Nitrogen oxide adsorbent and preparation method therefor, treatment device for automobile exhaust gas, and vehicle

Abstract

A nitrogen oxide adsorbent and a preparation method therefor, a treatment device for an automobile exhaust gas, and a vehicle. The nitrogen oxide adsorbent comprises a carrier, and an alkali metal species and a noble-metal-based species loaded on the carrier, wherein the alkali metal species comprise at least one of a potassium-based species, a rubidium-based species and a cesium-based species; the material of the carrier comprises aluminum oxide; and the carrier has pores.

Description

Nitrogen oxide adsorbent, preparation method thereof, automobile exhaust treatment device and vehicle

[0001] The present application claims priority to the Chinese patent application No. 202411359600.7, filed on September 26, 2024, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of automobile exhaust treatment, and in particular to a nitrogen oxide adsorbent, a preparation method thereof, an automobile exhaust treatment device and a vehicle. BACKGROUND

[0003] With the development of social economy, the number of automobiles is increasing, and automobile exhaust has become one of the main sources of air pollution. NO x is a representative harmful exhaust gas emitted by vehicles equipped with internal combustion engines. In the related art, the NO x in automobile exhaust is oxidized and converted into nitrate by a nitrogen oxide adsorbent having noble metal sites such as Pt and alkaline metal sites, thereby completing adsorption. SUMMARY

[0004] The present disclosure provides a nitrogen oxide adsorbent, a preparation method thereof, an automobile exhaust treatment device and a vehicle to solve the technical problem of low working temperature and poor catalytic stability of the nitrogen oxide adsorbent in the related art.

[0005] In a first aspect, a nitrogen oxide adsorbent is provided, including a carrier, and an alkaline metal species and a noble metal-based species supported on the carrier, the material of the carrier including alumina, and the carrier having pores, the alkaline metal species including at least one of a potassium-based species, a rubidium-based species and a cesium-based species.

[0006] In some embodiments, the material of the carrier includes γ-Al2O3.

[0007] In some embodiments, the carrier is a hollow sphere.

[0008] In some embodiments, the carrier satisfies at least one of the following: the D50 particle size of the carrier is 1-10 microns; the wall thickness of the carrier is 0.2-1.0 microns; and the specific surface area of the carrier is 100-300 m 2 / g.

[0009] In some embodiments, the alkaline metal species includes one or more of an alkaline metal carbonate, an alkaline metal oxide; and / or the noble metal-based species includes one or more of Pt, Pd and Rh.

[0010] In some embodiments, the noble metal-based species contains a noble metal element, and a mass of the noble metal element in the noble metal-based species is 0.1wt%-10.0wt% of a mass of the carrier; the alkali metal species contains an alkali metal element, and a mass of the alkali metal element in the alkali metal species is 3wt%-50wt% of the mass of the carrier.

[0011] In a second aspect, a preparation method of a nitrogen oxide adsorbent is provided, including: dissolving an aluminum-based precursor, an alkali metal precursor, and a first alkali source in water to perform a hydrothermal reaction to obtain a hydrothermal product, and performing calcination treatment on the hydrothermal product to obtain a carrier loaded with an alkali metal species; the alkali metal precursor includes at least one of a potassium-based precursor, a rubidium-based precursor, and a cesium-based precursor; after dispersing the carrier in water, a second alkali source is added to perform activation treatment, a noble metal-based precursor is further added, and drying treatment is performed to obtain an adsorbent precursor; and the adsorbent precursor is subjected to calcination treatment to obtain a nitrogen oxide adsorbent.

[0012] In some embodiments, the first alkali source is one or more of urea, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium bicarbonate; and / or the second alkali source is one or more of ammonia, sodium hydroxide, sodium bicarbonate.

[0013] In some embodiments, in the activation treatment, the pH of the system is controlled to be 11-14.

[0014] In some embodiments, the nitrogen oxide adsorbent satisfies at least one of the following: the aluminum-based precursor includes one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, potassium aluminum sulfate, and ammonium aluminum sulfate; the potassium-based precursor includes one or more of potassium nitrate, potassium sulfate, and potassium chloride; the rubidium-based precursor includes one or more of rubidium nitrate, rubidium carbonate, rubidium sulfate, and rubidium chloride; the cesium-based precursor includes one or more of cesium nitrate, cesium carbonate, cesium sulfate, and cesium chloride; and the noble metal-based precursor includes one or more of a Pt-based precursor, a Pd-based precursor, and a Rh-based precursor.

[0015] In some embodiments, the temperature of the hydrothermal reaction is 60-200°C, and the time is 0.5-24h; in the calcination treatment of the hydrothermal product, the calcination temperature is 300-600°C, and the time is 0.5-12h; in the calcination treatment of the adsorbent precursor, the calcination temperature is 300-600°C, and the time is 0.5-12h.

[0016] In some embodiments, the calcination treatment of the hydrothermal product includes: after the hydrothermal reaction is completed, the hydrothermal product is taken out to sequentially perform drying treatment and calcination treatment.

[0017] In a third aspect, provided is an automobile exhaust treatment device, which comprises the nitrogen oxide adsorbent provided in the first aspect or prepared by the preparation method provided in the second aspect.

[0018] In a fourth aspect, provided is a vehicle, which comprises an engine and the automobile exhaust treatment device provided in the first aspect.

