A CeO2-V2O5 catalyst, its preparation method and application

Abstract

The application provides a CeO2-V2O5 catalyst and a preparation method and application thereof, and relates to the technical field of catalyst preparation. A cerium-containing precursor slurry is prepared first, then the cerium-containing precursor slurry is subjected to hydrothermal reaction and calcination treatment, a rod-like CeO2 with a dominant exposed (110) crystal surface is obtained, finally, the rod-like CeO2 is immersed in a transparent vanadium precursor solution, and after the immersion, the calcination treatment is carried out, thereby obtaining the CeO2-V2O5 catalyst. The CeO2-V2O5 catalyst has excellent SO2 directional conversion capacity and long-term operation stability, effectively balances and optimizes the SO2 conversion rate and the SO3 yield, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to a CeO2-V2O5 catalyst, its preparation method, and its application. Background Technology

[0002] Alkylation is a core technology for producing high-octane clean gasoline. Industrial production uses large amounts of concentrated sulfuric acid as a catalyst, generating SO2-rich waste acid and liquid. Direct discharge of this waste acid would cause severe air pollution and waste of sulfur resources. Catalytically oxidizing the SO2 produced by the pyrolysis of alkylation waste acid to SO3, and further preparing high-concentration concentrated sulfuric acid, is a key pathway to achieving closed-loop sulfur resource recovery and promoting the green and low-carbon development of the petrochemical industry. The core of this technology lies in developing highly active, highly stable, and highly selective SO2 oxidation catalysts.

[0003] Currently, the mainstream SO2 oxidation catalysts in industry are supported V2O5-based catalysts, whose catalytic performance is highly dependent on their physicochemical properties. CeO2, as a typical fluorite-type rare earth oxide, possesses excellent oxygen storage and release capabilities and reversible CeO2 oxidation. 3+ / Ce 4+ Redox cycles and abundant oxygen vacancy defects can modulate the dispersion, electronic structure, and catalytic activity of the active component V₂O₅ through metal-strong interactions. Existing studies have shown that the exposed crystal faces of CeO₂ directly determine its surface atomic coordination, oxygen vacancy formation energy, and electron transport properties, thus significantly affecting the interfacial structure and catalytic behavior of supported catalysts.

[0004] In the existing technology, V2O5-CeO2 catalyst has the following technical defects: (1) CeO2 exposed crystal face is not precisely controlled, oxygen vacancy concentration is low and interfacial electron transfer efficiency is poor, resulting in low SO2 oxidation activity; (2) Inert bidentate sulfate is easily generated on the catalyst surface, blocking active sites and resulting in poor long-term operation stability; (3) SO2 conversion rate and SO3 yield are difficult to balance, and thermodynamic balance is significantly limited at high temperature, which cannot meet the industrial demand for alkylation waste acid resource utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a CeO2-V2O5 catalyst and its preparation method, which solves the technical problems of low SO2 conversion rate, poor stability, and difficulty in balancing SO2 conversion rate and SO3 yield in the prior art.

[0006] The first aspect of this invention provides a method for preparing a CeO2-V2O5 catalyst, comprising the following steps: S1. Ce(NO3)2·6H2O and NaOH are dissolved in deionized water in sequence to obtain cerium-containing precursor slurry; S2. The cerium-containing precursor slurry obtained in step S1 is transferred to a hydrothermal reactor for hydrothermal reaction, and then centrifuged, washed, dried and calcined in sequence to prepare rod-shaped CeO2 with dominant exposed (110) crystal planes. S3. The rod-shaped CeO2 obtained in step S2 is immersed in a transparent vanadium precursor solution, impregnated at room temperature, and then calcined at 450℃-500℃ for 3-4 hours to obtain the CeO2-V2O5 catalyst.

[0007] Optionally, the transparent vanadium precursor solution contains ammonium metavanadate and oxalic acid in a molar ratio of 1:(0.8-1.2).

[0008] Optionally, the length of the rod-shaped CeO2 is 1μm-5μm and the diameter is 200nm-500nm.

[0009] Optionally, the pore volume of the rod-shaped CeO2 is 0.50 cm³. 3 / g-0.55cm 3 / g, with a pore size of 24nm-25nm.

[0010] Optionally, the specific surface area of ​​the rod-shaped CeO2 is 80 m². 2 / g-86m 2 / g.

[0011] Optionally, the temperature of the hydrothermal reaction in step S2 is 170℃-180℃, and the reaction time is 20h-24h.

[0012] Optionally, the roasting temperature in step S2 is 400℃-500℃, and the roasting time is 3h-4h.

[0013] Optionally, the immersion time at room temperature in step S3 is 10-12 hours.

[0014] A second aspect of the present invention provides a CeO2-V2O5 catalyst prepared by the above-described preparation method, wherein the CeO2-V2O5 catalyst has a mesoporous structure and a specific surface area of ​​40 m². 2 / g-45m 2 / g.

