ratio in the recycled stream can be adjusted, for example, within the range of about 0.05 to 1, more specifically about 0.1 to 0.8, and even more specifically about 0.2 to 0.5.

[0066] Integrated pyrolysis and hydrogenation process An exemplary process for producing ethylene by combining a methane thermal cracking process and an acetylene hydrogenation process is shown in Figure 1. This is an example provided to facilitate understanding of the present disclosure, and in particular, the thermal cracking process prior to the hydrogenation reaction can be embodied in various ways, and should not be construed as being limited to the thermal cracking reaction described below.

[0067] Referring to the figure, a methane-containing gas 1 as a feedstock is combined with a recycled mixed gas (methane and hydrogen mixed gas; 12) to form a methane and hydrogen gas mixture 2, which is introduced into a thermal decomposition reactor 101. For example, the methane-containing gas 1 may be pure methane, or may be supplied to the thermal decomposition reactor 101 in a state where it further contains a diluent gas in addition to methane. For example, the diluent gas may be at least one selected from the group consisting of nitrogen, carbon dioxide, and hydrogen sulfide, and the content thereof may be, for example, at most about 20 mol%, specifically at most about 10 mol%, more specifically at most about 5 mol%, and particularly specifically at most about 3 mol%, but this may be understood as an example.

[0068] The pyrolysis reactor is not limited to a specific type, but may be a radial tube reactor in view of heat transfer efficiency. The material of the pyrolysis reactor, specifically the non-oxidative direct conversion reactor, may be at least one selected from the group consisting of alumina, SiC, FeCrAl alloy, and Inconel (NiCr).

[0069] On the other hand, methane is a nonpolar molecule similar to the stable structure of inert gases, with a CH bond energy of 435 kJ / mol, making it highly thermodynamically stable. This high chemical and thermodynamic stability makes methane difficult to convert into various compounds. In contrast, according to this specific example, methane is decomposed into C2+ hydrocarbons and hydrogen as a by-product by, for example, a direct non-oxidative coupling reaction or a plasma coupling reaction. The following description focuses on the thermal decomposition process involving a direct non-oxidative coupling reaction.

[0070] In the thermal cracking reaction, methane is activated to methyl radicals and then a radical reaction takes place. In order to increase the methane conversion rate and suppress coke formation, the reaction temperature and pressure conditions can be precisely controlled. For example, the thermal cracking temperature can be controlled within a range of, for example, about 1000 to 1400°C, specifically about 1050 to 1350°C, more specifically about 1100 to 1300°C, and particularly specifically about 1150 to 1250°C. The thermal cracking pressure can be controlled within a range of, for example, about 0.1 to 1 bar, specifically about 0.2 to 0.8 bar, more specifically about 0.3 to 0.7 bar, and particularly specifically about 0.4 to 0.6 bar. Furthermore, the high-space velocity (GHSV) can be controlled within a range of, for example, about 300 to 3600 h -1 Specifically, approximately 720 to 1800 hours -1 , more specifically, about 900 to 1600 hours -1 , specifically about 1200~1440hr -1 may be set in the range of

[0071] In the illustrated embodiment, as described above, the recycled mixed gas introduced into the reactor together with the fresh methane-containing feedstock contains methane and hydrogen. Therefore, a thermal cracking reaction occurs under the supply of hydrogen, which is effective in increasing the methane conversion rate while suppressing the formation of coke-forming materials. Under these reaction conditions, methane can be converted primarily to acetylene rather than ethylene among C2 hydrocarbons. In this regard, the composition within the thermal cracking reactor may satisfy the requirements expressed in Equation 2 below. [Number 2]

number

[0072] In the above formula, P H2 is the hydrogen partial pressure of the mixed gas introduced into the reactor, and P CH4 is the methane partial pressure in the mixed gas introduced into the reactor.

