Cu-re-aei catalyst, and preparation method and use thereof

Abstract

This invention relates to a Cu-Re-AEI catalyst, its preparation method, and its uses. The Cu-Re-AEI catalyst comprises an AEI molecular sieve support doped with Re (rare earth element) and Cu supported on the molecular sieve support. Based on a total mass of 100 wt% of the Cu-Re-AEI catalyst, the mass fraction of Re is 1.0 wt%–4.0 wt%, and the mass fraction of Cu is 1.5 wt%–4.5 wt%. The Cu occupies the aluminum pairs of the six-membered rings of the AEI molecular sieve, forming aluminum-copper pairs, while the rare earth elements occupy the isolated aluminum elements of the AEI molecular sieve. Compared to the Cu-AEI catalyst without rare earth element doping, the all-aluminum-copper Cu-Re-AEI catalyst prepared by this invention exhibits significantly improved hydrothermal stability, retaining excellent catalytic activity even after hydrothermal aging at 940℃ for 3 hours.

Description

Technical Field

[0001] This invention relates to the field of catalytic reduction technology of NH3, and more particularly to a Cu-Re-AEI catalyst, its preparation method and uses. Background Technology

[0002] In recent years, with the increase in transport vehicles, nitrogen oxide emissions have become increasingly serious, and related regulations have become more stringent. The selective catalytic reduction of NO3 by NH3... x It is currently widely used in the NO emission control of diesel vehicle exhaust. x Purification. Since the particulate filter upstream of the SCR catalyst requires periodic regeneration, exposing the SCR catalyst to a high-temperature and high-humidity environment, the hydrothermal stability of the SCR catalyst is crucial. Cu-AEI has attracted widespread attention due to its good hydrothermal stability. Hydrothermal aging leading to catalyst deactivation is mainly attributed to two reasons: the formation of copper oxide clusters and dealumination.

[0003] Cu-AEI molecular sieves exist in two forms of copper species: aluminum-copper (ACO) and monoaluminate-copper (PAC). ACO is more stable and does not easily transform into copper oxide during hydrothermal aging. Therefore, preparing all-aluminate-copper Cu-AEI can improve the hydrothermal stability of the catalyst. High-silica molecular sieves are less prone to dealuminization, but the synthesis of high-silica AEI still presents significant challenges.

[0004] Excess aluminum in aluminum-rich AEIs can easily lead to structural damage of molecular sieves and the formation of copper oxide clusters during hydrothermal aging. Therefore, it is urgent to develop a method to stabilize excess aluminum in aluminum-rich AEIs in order to improve their hydrothermal stability. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a Cu-Re-AEI catalyst, its preparation method, and its applications. The Cu-Re-AEI catalyst of the present invention loads copper onto aluminum-rich AEI doped with rare earth elements. Compared with the Cu-AEI catalyst without rare earth elements, the prepared all-aluminum-copper Cu-Re-AEI catalyst exhibits significantly improved hydrothermal stability and still possesses excellent catalytic activity after hydrothermal aging at 940℃ for 3 hours.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a Cu-Re-AEI catalyst, the Cu-Re-AEI catalyst comprising a Re-doped AEI molecular sieve support and Cu supported on the molecular sieve support; wherein the Re is a rare earth element; based on a total mass of 100 wt% of the Cu-Re-AEI catalyst, the mass fraction of the Re is 1.0 wt%-4.0 wt%, and the mass fraction of the Cu is 1.5 wt%-4.5 wt%; wherein the Cu occupies the aluminum pairs of the six-membered rings of the AEI molecular sieve to form aluminum-copper pairs, and the rare earth element occupies the isolated aluminum of the AEI molecular sieve.

[0008] Based on a total mass of 100 wt% for the Cu-Re-AEI catalyst, the mass fraction of Re is 1.0 wt% to 4.0 wt%, for example, it can be 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3.0 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt%, or 4.0 wt%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. Re is a rare earth element.

[0009] Based on a total mass of 100 wt% for the Cu-Re-AEI catalyst, the mass fraction of Cu is 1.5 wt% to 4.5 wt%, for example, it can be 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3.0 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt%, 4.0 wt%, 4.1 wt%, 4.2 wt%, 4.3 wt%, 4.4 wt%, or 4.5 wt%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0010] The Cu occupies the aluminum pair of the six-membered ring of the AEI molecular sieve to form an aluminum-copper pair, while rare earth elements occupy the isolated aluminum of the AEI molecular sieve.

