A monolithic supported palladium-based catalyst, its preparation method and use

Abstract

This invention relates to a monolithic supported palladium-based catalyst, its preparation method, and its application, belonging to the field of catalyst technology. The catalyst consists of a support of nickel foam (NF), a noble metal palladium (Pd), and another metal for catalyst surface modification, typically magnesium (Mg). The preparation process involves first growing magnesium on NF to form a robust Mg-NF matrix, and then loading palladium onto this matrix to obtain the monolithic supported palladium-based catalyst Pd / Mg-NF. This method is simple to prepare, has mild conditions, a controllable process, and strong reproducibility. The product exhibits both good reactivity and stability, and has promising prospects for practical applications.

Description

Technical Field

[0001] This invention application relates to the field of catalyst technology, and in particular to a monolithic supported palladium-based catalyst, its preparation method, and its application. Background Technology

[0002] With the increasing severity of energy shortages, natural gas, with its abundant reserves, low price, ease of use, and high thermal efficiency, is widely used in natural gas vehicles and urban heating. Methane (CH4) is one of the main components of natural gas, providing a significant amount of energy and heat for our daily lives. However, the greenhouse effect of methane is far greater than that of CO2, making the effective control of its emissions, especially low-concentration CH4 emissions, a crucial issue.

[0003] Methane, as one of the most chemically stable alkanes, requires extremely high reaction temperatures for direct combustion, and this process also produces byproducts of incomplete combustion (CO, NO). x This not only wastes a lot of energy but also causes secondary pollution to the environment. To achieve more efficient removal of low-concentration methane while reducing energy consumption, catalytic combustion technology is needed. The key to this technology lies in the development of highly active, thermally shock-resistant, and high-temperature-resistant catalytic combustion catalysts.

[0004] Currently, commonly used methane catalytic combustion catalysts include noble metal catalysts and transition metal oxide catalysts. Among them, palladium-based catalysts are recognized as having high activity for low-temperature methane oxidation. Chinese patent CN103131488A discloses a catalyst for low-concentration methane catalytic combustion and its preparation method. This catalyst includes catalytically active components (Pd, Pt, Ru, Rh, etc.), a catalyst support Al2O3, and a metal oxide co-support (Mg, La, Fe, Mn, Ni, Co, etc.). Using any one of the methods of impregnation, homogeneous precipitation, co-precipitation, or thermal decomposition, the catalyst exhibits significantly improved activity and stability compared to palladium catalysts without additives. However, the complete purification temperature of methane still needs to reach above 600℃, and palladium nanoparticles are prone to sintering under high-temperature conditions, leading to a decrease in catalyst activity and thermal stability. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned problems by providing an integral supported palladium-based catalyst for the catalytic combustion of methane. This catalyst disperses and stabilizes the noble metal palladium through strong interactions between a specific support and the active metal component. While promoting high dispersion and enhancing low-temperature catalytic activity, it also prevents the agglomeration and growth of the metal component, and possesses both good reactivity and stability.

[0006] The first aspect of this invention provides a method for preparing a monolithic supported palladium-based catalyst, which involves first growing metallic magnesium on NF to form a Mg-NF matrix, and then loading palladium onto the matrix to obtain a monolithic supported palladium-based catalyst Pd / Mg-NF, comprising the following steps:

[0007] S1. NF carrier pretreatment: Select an appropriate amount of NF raw material and clean the oil and impurities on the surface. After drying, the treated NF carrier is obtained.

[0008] S2, Preparation of Mg-NF matrix: The NF support obtained in S1 was mixed with a metal Mg salt solution and a precipitant. The mixture was placed in an oven to react, and after natural cooling, it was taken out and dried to obtain the Mg-NF matrix.

[0009] S3, Pd / Mg-NF preparation: The Mg-NF matrix obtained in S2 was mixed with a metal Pd salt solution and a precipitant. The mixture was placed in an oven for hydrothermal reaction. After natural cooling, it was taken out and dried to obtain the monolithic supported palladium catalyst Pd / Mg-NF.

[0010] By adopting the above technical solution, nickel foam (NF) is selected as a specific support, which has low cost and good thermal conductivity, thermal stability, and a porous structure with a high surface area. It provides a uniformly distributed space for the subsequent loading of the precious metal palladium. Modification of the nickel foam with magnesium solution can effectively prevent the spontaneous aggregation of palladium, thereby improving the dispersion of palladium and the thermal stability of the catalyst. This is conducive to improving the atomic utilization efficiency of the active component, achieving the catalytic conversion of methane at low temperature with a lower precious metal loading. The strong interaction between the specific support and the metal active component disperses and stabilizes the precious metal palladium, promoting its high dispersion and improving its low-temperature catalytic activity while preventing the aggregation and growth of the metal component. The product has both good reactivity and stability.

