Preparation method of hierarchical pore molecular sieve and characterization method of Ce setting condition in molecular sieve

Abstract

The invention discloses a preparation method of a hierarchical pore molecular sieve and a characterization method of a Ce setting condition in the molecular sieve, relates to the technical field of molecular sieves, and improves the utilization efficiency of rare earth elements in a Y-type molecular sieve. The xCeHY-J takes a hierarchical pore molecular sieve HY-J as a carrier, and the x is equal to 1-5wt% of Ce. The method comprises the following steps: dispersing a NaY molecular sieve in an ethylene diamine tetraacetic acid aqueous solution, refluxing and stirring, then centrifuging, washing and drying, dispersing the obtained solid product in a sodium hydroxide aqueous solution, stirring, then centrifuging, washing and drying, dispersing in an ammonium nitrate aqueous solution, stirring for ion exchange, centrifuging, washing and drying the product, and thus obtaining the product. And dispersing the hierarchical pore HY-J molecular sieve in deionized water, dropwise adding a cerium nitrate aqueous solution, stirring, drying by distillation, and calcining to obtain the xCeHY-J molecular sieve. The catalytic cracking catalyst can be applied to a catalytic cracking process in a crude oil secondary processing technical system.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a method for preparing a multi-level pore molecular sieve and a method for characterizing the Ce location in the molecular sieve. Background Art

[0002] In the crude oil secondary processing technology system, catalytic cracking process occupies a dominant position. Its catalyst active component, Y-type molecular sieve, relies on rare earth modification to improve hydrothermal stability, resistance to heavy metal pollution and cracking activity.

[0003] Although rare earth-modified molecular sieves such as REHY are widely used in catalytic cracking processes, their micropore-dominated pore systems present significant limitations. Narrow micropores hinder mass transfer of heavy oil macromolecules, reducing accessibility to active sites; restricted pores easily lead to carbon deposition and catalyst deactivation; and during conventional ion exchange, hydrated rare earth ions have difficulty entering the small cages and can only exchange for supercage sodium ions, requiring multiple "exchange-calcination" cycles and resulting in low efficiency. Chinese patent document CN119746919A provides a method for preparing a multi-level pore composite molecular sieve ZSM-5, which effectively enhances the catalyst's acidic sites and the diffusion of substrate and product molecules during the reaction, improving reaction conversion and suppressing coke formation. However, this method is specific to ZSM-5 molecular sieves and is not applicable to Y molecular sieves. Furthermore, Chinese patent document CN116262623A discloses a metal-modified, high-silicon Y molecular sieve with a multi-level pore structure that exhibits high catalytic activity in catalytic cracking reactions. However, this method involves a dealumination step, which significantly depletes the acidic sites of the molecular sieve itself.

[0004] Etching treatment will cause the molecular sieve to produce a certain multi-level pore structure, which significantly improves the accessibility of heavy oil macromolecules to the active center, while also enhancing the diffusion of products and inhibiting coke formation. Therefore, the preparation of multi-level pore rare earth molecular sieve catalysts through etching treatment not only greatly reduces the amount of rare earth elements used, but also improves the catalytic efficiency, which will promote the advancement of catalytic cracking catalysts, improve the efficiency of oil refining enterprises, and help my country achieve its "carbon emission reduction" goals smoothly. The distribution characteristics of rare earth elements and their placement behavior in the molecular sieve framework are key factors affecting catalyst performance. However, due to the complex orbital charge structure of rare earth ions, the current understanding of the structural information and structure-activity relationship of rare earth molecular sieves after etching is not in-depth, the rare earth loading efficiency is not high, and the imprecise control of rare earth ion placement has restricted further improvement of catalyst performance. Summary of the Invention

[0005] In order to improve the utilization efficiency of rare earth elements in Y-type molecular sieves and promote the advancement of catalytic cracking catalysts, the present invention proposes a method for preparing multi-level pore molecular sieves and a method for characterizing the Ce location in molecular sieves.

[0006] The technical solutions of the present invention are as follows: An xCeHY-J molecular sieve, wherein the xCeHY-J uses a multi-level pore molecular sieve HY-J as a carrier and is loaded with Ce in an amount of x=1-5wt%; The multi-level pore molecular sieve HY-J is obtained by sequentially treating NaY molecular sieve with ethylenediaminetetraacetic acid, sodium hydroxide and ammonium nitrate.

