Method for producing aluminosilicate SSZ-82

Abstract

A method for producing aluminosilicate SSZ-82 is disclosed. This method comprises (1) preparing a reaction mixture comprising an amorphous alumina source mainly containing aluminum hydroxide, an amorphous silica source mainly containing colloidal silica, a source of alkali metal cations, an organic structure directing agent including 1,6-bis(N-cyclohexylpyrrolidinium)hexanedication, hydroxide ions, a seed crystal comprising a crystalline molecular sieve having an SSZ-82 skeleton, and water; (2) heating the reaction mixture under crystallization conditions including a temperature of 100°C to 200°C for a time sufficient to form crystals of aluminosilicate zeolite; and (3) recovering at least a portion of the aluminosilicate zeolite from step (2).

Description

Technical Field

[0001] Current techniques relate to methods for directly synthesizing aluminosilicate zeolites having an SSZ-82 framework structure.

Background Art

[0002] Molecular sieve SSZ-82 is a single crystal phase material having a unique two-dimensional 12- / 10-member ring channel system. The framework structure of SSZ-82 has been assigned the three-letter code SEW by the Structure Commission of the International Zeolite Association.

[0003] The composition and characteristic powder X-ray diffraction pattern of SSZ-82 are disclosed in U.S. Patent No. 7,820,141. The patent also describes the synthesis of molecular sieves in the presence of 1,6-bis(N-cyclohexylpyrrolidinium)hexane dication.

[0004] Conventionally, SSZ-82 has been synthesized in borosilicate form. Borosilicates generally contain acid sites that are too weak in acid strength to catalyze hydrocarbon conversion reactions having commercial benefits. Methods for converting borosilicate zeolites (having weak intrinsic acidity) to aluminosilicate zeolites (having stronger acidity) by various post-synthesis techniques are known, but there remains a need to directly synthesize SSZ-82 in aluminosilicate form in order to eliminate the need for post-synthesis framework modification.

Summary of the Invention

[0005] In one aspect, a method for producing an aluminosilicate zeolite having the SSZ-82 framework structure is provided. This method comprises (1) a step of preparing a reaction mixture, wherein the reaction mixture comprises (a) an amorphous alumina source mainly comprising aluminum hydroxide, (b) an amorphous silica source mainly comprising colloidal silica, (c) a source of alkali metal cations [M], (d) an organic structure directing agent [Q] comprising 1,6-bis(N-cyclohexylpyrrolidinium)hexanedication, (e) hydroxide ions, (f) a seed crystal comprising a crystalline molecular sieve having the SSZ-82 framework, and (g) water; (2) a step of heating the reaction mixture under crystallization conditions including a temperature of 100°C to 200°C for a time sufficient to form crystals of aluminosilicate zeolite; and (3) a step of recovering at least a portion of the aluminosilicate zeolite from step (2). [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 shows a scanning electron microscope (SEM) image of aluminosilicate SSZ-82 immediately after manufacturing according to Example 1.

[0007] [Figure 2] Figure 2 shows the powder X-ray diffraction (XRD) patterns of SSZ-82 (top) and calcined SSZ-82 (bottom) materials immediately after manufacturing in Example 1. [Modes for carrying out the invention]

[0008] Definitions and Abbreviations The term "immediately after manufacturing" refers to the form of zeolite after crystallization and before the removal of organic structure-directing agents.

[0009] Where the “main” compound is referred to in this disclosure, it is understood to mean that the compound is the main compound among the compounds of the same type in the composition, i.e., that it has the largest weight ratio among the compounds of the same type. Thus, for example, the main alumina source refers to the alumina source that accounts for the largest weight relative to the total weight of alumina sources in the composition. Preferably, the term “main” is understood to mean that it is present in greater than 50%, preferably greater than 60%, 70%, 80%, 90%, or 95%, and more preferably the “main” compound accounts for 100%. The terms “main” and “principal” are synonymous and equivalent.

