Composite catalyst and preparation method therefor

Abstract

The present disclosure relates to a composite catalyst comprising: a hierarchical porous zeolite support; and cobalt-based nanoparticles supported on the support, wherein the zeolite support has, in an X-ray diffraction spectrum, a first peak (IA), which is the maximum peak in the range of 2θ= 23.0-23.50°, and a second peak (IB), which is the maximum peak in the range of 2θ= 29.50-30.50°, the intensity ratio of the first peak to the second peak satisfies expression 1, and the full width at half maximum (FWHM) (deg, 2θ) of the first peak (IA) is 0.425 or more. [Expression 1] 5.5< IA / IB <10.55

Description

Composite catalyst and method for manufacturing the same

[0001] The present disclosure relates to a composite catalyst and a method for manufacturing the same.

[0002] Metal-based catalysts can increase reaction efficiency by lowering the activation energy in various chemical reactions, and catalysts are primarily composed of a metal acting as the active material and a support on which the metal is supported. However, conventional catalyst supports, such as alumina or silica, tend to have uneven distribution of the active material, leading to concentration in specific regions or an increase in particle size due to sintering during the reaction process. This phenomenon reduces the active surface area of ​​the catalyst, thereby degrading its performance. Furthermore, since conventional catalyst supports primarily possess a micropore-centered structure, the diffusion of reactants and products may be hindered, and limited access to the interior of the catalyst can result in reduced reaction efficiency or decreased selectivity.

[0003] In addition, some supports may interact too strongly with the active material, hindering the conversion of the metal supported on the active material into an active state or causing structural deformation of the active material during the reaction, which can degrade the performance of the catalyst. Furthermore, since the catalyst must primarily operate under high temperature, high pressure, and long reaction conditions, phenomena such as sintering, particle growth, and deactivation of the active material may occur as described above, which can reduce the activity and lifespan of the catalyst.

[0004] Therefore, various studies are being conducted to develop catalysts with excellent stability, such as activity and long lifespan. Specifically, active research is underway to develop catalysts with enhanced performance by ensuring that the active metal is uniformly dispersed on the support and that the support improves the diffusivity and accessibility of reactants, while simultaneously optimizing the interaction between the support and the active material to minimize performance degradation caused by processes such as sintering.

[0005] Meanwhile, among various catalytic reactions, technologies that convert CO2 into other useful chemicals are gaining attention to mitigate climate change caused by increased carbon dioxide emissions. For example, the Fischer-Tropsch synthesis reaction, which converts CO2 into synthesis gas (CO+H2) and subsequently uses the synthesis gas to convert it into liquid fuels or hydrocarbons, is receiving particular attention. In these FT synthesis reactions, catalysts typically exhibit short lifespans due to activity limitations caused by strong interactions between the support and the active metal material, or due to sintering phenomena. As the climate crisis intensifies, there is a significant increase in industrial demand for catalysts with superior performance that are specifically optimized for these FT synthesis reactions.

[0006] The present disclosure is designed to solve the above-mentioned problems, and according to one aspect of the present disclosure, a composite catalyst having excellent performance such as high activity and a long catalyst life is provided by comprising: a nanosheet-type hierarchical porous zeolite support; and cobalt-based nanoparticles supported on the support.

[0007] According to another aspect of the present disclosure, a composite catalyst is provided that improves the selectivity and yield of C5-11 range hydrocarbons in the Fischer-Tropsch reaction and also suppresses the sintering of metal active particles and reaction imbalance phenomena.

[0008] The present disclosure relates to a composite catalyst comprising: a hierarchical porous zeolite support; and cobalt-based nanoparticles supported on the support; wherein the zeolite support has a first peak (I) which is a maximum peak in the range 2θ = 23.0˚ to 23.50˚ in the X-ray diffraction spectrum. A ) exists, and a second peak (I) which is the maximum peak in the range 2θ = 29.50˚ to 30.50˚ B ) exists, and the intensity ratio of the first peak and the second peak satisfies the following Equation 1, and the first peak (I AA composite catalyst is provided having a full width at half maximum (FWHM; deg, 2θ) of 0.425 or greater.

[0009] [Equation 1]

[0010] 5.5< I A / I B <10.55

[0011] In one embodiment of the present disclosure, the first peak (I A The full width at half maximum (FWHM; deg, 2θ) of ) may be within the range of 0.8 to 1.75.

[0012] In one embodiment of the present disclosure, the average thickness of the crystal of the support may be 1 to 40 nm.

[0013] In one embodiment of the present disclosure, the support may be formed by ultrathin layers of MFI crystals arranged in a lamellar structure and intertwined in three dimensions.

[0014] In one embodiment of the present disclosure, the support has a total pore volume of 0.1 to 2 cm² 3 It can be / g.

[0015] In one embodiment of the present disclosure, the support may exhibit a composite form of type I and type IV in the isotherm graph during a nitrogen adsorption / desorption test.

[0016] In one embodiment of the present disclosure, the mesopores of the support may have an average diameter of 2 to 10 nm.

[0017] In one embodiment of the present disclosure, the support may be a three-dimensionally interconnected mesoporous network structure.

[0018] In one embodiment of the present disclosure, the support has a BET specific surface area of ​​400 to 800 m² 2 / g, and external specific surface area of ​​200 to 600 m² 2 / g can be.

[0019] In one embodiment of the present disclosure, the support may comprise Brønsted acid sites at a concentration of 80 μmol / g to 300 μmol / g.

[0020] In one embodiment of the present disclosure, the molar concentration (BA_ext) of the Srønsted acid sites present on the outer surface of the support may be in the range of 30 μmol / g to 100 μmol / g.

[0021] In one embodiment of the present disclosure, the cobalt-based nanoparticles may be one or more selected from Co, CoO, Co2O3, and Co3O4.

[0022] In one embodiment of the present disclosure, the catalyst may comprise 1 to 20 weight percent of cobalt (Co).

[0023] In one embodiment of the present disclosure, the average diameter of the cobalt-based nanoparticles may be 1 to 10 nm.

[0024] In one embodiment of the present disclosure, the average diameter (D) of the cobalt-based nanoparticles Co ) and the average diameter (D) of the mesopores of the support. meso ) may satisfy Equation 2 below.

[0025] [Equation 2]

[0026] 0.05≤D Co / D meso ≤0.5

[0027] In one embodiment of the present disclosure, the support may be modified with one or more metal promoters selected from alkali metals, alkaline earth metals, and rare earth metals.

[0028] In one embodiment of the present disclosure, the modified support may comprise 1 to 10 weight percent of a metal promoter.

[0029] In another embodiment of the present disclosure, a catalyst for a Fischer-Tropsch synthesis reaction comprising the aforementioned composite catalyst may be provided.

[0030] In another embodiment of the present disclosure, a method for synthesizing hydrocarbons can be provided, wherein the hydrocarbons are synthesized by a Fischer-Tropsch synthesis reaction including the aforementioned composite catalyst.

[0031] In addition, the present disclosure may provide a method for manufacturing a composite catalyst comprising: a) mixing and gelling a support precursor comprising a silica source, an alumina source, and a surfactant-type structural indicator; b) heating the mixed gel to crystallize it into a zeolite; c) calcining the crystallized zeolite; d) ion-exchanging the calcined zeolite; and e) melting and infiltrating a cobalt precursor into the ion-exchanged zeolite and calcining it to support cobalt-based nanoparticles; wherein the zeolite is a hierarchical porous zeolite in the form of a nanosheet.

[0032] In one embodiment of the present disclosure, e) a step of modifying the ion-exchanged zeolite by impregnating and calcining it in a metal promoter solution before loading in step 1 may be further included.

[0033] In one embodiment of the present disclosure, the metal promoter solution may comprise one or more metals and compounds selected from alkali metals, alkaline earth metals, and rare earth metals.

[0034] In one embodiment of the present disclosure, the structural indicator may include an alkyl chain type quaternary ammonium-based surfactant.

[0035] In one embodiment of the present disclosure, the mixed gel may comprise 0.1 to 1 mole of alumina and 15 moles of a structural indicator based on 100 moles of silica.

[0036] A composite catalyst according to one embodiment of the present disclosure can provide long-term catalytic durability and stability even under high temperature and high pressure conditions by suppressing the sintering and aggregation of cobalt nanoparticles.

[0037] A composite catalyst according to one embodiment of the present disclosure has a large external surface area and an active metal is uniformly dispersed, so it can improve CO conversion productivity per unit metal content.

[0038] A composite catalyst according to one embodiment of the present disclosure can efficiently isomerize long-chain n-paraffins to convert them into high-octane isoparaffins.

[0039] A composite catalyst according to one embodiment of the disclosure can provide high selectivity and high yield for C5-11 gasoline range hydrocarbons in a Fischer-Tropsch synthesis reaction.

[0040] Figure 1 shows the XRD patterns of the supports of Preparation Examples 1 to 4 (MFI-x (2.5, 40, 300, 10,000 nm)).

[0041] Figure 2 shows the XRD pattern of MFI-2.5 of Preparation Example 1.

[0042] Figure 3 shows SEM images of the supports of Preparation Examples 2 to 4 and TEM images of Preparation Example 1 (MFI-2.5).

[0043] Figure 4 shows the nitrogen adsorption and desorption isotherms of Manufacturing Examples 1 to 4.

[0044] Figure 5 shows the analysis results of the NH3-TPD ammonia desorption test of Preparation Examples 1 to 4.

[0045] Figure 6 shows the FT-IR spectra of Preparation Examples 1 to 4 after pyridine adsorption.

[0046] Figure 7 shows TEM images of the catalysts of the Examples and Comparative Examples 1 to 3.

[0047] FIG. 8 illustrates how the CO conversion performance of the catalysts in Examples and Comparative Examples 1 to 3 changes over time.

[0048] Figure 9 illustrates the change in cobalt-time-yield, i.e., CO conversion productivity per unit amount of cobalt, according to the external surface area of ​​the Co / MFI-x catalyst.

[0049] Figure 10 shows the analysis results of C5-11 hydrocarbon selectivity (%) according to the external surface area of ​​the catalysts of the Examples and Comparative Examples 1 to 3.

[0050] FIG. 11 shows the external surface area and gasoline range C of the examples and comparative examples. 5-11 This is the result of plotting the correlation of hydrocarbon yields.

[0051] Figure 12 shows a graph visualizing the changes in CO conversion rate and gasoline yield according to the Si / Al ratio.

[0052] Figure 13 illustrates the change in i-paraffin selectivity according to the Si / Al ratio.

[0053] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described in detail below. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present disclosure is complete and to fully inform those skilled in the art of the scope of the invention, and the present disclosure is defined only by the scope of the claims.

[0054] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which this disclosure pertains.

[0055] Unless otherwise specifically indicated, the singular form of a term used in this specification may be interpreted to include the plural form.

