13x molecular sieve having a core-shell structure and a method for preparing the same

Abstract

The application provides a 13X molecular sieve with a core-shell structure and a preparation method thereof, and the preparation method comprises the following steps: filtering a 13X molecular sieve after first impregnation in a first solution to obtain a first solid; performing first calcination on the first solid after second impregnation in a second solution to obtain a 13X molecular sieve containing a nickel nanoparticle layer; mixing the 13X molecular sieve containing the nickel nanoparticle layer with a precursor solution, and sequentially performing incubation, drying and second calcination to obtain the 13X molecular sieve with the core-shell structure; and the precursor solution comprises a titanium-silicon molecular sieve precursor solution. The application can solve the problem of poor performance of the 13X molecular sieve prepared by the preparation method in the prior art, and is suitable for the technical field of molecular sieve preparation.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve preparation technology, and more specifically, to a 13X molecular sieve with a core-shell structure and its preparation method. Background Technology

[0002] Molecular sieves are aluminosilicate materials with uniform pore size, regular crystal structure, abundant channel system, large specific surface area, and good thermal stability. In particular, X-type molecular sieves exhibit good performance in olefin purification, effectively removing oxygen-containing compound impurities.

[0003] Adsorption separation is widely used in petroleum cracking and refinery catalytic cracking, primarily for removing oxides from hydrocarbons. Furthermore, hydrocarbon products from the indirect liquefaction of coal via Fischer-Tropsch synthesis exhibit diverse carbon number distributions, with a wide variety of oxygen-containing compounds within each product. Therefore, molecular sieves with uniformly ordered micropores, large specific surface areas, high adsorption capacities, and low heats of adsorption are required to meet the adsorption separation needs. However, existing 13X molecular sieves have relatively small surface areas and poor performance, making them unsuitable for large-scale industrial applications. Therefore, improvements to molecular sieves hold great promise for future applications. Summary of the Invention

[0004] The main objective of this invention is to provide a 13X molecular sieve with a core-shell structure and its preparation method, so as to solve the problem that the 13X molecular sieve prepared by existing methods has poor performance.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a method for preparing a 13X molecular sieve with a core-shell structure is provided. The method includes: first impregnating the 13X molecular sieve in a first solution and then filtering it to obtain a first solid; second impregnating the first solid in a second solution and then calcining it to obtain a 13X molecular sieve containing a nickel nanoparticle layer; mixing the 13X molecular sieve containing the nickel nanoparticle layer with a precursor solution and sequentially incubating, drying, and calcining it to obtain a 13X molecular sieve with a core-shell structure; wherein the precursor solution includes a titanium-silicon molecular sieve precursor solution.

[0006] Further, the first solution comprises any one or more aqueous solutions of the following: 3-aminopropyltriethoxysilane, tetraethoxysilane, or tetramethoxysilane; preferably, the first impregnation time is 6-15 h; preferably, the concentration of the first solution is 0.05-0.2 mol / L; preferably, the second solution comprises any one or more aqueous solutions of the following: nickel nitrate and / or nickel sulfate; preferably, the second impregnation time is 12-48 h; preferably, the concentration of the second solution is 0.01-0.2 M; preferably, the first calcination comprises: calcining in a gaseous atmosphere; preferably, the gaseous atmosphere includes a hydrogen atmosphere; preferably, the temperature of the first calcination is 200-1000 °C, and the time is 1-8 h.

[0007] Further, the titanium-silicon molecular sieve precursor solution comprises: silica, titanium dioxide, a template agent, a fluorine complex, and water; preferably, the molar ratio of silica to titanium dioxide is 1:(0.04-0.1); preferably, the molar ratio of silica to the template agent is 1:(0.1-0.3); preferably, the molar ratio of silica to the fluorine complex is 1:(0.04-0.1); preferably, the molar ratio of silica to water is 1:(20-50); preferably, the template agent comprises an organic amine and / or a quaternary ammonium salt; preferably, the fluorine complex comprises any one or more of sodium hexafluorophosphate, sodium hexafluoroacetylacetonate, or ammonium fluoride.

[0008] Furthermore, the incubation temperature is 100-500℃ and the time is 5-20h; preferably, the drying temperature is 80-200℃ and the time is 5-20h; preferably, the second calcination temperature is 300-600℃ and the time is 2-10h.

[0009] Further, the preparation method of 13X molecular sieve includes: sequentially subjecting a gel system containing silicon source and aluminum source to a first crystallization treatment and a second crystallization treatment to obtain a crystallized product; mixing the crystallized product with a gel mother liquor, and sequentially subjecting it to an aging treatment and a third crystallization treatment to obtain 13X molecular sieve; preferably, the preparation method of 13X molecular sieve includes: S1) dispersing a silicon source in water to obtain a silicon source dispersion; dispersing an aluminum source in water to obtain an aluminum source dispersion; S2) mixing the silicon source dispersion and the aluminum source dispersion, stirring, and adjusting the pH to 8.5–12.5 to obtain a gel system; S3) sequentially subjecting the gel system to a first crystallization treatment and a third crystallization treatment. S4) The crystallized product is subjected to a second crystallization treatment and a third crystallization treatment to obtain 13X molecular sieve; preferably, in S1), the mass concentration of the silicon source dispersion is 28-99 wt%; preferably, the silicon source includes one or more of silica sol, tetraethyl orthosilicate, coarse-porous silica gel, silica powder, fly ash or silica; preferably, the mass concentration of the aluminum source dispersion is 15-99 wt%; preferably, the aluminum source includes one or more of sodium aluminate, boehmite, aluminum sulfate or aluminum nitrate; preferably, in S2), the stirring temperature is 20-100℃ and the time is 0.1-24h.

