Nitrogen oxide adsorbent and preparation method thereof, automobile exhaust treatment device and vehicle
By loading alkali metals and noble metal species onto an alumina support, hollow spherical nitrogen oxide adsorbents with pores were prepared, solving the problem of poor catalytic stability at high temperatures in existing technologies and achieving efficient nitrogen oxide capture and emission control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2026-03-27
AI Technical Summary
Existing nitrogen oxide adsorbents are difficult to generate nitrates at high temperatures, and precious metal sites tend to aggregate, resulting in poor catalytic stability and inability to effectively treat exhaust gases during the lean-burn operation of gasoline engines.
Using alumina as a carrier, alkali metal species and noble metal-based species are loaded onto it. A nitrogen oxide adsorbent is prepared through hydrothermal reaction and calcination to form a hollow spherical structure with pores. The alkali metal species react with nitrogen dioxide at high temperature to generate nitrates, while the noble metal-based species are catalytically oxidized to nitrogen dioxide, thus enhancing the binding force and dispersibility.
It efficiently captures nitrogen oxides under high temperature conditions of 350-550℃, improves catalytic stability, and is suitable for nitrogen oxide emission control under lean-burn conditions of gasoline engines.
Smart Images
Figure CN121732104A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of automotive exhaust gas treatment technology, and in particular to a nitrogen oxide adsorbent and its preparation method, an automotive exhaust gas treatment device, and a vehicle. Background Technology
[0002] Currently, vehicle exhaust has become one of the main sources of air pollution, and NO... x Representative harmful exhaust gases emitted by vehicles equipped with internal combustion engines.
[0003] Existing technologies generally utilize nitrogen oxide adsorbents with noble metal sites such as Pt and alkaline metal sites to adsorb NO in automobile exhaust. x It undergoes oxidation and is converted into nitrate, thus completing the adsorption process.
[0004] However, existing nitrogen oxide adsorbents are difficult to generate nitrates in high-temperature ranges exceeding 300°C to complete the adsorption of nitrogen oxides, making them unsuitable for adsorption treatment of exhaust gas (exhaust temperature as high as 350-550°C) during the lean-burn operation of gasoline engines. In addition, the noble metal sites in existing nitrogen oxide adsorbents are prone to aggregation under high-temperature conditions and frequent adsorption / desorption cycles, which leads to a decrease in catalyst activity. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a nitrogen oxide adsorbent and its preparation method, an automobile exhaust gas treatment device and a vehicle, so as to solve the technical problems of low operating temperature and poor catalytic stability of existing nitrogen oxide adsorbents.
[0006] To solve the above problems, the present invention is achieved through the following technical solution:
[0007] This invention proposes a nitrogen oxide adsorbent, comprising a carrier and alkali metal species and noble metal-based species loaded on the carrier. The carrier is made of alumina and has pores. The alkali metal species includes at least one of potassium-based species, rubidium-based species, and cesium-based species.
[0008] Furthermore, in the nitrogen oxide adsorbent, the carrier is a hollow sphere.
[0009] Furthermore, in the nitrogen oxide adsorbent, the particle size of the support is 1–10 micrometers; and / or
[0010] The carrier has a wall thickness of 0.2–1.0 micrometers; and / or
[0011] The specific surface area of the carrier is 100-300 m². 2 / g.
[0012] Furthermore, in the nitrogen oxide adsorbent, the alkali metal species includes one or more of alkali metal carbonates and alkali metal oxides; and / or
[0013] The noble metal-based species include one or more of Pt, Pd, and Rh.
[0014] Furthermore, in the nitrogen oxide adsorbent, the noble metal element in the noble metal-based species accounts for 0.1 wt% to 10.0 wt% of the mass of the carrier, and the alkali metal element in the alkali metal species accounts for 3 wt% to 50 wt% of the mass of the carrier.
[0015] This invention also proposes a method for preparing a nitrogen oxide adsorbent, comprising:
[0016] An aluminum-based precursor, an alkali metal precursor, and a first alkali source are dissolved in water and subjected to a hydrothermal reaction. The hydrothermal product is then calcined to obtain a carrier loaded with 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.
[0017] The carrier is dispersed in water and then activated by adding a second alkali source. Then a noble metal-based precursor is added and dried to obtain the adsorbent precursor.
[0018] The adsorbent precursor is calcined to obtain a nitrogen oxide adsorbent.
[0019] Furthermore, in the preparation method, the first alkali source is one or more selected from urea, potassium hydroxide, potassium carbonate, potassium bicarbonate, and sodium bicarbonate; and / or
[0020] The second alkali source is one or more of ammonia, sodium hydroxide, and sodium bicarbonate.
