Preparation method and application of porous nanorod catalyst of CeO2 co-modified by HPW and Ru

Abstract

This invention discloses a method for preparing a CeO2 porous nanorod catalyst co-modified with HPW and Ru and its application, belonging to the field of catalytic materials technology. The invention includes the following steps: (1) preparation of cerium dioxide porous nanorods; (2) loading HPW onto cerium dioxide porous nanorods to obtain CeO2-HPW; (3) loading Ru nanoparticles onto CeO2-HPW to obtain the HPW and Ru co-modified CeO2 porous nanorod catalyst Ru / CeO2-HPW. The catalyst of this invention has a porous rod structure, characterized by high pore size, high acid capacity, multiple redox active sites, and resistance to water vapor. When applied to the catalytic oxidation of 1,2-DCE, the catalyst achieves a 90% conversion at temperature T. 90 It exhibits excellent catalytic performance at 273 °C, and the carbon dioxide mineralization rate of 1,2-DCE reaches 90% at 279 °C, reducing the formation of by-products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst materials, and particularly relates to a preparation method of a HPW and Ru co-modified CeO2 porous nanorod catalyst and application thereof. BACKGROUND

[0002] Chlorinated volatile organic compounds (CVOCs) are chlorinated hydrocarbons with high volatility, chemical stability and toxicity. 1,2-Dichloroethane (DCE) is a typical CVOC and is widely used in pharmaceuticals, coatings, printing and petrochemical industries. Common methods for treating CVOCs include adsorption, absorption, condensation, combustion, low-temperature plasma and catalytic oxidation. Among them, catalytic oxidation is an efficient and complete method for eliminating CVOCs. However, catalytic oxidation degradation of CVOCs faces challenges such as chlorine poisoning and water vapor interference, which are more difficult to solve compared with non-halogenated VOCs. Therefore, it is crucial to explore catalysts with high activity, water vapor resistance and chloride resistance in the catalytic oxidation of CVOCs.

[0003] CeO2 is a rare earth oxide with abundant reserves, and its Ce 3+ / Ce 4+ are easily converted into each other, endowing it with abundant oxygen vacancies and Lewis acidity. These characteristics make CeO2 an ideal redox carrier or active component, which is widely used in various catalytic researches. However, there are significant problems in using original CeO2 to catalyze chlorinated volatile organic compounds (CVOCs): first, inorganic chlorine (Cl) species will strongly occupy surface oxygen vacancies, leading to catalyst deactivation. Second, the oxygen storage capacity (OSC) and surface oxygen vacancy concentration of pure CeO2 are low, and the redox ability is insufficient, making it difficult to efficiently activate CVOCs molecules, and usually requiring high temperature to achieve complete oxidation, which is energy-consuming and easy to cause chlorine poisoning. In addition, Cl - released during the decomposition of CVOCs will strongly adsorb on the surface of CeO2, forming stable Ce-Cl bonds and covering active oxygen vacancies, further exacerbating catalyst deactivation. Accumulation of Cl - may also trigger secondary reactions to generate highly toxic polychlorinated byproducts or Cl2, reducing reaction selectivity and safety. At the same time, under high-temperature reaction conditions (especially in Cl-containing environments), CeO2 is prone to grain agglomeration and sintering, leading to a decrease in specific surface area and a reduction in active sites, further weakening its catalytic performance.

[0004] Ruthenium (Ru) is a noble metal, which has been applied in many catalytic oxidation studies of chlorinated volatile organic compounds (CVOCs) due to its excellent activity in Deacon reaction and outstanding chlorine handling ability. However, RuO xThe high redox properties (or Gaudican reactivity) of / CeO2 inevitably lead to the formation of a large amount of Cl2, which promotes further chlorination during the catalytic oxidation of CVOCs, generating more polychlorinated organic compounds (polychlorinated byproducts). Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a method for preparing a CeO2 porous nanorod catalyst co-modified with HPW and Ru and its application. The catalyst is obtained by loading phosphotungstic acid and ruthenium onto cerium dioxide porous nanorods. This catalyst has a porous rod-like structure with high pore size, high acid capacity, multiple redox active sites, and resistance to water vapor. It exhibits excellent catalytic performance in the 1,2-DCE reaction.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a CeO2 porous nanorod catalyst co-modified with HPW and Ru includes the following steps: preparing cerium dioxide CeO2 porous nanorods, adding the CeO2 porous nanorods to an aqueous solution of phosphotungstic acid HPW and stirring to react, thereby preparing CeO2-HPW, and then loading Ru nanoparticles to obtain the HPW and Ru co-modified CeO2 porous nanorod catalyst.

[0008] Furthermore, the preparation method of the HPW and Ru co-modified CeO2 porous nanorod catalyst specifically includes the following steps:

[0009] (1) Preparation of cerium dioxide porous nanorods: Cerium dioxide porous nanorods, denoted as CeO2, were prepared by hydrothermal method.

[0010] (2) Preparation of CeO2-HPW: The cerium dioxide porous nanorods from step (1) were immersed in an HPW aqueous solution with a mass concentration of 10-15 g / L and stirred at room temperature for 10-15 h. Then, the mixture was centrifuged, the precipitate was washed, dried, and calcined to obtain CeO2-HPW. The cerium dioxide porous nanorods were then placed in a phosphotungstic acid solution for phosphotungstic acid loading. 12 O 40 HPW dissociates into heteropoly anions [PW] after dissolving in water. 12 O 40 ] 3-Its unique Keggin structure (a central PO4 tetrahedron surrounded by 12 WO6 octahedra) endows it with strong acidity and redox activity; porous CeO2 (PN-CeO2) interacts with HPW anions through electrostatic adsorption or hydrogen bonding via its high specific surface area and surface hydroxyl groups (-OH); the mesoporous structure of CeO2 promotes uniform dispersion of HPW and prevents aggregation; at high temperatures, HPW may partially decompose into WO3 and P2O5, but the Keggin core ([PW... 12 O 40 ] 3- It can be retained and covalently bonded to the CeO2 lattice to form a WO-Ce interface; the residual WO3 forms a composite oxide with CeO2, which enhances thermal stability.

