Tungsten-modified nickel-alumina composite catalyst prepared through one-pot firing process

Abstract

The present invention relates to a catalyst manufacturing method in which a tungsten-modified nickel-alumina composite catalyst prepared through a one-pot firing process is charged into a reactor and subjected to an in-situ reduction treatment. According to the present invention, the addition of tungsten suppresses coke formation, and thus catalytic activity is excellent and persists without degrading even after a long reaction time.

Description

Tungsten-modified nickel-alumina composite catalyst produced via a one-pot calcination process

[0001] The present application claims priority based on Korean Patent Application No. 10-2025-0039956 filed on March 28, 2025, and all contents disclosed in the specification and drawings of said application are incorporated into the present application.

[0002] The present invention corresponds to a research outcome supported by the National Research Foundation of Korea (Research Project Name: Local Government-University Cooperation-based Regional Innovation Project; Project No.: 2025-RISE-07-001 / Research Project Name: Establishment of Science and Engineering Academic Research Infrastructure; Project No.: 2021R1A6A1A03038858 / Research Project Name: Support for Mid-career Researchers; Project No.: RS-2025-00523315) and the Ulsan Green Environment Support Center (Research Project Name: Ulsan Green Environment Support Center 2025 Research and Development Project; Project No.: 2025-4-90-94-01-02).

[0003] The present invention relates to a tungsten-modified nickel-alumina composite catalyst prepared through a one-pot calcination process, which is placed in a reactor and subjected to in-situ reduction treatment. In this invention, coke formation due to the addition of tungsten is suppressed, so that the catalytic activity is maintained without decreasing even after a long reaction time, and has the effect of excellent catalytic activity.

[0004] Reforming reactions for producing synthesis gas from natural gas can be classified according to the reforming material into steam reforming of methane (SRM), partial oxidation of methane (POM), carbon dioxide reforming of methane (CDR), and combined steam and CO2 reforming with methane (CSCR).

[0005] (1) Steam Reforming Reaction (SRM): CH4+H2O → 3H2+CO

[0006] (2) Partial Oxidation Reaction (POM): CH4+0.5O2→ 2H2+CO

[0007] (3) Carbon Dioxide Reforming Reaction (CDR): CH4+CO2→ 2H2+2CO

[0008] (4) Steam and Carbon Dioxide Combined Reforming Reaction (CSCR): 3CH4+2H2O+CO2→ 8H2+4CO

[0009] Due to the differences in the reforming materials used in the above reforming reactions, the molar ratio of hydrogen to carbon monoxide in the synthesis gas produced from each reaction varies. Therefore, the reforming material can be appropriately selected based on the optimal ratio required in the subsequent process to which the synthesis gas produced from each reforming reaction is applied. In other words, in this technical field, each reforming reaction is recognized as a distinct reaction system, and research is being conducted to develop optimal catalysts suitable for each reforming system.

[0010] Currently, various methods for producing synthesis gas capable of controlling the H2 / CO molar ratio by performing the reforming reaction of methane, represented by natural gas, are being researched. Among these, interest is growing in carbon dioxide reforming (CDR) and combined steam and carbon dioxide reforming (CSCR), due to the advantage of being able to utilize carbon dioxide, the main culprit of global warming, as a reactant.

[0011] Currently, nickel-based catalysts are known to be economically viable for carbon dioxide reforming (CDR) and steam-carbon dioxide combined reforming (CSCR), and numerous studies on this have been reported. However, it is known that known nickel-based catalysts suffer from a problem where coke forms and catalytic activity decreases as the reaction time increases.

[0012] Korean Patent Publication No. 10-2015-0129566 reports that a catalyst in which nickel (Ni) and chromium (Cr) are supported as active metals on an alumina support, or a catalyst in which a metal selected from lanthanum (La), cerium (Ce), and zirconium (Zr) is additionally supported thereon, has improved resistance to carbon deposition, catalytic stability under high pressure conditions, and catalytic activity compared to a catalyst supported with a single nickel component.

[0013] The present invention was completed by preparing a tungsten-modified nickel-alumina composite catalyst through calcination and reduction treatment, and by discovering that it has a significantly excellent effect in inhibiting coke formation and CH4 and CO2 conversion rates.

[0014] The object of the present invention is to provide a method for manufacturing a nickel-alumina composite catalyst modified with tungsten (W) that has undergone calcination and reduction treatment.

