Carbon dioxide conversion catalyst and method for producing the same

Abstract

The present invention relates to a core-shell type catalyst, wherein the core is in the form of secondary particles formed by the aggregation of a plurality of primary particles, and the shell is formed by the aggregation of a plurality of primary particles in a core-shell configuration, including primary particles and a shell layer surrounding those primary particles, and the average diameter r of the primary particles forming the shell and the average thickness l of the shell layer surrounding those primary particles satisfy formula 1. When the catalyst of the present invention is used in a carbon dioxide conversion reaction, the carbon dioxide conversion rate is high and the selectivity for hydrocarbons having 5 or more carbon atoms, which are useful components, is high.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0123491 dated September 15, 2023, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a novel carbon dioxide conversion catalyst that can increase the conversion rate of carbon dioxide and the selectivity of hydrocarbons having 5 or more carbon atoms in a reaction that converts carbon dioxide to hydrocarbons, and can maintain catalytic activity for a long period of time by minimizing sintering and coking phenomena that may occur during the reaction process. [Background technology]

[0003] Carbon dioxide accounts for a large proportion of greenhouse gases, and as a result, technologies to reduce the amount of carbon dioxide in the atmosphere are being researched in various fields. Typically, carbon capture and storage (CCS) technologies, which involve capturing and storing carbon dioxide, and carbon capture and utilization (CCU) technologies, which involve capturing carbon dioxide and then utilizing it in other fields, are being researched in various ways.

[0004] Of the two categories of carbon dioxide treatment technologies mentioned above, a representative example of a CCU technology that can utilize captured carbon dioxide beyond simply storing it is a technology that produces economically valuable hydrocarbons from captured carbon dioxide. Electrochemical, photochemical, and thermochemical methods can be used to produce hydrocarbons from carbon dioxide. 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 to actual industrial fields. On the other hand, thermochemical methods produce various hydrocarbon gases from carbon dioxide using various catalysts under high temperature and a hydrogen atmosphere. Compared to the two methods mentioned above, they have a higher carbon dioxide conversion rate and are currently the most widely used method.

[0005] Generally, the reaction to produce hydrocarbons from carbon dioxide is known to consist of two sequential reactions. The first reaction is the conversion of carbon dioxide to carbon monoxide via a reverse water-gas shift (RWGS) reaction, and the second reaction is the conversion of the carbon monoxide produced in the first reaction to hydrocarbons via a Fischer-Tropsch reaction. The first reaction is endothermic, while the second reaction is exothermic. A large amount of energy must be supplied to carry out the first reaction efficiently, but in the second reaction, the reaction heat must be rapidly removed to prevent catalyst sintering and deactivation. Due to the characteristics of such a two-stage reaction, it is by no means easy to operate the reaction process efficiently. In particular, if the reaction heat generated during the second reaction process is not rapidly removed, the reaction heat accumulates inside the catalyst particles, causing a sintering phenomenon where the catalyst particles aggregate, leading to a degradation problem where the activity of the catalyst itself decreases, and the selectivity for the target hydrocarbon may decrease.

[0006] Known methods to address these issues include controlling the reactivity of the catalyst layer by using both catalyst particles and inert supports or particles together when converting carbon dioxide using a fixed-bed reactor, or by using catalysts with new structures and properties. However, the former method has the problem of side effects caused by the inert supports or particles used, and newly developed catalysts have not yet shown results that simultaneously satisfy both carbon dioxide conversion efficiency and high-carbon hydrocarbon selectivity.

