Metal oxide / Pd-based SSZ-13 molecular sieve composite material as well as preparation method and application thereof

Abstract

The invention relates to a metal oxide / Pd-based SSZ-13 molecular sieve composite material as well as a preparation method and application thereof. Different metal oxides and the SSZ-13 molecular sieve are tightly compounded through a specific process, and the Pd active component is introduced in an impregnation loading manner, so that the efficient synergistic effect of the metal oxides, the Pd active component and the molecular sieve carrier can be exerted, the NOx adsorption capacity and low-temperature adsorption efficiency of the composite material are remarkably improved, and the NOx adsorption capacity and low-temperature adsorption efficiency of the composite material are improved. Meanwhile, the excellent hydrothermal aging stability of the composite material is kept. Compared with the prior art, the material disclosed by the invention is excellent in low-temperature NOx storage performance, high in stability and small in secondary pollution, can be coupled with a NOx catalytic reduction material, and is suitable for a motor vehicle exhaust aftertreatment system.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas adsorption materials technology, and in particular to a metal oxide / Pd-based SSZ-13 molecular sieve composite material, its preparation method and application. Background Technology

[0002] Nitrogen oxides (NO) x Fine particulate matter (PM2.5) is one of the major air pollutants. 2.5 NO is a major contributor to combined pollution of air and ozone (O3), seriously endangering the atmospheric environment and human health. x Emissions mainly come from stationary sources such as thermal power units and various industrial boilers / kilns, and mobile sources such as motor vehicles and ships. With the increasing NOx emissions from stationary sources... x Emissions have been gradually and effectively controlled, and NOx emissions from mobile source vehicle exhaust have been reduced. x Becoming an important target for air pollutant control requires achieving NOx emissions from vehicle exhaust. x Ultra-low emissions (<35 mg / km).

[0003] NO x Storage reduction (NSR), ammonia selective catalytic reduction of NO x Technologies such as NH3-SCR have been applied to vehicle exhaust aftertreatment systems. However, existing catalytic technologies are still insufficient for controlling NO emissions from vehicle exhaust. x Effective removal is not possible at low temperatures (≤150 ℃), low-temperature high-efficiency NO removal is required. x The research and application of catalyst removal technology has become a key area for NO removal in motor vehicle exhaust. x The key bottleneck to control.

[0004] Passive NO x PNA (Physical Adsorption) technology can rapidly adsorb NO at low temperatures (≤150 °C). x Once the exhaust gas temperature rises to the activation temperature of the aftertreatment system, the stored NO will be gradually released as the temperature increases. x Nitrate species are then effectively removed by the downstream tightly coupled selective catalytic reduction (SCR) unit, which is a solution for NO during the cold start phase of motor vehicles. x A key measure to address excessive emissions. Currently, Pd-based SSZ-13 molecular sieves are known for their excellent NO content. x Adsorption performance, thermal stability, and hydrothermal aging resistance have become research hotspots for Pd / SSZ-13 materials. However, Pd / SSZ-13 materials alone still exhibit NO degradation under low-temperature conditions (<150 °C). x Limited adsorption capacity, NO under high temperature conditions xA series of problems, such as difficulty in desorption and poor matching between the temperature range of temperature-increasing desorption and catalytic reduction, make it impossible to achieve continuous NO emission during the cold start phase. x Effective storage and efficient removal of pollutants are insufficient to meet stringent emission regulations.

[0005] CN116764674A discloses a molecular sieve core-shell structured material, its preparation method, and its application. This molecular sieve core-shell structured material uses SSZ-13 molecular sieve as the core and Al2O3 as the shell, with Pd metal supported on it. The core-shell structure improves the hydrothermal stability of the catalyst and the dispersibility of Pd species, thereby enhancing NO… x Adsorption and desorption efficiencies. However, the preparation steps of this core-shell structured catalytic material are cumbersome, require high control of reaction conditions, and are difficult to scale up. Meanwhile, its NO content... x There is still considerable room for improvement in adsorption performance.

[0006] CN111957342A discloses a microporous molecular sieve-supported bimetallic material for low-temperature removal of nitrogen oxides from diesel vehicle exhaust. A PdCe-SSZ-13 catalyst was successfully prepared by adding cerium (Ce) to a Pd-based molecular sieve, which can solve the NO removal problem during the cold start stage. x To address the problem of low removal efficiency and achieve efficient low-temperature NO removal. x The removal and improved material stability make it suitable for diesel vehicle exhaust treatment. However, this Ce ion-modified molecular sieve catalyst requires multiple ion exchange / impregnation and calcination processes, making the preparation steps cumbersome, and some process parameters (such as calcination at 500-600 °C) have high energy consumption.