[0056] The numerical ranges used herein include lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the defined range, all of which are limited values, and all possible combinations of upper and lower limits of the numerical range defined in different forms. Unless otherwise specifically defined in the specification of this disclosure, values ​​outside the numerical range that may occur due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0057] As used in this specification, "comprising" is an open description equivalent to expressions such as "comprising," "containing," "having," and "characteristics," and does not exclude elements, materials, or processes not additionally listed.

[0058] Hereinafter, the composite catalyst of the present disclosure and the method for manufacturing the same will be described in detail. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively.

[0059] Conventional catalysts have suffered from reduced catalytic performance due to issues such as uneven dispersion of metal nanoparticles, sintering problems, and instability of active materials. In particular, metal nanoparticles undergo sintering during the reaction process, leading to increased particle size and reduced active surface area, which in turn lowers reaction efficiency. Furthermore, existing zeolite supports are restricted in the diffusion of reactants and accessibility of active materials due to limitations in their pore structure, resulting in short catalyst lifespan and low reaction selectivity in high-efficiency catalytic reactions such as Fischer-Tropsch (FT) synthesis.

[0060] Accordingly, the inventors of the present disclosure have invented a composite catalyst in which cobalt (Co)-based nanoparticles are evenly dispersed using a hierarchical porous zeolite in the form of a nanosheet as a support.

[0061] The present disclosure relates to a composite catalyst comprising: a hierarchical porous zeolite support; and cobalt-based nanoparticles supported on the support; wherein the zeolite support has a first peak (I) which is a maximum peak in the range 2θ = 23.0˚ to 23.50˚ in the X-ray diffraction spectrum. A ) exists, and a second peak (I) which is the maximum peak in the range 2θ = 29.50˚ to 30.50˚ B ) exists, and the intensity ratio of the first peak and the second peak satisfies the following Equation 1, and the first peak (I A A composite catalyst can be provided in which the full width at half maximum (FWHM; deg, 2θ) of ) is 0.425 or greater.

[0062] [Equation 1]

[0063] 5.5< I A / I B <10.55

[0064] The aforementioned cobalt (Co)-based nanoparticles provide high activity, a long catalytic lifetime, and low hydrogen-to-gas conversion activity, making them suitable for synthesis gas sources with low CO2 content. Specifically, CO molecules are adsorbed on the cobalt surface, which weakens CO bonds and prepares CO for reaction. Furthermore, cobalt promotes important reactions such as CO decomposition, which can effectively induce the formation of hydrocarbons, for example, in Fischer-Tropsch synthesis. In other words, cobalt-based nanoparticles can provide excellent catalytic properties that enhance CO conversion rates, minimize CO2 generation, and maintain a long catalytic lifetime. This can be advantageous for the production of high-grade fuels, such as high-octane isoparaffins, in Fischer-Tropsch synthesis, and can enable efficient synthesis gas conversion.

[0065] However, although cobalt-based nanoparticles exhibit high selectivity for long-chain n-paraffins, this leads to the problem of simultaneous production of wax, intermediate distillates, and light hydrocarbons. Consequently, unwanted substances may be produced in excess during FT synthesis.

[0066] To solve these problems, the present disclosure includes a configuration in which cobalt-based nanoparticles are supported on a hierarchical porous zeolite. Additionally, the zeolite may provide Bronsted-Lowry sites in its internal microstructure and on its external surface.

[0067] In one embodiment, a zeolite support containing acid sites is obtained by hydrolyzing long-chain n-paraffin, which is a primary FT product, to obtain C5-C 11 It can be cut into a range, and then a secondary reaction can be performed to convert it into high-octane iso-paraffin through isomerization.

[0068] Specifically, cobalt-based nanoparticles primarily generate long-chain n-paraffins through the polymerization of CO and H2, while zeolite supports containing acid sites can secondarily form high-octane isoparaffins through hydrocracking and isomerization reactions. Such a dual-catalyst system can be advantageous for solving the problem of simultaneous production of light hydrocarbons and controlling the selectivity of high-octane isoparaffins. Therefore, the proportion of isoparaffins in FT synthesis can be increased, and C due to cracking 1-4 It can suppress the production of waxes and intermediate distillates, such as gas generation.

[0069] Therefore, the combination of a cobalt-based catalyst and an acidic support produces C through primary hydrocarbon formation and secondary conversion reactions. 5-11 By increasing selectivity, it is possible to efficiently produce isoparaffins with high octane ratings and solve the problem of simultaneous production of light hydrocarbons.

[0070] In one embodiment of the present disclosure, a first peak (I) which is a maximum peak in the range 2θ = 23.0˚ to 23.50˚ in the X-ray diffraction spectrum A ) exists, and a second peak (I) which is the maximum peak in the range 2θ = 29.50˚ to 30.50˚ B ) may exist. Also, the second peak (I B The intensity of ) is the first peak (I A It may be a weaker and gentler peak compared to the intensity.

[0071] Here, X-ray diffraction (XRD) was performed using a Rigaku Multiflex diffractometer and Cu Kα radiation (λ=1.5406).

[0072] To ensure linewidth accuracy, an instrumental broadening function was calculated using NIST standard samples (LaB6 or Si SRM), and the instrument contribution was desummated and corrected from the sample's full width at half maximum (FWHM) value.

[0073] Specifically, the intensity ratio (I) of the first peak and the second peak above A / I B ) may be 5.5 or higher, 5.6 or higher, 5.7 or higher, 5.8 or higher, 5.9 or higher, 6.0 or higher, 6.1 or higher, 6.2 or higher, 6.3 or higher, or 6.4 or higher as a lower limit, and may be 10.55 or lower, 10.0 or lower, 9.5 or lower, 9.0 or lower, 8.5 or lower, 8.0 or lower, 7.5 or lower, 7.0 or lower, or 6.5 or lower as an upper limit, or may be an intermediate value. More preferably, the intensity ratio (I) of the first peak and the second peak is A / I B ) may be within the range of 5.5 to 10.55, 5.5 to 8.0, 5.5 to 7.0, or 5.5 to 6.5, but is not necessarily limited thereto.

[0074] In addition, the zeolite support of the present disclosure includes a 2θ = 23 to 25˚ interval in the X-ray diffraction spectrum, and broad diffraction lines can be predominantly observed over the entire range of 2θ = 10 to 35˚.

[0075] As an example, the above first peak (I A The full width at half maximum (FWHM; deg, 2θ) of ) is 0.425 or greater, which can exhibit a significantly larger full width at half maximum value compared to the bulk zeolite support.

[0076] The full width at half maximum used in this invention was calculated from the X-ray diffraction spectrum of the sample through the following procedure: (1) The measured spectrum was input as discrete data consisting of coordinate values ​​corresponding to the horizontal axis and signal intensity values ​​corresponding to the vertical axis. (2) The point with the highest signal intensity among the entire data was set as the peak maximum value, and the coordinates at that point were defined as the peak center position. (3) The value obtained by dividing the peak maximum signal intensity by 2 was defined as the peak half height. If a background signal was present, the lowest value of the entire signal or the average of the low-frequency region was set as the background value, and the half value was calculated by subtracting this from the peak height. (4) Moving to the left from the peak center, the point where the signal intensity first becomes smaller than the half height was identified as the left intersection point, and moving to the right, the point where the signal intensity first becomes smaller than the half height was identified as the right intersection point. If a half height value existed between two adjacent data points, the exact coordinates intersecting the half height were calculated using linear interpolation with the coordinates and signal intensity values ​​of the two points. (5) The difference in coordinates between the left and right intersection points is defined as the half-width of the peak. That is, the half-width is the distance between the left and right intersection points at a signal strength corresponding to half the height of the peak.

[0077] Specifically, the above first peak (I AThe full width at half maximum (FWHM; deg, 2θ) of the lower limit may be 0.425˚ or more, 0.435˚ or more, 0.45˚ or more, 0.50˚ or more, 0.60˚ or more, 0.65˚ or more, 0.70˚ or more, 0.75˚ or more, 0.85˚ or more, 0.95˚ or more, 1.0˚ or more, 1.1˚ or more, 1.15˚ or more, 1.2˚ or more, 1.25˚ or more, or 1.3˚ or more, and the upper limit may not be specifically restricted but may be 2.0˚ or less, 1.9˚ or less, 1.8˚ or less, 1.7˚ or less, 1.5˚ or less, or 1.4˚ or less.

[0078] More specifically, the above first peak (I A The full width at half maximum (FWHM; deg, 2θ) of the ) may be in the range of 0.425 to 2.0˚, 0.5 to 2.0˚, 0.8 to 2.0˚, 0.8 to 1.75˚, 1.0 to 1.5˚, or 1.25 to 1.35˚, but is not necessarily limited thereto.

[0079] This broad X-ray diffraction (XRD) peak is attributed to the fine crystallite size resulting from the ultra-thin stacking of zeolite lamellae in the form of nanosheets. Consequently, the overall peak intensity tends to be lower compared to bulk zeolite.

[0080] In one embodiment of the present disclosure, the zeolite of the support may be a crystalline zeolite corresponding to an MFI framework. Additionally, the MFI crystal structure may exhibit a nanosheet-type structure formed by three-dimensionally intertwining of lamellar ultrathin film layers.

[0081] Specifically, a nanosheet-shaped support based on nanolamellae may have an average thickness of MFI crystals from a nanolayer of the MFI crystal structure of 1 to 40 nm. Here, the thickness of the MFI crystals refers to the average thickness measured along a single lamellar of the MFI crystal structure, i.e., along the c-axis (thickness direction).

[0082] Specifically, the average thickness of the above crystal may be 2 nm or more, 2 nm or more, or 3 nm or more as a lower limit, and may be 40 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 8 nm or less, 5 nm or less, 4 nm or less, or 3 nm or less as a lower limit. Or it may be a value between the above numerical ranges. More narrowly, it may be within the range of 1 to 10 nm or 1 to 5 nm, and even more narrowly, it may be 1 to 3 nm, but is not necessarily limited thereto.

[0083] Due to the crystal thickness of such thin nanolayers, the composite catalyst has a significantly increased external specific surface area, which facilitates reactant accessibility and can improve reaction efficiency on the catalyst surface. In addition, the thinner the crystal thickness, the more uniformly active metals, such as cobalt nanoparticles, can be dispersed, which can maximize the external surface area, thereby further increasing reactivity and improving the CO conversion rate.

[0084] In addition, a support containing an MFI crystal structure with a thickness in the above range has an increased external surface area and contains a large amount of Bronsted-Lowry acid sites, and these acid sites can promote secondary transformation reactions such as hydrogenolysis and isomerization.

[0085] Furthermore, the porous structure of the aforementioned hierarchical porous zeolite can contribute to the uniform distribution of cobalt (Co)-based nanoparticles and the wide distribution of active sites. This improves the reaction efficiency and lifespan of the catalyst and can provide excellent performance in various catalytic reactions, including Fischer-Tropsch synthesis reactions.

