Synthesis of SWY frame topological structure aluminosilicate molecular sieve

Abstract

A method of synthesizing an aluminosilicate molecular sieve of SWY framework topology by inter-zeolite conversion is described. The process comprises (1) a step of preparing a reaction mixture containing an aluminosilicate zeolite of FAU framework topology, a structure directing agent comprising 1-methyl-1-[7-(trimethylammonium) heptyl] piperidinium cations, a source of alkali metal cations, a source of hydroxyl ions, and water; and (2) heating the reaction mixture to obtain the aluminosilicate molecular sieve with the SWY framework topological structure.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority benefit of U.S. Provisional Application No. 63 / 384,627, filed on November 22, 2022, the disclosure of which is incorporated herein by reference. Technical field

[0003] This disclosure relates to methods for preparing aluminosilicate molecular sieves having an SWY framework topology. Background art

[0004] Molecular sieves are crystalline microporous materials formed by corner - sharing TO4 tetrahedra (T = Si, Al, P, Ge, B, Ti, Sn, etc.), interconnected by oxygen atoms to form pores and cavities of uniform size and shape precisely defined by their crystal structure. Molecular sieves have important commercial applications as absorbents, ion - exchange agents, and catalysts.

[0005] Molecular sieves are classified by the International Zeolite Association (IZA) according to the rules of the IUPAC Molecular Sieve Nomenclature Committee. Once the topology of a new framework is established, a three - letter code is assigned. The code defines the atomic structure of the framework, from which different X - ray diffraction patterns can be described.

[0006] SWY framework topology molecular sieves are members of the ABC - 6 zeolite structure family. SWY framework topology materials exhibit a 12 - layer stacking sequence AABAABAACAAC and contain parallel columns of can cages and double 6 - rings (d6r) units as well as parallel columns of gme and larger swy cages, with the latter two types of cages connected by 8 - membered ring windows. Examples of molecular sieves having an SWY framework topology include STA - 20 and STA - 30. SWY molecular sieves exhibit attractive properties as catalysts or catalyst components in the methanol - to - olefins (MTO) process and selective catalytic reduction of nitrogen oxides (SCR).

[0007] U.S. Patent No. 10,213,776 discloses the composition and characterization X - ray diffraction pattern of aluminophosphate STA - 20, and also describes the synthesis of molecular sieves in the presence of alkylamines (such as trimethylamine) and 1,6 - (1,4 - diazabicyclo[2.2.2]octane)hexyl (diDABCO - C6) cations as structure - directing agents.

[0008] A. Turrina and P. A. Wright et al. (Chem. Mater. 2021, 33, 5242 - 5256) disclose aluminosilicate STA - 30 and its synthesis in the presence of 1,8 - (1,4 - diazabicyclo[2.2.2]octane)octyl (diDABCO - C8) and potassium cations as structure - directing agents.

[0009] According to the present disclosure, it has now been found that in the presence of a structure-directing agent comprising 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium cations, an aluminosilicate molecular sieve having an SWY framework topology can be synthesized by the interzeolite conversion of high-silica FAU zeolite. SUMMARY OF THE INVENTION

[0010] In one aspect, the present disclosure relates to a method for synthesizing an aluminosilicate molecular sieve having an SWY framework topology, the method comprising: (1) preparing a reaction mixture comprising: (a) an aluminosilicate zeolite having an FAU framework topology, (b) a structure-directing agent comprising 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium cations, (c) a source of alkali metal cations, (d) a source of hydroxide ions, and (e) water; and (2) heating the reaction mixture to obtain an aluminosilicate molecular sieve having an SWY framework topology.

[0011] In another aspect, the present disclosure relates to an aluminosilicate molecular sieve having an SWY framework topology and, in its as-synthesized form, containing 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium cations in its pore structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Shows a scanning electron microscope (SEM) image of the as-synthesized SWY material of Example 1.

[0013] Figure 2 Shows the powder X-ray diffraction (XRD) patterns of the as-synthesized SWY (bottom figure) and calcined SWY (top figure) materials of Example 1. DETAILED DESCRIPTION

[0014] Definition

[0015] The term "SWY" refers to the SWY-type topology or framework recognized by the Structure Commission of the International Zeolite Association (IZA).

[0016] The term "FAU" refers to the FAU-type topology or framework recognized by the IZA Structure Commission, and the term "FAU zeolite" means an aluminosilicate in which the main crystalline phase is FAU.

