Palladium-containing RHO zeolite nitrogen oxide compound adsorbent and preparation method therefor

Abstract

The present invention relates to the technical field of nitrogen oxide compound gas purification, and specifically relates to a palladium-containing RHO zeolite nitrogen oxide compound adsorbent and a preparation method therefor. When an in-situ adsorption infrared analysis is performed on the adsorbent, the ratio of the intensity of an infrared absorption peak at 1840-1900 cm -1 to the intensity of an infrared absorption peak at 1780-1840 cm -1 is greater than 0.9. The adsorbent comprises at least silicon, aluminum, and oxygen as skeletal atoms, wherein the molar ratio of silicon atoms to aluminum atoms is (2-50): 1. Palladium in the adsorbent accounts for 0.1-5.0% of the mass of the RHO-type zeolite. The adsorbent not only has a relatively high NO x storage capacity, but also has a higher hydrothermal stability, and can be used as a PNA material to meet the actual needs of exhaust purification in a motor vehicle.

Description

Palladium-containing rho zeolite nitric oxide adsorbent and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to a palladium-containing rho zeolite nitric oxide adsorbent and a preparation method thereof, and belongs to the technical field of nitric oxide gas purification. BACKGROUND

[0002] Emission of nitrogen oxides (NO x ) has become a serious concern of society, in order to limit the impact of NO x on the environment and health, countries have developed increasingly stringent emission regulations. Cars as mobile sources are the main contributors to traffic pollution emissions, and the amount of NO x emitted by diesel vehicles accounts for more than 80% of the total amount of NO x emitted by vehicles. So far, lean NO x traps (LNT) and selective catalytic reduction (SCR) have been successfully developed and applied to NO x emission control. It is worth noting that LNT adsorbs and stores NO x under lean conditions, and releases NO x when it is rich, but its adsorption temperature is usually above 200℃. Selective catalytic reduction (SCR) technology with NH3 as a reducing agent is considered to be the most effective diesel vehicle NO x emission control technology, and copper-based small-pore zeolites can exhibit high NO x conversion rates in the range of 200℃ to 600℃. However, during vehicle cold start (3-5 min at temperatures below 180℃), both of the above technologies cannot efficiently control NO x emissions. In addition, urea is difficult to decompose into NH3 below 180℃, which sets a technical limit for the application of urea SCR technology at low temperatures.

[0003] In order to solve the problems faced by the SCR system, US Patent US8105559B2 proposes the concept of CSC catalyst (Cold-Start Catalysts) to address the problem of low-temperature exhaust emissions of diesel engines. The CSC catalyst takes a cerium oxide supported palladium-based catalyst as the core, which adsorbs and stores HCs and NO x at low temperatures, and then releases the adsorbed HCs and NO x at high temperatures. However, it has the problem of low NO x adsorption efficiency at low temperatures, which cannot meet the application requirements of low-temperature nitrogen oxide storage. US Patent US2015 / 0158019A1 discloses a passive NO xadsorber, PNA) technology, using CHA type zeolite containing noble metal elements as NO x adsorbing material. Compared with non-zeolite PNA materials, zeolite PNA materials containing noble metal elements exhibit good NO x storage performance and higher sulfur resistance. Compared with a palladium-containing CHA type zeolite PNA material, patent WO2017 / 001828A1 discloses a palladium-containing LTL type zeolite PNA material, which has higher NO x release temperature. In addition, OFF type zeolite containing noble metal (US20190217269A1), MAZ type zeolite (WO2016135465A1), STI type zeolite (WO2019 / 186163A1) are also used for PNA adsorbing materials. Patent WO2022 / 243164 proposes a palladium-containing AFX type zeolite PNA material, which not only has higher NO x storage capacity, but also has higher NO x desorption temperature. Since high-temperature water vapor is emitted during engine operation, the PNA material also needs to have high hydrothermal stability. The PNA materials disclosed in the known technologies will all cause the NO x adsorption capacity to decrease after high-temperature hydrothermal aging treatment, which cannot meet the actual application requirements.

[0004] The relevant literature (Angew. Chem. Int. Ed. 57 (2018) 16672-16677) considers that palladium ions are adsorption sites for NO x , so loading highly dispersed palladium ions in zeolite materials is the key to PNA materials. However, the dispersion degree of palladium ions is not only related to the preparation method, but also the stability of the zeolite structure is crucial to the dispersion degree of palladium ions and hydrothermal temperature. After hydrothermal treatment, the collapse of the zeolite structure will cause the agglomeration of palladium ions, thereby causing the NO x adsorption performance of the PNA material to decrease.

[0005] SUMMARY

[0006] The present application aims at the deficiencies in the prior art, and provides a palladium-containing RHO zeolite nitrogen oxide adsorbing agent and a preparation method thereof. The adsorbing agent not only has higher NO x storage capacity, but also has higher hydrothermal stability, and can meet the actual needs of motor vehicle exhaust purification as a PNA material.

[0007] The technical scheme for solving the above technical problem is as follows: The present inventors have found through in-depth research that the selection of a silicon source has an important influence on the synthesis of RHO zeolite with high silicon and high crystallinity. If a nanoscale liquid silicon source (such as a water-soluble silica sol) is used, the silicon source is dissolved into sodium silicate during the synthesis process, and it is not easy to form the double-8-membered ring structure of the RHO zeolite, so the synthesized RHO zeolite tends to have low crystallinity. If a powdery solid silicon source (such as fumed silica or white carbon black) with a particle size of less than 50 μm is used, the system viscosity increases sharply after the gel is added because of the strong water absorption of the silicon source, and the mass and heat transfer speed of the system is affected by the poor flowability of the initial gel, which in turn leads to the synthesized RHO zeolite being prone to producing impurities. If a powdery silica gel with a particle size of 50-300 μm is used as the silicon source, the initial coagulation viscosity is low, and the mass and heat transfer is sufficient, so the synthesized RHO zeolite has high crystallinity and is not prone to producing impurities. If a solid silicon source with a particle size of more than 300 μm is used, the silica is not easy to dissolve during the reaction process, so it is difficult for the RHO zeolite to crystallize. When the RHO zeolite synthesized by using the powdery silica gel with a particle size of 50-300 μm as the silicon source is loaded with palladium elements and then subjected to in-situ adsorption infrared analysis, the ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to the infrared absorption peak intensity at 1780-1840 cm-1 is greater than 0.9, and the RHO zeolite has very excellent nitrogen oxide adsorption performance. -1 -1

[0008] Further, the adsorbent at least contains silicon, aluminum and oxygen as framework atoms, wherein the molar ratio of silicon atoms to aluminum atoms is (2-50):1.