[0007] Therefore, there is a need to develop a novel catalyst that can produce hydrocarbons from carbon dioxide without requiring a separate two-stage reaction process, and that satisfies all requirements in terms of both carbon dioxide conversion efficiency and high-carbon hydrocarbon selectivity. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] KR10-2023-0040742A [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention aims to solve the above problems and provides a novel carbon dioxide conversion catalyst that is a secondary particulate catalyst formed by the aggregation of multiple primary particles, selectively introducing a shell layer only to primary particles distributed in the surface region, and optimizing the relationship between the diameter of the primary particles and the thickness of the shell layer, thereby minimizing the sintering phenomenon at high temperatures and enabling the production of high-carbon hydrocarbons, particularly those with 5 or more carbon atoms, with high selectivity. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides a novel carbon dioxide conversion catalyst and a method for converting carbon dioxide using the catalyst. Specifically, (1) the present invention provides a core-shell type catalyst, wherein the core is in the form of secondary particles formed by the aggregation of a plurality of primary particles, and the shell is formed by the aggregation of a plurality of primary particles in a core-shell configuration, the primary particles and the shell layer surrounding the primary particles, and the average diameter r of the primary particles forming the shell and the average thickness l of the shell layer surrounding the primary particles satisfy the following formula 1.

[0011] [Formula 1] 0.005 ≤ l / r ≤ 30

[0012] (2) The present invention provides the catalyst described in (1) above, wherein the l / r is 0.005 to 25.

[0013] (3) The present invention provides the catalyst described in (1) or (2) above, wherein the l / r is 0.005 to 0.05.

[0014] (4) In the present invention, there is provided the catalyst according to any one of (1) to (3), wherein the primary particles contain Fe.

[0015] (5) In the present invention, there is provided the catalyst according to any one of (1) to (4), wherein the primary particles are Fe bulk catalyst particles or catalyst particles in which Fe is supported as an active component on a support.

[0016] (6) In the present invention, there is provided the catalyst according to any one of (1) to (5), wherein the shell layer surrounding the primary particles contains Al, Ce, Cu, Co, Mo, oxides or nitrides thereof.

[0017] (7) In the present invention, there is provided the catalyst according to any one of (1) to (6), wherein l is 0.05 to 500 nm.

[0018] (8) In the present invention, there is provided the catalyst according to any one of (1) to (7), wherein r is 10 to 100 nm.

[0019] (9) In the present invention, there is provided the catalyst according to any one of (1) to (8), wherein the catalyst is used in a reaction for producing hydrocarbons from carbon dioxide.

[0020] (10) 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 according to any one of (1) to (9) to synthesize a mixed hydrocarbon gas. Effects of the Invention

[0021] The catalyst of the present invention has a structure in which a part of the surface of catalyst particles exhibiting catalytic activity is covered with a protective layer, thereby exhibiting excellent catalytic activity, suppressing sintering at high temperatures, enabling stable and highly efficient conversion of carbon dioxide into hydrocarbons, and in particular, enabling production of high-value-added hydrocarbons having 5 or more carbon atoms among hydrocarbons with high selectivity. Brief Description of Drawings

[0022] [Figure 1] This is a simplified diagram of the catalyst according to the present invention. [Modes for carrying out the invention]

[0023] The present invention will be described in more detail below. The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0024] Catalyst for carbon dioxide conversion The present invention provides a core-shell type catalyst, wherein the core is in the form of secondary particles formed by the aggregation of a plurality of primary particles, and the shell is formed by the aggregation of a plurality of primary particles in a core-shell configuration, each of which includes primary particles and a shell layer surrounding the primary particles, and the average diameter r of the primary particles forming the shell and the average thickness l of the shell layer surrounding the primary particles satisfy the following formula 1.

[0025] [Formula 1] 0.005 ≤ l / r ≤ 30

[0026] The present invention provides a novel carbon dioxide conversion catalyst that has a core-shell morphology, wherein the high-temperature stability of the catalyst itself can be enhanced by selectively forming a shell layer on primary particles distributed on the surface, and the final hydrocarbon mixture produced exhibits high selectivity for hydrocarbons with 5 or more carbon atoms, which have relatively high added value. The catalyst of the present invention will be described in more detail below.

[0027] core The catalyst provided by the present invention has a core-shell configuration. The core-shell configuration is a structure that includes a core and a shell surrounding the core, and is characterized in that the core can be protected by the shell.

