CeO2 / Co3O4 composite nanoprismatic catalysts, methods and applications

Abstract

The application provides a CeO2 / Co3O4 composite nanoprism catalyst, a method and application thereof, and the catalyst comprises: a nanoprism Co-based metal organic framework constructed by 2-methyl imidazole and adjusted in morphology by oxalic acid and CeO2 doped on the Co-based metal organic framework. The three-dimensional prism nanotube catalyst is synthesized through Co ion modulation and oxalic acid morphology regulation, and the Ce element is doped, so that the problems of low efficiency, poor stability and easy poisoning of the existing catalyst in catalytic oxidation of chlorobenzene are solved, and the catalytic oxidation performance of high efficiency, stability and resistance to phosphorus poisoning is realized.

Description

Technical Field

[0001] This invention belongs to the field of chemistry and chemical engineering technology, specifically to a CeO2 / Co3O4 composite nanoprismatic catalyst, its method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) are among the most important precursors to photochemical smog and fine particulate matter. Chlorinated VOCs (Cl-VOCs) are ubiquitous in the environment and highly toxic to organisms. Therefore, degrading harmful Cl-VOCs into non-toxic CO2, H2O, and soluble HCl has significant environmental implications. Catalytic combustion has been considered the most effective and feasible technology for eliminating VOCs. In this process, the catalyst is crucial, and its performance determines the efficiency and energy consumption of the catalytic combustion process.

[0003] Eco-friendly purification of chlorinated volatile organic compounds (Cl-VOCs) remains a significant challenge due to the ease with which catalysts deactivate. Research on the anti-poisoning properties of catalysts in phosphorus environments is limited; therefore, developing cost-effective catalysts with excellent chlorine resistance, organic byproduct inhibition capabilities, and phosphorus poisoning resistance is of great importance. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a CeO2 / Co3O4 composite nanoprismatic catalyst, method, and application. By modulating Co ions and controlling the morphology of oxalic acid, a three-dimensional prismatic nanotube catalyst is synthesized and doped with Ce element. This solves the problems of low efficiency, poor stability, and easy poisoning of existing catalysts in the catalytic oxidation of chlorobenzene, and achieves efficient, stable, and phosphorus-poison-resistant catalytic oxidation performance.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a CeO2 / Co3O4 composite nanoprismatic catalyst, the catalyst comprising: a nanoprismatic Co-based metal-organic framework constructed with 2-methylimidazole and morphology adjusted by oxalic acid, and CeO2 doped on the Co-based metal-organic framework.

[0006] Furthermore, the mass ratio of cobalt to 2-methylimidazole in the nanoprismatic Co-based metal-organic framework is 4:5.

[0007] Furthermore, the cerium content in the catalyst is m(Ce) = 5wt%.

[0008] Furthermore, oxalic acid was used to adjust the morphology using an oxalic acid solution with a pH of 2.1.

[0009] This invention also provides a method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst, the specific steps of which are as follows: Cobalt salt and 2-methylimidazole were added to a solvent and mixed. The mixture was stirred, filtered, washed and dried at room temperature to obtain a cobalt-based metal-organic framework precursor. The cobalt-based metal-organic framework precursor was placed in an oxalic acid solution with a pH of 2.1, stirred, filtered, washed, and dried at room temperature to obtain a prismatic cobalt-based metal-organic framework precursor. A prismatic cobalt-based metal-organic framework precursor was mixed with cerium salt in a solvent, and then stirred, filtered, washed, and dried at room temperature to obtain a cerium-doped composite catalyst. The cerium-doped composite catalyst was calcined to obtain a CeO2 / Co3O4 composite nanoprismatic catalyst.

[0010] Further, in the step of adding cobalt salt and 2-methylimidazole to a solvent, mixing, stirring at room temperature, filtering, washing, and drying to obtain the cobalt-based metal-organic framework precursor: The mass ratio of cobalt salt to 2-methylimidazole is 4:5, the stirring time is 4h~6h, the stirring speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. The washing process involves washing three times with pure water, followed by washing three times with anhydrous ethanol.