[0011] "Aluminum-copper" refers to the coordination of divalent copper ions with two aluminum atoms in the six-membered ring of the molecular sieve framework.

[0012] "Lone aluminum copper" refers to the coordination of a divalent copper ion with an aluminum atom in the molecular sieve framework.

[0013] In this invention, by doping the AEI molecular sieve with rare earth element Re, the framework aluminum in AEI can be stabilized. The rare earth element Re occupies the isolated aluminum, and Cu atoms occupy the six-membered ring aluminum pairs. Since aluminum has high hydrothermal stability against copper, and the doping of rare earth elements protects the excess aluminum in the molecular sieve during hydrothermal aging, a Cu-AEI molecular sieve with good hydrothermal stability is obtained. This ensures that the aluminum in the AEI molecular sieve maintains structural stability during hydrothermal aging and also prevents the formation of copper oxide clusters, greatly improving the hydrothermal stability of the catalyst. It still has excellent catalytic activity after hydrothermal aging at 940℃ for 3 hours. In contrast, the excessive discrete aluminum atoms in conventional AEI molecular sieves without rare earth element doping lead to very poor catalyst stability during use.

[0014] The amount of Re doping in the Cu-Re-AEI catalyst of this invention affects the low-temperature and high-temperature activities of the catalyst after hydrothermal aging. Increasing the amount of Re doping improves the hydrothermal stability of the catalyst, but when its content reaches a certain value, the hydrothermal stability decreases. The mass fraction of Cu affects the fresh activity of the catalyst (fresh activity refers to the activity of the catalyst before hydrothermal aging). If the Cu content is too high, it will reduce the high-temperature activity of the catalyst; if the Cu content is too low, it will reduce the low-temperature activity of the catalyst. Therefore, the doped Re content and the supported Cu content need to be within a reasonable range, and the two need to work together to achieve the best overall combination of low-temperature, high-temperature and hydrothermal aging catalyst activities.

[0015] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0016] Preferably, based on a total mass of 100 wt% for the Cu-Re-AEI catalyst, the mass fraction of Re is 1.6 wt%-3.0 wt%, and the mass fraction of Cu is 1.5 wt%-4.0 wt%.

[0017] In this invention, the mass fraction of Re is further controlled to be 1.6wt%-3.0wt% and the mass fraction of Cu is 1.5wt%-4.0wt%. At this point, the catalyst exhibits superior high-temperature and low-temperature catalytic activity and better hydrothermal stability.

[0018] In a second aspect, the present invention provides a method for preparing the Cu-Re-AEI catalyst as described in the first aspect, the method comprising the following steps:

[0019] Rare earth element salt solution is dropped onto H-AEI molecular sieve, and after first grinding, first drying and first calcination, Re-doped Re-AEI is obtained. Copper source solution is dropped onto Re-doped Re-AEI, and after second grinding, second drying and second calcination, Cu-Re-AEI catalyst is obtained.

[0020] This invention uses a modified initial wet impregnation method to dope rare earth elements and load copper onto H-AEI. This method can precisely control the content and position of Cu. Conventional ion exchange methods cannot precisely control the amount of copper loaded, which may result in too little or too much loading, thus failing to maximize the performance of the catalyst.

[0021] Conventional methods of loading copper typically involve directly adding the catalyst support to the copper source solution. In this case, the copper source solution is in excess, often resulting in a residue after ion exchange. Furthermore, subsequent operations such as filtration are required to separate the molecular sieve from the solution, making the process cumbersome, unpredictable, and wasteful of raw materials. This invention employs a pre-wet impregnation method, where rare earth element salt solutions and copper source solutions are dropwise added to the molecular sieve separately. First, rare earth elements achieve uniform Re doping through ion exchange, followed by Cu loading. This method not only ensures full utilization of the added rare earth element salts or copper source without waste but also eliminates the need for subsequent filtration, significantly simplifying the process and saving costs and time. The resulting fresh Cu-Re-AEI catalyst is obtained through calcination, and after hydrothermal aging, the treated Cu-Re-AEI catalyst is obtained.