[0015] In order to achieve the above objective,

[0016] The present invention comprises the step of preparing a mixed solution by mixing a tungsten (W) source, a nickel (Ni) source, and an alumina (Al-O) source in a solvent (Step 1);

[0017] Step 2: placing the above mixed solution into an autoclave, sealing it, heating it at 100-140°C for 4-8 hours, cooling it to room temperature, filtering the product to obtain a precipitate, and then drying the precipitate to obtain a dried product;

[0018] A step of calcining the above-mentioned dried material at 500-700°C in an air atmosphere for 4-8 hours to obtain calcined catalysts (Step 3); and

[0019] The method comprises the step (step 4) of loading the above-mentioned calcined catalysts into a reactor and reducing them at 700-900°C for 1-3 hours while supplying a continuous flow gas containing hydrogen to obtain reduced catalysts xW-NiAl-O;

[0020] In the above-mentioned reduced catalyst xW-NiAl-O, x is the tungsten (W) content of 1 to 35 weight%, and

[0021]

[0022] In the above-mentioned reduced catalyst xW-NiAl-O, the weight ratio of nickel (Ni) to alumina (Al-O) is 9:82-100,

[0023] A method for manufacturing a nickel-alumina composite catalyst modified with tungsten (W) that has undergone calcination and reduction treatment is provided.

[0024]

[0025] In the manufacturing method according to the present invention, step 1 is a step of preparing a mixed solution by mixing a tungsten (W) source, a nickel (Ni) source, and an alumina (Al-O) source in a solvent.

[0026] The above tungsten (W) source may be used alone or in a mixture of two or more types, such as (NH4)H2(W2O7)6, Na2WO4·2H2O, (NH4)2WO4, WO3, etc. In one embodiment, (NH4)H2(W2O7)6 may be used alone, but is not limited thereto.

[0027] The above nickel (Ni) source may be used alone or in a mixture of two or more types, such as Ni(NO3)2·6H2O, NiCl2·6H2O, and NiO. In one embodiment, Ni(NO3)2·6H2O may be used alone, but is not limited thereto.

[0028] The above alumina (Al-O) source is C 12 H 27AlO3, Al2O3, Al(OH)3, AlCl3, etc., can be used alone or in a mixture of two or more. In one embodiment, C 12 H 27 AlO3 may be used alone, but is not limited thereto.

[0029] The above solvent may be used alone or as a mixture of two or more types, such as 2-butanol, ethanol, water, acetone, cyclohexane, and dimethyl sulfoxide. In one embodiment, the alumina (Al-O) source may be dissolved in 2-butanol, and the tungsten (W) source and nickel (Ni) source may be dissolved in ethanol, respectively, and then all of these may be mixed to prepare a mixed solution, but is not limited thereto.

[0030] In one embodiment, C as an alumina (Al-O) source 12 H 27 A mixed solution can be prepared by completely dissolving AlO3 in a solvent, completely dissolving a nickel nitrate precursor as a nickel (Ni) source in a solvent and adding it to the solution, and then adding a solution in which (NH4)H2(W2O7)6 as a tungsten (W) source is completely dissolved in a solvent to the solution and stirring. Here, stirring devices such as an ultrasonic bath, static mixer, inline mixer, propeller mixer, turbine mixer, paddle mixer, ribbon mixer, planetary mixer, and valley mixer can be used as means for dissolution. Stirring can be performed at room temperature, but is not limited thereto.

[0031]

[0032] In the manufacturing method according to the present invention, step 2 is a step of placing the mixed solution into an autoclave, sealing it, heating it at 100-140°C for 4-8 hours, cooling it to room temperature, filtering the product to obtain a precipitate, and then drying it to obtain a dried product.

[0033] The above-mentioned autoclave may include a pressure cooker-type bench autoclave, a gravity displacement autoclave, a positive pressure displacement autoclave, a negative pressure displacement autoclave, a vertical autoclave, a horizontal autoclave, etc. In one embodiment, a stainless steel autoclave with a Teflon lining may be used, but is not limited thereto.

[0034] A sealed autoclave can be placed in an oven and heat-treated at 100-140°C (specifically, 110-130°C, 115-125°C) for 4-8 hours (specifically, 5-7 hours, 5.5-6.5 hours).

[0035] The product can be removed from a heat-treated sealed autoclave and filtered to obtain a precipitate, which can then be dried in an oven or the like to obtain a dried product.

[0036]

[0037] In the manufacturing method according to the present invention, step 3 is a step of calcining the dried material at 500-700°C in an air atmosphere for 4-8 hours to obtain calcined catalysts.

[0038] The firing treatment can be performed in an electric or gas furnace and can be performed at 500-700°C (specifically, 550-650°C, 575-625°C) for 4-8 hours (specifically, 5-7 hours, 5.5-6.5 hours).

[0039]

[0040] In the manufacturing method according to the present invention, step 4 is a step of loading the calcined catalysts into a reactor and reducing them at 700-900°C for 1-3 hours while supplying a continuous flow gas containing hydrogen to obtain reduced catalysts xW-NiAl-O.

[0041] The above reactor may be a quartz reactor, a corundum reactor, a ceramic reactor, a silica reactor, etc.

[0042] As the continuous flow gas containing hydrogen, a mixture of hydrogen gas and an inert gas may be used. The mixing ratio of the hydrogen gas and the inert gas is not specifically limited, but for example, a mixture of 45-65 volumes of inert gas and 45 volumes of hydrogen gas may be used. The injection rate of the continuous flow gas may be carried out at a level of 50-150 mL / min, but this can be appropriately adjusted depending on the size of the reactor and the amount of calcined catalysts charged. In one embodiment, argon gas, helium gas, neon gas, krypton gas, xenon gas, redon gas, etc. may be used as the inert gas.

