Flower-like CeO2 loaded transition metal oxide catalytic coating-mesh porous material as well as preparation method and application thereof

Abstract

The invention provides a flower-like CeO2 loaded transition metal oxide catalytic coating-mesh porous material as well as a preparation method and application thereof, and belongs to the technical field of porous medium combustion. A coprecipitation method is utilized, a precipitator and cerium salt are precipitated to prepare flower-shaped CeO2, then transition metal salt is added, flower-shaped CeO2 loaded transition metal oxide is prepared and sprayed to the surface of a net-shaped porous material, and the flower-shaped CeO2 loaded transition metal oxide catalytic coating-net-shaped porous material is obtained after heat treatment. The prepared flower-like CeO2 loaded transition metal oxide catalytic coating-mesh porous material has the characteristics of high infrared radiation performance and low NOx emission, and can be used for porous medium ammonia combustion.

Description

Technical Field

[0001] The invention relates to the technical field of porous medium combustion, and in particular to a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material and a preparation method and application thereof. Background Art

[0002] Ammonia is a new type of zero-carbon fuel and a good hydrogen storage medium. It has no carbon oxide emission during combustion and is a clean fuel with good prospects. However, there are still many problems with ammonia combustion. Compared with hydrocarbon fuels, it has low combustion stability, low combustion temperature, and NO x High emissions and low flame propagation speed. NO from ammonia combustion x It comes from two aspects: one is thermal NO x , that is, the combustion temperature is too high, causing the N2 in the air to react with O2 to produce NO x ; The second is fuel type NO x , that is, ammonia fuel contains N element, which is oxidized into NO during combustion x ; Among them, fuel type NO x is the main source, and fuel-type NO x The generation rate is higher than that of thermal NO x Much faster.

[0003] Porous media combustion is a "super-adiabatic" stable combustion of gas and combustion-supporting air in porous media materials with high temperature resistance and good heat transfer performance. The heat generated during the combustion process is transferred to the upstream of the burner through heat convection and heat conduction, thereby increasing the initial combustion temperature of the premixed gas, achieving direct combustion of low calorific value gas, and widening the lean combustion limit of the fuel and reducing NO x Currently, the stable combustion of pure ammonia can be achieved in porous media, reducing NO x However, there are still challenges in the combustion of ammonia in porous media. First, although porous media combustion technology can reduce NO x Emissions, but can only solve thermal NO x Emissions: The main fuel-type NO produced by ammonia combustion is x Secondly, although the porous medium combustion technology can achieve stable combustion of ammonia, due to the low laminar combustion velocity of ammonia and the fact that the combustion products are mainly H2O(g) and N2(g), it exhibits poor high-temperature radiation performance. As a result, the heat radiated to the outside when ammonia burns in the porous medium is lower than that of hydrocarbon fuels, and the combustion efficiency is not high, which restricts its practical application in industry.

[0004] At present, technicians have conducted in-depth research and technical development to solve the problem of ammonia combustion in porous media. For example, Chinese patent CN 116498980A discloses a porous media combustion device for catalytic pyrolysis combustion of ammonia. This technology uses the combustion flue gas to preheat the ammonia in the catalytic pyrolysis reactor, and partially pyrolyzes the ammonia into N2 and H2 under the action of the catalyst. The mixed gas after pyrolysis is passed into the porous media burner for combustion. This technology is carried out through the design of the burner. The high-temperature flue gas generated by the combustion not only transports energy to the outside, but also preheats the ammonia for catalytic pyrolysis of ammonia. It is very effective in improving combustion efficiency and reducing fuel-type NO x It is beneficial in terms of emissions, but part of the heat from ammonia combustion needs to be used for catalytic pyrolysis of ammonia, resulting in a loss of energy for external transmission, thus affecting the high-temperature radiation performance. At the same time, the added catalytic pyrolysis device also increases the complexity of the combustion system and increases the difficulty of practical application. Summary of the invention

[0005] The purpose of the present invention is to provide a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material and its preparation method and application, the porous medium ammonia combustion flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material NO x It has low emissions, excellent high-temperature infrared radiation efficiency, and a simple preparation process with low cost.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material, comprising the following steps:

[0008] The cerium salt, the first precipitant and water are mixed to perform a first coprecipitation reaction to obtain a flower-shaped cerium dioxide precursor;

