A ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides, and a preparation method and application thereof

Abstract

The present application relates to a kind of ruthenium cerium-based catalysts that can be passively adsorbed nitrogen oxide and its preparation method and application, the ruthenium cerium-based catalyst with modified nanometer cerium dioxide as carrier, its surface is loaded with 0.2~5.0 wt% ruthenium as active component, the modified nanometer cerium dioxide is nanometer cerium dioxide modified by modified metal element.The present application is by dissolving cerium salt and modified metal salt in water, through precipitation reaction, drying, calcination treatment, obtain modified nanometer cerium dioxide, again by noble metal ruthenium impregnation or deposition precipitation on the surface of modified cerium dioxide to obtain the ruthenium cerium-based catalyst.Compared with prior art, the catalyst of the present application shows excellent adsorption-desorption capacity and desorption efficiency at low temperature, has ideal adsorption-desorption temperature window, can efficiently adsorb and store nitrogen oxide in the exhaust gas of motor vehicle cold start stage;And preparation process is simple, raw material cost is low, easy to industrial production, has broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of nitrogen oxide adsorption and storage technology, and in particular to a ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NO) x NO is a significant precursor to photochemical smog, acid rain, and ozone layer depletion. Motor vehicle exhaust is a major source of NO. x The main source, of which diesel vehicles release NO x NH3 accounts for more than 80% of total vehicle emissions, and selective catalytic reduction (NH3-SCR) is the most effective NO reduction agent for diesel engines. x Emission control technologies have been developed and widely commercialized. However, due to limitations in catalyst SCR performance and urea decomposition temperature, current SCR operating temperatures are generally between 250 and 400 °C, which is insufficient to meet the exhaust gas purification requirements during the cold start phase (≤150 °C). Therefore, to meet more stringent emission standards, it is necessary to develop efficient low-temperature denitrification technologies. Based on existing technologies, this paper proposes developing efficient low-temperature SCR technology to further reduce the SCR operating temperature and simultaneously introduce PNA (Passive Noise Reduction). x Absorber technology is used to adsorb and store NO during the cold start phase. x NO is released when the exhaust gas temperature reaches the SCR operating temperature. x Then, through a highly efficient SCR catalyst, NO is finally achieved. x The purification process, namely PNA-SCR technology, is used to meet the NO requirements during the cold start phase of diesel engines. x Emissions.

[0003] Due to the increasing application of PNA technology in cold start-up denitrification processes, related research is on the subject. For practical applications, PNA should possess excellent NO emission characteristics. x Low-temperature storage capacity and capture efficiency, as well as suitable NO x Desorption temperature window to ensure the release of NO x It can be efficiently removed when passing through downstream catalysts. Due to the strong interaction between noble metals and cerium dioxide supports, cerium dioxide-supported noble metal PNA materials exhibit good stability and sufficient adsorption sites. Cerium dioxide, with its abundant oxygen vacancies and noble metal clusters, can utilize its surface-generated localized 4f electrons as an "electron memory," dynamically regulating electron transfer between the catalyst and adsorbate, effectively promoting the adsorption and activation of O2 and NO molecules. This provides theoretical guidance for the design and fabrication of highly efficient cerium dioxide-based PNA materials.

[0004] CN113404573A discloses the application of a supported palladium-cerium-based catalyst for low-temperature storage of nitrogen oxides in automotive cold start reactions, wherein the catalyst has a specific surface area of ​​100-200 m². 2 / g of cerium dioxide is used as a support for palladium, and the palladium loading in the catalyst is 0.5~4 wt%. When nitrogen oxides are stored at low temperatures, the nitrogen oxides are stored as nitrite species on the Pd-O-Ce species on the surface of the supported palladium-cerium catalyst. However, the desorption efficiency of the catalyst is less than 90% at 350 °C, and it requires the support of the noble metal palladium, resulting in high preparation costs, which are 3 to 4 times that of ruthenium.