[0073] According to an exemplary embodiment,

number

[0074] According to an illustrative example, the thermal decomposition reaction may be carried out in the presence of a catalyst (e.g., a supported catalyst). The metal having methane activation function may be at least one selected from iron (Fe), chromium (Cr), vanadium (V), molybdenum (Mo), tungsten (W), etc. The support may be a porous support made of an inorganic oxide material, such as at least one selected from alumina, silica, titania, zirconia, magnesia, ceria, etc. The content of the active metal in the catalyst may be adjusted, for example, within a range of about 0.1 to 10 wt %, specifically about 0.3 to 8 wt %, and more specifically about 0.5 to 5 wt %. The above-described catalyst composition is provided as an example and is not necessarily limited thereto.

[0075] According to an exemplary embodiment, during the pyrolysis reaction under the above-described reaction conditions, the methane conversion rate may be in the range of about 10 to 50%, and the lower the methane conversion rate, the higher the C 2+ The selectivity to hydrocarbons may tend to increase. For example, in the range of methane conversion from 0 to 10%, 2+ The selectivity to hydrocarbons is at least about 99.9%, and the methane conversion is in the range of 10-20%. 2+ The selectivity to hydrocarbons is at least about 99.5%, and the methane conversion is in the range of 20-30%. 2+ The selectivity to hydrocarbons is at least about 95%, and the methane conversion is in the range of 30-40%. 2+ The selectivity to hydrocarbons is at least about 90%, and the methane conversion is in the range of 40-50%. 2+ The selectivity to hydrocarbons can be at least about 80%. However, excessive methane conversion can lead to the degradation of C 2+ The selectivity to hydrocarbons decreases to about 70%, and if it is reduced too much, the yield may be problematic. Therefore, it may be advantageous to maintain the methane conversion in the range of, for example, about 10-50%, specifically about 20-40%, more specifically about 30-35%.

[0076] The selectivity for acetylene in the pyrolysis product may be, for example, at least about 55%, specifically at least about 60%, more specifically in the range of about 65 to 70%, and the selectivity for aromatics (particularly benzene) may be, for example, not more than about 30%, specifically in the range of about 5 to 25%, more specifically in the range of about 10 to 20%.

[0077] According to an exemplary embodiment, the pyrolysis product may further contain at least one compound selected from ethane, ethylene, C3-C5 hydrocarbons, etc., in addition to acetylene and aromatics, and the content thereof may be, for example, about 40% by volume or less, specifically about 30% by volume or less, more specifically about 20% by volume or less, based on the pyrolysis product.

[0078] Referring again to FIG. 1, the pyrolysis product 3 may be passed through a vacuum pump 102 to produce a reduced pressure stream 4, which may then be rapidly cooled in a quench tower 103, for example, to about −20 to 25° C. (specifically, about −10 to 0° C.). In the illustrated embodiment, C5 is used as the overhead flow. - a gas mixture 5 containing hydrocarbons and hydrogen, and C6 as the bottom flow; + The lower stream 7 is separated into benzene 20 and a heavier fraction 21 in a benzene column 105, allowing benzene to be recovered. Meanwhile, the upper stream 5 is a gas mixture that contains methane, hydrogen, and acetylene, as described above, and may optionally further contain C2 hydrocarbons other than acetylene (ethane and / or ethylene), and C3-C5 hydrocarbons. This gas mixture may be introduced into the acetylene converter 104, where the selective hydrogenation reaction of acetylene may be carried out, as described above.

[0079] The hydrogenated product 6 is then compressed, for example, to about 10 to 50 bar (specifically, about 15 to 30 bar) while passing through a process gas compressor 106, and the compressed stream 8 may be cooled, for example, to about −75 to −45° C. (specifically, about −60 to −55° C.) in a cold-box 107. The cooled stream 9 is transferred to a demethanizer 108, from which a mixture of methane and lighter hydrogen gases 10 is discharged as an upper stream, while C2+ hydrocarbons 11 are discharged as a lower stream. The C2 hydrocarbons 16 are then separated into C2 hydrocarbons 16 and C3-C5 hydrocarbons 17 in a deethanizer 110. The C2 hydrocarbons 16 are then separated into ethylene 18 and C2 hydrocarbons other than ethylene 19 in a C2 splitter 111. At this time, the demethanizer 108, the deethanizer 110 and the C2 splitter 111 are each operated under cryogenic conditions.

