Carbon dioxide conversion catalyst and method for producing same

Abstract

The present invention provides a catalyst in the form of a core-shell in which the core is in the form of a secondary particle formed by agglomerating a plurality of primary particles, and the shell is formed by agglomerating a plurality of primary particles in the form of a core-shell comprising a primary particle and a shell layer surrounding the primary particle, and wherein the distance a between the primary particles forming the core, the diameter r of the primary particles, and the thickness L of the shell formed by agglomerating a plurality of primary particles in the core-shell form satisfy Formula 1. When the catalyst of the present invention is used in a carbon dioxide conversion reaction, the conversion rate of carbon dioxide and the selectivity to hydrocarbons (which are useful components) having 5 or more carbon atoms are high.

Description

TECHNICAL FIELD

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0123493, filed September 15, 2023, the disclosure of which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0004] The present invention relates to a new carbon dioxide conversion catalyst that can improve carbon dioxide conversion rate and selectivity to hydrocarbons having 5 or more carbon atoms in a reaction of converting carbon dioxide into hydrocarbons, while maintaining catalytic activity for a long time by minimizing sintering and coking phenomena that can occur during the reaction process. BACKGROUND

[0005] Carbon dioxide accounts for a large proportion of greenhouse gases, and thus, technologies for reducing the amount of carbon dioxide in the atmosphere are being studied in various ways. Typically, carbon capture and storage (CCS) technology that captures and stores carbon dioxide and carbon capture and utilization (CCU) technology that captures carbon dioxide and then uses it in other fields are being studied in various ways.

[0006] Among the two categories of carbon dioxide treatment technologies, a representative technology in the CCU technology that can utilize captured carbon dioxide in addition to simple storage is a technology of producing economically valuable hydrocarbons from captured carbon dioxide. Methods of producing hydrocarbons from carbon dioxide include electrochemical, photochemical, and thermochemical methods. However, the electrochemical and photochemical methods are difficult to produce long-chain hydrocarbons and have a low carbon dioxide conversion rate, and thus require more in-depth research until they can be applied to actual industrial fields. On the other hand, the thermochemical method is a method of producing various hydrocarbon gases from carbon dioxide using various catalysts under a high temperature and hydrogen atmosphere, and is the most widely used method at present since the conversion rate of carbon dioxide is high compared to the above two methods.

[0007] It is known that a reaction for producing hydrocarbons from carbon dioxide generally consists of two consecutive reactions. The first reaction is a reaction in which carbon dioxide is converted into carbon monoxide through a reverse water gas shift (RWGS) reaction, and the second reaction is a reaction in which carbon monoxide produced through the first reaction is converted into hydrocarbons through a Fischer-Tropsch (F-T) reaction. The first reaction is an endothermic reaction, and the second reaction is an exothermic reaction. In order to effectively perform the first reaction, a large amount of energy must be supplied, but in the second reaction, the reaction heat must be rapidly removed to prevent sintering of the catalyst and deterioration of the activity, and due to such characteristics of the two-stage reaction, it is not easy to effectively operate the reaction process. In particular, if the reaction heat generated during the second reaction process is not rapidly removed, the reaction heat can accumulate inside the catalyst particles, causing a sintering phenomenon in which the catalyst particles agglomerate, and a deterioration problem in which the activity of the catalyst itself can decrease, thereby reducing the selectivity to the target hydrocarbons.

[0008] As a method for solving these problems, it is known to control the reactivity of the catalyst layer by using an inert carrier or inert particles together with the catalyst particles when converting carbon dioxide using a fixed bed reactor, or to use a catalyst having a new structure and characteristics. However, the former has a problem of side effects due to the inert carrier or particles used, and the newly developed catalyst does not show satisfactory results in both the conversion rate of carbon dioxide and the selectivity to higher carbon hydrocarbons.

