Catalyst La1-yCeyMn1-xFexO3 + delta for catalytic combustion of low-concentration methane and preparation method of catalyst La1-yCeyMn1-xFexO3 + delta

Abstract

The embodiment of the invention provides a catalyst La < 1-y > CeyMn < 1-x > FexO < 3 + delta > for catalytic combustion of low-concentration methane and a preparation method of the catalyst, and belongs to the field of catalytic combustion of methane. The catalyst La < 1-y > CeyMn < 1-x > FexO < 3 + delta > is of a perovskite ABO < 3 > structure, the A site is La and Ce elements, the B site is Mn and Fe elements, x is 0.05-0.3, y is 0.05-0.3, and delta represents a natural number of a non-stoichiometric vacancy of oxygen. In the invention, Ce and Fe are respectively doped into A-site and B-site cations of an ABO3 type perovskite structure by adopting a sol-gel method, and the molar weight ratio of La to Ce and the molar weight ratio of Mn to Fe are adjusted, so that the surface properties of perovskite are regulated and controlled, the catalytic activity of the perovskite type catalyst is improved, and the perovskite type catalyst has excellent anti-poisoning performance such as water vapor resistance and sulfur resistance.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to the prior application 202510033201.X filed on January 9, 2025, which is incorporated herein by reference in its entirety. Technical field

[0003] The present invention belongs to the field of methane catalytic combustion, and particularly relates to a catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ and its preparation method. Background art

[0004] In today's world, the energy use structure still mainly relies on the three traditional energy sources of oil, natural gas, and coal, and these energy industries account for approximately 40% of the total methane emissions caused by human activities. The greenhouse effect of methane is 23 - 28 times that of carbon dioxide, and it is considered a "super greenhouse gas". In particular, during coal mining, low - concentration methane is generated, with its methane content ranging from 0.1% to 1%, and the amount of escape is huge. If a large amount of methane is directly emitted into the atmosphere, it will exacerbate global climate change and cause great harm to the environment. Therefore, in order to protect the environment, it is necessary to appropriately convert and utilize the low - concentration methane generated from coal mining.

[0005] One way to convert and utilize methane is to combust methane, thereby converting methane into harmless substances. Among them, flame combustion and catalytic combustion are the two main ways of methane combustion. The activation energy of the C - H bond in the methane molecule is as high as 435 kJ / mol, which means that achieving complete combustion of methane requires consuming a considerable amount of energy. However, the traditional flame combustion method exhibits problems such as extremely high combustion temperature, high nitrogen oxide emissions, and low energy utilization efficiency, and cannot meet the requirements of current social and economic development and environmental protection. Against this background, extensive attention and research have been carried out on methane catalytic combustion. Methane catalytic combustion refers to the oxidation reaction of methane and oxygen at a lower temperature under the action of a catalyst, generating carbon dioxide and water and releasing a large amount of heat. Compared with traditional flame combustion, methane catalytic combustion has the advantages of lower operating temperature, higher combustion efficiency, lower pollutant emissions, lower methane concentration requirements, and stable and controllable combustion process. Therefore, it is considered an extremely attractive alternative to traditional flame combustion.

[0006] Catalysts are the core of methane catalytic combustion technology, and their performance directly affects the efficiency and stability of catalytic reactions. At present, common methane catalytic combustion catalysts mainly include two categories: noble metal catalysts and non-noble metal oxide catalysts. Noble metal catalysts with Pd, Pt, Rh, etc. as active components have excellent low-temperature activity, but also have disadvantages such as easy deactivation, easy poisoning, and high cost. Non-noble metal oxide catalysts mainly consist of metal oxides or composite oxides, such as perovskites, hexaaluminates, etc., which have advantages such as low cost and high stability, but their low-temperature activity is poor. The low-concentration methane mixed gas generated during coal mining has a complex composition, usually containing a certain amount of water vapor and sulfur-containing components, which will significantly affect the activity of the catalyst, cause poisoning, and have a very adverse impact on practical applications. Perovskite-type catalysts with the intrinsic structure of chemical formula ABO3 are considered potential substitutes for methane combustion catalysts due to their adjustable coordination environment, surface properties, and special structure. In the chemical formula ABO3, the A-site cations are usually rare earth elements, and the B-site cations are transition metal elements. In addition, the low cost and excellent stability are also the advantages of perovskite-type catalysts in the actual treatment of low-concentration methane.

[0007] Mg can be introduced into LaMnO3 perovskite by the sol-gel method. Among them, due to the introduction of Mg 2+ which replaces some Mn sites, it is beneficial to the activation and dissociation of the C-H bond of methane and accelerates the complete oxidation of methane. However, the complete conversion temperature of the above perovskite-type catalyst for methane is still relatively high. 2+

[0008] For another example, Chinese Patent Publication Document CN 107362791B discloses a non-stoichiometric perovskite-type Y 1-x In 1-y O 3+δ methane catalytic combustion catalyst, which increases the specific surface area, high-temperature thermal stability, defect sites, and catalytic activity by controlling the combustion and volatilization rate of glycine fuel and non-stoichiometric doping at the A or B site, but does not consider the negative effects of water vapor and sulfides on the catalyst. Therefore, it is particularly important to achieve high low-temperature activity and anti-poisoning performance of perovskite-type catalysts through simple surface regulation methods.