[0005] Currently, low-temperature storage technology still has limitations in treating NO in automobile exhaust. x The low storage capacity and desorption efficiency of nitrogen oxides present challenges, making the development of a catalyst with high adsorption and desorption efficiency crucial. Furthermore, key issues such as the impact mechanism of the interaction between noble metals and the cerium dioxide support on the PNA technology storage process also urgently need to be addressed. Summary of the Invention

[0006] The purpose of this invention is to provide a ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides, its preparation method, and its application. The catalyst exhibits excellent adsorption-desorption capacity and desorption efficiency under low-temperature conditions, and has an ideal adsorption-desorption temperature window, making it suitable for denitrification treatment of exhaust gas from mobile pollution sources. The catalyst also has significant advantages such as simple preparation process, low raw material cost, and ease of large-scale industrial production, and has broad application prospects in the field of motor vehicle exhaust purification.

[0007] The objective of this invention can be achieved through the following technical solutions: One objective of this invention is to provide a ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides. The ruthenium-cerium-based catalyst uses modified nano-cerium dioxide as a support, and the surface of the modified nano-cerium dioxide is loaded with ruthenium as an active component. The modified nano-cerium dioxide is nano-cerium dioxide obtained by modification with modified metal elements.

[0008] More preferably, the modification refers to the incorporation of a modified metal into the lattice of nano-cerium dioxide to form a composite nano-oxide with cerium dioxide.

[0009] Preferably, in the ruthenium-cerium-based catalyst, the content of ruthenium is 0.2~5.0 wt%, and the content of modified metal is 1wt%~20 wt%.

[0010] Preferably, the modified metal is any one of manganese, cobalt, nickel, copper, zinc, aluminum, zirconium, and niobium.

[0011] Preferably, the modified nano-cerium dioxide has a particle size of less than 50 nm and a specific surface area of ​​50~200 m². 2 / g.

[0012] Preferably, the ruthenium is loaded onto the surface of modified nano-cerium dioxide in an atomically dispersed state.

[0013] More preferably, the ruthenium exists in the form of ruthenium oxide.

[0014] More preferably, the ruthenium content in the ruthenium-cerium-based catalyst includes 0.2 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, and 2.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0015] In this invention, the catalyst support is a modified cerium dioxide-based nano-oxide. Compared with ordinary cerium dioxide, nano-modified cerium dioxide has a larger specific surface area and a higher oxygen defect concentration, making it easier for noble metals to be dispersed at the atomic level on the surface. This reduces the deactivation of noble metal elements due to agglomeration, thereby making the catalyst more capable of adsorbing nitrogen oxides and enabling rapid desorption at a suitable temperature.

[0016] The second objective of this invention is to provide a method for preparing the ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides, comprising the following steps: S1: Cerium salt and modified metal salt are dissolved in water, a precipitant is added to carry out a precipitation reaction, and after the reaction is completed, the mixture is successively filtered, dried and calcined to obtain modified nano-cerium dioxide. S2: Prepare a ruthenium salt solution, and load the ruthenium active component onto the surface of modified nano-cerium dioxide by impregnation or deposition precipitation method, followed by drying and calcination treatment to obtain the ruthenium-cerium-based catalyst.

[0017] Preferably, in step S1, the cerium salt includes cerium nitrate, and the modified metal salt is any one of manganese nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, aluminum nitrate, and zirconium nitrate.

[0018] Preferably, in step S1, the molar ratio of the cerium salt to the modified metal salt is 7:3 to 99:1.

[0019] Preferably, in step S1, the precipitation reaction refers to the reaction being stirred at 20~60 ℃ for 2~10 h after adding the precipitant, followed by aging for 1~24 h.

[0020] More preferably, in step S1, the amount of precipitant added (based on the final concentration in the reaction system) is 3 mol / L to 11 mol / L.

[0021] More preferably, in step S1, the precipitant comprises an aqueous ammonia solution.

[0022] More preferably, in step S1, the pH of the precipitation reaction is 8-14.

