Medium-entropy spinel-based monolithic catalyst MNFO / NF and preparation method and application thereof

Abstract

The invention discloses a medium-entropy spinel-based monolithic catalyst MNFO / NF as well as a preparation method and application thereof. The preparation method of the catalyst MNFO / NF comprises the following steps: S1, mixing a nickel source, an iron source, a doped metal source, a precipitator and foamed nickel in a solvent, carrying out a microwave heating reaction, and carrying out post-treatment to obtain a precursor; s2, calcining the precursor prepared in the step S1, and performing post-treatment to obtain the medium-entropy spinel-based monolithic catalyst MNFO / NF, the doped metal source is a copper source and / or a cobalt source. According to the catalyst provided by the invention, the foamed nickel is taken as a substrate, and the capability of adsorbing O3 by an active site Fe < 3 + > in the medium-entropy spinel-based monolithic catalyst MNFO / NF is effectively improved by introducing a specific type of doped metal, so that the capability of catalyzing ozone to degrade organic pollutants by the catalyst MNFO / NF is greatly improved; the catalyst also has excellent stability and moisture resistance at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst materials, and particularly relates to a medium-entropy spinel-based monolithic catalyst MNFO / NF, a preparation method thereof, and an application thereof. Background Art

[0002] With the acceleration of the modernization process and the rapid development of industry, the problem of air pollution has become increasingly prominent. The excessive use of fossil fuels and irregular emission behaviors have led to the large generation of industrial waste gas, posing a serious threat to the ecological environment and human health. Industrial waste gas contains various organic pollutants such as methanethiol, which has the characteristics of high activity, easy diffusion, and strong volatility. Direct emission into the atmosphere will seriously hinder the sustainable development of the ecological environment. Traditional treatment methods, such as adsorption method, photocatalysis method, and biological method, are difficult to effectively cope with the current complex air pollution situation due to disadvantages such as limited treatment range, high energy consumption, and low mineralization degree.

[0003] Under this background, the catalytic ozonation technology has become an effective means for removing organic pollutants in waste gas by virtue of its significant advantages such as clean and safe, strong oxidation ability, high efficiency and economy. In this technology, the preparation of the catalyst is the core link. In current research, spinel-based catalysts have attracted much attention in the application of catalytic ozonation for degrading organic pollutants due to their adjustable structure and excellent performance. Among them, NiFe2O4-based spinel catalysts are one of the catalysts that have been studied and applied more widely.

[0004] However, in the practical application of the catalytic ozonation technology, many challenges are faced, such as easy deactivation of the catalyst, poor stability, short service life and other problems. Catalyst deactivation is usually closely related to factors such as low electron transfer efficiency, slow cycle of active sites, and low ozone utilization rate. During the reaction process, O3 molecules are first adsorbed on the active sites and activated, and then decomposed into reactive oxygen species, which attack organic pollutants to achieve the degradation of pollutants. However, in traditional NiFe2O4-based spinel catalysts, due to insufficient metal synergistic effect and poor electron transfer, the redox cycle of metal species is blocked, and the active sites are difficult to regenerate. After long-term use, the utilization rate of O3 decreases significantly, and the activity and efficiency of the catalyst also decrease accordingly.

[0005] In addition, the catalysts used in most studies are usually applied in powder form, which has defects such as large bed pressure drop, low mass and heat transfer efficiency, and poor stability, limiting the application prospects of the catalytic ozonation technology. To solve this problem, some studies have tried to coat the powder catalyst on a carrier to enhance the mechanical strength of the catalyst. However, this method still has disadvantages such as uneven coating, easy shedding of active substances, and adhesives reducing conductivity, and fails to effectively make up for the inherent defects of the powdered catalyst. Therefore, developing an efficient, stable, green and economical catalytic ozone catalyst and broadening its application potential in actual industrial scenarios is one of the research directions worthy of attention in the future. Summary of the Invention

[0006] Aiming at the above existing technical problems, the primary object of the present invention is to provide a preparation method of a medium-entropy spinel-based monolithic catalyst MNFO / NF. The prepared catalyst can catalyze O3 to generate reactive oxygen species to convert organic pollutants into non-toxic small molecules such as H2O and CO2. The catalyst has excellent catalytic degradation rate and stability, and at the same time has excellent anti-wet performance.

