Aluminiferous ith zeolite, its preparation method and application

Abstract

The application provides an aluminum-rich ITH zeolite and a preparation method and application thereof, and relates to the technical field of zeolite materials. A water solution of a template agent and a silicon source are mixed, and the residue after drying is mixed with a fluorine source to obtain a mixture; the mixture is subjected to first crystallization to obtain a full-silicon ITH; an inorganic alkali source, an aluminum source, water and the full-silicon ITH are mixed to obtain an initial gel; and the initial gel is subjected to second crystallization to obtain the aluminum-rich ITH zeolite. Compared with the prior art, the aluminum-rich ITH zeolite prepared by the application has a significantly improved aluminum content, has the lowest silicon-aluminum ratio (Si / Al=4.8) among the currently reported ITHs, and does not introduce heteroatoms such as germanium and boron, and is a green and economic synthesis method. The aluminum-rich ITH zeolite prepared by the application has abundant acid sites, and has a wide application prospect as a catalyst in the fields of fluid liquefaction catalysis, isomerization, biomass catalysis and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of zeolite materials, and particularly relates to an aluminum-rich ITH type zeolite and a preparation method and application thereof. BACKGROUND

[0002] Zeolites are a kind of inorganic microporous materials with regular and uniform pore structures, and have a wide range of applications in the fields of adsorption, catalysis and ion exchange. Among them, ITH type zeolite has a three-dimensional 9x9x10 ring pore structure, and the pore sizes are about 4.0x4.8, 4.8x5.1 and Similar to the ZSM-5 pore structure. Due to its strong shape selectivity, ITH type zeolite has a wide range of applications in industry, such as alkane isomerization reaction, fluid cracking catalytic reaction and the like.

[0003] The ITH type zeolite disclosed in the prior art has a great difficulty in introducing aluminum atoms, and the aluminum content in the directly synthesized Al-ITH is low. The silicon-rich or full-silicon ITH has too little or even no aluminum, resulting in too few acid sites and poor activity in catalytic reactions. How to improve the aluminum content of ITH type zeolite has become a problem of concern to researchers.

[0004] Chinese patent CN201811358904.6 discloses a method for synthesizing AlGe-ITH type zeolite using an organic structure directing agent, which comprises: preparing a gel containing a silicon source, an aluminum source, an alkali, germanium oxide and water, then hydrothermally reacting the gel in a self-generated pressure autoclave reactor, and then separating to obtain a zeolite product with ITH topology.

[0005] Chinese patent CN200510059767.2 discloses a method for synthesizing AlB-ITH type zeolite using an organic structure directing agent, which comprises: (1) alcohol is removed from a mixture gel for synthesizing ITH structure borosilicate molecular sieve at 50-100 DEG C, and then the mixture gel is crystallized under hydrothermal conditions at 120-200 DEG C for 2-10 days to obtain ITH structure borosilicate molecular sieve, wherein the molar ratio of F- / SiO2 in the mixture gel is greater than 1 and less than or equal to 4; (2) the borosilicate molecular sieve obtained in (1) is treated with an acid solution at room temperature-100 DEG C; (3) the product of (2) is mixed with an inorganic aluminum salt solution, and then hydrothermally treated at 100-170 DEG C to obtain ITH structure silicon-aluminum molecular sieve. The method involves the introduction of boron element, which is high in cost and not environmentally friendly.

[0006] The above method for improving the aluminum content of ITH type zeolite requires the introduction of heteroatoms such as germanium, gallium and boron when introducing aluminum atoms, which is not conducive to the industrialization of green economy.

[0007] A method for directly synthesizing germanium-free ITH zeolites using a template method is disclosed in the document "Ye M, Junyi H, Kai F, et al. Design of an Organic Template for Synthesizing ITR Zeolites under Ge-Free Conditions [J]. J. Am. Chem. Soc. 2023, 145, 17284-17291". However, the ITH synthesized by this method has a low aluminum content (Si / Al = 45). SUMMARY

[0008] Therefore, the present application aims to provide an aluminum-rich ITH zeolite and a preparation method and application thereof. The aluminum-rich ITH zeolite prepared by the present application has a significantly increased aluminum content (silicon-aluminum ratio of 4.5-30) and does not introduce heteroatoms such as germanium and boron.