[0043] The reduction treatment can be performed for 1-3 hours (specifically, 1.5-2.5 hours, 1.75-2.25 hours) at an internal reactor temperature of 700-900°C (specifically, 750-850°C, 775-825°C) while supplying a continuous flow gas containing hydrogen.

[0044] In the above-mentioned reduced catalyst xW-NiAl-O, x can be used as the content of tungsten (W) in an amount of 1 to 35 wt%, 3 to 20 wt%, 6 to 17 wt%, or 9 to 17 wt%. Additionally, in the above-mentioned reduced catalyst xW-NiAl-O, the weight ratio of nickel (Ni) to alumina (Al-O) can be used as 9:82-100, 9:87-95, 9:89-93, or 9:90-92.

[0045] If the content of the tungsten (W) is below the lower limit of the range described above, there may be a problem of reduced catalytic activity or coke formation, and if it exceeds the upper limit, there may be a problem of reduced catalytic activity due to a decrease in the specific surface area of ​​the catalyst.

[0046] If the weight ratio of nickel (Ni) and alumina (Al-O) is below the lower limit of the alumina range described above, there may be a problem where the physical stability of the catalyst is reduced due to an insufficient amount of alumina acting as a support, and if it exceeds the upper limit, there may be a problem where the catalyst activity is reduced.

[0047]

[0048] In addition, the present invention provides a tungsten (W) modified nickel-alumina composite catalyst manufactured by the manufacturing method described above.

[0049] The tungsten (W) modified nickel-alumina composite catalyst according to the present invention can be used in carbon dioxide reforming reactions (CDR), but is not limited thereto.

[0050]

[0051] Furthermore, the present invention provides a method for producing hydrogen gas from methane by carbon dioxide reforming of methane (CDR) using the nickel-alumina composite catalyst.

[0052] Carbon Dioxide Reforming Reaction (CDR): CH4 + CO2 → 2H2 + 2CO

[0053] The present invention relates to a method for producing a catalyst by placing a tungsten-modified nickel-alumina composite catalyst, prepared through a one-pot calcination process, into a reactor and performing in-situ reduction treatment. In this method, coke formation due to the addition of tungsten is suppressed, so that the catalyst activity is maintained without decreasing even after a long reaction time, and the catalyst activity is excellent.

[0054] Figure 1 is a graph showing (a) the N2 adsorption-desorption isotherm and (b) the mesopore size distribution curve obtained from the N2 adsorption-desorption isotherm of calcined catalysts prepared in Comparative Example 2 (calcined xW-9NiAl-O) and Comparative Example 3 (calcined 0W-9NiAl-O).

[0055] Figure 2 is a graph showing (a) methane conversion rate and (b) carbon dioxide conversion rate measured after 5 hours of dry reforming of methane (DRM) test with the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0056] Figure 3 is a graph showing (a) methane conversion rate and (b) carbon dioxide conversion rate measured after 30 hours of dry reforming of methane (DRM) testing with the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0057] Figure 4 is a graph showing (a) methane conversion rate and (b) carbon dioxide conversion rate measured after 80 hours of dry reforming of methane (DRM) testing with the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0058] Figure 5 shows (a) the XRD pattern of the calcined catalysts prepared in Comparative Examples 2 and 3 and (b) the XRD pattern of the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0059] Figure 6 shows the XRD patterns measured after a DRM test with the reduced catalysts prepared in Example 1 and Comparative Example 1, including (a) the XRD pattern of the spent catalysts after 5 hours and (b) the XRD pattern of the spent catalysts after 30 hours.

[0060] Figure 7 is an HR-TEM image of the reduced catalysts prepared in Example 1 and Comparative Example 1. (a,b) 0W-9NiAl-O; (c,d) 9W-9NiAl-O; (e,f) 17W-9NiAl-O; (g,h,h') 20W-9NiAl-O; (i,j,j') 23W-9NiAl-O; and (k,l,l') 31W-9NiAl-O.

[0061] Figure 8 is a STEM-EDS mapping image of the 0W-9NiAl-O reduced catalysts prepared in Comparative Example 1.

[0062] Figure 9 is a STEM-EDS mapping image of the 9W-9NiAl-O reduced catalysts prepared in Example 1.

[0063] FIG. 10 is an HR-TEM image of the spent catalysts after 5 hours of the dry reforming of methane (DRM) reaction of the reduced catalysts prepared in Example 1 and Comparative Example 1. (a,b,c) 0W-9NiAl-SO; (d,e,f) 9W-9NiAl-SO; and (g,h,i) 17W-9NiAl-SO. (Here, 'S' is an abbreviation for 'spent' and does not refer to the element S.)

