A reverse-phase catalyst for dry reforming of methane and its preparation method

Abstract

This invention provides a reversed-phase catalyst for methane dry reforming, belonging to the field of catalytic materials. The reversed-phase catalyst uses a NiZn alloy as a support, on which metal oxides are loaded as active sites at the reversed-phase interface. Based on a 100% molar fraction of all metals in the catalyst, the molar fraction of the metal oxides is 5%-30%; and based on a 100% molar fraction of all metals in the NiZn alloy, the molar fraction of Zn is 10%-75%. This catalyst is constructed via a stepwise precipitation method, which can effectively increase the oxygen vacancy concentration on the catalyst surface, thereby enhancing the catalyst's activation ability for reactants. When applied to methane dry reforming, it exhibits higher activity and long-term stability than traditional supported catalysts at the same reaction temperature, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials, specifically relating to a reverse-phase catalyst for methane dry reforming reaction and its preparation method. Background Technology

[0002] Biogas, a biofuel obtained through the anaerobic digestion of organic waste such as livestock and poultry manure, mainly consists of CH4 and CO2 and occupies a key position in the renewable energy system. As a crucial method for agricultural waste treatment and carbon resource recycling, biogas projects are not only a major pathway for the harmless and resource-based utilization of livestock and poultry waste, but also play an important role in addressing climate change, promoting low-carbon agriculture, and facilitating the construction of new rural areas. Dry methane reforming (DRM) uses the greenhouse gas CH4 as a reducing agent to synergistically convert CO2, avoiding external hydrogen demand while achieving dual carbon emission reduction. The generated syngas (H2 and CO) can be directly coupled with a Fischer-Tropsch synthesis reaction to directionally produce green aviation fuel (SAF), constructing a closed-loop carbon cycle from greenhouse gases to high-value-added fuels. This technological route not only reduces hydrogen resource constraints but also improves economic efficiency through high-value-added products, holding strategic significance for the deep decarbonization of the aviation industry.

[0003] Methane dry reforming requires high temperatures to overcome the inertia of CH4 and CO2 molecules and achieve efficient conversion. However, the harsh reaction conditions pose significant challenges to catalysts: on the one hand, non-precious metal active components, such as nickel (Ni), are prone to migration and aggregation at high temperatures, leading to sintering deactivation. For example, patent CN116351430A discloses a method for preparing a Ni-Ce-based catalyst for methane-carbon dioxide dry reforming. This catalyst aims to enhance the specific surface area and mass transfer efficiency of the support through a two-dimensional nanotube structure, and improve anti-carbon deposition performance by combining the co-catalytic effect of MgO. Although this catalyst exhibits good activity and anti-carbon deposition properties in short-term reactions (e.g., within 5 hours), it still belongs to a traditional supported catalyst system. The structural stability and activity persistence under long-term high-temperature reaction conditions still face challenges, especially in terms of support morphology control and metal dispersion uniformity during industrial scale-up, which require further optimization.

[0004] For example, the invention patent with publication number CN120479441A discloses a high specific surface area Ni-based perovskite catalyst, which adopts a strategy of stabilizing small metal particles to improve the high temperature stability of the catalyst. This scheme disperses Ni nanoparticles through CeAlO3 generated during calcination, which is a normal-phase catalyst structure design strategy, resulting in relatively low catalytic activity.

[0005] On the other hand, carbon deposits generated by side reactions (such as methane cracking and CO disproportionation) can cover active sites or block support pores, causing catalyst deactivation. For example, invention patent CN120590283A discloses the application of a Ni-based reverse-phase catalyst in the catalytic hydrogenation reaction of nitro compounds. This Ni-based catalyst also has reverse-phase interfacial active sites, but because the bulk catalyst phase is large Ni metal, it is prone to over-activation of methane, leading to carbon deposition and deactivation, and is not suitable for dry reforming of methane. Therefore, improving the catalyst's resistance to sintering and carbon deposition while maintaining high activity is the core objective of DRM catalyst design. Appropriate structural design is needed to prevent the migration of Ni metal active sites during the reaction, stabilize the active components, and improve the catalyst's activity and stability. Summary of the Invention

[0006] To address the aforementioned technical problems in the prior art, this invention provides a reverse-phase catalyst for methane dry reforming and its preparation method, specifically a reverse-phase catalyst using NiZn alloy particles as a support and nano-metal oxides as the supported phase. This catalyst, constructed via a stepwise precipitation method, effectively increases the oxygen vacancy concentration on the catalyst surface, thereby enhancing its activation ability for reactants. When applied to methane dry reforming, it exhibits higher activity and long-term stability than traditional supported catalysts at the same reaction temperature, demonstrating promising application prospects.

