Process for the preparation of ruthenium-based nanocluster catalysts, applications and method for the simultaneous coupling of ammonia and carbon dioxide conversion

Abstract

The present disclosure provides a preparation method and application of a ruthenium-based nanocluster catalyst and a method for simultaneously coupling conversion of ammonia and carbon dioxide, wherein a magnesium-aluminum hydrotalcite is prepared by a coprecipitation method, the magnesium-aluminum hydrotalcite is dried and sieved, and then first calcination at 800-1200 DEG C is performed to obtain a magnesium-aluminum composite oxide carrier, the magnesium-aluminum composite oxide carrier comprises magnesium oxide and spinel structure magnesium aluminate, an equal-volume impregnation method is used to impregnate the magnesium-aluminum composite oxide carrier into a ruthenium salt solution, and then second calcination at 300-600 DEG C is performed after drying to obtain the ruthenium-based nanocluster catalyst. The ruthenium-based nanocluster catalyst prepared by the method of the present disclosure has a single-atom nanocatalytic structure, the atomically dispersed metal Ru provides a larger metal surface area for catalytic reaction to occur, the preparation process is simple, the purity is high, the selectivity is strong, and the ruthenium-based nanocluster catalyst exhibits strong stability when used for simultaneously coupling conversion of ammonia and carbon dioxide.

Description

Technical Field

[0001] This disclosure relates to the preparation and application of a catalyst for the efficient simultaneous conversion of carbon dioxide and ammonia, specifically to a method for preparing, applying, and simultaneously coupling the conversion of ammonia and carbon dioxide using a ruthenium-based nanocluster catalyst. Background Technology

[0002] The overuse of traditional energy sources such as coal, oil, and natural gas has led to problems such as environmental pollution, ecological imbalance, and excessive CO2 emissions. Based on industrial or transportation CO2 emissions, they can be divided into stationary carbon emissions (approximately 77%) and mobile carbon emissions (approximately 23%). To reduce stationary CO2 emissions, converting green hydrogen (such as H2 produced by renewable electricity electrolysis of water) and carbon capture CO2 into fuel is an effective way to reduce CO2 emissions.

[0003] For the transportation industry, which accounts for a quarter of CO2 emissions, on-site hydrogen refueling for transporting H2 is not economically feasible. Using NH3 as engine fuel has become a trend, but due to the difficulty in burning NH3, N2O and NO... x Due to its high emission rate, using NH3 to power engines is impractical until mature technologies are available. However, because of NH3's high hydrogen reserves and its liquid state at room temperature, it can be used as a hydrogen carrier to treat exhaust CO2 and convert it into fuels such as CH4 to power engines. However, CO2 methanation (CO2 + 4H2 → CH4 + 2H2O, ΔG) 298K =-130.8kJ / mol) is a typical exothermic reaction, NH3 decomposition (2NH3→3H2+N2, ΔG) 298K The reaction (87.2 kJ / mol) is a typical endothermic reaction. With the use of a catalyst, the optimal active temperature for CO2 methanation is typically 300–400 °C, while the temperature for complete decomposition of NH3 is generally above 500 °C. Therefore, considering the temperature difference between the two reactions, it is difficult to achieve simultaneous conversion of CO2 and NH3. Summary of the Invention

[0004] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, this disclosure provides a method for preparing, applying, and simultaneously coupling the conversion of ammonia and carbon dioxide using a ruthenium-based nanocluster catalyst.

[0005] As one aspect of this disclosure, a method for preparing a ruthenium-based nanocluster catalyst is provided, comprising:

[0006] Magnesium-aluminum hydrotalcite was prepared using a coprecipitation method;

[0007] After drying and sieving, magnesium-aluminum hydrotalcite is subjected to a first calcination at 800-1200℃ to obtain a magnesium-aluminum composite oxide carrier, which includes magnesium oxide and spinel-structured magnesium aluminate.

[0008] The magnesium-aluminum composite oxide support was impregnated into a ruthenium salt solution using an equal-volume impregnation method. After drying, it was calcined a second time at 300–600 °C to obtain a ruthenium-based nanocluster catalyst.

[0009] As another aspect of this disclosure, a method for the simultaneous coupled conversion of ammonia and carbon dioxide is provided, comprising:

[0010] Under the action of the ruthenium-based nanocluster catalyst prepared by the method disclosed herein, the reaction gas containing ammonia and carbon dioxide simultaneously undergoes the reaction of ammonia decomposition to produce hydrogen and carbon dioxide to produce methane at 400-600℃, so as to produce methane.

[0011] As another aspect of this disclosure, an application of the ruthenium-based nanocluster catalyst prepared by the method of this disclosure in the exhaust gas treatment of methane fuel engines is provided.