[0011] (3) Synthesis of Ru / CeO2-HPW: The CeO2-HPW from step (2) was ultrasonically dispersed in water, and a mixed solution of RuCl3·3H2O, isopropanol, and water was added to form a suspension. The pH of the suspension was adjusted to neutral, and after stirring, a prepared NaBH4 aqueous solution was injected into the suspension for mixing. After filtration, the precipitate was washed and dried. The dried powder was transferred to a tube furnace and a H2 / Ar mixed gas was introduced for reaction to obtain a CeO2 porous nanorod catalyst co-modified with HPW and Ru, denoted as Ru / CeO2-HPW. During this process, at neutral pH, the CeO2 surface is positively charged, and [Ru(H2O)6] is generated by the hydrolysis of RuCl3. 3+ Adsorption occurs via electrostatic interactions between the hydroxyl groups (-OH) on the CeO2 surface and the heteropolyanions ([PW]) of HPW. 12 O 40 ] 3- ) and Ru 3+ Formation of coordination bonds enhances metal-support interactions; NaBH4 rapidly converts Ru under neutral pH conditions. 3+ Reduced to metallic Ru 0 Isopropanol can reduce the polarity of aqueous solutions, slow down the nucleation rate of Ru NPs, and inhibit particle aggregation; in the subsequent reaction under a 5% H2 / Ar atmosphere, the residual Cl in the added RuCl is reduced, thus minimizing the impact of residual Cl on the catalyst's reactivity; it promotes Cl... - The desorption process purifies the catalyst surface.

[0012] Further, in step (1), Ce(NO3)3·6H2O aqueous solution is mixed with NaOH aqueous solution, stirred, and subjected to the first hydrothermal reaction. After the reaction is completed, it is naturally cooled to room temperature, centrifuged and the precipitate is collected to obtain the first product. The first product is washed and dried, and the dried product is added to water and subjected to the second hydrothermal reaction. After the reaction is completed, the second product is formed. The second product is calcined to obtain cerium dioxide porous nanorods, denoted as CeO2. The weight ratio of Ce(NO3)3·6H2O to NaOH is 1-2:18-20. The temperature of the first hydrothermal reaction is 90-110℃ and the time is 20-30h. The temperature of the second hydrothermal reaction is 150-180℃ and the time is 10-15h. The calcination conditions are as follows: heating at 5℃ / min, calcination temperature is 450-550℃, and calcination time is 1-3h. Hydrothermal conditions are set to promote the dehydration and crystallization of amorphous cerium hydroxide, forming CeO2 nanoparticles with a cubic fluorite structure. Secondary hydrothermal treatment at higher temperatures induces Ostwald ripening of the particles, with small particles dissolving and recrystallizing on the surface of large particles to form a more stable porous structure. Calcination removes residual hydroxyl groups and organic matter, further improving the crystallinity of CeO2 and stabilizing the porous structure.

[0013] Furthermore, in step (2), the calcination conditions are as follows: the temperature is increased by 5℃ / min, the calcination temperature is 450-550℃, and the calcination time is 1-3h.

[0014] Further, the specific operation steps of step (3) are as follows: 0.3-0.5g of CeO2-HPW from step (2) is ultrasonically dispersed in 90-110mL of water and ultrasonically sonicated for 20-50min to obtain a suspension; 1-3mL of isopropanol and 15-20mL of water are mixed, and then 0.01-0.02g of RuCl3·3H2O is added and mixed to obtain a mixed solution; the mixed solution is added to the suspension and mixed to form a suspension; the pH of the suspension is adjusted to neutral, and after stirring for 20-50min, 7-9mL of the prepared 10mM NaBH4 aqueous solution is injected into the suspension and mixed; after filtration, the precipitate is washed and dried; the dried powder is transferred into a tube furnace and 5% H2 / Ar mixed gas is introduced and reacted at 200-300℃ for 1-3h to obtain HPW and Ru co-modified CeO2 porous nanorod catalyst, denoted as Ru / CeO2-HPW.

[0015] Furthermore, the HPW and Ru co-modified CeO2 porous nanorod catalyst has a porous structure with a specific surface area of ​​75-76 m². 2 / g, pore volume is 0.35-0.40cm³ 3 / g, with an average pore size of 24.0-24.5 nm and a total acid content of 430-450 μmol / g; in the catalytic oxidation of 1,2-DCE, the HPW and Ru co-modified CeO2 porous nanorods catalyzed a 90% conversion at temperature T. 90 The temperature is 270-275℃.

[0016] The present invention also provides the application of the HPW and Ru co-modified CeO2 porous nanorod catalyst in the catalytic reaction of chlorine-containing volatile organic compounds.

[0017] Furthermore, the chlorine-containing volatile organic compound is 1,2-dichloroethane, i.e., 1,2-DCE.

