CN111375416A - Monolithic catalyst having perovskite oxide skeleton and method for producing same - Google Patents

Abstract

The invention discloses an integral catalyst with perovskite oxide skeleton and a manufacturing method thereof. There is a perovskite oxide framework layer directly on the perovskite oxide nanoparticle coating, and the perovskite oxide framework has interconnected hollow pores. By directly having the perovskite oxide skeleton layer on the perovskite oxide nanoparticle coating, the invention can fix the perovskite oxide skeleton layer in the honeycomb pores without using an adhesive, which is different from the traditional method. Compared with powder-coated catalysts, the macroporous structure can greatly improve the mutual contact between the catalyst and the gas-phase small molecules, increase the catalytic reaction active sites, and improve the gas-phase reactant diffusion efficiency, thereby improving the catalytic efficiency of the catalyst.

Description

Monolithic catalyst with perovskite oxide framework and method for making the same

technical field

The invention belongs to the field of environmental protection, in particular to a catalyst with a perovskite oxide framework and a manufacturing method thereof, in particular to a method for directly growing a three-dimensional ordered macroporous perovskite oxide framework onto the surface of a cordierite honeycomb ceramic .

Background technique

In the past half century, with the gradual increase of global industrial automation and technology, the problem of environmental pollution has become more and more serious. And bear the brunt of the problem of air pollution in cities. With the increase in the number of motor vehicles worldwide, carbon monoxide (CO), hydrocarbons (CHx), nitrogen oxides (NOx) and other pollutants emitted from the internal combustion engine of motor vehicles Sexual gases do great harm to human health, so governments and institutions around the world have successively formulated increasingly stringent exhaust emission standards. In my country, with the gradual implementation of the most stringent "National VI" emission regulations in history in 2020, this requires the post-treatment purification catalyst of motor vehicle exhaust to have higher catalytic efficiency.

Supported catalysts with precious metals Pt, Pd, Rh as active components are widely used commercial catalysts, but their high price and poor high temperature stability have been criticized in the industry. Some oxide catalysts, such as perovskite, CeOx, etc., have entered the public's field of vision due to their superior high temperature stability, low cost and easy availability. However, traditional powder-supported catalysts greatly limit the catalytic efficiency of catalysts due to their less exposed active sites, disordered pore structure, and poor coating adhesion of active components. The three-dimensionally ordered macroporous framework catalyst can expose more accessible active sites, and the ordered macroporous structure channels will also facilitate the diffusion of gas-phase reactants, both of which will promote the depth of small molecule pollutants fully oxidized. Therefore, the development and growth of three-dimensional ordered macroporous perovskite catalysts on the surface of cordierite honeycomb ceramics is of great significance for the efficient catalysis of gas-phase pollutants.

The invention patent of Chinese Patent Publication No. CN 104399480A discloses a method for preparing a monolithic three-dimensional ordered macroporous structure perovskite catalyst. The centrifugation method is used to assemble the polystyrene colloidal crystal template. The salt precursor is filled into the template, and finally the template is removed by high-temperature calcination to obtain a three-dimensional ordered macroporous structure perovskite catalyst; the three-dimensional ordered macroporous catalyst obtained above is a monolithic macroporous integrated body, which cannot be applied onto an actual cordierite carrier;

The invention patent of Chinese Patent Publication No. CN105642297A discloses a method for coating a perovskite oxide catalyst on the surface of cordierite, and the perovskite oxide with macroporous structure is supported on the γ-Al ₂ O ₃ coating Obtained, the specific method is: roasting the cordierite honeycomb ceramics, then carrying out acid treatment, washing and drying to obtain pretreated cordierite; then putting the pretreated cordierite into aluminum sol for dipping, and vacuum drying and roasting to obtain a pretreated cordierite. The cordierite of the coating; then the cordierite with the coating is put into the PMMA microsphere emulsion and dipped, and after drying, the PMMA microsphere-cordierite is obtained; Finally, the PMMA microsphere-cordierite is put into the catalyst precursor sol and dipped, A cordierite filter coated with a macroporous perovskite oxide catalyst is obtained through vacuum drying and roasting;

