Preparation method of small crystal SSZ-81 zeolite

Abstract

A method for making small crystal morphology of SSZ-81 zeolite is disclosed. The method includes forming a reaction mixture containing an alumina-coated silica sol, an alkali metal source, a structure-directing agent containing 1,5-bis(N-methylpiperidinium)pentane dications and / or 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications, a hydroxide ion source, and water, and subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the zeolite. Compositions made according to the method and various uses of the compositions are also disclosed.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Patent Application No. 18 / 177,309, filed March 2, 2023, the disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to small crystal size SSZ-81 zeolite, its synthesis, and use as an adsorbent and catalyst for organic conversion reactions. [Background technology]

[0003] Crystalline zeolite SSZ-81 and its conventional preparation using 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications and / or 1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications as structure directing agents are taught in U.S. Patent Nos. 8,540,963 and 8,545,798. Conventional SSZ-81 has a unique X-ray diffraction pattern that distinguishes it from other known crystalline materials, and SSZ-81 can be used as a catalyst in certain organic transformations.

[0004] Conventional crystallization of SSZ-81 reaction mixtures produces crystals approximately 500 nanometers in size. Such large crystals inherently have slow diffusion. For chemical reactions where diffusion is important, smaller crystal size shortens the diffusion path, thereby facilitating mass transfer and improving the desired reaction pathway, positively impacting the selectivity and conversion of such reactions.

[0005] In accordance with the present disclosure, small crystal morphology of zeolite SSZ-81 can be synthesized using an alumina-coated silica sol in the presence of a structure directing agent comprising 1,5-bis(N-methylpiperidinium)pentane dications and / or 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications. Summary of the Invention

[0006] In one embodiment, a zeolite is provided having a framework structure of SSZ-81 and a d50 crystal size of 250 nanometers or less.

[0007] In another aspect, a method for making a zeolite having a framework structure of SSZ-81 is provided. The method includes: (1) forming a reaction mixture containing: (a) an alumina-coated silica sol; (b) a source of alkali metal [M]; (c) a structure directing agent [Q] comprising one or more of 1,5-bis(N-methylpiperidinium)pentane dications and 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications; (d) a source of hydroxide ions; and (e) water; and (2) subjecting the reaction mixture to crystallization conditions sufficient to form zeolite crystals.

[0008] In a further aspect, there is provided a process for converting a feedstock comprising organic compounds to conversion products, comprising contacting the feedstock with a catalyst under organic compound conversion conditions, wherein the catalyst comprises a zeolite having a framework structure of SSZ-81 and having a d50 crystal size of 250 nanometers or less. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a scanning electron micrograph (SEM) image of the SSZ-81 material after preparation according to Example 1.

[0010] [Figure 2] 1 shows powder X-ray diffraction (XRD) patterns for the as-prepared SSZ-81 (bottom) and calcined SSZ-81 (top) materials of Example 1.

[0011] [Figure 3] 1 shows an SEM image of the SSZ-81 material after preparation according to Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] definition The term "sol" refers to a dispersion of colloidal (ie, particle diameter less than 1 micrometer) solid particles in a liquid.

[0013] The term "as-prepared" refers to the form of the zeolite after crystallization and before removal of the structure directing agent.

[0014] Molecular sieve synthesis SSZ-81 zeolite can be synthesized by (1) forming a reaction mixture containing (a) an alumina-coated silica sol, (b) a source of alkali metal [M], (c) a structure directing agent [Q] comprising one or more of 1,5-bis(N-methylpiperidinium)pentane dications and 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications, (d) a source of hydroxide ions, and (e) water; and (2) subjecting the reaction mixture to crystallization conditions sufficient to form zeolite crystals.

[0015] The reaction mixture may have a composition, in terms of molar ratios, within the ranges set forth in Table 1. [Table 1]

[0016] Alumina-coated silica sols are available from Nalco (Naperville, Illinois) in many different SiO / AlO molar ratios (e.g., 35, 80, 100, 127). The alumina-coated silica sols can include two or more alumina-coated silica sols. Typically, the two or more alumina-coated silica sols are materials with different SiO / AlO molar ratios. The alumina-coated silica sols can be used as the sole or primary source of silicon and aluminum in the reaction mixture.