[0009] Therefore, it is necessary to develop a new catalyst that can produce hydrocarbons from carbon dioxide without a separate two-stage reaction process, while showing satisfactory results in both the conversion rate of carbon dioxide and the selectivity to higher carbon hydrocarbons.

[0010] Prior Art Documents

[0011] (Patent Document 1) KR 10-2023-0040742 A SUMMARY

[0012] TECHNICAL PROBLEM

[0013] The present invention aims to solve the above problems, and aims to provide a new carbon dioxide conversion catalyst in the form of secondary particles formed by agglomerating a plurality of primary particles, in which a shell layer is selectively introduced to only the primary particles distributed on the surface region in the catalyst to produce a catalyst in the form of core-shell, and the relationship between the thickness of the shell, the diameter of the primary particles, and the distance between the primary particles forming the secondary particles is optimized, the catalyst is capable of producing higher carbon hydrocarbons, particularly hydrocarbons having 5 or more carbon atoms, with high selectivity, while minimizing the sintering phenomenon at high temperatures.

[0014] Technical solution

[0015] To address the aforementioned problems, 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 core-shell catalyst, wherein the core is in the form of a secondary particle formed by agglomerating a plurality of primary particles, and the shell is formed by agglomerating a plurality of primary particles in a core-shell form, comprising primary particles and a shell layer surrounding the primary particles, and wherein the average distance a between the primary particles forming the core, the average diameter r of the primary particles, and the average thickness L of the shell formed by agglomerating a plurality of primary particles in a core-shell form satisfy the following equation 1:

[0017] [Formula 1]

[0018] .

[0019] (2) The present invention provides a catalyst according to (1) above, wherein L / (r+a) is 60 to 400.

[0020] (3) The present invention provides a catalyst according to (1) or (2) above, wherein the primary particles contain Fe.

[0021] (4) The present invention provides a catalyst according to any one of (1) to (3) above, wherein the primary particles are Fe main catalyst particles or catalyst particles wherein Fe is an active component supported on a support.

[0022] (5) The present invention provides a catalyst according to any one of (1) to (4) above, wherein the shell surrounding the primary particle comprises Al, Ce, Cu, Co, Mo or oxides or nitrides thereof.

[0023] (6) The present invention provides a catalyst according to any one of (1) to (5) above, wherein L is 500 nm to 50,000 nm.

[0024] (7) The present invention provides a catalyst according to any one of (1) to (6) above, wherein r is 0.1 nm to 100 nm.

[0025] (8) The present invention provides a catalyst according to any one of (1) to (7) above, wherein a is 0.1 nm to 100 nm.

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

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

[0028] Beneficial effects

[0029] 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, and thus can exhibit 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 five or more carbon atoms with high selectivity. Attached Figure Description

[0030] Figure 1 A diagram illustrating the form of the catalyst of the present invention. Detailed Implementation

[0031] The invention will be described in more detail below.

[0032] The terms or words used in the specification and claims of this application should not be construed as limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts consistent with the technical spirit of the invention, based on the principle that the inventor can adequately define the concepts of the terms to best describe his invention.

[0033] Catalysts for carbon dioxide conversion

[0034] This invention provides a core-shell catalyst, wherein the core is in the form of a secondary particle formed by agglomerating a plurality of primary particles, and the shell is formed by agglomerating a plurality of core-shell primary particles comprising primary particles and a shell layer surrounding the primary particles, and wherein the average distance a between the primary particles forming the core, the average diameter r of the primary particles, and the average thickness L of the shell formed by agglomerating a plurality of core-shell primary particles satisfy the following equation:

[0035] [Formula 1]

[0036]

[0037] In this invention, the average distance between the primary particles forming the core, the average diameter of the primary particles, and the average thickness of the shell in the catalyst in the form of secondary particles with a core-shell configuration satisfy a specific relationship, thereby providing a novel carbon dioxide conversion catalyst that can improve the high-temperature stability of the catalyst itself while also achieving high selectivity for higher carbon hydrocarbons with five or more carbon atoms (which have relatively high added value in the final hydrocarbon mixture).