[0086] Specifically, the above support may exhibit a composite form of Type I and Type IV in the isotherm graph during the nitrogen adsorption-desorption test. Referring to Fig. 4, the initial low-pressure section of the graph (MFI-2.5) reflects monolayer / multilayer adsorption, and a large hysteresis loop is found between P / P0 and 0.9, indicating that it contains a mesopore structure.

[0087] In one embodiment of the present disclosure, the pores included in the hierarchical porous zeolite support may refer to a zeolite having micropores of 2 nm or less and mesopores of 2 to 50 nm simultaneously.

[0088] Specifically, the average diameter of the micropores may be 2 nm or less, 1.5 nm or less, 1 nm or less, 0.9 nm or less, 0.8 nm or less, 0.7 nm or less, or 0.6 nm, but is not necessarily limited thereto.

[0089] In addition, in one embodiment, the mesopores of the support may have an average diameter of 2 to 50 nm.

[0090] Specifically, the average diameter of the mesopores may be 50 nm or less, 40 nm or less, 30 nm or less, 28 nm or less, or 26 nm or less as an upper limit, and 2 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, 22 nm or more, or 25 nm or more as a lower limit, but is not necessarily limited thereto. More preferably, it may be within the range of 10 to 50 nm, 10 to 40 nm, 20 to 30 nm, or 22 to 27 nm.

[0091] Mesopores within the above range can facilitate the diffusion of reactants and improve reaction efficiency by providing a space where large molecules can easily access the catalyst. In particular, mesopores in the 22–27 nm range can increase the reaction rate by increasing the external surface area of ​​the support, thereby enhancing the accessibility of reactants. Additionally, within the size range of the mesopores, selective conversion of specific reactants and products can be induced.

[0092] Furthermore, the above-mentioned pore structure helps the active material to be evenly distributed on the support and increases the surface area of ​​the active metal, thereby improving reaction efficiency and selectivity. As a result, reactant accessibility and the active site of the catalyst are optimized, and in the Fischer-Tropsch synthesis reaction, C 5-11 It has the advantage of providing high selectivity.

[0093] In one embodiment of the present disclosure, the hierarchical porous zeolite support may be a mesoporous structure or a three-dimensionally interconnected mesoporous network structure.

[0094] Specifically, the hierarchical porous zeolite support has a randomly interconnected three-dimensional mesopore system in a nano-like form, such as a sheet, and can simultaneously have mesopores of uniform pore size and micropores of hierarchically arranged micropores.

[0095] The composite catalyst of the present disclosure can be supported in a form in which cobalt-based nanoparticles form an interconnected network within a 3D mesoporous system having the support and are embedded in the support.

[0096] The above-described porous structure shortens the transport path of substances, allowing reactants to reach the catalytic active site rapidly. In particular, in high-efficiency catalytic reactions such as Fischer-Tropsch synthesis, it facilitates the diffusion of reactants and products, thereby increasing the reaction rate. This structure can improve catalytic reaction efficiency.

[0097] Furthermore, the support containing the above-mentioned porous structure provides a high external surface area, allowing active materials such as Co-based nanoparticles to be uniformly distributed. This prevents the sintering and aggregation of Co-based nanoparticles. Consequently, it prevents the sintering and particle growth of Co nanoparticles, thereby improving catalyst durability and stability. This enables the maintenance of excellent activity even under high temperature and high pressure conditions.

[0098] In one embodiment of the present disclosure, the support has a total pore volume of 0.1 to 2 cm² 3 It can be within the range of / g. Here, the total pore volume is the total pore volume including micropores and mesopores (V tot It means ).

[0099] Specifically, the total pore volume is 0.1 cm at the lower limit. 3 / g or more, 0.2 cm 3 / g or more, 0.3 cm 3 / g or more, 0.4 cm 3 / g or more, 0.5 cm 3 / g or more, 0.6 cm 3 / g or more or 0.7 cm 3 It may be greater than / g, with an upper limit of 2 cm 3 / g or less, 1.8 cm 3 / g or less, 1.6 cm 3 / g or less, 1.4 cm 3 / g or less, 1.2 cm 3 / g or less, 1.0 cm 3 / g or less, 0.9 cm 3 / g or less or 0.8 cm 3 It may be less than or equal to / g, and may be a value between the above numerical ranges.

[0100] Preferably 0.1 to 2 cm 3 / g, 0.1 to 1.5 cm 3 / g, 0.1 to 1.0 cm 3 / g, 0.5 to 1.0 cm 3 / g, 0.6 to 0.9 cm 3 / g range may be possible, but is not necessarily limited to this.

[0101] In addition, in one embodiment, the support has a micropore volume of 0.05 to 0.3 cm 3 / g can be.

[0102] Specifically, the micropore volume of the support is 0.05 cm at the lower limit. 3 / g or more, 0.07 cm 3 / g or more, 0.08 cm 3 / g or more, 0.10 cm 3 / g or more, 0.12 cm 3 / g or more, 0.13 cm 3 / g or more, 0.14 cm 3 / g or more, 0.15 cm 3 / g or more or 0.16 cm 3 It may be greater than / g, with an upper limit of 0.3 cm 3 / g or less, 0.28 cm 3 / g or less, 0.26 cm 3 / g or less, 0.24 cm 3 / g or less, 0.22 cm 3 / g or less, 0.20 cm 3 / g or less, 0.18 cm 3 / g or less or 0.16 cm 3It may be less than or equal to / g, or a value within the above numerical range. If the above range is satisfied, effects such as efficient adsorption and activation of reactants, uniform metal dispersion, selective reaction promotion, and maintenance of high-temperature stability can be expected.

[0103] In one embodiment of the present disclosure, the support has a BET specific surface area of ​​400 to 800 m² 2 / g, and external specific surface area of ​​200 to 600 m² 2 / g can be.

[0104] Here, the BET specific surface area is a value calculated by applying the BET method (Brunauer-Emmett-Teller method) through nitrogen (N2) adsorption-desorption experiments at 77 K, and the external specific surface area is a value measured using the t-plot method.

[0105] The BET specific surface area of ​​the above support is 400 to 800 m² 2 / g may be. Specifically, the BET specific surface area of ​​the support is 400 m² at the lower limit. 2 / g or more, 420 m 2 / g or more, 440 m 2 / g or more, 460 m 2 / g or more, 480 m 2 / g or more, 500 m 2 / g or more, 520 m 2 / g or more, 540 m 2 / g or more, 560 m 2 / g or more, 580 m 2 / g or more, 600 m 2 / g or more, 610 m 2 / g or more or 620 m 2 It can be more than / g, and although there is no specific upper limit, 800 m 2 / g or less, 750 m 2 / g or less, 700 m 2 / g or less or 650 m 2It may be less than or equal to / g, and may represent a value between the above figures. More preferably, 400 to 800 m 2 / g, 500 to 800 m 2 / g, 600 to 700 m 2 / g or 600 to 650 m 2 / g range may be possible, but is not necessarily limited to this.

[0106] Supports with a high BET specific surface area as described above can uniformly disperse active metals such as cobalt nanoparticles to maximize the catalyst surface area and increase the CO conversion rate, and can promote isomerization and hydrocracking reactions by exposing more acidic sites of the zeolite, thereby inducing the production of high-grade fuels such as high-octane isoparaffins.

[0107] The external specific surface area of ​​the above support is 200 to 600 m² 2 It can be within the range of / g. Specifically, the external specific surface area of ​​the above support is 200m² at the lower limit. 2 / g or more, 250m 2 / g or more, 300m 2 / g or more, 320m 2 / g or more, 350m 2 / g or more, 370m 2 / g or more, 380m 2 / g or more, 390m 2 / g or more, 400m 2 / g or more, 410m 2 / g or more, 420m 2 / g or more, 430m 2 / g or more or 440m 2 It may be greater than / g, and while there is no specific upper limit, 600m 2 / g or less, 550m 2 / g or less, 500m 2 / g or less, 490m 2 / g or less, 480m 2 / g or less, 470m 2 / g or less, 460m 2 / g or less or 450m 2 It may be less than or equal to / g, and may be a numerical value within the above range. However, it is not necessarily limited to the above range and may vary depending on the BET specific surface area, pore volume, pore size, etc. of the support itself.

[0108] In one embodiment of the present disclosure, the molar ratio of Si / Al of the support may be in the range of 30 to 80.

[0109] Specifically, the molar ratio of Si / Al of the support may be 30 or more, 32 or more, 34 or more, 36 or more, 38 or more, 40 or more, 42 or more, 44 or more, 46 or more, 48 or more, or 50 or more as a lower limit, and may be 80 or less, 78 or less, 76 or less, 74 or less, 72 or less, 70 or less, 68 or less, 66 or less, 64 or less, 62 or less, 60 or less, 58 or less, 56 or less, 54 or less, 52 or less, or 50 or less as an upper limit, but is not necessarily limited thereto.

[0110] By satisfying the Si / Al molar ratio within the above range, the metal-acid functional interface area between cobalt nanoparticles and acid sites is controlled, thereby promoting the efficient branching of long-chain hydrocarbons in the FT synthesis reaction. Additionally, external acid sites and cobalt active sites are sufficiently exposed, so that the gasoline range (C 5-11 ) It can improve hydrocarbon yield and selectivity, and also improve the efficiency of branched (iso-) paraffin formation. Conversely, if the Si / Al molar ratio falls outside this range, acid sites may become excessive or insufficient, leading to a decrease in FT reaction efficiency due to excessive cracking or limitations in the formation of long-chain hydrocarbons.

[0111] In one embodiment of the present disclosure, the support may have Brønsted acid sites, which act as active sites to lower the activation energy of the reactants, thereby improving the reaction rate and facilitating the formation of intermediates, thereby improving reaction selectivity. Additionally, the Brønsted acid sites can optimize the balance of adsorption and desorption of reactants and products.

[0112] In one embodiment, the support of the present disclosure may have acid sites on the outer surface due to hierarchical porosity in which mesopores and micropores exist simultaneously, thereby exhibiting excellent accessibility of reactants. In contrast, a support having only micropores may have difficulty exhibiting Brønsted acid sites on the outer surface, which increases the diffusion resistance of reactants and may reduce reaction efficiency.

[0113] In one embodiment of the present disclosure, the support may include Brønsted acid sites at a concentration of 80 μmol / g to 300 μmol / g.

[0114] Specifically, the Brønsted acid points may include, as a lower limit, 80 μmol / g or more, 90 μmol / g or more, 100 μmol / g or more, 120 μmol / g or more, 130 μmol / g or more, 140 μmol / g or more, 150 μmol / g or more, or 160 μmol / g or more, and as an upper limit, 300 μmol / g or less, 280 μmol / g or less, 260 μmol / g or less, 240 μmol / g or less, 220 μmol / g or less, 200 μmol / g or less, 190 μmol / g or less, 180 μmol / g or less, 170 μmol / g or less, or 160 μmol / g or less, and may have numerical values ​​within the above ranges. However, it is not necessarily limited to the above range, and a person skilled in the art may appropriately select based on the Si / Al molar ratio, external surface area, specific surface area, pore structure, thickness of the support crystal, manufacturing conditions, and the purpose of use of the catalyst.