[0011] Furthermore, in the step of placing the cobalt-based metal-organic framework precursor in an oxalic acid solution with a pH of 2.1, stirring, filtering, washing, and drying at room temperature to obtain the prismatic cobalt-based metal-organic framework precursor: The stirring time is 4h~6h, the speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. The washing process involves washing three times with pure water, followed by washing three times with anhydrous ethanol.

[0012] Furthermore, in the step of mixing the prismatic cobalt-based metal-organic framework precursor with cerium salt in a solvent, stirring at room temperature, filtering, washing, and drying to obtain the cerium-doped composite catalyst: The catalyst contains cerium with a content of m(Ce) = 5wt%, the stirring time is 4h~5h, the stirring speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. The washing process involves washing three times with pure water, followed by washing three times with anhydrous ethanol.

[0013] Furthermore, in the step of calcining the cerium-doped composite catalyst to obtain the CeO2 / Co3O4 composite nanoprismatic catalyst: The calcination process involves heating the temperature to 450°C at a rate of 5°C / min, holding it at that temperature for 3 hours, and then allowing it to cool naturally to room temperature.

[0014] The present invention also provides a method for catalytic oxidation of chlorobenzene, using the above-mentioned CeO2 / Co3O4 composite nanoprismatic catalyst or a CeO2 / Co3O4 composite nanoprismatic catalyst prepared by the above preparation method; the catalytic oxidation temperature is 200℃~400℃.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a CeO2 / Co3O4 composite nanoprismatic catalyst. The catalyst uses 2-methylimidazole as a metal-organic framework building block and oxalic acid as a morphology modifier, resulting in a prismatic morphology that enhances material stability, increases specific surface area and active sites, and improves degradation rate. Utilizing two transition metals as raw materials, the catalyst exhibits excellent redox performance and stability. The synergistic effect between the two metals enables efficient catalytic oxidation of chlorobenzene at relatively low temperatures. The presence of Ce optimizes the synergistic effect of acid sites, improving the catalyst's resistance to phosphorus poisoning and ensuring high activity even under complex conditions. The catalyst demonstrates good stability and water resistance, while maintaining activity under simulated flue gas phosphorus poisoning conditions. This provides a feasible and promising strategy for designing efficient, poison-resistant catalysts for the industrial-scale destruction of Cl-CVOCs in heterogeneous thermocatalytic reactions.

[0016] The CeO2 / Co3O4 nanocatalyst of the present invention mainly uses two transition metals as raw materials, which have better stability and lower cost compared with noble metal catalysts, and are easy to use in industrial applications. The preparation method of this invention includes the synthesis of a cobalt-based metal-organic framework, morphology regulation, and synthesis of a composite catalyst. Specifically, it includes using oxalic acid as a morphology modifier, 2-methylimidazole as a metal framework building agent, cobalt- and cerium-containing compounds as raw materials, and pure water as a solvent to synthesize a cobalt-based metal framework precursor by precipitation, and a CeO2 / Co3O4 composite catalyst by impregnation. A three-dimensional (3D) Co-based metal-organic framework (Co-MOFs) is successfully synthesized by modulating and reconstructing the secondary building units (SBUs) with Co ions. A three-dimensional prismatic nanotube catalyst is synthesized by adjusting the pH of the oxalic acid solution, and Ce is then doped to obtain a CeO2 / Co3O4 nanoprismatic catalyst. This catalyst with this morphology is used for the catalytic oxidation of chlorobenzene. Studies have found that the presence of Ce induces oxygen vacancies (O... vThis can optimize the synergistic effect between Lewis acid sites (LAS) and Boucher acid sites (BAS) in Co-based catalysts. A series of characterizations verified that the three-dimensional nanoprismatic catalyst possesses more Co... 3+ and Ce 3+ Species with excellent redox properties (Ce 4+ +Co 2+ →Ce 3+ +Co 3+ These factors collectively promote the conversion of Cl-VOCs. Meanwhile, using a three-dimensional network CeO2 / Co3O4 nanocatalyst as a comparison, the effect of morphology on the catalytic oxidation efficiency of the catalyst was compared. Comparative experiments verified that the three-dimensional nanoprismatic catalyst exhibits excellent catalytic oxidation performance (1000 ppm; T 90 =290°C) and resistance to phosphorus poisoning.

