Nanosheet-like afx and cha co-crystal molecular sieve, method for preparing same, and use thereof

Abstract

The application discloses a nanosheet AFX and CHA eutectic molecular sieve, the maximum length of the nanosheet AFX and CHA eutectic molecular sieve is 150-500 nm. The application also discloses a preparation method of the eutectic molecular sieve and application of the eutectic molecular sieve as an adsorbent, a catalyst or a catalyst carrier. The preparation method comprises the following steps: (1) pre-treating a first molecular sieve in both AFX and CHA type molecular sieves to destroy the crystal structure of the first molecular sieve, so as to obtain a first molecular sieve precursor; (2) mixing the first molecular sieve precursor with a synthesis system of a second molecular sieve in both AFX and CHA type molecular sieves to obtain an initial mixture; (3) hydrothermally crystallizing the initial mixture obtained in the step (2) in a reaction kettle, the crystallization temperature is 160-240 DEG C, and the crystallization time is 2-24 h; and (4) after the crystallization is completed, the eutectic molecular sieve is obtained through post-treatment. The preparation method is simple, convenient to operate and capable of quickly synthesizing the nanosheet eutectic molecular sieve.

Description

Technical Field

[0001] This application belongs to the field of molecular sieve synthesis, specifically, it relates to a nanosheet-like AFX and CHA eutectic molecular sieve, its preparation method and application. Background Technology

[0002] The SAPO-n series of molecular sieves were developed by Union Carbide Corporation (UCC) in 1984.<USP 4,440,871> It is composed of [SiO4] 0 [AlO4] - [PO4] + The microporous crystal is composed of three tetrahedral units. Si atoms are isomorphously substituted for some P atoms or simultaneously for P and Al atoms in the neutral aluminum phosphate framework, giving the framework a net negative charge and introducing Brønsted acid centers, thereby endowing SAPO molecular sieves with catalytic and gas adsorption separation properties.

[0003] Aluminosilicate phosphate molecular sieves exhibit diverse structures. Among them, SAPO-56 is a small-pore molecular sieve with an AFX structure, featuring three-dimensional channels with eight-membered rings and a pore size of 0.34 nm × 0.36 nm; its basic structural unit is a double six-membered ring. SAPO-34 molecular sieve has a CHA structure, with double six-membered rings stacked in an ABC configuration to form a three-dimensional intersecting channel structure, with a pore size of 0.38 nm × 0.38 nm.

[0004] Existing technologies disclose the synthesis of SAPO-56 molecular sieves using a single organic template agent, N,N,N',N'-tetramethyl-1,6-hexanediamine (TMHDA). SAPO-56 molecular sieves are widely used in reactions such as cracking, hydrocracking, alkylation, isomerization, polymerization, methanation, and syngas reforming. Currently, research on SAPO-56 molecular sieves is limited. The reported synthesis methods all yield SAPO-56 molecular sieve crystals with micron-sized particles, and require the use of isopropylamine, di-n-butylamine, tripropylamine, etc., as co-template agents, making the synthesis methods complex. A team from Tianjin University proposed a hydrothermal synthesis method for SAPO-56 / SAPO-34 composite molecular sieves using TMDHA and triethylamine, but the particle size remains in the micron-sized range. Summary of the Invention

[0005] To overcome the aforementioned problems in the prior art, this application provides a nanosheet-like AFX and CHA eutectic molecular sieve with nanoscale dimensions.

[0006] Specifically, in a first aspect, this application provides a nanosheet-like AFX and CHA eutectic molecular sieve, wherein the maximum length of the nanosheet-like AFX and CHA eutectic molecular sieve is 150 to 500 nm.

[0007] Optionally, the thickness of the nanosheet-like AFX and CHA eutectic molecular sieve is 50–100 nm.

[0008] Optionally, the nanosheet-like AFX and CHA eutectic molecular sieves are selected from phosphate aluminum sieves and / or silica aluminum sieves having AFX and CHA eutectic molecular sieves.

[0009] Optionally, the X-ray diffraction pattern of the nanosheet-like AFX and CHA eutectic molecular sieve of this application exhibits the characteristic of both broad peaks and sharp peaks.

[0010] Secondly, this application provides a method for preparing the above-mentioned nanosheet-like AFX and CHA eutectic molecular sieves, characterized in that the method includes the following steps:

[0011] (1) Pre-treat the first molecular sieve of AFX and CHA type molecular sieves to destroy its crystal structure in order to obtain the first molecular sieve precursor.

[0012] (2) The first molecular sieve precursor obtained in step (1) is mixed with the synthesis system of the second molecular sieve between AFX and CHA type molecular sieves to obtain an initial mixture, wherein the synthesis system includes water and a template agent for synthesizing the second molecular sieve, which is different from the first molecular sieve.