The monolithic three-dimensional ordered macroporous catalyst prepared by the above method needs to be coated with a layer of γ-Al ₂ O ₃ on the surface, and γ-Al ₂ O ₃ is prone to phase transition at high temperature, which is easy to reduce the catalyst's performance at high temperature. The overall stability under low temperature, and the coating of γ-Al ₂ O ₃ sol coating will also increase the cost of catalyst preparation; in addition, the cordierite will be acid-treated in this method, which will also affect the structural stability of the cordierite substrate. will have a certain impact; therefore, a method for directly growing a three-dimensional ordered macroporous perovskite oxide catalyst on a cordierite substrate without a binder is particularly needed to solve the above-mentioned existing problems. The problem.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, an object of the present invention is to provide a monolithic catalyst with a perovskite oxide framework for the efficient catalysis of gas-phase pollutants. The monolithic catalyst of the present invention is different from ordinary pure catalysts or powder catalysts, and is a monolithic catalyst combining catalyst and substrate obtained by supporting or growing the catalyst on the surface of the substrate. In another aspect of the present invention, it also relates to a method for producing the above-mentioned monolithic catalyst having a perovskite oxide framework.

In order to solve the technical problem of the present invention, the following technical solutions are proposed:

One aspect of the present invention relates to a monolithic catalyst with a perovskite oxide framework, which is characterized in that a honeycomb ceramic with honeycomb pores is used as a carrier, and perovskite oxide nanoparticles with an average thickness of 1-500 nm are arranged on the surface of the honeycomb pores. The coating has a perovskite oxide framework layer directly on the perovskite oxide nanoparticle coating, and the perovskite oxide framework has interconnected hollow pores with an average diameter of 1-10 microns.

The honeycomb ceramics of the present invention include but are not limited to cordierite, mullite and/or silicon carbide ceramics, preferably cordierite honeycomb ceramics.

In a preferred embodiment of the present invention, the perovskite oxide is LaxSr1 _{- xCoO3} , wherein _x is 0.5-0.9, preferably 0.7-0.9.

In a preferred embodiment of the present invention, the honeycomb pores of the honeycomb ceramic have an average diameter of 0.5-3 mm.

In another preferred embodiment of the present invention, the average thickness of the perovskite oxide framework layer is 2-15 microns, preferably 3-10 microns.

By directly having the perovskite oxide skeleton layer on the perovskite oxide nanoparticle coating, the invention can fix the perovskite oxide skeleton layer in the honeycomb pores without using an adhesive, which is different from the traditional method. Compared with powder-coated catalysts, the macroporous structure can greatly improve the mutual contact between the catalyst and the gas-phase small molecules, increase the catalytic reaction active sites, and improve the gas-phase reactant diffusion efficiency, thereby improving the catalytic efficiency of the catalyst.

Another object of the present invention is to provide the application of the above-mentioned catalyst having a perovskite oxide framework in the catalytic oxidation of gas-phase pollutants.

In a preferred embodiment of the present invention, the gas phase pollutants include, but are not limited to, one or a combination of two or more of carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx).

In another aspect of the present invention, the present invention also relates to a method for the manufacture of a monolithic catalyst having a perovskite oxide framework, comprising the steps of:

After ultrasonically washing the honeycomb ceramics with distilled water and an organic solvent in turn, heating and drying to obtain a clean honeycomb ceramic substrate;

Putting the cleaned honeycomb ceramic substrate into the perovskite precursor colloid solution for dipping, and drying after ultrasonication; then roasting to obtain the honeycomb ceramic substrate with the perovskite oxide nanoparticle coating on the surface;

The above-mentioned honeycomb ceramic substrate loaded with the perovskite nanoparticle coating is placed obliquely in the PS microsphere emulsion at an angle of 15 to 75° and dipped to obtain the PS microsphere/perovskite oxide nanoparticle coating/honeycomb ceramic colloid crystal template;

The PS microspheres/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template was dipped in the perovskite precursor colloid solution, heated and dried, and the PS microspheres were calcined to remove the PS microspheres to obtain macroporous perovskite on the surface of honeycomb ceramics. Catalysts for mineral oxide frameworks.

In a preferred embodiment of the present invention, when the honeycomb ceramic substrate is tilted and immersed in the PS microsphere emulsion at a certain angle, the angle is 15-75°, preferably 30-60°, more preferably is 45°. Surprisingly, the inventors of the present invention found that when the honeycomb ceramic substrate is inclined at a certain angle, compared with the conventional vertical placement, the PS microspheres can be inhibited from settling in the honeycomb pores, thereby helping the calcium in the honeycomb ceramics. A uniform PS microsphere template was formed on the surface of the titanium oxide nanoparticle coating.