[0009] In view of this, the present invention provides a new catalyst La 1- y Ce y Mn 1-x Fe x O 3+δ for low-concentration methane catalytic combustion and its preparation method. Summary of the Invention

[0010] To address at least one of the above problems and deficiencies in the prior art, an embodiment of the present invention provides a catalyst La for low-concentration methane catalytic combustion 1-y Ce y Mn 1-x Fe x O 3+δ and its preparation method. By using the sol-gel method, the metal elements Ce and Fe are respectively doped into the A and B site cations of the ABO3-type perovskite structure, and the molar ratios of the metal elements La to Ce and Mn to Fe are adjusted to control the surface properties of the perovskite, so as to improve the catalytic activity of the perovskite-type catalyst and endow it with excellent anti-poisoning properties against water vapor and sulfur, thereby overcoming the problem in the prior art that it is difficult to balance the relatively high low-temperature catalytic activity of the methane catalytic combustion catalyst and the anti-poisoning properties against SO2 and water vapor.

[0011] According to one aspect of the present invention, there is provided a catalyst La for low-concentration methane catalytic combustion 1- y Ce y Mn 1-x Fe x O 3+δ , wherein the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ is of the perovskite-type ABO3 structure, where the A site is composed of La and Ce elements, the B site is composed of Mn and Fe elements, x is 0.05 to 0.3, y is 0.05 to 0.3, and δ represents a natural number of oxygen non-stoichiometric vacancies.

[0012] Optionally, in the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ ,

[0013] x is 0.1 and y is 0.05;

[0014] x is 0.1 and y is 0.15;

[0015] x is 0.1 and y is 0.2;

[0016] x is 0.1 and y is 0.25; or

[0017] x is 0.1 and y is 0.3.

[0018] On the other hand, the present invention provides a method for preparing a catalyst La for low-concentration methane catalytic combustion 1-y Cey Mn 1- x Fe x O 3+δ A method for

[0019] According to the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ The molar ratio of the required metal elements, where x is 0.05 to 0.3 and y is 0.05 to 0.3. Weigh the nitrates of La, Ce, Mn, and Fe respectively and dissolve them in water to obtain a nitrate solution;

[0020] Weigh citric acid such that the total molar amount of all La, Ce, Mn, and Fe ions: the molar amount of citric acid = 1:1.2;

[0021] After heating the nitrate solution at a constant temperature and stirring, add ethylene glycol and the citric acid to obtain a mixed solution. Then, heat, stir, and evaporate the mixed solution to form a gel;

[0022] Dry the gel to obtain an intermediate; and

[0023] Calcine the intermediate to obtain the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ .

[0024] In some embodiments, in the step of heating at a constant temperature and stirring, a water bath heating device can be used. The nitrate solution can be heated at a constant temperature and stirred uniformly within the temperature range of 70°C to 90°C; after stirring uniformly for 5 to 15 minutes, add the ethylene glycol and the citric acid; and using the water bath heating device, the mixed solution can be heated, stirred, and evaporated within the temperature range of 70°C to 90°C.

[0025] Furthermore, in some embodiments, in the step of heating at a constant temperature and stirring, the nitrate solution can be heated at a constant temperature of 80°C and stirred uniformly; after stirring uniformly for 10 minutes, add the ethylene glycol and the citric acid; and the mixed solution can be heated, stirred, and evaporated at 80°C.

[0026] In some embodiments, in the drying step, an oven can be used, and the gel can be dried at a temperature of 100°C to 120°C for 10 to 15 hours.

[0027] Further, in some embodiments, in the drying step, the gel can be dried at 110 °C for 12 h.

[0028] In some embodiments, in the calcination step, the intermediate can be transferred into a muffle furnace for calcination. It can be heated from room temperature to 500 °C - 900 °C at a heating rate of 4.9 - 5.1 °C / min and calcined continuously for 5 h.

[0029] Further, in some embodiments, in the calcination step, it can be heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined continuously for 5 h.

[0030] In some embodiments, for the preparation of the catalyst La 1- y Ce y Mn 1-x Fe x O 3+δ for low-concentration methane catalytic combustion according to the present invention, Ce and Fe are respectively doped into the A and B site cations of the ABO3-type perovskite structure by using the sol-gel method, and the molar ratios of La to Ce and Mn to Fe are adjusted to regulate the surface properties of the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ .

[0031] The catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ for low-concentration methane catalytic combustion provided by the embodiments of the present invention and its preparation method have at least one of the following advantages or a part of an advantage:

[0032] First, in the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δIn this case, due to the co-doping of Ce and Fe, with La and Ce elements at the A site and Mn and Fe elements at the B site, under the conditions where x is 0.05 - 0.3 and y is 0.05 - 0.3, it is beneficial to improve the catalytic activity of the perovskite-type catalyst; moreover, by doping the bimetallic elements Fe and Ce, not only can Ce act as a sacrificial agent to reduce the sulfation of active sites and improve the sulfur resistance of the catalyst, but also the dual doping of the metal elements Ce and Fe can inhibit the further adsorption and dissociation of water molecules to improve the water resistance of the catalyst, thereby achieving good anti-poisoning performance against water vapor and sulfur, enabling the present invention to at least overcome the problem that it is difficult to balance the relatively high low-temperature catalytic activity of the methane catalytic combustion catalyst in the prior art with the anti-poisoning performance and catalytic activity against SO2 and water vapor.

