Carbon dioxide conversion catalyst and manufacturing method thereof

Abstract

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

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. 10-2023-0123491, filed September 15, 2023, 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 conversion rate of carbon dioxide and the selectivity for hydrocarbons having a carbon number of 5 or more in a reaction for converting carbon dioxide into hydrocarbons, while minimizing sintering and coking phenomena that may occur during the reaction process, thereby maintaining catalytic activity for a long period of time.

[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]

[0014] The present invention is intended to solve the above-mentioned problem, and to provide 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 sintering phenomenon at high temperatures by selectively introducing a shell layer only to primary particles distributed in the surface area of ​​a catalyst in the form of secondary particles formed by agglomeration of a plurality of primary particles and optimizing the relationship between the diameter of the primary particles and the thickness of the shell layer.

[0015] In order to solve the above-mentioned problem, the present invention provides a novel carbon dioxide conversion catalyst and a carbon dioxide conversion method using the catalyst.

[0016] Specifically, (1) the present invention provides a catalyst in the form of a core-shell, wherein the core is in the form of a secondary particle formed by agglomeration of a plurality of primary particles, and the shell is formed by agglomeration of a plurality of core-shell primary particles including a primary particle and a shell layer surrounding the primary particle, and the catalyst is 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 particle satisfy the following equation 1:

[0017] [Formula 1]

[0018] 0.005 ≤ l / r ≤ 30

[0019] (2) The present invention provides a catalyst in the above (1) wherein l / r is 0.005 to 25.

[0020] (3) The present invention provides a catalyst in (1) or (2) above, wherein l / r is 0.005 to 0.05.

[0021] (4) The present invention provides a catalyst according to any one of the above (1) to (3), wherein the primary particle contains Fe.

[0022] (5) The present invention provides a catalyst according to any one of the above (1) to (4), wherein the primary particle is an Fe bulk catalyst particle or a catalyst particle in which Fe is supported as an active ingredient on a support.

[0023] (6) The present invention provides a catalyst in any one of the above (1) to (5), wherein the shell layer surrounding the primary particle includes Al, Ce, Cu, Co, Mo, or an oxide or nitride thereof.

[0024] (7) The present invention provides a catalyst according to any one of the above (1) to (6), wherein l is 0.05 to 500 nm.

[0025] (8) The present invention provides a catalyst according to any one of the above (1) to (7), wherein r is 10 to 100 nm.

[0026] (9) The present invention provides a catalyst according to any one of the above (1) to (8), wherein the catalyst is used in a reaction for producing a hydrocarbon from carbon dioxide.

[0027] (10) The present invention provides a method for converting carbon dioxide, including 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).

[0028] The catalyst of the present invention has a structure in which a portion of the surface of the catalyst particles exhibiting catalytic activity is covered by a protective layer, thereby exhibiting excellent catalytic activity, while suppressing sintering at high temperatures, thereby stably and efficiently converting carbon dioxide into hydrocarbons, and in particular, producing high value-added hydrocarbons having 5 or more carbon atoms with high selectivity.

[0029] Figure 1 is a simplified diagram of the shape of the catalyst of the present invention.

[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 in the form of a core-shell, wherein the core is in the form of a secondary particle formed by agglomeration of a plurality of primary particles, and the shell is formed by agglomeration of a plurality of core-shell primary particles including a primary particle and a shell layer surrounding the primary particle, and the catalyst is 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 particle satisfy the following equation 1:

[0035] [Formula 1]

[0036] 0.005 ≤ l / r ≤ 30

[0037]

[0038] The present invention provides a novel carbon dioxide conversion catalyst capable of increasing the high-temperature stability of the catalyst itself by selectively forming a shell layer on primary particles distributed on the surface of a catalyst in the form of secondary particles having a core-shell structure, while also obtaining a high selectivity for high-carbon hydrocarbons having a carbon number of 5 or more, which are relatively high in added value among the hydrocarbon mixtures ultimately produced.

[0039]

[0040] Hereinafter, the catalyst of the present invention will be described in more detail.

[0041]

[0042] Core

[0043] The catalyst provided by the present invention has a core-shell structure. The core-shell structure is a structure comprising a core and a shell surrounding the core, and has the characteristic that the core can be protected by the shell.

