Nano-island confined catalyst for methane dry reforming and application thereof

Abstract

The application belongs to the technical field of catalysts and methane dry reforming, and particularly relates to a nano-island confined catalyst for methane dry reforming and application thereof. The nano-island confined catalyst prepared by the application is prepared by depositing Pr(OH)3 on a specific carrier molecular sieve Hbeta, and forming Pr6O 11 after air calcination, and then performing Ru 3+ impregnation and reduction by a reducing gas. The method can form the nano-island confined catalyst with small particle size and uniform distribution. When the nano-island confined catalyst is applied to the methane dry reforming reaction, the catalyst has good catalytic activity in a wide temperature range, can be continuously operated for more than 450 hours stably, has excellent sintering resistance and carbon deposition resistance, and the ratio of product H2 / CO is close to 1, so that the catalyst has wide application value in the field of methane dry reforming.

Description

Technical Field

[0001] This invention belongs to the field of catalysts and methane dry reforming technology. More specifically, it relates to a nano-island confined catalyst for methane dry reforming and its applications. Background Technology

[0002] Dry reforming of methane (DRM) is a key reaction that converts methane (CH4) and carbon dioxide (CO2) into syngas (H2 / CO), with an H2 / CO ratio close to 1:1, making it particularly suitable for chemical processes such as Fischer-Tropsch synthesis. This technology not only efficiently utilizes two major greenhouse gases, alleviating environmental pressure, but also has the potential to convert inexpensive natural gas, shale gas, biogas, and industrial waste gases into high-value-added products. Therefore, it is considered one of the important pathways to achieving carbon recycling and sustainable energy development.

[0003] The DRM reaction itself is a strongly endothermic process (ΔH). 298 = +247kJ / mol), requiring high temperatures (typically 700-1000 °C) to achieve industrially acceptable conversion. However, this high-temperature operating environment presents significant engineering challenges, including high energy consumption, stringent requirements on reactor materials, and a sharp increase in the risk of catalyst deactivation. More importantly, the properties of the reactants directly lead to two main causes of catalyst deactivation: one is the deep cracking of CH4—on the catalyst surface, CH4 undergoes not only the desired activation to form CH4, but also... x Besides reacting with surface oxygen or hydroxyl groups, these substances are more prone to deep dissociation at high temperatures and certain metal sites, ultimately leading to carbon deposits. Secondly, there is competition from the reverse water-gas shift reaction; the generated H2 and CO2 may undergo a reverse water-gas shift reaction, consuming H2 and producing H2O, resulting in an H2 / CO ratio deviating from 1:1. To address these issues, Chinese patent application CN116173948A discloses a rare-earth oxide-silica supported noble metal catalyst. The resulting catalyst exhibits strong resistance to sintering and carbon deposition, maintaining high stability at high temperatures and high space velocities. However, the existing technology still has the following shortcomings: (1) It does not provide the specific ratio of H2 / CO in the reaction products, so it is impossible to determine whether the synthesis gas is really close to the ideal ratio of 1:1; (2) It only tested the performance at 800℃, and did not evaluate its conversion rate and selectivity in a lower temperature range (such as 600-700℃), while low temperature operation is of great value for reducing energy consumption, extending catalyst life and broadening the adaptability of raw materials; (3) The longest stability test is only 350 hours, which is not enough to fully meet the requirements of industrial applications for long-term stability, and the stability needs to be further improved.

[0004] Therefore, how to achieve good conversion rate, H2 / CO ratio close to 1:1, stable operation for a longer time (>350h) and strong resistance to carbon deposition in a wide temperature range (especially including the lower temperature range of 600-700°C) remains a technical challenge that needs to be solved in the field of DRM catalysts. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of existing DRM catalysts, which still do not meet the requirements of industrial application in terms of catalytic activity, anti-coking ability and overall stability. The present invention provides a nano-island confined catalyst that has good catalytic activity (>55%) at low temperature conditions (e.g., 600℃) and maintains high stability at longer reaction times (up to 470h).

