Composite oxide catalyst, method for producing the same, and use thereof

Abstract

The application provides a composite oxide catalyst and a preparation method and application thereof. The catalyst comprises a modified carrier and a vanadium-containing component and an antimony-containing component supported on the modified carrier. The content of the vanadium-containing component is 5-12 wt%, the content of the antimony-containing component is 3-10 wt%, the molar ratio of V 4+ / (V 4+ +V 5+ ) in the vanadium-containing component is greater than or equal to 0.67, and the molar ratio of Sb 3+ / (Sb 3+ +Sb 5+ ) in the antimony-containing component is greater than or equal to 0.25. The modified carrier has a multi-stage pore structure and oxygen vacancies. Relying on the pore confinement effect, the interface strong interaction between the modified carrier and the active component improves the structural stability and high-temperature anti-agglomeration sintering capacity of the active component. Meanwhile, through the content and valence state limitation of the active component, low-intensity acid sites are formed on the surface of the modified carrier, and the multi-stage pore structure cooperatively inhibits the side reaction, thereby improving the catalytic activity and selectivity of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of composite oxide catalysts, and more specifically, to a composite oxide catalyst, its preparation method, and its application. Background Technology

[0002] Propylene is a core raw material in the petrochemical industry, and market demand continues to grow. Traditional propane dehydrogenation without oxygen (PDH) processes are limited by thermodynamic equilibrium, resulting in high reaction temperatures (550-650℃) and high energy consumption. Propylene oxidative dehydrogenation (ODHP) processes can break thermodynamic equilibrium, offering advantages such as lower reaction temperatures (400-550℃) and higher propylene yields. Existing industrial catalysts are mainly vanadium-based: Patent CN111215045A discloses a supported cerium-based bimetallic oxide catalyst, in which the surface VO... x CeO2 in the bulk phase serves as an oxygen donor for the propane oxidative dehydrogenation reaction, achieving a propane conversion of 40-50% and a propylene selectivity of 85-95%. Propane dehydrogenation catalysts are classified into platinum-based and chromium-based types, both with significant drawbacks: platinum-based catalysts are expensive due to the high cost of precious metals, and Pt is prone to agglomeration and sintering at high temperatures, resulting in rapid activity decay and short lifespan; chromium-based catalysts contain highly toxic and carcinogenic hexavalent chromium, leading to high costs for solid waste disposal and significant environmental pollution risks. Patent CN117899861B discloses a single-atom system catalyst for propane oxidative dehydrogenation, its preparation method, and a method for producing propylene. This method prepares a core-shell nano-Pt-In catalyst with platinum as the active component and a Pt loading of up to 3%, but the preparation cost is high. However, single VO... x The excessive Lewis acidity on the catalyst surface easily triggers deep propane oxidation and excessive product cracking side reactions, resulting in low propylene selectivity. Furthermore, its high-temperature structural stability is poor, active components easily aggregate, leading to rapid catalyst deactivation and short lifespan. While existing modified V-Sb-O composite oxide catalysts can optimize vanadium-based catalytic performance, their preparation using high-purity reagents results in high raw material costs and poor industrial economics. Additionally, the uneven dispersion of active components and weak synergistic effects persist, leaving issues such as low propylene selectivity and insufficient high-temperature stability. On the other hand, copper electrolysis anode mud is rich in antimony, and current resource utilization technologies are immature, leading to a serious waste of antimony resources. Regarding support design, traditional catalysts often use conventional γ-Al₂O₃, which has a simple pore structure and limited specific surface area, making it difficult to effectively disperse active components. Although some studies have improved mass transfer performance by introducing mesoporous structures or composite oxide supports, modified γ-Al₂O₃ supports with hierarchical pore structures (such as NaAl(OH)₂CO₃ derivatives) have not yet been used in V-Sb-based ODHP catalysts. More importantly, current technologies lack the ability to effectively disperse V in the catalyst. 4+ / (V 4+ +V 5+ ) and Sb3+ / (Sb 3+ +Sb 5+ Precise control of the valence ratio, which is directly related to oxygen vacancy concentration and lattice oxygen activity, is a key factor determining propylene selectivity.

[0003] In summary, existing ODHP catalysts still have significant shortcomings in terms of raw material cost, active component dispersion, V / Sb valence synergy, and support pore structure. There is an urgent need to develop a composite oxide catalyst based on low-cost / solid waste raw materials, with a multi-level pore modified support, and with precise control of the vanadium-antimony valence ratio and oxygen vacancy concentration, in order to achieve high propylene selectivity and long-term stable operation. Summary of the Invention

[0004] The main objective of this invention is to provide a composite oxide catalyst, its preparation method, and its application, in order to solve the problems of high catalyst cost, poor dispersion of active components, and low selectivity in the prior art.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a composite oxide catalyst is provided, comprising: a modified support and an active component supported on the modified support, the active component comprising a vanadium-containing component and an antimony-containing component, wherein the modified support has a weight content of 85-92 wt%, the vanadium-containing component has a weight content of 5-12 wt%, and the antimony-containing component has a weight content of 3-10 wt%, and the modified support has a hierarchical porous structure; wherein, the vanadium-containing component contains V 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is ≥0.67. 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is ≥0.25.

[0006] Furthermore, V in the vanadium-containing component 4+ / (V 4+ +V 5+ The molar ratio of ) is 0.67~0.75.

[0007] Furthermore, Sb in the antimony-containing component 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is 0.25~0.33.

[0008] Furthermore, the molar ratio of vanadium in the vanadium-containing component to antimony in the antimony-containing component is 1:(0.1~1.2).

[0009] Furthermore, the vanadium-containing component includes vanadates and vanadium oxides, wherein the vanadates are selected from at least one of SbVO4, SbVO5, and SbV2O7, and the vanadium oxides are selected from at least one of VO, VO2, and V2O5.

[0010] Furthermore, the antimony-containing component is selected from at least one of SbO2, Sb2O3, and Sb2O5.

[0011] Furthermore, the composite oxide catalyst possesses oxygen vacancies, with an oxygen vacancy concentration of 1.0 × 10⁻⁶. 10 ~5.0×10 20 pcs / cm -3 .

[0012] Furthermore, the specific surface area of ​​the modified carrier is 400~900m². 2 / g.

[0013] Furthermore, the pore volume of the modified carrier is 0.8~1.5 cm³. 3 / g.

[0014] Furthermore, the average pore size of the modified support is 5~10 nm.

[0015] To achieve the above objectives, according to a second aspect of the present invention, a method for preparing a composite oxide catalyst is provided, the method comprising:

[0016] Step S1: Sodium aluminum filament is mixed with ammonium salt and subjected to metathesis reaction to obtain modified support precursor;

[0017] Step S2: Vanadium source and antimony source are dispersed in deionized water to prepare an impregnation solution. The modified support precursor is added to the impregnation solution for impregnation treatment to obtain the catalyst precursor.

[0018] Step S3: The catalyst precursor is calcined under a protective atmosphere to form a modified support, and the vanadium source and antimony source form vanadium-containing components and antimony-containing components respectively supported on the modified support, thus obtaining a composite oxide catalyst.

[0019] Further, in step S1, the preparation method of sodium aluminate includes: mixing sodium aluminate solution and surfactant to obtain a first mixed solution, and then introducing CO2 to carry out a carbonation precipitation reaction to obtain sodium aluminate.

[0020] Furthermore, the surfactant is selected from at least one of sodium stearate, polysorbate-80, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, hexadecyltrimethylammonium bromide, and polyethylene glycol.

[0021] Furthermore, the surfactant has a mass fraction of 0.1 to 1 wt% in the first mixed solution.

[0022] Furthermore, step S1 includes: dispersing sodium aluminum filament and ammonium salt in a first solvent to carry out a metathesis reaction to obtain a modified support precursor.

[0023] Furthermore, the first solvent is a mixture of deionized water and ethanol.

[0024] Furthermore, the volume ratio of deionized water to ethanol is (5~10):1.

[0025] Furthermore, ammonium salts include at least one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonium oxalate, and ammonium acetate.

[0026] Furthermore, with Al 3+ CO3 2- HCO3 - In terms of molar quantities, the molar ratio of sodium aluminate, ammonium carbonate, and ammonium bicarbonate is 1:(1~1.5):(0.8~1.2).

[0027] Furthermore, the total mass of sodium aluminate and ammonium salt and the solid-liquid ratio of the first solvent are 1 g: (10~20) mL.

[0028] Further, in step S2, the antimony source is SbOCl, and the preparation method of SbOCl is as follows: electrolytic copper floating anode mud is mixed with hydrochloric acid aqueous solution to obtain Sb-containing... 5+ Antimony powder was added to the acidic leachate to carry out a reduction reaction, yielding a chlorinated antimony compound. The chlorinated antimony compound was then hydrolyzed to obtain SbOCl.

[0029] Furthermore, the mass-to-volume ratio of electrolytic copper floating anode mud to hydrochloric acid aqueous solution is 1 g: (1~15) mL.

[0030] Furthermore, the molar concentration of the hydrochloric acid aqueous solution is (3~10) mol / L.

[0031] Furthermore, antimony powder and Sb-containing... 5+ Sb in acidic leachate 5+ The molar ratio is (1.2~1.5):1.

[0032] Furthermore, the reduction reaction temperature is 55~65℃, and the reduction reaction time is 30~60min.

[0033] Further, in step S2, the mass-to-volume ratio of the modified carrier precursor to the impregnation solution is (5~10) g: 1 mL.

[0034] Furthermore, the immersion treatment temperature is 55~65℃, and the immersion treatment time is 1~3h.

[0035] Furthermore, the vanadium source is selected from at least one of sodium metavanadate, ammonium orthovanadate, and ammonium metavanadate.

[0036] Furthermore, the antimony source is selected from at least one of SbOCl, SbCl3, Sb2O3, and C6H9O6Sb.

[0037] Furthermore, the molar ratio of vanadium in the vanadium source to antimony in the antimony source is 1:(0.1~1.2).

[0038] Furthermore, the impregnation solution also includes a complexing agent selected from at least one of oxalic acid, tartaric acid, citric acid, and ethylenediaminetetraacetic acid.

[0039] Furthermore, the mass ratio of the complexing agent to the total mass of the vanadium source and the antimony source is (5~10):100.

[0040] Furthermore, in step S3, the roasting process includes a first roasting process and a second roasting process.

[0041] Furthermore, the temperature of the first roasting treatment is 200~300℃, and the time of the first roasting treatment is 1~2h.

[0042] Furthermore, the temperature of the second roasting treatment is 500~600℃, and the time of the second roasting treatment is 3~4h.

[0043] Furthermore, the protective atmosphere is a mixture of hydrogen and nitrogen or a mixture of hydrogen and helium.

[0044] Furthermore, the volume fraction of hydrogen in the protective atmosphere is 5-10%.

[0045] According to a third aspect of the present invention, the application of a composite oxide catalyst provided by the first aspect of the present invention or a composite oxide catalyst prepared by the method for preparing a composite oxide catalyst provided by the second aspect of the present invention in the oxidative dehydrogenation of propane to propylene is provided.

[0046] Furthermore, in the propane oxidative dehydrogenation to propylene reaction, the reaction temperature is 500~600℃ and the space velocity is 8000~15000h. -1 The molar ratio of propane to oxygen is 1:(0.5~1), the propane conversion rate is ≥55%, the propylene selectivity is ≥65%, the activity decay rate is ≤5% after 100 hours of continuous operation, and the carbon deposition is ≤2wt%.