In a preferred embodiment of the present invention, when the honeycomb ceramic substrate is placed obliquely at a certain angle in the PS microsphere emulsion for dipping, preferably under the condition of forming a negative pressure by a vacuum pump above the upper surface of the honeycomb ceramic substrate Self-assembly. Compared with the case where a vacuum pump is not used, the preferred embodiment of the present invention can accelerate the volatilization of the emulsion, help to shorten the manufacturing time, and also facilitate the uniform formation of PS microspheres on the surface of the perovskite oxide nanoparticle coating of the honeycomb ceramics. PS microsphere template.

In a preferred embodiment of the present invention, when the honeycomb ceramic substrate is placed obliquely at a certain angle and immersed in the PS microsphere emulsion, self-assembly is carried out in a hot water bath, and the hot water bath is preferably Above 45°C and below 100°C. By setting the hot water bath at 45° C. or higher, the evaporation of the emulsion can be accelerated and the production time can be shortened. The damage of PS microspheres at high temperature can be prevented by setting the temperature below 100°C in the hot water bath.

In another preferred embodiment of the present invention, the PS microsphere/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template is heated at 110-130° C. for 3-10 min before impregnation. Compared with the case without heat treatment, the present invention can improve the stability of the template by heat-treating the template, and prevent the PS microspheres from falling off.

In another preferred embodiment of the present invention, after the impregnation of the PS microspheres/perovskite oxide nanoparticles coating/honeycomb ceramic colloidal crystal template, the PS microspheres/perovskite oxide nanoparticles are coated with air flow /The colloidal solution in the honeycomb pores in the honeycomb ceramic colloidal crystal template is blown off; preferably, before firing, the PS microspheres/perovskite oxide nanoparticle coating/honeycomb ceramic template is placed in an oven at 50-70 °C Heating and drying for 30-60h. In the present invention, the PS microspheres/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template after impregnation is treated by air flow, which can effectively prevent the honeycomb pores and their surfaces from being covered and blocked by excess sol, so it is preferred . In the present invention, heating treatment is performed before calcination, which can effectively remove the solvent, thereby ensuring the integrity of the perovskite oxide framework during the calcination process.

In a preferred embodiment of the present invention, the order of washing the honeycomb ceramic substrate with an organic solvent is: hexane, acetone and ethanol, and the ultrasonic washing time of each solvent is 8-12 minutes. By using the organic solvents of different polarities of the present invention for cleaning, impurities such as oil stains on the surface of the honeycomb ceramic substrate can be effectively removed, thereby facilitating the formation of the perovskite oxide nanoparticle coating.

In a preferred embodiment of the present invention, the cleaned honeycomb ceramic substrate is put into the perovskite precursor colloid solution for ultrasonic immersion, and after taking out, the colloid attached to the honeycomb ceramic channel due to the siphon effect needs to be blown off by air flow. solution.

In a preferred embodiment of the present invention, the calcination temperature is 650-800° C., the time is 1-3 h, and the heating rate is 3-7° C./min. The temperature programming of the present invention helps to ensure the integrity of the perovskite oxide framework during the roasting process.

In the manufacture method of the present invention, preferably, the preparation of described PS microsphere emulsion is as follows:

Dissolve polyvinylpyrrolidone (PVP) in a mixed solvent of ethanol and pure water, mix uniformly by ultrasonic, stir in a water bath, then vacuumize, and introduce nitrogen protective gas to obtain a pretreated mixed solution; mix styrene monomer and The initiator is added to the above-mentioned pretreated mixed solution, and the reaction is stirred under heating and nitrogen protection to obtain PS microsphere emulsion; the PS microsphere emulsion is centrifuged, the clear liquid is filtered off, and then the lower layer microspheres are washed with absolute ethanol, Ultrasonic dispersion.

In the above method, preferably, the initiator is azobisisobutyronitrile (AIBN);

In the above method, preferably, the centrifugal rotation speed is 5000-7000 rpm, and the time is 8-20 min;

In the above method, the PS microsphere emulsion is centrifuged and dried, weighed, and then diluted with ethanol to a solid content of 10%; the PS microspheres are monodispersed; preferably, the diameter of the PS microspheres is 1-2 um.