[0009] To achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0010] The present application provides a preparation method of an aluminum-rich ITH zeolite, comprising the following steps:

[0011] Mixing an aqueous solution of a template agent and a silicon source, drying the mixture, and then mixing the residue with a fluorine source to obtain a mixed material; the template agent is hexamethonium hydroxide;

[0012] Performing first crystallization on the mixed material to obtain a full-silicon ITH;

[0013] Mixing an inorganic alkali source, an aluminum source, water, and the full-silicon ITH to obtain an initial gel;

[0014] Performing second crystallization on the initial gel to obtain the aluminum-rich ITH zeolite.

[0015] Preferably, the silicon source includes one or more of sodium silicate, white carbon black, water glass, silica sol, and tetraethyl orthosilicate; and the fluorine source includes one or more of ammonium fluoride, hydrogen fluoride, sodium fluoride, and potassium fluoride.

[0016] Preferably, the silicon source is calculated as SiO2, the fluorine source is calculated as F, and the molar ratio of the silicon source, the fluorine source, the template agent, and water in the mixed material is 1:0.5-1.6:0.25-0.8:0-2.0, and the amount of water is not 0.

[0017] Preferably, the drying includes sequentially performing stir-drying and freeze-drying.

[0018] Preferably, the temperature of the first crystallization is 150-200°C, and the time is 5-30d.

[0019] Preferably, the inorganic alkali source comprises one or more of sodium carbonate, potassium carbonate, sodium aluminate, sodium hydroxide and potassium hydroxide; and the aluminum source comprises one or more of sodium aluminate, pseudoboehmite, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate and aluminum isopropoxide.

[0020] Preferably, the molar ratio of the all-silicon ITH, the aluminum source, the inorganic alkali source, the inorganic alkali source, the all-silicon ITH, the aluminum source and water is (1.01-1.93):(8.30-14.7):1.00:(151-290), and M in the M2O is a metal element of the inorganic alkali source.

[0021] Preferably, the temperature of the second crystallization is 120-200℃, and the time is 2h-8d.

[0022] The application provides an aluminum-rich ITH zeolite prepared by the preparation method.

[0023] The application provides an application of the aluminum-rich ITH zeolite as a catalyst.

[0024] The application provides a preparation method of an aluminum-rich ITH zeolite, which comprises the following steps: mixing an aqueous solution of a template agent and a silicon source, mixing the residue after drying with a fluorine source to obtain a mixture; the template agent is hexamethonium hydroxide; the mixture is subjected to first crystallization to obtain an all-silicon ITH; an inorganic alkali source, an aluminum source, water and the all-silicon ITH are mixed to obtain an initial gel; and the initial gel is subjected to second crystallization to obtain the aluminum-rich ITH zeolite. The application synthesizes an all-silicon ITH by crystallization, and then synthesizes a zeolite by re-crystallizing the all-silicon ITH with an inorganic alkali source, an aluminum source and water. Generally, in the crystallization process, silicoaluminate in the gel is excessively dissolved in an aqueous solution to form a silicoaluminate supersaturated solution, the solution forms crystal nuclei under slight disturbance, the crystal nuclei continue to grow by using the material in the solution, and meanwhile, the incompletely dissolved material in the gel continues to dissolve into the solution, thereby supplementing the material in the solution. The application uses an aluminum source as an aluminum supplement agent to desiliconize and supplement aluminum for the all-silicon ITH, promotes the generation of a silicoaluminate supersaturated solution and the generation of Al-ITH, that is, by using the difference in solubility of silicoaluminum species in an alkaline solution, the silicon on part of the sites of the molecular sieve is dissolved and removed (desiliconization process) by the alkalinity of the mother liquor, and aluminum is precipitated on the same sites at the same time (aluminum supplement process).