[0015] The third aspect of this invention realizes the application of CeO2-V2O5 catalyst in the catalytic oxidation of SO2 to prepare SO3.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention first precisely prepares rod-shaped CeO2 with predominantly exposed (110) crystal planes using a hydrothermal method. Then, combining an equal-volume impregnation method and high-temperature calcination, the rod-shaped CeO2 is loaded onto the surface of V2O5 to obtain a CeO2-V2O5 catalyst. The rod-shaped CeO2 has a high oxygen vacancy concentration, which enhances the specific adsorption and activation of SO2. Driven by the strong electronic interaction at the interface between the rod-shaped CeO2 and V2O5, V2O5 is activated via V2O5... 5+ / V 4+ The rapid redox cycle efficiently delivers lattice oxygen to rod-shaped CeO2, forming a low-energy-barrier oxygen species transport channel. This enables the CeO2-V2O5 catalyst to operate rapidly at low temperatures and effectively increases the reaction rate of SO2 to SO3 conversion. Simultaneously, the moderate adsorption characteristics of SO3 on the (110) crystal plane of the rod-shaped CeO2 facilitate rapid desorption of SO3, inhibiting the poisoning of active sites by inert bidentate sulfate. This synergistic mechanism enhances the directional conversion of SO2 by the CeO2-V2O5 catalyst at low temperatures and exhibits excellent long-term operational stability, effectively balancing and optimizing SO2 conversion and SO3 yield, avoiding thermodynamic equilibrium limitations at high temperatures. Furthermore, the preparation process of this invention is simple, the conditions are mild, the raw materials are readily available, and the cost is low, demonstrating good economic viability and industrialization prospects. Specifically, under catalytic conditions at 350℃, the CeO2-V2O5 catalyst can achieve a SO2 conversion rate of greater than or equal to 88.2%, and after continuous operation for 12 hours, the activity retention rate of the CeO2-V2O5 catalyst is greater than or equal to 95.4%.

[0017] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a method for preparing a CeO2-V2O5 catalyst according to an embodiment of the present invention; Figure 2 This is a scanning electron microscope image of the rod-shaped CeO2 from Example 1; Figure 3 This is a scanning electron microscope image of cubic CeO2 in Comparative Example 1; Figure 4 This is a scanning electron microscope image of the octahedral CeO2 in Comparative Example 2; Figure 5 This is a transmission electron microscope image of the rod-shaped CeO2 from Example 1; Figure 6 This is a transmission electron microscope image of cubic CeO2 in Comparative Example 1. Figure 7 This is a transmission electron microscope image of the octahedral CeO2 in Comparative Example 2. Figure 8 This is a scanning electron microscope image of the CeO2-V2O5 catalyst from Example 1; Figure 9 This is a transmission electron microscope image of the CeO2-V2O5 catalyst from Example 1; Figure 10 These are X-ray diffraction patterns of rod-shaped CeO2 from Example 1, cubic CeO2 from Comparative Example 1, and octahedral CeO2 from Comparative Example 2. Figure 11 These are X-ray diffraction patterns of the CeO2-V2O5 catalyst of Example 1, the CeO2-V2O5 catalyst of Comparative Example 1, and the CeO2-V2O5 catalyst of Comparative Example 2. Figure 12 These are the X-ray photoelectron spectra of rod-shaped CeO2 from Example 1, cubic CeO2 from Comparative Example 1, and octahedral CeO2 from Comparative Example 2. Figure 13 The X-ray photoelectron spectrum of the V2O5 catalyst in Comparative Example 3 is shown. Figure 14 This is the X-ray photoelectron spectrum of the CeO2-V2O5 catalyst in Example 1; Figure 15 This is a graph showing the electrostatic potential distribution and work function calculation of the rod-shaped CeO2 in Example 1; Figure 16 The graph shows the electrostatic potential distribution and work function calculation of V2O5 in Comparative Example 3. Figure 17 This is the diffuse reflectance infrared Fourier transform spectrum of the CeO2-V2O5 catalyst in Example 1; Figure 18 This is the diffuse reflectance infrared Fourier transform spectrum of the CeO2-V2O5 catalyst in Comparative Example 1. Figure 19 This is the diffuse reflectance infrared Fourier transform spectrum of the CeO2-V2O5 catalyst in Comparative Example 2. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0020] Figure 1 This is a schematic flowchart illustrating a method for preparing a CeO2-V2O5 catalyst according to an embodiment of the present invention.

[0021] Reference Figure 1 As shown, a method for preparing a CeO2-V2O5 catalyst includes the following steps: S1. Ce(NO3)2·6H2O and NaOH are dissolved in deionized water in sequence to obtain cerium-containing precursor slurry; S2. The cerium-containing precursor slurry obtained in step S1 is transferred to a hydrothermal reactor for hydrothermal reaction, and then centrifuged, washed, dried and calcined in sequence to prepare rod-shaped CeO2 with dominant exposed (110) crystal planes. S3. The rod-shaped CeO2 obtained in step S2 is immersed in a transparent vanadium precursor solution, impregnated at room temperature, and then calcined at 450℃-500℃ for 3-4 hours to obtain the CeO2-V2O5 catalyst.

