Aluminous hierarchical porous molecular sieve, its preparation method and application

Abstract

This invention discloses an alumina-rich hierarchical porous molecular sieve, its preparation method, and its applications. The preparation method uses a silica-alumina molecular sieve with a framework containing dual six-membered ring structural units and a SiO2 / Al2O3 molar ratio greater than or equal to 5 as the parent molecular sieve. The sieve is treated with an alkaline solution at a temperature of 25°C to 85°C. The product after alkaline treatment is centrifuged, washed, and dried to obtain the alumina-rich hierarchical porous molecular sieve. Based on this, metal ion-encapsulated or exchange-type alumina-rich hierarchical porous molecular sieves can be prepared by introducing ammonia or amine complexes containing metal ions into situ for encapsulation during alkaline treatment, or by ion exchange of the obtained molecular sieve. The preparation method of this series of molecular sieves is simple, efficient, and mild, and the prepared molecular sieves possess the dual advantages of being alumina-rich and hierarchical porous, showing significant application prospects in gas adsorption, heterogeneous catalysis, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to an aluminum-rich multi-level porous molecular sieve, its preparation method, and its application. Background Technology

[0002] The microporous structure of aluminosilicate molecular sieves (zeolites) possesses unique shape selectivity at the molecular scale, enabling precise identification of reactants, intermediates, and products based on molecular size and configuration, thus exhibiting unique catalytic, adsorption, and separation properties. However, the inherent microporosity of traditional zeolites, with its narrow pores (typically < 1 nm), restricts diffusion, often limiting mass transfer efficiency and thus affecting their performance. Constructing hierarchical porous structures in zeolites is an important means to alleviate the inherent diffusion limitations of the microporous framework.

[0003] Currently, the synthesis strategies for hierarchical porous zeolites can be broadly categorized into two types: (i) bottom-up methods, including controlled crystallization and the introduction of large-size organic templates (such as surfactants) or hard templates (such as carbon nanoparticles) during crystallization; and (ii) top-down post-modification methods, such as dealumination or desilication via steam, acid, or alkali treatment. Among these methods, post-processing approaches offer advantages in terms of ease of industrial-scale operation and low cost, and have been successfully applied in fluidized catalytic cracking (FCC) processes. However, existing post-processing methods still have significant limitations:

[0004] (1) The method of removing aluminum by steam or acid treatment is usually used for aluminum-rich zeolites (such as FAU type) to generate mesopores by selectively removing skeletal aluminum. However, the channels generated are often isolated from each other and have poor connectivity, which cannot effectively improve diffusion performance.

[0005] (2) Alkali treatment for desilication, which selectively dissolves Si–O–Si bonds in an alkaline medium, provides a more universal approach for most zeolites. However, its effectiveness is strongly limited by the Si / Al ratio of the zeolite framework. For alumina-rich zeolites with low Si / Al ratios (SiO2 / Al2O3 < 10), [OH-] - Leaching of silicon is hindered by the electrostatic shielding effect of high-density aluminum; and for silica-rich zeolites with a high silicon-to-aluminum ratio (SiO2 / Al2O3 > 20), there is a risk of structural collapse. Therefore, this method is generally only effective for zeolites with a medium silicon-to-aluminum ratio (taking ZSM-5 as an example, SiO2 / Al2O3 is 10-20).

[0006] (3) To overcome the limitations of the above single method, a two-step strategy of first removing aluminum and then removing silicon is often required for mordenite (MOR) and X / Y type alumina-rich zeolites. Although this strategy partially solves the problem, it leads to more complex process flow, longer production cycle, increased cost and reduced controllability.

[0007] Aluminum-rich molecular sieves have important applications in CO2 / NO adsorption, ion exchange, and catalysis. Preparing aluminum-rich hierarchical porous molecular sieves will significantly improve their performance and application range. However, as mentioned above, existing post-processing methods for zeolite dealuminization and desiliconization are all affected by the density of the framework aluminum. Apart from directly synthesizing nano-aluminum-rich molecular sieves via bottom-up methods, there is currently no simple and efficient method for preparing aluminum-rich hierarchical porous molecular sieves through post-processing. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide an alumina-rich hierarchical porous molecular sieve, its preparation method, and its application, to overcome the limitations of traditional preparation methods in obtaining molecular sieves that possess both alumina richness and a hierarchical porous structure. Furthermore, based on this, a method for efficiently preparing metal ion-encapsulated alumina-rich hierarchical porous molecular sieves and metal ion-exchange alumina-rich hierarchical porous molecular sieves under mild conditions is proposed.

[0009] To achieve the above objectives, the first aspect of this invention provides a method for preparing an alumina-rich hierarchical porous molecular sieve, comprising the following steps:

[0010] A silica-alumina molecular sieve with a framework containing double six-membered ring structural units is used as the parent molecular sieve, wherein the molar ratio of SiO2 / Al2O3 in the parent molecular sieve framework is greater than or equal to 5.

[0011] The parent molecular sieve is subjected to alkaline treatment using an alkaline solution at a temperature ranging from 25°C to 85°C.

[0012] The product after alkali treatment is centrifuged, washed, and dried to obtain the alumina-rich multi-level porous molecular sieve.

[0013] Preferably, the parent molecule is selected from at least one of molecular sieves having a CHA, AEI, FAU, EMT or GME topology.

[0014] Preferably, the parent molecule is selected from at least one of SSZ-13, SSZ-39, Y, and GME molecular sieves.