[0080] Meanwhile, mixed gas 10 is separated into recycle stream 12 and recovery stream 13, and the recycle stream is combined with a methane-containing feedstock before being introduced into thermal cracking reactor 101. Recovery stream 13 is introduced into pressure swing adsorber 109 and separated into hydrogen 14 and methane 15.

[0081] In the above-described embodiment, the operation principles of the separation and purification units after the thermal cracking reaction and the selective hydrogenation reaction are well known in the art, and detailed descriptions thereof will be omitted.

[0082] In another embodiment, the basic configuration of the process shown in FIG. 1 may be maintained while varying the arrangement of the quench tower, vacuum pump, acetylene converter, etc. For example, when a quench tower, vacuum pump, and acetylene converter are arranged in this order downstream of a methane pyrolysis reactor, the acetylene converter may be operated under pressure conditions above atmospheric pressure. Alternatively, the process may be arranged in the order of vacuum pump, acetylene converter, quench tower, acetylene converter, vacuum pump, and quench tower. Alternatively, the order of acetylene converter, vacuum pump, and quench tower or acetylene converter, quench tower, and vacuum pump may be used, but this may be undesirable because it may shorten the catalyst life if C6+ hydrocarbons are drawn into the acetylene conversion catalyst.

[0083] The present invention can be more clearly understood from the following examples, which are merely for the purpose of illustrating the present invention and are not intended to limit the scope of the invention.

[0084] Example catalyst manufacturing Trilobe-shaped alumina supports were purchased from Saint-Gobain (USA) and used without further purification. Prior to active metal loading, the supports were dried overnight at 80°C in a convection oven. Palladium ammonium nitrate (Sigma, 99.9%) as the first metal precursor and copper nitrate (Sigma, 99.9%), gold nitrate (Sigma, 99.9%), or silver nitrate (Sigma, 99.9%) as the second metal precursor were dissolved in an aqueous acid solution (acid content: 10 wt %, nitric acid). Metal loading was performed using a modified incipient wetness impregnation method. The resulting solids were dried in a convection oven at 80°C and then reduced with hydrogen at 300°C for 6 hours (heating rate: 5°C / min). Catalysts in which metals in alloy form were supported on an alumina support were expressed as x%Pdy%M (x and y represent the weight percent of each metal, and M represents the second metal (Cu, Ag, or Au)).

[0085] Methane pyrolysis and hydrogenation Methane pyrolysis and hydrogenation experiments were carried out in a continuous flow system. The structure of the apparatus used in this example is shown schematically in Figure 2.

[0086] Referring to the figure, the experimental equipment mainly includes a pyrolysis furnace 201, a chiller 202, a hydrogenation reactor 203, an online gas chromatograph 204, and a vacuum pump 205. A flow was mainly used between the hydrogenation reactor 203 and the vacuum pump 205, and during analysis, the flow was changed by the online gas chromatograph 204. Furthermore, TC and P correspond to a thermocouple and a pressure controller, respectively.

[0087] Specifically, in the methane pyrolysis zone, an alumina tube reactor (99.9%, 1 / 2" OD) was placed in the center of an electric furnace equipped with a molybdenum silicide (MoSi2) heating element. Prior to the reaction, the reactor was irradiated with air (10 mL min) to remove impurities. -1The reactor was heated at 700°C for 2 hours under 99.9% CO₂ at a heating rate of 10°C / min. A gas mixture of nitrogen, methane (99.999%, Rigas), and hydrogen (UHP, Riga) was introduced into the reactor using a mass flow controller (5850E, Brooks Instrument). The pyrolysis product effluent was quenched at -10°C, and trace amounts of polycyclic aromatic compounds were collected. The quenched gas was introduced into the hydrogenation zone, where a stainless steel reactor (½” OD, 300 mm L) was placed in the center of the electric furnace. For all experiments, the reaction system was operated below atmospheric pressure, and the reaction pressure was regulated by a chemically resistant solenoid valve (Parker) and a vacuum regulator (Buchi, V800) controlled by a diaphragm. The transfer lines were heated at 100 °C to prevent potential condensation. An online gas chromatograph (Agilent) equipped with an HP-PLOT / Al2O3 capillary column (50 m × 0.32 mm × 8.0 mm) for the FID (flame ionized detector) and an HP-Molesieve capillary column (30 m × 0.53 mm × 20 mm) for the TCD (thermal conductivity detector) was used. The products were sampled at 2-hour intervals using a GC column (Technology, 7890A). The GC column was configured to separate hydrogen, nitrogen, and hydrocarbons to calculate methane conversion and quantitatively analyze the concentrations of ethylene, ethane, acetylene, and benzene. Trace amounts of C3-C5 products were combined.

