Carbon dioxide conversion catalyst and production method therefor

Abstract

The present invention relates to a carbon dioxide conversion catalyst comprising Fe-based catalyst particles and a porous protective layer formed on the surface of the catalyst particles, wherein the ratio of the pore volume having a diameter of less than 0.7 nm to the pore volume having a diameter of less than 4 nm, as measured by the HK method, is 30% or more.

Description

Carbon dioxide conversion catalyst and method for producing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0045233, filed April 3, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a novel carbon dioxide conversion catalyst capable of increasing the selectivity for hydrocarbons having 5 or more carbon atoms in a reaction for converting carbon dioxide into hydrocarbons, and a method for producing the same.

[0005] Carbon dioxide accounts for a significant portion of greenhouse gases, and technologies to reduce its presence in the atmosphere are being studied in various fields. Representative examples include Carbon Capture and Storage (CCS), which captures and stores carbon dioxide, and Carbon Capture and Utilization (CCU), which captures carbon dioxide and then utilizes it for other purposes.

[0006] Among the two categories of carbon dioxide treatment technologies mentioned above, the representative CCU technology that can utilize captured carbon dioxide beyond simple storage is the technology that produces economically valuable hydrocarbons from captured carbon dioxide. Methods for producing hydrocarbons from carbon dioxide include electrochemical, photochemical, and thermochemical methods. However, electrochemical and photochemical methods have difficulty producing long-chain hydrocarbons and have low carbon dioxide conversion rates, requiring further research before they can be applied in actual industrial fields. On the other hand, thermochemical methods use various catalysts under high temperatures and a hydrogen atmosphere to produce various hydrocarbon gases from carbon dioxide. Compared to the two methods described above, thermochemical methods have a higher carbon dioxide conversion rate and are therefore the most widely used method at present.

[0007] It is generally known that the reaction for producing hydrocarbons from carbon dioxide consists of two consecutive reactions. The first reaction is a reaction in which carbon dioxide is converted into carbon monoxide through the reverse water gas shift (RWGS) reaction, and the second reaction is a reaction in which the carbon monoxide produced through the first reaction is converted into hydrocarbons through the Fischer-Tropsch reaction. While the first reaction is endothermic, the second reaction is exothermic. In order to efficiently perform the first reaction, a large amount of energy must be supplied, but in the second reaction, the heat of reaction must be quickly removed to prevent sintering and deactivation of the catalyst. Therefore, operating the reaction process efficiently due to the characteristics of this two-step reaction is by no means easy. In particular, if the heat of reaction generated during the second reaction process is not quickly removed, the heat of reaction may accumulate inside the catalyst particles, causing a sintering phenomenon in which the catalyst particles coagulate, and a deterioration problem in which the activity of the catalyst itself decreases may occur, resulting in a decrease in selectivity for the desired hydrocarbon.

[0008] Known methods to address these issues include controlling the reactivity of the catalyst layer by using inert supports or particles together with the catalyst particles in a fixed-bed reactor for carbon dioxide conversion, or using catalysts with novel structures and properties. However, the former approach suffers from the problem of side effects caused by the inert supports or particles used, and newly developed catalysts have not yet achieved satisfactory results in both carbon dioxide conversion and high-carbon hydrocarbon selectivity.

[0009] Therefore, there is a need to develop a novel catalyst that can produce hydrocarbons from carbon dioxide without a separate two-stage reaction process, while also achieving satisfactory results in both carbon dioxide conversion and high-carbon hydrocarbon selectivity.

[0010]

[0011] Prior art literature

[0012] (Patent Document 1) KR 10-2023-0040742 A

[0013] The present invention is intended to solve the above-mentioned problem, and provides a novel carbon dioxide conversion catalyst capable of producing high-carbon hydrocarbons, particularly hydrocarbons having 5 or more carbon atoms, with high selectivity while minimizing catalyst agglomeration by introducing a thin and uniform porous protective layer on the surface of a metal catalyst particle using an atomic layer deposition method and optimizing the volume ratio of high-diameter pores and low-diameter pores formed in the porous protective layer.