[0022] The H-AEI molecular sieve of the present invention is prepared by the following method:

[0023] The sample was prepared by Y-type molecular sieve transformation using N,N-dimethyl-3,5-dimethylpiperidine as a template agent. The synthetic steps were as follows: First, 4g of the template agent (25% N,N-dimethyl-3,5-dimethylpiperidine aqueous solution, anion OH-) was weighed out. -Kent Catalytic Materials Co., Ltd. dissolved 26g of the precursor in water, then added 3g of Y-type molecular sieve (Si / Al = 18.9), stirred for 3h, and then added 0.69g of NaOH, stirred for 2h. The homogeneous precursor solution was placed in a 100mL hydrothermal reactor and crystallized at 140℃ for 72h. After crystallization, it was filtered, washed with water until neutral, dried in an oven at 100℃ for 12h, and finally calcined in a muffle furnace at 600℃ for 6h at a heating rate of 1℃ / min to obtain Na-AEI molecular sieve. The Na-AEI molecular sieve support was ion-exchanged with ammonium nitrate solution (0.1mol / L) at 80℃ for 5h, then filtered and dried. After repeating the above steps, NH4-AEI was obtained. Finally, it was calcined in a muffle furnace at 600℃ for 6h at a heating rate of 1℃ / min to obtain H-AEI molecular sieve.

[0024] Preferably, the rare earth element salt in the rare earth element salt solution includes any one or a combination of at least two of nitrates, sulfates, and chlorides. Typical but non-limiting combinations include combinations of nitrates and sulfates, with nitrates being the most preferred.

[0025] The concentration of the rare earth element salt solution selected in this invention is related to the required percentage of rare earth element salt content and the saturated water absorption capacity of the H-AEI molecular sieve (i.e., the maximum water absorption capacity of the H-AEI molecular sieve when it is fully absorbed). The concentration is controlled to ensure that all the water in the rare earth element salt solution can wet the H-AEI molecular sieve, thereby guaranteeing that the rare earth elements in the solution are fully and uniformly distributed within the H-AEI molecular sieve.

[0026] Preferably, the mass ratio of rare earth elements in the rare earth element salt solution to H-AEI molecular sieve is (0.1-5):100, for example, it can be 0.1:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100 or 5:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the first grinding time is 0.25h-1h, for example, it can be 0.25h, 0.5h, 0.75h or 1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] In this invention, after the rare earth element salt solution is dropped onto the H-AEI molecular sieve, it is ground to ensure that the rare earth element salt is evenly distributed in the AEI molecular sieve, thereby making the doping more uniform.

[0029] Preferably, the temperature of the first drying is 50℃-80℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] Preferably, the first drying time is 8h-12h, for example, it can be 8h, 9h, 10h, 11h or 12h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the temperature of the first roasting is 400℃-700℃, for example, it can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃ or 700℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] The preferred temperature for the first calcination in this invention is 400℃-700℃. Re-AEI doped with rare earth elements is obtained through the first calcination. If the temperature of the first calcination is too high, the molecular sieve will undergo dealuminization and its structure will be destroyed; if the temperature of the first calcination is too low, the rare earth element salt cannot be decomposed.

[0033] Preferably, the first roasting time is 6h-10h, for example, it can be 6h, 7h, 8h, 9h or 10h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the copper source solution includes any one or a combination of at least two of copper nitrate solution, copper sulfate solution, copper chloride solution, or copper acetate solution. Typical but non-limiting combinations include combinations of copper nitrate solution and copper sulfate solution, combinations of copper sulfate solution and copper chloride solution, combinations of copper chloride solution and copper acetate solution, combinations of copper nitrate solution, copper sulfate solution and copper chloride solution, combinations of copper sulfate solution, copper chloride solution and copper acetate solution, and combinations of copper nitrate solution, copper sulfate solution, copper chloride solution and copper acetate solution. Copper nitrate solution is preferred.

[0035] The concentration of the copper source solution selected in this invention is related to the required percentage of copper source content and the saturated water absorption capacity of the Re-AEI molecular sieve (i.e., the maximum water absorption capacity of the Re-AEI molecular sieve when it is fully absorbed). The concentration is controlled to ensure that all the water in the copper source solution can wet the Re-AEI molecular sieve, thereby guaranteeing that the copper element in the copper source solution is completely and uniformly distributed within the Re-AEI molecular sieve.