[0033] Second, by using the sol-gel method to dope Ce and Fe elements into the A and B site cations of the ABO3-type perovskite structure respectively, and adjusting the molar ratio of the metal elements La and Ce, and the metal elements Mn and Fe, such that x is 0.05 - 0.3 and y is 0.05 - 0.3, to regulate the surface properties of the perovskite, so that the obtained catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ The catalyst has a large specific surface area, a relatively high Mn 4+ / Mn 3+ ratio, generates more oxygen vacancies, enhances the oxygen mobility, optimizes the methane combustion performance of the catalyst, significantly reduces the combustion temperature and activation, is beneficial to the occurrence of catalytic oxidation reaction at low temperature, has good low-temperature activity, and effectively improves the catalytic activity of the perovskite-type catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] These and / or other aspects and advantages of the present invention will become apparent and be readily understood from the following description of the preferred embodiments in conjunction with the accompanying drawings, in which:

[0035] Figure 1 Schematically shows a flowchart of a method for preparing a catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ for low-concentration methane catalytic combustion;

[0036] Figure 2 Respectively show the perovskite-type catalyst La in Example 4 according to the present invention 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O3+δ The XRD diffraction patterns of the catalyst and those of the catalysts in Comparative Example 1 and Comparative Example 3;

[0037] Figure 3 respectively show Figure 2 the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The XPS Mn 2p spectra of the catalyst and those of the catalysts in Comparative Example 1 and Comparative Example 3;

[0038] Figure 4 show Figure 2 the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The three-cycle performance graph;

[0039] Figure 5 show Figure 2 the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The thermal stability test graph under the conditions of 600 °C and 72 h;

[0040] Figure 6 show Figure 2 the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The stability test graphs of the catalyst and the catalysts in Comparative Example 1 and Comparative Example 3 respectively under the conditions of 500 °C and 10 vol% water vapor;

[0041] Figure 7 show Figure 2 the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The stability test graphs of the catalyst and the catalysts in Comparative Example 1 and Comparative Example 3 respectively under the conditions of 500 °C and 100 ppm SO2;

[0042] Figure 8 show Figure 2 the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe0.1 O 3+δ Scanning electron micrograph of Detailed implementation manners

[0043] The following provides a further specific description of the technical solution of the present invention through specific embodiments. The description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general concept of the present invention and should not be construed as a limitation to the present invention.

[0044] At present, due to the characteristics of low-concentration methane mixed gas generated during coal mine mining, such as large air volume and drastic concentration changes, and the gas contains a certain amount of water vapor and sulfides, these environmental factors can have a certain impact on the catalytic activity of existing catalysts, resulting in the problem that it is difficult to balance the anti-poisoning performance against SO2 and water vapor and the catalytic activity of the catalysts used in methane catalytic combustion in the prior art.

[0045] For this reason, an embodiment of the present invention provides a new catalyst La 1- y Ce y Mn 1-x Fe x O 3+δ .

[0046] Furthermore, an embodiment of the present invention also provides a method for preparing the above-mentioned catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ for low-concentration methane catalytic combustion. The method can respectively dope elements Ce and Fe into the A and B site cations of the ABO3-type perovskite structure LaMnO3 by using the sol-gel method, and adjust the molar ratio of La to Ce and the molar ratio of Mn to Fe to regulate the surface properties of La 1-y Ce y Mn 1-x Fe x O 3+δ perovskite, optimize the methane combustion performance of the catalyst, significantly reduce the combustion temperature and activation energy, facilitate the catalytic oxidation reaction at low temperatures, have good low-temperature activity, improve the catalytic activity of the perovskite-type catalyst, and enhance the anti-poisoning ability of the catalyst against water vapor and sulfur. In addition, in this article, "co-doping of Ce and Fe" can be abbreviated as "Ce-Fe co-doping", and "double doping of Ce and Fe" can be abbreviated as "Ce-Fe double doping".

[0047] Furthermore, La is a rare earth element. As a cation at the A-site, it has a relatively large ionic radius and an oxidation state of +3 (positive trivalent), and can effectively occupy the A-site in the perovskite structure of the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ . Its relatively high electronegativity enables it to form stable compounds with oxygen during the reaction, enhancing the crystal stability of the catalyst. Mn is a common catalytic active component with multiple oxidation states, such as Mn 2+ 、Mn 3+ and Mn 4+ . Its variable oxidation state makes it exhibit excellent catalytic ability in redox reactions. The introduction of Mn can not only improve the redox cycle efficiency of the catalyst but also increase the active sites of the catalyst by promoting the reaction between oxygen and reactants. As a transition metal, Fe has good electrical conductivity and multiple oxidation states, mainly +2 (positive divalent) and +3 (positive trivalent), and can effectively promote electron transfer in catalytic reactions. After doping with Fe, the electronic properties of the catalyst can be well regulated, enhancing the reaction rate and selectivity. The presence of Fe helps to enhance the reaction activity of the catalyst. In addition, the wide application and low cost of Fe make it not only improve the performance but also have good economic efficiency in the catalyst, making it suitable for industrial applications. Ce, as a rare earth element, has excellent anti-poisoning ability and good redox performance. In the presence of SO2, the catalyst will inevitably form metal sulfates. Ce can act as a sacrificial agent to reduce the sulfation of active sites and improve the sulfur resistance of the catalyst. In the presence of H2O, the competition between surface OH on the catalyst and gaseous adsorbed H2O for active sites is the main reason for the decrease in methane combustion activity. The doping of the bimetallic elements Fe and Ce can inhibit the further adsorption and dissociation of water molecules, thereby improving the water resistance of the catalyst. Therefore, the combination of the four metal elements La, Ce, Mn, and Fe is suitable as a catalyst for low-concentration methane catalytic combustion.

