Single-layer hollow spherical shell vanadium-based catalyst as well as preparation method and application thereof

Abstract

The invention provides a single-layer hollow spherical shell vanadium-based catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts.The method comprises the following steps: dissolving rodlike vanadium pentoxide and oxalic acid in a molar ratio of 1: 3 in deionized water, and stirring to obtain a mixed solution 1; adding the mixed solution 1 into an isopropanol solution of 0.0067 g / ml ascorbic acid according to a volume ratio of 2: 15 to obtain a mixed solution 2; heating the mixed solution 2 for hydrothermal reaction to obtain a precipitate, and washing, centrifuging and drying the precipitate to obtain a product 1; and carrying out two-stage calcination on the product 1 to obtain the single-layer hollow spherical shell vanadium-based catalyst. According to the method, the problems that a single metal vanadium-based catalyst is poor in low-temperature catalytic performance, a noble metal catalyst is high in cost and prone to poisoning, and a traditional catalyst is poor in pore structure are solved, and a direction is provided for design of an industrial CVOCs purification catalyst.

Description

Technical Field

[0001] This invention belongs to the field of chemistry and chemical engineering technology, specifically to a single-layer hollow spherical shell vanadium-based catalyst, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) are a major environmental concern, serving as crucial precursors to photochemical smog and fine particulate matter. Among the many VOCs, chlorinated volatile organic compounds (CVOCs) are widely present in the environment and exhibit extremely high toxicity to organisms. Therefore, effective treatment of CVOCs has become a critical issue in environmental governance. CVOC treatment technologies encompass various methods, including incineration, condensation, biological methods, and thermocatalysis. Among these, thermocatalysis technology is widely used for treating low-concentration waste gases due to its significant advantages such as high efficiency, low energy consumption, and no secondary pollution. The core of this technology lies in the selection and application of the catalyst; the catalyst's performance directly determines the treatment effect and efficiency of the thermocatalytic technology.

[0003] In the practical application of thermocatalytic technology for treating CVOCs, the choice of catalyst is crucial. Currently, noble metal catalysts are widely studied due to their excellent catalytic performance; however, these catalysts are susceptible to deactivation by water vapor and halogens, and their generally high cost limits their large-scale application. In contrast, non-noble metal catalysts, due to their lower cost and good catalytic performance, are gradually becoming the mainstream choice for CVOC catalytic treatment. However, non-noble metal catalysts face several problems in practical applications, such as poor moisture resistance and insufficient load capacity. Under actual operating conditions, these catalysts are easily affected by factors such as humidity, concentration, and space velocity, leading to a decrease in catalytic efficiency. To maintain catalytic efficiency, it is often necessary to increase the reaction temperature, which undoubtedly increases energy consumption and is inconsistent with the environmental protection concept of energy conservation and emission reduction.

[0004] To address a series of problems with catalysts used in thermocatalysis, researchers have conducted extensive studies and attempted to optimize catalyst performance through various methods. Among these, morphology control and element doping are two commonly used strategies: morphology control improves catalytic performance by altering the catalyst's microstructure, attempting to increase its surface area and the number of active sites; element doping, on the other hand, introduces other elements into the catalyst to change its electronic structure and surface properties, thereby improving its resistance to moisture, load tolerance, and catalytic stability.

[0005] Although researchers have made some progress in optimizing catalyst performance through the combination of morphology control and carbon doping strategies, there is still a lack of relevant thermocatalytic research on vanadium-based catalysts, which limits the exploration of their performance. Furthermore, while elemental doping improves the catalyst's resistance to moisture and load to some extent, its performance is still significantly affected under extreme conditions (such as high humidity, high concentration, or high space velocity). Therefore, further clarifying the synergistic mechanism of morphology control and carbon doping, and developing more efficient, stable, and interference-resistant CVOCs purification catalysts based on this understanding, remains a significant challenge in the field of environmental governance. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a single-layer hollow spherical shell vanadium-based catalyst, its preparation method, and its application. The method employs a hydrothermal-calcination process, combining morphology control with a carbon doping strategy to prepare the single-layer hollow spherical shell vanadium-based catalyst. This method solves the problems of poor low-temperature catalytic performance of single-metal vanadium-based catalysts, high cost and susceptibility to poisoning of precious metal catalysts, and undesirable pore structure of traditional catalysts. This invention achieves good catalytic performance at lower temperatures, reduces costs, and enhances resistance to poisoning. The preparation process is energy-saving and emission-reducing. The material has open pores, a large specific surface area, numerous active sites, stable structure, and high degradation rate. It also exhibits good stability and water resistance, providing direction for the design of industrial CVOCs purification catalysts.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a single-layer hollow spherical shell vanadium-based catalyst, the specific steps of which are as follows: A rod-shaped vanadium pentoxide and oxalic acid in a molar ratio of 1:3 were dissolved in deionized water and stirred to obtain mixture 1; Mixture 1 was added to a 0.0067 g / ml isopropanol solution of ascorbic acid at a volume ratio of 2:15 to obtain mixture 2; The mixture 2 was heated to carry out a hydrothermal reaction, and a precipitate was obtained after the reaction. The precipitate was washed, centrifuged and dried to obtain product 1. Product 1 was subjected to two-stage calcination to obtain a single-layer hollow spherical shell vanadium-based catalyst.

[0008] Furthermore, anhydrous glucose is added to mixture 1. The rod-shaped vanadium pentoxide is obtained by hydrothermal reaction of vanadium pentoxide and hydrogen peroxide, followed by two-stage calcination. The mass ratio of vanadium pentoxide to glucose is 1.82:0.1~0.3.

[0009] Further preparation of rod-shaped vanadium pentoxide is as follows: Vanadium pentoxide was added to a hydrogen peroxide solution with a volume concentration of 5%-10% to obtain mixture 3; Mixture 3 was heated to carry out a hydrothermal reaction, and a precipitate was obtained after the reaction. The precipitate was washed and dried to obtain product 2. Product 2 was subjected to two-stage calcination to obtain rod-shaped vanadium pentoxide.

