Method for preparing SSZ-43 type zeolites

Abstract

A small crystal borosilicate zeolite having the framework structure of SSZ-43 is provided. The zeolite may be synthesized by (a) preparing a synthesis mixture comprising a boron atom source, a silicon atom source, a structure directing agent comprising a (6R, 10S)- 6,10-dimethyl-5-azaspiro[4.5]decane cation, a source of hydroxide ions, a source of an alkaline and / or alkaline-earth metal, beta zeolite seeds, and water; (b) heating the synthesis mixture under crystallization conditions including a temperature of from 100°C to 200°C for a time sufficient to form crystals of the borosilicate zeolite; and (c) recovering at least a portion of the borosilicate zeolite from step (b).

Description

METHOD FOR PREPARING SSZ-43 TYPE ZEOLITESCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U. S. Provisional Application 63 / 746,415, filed January 17, 2025, the entirety of which is incorporated by reference herein.FIELD

[0002] The present disclosure relates to molecular sieve compositions, methods of making the same, and uses thereof.BACKGROUND

[0003] Molecular sieve materials, both natural and synthetic, may be used as adsorbents and have catalytic properties for hydrocarbon conversion reactions. Certain molecular sieves, such as zeolites, are porous crystalline materials which have an ordered structure as determined by X-ray diffraction. Within such materials there are a large number of uniform cavities and pores which may be interconnected by a number of channels. The sizes and dimensions of these cavities and pores are uniform within a specific molecular sieve material and allow for adsorption of molecules of certain sizes while rejecting those of larger dimensions. Due to their ability to adsorb molecules through size selections, molecular sieves and zeolites have many uses including hydrocarbon conversion processes, e.g., cracking, hydrocracking, disproportionation, alkylation, oligomerization, and isomerization.

[0004] 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 type zeolites and other crystalline microporous molecular sieves, for which a structure has been established, are assigned a three-letter code and are described in the “Atlas of Zeolite Framework Types", eds. Ch. Baerlocher, L. B. McCusker, and D. H. Olson, Elsevier, Sixth Revised Edition, 2007, which is hereby incorporated by reference.

[0005] Molecular sieves may have ordered or disordered structure. Ordered molecular sieves are ordered in three dimensions. When the crystal structure is ordered in all three dimensions, the structure is called an ordered end member structure. Disordered structures (intergrowths), on the other hand, show periodic ordering in less than three dimensions.

[0006] Zeolite SSZ-43 is a disordered molecular sieve material having a unique framework structure containing one-dimensional 12-ring sinusoidal channels (6.5x6.5 Aaperture, 6.5x8.9 A window) constructed from connecting 5461butterfly units. SSZ-43 crystals are intergrowths of two polytypes: about 90% orthorhombic polytype A with ABAB stacking of the 12-rings and about 10% monoclinic polytype B with ABCABC stacking. Such atypical features may potentially exhibit useful shape-selective catalytic properties in applications such as hydrocracking and hydroisomerization of linear alkanes, where isomer product distributions can be influenced significantly by using zeolites with appropriately sized pore openings and surrounding void environments.

[0007] Conventional crystallization of an SSZ-43 synthesis mixture produces large crystals in the range of 0.5 to 10 microns or more. Such large crystals inherently have slower diffusion. For chemical reactions where diffusivity is critical, having a smaller crystal size provides a shorter diffusion path and therefore, enhances the mass transfer, improving the desired reaction pathways with a positive impact on the selectivity and conversion of such reactions.

[0008] Therefore, there is a need for an SSZ-43 zeolite which has a smaller crystal size and more uniform morphology.SUMMARY

[0009] In a first aspect, the present disclosure relates to a method of making a borosilicate zeolite having an SSZ-43 framework structure with a mean crystal size of less than 500 nm. The method comprises the following steps: (a) preparing a synthesis mixture comprising a boron atom source, a silicon atom source, a structure directing agent (Q) comprising a (6R, 105)-6,10-dimethyl-5-azaspiro[4.5]decane cation, a source of hydroxide ions (OH), a source of an alkaline and / or alkaline-earth metal (M), beta zeolite seeds, and water; (b) heating the synthesis mixture under crystallization conditions including a temperature of from 100°C to 200°C for a time sufficient to form crystals of the borosilicate zeolite; and (c) recovering at least a portion of the borosilicate zeolite from step (b).

[0010] In a second aspect, the present disclosure relates to a borosilicate zeolite having an SSZ-43 framework structure, wherein the zeolite has a mean crystal size of less than 500 nm.