[0064] FIG. 11 is an HR-TEM image of the spent catalysts after 30 hours of the dry reforming of methane (DRM) reaction of the reduced catalysts prepared in Example 1 and Comparative Example 1. (a,b) 0W-9NiAl-SO; (c,d) 9W-9NiAl-SO; and (e,f) 17W-9NiAl-SO. (Here, 'S' is an abbreviation for 'spent' and does not refer to the element S.)

[0065] FIG. 12 is the Raman spectrum of the prepared catalysts, wherein (a) is the calcined catalyst prepared in Comparative Example 2; (b) is the reduced catalyst prepared in Example 1; (c) is the spent catalyst after 5 hours of DRM reaction of the reduced catalyst prepared in Example 1 and Comparative Example 1; (d) is the spent catalyst after 30 hours of DRM reaction of the reduced catalyst prepared in Example 1 and Comparative Example 1; and (e) is the Raman spectrum of the spent catalyst after 80 hours of DRM reaction of the reduced catalyst prepared in Example 1 and Comparative Example 1.

[0066] FIG. 13 is a schematic diagram of a method for preparing a tungsten-modified nickel-alumina composite catalyst in Example 1, in which the calcination treatment is initiated and the reduction treatment process is omitted.

[0067] The present invention will be explained in more detail below through the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited by the following examples.

[0068] The chemical used is aluminum-tri-second-butoxide (ASB, C 12 H 27 AlO3 (97.00%), nickel(II) nitrate hexahydrate (Ni(NO3)2·6H2O, 99.99%), and ammonium tungstate ((NH4)H2(W2O7)6, 99.99%) were purchased from Sigma-Aldrich Korea. 2-butanol (C4H 10 O (99.00%) was obtained from SAMCHUN pure chemical Company (Korea). Ethanol (C2H5OH, 99.90%) was purchased from DAEJUNG chemical Company (Korea).

[0069] Catalyst Performance Evaluation Method (DRM Reaction Test)

[0070] Dry reforming of methane (DRM) tests for all catalysts were performed in a fixed-bed quartz reactor (inner diameter = 9 mm) with a continuous flow under atmospheric pressure. Initially, 0.20 g of calcined catalysts was placed between two pieces of glass wool and positioned in the center of the quartz tube. Before starting the DRM test, the calcined catalysts were [injected] H2 (45 mL min -1 ) and Ar(55mL min -1 Reduced catalysts were prepared by undergoing in-situ reduction at 800°C for 2 hours under a continuous flow of ). Subsequently, the gas flow was set to a gas hourly space velocity (GHSV) of 24,000 h -1 Phosphorus supply gas (CH4 / CO2 / Ar = 45 / 45 / 10mL min -1 DRM tests were conducted by changing to ), and catalysts for which DRM testing was completed were named spent catalysts. Long-term stability tests were performed at 800°C for 30 and 80 hours. Reactants and products were analyzed using an online gas chromatograph (YL6500 GC, Youngin Chromass Co., Anyang, Gyeonggi-do, South Korea) equipped with a thermal conductivity detector (TCD), flame ionization detector (FID), Porapak for CO2 detection, and two parallel columns (including molecular sieves for CH4, H2, and CO detection). The results showed CH4 conversion (X CH4 ), CO2 conversion(X CO2 ), calculated using the H2 / CO ratio (Equations 1 to 3).

[0071] [Mathematical Formula 1]

[0072]

[0073] [Mathematical Formula 2]

[0074]

[0075] [Mathematical Formula 3]

[0076]

[0077] In the above mathematical formulas 1 to 3, f[i] in / out i represents the inflow / outflow concentration of each gas in the supply or effluent. The above i is CH4, CO2, CO, or H2.

[0078] Catalyst property evaluation method

[0079] BET measurement method

[0080] N2 adsorption-desorption isotherms were measured at -196°C using an ASAP 2020 instrument (Micromeritics, Norcross, GA, USA). Prior to analysis, approximately 150 mg of calcined catalysts were placed in a BET reactor and degassed at 300°C for 24 hours. Subsequently, the specific surface area and pore size / pore volume were determined by the Brunauer-Emmett-Teller (BET) and DFT methods, respectively.

[0081] XRD measurement method

[0082] Powder samples of calcined catalysts, reduced catalysts, and spent catalysts were analyzed by X-ray diffraction (XRD) using a Rigaku RAD-3C diffractometer (Rigaku Corp., Tokyo, Japan) with Cu Kα1 radiation (λ = 1.5418 A) at 2θ = 10⁻⁹° operating at 35 kV and 20 mA. For reduced catalysts, calcined catalysts were sterilized in H₂ (45 mL min -1 ) and Ar(55 mL min -1 It was reduced at 800°C for 2 hours under a continuous flow of ) and then used for XRD measurement.

[0083] HR-TEM / EDS measurement method

[0084] High-resolution transmission electron microscope (HRTEM) images of the sample were captured using a JEOL JEM-2100F instrument (JEOL Ltd., Tokyo, Japan) equipped with an energy dispersive X-ray (EDX) analyzer with a maximum acceleration voltage of 200 kV. To prepare the sample, it was dispersed in ethanol using an ultrasonic bath, and then a drop of the suspension formed on a carbon-copper TEM grid was evaporated at room temperature.