[0011] Preferably, the preparation method includes the following steps:

[0012] S1. Pretreatment of NF carrier: Select NF disc raw materials with a diameter of 32 mm and a thickness of 1 mm, immerse them in acetone solution and sonicate for 10-30 min, then take out the NF and wash it with deionized water, then place the NF in a hydrochloric acid solution with a concentration of 0.2-2 mol / L and sonicate for 2-20 min, then take out the NF and wash it with deionized water, finally place the NF in anhydrous ethanol solution and sonicate for 10-30 min to clean the oil and impurities on the surface, and dry it in an oven at 60-90℃ for 1-5 h to obtain the treated NF carrier;

[0013] S2, Preparation of Mg-NF matrix: Take 1-10 pieces of the NF support obtained in S1 and place them in a hydrothermal reactor. Prepare a modified mixture of Mg salt solution and precipitant. Add the modified mixture to the hydrothermal reactor and ultrasonically mix for 10-30 min. Then place the hydrothermal reactor in an oven at 100-200℃ and react for 1-10 h. After the reaction is completed, allow it to cool naturally. After cooling, clean the product and place it in an oven at 60-90℃ to dry for 1-5 minutes to obtain the Mg-NF matrix. The modified mixture is prepared as follows: Dissolve 0.1-1 mmol of Mg salt solution and 0.5-2 mmol of precipitant in 60-90 mL of deionized water. The Mg salt solution is magnesium nitrate solution and the precipitant is urea solution.

[0014] S3, Pd / Mg-NF Preparation: The Mg-NF matrix obtained in S2 was placed in a hydrothermal reactor. A loaded mixture of metal Pd salt solution and precipitant was prepared. The loaded mixture was added to the hydrothermal reactor and ultrasonically mixed for 10-30 min. Then, the hydrothermal reactor was placed in an oven at 100-200℃ for 1-10 h. After the reaction was completed, it was naturally cooled. The cooled product was washed and then dried in an oven at 60-90℃ for 1-5 h to obtain the monolithic supported palladium-based catalyst Pd / Mg-NF. The loading mixture was prepared as follows: 1.5-4.5 ml of metal Pd salt solution and 0.5-2 mmol of precipitant were dissolved in 60-90 mL of deionized water. The metal Pd salt solution was a palladium nitrate solution, and the precipitant was a urea solution.

[0015] Preferably, in the above preparation method, step S1 specifically includes: S1, NF carrier pretreatment: Select NF disc raw materials with a diameter of 32 mm and a thickness of 1 mm, immerse them in acetone solution and sonicate for 20 min, then take out the NF and rinse it 5 times with deionized water, then place the NF in a 1 mol / L hydrochloric acid solution and sonicate for 10 min, then take out the NF and wash it with deionized water, and finally place the NF in anhydrous ethanol solution and sonicate for 20 min to clean the oil and impurities on the surface, and dry it in an oven at 75°C for 3 h to obtain the treated NF carrier.

[0016] Preferably, in the above preparation method, step S2 specifically includes: S2, Mg-NF matrix preparation: Five pieces of the NF carrier obtained in S1 are placed in a 100ml hydrothermal reactor. A modified mixture of Mg salt solution and precipitant is prepared. The modified mixture is added to the hydrothermal reactor and ultrasonically mixed for 20 minutes. Then, the hydrothermal reactor is placed in a 160℃ oven for 6 hours. After the reaction is completed, the product is naturally cooled. After cooling, the product is cleaned and placed in a 75℃ oven for 3 hours to dry. After drying, the Mg-NF matrix is ​​obtained. The modified mixture is prepared as follows: 0.5 mmol magnesium nitrate solution and 1.5 mmol urea solution are mixed and then deionized water is added to make up to 80 mL.