[0088] The micro-kinematic simulations used in this example were performed using the CANTERA software package.

[0089] Results and Discussion -Methane pyrolysis simulation To determine the optimal reaction conditions for converting methane to highly loaded hydrocarbons as the main product, simulations of methane pyrolysis were conducted considering four reaction parameters (temperature: 1150–1250°C; pressure: 0.1–10 bar; H2 / CH4 ratio: 0–1; and residence time: 0–10 seconds). The effect of each reaction parameter on methane conversion and product yield is plotted as contour lines in Figures 3 and 4. Each graph in Figure 3 shows the effect of a combination of the four reaction parameters. Regardless of temperature, methane conversion generally increases with increasing residence time, but decreases with increasing H2 / CH4 ratio. However, the results differ depending on the operating pressure. At temperatures up to 1150°C, methane conversion exhibited a volcanic-like trend.

[0090] As an example, in Figure 3a, at 1100°C, the methane conversion rate started at approximately 45% at 0.2 bar, peaked at 60% at 1 bar, and then decreased to 45% at 10 bar (residence time: 6 seconds) (black arrow). Meanwhile, at 1250°C, the methane conversion rate gradually decreased as the reaction pressure increased (yellow arrow in Figure 3c), starting at 87% at 0.2 bar and reaching 10% at 10 bar (H2 / CH4 = 0; residence time: 6 seconds). At 1250°C, a similar trend was observed regardless of whether hydrogen was supplied (Figures 3d, 3h, and 3i). In this regard, it is important to note that the operating pressure in Figure 3 is plotted on a logarithmic scale, and the methane conversion rate is sensitive to the reaction pressure, especially at pressures below atmospheric pressure. Furthermore, the highest methane conversion rate was achieved below atmospheric pressure as the reaction temperature increased. This result is believed to be due to the fact that gas-phase hydrogen, which is easily formed during the methane pyrolysis process, thermodynamically suppresses the total methane conversion rate.

[0091] Next, the hydrocarbon yield was investigated. The yields of specific hydrocarbon species (ethane, ethylene, acetylene, and benzene) were measured by simulation, and the results are shown in Figure 4.

[0092] With the H2 / CH4 ratio fixed at 0, the yield of specific hydrocarbon products increased with increasing reaction pressure and residence time, regardless of temperature (yellow arrows in Figures 4a-c). At 1100 °C, the highest hydrocarbon yield region, regardless of hydrogen addition, is located in a similar region to the highest conversion shown in Figure 4i. However, as the temperature increased to 1200 °C (Figure 4f), the highest yield of specific products was obtained at 0.5 bar and a residence time of 3 seconds, which is distinct from the highest methane conversion observed (Figure 3g). This difference reflects the conversion of methane to other hydrocarbons, mostly polycyclic aromatic hydrocarbons. The simulated results confirm that adjusting the reaction pressure and co-supplying hydrogen are important considerations for methane pyrolysis reactions to selectively produce heavier hydrocarbons.