[0022] In this embodiment, rod-shaped CeO2 with predominantly exposed (110) crystal planes was first precisely prepared using a hydrothermal method. Then, an equal-volume impregnation method and high-temperature calcination were combined to load the rod-shaped CeO2 onto the surface of V2O5, yielding a CeO2-V2O5 catalyst. The rod-shaped CeO2 has a high oxygen vacancy concentration, which enhances the specific adsorption and activation of SO2. Driven by the strong electronic interaction at the interface between the rod-shaped CeO2 and V2O5, V2O5 is activated via V... 5+ / V 4+ The rapid redox cycle efficiently delivers lattice oxygen to rod-shaped CeO2, forming a low-energy-barrier oxygen species transport channel. This enables the CeO2-V2O5 catalyst to operate rapidly at low temperatures and effectively increases the reaction rate of SO2 to SO3 conversion. Simultaneously, the moderate adsorption characteristics of SO3 on the (110) crystal plane of the rod-shaped CeO2 facilitate rapid desorption of SO3, inhibiting the poisoning of active sites by inert bidentate sulfate. This synergistic mechanism enhances the directional conversion of SO2 by the CeO2-V2O5 catalyst at low temperatures and exhibits excellent long-term operational stability, effectively balancing and optimizing SO2 conversion and SO3 yield, avoiding thermodynamic equilibrium limitations at high temperatures. Furthermore, the preparation process of this invention is simple, the conditions are mild, the raw materials are readily available, and the cost is low, demonstrating good economic viability and industrialization prospects. Specifically, under catalytic conditions at 350℃, the CeO2-V2O5 catalyst can achieve a SO2 conversion rate of greater than or equal to 88.2%, and after continuous operation for 12 hours, the activity retention rate of the CeO2-V2O5 catalyst is greater than or equal to 95.4%.

[0023] In this embodiment, the (110) crystal plane of the rod-shaped CeO2 exhibits moderate adsorption characteristics for SO3. On the one hand, this allows the generated SO3 molecules to remain stably near the active sites, ensuring their smooth generation from the SO2 oxidation reaction and completion of surface migration. On the other hand, this adsorption characteristic is significantly lower than the activation energy threshold required for the formation of inert bidentate sulfate, allowing SO3 molecules to detach from the surface without overcoming an excessively high energy barrier. Under these conditions, the thermal vibration energy provided by the low reaction temperature (e.g., 350°C) can drive SO3 molecules to rapidly desorb and return to the gas phase along the low-resistance path of the (110) crystal plane, effectively preventing excessive accumulation of SO3 on the catalyst surface and further conversion to inert bidentate sulfate, thereby inhibiting the poisoning of the active sites.

[0024] In step S1, Ce(NO3)2·6H2O is dissolved in deionized water and then reacted with NaOH to form a Ce(OH)3 colloidal precipitate, thereby preparing a cerium-containing precursor slurry.

[0025] In step S2, during the initial stage of the hydrothermal reaction, Ce(OH)3 in the cerium-containing precursor slurry undergoes dehydration condensation under high temperature and pressure, generating CeO2 nanocrystals in situ. Simultaneously, a high concentration of OH in the reaction system... - Driven by thermodynamics, the (110) high surface energy crystal plane of CeO2 is preferentially anchored. By reducing the interfacial free energy of this crystal plane, its normal growth rate is suppressed, prompting CeO2 nanocrystals to undergo oriented attachment and anisotropic self-assembly along the (110) crystal axis, ultimately forming rod-shaped CeO2 to be calcined with the (110) crystal plane as the dominant exposed surface. In addition, the oxygen-deficient atmosphere of the closed hydrothermal system simultaneously induces the intrinsic generation of oxygen vacancies during the lattice growth of the rod-shaped CeO2 to be calcined, making CeO2 nanocrystals more oriented and anisotropically self-assembled. 3+ The rod-shaped CeO2 lattice framework to be calcined is pre-embedded. After the hydrothermal reaction is completed, the mixture is centrifuged and washed alternately with deionized water and ethanol until neutral, then vacuum dried at 60℃-80℃.

[0026] The temperature of the hydrothermal reaction can be, for example, 170℃, 175℃, or 180℃, or any value between 170℃ and 180℃. The duration of the hydrothermal reaction can be, for example, 20h, 22h, 23h, or 24h, or any value between 20h and 24h.

[0027] In step S2, high-temperature calcination is used to eliminate residual hydroxyl groups and adsorbates on the surface of the rod-shaped CeO2, driving the CeO2 lattice to relax from a metastable state to a thermodynamically stable state, thereby improving the crystal integrity and thermal stability of the rod-shaped CeO2. Simultaneously, the calcination process further stimulates the desorption and escape of oxygen from the rod-shaped CeO2 lattice, further enriching the surface oxygen vacancy concentration, thus enhancing the CeO2 crystal integrity and thermal stability. 3+ The relative content has been increased to over 15%.