[0011] In a third aspect, the present disclosure relates to a process of converting an organic compound to a conversion product comprises contacting the organic compound with a borosilicate zeolite having an SSZ-43 framework structure, wherein the zeolite has a mean crystal size of less than 500 nm.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 shows the powder X-ray diffraction (XRD) pattern of the as-synthesized product of Example 1.

[0013] FIG. 2 shows a Scanning Electron Microscopy (SEM) image of the as-synthesized product of Example 1.

[0014] FIG. 3 shows the powder XRD pattern of the calcined material of Example 1.DETAILED DESCRIPTION

[0015] The present disclosure relates to a method of making small crystal borosilicate zeolites having the framework structure of SSZ-43. The present disclosure also relates to zeolite materials obtained by the method and uses thereof.

[0016] In a first aspect, the present disclosure relates to a method of making a borosilicate zeolite having an SSZ-43 framework structure with a mean crystal size of less than 500 nm. The method comprises the following steps: (a) preparing a synthesis mixture comprising a boron atom source, a silicon atom source, a structure directing agent (Q) comprising a (6R, 105)-6,10-dimethyl-5-azaspiro[4.5]decane cation, a source of hydroxide ions (OH), a source of an alkaline and / or alkaline-earth metal (M), beta zeolite seeds, and water; (b) heating the synthesis mixture under crystallization conditions including a temperature of from 100°C to 200°C for a time sufficient to form crystals of the borosilicate zeolite; and (c) recovering at least a portion of the borosilicate zeolite from step (b).

[0017] The synthesis mixture comprises a boron atom source. Suitable boron atom sources include boric acid and borate salts such as sodium tetraborate or borax and potassium tetraborate.

[0018] The synthesis mixture comprises a silicon atom source. Suitable silicon atom sources include silicon alkoxides (e.g., tetramethylorthosilicate, tetraethylorthosilicate), fumed silica, precipitated silica, alkali metal silicates such as potassium silicate and sodium silicate, and aqueous colloidal suspensions of silica; preferably silicon alkoxides, fumed silica, precipitated silica, alkali metal silicates, and colloidal silica.

[0019] The synthesis mixture may have a SiO2 / B2O3 molar ratio from 30 to 150, such as 50 or 75 to 125.

[0020] The structure directing agent (Q) comprises a (6R, 105)-6,10-dimethyl-5-azaspiro[4.5]decane cation, represented by the following structure (1):

[0021] The structure directing agent (Q) may be present in any suitable form, for example as a halide, such as a fluoride, a chloride, an iodide or a bromide, as a hydroxide or as a nitrate, for instance in its hydroxide form. The structure directing agent (Q) may be present in the synthesis mixture in a Q / SiO2molar ratio of 0.01 to 1.0, such as at least 0.05, or at least 0.10, and up to at most 0.70, or at most 0.60, or at most 0.50, for instance 0.05 to 0.70, 0.10 to 0.60, or 0.10 to 0.50.

[0022] The synthesis mixture contains at least one source of hydroxide ions (OH). For example, hydroxide ions can be present as a counter ion of the organic template (Q). Suitable sources of hydroxide ions can also be selected from the group consisting of alkali metal hydroxides, alkaline-earth metal hydroxides, ammonium hydroxide, and mixtures thereof, such as from sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, ammonium hydroxide, and mixtures thereof. The synthesis mixture may comprise the hydroxide ions source in an OH / SiO2molar ratio of from 0.01 to 0.75, such as 0.05 to 0.70, 0.10 to 0.60, or 0.10 to 0.50.

[0023] The synthesis mixture comprises a source of alkali or alkaline-earth metal cation (M). The alkali or alkaline-earth metal cation is preferably selected from the group consisting of sodium, potassium, lithium, rubidium, calcium, magnesium and mixtures thereof, preferably sodium and / or potassium, more preferably sodium. The sodium source, when present, may be sodium hydroxide, sodium aluminate, sodium silicate, sodium aluminate or sodium salts such as NaCl, NaBr or sodium nitrate. The potassium source, when present, may be potassium hydroxide, potassium aluminate, potassium silicate, a potassium salt such as KC1 or KBr or potassium nitrate. The lithium source, when present, may be lithium hydroxide or lithium salts such as LiCl, LiBr, Lil, lithium nitrate, or lithium sulfate. The rubidium source, when present, may be rubidium hydroxide or rubidium salts such as RbCl, RbBr, Rbl, or rubidium nitrate. The calcium source, when present, may be calcium hydroxide, for example. The magnesium source, when present, may be magnesium hydroxide, for example. The alkali or alkaline-earth metal cation M may also be present in the one source of boron, such as sodium tetraborate, potassium tetraborate, and / or in the sources of silicon, such as sodium silicate and / or potassiumsilicate. The synthesis mixture may comprise the alkali or alkaline-earth metal cation (M) source in a M / SiO2molar ratio of 0.01 to 0.15, such as 0.02 to 0.15, 0.02 to 0.10, 0.03 to 0.15, or 0.03 to 0.10.