[0047] The composite oxide catalyst provided by this invention, on the one hand, utilizes the hierarchical porous structure and oxygen vacancies of the modified support to reduce the residence time of reactants and products within the pores, and achieves a physical confinement effect through pore confinement; on the other hand, it utilizes the interaction between the modified support and the active component interface to further improve the structural stability of the active component and its resistance to high-temperature agglomeration and sintering. Furthermore, the composite oxide catalyst provided by this invention also utilizes the oxygen vacancies of the modified support to regulate metal electron transfer, synergistically optimizing the redox properties of the active component.

[0048] Meanwhile, the composite oxide catalyst provided by this invention utilizes vanadium-containing and antimony-containing components as active components, and controls the weight content of the vanadium-containing component to be 5-12 wt%, the weight content of the antimony-containing component to be 3-10 wt%, and the vanadium-containing component to contain V 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is ≥0.67. 3+ / (Sb 3+ +Sb 5+ The molar ratio of vanadium and antimony components is ≥0.25. By limiting the weight content and valence state of the vanadium and antimony components, low-strength acid sites are formed on the surface of the modified support. The synergistic effect of the low-strength acid sites and the hierarchical porous structure of the modified support effectively suppresses side reactions, resulting in a significant improvement in catalytic activity and selectivity. Attached Figure Description

[0049] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0050] Figure 1 TEM image of the modified support prepared in Example 1;

[0051] Figure 2 The XRD patterns are of the modified carrier precursor and the modified carrier prepared in Example 1.

[0052] Figure 3 The image shows a TEM image of the composite oxide catalyst prepared in Example 1.

[0053] Figure 4 This is a size distribution diagram of the active metal particles in the composite oxide catalyst prepared in Example 1;

[0054] Figure 5 The graph shows the relative pressure-adsorption capacity curves of the composite oxide catalysts prepared in Example 1 and Comparative Example 1.

[0055] Figure 6The pore size distribution curves of the composite oxide catalysts prepared in Example 1 and Comparative Example 1 are shown. Detailed Implementation

[0056] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this invention can be combined with each other. The invention will now be described in detail with reference to the embodiments.

[0057] As described in the background section of this invention, existing technologies suffer from problems such as high catalyst cost, poor dispersion of active components, and low selectivity. To address these issues, this invention provides a composite oxide catalyst, its preparation method, and its applications.

[0058] In a first typical embodiment of the present invention, a composite oxide catalyst is provided, comprising: a modified support and an active component supported on the modified support, the active component comprising a vanadium-containing component and an antimony-containing component, wherein the weight content of the modified support is 85-92 wt%, the weight content of the vanadium-containing component is 5-12 wt%, and the weight content of the antimony-containing component is 3-10 wt%, and the modified support has a hierarchical porous structure; wherein, the vanadium-containing component contains V 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is ≥0.67. 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is ≥0.25.

[0059] The modified support used in the composite oxide catalyst of this invention has a hierarchical porous structure and oxygen vacancies. This not only reduces the residence time of reactants and products within the pores, achieving a physical confinement effect through pore confinement, but also further improves the structural stability and high-temperature anti-agglomeration sintering ability of the active component through the interfacial interaction between the modified support and the active component. Furthermore, the oxygen vacancies on the modified support can regulate metal electron transfer, synergistically optimizing the redox properties of the active component. The active component of the composite oxide catalyst is a vanadium-containing component and an antimony-containing component, with the vanadium-containing component having a weight content of 5-12 wt% and the antimony-containing component having a weight content of 3-10 wt%. The vanadium-containing component contains V... 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is ≥0.67. 3+ / (Sb 3+ +Sb 5+With a molar ratio ≥0.25, by limiting the weight content and valence state of the vanadium-containing and antimony-containing components, low-intensity acid sites can be formed on the surface of the modified support. These low-intensity acid sites, in synergy with the hierarchical pore structure of the modified support, effectively reduce the problems of deep oxidation of the catalyst, excessive cracking of products, and polymerization and coking. At the same time, by "regulating the properties of acid sites + optimizing the mass transfer process", the occurrence of side reactions during the catalytic reaction can be effectively suppressed, thereby improving the catalytic activity, target product selectivity and service life of the composite oxide catalyst.

[0060] In this invention, the weight content of the modified carrier is any value or a range between any two of 85wt%, 86wt%, 87wt%, 88wt%, 89wt%, 90wt%, 91wt%, and 92wt%; the weight content of the vanadium-containing component is any value or a range between any two of 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, and 12wt%; and the weight content of the antimony-containing component is any value or a range between any two of 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, and 10wt%.

[0061] In some embodiments, V in the vanadium-containing component 4+ / (V 4+ +V 5+ The molar ratio of vanadium in the vanadium-containing component is 0.67~0.75. 4+ / (V 4+ +V 5+ By adjusting the molar ratio, the oxygen vacancy concentration and redox performance on the catalyst surface can be optimized, thereby improving the catalytic activity and target product selectivity of the vanadium-antimony composite oxide catalyst. 4+ These are electron-deficient reduced vanadium sites, enabling rapid regeneration of oxygen vacancies: V 5+ With V 4+ Reversible transformation induces lattice oxygen desorption, generating surface oxygen vacancies; the ratio < 0.67, V 5+ If the ratio is too high, the number of oxygen vacancies on the catalyst surface is insufficient, making it difficult to effectively activate the CH bonds of propane molecules, resulting in low catalytic activity; if the ratio is >0.75, excess V 4+ This can lead to excessively high levels of active oxygen vacancies on the surface, easily triggering deep oxidation side reactions and reducing the selectivity of the target product. The active phase SbVO4 in the catalyst, through its valence state ratio, can achieve rapid electron transfer, lowering the rate-determining energy barrier and improving catalytic activity and target product selectivity. Specifically, V in the vanadium-containing component... 4+ / (V 4+ +V 5+() can be any value from 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75 or any value between any two.

[0062] In some embodiments, Sb in the antimony-containing component 3+ / (Sb 3+ +Sb 5+ The molar ratio of Sb in the antimony-containing component is 0.25~0.33. 3+ / (Sb 3+ +Sb 5+ The molar ratio of Sb is adjusted. 3+ Neutralizing the strong Lewis acid sites on γ-Al₂O₃ is beneficial for improving the catalytic activity and selectivity of the composite oxide catalyst. The strong Lewis acid sites on the γ-Al₂O₃ surface mainly originate from coordinate-unsaturated Al₂O₃ atoms. 3+ It possesses empty electron orbitals and acts as an electron pair acceptor, easily initiating side reactions such as deep oxidation of reactants, excessive pyrolysis of products, and molecular polymerization and coking; while Sb 3+ It possesses low electron density and coordinateable lone pairs of electrons, and is compatible with the unsaturated Al on the modified support surface. 3+ The empty orbitals coordinate with each other, occupying the empty orbitals of strong Lewis acid sites, thus passivating / neutralizing the acid sites and forming "Al". 3+ -Sb 3+ "Coordination complexes: Sb..." 3+ By effectively occupying the strong Lewis acid sites on the surface of the modified γ-Al₂O₃ support, the catalyst loses its ability to accept other electron pairs, thus achieving "neutralization." This coordination saturation effect is used to adjust the acidity or alkalinity of the material surface, weaken the side reactions initiated by strong acid sites, reduce the formation of carbon deposit precursors, and improve the catalyst's resistance to carbon deposition. 5+ It can regulate the interaction between oxygen on the catalyst surface and the metal-support interface, thereby improving its resistance to sintering and carbon deposition: Sb 5+ It possesses high electronegativity and oxidizing activity, enabling it to interact with lattice oxygen and adsorbed oxygen on the catalyst surface, regulating the chemical state and distribution of surface oxygen. These oxygen species can act as active sites during the reaction, participating in the oxidation and decarburization reactions, effectively removing carbonaceous intermediates and carbon deposit precursors generated on the catalyst surface, and inhibiting carbon deposition. Additionally, Sb... 5+The presence of [a specific substance] can alter the electronic structure of the modified support surface, enhancing the metal-support interaction between the active metal component and the modified support. This strong interaction can anchor the surface-active metal nanoparticles, effectively inhibiting the migration and aggregation of active components under high-temperature reaction conditions, effectively mitigating the high-temperature sintering deactivation of active metal particles, maintaining the specific surface area and the number of effective active sites of the catalyst, thereby improving the high-temperature structural stability and long-term catalytic activity of the catalyst.

[0063] If the antimony-containing component contains Sb 3+ / (Sb 3+ +Sb 5+ The molar ratio of Sb in the system is less than 0.25. 3+ Insufficient proportion, unable to fully neutralize the unsaturated Al coordination on the surface of the modified support γ-Al2O3. 3+ Strong Lewis acid sites and a large number of empty electron orbitals remaining on the support easily induce side reactions such as deep oxidation of reactants, excessive product pyrolysis, and molecular polymerization and coking, resulting in the formation of a large amount of carbon precursors and a decrease in the selectivity of the target product; at the same time, Sb 5+ An excess of antimony can easily lead to antimony species aggregation, which can cover the intrinsic active sites of the catalyst, block the pores of the modified support, reduce the effective specific surface area, and further weaken the catalytic activity of the catalyst. If the antimony-containing component contains Sb... 3+ / (Sb 3+ +Sb 5+ (Molar ratio higher than 0.33, Sb) 3+ An excessively high Sb content can lead to over-neutralization of the acid sites on the modified support, consuming all strong Lewis acid sites while disrupting the suitable acidic environment required for the reaction, resulting in a decrease in catalyst activity and selectivity for the target product; simultaneously, Sb 5+ The catalyst is relatively scarce. On the one hand, there are insufficient active oxygen species on the catalyst surface that can participate in oxidation and carbon removal, making it difficult to remove carbonaceous intermediates and carbon deposit precursors, leading to rapid carbon accumulation. On the other hand, the metal-support interaction is weakened, making it impossible to effectively anchor active metal nanoparticles. Under high-temperature conditions, the active components are prone to migration, agglomeration, and sintering, resulting in a decrease in the catalyst's specific surface area and a significant deterioration in high-temperature structural stability and long-term catalytic lifetime. Therefore, this invention uses Sb 3+ / (Sb 3+ +Sb 5+ The molar ratio is controlled within the range of 0.25 to 0.33 to achieve Sb 3+ Moderate neutralization of strong Lewis acid sites and Sb 5+ The synergistic effect of modulating surface oxygen and anchoring active metals balances catalyst activity, target product selectivity, anti-carbon deposition performance, and high-temperature long-term operational stability. Specifically, Sb in the antimony-containing component... 3+ / (Sb 3+ +Sb 5+The molar ratio of ) is any value among 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, and 0.33, or any value between two of them.

[0064] In some embodiments, the molar ratio of vanadium in the vanadium-containing component to antimony in the antimony-containing component is 1:(0.1~1.2). Further optimization of the molar ratio of vanadium in the vanadium-containing component to antimony in the antimony-containing component can effectively control the SbVO4-Sb2O3-VO4 composition. x The composition and structure of the composite active phase, along with the synergistic effect of the interface, improve the redox properties and adsorption activation performance of the catalyst surface, thereby significantly enhancing the catalytic activity, selectivity, and stability of the composite oxide catalyst, effectively suppressing the occurrence of side reactions and reducing the formation of by-products.