[0007] The second object of the present invention is to provide the medium-entropy spinel-based monolithic catalyst MNFO / NF prepared by the above preparation method.

[0008] The third object of the present invention is to provide the application of the medium-entropy spinel-based monolithic catalyst MNFO / NF in the catalytic ozonation degradation of organic pollutants.

[0009] The fourth object of the present invention is to provide a method for catalytic ozonation of organic pollutants.

[0010] In order to achieve the above objects, the present invention is realized through the following technical solutions:

[0011] The present invention claims a preparation method of a medium-entropy spinel-based monolithic catalyst MNFO / NF, comprising the following steps:

[0012] S1. Mix a nickel source, an iron source, a doped metal source, a precipitating agent and nickel foam in a solvent, heat for reaction, and perform post-treatment to obtain a precursor MNF(OH) x / NF;

[0013] S2. Calcinate the precursor MNF(OH) x / NF prepared in step S1, and perform post-treatment to obtain a medium-entropy spinel-based monolithic catalyst MNFO / NF;

[0014] The doped metal source is a copper source and / or a cobalt source;

[0015] The molar ratio of the nickel source, the iron source and the doped metal source is x:1:3-x; wherein, x ranges from 0 < x < 3.

[0016] The meso-entropy spinel-based monolithic catalyst MNFO / NF prepared by the present invention selects nickel foam (NF) material with high porosity and good diffusion performance as the substrate, and loads the meso-entropy spinel oxide MNFO on the NF by in-situ growth, solving the deficiencies of traditional powder catalysts and the existing defects of the coating method.

[0017] Based on NiFe2O4 spinel, the present invention modulates the electronic structure of the catalyst by introducing a specific type of doped metal M (M = Cu, Co). The successful substitution of the specific type of doped metal for the tetrahedral sites of NiFe2O4 spinel effectively enhances the synergistic effect of metals in the meso-entropy spinel oxide MNFO, and the subsequent optimization of the local electric field enhances the active site Fe 3+ 's ability to adsorb and activate O3 molecules. In addition, the differences in atomic radius, orbital electron arrangement, and electronegativity of the specific type of doped metal M (M = Cu, Co) will cause lattice distortion and moderate stretching of the Fe-O bond, which improves the charge transfer process of the catalyst and significantly enhances the cyclic regeneration ability of the active site. Based on the above two aspects, the meso-entropy spinel-based monolithic catalyst MNFO / NF prepared by the present invention can avoid catalyst deactivation and achieve efficient removal of organic pollutants in waste gas. In addition, in the present invention, it is necessary to control the molar ratio of the nickel source and the doped metal source to the iron source at 3:1 to prepare and form a spinel phase. When the molar ratio is too low or too high, it may cause competition problems in site occupation and is not conducive to the formation of the spinel phase.

[0018] The introduction of the specific type of doped metal M (M = Cu, Co) effectively improves the Fe active site in the meso-entropy spinel-based monolithic catalyst MNFO / NF 3+ 's ability to adsorb O3. In addition, due to the electron-rich characteristics of the doped metal, the adsorption sites of organic pollutants are also transformed from Fe 3+ to M 2+ . Compared with the NiFe2O4 catalyst, the competitive adsorption of organic pollutant molecules and O3 molecules is effectively reduced, and the O3 utilization rate is improved.

