Y molecular sieve rich in lanthanum element in supercage and preparation method thereof
By treating with ammonia water and controlling the calcination process, the migration of lanthanum during the calcination of Y molecular sieve is suppressed, and a Y molecular sieve rich in lanthanum in the super cage is achieved, which solves the problem of lanthanum migration and improves the catalytic activity.
Patent Information
- Application Number
- CN202510825777.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-19
- Publication Date
- 2025-09-26
AI Technical Summary
The existing technology is difficult to effectively inhibit the migration of lanthanum elements from supercages to sodalite cages during the calcination of Y molecular sieves, resulting in the difficulty of enriching lanthanum species in supercages, thus affecting their catalytic activity.
Lanthanum salt solution and ammonium-type Y molecular sieve are treated with an ammonia solution to generate lanthanum hydroxylate species. By controlling the heating rate and atmosphere during the calcination process, the migration of lanthanum elements is suppressed and retained in the super cage.
The efficient loading of lanthanum elements in the supercage was achieved, which significantly improved the catalytic efficiency of Y molecular sieve and the utilization rate of lanthanum elements, and enhanced the activity of the catalytic reaction.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a Y molecular sieve rich in lanthanum in a super cage and a preparation method thereof. Background Art
[0002] Lanthanum-modified Y zeolite exhibits remarkable catalytic activity in a variety of important catalytic reactions, including fluid catalytic cracking, plastic degradation, alkylation, and hydroisomerization. Lanthanum loading within the sodalite cages of the Y zeolite overcomes its inherent stability, particularly during zeolite pretreatment, catalytic reactions involving high-temperature hydrothermal conditions, and catalyst regeneration. This reduces the detachment of framework aluminum species under hydrothermal conditions and maximizes the retention of the zeolite framework. Furthermore, the lanthanum species within the supercages can enhance the reactivity of the Y zeolite in various catalytic reactions and alter product selectivity. The lanthanum ions within the Y zeolite supercages act as important active sites or synergistic active sites by synergistically polarizing the C-H bonds of alkane molecules during catalytic reactions, thereby enhancing the rate of hydrogen transfer reactions.
[0003] Lanthanum-loaded Y molecular sieves are now widely used in industry. Numerous studies have reported on the loading process of lanthanum species. It is generally believed that after hydrothermal ion exchange, lanthanum species first enter the Y molecular sieve supercage to form hydrated lanthanum ions. During the subsequent heating process, the hydrated lanthanum ions shed their hydration shells and migrate into the sodalite cages. This migration of lanthanum species is highly beneficial for improving the stability of Y molecular sieves. Studies have focused on the stabilization mechanism of lanthanum species within the sodalite cages, including their structure and interactions with the framework. However, less research has been conducted on catalytically active lanthanum species. However, lanthanum has abundant d-orbitals, which can bind to olefins, acetylenes, and aromatic compounds through d-π coordination, making it a potential active or synergistic site for catalytic reactions. Therefore, leveraging the catalytic activity of lanthanum is crucial for further improving reaction activity.
[0004] For lanthanum-loaded Y molecular sieves, on the one hand, due to the migration characteristics of lanthanum species, it is difficult for them to settle in the supercage. On the other hand, the supercage space of Y molecular sieve is limited, and only a certain amount of hydrated lanthanum ions (about 9.8wt%) can be loaded during ion exchange, which is much less than the maximum lanthanum loading capacity (about 19.5wt%) that can be accommodated by the theoretical sodalite cage. Further increasing the concentration of the lanthanum salt solution before loading also makes it difficult for lanthanum species to settle in the supercage. Therefore, in order to give full play to the catalytic properties of lanthanum species in lanthanum-loaded Y molecular sieves, it is urgent to develop a preparation method to inhibit the migration of lanthanum elements from the supercage to the sodalite cage during the calcination process, and retain them in the supercage that the reaction molecules can access. Summary of the Invention
[0005] Based on the above-mentioned prior art, the present invention provides a Y molecular sieve rich in lanthanum in a supercage and a preparation method thereof. The preparation method of the Y molecular sieve of the present invention is simple and easy to operate. More importantly, the method can effectively inhibit the migration of lanthanum from the supercage to the sodalite cage during the calcination process, thereby obtaining a Y molecular sieve rich in lanthanum in the supercage, which has broad application prospects in catalytic reactions such as alkane conversion.