[0015] Preferably, the molar ratio of SiO2 / Al2O3 in the parent molecular sieve framework is 5-15.

[0016] Preferably, the alkaline solution is selected from at least one of alkali metal hydroxide solution, alkaline earth metal hydroxide solution, or alkali metal carbonate solution, and the concentration of the alkaline solution is from 0.01 M to 0.5 M.

[0017] The alkali metal hydroxide is selected from at least one of LiOH, NaOH, KOH, and RbOH;

[0018] The alkaline earth metal hydroxide is selected from at least one of Sr(OH)2 and Ba(OH)2;

[0019] The alkali metal carbonate is selected from at least one of Na2CO3, K2CO3, and Rb2CO3.

[0020] Preferably, the alkali treatment time is 30 s to 5 h.

[0021] Preferably, the drying temperature is 60°C to 100°C, and the drying time is 10 h to 24 h.

[0022] A second aspect of this invention provides a method for preparing a metal ion-encapsulated alumina-rich hierarchical porous molecular sieve, comprising the following steps:

[0023] The above-described method for preparing alumina-rich hierarchical porous molecular sieves is implemented.

[0024] In the step of alkaline treatment using an alkaline solution, the alkaline solution also contains ammonia or amine complexes containing metal ions.

[0025] Furthermore, after the centrifugation, washing, and drying steps, a calcination process is also included to finally obtain the metal ion-encapsulated alumina-rich multi-level porous molecular sieve.

[0026] Preferably, the metal ion is selected from at least one of Cu, Co, Ni, Pd, Ru, Pt, Ir, and Rh.

[0027] Preferably, the calcination temperature is 350°C to 550°C, and the calcination time is 2 h to 6 h.

[0028] A third aspect of this invention provides a method for preparing a metal ion-exchange type alumina-rich hierarchical porous molecular sieve, comprising the following steps:

[0029] By implementing the above-described method for preparing alumina-rich hierarchical porous molecular sieves, alumina-rich hierarchical porous molecular sieves are obtained.

[0030] The alumina-rich hierarchical porous molecular sieve is subjected to ion exchange with a solution containing the target metal ions;

[0031] The ion-exchange product is centrifuged, washed, and dried to obtain the metal ion-exchange type alumina-rich hierarchical porous molecular sieve.

[0032] Preferably, the target metal ion is selected from at least one of Cu, Co, Ni, Pd, Ru, Pt, Ir, and Rh, and the ion exchange includes:

[0033] When the target metal ion is of the same type, the aluminum-rich hierarchical porous molecular sieve is subjected to a single ion exchange with a solution containing a single target metal ion.

[0034] When there are two or more target metal ions, a co-ion exchange method or a stepwise ion exchange method is used.

[0035] The co-ion exchange method includes performing a co-ion exchange between the alumina-rich hierarchical porous molecular sieve and a solution containing two or more target metal ions.

[0036] The stepwise ion exchange method involves performing multiple ion exchanges on the alumina-rich hierarchical porous molecular sieve, wherein each exchange uses a solution containing only one target metal ion, and the type of target metal ion used each time is different; after each ion exchange, the resulting product is centrifuged, washed and dried, and then the next ion exchange is performed, until all target metal ions have been exchanged.

[0037] Preferably, the concentration of the solution containing the target metal ion is from 0.0001 M to 0.5 M.

[0038] Preferably, the ion exchange temperature is 40°C to 80°C, and the time is 2 h to 12 h.

[0039] Preferably, the drying temperature is 60°C to 100°C, and the drying time is 10 to 24 hours.

[0040] A fourth aspect of this invention provides an alumina-rich hierarchical porous molecular sieve prepared by the above-described method, wherein the SiO2 / Al2O3 molar ratio of the molecular sieve framework is 1-5, and the external surface area is greater than or equal to 100 m². 2 / g.

[0041] The fifth aspect of this invention provides a metal ion-encapsulated alumina-rich hierarchical porous molecular sieve prepared by the above-described preparation method, wherein the content of the metal ions is 0.05-10 wt%.

[0042] The sixth aspect of this invention provides a metal ion exchange type alumina-rich hierarchical porous molecular sieve prepared by the above-described preparation method.

[0043] The seventh aspect of this invention proposes the application of the above-mentioned alumina-rich hierarchical porous molecular sieve, metal ion-encapsulated alumina-rich hierarchical porous molecular sieve, and / or metal ion-exchange alumina-rich hierarchical porous molecular sieve in gas adsorption and / or catalytic olefin conversion reactions.

[0044] Preferably, the gas is at least one of CO2 and NO.

[0045] Preferably, the catalytic olefin conversion reaction is at least one of olefin hydroformylation and olefin Wacker oxidation.

[0046] The beneficial effects of this invention are as follows:

[0047] (1) The method for preparing alumina-rich hierarchical porous molecular sieves of the present invention selects a specific parent molecular sieve with a double six-membered ring structural unit in its framework. Under mild single alkali treatment conditions, it utilizes the aluminum migration and local reagglomeration mechanism to selectively dissolve some silicon sites, thereby successfully constructing a hierarchical porous structure including micropores and mesopores while maintaining a high overall aluminum content. This method is simple, mild, and does not require complex templates or multiple processing steps. It solves the problem that traditional post-processing methods cannot simultaneously achieve high aluminum active sites and efficient mass transfer channels, and has strong industrial application value.

