Monolithic adsorbent based on 3D printing technology, preparation method and low-temperature cold start application thereof

Abstract

The application provides a monolithic adsorbent based on 3D printing technology. The application selects halloysite nanotubes and hydroxypropyl methyl cellulose as binders. The halloysite nanotubes have excellent high-temperature resistance, hardness and durability, and chemical stability, and can meet the application requirements of the catalyst under high-temperature complex working conditions, so that the catalyst structure remains mechanical stability. The hydroxypropyl methyl cellulose has processability and plasticity, and can help to print complex shapes and structures. The super strong bonding force and interlayer adhesion can effectively bond the printing materials, ensure the firmness and stability of the interlayer adhesion in the printing process, and help to reduce the distortion and deformation in the printing process. The monolithic passive NO x adsorbent provided by the application has a simple and feasible preparation method, is a non-noble metal adsorbent with economic benefits, and can be connected in series with a downstream SCR treatment unit to realize ultra-low emission in the NOx cold start stage.

Description

Technical Field

[0001] This invention belongs to the field of adsorbent technology, specifically relating to an integral adsorbent based on 3D printing technology, its preparation method, and its low-temperature cold start application. Background Technology

[0002] NO during the cold start phase of diesel vehicles x Emissions have always been a significant challenge for environmental protection. During the cold start phase, the engine and exhaust purification system operate at low temperatures, leading to incomplete combustion and inefficient catalytic reactions, resulting in high NOx levels. x Increased emissions. Therefore, reducing NO during the cold start phase of diesel vehicles is crucial. x Emissions have significant environmental implications and present engineering challenges.

[0003] Study on NO during the cold start phase of diesel vehicles x Emissions involve multiple considerations. First, it's necessary to understand the working principles of diesel engine and exhaust purification system under cold start conditions, as well as the factors affecting their performance. Second, it's necessary to explore technical means to improve the engine combustion process and exhaust purification system to increase NO emissions during the cold start phase. x Conversion efficiency. In addition, factors such as fuel ratio, catalyst activity, and temperature control system also need to be considered regarding the impact of NO conversion efficiency. x The impact of emissions, and the search for effective control strategies.

[0004] In recent years, with the increasing environmental protection requirements and technological development, there has been a growing emphasis on reducing NOx emissions during the cold start phase of diesel vehicles. x Research on emissions is receiving increasing attention. Some progress has been made through improvements in engine control strategies, optimization of exhaust purification system design, and the introduction of novel catalyst materials. However, further research and technological innovation are still needed to more effectively reduce NOx emissions during the cold start phase of diesel vehicles. x Emissions are reduced, thereby protecting the environment and improving air quality.

[0005] To reduce NO during the cold start phase x Emissions, passive NO x PNA (Plasma Adsorption) technology was developed to address this need. PNA can adsorb NO during the cold start phase. xThe adsorption occurs, and upon temperature increase, the adsorbed material is released to the downstream selective catalytic reduction (SCR) unit for catalytic conversion of nitrogen oxides. Palladium-supported molecular sieves are currently the most widely studied PNA materials, exhibiting excellent adsorption capacity and resistance to chemical poisoning. However, the high cost of noble metal catalysts is a significant factor limiting their widespread application. First, the rarity and preciousness of noble metals themselves lead to their high price. The high market prices of noble metals such as palladium, gold, platinum, and rhodium directly affect the preparation cost of noble metal adsorbents. Second, the preparation of high-performance noble metal adsorbents requires complex processes and precise control, which also increases their cost. From raw material selection and adsorbent synthesis to subsequent treatment and characterization, each step requires substantial resources and time. Furthermore, the recovery and reuse of noble metal catalysts also face technical challenges and cost pressures. Because noble metal adsorbents are typically used under high temperature and high pressure conditions, their surface activity is easily contaminated or deactivated, requiring periodic replacement or regeneration, all of which incur additional costs. Therefore, researchers have been working to find ways to reduce the cost of adsorbents, including developing new synthesis strategies, designing efficient support materials, and improving the stability and recyclability of adsorbents, in order to enable wider application of PNA adsorbents in industrial production.

[0006] Based on this, some researchers have turned their attention to materials supported by non-precious metals. Examples include molecular sieve adsorbents and oxides of Mn, Co, Ni, and Ce. Among these, Mn / Al₂O₃ powder is a high-performance non-precious metal supported material.

[0007] 3D printing is an advanced manufacturing technology that transforms digital models into physical objects, also known as additive manufacturing. Compared with traditional subtractive manufacturing, 3D printing has many advantages. For example, (1) 3D printing can customize products to meet individual needs. This is very useful for fields such as medical, consumer goods, and automobiles. (2) Traditional manufacturing methods may take weeks or even months to produce prototypes, while 3D printing can produce prototypes in hours or less, thus accelerating product development cycles. (3) Traditional processing methods usually require cutting raw materials into the desired shape, while 3D printing manufactures products by stacking materials layer by layer, thus saving a lot of material. (4) Traditional manufacturing methods usually require multiple processing steps, such as milling, turning, and casting, while 3D printing can integrate these steps into one process, thereby reducing production steps and production time. (5) 3D printing can produce products with complex geometries, which is difficult to achieve with traditional processing methods. This capability is very important for aerospace, medical, and engineering fields. (6) 3D printing technology can reduce waste and energy consumption because it typically uses precise amounts of material and can utilize recycled materials.

[0008] However, due to its poor flowability, Mn / Al2O3 powder materials suffer from problems such as uneven catalyst bulk structure, poor shape, or low mechanical strength when prepared using 3D printing methods. Therefore, by combining 3D printing technology, a monolithic non-precious metal adsorbent was developed and connected in series with a downstream SCR treatment unit to achieve NO... x Ultra-low emissions during the cold start phase are an issue that needs to be addressed. Summary of the Invention

[0009] In view of this, the technical problem to be solved by the present invention is to provide a monolithic adsorbent based on 3D printing technology, its preparation method, and its low-temperature cold start application. The present invention can realize the 3D printing of Mn / Al2O3 powder to prepare a monolithic non-precious metal adsorbent, which can then be connected in series with a downstream SCR treatment unit to achieve NO… x Ultra-low emissions during the cold start phase.

[0010] This invention provides a monolithic adsorbent based on 3D printing technology, which is prepared by 3D printing from the following raw materials in parts by weight:

[0011] 8-18 parts by weight of Mn / Al2O3 powder;

[0012] 1 to 6 parts by weight of halloysite nanotubes;

[0013] 0.1 to 1 part by weight of hydroxypropyl methylcellulose;

[0014] 80-90 parts by weight of solvent.

[0015] Preferably, the manganese loading in the Mn / Al2O3 powder is 0.1-20 wt.%, preferably 5 wt.%.

