High-activity carbon-deposition-resistant methane / carbon dioxide reforming conversion foam catalyst as well as preparation method and application thereof

Abstract

The invention discloses a high-activity carbon deposition-resistant methane / carbon dioxide reforming conversion foam catalyst and a preparation method and application thereof, the foam catalyst comprises a catalyst Ni / MnMgAlOx and a substrate SiC ceramic-based foam, and the catalyst Ni / MnMgAlOx is dispersed and coated on the surface of the SiC ceramic-based foam. The prepared foam catalyst can adapt to a concentrating solar system with non-uniform Gaussian distribution, and can be used for converting methane / carbon dioxide into high-value fuel directly driven by solar energy. The foam catalyst combines high catalytic activity of a Ni / MnMgAlOx catalyst and high thermal conductivity and high mechanical strength of porous foam, has high efficiency and high stability in a photo-thermal coupling catalytic carbon dioxide reforming reaction, can realize a stable and efficient fuel preparation process in a photo-thermal reactor by continuously introducing gaseous reactants, and has a wide application prospect. Meanwhile, the problems of serious carbon deposition and poor stability of a traditional catalyst are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar fuels, and particularly relates to a highly active carbon-resistant methane / carbon dioxide reforming and conversion foam catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of the global economy, the problems of energy shortage and greenhouse gas emissions have become increasingly severe, and have become two core challenges faced by human society. On the one hand, the over-reliance on traditional fossil fuels has led to a tight energy supply and an increased risk of energy crisis; on the other hand, the large-scale use of fossil fuels has caused a sharp increase in greenhouse gas emissions. Since the Industrial Revolution, the concentration of carbon dioxide in the atmosphere has risen from about 280 ppm to more than 420 ppm, and the concentration of methane has also increased significantly, resulting in intensified global climate change, frequent extreme weather, and posing a serious threat to the ecosystem and human survival. Therefore, the development of clean and efficient energy utilization technologies has become an urgent need for global sustainable development. The methane / carbon dioxide reforming technology has received extensive attention because it can convert two greenhouse gases into high-value syngas (H2 / CO). However, this technology needs to achieve the molecular activation of methane and carbon dioxide in a high-temperature environment above 600 °C. Traditional thermal catalysis relies on fossil fuel combustion for heating, resulting in high energy consumption and secondary carbon emissions, which seriously restricts its sustainable development. The solar-driven methane / carbon dioxide reforming technology provides an innovative path to solve the above contradictions. By directly converting solar radiation energy into the heat energy required for the reaction through a concentrating system, it can completely get rid of the dependence on fossil fuels and avoid greenhouse gas emissions from the source. At the same time, the photothermal catalytic system can achieve the efficient storage and utilization of solar energy, providing a feasible way to promote energy transformation and achieve sustainable development.

[0003] However, this technology still faces core challenges: nickel-based catalysts are prone to sintering and carbon deposition at high temperatures, resulting in a decrease in activity; the photo-fuel conversion efficiency of existing catalysts is mostly lower than 35%, which is difficult to meet the actual application requirements; and the stability is insufficient. Even under optimized conditions (such as Co / Mg-CoAl2O4 catalysts), the durability test usually does not exceed 60 hours. Existing studies have improved the performance through strategies such as alloying, doping, and support optimization, such as Ni-Co alloy nanoparticles (photo-fuel conversion efficiency of 29.7%) and Ni / MgAl2O4-SiO2 catalysts (photo-fuel conversion efficiency of 35.7%), but there are still problems such as high cost, complex manufacturing process, and difficulty in balancing activity and stability.

[0004] Due to its unique structural characteristics, the porous foam reactor has attracted much attention in the field of solar-driven thermochemical reactions. It has high thermal conduction efficiency, good mechanical strength, and excellent gas permeability, which can effectively solve the problems faced by traditional reactors, such as excessive gas pressure drop, blockage, and large temperature gradient in the catalytic bed, and become a potential solution to improve the performance of the reaction system. However, at present, such reactors still face many challenges in practical applications, such as severe catalyst carbon deposition affecting activity and stability, and uneven temperature distribution leading to large differences in local reaction rates, which seriously restrict their popularization and development in large-scale industrial applications. Summary of the Invention

[0005] Object of the Invention: Aiming at the problems existing in the prior art, the present invention proposes an innovative catalyst system based on a porous foam material carrier. Through the design of the Ni / MnMgAlOx active component and the innovation of the SiC foam carrier, the present invention realizes the synergistic improvement of activity, stability, and photothermal efficiency, providing a new solution for the large-scale conversion of greenhouse gases driven by solar energy.

[0006] The present invention also provides a preparation method and application of the high-activity carbon deposition-resistant methane / carbon dioxide reforming and conversion foam catalyst.

[0007] Technical Solution: To achieve the above object, the present invention provides a high-activity carbon deposition-resistant methane / carbon dioxide reforming and conversion foam catalyst, which comprises a catalyst Ni / MnMgAlO x and a substrate SiC ceramic-based foam, and the catalyst Ni / MnMgAlO x is dispersedly coated on the surface of the SiC ceramic-based foam.

