A CuO / CeO2 catalyst, its preparation method and application

Abstract

The present invention discloses a CuO / CeO2 catalyst, a preparation method thereof, and an application thereof. The preparation method includes step S1 of preparing CeO2 nanospheres; and step S2 of preparing the CuO / CeO2 catalyst. The prepared catalyst has a catalytic effect on the conversion of CO2 by dielectric barrier discharge low-temperature plasma catalysis. The present invention synthesizes hollow mesoporous CeO2 nanospheres, which have a rich pore and cavity structure, providing a good site for loading metals. Their rich oxygen vacancies enable CeO2 to continuously supply active oxygen to the active sites. The prepared CuO / CeO2 catalyst has uniform size and good dispersion. Its CuO-CeO2 interface structure can accelerate the electron transfer rate, providing rich adsorption sites for reactive species, and contributing to the conversion of CO2 to CO in a new catalytic system, namely dielectric barrier discharge plasma synergistic catalysis, showing good catalytic efficiency and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of plasma conversion, and particularly relates to a CuO / CeO2 catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Under the urgent global pursuit of sustainable energy and strict requirements for greenhouse gas emissions reduction, the research and development of technologies for converting greenhouse gases into hydrocarbon fuels has become a key exploration direction in the energy and environmental fields. Among them, the use of plasma-assisted greenhouse gas conversion has shown great potential. However, the current technology is still limited by the problem of low conversion efficiency of target chemicals and fuels. Dielectric barrier discharge plasma is the most widely studied plasma technology at present. Through the collision of high-energy electrons generated by the plasma, carbon dioxide can be directly decomposed into carbon monoxide and oxygen, and the dielectric barrier discharge plasma is used as energy input to promote the conversion of CO2. This application focuses on the research of developing efficient catalysts in the dielectric barrier discharge plasma catalytic system to provide higher CO conversion rate. Summary of the Invention

[0003] The first object of the present invention is to provide a preparation method of a CuO / CeO2 catalyst, which can synthesize hollow mesoporous CeO2 nanospheres, which provide a good site for loading metals. The prepared CuO / CeO2 catalyst helps to catalyze the conversion of CO2 to CO in dielectric barrier discharge plasma, showing good catalytic efficiency and stability.

[0004] The second object of the present invention is to provide a CuO / CeO2 catalyst.

[0005] The third object of the present invention is to provide an application of a CuO / CeO2 catalyst.

[0006] The first object of the present invention is implemented by the following technical solutions:

[0007] A preparation method of a CuO / CeO2 catalyst, which includes the following steps:

[0008] S1. Prepare CeO2 nanospheres;

[0009] S2. Prepare the CuO / CeO2 catalyst:

[0010] S21. Place the CeO₂ nanospheres prepared in step S1 into deionized water. After stirring evenly, add Cu(NO₃)₂·3H₂O and stir for 2 hours to obtain a mixed solution; add 30 mg of the CeO₂ nanospheres to each milliliter of the deionized water; the mass ratio of the Cu(NO₃)₂·3H₂O to the CeO₂ nanospheres does not exceed 1.48:1; by adjusting the mass ratio of the Cu(NO₃)₂·3H₂O to the CeO₂ nanospheres, CeO₂ nanospheres with different Cu contents can be obtained.

[0011] S22. Dry the mixed solution, grind the dried material to obtain a mixed powder.

[0012] S23. Calcinate the mixed powder under an N₂ atmosphere; take it out after cooling to obtain CeO₂-nanospheres composite with CuO and CeO₂, that is, the CuO / CeO₂ catalyst.

[0013] Further, step S1 includes the following steps:

[0014] S11. Mix deionized water and glacial acetic acid, then add Ce(NO₃)₃·6H₂O and stir until completely dissolved to obtain solution A.

[0015] S12. Pour solution A into the ethylene glycol solution, stir until transparent, then pour it into a reaction kettle and heat. After heating, obtain solution B.

[0016] S13. Centrifuge solution B, wash the obtained precipitate three times with deionized water and absolute ethanol respectively, then dry it overnight at 50 - 90 °C, and then grind it.

[0017] S14. Calcinate the ground sample; take it out after cooling to obtain the CeO₂ nanospheres.

[0018] Further, in step S11, the volume ratio of the deionized water to the glacial acetic acid is 1:1; add 0.5 g of Ce(NO₃)₃·6H₂O to each milliliter of the mixed solution of deionized water and glacial acetic acid.