[0007] Therefore, regarding the existing Pd-based SSZ-13 molecular sieve composites in the NO emissions from motor vehicle exhaust... x The problems existing in adsorption and desorption still require the development of a method to achieve NO x A novel Pd-based SSZ-13 molecular sieve material for low-temperature and high-efficiency storage. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of cumbersome preparation, harsh reaction conditions, and NO content in the existing technologies. x To address at least one defect where adsorption performance needs improvement, a metal oxide / Pd-based SSZ-13 molecular sieve composite material, its preparation method, and its application are provided.

[0009] The objective of this invention can be achieved through the following technical solutions: The present invention first provides a metal oxide / Pd-based SSZ-13 molecular sieve composite material, wherein the composite material uses SSZ-13 molecular sieve as a carrier and is loaded with Pd and modifying agents; The Pd is the active component, and its loading is 1-3% of the mass of SSZ-13 molecular sieve; The modifying agent is a metal oxide containing rare earth and / or transition metal elements, and its loading is 10-30% of the mass of SSZ-13 molecular sieve.

[0010] Furthermore, the loading of the metal oxide is preferably 15-25% of the mass of SSZ-13 molecular sieve, and more preferably 20%.

[0011] Furthermore, the Pd loading is preferably 2% of the mass of SSZ-13 molecular sieve.

[0012] Further, the metal oxide is at least one selected from CeO2, Fe2O3, CuO, MnO, NiO, La2O3, Sm2O3, Pr2O3, and Gd2O3.

[0013] Furthermore, the metal oxide is preferably CeO2, CuO, MnO, Sm2O3, or Gd2O3.

[0014] Furthermore, the silica-alumina ratio of the SSZ-13 molecular sieve is 13 to 31, which is adjustable within this range.

[0015] This invention also provides a method for preparing a metal oxide / Pd-based SSZ-13 molecular sieve composite material, the method comprising the following steps: S1, Preparation of NH 4+ -SSZ-13 molecular sieve: Ammonium chloride and H-SSZ-13 molecular sieve are mixed and reacted, and the product is collected to obtain NH. 4+ -SSZ-13 molecular sieve; S2, Preparation of metal oxide / SSZ-13 molecular sieve: The NH obtained in S1 4+ -SSZ-13 molecular sieve was mixed with metal oxide precursor salt and dispersed evenly, then transferred to a reaction vessel for hydrothermal reaction; the product was collected, ground and then subjected to initial calcination to obtain SSZ-13@metal oxide composite material; S3. Preparation of metal oxide / Pd-based SSZ-13 molecular sieve composite material: The metal oxide / SSZ-13 molecular sieve composite material obtained in S2 was mixed with palladium salt and then impregnated and stirred; the product was collected, ground and then calcined twice to obtain Pd / (SSZ-13@metal oxide) composite material. S4. Hydrothermal aging: The metal oxide / Pd-based SSZ-13 molecular sieve composite material prepared in S3 is subjected to hydrothermal aging to obtain the final composite material.

[0016] Further, in step S1, the mass ratio of ammonium chloride to H-SSZ-13 molecular sieve is (2-3):1.

[0017] Furthermore, in step S1, the reaction temperature is 80-90 °C.

[0018] Furthermore, in step S1, the reaction time is 2-4 hours.

[0019] Further, in step S2, the NH 4+ The mass ratio of SSZ-13 molecular sieve to metal oxide precursor salt is 1: (0.6-1.4).

[0020] Further, in step S2, the metal oxide precursor salt is any one or more of the chloride, nitrate, and sulfate salts corresponding to the metal oxide.

[0021] Furthermore, in step S2, the temperature of the hydrothermal reaction is 10-150 °C.

[0022] Furthermore, in step S2, the hydrothermal reaction takes 18-24 hours.

[0023] Furthermore, in step S2, the initial calcination temperature is 450-550 ℃.

[0024] Furthermore, in step S2, the initial calcination time is 3-5 hours.

[0025] Further, in step S3, the mass ratio of the metal oxide / SSZ-13 molecular sieve composite material to the palladium element in the palladium salt is 1:(0.01-0.03).

[0026] Further, in step S3, the palladium salt is any one or more of palladium nitrate, palladium chloride, and palladium sulfate.

[0027] Furthermore, in step S3, the reaction temperature is 60-80 °C.

[0028] Furthermore, in step S3, the reaction time is 18-24 h.

[0029] Furthermore, in step S3, the temperature of the secondary calcination is 450-550 ℃.

[0030] Furthermore, in step S3, the secondary calcination time is 3-5 hours.