[0017] The alkali metal [M] can be lithium, sodium, potassium, rubidium, cesium, or any combination thereof. Preferably, the alkali metal is sodium, potassium, or a mixture of sodium and potassium. Suitable alkali metal sources include alkali metal hydroxides, such as sodium hydroxide or potassium hydroxide.

[0018] The structure directing agent [Q] includes one or more of 1,5-bis(N-methylpiperidinium)pentane dications and 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications, which are represented by the following formulas (1) and (2), respectively. [ka]

[0019] Suitable sources of Q include hydroxides, chlorides, bromides, and / or other salts of the relevant diquaternary ammonium compounds.

[0020] The reaction mixture can further include seed crystals of a crystalline molecular sieve material, such as SSZ-81, from a previous synthesis. The amount of seed crystals is not particularly limited, but typically corresponds to 0.1 to 25 wt. % (e.g., 0.1 to 10 wt. %), based on the total weight of silica in the reaction mixture. Seeding can be advantageous in shortening the time required for complete crystallization to occur and / or to minimize the formation of other crystalline impurities.

[0021] The reaction mixture components can be supplied by more than one source, or more than one reaction mixture component can be provided by a single source.

[0022] The reaction mixture can be prepared by any conceivable means, but mixing by agitation, preferably stirring, is preferred. The reaction mixture can be prepared in batch mode, continuous mode, or semi-continuous mode.

[0023] 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.

[0024] Crystallization and post-synthesis treatment Crystallization of the zeolite 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 (e.g., 140°C to 180°C), for a period of time sufficient for crystallization to occur (e.g., about 1 day to 21 days, or 5 days to 15 days). Preferably, crystallization is carried out under autogenous pressure, preferably in an autoclave.

[0025] Once the desired zeolite crystals have formed, the solid product can be separated from the reaction mixture using standard mechanical separation techniques such as centrifugation or filtration. The recovered crystals are washed with water and then dried to obtain the as-prepared zeolite crystals, which can be dried for a few seconds to a few minutes (e.g., 5 seconds to 10 minutes for flash drying) or for several hours (e.g., 4 hours to 24 hours for oven drying at 75°C to 150°C). The drying step can be performed under vacuum or at atmospheric pressure.

[0026] As a result of the crystallization process, the recovered crystalline zeolite product contains within its pores at least a portion of the structure directing agent used in its synthesis.

[0027] The prepared zeolite can be further subjected to heat treatment, ozone treatment, or other treatment to remove all or part of the structure-directing agent used in the synthesis. The heat treatment (e.g., calcination) can be carried out by any method known in the art. For example, the prepared zeolite can be calcined at a temperature of 300°C to 800°C (e.g., 400°C to 650°C) for a period of 1 hour to 10 hours (e.g., 3 hours to 6 hours). Additionally, calcination is generally carried out in an oxygen-containing atmosphere, such as air or an oxygen atmosphere.

[0028] The SSZ-81 synthesized by the described method contains one or more extraframework alkali metal cations (e.g., Na + ). It is usually desirable to remove extraframework alkali metal cations from the zeolite by ion exchange or other known techniques and replace them with hydrogen, ammonium, or any desired metal ion. Particularly preferred cations are those that tailor the catalytic activity for a particular organic conversion reaction. These include hydrogen, rare earth metals, and metals from Groups 2 through 15 of the Periodic Table of the Elements. The amount of metal can range from 0.001 to 20% by weight (e.g., 0.01 to 10% by weight, or 0.1 to 5.0% by weight) of the catalyst.

[0029] Molecular sieve characterization The SSZ-81 synthesized by the methods described herein can have a SiO2 / Al2O3 molar ratio in the range of 10 to 60 (e.g., 10 to 50, or 10 to 40, or 10 to 35, or 20 to 60, or 20 to 50, or 20 to 40, or 25 to 60, or 25 to 50, or 25 to 40, or 25 to 35). The SiO2 / Al2O3 molar ratio of the zeolite can be determined by conventional analysis.