[0023] Preferably, in step S1, the drying temperature is 60~100 ℃ and the drying time is 12~48 h.

[0024] Preferably, in step S1, the calcination temperature is 300~800 ℃ and the calcination time is 3~6 h.

[0025] Preferably, in step S2, the ruthenium salt in the ruthenium salt solution is any one of ruthenium trichloride, ruthenium sulfate, and ruthenium nitrate.

[0026] Preferably, in step S2, the mass ratio of the ruthenium salt to the modified nano-cerium dioxide is 0.2~5.0 wt%.

[0027] More preferably, in step S2, the ruthenium salt solution is a ruthenium trichloride-hydrochloric acid solution or a ruthenium nitrate-nitric acid solution.

[0028] Preferably, in step S2, the precipitant used in the precipitation method is any one or more of sodium carbonate, ammonium carbonate, urea, and ammonia solution, and the pH of the precipitation reaction is 1 to 10.

[0029] More preferably, in step S2, the specific steps of the deposition precipitation method are as follows: add ruthenium salt solution to the modified nano-cerium dioxide dispersion, then add precipitant, and stir the reaction at 20~60 ℃ for 2~10 h, followed by aging for 1~24 h.

[0030] More preferably, in step S2, the modified nano-cerium dioxide from step S1 is dispersed in deionized water to obtain a modified nano-cerium dioxide dispersion, wherein the concentration of the modified nano-cerium dioxide dispersion is 10 g / L to 100 g / L.

[0031] More preferably, in step S2, the dosage of the precipitant is 1 mol / L to 10 mol / L.

[0032] Preferably, in step S2, ruthenium salt solution is added to the modified nano-cerium dioxide dispersion by impregnation, and the mixture is stirred and reacted at 20~70 °C for 1~20 h, and then rotary evaporation is carried out in a rotary evaporator at 40~60 °C.

[0033] More preferably, in step S2, the modified nano-cerium dioxide from step S1 is dispersed in deionized water to obtain a modified nano-cerium dioxide dispersion, wherein the concentration of the modified nano-cerium dioxide dispersion is 5 g / L to 20 g / L.

[0034] Preferably, in step S2, the drying temperature is 60~110 ℃ and the drying time is 12~48 h.

[0035] Preferably, in step S2, the calcination temperature is 300~900 ℃ and the calcination time is 3~8 h.

[0036] The preparation method described in this invention is simple to operate. Modified nano-cerium dioxide can be obtained through precipitation reaction, drying and calcination treatment. The obtained nano-cerium dioxide is then formulated into a dispersion, and the noble metal ruthenium is impregnated or deposited on the surface of the modified cerium dioxide. After drying and calcination treatment, a catalyst with good adsorption and desorption properties and an ideal adsorption and desorption temperature window can be obtained.

[0037] The third objective of this invention is to provide an application of the ruthenium-cerium-based catalyst that can passively adsorb nitrogen oxides in the low-temperature storage reaction of nitrogen oxides during the cold start phase of automobiles, wherein the ruthenium-cerium-based catalyst is used to passively adsorb nitrogen oxides in motor vehicle exhaust.

[0038] Preferably, the reaction temperature during the cold start phase of the vehicle is 80~200 ℃, and the reaction atmosphere is NO. x A mixture of O2, H2O, CO2, CO and N2 is reacted at atmospheric pressure with a volume hourly space velocity of 150,000~250,000 / h.

[0039] More preferably, the NO x The concentration of H2O is 200 ppm, the volume fraction of O2 is 10%, the volume fraction of H2O is 2%, and the volume fraction of CO2 is 5%.

[0040] More preferably, the ruthenium-cerium-based catalyst has an adsorption capacity and desorption capacity of 150~300 μmol / g, an adsorption temperature window of 60~100 ℃, a desorption temperature window of 150~300 ℃, and a desorption efficiency of over 95%.

[0041] More preferably, the desorption temperature window of the ruthenium-cerium-based catalyst is 200~300 °C.