[0085] Raman spectrum measurement method

[0086] Raman spectra of calcined catalysts, reduced catalysts, and spent catalysts were obtained using a DXR Raman microscope (Thermo Fisher Scientific, Waltham, MA, USA) equipped with a 532 nm laser beam. For reduced catalysts, the calcined catalysts were hydrated in H2 (45 mL min -1 ) and Ar(55 mL min -1 The sample was reduced at 800°C for 2 hours under a continuous flow of ) and then used for Raman spectrum measurements. For Raman measurements, a small amount of powder sample was placed on a clean glass slide and the surface was smoothed to ensure a consistent focus during the measurement. The spectrum was 100–3500 cm⁻¹. -1 It was recorded in the wavenumber range. To minimize fluorescence and thermal effects, the laser power was adjusted to 4 mW and the exposure time was set to 10 seconds per scan. To investigate the structural characteristics of coke, the D-band (~1350 cm⁻¹) was used. -1 ) and G-band (~1580 cm -1Specific regions corresponding to ) were analyzed. These bands were used to evaluate the degree of graphitization and structural disorder of the coke.

[0087] <Example 1> Preparation of tungsten-modified nickel-alumina composite catalyst (calcined and reduced xW-9NiAl-O)

[0088] A series of W-9Ni-Al2O3 catalysts with various tungsten (W) weight percentages (3, 6, 9, 17, 20, 23, 31 wt%) and a constant Ni-Al2O3 ratio (Ni:Al2O3 = 9:91 w / w) were synthesized using a simple one-pot method.

[0089] First, aluminum-tri-second-butoxide (ASB, C 12 H 27 AlO3) was dissolved in 2-butanol, and the resulting solution was stirred until ASB was completely dissolved.

[0090] Afterwards, the Ni nitrate precursor (Ni(NO3)2·6H2O) was dissolved separately in ethanol using an ultrasonic bath and added to the aforementioned mixture.

[0091] Next, a specified amount of (NH4)H2(W2O7)6 salt was dissolved in ethanol using an ultrasonic bath and added to the aforementioned mixture. The mixed solution was continuously stirred for 4 hours.

[0092] Then, 150 mL of the solution mixed above was transferred to a stainless steel autoclave lined with Teflon. The autoclave was sealed and placed in an oven at 120°C for 6 hours. Next, after cooling naturally to room temperature, the product was filtered and washed with water to obtain a precipitate, which was dried at 70°C for 24 hours.

[0093] Then, the dried material was calcined at 600°C in an air atmosphere for 6 hours to xW-9NiAl-O Calcined catalysts named (x=3, 6, 9, 17, 20, 23 and 31 wt%) were obtained.

[0094] FIG. 13 is a schematic diagram of a method for preparing a nickel-alumina composite catalyst modified with tungsten calcined in Example 1, wherein the reduction treatment process is omitted.

[0095] Next, for the reduction treatment of the calcined catalysts obtained above, the calcined catalysts were loaded into a fixed-bed quartz reactor (inner diameter = 9 mm) for the DRM (dry reforming of methane) test, and H2 (45 mL min) was applied under atmospheric pressure. -1 ) and Ar(55mL min -1 Reduced catalysts according to Example 1 were prepared by in-situ reduction treatment at 800°C for 2 hours while providing a continuous flow of ).

[0096] The reduced catalysts prepared in Example 1 above were immediately subjected to the DRM (dry reforming of methane) reaction in a reactor for the DRM test, with contact with oxygen excluded. Specifically, the continuous flow was set at a gas hourly space velocity (GHSV) of 24,000 h -1 Phosphorus supply gas (CH4 / CO2 / Ar = 45 / 45 / 10mL min -1 The DRM reaction was carried out by changing it to ). The catalyst that completed the DRM reaction was named the spent catalyst.

[0097] <Comparative Example 1> Preparation of nickel-alumina composite catalyst without added tungsten (0W-9NiAl-O calcined and reduced)

[0098] Calcined catalysts were prepared using the same method as in Example 1, except that no tungsten precursor was used to accurately evaluate the effect of tungsten, and then reduced catalysts were prepared as Comparative Example 1 by in-situ reduction treatment.

[0099] <Comparative Example 2> Preparation of tungsten-modified nickel-alumina composite catalyst (calcined xW-9NiAl-O)

[0100] The xW-9NiAl-O calcined catalysts from Example 1 were prepared as Comparative Example 2. The difference between Comparative Example 2 and Example 1 is that the in-situ reduction treatment was omitted.

[0101] <Comparative Example 3> Preparation of nickel-alumina composite catalyst without added tungsten (calcined 0W-9NiAl-O)

[0102] Calcined catalysts of 0W-9NiAl-O were prepared as Comparative Example 3 using the same method as Comparative Example 1, except that the in-situ reduction treatment in Comparative Example 1 was omitted.