[0013] (3) The initial mixture obtained in step (2) is subjected to hydrothermal crystallization under autogenous pressure in a reactor at a crystallization temperature of 160–240°C for 2–24 hours; and

[0014] (4) After crystallization, the solid product obtained in step (3) is washed and dried to obtain nanosheet-like AFX and CHA eutectic molecular sieves.

[0015] Optionally, the CHA molecular sieve is selected from at least one of SAPO-34 and SSZ-13, wherein the SAPO-34 has a silicon content (i.e., the mass content of SiO2 in the SAPO-34 molecular sieve) of 7% to 20%, and the SSZ-13 has a silicon-to-aluminum ratio (i.e., SiO2 / Al2O3) of 23 to 96.

[0016] Optionally, the AFX molecular sieve is selected from at least one of SAPO-56 and SSZ-16, wherein the SAPO-56 has a silicon content of 16% to 25% (i.e., the mass content of SiO2 in the SAPO-56 molecular sieve) and the SSZ-16 has a silicon-to-aluminum ratio (i.e., SiO2 / Al2O3) of 8 to 10.

[0017] Optionally, in step (1), before ball milling the first molecular sieve, the first molecular sieve is mixed with a liquid medium, wherein the mass ratio of the first molecular sieve to the liquid medium is 1:2 to 5.

[0018] Optionally, the first molecular sieve is calcined at 500-800°C and then pretreated to destroy its crystal structure.

[0019] In this application, the crystallization process is carried out under static conditions. Specifically, this means that during the crystallization process, the reactor containing the initial mixture is placed in an oven without stirring the mixture inside the reactor.

[0020] Optionally, the crystallization temperature is any value or a range determined by any two of 160°C, 200°C, and 240°C.

[0021] Optionally, the crystallization time is any value or a range determined by any two of the following: 2 hours, 7 hours, 19 hours, and 24 hours.

[0022] Optionally, the pretreatment includes ball milling, acid treatment, alkali treatment, a combination of ball milling and acid treatment, or a combination of ball milling and alkali treatment.

[0023] Optionally, the acid used in the acid treatment is H3PO4.

[0024] Optionally, the alkali used in the alkali treatment is diethylamine.

[0025] Optionally, the ball milling conditions are as follows: the first molecular sieve is dispersed in a liquid medium and ball milled in a ball mill at a speed of 500-600 rpm for 5-9 hours.

[0026] Optionally, the rotational speed is a range determined by any two values ​​among 500 rpm, 550 rpm, and 600 rpm.

[0027] Optionally, the ball milling time is a range determined by any two of the following: 5 hours, 6 hours, 7 hours, and 9 hours.

[0028] Optionally, the organic template agent R in step (2) is a template agent for synthesizing AFX, which is N,N,N',N'-tetramethyl-1,6-hexanediamine.

[0029] Optionally, the organic template agent R in step (2) is a template agent for the synthesis of CHA, which is selected from at least one of adamantane, N,N'-diisopropylethylamine, cyclohexylimine, morpholine, diethylamine, pyridine, piperidine, cyclohexylamine, tetramethylammonium hydroxide, triethylamine, imidazole, methylimidazole, piperazine, and ethylenediamine.

[0030] Optionally, in step (2), the mass ratio of each component in the initial mixture is: first molecular sieve precursor: H2O: organic template agent R = 1: 1~10: 0.1~10.

[0031] Optionally, in step (2), the mass ratio of each component in the initial mixture is, that is, the mass ratio of the first molecular sieve precursor: H2O: organic template agent R is any value or any two values ​​determined by the range of 1:1:0.1, 1:1:10, 1:10:0.1, 1:10:10, 1:10:1, 1:5:1 and 1:4:4.

[0032] Optionally, in step (2), the synthesis system of the second molecular sieve of the AFX and CHA type molecular sieves also contains additional silicon source and / or aluminum source and / or phosphorus source, and the molar ratio of each component in the synthesis system is: SiO2:Al2O3:P2O5:R:H2O=0~0.6:0~1.0:0~0.8:1~10:1~50.

[0033] Optionally, in step (2), the synthesis system of the second molecular sieve of the AFX and CHA type molecular sieves also contains additional aluminum and phosphorus sources, and the molar ratio of each component in the synthesis system is: Al2O3:P2O5:R:H2O=1.0:0.8:2.0:50.

[0034] Optionally, in step (2), the synthesis system of the second molecular sieve of the AFX and CHA type molecular sieves also contains additional silicon source, aluminum source and phosphorus source, and the molar ratio of each component in the synthesis system is: SiO2:Al2O3:P2O5:R:H2O=0.6:1.0:0.8:2.0:50.