[0009] The flower-shaped cerium dioxide precursor is subjected to a first calcination to obtain flower-shaped cerium dioxide;

[0010] The flower-shaped cerium dioxide, transition metal nitrate, a second precipitant and water are mixed to perform a second coprecipitation reaction to obtain a cerium dioxide-loaded transition metal oxide precursor;

[0011] calcining the ceria-supported transition metal oxide precursor for the second time to obtain a ceria-supported transition metal oxide;

[0012] The cerium dioxide loaded transition metal oxide is mixed with a binder, the obtained coating slurry is sprayed on the surface of the mesh porous material, and then dried and heat-treated in sequence to obtain a flower-shaped CeO2 loaded transition metal oxide catalytic coating-mesh porous material.

[0013] Preferably, the cerium salt includes cerium nitrate; the first precipitant includes ammonium bicarbonate, ammonium carbonate, sodium carbonate or sodium bicarbonate; and the molar ratio of the first precipitant to the cerium salt is 1 to 5:1.

[0014] Preferably, the step of mixing the cerium salt, the first precipitant and water comprises: mixing the cerium salt with water to obtain a cerium salt solution, mixing the first precipitant with water to obtain a first precipitant solution, and dropping the first precipitant solution into the cerium salt solution; the concentration of the cerium salt solution is 0.01 to 0.5 mol / L, and the concentration of the first precipitant solution is 0.01 to 0.5 mol / L;

[0015] The temperature of the first coprecipitation reaction is 0-80° C. and the time is 0.1-8 hours.

[0016] Preferably, the temperature of the first calcination is 500-600° C., the holding time is 1-4 hours, and the temperature is increased to the first calcination temperature at a rate of 0.5-5° C. / min.

[0017] Preferably, the transition metal nitrate includes one or more of copper nitrate, manganese nitrate, cobalt nitrate, iron nitrate and nickel nitrate; and the second precipitant includes ammonium bicarbonate, ammonium carbonate, sodium carbonate or sodium bicarbonate.

[0018] Preferably, the dosage ratio of the flower-shaped cerium dioxide, transition metal nitrate and the second precipitant is (10-100) g: (0.01-0.1) mol: (0.01-0.1) mol; and the molar ratio of the second precipitant to the transition metal nitrate is (1-5): 1;

[0019] The step of mixing the flower-shaped cerium dioxide, transition metal nitrate, a second precipitant and water comprises: dispersing the flower-shaped cerium dioxide in water to obtain a flower-shaped cerium dioxide suspension; mixing the transition metal nitrate with water to obtain a transition metal nitrate solution, and mixing the second precipitant with water to obtain a second precipitant solution; adding the transition metal nitrate solution to the flower-shaped cerium dioxide suspension, and then dripping the second precipitant solution; the content of flower-shaped CeO2 in the flower-shaped cerium dioxide suspension is 5 to 50 wt%; the concentration of the transition metal nitrate solution is 0.01 to 0.5 mol / L, and the concentration of the second precipitant solution is 0.01 to 0.5 mol / L.

[0020] Preferably, the temperature of the second coprecipitation reaction is 0-60°C, and the time is 0.5-6h; the temperature of the second calcination is 500-600°C, and the insulation time is 1-4h, and the temperature is increased to the second calcination temperature at a rate of 0.5-5°C / min.

[0021] Preferably, the material of the mesh porous material includes silicon carbide, aluminum oxide or zirconium oxide;

[0022] The heat treatment temperature is 500-650° C., and the heat preservation time is 1-4 hours; the temperature is raised to the heat treatment temperature at a rate of 0.5-3° C. / min.

[0023] The present invention provides a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material prepared by the preparation method described in the above technical solution.

[0024] The present invention provides the application of the flower-shaped CeO2 loaded transition metal oxide catalytic coating-net-shaped porous material described in the above technical solution in the field of porous medium ammonia combustion.

