High-activity cerium-zirconium composite oxide, and preparation method therefor and catalytic application thereof

Abstract

The present invention relates to the technical field of catalysts, and specifically relates to a high-activity cerium-zirconium composite oxide, and a preparation method therefor and a catalytic application thereof. The cerium-zirconium composite oxide has a general chemical formula of CexZryTzO2-αRδ, wherein, in terms of molar content, 0<x≤0.95, 0<y≤0.95, 0<z<0.3, x, y, and z satisfy x+y+z=1, 0≤α≤0.2, and 0≤δ≤0.1. The surface of the cerium-zirconium composite oxide contains adsorbed oxygen species, wherein an XPS peak intensity ratio of adsorbed oxygen to lattice oxygen, i.e., IOads / (IOads+IOlatt), is 0.3-0.8. In the present invention, the generation of more adsorbed oxygen species on the surface of the cerium-zirconium composite oxide is induced by constructing a non-uniform rare earth element doping structure and a grain boundary defect structure, and regulating and controlling the surface acidity and alkalinity. The adsorbed oxygen species on the surface can directly act as active oxygen to participate in a low-temperature catalytic reaction process, thereby promoting the activation of free O2, improving oxygen mobility and low-temperature co-catalytic activity, inhibiting the migration, agglomeration and growth of precious metals at high temperatures, and synergistically improving the high-temperature dispersity and catalytic activity of precious metals.

Description

A highly active cerium-zirconium composite oxide, its preparation method, and its catalytic applications.

[0001] Cross-references

[0002] This application is based on and claims priority to Chinese patent applications No. 202410792127.5, filed on June 19, 2024, and No. 202410792306.9, filed on June 19, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of catalyst technology, specifically to a highly active cerium-zirconium composite oxide, its preparation method, and its catalytic applications. Background Technology

[0004] With the increasing number of cars on the global road, vehicle exhaust pollution has become the primary source of urban air pollution, and the environmental problems caused by vehicle exhaust emissions are becoming increasingly serious. Catalytic converters for vehicle exhaust are an effective solution for purifying vehicle exhaust, and their core component is a three-way catalyst loaded with precious metals. Typically, a three-way catalyst for vehicle exhaust consists of a honeycomb carrier, precious metals, and an active coating. Its lifespan is mainly determined by the active coating material and manufacturing process. Active coating materials include cerium-zirconium composite oxides, with precious metals loaded onto these oxides. In the three-way catalytic reaction, surface-adsorbed oxygen is a reactive species that can directly participate in the reaction; therefore, the amount of surface-adsorbed oxygen has a significant impact on catalytic activity, especially during the low-temperature cold start stage. This is a similar issue in the field of VOC (Volatile Organic Compound) treatment: how to improve the catalytic conversion activity of organic waste gas at low temperatures. Meanwhile, in practical applications, the ambient temperature of the three-way catalyst for automobile exhaust is relatively high, sometimes reaching over 900°C. Due to the migration and coalescence (PMC) of precious metals and the Ostwald ripening effect, thermodynamically unstable precious metals are prone to migrate and agglomerate to form large particles, resulting in a decrease in the utilization rate of precious metals and catalytic activity. Summary of the Invention

[0005] (I) Purpose of the Invention

[0006] The purpose of this invention is to provide a highly active cerium-zirconium composite oxide that can improve low-temperature co-catalytic activity, its preparation method, and its catalytic applications.

[0007] (II) Technical Solution

[0008] To address the above problems, this invention provides a highly active cerium-zirconium composite oxide.

[0009] The cerium-zirconium composite oxide has the general chemical formula Ce. x Zr y T z O 2-α R δ T represents a cation dopant element, and R represents an anion dopant element. In terms of molar content, 0 < x ≤ 0.95, 0 < y ≤ 0.95, 0 < z < 0.3, and x, y, and z satisfy x + y + z = 1, 0 ≤ α ≤ 0.2, and 0 ≤ δ ≤ 0.1.

[0010] The surface of the cerium-zirconium composite oxide contains adsorbed oxygen species, wherein the XPS peak intensity ratio of adsorbed oxygen to lattice oxygen is I. Oads / (I Oads +I Olatt The value is 0.3–0.8. This is achieved by controlling the proportion of adsorbed oxygen species on the surface (I). Oads / (I Oads +I Olatt Within the range of 0.3 to 0.8, it is beneficial to promote the activation of free O2 and improve oxygen mobility, thereby enhancing low-temperature co-catalytic activity. It can also enhance the strong electronic interaction between cerium and zirconium and noble metals, inhibit the high-temperature migration and agglomeration of noble metals, and synergistically improve the high-temperature dispersibility and catalytic activity of noble metals.

[0011] Furthermore, the surface of the cerium-zirconium composite oxide contains one or more combinations of hydroxyl species, alkane groups, and olefinic species.