[0007] The present invention provides a reverse-phase catalyst for dry reforming of methane, using NiZn alloy as a support on which metal oxides are loaded as reverse-phase interfacial active sites. Assuming the molar fraction of all metals in the catalyst is 100%, the molar fraction of metal oxides is 5%-30%; assuming the molar fraction of all metals in the NiZn alloy is 100%, the molar fraction of Zn is 10%-75%.

[0008] This invention uses NiZn alloy as a support, with nano-metal oxides loaded on it as the supporting phase, to construct inverse interfacial active sites. This overturns the traditional definition of the active component / support role, utilizing NiZn alloy as both a support and an electronic aid to regulate the active sites of the metal oxides loaded on it. Specifically: The formation of NiZn alloy optimizes the electronic structure, while the introduction of zinc increases the oxygen vacancies on the catalyst surface, enhancing the adsorption and activation capacity of CH4 and CO2. In the reaction, CH4 can be cracked on the surface of NiZn alloy, while CO2 is activated on the oxygen vacancies at the metal oxide or interface. This spatial proximity and functional division of labor enables the reaction to proceed efficiently. Zn in NiZn alloys promotes the generation of surface-active OH* species, allowing adsorbed carbon species (C*) generated by CH4 cracking to rapidly migrate to the interface between NiZn alloys and metal oxides, react with active oxygen generated by CO2 decomposition to generate CO, thereby timely vaporization to eliminate carbon deposits generated in the reaction and avoid covering active sites and causing deactivation. After Ni and Zn are alloyed, the electronic properties of Ni can be adjusted to suppress its tendency to excessively decompose CH4 and cause carbon deposition, without sacrificing its activation ability for CH4. The unique structural design restricts the migration and agglomeration of Ni particles, while effectively suppressing the accumulation of carbon deposits that lead to deactivation. In summary, the reverse-phase catalyst with NiZn alloy particles as the carrier and nano-metal oxides as the supported phase provided by this invention will not over-activate methane and cause carbon deposition and deactivation, making it perfectly suited for methane dry reforming reactions.

[0009] Preferably, the metal oxide is CeO2, Al2O3, ZrO2, or MgO.

[0010] It is understood that the specific type of nano-metal oxide used as the supporting phase in the reverse-phase supported catalyst described in this invention is not uniquely limited. The core concept of this invention lies in constructing a reverse-phase structure with "NiZn alloy particles as the support and metal oxide as the supporting phase" to regulate the electronic interaction between the active component and the support, thereby inhibiting excessive methane cracking. Based on this concept, those skilled in the art can anticipate that as long as the metal oxide component itself possesses the ability to activate the substrate (CH4 and / or CO2) of methane dry reforming reaction and can form a suitable interface structure with NiZn alloy, the technical effects described in this invention can be achieved. Research has found that oxides such as Al2O3, ZrO2, and MgO are all well-known active components or support materials that can be used in methane dry reforming catalysts. Existing technologies (see Yu Lou et al.'s study on the stability of ZrO2 as a support (Journal of catalysis, 2017, 356: 147-156), Nhiem Pham-Ngoc et al.'s study on the structure of Ni / Al2O3 catalysts (Chemical Engineering Journal, 2024, 494: 153207), and Zhijun Zuo et al.'s study on the application of Ni / MgO in methane dry reforming (ACS Catal. 2018, 8, 9821-9835)) have confirmed that the aforementioned oxides can effectively participate in the adsorption and activation processes of reactants. Therefore, replacing a specific oxide (e.g., CeO2) verified in the embodiments of this invention with functionally equivalent ZrO2, Al2O3, or MgO is merely a conventional equivalent substitution or modification of the technical concept of this invention, and does not depart from the core scope of this invention to achieve reaction performance optimization through structural regulation. These alternatives not listed in detail should all be considered to fall within the protection scope of this invention.