[0019] Based on the mechanism of tandem catalysis of the meso-entropy spinel-based monolithic catalyst MNFO / NF, organic pollutants and intermediate products are attacked by reactive oxygen species generated by the activation of O3, and deeply mineralized into non-toxic products such as CO2 and H2O. The meso-entropy spinel-based monolithic catalyst MNFO / NF can continuously and stably activate O3 to generate reactive oxygen species to remove organic pollutants, can maintain high activity for a long time (stable operation for more than 800 min), and the degradation rate of gaseous organic pollutants can reach more than 80%. At the same time, it has excellent moisture resistance.

[0020] Preferably, x ranges from 0.8 to 2.5; more preferably, x ranges from 1.5 to 2.2; most preferably, x is 2. More specifically, x can take values such as 0.3, 0.5, 0.7, 1, 1.3, 1.7, 2, 2.3, 2.5, 2.8, 3, etc., and ranges such as 1.3≤x≤2.3, 1.5≤x≤2.5, etc. The present invention is not limited thereto.

[0021] Preferably, in the step S2, the calcination temperature is 300-500°C, and the calcination time is 1.5-5 h. More preferably, the calcination temperature is 300-400°C, and the calcination time is 2.5-3.5 h. Most preferably, the calcination temperature is 300°C, and the calcination time is 3 h.

[0022] Preferably, in the step S1, the molar ratio of the total addition amount of the nickel source, iron source, and doped metal source to the precipitating agent is 1-5:5-25. More preferably, the molar ratio is 2-3:10-15. Most preferably, the molar ratio is 2.5:12.5.

[0023] Preferably, in the step S1, the reaction is carried out under microwave conditions. By directly acting on polar molecules through the microwave electromagnetic field to initiate dipole polarization, molecular-level rapid bulk heating is achieved. Microwave synthesis helps the catalyst to form a higher specific surface area and abundant defect sites, and usually exhibits better activity.

[0024] Preferably, in the step S1, the temperature for the reaction by heating is 180-220°C, and the reaction time is 10-25 min. More preferably, the temperature for the reaction by heating is 190-210°C, and the reaction time is 15-22 min. Most preferably, the temperature for the reaction by heating is 200°C, and the reaction time is 20 min.

[0025] Preferably, in the step S1, the precipitating agent is a compound that decomposes to produce NH3. The present invention utilizes the property that the precipitating agent decomposes to produce NH3 during microwave heating to provide an appropriate weakly basic environment to convert the nickel source, iron source, and doped metal source into MNF(OH). x 。

[0026] More preferably, the precipitating agent is urea and / or ammonium carbonate.

[0027] Preferably, in the step S1, any one of the following (a) to (c) is selected:

[0028] (a) The nickel source is one or more of NiCl2·6H2O, Ni(NO3)2·6H2O, NiSO4·7H2O, Ni(CH3COO)2·4H2O, NiC2O4·2H2O;

[0029] (b) The iron source is one or more of FeCl3·6H2O, Fe(NO3)3·9H2O, Fe2(SO4)3·9H2O, and Fe(C2O4)3·5H2O;

[0030] (c) The doping metal source is one or more of CuSO4·5H2O, CuCl2·2H2O, Cu(NO3)2·6H2O, Cu(CH3COO)2·H2O, CuC2O4·0.5H2O, CoCl2·6H2O, CoSO4·7H2O, Co(NO3)2·6H2O, Co(CH3COO)2·4H2O, and CoC2O4·2H2O.

[0031] Specifically, in the step S2, the heating rate of the calcination is 2-10 °C / min. Further preferably, the heating rate of the calcination is 3-7 °C / min. Most preferably, the heating rate of the calcination is 5 °C / min.

[0032] Preferably, in the step S1, the nickel foam is pretreated to remove the oxide impurities on the surface of the nickel foam. Further preferably, the steps of the nickel foam pretreatment are: successively ultrasonically cleaning the nickel foam with acetone, dilute hydrochloric acid, and deionized water, drying, and then setting aside.

[0033] Preferably, the solvent is deionized water.

[0034] Preferably, the post-treatment is to wash with deionized water several times after cooling to room temperature and then dry.