[0010] Furthermore, the amount of vanadium pentoxide added is 5.49%-16.48%.

[0011] Furthermore, the hydrothermal reaction conditions are: reaction at 180℃ for 24 hours; drying at 40℃~80℃ for 24 hours; and the two-stage calcination is annealing at 300℃ for 2 hours with a heating rate of 1℃ / min, followed by annealing at 350℃ for 30 minutes with a temperature rise rate of 0.5℃ / min. Furthermore, the hydrothermal reaction conditions are a reaction at 200 °C for 12 h, and the drying conditions are vacuum drying at 40 °C to 80 °C.

[0012] Furthermore, the two-stage calcination consists of annealing at 300 °C for 2 h at a heating rate of 1 °C / min, and annealing at 350 °C for 30 min at a temperature rise rate of 0.5 °C / min. The present invention also provides a single-layer hollow spherical shell vanadium-based catalyst, which is prepared by the above-mentioned method for preparing a single-layer hollow spherical shell vanadium-based catalyst. The single-layer hollow spherical shell vanadium-based catalyst is used for the purification of chlorinated volatile organic compounds, wherein: rod-shaped vanadium pentoxide and oxalic acid in a molar ratio of 1:3 are dissolved in deionized water and stirred to obtain a mixed solution 1.

[0013] The present invention also provides a single-layer hollow spherical shell vanadium-based catalyst, which is prepared by the above-mentioned method for preparing a single-layer hollow spherical shell vanadium-based catalyst, wherein anhydrous glucose is added to the mixture 1, and the rod-shaped vanadium pentoxide is obtained by hydrothermal reaction of vanadium pentoxide and hydrogen peroxide and calcination in two stages; the mass ratio of vanadium pentoxide to glucose is 1.82:0.1~0.3.

[0014] This invention also provides the application of the above-mentioned single-layer hollow spherical shell vanadium-based catalyst in the purification of chlorinated volatile organic compounds.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a method for preparing a single-layer hollow spherical shell vanadium-based catalyst, using inexpensive transition metal vanadium as the core raw material, replacing the use of precious metal catalysts, significantly reducing raw material costs. Simultaneously, catalytic performance is improved through morphology control, avoiding the high costs caused by over-reliance on precious metals. The preparation employs a hydrothermal-calcination method, which is simple and highly controllable. The parameters for the hydrothermal reaction and two-stage calcination are well-defined and easily adjusted, allowing for precise control of the product morphology and structure. Furthermore, the entire preparation process has low energy consumption and minimal waste emissions, requiring no complex post-processing steps, aligning with the development concept of green chemistry. More importantly, the raw materials involved in the process (such as vanadium pentoxide, oxalic acid, ascorbic acid, etc.) are all industrially available chemicals, the reaction conditions are mild, facilitating large-scale production and possessing broad prospects for industrial application.

[0016] Furthermore, in the basic preparation process, the morphology and performance of the catalyst can be precisely controlled by adjusting the hydrothermal reaction temperature (180℃ or 200℃), reaction time (12h or 24h), drying method (conventional drying or vacuum drying), and calcination parameters. Further, by adding anhydrous glucose to mixture 1 and utilizing the morphology-regulating effect of glucose, the regularity of the single-layer hollow spherical shell structure can be further optimized and the carbon doping effect improved by controlling the mass ratio of vanadium pentoxide to glucose (1.82:0.1~0.3). Simultaneously, the preparation process of the rod-shaped vanadium pentoxide precursor is independent and optimizable. By adjusting the hydrogen peroxide solution concentration (5%-10%) and the vanadium pentoxide addition amount (5.49%-16.48%), a high-quality precursor can be provided for the subsequent preparation of the single-layer hollow spherical shell catalyst. This flexible process design not only meets the catalytic performance requirements of different application scenarios but also reserves ample room for subsequent process optimization and performance improvement.

[0017] In this invention, rod-shaped vanadium pentoxide serves as a key precursor for the preparation of monolayer hollow shell vanadium-based catalysts. Its morphology and structure directly affect the performance of the final product. Specifically, this invention utilizes the dissolution effect of hydrogen peroxide on vanadium pentoxide, combined with the directional growth effect of hydrothermal reaction and the crystal form optimization effect of calcination, to prepare rod-shaped vanadium pentoxide with uniform morphology and stable structure, which can provide a high-quality precursor for the subsequent preparation of monolayer hollow shell catalysts.

[0018] This invention also introduces anhydrous glucose into the basic preparation process, which can not only regulate the morphology of the precursor and promote the formation of a single-layer hollow spherical shell structure, but also provide a carbon source during calcination to achieve carbon doping, thereby further improving the specific surface area, number of active sites and structural stability of the catalyst, and enhancing its degradation performance of CVOCs.

[0019] The present invention also provides the application of the above-mentioned single-layer hollow spherical shell vanadium-based catalyst in the purification of chlorinated volatile organic compounds. The catalyst can efficiently degrade CVOCs such as chlorobenzene and has good stability, water resistance and sulfur poisoning resistance. It is suitable for industrial-scale heterogeneous thermocatalytic reactions for CVOCs destruction. Attached Figure Description

[0020] Figure 1 The XRD patterns of the catalysts SSHS-V2O5 and SSHS-V2O5:C of this invention are shown.

[0021] Figure 2 Lattice stripe images obtained by TEM: (a) SSHS-V2O5; (b) SSHS-V2O5:C.

[0022] Figure 3 The images shown are SEM, TEM, and EDS images of the catalysts of this invention: (a) SEM image of catalyst SSHS-V2O5; (b) SEM image of catalyst SSHS-V2O5:C; (c) TEM image of catalyst SSHS-V2O5; (d) TEM image of catalyst SSHS-V2O5:C; (e) EDS image of catalyst material SSHS-V2O5:C.