[0025] The present invention provides a method for preparing a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material. The method comprises the following steps: using a coprecipitation method, precipitating a precipitant and a cerium salt to obtain a flower-shaped CeO2, and then loading the transition metal oxide onto the flower-shaped CeO2 to form a special structure of flower-shaped CeO2-loaded transition metal oxide particles. The flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material is sprayed onto the surface of the net-shaped porous material, and the coating formed after heat treatment has high emissivity (mid-infrared emissivity: 91%), high specific surface area (92.7 m 2 / g), high active oxygen content (O active / (O active +O lattice )=54.8%). The prepared flower-shaped CeO2 loaded transition metal oxide catalytic coating-net-shaped porous material has high infrared radiation performance, low NO x The emission characteristics can be used for porous medium ammonia combustion, which can improve the high-temperature radiation performance of ammonia combustion in porous materials and reduce excessive fuel-type NOx emissions.

[0026] Compared with the prior art, the present invention has the following positive effects:

[0027] The present invention combines porous medium combustion technology with catalytic combustion technology, and utilizes the structural characteristics of porous materials with high surface area to spray and prepare flower-shaped CeO2-loaded transition metal oxide catalytic coating on the surface. Since the oxygen vacancies on the surface of cerium oxide have good oxygen storage capacity and redox ability, it is beneficial to utilize unreacted NH3 to NO in the combustion process. x Perform SCR reaction to reduce fuel-type NO x Emissions and reduce the leakage of unburned NH3.

[0028] First, the surface morphology of the coating is adjusted by utilizing the multiple pore structures generated inside the flower-like CeO2 particles and by stacking each other. Improving the microporous degree of the coating surface increases the projection depth and scattering area, which is beneficial to enhancing the absorption and emission of infrared waves in the coating, thereby improving the infrared emissivity. The improvement of infrared emissivity is beneficial to improving the infrared radiation performance of porous materials. Secondly, on the basis of flower-like CeO2, transition metal oxides are loaded to stimulate the oxygen vacancies of CeO2, increase the relative content of surface active oxygen and the lattice oxygen migration rate, thereby increasing the catalytic activity of CeO2. In addition, compared with single metal oxide catalysts, there is a synergistic effect between multi-component metal oxide catalysts, which can significantly improve the catalytic activity, promote the NH3-SCR reaction, and reduce NO x Furthermore, the loaded transition metal oxide is in the form of submicron particles, loaded on the flower-shaped CeO2, with good dispersion, which can inhibit sintering during the combustion process and delay the deactivation of the coating catalyst during the combustion process. The coating prepared by the present invention has the characteristics of high specific surface area, which is also beneficial to the adsorption of ammonia during the combustion process and promotes the catalytic combustion reaction.

[0029] The flower-shaped CeO2 loaded transition metal oxide coating-net-shaped porous material prepared by the present invention has been tested: the radiation efficiency of the porous medium burner at 800-1200°C is 80-92%, the heating efficiency of the porous medium burner is 39-43°C / min, and the NOx emission of the porous medium burner is reduced from 8000-10000ppm to meet the NOx emission standard compared with the porous medium burner without catalytic coating spraying. x Emission standards.

[0030] The present invention has the characteristics of simple process and low cost. The mesh porous material used is not limited to a specific material and has high application flexibility, which can greatly reduce the difficulty of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a SEM image of the flower-shaped CeO2 powder prepared in Example 1 of the present invention;

[0032] Figure 2 This is a SEM image of the flower-shaped CeO2-loaded copper oxide powder prepared in Example 1 of the present invention;

[0033] Figure 3 This is a SEM image of the flower-shaped CeO2 loaded copper and manganese oxide powder prepared in Example 2 of the present invention;

[0034] Figure 4 This is a cross-sectional SEM image of the pore-rib fracture of the flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-like porous material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0036] The present invention provides a method for preparing a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material, comprising the following steps:

[0037] The cerium salt, the first precipitant and water are mixed to perform a first coprecipitation reaction to obtain a flower-shaped cerium dioxide precursor;

[0038] The flower-shaped cerium dioxide precursor is subjected to a first calcination to obtain flower-shaped cerium dioxide;

[0039] The flower-shaped cerium dioxide, transition metal nitrate, a second precipitant and water are mixed to perform a second coprecipitation reaction to obtain a cerium dioxide-loaded transition metal oxide precursor;

[0040] calcining the ceria-supported transition metal oxide precursor for the second time to obtain a ceria-supported transition metal oxide;

[0041] The cerium dioxide loaded transition metal oxide is mixed with a binder, the obtained coating slurry is sprayed on the surface of the mesh porous material, and then dried and heat-treated in sequence to obtain a flower-shaped CeO2 loaded transition metal oxide catalytic coating-mesh porous material.