[0044] Meanwhile, in the present invention, the core has the form of a secondary particle formed by agglomeration of multiple primary particles. The primary particles constituting the core may be Fe-based catalyst particles. The 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.

[0045]

[0046] More specifically, the primary particles may be Fe bulk catalyst particles or catalyst particles in which Fe is supported as an active ingredient on a support. The Fe bulk catalyst particles refer to a catalyst composed solely 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.

[0047] Meanwhile, when the primary particles are catalyst particles in which Fe is supported as an active ingredient on a support, the support may be alumina or silica. These 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.

[0048] Furthermore, when the primary particle is a catalyst particle in which Fe is supported as an active ingredient on a support, a co-catalyst component may be supported together with the active ingredient Fe for the purpose of further increasing the catalytic activity of the active ingredient, and at least one selected from among Na, K, and Cu may be used as the co-catalyst component.

[0049]

[0050] Meanwhile, the core in the form of secondary particles formed by agglomeration 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 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 mechanical strength and activity aspects of the catalyst may be better.

[0051]

[0052] Shell

[0053] The above shell covers and protects the surface of the core described above, thereby suppressing catalyst sintering during the carbon dioxide conversion reaction process, thereby improving the conversion rate of carbon dioxide and the selectivity for high-carbon hydrocarbons.

[0054] The above shell, like the core described above, is formed by the aggregation of multiple primary particles. However, the primary particles constituting the shell are characterized by having a shell layer on their own. By having a shell layer on the primary particles constituting the shell, they can protect the core described above, and the shell layer acts as a protective layer to suppress the sintering phenomenon of the catalyst.

[0055] Meanwhile, 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 include Al, Ce, Cu, Co, Mo, or an oxide or nitride thereof. The above components do not lower the catalytic activity of the primary particles, and have excellent high-temperature and mechanical stability, so that the performance can be sufficiently maintained even when the catalyst is used under high-temperature conditions. More preferably, the protective layer may include Al.

[0056] The above shell layer can be formed through various methods, but is preferably formed through atomic layer deposition. More specifically, when a protective layer is formed on the surface of the catalyst particle described above using atomic layer deposition, the protective layer is formed in a shape in which the thickness is thin and uniform, and the protective layer covers only a portion of the surface of the catalyst particle. When the protective layer is formed in this shape, the conversion rate of carbon dioxide by the catalyst is improved, and the selectivity for high-carbon hydrocarbons also increases. Although the specific mechanism of this action cannot be clearly identified, it was expected that the selectivity would decrease because the surface area that exhibits activity would be narrowed when the catalyst surface is covered with a protective layer. However, it was confirmed that the selectivity was also improved along with the conversion rate expected to be improved by the protective layer, as in the present invention.

[0057]

[0058] Meanwhile, in the primary particle having a shell layer included in the shell, the average diameter r of the primary particle and the average thickness l of the shell layer surrounding the primary particle are characterized by satisfying the following equation 1:

[0059] [Formula 1]

[0060] 0.005 ≤ l / r ≤ 30

[0061]

[0062] When the ratio of the shell layer among the primary particles forming the shell is appropriate and satisfies the above formula 1, the carbon dioxide conversion rate and the selectivity for high-carbon hydrocarbons having 5 or more carbon atoms can be high at the same time. However, when the values ​​of r and l are not appropriate and the above formula 1 is not satisfied, one or more of the conversion rate and selectivity can decrease.

[0063] In particular, the value of l / r may be 0.005 or more, and 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. In the case where the value of l is reduced by forming a thin shell using a method such as an atomic layer deposition method, there may be a technical advantage of high uniformity of the shell by finely controlling the characteristics of the catalyst surface, and in the case where the value of l is relatively high by forming a relatively thick shell using a method such as a support method, there may be a technical advantage of being advantageous in terms of material transfer since the shell is formed relatively discontinuously.

[0064]

[0065] More specifically, l may be 0.05 to 500 nm. The l value may also have a specific range that varies depending on the method of forming the shell, and when the shell is formed using an atomic layer deposition method, l may be 0.05 to 5 nm, and preferably 0.05 nm or more, 0.06 nm or more, 0.07 nm or more, or 0.08 nm or more, and 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. Meanwhile, in the case of forming a shell using a support method, l may be 100 to 500 nm, and 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 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, It can be less than 310 nm or less than 300 nm.

[0066] The above 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 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.