[0012] According to embodiments of this disclosure, the ruthenium-based nanocluster catalyst prepared using the method of this disclosure possesses a single-atom nanocatalytic structure, with atomically dispersed metallic Ru providing a larger metal surface area for catalytic reactions. Simultaneously, it is obtained by high-temperature calcination of a magnesium-aluminum layered double hydroxide (MLD) precursor, exhibiting high thermal stability and a strong "anchoring" effect on noble metals, particularly Ru. Furthermore, the Mg-Al LTD is synthesized using a simple co-precipitation method, and its specific morphology creates a higher specific surface area and total pore volume for the support, accommodating more active sites. Ru / (Mg,Al)O supported on noble metal Ru. x Nanocluster catalysts have a simple preparation process, high purity, no byproducts, and do not cause environmental pollution, and have great potential for industrial-scale production.

[0013] According to embodiments of this disclosure, the ruthenium-based nanocluster catalyst prepared in this disclosure uses Mg-Al hydrotalcite as a support precursor, and further loads it with metallic Ru to obtain Ru / (Mg,Al)O. x The catalyst possesses suitable basic sites for adsorbing CO2 and NH3; atomically dispersed metallic Ru provides a larger metal surface area for the coupled conversion of CO2 and NH3 to CH4; the low-load noble metal Ru-based catalyst exhibits strong stability in the CO2-NH3 coupled conversion.

[0014] According to embodiments of this disclosure, in a methane-powered engine, a large amount of CO2 is generated by the combustion of methane. By introducing the catalyst of this disclosure, CO2 and NH3 can fully react to generate N2 and H2O, while CH4 is generated to continue to power the engine, thus achieving low-carbon or even zero-carbon emissions while recycling exhaust gas. Attached Figure Description

[0015] Figure 1 The in-situ diffuse reflectance infrared spectra and the inferred conversion mechanism diagram (e) collected for the catalyst in the embodiments of this disclosure during ammonia decomposition (a), carbon dioxide methanation (b), carbon dioxide adsorption (c), and simultaneous carbon dioxide-ammonia coupling conversion (d) are shown.

[0016] Figure 2 This is a flowchart illustrating the preparation method of the ruthenium-based nanocluster catalyst according to an embodiment of this disclosure;

[0017] Figure 3 This is a diagram of a device for the simultaneous coupling and conversion of ammonia and carbon dioxide according to an embodiment of this disclosure;

[0018] Figure 4 This is a schematic diagram of the formation process of the magnesium-aluminum composite oxide carrier according to an embodiment of the present disclosure;

[0019] Figure 5 The 5% Ru / (Mg,Al)O prepared in Example 1 x -800 Catalyst Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy;

[0020] Figure 6 The 5% Ru / (Mg,Al)O prepared in Example 1 x -800 catalyst aberration-corrected scanning transmission electron microscope image;

[0021] Figure 7 (a) 1% Ru / (Mg,Al)O prepared in Example 4 x -1000 catalyst and (b) 5% Ru / (Mg,Al)O prepared in Example 2 x Wavelet transform plot of extended X-ray absorption fine structure spectrum of the -1000 catalyst;

[0022] Figure 8 Examples 2, 4, and 5, and (Mg,Al)O x X-ray diffraction pattern of magnesium-aluminum hydrotalcite;

[0023] Figure 9 The graphs show the carbon dioxide conversion rate as a function of reaction temperature for Examples 6 and 7.

[0024] Figure 10 The graphs show the changes in ammonia conversion rate as a function of reaction temperature for Examples 8 and 9.

[0025] Figure 11 The graph shows the change in carbon dioxide conversion rate as a function of reaction temperature in the simultaneous carbon dioxide-ammonia coupling conversion of Examples 10 and 11.

[0026] Figure 12 The graph shows the change in ammonia conversion rate with reaction temperature for the simultaneous carbon dioxide-ammonia coupling conversion in Examples 10 and 11. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0028] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0031] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Similarly, when using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0032] In this document, the abbreviations are explained as follows:

[0033] (Mg,Al)O x Magnesium-aluminum composite oxide carrier.

[0034] 5% Ru / (Mg,Al)O x -1000: Ruthenium-based nanocluster catalyst with a Ru loading of 5% and a first calcination temperature of 1000℃.

[0035] 5% Ru / (Mg,Al)O x -800: Ruthenium-based nanocluster catalyst with 5% Ru loading and a first calcination temperature of 800℃.

[0036] 1% Ru / (Mg,Al)O x -1000: Ru-based nanocluster catalyst with 1% Ru loading and a first calcination temperature of 1000℃.