[0016] The preparation method of the Mn / Al2O3 powder includes one of the following: excess impregnation method, equal volume impregnation method, and solid grinding method;

[0017] Preferably, the method for preparing the Mn / Al2O3 powder includes the following steps:

[0018] Al2O3 and manganese salt were mixed in a solvent and reacted. After removing the solvent, the mixture was dried and calcined to obtain Mn / Al2O3 powder.

[0019] Preferably, the manganese salt is selected from manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.

[0020] Preferably, before mixing Al2O3 with manganese salt in a solvent, the Al2O3 is further modified with rare earth elements, wherein the rare earth metal elements are one or more selected from La, Pr, Nd, Y, Ce, Zr, Sm, Pm, Eu, and Gd, and the loading of the rare earth metal elements is 0.2 wt.% to 5.0 wt.%.

[0021] Preferably, the solvent is selected from ethanol.

[0022] The present invention also provides a method for preparing the above-mentioned monolithic adsorbent, comprising the following steps:

[0023] A) Mix Mn / Al2O3 powder, halloysite nanotubes and solvent, and heat to obtain a paste-like mixture;

[0024] The paste-like mixture was mixed and stirred with hydroxypropyl methylcellulose to obtain a 3D printing material;

[0025] B) The 3D printing material is placed in a 3D printer, and a path is established by computer programming. The extruded Mn / Al2O3 fibers are stacked through the 3D printing system to form the desired shape, thus obtaining an integral adsorbent precursor.

[0026] C) The monolithic adsorbent precursor is dried and then calcined to obtain the monolithic adsorbent;

[0027] Alternatively, it may include the following steps:

[0028] a) Al2O3, manganese salt and halloysite nanotubes were mixed in a solvent and heated to obtain a paste-like mixture;

[0029] The paste-like mixture was mixed and stirred with hydroxypropyl methylcellulose to obtain a 3D printing material;

[0030] b) The 3D printing material is placed in a 3D printer, and a path is established by computer programming. The extruded Mn / Al2O3 fibers are stacked through the 3D printing system to form the desired shape, thus obtaining an integral adsorbent precursor.

[0031] c) The monolithic adsorbent precursor is dried and then calcined to obtain the monolithic adsorbent.

[0032] Preferably, the heating temperature is 60-100℃; the calcination temperature is 500-650℃, and the time is 4-8h.

[0033] This invention also provides a monolithic adsorbent for achieving NO x Applications of ultra-low emissions during the cold start phase.

[0034] The present invention also provides a coaxial 3D printed tandem catalyst, comprising a core and a shell arranged coaxially, wherein the core is selected from the material of the above-mentioned monolithic adsorbent, and the shell is an oxide selective catalytic reduction unit.

[0035] Preferably, the main material of the shell is selected from one or more of Cu-SSZ-13, Cu-SSZ-39, Cu-SAPO-18, Cu-SAPO-34, Fe-SSZ-13, Fe-SSZ-39, and V2O5-WO3(MoO3) / TiO2;

[0036] Preferably, the mass ratio of the core to the shell is 4:1 to 1:4;

[0037] Preferably, the preparation method of the coaxial 3D printed tandem catalyst includes the following steps:

[0038] 1) Configure the core and shell layers separately as 3D printing materials;

[0039] Mn / Al2O3 powder, halloysite nanotubes, and solvent were mixed and heated to obtain a paste-like mixture; the paste-like mixture was then mixed and stirred with hydroxypropyl methylcellulose (HPMC) to obtain a core 3D printing material.

[0040] The shell material, halloysite nanotubes, and solvent are mixed and heated to obtain a paste-like mixture; the paste-like mixture is then mixed and stirred with hydroxypropyl methylcellulose (HPMC) to obtain the shell 3D printing material.

[0041] 2) The core 3D printing material and the shell 3D printing material are extruded through the coaxial needle of the 3D printing system and stacked into the desired shape to obtain the coaxial catalyst precursor;

[0042] 3) The coaxial catalyst precursor is dried and then calcined to obtain the coaxial catalyst.

[0043] This invention also provides a method for achieving NO using the aforementioned coaxial 3D-printed tandem catalyst. x Applications of ultra-low emissions during the cold start phase.

[0044] Compared with existing technologies, this invention provides a monolithic adsorbent based on 3D printing technology, prepared by 3D printing from the following raw materials in parts by weight: 8%–18% Mn / Al2O3 powder; 1%–6% halloysite nanotubes; 0.1%–1% hydroxypropyl methylcellulose (HPMC); and 80%–90% solvent. This invention selects halloysite nanotubes and hydroxypropyl methylcellulose (HPMC) as binders. Halloysite nanotubes possess excellent high-temperature resistance, hardness, durability, and chemical stability, meeting the application requirements of catalysts under complex high-temperature conditions and maintaining the mechanical stability of the catalyst structure. Hydroxypropyl methylcellulose (HPMC) has processability and plasticity, enabling the printing of complex shapes and structures, suitable for printing applications requiring high precision and complex designs. Its strong adhesion and interlayer bonding effectively bond the printing materials, ensuring the firmness and stability of interlayer adhesion during printing, and helping to reduce distortion and deformation during the printing process. A monolithic passive NO-generating structure composed of Mn / Al2O3 was constructed in one step using 3D printing technology. x The adsorbent, with a simple and feasible preparation method, addresses the issues of high cost and limited adsorption capacity of existing passive nitrogen oxide adsorbents by developing an economically viable non-precious metal adsorbent. This adsorbent is then connected in series with a downstream SCR treatment unit to achieve NO… x Ultra-low emissions during the cold start phase. Attached Figure Description

[0045] Figure 1 X-ray diffraction patterns of Mn(x) / Al2O3 with different Mn loadings (Example 1), where (x) represents the Mn loading;

[0046] Figure 2 X-ray photoelectron spectrum of Mn(x) / Al2O3 (Example 1);

[0047] Figure 3 Hydrogen-temperature-programmed reduction curve for Mn(x) / Al2O3 (Example 1);

[0048] Figure 4 The UV-Vis diffuse reflectance spectrum of Mn(x) / Al2O3 (Example 1);

[0049] Figure 5 Images of 3D-printed Mn(x) / Al2O3 blocks (Example 2);

[0050] Figure 6 NO for Mn(x) / Al2O3 x Concentration curve change graph (Application Example 1);

[0051] Figure 7 NO for Mn(x) / Al2O3x Adsorption capacity bar chart (Application Example 1);

[0052] Figure 8 NO for rare earth metal-doped Mn(2) / M-Al2O3 x Concentration curve variation (Example 3), where M represents rare earth metal;

[0053] Figure 9 NO for rare earth metal-doped Mn(2) / Al2O3 x Adsorption capacity bar chart (Example 3);

[0054] Figure 10 Image a is a comparison image based on Example 2 with a different printing ink ratio (Comparative Example 2);

[0055] Figure 10 b is the image without the addition of inorganic binder (Comparative Example 3);

[0056] Figure 10 c is the image without added organic binder (Comparative Example 4);

