CuO / CeO2 catalyst as well as preparation method and application thereof

Abstract

The invention discloses a CuO / CeO2 catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, preparing CeO2 nanospheres; and S2, preparing a CuO / CeO2 catalyst, wherein the prepared catalyst has a catalytic effect in the aspect of CO2 conversion catalyzed by dielectric barrier discharge low-temperature plasmas. The hollow mesoporous CeO2 nanosphere is synthesized, has abundant pore channels and cavity structures, provides a good place for metal loading, and is rich in oxygen vacancies, so that CeO2 continuously provides active oxygen for active sites. The prepared CuO / CeO2 catalyst is uniform in size and good in dispersity, the CuO-CeO2 interface structure of the CuO / CeO2 catalyst can accelerate the transfer rate of electrons, provides rich adsorption sites for reactivity species, is beneficial to CO catalytic conversion in a novel catalytic system, namely dielectric barrier discharge plasma cooperating with CO2, and shows good catalytic efficiency and stability.

Description

Technical Field

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

[0002] With the urgent global pursuit of sustainable energy and strict requirements for greenhouse gas emission reduction, the research and development of technologies for converting greenhouse gases into hydrocarbon fuels has become a key exploration direction in the field of energy and environment. Among them, the use of plasma to assist greenhouse gas conversion has shown great potential. However, the technology is still limited by the low conversion efficiency of target chemicals and fuels. Dielectric barrier discharge plasma is the most widely studied plasma technology. Carbon dioxide can be directly decomposed into carbon monoxide and oxygen through the collision of high-energy electrons generated by plasma. Dielectric barrier discharge plasma promotes CO2 conversion as energy input. This application is aimed at developing high-efficiency catalysts in dielectric barrier discharge plasma catalytic systems to provide higher CO conversion rates. Summary of the invention

[0003] The first object of the present invention is to provide a method for preparing a CuO / CeO2 catalyst, which can synthesize hollow mesoporous CeO2 nanospheres, which provide a good place for loading metals. The prepared CuO / CeO2 catalyst is helpful for catalytic conversion of CO in a dielectric barrier discharge plasma with CO2, and exhibits 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 CuO / CeO2 catalyst.

[0006] The first object of the present invention is implemented by the following technical solutions: A method for preparing a CuO / CeO2 catalyst comprises the following steps: S1, preparation of CeO2 nanospheres; S2. Preparation of CuO / CeO2 catalyst: S21, put the CeO2 nanospheres prepared in step S1 into deionized water, stir evenly, then add Cu(NO3)2·3H2O, stir for 2 hours to obtain a mixed solution; add 30 mg of the CeO2 nanospheres per 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 loaded with different Cu contents can be obtained; S22, drying the mixed liquid, and grinding the dried material to obtain a mixed powder; S23, calcining the mixed powder under N2 atmosphere; taking out after cooling, to obtain CeO2-nanospheres composited with CuO and CeO2, i.e., CuO / CeO2 catalyst.

[0007] Furthermore, the step S1 includes the following steps: S11, after mixing deionized water and glacial acetic acid, add Ce(NO3)3·6H2O, and stir until completely dissolved to obtain solution A; S12, pouring the solution A into the ethylene glycol solution, stirring until transparent, and then pouring into a reaction kettle and heating to obtain solution B; S13, centrifuging the solution B, washing the precipitate obtained after the centrifugation with deionized water and anhydrous ethanol three times respectively, drying it at 50-90 degrees Celsius overnight, and then grinding it; S14, calcining the ground sample; taking it out after cooling down to obtain the CeO2 nanospheres.

[0008] Furthermore, in the step S11, the volume ratio of the deionized water to the glacial acetic acid is 1:1; 0.5 g of Ce(NO3)3·6H2O is added to each milliliter of the mixed solution of deionized water and glacial acetic acid.

[0009] Furthermore, in step S12, the volume ratio of the ethylene glycol solution to the solution A is 15:1; the reactor is heated at a temperature of 150-200 degrees Celsius for 2-4 hours.