[0010] Further, in S3), the temperature of the second crystallization treatment is 20–100°C higher than the temperature of the first crystallization treatment; preferably, the temperature of the first crystallization treatment is 20–60°C and the time is 10–18 h; preferably, the temperature of the second crystallization treatment is 80–120°C and the time is 6–48 h; preferably, the components in the crystallization product include silicon dioxide, aluminum oxide, sodium oxide and water; preferably, the molar ratio of silicon dioxide to aluminum oxide is 0.01–2.5:1; preferably, the molar ratio of sodium oxide to silicon dioxide is 0.01–4.0:1; preferably, the molar ratio of water to silicon dioxide is 1.0–40.0:1.

[0011] Further, in S4), the preparation method of the gel mother liquor includes: subjecting a mixture of inorganic waste and flux to a third calcination to obtain a third calcination product; mixing the third calcination product with an acid solution, and obtaining filter residue and a first filtrate after a first solid-liquid separation; mixing the filter residue with an alkaline solution, and obtaining a second filtrate after a second solid-liquid separation; mixing the first filtrate and the second filtrate to obtain the gel mother liquor; preferably, the inorganic waste includes one or more of waste ZSM-5 molecular sieve catalyst, waste MTO catalyst, fly ash, waste FCC catalyst, or waste VOC adsorbent; preferably, the aging treatment temperature is 20–100℃ and the time is 0.1–24h; preferably, the third crystallization treatment temperature is 60–105℃ and the time is 0.1–36h; preferably, the mass ratio of the crystallization product to the gel mother liquor is 5–20:100.

[0012] Further, the mass ratio of inorganic waste to flux is 1:0.5-1:5; preferably, the third roasting temperature is 550-800℃ and the time is 60-120 min; preferably, the mass concentration of the acid solution is 10%-35%; preferably, the flux includes sodium carbonate and / or sodium sulfate; preferably, the acid in the acid solution is a monobasic acid, more preferably hydrochloric acid and / or nitric acid; preferably, the alkali in the alkaline solution includes sodium hydroxide and / or potassium hydroxide; preferably, the mass ratio of filter residue, alkali and water is... The ratio of the first filtrate to the second filtrate is preferably 0.1-100:40-60:50-400; preferably, the mass ratio of the first filtrate to the second filtrate is 1:(2.5-5.5); preferably, the components in the gel mother liquor include silica, alumina, sodium oxide and water; preferably, the molar ratio of silica to alumina is (0.5-6.0):1; preferably, the molar ratio of sodium oxide to silica is (0.5-6.0):1; preferably, the molar ratio of water to silica is (10-100):1.

[0013] Furthermore, the 13X molecular sieve with a core-shell structure has a silica-to-alumina ratio of 2.4–3.1 and a pore volume of 0.37–0.58 cm³. 3 / g, specific surface area is 850~1000m² 2 / g.

[0014] To achieve the above objectives, according to a second aspect of the present invention, a method for preparing a 13X molecular sieve with a core-shell structure as described above is provided. The 13X molecular sieve with a core-shell structure has a silica-to-alumina ratio of 2.4 to 3.1 and a pore volume of 0.37 to 0.58 cm³. 3 / g, specific surface area is 850~1000m² 2 / g.

[0015] By applying the technical solution of this invention, the first solid obtained by impregnating and filtering 13X molecular sieve with a first solution is impregnated in a second solution. After the reaction is complete, a first calcination is performed to obtain a 13X molecular sieve containing a nickel nanoparticle layer. The 13X molecular sieve containing the nickel nanoparticle layer is mixed with a titanium-silicon molecular sieve precursor solution and then heated, dried and calcined in sequence to obtain a 13X molecular sieve that has both a nickel nanoparticle layer and a titanium-silicon shell. This core-shell structure has a larger surface area, which improves the performance of 13X molecular sieves in the prior art. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0017] As mentioned in the background section, the size and morphology of 13X molecular sieves prepared in the prior art are difficult to control, and their dispersibility is poor. Therefore, in this application, the inventors attempted to develop a new method for preparing 13X molecular sieves with a core-shell structure, and thus proposed a series of protection schemes in this application.

[0018] In a first typical embodiment of this application, a method for preparing a 13X molecular sieve with a core-shell structure is provided. The method includes: first impregnating the 13X molecular sieve in a first solution and then filtering it to obtain a first solid; second impregnating the first solid in a second solution and then calcining it to obtain a 13X molecular sieve containing a nickel nanoparticle layer; mixing the 13X molecular sieve containing the nickel nanoparticle layer with a precursor solution and sequentially incubating, drying, and calcining it to obtain a 13X molecular sieve with a core-shell structure; wherein the precursor solution includes a titanium-silicon molecular sieve precursor solution.

[0019] In existing technologies, improving the performance of molecular sieves by adding a core-shell structure is typically achieved by increasing the outer shell without altering the sieve's properties. Nickel nanoparticle layers exhibit good dispersion stability, while titanium-silicon shells offer excellent pore penetration. However, current technologies struggle to crosslink the nickel nanoparticle layers and titanium-silicon shells, making it impossible to obtain a core-shell structure that combines the advantages of both outer layers (shells).

[0020] This application utilizes a first impregnation treatment and a second impregnation treatment to sequentially form a nickel nanoparticle intermediate layer and a titanium-silicon molecular sieve outer shell on the surface of 13X molecular sieve, creating a core-shell gradient structure. This structure helps improve the mechanical strength and thermal stability of the 13X molecular sieve. During this process, the structure of the 13X molecular sieve is optimized, resulting in a core-shell structure 13X molecular sieve with specific surface area and porosity within a certain range. This application also involves the interaction between the titanium-silicon molecular sieve precursor solution and the nickel nanoparticles in the nickel nanolayer on the surface of the 13X molecular sieve. Through metal-support interaction reactions, structures such as metal-organic frameworks (MOFs) are formed, thereby creating a new core-shell structure on the surface of the 13X molecular sieve. The 13X molecular sieve with a core-shell structure in this application combines the advantages of good dispersion stability of nickel nanoparticle layers with the advantages of large pore volume and good pore penetration of titanium-silicon shells. It can also fully utilize the performance of 13X molecular sieves to form a hierarchical porous molecular sieve material with controllable micro-mesopores, large specific surface area and pore volume. Furthermore, it can further improve the adsorption capacity of this type of molecular sieve, thereby enabling it to have a wider range of applications in the field of shape-selective adsorption.