[0021] Furthermore, in the preparation method, during the activation treatment, the pH of the system is controlled to be 11-14.
[0022] Furthermore, in the preparation method, the aluminum-based precursor includes one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, potassium aluminum sulfate, and ammonium aluminum sulfate; and / or
[0023] The potassium-based precursor includes one or more of potassium nitrate, potassium sulfate, and potassium chloride; and / or
[0024] The rubidium-based precursor includes one or more of rubidium nitrate, rubidium carbonate, rubidium sulfate, and rubidium chloride; and / or
[0025] The cesium-based precursor includes one or more of cesium nitrate, cesium carbonate, cesium sulfate, and cesium chloride; and / or
[0026] The noble metal-based precursor includes one or more of Pt-based, Pd-based, and Rh-based precursors.
[0027] Furthermore, in the preparation method, the hydrothermal reaction temperature is 60–200°C and the time is 0.5–24 h;
[0028] In the calcination treatment of hydrothermal products, the calcination temperature is 300-600℃ and the time is 0.5-12h;
[0029] In the calcination treatment of the adsorbent precursor, the calcination temperature is 300-600℃ and the time is 0.5-12h.
[0030] Furthermore, in the preparation method, the hydrothermal product is subjected to calcination treatment, including:
[0031] After the hydrothermal reaction is completed, the hydrothermal products are taken out and subjected to drying and calcination treatments in sequence.
[0032] The present invention also proposes an automobile exhaust gas treatment device, wherein the device includes a nitrogen oxide adsorbent as described above, or a nitrogen oxide adsorbent prepared by the preparation method described above.
[0033] The present invention also proposes a vehicle including an engine, wherein the vehicle exhaust treatment device as described above is also included.
[0034] Compared with the prior art, the embodiments of the present invention have the following advantages:
[0035] In this embodiment of the invention, the provided nitrogen oxide adsorbent includes a support and alkali metal species and noble metal-based species loaded on the support. The alkali metal species include at least one of potassium-based species, rubidium-based species, and cesium-based species. The support material includes alumina, and the support has pores. Using alkali metal species as active sites for nitrogen oxide adsorption allows for efficient nitrogen oxide capture at high temperatures of 350–550°C, suitable for controlling nitrogen oxide emissions under lean-burn conditions in gasoline engines. Using alumina as the support material and forming pores on its surface not only gives it a larger specific surface area, enabling it to load more alkali metal species and noble metal-based species while ensuring high dispersibility, but also enhances the binding force between the alkali metal species and noble metal-based species and the support, thereby improving the catalytic stability of the adsorbent. This alleviates the problem of noble metal sites agglomerating under high-temperature conditions and frequent adsorption / desorption cycles, thus effectively solving the technical problems of low operating temperature and poor catalytic stability in existing nitrogen oxide adsorbents.
[0036] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description
[0037] Fig. 1 This is a schematic diagram of the structure of the nitrogen oxide adsorbent provided in the embodiments of the present invention;
[0038] Fig. 2 This is a cross-sectional schematic diagram of the nitrogen oxide adsorbent provided in an embodiment of the present invention;
[0039] Fig. 3 This is a schematic diagram illustrating the working principle of the nitrogen oxide adsorbent provided in the embodiments of the present invention;
[0040] Fig. 4 This is a flowchart of the nitrogen oxide adsorbent preparation method provided in the embodiments of the present invention;
[0041] Fig. 5 This is a scanning electron microscope image of the nitrogen oxide adsorbent prepared in Example 1 of the present invention;
[0042] Fig. 6 This is a transmission electron microscope image of the nitrogen oxide adsorbent prepared in Example 1 of the present invention;
[0043] Fig. 7 This is a scanning electron microscope image of the nitrogen oxide adsorbent prepared in Comparative Example 1 of the present invention.
[0044] Figure label:
[0045] 11-Carrier, 12-Noble metal species, 13-Noble metal-based species. Detailed Implementation
[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0047] An embodiment of the present invention provides a nitrogen oxide adsorbent, such as... Figs. 1-2 As shown, it includes a carrier 11 and alkali metal species 12 and noble metal-based species 13 loaded on the carrier 11. The material of the carrier 11 includes alumina and the carrier 11 has pores. The alkali metal species include at least one of potassium-based species, rubidium-based species and cesium-based species.
[0048] The nitrogen oxide adsorbent provided in this invention can be directly loaded into the vehicle exhaust treatment device as an active ingredient.