[0017] Preferably, in the above preparation method, step S3 specifically includes: S3, Pd / Mg-NF preparation: Five pieces of the Mg-NF matrix obtained in S2 are placed in a 100ml hydrothermal reactor. A loading mixture of metal Pd salt solution and precipitant is prepared. The loading mixture is added to the hydrothermal reactor and ultrasonically mixed for 20 minutes. Then, the hydrothermal reactor is placed in a 160℃ oven for 6 hours. After the reaction is completed, it is naturally cooled. The cooled product is washed and then dried in a 75℃ oven for 3 hours. After drying, an integral supported palladium-based catalyst Pd / Mg-NF is obtained. The loading mixture is prepared as follows: 3mL of palladium nitrate solution and 1.5mmol of urea solution are mixed and then deionized water is added to make up to 80mL.

[0018] Preferably, in step S2, the magnesium nitrate solution is obtained by dissolving 0.1282 g of magnesium nitrate hexahydrate in deionized water.

[0019] Preferably, in step S3, the palladium nitrate solution is obtained by dissolving 1g of palladium nitrate dihydrate in 500g of deionized water.

[0020] Preferably, in step S3, the urea solution is obtained by dissolving 1.8021g of urea in deionized water.

[0021] By adopting the above technical solution, the specific steps of the preparation method are optimized to obtain a supported palladium-based catalyst with better performance.

[0022] A second aspect of the present invention provides an integral supported palladium-based catalyst, which is obtained by any of the preparation methods described above.

[0023] A third aspect of the present invention provides the application of the above-described monolithic supported palladium-based catalyst in the catalytic combustion of methane.

[0024] In summary, this application includes at least one of the following beneficial technical effects:

[0025] 1. Choosing nickel foam (NF) as a specific support is cost-effective and provides excellent thermal conductivity, thermal stability, and a porous structure with a high surface area, offering a uniformly distributed space for the subsequent loading of the precious metal palladium. Modifying the nickel foam with a magnesium solution effectively prevents the spontaneous aggregation of palladium, thereby improving the dispersion of palladium and enhancing the thermal stability of the catalyst. This, in turn, improves the atomic utilization efficiency of the active component, enabling the low-temperature catalytic conversion of methane with a lower precious metal loading. The strong interaction between the specific support and the active metal component disperses and stabilizes the precious metal palladium, promoting high dispersion and enhancing low-temperature catalytic activity while preventing the aggregation and growth of the metal component. The product exhibits both good reactivity and stability.

[0026] 2. The catalyst prepared by this method can be used for the catalytic combustion reaction of methane, and complete conversion of methane can be achieved at around 450℃.

[0027] 3. The preparation method is simple, the conditions are mild, the process is controllable and highly reproducible, and it has good prospects for practical application. Attached Figure Description

[0028] Figure 1 This is a comparison curve of the conversion rates of Examples 1-3 in this application at the same methane concentration;

[0029] Figure 2 This is a conversion curve of Example 2 of this application at different methane concentrations;

[0030] Figure 3 This is a conversion curve of NF of this application, Example 2 and Comparative Example 1 at a methane concentration of 1 vol%.

[0031] Figure 4 These are conversion curves of the catalysts of Examples 2 and Comparative Examples 2-4 of this application at a methane concentration of 1 vol%.

[0032] Figure 5 These are physical images of the catalysts used in this application NF, Example 2, and Comparative Examples 1-4;

[0033] Figure 6 This is the SEM-EDS image before use in Embodiment 2 of this application;

[0034] Figure 7 This is a SEM-EDS image after use in Embodiment 2 of this application;

[0035] Figure 8 These are SEM images of Embodiment 2 of this application before and after use;

[0036] Figure 9 This is a comparison diagram of the thermal stability of the catalysts in Example 2 and Comparative Example 1 of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0038] Information on the reagents, instruments and equipment used in the following examples is shown in Tables 1.1 and 1.2. All reagents and chemicals were used as is without further processing. Other specific conditions not specified were performed according to standard conditions or the manufacturer's recommendations. Reagents or instruments whose manufacturers are not specified were all commercially available products.

[0039] Table 1.1 Information on Reagents Used

[0040]

[0041] Table 1.2 Information on Instruments and Equipment Used

[0042]

[0043] I. Implementation Examples

[0044] Example 1

[0045] A method for preparing an integral supported palladium-based catalyst includes the following steps:

[0046] S1. Pretreatment of NF carrier: Select NF discs with a diameter of 32 mm and a thickness of 1 mm, immerse them in acetone solution and sonicate for 10 min. Then, remove the NF and rinse it 5 times with deionized water. Next, place the NF in a 0.2 mol / L hydrochloric acid solution and sonicate for 2 min. Then, remove the NF and rinse it 5 times with deionized water. Finally, place the NF in anhydrous ethanol solution and sonicate for 10 min to clean the oil, impurities and residues on the surface. After drying in an oven at 60℃ for 1 h, the treated NF carrier is obtained. The acetone solution, hydrochloric acid solution and anhydrous ethanol solution are all purchased products and do not require further treatment.

