One-Pot Synthesis of Layered Zeolite

Abstract

A method for preparing delaminated Al-SSZ-70 zeolite is provided. The method combines CTA + cations and imidazolium OSDA in direct hydrothermal synthesis. High-shear mixing treatment after synthesis is also preferred. In one embodiment, seeds of Al-SSZ-70 zeolite with an Si / Al ratio of preferably 50 or more are used.

Description

Technical Field

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 344,806, filed May 23, 2022, the entire disclosure of which is incorporated herein by reference in its entirety. This invention was made with government support under DE-FG02-05ER15696 from the U.S. Department of Energy. The U.S. government has certain rights in this invention.

[0002] This disclosure relates to the synthesis of exfoliated, layered zeolite materials useful in reactions involving sterically bulky reactants. The synthesis is a direct one-pot synthesis.

Background Art

[0003] Zeolites are microporous materials composed of aluminosilicate TO4 tetrahedra, with a unique crystal structure consisting of molecular tube pores and cavities. Zeolites are applied in many fields such as catalysis, gas separation, and adsorption due to their unique three-dimensional occlusion controlled by microporosity, but the main applications are limited to those involving molecules small enough to freely access the internal voids of the zeolite. In many cases, sterically bulky molecules are subject to significant diffusion constraints because their large molecular size hinders their own entry into the microporous tube pores of the zeolite. Therefore, various methods have been developed to introduce hierarchical porosity into conventional microporous zeolites to expand the capabilities of zeolites and include sterically bulky molecules, such as soft / hard templates, dealumination, etc.

[0004] Specifically, the synthesis of hierarchical zeolites by the exfoliation of two-dimensional (2D) layered zeolite precursors has attracted significant attention. A part of this endeavor has been motivated by the partial occlusion of the external surface pockets of 2D MWW-type zeolite layers in recent experimental demonstrations, which promotes catalytic reactions in both gas and liquid phases. The synthesis of 2D MWW-type zeolite layers by exfoliation after the synthesis of layered zeolite precursors was pioneered in 1998 by Corma and colleagues, together with the synthesis of ITQ-2 zeolite with an external surface area of approximately 700 m 2 / g. However, due to the high pH and high-temperature post-treatment conditions involved in exfoliation, undesirable results such as silica dissolution and amorphization of the zeolite may occur. Therefore, in order to maintain the integrity of the layers inside the structure of exfoliated zeolites and avoid a decrease in the Si / Al ratio associated with the dissolution of framework silica, consistent efforts have continued in subsequent attempts to relax the exfoliation conditions. In this regard, the synthesis of UCB-3 zeolite with exfoliated MWW layers under mild conditions has been reported, but the use of corrosive halide reagents such as fluoride and sonication are also required, as was also required for all previously reported exfoliated zeolite variants. Faced the difficulty of scale-up.

[0005] However, regardless of the post-treatment method, it is more desirable to synthesize MWW-type zeolites directly exfoliated by hydrothermal synthesis, but it is very difficult. Recent studies have shown that both MIT-1 and DS-ITQ-2 zeolites consist of exfoliated MWW layers that can be prepared during the direct hydrothermal synthesis process, but in practical terms, it may be limited by the need to use dikwatt organic structure-directing agents (OSDAs). DS-ITQ-2 is reported to consist of 70% single and double MWW layers, with an external surface area of approximately 300 m 2It has a surface area of / g, but less than half of the surface area reported for ITQ-2. Recently, Rimer and colleagues demonstrated that combining an OSDA containing hexamethyleneimine (HMI) with a simple surfactant, cetyltrimethylammonium bromide (CTAB), in direct synthesis results in delaminated MCM-22 zeolite. However, when using this approach, a narrow range of Si / Al ratios is required to avoid the synthesis of amorphous phases, which is restricted to a low Si / Al value range, i.e., a range that is not very desirable for catalysis. Furthermore, important PXRD data at low angles of approximately 5 degrees 2θ or less are missing from the report. Such data are required to evaluate the presence of a reticulated, mesoporous, amorphous silica phase. The possibility of the existence of such a phase remains an important fundamental issue. This is because the synthesis of delaminated zeolites inherently requires not only the disruption of three-dimensional order between nanosheets but also the maintenance of two-dimensional order in the zeolite nanosheets, separating the nanosheets in an arrangement reminiscent of a house made of cards. The nature of this ongoing challenge is summarized by the following typical problems. What is the selective synthesis method for maintaining order in the nanosheets while avoiding the appearance of amorphous phases when breaking the bonds between nanosheets? Furthermore, the lack of obviousness of this problem is raised by methods that need to be environmentally friendly (without halide reagents), measurable (without sonication), and practical from a cost perspective (synthesis without using expensive surfactants).