[0035] Furthermore, the present invention claims the medium-entropy spinel-based monolithic catalyst MNFO / NF prepared by the above preparation method.

[0036] Furthermore, the present invention claims the application of the medium-entropy spinel-based monolithic catalyst MNFO / NF in the catalytic ozonation for degrading organic pollutants.

[0037] More specifically, the source of the organic pollutants can be from industrial waste gas. More specifically, the organic pollutants are one or more of methanethiol, methane, toluene, acetone, styrene, ethyl acetate, aromatic hydrocarbons, xylene, n-hexane, etc.

[0038] Preferably, the organic pollutant is methanethiol. The medium-entropy spinel-based monolithic catalyst MNFO / NF provided by the present invention has excellent catalytic degradation effect on methanethiol, can continuously and stably activate O3 to generate reactive oxygen species to remove methanethiol, can maintain a high activity for a long time, and has excellent stability.

[0039] Further, the present invention claims a method for catalytic oxidation of organic pollutants by ozone, and the specific steps are as follows: mixing the organic pollutants, O3 and the prepared MNFO / NF catalyst.

[0040] Preferably, in the method, the concentration of O3 is 2 - 8 mg / L, and the gas flow rate is controlled at 0.10 - 0.2 L / min.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The medium-entropy spinel-based monolithic catalyst MNFO / NF of the present invention has good application effects in the field of treating organic pollutants in industrial waste gas. The MNFO / NF catalyst can catalyze O3 to generate reactive oxygen species to convert organic pollutants into non-toxic small molecules such as H2O and CO2. The degradation rate of gaseous organic pollutants can reach more than 80%, and it can operate stably for 800 min. At the same time, it can maintain excellent catalytic activity in an environment with a humidity of 0% - 60%.

[0043] (2) The medium-entropy spinel-based monolithic catalyst MNFO / NF of the present invention realizes the optimization of the local electric field through the synergistic effect of multiple metals, moderately modulates the electronic structure of the active sites, and enhances its ability to adsorb and activate O3. At the same time, due to the lattice distortion and the moderate stretching of the Fe - O bond caused by the differences in the atomic radius, electronegativity and orbital electron arrangement of the doped metal M (M = Cu, Co), the electron transfer rate can be significantly accelerated, and the recycling regeneration of the active sites can be realized. The medium-entropy spinel-based monolithic catalyst MNFO / NF of the present invention makes up for the defects and deficiencies of the traditional NiFe2O4 spinel-based ozone catalyst with poor stability and low ozone utilization rate.

[0044] (3) The medium-entropy spinel-based monolithic catalyst MNFO / NF of the present invention has the advantages of simple recovery, strong stability, high mechanical strength, long service life, etc. compared with the traditional powder catalyst. While improving the removal of organic pollutants, it can avoid frequent replacement of the catalyst, expands the potential of practical application, and is more suitable for industrial actual production. Description of the Drawings

[0045] Figure 1 It is a sample diagram of the CuNFO / NF - 0.5 catalyst in Example 1 and the CoNFO / NF - 0.5 catalyst in Example 4.

[0046] Figure 2 It is a scanning electron microscope diagram of the CuNFO / NF - 0.5 catalyst in Example 1.

[0047] Figure 3 It is an XRD diagram of CuNFO - 0.5 and CoNFO - 0.5 without NF.

[0048] Figure 4 For the degradation effect diagram of Test Example 3. Detailed implementation mode

[0049] The present invention will be further described below in conjunction with the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0050] Entropy spinel-based monolithic catalyst CuNFO / NF-0.5 in Example 1

[0051] (1) The nickel foam (NF) with a shape of 2 cm × 4 cm was successively ultrasonically cleaned with acetone, dilute hydrochloric acid with a concentration of 3 M, and deionized water for 20 min, placed in an oven at 70 °C for 12 h for drying, and reserved.

