Preparation method and application of a composite metal oxide catalyst

Abstract

This invention discloses an M1Co3Ni6O for low-temperature catalytic combustion of methane. x A method for preparing a composite metal oxide catalyst, wherein the catalytic combustion reaction of methane is carried out at a temperature range of 250–500 °C under normal pressure. The preparation method includes the following steps: Step 1, synthesis of a mixed metal ion solution L1; Step 2, preparation of an alkaline ammonium carbonate solution L2; Step 3, titration of solutions L1 and L2; Step 4, M1Co3Ni6O x Synthesis of composite metal oxides. The catalyst prepared by this invention exhibits superior methane combustion catalytic activity, structural stability, and strong resistance to sintering. The M1Co3Ni6O prepared by this invention... x Composite metal oxide materials are used as catalysts for the low-temperature catalytic combustion of methane to further improve the methane conversion rate and the selectivity of CO2 products.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a low-temperature catalytic combustion of methane using M1Co3Ni6O. x Preparation method of composite metal oxide catalyst. Background Technology

[0002] Methane is the main component of natural gas, accounting for more than 90%, and its combustion emits CO and NO. x And SO x It produces fewer harmful byproducts and, compared to coal and oil, is a high-quality, efficient, and clean energy source that is widely used in people's production and daily life.

[0003] Traditional methane combustion requires very high combustion conversion temperatures, reaching up to 1600℃. Furthermore, incompletely combusted methane emits a strong greenhouse effect, approximately 21 times more potent than carbon dioxide. Therefore, low-temperature catalytic combustion of methane into CO2 and H2O is a promising technology for effectively reducing methane emissions and maximizing the use of clean energy. Catalytic combustion is a flameless combustion with a catalyst at low ignition temperatures (200–500℃). Essentially, catalytic combustion is a vigorous oxidation reaction involving active oxygen. The active component of the catalyst activates oxygen in the air, and when it comes into contact with reactant molecules, energy transfer occurs. The reactant molecules are adsorbed and activated on the catalyst surface, then decompose on the catalyst surface, and subsequently recombine to form products. Finally, the products desorb from the surface.

[0004] The reaction equation is: CH4 + 2O2 → CO2 + 2H2O

[0005] Methane molecules contain only four CH bonds, making them difficult to oxidize deeply, which necessitates catalysts with sufficiently high catalytic combustion activity. In recent years, supported noble metal (especially Pd-based) catalysts have exhibited outstanding activity. However, noble metal catalysts are not entirely satisfactory due to poor thermal stability, susceptibility to sintering and deactivation, and high cost. Non-noble metal composite oxide catalysts, on the other hand, have attracted considerable attention due to their low cost and good catalytic oxidation performance. Because non-noble metal oxide catalysts possess multiple valence states, they readily form redox cycles, allowing for the smooth release and repair of lattice oxygen, thus exhibiting excellent catalytic activity.

[0006] Research has found that cobalt-nickel-based composite oxide catalysts exhibit excellent performance in catalyzing the low-temperature combustion of methane. 3+ As a dissociation site for CH4, it can promote the CH cleavage of CH4, thereby improving the redox performance of the catalyst and its ability to activate CH4. 3+ Also through Ni 3+The cooperative interaction of sites plays an important role in the combustion of CH4 catalysts, and the surface-rich Co 3+ Through Co 3+ and Co 2+ The redox cycle between them provides nearby oxygen for the CH4 oxidation reaction, enhancing the oxidation activity of CH4. In-situ doping of the cobalt-nickel based catalyst with M metal (M being a transition metal cation) effectively increases the number of surface defect oxygen sites (oxygen vacancies), which is beneficial for the reaction of oxygen clusters with Ni. 3+ The interaction between the surface and the surface modulates the electronic properties and coordination structure, reduces the bonding energy of O2 adsorption, improves the oxygen mobility between the bulk phase and the surface, and enhances the catalytic oxidation performance of CH4. Summary of the Invention

[0007] The purpose of this invention is to provide M1Co3Ni6O for low-temperature catalytic combustion of methane. x The present invention discloses a method for preparing a composite metal oxide catalyst. The method uses nitrates of M, Co, and Ni as precursors, which are vigorously stirred and mixed to form a transparent homogeneous solution. Then, an ammonium carbonate alkaline solution is added dropwise to form a pale purple flocculent metal complex precipitate. After aging overnight at room temperature, the precipitate is centrifuged, washed, dried at low temperature, and calcined at high temperature to form M1Co3Ni6O. x The composite metal oxide catalyst exhibits superior methane catalytic combustion activity. The doping of the M metal effectively increases surface oxygen vacancies, activates CH4 and O2, lowers the energy barrier of chemisorption, improves oxygen mobility, and enhances the low-temperature catalytic combustion performance of CH4.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] M1Co3Ni6O for low-temperature catalytic combustion of methane x A method for preparing composite metal oxide catalysts includes the following steps:

[0010] Step one, the synthesis of the metal mixed solution L1, consists of the following steps:

[0011] First, weigh out a certain amount of hydrated nitrate salts of M, Co, and Ni and place them in a 250 mL beaker. Add a certain amount of deionized water and ethanol aqueous solution. Sonicate the sample for 2 hours, then place it on a magnetic stirrer and stir magnetically at room temperature for 60–120 minutes until completely dissolved, forming a homogeneous and clear solution L1 of metal ions. The concentration of M metal ions is 50–55 μmol / mL, the concentration of Co metal ions is 150 μmol / mL, and the concentration of Ni metal ions is 300 μmol / mL.

[0012] Step two, preparation of ammonium carbonate alkaline solution L2, the steps are as follows:

[0013] A certain amount of (NH4)2CO3 solid was used as a precipitant and placed in a 1000mL volumetric flask. The mixture was magnetically stirred at room temperature for 2 hours until the ammonium carbonate solid was completely dissolved, forming an alkaline ammonium carbonate solution L2 with a concentration of 1.0mol / L.

[0014] Step 3, titration of solutions L1 and L2, includes the following steps:

[0015] 1) Quickly add the alkaline solution of (NH4)2CO3 prepared in step 2 to the clear solution L1 prepared in step 1. The addition temperature is controlled at 60℃. Stir quickly with a magnetic stirrer to complete the titration quickly. Finally, a light purple flocculent precipitate is obtained. Stop the titration when the pH value is 9 to 10 as measured by pH test paper. Continue heating and stirring for 60 to 120 minutes to ensure sufficient precipitation and finally reach phase equilibrium.

[0016] 2) Aging the mixed solution prepared in step 1) at room temperature for 12 hours.