[0014] In order to solve the above-mentioned problem, the present invention provides a novel carbon dioxide conversion catalyst, a method for producing the same, and a method for converting carbon dioxide using the catalyst.

[0015] Specifically, (1) the present invention provides a catalyst for carbon dioxide conversion, comprising Fe-based catalyst particles and a porous protective layer formed on the surface of the catalyst particles, wherein the ratio of the pore volume of less than 0.7 nm in diameter to the pore volume of less than 4 nm in diameter as measured by the HK method is 30% or more.

[0016] (2) In the present invention, in the above (1), the specific surface area of ​​the catalyst is 1 to 250 m 2 / g provides a catalyst for carbon dioxide conversion.

[0017] (3) In the present invention, in the above (1) or (2), the total volume of the pores having a diameter of less than 0.7 nm is 0.003 cm 3 / g or more of a catalyst for carbon dioxide conversion is provided.

[0018] (4) The present invention provides a catalyst for carbon dioxide conversion, wherein the thickness of the protective layer is 0.5 nm or more and 10 nm or less, in any one of the above (1) to (3).

[0019] (5) The present invention provides a catalyst for carbon dioxide conversion, wherein the content of the protective layer based on the weight of the entire catalyst is 1 to 50 wt% in any one of (1) to (4).

[0020] (6) The present invention provides a catalyst for carbon dioxide conversion, wherein the protective layer comprises Al, Ce, Cu, Co, Mo, or an oxide or nitride thereof in any one of (1) to (5).

[0021] (7) The present invention provides a catalyst for carbon dioxide conversion, wherein the Fe-based catalyst particles are Fe bulk catalysts or catalyst particles in which Fe is supported as an active ingredient on a support, in any one of the above (1) to (6).

[0022] (8) The present invention provides a catalyst for converting carbon dioxide, wherein the support is cerium, alumina or silica, in any one of (1) to (7).

[0023] (9) The present invention provides a catalyst for carbon dioxide conversion, wherein the Fe-based catalyst particle is a catalyst particle in which Fe is supported as an active component on a support, and at least one selected from Na, K, and Cu is further supported as a cocatalyst component, in any one of the above (1) to (8).

[0024] (10) The present invention provides a method for producing a catalyst according to any one of (1) to (9), including the steps of forming a protective layer on the surface of an Fe-based catalyst particle using an atomic layer deposition method, adsorbing a porous forming material onto the protective layer, and removing the adsorbed porous forming material by heat treatment to form a porous structure.

[0025] (11) The present invention provides a method for producing a catalyst in the above (10), wherein the porous forming material is at least one selected from the group consisting of acetylacetone, ethylene glycol, dipivaloylmethane, hydroquinone, and glycerol.

[0026] (12) The present invention provides a method for producing a catalyst, wherein the heat treatment is performed at 300 to 700°C in the above (10) or (11).

[0027] (13) The present invention provides a method for producing a catalyst, wherein the heat treatment is performed for a time of 1 hour or more and 10 hours or less in any one of the above (10) to (12).

[0028] (14) The present invention provides a method for converting carbon dioxide, comprising a step of synthesizing a mixed hydrocarbon gas by heating a reaction gas containing carbon dioxide in the presence of a catalyst according to any one of (1) to (9) above.

[0029] The carbon dioxide conversion catalyst of the present invention has a structure in which the surface of catalyst particles exhibiting catalytic activity is covered by a porous protective layer, thereby exhibiting excellent catalytic activity while minimizing the agglomeration of the catalyst, thereby stably and efficiently converting carbon dioxide into hydrocarbons, and in particular, producing high value-added hydrocarbons having 5 or more carbon atoms among hydrocarbons with high selectivity.

[0030] Hereinafter, the present invention will be described in more detail.

[0031] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0032]

[0033] Catalyst for carbon dioxide conversion

[0034] The present invention provides a catalyst for carbon dioxide conversion, comprising Fe-based catalyst particles and a porous protective layer formed on the surface of the catalyst particles, wherein the ratio of the pore volume of less than 0.7 nm in diameter to the pore volume of less than 4 nm in diameter as measured by the HK method is 30% or more.