[0049] Among them, noble metal-based species can catalytically oxidize NO to NO2, while alkali metal species can further adsorb NO2 and convert it into nitrate, thus completing the adsorption of nitrogen oxides. The specific working principle is as follows: Fig. 3 As shown.
[0050] Among them, using alkali metal species as active sites for nitrogen oxide adsorption, alkali metal elements have a high chemical equilibrium constant for reacting with nitrogen dioxide to form nitrates at high temperatures, enabling them to store more nitrogen oxides at high temperatures. This allows for efficient nitrogen oxide capture under high temperature conditions of 350–550℃, making it suitable for controlling nitrogen oxide emissions under lean-burn conditions in gasoline engines. Using alumina as a carrier material with pores on its surface not only gives it a larger specific surface area, allowing it to load more alkali metal species and noble metal-based species while ensuring high dispersibility, but also enhances the binding force between alkali metal species and noble metal-based species and the carrier, thereby improving the catalytic stability of the adsorbent. This can alleviate the problem of noble metal sites agglomerating under high temperature conditions and frequent adsorption / desorption cycles, thus effectively solving the technical problems of low operating temperature and poor catalytic stability of existing nitrogen oxide adsorbents.
[0051] Specifically, the alumina in the aforementioned carrier can be γ-Al2O3 material, which not only has a high specific surface area and good thermal stability, but also good chemical stability in acidic and alkaline environments, making it easy to load noble metal-based species onto the carrier through methods such as ammonia evaporation.
[0052] Optionally, in one embodiment, the above-mentioned noble metal-based species are loaded onto the carrier by the attraction between positive and negative charges, so that the noble metal-based species can be firmly loaded on the carrier surface and are not prone to aggregation or detachment.
[0053] In this embodiment of the invention, the aforementioned holes may exist on the surface of the carrier 11, inside the carrier 11, or both on the surface and inside the carrier 11.
[0054] Optionally, in the nitrogen oxide adsorbent provided in the embodiments of the present invention, such as Fig. 2 As shown, the aforementioned support is a hollow sphere. By utilizing hollow spherical alumina as a support, noble metal sites and alkali metal species can be effectively dispersed, thereby enhancing the catalytic activity and adsorption capacity for nitrogen oxides.
[0055] Optionally, in one embodiment, the particle size of the hollow spherical carrier is 1 to 10 micrometers, which can effectively increase the specific surface area of the carrier while ensuring the overall structural stability of the adsorbent, thereby increasing the loading capacity of alkali metal species and noble metal-based species. Optionally, the particle size of the hollow spherical carrier can be one or any two of the following: 1 micrometer, 2 micrometers, 5 micrometers, 8 micrometers, and 10 micrometers.
[0056] Optionally, in one embodiment, the wall thickness of the hollow spherical carrier is 0.2 to 1.0 micrometers, which can effectively increase the specific surface area of the carrier while ensuring the overall structural stability of the adsorbent, thereby increasing the loading capacity of alkali metal species and noble metal-based species. Optionally, the wall thickness of the hollow spherical carrier can be one or any two of the following: 0.2 micrometers, 0.3 micrometers, 0.4 micrometers, 0.5 micrometers, 0.8 micrometers, and 1.0 micrometers.
[0057] Optionally, in one embodiment, the specific surface area of the hollow spherical carrier is 100–300 m². 2 / g, which can effectively increase the loading of alkali metal species and noble metal-based species while ensuring the overall structural stability of the adsorbent, resulting in a more active adsorbent. Optionally, the specific surface area of the hollow spherical support can be 100m². 2 / g、120m 2 / g, 150m 2 / g、200m 2 / g、250m 2 / g、300m 2 The range of one or both of the values in / g.
[0058] Optionally, in the nitrogen oxide adsorbent provided in the embodiments of the present invention, the alkali metal species include alkali metal carbonates and alkali metal oxides, that is, potassium-based species include one or more of potassium carbonate and potassium oxide, rubidium-based species include one or more of rubidium carbonate and rubidium oxide, and cesium-based species include one or more of cesium carbonate and cesium oxide, which can achieve efficient capture of nitrogen oxides at low cost under high temperature conditions of 350 to 550°C.
[0059] Optionally, in the nitrogen oxide adsorbent provided in the embodiments of the present invention, the noble metal-based species include one or more of Pt, Pd and Rh, which can effectively oxidize NO to NO2, and then convert it into nitrate by alkali metal species, thereby completing the adsorption of nitrogen oxides.