[0028] The roasting temperature can be, for example, 400℃, 450℃ or 500℃, or any other value between 400℃ and 500℃, and the roasting time can be, for example, 3h, 3.5h and 4h, or any other value between 3h and 4h.

[0029] The length of the rod-shaped CeO2 can be, for example, 1 μm, 3 μm, or 5 μm, or any value within the range of 1 μm to 5 μm. The diameter of the rod-shaped CeO2 can be, for example, 200 nm, 300 nm, 400 nm, or 500 nm, or any value within the range of 200 nm to 500 nm. The pore volume of the rod-shaped CeO2 can be, for example, 0.50 cm³.3 / g, 0.53cm 3 / g or 0.55cm 3 / g, or 0.50cm 3 / g-0.55cm 3 The pore size can be any other value in / g, for example, 24 nm, 24.5 nm, or 25 nm, or any other value between 24 nm and 25 nm. The specific surface area of ​​rod-shaped CeO2 is 80 m². 2 / g、85m 2 / g or 86m 2 / g, or 80m 2 / g-86m 2 Any other value in / g.

[0030] In step S3, rod-shaped CeO2 is immersed in a transparent vanadium precursor solution for 10-12 hours, followed by high-temperature calcination to load the rod-shaped CeO2 onto the V2O5 surface, thereby preparing the CeO2-V2O5 catalyst. The high-temperature calcination further drives atomic interdiffusion and electron rearrangement at the CeO2-V2O5 interface, strengthening the VO-Ce interfacial bonding and optimizing the V2O5 interface. 5+ / V 4+ The redox ratio is adjusted to enhance the migration rate of lattice oxygen at the interface, thereby constructing a CeO2-V2O5 catalyst with strong interfacial electronic interactions. The molar ratio of ammonium metavanadate to oxalic acid in the transparent vanadium precursor solution can be, for example, 1:0.8, 1:1, 1:1.1, or 1:1.1, or any other value from 1:(0.8-1.2).

[0031] In another embodiment, the surface area relative to V2O5 is 1.99 m². 2 / g, the specific surface area of ​​the CeO2-V2O5 catalyst is 40m². 2 / g-45m 2 The specific surface area of ​​the CeO2-V2O5 catalyst increased by more than 20 times, significantly increasing the number of SO2 adsorption sites per unit mass and exposing more CeO2(110) active crystal faces. These faces, rich in oxygen vacancies, have a specific adsorption capacity for SO2, thus greatly improving the SO2 capture efficiency and initial activation rate. Furthermore, the high specific surface area of ​​the CeO2-V2O5 catalyst creates more VO-Ce interface sites, providing abundant interfacial channels for electron transfer from CeO2 to V2O5 and lattice oxygen transport from V2O5 to CeO2, accelerating the redox cycle. The specific surface area of ​​the CeO2-V2O5 catalyst is 40 m² / g. 2 / g、43m 2 / g or 45m 2 / g, or 40m2 / g-45m 2 Any other value in / g.

[0032] The following detailed description uses specific embodiments and comparative examples.

[0033] Example 1: Reference Figure 2 , Figure 5 , Figure 8-12 , Figure 14 , Figure 15 and Figure 17 Example 1 provides a method for preparing a CeO2-V2O5 catalyst, the method comprising: Step S111: Dissolve 1.74gCe(NO3)2·6H2O in 30mL of deionized water, and then add 7.2gNaOH to obtain a cerium-containing precursor slurry. Step S121: The cerium-containing precursor slurry obtained in step S111 is transferred to a 50 mL hydrothermal reactor and hydrothermally reacted at 180 °C for 20 h. After centrifugation, washing three times each with deionized water and ethanol, and drying at 80 °C for 12 h, it is calcined at 500 °C for 3 h to prepare rod-shaped CeO2 with predominantly exposed (110) crystal planes. The rod-shaped CeO2 has a length of 2 μm-4 μm, a diameter of 300 nm-400 nm, and a specific surface area of ​​84.6 m². 2 / g, pore volume 0.53cm 3 / g, with a pore size of 24.8nm; Step S131: Dissolve 0.234 g of ammonium metavanadate and 0.18 g of oxalic acid in 10 mL of deionized water to obtain a transparent vanadium precursor solution. Then, immerse 2 g of rod-shaped CeO2 in the transparent vanadium precursor solution and impregnate at room temperature for 12 h with an equal volume. Dry at 80 °C overnight and calcine at 500 °C for 3 h to obtain a V2O5 loading of 10% and a specific surface area of ​​43.41 m². 2 / g and a pore volume of 0.05cm 3 / g of CeO2-V2O5 catalyst.