[0042] The invention mixes cerium salt, a first precipitant and water, performs a first coprecipitation reaction and obtains a flower-shaped cerium dioxide precursor.

[0043] In the present invention, the cerium salt preferably includes cerium nitrate; the first precipitant includes ammonium bicarbonate, ammonium carbonate, sodium carbonate or sodium bicarbonate; the molar ratio of the first precipitant to the cerium salt is preferably 1 to 5:1, more preferably 2 to 3:1.

[0044] In the present invention, the step of mixing the cerium salt, the first precipitant and water preferably comprises: mixing the cerium salt with water to obtain a cerium salt solution, mixing the first precipitant with water to obtain a first precipitant solution, and dropping the first precipitant solution into the cerium salt solution. In the present invention, the cerium salt is preferably dissolved in water, stirred in a temperature range of 0 to 80°C to obtain a cerium salt solution, the precipitant is dissolved in water, stirred in a temperature range of 0 to 80°C to obtain a first precipitant solution, the cerium salt solution is kept stirred continuously in a temperature range of 0 to 80°C, the first precipitant solution is dropped into the cerium salt solution, and the stirring is continued for 0.1 to 3 hours, more preferably 2 hours after the dropwise addition, and then the first coprecipitation reaction is carried out under static conditions.

[0045] In the present invention, the concentration of the cerium salt solution is preferably 0.01-0.5 mol / L, more preferably 0.1-0.3 mol / L; the concentration of the first precipitant solution is preferably 0.01-0.5 mol / L, more preferably 0.1-0.3 mol / L.

[0046] The amount of water used for mixing the cerium salt, the first precipitant and water in the present invention only needs to satisfy the above-mentioned concentrations of the solutions.

[0047] In the present invention, the temperature of the first coprecipitation reaction is preferably 0-80°C, more preferably 0-50°C, further preferably 25-30°C, and the time is preferably 0.1-8h, more preferably 2-6h; the first coprecipitation reaction is preferably carried out under static conditions.

[0048] After completing the first coprecipitation reaction, the present invention preferably filters the obtained product, collects the precipitate by centrifugation, washes the precipitate alternately with deionized water and ethanol, and dries at 80-110° C. for 12-36 hours to obtain a flower-shaped CeO2 precursor powder.

[0049] After obtaining the flower-shaped cerium dioxide precursor, the present invention performs a first calcination on the flower-shaped cerium dioxide precursor to obtain the flower-shaped cerium dioxide.

[0050] In the present invention, the temperature of the first calcination is preferably 500-600°C, more preferably 500-550°C; the holding time is preferably 1-4h, more preferably 2-3h; the temperature is raised to the temperature of the first calcination at a rate of 0.5-5°C / min (more preferably 1-3°C / min); the first calcination is preferably carried out in an air atmosphere. After the calcination is completed, the furnace is cooled to room temperature to obtain a flower-shaped CeO2 powder.

[0051] After obtaining the flower-shaped cerium dioxide, the present invention mixes the flower-shaped cerium dioxide, transition metal nitrate, a second precipitant and water to carry out a second coprecipitation reaction to obtain a cerium dioxide-loaded transition metal oxide precursor.

[0052] In the present invention, the transition metal nitrate preferably includes one or more of copper nitrate, manganese nitrate, cobalt nitrate, iron nitrate and nickel nitrate; the second precipitant preferably includes ammonium bicarbonate, ammonium carbonate, sodium carbonate or sodium bicarbonate. When the transition metal nitrate is two or more of the above, the present invention has no special limitation on the ratio of different types of transition metal nitrates, and any ratio is acceptable.

[0053] In the present invention, the dosage ratio of the flower-shaped cerium dioxide, transition metal nitrate and the second precipitant is preferably 10-100 g:0.01-0.1 mol:0.01-0.1 mol and the molar ratio of the second precipitant to the transition metal nitrate is preferably (1-5):1.