[0006] The purpose of this invention is to provide applications of the nanoisland confined catalyst.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution: This invention protects a nano-island confined catalyst, which is prepared by the following steps: (1) After mixing Hβ molecular sieve and praseodymium salt in water, ammonia water is added to adjust the pH to an alkaline environment. The mixture is filtered, and the precipitate is washed and dried to obtain the catalyst precursor. (2) The catalyst precursor obtained in step (1) was calcined at 700~900℃ in an air atmosphere until the reaction was complete, yielding Pr6O. 11 -Hβ; (3) Add the Pr6O obtained in step (2) 11 Water and ruthenium salt are added to -Hβ, mixed well, and dried to obtain Ru / Pr6O. 11 -Hβ precursor; (4) Under a reducing gas atmosphere, the Ru / Pr6O obtained in step (3) is subjected to... 11 The -Hβ precursor was calcined at 500–700 °C, and the reaction was completed to obtain the nano-island confined catalyst Ru / Pr6O. 11 -Hβ; In step (1), the mixing ratio of praseodymium in the Hβ molecular sieve and praseodymium salt is 1g:(0.8~1.2)mmol; In step (3), the Pr6O 11 The mixing ratio of ruthenium in Hβ and ruthenium salt is 1 g: (0.04~0.08) mmol.

[0008] The nano-island confined catalyst prepared in this invention is formed by precipitating Pr(OH)3 on a Si-source molecular sieve Hβ and then calcining it in air to form Pr6O. 11 -Hβ, to perform Ru 3+The process involves impregnation followed by reduction with reducing gas to obtain the final product. During the impregnation process, molecular sieves Hβ and Pr6O... 11 Ru occurs to varying degrees on the islands of Namibia. 3+ Electrostatic adsorption, followed by reduction with reducing gas, Hβ support and Pr6O 11 Small, uniformly distributed Ru nanoparticles are formed on the nanoislands, providing numerous active sites for methane dry reforming. When applied to methane dry reforming, this nanoisland-confined catalyst exhibits good catalytic activity over a wide temperature range, can operate stably and continuously for over 450 hours, demonstrates excellent resistance to sintering and carbon deposition, and achieves a product H2 / CO ratio close to 1.

[0009] Preferably, in step (1), the mixing ratio of praseodymium in the Hβ molecular sieve and praseodymium salt is 1g:(0.9~1)mmol.

[0010] Preferably, in step (3), the Pr6O 11 The mixing ratio of -Hβ and ruthenium in the ruthenium salt is 1 g: (0.05~0.07) mmol, more preferably 1 g: (0.055~0.065).

[0011] Specifically, the mixing ratio of praseodymium in the Hβ molecular sieve and praseodymium salt can be 1g:0.8mmol, 1g:0.9mmol, 1g:0.95mmol, 1g:0.97mmol, 1g:1mmol, 1g:1.1mmol, 1g:1.2mmol, etc., or any specific ratio between the above values, or any range of these specific ratios. For the sake of simplicity, not all possible point values ​​or range values ​​are listed here.

[0012] Specifically, the Pr6O 11 The mixing ratio of -Hβ and ruthenium in ruthenium salts can be 1g:0.04mmol, 1g:0.05mmol, 1g:0.055mmol, 1g:0.06mmol, 1g:0.061mmol, 1g:0.065mmol, 1g:0.07mmol, 1g:0.08mmol, etc., or any specific ratio between the above values, or any range of these specific ratios. For simplicity, not all possible point values ​​or range values ​​are listed here.

[0013] Furthermore, the Hβ molecular sieve is a hydrogen-type beta zeolite with a three-dimensional twelve-membered ring channel structure, which can be obtained through market purchase.

[0014] Furthermore, the silicon-to-aluminum ratio (i.e., the molar ratio of SiO2 to Al2O3) of the Hβ molecular sieve is 25-30, preferably 26-28.

[0015] Furthermore, the silicon-to-aluminum ratio is determined by a chemical method.

[0016] Furthermore, in step (1), the mixing method is stirring.

[0017] Furthermore, the stirring conditions are: stirring at 300-500 r / min for 5-30 min.