[0018] Furthermore, the application of the HPW and Ru co-modified CeO2 porous nanorod catalyst in the catalytic reaction of chlorine-containing volatile organic compounds includes the following steps: 150-250 mg of the HPW and Ru co-modified CeO2 porous nanorod catalyst is loaded into a reactor; 1,2-dichloroethane is introduced into the reactor at a concentration of 900-1200 ppm; simultaneously, a mixture of nitrogen and oxygen is introduced at a total flow rate of 100 mL / min, and the oxygen content is 10% by volume.

[0019] The present invention has the following beneficial effects:

[0020] 1. This invention prepares porous cerium dioxide nanorods via a two-step hydrothermal method. The obtained cerium dioxide is loaded with phosphotungstic acid, followed by loading a precursor with ruthenium nanoparticles. After treatment with 5% H₂ / Ar, a porous cerium dioxide nanorod catalyst co-modified with phosphotungstic acid and ruthenium nanoparticles is obtained. This catalyst has a porous structure and a specific surface area of ​​75.15 m². 2 / g, pore volume is 0.390cm³ 3 With an average pore size of 24.17 nm, the high pore size and numerous active sites give it excellent catalytic performance in chlorinated volatile organic compounds (CVOCs) such as 1,2-DCE.

[0021] 2. The secondary hydrothermal reaction of this invention forms a porous cerium dioxide structure and supports phosphotungstic acid, which together provide electron transfer channels and promote the high dispersion and stability of RuNPs; the addition of NaBH4 reaction achieves small-sized, highly dispersed RuNPs; the redox properties of CeO2, the acidity of HPW, and the metal activity of Ru work together to form a multifunctional catalytic interface, which can provide more catalytic active sites for the 1,2-DCE reaction.

[0022] 3. The catalyst of the present invention is applied to the catalytic oxidation of 1,2-DCE, and it achieves a 90% conversion at temperature T. 90At a temperature of 273℃, it exhibited excellent catalytic performance. Ru loading facilitated the formation of Ru-O-Ce bonds, enhancing the activity and migration ability of oxygen species. The carbon dioxide mineralization rate of 1,2-DCE reached 90% at 279℃, reducing the formation of byproducts. HPW loading generated a large number of acidic sites, especially... Acidic sites facilitate the formation of HCl. The synergistic effect of acidic sites and active sites promotes the catalytic degradation of 1,2-DCE and inhibits the formation of polychlorinated byproducts, demonstrating good potential for industrial applications. Attached Figure Description

[0023] Figure 1 The images show the XRD patterns of Ru / CeO2-HPW, CeO2, CeO2-HPW and Ru / CeO2 prepared in Example 1 and Comparative Examples 1-3, respectively.

[0024] Figure 2 The image shows a TEM image of Ru / CeO2-HPW prepared in Example 1.

[0025] Figure 3 The image shows the EDS elemental distribution of Ru / CeO2-HPW prepared in Example 1.

[0026] Figure 4 XPS image of Ru / CeO2-HPW prepared in Example 1;

[0027] Figure 5 The N2 adsorption-desorption isotherm and pore size distribution curve of Ru / CeO2-HPW prepared in Example 1 are shown.

[0028] Figure 6 The graphs show the 1,2-DCE conversion and carbon dioxide yield of Ru / CeO2-HPW, CeO2, CeO2-HPW, Ru / CeO2, and Ru / CeO2-HPW(air) in Application Example 1 and Comparative Examples 1-4.

[0029] Figure 7 The results of the 24-hour durability test of Ru / CeO2-HPW prepared in Example 1 with 1 vol% water vapor are shown. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] A method for preparing a CeO2 porous nanorod catalyst co-modified with HPW and Ru includes the following steps:

[0033] (1) Preparation of cerium dioxide porous nanorods: An aqueous solution of Ce(NO3)3·6H2O (1.736 g, dissolved in 10 mL of deionized water) was mixed with an aqueous solution of NaOH (19.2 g, dissolved in 70 mL of deionized water). The mixture was aged for 30 min under continuous stirring, and then the first hydrothermal reaction was carried out at 100 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged and the precipitate was collected to obtain the first product. The first product was thoroughly washed with deionized water until neutral, and then dried in an oven at 60 °C. 1 g of the dried product was added to 80 mL of water and the second hydrothermal reaction was carried out at 160 °C for 12 h. After the reaction was completed, the second product was formed. The second product was calcined in a muffle furnace at a temperature increase of 5 °C / min for 500 °C / 2 h to obtain cerium dioxide porous nanorods, denoted as CeO2.

[0034] (2) Preparation of CeO2-HPW: 0.48g of phosphotungstic acid H3PW 12 O 40 The cerium dioxide porous nanorods (CeO2) from step (1) were dissolved in 40 mL of deionized water to form a 12 g / L HPW aqueous solution. Then, 0.8 g of the cerium dioxide porous nanorods (CeO2) from step (1) were weighed and added to the above HPW aqueous solution. The mixture was stirred at room temperature for 12 h, centrifuged, and the precipitate was washed three times and collected by filtration again. The resulting solid was dried in an oven at 80 °C for 12 h. Finally, the temperature was increased by 5 °C / min and calcined at 500 °C for 2 h to obtain CeO2-HPW powder.