[0025] Compared with the prior art, the prepared aluminum-rich ITH zeolite has a significantly increased aluminum content, has the lowest silicon aluminum ratio (Si / Al=4.8) among the currently reported ITH, and does not introduce germanium, boron and other heteroatoms, and is a green and economic synthesis method. The prepared aluminum-rich ITH zeolite has rich acid sites, and has a wide application prospect as a catalyst in fluid liquefaction catalysis, isomerization, biomass catalysis and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 PXRD (powder X-ray diffraction) of the product in the examples and comparative examples;

[0027] Figure 2 SEM (scanning electron microscope) of the product H1 in Example 1;

[0028] Figure 3 N2 adsorption of the product H1 in Example 1; 27 Al-NMR (Al nuclear magnetic resonance);

[0029] Figure 4 SEM of the product H2 in Example 2;

[0030] Figure 5 SEM of the product H3 in Example 3;

[0031] Figure 6 PXRD and SEM of the product H4 in Comparative Example 1, Figure 6 A is the PXRD of H4, and B is the SEM of H4;

[0032] Figure 7 SEM of the product H5 in Comparative Example 2;

[0033] Figure 8 PXRD of the product H6 in Comparative Example 3; 27 Al-NMR;

[0034] Figure 9 PXRD of the product H7 in Comparative Example 4; 27 Al-NMR;

[0035] Figure 10 PXRD of the product H8 in Comparative Example 5; 27 Al-NMR;

[0036] Figure 11 N2 adsorption of H1 in Example 1 and full-silicon ITH;

[0037] Figure 12 PXRD of the product H11 in Comparative Example 8;

[0038] Figure 13PXRD pattern of the product H12 of Comparative Example 9. DETAILED DESCRIPTION

[0039] The present application provides a method for preparing an aluminum-rich ITH zeolite, comprising the following steps:

[0040] The aqueous solution of the template agent and the silicon source are mixed, and the residue after drying is mixed with a fluorine source to obtain a mixture; the template agent is hexamethonium hydroxide;

[0041] The mixture is subjected to first crystallization to obtain a full-silicon ITH;

[0042] An inorganic alkali source, an aluminum source, water and the full-silicon ITH are mixed to obtain an initial gel;

[0043] The initial gel is subjected to second crystallization to obtain the aluminum-rich ITH zeolite.

[0044] In the present application, the raw materials involved are all commercially available products well known in the art, unless otherwise specified.

[0045] In the present application, the aqueous solution of the template agent and the silicon source are mixed, and the residue after drying is mixed with a fluorine source to obtain a mixture. In the present application, the silicon source preferably includes one or more of sodium silicate, white carbon black, water glass, silica sol and tetraethyl orthosilicate, and more preferably is tetraethyl orthosilicate. In the present application, the template agent is hexamethonium hydroxide, and the mass fraction of the aqueous solution of the template agent is preferably 15-40%, and more preferably is 25%.

[0046] In the present application, the drying preferably includes stirring and drying and freeze-drying in sequence. In the present application, the stirring and drying preferably involves open stirring of the mixed solution until the water is naturally evaporated; the freeze-drying is preferably performed for more than 24 h, and more preferably for 1.5 d; and the freeze-drying is preferably performed in a freeze-drying machine. In the present application, the stirring and drying can only naturally evaporate to no obvious water (H2O / Si = 5-10), and the freeze-drying can reach a lower water content (H2O / Si < 2); and a high water content will result in that the full-silicon ITH cannot be crystallized, and all the generated products are amorphous.

[0047] In the present application, the fluorine source preferably includes one or more of ammonium fluoride, hydrogen fluoride, sodium fluoride and potassium fluoride, and more preferably is ammonium fluoride. In the present application, the method for mixing the residue with the fluorine source is preferably grinding and mixing. In the present application, the silicon source is calculated as SiO2, the fluorine source is calculated as F, and the molar ratio of the silicon source, the fluorine source, the template agent and water in the mixture is preferably 1:0.5-1.6:0.25-0.8:0-2.0, and more preferably is 1:0.5-0.8:0.3-0.4:0-2.0, and the amount of water is not 0.

[0048] After obtaining the mixture, the present application carries out first crystallization on the mixture to obtain full-silicon ITH. In the present application, the temperature of the first crystallization is preferably 150-200°C, more preferably 180°C, and the time is preferably 5-30 days, more preferably 7-10 days. The first crystallization is preferably carried out in a reaction kettle with a polytetrafluoroethylene lining. After the first crystallization is completed, the present application preferably carries out water washing and drying on the obtained solid product in sequence. The temperature of the drying is preferably 75°C, and the time is preferably 12 hours.

[0049] The present application synthesizes full-silicon ITH by a method of crystallization, and then desiliconizes and supplements aluminum on the full-silicon ITH to obtain an ITH type zeolite with extremely low silicon aluminum ratio and no germanium.