[0018] Preferably, the stirring conditions are: stirring at 350-450 r / min for 5-15 min.

[0019] Furthermore, in step (1), the washing is done with water.

[0020] Furthermore, in step (1), the drying is oven drying.

[0021] Furthermore, the drying temperature is 50~90℃, and the drying time is 6~12h.

[0022] Preferably, the drying temperature is 55~65℃ and the drying time is 7~9h.

[0023] Furthermore, in step (2), the calcination temperature is 750~850℃, more preferably 780~820℃.

[0024] Furthermore, in step (2), the calcination time is 0.5~3h, more preferably 0.8~1.2h.

[0025] Furthermore, in step (2), the air atmosphere is an atmospheric atmosphere.

[0026] Furthermore, the airflow rate in the air atmosphere is 100~200mL / min, preferably 120~180mL / min.

[0027] Furthermore, the praseodymium salt is a soluble praseodymium salt, which includes at least one of praseodymium nitrate or its hydrate, praseodymium chloride or its hydrate, and praseodymium sulfate or its hydrate.

[0028] Furthermore, the ruthenium salt is a soluble ruthenium salt, which includes at least one of ruthenium trichloride or its hydrate, and ruthenium nitrate or its hydrate.

[0029] Furthermore, the ruthenium content in the nanoisland confined catalyst is 0.5wt%~0.7wt%, preferably 0.58wt%~0.68wt%, and more preferably 0.6wt%~0.65wt%.

[0030] Furthermore, the metal element content in the nanoisland confined catalyst is ≤15wt%, preferably 10wt%~13wt%.

[0031] Furthermore, in step (3), the mixing method is oscillation.

[0032] Furthermore, the oscillation conditions are: oscillation at 100-300 r / min for 0.1-2 h.

[0033] Preferably, the stirring conditions are: stirring at 150-250 r / min for 0.5-1.5 h.

[0034] Furthermore, in step (3), the drying is oven drying.

[0035] Furthermore, the drying temperature is 80~120℃, and the drying time is 6~12h.

[0036] Preferably, the drying temperature is 100~110℃ and the drying time is 7~9h.

[0037] Furthermore, in step (4), the calcination temperature is 550~650℃, more preferably 580~620℃.

[0038] Furthermore, in step (4), the calcination time is 0.5~2h, more preferably 0.8~1.2h.

[0039] Further, in step (4), the reducing gas is a mixture of N2 and H2 or H2.

[0040] Preferably, the reducing gas is a mixture of N2 and H2, which is obtained by mixing N2 and H2 in a volume ratio of 1:(8~10).

[0041] More preferably, the mixed gas is obtained by mixing N2 and H2 in a volume ratio of 1:(8.5~9.5).

[0042] Furthermore, the flow rate of the reducing gas is 50~200 mL / min, preferably 80~120 mL / min.

[0043] Further, in step (1), the mass-to-volume ratio of the Hβ molecular sieve to water is 1g:(8~12)mL, preferably 1g:(9~11)mL.

[0044] Further, in step (1), the pH is 7.5-9, preferably 7.8-8.2. The purpose of adjusting the pH to alkaline is to precipitate Pr(OH)3 on the molecular sieve Hβ.

[0045] Further, in step (3), the Pr6O 11 The mass-to-volume ratio of Hβ to water is 1 g:(15~60) mL, preferably 1 g:(20~40) mL, and more preferably 1 g:(30~35) mL.

[0046] Further, in step (2) or step (4), the heating rate of the calcination is 5~15℃ / min, preferably 8~12℃ / min.

[0047] This invention also protects the application of the nano-island confined catalyst in the dry reforming of methane to produce syngas.

[0048] Furthermore, the reaction temperature for the dry reforming of methane to prepare syngas is 600~800℃, more preferably 700~800℃.

[0049] Furthermore, the space velocity of the syngas prepared by the dry reforming of methane is 12000~150000 mL·g. -1 ·h -1 The preferred concentration is 15000~120000 mL·g -1 ·h -1 More preferably, it is 15000~60000 mL·g -1 ·h -1 More preferably, it is 15000~30000 mL·g -1 ·h -1 .