[0035] (3) Synthesis of Ru / CeO2-HPW: 0.4g of CeO2-HPW powder from step (2) was ultrasonically dispersed in 100mL of water and ultrasonicated for 30min to obtain a suspension; 2mL of isopropanol and 18mL of water were mixed, and then 0.01034g of RuCl3·3H2O was added and mixed to obtain a mixed solution; the mixed solution was added to the suspension and mixed to form a suspension; the pH of the suspension was adjusted to 7 with 0.1M NaOH aqueous solution, and after stirring for 30min, 7.915mL of the prepared 10mM NaBH4 aqueous solution was injected into the suspension to mix and react to produce a precipitate; the precipitate was collected after filtration and washed 3 times, dried in a vacuum oven at 60℃ for 12h, and the dried powder was loaded into a porcelain boat and then transferred into a tube furnace and 5% oxygen was introduced. A mixture of H2 / Ar gas was reacted at 250℃ for 2 h to obtain a CeO2 porous nanorod catalyst co-modified with HPW and Ru, denoted as Ru / CeO2-HPW.

[0036] Example 2

[0037] A method for preparing a CeO2 porous nanorod catalyst co-modified with HPW and Ru includes the following steps:

[0038] (1) Preparation of cerium dioxide porous nanorods: An aqueous solution of Ce(NO3)3·6H2O (1.239 g, dissolved in 10 mL of deionized water) was mixed with an aqueous solution of NaOH (18.7 g, dissolved in 70 mL of deionized water). The mixture was aged for 30 min under continuous stirring, and then a first hydrothermal reaction was carried out at 95 °C for 30 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged and the precipitate was collected to obtain the first product. The first product was thoroughly washed with deionized water until neutral, and then dried in an oven at 60 °C. 1 g of the dried product was added to 80 mL of water and a second hydrothermal reaction was carried out at 150 °C for 15 h. After the reaction was completed, a second product was formed. The second product was calcined in a muffle furnace at a temperature increase of 5 °C / min for 3 h at 450 °C to obtain cerium dioxide porous nanorods, denoted as CeO2.

[0039] (2) Preparation of CeO2-HPW: 0.48g of phosphotungstic acid H3PW 12 O 40 The cerium dioxide porous nanorods (CeO2) from step (1) were dissolved in 40 mL of deionized water to form a 12 g / L HPW aqueous solution. Then, 0.8 g of the cerium dioxide porous nanorods (CeO2) from step (1) were weighed and added to the above HPW aqueous solution. The mixture was stirred at room temperature for 10 h. The mixture was then centrifuged, the precipitate was washed three times, and collected by filtration again. The resulting solid was dried in an oven at 80 °C for 12 h. Finally, the temperature was increased by 5 °C / min and calcined at 550 °C for 1 h to obtain CeO2-HPW powder.

[0040] (3) Synthesis of Ru / CeO2-HPW: 0.5g of CeO2-HPW powder from step (2) was ultrasonically dispersed in 110mL of water and ultrasonicated for 50min to obtain a suspension; 3mL of isopropanol and 20mL of water were mixed, and then 0.02g of RuCl3·3H2O was added and mixed to obtain a mixed solution; the mixed solution was added to the suspension and mixed to form a suspension; the pH of the suspension was adjusted to neutral; after stirring for 40min, 9mL of the prepared 10mM NaBH4 aqueous solution was injected into the suspension and mixed; after filtration, the precipitate was washed and dried; the dried powder was transferred into a tube furnace and 5% H2 / Ar mixed gas was introduced and reacted at 300℃ for 1.5h to obtain HPW and Ru co-modified CeO2 porous nanorod catalyst, denoted as Ru / CeO2-HPW.

[0041] Example 3

[0042] A method for preparing a CeO2 porous nanorod catalyst co-modified with HPW and Ru includes the following steps:

[0043] (1) Preparation of cerium dioxide porous nanorods: An aqueous solution of Ce(NO3)3·6H2O (2.000 g, dissolved in 10 mL of deionized water) was mixed with an aqueous solution of NaOH (19.8 g, dissolved in 70 mL of deionized water). The mixture was aged for 30 min under continuous stirring, and then the first hydrothermal reaction was carried out at 110 °C for 20 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged and the precipitate was collected to obtain the first product. The first product was thoroughly washed with deionized water until neutral, and then dried in an oven at 60 °C. 1 g of the dried product was added to 80 mL of water and the second hydrothermal reaction was carried out at 180 °C for 10 h. After the reaction was completed, the second product was formed. The second product was calcined in a muffle furnace at a temperature increase of 5 °C / min for 550 °C / 1 h to obtain cerium dioxide porous nanorods, denoted as CeO2.

[0044] (2) Preparation of CeO2-HPW: 0.48g of phosphotungstic acid H3PW 12 O 40 The cerium dioxide porous nanorods (CeO2) from step (1) were dissolved in 40 mL of deionized water to form a 12 g / L HPW aqueous solution. Then, 0.8 g of the cerium dioxide porous nanorods (CeO2) from step (1) were weighed and added to the above HPW aqueous solution. The mixture was stirred at room temperature for 15 h. The mixture was then centrifuged, the precipitate was washed three times, and collected by filtration again. The resulting solid was dried in an oven at 80 °C for 12 h. Finally, the solid was calcined at 450 °C for 3 h at a rate of 5 °C / min to obtain CeO2-HPW powder.

[0045] (3) Synthesis of Ru / CeO2-HPW: 0.3g of CeO2-HPW powder from step (2) was ultrasonically dispersed in 90mL of water and ultrasonicated for 20min to obtain a suspension; 1mL of isopropanol and 15mL of water were mixed, and then 0.01g of RuCl3·3H2O was added and mixed to obtain a mixed solution; the mixed solution was added to the suspension and mixed to form a suspension; the pH of the suspension was adjusted to neutral; after stirring for 20min, 7mL of the prepared 10mM NaBH4 aqueous solution was injected into the suspension and mixed; after filtration, the precipitate was washed and dried; the dried powder was transferred into a tube furnace and 5% H2 / Ar mixed gas was introduced and reacted at 200℃ for 3h to obtain HPW and Ru co-modified CeO2 porous nanorod catalyst, denoted as Ru / CeO2-HPW.