[0008] Among them, the foam catalyst is synthesized by a co-precipitation method to obtain a Ni / MnMgAlO x catalyst with MnMgAlO x as the carrier and nickel as the active metal component. An organic gel is used to dispersedly coat the catalyst on the SiC ceramic-based foam, and after calcination and reduction, a Ni / MnMgAlO x @SiC foam catalyst is obtained.

[0009] The preparation method of the high-activity carbon deposition-resistant methane / carbon dioxide reforming and conversion foam catalyst of the present invention comprises the following steps:

[0010] (1) Dissolve nickel nitrate hexahydrate, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and manganese nitrate tetrahydrate in deionized water, and stir at room temperature to form a nitrate solution;

[0011] (2) Mix the nitrate solution and the alkaline solution to form a precipitate, wash and dry the precipitate to obtain a Ni / MnMgAlOx catalyst;

[0012] (3) Add the obtained Ni / MnMgAlO x catalyst and polyvinyl butyral into absolute ethanol, heat and stir to form a gel, coat it on the surface of SiC ceramic foam, and dry to obtain a foam catalyst precursor;

[0013] (4) Heat the obtained foam catalyst precursor in air by calcination, and then place it in an atmosphere of H2 and N2 to increase the temperature for reduction, and cool it to room temperature to obtain Ni / MnMgAlO x @SiC foam catalyst.

[0014] Among them, in step (1), the molar ratio of nickel, magnesium, and aluminum is 9:71:20:(1 - 9).

[0015] Among them, catalysts with different manganese doping ratios are synthesized by adding manganese (Mn), and their molar ratios are Ni:Mn = 1:0, 1:0.33, 1:0.66, 1:1 respectively.

[0016] Preferably, when the manganese doping ratio in the nitrate solution is Ni:Mn = 1:0.33, the best photothermal catalytic efficiency and stability are achieved.

[0017] Among them, in step (2), the alkaline solution is formed by dissolving sodium hydroxide and anhydrous sodium carbonate in deionized water at a molar ratio of 1:1 and stirring at room temperature.

[0018] Preferably, the diameter and height of the SiC ceramic-based foam used in step (3) are 30 mm, and the specification is 40 ppi.

[0019] Among them, in step (4), the foam catalyst precursor is heated in air at a heating rate of 5 - 15 °C / min to 700 - 900 °C for calcination for 3 - 5 hours; then it is heated in a tubular furnace with an atmosphere of 5 - 10% H2 and 90 - 95% N2 at a heating rate of 5 - 15 °C / min to 700 - 900 °C for reduction for 2 - 3 hours.

[0020] Preferably, the foam catalyst precursor is heated in air at a heating rate of 10 °C / min to 800 °C for calcination for 4 hours; then it is heated in a tubular furnace with an atmosphere of 10% H2 and 90% N2 at a heating rate of 10 °C / min to 800 °C for reduction for 2 hours.

[0021] Preferably, the preparation method includes the following steps:

[0022] (1) Dissolve nickel nitrate hexahydrate, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and manganese nitrate tetrahydrate in deionized water, and stir magnetically at room temperature for 30 min to form a nitrate solution;

[0023] (2) Dissolve sodium hydroxide and anhydrous sodium carbonate in deionized water, and magnetically stir for 30 min at room temperature to form an alkaline solution;

[0024] (3) Dropwise add the stirred solutions in (1) and (2) into magnetically stirred deionized water for precipitation, maintaining the pH = 10 ± 0.1 during the process. After the addition is complete, let it stand for precipitation;

[0025] (4) Centrifuge and wash the precipitate obtained in (3) twice with water and ethanol at 6000 r / min;

[0026] (5) Dry the precipitate obtained in (4) overnight at 80 °C and then grind it to obtain the Ni / MnMgAlO x catalyst;

[0027] (6) Add the Ni / MnMgAlO x catalyst obtained in (5) and a certain proportion of polyvinyl butyral into absolute ethanol, heat and magnetically stir at 100 °C for 1 hour, make a gel and coat it on the surface of SiC foam, and dry it overnight at 80 °C to obtain the foam catalyst precursor;

[0028] (7) Heat the foam catalyst precursor obtained in (6) in air at a heating rate of 10 °C / min to 800 °C and calcine for 4 hours, then heat it in a tubular furnace with a 10% H2 and 90% N2 atmosphere at a heating rate of 10 °C / min to 800 °C, reduce it for 2 hours, and cool it to room temperature with the furnace to obtain the Ni / MnMgAlO x @SiC foam catalyst.

[0029] Application of the highly active carbon deposition-resistant methane / carbon dioxide reforming conversion foam catalyst described in the present invention in catalytically converting methane / carbon dioxide into fuel directly driven by solar energy.