[0023] Figure 4 These are the isothermal adsorption-desorption curves of the catalyst material of this invention.

[0024] Figure 5 This is a pore size distribution diagram (surface area type) of the catalyst material of the present invention.

[0025] Figure 6 This is a pore size distribution diagram (pore volume type) of the catalyst material of the present invention.

[0026] Figure 7 These are the XPS spectra of the catalyst of this invention: (a) Survey; (b) C1s; (c) O1s; (d) V2p.

[0027] Figure 8 This refers to the CB degradation rate of the catalyst of this invention under 1000 ppm CB and different temperature conditions.

[0028] Figure 9 This refers to the CB degradation rate of the catalyst of this invention under continuous thermal catalysis at 1000 ppm CB and different temperatures for a period of time.

[0029] Figure 10 This invention relates to the reaction stability of the catalyst for CB degradation under different humidity and temperature conditions.

[0030] Figure 11This describes the CB catalytic activity of the catalyst of this invention under the conditions of 1000ppm CB + 100ppm SO2 + 5vol.% H2O.

[0031] Figure 12 This is a diagram illustrating the sulfur resistance mechanism of the carbon-doped single-layer hollow spherical vanadium pentoxide SSHS-V2O5:C catalyst of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] This invention provides a single-layer hollow spherical shell vanadium-based catalyst, comprising the following preparation steps: Step 1: Preparation of rod-shaped vanadium pentoxide (R-V₂O₅): 1) Add vanadium pentoxide (V2O5) to a hydrogen peroxide solution (H2O2) with a volume concentration of 5%-10%. When the orange suspension turns into a dark red transparent solution, the stirring is complete and a mixture is obtained. V2O5 is slightly soluble in water but soluble in hydrogen peroxide solution. 2) Once the reaction in the mixture is no longer vigorous, react the mixture at 180℃ for 24 hours, cool it to room temperature, and collect the precipitate; 3) The precipitate was first washed with deionized water, then washed with anhydrous ethanol, and then dried at 40℃~80℃ for 24h to obtain a blue-green product. 4) The blue-green product was subjected to two-stage calcination: annealing at 300℃ for 2 hours with a heating rate of 1℃ / min, and annealing at 350℃ for 30 minutes with a temperature rise rate of 0.5℃ / min. R-V2O5 was obtained after calcination.

[0034] Step 2: Preparation of monolayer hollow spherical shell vanadium-based catalyst (SSHS-V2O5): 1) Dissolve rod-shaped vanadium pentoxide and oxalic acid in deionized water at a molar ratio of 1:3 and stir to obtain a blue precursor VOC2O4 solution; Furthermore, anhydrous glucose (C6H) can be added. 12 The mass ratio of vanadium pentoxide to glucose is 1.82:0.1~0.3.

[0035] 2) Dissolve ascorbic acid in isopropanol to obtain an isopropanol solution of ascorbic acid; 3) Add VOC2O4 solution to 0.0067 g / ml isopropanol solution of ascorbic acid at a volume ratio of 2:15, stir at room temperature for 30 min to obtain a mixture; 4) React the mixture at 200 °C for 12 h, cool to room temperature, collect the precipitate by centrifugation, wash the precipitate with anhydrous ethanol and centrifuge it several times, and then dry it under vacuum at 40 °C~80 °C to obtain a black product. 5) The product was subjected to two-stage calcination: annealing at 300 °C for 2 h at a heating rate of 1 °C / min, and annealing at 350 °C for 30 min at a temperature rise rate of 0.5 °C / min. After calcination, a single-layer hollow spherical shell vanadium-based catalyst (SSHS-V2O5) or a carbon-doped single-layer hollow spherical shell vanadium pentoxide (SSHS-V2O5:C) was obtained.

[0036] This catalyst is prepared by a hydrothermal method. The reaction temperature and calcination temperature directly affect the valence of V. By adjusting the temperature, catalysts with specific valences can be prepared. In addition, excessively high calcination temperatures may affect the morphology of the catalyst (such as causing sintering).

[0037] Example 1 The present invention discloses a method for preparing a single-layer hollow spherical shell vanadium-based catalyst, comprising the following steps: Step 1: Preparation of rod-shaped vanadium pentoxide (R-V₂O₅): 1.82 g of vanadium pentoxide (V₂O₅) was added to 80 ml of 6 vol.% hydrogen peroxide solution (H₂O₂). The mixture was stirred continuously for 1 hour at room temperature using a magnetic stirrer. Stirring was complete when the orange suspension turned into a blood-red transparent solution. The solution was then transferred to a 100 ml reaction vessel and placed in an electrically heated drying oven at 180 °C for 24 hours. After cooling to room temperature, the collected precipitate was washed first with deionized water, then with anhydrous ethanol, and then placed in a petri dish and dried at 60 °C for 24 hours. The dried product was blue-green. It was then calcined in a muffle furnace, annealed at 300 °C for 2 hours at a heating rate of 1 °C / min, and then annealed at 350 °C for 30 minutes at a temperature rise rate of 0.5 °C / min. Calcination yielded R-V₂O₅.

[0038] Step 2: Using R-V₂O₅ (1.2 g) and oxalic acid (1.78 g) as raw materials, dissolve them in 40 ml of deionized water at a molar ratio of 1:3 and stir vigorously at 80 °C until a clear blue VOC₂O₄ solution is formed. Dissolve 0.4 g of ascorbic acid in 60 ml of isopropanol at room temperature, then add 8 ml of the prepared VOC₂O₄ solution. After stirring at room temperature for 30 min, transfer the mixture to a 100 ml reaction vessel, place it in an electrically heated drying oven, and react at 200 °C for 12 h. After cooling to room temperature, centrifuge and wash the collected precipitate with anhydrous ethanol three times, and then dry it under vacuum at 80 °C. After drying, the finished product is a black powder, which is then placed in a muffle furnace for calcination. It is annealed at 300 °C for 2 hours with a heating rate of 1 °C / min, and then annealed at 350 °C for 30 minutes with a temperature rise rate of 0.5 °C / min. After calcination, SSHS-V2O5 is obtained.