[0034] Example 2: Example 2 provides a method for preparing a CeO2-V2O5 catalyst, the method comprising: Step S111: Dissolve 1.74gCe(NO3)2·6H2O in 30mL of deionized water, and then add 7.2gNaOH to obtain a cerium-containing precursor slurry. In step S121, the cerium-containing precursor slurry obtained in step S111 is transferred to a 50 mL hydrothermal reactor and reacted hydrothermally at 170 °C for 24 h. After centrifugation, washing three times each with deionized water and ethanol, and drying at 80 °C for 12 h, it is calcined at 400 °C for 4 h to prepare rod-shaped CeO2 with predominantly exposed (110) crystal planes. The rod-shaped CeO2 has a length of 2.8 μm-3.6 μm, a diameter of 320 nm-380 nm, and a specific surface area of ​​85.8 m². 2 / g, pore volume 0.54cm 3 / g, pore size is 24.2nm; In step S131, 0.234 g of ammonium metavanadate and 0.144 g of oxalic acid were dissolved in 10 mL of deionized water to obtain a transparent vanadium precursor solution. Then, 2 g of the rod-shaped CeO2 obtained in step S121 was immersed in the transparent vanadium precursor solution and impregnated at room temperature for 10 h by equal volume. The mixture was then dried overnight at 80 °C and calcined at 450 °C for 4 h to obtain a V2O5 loading of 10% and a specific surface area of ​​44.15 m². 2 / g and a pore volume of 0.07cm 3 / g of CeO2-V2O5 catalyst.

[0035] Example 3: Example 3 provides a method for preparing a CeO2-V2O5 catalyst, the method comprising: Step S111: Dissolve 1.74gCe(NO3)2·6H2O in 30mL of deionized water, and then add 7.2gNaOH to obtain a cerium-containing precursor slurry. In step S121, the cerium-containing precursor slurry obtained in step S111 is transferred to a 50 mL hydrothermal reactor and hydrothermally reacted at 175 °C for 22 h. After centrifugation, washing three times each with deionized water and ethanol, and drying at 80 °C for 12 h, it is calcined at 450 °C for 3.5 h to prepare rod-shaped CeO2 with predominantly exposed (110) crystal planes. The rod-shaped CeO2 has a length of 2.4 μm-3.8 μm, a diameter of 310 nm-390 nm, and a specific surface area of ​​85.2 m². 2 / g, pore volume 0.52cm 3 / g, pore size is 24.5nm; In step S131, 0.234 g of ammonium metavanadate and 0.144 g of oxalic acid were dissolved in 10 mL of deionized water to obtain a transparent vanadium precursor solution. Then, 2 g of the rod-shaped CeO2 obtained in step S121 was immersed in the transparent vanadium precursor solution and impregnated at room temperature for 11 h with an equal volume. The mixture was then dried overnight at 80 °C and calcined at 480 °C for 3.5 h to obtain a V2O5 loading of 10% and a specific surface area of ​​43.78 m². 2 / g and a pore volume of 0.06cm 3 / g of CeO2-V2O5 catalyst.

[0036] Comparative Example 1: Reference Figure 3 , Figure 6 , Figure 10 , Figure 11 and Figure 18 The difference between Comparative Example 1 and Example 1 is that 0.3g of trisodium phosphate dodecahydrate is added to the cerium-containing precursor slurry in step S111 to obtain a side length of 1μm-1.5μm and a specific surface area of ​​17.82m². 2 / g, pore volume 0.1cm 3 / g of cubic CeO2 with predominantly exposed (100) crystal planes was used to prepare V2O5 with a loading of 5% and a specific surface area of ​​10.34m². 2 / g and a pore volume of 0.08cm 3 / g of CeO2-V2O5 catalyst.

[0037] Comparative Example 2: Reference Figure 4 , Figure 7 , Figure 10 , Figure 11 and Figure 19 The difference between Comparative Example 2 and Example 1 is that 0.02 g of trisodium phosphate dodecahydrate needs to be added to the cerium-containing precursor slurry in step S111, and the hydrothermal reaction temperature is 160°C, resulting in particles with a diameter of 1.5 μm-2.5 μm and a specific surface area of ​​9.8 m². 2 / g, pore volume 0.08cm 3 / g and predominantly exposed (111) crystal planes of octahedral CeO2. Comparative Example 2 prepared V2O5 with a loading of 5% and a specific surface area of ​​6.02 m². 2 / g and a pore volume of 0.05cm 3 / g of CeO2-V2O5 catalyst.

[0038] Comparative Example 3: Reference Figure 13 and Figure 16 Comparative Example 3 provides a pure V₂O₅ catalyst, which differs from Example 1 in that it uses only V₂O₅ as the active component and does not include rod-shaped CeO₂. The surface area of ​​the V₂O₅ catalyst is 1.99 m². 2 / g, pore volume is 0.28cm 3 / g.