[0012] In another aspect of the present invention, preferably, the XPS peak intensity ratio I of the adsorbed oxygen to lattice oxygen in the cerium-zirconium composite oxide is... Oads / (I Oads +I Olatt The value is 0.5 to 0.7.

[0013] Based on the O1s orbital spectrum from XPS measurements, two surface oxygen species can be identified through peak fitting: lattice oxygen (denoted as O) at 530.52 and 530.79 eV. latt ) and surface adsorbed oxygen (denoted as O) at 532.60 and 532.37 eV. ads ), whose peak intensities correspond to I respectively. Olatt and I Oads Further convert it into a ratio I Oads / (I Oads +I Olatt ), I Oads / (I Oads +I OlattThe calculation process is simple and can quickly and quantitatively describe the relative content of adsorbed oxygen species on the surface. Furthermore, the cerium-zirconium composite oxide surface contains one or more combinations of hydroxyl, alkane, and olefinic species; the surface hydroxyl species are conducive to the reaction with reactive gas molecules CO and NO. X The formation of intermediate products with O2 promotes O2 dissociation and low-energy-barrier surface elementary reactions, enhancing oxygen storage and co-catalytic activity. Alkyl and olefinic species adsorb onto the surface of cerium-zirconium particles, altering the surface charge and structure, increasing electrostatic repulsion, and reducing particle agglomeration caused by hydrogen bonding and capillary forces. Simultaneously, the hydrophobic long chains of alkane and olefinic groups coil and fold on the particle surface, increasing interparticle repulsion and filling the pores between particles, thus supporting the pore structure and reducing pore collapse after heat treatment.

[0014] The method for statistically analyzing the proportion of grain boundaries is to distinguish different types of grain boundaries based on lattice fringes and spacing in high-magnification transmission TEM images of no less than 50 grains, and then divide the number of grain boundaries constructed by specific crystal planes by the total number of grain boundaries.

[0015] Furthermore, theoretical calculations revealed that, unlike surfaces without grain boundaries, grain boundaries are regions with periodic interruptions, twists, and symmetrical tilts, possessing higher interfacial energy and unbalanced charges. They also contain a large number of vacancy defects and groove defects, resulting in greater oxygen adsorption energy. The oxygen adsorption energy is highest at the ∑

[0110] / (110) grain boundary and second highest at the ∑

[0111] / (111) grain boundary, leading to a higher total oxygen adsorption content on the surface. At the same time, the steric hindrance of grain boundaries is more conducive to enhancing the anchoring effect of cerium and zirconium with noble metals and transition metal active components, thereby improving thermal stability.

[0016] Furthermore, the H2-TPR of the cerium-zirconium composite oxide loaded with noble metals exhibits a dual reduction peak characteristic, with the first peak corresponding to a temperature range of 50-200℃ and the second peak corresponding to a temperature range of 400-600℃.

[0017] In another aspect of the present invention, preferably, the proportion of grain boundary structures constructed by the 110 crystal plane in the cerium-zirconium composite oxide is 0.4 to 0.9; the proportion of grain boundary structures constructed by the 111 crystal plane is 0.1 to 0.4; and the rotation angle between two grains in the grain boundary is between 5° and 60°.

[0018] In another aspect of the present invention, preferably, the proportion of grain boundary structures constructed by the 110 crystal plane in the cerium-zirconium composite oxide is 0.5 to 0.8; the proportion of grain boundary structures constructed by the 111 crystal plane is 0.2 to 0.3; and the rotation angle between two grains in the grain boundary is between 10° and 30°.

[0019] In another aspect of the present invention, preferably, the cation doping element T is one or more of the following: non-cerium rare earth elements, transition metal elements other than zirconium and rare earth elements, alkaline earth metal elements, Al, Si, Ga, Sn, and Bi.

[0020] The non-cerium rare earth elements include La, Pr, Nd, Sm, Eu, Gd, Tm, Yb, or Y;

[0021] The transition metal elements include Ti, Mn, Fe, Co, Ni, Cu, Nb, Hf, W, or Mo;

[0022] The alkaline earth metal elements include Mg, Sr, or Ba.

[0023] In another aspect of the invention, preferably, the anionic dopant R is one or a combination of more than one of C, N, F, S, and P. S and P may be present in sulfate or phosphate form.

[0024] In another aspect of the present invention, preferably, the cerium-zirconium composite oxide structure comprises an elemental gradient distribution structure or a core-shell structure. Further features and advantages of the core-shell structured cerium-zirconium composite oxide can be found in Chinese Patent Application No. CN202010982980.5, filed on September 17, 2020, entitled "A Core-Shell Structured Cerium-Zirconium-Based Composite Oxide and its Preparation Method Thereof," and its entire contents. Further features and advantages of rare-earth zirconium-based oxides with elemental gradient distribution can be found in Chinese Patent Application No. CN 202010982979.2, filed on September 17, 2020, entitled "A Cerium-Zirconium-Based Composite Oxide with Elemental Gradient Distribution and its Preparation Method Thereof," and its entire contents.