[0115] In one embodiment of the present disclosure, the molar concentration (BA_ext) of the Srønsted acid sites present on the outer surface of the support may be in the range of 30 μmol / g to 100 μmol / g.

[0116] External Brønsted acid sites are located on the catalyst surface, providing excellent reactant accessibility, allowing even bulky Fischer-Tropsch products to be easily accessed and isomerized. Consequently, isomerization and cracking reactions occur effectively on the external surface of the catalyst, resulting in high-octane branched gasoline ranges (iC 5-11 ) Hydrocarbon production can be significantly enhanced. In addition, acid site density within the above range maintains a balance between isomerization and cracking reactions, thereby suppressing excessive decomposition and the formation of unnecessary light byproducts, and providing the effect of increasing the selectivity of heavy branched hydrocarbons.

[0117] Conversely, at BA_ext too low (30 μmol / g or less), isomerization and cracking reactions are insufficient, so long-chain hydrocarbons / straight-chain alkanes are mainly produced, and the selectivity for high-value fuels may be reduced. On the other hand, at BA_ext too high (100 μmol / g or more), excessive cracking occurs due to excessive acid catalytic activity, gaseous (C1-C4) lower hydrocarbons increase, and the efficiency of producing intermediate branched isoparaffins may actually decrease.

[0118] In one embodiment of the present disclosure, the cobalt-based nanoparticles may include one or more selected from the group consisting of Co, CoO, Co2O3, and Co3O4.

[0119] More specifically, it may be one or more selected from Co, CoO, Co2O3, and Co3O4, and more specifically, the cobalt-based precursor may be converted into the form of cobalt oxide (Co, CoO, Co2O3, Co3O4) or metallic cobalt (Co) through oxidation and reduction processes during the process of being supported on a support.

[0120] When such cobalt oxide and metallic cobalt are properly formed, activation of Co nanoparticles and efficient conversion of Co in redox reactions such as Fischer-Tropsch synthesis become possible, preventing the sintering of Co nanoparticles and minimizing aggregation.

[0121] In one embodiment of the present disclosure, the catalyst may exhibit a rod-like structure, and the cobalt-based nanoparticles supported within the support may exhibit a straight or curved shape depending on the curvature of the surface of the mesopore walls of the support. Additionally, the cobalt-based nanoparticles may appear in a nanowire form as the content increases.

[0122] In one embodiment of the present disclosure, the catalyst may comprise 1 to 20 weight percent of cobalt (Co).

[0123] Specifically, based on 100 parts by weight of the catalyst, the lower limit may be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt% or more, and the upper limit may be 20 wt% or less, 19 wt% or less, 18 wt% or less, 17 wt% or less, 16 wt% or less, 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, or 11 wt% or less, and the numerical value may be within the above range. However, it is not necessarily limited to the above range, and a person skilled in the art may appropriately select it depending on the specific surface area, pore structure, and scatter point distribution of the support, etc. When using a support with a high specific surface area and micropores, a relatively lower Co content may be suitable to obtain the same catalytic activity, and conversely, a somewhat higher Co content may be desirable for a support with a small specific surface area or a large pore diffusion limitation.

[0124] In one embodiment of the present disclosure, the average diameter of the cobalt-based nanoparticles may be in the range of 1 to 10 nm.

[0125] Specifically, the average diameter of the cobalt-based nanoparticles is not specifically limited to a lower limit but may be 1 nm or more, 2 nm or more, 3 nm or more, or 4 nm or more, and the upper limit may be 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, or 5 nm or less. More specifically, it may be within the range of 1 to 10 nm, 1 to 8 nm, 1 to 6 nm, or 3 to 6 nm, but is not necessarily limited thereto.

[0126] If the average diameter of the cobalt-based nanoparticles exceeds the above range, the dispersion of the metal particles decreases, which may lead to a reduction in the external specific surface area. Furthermore, inhibition of the internal diffusion of the metal nanoparticles within the support can cause the Turnover Frequency (TOF) to saturate, resulting in lower catalytic efficiency; additionally, the weakened interaction between the cobalt-based nanoparticles and the support poses a risk of aggregation during high-temperature reduction reactions. Therefore, since the cobalt-based nanoparticles satisfy an average diameter within the above range, they can provide high active site density, a stable metallic phase, and excellent dispersion; consequently, C in the Fischer-Tropsch synthesis process 5-11 It can be advantageous for iso-paraffin formation.

[0127] In one embodiment of the present disclosure, the average diameter (D) of the cobalt-based nanoparticles Co ) and the average diameter (D) of the mesopores of the support. meso ) may satisfy Equation 2 below.

[0128] [Equation 2]

[0129] 0.05≤D Co / D meso ≤0.5

[0130] In this way, when the average diameter of the cobalt-based nanoparticles is smaller than the average diameter of the mesopores of the support, the cobalt-based nanoparticles are supported in an embedded form within the 3D mesoporous system of the support, so the activity and stability of the catalyst can be excellent.

[0131] Specifically, D Co / D meso The lower limit may be 0.05 or more, 0.075 or more, 0.1 or more, 0.15 or more, or 0.2 or more, and the upper limit may be 0.5 or less, 0.45 or less, 0.4 or less, 0.35 or less, 0.3 or less, 0.25 or less, or 0.2 or less, but is not necessarily limited thereto.

[0132] Specifically, within the above range, cobalt nanoparticles are uniformly dispersed within the mesopores, and the surface of each particle is exposed to the maximum extent, allowing catalytic efficiency to be enhanced through interactions between metal active sites and acid sites. As a result, in the FT reaction, the branching of long-chain hydrocarbons, CO conversion rate, and gasoline range (C 5-11 The hydrocarbon selectivity and catalyst stability of ) can be improved simultaneously.

[0133] Conversely, if the DCo / Dmeso ratio is less than 0.05, the cobalt particles are excessively fine compared to the mesopores, which may lead to metal loss and a reduction in active sites due to excessive dispersion or surface desorption. On the other hand, if the ratio exceeds 0.5, the cobalt particles may clog or accumulate in the pores, which may degrade catalytic performance due to a reduction in the catalyst's specific surface area and restricted access to reactants.

[0134] Therefore, when the above range is satisfied, cobalt particles are stably fixed within the mesopores, and reactants can freely access the particle surface, thereby improving particle dispersion, exposure of active sites, and molecular diffusion within the pores. As a result, long-term stable operation without pore clogging, inhibition of metal accumulation and deactivation, gasoline range (C 5-11It enables the production efficiency of high-grade fuels and can simultaneously provide catalytic activity, selectivity, and stability in the FT reaction.

[0135] In one embodiment of the present disclosure, the support may be modified with one or more metal promoters selected from alkali metals, alkaline earth metals, and rare earth metals.

[0136] For example, it may be one or more selected from K, Na, Mg, Sc, Cu, Mn, Zn, Cr, Ca, Ce, Nd, and Y. The precursor of the metal promoter may be used in the form of their nitrides, oxides, chlorides, etc. Preferably, Mg and K, and even more preferably Mg, are used because more electrons can be released from these elements, thereby further enhancing the reducing properties of the cobalt-based nanoparticles and allowing the catalyst to exhibit high activity.

[0137] In one embodiment of the present disclosure, the modified support may comprise 1 to 10 weight percent of a metal promoter.

[0138] In one embodiment, the modified support may comprise 1 to 10 weight percent of a metal promoter. Specifically, the lower limit may be 1 weight percent or more, 2 weight percent or more, 3 weight percent or more, 4 weight percent or more, or 5 weight percent or more, and the upper limit may be 10 weight percent or less, 9 weight percent or less, 8 weight percent or less, 7 weight percent or less, 6 weight percent or less, or 5 weight percent or less. Or it may be a value between the above numerical ranges. Preferably, when comprising 3 weight percent to 7 weight percent of a metal promoter, the metal promoter is highly dispersed and effectively suppresses the sintering of cobalt-based nanoparticles, so excellent catalytic activity may be exhibited.

[0139] In one embodiment of the present disclosure, a catalyst for a Fischer-Tropsch synthesis reaction may be provided, comprising the aforementioned hierarchical porous zeolite-supported cobalt catalyst.

[0140] As an example, the above hierarchical porous zeolite-supported cobalt catalyst can be used by reducing cobalt oxide to a metal cobalt active phase under inert gas conditions before the Fischer-Tropsch synthesis reaction.

[0141] In one embodiment of the present disclosure, the aforementioned hierarchical porous zeolite-supported cobalt catalyst is an H2 / CO mixed gas (molar ratio 2:1) with a total of 20 cm 3 Flow velocity of / min, space velocity (GHSV) of 2.4 L·h - 1g -1 In a CO conversion reaction under reaction conditions of 20 bar pressure and 493 K, the CO conversion rate may be 60% or higher.

[0142] Specifically, under the above conditions, the CO conversion rate may be 50% or more, 55% or more, or 60% or more during the initial reaction (reaction time of 10 hours or less), and when the reaction time is 20 hours or more, the CO conversion rate may be 65% or more, 70% or more, 75% or more, or 80% or more.

[0143] The above results indicate that the CO conversion rate is maintained stably at a high level from the beginning of the reaction, and that the catalyst activity and durability are excellent even during long-term operation.

[0144] In one embodiment of the present disclosure, the catalyst is C in the Fischer-Tropsch synthesis reaction. 5-11 The hydrocarbon selectivity may be 60% or higher.

[0145] Specifically, C 5-11 Hydrocarbon selectivity may be high, such as 60% or more, 62% or more, 64% or more, 66% or more, 68% or more, 70% or more, 71% or more, 72% or more, 73% or more, or 74% or more.

[0146] C 5-11By applying catalysts with high selectivity for hydrocarbons (gasoline range, including iso / n-paraffin), it is possible to produce high-value fuels in the FT synthesis process. Furthermore, when using a highly selective catalyst relative to an equivalent input of raw material (syngas), the target hydrocarbon (C 5-11 ) The yield can be significantly increased, which may enable reduced operating costs and improved energy efficiency.

[0147] A method for synthesizing hydrocarbons can be provided, comprising synthesizing hydrocarbons by a Fischer-Tropsch synthesis reaction including a hierarchical porous zeolite-supported cobalt catalyst of the present disclosure.

[0148] Specifically, the hydrocarbon synthesis method involves an H2 / CO mixed gas (molar ratio 2:1) of a total of 15 to 30 cm 3 ·min -1 The flow velocity, space velocity (GHSV) is 2.4 L·h -1 ·g -1 It may be carried out under Fischer-Tropsch synthesis reaction conditions of 10 to 40 bar pressure and 150 to 400 ℃.

[0149] In addition, the hydrocarbon synthesis method is C 5-11 There is an advantage in that the yield of hydrocarbons can be high, such as 50% or more, 60% or more, 70% or more, 75% or more, 80% or more, or 81% or more.