[0006] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:
[0007] A method for preparing a Y molecular sieve rich in lanthanum in a super cage comprises the following steps:
[0008] S1. Disperse ammonium-type Y molecular sieve in a lanthanum salt solution, stir at 60-100° C. for 2-12 hours, filter, and dry to obtain solid powder A;
[0009] S2. Dispersing solid powder A in aqueous ammonia solution, stirring at room temperature for 2-24 hours, filtering, and drying to obtain solid powder B;
[0010] S3. calcining the solid powder B at 400-800° C. to obtain a Y molecular sieve rich in lanthanum in the super cage.
[0011] Furthermore, the lanthanum salt is selected from at least one of lanthanum nitrate, lanthanum sulfate, and lanthanum halide.
[0012] Furthermore, the lanthanum halide is selected from at least one of lanthanum chloride, lanthanum bromide and lanthanum iodide.
[0013] Furthermore, the concentration of the lanthanum salt solution is 0.01-1M.
[0014] Furthermore, the mass ratio of the lanthanum element to the NH4Y molecular sieve is 0.001-0.5.
[0015] Furthermore, the heating rate during the calcination is 1-20°C / min.
[0016] Furthermore, the concentration of the ammonia water is 0.1-5M, and the mass ratio of the ammonia water to the molecular sieve is 1-100.
[0017] A Y molecular sieve rich in lanthanum in a super cage prepared by any of the above methods.
[0018] Compared with the prior art, the advantages and beneficial effects of the present invention are:
[0019] 1. The present invention proposes for the first time that during the loading process of lanthanum, ammonia solution is used to react with hydrated lanthanum ions in the supercage to generate hydroxylated lanthanum species. This inhibits the migration of lanthanum ions during the subsequent calcination process, adjusts the location of lanthanum on the Y molecular sieve, and retains the lanthanum species in the supercage space accessible to the reactive molecules, thereby obtaining a Y molecular sieve rich in lanthanum in the supercage.
[0020] 2. The method of the present invention can effectively inhibit the migration of lanthanum from the supercage to the sodalite cage during the calcination process, thereby obtaining a Y molecular sieve rich in lanthanum in the supercage, effectively improving the utilization rate of lanthanum, and further exerting the catalytic effect of lanthanum, thereby significantly improving the catalytic efficiency of the Y molecular sieve.
[0021] 3. The method of the present invention is simple to operate, easy to operate and implement, highly practical, and can be promoted and applied on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 The Y molecular sieve prepared in Examples 1-3 and Comparative Example 2 1 H- 139 La S-RESPDOR NMR spectrum.
[0023] Figure (1a) shows the Y molecular sieve OH-8La-Y-SA prepared in Example 1. 1 H- 139 La S-RESPDOR NMR spectrum; Figure (1b) Y molecular sieve OH-8La-Y-FN prepared in Example 2 1 H- 139 La S-RESPDOR NMR spectrum; Figure (1c) is the Y molecular sieve OH-21La-Y-FN prepared in Example 3 1 H- 139 La S-RESPDOR NMR spectrum; Figure (1d) is the Y molecular sieve 8La-Y-ref prepared in Comparative Example 1 1 H- 139 La S-RESPDOR NMR spectrum. DETAILED DESCRIPTION
[0024] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.
[0025] The preparation method of a lanthanum (La)-modified Y molecular sieve with high catalytic activity and its application are described in detail below with reference to the accompanying drawings.