[0017] 3) Then wash three times with deionized water and anhydrous ethanol respectively, and then dry in a forced-air drying oven at 60°C for 12 hours to obtain a block solid sample.

[0018] 4) Place the blocky solid sample into an agate mortar and grind it into powder for 20 minutes.

[0019] Step 4, M1Co3Ni6O x The synthesis of composite metal oxides involves the following steps:

[0020] The powder ground in step three above was placed in a corundum crucible and then calcined in a muffle furnace at 500°C for 6 hours in a static air atmosphere. The heating rate from room temperature to the calcination temperature was 5°C / min, and finally a black powder catalyst was obtained.

[0021] Furthermore, the metal ion raw materials are Mn(NO3)2·4H2O (or Zr(NO3)4·5H2O or Cu(NO3)2·6H2O), Co(NO3)2·6H2O and Ni(NO3)2·6H2O, the total molar amount of transition metal ions is 0.05 mol, the molar ratio of metal ions is M:Co:Ni=1:3:6, and the concentration of M metal cation is 50~55μmol / mL.

[0022] Furthermore, the stirring time for the mixed solution of the three nitrates in step one is controlled to be 2 hours.

[0023] Furthermore, in step one, the total volume of the mixed solution of deionized water and ethanol added to the beaker is 100 mL, comprising 80 mL of deionized water and 20 mL of ethanol, wherein V 乙醇 :V水 =1:4.

[0024] Furthermore, in step two, the amount of (NH4)2CO3 used is 96g, which is diluted and dissolved with deionized water and then brought to a final volume in a 1000mL volumetric flask, resulting in a solution concentration of 1–1.02mol / L.

[0025] Furthermore, the titration time in step three is controlled to be completed within 5 minutes. After adding (NH4)2CO3 solution, a precipitate is formed and the mixture is heated and stirred at 60°C for another 60 minutes.

[0026] Furthermore, the black powder in step four is Mn1Co3Ni6O. x Cu1Co3Ni6O x Zr1Co3Ni6O x , where x is the coordination number of oxygen (-2 valence) calculated based on the stoichiometry of the metal. For Mn1Co3Ni6O x Based on the highest oxidation states of Mn, Co, and Ni being +7, +5, and +3 respectively, and their molar ratio being 1:3:6, the highest coordination number of x is 20. Based on the lowest oxidation states of Mn, Co, and Ni being +2, +2, and +2 respectively, and their molar ratio being 1:3:6, the lowest coordination number of x is 10. Therefore, the range of x is 10–20. For Cu1Co3Ni6O x The highest coordination number of x is 24.5, and the lowest coordination number is 9.5, so the range of x is 9.5 to 24.5. For Zr1Co3Ni6O x The highest coordination number of x is 18.5 and the lowest coordination number is 10, so the range of x is 10 to 18.5.

[0027] The preparation method of this invention uses nitrates of M, Co, and Ni as precursors, which are vigorously stirred and mixed to form a transparent homogeneous solution. Then, an ammonium carbonate alkaline solution is added dropwise to form a light purple flocculent metal complex precipitate. The prepared precipitate is aged overnight at room temperature, and then centrifuged, washed, dried at low temperature, and calcined at high temperature to form M1Co3Ni6O. x This invention relates to a composite metal oxide catalyst exhibiting superior methane combustion catalytic activity, structural stability, and strong resistance to sintering. The M1Co3Ni6O catalyst prepared in this invention... x Composite metal oxide materials are used as catalysts for the low-temperature catalytic combustion of methane to further improve the methane conversion rate and the selectivity of CO2 products.

[0028] The beneficial effects of this invention are:

[0029] 1. The catalyst preparation method of this invention utilizes (NH4)2CO3 as a precipitant, introduces M metal using an in-situ doping method, and calcines it at 500°C in air for 6 hours to obtain M1Co3Ni6O containing highly dispersed metal particles. x Composite oxide catalyst.

[0030] 2. The catalyst preparation method of the present invention incorporates M metal (M is Mn, Cu, Zr), which can increase the oxygen vacancies on the surface of the composite oxide, enhance the redox performance of the catalyst, improve oxygen mobility, reduce the formation energy of chemical adsorption, and is more conducive to the activation of CH4 and O2. At the same time, the prepared catalyst has more stable performance and effectively inhibits the problems of surface metal cation aggregation and sintering deactivation.

[0031] 3. The Mn1Co3Ni6O prepared by this invention x Three-way catalyst (T) 10％ =226℃, T 50％ =306℃, T 90％ =375℃), Cu1Co3Ni6O x Three-way catalyst (T) 10％ =237℃, T 50％ =306℃, T 90％ =363℃), Zr1Co3Ni6O x Three-way catalyst (T) 10％ =230℃, T 50％ =309℃, T 90％ The catalyst prepared at 375℃ exhibits superior performance compared to catalysts prepared by the gel-sol method and solid-state milling method, as well as those using NaOH as a precipitant, and is superior to supported catalysts of 10wt.% Cu / Co3Ni6O. x The catalyst exhibits superior performance compared to 1 wt.% Pd / Co3Ni6O4, a precious metal. x The catalyst exhibits superior performance compared to the binary cobalt-nickel catalyst Co3Ni6O. x Its performance is excellent.

[0032] 4. The synergistic effect of incorporating M, Co, and Ni ternary metals in the catalyst preparation method of this invention can promote the complete low-temperature oxidation of CH4 to CO2 and improve the catalytic combustion performance of methane.

[0033] 5. The ternary metal catalyst M1Co3Ni6O in the catalyst preparation method of this invention x Having more oxygen vacancies is beneficial for the activation of CH4 and the generation of CO2 products, thus improving both the conversion rate of CH4 and the selectivity of CO2.