[0150] Hereinafter, the method for manufacturing the aforementioned composite catalyst will be described in detail.

[0151] In another embodiment of the present disclosure, a method for preparing a composite catalyst may be provided, comprising: a) mixing and gelling a support precursor comprising a silica source, an alumina source, and a surfactant-type structural indicator; b) heating the mixed gel to crystallize it into a zeolite; c) calcining the crystallized zeolite; d) ion-exchanging the calcined zeolite; and e) melting and infiltrating a cobalt precursor into the ion-exchanged zeolite and calcining it to support cobalt-based nanoparticles; wherein the zeolite is a hierarchical porous zeolite in the form of a nanosheet.

[0152] The catalyst produced from the above manufacturing method may be identical or equivalent to the catalyst described above, and any omitted details may be referenced from the previously described contents.

[0153] In one embodiment, the silica source may be sodium silicate, silica powder, colloidal silica, tetraethylorthosilicate (TEOS), fumed silica, etc.

[0154] The above alumina source may be aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetylacetonate, etc., but is not necessarily limited thereto, and

[0155] In addition, in one embodiment, the structural indicator may include one or more surfactants selected from the alkyl chain type quaternary ammonium series, and specifically, C a-b-c In the alkyl chain type quaternary ammonium represented by, a may be 10 or more, and b and c may be 5 or more and 4 or more, respectively. An example is a decathionic surfactant [C 18 H 37 N + (CH3)2-C6H 12 -N + (CH3)2-C4H9]Br2(C18-6-4), C22-6-6 (C 22 H 45 -N + (CH3)2-C6H 12 -N + CH3)2-6H 13 It may include (Br)2), C22-6-6-6, C22-6-6-6-6, C22-8-6, etc.

[0156] The above structural indicator can induce zeolite crystals to form a mesoporous structure connected three-dimensionally with a nanoscale layered structure, and by limiting crystal growth, allows for a particularly thin nanolayer crystal thickness. In addition, the support from the above structural indicator can form uniform mesopores, and Brønsted acid sites can be activated on the outer surface as well.

[0157] In one embodiment, the mixed gel may comprise 0.1 to 1 mole of alumina and 1 to 15 moles of a structural indicator based on 100 moles of silica. When the mixed gel has such a composition, it may be desirable to produce a hierarchical porous zeolite in the form of a nanosheet having mesopores and micropores simultaneously, a high specific surface area, and external Brønsted acid sites.

[0158] In addition, in one embodiment, the mixed gel may further include NaOH, H2SO4, and distilled water, and more specifically, may further include 20 to 40 moles of Na2O, 10 to 30 moles of H2SO4, and 4000 to 6000 moles of H2O based on 100 moles of silica.

[0159] Hereinafter, b) the step of heating the above mixed gel to crystallize it into zeolite; will be described in detail. The above mixed gel can be converted into a hierarchical porous MFI zeolite through hydrothermal crystallization.

[0160] The above hydrothermal reaction can heat the mixed gel within a temperature range of 100 to 250°C. Specifically, it can be heated within a temperature range of 100 to 250°C, 100 to 200°C, 100 to 180°C, or 130 to 170°C. When the temperature within the above range is satisfied, a meso+micro composite structure can be stably secured and the crystallization time can be shortened. On the other hand, if the temperature exceeds the above range, there is a risk of thermal decomposition of the structure indicator and aggregation of excess silica. As a result, the pore structure of the zeolite becomes unstable and the catalytic performance may be degraded.

[0161] In addition, in one embodiment of the present disclosure, the hydrothermal reaction temperature can be controlled so that the heating rate gradually increases within the range of 0.5 to 5 ℃ / min. This prevents local excess or non-uniform structure formation caused by rapid temperature changes and contributes to promoting uniform crystallization.

[0162] In addition, the above hydrothermal reaction can be performed without stirring, or it can be carried out with light stirring at 30-100 rpm to improve the uniformity of heat and composition. When the hydrothermal reaction is carried out without stirring, natural diffusion and homogenization occur within the mixed gel, and the heat distribution can be maintained relatively evenly. Furthermore, using light stirring improves the uniformity of composition during the reaction and increases heat transfer efficiency, which can shorten the crystallization time and further improve the uniformity of the structure.

[0163] A stirring speed of 30-100 rpm allows for the maintenance of a uniform temperature distribution and component distribution while avoiding excessive shear force. This enables the pore structure of the hierarchical porous zeolite to be formed more precisely.

[0164] Hereinafter, c) the step of calcining the crystallized zeolite will be described in detail. Step c) is a step of removing organic matter (surfactant, TPABr, etc.) immediately after crystallization. The crystallized zeolite may be calcined after undergoing filtration, washing, and drying processes.

[0165] c) The firing temperature of the step may be performed within a temperature range of 400 to 700 ℃. More specifically, the lower limit may be 400 ℃ or higher, 450 ℃ or higher, 500 ℃ or higher, or 550 ℃ or higher, and the upper limit may be 700 ℃ or lower, 650 ℃ or lower, 600 ℃ or lower, or 590 ℃ or lower, but is not necessarily limited thereto, and a person skilled in the art may perform firing within an appropriate temperature range depending on the structural indicator, precursor, etc. used. For example, the firing time may be 1 hour to 12 hours.

[0166] Hereinafter, step d) ion-exchanging the calcined zeolite will be explained in detail. Step d) involves the Na of the Al-containing MFI zeolite from which organic structure-directing agents have been removed by calcination. + or residual structural cation (TPA + , C18-6-4, etc.) are NH4 + Completely substituted with, and NH4 in the subsequent calcination of step e). + → H + The purpose is to impart Bronsted-Lowry acid sites by causing thermal decomposition.

[0167] The above ion conversion is H + The ion conversion may be in the form of, for example, the zeolite calcined in a solution containing one or more selected from NH4NO3, NH4Cl, (NH4)2CO3, NH4CO2NH2, etc. may be treated by ion exchange.

[0168] In one embodiment of the present disclosure, e) a step of modifying the ion-exchanged zeolite by impregnating and calcining it in a metal promoter solution before loading in step may be further included.

[0169] In one embodiment, the metal promoter solution may include one or more selected from alkali metals, alkaline earth metals, and rare earth metals, and nitrides, oxides, chlorides, etc. of the selected one or more metals may be used as precursors. As an example, it may be one or more metals selected from K, Na, Mg, Sc, Cu, Mn, Zn, Cr, Ca, Ce, Nd, and Y. Preferably, Mg and K, and even more preferably Mg, are used because more electrons can be released from these elements, thereby further enhancing the reducing properties of cobalt-based nanoparticles and enabling the production of a catalyst exhibiting high activity.

[0170] Hereinafter, e) the step of melting and infiltrating a cobalt precursor into the ion-exchanged zeolite and calcining it to support cobalt-based nanoparticles; will be explained in detail.

[0171] In one embodiment, the ion-exchanged zeolite may be used after being degassed in a vacuum. As a non-limiting example, the degassing may be performed at 250 to 350°C for 1 to 6 hours. The degassing is intended to remove adsorbed moisture and residual ammonium salt within the pores to allow the molten cobalt precursor to penetrate smoothly.

[0172] The mixture of the zeolite and the cobalt precursor may be heated to allow the cobalt precursor to melt and penetrate, and the cobalt melt penetration temperature, i.e., the heating temperature of the mixture, may be a temperature above the melting point of the cobalt precursor. In addition, as an example, the heating time may be 6 to 24 hours, but may vary depending on the type and content of the cobalt precursor.

[0173] The above cobalt precursor may include one or more selected from cobalt nitrates. For example, the above cobalt nitrates may include Co(NO3)2, Co(NO3)2·6H2O, Co(OH2)6(NO3)2, etc., but are not necessarily limited thereto.

[0174] In addition, in one embodiment, the mass ratio of the precursor / zeolite support can be calculated and mixed so that the content of cobalt included per 100 parts by weight of the support is 1 to 20 parts by weight.

[0175] In one embodiment of the present disclosure, the penetration temperature in the melt penetration process can be performed at a temperature 20 to 30°C higher than the melting point of the precursor.

[0176] In addition, the temperature can be increased at a heating rate within the range of 1 to 5 ℃ / min up to the melt penetration temperature. This prevents the phenomenon where the salt melts and aggregates only locally on the surface, unlike when heated rapidly, allowing the cobalt precursor to penetrate evenly into the micropores. As a result, the particle size distribution of the Co nanoparticles generated after reduction is narrowed, and fine cobalt nanoparticles are formed, thereby increasing the number of active sites.

[0177] In one embodiment, calcination after melt penetration can be performed at a temperature of 500 to 700 K, and in another embodiment, the mixture of zeolite and cobalt precursor heated to the melt penetration temperature before calcination may additionally include a drying process for dehydration.

[0178] In one embodiment of the present disclosure, the firing of step e) may be performed within a temperature range of 300 to 600°C. Specifically, it may be performed within a temperature range of 300 to 600°C, 300 to 550°C, or 400 to 500°C, and more preferably within a range of 430 to 500°C.

[0179] By performing the above calcination, the Co-O-Si(Al) bond can be strengthened to suppress metal detachment and aggregation during the reaction, and the CO conversion rate can be improved by increasing the number of nano-sized Co particles. In addition, external acid sites can be exposed by removing organic matter and hydrates.

[0180] The composite catalyst prepared according to the above manufacturing method possesses both a mesoporous network and a complete microporous lattice, thereby providing a high specific surface area and an excellent pore structure. Furthermore, the active sites and Brønsted-Lowry acid sites of the highly dispersed Co nanoparticles are exposed, maximizing the efficiency of hydrocarbon rearrangement reactions and high-octane gasoline (iso-C 5-11 It is possible to provide a catalyst that can increase the selectivity of hydrocarbons within the range.

[0181] To facilitate understanding of the present disclosure, it will be described in detail below through examples and the like. However, the embodiments according to the present disclosure are not limited to the embodiments described herein and may be modified in various other forms, and the scope of the present disclosure should not be interpreted as being limited to the following embodiments. The embodiments of the present disclosure are provided to more completely explain the present disclosure to those with average knowledge in the art, and are provided merely to sufficiently convey the concept of the present disclosure to those skilled in the art.

[0182] [Evaluation Method]

[0183] 1. SEM / TEM

[0184] SEM analysis was performed using a Thermo Fisher Scientific Verios 460L field-emission SEM. Powder samples were attached to aluminum stubs and coated with Pt to a thickness of 5 nm to minimize charge accumulation. Observations were performed using a low acceleration voltage of 1 kV and in SE (Secondary Electron) mode.

[0185] TEM analysis was performed using TEM / HAADF-STEM measurements with a Thermo Fisher Scientific Titan ETEM G2 (200 kV). The sample was dispersed in ethanol, dropped in small amounts onto a holly-carbon coated Cu grid, and then air-dried.