[0030] SSZ-81 crystals prepared as described herein can have a d50 crystal size of 250 nanometers or less (e.g., 200 nanometers or less, 100 nanometers or less, 20-250 nanometers, 20-200 nanometers, or 20-100 nanometers). More preferably, the SSZ-81 crystals have a d90 crystal size of 250 nanometers or less (e.g., 200 nanometers or less, 100 nanometers or less, 20-250 nanometers, 20-200 nanometers, or 20-100 nanometers). The SSZ-81 crystals may have both the d50 and d90 values ​​described above.

[0031] Crystal size is based on individual crystals. Crystal size is the length of the longest diagonal of a three-dimensional crystal. Direct measurement of crystal size can be performed using microscopy techniques such as SEM and TEM. For example, SEM measurements involve examining the morphology of a material at high magnification (typically 1000x to 100,000x). SEM can be performed by distributing a representative portion of molecular sieve powder on a suitable mount so that individual particles are reasonably evenly spread across the entire field of view at 1000x to 10,000x magnification. From this population, a statistically significant sample of random individual crystals (e.g., 50-200) is examined, and the longest diagonal of each individual crystal is measured and recorded. (Particles that are clearly large polycrystalline aggregates should not be included in the measurement.) Based on these measurements, the d50 and d90 values ​​of the sample crystal size are calculated.

[0032] The methods described herein can produce high-purity, and preferably phase-pure, SSZ-81 crystals. As used herein, the term "phase-pure" means that the SSZ-81 zeolite composition can comprise at least 95 wt. % (e.g., at least 97 wt. %, or at least 99 wt. %) zeolite having the SSZ-81 framework structure, based on the total weight of the composition, as measured by powder XRD or NMR, or other known methods for such measurements. The remainder of the composition is non-SSZ-81 material, which can include amorphous material, a different crystalline phase, a different framework type, or any combination thereof.

[0033] The powder X-ray diffraction data reported herein were collected by standard techniques using copper K-α radiation. Minor variations in the diffraction pattern may be due to variations in the molar ratio of framework species in a particular sample, resulting in changes in the lattice constants. Furthermore, sufficiently small crystals affect peak shape and intensity, causing significant peak broadening. Subtle changes in the diffraction pattern may also result from changes in the organic compounds used in the preparation. Calcination may also cause slight shifts in the XRD pattern. Despite these small perturbations, the basic crystal lattice structure remains unchanged.

[0034] Use of small crystal SSZ-81 zeolite Small crystal SSZ-81 zeolites (with some or all of the structure directing agent removed) can be used as adsorbents or catalysts to catalyze a variety of organic compound conversion processes. Examples of chemical conversion processes that can be effectively catalyzed by the SSZ-81 zeolites described herein, alone or in combination with one or more other catalytically active materials (including other crystalline catalysts), include those requiring catalysts with acid activity. Examples of organic conversion processes that can be catalyzed by the SSZ-81 zeolites described herein include cracking, hydrocracking, disproportionation, alkylation, oligomerization, and isomerization.

[0035] Small crystal SSZ-81 zeolite (with some or all of the structure directing agent removed) can be incorporated with other materials that are resistant to the temperatures and other conditions used in organic conversion processes. Such resistant materials can be selected from active materials, inert materials, synthetic zeolites, naturally occurring zeolites, inorganic materials, or mixtures thereof. Examples of such resistant materials can be selected from clay, silica, metal oxides (such as alumina), or mixtures thereof. The inorganic materials may be naturally occurring or in the form of gelatinous precipitates or gels containing mixtures of silica and metal oxides. The use of resistant materials in combination with small crystal SSZ-81 zeolite (i.e., combined with or present during the synthesis of SSZ-81 crystals after the crystals are active) tends to alter the conversion and / or selectivity of the catalyst in certain organic conversion processes. Inert resistant materials preferably function as diluents to control the amount of conversion in a given process so that products can be obtained in an economical and orderly manner without employing other means to control the reaction rate. These materials can be incorporated into natural clays (e.g., bentonite and kaolin) to improve the crush strength of the catalyst under commercial operating conditions. The inert, resistant materials (i.e., clays, oxides, etc.) act as binders for the catalyst. In commercial applications, it is desirable to prevent the catalyst from breaking down into powder-like materials, so a catalyst with good crush strength can be beneficial.