[0054] In the present invention, the step of mixing the flower-shaped cerium dioxide, transition metal nitrate, second precipitant and water preferably includes: dispersing the flower-shaped cerium dioxide in water to obtain a flower-shaped cerium dioxide suspension; mixing the transition metal nitrate with water to obtain a transition metal nitrate solution, mixing the second precipitant with water to obtain a second precipitant solution; adding the transition metal nitrate solution to the flower-shaped cerium dioxide suspension, and then dripping the second precipitant solution. The present invention preferably ultrasonically disperses the flower-shaped CeO2 in water for 1 to 30 minutes, more preferably 10 minutes, to obtain a flower-shaped CeO2 suspension, stirs the above suspension at a speed of 100 to 500 rpm, more preferably 200 rpm, keeps stirring, adds the transition metal nitrate solution, continues stirring for 0.5 to 3 hours to mix evenly, keeps stirring, drips the second precipitant solution into the above suspension, and performs a second coprecipitation reaction.

[0055] In the present invention, the content of flower-shaped CeO2 in the flower-shaped CeO2 suspension is 5-50wt%, more preferably 20-30wt%, the concentration of the transition metal nitrate solution is 0.01-0.5mol / L, more preferably 0.02-0.3mol / L; the concentration of the second precipitant solution is preferably 0.01-0.5mol / L, more preferably 0.04-0.1mol / L.

[0056] The amount of water used in the mixture of the flower-shaped cerium dioxide, transition metal nitrate, second precipitant and water in the present invention only needs to satisfy the above-mentioned concentration ranges of each solution.

[0057] In the present invention, the temperature of the second coprecipitation reaction is preferably 0-60°C, more preferably 25-30°C; the time is preferably 0.5-6h, more preferably 2-5h.

[0058] After completing the second coprecipitation reaction, the present invention preferably filters the obtained product, collects the precipitate by centrifugation, washes the precipitate alternately with deionized water and ethanol, and dries at 80-110° C. for 12-36 hours to obtain a flower-shaped CeO2-loaded transition metal oxide precursor powder.

[0059] After obtaining the ceria-supported transition metal oxide precursor, the present invention performs a second calcination on the ceria-supported transition metal oxide precursor to obtain the ceria-supported transition metal oxide.

[0060] In the present invention, the temperature of the second calcination is preferably 500-600°C, the holding time is preferably 1-4h, more preferably 2-3h, and the temperature is increased to the second calcination temperature at a rate of 0.5-5°C / min (more preferably 1-2°C / min); the second calcination is preferably carried out in an air atmosphere.

[0061] After obtaining the cerium dioxide loaded transition metal oxide, the present invention mixes the cerium dioxide loaded transition metal oxide with a binder, sprays the obtained coating slurry on the surface of the mesh porous material, and sequentially performs drying and heat treatment to obtain a flower-shaped CeO2 loaded transition metal oxide catalytic coating-mesh porous material.

[0062] In the present invention, the binder preferably includes aluminum sol or silica sol; the mass ratio of the ceria-loaded transition metal oxide to the binder is 3:7 to 7:3, more preferably 4:5.

[0063] In the present invention, the material of the mesh porous material preferably includes silicon carbide, aluminum oxide or zirconium oxide; the present invention has no special limitation on the preparation method of the mesh porous material, and the material can be prepared according to methods well known in the art.

[0064] In the embodiment of the present invention, an aluminum oxide mesh porous material is taken as an example: a polyurethane sponge is used as a template, and a slurry coating process is adopted to prepare an Al2O3 mesh porous material:

[0065] 80wt% of corundum fine powder (325 mesh) for plate bricks and 20wt% of α-Al2O3 powder (<1.2μm) were placed in a stirring pot, and 1.5wt% of ammonium lignin sulfonate, 0.4wt% of sodium carboxymethyl cellulose and 0.3wt% of polycarboxylate were added to the mixed powder, and mixed with deionized water. After continuous stirring for 60min, an alumina slurry (solid content of 77.4wt%) was obtained. A polyurethane sponge template was immersed in the alumina slurry, and the excess slurry was squeezed out using a double-roll mill. The obtained blank was placed on a plate. After drying in an oven at 110°C and pre-calcining at 1300°C for 2h, an alumina porous ceramic preform was obtained; subsequently, α-Al2O3 micropowder and deionized water were used as raw materials and ball-milled in a planetary ball mill for 3h to prepare an impregnation slurry (solid content is 71.4wt%); using the above-mentioned impregnation slurry, the alumina porous ceramic preform was impregnated for 0.5h by a vacuum impregnation method, the sample was taken out and dried at 110°C, and then sintered at 1500°C for 2h to obtain an alumina mesh porous material with a specification of 50*50*20mm and a pore density of 10ppi.