[0006] As a result, although there has been remarkable progress in the synthesis of adjacent single-sheet MWW materials, existing synthesis tests highlight the difficulty of synthesizing hierarchical MWW-type zeolites with highly delaminated structures that are subject to the above constraints, especially when minimizing the appearance of amorphous phases. It would be highly desirable to expand the synthesis of single-sheet MWW materials to a wider range of Si / Al compositions, particularly relatively high framework Si / Al ratios, according to the requirements of catalysis. Summary of the Invention

[0007] CTA+ (Cetyltrimethylammonium) cations, and a method of combining direct hydrothermal synthesis with OSDA and, in one embodiment, high shear mixing treatment after synthesis are provided. This method synthesizes highly exfoliated Al-SSZ-70 zeolite. The zeolite can exhibit a wide external surface area of 340 m 2 / g, for example, 347 m 2 / g or more. The presence of two organic additives in the hydrothermal synthesis is thought to effectively suppress the stacking of MWW by capping the external surface of the MWW layer with a surfactant. This unique synthesis method synthesizes highly siliceous exfoliated MWW-type zeolites with little or no amorphous phase, which has not been achieved heretofore by direct synthesis using a simple surfactant based on CTA + cations. In one embodiment, the molar % of CTA + is in the range of 10 mol% to 60 mol% with respect to the total organic components (OSDA + CTA + ). In one embodiment, the Al-SSZ-70 zeolite has an Si / Al ratio of 50 or more.

[0008] Among other factors, a novel synthesis method leading to highly siliceous exfoliated MWW-type zeolite Al-SSZ-70 is provided. From the high shear mixing after the synthesis of the layered zeolite precursor, the merit acting on further exfoliation is also realized. The obtained exfoliated zeolite exhibits a similar Bronsted / Lewis acid site distribution (as characterized by FTIR spectroscopy of adsorbed pyridine at various temperatures), enhancing the acid catalytic properties of the non-exfoliated zeolite.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0016] This method enables the preparation of exfoliated Al-SSZ-70 zeolite. The process involves contacting a reaction mixture containing (1) an Al2O3 source, (2) a silica source, (3) an imidazolium cation (OSDA), and (4) a cetyltrimethylammonium cation (CTA + ) under crystallization conditions. In one embodiment, the reaction mixture further contains (5) seeds of Al-SSZ-70 zeolite. The seeds of Al-SSZ-70 preferably have a Si / Al ratio of 50 or more. The term Si / Al (ratio of silica to aluminum) means the molar ratio of silicon dioxide (SiO2) to aluminum oxide (Al2O3).

[0017] CTA + The molar percentage of is generally in the range of 10 mol% to 60 mol% relative to the total organic components (OSDA + CTA + ). This is important. In another embodiment, the amount of CTA + is in the range of 10 mol% to 50 mol%. In another embodiment, CTA + is in the range of 30 mol% to 60 mol%, or even 50 mol% to 60 mol% relative to the total organics in the reaction mixture. CTA +The cation can be supplied when associated with any suitable anion, and the preferred anion is hydroxide. In the reaction mixture, CTA is supplied as CTAOH + preferably.

[0018] In the preparation of SSZ-70, an imidazolium cation selected from the group consisting of 1,3-diisopropylimidazolium cation, 1,3-diisobutylimidazolium cation, and 1,3-dicyclohexylimidazolium cation is used as a structure-directing agent (「OSDA」), also known as a crystallization template. The OSDA useful for the preparation of SSZ-70 is represented by the following structures (1), (2), and (3).

Chemical formula

[0019] The OSDA cation is usually associated with an anion that can be any anion that does not adversely affect the formation of the zeolite. Representative anions include elements of Group 17 of the periodic table (e.g., fluoride, chloride, bromide, and iodide), acetate, carboxylate, hydroxide, sulfate, etc.

[0020] The alumina source may contain a zeolite with a FAU framework. The FAU framework-type zeolite can be an ammonium-type zeolite or a hydrogen-type zeolite. Examples of the FAU framework-type zeolite include zeolite Y (e.g., CBV720, CBV760, CBV780, HSZ-HUA385, and HSZ-HUA390). Zeolite Y can have a molar ratio of SiO2 / Al2O3 of 30 to 500. The FAU framework-type zeolite can contain two or more zeolites. The two or more zeolites can be Y zeolites with different molar ratios of silica and alumina. The FAU framework-type zeolite can be a sole or major source of silicon and aluminum. Another suitable alumina source can be sodium aluminate.

[0021] Examples of independent silicon sources include colloidal silica, fumed silica, precipitated silica, alkali metal silicate, and tetraalkyl orthosilicate.

[0022] Crystallization of the molecular sieve of SSZ-121 from the above reaction mixture can be carried out in a suitable reactor (e.g., a polypropylene jar, or a Teflon-lined or stainless steel autoclave) at a temperature of 100 °C to 200 °C (e.g., 150 °C to 175 °C) for a time sufficient to cause crystallization at the temperature used (e.g., 1 day to 14 days, or 2 days to 10 days) under any of static, rotating or stirring conditions. The hydrothermal crystallization process is usually carried out under pressure, such as in an autoclave, and preferably under autogenous pressure.

[0023] Once the crystals of the molecular sieve are formed, the solid product can be recovered from the reaction mixture by standard mechanical separation techniques such as centrifugation or filtration. The recovered crystals are washed with water and then dried to obtain the as-synthesized molecular sieve crystals. The drying step can be carried out at a high temperature (e.g., 75 °C to 150 °C) for several hours (e.g., about 4 to 24 hours). The drying step can be carried out under vacuum or at atmospheric pressure.

[0024] Once crystallized, the delaminated Al-SSZ-70 zeolite is recovered. The zeolite can be calcined or treated with ozone to remove the OSDA. The recovered zeolite can exhibit an Si / Al ratio of 50 or more. In one embodiment, the Si / Al ratio ranges from 50 to 75.