[0039] Figure 2 This is a scanning electron microscope image of the rod-shaped CeO2 from Example 1. Figure 3 This is a scanning electron microscope image of cubic CeO2 in Comparative Example 1. Figure 4This is a scanning electron microscope image of the octahedral CeO2 of Comparative Example 2.

[0040] Depend on Figure 2 As can be seen, Example 1 can precisely control the morphology of rod-shaped CeO2, making the rod-shaped CeO2 exhibit a regular and uniform rod-shaped morphology, with a length distribution of 2μm-4μm and a diameter distribution of 300nm-400nm, and a smooth surface without obvious agglomeration. Figure 3 It can be seen that cubic CeO2 exhibits a regular cubic structure with side lengths of 1μm-1.5μm. From... Figure 4 It can be seen that octahedral CeO2 exhibits a regular octahedral morphology with a particle size of 1.5 μm-2.5 μm. In contrast, the crystal size of rod-shaped CeO2 is smaller than that of cubic CeO2 and octahedral CeO2, indicating that a greater number of rod-shaped CeO2 particles can be loaded on a unit V2O5 surface. This provides direct morphological and size evidence for the highest activity exhibited by the CeO2-V2O5 catalyst in the catalytic oxidation of SO2.

[0041] Figure 5 This is a transmission electron microscope image of the rod-shaped CeO2 from Example 1. Figure 6 This is a transmission electron microscope image of cubic CeO2 in Comparative Example 1. Figure 7 This is a transmission electron microscope image of the octahedral CeO2 of Comparative Example 2.

[0042] Depend on Figure 5 It can be seen that the lattice fringes of rod-shaped CeO2 are clear, with a fringe spacing of 0.26 nm, corresponding to the (220) crystal plane of rod-shaped CeO2. This (220) crystal plane is the bulk lattice projection observed when the electron beam is incident along the cross-sectional direction of rod-shaped CeO2, while the outer surface of rod-shaped CeO2 is still dominated by the (110) crystal plane. Both describe the crystallographic characteristics of the catalyst from the bulk and surface dimensions, respectively, and are not contradictory. The distortion of the lattice fringes indicates that there are a large number of oxygen vacancies in rod-shaped CeO2. Figure 6 It can be seen that the lattice fringes of cubic CeO2 are clear, corresponding to the (200) crystal plane of cubic CeO2. This crystal plane is the bulk lattice in the direction of electron beam projection, which is different from the (100) outer surface mainly exposed in cubic CeO2, and the number of oxygen vacancies is less than that in rod-shaped CeO2. Figure 7 It can be seen that the lattice fringes of octahedral CeO2 are clear, corresponding to the (111) crystal plane of octahedral CeO2. This crystal plane is the bulk lattice in the direction of electron beam projection, consistent with the (111) outer surface of octahedral CeO2 that is mainly exposed. Figure 5 and Figure 6 Compared to rod-shaped CeO2 and cubic CeO2, octahedral CeO2 has regular lattice fringes and the lowest degree of edge distortion, indicating that it has fewer oxygen vacancies on its surface than cubic CeO2 and even fewer than rod-shaped CeO2.

[0043] Figure 8 This is a scanning electron microscope image of the CeO2-V2O5 catalyst from Example 1. Figure 9 This is a transmission electron microscope image of the CeO2-V2O5 catalyst from Example 1.

[0044] Depend on Figure 8 and Figure 9 It can be seen that the rod-shaped CeO2 on the surface of the CeO2-V2O5 catalyst in Example 1 still retains its rod-shaped morphology, without obvious agglomeration, and the rod-shaped CeO2 is uniformly attached to the V2O5 surface, forming a tight heterogeneous interface with V2O5.

[0045] Figure 10 These are X-ray diffraction patterns of rod-shaped CeO2 from Example 1, cubic CeO2 from Comparative Example 1, and octahedral CeO2 from Comparative Example 2.

[0046] Depend on Figure 10 It can be seen that rod-shaped, cubic, and octahedral CeO2 all exhibit typical fluorite-type crystal structures without impurity phases. Among them, by comparing the diffraction intensity ratios of different CeO2 morphologies with the standard card, it can be seen that the ratio of the (200) diffraction peak intensity to the (111) diffraction peak intensity of cubic CeO2 is higher than the standard value, indicating that it predominantly exposes the (100) crystal plane. The ratio of the (220) diffraction peak intensity to the (111) diffraction peak intensity of rod-shaped CeO2 is higher than the standard value, indicating that it predominantly exposes the (110) active crystal plane. And the ratio of the (111) diffraction peak intensity to the (200) diffraction peak intensity of octahedral CeO2 is higher than the standard value, indicating that it exhibits a stable (111) crystal plane exposure characteristic.

[0047] Figure 11 These are X-ray diffraction patterns of the CeO2-V2O5 catalyst of Example 1, the CeO2-V2O5 catalyst of Comparative Example 1, and the CeO2-V2O5 catalyst of Comparative Example 2.

