A perovskite catalyst for catalytic combustion of methane, its preparation method and application

Abstract

This invention discloses a perovskite catalyst for methane catalytic combustion, its preparation method, and its application. The method involves dissolving equimolar amounts of different nitrates in water, ultrasonically stirring, adding an alkaline solution to adjust to a weakly alkaline state, then treating with ionizing radiation for a period of time. After centrifugation, washing, and drying, the catalyst is calcined in air to obtain an amorphous perovskite catalyst with small particle size, large specific surface area, and abundant pores and defects. The radiation method of this invention is simple, requires minimal equipment, has low energy consumption, and is highly reproducible, allowing for large-scale industrial production. Furthermore, the catalyst of this invention has low cost and high catalytic activity, making it suitable for environmental catalysis fields such as methane catalytic combustion, and has promising industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of catalytic combustion environmental protection technology, and in particular to a perovskite catalyst for methane catalytic combustion, its preparation method and application. Background Technology

[0002] Methane (CH4) is the second largest greenhouse gas after carbon dioxide (CO2). Its sources are diverse, including coal, oil and natural gas production, agriculture, and waste disposal. Although methane has an atmospheric lifetime of only a little over a decade, its potential warming capacity is more than 80 times that of CO2, and it contributes approximately 30% to global warming.

[0003] Catalytic combustion technology is a green, economical, and environmentally friendly method for CH4 removal. It can operate effectively at low CH4 concentrations and can completely convert CH4 at relatively low temperatures, achieving NO removal. x Catalytic combustion technology achieves ultra-low or even zero emissions of secondary pollutants such as CH4. Currently, it is widely used in areas such as natural gas vehicle exhaust purification and thermal power plant exhaust treatment. The core of catalytic combustion technology is the catalyst, and the selection of an effective catalyst plays a crucial role in effectively eliminating CH4.

[0004] Noble metal catalysts, including Pt, Pd, Rh, and Ir, have been extensively studied due to their low ignition temperatures and high specific surface areas, and their preparation methods and reaction mechanisms are well-established. However, their high cost and tendency to deactivate at high temperatures hinder their widespread application. In contrast, perovskites, as a class of composite metal oxides, possess characteristics such as low cost, good stability, and tunable structure, and are expected to become ideal catalytic materials for methane removal.

[0005] However, traditional perovskite catalyst synthesis methods, such as the sol-gel method, are limited to research applications due to their high production costs, making them difficult to widely implement in large-scale industrial production. Precipitation methods involve adding precipitants and inhibitors to metal alkoxides to control the reaction rate, followed by drying and calcination to obtain the final product. Commonly used precipitants in this method, such as ammonia, citric acid, and ethanolamine, can pollute the environment, solvent recovery is challenging, and biocompatibility is low. These drawbacks make precipitation methods difficult to implement in industrial production. Hydrothermal methods involve reactions in specially designed closed high-pressure reactors, requiring precise control of parameters such as reaction time, temperature, and pH. However, cerium oxide produced by this method is prone to severe agglomeration, which undoubtedly adds safety hazards to industrial production and limits its large-scale industrial application. Therefore, developing a method for preparing perovskite catalysts that is suitable for large-scale production and has high reproducibility is of great significance. Summary of the Invention

[0006] To address the problems of complex preparation processes and easy agglomeration after calcination in traditional catalysts, this invention proposes a method for preparing a perovskite catalyst for methane catalytic combustion. The preparation method of this invention is simple, reproducible, and uses inexpensive materials. The resulting catalyst has advantages such as amorphization, small particle size, large specific surface area, and abundant pores and defects.

[0007] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0008] A method for preparing a perovskite catalyst for methane catalytic combustion includes: weighing nitrate A and nitrate B in equal amounts and dissolving them in water; ultrasonically stirring until homogeneous; adding an alkaline solution to adjust the mixed solution to a weakly alkaline state; subjecting the reaction to ionizing radiation; centrifuging, washing, and drying; and calcining the dried solid in air to obtain the perovskite catalyst, denoted as ABO3. In the nitrate A salt, metal A is one or more of rare earth metals La, Ce, Sr, or Ca; and in the nitrate B salt, metal B is one or more of transition metals Co, Ni, Mn, or Fe.