[0011] More preferably, the metal oxide is CeO2.

[0012] The method for preparing the reverse-phase catalyst for dry reforming of methane provided by the present invention includes the following steps: (1) After adding the corresponding nitrates of metallic Ni and metallic Zn to the solvent, a precipitant is added to obtain a precipitate; (2) The precipitate is dispersed in a solvent, metal oxide and precipitant are added, and then calcined and reduced to obtain the reverse catalyst.

[0013] Preferably, the solvent used in steps (1) and (2) is ethanol.

[0014] Preferably, the precipitant in steps (1) and (2) is an oxalic acid ethanol solution; the precipitant is 2-4 times the total molar amount of dissolved metal nitrate, based on the molar amount of oxalic acid.

[0015] Preferably, the calcination in step (2) is carried out in an air atmosphere, the calcination temperature is 400℃-600℃, and the calcination time is 4-6 h.

[0016] Preferably, the reduction in step (2) is carried out in a mixed atmosphere of hydrogen and argon, with the volume fraction of hydrogen being 4%-10% based on the volume of the mixed atmosphere.

[0017] More preferably, the reduction temperature in step (2) is 580℃-620℃ and the reduction time is 4-6 h.

[0018] The present invention also provides the application of the aforementioned reversed-phase catalyst in the dry reforming reaction of methane.

[0019] Preferably, the application process includes: placing the reversed catalyst in a fixed-bed reactor and heating it to a target temperature, then introducing a mixture of methane and carbon dioxide at a certain gas flow rate to carry out a catalytic reaction to obtain hydrogen and carbon monoxide.

[0020] More preferably, the temperature of the catalytic reaction is 450-750℃; the mass hourly space velocity of the catalyst reaction is 10.5-210 L / (g·h).

[0021] Preferably, the target temperature is 450℃-750℃; the gas flow rate is 10.5-210 L / (g·h); and the volume ratio of methane to carbon dioxide is 1:1.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The reversed-phase catalyst disclosed in this patent exhibits high activity and long-term stability in the dry reforming reaction of methane under the same temperature conditions. Under the same temperature conditions, the reversed-phase catalyst has higher activity than the supported catalyst, achieving a methane conversion rate of 51.9% and a CO2 conversion rate of 62.2%, with a product hydrogen-to-carbon ratio of 0.8; under the same temperature conditions, the reversed-phase catalyst can operate stably for more than 100 h.

[0023] (2) The catalyst is simple to synthesize and the resulting catalyst has a stable and reliable structure.

[0024] (3) The reverse catalyst synthesized in this invention has significant advantages in terms of activity, stability and ease of preparation. It will not overactivate methane and cause carbon deposition and deactivation, and can be effectively applied to the dry reforming reaction of methane. Attached Figure Description

[0025] Figure 1Transmission electron microscope (TEM) image of the reversed catalyst prepared in Example 1 of this invention.

[0026] Figure 2 The O1s XPS spectra of the catalysts prepared in Example 1 and Comparative Example 1 of this invention are shown.

[0027] Figure 3 This invention compares the methane conversion rates of Example 1 and Comparative Example 1 in the catalytic dry reforming reaction of methane at 450℃-750℃.

[0028] Figure 4 This is a comparison of the stability of catalytic dry reforming of methane at 550°C between Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] All raw materials are available for purchase on the market.

[0031] The purpose of this invention is to provide a reverse-phase catalyst for methane dry reforming and its preparation method, thereby achieving a highly efficient methane dry reforming reaction. This catalyst can remain stable under long-term reaction conditions and has significantly higher catalytic activity than traditional supported catalysts.

[0032] To make the above-mentioned objectives, features and advantages of the present invention clearer and easier to understand, the following detailed description will be provided in conjunction with specific embodiments.