[0009] Further, the palladium accounts for 0.1-5.0% of the mass of the RHO zeolite in the adsorbent.

[0010] Further, the adsorbent further contains one or more other elements selected from alkali metals, alkaline earth metals, rare earth metals and transition metals.

[0011] The present application also discloses a preparation method of the palladium-containing RHO zeolite nitrogen oxide adsorbent.

[0012] S1, mixing a mixture containing at least a silicon source, an aluminum source, an organic template and an inorganic base in water to obtain a primary gel;

[0013] S2, obtaining a reaction product after the primary gel is subjected to aging and hydrothermal synthesis reaction;

[0014] S3, obtaining a RHO zeolite by removing the organic template from the reaction product;

[0015] S4, ion exchanging the RHO zeolite with an ammonium salt and then performing calcination treatment again; ​​

[0016] S5, after the calcination treatment, the powder is uniformly mixed with a solution containing palladium element, water is removed, and then calcination is performed again to obtain a palladium-containing RHO zeolite nitrogen oxide compound adsorbent.

[0017] Further, the silicon source is at least one of powdered silica gel, fumed silica, white carbon black, sodium silicate, silica sol, trimethylethoxysilane, and tetraethyl orthosilicate.

[0018] The aluminum source is at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum oxide, aluminum hydroxide, boehmite, aluminum chloride, aluminum silicate gel, and metallic aluminum.

[0019] The organic template agent is 18-crown-6.

[0020] The inorganic base is an alkali metal hydroxide.

[0021] Preferably, the silicon source is powdered silica gel, and further, the particle size of the powdered silica gel is 50-300 μm.

[0022] The aluminum source is sodium aluminate.

[0023] The organic template agent is 18-crown-6.

[0024] The inorganic base is at least one of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide.

[0025] Further, the solution containing palladium element is at least one of palladium nitrate solution, palladium dichloride solution, dichlorotetraammine palladium solution, palladium sulfate solution, and ammonium tetrachloropalladate solution.

[0026] Further, a catalytic reactor for purifying nitrogen oxides is provided, and the purification device is provided with the palladium-containing RHO zeolite nitrogen oxide compound adsorbent described herein or prepared according to the method described herein.

[0027] The present application has the following advantages:

[0028] In the preparation process of the palladium-containing RHO zeolite nitrogen oxide compound adsorbent, the use of powdered silica gel as the silicon source for preparing the initial gel can greatly reduce the viscosity of the gel system, so that the synthesized RHO zeolite has higher crystallinity and is less likely to produce impurities, and thus the finally prepared palladium-containing RHO zeolite nitrogen oxide compound adsorbent has higher NOx storage capacity and hydrothermal stability.

[0029] Further, the Pd-containing RHO zeolite nitric oxide adsorbent has a lower framework density and greater framework flexibility than other Pd-containing small-pore zeolite nitric oxide adsorbents, and when Pd is loaded, Pd species are more easily dispersed into the zeolite channels, and there are more ionic Pd species. Therefore, the Pd-containing RHO zeolite has more NO x effective adsorption sites, and can exhibit high NO x storage capacity under aqueous conditions, and the Pd-containing RHO zeolite is less likely to cause Pd species to agglomerate under high-temperature hydrothermal conditions, and exhibits excellent hydrothermal stability. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is an XRD pattern of the zeolite A prepared in Example 1;

[0031] Figure 2 is an XRD pattern of the zeolite prepared in Comparative Example 5;

[0032] Figure 3 is an XRD pattern of the zeolite prepared in Comparative Example 6;

[0033] Figure 4 is an in-situ NO adsorption infrared spectrum of the PNA1A fresh adsorbent prepared in Example 1 (hi in the figure is an infrared absorption peak at 1840-1900 cm -1 , and h2 is an infrared absorption peak at 1780-1840 cm -1 );

[0034] Figure 5 is an in-situ NO adsorption infrared spectrum of the PNA1A aged adsorbent prepared in Example 1 (hi in the figure is an infrared absorption peak at 1840-1900 cm -1 , and h2 is an infrared absorption peak at 1780-1840 cm -1 );

[0035] Figure 6 is an in-situ NO adsorption infrared spectrum of the PNA1B fresh adsorbent prepared in Example 2 (hi in the figure is an infrared absorption peak at 1840-1900 cm -1 , and h2 is an infrared absorption peak at 1780-1840 cm -1 );

[0036] Figure 7 is an in-situ NO adsorption infrared spectrum of the PNA1B aged adsorbent prepared in Example 2 (hi in the figure is an infrared absorption peak at 1840-1900 cm -1 , and h2 is an infrared absorption peak at 1780-1840 cm -1 );

[0037] Figure 8 is an in-situ NO adsorption infrared spectrum of the PNA1C fresh adsorbent prepared in Example 3 (hi in the figure is an infrared absorption peak at 1840-1900 cm -1 , and h2 is an infrared absorption peak at 1780-1840 cm -1(Infrared absorption peak at the location);

[0038] Figure 9 shows the in-situ NO adsorption infrared spectrum of the PNA1C aging adsorbent prepared in Example 3 (h1 in the figure is 1840-1900 cm⁻¹). -1 The infrared absorption peak at h2 is 1780–1840 cm⁻¹. -1 (Infrared absorption peak at the location);

[0039] Figure 10 shows the in-situ NO adsorption infrared spectrum of the fresh PNA2A adsorbent prepared in Comparative Example 1 (h1 in the figure is 1840–1900 cm⁻¹). -1 The infrared absorption peak at h2 is 1780–1840 cm⁻¹. -1 (Infrared absorption peak at the location);

[0040] Figure 11 shows the in-situ NO adsorption infrared spectrum of the aged PNA2A adsorbent prepared in Comparative Example 1 (h1 in the figure is 1840–1900 cm⁻¹). -1 The infrared absorption peak at h2 is 1780–1840 cm⁻¹. -1 (Infrared absorption peak at the location);

[0041] Figure 12 shows the in-situ NO adsorption infrared spectrum of the fresh PNA2B adsorbent prepared in Comparative Example 2 (h1 in the figure is 1840–1900 cm⁻¹). -1 The infrared absorption peak at h2 is 1780–1840 cm⁻¹. -1 (Infrared absorption peak at the location);