[0050] Furthermore, the product ratio of the raw material gases methane and carbon dioxide in the methane dry reforming synthesis gas is (2.4~3.6):3, preferably (2.8~3.2):3, and more preferably 1:1.

[0051] Furthermore, the reaction for preparing syngas from methane dry reforming is carried out under a protective gas atmosphere.

[0052] Furthermore, the protective gas is preferably nitrogen.

[0053] Furthermore, the volume ratio of the raw material gases methane, carbon dioxide and nitrogen in the methane dry reforming to prepare syngas is (2.4~3.6):3:(3.2~4.8), preferably (2.8~3.2):3:(3.8~4.2), and more preferably 3:3:4.

[0054] Furthermore, the reaction pressure for preparing syngas by dry reforming methane is 0.1~2.1 bar, preferably 0.9~1.1 bar.

[0055] Optionally, the reaction pressure for the methane dry reforming to prepare syngas is atmospheric pressure (i.e., 1.01325 bar).

[0056] Compared with the prior art, the present invention has the following beneficial effects: The nano-island confined catalyst prepared in this invention is formed by precipitating Pr(OH)3 on a Si-source molecular sieve Hβ and then calcining it in air to form Pr6O. 11 -Hβ, to perform Ru 3+ The process involves impregnation followed by reduction with reducing gas to obtain the final product. During the impregnation process, molecular sieves Hβ and Pr6O... 11 Ru occurs to varying degrees on the islands of Namibia. 3+ Electrostatic adsorption, followed by reduction with reducing gas, Hβ support and Pr6O 11 Small, uniformly distributed Ru nanoparticles are formed on the nanoislands, providing numerous active sites for methane dry reforming. When applied to methane dry reforming, this nanoisland-confined catalyst exhibits excellent catalytic activity over a wide temperature range, can operate stably and continuously for over 450 hours, demonstrates superior resistance to sintering and carbon deposition, and produces an H2 / CO ratio close to 1, making it a promising candidate for methane dry reforming. Attached Figure Description

[0057] Figure 1 This is a statistical graph showing the CH4 conversion rate of the nano-island confined catalyst prepared in Example 1 at different temperatures.

[0058] Figure 2 This is a statistical graph showing the CO2 conversion rate of the nano-island confined catalyst prepared in Example 1 at different temperatures.

[0059] Figure 3 This is a statistical graph showing the conversion rates of CH4 and CO2 at different space velocities of the nanoisland confined catalyst prepared in Example 1.

[0060] Figure 4 This is a graph showing the stability of the nano-island confined catalyst prepared in Example 1 under dry reforming with methane.

[0061] Figure 5 This is a transmission electron microscope (TEM)-energy dispersive spectroscopy (EDS) image of the nanoisland confined catalyst prepared in Example 1 before the application of methane dry reforming.

[0062] Figure 6 This is a TEM-EDS image of the nanoisland confined catalyst prepared in Example 1 after 470 h of reaction.

[0063] Figure 7 The graphs show the stability of the catalysts prepared in Comparative Examples 1 to 4 under dry reforming with methane.

[0064] Figure 8These are TEM images of the catalyst prepared in Comparative Example 1 before and after 150 h of reaction.

[0065] Figure 9 These are TEM-EDS images of the catalyst prepared in Comparative Example 2 before and after 123 h of reaction.

[0066] Figure 10 These are TEM-EDS images of the catalyst prepared in Comparative Example 3 before and after 150 h of reaction.

[0067] Figure 11 These are TEM-EDS images of the catalyst prepared in Comparative Example 4 before and after 250 h of reaction. Detailed Implementation

[0068] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0069] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0070] Hβ molecular sieves were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., and their silicon-to-aluminum ratio is 27.

[0071] Silica (SiO2) was purchased from Macklin.

