Synthesis of aluminum-containing molecular sieve SSZ-60

Abstract

A method for preparing an aluminosilicate molecular sieve having an SSY framework structure is described. The method includes (1) preparing a reaction mixture containing an aluminosilicate zeolite having an FAU framework type, N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation and / or N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation, an alkali metal, hydroxide ions, seed crystals, and water, and (2) subjecting the reaction mixture to crystallization conditions sufficient to form aluminosilicate molecular sieve crystals. The resulting molecular sieve is useful as a catalyst, particularly when used in combination with exchanged transition metal(s).

Description

[Technical Field]

[0001] The present disclosure relates to the synthesis of crystalline aluminosilicate molecular sieves having an SSY framework structure, such as SSZ-60. [Background technology]

[0002] Molecular sieves are a group of porous materials with a regular inorganic framework structure and a plurality of pores or channels of defined sizes. The pore or channel size varies among different molecular sieves and determines the range of molecules that can fit within a particular molecular sieve. Due to their microporosity of defined sizes and the resulting molecular specificity, molecular sieves are often considered particularly useful in adsorption, ion exchange, gas separation, and catalytic applications.

[0003] Molecular sieves are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, framework zeolites and other crystalline microporous molecular sieves whose structures have been established are assigned unique three-letter codes. The various molecular sieve framework structures recognized by the Structure Commission of the International Zeolite Association are maintained in a structure database accessible at http: / / www.iza-structure.org / databases.

[0004] SSZ-60 is a molecular sieve material with a unique one-dimensional channel system, with pores defined by 12-membered rings. The structure of SSZ-60 can be derived by modifying the framework of ZSM-23 (MTT), which has pores of one-dimensional 10-membered rings. The framework structure of SSZ-60 has been assigned the three-letter code SSY by the Structure Commission of the International Zeolite Association.

[0005] The composition and characterization X-ray diffraction pattern of SSZ-60 are described in U.S. Pat. No. 6,620,401, which also describes the synthesis of the molecular sieve in the presence of a structure directing agent comprising an N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation or an N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation.

[0006] SSZ-60 is typically prepared directly as a borosilicate. However, borosilicate molecular sieves are not catalytically active enough to be viable for certain hydrocarbon conversion processes. The catalytic activity of molecular sieves can be enhanced by substituting aluminum for boron in the molecular sieve framework via post-synthesis treatment methods.

[0007] According to the present disclosure, a method for the direct synthesis of aluminosilicate SSZ-60 (Al-SSZ-60) is provided, thereby avoiding extraneous post-synthesis processing steps. In addition, the crystallographic T-site locations of framework aluminum atoms in Al-SSZ-60 materials using the direct method described herein may differ from aluminum-containing SSZ-60 materials prepared by conventional post-synthesis aluminum exchange methods. Summary of the Invention

[0008] In one embodiment, a method for synthesizing an aluminosilicate molecular sieve having an SSY framework is provided, the method comprising: (1) preparing a reaction mixture comprising: (a) a source of aluminum and silicon, wherein the source of both aluminum and silicon is an aluminosilicate zeolite having an FAU framework; (b) a structure directing agent [Q] comprising N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation and / or N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation; (c) a source of alkali metal [M]; (d) a source of hydroxide ions; (e) seed crystals; and (f) water; and (2) subjecting the reaction mixture to crystallization conditions sufficient to form aluminosilicate molecular sieve crystals.

[0009] In another aspect, there is provided an aluminosilicate molecular sieve having an SSY framework and, as formed, having N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cations and / or N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cations within its pore structure. [Brief explanation of the drawings]

[0010] [Figure 1] 1 shows the powder X-ray diffraction (XRD) pattern of the finished product of Example 3.

[0011] [Figure 2] 1 shows a scanning electron microscopy (SEM) image of the finished product of Example 3.

[0012] [Figure 3] 1 is a graph showing conversion or yield as a function of temperature for the hydroconversion of n-decane over a Pd / Al-SSZ-60 catalyst. DETAILED DESCRIPTION OF THE INVENTION

[0013] Glossary The term "SSY" refers to the SSY topology or framework as recognized by the International Zeolite Association (IZA) Structure Commission.

[0014] The term "FAU" refers to an FAU-type framework as recognized by the IZA Structure Commission, and the term "FAU zeolite" means an aluminosilicate whose primary crystalline phase is FAU.