[0042] Figure 13 shows the in-situ NO adsorption infrared spectrum of the aged PNA2B adsorbent prepared in Comparative Example 2 (h1 in the figure is 1840–1900 cm⁻¹). -1 The infrared absorption peak at h2 is 1780–1840 cm⁻¹. -1 (Infrared absorption peak at the location);

[0043] Figure 14 shows the in-situ NO adsorption infrared spectrum of the fresh PNA3A adsorbent prepared in Comparative Example 3 (h1 in the figure is 1840–1900 cm⁻¹). -1 The infrared absorption peak at h2 is 1780–1840 cm⁻¹. -1 (Infrared absorption peak at the location);

[0044] Figure 15 shows the in-situ NO adsorption infrared spectrum of the aged PNA3A adsorbent prepared in Comparative Example 3 (h1 in the figure is 1840–1900 cm⁻¹). -1 The infrared absorption peak at h2 is 1780–1840 cm⁻¹. -1 (Infrared absorption peak at the location);

[0045] Figure 16 is an in-situ adsorption infrared spectrum of NO for the fresh PNA3B adsorbent prepared in Comparative Example 4 (hi is the infrared absorption peak at 1840-1900 cm -1 in the figure, h2 is the infrared absorption peak at 1780-1840 cm -1 in the figure).

[0046] Figure 17 is an in-situ adsorption infrared spectrum of NO for the aged PNA3B adsorbent prepared in Comparative Example 4 (hi is the infrared absorption peak at 1840-1900 cm -1 in the figure, h2 is the infrared absorption peak at 1780-1840 cm -1 in the figure).

[0047] Figure 18 is a graph of NO storage and release versus time for the fresh PNA1B, PNA2A and PNA3A adsorbents. x

[0048] Figure 19 is a graph of NO storage and release versus time for the aged PNA1B, PNA2A and PNA3A adsorbents. x DETAILED DESCRIPTION

[0049] The present application is described in detail below. The present application can be implemented in various ways other than those described herein without departing from the spirit of the present application, and those skilled in the art can make similar modifications without departing from the scope of the present application, and thus the present application is not limited to the specific embodiments disclosed.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used only for describing specific embodiments is not intended to limit the present application.

[0051] I. Zeolite

[0052] The zeolite referred to in the present application means a RHO-type zeolite as defined by the International Zeolite Association (hereinafter referred to as IZA). The zeolite is generally a regular net-like structure formed by the oxygen atoms at each vertex of a tetrahedron of framework atoms (e.g., SiO4 tetrahedron, AlO4 tetrahedron or PO4 tetrahedron, and the element atoms other than oxygen are referred to as non-oxygen atoms or T atoms) being linked by sharing. For the RHO-type zeolite, the structure can be determined by X-ray diffraction (XRD), and at least the interplanar spacing shown in Table 1 below should be detected, and if the interplanar spacing shown in Table 1 below is present, the zeolite can be a RHO-type zeolite.

[0053] Table 1 Interplanar spacing ​​

[0054] II. Synthesis of Zeolite

[0055] In the present disclosure, the method for synthesizing the zeolite employs a hydrothermal synthesis method, in which raw materials are prepared into a preliminary gel by being mixed with water, and then subjected to a hydrothermal synthesis reaction in a reaction vessel to thereby synthesize the zeolite.

[0056] <Raw Materials>

[0057] The raw materials used in the process of manufacturing the RHO-type zeolite of the present disclosure mainly include a silicon source, an aluminum source, an organic template agent, an optional inorganic base, and water. In addition, a component having a crystallization promoting effect such as a seed crystal can also be added.

[0058] The silicon source can use at least one of powdered silica gel, fumed silica, white carbon black, sodium silicate, silica sol, trimethylethoxysilane, and tetraethyl orthosilicate. The aluminum source can use at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum oxide, aluminum hydroxide, boehmite, aluminum chloride, aluminum silicate gel, and metallic aluminum.

[0059] The inorganic base can use at least one of alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. In the process of manufacturing the zeolite, as the alkali metal ion or alkaline earth metal ion, it is preferable to use at least one metal ion selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, calcium, magnesium, strontium, and barium for crystallization. By including these alkali metal ions, crystallization is easily performed and the generation of by-products (impurity crystals) is less likely. Note that, when calculating the molar ratio of the components in the gel, the corresponding oxide A2O of the inorganic base AOH is generally used to calculate the molar ratio.

[0060] <Preparation of Aluminum Source Solution>

[0061] The aluminum source solution is prepared by dissolving the above-described aluminum source in water. The aluminum source concentration of the aluminum source solution is preferably 5 to 50% by weight, and particularly preferably 10 to 40% by weight, in consideration of the ease of gel preparation and production efficiency.

[0062] Note that the aluminum source solution does not substantially contain silicon atoms. Here, "does not substantially contain" means that the silicon content in the aluminum source solution is 1% by weight or less, and preferably does not contain silicon at all.

[0063] <Preparation of Aqueous Gel>

[0064] The inorganic base solution is prepared by adding an inorganic base to an aqueous solution. Then, the inorganic base solution, the silicon source solution, the aluminum source solution, and the organic template agent are uniformly mixed to prepare a gel-like mixture, which is the aqueous gel used for the next reaction.

[0065] The addition rate of each raw material solution during preparation of the gel-like mixture is not limited and can be appropriately selected depending on the use conditions.

[0066] Note that if the silicon source is a liquid, it can be used as long as it is prepared as a water dispersion of about 5 to 60% by weight of silicon dioxide, like a silica gel. When preparing a liquid of another silicon atom-containing raw material, it is preferable to prepare a water solution or water dispersion of the silicon atom-containing raw material having a concentration of 5% by weight or more, particularly 10% by weight or more, and 60% by weight or less, particularly 50% by weight or less.

[0067] Like the aluminum source solution, the liquid of the silicon source substantially does not contain aluminum atoms. Here, "substantially does not contain" means that the content of aluminum in the liquid of the silicon source is 1% by weight or less, and it is preferable that it does not contain aluminum at all.