[0036] Preferably, the mass ratio of copper to Re-AEI doped with Re in the copper source solution is (0.1-5):100, for example, it can be 0.1:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100 or 5:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the second grinding time is 0.25h-1h, for example, it can be 0.25h, 0.5h, 0.75h or 1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] In this invention, after the copper source solution is dropped onto the Re-AEI molecular sieve, the copper source is uniformly loaded onto the Re-AEI molecular sieve by grinding.

[0039] Preferably, the temperature of the second drying is 50℃-80℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0040] Preferably, the second drying time is 8h-12h, for example, it can be 8h, 9h, 10h, 11h or 12h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the second calcination temperature is 750℃-950℃, for example, it can be 750℃, 800℃, 850℃, 900℃ or 950℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0042] Preferably, the second calcination time is 6h-10h, for example, it can be 6h, 7h, 8h, 9h or 10h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0044] A rare earth element salt solution was dropped onto H-AEI molecular sieve, with the mass ratio of rare earth elements to H-AEI molecular sieve in the rare earth element salt solution being (0.1-5):100. The mixture was first ground in a mortar for 0.25-1 h, then dried for 8-12 h at 50-80℃, and finally calcined in a muffle furnace at 400-700℃ for 6-10 h to obtain Re-doped Re-AEI.

[0045] A copper nitrate solution was dropped onto Re-AEI doped with Re, wherein the mass ratio of copper in the copper nitrate solution to Re-AEI doped with Re was (0.1-5):100. The mixture was then ground in a mortar for 0.25-1 hour, dried at 50-80°C for 8-12 hours, and calcined in a muffle furnace at 750-950°C for 6-10 hours to obtain the Cu-Re-AEI catalyst.

[0046] Thirdly, the present invention provides the use of the Cu-Re-AEI catalyst as described in the first aspect, wherein the Cu-Re-AEI catalyst is used in the NH3-SCR reaction.

[0047] The Cu-Re-AEI catalyst prepared by this invention exhibits excellent hydrothermal stability in the NH3-SCR reaction. Even after high-temperature hydrothermal aging at 940℃, it still maintains excellent catalytic activity, and its environmental adaptability is greatly improved.

[0048] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] (1) This invention stabilizes the aluminum framework of the molecular sieve by doping rare earth elements into aluminum-rich AEI. The rare earth element Re occupies the isolated aluminum of the AEI molecular sieve, and Cu atoms occupy the aluminum pairs of the AEI molecular sieve to form aluminum-copper pairs. This makes the molecular sieve structurally stable during hydrothermal aging, prevents the formation of copper oxide clusters, and greatly improves the hydrothermal stability of the catalyst. The Cu-Re-AEI catalyst with all aluminum-copper pairs prepared still has excellent catalytic activity after hydrothermal aging at 940℃ for 3 hours.

[0051] (2) The present invention adopts the initial wet impregnation method, in which rare earth element salt solution and copper source solution are dropped onto molecular sieve respectively. This method can precisely control the content and position of Cu, achieve uniform doping of rare earth elements and loading of Cu. This preparation method can precisely control the content of rare earth elements and copper content, so that all copper species exist in the form of aluminum-copper, thereby improving the hydrothermal stability of the catalyst. The preparation process is simple to operate, low in cost and easy to implement. Attached Figure Description

[0052] Figure 1 The NO content before and after hydrothermal aging treatment of the catalysts prepared in Example 1 and Comparative Example 1 of this invention is shown. x Conversion rate chart;

[0053] Figure 2These are the XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1 of this invention before and after hydrothermal aging treatment;

[0054] Figure 3 These are H2-TPR diagrams of the catalysts prepared in Example 1 and Comparative Example 1 of this invention before and after hydrothermal aging treatment.

[0055] Figure 4 These are the NH3-DRIFTS spectra of the catalysts prepared in Example 1 and Comparative Example 1 of this invention before and after hydrothermal aging treatment.

[0056] Figure 5 The NO content before and after hydrothermal aging treatment of the catalysts prepared in Examples 1 and 2 of this invention is shown. x Conversion rate chart;

[0057] Figure 6 These are the XRD patterns of the catalysts prepared in Examples 1 and 2 of this invention before and after hydrothermal aging treatment;

[0058] Figure 7 The NO content before and after hydrothermal aging treatment of the catalysts prepared in Examples 1 and 3-4 of this invention is shown. x Conversion rate chart;

[0059] Figure 8 These are the XRD patterns of the catalysts prepared in Examples 1 and 3-4 of this invention before and after hydrothermal aging treatment;

[0060] Figure 9 The NO content of the catalysts prepared in Examples 5-19 of this invention before and after hydrothermal aging treatment is... x Conversion rate chart. Detailed Implementation

[0061] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0062] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used are conventional methods and techniques in the art.