[0046] Comparative Example 1

[0047] The difference between Comparative Example 1 and Example 1 is that the cerium dioxide porous nanorods in Comparative Example 1 are not modified with phosphotungstic acid and ruthenium nanoparticles. The rest of the preparation process and conditions are the same as those in Example 1, and cerium dioxide porous nanorod catalyst (CeO2) is obtained.

[0048] The specific preparation steps are as follows: An aqueous solution of Ce(NO3)3·6H2O (1.736 g, dissolved in 10 mL of deionized water) was mixed with an aqueous solution of NaOH (19.2 g, dissolved in 70 mL of deionized water). The mixture was aged for 30 min under continuous stirring, and then a first hydrothermal reaction was carried out at 100 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged, and the precipitate was collected to obtain the first product. The first product was thoroughly washed with deionized water until neutral, and then dried in an oven at 60 °C. 1 g of the dried product was added to 80 mL of water and a second hydrothermal reaction was carried out at 160 °C for 12 h. After the reaction was completed, the second product was formed. The second product was calcined in a muffle furnace at a heating rate of 5 °C / min for 500 °C / 2 h to obtain a cerium dioxide porous nanorod catalyst, denoted as CeO2.

[0049] Comparative Example 2

[0050] The difference between Comparative Example 2 and Example 1 is that the cerium dioxide porous nanorods in Comparative Example 2 are not modified with Ru, i.e., step (3) is omitted. The rest of the preparation process and conditions are the same as those in Example 1, and a phosphotungstic acid supported CeO2 catalyst (denoted as CeO2-HPW) is obtained. The specific preparation steps are as follows:

[0051] (1) Preparation of cerium dioxide porous nanorods: An aqueous solution of Ce(NO3)3·6H2O (1.736 g, dissolved in 10 mL of deionized water) was mixed with an aqueous solution of NaOH (19.2 g, dissolved in 70 mL of deionized water). The mixture was aged for 30 min under continuous stirring, and then the first hydrothermal reaction was carried out at 100 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged and the precipitate was collected to obtain the first product. The first product was thoroughly washed with deionized water until neutral, and then dried in an oven at 60 °C. 1 g of the dried product was added to 80 mL of water and the second hydrothermal reaction was carried out at 160 °C for 12 h. After the reaction was completed, the second product was formed. The second product was calcined in a muffle furnace at a temperature increase of 5 °C / min for 500 °C / 2 h to obtain cerium dioxide porous nanorods, denoted as CeO2.

[0052] (2) Preparation of CeO2-HPW: 0.48g of phosphotungstic acid H3PW 12 O 40 The cerium dioxide porous nanorods CeO2 from step (1) were dissolved in 40 mL of deionized water to form a 12 g / L HPW aqueous solution. Then, 0.8 g of the cerium dioxide porous nanorods CeO2 from step (1) were weighed and added to the above HPW aqueous solution. The mixture was stirred at room temperature for 12 h, centrifuged, and the precipitate was washed three times and collected by filtration again. The resulting solid was dried in an oven at 80 °C for 12 h. Finally, the temperature was increased by 5 °C / min and calcined at 500 °C for 2 h to obtain the CeO2-HPW catalyst.

[0053] Comparative Example 3

[0054] The difference between Comparative Example 3 and Example 1 is that the cerium dioxide porous nanorods in Comparative Example 3 were not modified with phosphotungstic acid. All other preparation processes and conditions were the same as in Example 1, resulting in a ruthenium nanoparticle-supported CeO2 catalyst (denoted as Ru / CeO2). The specific preparation steps are as follows:

[0055] (1) Preparation of cerium dioxide porous nanorods: An aqueous solution of Ce(NO3)3·6H2O (1.736 g, dissolved in 10 mL of deionized water) was mixed with an aqueous solution of NaOH (19.2 g, dissolved in 70 mL of deionized water). The mixture was aged for 30 min under continuous stirring, and then the first hydrothermal reaction was carried out at 100 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged and the precipitate was collected to obtain the first product. The first product was thoroughly washed with deionized water until neutral, and then dried in an oven at 60 °C. 1 g of the dried product was added to 80 mL of water and the second hydrothermal reaction was carried out at 160 °C for 12 h. After the reaction was completed, the second product was formed. The second product was calcined in a muffle furnace at a temperature increase of 5 °C / min for 500 °C / 2 h to obtain cerium dioxide porous nanorods, denoted as CeO2.

[0056] (2) Preparation of Ru / CeO2: 0.4 g of cerium dioxide porous nanorods were ultrasonically dispersed in 100 mL of deionized water and ultrasonicated for 30 min to obtain a suspension; 2 mL of isopropanol and 18 mL of water were mixed, and then 0.01034 g of RuCl3·3H2O was added and mixed to obtain a mixed solution; the mixed solution was added to the suspension and mixed to form a suspension; the pH of the suspension was adjusted to 7 with 0.1 M NaOH aqueous solution, and stirred for 30 min. Then, 7.915 mL of the prepared 10 mM NaBH4 aqueous solution was injected into the suspension and mixed. After filtration, the precipitate was washed 3 times and dried in a vacuum oven at 60 °C for 12 h. The dried powder was transferred into a tube furnace and 5% H2 / Ar mixed gas was introduced and reacted at 250 °C for 2 h to obtain the Ru / CeO2 catalyst.