[0036] Natural clays that can be composited with SSZ-81 include the montmorillonite and kaolin families, including sub-bentonites, commonly known as Dixie, McNamee, Georgia, and Florida clays, in which the primary mineral component is halloysite, kaolinite, dickite, nacrite, or anaxite. Such clays can be used in their original as-mined state or after initial calcination, acid treatment, or chemical modification. Binders useful for composites with SSZ-81 also include inorganic oxides selected from silica, zirconia, titania, magnesia, beryllia, alumina, or mixtures thereof.

[0037] Small crystal SSZ-81 zeolite (with some or all of the structure directing agent removed) can be composited with porous matrix materials such as silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, and ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia, and silica-magnesia-zirconia.

[0038] The relative proportions of SSZ-81 zeolite and inorganic oxide matrix can vary widely, with the SSZ-81 zeolite content ranging from 1 to 90 wt % (eg, 2 to 80 wt %) of the composite. [Example]

[0039] The following examples are intended to be illustrative and non-limiting.

[0040] Example 1 Synthesis of small crystals of SSZ-81 The following components were added to a Teflon liner in order: deionized water (0.73 g), NaOH (50% solution) (0.25 g), 1,5-bis(N-methylpiperidinium)pentane dihydroxide (9.23% solution) (5.20 g), and Nalco aluminosilicate sol (SiO / AlO molar ratio = 35; 25 wt% solids in water) (4.00 g). The final molar ratio of the gel was SiO / AlO / NaOH / SDA / H2O = 1 / 0.0286 / 0.20 / 0.1 / 30. The liner was sealed in a stainless steel autoclave and heated in an oven at 160 °C for 10 days with a rotation speed of 43 rpm. After crystallization, the solid product was isolated by filtration, washed with excess deionized water, and dried in an oven at 95 °C.

[0041] An SEM image of the product after preparation is shown in FIG.

[0042] The resulting product had a SiO2 / Al2O3 molar ratio of 28 as determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0043] A sample of the fabricated product was calcined to 550° C. for 5 hours in flowing air using standard calcination procedures to remove the structure directing agent.

[0044] Analysis of both the as-prepared and calcined products by powder XRD (FIG. 2) revealed that both products were SSZ-81.

[0045] A sample of the calcined material was then ion-exchanged to the NH- form by heating with a solution of ammonium nitrate (typically 1 g NH4NO3 / 1 g zeolite in 10 mL deionized water for 2 hours at 95°C). The zeolite was then filtered. This was repeated twice for a total of three exchanges. The zeolite was washed with deionized water until the conductivity was less than 50 μS / cm and dried in air at 95°C. The resulting NH- form zeolite was converted to the H form by calcination using standard calcination procedures.

[0046] Analysis by n-propylamine temperature-programmed desorption showed that the product had an acidic site density of 495 μmol H + It was revealed that the concentration was / g.

[0047] Analysis of the nitrogen physisorption data by the t-plot method showed that the product was 169m 2 / g and an external surface area of ​​0.20 cm 3 It was revealed that the micropore volume was 10 ...

[0048] The chemical and physical properties of the products are summarized in Table 2.

[0049] Example 2 Synthesis of small crystals of SSZ-81 The following components were added to a Teflon liner in order: deionized water (0.97 g), NaOH (50% solution) (0.25 g), 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dihydroxide (10.36% solution) (5.00 g), and Nalco alumina-coated silica sol (SiO2 / Al2O3 molar ratio = 35; 25 wt% solids in water) (4.00 g). The final molar ratio of the gel was SiO2 / Al2O3 / NaOH / SDA / HO = 1 / 0.0286 / 0.20 / 0.1 / 30. The liner was sealed in a stainless steel autoclave and heated in an oven at 160 °C for 10 days with a rotation speed of 43 rpm. The solid product was washed with excess deionized water and dried in an oven at 95 °C. The product was characterized by powder XRD and found to be phase pure SSZ-81.