[0052] (2) 0.625 mmol of Fe(NO3)3·9H2O, 1.25 mmol of NiCl2·6H2O, 0.625 mmol of CuCl2·6H2O, and 12.5 mmol of urea were mixed in 50 mL of deionized water (the total dosage of CuCl2·6H2O and NiCl2·6H2O was 1.875 mmol, and the molar ratio was 1:2), ultrasonically treated for 20 min to obtain CuNFO-0.5. Subsequently, the mixed solution and the NF obtained in step (1) were transferred to a reaction kettle, the microwave power was set to 850 W, and a microwave heating reaction at 200 °C was carried out for 20 min. After cooling to room temperature, it was washed several times with deionized water, and then dried at 70 °C for 24 h to obtain the precursor CuNF(OH)x / NF-0.5.

[0053] (3) The CuNF(OH)x / NF-0.5 obtained in step (2) was placed in a muffle furnace and calcined at 350 °C for 3 h, with a heating rate of 5 °C / min. After cooling to room temperature, CuNFO / NF-0.5 was obtained.

[0054] Entropy spinel-based monolithic catalyst CuNFO / NF-1 in Example 2

[0055] The difference between this example and Example 1 is that in step (2), the molar ratio of CuCl2·6H2O to NiCl2·6H2O is 1:1.

[0056] Entropy spinel-based monolithic catalyst CuNFO / NF-2 in Example 3

[0057] The difference between this example and Example 1 is that in step (2), the molar ratio of CuCl2·6H2O to NiCl2·6H2O is 2:1.

[0058] Entropy spinel-based monolithic catalyst CoNFO / NF-0.5 in Example 4

[0059] The difference between this example and Example 1 is that in step (2), CuCl2·6H2O is replaced with Co(NO3)2·6H2O.

[0060] Entropy spinel-based monolithic catalyst CoNFO / NF-1 in Example 5

[0061] The difference between this example and Example 1 is that in step (2), CuCl2·6H2O is replaced with Co(NO3)2·6H2O, the total dosage of Co(NO3)2·6H2O and NiCl2·6H2O is 1.875 mmol, and the molar ratio of Co(NO3)2·6H2O to NiCl2·6H2O is 1:1.

[0062] Entropy spinel-based monolithic catalyst CoNFO / NF-2 in Example 6

[0063] The difference between this example and Example 1 is that in step (2), CuCl2·6H2O is replaced with Co(NO3)2·6H2O, the total dosage of Co(NO3)2·6H2O and NiCl2·6H2O is 1.875 mmol, and the molar ratio of Co(NO3)2·6H2O to NiCl2·6H2O is 2:1.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that operations in steps (2) and (3) are not carried out, and only the nickel foam is pretreated.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 1 is that only operations in steps (1) and (2) are carried out, and operation in step (3) is not carried out.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 1 is that only operations in steps (1) and (2) are carried out, and operation in step (3) is not carried out; in step (2), CuCl2·6H2O is replaced with Co(NO3)2·6H2O.

[0070] Comparative Example 4

[0071] The difference between this comparative example and Example 1 is that operation in step (1) is not carried out, and nickel foam NF is not added in step (2).

[0072] Comparative Example 5

[0073] The difference between this comparative example and Example 1 is as follows: The operation in step (1) is not carried out. In step (2), nickel foam NF is not added, and CuCl2·6H2O is replaced with Co(NO3)2·6H2O.

[0074] Comparative Example 6

[0075] The difference between this comparative example and Example 1 is as follows: In step (2), CuCl2·6H2O is not added, and the dosage of NiCl2·6H2O is 1.875 mmol.

[0076] Comparative Example 7

[0077] The difference between this comparative example and Example 1 is as follows: In step (2), NiCl2·6H2O is not added, and the dosage of CuCl2·6H2O is 1.875 mmol.

[0078] Comparative Example 8

[0079] The difference between this comparative example and Example 1 is as follows: In step (2), NiCl2·6H2O is not added, CuCl2·6H2O is replaced with Co(NO3)2·6H2O, and the dosage of Co(NO3)2·6H2O is 1.875 mmol.