[0048] (2) This invention innovatively introduces ammonia or amine complexes of metal ions during the alkali treatment process, utilizing the dynamic process of Si-Al reconstruction of the molecular sieve framework to encapsulate metal ions in situ within the molecular sieve cages or channels. Compared to traditional high-temperature hydrothermal in-situ encapsulation technology, this method can be carried out under milder conditions, avoiding the hydrolysis, decomposition, and aggregation of metal precursors during high-temperature hydrothermal synthesis, ensuring uniform dispersion of metal ions within the molecular sieve. Simultaneously, this method overcomes the limitations of traditional encapsulation technology imposed by the molecular sieve pore size, enabling selective encapsulation of various metal ions, providing a universal and efficient technical solution for preparing high-performance encapsulated alumina-rich hierarchical porous molecular sieves.

[0049] (3) The alumina-rich hierarchical porous molecular sieve prepared by this invention has the dual structural advantages of being both alumina-rich and hierarchical. On the one hand, the alumina-rich characteristic provides abundant aluminum active sites, ion exchange sites, and gas adsorption sites; on the other hand, the hierarchical porous structure effectively reduces mass transfer resistance and promotes the diffusion and migration of reactants, products, and metal ions within the molecular sieve. These dual structural advantages expand the application potential of molecular sieves in ion exchange, gas adsorption, heterogeneous catalysis, and other fields, and significantly enhance the industrial application value of molecular sieves. Attached Figure Description

[0050] Figure 1 The XRD diffraction pattern and N2 adsorption-desorption isotherm curve of the alumina-rich hierarchical porous SSZ-13 molecular sieve obtained in Example 1 are shown.

[0051] Figure 2 The XRD diffraction pattern and N2 adsorption-desorption isotherm curve of the alumina-rich hierarchical porous SSZ-39 molecular sieve obtained in Example 2 are shown.

[0052] Figure 3 The XRD diffraction pattern of the alumina-rich hierarchical porous Y molecular sieve obtained in Example 3;

[0053] Figure 4 XRD diffraction patterns of MOR molecular sieve before and after alkali treatment in Comparative Example 1 and 29 Si MAS NMR spectrum;

[0054] Figure 5 The graph shows the CO2 adsorption performance of the alumina-rich hierarchical porous SSZ-13 molecular sieve in Example 6.

[0055] Figure 6 This is a distribution diagram of the olefin hydroformylation products in Example 7;

[0056] Figure 7 This is a diagram showing the results of Wacker oxidation of olefins in Example 8. Detailed Implementation

[0057] To make the objectives and technical solutions of this invention clearer and more complete, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the technical solutions of this invention, are all within the scope of protection of this invention.

[0058] Unless otherwise specified, all reagents and materials involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels.

[0059] This invention provides a method for preparing an alumina-rich hierarchical porous molecular sieve, comprising the following steps:

[0060] S1 uses a silica-alumina molecular sieve with a framework containing double six-membered ring structural units as the parent molecular sieve, and the molar ratio of SiO2 / Al2O3 in the parent molecular sieve framework is greater than or equal to 5.

[0061] The silica-alumina molecular sieves containing dual six-membered ring (D6R) structural units in their framework include molecular sieves with topologies such as CHA, AEI, FAU, EMT, or GME. More specifically, the parent molecular sieve can be selected from at least one of silica-alumina molecular sieves with dual six-membered ring structural units, such as SSZ-13 (containing CHA topology), SSZ-39 (containing AEI topology), Y (containing FAU topology), and GME (containing GME topology). Preferably, the molar ratio of SiO2 / Al2O3 in the selected parent molecular sieve framework is greater than or equal to 5; more preferably, the molar ratio of SiO2 / Al2O3 in the parent molecular sieve framework is 5-15. It should be noted that the SiO2 / Al2O3 mentioned in this invention refers to the molar ratio of SiO2 / Al2O3 in the molecular sieve framework, that is, the silica-alumina ratio of the molecular sieve framework.

[0062] S2 involves treating the parent molecular sieve with an alkaline solution at temperatures ranging from 25°C to 85°C.

[0063] The alkaline solution used for the alkali treatment is selected from at least one of alkali metal hydroxide solution, alkaline earth metal hydroxide solution, and alkali metal carbonate solution. Specifically, the alkali metal hydroxide is selected from at least one of LiOH, NaOH, KOH, and RbOH; the alkaline earth metal hydroxide is selected from at least one of Sr(OH)2 and Ba(OH)2; and the alkali metal carbonate is selected from at least one of Na2CO3, K2CO3, and Rb2CO3. The strength and concentration of the selected alkali can be determined according to the aluminum content of the target product, and the preferred concentration is 0.01 M to 0.5 M. The preferred temperature for alkali treatment is between 25°C and 85°C, and the preferred treatment time is between 30 s and 5 h.

[0064] S3. The product after alkali treatment is centrifuged, washed and dried to obtain the target alumina-rich hierarchical porous molecular sieve.

[0065] Preferably, the product after alkali treatment is washed by centrifugation with deionized water until the pH is approximately 7, and then dried in an oven at 60°C to 100°C for 10 to 24 hours to obtain the corresponding alumina-rich hierarchical porous molecular sieve.