[0015] Reaction mixture Generally, an aluminosilicate molecular sieve having an SSY framework may be synthesized by (1) preparing a reaction mixture containing: (a) a source of aluminum and silicon, wherein the source of both aluminum and silicon is an aluminosilicate zeolite having an FAU framework; (b) a structure directing agent [Q] comprising N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation and / or N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation; (c) a source of alkali metal [M]; (d) a source of hydroxide ions; (e) seed crystals; and (f) water; and (2) subjecting the reaction mixture to crystallization conditions sufficient to form aluminosilicate molecular sieve crystals.

[0016] The reaction mixture may have a composition, in terms of molar ratios, within the ranges shown in Table 1. [Table 1]

[0017] The aluminosilicate zeolite with an FAU framework can be a single type of FAU zeolite or a mixture of two or more FAU zeolites. The FAU zeolite can be zeolite Y. The FAU zeolite can be two or more Y zeolites with different silica to alumina molar ratios.

[0018] The source of silicon and / or aluminum may further include one or more additional components, wherein the one or more additional components are present in an amount such that at least 80% (e.g., at least 90%, or at least 95%) of the silicon and / or aluminum is provided by the aluminosilicate zeolite having an FAU framework.

[0019] In addition to the aluminosilicate FAU zeolite, sources of aluminum can include hydrated alumina, aluminum hydroxide, alkali metal aluminates, aluminum alkoxides, water-soluble aluminum salts (e.g., aluminum nitrate), and any combination thereof.

[0020] In addition to the aluminosilicate FAU zeolite, sources of silicon can include colloidal silica, precipitated silica, fumed silica, alkali metal silicates, tetraalkyl orthosilicates (e.g., tetraethyl orthosilicate), and any combination thereof.

[0021] The alkali metal [M] can be lithium, sodium, potassium, rubidium, cesium, or any combination thereof. In some embodiments, the alkali metal is sodium, potassium, or a mixture of sodium and potassium. Examples of suitable alkali metal sources include alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide).

[0022] The structure directing agent [Q] comprises an N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation and / or an N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation, represented by the following structures (1) and (2), respectively. [ka]

[0023] Suitable sources of Q are the hydroxides, chlorides, bromides, iodides and / or other salts of suitable quaternary ammonium compounds.

[0024] The reaction mixture also contains seed crystals of a crystalline molecular sieve material, such as a crystalline molecular sieve having an SSY framework (e.g., borosilicate SSZ-60, aluminosilicate SSZ-60), from a previous synthesis. Preferably, the weight ratio of seed crystals to silica in the aluminosilicate FAU zeolite in the reaction mixture ranges from 0.001:1 to 0.2:1 (e.g., 0.005:1 to 0.15:1, or 0.01:1 to 0.1:1). Seeding can be advantageous for improving SSY selectivity and / or shortening the crystallization process.

[0025] The reaction mixture components can be supplied by two or more sources. Similarly, two or more reaction mixture components can be provided by one source.

[0026] The reaction mixture can be prepared by any conceivable means, although mixing by agitation is preferred, preferably by stirring. The reaction mixture can be prepared in batch, continuous, or semi-continuous mode.

[0027] The reaction mixture may be in the form of a solution, a colloidal dispersion (colloidal sol), a gel, or a paste, with a gel being preferred.

[0028] Crystallization and post-synthesis treatment Crystallization of the molecular sieve from the reaction mixture may be carried out under static or stirred conditions in a suitable reaction vessel, such as a polypropylene jar or Teflon-lined or stainless steel autoclave, contained in a convection oven maintained at a temperature of 100°C to 200°C, for a period of time sufficient for crystallization to occur (e.g., about 1 day to 21 days, or 1 day to 14 days). In some embodiments, crystallization is carried out under static conditions (i.e., without any specific means of stirring during the crystallization process). Preferably, the crystallization process is carried out under autogenous pressure, preferably in an autoclave.

[0029] Once the desired molecular sieve crystals have formed, the solid product can be separated from the reaction mixture by standard mechanical separation techniques such as centrifugation or filtration. The recovered crystals are washed with water and then dried for a few seconds to a few minutes (e.g., 5 seconds to 10 minutes for rapid drying) or for several hours (e.g., 4 hours to 24 hours for oven drying at 75°C to 150°C) to yield the finished molecular sieve crystals. The drying step can be carried out under vacuum or atmospheric pressure.

[0030] As a result of the crystallization process, the recovered finished crystalline molecular sieve product contains within its pore structure at least a portion of the structure directing agent used in its synthesis.