[0035]

[0036] As explained above, the reaction of converting carbon dioxide into hydrocarbons is carried out in a two-step reaction, and it is known that the Fe-based catalyst exhibits relatively excellent activity in both of these reactions. However, when Fe-based catalyst particles are used as they are, the activity decreases due to sintering and agglomeration of the catalyst during the reaction process, and thus, at least one of the selectivity and conversion rate mentioned above is not sufficiently high to be satisfied. To overcome this drawback, the present invention introduces a porous protective layer covering the surface of the Fe-based catalyst particles using atomic layer deposition (ALD), and by optimizing the ratio of pore volume by this porous protective layer, agglomeration of the catalyst itself is prevented, thereby providing a novel catalyst for carbon dioxide conversion that can obtain high selectivity for high-carbon hydrocarbons with a carbon number of 5 or more, which have high added value.

[0037]

[0038] Hereinafter, the catalyst of the present invention will be described in more detail.

[0039]

[0040] Fe-based catalyst particles

[0041] Fe-based catalyst particles refer to catalyst particles containing Fe, which have been conventionally used in carbon dioxide conversion reactions. A reaction of converting carbon dioxide into hydrocarbons can be performed by the activity of the Fe-based catalyst particles.

[0042] More specifically, the Fe-based catalyst particles may be Fe bulk catalysts or catalyst particles in which Fe is supported as an active ingredient on a support. The Fe bulk catalyst refers to a catalyst composed only of an Fe-based component as an active ingredient without a separate support. More specifically, Fe metal or a compound containing Fe may be used as the bulk catalyst.

[0043] Meanwhile, when the Fe-based catalyst particles are catalyst particles in which Fe is supported as an active ingredient on a support, the support may be cerium, alumina, or silica. The above types of supports have a large specific surface area, making them advantageous for supporting the active ingredient, and when Fe is supported, they can be particularly excellent in terms of catalytic activity and durability.

[0044] Furthermore, when the Fe-based catalyst particle is a catalyst particle in which Fe is supported as an active component on a support, a co-catalyst component may be supported together with the active component Fe for the purpose of further increasing the catalytic activity of the active component, and at least one selected from among Na, K, and Cu may be used as the co-catalyst component.

[0045]

[0046] The above Fe-based catalyst particles may be in the form of secondary particles formed by agglomeration of a plurality of primary particles. The primary particles may be nanoparticles having a diameter in the nm range, and more specifically, the diameter of the primary particles may be 100 nm or less, and particularly preferably 80 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less, and at least 1 nm, 3 nm or more, 5 nm or more, or 10 nm or more. In addition, the diameter of the secondary particles formed by agglomeration of a plurality of primary particles may be 10 μm or more, and more preferably 30 μm or more, 50 μm or more, 70 μm or more, or 100 μm or more, and at most 1,000 μm, 800 μm or less, 600 μm or less, or 500 μm or less. When the diameters of the primary and secondary particles of the Fe-based catalyst particles are within the above-described range, the balance in terms of mechanical strength and catalytic activity can be appropriate.

[0047]

[0048] protective layer

[0049] The above protective layer covers the surface of the catalyst particles described above, thereby suppressing catalyst sintering and agglomeration during the carbon dioxide conversion reaction process, thereby improving the conversion rate of carbon dioxide and the selectivity for high-carbon hydrocarbons.

[0050] In particular, the protective layer has porosity, so that it can suppress agglomeration of the catalyst particles themselves, while maintaining contact between carbon dioxide and the Fe-based catalyst particles formed inside the catalyst, thereby simultaneously improving the conversion rate of carbon dioxide and the selectivity of high-carbon hydrocarbons.