[0017] This invention utilizes a CeO2 / Co3O4 composite nanoprismatic catalyst to achieve highly efficient catalytic oxidation of chlorobenzene at a relatively low temperature, with a T90 of only 290℃. This helps reduce energy consumption and improve reaction efficiency. Simultaneously, the catalyst exhibits excellent chlorine resistance, organic byproduct inhibition ability, and phosphorus poisoning resistance, ensuring the stability and durability of the catalytic process. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a SEM image of the prismatic Co-MOF precursor obtained in Example 1 of this invention.

[0020] Figure 2 This is a SEM image of the network Co-MOFs precursor prepared in Comparative Example 1.

[0021] Figure 3 These are SEM images of CeO2 / Co3O4 composite nanocatalysts with different morphologies in Example 1 and Comparative Example 1.

[0022] Figure 4 These are the XRD patterns of the composite catalysts prepared in Example 1 and Comparative Example 1, as well as standard Co3O4 and CeO2.

[0023] Figure 5The graph shows the test results of the CB catalytic combustion activity of the composite catalysts prepared in Example 1 and Comparative Example 1.

[0024] Figure 6 The graph shows the test results of the anti-phosphorus poisoning catalytic combustion activity of the composite catalysts prepared in Example 1 and Comparative Example 1.

[0025] Figure 7 The graph shows the test results of the water-resistant catalytic combustion activity of the composite catalysts prepared in Example 1 and Comparative Example 1 under water vapor at 1.0 vol%, 3.0 vol%, 5.0 vol%, and 10.0 vol%.

[0026] Figure 8 This is a cyclic stability diagram of the chlorobenzene catalytic combustion of the composite catalyst prepared in Example 1. Detailed Implementation

[0027] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0028] This invention provides a CeO2 / Co3O4 composite nanoprismatic catalyst with a Co-based metal-organic framework as a precursor. The catalyst comprises a nanoprismatic Co-based metal-organic framework constructed using 2-methylimidazolium and morphology adjusted with oxalic acid, and CeO2 doped onto the Co-based metal-organic framework. The catalyst has a pore size of 17.92 nm and a specific surface area of ​​52.1631 m². 2 / g.

[0029] In this catalyst, the mass ratio of cobalt to 2-methylimidazole in the Co-based metal-organic framework is 4:5, and the content of cerium doped in the catalyst is m(Ce)=5wt%.

[0030] The preparation method of the above-mentioned CeO2 / Co3O4 composite nanoprismatic catalyst with Co-based metal-organic framework as precursor includes the following steps: Step 1: Preparation of Co-MOF precursors: Cobalt nitrate hexahydrate and 2-methylimidazole were dissolved in water, and the mixture was stirred, filtered, washed and dried at room temperature to obtain a cobalt-based metal-organic framework precursor. Step 2: Morphology regulation of Co-MOF precursors: The cobalt-based metal-organic framework precursor was dissolved in oxalic acid solution, and after stirring, filtering, washing and drying at room temperature, a prismatic cobalt-based metal-organic framework precursor was obtained. Step 3: CeO2 doping: A prismatic cobalt-based metal-organic framework precursor was dissolved in ethanol solution with cerium nitrate hexahydrate, and the mixture was stirred, filtered, washed and dried at room temperature to obtain a cerium-doped composite catalyst. Step 4: Preparation of CeO2 / Co3O4 composite catalyst: The composite catalyst was calcined and cooled to obtain the CeO2 / Co3O4 composite nanoprismatic catalyst.