[0035] Optionally, in step (2), the content of the first molecular sieve precursor in the initial mixture is 20 wt% to 90 wt% of the sum of the mass of the additional silicon source and / or aluminum source and / or phosphorus source; wherein the mass of the silicon source, aluminum source and phosphorus source is the sum of the mass of SiO2, Al2O3 and P2O5 contained therein.

[0036] Optionally, in step (2), the content of the first molecular sieve precursor in the initial mixture is any value or a range determined by any two of the following: 20 wt%, 50 wt%, 70 wt%, and 90 wt% of the sum of the masses of the additional silicon source and / or aluminum source and / or phosphorus source; wherein the mass of the silicon source, aluminum source, and phosphorus source is the sum of the masses of SiO2, Al2O3, and P2O5 contained therein.

[0037] Optionally, in step (2), the additional silicon source is selected from at least one of tetraethyl orthosilicate, silica sol, silica gel, silica fume, silica, water glass, and diatomaceous earth.

[0038] Optionally, the additional aluminum source is at least one of boehmite, aluminum isopropoxide, sodium aluminate, aluminum foil, aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum hydroxide.

[0039] Optionally, the additional phosphorus source is at least one of phosphoric acid and ammonium dihydrogen phosphate.

[0040] Thirdly, this application provides the application of the above-mentioned nano-AFX and CHA eutectic molecular sieves and / or nano-AFX and CHA eutectic molecular sieves prepared according to the above method as adsorbents, catalysts or catalyst supports.

[0041] The beneficial effects that this application may produce include at least the following:

[0042] (1) The nanosheet-like AFX and CHA eutectic molecular sieves provided in this application provide a basis for industrial applications.

[0043] (2) The preparation method of nanosheet AFX and CHA eutectic molecular sieve provided in this application not only has the advantages of simple process, convenient operation and large-scale industrial production, but also has the advantages of short crystallization time and high yield. Attached Figure Description

[0044] Figure 1 The image shows the X-ray diffraction pattern of sample 1.

[0045] Figure 2 This is a scanning electron microscope image of sample 1.

[0046] Figure 3 The image shows the X-ray diffraction pattern of sample 6.

[0047] Figure 4 This is a scanning electron microscope image of sample 7. Detailed Implementation

[0048] The present application is further illustrated below with reference to specific embodiments. The following descriptions are merely a few embodiments of the present application and are not intended to limit the present application in any way. Although the present application discloses preferred embodiments as follows, they are not intended to limit the present application. Any modifications or variations made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

[0049] Unless otherwise specified, the raw materials used in the embodiments of this application are all purchased commercially and used directly without any special treatment.

[0050] Unless otherwise specified, the analytical methods in the embodiments all adopt conventional instrument or equipment settings and conventional analytical methods.

[0051] The analysis method in the embodiments of this application is as follows:

[0052] X-ray powder diffraction (XRD) phase analysis was performed using an X'Pert PRO X-ray diffractometer from PANalytical, Netherlands, with a Cu target, Kα radiation source (λ = 0.15418 nm), voltage 40 kV, and current 40 mA.

[0053] The scanning electron microscope (SEM) used for testing was a Hitachi SU8020 field emission scanning electron microscope with an accelerating voltage of 2kV.

[0054] Molecular sieve precursors were prepared by mechanical crushing on a QM-3SP2 planetary ball mill.

[0055] Preparation of SAPO-34 (aluminosilicate phosphate CHA type molecular sieve) precursor

[0056] The preparation of SAPO-34 precursor includes ball milling, acid treatment, alkali treatment, a combination of ball milling and acid treatment, or ball milling... A combination of grinding and alkali treatment.

[0057] (1) Ball milling treatment: The SAPO-34 molecular sieve (Si) is subjected to ball milling treatment. 0.200 P 0.341 Al 0.459 The mixture of 1:2 by mass with H2O was placed in an agate jar and ball-milled for 6 hours at 550 rpm to obtain the SAPO-34 molecular sieve precursor.

[0058] (2) Acid treatment: SAPO-34 molecular sieve and H3PO4 aqueous solution were mixed at a mass ratio of 1:2 and stirred at room temperature for 24 hours to obtain SAPO-34 molecular sieve precursor.

[0059] (3) Alkali treatment: SAPO-34 molecular sieve and diethylamine aqueous solution were mixed at a mass ratio of 1:2 and stirred at room temperature for 24 hours to obtain SAPO-34 molecular sieve precursor.

[0060] (4) Combination of ball milling and acid treatment: The solid sample obtained in (1) above is mixed with H3PO4 aqueous solution at a mass ratio of 1:2 and stirred at room temperature for 24 hours to obtain SAPO-34 molecular sieve precursor.