[0025] In one embodiment, the recovered delaminated Al-SSZ-70 zeolite is also recovered and subjected to high-shear mixing. This can be done before firing. High-shear mixing can include high-shear treatment at 1,500 RPM or more for 1 minute or more. In one embodiment, high-shear mixing includes high-shear treatment at 1,500 to 3,000 RPM or more for a time within the range of 1 minute to 30 minutes. In another embodiment, high-shear mixing includes high-shear treatment at 2,500 RPM or more for 2 minutes or more, followed by a second high-shear treatment at 1,700 RPM or more for 1 minute or more.

[0026] The use of high-shear mixing has been confirmed to cause additional delamination and result in an increase in surface area. In one embodiment, the recovered product can exhibit a surface area of 250 m 2 / g or more. In another embodiment, the zeolite product recovered after high-shear mixing is 300 m 2 / g or more, or even 340 m 2 / g or more. The product can also exhibit a micropore volume of more than 0.1 cm 3 / g and exhibit a substantial crystal structure.

[0027] In the following discussions and examples, powder X-ray diffraction patterns (PXRD) were collected using a Rigaku UltimaIV diffractometer equipped with a CuKα radiation source (λ = 1.5406 Å, 35 kV, 25 mA). SEM images were taken with a Hitachi S5000 microscope. High-resolution transmission electron microscope (HRTEM) images were taken using a JEOL JEM2010 microscope in low-dose mode operating at an acceleration voltage of 200 kV equipped with a LaB6 electron gun. Samples were prepared by embedding in epoxy resin, curing, and then cutting out thin slices (about 30 - 50 nm) with a Leica EM UC7 ultramicrotome. The thin slices were placed on a 300-mesh Cu grid with a thin (20 - 30 nm) lacey carbon support film. Images were taken using a Gatan OneView 4k×4k camera. N2 adsorption isotherms were measured at 77 K with a Micromeritics ASAP2020 adsorption apparatus. Solid 1313C MAS NMR spectra were recorded on a Bruker DSX500 spectrometer and a Bruker 4 mm MAS probe under the conditions of the Bloch decay method and the cross-polarization MAS method. Thermogravimetric analysis (TG) was carried out on a TA Instruments 2950 thermogravimetric analyzer.

[0028] More specifically, for this synthesis, the molar ratio of CTAOH to OSDA in the reaction mixture is used in the range of 1:9 to 6:4. One-pot syntheses of interlayer-exfoliated Al-SSZ-70 zeolite are carried out using different ratios of CTAOH to OSDA, and this importance can be recognized when maintaining a constant total organic hydroxide content. The PXRD patterns of the corresponding as-synthesized samples are shown in Figure 1A. The samples are prepared in (Examples 1-3). The synthesis conditions are listed in Table 4 below.

[0029] Samples consisting of 10 mol% to 50 mol% of CTAOH of the total organic hydroxide (defined as the sum of CTAOH + OSDA in moles) exhibit the PXRD pattern characteristic of Al-SSZ-70 zeolite. As-synthesized zeolites obtained with 10 mol% CTAOH show a PXRD pattern with higher resolution, indicating that they have a highly crystalline MWW-type structure. As the content of the surfactant CTAOH in the total organic hydroxide is further increased to 60 mol% CTAOH, as shown in Figure 1A, zeolite products with much weaker PXRD intensities of the MWW structure result, suggesting that CTAOH has a significant impact on the growth of zeolite crystals. Furthermore, a small amount of additional phase is observed in the as-synthesized zeolite products of the 50 mol% and 60 mol% CTAOH samples in Figure 1A, as indicated by the appearance of small PXRD peaks at approximately 5 degrees. This is likely due to the presence of a small amount of mesoporous amorphous silica phase in these two materials. Since the (310) reflection at 26 - 27 degrees 2θ value remains resolved, crystalline Al-SSZ-70 zeolite is dominant as the main phase over the amorphous phase in the product. This indicates the long-range order of the crystalline MWW layers. At amounts of the CTAOH surfactant in the synthesis gel further exceeding 70 mol% to 90 mol%, more amorphous silica was observed in the mixed phase, and in addition, an MFI impurity phase was present in the as-synthesized products of Figure 1A. This result shows that with less OSDA (i.e., diisobutylimidazolium hydroxide), CTA + The surfactant is suggested to play a major role in the orientation of the formation of amorphous silicate materials, similar to the additional trace impurity phase consisting of MFI-type zeolite. Therefore, the above data indicate that the amount of CTAOH surfactant should be carefully controlled within 10 mol% to 60 mol% to achieve a cleaner synthesis of the desired interlayer-exfoliated SSZ-70 zeolite as the main phase. The PXRD pattern of the calcined samples is shown in Figure 1B and exhibits a well-resolved PXRD pattern corresponding to Al-SSZ-70 zeolite.

[0030] In addition to direct calcination, high-shear mixing of as-synthesized Al-SSZ-70 zeolite is employed. This acts on further delamination. The PXRD patterns of these high-shear mixed samples after calcination are shown in Figure 1C and exhibit PXRD patterns similar to those of the corresponding directly calcined Al-SSZ-70 zeolite material without high-shear mixing shown in Figure 1C. This result indicates that the crystal structure remains intact without significant decomposition during high-shear mixing treatment.