[0048] According to an embodiment of the present invention, a catalyst La for low-concentration methane catalytic combustion is provided 1- y Ce y Mn 1-x Fe x O 3+δ , wherein, the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δIt has a perovskite ABO3 structure, where the A site contains La and Ce elements, the B site contains Mn and Fe elements, x ranges from 0.05 to 0.3, y ranges from 0.05 to 0.3, and δ represents a natural number of non-stoichiometric vacancies of O (oxygen).

[0049] Optionally, in the above catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ , x is 0.1 and y is 0.05; x is 0.1 and y is 0.15; x is 0.1 and y is 0.2; x is 0.1 and y is 0.25; or x is 0.1 and y is 0.3.

[0050] See Figure 1 , which shows a method for preparing a catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ for catalytic combustion of low-concentration methane according to another embodiment of the present invention, which includes the following steps:

[0051] According to the molar ratio of the metal element required for the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ , where x ranges from 0.05 to 0.3 and y ranges from 0.05 to 0.3, weigh out nitrates of La, Ce, Mn, and Fe and dissolve them in water to obtain a nitrate solution;

[0052] Weigh citric acid so that the total molar amount of all La, Ce, Mn, and Fe ions: the molar amount of citric acid = 1:1.2;

[0053] After heating the nitrate solution at a constant temperature and stirring, add ethylene glycol and the citric acid to obtain a mixed solution, and then heat, stir, and evaporate the mixed solution to form a gel;

[0054] Dry the gel to obtain an intermediate; and

[0055] Calcine the intermediate to obtain the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ .

[0056] In some embodiments, in the step of constant temperature heating and stirring, a water bath heating device, such as a water bath pot, can be used to heat the nitrate solution at a constant temperature and stir it evenly within a temperature range of 70°C to 90°C; after stirring evenly for 5 to 15 minutes, the ethylene glycol and the citric acid can be added; and by using the water bath heating device, the mixed solution can be heated, stirred, and evaporated within a temperature range of 70°C to 90°C.

[0057] Further, in some embodiments, in the step of constant temperature heating and stirring, the nitrate solution can be heated at a constant temperature and stirred evenly at 80°C; after stirring evenly for 10 minutes, the ethylene glycol and the citric acid can be added; and the mixed solution can be heated, stirred, and evaporated at 80°C.

[0058] In some embodiments, in the drying step, an oven can be used to dry the gel within a temperature range of 100°C to 120°C for 10 to 15 hours.

[0059] Further, in some embodiments, in the drying step, the gel can be dried at 110°C for 12 hours.

[0060] In some embodiments, in the calcination step, the intermediate can be transferred into a muffle furnace for calcination, heated from room temperature to 500°C to 900°C at a heating rate of 4.9 to 5.1°C / min, and calcined continuously for 5 hours.

[0061] Further, in some embodiments, in the calcination step, it can be heated from room temperature to 800°C at a heating rate of 5°C / min and calcined continuously for 5 hours.

[0062] In some embodiments, for the preparation of the catalyst La 1- y Ce y Mn 1-x Fe x O 3+δ for low-concentration methane catalytic combustion according to the present invention, the method can be to dope Ce and Fe into the A and B site cations of the ABO3-type perovskite structure respectively by using the sol-gel method, and adjust the molar ratios of La to Ce and Mn to Fe to regulate the surface properties of the catalyst La 1-y Ce y Mn 1- x Fe x O 3+δ .

[0063] In some embodiments, the water can include deionized water.

[0064] In some embodiments, after the drying step, a grinder may be used to grind the dried intermediate.

[0065] In some embodiments, after the heating and calcination steps, the catalyst La may be cooled evenly 1-y Ce y Mn 1- x Fe x O 3+δ , for example, air cooling.

[0066] The following are specific examples and comparative examples to illustrate a method for preparing a catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ for catalytic combustion of low-concentration methane.

[0067] Comparative Example 1:

[0068] At room temperature, 0.01 mol of La(NO3)3·6H2O and 0.01 mol of Mn(NO3)2·4H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure that the metal ions were fully dispersed in the solution. Next, citric acid was weighed such that the total molar amount of all La and Mn ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the perovskite composition. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further formed into a gel; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst LaMnO3.