[0072] Example 1: Nanoisland confined catalyst Ru / 4Pr6O 11 Preparation of -Hβ Nano-island confined catalyst Ru / 4Pr6O 11 The preparation of -Hβ includes the following steps: (1) Weigh 2g of Hβ molecular sieve in beaker 1 and place it in an oven overnight. Add 20mL of deionized water. At the same time, take out beaker 2 and weigh 842mg of praseodymium(III) hexahydrate (1.94mmol). Add 20mL of deionized water and stir at room temperature (400r / min, stirring for 10min). Then pour the solution in beaker 2 into beaker 1 and stir at room temperature (400r / min, stirring for 10min). Add the prepared dilute ammonia solution (5.3wt%) and adjust the pH to 8.0. Filter and wash with 600mL of deionized water and dry in an oven at 60℃ for 8h to obtain the catalyst precursor. (2) The catalyst precursor obtained in step (1) was placed in a muffle furnace for calcination. The calcination atmosphere was air with an air flow rate of 150 mL / min. During calcination, the temperature was increased to 800 °C at a heating rate of 10 °C / min. The calcination was carried out at 800 °C for 1 h. After cooling to room temperature, 4Pr6O was obtained. 11 -Hβ; (3) Take 600mg of the 4Pr6O obtained in step (2). 11 -Hβ was added to a 50 mL Erlenmeyer flask, followed by 20 mL of deionized water, and then ruthenium trichloride hydrate (8.2 mg, 0.036 mmol). The mixture was shaken on a shaker (200 r / min, 1 h) and then dried in an oven at 105 °C for 8 h to obtain Ru / 4Pr6O. 11 -Hβ precursor.

[0073] (4) Take the Ru / 4Pr6O obtained in step (3) 11 The -Hβ precursor was placed in a N2 and H2 mixed atmosphere (H2 to N2 volume ratio 1:9, flow rate 100 mL / min) and calcined in a pyrolysis furnace at 600 °C (heating rate 10 °C / min) for 1 h, followed by cooling to room temperature to obtain the nano-island confined catalyst Ru / 4Pr6O. 11 -Hβ.

[0074] Example 2: Nanoisland confined catalyst Ru / Pr6O 11 Preparation of -Hβ The difference from Example 1 is that in step (1), 842 mg (1.94 mmol) of praseodymium(III) nitrate hexahydrate is replaced with 191 mg (0.44 mmol) of praseodymium(III) nitrate hexahydrate.

[0075] The other steps and parameters are the same as in Example 1.

[0076] Example 3: Nano-island confined catalyst Ru / 2Pr6O 11 Preparation of -Hβ The difference from Example 1 is that in step (1), 842 mg (1.94 mmol) of praseodymium(III) nitrate hexahydrate is replaced with 394 mg (0.91 mmol) of praseodymium(III) nitrate hexahydrate.

[0077] The other steps and parameters are the same as in Example 1.

[0078] Comparative Example 1: Preparation of the catalyst Ru / Hβ The difference from Example 1 is that praseodymium(III) nitrate hexahydrate is not added in step (1).

[0079] The other steps and parameters are the same as in Example 1.

[0080] Comparative Example 2: Catalyst Ru / 4Pr6O 11 Preparation The difference from Example 1 is that Hβ molecular sieve is not added in step (1).

[0081] The other steps and parameters are the same as in Example 1.

[0082] Comparative Example 3: Preparation of the catalyst Ru / 4Pr2O3-Hβ The difference from Example 1 is that in step (2), the calcination atmosphere is changed from air to a mixture of H2 and N2 (the volume ratio of H2 to N2 is 1:9).

[0083] The other steps and parameters are the same as in Example 1.

[0084] Comparative Example 4: Catalyst Ru / 4Pr6O 11 Preparation of SiO2 The difference from Example 1 is that in step (1), the molecular sieve Hβ (2g) is replaced with SiO2 (2g).

[0085] The other steps and parameters are the same as in Example 1.