[0080] Comparative Example 9

[0081] The difference between this comparative example and Example 1 is as follows: In step (2), CuCl2·6H2O is replaced with ZnCl2·6H2O.

[0082] Comparative Example 10

[0083] The difference between this comparative example and Example 1 is as follows: In step (2), CuCl2·6H2O is replaced with MgCl2·6H2O.

[0084] Test Example 1

[0085] Experimental materials: The medium-entropy spinel-based monolithic catalyst CuNFO / NF-0.5 prepared in Example 1 and the medium-entropy spinel-based monolithic catalyst CoNFO / NF-0.5 prepared in Example 4.

[0086] From Figure 1 It can be seen that the CuNFO / NF-0.5 and CoNFO / NF-0.5 catalysts prepared by the present invention are both in the form of flakes with a size of 2 cm × 4 cm, having a rough surface and a flexible structure. It is observed that the brownish-black substances (CuNFO, CoNFO) are uniformly dispersed on the surface of NF.

[0087] From Figure 2It can be seen that the CuNFO / NF-0.5 catalyst prepared by the present invention retains the three-dimensional pore structure of nickel foam NF, and the pore walls are rough and wrinkled, which is attributed to the loading and dispersion of the medium-entropy spinel oxide CuNFO. The microscopic morphology of CuNFO is in the shape of a sea urchin, which is beneficial to the exposure of active sites, and the specific surface area is increased, which is conducive to the contact between the catalyst and O3 molecules.

[0088] Since the strong characteristic peaks of nickel foam will affect the determination of other diffraction plane peaks, referring to the preparation steps of Example 1 and Example 4, nickel foam NF was not added during the preparation process, and the prepared products CuNFO-0.5 and CoNFO-0.5 were subjected to XRD tests. From Figure 3 It can be seen that CuNFO-0.5 and CoNFO-0.5 show different peaks at 36.6°, 42.3°, 62.2°, 74.4°, and 78.5°, corresponding to the diffraction planes of (222), (400), (440), (533), and (622) (PDF#00-010-0325), indicating that the introduction of doped metal M (M = Cu, Co) does not change the spinel structure of the catalyst. In addition, it was observed that the diffraction peaks attributed to (222) and (400) showed slight shifts with the incorporation of Cu and Co, which is related to the lattice distortion caused by the larger atomic radius of the doped metal.

[0089] Test Example 2

[0090] Experimental materials: The catalysts prepared in Examples 1-6 and Comparative Examples 1-10.

[0091] Experimental method: The catalyst samples of Examples 1-6 and Comparative Examples 1-10 were respectively placed in a methanethiol degradation reaction device, and a mixed gas with an initial methanethiol concentration of 50 ppm was input into the device from the inlet end through an ozone and methanethiol generator. The gas flow rate was controlled at 0.15 L / min, and the reaction time was 60 min. The catalyst was used to decompose ozone to generate various reactive oxygen species to degrade organic pollutants such as methanethiol, and convert them into small molecule substances such as non-toxic carbon dioxide and water. Methanethiol detectors were installed at the inlet end and the outlet end to measure the initial concentration and emission concentration of methanethiol. The degradation rate was calculated by the following formula to evaluate the degradation effect of different catalysts on methanethiol in the catalytic ozone oxidation system:

[0092]

[0093] In Equation 1: R is the degradation efficiency of the organic pollutant; C0 is the initial concentration of the organic pollutant at the inlet end (ppm); C t is the concentration of the organic pollutant at the outlet end (ppm).

[0094] Experimental results: The degradation of methanethiol is shown in Table 1. It can be clearly seen from the data in Table 1 that the degradation efficiency of the medium-entropy spinel-based monolithic catalyst MNFO / NF prepared in the examples of the present invention for methanethiol is much higher than that of the catalyst materials in Comparative Examples 1-10, and it has a significant effect on purifying organic pollutants. It is worth noting that when the molar ratio of the doped metal source to the nickel source is 1:2, the materials obtained, namely Examples 1 and 4, have the best effect on catalyzing the degradation of methanethiol by ozone, and the degradation rate is close to 100%.