[0030] Among them, the process of the application is as follows:

[0031] (1) Place the Ni / MnMgAlO x @SiC foam catalyst in a reactor;

[0032] (2) Continuously transport a mixed gas of methane, carbon dioxide, and nitrogen in the pipeline of the reactor to purge the miscellaneous gas in the pipeline, and continuously introduce the mixed gas of methane, carbon dioxide, and nitrogen;

[0033] (3) Generate a Gaussian distribution beam through solar energy or photothermal energy through a concentrating system, and irradiate it on the surface of the Ni / MnMgAlO x @SiC foam catalyst;

[0034] (4) Ni / MnMgAlO x@The SiC foam catalyst absorbs light energy and converts it into heat, rapidly raising the temperature to reach the reaction temperature required for solar or photothermal methane / carbon dioxide reforming reactions to convert into fuels.

[0035] Among them, the catalyst of the present invention can be carried out in a methane / carbon dioxide reforming conversion reactor directly driven by simulated solar energy at the hundred-watt level.

[0036] Among them, in step (2), the volume ratio of methane to carbon dioxide in the mixed gas is 1:1 to 1:1.5, the proportion of nitrogen in the total gas is 10% to 20%, and the total flow rate of the mixed gas is 500 to 2000 ml / min.

[0037] Among them, in step (3), a solar simulator powered by a xenon lamp is used as the only energy input device, and no other heating devices are required; among them, the diameter of the focused illumination spot is 30 mm, and the received power on the surface of the foam catalyst is 100 to 150 W.

[0038] Preferably, the received power on the surface of the foam catalyst is 145 W.

[0039] The foam catalyst prepared by the present invention has high activity and carbon deposition resistance characteristics and is suitable for methane / carbon dioxide reforming conversion reactions. The foam catalyst in the present invention can adapt to a non-uniform Gaussian distribution of concentrating solar energy systems and can be used for directly driving solar energy to convert methane / carbon dioxide into high-value fuels. The foam catalyst of the present invention combines the high catalytic activity of the Ni / MnMgAlO x catalyst and the high thermal conductivity and high mechanical strength of the porous foam, and has high efficiency and strong stability in the photothermal coupling catalytic carbon dioxide reforming reaction. Ni / MnMgAlO x The excellent performance of the catalyst is attributed to the decrease in the particle size of Ni particles and the increase in the content of oxygen vacancies caused by MnO x doping. While improving the catalytic activity, it helps the conversion and elimination of carbon species during the reaction process, effectively alleviates the carbon deposition problem on the catalyst surface, and significantly improves the durability and stability of the catalyst.

[0040] The foam catalyst prepared by the present invention shows excellent efficiency and stability in the photothermal coupling catalytic methane / carbon dioxide reforming reaction by loading the high catalytic activity Ni / MnMgAlO x catalyst on a porous foam carrier with high thermal conductivity and high mechanical strength. Among them, MnO xThe doping significantly reduces the particle size of the Ni active component and increases the content of oxygen vacancies in the catalyst, which not only improves the catalytic activity, but also promotes the conversion and elimination of carbon species during the reaction, effectively inhibits the carbon deposition problem on the catalyst surface, and thus significantly improves the durability and stability of the catalyst. In addition, the high thermal conductivity and mechanical strength of the porous foam support further improve the temperature distribution uniformity of the reactor and enhance the long-term operation stability of the system.

[0041] In the present invention, by coating the Ni / MnMgAlOx catalyst on the surface of the porous foam material support, the MnOx doping reduces the Ni particle size from 22.95 nm to 7.48 nm, increases the specific surface area (BET 164.17 cm 2 / g), and significantly improves the activity; the regulation of oxygen vacancies (O V ) (the proportion of O V increases from 27.4% to 36.8%) promotes the oxidation of carbon species, and the carbon deposition is reduced to 4.26 mg c g cat -1 h -1 ; the high thermal conductivity (10 W / (m·K)) of the SiC foam support evenly disperses heat, adapts to the Gaussian distribution concentrating solar field, and the light-fuel conversion efficiency reaches 40.46%; the synergistic effect of MnOx and the support fixes the Ni particles through strong metal-support interaction (SMSI) and inhibits sintering; the high mechanical strength (compressive strength > 10 MPa) of the SiC foam resists the carbon deposition stress, and the stability exceeds 86 hours.

[0042] In the present invention, the MnOx doping significantly reduces the particle size of the Ni active component, inhibits the sintering phenomenon at high temperatures while improving the catalytic activity. It increases the content of defective oxygen in the catalyst (the proportion of OV increases from 27.40% to 36.82%), promotes the conversion and elimination of carbon species during the reaction, and reduces the carbon deposition formation rate. By regulating the oxygen vacancy content, the redox ability of the catalyst is enhanced, further enhancing the catalytic activity.

[0043] The preparation process of the present invention is simple: the Ni / MnMgAlOx catalyst is loaded on the SiC foam support by the impregnation coating method, and the preparation process is simple and easy for large-scale production. It has high cost-effectiveness: by using MnOx doping and SiC foam support, the amount of precious metal used is reduced, while the durability of the catalyst is improved and the operation cost is reduced.