[0019] Compared with the related art, some embodiments of the present disclosure have the following advantages:

[0020] In some embodiments of the present disclosure, the provided nitrogen oxide adsorbent comprises a carrier and an alkali metal species and a noble metal-based species supported on the carrier, the alkali metal species comprises at least one of a potassium-based species, a rubidium-based species and a cesium-based species, the material of the carrier comprises alumina, and the carrier has pores.

[0021] The alkali metal species serves as an active site for nitrogen oxide adsorption, and efficient capture of nitrogen oxide can be achieved at a high temperature of 350-550°C, which is suitable for controlling nitrogen oxide emission under the lean-burn condition of a gasoline engine.

[0022] The alumina carrier material has a larger specific surface area, can support more alkali metal species and noble metal-based species and ensure high dispersity, and can enhance the binding force between the alkali metal species and the noble metal-based species and the carrier, thereby improving the catalytic stability of the adsorbent and relieving the problem of aggregation of noble metal sites under high-temperature conditions and frequent adsorption / desorption cycles, thus effectively solving the technical problems of low working temperature and poor catalytic stability of the nitrogen oxide adsorbent in the related art.

[0023] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and are not limiting to the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1 is a schematic diagram of a structure of a nitrogen oxide adsorbent according to some embodiments;

[0025] FIG. 2 is a cross-sectional view of a nitrogen oxide adsorbent according to some embodiments;

[0026] FIG. 3 is a schematic diagram of the working principle of a nitrogen oxide adsorbent according to some embodiments;

[0027] FIG. 4 is a flowchart of a preparation method of a nitrogen oxide adsorbent according to some embodiments;

[0028] FIG. 5A is a scanning electron microscope image of a nitrogen oxide adsorbent prepared according to Example 1;

[0029] FIG. 5B is another scanning electron microscope image of the nitrogen oxide adsorbent made according to Example 1;

[0030] FIG. 6A is a transmission electron microscope image of the nitrogen oxide adsorbent made according to Example 1;

[0031] FIG. 6B is another transmission electron microscope image of the nitrogen oxide adsorbent made according to Example 1;

[0032] FIG. 7 is a scanning electron microscope image of the nitrogen oxide adsorbent made according to Comparative Example 1;

[0033] FIG. 8 is a block diagram of an automobile exhaust treatment device according to some embodiments;

[0034] FIG. 9 is a block diagram of a vehicle according to some embodiments.

[0035] Reference numerals: 11 - carrier, 12 - alkali metal species, 13 - noble metal-based species, 100 - automobile exhaust treatment device, 200 - engine, 1000 - vehicle. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present disclosure more obvious and easy to understand, the present disclosure will be further described in detail below with reference to the drawings and specific embodiments.

[0037] In the related art, the NOx in the automobile exhaust is generally adsorbed by a nitrogen oxide adsorbent having noble metal sites such as Pt and alkali metal sites, and then oxidized and converted into nitrate, so as to complete the adsorption. x

[0038] However, the nitrogen oxide adsorbent in the related art is difficult to generate nitrate to complete the adsorption of nitrogen oxide at a high temperature section exceeding 300°C, and is not suitable for adsorption treatment of the exhaust gas of a gasoline engine in a lean burn operation stage (the exhaust temperature is as high as 350-550°C); in addition, the noble metal sites in the nitrogen oxide adsorbent in the related art are prone to aggregation under high temperature conditions and frequent adsorption / desorption cycles, and thus lead to a decrease in catalyst activity.

[0039] Based on this, some embodiments of the present disclosure provide a nitrogen oxide adsorbent, as shown in FIGS. 1-2, the nitrogen oxide adsorbent 10 includes a carrier 11, and an alkali metal species 12 and a noble metal-based species 13 loaded on the carrier 11, the material of the carrier 11 includes alumina, and the carrier 11 has pores, and the alkali metal species includes at least one of a potassium-based species, a rubidium-based species, and a cesium-based species.

[0040] The nitrogen oxide adsorbent provided by some embodiments of the present disclosure can be directly used as an active ingredient in an automobile exhaust treatment device and loaded into the automobile exhaust treatment device.

[0041] ​For example, the noble metal-based species can catalytically oxidize NO to NO2, and the alkali metal species can further adsorb NO2 to convert it into nitrate, thereby completing the adsorption of nitrogen oxides. The working principle of the nitrogen oxide adsorbent is shown in FIG. 3.

[0042] It can be understood that, by taking the alkali metal species as the active site for the adsorption of nitrogen oxides, the chemical equilibrium constant of the reaction of the alkali metal element with nitrogen dioxide to generate nitrate is high at high temperatures, and more nitrogen oxides can be stored at high temperatures. The efficient capture of nitrogen oxides can be completed at high temperatures of 350-550°C, and the nitrogen oxide adsorbent is suitable for controlling the emission of nitrogen oxides under the lean-burn condition of a gasoline engine.

[0043] The use of alumina as the carrier material and the formation of pores on the surface thereof not only make it have a larger specific surface area, can load more alkali metal species and noble metal-based species and ensure high dispersity, but also can enhance the binding force between the alkali metal species and the noble metal-based species and the carrier, thereby improving the catalytic stability of the adsorbent and relieving the problem of aggregation of noble metal sites under high-temperature conditions and frequent adsorption / desorption cycles, and thus the technical problems of the nitrogen oxide adsorbent in the related art, such as low working temperature and poor catalytic stability, can be effectively solved.