[0066] In a preferred embodiment, a certain amount of alkali, namely at least one of the alkali metal hydroxide, alkaline earth metal hydroxide, and alkali metal carbonate mentioned in step S2, is weighed and dissolved in deionized water to prepare an alkali solution with a concentration of 0.01 M to 0.5 M. 1 g of the parent molecular sieve (SiO2 / Al2O3 ≥ 5) is dispersed in a certain amount of the above solution and treated at a temperature of 25°C to 85°C for 30 s to 5 h. After centrifugation, washing, and drying, the target alumina-rich hierarchical porous molecular sieve is obtained. The obtained molecular sieve framework has a SiO2 / Al2O3 ratio of 1-5 and an external surface area ≥ 100 m². 2 / g, while retaining the original micropores and forming interconnected mesopores. In this field, the external surface area of ​​a molecular sieve is obtained by subtracting its micropore surface area from the total specific surface area.

[0067] It should be noted that the silica-alumina molecular sieve with a framework containing double six-membered ring structural units was selected as the parent molecular sieve in this embodiment of the invention because this structural unit has specific dynamic instabilities. Its framework aluminum is easily hydrolyzed and migrated under mild alkaline treatment, but not completely lost. During alkaline treatment, these migrated aluminum species recombine into clusters within the nanospace inside the molecular sieve. This aluminum migration and recombination process locally reduces the aluminum density, removing its electrostatic shielding of the Si-O-Si silicon-oxygen bonds, thereby allowing OH... -It can selectively dissolve some silicon, creating mesopores in situ. Ultimately, the re-aggregated aluminum clusters remain within the system, ensuring that the product as a whole remains aluminum-rich (the final product's SiO2 / Al2O3 ratio is 1-5). At the same time, it achieves interconnected hierarchical channels, successfully solving the problem in traditional post-processing methods of achieving both high aluminum content (representing more active sites) and hierarchical pore structures (including micropores and mesopores, used to improve diffusion efficiency).

[0068] Furthermore, this invention also provides a method for preparing a metal ion-encapsulated alumina-rich hierarchical porous molecular sieve, which is basically the same as the above-mentioned method for preparing alumina-rich hierarchical porous molecular sieve, with the main difference being:

[0069] (1) In the alkaline treatment step of S2, the alkaline solution is also mixed with an ammonia or amine complex of metal ions. The metal ions include, but are not limited to, at least one of Cu, Co, Ni, Pd, Ru, Pt, Ir, and Rh, and the corresponding ammonia or amine complex may be Cu(NH3)4. 2+ Cu(en)3 2+ Pd(NH3)4 2+ Pt(NH3)4 2+ Ru(NH3)6 3+ Rh(NH3)6 3+ The components are dissolved in the alkaline solution used to prepare the alumina-rich hierarchical porous molecular sieve, according to the target loading. It should be understood that the above complexes can be prepared directly using their commercially available nitrates or chlorides; or they can be prepared on-site by adding ammonia or organic amines (such as ethylenediamine) to the aqueous solution of the corresponding metal salt (such as chloride or nitrate) to form a stable soluble complex precursor solution.

[0070] (2) In step S3, after centrifugation, washing, and drying, the treated product needs to be calcined in air at 350°C to 550°C for 2 to 6 hours to remove organic matter from the complex, so that the metal is stably encapsulated in the molecular sieve cage in the form of ions or nanoparticles, and finally the corresponding metal ion-encapsulated alumina-rich hierarchical porous molecular sieve is obtained. The content of metal ions accounts for 0.05-10 wt% of the total mass of the molecular sieve.

[0071] It should be noted that in this embodiment of the invention, the ammonia or amine complex of the aforementioned metal ions is mixed in an alkaline solution subjected to alkali treatment. During the alkali treatment process, localized silica dissolution and aluminum re-aggregation occur in the molecular sieve framework, causing a temporary expansion of the pores or cage structure. At this time, the pre-added ammonia or amine complex of the metal ions enters the molecular sieve cage in situ through ion exchange. During subsequent processing and calcination, the framework structure re-heals, stably encapsulating the metal ions within the cages, thereby enabling the introduction and encapsulation of multiple metal ions. This preparation method ingeniously utilizes the dynamic reconstruction process of the framework, overcoming the limitations of molecular sieve pore size. Compared to the traditional method of in-situ encapsulation of metal ions during high-temperature hydrothermal synthesis of molecular sieves, this method operates under milder conditions, avoiding the decomposition and aggregation of metal precursors during high-temperature hydrothermal synthesis.

[0072] Furthermore, this embodiment of the invention also provides a method for preparing a metal ion exchange type alumina-rich hierarchical porous molecular sieve.

[0073] It should be noted that the alumina-rich hierarchical porous molecular sieve prepared by the aforementioned method contains abundant aluminum pairs, thus possessing abundant ion exchange sites, and its hierarchical pore structure also facilitates the diffusion and migration of metal ions. Based on this, one or more metal ions can be efficiently introduced into the aforementioned alumina-rich hierarchical porous molecular sieve through ion exchange.

[0074] Specifically, the preparation method includes the following steps:

[0075] The alumina-rich hierarchical porous molecular sieve prepared above is dispersed in a solution containing target metal ions, and an ion exchange reaction is carried out at a suitable temperature. After the reaction is completed, the product is centrifuged, washed, and dried to obtain a metal ion-exchange type alumina-rich hierarchical porous molecular sieve, wherein the metal ion content can reach 10 wt%. Preferably, the ion exchange temperature is 40℃ to 80℃, and the time is 2 h to 12 h. The drying temperature is 60℃ to 100℃, and the drying time is 10 h to 24 h.