In the above method, preferably, the preparation process of the perovskite precursor colloidal solution includes:

Lanthanum nitrate, strontium nitrate and cobalt nitrate are dissolved in a mixed solvent of ethylene glycol and methanol in a certain proportion, and stirred at room temperature to obtain a mixed sol of perovskite precursors.

Through a series of experimental data of the present invention, it is sufficient to prove that the method for growing the three-dimensional ordered macroporous perovskite oxide framework on the surface of the honeycomb ceramic provided by the present invention is effective and can stably grow the macroporous structure on the surface of the cordierite, It is not easy to fall off; the three-dimensional ordered macroporous monolithic catalyst of the present invention is used for the efficient catalytic oxidation of small molecules of gas-phase pollutants.

For the manufacturing method of the present invention, it has at least one or more or all of the following advantages:

(1) The manufacturing provided in the present invention is to controllably grow the ordered macroporous skeleton of perovskite on the honeycomb ceramic substrate without the need of an adhesive. The manufacturing method of the present invention will not only prevent the honeycomb The porosity of the ceramic has an impact, and it also avoids the potential harm caused by the unstable phase transition of the secondary substrate adhesive at high temperatures;

(2) The manufacturing method provided in the present invention can control the morphology of the perovskite oxide supported on the honeycomb ceramic, the ordered macroporous morphology of the surface-loaded perovskite oxide, and enhance the gas phase reactant. The diffusion efficiency also allows the perovskite oxide to expose more active sites, which promotes the gas-phase catalytic reaction efficiency;

(3) The manufacturing method provided by the present invention has strong controllability and can be regulated in detail according to specific catalytic efficiency requirements. For example, the thickness of the supported perovskite oxide can be determined by the concentration and self-assembly of the PS microsphere emulsion. The number of times can be adjusted; the size of the overall catalyst can be adjusted by the size of the initial substrate cut, etc.

Description of drawings

FIG. 1 is a front-side scanning electron microscope image of a cordierite substrate loaded with perovskite seed nanoparticles in an embodiment.

2-3 are respectively the front and cross-sectional scanning electron microscope images of the PS microsphere-cordierite colloidal crystal template obtained in the embodiment.

FIG. 4 is the PS microsphere-cordierite colloidal crystal template after immersion in the perovskite precursor colloidal solution in the embodiment.

Figures 5-8 are the front scanning electron microscope images of the La _0.8 Sr _0.2 CoO ₃ macroporous morphology perovskite catalyst in the cordierite honeycomb ceramic in the embodiment.

Fig. 9 is the SEM image of the cross-section of the La _0.8 Sr _0.2 CoO ₃ macroporous morphology perovskite catalyst in the cordierite honeycomb ceramic in the embodiment. Compared with the almost non-porous structure of the traditional powder-coated catalyst, the present invention The macroporous structure on the three-dimensional ordered macroporous perovskite monolith catalyst can greatly improve the mutual contact between the catalyst and gas-phase small molecules, increase the catalytic reaction active sites, and improve the gas-phase reactant diffusion efficiency, thereby improving the catalytic efficiency of the catalyst.

10 is a graph showing the activity evaluation curve of the three-dimensional ordered macroporous La _0.8 Sr _0.2 CoO ₃ monolith catalyst prepared in Example 1 and the powder type La _0.8 Sr _0.2 CoO ₃ monolith catalyst for catalytic combustion of methane.

11 is a graph showing the activity evaluation curve of the three-dimensional ordered macroporous La _0.8 Sr _0.2 CoO ₃ monolith catalyst prepared in Example 1 and the powder formula La _0.8 Sr _0.2 CoO ₃ monolith catalyst for carbon monoxide catalytic oxidation.

Detailed ways

In order to further illustrate the technical solutions of the present invention, the above-mentioned technical solutions are described in detail below with specific examples, but the present invention is not limited to the following embodiments.