[0028] On the other hand, in the present invention, the core has a secondary particulate structure formed by the aggregation of multiple primary particles. The primary particles constituting the core may be Fe-based catalyst particles. Fe-based catalyst particles refer to catalyst particles containing Fe that have been used in conventional carbon dioxide conversion reactions. The activity of the Fe-based catalyst particles enables the conversion of carbon dioxide into hydrocarbons.

[0029] More specifically, the primary particles may be Fe bulk catalyst particles or catalyst particles on which Fe is supported as an active component. The Fe bulk catalyst particles refer to a catalyst composed solely of Fe-based components, which are the active components, without the need for another support. More specifically, Fe metal or a compound containing Fe may be used as the bulk catalyst.

[0030] On the other hand, if the primary particles are catalyst particles on which Fe is supported as an active ingredient on a support, the support may be alumina or silica. These types of support have a large specific surface area, which is advantageous for supporting the active ingredient, and when Fe is supported, they can be particularly excellent in terms of catalytic activity and durability.

[0031] Furthermore, if the primary particles are catalyst particles on which Fe is supported as an active ingredient on a support, co-catalyst components may be supported together with the Fe to further enhance the catalytic activity of the active ingredient, and one or more of Na, K, and Cu may be used as the co-catalyst components.

[0032] On the other hand, the secondary particulate core formed by the aggregation of multiple primary particles may have a diameter of 1 μm or more, more preferably 10 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, or 100 μm or more, and may also be 1,000 μm or less, 800 μm or less, 600 μm or less, or 500 μm or less. When the diameter of the core is appropriate, the catalyst can be superior in terms of mechanical strength and activity.

[0033] shell The aforementioned shell protects the surface of the core by covering it, thereby suppressing catalyst sintering during the carbon dioxide conversion reaction process, and thereby improving the carbon dioxide conversion rate and selectivity for high-carbon hydrocarbons.

[0034] The aforementioned shell, like the core described above, is formed by the aggregation of multiple primary particles, but the primary particles constituting the shell are characterized by having a shell layer on themselves. The primary particles constituting the shell have a shell layer, which protects the aforementioned core, and the shell layer acts as a protective layer to suppress the sintering phenomenon of the catalyst.

[0035] On the other hand, the primary particles constituting the shell may be the same as the primary particles in the core described above. Furthermore, the shell layer formed on the primary particles constituting the shell may contain Al, Ce, Cu, Co, Mo, or oxides or nitrides thereof. These components do not reduce the catalytic activity of the primary particles and have excellent high-temperature and mechanical stability, so that the performance of the catalyst can be sufficiently maintained even when used under high-temperature conditions. More preferably, the protective layer may contain Al.

[0036] The shell layer may be formed by various methods, but preferably by atomic layer deposition. More specifically, when a protective layer is formed on the surface of the catalyst particles using atomic layer deposition, if the protective layer is thin and uniform in thickness, and covers only a portion of the surface of the catalyst particles, then the conversion rate of carbon dioxide by the catalyst is improved, and the selectivity of high-carbon hydrocarbons also increases. Although the specific mechanism of this effect cannot be elucidated, it was expected that when the catalyst surface is covered by the protective layer, the surface area that exhibits activity will be reduced, resulting in a less favorable effect in terms of selectivity. However, it was confirmed that, as in the present invention, both the conversion rate, which is expected to be improved by the protective layer, and the selectivity are improved.

[0037] On the other hand, in a primary particle having a shell layer contained in the shell, the average diameter r of the primary particle and the average thickness l of the shell layer surrounding the primary particle satisfy the following equation 1.

[0038] [Formula 1] 0.005 ≤ l / r ≤ 30

[0039] If the proportion of the shell layer in the primary particles forming the shell is appropriate and satisfies formula 1, the carbon dioxide conversion rate and the selectivity of hydrocarbons with 5 or more carbon atoms may increase simultaneously. If the values ​​of r and l are not appropriate and formula 1 is not satisfied, one or more of the conversion rate and selectivity may decrease.