[0066] The loading amount of the flower-shaped CeO2-loaded transition metal oxide catalytic coating on the mesh-like porous material of the present invention is preferably 1 to 12 wt %, and more preferably 5 to 8 wt %.

[0067] After spraying the coating slurry onto the surface of the mesh porous material, the present invention preferably dries it at a temperature range of 80 to 110° C. for 12 to 36 hours, performs a heat treatment, and cools it to room temperature with the furnace to obtain a flower-shaped CeO2-loaded transition metal oxide catalytic coating-mesh porous material.

[0068] In the present invention, the heat treatment temperature is preferably 500-650°C, more preferably 500-550°C; the holding time is preferably 1-4h, more preferably 1-2h; the temperature is raised to the heat treatment temperature at a rate of 0.5-3°C / min (more preferably 1-2°C / min).

[0069] The present invention provides a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material prepared by the preparation method described in the above technical solution.

[0070] The present invention provides the application of the flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material in the porous medium ammonia combustion field. The present invention has no special limitation on the application method, and the application can be carried out according to the method known in the art.

[0071] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0072] In the following examples, the preparation of the alumina mesh porous material is as described above.

[0073] Example 1

[0074] 1) Dissolve 21.72g of cerium nitrate hexahydrate in 500mL of deionized water, and stir at 0°C to obtain a cerium nitrate solution with a concentration of 0.1mol / L; dissolve 11.86g of ammonium bicarbonate in 500mL of deionized water, and stir at 0°C to obtain an ammonium bicarbonate solution with a concentration of 0.3mol / L; keep the above cerium nitrate solution at 0°C and continue stirring, add the ammonium bicarbonate solution dropwise to the cerium nitrate solution to obtain a precipitation solution, continue stirring for 2h, keep the above precipitation solution at 0°C and let it stand for 6h, filter and centrifuge to collect the precipitate, wash the precipitate with deionized water and ethanol alternately, and dry it at 110°C for 36h to obtain a flower-shaped CeO2 precursor powder;

[0075] 2) placing the flower-shaped CeO2 precursor powder in a muffle furnace, heating it to 500°C at a rate of 1°C / min in an air atmosphere, keeping it at that temperature for 2 hours, and cooling it to room temperature with the furnace to obtain a flower-shaped CeO2 powder;

[0076] 3) Take 30g of flower-shaped CeO2 powder and place it in deionized water, control the content of flower-shaped CeO2 powder to 20wt%, ultrasonically disperse for 10min, and obtain a flower-shaped CeO2 suspension. Stir the above suspension at a speed of 200rpm, keep stirring, add 100mL of 0.2mol / L copper nitrate (0.02mol) solution, continue stirring for 0.5h to mix evenly, keep stirring, drop 100mL of 0.4mol / L ammonium bicarbonate (0.04mol) aqueous solution into the above suspension to obtain a precipitation solution, continue stirring at 25°C for 5h, filter and centrifuge to collect the precipitate, wash the precipitate alternately with deionized water and ethanol, and dry it at 110°C for 36h to obtain a flower-shaped CeO2-loaded transition metal oxide precursor powder;

[0077] 4) placing the flower-shaped CeO2-loaded transition metal oxide precursor powder into a muffle furnace, heating it to 600°C at a rate of 2°C / min in an air atmosphere, keeping it at that temperature for 2 hours, and cooling it to room temperature with the furnace to obtain a flower-shaped CeO2-loaded transition metal oxide powder;

[0078] 5) Mix the above-mentioned 20g flower-shaped CeO2-loaded transition metal oxide powder with 25g binder (aluminum sol) to prepare a coating slurry, and spray it onto the surface of an alumina mesh porous material (the pore density for each 50*50*20mm is 10ppi). After spraying the coating slurry, dry it at 110°C for 12h, and the loading amount of the formed coating on the mesh porous material is 8wt%; then heat it to 500°C at a rate of 1°C / min, keep it warm for 1h, and cool it to room temperature with the furnace to obtain a flower-shaped CeO2-loaded transition metal oxide catalytic coating-alumina mesh porous material.