[0076] The target metal ion includes, but is not limited to, at least one of Cu, Co, Ni, Pd, Ru, Pt, Ir, and Rh. The solution of the metal ion is a soluble salt solution of the corresponding metal ion, or a salt solution of its ammonia or amine complex, such as a nitrate or chloride solution. The concentration can be prepared according to the target loading, preferably from 0.0001 M to 0.5 M.

[0077] Furthermore, to achieve the introduction of multiple metal ions, the above-mentioned ion exchange can be carried out in the following manner:

[0078] (1) When a single metal ion is introduced, a solution containing the single metal ion is used for one exchange to obtain a single metal-loaded alumina-rich hierarchical porous molecular sieve.

[0079] (2) When two or more metal ions are introduced, they can be prepared into a mixed solution for a single co-exchange; alternatively, the molecular sieve can be sequentially dispersed in a solution containing only one type of metal ion, with different types of metal ions used each time, to perform multiple ion exchanges. After each exchange, the resulting product must be centrifuged, washed, and dried before the next ion exchange. Specifically, multiple ion exchanges can be performed by first exchanging the molecular sieve with a solution containing the first type of metal ion, followed by centrifugation, washing, and drying, and then exchanging the resulting intermediate product with a solution containing the second type of metal ion, repeating this process until all target metal ions have been exchanged. This method allows for the co-loading of multiple metal ions.

[0080] In a preferred embodiment, the prepared alumina-rich hierarchical porous SSZ-13, SSZ-39, Y molecular sieves, etc., can be dispersed in an aqueous solution of Cu(NO3)2, stirred at 40°C for 4 h, and then centrifuged, washed, and dried to obtain Cu. 2+ The molecular sieves were further dispersed in a Pd(NH3)4(NO3)2 solution, stirred at 75°C for 12 h, and then centrifuged, washed and dried to finally obtain the corresponding Cu and Pd ion-exchange molecular sieve catalysts.

[0081] Furthermore, embodiments of the present invention also provide alumina-rich hierarchical porous molecular sieves, metal ion-encapsulated alumina-rich hierarchical porous molecular sieves, and metal ion-exchange alumina-rich hierarchical porous molecular sieves prepared by the above-described methods. These molecular sieves are all aluminosilicate molecular sieves with a SiO2 / Al2O3 ratio of 1-5, belonging to the category of alumina-rich molecular sieves; simultaneously, they possess both microporous and mesoporous structures, forming a hierarchical pore system.

[0082] Furthermore, embodiments of the present invention also provide an application of the alumina-rich hierarchical porous molecular sieve, the metal ion-encapsulated alumina-rich hierarchical porous molecular sieve, and / or the metal ion-exchange alumina-rich hierarchical porous molecular sieve prepared by the above preparation method in gas adsorption and / or catalytic olefin conversion reactions.

[0083] When applied to gas adsorption, it includes, but is not limited to, the adsorption of CO2 and NO.

[0084] When applied to catalyze olefin conversion reactions, including but not limited to olefin hydroformylation and olefin Wacker oxidation, the olefins involved are terminal olefins such as styrene, 1-octene, ethylene, and 1-hexene.

[0085] Specifically, in a preferred embodiment, at least one of the above-mentioned molecular sieves is used in the hydroformylation reaction of olefins. The catalytic reaction can be carried out in a continuous flow fixed-bed reactor or a high-pressure autoclave reactor. When used in a continuous flow fixed-bed reactor, the molecular sieve needs to be pre-formed. When used in a high-pressure autoclave reactor, a certain amount of molecular sieve is added to the reaction solution, and syngas (CO / H2) at a certain pressure is introduced into the high-pressure autoclave reactor, and the reaction is carried out under set conditions. The reaction products are analyzed by gas chromatography.

[0086] The hydrogen pressure is 0.01-10 MPa, preferably 0.1-5 MPa;

[0087] The reaction temperature is 10-300℃, preferably 50-150℃;

[0088] The reaction time is 0.01-48 h, preferably 0.1-10 h;

[0089] The solvents are n-heptane, toluene, etc.

[0090] In a preferred embodiment, at least one of the above-mentioned molecular sieves is used in the Wacker oxidation reaction of olefins. The catalytic reaction can be carried out in a continuous flow fixed-bed reactor or a high-pressure autoclave reactor. When used in a continuous flow fixed-bed reactor, the molecular sieve needs to be pre-formed. When used in a high-pressure autoclave reactor, a certain amount of molecular sieve is added to the reaction solution, and oxygen or air at a certain pressure is introduced into the high-pressure autoclave reactor. The reaction is carried out under set conditions, and the reaction products are analyzed by gas chromatography.

[0091] The oxygen pressure is 0.01-0.5 MPa, preferably 0.1-0.2 MPa;

[0092] The reaction temperature is 10-100℃, preferably 50-90℃;

[0093] The reaction time is 0.01-48 h, preferably 0.1-10 h;

[0094] Solvents include DMF (N,N-Dimethylformamide), DMA (N,N-Dimethylacetamide), and THF (Tetrahydrofuran).

[0095] The preparation methods and applications of the alumina-rich multi-level porous molecular sieve, the metal ion-encapsulated alumina-rich multi-level porous molecular sieve, and the metal ion-exchange alumina-rich multi-level porous molecular sieve provided by the present invention will be further explained below with reference to specific embodiments.