[0057] Figure 11 Cross-sectional electron microscope images of ink prepared according to Example 2 with ethanol replaced by water (Comparative Example 5);

[0058] Figure 12 Image of a monolithic adsorbent fabricated by 3D printing after physically mixing Al2O3 with manganese oxides (MnO2, Mn2O3, Mn3O4, MnO) (Comparative Example 6);

[0059] Figure 13 NO is a monolithic adsorbent fabricated by 3D printing from a physical mixture of Al2O3 and manganese oxides (MnO2, Mn2O3, Mn3O4, MnO). x Concentration curve change graph (compare with application example 1);

[0060] Figure 14 2.0 wt.% Pd-loaded Al2O3 (Pd(2) / Al2O3) and 2.0 wt.% Pd-loaded SSZ-13 (Pd(2) / SSZ-13) with Mn(2) / Al2O3 NO x Concentration curve change graph (compare with application example 2);

[0061] Figure 15 Images of catalysts formed by coaxial 3D printing of Mn / Al2O3 and SCR catalyst Cu-SSZ-13, with cordierite double coating and physical mixing (Application Example 2, Application Example 3 and Application Example 4).

[0062] Figure 16Cross-sectional scanning electron microscope images of catalysts formed by coaxial 3D printing of core-shell structure of Mn / Al2O3 and SCR catalyst Cu-SSZ-13, cordierite double-layer coating and physical mixing (Application Example 2, Application Example 3 and Application Example 4);

[0063] Figure 17 NO under dry conditions is a catalyst formed by coaxial 3D printing of a core-shell structure of Mn / Al2O3 and SCR catalyst Cu-SSZ-13, with cordierite double-layer coating and physical mixing. x Concentration curve change graphs (Application Examples 2, 3, and 4);

[0064] Figure 18 NO production under conditions containing 5% H2O is achieved by cascading Mn / Al2O3 and SCR catalyst Cu-SSZ-13 using a coaxial 3D-printed core-shell structure, cordierite double-layer coating, and physical mixing. x Concentration curve changes (Application Examples 2, 3 and 4).

[0065] Figure 19 NO in three forms: 3D printing, cordierite coating, and powder, for Mn / Al2O3. x Concentration curve change graph;

[0066] Figure 20 To replace the inorganic binder halloysite nanotubes with bentonite in the preparation of Mn / Al2O3 bulk NO x Adsorption / desorption capacity bar chart. Detailed Implementation

[0067] This invention provides a monolithic adsorbent based on 3D printing technology, which is prepared by 3D printing from the following raw materials in parts by weight:

[0068] 8-18 parts by weight of Mn / Al2O3 powder;

[0069] 1 to 6 parts by weight of halloysite nanotubes;

[0070] 0.1 to 1 part by weight of hydroxypropyl methylcellulose (HPMC);

[0071] 80-90 parts by weight of solvent.

[0072] The raw materials for preparing the monolithic adsorbent based on 3D printing technology provided by the present invention include 8 to 18 parts by mass of Mn / Al2O3 powder, which can be 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or any value between 8 and 18 parts by mass.

[0073] The preparation method of the Mn / Al2O3 powder includes one of the following: excess impregnation method, equal volume impregnation method, and solid grinding method.

[0074] In some specific embodiments of the present invention, the method for preparing the Mn / Al2O3 powder includes the following steps:

[0075] Al2O3 and manganese salt were mixed in a solvent and reacted. After removing the solvent, the mixture was dried and calcined to obtain Mn / Al2O3 powder.

[0076] The manganese salt is selected from manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride, preferably manganese acetate.

[0077] The reaction temperature is defined as room temperature, specifically 25±5℃ in this invention. The solvent removal method involves heating to evaporate the moisture. The drying process is oven drying. After drying, the calcination temperature is 500–650℃, which can be any value between 500, 550, 600, 650℃, or 500–650℃. The calcination time is 4–8 hours, which can be any value between 4, 5, 6, 7, 8 hours, or 4–8 hours.

[0078] Before mixing Al2O3 with manganese salt in a solvent, the process further includes rare earth modification of the Al2O3, wherein the rare earth metal element is one or more selected from La, Pr, Nd, Y, Ce, Zr, Sm, Pm, Eu, and Gd, and the loading of the rare earth metal element is 0.2 wt.% to 5.0 wt.%, which can be 0.2 wt.%, 0.5 wt.%, 0.8 wt.%, 1 wt.%, 1.5 wt.%, 2 wt.%, 2.5 wt.%, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, or any value between 0.2 wt.% and 5.0 wt.%.

[0079] The modified material can, on the one hand, regulate the desorption behavior of Mn / Al2O3, bringing the desorption temperature within the optimal range; on the other hand, it can further enhance the adsorption performance of Mn / Al2O3 by providing new adsorption sites or improving the dispersibility of active sites. The specific modification method is the equal-volume impregnation method.

[0080] In this invention, the manganese loading in the Mn / Al2O3 powder is 0.1 to 20 wt.%, and can be any value between 0.1, 0.5, 0.6, 0.7, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 0.1 to 20 wt.%, preferably 5 wt.%.

[0081] The raw materials for preparing the monolithic adsorbent based on 3D printing technology provided by the present invention also include 1 to 6 parts by mass of halloysite nanotubes, which can be 1, 2, 3, 4, 5, 6, or any value between 1 and 6 parts by mass.

[0082] The raw materials for preparing the monolithic adsorbent based on 3D printing technology provided by the present invention further include 0.1 to 1 parts by mass of hydroxypropyl methylcellulose (HPMC), which can be any value between 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or 0.1 to 1 parts by mass.

[0083] The raw materials for preparing the monolithic adsorbent based on 3D printing technology provided by this invention further include 80-90 parts by weight of solvent, which can be 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, or any value between 80 and 90 parts by weight. Preferably, the solvent is selected from ethanol. Ethanol can not only be used as a solvent, but it also has high safety and a low boiling point. Ethanol can also act as an antifoaming agent to avoid interference from air bubbles during printing, ensuring the structural stability and consistency of the monolithic catalyst.

[0084] Monolithic catalysts typically refer to catalysts with a single, monolithic structure containing numerous narrow, straight, or curved parallel channels. Because early ceramic-supported catalysts had a honeycomb cross-section, they were also called honeycomb catalysts. In this invention, the monolithic catalyst is a monolithic catalyst with a honeycomb cross-section.

[0085] The present invention also provides a method for preparing the above-mentioned monolithic adsorbent, comprising the following steps:

[0086] A) Mix Mn / Al2O3 powder, halloysite nanotubes and solvent, and heat to obtain a paste-like mixture;

[0087] The paste mixture was mixed and stirred with hydroxypropyl methylcellulose (HPMC) to obtain a 3D printing material;

[0088] B) The 3D printing material is placed in a 3D printer, and a path is established by computer programming. The extruded Mn / Al2O3 fibers are stacked through the 3D printing system to form the desired shape, thus obtaining an integral adsorbent precursor.