[0021] In a preferred embodiment, the first solution comprises any one or more aqueous solutions of 3-aminopropyltriethoxysilane, tetraethoxysilane, or tetramethoxysilane; preferably, the first immersion time is 6-15 hours, including but not limited to 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 hours; preferably, the concentration of the first solution is 0.05-0.2 mol / L, including but not limited to 0.05, 0.06, 0.07, 0.08, 0.09, 0. 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, or 0.2 mol / L; preferably, the second solution comprises any one or more of the following aqueous solutions: nickel nitrate and / or nickel sulfate; preferably, the second impregnation time is 12-48 h, including but not limited to 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28 h. 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47 or 48h; preferably, the concentration of the second solution is 0.01-0.2M, including but not limited to 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0. 16, 0.17, 0.18, 0.19, 0.2M; preferably, the first calcination includes: calcining in a gaseous atmosphere; preferably, the gaseous atmosphere includes a hydrogen atmosphere; preferably, the temperature of the first calcination is 200-1000℃, including but not limited to 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃ or 1000℃, and the time is 1-8h, including but not limited to 1, 2, 3, 4, 5, 6, 7 or 8h. In the first calcination, the nickel compound attached to the surface of the 13X molecular sieve decomposes at high temperature to form nickel oxide, and hydrogen reduces the nickel oxide to nickel nanoparticles. Controlling the temperature and time of the first calcination within the above range helps to improve the efficiency of forming nickel nanoparticles on the surface of the 13X molecular sieve.

[0022] In a preferred embodiment, the titanium-silicon molecular sieve precursor solution comprises: silica, titanium dioxide, a template agent, a fluorine complex, and water; preferably, the molar ratio of silica to titanium dioxide is 1:(0.04-0.1), including but not limited to 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.0, 1:0.09, or 1:0.1; preferably, the molar ratio of silica to the template agent is 1:(0.1-0.3), including but not limited to 1:0.1, 1:0.2, or 1:0.3; preferably, silica... The molar ratio of silica to water is 1:(0.04-0.1), including but not limited to 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.0, 1:0.09 or 1:0.1; preferably, the molar ratio of silica to water is 1:(20-50), including but not limited to 1:20, 1:25, 1:30, 1:40 or 1:50; preferably, the template agent includes organic amines and / or quaternary ammonium salts; preferably, the fluorine complex includes any one or more of sodium hexafluorophosphate, sodium hexafluoroacetylacetonate or ammonium fluoride.

[0023] This application utilizes a first solution containing silicon to impregnate 13X molecular sieves, obtaining a first solid. This solid is then subjected to a second impregnation with a second solution containing nickel, followed by a first calcination. The resulting nickel nanoparticle layer contains silicon. This nickel nanoparticle layer reacts and cross-links with components in the titanium-silicon molecular sieve precursor solution, forming a titanium-silicon shell around the nickel nanoparticle layer, ultimately yielding a 13X molecular sieve with both a nickel nanoparticle layer and a titanium-silicon shell. By controlling the first impregnation time, the second impregnation time, and the concentrations of the first and second solutions within the aforementioned ranges, this application helps control the quality of the nickel nanoparticle layer, improves the wetting effect of the first and second solutions on the 13X molecular sieve, and enhances the cross-linking degree between the nickel nanoparticle layer and the titanium-silicon shell. This allows for the synergistic utilization of the advantages of both core-shell structures without altering the inherent properties of the 13X molecular sieve. Compared to 13X molecular sieves without a core-shell structure, the molecular sieve with this core-shell structure exhibits better dispersion stability, stronger pore penetration, and larger pore volume and specific surface area.

[0024] In a preferred embodiment, the incubation temperature is 100-500°C, including but not limited to 100°C, 200°C, 300°C, 400°C, or 500°C, and the incubation time is 5-20 hours, including but not limited to 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 hours; preferably, the drying temperature is 80-200°C, including but not limited to 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, or 140°C. The second calcination temperature is 150℃, 160℃, 170℃, 180℃, 190℃, or 200℃, for 5-20 hours, including but not limited to 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 hours; preferably, the second calcination temperature is 300-600℃, including but not limited to 300℃, 400℃, 500℃, or 600℃, for 2-10 hours, including but not limited to 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours. By controlling the temperature and time of the second calcination, the peptide-silicon composite shell can be better cross-linked with the nickel nanoparticle layer, improving the reaction efficiency and obtaining a nickel nanoparticle layer-peptide-silicon composite shell with a moderate degree of cross-linking. This is beneficial for forming a 13X molecular sieve that combines the advantages of both shells and improves overall performance.

[0025] In a preferred embodiment, the preparation method of 13X molecular sieve includes: sequentially performing a first crystallization treatment and a second crystallization treatment on a gel system containing a silicon source and an aluminum source to obtain a crystallized product; mixing the crystallized product with a gel mother liquor, and sequentially performing an aging treatment and a third crystallization treatment to obtain 13X molecular sieve.