[0186] 2. XRD

[0187] It was performed using a Rigaku SmartLab diffractometer and Cu Kα radiation at 40 kV and 30 mA.

[0188] 3. Analysis of Pores and Surface Characteristics

[0189] 1) Si / Al molar ratio analysis

[0190] After measuring the Si and Al content (ppm) in the sample using ICP-AES (Inductively Coupled Plasma Atomic Emission Analysis), the Si / Al molar ratio was calculated by dividing by the atomic weight of each element to convert it into molar concentration.

[0191] 2) Nitrogen adsorption / desorption isotherm

[0192] The nitrogen adsorption-desorption isotherm was measured at liquid nitrogen temperature (77 K) using a Micromeritics TriStar II 3020 automatic gas adsorber.

[0193] 3) Total pore volume and average diameter of mesopores

[0194] The total pore volume was calculated using the amount of nitrogen adsorbed at P / P0=0.95, and the micropore volume was calculated by t-plot analysis. In addition, the average diameter of the mesopores was calculated from the BJH pore size distribution curve obtained from the adsorption branch.

[0195] 4) Surface area

[0196] The surface area was calculated from nitrogen (N2) adsorption in the range of P / P0 = 0.05 to 0.2 using the BET (Brunauer-Emmett-Teller) method, and the external specific surface area was calculated using the tplot method.

[0197] 5) Concentration of Brønsted acid sites

[0198] The total concentration of Brønsted acid sites was measured by FT-IR after pyridine absorption, and the external surface concentration was measured by FT-IR after 2,6-di-tert-butyl pyridine absorption.

[0199] 6) Fischer-Tropsch (FT) synthesis reaction

[0200] 0.4 g of catalyst and a fixed-bed reactor (inner diameter: 7 mm) made of stainless steel were used. Prior to the synthesis reaction, high-purity hydrogen (H₂) gas was introduced at a depth of 50 cm 3 The catalyst is pretreated and reduced at 673 K for 12 hours at a flow rate of / min.

[0201] After the reduction is complete, the gas is cooled to room temperature and hydrogen is removed, and then a synthesis gas with a molar ratio of H2:CO:Ar = 6:3:1 is poured over a total of 20 cm³ 3 The system was pressurized to 20 bar while injecting at a rate of / min. Then, the reaction was initiated when the temperature reached 493 K at a heating rate of 1 ℃ min.

[0202] During the reaction, the gaseous products were analyzed using on-line gas chromatography (GC) equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD), with Porapak Q columns and Gaspro columns used in parallel. Simultaneously, the liquid products were collected in a cold trap (278K) and analyzed using off-line gas chromatography (GC) equipped with an HP-1 column.

[0203] In the above reaction, the CO conversion rate over time was confirmed under the conditions of a reaction temperature of 493K, a reaction pressure of 20 bar, and a ratio of H2 / CO=2.

[0204] [Preparation Example 1] MFI-2.4 nanosheet-type support

[0205] Sodium silicate solution (Si / Na=1.75, 27.5 wt% SiO2) and anhydrous aluminum sulfate (Al2(SO4)3·18H2O) were used as the silica and alumina sources, respectively. These were used as the structural indicator (SDA) ([C 18 H 37 N + (CH3)2-C6H 12 -N + (CH3)2-C4H9(Br - )2]) A mixed gel was prepared by mixing with NaOH, H2SO4, and distilled water.

[0206] The above mixed gel has a composition with a molar ratio of 100 SiO2: 1 Al2O3: 7.5 C18-6-4 : 30 Na2O : 24 H2SO4: 4000 H2O.

[0207] Subsequently, crystallization was carried out by heating in an autoclave at 150°C for 2.5 days, and the crystallized zeolite was filtered, washed, and dried at 100°C. The obtained zeolite was calcined in air at 550°C for 4 hours to remove the structural indicator. Subsequently, it was subjected to ion exchange treatment three times with a 1M NH4NO3 solution and re-calcined at 550°C to H + Ion conversion was performed in the form of [the material]. From this, a hierarchical porous MFI zeolite support (MFI-2.4) in the form of a nanosheet was prepared.

[0208] [Preparation Example 2] MFI-40 support

[0209] Commercial ZSM-5 powder from ZeoChem (CBV-8014, nominal Si / Al = 40, average crystal thickness 40 nm) was used as is. The raw powder was washed three times with distilled water and filtered in a 500 ml beaker to remove residual dust and water-soluble impurities, and dried at 110 °C for 6 h. Subsequently, it was ion-exchanged twice with a 1 M NH4NO3 solution (80 °C, 2 h), followed by water washing and drying (110 °C, 6 h), and air calcination at 550 °C (heating increase 2 °C / min, 4 h) to H + A type MFI-40 support was obtained.

[0210] [Preparation Example 3] MFI-50 support

[0211] In Preparation Example 1, the MFI-300 support was prepared in the same manner as in Preparation Example 1, except that TPABr was used as a structural indicator. By doing so, the MFI-300 support was obtained.

[0212] [Preparation Example 4] MFI-1000 support

[0213] In Preparation Example 1, a gel having a composition of 100 SiO2: 1 Al2O3: 20 TPABr: 10 NH4F: 2,000 H2O (molar ratio) was prepared by the same method as in Preparation Example 1, except that TPABr was used as a structural indicator and NH4F was added instead of sulfuric acid. By doing so, an MFI-1000 support was obtained.

[0214] - The Si / Al ratio, BET specific surface area (S_BET), external specific surface area (S_ext), total pore volume (V_tot), total Brønsted acid site concentration (BA_tot) and external Brønsted acid site concentration (BA_ext) of the zeolite supports of Preparation Examples 1 to 4 are as shown in Table 1 below.

[0215] CatalystsSi / AlS_BET (m 2 / g)S_ext (m 2 / g)V_tot ( cm 3 / g)TA_tot (μmol / g)BA_tot (μmol / g)BA_ext (μmol / g)Preparation Example 1 (MFI-2.5) 486304400.7246016050Preparation Example 2 (MFI-40) 404001100.1945016720Preparation Example 3 (MFI-300) 52360400.175101785Preparation Example 4 (MFI-1000) 51360200.165201751

[0216] In addition, in the X-ray diffraction analysis of Preparation Examples 1 to 4, I A and I B The results of the analysis are shown in Table 2 below.

[0217] I A (au)I B (au)I A / I B I A FAWHM(˚) Preparation Example 1 (MFI-2.5) 1818 (θ=23.25˚) 284 (θ=30.05˚) 6.40 1.3 Preparation Example 2 (MFI-40) 5598 (θ=23.05˚) 532 (θ=29.90˚) 10.52 0.45 Preparation Example 3 (MFI-300) 6860 (θ=23.15˚) 703 (θ=30.0˚) 9.758 0.40 Preparation Example 4 (MFI-1000) 22500 (θ=23.05˚) 884 (θ=30.0˚) 25.45 0.27

[0218] [Example] A catalyst was prepared using the MFI-2.5 support of Co / MFI-2.5 Preparation Example 1.

[0219] Specifically, high-purity Co(NO3)2·6H2O was dissolved in distilled water, and the concentration was adjusted so that the Co content was 10 wt% based on the weight of the support. Pretreated H + Place the MFI-2.5 powder into a rotary mixer and spray the prepared cobalt nitrate solution while rotating at a low speed. Mix for about 5 minutes until the solution is completely absorbed into the powder, ensuring that the precursor penetrates uniformly into the pores of the support.

[0220] After the infiltration was complete, the sample was dried at 100°C for 6 hours (heating rate 2°C / min) to remove residual moisture, and then the dried sample was calcined at 400°C for 4 hours to completely convert Co(NO3)2 into Co3O4 nanoparticles. Subsequently, H2 flow (50 cm 3 Co3O4 was reduced to the metallic Co active phase by reducing it at 400°C for 12 hours (heating rate 2°C / min) under a heating rate of 2°C / min. Thus, a Co / MFI-2.5 catalyst was prepared.

[0221] [Comparative Example 1] Co / MFI-40

[0222] A catalyst was prepared in the same manner as in Example 1, except that MFI-40 of Preparation Example 2 was used as the zeolite support.

[0223] [Comparative Example 2] Co / MFI-300

[0224] A catalyst was prepared in the same manner as in Example 1, except that MFI-300 of Preparation Example 3 was used as the zeolite support.

[0225] [Comparative Example 3] Co / MFI-1000

[0226] A catalyst was prepared in the same manner as in Example 1, except that MFI-1000 of Preparation Example 3 was used as the zeolite support.

[0227]

[0228] Evaluation Example 1: XRD, SEM, and TEM analysis evaluation of zeolite support.

[0229] Figure 1 shows the XRD patterns of the supports of Preparation Examples 1 to 4 (MFI-x (2.5, 40, 300, 10,000 nm)). Referring to Figure 1, it can be seen that all of MFI-x (2.5, 40, 300, 10,000 nm) exhibit (101), (200), and (501) diffraction lines characteristic of MFI (tetragonal structure) at the same 2θ position.

[0230] Specifically, Preparation Example 1 (MFI-2.5) exhibited the widest full width per minute (FWHM) of the diffraction lines; consequently, it can be seen that the grain size is very small and the regularity of the crystal planes is refined. In particular, referring to FIG. 2 and Table 2 above, I A Peak (2θ = 23˚) and I B The intensity ratio of the peak (2θ = 30˚) is low at approximately 6.4, and I A It can be seen that the peak's full width at half maximum is 1.3˚, indicating a broad peak. These broad diffraction lines and low I A / I B The intensity ratio is interpreted to be due to the miniaturization of grain size and the stacked structure of ultrathin nanosheets with thickness limited to the nanometer level.

[0231] On the other hand, it was confirmed that as we move toward Preparation Example 2 (MFI-40), Preparation Example 3 (MFI-300), and Preparation Example 4 (MFI-10000), the crystal size becomes relatively larger, and as a result, the linewidth of the diffraction line becomes narrower and shows a more distinct peak.

[0232] Figure 3 shows SEM images of the supports of Preparation Examples 2 to 4 and TEM images of Preparation Example 1 (MFI-2.5).

[0233] Referring to Fig. 3(a), it can be seen that the support of Preparation Example 4 has a well-developed large single crystal, and the crystal thickness is about 10 μm, which has a relatively large crystal size, and this was confirmed to be consistent with the narrow diffraction line in Fig. 1.

[0234] It was confirmed that Figures 3 (b) and (c) also have crystal thicknesses of 300 nm and 40 nm, respectively, which are smaller than those of Example 1.

[0235] On the other hand, referring to Fig. 3(d), Preparation Example 1 has a multilayer lamilla-type stacked structure, which represents a structure formed by stacking layers of ultrafine-sized MFI crystals. This lamilla-type structure has the characteristic of being able to contain mesopores, which can be interpreted as the reason why the MFI-2.5 support provides a high external surface area.

[0236] In other words, it was confirmed that the multilayer laminar structure of MFI-2.5 allows for the irregular connection of fine crystals within it, providing pores of various sizes and a multilayered structure.