[0089] C) The monolithic adsorbent precursor is dried and then calcined to obtain the monolithic adsorbent.

[0090] This invention first mixes Mn / Al2O3 powder, halloysite nanotubes, and a solvent, preferably by ultrasonic mixing, followed by heating, preferably by water bath heating at 60–100°C, where the heating temperature can be any value between 60, 70, 80, 90, 100°C, or 60–100°C. Finally, a paste-like mixture is obtained.

[0091] Then, the paste mixture is mixed and stirred with hydroxypropyl methylcellulose (HPMC) until the Mn / Al2O3 ink can be smoothly printed through the needle to obtain the 3D printing material.

[0092] Next, the 3D printing material is placed in a 3D printer, and a path is established by computer programming. The extruded Mn / Al2O3 fibers are stacked through the 3D printing system to form the desired shape, thus obtaining an integral adsorbent precursor.

[0093] Specifically, Mn / Al2O3 ink is extruded from a stainless steel bayonet needle using a pneumatic jet 3D printing system, and stacked to form the desired shape, resulting in a monolithic adsorbent precursor. The needle type can be adjusted as needed.

[0094] The monolithic adsorbent precursor is dried and then calcined to obtain the monolithic adsorbent. The calcination temperature is 500–650°C, which can be any value between 500, 550, 600, 650°C, or 500–650°C, and the calcination time is 4–8 hours, which can be any value between 4, 5, 6, 7, 8 hours, or 4–8 hours.

[0095] This invention also provides a monolithic adsorbent for achieving NO x Applications of ultra-low emissions during the cold start phase.

[0096] The present invention also provides a coaxial 3D printed tandem catalyst, with Mn / Al2O3 as the core and a shell layer covering the surface of the core.

[0097] The core is prepared by using Mn / Al2O3 powder, halloysite nanotubes, hydroxypropyl methylcellulose and solvent.

[0098] The shell layer is an oxide selective catalytic reduction (SCR) unit. The main material of the shell layer is selected from one or more of Cu-SSZ-13, Cu-SSZ-39, Cu-SAPO-18, Cu-SAPO-34, Fe-SSZ-13, Fe-SSZ-39, and V2O5-WO3(MoO3) / TiO2. The mass ratio of the core to the shell layer is 4:1 to 1:4, and can be 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, or any value between 4:1 and 1:4.

[0099] The coaxial 3D-printed tandem catalyst provided by this invention exhibits enhanced catalytic activity and nitrogen selectivity compared to existing tandem methods (such as cordierite double-layer coating or physical mixing). The core layer stores NO at low temperatures. x The adsorbent is stored and then desorbed at high temperatures, releasing it to the shell SCR unit, thereby enhancing catalytic activity. Furthermore, the shell tightly encapsulates the core layer, effectively protecting it from environmental deactivation factors and extending the adsorbent's lifespan. Simultaneously, the shell restricts the diffusion pathways of reactants and products, effectively suppressing side reactions and improving the efficiency and selectivity of the denitrification process.

[0100] The tandem catalyst is a coaxial catalyst, and its preparation method includes the following steps:

[0101] The core and shell layers are each configured as 3D printing materials. The configuration method for the core 3D printing material is as described above and will not be repeated here. The configuration method for the shell 3D printing material can preferably follow the same method as the core layer. Specifically, the shell material, halloysite nanotubes, and solvent are mixed and heated to obtain a paste-like mixture; the paste-like mixture is then mixed and stirred with hydroxypropyl methylcellulose (HPMC) to obtain the shell 3D printing material.

[0102] The core 3D printing material and the shell 3D printing material are then extruded through the coaxial needle of the 3D printing system and stacked into the desired shape to obtain the coaxial catalyst precursor.

[0103] The coaxial catalyst precursor was dried and then calcined to obtain the coaxial catalyst.

[0104] The calcination temperature is 500–650°C, which can be any value between 500, 550, 600, 650, or 500–650°C, and the time is 4–8 hours, which can be any value between 4, 5, 6, 7, 8, or 4–8 hours.

[0105] This invention also provides a method for achieving NO using the aforementioned coaxial 3D-printed tandem catalyst. x Applications of ultra-low emissions during the cold start phase.

[0106] A cold start refers to starting the engine after it has been off for a period of time and its temperature has cooled down to below its normal operating temperature, with most of the engine oil having flowed back into the engine. Generally, the ambient temperature can be used as a guide; the engine temperature should be allowed to cool slowly to below 40°C after being off for about two hours before starting the engine.

[0107] This invention provides a non-precious metal adsorbent based on 3D printing technology, including its preparation method and its application in low-temperature cold starts of automobiles. This adsorbent preparation method is flexible and easy to implement, exhibits excellent adsorption / desorption performance, and also possesses high economic benefits and industrial application potential.

[0108] To further understand the present invention, the following embodiments illustrate the integral adsorbent based on 3D printing technology, its preparation method, and its low-temperature cold start application. The scope of protection of the present invention is not limited by the following embodiments.

[0109] Example 1

[0110] Mn / Al2O3 was prepared by excess impregnation method, with manganese acetate as the metal precursor. The theoretical Mn loadings were 1.0 wt.%, 2.0 wt.%, 3.0 wt.%, 5.0 wt.%, and 10.0 wt.%. The support for the synthesis of Mn / Al2O3 was commercial Al2O3 (Aladdin Reagent (Shanghai) Co., Ltd.).

[0111] The general preparation method is as follows: 10g Al2O3 is mixed with 40mL manganese solution, sonicated for 30 minutes, stirred at room temperature for 8 hours, and the moisture is evaporated on a heated stirring table. Then it is dried in an oven at 80℃ and calcined in a muffle furnace at 600℃ for 5 hours to obtain Mn(x) / Al2O3 powder.

[0112] See Figures 1-4 , Figure 1 X-ray diffraction patterns of Mn(x) / Al2O3 with different Mn loadings (Example 1), where (x) represents the Mn loading, i.e., x=1 represents a loading of 1.0 wt.%, x=2 represents a loading of 2.0 wt.%, x=3 represents a loading of 3.0 wt.%, x=5 represents a loading of 5.0 wt.%, and x=10 represents a loading of 10.0 wt.%.

[0113] Figure 2 The X-ray photoelectron spectrum of Mn(x) / Al2O3 (Example 1) shows that Mn in Mn(x) / Al2O3 has three oxidation states, namely +2, +3 and +4 valences.

[0114] Figure 3 The figure shows the hydrogen-temperature-programmed reduction curve of Mn(x) / Al2O3 (Example 1). The reduction peaks in the figure correspond to the reduction of MnO2—Mn2O3—Mn3O4—MnO.