[0025] In another aspect of the present invention, preferably, the fresh static oxygen storage capacity of the cerium-zirconium composite oxide is ≥700 μmol O2 / g, and the static oxygen storage capacity after being kept at 1000℃ for 10 h is ≥600 μmol O2 / g.

[0026] Furthermore, the highly active cerium-zirconium composite oxide has the following characteristics:

[0027] After heat treatment in air at 1000℃ for 4 hours, the specific surface area is greater than 60 m2 / g;

[0028] After heat treatment at 1100℃ in air for 4 hours, the specific surface area is greater than 50 m2 / g.

[0029] Furthermore, the intensity ratio I of the characteristic peaks of different crystal planes in the X-ray diffraction of the cerium-zirconium composite oxide 110 / (I 111 +I 100 The value is 0.4-1.5.

[0030] Preferably, the intensity ratio I1 of the characteristic peaks of different crystal planes in the X-ray diffraction of the cerium-zirconium composite oxide is... 10 / (I 111 +I 100 The value is 0.5-1.2.

[0031] The peak intensity value of the

[0110] plane, determined by X-ray diffraction, is set as I. 110 The peak intensity value of the

[0111] surface is set to I. 111 The peak intensity value of the

[0100] plane is set to I. 100 , {I 110 / (I 111 +I 100 The value of x100 is 0.4-1.5, preferably 0.5-1.2. According to theoretical design, oxygen vacancy formation is strongly correlated with the crystal facet type of cerium-zirconium composite oxide. The ease of oxygen vacancy formation is in descending order as

[0110] >

[0111] >

[0100] . Therefore, a higher proportion of

[0110] crystal facets is more conducive to oxygen vacancy generation, thereby improving the static and dynamic oxygen storage and release performance.

[0032] In another aspect of the present invention, preferably, a method for preparing the highly active cerium-zirconium composite oxide as described above includes the following steps:

[0033] According to the general chemical formula, solutions containing cerium, zirconium, cationic dopant element T, and anionic dopant element R are weighed and mixed to obtain a first mixture; the concentration of the cerium, zirconium, cationic dopant element T, and anionic dopant element R is 0.1-5 mol / L, preferably 0.2-2.0 mol / L.

[0034] An alkaline substance is added to the first mixture to carry out a one- or two-step precipitation reaction to obtain a second mixture;

[0035] The second mixture was washed, filtered, and calcined to obtain crude cerium-zirconium composite oxide.

[0036] The crude cerium-zirconium composite oxide is subjected to surface treatment, washing, and drying to obtain a highly active cerium-zirconium composite oxide.

[0037] Surface treatment and calcination can help change the surface atomic structure and promote the formation of surface oxygen vacancies, induce O2 adsorption, and improve the surface adsorbed oxygen content and activity.

[0038] Furthermore, the slurry obtained after sedimentation and washing is subjected to aging treatment, preferably aging treatment under a hydrothermal environment. Hydrothermal aging treatment promotes the formation of oxygen vacancies on the surface, induces O2 adsorption, and increases the surface adsorbed oxygen content and activity.

[0039] Furthermore, through one or two-step precipitation reactions, it is beneficial to change the surface atomic structure and promote the formation of surface oxygen vacancies, induce O2 adsorption, and increase the surface adsorbed oxygen content and activity.

[0040] In another aspect of the present invention, preferably, the reagent used for the surface treatment is one or more of nitric acid, sulfuric acid, sulfate, inorganic phosphoric acid, organic phosphoric acid, inorganic phosphate and organic phosphate;

[0041] The ratio of reagent to rare earth ions used in the surface treatment is 0.2–3.0, and the reagent concentration is 0.5–3.5 mol / L. By controlling the ratio and concentration of the reagent used in the surface treatment, the acidity and alkalinity of the surface sites can be adjusted, thereby increasing the content of adsorbed oxygen species on the surface.

[0042] In another aspect of the present invention, preferably, when adding an alkaline substance to the first mixture to carry out a two-step precipitation reaction, the first mixture is divided into two parts. The first part is added during the first precipitation reaction, and the second part is added during the second precipitation reaction. Here, the first mixture is divided into two parts, and the contents of the two parts can be the same. Alternatively, the first part can include all or part of cerium, all or part of zirconium, all or part of cationic dopant element T, and all or part of anionic dopant element R, and the second part is the remaining cerium, zirconium, T, and R. Alternatively, the first part can include all or part of cerium, all or part of zirconium, and all or part of cationic dopant element T, and the second part includes the remaining cerium, zirconium, and cationic dopant element T.

