A nitro-functional modified CeO2 catalyst, a preparation method and application thereof
The nitro-functionalized CeO2 catalyst prepared by modifying Ce-MOF ligands with electrophilic -NO2 groups solves the problem of low oxidation efficiency of CeO2 photocatalysts in aromatic VOCs and achieves a highly efficient VOCs mineralization effect.
Patent Information
- Application Number
- CN202311513175.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-14
- Publication Date
- 2025-12-05
- Estimated Expiration
- 2043-11-14
AI Technical Summary
Existing CeO2 photocatalysts have low efficiency in the oxidation of aromatic volatile organic compounds (VOCs), and uneven oxygen vacancies lead to the release of reaction intermediates, making it difficult to achieve deep mineralization of aromatic VOCs.
CeO2 materials rich in uniform oxygen vacancies were prepared by introducing electrophilic NO2 groups to modify Ce-MOF organic ligands. Nitro functionalized CeO2 catalysts were formed by solvothermal method and calcination process.
This improved the photoresponse capability and charge separation efficiency of CeO2 materials, enhanced their adsorption and activation capabilities for reactants, provided more active sites, and enabled efficient mineralization of VOCs pollutant molecules.
Smart Images
Figure CN117583012B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of material preparation and photocatalytic oxidation of VOCs, and particularly relates to a CeO2 catalyst modified by a nitro functional group and a preparation method and application thereof. BACKGROUND
[0002] Indoor environment is one of the most frequent and closest environments we contact, in which volatile organic compounds (VOCs) are the main source of poor indoor air quality and sick building syndrome, which can induce respiratory diseases, heart disease, and even cancer, and is extremely harmful to human health. Compared with other methods for eliminating VOCs, photocatalytic oxidation is a recognized green, safe and efficient control technology. Therefore, it is very important and urgent to develop a photocatalyst for efficiently eliminating indoor VOCs. However, in the research field of photocatalytic oxidation of VOCs, aromatic VOCs are extremely stable and difficult to be ring-opening mineralized, and even in the presence of typical indoor low-concentration VOCs, reaction intermediates are released, so the deep oxidation of aromatic VOCs is the main challenge in this research field.
[0003] It is known that cerium dioxide (CeO2) is an n-type semiconductor, has abundant surface oxygen vacancies, and a cyclic Ce 3+ / Ce 4+ pair, which can provide a mobile electron environment for catalytic reactions, and is a photocatalytic material with potential application prospects. However, the photocatalytic efficiency of ordinary CeO2 is low, and the introduction of more oxygen vacancies can form an indefinite energy level for the local electrons, expand the light response range, effectively inhibit the carrier recombination by capturing electrons, and the surrounding unsaturated coordination active sites can also effectively adsorb and activate the reactants, reduce the activation energy barrier, thereby accelerating the surface catalytic reaction. However, the introduction of most oxygen vacancies is mainly through post-processing in a reducing atmosphere, which may lead to uneven formation of oxygen vacancies. In recent years, metal-organic framework (MOF) materials have been widely concerned due to their topological structure characteristics of uniform connection of metal nodes by organic ligands, and therefore, pyrolysis of MOF materials is an economic and effective strategy to realize uniform generation of oxygen vacancies. During the pyrolysis process of MOF materials, nanoparticles are not easy to agglomerate, and a large number of ordered pores are also formed, improving the chemical stability. The electrophilic group (-NO2) modified organic ligand can effectively increase the amount of Lewis acid of the metal node, promote the generation of hydroxyl radicals, and is an ideal modified functional group to improve the mineralization rate of photocatalytic oxidation of VOCs. SUMMARY
[0004] In view of the deficiencies of the prior art, the technical problems to be solved by the present application are to provide a high-performance CeO2 material rich in uniform oxygen vacancies obtained by modifying Ce-MOF organic ligands with an electrophilic group-NO2, to provide a specific preparation method of the aforementioned nitro functional group modified CeO2 photocatalyst, and to provide specific applications of the aforementioned nitro functional group modified CeO2 photocatalyst.
[0005] To solve the above problems, the technical solutions adopted by the present application are as follows:
[0006] A preparation method of a nitro functional group modified CeO2 catalyst comprises the following steps: dropping cerium ammonium nitrate dissolved in deionized water into a 2-nitroterephthalic acid solution dissolved in N,N-dimethylformamide to obtain a mixed solution; subjecting the mixed solution to a hydrothermal reaction to obtain a suspension; subjecting the suspension to centrifugal washing and drying treatment to obtain Ce-MOF-NO2 solid; and grinding and calcining the Ce-MOF-NO2 solid to obtain the nitro functional group modified CeO2 photocatalyst.