[0115] Figure 4 The UV-Vis diffuse reflectance spectrum of Mn(x) / Al2O3 (Example 1) shows that Mn exists in Mn(x) / Al2O3 in the form of Mn ions and Mn oxides;

[0116] Example 2

[0117] 8.0 g of the Mn / Al2O3 powder, 2.0 g of halloysite nanotubes, and 40 mL of ethanol from Example 1 were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste. Subsequently, 3.0 g of hydroxypropyl methylcellulose (HPMC) (3.0 wt.%) was added to the paste, and the mixture was stirred with a glass rod until the Mn / Al2O3 ink could be smoothly printed through the needle tip.

[0118] Mn / Al2O3 ink was extruded from a stainless steel bayonet nozzle (19G) using a pneumatic jet 3D printing system, stacking to form honeycomb-shaped cylinders with a diameter of approximately 9 mm and a height of approximately 0.5 cm. After natural drying, the 3D-printed Mn / Al2O3 blocks were calcined in air at 600°C for 5 hours to remove hydroxypropyl methylcellulose (HPMC) and maintain structural stability.

[0119] Figure 5 Image of a 3D-printed Mn(x) / Al2O3 block (Example 2). As can be seen from the image, the cylindrical block has a honeycomb structure with intersecting channels and a diameter of approximately 9 mm.

[0120] Example 3

[0121] Example 3 is based on Example 1. Before over-impregnation with Mn, Al2O3 was modified with rare earth metals. The selected rare earth metals were La, Pr, Nd, and Y. The modification method was over-impregnation. The modified Mn / Al2O3 was labeled as M-Al2O3. The preparation of Mn(2) / M-Al2O3 was carried out according to the preparation method of 2.0 wt.% Mn / Al2O3 in Example 1. Then, Mn(2) / M-Al2O3 was 3D printed to form a monolithic adsorbent similar to Mn / Al2O3, that is, only "Mn / Al2O3" in Example 2 was replaced with "Mn(2) / M-Al2O3" while other conditions remained unchanged.

[0122] Example 4

[0123] Example 4 is based on Example 1, in which the manganese metal precursor is replaced with one of manganese nitrate, manganese chloride, and manganese sulfate, and the Mn loading is 1.0 wt.%, 2.0 wt.%, 3.0 wt.%, 5.0 wt.%, and 10.0 wt.%, respectively.

[0124] Example 5

[0125] Example 5 further simplifies the catalyst preparation method based on Examples 1 and 2, employing a one-step printing method for Mn / Al2O3. The specific operation is as follows: 8g Al2O3 is mixed with 40mL manganese salt solution, sonicated for 30 minutes, and stirred at room temperature for 8 hours. Then, 2.0g halloysite nanotubes are added, and the mixture is evaporated to dryness on a heated stirring table to form a viscous paste. Subsequently, 3.0g of hydroxypropyl methylcellulose (HPMC) (3.0wt.%) is added to the slurry, along with 2mL of ethanol as an antifoaming agent. Stirring continues with a glass rod until the ink can smoothly pass through the printing nozzle. The Mn / Al2O3 ink is extruded from a stainless steel bayonet nozzle (19G) using a pneumatic jet 3D printing system, stacking to form honeycomb cylinders with a diameter of approximately 9mm and a height of approximately 0.5cm. After natural drying, the 3D-printed Mn / Al2O3 bulk is calcined in air at 600°C for 5 hours to remove hydroxypropyl methylcellulose (HPMC) and maintain structural stability.

[0126] Example 6

[0127] Example 6 further optimizes the catalyst preparation based on Example 5 by adding one or more rare earth metal salts (cerium nitrate, zirconium nitrate, lanthanum nitrate, samarium nitrate, praseodymium nitrate, neodymium nitrate, yttrium nitrate, etc.) to the manganese solution to increase the mechanical strength of the bulk. The loading of rare earth metals is 1.0 wt.%.

[0128] Comparative Example 1

[0129] Weigh 2.0 g of Al₂O₃, 158.2 mg of MnO₂ (or 143.7 mg of Mn₂O₃, or 138.8 mg of Mn₃O₄, or 129.1 mg of MnO), 0.5 g of halloysite nanotubes, and 10 mL of ethanol into a glass beaker. After ultrasonic dispersion for 30 min, place in a 70 °C water bath to form a viscous paste. Subsequently, add 1.0 g of hydroxypropyl methylcellulose (HPMC) (3.0 wt.%) to the paste and stir with a glass rod until the ink flows smoothly through the needle tip for printing. Extrude the ink from the needle (19G) using a pneumatic jet 3D printing system to stack honeycomb cylinders with a diameter of approximately 9 mm and a height of approximately 0.5 cm. After natural drying, calcine in air at 600 °C for 5 hours to remove organic binders and maintain structural stability. The prepared adsorbents were labeled as: MnO2+Al2O3, Mn2O3+Al2O3, Mn3O4+Al2O3, and MnO+Al2O3. Figure 12 The image shows a monolithic adsorbent (Comparative Example 1) produced by 3D printing after physically mixing Al2O3 with manganese oxides (MnO2, Mn2O3, Mn3O4, MnO). As can be seen from the image, the cylindrical block has a honeycomb structure with intersecting channels and a diameter of approximately 9 mm.

[0130] Comparative Example 2

[0131] Comparative Example 2 is based on Example 2, with adjustments made to the ink formulation. 8.0 g of the Mn / Al₂O₃ powder, 0.5 g of halloysite nanotubes, and 40 mL of ethanol from Example 1 were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste. Subsequently, 1 g of hydroxypropyl methylcellulose (HPMC) (3.0 wt.%) was added to the paste, and the mixture was stirred with a glass rod until the Mn / Al₂O₃ ink could be smoothly printed through the needle.

[0132] See Figure 10 a, Figure 10 Image a is a picture showing the printing ink ratio changed based on Example 2 (Comparative Example 2). Figure 10 b is the image without inorganic binder (Comparative Example 3); Figure 10 Image c shows the image without organic binder (Comparative Example 4); as can be seen from the image, changing the printing ink ratio or omitting the binder will reduce the mechanical properties of the block.

[0133] Comparative Example 3

[0134] Comparative Example 3 is based on Example 2, but without the addition of halloysite nanotubes when preparing the printing ink. 8.0 g of the Mn / Al₂O₃ powder from Example 1 and 40 mL of ethanol were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste. Subsequently, 3 g of hydroxypropyl methylcellulose (HPMC) (3.0 wt.%) was added to the paste, and the mixture was stirred with a glass rod until the Mn / Al₂O₃ ink could be smoothly printed through the needle.

[0135] Comparative Example 4

[0136] Comparative Example 4 is based on Example 2, but without the addition of hydroxypropyl methylcellulose (HPMC) when preparing the printing ink. 8.0 g of the Mn / Al₂O₃ powder, 2.0 g of halloysite nanotubes, and 40 mL of ethanol from Example 1 were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste.