[0065] When the antimony content is too low, i.e., the vanadium-antimony molar ratio is greater than 1:0.1, the amount of antimony used is low, making it difficult to fully generate the SbVO4 active phase, and the system contains a large amount of pure VO4. x The main phase is SbVO4-Sb2O3-VO x Insufficient heterogeneous interfaces lead to a lack of interfacial synergistic effects, resulting in an imbalance in the catalyst's redox properties, decreased reactant adsorption and activation capacity, and reduced catalytic activity. An excessively high proportion of vanadium oxides introduces too many strong acidic sites and excessive oxidizing power, easily inducing side reactions such as deep oxidation and excessive cracking, leading to an increase in byproducts. Simultaneously, it can be used to neutralize Sb at strong Lewis acid sites on the modified support. 3+ Insufficient total amount exacerbates carbon buildup, Sb 5+ Limited antimony content weakens resistance to carbon buildup and sintering, leading to decreased stability during long-term operation. When the antimony content is too high, i.e., the vanadium-antimony molar ratio is less than 1:1.2, antimony is relatively excessive, and the vanadium component is insufficient to bind all the antimony to form SbVO4, resulting in the precipitation of a large amount of free Sb2O3 and other antimony oxides. Excessive free antimony species are prone to agglomeration, covering VO4. x SbVO4 intrinsic active sites block the pores of the modified support, reducing the effective specific surface area and decreasing catalytic activity; excessive Sb 3+ It can also excessively neutralize the acidic sites of the modified support, disrupting the suitable acidic environment for reaction and causing a loss of activity and selectivity; at the same time, it can damage the SbVO4-Sb2O3- ... xThe optimal interfacial synergy relationship is crucial. An imbalance in the redox window, coupled with the easy volatilization and loss of excess antimony oxide at high temperatures, leads to the disintegration of the active phase and rapid catalyst deactivation over time. Only by controlling the molar ratio of vanadium in the vanadium-containing component to antimony in the antimony-containing component within the range of 1:(0.1~1.2) can the acid site regulation of the modified support, the construction of the composite active phase, and the optimization of redox performance be synergistically achieved, while simultaneously ensuring high catalyst activity, high selectivity, excellent resistance to carbon deposition, and long-term high-temperature stability against sintering. Specifically, the molar ratio of vanadium in the vanadium-containing component to antimony in the antimony-containing component can be any value from 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, or any value within a range of either.

[0066] In some specific embodiments, the vanadium-containing component includes vanadates and vanadium-containing oxides, wherein the vanadates are selected from at least one of SbVO4, SbVO5, and SbV2O7, and the vanadium-containing oxides are selected from at least one of VO, VO2, and V2O5; the antimony-containing component includes at least one of SbO2, Sb2O3, and Sb2O5. Sb is present. 3+ / Sb 5+ Reversible valence state cycle, forming a VO-Sb interface structure with the main active metal (V), resulting in interfacial electron transfer: Sb 3+ It supplies electrons to the adjacent active metal V, modulates the center of the d-band of the active metal vanadium, and weakens the metal-oxygen bond binding energy; at the same time, Sb 3+ / Sb 5+ Doping into the vanadium oxide lattice induces lattice distortion, generating a large number of surface oxygen vacancies, which synergistically enhances redox properties. In addition, Sb inhibits the aggregation of active metal vanadium oxides, reduces grain size, increases specific surface area, and exposes more interfacial active sites.

[0067] In some embodiments, the composite oxide catalyst has oxygen vacancies with an oxygen vacancy concentration of 1.0 × 10⁻⁶. 10 ~5.0×10 20 pcs / cm -3 Further regulation of the oxygen vacancy concentration in the composite oxide catalyst can provide more active sites. Oxygen vacancies are defect structures on the surface or in the crystal lattice of composite oxides; their presence alters the local electronic structure, forming new active sites. Furthermore, the enhanced adsorption and activation capacity of reactants is due to the higher electron density at oxygen vacancies, thus improving the activity of the composite oxide catalyst. By rationally regulating the oxygen vacancy concentration in the composite oxide catalyst, its electronic structure can be effectively optimized, active sites increased, and reactant adsorption and activation capacity enhanced, thereby significantly improving catalytic performance. Additionally, oxygen vacancies introduce surrounding metal coordination defects, becoming reactant adsorption and activation centers.4+ / (V 4+ +V 5+ V is achieved by relying on oxygen vacancies 4+ / V 5+ Reversible transformation weakens the VO-Al bond, enhances the reducing power of the vanadium center, and improves the catalytic activity of the catalyst. Specifically, the oxygen vacancy concentration is 1.0 × 10⁻⁶. 10 pcs / cm -3 1.0×10 11 pcs / cm -3 1.0×10 12 pcs / cm -3 1.0×10 13 pcs / cm -3 1.0×10 14 pcs / cm -3 1.0×10 15 pcs / cm -3 1.0×10 20 pcs / cm -3 5.0×10 20 pcs / cm -3 Any value in the range or any value between the two.

[0068] In some embodiments, the specific surface area of ​​the modified support is 400~900 m² / g. The high specific surface area of ​​the modified support is beneficial for improving the dispersibility of the active components and the density of active sites. In this composite oxide catalyst, the modified support, through the synergistic effect of its hierarchical porous structure and high specific surface area, enables highly dispersed active components, while its oxygen vacancies provide abundant active sites, enhancing the adsorption and activation capacity of reactants. 4+ A higher proportion of Sb is beneficial for forming suitable redox properties and improving catalytic activity; 3+ Neutralizing the Lewis acid sites on the surface of the modified support inhibits carbon deposition, while Sb 5 + It helps to regulate surface oxygen species and enhance the ability to resist high-temperature agglomeration and sintering and resist carbon deposition; the low-intensity acid sites and multi-level pore structure work together to effectively shorten the residence time of reactants and achieve a physical confinement effect, thereby improving the selectivity and stability of the catalyst.

[0069] Specifically, the specific surface area of ​​the modified carrier is any value or a range between any two of the following: 400 m² / g, 486 m² / g, 539 m² / g, 582 m² / g, 652 m² / g, 680 m² / g, 762 m² / g, 863 m² / g, 871 m² / g, and 900 m² / g.

[0070] In some embodiments, the pore volume of the modified carrier is 0.8~1.5 cm³.3 / g. Reasonably limiting the pore volume can improve the reaction efficiency of the composite oxide catalyst and enhance its adsorption performance and selectivity while ensuring a high surface area of ​​the modified support. By adjusting the amount of ammonium salt added, the pore volume of the modified support can be precisely controlled, and key heat treatment parameters such as calcination temperature, holding time, and heating rate can be optimized to achieve synergistic control of the pore volume of the modified support. Specifically, the pore volume of the modified support is 0.8 cm³. 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.22cm 3 / g, 1.38cm 3 / g, 1.47cm 3 / g, 1.49cm 3 / g, 1.5cm 3 Any value in / g or a range of values ​​between both.

[0071] To further increase the specific surface area of ​​the modified support and prevent pore blockage and carbon buildup, in some embodiments, the average pore size of the modified support is 5-10 nm. Specifically, the average pore size of the modified support is any value among 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, or a range between any two.

[0072] In a second typical embodiment of the present invention, a method for preparing a composite oxide catalyst is provided, the method comprising:

[0073] Step S1: Sodium aluminum filament is mixed with ammonium salt and subjected to metathesis reaction to obtain modified support precursor;

[0074] Step S2: Vanadium source and antimony source are dispersed in deionized water to prepare an impregnation solution. The modified support precursor is added to the impregnation solution for impregnation treatment to obtain the catalyst precursor.

[0075] Step S3: The catalyst precursor is calcined under a protective atmosphere to form a modified support, and the vanadium source and antimony source form vanadium-containing components and antimony-containing components respectively supported on the modified support, thus obtaining a composite oxide catalyst.

[0076] In the preparation method of the composite oxide catalyst provided by this invention, step S1 involves preparing a modified support precursor by metathesis reaction of sodium cerium phosphate (SCAP) and ammonium salt. The ammonium ions in the ammonium salt exchange with the sodium ions loaded on the layered porous framework of SAPAP, which not only modifies the layered porous framework of SAPAP but also constructs an interconnected porous channel structure within the porous framework, generating numerous lattice defects and forming an in-situ modified support rich in oxygen vacancies. On one hand, the multi-level porous structure modified support can effectively shorten the residence time of reactants and products within the channels and form a stable physical confinement effect through the channel confinement effect, significantly improving the structural stability of the active components and enhancing their resistance to high-temperature agglomeration and sintering. On the other hand, the oxygen vacancies on the surface of the modified support can regulate the electron transfer of metal active sites, synergistically optimizing the redox properties of the active components.

[0077] In step S2 of this application, a co-impregnation process is used to simultaneously load vanadium and antimony active components. This not only ensures that the two active components are evenly distributed and stably proportioned on the surface of the modified support precursor, but also enables the active components to form a tight interfacial contact structure with the modified support precursor. This provides good catalyst precursor structural conditions for interfacial bonding, electron transfer, and valence state regulation during subsequent calcination, effectively solving the defects of traditional stepwise loading processes, such as uneven component distribution, weak interfacial bonding between the support and active components, and overlapping or missing active sites.

[0078] In step S3 of this application, the catalyst precursor is calcined under a protective atmosphere. Through the interfacial reaction coupled with the atmosphere during the calcination process, and utilizing the strong interfacial interaction between the oxygen vacancies on the modified support and the dual active components of vanadium and antimony, the valence state distribution of vanadium and antimony is precisely controlled, achieving a controllable ratio of the valence states of the active components. This results in a higher valence state of V in the vanadium-containing component of the composite oxide catalyst. 4+ / (V 4+ +V 5+ Molar ratio ≥ 0.67, Sb in antimony-containing components 3+ / (Sb 3+ +Sb 5+ With a molar ratio ≥0.25, a vanadium loading of 5~12wt%, and an antimony loading of 3~10wt%, a large number of low-intensity acid sites are formed on the surface of the modified support, optimizing the acidity distribution and reactive site structure on the surface of the composite oxide catalyst, and significantly improving the catalytic activity and target product selectivity of the composite oxide catalyst.

[0079] In some embodiments, step S1, the preparation method of sodium aluminate filament includes: mixing sodium aluminate solution and surfactant to obtain a first mixed solution, and then introducing CO2 into the first mixed solution to carry out a carbonation precipitation reaction to obtain sodium aluminate filament. The preparation process of the sodium aluminate solution is as follows: first, add an appropriate amount of water to a stainless steel reaction vessel to dissolve industrial sodium hydroxide to obtain an alkaline solution; then, slowly add industrial aluminum hydroxide under stirring conditions, heat the system, and the aluminum hydroxide reacts with sodium hydroxide to generate sodium tetrahydroxyaluminate. After the solid is fully dissolved, a sodium aluminate solution is obtained; this solution is a strongly alkaline aqueous solution containing Na[Al(OH)4]. In this invention, sodium aluminate filament is prepared by CO2 precipitation, and the prepared sodium aluminate filament is fibrous, which is beneficial for subsequent preparation of fibrous modified carrier γ-Al2O3.

[0080] In some embodiments of this application, fibrous sodium aluminum oxide undergoes a metathesis reaction with ammonium salts (such as ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonium oxalate, ammonium acetate, etc.) to prepare a modified carrier precursor (ammonium aluminum carbonate), which is then thermally decomposed to obtain the modified carrier γ-Al2O3. This modified carrier retains its fibrous structure, forming an interlocking fibrous network of pores (through macropores + mesopore hierarchical channels, resulting in low material diffusion resistance and effectively improving mass transfer efficiency). In contrast, traditional methods for preparing activated alumina (γ-Al2O3) carriers include: alkali neutralization of aluminum salts, acid washing, molding and calcination. The products are mostly irregularly packed pores with particle agglomeration (mainly mesopores, where reactants easily clog the channels during the reaction, resulting in poor internal diffusion performance, directly affecting reaction efficiency and performance). Meanwhile, in the preparation method of the composite oxide provided in this application, the pore structure of the modified carrier can be precisely controlled by surfactants and carbonation rate to adjust the fiber aspect ratio and fiber packing voids, achieving a wide range of precise and controllable control over the pore size, pore volume, and specific surface area of ​​the modified carrier. In contrast, the pore structure of activated alumina prepared by traditional acid methods is highly dependent on precipitation pH, washing process, and other conditions, resulting in a narrow controllable window and a tendency for products to have an excessively high proportion of micropores and a lack of macropores, leading to poor pore structure adaptability. Furthermore, in terms of anti-carbon deposition, pollution resistance, and regeneration performance, the interconnected network pores of fibrous activated alumina are not easily blocked by reaction carbon deposits and process impurities, resulting in superior structural stability. Traditional acid-processed granular activated alumina contains closed micropores, which are prone to carbon deposition during the reaction process, leading to carrier deactivation. Moreover, carbon deposits and impurities are difficult to remove, making carrier regeneration difficult and reusability poor.