[0034] 6. The catalyst preparation method of this invention is simple, low-cost, and exhibits superior catalytic performance compared to 1 wt.% Pd / Co3Ni6O.x The catalyst is resistant to sintering, more stable, and has more active sites than supported catalysts. Through research on preparation methods, the catalyst prepared by the co-precipitation method using ammonium carbonate as a precipitant exhibits the best performance. Attached Figure Description

[0035] Figure 1 This is a diagram of a fixed-bed reactor; where 1-raw material gas cylinder; 2-pressure reducing valve; 3-stop valve; 4-fixed-bed reaction tube; 5-heat tracing controller; 6-heat tracing pipe; 7-gas chromatograph;

[0036] Figure 2 The present invention relates to a M-doped ternary cobalt-nickel catalyst (Mn1Co3Ni6O). x Cu1Co3Ni6O x Zr1Co3Ni6O x ) and binary cobalt-nickel catalyst Co3Ni6O x And a comparison chart of blank's methane conversion rates;

[0037] Figure 3 This invention uses a different preparation method for a ternary cobalt-nickel catalyst (Cu1Co3Ni6O). x Cu1Co3Ni6O x -1, Cu1Co3Ni6O x -2, Cu1Co3Ni6O x -3) Comparison of methane conversion rates with blank;

[0038] Figure 4 This invention relates to cobalt-nickel catalysts (Cu1Co3Ni6O) prepared by different supporting methods. x 10wt% Cu / Co3Ni6O x 1wt% Pd / Co3Ni6O x ) and binary cobalt-nickel catalyst Co3Ni6O x A comparison chart of methane conversion rates;

[0039] Figure 5 The present invention uses cobalt-nickel catalysts (Cu1Co) in different proportions. 2.5 Ni 6.5 O x Cu1Co3Ni6O x Cu1Co 3.5 Ni 5.5 O x Cu1Co 4.5 Ni 4.5 O x A comparison chart of methane conversion rates;

[0040] Figure 6This invention relates to a M-doped ternary cobalt-nickel catalyst (Mn1Co3Ni6O). x Cu1Co3Ni6O x Zr1Co3Ni6O x ) and binary cobalt-nickel catalyst Co3Ni6O x T 10％ T 50％ T 90％ Comparison chart;

[0041] Figure 7 These are ternary cobalt-nickel catalysts (Cu1Co3Ni6O) prepared using different methods. x Cu1Co3Ni6O x -1, Cu1Co3Ni6O x -2, Cu1Co3Ni6O x -3) of T 10％ T 50％ T 90％ Comparison chart;

[0042] Figure 8 These are cobalt-nickel catalysts with different support methods (Cu1Co3Ni6O) x 10 wt.% Cu / Co3Ni6O x 1 wt.% Pd / Co3Ni6O x ) and binary cobalt-nickel catalyst Co3Ni6O x T 10％ T 50％ T 90％ Comparison chart;

[0043] Figure 9 The present invention uses cobalt-nickel catalysts (Cu1Co) in different proportions. 2.5 Ni 6.5 O x Cu1Co3Ni6O x Cu1Co 3.5 Ni 5.5 O x Cu1Co 4.5 Ni 4.5 O x ) of T 10％ T 50％ T 90％ Comparison chart;

[0044] Figure 10 This invention is Cu1Co3Ni6O x Stability test results at 320℃ and normal pressure for 100 hours. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the invention to the following embodiments. Various substitutions and modifications made based on common technical knowledge and conventional methods in the art without departing from the technical concept of the present invention should be included within the scope of the present invention.

[0046] Example 1

[0047] A Mn1Co3Ni6O for low-temperature catalytic combustion of methane x The preparation method of composite metal oxide catalysts (co-precipitation method) includes the following steps:

[0048] Step 1, synthesis of metal mixed solution L1: First, weigh 1.26g Mn(NO3)2·4H2O, 4.37g Co(NO3)2·6H2O, and 8.73g Ni(NO3)2·6H2O samples (all from Sinopharm) and place them in a 250mL beaker. Add 80mL of deionized water and 20mL of ethanol. Sonicate the mixed solution for 2 hours, then place it on a magnetic stirrer and stir magnetically at room temperature for 2 hours until it is completely dissolved, forming a homogeneous and clear solution L1 of metal ions. The total molar amount of all metal cations is 0.05mol, and the molar ratio of the three metal ions is Mn:Co:Ni = 1:3:6, where the concentration of Mn metal cation is 0.05mol / L.

[0049] Step 2, preparation of ammonium carbonate alkaline solution L2: Weigh 96g of (NH4)2CO3 solid into a 1000mL volumetric flask, stir magnetically at room temperature for 2h until the ammonium carbonate solid is completely dissolved to form ammonium carbonate alkaline solution L2 with a concentration of 1.0mol / L.

[0050] Step 3, titration of solutions L1 and L2, includes: 1) adding the (NH4+) solution prepared in step 2 to the clear solution L1 prepared in step 1. 4)2 L2 of alkaline CO3 solution was added, with the temperature controlled at 60℃. The titration was completed within 5 minutes, and the solution was rapidly stirred with a magnetic stirrer. A light purple flocculent precipitate was formed, and the pH value was measured to be 9.6 using pH paper. The solution was then heated and stirred at 60℃ for another 60 minutes to ensure complete precipitation and eventual phase equilibrium. The solid and liquid phases were separated by centrifugation, yielding a light purple flocculent precipitate. The precipitate was aged at room temperature for 12 hours. It was then washed three times with deionized water and anhydrous ethanol, respectively, and dried in a forced-air drying oven at 60℃ for 12 hours to obtain a blocky solid sample. The blocky solid sample was then placed in an agate mortar and ground into powder for 20 minutes.

[0051] Step 4, Mn1Co3Ni6O xThe synthesis of the composite metal oxide involves the following steps: The powder ground in step three is placed in a corundum crucible and then calcined in a muffle furnace at 500°C for 6 hours under static air. The heating rate from room temperature to the calcination temperature is 5°C / min. The resulting black powder catalyst is named Mn1Co3Ni6O. x The prepared catalyst is pressed into tablets and sieved through a 40-60 mesh for later use.

[0052] Example 2

[0053] A Cu1Co3Ni6O for low-temperature catalytic combustion of methane x The preparation method of composite metal oxide catalysts (co-precipitation method) includes the following steps:

[0054] Step 1, synthesis of metal mixed solution L1: First, weigh 1.21g Cu(NO3)2·6H2O, 4.37g Co(NO3)2·6H2O, and 8.73g Ni(NO3)2·6H2O samples (all from Sinopharm) and place them in a 250mL beaker. Add 80mL of deionized water and 20mL of ethanol. Sonicate the mixed solution for 2 hours, then place it on a magnetic stirrer and stir magnetically at room temperature for 2 hours until it is completely dissolved, forming a homogeneous and clear solution L1 of metal ions. The total molar amount of all metal cations is 0.05mol, and the molar ratio of the three metal ions is Cu:Co:Ni = 1:3:6, where the concentration of Cu metal cation is 0.05mol / L.

[0055] Step 2, preparation of ammonium carbonate alkaline solution L2: Weigh 96g of (NH4)2CO3 solid into a 1000mL volumetric flask, stir magnetically at room temperature for 2 hours until the ammonium carbonate solid is completely dissolved to form ammonium carbonate alkaline solution L2.