[0019] Further, in step S12, the volume ratio of the ethylene glycol solution to solution A is 15:1; the heating temperature of the reaction kettle is 150 - 200 °C and the time is 2 - 4 hours.

[0020] Further, in step S14, the calcination temperature is 300 - 500 °C, the time is 3 - 5 hours, and the heating rate is 2 °C per minute.

[0021] Further, in the step S22, the temperature for drying the mixture is 70-90 °C and the time is 18-30 hours.

[0022] Further, in the step S23, the calcination temperature is 300-500 °C, the time is 3-5 hours, and the heating rate is 2 °C / minute.

[0023] The second object of the present invention is implemented by the following technical solution:

[0024] A CuO / CeO2 catalyst prepared by a method for preparing a CuO / CeO2 catalyst.

[0025] The third object of the present invention is implemented by the following technical solution:

[0026] Application of the CuO / CeO2 catalyst in the conversion of CO2 to CO by dielectric barrier discharge plasma.

[0027] Advantages of the present invention:

[0028] The present invention synthesizes hollow mesoporous CeO2 nanospheres, which have a rich pore and cavity structure, providing a good site for loading metals. Their rich oxygen vacancies enable CeO2 to continuously supply active oxygen to the active sites. By impregnation calcination method for modification treatment, CuO / CeO2 catalysts with different metal Cu loadings are prepared. They have uniform size and good dispersion, and the CuO-CeO2 interface structure can accelerate the electron transfer rate, providing rich adsorption sites for reactive species, which is helpful for the catalytic conversion of CO2 to CO by dielectric barrier discharge plasma, showing good catalytic efficiency and stability. Description of the drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a schematic diagram of the steps of a method for preparing a CuO / CeO2 catalyst;

[0031] Figure 2 It is a flow chart of a dielectric barrier discharge plasma catalytic system;

[0032] Figure 3Scanning electron micrographs of CuO / CeO2 catalysts with different Cu contents in Example 4: (a, b) CuO / CeO2-sphere-1wt%; (c, d) CuO / CeO2-sphere-5wt%; (e, f) CuO / CeO2-sphere-10wt% SEM;

[0033] Figure 4 TEM at different scales of CuO / CeO2-sphere-5wt% in Example 4: (a, b); (c) HRTEM; (d-g) EDX elemental surface distribution maps;

[0034] Figure 5 Conversion rate within 30 min of the catalyst participating in the reaction;

[0035] Figure 6 CO production rate of the catalyst;

[0036] Figure 7 XRD patterns of the catalyst before and after the reaction (marked as -a in the figure). Detailed implementation manners

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] Example 1

[0039] A preparation method of a CuO / CeO2 catalyst, as Figure 1 shown, which includes steps S1 and S2.

[0040] S1. Prepare CeO2 nanospheres. Step S1 specifically includes:

[0041] S11. Add 2 mL of deionized water and 2 mL of glacial acetic acid (concentration 99.5 wt%) into a beaker. After mixing, add 2 g of Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution A;

[0042] S12. Add 60 mL of ethylene glycol solution (concentration 99.9 wt%) into another beaker, then pour the solution A prepared in step S11 into the beaker, stir vigorously until transparent, and then pour it into a reaction kettle with a volume of 100 mL and heat at 180 °C for 3 h. After heating, obtain solution B;

[0043] S13. Centrifuge solution B at 8000 rpm for 3 min. Wash the obtained precipitate three times with deionized water and anhydrous ethanol respectively, then dry it overnight at 70 °C, and then grind it. The particle size after grinding is ≤100 nm.

[0044] S14. Put the ground sample into a muffle furnace and calcine it at 400 °C for 4 h with a heating rate of 2 °C / min. After cooling to room temperature, take it out to obtain CeO2 nanospheres, denoted as CeO2-sphere.

[0045] S2. Prepare the CuO / CeO2 catalyst. Step S2 specifically includes:

[0046] S21. Add 10 mL of deionized water to a beaker, then put 300 mg of the CeO2-sphere prepared in step S1, stir evenly, and then add 8.86 mg of Cu(NO3)2·3H2O. After vigorously stirring for 24 h, a mixed solution is obtained.