[0050] After obtaining the full-silicon ITH, the present application mixes an inorganic alkali source, an aluminum source, water and the full-silicon ITH to obtain an initial gel. In the present application, the inorganic alkali source preferably includes one or more of sodium carbonate, potassium carbonate, sodium aluminate, sodium hydroxide and potassium hydroxide, and is preferably sodium hydroxide. In the present application, the aluminum source preferably includes one or more of sodium aluminate, pseudo-boehmite, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate and aluminum isopropoxide, and is more preferably water-soluble sodium aluminate (sodium aluminate can simultaneously serve as an aluminum source and an inorganic alkali source). In the present application, the water is preferably deionized water. In the present application, the full-silicon ITH is calculated based on SiO2, the aluminum source is calculated based on Al2O3, the inorganic alkali source is calculated based on M2O, and the molar ratio of the inorganic alkali source, the full-silicon ITH, the aluminum source and the water is preferably (1.01-1.93):(8.30-14.7):1.00:(151-290), more preferably (1.19-1.64):(9.86-13.7):1.00:(178-247), and further preferably 1.40:11.6:1.00:210. M in M2O is a metal element of the inorganic alkali source.

[0051] In the present application, the mixing of the inorganic alkali source, the aluminum source, the water and the full-silicon ITH is preferably carried out under a closed condition, and the mixing is preferably stirring mixing. The present application does not have special requirements for the conditions of the stirring mixing, and it is only required to ensure that the components are uniformly mixed.

[0052] In the present application, the temperature of the second crystallization is preferably 120-200°C, more preferably 150-180°C, and the time is preferably 2 hours-8 days, more preferably 15 hours-4 days. The second crystallization is preferably carried out in a reaction kettle with a polytetrafluoroethylene lining. In the process of the second crystallization, the silicon of part of the sites in the full-silicon ITH is dissolved by utilizing the basicity of the solution, and the aluminum oversaturated in the solution is precipitated from the solution and combined with the sites from which the silicon is removed.

[0053] After the second crystallization is completed, the application preferably performs solid-liquid separation, solid-phase water washing and drying on the obtained crystallization reaction liquid to obtain an initial gel. In the application, the solid-liquid separation is preferably centrifugation, the drying temperature is preferably 75-120 DEG C, and the drying time is until the constant weight.

[0054] The preparation method provided by the application can obtain ITH zeolite rich in aluminum with a very low silicon-aluminum ratio, and compared with the synthesis process of traditional Al-ITH, the method does not introduce heteroatoms such as germanium and boron, and is a green and economic synthesis method.

[0055] The application provides ITH zeolite rich in aluminum prepared by the preparation method.

[0056] The application provides application of the ITH zeolite rich in aluminum as a catalyst. The ITH zeolite rich in aluminum prepared by the application has a very low silicon-aluminum ratio and rich acid sites, and has a wide application prospect in the fields of fluid liquefaction catalysis, isomerization, biomass catalysis and the like.

[0057] In order to further illustrate the application, the ITH zeolite rich in aluminum and the preparation method and application thereof provided by the application are described in detail below with examples, but they should not be understood as limitations to the protection scope of the application.

[0058] Example 1

[0059] The ITH zeolite rich in aluminum is prepared in the following method:

[0060] (1) 4.5 g of tetraethyl orthosilicate and 6.2 g of 25% aqueous methylammonium hydroxide solution are stirred in an open state until water is naturally evaporated, and the remaining substance is transferred to a freeze dryer for drying for 1.5 days. After the drying is completed, the solid is fully ground with 0.5 g of ammonium fluoride in a mortar, and then transferred to a reaction kettle with a polytetrafluoroethylene lining, and crystallized at 180 DEG C for 7 days. After the hydrothermal reaction is completed, the solid product is washed with water, and dried in a 75 DEG C oven for 12 hours to obtain a full-silicon ITH powder.

[0061] (2) 3 mL of distilled water, 0.5 g of full-silicon ITH powder and 0.152 g of sodium aluminate (41wt% Na2O, 48wt% Al2O3) are added to a reaction container, and stirred uniformly under a closed and room temperature condition, and the reaction liquid is loaded into a reaction kettle with a polytetrafluoroethylene lining, and crystallized at 180 DEG C for 15 hours; after the hydrothermal reaction is completed, the solid-liquid separation is performed by using a centrifugal device, the solid product is washed with water, and dried in a 75 DEG C oven for 12 hours to obtain a product, which is recorded as H1.