[0061] (5) Combination of ball milling and alkali treatment: The solid sample obtained in (1) above is mixed with diethylamine aqueous solution at a mass ratio of 1:2 and stirred at room temperature for 24 hours to obtain SAPO-34 molecular sieve precursor.

[0062] Preparation of SAPO-56 (AFX type molecular sieve with silica alumina) precursor

[0063] The preparation of SAPO-56 precursor is the same as that of SAPO-34 molecular sieve precursor (1), the only difference being the use of SAPO-56 molecular sieve (Si). 0.222 P 0.341 Al 0.437 (and replace SAPO-34 molecular sieve)

[0064] Preparation of SSZ-13 (Silica-alumina CHA type molecular sieve) precursor

[0065] The preparation of SSZ-13 precursor is the same as that of SAPO-34 molecular sieve precursor, except that SSZ-13 (SiO2 / Al2O3=25) is used instead of SAPO-34 molecular sieve.

[0066] Preparation of SSZ-16 (Silica-Alumina AFX type molecular sieve) precursor

[0067] The preparation of SSZ-16 precursor is the same as that of SAPO-34 molecular sieve precursor, except that SSZ-16 (SiO2 / Al2O3=9) is used instead of SAPO-34 molecular sieve.

[0068] Preparation of AFX and CHA eutectic molecular sieves

[0069] Example 1: Preparation of Sample 1

[0070] The raw materials were prepared according to the mass ratios described in Table 1. First, 0.1 g of ball-milled SAPO-34 molecular sieve precursor was added to deionized water, followed by the organic template agent N,N,N',N'-tetramethyl-1,6-hexanediamine. After thorough mixing, the gel was placed in a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 200°C for 7 hours. The resulting solid product was centrifuged, washed with deionized water until neutral, and dried in air at 120°C to obtain the raw powder, designated as Sample 1. X-ray diffraction analysis of Sample 1 showed that the synthesized product exhibited the characteristics of a co-existing structure of AFX and CHA (X-ray spectrum shown in [reference needed]). Figure 1 Scanning electron microscopy (SEM) images show that the molecular sieve has a plate-like morphology, with a maximum length of 150–500 nm and a thickness of 50–100 nm. The SEM spectra are shown below. Figure 2 .

[0071] Examples 1-1 to 1-4: Preparation of Samples 1-1 to 1-4

[0072] The only difference between Examples 1-1 to 1-4 and Example 1 is that the precursors used are SAPO-34 molecular sieve precursors obtained through acid treatment, alkali treatment, a combination of ball milling and acid treatment, and a combination of ball milling and alkali treatment, respectively. Otherwise, they are the same as in Example 1. X-ray diffraction analysis was performed on the samples (sample 1-1, sample 1-2, sample 1-3, and sample 1-4) obtained in Examples 1-1 to 1-4. The X-ray diffraction patterns of these samples have the same characteristics as... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic aluminosilicate molecular sieves were successfully synthesized. The XRD pattern of this sample will not be repeated here.

[0073] Example 2: Preparation of Sample 2

[0074] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the precursor was ball-milled SSZ-13 (silica-alumina CHA type molecular sieve). X-ray diffraction analysis was performed on the synthesized Sample 2. The X-ray diffraction pattern of Sample 2 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic aluminosilicate molecular sieves were successfully synthesized. The XRD pattern of this sample will not be repeated here.

[0075] Example 3: Preparation of Sample 3

[0076] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the precursor was ball-milled SAPO-56 and the organic template agent was morpholine. X-ray diffraction analysis was performed on the synthesized Sample 3. The X-ray diffraction pattern of Sample 3 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0077] Example 4: Preparation of Sample 4

[0078] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as for Sample 1 in Example 1, except that the precursor was ball-milled SSZ-16 (silica-alumina AFX type molecular sieve), and the organic template agent was adamantane. X-ray diffraction analysis was performed on the synthesized Sample 4. The X-ray diffraction pattern of Sample 4 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic aluminosilicate molecular sieves were successfully synthesized. The XRD pattern of this sample will not be repeated here.

[0079] Example 5: Preparation of Sample 5

[0080] The raw materials were prepared according to the mass ratios described in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the crystallization time was extended to 24 hours. X-ray diffraction analysis was performed on the synthesized Sample 5, and the results were the same as those for Sample 1. The solid yield was 90.4%, indicating high atom economy.