[0039] Example 2 The present invention discloses a method for preparing a single-layer hollow spherical shell vanadium-based catalyst, comprising the following steps: Step 1: The preparation of rod-shaped vanadium pentoxide (R-V2O5) is the same as in Example 1; Step 2: Using R-V₂O₅ (1.2 g) and oxalic acid (1.78 g) as raw materials, dissolve them in 40 ml of deionized water at a molar ratio of 1:3 and stir vigorously at 80 °C until a clear blue VOC₂O₄ solution is formed. Dissolve 0.4 g of ascorbic acid in 60 ml of isopropanol at room temperature, then add 8 ml of the prepared VOC₂O₄ solution. After stirring at room temperature for 30 min, transfer the mixture to a 100 ml reaction vessel, place it in an electrically heated drying oven, and react at 200 °C for 12 h. After cooling to room temperature, centrifuge and wash the collected precipitate with anhydrous ethanol three times, and then dry it under vacuum at 60 °C. After drying, the finished product is a black powder, which is then placed in a muffle furnace for calcination. It is annealed at 300 °C for 2 h at a heating rate of 1 °C / min, and then annealed at 350 °C for 30 min at a temperature rise rate of 0.5 °C / min. After calcination, SSHS-V2O5 is obtained.

[0040] Example 3 The present invention discloses a method for preparing a single-layer hollow spherical shell vanadium-based catalyst, comprising the following steps: Step 1: The preparation of rod-shaped vanadium pentoxide (R-V2O5) is the same as in Example 1; Step 2: Using R-V₂O₅ (1.2 g) and oxalic acid (1.78 g) as raw materials, dissolve them in 40 ml of deionized water at a molar ratio of 1:3 and stir vigorously at 80 °C until a clear blue VOC₂O₄ solution is formed. Dissolve 0.4 g of ascorbic acid in 60 ml of isopropanol at room temperature, then add 8 ml of the prepared VOC₂O₄ solution. After stirring at room temperature for 30 min, transfer the mixture to a 100 ml reaction vessel, place it in an electrically heated drying oven, and react at 200 °C for 12 h. After cooling to room temperature, centrifuge and wash the collected precipitate with anhydrous ethanol three times, and then dry it under vacuum at 40 °C. After drying, the finished product is a black powder, which is then placed in a muffle furnace for calcination. It is annealed at 300 °C for 2 h at a heating rate of 1 °C / min, and then annealed at 350 °C for 30 min at a temperature rise rate of 0.5 °C / min. After calcination, SSHS-V2O5 is obtained.

[0041] Example 4 The preparation method of the carbon-doped single-layer hollow spherical shell vanadium pentoxide (SSHS-V2O5:C) catalyst of the present invention includes the following steps: Step 1: The preparation of rod-shaped vanadium pentoxide (R-V2O5) is the same as in Example 1; Step 2: Using R-V2O5 (1.2 g) and oxalic acid (1.78 g) as raw materials, dissolve them in 40 ml of deionized water at a molar ratio of 1:3, and then add 0.2 g of anhydrous glucose. The remaining steps are the same as in Example 1.

[0042] Example 5 Step 1: The preparation of rod-shaped vanadium pentoxide (R-V2O5) is the same as in Example 1; Step 2: Using R-V2O5 (1.2 g) and oxalic acid (1.78 g) as raw materials, dissolve them in 40 ml of deionized water at a molar ratio of 1:3, and then add 0.1 g of anhydrous glucose. The remaining steps are the same as in Example 1.

[0043] Example 6 Step 1: The preparation of rod-shaped vanadium pentoxide (R-V2O5) is the same as in Example 1; Step 2: Using R-V2O5 (1.2 g) and oxalic acid (1.78 g) as raw materials, dissolve them in 40 ml of deionized water at a molar ratio of 1:3, and then add 0.3 g of anhydrous glucose. The remaining steps are the same as in Example 1.

[0044] To explain its beneficial effects, the monolayer hollow spherical shell vanadium pentoxide catalyst of Example 1 and the carbon-doped monolayer hollow spherical shell vanadium pentoxide catalyst of Example 4 were characterized and tested as follows: X-ray diffraction analysis method The phase and structure of the catalyst were analyzed by X-ray diffraction (XRD) using a Bruker D8 Advance X-ray diffractometer (Germany), with a scanning speed of 10 ° / min and a scanning range of 5–90 °.

[0045] X-ray photoelectron spectroscopy analysis method The elemental composition and valence state of the catalyst were analyzed using X-ray photoelectron spectroscopy (XPS). A Thermo Scientific Escalab Xi+ X-ray photoelectron spectrometer was used, with the following parameters: monochromatic Al target (E = 1486.68 eV); voltage 15242.60 V; current 14.9 mA; vacuum degree P < 10. -9 mBar; Power: 100 eV for the full spectrum, 20 eV for the fine spectrum; Work function: 5.04 eV; Beam spot diameter: 500 μm.

[0046] Field emission scanning electron microscopy characterization methods The morphology of the catalyst was analyzed using scanning electron microscopy (SEM) with a Zeiss GeminiSEM 360 microscope and an Oxford Instruments UILTIM MAX 40-Oxford EBSD C-SWIFT spectrometer. Au was used as the target material for the coating. The main specifications and technical indicators of the equipment were as follows: resolution: 0.7 nm @ 15 kV (in non-stage deceleration mode, without magnetic leakage), 1.2 nm @ 1 kV (in non-stage deceleration mode, without magnetic leakage); magnification: 8 x-200 W x; accelerating voltage: 0.02 kV-30 kV; probe accelerating current: 3 pA-20 nA.