[0048] Depend on Figure 11 It can be seen that weak V2O5 characteristic diffraction peaks (such as around 20°) were observed in the CeO2-V2O5 catalyst of Example 1, the CeO2-V2O5 catalyst of Comparative Example 1, and the CeO2-V2O5 catalyst of Comparative Example 2, and no diffraction signals of other impurity phases were observed. The (220) diffraction peak belonging to the (110) crystal plane family still maintained a high relative intensity after loading, indicating that the equal volume impregnation and calcination process did not damage the crystal phase structure of rod-shaped CeO2 and the dominant exposure characteristics of the (110) crystal plane, thus confirming the successful preparation of the CeO2-V2O5 catalyst of Example 1. The interface is chemically bonded, effectively preserving the crystal phase characteristics and redox function of CeO2 and V2O5, providing a crystal phase structure guarantee for the high activity and high stability of the CeO2-V2O5 catalyst of Example 1.

[0049] Figure 12 This is the X-ray photoelectron spectrum of the rod-shaped CeO2 from Example 1. Figure 13 This is the X-ray photoelectron spectrum of the V2O5 catalyst in Comparative Example 3. Figure 14 This is the X-ray photoelectron spectrum of the CeO2-V2O5 catalyst in Example 1.

[0050] Depend on Figure 12 It can be seen that the Ce3d orbitals of rod-shaped CeO2 contain Ce 3+ With Ce 4+ Characteristic peak, Ce 3+ A relative content greater than or equal to 15% indicates that rod-shaped CeO2 has a high surface oxygen vacancy concentration, providing abundant specific adsorption and activation sites for SO2 molecules. Figure 13 It can be seen that the V2p orbital of V2O5 exhibits a typical and symmetrical characteristic photoelectron emission double peak. After peak fitting, the binding energies of its V2p_3 / 2 and V2p_1 / 2 are 517.39 eV and 524.97 eV, respectively, corresponding to V 5+ Oxidized state, and V is almost undetectable in the spectrum. 4+ The signal indicates that V₂O₅, when not combined with CeO₂, is in a thermodynamically stable saturated state, making it difficult to spontaneously generate a redox couple. However, due to... Figure 14 It can be seen that the V2p orbital of the CeO2-V2O5 catalyst in Example 1 exhibits V... 5+ With V 4+ Characteristic peak, V 5+ / V 4+ The appropriate ratio and high proportion of adsorbed oxygen in the O1s orbitals indicate a strong electronic interaction at the interface between rod-shaped CeO2 and V2O5. Electrons spontaneously migrate from rod-shaped CeO2 to V2O5, promoting the V2O5... 5+ Partially restored to V 4+ Optimized V 5+ / V 4+ The redox couple exhibits electronic buffering capacity. Simultaneously, interfacial electron rearrangement induces the generation of more oxygen vacancies on the rod-shaped CeO2 side, enhancing the adsorption and activation of gaseous O2 and increasing the coverage of surface active oxygen species. This constructs a highly efficient electron-oxygen species coupling transport channel from V2O5 to the rod-shaped CeO2 surface via the VO-Ce interface, accelerating the overall turnover rate of the redox cycle.

[0051] Figure 15 This is a graph showing the electrostatic potential distribution and work function calculation of the rod-shaped CeO2 in Example 1. Figure 16 The graph shows the electrostatic potential distribution and work function calculation of V2O5 in Comparative Example 3.

[0052] At the electronic structure level, density functional theory work function calculations can reveal the intrinsic regulatory mechanisms of electron transfer behavior between crystal planes and interfaces. Figure 15 and Figure 16 It is known that the work function of the exposed (110) crystal plane of rod-shaped CeO2 is only 4.07 eV, significantly lower than that of pure V2O5 (5.21 eV). According to the semiconductor heterojunction theory, the difference in work function constitutes the intrinsic driving force for interfacial electron rearrangement. When rod-shaped CeO2 and V2O5 are in close contact to form a VO-Ce interface, electrons will spontaneously migrate from the low work function rod-shaped CeO2 (110) crystal plane to the high work function V2O5 in order to reach Fermi level equilibrium. This spontaneous charge transfer effect strengthens the interfacial VO-Ce bonding strength, elucidating the formation mechanism of strong electron interaction at the CeO2-V2O5 catalyst interface in Example 1 from the perspective of electronic structure.

[0053] Figure 17 This is the diffuse reflectance infrared Fourier transform spectrum of the CeO2-V2O5 catalyst in Example 1. Figure 18 This is the diffuse reflectance infrared Fourier transform spectrum of the CeO2-V2O5 catalyst in Comparative Example 1. Figure 19 This is the diffuse reflectance infrared Fourier transform spectrum of the CeO2-V2O5 catalyst in Comparative Example 2.