[0081] Example 6: Preparation of Sample 6

[0082] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the mass ratio of precursor / H2O / TMHDA was 1 / 5 / 1, which is equivalent to increasing the alkalinity of the system. X-ray diffraction analysis was performed on the synthesized Sample 6. The X-ray diffraction pattern of Sample 6 showed similarities to... Figure 1 Similar characteristics indicate that the product is a eutectic SAPO molecular sieve of AFX and CHA. In the XRD diffraction pattern of this sample, the positions of some peaks shifted, and the relative intensities also changed. Furthermore, the peak broadening in the XRD pattern of this sample was more severe; please refer to [link to relevant documentation] for details. Figure 3 This indicates that by increasing the alkalinity of the system, the relative proportions of the AFX and CHA phases will change.

[0083] Example 7: Preparation of Sample 7

[0084] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for sample 6 in Example 6, except that the crystallization time was shortened to 2 hours. X-ray diffraction analysis was performed on the synthesized sample 7. The X-ray diffraction pattern of sample 7 showed similar characteristics to... Figure 3 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0085] In addition, scanning electron microscope images ( Figure 4 The results show that sample 7 not only has a plate-like structure (i.e., the eutectic SAPO molecular sieve of AFX and CHA), but also other amorphous parts, indicating the presence of amorphous regions. This suggests that the crystallization time was shortened, the eutectic molecular sieve was not fully crystallized, and there was an uncrystallized precursor.

[0086] Example 8: Preparation of Sample 8

[0087] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for sample 6 in Example 6, except that the crystallization time was extended to 19 hours. X-ray diffraction analysis was performed on the synthesized sample 8. The X-ray diffraction pattern of sample 8 showed similar characteristics to... Figure 3 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0088] Example 9: Preparation of Sample 9

[0089] Prepare the ingredients according to the mass ratios of the raw materials described in Table 1. The specific preparation process is the same as in Example 1.

[0090] The specific ingredient preparation process is the same as that of Sample 6 in Example 6, except that the crystallization time is extended to 24 hours. X-ray diffraction analysis was performed on the synthesized Sample 9, and the X-ray diffraction pattern of Sample 9 has the same characteristics as... Figure 3 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0091] Please refer to Table 1 for the yields of samples 1 to 9.

[0092] As shown in Table 1, by comparing samples 1 and 6, and samples 5 and 9, it can be seen that increasing the alkalinity of the system will reduce the yield of the eutectic molecular sieve. This is because in a system with high alkalinity, the eutectic molecular sieve is more likely to dissolve, which in turn leads to low atom economy.

[0093] Comparison of samples 6 to 9 shows that extending the crystallization time is beneficial to improving the yield of eutectic molecular sieves.

[0094] Example 10: Preparation of Sample 10

[0095] The raw materials were prepared according to the mass ratios described in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the crystallization temperature was increased to 240°C and the crystallization time was shortened to 2 hours.

[0096] X-ray diffraction analysis was performed on the synthesized sample 10. The X-ray diffraction pattern of sample 10 has the same characteristics as... Figure 1 Similar characteristics indicate that AFX and CHA eutectic SAPO molecular sieves can be successfully synthesized at 240℃. The XRD pattern of this sample will not be repeated here.

[0097] Example 11: Preparation of Sample 11

[0098] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the crystallization temperature was lowered to 160°C and the crystallization time was extended to 24 hours. X-ray diffraction analysis was performed on the synthesized sample 11. The X-ray diffraction pattern of sample 11 showed characteristics similar to... Figure 1 Similar characteristics indicate that AFX and CHA eutectic SAPO molecular sieves can be successfully synthesized at 160℃. The XRD pattern of this sample will not be repeated here.

[0099] Example 12: Preparation of Sample 12

[0100] The raw materials were prepared according to the mass ratios described in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the crystallization temperature was lowered to 150°C and the crystallization time was extended to 24 hours. X-ray diffraction analysis of the product showed a very low degree of crystallinity. At 150°C, due to thermodynamic limitations, the crystallization process was difficult to occur, resulting in a yield of 0 for the AFX and CHA eutectic SAPO molecular sieve. This further illustrates that the crystallization temperature is a key condition for the synthesis of AFX and CHA eutectic SAPO molecular sieves.

[0101] Example 13: Preparation of Sample 13

[0102] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the mass ratio of precursor / H2O / TMHDA was 1 / 1 / 0.1. X-ray diffraction analysis was performed on the synthesized Sample 13. The X-ray diffraction pattern of Sample 13 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0103] Example 14: Preparation of Sample 14

[0104] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the mass ratio of precursor / H2O / TMHDA was 1 / 10 / 0.1. X-ray diffraction analysis was performed on the synthesized sample 14. The X-ray diffraction pattern of sample 14 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0105] Example 15: Preparation of Sample 15

[0106] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the mass ratio of precursor / H2O / TMHDA was 1 / 1 / 10. X-ray diffraction analysis was performed on the synthesized sample 15. The X-ray diffraction pattern of sample 15 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0107] Example 16: Preparation of Sample 16