[0086] Experimental Example 1: Inductively Coupled Plasma Mass Spectrometry 1. Experimental Methods The metal content in the catalyst was determined using inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7700X). Before testing, the sample was digested in a mixed acid solution of H2SO4, HNO3, and HF using microwave, followed by dilution and volume adjustment before analysis. The specific steps are as follows: The sample (e.g., 0.1 g) was digested in a mixed acid solution of H2SO4-HNO3-HF using microwave, and then the volume was adjusted to 120 mL. The sample was then analyzed using an Agilent 7700X ICP-MS in He collision mode (He flow rate 5 mL / min). 99 Ru or 101 Ru is the analytical mass number, 115 In is used as an internal standard for quantitative determination.

[0087] 2. Experimental Results Table 1. Metal loading content of different catalysts

[0088] As shown in Table 1, the Ru metal loading in each embodiment and comparative example is approximately 0.6 wt% Ru. However, combined with subsequent data, it can be seen that the catalyst obtained in Example 1 has better catalytic activity and stability.

[0089] Example 2: Evaluation of Catalytic Dry Reforming of Methane 1. Experimental Methods The catalysts prepared in Examples 1-3 and Comparative Examples 1-4 were used as the subjects for methane dry reforming reactions, and the specific steps are as follows: A 0.10 g catalyst (20-40 mesh) was charged into a quartz tube fixed-bed reactor under atmospheric pressure (1.01325 bar) and diluted with 0.3 g of quartz sand. The reaction temperature was raised to 600 °C under a N2 atmosphere. The feed gas (CH4) and CO2, along with the internal standard gas (N2), were then introduced into the reactor at a volume ratio of 3:3:4, with a space velocity of 60000 mL·g⁻¹. -1 ·h -1 Sampling began 1 hour after the reaction, and quantitative analysis was performed using an Agilent 6820 gas chromatograph equipped with an HP-PLOT / Q column. The conversion rates of CH4 and CO2, and the H2 / CO ratio were calculated using the following formulas.

[0090] Conversion rate (%) = (Infeed amount - Discharge amount) / Feed amount × 100% (Formula 1) H2 / CO ratio (%) = H2 discharge rate / CO discharge rate (Formula 2) 2. Experimental Results Table 2 Conversion efficiency of methane dry reforming with different catalysts

[0091] The experimental results are shown in Table 2. The catalyst Ru / 4Pr6O obtained in Example 1 11 -Hβ exhibits good CH4 and CO2 conversion rates and H2 / CO ratios for dry reforming of methane under mild conditions, with CH4 conversion >55%, CO2 conversion >57%, and H2 / CO ratio ≥0.98. However, Examples 2 and 3 have lower praseodymium content, resulting in lower CH4 and CO2 conversion rates (below 50%) and a lower H2 / CO ratio compared to Example 1. Comparative Example 1, without the addition of praseodymium nitrate, produces a catalyst Ru / Hβ with poor CH4 and CO2 conversion rates, both below 21%. Comparative Example 2, without the addition of Hβ molecular sieve, produces a catalyst Ru / 4Pr6O 11 The conversion rates of CH4 and CO2 were also poor, both below 36%. In Comparative Example 3, step (2) involved calcination under an H2 / N2 atmosphere, where praseodymium ions formed Pr2O3. The resulting catalyst Ru / 4Pr2O3-Hβ had a lower conversion rate and H2 / CO ratio than the catalyst Ru / 4Pr6O in Example 1. 11 -Hβ. In step (1) of Comparative Example 4, using SiO2 as a support, the resulting catalyst Ru / 4Pr6O 11 The conversion rate of SiO2 and the H2 / CO ratio are both worse than those of the catalyst Ru / 4Pr6O in Example 1. 11 -Hβ.

[0092] Experimental Example 3: The Effect of Temperature on the Dry Reforming of Methane Using the catalyst obtained in Example 1 as the research object, the effects of different temperatures (600℃, 700℃ and 800℃) on the dry reforming of methane were investigated.

[0093] For detailed operating procedures, please refer to Experiment Example 2.