[0060] Optionally, in the nitrogen oxide adsorbent provided in the embodiments of the present invention, the noble metal element in the noble metal-based species accounts for 0.1wt% to 10.0wt% of the mass of the carrier, which can effectively balance its catalytic activity in catalyzing the oxidation of NO to NO2 and its cost; Optionally, the noble metal element in the noble metal-based species can be one or any two of the following ranges: 0.1wt%, 0.2wt%, 0.5wt%, 1.0wt%, 2.0wt%, 5.0wt%, 8.0wt%, 10.0wt%.
[0061] Optionally, in the nitrogen oxide adsorbent provided in the embodiments of the present invention, the alkali metal element in the alkali metal species accounts for 3 wt% to 50 wt% of the mass of the carrier, which can effectively balance its adsorption performance and dispersibility for nitrogen oxides. Optionally, the mass content of the alkali metal element in the alkali metal species as a percentage of the carrier can be one or any two of the following: 3 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt%.
[0062] This invention also provides a method for preparing a nitrogen oxide adsorbent, wherein, as shown in the embodiments, Fig. 4 As shown, steps 401 to 403 are included:
[0063] Step 401: Dissolve the aluminum-based precursor, the alkali metal precursor, and the first alkali source in water and carry out a hydrothermal reaction, and calcine the hydrothermal product to obtain a carrier loaded with alkali metal species; wherein the alkali metal precursor includes at least one of potassium-based precursor, rubidium-based precursor, and cesium-based precursor.
[0064] Step 402: After dispersing the carrier in water, add a second alkali source for activation treatment, then add a noble metal-based precursor and dry it to obtain the adsorbent precursor.
[0065] Step 403: Calcine the adsorbent precursor to obtain a nitrogen oxide adsorbent.
[0066] In this embodiment of the invention, alkali metal ions in the alkali metal precursor are first used to regulate the crystal growth process of the alumina precursor during hydrothermal treatment. After the hydrothermal reaction, the alkali metal species are retained as adsorbent species. This not only leverages the regulatory role of alkali metal ions such as potassium, rubidium, and cesium to grow alumina into a porous morphology, but also allows for the loading of more alkali metal species and noble metal-based species. The operation is simple, and the resulting adsorbent can achieve efficient capture of nitrogen oxides under high temperature conditions of 350–550°C.
[0067] Simultaneously, the support formed by calcining hydrothermal products and loading alkali metal species is mixed with a second alkali source, making the support surface exhibit a certain negative charge, which is conducive to the deposition of positively charged noble metal-based cations. This enhances the interaction between noble metal-based species and the support, as well as the dispersion and stability of the noble metal-based species. It can not only load more noble metal-based species and ensure high dispersion, but also enhance the binding force between noble metal-based species and the support, thereby improving the catalytic stability of the adsorbent. It can alleviate the problem of noble metal sites agglomerating under high temperature conditions and frequent adsorption / desorption cycles, thus effectively solving the technical problems of low operating temperature and poor catalytic stability of existing nitrogen oxide adsorbents.
[0068] In step 401 above, the aluminum-based precursor, alkali metal precursor, and first alkali source are dissolved in water and mixed evenly by stirring or other means. Then, the mixture is placed in a closed container such as a hydrothermal reactor for hydrothermal reaction. The first alkali source reacts with aluminum ions in the aluminum-based precursor to form aluminum hydroxide precipitate loaded with alkali metal precursor, which is the above-mentioned hydrothermal product. The hydrothermal product is then placed in a calcination device such as a muffle furnace for calcination treatment, which converts aluminum hydroxide into aluminum oxide and alkali metal precursor into alkali metal species.
[0069] The aluminum-based precursor is a water-soluble aluminum salt, which allows the alkali metal ions to be used in the subsequent hydrothermal reaction to self-assemble the sheet aluminum hydroxide (alumina) into a porous morphology, specifically a hollow spherical morphology.
[0070] Optionally, the aluminum-based precursor specifically includes one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, potassium aluminum sulfate, and ammonium aluminum sulfate, and the first alkali source is 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 precipitate.
[0071] Optionally, 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 onto aluminum hydroxide precipitate.
[0072] In this embodiment of the invention, 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 aluminum hydroxide precipitate. Optionally, the temperature of the hydrothermal reaction can be one or any two of 60°C, 90°C, 100°C, 150°C, 180°C, and 200°C, and the time can be one or any two of 0.5h, 1h, 2h, 5h, 8h, 12h, 15h, and 24h.