[0057] Comparative Example 4

[0058] The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, the 5% H2 / Ar mixed gas was replaced with air in step (3). The rest of the preparation process and conditions were the same as in Example 1, and a cerium dioxide catalyst supported on phosphotungstic acid and ruthenium nanoparticles (denoted as Ru / CeO2-HPW(air)) was obtained. The specific preparation steps are as follows:

[0059] (1) Preparation of cerium dioxide porous nanorods: An aqueous solution of Ce(NO3)3·6H2O (1.736 g, dissolved in 10 mL of deionized water) was mixed with an aqueous solution of NaOH (19.2 g, dissolved in 70 mL of deionized water). The mixture was aged for 30 min under continuous stirring, and then the first hydrothermal reaction was carried out at 100 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged and the precipitate was collected to obtain the first product. The first product was thoroughly washed with deionized water until neutral, and then dried in an oven at 60 °C. 1 g of the dried product was added to 80 mL of water and the second hydrothermal reaction was carried out at 160 °C for 12 h. After the reaction was completed, the second product was formed. The second product was calcined in a muffle furnace at a temperature increase of 5 °C / min for 500 °C / 2 h to obtain cerium dioxide porous nanorods, denoted as CeO2.

[0060] (2) Preparation of CeO2-HPW: 0.48g of phosphotungstic acid H3PW 12 O 40 The cerium dioxide porous nanorods (CeO2) from step (1) were dissolved in 40 mL of deionized water to form a 12 g / L HPW aqueous solution. Then, 0.8 g of the cerium dioxide porous nanorods (CeO2) from step (1) were weighed and added to the above HPW aqueous solution. The mixture was stirred at room temperature for 12 h, centrifuged, and the precipitate was washed three times and collected by filtration again. The resulting solid was dried in an oven at 80 °C for 12 h. Finally, the temperature was increased by 5 °C / min and calcined at 500 °C for 2 h to obtain CeO2-HPW powder.

[0061] (3) Synthesis of Ru / CeO2-HPW: 0.4g of CeO2-HPW powder from step (2) was ultrasonically dispersed in 100mL of water and ultrasonicated for 30min to obtain a suspension; 2mL of isopropanol and 18mL of water were mixed, and then 0.01034g of RuCl3·3H2O was added and mixed to obtain a mixed solution; the mixed solution was added to the suspension and mixed to form a suspension; the pH of the suspension was adjusted to 7 by 0.1M NaOH aqueous solution, and after stirring for 30min, 7.915mL of 10mM NaBH4 aqueous solution was injected into the suspension and mixed; after filtration, the precipitate was washed 3 times and dried in a vacuum oven at 60℃ for 12h; the dried powder was loaded into a ceramic boat and then transferred into a tube furnace and air was introduced; and the reaction was carried out at 250℃ for 2h to obtain HPW and Ru co-modified CeO2 porous nanorod catalyst, denoted as Ru / CeO2-HPW(air).

[0062] The characterization and analysis of the prepared catalyst material are as follows:

[0063] (I) X-ray diffraction (XRD) analysis

[0064] X-ray diffraction (XRD) was used to characterize Ru / CeO2-HPW, CeO2, CeO2-HPW, and Ru / CeO2 prepared in Example 1 and Comparative Examples 1-3, respectively, to reveal the crystal structure of the prepared samples. The characterization results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the loading of HPW, Ru, or HPW and Ru has no significant effect on the phase composition and crystal structure of the final sample. All CeO2-based catalysts exhibited characteristic diffraction peaks of cubic fluorite CeO2 (PDF#34-0394) at 28.6°, 33.3°, 47.5°, 56.5°, and 59.2°, but no crystalline phase peaks of Ru or HPW were detected, confirming that Ru and HPW exist in amorphous or highly dispersed nanoparticle form. This high dispersion characteristic helps to more fully expose the catalyst's active sites to the reactants, thereby improving its catalytic performance.

[0065] (II) Transmission Electron Microscopy (TEM) Analysis

[0066] The Ru / CeO2-HPW prepared in Example 1 was characterized and analyzed using scanning electron microscopy (TEM). The characterization results are as follows: Figure 2 As shown, the morphological characteristics of different phosphotungstic acid and ruthenium-supported cerium oxide were analyzed using HR-TEM. The results showed that the phosphotungstic acid and ruthenium-supported cerium oxide did not alter the overall morphology; the cerium oxide remained predominantly in the form of porous nanorods. This indicates that the introduced phosphotungstic acid and ruthenium species are highly dispersed on CeO2 without changing the crystal structure of CeO2, significantly increasing the exposure density of active sites on the catalyst surface. Simultaneously, the porous nanorod structure provides a high specific surface area and abundant mass transfer channels, which is beneficial for reactant molecule adsorption and intermediate product diffusion. These structural characteristics may synergistically enhance catalytic activity and stability.

[0067] (III) Energy Dispersive Spectroscopy (EDS) Analysis

[0068] The structure, composition, and elemental distribution of the Ru / CeO2-HPW catalyst surface prepared in Example 1 were investigated using EDS elemental mapping. Figure 3 As shown, no aggregated particles of Ru or HPW species were directly observed. However, the presence of P, W and Ru was confirmed by elemental surface scanning analysis, indicating that these species are uniformly distributed on the catalyst surface in the form of highly dispersed nanoparticles. This highly dispersed characteristic helps to increase the contact area between the reactants and the catalyst, improve the efficiency of the catalytic reaction, and thus may improve the conversion rate.