[0056] Step 3, titration of solutions L1 and L2, includes the following steps: 1) Add the alkaline solution of (NH4)2CO3 prepared in step 2 to the clear solution L1 prepared in step 1. The addition temperature is controlled at 60℃, and the titration is completed within 5 minutes. Stir rapidly with a magnetic stirrer until a light purple flocculent precipitate forms. The pH value is measured to be 9.6 using pH paper. Continue heating and stirring at 60℃ for 60 minutes to ensure sufficient precipitation and final phase equilibrium. Centrifuge to separate the solid and liquid phases, and obtain a light purple flocculent precipitate. Aging the prepared precipitate at room temperature overnight. Then wash it three times with deionized water and anhydrous ethanol respectively, and place it in a forced-air drying oven to dry at 60℃ for 12 hours to obtain a block solid sample. Place the block solid sample in an agate mortar and grind it into powder for 20 minutes.

[0057] Step 4, Cu1Co3Ni6O xThe synthesis of the composite metal oxide involves the following steps: The powder ground in step three is placed in a corundum crucible and then calcined in a muffle furnace at 500°C for 6 hours under static air. The heating rate from room temperature to the calcination temperature is 5°C / min. The resulting black powder catalyst is named Cu1Co3Ni6O. x The prepared catalyst is pressed into tablets and sieved through a 40-60 mesh for later use.

[0058] Example 3

[0059] A Zr1Co3Ni6O for low-temperature catalytic combustion of methane x The preparation method of composite metal oxide catalysts (co-precipitation method) includes the following steps:

[0060] Step 1, synthesis of metal mixed solution L1: First, weigh 2.15g Zr(NO3)4·5H2O, 4.37g Co(NO3)2·6H2O, and 8.73g Ni(NO3)2·6H2O samples (all from Sinopharm) and place them in a 250mL beaker. Add 80mL of deionized water and 20mL of ethanol. Sonicate the mixed solution for 2 hours, then place it on a magnetic stirrer and stir magnetically at room temperature for 2 hours until it is completely dissolved, forming a homogeneous and clear solution L1 of metal ions. The total molar amount of all metal cations is 0.05mol, and the molar ratio of the three metal ions is Zr:Co:Ni=1:3:6, where the concentration of Zr metal cation is 0.05mol / L.

[0061] Step 2, preparation of ammonium carbonate alkaline solution L2: Weigh 96g of (NH4)2CO3 solid into a 1000mL volumetric flask, stir magnetically at room temperature for 2 hours until the ammonium carbonate solid is completely dissolved to form ammonium carbonate alkaline solution L2.

[0062] Step 3, titration of solutions L1 and L2, includes the following steps: 1) Add the alkaline solution L2 of (NH4)2CO3 prepared in step 2 to the clear solution L1 prepared in step 1. The addition temperature is controlled at 60℃, and the titration is completed within 5 minutes. Stir rapidly with a magnetic stirrer until a light purple flocculent precipitate forms. The pH value is measured to be 9.6 using pH paper. Continue heating and stirring at 60℃ for 60 minutes to ensure sufficient precipitation and final phase equilibrium. Centrifuge to separate the solid and liquid phases, and obtain a light purple flocculent precipitate. Aging the prepared precipitate at room temperature overnight. Then wash it three times with deionized water and anhydrous ethanol respectively, and place it in a forced-air drying oven to dry at 60℃ for 12 hours to obtain a block solid sample. Place the block solid sample in an agate mortar and grind it into powder for 20 minutes.

[0063] Step 4, Zr1Co3Ni6O xThe synthesis of the composite metal oxide involves the following steps: The powder ground in step three is placed in a corundum crucible and then calcined in a muffle furnace at 500°C for 6 hours under static air. The heating rate from room temperature to the calcination temperature is 5°C / min. The resulting black powder catalyst is named Zr1Co3Ni6O. x The prepared catalyst is pressed into tablets and sieved through a 40-60 mesh for later use.

[0064] Example 4

[0065] The catalyst was prepared using the same method and steps as in Example 2, except that Cu(NO3)2·6H2O was not added to the mixed solution L1 in step one. Other steps and conditions were consistent with Example 2. The prepared catalyst was named Co3Ni6O. x Compress the tablets and sieve them to a mesh size of 40-60 for later use.

[0066] Test process:

[0067] An atmospheric pressure fixed-bed reactor was used to test the CH4 catalytic combustion activity of the catalyst. First, 200 mg of 40-60 mesh catalyst particles prepared in Examples 1-3 and Comparative Examples 1-6 were weighed out and mixed evenly with 400 mg of 40-60 mesh quartz sand particles. The mixture was then loaded into a Φ8 mm reaction tube (e.g., a fixed-bed reactor). Figure 1 (As shown), then 1 vol.% CH4 (raw material gas) is introduced, with air used as the balance gas. The gas flows out from gas cylinder 1, passing sequentially through pressure reducing valve 2 and shut-off valve 3. The flow rate is controlled at 40 mL / min by the flow meter of the fixed-bed controller 4. The raw material gas enters reaction tube 5 to undergo the reaction. The outlet gas is heated to 120°C by temperature controller 6 to prevent liquefaction and blockage of the gas path. A portion of the outlet gas is sent to a gas chromatograph to determine the catalyst activity, while the remainder is vented. The reaction space velocity (GHSV) is 12000 mL / h. -1 ·g -1 The pressure gauge was maintained at 0 MPa (relative to atmospheric pressure). Qualitative and quantitative analysis of the products of CH4 catalytic combustion was performed using gas chromatography (GC).

[0068] Test conditions:

[0069] The test temperature is 250-500℃, and the measurement is taken every 50℃. Each temperature point is maintained for 30 minutes and then measured 3 times to obtain the average value.

[0070] Comparative Example 1

[0071] The catalyst Cu1Co3Ni6O was prepared using the same method and steps as in Example 2. x-1, but the difference from Example 2 is that NaOH is used as the precipitant in step two (replacing ammonium carbonate), and the concentration is prepared to be 1.0 mol / L. Other steps and conditions are the same as in Example 2, and a black powder catalyst is finally obtained, named Cu1Co3Ni6O. x -1. Compress the prepared catalyst into tablets and sieve them through a 40-60 mesh for later use.

[0072] Comparative Example 2

[0073] Preparation of Cu1Co3Ni6O catalyst using the sol-gel method x -2, the preparation method is as follows:

[0074] Step 1: Weigh 1.21g Cu(NO3)2·6H2O, 4.37g Co(NO3)2·6H2O, and 8.73g Ni(NO3)2·6H2O into a 250mL beaker, add 20mL of deionized water, and heat and stir at 60℃ for 60-120min. After the solids are completely dissolved, a transparent liquid L1 is formed, in which the molar ratio of Cu, Co, and Ni is 1:3:6, the concentration of Cu metal ions is 0.05mol / L, the concentration of Co metal ions is 0.15mol / L, and the concentration of Ni metal ions is 0.30mol / L.