[0093] The effects of low pressure and the simultaneous supply of hydrocarbons and hydrogen on hydrocarbon selectivity during the methane pyrolysis reaction can be seen in the plot of conversion vs. selectivity shown in Figure 5. To clarify the effects of reaction pressure and hydrogen supply in the simulation, the experimental conditions at a constant temperature of 1200°C were divided into three zones: with hydrogen supply (Figures 5A-5C), without hydrogen supply (Figures 5D-5I), operating pressures below atmospheric pressure (Figures 5G-5I), and operating pressures above atmospheric pressure (Figures 5A-5F).

[0094] The measured methane conversion versus hydrocarbon selectivity (ethane, ethylene, acetylene, and benzene) can be used to predict the ideal product composition, which is highly dependent on the operating conditions. Comparing Figures 5A and 5D, the total methane conversion decreased when hydrogen was co-fed, but the hydrocarbon selectivity increased. For example, under normal operating conditions, the C2 + C6 selectivity obtained at 50% methane conversion was approximately 60% (dotted line in Figure 5), whereas with hydrogen co-fed, it reached an 80% level. This improvement can be primarily attributed to the increase in C2 selectivity (see Figures 5B and 5E). This indicates that hydrogen has a significant effect in suppressing the formation of polycyclic aromatic hydrocarbons.

[0095] Subsequently, when the operating pressure in the methane pyrolysis reaction is set below atmospheric pressure, the selectivity range for methane conversion can be narrowed. For example, at a methane conversion of about 50%, the selectivity ranges from 60 to 80% at 1 to 10 bar, while it is about 85% at 0.1 to 0.5 bar. These distinct results suggest that the selectivity for C2+C6 hydrocarbons can be maximized during the methane pyrolysis reaction when the operating pressure is adjusted below atmospheric pressure and hydrogen is supplied.

[0096] Experimental effectiveness study An additional experiment was conducted by supplying hydrogen and setting the methane pyrolysis pressure below atmospheric pressure. To sample the gas-phase products discharged from the reactor equipped with a vacuum pump, volatile solids in the gas effluent stream were collected under mild conditions. The collected hydrocarbons were analyzed for trace amounts of polycyclic aromatic hydrocarbons such as naphthalene, anthracene, and pyrene (data not shown). The gas-phase products were then rapidly transferred to the analytical equipment over a period of approximately 1 minute (see Figure 2).

[0097] The results of the methane pyrolysis experiment are shown in Figures 6A and 6B. The temperature was 1240°C, the H2 / CH4 ratio was 1, the pressure was 0.5 bar, and the GHSV was 1415 h -1These operating conditions were selected as the base experimental conditions for the methane pyrolysis reaction. Under these conditions, the average methane conversion was 34%, and the selectivity to heavy hydrocarbons up to benzene was 93%. As the operating pressure increased to 0.6 bar, the initial conversion increased to 41% and then gradually decreased to 36%. This result can be attributed to heat transfer issues caused by coke formation on the walls of the alumina tubular reactor. Meanwhile, starting with a reaction pressure of 0.4 bar, the average methane conversion dropped sharply to 21%, which is consistent with the simulation results showing that methane conversion is sensitive to reaction pressure, as mentioned above. When the temperature was increased under fixed operating pressure conditions, the initial conversion increased by 43%, but after 30 hours it was 32%. These results indicate that a reaction temperature appropriate for stable hydrocarbon production must be selected during the methane pyrolysis reaction. Additionally, a stable methane conversion of 26% and hydrocarbon selectivity of 95% were achieved under the mildest conditions of 1220°C and 0.5 bar.

[0098] Meanwhile, Figure 7 shows the experimental results plotting conversion rate versus selectivity for specific hydrocarbons. Similar to the method used to divide the simulation results shown in Figure 7, the experimental results were divided into three regions depending on the presence or absence of hydrogen supply and reaction pressure. In this experiment, the temperature was adjusted within the range of 1000 to 1260°C to achieve the target methane conversion rate.