[0096] Example 1: Preparation of alumina-rich hierarchical porous SSZ-13 molecular sieve by alkali treatment

[0097] 1 g of commercially available SSZ-13 (SiO2 / Al2O3 = 5.7, Zhongchumei New Materials Co., Ltd.) was weighed and dispersed in 75 ml of Na2CO3 solution (8.48 g Na2CO3 dissolved in 160 mL of deionized water). After stirring in a water bath at 75 ℃ for 4 h, the mixture was washed with deionized water by centrifugation until the pH was approximately 7. It was then dried in an oven at 60 ℃ for 12 h to obtain an alumina-rich hierarchical porous SSZ-13 molecular sieve. Its X-ray diffraction pattern is shown below. Figure 1 As shown in Figure a, its nitrogen adsorption and desorption are illustrated in the attached figure. Figure 1 As shown in b in the figure, the alkali-treated SSZ-13 molecular sieve clearly exhibits the characteristic diffraction peaks of the CHA structure at 9.5°, 12.9°, 16.2°, 20.7°, and 25.1°, proving that its basic crystal framework is completely preserved after treatment. Meanwhile, the N2 adsorption-desorption isotherms show that adsorption in the low-pressure region (P / P0 < 0.1) confirms the existence of the microporous structure, while the obvious hysteresis loop in the medium-high pressure region (P / P0 = 0.45-1.0) proves the formation of a new mesoporous structure. In summary, these characterization results directly confirm that, after alkali treatment, a microporous-mesoporous hierarchical structure was successfully constructed while retaining the SSZ-13 microporous framework. The external surface area of ​​the obtained hierarchical porous SSZ-13 molecular sieve is calculated to be 100 m² using the Brunauer-Emmett-Teller (BET) method. 2 / g. Using 29 The SiO2 / Al2O3 molar ratio of the molecular sieve framework was measured to be 2.6 by solid-state nuclear magnetic resonance.

[0098] Example 2: Preparation of alumina-rich hierarchical porous SSZ-39 molecular sieve by alkali treatment

[0099] Weigh 1 g of commercial SSZ-39 (SiO2 / Al2O3 = 6.7, Zhongchumei New Materials Co., Ltd.) and disperse it in 75 ml of NaOH solution (0.96 g NaOH). Dissolved in 80 mL of deionized water, stirred in a 75 ℃ water bath for 2 h, then washed with deionized water by centrifugation until the pH was approximately 7, and dried in a 60 ℃ oven for 12 h to obtain alumina-rich hierarchical porous SSZ-39 molecular sieve. Its X-ray diffraction pattern is shown below. Figure 2 As shown in Figure a, its nitrogen adsorption and desorption are illustrated in the attached figure. Figure 2As shown in b in the figure, the SSZ-39 molecular sieve, after alkali treatment, maintains a well-preserved AEI framework structure. For example, the N2 adsorption-desorption isotherm shows that the sample exhibits a type IV isotherm with a significant hysteresis loop. These results collectively indicate that alkali treatment selectively removes framework silicon (achieving aluminum enrichment) while simultaneously constructing an interconnected mesoporous network in situ within the molecular sieve crystals. Calculations using the Brunauer-Emmett-Teller (BET) method show that the resulting hierarchical porous SSZ-39 molecular sieve has an external surface area of ​​209 m². 2 / g. Using 29 The SiO2 / Al2O3 molar ratio of the molecular sieve framework was determined to be 1.0 by solid-state nuclear magnetic resonance.

[0100] Example 3: Preparation of Aluminum-Rich Hierarchical Porous Y-Type Molecular Sieves by Alkali Treatment

[0101] This embodiment is basically the same as Embodiment 1, except that the parent molecular sieve used is a Y molecular sieve (SiO2 / Al2O3 = 12, Zeolyst International), resulting in an alumina-rich hierarchical porous Y-type molecular sieve, the X-ray diffraction pattern of which is shown below. Figure 3 As shown. Meanwhile, the SiO2 / Al2O3 molar ratio was measured to be 2.0 using the aforementioned method.

[0102] Comparative Example 1: Alkali-treated MOR molecular sieve

[0103] 1 g of laboratory-synthesized MOR molecular sieve (without a bi-six-membered ring structural unit in its framework) was weighed and dispersed in 75 ml of NaOH solution (0.48 g NaOH dissolved in 80 mL of deionized water). After stirring in a water bath at 75°C for 4 h, the mixture was washed with deionized water by centrifugation until the pH reached approximately 7. It was then dried in an oven at 60°C for 12 h. Its X-ray diffraction pattern is shown below. Figure 4 As shown in a, 29 Si MAS NMR spectrum as shown Figure 4 As shown in b in the figure, the MOR molecular sieve after alkali treatment still retains the MOR topology. However, the solid-state NMR shows that only a partial decrease in the Si(4Si) signal occurs under alkali treatment conditions, indicating that only desilication occurs and no new Si-O-Al bonds are formed. This demonstrates that molecular sieves with the MOR topology cannot be used to prepare alumina-rich hierarchical porous molecular sieves under alkali treatment conditions.

[0104] Example 4: Alkali treatment for in-situ encapsulated metal ions

[0105] Taking the in-situ encapsulation of Rh in SSZ-13 molecular sieve as an example: 1 g of commercial SSZ-13 molecular sieve (SiO2 / Al2O3 = 5.7, Zhongshunmei New Materials Co., Ltd.) was weighed and dispersed in 160 mL of 0.15 M Na2CO3 solution. A certain amount of Rh-EDA solution (5 mg of RhCl3·3H2O was weighed and dissolved in 4.5 g of deionized water, and after complete dissolution, 0.5 mL of ethylenediamine was added dropwise, and the solution was sonicated for 30 min. After stirring in a water bath at 75 ℃ for 2 h, the solution was centrifuged and washed with deionized water until the pH was approximately 7, and then dried in an oven at 60 ℃ for 12 h. The resulting solid powder was placed in a muffle furnace and calcined in air at 350 ℃ (2 ℃ / min) for 240 min to obtain Rh@SSZ-13.