[0026] Preferably, the preparation method of 13X molecular sieve includes: S1) dispersing a silicon source in water to obtain a silicon source dispersion; dispersing an aluminum source in water to obtain an aluminum source dispersion; S2) mixing the silicon source dispersion and the aluminum source dispersion, stirring, and adjusting the pH to 8.5–12.5, including but not limited to 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, or 12.5, to obtain a gel system; S3) subjecting the gel system to a first crystallization treatment and a second crystallization treatment sequentially to obtain crystallized... Product; S4) The crystallized product and the gel mother liquor are sequentially aged and subjected to a third crystallization treatment to obtain 13X molecular sieve; Preferably, in S1), the mass concentration of the silicon source dispersion is 28-99 wt%, including but not limited to 28, 29, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 99 wt%; Preferably, the silicon source includes silica sol, tetraethyl orthosilicate, coarse-porous silica gel (type C silica gel), silica powder, fly ash or white silica gel. One or more of carbon black; preferably, the mass concentration of the aluminum source dispersion is 15-99 wt%, including but not limited to 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 99 wt%; preferably, the aluminum source includes one or more of sodium aluminate, boehmite, aluminum sulfate or aluminum nitrate; preferably... Optionally, the first solvent and the second solvent include water; preferably, in S2), the stirring temperature is 20 to 100°C, including but not limited to 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, and the stirring time is 0.1 to 24 hours, including but not limited to 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24 hours.

[0027] Compared to traditional methods that involve a single crystallization stage to obtain a crystallized product system, the two-stage crystallization process described above for a gel system containing silicon and aluminum sources effectively controls the formation and growth of seed crystals. The first crystallization stage, conducted at lower temperatures and times, facilitates the initial formation of seed crystals. The second crystallization stage, conducted at higher temperatures and times, promotes further growth and refinement of the seed crystals, improving their quality and controllability. Furthermore, mixing the mother liquor obtained from the treatment of inorganic waste containing the aforementioned specific elements with the crystallized product system to prepare 13X-type molecular sieves increases the recycling rate of inorganic waste and enhances its utilization value. In the above method, after stirring, the pH is adjusted to 8.5-12.5. Compared with pouring the aluminum source dispersion into the silicon source dispersion, adding the aluminum source dispersion dropwise into the silicon source dispersion is beneficial to improving the crystallinity and purity of the crystallization product. At the same time, adjusting the pH within the above range is beneficial to accelerating the crystallization rate of the subsequent two-stage crystallization treatment, shortening the crystallization time, and facilitating the subsequent formation of the molecular sieve with the specific crystal form of this application.

[0028] The method for preparing 13X molecular sieve in this application utilizes recycled silicon-rich and aluminum-rich extracts to replace part of the raw materials, precisely controls the pH value, performs segmented crystallization, adds an appropriate amount of seed solution, and uses other raw materials to replace part of the aluminum-rich and silicon-rich solutions, effectively controlling the crystal growth rate and final size, and is able to prepare 13X molecular sieves with smooth crystal surfaces free of impurities.

[0029] In a preferred embodiment, in S3), the temperature of the second crystallization treatment is 20–100°C higher than the temperature of the first crystallization treatment; preferably, the temperature of the first crystallization treatment is 20–60°C, including but not limited to 20°C, 30°C, 40°C, 50°C, or 60°C, and the time is 4–24 hours, including but not limited to 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 2 The second crystallization treatment is performed over a period of 4 hours; preferably, the temperature of the second crystallization treatment is 80–120°C, including but not limited to 80, 90, 100, 110, or 120°C, and the time is 6–48 hours, including but not limited to 6, 7, 8, 9, 10, 11, 12, 24, 36, or 48 hours; preferably, the components in the crystallization product include silicon dioxide, aluminum oxide, sodium oxide, and water; preferably, the molar ratio of silicon dioxide to aluminum oxide is 0.01–2.5:1, including but not limited to 0.01: 1. 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 1:1, 1.5:1, 2:1, or 2.5:1; preferably, the molar ratio of sodium oxide to silicon dioxide is 0.01 to 4.0:1, including but not limited to 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, and 0.07:1. The molar ratios of water and silica are 0.08:1, 0.09:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 2:1, 3:1, or 4:1; preferably, the molar ratio of water to silica is 1.0 to 40.0:1, including but not limited to 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, or 40:1.

[0030] In this application, the temperature difference between the first crystallization treatment and the second crystallization treatment allows for more flexible adjustment of the silicon-to-aluminum ratio of the molecular sieve, which is beneficial for the subsequent formation of a 13X-type molecular sieve with controllable morphology and size and a wide silicon-to-aluminum ratio, thereby improving the overall performance of the molecular sieve.

[0031] In a preferred embodiment, in step S4), the method for preparing the gel mother liquor includes: subjecting a mixture of inorganic waste and flux to a third calcination to obtain a third calcination product; mixing the third calcination product with an acid solution, and obtaining a filter residue and a first filtrate after a first solid-liquid separation; mixing the filter residue with an alkaline solution, and obtaining a second filtrate after a second solid-liquid separation; and mixing the first filtrate and the second filtrate to obtain the gel mother liquor; preferably, the inorganic waste includes waste ZSM-5 molecular sieve catalyst, waste MTO catalyst, and powder. One or more of coal ash, spent FCC catalyst, or spent VOC adsorbent; preferably, the aging treatment temperature is 20–100℃, including but not limited to 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, or 100℃, and the time is 0.1–24h, including but not limited to 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22. 23 or 24 hours; the aging process is carried out under stirring conditions; preferably, the third crystallization treatment includes a crystallization temperature of 60–105°C, including but not limited to 60°C, 70°C, 80°C, 90°C, 100°C, 101°C, 102°C, 103°C, 104°C, or 105°C, and a time of 0.1–36 hours, including but not limited to 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 2 0, 21, 22, 23 or 24h; preferably, the mass ratio of the crystallized product to the gel mother liquor is 5 to 20:100, including but not limited to 5:100, 6:100, 6:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100, 15:100, 16:100, 17:100, 18:100, 19:100 or 20:100.