[0137] Comparative Example 5

[0138] Comparative Example 5 is based on Example 2, except that the solvent ethanol was replaced with water when preparing the printing ink. 8.0 g of the Mn / Al2O3 powder, 2.0 g of halloysite nanotubes, and 40 mL of water from Example 1 were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste. Subsequently, 3.0 g of hydroxypropyl methylcellulose (HPMC) (3.0 wt.%) was added to the paste, and the mixture was stirred with a glass rod until the Mn / Al2O3 ink could be smoothly printed through the needle. Figure 11 The image shows a cross-sectional electron microscope image of water (Comparative Example 5) when ethanol was replaced with water in the ink preparation based on Example 2. As can be seen from the image, bubbles (black boxes) are formed after ethanol is replaced with water.

[0139] Comparative Example 6

[0140] Preparation and Printing of Pd(2) / Al2O3: The preparation of Pd(2) / Al2O3 was carried out using a method similar to that used for Mn(2) / Al2O3. The metal precursor solution was palladium chloride solution. The theoretical Pd loading was 2.0 wt.%. The support for synthesizing Mn / Al2O3 was commercial Al2O3 (Aladdin Reagent (Shanghai) Co., Ltd.). The general preparation method was as follows: 2 g of Al2O3 was mixed with 10 mL of palladium chloride solution, sonicated for 30 minutes, stirred at room temperature for 8 hours, and the moisture was evaporated on a heated stirring table. Then it was dried in an oven at 80 °C and calcined in a muffle furnace at 600 °C for 5 hours to obtain Mn / Al2O3 powder. The printing of Pd(2) / Al2O3 was carried out using the same method as that used for Mn(2) / Al2O3, and will not be described in detail here.

[0141] Preparation and Printing of Pd(2) / SSZ-13: The preparation of Pd(2) / SSZ-13 was carried out using a method similar to that used for Pd(2) / Al2O3. The difference was that the Al2O3 support was replaced with SSZ-13 (from the Nankai University Catalyst Factory). The printing method for Pd(2) / SSZ-13 was the same as that for Pd(2) / Al2O3.

[0142] Comparative Example 7

[0143] Comparative Example 7 is based on Example 2, but the inorganic binder, halloysite nanotubes, is replaced with bentonite. 8.0 g of the Mn / Al2O3 powder from Example 1, 2.0 g of bentonite, and 40 mL of ethanol were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste. Subsequently, 3.0 g of HPMC gel (3.0 wt.%) was added to the paste, and the mixture was stirred with a glass rod until the Mn / Al2O3 ink could be smoothly printed through the needle.

[0144] Mn / Al2O3 ink was extruded from a stainless steel bayonet nozzle (19G) using a pneumatic jet 3D printing system, stacking to form honeycomb-shaped cylinders with a diameter of approximately 9 mm and a height of approximately 0.5 cm. After natural drying, the 3D-printed Mn / Al2O3 blocks were calcined in air at 600°C for 5 hours to remove organic binders.

[0145] Comparative Example 8

[0146] Comparative Example 8 is based on Example 2, but the organic binder hydroxypropyl methylcellulose (HPMC) is replaced with polyvinyl alcohol. 8.0 g of the Mn / Al₂O₃ powder, 2.0 g of halloysite nanotubes, and 40 mL of ethanol from Example 1 were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste. Subsequently, 3.0 g of polyvinyl alcohol (3.0 wt.%) was added to the paste, and the mixture was stirred with a glass rod until the Mn / Al₂O₃ ink could pass smoothly through a needle.

[0147] Mn / Al2O3 ink was extruded from a stainless steel bayonet nozzle (19G) using a pneumatic jet 3D printing system, stacking to form honeycomb-shaped cylinders with a diameter of approximately 9 mm and a height of approximately 0.5 cm. After natural drying, the 3D-printed Mn / Al2O3 blocks were calcined in air at 600°C for 5 hours to remove organic binders.

[0148] Comparative Example 9

[0149] Comparative Example 9, based on Example 2, replaced the inorganic binder halloysite nanotubes and the organic binder hydroxypropyl methylcellulose (HPMC) with bentonite and polyvinyl alcohol, respectively. 8.0 g of the Mn / Al₂O₃ powder, 2.0 g of bentonite, and 40 mL of ethanol from Example 1 were weighed and added to a glass beaker. After ultrasonic dispersion for 30 min, the beaker was placed in a 70°C water bath to form a viscous paste. Subsequently, 3.0 g of polyvinyl alcohol (3.0 wt.%) was added to the paste, and the mixture was stirred with a glass rod until the Mn / Al₂O₃ ink could pass smoothly through a needle.

[0150] Mn / Al2O3 ink was extruded from a stainless steel bayonet nozzle (19G) using a pneumatic jet 3D printing system, stacking to form honeycomb-shaped cylinders with a diameter of approximately 9 mm and a height of approximately 0.5 cm. After natural drying, the 3D-printed Mn / Al2O3 blocks were calcined in air at 600°C for 5 hours to remove organic binders.

[0151] Figure 20 To replace the NO in the prepared Mn / Al2O3 bulk with inorganic and organic binders, respectively or simultaneously. xAdsorption capacity histogram. As shown in the figure, the Mn / Al2O3 bulk material prepared using halloysite nanotubes as the inorganic binder and hydroxypropyl methylcellulose (HPMC) as the organic binder exhibits the highest NO content. x Adsorption capacity.

[0152] Application Example 1

[0153] The Mn / Al2O3 bulk material prepared in Example 2 was used as a monolithic NO. x Adsorbent. The activity evaluation device consists of a gas mixing and catalytic reaction experimental apparatus and a Fourier transform infrared spectrometer. The gas flow rate is controlled by a mass flow meter in the gas mixing and catalytic reaction experimental apparatus. Table 1 shows the gas composition and concentration of each component. The total gas flow rate is set to 200 mL / min. The catalyst pretreatment and adsorption-desorption test processes are completed in the reactor of the gas mixing and catalytic reaction experimental apparatus. The reactor is equipped with a type K thermocouple to monitor temperature changes during the reaction process. The gas concentration at the outlet is analyzed by the Fourier transform infrared spectrometer. The specific test process is as follows: 300 mg of Mn / Al2O3 block is weighed and placed in a quartz tube with a diameter of 1 cm. The temperature control program is started, and the temperature is increased from room temperature to 500 °C at a rate of 10 °C / min. Pretreatment is carried out at 500 °C for 30 min. After the pretreatment is completed, the reactor is cooled to 100 °C and kept at a constant temperature. The gas route is switched from the reaction tube to the bypass route. After switching to the bypass, set the gas flow rate according to the gas conditions required for the activity test in Table 1. Once the concentration of the feed gas stabilizes, switch the gas route from the bypass to the reaction tube. After adsorption for 10 minutes, increase the temperature from 100℃ to 500℃ at a rate of 10℃ / min. The concentration of the outlet gas was recorded throughout the process using an MKS MultiGas 2030FTIR gas analyzer.