[0073] In this embodiment of the invention, the calcination treatment of the hydrothermal product is carried out at a temperature of 300-600°C and a time of 0.5-12h, which can effectively convert the aluminum hydroxide precipitate loaded with alkali metal precursors into an alumina support loaded with alkali metal species. The calcination temperature can be any one or any two of 300°C, 350°C, 400°C, 500°C, and 600°C, and the time can be any one or any two of 0.5h, 1h, 2h, 5h, 8h, and 12h.
[0074] Optionally, in one embodiment, the hydrothermal product is subjected to calcination treatment, including:
[0075] After the hydrothermal reaction is completed, the hydrothermal products are taken out and subjected to drying and calcination treatments in sequence.
[0076] In this embodiment, after the hydrothermal reaction is completed, the hydrothermal product is taken out and dried by heating or other means. During the drying process, stirring is maintained to retain the alkali metal species. Then, the dried solid product is transferred to a calcination device such as a muffle furnace for calcination to obtain gamma alumina carriers (K / γ-Al2O3, Rb / γ-Al2O3, Cs / γ-Al2O3) loaded with alkali metal species.
[0077] Optionally, in one embodiment, in step 401 above, the first alkali source is urea. 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 hydroxide ions are slightly in excess, which can fully precipitate aluminum ions.
[0078] In practical applications, the concentration of alkali metal species can be adjusted by regulating the amount of deionized water added during the hydrothermal reaction, resulting in greater hollowness and a larger specific surface area.
[0079] In step 402 above, the alumina support loaded with alkali metal species is dispersed in deionized water, and then an appropriate amount of second alkali source is added for activation treatment, so that the surface of the support exhibits a certain negative charge; then a water-soluble noble metal-based precursor is added. Because the surface of the support exhibits a certain negative charge, under the mutual attraction of positive and negative charges, the noble metal-based cations can not only be deposited on the surface of the support, but also the interaction between the noble metal-based cations and the support can be enhanced; then the solution is dried by evaporation or other methods to obtain the alumina support loaded with noble metal-based cation groups and alkali metal species, that is, the above-mentioned adsorbent precursor.
[0080] In the activation process, the pH of the system is controlled at 11-14, which ensures that the negative charge on the carrier surface is sufficient to bind noble metal-based cationic groups, while avoiding the precipitation of noble metal-based cationic groups.
[0081] Optionally, in one embodiment, the mass ratio between the amount of the noble metal-based precursor and the alumina support is controlled to be 1:850 to 1:8.5, so that the prepared adsorbent can effectively balance its catalytic activity in catalyzing the oxidation of NO to NO2 and its cost.
[0082] Optionally, in one specific embodiment, the activation treatment temperature is 60-100°C and the time is 5-60 min, so as to fully and quickly utilize hydroxide ions to activate the support and make the support surface present with sufficient negative charge; Optionally, the activation reaction temperature can be one or any two of 60°C, 65°C, 70°C, 80°C, 90°C, 100°C, and the time can be one or any two of 5 min, 8 min, 10 min, 15 min, 20 min, 40 min, 50 min, 60 min.
[0083] The second alkali source mentioned above includes one or more of ammonia, sodium hydroxide, and sodium bicarbonate.
[0084] Optionally, in one embodiment, the second alkali source can be ammonia water, which can not only make the surface of the carrier present a certain negative charge, facilitating the deposition of noble metal-based precursors, but also partially dissolve the carrier material during evaporation at a higher temperature, causing defects on its surface. These defect sites can better stabilize the noble metal-based precursors, thereby better anchoring the noble metal-based species.
[0085] In this embodiment, the activation process needs to be kept in a sealed state to prevent the ammonia water from being extracted and evaporated.
[0086] Optionally, in one specific embodiment, the evaporation temperature can be 60-200°C, and stirring is maintained during the evaporation process to quickly evaporate the ammonia water, thereby forming an alumina carrier loaded with noble metal-based cationic groups and alkali metal species; Optionally, the evaporation temperature can be one or any two of 60°C, 90°C, 100°C, 150°C, and 200°C.
[0087] In this embodiment, noble metal-based species are introduced by ammonia evaporation. The high dispersion of noble metal-based species results in better catalytic activity of the adsorbent.
[0088] Optionally, the aforementioned noble metal-based precursors include one or more of Pt-based species precursors, Pd-based species precursors, and Rh-based species precursors, specifically water-soluble Pt, Pd, and Rh nitrates, sulfates, hydrochlorides, etc.
[0089] In step 403 above, the noble metal-based precursor is transformed into an oxidized state or a mixture of oxidized and metallic states through calcination treatment, thereby forming the aforementioned noble metal-based species.