[0108] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the mass ratio of precursor / H2O / TMHDA was 1 / 10 / 10. X-ray diffraction analysis was performed on the synthesized sample 16. The X-ray diffraction pattern of sample 16 showed characteristics similar to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0109] Example 17: Preparation of Sample 17

[0110] The raw materials were prepared according to the mass ratios shown in Table 1. The specific preparation process was the same as that for Sample 1 in Example 1, except that the mass ratio of precursor / H2O / TMHDA was 1 / 4 / 4, and the crystallization time was shortened to 2 hours. X-ray diffraction analysis was performed on the synthesized Sample 17. The X-ray diffraction pattern of Sample 17 showed similarities to... Figure 1 Similar characteristics indicate that the product is a eutectic SAPO molecular sieve of AFX and CHA. The XRD pattern of this sample will not be repeated.

[0111] Example 18: Preparation of Sample 18

[0112] The raw materials were prepared according to the molar ratios described in Table 2. First, 0.25 g of pseudoboehmite (Al2O3 mass fraction 68.16%) was added to deionized water and stirred with a glass rod until completely dissolved. Then, an aqueous solution of phosphoric acid (H3PO4 mass fraction 80%) was added and mixed thoroughly. Next, silica sol (SiO2 mass fraction 27.3%) was added. After stirring thoroughly at room temperature, the template agent TMDHA was added, and stirring was continued at room temperature until a homogeneous gel was formed. Finally, the SAPO-34 precursor was added and stirred thoroughly to obtain an initial gel formulation with the following ratio: 0.6SiO2:1.0Al2O3:0.8P2O5:2.0TMHDA:50H2O +70wt% SAPO-34 precursor. The gel was placed in a stainless steel reactor lined with polytetrafluoroethylene and sealed. The mixture was heated to 200°C and crystallized for 24 hours. The resulting solid product was centrifuged, washed with deionized water until neutral, and dried in air at 120°C. The solid product was collected and designated as sample 18. X-ray diffraction analysis was performed on the product. The X-ray diffraction pattern of the product showed characteristics similar to... Figure 1 Similar characteristics are not repeated in the XRD pattern of this sample, indicating that the product is a eutectic SAPO molecular sieve of AFX and CHA.

[0113] Example 19: Preparation of Sample 19

[0114] The raw materials were prepared according to the molar ratios described in Table 2. The specific preparation process was the same as that for sample 18 in Example 18, except that the amount of precursor added was increased, resulting in an initial gel formulation of 0.6SiO2:1.0Al2O3:0.8P2O5:2.0TMHDA:50H2O + 90wt%-SAPO-34 precursor. X-ray diffraction analysis was performed on the synthesized sample 19. The X-ray diffraction pattern of sample 19 showed similar characteristics to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0115] Example 20: Preparation of Sample 20

[0116] The raw materials were prepared according to the molar ratios described in Table 2. The specific preparation process was the same as in Example 18, except that no additional silicon source was added and the amount of precursor was reduced, resulting in an initial gel preparation ratio of: 1.0Al₂O₃:0.8P₂O₅:2.0TMHDA:50H₂O + 20wt%-SAPO-34 precursor. X-ray diffraction analysis was performed on the synthesized sample 20. The X-ray diffraction pattern of sample 20 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0117] Example 21: Preparation of Sample 21

[0118] The raw materials were prepared according to the molar ratios described in Table 2. The specific preparation process was the same as in Example 18, except that no additional silicon source was added and the amount of precursor was reduced, resulting in an initial gel preparation ratio of: 1.0Al₂O₃:0.8P₂O₅:2.0TMHDA:50H₂O + 50wt%-SAPO-34 precursor. X-ray diffraction analysis was performed on the synthesized sample 21. The X-ray diffraction pattern of sample 21 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0119] Example 22: Preparation of Sample 22

[0120] The raw materials were prepared according to the molar ratios described in Table 2. The specific preparation process was the same as in Example 18, except that no additional phosphorus source was added, resulting in an initial gel preparation ratio of: 0.6SiO2:1.0Al2O3:2.0TMHDA:50H2O + 70wt%-SAPO-34 precursor. X-ray diffraction analysis was performed on the synthesized sample 22. The X-ray diffraction pattern of sample 22 showed similarities to... Figure 1Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0121] Example 23: Preparation of Sample 23

[0122] The raw materials were prepared according to the molar ratios described in Table 2. The specific preparation process was the same as in Example 18, except that the amount of organic template agent added was increased, resulting in an initial gel preparation ratio of: 0.6SiO2:1.0Al2O3:0.8P2O5:8.0TMHDA:50H2O + 70wt%-SAPO-34 precursor. X-ray diffraction analysis was performed on the synthesized sample 23. The X-ray diffraction pattern of sample 23 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0123] Example 24: Preparation of Sample 24