[0067]

[0068] Carbon dioxide conversion method

[0069] 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.

[0070] 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 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 has the core-shell structure described above, and is characterized in that the conversion rate of carbon dioxide and the selectivity for high-carbon hydrocarbons are simultaneously high when a carbon dioxide conversion reaction is performed using the catalyst.

[0071] 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.

[0072]

[0073] 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.

[0074]

[0075] Manufacturing Example 1

[0076] An 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 stirring at 400 rpm. Thereafter, a precipitant aqueous solution was added to the reaction vessel at a rate of 2 ml / min using a syringe pump. When the pH reached 7 to 8, the precipitant addition was stopped, and the same temperature and stirring speed were maintained for 2 hours. Thereafter, the precipitate and the solvent were separated using a filtration device, the precipitate was washed with deionized water, and then dried at 110°C until completely dry. After drying, it was calcined at 400°C for 3 hours, and secondary particles in the form of aggregates of primary particles having a particle size of 10 to 20 nm were obtained. The secondary particles were separated using a sieve to separate secondary particles having a particle size of approximately 100 to 300 μm.

[0077] Separately, a cocatalyst Cu precursor (copper nitrate) and K precursor (potassium nitrate) were added to deionized water to prepare a cocatalyst precursor solution, and the secondary particles were added to the cocatalyst precursor solution and mixed. After loading the cocatalyst component, it was dried at 110°C until completely dry, and then calcined at 400°C for an additional 3 hours.

[0078]

[0079] Manufacturing Example 2

[0080] Secondary particles were obtained by performing the same procedure as in Manufacturing Example 1 above, except that the firing was performed at 1,000°C during the secondary particle manufacturing process.

[0081]

[0082] Example 1

[0083] A certain amount of the secondary particles obtained in the above Manufacturing Example 1 were applied and loaded onto a square tray. The tray was then placed in a chamber within an ALD equipment, and the temperature within the chamber 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 3 seconds, maintained for 100 seconds, and purged for 20 seconds. This process was repeated 3 times. Thereafter, purging was performed again for 600 seconds, and the process of injecting water instead of trimethylaluminum in the previous process for 3 seconds in a pulse, maintaining for 100 seconds, and purging for 20 seconds was repeated 3 more times. This process was considered 1 cycle, and the cycle was repeated 16 times to obtain a catalyst.

[0084]

[0085] Example 2

[0086] A catalyst was obtained by performing the same procedure as in Example 1 above, except that the number of cycle repetitions was adjusted to 8.

[0087]

[0088] Example 3

[0089] A catalyst was obtained by performing the same procedure as in Example 1 above, except that the number of cycle repetitions was adjusted to 4.

[0090]

[0091] Example 4

[0092] A catalyst was obtained by performing the same procedure as in Example 1 above, except that the number of cycle repetitions was adjusted to 1.

[0093]

[0094] Example 5

[0095] A certain amount of secondary particles not loaded with Cu and K obtained in the manufacturing process of the above Manufacturing Example 1 were mixed with a precursor solution containing copper nitrate, potassium nitrate, and aluminum nitrate dissolved therein. The concentration of the aluminum precursor in the mixture was adjusted to 40 wt%, and the secondary particles and the precursor solution were mixed so that the weight of aluminum element in the final catalyst was 10 wt%. The mixture was stirred at room temperature, dried at 100°C for 8 hours, and calcined at 400°C for 3 hours to obtain a catalyst.

[0096]

[0097] Example 6

[0098] In the above Example 5, a catalyst was obtained by performing the same procedure except that the weight of aluminum element in the final catalyst was 15 wt%.

[0099]

[0100] Example 7

[0101] In the above Example 5, a catalyst was obtained by performing the same procedure except that the weight of the aluminum element in the final catalyst was set to 20 wt%.

[0102]

[0103] Example 8

[0104] A catalyst was obtained by performing the same procedure as in Example 5 above, except that the weight of aluminum element in the final catalyst was 4 wt%.

[0105]

[0106] Example 9

[0107] In the above Example 8, a catalyst was obtained by performing the same procedure except that the secondary particles obtained in the manufacturing process of Manufacturing Example 2 were used.

[0108]

[0109] Comparative Example 1

[0110] The secondary particles obtained in the above manufacturing example 1 were used as a catalyst.