[0090] Optionally, in the calcination treatment of the above-mentioned adsorbent precursor, the calcination temperature is 300–600℃ and the time is 0.5–12 h, which can rapidly and effectively convert the noble metal-based precursor loaded on the support into noble metal-based species. Optionally, the calcination temperature can be one or any two of 300℃, 350℃, 400℃, 500℃, and 600℃, and the time can be one or any two of 0.5 h, 1 h, 2 h, 5 h, 8 h, and 12 h.
[0091] The present invention also proposes an automobile exhaust gas treatment device, wherein the device includes a nitrogen oxide adsorbent as described above, or a nitrogen oxide adsorbent prepared by the preparation method described above.
[0092] The present invention also proposes a vehicle, including an engine, and further including the vehicle exhaust treatment device as described above.
[0093] The above-described automotive exhaust treatment device and vehicle embodiments include the aforementioned nitrogen oxide adsorbent and achieve the same technical effect. To avoid repetition, they will not be described again here. For relevant details, please refer to the description of the nitrogen oxide adsorbent embodiments.
[0094] The present invention will be described in detail below through embodiments.
[0095] Test method:
[0096] (1) Morphology test: The surface morphology of the carrier in this application was observed at high magnification using scanning electron microscopy (SEM) and transmission electron microscopy (TEM);
[0097] (2) Elemental analysis of the adsorbent carrier surface: During the observation of the electrode surface morphology using a scanning electron microscope, the various elemental components and percentage mass content of the electrode surface were analyzed using an energy dispersive spectroscopy (EDS) instrument.
[0098] (3) Nitrogen oxide adsorption performance test: The obtained nitrogen oxide adsorbent was deposited on the surface of an integral honeycomb ceramic with a size of 15*15*60mm and placed in a performance evaluation device. The evaluation device was preheated to 400℃. An atmosphere containing 250ppm NO and 8% O2 (the remaining carrier gas was N2) was introduced into the performance evaluation device to adsorb nitrogen oxides at 400℃ until saturation.
[0099] (4) Nitrogen oxide adsorption performance test of aged samples: Freshly prepared samples with deposited nitrogen oxide adsorbent were aged at 800℃ under hydrothermal conditions containing 10 vol% water vapor for 16 hours to obtain aged samples. The nitrogen oxide adsorption test of aged samples was the same as that of fresh samples;
[0100] (5) Specific surface area test: After degassing the nitrogen oxide adsorbent, the sample was placed in a nitrogen atmosphere to allow it to adsorb nitrogen until saturation. After the adsorption test, the specific surface area of the nitrogen oxide adsorbent was calculated based on the amount of nitrogen adsorbed and the Brunauer-Emmett-Teller model.
[0101] Example 1
[0102] (1) Preparation of alumina carrier materials
[0103] 6.0 g Al(NO3)3·9H2O, 0.289 g K2CO3 and 1.922 g CO(NH2)2 as the first alkali source were dissolved in 160 mL of deionized water and stirred at 800 rpm for 10 min. The mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction in an oven at 180 °C for 12 h.
[0104] After the hydrothermal reaction is completed, the hydrothermal product is taken out and heated to 90°C. Stirring is maintained until the solid product is dry. The dried solid product is then transferred to a muffle furnace and calcined at 500°C for 2 hours to obtain an alumina carrier material loaded with alkali metal species.
[0105] (2) Preparation of nitrogen oxide adsorbent
[0106] 1.0 g of alumina carrier material was dispersed in 15 mL of deionized water and 1.0 mL of saturated NH3·H2O was added as a second alkali source. The pH of the system was controlled at 12. The mixture was sealed with a sealing film, heated to 90 °C and stirred for 10 min for activation treatment. Then, a platinum nitrate solution with a Pt content of 20 mg was added to the mixture and the sealing film was removed. Stirring was continued until the ammonia evaporated to obtain a dry adsorbent precursor.
[0107] The above-mentioned adsorbent precursor was transferred to a muffle furnace and calcined at 500°C for 2 hours to obtain the final nitrogen oxide adsorbent.
[0108] Example 2
[0109] The difference between Example 2 and Example 1 is that in step (1), the amount of deionized water is adjusted to 100 mL.
[0110] Example 3
[0111] The difference between Example 3 and Example 1 is that in step (1), the amount of deionized water is adjusted to 300 mL.
[0112] Example 4
[0113] The difference between Example 4 and Example 1 is that in step (1), the amount of K2CO3 added is adjusted to 0.045g; and in step (2), the amount of platinum nitrate solution with a Pt content of 1mg is added.