[0010] Furthermore, in step S14, the calcination temperature is 300-500° C., the time is 3-5 hours, and the heating rate is 2° C. / minute.

[0011] Furthermore, in step S22, the mixed solution is dried at a temperature of 70 to 90 degrees Celsius for 18 to 30 hours.

[0012] Furthermore, in step S23, the calcination temperature is 300-500 degrees Celsius, the time is 3-5 hours, and the heating rate is 2 degrees Celsius / minute.

[0013] The second object of the present invention is implemented by the following technical solutions: A CuO / CeO2 catalyst is prepared by a CuO / CeO2 catalyst preparation method.

[0014] The third object of the present invention is implemented by the following technical solutions: Application of CuO / CeO2 catalyst in dielectric barrier discharge plasma synergistic CO2 conversion to CO.

[0015] Advantages of the present invention: The present invention synthesizes hollow mesoporous CeO2 nanospheres with rich pores and cavity structures, which provide a good place for loading metals, and the rich oxygen vacancies enable CeO2 to continuously provide active oxygen to active sites. The CuO / CeO2 catalyst with different metal Cu loadings is prepared by modification treatment by an impregnation calcination method, and the catalyst has uniform size and good dispersibility. The CuO-CeO2 interface structure can accelerate the transfer rate of electrons, provide rich adsorption sites for reactive species, and help catalyze CO2 to convert CO in dielectric barrier discharge plasma, showing good catalytic efficiency and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the steps of a method for preparing a CuO / CeO2 catalyst; Figure 2 This is a flow chart of the dielectric barrier discharge plasma catalytic system; Figure 3 The scanning electron micrographs of the CuO / CeO2 catalysts loaded with different Cu contents in Example 4 are as follows: (a, b) CuO / CeO2-sphere-1wt%; (c, d) CuO / CeO2-sphere-5wt%; (e, f) CuO / CeO2-sphere-10wt% SEM; Figure 4 (a, b) TEM at different scales of CuO / CeO2-sphere-5wt% of Example 4; (c) HRTEM; (dg) EDX element surface distribution map; Figure 5 The conversion rate of the catalyst within 30 min of reaction; Figure 6 is the CO generation rate of the catalyst; Figure 7 These are the XRD patterns of the catalyst before and after it participates in the reaction (marked as -a in the figure). DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1 A method for preparing a CuO / CeO2 catalyst, Figure 1 As shown, it includes steps S1 and S2.

[0020] S1, preparing CeO2 nanospheres. Step S1 specifically includes: S11. Add 2 mL of deionized water and 2 mL of glacial acetic acid (99.5 wt%) into a beaker, mix, then add 2 g of Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution A. S12, add 60 mL of ethylene glycol solution (concentration of 99.9 wt%) into another beaker, then pour the solution A prepared in step S11 into the beaker, stir vigorously until transparent, then pour into a reactor with a volume of 100 mL and heat at 180° C. for 3 h to obtain solution B after heating; 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; 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.

[0021] S2, preparing CuO / CeO2 catalyst. Step S2 specifically comprises: S21, add 10 mL of deionized water to a beaker, then add 300 mg of CeO2-sphere prepared in step S1, stir evenly, then add 8.86 mg of Cu(NO3)2·3H2O, and stir vigorously for 24 h to obtain a mixed solution; S22, heating the mixed solution at 80° C. for 24 h to complete drying, grinding the dried material to obtain a particle size of ≤100 nm to obtain a mixed powder; 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 1 wt%, i.e., a CuO / CeO2 catalyst, recorded as CuO / CeO2-sphere-1wt%.

[0022] Example 2 A method for preparing a CuO / CeO2 catalyst comprises steps S1 and S2.

[0023] S1, preparing CeO2 nanospheres. Step S1 specifically includes: S11. Add 2 mL of deionized water and 2 mL of glacial acetic acid (99.5 wt%) into a beaker, mix, then add 2 g of Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution A. S12, add 60 mL of ethylene glycol solution (concentration of 99.9 wt%) into another beaker, then pour the solution A prepared in step S11 into the beaker, stir vigorously until transparent, then pour into a reactor with a volume of 100 mL and heat at 180° C. for 3 h to obtain solution B after heating; 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; 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.