Example 1:

The present embodiment provides a method for growing a three-dimensional ordered macroporous perovskite La _0.8 Sr _0.2 CoO ₃ framework onto the surface of a cordierite honeycomb ceramic. The specific steps are as follows:

1. Washing of the cordierite carrier

The commercial cordierite honeycomb ceramics (square channel is 1mm × 1mm) were cut into cube-shaped samples with a size of 1cm × 1cm × 1cm, and then ultrasonically cleaned with distilled water, hexane, acetone, and ethanol in turn. The cleaning time of each solvent was 10min; then put the cleaned honeycomb ceramic carrier into an oven at 80°C to dry for 4h to obtain a clean honeycomb ceramic substrate for use;

2. Preparation of Perovskite Precursor Colloidal Solution

Dissolve 1.92 mM lanthanum nitrate, 0.48 mM strontium nitrate, and 2.4 mM cobalt nitrate in a mixed solvent of 15 mL of ethylene glycol and 10 mL of methanol, sonicate to completely dissolve and disperse, then continue stirring at room temperature for 4 hours, and finally stand for 24 hours to obtain calcium Titanite precursor La _0.8 Sr _0.2 CoO ₃ colloidal solution;

3. Coating of perovskite seed nanoparticles

The cleaned honeycomb ceramic substrate was immersed in the perovskite precursor colloidal solution, ultrasonicated for 1 min, taken out, and the excess colloidal solution remaining in the pores was blown off with an ear-washing ball, and placed in a 300°C oven for heating and drying for 10 min; Then, it was calcined at 700 °C for 2 h in a muffle furnace to obtain a cordierite honeycomb ceramic substrate coated with a perovskite seed nanoparticle coating, and the heating rate of the muffle furnace was 5 °C/min;

Fourth, the preparation of PS microsphere emulsion

Weigh 0.84g of polyvinylpyrrolidone (PVP) and dissolve it in a mixed solvent of 80mL of ethanol and 20mL of pure water, and after ultrasonically mixing evenly, pour it into a 250mL three-necked flask; evacuate and introduce N ₂ , and heat the flask to 70°C;

10.9g (12mL) of styrene monomer was added to the above flask with a syringe; then 0.21g of azobisisobutyronitrile (AIBN) was added to 10mL of ethanol, dissolved by ultrasonic, and added to the above flask with a syringe, and finally 2.5mL of distilled water was added to the flask with a syringe and mixed, and the reaction was performed at a constant temperature of 70°C for 24h to obtain a crude PS microsphere emulsion;

The above-mentioned crude PS microsphere emulsion was centrifuged for 12 min at a rotating speed of 6000 rpm, then the supernatant was filtered off, the lower layer microspheres were washed with absolute ethanol, and ultrasonically dispersed; after the above process was repeated three times, a refined PS microsphere emulsion was obtained;

The above-mentioned refined PS microsphere emulsion was centrifuged at 6000rpm for 12min, the supernatant was filtered off, dried at room temperature for 24h, weighed, and then diluted with ethanol to obtain a PS microsphere emulsion with a solid content of 10%; PS obtained by this method The microspheres are monodispersed, and the diameter of the microspheres is about 1.5um;

V. Preparation of PS Microspheres/Perovskite Oxide Nanoparticle Coating/Honeycomb Ceramic Colloidal Crystal Template

Take 1 mL of PS microsphere emulsion with a solid content of 10% and dilute it in a 25 mL small beaker to a solid content of 0.5%; place the coated honeycomb ceramic substrate in the third step at a 45° inclination angle in the beaker , ultrasonic for 30s, connect a circulating water vacuum pump at 1cm above the honeycomb ceramic substrate, the negative pressure is 0.1MPa, and start self-assembly in a constant temperature water bath at 55 °C to obtain PS microspheres/perovskite oxide nanoparticles coating/honeycomb ceramics colloidal crystal template;

6. Preparation of three-dimensional ordered macroporous perovskite catalysts

The PS microsphere/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template prepared in the fifth step was heated at 120 °C for 5 min to improve the stability of the colloidal crystal template; The sphere-cordierite colloidal crystal template was immersed in the perovskite precursor colloidal solution for 8h; after taking it out, the surface of the PS microsphere-cordierite colloidal crystal template and the excess colloidal solution in the channel were blown off with a 430L/h N ₂ gas flow; It was then heated and dried in an oven at 55 °C for 48 h, and finally calcined in a muffle furnace in a temperature-programmed mode to remove the colloidal crystal template to obtain a monolithic catalyst with a three-dimensional ordered macroporous perovskite LSCO framework supported on the surface;