[0047] Transmission electron microscopy characterization methods The morphology and energy dispersive spectroscopy of the catalyst were performed using transmission electron microscopy (TEM). A JEOL F200 TEM was used with an accelerating voltage of 200 kV and an energy dispersive spectroscopy (EDS) spectrometer of Oxford X-MaxN 80TIE250.

[0048] BET specific surface area and pore size analysis method Specific surface area and pore size were analyzed using a BET fully automated specific surface area analyzer, specifically a Micromeritics ASAP 2460 (USA) or a BELSORP MaxII (Japan). Appropriate sample amounts were weighed based on the specific surface area. Degassing was performed by pretreating the samples under vacuum at 150 °C for 6 hours. Nitrogen adsorption-desorption tests were then conducted on the samples using the BET fully automated specific surface area analyzer under liquid nitrogen conditions at 77 K. Isothermal adsorption-desorption curves were obtained after the instrument analysis was completed. Finally, BET model data processing was performed.

[0049] Inorganic carbon and sulfur testing methods A COREY-200 high-frequency infrared carbon-sulfur analyzer was used. Utilizing the strong characteristic absorption of CO2 at 4.26 μm and 7.4 μm, the CO2 content was analyzed by measuring the intensity of the absorbed light, thus indirectly determining the carbon content in the sample. The detection method was non-dispersive infrared absorption, with a carbon elemental determination range of 0.0001%–99.9%. COREY-1 co-solvent was used, the analytical flow rate was 3.5 L / min, the analytical pressure was 0.08 MPa, and the oxygen blowing flow rate was 1.2–2.6 L / min. The quantitative principle of infrared absorption was based on the Lambert-Beer law.

[0050] Experimental procedure for analyzing catalytic degradation performance The catalytic activity, stability, water resistance, and sulfur resistance of the catalyst were tested in a single-stage catalytic activity evaluation system (VOCs reactor). The prepared catalyst (0.15 g) was added to a quartz necked reaction tube with an inner diameter of 6 mm. The tube was sealed with quartz wool before addition and placed in a fixed-bed quartz tubular reactor. Chlorobenzene (CB) vapor was generated by evaporating liquid chlorobenzene at a constant temperature of 42 °C in a constant-temperature water bath. Water vapor was generated by evaporating deionized water at a constant temperature of 50 °C using a thermally heated magnetic stirrer. High-purity air was used as the carrier gas to carry and dilute the chlorobenzene gas; the concentration of chlorobenzene in the reactor could be controlled by adjusting the carrier gas flow rate and temperature. For the catalytic degradation of chlorobenzene, the reactant feed consisted of 12 mL / min chlorobenzene and 88 mL / min high-purity air, with the total flow rate maintained at 100 mL / min. For the water resistance test, the reactant feed consisted of 12 mL / min chlorobenzene and balanced high-purity air, with the water content of the gas stream controlled at 1%, 3%, and 5%, respectively, and the total flow rate maintained at 100 mL / min. For the water resistance test, the reactant feed consisted of 12 mL / min chlorobenzene, 2 mL / min sulfur dioxide, and balanced high-purity air, with the water content of the gas stream controlled at 5%, and the total flow rate maintained at 100 mL / min.

[0051] The inlet gas flow rate was regulated using a flow controller, and the reaction temperature was monitored by a thermocouple loaded in the catalyst bed core, with a measurement range of 0–500 °C. The concentration of CB in the outlet reaction product was quantitatively analyzed by gas chromatography.

[0052] Analytical methods for catalytic degradation performance The formula for calculating CB removal rate is: (1) In the formula: C CB,in C represents the concentration of chlorobenzene measured before the reaction. CB,out The concentration of chlorobenzene was measured after the reaction.

[0053] Based on the characterization results, the principle behind its beneficial effects is explained below in conjunction with the accompanying drawings: Figure 1 This is the XRD pattern of the catalysts SSHS-V2O5 and SSHS-V2O5:C of this invention. Figure 1 It can be seen that the single-layer hollow spherical shell morphology sample of the catalyst of this invention matches the PDF standard card PDF#85-0601 of V2O5, with corresponding cell parameters of a=3.564Å, b=11.519Å, c=4.373Å, and α, β, and γ angles all being 90°, indicating that the crystal form of V2O5 is an orthorhombic phase crystal structure of oP14 (O5V2). The single-layer hollow spherical shell morphology sample has obvious diffraction peaks at 2θ of 15.4°, 20.3°, 26.2°, 31.0°, 34.3°, and 51.2°, showing consistency with the characteristic peaks of the (020), (001), (110), (031), (130), and (200) crystal planes of PDF#85-0601 (some crystal planes are shown in [reference]). Figure 2: Lattice fringe images obtained by TEM: (a) SSHS-V2O5; (b) SSHS-V2O5:C). The undoped sample shows stronger diffraction peaks, while the carbon-doped sample shows weaker diffraction peaks. This phenomenon may be due to the fact that after C atoms are incorporated into the V2O5 lattice, they occupy interstitial sites or replace V atoms, leading to local lattice distortion (such as symmetry disruption), which in turn partially disrupts the periodicity of the atomic arrangement. Furthermore, when carbon is incorporated, if C atoms occupy interstitial sites, additional destructive interference may be introduced, directly reducing the scattering intensity at the average lattice position; if carbon replaces V atoms (substitution doping), its weak scattering ability will further weaken the diffraction peaks. However, SSHS-V2O5:C shows a significant peak intensity enhancement compared to SSHS-V2O5, which may be due to carbon doping inducing preferential growth of grains along specific crystal planes, resulting in an abnormally enhanced diffraction peak intensity corresponding to those crystal planes. Furthermore, carbon doping accompanied by annealing may repair intrinsic defects (vacancies, dislocations), improve long-range order, sharpen diffraction peaks and increase intensity, thereby enhancing crystallinity and generating nanocrystalline phases.