[0031] This invention uses 2-methylimidazole as a metal-organic framework building agent and oxalic acid as a morphology modifier. The metal-organic framework structure is altered by forming organic ligands with oxalic acid. Both cobalt nitrate hexahydrate and cerium nitrate hexahydrate anions are nitrate ions, facilitating removal during experiments without introducing new impurities and ensuring experimental accuracy. A micro-modification precipitation method is used to construct the metal-organic framework, making the catalyst structure more stable. The prismatic morphology increases the specific surface area of ​​the catalyst and simultaneously increases the number of active sites. Cerium-based doping is performed using an impregnation method to enhance intermetallic synergy and further improve catalyst degradation efficiency. The calcination process reduces the catalyst particle size, resulting in a hollow porous structure with stable morphology. The calcination process does not affect the original morphology of the catalyst, ensuring its high efficiency and stability in practical applications.

[0032] Preferably, in step one, the mass ratio of cobalt nitrate hexahydrate to 2-methylimidazole is 4:5, the stirring time is 4h~6h, the stirring speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. Preferably, in step two, the pH value of the oxalic acid solution is adjusted to 2.1 precisely, the stirring time is 4h~6h, the stirring speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. Preferably, in step three, the cerium-based mass doping is 5wt%, the stirring time is 4h~5h, the stirring speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. Preferably, in step four, the calcination treatment involves heating to 450°C at a rate of 5°C / min, holding at that temperature for 3 hours, and then allowing it to cool naturally to room temperature. Preferably, in steps one, two, and three, the washing process involves washing three times with pure water and then washing three times with anhydrous ethanol. The CeO2 / Co3O4 composite nanoprismatic catalyst prepared by this invention can be used in the catalytic oxidation of chlorobenzene at a catalytic oxidation temperature of 200℃~400℃.

[0033] Example 1: A CeO2 / Co3O4 composite nanoprismatic catalyst, the preparation method includes the following steps: Step 1: Preparation of Co-MOF precursors: 1) Take 75 mL of water containing 5.46 g Co(NO3)2·6H2O and 6.16 g 2-methylimidazole, and stir continuously at room temperature for 5 h at a speed of 1500 rpm; 2) Centrifuge to collect the purple precipitate, and wash it three times with pure water and ethanol respectively; 3) The obtained purple solid was dried at 70°C for 7 hours to obtain the metal-organic framework Co-MOF precursor.

[0034] Step 2: Morphology regulation of Co-MOF precursors: 1) The Co-MOFs-NC precursor was placed in an oxalic acid solution with a pH of 2.1 and stirred continuously at room temperature for 5 hours at a speed of 1500 rpm to obtain a pink suspension. 2) Then, the pink suspension was collected by centrifugation and washed three times with pure water and ethanol, respectively. 3) The obtained pink solid was dried at 70°C for 7 hours to obtain a prismatic metal-organic framework Co-MOF precursor.

[0035] Step 3: CeO2 doping: 1) The prepared 1.2g Co-MOFs precursor was added to 50 mL of ethanol solution containing 0.2327g cerium nitrate Ce(NO3)3·6H2O (m(Ce)=10 wt.%). After stirring continuously at room temperature for 4.5h, the mixture was collected by centrifugation at 1500rpm, washed three times with pure water and ethanol respectively, and dried at 70°C for 7h to obtain cerium-doped composite catalyst.

[0036] Step 4: Preparation of CeO2 / Co3O4 composite catalyst: The cerium-doped composite catalyst was heated to 450℃ at a rate of 5℃ / min, held at that temperature for 3h, and then allowed to cool naturally to room temperature to obtain the CeO2 / Co3O4 composite nanoprismatic catalyst.

[0037] Figure 1 This is a SEM image of the prismatic Co-MOF precursor obtained in Example 1. (From...) Figure 1 As can be seen from a and 1b, 2-methylimidazole contributes to the formation of metal-organic frameworks. At the same time, when oxalic acid (OA) is used as a structure modifier to regulate the morphology of metal-organic frameworks Co-MOFs, the adjustment of pH value leads to the reconstruction of their metal-organic framework structure, thereby forming a nanoprismatic structure.

[0038] Comparative Example 1: A CeO2 / Co3O4 composite nanocatalyst is presented. The difference between this comparative example and Example 1 is that the oxalic acid solution in this comparative example has a pH value of 4.1, forming a network metal-organic framework morphology. The remaining components and preparation steps are the same as in Example 1, thereby comparing the effects of different morphologies on the catalyst structure and performance.