[0069] (iv) X-ray photoelectron spectroscopy (XPS) analysis

[0070] The Ru / CeO2-HPW prepared in Example 1 was analyzed by X-ray photoelectron spectroscopy, such as... Figure 4As shown, it can be concluded that after post-treatment with a 5% H2 / Ar mixed gas, the residual Cl in the added RuCl is less, which reduces the impact of residual Cl on the catalyst reaction activity and thus improves the conversion rate of CVOCs. This effect cannot be achieved by using other gases such as air.

[0071] (V) Specific surface area and pore size analysis

[0072] The specific surface area and pore size of Ru / CeO2-HPW prepared in Example 1 were analyzed, and the results are as follows: Figure 5 As shown. By Figure 5 (a) Typical type IV adsorption isotherms and H1 hysteresis loops can be observed, which are characteristic of mesoporous structures; its BET area reaches 75.15 m². 2 / g, pore volume is 0.390cm³ 3 / g, with an average pore size of 24.17nm, can provide catalysts to expose active sites during the catalytic reaction of 1,2-dichloroethane. Figure 5 (b) It is shown that the pore size of Ru / CeO2-HPW is mainly distributed in mesopores, but macropores and micropores also exist; this porous structure can provide more reaction sites for 1,2-dichloroethane and improve molecular diffusion efficiency; a certain surface area and the formation of a porous structure can improve the catalytic activity of the 1,2-dichloroethane reaction and accelerate electron migration.

[0073] Application examples

[0074] The catalyst samples prepared in Example 1 (Ru / CeO2-HPW), Comparative Example 1 (CeO2), Comparative Example 2 (CeO2-HPW), Comparative Example 3 (Ru / CeO2), and Comparative Example 4 (Ru / CeO2-HPW(air)) were applied to the catalytic oxidation reaction of CVOCs, and the steps are as follows:

[0075] A quartz tube with an outer diameter of 10 mm and an inner diameter of 8 mm was used as the catalytic reactor. 200 mg of catalyst sample was loaded into the quartz reaction tube, both ends were plugged with quartz wool, and the tube was placed in an electric heating furnace equipped with temperature control for catalyst activity testing. Online GC-MS (Agilent Technologies, USA) was used to analyze various components in the exhaust gas, with high-purity nitrogen as the carrier gas. 1,2-DCE was introduced into the reaction system via high-purity nitrogen bubbling (concentration approximately 1000 ppm). The total gas flow rate was then controlled to be 100 mL / min, with an oxygen content of 10% by volume and a space velocity of 30000 mL / (g·h).

[0076] Experimental results are as follows Figure 6(a) and 6(c) show that the conversion rate of 1,2-DCE of Ru / CeO2-HPW in Example 1 is 90% at 273 °C; the CeO2 in Comparative Example 1 requires a temperature of 346 °C for the conversion rate of 1,2-DCE to be 90%; the CeO2-HPW in Comparative Example 2 requires a temperature of 274 °C for the conversion rate of 1,2-DCE to be 90%; the Ru / CeO2 in Comparative Example 3 requires a temperature of 299 °C for the conversion rate of 1,2-DCE to be 90%; the Ru / CeO2-HPW(air) in Comparative Example 4 requires a temperature of 342 °C for the conversion rate of 1,2-DCE to be 90%.

[0077] Analysis of the catalytic performance of materials

[0078] For the CeO2, CeO2-HPW, Ru / CeO 2、 Ru / CeO2-HPW and Ru / CeO2-HPW(air) catalysts in Application Example 1 and Application Comparative Examples 1-4, the catalytic performance was analyzed. By Figure 6 (a), the performance of each catalyst for the catalytic combustion of 1,2-dichloroethane (DCE) was evaluated. The T 90 values (temperatures corresponding to 90% conversion rate) of each catalyst are in turn: Ru / CeO2-HPW (273 °C) < CeO2-HPW (274 °C) < Ru / CeO2 (299 °C) < Ru / CeO2-HPW(air) (342 °C) < CeO2 (346 °C). Compared with the unmodified CeO2, all HPW (phosphotungstic acid)-modified catalysts showed better activity. The pure CeO2 support showed poor catalytic oxidation and mineralization ability ( Figure 6 (b)), while after introducing HPW, although CeO2-HPW can achieve 90% DCE conversion rate at 274 °C, its CO2 yield is low and it is not completely mineralized even at 500 °C. In addition, after loading ruthenium (Ru), the mineralization ability of the Ru / CeO2-HPW catalyst was significantly improved, and the CO2 yield reached 90% at 279 °C. Although the Ru / CeO2 catalyst has excellent redox performance, due to the lack of acidic sites, its DCE catalytic activity is still low. Compared with the Ru / CeO2-HPW catalyst, the performance of the Ru / CeO2-HPW(air) catalyst decreased because under high-temperature reaction conditions (especially in a Cl-containing environment), CeO2 is prone to grain agglomeration and sintering, resulting in a reduction in active sites. Therefore, Ru / CeO2-HPW achieved a significant improvement in the catalytic activity of 1,2-DCE by synergistically optimizing the redox performance and surface acidity.

[0079] To investigate the influence of water vapor on the stability of the catalyst prepared by the present invention, a 24-hour durability test was carried out on the Ru / CeO2-HPW catalyst prepared in Example 1 under the condition of containing 1 vol% water vapor. The results are as Figure 7The results show that the 1,2-DCE conversion of Ru / CeO2-HPW remains at around 90%, which confirms that the Ru / CeO2-HPW catalyst can maintain excellent durability in humid environments.