[0051]

[0052] More specifically, due to the porous protective layer, the catalyst for carbon dioxide conversion may have a ratio of a pore volume of less than 0.7 nm in diameter to a pore volume of less than 4 nm in diameter as measured by the HK method of 30% or more, more preferably 30% or more, 30.5% or more, 31% or more, 31.5% or more, 32% or more, or 32.5% or more, and 50% or less, 49% or less, 48% or less, 47% or less, 46% or less, 45% or less, 44% or less, 43% or less, 42% or less, 41% or less, 40% or less, 39% or less, 38% or less, 37% or less, 36% or less, or 35% or less. In addition, the total volume of the pores of less than 0.7 nm in diameter may be 0.003 cm 3 / g or more, preferably 0.003cm 3 / g or more, 0.0032cm 3 / g or more, 0.0034cm 3 / g or more, 0.0036cm 3 / g or more, 0.0038cm 3 / g or more, 0.004cm 3 / g or more, 0.0045cm 3 / g or more, 0.0048cm 3 / g or more or 0.005cm 3 / g or more, 0.03cm 3 / g or less, 0.025cm 3 / g or less, 0.02cm 3 / g or less, 0.018cm 3 / g or less, 0.016cm 3 / g or less, 0.015cm 3 / g or less, 0.013cm 3 / g or less, 0.011cm 3 / g or less or 0.01cm 3 / g or less. When the volume and ratio of pores formed by the protective layer satisfy the above conditions, the conversion rate of carbon dioxide and the selectivity for hydrocarbons having 5 or more carbon atoms can be improved simultaneously.

[0053]

[0054] In the catalyst of the present invention, the specific surface area of ​​the catalyst after the protective layer is formed is 1 to 250 m 2 / g can be, preferably 1m 2 / g or more, 5m 2 / g or more, 10m 2 / g or more, 15m 2 / g or more, 20m 2 / g or more or 25m 2 / g or more, 250m 2 / g or less, 230m 2 / g or less, 200m 2 / g or less, 180m 2 / g or less, 150m 2 / g or less, 130m 2 / g or less, 100m 2 / g or less, 90m 2 / g or less, 80m 2 / g or less, 70m 2 / g or less, 65m 2 / g or less, 60m 2 / g or less, 55m 2 / g or less or 50m 2 / g or less. The catalyst of the present invention has a sufficiently large specific surface area as described above, so that the contact area between the catalyst and carbon dioxide can be sufficiently large, and thus the carbon dioxide conversion rate can be high.

[0055]

[0056] Furthermore, the thickness of the protective layer may be 0.5 nm or more and 10 nm or less, and preferably 0.5 nm or more, 1 nm or more, or 1.5 nm or more, and 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3.5 nm or less, 3 nm or less, or 2.5 nm or less. If the thickness of the protective layer is too thin, the effect of the protective layer may not be greatly exerted, and if the thickness of the protective layer is too thick, the protective layer may interfere with the contact between the Fe-based catalyst particles and carbon dioxide, resulting in a decrease in catalytic activity. Meanwhile, in the present invention, the thickness of the protective layer can be controlled within the above-described thin range and made uniform because the protective layer is formed using an atomic layer deposition method. The thickness of the protective layer can be measured from a cross-sectional TEM of the manufactured catalyst.

[0057] In the catalyst of the present invention, the content of the protective layer based on the weight of the entire catalyst may be 1 to 50 wt%, and preferably 1 wt% or more, 1.5 wt% or more, 2 wt% or more, 2.5 wt% or more, 3 wt% or more, 3.2 wt% or more, 3.5 wt% or more, 4 wt% or more, 4.2 wt% or more, or 4.5 wt% or more, and 30 wt% or less, 28 wt% or less, 25 wt% or less, 23 wt% or less, 20 wt% or less, 18 wt% or less, 15 wt% or less, 13 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, or 7 wt% or less. When the content of the protective layer is within the above-mentioned range, the improvement effect by the protective layer can be maximized.

[0058]

[0059] Additionally, the protective layer may include Al, Ce, Cu, Co, Mo, or oxides or nitrides thereof. These components ensure excellent high-temperature and mechanical stability without reducing the catalytic activity of the Fe-based catalyst particles, thereby sufficiently maintaining the performance even when the catalyst is used under high-temperature conditions. More preferably, the protective layer may include Al.