[0017] The "as-synthesized" (or "as-made") aluminosilicate molecular sieve of the present disclosure (i.e., before any optional heat treatment or other treatment to remove the structure-directing agent from the pores) typically includes a structure-directing agent within its pores, which is one of the components in the reaction mixture. The aluminosilicate molecular sieve of the present disclosure in which some or all of the structure-directing agent has been removed (e.g., via heat treatment or other treatment to remove the structure-directing agent from the pores) is an at least partially calcined or "calcined" material.

[0018] Reaction mixture

[0019] Typically, an aluminosilicate molecular sieve having a SWY framework topology can be synthesized by: (1) preparing a reaction mixture comprising: (a) a silicoaluminate zeolite having a FAU framework topology, (b) a structure-directing agent [Q] comprising 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium cations, (c) a source of alkali metal cations [M], (d) a source of hydroxide ions [OH], and (e) water; and (2) heating the reaction mixture to obtain a silicoaluminate molecular sieve having a SWY framework topology.

[0020] The reaction mixture can have a composition in terms of molar ratios within the ranges shown in Table 1.

[0021] Table 1

[0022]

[0023]

[0024] The silicoaluminate zeolite of the FAU framework topology type can be a single type of silicoaluminate FAU zeolite, or a mixture of two or more silicoaluminate FAU zeolites. The silicoaluminate FAU zeolite can be zeolite Y. The silicoaluminate FAU zeolite can be two or more zeolite Ys having different SiO2 / Al2O3 molar ratios.

[0025] The reaction mixture contains one or more sources of alkali metal cations [M]. The alkali metal is preferably selected from the group consisting of sodium, potassium, lithium, rubidium, and mixtures thereof, preferably sodium and / or potassium, more preferably potassium. When present, the sodium source can be sodium hydroxide, sodium aluminate, sodium silicate, sodium aluminate or a sodium salt, such as NaCl, NaBr or sodium nitrate. When present, the potassium source can be potassium hydroxide, potassium aluminate, potassium silicate, a potassium salt such as KCl or KBr or potassium nitrate. When present, the lithium source can be lithium hydroxide or a lithium salt, such as LiCl, LiBr, LiI, lithium nitrate or lithium sulfate. When present, the rubidium source can be rubidium hydroxide or a rubidium salt, such as RbCl, RbBr, RbI or rubidium nitrate.

[0026] The structure-directing agent [Q] comprises 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium cations represented by the following structure (1):

[0027]

[0028] The structure-directing agent [Q] can be in any suitable form, such as a halide, such as iodide or bromide, or as a hydroxide, for example in the form of its hydroxide.

[0029] The synthesis mixture contains at least one source of hydroxide ions [OH]. For example, the hydroxide ions can be present as counterions of the structure-directing agent [Q]. Suitable sources of hydroxide ions can also be selected from the group consisting of: alkali metal hydroxides, ammonium hydroxide and mixtures thereof; for example sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, ammonium hydroxide and mixtures thereof; more commonly sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide and mixtures thereof; most commonly sodium hydroxide and / or potassium hydroxide.

[0030] The reaction mixture can also contain seeds of the crystalline molecular sieve material, such as a crystalline molecular sieve of the SWY framework topology. The amount of seeds is not particularly limited and generally ranges from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, based on 100% by weight of the SiO2 content in the aluminosilicate FAU zeolite framework structure.

[0031] The reaction mixture can be prepared by any conceivable means, and mixing by shaking is preferred, preferably by means of stirring. The reaction mixture can be prepared in batch, continuous or semi-continuous mode.

[0032] The reaction mixture can be in the form of a solution, a colloidal dispersion (colloidal solution), a gel or a paste, with a gel being preferred.

[0033] Crystallization and post-synthesis treatment

[0034] Then the reaction mixture is subjected to crystallization conditions suitable for forming the aluminosilicate SWY molecular sieve. Crystallization can be carried out under static or stirred conditions in a suitable reaction vessel (e.g., a lined or stainless steel autoclave placed in a convection oven maintained at an appropriate temperature). Preferably, crystallization is carried out under autogenous pressure, preferably in an autoclave.

[0035] Crystallization is typically carried out at a temperature of 100 °C to 200 °C (e.g., 120 °C to 170 °C) for a time sufficient for crystallization to occur at the temperature used. For example, at higher temperatures, the crystallization time can be reduced. For example, the crystallization conditions can include heating for 1 day to 20 days (e.g., at least 1 day or at least 3 days up to 15 days or 10 days). The crystallization time can be determined by methods known in the art, such as by sampling the synthesis mixture at different times and determining the yield of the precipitated solid and the X-ray crystallinity.