[0007] Preferably, the silicon-aluminum ratio of the multi-level pore molecular sieve HY-J is SiO2 / Al2O3=1.0~10.0.

[0008] The present invention also provides a method for preparing the above-mentioned xCeHY-J molecular sieve, comprising the following steps: S1. Dispersing NaY molecular sieves in an ethylenediaminetetraacetic acid aqueous solution, refluxing and stirring, and then centrifuging, washing, and drying to obtain a solid product; S2, dispersing the solid product in a sodium hydroxide aqueous solution, stirring, then centrifuging, washing, and drying to obtain a hierarchical pore NaY-J molecular sieve; S3, dispersing the multi-level pore NaY-J molecular sieve in an aqueous ammonium nitrate solution and stirring to perform ion exchange; centrifuging, washing, and drying the product to obtain a multi-level pore HY-J molecular sieve; S4. Disperse the multi-level pore HY-J molecular sieve in deionized water, inject cerium nitrate aqueous solution dropwise, stir and evaporate to dryness in an oil bath, and finally calcine to obtain xCeHY-J molecular sieve.

[0009] Preferably, the molar concentration of the EDTA aqueous solution is 0.01-1 mol / L; and the ratio of the NaY molecular sieve to the EDTA aqueous solution is 1-10 g:100 mL.

[0010] Preferably, the reflux temperature in step S1 is 50-200° C.; and the stirring time is 2-12 h.

[0011] Preferably, the molar concentration of the sodium hydroxide aqueous solution is 0.01-1 mol / L; and the ratio of the solid product to the sodium hydroxide aqueous solution is 1-5 g:50 mL.

[0012] Preferably, the stirring temperature in step S2 is 50-100° C., and the stirring time is 0.5-2 h; and the stirring temperature in step S3 is 50-150° C., and the stirring time is at least 24 h.

[0013] Preferably, the molar concentration of the ammonium nitrate aqueous solution is 0.5-2 mol / L; and the ratio of the multi-level pore NaY-J molecular sieve to the ammonium nitrate aqueous solution is 0.5-2 g:50 mL.

[0014] Preferably, the ratio of the multi-level pore HY-J molecular sieve to deionized water is 400 mg:50 mL.

[0015] Preferably, the stirring time is 2 to 6 hours, the oil bath temperature is 50 to 100° C.; the calcination temperature is 300 to 600° C., and the calcination time is 2 to 5 hours.

[0016] The present invention also provides a method for characterizing the Ce location in a molecular sieve, wherein the molecular sieve is the multi-level pore molecular sieve described above, and the characterization method is specifically as follows: Raman spectroscopy was used to determine that the Y-type molecular sieves were respectively classified as 6-ring II 、6-ring I and the characteristic vibration peaks of the 4-ring vibration mode, and observe whether the characteristic peaks of the samples before and after treatment show a blue shift; if the characteristic peaks blue shift, it is judged that the introduction of Ce species has enhanced the repulsion between atoms in the limited SOD cage space of the molecular sieve, and the molecular sieve framework has undergone local structural distortion; if the characteristic peak position is stable, it is judged that the multi-level pore structure has expanded the pore space of the molecular sieve, providing a suitable coordination environment for the Ce species; or: The X-ray diffraction technique was used to determine the characteristic peaks of the (311) and (222) planes of the Y molecular sieve in the XRD patterns within the range of 11°~13°. The intensities of the two peaks were used to determine the placement of the rare earth ions in the SOD cage and supercage of the Y molecular sieve. The proportion of rare earth ions in the supercage was calculated as I 12.4° / I (12.4°+11.8°) .

[0017] Compared with the prior art, the present invention has the following specific beneficial effects: This invention innovatively uses a directional etching method to prepare a multi-level pore xCeHY-J zeolite. The open pore structure improves the positioning accuracy of rare earth elements in the supercage, achieving the first selective enrichment of rare earth Ce species in the Y-type zeolite supercage. This overcomes the uncontrollable rare earth distribution limitations of traditional ion exchange methods, reduces the amount of rare earth in the catalyst by 10% to 30%, and significantly alleviates the supply and demand contradiction of rare earth resources. The introduction of a multi-level pore structure effectively expands the pore space of the zeolite, providing a more suitable coordination environment for the stable existence of rare earth ions, thereby ensuring the stability of the zeolite structure. XRD analysis results show that the etching treatment significantly increases the relative content of Ce species in the zeolite supercage. Raman spectroscopy characterization shows that the introduction of Ce species causes significant structural ring distortion in the unetched zeolite, but has little effect on the skeleton structure of the etched zeolite. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The scanning electron microscope image of the original microporous NaY molecular sieve was obtained; Figure 2 This is a scanning electron microscope image of the multi-level pore HY-J prepared in Example 1; Figure 3 XRD patterns of conventional hydrogen molecular sieve and hierarchical pore HY-J prepared in Example 1; Figure 4 is the Raman spectrum of the unetched xCeHY sample; Figure 5 is the Raman spectrum of xCeHY-J; Figure 6 XRD spectrum of the unetched xCeHY sample in the range of 11-13°; Figure 7 XRD spectrum of xCeHY-J in the range of 11~13°. DETAILED DESCRIPTION