[0060]

[0061] Method for manufacturing a catalyst

[0062] The present invention provides a method for producing a catalyst for carbon dioxide conversion as described above. Specifically, the present invention provides a method for producing a catalyst, comprising the steps of forming a protective layer on the surface of an iron-based catalyst particle using an atomic layer deposition method, adsorbing a porous material onto the protective layer, and removing the adsorbed porous material by heat treatment to form a porous structure.

[0063]

[0064] A key technical feature of the catalyst of the present invention is its protective layer, which is formed using atomic layer deposition. Using atomic layer deposition, a uniformly thick protective layer can be formed even on complex 3D-shaped Fe-based catalyst particles, and the thickness of the protective layer can be controlled to a thin level.

[0065]

[0066] The process of forming a protective layer using an atomic layer deposition method can be performed by a conventional method, and after loading Fe-based catalyst particles into an atomic layer deposition facility, the process of injecting and depositing the protective layer raw material, the process of oxidizing or reducing, and the process of purging are combined into one cycle, and the cycle can be repeated multiple times. In the above process, water (H2O), ozone (O3), or oxygen (O2) plasma can be injected to form a metal oxide, and hydrogen gas can be injected to form a metal layer.

[0067]

[0068] Meanwhile, after forming the protective layer, a porous structure can be formed by introducing a porous forming material into the ALD chamber. More specifically, the process of forming a protective layer through the process described above is repeated multiple times to form a primary protective layer, and then a porous forming material is adsorbed onto the formed protective layer, and then only the porous forming material is selectively removed through a subsequent heat treatment process, thereby forming a porous structure.

[0069] As the porous forming material, at least one selected from the group consisting of acetylacetone, ethylene glycol, dipivaloylmethane, hydroquinone, and glycerol can be used.

[0070] For example, when the porous forming material is acetylacetone, acetylacetone introduced into the ALD chamber is randomly adsorbed between atoms of the formed protective layer, and can be selectively removed through a subsequent heat treatment process to form a porous structure.

[0071] As another example, when the porous forming material is ethylene glycol, the ethylene glycol can be introduced instead of water introduced during the process of forming a protective layer, and in this case, by repeating the process of alternately injecting and purging the protective layer raw material introduced to form the protective layer and ethylene glycol, a protective layer containing ethylene glycol chemically bonded thereto can be formed, and through a subsequent heat treatment process, the ethylene glycol can be selectively removed to form a porous structure.

[0072] The temperature at which the heat treatment is performed in this process may vary somewhat depending on the type of the porous forming material to be injected, but may be performed at a temperature of 300 to 700°C, or may be performed at a temperature of 300°C or higher, 350°C or higher, or 400°C or higher, and 700°C or lower, 650°C or lower, or 600°C or lower. If the heat treatment temperature in this process is too high, it may have a negative effect on the durability of the formed protective layer itself, and if the heat treatment temperature is too low, the porous forming material may not be sufficiently removed, and thus pores as intended by the present invention may not be formed.

[0073]

[0074] In addition, the heat treatment may be performed for 1 hour or more and 10 hours or less, and preferably 1 hour or more, 1.5 hours or more, 2 hours or more, 2.5 hours or more, or 3 hours or more, and 10 hours or less, 8 hours or less, 7 hours or less, or 6 hours or less. If the heat treatment is performed for too long or too short, a problem may arise in which the pore structure is not sufficiently formed or the durability of the protective layer itself is deteriorated.

[0075]

[0076] Carbon dioxide conversion method

[0077] The present invention provides a method for converting carbon dioxide using the catalyst described above. More specifically, the present invention provides a method for converting carbon dioxide, comprising the step of heating a reaction gas containing carbon dioxide in the presence of the catalyst to synthesize a mixed hydrocarbon gas.