[0124] The raw materials were prepared according to the molar ratios described in Table 2. The specific preparation process was the same as in Example 18, except that the amount of H2O added was reduced, resulting in an initial gel formulation of: 0.6SiO2:1.0Al2O3:0.8P2O5:2.0TMHDA:1.0H2O + 70wt%-SAPO-34 precursor. X-ray diffraction analysis was performed on the synthesized sample 24. The X-ray diffraction pattern of sample 24 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0125] Example 25: Preparation of Sample 25

[0126] The raw materials were prepared according to the molar ratios described in Table 2. The specific preparation process was the same as in Example 18, except that the silicon source was tetraethyl orthosilicate and the aluminum source was aluminum isopropoxide, resulting in an initial gel preparation ratio of: 0.6SiO2:1.0Al2O3:0.8P2O5:2.0TMHDA:50H2O + 70wt%-SAPO-34 precursor. X-ray diffraction analysis was performed on the synthesized sample 25. The X-ray diffraction pattern of sample 25 showed similarities to... Figure 1 Similar characteristics indicate that the AFX and CHA eutectic SAPO molecular sieve was successfully synthesized; the XRD pattern of this sample will not be repeated here.

[0127] The yields of the AFX and CHA eutectic SAPO molecular sieves in Examples 18 to 25 above are shown in Table 2. Comparison of Examples 18 and 19, or Examples 20 and 21, shows that increasing the precursor content is beneficial for improving the yield of the AFX and CHA eutectic SAPO molecular sieves.

[0128] Table 1. Molecular sieve synthesis ingredients and crystallization conditions

[0129] 1 1 / 10 / 1 SAPO-34 TMHDA 200 7 50.0 1-1 1 / 10 / 1 SAPO-34 TMHDA 200 7 47.9 1-2 1 / 10 / 1 SAPO-34 TMHDA 200 7 50.9 1-3 1 / 10 / 1 SAPO-34 TMHDA 200 7 49.0 1-4 1 / 10 / 1 SAPO-34 TMHDA 200 7 53.8 2 1 / 10 / 1 SSZ-13 TMHDA 200 7 49.7 3 1 / 10 / 1 SAPO-56 MOR 200 7 52.3 4 1 / 10 / 1 SSZ-16 TMADaOH 200 7 53.0 5 1 / 10 / 1 SAPO-34 TMHDA 200 24 90.4 6 1 / 5 / 1 SAPO-34 TMHDA 200 7 46.1 7 1 / 5 / 1 SAPO-34 TMHDA 200 2 43.7 8 1 / 5 / 1 SAPO-34 TMHDA 200 19 52.1 9 1 / 5 / 1 SAPO-34 TMHDA 200 24 78.2 10 1 / 10 / 1 SAPO-34 TMHDA 240 2 48.0 11 1 / 10 / 1 SAPO-34 TMHDA 160 24 81.8 12 1 / 10 / 1 SAPO-34 TMHDA 150 24 0 13 1 / 1 / 0.1 SAPO-34 TMHDA 200 7 55.0 14 1 / 10 / 0.1 SAPO-34 TMHDA 200 7 52.4 15 1 / 1 / 10 SAPO-34 TMHDA 200 7 30.9 16 1 / 10 / 10 SAPO-34 TMHDA 200 7 37.8 17 1 / 4 / 4 SAPO-34 TMHDA 200 2 39.0

[0130] Note a Template agents R: N,N,N',N'-Tetramethyl-1,6-hexanediamine (abbreviated as TMDHA); Morpholine (abbreviated as MOR); Amantadine (abbreviated as TMADaOH).

[0131] Note b Yield = 0.85 * sample mass / (sum of SiO2, Al2O3 and P2O5 masses + precursor mass) * 100%.

[0132] Here, 0.85 refers to the ratio of the mass of the remaining sample after the sample has been treated with high-temperature water and the template agent has evaporated to the mass of the original powder.

[0133] Table 2. Molecular sieve synthesis ingredients and crystallization conditions

[0134]

[0135] Note a Silicon source: Samples 18-24, silica sol; Sample 25, tetraethyl orthosilicate;

[0136] Note b Aluminum source: Samples 18-24, boehmite; Sample 25, aluminum isopropoxide;

[0137] Note c Phosphorus source: 80wt% phosphoric acid aqueous solution;

[0138] Note d Template agent R: N,N,N',N'-Tetramethyl-1,6-hexanediamine (abbreviated as TMHDA);

[0139] Note e : The ratio of the mass of the SAPO-34 precursor to the sum of the masses of additional SiO2, Al2O3 and P2O5.