[0040] In particular, the l / r value is 0.005 or greater, and may be 30 or less, 28 or less, 25 or less, 24 or less, 22 or less, 20 or less, 18 or less, 15 or less, 13 or less, 11 or less, 10 or less, 8 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, 0.1 or less, or 0.05 or less. When the l value becomes small by forming a thin shell using a method such as atomic layer deposition, there is a technical advantage in that the properties of the catalyst surface can be finely adjusted and the uniformity of the shell is high. When the l value becomes relatively high by forming a relatively thick shell using a method such as a loading method, there is a technical advantage in that the shell is formed discontinuously, which is advantageous in terms of mass transfer.

[0041] More specifically, l may be in the range of 0.05 to 500 nm. The specific range of the l value may also differ depending on the method of forming the shell. When forming the shell using atomic layer deposition, l may be in the range of 0.05 to 5 nm, preferably 0.05 nm or more, 0.06 nm or more, 0.07 nm or more, or 0.08 nm or more, and may be 5 nm or less, 4 nm or less, 3.5 nm or less, 3 nm or less, 2.5 nm or less, or 2.4 nm or less. On the other hand, when forming a shell using a support method, the length l may be 100 to 500 nm, preferably 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, 190 nm or more, or 200 nm or more, and may be 500 nm or less, 490 nm or less, 480 nm or less, 470 nm or less, 460 nm or less, 450 nm or less, 440 nm or less, 430 nm or less, 420 nm or less, 410 nm or less, 400 nm or less, 390 nm or less, 380 nm or less, 370 nm or less, 360 nm or less, 350 nm or less, 340 nm or less, 330 nm or less, 320 nm or less, 310 nm or less, or 300 nm or less.

[0042] The aforementioned r may be 10 to 100 nm, preferably 10 nm or more, 11 nm or more, 12 nm or more, or 13 nm or more, and may also be 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 25 nm or less, or 20 nm or less.

[0043] Methods for converting carbon dioxide 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.

[0044] The hydrocarbon selectivity of high-carbon number hydrocarbons with 5 or more carbon atoms in the mixed hydrocarbon gas produced using the catalyst of the present invention may be 40% or more, preferably 45% or more, 50% or more, 55% or more, 60% or more, or 65% or more. The catalyst of the present invention is characterized by having the aforementioned core-shell structure, which simultaneously provides a high carbon dioxide conversion rate and high-carbon number hydrocarbon selectivity during the carbon dioxide conversion reaction using the catalyst.

[0045] The aforementioned conversion reaction can be carried out without particular limitations under conditions applicable to the thermochemical conversion reaction of carbon dioxide, and the reactor and other equipment used in the present invention are not particularly limited. Furthermore, the temperature at which the reaction takes place is not particularly limited as long as it is a temperature sufficient for the conversion of carbon dioxide, and because the catalyst of the present invention has a protective layer, the sintering phenomenon can be minimized even under high-temperature conditions, thus enabling the carbon dioxide conversion reaction to be carried out stably even at relatively high temperatures.

[0046] The present invention will be described in more detail below with reference to examples and experimental examples, but the present invention is not limited to these examples and experimental examples. The examples of the present invention may be modified into 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 give a more complete explanation of the present invention to a person of average knowledge in the industry.

[0047] Manufacturing Example 1 Fe precursor, silica as a support, and deionized water as a solvent were added to a precipitation reaction vessel. The solution was heated to 60°C while being stirred at 400 rpm. Then, an aqueous solution of the precipitant was added to the reaction vessel at a rate of 2 ml / min using a syringe pump. When the pH reached 7-8, the addition of the precipitant was stopped, and the same temperature and stirring speed were maintained for 2 hours. After that, the precipitate and solvent were separated using a filtration device, the precipitate was washed with deionized water, and then dried at 110°C until the precipitate was completely dry. After drying, it was calcined at 400°C for 3 hours to obtain secondary particles in the form of aggregated primary particles with a particle size of 10-20 nm. The secondary particles were separated using a sieve to separate secondary particles with a particle size of approximately 100-300 μm.