[0078] The selectivity for high-carbon hydrocarbons having 5 or more carbon atoms in a mixed hydrocarbon gas produced using the catalyst of the present invention may be 30% or more, preferably 35% or more, 40% or more, or 45% or more, and 80% or less, 75% or less, 70% or less, or 65% or less. In addition, when using the catalyst of the present invention, the conversion rate of carbon dioxide may be 30% or more, preferably 30% or more, 35% or more, or 40% or more, and 70% or less, 65% or less, 60% or less, or 55% or less. The catalyst of the present invention is characterized in that the conversion rate of carbon dioxide and the selectivity for high-carbon hydrocarbons are simultaneously high during a carbon dioxide conversion reaction using the catalyst by introducing the protective layer described above.

[0079] The above conversion reaction can be carried out without any particular limitation under conditions applicable to the thermochemical conversion reaction of carbon dioxide, and the reactor used in the present invention is not particularly limited. Furthermore, the temperature at which the reaction is carried out is also not particularly limited as long as it is a temperature sufficient for the conversion of carbon dioxide, and the catalyst of the present invention can minimize sintering even under high-temperature conditions by having a protective layer, thereby allowing the carbon dioxide conversion reaction to proceed stably even at relatively high temperatures.

[0080]

[0081] Hereinafter, the present invention will be described in more detail with examples and experimental examples to specifically explain the present invention. However, the present invention is not limited to these examples and experimental examples. The examples according to the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those of average skill in the art.

[0082]

[0083] ingredient

[0084] Two types of catalysts, K-Cu / Fe-Ce and K-Cu / Fe-Si, were used as Fe-based catalyst particles. The K-Cu / Fe-Ce refers to a catalyst in which Fe is supported on a Ce support, and K and Cu are supported together as cocatalyst components, and the Ce acts as both a support and a cocatalyst. In addition, the K-Cu / Fe-Si refers to a catalyst in which Fe is supported on a Si support, and K and Cu are supported together as cocatalyst components.

[0085]

[0086] Comparative example

[0087] The prepared Fe-based catalyst particles (0.5 g) were applied and loaded onto a square tray. The tray was then placed in a chamber within the ALD equipment, and the chamber temperature was set to 150°C and the process pressure to 1 Torr. Thereafter, trimethylaluminum (TMA) at 20°C was pulse-injected into the chamber together with 100 sccm of nitrogen gas as a carrier gas for 5 seconds, followed by purging for 20 seconds. This process was repeated twice. Then, purging was performed again for 600 seconds, and the same process of pulse-injecting water at 14°C instead of trimethylaluminum for 5 seconds and purging for 20 seconds was repeated twice again, and then purging again for 600 seconds. This process was considered one cycle, and the cycle was repeated 4 to 20 times, and heat-treating was performed at a specific temperature for a certain period of time to form a protective layer containing aluminum oxide on the surface of the Fe-based catalyst particles.

[0088]

[0089] Examples 1 to 3

[0090] The cycle in the above comparative example was repeated twice, and the process of pulse-injecting acetylacetone for 5 seconds and purging for 20 seconds was repeated twice, followed by one process of purging for 600 seconds. This cycle of protective layer formation and porous structure formation was repeated 4 to 20 times, and heat treatment was performed at a specific temperature for a certain period of time to obtain a catalyst having a porous protective layer.

[0091]

[0092] Example 4

[0093] In the above comparative example, ethylene glycol at 60°C was pulse-injected for 100 seconds instead of water, followed by purging for 600 seconds. This process was considered one cycle, and the cycle was repeated 4 to 40 times, followed by heat treatment at a specific temperature for a certain period of time, thereby obtaining a catalyst having a porous protective layer.

[0094]

[0095] Example 5

[0096] In the above Example 4, a catalyst was obtained by performing the same procedure except that the number of cycle repetitions was 30 to 60 and the thickness of the protective layer was increased.

[0097]

[0098] Details regarding the catalysts manufactured in each example and comparative example are summarized in Table 1 below.