[0044] In the present disclosure, the "alkali metal species" refers to a substance containing an alkali metal element, and the "noble metal-based species" refers to a substance containing a noble metal element.

[0045] For example, the alumina in the above carrier can be γ-Al2O3 material, which not only has a high specific surface area and good thermal stability, but also has good chemical stability in acidic and alkaline environments, and facilitates the loading of the noble metal-based species on the carrier by means of ammonia evaporation and the like.

[0046] In some embodiments, the noble metal-based species is loaded on the carrier by positive and negative charge attraction, so that the noble metal-based species can be firmly loaded on the surface of the carrier and is not prone to aggregation or falling off.

[0047] In some embodiments of the present disclosure, the pores can exist on the surface of the carrier 11, in the interior of the carrier 11, or both on the surface and in the interior of the carrier 11.

[0048] In the nitrogen oxide adsorbent provided in some embodiments of the present disclosure, as shown in FIG. 2, the carrier is a hollow spherical shape. By using hollow spherical alumina as the carrier, the noble metal sites and the alkali metal species can be effectively dispersed, thereby improving the catalytic activity and adsorption capacity for nitrogen oxides.

[0049] In some embodiments, the hollow spherical carrier has a particle size of 1-10 microns, which can effectively increase the specific surface area of the carrier under the premise of ensuring the stability of the overall structure of the adsorbent, thereby improving the loading capacity of alkali metal species and noble metal-based species.

[0050] For example, the hollow spherical carrier can have a particle size of one of 1 micron, 2 microns, 5 microns, 8 microns, 10 microns, or a range value of any two thereof; in some embodiments of the present disclosure, the hollow spherical carrier can have a particle size of 1-5 microns, 2-8 microns, 5-8 microns, or 6-10 microns.

[0051] In some embodiments, the hollow spherical carrier has a wall thickness of 0.2-1.0 microns, which can effectively increase the specific surface area of the carrier under the premise of ensuring the stability of the overall structure of the adsorbent, thereby improving the loading capacity of alkali metal species and noble metal-based species.

[0052] For example, the hollow spherical carrier can have a wall thickness of one of 0.2 microns, 0.3 microns, 0.4 microns, 0.5 microns, 0.8 microns, 1.0 microns, or a range value of any two thereof; in some embodiments of the present disclosure, the hollow spherical carrier can have a wall thickness of 0.2-0.5 microns, 0.4-0.8 microns, or 0.5-1.0 microns.

[0053] In some embodiments, the hollow spherical carrier has a specific surface area of 100-300 m 2 / g, which can effectively increase the loading capacity of alkali metal species and noble metal-based species under the premise of ensuring the stability of the overall structure of the adsorbent, so that the prepared adsorbent has higher activity.

[0054] For example, the hollow spherical carrier can have a specific surface area of one of 100 m 2 / g, 120 m 2 / g, 150 m 2 / g, 200 m 2 / g, 250 m 2 / g, 300 m 2 / g, or a range value of any two thereof; in some embodiments of the present disclosure, the hollow spherical carrier can have a specific surface area of 100 m 2 / g-150 m 2 / g, 120 m 2 / g-200 m 2 / g, 150 m 2 / g-250 m 2 / g, or 200 m 2 / g-300 m 2 / g.

[0055] In the nitrogen oxide adsorbent provided by some embodiments of the present disclosure, the alkali metal species includes one or more of alkali metal carbonates and alkali metal oxides, i.e., the potassium-based species includes one or more of potassium carbonate and potassium oxide, the rubidium-based species includes one or more of rubidium carbonate and rubidium oxide, and the cesium-based species includes one or more of cesium carbonate and cesium oxide, which can effectively capture nitrogen oxides at a low cost under high-temperature conditions of 350-550°C.

[0056] In the nitrogen oxide adsorbent provided by some embodiments of the present disclosure, the noble metal-based species includes one or more of Pt (platinum), Pd (palladium), and Rh (rhodium), which can effectively oxidize NO to NO2, and then convert it to nitrate by the alkali metal species, thereby completing the adsorption of nitrogen oxides.

[0057] In the nitrogen oxide adsorbent provided by some embodiments of the present disclosure, the noble metal-based species contains noble metal elements, and the mass of the noble metal elements in the noble metal-based species is 0.1wt%-10.0wt% of the mass of the carrier, which can effectively balance the catalytic activity of the noble metal-based species in catalyzing the oxidation of NO to NO2 and the cost.

[0058] For example, the mass of the noble metal elements in the noble metal-based species can be one or a range value of any two of 0.1wt%, 0.2wt%, 0.5wt%, 1.0wt%, 2.0wt%, 5.0wt%, 8.0wt%, and 10.0wt% of the mass of the carrier; in some embodiments of the present disclosure, the mass of the noble metal elements in the noble metal-based species can be 0.1wt%-0.5wt%, 0.2wt%-1.0wt%, 0.5wt%-2.0wt%, 1.0wt%-2.0wt%, 2.0wt%-5.0wt%, 2.0wt%-8.0wt%, 5.0wt%-8.0wt%, or 5.0wt%-10.0wt% of the mass of the carrier.

[0059] In the nitrogen oxide adsorbent provided by some embodiments of the present disclosure, the alkali metal species contains alkali metal elements, and the mass of the alkali metal elements in the alkali metal species is 3wt%-50wt% of the mass of the carrier, which can effectively balance the adsorption performance and dispersibility of the alkali metal species for nitrogen oxides.