[0039] Step 1: Preparation of Co-MOF precursors: 1) Take 75 mL of water containing 5.46 g Co(NO3)2·6H2O and 6.16 g 2-methylimidazole, and stir continuously at room temperature for 4 to 6 hours; 2) Centrifuge to collect the purple precipitate, and wash it three times with pure water and ethanol respectively; 3) The obtained purple solid was dried at 80°C overnight to obtain the metal-organic framework Co-MOF precursor.

[0040] Step 2: Morphology regulation of Co-MOF precursors: 1) The Co-MOFs-NC precursor was placed in an oxalic acid solution with a pH of 4.1 and stirred continuously at room temperature for 6 h to obtain a pink suspension; 2) Then, the blue suspension was collected by centrifugation and washed three times with pure water and ethanol, respectively. 3) The obtained blue solid was dried at 80°C overnight to obtain a network metal-organic framework Co-MOF precursor.

[0041] Step 3: CeO2 doping: 1) The prepared 0.96 Co-MOFs precursor was added to 50 mL of ethanol solution containing 0.2327 g cerium nitrate Ce(NO3)3·6H2O (m(Ce)=5 wt.%). After stirring continuously for 5 h at room temperature, the mixture was collected by centrifugation and washed three times with pure water and ethanol respectively.

[0042] Step 4: Preparation of CeO2 / Co3O4 composite catalyst: 1) The prepared CeCoOx catalyst was dried at 80°C overnight to obtain a solid, which was then calcined in air at 450°C for 3 hours to obtain the CeO2 / Co3O4 composite nano-network catalyst.

[0043] Figure 2 This is a SEM image of the network Co-MOFs precursor obtained in Comparative Example 1. Figure 2As shown in a and 2b, 2-methylimidazole contributes to the formation of the metal-organic framework (MOF), while oxalic acid (OA) is used as a structure modifier to regulate the morphology of the Co-MOFs, thereby forming a nano-network structure. Compared with Example 1, the nano-network structure can be obtained by using a low-concentration oxalic acid solution as a structure modifier, while the nano-prismatic structure is formed in a high-concentration oxalic acid solution. The prismatic structure catalyst has a larger specific surface area than the network structure catalyst, and it also increases the number of active sites, thereby improving the catalytic oxidation efficiency.

[0044] Figure 3 These are SEM images of CeO2 / Co3O4 composite nanocatalysts with different morphologies from Example 1 and Comparative Example 1. It was observed that the two CeCoOx catalysts with different morphologies still exhibited the morphology of metal-organic framework precursors after calcination at 450℃. Unlike the precursors, however, they formed porous hollow structures after calcination. The prismatic nanotube shape of the catalyst in Example 1 remained unchanged after calcination, as did the prismatic nanonetwork shape of the catalyst in Comparative Example 1. The difference in morphology affects the degradation efficiency of the catalysts.

[0045] Figure 4 These are the XRD patterns of the composite catalysts prepared in Example 1 and Comparative Example 1, as well as standard Co3O4 and CeO2. Figure 4 It can be seen that the phase composition of all samples is consistent and is related to the contributions of CeO2 and Co3O4 species. The diffraction peaks at 28.5°, 47.5°, and 76.7° correspond to the (111), (220), and (331) planes of the cubic CeO2 phase (PDF#75-0120), respectively. The diffraction peaks at 31.3°, 36.9°, 44.9°, 59.5°, and 65.2° are related to the (220), (311), (400), (511), and (440) planes of the cubic Co3O4 phase (PDF#74-2120), respectively. The difference in peak intensity is related to the difference in crystal size. Calculations show that the crystallite size of the nanoprismatic catalyst in Example 1 is smaller than that of the nanomesh catalyst in Comparative Example 1. It was also found that the CeO2 phase in Example 1 and Comparative Example 1 both exhibited some weak diffraction peaks, which is due to the low Ce species content (5wt%). Therefore, it can be concluded that the nanoprismatic catalyst structure of the present invention has the smallest Co3O4 grain size.