[0069] Comparative Example 2:

[0070] At room temperature, 0.01 mol of La(NO3)3·6H2O, 0.0095 mol of Mn(NO3)2·4H2O and 0.0005 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure that the metal ions were fully dispersed in the solution. Next, citric acid was weighed such that the total molar amount of all La, Mn and Fe ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the components in the perovskite. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst LaMn 0.95 Fe 0.05 O 3+δ 。

[0071] Comparative Example 3:

[0072] At room temperature, 0.01 mol of La(NO3)3·6H2O, 0.009 mol of Mn(NO3)2·4H2O and 0.001 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure that the metal ions were fully dispersed in the solution. Next, citric acid was weighed such that the total molar amount of all La, Mn and Fe ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the components in the perovskite. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst LaMn 0.9 Fe 0.1 O 3+δ 。

[0073] Comparative Example 4:

[0074] At room temperature, 0.01 mol of La(NO3)3·6H2O, 0.0085 mol of Mn(NO3)2·4H2O and 0.0015 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure the full dispersion of metal ions in the solution. Next, citric acid was weighed such that the total molar amount of all La, Mn and Fe ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the components in the perovskite. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst LaMn 0.85 Fe 0.15 O 3+δ 。

[0075] Comparative Example 5:

[0076] At room temperature, 0.01 mol of La(NO3)3·6H2O, 0.008 mol of Mn(NO3)2·4H2O and 0.002 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure the full dispersion of metal ions in the solution. Next, citric acid was weighed such that the total molar amount of all La, Mn and Fe ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the components in the perovskite. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst LaMn 0.8 Fe 0.2 O 3+δ 。

[0077] Comparative Example 6:

[0078] At room temperature, 0.01 mol of La(NO3)3·6H2O, 0.007 mol of Mn(NO3)2·4H2O and 0.003 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure the full dispersion of metal ions in the solution. Next, citric acid was weighed such that the total molar amount of all La, Mn and Fe ions: the molar amount of citric acid = 1:1.2, then the above citric acid solid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the components in the perovskite. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst LaMn 0.7 Fe 0.3 O 3+δ 。

[0079] Example 1:

[0080] At room temperature, 0.0095 mol of La(NO3)3·6H2O, 0.0005 mol of Ce(NO3)3·6H2O, 0.009 mol of Mn(NO3)2·4H2O and 0.001 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure the full dispersion of metal ions in the solution. Next, citric acid was weighed such that the total molar amount of all La, Ce, Mn and Fe ions: the molar amount of citric acid = 1:1.2, then the above citric acid solid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the components in the perovskite. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst La 0.95 Ce 0.05 Mn 0.9 Fe 0.1 O 3+δ 。

[0081] Example 2:

[0082] At room temperature, 0.009 mol of La(NO3)3·6H2O, 0.001 mol of Ce(NO3)3·6H2O, 0.009 mol of Mn(NO3)2·4H2O and 0.001 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure the full dispersion of metal ions in the solution. Next, citric acid was weighed such that the total molar amount of all La, Ce, Mn and Fe ions: the molar amount of citric acid = 1:1.2, then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the perovskite composition. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst La 0.9 Ce 0.1 Mn 0.9 Fe 0.1 O 3+δ 。

[0083] Example 3:

[0084] At room temperature, 0.0085 mol of La(NO3)3·6H2O, 0.0015 mol of Ce(NO3)3·6H2O, 0.009 mol of Mn(NO3)2·4H2O and 0.001 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure the full dispersion of metal ions in the solution. Next, citric acid was weighed such that the total molar amount of all La, Ce, Mn and Fe ions: the molar amount of citric acid = 1:1.2, then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the perovskite composition. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst La 0.85 Ce 0.15 Mn 0.9 Fe 0.1 O3+δ .

[0085] Example 4:

[0086] At room temperature, 0.008 mol of La(NO3)3·6H2O, 0.002 mol of Ce(NO3)3·6H2O, 0.009 mol of Mn(NO3)2·4H2O and 0.001 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure that the metal ions were fully dispersed in the solution. Next, citric acid was weighed such that the total molar amount of all La, Ce, Mn and Fe ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the perovskite composition. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ .

[0087] Example 5:

[0088] At room temperature, 0.0075 mol of La(NO3)3·6H2O, 0.0025 mol of Ce(NO3)3·6H2O, 0.009 mol of Mn(NO3)2·4H2O and 0.001 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure that the metal ions were fully dispersed in the solution. Next, citric acid was weighed such that the total molar amount of all La, Ce, Mn and Fe ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the perovskite composition. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst La0.75 Ce 0.25 Mn 0.9 Fe 0.1 O 3+δ 。

[0089] Example 6:

[0090] At room temperature, 0.007 mol of La(NO3)3·6H2O, 0.003 mol of Ce(NO3)3·6H2O, 0.009 mol of Mn(NO3)2·4H2O and 0.001 mol of Fe(NO3)3·9H2O were dissolved in 27 mL of deionized water to form a nitrate solution; then, the nitrate solution was transferred to a water bath at 80 °C and heated with stirring for 10 min to ensure the full dispersion of metal ions in the solution. Next, citric acid was weighed so that the total molar amount of all La, Ce, Mn and Fe ions: the molar amount of citric acid = 1:1.2, and then the above-mentioned solid citric acid was slowly added to the nitrate solution, and an appropriate amount of ethylene glycol was added to reduce the segregation of metal ions and ensure the uniformity of the perovskite composition. Next, the mixed solution was continuously heated with stirring and evaporated at 80 °C until a solution was formed and further a gel was formed; next, the obtained gel was placed in an oven at 110 °C and dried for 12 h to obtain a dried intermediate. Finally, the above-mentioned dried intermediate was placed in a muffle furnace and heated from room temperature to 800 °C at a heating rate of 5 °C / min and calcined at this temperature for 5 h to obtain the catalyst La 0.7 Ce 0.3 Mn 0.9 Fe 0.1 O 3+δ 。