[0031] In addition to the crystal structure, attention is also paid to the porosity of the obtained zeolite samples. The N2 physical adsorption isotherms of the corresponding directly calcined zeolite products (CTAOH in hydrothermal synthesis is 10 mol%, 30 mol%, 50 mol%, and 60 mol%) are shown in Figures 2A - D. Considering the types of Al-SSZ-70 zeolite (used in an amount of 5 wt.% in each zeolite synthesis), when synthesized without CTAOH, the directly calcined zeolite of control Al-SSZ-70(0%) has an external surface area of 161 m 2 / g as shown in Table 2. This is equivalent to some MWW-type zeolite materials in the literature, indicating that a certain degree of delamination occurs during synthesis. The external surface area of the zeolite calcined with 10 mol% CTAOH (the synthesis conditions are item 1 in Table 4 of (Example 2)) is 117 m 2 / g (Table 1 below, Al-SSZ-70(10%)), indicating that a small amount of CTAOH surfactant does not increase the degree of delamination of the MWW-type zeolite layers during synthesis and may actually slightly reduce it. This is consistent with the highly decomposed PXRD pattern shown in Figure 1B.

[0032] However, when the molar fraction of CTAOH in the synthesis gel increases beyond 30 mol%, the external surface area of the directly calcined zeolite in Table 1 increases significantly, consistent with the increased degree of delamination. The external surface areas of the corresponding directly calcined Al-SSZ-70 zeolites using 50 mol% or 60 mol% CTAOH in the synthesis gel are 257 m 2 / g or 301 m2 It should be noted that it is / g. These values are significantly larger than those of the previously reported exfoliated Al-SSZ-70 zeolite. They approach and are comparable to the previously reported surface area of the exfoliated DS-ITQ-2 of dickite. Therefore, the physical adsorption results show that the partial replacement with the surfactant CTA of the OSDA + is favorable for the interlayer exfoliation of the MWW layer during hydrothermal synthesis. In addition to the external surface area, as the amount of CTAOH in the synthesis gel increased from 10 mol% to 60 mol%, the mesopore volume also increased, while both the micropore surface area and the micropore volume decreased accordingly. For example, based on the data in Table 1, the directly calcined zeolite using 60 mol% CTAOH has a small micropore volume of 0.107 cm 3 / g, which is significantly smaller than 0.134 cm of Al-SSZ-70 synthesized without the CTAOH surfactant 3 / g. This further promotes the interlayer exfoliation of the MWW layer with the help of the CTAOH surfactant. It should be mentioned that the increased external surface area and mesopore volume are unlikely to be caused by the formation of an amorphous mesoporous phase, as shown by the PXRD data in Figure 1C. It is because the micropore volume exceeding 0.1 cm 3 / g still shows a high proportion of amorphous microporous phase.

[0033] The influence of the high-shear mixing treatment before calcination in the as-synthesized Al-SSZ-70 zeolite without CTAOH is the same as that of those materials synthesized in the synthesis gel with 10 mol% - 60 mol% CTAOH, and it proves to have a good influence on the interlayer exfoliation when using CTA + Based on the N2 physical adsorption results, the external surface area of 146 m 2 / g in Table 1 slightly decreases in the Al-SSZ-70 zeolite after high-shear mixing with 0 mol% CTAOH compared to the directly calcined analog (161 m in Table 1 2(compared with / g). This indicates that this post-synthesis method is ineffective in exfoliating the MWW-type zeolite layer by itself in the absence of CTAOH. On the other hand, the external surface area of as-synthesized Al-SSZ-70 zeolite synthesized with 10 mol% - 60 mol% of the surfactant CTAOH increased after high-shear mixing treatment compared to the corresponding directly calcined samples in Table 1. The Al-SSZ-70 zeolite synthesized with 60 mol% of CTAOH showed an external surface area of 347 m 2 g -1 (compared with 301 m of the directly calcined external surface area 2 g -1 ). This increase in the external surface area during high-shear mixing of as-synthesized Al-SSZ-70 zeolite emphasizes the unique feature of this synthesis route. The presence of the surfactant CTAOH during hydrothermal synthesis is not only advantageous for direct exfoliation to form a hierarchical porous system during hydrothermal synthesis but also facilitates the formation of a higher degree of exfoliation through post-synthesis high-shear mixing. Therefore, the present method using the surfactant CTAOH and OSDA as two organic additives during the synthesis of Al-SSZ-70 zeolite demonstrates the possibility of constructing a highly exfoliated structure and a hierarchical MWW-type zeolite with a high framework of Si / Al composition of 50 by using this combined method.

Table 1

[0034] The partial replacement of the surfactant CTAOH with OSDA was also confirmed by the combination of TGA and CHN analysis data. As shown in Figures 3A and B, an increase in the amount of CTAOH in the synthesis gel caused an increase in the corresponding surfactant content in the as-synthesized zeolite product. For example, the weight percentages of CTA + in as-synthesized zeolite products of Al-SSZ-70(50%) and Al-SSZ-70(60%) were found to be in the range of 30 wt.% - 35 wt.%, and the corresponding CTA +The molar percentage was calculated to be about 70 mol% to 80 mol% in the final as-synthesized zeolite. The effect of this replacement of OSDA by CTAOH surfactant in the as-synthesized Al-SSZ-70 zeolite sample is the CTA + It is consistent with the observation of the enhanced external surface area with the increase in the amount of surfactant. This result supports the hypothesis that the presence of a large amount of surfactant is favorable for the formation of highly exfoliated Al-SSZ-70 zeolite during hydrothermal synthesis.