[0044] The present invention has high photo-thermal coupling catalytic efficiency: in a concentrated solar energy system, the light-fuel efficiency reaches 40.46%, significantly higher than that of traditional catalytic systems. It has strong adaptability: it can adapt to a concentrated solar energy system with a non-uniform Gaussian distribution, solving the problem of uneven temperature distribution. It has the potential for large-scale application: the present invention provides a practical solution for the large-scale application of methane / carbon dioxide reforming and conversion, with broad market prospects.

[0045] In the present invention, through the doping of MnOx, the particle size of the Ni active component is significantly reduced (from 22.95 nm to 7.48 nm), the specific surface area of the particles is significantly increased, exposing more active sites, thereby enhancing the catalytic activity. At the same time, through the doping of MnOx, the oxygen vacancy content in the catalyst is increased, promoting the conversion and elimination of carbon species, and effectively suppressing the carbon deposition problem. The doping of MnOx also optimizes the reduction performance of the catalyst, enabling the reduction of NiO and MnOx at a lower temperature (the H2-TPR results show that the α peak and β peak shift towards lower temperatures). A unique flower-like matrix structure (MnMgAlOx mixed oxide) is formed inside the catalyst of the present invention, significantly increasing the specific surface area of the catalyst (the BET surface area increases from 149.72 cm 2 / g to 164.17 cm 2 / g), providing more contact interfaces for the reactants. The flower-like structure also promotes the uniform dispersion of the Ni active component, effectively suppressing the agglomeration and sintering of the active centers.

[0046] The high thermal conductivity of the SiC foam used in the present invention improves the problem of uneven temperature distribution in the concentrated solar energy system and inhibits the formation of carbon deposition. The high mechanical strength of the SiC foam can resist the stress generated by carbon deposition, avoid structural damage, and further improve the long-term operation stability of the system.

[0047] The present invention innovatively combines a highly efficient catalyst (Ni / MnMgAlOx) with a porous foam carrier (SiC ceramic-based foam) with high thermal conductivity and high mechanical strength, and optimizes the microstructure and performance of the catalyst through the doping of MnOx, solving the problems of low activity, easy carbon deposition, and poor stability of traditional catalysts in the methane / carbon dioxide reforming reaction. A single highly efficient catalyst (Ni / MnMgAlOx) cannot be used in the system of the present invention, and a single SiC ceramic-based foam does not have reaction characteristics. In addition, the present invention first proposes to apply a foam catalyst to a concentrated solar energy system with a non-uniform Gaussian distribution, realizing the direct conversion of solar energy to methane / carbon dioxide into high-value fuels, providing a new way for the efficient utilization of renewable energy.

[0048] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0049] The catalyst prepared by the present invention uses MnMgAlO x flower-like mixed oxide as the support structure, realizing the uniform distribution of Ni active component inside the catalyst. The introduction of MnO x significantly reduces the particle size of the Ni active component, effectively inhibits the sintering phenomenon at high temperatures, and at the same time reduces the formation rate of catalyst carbon deposition by increasing the content of defective oxygen in the catalyst, thereby significantly improving the stability and durability of the catalyst. Using SiC ceramic-based foam as the catalyst carrier, its high thermal conductivity and high mechanical strength effectively improve the problem of uneven temperature distribution caused by unilateral heating and uneven surface radiation in the concentrating solar energy system, and inhibit the formation of carbon deposition. In addition, the high mechanical strength of the SiC foam can resist the stress generated by carbon deposition and avoid structural damage, further improving the operating stability of the system.

[0050] The present invention uses MnOx doping and SiC foam carrier, reducing the amount of noble metal used, while improving the durability of the catalyst and reducing the operating cost. The preparation process of the present invention is simple. By loading the highly catalytically active Ni / MnMgAlOx catalyst on a porous foam carrier with high thermal conductivity and high mechanical strength, the efficient combination of the catalyst and the foam is achieved. The catalyst prepared by the present invention is not only suitable for laboratory research, but also provides a feasible way for the large-scale application of methane / carbon dioxide reforming conversion. Description of the Drawings

[0051] Figure 1 is a schematic diagram of a photothermal-driven methane / carbon dioxide reforming reactor;

[0052] Figure 2 is the TEM electron micrograph of the photothermal-driven methane / carbon dioxide reforming catalysts Ni / MnMgAlO x 、Ni / MnMgAlO x ;

[0053] Figure 3 is the XRD pattern of the photothermal-driven methane / carbon dioxide reforming catalyst;

[0054] Figure 4 is the (a) BET specific surface area, (b) H2-TPR pattern, (c) XPS analysis O1s spectrum, (d) CH4-TPMD pattern of the photothermal-driven methane / carbon dioxide reforming catalyst;

[0055] Figure 5 is the comparison diagram of the reaction gas conversion rate and efficiency of the photothermal-driven methane / carbon dioxide reforming foam catalyst;

[0056] Figure 6 is the comparison diagram of the stability of the photothermal-driven methane / carbon dioxide reforming foam catalyst;

[0057] Figure 7 It is the thermogravimetric analysis diagram after the reaction of the photocatalytically driven methane / carbon dioxide reforming foam catalyst. Specific embodiments

[0058] The present invention will be further described below in conjunction with embodiments and the accompanying drawings.