[0037] In realizing the inventive concept of this disclosure, it was discovered that designing a system that narrows the temperature difference between the CO2 methanation and NH3 decomposition reactions facilitates the simultaneous conversion of CO2 and NH3. Further, it was found that calcined magnesium-aluminum hydrotalcite can form a magnesium-aluminum composite oxide spinel structure with high thermal stability and abundant basic sites. When loaded with metals, especially noble metals, it can form a strong metal-support interaction. It is precisely because of this strong metal-support interaction that the exothermic CO2 methanation reaction can reach the optimal temperature range suitable for NH3 decomposition. The abundant basic sites and low content of noble metal ruthenium-based nanoclusters in the catalyst greatly enhance the adsorption and conversion of reactants, significantly improving the selectivity and stability of methane production.

[0038] In-situ diffuse reflectance infrared spectroscopy was used to study 5% Ru / (Mg,Al)O x The pathway for NH3 to produce H2 at -1000 is as follows: Figure 1 As shown in (a), gaseous NH3 and / or physically adsorbed NH3 can be observed at temperatures of 400–600 °C; at 1627 cm⁻¹ -1 Active *NH3 species coordinated with Lewis acid sites can be observed at the site, and NH3 species coordinated with Brønsted acid sites can also be detected. 4+ Species (center 1461cm) -1 ); at 3332cm -1 Highly reactive *NH species were observed. Due to the endothermic nature of NH3 decomposition, the intensity of all N-related species decreased when the temperature increased from 400℃ to 600℃, which is consistent with the trend of NH3 decomposition activity.

[0039] In CO2 methanation, in-situ diffuse reflectance infrared spectroscopy revealed the infrared bands of strongly adsorbed *CO2 and surface *OH species, such as... Figure 1 As shown in (b), distinct carbon-containing species, such as bicarbonate *HCO3, monocarbonate *CO3, and formate *HCOO, can also be observed; especially at 2040 cm⁻¹. -1 *CO species associated with the carbon dioxide methane desorption pathway were observed. Furthermore, CO2 adsorption was also performed on Ru / MAO catalysts with different Ru loadings. Figure 1 (c) shows 10% Ru / (Mg,Al)O x -1000 has a high CO3 content (at 1332 cm⁻¹) -1 (at a certain location), but when adsorbing CO2, *HCO3 (at 1219 cm⁻¹) -1 The (location) disappeared. In 10% Ru / (Mg,Al)O x The presence of a large amount of *HCOO at -1000 indicates that Ru particles (or highly metal-supported catalysts) can promote the conversion of *CO3 and HCO3. This is in contrast to 1% Ru / (Mg,Al)O x Compared to -1000, 5% Ru / (Mg,Al)O x -1000 exhibits stronger CO3, indicating differences in adsorption behavior on surfaces with different Ru loading rates.

[0040] like Figure 1 As shown in (d), gaseous NH3 and NH3 coordinated with Lewis acid sites can also be observed during the simultaneous CO2-NH3 conversion. After the introduction of CO2, the *N2H2, *N2H, and *NH species disappear, but the major species associated with CO2 methanation are still observable, demonstrating that NH3 is more likely to be adsorbed to generate H atoms for direct use in the subsequent CO2 hydrogenation reaction. Furthermore, *HCO3 (1650 cm⁻¹) was not detected compared to CO2 methanation alone. -1 ) and the bidentate *HCOO species (2587cm) -1 Strong linear *CO species and gaseous CO were observed during the CO2-NH3 catalytic conversion, indicating that linear *CO may be involved in the simultaneous coupled conversion. Therefore, the CO2-NH3 simultaneous conversion using the catalyst disclosed herein is not two independent reactions, but a simultaneous coupled conversion at the mechanistic level.

[0041] To achieve the above technical objectives, this disclosure provides the following technical solutions:

[0042] According to embodiments of this disclosure, a method for preparing a ruthenium-based nanocluster catalyst is provided, the process of which is as follows: Figure 2 As shown, steps S1 to S4 are included:

[0043] Step S1: Dissolve magnesium salt and aluminum salt in water to obtain a salt solution; add a precipitant to the salt solution and adjust the pH to 8-12 to obtain a precipitate solution;

[0044] Step S2: After stirring and aging the precipitate solution under heating conditions, the aged precipitate is dried to obtain magnesium-aluminum hydrotalcite. The principle of the process is as follows: Figure 4 As shown;

[0045] Step S3: After drying and sieving the magnesium-aluminum hydrotalcite, it is calcined at 800-1200℃ to obtain a magnesium-aluminum composite oxide carrier, which includes magnesium oxide and spinel-structured magnesium aluminate.

[0046] Step S4: Using the equal-volume impregnation method, the magnesium-aluminum composite oxide support is impregnated into a ruthenium salt solution, dried, and then calcined at 300-600℃ to obtain a ruthenium-based nanocluster catalyst.