[0043] The rare earth solution added in the second precipitation reaction is preferably containing two or more of Ce, La, Y, Pr, Nd, Gd, and Eu, and the non-rare earth solution added is preferably containing one or more of the transition metals Zr, Al, Mn, Ni, and Co.

[0044] In another aspect of the present invention, preferably, the second mixture is subjected to hydrothermal treatment before calcination, wherein the hydrothermal treatment temperature is 60-250°C, preferably 100-150°C; the hydrothermal treatment time is 0.5-48h, preferably 1-24h; and the hydrothermal treatment pH value is 3-13, preferably 7-10.

[0045] In another aspect of the present invention, preferably, the pH value during the precipitation reaction is controlled at 4.5 to 14, more preferably 5 to 11; the pH value at the precipitation endpoint is controlled at 8 to 13, more preferably 9 to 11; and the reaction temperature during the precipitation process is 0 to 120°C, more preferably 20 to 80°C.

[0046] In another aspect of the present invention, preferably, the calcination temperature is 500℃~1200℃ and the time is 1h~24h; more preferably, the calcination temperature is 600℃~1150℃ and the time is 3h~12h.

[0047] In another aspect of the present invention, preferably, the solution of the cerium salt and the cation dopant element T is one or a combination of more than one of the following: nitrate solution, chloride solution, sulfate solution, and acetate solution;

[0048] The aqueous solution of zirconium salt is one or a combination of zirconium oxynitrate solution, zirconium oxysulfate solution, zirconium oxychloride solution, and zirconium acetate solution;

[0049] The solution of the anion dopant element R includes one or more of the following: carbonate solution, nitrate solution, fluoride solution, phosphate solution, and sulfate solution.

[0050] In another aspect of the present invention, preferably, the alkaline substance is one or a combination of more than one of sodium hydroxide, ammonium hydroxide, potassium hydroxide, urea, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate.

[0051] In another aspect of the present invention, preferably, the roasting atmosphere includes one or two of air, O2, N2, CO, and CO2.

[0052] Furthermore, a ligand ion may be added to the first mixture, with a molar ratio of ligand ion to zirconium ion of 0.2-3.0, wherein the ligand ion is a sulfate anion. By controlling the proportion of ligand ion added, the acidity / alkalinity of the surface sites can be adjusted, thereby increasing the content of adsorbed oxygen species on the surface.

[0053] Furthermore, a modifier may be added to the second mixture. The modifier may include one or more of the following: anionic surfactants, nonionic surfactants, polyethylene glycol, carboxylic acids and their salts, and carboxymethylated fatty alcohol ethoxylates. By adding the modifier, the number of surface hydroxyl, alkane, and olefin species can be controlled, thereby increasing the content of adsorbed oxygen species on the surface.

[0054] Furthermore, the molar ratio of the ligand ion to the zirconium ion is 0.5-2.5.

[0055] In another aspect of the present invention, preferably, a catalyst comprising the cerium-zirconium composite oxide as described above or comprising the cerium-zirconium composite oxide prepared by the preparation method described above.

[0056] In another aspect, preferably, the application of the cerium-zirconium composite oxide as described above, the cerium-zirconium composite oxide prepared by the preparation method as described above, or the catalyst as described above in the fields of motor vehicle exhaust purification, natural gas catalytic combustion, organic waste gas purification, and industrial flue gas denitrification treatment.

[0057] Furthermore, the cerium-zirconium composite oxide is further combined with noble metals and / or transition metals to prepare a catalyst, and the preparation steps are as follows:

[0058] S1. Mix the cerium-zirconium composite oxide with a liquid salt of a noble metal and / or transition metal until homogeneous;

[0059] S2. The product obtained in step S1 is dried and subjected to one or two heat treatments.

[0060] S3. The product obtained in step S2 is calcined once or multiple times under an oxidizing or reducing atmosphere to obtain a cerium-zirconium supported noble metal and / or transition metal catalyst.

[0061] Furthermore, the liquid salts of the noble metals and / or transition metals include one or more of the following: molten salts or aqueous solutions of chlorides, nitrates, acetates, and citrates.

[0062] Furthermore, the oxidizing atmosphere includes one or more of pure oxygen, air, and water vapor, and the reducing atmosphere includes one or more of CO and H2.

[0063] Furthermore, after undergoing a high-temperature aging treatment at 1000℃ for 4 hours, the size of the precious metal is less than 5nm, preferably less than 3nm.

[0064] Furthermore, after undergoing a high-temperature aging treatment at 1000℃ for 4 hours, the catalyst exhibits a T50 ignition temperature ≤200℃ for CO, ≤250℃ for NO, and ≤250℃ for HC. Preferably, after the same treatment, the catalyst exhibits a T50 ignition temperature ≤150℃ for CO, ≤200℃ for NO, and ≤200℃ for HC.