[0237]

[0238] Evaluation Example 2: Porosity analysis evaluation of zeolite support.

[0239] Figure 4 shows the N2 adsorption and desorption isotherms of Preparation Examples 1 to 4, through which the pore structure and surface area of ​​the support were analyzed. Nitrogen adsorption and desorption experiments were performed at 77 K (liquid nitrogen temperature) using a Micromeritics TriStar II instrument.

[0240] Referring to Fig. 4, it can be seen that the supports of MFI-10000, MFI-300, and MFI-40 exhibit Type I isotherms. Type I isotherms generally appear in materials that have only micropores (pore size <2 nm), and these supports indicate that they have a structure with very small pore sizes.

[0241] In addition, it can be seen that MFI-10000 exhibits the smallest surface area, and as the surface area increases from MFI-300 to MFI-40, it shows greater nitrogen adsorption.

[0242] On the other hand, the MFI-2.5 support (Preparation Example 1) exhibits a complex form of Type I isotherms as well as Type IV isotherms. Type IV isotherms are a typical form found in materials containing mesopores, where mesopores refer to pores with a size of 2 to 50 nm. Therefore, it can be confirmed that the support of Preparation Example 1 has a structure containing both micropores and mesopores.

[0243] In addition, Preparation Example 1 exhibits a distinct hysteresis loop in the adsorption-desorption curve. This implies irreversible adsorption and desorption occurring in the mesopores, suggesting that the MFI-2.5 sample provides a high external surface area. These characteristics represent structural features favorable for promoting efficient reactant diffusion and reaction activation.

[0244] Figure 5 shows the analysis results of the NH3-TPD ammonia desorption test for Preparation Examples 1 to 4, which analyzes the acidity characteristics of each support. The acidity intensity and acidity distribution were evaluated by measuring the concentrations of Brønsted acid and Lewis acid.

[0245] Referring to FIG. 5, the supports of Preparation Examples 1 to 4 all exhibit distinct peaks at approximately 460 K (weak acid) and 680 K (medium-strong acid), and Preparation Examples 1 to 4 have a total acid amount (470–520 μmol·g -1 You can confirm that ) is almost identical.

[0246] Figure 6 shows the FT-IR spectra of Preparation Examples 1 to 4 after pyridine adsorption. Through Figure 6, the type and distribution location of Brønsted acid can be confirmed.

[0247] Referring to Fig. 6(a), Mount Brønsted is 1546 cm -1 At a strong peak, Mount Lewis is 1455 cm -1Peaks are shown. In particular, Preparation Example 1 (MFI-2.5) has a relatively high concentration of Brønsted acid and it can be confirmed that acid sites are highly concentrated on the outer surface. On the other hand, Preparation Examples 2 to 4 show the same peaks, but the peak intensity is weak, which means that the concentration of Brønsted acid is relatively low.

[0248] Figure 6(b) is an FT-IR spectrum of a support adsorbed with 2,6-di-tert-butylpyridine (DTBP), where DTBP is a bulky molecule that is selectively adsorbed to acidic sites on the outer surface rather than the inner pores.

[0249] Preparation Example 1 (MFI-2.5) shows a strong peak on the outer surface, confirming that approximately 31.2% of the total Brønsted acid is present on the outer surface, while Preparation Examples 2 to 4 show 12.0%, 2.8%, and 0.6%, respectively, present on the outer surface. In other words, as the outer surface area decreases from Preparation Examples 2 to 4, the exposure ratio of external acid sites decreases even if the total acid amount remains similar, which means that the accessibility of external reactants and the acid catalyst activation efficiency gradually decrease.

[0250] In conclusion, although the total acid amount in Preparation Examples 1 to 4 is nearly identical, it can be confirmed that the same acid amount is dispersed over a much wider external surface in the MFI-2.5 support, resulting in a lower acid density per unit area and a maximum exposed area of ​​external acid sites. This enables an efficient acid catalytic reaction while suppressing excessive cracking by ensuring that acid sites are evenly distributed.

[0251] In particular, MFI-2.5 has an ultrathin crystal structure that minimizes diffusion impediments, and a large external surface that exposes both acidic and metal active sites, allowing catalytic reactions to proceed efficiently, and provides structural advantages such as promoting isomerization reactions with appropriately diluted Brønsted acid and inhibiting over-decomposition.

[0252]

[0253] Evaluation Example 3: Performance evaluation according to the Si / Al ratio of MFI-2.5 support.

[0254] BET specific surface area (S_BET), external specific surface area (S_ext), total pore volume (V_tot), total Brønsted acid site concentration (BA_tot) and external Brønsted acid site concentration (BA_ext) were evaluated according to the Si / Al ratio of Preparation Example 1.

[0255] CatalystsSi / AlS_BET (m 2 / g)S_ext (m 2 / g)V_tot ( cm 3 / g)BA_tot (μmol / g)BA_ext (μmol / g)MFI-2.5-(25)226204200.69300120MFI-2.5-(50)486304400.7216050MFI-2.5-( 100)1026104350.687529MFI-2.5-(200)2106154200.74015MFI-2.5-(∞)na6504600.75ndnd

[0256] Figure 12 shows a graph visualizing the changes in CO conversion rate and gasoline yield according to the Si / Al ratio, and Figure 13 shows the changes in i-paraffin selectivity under the same conditions. Table 3, Figure 12, and Figure 13 show the Fischer-Tropsch synthesis performance of the Co catalyst, in particular, according to the change in the Si / Al ratio of the MFI-2.5 support. 5-11This shows the results of evaluating the effect on gasoline range hydrocarbon yield and selectivity. According to Table 3, it was confirmed that adjusting the Si / Al ratio changes the total Brønsted acid site density and the external acid site density. When the Si / Al ratio is low, both the total acid sites and the external acid sites increase, whereas as the Si / Al ratio increases, the acid site density decreases sharply. For example, it was confirmed that at Si / Al=22, the total Brønsted acid sites were approximately 300 μmol / g and the external acid sites were 120 μmol / g, whereas at Si / Al=210, the total was only 40 μmol / g and the external was 15 μmol / g. C in Fig. 12 5-11 The hydrocarbon selectivity distribution shows a parabolic curve depending on the Si / Al ratio, and it can be seen that the selectivity reaches a maximum of about 25.6% at Si / Al=50.

[0257] In Figure 13, changes in the iso / n-paraffin ratio can be observed. The ratio of branched (iso-) and linear (n-) paraffins was converted to the highest level at approximately 23% at Si / Al=50, which indicates that the production efficiency of high-octane fuel components is higher at the acid site concentration when Si / Al=50.

[0258] In addition, under the same conditions, the gasoline range (C 5-11 ) and diesel range(C 12-16 The yield of hydrocarbons was also highest at Si / Al=50. This is because, thanks to the ultrathin nanosheet structure and high external surface area of ​​the MFI-2.5 support, the superdispersion of cobalt nanoparticles and the concentration of external Brønsted sites were optimized, thereby simultaneously promoting the generation of long-chain hydrocarbons and branching in the FT reaction.

[0259] Conversely, when the Si / Al ratio is low and Al is in excess, reactivity is excessively high, leading to excessive cracking and increased formation of C1-C4 byproducts, and C 5-11 and C 12-16The yield decreases. Conversely, if the Si / Al ratio is excessively high or if it is pure silica (∞), long-chain hydrocarbons are predominantly produced due to a lack of external acid sites, but active sites participating in the FT reaction are limited, so C 5-11 and C 12-16 The yield appears low.

[0260] As a result of quantitative comparison, at Si / Al=50, C relative to pure silica 5-11 Selectivity increases by approximately 10 times, and the iso / n-paraffin ratio increases by tens of times; compared to Si / Al=22, the branching ratio (iso / n-paraffin ratio) is approximately 1.7 times, C 5-11 Selectivity is improved by about 1.5 times, confirming that the performance is significantly superior to that under conditions of Al excess or scatter insufficient.

[0261] In other words, it can be seen that the combination of acid site concentration control and a high external surface area can improve FT synthesis efficiency in both high-octane and heavy fuel production. In conclusion, it was confirmed that the Si / Al=50 condition in the MFI-2.5-based Co catalyst can provide high-efficiency, high-selectivity, high-octane fuel synthesis efficiency in the FT reaction through the combination of an appropriate acid site concentration and an external surface area.

[0262] Evaluation Example 4: TEM Analysis of Co / MFI-x Catalyst

[0263] Figure 7 shows TEM images of the catalysts of the Examples and Comparative Examples 1 to 3.

[0264] Referring to Fig. 7, a non-uniform distribution of cobalt particles is observed in Comparative Example 3. It was confirmed that the cobalt nanoparticles formed relatively large particles with a size of 400 nm. This can lead to delayed internal diffusion of the reactants and particle aggregation. Such aggregation causes the persistence of inactive CC bonds and may result in the formation of heavy substances and waxes, as well as the overproduction of methane. Additionally, the large particle size can reduce the activity of the catalyst.

[0265] Referring to Comparative Examples 1 and 2, the cobalt particles are 20 nm and 50 nm in size, respectively, showing a relatively uniformly dispersed form compared to Comparative Example 3; however, since the size of the cobalt nanoparticles is still large, excessive cracking or aggregation may occur, resulting in low reaction efficiency.

[0266] In contrast, in the example (Co / MFI-2.5), it was confirmed that cobalt nanoparticles were uniformly distributed at a thickness of approximately 4 nm. MFI-2.5 has an ultrathin nanosheet structure (2.5 nm thickness), with an external surface area of ​​440 m² 2 It is very large at / g. In addition, it contains micro and mesopores, which can prevent diffusion / aggregation during the sintering process. This structure helps cobalt particles to be uniformly dispersed and can contribute to maintaining the particle size at 4 nm.

[0267] Co / MFI-2.5 has many surface Si-O-Al defects, so Co 2+ The oxygen bridge bond is strengthened. This enhances metal-support interactions, which can prevent particle growth during the reduction and activation process. Particle growth inhibition can maintain catalytic performance and the size of cobalt nanoparticles.

[0268] Evaluation Example 5: CO conversion rate of Co / MFI-x catalyst (x = 2.5, 40, 300, 10000),

[0269] FIG. 8 illustrates how the CO conversion performance of the catalysts in Examples and Comparative Examples 1 to 3 changes over time.

[0270] The CO conversion reaction was carried out in a fixed-bed stainless steel reactor, and 0.4 g of catalyst was used in a form ground and sieved to 40-60 mesh. Prior to the reaction, the catalyst was reduced with hydrogen at 493 K for 12 hours, and thereafter, an H2:CO:Ar gas mixture (molar ratio 6:3:1) was introduced to a total of 20 cm 3 It was performed at a flow rate of / min, a pressure of 20 bar, and a reaction temperature of 493 K.