[0081] In addition, the acidity characteristics of the activated alumina supports prepared by the two processes differ significantly. The traditional acid method uses aluminum nitrate and aluminum sulfate as raw materials, which are neutralized and calcined to prepare activated alumina supports with strong Lewis acid sites and strong Brønsted acid sites on the surface. The overall acidity is too strong, which can easily cause side reactions such as deep oxidation and excessive product decomposition during the catalytic reaction, reducing the selectivity of the catalytic reaction. The present process prepares sodium aluminate by carbonation reaction of sodium aluminate solution, and then prepares modified aluminum ammonium carbonate (NH4Al(OH)2CO3) as a modified support precursor through aluminum-containing phase transformation. The modified support activated alumina is then obtained by thermal decomposition. The ratio of weak acid to medium strong acid on the surface of the modified support can be precisely controlled, and there are no excessive strong acid sites. The occurrence of side reactions is effectively suppressed, which is conducive to improving catalytic selectivity and stability. The relevant chemical reaction equations are as follows: NaAl(OH)4 + CO2 = NaAl(OH)2CO3↓ + H2O is synthesized from sodium aluminate; NaAl(OH)2CO3 + NH4HCO3 = NH4Al(OH)2CO3↓ + NaHCO3 and / or 2NaAl(OH)2CO3 + (NH4)2CO3 = 2NH4Al(OH)2CO3↓ + Na2CO3 is transformed; γ-Al2O3 is prepared by thermal decomposition of the modified support precursor: 2NH4Al(OH)2CO3 = γ-Al2O3 + 2NH3 + 2CO2 + 3H2O (at a reaction temperature of 500~600℃, the obtained modified support γ-Al2O3 is dominated by weak acid / medium-strong acid sites, exhibiting excellent acidic structure compatibility).

[0082] In some embodiments, the mass concentration of sodium hydroxide in the sodium aluminate solution is 120~180 g / L. A suitable sodium hydroxide concentration in the sodium aluminate solution is beneficial for further improving the purity of gibbsite; excessively high or low sodium hydroxide concentrations are detrimental to obtaining high-performance gibbsite. When the NaOH mass concentration is <120 g / L, after CO2 is introduced into the sodium aluminate solution, the pH of the system decreases, localized supercarbonation occurs, and a side reaction occurs to generate gibbsite trihydrate: NaAl(OH)4 + CO2 = Al(OH)3↓ + NaHCO3. The product contains amorphous aluminum hydroxide impurities, resulting in poor crystallinity and decreased purity of the gibbsite. Subsequent aluminum-containing phase transformation is incomplete, and sodium impurities remain in the alumina, generating strong acidic sites and thus reducing the catalytic activity of the catalyst. When the mass concentration of the sodium hydroxide solution is >180 g / L, excess free -OH inhibits the combination of carbonate and aluminate ions, resulting in slow kinetics of gibbsite precipitation and incomplete crystallization: NaAl(OH)2CO3 + 2OH... - =NaAl(OH)4 + CO3 2-Excessive free alkali can coat the crystals, and residual sodium alkali can be carried into the modified support γ-Al₂O₃, forming strongly acidic active sites and reducing catalytic selectivity. Specifically, the mass concentration of sodium hydroxide in the sodium aluminate solution is any value or a range between 120 g / L, 130 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, and 180 g / L.

[0083] In some embodiments, the mass concentration of aluminum hydroxide in the sodium aluminate solution is 80-120 g / L. A suitable aluminum hydroxide mass concentration is beneficial for improving the quality and purity of sodium ferrophosphate, thus laying a good structural foundation for the subsequent preparation of the modified support. When the aluminum hydroxide concentration is below 80 g / L, the aluminate activity is low, leading to rapid nucleation and the formation of ultrafine crystals with a large specific surface area, adsorption of the alkali metal sodium from the mother liquor, and incomplete sodium ion replacement via ammonium exchange. When the aluminum hydroxide concentration is above 120 g / L, the solution viscosity increases, mass transfer is hindered, particles agglomerate and clump together, internally encapsulating the mother liquor, and easily forming aluminum-containing compound impurities. Ultimately, the modified support γ-Al₂O₃ has a simple pore structure and the acid sites cannot be precisely controlled. Specifically, the mass concentration of aluminum hydroxide in the sodium aluminate solution is any value from 80 g / L, 90 g / L, 100 g / L, 110 g / L, and 120 g / L, or any value between two of these ranges.

[0084] In some embodiments, the first solvent is a mixture of deionized water and ethanol, preferably with a volume ratio of (5~10):1. A suitable volume ratio of deionized water to ethanol in the first solvent allows for better uniform mixing of the sodium aluminate solution and surfactant, thus facilitating the carbonation precipitation reaction and promoting directional nucleation and uniform grain growth of sialic acid aluminum silicate. When the volume ratio of deionized water to ethanol is less than 5:1, the ethanol content in the system is too high, reducing solvent polarity and easily causing local solute agglomeration and uneven dispersion. This leads to an imbalance in the local reaction rate of the carbonation reaction, triggering grain agglomeration and the formation of impurity phases, reducing the purity and crystal integrity of the sialic acid aluminum silicate product. When the volume ratio of deionized water to ethanol is greater than 10:1, the dispersing modification and grain agglomeration inhibition effects of ethanol are reduced, and the surfactant is prone to aggregate in the aqueous phase, resulting in a wide grain size distribution and particle agglomeration of sialic acid aluminum silicate. Specifically, the volume ratio of deionized water to ethanol is any value among 5:1, 6:1, 7:1, 8:1, 9:1, and 10:1, or any range between the two.

[0085] In some embodiments, the surfactant is selected from at least one of sodium stearate, polysorbate-80, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, hexadecyltrimethylammonium bromide, and polyethylene glycol; the mass fraction of the surfactant in the first mixed solution is 0.1~1.0 wt%. By limiting the type of surfactant and its mass fraction in the first mixed solution, it is beneficial to further improve the dispersibility of the sodium aluminate solution and optimize the morphology of the prepared sodium aluminate filament. Specifically, the mass fraction of the surfactant in the first mixed solution is any value from 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, and 1.0 wt%, or a range between any two.

[0086] In some specific embodiments, the ammonium salt includes at least one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonium oxalate, and ammonium acetate.

[0087] In some embodiments, Al 3+ CO3 2- HCO3 - The molar ratio of sodium ferricyanide, ammonium carbonate, and ammonium bicarbonate is 1:(1~1.5):(0.8~1.2). Further limiting the molar ratio of sodium ferricyanide, ammonium carbonate, and ammonium bicarbonate facilitates the preparation of fibrous modified carrier precursor ammonium aluminum carbonate. This modified carrier precursor is then calcined at high temperature to transform into a modified carrier γ-Al2O3 with a high specific surface area and hierarchical porous structure. This modified carrier has few strong acid sites, strong anti-agglomeration sintering ability at high temperatures, and good dispersion of active components. Outside the specified range, aluminum-containing phase transformation easily leads to the formation of blocky and granular agglomerates, and the calcined product is dense; additionally, limiting CO3... 2- HCO3 - The proportion can be adjusted to control the thermal decomposition pathway of the modified support precursor, ammonium aluminum carbonate, reduce four-coordinate aluminum defects on the surface of the modified support, decrease the number of strong acid sites, and inhibit catalytic side reactions. Specifically, using Al... 3+ CO3 2- HCO3 - The molar ratio of sodium cerium carbonate, ammonium carbonate, and ammonium bicarbonate is any value or a range between any two of the following: 1:1:0.8, 1:1.1:0.8, 1:1.2:0.8, 1:1.3:0.8, 1:1.4:0.8, 1:1.5:0.8, 1:1:0.9, 1:1:1, 1:1:1.1, 1:1:1.2, 1:1.5:0.9, 1:1.5:1.0, and 1:1.5:1.2.

[0088] To further improve the reaction efficiency of the coordination reaction, in some embodiments, the solid-liquid ratio of the total mass of ferrous sulfate and ammonium salt to the first solvent is 1 g: (10~20) mL. Specifically, the solid-liquid ratio of the total mass of ferrous sulfate and ammonium salt to the first solvent is any value or a range between 1 g:10 mL, 1 g:11 mL, 1 g:12 mL, 1 g:13 mL, 1 g:14 mL, 1 g:15 mL, 1 g:16 mL, 1 g:17 mL, 1 g:18 mL, 1 g:19 mL, and 1 g:20 mL.

[0089] In some embodiments, the antimony source is SbOCl, and the preparation method of SbOCl is as follows: mixing copper electrolytic floating anode mud with hydrochloric acid aqueous solution to obtain Sb-containing... 5+ Antimony powder is added to the acidic leachate for a reduction reaction to obtain a chlorinated antimony compound. This chlorinated antimony compound is then hydrolyzed to yield SbOCl. Using copper electrolytic floating anode mud as a raw material to prepare SbOCl enables efficient antimony recovery and utilization, reduces raw material costs, and eliminates heavy metal pollution. The relevant chemical reaction equation is: Anode mud hydrochloric acid leaching Sb₂O₅ + 10HCl = 2SbCl₅ + 5H₂O. The metallic antimony in the anode mud is released as SbO₅. 5+ SbCl6 complex with antimony chloride ions - Upon entering the solution, antimony powder reduces Sb(V) to Sb(III): 3SbCl₅ + 2Sb = 5SbCl₃; SbCl₃ undergoes stepwise hydrolysis, precipitating sparingly soluble SbOCl: SbCl₃ + H₂O Sb(OH)Cl₂ + HCl, Sb(OH)Cl₂ SbOCl↓+HCl. Anode mud contains associated heavy metals such as Cu and Pb. After leaching, antimony can be selectively enriched and purified through a stepwise reduction-hydrolysis process.

[0090] In this invention, the copper electrolytic floating anode mud is a solid byproduct that is insoluble in the electrolyte and is produced during copper electrolytic refining. Its main components include precious metals (gold, silver, platinum, palladium), copper, lead, selenium, tellurium, bismuth, antimony, nickel, sulfur, tin, and a large amount of water.

[0091] In some embodiments, the mass-to-volume ratio of copper electrolytic floating anode slime to hydrochloric acid aqueous solution is 1 g: (1~15) mL. Further limiting the mass-to-volume ratio of copper electrolytic floating anode slime to hydrochloric acid aqueous solution is beneficial for obtaining Sb-containing solutions. 5+ Acidic leachate is more conducive to the subsequent enrichment and purification of antimony in SbOCl. When the solid-liquid ratio is less than 1g:1mL, the amount of hydrochloric acid is insufficient, and the acidity and chloride ion concentration of the system are low: pentavalent antimony oxides in the anode mud are difficult to fully complex and dissolve, and Sb... 5+The leaching rate decreases; antimony hydroxides and basic antimony salts are easily formed, making it impossible to obtain clear Sb-containing precipitates. 5+ Acidic leachate. When the solid-liquid ratio is higher than 1g:15mL, hydrochloric acid is in excess: the system acidity is too high, and free Cl-... - High concentrations of HCl can inhibit the hydrolysis of SbCl3 to form SbOCl during the hydrolysis reaction (SbCl3 + H2O = SbOCl + 2HCl).