[0031] Furthermore, in step S4, the hydrothermal aging is carried out in an air atmosphere containing 5-15 vol.% water vapor.

[0032] Furthermore, in step S4, the temperature of the hydrothermal aging is 700-750 ℃.

[0033] Furthermore, in step S4, the hydrothermal aging time is 12-16 hours.

[0034] This invention also provides a metal oxide / Pd-based SSZ-13 molecular sieve composite material for low-temperature and high-efficiency NO storage. x Applications in [the context of the text].

[0035] Furthermore, the metal oxide / Pd-based SSZ-13 molecular sieve composite material is widely adaptable to NO emissions from various motor vehicle exhaust gases. x The low-temperature adsorption module, in conjunction with the downstream SCR unit, efficiently solves NO2 during cold starts in motor vehicles. x Emissions issues.

[0036] Rare earth and transition metal oxides (such as CeO2, Fe2O3, CuO, etc.) have unique redox properties and diverse surface acid-base site distribution characteristics, making them suitable for use in traditional NO42-NO ... x It exhibits excellent potential during adsorption and activation. Effective combination of metal oxides and molecular sieves can often better leverage their synergistic coupling effect; for example, metal oxides can provide additional NO. x On the one hand, it enhances adsorption by creating adsorption sites and promoting the oxidation of NO to nitrate species. On the other hand, it can effectively regulate the chemical coordination environment of the Pd active component through a special charge compensation effect, thereby improving the NO adsorption of the coupling material. x Low-temperature adsorption performance.

[0037] However, in existing traditional composite methods, the weak interfacial bonding between metal oxides and molecular sieves and the poor dispersion of active species make the catalytic material prone to aggregation or detachment under the thermal aging and regeneration conditions of motor vehicle exhaust aftertreatment systems, leading to a decline in adsorption, storage, and catalytic reaction performance. Furthermore, the synergistic effect between metal oxides and Pd active species needs further in-depth investigation to maximize the NO content of the composite material. x Adsorption capacity and efficiency.

[0038] Based on this, the present invention achieves a highly efficient synergistic effect between the metal oxide, Pd active species, and the molecular sieve support by introducing Pd active components through impregnation loading using a specific process, thereby significantly improving NO content. x It achieves high adsorption capacity and low-temperature adsorption efficiency while maintaining excellent hydrothermal stability of the composite material.

[0039] This application constructs an SSZ-13 / CeO2 composite support via hydrothermal synthesis and employs an innovative two-step process of impregnation and loading Pd to achieve a tight interface between CeO2 and SSZ-13 through Ce-O-Si / Ce-O-Al chemical bonds. This process not only inhibits the hydrothermal aging and dealumination of the molecular sieve to retain Pd ion exchange sites, but also facilitates the formation of a tight interface between CeO2 and SSZ-13 through Ce-O-Si / Ce-O-Al chemical bonds. 3+ / Ce 4+ Cyclic regulation of Pd 2+ This is an electronic defect state, which is then preferentially guided to form highly active Z-[Pd(OH)] at the eight-membered ring framework site of the molecular sieve. + This also improves the dispersibility and stability of Pd species, completely solving the problems of weak interfacial bonding between metal oxides and molecular sieves and easy aggregation and detachment of active species in traditional composite methods, and significantly enhancing the low-temperature NO content of the composite material. x Adsorption capacity and cycling stability.

[0040] Compared with the prior art, the present invention has the following technical advantages: (1) This invention achieves a highly efficient synergistic effect between the metal oxide and SSZ-13 molecular sieve through a specific process, and introduces Pd active components through impregnation loading, thereby significantly improving the NO content. x It achieves high adsorption capacity and low-temperature adsorption efficiency while maintaining excellent hydrothermal stability of the composite material.

[0041] (2) The present invention introduces a material by tightly combining metal oxides with SSZ-13 via a hydrothermal method and then introducing the Pd active component. The introduction of metal oxides can not only effectively inhibit the damage to the molecular sieve framework structure during the hydrothermal aging process, but also effectively regulate the Pd active component. 2+ The electronic effects of the active site significantly promote NO. x The low-temperature adsorption capacity of the composite material is significantly improved; at the same time, the introduction of metal oxide components can also significantly promote the oxidation process of NO, thus significantly enhancing the low-temperature NO adsorption capacity of the composite material. x Adsorption capacity and adsorption efficiency.

[0042] (3) This invention uses a specific process to tightly combine different metal oxides with SSZ-13 molecular sieves and introduces Pd active components through impregnation loading, thus successfully achieving the efficient synergistic effect of metal oxides, Pd active species and molecular sieve carriers.