[0007] Further, the molar ratio of cerium ammonium nitrate to 2-nitroterephthalic acid is 1:1.
[0008] Further, the temperature of the hydrothermal reaction is 120 DEG C, and the time of the hydrothermal reaction is 15 min.
[0009] Further, the washing liquid is N,N-dimethylformamide and acetone, and the washing frequency is 3 times.
[0010] Further, the drying temperature is 80 DEG C, and the drying time is 12 h.
[0011] Further, the calcination temperature is 700 DEG C, the calcination heating rate is 5 DEG C / min, and the calcination time is 3 h.
[0012] Further, the preparation method of the aforementioned nitro functional group modified CeO2 catalyst comprises the following specific steps:
[0013] (1) cerium ammonium nitrate solid is weighed and dissolved in deionized water, and magnetic stirring is performed to obtain solution A; 2-nitroterephthalic acid is weighed and placed in a heat-resistant glass bottle containing N,N-dimethylformamide, and after 0.5 h of ultrasonic treatment, a uniformly dispersed solution B is obtained, then solution A is dropped into solution B to obtain an orange-red mixed solution;
[0014] (2) the orange-red mixed solution obtained in step (1) is placed in an oven, and subjected to a 120 DEG C constant temperature hydrothermal reaction for 15 min, and after the reaction is completed, the solution is naturally cooled to room temperature to obtain a light yellow suspension;
[0015] (3) The light yellow suspension obtained in step (2) is centrifuged and washed with N,N-dimethylformamide and acetone three times, respectively, and then is placed in an oven and dried at 80°C for 12h to obtain Ce-MOF-NO2 solid.
[0016] (4) The Ce-MOF-NO2 solid obtained in step (3) is ground into powder and dispersed in a porcelain boat, which is placed in a muffle furnace and calcined at 700°C for 3h under an air atmosphere at a temperature rising rate of 5°C / min, and after the end, is naturally cooled to room temperature to obtain a nitro-functional group modified CeO2 photocatalyst.
[0017] Further, the nitro-functional group modified CeO2 catalyst is prepared according to the preparation method of the nitro-functional group modified CeO2 catalyst.
[0018] Further, the application of the nitro-functional group modified CeO2 catalyst in photocatalytic oxidation of VOCs.
[0019] Further, the application of the nitro-functional group modified CeO2 catalyst in photocatalytic oxidation of VOCs, the steps are as follows:
[0020] (1) A photocatalyst sample is weighed and uniformly dispersed on a 400-mesh sieve and placed in a reactor;
[0021] (2) A mixture gas of 20ppm toluene / air with a humidity of 50%RH is continuously introduced into the reactor at a flow rate of 50mL / min, and after dark treatment for 40min to reach toluene adsorption-desorption equilibrium, a 280W xenon lamp is turned on for photocatalytic reaction.
[0022] Compared with the prior art, the advantages of the present application are:
[0023] (1) The preparation process of the nitro-functional group modified CeO2 material provided by the present application is simple, the raw materials used are cheap and easy to obtain, the operation is simple, the period is short, and the material can be produced on a large scale, and has a broad application prospect in efficient elimination of indoor VOCs.
[0024] (2) The nitro-functional group modified CeO2 material provided by the present application has strong light response ability and high efficient charge separation and transfer efficiency.
[0025] (3) The nitro-functional group modified CeO2 material provided by the present application has more oxygen vacancies on the surface and good hydrophilicity, which can effectively adsorb and activate reactant molecules, and the large specific surface area and pore size provide more active sites and promote charge transmission, thereby efficiently mineralizing VOCs pollutant molecules. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 A is the XRD spectrum of the Ce-MOF-NO2 material,Figure 1 B is the XRD pattern of n-CeO2 and CeMO-NO2 catalysts;
[0027] Figure 2 is the N2 adsorption-desorption curve (A) and pore distribution (B) of the prepared n-CeO2 and CeMO-NO2 samples; Figure 2 A) and pore distribution (B) of n-CeO2 and CeMO-NO2 catalysts; Figure 2
[0028] Figure 3 is the Raman spectrum (A-B) and water contact angle (C-D) of n-CeO2 and CeMO-NO2 catalysts; Figure 3 Figure 3
[0029] Figure 4 is the UV-Vis DRS (A) and EIS (B) spectrum of n-CeO2 and CeMO-NO2 catalysts; Figure 4 Figure 4
[0030] Figure 5 A-B is the catalytic performance diagram of n-CeO2 and CeMO-NO2 samples for toluene oxidation under full spectrum irradiation, Figure 5 C is the 12h lifetime result diagram of CeMO-NO2 sample for photocatalytic oxidation of toluene, Figure 5 D is the 3-cycle test result diagram of CeMO-NO2 sample for photocatalytic oxidation of toluene. DETAILED DESCRIPTION
[0031] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below.