[0042] The catalyst described in this invention is used in the passive adsorption of nitrogen oxides at low temperatures. The ruthenium-cerium-based composite oxide can effectively adsorb nitrogen oxides and desorb them at a suitable temperature, exhibiting excellent adsorption and desorption performance.

[0043] In summary, this invention provides a ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides, its preparation method, and its application. The ruthenium-cerium-based catalyst is a ruthenium-cerium-based composite oxide with 0.2-5.0 wt% ruthenium supported on a modified nano-cerium dioxide carrier. This catalyst exhibits excellent adsorption / desorption capacity, adsorption / desorption efficiency, and hydrothermal stability, enabling efficient adsorption and storage of nitrogen oxides in vehicle exhaust during cold starts. Furthermore, the preparation process of this ruthenium-cerium-based catalyst is simple, the raw material cost is low, and it is easy to mass-produce industrially, showing broad application prospects in the field of vehicle exhaust purification.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The present invention provides a ruthenium-cerium-based catalyst that can passively adsorb nitrogen oxides. The catalyst uses modified nano-cerium dioxide as a support and noble metal ruthenium as an active component. It exhibits excellent adsorption-desorption capacity and desorption efficiency under low temperature conditions and has an ideal adsorption-desorption temperature window.

[0046] (2) This invention is the first to apply ruthenium-cerium-based materials doped with transition metals (such as Mn, Co, Ni, etc.) to the field of nitrogen oxide purification during cold start of motor vehicles. In view of the shortcomings of existing passive adsorption (PNA) materials such as weak low-temperature adsorption capacity, excessively high desorption temperature of alkali metal-based materials, and high cost of precious metals, through the synergistic design of carrier modification and active component regulation, efficient adsorption of nitrogen oxides in the low temperature range of 80~200℃ and rapid desorption at suitable temperature are achieved, which effectively matches the emission control requirements of motor vehicle cold start stage.

[0047] (3) The present invention uses modified nano-cerium dioxide as a catalyst support. Compared with ordinary cerium dioxide, nano-modified cerium dioxide has a larger specific surface area and a higher oxygen defect concentration. The high specific surface area provides abundant dispersion sites for the noble metal active components, which can effectively inhibit the deactivation of ruthenium due to agglomeration; while the high concentration of oxygen defects can serve as active sites to enhance the adsorption and activation process of nitrogen oxides, significantly improving the adsorption capacity and reactivity of the material.

[0048] (4) This invention induces ruthenium to be highly dispersed on the carrier surface in the form of single atoms or sub-nanometer clusters by using extremely low ruthenium loading (0.2~5.0wt%). At the same time, combined with the multivalent state characteristics of transition metals, a unique oxygen vacancy "electron pump" structure is constructed on the surface of cerium dioxide. This structure can regulate the adsorption and desorption behavior of nitrogen oxides through electronic effects, which not only overcomes the problem of weak low-temperature adsorption of traditional PNA materials, but also avoids the defect of excessively high desorption temperature of alkali metal-based materials. At the same time, it significantly reduces the amount of precious metals used, and significantly improves the cost performance and industrial application potential of the material.

[0049] (5) The preparation method of the catalyst described in this invention is simple, the raw materials are cheap and readily available, no complex equipment or harsh reaction conditions are required, and it is easy to realize large-scale industrial production. It has outstanding substantive features and broad application prospects.

[0050] (6) The catalyst described in this invention has a desorption temperature window of 150~300℃, a desorption efficiency of over 95%, and an adsorption and desorption capacity of 150~300μmol / g, which solves the defects of traditional passive adsorption materials such as excessively high desorption temperature, insufficient desorption efficiency, or low adsorption capacity. Attached Figure Description

[0051] Figure 1 This is a graph showing the adsorption and desorption performance of nitrogen oxides by the passive adsorption catalyst for nitrogen oxides in Example 1.