[0103] <Experimental Example 1> Catalyst Characteristics and Physical Properties

[0104] The surface area BET, pore volume, and pore size of the calcined catalysts prepared in Comparative Example 2 (calcined xW-9NiAl-O) and Comparative Example 3 (calcined 0W-9NiAl-O) were measured, and the results are shown in Fig. 1 and Table 1 below.

[0105] Figure 1 is a graph showing (a) the N2 adsorption-desorption isotherm and (b) the mesopore size distribution curve obtained from the N2 adsorption-desorption isotherm of calcined catalysts prepared in Comparative Example 2 (calcined xW-9NiAl-O) and Comparative Example 3 (calcined 0W-9NiAl-O).

[0106] [Table 1]

[0107]

[0108] As shown in Table 1 above, it was confirmed that the specific surface area of ​​the catalyst tended to decrease as the tungsten loading increased.

[0109] <Experimental Example 2> Evaluation of Methane and Carbon Dioxide Conversion Rates (Catalytic Activity)

[0110] The DRM (dry reforming of methane) test was performed using the reduced catalysts prepared in Example 1 and Comparative Example 1, and the methane conversion rate and carbon dioxide conversion rate were measured. The results are shown in Figures 2 to 4 and Table 2 below.

[0111] Figure 2 is a graph showing (a) methane conversion rate and (b) carbon dioxide conversion rate measured after 5 hours of dry reforming of methane (DRM) test with the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0112] Figure 3 is a graph showing (a) methane conversion rate and (b) carbon dioxide conversion rate measured after 30 hours of dry reforming of methane (DRM) testing with the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0113] Figure 4 is a graph showing (a) methane conversion rate and (b) carbon dioxide conversion rate measured after 80 hours of dry reforming of methane (DRM) testing with the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0114] Reaction conditions of Fig. 2: T = 800℃, CH4 / CO2 / Ar = 45:45:10, GHSV = 30000 mL g -1 h -1 , TOS = 5 h

[0115] Reaction conditions of Fig. 3: T = 800℃, CH4 / CO2 / Ar = 45:45:10, GHSV = 30000 mL g -1 h -1 , TOS = 30 h

[0116] Reaction conditions of Fig. 4: T = 800℃, CH4 / CO2 / Ar = 45:45:10, GHSV = 30000 mL g -1 h -1 , TOS = 80 h

[0117] Reaction conditions in Table 2: T = 800℃, CH4 / CO2 / Ar = 45:45:10, GHSV = 24000 mL g -1 h -1 , TOS = 5 and 30 h

[0118] [Table 2]

[0119]

[0120] As shown in FIGS. 2 to 4 and Table 2,

[0121] In the case of methane conversion rate, a tendency was observed where the initial methane conversion rate decreased as the tungsten (W) loading increased. It was confirmed that the conversion rate decreased as the reaction progressed when only Ni was loaded (Comparative Example 1), whereas it was confirmed that the methane conversion rate gradually recovered and was maintained when tungsten (W) was loaded (Example 1). The carbon dioxide conversion rate exhibited behavior similar to that of the methane conversion rate. In particular, regarding catalytic activity, the methane and carbon dioxide conversion rates continuously decreased when only Ni was loaded (Comparative Example 1), whereas when tungsten (W) was loaded (Example 1), no decrease in conversion rate occurred after the initial conversion rate was recovered.

[0122] <Experimental Example 3> Evaluation of the active sites of the catalyst

[0123] Figure 5 shows (a) the XRD pattern of the calcined catalysts prepared in Comparative Examples 2 and 3 and (b) the XRD pattern of the reduced catalysts prepared in Example 1 and Comparative Example 1.

[0124] As shown in Fig. 5, in the calcined catalysts according to Comparative Example 2, it can be confirmed that catalytic active sites exist in the form of various metal oxides including NiAl2O4 and WO3 (see Fig. 5(b)). Meanwhile, in the reduced catalysts according to Example 1, the tungsten (W) chemical species exists in the form of metal and is presumed to have no reaction activity.

[0125] Figure 6 shows the XRD patterns measured after a DRM test with the reduced catalysts prepared in Example 1 (xW-9NiAl-O) and Comparative Example 1 (0W-9NiAl-O), including (a) the XRD pattern of the spent catalysts after 5 hours and (b) the XRD pattern of the spent catalysts after 30 hours.

[0126] As shown in Figure 6, it can be confirmed that the W metal is converted into the WC form in the spent catalysts used after the DRM reaction. The formation of WC is considered to be a new catalytic active site.

[0127] <Experimental Example 4> Analysis of the Physical Properties of the Catalyst

[0128] Figure 7 is an HR-TEM image of the reduced catalysts prepared in Example 1 and Comparative Example 1. (a,b) 0W-9NiAl-O; (c,d) 9W-9NiAl-O; (e,f) 17W-9NiAl-O; (g,h,h') 20W-9NiAl-O; (i,j,j') 23W-9NiAl-O; and (k,l,l') 31W-9NiAl-O.