[0032] The temperature and time of the third crystallization treatment include, but are not limited to, the ranges mentioned above. Limiting these ranges helps improve the crystal purity of the obtained molecular sieve, reduces impurities, and increases the adsorption sites and internal pore volume of the obtained 13X molecular sieve, thereby improving its adsorption performance. This also allows for better formation of a core-shell structure with a nickel nanoparticle layer and a peptide-silicon shell on its surface. The aforementioned inorganic waste includes, but is not limited to, one or more of ZSM-5 molecular sieve catalysts, spent MTO catalysts, fly ash, spent FCC catalysts, or spent VOC adsorbents, and may also include one or more other spent molecular sieve adsorbents or spent catalysts.

[0033] In a preferred embodiment, the mass ratio of inorganic waste to flux is 1:0.5-1:5, including but not limited to: 0.5, 1:1, 1:1.5; preferably, the third roasting temperature is 550-800℃, including but not limited to 550℃, 560℃, 570℃, 580℃, 600℃, 700℃ or 800℃, and the time is 60-120min, including but not limited to 60, 70, 80, 90, 100, 110 or 120min; preferably, the mass concentration of the acid aqueous solution is 10%-35%, including but not limited to 10, 15, 20, 25, 30 or 35%; preferably, the flux includes sodium carbonate and / or sodium sulfate; preferably, the acid in the acid solution is a monobasic acid, more preferably hydrochloric acid and / or nitric acid; preferably, the alkali in the alkaline solution includes sodium hydroxide and / or potassium hydroxide; preferably, the mass ratio of filter residue, alkali and water is 0.1-100:40-60:50-400; Preferably, the mass ratio of the first filtrate to the second filtrate is 1:(2.5-5.5), including but not limited to 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or 1:5.5; preferably, the components in the gel mother liquor include silica, alumina, sodium oxide, and water; preferably, the molar ratio of silica to alumina is (0.5-6.0):1, including but not limited to 0.5:1, 1:1, 2:1, 3:1, or 4:1. The molar ratio of sodium oxide to silicon dioxide is preferably (0.5-6.0):1, including but not limited to 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1 or 6:1; the molar ratio of water to silicon dioxide is preferably (10-100):1, including but not limited to 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1.

[0034] In a preferred embodiment, the 13X molecular sieve with a core-shell structure has a silica-to-alumina ratio of 2.4–3.1 and a pore volume of 0.37–0.58 cm³. 3 / g, specific surface area is 850~1000m² 2 / g.

[0035] In a second typical embodiment of this application, a 13X molecular sieve with a core-shell structure, prepared by any of the above-mentioned methods, is provided. This 13X molecular sieve has a silica-to-alumina ratio of 2.4–3.1 and a pore volume of 0.37–0.58 cm³. 3 / g, specific surface area is 850~1000m² 2 / g.

[0036] The 13X molecular sieve with a core-shell structure in this application has a large specific surface area, contains more adsorption sites, and exhibits better adsorption performance. In the molecular sieve of this application, mesoporous channels are introduced by incorporating a nickel nanoparticle layer and a titanium-silicon shell, increasing the pore volume within the molecular sieve crystal, improving the flow and diffusion performance of guest molecules within the molecular sieve, and resulting in uniformly dispersed nanoparticles with regular morphology. Furthermore, the 13X molecular sieve prepared by the above-described method also has a high silicon-to-aluminum ratio, high silicon source utilization, and better selectivity for crosslinking with the two shells. This allows for regulation based on different adsorbed molecules, thereby significantly reducing the carbon deposition rate of the molecular sieve and improving the diffusion performance of the adsorbent.

[0037] The beneficial effects of this application will be explained in more detail below with reference to specific embodiments.

[0038] Example 1

[0039] A method for preparing a 13X type molecular sieve with a core-shell structure includes the following steps:

[0040] (1) Dissolve 21.0g of silica sol in 36.0g of deionized water, and pretreat it in a closed reactor at 25°C for 1h to obtain a silica source dispersion;

[0041] 24g of aluminum sulfate was dissolved in 18.0g of deionized water and stirred at 25℃ for 1h to obtain an aluminum source dispersion.

[0042] The aluminum source dispersion was added dropwise to the silicon source dispersion, and the mixture was stirred at 60°C for 8 hours to obtain a gel solution.

[0043] 6.74 g of NaOH was dissolved in 36 g of deionized water to obtain an aqueous NaOH solution. This aqueous NaOH solution was added to the gel solution, and the pH was adjusted to 12.2 to obtain a gel system containing silicon and aluminum sources.

[0044] The gel system was transferred to a hydrothermal reactor for two-stage temperature-controlled crystallization (i.e., the first crystallization treatment and the second crystallization treatment): the temperature of the first crystallization treatment was 40°C and the time was 12h; the temperature of the second crystallization treatment was 95°C and the time was 24h.

[0045] A crystallized product (white) was obtained;

[0046] In this crystallized product, the molar ratio of SiO2 to Al2O3 is 1.5:1, the molar ratio of Na2O to SiO2 is 1.6:1, and the molar ratio of H2O to SiO2 is 32:1.

[0047] (2) Mix 10g of the above-mentioned 200-mesh waste ZSM-5 molecular sieve catalyst with 8g of Na2CO3 and calcine at 650℃ for 120min to obtain the third calcination product; then use a 25% nitric acid solution to dissolve and filter the third calcination product to obtain filter residue; the specific composition of the above-mentioned waste ZSM-5 molecular sieve is shown in Table 1.

[0048] Take 10g of filter residue and mix it with 6g of NaOH and 40g of water; mix the silica-rich solution and aluminum-rich solution in a weight ratio of 4:1 to obtain the gel mother liquor;

[0049] The molar ratio of SiO2 to Al2O3 in the gel mother liquor is 3.5:1, the molar ratio of Na2O to SiO2 is 2.8:1, and the molar ratio of H2O to SiO2 is 80:1.