[0075] Step 2: Add 14.409g of citric acid to solution L1 and mix vigorously to obtain a homogeneous viscous solution, forming metal precursor solution L2. The molar ratio of citric acid to metal is maintained at 1.5:1.

[0076] Step 3: Stir the metal precursor solution L2 continuously at 60°C for 30-60 minutes to evaporate excess solvent and form a sponge-like gel L3, and age it at 60°C for 4 hours.

[0077] Step 4: Transfer L3 to an oven at 60°C and dry for 12 hours. After the sample is completely dry, grind it into powder using a mortar and pestle for 20 minutes.

[0078] Step 5: Transfer the powder to a muffle furnace and calcine it at 500°C in air at a heating rate of 5°C / min for 6 hours. The resulting catalyst is named: Cu1Co3Ni6O x -2, compress into tablets and sieve to 40-60 mesh for later use.

[0079] Comparative Example 3

[0080] Catalyst preparation using solid-state grinding method to prepare Cu1Co3Ni6O x -3, the preparation method is as follows:

[0081] Step 1: Weigh 1.21g Cu(NO3)2·6H2O, 4.37g Co(NO3)2·6H2O and 8.73g Ni(NO3)2·6H2O and put them into an agate mortar and grind them manually for 30 to 60 minutes to achieve homogeneity and form a solid mixture S1.

[0082] Step 2: Add 20g (NH4)2CO3 to S1, then mix and grind for 30-60 minutes until a uniform paste S2 is formed.

[0083] Step 3: Wash S2 three times by centrifugation with deionized water and ethanol respectively, and dry it in an oven at 60℃ for 12 hours until the sample is completely dry. Grind the obtained solid sample in an agate mortar for 30-60 minutes.

[0084] Step four: Transfer the solid sample obtained in step three to a muffle furnace. The heating rate should be 5℃ / min. Calcinate in air at 500℃ for 6 hours. Press the calcined sample into tablets and sieve them to 40-60 mesh. The prepared catalyst is named Cu1Co3Ni6O. x -3, compress into tablets and sieve to 40-60 mesh for later use.

[0085] Comparative Example 4

[0086] A non-precious metal supported catalyst, 10 wt.% Cu / Co3Ni6O, was prepared by in-situ impregnation. x The specific steps are as follows:

[0087] Step 1: Weigh 755 mg Cu(NO3)2·6H2O into a 25 mL volumetric flask, add 20 mL of deionized water, and stir at room temperature for 60–120 min to form a Cu metal solution L1.

[0088] Step 2: Add 2g of Co3Ni6O to L1 x The powder was ultrasonically treated for 2 hours, then stirred overnight. It was then impregnated at 60°C for 60 minutes until completely evaporated to form a solid precursor S1.

[0089] Step 3: Transfer S1 to a vacuum drying oven at 60℃ for 12 hours. After complete drying, grind it finely in a mortar and pestle, then scrape it off with a spatula and place it in a corundum crucible. Place the crucible in a tube furnace under a pure hydrogen atmosphere (flow rate of 100 mL / min), a heating rate of 3℃ / min, and a calcination temperature of 400℃ for 2 hours. After naturally cooling to room temperature, remove the catalyst. The prepared catalyst is named: 10wt.% Cu / Co3Ni6O x Compress the tablets and sieve them to a mesh size of 40-60 for later use.

[0090] Comparative Example 5

[0091] A noble metal supported catalyst, 1 wt.% Pd / Co3Ni6O, was prepared by in-situ impregnation. x The specific steps are as follows:

[0092] Step 1: Weigh 26.5 mg of palladium chloride into a 10 mL volumetric flask, add 8 mL of deionized water and 2 mL of hydrochloric acid to prepare a 0.01 mg / mL PdCl2 solution.

[0093] Step two, add the weighed 1g Co3Ni6O x Add 10 mL of PdCl2 solution to the powder, sonicate for 2 h, and then stir at room temperature for 12 h. Then soak at 60 °C for 2 h, transfer the beaker to a vacuum drying oven and dry at 110 °C for 12 h; grind the dried sample in a mortar and pestle for 60 min.

[0094] Step 3: After scraping the sample with a spatula, place it in a corundum crucible and put it in a tube furnace. Under a pure hydrogen atmosphere (flow rate of 100 mL / min), the temperature is increased at a rate of 3 °C / min, and the calcination temperature is 400 °C for 2 hours. After naturally cooling to room temperature, remove the sample, grind it finely with a mortar and pestle, and then press it into tablets and sieve it to 40–60 mesh. The resulting catalyst is named 1 wt.% Pd / Co3Ni6O x Compress the tablets and sieve them for later use.

[0095] Comparative Example 6

[0096] The catalyst Cu1Co was prepared using the same method as in Example 2. 2.5 Ni 6.5 O x However, compared to Example 2, the sample amounts weighed in step one were 1.21g Cu(NO3)2·6H2O, 3.64g Co(NO3)2·6H2O, and 9.46g Ni(NO3)2·6H2O (all from Sinopharm), ultimately yielding a black powder catalyst named Cu1Co. 2.5 Ni 6.5 O x The prepared catalyst is pressed into tablets and sieved through a 40-60 mesh for later use.

[0097] Comparative Example 7

[0098] The catalyst Cu1Co was prepared using the same method as in Example 2. 3.5 Ni 5.5 O x However, compared to Example 2, the sample amounts weighed in step one were 1.21g Cu(NO3)2·6H2O, 5.10g Co(NO3)2·6H2O, and 8.00g Ni(NO3)2·6H2O (all from Sinopharm), ultimately yielding a black powder catalyst named Cu1Co. 3.5 Ni5.5 O x The prepared catalyst is pressed into tablets and sieved through a 40-60 mesh for later use.

[0099] Comparative Example 8

[0100] The catalyst Cu1Co was prepared using the same method as in Example 2. 4.5 Ni 4.5 O x However, unlike Example 2, the sample amounts weighed in step one were 1.21g Cu(NO3)2·6H2O, 6.56g Co(NO3)2·6H2O, and 6.56g Ni(NO3)2·6H2O (all from Sinopharm), ultimately yielding a black powder catalyst named Cu1Co. 4.5 Ni 4.5 O x The prepared catalyst is pressed into tablets and sieved through a 40-60 mesh for later use.