[0038] The catalyst of the present invention will be described in more detail below.

[0039] Core

[0040] The catalyst provided by this invention has a core-shell form. This core-shell form has a structure comprising a core and a shell surrounding the core, and has the property that the core can be protected by the shell.

[0041] Furthermore, in this invention, the core has the form of secondary particles formed by agglomerating a plurality of primary particles. The primary particles constituting the core can be Fe-based catalyst particles. Fe-based catalyst particles refer to Fe-containing catalyst particles used in conventional carbon dioxide conversion reactions. The reaction of converting carbon dioxide into hydrocarbons can be carried out through the activity of the Fe-based catalyst particles.

[0042] More specifically, the primary particles can be Fe-based catalyst particles, or catalyst particles in which Fe is supported on a support as the active component. Fe-based catalyst particles refer to catalysts consisting solely of Fe-based components as the active component without a separate support. More specifically, Fe metal or Fe-containing compounds can be used as the host catalyst.

[0043] Meanwhile, when the primary particles are catalyst particles in which Fe is the active component supported on a support, the support can be alumina or silica. These types of supports have a large specific surface area, which is beneficial for loading the active component, and when Fe is loaded, the catalytic activity and durability can be particularly excellent.

[0044] Furthermore, when the primary particles are catalyst particles in which Fe is the active component supported on a support, in order to further improve the catalytic activity of the active component, the co-catalyst component can be supported together with the active component Fe, and at least one selected from Na, K and Cu can be used as the co-catalyst component.

[0045] Meanwhile, the diameter of the core, which takes the form of secondary particles formed by the aggregation of multiple primary particles, can be 10 μm or larger, and more preferably 30 μm or larger, 50 μm or larger, 70 μm or larger, or 100 μm or larger, and can also be 1,000 μm or smaller, 800 μm or smaller, 600 μm or smaller, or 500 μm or smaller. When the core diameter is appropriate, the catalyst can have better mechanical strength and activity.

[0046] Shell

[0047] The shell, by covering and protecting the surface of the core, inhibits catalyst sintering during the carbon dioxide conversion reaction, thereby improving the carbon dioxide conversion rate and selectivity for higher hydrocarbons.

[0048] Similar to the core described above, the shell is also formed by agglomerating multiple primary particles, but the primary particles constituting the shell are characterized by having a shell layer on their own. Because the primary particles constituting the shell have a shell layer, the aforementioned core can be protected, and the shell layer can act as a protective layer to suppress the sintering of the catalyst.

[0049] Meanwhile, the primary particles constituting the shell can be the same as the primary particles in the core described above. Furthermore, the shell layer formed on the primary particles constituting the shell can contain Al, Ce, Cu, Co, Mo, or their oxides or nitrides. These components do not reduce the catalytic activity of the primary particles and possess excellent high-temperature stability and mechanical stability, allowing the catalyst to maintain its performance even when used under high-temperature conditions. More preferably, the protective layer can contain Al.

[0050] The shell can be formed by various methods, but is preferably formed by atomic layer deposition (ALD). More specifically, when a protective layer is formed on the surface of the catalyst particles using ALD, the protective layer is formed in a shape that covers only a portion of the surface of the catalyst particles while having a thin and uniform thickness. When the protective layer is formed in this shape, the catalyst's conversion of carbon dioxide is increased, while the selectivity for higher hydrocarbons is also increased. Although the specific mechanism of this effect cannot be clearly explained, it is expected that the selectivity would decrease due to the reduced surface area exhibiting activity when the catalyst surface is covered by the protective layer; however, conversely, it has been confirmed that the selectivity is also increased along with the expected increase in conversion due to the protective layer as described in this invention.