[0010] A "secondary" compound refers to a compound whose weight fraction is not the highest among compounds of the same type. The phrases "secondary" and "secondary degree" are synonymous and equivalent.

[0011] In this disclosure and the following experimental sections, the following abbreviations apply: Al-SSZ-82 (aluminosilicate SSZ-82), B-SSZ-82 (borosilicate SSZ-82), OSDA (organic structure directing agent), d (day), M (mol), g (gram), μmol (micromol), and cm 3 (cubic centimeters).

[0012] Zeolite synthesis Aluminosilicate zeolite having the SSZ-82 framework structure can be synthesized directly by (1) preparing a reaction mixture comprising (a) an amorphous alumina source mainly containing aluminum hydroxide, (b) an amorphous silica source mainly containing colloidal silica, (c) a source of alkali metal cations [M], (d) an organic structure directing agent [Q] containing 1,6-bis(N-cyclohexylpyrrolidinium)hexanedication, (e) hydroxide ions, (f) a seed crystal containing a crystalline molecular sieve having the SSZ-82 framework, and (g) water; (2) heating the reaction mixture under crystallization conditions including a temperature of 100°C to 200°C for a time sufficient to form crystals of aluminosilicate zeolite; and (3) recovering at least a portion of the aluminosilicate zeolite from step (2).

[0013] The reaction mixture may have a composition within the range shown in Table 1, in terms of molar ratio. [Table 1]

[0014] Amorphous alumina sources mainly consist of aluminum hydroxide. Amorphous alumina sources optionally contain small amounts of any type of amorphous alumina other than aluminum hydroxide. For example, amorphous alumina sources may optionally contain small amounts of water-soluble aluminum salts (e.g., aluminum nitrate, aluminum sulfate), aluminum alkoxides (e.g., aluminum isopropoxide), alkali metal aluminates (e.g., sodium aluminate, potassium aluminate), and any combination thereof.

[0015] Amorphous silica sources primarily consist of colloidal silica. Amorphous silica sources may optionally contain small amounts of any other type of amorphous silica besides colloidal silica. For example, amorphous silica sources may optionally contain small amounts of fumed silica, precipitated silica, alkali metal silicates (e.g., sodium silicate, potassium silicate), tetraalkyl orthosilicate (e.g., tetraethyl orthosilicate), and any combination thereof.

[0016] The reaction mixture for forming Al-SSZ-82 preferably does not contain, or substantially contains, crystalline aluminosilicate molecular sieves having a FAU skeleton structure (e.g., zeolite Y). The term "substantially contained" usually means that the reaction mixture composition optionally contains less than 0.1 wt.%, preferably less than 0.05 wt.%, of aluminosilicate molecular sieves having a FAU skeleton structure.

[0017] The alkali metal cation [M] is preferably selected from the group consisting of sodium, potassium, lithium, rubidium, cesium, and mixtures thereof, preferably sodium and / or potassium, more preferably sodium. Suitable sources of alkali metals include alkali metal hydroxides, such as sodium hydroxide and / or potassium hydroxide.

[0018] The organic structure-directing agent [Q] contains 1,6-bis(N-cyclohexylpyrrolidinium) hexane dication represented by the following structure (1). [Chemical formula]

[0019] The organic structure-directing agent [Q] can be present in any suitable form, such as a halide, for example, iodide or bromide, or a hydroxide, such as its hydroxide form.

[0020] The reaction mixture contains at least one source of hydroxide ions. Suitable sources of hydroxide ions include alkali metal hydroxides, ammonium hydroxide, and mixtures thereof. For example, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, ammonium hydroxide, and mixtures thereof, more generally, sodium hydroxide, potassium hydroxide, ammonium hydroxide, and mixtures thereof, and most generally, sodium hydroxide and / or potassium hydroxide. The organic structure-directing agent and / or aluminum hydroxide are used as a source of hydroxide ions.