[0065] Furthermore, this catalyst exhibits excellent low-temperature catalytic activity and stability for the treatment of volatile organic compounds (VOCs). By modulating the doping structure, grain boundary structure, and surface acidity / basicity of the cerium-zirconium composite oxide, the surface adsorbed oxygen content is increased, promoting the low-temperature catalytic conversion of VOCs and improving resistance to poisoning.

[0066] Furthermore, the liquid salts of the noble metals and / or transition metals include one or more combinations of molten salts or aqueous solutions of chlorides, nitrates, acetates, and citrates. (III) Beneficial Effects

[0067] The above-described technical solution of the present invention has the following beneficial technical effects:

[0068] This invention constructs a non-uniform rare earth element doping structure, a grain boundary defect structure, and a surface acid-base regulation through stepwise precipitation control and surface acid-base regulation. This induces the generation of more adsorbed oxygen species on the cerium-zirconium surface. These adsorbed oxygen species can directly participate in low-temperature catalytic reaction processes as active oxygen, promoting the activation of free O2 and increasing oxygen mobility, thereby improving low-temperature co-catalytic activity. Furthermore, the adsorbed oxygen can regulate the valence state of noble metals, generating strong electron interactions that enhance the interaction between cerium-zirconium and noble metals, anchoring the noble metals, inhibiting their high-temperature migration and agglomeration, and synergistically improving their high-temperature dispersion and catalytic activity. This meets the requirements for catalysts used in vehicle exhaust purification, VOC treatment, or catalytic combustion. Attached Figure Description

[0069] Figure 1 is an overall flowchart of an embodiment of the present invention. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0071] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0072] In the description of this invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0073] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0074] Comparative Example 1:

[0075] According to the molar distribution of cerium-zirconium composite oxide Ce 0.11 Zr 0.83 La 0.02 Nd 0.04Prepare 250 mL of a mixture of Ce(NO3)3, ZrO(NO3)2, La(NO3)3, and Nd(NO3)3 with a total metal ion molar concentration of 1.5 mol / L using O2. Mix this mixture with a 2.5 mol / L ammonia solution to carry out a precipitation reaction at a temperature of 20-50℃. The pH value during the precipitation process is 10±2, and the pH value at the precipitation endpoint is 11±1. After filtering and washing, the precipitate is processed to obtain a precursor. The precursor is then dried at 110℃ for 10 hours and calcined at 850℃ for 5 hours to obtain a fresh sample of cerium-zirconium composite oxide. Further calcination at 1000℃ for 10 hours yields an aged sample of cerium-zirconium composite oxide.

[0076] A certain volume of palladium nitrate and platinum nitrate solution was prepared with the above Ce loading of 0.9% palladium and 0.3% platinum. 0.11 Zr 0.83 La 0.02 Nd 0.04 The fresh O2 powder sample was mixed evenly, and the sample was dried at 110℃ for 4 hours. Then, the dried sample was calcined at 600℃ for 5 hours in air to obtain a fresh sample of cerium-zirconium supported noble metal catalyst. Further calcination at 1000℃ for 4 hours yielded an aged sample of the cerium-zirconium supported noble metal catalyst.

[0077] Comparative Examples 2-4:

[0078] Unless otherwise indicated below, the same procedure as Comparative Example 1 was followed. The components and process parameters of the Comparative Example are shown in Table 1.

[0079] Example 1

[0080] This embodiment relates to Ce in terms of oxide mole fraction. 0.52 Zr 0.36 La 0.05 Y 0.07 Preparation of O2.

[0081] Two mixed chloride salt solutions were prepared in advance: solution A, containing cerium, zirconium, lanthanum, and 30 mol% yttrium; and solution B, containing the remaining yttrium from the designed proportions. Solution A was added to an appropriate amount of sodium hydroxide to precipitate. After adding solution A, solution B was added, along with sodium hydroxide solution, to precipitate again, maintaining the pH at 8 ± 2. The precipitate was filtered and washed to obtain a composite hydroxide precipitate containing cerium, zirconium, or cerium, zirconium, and optionally one or more rare earth salts (excluding Ce) and non-rare earth metal salts (excluding zirconium). The precipitate was then slurried and placed in an autoclave, where it was heated to 120°C for 2 hours. A modifier was added, and the mixture was stirred for a period before filtration. The resulting filter cake was calcined at 850°C for 5 hours to obtain a fresh cerium-zirconium composite oxide sample, which was further calcined at 1000°C for 10 hours to obtain an aged cerium-zirconium composite oxide sample.