[0051] Meanwhile, the average distance *a* between the primary particles forming the nucleus, the average diameter *r* of the primary particles, and the average thickness *L* of the shell formed by agglomerating a plurality of primary particles in a nucleus-shell configuration are characterized by satisfying the following equation:

[0052] [Formula 1]

[0053]

[0054] When the value of L / (r+a) (which is the ratio of the average thickness of the shell to the sum of the average diameter of the primary particles and the average distance between the primary particles) is within the above range, both the carbon dioxide conversion rate and the selectivity for higher hydrocarbons having five or more carbon atoms can be high. However, when the values ​​of L, r, and a are unsuitable and do not satisfy Equation 1, at least one of the conversion rate and selectivity may decrease. The value of L / (r+a) can be more preferably 50 or greater, 55 or greater, or 60 or greater, and 950 or less, 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 300 or less, or 200 or less.

[0055] More specifically, the thickness L of the shell can be from 500 nm to 50,000 nm, preferably 500 nm or greater, 1,000 nm or greater, or 1,500 nm or greater, and 50,000 nm or less, 45,000 nm or less, 40,000 nm or less, 35,000 nm or less, 30,000 nm or less, 25,000 nm or less, 20,000 nm or less, 15,000 nm or less, 10,000 nm or less, or 5,000 nm or less.

[0056] Furthermore, the distance 'a' between primary particles can be from 0.1 nm to 100 nm, preferably 0.1 nm or greater, 0.5 nm or greater, 1 nm or greater, 3 nm or greater, 5 nm or greater, 7 nm or greater, 10 nm or greater, 15 nm or greater, 18 nm or greater, 20 nm or greater, or 22 nm or greater, and can 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, or 40 nm or less.

[0057] Furthermore, the average diameter r of the primary particles can be from 0.1 nm to 100 nm, preferably 0.1 nm or larger, 0.5 nm or larger, 1 nm or larger, 3 nm or larger, 5 nm or larger, 7 nm or larger, 10 nm or larger, 15 nm or larger, or 18 nm or larger, and can be 100 nm or smaller, 90 nm or smaller, 80 nm or smaller, 70 nm or smaller, 60 nm or smaller, 50 nm or smaller, or 40 nm or smaller.

[0058] Meanwhile, the values ​​of r and a can be adjusted by controlling the content of each component used, reaction time, calcination temperature and time, etc., during the manufacturing of primary particles, and L can be adjusted during the formation of primary particles with shells that constitute the shell. More specifically, when forming primary particles with shells using atomic layer deposition, the shell thickness L can be controlled by adjusting the amount of shell precursor to be injected or by adjusting the flow rate, and when forming primary particles with shells using a loading method, the shell thickness L can be controlled by adjusting the precursor concentration in the precursor solution, etc.

[0059] Method for converting carbon dioxide

[0060] This invention provides a method for converting carbon dioxide using the above-described catalyst. More specifically, this invention provides a method for converting carbon dioxide, the method comprising the step of synthesizing a mixed hydrocarbon gas by heating a reaction gas containing carbon dioxide in the presence of the above-described catalyst.

[0061] The selectivity for higher hydrocarbons having five or more carbon atoms in the mixed hydrocarbon gas produced using the catalyst of the present invention can be 40% or greater, preferably 45% or greater, 50% or greater, 55% or greater, 60% or greater, or 65% or greater. The catalyst of the present invention is characterized by having the above-described core-shell structure, resulting in both high carbon dioxide conversion and high selectivity for higher hydrocarbons when using the catalyst in the carbon dioxide conversion reaction.

[0062] Under suitable conditions for the thermochemical conversion of carbon dioxide, the conversion reaction can proceed without any specific limitations, and the reactor used in this invention is not particularly limited. Furthermore, the reaction temperature is not particularly limited, as long as it is sufficient to convert the carbon dioxide. The catalyst of this invention, by having a protective layer, minimizes sintering even under high-temperature conditions, allowing the carbon dioxide conversion reaction to proceed stably even at relatively high temperatures.