[0043] (4) NO of the present invention x The low-temperature, high-efficiency storage material has a simple synthesis process, good repeatability, and strong stability in cyclic testing, making it suitable for the thermal aging and regeneration conditions of vehicle exhaust aftertreatment. This material is widely applicable to various types of vehicle exhaust NO₂. x The low-temperature adsorption module, in conjunction with the downstream SCR unit, efficiently solves NO2 during cold starts in motor vehicles.x Emissions issues. Attached Figure Description

[0044] Figure 1 The Pd / (SSZ-13@CeO2)NO prepared in Example 1 of this invention x TEM image of a low-temperature, high-efficiency storage material.

[0045] Figure 2 The Pd / (SSZ-13@CeO2)NO prepared in Example 1 of this invention x XRD pattern of low-temperature high-efficiency storage materials.

[0046] Figure 3 The Pd / SSZ-13 NO prepared as Comparative Example 1 of this invention x Adsorption-desorption performance test curves of composite materials.

[0047] Figure 4 The Pd / SSZ-13 NO prepared as Comparative Example 1 of this invention x NO in composite materials x Adsorption / desorption volume bar chart.

[0048] Figure 5 The Pd / (SSZ-13@CeO2)NO prepared in Example 1 of this invention x Adsorption-desorption performance test curves of low-temperature high-efficiency storage materials.

[0049] Figure 6 The Pd / (SSZ-13@CeO2)NO prepared in Example 1 of this invention x NO in low-temperature high-efficiency storage materials x Adsorption / desorption volume bar chart. Detailed Implementation

[0050] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0051] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0052] Example 1: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@CeO2), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve (silicon-to-aluminum ratio of 3:1) and add it to the solution while stirring. Place the flask in an 80 °C constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 °C oven to dry, grind and obtain NH4. + -SSZ-13.

[0053] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.398 g of cerium nitrate hexahydrate was added to the solution, and the mixture was ultrasonically dispersed for 30 min. The mixture was then transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 100 ℃ for 18 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 550 ℃ for 4 h. The resulting product was the SSZ-13@CeO2 composite material.

[0054] (3) Take 5 mL of deionized water into a round-bottom flask, dissolve the SSZ-13@CeO2 material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of Pd(NO3)2 solution with a mass fraction of 18.09 wt.% and add it to the solution while stirring. Then, impregnate and stir for 18 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 550 ℃ for 4 h. The product obtained is Pd / (SSZ-13@CeO2)NO x Low-temperature, high-efficiency storage materials.

[0055] (4) The obtained material was placed in a tube furnace and hydrothermally treated at 700 °C for 16 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged composite material.

[0056] like Figure 1 As shown in the TEM image of Pd / (SSZ-13@CeO2) prepared in this embodiment, CeO2 particles are observed to stack to form a continuous shell, encapsulating the surface of SSZ-13 and forming a clear composite structure; no obvious large-sized PdO particles are observed. x Pd exists as dispersed nanoparticles.

[0057] like Figure 2As shown, in the XRD results of this embodiment, all samples exhibited characteristic diffraction peaks of CHA-type zeolite (SSZ-13), indicating that the zeolite framework remained intact after hydrothermal aging and CeO2 composite formation. No obvious PdO characteristic peaks were detected, indicating that the Pd species were highly dispersed; the CeO2 characteristic peaks were extremely weak, attributed to their small particle size or the formation of a thin shell structure.

[0058] Example 2: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@CuO), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in an 80 ℃ constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind and obtain NH4. + -SSZ-13.

[0059] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.3797 g of copper nitrate trihydrate was added to the solution, and ultrasonic dispersion was performed for 30 min. Then, the mixed solution was transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 120 ℃ for 16 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 550 ℃ for 4 h. The resulting product was the SSZ-13@CuO composite material.

[0060] (3) Take 5 mL of deionized water into a round-bottom flask, dissolve the SSZ-13@CuO material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of a 18.09 wt.% Pd(NO3)2 solution and add it to the solution while stirring. Then, impregnate and stir for 24 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 550 ℃ for 4 h. The product obtained is Pd / (SSZ-13@CuO)NO x Low-temperature, high-efficiency storage materials.

[0061] (4) The obtained material was placed in a tube furnace and hydrothermally treated at 750 °C for 14 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0062] Example 3: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@MnO), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in an 80 ℃ constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind and obtain NH4. + -SSZ-13.

[0063] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.4423 g of manganese nitrate tetrahydrate was added to the solution, and ultrasonic dispersion was performed for 30 min. Then, the mixed solution was transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 120 ℃ for 16 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 500 ℃ for 4 h. The resulting product is the SSZ-13@MnO composite material.