[0046] Example 2 A method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst with a Co-based metal-organic framework as a precursor includes the following steps: Step 1: Preparation of Co-MOF precursors: Take 75 mL of water containing 5.46 g Co(NO3)2·6H2O and 6.16 g 2-methylimidazole, stir at room temperature for 6 h at a speed of 2000 rpm, filter, wash three times with pure water and then wash three times with anhydrous ethanol, dry at 80℃ for 8 h to obtain the metal-organic framework Co-MOFs precursor.

[0047] Step 2: Morphology regulation of Co-MOF precursors: The Co-MOFs-NC precursor was placed in an oxalic acid solution with a pH of 2.1 and stirred at room temperature for 6 hours at a speed of 2000 rpm. After filtration, it was washed three times with pure water and then three times with anhydrous ethanol. The drying temperature was 80℃ and the drying time was 8 hours to obtain the prismatic metal-organic framework Co-MOFs precursor.

[0048] Step 3, CeO2 doping: The prepared 1.2g Co-MOFs precursor was added to 50 mL of ethanol solution containing 0.2327g cerium nitrate Ce(NO3)3·6H2O (m(Ce)=10 wt.%). The mixture was stirred at room temperature for 5 h at a speed of 2000 rpm, filtered, washed three times with pure water, and then washed three times with anhydrous ethanol. The mixture was dried at 80℃ for 8 h to obtain the cerium-doped composite catalyst.

[0049] Step 4: Preparation of CeO2 / Co3O4 composite catalyst: The cerium-doped composite catalyst obtained in step 3 was heated to 450℃ at a rate of 5℃ / min, held at that temperature for 3h, and then allowed to cool naturally to room temperature to obtain the CeO2 / Co3O4 composite nanoprismatic catalyst.

[0050] Example 3 A method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst with a Co-based metal-organic framework as a precursor includes the following steps: Step 1: Preparation of Co-MOF precursors: Take 75 mL of water containing 5.46 g Co(NO3)2·6H2O and 6.16 g 2-methylimidazole, stir at room temperature for 4 h at a speed of 1000 rpm, filter, wash three times with pure water and then wash three times with anhydrous ethanol, dry at 60℃ for 6 h to obtain the metal-organic framework Co-MOFs precursor.

[0051] Step 2: Morphology regulation of Co-MOF precursors: The Co-MOFs-NC precursor was placed in an oxalic acid solution with a pH of 2.1 and stirred at room temperature for 4 hours at a speed of 1000 rpm. After filtration, it was washed three times with pure water and then three times with anhydrous ethanol. The drying temperature was 60℃ and the drying time was 6 hours to obtain the prismatic metal-organic framework Co-MOFs precursor.

[0052] Step 3, CeO2 doping: The prepared 1.2g Co-MOFs precursor was added to 50 mL of ethanol solution containing 0.2327g cerium nitrate Ce(NO3)3·6H2O (m(Ce)=10 wt.%). The mixture was stirred at room temperature for 4 h at a speed of 1000 rpm, filtered, washed three times with pure water, and then washed three times with anhydrous ethanol. The mixture was dried at 60℃ for 6 h to obtain the cerium-doped composite catalyst.

[0053] Step 4: Preparation of CeO2 / Co3O4 composite catalyst: The cerium-doped composite catalyst obtained in step 3 was heated to 450℃ at a rate of 5℃ / min, held at that temperature for 3h, and then allowed to cool naturally to room temperature to obtain the CeO2 / Co3O4 composite nanoprismatic catalyst.

[0054] Example 4 Application of a CeO2 / Co3O4 composite nanoprismatic catalyst in the catalytic oxidation of chlorobenzene. Specifically, the CeO2 / Co3O4 composite nanocatalysts with different morphologies prepared in Example 1 and Comparative Example 1 were used to catalytically oxidize chlorobenzene at catalytic oxidation temperatures of 200℃, 250℃, 300℃, 350℃, and 400℃, with a chlorobenzene concentration of 1000ppm.