[0095] Comparative Examples 6-8 are different from Example 1 and Example 4 in terms of the number of metal types contained in the catalyst. It can be seen from the experimental results that the catalytic activity (100%) of the medium-entropy spinel-based monolithic catalyst MNFO / NF is significantly higher than that of the binary spinel-based monolithic catalyst MFO / NF (lower than 80%). This shows that the multi-metal synergistic effect caused by the medium-entropy effect plays a significant role in the reaction process of the medium-entropy spinel-based monolithic catalyst MNFO / NF catalyzing the ozonation degradation of gaseous organic pollutants.

[0096] The degradation efficiencies of Comparative Examples 9 and 10 do not exceed 40%, which are far lower than the degradation effects of Example 1 and Example 4. This shows that not all doped metals can achieve good catalytic degradation effects. Only when the doped metal M = Cu or Co, can it have a good catalytic ozone degradation effect. Replacing M with other metals such as Zn and Mg cannot achieve the application objectives described in this application.

[0097] Table 1 Test results of degradation efficiency

[0098] Sample Degradation rate / % Sample Degradation rate / % Example 1 100 Comparative Example 3 69.9 Example 2 90.7 Comparative Example 4 78.8 Example 3 88.9 Comparative Example 5 79.6 Example 4 100 Comparative Example 6 53.2 Example 5 91.2 Comparative Example 7 77.5 Example 6 86.6 Comparative Example 8 76.7 Comparative Example 1 23.4 Comparative Example 9 38.2 Comparative Example 2 70.3 Comparative Example 10 37.9

[0099] Test Example 3

[0100] Experimental materials: Catalysts prepared in Example 1, Comparative Example 6, Comparative Example 9, and Comparative Example 10.

[0101] Experimental method: Place the catalysts prepared in Example 1, Comparative Example 6, Comparative Example 9, and Comparative Example 10 in a methanethiol degradation device. Through an ozone, methanethiol, and water vapor generator, a mixed gas of methanethiol, ozone, and water vapor is formed in the device, and the degradation of methanethiol by the catalyst is measured under different humidity conditions (0%, 10%, 30%, 60%) respectively to evaluate the anti-humidity effects of the catalyst samples of the examples and comparative examples.

[0102] Experimental results: The degradation of methanethiol in Test Example 3 is shown in Table 2. As can be seen from Table 2, the CuNFO / NF-0.5 catalyst prepared by the present invention exhibits excellent catalytic ozonation degradation performance of methanethiol not less than 97% under various humidity conditions, has strong moisture resistance, is suitable for various environmental conditions, and can be widely used for the removal of gaseous organic pollutants. Compared with the humidity of 0%, the catalytic degradation rate of the catalyst prepared in Example 1 only decreased by 1.3% when the humidity was 60%. For the catalysts prepared in Comparative Example 6, Comparative Example 9 and Comparative Example 10, the degradation rates decreased by 20.5%, 7.9%, and 8.2% respectively when the humidity was 60%. It can be seen that the catalysts prepared in the examples of the present invention have more excellent moisture resistance performance.

[0103] Table 2 Moisture resistance test results

[0104] Humidity 0％ 10％ 30％ 60％ Degradation rate of Example 1 98.6％ 100.0％ 100％ 97.3％ Degradation rate of Comparative Example 6 53.2％ 50.4％ 46.5％ 42.3％ Degradation rate of Comparative Example 9 38.2％ 37.9％ 35.5％ 35.2％ Degradation rate of Comparative Example 10 37.9％ 36.9％ 35.5％ 34.8％

[0105] Test Example 4

[0106] Experimental materials: The catalysts prepared in Example 1, Comparative Example 6 and Comparative Example 9.