[0080] In summary, the HPW and Ru co-modified CeO2 porous nanorod catalyst prepared in this invention exists in the form of amorphous or highly dispersed nanoparticles. This high dispersion characteristic helps to fully expose the active sites of the catalyst to the reactants, thereby improving its catalytic performance. The Ru / CeO2-HPW catalyst exhibits a higher oxygen vacancy concentration due to the synergistic effect of the monotungstate structure (WO5) and the Ru-O-Ce bond, thus significantly improving its redox performance. The HPW and Ru loading enhances the catalyst's catalytic activity and deep oxidation capability. The To of the Ru / CeO2-HPW catalyst... 90 The temperature was 273℃, which was 58℃ lower than that of the CeO2 catalyst. The mineralization rate of 1,2-DCE reached 90% at 279℃, reducing the formation of by-products.

[0081] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the claims.

Claims

1. A method for preparing a HPW and Ru co-modified CeO2 porous nanorod catalyst, characterized in that, The method comprises the following steps: (1) Preparation of porous ceria nanorods: mixing Ce(NO3)3.6H2O aqueous solution and NaOH aqueous solution, stirring, and then performing first hydrothermal reaction, after the reaction, naturally cooling to room temperature, centrifuging and collecting the precipitate to obtain a first product, washing and drying the first product, adding water to the dried product and performing second hydrothermal reaction, after the reaction, forming a second product, calcining the second product to obtain porous ceria nanorods, denoted as CeO2; the weight ratio of Ce(NO3)3.6H2O to NaOH is 1-2:18-20; the temperature of the first hydrothermal reaction is 90-110 DEG C, and the time is 20-30 h; the temperature of the second hydrothermal reaction is 150-180 DEG C, and the time is 10-15 h; (2) Preparation of CeO2-HPW: immersing the porous ceria nanorods of step (1) in HPW aqueous solution with a mass concentration of 10-15 g / L, stirring at room temperature for 10-15 h, then performing centrifugation, washing the precipitate, drying, and calcining to obtain CeO2-HPW; (3) Synthesis of Ru / CeO2-HPW: ultrasonic dispersion of CeO2-HPW of step (2) in water, then adding a mixed solution of RuCl3.3H2O, isopropanol, and water to form a suspension, adjusting the pH of the suspension to neutral, stirring, then injecting NaBH4 aqueous solution into the suspension, filtering, washing and drying the precipitate, transferring the dried powder into a tube furnace, and introducing H2 / Ar mixed gas to perform reaction, to obtain HPW and Ru co-modified CeO2 porous nanorod catalyst, denoted as Ru / CeO2-HPW.

2. The preparation method of the HPW and Ru co-modified CeO2 porous nanorod catalyst according to claim 1, characterized in that: In step (1), the calcination conditions are as follows: heating at 5 DEG C / min, calcination temperature is 450-550 DEG C, and calcination time is 1-3 h.

3. The preparation method of the HPW and Ru co-modified CeO2 porous nanorod catalyst according to claim 1, characterized in that: In step (2), the calcination conditions are as follows: heating at 5 DEG C / min, calcination temperature is 450-550 DEG C, and calcination time is 1-3 h.

4. The method for preparing a HPW and Ru co-modified CeO2 porous nanorod catalyst according to claim 1, characterized in that, The specific operation steps of step (3) are as follows: ultrasonic dispersion of 0.3-0.5 g CeO2-HPW of step (2) in 90-110 mL water for 20-50 min to obtain a suspension; mixing 1-3 mL isopropanol and 15-20 mL water, then adding 0.01-0.02 g RuCl3.3H2O to obtain a mixed solution; adding the mixed solution into the suspension to form a suspension, adjusting the pH of the suspension to neutral, stirring for 20-50 min, then injecting 7-9 mL of prepared 10 mM NaBH4 aqueous solution into the suspension, filtering, washing and drying the precipitate, transferring the dried powder into a tube furnace, introducing 5% H2 / Ar mixed gas, and reacting at 200-300 DEG C for 1-3 h to obtain HPW and Ru co-modified CeO2 porous nanorod catalyst, denoted as Ru / CeO2-HPW.

5. The HPW and Ru co-modified CeO2 porous nanorod catalyst prepared by the preparation method of any one of claims 1-4, characterized in that: The HPW and Ru co-modified CeO2 porous nanorod catalyst has a porous structure, a specific surface area of 75-76 m 2 / g, a pore volume of 0.35-0.40 cm 3 / g, an average pore diameter of 24.0-24.5 nm, and a total acid amount of 430-450 umol / g.

6. The use of the HPW and Ru co-modified CeO2 porous nanorod catalyst of claim 5 in catalyzing reactions of volatile organic compounds containing chlorine.

7. Use according to claim 6, wherein: The chlorine-containing volatile organic compound is 1,2-dichloroethane; in the catalytic oxidation reaction of 1,2-dichloroethane, the HPW and Ru co-modified CeO2 porous nanorod catalyst has T 90 The temperature is 270-275℃.

8. Use according to claim 7, wherein the compound is ###0002### The method comprises the following steps: loading 150-250 mg of the HPW and Ru co-modified CeO2 porous nanorod catalyst into a reactor, introducing 1, 2-dichloroethane into the reactor, wherein the concentration of the introduced 1, 2-dichloroethane is 900-1200 ppm; and simultaneously introducing a mixed gas of nitrogen and oxygen into the reactor, wherein the total flow rate of the mixed gas is 100 mL / min, and the content of the oxygen is 10% by volume.

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