[0106] Example 5: Ion exchange performance of alumina-rich hierarchical porous molecular sieves

[0107] 1 g of the alumina-rich hierarchical porous SSZ-39 molecular sieve prepared in Example 2 was dispersed in Cu 2+ The solution (0.02 g Cu(NO3)2·3H2O dissolved in 50 g deionized water) was stirred in a 40 °C water bath for 2 h. The resulting liquid was repeatedly centrifuged and washed with deionized water to collect the solid sample, which was then dried in a 100 °C oven for 12 h. Subsequently, 1 g of the above copper-exchanged molecular sieve was dispersed in a Pd(NH3)4(NO3)2 solution (0.028 g Pd(NH3)4(NO3)2 dissolved in 50 g deionized water) and stirred in a 70 °C water bath for 12 h. After four centrifugations and washings, it was dried in a 100 °C oven for 12 h to obtain Cu, Pd ion-exchanged alumina-rich hierarchical porous SSZ-39 molecular sieve (Al rich-Cu-Pd / SSZ-39). The Cu and Pd contents were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the results are shown in Table 1.

[0108] Table 1. Cu and Pd content in ion-exchange SSZ-39 molecular sieve determined by ICP-OES.

[0109]

[0110] As can be seen from the table, compared with the Cu-Pd / SSZ-39 (control group) obtained by conventional molecular sieve exchange without alkali treatment, the Cu and Pd contents in Al rich-Cu-Pd / SSZ-39 are significantly increased, and the Cu content is much higher than that in the control group.

[0111] Example 6: CO2 adsorption performance of alumina-rich hierarchical porous molecular sieves

[0112] Weigh 1 g of commercially available SSZ-13 (SiO2 / Al2O3 = 5.7, Zhongchumei New Materials Co., Ltd.) and disperse it in 75 ml of NaOH solution (0.096 g NaOH). Dissolved in 80 mL of deionized water, stirred in a water bath at 75 °C for 4 h, then washed by centrifugation with deionized water until the pH was approximately 7, and dried in an oven at 60 °C for 12 h to obtain aluminum-rich hierarchical porous Na-SSZ-13 molecular sieve, i.e., sodium-type SSZ-13.

[0113] 100 mg of the alumina-rich hierarchical porous Na-SSZ-13 molecular sieve prepared by the above-mentioned alkali treatment was vacuum dehydrated at 350 ºC, cooled to room temperature, and the CO2 adsorption capacity of the sample under different CO2 pressures was tested on a Mack ASAP2040. The results are as follows. Figure 5 As shown, the CO2 adsorption capacity of the sample treated with 0.03 M NaOH is significantly improved in the low-pressure region. Under the condition of 0.1 Bar (about 0.1 atmospheres), the CO2 adsorption capacity is as high as 3.1 mmol / g, which is more than twice that of the conventional molecular sieve (Parent in the figure) without alkali treatment. This indicates that the aluminum-rich structure of the molecular sieve can provide stronger CO2 adsorption sites.

[0114] Example 7: Catalytic performance of aluminum-rich hierarchical porous molecular sieves in olefin hydroformylation

[0115] Catalytic activity tests were conducted on the hydrogenation of 1-hexene: 20 mg of Rh@SSZ-13 molecular sieve catalyst was dispersed in 4 mL of toluene, 84.16 mg of 1-hexene was added, and 15 mg of n-undecane was used as an internal standard. The reaction flask was transferred to an autoclave, and after purging with high-pressure hydrogen six times, 2 MPa H2 and 2 MPa CO were introduced. The reaction was carried out at 90 ºC for 5 h, and the products were analyzed by gas chromatography. The obtained products included 2-hexene, n-hexane, 2-methylhexanal, heptanal, and heptanol. The conversion rate of 1-hexene and the n / iso ratio (linear aldehyde / branched aldehyde) were calculated based on the standard curve. The reaction results are as follows. Figure 6 As shown, the alumina-rich hierarchical porous Rh@SSZ-13 molecular sieves with different loadings all exhibit high conversion rates and excellent chemoselectivity in the 1-hexene hydroformylation reaction.

[0116] Example 8: Catalytic Wacker oxidation performance of alumina-rich hierarchical porous molecular sieves

[0117] The Wacker oxidation of olefins is an important method for preparing carbonyl-containing compounds from olefins by oxidizing C=C to C=O. Catalytic activity tests were conducted on the Wacker oxidation of various olefins: 25 mg of ion-exchange Cu-Pd / SSZ-39 molecular sieve catalyst was dispersed in 2.15 mL of a mixed solution (2 mL DMA and 0.15 mL 0.06 M sodium chloride solution), and 0.25 mmol of olefin was added. Using biphenyl as an internal standard, the reaction flask was transferred to an autoclave and equilibrated at 80 °C for 30 min, with O2 purging five times. After adjusting the final pressure to 0.2 MPa, the reaction mixture was vigorously stirred to initiate the reaction. After the reaction, the solid catalyst was separated by centrifugation, the filtrate was collected, and analyzed using an Agilent 8890 gas chromatograph (equipped with an HP-Innowax capillary column: 30 m × 0.32 mm × 0.25 μm). The results are as follows: Figure 7 As shown in the figure, the conventional molecular sieve catalyst with Cu and Pd metal ion exchange (Cu-Pd-AEI) achieves a conversion rate of only 3% and a selectivity of approximately 65% ​​in the styrene oxidation reaction. In contrast, the alumina-rich hierarchical porous molecular sieve catalyst with Cu and Pd metal ion exchange (Cu-Pd-AEI(H)) achieves conversion rates exceeding 80% in the oxidation reactions of styrene, styrene derivatives, and long-chain olefins, with corresponding ketone selectivity also exceeding 80%. Specifically, the conversion rate of 1-octene exceeds 99%, and the selectivity of 2-octanone reaches over 92%.