[0047] S22. Heat the mixed solution at 80 °C for 24 h to complete drying. Grind the dried material, and the particle size after grinding is ≤100 nm to obtain a mixed powder.

[0048] S23. Put the mixed powder into a tube furnace and calcine it at 400 °C for 4 h under a N2 atmosphere. After cooling to room temperature, take it out to obtain CeO2-sphere with a Cu loading of 1 wt%, that is, the CuO / CeO2 catalyst, denoted as CuO / CeO2-sphere-1wt%.

[0049] Example 2

[0050] A method for preparing a CuO / CeO2 catalyst, which includes steps S1 and S2.

[0051] S1. Prepare CeO2 nanospheres. Step S1 specifically includes:

[0052] S11. Add 2 mL of deionized water and 2 mL of glacial acetic acid (concentration 99.5 wt%) to a beaker. After mixing, add 2 g of Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution A.

[0053] S12. Add 60 mL of ethylene glycol solution (concentration 99.9 wt%) to another beaker, then pour the solution A prepared in step S11 into the beaker, stir vigorously until transparent, and then pour it into a 100 mL reaction kettle and heat it at 180 °C for 3 h to obtain solution B.

[0054] S13. Centrifuge solution B at 8000 rpm for 3 min. Wash the precipitate obtained after centrifugation three times with deionized water and anhydrous ethanol respectively, then dry it overnight at 70 °C, and then grind it. The particle size after grinding is ≤100 nm;

[0055] S14. Put the ground sample into a muffle furnace and calcine it at 400 °C for 4 h with a heating rate of 2 °C / min. Take it out after cooling to room temperature to obtain CeO2 nanospheres, denoted as CeO2-sphere.

[0056] S2. Prepare the CuO / CeO2 catalyst. Step S2 specifically includes:

[0057] S21. Add 10 mL of deionized water to a beaker, then put 300 mg of the CeO2-sphere prepared in step S1, stir evenly, and then add 44.28 mg of Cu(NO3)2·3H2O. After stirring vigorously for 24 h, a mixed solution is obtained;

[0058] S22. Heat the mixed solution at 80 °C for 24 h to complete drying, grind the dried material, and the particle size after grinding is ≤100 nm to obtain a mixed powder;

[0059] S23. Put the mixed powder into a tubular furnace and calcine it at 400 °C for 4 h under a N2 atmosphere; take it out after cooling to room temperature to obtain CeO2-sphere with a Cu loading of 5 wt%, that is, the CuO / CeO2 catalyst, denoted as CuO / CeO2-sphere-5wt%.

[0060] Example 3

[0061] A method for preparing a CuO / CeO2 catalyst, which includes steps S1 and S2.

[0062] S1. Prepare CeO2 nanospheres. Step S1 specifically includes:

[0063] S11. Add 2 mL of deionized water and 2 mL of glacial acetic acid (concentration 99.5 wt%) to a beaker. After mixing, add 2 g of Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution A;

[0064] S12. Add 60 mL of ethylene glycol solution (concentration 99.9 wt%) to another beaker, then pour the solution A prepared in step S11 into the beaker, stir vigorously until transparent, and then pour it into a 100 mL reaction kettle and heat it at 180 °C for 3 h to obtain solution B;

[0065] S13, centrifuging solution B at 8000 rpm for 3 min, washing the precipitate obtained after centrifugation with deionized water and anhydrous ethanol three times respectively, drying at 70°C overnight, and then grinding. The particle size after grinding is ≤100 nm;

[0066] S14. The ground sample was placed in a muffle furnace and calcined at 400°C for 4 h with a heating rate of 2°C / min. After cooling to room temperature, the sample was taken out to obtain CeO2 nanospheres, which were recorded as CeO2-spheres.

[0067] S2, preparing CuO / CeO2 catalyst. Step S2 specifically comprises:

[0068] S21, add 10 mL of deionized water to a beaker, add 300 mg of CeO2-sphere prepared in step S1, stir evenly, then add 88.55 mg of Cu(NO3)2·3H2O, stir vigorously for 24 h to obtain a mixed solution;

[0069] S22, heating the mixed solution at 80° C. for 24 h to complete drying, grinding the dried material, and grinding the particle size to ≤100 nm to obtain a mixed powder;

[0070] S23. The mixed powder is placed in a tubular furnace and calcined at 400°C for 4 h under a N2 atmosphere; the mixture is taken out after being cooled to room temperature to obtain a CeO2-sphere with a loaded Cu content of 10 wt%, i.e., a CuO / CeO2 catalyst, recorded as CuO / CeO2-sphere-10wt%.