[0094] The results are as follows Figure 1 and Figure 2 As shown, the higher the temperature, the higher the conversion rate of CH4 and CO2, with the highest catalytic activity at 800℃. Overall, the Ru / 4Pr6O prepared in Example 1... 11 The -Hβ catalyst exhibits good catalytic activity (>55%) at lower temperatures (600 °C) and even higher catalytic activity (>76%) at higher temperatures (700~800 °C), demonstrating its strong ability to activate reactive gases.

[0095] Experimental Example 4: Effect of space velocity on the dry reforming reaction of methane Using the catalyst from Example 1 as the subject, the study investigated different space velocities (15000 mL·g⁻¹). -1 ·h -1 30000mL·g -1 ·h -1 60000mL·g -1 ·h -1 and 120000mL·g -1 ·h -1 The effect of this on the dry reforming of methane. The temperature of the dry reforming reaction of methane was 800℃, and other operating procedures were as described in Experimental Example 2.

[0096] The results are as follows Figure 3 As shown, at space velocities of 15000~120000 mL·g -1 ·h -1 Within the range of 15000–30000 mL·g⁻¹, the conversion rates of both CH₄ and CO₂ were greater than 75%; at space velocities of 15000–30000 mL·g⁻¹ -1 ·h -1 Within the specified range, the conversion rates of both CH4 and CO2 are greater than 90%. This indicates that the catalyst obtained in this application can achieve good conversion rates under the aforementioned space velocity conditions, even at lower space velocities of 15000~30000 mL·g. -1 ·h -1 The range has a better conversion rate.

[0097] Experiment Example 5 Stability Test Using the catalysts obtained in Example 1 and Comparative Examples 1 to 4 as examples, their high-temperature (800°C) and high-space-velocity (60000 mL·g) performance was investigated. -1 ·h-1 The stability of the methane dry reforming reaction was evaluated. The specific operating procedures are described in Experimental Example 2. The reaction was carried out continuously for 470 h to assess the stability of the catalyst in the methane dry reforming reaction.

[0098] The results are as follows Figure 4 As shown, the catalyst obtained in Example 1 maintained a CH4 and CO2 conversion rate of over 80% and an H2 / CO ratio of over 0.94 within 470 h. (This is in contrast to the reaction before...) Figure 5 ) and after the reaction ( Figure 6 The transmission electron microscopy (TEM)-energy dispersive spectroscopy (EDS) results show that the Ru particles were around 3.0 nm in size before the reaction, and after 470 h of reaction, the Ru nanoparticles remained at around 3.2 nm, with very little change in particle size. This indicates that the catalyst obtained in Example 1 did not exhibit sintering, and the Ru nanoparticles largely migrated to Pr6O. 11 The nanoisland demonstrated the high resistance to sintering and carbon deposition of the active site-nanoisland-carrier structure.

[0099] The results are as follows Figure 7 As shown, the catalyst obtained in Comparative Example 1 gradually decreased in conversion rate and H2 / CO ratio over a test time range of 0 to 250 h. Figure 8 According to the TEM-EDS results, the Ru nanoparticles of the catalyst Ru / Hβ obtained in Comparative Example 1 increased from about 3.4 nm to about 15.7 nm after 150 h of reaction, indicating that the catalyst exhibited obvious sintering.

[0100] Depend on Figure 7 It can be seen that, within the test time range of 0~250h, the conversion rate and H2 / CO ratio of the catalyst obtained in Comparative Example 2 gradually decreased with the extension of time. From... Figure 9 According to the TEM-EDS results, the catalyst Ru / 4Pr6O obtained in Comparative Example 2... 11 After 123 hours of reaction, the Ru nanoparticles grew from about 5.0 nm to about 6.03 nm, indicating that the catalyst exhibited slight sintering.

[0101] Depend on Figure 7 It can be seen that, within the test time range of 0~250h, the conversion rate and H2 / CO ratio of the catalyst obtained in Comparative Example 3 gradually decreased with the extension of time. From... Figure 10 TEM-EDS results show that, after 150 h of reaction, the Ru / 4Pr2O3-Hβ catalyst obtained in Comparative Example 3 exhibits a significant agglomeration and sintering, with most Ru particles dispersed on the Hβ support. The particle size increases from approximately 5.0 nm to approximately 8.9 nm. Figure 10The presence of carbon nanotubes in the EDS results indicates that carbon deposition also occurred in the catalyst.