[0052] Figure 2 This is a bar chart showing the adsorption and desorption amounts of nitrogen oxides by the passive adsorption catalyst for nitrogen oxides in Example 2.

[0053] Figure 3 This is a bar chart showing the adsorption and desorption amounts of nitrogen oxides by the passive adsorption catalyst in Comparative Example 1.

[0054] Figure 4 The data are from the hydrogen temperature programmed reduction (H2-TPR) of NbCeO2 and pure CeO2 in Example 5.

[0055] Figure 5 The image shows the X-ray diffraction (XRD) pattern of the nitrogen oxide passive adsorption catalyst in Example 1. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0057] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0058] Example 1 This embodiment provides a method for preparing a ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides, the preparation method comprising the following steps: (1) Using cerium nitrate hexahydrate and manganese nitrate as precursors (molar ratio 9:1), a certain amount of deionized water was added to dissolve them. Specifically, 3.9 g of cerium nitrate hexahydrate and 0.18 g of manganese nitrate were added to 100 mL of deionized water, and a precipitation reaction was carried out at 25 °C. After stirring, aging and filtration, manganese-modified nano-cerium dioxide precursor was obtained. The precipitant used in the precipitation reaction was 20 mL of 5 wt% ammonia solution. The pH of the solution in the precipitation reaction was adjusted to 9.0. The stirring time was 2 h. The aging time was 2 h.

[0059] (2) The manganese-modified nano-cerium dioxide precursor was dried at 80 °C for 12 h and calcined at 400 °C for 4 h to obtain the manganese-modified nano-cerium dioxide carrier.

[0060] (3) Disperse 1g of the manganese-modified nano-cerium dioxide in 100 mL of deionized water and sonicate for 30 min to obtain a manganese-modified nano-cerium dioxide dispersion; stir the dispersion in a water bath at 75 °C for 30 min, add 40 mL of 0.1wt% ruthenium trichloride-hydrochloric acid solution dropwise, stir for 15 min and carry out a deposition and precipitation reaction, and then carry out aging and filtration treatment to obtain ruthenium oxide-supported manganese-modified nano-cerium dioxide; the precipitant used in the deposition and precipitation reaction is 20 mL of sodium carbonate solution with a concentration of 1 mol / L; the solution is adjusted to pH 10.0 in the deposition and precipitation reaction; the aging time is 1 h.

[0061] (4) The ruthenium oxide-supported manganese-modified nano-cerium dioxide was dried at 80 °C for 12 h and calcined at 500 °C for 4 h to obtain the ruthenium-cerium-based catalyst.

[0062] The ruthenium loading in the passively adsorbable nitrogen oxide catalyst prepared in this embodiment is 2.0 wt%.

[0063] like Figure 5 As shown, XRD characterization revealed that manganese-modified cerium dioxide still maintained a typical cubic fluorite structure, and no diffraction peaks of manganese oxide species were observed. This indicates that manganese was uniformly doped into the cerium dioxide lattice but did not cause its structure to collapse. Furthermore, the structure was maintained even after ruthenium loading.

[0064] Example 2 The difference between this embodiment and Example 1 is that the modified metal precursor salt is replaced with copper nitrate in the catalyst preparation process, while other parameters and conditions are exactly the same as in Example 1.

[0065] The ruthenium loading in the passively adsorbable nitrogen oxide catalyst prepared in this embodiment is 2.0 wt%.

[0066] Example 3 The difference between this embodiment and Example 1 is that the Ru source solution is replaced with ruthenium nitrate-nitric acid solution in the catalyst preparation process, and the amount is replaced with 20 mL. Other parameters and conditions are exactly the same as in Example 1.

[0067] The ruthenium loading in the passively adsorbable nitrogen oxide catalyst prepared in this embodiment is 1 wt%.

[0068] Example 4 The difference between this embodiment and Example 1 is that the precipitant in the catalyst preparation process is replaced with a urea solution with a concentration of 40 wt% by mass, while other parameters and conditions are exactly the same as in Example 1.