[0024] The synthesis mixture typically comprises water in a H2O / SiO2molar ratio of from 1 to 100, such as 5 to 80, or 10 to 50. Depending on the nature of the components in the base mixture, the amount of solvent (e.g., water from the hydroxide solution, and optionally methanol and ethanol from the hydrolysis of silica sources) of the base mixture may be removed such that a desired solvent to SiO2molar ratio is achieved for the synthesis mixture. Suitable methods for reducing the solvent content may include evaporation under a static or flowing atmosphere such as ambient air, dry nitrogen, dry air, or by spray drying or freeze drying. Water may be added to the resulting mixture to achieve a desired H2O / SiO2molar ratio when too much water is removed during the solvent removal process. In some examples, water removal is not necessary when the preparation have sufficient H2O / SiO2molar ratio.

[0025] The amount of beta zeolite seeds in the synthesis mixture can be 0.1 wt. % to 10 wt. % (or 0.5 wt. % to 7 wt. %, or 1 wt. % to 5 wt. %), based on the weight of the silicon atom source in the synthesis mixture. In embodiments, the beta zeolite seeds may have a SiO2 / B2O3 molar ratio of 10 to 200, for example 10 to 150, or 10 to 100, or 10 to 50, or 20 to 200, or 20 to 150, or 20 to 100, or 20 to 50.

[0026] In one or more embodiments, the synthesis mixture after solvent adjustment (e.g., where the desired water to silica ratio is achieved) may be mixed by a mechanical process such as stirring or high shear blending to assure suitable homogenization of the base mixture, for example, using dual asymmetric centrifugal mixing with a mixing speed of 1000 rpm to 3000 rpm.

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

[0028] The synthesis mixture can be prepared according to conventional methods. The components of the synthesis mixture may be combined in any order.

[0029] The synthesis mixture is then subject to crystallization conditions suitable for the borosilicate zeolite to form. Crystallization of the zeolite may be carried out under static or stirred conditions in a suitable reactor vessel, such as for example Teflon® lined or stainless steel autoclaves placed in a convection oven maintained at an appropriate temperature.

[0030] The crystallization in step (b) of the method is typically carried out at a temperature of 100°C to 200°C, such as 120°C to 180°C, preferably 150°C to 170°C, for atime sufficient for crystallization to occur at the temperature used. For instance, at highertemperatures, the crystallization time may be reduced. For instance, the crystallization conditions in step (b) of the method may include heating for a period of from 1 day to 100 days, such as from 1 day to 50 days, for example from 1 day to 30 days, e.g., at least 1 day or at least 5 days up to 20 days or 15 days. The crystallization time can be established by methods known in the art such as by sampling the synthesis mixture at various times and determining the yield and x-ray crystallinity of precipitated solid.

[0031] Typically, the borosilicate zeolite is formed in solution and can be recovered by standard means, such as by centrifugation or filtration. The separated zeolite can also be washed, recovered by centrifugation or filtration and dried.

[0032] As a result of the crystallization process, the recovered product contains within its pores at least a portion of the structure directing agent used in the synthesis. The as- synthesized borosilicate zeolite recovered from step (c) is thus subjected to thermal treatment (e.g., calcination) to remove part or all of the structure directing agent incorporated into its pores during the synthesis. The thermal treatment may be carried out at a temperature in the range of from 300°C to 900°C, for example 350°C to 700°C, or 400°C to 650°C. Particularly, the thermal treatment may be performed in a gas atmosphere having a temperature in the above- described ranges, which may be air, oxygen, nitrogen, or a mixture of two or more thereof Preferably, the thermal treatment is performed for a period in the range of 0.5 to 10 hours, for example 3 to 7 hours, or 4 to 6 hours.