[0099] Experimental results showed that high hydrocarbon (C2 + C6) selectivity was achieved at methane conversions below 10% (black squares in Figure 7). However, as methane conversion increased to approximately 40%, hydrocarbon selectivity dropped sharply to approximately 30%, which is primarily due to polycyclic aromatic hydrocarbons and / or coke formation. With hydrogen feeding, the achievable selectivity at 40% methane conversion was approximately 80% (blue triangles in Figure 7). This is due to improved C2 selectivity, indicating that hydrogen has a significant effect on suppressing the formation of polycyclic aromatic hydrocarbons. Furthermore, selectivity increased when methane pyrolysis was operated below atmospheric pressure; for example, at 50% methane conversion, hydrocarbon selectivity was at the 90% level at operating pressures of 0.3 to 0.5 bar. Experimental results showed that the highest hydrocarbon yield was observed at 1275 °C and 0.3 bar, with an average methane conversion of 36.9%. These experimental results suggest that methane pyrolysis is promising for producing three main species, namely, acetylene, hydrogen, and benzene, under conditions where the formation of coke precursors such as polycyclic aromatic hydrocarbons is suppressed.

[0100] Performance evaluation of hydrogenation catalysts The methane pyrolysis reaction described above produced an effluent gas with a specific chemical composition. The methane conversion rate was maintained at 30% during the methane pyrolysis reaction, and the C7 and higher hydrocarbons were removed before being introduced as a feedstock for the hydrogenation reaction. Polycyclic aromatic hydrocarbons were removed from the methane pyrolysis product, and C3-C5 hydrocarbons, which were present in trace amounts, were not considered. The composition of these gases is shown in Table 1 below.

[0101] [Table 1]

[0102] In the table above, when the methane conversion rate was approximately 30%, the respective concentrations of methane, hydrogen, and acetylene in the gas mixture introduced into the hydrogenation reactor were 32.2%, 62.5%, and 4.5%. This was higher than the gas composition used in commercial acetylene converters, which have used palladium catalysts for decades. Taking this into consideration, in this example, catalysts with PdCu, PdAu, and PdAg supported on alumina supports were used. For screening, the catalysts were prepared using the incipient wetness impregnation method, with the metal composition adjusted in a simple manner.

[0103] Figure 8A shows the overall yields of acetylene and benzene obtained from a hybrid system of methane pyrolysis and hydrogenation using a PdCu catalyst. In the hydrogenation reaction, the PdCu catalyst converted 99.5% of acetylene to ethylene, with no catalyst deactivation observed after 65 hours. The yields of ethylene and C2+C6 in the hybrid system were 20% and 24%, respectively. While the PdAg and PdAu catalysts exhibited lower catalytic performance than the PdCu catalyst, the PdAg catalyst also showed relatively high selectivity (98%) at approximately 60% methane conversion, demonstrating its potential (Figure 8B). Although high acetylene conversion was achieved using the PdAu catalyst, ethane was the main product, indicating limitations in the selective hydrogenation of gas mixtures with high acetylene and hydrogen concentrations. These results suggest that the hybrid system according to this example has great potential for the continuous production of high-value-added ethylene from methane.

[0104] Meanwhile, the weight ratio of Pd and Cu supported on the hydrogenation catalyst was adjusted as shown in Table 2 below.

[0105] [Table 2]

[0106] [Table 3]

[0107] As can be seen from the table above, the Cu-free 0.2Pd (comparative example) exhibited a higher conversion rate but lower selectivity to ethylene compared to the Cu-containing 0.2Pd1Cu, 0.2Pd2Cu, and 0.2Pd3Cu catalysts, but the Pd-free 1Cu (comparative example) exhibited significantly lower acetylene hydrogenation performance. In the Pd and Cu-containing catalyst examples, a general trend was observed in which the conversion rate decreased at the same temperature as the Cu content increased, but the ethylene selectivity increased. In particular, the tendency for selectivity to increase as the Cu content increased from 1 wt% to 3 wt% is believed to be due to the Pd atoms being located on Cu nanoparticles in the catalyst, which have poor acetylene hydrogenation performance, creating an environment in which the Pd atoms can selectively hydrogenate acetylene, resulting in the selective hydrogenation of highly concentrated acetylene.