[0047] According to embodiments of this disclosure, in step S1, the pH value of the mixed solution can be 8, 9, 10, 11, or 12, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0048] According to an embodiment of this disclosure, in step S2, the heating condition is stirring at 90 to 110°C. It can be 90°C, 100°C, or 110°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] According to embodiments of this disclosure, the ruthenium-based nanocluster catalyst prepared using the method of this disclosure possesses a single-atom nanocatalytic structure, with atomically dispersed metallic Ru providing a larger metal surface area for catalytic reactions. Simultaneously, it is obtained by high-temperature calcination of a magnesium-aluminum hydrotalcite precursor, exhibiting high thermal stability and a strong "anchoring" effect on noble metals, particularly Ru. Furthermore, the Mg-Al hydrotalcite is synthesized using a simple co-precipitation method, and its specific morphology creates a higher specific surface area and total pore volume for the support, accommodating more active sites. The preparation process of the Ru / (Mg,Al)Ox nanocluster catalyst supported on noble metal Ru is simple, has high purity, produces no byproducts, and does not cause environmental pollution, showing great potential for industrial-scale production; the catalyst has a specific surface area of ​​128 m². 2 / g, metal dispersion reaches 64%, and basic sites reach 5.43mmol / g. cat .

[0050] According to embodiments of this disclosure, the magnesium salt is selected from at least one of its soluble salts, preferably nitrates or chlorides;

[0051] Magnesium salts are selected from at least one of their soluble salts, namely nitrates and chlorides;

[0052] Aluminum salts are selected from at least one of their soluble salts, namely nitrates and chlorides;

[0053] The molar ratio of magnesium salt to aluminum salt is (1.5–3):1;

[0054] The precipitant is at least one of ammonia, sodium hydroxide, or sodium carbonate solution, and the concentration of the precipitant is 0–3 mol / L.

[0055] According to embodiments of this disclosure, soluble magnesium salts and aluminum salts are mixed in a solution to form a homogeneous phase. By adding a precipitant, a homogeneous precipitate can be obtained after a precipitation reaction. The precipitant can be one or a combination of ammonia, sodium hydroxide, and sodium carbonate solutions, all of which can produce homogeneous precipitation. The molar ratio of magnesium salt to aluminum salt can be 1.5:1, 2:1, 2.5:1, or 3:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, thereby forming a composite structure of MgO and MgAl2O4.

[0056] According to embodiments of this disclosure, the concentration of the precipitant can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. If the concentration of the precipitant is too high, it may change the ionic strength in the solution, thereby affecting the solubility of the precipitate.

[0057] According to an embodiment of this disclosure, the heating program for the first calcination is to heat to 800-1200°C at a rate of 5-30°C / min, and then hold at 800-1200°C for 2-5 hours.

[0058] According to embodiments of this disclosure, the first calcination temperature can be 800°C, 900°C, 1000°C, 1100°C, or 1200°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Calcination at temperatures above 800°C can yield a stable spinel structure. In this disclosure, the actual structure is a composite structure of MgO and MgAl2O4. If the calcination temperature is too low, the material may not be able to crystallize completely, while if the temperature is too high, the crystal structure may change or be destroyed.

[0059] According to embodiments of this disclosure, the ruthenium salt is selected from at least one of its soluble salts, including nitrates and chlorides.

[0060] According to embodiments of this disclosure, soluble salts can be uniformly distributed in the pores of the support, ensuring uniform distribution of the active component throughout the catalyst, thereby improving the catalyst's performance.

[0061] According to an embodiment of this disclosure, the second calcination heating program is to heat to 300-600°C at a rate of 5-30°C / min, and then hold at 300-600°C for 2-5 hours.

[0062] According to embodiments of this disclosure, the second calcination temperature can be 300°C, 400°C, 500°C, or 600°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Excessively high calcination temperatures can lead to increased adhesion between particles, resulting in Ru sintering.

[0063] According to embodiments of this disclosure, a method for simultaneously coupling and converting ammonia and carbon dioxide is provided, comprising:

[0064] Under the action of the ruthenium-based nanocluster catalyst prepared in this disclosure, the reaction gas containing ammonia and carbon dioxide simultaneously undergoes the reaction of ammonia decomposition to produce hydrogen and carbon dioxide to produce methane at 400-600℃, so as to produce methane.

[0065] According to embodiments of this disclosure, under the action of a catalyst, the reaction of ammonia decomposition to produce hydrogen and carbon dioxide to produce methane occurring simultaneously at 400–600°C includes:

[0066] Step S201: Introduce a reaction gas containing ammonia and carbon dioxide into a fixed-bed reactor containing a catalyst;

[0067] Step S202: Control the temperature of the reactor at 400-600℃ so that the reaction gas can simultaneously undergo the reaction of ammonia decomposition to produce hydrogen and carbon dioxide to produce methane.