[0035] In Figures 4A, C, E, and G, the SEM images of the calcined Al-SSZ-70 zeolite synthesized with 10 mol%, 30 mol%, 50 mol%, and 60 mol% of CTAOH show the typical flower-like morphology of the MWW-type zeolite, and the further observed crystal thickness decreases during synthesis with a high CTAOH content. Specifically, the Al-SSZ-70 zeolite using 60 mol% of CTAOH shows a morphology consisting of much thinner layers (Figure 4G), which are bent and curved. The corresponding zeolite after high-shear mixing treatment exhibits a similar morphology like its directly calcined analog, but the crystal particles are further fragmented into smaller pieces (Figures 4B, 4D, 4F, and 4H), which is also consistent with what is expected for zeolite exfoliation.

[0036] To better understand the effect of the combination of high-shear mixing after synthesis and hydrothermal synthesis with CTAOH, the high-shear mixed Al-SSZ-70 zeolite synthesized with 0 mol% and 60 mol% of CTAOH can be observed by TEM images. The images of the latter sample are shown in Figures 5E and 5F. In these data, a large proportion of single MWW layers are confirmed, which are well exfoliated and stacked disorderly. Most of these single MWW layers are curved, similar to the morphology observed by SEM, and consistent with the exfoliated layers. These images are in contrast to the images in Figures 5A and 5B, corresponding to the control Al-SSZ-70 zeolite after high-shear mixing using a synthesis gel with 0 mol% of CTAOH, representing a bulk crystal morphology composed of multiple MWW layers.

[0037] In FIGS. 5G and 5H, some reticular mesoporous amorphous phases are observed in the same delaminated material as shown in FIGS. 5E and 5F above (i.e., Al-SSZ-70(60%)-HSM). This indicates that even at a substitution level of 60 mol% of CTAOH with respect to a high content of surfactant, e.g., OSDA, it induces the formation of a trace amount of amorphous aluminosilicate phase during hydrothermal synthesis. This amorphous phase is thought to be responsible for the small PXRD peak at approximately 5 degrees 2θ of the as-synthesized material synthesized with 60 mol% of CTAOH in FIG. 1A. This assignment is consistent with past observations of PXRD in amorphous mesoporous materials with 5 degrees 2θ per reflection. The presence of this small peak cannot be attributed to the swollen MWW layers in the precursor. This is because such swollen MWW layers were not observed in the TEM images.

[0038] 13 It is interesting to compare the amorphous phases of Al-SSZ-70 zeolite samples synthesized with a synthesis gel of 60 mol% CTAOH using C MAS NMR spectral analysis. There is a possibility that an amorphous phase exists in Al-SSZ-70 materials synthesized at lower CTAOH substitution levels of 10 mol% and 50 mol% of CTAOH. Al-SSZ-70 using 10 mol% CTAOH shows NMR resonances arising from both OSDA and CTA + cations, as shown in FIG. 6. The coexistence of OSDA and CTA + cations is consistent with the organic composition in the as-synthesized zeolite according to the CHN analysis data in FIGS. 3A and B. The sharpness of the CTA + resonance in FIG. 6 suggests the mobile environment of the CTA + cation in Al-SSZ-70(10%). However, the NMR spectra of zeolites obtained with high contents of 50 mol% and 60 mol% of CTA + surfactants show that the CTA +Two different environments of the cation are shown. One environment corresponds to the resonance at about 14.5 - 15 ppm in Figure 6, representing a sharp resonance characteristic of the Al-SSZ-70 zeolite synthesized with 10 mol% CTAOH. Further, a shoulder at around 15 ppm was observed for the Al-SSZ-70 zeolite using 50 mol% and 60 mol% CTAOH, with the same CTA + It is considered to be due to the head group of the cation, and it is in a more restricted and less mobile environment that is part of the surfactant aggregate. The enhanced signal intensity is observed in the resonance at 15 ppm of the Al-SSZ-70 zeolite with 60 mol% CTAOH, compared to that synthesized with 50 mol% CTAOH. Considering the presence of an amorphous phase in the Al-SSZ-70 zeolite using 60 mol% CTAOH from TEM observations, it is templated by the surfactant aggregate, and this amorphous phase may be responsible for the appearance of the NMR shoulder at 15 ppm, with CTA trapped in the mesoporous tubular pores + is related to the cation. Therefore, the above results indicate that the use of 60 mol% CTAOH made it easier to generate the formation of a trace amount of amorphous phase in the final product.

[0039] The above results emphasize that the challenge of disrupting the order in the z (i.e., parallel to the c-axis) direction in the precursor still persists without synthesizing an amorphous phase. The substitution level of CTAOH used in this method for Al-SSZ-70 synthesis is in the range of 50 mol% - 60 mol% with a minimum amorphous phase.

[0040] The distribution of acid sites of the interlayer exfoliated Al-SSZ-70 prepared by this method is also interesting. Studies were conducted on the (H)Al-SSZ-70(60%)-HSM catalyst and two Al-SSZ-70 controls synthesized without the presence of the CTA surfactant with and without high-shear mixing ((H)Al-SSZ-70(0%) and (H)Al-SSZ-70(0%)-HSM), using pyridine as the relevant probe. The procedure is described in Example 4 below.