In the above process, the temperature-programmed calcination process is as follows: gradually heat up from room temperature to 200 °C, and hold for 2 hours; then from 200 °C to 400 °C, and hold for 2 hours; then from 400 °C to 600 °C, hold for 6 hours; 700°C, hold for 3h; the heating rate is always maintained at 1°C/min;

The SEM characterization results of the cordierite honeycomb ceramic substrate coated with the perovskite seed nanoparticle coating obtained in this example are shown in FIG. 1 . The scanning electron microscope (SEM) characterization results of PS microspheres/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template obtained by self-assembly of PS microspheres on the surface of cordierite are shown in Fig. 2, the PS microspheres are uniform and dense The surface of the cordierite is arranged neatly, referring to the SEM characterization of the cross section in Figure 3, the arrangement of the PS microspheres on the surface of the substrate is not a thin layer, and can be continuously stacked and arranged. Figure 4 shows the PS microspheres/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template after impregnating the perovskite colloidal crystal sol, and then drying. It can be observed that the assembly of the PS microspheres on the surface of the substrate is very good. Firm, almost no shedding occurred. Figure 5-8 shows the final calcined three-dimensional ordered macroporous structure perovskite oxide catalyst. It can be observed that its structure is dense and orderly, and the macropores are uniform and interconnected, which is extremely important for improving the sufficient contact between gas-phase small molecules and the catalyst. important, and greatly affects its catalytic activity. As shown in Figure 9, the catalyst with macroporous structure does not form a thick stack on the surface of the substrate, but forms a thin layer of macroporous structure, which promotes the diffusion of gas-phase reactants, so the macroporous framework perovskite Ore catalysts can be used for efficient catalysis of gas _- phase pollutants (such as CO, CH, etc.).

Example 2:

In order to further evaluate the catalytic activity of the catalyst of the present invention, the present invention adopts a gas-phase catalytic oxidation activity evaluation experiment for evaluation.

The catalytic combustion activity evaluation test for methane (CH ₄ ) was carried out in a fixed bed reactor simulated by a quartz tube with a diameter of 23 mm. 700 mg of the monolithic catalyst (about 60-70 mg of perovskite active components) was packed in a quartz tube, the quartz tube was placed in a tube furnace, and the temperature was programmed to increase from room temperature to 750 °C. The reaction gas composition (volume fraction) was: 1% CH ₄ , 20% O ₂ , 79% N ₂ , the total flow was 50 mL/min, and the mass space velocity was 43000 mL/(gh). Finally, the components of the reaction tail gas were analyzed online by Fuli GC-9790 gas chromatograph, and the calculation formula of _CH4 conversion rate was:

_CH4 conversion rate (%) = (inlet _CH4 peak area - outlet _CH4 peak area)/ _CH4 methane peak area × 100%

The test results are shown in Fig. 10. It can be seen from the figure that compared with the powder-supported perovskite La _0.8 Sr _0.2 CoO ₃ monolithic catalyst, the three-dimensional ordered macroporous La _0.8 Sr _0.2 CoO ₃ monolith catalyst performs For example, at 50% methane conversion (T ₅₀ ), the conversion temperature of the three-dimensional ordered macroporous La _0.8 Sr _0.2 CoO ₃ monolith catalyst is 552 °C, while the powder type La _0.8 Sr _0.2 CoO ₃ The conversion temperature of the monolithic catalyst reached 600°C, an increase of 48°C.

The catalytic oxidation activity evaluation test of carbon monoxide (CO) was carried out in a fixed bed reactor simulated by a quartz tube with a diameter of 23 mm. 700 mg of the monolithic catalyst (about 60-70 mg of perovskite active components) was packed in a quartz tube, the quartz tube was placed in a tube furnace, and the temperature was programmed to increase from room temperature to 300 °C. The reaction gas composition (volume fraction) was: 1% CO, 5% O ₂ , 94% N ₂ , the total flow was 50 mL/min, and the mass space velocity was 43000 mL/(gh). Finally, the components of the reaction tail gas were analyzed online by Fuli GC-9790 gas chromatograph. The calculation formula of CO conversion rate is:

CO conversion rate (%) = (inlet CO peak area - outlet CO peak area)/inlet CO peak area × 100%