[0271] Referring to Figure 8, based on the CO conversion rate after 50 hours, Example (Co / MFI-2.5) was the highest at 82%, Comparative Example 1 (Co / MFI-40) was 52%, Comparative Example 2 (Co / MFI-300) was 20%, and Comparative Example 3 (Co / MFI-10000) was only 8%.

[0272] Furthermore, at the beginning of the reaction, Co / MFI-2.5 and Co / MFI-40 rapidly entered an active state and maintained high CO conversion rates for an extended period, whereas Co / MFI-300 showed a gradual decrease in activity after a certain time, and Co / MFI-10000 exhibited a pattern of continuously declining CO conversion rates from the start.

[0273] These results confirmed that as the crystal thickness of the support decreases, the external surface area of ​​the support increases significantly, maximizing the dispersion effect of acidic active sites and cobalt nanoparticles, thereby enabling the achievement of a high CO conversion rate and excellent catalytic durability.

[0274] Evaluation Example 6: Cobalt-time-yield for Co / MFI-x catalyst (x = 2.5, 40, 300, 10000)

[0275] Figure 9 illustrates the change in cobalt-time-yield, i.e., CO conversion productivity per unit amount of cobalt, according to the external surface area of ​​the Co / MFI-x catalyst.

[0276] The experiment was conducted under Fischer-Tropsch synthesis reaction conditions, namely GHSV 2.4 L·h -1 ·g -1 The experiment was conducted at a reaction temperature of 493 K, a pressure of 20 bar, an H2 / CO ratio of 2, and after 50 hours. Catalysts were prepared with the same cobalt content (10 wt.%) using each MFI support and compared.

[0277] As a result, it can be confirmed that the cobalt-time-yield increases dramatically as the external surface area increases. Specifically, the MFI-10000 catalyst (external surface area 20 m²) 2 / g) had the lowest productivity, and the MFI-2.5 catalyst (external surface area 440 m²) 2 / g) recorded a record high. This is due to a structural effect in which the number of actual reactive active sites (surface Co atoms) per unit weight of cobalt becomes overwhelmingly large as the ultrathin nanosheet-type MFI support provides superdispersion of cobalt. In particular, the MFI-2.5 catalyst, in which cobalt particles are dispersed at the 4 nm level, is highly advantageous for CO conversion, and the efficiency and productivity of the FT reaction are maximized based on a typical large-area, highly dispersed structure.

[0278] Catalysts using conventional bulk-type or general ZSM-5 series supports (Co / MFI-10000, Co / MFI-300) suffer from a lack of active sites capable of participating in the actual reaction, as cobalt aggregates into large clusters or contacts between acid sites and metals are insufficient. In contrast, it has been confirmed that the composite catalyst comprising the MFI-2.5 nanosheet structure of the present disclosure can simultaneously achieve maximum metal utilization and high-efficiency fuel synthesis performance in the actual reaction.

[0279] Evaluation Example 7: Carbon selectivity for Co / MFI-x catalyst (x = 2.5, 40, 300, 10000)

[0280] 1) Evaluation of C5-11 Hydrocarbon Selectivity (%)

[0281] FIG. 10 shows C according to the external surface area of ​​the catalysts of the Examples and Comparative Examples 1 to 3. 5-11 This shows the analysis results of hydrocarbon selectivity (%).

[0282] Referring to Figure 10, it was confirmed that the Co / MFI-2.5 catalyst exhibited excellent performance with a selectivity of 74% for C5-11 hydrocarbons, ranging from a minimum of 48% to a maximum of 270% compared to Co / MFI-10000 (20%), Co / MFI-300 (42%), and Co / MFI-40 (50%).

[0283] These results are attributed to the uniform dispersion of cobalt nanoparticles with a size of 2 nm to 10 nm in the embodiments of the present disclosure, the high exposure rate of external acid sites, and the composition of the support containing mesopores. These structural features can provide the effect of minimizing diffusion impediments of reactants and products during the synthesis process, efficiently branching long-chain hydrocarbons, and significantly increasing gasoline range yields.

[0284] On the other hand, the comparative examples have a small external surface area and non-uniformly distributed cobalt nanoparticles or form excessive particles, resulting in C due to delayed internal diffusion and excessive cracking. 5-11 Selectivity decreases and CH4·C 2-4 It can be seen that there is a tendency for production to become excessive.

[0285] Therefore, the present disclosure relates to structural features such as an ultrathin nanosheet structure, a high external surface area, a concentration of external scatter sites, and a uniform dispersion of cobalt nanoparticles interacting to achieve high activity in the FT reaction and C 5-11 It has the advantage of simultaneously providing high selectivity.

[0286] 2) Evaluation of C5-11 Hydrocarbon Yield (%)

[0287] FIG. 11 shows the external surface area and gasoline range C of the examples and comparative examples. 5-11 This is the result of plotting the correlation of hydrocarbon yields.

[0288] All catalysts were tested under identical reaction conditions (gas residence time GHSV 2.4 L·h) -1 ·g -1It was measured at a reaction temperature of 200℃, a pressure of 20 bar, an H2 / CO ratio of 2, and a reaction time of 50 hours, and the yield was calculated based on the CO conversion rate and C 5-11 It refers to the actual gasoline production (%) calculated by multiplying by selectivity.

[0289] Referring to Fig. 11, as the external surface area of ​​the MFI support increases, C 5-11 It can be seen that the yield of hydrocarbons increases proportionally. Specifically, in an example (external surface area approximately 440 m²) 2 / g) is C 5-11 The yield of hydrocarbons was approximately 82%, Comparative Example 4 (external surface area 20 m²) 2 It showed a yield approximately 10 times higher than / g, yield 8%).

[0290] Comparative Example 2 (40 m 2 / g) yielded about 20%, Comparative Example 1 (110 m 2 / g) yields about 52%, and it can be observed that as the external surface area increases, the yield of gasoline range hydrocarbons tends to increase exponentially.

[0291] This performance improvement is attributed to the hierarchical porous zeolite support in the form of a nanosheet of the example. The hierarchical porous structure in the form of a nanosheet provides sufficient dispersion of cobalt nanoparticles and externally exposed Brønsted acid sites, thereby simultaneously improving activity, durability, and hydrocarbon branching efficiency in the FT synthesis reaction.

[0292] In particular, since tracer molecules can rapidly diffuse and react on the surface of fine cobalt nanoparticles, the production rate of high-value gasoline can be improved. Conversely, in the catalyst of the comparative example, which has a small external surface area or aggregated cobalt particles, there is a lack of active sites capable of participating in the actual reaction due to the clustering of cobalt particles and limited exposure of acid sites, and as a result C 5-11 It was confirmed that the hydrocarbon yield was low.

[0293] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Hierarchical porous zeolite support; and A composite catalyst comprising cobalt-based nanoparticles supported on the above support, The zeolite support has a first peak (I) which is a maximum peak in the range 2θ = 23.0˚ to 23.50˚ in the X-ray diffraction spectrum. A ) exists, and a second peak (I) which is the maximum peak in the range 2θ = 29.50˚ to 30.50˚ B ) exists, and the intensity ratio of the first peak and the second peak satisfies the following Equation 1, and The above first peak (I A A composite catalyst having a full width at half maximum (FWHM; deg, 2θ) of 0.425 or greater. [Equation 1] 5.5< I A / I B <10. 55 In paragraph 1, The above first peak (I A A composite catalyst having a full width at half maximum (FWHM; deg, 2θ) within the range of 0.8 to 1.

75. In paragraph 1, The above support is a composite catalyst having an average crystal thickness of 1 to 40 nm. In paragraph 1, The above support is a composite catalyst formed by ultrathin layers of MFI crystals arranged in a lamellar structure and intertwined in three dimensions. In paragraph 1, The above support has a total pore volume of 0.1 to 2 cm² 3 / g, composite catalyst. In paragraph 1, The above support is a composite catalyst in which the isotherm graph in a nitrogen adsorption / desorption test shows a composite form of type I and type IV. In paragraph 1, The mesopores of the above support have an average diameter of 2 to 10 nm, forming a composite catalyst. In paragraph 1, The above support is a composite catalyst having a three-dimensionally interconnected mesoporous network structure. In paragraph 1, The above support has a BET specific surface area of ​​400 to 800 m² 2 / g, and external specific surface area of ​​200 to 600 m² 2 / g, composite catalyst. In paragraph 1, The above support is a composite catalyst comprising Brønsted acid sites at a concentration of 80 μmol / g to 300 μmol / g. In Paragraph 10, A composite catalyst in which the molar concentration (BA_ext) of Srønsted acid sites present on the outer surface of the support is within the range of 30 μmol / g to 100 μmol / g. In paragraph 1, The above-mentioned cobalt-based nanoparticles are one or more selected from Co, CoO, Co2O3, and Co3O4, forming a composite catalyst. In paragraph 1, The above catalyst is a composite catalyst comprising 1 to 20 weight percent of cobalt (Co). In paragraph 1, A composite catalyst having an average diameter of 1 to 10 nm of the above-mentioned cobalt-based nanoparticles. In paragraph 1, Average diameter (D of the above cobalt-based nanoparticles) Co ) and the average diameter (D) of the mesopores of the support. meso ) is a composite catalyst satisfying Equation 2 below. [Equation 2] 0.05 ≤ D Co / D meso ≤0. 5 In paragraph 1, The above support is a composite catalyst modified with one or more metal promoters selected from alkali metals, alkaline earth metals, and rare earth metals. In Paragraph 16, A composite catalyst in which the above-mentioned modified support comprises 1 to 10 weight percent of a metal promoter. A catalyst for a Fischer-Tropsch synthesis reaction comprising a composite catalyst according to any one of claims 1 to 17. A method for synthesizing hydrocarbons by a Fischer-Tropsch synthesis reaction comprising a composite catalyst according to any one of claims 1 to 17. a) a step of mixing and gelling a support precursor comprising a silica source, an alumina source, and a surfactant-type structural indicator; b) a step of heating the above mixed gel to crystallize it into zeolite; c) a step of calcining the crystallized zeolite; d) a step of ion-exchanging the calcined zeolite; and e) a step of melt-infiltrating and calcining a cobalt precursor into the ion-exchanged zeolite to support cobalt-based nanoparticles; comprising, A method for preparing a composite catalyst in which the above zeolite is a hierarchical porous zeolite in the form of a nanosheet. In paragraph 20, e) a step of modifying the ion-exchanged zeolite by impregnating it in a metal promoter solution and calcining it before the loading step; further comprising a method for manufacturing a composite catalyst. In paragraph 21, A method for preparing a composite catalyst, wherein the metal promoter solution comprises one or more metals and compounds selected from alkali metals, alkaline earth metals, and rare earth metals. In paragraph 20, A method for preparing a composite catalyst, wherein the above structural indicator comprises an alkyl chain type quaternary ammonium-based surfactant. In paragraph 20, A method for preparing a composite catalyst, wherein the above-mentioned mixed gel comprises 0.1 to 1 mole of alumina and 15 moles of a structural indicator based on 100 moles of silica.

Images