[0048] Separately, a co-catalyst precursor solution was prepared by adding a Cu precursor (copper nitrate) and a K precursor (potassium nitrate) to deionized water, and the secondary particles were added to the co-catalyst precursor solution and mixed. After supporting the co-catalyst components, the material was dried at 110°C until completely dry, and then calcined at 400°C for 3 hours.

[0049] Manufacturing Example 2 In the above-mentioned manufacturing example 1, the process was carried out similarly except that the calcination in the secondary particle manufacturing process was performed at 1,000°C, and secondary particles were obtained.

[0050] Example 1 A certain amount of the secondary particles obtained in Production Example 1 was coated onto a rectangular tray and loaded. The tray was then placed into a chamber in the ALD apparatus, and the process pressure was set to 1 Torr so that the temperature inside the chamber reached 150°C. Then, 20°C trimethylaluminum (TMA) was pulsed into the chamber with 100 sccm of nitrogen gas as the transport gas for 3 seconds, maintained for 100 seconds, and then purged for 20 seconds. This process was repeated three times. After that, the chamber was purged again for 600 seconds, and water was pulsed in for 3 seconds instead of trimethylaluminum in the previous process, maintained for 100 seconds, and then purged for 20 seconds. This process was repeated three more times. This process constituted one cycle, and the cycle was repeated 16 times to obtain the catalyst.

[0051] Example 2 In the above-described Example 1, the procedure was carried out in the same manner except that the number of cycle repetitions was adjusted to 8 times, and a catalyst was obtained.

[0052] Example 3 In Example 1, the procedure was carried out similarly, except that the number of cycle repetitions was adjusted to four, to obtain a catalyst.

[0053] Example 4 In Example 1, the procedure was carried out similarly, except that the number of cycle repetitions was adjusted to one, to obtain a catalyst.

[0054] Example 5 A certain amount of secondary particles without supporting Cu and K, obtained in the manufacturing process of Production Example 1, was mixed with a precursor solution containing dissolved copper nitrate, potassium nitrate, and aluminum nitrate. The secondary particles and precursor solution were mixed so that the concentration of aluminum precursor in the mixture was 40% by weight, and the weight of aluminum element in the final catalyst was 10% by weight. The mixture was stirred at room temperature, dried at 100°C for 8 hours, and then calcined at 400°C for 3 hours to obtain the catalyst.

[0055] Example 6 In Example 5, the procedure was carried out similarly, except that the weight of aluminum element in the final catalyst was set to 15% by weight, and a catalyst was obtained.

[0056] Example 7 In Example 5, the procedure was carried out similarly, except that the weight of aluminum element in the final catalyst was set to 20% by weight, and a catalyst was obtained.

[0057] Example 8 In Example 5, the procedure was carried out similarly, except that the weight of aluminum element in the final catalyst was set to 4% by weight, and a catalyst was obtained.

[0058] Example 9 In Example 8, the procedure was carried out similarly, except that secondary particles obtained in the manufacturing process of Manufacturing Example 2 were used, to obtain a catalyst.

[0059] Comparative Example 1 The secondary particles obtained in the above manufacturing example 1 were used directly as a catalyst.

[0060] Comparative Example 2 In Example 5, the procedure was carried out similarly, except that the weight of aluminum element in the final catalyst was set to 40% by weight, and a catalyst was obtained.

[0061] Comparative Example 3 In Example 5, the procedure was carried out similarly, except that the weight of aluminum element in the final catalyst was set to 50% by weight, and a catalyst was obtained.