[0154] Table 1 Gas composition and concentration settings for pretreatment and adsorption-desorption tests

[0155]

[0156] See Figure 6 and Figure 7 , Figure 6 NO for Mn(x) / Al2O3 x The concentration curve (Application Example 1) shows that Mn(x) / Al2O3 with different Mn contents can rapidly adsorb NO. x Two distinct desorption peaks were observed. Figure 7 NO for Mn(x) / Al2O3 x The adsorption capacity bar chart (Application Example 1) shows that the adsorption capacity of Mn(x) / Al2O3 with different Mn contents increases with increasing Mn content.

[0157] The Mn(2) / M-Al2O3 bulk material prepared in Example 3 was used as the monolithic NO. x Adsorbent. The specific method is the same as above; see results below. Figure 8 and Figure 9 , Figure 8 NO for rare earth metal-doped Mn(2) / M-Al2O3 x Concentration curve change graph (Example 3), M represents rare earth metal. As can be seen from the graph, the desorption temperature shifts to a higher temperature after doping with rare earth metal, indicating that rare earth metal can optimize the desorption behavior of Mn / Al2O3. Figure 9 NO for rare earth metal-doped Mn(2) / Al2O3 x The adsorption capacity bar chart (Example 3) shows that the adsorption capacity is improved after rare earth metal doping.

[0158] Application Example 2

[0159] Coaxial 3D printing technology was used to connect Mn / Al2O3 and Cu-SSZ-13 (Cu-SSZ-13 was prepared by ion exchange) in Example 1 in a core-shell structure, with Mn / Al2O3 as the core layer and Cu-SSZ-13 as the shell layer. First, printing inks for Mn / Al2O3 and Cu-SSZ-13 were prepared according to the ink preparation method in Example 2. The prepared Mn / Al2O3 and Cu-SSZ-13 inks were extruded from a coaxial nozzle (20G / 16G) using a pneumatic jet 3D printing system, stacking to form a honeycomb cylinder with a diameter of approximately 9 mm and a height of approximately 5 mm. The gas pressure for extruding Mn / Al2O3 into the core layer was 0.2 MPa, and the gas pressure for extruding Cu-SSZ-13 into the shell layer was also 0.2 MPa. The core-shell ratio was 1:1. After natural drying, the 3D-printed Mn / Al2O3@Cu-SSZ-13 bulk was calcined in air at 600℃ for 5 hours to remove hydroxypropyl methylcellulose (HPMC), resulting in a structurally stable core-shell tandem catalyst. The catalyst mass during testing was 300 mg.

[0160] Figure 15 Images of catalysts formed by coaxial 3D printing of Mn / Al2O3 and SCR catalyst Cu-SSZ-13, with cordierite double coating and physical mixing (Application Example 2, Application Example 3 and Application Example 4).

[0161] Figure 16 Cross-sectional scanning electron microscope (SEM) image of a catalyst formed by coaxial 3D printing of a core-shell structure of Mn / Al2O3 and SCR catalyst Cu-SSZ-13, with cordierite double-layer coating and physical mixing (Application Example 2). Figure 16 a) Application Example 3 ( Figure 16b) and Application Example 4 ( Figure 16 c));

[0162] Figure 17 NO under dry conditions is a catalyst formed by coaxial 3D printing of a core-shell structure of Mn / Al2O3 and SCR catalyst Cu-SSZ-13, with cordierite double-layer coating and physical mixing. x Concentration curve change graphs (Application Examples 2, 3, and 4);

[0163] Figure 18 NO production under conditions containing 5% H2O is achieved by cascading Mn / Al2O3 and SCR catalyst Cu-SSZ-13 using a coaxial 3D-printed core-shell structure, cordierite double-layer coating, and physical mixing. x Concentration curve changes (Application Examples 2, 3 and 4).

[0164] Application Example 3

[0165] Take 400 cpsi cordierite and cut it into a cylindrical shape approximately 23 mm long and 9 mm in diameter. Figure 15 (In the example above). Mn / Al2O3 and Cu-SSZ-13 from Example 1 were coated onto cordierite, with Mn / Al2O3 as the bottom layer and Cu-SSZ-13 as the top layer. Each layer used 120 mg of powder and 30 mg of halloysite nanotubes. A single layer of Cu-SSZ-13 coating used 240 mg of powder and 60 mg of halloysite nanotubes. The activity evaluation device consisted of a gas mixing and catalytic reaction experimental apparatus and a Fourier transform infrared spectrometer. The gas flow rate was controlled by a mass flow meter in the gas mixing and catalytic reaction experimental apparatus. Table 2 shows the gas composition and concentration of gas components, and the total gas flow rate was set to 200 mL / min. The catalyst pretreatment and adsorption-desorption test processes were completed in the reactor of the gas mixing and catalytic reaction experimental apparatus. The reactor was equipped with a K-type thermocouple to monitor temperature changes during the reaction process. The gas concentration at the outlet was analyzed by a Fourier transform infrared spectrometer. The specific testing procedure is as follows: The coated cordierite was placed in a quartz tube with a diameter of 1 cm. The gas flow rate was set according to Table 2, and the circuit was switched to the bypass. After the gas concentration stabilized, the temperature control program was started, raising the temperature from room temperature to 50°C at a rate of 10°C / min. The gas was then switched from the bypass to the sample tube, and simultaneously, the temperature was raised from 50°C to 500°C at a rate of 15°C / min. NH3 was introduced at 170°C. 5% H2O was introduced as needed.

[0166] Table 2 Gas composition and concentration settings for pretreatment and adsorption-desorption tests

[0167]

[0168] Application Example 4

[0169] Weigh 2.0g each of Mn / Al2O3 and Cu-SSZ-13 powder, 1.0g of halloysite nanotubes, and 20mL of ethanol into a glass beaker. After ultrasonic dispersion for 30min, place in a 70℃ water bath to form a viscous paste. Then, add 2g of hydroxypropyl methylcellulose (HPMC) to the paste and stir with a glass rod until the ink flows smoothly through the needle and is printed.

[0170] Ink is extruded from a needle (19G) using a pneumatic jet 3D printing system and stacked to form honeycomb cylinders with a diameter of approximately 1 cm and a height of approximately 0.5 cm. After natural drying, the cylinders are calcined in air at 600°C for 5 hours to remove the binder and maintain structural stability.

[0171] The printing process for Cu-SSZ-13 bulk materials is the same as that for Mn / Al2O3. The activity testing procedure for the physical mixture of Mn / Al2O3 and Cu-SSZ-13 is the same as in Application Example 2 and will not be repeated here. The catalyst mass was 300 mg during the test.

[0172] Application Example 5

[0173] Application Example 5 is based on Application Examples 2, 3, and 4, but replaces Cu-SSZ-13 with other denitrification catalysts, namely Cu-SSZ-39, Cu-SAPO-18, Cu-SAPO-34, Fe-SSZ-13, Fe-SSZ-39, V2O5-WO3(MoO3) / TiO2, etc., and connects them in series with Mn / Al2O3 in the same way as in Application Examples 2, 3, and 4.