[0031] To form a material that is substantially free of structure-directing agents (e.g., greater than 50%, 60%, 70%, 80%, 90%, 95%, or 99% by weight free of structure-directing agents), some or all of the structure-directing agents used during the synthesis of the resulting material may be removed by heat treatment (e.g., calcination), ozone treatment, or other treatment. Calcination may be carried out in any manner conventionally known in the art; for example, the calcination temperature is generally 300°C to 750°C (e.g., 400°C to 600°C), and the calcination duration is generally 1 to 10 hours (e.g., 3 to 6 hours). In addition, calcination is generally carried out in an oxygen-containing atmosphere, such as air or an oxygen atmosphere.

[0032] To the extent desired, any extraframework alkali metal cations in the finished molecular sieve can be replaced with other cations according to techniques well known in the art (e.g., by ion exchange). Preferred replacement cations include metal ions, hydrogen ions, hydrogen precursors (e.g., ammonium ions), and mixtures thereof. Particularly preferred cations include cations that adjust the catalytic activity of specific hydrocarbon conversion reactions. These can include hydrogen, rare earth metals, and metals from Groups 2 through 15 of the Periodic Table of the Elements.

[0033] Molecular sieve characterization The aluminosilicate molecular sieves produced according to the methods described herein may have a SiO2 / Al2O3 molar ratio (SAR) in the range of 20 to 200 (e.g., 20 to 150, or 20 to 100, or 20 to 75, or 30 to 200, or 30 to 150, or 30 to 100, or 30 to 75, or 40 to 200, or 40 to 150, or 40 to 100, or 40 to 75). The silica to alumina molar ratio of the molecular sieve may be measured by conventional analysis such as atomic absorption spectroscopy (AAS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), or X-ray fluorescence (XRF).

[0034] The aluminosilicate molecular sieve may comprise at least 90 wt.%, or at least 95 wt.%, or at least 97 wt.%, or at least 99 wt.%, based on the total weight of the composition, of a phase-pure SSY framework, as determined by powder XRD or NMR, or other known methods for such determination. The remainder of the composition is non-SSY material, which may include amorphous material, a different crystalline phase, a different framework type (e.g., undissolved FAU), or a combination thereof.

[0035] The powder XRD patterns presented herein were characterized by standard techniques. The radiation was a copper Kα / doublet. Slight variations in the diffraction pattern values ​​may be due to variations in the organic compounds used in the preparation of the molecular sieves and variations in the molar ratio of framework species between samples. Calcination may also produce slight shifts in the XRD pattern. Despite these slight disturbances, the basic crystal lattice structure remains substantially unchanged. [Example]

[0034] The following illustrative examples are intended to be non-limiting.

[0035] Example 1 Synthesis of structure-directing agents The structure directing agent, N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium hydroxide, was prepared according to Example 1 of US Pat. No. 6,620,401.

[0036] Example 2 Synthesis of borosilicate SSZ-60 (B-SSZ-60) Borosilicate SSZ-60 was prepared according to Example 3 of US Pat. No. 6,620,401.

[0037] Example 3 Synthesis of aluminosilicate SSZ-60 (Al-SSZ-60) The following components were added (in order) to a 23 mL Teflon liner: 0.89 g deionized water, 0.27 g of aqueous NaOH (50%), 6.87 g of the OSDA solution (12%) from Example 1, 0.60 g of Tosoh 385HUA USY zeolite (SAR = 100), and 0.06 g of the as-synthesized B-SSZ-60 seeds from Example 2. The final molar ratio of the gel was as follows: 1 SiO / 0.01 AlO / 0.35 NaOH / 0.35 OSDA / 40 HO / 0.1 B-SSZ-60 seeds. The liner was then capped, placed in an autoclave, and heated in a convection oven at 160 °C under tumbling conditions (43 rpm) for 7 days. The solid was then isolated by filtration, washed with deionized water, and dried in an oven at 95 °C.

[0038] Powder XRD analysis revealed that the resulting product was phase-pure SSZ-60. Figure 1 shows the powder XRD of the product.

[0039] The resulting product had a SiO2 / Al2O3 molar ratio of 58 as determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) elemental analysis.

[0040] Example 4 Example 3 was repeated except that no B-SSZ-60 seed crystals were added.

[0041] Powder XRD analysis revealed that the product was a phase other than SSZ-60.

[0042] Example 5 Physicochemical characterization of Al-SSZ-60 The finished product of Example 3 was calcined inside a muffle furnace under a flow of air heated at a rate of 1°C / min to 595°C and held at 595°C for 5 hours, after which the sample was allowed to cool to room temperature.