[0050] Table 1

[0051] Waste ZSM-5 molecular sieve catalyst 0.050 19.84 79.64 0.31 0.18

[0052] (3) Take 25g of the crystallized product obtained in step (1) and add it to the gel mother liquor prepared in step (2). Aged at 60℃ for 12h, and placed in a hydrothermal reactor for a third crystallization treatment. The temperature of the third crystallization treatment is 98℃ and the time is 24h. Filter and wash until the pH is 7, and dry at 90℃ to obtain 13X type molecular sieve.

[0053] (4) The 13X molecular sieve was first impregnated in 500 mL of 0.2 mol / L aqueous solution of 3-aminopropyltriethoxysilane (APTES) (first solution) for 8 hours. Then, the 13X molecular sieve (first solid) after the first impregnation was impregnated in 0.1 M nickel nitrate solution (second solution), and the pH was adjusted to 9 with sodium hydroxide. After impregnation for 24 hours, it was first calcined at 500 °C for 2 hours under a hydrogen atmosphere to form a nickel nanoparticle deposition layer on the outside, thus obtaining a 13X molecular sieve containing a nickel nanoparticle layer.

[0054] (5) A titanium-silicon molecular sieve precursor solution was obtained by mixing SiO2:TiO2:organic amine:sodium hexafluorophosphate:water in a molar ratio of 1:(0.04):(0.1):(0.03):(20). 13X molecular sieves containing nickel nanoparticle layers were added to the titanium-silicon molecular sieve precursor solution and thoroughly mixed. The mixture was then transferred to a reaction vessel. A hydrothermal reaction was carried out at 150°C for 12 hours to form a titanium-silicon composite shell (incubation). After the reaction was completed, the mixture was filtered and washed with deionized water, then dried at 110°C for 12 hours, and finally calcined at 450°C for 4 hours to obtain a 13X molecular sieve with a core-shell structure.

[0055] Example 2

[0056] The difference from Example 1 is that: (1) 1g of silicon powder was dissolved in 18.0g of deionized water and pretreated in a closed reactor at 25°C for 1h to obtain a silicon source dispersion;

[0057] 12g of aluminum nitrate was dissolved in 18g of deionized water and stirred at 25°C for 1 hour to obtain an aluminum source dispersion.

[0058] The aluminum source dispersion was added dropwise to the silicon source dispersion, and the mixture was stirred at 50°C for 6 hours to obtain a gel solution.

[0059] 2g of NaOH was dissolved in 36g of deionized water to obtain an aqueous NaOH solution. This aqueous NaOH solution was added to the gel solution, and the pH was adjusted to 11.8 to obtain a gel system containing silicon and aluminum sources.

[0060] The above gel system was transferred to a hydrothermal reactor for two-stage temperature-controlled crystallization (i.e., the first crystallization treatment and the second crystallization treatment): the first crystallization treatment was carried out at a temperature of 40℃ for 14 hours; the second crystallization treatment was carried out at a temperature of 100℃ for 18 hours. A crystalline product (pale yellow) was obtained.

[0061] In this crystallized product, the molar ratio of SiO2 to Al2O3 is 0.6:1, the molar ratio of Na2O to SiO2 is 3:1, and the molar ratio of H2O to SiO2 is 20:1.

[0062] (2), (3), (4) and (5) are consistent with the steps in Example 1.

[0063] Example 3

[0064] The difference from Example 1 is as follows:

[0065] (1) Mix 14.65g of tetraethyl orthosilicate and 36g of deionized water at a mass ratio of 1:1, and pretreat in a sealed reactor at 25°C for 1 hour to obtain a silicon source dispersion.

[0066] 12g of aluminum nitrate was dissolved in 18.0g of deionized water and stirred at 35°C for 1 hour to obtain an aluminum source dispersion.

[0067] The aluminum source dispersion was gradually added dropwise to the silicon source dispersion, and the mixture was stirred at 20°C for 0.1 hours to prepare a gel solution.

[0068] 0.56 g of NaOH was dissolved in 6 g of deionized water to obtain an aqueous NaOH solution. This aqueous NaOH solution was added to the gel solution, and the pH was adjusted to 8.5 to obtain a gel system containing silicon and aluminum sources.

[0069] The gel system was transferred to a hydrothermal reactor for two-stage temperature-controlled crystallization (i.e., the first crystallization treatment and the second crystallization treatment): the first crystallization temperature was 20°C and the time was 4 hours; the second crystallization treatment temperature was 80°C and the time was 6 hours, finally yielding a white solid 13X molecular sieve.

[0070] Steps (2) to (5) are the same as those in Example 1.

[0071] Example 4

[0072] The difference from Example 1 is that: (1) 0.17g of silicon powder was dissolved in 6g of deionized water and pretreated in a closed reactor at 25°C for 1h to obtain a silicon source dispersion;

[0073] 12g of aluminum nitrate was dissolved in 18g of deionized water and stirred at 35℃ for 1h to obtain an aluminum source dispersion.

[0074] The aluminum source dispersion was added dropwise to the silicon source dispersion, and the mixture was stirred at 100°C for 24 hours to obtain a gel solution.

[0075] Dissolve 0.9g NaOH in 6g deionized water to obtain an aqueous NaOH solution. Add the aqueous NaOH solution to the gel solution and adjust the pH to 12.5 to obtain a gel system containing silicon and aluminum sources.

[0076] The above gel system was transferred to a hydrothermal reactor for two-stage temperature-controlled crystallization (i.e., the first crystallization treatment and the second crystallization treatment): the first crystallization treatment was carried out at a temperature of 60℃ for 24 hours; the second crystallization treatment was carried out at a temperature of 120℃ for 48 hours. A crystalline product (pale yellow) was obtained.

[0077] In this crystallized product, the molar ratio of SiO2 to Al2O3 is 0.1:1, the molar ratio of Na2O to SiO2 is 4:1, and the molar ratio of H2O to SiO2 is 1:1.