[0091] Then, the above-obtained catalysts were subjected to performance tests. For example, the catalytic performance can be tested in an atmospheric fixed-bed reactor, and 400 mg of the catalyst can be used, for example, it can be 40-60 mesh. Before each test, the reactor can be heated to 300 °C at a heating rate of 10 °C / min and maintained for 30 min under a N2 atmosphere input at a flow rate of 200 mL / min to remove the water and impurities that may be adsorbed on the catalyst. Then, the reaction gas including 1% CH4, 20% O2 and balance N2 can be introduced into the reactor at a flow rate of 100 mL / min. In order to record the light-off curve, the catalyst bed can be further heated to 700 °C, and the heating rate can be 10 °C / min. The outlet gas can be monitored online by an infrared methane online monitor, such as FQ-1150E.

[0092] After the test, the catalyst La including four metal elements of La, Ce, Mn and Fe according to some embodiments of the present invention will be utilized 1-y Ce y Mn1-x Fe x O 3+δ The comparison results of the methane catalytic combustion activity tests performed in Examples 1 to 6 of 10 T 50 T 90 T 100 and T 10 T 50 T 90 T 100 and the methane catalytic combustion activity tests performed in Comparative Examples 1 to 6 using catalysts not including the Ce metal element are shown in Table 1. In Table 1, T 1-y Ce y Mn 1-x Fe x O 3+δ are respectively defined as the temperatures corresponding to a methane conversion rate of 10%, 50%, 90% and 100%. As shown in Table 1, according to the temperature comparison of T 10 T 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ the methane catalytic combustion temperature in Examples 1 to 6 of the catalyst La 100 T 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ of the present invention is significantly lower than the methane catalytic combustion temperature in Comparative Examples 1 to 6, and the methane catalytic combustion activity of the former is relatively stronger. For example, at T

[0093] Table 1 shows the comparison results of the methane catalytic combustion activity in Comparative Examples 1 to 6 and Examples 1 to 6

[0094]

[0095] Below, taking Example 4 in an embodiment of the present invention as an example, the various performance tests of the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ will be further described in detail by way of example.

[0096] Figure 2 The XRD diffraction patterns of the catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ according to Example 4 of the present invention are shown respectively, together with the XRD diffraction patterns of the catalysts in Comparative Example 1 and Comparative Example 3. As Figure 2 shown, for the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ according to Example 4 of the present invention above, the peaks are smaller than those of the perovskite-type catalysts LaMnO3 and LaMn 0.9 Fe 0.1 O 3+δ Therefore, for the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ according to Example 4 of the present invention above, the crystallinity is lower than that of the perovskite-type catalysts LaMnO3 and LaMn 0.9 Fe 0.1 O 3+δ However, its catalytic activity is stronger. As some studies have shown, particles with lower crystallinity can improve catalytic performance. As the A and B sites of the catalyst LaMnO3 are gradually replaced, not only the crystallinity decreases, but also the grain size gradually becomes smaller, and the CH4 catalytic activity gradually becomes stronger. This is because a catalyst with a smaller grain size has a larger surface area, thus providing more active sites for it and promoting more CH4 adsorption and cracking. Similarly, after testing, the perovskite-type catalysts La 1-y Ce y Mn 1-x Fe x O 3+δ in Examples 1 to 3, Example 5 and Example 6 according to some embodiments of the present invention also show a similar performance trend. Therefore, the above examples prove that for the perovskite-type catalyst La 1-y Ce y Mn 1- x Fe x O 3+δ due to the co-doping of Ce and Fe, with La and Ce elements at the A site and Mn and Fe elements at the B site, under the conditions that x is 0.05 to 0.3 and y is 0.05 to 0.3, it is beneficial to improve the catalytic activity of the perovskite-type catalyst.

[0097] Furthermore, Figure 3 are shown respectively Figure 2The perovskite catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ XPS Mn2p spectra of and the XPS Mn 2p spectra of the catalysts in Comparative Example 1 and Comparative Example 3. The surface Mn 4+ / Mn 3+ ratio trend is La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ (0.41) > LaMn 0.9 Fe 0.1 O 3+δ (0.17) > LaMnO3(0.15), where the Mn 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ of Mn 4+ / Mn 3+ ratio is 0.41, the Mn 0.9 Fe 0.1 O 3+δ of Mn 4+ / Mn 3+ ratio is 0.17, and the Mn 4+ / Mn 3+ ratio of LaMnO3 is 0.15. Compared with LaMnO3, LaMn 0.9 Fe 0.1 O 3+δ has a slightly increased Mn 4+ content. After Ce-Fe double doping, La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ catalyst has the highest Mn 4+ / Mn 3+ ratio, which not only indicates that doping an appropriate amount of Fe is beneficial to the formation of Mn 4+ , but also may be because Ce has the effect of weakening the Mn-O bond, generating unstable Mn 3+ , thus promoting the formation of Mn 4+ again. The higher surface Mn 4+ / Mn 3+ ratio is beneficial to enhancing Mn 3+ and Mn 4+The redox cycle process increases the oxygen vacancies in the catalyst, which is beneficial to the adsorption and activation of oxygen in the gas phase and the migration of lattice oxygen, thereby improving the catalytic activity of methane combustion. Similarly, after testing, the perovskite catalysts La according to Examples 1 to 3, Example 5, and Example 6 in some embodiments of the present invention 1-y Ce y Mn 1-x Fe x O 3+δ also show a similar performance trend. Therefore, the above examples further prove that the perovskite catalyst La according to the present invention 1-y Ce y Mn 1-x Fe x O 3+δ Due to the co-doping of Ce and Fe, with La and Ce elements in the A-site and Mn and Fe elements in the B-site, under the conditions where x is 0.05 to 0.3 and y is 0.05 to 0.3, it is beneficial to improve the catalytic activity of the perovskite catalyst.