[0059] The materials, reagents, etc. used in the following embodiments can be obtained from commercial sources without special instructions. The experimental methods without specific conditions in the embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0060] In the embodiments of the present invention, the SiC foam ceramic material used is purchased from Suzhou Christie Foam Metal Co., Ltd., and its specifications are a diameter of 30 mm, a height of 30 mm, and a pore density of 40 ppi.

[0061] Example 1

[0062] A preparation method of a highly active carbon deposition-resistant methane / carbon dioxide reforming conversion foam catalyst is specifically prepared by the following method:

[0063] (1) Dissolve 0.009 mol of nickel nitrate hexahydrate, 0.071 mol of magnesium nitrate hexahydrate, and 0.02 mol of aluminum nitrate nonahydrate in 300 ml of deionized water, and stir at room temperature for 30 min to form a nitrate solution;

[0064] (2) Dissolve 0.1 mol of sodium hydroxide and 0.1 mol of anhydrous sodium carbonate in 200 ml of deionized water, and stir at room temperature for 30 min to form an alkaline solution;

[0065] (3) Dropwise add the stirred solutions in steps (1) and (2) into the stirred deionized water for precipitation, and maintain the pH = 10 ± 0.1 during the process. After dropping, let it stand for precipitation;

[0066] (4) Centrifuge and wash the precipitate obtained in step (3) twice each with water and ethanol at 6000 r / min;

[0067] (5) Dry the precipitate obtained in step (4) overnight at 80 °C and then grind it to obtain Ni / MgAlO x catalyst;

[0068] (6) Take 1 g of Ni / MgAlO obtained in step (5) xThe catalyst and 2 g of polyvinyl butyral (PVB, Polyvinyl Butyral, M.W. 70,000 - 100,000 g / mol) were added to 15 ml of absolute ethanol, and heated and stirred at 100 °C for 1 hour to obtain a gel. The gel was repeatedly impregnated and coated on the surface of the SiC ceramic foam until all the gel was loaded, ensuring that the entire surface of the foam was coated with the gel. After drying overnight at 80 °C, a foam catalyst precursor was obtained;

[0069] (7) The foam catalyst precursor obtained in step (6) was heated in air at a heating rate of 10 °C / min to 800 °C and calcined for 4 hours, then heated in a tubular furnace with a 10% H2, 90% N2 atmosphere at a heating rate of 10 °C / min to 800 °C, reduced for 2 hours, and cooled to room temperature with the furnace to obtain Ni / MgAlO x @SiC foam catalyst.

[0070] Example 2

[0071] A preparation method of a highly active and carbon deposition-resistant methane / carbon dioxide reforming and conversion foam catalyst is specifically prepared by the following method:

[0072] (1) 0.009 mol of nickel nitrate hexahydrate, 0.071 mol of magnesium nitrate hexahydrate, and 0.02 mol of aluminum nitrate nonahydrate were dissolved in 300 ml of deionized water, and 0.003 mol, 0.006 mol, and 0.009 mol of manganese nitrate tetrahydrate were respectively added, and magnetically stirred at room temperature for 30 min to form a nitrate solution;

[0073] (2) 0.1 mol of sodium hydroxide and 0.1 mol of anhydrous sodium carbonate were dissolved in 200 ml of deionized water and stirred at room temperature for 30 min to form an alkaline solution;

[0074] (3) The stirred solutions in steps (1) and (2) were added dropwise to the stirred deionized water for precipitation, while maintaining pH = 10 ± 0.1 during the process. After the addition was completed, the mixture was allowed to stand for precipitation;

[0075] (4) The precipitate obtained after standing in step (3) was centrifuged and washed twice with water and ethanol at 6000 r / min;

[0076] (5) The precipitate obtained in step (4) was dried overnight at 80 °C and then ground to obtain Ni / Mn x MgAlO x catalyst (x = 0.33, 0.66, 1);

[0077] (6) 1 g of Ni / Mn obtained in step (5) x MgAlO xThe catalyst and 2 g of polyvinyl butyral (PVB, Polyvinyl Butyral, M.W. 70,000 - 100,000 g / mol) were added to 15 ml of absolute ethanol, and heated with magnetic stirring at 100 °C for 1 hour to obtain a gel. The gel was repeatedly impregnated and coated on the surface of the SiC ceramic foam until all the gel was loaded, ensuring that the entire surface of the foam was coated with the gel. It was dried overnight at 80 °C to obtain the foam catalyst precursor;

[0078] (7) The foam catalyst precursor obtained in step (6) was heated in air at a heating rate of 10 °C / min to 800 °C and calcined for 4 hours, then heated in a tubular furnace with a 10% H2 and 90% N2 atmosphere at a heating rate of 10 °C / min to 800 °C and reduced for 2 hours, and cooled to room temperature with the furnace to obtain Ni / Mn x MgAlO x @SiC foam catalyst.

[0079] Example 3

[0080] The activity and stability of the foam catalyst for photo-thermally driven carbon dioxide reforming to fuel in Example 1 were tested.