[0009] Preferably, the concentration of the alkaline solution is 1-3 mol / L.

[0010] Preferably, the alkaline solution is a NaOH, NaHCO3, or Na2CO3 solution.

[0011] Preferably, the weak alkalinity of the mixed solution is 8-9.5.

[0012] Preferably, the ionizing radiation source is 60 Co-γ rays, X-rays, or electron accelerators.

[0013] Preferably, the absorbed dose range of the irradiation reaction is 50-500 kGy, and the time is 24-72 h.

[0014] Preferably, the roasting temperature is 500-800℃ and the time is 2-4h.

[0015] The perovskite catalyst prepared by the above method has the characteristics of amorphization, small particle size, large specific surface area, and abundant pores and defects.

[0016] Application of the perovskite catalyst prepared by the above method in the catalytic combustion of methane.

[0017] Preferably, the concentration of methane in the application is 0.5-2 vol.%, and the space velocity is 10000-30000 L / (kg·h).

[0018] Beneficial effects:

[0019] Compared with the prior art, the method for preparing a perovskite catalyst for methane catalytic combustion of the present invention has the following advantages:

[0020] (1) The present invention uses radiation technology to prepare perovskite catalysts, which improves the material’s advantages such as amorphization, small particle size, large specific surface area, abundant pores and defects.

[0021] (2) The preparation process of the present invention is suitable for large-scale production and has strong repeatability.

[0022] (3) The catalyst of the present invention is a low-cost perovskite material, and has high catalytic combustion activity for methane, and has good industrial application prospects. Attached Figure Description

[0023] Figure 1 The XRD patterns of CeNiO3 perovskite catalysts prepared in Example 2 and Comparative Example 2 of the present invention are shown, where (1) is Example 2 and (2) is Comparative Example 2.

[0024] Figure 2 The images are SEM images of CeNiO3 perovskite catalysts prepared in Example 2 and Comparative Example 2 of the present invention, where (1) is Example 2 and (2) is Comparative Example 2.

[0025] Figure 3 The images show the activity curves of CeNiO3 perovskite catalysts prepared in Example 2 and Comparative Example 2 for methane catalytic combustion, where (1) is Example 2 and (2) is Comparative Example 2. Detailed Implementation

[0026] The present invention will be described in detail through the following specific embodiments. It should be understood that these specific embodiments are only used to illustrate and explain the present invention, and do not constitute any limitation on the scope of the present invention.

[0027] Example 1

[0028] 4.3301 g of La(NO3)2·6H2O and 2.9103 g of Co(NO3)2·6H2O were weighed and dissolved in 200 mL of deionized water. After ultrasonic stirring until homogeneous, 3 mol / L Na2CO3 solution was added to adjust the pH of the mixed solution to 9. The reaction was irradiated for 24 h using an electron accelerator as the ionizing radiation source at an absorbed dose of 200 kGy. After centrifugation, washing, and drying, the solution was calcined in air at 500 °C for 2 h to obtain the LaCoO3 catalyst. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption, and the measured specific surface area of ​​LaCoO3 was 15.1 m². 2 / g.

[0029] 0.1 g of LaCoO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm in a continuous flow fixed bed. The methane concentration in the feed gas was 0.5 vol.%, and the space velocity was 20000 L / (kg·h). The mixture was flowed at 5℃·min. -1 The rate of heating was increased to 800℃, and the reaction temperature was 638℃ when the methane conversion rate was 90%.