[0071] Example 4

[0072] The CuO / CeO2 catalyst preparation methods of Examples 1, 2, and 3 prepare CuO / CeO2 catalysts loaded with different Cu contents, including: CeO2-sphere loaded with a Cu content of 1wt% (CuO / CeO2-sphere-1wt%), CeO2-sphere loaded with a Cu content of 5wt% (CuO / CeO2-sphere-5wt%), and CeO2-sphere loaded with a Cu content of 10wt% (CuO / CeO2-sphere-10wt%).

[0073] like Figure 3 , 4 As shown, the prepared CuO / CeO2 catalyst is a spherical morphology with CeO2-sphere as the main body, which is relatively evenly distributed, with a particle size of 80~140 nm and a wall thickness of 20~40 nm. The blocky substances attached to the surface are nanoparticles loaded with CuO.

[0074] Transmission electron microscopy observation and X-ray energy spectrum analysis were carried out on CuO / CeO2-sphere-5wt%, as Figure 4 shown. CeO2-sphere is a hollow mesoporous sphere with rich pore and cavity structures, which can provide loading sites for active metals and provide active oxygen. The Ce, Cu, and O elements are relatively evenly distributed on CuO / CeO2-sphere-5wt%, indicating good dispersion of CuO on CeO2-sphere.

[0075] Example 5

[0076] Application of the CuO / CeO2 catalyst of Example 4 in the catalytic conversion of CO2 to CO.

[0077] The CeO2-sphere prepared in step S1 of Example 2, and different catalysts such as CuO / CeO2-sphere-1wt%, CuO / CeO2-sphere-5wt%, and CuO / CeO2-sphere-10wt% of Example 4 were respectively filled into a plasma reactor, and CO2 was introduced and plasma discharge reaction was carried out by using a dielectric barrier discharge (DBD) plasma catalytic system, as Figure 2 shown, to reduce CO2 to CO. The reaction process includes four parts: a gas distribution system, a plasma generation device, a plasma reaction device, and a product detection system, which are used for the reaction research on the novel low-cost and high-efficiency catalytic conversion of CO2 to CO. The present invention discloses a novel conversion method for catalytically converting CO2 to CO by a dielectric barrier discharge (DBD) plasma using a CuO catalyst with different Cu metal contents loaded on hollow CeO2 spheres with a large specific surface area. Thermal catalysis requires burning fossil fuels to provide driving force, resulting in high energy costs and additional CO2 emissions, which do not meet the requirements of energy sustainable development; photocatalysis and electrocatalysis methods use renewable energy to drive, reducing energy costs, but CO2 molecules have thermodynamic stability and kinetic inertness, resulting in problems such as too low CO2 conversion rate and poor selectivity of single target products. For the above conversion methods with high costs, low conversion rates, and difficult conversions, low-temperature plasma can generate highly active substances and electrons (average electron energy is 1-10 eV) to excite molecules and thus break their chemical bonds under environmental conditions, which enables reactions that are difficult to occur thermodynamically to be efficiently converted at a reasonable energy cost. The synergistic catalysis of CuO and CeO2 with oxygen vacancy defects improves the gas conversion rate in the DBD plasma conversion.

[0078] As Figure 5As shown, within 9 - 12 minutes at the start of the plasma-catalytic CO₂ reduction to CO reaction, the conversion rates of CuO / CeO₂-sphere-1wt%, CuO / CeO₂-sphere-5wt%, and CuO / CeO₂-sphere-10wt% all increased significantly. The conversion rate of CuO / CeO₂-sphere-5wt% was the highest, reaching 24.3% at around 12 minutes. It can be seen that the prepared catalyst can efficiently catalyze the reaction process of CO₂ to CO; CuO / CeO₂-sphere-5wt% had an approximately 10% increase compared to the stabilized CeO₂-sphere, indicating that the CeO₂ spheres with 5wt% CuO composite had better catalytic performance in the plasma-catalytic CO₂ reduction reaction.