[0082] A certain volume of palladium nitrate and platinum nitrate solution was prepared with the above Ce loading of 0.9% palladium and 0.3% platinum. 0.52 Zr 0.36 La 0.05 Y 0.07 The fresh O2 powder sample was mixed evenly, and the sample was dried at 110℃ for 4 hours. Then, the dried sample was calcined at 600℃ for 5 hours in air to obtain a fresh sample of cerium-zirconium supported noble metal catalyst. Further calcination at 1000℃ for 4 hours yielded an aged sample of the cerium-zirconium supported noble metal catalyst.

[0083] Example 2-44:

[0084] Unless otherwise indicated below, the same procedures as in Example 1 were followed. Specific components and process parameters for the examples are shown in Tables 1 and 2. The surface reactive oxygen species characteristic values ​​and performance test results for the comparative examples and examples are shown in Table 3.

[0085] Table 1. Specific components of comparative examples and embodiments.

[0086] Table 2. Specific process parameters for comparative examples and embodiments.

[0087] Table 3 Performance of Comparative Examples and Embodiments

[0088] *CO and NO in the table above XT50 (°C) for CH represents the catalytic performance test results of the cerium-zirconium composite oxide supported noble metal catalyst after aging at 1000°C for 4 hours; the others represent the test results of the cerium-zirconium composite oxide.

[0089] Characteristic value I of adsorbed oxygen ratio in Examples 1-44 Oads / (I Oads +I Olatt The values ​​were all between 0.3 and 0.8. The oxygen storage of fresh samples in Examples 1-44 and the oxygen storage at 1000℃ for 10h were all higher than those in Comparative Examples 1-4. The performance of CO / T50 (℃) (aged at 1000℃ for 4h), NOx / T50 (℃) (aged at 1000℃ for 4h), and CH / T50 (℃) (aged at 1000℃ for 4h) in Examples 1-44 were all better than those in Comparative Examples 1-4.

[0090] Furthermore, the intensity ratio of characteristic peaks on different crystal planes in the X-ray diffraction of cerium-zirconium composite oxides is I. 110 / (I 111 +I 100 The ratio of the characteristic peak intensities of different crystal planes in the X-ray diffraction of the cerium-zirconium composite oxide is 0.4-1.5. Preferably, the ratio of the characteristic peak intensities of different crystal planes in the X-ray diffraction of the cerium-zirconium composite oxide is I. 110 / (I 111 +I 100 The value is 0.5-1.2.

[0091] The peak intensity value of the

[0110] plane, determined by X-ray diffraction, is set as I. 110 The peak intensity value of the

[0111] surface is set to I. 111 The peak intensity value of the

[0100] plane is set to I. 100 , {I 110 / (I 111 +I 100 The value of x100 is 0.4-1.5, preferably 0.5-1.2. According to theoretical design, oxygen vacancy formation is strongly correlated with the crystal facet type of cerium-zirconium composite oxide. The ease of oxygen vacancy formation is in descending order as

[0110] >

[0111] >

[0100] . Therefore, a higher proportion of

[0110] crystal facets is more conducive to oxygen vacancy generation, thereby improving the static and dynamic oxygen storage and release performance.

[0092] By controlling the stepwise precipitation preparation method, hydrothermal crystallization process, and calcination atmosphere of cerium-zirconium composite oxides, the goal of crystal facet selectivity can be achieved, thereby improving... <110> The proportion of crystal faces promotes the formation of surface oxygen vacancies, resulting in more oxygen vacancy defects. The unsaturated coordination environment of these oxygen vacancies enhances the static and dynamic oxygen storage and release performance of cerium zirconium. The generation of these oxygen vacancies is conducive to enhancing the strong interaction between cerium zirconium and noble metals, acting as an anchor for noble metals, inhibiting the high-temperature migration and agglomeration growth of noble metals, and simultaneously utilizing oxygen vacancies to synergistically enhance the catalytic activity of noble metals, so as to meet the application requirements of catalysts for vehicle exhaust purification, VOC treatment, or catalytic combustion.

[0093] Comparative Example 5

[0094] According to the molar distribution of Ce in cerium-zirconium based composite oxide 0.55 Zr 0.35 La 0.05 Y 0.05 O 1.98 Prepare 250 mL of a mixed solution of Ce(NO3)3, ZrO(NO3)2, La(NO3)3, and Y(NO3)3 with a total metal ion molar concentration of 1.5 mol / L. Mix this mixed solution with a 2.5 mol / L ammonia solution to carry out a precipitation reaction at a temperature of 25-50℃. The pH value during the precipitation process is 9±3, and the pH value at the precipitation endpoint is 10±2. After filtering, washing, aging, and modification, the precipitate is subjected to post-treatment to obtain a precursor. The precursor is then dried at 110℃ for 10 hours and calcined at 850℃ for 5 hours to obtain a fresh sample of cerium-zirconium-based composite oxide. Further calcination at 1000℃ for 10 hours yields an aged sample of cerium-zirconium composite oxide.