[0129] As shown in FIG. 7, the W (110) metallic phase of the reduced catalysts was identified, and also Ni 17 The W3(220) alloy phase was confirmed. (a,b) In the case of 0W-NiAl-O, the distribution of Ni nanoparticles with a lattice layer d = 0.20 nm on the catalyst is clearly visible. (c,d), (i,j,j') In the tungsten-modified catalyst, metallic W (lattice layer d = 0.22 nm) and highly dispersed Ni 17 A new phase including W3 (lattice layer d = 0.18 nm) is observed. Ni 17 W3 is formed due to the interaction between Ni and W, which acts as the active site for CH4 conversion. Considering the catalytic performance data, Ni serves as the CH4 active site in the 0W-NiAl-O catalyst. However, the instability of Ni indicates weak interactions between Ni and Al, which allows for the diffusion of carbon (C*) into the Ni lattice. On the other hand, in the tungsten-modified catalyst, Ni 17 The presence of W3 provides a stable active site. Ni, the active site of CH4. 17The W3 phase is thermodynamically more stable than pure Ni and forms a unique surface structure in which active Ni sites are surrounded by W atoms. These W atoms act as a barrier, effectively limiting carbon diffusion into the Ni lattice and suppressing coke formation. Additionally, TEM images of the tungsten-modified catalyst reveal another phase associated with W. The particle size of W increases with increasing tungsten content, suggesting that the dynamic behavior of the catalyst in the initial stages is influenced by the coating of active sites by W.

[0130] Figure 8 is a STEM-EDS mapping image of the 0W-9NiAl-O reduced catalysts prepared in Comparative Example 1.

[0131] Figure 9 is a STEM-EDS mapping image of the 9W-9NiAl-O reduced catalysts prepared in Example 1.

[0132] As shown in Fig. 8, the STEM-EDS mapping image of the 0W-NiAl-O reduced catalysts shows high dispersion of Ni particles.

[0133] As shown in Fig. 9, the STEM-EDS mapping image of the 9W-9NiAl-O reduced catalysts confirms that Ni and W are distributed at the same location, which indicates the interaction between Ni and W and Ni 17 It suggests the existence of a W3 alloy phase and also confirms the possibility of W metallic phase formation.

[0134] FIG. 10 is an HR-TEM image of the spent catalysts after 5 hours of the dry reforming of methane (DRM) reaction of the reduced catalysts prepared in Example 1 and Comparative Example 1. (a,b,c) 0W-9NiAl-SO; (d,e,f) 9W-9NiAl-SO; and (g,h,i) 17W-9NiAl-SO. (Here, 'S' is an abbreviation for 'spent' and does not refer to the element S.)

[0135] FIG. 11 is an HR-TEM image of the spent catalysts after 30 hours of the dry reforming of methane (DRM) reaction of the reduced catalysts prepared in Example 1 and Comparative Example 1. (a,b) 0W-9NiAl-SO; (c,d) 9W-9NiAl-SO; and (e,f) 17W-9NiAl-SO. (Here, 'S' is an abbreviation for 'spent' and does not refer to the element S.)

[0136] As shown in Fig. 10, in the case of the spent catalyst 0W-9NiAl-SO after a 5-hour DRM test reaction, a large number of carbon nanotube (CNT)-shaped coke with Ni particles on top were observed after the reaction. The significant formation of CNTs in 0W-9NiAl-SO hinders the migration of O* to the coke precursor, leading to the initial deactivation of the catalyst (a,b,c). On the other hand, in the spent catalysts 9W-9NiAl-SO and 17W-9NiAl-SO after a 5-hour DRM test reaction, it is difficult to find CNT-like coke (d,e,f,g,h,i). Instead, the formation of a new active phase of tungsten carbide (WC) is clearly evident in these samples. This transformation occurs through the migration of C* deposited from the Ni surface to W, ultimately leading to the formation of WC. Considering the TEM images of the spent catalysts and their performance after 5 hours of reaction, it is clear that in the early stages of the reaction, the Ni-W alloy is responsible for the activity of CH4, while the W species is inactive. However, as the reaction proceeds, tungsten carbide (WC) is formed and begins to contribute significantly to CO₂ conversion, thereby improving the performance of the catalyst and its resistance to coke formation.

[0137] As shown in Fig. 11, in the case of the spent catalyst 0W-9NiAl-SO after 30 hours of DRM testing, graphite coke covering the Ni particles was clearly observed, which is thought to cause catalyst deactivation. On the other hand, in the spent catalysts 9W-9NiAl-SO and 17W-9NiAl-O after 30 hours of DRM testing, coke is difficult to find, and WC remains stable on the catalyst. Considering the stability of the tungsten-modified catalysts during the long reaction time and the TEM images, it is clear that WC acts as an active site for CO2 activation. WC supplies abundant oxygen to the catalyst surface, promoting coke gasification and removing the Ni active phase. W2C and WO2 are known byproducts of WC formation during DRM testing.