[0033] The borosilicate zeolite prepared according to the present disclosure may also be subjected to an ion-exchange treatment, for example, with aqueous ammonium salts, such as ammonium nitrates, ammonium chlorides, and ammonium acetates, in order to remove remaining alkali metal cations and / or alkaline earth metal cations and to replace them with protons thereby producing the acid form of the zeolite. ’To the extent desired, the original cations of the as-synthesized material, such as alkali metal cations, can be replaced by ion exchange with other cations. Preferred replacing cations can include hydrogen ions, hydrogen precursor ions (e.g., ammonium ions), and mixtures thereof. The ion exchange step may take place after the as-synthesized zeolite is dried. The ion-exchange step may take place either before or after a calcination step.

[0034] The borosilicate zeolite may also be subjected to other treatments such as steaming and / or washing with solvent. Such treatments are well-known to the skilled person and are carried out in order to modify the properties of the zeolite as desired.

[0035] In a second aspect, the present disclosure relates to a borosilicate zeolite having an SSZ-43 framework structure, wherein the zeolite has a mean crystal size of less than 500 nm.

[0036] The crystals of the borosilicate zeolite can have a mean crystal size of less than 400 nm, less than 300 nm, less than 200 nm, or less than 100 nm. Alternatively, the crystals of borosilicate zeolite can have a mean crystal size of 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm. The crystal size is based on individual crystals. Crystal size is the length of longest diagonal of the three-dimensional crystal. Such an average crystal size may be determined by using standard microscopic techniques such as scanning electron microscopy (SEM). The measurement is taken over a statistically meaningful portion of the zeolites produced.

[0037] The borosilicate zeolite can have a SiO2 / B2O3molar ratio of 50 to 150, such as 50 to 100, or 75 to 125.

[0038] It will be understood by a person skilled in the art that the borosilicate zeolite of the present disclosure may contain impurities, such as amorphous materials, unit cells having different topologies (e.g., quartz or molecular sieves of different framework type, that may or may not impact the performance of the resulting catalyst), and / or other impurities (e.g., heavy metals and / or organic hydrocarbons). The zeolite of the present disclosure is preferably substantially free of impurities. The term “substantially free of impurities” (or in the alternative “substantially pure”) used herein means the zeolite contains a minor proportion (less than 50 wt. %), preferably less than 20 wt. %, more preferably less than 10 wt. %, even more preferably less than 5 wt. % and most preferably less than 1 wt. % (e.g., less than 0.5 wt. % or 0.1 wt. %), of such impurities (e.g., “non-SSZ-43 material”), which weight percent (wt. %) values are based on the combined weight of impurities and pure zeolite. The amount of impurities can be appropriately determined by powder XRD, rotating electron diffraction, and / or SEM / TEM (e.g., different crystal morphologies).

[0039] The borosilicate zeolite described herein is substantially crystalline. As used herein, the term “crystalline” refers to a crystalline solid form of a material, including, but not limited to, a single-component or multiple-component crystal form, e.g., including solvates, hydrates, and a co-crystal. Crystalline can mean having a regularly repeating and / or ordered arrangement of molecules and possessing a distinguishable crystal lattice. For example, the zeolite can have different water or solvent content. The different crystalline lattices can be identified by solid state characterization methods such as by XRD (e.g., powder XRD). Other characterization methods known to a person of ordinary skill in the relevant art can further helpidentify the crystalline form as well as help determine stability and solvent / water content. As used herein, the term “substantially crystalline” means a majority (greater than 50 wt. %) of the weight of a sample of a material described is crystalline and the remainder of the sample is a non-crystalline form. In one or more aspects, a substantially crystalline sample has at least 95% crystallinity (e.g., 5% of the non-crystalline form), at least 96% crystallinity (e.g., 4% of the non-crystalline form), at least 97% crystallinity (e.g., 3% of the non-crystalline form), at least 98% crystallinity (e.g., about 2% of the non-crystalline form), at least 99% crystallinity (e.g., 1% of the non-crystalline form), and 100% crystallinity (e.g., 0% of the non-crystalline form).

[0040] T he borosilicate zeolite of the present disclosure, where part or all of the structure directing agent has been removed, may be used as an adsorbent or as a catalyst or support for catalyst in a wide variety of hydrocarbon conversions (e.g., conversion of organic compounds to a converted product).

[0041] The borosilicate zeolite of the present disclosure (where part, or all of the structure directing agent is removed) may be used as an adsorbent, such as for separating at least one component from a mixture of components in the vapor or liquid phase having differential sorption characteristics with respect to the material. Therefore, at least one component can be partially or substantially totally separated from a mixture of components having differential sorption characteristics with respect to the zeolite by contacting the mixture with the zeolite to selectively sorb the one component. For instance, in a process for selectively separating one or more desired components of a feedstock from remaining components of the feedstock, the feedstock may be contacted with a sorbent that comprises the zeolite of the present disclosure at effective sorption conditions, thereby forming a sorbed product and an effluent product. One or more of the desired components are recovered from either the sorbed product or the effluent product.