[0068] According to embodiments of this disclosure, the ruthenium-based nanocluster catalyst prepared in this disclosure uses Mg-Al hydrotalcite as a support precursor, and further loads it with metallic Ru to obtain Ru / (Mg,Al)O. x The catalyst possesses suitable basic sites for adsorbing CO2 and NH3; atomically dispersed metallic Ru provides a larger metal surface area for the coupled conversion of CO2 and NH3 to CH4; the low-load noble metal Ru-based catalyst exhibits strong stability in the CO2-NH3 coupled conversion; when applied to CO2 methanation and NH3 decomposition respectively, the CO2 and NH3 conversion rates can reach up to 70% and 100% respectively; when directly applied to the simultaneous coupled conversion of CO2 and NH3, the CO2 and NH3 conversion rates can still reach 49% and 80% respectively, demonstrating high stability and catalytic activity.

[0069] According to embodiments of this disclosure, ruthenium-based nanocluster catalysts can catalyze the CO2 methanation reaction, increase the reaction rate, increase product selectivity, and reduce energy consumption and byproduct formation. Unlike conventional catalysts, which exhibit high activity at lower reaction temperatures, the ruthenium-based nanocluster catalysts of this disclosure exhibit higher catalytic activity at higher reaction temperatures, which is more conducive to narrowing the temperature difference with the NH3 decomposition reaction.

[0070] According to embodiments of this disclosure, ruthenium-based nanocluster catalysts can catalyze the decomposition reaction of NH3, provide the active sites required for the reaction, reduce the activation energy of the ammonia decomposition reaction, and enable the reaction to proceed at lower temperatures and pressures, which is beneficial for narrowing the temperature difference with the CO2 methanation reaction.

[0071] According to embodiments of this disclosure, the reaction apparatus used in the above method can be selected from... Figure 3 The apparatus shown includes a fixed-bed reactor, a resistance furnace, a temperature controller, and a thermocouple. The fixed-bed reactor is located inside the resistance furnace and is heated by the resistance furnace. The temperature controller is used to control the heating temperature, and the thermocouple is located inside the fixed-bed reactor to monitor the reaction temperature.

[0072] According to embodiments of this disclosure, the volume ratio of ammonia to carbon dioxide is (8-10):(2-5).

[0073] According to embodiments of this disclosure, the volume ratio of ammonia to carbon dioxide can be, for example, 8:2, 10:2, 8:3, 10:3, 8:5, 10:5, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0074] According to the embodiments of this disclosure, based on the chemical reaction balancing of CO2 methanation (CO2+4H2→CH4+2H2O) and NH3 decomposition (2NH3→3H2+N2), it can be seen that when the volume ratio of ammonia to carbon dioxide is (8~10):(2~5), the reactants and products can be fully utilized, synchronous coupling can be achieved, byproducts can be reduced, reactant waste can be avoided, and the optimal reaction equilibrium can be achieved.

[0075] Furthermore, according to embodiments of this disclosure, the application of the above-mentioned ruthenium-based nanocluster catalyst in CO2 methanation, NH3 decomposition, and simultaneous CO2-NH3 conversion is provided.

[0076] According to embodiments of this disclosure, this disclosure also provides an application of ruthenium-based nanocluster catalysts in the exhaust gas treatment of methane fuel engines.

[0077] According to embodiments of this disclosure, in a methane-powered engine, a large amount of CO2 is generated by the combustion of methane. By introducing the catalyst of this disclosure, CO2 and NH3 can fully react to generate N2 and H2O, while CH4 is generated to continue to power the engine, thus achieving low-carbon or even zero-carbon emissions while recycling exhaust gas.

[0078] In this disclosure, the embodiments use spherical aberration scanning transmission electron microscopy (STEM) to observe Ru / (Mg,Al)O x The size and distribution of Ru particles in the catalyst were determined using a FEI Titan Cubed Themis G2 300 instrument, manufactured by Thermo Fisher Scientific, USA. In the examples, scanning electron microscopy was used to observe the Ru / (Mg,Al)O ratio. x The surface morphology of the catalyst was determined using a GeminiSEM 500 (Zeiss AG, Germany). In this disclosure, the gas composition was analyzed using a gas chromatograph (Asicotech M3, China XuanYi Intelligent Technology Co., Ltd.).