[0054] Figure 3 These are SEM or TEM / EDS images of the catalysts of this invention: (a) SEM image of catalyst SSHS-V2O5; (b) SEM image of catalyst SSHS-V2O5:C; (c) TEM image of catalyst SSHS-V2O5; (d) TEM image of catalyst SSHS-V2O5:C; (e) EDS image of catalyst material SSHS-V2O5:C. From... Figure 3 As can be seen from (a) and (b), the surface morphology of both SSHS-V2O5 and SSHS-V2O5:C catalyst materials consists of spherical structures formed by uniformly sized microparticles, with diameters ranging from 1 to 8 μm, and there is no significant difference before and after carbon doping. Figure 3 The TEM images in (c) and (d) further confirm that both SSHS-V2O5 and SSHS-V2O5:C show to be single-layer hollow spherical shell structures. Figure 3 (c) The SSHS-V2O5 sample has a diameter of approximately 1.7 μm and an average shell thickness of 0.3 μm; Figure 3(d) The SSHS-V₂O₅:C sample has a diameter of approximately 5.1 μm and an average shell thickness of 0.5 μm. It was found that the hollow structure of the single-layer hollow spherical shell increases the specific surface area of ​​the material to some extent. EDS Mapping results show that V, O, and C elements in the SSHS-V₂O₅:C sample exhibit distinct spatial distribution characteristics. The elemental distribution could not be directly obtained from the shell portion where electron beam penetration is weak, appearing as a darker ring region in the figure. However, the edges and hollow portions of the single-layer shell, due to their thinner thickness in the electron beam incident direction, exhibit high-density elemental distribution with good penetration. This distribution clearly delineates the inner and outer boundaries of the single-layer hollow spherical shell structure, confirming that the sample is a typical single-layer hollow spherical shell structure. It is worth noting that the V, O, and C element signals can be detected through the shell in some areas. Combined with the mesoporous characteristics shown by the BET specific surface area test in Table 1, this indicates that the single-layer hollow spherical shell structure is a mesoporous structure. The carbon doping exhibits a precise spatially regulated distribution, especially the carbon enrichment layer formed at the interface, which may significantly enhance the interfacial electronic conduction. The carbon modification on the shell surface may provide additional active sites.

[0055] Table 1. BET test data for the two catalyst materials

[0056] Figure 4 These are the isothermal adsorption-desorption curves of the catalyst material of this invention. Figure 4 It can be seen that the SSHS-V2O5 and SSHS-V2O5:C isotherms belong to the H3 type hysteresis loop isotherms. The location of the hysteresis loop closure point indicates that the specific surface area of ​​the single-layer hollow spherical shell structure material is larger than that of other common morphologies.

[0057] Figure 5 This is a pore size distribution diagram (surface area type) of the catalyst material of this invention. Combined with the data in Table 1, it can be found that SSHS-V2O5:C, as a carbon-doped material, performs worse than SSHS-V2O5 in terms of cumulative pore volume and average BJH desorption pore size, but its cumulative BJH desorption surface area increases. This indicates that after carbon doping, the deposited carbon may block some pores or cause material shrinkage, reducing the number of macropores in the material, thereby shifting the pore size distribution towards the mesoporous region. In other words, carbon doping has a surface modification effect on the material, optimizing the pore structure.

[0058] Figure 6 This is a pore size distribution (pore volume type) diagram of the catalyst material of the present invention. It shows that the catalyst of the present invention is a mesoporous material that generates slits.

[0059] Table 2 shows the elemental analysis results of the two catalyst materials.

[0060] An inorganic carbon-sulfur analyzer was used to test the carbon doping content of the two samples, and the results are shown in Table 2. Table 2 shows that the carbon content of the two samples, detected by three repeated inorganic carbon-sulfur tests, was consistent with expectations: the carbon content of the carbon-doped SSHS-V2O5:C sample was higher than that of SSHS-V2O5, indicating the successful preparation of the carbon-doped single-layer hollow vanadium pentoxide catalyst SSHS-V2O5:C material.

[0061] Figure 7 These are the XPS spectra of the catalyst of this invention: (a) Survey; (b) C1s; (c) O1s; (d) V2p. The elemental states of the surface of SSHS-V2O5 and SSHS-V2O5:C samples were analyzed by XPS, and the data were calibrated using the C1s peak (284.8 eV). Figure 7 (a) shows the full XPS spectrum of the sample, detecting three characteristic peaks corresponding to C1s (280–294 eV), O1s (526–536 eV), and V2p (514–528 eV), respectively. Figure 7 As shown in (b), the C1s energy spectra of the two materials show three peaks at 284.8 eV, 286.4 eV, and 288.8 eV, corresponding to C-C bonds, CO bonds, and C=O bonds, respectively. It is noteworthy that compared to SSHS-V2O5, the peak intensities of C-C bonds, CO bonds, and C=O bonds in SSHS-V2O5:C are all attenuated to some extent, and the corresponding C1s atomic percentage decreases by 13.09% as shown in Table 2. Based on EDS and inorganic carbon-sulfur test results, it is speculated that the main reason for this is that XPS characterization is a surface chemical analysis of the sample and cannot accurately detect the elemental composition inside the single-layer hollow spherical shell structure, while C elements are mostly distributed inside the shell structure after doping. Figure 7 (c) It can be seen that the O1s composition consists of three parts: 532.4 eV, 531.1 eV, and 530.4 eV, which are attributed to hydroxyl groups on the sample surface, surface oxygen, and lattice oxygen, respectively. The presence of oxygen vacancies typically significantly promotes the oxidation kinetics of materials. As active sites, they weaken the binding energy of neighboring oxygen atoms, lower the dissociation barrier of surface oxygen species, and enhance the mobility of lattice oxygen, providing more active oxygen sources for the oxidation reaction. This effectively improves the oxygen exchange capacity and activation efficiency of the material surface, thereby optimizing the oxidation performance of the catalytic system. Figure 7 (d) shows the characteristic peaks of the catalyst at V2p, revealing that in addition to the peaks originating from V2p... 5+ In addition to the peak at 517.7 eV, there is also a V peak at 516.1 eV for 2p 3 / 2. 4+The 2p 3 / 2 peak confirms the presence of oxygen vacancies in the sample. It can be seen that V in the SSHS-V2O5:C sample... 5+ The binding energy of 2p³ / 2 shifts to higher energies by 0.1 eV, indicating that V 5+ Stability improved. Two types of calculations were performed on the oxygen vacancy ratio of the four samples (as shown in Table 2). It was found that the number of oxygen vacancies in the carbon-doped catalyst material increased slightly, which is more conducive to the accumulation of surrounding electrons and improves catalytic activity.