[0098] Figure 4 shows Figure 2 the perovskite catalyst La in 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ of the three-cycle performance graph. As Figure 4 shown, the catalyst La according to Example 4 in the present invention 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ after three cycles, no downward trend in catalytic performance was found, indicating that the catalyst has good cycle stability; moreover, the catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ achieved complete conversion of methane at 500 °C. Further, after testing, the inventors found that the activation energy of the catalyst in Example 4 was 96.51 kJ / mol, lower than the activation energy of Comparative Example 1, which was 109.60 kJ / mol, and that of Comparative Example 3, which was 105.64 kJ / mol. Similarly, after testing, the perovskite catalysts according to Examples 1 to 3, Example 5, and Example 6 in the embodiments of the present invention also showed a similar performance trend.

[0099] In summary, through the research and testing of the Fe and Ce doping of the LaMnO3-based perovskite, the inventors found that compared with the prior art, the catalyst La according to the present invention 1-y Ce y Mn1-x Fe x O 3+δ , the methane combustion performance of the perovskite catalyst was optimized under the conditions that La and Ce elements were in the A-site, Mn and Fe elements were in the B-site, and x was 0.05 - 0.3 and y was 0.05 - 0.3. The combustion temperature and activation energy were significantly reduced, and it had good cyclic stability.

[0100] Figure 5 Show Figure 2 The perovskite catalyst La in 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The thermal stability test chart at 600 °C and for 72 h. As Figure 5 Shown, the catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ During the process of continuous heating at 600 °C for 72 h, the generally horizontal straight line indicates that the conversion rate remains stable continuously and hardly changes significantly, showing good thermal stability. Similarly, after testing, according to Examples 1 - 3, 5 and 6 in the embodiments of the present invention, the perovskite catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ , under the conditions that La and Ce elements are in the A-site, Mn and Fe elements are in the B-site, and x is 0.05 - 0.3 and y is 0.05 - 0.3, shows good thermal stability.

[0101] Figure 6 Show Figure 2 The perovskite catalyst La in 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The stability test charts of the catalyst in Comparative Example 1 and Comparative Example 3 respectively under the conditions of 500 °C and 10 vol% water vapor. In Figure 6 , "10 vol% H2O on" means starting to introduce 10 vol% H2O water vapor, and "10 vol% H2O off" means closing or ending the introduction of 10 vol% H2O water vapor. Compared with the activity under dry conditions, the catalytic activity of the perovskite catalyst LaMnO3 decreased by about 20%, and the catalytic activity of the perovskite catalyst LaMn 0.9 Fe 0.1 O 3+δ The catalytic activity decreased by 5%, while the perovskite catalyst La0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ The catalytic activity of Ce-Fe double-doped perovskite-type catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ basically remains unchanged. Similarly, after testing, the perovskite-type catalysts according to Examples 1 to 3 and Examples 5 and 6 in the embodiments of the present invention also show similar performance. Therefore, the test results prove that the Ce-Fe double-doped perovskite-type catalyst La

[0102] Figure 7 shows Figure 2 the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ has good anti-steam performance under the conditions that La and Ce are elements at the A-site, Mn and Fe are elements at the B-site, and x is 0.05 to 0.3, and y is 0.05 to 0.3. Figure 5 As 0.9 Fe 0.1 O 3+δ shown, the catalytic activity of the perovskite catalyst LaMnO3 decreased by about 43% in 20 h, and the catalytic activity of the perovskite catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ decreased by 12% in 20 h, while the perovskite catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ only decreased by 8%. Similarly, after testing, the perovskite-type catalysts according to Examples 1 to 3 and Examples 5 and 6 in the embodiments of the present invention also show similar performance. Therefore, the test results prove that under the conditions that La and Ce are elements at the A-site, Mn and Fe are elements at the B-site, and x is 0.05 to 0.3, and y is 0.05 to 0.3 of the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ Ce-Fe double doping has a positive effect on the sulfur resistance of the perovskite-type catalyst La

[0103] Figure 8 The scanning electron micrograph of the perovskite-type catalyst La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ according to Example 4 of the present invention is shown. It can be observed by means of the electron microscope that the Ce-Fe co-doped La 0.8 Ce 0.2 Mn 0.9 Fe 0.1 O 3+δ perovskite presents a rough and wrinkled surface, has a porous structure, generates a rich mesoporous-macroporous structure, and increases the specific surface area.