[0079] Example 1

[0080] Preparation of 5% Ru / (Mg,Al)O x -800 catalyst

[0081] Step S1: Weigh 19.2305g of Mg(NO3)2·6H2O and 11.2540g of Al(NO3)3·9H2O, add 100mL of deionized water to fully dissolve them to obtain a salt solution, then mix 3mol / L sodium hydroxide and 2mol / L sodium carbonate to form a precipitant, and titrate the salt solution until the pH is 10 to obtain a precipitate solution;

[0082] Step S2: After stirring the precipitate solution at 100℃ and aging it for 24 hours, the aged precipitate was thoroughly dried in a forced-air drying oven at 120℃ to obtain the carrier precursor magnesium-aluminum hydrotalcite.

[0083] Step S3: The magnesium-aluminum hydrotalcite precursor is crushed, sieved, and then calcined in a muffle furnace at 800℃ for 2 hours (first calcination) to obtain (Mg,Al)O. x The carrier, namely the magnesium-aluminum composite oxide carrier, is shown in the diagram below. Figure 4 As shown;

[0084] Step S4: Remove the calcined (Mg,Al)O x After loading 5% metallic Ru onto the carrier using an equal-volume impregnation method, the carrier is calcined in a muffle furnace at 500℃ for 2 hours (the second calcination) to obtain 5% Ru / (Mg,Al)O, which effectively and simultaneously converts CO2 and NH3. x-800 nano-cluster catalyst.

[0085] Figure 5 The 5% Ru / (Mg,Al)O prepared in Example 1 x -800 Catalyst Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy; Figure 6 The 5% Ru / (Mg,Al)O prepared in Example 1 x -800 Catalyst Aberration Corrected Scanning Transmission Electron Microscopy Image.

[0086] according to Figure 5 and Figure 6 As can be seen, the scanning electron microscope (SEM) image and energy dispersive spectroscopy (EDS) image show that the catalyst is loose and porous with highly dispersed Ru particles, while aberration-corrected transmission electron microscopy shows that Ru clusters with a size of about 2 nm are formed.

[0087] Example 2

[0088] Preparation of 5% Ru / (Mg,Al)O x -1000 catalyst

[0089] The preparation steps are the same as in Example 1, except that the first calcination temperature is different, which is 1000°C.

[0090] Example 3

[0091] Preparation of 1% Ru / (Mg,Al)Ox-800 catalyst

[0092] The preparation steps are the same as in Example 1, except that the Ru loading is different. The loading of the equal volume impregnation method is 1% metallic Ru.

[0093] Example 4

[0094] Preparation of 1% Ru / (Mg,Al)O x -1000 catalyst

[0095] The preparation steps are the same as in Example 1, except that the first calcination temperature is different at 1000°C; and the Ru loading is different, with the loading of metallic Ru in the equal volume impregnation method being 1%.

[0096] Figure 7 (a) 1% Ru / (Mg,Al)O prepared in Example 4 x -1000 catalyst and (b) 5% Ru / (Mg,Al)O prepared in Example 2 x Wavelet transform of the extended X-ray absorption fine structure map of the -1000 catalyst.

[0097] according to Figure 7 It can be seen that both catalysts are and Two fragments were generated at the site, representing Ru-Ru coordination and Ru-O coordination, respectively. EXAFS data fitting results showed that the Ru-Ru coordination number gradually increased with increasing Ru loading, while the coordination number of 5% Ru / MAO reached 7.9, which is still lower than that of elemental Ru, indicating the successful preparation of Ru clusters.

[0098] Example 5

[0099] Preparation of 10% Ru / (Mg,Al)O x -1000 catalyst

[0100] The preparation steps are the same as in Example 1, except that the first calcination temperature is different at 1000°C; and the Ru loading is different, with the loading of metallic Ru in the equal volume impregnation method being 10%.

[0101] The 5% Ru / (Mg,Al)O prepared in Examples 2, 4, and 5 x -1000, 1% Ru / (Mg,Al)O x -1000, 10% Ru / (Mg,Al)O x -1000, and (Mg,Al)O x XRD characterization of magnesium-aluminum hydrotalcite was performed, and the characterization results are as follows: Figure 8 As shown.

[0102] Figure 8 Examples 2, 4, and 5, and (Mg,Al)O x X-ray diffraction pattern of magnesium-aluminum hydrotalcite.

[0103] according to Figure 8 It can be seen that the Ru particles in the catalysts with 1% and 5% Ru loadings are relatively small crystals, and the (Mg,Al)O... x The composite oxides are mainly composed of MgO and MgAl2O4 spinel structures.

[0104] Example 6

[0105] 5% Ru / (Mg,Al)O x -1000 Catalytic reaction of carbon dioxide to produce methane

[0106] Reaction apparatus such as Figure 3 As shown, the catalyst was treated with H2 at 500℃ for 2h at 50mL / min before participating in the catalytic reaction.