[0102] Depend on Figure 7 As shown, the catalyst obtained in Comparative Example 4 maintained stable conversion rate and H2 / CO ratio over a test time range of 0–250 h. Figure 11 According to the TEM-EDS results, the catalyst Ru / 4Pr6O obtained in Comparative Example 4... 11 After 250 hours of reaction, the Ru nanoparticles of SiO2 increased from approximately 3.3 nm to approximately 4.4 nm, indicating slight sintering of the catalyst. This suggests that Pr6O 11 The performance of nanoislands on SiO2 support is worse than that on Hβ support.

[0103] In summary, the nano-island confined catalyst prepared in this invention is formed by precipitating Pr(OH)3 on molecular sieve Hβ and then calcining it in air to form Pr6O. 11 -Hβ vector, for Ru 3+ The catalyst is prepared by impregnation followed by reduction with reducing gas. This method can form nano-island confined catalysts with small particle size and relatively uniform distribution. When applied to the dry reforming reaction of methane, this nano-island confined catalyst exhibits good catalytic activity (>55%) over a wide temperature range (600~800℃), can operate stably and continuously for at least 470h, and has excellent resistance to sintering and carbon deposition. The H2 / CO ratio of the product is close to 1.

[0104] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A nano-island confined catalyst, characterized in that, The preparation process includes the following steps: (1) After mixing Hβ molecular sieve and soluble praseodymium salt in water, ammonia water is added to adjust the pH to an alkaline environment. The mixture is filtered, and the precipitate is washed and dried to obtain the catalyst precursor. (2) The catalyst precursor obtained in step (1) was calcined at 700~900℃ in an air atmosphere until the reaction was complete, yielding Pr6O. 11 -Hβ; (3) Add the Pr6O obtained in step (2) 11 Water and soluble ruthenium salt are added to -Hβ, mixed well, and dried to obtain Ru / Pr6O. 11 -Hβ precursor; (4) Under a reducing gas atmosphere, the Ru / Pr6O obtained in step (3) is subjected to... 11 The -Hβ precursor was calcined at 500–700 °C, and the reaction was complete, yielding the nano-island confined catalyst Ru / Pr6O. 11 -Hβ; In step (1), the mixing ratio of praseodymium in the Hβ molecular sieve and praseodymium salt is 1g:(0.8~1.2)mmol; In step (3), the Pr6O 11 The mixing ratio of ruthenium in Hβ and ruthenium salt is 1 g : (0.04~0.08) mmol; The ruthenium content in the nanoisland confined catalyst is 0.5wt%~0.7wt%. The metal element content in the nanoisland confined catalyst is 10wt%~13wt%.

2. The nano-island confined catalyst according to claim 1, characterized in that, The soluble praseodymium salts include at least one of praseodymium nitrate or its hydrate, praseodymium chloride or its hydrate, and praseodymium sulfate or its hydrate.

3. The nano-island confined catalyst according to claim 1, characterized in that, The soluble ruthenium salt includes at least one of ruthenium trichloride or its hydrate, and ruthenium nitrate or its hydrate.

4. The nano-island confined catalyst according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of the Hβ molecular sieve to water is 1 g: (8~12) mL.

5. The nano-island confined catalyst according to claim 1, characterized in that, In step (3), the Pr6O 11 The mass-to-volume ratio of Hβ to water is 1 g: (15~60) mL.

6. The nanoisland confined catalyst according to claim 1, characterized in that, In step (2) or step (4), the heating rate of calcination is 5~15℃ / min.

7. The application of the nano-island confined catalyst according to any one of claims 1 to 6 in the dry reforming of methane to produce syngas, characterized in that, The reaction temperature for the dry reforming of methane to prepare syngas is 600~800℃; the space velocity of the syngas prepared by the dry reforming of methane is 15000~120000 mL·g -1 ·h -1 .

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