[0078] (2), (3), (4) and (5) are consistent with the steps in Example 1.

[0079] Example 5

[0080] Steps (1) to (4) and (5) in this embodiment are the same as in Embodiment 1;

[0081] In (4), the difference from Example 1 is that the first impregnation time is 15h and the solution concentration is 0.04mol / L; the second impregnation time is 48h and the solution concentration is 0.01M; and the first calcination is carried out at 1000℃ for 1h.

[0082] Example 6

[0083] Steps (1) to (3) and (5) in this embodiment are the same as in Embodiment 1;

[0084] In (4), the difference from Example 1 is that the first impregnation time is 6h and the solution concentration is 0.2mol / L; the second impregnation time is 12h and the solution concentration is 0.2M; and the first calcination is carried out at 200℃ for 8h.

[0085] Example 7

[0086] Steps (1) to (4) and (5) in this embodiment are the same as in Embodiment 1;

[0087] In (5), the difference from Example 1 is that the molar ratio of SiO2:TiO2:organic amine:sodium hexafluorophosphate:water is 1:0.04:0.1:0.04:20.

[0088] Example 8

[0089] In this embodiment, steps (1) to (4) are the same as in embodiment 1;

[0090] In (5), the difference from Example 1 is that the molar ratio of SiO2:TiO2:organic amine:sodium hexafluorophosphate:water is 1:0.1:0.3:0.1:50.

[0091] Example 9

[0092] In this embodiment, steps (1) to (4) are the same as in embodiment 1;

[0093] (5) The incubation temperature is 100℃ and the time is 20h; the second roasting temperature is 300℃ and the time is 10h.

[0094] Example 10

[0095] In this embodiment, steps (1) to (4) are the same as in embodiment 1;

[0096] (5) The incubation temperature is 500℃ and the time is 5h; the second roasting temperature is 600℃ and the time is 2h.

[0097] Comparative Example 1

[0098] In this comparative example, steps (1) to (3) and (5) are the same as in Example 1;

[0099] In step (4), the difference from Example 1 is that after obtaining the 13X molecular sieve, the first impregnation is not carried out in the first solution, but the second impregnation is carried out directly in nickel nitrate. The subsequent steps are the same as the other steps in step (4) of Example 1 to obtain the 13X molecular sieve.

[0100] Comparative Example 2

[0101] In this comparative example, steps (1) to (3) and (5) are the same as in Example 1;

[0102] This comparative example omits step (4). After completing step (3), it proceeds directly to step (5) to obtain 13X molecular sieve.

[0103] Comparative Example 3

[0104] In this embodiment, steps (1) to (4) are the same as in embodiment 1;

[0105] This comparative example omits step (5) and obtains 13X molecular sieve.

[0106] Table 2 shows the silicon-to-aluminum ratio (SBR), BET specific surface area, pore volume, average pore size for BJH adsorption, and silicon source conversion rate of the molecular sieves prepared in Examples 1-10 and Comparative Examples 1-3 of this application. Micropores refer to pores with a diameter <2 nm, and mesopores refer to pores with a diameter of 2–50 nm.

[0107] Table 2

[0108]

[0109] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0110] The 13X molecular sieve with a nickel nanoparticle layer and a titanium-silicon shell prepared by the preparation method in this application has improved the specific surface area, pore volume and pore capacity compared with the core-shell-less 13X molecular sieve prepared by the prior art. Finally, a core-shell structured 13X molecular sieve with large surface area, controllable morphology and size and better dispersibility is obtained.

[0111] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing 13X molecular sieve with a core-shell structure, characterized in that, The preparation method includes: The 13X molecular sieve was first impregnated in a first solution and then filtered to obtain a first solid; the first solid was then second impregnated in a second solution and then first calcined to obtain a 13X molecular sieve containing a nickel nanoparticle layer. The 13X molecular sieve containing nickel nanoparticle layers was mixed with a precursor solution and then incubated, dried and calcined in sequence to obtain the 13X molecular sieve with a core-shell structure. The precursor solution includes a titanium-silicon molecular sieve precursor solution; The first solution comprises any one or more aqueous solutions of the following: 3-aminopropyltriethoxysilane, tetraethoxysilane, or tetramethoxysilane; The second solution comprises any one or more aqueous solutions of nickel nitrate and / or nickel sulfate; The incubation temperature is 100-500℃, and the time is 5-20 hours; The preparation method of the 13X molecular sieve includes: S1) Disperse the silicon source in water to obtain a silicon source dispersion; disperse the aluminum source in water to obtain an aluminum source dispersion; S2) The silicon source dispersion and the aluminum source dispersion are mixed, and the pH is adjusted to 8.5-12.5 after stirring to obtain a gel system; S3) The gel system is subjected to a first crystallization treatment and a second crystallization treatment in sequence to obtain a crystallized product; S4) The crystallized product and the gel mother liquor are subjected to aging treatment and third crystallization treatment in sequence to obtain the 13X molecular sieve; In step S1), the mass concentration of the silicon source dispersion is 28–99 wt%. In step S4), the method for preparing the gel mother liquor includes: subjecting a mixture of inorganic waste and flux to a third calcination to obtain a third calcination product; The third calcination product is mixed with an acid solution, and after a first solid-liquid separation, filter residue and a first filtrate are obtained. The filter residue is mixed with an alkaline solution, and a second filtrate is obtained after a second solid-liquid separation. The first filtrate and the second filtrate are mixed to obtain the gel mother liquor; The inorganic waste includes one or more of the following: waste ZSM-5 molecular sieve catalyst, waste MTO catalyst, fly ash, waste FCC catalyst, or waste VOC adsorbent.

2. The preparation method according to claim 1, characterized in that, The first immersion time is 6-15 hours.

3. The preparation method according to claim 1, characterized in that, The concentration of the first solution is 0.05~0.2 mol / L.