[0108] Simple variations and modifications of the present invention are readily available to those skilled in the art, and all such variations and modifications are within the scope of the present invention.

Claims

1. a) providing a gas mixture containing at least 2 mol% acetylene, at least 50 mol% hydrogen, and up to 48 mol% methane; b) a first metal (M) having hydrogenation activity on a porous support; １ ) and a second metal (M ２ hydrogenating the gas mixture in the presence of a hydrogenation catalyst supported on the catalyst to form a hydrogenation product having an increased ethylene concentration relative to the gas mixture; and c) separating and recovering ethylene and hydrogen from the hydrogenation product; Including, Here, the first metal (M １ ) is at least one selected from the group consisting of Pd, Pt, Rh, Ir, Ni and Co, and the second metal (M ２ ) is at least one selected from the group consisting of Cu, Ag, Au, Zn, Ga, and Sn; The first metal (M １ ) and a second metal (M ２ ) are in the range of 0.15 to 2% by weight and 0.8 to 30% by weight, respectively; and A selective hydrogenation method that satisfies the following formula 1: [Equation 1] [Equation 1] In the above formula, W Ｍ１ is the weight percent of the first metal in the hydrogenation catalyst, and W Ｍ２ is the weight percent of the second metal in the hydrogenation catalyst.

2. 2. The method of claim 1, wherein the gas mixture provided in step a) is a dearomatic product of the pyrolysis of methane.

3. 2. The method of claim 1, wherein the source of methane is at least one selected from the group consisting of methane, natural gas, and biogas.

4. 2. The method of claim 1, further comprising recycling at least a portion of the methane and hydrogen in the hydrogenation product by a thermal decomposition reaction of methane.

5. The recycled CH ４ / H ２ The method according to claim 4, characterized in that the molar ratio of is in the range of 0.05 to 1.

6. 2. The method of claim 1, wherein the gas mixture contains 3 to 10 mol % acetylene, 52 to 75 mol % hydrogen, and 18 to 45 mol % methane.

7. 2. The method of claim 1, further comprising the step of: adding a C2 hydrocarbon other than acetylene to the gas mixture; and wherein the concentration of the C2 hydrocarbon other than acetylene is less than 1 mol %.

8. 8. The method according to claim 7, wherein the gas mixture further contains at least one selected from the group consisting of C3 to C5 hydrocarbons, the concentration of which is less than 1 mol %.

9. 2. The method of claim 1, wherein step b) is carried out without a separate external hydrogen supply.

10. The first metal (M １ ) and a second metal (M ２ 2. The method of claim 1, wherein the metals P and Cu are palladium (Pd) and copper (Cu), respectively.

11. 2. The method according to claim 1, wherein the porous support in the hydrogenation catalyst is at least one selected from the group consisting of alumina, silica, carbon, zirconia, titania, ceria, and silicon carbide.

12. The porous support has a thickness of at least 300 m ２ Specific surface area (BET) of at least 0.5 cm ３ / g and an average pore size of 50 to 200 Å.

13. The hydrogenation catalyst is a first metal (M １ ) precursor and second metal (M ２ 2. The method according to claim 1, wherein the precursor solid is produced by a method comprising the step of impregnating a support with a solution of a composite precursor obtained by combining precursors of the above-mentioned compounds by a spray method to produce the precursor solid.

14. The first metal (M １ ) precursor and second metal (M ２ 14. The method according to claim 13, further comprising the step of reducing a precursor of (I) in a reducing atmosphere at a temperature of 200 to 400°C.

15. 15. The method according to claim 14, wherein the reduction step is performed in an atmosphere of hydrogen alone or in an inert gas diluted with hydrogen.

16. 2. The method according to claim 1, wherein the hydrogenation reaction in step b) is carried out at a temperature of from room temperature to 250° C. and a pressure of from 0.2 to 1 bar.

17. The step b) is carried out in a continuous mode, and the space velocity is 1-15 L / g. ｃａｔ ・hr －１ 17. The method of claim 16, wherein the temperature is adjusted in the range of

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