[0068] The aqueous gel prepared by the above operation can be subjected to hydrothermal synthesis immediately after preparation, but in order to obtain a zeolite having high crystallinity, it is preferable to mature it under prescribed temperature conditions for a certain period of time. The maturation temperature is usually 100°C or lower, preferably 80°C or lower, more preferably 60°C or lower, and the lower limit is not particularly limited, but is usually 0°C or higher, preferably 10°C or higher. The maturation temperature can be constant or gradually changed during maturation. The maturation time is not particularly limited, but is usually 2 hours or more, 3 hours or more, 5 hours or more, or 8 hours or more, and is usually 30 days or less, 10 days or less, 4 days or less, or 2 days or less.

[0069] <Hydrothermal Synthesis>

[0070] The hydrothermal synthesis is performed by placing the aqueous gel prepared by the above operation in a pressure-resistant container, and keeping the temperature under autogenous pressure, or under gas pressure to the extent that crystallization is not hindered, under stirring conditions, or under conditions in which the container is rotated or shaken, or under a stationary state, thereby performing the hydrothermal synthesis.

[0071] The reaction temperature during the hydrothermal synthesis is usually 90°C or higher, preferably 120°C or higher, and is usually 300°C or lower, preferably 250°C or lower, further preferably 200°C or lower. The reaction time is not particularly limited, but is usually 2 hours or more, 6 hours or more, 12 hours or more, and is usually 30 days or less, 10 days or less, 7 days or less. The reaction temperature can be constant or gradually changed during the reaction.

[0072] After the above hydrothermal synthesis, the RHO-type zeolite as a product is separated from the hydrothermal synthesis reaction liquid. The obtained RHO-type zeolite (hereinafter referred to as "RHO-type zeolite containing a template or the like") contains one or more of the organic template and the alkali metal in the fine pores. The method for separating the RHO-type zeolite containing a template or the like from the hydrothermal synthesis reaction liquid is not particularly limited, and methods such as filtration, decantation, or direct drying can be generally exemplified.

[0073] <Removal of impurities, calcination, and ion exchange>

[0074] In order to remove the organic template and the alkali metal ion or the like used in the manufacturing process, the RHO-type zeolite containing a template or the like recovered from the hydrothermal synthesis reaction liquid can be subjected to subsequent removal of the organic template and the alkali metal ion after water washing and drying (for example, drying at 80°C to 100°C for 1 hour to 12 hours) as needed.

[0075] The removal treatment of the template and / or the alkali metal can employ liquid phase treatment using an acidic solution, a chemical solution containing a template decomposition component, ion exchange treatment using a resin or the like, thermal decomposition treatment, and these treatments can also be used in combination. In general, the contained organic substance (template or the like) can be removed by calcination at a temperature of 300°C to 800°C in an atmosphere of air or a non-active gas atmosphere containing oxygen, or a non-active gas atmosphere, or extraction using an organic solvent such as an ethanol aqueous solution.

[0076] From the viewpoint of manufacturing, it is preferable to remove the template or the like by calcination. At this time, the calcination temperature is preferably 400°C or higher, more preferably 450°C or higher, and further preferably 500°C or higher, and is preferably 900°C or lower, more preferably 850°C or lower, and further preferably 800°C or lower. As the non-active gas, a gas such as nitrogen or the like can be used, and a non-active component such as water vapor (for example, 5% to 10% water vapor) can be added to the gas.

[0077] In addition, the alkali metal can be partially converted to the H-type or the NH4-type using the ion exchange ability of the zeolite, and the method can employ a publicly known technique. The zeolite of the NH4-type can be further converted to the H-type zeolite by treatment at room temperature to 100°C using an ammonium salt such as NH4NO3, NH4Cl, (NH4)2SO4, or an acidic solution such as hydrochloric acid, followed by water washing. As the non-active gas, a gas such as nitrogen or the like can be used, and a non-active component such as water vapor (for example, 5% to 10% water vapor) can be added to the gas.

[0078] The palladium metal can be added to the RHO framework zeolite by any known means, for example, a palladium-containing compound can be supported on the zeolite by impregnation, adsorption, ion exchange, precipitation, spray drying, or the like. The exchanged zeolite is then dried (for example, at 80°C to 100°C for 1 hour to 12 hours) and calcined. As the non-reactive gas, a gas such as nitrogen can be used, or a non-reactive component such as water vapor (for example, 5% to 10% water vapor) can be added to the gas.

[0079] The calcination apparatus of the present disclosure is not particularly limited, and a common industrial kiln such as a muffle furnace, a tunnel kiln, or a rotary kiln can be used. From the viewpoint of convenience for continuous production, a rotary kiln is preferably used.

[0080] Method for using the palladium-containing RHO zeolite nitrogen oxide adsorbent:

[0081] The palladium-containing RHO zeolite nitrogen oxide adsorbent can be used directly in powder form, or can be mixed with a binder to form a mixture containing the zeolite and then used. The binder used can be an inorganic binder such as silica, alumina, or zirconia, or a polysiloxane-based organic binder. The polysiloxane-based refers to an oligomer or polymer having a polysiloxane bond in the main chain, and also includes a substance in which a part of the substituents of the main chain of the polysiloxane bond is hydrolyzed to form a hydroxyl group. The amount of the binder used is not particularly limited, and can be typically 1 to 20% by weight, and from the viewpoint of strength during molding, 2 to 15% by weight.

[0082] The palladium-containing RHO zeolite nitrogen oxide adsorbent or the mixture containing the zeolite of the present disclosure can also be used after being granulated or molded. The method for granulating or molding is not particularly limited, and various publicly known methods can be used. Typically, the mixture of the zeolite is molded and used as a molded body. The shape of the molded body can be various. For example, when the zeolite of the present disclosure is used as a catalyst for purifying nitrogen oxides in exhaust gas of a mobile source (vehicle, ship, or the like), the method in which the zeolite is applied can be a coating method or a molding method to form the zeolite into a honeycomb-shaped adsorbent. The coating method is typically a method in which the zeolite is mixed with an inorganic binder such as silica, alumina, or zirconia to prepare a slurry, the slurry is coated on the surface of a honeycomb-shaped article made of an inorganic material such as cordierite, and then dried and fired. The molding method is typically a method in which the zeolite is mixed with an inorganic binder such as silica, alumina, or zirconia, or an inorganic fiber such as alumina fiber or glass fiber, and then molded into a honeycomb shape by an extrusion method or a compression method, and further dried and fired.