[0032] Example 1
[0033] The preparation method of nitro-functionalized CeO2 material by solvothermal method is as follows:
[0034] (1) Accurately weigh 1.169g of cerium ammonium nitrate solid into 4mL of deionized water, magnetically stir uniformly to obtain solution A; accurately weigh 0.450g of 2-nitroterephthalic acid into a heat-resistant glass bottle containing 12mL of N,N-dimethylformamide, after 0.5h of ultrasonic treatment, a uniformly dispersed solution B is obtained; then solution A is added dropwise into solution B to obtain an orange-red mixed solution;
[0035] (2) The orange-red mixed solution obtained above is placed in an oven, and hydrothermal reaction is carried out at 120℃ for 15min, and then naturally cooled to room temperature to obtain a light yellow suspension;
[0036] (3) The light yellow suspension was washed with N,N-dimethylformamide and acetone three times, respectively, to remove the excess organic ligand 2-nitroterephthalic acid, and then dried in an oven at 80 °C for 12 h to obtain 0.491 g of Ce-MOF-NO2 solid.
[0037] (4) The obtained Ce-MOF-NO2 solid was ground into powder and dispersed in a porcelain boat, which was placed in a muffle furnace and calcined at 700 °C for 3 h under air atmosphere at a heating rate of 5 °C / min. After the end of the calcination, the sample was allowed to cool to room temperature naturally to obtain a light yellow solid, i.e. a nitro-functionalized CeO2 photocatalyst (0.152 g of CeMO-NO2).
[0038] Example 2
[0039] The method for preparing the common CeO2 material without organic ligand was as follows:
[0040] (1) 1.169 g of accurately weighed cerium ammonium nitrate solid was dissolved in 4 mL of deionized water, and the solution was uniformly stirred by magnetic stirring to obtain solution A. 12 mL of N,N-dimethylformamide was accurately measured and added dropwise into solution A. After ultrasonic treatment for 0.5 h, a uniformly dispersed orange-red mixed solution was obtained;
[0041] (2) The above obtained orange-red mixed solution was placed in an oven and subjected to hydrothermal reaction at 120 °C for 15 min. After the end of the reaction, the sample was allowed to cool to room temperature naturally to obtain a light yellow suspension;
[0042] (3) The light yellow suspension was washed with N,N-dimethylformamide and acetone three times, respectively, and then dried in an oven at 80 °C for 12 h to obtain a yellow fluid.
[0043] (4) The obtained yellow fluid was placed in a porcelain boat, which was placed in a muffle furnace and calcined at 700 °C for 3 h under air atmosphere at a heating rate of 5 °C / min. After the end of the calcination, the sample was allowed to cool to room temperature naturally to obtain a light yellow solid, i.e. a common CeO2 photocatalyst (0.217 g of n-CeO2).
[0044] Figure 1 A is the XRD spectrum of the Ce-MOF-NO2 material, Figure 1 B is the XRD spectrum of the n-CeO2 and CeMO-NO2 catalysts. In Figure 1 In A, the XRD diffraction peak at low angle confirms the successful synthesis of the Ce-MOF-NO2 structure. As can be seen from Figure 1 B, the prepared n-CeO2 and CeMO-NO2 catalysts both exhibit the crystal phase of cubic fluorite CeO2.
[0045] Table 1: Specific surface area and pore size results of n-CeO2 and CeMO-NO2 catalysts
[0046] Sample Specific surface area (m 2 g -1 )]]> Specific surface area (m2 / g 3 g -1 )]]> Pore size (nm) [n-CeO2] 5.9 0.03 18.03 CeMONO2 22.0 0.11 19.84
[0047] Figure 2 are N2 adsorption-desorption curves (A) and pore distribution diagrams (B) of the prepared n-CeO2 and CeMO-NO2 samples. Figure 2 A-B) and water contact angle diagrams (C-D) of n-CeO2 and CeMO-NO2 catalysts. From Figure 2 C-D, it can be seen that CeMO-NO2 catalysts have better hydrophilicity, which can enhance the affinity for reactant molecules, promote the adsorption and activation of reactant molecules, and thus accelerate the progress of surface catalytic reactions. Figure 2 and Table 1, CeMO-NO2 has larger specific surface area and pore size, which can provide more active sites and facilitate the diffusion of reactants, intermediates and charge transport.