[0079] As Figure 6 shown, the CO production rates of CuO / CeO₂-sphere-1wt%, CuO / CeO₂-sphere-5wt%, and CuO / CeO₂-sphere-10wt% were calculated at the highest conversion rate and at 30 minutes respectively. The results showed that among the comparisons of the rate differences at the two times, the difference of CuO / CeO₂-sphere-5wt% was the smallest, indicating that CuO / CeO₂-sphere-5wt% had better stability.

[0080] As Figure 7 shown, X-ray diffraction analysis was carried out on CuO / CeO₂-sphere-1wt%, CuO / CeO₂-sphere-5wt%, and CuO / CeO₂-sphere-10wt% before and after the plasma-catalytic CO₂ reduction to CO reaction, as well as on CeO₂-sphere. The positions of the diffraction peaks of CuO / CeO₂-sphere with different Cu contents were relatively consistent, and were relatively coincident with the peak positions of CeO₂-sphere. The main diffraction peaks were located at 28.5°, 33.1°, 47.5°, and 56.3° respectively; compared with CeO₂-sphere, no new peaks appeared after loading the CuO catalyst, indicating that the CuO particle size was small and evenly dispersed on the CeO₂-sphere; by analyzing and comparing the XRD patterns before and after the reaction (denoted as CuO / CeO₂-sphere-x wt%-a, x = 1, 5, 10), no obvious change in the peak positions was found, indicating that the catalyst could remain stable during the plasma-assisted reaction process, providing a prerequisite for the smooth progress of the catalytic reaction.

[0081] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a CuO / CeO2 catalyst, characterized in that, It includes the following steps: S1. Prepare CeO2 nanospheres, and the CeO2 nanospheres are hollow mesoporous spheres; S2. Prepare a CuO / CeO2 catalyst: S21. Put the CeO2 nanospheres prepared in the above step S1 into deionized water. After stirring evenly, add Cu(NO3)2·3H2O and stir for 2 hours to obtain a mixed solution; add 30 mg of the CeO2 nanospheres to each milliliter of the deionized water; the mass ratio of the Cu(NO3)2·3H2O to the CeO2 nanospheres is 0.0295:1 or 0.1476:1; S22. Dry the mixed solution, grind the dried material to obtain a mixed powder; S23. Calcinate the mixed powder in an N2 atmosphere; take it out after cooling to obtain CeO2-nanospheres composite with CuO and CeO2, that is, a CuO / CeO2 catalyst.

2. The preparation method of a CuO / CeO2 catalyst according to claim 1, characterized in that, The above step S1 includes the following steps: S11. Mix deionized water and glacial acetic acid, then add Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution A; S12. Pour solution A into an ethylene glycol solution, stir until transparent, then pour it into a reaction kettle and heat. After heating, obtain solution B; S13. Centrifuge solution B, wash the obtained precipitate three times with deionized water and absolute ethanol respectively, then dry it overnight at 50-90 °C, and then grind it; S14. Calcinate the ground sample; take it out after cooling to obtain the CeO2 nanospheres.

3. A method for preparing a CuO / CeO2 catalyst according to claim 2, characterized in that, In the above step S11, the volume ratio of the deionized water to the glacial acetic acid is 1:1; add 0.5 g of Ce(NO3)3·6H2O to each milliliter of the mixed solution of deionized water and glacial acetic acid.

4. A preparation method of a CuO / CeO2 catalyst according to claim 2, characterized in that, In the above step S12, the volume ratio of the ethylene glycol solution to solution A is 15:1; the heating temperature of the reaction kettle is 150-200 °C and the time is 2-4 hours.

5. A method for preparing a CuO / CeO2 catalyst according to claim 2, characterized in that, In the above step S14, the calcination temperature is 300-500 °C, the time is 3-5 hours, and the heating rate is 2 °C per minute.

6. A method for preparing a CuO / CeO2 catalyst according to claim 1, characterized in that, In the above step S22, the drying temperature of the mixed solution is 70-90 °C and the time is 18-30 hours.

7. A method for preparing a CuO / CeO2 catalyst according to claim 1, characterized in that, In the above step S23, the calcination temperature is 300-500 °C, the time is 3-5 hours, and the heating rate is 2 °C per minute.

8. A CuO / CeO2 catalyst prepared by the method for preparing a CuO / CeO2 catalyst according to any one of claims 1-7.

9. Use of the CuO / CeO2 catalyst according to claim 8 in the conversion of CO2 to CO by dielectric barrier discharge plasma synergism.

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