[0030] Example 2

[0031] Weigh 4.3422g Ce(NO3)2·6H2O and 2.9079g Ni(NO3)2·6H2O, dissolve them in 200mL deionized water, sonicate and stir until homogeneous, then add 1mol / L NaOH solution to adjust the pH of the mixed solution to 8. 60 Using Co-γ rays as the ionizing radiation source, the reaction was irradiated for 36 h at an absorbed dose of 100 kGy. After centrifugation, washing, and drying, the catalyst was calcined in air at 550 °C for 3 h to obtain CeNiO3 catalyst.

[0032] The test results are as follows:

[0033] Figure 1 Image (1) shows the XRD pattern of the CeNiO3 perovskite catalyst prepared by radiation method in Example 2. After comparison with the standard spectrum, Figure 1 (1) All characteristic peaks and the standard spectrum of CeNiO3 Figure 1 The presence of these peaks indicates that the prepared product is CeNiO3, and the stronger diffraction peak intensity suggests that radiation treatment of the catalyst can induce the formation of a better perovskite crystal phase structure.

[0034] Figure 2 Image (1) shows the SEM image of the CeNiO3 perovskite catalyst prepared by radiation method in Example 2. It can be seen from the image that the CeNiO3 prepared by radiation method has smaller particles and more defects. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption, and the results showed that the CeNiO3 prepared by radiation method has a large specific surface area (20.6 m²). 2 This allows the catalyst to come into full contact with the reactant molecules, thereby accelerating the catalytic reaction.

[0035] 0.1 g of CeNiO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm in a continuous flow fixed bed. The methane concentration in the feed gas was 1 vol.%, and the space velocity was 10000 L / (kg·h). The mixture was flowed at 5℃·min. -1 The temperature was increased to 800℃ at a rate of [missing information]. The results were as follows: Figure 3As shown in the figure, (1) is the activity curve of the CeNiO3 perovskite catalyst prepared in Example 2 for the catalytic combustion of methane. It can be seen from the figure that the T of the radiation-prepared CeNiO3 catalyst is significantly higher than that of methane. 90 The temperature (representing the temperature corresponding to a methane conversion rate of 90%) is significantly lower (585℃), indicating that the radiation-prepared catalyst CeNiO3 exhibits better catalytic activity.

[0036] Example 3

[0037] 2.1163 g of Sr(NO3)2 and 3.579 g of Mn(NO3)2 solution (50 wt.%) were weighed and dissolved in 200 mL of deionized water. After ultrasonic stirring, 2 mol / L NaHCO3 solution was added to adjust the pH of the mixed solution to 8.5. The reaction was irradiated for 72 h using X-rays as the ionizing radiation source at an absorbed dose of 500 kGy. After centrifugation, washing, and drying, the solution was calcined in air at 600 °C for 4 h to obtain the SrMnO3 catalyst. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption, and the specific surface area of ​​SrMnO3 was measured to be 16.5 m². 2 / g.

[0038] 0.1 g of SrMnO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm. The methane concentration in the feed gas was 1.5 vol.%, and the space velocity was 30000 L / (kg·h). The mixture was then heated at 5℃·min. -1 The rate of heating was increased to 800℃, and the reaction temperature was 620℃ when the methane conversion rate was 90%.

[0039] Example 4

[0040] 4.3301 g of La(NO3)2·6H2O and 2.9079 g of Ni(NO3)2·6H2O were weighed and dissolved in 200 mL of deionized water. After ultrasonic stirring until homogeneous, 2 mol / L NaOH solution was added to adjust the pH of the mixed solution to 9.5. The reaction was carried out using an electron accelerator as the ionizing radiation source at an absorbed dose range of 400 kGy for 48 h. After centrifugation, washing, and drying, the catalyst was calcined in air at 650 °C for 4 h to obtain the LaNiO3 catalyst. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption, and the specific surface area of ​​SrNiO3 was measured to be 13.8 m². 2 / g.

[0041] 0.1 g of LaNiO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm. The methane concentration in the feed gas was 0.5 vol.%, and the space velocity was 10000 L / (kg·h). The mixture was then heated at 5 °C·min. -1The rate of heating was increased to 800℃, and the reaction temperature was 605℃ when the methane conversion rate was 90%.