[0064] (3) Take 5 mL of deionized water into a round-bottom flask, dissolve the SSZ-13@MnO material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of Pd(NO3)2 solution with a mass fraction of 18.09 wt.% and add it to the solution while stirring. Then, impregnate and stir for 24 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 500 ℃ for 4 h. The product obtained is Pd / (SSZ-13@MnO)NO x Low-temperature, high-efficiency storage materials.

[0065] (4) The obtained material is placed in a tube furnace and hydrothermally treated at 700 °C for 12 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0066] Example 4: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@Sm2O3), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in a constant temperature oil bath at 90 ℃, reflux and stir for 4 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an oven at 80 ℃ to dry, grind and obtain NH4. + -SSZ-13.

[0067] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.3186 g of samarium nitrate hexahydrate was added to the solution, and the mixture was ultrasonically dispersed for 30 min. The mixture was then transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 140 ℃ for 18 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 550 ℃ for 4 h. The resulting product was the SSZ-13@Sm2O3 composite material.

[0068] (3) Take 5 mL of deionized water into a round-bottom flask, dissolve the SSZ-13@Sm2O3 material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of Pd(NO3)2 solution with a mass fraction of 18.09 wt.% and add it to the solution while stirring. Then, impregnate and stir for 20 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 550 ℃ for 4 h. The product obtained is Pd / (SSZ-13@Sm2O3)NO x Low-temperature, high-efficiency storage materials.

[0069] (4) The obtained material is placed in a tube furnace and hydrothermally treated at 750 °C for 12 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0070] Example 5: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@Gd2O3), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in an 80 ℃ constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind and obtain NH4.+ -SSZ-13.

[0071] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.3113 g of gadolinium nitrate hexahydrate was added to the solution, and the mixture was ultrasonically dispersed for 30 min. The mixture was then transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 120 ℃ for 18 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 550 ℃ for 4 h. The resulting product was the SSZ-13@Gd2O3 composite material.

[0072] (3) Take 5 mL of deionized water into a round-bottom flask, dissolve the SSZ-13@Gd2O3 material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of Pd(NO3)2 solution with a mass fraction of 18.09 wt.% and add it to the solution while stirring. Then, impregnate and stir for 24 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 550 ℃ for 4 h. The product obtained is Pd / (SSZ-13@Gd2O3)NO x Low-temperature, high-efficiency storage materials.

[0073] (4) The obtained material was placed in a tube furnace and hydrothermally treated at 750 °C for 16 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0074] Comparative Example 1: This comparative example is a Pd-based SSZ-13 molecular sieve supported only on Pd, without any metal oxide additives. The specific preparation method is as follows: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in an 80 ℃ constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind and obtain NH4. + -SSZ-13.

[0075] (2) Take 5 mL of deionized water into a round-bottomed flask, and add the NH4 obtained in step (1). +-SSZ-13 material was dissolved in water, and stirred with a magnetic stirrer until the solid dissolved. 0.0554 g of a 18.09 wt.% Pd(NO3)2 solution was weighed and added to the solution while stirring. The mixture was then impregnated and stirred for 18 h. After the reaction, the mixture was centrifuged and washed until the supernatant was neutral. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 550 ℃ for 4 h. The resulting product was Pd / SSZ-13 NO3-. x Low-temperature, high-efficiency storage materials.

[0076] (3) The obtained composite material was placed in a tube furnace and hydrothermally treated at 700 °C for 16 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged composite material.

[0077] Comparative Example 2: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@Fe2O3), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in an 80 ℃ constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind and obtain NH4. + -SSZ-13.

[0078] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.6325 g of ferric nitrate nonahydrate was added to the solution, and ultrasonic dispersion was performed for 30 min. Then, the mixed solution was transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 100 ℃ for 18 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 450 ℃ for 4 h. The resulting product is the SSZ-13@Fe2O3 composite material.

[0079] (3) Take 5 mL of deionized water into a round-bottom flask, dissolve the SSZ-13@Fe2O3 material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of Pd(NO3)2 solution with a mass fraction of 18.09 wt.% and add it to the solution while stirring. Then, impregnate and stir for 24 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 450 ℃ for 4 h. The product obtained is Pd / (SSZ-13@Fe2O3)NO x Low-temperature, high-efficiency storage materials.

[0080] (4) The obtained material was placed in a tube furnace and hydrothermally treated at 750 °C for 16 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0081] Comparative Example 3: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@NiO), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in an 80 ℃ constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind and obtain NH4. + -SSZ-13.