[0107] Experimental method: Place the catalyst samples prepared in the examples and comparative examples in a methanethiol degradation device, and input a mixed gas with an initial methanethiol concentration of 50 ppm into the device through an ozone and methanethiol generator. The gas flow rate is controlled at 0.15 L / min, and the reaction time is 800 min to test the degradation stability of the catalyst.

[0108] Experimental results: As can be seen from Figure 4 it, the CuNFO / NF-0.5 catalyst prepared in Example 1 of the present application has good catalytic ozonation degradation activity of methanethiol; it has high degradation stability, can continuously react for 800 min, and the catalytic activity does not decrease significantly. For the catalysts prepared in Comparative Example 6 and Comparative Example 9, the catalyst activity decreased significantly when continuously reacting for 100 min (the catalyst activity decreased > 20%. Considering time and cost issues, the catalysts prepared in the comparative examples were only tested for 120 min). The above results show that the monolithic catalyst CuNFO / NF-0.5 of the present invention has high stability during the degradation process and has significant technological progress.

[0109] The foregoing examples are illustrative only and are used to explain some of the features of the method of the present invention. The appended claims are intended to claim the broadest scope conceivable, and the examples presented herein are supported by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims are not limited by the selection of examples that illustrate the features of the present invention. Some of the numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be construed as being covered by the appended claims whenever possible.

Claims

1. A preparation method of a medium-entropy spinel-based monolithic catalyst MNFO / NF, characterized in that, It includes the following steps: S1. Mix a nickel source, an iron source, a doped metal source, a precipitant, and nickel foam in a solvent, heat for reaction, and perform post-treatment to obtain a precursor; S2. Calcinate the precursor prepared in step S1 and perform post-treatment to obtain a medium-entropy spinel-based monolithic catalyst MNFO / NF; The doped metal source is a copper source and / or a cobalt source; The molar ratio of the nickel source, the iron source, and the doped metal source is x:1:3 - x; wherein, x ranges from 0 < x < 3.

2. The preparation method according to claim 1, characterized in that, In step S2, the calcination temperature is 300 - 500 °C and the calcination time is 1.5 - 5 h.

3. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of the total addition amount of the nickel source, the iron source, and the doped metal source to the precipitant is 1 - 5:5 - 25.

4. The preparation method according to claim 1, characterized in that, In step S1, heat for reaction under microwave conditions.

5. The preparation method according to claim 1 or 4, characterized in that, In step S1, the temperature for heating for reaction is 180 - 220 °C and the reaction time is 10 - 25 min.

6. The preparation method according to claim 1, characterized in that, The precipitant is a compound that decomposes to produce NH3.

7. According to the preparation method described in any one of claims 1-6, it is characterized in that, It is selected from any one of the following (a) to (c): (a) The nickel source is one or more of NiCl2·6H2O, Ni(NO3)2·6H2O, NiSO4·7H2O, Ni(CH3COO)2·4H2O, NiC2O4·2H2O; (b) The iron source is one or more of FeCl3·6H2O, Fe(NO3)3·9H2O, Fe2(SO4)3·9H2O, Fe(C2O4)3·5H2O; (c) The doped metal source is one or more of CuSO4·5H2O, CuCl2·2H2O, Cu(NO3)2·6H2O, Cu(CH3COO)2·H2O, CuC2O4·0.5H2O, CoCl2·6H2O, CoSO4·7H2O, Co(NO3)2·6H2O, Co(CH3COO)2·4H2O, CoC2O4·2H2O.

8. The medium-entropy spinel-based monolithic catalyst MNFO / NF prepared by the preparation method according to any one of claims 1 - 7.

9. The application of the medium-entropy spinel-based monolithic catalyst MNFO / NF according to claim 8 in the catalytic ozonation degradation of organic pollutants.

10. The application according to claim 9, wherein The organic pollutants are one or more of methanethiol, methane, toluene, acetone, styrene, ethyl acetate, aromatic hydrocarbons, xylene, and n-hexane.

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