[0055] Figure 5 The graphs show the test results of the composite catalysts described in Example 1 and Comparative Example 1 for the catalytic combustion activity of CB. The temperatures required to achieve 50% and 90% CB conversion rates in this invention (T0, T0, respectively) are also shown. 50 and T 90 The catalytic activity of the catalysts in Example 1 and Comparative Example 1 was evaluated using [the following method / method]. Figure 5 It can be seen that in the CB oxidation reaction, the T values ​​of these catalysts... 50 The values ​​are in the following order: CeCoOx - Example 1 > CeCoOx - Comparative Example 1 > Co-MOFs - Precursor, indicating that Ce doping can effectively improve the CB conversion rate of the catalyst; CeCoOx - Example 1 has the highest CB destruction activity, T 90 (280℃) is much lower than that of Co-MOFs precursors (T 90 =450℃), this is because the prismatic structure has a large specific surface area and more active sites and oxygen vacancies, which can accelerate C during the catalytic process. Cl bond cleavage and promotion of lattice oxygen migration, while improving the low-temperature reducibility and deep oxidation of benzene series compounds, thus exhibiting higher CB catalytic oxidation activity, all of which indicate that the morphology of the catalyst is crucial to regulating its catalytic performance.

[0056] Example 5 The anti-poisoning properties of catalysts are crucial for their large-scale production applications. Specifically, 5 wt% ammonium dihydrogen phosphate was added to the CeO2 / Co3O4 composite nanocatalysts with different morphologies prepared in Example 1 and Comparative Example 1 to study the effect of phosphorus poisoning on the activity of CeCoOx catalysts with different morphologies in a CB catalytic reactor, with a chlorobenzene concentration of 1000 ppm.

[0057] Figure 6 The graph shows the test results of the anti-phosphorus poisoning catalytic combustion activity of the composite catalysts prepared in Example 1 and Comparative Example 1, respectively. The temperature (T) required to achieve 50% CB conversion is also shown. 50 The catalytic activity of a catalyst is evaluated using [method / method]. Figure 6 It can be seen that the T50 values ​​of these catalysts are in the following order: CeCoOx - Example 1 > CeCoOx - Comparative Example 1, indicating that the prismatic structure can effectively improve the catalyst's resistance to phosphorus poisoning.

[0058] Example 6 Application of a CeO2 / Co3O4 composite nanoprismatic catalyst in the catalytic oxidation of chlorobenzene, demonstrating its water resistance. Specifically, CeO2 / Co3O4 composite nanocatalysts with different morphologies prepared in Example 1 and Comparative Example 1 were used to catalytically oxidize chlorobenzene, with water vapor concentrations of 1.0 vol%, 3.0 vol%, 5.0 vol%, and 10.0 vol% respectively introduced, and the chlorobenzene concentration was 1000 ppm.

[0059] Figure 7 The graph shows the test results of the water-resistant catalytic combustion activity of the composite catalysts prepared in Example 1 and Comparative Example 1 under water vapor conditions of 1.0 vol%, 3.0 vol%, 5.0 vol%, and 10.0 vol%. Figure 7 It can be seen that the reaction efficiency is slightly higher under the condition of adding 1.0 vol% water vapor than under the dry condition, indicating that the appropriate introduction of water vapor increases the hydroxyl concentration, thereby improving the reaction efficiency in Co. 3+After site dissociation, BAS is formed, which promotes the adsorption of CB molecules and accelerates the formation and desorption of inorganic chlorine seeds. When the water vapor content further increases (3.0 and 5.0 vol%), the CB destruction activity of CeCoOx decreases (approximately 3% and 6%), and when the water vapor content increases to 10.0 vol%, the CB destruction activity of CeCoOx decreases by 10%. The deactivation of the cobalt-based catalyst in the presence of water vapor is attributed to the competitive adsorption of water molecules and CB. The CB destruction activity of the nanoprismatic catalyst prepared in Example 1 can be rapidly restored to its original level within 15 min after the water vapor is turned off. In addition, the catalyst maintains stable and non-deactivated CB destruction activity under 10 vol% H2O conditions for a long time, and can still recover its original catalytic activity after the water vapor is cut off, which confirms its good water resistance.