[0021] The reaction mixture further contains a certain amount of seed crystals of a crystalline molecular sieve having an SSZ-82 framework (e.g., borosilicate SSZ-82, aluminosilicate SSZ-82). The amount of the seed crystals is not particularly limited, but usually corresponds to 0.1 to 25% by weight (e.g., 0.1 to 10% by weight) based on the total weight of silica in the reaction mixture. Using SSZ-82 crystals as seed material is advantageous for shortening the time required for complete crystallization and / or minimizing the formation of other crystalline impurities.

[0022] The reaction mixture components can be supplied from a plurality of sources. Also, two or more reaction mixture components can be provided by one source.

[0023] This 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.

[0024] The reaction mixture can be in the form of a solution, colloidal dispersion (colloidal sol), gel, or paste, but a gel is preferred.

[0025] Crystallization and Synthetic Post-treatment Subsequently, the reaction mixture is subjected to crystallization conditions suitable for forming an aluminosilicate zeolite. The crystallization of the aluminosilicate zeolite may be carried out in a suitable reactor (e.g., a Teflon (registered trademark) liner or a stainless-steel autoclave placed in a convection oven maintained at a suitable temperature) under static or agitated conditions.

[0026] Crystallization in step (b) of the method is typically carried out at a temperature of 100°C to 200°C (e.g., 140°C to 180°C) for a sufficient time for crystallization to occur at the temperature used. For example, at higher temperatures, the crystallization time may be shortened. For example, the crystallization conditions in step (b) of the method may include heating over a period of 1 to 30 days (e.g., at least 1 day or at least 5 days, or 10 to 25 or 21 days). The crystallization time can be determined by methods known in the art, such as sampling the synthetic mixture at various times and measuring the yield and X-ray crystallinity of the precipitated solid. Unless otherwise stated herein, the temperature measured is the temperature of the ambient environment surrounding the material being heated, e.g., the temperature of the atmosphere in which the material is heated. Preferably, crystallization is carried out under autogenous pressure, preferably in an autoclave.

[0027] Typically, aluminosilicate zeolites form in solution and can be recovered by standard methods such as centrifugation or filtration. The separated aluminosilicate zeolites can be further washed, recovered by centrifugation or filtration, and dried.

[0028] As a result of the crystallization process, the recovered fresh product contains at least some of the organic structure-directing agents used in the synthesis within its pores. Therefore, the fresh aluminosilicate zeolite recovered from step (c) may be subjected to heat treatment or other treatment to remove some or all of the organic structure-directing agents incorporated into its pores during synthesis. Heat treatment (e.g., calcination) of the fresh aluminosilicate zeolite typically involves exposing the material to a temperature high enough to remove some or all of the organic structure-directing agents in a furnace in an atmosphere selected from air, nitrogen, ozone, or a mixture thereof. The heat treatment may be carried out at a temperature of 300°C to 800°C (e.g., 400°C to 650°C) for a range of 1 to 10 hours (e.g., 3 to 6 hours). The heat treatment (e.g., calcination) may be carried out in a box furnace in dry air (exposed to a drying tube containing a desiccant to remove moisture from the air). The heat treatment may be carried out first in a nitrogen atmosphere, and then the atmosphere may be switched to air and / or ozone.

[0029] Aluminosilicate zeolites can be further subjected to ion exchange treatment, for example, with aqueous ammonium salts (e.g., ammonium nitrate, ammonium chloride, and ammonium acetate), to remove any remaining alkali metal cations and replace them with protons, thereby producing an acidic form of the zeolite. To the extent desired, the original cations (e.g., alkali metal cations) of the material immediately after production can be replaced by ion exchange with other cations. Preferred substitution cations include hydrogen ions, hydrogen precursors (e.g., ammonium ions), and mixtures thereof. The ion exchange process may be carried out after the zeolite has been dried immediately after production. The ion exchange process may be carried out before or after the calcination process.