[0081] The multi-watt photo-thermal catalytic reaction system used in this example is as Figure 1 shown, mainly composed of a solar simulator, a photo-thermal reactor, a heat exchanger, a gas chromatographic analysis device, and a gas supply control system. The solar simulator provides light through a xenon lamp, accurately simulating the Gaussian distribution characteristics of a concentrating solar energy device. A thermal power sensor (Ophir 50(150)A-BB-26) was used to measure the radiation power. The photo-thermal reactor uses a high-temperature-resistant corundum crucible, and the Ni / Mn x MgAlO x @SiC foam catalyst is placed inside to receive simulated solar radiation. Before the reaction gas enters the reactor, it passes through a shell-and-tube heat exchanger, enabling the reaction system to more effectively utilize waste heat during the catalytic reaction process and improving the overall energy conversion efficiency. The gas supply control system ensures that the mixed gas flows steadily into the photo-thermal reactor at a constant flow rate through a mass flow controller. The gas chromatographic analysis device is used to efficiently separate and detect various gas components during the reaction process, including the consumption of reaction raw materials and the production amount of target products, and gas samples are collected every 18 min.

[0082] The specific test method is as follows:

[0083] (1) Turn on the solar simulator, measure the radiation power using a thermal power sensor, the measured spot size is 30 mm, the incident radiation is set to 145 W, and then turn off the solar simulator;

[0084] (2) The Ni / MgAlOx The SiC foam catalyst is placed in a high-temperature-resistant corundum crucible in the reactor;

[0085] (3) Continuously transport a mixed gas of methane, carbon dioxide, and nitrogen in the pipeline of the reactor to purge the air in the pipeline;

[0086] (4) The volume ratio of methane, carbon dioxide, and nitrogen introduced in front of the reaction tube is 38.8% / 42.5% / 18.7%, and the total flow rate of the mixed gas is 1000 ml / min; continuously introduce the above gases;

[0087] (5) Turn on the solar light simulator again to simulate sunlight for concentrating irradiation on the surface of the Ni / MgAlO x @SiC foam catalyst;

[0088] (6) The Ni / MgAlO x @SiC foam catalyst absorbs light energy and is converted into heat to rapidly increase the temperature to reach the reaction temperature and maintain it (the temperature reaches 900 °C, measured by a thermocouple), and starts the photo-thermal coupling methane / carbon dioxide reforming reaction;

[0089] (7) Continuously introduce gas for reaction during the reaction process, and perform real-time detection on the outlet gas. Set the program to collect gas once every 18 minutes by gas chromatography, collect 10 mL from the outlet gas each time, and use the external standard method of area for quantitative analysis;

[0090] The components that can be measured by the chromatograph are H2, CH4, N2, CO2, CO. The volume fraction of the outlet gas is obtained by integrating through the external standard method of area. The set range of the column head pressure: 0 - 100 psi; the set accuracy of the column head pressure control: 0.001 psi; the set range of the total flow rate: 0 - 100 mL / min; the set accuracy of the flow rate: 0.001 mL / min

[0091] CH4 and CO2 The conversion rates of are calculated as follows:

[0092]

[0093] In the above formula, F is the flow rate of the gas in the system, mL / min.

[0094] The light - fuel efficiency (η, %) is a key indicator for evaluating the DRM reaction system. The formula is as follows:

[0095]

[0096] In the above formula, r CO and The reaction rates of H2, CO, and CH4 are mol / (m 3 ·s); and are the standard combustion calorific values of H2, CO, and CH4, which are 285.8 kJ / mol, 283 kJ / mol, and 890.3 kJ / mol respectively; P light represents the concentrated solar power irradiated on the catalyst surface, in W.

[0097] (8) Take the catalyst after the reaction for thermogravimetric analysis. During the experiment, set the flow rate of the purge air to 100 ml / min, and place the sample after the experiment in an alumina crucible and heat it to 800 °C at a heating rate of 10 °C / min to record the change in the sample mass;

[0098] Detected by a gas chromatograph and calculated, it can be known that the average CO2 conversion rate of the foam catalyst for photo-thermal coupling methane / carbon dioxide reforming to fuel in Example 1 is 68.78%, the CH4 conversion rate is 79.14%, the photo-fuel efficiency is 33.68%, and it has been stably operated for 23 hours.

[0099] Example 4

[0100] Perform an activity test on the foam catalyst for photo-thermal driven methane / carbon dioxide reforming and conversion prepared in Example 2. The specific test method is the same as that in Example 3 below.

[0101] Detected by a gas chromatograph and calculated, it can be known that the Ni / Mn of the foam catalyst for photo-thermal coupling methane / carbon dioxide reforming to fuel in Example 2 0.33 MgAlO x @SiC foam catalyst has the best performance, with an average CO2 conversion rate of 82.39%, a CH4 conversion rate of 88.12%, a photo-fuel efficiency of 40.46%, and it has been stably operated for 86 hours. With the increase of the MnOx doping amount, the efficiency decreases slightly (Ni / Mn 0.66 MgAlO x @SiC is 39.09%, Ni / Mn1MgAlO x @SiC is 36.87%). As a preference, the best photo-thermal catalytic efficiency and stability are obtained when the manganese doping ratio in the nitrate solution is Ni:Mn = 1:0.33.