[0047] S2, Preparation of Mg-NF matrix: Take one piece of NF carrier obtained from S1 and place it in a 100ml hydrothermal reactor. Prepare a modified mixture of metal Mg salt solution and precipitant. Add the modified mixture to the hydrothermal reactor and ultrasonically mix for 10min. Then place the hydrothermal reactor in a 100℃ oven and react for 1h. After the reaction is completed, allow it to cool naturally. After cooling, clean the product and place it in a 60℃ oven to dry for 1h to obtain the Mg-NF matrix.

[0048] The modified mixture is prepared as follows: Dissolve 0.02564g of magnesium nitrate hexahydrate in 10mL of deionized water to obtain a magnesium nitrate solution, dissolve 0.6007g of urea in 10mL of deionized water to obtain a urea solution, then mix 0.1mmol of magnesium nitrate solution and 0.5mmol of urea solution, and add deionized water to make up to 60mL to obtain the modified mixture.

[0049] S3, Pd / Mg-NF preparation: The Mg-NF matrix obtained in S2 was placed in a 100ml hydrothermal reactor. A loaded mixture of metal Pd salt solution and precipitant was prepared. The loaded mixture was added to the hydrothermal reactor and ultrasonically mixed for 10min. Then, the hydrothermal reactor was placed in a 100℃ oven and reacted for 1h. After the reaction was completed, it was naturally cooled. The cooled product was washed and then dried in a 60℃ oven for 1h to obtain the monolithic supported palladium catalyst Pd / Mg-NF.

[0050] The loading mixture is prepared as follows: Dissolve 1g of palladium nitrate dihydrate in 500g of deionized water to obtain a palladium nitrate solution; dissolve 0.6007g of urea in 10mL of deionized water to obtain a urea solution; mix 1.5mL of palladium nitrate solution and 0.5mmol of urea solution; add deionized water to make up to 60mL to obtain the loading mixture.

[0051] Example 2

[0052] A method for preparing an integral supported palladium-based catalyst includes the following steps:

[0053] S1. Pretreatment of NF carrier: Select NF discs with a diameter of 32 mm and a thickness of 1 mm, immerse them in acetone solution and sonicate for 20 min. Then, remove the NF and rinse it 5 times with deionized water. Next, place the NF in a 1 mol / L hydrochloric acid solution and sonicate for 10 min. Then, remove the NF and rinse it 5 times with deionized water. Finally, place the NF in anhydrous ethanol solution and sonicate for 20 min to clean the surface oil, impurities and residues. After drying in an oven at 75℃ for 3 h, the treated NF carrier is obtained. The acetone solution, hydrochloric acid solution and anhydrous ethanol solution are all purchased products and do not require further treatment.

[0054] S2, Preparation of Mg-NF matrix: Take 5 pieces of NF carrier obtained from S1 and place them in a 100ml hydrothermal reactor. Prepare a modified mixture of metal Mg salt solution and precipitant. Add the modified mixture to the hydrothermal reactor and ultrasonically mix for 20min. Then place the hydrothermal reactor in a 160℃ oven for 6h. After the reaction is completed, allow it to cool naturally. After cooling, clean the product and place it in a 75℃ oven for 3h to dry to obtain the Mg-NF matrix.

[0055] The modified mixture is prepared as follows: Dissolve 0.1282g of magnesium nitrate hexahydrate in 20mL of deionized water to obtain a magnesium nitrate solution, dissolve 1.8021g of urea in 30mL of deionized water to obtain a urea solution, then mix 0.1mmol of magnesium nitrate solution and 0.5mmol of urea solution, and add deionized water to make up to 80mL to obtain the modified mixture.

[0056] S3, Pd / Mg-NF preparation: The Mg-NF matrix obtained in S2 was placed in a 100ml hydrothermal reactor. A loaded mixture of metal Pd salt solution and precipitant was prepared. The loaded mixture was added to the hydrothermal reactor and ultrasonically mixed for 20min. Then, the hydrothermal reactor was placed in a 160℃ oven for 6h. After the reaction was completed, it was naturally cooled. The cooled product was washed and then dried in a 75℃ oven for 3h to obtain the monolithic supported palladium catalyst Pd / Mg-NF.