[0033] Example 1 A reverse-phase catalyst for dry reforming of methane comprises a NiZn alloy support and a nano-metal oxide CeO2 supported thereon. The molar fraction of Ce in the supported phase is 30% based on the total molar fraction of all metals in the catalyst being 100%, and the molar fraction of Zn is 25% based on the total molar fraction of all metals in the NiZn alloy being 100%.

[0034] The above-mentioned reverse-phase catalyst preparation method is as follows: (1) Dissolve 1.1450 g of nickel nitrate hexahydrate and 0.3905 g of zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.9771 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash, dry and grind into powder. (5) The powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 hours. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 hours to finally obtain the reverse catalyst.

[0035] like Figure 1 The image shows a TEM image of the reversed-phase catalyst. The NiZn alloy support and the CeO2 metal oxide particles loaded on it are clearly visible. Further analysis of the O1s XPS spectra of the reversed-phase catalyst reveals O... V The peak representing the attribution of oxygen vacancies, O L The peak representing the assignment of oxygen in the lattice, O V With O L The ratio of peak areas reflects the concentration of oxygen vacancies on the catalyst surface, such as... Figure 2 As shown, O in Example 1 V With O L The peak area ratio is greater than that of Comparative Example 1, proving that the surface oxygen vacancy concentration of Example 1 is relatively higher.

[0036] Application of the reversed-phase catalyst for methane dry reforming: A fixed-bed quartz tube reactor was used to evaluate the catalyst prepared above, with a catalyst loading of 0.05 g. K-type thermocouples were placed in the reactor to measure the temperature of the catalyst bed. The flow rates of methane and carbon dioxide gases were controlled using mass flow meters, and the conversion and selectivity were measured at atmospheric pressure and a mass hourly space velocity (HHSV) of 42 L / (g·h) at 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, and 750℃. Gas products were analyzed online using gas chromatography, and the methane conversion results were obtained as follows: Figure 3 As shown.

[0037] Example 2 The difference between Example 2 and Example 1 is that, based on the molar fraction of all metals in the catalyst being 100%, the molar fraction of the supported phase Ce is 20%; and based on the molar fraction of all metals in the NiZn alloy being 100%, the molar fraction of Zn is 25%.

[0038] The above-mentioned reverse-phase catalyst preparation method is as follows: (1) Dissolve 1.3086 g of nickel nitrate hexahydrate and 0.4463 g of zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.6514 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash and dry, and grind into powder. (5) The solid powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 h. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 h to finally obtain the reverse catalyst.

[0039] The gaseous products were analyzed online using a gas chromatograph, and the reaction results are shown in Table 1.

[0040] Example 3 The difference between Example 3 and Example 1 is that, based on the molar fraction of all metals in the catalyst being 100%, the molar fraction of the supported phase Ce is 15%; and based on the molar fraction of all metals in the NiZn alloy being 100%, the molar fraction of Zn is 25%.

[0041] The above-mentioned reverse-phase catalyst preparation method is as follows: (1) Dissolve 1.3904 g of nickel nitrate hexahydrate and 0.4742 g of zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.4886 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash, dry and grind into powder. (5) The solid powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 h. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 h to finally obtain the reverse catalyst.

[0042] The gaseous products were analyzed online using a gas chromatograph, and the reaction results are shown in Table 1.

[0043] Example 4 The difference between Example 4 and Example 1 is that, based on the molar fraction of all metals in the catalyst being 100%, the molar fraction of the supported phase Ce is 10%; and based on the molar fraction of all metals in the NiZn alloy being 100%, the molar fraction of Zn is 25%.

[0044] The above-mentioned reverse-phase catalyst preparation method is as follows: (1) Dissolve 1.4721 g of nickel nitrate hexahydrate and 0.5021 g of zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.3257 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash, dry and grind into powder. (5) The solid powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 h. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 h to finally obtain the reverse catalyst.

[0045] The gaseous products were analyzed online using a gas chromatograph, and the reaction results are shown in Table 1.