[0062] If R is the diameter (core diameter) of the secondary particles of the manufactured catalyst, L is the thickness of the shell, r is the average diameter of the primary particles forming the shell, l is the average thickness of the shell layer surrounding the primary particles, and a is the distance between the primary particles, then each value can be measured and calculated by the following method.

[0063] 1) Method for measuring L and R values After the produced catalyst is epoxy-molded and cut to obtain a cross section, the cross section is subjected to SEM and EDS analysis to obtain an image.

[0064] More specifically, a clear element distribution image is obtained by long-time exposure of 4 hours or more using EDS mapping analysis. For the obtained image, the distribution images of Al and Fe elements are processed based on the DBSCAN (Density-based spatial clustering of applications with noise) algorithm, and the cross-sectional boundaries of Fe and Al are defined by drawing them with closed curves. In this process, the distribution of Fe elements is amorphous, may have pores, and may contain a molded body other than Fe elements inside.

[0065] The amorphous figure that is the distribution form of the Fe element is divided into very small polygons, and portions with pores and the molded body portion are excluded in this process. Let the center of mass of each polygon be (x i , y i ), and let the area of each polygon be A i , then after summing all values obtained by multiplying the center of mass of each polygon by the area, the result is divided by the total area to obtain the center of mass (C x , C y ) of the entire figure. On the other hand, the centroid coordinate of each polygon is the average of the vertex coordinates of each figure.

Formula

[0066] On the other hand, from the A value obtained by summing all the area values A i of each of the polygons, the R value can be calculated by the following formula. R=2(A / π) 1 / 2

[0067] Further, the cross-sectional boundary of Al is similarly defined by drawing it with a closed curve, the amorphous figure that is the distribution of Al element is divided into very small polygons, and portions with pores and the molded body portion are excluded in this process. Let each area value of the small polygons be B i , then the total area B of the shell is the B iThe calculation can be performed by summing the values.

[0068] Also, the above obtained (C x , C y ) and calculate the distance between the center of each polygonal figure divided by the shell, and the average of these distances is L start This is defined as follows. In this case, the shell thickness L is determined from B and L which were determined earlier. start The following equation is satisfied, and the L value can be calculated using the following formula. B=π((L start +L) 2 -(L start ) 2 )

[0069] 2) Method for measuring r, a, and l values The catalyst is cut using a Focused Ion Beam apparatus, and images of the cross-section are obtained by TEM and EDS analysis. The Fe element spectrum is extracted from the image to visualize the distribution morphology of the Fe element, and the cross-sectional boundary of Fe is defined by drawing a closed curve.

[0070] In the distribution morphology of nano-sized primary Fe particles, the irregular shape of a single Fe particle is divided into very small polygonal shapes, excluding the parts with holes and molded parts during this process. The area values ​​of the small polygonal shapes are added together to calculate the total area of ​​one primary Fe particle, and after performing the same process for 10 or more samples, the average value of the total area of ​​the primary particles (A avg ) is determined. From the average value of the total area, the value of the average diameter r of the Fe primary particles is calculated using the following formula. r=2(A avg / π) 1 / 2

[0071] In the process of measuring the r value, the mass centers of the primary particles are determined from the divided polygonal figures. The mass center coordinates of each primary particle are set to (x i , y iIf we let Ai be the area of ​​the primary particle, then the average distance a between the primary particles can be calculated as the average distance between the mass center coordinates of the primary particles based on the nearest neighbor algorithm (k-Nearest Neighbors).

[0072] Furthermore, assuming that primary particles in a core-shell configuration having n shell layers are distributed within the shell, the area B can be assumed to be a rectangle with many n primary particle circles distributed at intervals of a. Therefore, B can be calculated using the following formula, and the value of n can be calculated from this. B = n × a 2

[0073] Furthermore, B is calculated by assuming that the areas of n primary particles in a core-shell configuration, each having a shell layer, are summed up, and in this case, B can be calculated using the following formula. B = n × π(r / 2 + l) 2

[0074] By utilizing the fact that the B values ​​calculated through the two processes described above are the same, the following equation can be derived, which allows us to calculate l, the thickness of the shell layer of the primary particle. a=π 1 / 2 (r / 2+l) Using the method described above, the r and l values ​​for the catalysts of the examples and comparative examples were measured, and the l / r values ​​were calculated and summarized in Table 1 below.