[0062] Figure 8 This describes the CB degradation rate of the catalyst of this invention under 1000 ppm CB and different temperature conditions. The performance of this catalyst was investigated using chlorobenzene as a CVOC simulated pollutant. The temperature difference between the SSHS-V2O5:C and SSHS-V2O5 catalysts was not measured. 90 The maximum degradation rate and temperature were 86.7% (370 ℃) and 83.2% (410 ℃), respectively.

[0063] like Figure 9 As shown, after 13 h of continuous catalysis, the chlorobenzene degradation rates of the two prepared catalysts fluctuated within a certain range and were relatively stable. Among them, SSHS-V2O5:C had the highest stability, with a degradation rate decrease of 1.2%. The high stability of SSHS-V2O5:C is due to the (110) crystal facet rich in VOV-bridged oxygen. Its structure has higher thermodynamic stability at high temperatures than the (001) crystal facet rich in V=O bonds, exhibiting lower surface energy and being less prone to sintering and agglomeration. Moreover, since uniformly dispersed C atoms may form "pinning points" at grain boundaries, they inhibit the Ostwald ripening of V2O5 grains at high temperatures, hindering grain boundary migration and maintaining the crystal facet with current catalytic activity. In addition, XPS analysis shows that there is a C-induced charge redistribution. The C atoms uniformly doped in each part of the monolayer hollow spherical shell structure can slightly pull electrons, causing the adjacent V=O bonds to redistribute. 5+ The electron cloud density decreases, making V 5+ +e - →V 4+ It is less likely to occur, thus enhancing its oxidizing ability.

[0064] Figure 10 This invention relates to the reaction stability of the catalyst in the degradation of CB under different humidity and temperature conditions. The water resistance of the two catalyst materials was tested, such as... Figure 10 As shown, under the condition of 1 vol.% H2O, trace amounts of H2O vapor increased the surface area of ​​SSHS-V2O5 and SSHS-V2O5:C catalysts. The concentration of OH groups and their dissociation to form Brønsted acid sites accelerates CB adsorption. Under dry conditions, although water molecule competition for adsorption is avoided, the lack of proton supply results in slightly lower activity. After adding 3 vol.% H2O, in addition to water vapor competition for adsorption, water molecules also form a monolayer adsorption on the shell surface, partially blocking the mass transfer channels of the monolayer hollow spherical shell structure and covering the Lewis acid sites (V). 5+ The presence of water at 5 vol.% H2O resulted in a low activity level. Adding 5 vol.% H2O improved the chlorobenzene degradation rate of SSHS-V2O5 compared to adding 3 vol.% H2O, while slightly decreasing the degradation rate of chlorobenzene in SSHS-V2O5:C. At 5 vol.% H2O, the high water content effectively flushed away adsorbed chlorine species (VOCl3) and forced the activation shell, but excessive hydroxylation (V2O5→V-OH) limited the recovery of activity. Finally, restoring the conditions to dryness revealed almost no difference in the chlorobenzene catalytic performance of both catalysts compared to the initial conditions. This indicates that the presence of water dynamically regulates the catalytic process rather than permanently altering the intrinsic activity of the catalyst.

[0065] Figure 11 This invention describes the CB catalytic activity of the catalyst under the conditions of 1000 ppm CB + 100 ppm SO2 + 5 vol.% H2O. Under the condition of 100 ppm SO2, the chlorobenzene catalytic activity of both catalyst materials was found to be slightly reduced compared to the blank condition. This is attributed to the competitive adsorption of SO2 at the active sites on the catalyst surface, and the fact that SO2 can be oxidized to SO3, reacting with the V2O5 surface to form sulfites or sulfates, covering the active sites or changing the surface acidity. Simultaneously, the reducing power of SO2 also leads to some V2O5 degradation. 5+ The chlorobenzene catalytic activity was reduced to a low-activity valence state. After stopping the SO2 supply, the activity of both catalysts returned to their initial levels, indicating that SO2 only participates in reversible reactions involving physical adsorption or weak chemisorption, and the original active sites are restored after the SO2 supply is stopped. Adding 5 vol.% H2O to the 100 ppm SO2 condition further reduced the chlorobenzene catalytic activity of both catalysts. This can be attributed to the excessive formation of Brønsted acid sites on the catalyst surface, which promotes the adsorption of H2O molecules as Lewis bases and intensifies the competitive adsorption between H2O and CB. However, when the SO2 supply was stopped and the steam was shut off, the chlorobenzene catalytic performance of both catalysts showed a slight improvement compared to the previous blank stage, indicating that SO42- on the catalyst surface... 2- Ions can effectively capture protons (H+) in H2O molecules. +This leads to the formation of additional Brønsted acid sites, promoting the destruction of CB. Interestingly, at this stage, the catalytic performance of SSHS-V2O5 improves to a level close to that of SSHS-V2O5:C. This is attributed to the rapid adsorption and reaction of water molecules on the surface of the high specific surface area monolayer hollow spherical shell structure of V2O5, forming polar surface hydroxyl groups (—OH), which subsequently form strong hydrogen bonds with water molecules, significantly enhancing the hydrophilicity of the material and forming a high-density water molecule adsorption layer, thus strengthening the influence of water molecules on sulfur species. While SSHS-V2O5:C has the same structure, the doped C atoms form CS bonds with SO2, hindering the complete desorption of SO2, and the contact between carbon and V2O5 at the interface slightly reduces V. 5+ The electron density makes it more difficult for some sulfur species to desorb, and the performance enhancement is not significant.