[0041] The data shown in Table 2 prove that all three catalysts have the same total number of acid sites, which is approximately 290 μmol / g as probed by gravimetry using pyridine adsorption at a temperature of 423 K. The count value of the total acid sites of pyridine for (H)Al-SSZ-70(0%) in Table 2 is the same as the previously reported one for Al-SSZ-70. The delamination procedure incorporating high-shear mixing does not change the number density of the total acid sites in the zeolite. Regarding the distribution of acid sites, the data in FIGS. 7A and B prove both normal Lewis (1,454 cm -1 ), Bronsted (1,544 cm -1 ), and weakly physically adsorbed pyridine (1,445 cm -1 ). These data show similar normalized L / B (Lewis to Bronsted) band area ratios for both the delaminated (H)Al-SSZ-70(60%)-HSM sample and the control Al-SSZ-70 material synthesized in the absence of CTA + . Neither high-shear mixing nor OSDA for the CTA + surfactant changes these ratios (in other words, the distribution of acid sites) by any significant means.

Table 2

[0042] As related probe reactions, the Friedel-Crafts acylation reaction of 2-methoxynaphthalene (2-MN) and acetic anhydride has also been studied, and the details of the operation are described in the following (Example 5). The exfoliated (H)Al-SSZ-70 (60%)-HSM was compared with two other calcined control catalysts consisting of the same two materials studied with (H)Al-SSZ-70 (0%) and (H)Al-SSZ-70 (0%)-HSM) in Figures 7A and B and Table 2 above. The data shown in Table 3 below summarizes the results. For all catalysts, the dominant product observed (>90%) was 1-acetyl-2-methoxynaphthalene (1,2-AMN), consistent with previous studies. Due to the severe reaction conditions (120 °C and not strict anhydrous conditions), significant coking during catalysis (the catalyst used was black), and lack of completeness of the mass balance closure were observed. Nevertheless, the data shown in Table 4 demonstrates that both control catalysts have the same formation rate of 1,2-AMN product, leading to the conclusion that high shear mixing itself was not effective in increasing the accessibility to external acid sites. In comparison, Al-SSZ-70 exfoliated in a synthesis gel with 60% CTAOH, which has the largest external surface area, has a 1.7-fold higher formation rate of 1,2-AMN product. Furthermore, this catalyst has a reaction rate of 2-MN at least 1.2 times higher than either of the two controls. Al-SSZ-70 exfoliated in a synthesis gel with 60% CTAOH is an excellent catalyst, and its enhanced catalytic performance is correlated with the increased external surface area and accessibility of external acid sites.

Table 3

[0043] The following examples are provided merely as illustrations and not meant to be limiting.

Example

[0044] (Example 1) Synthesis of Conventional Al-SSZ-70 Zeolite with Si / Al = 50

[0045] A conventional microporous zeolite Al-SSZ-70 with Si / Al = 50 was synthesized and used as a seed for the direct hydrothermal synthesis of exfoliated zeolite Al-SSZ-70 using the method described in detail below. In a typical synthesis of the zeolite seed, 0.0436 g of sodium aluminate (Na₂O·Al₂O₃·3H₂O) was dissolved in a mixture of 2.89 g of deionized water and 0.128 g of a 50 wt.% NaOH aqueous solution. After stirring, 8.70 g of an OSDA solution consisting of 9.7 wt.% diisobutylimidazolium (DIBI) hydroxide was added dropwise. A clear mixture was obtained, and 1.14 g of a silica source (AEROSIL® 200 fumed silica) and 0.06 g of a seed (including Al-SSZ-70 zeolite with a calcined Si / Al ratio of 50) were slowly added and manually stirred. After forming a homogeneous mixture, a resulting synthesis gel with a chemical composition of 1.0 SiO₂:0.01 Al₂O₃:0.1 NaOH:0.2 OSDA:30 H₂O was obtained. This mixed gel was sealed in a 23 mL autoclave with a Teflon container and heated at a rotation speed of 27 RPM, 150 °C for 11 days. After hydrothermal synthesis, the as-synthesized zeolite powder was filtered, washed with deionized (DI) water until the measured pH < 8.0, and recovered after drying overnight at 80 °C. The directly calcined Al-SSZ-70 zeolite product was obtained by calcining the as-synthesized zeolite in air at 580 °C for 5 hours to produce a white powder.

[0046] (Example 2) Synthesis of Exfoliated Al-SSZ-70 Zeolite with Different Amounts of CTAOH Surfactant

[0047] The delaminated Al-SSZ-70 zeolite was hydrothermally synthesized in the presence of different amounts of surfactant CTAOH solution. The synthesis procedure is similar to that of the Al-SSZ-70 zeolite without surfactant CTAOH as shown above. However, compared with the above synthesis in the absence of CTAOH, a part of the OSDA was replaced by CTAOH, but the total molar ratio of organic matter / SiO2 (organic matter consisting of OSDA and CTAOH) in the synthesis gel was constant at 0.2. As a result, the relative molar ratio of the total content of CTAOH and organic matter changed from 10 mol% to 90 mol%, but the hydroxide concentration was maintained constant. The detailed information on the synthetic chemical composition is summarized in Table 4 below.