[0060] For example, the mass of the alkali metal elements in the alkali metal species can be one or a range value of any two of 3wt%, 5wt%, 10wt%, 20wt%, 30wt%, 40wt%, and 50wt% of the mass of the carrier; in some embodiments of the present disclosure, the mass of the alkali metal elements in the alkali metal species can be 3wt%-10wt%, 5wt%-20wt%, 10wt%-30wt%, 20wt%-40wt%, or 30wt%-50wt% of the mass of the carrier.

[0061] Some embodiments of the present disclosure also provide a method for preparing a nitrogen oxide adsorbent, as shown in FIG. 4, which comprises steps 401-403.

[0062] In step 401, the aluminum-based precursor, the alkali metal precursor, and the first alkali source are dissolved in water and subjected to a hydrothermal reaction to obtain a hydrothermal product, and the hydrothermal product is subjected to calcination treatment to obtain a carrier loaded with alkali metal species; the alkali metal precursor comprises at least one of a potassium-based precursor, a rubidium-based precursor, and a cesium-based precursor.

[0063] In step 402, the carrier is dispersed in water, a second alkali source is added for activation treatment, a noble metal-based precursor is added and subjected to drying treatment to obtain an adsorbent precursor.

[0064] In step 403, the adsorbent precursor is subjected to calcination treatment to obtain a nitrogen oxide adsorbent.

[0065] In some embodiments of the present disclosure, the alkali metal ions in the alkali metal precursor are used to regulate the crystal growth process of the aluminum oxide precursor in the hydrothermal process, and the alkali metal species can be retained as adsorbent species after the hydrothermal reaction, which not only regulates the growth of the aluminum oxide into a hole morphology by using potassium, rubidium, cesium and other alkali metal ions, but also loads more alkali metal species and noble metal-based species, and the operation is simple, and finally the obtained adsorbent can efficiently capture nitrogen oxides at a high temperature of 350-550°C.

[0066] Moreover, the carrier loaded with alkali metal species after calcination of the hydrothermal product is mixed with the second alkali source, so that the surface of the carrier presents a certain negative charge, which is beneficial to the deposition of noble metal-based cations with positive charge, thereby improving the interaction between the noble metal-based species and the carrier, as well as the dispersion and stability of the noble metal-based species, which not only can load more noble metal-based species and ensure high dispersion, but also can enhance the binding force between the noble metal-based species and the carrier, thereby improving the catalytic stability of the adsorbent, and can alleviate the problem of aggregation of noble metal sites under high temperature conditions and frequent adsorption or desorption cycles, thus effectively solving the technical problems of low working temperature and poor catalytic stability of the nitrogen oxide adsorbent in the related art.

[0067] In the above step 401, the aluminum-based precursor, the alkali metal precursor, and the first alkali source are dissolved in water, which can be uniformly mixed by stirring or the like, and then placed in a sealed container such as a hydrothermal kettle for hydrothermal reaction, which can utilize the reaction between the first alkali source and aluminum ions in the aluminum-based precursor to form aluminum hydroxide precipitate loaded with the alkali metal precursor as the above hydrothermal product, and the hydrothermal product can be placed in a calcination device such as a muffle furnace for calcination treatment, which can convert the aluminum hydroxide into aluminum oxide and convert the alkali metal precursor into alkali metal species.

[0068] For example, the aluminum-based precursor is an aluminum salt soluble in water, so that the aluminum hydroxide (aluminum oxide) layers can be self-assembled into a porous hole morphology, such as a hollow spherical morphology, by using alkali metal ions in a subsequent hydrothermal reaction.

[0069] For example, the aluminum-based precursor includes one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, potassium aluminum sulfate, and ammonium aluminum sulfate, and the first alkali source includes one or more of urea, potassium hydroxide, potassium carbonate, potassium bicarbonate, and sodium bicarbonate, which can precipitate aluminum ions in the aluminum-based precursor as aluminum hydroxide.

[0070] For example, the potassium-based precursor includes one or more of potassium nitrate, potassium sulfate, and potassium chloride, the rubidium-based precursor includes one or more of rubidium nitrate, rubidium carbonate, rubidium sulfate, and rubidium chloride, and the cesium-based precursor includes one or more of cesium nitrate, cesium carbonate, cesium sulfate, and cesium chloride, which can be effectively loaded on the aluminum hydroxide precipitate.

[0071] In some embodiments of the present disclosure, the temperature of the hydrothermal reaction is 60-200°C, and the time is 0.5-24h, which can effectively convert the aluminum-based precursor into the aluminum hydroxide precipitate.

[0072] For example, the temperature of the hydrothermal reaction can be one or a range value of any two of 60°C, 90°C, 100°C, 150°C, 180°C, and 200°C, and the time can be one or a range value of any two of 0.5h, 1h, 2h, 5h, 8h, 12h, and 24h.

[0073] In some embodiments of the present disclosure, the calcination temperature of the calcination treatment of the hydrothermal product is 300-600°C, and the time is 0.5-12h, which can effectively convert the aluminum hydroxide precipitate loaded with the alkali metal precursor into the aluminum oxide carrier loaded with the alkali metal species. For example, the calcination temperature can be one or a range value of any two of 300°C, 350°C, 400°C, 500°C, and 600°C, and the time can be one or a range value of any two of 0.5h, 1h, 2h, 5h, 8h, and 12h.