[0026] The NH4Y molecular sieve used in the following examples and comparative examples was prepared by ion exchange between commercial Na-Y molecular sieve and ammonium chloride solution. The specific method is as follows: 1. Disperse 1 g of commercial NaY molecular sieve in 30 mL of 1 M ammonium chloride solution to obtain a mixed solution. The mixed solution is stirred in a 90°C oil bath for 6 h, filtered, and dried to obtain a solid powder. 2. Repeat the treatment of the solid powder according to step 1 twice to obtain NH4Y molecular sieve.
[0027] Example 1
[0028] 1. Disperse 4 g of NH4Y molecular sieve in 40 mL of 0.06 M lanthanum nitrate solution to obtain a mixed solution. Place the mixed solution in a 90°C oil bath, stir for 4 h, filter, and dry to obtain solid powder A.
[0029] 2. Add 1 g of solid powder A to 30 mL of 0.43 M ammonia solution, stir and disperse evenly, then stir at room temperature for 12 h, filter, and dry to obtain solid powder B.
[0030] 3. Fill the solid powder B into an alumina porcelain boat, place the alumina porcelain boat in a tube furnace, and heat the alumina porcelain boat. The temperature in the alumina porcelain boat is rapidly increased from room temperature to 500°C at a heating rate of 15°C / min, and then the reaction is maintained at 500°C for 4 hours. After the reaction is completed, it is naturally cooled to room temperature to obtain a Y molecular sieve rich in lanthanum in a super cage with a feed mass ratio of lanthanum to NH4Y molecular sieve of 8%, which is marked as OH-8La-Y-SA.
[0031] Comparative Example 1
[0032] 1. Disperse 4 g of NH4Y molecular sieve in 40 mL of 0.06 M lanthanum nitrate solution to obtain a mixed solution. Place the mixed solution in a 90°C oil bath, stir for 4 h, filter, and dry to obtain a solid powder.
[0033] 3. Fill the solid powder into an alumina porcelain boat, place the alumina porcelain boat in a tube furnace, and heat the alumina porcelain boat. The temperature in the alumina porcelain boat is rapidly increased from room temperature to 500°C at a heating rate of 15°C / min, and then the reaction is maintained at 500°C for 4 hours. After the reaction is completed, it is naturally cooled to room temperature. The feed mass ratio of lanthanum element to NH4Y molecular sieve is 8% Y molecular sieve, marked as 8La-Y-ref.
[0034] Example 2
[0035] 1. Disperse 4 g of NH4Y molecular sieve in 40 mL of 0.06 M lanthanum nitrate solution to obtain a mixed solution. Place the mixed solution in a 90°C oil bath, stir for 4 h, filter, and dry to obtain solid powder A.
[0036] 2. Add 1 g of solid powder A to 30 mL of 0.43 M ammonia solution, stir and disperse evenly, then stir at room temperature for 12 h, filter, and dry to obtain solid powder B.
[0037] 3. The solid powder is filled into a quartz tube with ventilation at both ends, and then the quartz tube is placed in a heatable tempered sleeve. Dry high-purity nitrogen is introduced while heating, and the nitrogen flow rate is 80 mL / min. The temperature in the quartz tube is rapidly increased from room temperature to 500°C at a heating rate of 15°C / min. Then, the reaction is maintained at 500°C and nitrogen is circulated for 4 hours. After the reaction is completed, dry circulating gas is continued to be introduced, and it is naturally cooled to room temperature to obtain a Y molecular sieve rich in lanthanum in a super cage with a feed mass ratio of lanthanum to NH4Y molecular sieve of 8%, which is marked as OH-8La-Y-FN.
[0038] Example 3
[0039] 1. Disperse 4 g of NH4Y molecular sieve in 40 mL of 0.15 M lanthanum nitrate solution to obtain a mixed solution. Place the mixed solution in a 90°C oil bath, stir for 4 h, filter, and dry to obtain solid powder A.