[0019] In order to make the technical solution of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the specification of the present invention. It should be noted that the following embodiments are only used to better understand the technical solution of the present invention and should not be understood as limiting the present invention.

[0020] Example 1. In this example, 2 g of microporous NaY molecular sieve was dispersed in 100 mL of ethylenediaminetetraacetic acid aqueous solution (0.04 mol / L), refluxed at 100 °C and stirred for 6 h, centrifuged, washed, and dried to obtain a solid product. 1.7 g of the solid product was dispersed in 50 mL of a 0.4 mol / L sodium hydroxide aqueous solution, stirred at 65 °C for 0.5 h, centrifuged, washed, and dried to obtain hierarchical NaY-J. 1 g of NaY-J molecular sieve was dispersed in 50 mL of ammonium nitrate aqueous solution (1 mol / L) and stirred at 80 °C for 24 h for ion exchange. Finally, the solid product was centrifuged, washed, and dried to obtain hierarchical pore HY-J.

[0021] Figure 1 A scanning electron micrograph of a pristine microporous NaY molecular sieve shows a typical NaY molecular sieve in its native state, with a dense, blocky structure and a smooth surface, free of visible pores or cracks. No micropores (<2 nm) are visible at the 200 nm scale, confirming the material's pure microporous nature. Micropores are invisible at the SEM's resolution limit. Figure 2 This is a scanning electron microscope image of the multi-level porous HY-J prepared in Example 1. It can be seen that the surface of the particles is significantly roughened, and a large number of holes and concave-convex structures appear, indicating the formation of a multi-level porous structure.

[0022] Figure 3The XRD patterns of a conventional hydrogen-type molecular sieve and the hierarchical pore HY-J prepared in Example 1 are shown. The characteristic peaks of the NaY standard card (PDF#38-0239) are clearly visible in both the HY and HY-J curves, demonstrating that the modification in Example 1 did not destroy the framework structure of the Y-type molecular sieve. The decreased intensity of the HY-J peak indicates that the etching treatment caused the formation of hierarchical pores and lattice distortion.

[0023] Example 2. 400 mg of the HY-J molecular sieve prepared in Example 1 was dispersed in 50 mL of water, and 10 mL of a 0.003 mol / L cerium nitrate aqueous solution (the amount of Ce introduced was 1 wt %) was added dropwise. After stirring for 6 h, the mixture was evaporated to dryness in an 80°C oil bath, and then calcined at 400°C for 2 h to obtain 1CeHY-J molecular sieve.

[0024] Example 3. 400 mg of the HY-J molecular sieve prepared in Example 1 was dispersed in 50 mL of water, and 10 mL of a 0.009 mol / L cerium nitrate aqueous solution (the amount of Ce introduced was 3 wt %) was added dropwise. After stirring for 6 h, the mixture was evaporated to dryness in an 80°C oil bath, and then calcined at 400°C for 2 h to obtain 3CeHY-J molecular sieve.

[0025] Example 4. 400 mg of the HY-J molecular sieve prepared in Example 1 was dispersed in 50 mL of water, and 10 mL of a 0.015 mol / L cerium nitrate aqueous solution (the amount of Ce introduced was 5 wt %) was added dropwise. After stirring for 6 h, the mixture was evaporated to dryness in an 80°C oil bath, and then calcined at 400°C for 2 h to obtain 5CeHY-J molecular sieve.

[0026] Comparative Example 1. In this comparative example, 1 g of NaY molecular sieve was dispersed in 50 mL of ammonium nitrate aqueous solution (1 mol / L) and stirred at 80 °C for 24 h for ion exchange. Finally, the solid product was centrifuged, washed, and dried to obtain HY.