[0074] In some embodiments, the calcination treatment of the hydrothermal product includes: after the hydrothermal reaction is completed, the hydrothermal product is taken out and sequentially subjected to drying treatment and calcination treatment.

[0075] For example, after the hydrothermal reaction is completed, the hydrothermal product is taken out and dried by heating or the like, stirring is maintained during the drying process to retain the alkali metal species, and then the dried solid product is transferred to a calcination device such as a muffle furnace for calcination, thereby obtaining the gamma aluminum oxide carrier loaded with the alkali metal species (K / γ-Al2O3, Rb / γ-Al2O3, Cs / γ-Al2O3).

[0076] In some embodiments, in step 401, the first alkali source is urea, and in the hydrothermal reaction, the molar ratio between the aluminum-based precursor, the alkali metal precursor and the first alkali source is controlled to satisfy 4:1:8, so that the hydroxyl ions are slightly excessive, and the aluminum ions can be fully precipitated.

[0077] In practical applications, the concentration of the alkali metal species can be adjusted by adjusting the amount of deionized water added in the hydrothermal reaction, so that the hollow degree is stronger and the specific surface area is larger.

[0078] In step 402, the alumina carrier loaded with the alkali metal species is dispersed in deionized water, and an appropriate amount of second alkali source is added for activation treatment, so that the surface of the carrier has a certain negative charge;

[0079] Then, a water-soluble noble metal-based precursor is added, and due to the certain negative charge on the surface of the carrier, under the mutual attraction of positive and negative charges, the noble metal-based cations can not only be deposited on the surface of the carrier, but also can improve the interaction between the noble metal-based cations and the carrier.

[0080] Next, the solution is dried by evaporation or other methods, and an alumina carrier loaded with noble metal-based cation groups and alkali metal species, i.e., the above-mentioned adsorbent precursor, is obtained.

[0081] For example, in the activation treatment, the pH of the system is controlled to be 11-14, which can not only make the negative charge on the surface of the carrier sufficient to bind the noble metal-based cation groups, but also avoid the precipitation of the noble metal-based cation groups.

[0082] In some embodiments, the mass ratio between the amount of the noble metal-based precursor added and the alumina carrier is controlled to satisfy 1:850-1:8.5, so that the prepared adsorbent can effectively balance its catalytic activity of catalyzing NO to be oxidized to NO2 and cost.

[0083] In some embodiments, the activation treatment is performed at a temperature of 60-100°C for 5-60 min, so that the carrier surface can be sufficiently and quickly activated by the hydroxyl ions to have sufficient negative charge.

[0084] For example, the activation reaction temperature can be one of 60°C, 65°C, 70°C, 80°C, 90°C, 100°C or a range value of any two thereof, and the time can be one of 5 min, 8 min, 10 min, 15 min, 20 min, 40 min, 50 min, 60 min or a range value of any two thereof.

[0085] For example, the second alkali source includes one or more of ammonia, sodium hydroxide and sodium bicarbonate.

[0086] In some embodiments, the second alkali source described above can be ammonia water, which not only enables the carrier surface to exhibit a certain negative charge, facilitating the deposition of the noble metal-based precursor, but also can partially dissolve the carrier material at a higher temperature during evaporation, so that defects are generated on the surface of the carrier material, and the defect sites can better stabilize the noble metal-based precursor, thereby better anchoring the noble metal-based species.

[0087] For example, the sealing state needs to be maintained during the activation process to avoid ammonia water evaporation.

[0088] In some embodiments, the evaporation temperature can be 60-200℃, and stirring is maintained during the evaporation process, which can quickly evaporate the ammonia water, thereby forming an alumina carrier loaded with noble metal-based cationic groups and alkali metal species.

[0089] For example, the evaporation temperature can be one of 60℃, 90℃, 100℃, 150℃, 200℃ or a range value of any two thereof.

[0090] It can be understood that the noble metal-based species is introduced by using the ammonia water evaporation method, and the dispersion of the noble metal-based species is high, so that the catalytic activity of the adsorbent is better.

[0091] For example, the noble metal-based precursor described above includes one or more of Pt-based species precursor, Pd-based species precursor, and Rh-based species precursor, such as water-soluble Pt, Pd, Rh nitrate, sulfate, hydrochloride, etc.

[0092] In the step 403 described above, the noble metal-based precursor is converted into an oxidation state or a mixture of oxidation state and metal state by calcination treatment, thereby forming the noble metal-based species described above.

[0093] For example, in the calcination treatment of the adsorbent precursor described above, the calcination temperature is 300-600℃, and the time is 0.5-12h, which can quickly and effectively convert the noble metal-based precursor loaded on the carrier into the noble metal-based species.

[0094] For example, the calcination temperature can be one of 300℃, 350℃, 400℃, 500℃, 600℃ or a range value of any two thereof, and the time can be one of 0.5h, 1h, 2h, 5h, 8h, 12h or a range value of any two thereof.

[0095] Some embodiments of the present disclosure also provide an automobile exhaust treatment device, as shown in FIG. 8, which includes the nitrogen oxide adsorbent 10 described above or the nitrogen oxide adsorbent 10 prepared by the preparation method described above.

[0096] Some embodiments of the present disclosure also provide a vehicle, as shown in FIG. 9, the vehicle 1000 comprises an engine 200, and the automobile exhaust treatment device 100 described above.