[0092] Specifically, the mass-to-volume ratio of copper electrolytic floating anode mud to hydrochloric acid aqueous solution is any value or a range between any two of the following: 1g:1mL, 1g:2mL, 1g:3mL, 1g:4mL, 1g:5mL, 1g:6mL, 1g:7mL, 1g:8mL, 1g:9mL, 1g:10mL, and 1g:15mL.

[0093] In some embodiments, the molar concentration of the hydrochloric acid aqueous solution is 3–10 mol / L. Further limiting the mass concentration of the hydrochloric acid aqueous solution allows for better dissolution of metallic antimony in the copper electrolysis floating anode mud, improving the recovery rate of metallic antimony and facilitating subsequent antimony enrichment and impurity leaching and separation. Specifically, the mass concentration of the hydrochloric acid aqueous solution is any value from 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, and 10 mol / L, or a range between any two.

[0094] In some embodiments, antimony powder and Sb-containing 5+ Sb in acidic leachate 5+ The molar ratio is (1.2~1.5):1. This was determined by analyzing antimony powder and Sb-containing... 5+ Sb in acidic leachate 5+ Adjusting the molar ratio can benefit Sb 5+ Complete conversion bit Sb 3+ This improves the reduction conversion rate and product purity. Specifically, antimony powder and Sb-containing... 5+ Sb in acidic leachate 5+ The molar ratio is any value among 1.2:1, 1.3:1, 1.4:1, 1.5:1, or any value between two of them.

[0095] To further improve the efficiency of the reduction reaction, in some embodiments, the reaction temperature is 55-65°C, and the reaction time is 30-60 min. Specifically, the reaction temperature is any value or a range between any two of 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, and 65°C; the reaction time is any value or a range between any two of 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, and 60 min.

[0096] In some embodiments, in step S2, the mass-to-volume ratio of the modified carrier precursor to the impregnation solution is (5~10) g:1 mL. By further limiting the mass-to-volume ratio of the modified carrier precursor to the impregnation solution, it is beneficial for the active components to be uniformly loaded onto the surface of the modified carrier precursor; simultaneously, it is beneficial for the Sb and V components to react with each other during heat treatment, i.e., to generate SbVO4-Sb2O3-VO4 in situ. x The composite oxide active phase synergistically enhances the catalytic activity and target product selectivity of the catalyst through the number of active sites and the composite oxide phase structure. Specifically, the mass-to-volume ratio of the modified support precursor to the impregnation solution is any value from 5g:1mL, 6g:1mL, 7g:1mL, 8g:1mL, 9g:1mL, 10g:1mL, or any range between the two.

[0097] To further improve the impregnation efficiency and ensure more uniform loading of the active component onto the modified carrier precursor, in some embodiments, the impregnation temperature is 55-65°C, and the impregnation time is 1-3 hours. Specifically, the impregnation temperature is any value or a range between 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, and 65°C; the impregnation time is any value or a range between 1 hour, 1.5 hours, 2 hours, 2.5 hours, and 3 hours.

[0098] In some specific embodiments, the vanadium source is selected from at least one of sodium metavanadate, ammonium orthovanadate, and ammonium metavanadate.

[0099] In some embodiments, the molar ratio of vanadium in the vanadium source to antimony in the antimony source is 1:(0.1~1.2). Further adjustment of the molar ratio of vanadium in the vanadium source to antimony in the antimony source is beneficial for optimizing V. 4+ / (V 4+ +V 5+ ),Sb 3+ / (Sb 3+ +Sb 5+The appropriate molar ratio of ions and the suitable proportion of low-valence metal ions can precisely control the number of oxygen vacancies, which is beneficial for the formation of SbVO4-Sb2O3-VO4. x The composite active phase structure enhances the catalytic activity and product selectivity of the composite oxide catalyst. Specifically, the molar ratio of vanadium in the vanadium source to antimony in the antimony source is any value or a range between 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, and 1:1.2.

[0100] In some embodiments, the impregnation solution further includes a complexing agent selected from at least one of oxalic acid, tartaric acid, citric acid, and ethylenediaminetetraacetic acid. Preferably, the mass ratio of the complexing agent to the total mass of the vanadium and antimony sources is (5~10):100. By controlling the type of complexing agent and the mass ratio of the complexing agent to the total mass of the vanadium and antimony sources, the morphology of the active components in the impregnation solution is effectively improved, the dispersion performance of the active components is inhibited, and particle agglomeration is suppressed. At the same time, the interfacial interaction between the active components and the modified support precursor is strengthened, preventing the active components from detaching or being lost during preparation and reaction, thereby improving the stability of the catalyst structure and performance. Specifically, the mass ratio of the complexing agent to the total mass of the vanadium and antimony sources is any value from 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, or any value between any two.

[0101] In some embodiments, the calcination treatment includes a first calcination treatment and a second calcination treatment. The temperature of the first calcination treatment is 200~300℃, and the holding time is 1~2h; the temperature of the second calcination treatment is 500~600℃, and the holding time is 3~4h. By employing segmented gradient calcination of the catalyst precursor, the phase transformation can be precisely controlled, which is beneficial for better formation of SbVO4-Sb2O3-VO4. xThe composite active phase consists of a first low-temperature calcination treatment that can fully remove residual organic matter and water of crystallization from the catalyst precursor, avoiding rapid decomposition of organic matter at high temperatures that could lead to powder sintering and pore collapse; and a second high-temperature calcination treatment that can decompose the modified support precursor ammonium aluminum carbonate to generate a high-surface-area modified support γ-Al2O3 while retaining a multi-level pore structure; and simultaneously causing V and Sb in the active components to undergo a solid-phase reaction, transforming them into a composite oxide active phase. Specifically, the temperature of the first roasting treatment is any value or a range between any two of 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, and 300℃; the time of the first roasting treatment is any value or a range between any two of 1h, 1.25h, 1.5h, 1.75h, and 2h; the temperature of the second roasting treatment is any value or a range between any two of 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, and 600℃; and the time of the second roasting treatment is any value or a range between any two of 3h, 3.25h, 3.5h, 3.75h, and 4h.

[0102] A two-stage programmed temperature roasting process was used to treat the impregnated and dried catalyst precursor: firstly, a low-temperature roasting was carried out at 1~2℃ min. -1 The temperature is raised to 200-300℃ and held for 1-2 hours to remove residual organic matter and adsorbed water from the sample and to pre-decompose vanadium and antimony precursors, ensuring uniform dispersion of the active components on the modified γ-Al2O3 support surface. Subsequently, the temperature is raised to 500-600℃ for the second stage of high-temperature calcination, held for 3-4 hours to promote the complete decomposition of oxychloride and antimony, releasing chlorine gas. Simultaneously, through the solid-phase interface reaction between vanadium and antimony oxides, V... 4+ / (V 4+ +V 5+ ),Sb 3+ / (Sb 3+ +Sb 5+ This involves increasing the active sites of the catalyst. Simultaneously, at high temperatures (500-600℃), a large number of surface hydroxyl groups on alumina can be removed, excess Brønsted strong acid can be eliminated, and acid sites can be optimized, thereby obtaining a structurally stable composite oxide catalyst with excellent catalytic performance.

[0103] To facilitate the calcination process, in some embodiments, the protective atmosphere is a mixture of hydrogen, nitrogen, and helium, preferably with a hydrogen volume fraction of 5-10%. A weakly reducing atmosphere can moderately adjust the valence state distribution of the active metals vanadium and antimony, which is beneficial for the SbVO4-Sb2O3-VO4 phase. xThe composite active phase is generated, while simultaneously inhibiting excessive oxidation of active components and powder agglomeration during the high-temperature calcination stage. Specifically, the volume fraction of hydrogen in the protective atmosphere is any value from 5%, 6%, 7%, 8%, 9%, and 10%, or any value between two of these.

[0104] In some embodiments, the protective atmosphere is a mixture of hydrogen and nitrogen or a mixture of hydrogen and helium, with hydrogen accounting for 5-10% of the volume, to further promote precise control of the valence state of the vanadium and antimony active components.

[0105] In some specific embodiments, the present invention achieves precise control of the valence states of vanadium and antimony active components in the composite oxide catalyst through segmented controllable calcination and a weak reducing protective atmosphere: the vanadium active components are ammonium metavanadate, sodium metavanadate, and ammonium orthovanadate (initial valence state V). 5+ The vanadium source is V, and the valence state control target is V. 4+ The proportion is ≥0.67%. A weak reducing atmosphere is used, relying on the selective reduction effect of hydrogen to reduce V. 5+ Directed conversion to highly active V 4+ At the same time, the reduction intensity is controlled by using an inert dilution gas to avoid over-reduction of V. 3+ Generation. Matching segmented roasting process: low-temperature pre-roasting at 200~300℃ removes moisture and impurities, and high-temperature stage at 500~600℃ completes the main reduction reaction of vanadium species; temperatures above 600℃ will cause V 4+ Deep reduction and carrier pore structure collapse occur; below 500℃, reduction kinetics are insufficient, failing to meet V standards. 4+ Proportion. The antimony active components selected were SbOCl, SbCl3, Sb2O3, and C6H9O6Sb as antimony sources, with the target being Sb. 3+ The proportion is ≥0.25%. A weakly reducing atmosphere formed by a mixture of H2 and N2 or a mixture of H2 and He can isolate oxygen and inhibit Sb. 3+ Oxidation to inert Sb 5+ And can reduce the amount of Sb 5+ Reduced to active Sb 3+ Meanwhile, the pore confinement and anchoring effect of the sodium aluminum silicate-based hierarchical porous carrier can effectively prevent Sb from entering the environment. 3+ Migration, aggregation, and oxidative deactivation stabilize the active structure of low-valent antimony.

[0106] The composite oxide catalyst (propane oxidative dehydrogenation to propylene) provided by this invention utilizes a two-stage gradient temperature-programmed calcination process, combined with a weakly reducing protective atmosphere, and is matched with a modified support γ-Al2O3 with a multi-level porous structure to precisely control the loading of active components and V. 4+ / (V 4+ +V 5+ ),Sb 3+ / (Sb 3+ +Sb5+ Valence ratio, constructing SbVO4-Sb2O3-VO x A composite active phase, through synergistic pore confinement, interfacial effects, and acid site regulation, achieves high activity and high propylene selectivity in propane oxidative dehydrogenation. The modified γ-Al₂O₃ support possesses hierarchical pores and intrinsic oxygen vacancies, forming multiple synergies with two-stage calcination and valence state regulation. First, the hierarchical pore structure and pore confinement effect shorten the residence time of propane and propylene products within the pores, reducing excessive oxidation of propylene on the catalyst surface and improving propylene selectivity. Simultaneously, the pore space constraint inhibits the growth of active component grains, enhancing anti-sintering ability. Second, during the two-stage calcination process, the modified γ-Al₂O₃ support forms a strong interfacial interaction with V-Sb species, anchoring the active component and further improving high-temperature anti-agglomeration sintering performance. The oxygen vacancies in the modified γ-Al₂O₃ support participate in the metal-support electron transfer, synergistically modulating the V / Sb redox cycle and optimizing the dehydrogenation reaction kinetics. Finally, two stages of high-temperature calcination remove a large amount of Brønsted strong acid from the support surface. Combined with V-Sb loading and valence state regulation, a dual active center of "low-strength acid site - suitable redox site" is constructed: the redox site is responsible for the activation and dehydrogenation of propane CH bond; the weak acid site assists molecular adsorption and effectively inhibits the cracking side reaction caused by strong acid, ultimately achieving high activity and high propylene selectivity in the propane oxidative dehydrogenation reaction.