[0102] As Figure 5 shown, when the manganese doping ratio is Ni:Mn = 1:0.33, the synthesized Ni / Mn 0.33 MgAlO x @SiC foam catalyst shows significant advantages in terms of the reaction gas conversion rate and photo-fuel conversion efficiency. As Figure 6As shown, in the stability test of a 145W photo-thermal coupling methane / carbon dioxide reforming system without an external heat source, the photo-fuel conversion efficiency of the Ni / Mn 0.33 MgAlO x @SiC foam catalyst is as high as 40.46%, and the stable operation time reaches 86 hours. At the same time, as Figure 7 shown, the thermogravimetric test of the Ni / MnMgAlO x catalyst after the stability test shows that the carbon deposition amount is less, and the mass loss is significantly reduced to 11.1%. The corresponding carbon deposition rate is only 4.26mg c g cat -1 h -1 .

[0103] Example 5

[0104] Take an appropriate amount of the Ni / MgAlO x catalyst or Ni / Mn x MgAlO x catalyst powder on the surface of the foam catalyst prepared in Example 1 or 2 for characterization tests such as transmission electron microscopy (TEM), X-ray diffraction analysis technology (XRD), N2 isothermal physical adsorption and desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), and CH4 temperature-programmed pyrolysis (CH4-TPMD).

[0105] The Ni / MgAlO x catalyst and Ni / Mn x MgAlO x catalyst on the surface of the SiC ceramic foam can be prepared according to the method of removing step (6) in Example 1 or 2.

[0106] As Figure 2 shown, the morphological characteristics of the reduced Ni / MgAlO x (2a) and Ni / Mn 0.33 MgAlO x catalyst were observed by transmission electron microscopy (TEM). Compared with the Ni / MgAlO x catalyst, the average size of Ni particles in the Ni / Mn 0.33 MgAlO x catalyst is significantly reduced, and the distribution is significantly more dispersed. Specifically, the average size of Ni particles in the Ni / MgAlO x catalyst is relatively large, reaching 26.95nm. In contrast, after doping with MnOx, the Ni / Mn 0.33 MgAlO xThe average particle size of Ni in the catalyst decreased significantly to 7.48 nm. This significant change not only greatly increased the exposure of surface atoms of Ni particles, thereby improving the catalytic activity, but also made the smaller particles more evenly dispersed inside the catalyst, effectively preventing the agglomeration and sintering between particles, and further improving the stability of the catalytic reaction.

[0107] Combined with Figure 3 the XRD pattern of the catalyst, Ni / MnMgAlO x The catalyst support is a manganese-magnesium-aluminum mixed layered oxide, indicating that the prepared catalyst is a nickel-based catalyst Ni / MnMgAlO x and is in an amorphous structure.

[0108] As Figure 4 (a) shows, the doping of an appropriate amount of MnOx significantly increased the specific surface area of the catalyst (the BET surface area increased from 149.72 cm 2 / g to 164.17 cm 2 / g), providing more contact interfaces for the reactants. As Figure 4 (b) shows, the doping of MnOx also optimized the reduction performance of the catalyst, enabling the reduction of NiO and MnOx to be achieved at a lower temperature (the H2-TPR results showed that the reduction peak shifted towards the low temperature direction). As Figure 4 (c) shows, the doping of MnOx increased the content of oxygen vacancies (O V ) in the catalyst. Combined with Figure 4 (d) analysis shows that defective oxygen, as the active center of the catalytic reaction, can absorb light energy and promote the dissociation and conversion of CH4 and CO2, while accelerating the gasification process of carbon deposition and effectively inhibiting the formation of carbon deposition.

[0109] Example 6

[0110] This example compares the performance differences between the Ni / Mn x MgAlO x @SiC foam catalyst prepared in Example 2 of the present invention and the catalysts in the prior art, as shown in Table 1 specifically.

[0111] Table 1

[0112]

[0113] [1] X. Liu et al., "Solar-Enhanced CO2 Conversion with CH4 over Synergetic NiCo Alloy Catalysts with Light-to-Fuel Efficiency of 33.8%," SolarRRL, vol. 5, no. 8, 2021, doi: 10.1002 / solr.202100185.

[0114] [2] X. Liu et al., "Efficient solar-driven CO2-to-fuel conversion via Ni / MgAlO@SiO2 nanocomposites at low temperature," Fundamental Research, vol. 4, no. 1, pp. 131-139, 2024, doi: 10.1016 / j.fmre.2022.04.011.

[0115] [3] H. Shi et al., "Ni-phyllosilicate nanotubes coated by CeO2 for ultra-efficiency of 36.9% and near-limit CO2 conversion in solar-driven conversion of CO2-to-fuel," Chemical Engineering Journal, vol. 454, 2023, doi: 10.1016 / j.cej.2022.140063.