[0107] Take 100 mg of 5% Ru / (Mg,Al)O obtained in Example 2 (40-60 mesh). x-1000 catalyst was mixed with 600 mg of quartz sand and placed in a quartz reactor with a diameter of 1 cm. Then it was placed in a fixed-bed reactor and the reaction gas (64% H2 + 16% CO2 + 20% H2) and N2 internal standard gas (64 vol.% H2 + 16 vol.% CO2 + 20% N2) with a total flow rate of 50 mL / min were introduced to carry out CO2 conversion.

[0108] Set the fixed bed temperature to 200-500℃, start the reaction, and use a gas chromatograph to perform real-time online analysis of the product gas passing through the heating zone.

[0109] The method for calculating CO2 conversion rate is as follows:

[0110] X(CO2)=(CO2,in-CO2,out) / CO2,in×100%

[0111] X(CO2) represents the CO2 conversion rate; CO2,in and CO2,out represent the amount of CO2 input moles and CO2 output moles, respectively.

[0112] The calculated CO2 conversion rate is 1.1%–70.1%.

[0113] Example 7

[0114] 1% Ru / (Mg,Al)O x -1000 Catalytic reaction of carbon dioxide to produce methane

[0115] The reaction conditions and process were the same as in Example 6, except for the catalyst used, which was the 1% Ru / (Mg,Al)O prepared in Example 4. x -1000.

[0116] Figure 9 The graph shows the change in carbon dioxide conversion rate with reaction temperature for Examples 6 and 7.

[0117] according to Figure 9 As can be seen, unlike conventional methanation catalysts, the catalyst disclosed herein does not exhibit high methanation activity in the low-temperature region, but instead shows a CO2 conversion rate close to equilibrium in the high-temperature region.

[0118] Example 8

[0119] 1% Ru / (Mg,Al)O x -1000 Catalytic ammonia decomposition to produce hydrogen

[0120] Reaction apparatus such as Figure 3 As shown, the catalyst was treated with H2 at 500℃ for 2h at 50mL / min before participating in the catalytic reaction.

[0121] Take 100 mg of 1% Ru / (Mg,Al)O obtained in Example 4 (40-60 mesh). x -1000 catalyst was mixed with 600mg of quartz sand and then placed into a quartz reactor with a diameter of 1cm.

[0122] Then, it is placed in a fixed-bed reactor, and the adjusted reaction gas (16% NH3 + 84% Ar) with a total flow rate of 50 mL / min is introduced to decompose NH3; the fixed-bed temperature is set to 400-600℃, the reaction is started, and the product gas passing through the heating zone is analyzed in real time online using a gas chromatograph.

[0123] The NH3 conversion rate is calculated as follows:

[0124] X(NH3)=(NH3,in-NH3,out) / NH3,in×100%

[0125] X(NH3) represents the NH3 conversion rate; NH3,in and NH3,out represent the molar amounts of NH3 input and output, respectively.

[0126] The calculated conversion rate of NH3 is 1.2%-99.8%.

[0127] Example 9

[0128] 5% Ru / (Mg,Al)O x -1000 Catalytic ammonia decomposition to produce hydrogen

[0129] The reaction conditions and process were the same as in Example 8, except for the catalyst used, which was the 5% Ru / (Mg,Al)O prepared in Example 2. x -1000.

[0130] Figure 10 The graph shows the change in ammonia conversion rate with reaction temperature for Examples 8 and 9.

[0131] according to Figure 10 It can be seen that the catalyst disclosed herein exhibits 100% conversion at relatively low temperatures, thus reducing the temperature difference and providing the temperature conditions for synchronous coupling.

[0132] Example 10

[0133] 5% Ru / (Mg,Al)O x -1000 Catalytic simultaneous coupling conversion of carbon dioxide and ammonia to methane

[0134] Reaction apparatus such as Figure 3 As shown, the catalyst was treated with H2 at 500℃ for 2h at 50mL / min before participating in the catalytic reaction.

[0135] Step S201: Take 100 mg of 5% Ru / (Mg,Al)O2 prepared in Example 2 with a 40-60 mesh surface. x -1000 catalyst was mixed with 600 mg of quartz sand and placed in a quartz reactor with a diameter of 1 cm. Then it was placed in a fixed bed reactor and a reaction gas (16 vol.% NH3 + 6 vol.% CO2 + 78 vol.% Ar) with a total flow rate of 50 mL / min was introduced to carry out CO2-NH3 conversion.

[0136] Step S202: Set the fixed bed temperature to 400-600℃, start the reaction, and analyze the composition of the produced gas online using a gas chromatograph.