[0083] Nitrogen oxides and purification thereof

[0084] The palladium-containing RHO zeolite nitrogen oxide adsorbent purifies nitrogen oxides by contacting with exhaust gas containing nitrogen oxides. The nitrogen oxides to be purified include nitric oxide, nitrogen dioxide, nitrous oxide, and the like. The palladium-containing RHO zeolite nitrogen oxide adsorbent can effectively adsorb nitrogen oxides at low temperatures and release the adsorbed nitrogen oxides when the temperature is raised to a certain temperature. When the zeolite of the present disclosure is used as an adsorbent, nitrogen oxides contained in various exhaust gases discharged from diesel vehicles, gasoline vehicles, stationary power generation ships, agricultural machines, construction machines, two- or three-wheeled motor vehicles, various gasoline or diesel engines for aircraft, boilers, gas turbines, and the like can be purified.

[0085] A palladium-containing RHO zeolite nitrogen oxide adsorbent, when subjected to in-situ adsorption infrared analysis, has a ratio of infrared absorption peak intensity at 1840 to 1900 cm -1 to the infrared absorption peak intensity at 1780 to 1840 cm -1 is greater than 0.9.

[0086] More specifically, the adsorbent contains at least silicon, aluminum, and oxygen as framework atoms, and the molar ratio of silicon atoms to aluminum atoms is (2 to 50): 1.

[0087] More specifically, the palladium content in the palladium-containing RHO zeolite nitrogen oxide adsorbent is 0.1 to 5.0% by mass of the RHO zeolite.

[0088] More specifically, the palladium-containing RHO zeolite nitrogen oxide adsorbent can further contain one or more other elements selected from alkali metals, alkaline earth metals, rare earth metals, and transition metals.

[0089] A method for preparing a palladium-containing RHO zeolite nitrogen oxide adsorbent, the method comprising:

[0090] S1, mixing a mixture containing at least a silicon source, an aluminum source, an organic template agent, and an inorganic base in water to obtain a primary gel;

[0091] S2, subjecting the primary gel to a maturation and hydrothermal synthesis reaction to obtain a reaction product;

[0092] S3, calcining the reaction product to remove the organic template agent to obtain a RHO zeolite;

[0093] S4, ion-exchanging the RHO zeolite with an ammonium salt and performing a calcination treatment again;

[0094] S5, uniformly mixing the powder after the calcination treatment with a solution containing palladium elements, removing the water, and performing a calcination again to obtain a palladium-containing RHO zeolite nitrogen oxide adsorbent.

[0095] The silicon source is at least one of powdered silica gel, fumed silica, white carbon black, sodium silicate, silica sol, trimethylethoxysilane, and tetraethyl orthosilicate;

[0096] The aluminum source is at least one of sodium metaaluminate, aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum oxide, aluminum hydroxide, boehmite, aluminum chloride, aluminum silicate gel, and metallic aluminum;

[0097] The organic template is 18-crown-6;

[0098] The inorganic base is an alkali hydroxide;

[0099] Preferably, the silicon source is powdered silica gel, and the particle size of the powdered silica gel is 50-300 μm;

[0100] Specifically, in the initial gel, the molar ratio of SiO2, Al2O3, R, A2O, and H2O in the silicon source, the aluminum source, the organic template, the inorganic base, and water is (5-100) : 1 : (5-20) : (2-20) : (100-1000).

[0101] Specifically, the solution containing the palladium element is at least one of palladium nitrate solution, palladium dichloride solution, dichlorotetraamine palladium solution, palladium sulfate solution, and ammonium tetrachloropalladate solution.

[0102] Specifically, in step S2, the temperature condition of the maturation is 10-60 °C, and the time of the maturation is 8-48 h.

[0103] The temperature of the hydrothermal synthesis reaction is 120-200 °C, and the time of the hydrothermal synthesis reaction is 1-7 days.

[0104] In step S4, the temperature of the calcination treatment is 300-700 °C, and the time of the calcination treatment is 2-72 h.

[0105] In step S5, the temperature of the calcination treatment is 300-800 °C, and the time of the calcination treatment is 2-72 h. In actual production or experiments, appropriate process parameters can be selected within the above condition range, but are not limited to only within the condition parameters.

[0106] Specifically, a catalytic reactor for purifying nitrogen oxides is provided, and the purification device is provided with the palladium-containing RHO-type zeolite nitrogen oxide adsorbent described herein or prepared according to the method described herein.

[0107] In the following examples, the experimental methods are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0108] The performance measurement method involved in the embodiments is as follows:

[0109] (1) Measurement of powder XRD

[0110] The X-ray diffraction measurement instrument is a Rigaku MiniFlex600, the detection light source is Cu Ka, the tube voltage is 40 kV, the tube current is 40 mA, the detection angle range is 3-55°, and the scanning speed is 8° / min. The phase structure of the synthesized zeolite is determined by X-ray diffraction: the ground sample powder is added into a square hole on a glass flat, then the glass flat is inserted into the axis position of the goniometer, and the probe is rotated at a speed of 2θ / min under the irradiation of the Cu Ka light source.

[0111] (2) Adsorption and desorption test of sample NO x

[0112] After the prepared catalyst is punched and formed, it is crushed and granulated. The granulated zeolite (0.7 g) is filled into a constant bed flow-through reaction tube. The gas containing the composition in Table 2 is made to flow through the catalyst layer, and the catalyst layer is heated at the same time. The adsorption temperature is 100°C, and the adsorption time is 30 min. After the adsorption is completed, the temperature programmed desorption is carried out under the atmosphere, and the temperature is raised to 500°C at a rate of 10°C / min. The FTIR analyzer is used to measure the concentrations of substances NO, NO2, NH3, N2O, H2O, O2 at the outlet of the reactor.