[0057] The loading mixture is prepared as follows: Dissolve 1g of palladium nitrate dihydrate in 500g of deionized water to obtain a palladium nitrate solution; dissolve 1.8021g of urea in 30mL of deionized water to obtain a urea solution; mix 3mL of palladium nitrate solution and 1.5mmol of urea solution; add deionized water to bring the volume to 80mL to obtain the loading mixture.

[0058] Example 3

[0059] A method for preparing an integral supported palladium-based catalyst includes the following steps:

[0060] S1. Pretreatment of NF carrier: Select NF discs with a diameter of 32 mm and a thickness of 1 mm, immerse them in acetone solution and sonicate for 30 min. Then, remove the NF and rinse it 5 times with deionized water. Next, place the NF in a 2 mol / L hydrochloric acid solution and sonicate for 20 min. Then, remove the NF and wash it 5 times with deionized water. Finally, place the NF in anhydrous ethanol solution and sonicate for 30 min to clean the oil and impurities on the surface. After drying in an oven at 90℃ for 5 h, the treated NF carrier is obtained. The acetone solution, hydrochloric acid solution, and anhydrous ethanol solution are all purchased products and do not require further treatment.

[0061] S2, Preparation of Mg-NF matrix: Take 10 NF carriers obtained from S1 and place them in a 100ml hydrothermal reactor. Prepare a modified mixture of Mg salt solution and precipitant. Add the modified mixture to the hydrothermal reactor and ultrasonically mix for 30min. Then place the hydrothermal reactor in a 200℃ oven and react for 10h. After the reaction is completed, allow it to cool naturally. After cooling, clean the product and place it in a 90℃ oven to dry for 5h to obtain the Mg-NF matrix.

[0062] The modified mixture is prepared as follows: dissolve 0.2564g of magnesium nitrate hexahydrate in 30mL of deionized water to obtain a magnesium nitrate solution, dissolve 2.4028g of urea in 40mL of deionized water to obtain a urea solution, mix 1mmol of magnesium nitrate solution and 2mmol of urea solution, and add deionized water to make up to 90mL to obtain the modified mixture.

[0063] Preparation of S3 and Pd / Mg-NF: 10 pieces of Mg-NF matrix obtained from S2 were placed in a 100ml hydrothermal reactor. A loading mixture of metal Pd salt solution and precipitant was prepared. The loading mixture was added to the hydrothermal reactor and ultrasonically mixed for 30min. Then the hydrothermal reactor was placed in a 200℃ oven for 10h. After the reaction was completed, it was naturally cooled. The cooled product was washed and then dried in a 90℃ oven for 5h. After drying, the monolithic supported palladium catalyst Pd / Mg-NF was obtained.

[0064] The loading mixture is prepared as follows: Dissolve 1g of palladium nitrate dihydrate in 500g of deionized water to obtain a palladium nitrate solution; dissolve 2.4028g of urea in 40mL of deionized water to obtain a urea solution; mix 4.5mL of palladium nitrate solution and 2mmol of urea solution; add deionized water to make up to 90mL to obtain the loading mixture.

[0065] The catalysts prepared in Examples 1-3 of this application are used in a fixed-bed reactor for the catalytic combustion of methane.

[0066] II. Comparative Example

[0067] Comparative Example 1

[0068] A method for preparing an integral supported palladium-based catalyst differs from Example 2 in that step S2 is omitted, and step S3 is performed directly after step S1 to obtain the Pd-NF catalyst.

[0069] Comparative Example 2

[0070] A method for preparing an integral supported palladium-based catalyst differs from Example 2 in that the Pd / Mg-NF obtained in S3 is calcined at 300°C for 4 hours to obtain the Pd / Mg-NF 300 catalyst.

[0071] Comparative Example 3

[0072] A method for preparing an integral supported palladium-based catalyst differs from Example 2 in that the Pd / Mg-NF obtained in S3 is calcined at 500°C for 4 hours to obtain the Pd / Mg-NF 500 catalyst.

[0073] Comparative Example 4

[0074] A method for preparing an integral supported palladium-based catalyst differs from Example 2 in that the Pd / Mg-NF obtained in S3 is calcined at 800°C for 4 hours to obtain the Pd / Mg-NF 800 catalyst.