[0063] The invention will be described in more detail below by way of examples and experimental examples to illustrate the invention, but the invention is not limited to these examples and experimental examples. However, embodiments of the invention can be modified in various different forms, and the scope of the invention should not be construed as limited to the embodiments described in the following detailed description. Embodiments of the invention are provided to illustrate the invention more completely to those skilled in the art.

[0064] Preparation Example 1

[0065] Fe precursor, silica as a support, and deionized water as a solvent were added to the precipitation reaction vessel. The solution was heated to 60°C while stirring at 400 rpm. Then, the aqueous precipitant 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 addition of the precipitant was stopped, and the same temperature and stirring speed were maintained for 2 hours. Subsequently, the precipitate was separated from the solvent using a filtration device, washed with deionized water, and then dried at 110°C until completely dry. After drying, it was calcined at 400°C for 3 hours to obtain secondary particles in which primary particles with a particle size of 10 nm to 20 nm agglomerated.

[0066] Independently, Cu precursors (copper nitrate) and K precursors (potassium nitrate) were added to deionized water to prepare a cocatalyst precursor solution, and secondary particles were added to the cocatalyst precursor solution and mixed. After loading the cocatalyst components, the solution was dried at 110 °C until completely dry, and then calcined at 400 °C for an additional 3 hours.

[0067] Preparation Example 2

[0068] Secondary particles were obtained in the same manner as in Preparation Example 1 above, except that the calcination during the preparation of secondary particles was carried out at 800°C.

[0069] Preparation Example 3

[0070] Secondary particles were obtained in the same manner as in Preparation Example 1 above, except that the calcination during the preparation of secondary particles was carried out at 1000°C.

[0071] Example 1

[0072] The secondary particles obtained during the manufacturing process of the above preparation example were sieved to select particles with a secondary particle size of 45 μm to 53 μm, and Cu and K were loaded onto the selected secondary particles through the process of the above preparation example. Subsequently, a certain amount of the obtained secondary particles was applied and loaded onto a square tray. The tray was then placed in a chamber of the ALD apparatus, and the chamber was set to a temperature of 150°C and a process pressure of 1 tort. This process was then repeated three times: trimethylaluminum (TMA) at 20°C was pulsed into the chamber with nitrogen at 100 sccm as the carrier gas for 3 seconds, held for 100 seconds, and then purged for 20 seconds. This process was then repeated three more times: purging was performed again for 600 seconds, and water was pulsed in the same manner instead of trimethylaluminum in the previous process for 3 seconds, held for 100 seconds, and then purged for 20 seconds. These processes were considered as one cycle, and 16 cycles were repeated to obtain a catalyst in a core-shell form.

[0073] Example 2

[0074] The catalyst was obtained in the same manner as in Example 1 above, except that particles with a secondary particle size of 100 μm to 300 μm were selected and used.

[0075] Example 3

[0076] The catalyst was obtained in the same manner as in Example 1 above, except that the secondary particles manufactured in the manufacturing process of Preparation Example 2 were used, and particles with a size of 100 μm to 300 μm were selected and used.

[0077] Example 4

[0078] The catalyst was obtained in the same manner as in Example 1 above, except that the secondary particles manufactured in the manufacturing process of Preparation Example 3 were used, and particles with a size of 100 μm to 300 μm were selected and used.

[0079] Example 5

[0080] The secondary particles obtained during the manufacturing process of Preparation Example 1 above were passed through a sieve to select secondary particles with a size of 100 μm to 300 μm. The selected secondary particles were then mixed with a precursor solution in which copper nitrate, potassium nitrate, and aluminum nitrate were dissolved. The concentration of the aluminum precursor in the mixture was adjusted to 40% by weight, and the secondary particles and precursor solution were mixed so that the final catalyst contained 20% by weight of aluminum. 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.