[0107] In a third typical embodiment of the present invention, an application is provided in the propane oxidative dehydrogenation to propylene reaction using a composite oxide catalyst provided in the first typical embodiment of the present invention or a composite oxide catalyst prepared by the method for preparing the composite oxide catalyst provided in the third typical embodiment of the present invention. The composite oxide catalyst provided in this invention can be used in the propane oxidative dehydrogenation to propylene reaction and exhibits superior catalytic activity in this reaction. It achieves high-value conversion and utilization of solid waste while possessing multiple advantages such as high cost-effectiveness, good selectivity, and long service life.

[0108] The present invention applies the composite oxide catalyst provided in the first typical embodiment or the composite oxide catalyst prepared according to the second typical embodiment as a catalyst in the oxidative dehydrogenation reaction of propane to propylene. Under mild reaction conditions, it can improve the selectivity and long-term operation stability of propylene, and has broad application prospects in the field of propylene preparation.

[0109] In some embodiments, in the propane oxidative dehydrogenation to propylene reaction, the reaction temperature is 500-600°C and the space velocity is 8000-15000 h⁻¹. -1The propane to oxygen molar ratio is 1:(0.5~1), propane conversion rate is ≥55%, propylene selectivity is ≥65%, activity decay rate is ≤5% after 100 hours of continuous operation, and carbon deposition is ≤2wt%. The composite oxide catalyst prepared by this invention exhibits excellent catalytic activity in promoting the oxidative dehydrogenation of propane to propylene. Moreover, while achieving high-value conversion and utilization of solid waste, it also has multiple advantages such as high cost-effectiveness, good selectivity, and long service life.

[0110] Specifically, the reaction temperature is any value or a range between 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, and 600℃; the space velocity is 8000 h⁻¹. -1 9000h -1 10000h -1 11000h -1 12000h -1 13000h -1 14000h -1 15000h -1 The values ​​in the following ranges are specified: any value in the range of 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1; any value in the range of 55%, 60%, 65%; any value in the range of 65%, 66%, 70%; any value in the range of 1%, 2%, 3%, 4%, 5%; and any value in the range of 0.1wt%, 0.2wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%.

[0111] The beneficial effects of the present invention will be further illustrated below with reference to embodiments and comparative examples.

[0112] Example 1

[0113] This embodiment provides a composite oxide catalyst, the preparation method of which includes the following steps:

[0114] (1) Add sodium aluminate solution and surfactant (sodium stearate) to the reaction vessel and stir to mix evenly (wherein, the mass concentration of NaOH in the sodium aluminate solution is 150 g / L and the mass concentration of aluminum hydroxide is 110 g / L) to obtain the first mixed solution, wherein the mass fraction of surfactant in the first mixed solution is 0.1 wt%. Heat the reaction vessel to 45°C and continuously introduce CO2 gas with a purity of 99.9% at a rate of 20 mL / min. When the pH value drops to 10.5, stop the gas introduction and continue stirring for 15 min to obtain the reaction precipitate mixture. Transfer the reaction precipitate mixture to a vacuum filtration device and use a 0.45 μm organic phase filter membrane for filtration separation. Wash the obtained filter cake with deionized water and dry it under vacuum at 80°C for 7 h to obtain sodium aluminate.

[0115] (2) With Al 3+ CO3 2- HCO3 - The raw materials were weighed according to the molar ratio of sodium aluminum filament, ammonium carbonate, and ammonium bicarbonate of 1:1.2:1.0. The weighed raw materials were added to the first solvent to obtain the first mixed solution. The first solvent was a mixed solution of deionized water and ethanol, and the volume ratio of deionized water to ethanol was 10:1. The solid-liquid ratio of the total weight of the first solvent and the raw materials was 1:20 (g / mL). The first mixed solution was stirred at 50℃ and 300 rpm for a metathesis reaction for 1.5 h. After the reaction was completed, the solid product was collected and vacuum dried at 75℃ for 6 h to obtain the modified carrier precursor.

[0116] (3) Copper electrolytic floating anode mud and hydrochloric acid aqueous solution (concentration 8mol / L) were mixed at a mass-to-volume ratio of 1:5g / mL and stirred at 80℃ and 250rpm for 1.5h to obtain Sb-containing 5+ The acidic leachate, according to the antimony powder and Sb-containing 5+ The molar ratio of the acidic leachate to Sb was 1.3:1. Antimony powder (99.99% purity, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) was weighed and added to the solution containing Sb. 5+ In the acidic leachate, a reduction reaction was carried out at 60℃ and 200 rpm for 45 min to obtain a chlorinated antimony compound. The chlorinated antimony compound and deionized water were mixed at a volume ratio of 5:1 and hydrolyzed to obtain SbOCl.

[0117] (4) According to the molar ratio of vanadium to antimony of 1:0.34, ammonium metavanadate (vanadium source) and SbOCl (antimony source) were weighed respectively, and an appropriate amount of deionized water and complexing agent (oxalic acid) were added to prepare an impregnation solution (solid content of 0.1wt%). The mass ratio of the complexing agent to the total mass of vanadium source and antimony source was 8:100. The modified support precursor and impregnation solution were mixed at a mass-volume ratio of 8:1 (g:mL), stirred at 70℃ and 300rpm for 45min, filtered and collected the precipitate, and the precipitate was vacuum dried at 65℃ for 7h to obtain the catalyst precursor.

[0118] (5) The catalyst precursor was subjected to a first calcination treatment and a second calcination treatment in a protective atmosphere (a mixture of hydrogen and nitrogen, with a hydrogen volume fraction of 10%) to obtain a composite oxide catalyst. The temperature of the first calcination treatment was 200℃ and the time was 1.5h; the temperature of the second calcination treatment was 550℃ and the time was 3.5h.

[0119] The modified support in the composite oxide catalyst has a specific surface area of ​​739 m² / g and a pore volume of 1.2 cm³. 3 / g, the average pore size of the modified support is 5.5nm. The vanadium-containing component has a weight content of 10wt%, and the antimony-containing component has a weight content of 8wt%.

[0120] Example 2

[0121] The difference between this embodiment and embodiment 1 is that, in adjustment step (2), Al is used. 3+ CO3 2- HCO3 - The raw materials were weighed according to the molar ratio of sodium aluminum silicate, ammonium carbonate, and ammonium bicarbonate of 1:1:0.8.

[0122] Example 3

[0123] The difference between this embodiment and embodiment 1 is that, in adjustment step (2), Al is used. 3+ CO3 2- HCO3 - The raw materials were weighed according to the molar ratio of sodium aluminate, ammonium carbonate, and ammonium bicarbonate of 1:1.5:1.2.

[0124] Example 4

[0125] The difference between this embodiment and Embodiment 1 is that, in step (3), the antimony powder and Sb-containing... 5+ Sb in acidic leachate 5+ The molar ratio of antimony powder is 1.2:1.

[0126] Example 5

[0127] The difference between this embodiment and Embodiment 1 is that, in step (3), the antimony powder and Sb-containing... 5+ Sb in acidic leachate 5+ The molar ratio of antimony powder is 1.5:1.

[0128] Example 6

[0129] The difference between this embodiment and embodiment 1 is that, in step (4), the molar ratio of vanadium in the vanadium source to antimony in the antimony source is 1:0.1.

[0130] Example 7

[0131] The difference between this embodiment and embodiment 1 is that, in step (4), the molar ratio of vanadium in the vanadium source to antimony in the antimony source is 1:1.2.

[0132] Example 8

[0133] The difference between this embodiment and embodiment 1 is that in step (4), the mass-to-volume ratio of the modified carrier precursor to the impregnation solution is 5:1 (g:mL).

[0134] Example 9

[0135] The difference between this embodiment and embodiment 1 is that in step (4), the mass-to-volume ratio of the modified carrier precursor to the impregnation solution is 10:1 (g:mL).

[0136] Example 10

[0137] The difference between this embodiment and embodiment 1 is that, in adjustment step (2), Al is used. 3+ CO3 2- HCO3 - The raw materials were weighed according to the molar ratio of sodium aluminate, ammonium carbonate, and ammonium bicarbonate of 1:2:0.8.

[0138] Example 11

[0139] The difference between this embodiment and embodiment 1 is that, in adjustment step (2), Al is used. 3+ CO3 2- HCO3 - The raw materials were weighed according to the molar ratio of sodium aluminum silicate, ammonium carbonate, and ammonium bicarbonate of 1:0.8:1.5.

[0140] Example 12

[0141] The difference between this embodiment and Embodiment 1 is that, in step (3), the antimony powder and Sb-containing... 5+ Sb in acidic leachate 5+ Antimony powder was weighed at a molar ratio of 1:1.

[0142] Example 13

[0143] The difference between this embodiment and Embodiment 1 is that, in step (3), the antimony powder and Sb-containing... 5+ Sb in acidic leachate 5+ The molar ratio of antimony powder is 1.8:1.

[0144] Example 14

[0145] The difference between this embodiment and embodiment 1 is that, in step (4), the molar ratio of vanadium in the vanadium source to antimony in the antimony source is 1:0.05.

[0146] Example 15

[0147] The difference between this embodiment and embodiment 1 is that, in step (4), the molar ratio of vanadium in the vanadium source to antimony in the antimony source is 1:1.5.

[0148] Example 16

[0149] The difference between this embodiment and embodiment 1 is that in step (4), the mass-to-volume ratio of the modified carrier precursor to the impregnation solution is 2:1.

[0150] Example 17

[0151] The difference between this embodiment and embodiment 1 is that, in step (4), the mass-to-volume ratio of the modified carrier precursor to the impregnation solution is 15:1.

[0152] Example 18

[0153] The difference between this embodiment and embodiment 1 is that in step (4), SbOCl is replaced with SbCl3.

[0154] Example 19

[0155] The difference between this embodiment and embodiment 1 is that the amount of vanadium source and antimony source in step (4) is adjusted so that the weight content of vanadium-containing component in the active component of the composite oxide catalyst is 5wt% and the weight content of antimony-containing component is 10wt%.

[0156] Example 20

[0157] The difference between this embodiment and embodiment 1 is that the amount of vanadium source and antimony source in step (4) is adjusted so that the weight content of vanadium-containing component in the active component of the composite oxide catalyst is 12wt% and the weight content of antimony-containing component is 3wt%.

[0158] Example 21

[0159] The difference between this embodiment and Embodiment 1 is that the amounts of vanadium source and antimony source in step (4) are adjusted to increase the V content in the vanadium-containing component. 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is 0.67. 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is 0.33.

[0160] Example 22

[0161] The difference between this embodiment and Embodiment 1 is that the amounts of vanadium source and antimony source in step (4) are adjusted to increase the V content in the vanadium-containing component. 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is 0.75. 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is 0.25.

[0162] Comparative Example 1

[0163] The difference between this comparative example and Example 1 is that steps (1) and (2) are omitted, and the modified support is replaced with a γ-Al2O3 support.

[0164] Comparative Example 2

[0165] The difference between this comparative example and Example 1 is that step (3) is not performed, and ammonium metavanadate is used as the active component and complexing agent to prepare the impregnation solution.

[0166] Comparative Example 3

[0167] The difference between this comparative example and Example 1 is that in step (4), only SbOCl is used as the active component and complexing agent to prepare the impregnation solution.