[0040] 2. Add 1 g of solid powder A to 30 mL of 0.43 M ammonia solution, stir and disperse evenly, then stir at room temperature for 12 h, filter, and dry to obtain solid powder B.
[0041] 3. The solid powder is filled into a quartz tube with ventilation at both ends, and then the quartz tube is placed in a heatable tempered sleeve. Dry high-purity nitrogen is introduced while heating, and the nitrogen flow rate is 80 mL / min. The temperature in the quartz tube is rapidly increased from room temperature to 500°C at a heating rate of 15°C / min. Then, the reaction is maintained at 500°C and nitrogen is circulated for 4 hours. After the reaction is completed, dry circulating gas is continued to be introduced, and it is naturally cooled to room temperature to obtain a Y molecular sieve rich in lanthanum in a super cage with a feed mass ratio of lanthanum to NH4Y molecular sieve of 20%, which is marked as OH-20La-Y-FN.
[0042] Example 4
[0043] 1. Disperse 4 g of NH4Y molecular sieve in 40 mL of 0.02 M lanthanum nitrate solution to obtain a mixed solution. Place the mixed solution in a 90°C oil bath, stir for 4 h, filter, and dry to obtain solid powder A.
[0044] 2. Add 1 g of solid powder A to 30 mL of 0.43 M ammonia solution, stir and disperse evenly, then stir at room temperature for 12 h, filter, and dry to obtain solid powder B.
[0045] 3. The solid powder is filled into a quartz tube with ventilation at both ends, and then the quartz tube is placed in a heatable tempered sleeve. Dry high-purity nitrogen is introduced while heating, and the nitrogen flow rate is 80 mL / min. The temperature in the quartz tube is rapidly increased from room temperature to 500°C at a heating rate of 15°C / min. Then, the reaction is maintained at 500°C and nitrogen is circulated for 4 hours. After the reaction is completed, dry circulating gas is continued to be introduced, and it is naturally cooled to room temperature to obtain a Y molecular sieve rich in lanthanum in a super cage with a feed mass ratio of lanthanum to NH4Y molecular sieve of 2%, which is marked as OH-2La-Y-FN.
[0046] The Y molecular sieves prepared in Examples 1-3 and Comparative Example 1 were subjected to 1H-139La S-RESPDOR nuclear magnetic resonance experiments. After sampling, two 1H NMR spectra were extracted (NMR spectra of the 139La channel before and after saturation radio frequency pulse irradiation, S0 and S), and a difference spectrum ΔS=S0-S was obtained, i.e., the 1H-139La S-RESPDOR NMR spectrum. The obtained 1H-139La S-RESPDOR NMR spectrum is shown in FIG. Figure 1 As shown by Figure 1 It can be seen that the lanthanum species on the Y molecular sieve prepared in Examples 1-3 have a strong correlation with the B acid site (3.8ppm) in the super cage ( Figure 1 a, 1b, 1c), indicating that after ammonia treatment, the lanthanum species are located in the supercage of the Y molecular sieve. In contrast, the lanthanum species on the 8La-Y-SA molecular sieve obtained by the conventional method in Comparative Example 1 have almost no correlation with the B acid sites within the supercage. Instead, they migrate to the sodalite cage, where the reactants cannot reach, to form La-OH species (5.7 ppm). These results indicate that ammonia treatment inhibits the migration of lanthanum, resulting in a Y molecular sieve rich in lanthanum species within the supercage.
[0047] Experiment 1: Catalytic activity test of the Y molecular sieve rich in lanthanum in the super cage of the present invention
[0048] Experimental methods:
[0049] 1. The lanthanum-modified Y molecular sieve prepared in Example 2 was filled into a quartz glass tube, and a n-hexane cracking reaction was carried out in a fixed-bed reactor connected to a gas chromatograph detector. The concentration of n-hexane in the product after cracking at 600°C was detected by a gas chromatograph detector, and the conversion rate of n-hexane was calculated based on the detection results.