[0048] In the typical synthesis of delaminated Al-SSZ-70 of the samples shown in Table 4, 0.0436 g of sodium aluminate (Na2O·Al2O3·3H2O) was dissolved in a mixture of 2.8895 g of DI water and 0.128 g of 50 wt.% NaOH aqueous solution. After stirring, the required amounts of diisobutylimidazolium hydroxide solution (9.7 wt.%) and CTAOH solution (10 wt.%) were added dropwise. Next, 1.14 g of silica source (AEROSIL® 200) and 0.06 g of seed containing the calcined form of the conventional Al-SSZ-70 zeolite with Si / Al = 50 were added and stirred manually. After the formation of a homogeneous gel, the obtained synthesis gel was sealed in an autoclave with a 23 mL Teflon container and heated at a rotation speed of 27 RPM, 150 °C for 11 days. After synthesis, the as-synthesized zeolite powder was filtered, washed with deionized water until the measured pH < 8.0, dried at 80 °C overnight, and then recovered. The obtained dry powder was calcined in air at 580 °C for 5 hours to synthesize the calcined form of delaminated Al-SSZ-70 (x%) zeolite (x represents the molar ratio of CTAOH in the total organic matter used in the synthesis).

Table 4

[0049] (Example 3) High-shear mixing of as-synthesized Al-SSZ-70 zeolite

[0050] As an alternative to direct calcination, high-shear mixing treatment of as-synthesized materials corresponding to products containing different amounts of CTAOH surfactant (10 mol%, 30 mol%, 50 mol%, and 60 mol% CTAOH) was carried out. This procedure was implemented, generating a greater degree of exfoliation and avoiding the need for sonication, which is difficult to scale up, as required in the synthesis of conventional exfoliated zeolites. In a typical procedure, approximately 5 mL of water was mixed with 0.5 g of the as-synthesized material, and then the as-synthesized zeolite material was made into a wet paste for high-shear mixing by centrifuging at 8,000 RPM for 5 minutes. The supernatant was discarded, and the remaining wet paste was high-shear mixed using a double asymmetric centrifugal mixer (DAC150.1FVZ SpeedMiXer, manufactured by FlacKTec, Inc.) according to the following procedure. Typically, 0.75 - 1.25 g of the wet paste was placed in a 10 g material container together with two cylindrical zirconium beads (d = 9.5 mm, l = 10 mm). The resulting mixture was subjected to high-shear treatment at 2,500 RPM for 2 minutes, after which 100 μL of deionized water was added. Next, the mixture was high-shear mixed again under the same conditions. 10 μL of 1M NH4OH solution was added to the resulting material, and the resulting slurry was high-shear mixed at 1,700 RPM for 1 minute. Then, the material was dried at 60 °C overnight and calcined in air at 580 °C for 5 hours. The resulting samples were designated as Al-SSZ-70(x%)-HSM, where x represents the molar ratio of CTAOH in the total organics used in the synthesis, and HSM means high-shear mixing.

[0051] (Example 4) In-situ permeation FTIR desorption

[0052] Self-supporting wafers for transmission Fourier transform infrared (FTIR) spectroscopy with a spectral resolution of 2 cm -1、and recorded using a Nicolet 6700 FTIR spectrometer with 256 scans. The wafer was placed in an in-situ flow cell (In-situ Research Instruments, Inc., South Bend, IN), treated at 523 K under vacuum, and the sample was dehydrated before pyridine uptake. The background spectrum was collected under the same conditions at 323 K under vacuum with no wafer present. An excess amount of pyridine (20 mL) was injected into the heated gas manifold (423 K), and the zeolite wafer was exposed in the sample cell at 323 K for 1 h under an Ar flow rate (50 mL / min). Subsequently, desorption of pyridine was carried out at 323 K, 423 K, 473 K, 523 K, and 573 K under an Ar flow rate (50 cm3 / min), and each temperature was maintained isothermally for 1 h. Next, the cell was evacuated again, cooled back to 323 K, and spectra were obtained. The integral intensity of the overtone of the skeletal Si-O-Si in the range of 1,740 - 2,080 cm -1 was used to normalize the spectra. The integration of the Lewis and Brønsted bands corresponding to ν(PyH -1 ) at 1,544 cm + , and ν(PyL) at 1,454 cm -1 was used to determine the L / B ratio.

[0053] (Example 5) Consideration of Catalysis

[0054] The Friedel-Crafts acylation reaction of 2-methoxynaphthalene (2-MN) using acetic anhydride as an acylating agent was used as a probe reaction to determine the catalytic activity of the synthesized H-type Al-SSZ-70 zeolite. This reaction was selected as a relevant probe because it has previously been demonstrated that its activity serves as a surrogate for the density of external acid sites on aluminosilicate zeolites. Catalysis was carried out in a 48 mL thick-walled glass reactor with a Teflon cap equipped with a magnetic stirrer and heated in an oil bath set at 120 °C for 6 h under autogenous pressure conditions. 100 mg of the H-type Al-SSZ-70 zeolite catalyst was placed in the reactor together with 10 mL of a 1,2-dichloroethane solvent in which 2-methoxynaphthalene was 0.987 mmol and acetic anhydride (10 mol.% excess acetic anhydride) was 1.1 mmol, and the vessel was inserted into the oil bath. After completion of the reaction, it was placed in an ice bath for 8 min. 1.1 mmol of the internal standard dodecane was added to the final product immediately before filtering the solution through a 0.200 μm syringe filter for gas chromatography analysis. The chemicals used in this procedure were used as received from the manufacturer and no attempt was made to rigorously remove moisture from the atmosphere. These conditions cause severe deactivation, extensive visible coking in the catalyst after the reaction, and lack of completeness of the mass balance closure.