[0027] Comparative Example 2. 400 mg of the HY molecular sieve prepared in Comparative Example 1 was dispersed in 50 mL of water, and 10 mL of a 0.003 mol / L cerium nitrate aqueous solution (the amount of Ce introduced was 1 wt %) was added dropwise. After stirring for 6 h, the mixture was evaporated to dryness in an 80 °C oil bath, and then calcined at 400 °C for 2 h to obtain 1CeHY molecular sieve.

[0028] Comparative Example 3. 400 mg of the HY molecular sieve prepared in Comparative Example 1 was dispersed in 50 mL of water, and 10 mL of a 0.009 mol / L cerium nitrate aqueous solution (the amount of Ce introduced was 3 wt %) was added dropwise. After stirring for 6 h, the mixture was evaporated to dryness in an 80°C oil bath, and then calcined at 400°C for 2 h to obtain 3CeHY molecular sieve.

[0029] Comparative Example 4. 400 mg of the HY molecular sieve prepared in Comparative Example 1 was dispersed in 50 mL of water, and 10 mL of a 0.015 mol / L cerium nitrate aqueous solution (the amount of Ce introduced was 5 wt %) was added dropwise. After stirring for 6 h, the mixture was evaporated to dryness in an 80°C oil bath, and then calcined at 400°C for 2 h to obtain 5CeHY molecular sieve.

[0030] Test example. Raman spectroscopy and X-ray diffraction (XRD) techniques were used to analyze the effect of the etching process on the Ce placement in the molecular sieve in the above embodiment: Method 1: Raman spectroscopy: Raman spectroscopy was used to systematically study the effect of etching treatment on the structure of molecular sieves with different Ce contents. -1 The characteristic vibration peaks of Y-type molecular sieves are respectively attributed to the 6-ring of the double six-membered ring (D6R) structure. II 、6-ring I and 4-ring vibration modes. With the increase of Ce content, the characteristic peaks of the unetched xCeHY sample show a slight blue shift, such as Figure 4 This is because the introduction of Ce species in the limited SOD cage space of the unetched molecular sieve enhances the repulsion between atoms, resulting in local structural distortion of the molecular sieve framework. In contrast, with the increase of Ce content, the Raman characteristic peak position of the xCeHY-J molecular sieve sample after etching remains relatively stable, and no obvious displacement phenomenon is observed, as shown in Figure 2. Figure 5 This result shows that the multi-level pore structure formed by etching effectively expands the pore space of the molecular sieve, providing a more suitable coordination environment for Ce species, thereby avoiding significant changes in the framework structure.

[0031] Method 2: X-ray diffraction (XRD) technology: The X-ray diffraction (XRD) technique was used to analyze the placement of Ce species in the Y molecular sieve before and after etching. In the XRD spectrum within the range of 11°-13°, the peaks at 11.8° and 12.4° are attributed to the (311) and (222) planes of the Y molecular sieve, respectively. The intensities of the two are often used to determine the placement of rare earth ions in the SOD cage and supercage of the Y molecular sieve. The proportion of rare earth ions in the supercage is expressed as I 12.4° / I(12.4°+11.8°) express. Figure 6 The XRD spectrum of xCeHY in the range of 11-13° is shown. It is found that when the Ce content is 1 wt% (1CeHY), only 2 θ =11.8°, indicating that Ce species preferentially occupy the SOD cage of Y molecular sieve. As the Ce content increases from 3 wt% (3Ce-HY) to 5 wt% (5CeHY), 2 θ =12.4° gradually increases, and the proportion of rare earth ions in the supercage also increases from 3.5% to 18.6%, indicating that Ce species fills up SOD and begins to distribute in the supercage. Figure 7 As shown in the figure, for the xCeHY-J system, when the Ce content is as low as 1 wt% (1CeHY-J), the proportion of Ce ions in the supercage is as high as 6.5%, which is even 1.86 times that of the unetched 3CeHY. This shows that the etching destroys the SOD cage structure of the Y molecular sieve, resulting in limited migration of Ce ions to the SOD cage, and they can only be more distributed in the supercage. With the increase of Ce content, the proportion of Ce ions in the supercage in 3CeHY-J is 18.7%, which is comparable to the 18.6% in 5CeHY. In 5CeHY-J, the proportion of Ce ions in the supercage is as high as 31.1%, which shows that the etching treatment increases the proportion of rare earth species in the supercage.