[0062] The crystallinity and the silicon aluminum ratio (Si / Al) of H1 were determined, and the silicon aluminum ratio is listed in Table 1. The crystallinity of H1 was calculated from XRD diffraction data, and the calculation method is a conventional technical method in the art; the silicon aluminum ratio (Si / Al) was calculated from atomic emission spectroscopy (ICP) data, and the calculation method is a conventional technical method in the art.

[0063] Figure 1 The X-ray diffraction pattern of H1 in Example 1 is shown in the middle curve H1, and by comparison with the standard diffraction pattern published by the International Zeolite Association (i.e. Figure 1 The ITH simulation shows that H1 is a zeolite with ITH structure.

[0064] Figure 2 The scanning electron micrograph of H1 shows that H1 is a spherical shape formed by accumulation of block crystals.

[0065] Figure 3 The Al-NMR spectrum of H1 shows that there is no peak at 0 ppm, indicating that all the aluminum in H1 enters the framework, and there is no extra-framework aluminum. 27

[0066] Example 2

[0067] 0.015 g of sodium hydroxide, 1.5 mL of distilled water, 0.25 g of the all-silicon ITH synthesized in Example 1, and 0.09 g of sodium aluminate (41 wt% Na2O, 48 wt% Al2O3) were added to a reaction vessel, and stirred uniformly at room temperature in a closed condition. The reaction liquid was loaded into a reaction kettle with a polytetrafluoroethylene liner, and crystallized at 150°C for 4d. After the hydrothermal reaction was completed, a centrifugal device was used for solid-liquid separation, and the solid product was washed with water and dried in an oven at 100°C for 6h to obtain a product, which is denoted as H2.

[0068] The crystallinity and the silicon aluminum ratio (Si / Al) of H2 were determined, and the silicon aluminum ratio is listed in Table 1.

[0069] Figure 1 The X-ray diffraction pattern of H2 in Example 2 is shown in the middle curve H2, and by comparison with the standard diffraction pattern published by the International Zeolite Association, it can be seen that H2 is a zeolite with ITH structure. Figure 4 The scanning electron micrograph of H2 is shown in the middle curve H2.

[0070] Example 3

[0071] ​Into a reaction vessel was added 0.0006 g of sodium hydroxide, 1.0 mL of distilled water, 0.18 g of the all-silicon ITH synthesized in Example 1, and 0.05 g of sodium aluminate (41 wt% Na2O, 48 wt% Al2O3), which was stirred uniformly at room temperature in a closed state, and the reaction solution was charged into a reaction kettle with a polytetrafluoroethylene liner, and crystallization was performed at 150°C for 4 days. After the hydrothermal reaction was completed, the solid-liquid separation was performed using a centrifugal device, and the solid product was washed with water and dried in an oven at 120°C for 3 h to obtain the product, which was denoted as H3.

[0072] The crystallinity and the silicon-to-aluminum ratio (Si / Al) of H3 were determined, and the silicon-to-aluminum ratio is listed in Table 1.

[0073] Figure 1 The middle curve H3 is the X-ray diffraction pattern of the product H3 of Example 3, which, by comparison with the standard diffraction patterns published by the International Zeolite Association, is a zeolite having an ITH structure. Figure 5 The scanning electron microscope image of H3 is shown in FIG. 2B.

[0074] Comparative Example 1

[0075] The product described in the reference Angew. Chem. Int. Ed. 10.1002 / anie.202003282 was prepared as follows:

[0076] Into a reaction vessel was added 0.935 g of white carbon black, 0.013 g of aluminum fluoride, 10.61 g of a 0.36 mol / L aqueous solution of a cationic polymer organic template, 0.168 mL of a 40% aqueous solution of hydrofluoric acid, and 0.05 g of all-silicon ITH seeds, which were stirred to form a uniform gel, and 8.94 g of water was naturally evaporated, and then the gel was transferred to a reaction kettle, and crystallization was performed at 160°C for 7 days. The solid in the reaction kettle was removed, washed, and dried to obtain an ITH molecular sieve having a silicon-to-aluminum ratio of about 100, which was denoted as H4.