[0081] Example 6

[0082] The catalyst was obtained in the same manner as in Example 1 above, except that an atomic layer deposition cycle was performed.

[0083] Comparative Example 1

[0084] The secondary particles obtained in Preparation Example 1 above were used as catalysts.

[0085] Comparative Example 2

[0086] The catalyst was obtained in the same manner as in Example 5 above, except that the weight of aluminum in the final catalyst was adjusted to 40% by weight.

[0087] Comparative Example 3

[0088] The catalyst was obtained in the same manner as in Example 5 above, except that the weight of aluminum in the final catalyst was adjusted to 50% by weight.

[0089] When the secondary particle diameter (core diameter) of the prepared catalyst is R, the shell thickness 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 of these values ​​can be measured and calculated by the following method.

[0090] 1) Methods for measuring L and R values

[0091] The prepared catalyst was epoxidized and cut to obtain a cross-section, and the cross-section was analyzed by SEM, EDS and EPMA to obtain images.

[0092] More specifically, using EDS mapping analysis, clear images of elemental distributions are obtained through long-term exposures of 4 hours or more. For the obtained images, the Al and Fe elemental distribution images are defined by plotting the cross-sectional boundaries of Fe and Al as closed curves according to the density-based spatial clustering of applications with noise (DBSCAN) algorithm. In this case, the distribution of Fe may be atypical, with pores and shaped bodies in addition to the internal Fe elements.

[0093] The atypical diagram representing the distribution of Fe element is divided into very small polygons, excluding portions with holes and shaped parts in the process. When the centroid of each polygon is (x... i ,y i And the area of ​​each polygon is A. i To obtain the centroid (C0) of the entire graph, add the products of the centroid and area of ​​each polygon, then divide by the total area. x C y Meanwhile, the coordinates of the centroid of each polygon are the average of the vertex coordinates of each polygon.

[0094]

[0095] At the same time, the R value can be obtained by applying the following formula to all area values ​​A of each polygon. i The value of A obtained by summing is used to calculate:

[0096]

[0097] Furthermore, the cross-sectional boundaries of Al are similarly defined by drawing them as closed curves, and the atypical diagrams, which represent the distribution of Al elements, are divided into very small polygons, excluding portions with holes and shaped parts in the process. When the area value of each small polygon is B... iWhen the total area B of the shell is reached, it can be calculated as B. i The sum of values.

[0098] In addition, calculate the previously obtained (C) x C y The distance between the center of each polygon in the shell and the center of the polygon is defined as L. 起始 In this case, the shell thickness L satisfies the previously obtained B and L. 起始 And the following formula, and the value of L can be calculated using the following formula:

[0099]

[0100] 2) Methods for measuring r, a, and l values

[0101] The catalyst was cut using a focused ion beam apparatus, and images of the cross-section were obtained by observing it via TEM and EDS analysis. Fe elemental spectra were extracted from the images to depict the distribution of Fe, and the cross-sectional boundaries of Fe were defined by plotting them as closed curves.

[0102] In the distribution of nanoscale Fe primary particles, an atypical pattern of a Fe particle is divided into very small polygonal patterns, excluding porous and shaped portions in the process. The area values ​​of the small polygonal patterns are summed to calculate the total area of ​​a Fe primary particle, and the same process is performed on 10 or more samples to obtain the average total area of ​​the primary particles (A). 平均 The average diameter r of the Fe primary particles is calculated from the average total area using the following formula:

[0103]

[0104] The centroids of the primary particles are obtained from the polygon diagrams created during the measurement of r. When the centroid coordinates of each primary particle are (x... i ,y i ), and A i When the area of ​​the corresponding primary particle is given, the average distance 'a' between primary particles can be calculated as the average distance between the centroid coordinates of the primary particles based on the k-nearest neighbor algorithm.

[0105] Furthermore, assuming that primary particles with n shells are distributed in a core-shell configuration within the shell, the area B can be assumed to be a rectangle in which the n primary particles are distributed in circles at intervals of a. Therefore, B can be calculated using the following formula, and the value of n can be calculated from it.