[0082] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.4867 g of nickel nitrate hexahydrate was added to the solution, and ultrasonic dispersion was performed for 30 min. Then, the mixed solution was transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 100 ℃ for 16 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 450 ℃ for 4 h. The resulting product is the SSZ-13@NiO composite material.

[0083] (3) Take 5 mL of deionized water into a round-bottomed flask, dissolve the SSZ-13@NiO material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of a 18.09 wt.% Pd(NO3)2 solution and add it to the solution while stirring. Then, impregnate and stir for 18 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 450 ℃ for 4 h. The product obtained is Pd / (SSZ-13@NiO)NO x Low-temperature, high-efficiency storage materials.

[0084] (4) The obtained material was placed in a tube furnace and hydrothermally treated at 700 °C for 16 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0085] Comparative Example 4: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@La2O3), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in an 80 ℃ constant temperature oil bath, reflux and stir for 2 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind and obtain NH4. + -SSZ-13.

[0086] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.3323 g of lanthanum nitrate hexahydrate was added to the solution, and the mixture was ultrasonically dispersed for 30 min. The mixture was then transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 140 ℃ for 18 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 500 ℃ for 4 h. The resulting product was the SSZ-13@La2O3 composite material.

[0087] (3) Take 5 mL of deionized water into a round-bottom flask, dissolve the SSZ-13@La2O3 material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of a 18.09 wt.% Pd(NO3)2 solution and add it to the solution while stirring. Then, impregnate and stir for 24 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 500 ℃ for 4 h. The product obtained is Pd / (SSZ-13@La2O3)NO x Low-temperature, high-efficiency storage materials.

[0088] (4) The obtained material was placed in a tube furnace and hydrothermally treated at 750 °C for 14 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0089] Comparative Example 5: This embodiment provides a metal oxide composite Pd-based SSZ-13 molecular sieve type NO. x The low-temperature high-efficiency storage material, specifically Pd / (SSZ-13@Pr2O3), is prepared using the following method: (1) Take 50 mL of deionized water into a flask, weigh 2.6745 g of ammonium chloride solid and dissolve it in the water. Add a magnetic stir bar and stir until the solid dissolves. Weigh 1 g of H-SSZ-13 molecular sieve and add it to the solution while stirring. Place the flask in a constant temperature oil bath at 90 ℃, reflux and stir for 4 h. After the oil bath, centrifuge and wash until the supernatant is neutral. Place it in an oven at 80 ℃ to dry, grind and obtain NH4. + -SSZ-13.

[0090] (2) Take 50 mL of deionized water into a pear-shaped flask and weigh 0.5 g of NH4. + - SSZ-13 was dissolved in water, and a magnetic stirrer was added. While stirring, 0.3297 g of praseodymium nitrate hexahydrate was added to the solution, and the mixture was ultrasonically dispersed for 30 min. The mixture was then transferred to a stainless steel high-pressure reactor and hydrothermally reacted at 150 ℃ for 18 h. After the reaction, the mixture was centrifuged and washed until the pH value was 7. It was then dried in an 80 ℃ oven, ground, and calcined in a muffle furnace at 450 ℃ for 4 h. The resulting product was the SSZ-13@Pr2O3 composite material.

[0091] (3) Take 5 mL of deionized water into a round-bottomed flask, dissolve the SSZ-13@Pr2O3 material in the water, add a magnetic stir bar and stir until the solid dissolves. Weigh 0.0554 g of Pd(NO3)2 solution with a mass fraction of 18.09 wt.% and add it to the solution while stirring. Then, impregnate and stir for 24 h. After the reaction is complete, centrifuge and wash until the supernatant is neutral. Place it in an 80 ℃ oven to dry, grind it, and then place it in a muffle furnace to calcine at 450 ℃ for 4 h. The product obtained is Pd / (SSZ-13@Pr2O3)NO x Low-temperature, high-efficiency storage materials.

[0092] (4) The obtained material was placed in a tube furnace and hydrothermally treated at 750 °C for 14 h in an air atmosphere containing 10 vol.% water vapor to obtain the hydrothermally aged material.

[0093] Information on the products obtained in Examples 1-5 and Comparative Examples 1-5 is summarized in Table 1.

[0094] Table 1 Summary of the product composition of Examples 1-5 and Comparative Examples 1-5

[0095] Based on the successful preparation of the above embodiments and comparative examples, this invention further explores the application of the above materials in low-temperature and high-efficiency NO storage. x Applications in [the context of the text].