[0055] The conversion of 2-MN is defined as follows.

[0056]

Equation

[0057] The yield of the acylation product is defined as follows.

[0058]

Equation

[0059] The selectivity of the acylation product is defined as follows.

[0060] [Number]

[0061] Define the initial rates of reaction and formation as follows.

[0062] [Number]

[0063] As used in this disclosure, the term "comprises" or "comprising" is intended as an open-ended transitional term and means including the recited element but not necessarily excluding other unrecited elements. The phrase "consists essentially of" or "consisting essentially of" is intended to mean excluding other elements that are essential to the composition. The phrase "consisting of" or "consists of" is intended as a transitional phrase that excludes everything other than the recited elements, except for traces of minor impurities.

[0064] All patents and publications referenced herein are incorporated herein by reference to the extent not inconsistent therewith. It should be understood that the specific structural formulas, functions, and operations of the above-described embodiments are not necessary for practicing the present invention and are merely incorporated in the description to complete exemplary embodiments or embodiments. Further, it should be understood that the specific structural formulas, functions, and operations described in the above-referenced patents and publications can be practiced in combination with the present invention, but they are not essential for its practice. It should be understood that the present invention is practiced as specifically described without actually departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

**Claim 1** A method for preparing delaminated Al-SSZ-70 zeolite, comprising (1)Al ２ O ３ source, (2) a silica source, (3) an imidazolium cation (OSDA), and (4)Cetyltrimethylammonium cation (CTA ＋ ), contacting a reaction mixture containing the same under crystallization conditions. **Claim 2** The method according to claim 1, wherein the reaction mixture further comprises (5) seeds of Al-SSZ-70 zeolite. **Claim 3** The method according to claim 2, wherein the seeds of Al-SSZ-70 zeolite have an Si / Al ratio of 50 or more. **Claim 4** Said CTA ＋ is in the range of 10 mol% to 60 mol% of said total organic components (OSDA + CTA ＋ ), the method according to claim 1. **Claim 5** Said CTA ＋ The method according to claim 4, wherein the mol% of is in the range of 10 mol% to 50 mol%. **Claim 6** Said CTA ＋ The method according to claim 4, wherein the mol% is in the range of 30 mol% to 60 mol%. **Claim 7** The CTA ＋ The method according to claim 4, wherein the mol% of ＋ is in the range of 50 to 60 mol%. **Claim 8** The method according to claim 2, wherein delaminated Al-SSZ-70 zeolite having an Si / Al ratio of 50 or more is recovered. **Claim 9** The method according to claim 8, wherein the Si / Al ratio is in the range of 50 to 75 mol%. **Claim 10** The method according to claim 1, wherein the Al-SSZ-70 zeolite is recovered and calcined. **Claim 11** The method according to claim 1, wherein the Al-SSZ-70 zeolite is recovered and subjected to high-shear mixing. **Claim 12** The method according to claim 11, wherein the Al-SSZ-70 zeolite is recovered from the high-shear mixing and calcined. **Claim 13** The method according to claim 11, wherein the high-shear mixing comprises a high-shear treatment at 1,500 RPM or more for 1 minute or more. **Claim 14** The method according to claim 13, wherein the high-shear mixing comprises a high-shear treatment at 1,500 to 3,000 RPM or more for a time within the range of 1 minute to 30 minutes. **Claim 15** The method according to claim 11, wherein the high-shear mixing comprises a high-shear treatment at 2,500 RPM or more for 2 minutes or more, followed by a second high-shear treatment at 1,700 RPM or more for 1 minute or more. **Claim 16** The method according to claim 1, wherein the imidazolium cation is selected from the group consisting of 1,3-diisopropylimidazolium cation, 1,3-diisobutylimidazolium cation, and 1,3-dicyclohexylimidazolium cation. **Claim 17** The method according to claim 1, wherein the imidazolium cation is supplied to the reaction mixture as a hydroxide. **Claim 18** Said CTA ＋ The method according to claim 1, wherein the cation is supplied to the reaction mixture as hydroxide. **Claim 19** The method according to claim 3, wherein the Al-SSZ-70 zeolite is recovered, subjected to high-shear mixing, and then the product recovered from the high-shear mixing is calcined. **Claim 20** A delaminated Al-SSZ-70 product prepared by the method according to claim 3. **Claim 21** An exfoliated Al-SSZ-70 product prepared by the method according to Claim 11. **Claim 22** 250 m ２ The product according to claim 21, having a surface area of 250 m / g or more. **Claim 23** 300 m ２ The product according to claim 21, which exhibits a surface area of 300 m ２ / g or more. **Claim 24** 340 m ２ The product according to claim 21, which exhibits a surface area of 340 m / g or more. **Claim 25** 0.1 cm ３ The product according to claim 21, showing a micropore volume of more than / g.

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