[0106]

[0107] Alternatively, B can be calculated as the sum of the areas of n primary particles in a core-shell configuration with shells, and in this case, B can be calculated using the following formula:

[0108]

[0109] Using the fact that the B value calculated by the two methods above is the same, the following formula can be derived, and from this, the thickness l of the shell of the primary particle can be calculated.

[0110]

[0111] The L, r, and a values ​​of each catalyst manufactured in the examples and comparative examples were measured, and the L / (r+a) value was calculated and shown in Table 1 below.

[0112] [Table 1]

[0113]

[0114] Experimental Example 1. Measurement of Conversion Rate and Selectivity in Carbon Dioxide Conversion Reactions Using Catalysts

[0115] The catalysts prepared in the above examples and comparative examples were used to prepare mixed hydrocarbons from carbon dioxide. Specifically, 0.5 g of catalyst was loaded into a fixed-bed tubular reactor (stainless steel, 1 / 2 inch in diameter) and activated by reduction treatment at 400 °C in a carbon monoxide atmosphere (>99.9 vol%) 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 to carry out the reaction at 340 °C and 20 bar.

[0116] The reaction products, which are formed as a result of the reaction, are passed through a constant-temperature water bath set to 0°C to collect liquid hydrocarbons with five or more carbon atoms, and the gaseous products are analyzed in real time using gas chromatography. The reaction is carried out continuously for 48 hours or longer.

[0117] The following methods are used to measure / calculate carbon dioxide conversion and selectivity for hydrocarbons with five or more carbon atoms.

[0118] 1) Conversion rate: Calculated using the following formula:

[0119] Carbon dioxide conversion rate = {(Input CO2 flow rate - Output CO2 flow rate) / (Input CO2 flow rate)} * 100%

[0120] 2) Selectivity: Calculated using the following formula:

[0121] Selectivity for gaseous products = {(C A H B(Flow rate * A) / (Input CO2 flow rate - Exhaust CO2 flow rate) * 100%

[0122] Selectivity for liquid hydrocarbons with 5 or more carbon atoms = 100% - (total selectivity for gaseous products)

[0123] The measured conversion and selectivity values ​​are summarized in Table 2 below.

[0124] [Table 2]

[0125]

[0126] As can be seen from Table 2 above, it is determined that when using the catalyst of the embodiments of the present invention, the carbon dioxide conversion rate and the selectivity for liquid hydrocarbons with five or more carbon atoms having high added value are higher than when using the catalyst of the comparative examples whose L / (r+a) values ​​are outside the scope of the present invention.

Claims

1. A core-shell catalyst, The nucleus is in the form of secondary particles formed by agglomerating a plurality of primary particles, and The shell is formed by agglomerating a plurality of primary particles in a core-shell configuration, comprising primary particles and a shell layer surrounding the primary particles. The average distance *a* between the primary particles forming the core, the average diameter *r* of the primary particles, and the average thickness *L* of the shell formed by agglomerating a plurality of primary particles in a core-shell configuration satisfy the following equation: [Formula 1] 。 2. The catalyst according to claim 1, wherein L / (r+a) is 60 to 400.

3. The catalyst according to claim 1, wherein the primary particles comprise Fe.

4. The catalyst according to claim 1, wherein the primary particles are Fe-based catalyst particles or catalyst particles in which Fe is supported on a support as an active component.

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

6. The catalyst according to claim 1, wherein L is from 500 nm to 50,000 nm.

7. The catalyst according to claim 1, wherein r is from 0.1 nm to 100 nm.

8. The catalyst according to claim 1, wherein a is from 0.1 nm 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, the method comprising the step of synthesizing a mixed hydrocarbon gas by heating a reaction gas containing carbon dioxide in the presence of a catalyst according to claim 1.

Images