[0174] Comparative Application Example 1

[0175] Similarly, MnO2+Al2O3, Mn2O3+Al2O3, Mn3O4+Al2O3, and MnO+Al2O3 from Comparative Example 1 are used as the monolithic NO. x Adsorbent. The evaluation method is the same as that used for evaluating the activity of the Mn / Al2O3 bulk in Application Example 1.

[0176] Figure 13 NO is a monolithic adsorbent fabricated by 3D printing from a physical mixture of Al2O3 and manganese oxides (MnO2, Mn2O3, Mn3O4, MnO). x The concentration curve (compared to application example 1) shows that the physical mixture of Al2O3 and manganese oxide has poor adsorption activity at low temperatures.

[0177] Comparative application 2

[0178] Similarly, the Pd(2) / Al2O3 and Pd(2) / SSZ-13 blocks from Comparative Example 6 were used as the monolithic NO. x Adsorbent. The evaluation method is the same as that used for evaluating the activity of the Mn / Al2O3 bulk in Application Example 1.

[0179] Figure 14 2.0 wt.% Pd-loaded Al2O3 (Pd(2) / Al2O3) and 2.0 wt.% Pd-loaded SSZ-13 (Pd(2) / SSZ-13) with Mn(2) / Al2O3 NO x Concentration curve variation graph (compared to application example 2) shows that the adsorption activities of the non-precious metal adsorbent Mn(2) / Al2O3 and the noble metal Pd supported adsorbent are comparable.

[0180] Comparative application 3

[0181] Comparative Example 3, based on Application Example 1, evaluated the activity of Mn / Al2O3 in both cordierite-coated and powder forms. For the cordierite coating method, referencing Application Example 3, 400 cpsi cordierite was cut into cylindrical shapes approximately 23 mm long and 9 mm in diameter. The Mn / Al2O3 from Example 1 was coated onto the cordierite in multiple applications, using 240 mg of Mn / Al2O3 and 60 mg of halloysite nanotubes. For the powder form, a conventional tableting and sieving method was used, compressing the Mn / Al2O3 into tablets and sieving them to 60–80 mesh. The tested sample weighed 240 mg.

[0182] Figure 19 NO in three forms: 3D printing, cordierite coating, and powder, for Mn / Al2O3. x The concentration curve shows that Mn / Al2O3 exhibits the best NO adsorption activity when 3D printed.

[0183] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A coaxial 3D-printed tandem catalyst, characterized in that, It includes a core and a shell arranged coaxially, wherein the core is made of a monolithic adsorbent material and the shell is a nitrogen oxide selective catalytic reduction unit; The monolithic adsorbent is prepared by 3D printing from the following parts by weight of raw materials: 8-18 parts by weight of Mn / Al2O3 powder; 1-6 parts by weight of halloysite nanotubes; 0.1 to 1 part by weight of hydroxypropyl methylcellulose; 80-90 parts by weight of solvent ethanol.

2. The coaxial 3D-printed tandem catalyst according to claim 1, characterized in that, The manganese loading in the Mn / Al2O3 powder is 0.1~20 wt.%; The preparation method of the Mn / Al2O3 powder includes one of the following: excess impregnation method, equal volume impregnation method, and solid grinding method; The preparation method of the Mn / Al2O3 powder includes the following steps: Al2O3 and manganese salt were mixed in a solvent and reacted. After removing the solvent, the mixture was dried and calcined to obtain Mn / Al2O3 powder. The manganese salt is selected from one of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.

3. The coaxial 3D-printed tandem catalyst according to claim 1, characterized in that, Before mixing Al2O3 with manganese salt in a solvent, the Al2O3 is further modified with rare earth elements, wherein the rare earth metal elements are one or more of La, Pr, Nd, Y, Ce, Zr, Sm, Pm, Eu, and Gd, and the loading of the rare earth metal elements is 0.2 wt.%-5.0 wt.%.

4. The coaxial 3D-printed tandem catalyst according to claim 1, characterized in that, The preparation method of the monolithic adsorbent includes the following steps: A) Mix Mn / Al2O3 powder, halloysite nanotubes and solvent, and heat to obtain a paste-like mixture; The paste-like mixture was mixed and stirred with hydroxypropyl methylcellulose to obtain a 3D printing material; B) The 3D printing material is placed in a 3D printer, and a path is established by computer programming. The extruded Mn / Al2O3 fibers are stacked through the 3D printing system to form the desired shape, thus obtaining an integral adsorbent precursor. C) The monolithic adsorbent precursor is dried and then calcined to obtain the monolithic adsorbent; Alternatively, it may include the following steps: a) Al2O3, manganese salt and halloysite nanotubes were mixed in a solvent and heated to obtain a paste-like mixture; The paste-like mixture was mixed and stirred with hydroxypropyl methylcellulose to obtain a 3D printing material; b) The 3D printing material is placed in a 3D printer, and a path is established by computer programming. The extruded Mn / Al2O3 fibers are stacked through the 3D printing system to form the desired shape, thus obtaining an integral adsorbent precursor. c) The monolithic adsorbent precursor is dried and then calcined to obtain the monolithic adsorbent.

5. The coaxial 3D-printed tandem catalyst according to claim 4, characterized in that, The heating temperature is 60~100℃; the calcination temperature is 500~650℃, and the time is 4~8h.

6. The coaxial 3D-printed tandem catalyst according to claim 1, characterized in that, The main material of the shell is selected from one or more of Cu-SSZ-13, Cu-SSZ-39, Cu-SAPO-18, Cu-SAPO-34, Fe-SSZ-13, Fe-SSZ-39, V2O5-WO3 / TiO2, and V2O5-MoO3 / TiO2; The mass ratio of the core to the shell is 4:1 to 1:4; The preparation method of the coaxial 3D printed tandem catalyst includes the following steps: 1) Configure the core and shell layers separately as 3D printing materials; Mn / Al2O3 powder, halloysite nanotubes, and solvent were mixed and heated to obtain a paste-like mixture; the paste-like mixture was then mixed and stirred with hydroxypropyl methylcellulose to obtain a core 3D printing material. The shell material, halloysite nanotubes, and solvent are mixed and heated to obtain a paste-like mixture; the paste-like mixture is then mixed and stirred with hydroxypropyl methylcellulose to obtain the shell 3D printing material. 2) The core 3D printing material and the shell 3D printing material are extruded through the coaxial needle of the 3D printing system and stacked into the desired shape to obtain the coaxial catalyst precursor; 3) The coaxial catalyst precursor is dried and then calcined to obtain the coaxial catalyst.

7. A coaxial 3D-printed tandem catalyst as described in any one of claims 1 to 6 for achieving NO x Applications of ultra-low emissions during the cold start phase.

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