[0069] The ruthenium loading in the passively adsorbable nitrogen oxide catalyst prepared in this embodiment is 2 wt%.

[0070] Example 5 The difference between this embodiment and Example 1 is that the modified metal precursor salt is replaced with niobium nitrate in the catalyst preparation process, while other parameters and conditions are exactly the same as in Example 1.

[0071] In the passive adsorption catalyst for nitrogen oxides prepared in this embodiment, the support is Nb-modified CeO2, denoted as NbCeO2, and the ruthenium loading on it is 2.0 wt%.

[0072] H2-TPR characterization was performed on pure CeO2 and NbCeO2 samples, and the results are as follows: Figure 4 As shown, the bulk reduction peak shifts significantly towards lower temperatures after Nb doping, indicating that Nb doping significantly promotes the reduction of bulk oxygen and increases the oxygen defect concentration of CeO2.

[0073] Comparative Example 1 The difference between this comparative example and Example 1 is that no modified metal precursor salt is added during the catalyst preparation process; only cerium nitrate precursor salt is added. Other parameters and conditions are exactly the same as in Example 1.

[0074] The ruthenium loading in the passively adsorbable nitrogen oxide catalyst prepared in this comparative example is 0.2~2.0 wt%.

[0075] Adsorption performance test of catalysts capable of passively adsorbing nitrogen oxides: The adsorption performance of the passive adsorption catalyst for nitrogen oxides was tested in a fixed-bed reactor with a quartz tube and an inner diameter of 6 mm. The flow rates of all gases required for the experiment were adjusted and controlled by mass flow meters, and the gases were mixed and flowed into the reactor. 150 mg of the catalyst was incubated at 500 °C under a 20% O₂ / N₂ atmosphere. oAfter C pretreatment for 1 h, the temperature was lowered to 30 °C. Subsequently, the atmosphere was adjusted to 200 ppm NO / 10% O2 / 2% H2O / 5% CO2 / N2 (all contents are volume contents), and the gas hourly space velocity was 200,000 / h. After the atmosphere stabilized, adsorption was carried out at 100 °C for 30 min.

[0076] Desorption performance test of passively adsorbable nitrogen oxide catalysts: The desorption performance of the passive adsorption catalyst for nitrogen oxides was tested in a fixed-bed reactor using a quartz tube with an inner diameter of 6 mm. To determine the desorption temperature of the catalyst, after adsorption was complete, NO flow was stopped, and the atmosphere was adjusted to 20% O2 / N2 for 20 min of purging. Subsequently, the atmosphere was adjusted to 10% O2 / 2% H2O / 5% CO2 / N2, and the temperature was programmed to rise to 500 °C at a rate of 10 °C / min. During this process, the outlet NO concentration was recorded. x concentration.

[0077] The nitrogen oxide adsorption and desorption curves of the nitrogen oxide passive adsorption catalysts obtained in Examples 1, 2, and Comparative Example 1 are shown below. Figure 1 , Figure 2 and Figure 3 As shown.

[0078] The adsorption and desorption amounts of nitrogen oxides by the passively adsorbable nitrogen oxide catalysts in the above examples and comparative examples were obtained from the adsorption-desorption curves, as shown in Table 1.