[0030] Zeolite Characterization Aluminosilicate SSZ-82 zeolite can have a molar ratio of SiO2 / Al2O3 in the range of 20 to 150 (e.g., 20 to 100, 20 to 50, or 20 to 40, or 25 to 60, 25 to 150, or 25 to 100, or 25 to 50, or 25 to 40). The molar ratio of SiO2 / Al2O3 of the zeolite can be determined by conventional analysis.

[0031] Aluminosilicate SSZ-82 crystals produced according to the method described herein may have a d50 crystal size of 2.0 μm or less (e.g., 1.5 μm or less, or 0.5 to 2.0 μm, or 0.5 to 1.5 μm). More preferably, aluminosilicate SSZ-82 crystals may have a d90 crystal size of 2.0 μm or less (e.g., 1.5 μm or less, or 0.5 to 2.0 μm, or 0.5 to 1.5 μm). Aluminosilicate SSZ-82 crystals may have both the above-described d50 and d90 values.

[0032] 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 measurement involves examining the morphology of the material at high magnification (usually 1,000x to 100,000x). The SEM method can be performed by distributing a representative portion of molecular sieve powder onto a suitable mount so that individual particles are spread reasonably evenly across the entire field of view at 1,000x-100,000x 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 sample crystal sizes d50 and d90 are calculated.

[0033] The applicants have found that the synthesis method described herein can produce aluminosilicate SSZ-82 zeolite with high phase purity (e.g., 95% to 99% by weight as determined by Rietveld XRD analysis). The term “phase purity” as used herein with respect to zeolite means the amount (e.g., on a weight basis) of the single crystalline phase of the zeolite relative to the total weight of all phases (crystalline and amorphous) in the zeolite material. Thus, while other crystalline phases may be present in aluminosilicate SSZ-82 zeolite, aluminosilicate SSZ-82 zeolite comprises at least 95% by weight of SSZ-82, preferably at least 98% by weight of SSZ-82, more preferably at least 99% by weight or at least 99.9% by weight of SSZ-82 as the main crystalline phase, where the weight percent of SSZ-82 is provided based on the total weight of the zeolite crystalline phase present in the composition.

[0034] The powder X-ray diffraction data reported herein were collected using standard techniques with copper K-α emission. Slight variations in diffraction patterns may be due to variations in the molar ratio of skeletal species in specific samples due to changes in lattice constants. Furthermore, sufficiently small crystals affect peak shape and intensity, causing significant peak broadening. Subtle changes in diffraction patterns can also occur due to changes in the organic compounds used in preparation. Calcination can also cause slight shifts in the XRD pattern. Despite these minor perturbations, the fundamental crystal lattice structure remains unchanged. [Examples]

[0035] The following examples are illustrative and not limiting.

[0036] Example 1 Synthesis of Al-SSZ-82 The following components were added sequentially to a Teflon liner: 3.28 g of deionized H2O, 3.04 g of NaOH solution (1M), 2.75 g of 1,6-bis(N-cyclohexylpyrrolidinium)hexanedihydroxyd solution (20.5 wt.%), 0.06 g of aluminum hydroxide (Alfa Aesar, 80.9%), 2.00 g of LUDOX® HS-40 colloidal silica (40% silica solid dispersion), and 0.08 g of B-SSZ-82 species. The final molar ratio in the gel was 1.00 SiO2 / 0.02 Al2O3 / 0.25 NaOH / 0.10 1,6-bis(N-cyclohexylpyrrolidinium)hexanedihydroxyd / 0.10 B-SSZ-82 species / 40.00 H2O. The liner was sealed in a stainless steel autoclaver, and synthesis was carried out for 20 days while rotating at 43 rpm in a 160°C oven. After crystallization, the solid product was isolated by filtration, washed with excess deionized H2O, and dried in a 95°C oven.

[0037] Figure 1 shows the SEM image of the product immediately after manufacturing.

[0038] Samples of the product immediately after manufacturing were calcined in an airflow for 5 hours at 595°C using a standard calcination procedure to remove organic structure-directing agents.

[0039] Powder XRD analysis of the product immediately after manufacturing and after calcination (Figure 2) revealed that both of these products were pure SSZ-82 phase.