[0101] Catalyst activity tests were performed on Examples 1-4 and Comparative Examples 1-8, and compared with blank experiments (without any catalyst added):

[0102] Online analysis of the products was performed using a GC-950 gas chromatograph (Haixin Chromatography, China) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID). The TCD column was 2 m long, packed with TDX-01 carbon molecular sieve, and helium (He) was used as the carrier gas. The FID column was a Plot Q capillary column with dimensions of 30 m × 0.32 mm × 10 μm, and He was used as the carrier gas. The conversion rate of CH4 in the main analytical gas was analyzed.

[0103] The formula for calculating the conversion rate of CH4 is:

[0104]

[0105] Among them, [CH4] in Indicates the volume fraction (vol.%) of CH4 before the reaction, [CH4] out This indicates the volume fraction (vol.%) of CH4 after the reaction.

[0106] The activity test effect is achieved using T. 10％ T 50％ T 90％ As an indicator for evaluating catalyst activity, T refers to CH4 conversion rates of 10%, 50%, and 90%, respectively. 10％ T represents the ignition temperature of the methane combustion reaction. 50％ T represents the moderate transition temperature. 90％ Representing the complete combustion temperature, it is an important indicator for measuring the catalytic combustion activity of CH4.

[0107] Cu1Co3Ni6O prepared by coprecipitation method was tested using an atmospheric pressure fixed-bed reactor. x The stability of the catalyst in the combustion of CH4 was tested (test duration: 100 h). The catalyst particle size was 40-60 mesh, the catalyst dosage was 200 mg, and it was uniformly mixed with 400 mg of 40-60 mesh quartz sand particles and then loaded into a Φ8 mm reaction tube (e.g., Figure 1 (As shown), then 1 vol.% CH4 of the raw material gas is introduced, with air as the equilibrium gas. The gas flow rate is 40 mL / min, and the reaction space velocity is GHSV = 12000 mL·h. -1 ·g -1 The pressure gauge was maintained at 0 MPa (relative to atmospheric pressure). Qualitative and quantitative analysis of the products of CH4 catalytic combustion was performed using gas chromatography (GC).

[0108] The test temperature was kept constant at 320℃, and tests were conducted once every 1 hour, for a total of 100 data points. The test results are as follows: Figure 10 As shown.

[0109] Table 1 shows the Mn1Co3Ni6O prepared according to the present invention. x Cu1Co3Ni6O x Zr1Co3Ni6O x A comparison of the performance of ternary catalysts prepared by co-precipitation with NaOH, gel-sol method, and solid-state grinding method, and their performance with that of a non-noble metal supported catalyst 10wt.% Cu / Co3Ni6O x And precious metals 1 wt.% Pd / Co3Ni6O x Catalyst performance comparison with binary cobalt-nickel catalyst Co3Ni6O x The activity comparison.

[0110] Table 1 shows the low-temperature catalytic combustion catalyst for methane, M1Co3Ni6O. x Performance comparison chart

[0111]

[0112] Table 1 shows the T values ​​of catalytic CH4 combustion obtained from four examples and eight comparative examples prepared in this invention. 10％ T 50％ T 90％ Table 1. Analysis of Table 1 leads to the conclusion that Mn1Co3Ni6O prepared by co-precipitation method (ammonium carbonate as the precipitant)... x Cu1Co3Ni6O x Zr1Co3Ni6O xTernary composite metal oxide catalysts exhibit the best performance in low-temperature catalytic CH4 combustion, with a significant reduction in intermediate and complete conversion temperatures. This indicates that doping cobalt-nickel catalysts with transition metals such as Mn, Cu, and Zr has a remarkable effect on improving the performance of methane catalytic combustion, providing experimental evidence and scientific guidance for industrial applications such as low-temperature and high-efficiency combustion of natural gas.

[0113] Figure 2 This is a comparison of the CH4 combustion conversion rates of cobalt-nickel catalysts doped with M (Mn, Cu, Zr) and those without M doping. Figure 2 The cobalt-nickel catalysts doped with M (Mn1Co3Ni6O) were obtained. x Cu1Co3Ni6O x Zr1Co3Ni6O x The conversion rate of CH4 combustion catalyzed by the catalyst was significantly improved compared with that of the cobalt-nickel catalyst without M doping. The CH4 conversion rate reached 100% at around 380℃, while the CH4 conversion rate of the cobalt-nickel catalyst without M doping at 380℃ was only about 75%.

[0114] Figure 3 Catalysts (Cu1Co3Ni6O) prepared by four different methods (coprecipitation method with ammonium carbonate as precipitant), coprecipitation method with NaOH as precipitant, sol-gel method, and solid-state grinding method) are respectively prepared using these methods. x Cu1Co3Ni6O x -1, Cu1Co3Ni6O x -2, Cu1Co3Ni6O x -3) and a comparison graph of CH4 combustion conversion rates with the blank experiment (without any catalyst). Figure 3 The results showed that CuCoNi ternary composite metal oxide catalysts prepared by different methods all exhibited catalytic activity. However, the catalyst Cu1Co3Ni6O prepared by the co-precipitation method with ammonium carbonate as the precipitant showed the best catalytic activity. x The catalytic combustion of CH4 is most effective, with a CH4 conversion rate of 50% achieved at a temperature of 306℃, which is higher than that of Cu1Co3Ni6O prepared using NaOH as a precipitant. x The temperature is 23°C lower than that of Cu1Co3Ni6O prepared by the sol-gel method, which is lower than that of Cu1Co3Ni6O prepared by the sol-gel method. x The temperature is 120°C lower than that of Cu1Co3Ni6O prepared by solid-state grinding, which is lower than that of Cu1Co3Ni6O prepared by solid-state grinding. x The temperature at -3°C is 14°C lower. This indicates that the catalyst Cu1Co3Ni6O prepared by the co-precipitation method (with ammonium carbonate as the precipitant) is... xDuring methane combustion, it can increase the oxygen vacancies on the surface of the composite oxide, enhance the oxygen mobility on the catalyst surface, and is more conducive to activating CH4 and O2. Therefore, it has the best activity in catalyzing CH4 combustion.