[0032] Table 1

[0033] Note: The proportion of rare earth ions in the supercage is expressed in I 12.4° / I (12.4°+11.8°) express.

[0034] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A multi-level pore molecular sieve, characterized in that: The multi-level pore molecular sieve uses the multi-level pore HY-J molecular sieve as a carrier and loads 1-5 wt% of Ce; The multi-level pore HY-J molecular sieve is obtained by sequentially treating NaY molecular sieve with ethylenediaminetetraacetic acid, sodium hydroxide and ammonium nitrate.

2. A method for preparing a multi-level pore molecular sieve according to claim 1, characterized in that: The steps include: S1. Dispersing NaY molecular sieves in an ethylenediaminetetraacetic acid aqueous solution, refluxing and stirring, and then centrifuging, washing, and drying to obtain a solid product; S2, dispersing the solid product in a sodium hydroxide aqueous solution, stirring, then centrifuging, washing, and drying to obtain a hierarchical pore NaY-J molecular sieve; S3, dispersing the multi-level pore NaY-J molecular sieve in an aqueous ammonium nitrate solution and stirring to perform ion exchange; Finally, the solid product is centrifuged, washed, and dried to obtain the hierarchical pore HY-J molecular sieve; S4. Disperse the multi-level pore HY-J molecular sieve in deionized water, inject cerium nitrate aqueous solution dropwise, stir and evaporate to dryness in an oil bath, and finally calcine to obtain the multi-level pore xCeHY-J molecular sieve.

3. The method for preparing a multi-level pore molecular sieve according to claim 2, characterized in that: The molar concentration of the ethylenediaminetetraacetic acid aqueous solution is 0.01-1 mol / L; the ratio of the NaY molecular sieve to the ethylenediaminetetraacetic acid aqueous solution is 1-10 g:100 mL.

4. The method for preparing a multi-level pore molecular sieve according to claim 2, wherein: The molar concentration of the sodium hydroxide aqueous solution is 0.01-1 mol / L; the ratio of the solid product to the sodium hydroxide aqueous solution is 1-5 g:50 mL.

5. The method for preparing a multi-level pore molecular sieve according to claim 2, characterized in that: The reflux temperature in step S1 is 50-200°C; the stirring time is 2-12 hours; the stirring temperature in step S2 is 50-100°C, and the stirring time is 0.5-2 hours; the stirring temperature in step S3 is 50-150°C, and the stirring time is at least 24 hours.

6. The method for preparing a multi-level pore molecular sieve according to claim 2, characterized in that: The molar concentration of the ammonium nitrate aqueous solution is 0.5-2 mol / L; the ratio of the multi-level pore NaY-J molecular sieve to the ammonium nitrate aqueous solution is 0.5-2 g:50 mL.

7. The method for preparing a multi-level pore molecular sieve according to claim 2, characterized in that: The ratio of the multi-level pore HY-J molecular sieve to deionized water is 400 mg:50 mL.

8. The method for preparing a multi-level pore molecular sieve according to claim 2, characterized in that: The stirring time is 2-6 hours, and the temperature of the oil bath is 50-100°C.

9. The method for preparing a multi-level pore molecular sieve according to claim 2, characterized in that: The calcination temperature is 300-600° C., and the calcination time is 2-5 hours.

10. A method for characterizing the Ce location in a molecular sieve, characterized in that: The molecular sieve is the multi-level pore molecular sieve according to claim 1, and the characterization method is specifically: Raman spectroscopy was used to determine that the Y-type molecular sieves were respectively classified as 6-ring II 、6-ring I and the characteristic vibration peaks of the 4-ring vibration mode, and observe whether the characteristic peaks of the samples before and after treatment appear blue-shifted; If the characteristic peak is blue-shifted, it is judged that the introduction of Ce species in the limited SOD cage space of the molecular sieve has enhanced the repulsive effect between atoms, and the molecular sieve framework has undergone local structural distortion; If the characteristic peak position is stable, it is judged that the multi-level pore structure expands the pore space of the molecular sieve and provides a suitable coordination environment for Ce species; or: The X-ray diffraction technique was used to determine the characteristic peaks of the 311 and 222 planes of the Y molecular sieve in the XRD pattern within the range of 11° to 13°. The intensities of the two peaks were used to determine the placement of rare earth ions in the SOD cage and supercage of the Y molecular sieve, and the proportion of rare earth ions in the supercage was calculated as I. 12.4° / I (12.4°+11.8°) .

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