[0043] The calcined molecular sieves were ion-exchanged to the ammonium form by treating them with 10 mL (per gram of molecular sieve) of 1 N ammonium nitrate solution at 95°C for 2 hours. The solution was cooled, decanted, and the same process was repeated twice. The solids were then separated by filtration, washed with deionized water, and dried in an oven at 95°C. The molecular sieves were then converted to the proton form by calcining them from ambient conditions to 500°C at a rate of 1°C / min, holding at 500°C for 3 hours, and then allowing the sample to cool to room temperature.

[0044] The proton form molecular sieve had a SiO2 / Al2O3 molar ratio of 64 as determined by ICP-AES.

[0045] Analysis of the nitrogen physisorption data by the t-plot method revealed that the material had a micropore volume of 0.18 cm 3 / g, total pore volume 0.30 cm 3 / g, and an external surface area of ​​23.83 m 2 It was revealed that the concentration was / g.

[0046] Analysis by n-propylamine temperature programmed desorption spectroscopy revealed that the molecular sieve had an acid site density of 388 μmol / g.

[0047] Example 6 n-Decane Hydroconversion The calcined Al-SSZ-60 product was impregnated with palladium at a loading of 0.5 wt % using the required amount of Pd(NH3)4(NO3)2 dissolved in deionized water (buffered to pH = 10). The exchanged molecular sieve was dried at 85 °C overnight and then calcined at 482 °C for 3 hours in air. The Pd / Al-SSZ-60 catalyst was then pelletized at 5 kpsi, crushed, and sieved to 20-40 mesh.

[0048] For catalytic testing, 0.5 g of Pd / Al-SSZ-60 TON catalyst (weight of anhydrous sample as determined by thermogravimetric analysis at 600 °C) was loaded into the center of a 23-inch long × 1 / 4-inch OD stainless steel reactor tube, with alundum packed upstream of the catalyst to preheat the feedstock (total pressure 1200 psig; downflow hydrogen rate 12.5 mL / min measured at 1 atmosphere and 25 °C; and downflow liquid feed rate 1 mL / hr). The catalyst was first reduced in flowing hydrogen at 315 °C for 1 hour. Catalytic testing was carried out at temperatures from 400 °F to approximately 610 °F. Products were analyzed by online capillary gas chromatography (GC) approximately once every 60 minutes. Raw data from the GC were collected by an automated data acquisition / processing system, and hydrocarbon conversion was calculated from the raw data. Conversion is defined as the amount (mol%) of n-decane reacted to form other products (including iso-C10). Yields are expressed as mol% of products other than n-decane and include the iso-C10 isomer as a product. The results are shown in Figure 3.

Claims

1. A method for synthesizing aluminosilicate molecular sieves having an SSY skeleton, （１） (a) A source of aluminum and silicon, wherein both the aluminum and silicon sources are aluminosilicate zeolites having a FAU skeleton, and (b) A structure-directing agent [Q] comprising an N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation and / or an N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation, (c) Sources of alkali metals [M] and (d) Sources of hydroxide ions, (e) Seed crystal and, (f) Prepare a reaction mixture containing water, (2) The method comprising providing the reaction mixture to conditions sufficient for crystallization to form crystals of the aluminosilicate molecular sieve, The seed crystal comprises a crystalline molecular sieve having an SSY skeleton. The method wherein the reaction mixture has the following composition in terms of molar ratio. Table 1-2

2. The method according to claim 1, wherein the aluminosilicate zeolite having the FAU skeleton is zeolite Y.

3. The method according to claim 1, wherein the alkali metal includes sodium, potassium, or a mixture of sodium and potassium.

4. The method according to claim 1, wherein in the reaction mixture, the weight ratio of the seed crystal to the silica in the aluminosilicate zeolite having the FAU skeleton is in the range of 0.001:1 to 0.2:

1.

5. The method according to claim 1, wherein the crystallization conditions include heating the reaction mixture at a temperature of 100°C to 200°C under self-generated pressure.

6. An aluminosilicate molecular sieve having an SSY skeleton and, in its completed state, having an N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation and / or an N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation in its pore structure, The aluminosilicate molecular sieve is an aluminosilicate molecular sieve having a molar ratio of SiO₂ / Al₂O₃ in the range of 20 to 200.

7. The aluminosilicate molecular sieve is SiO ２ / Al ２ O ３ The aluminosilicate molecular sieve according to claim 6, wherein the molar ratio of is in the range of 30 to 100.

8. The aluminosilicate molecular sieve according to claim 6, wherein the aluminosilicate molecular sieve has a phase purity of at least 95% by weight.

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