[0036] Typically, aluminosilicate SWY zeolites are formed in solution and can be recovered by standard methods such as centrifugation or filtration. The separated aluminosilicate zeolite product can also be washed, recovered by centrifugation or filtration and dried.

[0037] As a result of the crystallization process, the recovered as-synthesized crystalline zeolite product contains at least a portion of the structure-directing agent used in the synthesis within its pore structure.

[0038] The as-synthesized zeolite can be further subjected to heat treatment, ozone treatment or other treatments to remove all or part of the structure-directing agent used in its synthesis. Heat treatment (e.g., calcination) of the as-synthesized aluminosilicate zeolite typically involves exposing the material in a furnace to a high temperature in an atmosphere selected from air, nitrogen, ozone or mixtures thereof sufficient to remove part or all of the structure-directing agent. The heat treatment can be carried out at a temperature in the range of 300 °C to 800 °C (e.g., 400 °C to 650 °C) for a period of time in the range of 1 hour to 10 hours (e.g., 3 hours to 6 hours).

[0039] The aluminosilicate SWY zeolite can also be subjected to ion exchange treatment, such as treatment with aqueous ammonium salts (e.g., ammonium nitrate, ammonium chloride and ammonium acetate), to remove the remaining alkali metal cations and replace them with protons, thereby producing the acid form of the zeolite. Within the desired range, the original cations (e.g., alkali metal cations) of the synthetic material can be replaced by ion exchange with other cations. Preferred replacement cations can include hydrogen ions, hydrogen precursors (e.g., ammonium ions) and mixtures thereof. The ion exchange step can be carried out after drying the zeolite to be made. The ion exchange step can be carried out before or after the calcination step.

[0040] Characterization of molecular sieve

[0041] The SWY zeolite synthesized by the methods described herein can have a SiO2 / Al2O3 molar ratio of 10 to 50 (e.g., 15 to 40, or 20 to 35). The molar ratio of silica to alumina of the zeolite can be determined by conventional analysis.

[0042] The synthesis methods described herein can produce aluminosilicate SWY crystals with high purity and are preferably in a pure phase. As used herein, the term "pure phase" means that the aluminosilicate SWY zeolite composition can contain at least 95 wt% (e.g., at least 97 wt% or at least 99 wt%) of the zeolite having the SWY topology, based on the total weight of the composition, as determined by powder XRD or NMR or other measurement methods known for such determinations. The remainder of the composition is non-SWY material, which can include amorphous material, different crystalline phases, different framework types (e.g., undissolved FAU), or any combination thereof.

[0043] The crystals of the aluminosilicate SWY zeolite produced according to the methods described herein can be uniform, with little or no twinning and / or multiple twinning, or can form aggregates.

[0044] The aluminosilicate SWY zeolite crystals prepared according to the methods described herein can have an average crystal size of 0.1 to 10 μm (e.g., 0.1 to 3 μm, or 0.5 to 5 μm, or 1 to 3 μm). The crystal size is based on individual crystals (including twins), but does not include aggregates of crystals. The crystal size is the length of the longest diagonal of the three-dimensional crystal. Direct measurements of the crystal size can be made using microscopic methods such as SEM and TEM. For example, measurements by SEM involve examining the morphology of the material at high magnification (e.g., 1000× to 10,000×). The SEM method can be carried out as follows: A representative portion of the zeolite powder is distributed in a suitable amount such that individual particles are reasonably uniformly dispersed throughout the field of view at 1000× to 10,000× magnification. From this population, a statistically significant sample of random individual crystals (e.g., 50 - 200) is examined, and the longest diagonal of the individual crystals is measured and recorded. Particles that are clearly large polycrystalline aggregates should not be included in the measurement results. Based on these measurement results, the arithmetic mean of the sample crystal size is calculated.

[0045] Examples

[0046] The following illustrative examples are intended to be non-limiting.

[0047] Example 1

[0048] Mix 0.70 g of 45% KOH solution, 3.94 g of deionized water, 3.39 g of 13.80% 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium hydroxide solution and 1.00 g of Zeolyst CBV720 Y-type zeolite (SiO2 / Al2O3 molar ratio = 30) powder in a polytetrafluoroethylene liner. Stir the resulting gel until it becomes homogeneous. Then cover the liner and place it inside a Parr Steel autoclave reactor. Then place the autoclave in an oven heated at 150 °C and heat for 6 days under static conditions. Recover the solid product from the cooled reactor by centrifugation, wash with deionized water and dry at 95 °C.

[0049] The SEM image of the as-synthesized product is shown as Figure 1 follows.

[0050] Calcine the as-synthesized product in a muffle furnace, heat it to 540 °C at a rate of 1 °C / min under an air flow and hold at 540 °C for 5 hours, cool it, and then analyze it by powder XRD.