[0046] Example 5 Example 5 differs from Example 1 in that: based on the molar fraction of all metals in the catalyst being 100%, the molar fraction of the supported phase Ce is 5%; based on the molar fraction of all metals in the NiZn alloy being 100%, the molar fraction of Zn is 25%.

[0047] The above-mentioned reverse-phase catalyst preparation method is as follows: (1) Dissolve 1.5539 g of nickel nitrate hexahydrate and 0.5300 g of zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.1629 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash, dry and grind into powder. (5) The solid powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 h. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 h to finally obtain the reverse catalyst.

[0048] The gaseous products were analyzed online using a gas chromatograph, and the reaction results are shown in Table 1.

[0049] Example 6 The difference between Example 6 and Example 1 is that, based on the molar fraction of all metals in the catalyst being 100%, the molar fraction of the supported phase Ce is 30%; and based on the molar fraction of all metals in the NiZn alloy being 100%, the molar fraction of Zn is 20%.

[0050] The above-mentioned reverse-phase catalyst preparation method is as follows: (1) Dissolve 1.2213 g of nickel nitrate hexahydrate and 0.3124 g of zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.9771 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash, dry and grind into powder. (5) The solid powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 h. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 h to finally obtain the reverse catalyst.

[0051] The gaseous products were analyzed online using a gas chromatograph, and the reaction results are shown in Table 1.

[0052] Example 7 The difference between Example 7 and Example 1 is that, based on the molar fraction of all metals in the catalyst being 100%, the molar fraction of the supported phase Ce is 30%; and based on the molar fraction of all metals in the NiZn alloy being 100%, the molar fraction of Zn is 30%.

[0053] The above-mentioned Ni-based reverse-phase catalyst preparation method is as follows: (1) Dissolve 1.0687 g of nickel nitrate hexahydrate and 0.4686 g of zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.9771 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash, dry and grind into powder. (5) The solid powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 h. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 h to finally obtain the reverse catalyst.

[0054] The gaseous products were analyzed online using a gas chromatograph, and the reaction results are shown in Table 1.

[0055] Example 8 The difference between Example 8 and Example 1 is that, based on the molar fraction of all metals in the catalyst being 100%, the molar fraction of the supported phase Ce is 30%; and based on the molar fraction of all metals in the NiZn alloy being 100%, the molar fraction of Zn is 75%.

[0056] The above-mentioned Ni-based reverse-phase catalyst preparation method is as follows: (1) Dissolve 0.3817 g nickel nitrate hexahydrate and 1.1715 g zinc nitrate hexahydrate in ethanol and stir at room temperature and 1000 rpm until completely dissolved; (2) While stirring continuously, add 0.5 M oxalic acid ethanol solution to the solution in step (1). After the addition is complete, centrifuge to obtain the precipitate. (3) Disperse the precipitate obtained by centrifugation in step (2) with ethanol and stir continuously at room temperature and 1000 rpm. (4) Weigh 0.9771 g of cerium nitrate hexahydrate and dissolve it in ethanol. Add it dropwise to the dispersion system in step (3) along with 0.5 M oxalic acid solution. Stir continuously for 3 h at room temperature and 1000 rpm, then centrifuge, wash, dry and grind into powder. (5) The solid powder obtained in step (4) is placed in a tube furnace and calcined at 400°C and 100 mL / min in an air atmosphere for 5 h. After calcination, it is reduced at 600°C and 100 mL / min in a mixture of hydrogen and argon (the volume percentage of hydrogen in the mixture of hydrogen and argon is 4%) for 4 h to finally obtain the reverse catalyst.

[0057] The gaseous products were analyzed online using a gas chromatograph, and the reaction results are shown in Table 1.

[0058] Comparative Example 1 A conventional supported catalyst was prepared by impregnation using nickel nitrate hexahydrate as the nickel source. The method is as follows: (1) Weigh 1.5 g of nano CeO2 into a beaker; (2) Weigh 0.0743 g of nickel nitrate hexahydrate and dissolve it in 0.293 mL of pure water. Add the solution dropwise to the beaker described in (1) and stir evenly. (3) The stirred solid sample was placed in a 60℃ oven and dried for 12 h. After grinding, it was placed in a tube furnace and reduced for 4 h in a hydrogen and argon mixture at 500℃ and 100 mL / min (the volume percentage of hydrogen in the hydrogen and argon mixture was 4%) to finally obtain the supported catalyst.