[0050] 2. The Y molecular sieves prepared in Examples 3-4 and Comparative Example 1 were subjected to experiments according to the method of step 1.
[0051] Experimental results:
[0052] The Y molecular sieves prepared in Examples 2-4 and Comparative Example 1 were used as catalysts to conduct n-hexane cracking experiments. The conversion rates of n-hexane are shown in Table 1 below:
[0053] Table 1 Comparison of catalytic activity of Y molecular sieve catalysts with different lanthanum feed ratios for n-hexane cracking
[0054] catalyst Feed value (wt%) n-Hexane conversion OH-2La-Y-FN 2 31.1％ OH-8La-Y-FN 8 47.5％ OH-20La-Y-FN 20 65.7％ 8La-Y-ref 8 19.0％
[0055] As shown in the table above, compared to the Y molecular sieve prepared using the conventional loading method in Comparative Example 1, the lanthanum-modified Y molecular sieve prepared in the present invention, with its lanthanum-rich supercage, significantly improved the conversion of n-hexane when catalyzing the cracking of n-hexane. This demonstrates that the present invention retains the lanthanum species within the supercage, where it is accessible to alkane molecules, allowing the catalytic properties of the lanthanum species to be fully utilized, significantly enhancing the catalytic activity of n-hexane.
Claims
1. A method for preparing a Y molecular sieve rich in lanthanum in a super cage, characterized in that The steps include: S1. Disperse ammonium-type Y molecular sieve in a lanthanum salt solution, stir at 60-100° C. for 2-12 hours, filter, and dry to obtain solid powder A; S2. Dispersing solid powder A in aqueous ammonia solution, stirring at room temperature for 2-24 hours, filtering, and drying to obtain solid powder B; S3. calcining the solid powder B at 400-800° C. to obtain a Y molecular sieve rich in lanthanum in the super cage.
2. The method for preparing a Y molecular sieve rich in lanthanum in a super cage according to claim 1, characterized in that: The lanthanum salt is selected from at least one of lanthanum nitrate, lanthanum sulfate and lanthanum halide.
3. The method for preparing a Y molecular sieve rich in lanthanum in a super cage according to claim 2, characterized in that: The lanthanum halide is selected from at least one of lanthanum chloride, lanthanum bromide and lanthanum iodide.
4. The method for preparing a Y molecular sieve rich in lanthanum in a super cage according to claim 1, characterized in that: The concentration of the lanthanum salt solution is 0.01-1M.
5. The method for preparing a lanthanum (La)-modified Y molecular sieve having high catalytic activity according to claim 1, characterized in that: The mass ratio of the lanthanum element to the NH4Y molecular sieve is 0.001-0.
5.
6. The method for preparing a lanthanum-modified Y molecular sieve having high catalytic activity according to claim 1, wherein: The heating rate during the calcination is 1-20°C / min.
7. The method for preparing a lanthanum-modified Y molecular sieve with high catalytic activity according to claim 1, wherein: The concentration of the ammonia water is 0.1-5M, and the mass ratio of the ammonia water to the molecular sieve is 1-100.
8. The method for preparing the lanthanum-modified Y molecular sieve with high catalytic activity according to claim 1, characterized in that The calcination method comprises the following steps: filling a solid powder into a quartz tube with ventilation at both ends, then heating the quartz tube while introducing dry circulating air, heating the quartz tube to 400-800° C., then maintaining the reaction at 400-800° C. and under the circulating air for 2-24 hours, and after the reaction is completed, continuing to introduce dry circulating air and naturally cooling to obtain a Y molecular sieve rich in lanthanum elements in the super cage.
9. The method for preparing a lanthanum-modified Y molecular sieve having high catalytic activity according to claim 8, characterized in that: The circulating gas is at least one of N2, He, Ar, air, O2, CO2 and CO.
10. A Y molecular sieve rich in lanthanum in a super cage prepared by the method according to any one of claims 1 to 9.