[0097] For the above-mentioned embodiments of the automobile exhaust treatment device and the vehicle, they comprise the above-mentioned nitrogen oxide adsorbent and can achieve the same technical effects. To avoid repetition, the relevant parts can be referred to the part of the description of the embodiments of the nitrogen oxide adsorbent.

[0098] Some embodiments of the present disclosure are described below.

[0099] Test method:

[0100] (1) Topography test: The topography of the surface of the carrier in some embodiments of the present disclosure is observed under high magnification by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

[0101] (2) Adsorbent carrier surface element analysis test: During the observation of the electrode surface topography by scanning electron microscopy, the energy dispersive spectrometer (EDS) is used to analyze the various element compositions and percentage mass contents on the electrode surface.

[0102] (3) Nitrogen oxide adsorption performance test: The obtained nitrogen oxide adsorbent is deposited on the surface of a monolithic honeycomb ceramic with a size of 15*15*60mm and loaded into a performance evaluation device. The evaluation device is preheated to 400°C. An atmosphere containing 250ppm NO and 8% O2 (the remaining carrier gas is N2) is introduced into the performance evaluation device, so that the nitrogen oxide adsorbent adsorbs nitrogen oxides at 400°C until saturation. According to the concentration curve of the nitrogen oxide adsorption process, the atmosphere mass flow and the relative molecular mass of NO, the nitrogen oxide adsorption capacity of the fresh sample can be calculated.

[0103] Specific calculation method: Before the nitrogen oxide adsorbent is saturated, the measured NO concentration in the atmosphere will be lower than 250ppm. The difference between the nitrogen oxide concentration in the original atmosphere (250ppm) and the concentration value before saturation is integrated, multiplied by the atmosphere mass flow and the relative molecular mass of NO, and the nitrogen oxide adsorption capacity of the fresh sample is obtained. The above-mentioned value is divided by the mass of the nitrogen oxide adsorbent, and the nitrogen oxide adsorption capacity of the unit mass of the nitrogen oxide adsorbent is obtained.

[0104] (4) Aging sample nitrogen oxide adsorption performance test: The obtained nitrogen oxide adsorbent is deposited on the surface of a monolithic honeycomb ceramic with a size of 15*15*60mm to obtain a fresh sample. The fresh sample is aged under hydrothermal conditions at 800°C for 16 hours in an atmosphere containing 10vol% water vapor to obtain an aged sample. The aged sample is loaded into a performance evaluation device, and the evaluation device is preheated to 400°C. An atmosphere containing 250ppm NO and 8% O2 (the remaining carrier gas is N2) is introduced into the performance evaluation device, and the nitrogen oxide adsorbent is allowed to adsorb nitrogen oxides at 400°C until saturation. According to the concentration curve of the nitrogen oxide adsorption process, the mass flow of the atmosphere, and the relative molecular mass of NO, the nitrogen oxide adsorption capacity of the aged sample can be calculated.

[0105] Specific calculation method: Before the nitrogen oxide adsorbent is saturated, the measured NO concentration in the atmosphere will be lower than 250ppm. The difference between the nitrogen oxide concentration in the original atmosphere (250ppm) and the concentration value before saturation is integrated, multiplied by the mass flow of the atmosphere and the relative molecular mass of NO, and the nitrogen oxide adsorption capacity of the aged sample is obtained. The above value is divided by the mass of the nitrogen oxide adsorbent to obtain the nitrogen oxide adsorption capacity of the unit mass of the nitrogen oxide adsorbent.

[0106] (5) Specific surface area test: After degassing, the nitrogen oxide adsorbent is placed in a nitrogen atmosphere, and the degassed nitrogen oxide adsorbent sample is allowed to adsorb nitrogen until saturation. After the adsorption test is completed, the specific surface area of the nitrogen oxide adsorbent is calculated based on the Brunauer-Emmett-Teller model according to the nitrogen adsorption capacity.

[0107] Example 1

[0108] (1) Preparation of alumina support material

[0109] 6.0g of Al(NO3)3·9H2O, 0.289g of K2CO3, and 1.922g of the first alkali source CO(NH2)2 are dissolved in 160mL of deionized water, and after stirring at a speed of 800rpm for 10min, the mixture is transferred to a hydrothermal kettle and subjected to a hydrothermal reaction in an oven, for example, at a hydrothermal reaction temperature of 180°C for 12h.

[0110] After the hydrothermal reaction is completed, the hydrothermal product is removed and heated to 90°C while stirring until the solid product is dried. Subsequently, the dried solid product is transferred to a muffle furnace and calcined at 500°C for 2h to obtain an alumina support material loaded with alkali metal species.

[0111] (2) Preparation of a nitrogen oxide adsorbent

[0112] 1.0 g of an alumina support material was dispersed in 15 mL of deionized water and 1.0 mL of a second alkali source saturated with NH3H2O was added, the pH of the resulting mixture system was controlled to be 12, the above mixture was sealed with a sealing film and activated by heating to 90°C and stirring for 10 min, then 20 mg of a platinum nitrate solution was added to the above mixture and the sealing film was removed, stirring was maintained until the ammonia water evaporated, and a dry adsorbent precursor was obtained.

[0113] The above adsorbent precursor was transferred to a muffle furnace and calcined at 500°C for 2 h to obtain the final nitrogen oxide adsorbent.