[0095] Comparative Examples 6-8:

[0096] Unless otherwise indicated below, the same procedure as in Comparative Example 5 was followed. The components and process parameters of the Comparative Example are shown in Table 4.

[0097] Example 45

[0098] This embodiment relates to Ce in terms of oxide mole fraction. 0.55 Zr 0.35 La 0.05 Y 0.05 O 1.98 Preparation of .

[0099] Two mixed chloride salt solutions were prepared in advance: solution A, containing a total of 100 mol% cerium, 100 mol% zirconium, 100 mol% lanthanum, and 8 mol% yttrium; and solution B, containing the remaining yttrium chloride from the designed formulation. Solution A was added to an appropriate amount of sodium hydroxide to precipitate the chloride. After adding solution A, solution B was added, along with sodium hydroxide solution, to precipitate the chloride while maintaining the pH at 9 ± 3. The precipitate was filtered and washed to obtain a composite hydroxide precipitate containing cerium, zirconium, lanthanum, and yttrium. The precipitate was then slurried and placed in an autoclave, where it was heated to 150°C for 5 hours. A modifier was added, and the mixture was stirred for a period of time before filtration. The resulting filter cake was calcined at 850°C for 5 hours to obtain a fresh sample of cerium-zirconium-based composite oxide, which was further calcined at 1000°C for 10 hours to obtain an aged sample of cerium-zirconium-based composite oxide.

[0100] Examples 46-54: Unless otherwise indicated below, they are carried out in the same manner as Example 45. Specific parameters for the examples are shown in Table 4.

[0101] Table 4. Process parameters for Comparative Examples 5-8 and Examples 45-54

[0102] Table 5 Performance parameters of Comparative Examples 5-8 and Examples 45-54

[0103] The peak intensity value of the

[0110] plane, determined by X-ray diffraction, is set as I. 110 The peak intensity value of the

[0111] surface is set to I. 111 The peak intensity value of the

[0100] plane is set to I. 100 The intensity ratio of characteristic peaks on different crystal planes of cerium-zirconium composite oxides in X-ray diffraction of Examples 45-54 110 / (I 111 +I 100 The values ​​were all between 0.4 and 1.5, which was higher than that of Comparative Examples 5-8. The fresh static oxygen storage capacity of the cerium-zirconium composite oxides in Examples 45-54 was ≥700 μmol O2 / g, and the static oxygen storage capacity after holding at 1000℃ for 10h was ≥600 μmol O2 / g, which were both better than those of the cerium-zirconium composite oxides in Comparative Examples 5-8.

[0104] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

[0105] The present invention has been described above with reference to embodiments thereof. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

[0106] Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit and scope of the invention.

[0107] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A highly active cerium-zirconium composite oxide, characterized in that, The cerium-zirconium composite oxide has the general chemical formula Ce. x Zr y T z O 2-α R δ T represents a cation dopant, and R represents an anion dopant. Based on molar content, 0 < x ≤ 0.95, 0 < y ≤ 0.95, 0 < z < 0.3, and x, y, and z satisfy x + y + z = 1, 0 ≤ α ≤ 0.2, and 0 ≤ δ ≤ 0.

1. The surface of the cerium-zirconium composite oxide contains adsorbed oxygen species, wherein the XPS peak intensity ratio of adsorbed oxygen to lattice oxygen is I. Oads / (I Oads +I Olatt The value ranges from 0.3 to 0.

8.

2. The cerium-zirconium composite oxide according to claim 1, characterized in that, The XPS peak intensity ratio I of the adsorbed oxygen to lattice oxygen in the cerium-zirconium composite oxide Oads / (I Oads +I Olatt The value is 0.5 to 0.

7.

3. The cerium-zirconium composite oxide according to claim 1, characterized in that, The proportion of grain boundary structures formed by the 110 crystal plane in the cerium-zirconium composite oxide is 0.4 to 0.9; the proportion of grain boundary structures formed by the 111 crystal plane is 0.1 to 0.4; and the rotation angle between two grains in the grain boundary is between 5° and 60°.

4. The cerium-zirconium composite oxide according to claim 3, characterized in that, The proportion of grain boundary structures constructed by the 110 crystal plane in the cerium-zirconium composite oxide is 0.5–0.8%; the proportion of grain boundary structures constructed by the 111 crystal plane is 0.2–0.3%; and the rotation angle between two grains in the grain boundary is between 10° and 30°.

5. The cerium-zirconium composite oxide according to any one of claims 1-4, characterized in that, The cation doping element T is one or more of the following: non-cerium rare earth elements, transition metal elements other than zirconium and rare earth elements, alkaline earth metal elements, Al, Si, Ga, Sn, and Bi. The non-cerium rare earth elements include La, Pr, Nd, Sm, Eu, Gd, Tm, Yb, or Y; The transition metal elements include Ti, Mn, Fe, Co, Ni, Cu, Nb, Hf, W, or Mo; The alkaline earth metal elements include Mg, Sr, or Ba.