[0096] NO x The specific procedure for the adsorption / desorption test is as follows: The prepared catalyst was granulated to 40-60 mesh and placed in a reactor for constant-temperature NO reaction. x Adsorption and temperature-programmed desorption tests were conducted. (Regarding the adsorption of NO...) x Before pretreatment, 120 mg of sample was first pretreated in a 20% O2 flowing gas balanced with nitrogen at 500 °C for 1 h, and then the temperature was lowered to 100 °C and 200 ppm NO was introduced. x A gas feed of 10% O2, 5% H2O and 5% CO2 at a total flow rate of 400 mL / min is used for NO treatment. x Adsorption process. Desorption process: NO feed is shut off, and the temperature is increased to 500 °C at a rate of 10 °C / min.

[0097] like Figure 3-4 As shown, NO in Pd / SSZ-13 in Comparative Example 1 x The adsorption capacity is 157.8 μmol·g. -1 The desorption capacity reached 95.4 μmol·g -1In contrast, the NO content of the Pd / (SSZ-13@CeO2) material prepared by the hydrothermal method in Example 1 was significantly lower. x Adsorption and desorption performance is significantly improved. For example... Figure 5-6 As shown, its NO after hydrothermal aging x The adsorption capacity and desorption capacity reached 187.9 μmol·g. -1 and 114.1 μmol·g -1 .

[0098] The results above show that the introduction of CeO2 in Example 1 not only effectively inhibited the damage to the molecular sieve framework structure caused by hydrothermal aging, but also regulated the Pd content. 2+ The electronic state of the active site, thereby effectively promoting NO x Low-temperature adsorption storage; simultaneously, the presence of metal oxides can also promote the oxidation of NO, significantly enhancing the low-temperature NO absorption capacity. x Adsorption capacity and adsorption efficiency.

[0099] Furthermore, the metal oxides introduced in Examples 2-5 all significantly improved the low-temperature NO content. x Adsorption capacity and adsorption efficiency. In Example 2, the introduction of CuO provides abundant lattice oxygen at low temperatures, accelerating the NO oxidation reaction cycle and significantly improving the material's low-temperature NO adsorption capacity and efficiency. x Adsorption capacity and adsorption efficiency.

[0100] In Example 3, the introduction of MnO2 can dynamically control Pd. 2+ The redox state of the active site enhances its resistance to NO. x Its capture capability effectively promotes NO. x Adsorption; simultaneously, MnO2 itself has strong oxidizing properties, which can accelerate the oxidation of NO at low temperatures, ultimately effectively improving the material's low-temperature NO adsorption capacity. x Adsorption capacity and adsorption efficiency.

[0101] In Example 4, the introduction of Sm2O3 not only enhances the chemical bond stability of the molecular sieve framework by forming stable bonds with it, effectively suppressing desilication caused by hydrothermal aging, but also regulates Pd through synergistic effects. 2+ The spatial configuration of the active site effectively promotes NO. x Adsorption.

[0102] In Example 5, the introduction of Gd₂O₃ not only effectively inhibited the damage to the molecular sieve framework structure caused by hydrothermal aging, but also promoted the oxidation of NO, significantly improving the low-temperature NO reduction of the material. x Adsorption capacity and adsorption efficiency.

[0103] In summary, the effective introduction of rare earth metals or transition metal oxides not only effectively inhibits the damage to the molecular sieve framework structure caused by hydrothermal aging, but also effectively promotes NO x It can also promote the low-temperature adsorption and storage of NO; ​​at the same time, it can also promote the oxidation of NO and significantly enhance the low-temperature NO absorption capacity. x Adsorption capacity and adsorption efficiency.

[0104] In contrast, the introduction of Fe2O3 in Comparative Example 2 could not effectively suppress the damage to the molecular sieve framework structure caused by hydrothermal aging, therefore NO2O3 increased after hydrothermal aging. x There was no significant improvement in adsorption performance.

[0105] The NiO introduced in Comparative Example 3 has weak interfacial bonding with the molecular sieve, failing to effectively lower the activation barrier of the NO oxidation reaction. This hinders the migration of reactive oxygen species within the material, making it difficult to improve the NO oxidation efficiency at low temperatures. x Adsorption capacity and efficiency.

[0106] The introduction of La2O3 in Comparative Example 4 resulted in excessively high acidity sites on the material surface, which in turn caused the adsorption products to easily desorb, making it impossible to improve the low-temperature NO levels of the material through stable adsorption. x Adsorption capacity and efficiency.

[0107] In Comparative Example 5, the introduction of Pr₂O₃ could not effectively suppress the damage to the molecular sieve framework structure caused by hydrothermal aging; therefore, NO₂ increased after hydrothermal aging. x There was no significant improvement in adsorption performance.