[0063] The H-AEI molecular sieves used in the embodiments of this invention are all synthesized by a hydrothermal method. The specific preparation method includes the following steps:

[0064] The sample was prepared by Y-type molecular sieve transformation using N,N-dimethyl-3,5-dimethylpiperidine as a template agent. The synthetic steps were as follows: First, 4g of the template agent (25% N,N-dimethyl-3,5-dimethylpiperidine aqueous solution, anion OH-) was weighed out. - Kent Catalytic Materials Co., Ltd. dissolved 26g of the precursor in water, then added 3g of Y-type molecular sieve (Si / Al = 18.9), stirred for 3h, and then added 0.69g of NaOH, stirred for 2h. The homogeneous precursor solution was placed in a 100mL hydrothermal reactor and crystallized at 140℃ for 72h. After crystallization, it was filtered, washed with water until neutral, dried in an oven at 100℃ for 12h, and finally calcined in a muffle furnace at 600℃ for 6h at a heating rate of 1℃ / min to obtain Na-AEI molecular sieve. The Na-AEI molecular sieve support was ion-exchanged with ammonium nitrate solution (0.1mol / L) at 80℃ for 5h, then filtered and dried. After repeating the above steps, NH4-AEI was obtained. Finally, it was calcined in a muffle furnace at 600℃ for 6h at a heating rate of 1℃ / min to obtain H-AEI molecular sieve.

[0065] The rare earth element-doped Cu-Re-AEI catalysts prepared in the embodiments and comparative examples of this invention are named Cu(x)-Re(y)-AEI z, where x represents the copper content (wt%), y represents the rare earth element content (wt%), and z represents the catalyst state (fresh is denoted as F; for Examples 1-4 and Comparative Examples 1-2, aged at 940°C for 3 hours is denoted as A; for Examples 5-19, aged at 910°C for 12 hours is denoted as A). Correspondingly, the undoped catalyst is named Cu(x)-AEI z, and the catalyst doped only with Y and not loaded with copper is named Y(y)-AEI z.

[0066] Example 1

[0067] This embodiment provides a Cu-Y-AEI catalyst, which includes a Y-doped AEI molecular sieve support and Cu supported on the molecular sieve support; based on a total mass of 100 wt% for the Cu-Y-AEI catalyst, the mass fraction of Cu is 1.6 wt% and the mass fraction of Y is 2.0 wt%.

[0068] The preparation method of the Cu-Y-AEI catalyst provided in this embodiment includes the following steps:

[0069] H-AEI molecular sieve was weighed and placed in an agate mortar. A 0.71 mol / L yttrium nitrate solution with saturated water absorption was added dropwise and the mixture was ground thoroughly. After drying, it was calcined in a muffle furnace at 550℃ for 8 hours to obtain Y-AEI. Y-AEI was weighed and placed in an agate mortar. A 0.79 mol / L copper nitrate solution with saturated water absorption was added dropwise and the mixture was ground thoroughly. After drying, it was calcined in a muffle furnace at 850℃ for 8 hours to obtain Cu(1.6)-Y(2.0)-AEI F catalyst.

[0070] The obtained Cu(1.6)-Y(2.0)-AEI F catalyst was aged at 940℃ for 3 hours to obtain Cu(1.6)-Y(2.0)-AEI A catalyst.

[0071] The NO content of the prepared Cu(1.6)-Y(2.0)-AEI catalyst before and after hydrothermal aging treatment x Conversion rate graph as shown Figure 1 As shown. XRD pattern as follows. Figure 2 As shown in the figure, the framework structure of undoped Cu-AEI collapses after hydrothermal aging, while the framework structure of Y-doped Cu-AEI remains stable after hydrothermal aging.

[0072] The H2-TPR diagrams of the prepared catalyst before and after hydrothermal aging treatment are shown below. Figure 3 As shown in the figure, the undoped Cu-AEI exhibited a copper aluminate peak after hydrothermal aging, indicating severe dealuminization of the molecular sieve. The doped Cu-AEI, after hydrothermal aging, still maintained a peak with only aluminum and copper, without dealuminization.