[0077] The silicon-to-aluminum ratio (Si / Al) of H4 is listed in Table 1. Figure 6 The middle curve A is the PXRD pattern of H4, which is a zeolite having an ITH structure. Figure 6 The scanning electron microscope image of H4 is shown in FIG. 3B, which shows that H4 has a sheet-like structure.

[0078] Comparative Example 2

[0079] The all-silicon ITH in Example 1 was dispersed in distilled water and stirred for 4 h, and then the solid-liquid separation was performed using a centrifuge, and the solid product was dried in an oven at 100°C for 4 h to obtain the product, which was denoted as H5.

[0080] The crystallinity and the silicon-to-aluminum ratio (Si / Al) of H5 were determined, and the silicon-to-aluminum ratio is listed in Table 1.

[0081] Figure 1The middle curve H5 is the X-ray diffraction pattern of the product H5 of Comparative Example 2, and it can be seen that H5 is a zeolite with ITH structure. Figure 7 The scanning electron micrograph of H5 is shown in Figure 2, and it can be seen that H5 has a sheet-like structure.

[0082] Comparative Example 3

[0083] Comparative Example 2 was prepared in the same manner as Example 2 except that sodium hydroxide was not added, and the product was denoted as H6.

[0084] Figure 1 The middle curve H6 is the X-ray diffraction pattern of the product H6 of Comparative Example 3, and it can be seen that H6 is a zeolite with ITH structure.

[0085] Figure 8 The scanning electron micrograph of H6 is shown in Figure 3, and it can be seen that H6 has a sheet-like structure. 27 Al-NMR, the spectrum has a large peak at 0 ppm, indicating that the added aluminum is amorphous aluminum and does not enter the ITH framework.

[0086] Comparative Example 4

[0087] Comparative Example 4 was prepared in the same manner as Example 3 except that sodium hydroxide was not added, and the product was denoted as H7.

[0088] Figure 1 The middle curve H7 is the X-ray diffraction pattern of the product H7 of Comparative Example 4, and it can be seen that H7 is a zeolite with ITH structure.

[0089] Figure 9 The scanning electron micrograph of H7 is shown in Figure 4, and it can be seen that H7 has a sheet-like structure. 27 Al-NMR, the spectrum has a large peak at 0 ppm, indicating that the added aluminum is amorphous aluminum and does not enter the ITH framework.

[0090] Comparative Example 5

[0091] Comparative Example 5 was prepared in the same manner as Example 1 except that the crystallization time in step (2) was changed to 1 h, and the product was denoted as H8.

[0092] Figure 1 The middle curve H8 is the X-ray diffraction pattern of the product H8 of Comparative Example 5, and it can be seen that H8 is a zeolite with ITH structure.

[0093] Figure 10 The scanning electron micrograph of H8 is shown in Figure 5, and it can be seen that H8 has a sheet-like structure. 27 Al-NMR, the spectrum has a large peak at 0 ppm, indicating that the added aluminum is amorphous aluminum and does not enter the ITH framework.

[0094] Comparative Example 6

[0095] The crystallization temperature in step (2) of Example 1 is changed to 80°C, and the rest of the procedures are the same as those in Example 1 to prepare a comparative product, which is denoted as H9.

[0096] Figure 1 The middle curve H9 is the X-ray diffraction pattern of the product H9 of Comparative Example 6. It can be seen from the X-ray diffraction pattern of H9 that H9 is a zeolite having ITH structure.

[0097] The Si / Al of H9 is determined and listed in Table 1. Since H9 has a too high Si / Al ratio, most of the Al exists in the liquid phase and does not enter the ITH framework.

[0098] Comparative Example 7

[0099] Comparative Example 7 is prepared in the same way as Example 1 except that 0.3 g of sodium aluminate is added, and the product is denoted as H10.

[0100] Figure 1 The middle curve H10 is the X-ray diffraction pattern (PXRD) of the product H10 of Comparative Example 7. It can be seen from the PXRD pattern of H10 that H10 is amorphous and is not an ITH zeolite.