[0116] [4] Z. Mu et al., "A highly efficient solar-driven CO2 reforming of methane on Ni / MgAlOx-LDH loaded Ni foam reactors with heat recovery: Experimental measurements and numerical simulations," (in en), Chemical Engineering Journal, vol. 446, p. 137437, 2022-10-15 2022, doi: 10.1016 / j.cej.2022.137437.

[0117] As can be seen from Table 1 above, the present invention optimizes the active sites of the catalyst through MnOx doping and synergistically enhances heat / mass transfer with the SiC foam carrier, being significantly superior to the prior art in terms of high light intensity adaptability, catalytic efficiency and long-term stability, and providing an innovative solution for the large-scale application of solar-driven methane dry reforming technology. At the same time, the present invention is significantly superior to the prior art in terms of initial material cost, preparation energy consumption and long-term maintenance cost through the selection of low-cost materials (MnOx / SiC), process simplification (single impregnation) and long-life design.

Claims

1. A highly active and carbon-deposition-resistant methane / carbon dioxide reforming conversion foam catalyst, characterized in that: The foam catalyst comprises a catalyst Ni / MnMgAlO x and a SiC ceramic-based foam substrate, the catalyst Ni / MnMgAlO x Dispersed and coated on the surface of SiC ceramic-based foam.

2. The highly active carbon deposition-resistant methane / carbon dioxide reforming conversion foam catalyst according to claim 1, characterized in that: The foam catalyst is synthesized by coprecipitation method with MnMgAlO x Ni / MnMgAlO x Catalyst, the catalyst is dispersed and coated on SiC ceramic foam using organic gel, and then calcined and reduced to make Ni / MnMgAlO x @SiC foam catalyst.

3. A method for preparing the highly active and carbon-deposition-resistant methane / carbon dioxide reforming conversion foam catalyst according to claim 1, characterized in that: The steps include: (1) dissolving nickel nitrate hexahydrate, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and manganese nitrate tetrahydrate in deionized water and stirring at room temperature to form a nitrate solution; (2) Mixing the nitrate solution and the alkaline solution to form a precipitate, washing and drying the precipitate to obtain Ni / MnMgAlO x catalyst; (3) The obtained Ni / MnMgAlO x The catalyst and polyvinyl butyral are added into anhydrous ethanol, heated and stirred to form a gel which is coated on the surface of SiC ceramic foam, and dried to obtain a foam catalyst precursor; (4) The obtained foam catalyst precursor is heated and then calcined in air, then placed in a H2 and N2 atmosphere and reduced at a high temperature, and cooled to room temperature to obtain Ni / MnMgAlO x @SiC foam catalyst.

4. The method for preparing the highly active carbon deposition resistant methane / carbon dioxide reforming conversion foam catalyst according to claim 3, characterized in that: The molar ratio of nickel, magnesium, aluminum and manganese in step (1) is preferably 9:71:20:(1-9).

5. The method for preparing the highly active and carbon-deposition-resistant methane / carbon dioxide reforming conversion foam catalyst according to claim 3, characterized in that: The alkaline solution in step (2) is prepared by dissolving sodium hydroxide and anhydrous sodium carbonate in deionized water and stirring at room temperature to form an alkaline solution.

6. The method for preparing the highly active and carbon-deposition-resistant methane / carbon dioxide reforming conversion foam catalyst according to claim 3, characterized in that: In step (4), the foamed catalyst precursor is heated to 700-900°C in air at a heating rate of 5-15°C / min and calcined for 3-5 hours; then heated to 700-900°C in a tubular furnace in a 5-10% H2, 90-95% N2 atmosphere at a heating rate of 5-15°C / min, and reduced for 2-3 hours.

7. Use of the highly active and carbon-deposition-resistant methane / carbon dioxide reforming conversion foam catalyst according to claim 1 in catalyzing solar energy-directly driven methane / carbon dioxide conversion into fuel.

8. The use according to claim 7, characterized in that: The process of the application is: (1) Ni / MnMgAlO x @SiC foam catalyst is placed in the reactor; (2) continuously delivering a mixed gas of methane, carbon dioxide, and nitrogen in the pipeline of the reactor to purge the impurities in the pipeline, and continuously introducing a mixed gas of methane, carbon dioxide, and nitrogen; (3) Solar energy or thermal energy is used to generate a Gaussian distribution beam through a concentrating system and irradiate the Ni / MnMgAlO x @SiC foam catalyst surface; (4)Ni / MnMgAlO x @SiC foam catalyst absorbs light energy and converts it into heat, rapidly heating up to the temperature required for the reaction, and converting it into fuel through solar or photothermal methane / carbon dioxide reforming reaction.

9. The use according to claim 8, characterized in that: In step (2), the volume ratio of methane to carbon dioxide in the mixed gas is 1:1 to 1:1.5, the proportion of nitrogen in the total gas is 10% to 20%, and the total flow rate of the mixed gas is 500 to 2000 ml / min.

10. The use according to claim 8, characterized in that: In step (3), a solar simulator powered by a xenon lamp is used as the only energy input device, and no other heating device is required; wherein the focused illumination spot diameter is 30-40 mm, and the power received by the foam catalyst surface is 100-150 W.

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