[0042] Example 5

[0043] 4.3422 g of Ce(NO3)2·6H2O and 2.9103 g of Co(NO3)2·6H2O were weighed and dissolved in 200 mL of deionized water. After ultrasonic stirring until homogeneous, 3 mol / L Na2CO3 solution was added to adjust the pH of the mixed solution to 8.8. The reaction was irradiated for 36 h using X-rays as the ionizing radiation source at an absorbed dose range of 300 kGy. After centrifugation, washing, and drying, the catalyst was calcined in air at 700 °C for 3 h to obtain the CeCoO3 catalyst. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption, and the measured specific surface area of ​​CeCoO3 was 17.3 m² / s. 2 / g.

[0044] 0.1 g of CeCoO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm. The methane concentration in the feed gas was 2 vol.%, and the space velocity was 20000 L / (kg·h). The mixture was then heated at 5 °C·min. -1 The rate of heating was increased to 800℃, and the reaction temperature was 631℃ when the methane conversion rate was 90%.

[0045] Example 6

[0046] 2.1163 g of Sr(NO3)2 and 4.04 g of Fe(NO3)3·9H2O were weighed and dissolved in 200 mL of deionized water. After ultrasonic stirring, the mixture was adjusted to pH 9.2 with 2 mol / L NaHCO3 solution. The reaction was carried out under X-ray irradiation at an absorbed dose of 50 kGy for 60 h. After centrifugation, washing, and drying, the mixture was calcined in air at 800 °C for 2 h to obtain the SrFeO3 catalyst. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption, and the specific surface area of ​​SrFeO3 was measured to be 12.6 m². 2 / g.

[0047] 0.1 g of SrFeO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm. The methane concentration in the feed gas was 1.5 vol.%, and the space velocity was 20000 L / (kg·h). The mixture was then heated at 5℃·min. -1 The rate of heating was increased to 800℃, and the reaction temperature was 625℃ when the methane conversion rate was 90%.

[0048] Comparative Example 1

[0049] Referring to Example 1, without adding Na2CO3 solution to adjust the pH of the mixed solution, a 1-LaCoO3 catalyst was obtained. The same application test was then performed, and the specific surface area of ​​LaCoO3 was measured to be 13.4 m². 2 / g.

[0050] 0.1 g of 1-LaCoO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm. The methane concentration in the feed gas was 1.5 vol.%, and the space velocity was 20000 L / (kg·h). The mixture was then heated at 5℃·min. -1 The rate of heating is increased to 800℃, and the reaction temperature is 750℃ when the methane conversion rate is 90%.

[0051] Comparative Example 2

[0052] Referring to Example 2, a 2-CeNiO3 catalyst was obtained without an ionizing radiation source, and then the same application test was performed.

[0053] The test results are as follows:

[0054] Figure 1 (1) is the XRD pattern of the CeNiO3 perovskite catalyst prepared without radiation in Comparative Example 2. After comparison with the standard pattern, Figure 1 (1) All characteristic peaks and the standard spectrum of CeNiO3 Figure 1 This indicates that the prepared product is CeNiO3. Figure 1 (1) Compared to the previous one, the diffraction peak intensity is weaker, indicating that the perovskite formed without radiation treatment has lower crystallinity.

[0055] Figure 2 Image (2) shows the SEM image of the CeNiO3 perovskite catalyst prepared without radiation in Comparative Example 2. The image shows that it has larger particles and fewer defects. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption. The results showed that the CeNiO3 prepared without radiation had a smaller specific surface area (14.8 m²). 2 / g), which is not conducive to sufficient contact between the catalyst and reactant molecules, thus hindering the catalytic reaction.