[0168] Comparative Example 4

[0169] The difference between this comparative example and Example 1 is that the amount of vanadium source and antimony source in step (4) is adjusted so that the weight content of vanadium-containing component in the active component of the composite oxide catalyst is 3wt% and the weight content of antimony-containing component is 12wt%.

[0170] Comparative Example 5

[0171] The difference between this comparative example and Example 1 is that the amount of vanadium source and antimony source in step (4) is adjusted so that the weight content of vanadium-containing component in the active component of the composite oxide catalyst is 15wt% and the weight content of antimony-containing component is 1wt%.

[0172] Comparative Example 6

[0173] The difference between this comparative example and Example 1 is that the amounts of vanadium source and antimony source in step (4) are adjusted to increase the V content in the vanadium-containing component. 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is 0.55. 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is 0.4.

[0174] Comparative Example 7

[0175] The difference between this comparative example and Example 1 is that the amounts of vanadium source and antimony source in step (4) are adjusted to increase the V content in the vanadium-containing component. 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is 0.8. 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is 0.2.

[0176] Comparative Example 8

[0177] The difference between this comparative example and Example 1 is that the vanadium-containing component in the composite oxide catalyst contains only V. 5 + .

[0178] Comparative Example 9

[0179] The difference between this comparative example and Example 1 is that the antimony-containing component in the composite oxide catalyst contains only Sb. 5+ .

[0180] Experimental Example 1

[0181] The catalysts prepared in the above examples and comparative examples were subjected to performance testing. The specific testing methods are as follows:

[0182] (1) V 4+ / (V 4+ +V 5+ molar ratio of )

[0183] The valence state distribution of vanadium was determined using X-ray photoelectron spectroscopy (XPS), with the C 1s binding energy of 284.8 eV as the charge correction reference. A fine scan of the V 2p orbital characteristic peaks was performed, scanning the binding energy range from 510 eV to 530 eV, where V... 4+ The characteristic binding energy is 516.2 eV, V 5+ The characteristic binding energy is 517.4 eV. V was obtained by fitting the integral area through peak segmentation. 4+ V 5+ Relative content, according to the formula: V 4+ / (V 4+ +V 5+ The relative molar percentage of vanadium in tetravalent form was calculated. Each sample was tested in parallel three times, and the arithmetic mean was taken as the final result.

[0184] (2) Sb 3+ / (Sb 3+ +Sb 5+ molar ratio of )

[0185] The valence state distribution of antimony was determined using X-ray photoelectron spectroscopy (XPS), with the C 1s binding energy of 284.8 eV as the charge correction reference. The characteristic peaks of the Sb 3d orbital were finely scanned, with a binding energy range of 525 eV–545 eV. 3+ The characteristic binding energy is 530.0 eV, Sb 5+ The characteristic binding energy is 531.2 eV. During fitting, O1s signals were simultaneously analyzed to subtract oxygen signal interference, and Sb was obtained by fitting the integral area through peak segmentation. 3+ Sb 5+ The peak area is then used to obtain Sb. 3+ Sb 5+ Relative content, according to the formula: Sb 3+ / (Sb 3+ +Sb 5+ To calculate the relative molar percentage of trivalent antimony, each batch of samples was tested in parallel three times, and the arithmetic mean was taken as the final result.

[0186] (3) Oxygen vacancy concentration: The oxygen vacancy defects in the catalyst were characterized by electron paramagnetic resonance (EPR) spectroscopy. The test conditions were room temperature and X-band (9.8 GHz). The test parameters were set as follows: central magnetic field 3200~3600 G, sweep width 400 G, microwave power 20 mW, modulation frequency 100 kHz, and modulation amplitude 1 G. Oxygen vacancies in the catalyst belong to unpaired electron trapping centers, which are represented by characteristic resonance peaks in the EPR spectrum. The EPR characteristic peak position corresponding to oxygen vacancies in the catalyst is approximately g=2.003 (due to the interaction between the modified support and vanadium species, there may be interaction and possible shift). The intensity of this peak is positively correlated with the number of oxygen vacancies. Therefore, the relative concentration of oxygen vacancies is quantitatively characterized by the integral area of ​​the EPR characteristic peak: the baseline-corrected oxygen vacancy characteristic peak is integrated using Origin software to obtain the integral area S of the characteristic peak. EPR (Unit: au); Divide the integrated area by the sample mass (m, unit: g) to obtain the normalized integrated area S. norm Calculation formula: S norm =S EPR / m; where: S norm S is the integral area of ​​the normalized EPR characteristic peak; EPR α represents the original integrated area (au) of the oxygen vacancy characteristic peak; m represents the mass (g) of the test sample.

[0187] (4) Analysis of catalyst pore structure

[0188] The Digisob-2500 automated adsorption analyzer from Micromeritics, USA; calculation methods: BET nitrogen adsorption capacity method for determining specific surface area and pore volume, and BJH method for determining pore distribution.

[0189] The test results are shown in Table 1.

[0190] Table 1

[0191]

[0192]

[0193] Note: "-" indicates that the component was not detected and there is no molar ratio of that valence state.

[0194] Experimental Example 2

[0195] The composite oxide catalysts prepared in the above examples and comparative examples were tested for propane oxidative dehydrogenation to propylene:

[0196] Propylene selectivity, propane conversion, and propylene yield were used as performance evaluation indicators for the catalyst. The calculation method is as follows: Propylene conversion (%) = (Propylene content in feedstock - Propylene content in product) / Propylene content in feedstock × 100%

[0197] Propylene selectivity (%) = (Number of carbon atoms in the product / (Number of carbon atoms in propane before reaction - Number of carbon atoms in propane after reaction)) × 100%

[0198] Propylene yield (%) = Propane conversion × Propylene selectivity × 100%

[0199] In the following examples and comparative examples, the calculation method for reaction spacetime velocity is as follows:

[0200] Reaction space velocity = volume of reaction gas per hour (L) / mass of catalyst (g).

[0201] Unless otherwise specified, the calcination in the following examples and comparative examples was carried out in air.

[0202] The gas chromatographic conditions for testing propylene were as follows: FID detector temperature 250℃, hydrogen flow rate 40 mL / min, air flow rate 400 mL / min, column oven temperature 35℃ for 2 min, then increased to 85℃ at a rate of 10℃ / min. Column flow rate was 7 mL / min.

[0203] The test results are shown in Table 2.

[0204] Table 2

[0205]

[0206]

[0207] Figure 1 This is a TEM image of the modified support γ-Al₂O₃ prepared in Example 1. Figure 1 It can be seen that the modified active alumina support exhibits a uniform one-dimensional fibrous / rod-like microstructure. The modified support fibers have a diameter of approximately 60 nm and a length of up to 1.2 μm, exhibiting a typical mesoporous fiber structure. This morphology provides a high specific surface area loading framework for the catalytically active components, providing sufficient attachment sites for the uniform loading of the catalytically active components. At the same time, it ensures good pore connectivity within the modified support, reduces mass transfer resistance during the catalytic reaction, and provides an excellent microstructural basis for the diffusion and transfer of reactants and products during the reaction.

[0208] Figure 2 The images show the XRD patterns of the modified support precursor, ammonium aluminum carbonate, and the modified support prepared in Example 1. Figure 2It can be seen that the modified support obtained by calcining the modified support precursor, ammonium aluminum carbonate, is γ-Al₂O₃. Its diffraction peaks exhibit obvious dispersion and broadening characteristics, indicating that the obtained material has low crystallinity and poor crystal integrity. This low-crystallinity γ-Al₂O₃ has a large number of coordination unsaturated defect sites on its surface, effectively enhancing the surface reactivity of the modified support. These dispersion peaks originate from the gas released during the thermal decomposition of the modified support precursor, ammonium aluminum carbonate, during calcination, effectively inhibiting grain agglomeration and excessive growth, ultimately forming nanoscale microcrystals. Simultaneously, various lattice defects such as oxygen vacancies and dislocations are introduced into the crystal. The synergistic effect of grain refinement and defect enrichment leads to the formation of coordination unsaturated Al₂O₃ sites on the surface of the modified support. 3+ The number of catalytic sites is significantly increased, and these sites possess strong Lewis acidity. The excessive acidity of these sites can be modulated and weakened by introducing Sb, which is beneficial for the efficient adsorption and activation of reactant molecules. Simultaneously, oxygen vacancies promote electron transfer and oxygen species activation, further enhancing the catalyst's reactivity. Furthermore, the nanocrystalline structure, accompanied by high specific surface area and mesoporous channels, further exposes active sites and optimizes mass transfer efficiency. Therefore, the low-crystallinity modified support γ-Al₂O₃ exhibits excellent catalytic performance due to its abundant defects, numerous coordination unsaturated sites, and high specific surface area.

[0209] Figure 3 This is a TEM image of the composite oxide catalyst prepared in Example 1. Figure 3 It can be seen that the active metal particles in the composite oxide catalyst are uniformly dispersed on the surface of the modified support, with no obvious agglomeration. The particles are evenly distributed and exhibit a good dispersion state, which can effectively expose the active centers and provide sufficient active sites for the catalytic reaction.

[0210] Figure 4 This is a size distribution diagram of the active metal particles in the composite oxide catalyst prepared in Example 1. Figure 4 It can be seen that the particle size of the active metal particles in the composite oxide catalyst is mainly distributed in the range of 3.0~4.2nm, with an average particle size of about 3.6nm. The narrow particle size distribution shows good particle size uniformity, which is beneficial to improving the reaction activity and stability of the catalyst.

[0211] The composite oxide catalysts prepared in Example 1 and Comparative Example 1 were characterized by N2 adsorption-desorption specific surface area. Figure 5 This is a relative pressure-adsorption capacity curve for the composite oxide catalysts prepared in Example 1 and Comparative Example 1. Figure 5It can be seen that the adsorption isotherms of Example 1 and Comparative Example 1 are both typical Type IV isotherms with obvious hysteresis loops, indicating that the samples have a mesoporous structure. At the same time, the adsorption amount of Example 1 is higher than that of Comparative Example 1, indicating that the modified composite oxide catalyst has a larger specific surface area and can provide more adsorption active sites and catalytic reaction sites.

[0212] Figure 6 The figures show the pore size distribution curves of the composite oxide catalysts prepared in Example 1 and Comparative Example 1. Figure 6 It can be seen that the catalyst in Example 1 has a more concentrated pore size distribution and a distinct mesoporous peak at about 20 nm, with a uniform pore size distribution; while the catalyst in Comparative Example 1 has a wider pore size distribution and a lower pore volume. This indicates that the modification treatment optimizes the pore structure of the catalyst, which is more conducive to the diffusion of reactants and products, accelerates the mass transfer process, and thus effectively improves the catalytic reaction efficiency.

[0213] Comparing Examples 1-22 with Comparative Examples 1-9, it can be seen that the composite oxide catalysts prepared in Examples 1-22 possess a hierarchical porous structure and abundant oxygen vacancy defects. This not only reduces the residence time of reactants and products within the catalyst pores, enhancing mass transfer and diffusion efficiency, but also achieves physical confinement through pore confinement. Furthermore, the interfacial interaction between the modified support and the active component further improves the structural stability of the active component and its resistance to high-temperature agglomeration and sintering. In addition, the oxygen vacancies on the modified support can regulate the electron transfer of the active metal, synergistically optimizing the redox properties of the active component. The active components of the composite oxide catalyst provided by this invention are vanadium-containing and antimony-containing components. By limiting the weight content and valence state of the vanadium-containing and antimony-containing components, low-intensity acid sites can be formed on the surface of the modified support. These low-intensity acid sites, in synergy with the hierarchical porous structure of the modified support, can effectively suppress side reactions, thereby enhancing the catalytic activity and selectivity of the composite oxide catalyst.