[0101] Table 1: Si / Al of the products of Examples and Comparative Examples

[0102] Product H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 Si / Al 4.8 26.7 6.5 100 - - - - 77.2 -

[0103] In Table 1, H5 is a full-silicon ITH without aluminum and has an infinite Si / Al ratio; H6 to H8 have a large amount of extra-framework aluminum which does not enter the framework and are mixtures of high-silicon or full-silicon ITH and amorphous extra-framework aluminum and are not pure ITH zeolites; and H10 is also not an ITH molecular sieve.

[0104] Figure 11 The N2 adsorption-desorption patterns of H1 (i.e. the synthesized low-silicon ITH) and full-silicon ITH are shown in Figure 1. Figure 11 It can be seen that the aluminum supplementing process has no obvious effect on the pore channels.

[0105] Comparative Example 8

[0106] 3 mL of distilled water, 1.73 g of tetraethyl orthosilicate (silicon dioxide content: 28%) and 0.152 g of sodium aluminate are added to a reaction vessel, and the reaction liquid is loaded into a reaction kettle with a polytetrafluoroethylene liner under the condition of being closed and at room temperature. The reaction liquid is stirred uniformly, and the reaction is carried out at 180°C for 15 h. After the hydrothermal reaction is completed, the solid-liquid separation is performed using a centrifugal device, and the solid product is washed with water and dried in an oven at 75°C for 12 h to obtain a product, which is denoted as H11.

[0107] Figure 12 The PXRD pattern of H11 is shown in Figure 2. It can be seen that H11 is not an ITH zeolite.

[0108] Comparative Example 9

[0109] Into a reaction vessel, 3 mL of distilled water, 0.5 g of white carbon black and 0.152 g of sodium aluminate were added and stirred uniformly at a closed and room temperature condition, the reaction solution was loaded into a reaction kettle with a polytetrafluoroethylene lining, and crystallized at 180°C for 15 h. After the hydrothermal reaction was completed, a centrifugal device was used for solid-liquid separation, and the solid product was washed with water and dried in an oven at 100°C for 6 h to obtain the product, which was recorded as H12.

[0110] Figure 13 The PXRD pattern of H12 showed that H12 was not ITH zeolite.

[0111] The above description is only preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for preparing aluminum-rich ITH zeolite, characterized in that: The following steps are involved: An aqueous solution of a template and a silicon source are mixed, and after drying, the residue is mixed with a fluorine source to obtain a mixture; the template is hexamethonium hydroxide; the drying comprises stirring and freeze-drying in sequence; the silicon source is calculated as SiO2, the fluorine source is calculated as F, and the molar ratio of the silicon source, the fluorine source, the template and water in the mixture is 1:0.5-1.6:0.25-0.8:0-2.0, and the amount of water is not zero; Performing a first crystallization on the mixture to obtain an all-silicon ITH; the first crystallization temperature is 150-200° C. and the time is 5-30 days; An inorganic alkali source, an aluminum source, water, and the all-silicon ITH are mixed to obtain an initial gel; the all-silicon ITH is calculated as SiO2, the aluminum source is calculated as Al2O3, and the inorganic alkali source is calculated as M2O; the molar ratio of the inorganic alkali source, the all-silicon ITH, the aluminum source, and the water is (1.01-1.93):(8.30-14.7):1.00:(151-290), where M in M2O is a metal element of the inorganic alkali source; The initial gel is subjected to a second crystallization to obtain the aluminum-rich ITH zeolite; the temperature of the second crystallization is 120-200° C., and the time is 2 hours to 8 days.

2. The preparation method according to claim 1, characterized in that The silicon source includes one or more of sodium silicate, white carbon black, water glass, silica sol and tetraethyl orthosilicate; the fluorine source includes one or more of ammonium fluoride, hydrogen fluoride, sodium fluoride and potassium fluoride.

3. The preparation method according to claim 1, characterized in that The inorganic alkali source includes one or more of sodium carbonate, potassium carbonate, sodium aluminate, sodium hydroxide and potassium hydroxide; the aluminum source includes one or more of sodium aluminate, pseudo-boehmite, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate and aluminum isopropoxide.

4. The aluminum-rich ITH zeolite prepared by the preparation method according to any one of claims 1 to 3, wherein the silicon-aluminum ratio of the aluminum-rich ITH zeolite is 4.5 to 30.

5. Use of the aluminum-rich ITH zeolite according to claim 4 as a catalyst.

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