[0099]

[0100] Comparative Example 1 Example 1 Comparative Example 2 Example 2 Example 3 Example 4 Example 5 Fe-based catalyst particle type K-Cu / Fe-Ce K-Cu / Fe-Si Protective layer thickness (nm) 23.5 Protective layer (Al) content (wt%) 2.8 4.14.7 26.88 4.77 3.2 2 4.9 Pore formation XOXOOOO Pore forming material XHACACXHACACHACACEGEG Heat treatment temperature (℃) / time (hr) 600℃ / 3hr 400℃ / 6hr Catalyst specific surface area (m 2 / g)19.220.625.326.549.064.654.6<0.7nm Pore volume (cm) 3 / g)0.00320.00360.00400.00520.00990.01240.0167<0.7nm pore volume / <4nm pore volume (%)28.732.526.933.334.936.743.0

[0101] HACAC: acetylacetone

[0102] EG: Ethylene glycol

[0103]

[0104] Meanwhile, the characteristics measured in Tables 1 and 2 above were measured using the following method.

[0105] 1) Protective layer thickness: After depositing (sputtering) platinum (Pt) or carbon to a thickness of 100 nm on the protective layer of the catalyst particle, FIB (Focused ion beam) or Ar + Cross-sectional specimens were fabricated using ion milling. The thickness of the catalyst layer was measured by TEM analysis of the fabricated specimens.

[0106] 2) Protective layer content: The catalyst content was confirmed through ICP component analysis. 0.1 g of catalyst particles were dissolved in 1 ml of hydrochloric acid, diluted 10 times, and then ICP-OES analysis was performed. Meanwhile, the protective layer content refers only to the Al content included in the protective layer, excluding the Al content derived from the support.

[0107] Measurement equipment: ICP-OES Agilent 5110

[0108] Measurement conditions: RF Power 1300W, Torch Height 15mm, Plasma gas flow 15L / min, Sample Gas flow 0.8L / min, Aux. Gas flow 0.2L / min, Pump Speed ​​1.5ml / min

[0109] 3) Catalyst surface area and pore volume: The specific surface area and pore volume of the catalyst were measured using BET N2 adsorption curves. Pores smaller than 0.7 nm and pores smaller than 4.0 nm were measured by calculating the sum of pore volumes by pore size from the HK plot measured during the N2 desorption process. The measuring equipment and conditions are as follows.

[0110] Measuring equipment: BET (Belsorp MAX)

[0111] Measurement conditions: N2 (77K) adsorption / desorption, AFSM mode, relative pressure (P / P0) range: 0.05-0.99

[0112]

[0113] Considering the results of Table 1 above, even if the protective layer is formed in the same manner, it was confirmed that when the protective layer having porosity is formed, the overall specific surface area of ​​the catalyst increases, and the pore volume ratio of relatively small pores with a pore size of less than 0.7 nm increases.

[0114]

[0115] Experimental Example 1. Measurement of conversion rate and selectivity in carbon dioxide conversion reaction using a catalyst.

[0116] The catalysts manufactured in the above examples and comparative examples were used to produce mixed hydrocarbons from carbon dioxide. Specifically, the manufactured catalysts were placed in a reactor, heated to 500°C, and pretreated by flowing 5% CO2 / N2 (250 sccm) for 3 hours. Thereafter, the temperature inside the reactor was lowered to 350°C, and 25% CO2 / H2 (75 sccm) was flowed for 6 hours under 20 bar pressure conditions to induce a reaction.

[0117]

[0118] The reaction product formed as a result of the reaction was passed through a constant temperature water bath trap set to 0℃ to collect liquid hydrocarbons with a carbon number of 5 or more, and the gaseous product was analyzed in real time using gas chromatography. The reaction was performed continuously for more than 48 hours.

[0119] Carbon dioxide conversion rate and selectivity for hydrocarbons with carbon number of 5 or more were measured / calculated using the following methods.

[0120] 1) Conversion rate: Calculated using the following formula.

[0121] Carbon dioxide conversion rate = (input CO2 flow - exhaust CO2 flow) / (input CO2 flow) * 100%

[0122] 2) Selectivity: Calculated using the following formula.