[0056] 0.1 g of 2-CeNiO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm. The methane concentration in the feed gas was 1.5 vol.%, and the space velocity was 10000 L / (kg·h). The mixture was then heated at 5 °C·min. -1 The temperature rises to 800℃ at a rate of [missing information]. Figure 3 (2) shows the activity curve of the CeNiO3 perovskite catalyst prepared in Comparative Example 2 for the catalytic combustion of methane. It can be seen that the T of the CeNiO3 catalyst prepared without radiation is significantly higher. 90The temperature is significantly higher, indicating that the CeNiO3 catalyst prepared without radiation exhibits worse catalytic activity (764℃).

[0057] Comparative Example 3

[0058] Referring to Example 3, without calcination, a 3-SrMnO3 catalyst was obtained, and then the same application tests were performed. The specific surface area of ​​the catalyst was characterized and analyzed using N2-sorption-desorption, and the specific surface area of ​​SrMnO3 was measured to be 14.9 m². 2 / g.

[0059] 0.1 g of 3-SrMnO3 catalyst was mixed with 0.3 g of quartz sand and added to a quartz tube with an inner diameter of 8 mm. The methane concentration in the feed gas was 1.5 vol.%, and the space velocity was 30000 L / (kg·h). The mixture was then heated at 5℃·min. -1 The rate of heating is increased to 800℃, and the reaction temperature is 789℃ when the methane conversion rate is 90%.

[0060] The results of the above embodiments and comparative examples are summarized in Table 1 below.

[0061] Table 1. Methane conversion rates of different catalysts in temperature-programmed oxidation tests.

[0062]

[0063] As shown in Table 1, the preparation method of the perovskite catalyst for methane catalytic combustion of this invention has the advantages of simple process, low equipment requirements, low energy consumption, and high repeatability. Compared with the problems of poor processing precision and uniformity, safety hazards and environmental pollution, high cost and limited processing range of the plasma treatment technology mentioned in the prior art, this invention has the advantage of realizing large-scale industrial preparation. The catalyst has low cost and high catalytic activity, and is suitable for environmental catalysis fields such as methane catalytic combustion, and has good industrial application prospects.

Claims

1. A method for preparing a perovskite catalyst for the catalytic combustion of methane, characterized in that, The preparation method is as follows: Nitrate A and nitrate B are weighed in equal amounts and dissolved in water. After ultrasonic stirring until homogeneous, an alkaline solution is added to adjust the mixed solution to a weakly alkaline pH of 8-9.

5. The mixture is then subjected to ionizing radiation, followed by centrifugation, washing, and drying. The dried solid is then calcined in air to obtain the perovskite catalyst, denoted as ABO3. In nitrate A, metal A is one or more of rare earth metals La, Ce, Sr, or Ca. In nitrate B, metal B is one or more of transition metals Co, Ni, Mn, or Fe. The absorbed dose range of the irradiation reaction is 50-500 kGy, and the time is 24-72 h.

2. The method for preparing a perovskite catalyst for catalytic combustion of methane according to claim 1, characterized in that, The concentration of the alkaline solution is 1-3 mol / L.

3. The method for preparing a perovskite catalyst for catalytic combustion of methane according to claim 1, characterized in that, The alkaline solution is a NaOH, NaHCO3, or Na2CO3 solution.

4. The method for preparing a perovskite catalyst for catalytic combustion of methane according to claim 1, characterized in that, The ionizing radiation source is 60 Co-γ rays, X-rays, or electron accelerators.

5. The method for preparing a perovskite catalyst for catalytic combustion of methane according to claim 1, characterized in that, The roasting temperature is 500-800℃, and the time is 2-4 hours.

6. The perovskite catalyst prepared by any one of the preparation methods according to claims 1-5, characterized in that, The perovskite catalyst is amorphous, has small particle size, large specific surface area, and abundant pores and defects.

7. The application of the perovskite catalyst prepared by any one of the preparation methods in claims 1-5 in the catalytic combustion of methane.

8. The application according to claim 7, characterized in that, The concentration of methane in the application is 0.5-2 vol.%, and the space velocity is 10000-30000 L / (kg·h).

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