[0054] Depend on Figures 17 to 19 It can be seen that the characteristic peak at 1046.54 cm⁻¹, belonging to monodentate sulfate, is present on the surface of the CeO₂-V₂O₅ catalyst in Example 1. -1 The highest intensity was observed at the SO-Ce / V bridge vibration peak (1129.98 cm⁻¹). - ¹) is the most significant, while the peak corresponding to the inert bidentate sulfate species (1225.46 cm⁻¹) is the most prominent. - ¹) The smallest contribution indicates that the (110) crystal plane can efficiently activate SO2 and preferentially generate active intermediates, while inhibiting the deposition of inert species. For the CeO2-V2O5 catalyst of Comparative Example 1, the intensity of the monodentate sulfate peak decreases and the contribution of the bidentate sulfate peak increases, indicating that the activation efficiency of the CeO2-V2O5 catalyst of Comparative Example 1 is moderate and it is more inclined to form inert species. In contrast, the CeO2-V2O5 catalyst of Comparative Example 2 has the weakest peak intensity across the entire wavelength range and the highest proportion of the bidentate sulfate peak, indicating that the (111) crystal plane of the CeO2-V2O5 catalyst of Comparative Example 2 is difficult to effectively activate SO2 due to its dense lattice and scarce oxygen vacancies, resulting in the accumulation of inert substances and blocking of active sites.

[0055] The SO2 oxidation performance of the catalysts corresponding to each example and comparative example was evaluated using a fixed-bed reactor. The reaction conditions were: 0.1 g catalyst, reaction gas composition of 600 ppm SO2 and 3% O2, N2 as balance gas, total flow rate of 500 mL / min, and reaction temperature of 350 °C. The test results are shown in Table 1.

[0056] Table 1

[0057] As shown in Table 1, the CeO2-V2O5 catalysts prepared in Examples 1-3 exhibit significantly better SO2 oxidation performance than the comparative examples. Under the same reaction conditions, the SO2 conversion rate in Example 1 was 88.2%, while the SO2 conversion rates in Examples 2 and 3 remained at high levels of 85.6% and 86.9%, respectively, all significantly higher than the 71.5% of Comparative Example 1, 53.5% of Comparative Example 2, and 42.0% of Comparative Example 3. In terms of yield, the SO3 yields in Examples 1-3 were all above 750 μmol·g. -1 ·h -1 The above values ​​are also significantly higher than the 517.20 μmol·g of Comparative Example 1. -1 ·h -1 316.84 μmol·g of Comparative Example 2 -1 ·h -1 and 233.70 μmol·g of Comparative Example 3 -1 ·h -1 Furthermore, the lowest activity retention rate (94.8%) after 12 hours of reaction in Examples 1-3 was also superior to the comparative examples. In summary, the CeO2-V2O5 catalyst prepared in this application not only possesses high catalytic activity and SO3 generation rate but also excellent stability, making it suitable for the efficient resource conversion of SO2 from alkylation waste acid pyrolysis gas and demonstrating promising prospects for industrial application.

[0058] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing a CeO2-V2O5 catalyst, characterized in that, Includes the following steps: S1. Ce(NO3)2·6H2O and NaOH are dissolved in deionized water in sequence to obtain cerium-containing precursor slurry; S2. The cerium-containing precursor slurry obtained in step S1 is transferred to a hydrothermal reactor for hydrothermal reaction, and then centrifuged, washed, dried and calcined in sequence to prepare rod-shaped CeO2 with dominant exposed (110) crystal planes. S3. The rod-shaped CeO2 obtained in step S2 is immersed in a transparent vanadium precursor solution, impregnated at room temperature, and then calcined at 450℃-500℃ for 3-4 hours to obtain the CeO2-V2O5 catalyst.

2. The preparation method according to claim 1, characterized in that, The transparent vanadium precursor solution contains ammonium metavanadate and oxalic acid in a molar ratio of 1:(0.8-1.2).

3. The preparation method according to claim 1, characterized in that, The length of the rod-shaped CeO2 is 1μm-5μm and the diameter is 200nm-500nm.

4. The preparation method according to claim 1, characterized in that, The rod-shaped CeO2 has a pore volume of 0.50 cm³. 3 / g-0.55cm 3 / g, with a pore size of 24nm-25nm.

5. The preparation method according to claim 1, characterized in that, The specific surface area of ​​the rod-shaped CeO2 is 80 m². 2 / g-86m 2 / g.

6. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the hydrothermal reaction is 170℃-180℃, and the reaction time is 20h-24h.

7. The preparation method according to claim 1, characterized in that, In step S2, the roasting temperature is 400℃-500℃ and the roasting time is 3h-4h.

8. The preparation method according to claim 1, characterized in that, The soaking time at room temperature in step S3 is 10-12 hours.

9. The CeO2-V2O5 catalyst prepared by the method according to any one of claims 1-5, characterized in that, The CeO2-V2O5 catalyst has a mesoporous structure and a specific surface area of ​​40 m². 2 / g-45m 2 / g.

10. The application of the CeO2-V2O5 catalyst as described in claim 9 in the catalytic oxidation of SO2 to SO3.

Images