[0113] Table 2 Composition of the gas flowing through the catalyst layer

[0114] (3) In-situ NO adsorption infrared (FT-IR) analysis

[0115] The pressed zeolite sheet is placed in an in-situ transmission cell, and 50 mL / min of mixed gas (10% by volume fraction of O2, 90% by volume fraction of N2) is introduced. The sample is heated to 500°C and treated for 0.5 h, and then cooled to 100°C. The infrared spectrum is collected at this temperature as the background spectrum. 200 ppm of NO gas (10% by volume fraction of O2, 2.5% by volume fraction of H2O, the balance gas is N2, and the total gas flow is still 50 mL / min) is introduced, and the infrared spectrum data of the zeolite after 30 min of saturation adsorption is recorded. Because the infrared vibration peak positions of the palladium ions and palladium oxides loaded on the zeolite after adsorbing NO are different, the palladium species loaded on the zeolite can be qualitatively and quantitatively analyzed according to the infrared absorption peak intensity at different positions. When the in-situ NO adsorption infrared analysis of the zeolite containing palladium described in this paper is performed, the infrared absorption peak intensity at 1840-1900 cm -1 and the infrared absorption peak intensity at 1780-1840 cm -1 ​The infrared absorption peak intensity at this location is between 2000 and 2200 cm⁻¹. -1 Using the baseline at a certain point and the highest point of the peak within the corresponding interval as the vertex, the height of the absorption peak is calculated as the intensity of the absorption peak. Studies have found that the palladium-containing RHO-type zeolite in this invention has an absorption peak intensity between 1840 and 1900 cm⁻¹. -1 The infrared absorption peak intensity at 1780–1840 cm⁻¹ is similar to that at 1780–1840 cm⁻¹. -1 The ratio of the infrared absorption peak intensity at the above location is greater than 0.9. Palladium-containing RHO-type zeolites with the above characteristics have excellent adsorption performance of nitrogen oxides, are less affected by water in the ambient atmosphere, and have high hydrothermal stability.

[0116] (4) Hydrothermal aging test

[0117] 2.0 g of zeolite sample was placed in a tube furnace with an air flow rate of 300 mL / min and a water vapor content of 10%. The hydrothermal treatment temperature was 850℃ and the hydrothermal treatment time was 12 h.

[0118] Example 1

[0119] The preparation steps of a palladium-containing RHO zeolite nitrogen oxide adsorbent (0.5% wt palladium-containing RHO type zeolite) are as follows:

[0120] 42.4 g of 18-crown ether-6 (manufactured by Shanghai Sigma-Aldrich Co., Ltd.) was dissolved in 28.0 g of deionized water. Then, 5.8 g of sodium hydroxide (manufactured by Tianjin Fengchuan Chemical Reagent Co., Ltd.) and 16.0 g of cesium hydroxide (cesium hydroxide concentration: 50 wt%, manufactured by Shanghai Sigma-Aldrich Co., Ltd.) were added sequentially to form a mixed solution. The mixed solution was then heated and stirred at 70 °C for 3 h to obtain crown ether complex A solution. In a polytetrafluoroethylene bottle, 0.64 g of sodium aluminate (alumina content: 45 wt%; sodium oxide content: 38 wt%, manufactured by Tianjin Fengchuan Chemical Reagent Co., Ltd.) and 0.2 g of sodium fluoride (manufactured by Tianjin Fengchuan Chemical Reagent Co., Ltd.) were weighed and dissolved in 2.8 g of deionized water. Subsequently, 8.45 g of silica sol (silica concentration: 40 wt%, manufactured by Shanghai Sigma-Aldrich Co., Ltd.), 9 g of crown ether complex A solution, and 10 g of deionized water were added sequentially to form a mixed gel. After the gel was thoroughly stirred, the polytetrafluoroethylene bottle was sealed and transferred to a stainless steel autoclave, which was then placed in a rotary oven at 140°C for 6 days for synthesis. After removal, the solid was filtered, washed with water, and then dried overnight in a 100°C rotary oven. The final powder sample was named RHO seed crystals.

[0121] Dissolve 3.2 g of sodium metaaluminate (alumina content: 45 wt%, sodium oxide content: 38 wt%, Tianjin Fushen Chemical Reagent Co., Ltd.) in 89 g of water, add 21.9 g of powdered silica gel (silica content: 85 mass%, particle size: 50-300 μm, Qingdao Kangye Xin), then add 45.0 g of crown ether complex A solution and 0.8 g of RHO seed crystals, and stir to obtain an aqueous gel. After stirring and aging at room temperature (25°C) for 12 hours, the aqueous gel is placed in a temperature-resistant and pressure-resistant container, and hydrothermal synthesis is performed at 140°C for 96 hours. The reaction solution is cooled, and the obtained powder is recovered by filtration and dried at 100°C overnight to obtain a zeolite A1 containing a template agent. The XRD measurement result of the zeolite A1 is shown in FIG. 1, and the zeolite is an RHO-type zeolite. The molar ratio of SiO2 to Al2O3 of the zeolite is 16.3 as measured by ICP. The zeolite A1 is calcined at 560°C in air for 6 hours to remove the organic template agent, and a zeolite A2 is obtained.

[0122] Dissolve 5.4 g of ammonium chloride (Tianjin Fushen Chemical Reagent Co., Ltd.) in 100 g of water, then add 10 g of the zeolite A2 to form a slurry, and perform ion exchange at 80°C for 2 hours. The reaction solution is cooled, and the obtained powder is recovered by filtration and dried at 100°C for 2 hours. After repeating the above steps for ion exchange for 5 times, the obtained powder is calcined at 550°C in air for 6 hours to obtain a zeolite A.

[0123] Dissolve 0.0675 g of ammonium tetrachloropalladate (palladium content: 36.7 wt%, Shaanxi Ruikexin New Material Co., Ltd.) in 4.5 g of deionized water, and add the ammonium tetrachloropalladate solution to 5 g of the zeolite A by the method of equal volume impregnation. After drying at 100°C, the sample is calcined at 550°C in air for 4 hours to obtain a sorbent PNA1A. The NO in-situ adsorption infrared analysis of the sorbent PNA1A is shown in FIG. 4, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 is 1.03. The nitrogen oxide adsorption performance of PNA1A is shown in Table 3.

[0124] The NO in-situ adsorption infrared analysis of the aged sample of PNA1A is shown in FIG. 5, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 is 1.37. The nitrogen oxide adsorption performance of the aged sample of PNA1A is shown in Table 3.

[0125] Example 2

[0126] A preparation procedure of a palladium-containing RHO zeolite nitrogen oxide sorbent (1.0% wt of a palladium-containing RHO zeolite) is as follows:

[0127] PNA1B was prepared by impregnating 5 g of zeolite A with 0.135 g of ammonium tetrachloropalladate (palladium content: 36.7 wt%, Shaanxi Ruikexin New Material Co., Ltd.) dissolved in 4.5 g of deionized water. After drying at 100 °C, the sample was calcined in air at 550 °C for 4 hours. The NO in-situ adsorption FTIR analysis of the adsorbent PNA1B is shown in Figure 6, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 was 1.27. The Pd loading of PNA1B was 1.0%. The nitrogen oxide adsorption performance of PNA1B is shown in Table 3 and Figure 18.