6. The cerium-zirconium composite oxide according to any one of claims 1-4, characterized in that, The anion doping element R is one or more of C, N, F, S and P.

7. The cerium-zirconium composite oxide according to any one of claims 1-4, characterized in that, The cerium-zirconium composite oxide structure includes an elemental gradient distribution structure or a core-shell structure.

8. The cerium-zirconium composite oxide according to any one of claims 1-4, characterized in that, The cerium-zirconium composite oxide has a fresh static oxygen storage capacity of ≥700 μmol O2 / g, and a static oxygen storage capacity of ≥600 μmol O2 / g after being kept at 1000℃ for 10h.

9. The cerium-zirconium composite oxide according to any one of claims 1-4, characterized in that, The intensity ratio of different crystal plane characteristic peaks in the X-ray diffraction of the cerium-zirconium composite oxide is I 110 / (I 111 +I 100 The value is 0.4-1.

5.

10. The cerium-zirconium composite oxide according to claim 9, characterized in that, The intensity ratio of different crystal plane characteristic peaks in the X-ray diffraction of the cerium-zirconium composite oxide is I 110 / (I 111 +I 100 The value is 0.5-1.

2.

11. A method for preparing the highly active cerium-zirconium composite oxide as described in any one of claims 1-10, characterized in that, Includes the following steps: According to the general chemical formula, solutions containing cerium, zirconium, cation dopant element T and anion dopant element R are weighed and mixed to obtain the first mixture; An alkaline substance is added to the first mixture to carry out a one- or two-step precipitation reaction to obtain a second mixture; The second mixture was washed, filtered, and calcined to obtain crude cerium-zirconium composite oxide. The crude cerium-zirconium composite oxide is subjected to surface treatment, washing, and drying to obtain a highly active cerium-zirconium composite oxide.

12. The method according to claim 11, characterized in that, The reagents used in the surface treatment are one or more of nitric acid, sulfuric acid, sulfate, inorganic phosphoric acid, organic phosphoric acid, inorganic phosphate and organic phosphate; The molar ratio of the reagent to rare earth ions used in the surface treatment is 0.2 to 3.0, and the concentration of the reagent is 0.5 to 3.5 mol / L.

13. The method according to claim 11, characterized in that, When adding an alkaline substance to the first mixture to carry out a two-step precipitation reaction, the first mixture is divided into two parts. The first part is added during the first step of the precipitation reaction, and the second part is added during the second step of the precipitation reaction.

14. The method according to claim 11, characterized in that, The second mixture is subjected to hydrothermal treatment before calcination. The hydrothermal treatment temperature is 60-250℃, preferably 100-150℃; the hydrothermal treatment time is 0.5-48h, preferably 1-24h; and the hydrothermal treatment pH value is 3-13, preferably 7-10.

15. The method according to claim 11, characterized in that, The pH value during the precipitation reaction is controlled at 4.5-14, preferably 5-11; the pH value at the precipitation endpoint is controlled at 8-13, preferably 9-11; the reaction temperature during the precipitation process is 0-120℃, preferably 20-80℃.

16. The method according to claim 11, characterized in that, The roasting temperature is 500℃~1200℃, and the time is 1h~24h; preferably, the roasting temperature is 600℃~1150℃, and the time is 3h~12h.

17. The method according to claim 11, characterized in that, The solution of cerium salt and cation dopant element T is one or a combination of nitrate solution, chloride solution, sulfate solution, and acetate solution; The aqueous solution of zirconium salt is one or a combination of zirconium oxynitrate solution, zirconium oxysulfate solution, zirconium oxychloride solution, and zirconium acetate solution; The solution of the anion dopant element R includes one or more of the following: carbonate solution, nitrate solution, fluoride solution, phosphate solution, and sulfate solution.

18. The method according to claim 11, characterized in that, The alkaline substance is one or a combination of more than one of sodium hydroxide, ammonium hydroxide, potassium hydroxide, urea, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate.

19. The method according to claim 11, characterized in that, The roasting atmosphere includes one or two of air, O2, N2, CO, and CO2.

20. A catalyst, characterized in that, The catalyst comprises cerium-zirconium composite oxide as described in any one of claims 1-10 or cerium-zirconium composite oxide prepared by the preparation method as described in any one of claims 11-19.

21. The application of a cerium-zirconium composite oxide as described in claims 1-10, a cerium-zirconium composite oxide prepared by the preparation method according to any one of claims 11-19, or a catalyst as described in claim 20 in the fields of motor vehicle exhaust purification, natural gas catalytic combustion, organic waste gas purification, and industrial flue gas denitrification treatment.

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