The experimental results are shown in Fig. 11. It can be seen from the figure that, compared with the powder-supported perovskite La _0.8 Sr _0.2 CoO ₃ monolith catalyst, the three-dimensional ordered macroporous La _0.8 Sr _0.2 CoO ₃ monolith catalyst also showed obvious activity advantages; for example, at 50% carbon monoxide conversion (T ₅₀ ), the conversion temperature of the three-dimensional ordered macroporous La _0.8 Sr _0.2 CoO ₃ monolith catalyst was 186 °C, while the powder type La _0.8 Sr _0.2 CoO ₃ The conversion temperature of the monolithic catalyst reached 205℃. It is more obvious that at 200 °C, the three-dimensional ordered macroporous La _0.8 Sr _0.2 CoO ₃ monolith catalyst can achieve a CO conversion rate of 77.1%, while the powder type La _0.8 Sr _0.2 CoO ₃ monolith catalyst can only reach 42.4%. CO conversion rate.

To sum up, the method of the present invention for preparing macroporous catalyst on a honeycomb ceramic substrate does not require the coating of secondary substrate adhesive, the price of raw materials is relatively cheap, the preparation process is relatively simple, and the size of the substrate is also controllable to a certain extent , and the prepared catalyst can have very high catalytic activity.

The applicant declares that the present invention is described in detail by the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed embodiments. Personnel should understand that any improvement of the present invention, equivalent replacement and addition of the product of the present invention, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (10)

1. The monolithic catalyst with the perovskite oxide skeleton is characterized in that honeycomb ceramics with honeycomb pore canals are used as a carrier, a perovskite oxide nano particle coating with the average thickness of 1-500 nm is arranged on the surfaces of the honeycomb pore canals, a perovskite oxide skeleton layer is directly arranged on the perovskite oxide nano particle coating, and the perovskite oxide skeleton has hollow holes which are mutually communicated and have the average pore diameter of 1-10 microns.

2. The catalyst of claim 1, wherein the honeycomb ceramic is selected from one or a combination of two or more of cordierite, mullite, and silicon carbide ceramics.

3. The catalyst according to claim 1, wherein the perovskite oxide is La_xSr_1-xCoO₃Wherein x is 0.5 to 0.9, preferably 0.7 to 0.9.

4. The catalyst according to claim 1, wherein the average diameter of the honeycomb channels of the honeycomb ceramic is 0.5-3 mm.

5. A catalyst according to claim 1, the perovskite oxide skeleton layer having an average thickness of from 2 to 15 microns, preferably from 3 to 10 microns.

6. A method for producing a catalyst having a perovskite oxide skeleton, comprising the steps of:

ultrasonically washing the honeycomb ceramic with distilled water and an organic solvent in sequence, and heating and drying to obtain a clean honeycomb ceramic substrate;

soaking the cleaned honeycomb ceramic substrate in a perovskite precursor colloidal solution, performing ultrasonic treatment, purging and drying; then roasting to obtain a honeycomb ceramic substrate with a perovskite oxide nano particle coating loaded on the surface;

placing the honeycomb ceramic substrate loaded with the perovskite nano particle coating into Polystyrene (PS) microsphere emulsion in an inclined manner at an angle of 15-75 degrees for dipping to obtain a PS microsphere/perovskite oxide nano particle coating/honeycomb ceramic colloidal crystal template;

soaking the PS microspheres/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template in a perovskite precursor colloidal solution, heating and drying, and roasting to remove the PS microspheres to obtain the catalyst with the macroporous perovskite oxide skeleton growing on the surface of the honeycomb ceramic.

7. The method according to claim 6, wherein the honeycomb ceramic substrate is obliquely placed in the PS microsphere emulsion at an angle of 30-60 degrees when being immersed in the PS microsphere emulsion.

8. The method according to claim 6, wherein the honeycomb ceramic substrate is dipped in the PS microsphere emulsion while being tilted at a predetermined angle, and self-assembled while a negative pressure is formed above the upper surface of the honeycomb ceramic substrate by a vacuum pump.

9. The method according to claim 6, wherein the honeycomb ceramic substrate is dipped in the PS microsphere emulsion at an angle and self-assembled in a hot water bath at a temperature of 45 ℃ to 100 ℃.

10. The method according to claim 6, wherein after the PS microsphere/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template is impregnated, the colloidal solution on the surface of the PS microsphere/perovskite oxide nanoparticle coating/honeycomb ceramic colloidal crystal template and in part of the honeycomb channels is blown off by air flow.

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