[0128] The NO in-situ adsorption FTIR analysis of the aged sample of PNA1B is shown in Figure 7, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 was 0.95. The nitrogen oxide adsorption performance of the aged sample of PNA1B is shown in Table 3 and Figure 19.

[0129] Example 3

[0130] A preparation procedure of a palladium-containing RHO zeolite nitrogen oxide adsorbent (2.0% wt of palladium-containing RHO zeolite) is as follows:

[0131] PNA1C was prepared by impregnating 5 g of zeolite A with 0.27 g of ammonium tetrachloropalladate (palladium content: 36.7 wt%, Shaanxi Ruikexin New Material Co., Ltd.) dissolved in 4.5 g of deionized water. After drying at 100 °C, the sample was calcined in air at 550 °C for 4 hours. The NO in-situ adsorption FTIR analysis of the adsorbent PNA1C is shown in Figure 8, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 was 1.13. The Pd loading of PNA1C was 2.0%. The nitrogen oxide adsorption performance of PNA1C is shown in Table 3.

[0132] The NO in-situ adsorption FTIR analysis of the aged sample of PNA1C is shown in Figure 9, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 was 1.18. The nitrogen oxide adsorption performance of the aged sample of PNA1C is shown in Table 3.

[0133] Comparative Example 1

[0134] PNA2A: 1% wt Pd-containing CHA zeolite

[0135] Ammonium tetrachloropalladate (Pd content: 36.7 wt%, Shanxi Ruikexin New Material Co., Ltd.) was dissolved in 4.6 g of deionized water, and the ammonium tetrachloropalladate solution was added to 5 g of CHA zeolite (molar ratio of SiO2 to Al2O3 was 16.0, made by Zhuo Ran Environmental Protection Technology Co., Ltd.) by the method of equal volume impregnation. After drying at 100°C, the sample was calcined in air at 550°C for 4 hours to obtain the adsorbent PNA2A. The NO in-situ adsorption infrared analysis of the adsorbent PNA2A is shown in FIG. 10, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 was 0.60. The Pd loading of PNA2A was 1.0%. The nitrogen oxide adsorption performance of PNA2A is shown in Table 3 and FIG. 18.

[0136] The NO in-situ adsorption infrared analysis of the aged sample of PNA2A is shown in FIG. 11, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 was 0.77. The nitrogen oxide adsorption performance of the aged sample of PNA2A is shown in Table 3 and FIG. 19.

[0137] Comparative Example 2

[0138] PNA2B: 2% wt Pd-containing CHA zeolite

[0139] Ammonium tetrachloropalladate (Pd content: 36.7 wt%, Shanxi Ruikexin New Material Co., Ltd.) was dissolved in 4.6 g of deionized water, and the ammonium tetrachloropalladate solution was added to 5 g of CHA zeolite (molar ratio of SiO2 to Al2O3 was 16.0, made by Zhuo Ran Environmental Protection Technology Co., Ltd.) by the method of equal volume impregnation. After drying at 100°C, the sample was calcined in air at 550°C for 4 hours to obtain the adsorbent PNA2B. The NO in-situ adsorption infrared analysis of the adsorbent PNA2B is shown in FIG. 12, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 was 0.80. The Pd loading of PNA2B was 2.0%. The nitrogen oxide adsorption performance of PNA2B is shown in Table 3.

[0140] The NO in-situ adsorption infrared analysis of the aged sample of PNA2B is shown in FIG. 13, and the ratio of the infrared absorption peak intensity at 1840-1900 cm-1 the ratio of the infrared absorption peak intensity at 1780-1840 cm -1 -1 was 0.78. The nitrogen oxide adsorption performance of the PNA2B aging sample is shown in Table 3.

[0141] Comparative Example 3

[0142] PNA3A: 1% wt. palladium-containing AEI zeolite

[0143] 0.135 g of ammonium tetrachloropalladate (palladium content: 36.7 wt.%, Shaanxi Ruikexin New Material Co., Ltd.) was dissolved in 4.0 g of deionized water, and the ammonium tetrachloropalladate solution was added to 5 g of AEI zeolite (molar ratio of SiO2 to Al2O3 was 16.7, made by Zhuo Ran Environmental Protection Technology Co., Ltd.) by equal volume impregnation method. After drying at 100°C, the sample was calcined in air at 550°C for 4 hours to obtain the adsorbent PNA3A. The NO in-situ adsorption infrared analysis of the adsorbent PNA3A is shown in FIG. 14, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 -1 to that at 1780-1840 cm -1 -1 was 0.51. The Pd loading of PNA3A was 1.0%. The nitrogen oxide adsorption performance of PNA3A is shown in Table 3 and FIG. 16.

[0144] The NO in-situ adsorption infrared analysis of the PNA3A aging sample is shown in FIG. 15, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 -1 to that at 1780-1840 cm -1 -1 was 0.68. The nitrogen oxide adsorption performance of the PNA3A aging sample is shown in Table 3 and FIG. 19.

[0145] Comparative Example 4

[0146] PNA3B: 2% wt. palladium-containing AEI zeolite

[0147] 0.135 g of ammonium tetrachloropalladate (palladium content: 36.7 wt.%, Shaanxi Ruikexin New Material Co., Ltd.) was dissolved in 4.0 g of deionized water, and the ammonium tetrachloropalladate solution was added to 5 g of AEI zeolite (molar ratio of SiO2 to Al2O3 was 16.7, made by Zhuo Ran Environmental Protection Technology Co., Ltd.) by equal volume impregnation method. After drying at 100°C, the sample was calcined in air at 550°C for 4 hours to obtain the adsorbent PNA3A. The NO in-situ adsorption infrared analysis of the adsorbent PNA3A is shown in FIG. 14, and the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 -1 to that at 1780-1840 cm -1The ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to that at 1780-1840 cm-1 of the PNA3A sample was 0.87. The Pd loading of the PNA3A was 2.0%. The nitrogen oxide adsorption performance of the PNA3B sample is shown in Table 3.

[0148] The NO in-situ adsorption infrared analysis of the PNA3B aging sample is shown in Figure 17, and the ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to that at 1780-1840 cm-1 was 0.63. The nitrogen oxide adsorption performance of the PNA3B aging sample is shown in Table 3. -1 The ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to that at 1780-1840 cm-1 of the PNA3A sample was 0.87. The Pd loading of the PNA3A was 2.0%. The nitrogen oxide adsorption performance of the PNA3B sample is shown in Table 3. -1 The ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to that at 1780-1840 cm-1 of the PNA3A sample was 0.87. The Pd loading of the PNA3A was 2.0%. The nitrogen oxide adsorption performance of the PNA3B sample is shown in Table 3.