[0079] Example 2

[0080] The only difference from Example 1 is that in step 3), a copper nitrate solution and a manganese nitrate solution with a concentration of 0.2 mol / L are respectively prepared, the copper nitrate solution and the manganese nitrate solution are mixed according to a copper: manganese molar ratio of 1:1 to obtain a copper-manganese mixed solution, and the copper-manganese mixed solution is added to the flower-shaped CeO2 suspension, and the total molar number of the copper and manganese metal salts is 0.02 mol.

[0081] Example 3

[0082] The only difference from Example 1 is that in step 3), copper nitrate solution, manganese nitrate solution and cobalt nitrate solution with a concentration of 0.2 mol / L are respectively prepared, and the three solutions are mixed in a copper: manganese: cobalt molar ratio of 1:1:1 to obtain a copper-manganese-cobalt mixed solution, and the copper-manganese-cobalt mixed solution is added to the flower-shaped CeO2 suspension, and the total molar number of the three metal salts of copper, manganese and cobalt is 0.02 mol.

[0083] Characterization and testing

[0084] Figure 1 This is a SEM image of the flower-shaped CeO2 powder prepared in Example 1 of the present invention; Figure 1 It can be seen that the prepared powder presents a flower-like structure with uniform particle size distribution. There are pores inside and between the flower-like particles, forming a multi-layer pore structure. This structure is conducive to improving the absorption and emission of infrared waves in the final coating, thereby improving the infrared emissivity and the high-temperature radiation performance of the porous medium.

[0085] Figure 2 This is a SEM image of the flower-shaped CeO2-loaded copper oxide powder prepared in Example 1 of the present invention; Figure 2 It can be seen that copper oxide is in the form of submicron particles, well dispersed, and loaded on flower-like CeO2 particles.

[0086] Figure 3 This is a SEM image of the flower-shaped CeO2 loaded copper and manganese oxide powder prepared in Example 2 of the present invention; Figure 3 It can be seen that the copper and manganese oxides are in the form of micron-sized particles, which are loaded on the flower-shaped CeO2 particles.

[0087] Figure 4 This is a cross-sectional SEM image of the pore-rib fracture of the flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material prepared in Example 1 of the present invention; Figure 4 It can be seen that the coating is well bonded to the skeleton and the coating has a porous structure.

[0088] Test Case

[0089] The prepared material was placed in a porous media burner for combustion evaluation. The specific tests are as follows:

[0090] NO x Test conditions: The prepared material was placed in a porous medium burner. The test conditions were ammonia flow rate of 4.21 NL / min, air flow rate of 10.02-18.79 NL / min, and the equivalent ratio of ammonia to air was adjusted to 0.8-1.5. The tail gas NO was measured. x emission.

[0091] Heating efficiency test: Place a beaker filled with pure water directly above the porous media burner, monitor the change in water temperature over time, and determine the heating efficiency of the burner.

[0092] The results show that:

[0093] The flower-shaped CeO2-loaded transition metal oxide coating-net-shaped porous material prepared in Example 1 was tested: the mid-infrared emissivity of the flower-shaped CeO2-loaded transition metal oxide powder was as high as 91%, and the specific surface area was 92.7 m 2 / g, with high active oxygen content (O active / (O active +O lattice )=54.8%. The radiation efficiency of the porous medium burner at a combustion temperature of 1000~1200℃ is 80~83%, the heating efficiency of the porous medium burner is 39~40℃ / min, and the NO of the porous medium burner is lower than that of the porous medium burner without catalytic coating. x The emission volume was reduced from 8000-10000ppm to meet the national NO x Emission standard (30mg / m 3 the following).

[0094] The porous medium ammonia combustion flower-shaped CeO2-loaded transition metal oxide coating-net-shaped porous material prepared in Example 2 was tested: the radiation efficiency of the porous medium burner at a combustion temperature of 900-1000°C was 85-88%, the heating efficiency of the porous medium burner was 39-41°C / min, and the NO of the porous medium burner was lower than that of the porous medium burner without catalytic coating. x The emission volume was reduced from 8000-10000ppm to meet the national NO x Emission standard (30mg / m 3 the following).

[0095] The porous medium ammonia combustion flower-shaped CeO2-loaded transition metal oxide coating-net-shaped porous material prepared in Example 3 was tested: the radiation efficiency of the porous medium burner at a combustion temperature of 800-900°C was 88-92%, the heating efficiency of the porous medium burner was 40-43°C / min, and the NO of the porous medium burner was lower than that of the porous medium burner without catalytic coating. x The emission volume was reduced from 8000-10000ppm to meet the national NO x Emission standard (30mg / m 3 the following).