[0108] In summary, this invention relates to a method with good NO content. x NO2-low temperature storage capacity and water-heat aging stability x Storage catalytic material. Pd / SSZ-13 exhibits excellent adsorption performance and thermal stability. This invention innovatively combines different metal oxides with SSZ-13 molecular sieves through a specific process, and introduces Pd active components through impregnation loading. This achieves a highly efficient synergistic effect between the metal oxides, Pd active species, and the molecular sieve support, significantly improving the NO storage performance of the composite material. x It achieves both high adsorption capacity and low-temperature adsorption efficiency while maintaining excellent hydrothermal aging stability of the composite material.

[0109] The metal oxide / Pd-based SSZ-13 molecular sieve composite material prepared by this invention exhibits low-temperature NO content. x It boasts advantages such as excellent storage performance, high stability, and minimal secondary pollution, and can be coupled with NO. x Catalytic reduction raw materials are widely applicable to NO emissions from various motor vehicle exhaust gases. x The low-temperature adsorption module, in conjunction with a downstream SCR unit, is suitable for automotive exhaust aftertreatment systems and can efficiently solve NO2 emissions during cold starts of motor vehicles. x Emissions issues.

[0110] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A metal oxide / Pd-based SSZ-13 molecular sieve composite material, characterized in that, The composite material uses SSZ-13 molecular sieve as a carrier and is loaded with Pd and modifying agents; The Pd is the active component, and its loading is 1-3% of the mass of SSZ-13 molecular sieve; The modifying agent is a metal oxide containing rare earth and / or transition metal elements, and its loading is 10-30% of the mass of SSZ-13 molecular sieve.

2. The metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 1, characterized in that, The metal oxide is at least one of CeO2, Fe2O3, CuO, MnO, NiO, La2O3, Sm2O3, Pr2O3, and Gd2O3.

3. A method for preparing the metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: S1, Preparation of NH 4+ -SSZ-13 molecular sieve: Ammonium chloride and H-SSZ-13 molecular sieve are mixed and reacted, and the product is collected to obtain NH. 4+ -SSZ-13 molecular sieve; S2, Preparation of metal oxide / SSZ-13 molecular sieve: The NH obtained in S1 4+ -SSZ-13 molecular sieve was mixed with metal oxide precursor salt and dispersed evenly, then transferred to a reaction vessel for hydrothermal reaction; the product was collected, ground and then subjected to initial calcination to obtain SSZ-13@metal oxide composite material; S3. Preparation of metal oxide / Pd-based SSZ-13 molecular sieve composite material: The metal oxide / SSZ-13 molecular sieve composite material obtained in S2 was mixed with palladium salt and then impregnated and stirred; the product was collected, ground and then calcined twice to obtain Pd / (SSZ-13@metal oxide) composite material. S4. Hydrothermal aging: The metal oxide / Pd-based SSZ-13 molecular sieve composite material prepared in S3 is subjected to hydrothermal aging to obtain the final composite material.

4. The method for preparing the metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 3, characterized in that, In step S1, the mass ratio of ammonium chloride to H-SSZ-13 molecular sieve is (2-3):1; The reaction temperature is 80-90 ℃, and the reaction time is 2-4 h.

5. The method for preparing the metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 3, characterized in that, In step S2, the NH 4+ The mass ratio of SSZ-13 molecular sieve to metal oxide precursor salt is 1: (0.6-1.4). The metal oxide precursor salt is any one or more of the chloride, nitrate, and sulfate salts corresponding to the metal oxide.

6. The method for preparing the metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 3, characterized in that, In step S2, the temperature of the hydrothermal reaction is 10-150 °C, and the time of the hydrothermal reaction is 18-24 h. The initial calcination temperature is 450-550 ℃, and the initial calcination time is 3-5 h.

7. The method for preparing the metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 3, characterized in that, In step S3, the mass ratio of the metal oxide / SSZ-13 molecular sieve composite material to the palladium element in the palladium salt is 1:(0.01-0.03); The palladium salt is any one or more of palladium nitrate, palladium chloride, and palladium sulfate.

8. The method for preparing the metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 3, characterized in that, In step S3, the reaction temperature is 60-80 °C, and the reaction time is 18-24 h; The secondary calcination temperature is 450-550 ℃, and the secondary calcination time is 3-5 h.

9. The method for preparing the metal oxide / Pd-based SSZ-13 molecular sieve composite material according to claim 3, characterized in that, In step S4, the hydrothermal aging is carried out in an air atmosphere containing 5-15 vol.% water vapor; The hydrothermal aging temperature is 700-750 ℃, and the hydrothermal aging time is 12-16 h.

10. A metal oxide / Pd-based SSZ-13 molecular sieve composite material as described in claim 1 or 2 for low-temperature, high-efficiency storage of NO. x Applications in [the context of the text].

Images