[0073] The NH3-DRIFTS spectra of the prepared catalyst before and after hydrothermal aging treatment are shown in the figure below. Figure 4 As shown in the figure, the copper peak of the undoped Cu-AEI disappears after hydrothermal aging, indicating that the molecular sieve is severely deactivated. The Y-doped Cu-AEI can still maintain the aluminum peak for copper after hydrothermal aging, so its activity can be maintained.

[0074] Example 2

[0075] This embodiment provides a Cu-Y-AEI catalyst, which includes a Y-doped AEI molecular sieve support and Cu supported on the molecular sieve support; based on a total mass of 100 wt% for the Cu-Y-AEI catalyst, the mass fraction of Cu is 2.0 wt% and the mass fraction of Y is 2.0 wt%.

[0076] The preparation method of the Cu-Y-AEI catalyst provided in this embodiment includes the following steps:

[0077] H-AEI molecular sieve was weighed and placed in an agate mortar. A yttrium nitrate solution with a saturated water absorption concentration of 0.71 mol / L was added dropwise and the mixture was ground thoroughly. After drying, it was calcined in a muffle furnace at 550℃ for 8 hours to obtain Y-AEI. Y-AEI was weighed and placed in an agate mortar. A copper nitrate solution with a saturated water absorption concentration of 0.99 mol / L was added dropwise and the mixture was ground thoroughly. After drying, it was calcined in a muffle furnace at 850℃ for 8 hours to obtain Cu(2.0)-Y(2.0)-AEI F catalyst.

[0078] The obtained Cu(2.0)-Y(2.0)-AEI F catalyst was aged at 940℃ for 3 hours to obtain Cu(2.0)-Y(2.0)-AEI A catalyst.

[0079] NO content of the prepared Cu(2.0)-Y(2.0)-AEI catalyst before and after hydrothermal aging x Conversion rate graph as shown Figure 5 As shown, the XRD pattern is as follows Figure 6 As shown.

[0080] Example 3

[0081] This embodiment provides a Cu-Y-AEI catalyst, which includes a Y-doped AEI molecular sieve support and Cu supported on the molecular sieve support; based on a total mass of 100 wt% for the Cu-Y-AEI catalyst, the mass fraction of Cu is 1.6 wt% and the mass fraction of Y is 1.5 wt%.

[0082] The preparation method of the Cu-Y-AEI catalyst provided in this embodiment includes the following steps:

[0083] H-AEI molecular sieve was weighed and placed in an agate mortar. A 0.53 mol / L yttrium nitrate solution with saturated water absorption was added dropwise and the mixture was ground thoroughly. After drying, it was calcined in a muffle furnace at 550℃ for 8 hours to obtain Y-AEI. Y-AEI was weighed and placed in an agate mortar. A 0.79 mol / L copper nitrate solution with saturated water absorption was added dropwise and the mixture was ground thoroughly. After drying, it was calcined in a muffle furnace at 850℃ for 8 hours to obtain Cu(1.6)-Y(1.5)-AEI F catalyst.

[0084] The obtained Cu(1.6)-Y(1.5)-AEI F catalyst was aged at 940℃ for 3 hours to obtain Cu(1.6)-Y(1.5)-AEI A catalyst.

[0085] NO content of the prepared Cu(1.6)-Y(1.5)-AEI catalyst before and after hydrothermal aging x Conversion rate graph as shown Figure 7As shown, the XRD pattern is as follows Figure 8 As shown.

[0086] Example 4

[0087] This embodiment provides a Cu-Y-AEI catalyst, which includes a Y-doped AEI molecular sieve support and Cu supported on the molecular sieve support; based on a total mass of 100 wt% for the Cu-Y-AEI catalyst, the mass fraction of Cu is 1.6 wt% and the mass fraction of Y is 2.5 wt%.

[0088] The preparation method of the Cu-Y-AEI catalyst provided in this embodiment includes the following steps:

[0089] H-AEI molecular sieve was weighed and placed in an agate mortar. A 0.88 mol / L yttrium nitrate solution with saturated water absorption was added dropwise and the mixture was ground thoroughly. After drying, the mixture was calcined in a muffle furnace at 550℃ for 8 hours to obtain Y-AEI. Y-AEI was weighed and placed in an agate mortar. A 0.79 mol / L copper nitrate solution with saturated water absorption was added dropwise and the mixture was ground thoroughly. After drying, the mixture was calcined in a muffle furnace at 850℃ for 8 hours to obtain Cu(1.6)-Y(2.5)-AEI F catalyst.