[0114] Example 5
[0115] The difference between Example 5 and Example 2 is that in step (1), the amount of K2CO3 added is adjusted to 0.726g; and in step (2), the amount of platinum nitrate solution with a Pt content of 100mg is added.
[0116] Example 6
[0117] The difference between Example 6 and Example 1 is that in step (1), Al(NO3)3·9H2O is changed to aluminum sulfate and K2CO3 is changed to KNO3;
[0118] In step (2), platinum nitrate is replaced with palladium chloride.
[0119] Example 7
[0120] The difference between Example 7 and Example 1 is that in step (2), the amount of the second alkali source added is adjusted so that the pH of the system is 11.
[0121] Example 8
[0122] The difference between Example 8 and Example 1 is that in step (2), the amount of the second alkali source added is adjusted so that the pH of the system is 14.
[0123] Example 9
[0124] The difference between Example 9 and Example 1 is that, in step (1), the first alkali source is adjusted to potassium hydroxide;
[0125] In step (2), the second alkali source is adjusted to sodium bicarbonate.
[0126] Example 10
[0127] The difference between Example 10 and Example 1 is that, in step (1), the temperature of the hydrothermal reaction is adjusted to 60°C and the time is 0.5h; the temperature of the calcination treatment is adjusted to 300°C and the time is 0.5h.
[0128] In step (2), the calcination temperature is adjusted to 300℃ and the time is 0.5h.
[0129] Example 11
[0130] The difference between Example 11 and Example 1 is that, in step (1), the temperature of the hydrothermal reaction is adjusted to 200°C and the time is 24 hours; the temperature of the calcination treatment is adjusted to 600°C and the time is 12 hours.
[0131] In step (2), the calcination temperature is adjusted to 600℃ and the time is 12h.
[0132] Example 12
[0133] The difference between Example 12 and Example 1 is that in step (1), 0.289g K2CO3 is adjusted to 0.220g Rb2CO3.
[0134] Comparative Example 1
[0135] The difference between Comparative Example 1 and Example 1 is that in step (1), K2CO3 is changed to BaCl2.
[0136] Sample performance testing:
[0137] The nitrogen oxide adsorbents prepared in each embodiment and comparative example were subjected to morphology testing, surface elemental analysis, catalytic performance testing, catalytic lifetime testing, and specific surface area testing in sequence. The results are shown in Table 1. Among them, the morphology test results of the nitrogen oxide adsorbent prepared in Example 1 are as follows: Fig. 5 and 6 As shown, the morphology test results of the nitrogen oxide adsorbent prepared in Comparative Example 1 are as follows. Fig. 7 As shown.
[0138] Table 1
[0139]
[0140]
[0141] Through Table 1 and Figs. 5-7 As can be seen from Comparative Example 1 and Comparative Example 1, the introduction of alkali metal ions in hydrothermal synthesis will cause the alumina material to form a spherical hollow morphology, which not only gives it a larger specific surface area, enabling it to load more alkali metal species and noble metal-based species while ensuring high dispersibility, but also enhances the binding force between alkali metal species and noble metal-based species and the support, thereby improving the catalytic stability of the adsorbent.
[0142] As can be seen from the comparison of the various embodiments in Table 1, the hydrothermal reaction of potassium ions in the potassium-based precursor at a reasonable temperature can regulate the crystal growth process of the alumina precursor, thereby growing the alumina into a porous morphology, which can support more alkali metal species and noble metal-based species. At the same time, the carrier loaded with alkali metal species formed by calcining the hydrothermal product is mixed with an appropriate amount of second alkali source and activated at a suitable temperature, which can make the carrier surface exhibit moderate negative charge, which is more conducive to the deposition of positively charged noble metal-based cations, and ensures the dispersion and stability of noble metal-based species. The resulting nitrogen oxide adsorbent has particularly good performance.
[0143] The nitrogen oxide adsorbent provided in this invention can efficiently capture nitrogen oxides at high temperatures of 350–550°C, and is suitable for controlling nitrogen oxide emissions under lean-burn conditions in gasoline engines.