4. The preparation method according to claim 1, characterized in that, The second immersion time is 12-48 hours.

5. The preparation method according to claim 1, characterized in that, The concentration of the second solution is 0.01-0.2M.

6. The preparation method according to claim 1, characterized in that, The first roasting includes: performing the first roasting in a gaseous atmosphere.

7. The preparation method according to claim 6, characterized in that, The gas atmosphere includes a hydrogen atmosphere.

8. The preparation method according to claim 6, characterized in that, The first roasting temperature is 200-1000℃, and the time is 1-8h.

9. The preparation method according to claim 1, characterized in that, The titanium-silicon molecular sieve precursor solution comprises: silicon dioxide, titanium dioxide, template agent, fluorine complex and water.

10. The preparation method according to claim 9, characterized in that, The molar ratio of silicon dioxide to titanium dioxide is 1:(0.04-0.1).

11. The preparation method according to claim 9, characterized in that, The molar ratio of the silica to the template agent is 1:(0.1-0.3).

12. The preparation method according to claim 9, characterized in that, The molar ratio of the silica to the fluorine complex is 1:(0.04-0.1).

13. The preparation method according to claim 9, characterized in that, The molar ratio of the silica to the water is 1:(20-50).

14. The preparation method according to claim 9, characterized in that, The template agent includes organic amines and / or quaternary ammonium salts.

15. The preparation method according to claim 9, characterized in that, The fluorine complex includes any one or more of sodium hexafluorophosphate, sodium hexafluoroacetylacetonate, or ammonium fluoride.

16. The preparation method according to claim 1, characterized in that, The drying temperature is 80-200℃, and the time is 5-20h.

17. The preparation method according to claim 1, characterized in that, The second roasting temperature is 300-600℃, and the time is 2-10h.

18. The preparation method according to claim 1, characterized in that, The silicon source includes one or more of silica sol, tetraethyl orthosilicate, coarse-porous silica gel, silica powder, fly ash, or silica.

19. The preparation method according to claim 1, characterized in that, The mass concentration of the aluminum source dispersion is 15–99 wt%.

20. The preparation method according to claim 1, characterized in that, The aluminum source includes one or more of sodium aluminate, boehmite, aluminum sulfate, or aluminum nitrate.

21. The preparation method according to claim 1, characterized in that, In step S2), the stirring temperature is 20–100°C and the stirring time is 0.1–24 h.

22. The preparation method according to claim 1, characterized in that, In step S3), the temperature of the second crystallization treatment is 20 to 100°C higher than the temperature of the first crystallization treatment.

23. The preparation method according to claim 22, characterized in that, The temperature of the first crystallization treatment is 20~60℃, and the time is 10~18h.

24. The preparation method according to claim 22, characterized in that, The second crystallization treatment is carried out at a temperature of 80–120°C for a time of 6–48 hours.

25. The preparation method according to claim 1, characterized in that, The components in the crystallized product include silicon dioxide, aluminum oxide, sodium oxide, and water.

26. The preparation method according to claim 25, characterized in that, The molar ratio of silicon dioxide to aluminum oxide is 0.01~2.5:

1.

27. The preparation method according to claim 25, characterized in that, The molar ratio of sodium oxide to silicon dioxide is 0.01 to 4.0:

1.

28. The preparation method according to claim 25, characterized in that, The molar ratio of water to silica is 1.0 to 40.0:

1.

29. The preparation method according to claim 1, characterized in that, The aging process is carried out at a temperature of 20~100℃ for a time of 0.1~24h.

30. The preparation method according to claim 1, characterized in that, The third crystallization treatment is performed at a temperature of 60~105℃ for a time of 0.1~36h.

31. The preparation method according to claim 1, characterized in that, The mass ratio of the crystallized product to the gel mother liquor is 5-20:

100.

32. The preparation method according to claim 1, characterized in that, The mass ratio of the inorganic waste to the flux is 1:0.5-1:

5.

33. The preparation method according to claim 1, characterized in that, The third roasting temperature is 550-800℃, and the time is 60-120 minutes.

34. The preparation method according to claim 1, characterized in that, The mass concentration of the acid solution is 10%-35%.

35. The preparation method according to claim 1, characterized in that, The flux includes sodium carbonate and / or sodium sulfate.

36. The preparation method according to claim 1, characterized in that, The acid in the acid solution is a monoprotic acid.

37. The preparation method according to claim 1, characterized in that, The acid solution includes hydrochloric acid and / or nitric acid.

38. The preparation method according to claim 1, characterized in that, The alkali in the alkaline solution includes sodium hydroxide and / or potassium hydroxide.

39. The preparation method according to claim 1, characterized in that, The mass ratio of the first filtrate to the second filtrate is 1:(2.5 to 5.5).

40. The preparation method according to claim 1, characterized in that, The components of the gel mother liquor include silica, aluminum oxide, sodium oxide, and water.

41. The preparation method according to claim 40, characterized in that, The molar ratio of silicon dioxide to aluminum oxide is (0.5–6.0):

1.

42. The preparation method according to claim 40, characterized in that, The molar ratio of sodium oxide to silicon dioxide is (0.5–6.0):

1.

43. The preparation method according to claim 40, characterized in that, The molar ratio of water to silicon dioxide is (10-100):

1.

44. The preparation method according to claim 1, characterized in that, The 13X molecular sieve with a core-shell structure has a silicon-to-aluminum ratio of 2.4 to 3.1 and a pore volume of 0.37 to 0.58 cm³. 3 / g, specific surface area is 850~1000m² 2 / g.

45. A method for preparing a 13X molecular sieve with a core-shell structure according to any one of claims 1-44, characterized in that, The 13X molecular sieve with a core-shell structure has a silicon-to-aluminum ratio of 2.4 to 3.1 and a pore volume of 0.37 to 0.58 cm³. 3 / g, specific surface area is 850~1000m² 2 / g.

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