[0024] S2, preparing CuO / CeO2 catalyst. Step S2 specifically comprises: S21, add 10 mL of deionized water to a beaker, then add 300 mg of CeO2-sphere prepared in step S1, stir evenly, then add 44.28 mg of Cu(NO3)2·3H2O, and stir vigorously for 24 h to obtain a mixed solution; S22, heating the mixed solution at 80° C. for 24 h to complete drying, grinding the dried material to obtain a particle size of ≤100 nm to obtain a mixed powder; 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 5 wt%, i.e., a CuO / CeO2 catalyst, recorded as CuO / CeO2-sphere-5wt%.

[0025] Example 3 A method for preparing a CuO / CeO2 catalyst comprises steps S1 and S2.

[0026] S1, preparing CeO2 nanospheres. Step S1 specifically includes: S11. Add 2 mL of deionized water and 2 mL of glacial acetic acid (99.5 wt%) into a beaker, mix, then add 2 g of Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution A. S12, add 60 mL of ethylene glycol solution (concentration of 99.9 wt%) into another beaker, then pour the solution A prepared in step S11 into the beaker, stir vigorously until transparent, then pour into a reactor with a volume of 100 mL and heat at 180° C. for 3 h to obtain solution B after heating; 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; 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.

[0027] S2, preparing CuO / CeO2 catalyst. Step S2 specifically comprises: 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; S22, heating the mixed solution at 80° C. for 24 h to complete drying, grinding the dried material to obtain a particle size of ≤100 nm to obtain a mixed powder; 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%.

[0028] Example 4 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%).

[0029] 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.

[0030] CuO / CeO2-sphere-5wt% was observed by transmission electron microscopy and X-ray energy spectrum analysis, such as Figure 4 As shown in the figure, CeO2-sphere is a hollow mesoporous sphere with rich pores and cavity structure, which can provide loading sites for active metals and provide active oxygen. Ce, Cu and O elements are evenly distributed on CuO / CeO2-sphere-5wt%, indicating that CuO is well dispersed on CeO2-sphere.

[0031] Example 5 Application of the CuO / CeO2 catalyst of Example 4 in catalyzing CO2 to produce CO.

[0032] 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 a dielectric barrier discharge (DBD) plasma catalytic system was used, such as Figure 2As shown, CO2 is introduced and a plasma discharge reaction is carried out to reduce CO2 to CO. The reaction process includes four parts: a gas distribution system, a plasma generating device, a plasma reaction device and a product detection system, and is used for a new low-cost and high-efficiency catalytic reaction study on the conversion of CO2 to CO. The present invention discloses a new conversion method in which a CuO catalyst with different Cu metal contents is loaded on a hollow CeO2 ball with a large specific surface area, and CO2 is converted to CO by dielectric barrier discharge (DBD) plasma catalysis. Thermal catalysis requires the combustion of fossil fuels to provide a driving force, resulting in high energy costs and additional CO2 emissions, which does not meet the requirements of sustainable energy development; photocatalysis and electrocatalysis methods use renewable energy to drive and reduce energy costs, but CO2 molecules have thermodynamic stability and kinetic inertness, resulting in problems such as low CO2 conversion rate and poor selectivity for a single target product. In order to solve the disadvantages of the above conversion methods such as high cost, low conversion rate and difficulty in conversion, low-temperature plasma can produce highly active substances and electrons (average electron energy is 1-10 eV) to excite molecules and thus break their chemical bonds under ambient conditions, which makes the reactions that are difficult to occur in thermodynamics efficiently converted at a reasonable energy cost. The synergistic catalysis of CuO and CeO2 with oxygen vacancy defects improves the gas conversion rate in DBD plasma conversion.