[0114] Example 2

[0115] Example 2 differs from Example 1 in that in step (1), the amount of deionized water is adjusted to 100 mL.

[0116] Example 3

[0117] Example 3 differs from Example 1 in that in step (1), the amount of deionized water is adjusted to 300 mL.

[0118] Example 4

[0119] Example 4 differs from Example 1 in that in step (1), the amount of K2CO3 added is adjusted to 0.045 g; in step (2), 1 mg of a platinum nitrate solution is added.

[0120] Example 5

[0121] Example 5 differs from Example 2 in that in step (1), the amount of K2CO3 added is adjusted to 0.726 g; in step (2), 100 mg of a platinum nitrate solution is added.

[0122] Example 6

[0123] Example 6 differs from Example 1 in that in step (1), Al(NO3)3·9H2O is adjusted to aluminum sulfate and K2CO3 is adjusted to KNO3.

[0124] In step (2), platinum nitrate is adjusted to palladium chloride.

[0125] Example 7

[0126] Example 7 differs from Example 1 in that in step (2), the amount of the second alkali source added is adjusted so that the pH of the system is 11.

[0127] Example 8

[0128] Example 8 differs from Example 1 in that in step (2), the amount of the second alkali source is adjusted so that the pH of the system is 14.

[0129] Example 9

[0130] Example 9 differs from Example 1 in that in step (1), the first alkali source is adjusted to be potassium hydroxide.

[0131] In step (2), the second alkali source is adjusted to be sodium bicarbonate.

[0132] Example 10

[0133] Example 10 differs from Example 1 in that in step (1), the temperature of the hydrothermal reaction is adjusted to be 60°C, and the time is adjusted to be 0.5h; the temperature of the calcination treatment is adjusted to be 300°C, and the time is adjusted to be 0.5h.

[0134] In step (2), the temperature of the calcination treatment is adjusted to be 300°C, and the time is adjusted to be 0.5h.

[0135] Example 11

[0136] Example 11 differs from Example 1 in that in step (1), the temperature of the hydrothermal reaction is adjusted to be 200°C, and the time is adjusted to be 24h; the temperature of the calcination treatment is adjusted to be 600°C, and the time is adjusted to be 12h.

[0137] In step (2), the temperature of the calcination treatment is adjusted to be 600°C, and the time is adjusted to be 12h.

[0138] Example 12

[0139] Example 12 differs from Example 1 in that in step (1), 0.289g of K2CO3 is adjusted to be 0.220g of Rb2CO3.

[0140] Comparative Example 1

[0141] Comparative Example 1 differs from Example 1 in that in step (1), K2CO3 is adjusted to be BaCl2.

[0142] Sample performance test:

[0143] The nitric oxide adsorbents prepared in each of the examples and the comparative example were subjected to morphology testing, surface element analysis, catalytic performance testing, catalytic life testing, and specific surface area testing in sequence, and the results are shown in Table 1. The morphology testing results of the nitric oxide adsorbent prepared in Example 1 are shown in FIGS. 5A, 5B, 6A, and 6B, and the morphology testing results of the nitric oxide adsorbent prepared in Comparative Example 1 are shown in FIG. 7.

[0144] Table 1

[0145] As can be seen from Table 1 and FIGS. 5A, 5B, 6A, 6B, 7, Comparative Example 1 and Comparative Example 1, the introduction of alkali metal ions in the hydrothermal synthesis will make the alumina material form a spherical hollow morphology, not only making it have a larger specific surface area, being able to load more alkali metal species and noble metal-based species and ensuring high dispersity, but also being able to enhance the binding force between the alkali metal species and the noble metal-based species and the carrier, thereby improving the catalytic stability of the adsorbent.

[0146] As can be seen from Table 1, by using potassium ions in the potassium-based precursor to perform a hydrothermal reaction at a reasonable temperature, the crystal growth process of the alumina precursor can be controlled, so as to grow the alumina into a hole morphology, which is able to load more alkali metal species and noble metal-based species.

[0147] Moreover, after calcining the hydrothermal product to form a carrier loaded with alkali metal species and mixing the carrier with an appropriate amount of a second alkali source and activating the mixture at a suitable temperature, the surface of the carrier can present moderate negative electrification, which is more conducive to the deposition of positively electrified noble metal-based cations, and ensures the dispersity and stability of the noble metal-based species, and the performance of the prepared nitrogen oxide adsorbent is particularly good.

[0148] The nitrogen oxide adsorbent provided in some embodiments of the present disclosure can complete efficient capture of nitrogen oxides under high-temperature conditions of 350-550°C, and is suitable for controlling nitrogen oxide emissions under the lean-burn working condition of a gasoline engine.

[0149] In summary, the nitrogen oxide adsorbent provided in some embodiments of the present disclosure includes a carrier and alkali metal species and noble metal-based species loaded on the carrier, the material of the carrier includes alumina, and the carrier has holes.

[0150] For example, by taking the alkali metal species as the active site for nitrogen oxide adsorption, efficient capture of nitrogen oxides can be completed under high-temperature conditions of 350-550°C, and the nitrogen oxide adsorbent is suitable for controlling nitrogen oxide emissions under the lean-burn working condition of a gasoline engine.