[0144] In summary, the nitrogen oxide adsorbent provided in this embodiment includes a support and alkali metal species and noble metal-based species loaded on the support. The support material includes alumina, and the support has pores. Using alkali metal species as active sites for nitrogen oxide adsorption allows for efficient nitrogen oxide capture at high temperatures of 350–550°C, suitable for controlling nitrogen oxide emissions under lean-burn conditions in gasoline engines. Using alumina as the support material and forming pores on its surface not only gives it a larger specific surface area, enabling it to load more alkali metal species and noble metal-based species while ensuring high dispersibility, but also enhances the binding force between the alkali metal species and noble metal-based species and the support, thereby improving the catalytic stability of the adsorbent. This alleviates the problem of noble metal sites agglomerating under high-temperature conditions and frequent adsorption / desorption cycles, thus effectively solving the technical problems of low operating temperature and poor catalytic stability in existing nitrogen oxide adsorbents.
[0145] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.
[0146] The present invention provides a detailed description of a nitrogen oxide adsorbent, its preparation method, and an automobile exhaust treatment device. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A nitrogen oxide adsorbent, characterized in that, The invention includes a carrier and alkali metal species and noble metal-based species loaded on the carrier. The carrier is made of alumina and has pores. The alkali metal species include at least one of potassium-based species, rubidium-based species, and cesium-based species.
2. The nitrogen oxide adsorbent according to claim 1, characterized in that, The material of the carrier includes γ-Al2O3.
3. The nitrogen oxide adsorbent according to claim 1, characterized in that, The carrier is a hollow sphere.
4. The nitrogen oxide adsorbent according to claim 3, characterized in that, The particle size of the carrier is 1–10 micrometers; and / or The carrier has a wall thickness of 0.2–1.0 micrometers; and / or The specific surface area of the carrier is 100-300 m². 2 / g.
5. The nitrogen oxide adsorbent according to claim 1, characterized in that, The alkali metal species include one or more of alkali metal carbonates and alkali metal oxides; and / or The noble metal-based species include one or more of Pt, Pd, and Rh.
6. The nitrogen oxide adsorbent according to claim 1, characterized in that, In the nitrogen oxide adsorbent, the noble metal element in the noble metal-based species accounts for 0.1 wt% to 10.0 wt% of the mass of the carrier, and the alkali metal element in the alkali metal species accounts for 3 wt% to 50 wt% of the mass of the carrier.
7. A method for preparing a nitrogen oxide adsorbent, characterized in that, include: An aluminum-based precursor, an alkali metal precursor, and a first alkali source are dissolved in water and subjected to a hydrothermal reaction. The hydrothermal product is then calcined to obtain a carrier loaded with 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. The carrier is dispersed in water and then activated by adding a second alkali source. Then a noble metal-based precursor is added and dried to obtain the adsorbent precursor. The adsorbent precursor is calcined to obtain a nitrogen oxide adsorbent.
8. The preparation method according to claim 7, characterized in that, The first alkali source is one or more of urea, potassium hydroxide, potassium carbonate, potassium bicarbonate, and sodium bicarbonate; and / or The second alkali source is one or more of ammonia, sodium hydroxide, and sodium bicarbonate.
9. The preparation method according to claim 7, characterized in that, During the activation process, the pH of the system is controlled at 11–14.
10. The preparation method according to claim 7, characterized in that, The aluminum-based precursor includes one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, potassium aluminum sulfate, and ammonium aluminum sulfate; and / or The potassium-based precursor includes one or more of potassium nitrate, potassium carbonate, potassium sulfate, and potassium chloride; and / or The rubidium-based precursor includes one or more of rubidium nitrate, rubidium carbonate, rubidium sulfate, and rubidium chloride; and / or The cesium-based precursor includes one or more of cesium nitrate, cesium carbonate, cesium sulfate, and cesium chloride; and / or The noble metal-based precursor includes one or more of Pt-based, Pd-based, and Rh-based precursors.
11. The preparation method according to claim 7, characterized in that, The hydrothermal reaction is carried out at a temperature of 60–200°C for a time of 0.5–24 hours. In the calcination treatment of hydrothermal products, the calcination temperature is 300-600℃ and the time is 0.5-12h; In the calcination treatment of the adsorbent precursor, the calcination temperature is 300-600℃ and the time is 0.5-12h.
12. The preparation method according to claim 7, characterized in that, The hydrothermal products are subjected to calcination treatment, including: After the hydrothermal reaction is completed, the hydrothermal products are taken out and subjected to drying and calcination treatments in sequence.
13. A vehicle exhaust gas treatment device, characterized in that, It includes nitrogen oxide adsorbents as described in any one of claims 1 to 6, or nitrogen oxide adsorbents prepared by the preparation method as described in any one of claims 7 to 12.
14. A vehicle, comprising an engine, characterized in that, It also includes the vehicle exhaust treatment device as described in claim 13.