[0149] Comparative Example 5

[0150] The RHO zeolite was prepared by the same method as in Example 1, except that the powdered silica gel was replaced by silica sol (silica concentration: 40% by mass, Shanghai Sigma-Aldrich Co., Ltd.). The XRD measurement results of the synthesized zeolite are shown in Figure 2.

[0151] Comparative Example 6

[0152] The RHO zeolite was prepared by the same method as in Example 1, except that the powdered silica gel was replaced by fumed silica (Shanghai Simen Chemical Co., Ltd.). The XRD measurement results of the synthesized zeolite are shown in Figure 3.

[0153] Table 3 Adsorption performance data

[0154] (h1 / h2) in the table is the ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to that at 1780-1840 cm-1 in the NO in-situ adsorption infrared spectrum of the sample. -1 (h1 / h2) in the table is the ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to that at 1780-1840 cm-1 in the NO in-situ adsorption infrared spectrum of the sample. -1 (h1 / h2) in the table is the ratio of the infrared absorption peak intensity at 1840-1900 cm-1 to that at 1780-1840 cm-1 in the NO in-situ adsorption infrared spectrum of the sample.

[0155] From the experimental data of Example 1 and Comparative Example 5, it can be seen that if the silicon source is replaced by silica sol, the crystallinity of the synthesized RHO zeolite is significantly lower, because the particle size of the silica sol is at the nanometer level, and it is easy to completely dissolve into sodium silicate during the synthesis process, affecting the growth of the crystal.

[0156] From the experimental data of Example 1 and Comparative Example 6, it can be seen that if the silicon source is replaced by fumed silica, the synthesized RHO zeolite will have a significant MOR impurity phase, because the fumed silica is a small particle of solid flocculation, and has very strong water absorption. After being added, the gel basically has no flowability, seriously affecting the mass transfer and heat transfer speed in the synthesis process, leading to local unevenness and the generation of impurities.

[0157] The results in Table 3 show that the in-situ adsorption infrared spectrum of the palladium-containing RHO zeolite nitrogen oxide adsorbent prepared by the preparation method of the present application in Examples 1-3 shows a strong infrared absorption peak at 1840-1900 cm -1 The results in Table 3 show that the in-situ adsorption infrared spectrum of the palladium-containing RHO zeolite nitrogen oxide adsorbent prepared by the preparation method of the present application in Examples 1-3 shows a strong infrared absorption peak at 1840-1900 cm

[0158] In addition, it can be seen from the experimental data of Comparative Examples 1-4 and Examples 1-3 that the palladium-containing RHO zeolite nitrogen oxide adsorbent of the present application is far superior to the palladium-containing CHA zeolite and the palladium-containing AEI zeolite synthesized by the prior art in terms of hydrothermal stability, low-temperature NOx adsorption capacity and adsorption efficiency of the loaded Pd.

[0159] The technical features of the above-described examples can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above-described examples are not listed, but as long as the combinations of the technical features do not contradict each other, they should be considered as falling within the scope of the present disclosure.

[0160] For those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of the present application. The scope of protection of the present application is subject to the appended claims.

Claims

1. A palladium-containing RHO zeolite nitric oxide adsorbent, characterized in that, When the adsorbent is subjected to in-situ adsorption infrared analysis, the ratio of the infrared absorption peak intensity at 1840-1900 cm -1 to the infrared absorption peak intensity at 1780-1840 cm -1 is greater than 0.

9.

2. The palladium-containing RHO zeolite nitric oxide adsorbent of claim 1, wherein, The adsorbent comprises at least silicon, aluminum and oxygen as framework atoms, wherein the molar ratio of silicon atoms to aluminum atoms is (2-50):

1.

3. The palladium-containing RHO zeolite nitric oxide adsorbent of claim 1, wherein, The palladium in the adsorbent accounts for 0.1-5.0% of the mass of the RHO-type zeolite.

4. The palladium-containing RHO zeolite nitric oxide adsorbent of claim 1, wherein, The adsorbent further comprises one or more other elements selected from alkali metals, alkaline earth metals, rare earth metals and transition metals.

5. A method of preparing a palladium-containing RHO zeolite nitric oxide adsorbent according to any one of claims 1 to 4, characterized in that, The preparation method is: S1, mixing a mixture comprising at least a silicon source, an aluminum source, an organic template agent and an inorganic base in water to obtain a primary gel; S2, after the primary gel is subjected to aging and hydrothermal synthesis reaction, a reaction product is obtained; S3, the RHO-type zeolite obtained by removing the organic template agent from the reaction product; S4, ion exchange of the RHO-type zeolite with an ammonium salt and re-calcination treatment; S5, after the powder after the calcination treatment is uniformly mixed with a solution containing palladium elements, water is removed, and re-calcination is performed to obtain a palladium-containing RHO zeolite nitrogen oxide adsorbent.

6. The method of claim 5, wherein the palladium-containing RHO zeolite nitride oxide adsorbent is prepared by the steps of: The silicon source is at least one of powdered silica gel, fumed silica, white carbon black, sodium silicate, silica sol, trimethylethoxysilane and tetraethyl orthosilicate.

7. The method of claim 5, wherein the palladium-containing RHO zeolite nitride oxide adsorbent is prepared by the steps of: The aluminum source is at least one of sodium metaaluminate, aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum oxide, aluminum hydroxide, boehmite, aluminum chloride, aluminum silicate salt gel and metallic aluminum. The organic template agent is 18-crown-6 ether. The inorganic base is an alkali metal hydroxide.

8. The method of claim 5-7, wherein the method is characterized by, The silicon source is powdered silica gel, and the particle size of the powdered silica gel is 50-300 μm.

9. The method of claim 5, wherein the palladium-containing RHO zeolite nitride oxide adsorbent is prepared by the steps of: The solution containing palladium elements is at least one of palladium nitrate solution, palladium dichloride solution, dichlorotetraammine palladium solution, palladium sulfate solution and ammonium tetrachloropalladate solution.

10. A gas purification apparatus wherein, The purification device is provided with the palladium-containing RHO zeolite nitrogen oxide adsorbent according to any one of claims 1-4 or prepared by the method according to any one of claims 5-9.

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