[0115] Figure 4 To prepare a non-noble metal supported catalyst 10 wt.% Cu / Co3Ni6O using co-precipitation (ammonium carbonate as precipitant) and in-situ impregnation methods respectively. x And noble metal supported catalyst 1 wt.% Pd / Co3Ni6O x And a comparison chart of CH4 catalytic combustion conversion rates for binary cobalt-nickel catalysts. Figure 4 It can be concluded that in Co3Ni6O x The CH4 conversion rate of catalysts with 10 wt.% Cu was higher than that of catalysts with 1 wt.% Pd, and even higher than that of cobalt-nickel catalysts without metal support. However, neither of these methods produced Cu1Co3Ni6O prepared by co-precipitation (using ammonium carbonate as the precipitant). x It exhibits high catalytic activity for CH4 combustion. Therefore, a co-precipitation method (using ammonium carbonate as the precipitant) was employed to prepare the ternary composite metal oxide catalyst Cu1Co3Ni6O. x It can achieve higher CH4 catalytic combustion activity than other supported catalysts because Cu1Co3Ni6O x The three elements exist in solid solution form, which can expose more active sites on the catalyst surface, which is conducive to the adsorption and activation of CH4, improves the redox performance of the catalyst surface, and lowers the barrier of CH4 oxidation reaction, so that complete oxidation of CH4 can be achieved at a lower temperature.

[0116] Figure 5 This study investigated the effect of the Co / Ni ratio on the catalytic activity of Cu1Co3Ni6O on CH4 combustion while maintaining a constant copper doping level. Four different Cu:Co:Ni ratios of 1:2.5:6.5, 1:3:6, 1:3.5:5.5, and 1:4.5:4.5 were used to prepare CuCoNi ternary composite metal oxide catalysts via a co-precipitation method (ammonium carbonate as the precipitant). The results showed that the catalyst with a molar ratio of Cu:Co:Ni = 1:3:6 was Cu1Co3Ni6O. x It exhibits the strongest intermetallic synergistic effect, achieving the best CH4 catalytic combustion conversion rate under the same test conditions, and T 50％ The temperature dropped significantly by 7 to 18 degrees Celsius.

[0117] Figure 6 T is the T-phase of CH4 combustion between M-doped (Mn, Cu, Zr) cobalt-nickel catalyst and undoped M cobalt-nickel catalyst. 10％ T 50％ T 90％ Comparison chart. (By...) Figure 6The cobalt-nickel catalysts doped with M (Mn1Co3Ni6O) were obtained. x Cu1Co3Ni6O x Zr1Co3Ni6O x T catalyzes the combustion of CH4 10％ T 50％ T 90％ Compared with undoped cobalt-nickel catalysts, all showed significant reductions, with Cu1Co3Ni6O x For example, T 10％ ≈237℃, T 50％ ≈306℃, T 90％ It has a temperature of approximately 363℃, which is 24–87℃ lower than that of binary cobalt-nickel catalysts without Cu doping.

[0118] Figure 7 Catalysts (Cu1Co3Ni6O) prepared by four different methods (coprecipitation method with ammonium carbonate as precipitant), coprecipitation method with NaOH as precipitant, sol-gel method, and solid-state grinding method) are respectively prepared using these methods. x Cu1Co3Ni6O x -1, Cu1Co3Ni6O x -2, Cu1Co3Ni6O x -3) and the T of CH4 combustion compared with the blank experiment (without any catalyst). 10％ T 50％ T 90％ Comparison chart. (By...) Figure 7 The results showed that the catalytic performance of ternary composite oxide catalysts prepared by different methods varied significantly. Among them, the catalyst Cu1Co3Ni6O prepared by the co-precipitation method (with ammonium carbonate as the precipitant) exhibited the best performance. x CH4 has the lowest catalytic combustion conversion temperature, its T 10％ T 50％ T 90％ Compared to Cu1Co3Ni6O x -2 (sol-gel method) T 10％ T 50％ T 90％ They were approximately 81°C, 120°C, and 238°C lower, respectively.

[0119] Figure 8 To prepare a non-noble metal supported catalyst 10 wt.% Cu / Co3Ni6O using co-precipitation (ammonium carbonate as precipitant) and in-situ impregnation methods respectively. x And noble metal supported catalyst 1 wt.% Pd / Co3Ni6O x And the T of CH4 catalytic combustion by binary cobalt-nickel catalyst 10％ T 50％ T 90％Comparison chart. (By...) Figure 8 The ternary composite metal oxide catalyst Cu1Co3Ni6O was obtained x Co3Ni6O supported by noble metal (1 wt.% Pd) and non-noble metal (10 wt.% Cu) x The catalyst exhibits outstanding CH4 catalytic combustion performance, with its T 10％ T 50％ T 90％ 10 wt.% Cu / Co3Ni6O x (In-situ impregnation method) T 10％ T 50％ T 90％ The temperatures are approximately 199℃, 294℃, and 438℃ lower, respectively, thus enabling better complete oxidation of CH4 at medium and low temperatures (≤500℃).

[0120] Figure 9 The T values ​​of CH4 combustion under different proportions of Cu, Co, and Ni (1:2.5:6.5, 1:3:6, 1:3.5:5.5, and 1:4.5:4.5, respectively) are given. 10％ T 50％ T 90％ Comparison chart. The study found that Cu1Co3Ni6O x The conversion temperature of catalytic CH4 combustion is significantly reduced, and its T0 10％ T 50％ T 90％ Compared to Cu1Co 3.5 Ni 5.5 O x T 10％ T 50％ T 90％ The temperatures are approximately 13°C, 16°C, and 26°C lower, respectively. Therefore, a suitable Co / Ni ratio is of great significance for the catalytic combustion of CH4.

[0121] Cu1Co3Ni6O was tested using an atmospheric pressure fixed-bed reactor. x The 100-hour stability of the catalyst in the catalytic combustion of CH4 was determined using 200 mg of catalyst, uniformly mixed with 400 mg of quartz sand, and 1 vol.% CH4 was introduced as the feed gas. Air was used as the equilibrium gas at a flow rate of 40 mL / min and a reaction space velocity (GHSV) of 12000 mL·h. -1 ·g -1 The pressure gauge was kept at 0 MPa (relative to atmospheric pressure). The test temperature was kept constant at 320℃, and tests were conducted once every 1 hour of reaction, for a total of 100 data points. Figure 10 To test the stability, the results of the Cu1Co3Ni6O test were obtained. xThe catalyst exhibits superior catalytic activity, stable structure, and strong resistance to sintering during the isothermal catalytic combustion of CH4. The conversion rate of CH4 remains essentially unchanged during the 100-hour test period.