[0214] In Comparative Example 1, γ-Al₂O₃ was used as the support for the composite oxide catalyst. The unmodified γ-Al₂O₃ support lacks a hierarchical pore structure, and this single-pore structure leads to increased mass transfer resistance and low mass transfer efficiency between reactant and product molecules. Furthermore, the lack of defect-controlled support weakens the electronic regulation ability of the active components. In addition, the unmodified γ-Al₂O₃ support has a highly acidic surface and disordered distribution of acidic sites, which weakens the synergistic catalytic effect between active components.

[0215] Comparative Example 2 does not contain antimony-containing components. The catalyst has a single type of active site and an imperfect functional structure, resulting in insufficient redox performance. Furthermore, the surface acidic sites cannot be precisely controlled, making it difficult to achieve both high-efficiency conversion and high product selectivity.

[0216] Comparative Example 3 lacks vanadium-containing components, resulting in the absence of core catalytic active sites and a decrease in overall catalytic activity. In Comparative Examples 4-5, insufficient vanadium content leads to fewer effective active sites on the catalyst, resulting in weak redox reaction capacity and limited conversion efficiency of the main reaction. Excessive vanadium content causes active components to agglomerate, clogging catalyst channels and covering active sites, which can easily trigger side reactions. Insufficient antimony content makes it difficult to effectively control the electronic structure and surface acidic site distribution of active components, making it difficult to exert the synergistic effect between vanadium and antimony components. Excessive antimony content dilutes the density of vanadium active sites, reducing the structural stability and selectivity of the catalyst.

[0217] In Comparative Examples 6-7, the unoptimized distribution of the valence state of the active components led to an imbalance in the strength and proportion of acid sites on the catalyst surface and the oxygen vacancy concentration being in a non-optimal range. This resulted in an inability to achieve precise matching between acid sites and redox properties, and poor side reaction suppression. In Comparative Examples 8-9, the catalysts only had single vanadium and antimony active metal valence states. The single structure of the active metal valence states prevented the controllable regulation of oxygen vacancies and the efficient transfer and precise regulation of electrons on the active metal surface, resulting in low intrinsic catalyst activity and poor cycle stability.

[0218] Comparing Examples 1-9, 18-22, and 10-11, it can be seen that in Examples 1-9 and 18-22, Al... 3+ CO3 2- HCO3 - The appropriate molar ratio of sodium aluminate, ammonium carbonate, and ammonium bicarbonate is beneficial for preparing the fibrous modified carrier precursor, ammonium aluminum carbonate. This precursor, after high-temperature calcination, transforms into the modified carrier γ-Al₂O₃, which has a high specific surface area and a hierarchical porous structure. This carrier has a low content of strong acid sites and strong anti-agglomeration sintering ability at high temperatures, which is conducive to the high dispersion of active components. Too high or too low a molar ratio can easily lead to the formation of blocky or granular agglomerates of the precursor during the aluminum-containing phase transformation, resulting in an overly dense structure of the calcined product; furthermore, CO₃²⁻... 2- and HCO3 - An appropriate ratio can further regulate the thermal decomposition pathway of the modified support precursor, ammonium aluminum carbonate, reduce the number of tetracoordinated aluminum defects on the surface of the modified support, decrease the number of strong acid sites, and inhibit the occurrence of side reactions during catalysis.

[0219] Compared with Examples 1-9, 18-22 and 12-13, it can be seen that in Examples 1-9 and 18-22, antimony powder and Sb-containing powder... 5+ Sb in acidic leachate 5+ A suitable molar ratio can be beneficial to Sb 5+ Complete conversion bit Sb 3+This improves the reduction conversion rate and product purity, and further endows the composite oxide catalyst with excellent structural stability, high-temperature anti-agglomeration and sintering ability, effective suppression of side reactions, and excellent catalytic activity and selectivity.

[0220] Compared with Examples 1-9, 18-22, and 14-15, it can be seen that in Examples 1-9 and 18-22, the appropriate molar ratio of vanadium in the vanadium-containing component to antimony in the antimony-containing component is beneficial for optimizing V. 4+ / (V 4+ +V 5+ ),Sb 3 + / (Sb 3+ +Sb 5+ The appropriate molar ratio of ions and the suitable proportion of low-valence metal ions can precisely control the number of oxygen vacancies, which is beneficial for the formation of SbVO4-Sb2O3-VO4. x The composite active phase structure enhances the catalytic activity and product selectivity of the composite oxide catalyst.

[0221] Compared with Examples 1-9, 18-22, and 16-17, it can be seen that in Examples 1-9 and 18-22, the appropriate mass-to-volume ratio of the modified carrier precursor to the impregnation solution is beneficial for the uniform loading of the active component onto the surface of the modified carrier precursor; at the same time, it is beneficial for the mutual reaction of Sb and V components during heat treatment, i.e., the in-situ generation of SbVO4-Sb2O3-VO x The composite oxide active phase synergistically enhances the catalytic activity and target product selectivity of the catalyst by combining the number of active sites with the phase structure of the composite oxide.

[0222] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0223] The composite oxide catalyst provided by this invention, on the one hand, utilizes the hierarchical porous structure and oxygen vacancies of the modified support to reduce the residence time of reactants and products within the pores, and achieves a physical confinement effect through pore confinement; on the other hand, it utilizes the interaction between the modified support and the active component interface to further improve the structural stability of the active component and its resistance to high-temperature agglomeration and sintering. Furthermore, the composite oxide catalyst provided by this invention also utilizes the oxygen vacancies of the modified support to regulate metal electron transfer, synergistically optimizing the redox properties of the active component.

[0224] Meanwhile, the composite oxide catalyst provided by this invention utilizes vanadium-containing and antimony-containing components as active components, and controls the weight content of the vanadium-containing component to be 5-12 wt%, the weight content of the antimony-containing component to be 3-10 wt%, and the vanadium-containing component to contain V 4+ / (V 4+ +V5+ The molar ratio of Sb in the antimony-containing component is ≥0.67. 3+ / (Sb 3+ +Sb 5+ The molar ratio of vanadium and antimony components is ≥0.25. By limiting the weight content and valence state of the vanadium and antimony components, low-strength acid sites are formed on the surface of the modified support. The synergistic effect of the low-strength acid sites and the hierarchical porous structure of the modified support effectively suppresses side reactions, resulting in a significant improvement in catalytic activity and selectivity.

[0225] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite oxide catalyst, characterized in that, The composite oxide catalyst comprises: a modified support and an active component supported on the modified support. The active component includes a vanadium-containing component and an antimony-containing component. The modified support has a weight content of 85-92 wt%, the vanadium-containing component has a weight content of 5-12 wt%, and the antimony-containing component has a weight content of 3-10 wt%. The modified support has a hierarchical porous structure. The vanadium-containing component contains V... 4+ / (V 4+ +V 5+ The molar ratio of Sb in the antimony-containing component is ≥0.

67. 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is ≥0.

25.

2. The composite oxide catalyst according to claim 1, characterized in that, V in the vanadium-containing component 4+ / (V 4+ +V 5 + The molar ratio of ) is 0.67~0.75; And / or, the antimony-containing component contains Sb 3+ / (Sb 3+ +Sb 5+ The molar ratio of ) is 0.25~0.33; And / or, the molar ratio of vanadium in the vanadium-containing component to antimony in the antimony-containing component is 1:(0.1~1.2).

3. The composite oxide catalyst according to claim 1 or 2, characterized in that, The composite oxide catalyst has oxygen vacancies, and the oxygen vacancy concentration is 1.0 × 10⁻⁶. 10 ~5.0×10 20 pcs / cm -3 ; And / or, the specific surface area of ​​the modified carrier is 400~900m². 2 / g; And / or, the pore volume of the modified carrier is 0.8~1.5 cm³. 3 / g; And / or, the average pore size of the modified support is 5~10 nm.

4. The method for preparing the composite oxide catalyst according to any one of claims 1 to 3, characterized in that, The preparation method includes: Step S1: Sodium aluminum filament is mixed with ammonium salt and subjected to metathesis reaction to obtain modified support precursor; Step S2: Disperse the vanadium source and antimony source in deionized water to prepare an impregnation solution. Add the modified support precursor to the impregnation solution for impregnation treatment to obtain the catalyst precursor. The vanadium source is selected from at least one of sodium metavanadate, ammonium orthovanadate, and ammonium metavanadate, and the antimony source is selected from at least one of SbOCl, SbCl3, Sb2O3, and C6H9O6Sb. Step S3: The catalyst precursor is calcined under a protective atmosphere to form a modified support, and the vanadium source and the antimony source respectively form a vanadium-containing component and an antimony-containing component supported on the modified support, thereby obtaining the composite oxide catalyst. The roasting process includes a first roasting process and a second roasting process. The temperature of the first roasting process is 200~300℃ and the time of the first roasting process is 1~2h. The temperature of the second roasting process is 500~600℃ and the time of the second roasting process is 3~4h. The protective atmosphere is a mixture of hydrogen and nitrogen or a mixture of hydrogen and helium, with the volume fraction of hydrogen in the protective atmosphere being 5-10%.

5. The preparation method according to claim 4, characterized in that, In step S1, the preparation method of sodium aluminate includes: mixing sodium aluminate solution and surfactant to obtain a first mixed solution, and introducing CO2 into the first mixed solution to carry out a carbonation precipitation reaction to obtain sodium aluminate. The surfactant is selected from at least one of sodium stearate, polysorbate-80, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, hexadecyltrimethylammonium bromide, and polyethylene glycol; And / or, step S1 includes: dispersing sodium aluminum filament and the ammonium salt in a first solvent to carry out the metathesis reaction to obtain the modified support precursor; And / or, the ammonium salt includes at least one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonium oxalate, and ammonium acetate.

6. The preparation method according to claim 4, characterized in that, In step S2, the antimony source is SbOCl, and the preparation method of SbOCl is as follows: electrolytic copper floating anode mud is mixed with hydrochloric acid aqueous solution to obtain Sb-containing... 5+ An acidic leachate is used to reduce antimony powder, which is then added to the acidic leachate to obtain a chlorinated antimony compound. The chlorinated antimony compound is then hydrolyzed to obtain SbOCl. Among them, the antimony powder and the Sb-containing 5+ Sb in acidic leachate 5+ The molar ratio is (1.2~1.5):

1.

7. The preparation method according to claim 4, characterized in that, In step S2, the mass-to-volume ratio of the modified carrier precursor to the impregnation solution is (5~10) g: 1 mL; And / or, the temperature of the impregnation treatment is 55~65℃, and the time of the impregnation treatment is 1~3h.

8. The preparation method according to any one of claims 4 to 7, characterized in that, In step S2, the molar ratio of vanadium in the vanadium source to antimony in the antimony source is 1:(0.1~1.2). And / or, the impregnation solution further includes a complexing agent selected from at least one of oxalic acid, tartaric acid, citric acid, and ethylenediaminetetraacetic acid.

9. The application of the composite oxide catalyst prepared by any one of claims 1 to 3 or by any one of claims 4 to 8 in the oxidative dehydrogenation of propane to propylene.

10. The application according to claim 9, characterized in that, In the propane oxidative dehydrogenation to propylene reaction, the reaction temperature is 500~600℃ and the space velocity is 8000~15000h. -1 The molar ratio of propane to oxygen is 1:(0.5~1), the propane conversion rate is ≥55%, the propylene selectivity is ≥65%, the activity decay rate is ≤5% after 100 hours of continuous operation, and the carbon deposition is ≤2wt%.

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