[0033] like Figure 5 As shown in the figure, within 9 to 12 minutes after the plasma-catalyzed CO2 reduction reaction, the conversion rates of CuO / CeO2-sphere-1wt%, CuO / CeO2-sphere-5wt%, and CuO / CeO2-sphere-10wt% were significantly improved, and 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% has an improvement of about 10% compared to the stabilized CeO2-sphere, indicating that CeO2 balls with a composite amount of 5wt% CuO have better catalytic performance in the plasma-catalyzed CO2 reduction reaction.

[0034] like Figure 6 As shown in the figure, the CO generation rates of CuO / CeO2-sphere-1wt%, CuO / CeO2-sphere-5wt%, and CuO / CeO2-sphere-10wt% at the highest conversion rate and 30 min were calculated respectively. The results show that in the comparison of the rate difference at the two times, the difference of CuO / CeO2-sphere-5wt% is the smallest, indicating that CuO / CeO2-sphere-5wt% has better stability.

[0035] like Figure 7 As shown, X-ray diffraction analysis was performed on CuO / CeO2-sphere-1wt%, CuO / CeO2-sphere-5wt% and CuO / CeO2-sphere-10wt% before and after plasma catalytic CO2 reduction to CO reaction, as well as CeO2-sphere. The positions of the diffraction peaks of CuO / CeO2-sphere with different Cu contents are relatively consistent, and overlap with the peak positions of CeO2-sphere. The main diffraction peaks are located at 28.5°, 33.1°, 47.5° and 56.3°, respectively. Compared with CeO2-sphere, no new peaks appeared after the catalyst loaded with CuO, indicating that the CuO particles are small in size and evenly dispersed on the CeO2-sphere. By analyzing and comparing the XRD spectra before and after the reaction (denoted as CuO / CeO2-sphere-x wt%-a, x = 1, 5, 10), no obvious changes in the peak positions were found, indicating that the catalyst can remain stable during the plasma synergistic reaction, providing a prerequisite for the smooth progress of the catalytic reaction.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a CuO / CeO2 catalyst, characterized in that: It includes the following steps: S1, preparation of CeO2 nanospheres; S2. Preparation of CuO / CeO2 catalyst: S21, put the CeO2 nanospheres prepared in step S1 into deionized water, stir evenly, then add Cu(NO3)2·3H2O, stir for 2 hours to obtain a mixed solution; add 30 mg of the CeO2 nanospheres per ml of the deionized water; the mass ratio of the Cu(NO3)2·3H2O to the CeO2 nanospheres is not more than 1.48:1; S22, drying the mixed liquid, and grinding the dried material to obtain a mixed powder; S23, calcining the mixed powder under N2 atmosphere; taking out after cooling, to obtain CeO2-nanospheres composited with CuO and CeO2, i.e., CuO / CeO2 catalyst.

2. The method for preparing a CuO / CeO2 catalyst according to claim 1, characterized in that: The step S1 comprises the following steps: S11, after mixing deionized water and glacial acetic acid, add Ce(NO3)3·6H2O, and stir until completely dissolved to obtain solution A; S12, pouring the solution A into the ethylene glycol solution, stirring until transparent, and then pouring into a reaction kettle and heating to obtain solution B; S13, centrifuging the solution B, washing the precipitate obtained after the centrifugation with deionized water and anhydrous ethanol three times respectively, drying it at 50-90 degrees Celsius overnight, and then grinding it; S14, calcining the ground sample; taking it out after cooling down to obtain the CeO2 nanospheres.

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

4. The method for preparing a CuO / CeO2 catalyst according to claim 2, characterized in that: In the step S12, the volume ratio of the ethylene glycol solution to the solution A is 15:1; the reactor is heated at a temperature of 150-200 degrees Celsius for 2-4 hours.

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

6. The method for preparing a CuO / CeO2 catalyst according to claim 1, characterized in that: In step S22, the mixed solution is dried at a temperature of 70 to 90 degrees Celsius for 18 to 30 hours.

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

8. The CuO / CeO2 catalyst prepared by the CuO / CeO2 catalyst preparation method according to any one of claims 1 to 7.

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

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