[0096] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material, characterized in that: The following steps are involved: The cerium salt, the first precipitant and water are mixed to perform a first coprecipitation reaction to obtain a flower-shaped cerium dioxide precursor; The flower-shaped cerium dioxide precursor is subjected to a first calcination to obtain flower-shaped cerium dioxide; The flower-shaped cerium dioxide, transition metal nitrate, a second precipitant and water are mixed to perform a second coprecipitation reaction to obtain a cerium dioxide-loaded transition metal oxide precursor; calcining the ceria-supported transition metal oxide precursor for the second time to obtain a ceria-supported transition metal oxide; The cerium dioxide loaded transition metal oxide is mixed with a binder, the obtained coating slurry is sprayed on the surface of the mesh porous material, and then dried and heat-treated in sequence to obtain a flower-shaped CeO2 loaded transition metal oxide catalytic coating-mesh porous material.

2. The preparation method according to claim 1, characterized in that: The cerium salt includes cerium nitrate; the first precipitant includes ammonium bicarbonate, ammonium carbonate, sodium carbonate or sodium bicarbonate; and the molar ratio of the first precipitant to the cerium salt is 1 to 5:

1.

3. The preparation method according to claim 2, characterized in that: The step of mixing the cerium salt, the first precipitant and water comprises: mixing the cerium salt with water to obtain a cerium salt solution, mixing the first precipitant with water to obtain a first precipitant solution, and dropping the first precipitant solution into the cerium salt solution; the concentration of the cerium salt solution is 0.01 to 0.5 mol / L, and the concentration of the first precipitant solution is 0.01 to 0.5 mol / L; The temperature of the first coprecipitation reaction is 0-80° C. and the time is 0.1-8 hours.

4. The preparation method according to claim 3, characterized in that: The temperature of the first calcination is 500-600° C., the holding time is 1-4 hours, and the temperature is raised to the first calcination temperature at a rate of 0.5-5° C. / min.

5. The preparation method according to claim 1, characterized in that: The transition metal nitrate includes one or more of copper nitrate, manganese nitrate, cobalt nitrate, iron nitrate and nickel nitrate; the second precipitant includes ammonium bicarbonate, ammonium carbonate, sodium carbonate or sodium bicarbonate.

6. The preparation method according to claim 1 or 5, characterized in that: The dosage ratio of the flower-shaped cerium dioxide, transition metal nitrate and the second precipitant is (10-100) g: (0.01-0.1) mol: (0.01-0.1) mol; and the molar ratio of the second precipitant to the transition metal nitrate is (1-5): 1; The step of mixing the flower-shaped cerium dioxide, transition metal nitrate, a second precipitant and water comprises: dispersing the flower-shaped cerium dioxide in water to obtain a flower-shaped cerium dioxide suspension; mixing the transition metal nitrate with water to obtain a transition metal nitrate solution, and mixing the second precipitant with water to obtain a second precipitant solution; adding the transition metal nitrate solution to the flower-shaped cerium dioxide suspension, and then dripping the second precipitant solution; the content of flower-shaped CeO2 in the flower-shaped cerium dioxide suspension is 5 to 50 wt%; the concentration of the transition metal nitrate solution is 0.01 to 0.5 mol / L, and the concentration of the second precipitant solution is 0.01 to 0.5 mol / L.

7. The preparation method according to claim 6, characterized in that: The temperature of the second coprecipitation reaction is 0-60°C, and the time is 0.5-6h; the temperature of the second calcination is 500-600°C, and the insulation time is 1-4h, and the temperature is increased to the second calcination temperature at a rate of 0.5-5°C / min.

8. The preparation method according to claim 1, characterized in that: The material of the mesh porous material includes silicon carbide, aluminum oxide or zirconium oxide; The heat treatment temperature is 500-650° C., and the heat preservation time is 1-4 hours; the temperature is raised to the heat treatment temperature at a rate of 0.5-3° C. / min.

9. The flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the flower-shaped CeO2-loaded transition metal oxide catalytic coating-net-shaped porous material as claimed in claim 9 in the field of porous medium ammonia combustion.

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