[0123] Selectivity of gaseous products = (C A H B Flow rate * A) / (input CO2 flow rate - exhaust CO2 flow rate) * 100%

[0124] Selectivity for liquid hydrocarbons with 5 or more carbon atoms = 100% - (sum of selectivities for gaseous products)

[0125] 3) Yield: The yield of hydrocarbons with 5 or more carbon atoms was calculated by multiplying the carbon dioxide conversion rate and selectivity.

[0126]

[0127] The measured conversion rate and selectivity values ​​are summarized in Table 2 below.

[0128] Comparative Example 1 Example 1 Comparative Example 2 Example 2 Example 3 Example 4 Carbon dioxide conversion rate (%) 343647.648.749.149.6 C5+ selectivity 475462.864.664.961.0 C5+ yield 16.0 19.4 29.931.531.930.3

[0129] As can be seen from Table 2 above, it was confirmed that when the catalyst of the example of the present invention was used, the carbon dioxide conversion rate and the selectivity for liquid hydrocarbons having a carbon number of 5 or more with high added value were higher than when the catalyst of the comparative example was used. When the same Fe-based catalyst particles were used as a standard, the example having a porous protective layer showed a higher yield of hydrocarbons having a carbon number of 5 or more than the comparative example. Through this, it was confirmed that when a catalyst having a porous protective layer satisfying the pore volume conditions required by the present invention is used, the carbon dioxide conversion rate and the selectivity for hydrocarbons having a carbon number of 5 or more can be improved.

Claims

1. Fe-based catalyst particles; and A porous protective layer formed on the surface of the catalyst particle; A catalyst for carbon dioxide conversion, wherein the ratio of pore volumes with a diameter of less than 0.7 nm to pore volumes with a diameter of less than 4 nm measured by the HK method is 30% or more.

2. In paragraph 1, The specific surface area of ​​the above catalyst is 1 to 250 m 2 / g catalyst for carbon dioxide conversion.

3. In paragraph 1, The total volume of the pores with a diameter of less than 0.7 nm is 0.003 cm 3 Catalyst for carbon dioxide conversion of more than / g.

4. In paragraph 1, A catalyst for carbon dioxide conversion, wherein the thickness of the protective layer is 0.5 nm or more and 10 nm or less.

5. In paragraph 1, A catalyst for carbon dioxide conversion, wherein the content of the protective layer is 1 to 50 wt% based on the weight of the entire catalyst.

6. In paragraph 1, A catalyst for carbon dioxide conversion, wherein the protective layer comprises Al, Ce, Cu, Co, Mo, or an oxide or nitride thereof.

7. In paragraph 1, A catalyst for carbon dioxide conversion, wherein the above Fe-based catalyst particles are Fe bulk catalysts or catalyst particles in which Fe is supported as an active ingredient on a support.

8. In paragraph 7, The above support is a catalyst for carbon dioxide conversion, wherein the catalyst is cerium, alumina or silica.

9. In paragraph 7, The above Fe-based catalyst particles are catalyst particles in which Fe is supported as an active ingredient on a support. A catalyst for carbon dioxide conversion, wherein at least one selected from among Na, K, and Cu is further supported as a cocatalyst component.

10. A step of forming a protective layer on the surface of Fe-based catalyst particles using an atomic layer deposition method; A step of adsorbing a porous forming material onto the protective layer; and A method for producing a catalyst according to claim 1, comprising: a step of forming a porous structure by removing an adsorbed porous forming material through heat treatment.

11. In paragraph 10, A method for producing a catalyst, wherein the porous forming material is at least one selected from the group consisting of acetylacetone, ethylene glycol, dipivaloylmethane, hydroquinone, and glycerol.

12. In paragraph 10, A method for producing a catalyst, wherein the above heat treatment is performed at 300 to 700°C.

13. In paragraph 10, A method for producing a catalyst, wherein the above heat treatment is performed for a period of 1 hour or more and 10 hours or less.

14. A method for converting carbon dioxide, comprising the step of synthesizing a mixed hydrocarbon gas by heating a reaction gas containing carbon dioxide in the presence of the catalyst of paragraph 1.