[0059] A fixed-bed quartz tube reactor was used to evaluate the catalyst prepared above, with a catalyst loading of 0.05 g. K-type thermocouples were placed in the reactor to measure the temperature of the catalyst bed. The flow rates of methane and carbon dioxide gases were controlled using mass flow meters, and the conversion and selectivity were measured at atmospheric pressure and a mass hourly space velocity (HHSV) of 42 L / (g·h) at 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, and 750℃. The gaseous products were analyzed online using gas chromatography, and the methane conversion results are shown below. Figure 3 As shown.

[0060] Table 1. Methane conversion, carbon dioxide conversion, and hydrogen-to-carbon ratio of the catalyst in Examples 1-8 and Comparative Example 1 at 600°C. Compared with Comparative Example 1, Examples 1-8 showed higher methane dry reforming reaction activity, demonstrating the superiority of the designed metal oxide-alloy structure catalyst over the conventional supported catalyst in the methane dry reforming reaction.

[0061] Compared with Examples 2-5, Example 1 showed higher methane dry reforming activity, reflecting the preferred molar fraction of Ce in the catalyst as the supported phase metal is 30% of the total metal.

[0062] As can be seen from Examples 1, 6-8, the percentage of Zn in the total molar number of Ni and Zn in the catalyst NiZn alloy is preferably 25%.

[0063] Combination Figure 4 The stability results show that the reversed catalyst synthesized in this invention exhibits significant advantages in stability, does not over-activate methane and cause carbon deposition and deactivation, and can be effectively applied to methane dry reforming reaction.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A reverse-phase catalyst for dry reforming of methane, characterized in that, Using NiZn alloy as a support, metal oxides are loaded onto it as active sites for the reverse phase interface; Assuming the molar fraction of all metals in the catalyst is 100%, the molar fraction of metal oxides is 5%-30%; assuming the molar fraction of all metals in the NiZn alloy is 100%, the molar fraction of Zn is 10%-75%.

2. The reversed-phase catalyst according to claim 1, characterized in that, The metal oxide is CeO2, Al2O3, ZrO2 or MgO.

3. The method for preparing the reversed-phase catalyst according to claim 1 or 2, characterized in that, Includes the following steps: (1) After adding the corresponding nitrates of metallic Ni and metallic Zn to the solvent, a precipitant is added to obtain a precipitate; (2) The precipitate is dispersed in a solvent, metal oxide and precipitant are added, and then calcined and reduced to obtain the reverse catalyst.

4. The preparation method according to claim 3, characterized in that, The solvent mentioned in steps (1) and (2) is ethanol.

5. The preparation method according to claim 3, characterized in that, The precipitant mentioned in steps (1) and (2) is an oxalic acid ethanol solution; the precipitant is 2-4 times the total molar amount of dissolved metal nitrates, based on the molar amount of oxalic acid.

6. The preparation method according to claim 3, characterized in that, The calcination in step (2) is carried out in an air atmosphere at a temperature of 400℃-600℃ for 4-6 hours.

7. The preparation method according to claim 3, characterized in that, The reduction in step (2) is carried out in a mixed atmosphere of hydrogen and argon, with the volume fraction of hydrogen being 4%-10% based on the volume of the mixed atmosphere.

8. The preparation method according to claim 3, characterized in that, The reduction temperature in step (2) is 580℃-620℃, and the reduction time is 4-6 h.

9. The application of the reversed-phase catalyst according to claim 1 or 2 in the dry reforming reaction of methane.

10. The application according to claim 9, characterized in that, The reversed-phase catalyst according to claim 1 or 2 is placed in a fixed-bed reactor for catalytic reaction; The temperature of the catalytic reaction is 450℃-750℃, and the mass hourly space velocity of the catalyst reaction is 10.5-210 L / (g·h).

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