[0066] Figure 12 This is a mechanism diagram of the carbon-doped single-layer hollow spherical vanadium pentoxide (SSHS-V₂O₅:C) catalyst of this invention. Based on the reaction mechanism shown in the diagram, the following can be explained more intuitively. Figure 8 , 9 The underlying mechanisms and pathways of the test results corresponding to 10.

[0067] In summary, this invention combines morphology control with carbon doping strategies to prepare a monolayer hollow spherical vanadium-based catalyst using a solvothermal-calcination method. The synergistic effect of the monolayer hollow spherical shell morphology and carbon doping on the activity, stability, and resistance to water and sulfur poisoning in the thermal catalytic degradation of chlorobenzene was systematically investigated. The mechanism by which carbon doping affects the catalyst's microstructure and surface elemental chemical states was clarified, and the intrinsic mechanism by which the two synergistically enhance the catalyst's performance in CVOCs degradation was elucidated. This catalyst, using inexpensive vanadium as its core, exhibits good catalytic performance at lower temperatures compared to single-metal vanadium-based catalysts, and significantly reduces costs while demonstrating stronger resistance to poisoning compared to precious metal catalysts. Carbon doping increases the pore volume, optimizes the pore structure, and increases the specific surface area and active sites, thereby improving both the degradation rate and structural stability. Simultaneously, this catalyst possesses excellent stability, water resistance, and activity retention under water and sulfur poisoning conditions. This invention provides important theoretical basis and practical guidance for the design of efficient, stable, and interference-resistant CVOCs purification catalysts, and also provides a feasible strategy for the development of efficient, poison-resistant catalysts for industrial-scale CVOCs destruction.

Claims

1. A method for preparing a single-layer hollow spherical shell vanadium-based catalyst, characterized in that, The specific steps are as follows: A rod-shaped vanadium pentoxide and oxalic acid in a molar ratio of 1:3 were dissolved in deionized water and stirred to obtain mixture 1; Mixture 1 was added to a 0.0067 g / ml isopropanol solution of ascorbic acid at a volume ratio of 2:15 to obtain mixture 2; The mixture 2 was heated to carry out a hydrothermal reaction. After the reaction, a precipitate was obtained. The precipitate was washed, centrifuged and dried to obtain product 1. Product 1 was subjected to two-stage calcination to obtain a single-layer hollow spherical shell vanadium-based catalyst.

2. The method for preparing a single-layer hollow spherical shell vanadium-based catalyst according to claim 1, characterized in that, Anhydrous glucose was also added to the mixture 1. The rod-shaped vanadium pentoxide was obtained by hydrothermal reaction of vanadium pentoxide and hydrogen peroxide and calcination in two stages. The mass ratio of vanadium pentoxide to glucose was 1.82:0.1~0.

3.

3. The method for preparing a single-layer hollow spherical shell vanadium-based catalyst according to claim 1, characterized in that, The preparation of rod-shaped vanadium pentoxide is as follows: Vanadium pentoxide was added to a hydrogen peroxide solution with a volume concentration of 5%-10% to obtain mixture 3; Mixture 3 was heated to carry out a hydrothermal reaction, and a precipitate was obtained after the reaction. The precipitate was washed and dried to obtain product 2. Product 2 was subjected to two-stage calcination to obtain rod-shaped vanadium pentoxide.

4. The method for preparing a single-layer hollow spherical shell vanadium-based catalyst according to claim 3, characterized in that, The amount of vanadium pentoxide added is 5.49%-16.48%.

5. The method for preparing a single-layer hollow spherical shell vanadium-based catalyst according to claim 3, characterized in that, The hydrothermal reaction conditions are: reaction at 180℃ for 24 hours; drying at 40℃~80℃ for 24 hours; and two-stage calcination, which involves annealing at 300℃ for 2 hours at a heating rate of 1℃ / min and annealing at 350℃ for 30 minutes at a temperature rise rate of 0.5℃ / min.

6. The method for preparing a single-layer hollow spherical shell vanadium-based catalyst according to claim 1, characterized in that, The hydrothermal reaction conditions are 200 °C for 12 h, and the drying conditions are vacuum drying at 40 °C to 80 °C.

7. The method for preparing a single-layer hollow spherical shell vanadium-based catalyst according to claim 1, characterized in that, The two-stage calcination consisted of annealing at 300 °C for 2 h at a heating rate of 1 °C / min, and annealing at 350 °C for 30 min at a temperature rise rate of 0.5 °C / min.

8. A single-layer hollow spherical shell vanadium-based catalyst, characterized in that, The catalyst is prepared by the method described in claim 1, 3, 4, 5, or 6, and is used for the purification of chlorinated volatile organic compounds.

9. A single-layer hollow spherical shell vanadium-based catalyst, characterized in that, The catalyst was prepared using the method described in claim 1, 2, 4, 5, or 6 for a single-layer hollow spherical shell vanadium-based catalyst.

10. The application of the single-layer hollow spherical shell vanadium-based catalyst according to claim 9 in the purification of chlorinated volatile organic compounds.

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