[0138] In other words, after the DRM reaction, carbon nanotube (CNT) and graphite-type cokes were produced in catalysts used with 0W-9NiAl-SO, whereas it was difficult to observe coke formation in catalysts used with 9W-9-NiAl-SO. This implies that the formation of the WC phase was clearly evident.

[0139] FIG. 12 is the Raman spectrum of the prepared catalysts, wherein (a) is the calcined catalyst prepared in Comparative Example 2; (b) is the reduced catalyst prepared in Example 1; (c) is the spent catalyst after 5 hours of DRM reaction of the reduced catalyst prepared in Example 1 and Comparative Example 1; (d) is the spent catalyst after 30 hours of DRM reaction of the reduced catalyst prepared in Example 1 and Comparative Example 1; and (e) is the Raman spectrum of the spent catalyst after 80 hours of DRM reaction of the reduced catalyst prepared in Example 1 and Comparative Example 1.

[0140] As shown in Figure 12, the formation of CNT (carbon nanotube) and graphite-type coke is confirmed in 0W-9NiAl-SO after the reaction through the D, G, and G' peaks. On the other hand, it can be seen that the formation of the corresponding peaks is suppressed in the tungsten (W) added catalyst. In other words, it is determined that the formation of coke is suppressed by the addition of tungsten (W).

[0141] The present invention has been described above with reference to its preferred embodiments. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined not by the foregoing description but particularly by the claims, and all variations within the equivalent scope should be interpreted as being included in the invention.

Claims

1. A step of preparing a mixed solution by mixing a tungsten (W) source, a nickel (Ni) source, and an alumina (Al-O) source in a solvent (Step 1); Step 2: placing the above mixed solution into an autoclave, sealing it, heating it at 100-140°C for 4-8 hours, cooling it to room temperature, filtering the product to obtain a precipitate, and then drying the precipitate to obtain a dried product; A step of calcining the above-mentioned dried material at 500-700°C in an air atmosphere for 4-8 hours to obtain calcined catalysts (Step 3); and The method comprises the step (step 4) of loading the above-mentioned calcined catalysts into a reactor and reducing them at 700-900°C for 1-3 hours while supplying a continuous flow gas containing hydrogen to obtain reduced catalysts xW-NiAl-O; In the above-mentioned reduced catalyst xW-NiAl-O, x is 1 to 35 weight% as the content of tungsten (W), and In the above-mentioned reduced catalyst xW-NiAl-O, the weight ratio of nickel (Ni) to alumina (Al-O) is 9:82-100, Method for preparing a nickel-alumina composite catalyst modified with tungsten (W) that has undergone calcination and reduction treatment.

2. In Paragraph 1, A method of manufacturing in which the above tungsten (W) source is one or more selected from the group consisting of (NH4)H2(W2O7)6, Na2WO4·2H2O, (NH4)2WO4 and WO3.

3. In Paragraph 1, A manufacturing method in which the nickel (Ni) source is one or more selected from the group consisting of Ni(NO3)2·6H2O, NiCl2·6H2O, and NiO.

4. In Paragraph 1, The above alumina (Al-O) source is C 12 H 27 A manufacturing method comprising one or more selected from the group consisting of AlO3, Al2O3, Al(OH)3, and AlCl3.

5. In Paragraph 1, A method of manufacturing in which the solvent is one or more selected from the group consisting of 2-butanol, ethanol, water, acetone, cyclohexane, and dimethyl sulfoxide.

6. In Paragraph 1, A method of manufacturing in which the reactor is a quartz reactor, a corundum reactor, a ceramic reactor, or a silica reactor.

7. In Paragraph 1, In the above-mentioned reduced catalyst xW-NiAl-O, x is 3 to 20 weight% as the content of tungsten (W), and A method of manufacturing in which the weight ratio of nickel (Ni) and alumina (Al-O) in the above-mentioned reduced catalysts xW-NiAl-O is 9:87-95.

8. In Paragraph 7, In the above-mentioned reduced catalyst xW-NiAl-O, x is 6 to 17 weight% as the content of tungsten (W), and A method of manufacturing in which the weight ratio of nickel (Ni) and alumina (Al-O) in the above-mentioned reduced catalysts xW-NiAl-O is 9:89-93.

9. In Paragraph 8, In the above-mentioned reduced catalyst xW-NiAl-O, x is 9 to 17 weight% as the content of tungsten (W), and A method of manufacturing in which the weight ratio of nickel (Ni) and alumina (Al-O) in the above-mentioned reduced catalysts xW-NiAl-O is 9:90-92.

10. A tungsten (W) modified nickel-alumina composite catalyst manufactured by the manufacturing method of claim 1.

11. In Paragraph 10, A tungsten (W) modified nickel-alumina composite catalyst used in carbon dioxide reforming reaction (CDR).

12. A method for producing hydrogen gas from methane by carbon dioxide reforming reaction (CDR) using the nickel-alumina composite catalyst of claim 10.

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