[0079] Table 1. Adsorption-desorption performance statistics of Examples 1, 2 and Comparative Example 1 From Table 1 and Figure 1-3 It can be seen that: (1) The adsorbent described in this invention uses modified nano-cerium dioxide as a carrier and noble metal ruthenium as an active component. It has a large adsorption capacity for nitrogen oxides, high desorption efficiency, and suitable adsorption and desorption temperature. (2) It can be seen from the combined results of Examples 1 and Examples 2-4 that the passive adsorption catalyst for nitrogen oxides in Example 1 contains Ru / Ce. x Mn y O2, and the ruthenium element loading is 2.0 wt%, with an adsorption capacity of 283. mol / g, desorption capacity is 266 mol / g; The adsorption and desorption capacities of the passively adsorbable nitrogen oxide catalysts in Examples 2-4 were 212 mol / g, respectively. mol / g ~182 mol / g, 220 mol / g ~210 mol / g and 272 mol / g ~256 In Example 1, the passive adsorption catalyst for nitrogen oxides exhibited higher adsorption and desorption capacities. In Comparative Example 1, the adsorption and desorption capacities of nitrogen oxides by the unmodified cerium dioxide-supported ruthenium catalyst were significantly lower than those in Example 1.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides, characterized in that, The ruthenium-cerium-based catalyst uses modified nano-cerium dioxide as a support, and the surface of the modified nano-cerium dioxide is loaded with ruthenium as an active component. The modified nano-cerium dioxide is nano-cerium dioxide obtained by modification with modified metal elements.

2. The ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides according to claim 1, characterized in that, In the ruthenium-cerium-based catalyst, the content of ruthenium is 0.2~5.0 wt%, and the content of the modified metal is 1 wt%~20 wt%; the modified metal is any one of manganese, cobalt, nickel, copper, zinc, aluminum, zirconium, and niobium.

3. The ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides according to claim 1, characterized in that, The modified nano-cerium dioxide has a particle size of less than 50 nm and a specific surface area of ​​50~200 m². 2 / g, wherein the ruthenium is loaded onto the surface of modified nano-cerium dioxide in an atomically dispersed state.

4. A method for preparing a ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Cerium salt and modified metal salt are dissolved in water, a precipitant is added to carry out a precipitation reaction, and after the reaction is completed, the mixture is successively filtered, dried and calcined to obtain modified nano-cerium dioxide. S2: Prepare a ruthenium salt solution, and load the ruthenium active component onto the surface of modified nano-cerium dioxide by impregnation or deposition precipitation method, followed by drying and calcination treatment to obtain the ruthenium-cerium-based catalyst.

5. The method for preparing the ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides according to claim 4, characterized in that, In step S1, the cerium salt includes cerium nitrate, and the modified metal salt is any one of manganese nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, aluminum nitrate, and zirconium nitrate; the molar ratio of the cerium salt to the modified metal salt is 7:3 to 99:1; the dosage of the precipitant is 3 mol / L to 11 mol / L, the precipitant includes an ammonia solution, and the pH of the precipitation reaction is 8 to 14.

6. The method for preparing the ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides according to claim 4, characterized in that, In step S1, the drying temperature is 60~100 ℃ and the drying time is 12~48 h, and the calcination temperature is 300~800 ℃ and the calcination time is 3~6 h.

7. The method for preparing the ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides according to claim 4, characterized in that, In step S2, the ruthenium salt in the ruthenium salt solution is any one of ruthenium trichloride, ruthenium sulfate, and ruthenium nitrate, and the mass ratio of the ruthenium salt to the modified nano-cerium dioxide is 0.2~5.0 wt%. When using the precipitation method, the precipitant is any one or more of sodium carbonate, ammonium carbonate, urea, and ammonia solution, and the pH of the precipitation reaction is 1 to 10.

8. The method for preparing the ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides according to claim 4, characterized in that, In step S2, the drying temperature is 60~110 ℃, the drying time is 12~48 h, the calcination temperature is 300~900 ℃, and the calcination time is 3~8 h.

9. The application of a ruthenium-cerium-based catalyst capable of passively adsorbing nitrogen oxides as described in any one of claims 1 to 3 in the low-temperature storage reaction of nitrogen oxides during the cold start phase of automobiles, characterized in that, The ruthenium-cerium-based catalyst is used for the passive adsorption of nitrogen oxides in motor vehicle exhaust.

10. The application according to claim 9, characterized in that, The reaction temperature during the cold start phase of a car is 80~200℃, and the reaction atmosphere is NO. x A mixture of O2, H2O, CO2, CO and N2 is reacted at atmospheric pressure with a volume hourly space velocity of 150,000~250,000 / h.

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