[0075] III. Performance Test Experiments and Results

[0076] 1. Catalyst activity test for methane catalytic combustion reaction

[0077] The methane catalytic combustion activity of NF, the catalysts obtained in Examples 1-3, and Comparative Examples 1-4 were tested respectively, and the test methods are as follows:

[0078] The test was conducted using a fixed-bed reactor. A mixture of 0.2 vol%–2 vol% CH4 and air was introduced into the fixed-bed reactor containing the catalyst at a total flow rate of 400 ml / min. The test temperature range was 200–800 °C, and the pressure was atmospheric pressure. An online methane detector was connected to the outlet to calculate the conversion rate.

[0079] The CH4 conversion rate is calculated as follows:

[0080] CH4 conversion(%)={([CH4]in–[CH4]out) / [CH4]in}×100%

[0081] Wherein, [CH4]in and [CH4]out are the methane concentrations at the feed and reactor outlet, respectively.

[0082] When the catalysts obtained in Examples 1-3 were used in the methane combustion reaction, complete conversion was achieved at relatively low temperatures. The methane conversion rate curves at the same concentration are shown in the figure below. Figure 1 As shown, by Figure 1 It can be seen that the catalyst obtained in Example 2 has better low-temperature catalytic activity and is the best example. Therefore, the Pd / Mg-NF catalyst obtained in Example 2 was used for subsequent testing.

[0083] Example 2: Conversion curves of methane at different concentrations are shown in the figure. Figure 2 As shown, by Figure 2It is known that under the conditions of methane content of 0.2 vol%-2 vol% and total flow rate of 400 ml / min, methane can be completely catalytically combusted at around 430℃-460℃. Therefore, when the catalyst prepared by this method is used for the catalytic combustion of methane, it can realize the catalytic conversion of methane at low temperature, thereby improving the catalyst performance.

[0084] The conversion curves of the catalysts obtained by NF, Example 2, and Comparative Example 1 at a methane concentration of 1 vol% are shown in the figure below. Figure 3 As shown, by Figure 3 It is known that when the catalyst prepared by the method provided by this invention is used in the methane combustion reaction, the complete conversion of methane can be achieved at around 450°C. Under the same conditions, the catalytic effect is better than that of NF feedstock and unmodified Pd-NF catalyst. This is because the modification of magnesium can effectively prevent the spontaneous aggregation of palladium, thereby improving the dispersion of palladium. In addition, the use of foam nickel discs with high surface area and porous structure as a specific support provides a uniformly distributed space for the loading of the noble metal palladium. The strong interaction between the specific support and the metal active component disperses and stabilizes the noble metal palladium, which not only promotes its high dispersion, but also improves its low-temperature catalytic activity.

[0085] The conversion curves of the catalysts obtained in Example 2 and Comparative Examples 2-4 at a methane concentration of 1 vol% are shown below. Figure 4 As shown, by Figure 4 It can be seen that catalysts calcined at 300℃ and 500℃ still have good catalytic performance. However, if the calcination temperature is too high, they are prone to sintering.

[0086] 2. Visual inspection

[0087] The appearance of the catalysts obtained from NF, Example 2, and Comparative Examples 1-4 were observed respectively. The actual appearance images of the catalysts are shown below. Figure 5 As shown in the appearance, the color indicates that Comparative Example 1 showed a clear metallic luster after only adding Pd, indicating that Pd was uniformly loaded onto NF. After adding Pd and Mg, the metallic luster of Example 2 was weakened compared to Comparative Example 1, indicating that Mg was successfully loaded. Comparative Examples 2-4 were slightly black, indicating that sintering may have occurred.

[0088] 3. Structural Characterization

[0089] The Pd / Mg-NF catalyst of Example 2 before and after use was scanned using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The SEM-EDS images were obtained. The scanning results before use are shown in the figure. Figure 6 As shown, the scan results after use are as follows: Figure 7 As shown, the Pd / Mg-NF obtained in Example 2 was scanned before and after use using a scanning electron microscope (SEM), and the SEM images were obtained. The scanning results are as follows. Figure 8As shown.

[0090] Depend on Figure 6-8 It can be seen that both Mg and Pd were successfully loaded onto the NF support. Before and after use, Pd nanoparticles were uniformly distributed on the NF surface, and magnesium crystals grew uniformly on the NF surface. No large sintered particles or agglomeration were observed in the microstructure before and after use. Therefore, this proves that the preparation method provided by this invention effectively organizes catalyst sintering, combined with the attached... Figure 1-3 It was found that magnesium modification can effectively prevent the spontaneous aggregation of palladium, thereby improving the dispersibility of palladium in the subsequent process. It also helps to improve the atomic utilization efficiency of the active component, enabling the catalytic conversion of methane at low temperatures with a lower noble metal loading. The noble metal palladium is dispersed and stabilized through the strong interaction between the specific support and the metal active component. While promoting its high dispersion and improving its low-temperature catalytic activity, it can prevent the agglomeration and growth of the metal component, resulting in a product with good reactivity.