[0075] [Table 1]

[0076] Experimental Example 1. Measurement of conversion rate and selectivity in a carbon dioxide conversion reaction using a catalyst. Mixed hydrocarbons were produced from carbon dioxide using the catalysts manufactured in the above examples and comparative examples. Specifically, 0.5 g of catalyst was charged into a fixed-bed reactor (stainless steel, 1 / 2 inch diameter), and the catalyst was activated by reduction treatment under a carbon monoxide atmosphere (>99.9 vol%) at 400°C for 8 hours. Subsequently, a mixed gas with a volume ratio of H2:CO2:N2 = 54:18:3 was flowed at a flow rate of 75 ml / min, and the reaction was carried out under conditions of 340°C and 20 bar.

[0077] The reaction products formed as a result of the reaction were passed through a constant-temperature water bath trap set to 0°C to collect liquid hydrocarbons with 5 or more carbon atoms. The gas phase products were analyzed in real time by gas chromatography. The reaction was carried out continuously for more than 48 hours.

[0078] The carbon dioxide conversion rate and the selectivity of hydrocarbons with 5 or more carbon atoms were measured / calculated using the following methods. 1) Conversion rate: Calculated using the following formula. Carbon dioxide conversion rate = {(input CO2 flow rate - exhaust CO2 flow rate) / (input CO2 flow rate)}*100%

[0079] 2) Selectivity: Calculated using the following formula. Gas phase product selectivity = {(C A H B Flow rate *A) / (Input CO2 flow rate - Exhaust CO2 flow rate)}*100% Selectivity of liquid hydrocarbons with 5 or more carbon atoms = 100% - (sum of gas phase product selectivity) The measured conversion rates and selectivity values ​​are summarized in Table 2 below.

[0080] [Table 2]

[0081] As can be seen from Table 2 above, it was confirmed that when the catalyst of the present invention was used, the carbon dioxide conversion rate and the selectivity for high-value liquid hydrocarbons with 5 or more carbon atoms were higher compared to when the catalyst of the comparative example, in which the l / r value falls outside the range of the present invention, was used.

Claims

1. It is a core-shell type catalyst, The core is in the form of secondary particles formed by the aggregation of multiple primary particles. The aforementioned shell is formed by the aggregation of multiple primary particles in a core-shell configuration, which includes primary particles and a shell layer surrounding those primary particles. A catalyst characterized in that the average diameter r of the primary particles forming the shell and the average thickness l of the shell layer surrounding the primary particles satisfy the following formula 1. [Formula 1] 0.005 ≤ l / r ≤ 30

2. The catalyst according to claim 1, wherein the l / r is 0.005 to 25.

3. The catalyst according to claim 1, wherein the l / r is 0.005 to 0.

05.

4. The catalyst according to claim 1, wherein the primary particles include Fe.

5. The catalyst according to claim 1, wherein the primary particles are Fe bulk catalyst particles or catalyst particles on which Fe is supported as an active ingredient on a support.

6. The catalyst according to claim 1, wherein the shell layer surrounding the primary particles comprises Al, Ce, Cu, Co, Mo, oxides or nitrides thereof.

7. The catalyst according to claim 1, wherein l is 0.05 to 500 nm.

8. The catalyst according to claim 1, wherein r is 10 to 100 nm.

9. The catalyst according to claim 1, wherein the catalyst is used in a reaction to produce hydrocarbons from carbon dioxide.

10. A method for converting carbon dioxide, comprising the step of heating a reaction gas containing carbon dioxide in the presence of the catalyst described in claim 1 to synthesize a mixed hydrocarbon gas.

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