Claims

1. A method for preparing an alumina-rich hierarchical porous molecular sieve, characterized in that, Includes the following steps: A silica-alumina molecular sieve with a framework containing double six-membered ring structural units is used as the parent molecular sieve, wherein the molar ratio of SiO2 / Al2O3 in the parent molecular sieve framework is greater than or equal to 5. The parent molecular sieve is subjected to alkaline treatment using an alkaline solution at a temperature ranging from 25°C to 85°C. The product after alkali treatment is centrifuged, washed, and dried to obtain the alumina-rich multi-level porous molecular sieve.

2. The preparation method according to claim 1, characterized in that, The parent molecule is selected from at least one of the molecular sieves having a CHA, AEI, FAU, EMT or GME topology.

3. The preparation method according to claim 2, characterized in that, The parent molecule is selected from at least one of SSZ-13, SSZ-39, Y, and GME molecular sieves.

4. The preparation method according to claim 1, characterized in that, The alkaline solution is selected from at least one of alkali metal hydroxide solution, alkaline earth metal hydroxide solution, or alkali metal carbonate solution, and the concentration of the alkaline solution is from 0.01 M to 0.5 M. The alkali metal hydroxide is selected from at least one of LiOH, NaOH, KOH, and RbOH; The alkaline earth metal hydroxide is selected from at least one of Sr(OH)2 and Ba(OH)2; The alkali metal carbonate is selected from at least one of Na2CO3, K2CO3, and Rb2CO3.

5. A method for preparing a metal ion-encapsulated alumina-rich hierarchical porous molecular sieve, characterized in that, Includes the following steps: The preparation method according to any one of claims 1-4 shall be implemented; In the step of alkaline treatment using an alkaline solution, the alkaline solution also contains ammonia or amine complexes containing metal ions. Furthermore, after the centrifugation, washing, and drying steps, a calcination process is also included to finally obtain the metal ion-encapsulated alumina-rich multi-level porous molecular sieve.

6. The preparation method according to claim 5, characterized in that, The metal ion is selected from at least one of Cu, Co, Ni, Pd, Ru, Pt, Ir, and Rh.

7. A method for preparing a metal ion-exchange type alumina-rich hierarchical porous molecular sieve, characterized in that, Includes the following steps: By implementing the preparation method according to any one of claims 1-4, an aluminum-rich hierarchical porous molecular sieve is obtained; The alumina-rich hierarchical porous molecular sieve is subjected to ion exchange with a solution containing the target metal ions; The ion-exchange product is centrifuged, washed, and dried to obtain the metal ion-exchange type alumina-rich hierarchical porous molecular sieve.

8. The preparation method according to claim 7, characterized in that, The target metal ion is selected from at least one of Cu, Co, Ni, Pd, Ru, Pt, Ir, and Rh, and the ion exchange includes: When the target metal ion is of the same type, the alumina-rich hierarchical porous molecular sieve is subjected to a single ion exchange with a solution containing a single target metal ion. When there are two or more target metal ions, a co-ion exchange method or a stepwise ion exchange method is used. The co-ion exchange method includes performing a co-ion exchange between the alumina-rich hierarchical porous molecular sieve and a solution containing two or more target metal ions. The stepwise ion exchange method involves performing multiple ion exchanges on the alumina-rich hierarchical porous molecular sieve, wherein each exchange uses a solution containing only one target metal ion, and the type of target metal ion used each time is different; after each ion exchange, the resulting product is centrifuged, washed and dried, and then the next ion exchange is performed, until all target metal ions have been exchanged.

9. The alumina-rich hierarchical porous molecular sieve prepared by the preparation method according to any one of claims 1-4, characterized in that, The SiO2 / Al2O3 molar ratio of the alumina-rich hierarchical porous molecular sieve framework is 1-5, and the external surface area is greater than or equal to 100 m². 2 / g.

10. The metal ion-encapsulated alumina-rich hierarchical porous molecular sieve prepared by the preparation method according to any one of claims 5-6, characterized in that, The content of the metal ions is 0.05-10 wt%.

11. The metal ion exchange type alumina-rich hierarchical porous molecular sieve prepared by the preparation method according to any one of claims 7-8.

12. The application of the alumina-rich hierarchical porous molecular sieve of claim 9, the metal ion-encapsulated alumina-rich hierarchical porous molecular sieve of claim 10, and / or the metal ion-exchange alumina-rich hierarchical porous molecular sieve of claim 11 in gas adsorption and / or catalytic olefin conversion reactions.

13. The application according to claim 12, characterized in that, The gas is at least one of CO2 and NO.

14. The application according to claim 12, characterized in that, The catalytic olefin conversion reaction is at least one of olefin hydroformylation and olefin Wacker oxidation.

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