[0091] 4. Thermal stability testing

[0092] The thermal stability of the catalysts obtained in Example 2 and Comparative Example 1 was tested. The comparison results of the thermal stability of the catalysts obtained in Example 2 and Comparative Example 1 at 500°C are shown in the attached figure. Figure 9 As shown, by Figure 9 It can be seen that the thermal stability of the catalyst obtained in Example 2 is significantly better than that of the catalyst obtained in Comparative Example 1. (Combined with the attached...) Figure 1-3 It was found that the noble metal palladium was dispersed and stabilized through the strong interaction between the nickel foam discs and magnesium elements on a specific carrier. This not only promoted its high dispersion and improved its low-temperature catalytic activity, but also prevented the agglomeration and growth of the metal components. Furthermore, the product exhibited both good reactivity and stability.

[0093] 5. Performance Comparison

[0094] The performance of the Pd / Mg-NF prepared in Example 2 was compared with that of existing reported catalysts (see references 1-3). The following table shows the T values. 90 To achieve a 90% conversion rate, thermal stability is related to the test temperature. The higher the test temperature, the easier it is for the catalyst to sinter. Testing at high temperatures better reflects thermal stability, i.e., resistance to sintering. Comparison shows that the Pd / Mg-NF prepared in Example 2 has excellent performance. Its low-temperature catalytic activity and thermal stability exceed those of a large number of palladium-based catalysts reported in this field (see Table 2).

[0095] Table 2. Performance Comparison of Example 2 and Palladium-based Catalysts in Existing Reports

[0096]

[0097]

[0098] In summary, through characterization and performance determination of Pd / Mg-NF, it can be concluded that the Pd / Mg-NF catalyst prepared by this method can completely catalytically combust methane at around 430℃-460℃ under the conditions of methane content of 0.2 vol%-2 vol% and total flow rate of 400 ml / min.

[0099] This method selects nickel foam (NF) as a specific support, utilizing its excellent thermal conductivity, thermal stability, and porous structure with a high surface area to provide a uniformly distributed space for the subsequent loading of the noble metal palladium. Modification of the nickel foam with a magnesium solution effectively prevents the spontaneous aggregation of palladium, improving the dispersion of palladium and enhancing the thermal stability of the catalyst. This, in turn, improves the atom utilization efficiency of the active component, enabling the low-temperature catalytic conversion of methane with a relatively low noble metal loading. The strong interaction between the specific support and the active metal component disperses and stabilizes the noble metal palladium, promoting high dispersion and enhancing low-temperature catalytic activity while preventing the aggregation and growth of the metal component. The product exhibits both good reactivity and stability. Furthermore, this method is simple to prepare, operates under mild conditions, is controllable, and highly reproducible, showing promising prospects for practical applications.

[0100] References 1-3 are as follows:

[0101] [1]Lin J, Xu Y, Chen

[0102] [2]Fazlikeshteli S,Vendrell

[0103] [3]Cai J,Wang J,Liu C,et al.Electron transferring with oxygen defectson Ni-promoted Pd / Al2O3

[0104] catalysts for low-temperature lean methane combustion[J].Journal ofColloid and InterfaceScience,2024.