[0151] By taking alumina as the carrier material and forming holes on the surface thereof, not only does it have a larger specific surface area, being able to load more alkali metal species and noble metal-based species and ensuring high dispersity, but also it can enhance the binding force between the alkali metal species and the noble metal-based species and the carrier, thereby improving the catalytic stability of the adsorbent and being able to effectively solve the technical problems of the nitrogen oxide adsorbent in the related art, such as low working temperature and poor catalytic stability.

[0152] While portions of the embodiments of the present disclosure have been described as being implemented, additional changes and modifications can be made to the embodiments by those skilled in the art once given the benefit of the basic inventive concepts. Therefore, the claims are intended to cover all changes and modifications of the embodiments of the present disclosure which fall within the scope of the embodiments of the present disclosure.

[0153] The nitrogen oxide adsorbent and the preparation method thereof, and the automobile exhaust treatment device provided by the present disclosure are described in detail above, and the principles and implementation manners of the present disclosure are described by using examples. The above description of the embodiments is only used to help understand the method of the present disclosure and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present disclosure, the specific implementation manners and application ranges can be changed. In summary, the content of the present description should not be understood as a limitation of the present disclosure.

Claims

1. A nitrogen oxide adsorbent (10) comprising a carrier (11), and an alkali metal species (12) and a noble metal-based species (13) supported on the carrier (11); a material of the carrier (11) comprises alumina, and the carrier (11) has pores; the alkali metal species (12) comprises at least one of a potassium-based species, a rubidium-based species, and a cesium-based species.

2. The nitrogen oxide adsorbent (10) according to claim 1, wherein The material of the carrier (11) comprises γ-Al2O3.

3. The nitrogen oxide adsorbent (10) according to claim 1 or 2, wherein The carrier (11) is a hollow sphere.

4. The nitrogen oxide adsorbent (10) according to claim 3, wherein The carrier (11) satisfies at least one of: The D50 particle size of the carrier (11) is 1-10 microns; The wall thickness of the carrier (11) is 0.2-1.0 microns; and The specific surface area of the support (11) is between 100 and 300 m 2 / g.

5. The nitrogen oxide adsorbent (10) according to any one of claims 1-4, wherein, The alkali metal species (12) comprises one or more of an alkali metal carbonate, an alkali metal oxide; and / or The noble metal-based species (13) comprises one or more of Pt, Pd, and Rh.

6. The nitrogen oxide adsorbent (10) according to any one of claims 1-5, wherein, The noble metal-based species (13) contains a noble metal element, and the mass of the noble metal element in the noble metal-based species (13) is 0.1wt%-10.0wt% of the mass of the carrier (11); the alkali metal species (12) contains an alkali metal element, and the mass of the alkali metal element in the alkali metal species (12) is 3wt%-50wt% of the mass of the carrier (11).

7. A preparation method of a nitrogen oxide adsorbent, comprising: dissolving an aluminum-based precursor, an alkali metal precursor, and a first alkali source in water, performing a hydrothermal reaction to obtain a hydrothermal product, and performing calcination treatment on the hydrothermal product to obtain a carrier loaded with an alkali metal species; wherein the alkali metal precursor comprises at least one of a potassium-based precursor, a rubidium-based precursor, and a cesium-based precursor; after dispersing the carrier in water, adding a second alkali source to perform activation treatment, then adding a noble metal-based precursor and performing drying treatment to obtain an adsorbent precursor; and performing calcination treatment on the adsorbent precursor to obtain a nitrogen oxide adsorbent.

8. The preparation method according to claim 7, wherein, The first alkali source is one or more of urea, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium bicarbonate; and / or The second alkali source is one or more of ammonia, sodium hydroxide, sodium bicarbonate.

9. The production method according to claim 7 or 8, wherein In the activation treatment, the pH of the system is controlled to be 11-14.

10. The production process according to any one of claims 7 to 9, wherein, The nitrogen oxide adsorbent satisfies at least one of: The aluminum-based precursor comprises one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, potassium aluminum sulfate, ammonium aluminum sulfate; The potassium-based precursor comprises one or more of potassium nitrate, potassium carbonate, potassium sulfate, potassium chloride; The rubidium-based precursor comprises one or more of rubidium nitrate, rubidium carbonate, rubidium sulfate, rubidium chloride; The cesium-based precursor comprises one or more of cesium nitrate, cesium carbonate, cesium sulfate, cesium chloride; and The noble metal-based precursor comprises one or more of a Pt-based precursor, a Pd-based precursor, a Rh-based precursor.

11. The preparation method according to any one of claims 7-10, wherein, The temperature of the hydrothermal reaction is 60-200℃, and the time is 0.5-24h; The hydrothermal product is subjected to calcination treatment, the calcination temperature is 300-600℃, and the time is 0.5-12h. The adsorbent precursor is subjected to calcination treatment, the calcination temperature is 300-600℃, and the time is 0.5-12h.

12. The production process according to any one of claims 7 to 11, wherein, The hydrothermal product is subjected to calcination treatment, including: After the hydrothermal reaction is completed, the hydrothermal product is taken out and sequentially subjected to drying treatment and calcination treatment.

13. An automobile exhaust treatment device (100) comprising one of: The nitrogen oxide adsorbent (10) according to any one of claims 1-6, or, The nitrogen oxide adsorbent (10) prepared by the preparation method according to any one of claims 7-12.

14. A vehicle (1000) comprising an engine (200) and the automobile exhaust treatment device (100) according to claim 13.

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