[0090] The obtained Cu(1.6)-Y(2.5)-AEI F catalyst was aged at 940℃ for 3 hours to obtain Cu(1.6)-Y(2.5)-AEI A catalyst.

[0091] NO content of the prepared Cu(1.6)-Y(2.5)-AEI catalyst before and after hydrothermal aging x Conversion rate graph as shown Figure 7 As shown, the XRD pattern is as follows Figure 8 As shown.

[0092] Examples 5-17

[0093] This embodiment provides a Cu(1.6)-Re(2.0)-AEI F catalyst, which differs from Example 1 only in that yttrium nitrate is replaced with an equimolar amount of a single rare earth element nitrate. The rare earth elements contained in Examples 5-17 are, respectively: La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. All other operating steps remain unchanged.

[0094] The obtained catalyst was aged at 910℃ for 12 hours to obtain Cu(1.6)-Re(2.0)-AEI A.

[0095] Cu(1.6)-Re(2.0)-AEI A catalyst at 250℃ NOx Conversion rate Figure 9 As shown, from Figure 9 It is known that the catalysts doped with rare earth elements provided by the present invention have similar catalytic activities and all have excellent resistance to hydrothermal aging.

[0096] Comparative Example 1

[0097] This comparative example provides a Cu-AEI catalyst, which includes an AEI molecular sieve support and Cu supported on the molecular sieve support; based on a total mass of 100 wt% for the Cu-AEI catalyst, the mass fraction of Cu is 1.6 wt%.

[0098] The only difference from Example 1 is that, when preparing this catalyst, yttrium nitrate solution is not added dropwise, but only copper nitrate solution with saturated water absorption capacity is added dropwise. The other operation steps remain unchanged, and Cu(1.6)-AEI F is prepared.

[0099] The obtained Cu(1.6)-AEI F catalyst was aged at 940℃ for 3 hours to obtain Cu(1.6)-AEI A catalyst.

[0100] Comparative Example 2

[0101] This comparative example provides a Y-AEI catalyst, which includes an AEI molecular sieve support and Y supported on the molecular sieve support; based on a total mass of 100 wt% for the Y-AEI catalyst, the mass fraction of Y is 2.0 wt%.

[0102] The only difference from Example 1 is that, when preparing this catalyst, copper nitrate solution is not added dropwise, but only yttrium nitrate solution with saturated water absorption capacity is added dropwise. The other operation steps remain unchanged, and Y(2.0)-AEI F is prepared.

[0103] The obtained Y(2.0)-AEI F catalyst was aged at 940℃ for 3 hours to obtain Y(2.0)-AEI A catalyst.

[0104] Test method: Take a certain amount of the above catalyst, compress it into tablets, grind it, and sieve it. Take 40-60 mesh particles and test the NH3-SCR reaction activity in a fixed bed reactor.

[0105] The test conditions were: [NO] = [NH3] = 500 ppm, [O2] = 5%, [H2O] = 10%, N2 as the balance gas, total gas flow rate of 500 mL / min, and reaction space velocity of 100,000 h⁻¹. -1 The reaction temperature was 150–600℃. NO, NH3, and byproducts N2O and NO2 were all determined using an infrared gas analyzer (Antaris IGS).

[0106] Table 1

[0107]

[0108] The test results show that:

[0109] (1) As can be seen from Examples 1-4, the all-aluminum Cu-Re-AEI catalyst prepared by loading copper onto rare-earth element-doped aluminum-rich AEI exhibits significantly improved hydrothermal stability compared to the undoped Cu-AEI catalyst. It still demonstrates excellent catalytic activity after 3 hours of hydrothermal aging at 940℃. Examples 5-17 and... Figure 9 As can be seen, hydrothermally stable catalysts can also be prepared when other rare earth elements are doped.

[0110] (2) Combining Example 1 and Comparative Example 1 Figure 1 As can be seen, by doping rare earth elements into AEI, this invention can stabilize the framework aluminum in AEI, so that the molecular sieve can maintain structural stability during hydrothermal aging, prevent the formation of copper oxide clusters, and greatly improve the hydrothermal stability of the catalyst. It still has excellent catalytic activity after hydrothermal aging at 940℃ for 3 hours.