Claims

1. The application of a composite metal oxide catalyst in the low-temperature catalytic combustion of methane, characterized in that, The preparation method includes the following steps: Step 1, the synthesis of the metal mixed solution L1, is as follows: First, weigh out the metal nitrates of metals M, Co, and Ni respectively, put them into a container, add deionized water and aqueous solution of ethanol, and mix until the salts dissolve to form solution L1; wherein the molar ratio of M, Co, and Ni is M:Co:Ni=1:3:6; wherein the concentration of metal ions of M in the aqueous solution is 50~55μmol / mL; Step 2, preparation of ammonium carbonate alkaline solution L2, the steps are as follows: use (NH4)2CO3 solid as precipitant, and prepare (NH4)2CO3 solution with a concentration of 1~1.15mol / L; Step 3, titration of solutions L1 and L2, includes the following steps: 1) Add the alkaline solution L2 of (NH4)2CO3 prepared in step 2 to solution L1 prepared in step 1, controlling the addition temperature at 55~60℃, while stirring and titrating. Stop titrating when the pH of solution L1 is measured to be 9~10, and continue stirring at 55~60℃ for 60~120 min to separate the solid and liquid, and collect the precipitate; 2) Age the precipitate prepared in step 1) at room temperature for 10~12 h; 3) Then wash with deionized water and anhydrous ethanol 3~4 times respectively, and dry at 60~80℃ for 8~12 h to obtain a block solid sample; 4) Grind the block solid sample into powder. Step 4, M1Co3Ni6O x Synthesis of composite metal oxide: The powder ground in step three above was placed in a muffle furnace and calcined at 490-510℃ for 3-6 h in a static air atmosphere. The heating rate from room temperature to the calcination temperature was 3-5℃ / min. Finally, a black powder catalyst was obtained, named M1Co3Ni6O. x x is the coordination number of oxygen calculated based on the stoichiometry of the metal valence state; The black powder in step four is Mn1Co3Ni6O. x Cu1Co3Ni6O x or Zr1Co3Ni6O x , where x is the coordination number of oxygen in the three oxides, calculated based on the stoichiometric coefficients of the metal valence states.

2. The application according to claim 1, characterized in that, The preparation method includes the following steps: Step 1, the synthesis of the metal mixed solution L1, is as follows: First, weigh out the metal nitrates of metals M, Co, and Ni respectively, put them into a container, add deionized water and aqueous solution of ethanol, and mix until the salts dissolve to form solution L1; wherein the molar ratio of M, Co, and Ni is M:Co:Ni=1:3:6; wherein the concentration of metal ions of M in the aqueous solution is 50.5~52.5μmol / mL; Step 2, preparation of ammonium carbonate alkaline solution L2, the steps are as follows: use (NH4)2CO3 solid as precipitant, and prepare (NH4)2CO3 solution with a concentration of 1~1.05 mol / L; Step 3, titration of solutions L1 and L2, includes the following steps: 1) Add the alkaline solution L2 of (NH4)2CO3 prepared in step 2 to solution L1 prepared in step 1, controlling the addition temperature at 55~60℃, while stirring and titrating. Stop titrating when the pH of solution L1 is measured to be 9.2~9.6, and continue stirring at 55~60℃ for 60~80 min to separate solid and liquid, and collect the precipitate; 2) Age the precipitate prepared in step 1) at room temperature for 10~12 h; 3) Then wash with deionized water and anhydrous ethanol 3~4 times respectively, and dry at 60~80℃ for 8~12 h to obtain a block solid sample; 4) Grind the block solid sample into powder; Step 4, M1Co3Ni6O x Synthesis of composite metal oxide: The powder ground in step three above was calcined in a muffle furnace at 495-505℃ for 5.5-6 h under static air atmosphere. The heating rate from room temperature to the calcination temperature was 3-5℃ / min. Finally, a black powder catalyst was obtained, named M1Co3Ni6O. x M represents Mn, Cu, and Zr, respectively, and x is the coordination number of oxygen calculated based on the stoichiometric coefficients of the metal valence states.

3. The application according to claim 1, characterized in that, In step one, the nitrate of M is Mn(NO3)2·4H2O, Zr(NO3)4·5H2O or Cu(NO3)2·6H2O, the nitrate of Co is Co(NO3)2·6H2O, and the nitrate of Ni is Ni(NO3)2·6H2O.

4. The application according to claim 1, characterized in that, In step one, the sample is sonicated for 1.5 to 2.0 hours, and then placed on a magnetic stirrer and magnetically stirred at room temperature for 60 to 120 minutes until completely dissolved.

5. The application according to claim 4, characterized in that, In step one, the sample is sonicated for 1.8 to 2.0 hours, and then placed on a magnetic stirrer and magnetically stirred at room temperature for 80 to 120 minutes until completely dissolved.

6. The application according to claim 1, characterized in that, V of the mixed solution in step one 乙醇 :V 水 =1:3.85~4.

2.

7. The application according to claim 6, characterized in that, V of the mixed solution in step one 乙醇 :V 水 = 1:3.95~4.

10.

8. The application according to claim 1, characterized in that, In step two, the amount of (NH4)2CO3 used is 96~96.5g, which is diluted and dissolved with deionized water and then diluted to volume in a 1000mL volumetric flask. The concentration of the (NH4)2CO3 solution is determined to be 1~1.15 mol / L.

9. The application according to claim 8, characterized in that, In step two, the amount of (NH4)2CO3 used is 96~96.5g, which is diluted and dissolved with deionized water and then diluted to volume in a 1000mL volumetric flask. The concentration of the (NH4)2CO3 solution is determined to be 1~1.05mol / L.

10. The application according to claim 1, characterized in that, The titration time in step three is controlled at 5-10 min. After adding (NH4)2CO3 solution, a precipitate is formed, and the mixture is heated and stirred at 55-60°C for 60-120 min.

11. The application according to claim 10, characterized in that, The titration time in step three is controlled at 5-7 min. After adding (NH4)2CO3 solution, a precipitate is formed, and the mixture is heated and stirred at 55-60℃ for 60-80 min.

12. The application according to claim 1, characterized in that, The conditions for the low-temperature catalytic combustion of methane are as follows: the feed gas is 1.0~1.2 vol.% CH4, air and / or oxygen are used as the balance gas, and the reaction space velocity is GHSV = 12000~12500 mL·h. -1 ·g -1 The reaction temperature range is 200~500℃, and the reaction pressure gauge pressure is 0~0.1 MPa.

13. The application according to claim 12, characterized in that, The conditions for the low-temperature catalytic combustion of methane are as follows: the feed gas is 1.0~1.05 vol.% CH4, air and / or oxygen are used as the equilibrium gas, and the reaction space velocity is GHSV = 12000~12500 mL·h. -1 ·g -1 The reaction temperature range is 212~475℃, and the reaction pressure gauge pressure is 0~0.05 MPa.

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