[0137] The calculation methods for CO2 conversion rate and NH3 conversion rate are as follows:

[0138] X(CO2)=(CO2,in-CO2,out) / CO2,in×100%

[0139] X(NH3)=(NH3,in-NH3,out) / NH3,in×100%

[0140] Here, X(CO2) and X(NH3) represent the conversion rates of CO2 and NH3, respectively; CO2,in, CO2,out, NH3,in and NH3,out represent the molar amounts of CO2 input, CO2 output, NH3 input, and NH3 output, respectively.

[0141] The calculated CO2 conversion rate is 4.1%-48.7%, and the NH3 conversion rate is 1.7%-80.1%.

[0142] Example 11

[0143] 1% Ru / (Mg,Al)O x -1000 Catalytic simultaneous coupling conversion of carbon dioxide and ammonia to methane

[0144] The reaction apparatus, steps, and calculation methods are the same as in Example 8, the only difference being that the catalyst is the 1% Ru / (Mg,Al)O prepared in Example 4. x -1000.

[0145] The calculated CO2 conversion rate is 0.5%-42.4%, and the NH3 conversion rate is 0%-69.2%.

[0146] Figure 11 The graph shows the change in carbon dioxide conversion rate with reaction temperature for the simultaneous carbon dioxide-ammonia coupling conversion in Examples 10 and 11.

[0147] Figure 12The graph shows the change in ammonia conversion rate with reaction temperature for the simultaneous carbon dioxide-ammonia coupling conversion in Examples 10 and 11.

[0148] according to Figure 11 and Figure 12 It can be seen that CO2 and NH3 still maintain a high conversion rate during the catalytic simultaneous coupling conversion reaction of carbon dioxide and ammonia.

[0149] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for the simultaneous coupled conversion of ammonia and carbon dioxide, comprising: Under the action of a catalyst, the reaction gas containing ammonia and carbon dioxide simultaneously undergoes the reaction of ammonia decomposition to produce hydrogen and carbon dioxide to produce methane at 400~600℃, so as to produce methane. The catalyst mentioned above is a ruthenium-based nanocluster catalyst; The preparation method of the ruthenium-based nanocluster catalyst includes: Magnesium-aluminum hydrotalcite was prepared using a coprecipitation method; After drying and sieving, the magnesium-aluminum hydrotalcite is subjected to a first calcination at 800~1200℃ to obtain a magnesium-aluminum composite oxide carrier, which includes magnesium oxide and spinel-structured magnesium aluminate. The magnesium-aluminum composite oxide support was impregnated in a ruthenium salt solution using an equal-volume impregnation method, dried, and then calcined a second time at 300-600°C to obtain a ruthenium-based nanocluster catalyst.

2. The method according to claim 1, wherein, The preparation method of the magnesium-aluminum hydrotalcite includes: Magnesium and aluminum salts are dissolved in water to obtain a salt solution; A precipitant is added to the salt solution, and the pH value is adjusted to 8-12 to obtain a precipitate solution. The precipitate solution was stirred and aged under heating conditions, and then the aged precipitate was dried to obtain magnesium-aluminum hydrotalcite.

3. The method according to claim 2, wherein, The magnesium salt is selected from at least one of magnesium nitrates and magnesium chlorides; The aluminum salt is selected from at least one of aluminum nitrates and aluminum chlorides; The molar ratio of the magnesium salt to the aluminum salt is (1.5~3):1; The precipitant is at least one of ammonia water, sodium hydroxide, and sodium carbonate solution; The concentration of the precipitant is 0~3 mol / L, and the concentration of the precipitant is not 0 mol / L.

4. The method according to claim 1, wherein, The heating program for the first calcination is to raise the temperature to 800-1200℃ at a rate of 5-30℃ / min, and then hold it at 800-1200℃ for 2-5 hours.

5. The method according to claim 1, wherein, The ruthenium salt is selected from at least one of ruthenium nitrate and ruthenium chloride.

6. The method according to claim 1, wherein, The second calcination heating program is to raise the temperature to 300-600℃ at a rate of 5-30℃ / min, and then hold it at 300-600℃ for 2-5 hours.

7. The method according to claim 1, wherein, Under the action of a catalyst, the reaction gas containing ammonia and carbon dioxide simultaneously undergoes the decomposition of ammonia to produce hydrogen and the production of methane from carbon dioxide at 400~600℃, including the following reactions: The reaction gas containing ammonia and carbon dioxide is introduced into a fixed-bed reactor containing the catalyst; The temperature of the reactor is controlled at 400~600℃, so that the reaction gas simultaneously undergoes the reaction of ammonia decomposition to produce hydrogen and carbon dioxide to produce methane.

8. The method according to claim 7, wherein, The volume ratio of ammonia to carbon dioxide is (8~10):(2~5).

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