[0111]

[0112] Comparative Example 2

[0113] A catalyst was obtained by performing the same procedure as in Example 5 above, except that the weight of the aluminum element in the final catalyst was set to 40 wt%.

[0114]

[0115] Comparative Example 3

[0116] In the above Example 5, a catalyst was obtained by performing the same procedure except that the weight of the aluminum element in the final catalyst was set to 50 wt%.

[0117]

[0118] When the secondary particle diameter (core diameter) of the manufactured catalyst is R, the thickness of the shell is L, the average diameter of the primary particles forming the shell is r, the average thickness of the shell layer surrounding the primary particles is l, and the distance between the primary particles is a, each value can be measured and calculated by the following method.

[0119]

[0120] 1) Method of measuring L and R values

[0121] The manufactured catalyst is epoxy molded and cut to obtain a cross-section, and then the cross-section is analyzed by SEM and EDS to obtain an image.

[0122] More specifically, using EDS mapping analysis, a clear element distribution image is obtained with a long exposure time of more than 4 hours, and for the obtained image, the Al and Fe element distribution images are defined by drawing the cross-sectional boundaries of Fe and Al as closed curves based on the DBSCAN (Density-based spatial clustering of applications with noise) algorithm. At this time, the distribution of Fe element is irregular, there may be holes, and there may be formed bodies other than Fe elements inside.

[0123] The above Fe element distribution shape is divided into very small polygons, and in this process, the parts with holes and the molded parts are excluded. The center of mass of each polygon is (x i , y i ) and the area of ​​each polygon is A i When , the center of mass of each polygon is multiplied by the area, and then the total mass of the entire shape is calculated by adding up the values ​​and dividing by the total area. x , C y ) is obtained. Meanwhile, the center of mass coordinates of each polygon are the average of the vertex coordinates of each shape.

[0124]

[0125] Meanwhile, the area value A of each of the above polygons i From the A value that adds up all of them, the R value can be calculated using the following formula.

[0126] R = 2(A / π) 1 / 2

[0127] In addition, the cross-sectional boundary of Al is defined by drawing a closed curve, and the irregular shape of the Al element distribution is divided into very small polygons, and in this process, the part with the hole and the molded part are excluded. The area value of each of the small polygons is B i When , the total area B of the shell is Bi It can be calculated as the sum of the values.

[0128] Also, previously obtained (C x , C y ) and calculate the distance between the centers of each polygonal shape divided in the shell, and take the average as L start is defined as . At this time, the thickness L of the shell is determined by the previously obtained B and L start And the following equation is satisfied, and the L value can be calculated through the following equation.

[0129] B = π((L start + L) 2 -(L start ) 2 )

[0130]

[0131] 2) Method of measuring r, a, and l values

[0132] The catalyst is cut using a Focused Ion Beam device, and images of the cross-section are obtained by observing it through TEM and EDS analysis. The Fe element spectrum is extracted from the image, and the Fe element distribution pattern is imaged, and the cross-sectional boundary of Fe is defined by drawing a closed curve.

[0133] In the distribution form of nano-sized Fe primary particles, the irregular shape of one Fe particle is divided into very small polygonal shapes, and in the process, the part with holes and the part of the molded body are excluded. The area values ​​of the small polygonal shapes are added to calculate the total area of ​​one Fe primary particle, and after performing the same process for 10 or more samples, the average value of the total area of ​​the primary particle (A avg ) is obtained. From the average value of the total area above, the average diameter r value of the Fe primary particles is calculated using the following formula.

[0134] r = 2(A avg / π) 1 / 2

[0135] In the process of measuring the above r value, the center of mass of each primary particle is obtained from the divided polygonal shapes. The coordinates of the center of mass of each primary particle are (x i , y i ) and when Ai is the area of ​​the primary particles, the average distance a between the primary particles can be calculated as the average distance between the center of mass coordinates of the primary particles based on the k-Nearest Neighbors algorithm.

[0136] In addition, assuming that primary particles in the form of core-shell having n shell layers are distributed in the above shell, the area B can be assumed to be a rectangle in which a large number of n primary particle circles are distributed at intervals of a. Therefore, B can be calculated by the following equation, through which the value of n can be calculated.

[0137] B = nxa 2

[0138] In addition, the above B can also be calculated as the sum of the areas of n primary particles in the core-shell form having a shell layer, in which case B can be calculated by the following equation.