[0104] In summary, a catalyst La 1-y Ce y Mn 1- x Fe x O 3+δ for low-concentration methane catalytic combustion according to an embodiment of the present invention and its preparation method have at least one or a part of at least one of the following advantages:

[0105] First, in the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ since Ce and Fe co-doping is adopted, where the A-site is La and Ce elements, and the B-site is Mn and Fe elements, under the conditions that x is 0.05-0.3 and y is 0.05-0.3, it is beneficial to improve the catalytic activity of the perovskite-type catalyst; and, by doping the bimetallic elements Fe and Ce, not only can Ce be used as a sacrificial agent to reduce the sulfation of active sites and improve the sulfur resistance of the catalyst, but also the co-doping of the metal elements Ce and Fe can inhibit the further adsorption and dissociation of water molecules to improve the water resistance of the catalyst, thereby realizing the anti-poisoning performance of good anti-water vapor and anti-sulfur performance, making the present invention at least overcome the problem that it is difficult to balance the relatively high low-temperature catalytic activity and the anti-poisoning performance and catalytic activity against SO2 and water vapor in the prior art methane catalytic combustion catalyst.

[0106] Second, by using the sol-gel method to dope Ce and Fe elements into the A and B-site cations of the ABO3-type perovskite structure respectively, and adjusting the molar ratio of the metal elements La to Ce and the metal elements Mn to Fe, so that x is 0.05-0.3 and y is 0.05-0.3, to regulate the surface properties of the perovskite, so that the obtained catalyst La 1-y Ce y Mn 1-x Fex O 3+δ The catalyst has a large specific surface area and a high Mn 4+ / Mn 3+ ratio, generating more oxygen vacancies, enhancing the oxygen mobility, optimizing the methane combustion performance of the catalyst, significantly reducing the combustion temperature and activation, facilitating the catalytic oxidation reaction at low temperatures, having good low-temperature activity, and effectively improving the catalytic activity of the perovskite-type catalyst.

[0107] Although some embodiments of the general concept of the present invention have been exemplarily shown and described above, those of ordinary skill in the art will understand that these embodiments can be changed, replaced, and supplemented without departing from the principles and spirit of the general concept of the present invention. The protection scope of the present invention is defined by the claims and their equivalents.

Claims

1. A catalyst La for catalytic combustion of low concentration methane 1-y Ce y Mn 1-x Fe x O 3+δ , characterized in that, The catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ It is a perovskite-type ABO3 structure, in which the A position is La and Ce elements, the B position is Mn and Fe elements, x is 0.05-0.3, y is 0.05-0.3, and δ represents the natural number of non-stoichiometric oxygen vacancies.

2. The catalyst La as claimed in claim 1 1-y Ce y Mn 1-x Fe x O 3+δ , characterized in that, x is 0.1, y is 0.05; x is 0.1, y is 0.15; x is 0.1, y is 0.2; x is 0.1 and y is 0.25; or x is 0.1 and y is 0.

3.

3. A method for preparing the catalyst La for catalytic combustion of low-concentration methane as claimed in claim 1 or 2 1-y Ce y Mn 1- x Fe x O 3+δ The method is characterized in that The method comprises the steps of: According to the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ The required molar ratio of the metal elements, wherein x is 0.05 to 0.3 and y is 0.05 to 0.3, nitrates of La, Ce, Mn and Fe are weighed and dissolved in water to obtain nitrate solutions; Weigh citric acid so that the total molar amount of all La, Ce, Mn and Fe ions: the molar amount of citric acid = 1:1.2; After the nitrate solution is heated and stirred at a constant temperature, ethylene glycol and the citric acid are added to obtain a mixed solution, and then the mixed solution is heated, stirred and evaporated to form a gel; drying the gel to obtain an intermediate; as well as The intermediate is calcined to obtain the catalyst La 1-y Ce y Mn 1-x Fe x O 3+δ .

4. The method according to claim 3, characterized in that In the step of constant temperature heating and stirring, a water bath heating device is used to constant temperature heat the nitrate solution in a temperature range of 70° C. to 90° C. and stir it uniformly at the same time; After uniformly stirring for 5 to 15 minutes, adding the ethylene glycol and the citric acid; The water bath heating device is used to heat, stir and evaporate the mixed solution within a temperature range of 70° C. to 90° C.

5. The method according to claim 4, characterized in that In the step of constant temperature heating and stirring, the nitrate solution is constant temperature heated at 80° C. and stirred uniformly at the same time; After uniformly stirring for 10 minutes, adding the ethylene glycol and the citric acid; The mixed solution was heated at 80°C with stirring and evaporation.

6. The method according to claim 3, characterized in that In the drying step, the gel is dried in an oven at a temperature range of 100° C. to 120° C. for 10 to 15 hours.

7. The method according to claim 6, characterized in that In the drying step, the gel was dried at 110° C. for 12 h.

8. The method according to claim 3, characterized in that In the calcination step, the intermediate is moved into a muffle furnace for calcination, heated from room temperature to 500° C. to 900° C. at a heating rate of 4.9 to 5.1° C. / min, and the calcination is continued for 5 hours.

9. The method according to claim 8, characterized in that In the calcination step, the temperature was increased from room temperature to 800° C. at a heating rate of 5° C. / min, and the calcination was continued for 5 h.

10. The method according to any one of claims 3 to 9, characterized in that Ce and Fe are doped into the A and B cations of the ABO3 perovskite structure by a sol-gel method, respectively, and the molar ratios of La to Ce and Mn to Fe are adjusted to control the catalyst La. 1-y Ce y Mn 1-x Fe x O 3+δ surface properties.

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