[0140] Note f Yield = 0.85 * sample mass / (sum of SiO2, Al2O3 and P2O5 masses + precursor mass) * 100%.

[0141] Here, 0.85 refers to the ratio of the mass of the remaining sample after the sample has been treated with high-temperature water and the template agent has evaporated to the mass of the original powder.

[0142] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing nanosheet-like AFX and CHA eutectic molecular sieves, characterized in that, The maximum length of the nanosheet-like AFX and CHA eutectic molecular sieve is 150~500 nm; The thickness of the nanosheet-like AFX and CHA eutectic molecular sieve is 50~100 nm; The preparation method of the nanosheet-like AFX and CHA eutectic molecular sieve includes the following steps: (1) The first molecular sieve of AFX and CHA type molecular sieves is pretreated to destroy its crystal structure in order to obtain the first molecular sieve precursor; (2) The first molecular sieve precursor obtained in step (1) is mixed with the synthesis system of the second molecular sieve of AFX and CHA type molecular sieves to obtain an initial mixture, wherein the synthesis system includes water and a template agent for synthesizing the second molecular sieve, which is different from the first molecular sieve. (3) The initial mixture obtained in step (2) is subjected to hydrothermal crystallization under autogenous pressure in a reactor at a crystallization temperature of 160~240 ℃ and a crystallization time of 2~24 h; and (4) After crystallization, the solid product obtained in step (3) is washed and dried to obtain nanosheet-like AFX and CHA eutectic molecular sieves; The X-ray diffraction pattern of the nanosheet-like AFX and CHA eutectic molecular sieve exhibits the characteristic of both broad peaks and sharp peaks. The nanosheet-like AFX and CHA eutectic molecular sieves are selected from phosphate aluminum sieves and / or silica aluminum sieves containing AFX and CHA eutectic molecular sieves.

2. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 1, characterized in that, The pretreatment includes ball milling, acid treatment, alkali treatment, a combination of ball milling and acid treatment, or a combination of ball milling and alkali treatment.

3. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 2, characterized in that, The acid used in the acid treatment is H3PO4; The alkali used in the alkaline treatment is diethylamine.

4. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 2, characterized in that, The conditions for ball milling are as follows: the first molecular sieve is dispersed in a liquid medium and ball milled in a ball mill at a speed of 500-600 rpm for 5-9 hours.

5. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 1, characterized in that, The template agent mentioned in step (2) is the template agent for synthesizing AFX, which is N,N,N',N'-tetramethyl-1,6-hexanediamine.

6. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 1, characterized in that, The template agent mentioned in step (2) is a template agent for the synthesis of CHA, which is selected from at least one of adamantane, N,N'-diisopropylethylamine, cyclohexylimine, morpholine, diethylamine, pyridine, piperidine, cyclohexylamine, tetramethylammonium hydroxide, triethylamine, imidazole, methylimidazole, piperazine, and ethylenediamine.

7. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 1, characterized in that, In step (2), the mass ratio of each component in the resulting initial mixture is: First molecular sieve precursor: H2O: template agent = 1:1~10:0.1~10.

8. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 1, characterized in that, In step (2), the synthesis system of the second molecular sieve of the AFX and CHA type molecular sieves also contains additional silicon source and / or aluminum source and / or phosphorus source, and the molar ratio of each component in the synthesis system is: The ratio of SiO2:Al2O3:P2O5:template agent:H2O is 0~0.6:0~1.0:0~0.8:1~10:1~50, and the molar content of SiO2:Al2O3:P2O5 is not 0 at the same time.

9. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 8, characterized in that, In step (2), the content of the first molecular sieve precursor in the initial mixture is 20 wt% to 90 wt% of the sum of the mass of the additional silicon source and / or aluminum source and / or phosphorus source; wherein the mass of the silicon source, aluminum source and phosphorus source is the sum of the mass of SiO2, Al2O3 and P2O5 contained therein.

10. The method for preparing nanosheet-like AFX and CHA eutectic molecular sieves according to claim 8, characterized in that, In step (2), the additional silicon source is selected from at least one of tetraethyl orthosilicate, silica sol, silica gel, silica fume, silica, water glass, and diatomaceous earth; the additional aluminum source is at least one of boehmite, aluminum isopropoxide, sodium aluminate, aluminum foil, aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum hydroxide; and the additional phosphorus source is at least one of phosphoric acid and ammonium dihydrogen phosphate.

11. The application of the nano-AFX and CHA eutectic molecular sieve prepared by any one of claims 1 to 10 as an adsorbent, catalyst or catalyst support.

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