[0051] Figure 2 The powder XRD patterns of the as-synthesized product and the calcined product are shown graphically, confirming that the synthesized material has a SWY structure.

[0052] Treat the calcined material with 10 mL (per g of zeolite) of 1N ammonium nitrate solution at 90 °C for 2 hours. Cool the solution, decant and repeat the same process.

[0053] Use N2 as the adsorbate and perform micropore volume analysis on the dried ammonium-exchanged product by the BET method. The molecular sieve exhibits a micropore volume of 0.30 cm 3 3 / g.

[0054] Example 2

[0055] Mix 0.60 g of 45% KOH solution, 6.17 g of deionized water, 5.09 g of 13.80% 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium hydroxide solution and 1.50 g of Zeolyst CBV720 Y-type zeolite powder in a polytetrafluoroethylene liner. Stir the gel until it becomes homogeneous. Then cover the liner and place it inside a Parr Steel autoclave reactor. Then place the autoclave in an oven heated at 150 °C for 11 days. Recover the solid product from the cooled reactor by centrifugation, wash with deionized water and dry at 95 °C.

[0056] Powder XRD analysis shows that the product is a pure-phase SWY molecular sieve.

[0057] Example 3

[0058] Mix 1.36 g of 45% KOH solution, 7.94 g of deionized water, 2.54 g of 13.80% 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium hydroxide solution and 1.50 g of Zeolyst CBV720 Y-type zeolite powder in a Teflon liner. Stir the gel until it becomes homogeneous. Then cover the liner and place it inside a Parr Steel autoclave reactor. Then place the autoclave in an oven heated at 150 °C for 5 days. Recover the solid product from the cooled reactor by centrifugation, wash it with deionized water and dry it at 95 °C.

[0059] Powder XRD analysis shows that the product is a pure-phase SWY zeolite molecular sieve.

[0060] Example 4

[0061] Mix 0.80 g of 45% KOH solution, 3.89 g of deionized water, 3.39 g of 13.80% 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium hydroxide solution and 1.00 g of Zeolyst CBV760 Y-type zeolite (SiO2 / Al2O3 molar ratio = 60) powder in a Teflon liner. Stir the gel until it becomes homogeneous. Then cover the liner and place it inside a Parr Steel autoclave reactor. Then place the autoclave in an oven heated at 150 °C for 6 days. Recover the solid product from the cooled reactor by centrifugation, wash it with deionized water and dry it at 95 °C.

[0062] Powder XRD analysis shows that the product is a pure-phase SWY zeolite molecular sieve.

Claims

1. A method for synthesizing an aluminosilicate molecular sieve with a SWY framework topology, the method comprising: (1) Preparing a reaction mixture, the reaction mixture comprising: (a) An aluminosilicate zeolite with a FAU framework topology, (b) A structure-directing agent [Q], which comprises 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium cations, (c) A source of alkali metal cations [M], (d) A source of hydroxide ions [OH], and (e) Water; and (2) Heating the reaction mixture to obtain an aluminosilicate molecular sieve with a SWY framework topology.

2. The method according to claim 1, wherein the reaction mixture has the following composition in terms of molar ratios:

3. The method according to claim 1, wherein the reaction mixture has the following composition in terms of molar ratios:

4. The method according to claim 1, wherein the aluminosilicate zeolite with a FAU framework topology is zeolite Y.

5. The method according to claim 1, wherein the alkali metal includes potassium.

6. The method according to claim 1, wherein the heating is carried out at a temperature in the range of 100 °C to 200 °C.

7. The method according to claim 1, wherein the heating is carried out under autogenous pressure.

8. The method according to claim 1, the method further comprising calcining the aluminosilicate molecular sieve with a SWY framework topology.

9. The method according to claim 1, the method further comprising ion-exchanging the aluminosilicate molecular sieve with a SWY framework topology.

10. An aluminosilicate molecular sieve with a SWY framework topology, and in its as-synthesized form, it contains 1-methyl-1-[7-(trimethylammonio)heptyl]piperidinium cations within its pore structure.

11. The aluminosilicate molecular sieve according to claim 10, wherein the aluminosilicate molecular sieve has a SiO2 / Al2O3 molar ratio of 10 to 50.

12. The aluminosilicate molecular sieve according to claim 10, wherein the aluminosilicate molecular sieve has a SiO2 / Al2O3 molar ratio of 20 to 35.

13. The aluminosilicate molecular sieve according to claim 10, wherein the aluminosilicate molecular sieve has a phase purity of at least 95 wt%.

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