[0139] B = nx π(r / 2 + l) 2

[0140] Using the fact that the B values ​​calculated through the above two processes are the same, the following equation can be derived, through which the shell layer thickness l of the primary particle can be calculated.

[0141] a = π 1 / 2 (r / 2 + l)

[0142]

[0143] Through the above method, the r and l values ​​for the example and comparative example catalysts were measured, and the l / r value was calculated, which was summarized in Table 1 below.

[0144]

[0145] l value (nm) r value (nm) l / r Example 12.3 225.5 0.090 Example 21.5 8 20.5 0.077 Example 30.5 8 18.8 0.031 Example 40.08 13.5 0.006 Example 5 225 20.5 10.976 Example 6 338 15.8 21.392 Example 7 46 119.7 23.401 Example 8 110 21.15 213 Example 9 120 55.02 182 Comparative Example 10 24.00 Comparative Example 288 0 24.03 6.667 Comparative Example 3 124 5 29.04 2.931

[0146] Experimental Example 1. Measurement of conversion rate and selectivity in carbon dioxide conversion reaction using a catalyst.

[0147] Mixed hydrocarbons were produced from carbon dioxide using the catalysts manufactured in the above examples and comparative examples. Specifically, 0.5 g of the catalyst was placed in a fixed-bed tubular reactor (stainless steel, 1 / 2 inch diameter) and the catalyst was activated by reduction treatment for 8 hours in a carbon monoxide atmosphere (>99.9 vol%) at 400°C. Thereafter, a mixed gas mixed in a volume ratio of H2:CO2:N2=54:18:3 was flowed at a flow rate of 75 ml / min, and the reaction was performed under conditions of 20 bar and 340°C.

[0148] 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.

[0149] Carbon dioxide conversion rate and selectivity for hydrocarbons with carbon number of 5 or more were measured / calculated using the following methods.

[0150] 1) Conversion rate: Calculated using the following formula.

[0151] Carbon dioxide conversion rate = {(input CO2 flow rate - exhaust CO2 flow rate) / (input CO2 flow rate)} * 100%

[0152] 2) Selectivity: Calculated using the following formula.

[0153] Selectivity of gaseous products = {(C A H B Flow rate * A) / (input CO2 flow rate - exhaust CO2 flow rate) * 100%

[0154] Selectivity for liquid hydrocarbons with 5 or more carbon atoms = 100% - (sum of selectivities for gaseous products)

[0155]

[0156] The measured conversion rate and selectivity values ​​are summarized in Table 2 below.

[0157] CO2 conversion rate (%) C5+ selectivity (%) Example 150.667.9 Example 25267.4 Example 352.569.1 Example 45870.6 Example 555.467.1 Example 654.866.2 Example 754.565.2 Example 855.467.7 Example 954.266.7 Comparative example 144.446.5 Comparative example 247.755.5 Comparative example 346.454.4

[0158] As can be seen from Table 2 above, in the case where the catalyst of the present invention was used, the value of l / r was higher than in the case where the catalyst of the comparative example was used, which was outside the range of the present invention, and 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.

Claims

1. As a core-shell type catalyst, The above core is in the form of a secondary particle formed by agglomeration of multiple primary particles, The above shell is formed by agglomeration of multiple core-shell primary particles including primary particles and a shell layer surrounding the 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 equation 1: [Formula 1] 0.005 ≤ l / r ≤ 30 2. In paragraph 1, A catalyst wherein the above l / r is 0.005 to 25.

3. In paragraph 1, A catalyst wherein the above l / r is 0.005 to 0.

05.

4. In paragraph 1, A catalyst wherein the above primary particles contain Fe.

5. In paragraph 1, A catalyst wherein the above primary particles are Fe bulk catalyst particles or catalyst particles in which Fe is supported as an active ingredient on a support.

6. In paragraph 1, A catalyst wherein the shell layer surrounding the primary particle comprises Al, Ce, Cu, Co, Mo, or an oxide or nitride thereof.

7. In paragraph 1, The above l is a catalyst having a diameter of 0.05 to 500 nm.

8. In paragraph 1, The catalyst wherein the above r is 10 to 100 nm.

9. In paragraph 1, The above catalyst is a catalyst used in a reaction for producing hydrocarbons from carbon dioxide.

10. 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.

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