[0048] Figure 3 are Raman spectra (A-B) and EIS (B) diagrams of n-CeO2 and CeMO-NO2 catalysts; from Figure 3 A-B, it can be seen that CeMO-NO2 catalysts have higher surface and bulk oxygen vacancy concentrations, surface oxygen vacancies can effectively capture and activate gaseous oxygen, promoting the generation of superoxide radicals, and bulk oxygen vacancies are beneficial to the mineralization of toluene, which may be one of the main reasons for the excellent photocatalytic performance of CeMO-NO2 materials. Figure 3 C-D clearly shows that CeMO-NO2 has good hydrophilicity, which can enhance the affinity for reactant molecules, promote the adsorption and activation of reactant molecules, and thus accelerate the progress of surface catalytic reactions. Figure 3 Figure 3 are UV-Vis DRS (A) and EIS (B) spectra of n-CeO2 and CeMO-NO2 catalysts; from
[0049] A, it can be seen that CeMO-NO2 catalysts exhibit stronger light response ability, indicating that their light utilization rate is relatively large. Figure 4 B shows that the charge transfer resistance of CeMO-NO2 is smaller, indicating that CeMO-NO2 can more efficiently separate and transfer photo-generated carriers under light, so that more effective photo-generated electrons and holes participate in the photocatalytic oxidation of VOCs, thereby exhibiting high-efficiency VOCs elimination performance. Figure 4 Figure 4 Example 3 Figure 4 Figure 4 The photocatalysts prepared in Examples 1-2 were applied to oxidize toluene, and the experimental steps were as follows:
[0050] The photocatalysts prepared in Examples 1-2 were applied to oxidize toluene, and the experimental steps were as follows:
[0051] The photocatalysts prepared in Examples 1-2 were applied to oxidize toluene, and the experimental steps were as follows:
[0052] The photocatalytic oxidation of toluene reaction test was carried out in a continuous flow reactor. 50 mg of photocatalyst sample was weighed, uniformly dispersed on a 400 mesh screen, placed in a 650 mL stainless steel reactor, covered with a stainless steel cover with a 4.5 cm diameter quartz open window, and 50% RH, 20 ppm toluene / air mixture was continuously introduced into the reactor at a flow rate of 50 mL / min. After 40 min of dark treatment to reach toluene adsorption-desorption equilibrium, the photocatalytic reaction was carried out by opening the 280 W xenon lamp. The reaction time for activity test and lifetime test was 2 h and 12 h, respectively. The products were detected and analyzed by online gas chromatography GC-7920 periodically (10 min), and the toluene conversion rate and toluene mineralization rate were calculated by the following formula:
[0053]
[0054]
[0055] In the formula: [Toluene]in and [Toluene]out are the toluene concentrations (ppm) at the inlet and outlet of the reactor, respectively, and [CO2]out is the CO2 concentration (ppm) at the outlet of the reactor.
[0056] Figure 5 A-B is a graph of the catalytic performance of n-CeO2 and CeMO-NO2 samples for toluene oxidation under full spectrum irradiation. It is found that compared with ordinary CeO2, CeMO-NO2 exhibits excellent toluene conversion rate and mineralization rate. Figure 5 C is the 12 h lifetime result of the photocatalytic oxidation of toluene by the CeMO-NO2 sample, Figure 5 D is the 3 cycle test result of the photocatalytic oxidation of toluene by the CeMO-NO2 sample. From Figure 5 C-D, it can be seen that the CeMO-NO2 catalyst has good stability.
[0057] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing a nitro-functional modified CeO2 catalyst, characterized by, The specific steps are as follows: (1) A certain amount of cerium ammonium nitrate is weighed and dissolved in deionized water, and then magnetically stirred to obtain solution A. 2-nitroterephthalic acid is weighed and placed in a heat-resistant glass bottle containing N,N-dimethylformamide, and after ultrasonic treatment for 0.5 h, a uniformly dispersed solution B is obtained. Then, solution A is added dropwise into solution B to obtain an orange-red mixed solution. The molar ratio of cerium ammonium nitrate to 2-nitroterephthalic acid is 1:1; (2) The orange-red mixed solution obtained in step (1) is placed in an oven and subjected to hydrothermal reaction at 120°C for 15 min. After the reaction, the solution is naturally cooled to room temperature to obtain a light yellow suspension; (3) The light yellow suspension obtained in step (2) is washed with N,N-dimethylformamide and acetone by centrifugation for three times, and then placed in an oven and dried at 80°C for 12 h to obtain Ce-MOF-NO2 solid; (4) The Ce-MOF-NO2 solid obtained in step (3) is ground into powder and dispersed in a porcelain boat, which is placed in a muffle furnace and calcined at 700°C for 3 h under air atmosphere at a heating rate of 5°C / min. After the calcination, the sample is naturally cooled to room temperature to obtain a nitro-functionalized CeO2 photocatalyst.
2. The nitro-functionalized CeO2 catalyst prepared by the preparation method of claim 1.