[0050] The chemical and physical properties of the product are reported in Table 2.

[0051] Example 3 Synthesis of small crystals of SSZ-81 The following components were added to a Teflon liner in order: deionized water (0.88 g), KOH (45% solution) (0.40 g), 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dihydroxide (10.36% solution) (5.00 g), and Nalco alumina-coated silica sol (SiO / AlO molar ratio = 35; 25 wt% solids in water) (4.00 g). The final molar ratio of the gel was SiO / AlO / KOH / SDA / HO = 1 / 0.0286 / 0.20 / 0.1 / 30. The liner was sealed in a stainless steel autoclave and heated in an oven at 160 °C for 10 days with a rotation speed of 43 rpm. The solid product was washed with excess deionized water and dried in an oven at 95 °C. The product was characterized by powder XRD and found to be phase pure SSZ-81.

[0052] The chemical and physical properties of the product are reported in Table 2.

[0053] Example 4 (Comparative) Conventional SSZ-81 synthesis Example 4 was prepared according to the examples in US Pat. No. 8,540,963.

[0054] 3.15 g of 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dihydroxide (10.36% solution) was added to a Teflon container. 0.18 g of aluminosilicate zeolite Y-52 (Union Carbide Corporation), 0.12 g of NaOH (50% solution), and 3.75 g of deionized water were then added to the container. The final molar ratio of the gel was SiO / AlO / NaOH / SDA / HO = 1 / 0.0385 / 0.20 / 0.1 / 35. The final molar ratio of the gel was SiO / AlO / NaOH / SDA / HO = 1 / 0.0385 / 0.20 / 0.1 / 35. The Teflon liner was then capped and sealed in a steel Parr autoclave. The autoclave was placed in a spit in a convection oven at 160°C. The autoclave was shaken at 43 rpm in the heated oven for 14 days. The autoclave was then removed and allowed to cool to room temperature. The solid was then removed by filtration and washed thoroughly with deionized water. The solid was allowed to dry at room temperature.

[0055] The product was characterized by powder XRD and found to be phase pure SSZ-81.

[0056] The chemical and physical properties of the product are reported in Table 2. [Table 2]

Claims

1. A zeolite having the SSZ-81 skeletal structure and a d50 crystal size of 250 nanometers or less.

2. 10 to 60 SiO ２ / Al ２ O ３ A zeolite according to claim 1, having a molar ratio.

3. 20-40 SiO ２ / Al ２ O ３ A zeolite according to claim 1, having a molar ratio.

4. The zeolite according to claim 1, having a d50 crystal size of 20 to 100 nanometers and a d90 crystal size of less than 250 nanometers.

5. The zeolite according to claim 1, further comprising 1,5-bis(N-methylpiperidinium)pentanedications and / or 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentanedications within its pore structure.

6. A method for producing a zeolite having the SSZ-81 skeletal structure, wherein the method is: （１） (a) Alumina-coated silica sol and (b) Alkali metal [M] source, (c) A structural indicator [Q] comprising 1,5-bis(N-methylpiperidinium)pentanedicates and / or 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentanedicates, (d) Hydroxide ion source, (e) Forming a reaction mixture containing water, (2) The reaction mixture is subjected to crystallization conditions sufficient to form crystals of the zeolite, The method, including the method described above.

7. The method according to claim 6, wherein the alkali metal includes sodium, potassium, or a mixture of sodium and potassium.

8. The method according to claim 6, wherein the crystallization conditions include heating the reaction mixture at a temperature of 100°C to 200°C under self-generated pressure.

9. The method according to claim 6, wherein the reaction mixture has the following composition in terms of molar ratio. Table 1

10. The method according to claim 6, wherein the reaction mixture has the following composition in terms of molar ratio. Table 2

11. A process for converting a raw material containing an organic compound into a conversion product, comprising contacting the raw material with a catalyst under organic compound conversion conditions, wherein the catalyst includes a zeolite having a skeletal structure and a d50 crystal size of 250 nanometers or less.

12. The process according to claim 11, wherein the conversion process is at least one of a cracking process, a hydrocracking process, a disproportionation process, an alkylation process, an oligomerization process, or an isomerization process.

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