[0060] Example 7 Application of a CeO2 / Co3O4 composite nanoprismatic catalyst in the catalytic oxidation of chlorobenzene. Specifically, the CeO2 / Co3O4 composite nanocatalysts with different morphologies prepared in Example 1 were used for the catalytic oxidation of chlorobenzene for more than 24 hours, at catalytic oxidation temperatures of T... 50 T 100 At that temperature, the concentration of chlorobenzene was 1000 ppm.

[0061] Figure 8 This is a cyclic stability diagram of the chlorobenzene catalytic combustion of the composite catalyst described in Example 7. Figure 8 It can be seen that the CB conversion rate is controlled at around 98% at a relatively high reaction temperature, and the CB conversion rate in Example 1 can be maintained at around 98% for 40 hours. Meanwhile, at T... 50 Even at 248℃, the CB conversion rate can be maintained at around 50% for 40 hours. These results demonstrate that the nano-prismatic CeCoOx catalysts exhibit good long-term thermal stability.

Claims

1. A method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst, characterized in that, The specific steps are as follows: Cobalt salt and 2-methylimidazole were added to a solvent and mixed. The mixture was stirred, filtered, washed and dried at room temperature to obtain a cobalt-based metal-organic framework precursor. The cobalt-based metal-organic framework precursor was placed in an oxalic acid solution with a pH of 2.1, stirred, filtered, washed, and dried at room temperature to obtain a prismatic cobalt-based metal-organic framework precursor. A prismatic cobalt-based metal-organic framework precursor was mixed with cerium salt in a solvent, and then stirred, filtered, washed, and dried at room temperature to obtain a cerium-doped composite catalyst. The cerium-doped composite catalyst was calcined to obtain a CeO2 / Co3O4 composite nanoprismatic catalyst.

2. The method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst according to claim 1, characterized in that, In the step of adding cobalt salt and 2-methylimidazole to a solvent, mixing, stirring at room temperature, filtering, washing, and drying to obtain the cobalt-based metal-organic framework precursor: The mass ratio of cobalt salt to 2-methylimidazole is 4:5, the stirring time is 4h~6h, the stirring speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. The washing process involves washing three times with pure water, followed by washing three times with anhydrous ethanol.

3. The method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst according to claim 1, characterized in that, The step of placing the cobalt-based metal-organic framework precursor in an oxalic acid solution with a pH of 2.1, stirring at room temperature, filtering, washing, and drying to obtain the prismatic cobalt-based metal-organic framework precursor is as follows: The stirring time is 4h~6h, the speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. The washing process involves washing three times with pure water, followed by washing three times with anhydrous ethanol.

4. The method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst according to claim 1, characterized in that, In the step of mixing the prismatic cobalt-based metal-organic framework precursor with cerium salt in a solvent, stirring at room temperature, filtering, washing, and drying to obtain the cerium-doped composite catalyst: The catalyst contains cerium with a content of m(Ce) = 5wt%, the stirring time is 4h~5h, the stirring speed is 1000rpm~2000rpm, the drying temperature is 60℃~80℃, and the drying time is 6h~8h. The washing process involves washing three times with pure water, followed by washing three times with anhydrous ethanol.

5. The method for preparing a CeO2 / Co3O4 composite nanoprismatic catalyst according to claim 1, characterized in that, In the step of calcining the cerium-doped composite catalyst to obtain the CeO2 / Co3O4 composite nanoprismatic catalyst: The calcination process involves heating the temperature to 450°C at a rate of 5°C / min, holding it at that temperature for 3 hours, and then allowing it to cool naturally to room temperature.

6. A CeO2 / Co3O4 composite nanoprismatic catalyst, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 5.

7. A method for catalytic oxidation of chlorobenzene, characterized in that, The catalytic oxidation temperature using the CeO2 / Co3O4 composite nanoprismatic catalyst as described in claim 6 is 200℃~400℃.

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