[0111] In summary, this invention employs a wet impregnation method to load copper onto aluminum-rich AEI doped with rare earth elements. The resulting all-aluminum-copper Cu-Re-AEI catalyst, compared to the undoped Cu-AEI catalyst, exhibits significantly improved hydrothermal stability through further control of the Re doping content and the loaded Cu content. Furthermore, it retains excellent catalytic activity even after 3 hours of hydrothermal aging at 940℃. The preparation method of this invention allows for precise control of the rare earth element and copper content, ensuring that all copper species exist in the form of aluminum-copper, thereby enhancing the catalyst's hydrothermal stability. The preparation process is simple, low-cost, and easy to implement.

[0112] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A Cu-Re-AEI catalyst, characterized in that, The Cu-Re-AEI catalyst comprises a Re-doped AEI molecular sieve support and Cu supported on the molecular sieve support; wherein Re is a rare earth element. Based on a total mass of 100 wt% for the Cu-Re-AEI catalyst, the mass fraction of Re is 1.0 wt%-4.0 wt%, and the mass fraction of Cu is 1.5 wt%-4.5 wt%. The Cu occupies the aluminum pair of the six-membered ring of the AEI molecular sieve to form an aluminum-copper pair, while rare earth elements occupy the isolated aluminum of the AEI molecular sieve.

2. The catalyst according to claim 1, characterized in that, Based on a total mass of 100 wt% for the Cu-Re-AEI catalyst, the mass fraction of Re is 1.6 wt%-3.0 wt%, and the mass fraction of Cu is 1.5 wt%-4.0 wt%.

3. A method for preparing the Cu-Re-AEI catalyst as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: Rare earth element salt solution is dropped onto H-AEI molecular sieve, and after first grinding, first drying and first calcination, Re-doped Re-AEI is obtained. Copper source solution is dropped onto Re-doped Re-AEI, and after second grinding, second drying and second calcination, Cu-Re-AEI catalyst is obtained.

4. The preparation method according to claim 3, characterized in that, The rare earth element salt in the rare earth element salt solution includes any one or a combination of at least two of nitrates, sulfates, and chlorides, preferably nitrates.

5. The preparation method according to claim 3 or 4, characterized in that, The mass ratio of rare earth elements in the rare earth element salt solution to H-AEI molecular sieve is (0.1-5):100; Preferably, the first grinding time is 0.25h-1h.

6. The preparation method according to any one of claims 3-5, characterized in that, The temperature for the first drying step is 50℃-80℃; Preferably, the first drying time is 8h-12h; Preferably, the temperature of the first calcination is 400℃-700℃; Preferably, the first roasting time is 6h-10h.

7. The preparation method according to any one of claims 3-6, characterized in that, The copper source solution includes any one or a combination of at least two of copper nitrate solution, copper sulfate solution, copper chloride solution, or copper acetate solution, preferably copper nitrate solution. Preferably, the mass ratio of copper to Re-AEI doped with Re in the copper source solution is (0.1-5):100; Preferably, the second grinding time is 0.25h-1h.

8. The preparation method according to any one of claims 3-6, characterized in that, The second drying temperature is 50℃-80℃; Preferably, the second drying time is 8h-12h; Preferably, the temperature of the second calcination is 750℃-950℃; Preferably, the second roasting time is 6h-10h.

9. The preparation method according to any one of claims 3-8, characterized in that, The preparation method includes the following steps: A rare earth element salt solution was dropped onto H-AEI molecular sieve, with the mass ratio of rare earth elements to H-AEI molecular sieve in the rare earth element salt solution being (0.1-5):

100. The mixture was first ground in a mortar for 0.25-1 h, then dried for 8-12 h at 50-80℃, and finally calcined in a muffle furnace at 400-700℃ for 6-10 h to obtain Re-doped Re-AEI. A copper nitrate solution was dropped onto Re-AEI doped with Re, wherein the mass ratio of copper in the copper nitrate solution to Re-AEI doped with Re was (0.1-5):

100. The mixture was then ground in a mortar for 0.25-1 hour, dried at 50-80°C for 8-12 hours, and calcined in a muffle furnace at 750-950°C for 6-10 hours to obtain the Cu-Re-AEI catalyst.

10. Use of the Cu-Re-AEI catalyst as described in claim 1 or 2, characterized in that, The Cu-Re-AEI catalyst is used for the NH3-SCR reaction.

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