[0040] The product immediately after manufacturing and the product after calcination were measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the molar ratio of SiO2 / Al2O3 was found to be 33.

[0041] Next, the calcined material sample was converted to the NH4- form by ion exchange by heating in an ammonium nitrate solution (typically at 95°C for at least 2 hours, using 1 g of NH4NO3 / 1 g of zeolite in 10 mL of deionized water). The zeolite was then filtered. This process was repeated twice for a total of three exchanges. The zeolite was washed with deionized water until its conductivity was less than 50 μS / cm, and then dried in air at 95°C. The resulting NH4- form zeolite was converted to the H form by calcination using a standard calcination method.

[0042] Analysis by the n-propylamine thermal desorption method revealed that the product is H with an acid site density of 922 μmol. + It was revealed that the value is / g.

[0043] Analysis of nitrogen physicoadsorption data using the t-plot method revealed that the pore volume of the product was 0.22 cm³. 3 It was shown to be / g.

[0044] Example 2 Example 1 was repeated, but the amount of aluminum hydroxide was changed to 0.03 g. After heating at 160°C for 14 days, a pure SSZ-82 phase product was obtained, as identified by powder XRD pattern.

[0045] Example 3-15 (Comparative Example) These examples were carried out in the same manner as described in Example 1, using different Si / Al molar ratios, Si and Al sources, and process conditions (shown in Table 2). The colloidal silica source was LUDOX® HS-40 (Grace). The pseudo-boehmite source was Versal® 250 (UOP).

[0046] The results indicated that the obtained product was an amorphous material, a mixed-phase material (i.e., a material containing more than 10% by weight of a phase other than SSZ-82), or a zeolite material having a non-SSZ-82 skeletal structure (e.g., MOR). [Table 2]

Claims

1. A method for producing an aluminosilicate zeolite having the SSZ-82 skeletal structure, (1) A step of preparing a reaction mixture, wherein the reaction mixture is (a) an amorphous alumina source mainly containing aluminum hydroxide, (b) an amorphous silica source mainly containing colloidal silica, (c) Sources of alkali metal cations [M], (d) an organic structure directing agent [Q] containing a 1,6-bis(N-cyclohexylpyrrolidinium)hexanedication, (e) hydroxide ions, (f) A seed crystal containing a crystalline molecular sieve having an SSZ-82 skeleton, (g) The above step, which includes water, (2) The reaction mixture is heated under crystallization conditions including a temperature of 100°C to 200°C for a sufficient time to form crystals of the aluminosilicate zeolite, (3) The method comprising recovering at least a portion of the aluminosilicate zeolite from step (2).

2. The method according to claim 1, wherein the amorphous alumina source contains more than 90% by weight of aluminum oxide.

3. The method according to claim 1, wherein the amorphous silica source contains more than 90% by weight of colloidal silica.

4. The method according to claim 1, wherein the source of the alkali metal cation includes an alkali metal hydroxide.

5. The method according to claim 1, wherein the alkali metal cation is selected from the group consisting of sodium, potassium, and mixtures thereof.

6. The method according to claim 1, wherein the organic structure directing agent [Q] is in its hydroxide form.

7. The method according to claim 1, wherein the amount of the seed crystal corresponds to 0.1 to 25% based on the total amount of silica in the reaction mixture.

8. The method according to claim 1, wherein the reaction mixture has the following composition in molar ratio. Table 1A

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

10. The method according to claim 1, wherein the reaction mixture does not contain a crystalline aluminosilicate molecular sieve having a FAU skeleton structure.

11. The method according to claim 1, wherein the aluminosilicate zeolite has a phase purity of at least 95% by weight.

12. The method according to claim 1, wherein the crystallization conditions in step (2) include heating under self-stimulating pressure.

13. The method according to claim 1, further comprising treating the aluminosilicate zeolite recovered in step (3) to remove at least a portion of the organic structure directing agent [Q].

Images