Claims

1. A method for preparing an integral supported palladium-based catalyst, characterized in that: The process involves first growing metallic magnesium on NF to form a Mg-NF matrix, where NF is nickel foam, and then loading palladium onto this matrix to prepare a monolithic supported palladium catalyst Pd / Mg-NF. This includes the following steps: S1. Pretreatment of NF carrier: Select NF disc raw materials with a diameter of 32 mm and a thickness of 1 mm, immerse them in acetone solution and sonicate for 10-30 min, then remove the NF and wash with deionized water, then place the NF in a hydrochloric acid solution with a concentration of 0.2-2 mol / L and sonicate for 2-20 min, then remove the NF and wash with deionized water, finally place the NF in anhydrous ethanol solution and sonicate for 10-30 min to clean the surface oil and impurities and residual solution, then transfer it to an oven at 60-90℃ and dry for 1-5 h to obtain the treated NF carrier; S2, Preparation of Mg-NF matrix: Take 1-10 pieces of the NF support obtained in S1 and place them in a hydrothermal reactor. Prepare a modified mixture of metal Mg salt solution and precipitant. Add the modified mixture to the hydrothermal reactor and ultrasonically mix for 10-30 min. Then place the hydrothermal reactor in an oven at 100-200℃ and react for 1-10 h. After the reaction is completed, allow it to cool naturally. After cooling, clean the product and place it in an oven at 60-90℃ to dry for 1-5 h to obtain the Mg-NF matrix. The modified mixture is prepared as follows: Dissolve 0.1-1 mmol of metal Mg salt solution and 0.5-2 mmol of precipitant in 60-90 mL of deionized water. The metal Mg salt solution is magnesium nitrate solution and the precipitant is urea solution. S3, Pd / Mg-NF Preparation: The Mg-NF matrix obtained in S2 was placed in a hydrothermal reactor. A loaded mixture of metal Pd salt solution and precipitant was prepared. The loaded mixture was added to the hydrothermal reactor and ultrasonically mixed for 10-30 min. Then, the hydrothermal reactor was placed in an oven at 100-200℃ for 1-10 h. After the reaction was completed, it was naturally cooled. The cooled product was washed and then dried in an oven at 60-90℃ for 1-5 h to obtain the monolithic supported palladium-based catalyst Pd / Mg-NF. The loading mixture was prepared as follows: 1.5-4.5 mL of metal Pd salt solution and 0.5-2 mmol of precipitant were dissolved in 60-90 mL of deionized water. The metal Pd salt solution was a palladium nitrate solution, and the precipitant was a urea solution.

2. The preparation method according to claim 1, characterized in that: S1. Pretreatment of NF carrier: Select NF disc raw materials with a diameter of 32 mm and a thickness of 1 mm, immerse them in acetone solution and sonicate for 20 min. Then take out the NF and rinse it 5 times with deionized water. Then place the NF in a 1 mol / L hydrochloric acid solution and sonicate for 10 min. Then take out the NF and rinse it 5 times with deionized water. Finally, place the NF in anhydrous ethanol solution and sonicate for 20 min to clean the oil and impurities on the surface. After drying in an oven at 75℃ for 3 h, the treated NF carrier is obtained.

3. The preparation method according to claim 1, characterized in that: S2, Preparation of Mg-NF matrix: Five NF carriers obtained in S1 were placed in a 100ml hydrothermal reactor. A modified mixture of Mg salt solution and precipitant was prepared. The modified mixture was added to the hydrothermal reactor and ultrasonically mixed for 20 minutes. The hydrothermal reactor was then placed in a 160℃ oven for 6 hours. After the reaction was completed, the mixture was allowed to cool naturally. The cooled product was cleaned and then placed in a 75℃ oven for 3 hours to dry. The Mg-NF matrix was obtained after drying. The modified mixture was prepared as follows: 0.5 mmol magnesium nitrate solution and 1.5 mmol urea solution were mixed and then deionized water was added to bring the volume to 80 mL.

4. The preparation method according to claim 1, characterized in that: S3, Pd / Mg-NF preparation: Five pieces of the Mg-NF matrix obtained in S2 were placed in a 100ml hydrothermal reactor. A loading mixture of metal Pd salt solution and precipitant was prepared. The loading mixture was added to the hydrothermal reactor and ultrasonically mixed for 20min. Then, the hydrothermal reactor was placed in a 160℃ oven for 6h. After the reaction was completed, it was naturally cooled. The cooled product was washed and then dried in a 75℃ oven for 3h. After drying, the monolithic supported palladium-based catalyst Pd / Mg-NF was obtained. The loading mixture was prepared as follows: 3mL of palladium nitrate solution and 1.5mmol of urea solution were mixed and then deionized water was added to make up to 80mL.

5. The preparation method according to claim 1, characterized in that: In S2, the magnesium nitrate solution is obtained by dissolving 0.1282g of magnesium nitrate hexahydrate in deionized water.

6. The preparation method according to claim 1, characterized in that: In step S3, the palladium nitrate solution is obtained by dissolving 1g of palladium nitrate dihydrate in 500g of deionized water.

7. The preparation method according to claim 1, characterized in that: In step S3, the urea solution is obtained by dissolving 1.8021g of urea in deionized water.

8. A monolithic supported palladium-based catalyst, characterized in that: It is prepared by the preparation method according to any one of claims 1-7.

9. The application of the monolithic supported palladium-based catalyst according to claim 8 in the catalytic combustion of methane.

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