[0042] The borosilicate zeolite of the present disclosure (where part or all of the structure directing agent is removed) may also be used as a catalyst to catalyze a wide variety of organic compound conversion processes. Examples of chemical conversion processes, which are effectively catalyzed by the zeolite described herein, either alone or in combination with one or more other catalytically active substances including other crystalline catalysts, include those requiring a catalyst with acid activity. Examples of organic conversion processes, which may be catalyzed by the zeolite described herein include cracking, hydrocracking, isomerization, polymeri ation, reforming, hydrogenation, dehydrogenation, dewaxing, hydrodewaxing, adsorption, alkylation, transalkylation, dealkylation, hydrodecylization,disproportionation, oligomerization, dehydrocyclization, conversion of methanol to olefins, deNOx applications, and combinations thereof. The conversion of hydrocarbon feeds can take place in any convenient mode, for example in fluidized bed, moving bed, or fixed bed reactors depending on the types of process desired.

[0043] The borosilicate zeolite of the present disclosure may be formulated into product compositions by combination with other materials, such as binders and / or matrix materials that provide additional hardness to the finished product. These other materials can be inert or catalytically active material.

[0044] For instance, it may be desirable to incorporate the borosilicate zeolite of the present disclosure with another material that is resistant to the temperatures and other conditions employed during use. Such materials include synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and / or metal oxides such as alumina and mixtures thereof. ’The metal oxides may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Use of a resistant material in conjunction with the zeolite of the present disclosure, i.e., combined therewith or present during synthesis of the as-synthesized zeolite, which crystal is active, tends to change the conversion and / or selectivity of the catalyst in certain organic conversion processes. Inactive resistant materials suitably serve as diluents to control the amount of conversion in a given process so that products can be obtained in an economic and orderly manner without employing other means for controlling the rate of reaction. These materials may be incorporated into naturally occurring clays (e.g., bentonite and kaolin) to improve the crush strength of the product under commercial operating conditions. These inactive resistant materials (i.e., clays, oxides, etc.) function as binders for the catalyst. A catalyst having good crush strength can be beneficial because in commercial use, it is desirable to prevent the catalyst from breaking down into powder-like materials.

[0045] Naturally occurring clays which may be used include the montmorillonite and kaolin family, which families include the subbentonites, and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite, or anauxite. Such clays can be used in the raw state as originally mined or after being subjected to calcination, acid treatment or chemical modification. Binders useful for compositing with the borosilicate zeolite of the present disclosure also include inorganic oxides selected from silica, zirconia, titania, magnesia, beryllia, alumina, yttria, gallium oxide, zinc oxide and mixtures thereof.

[0046] In addition to the foregoing materials, the borosilicate zeolite of the present disclosure may be composited with a porous matrix material such as silica-alumina, silica- magnesia, si lica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and sil i ca-magnesia- zirconia.

[0047] T hese binder materials are resistant to the temperatures and other conditions (e.g., mechanical attrition) which occur in various hydrocarbon separation processes. Thus, the borosilicate zeolite of the present disclosure may be used in the form of an extrudate with a binder. They are typically bound by forming a pill, sphere, or extrudate. The extrudate is usually formed by extruding the zeolite, optionally in the presence of a binder, and drying and calcining the resulting extrudate. Further treatments such as steaming, and / or ion exchange may be earned out as required. The zeolite may optionally be bound with a binder having a surface area of at least 100 m2 / g, for instance at least 200 m2 / g, or at least 300 m / g.

[0048] The relative proportions of zeolite and inorganic oxide matrix may vary widely, with the zeolite content ranging from 1 to 90 wt. % and more usually in the range of 2 to 80 wt. % of the composite. An exemplary matrix content range can be from 10 wt. % to 50 wt. %.EXAMPLES

[0049] The present disclosure is further illustrated below without limiting the scope thereto.

[0050] The micropore volume (Vmicro) of the materials can be determined using methods known in the relevant art. For example, the micropore volume of the materials can be measured with nitrogen physisorption, and the data can be analyzed by the t-plot method described by B. C. Lippens et al. “Studies on pore systems in catalysts: V. The t method” J. Catal. 1965, 4, 319-323, which describes the micropore volume method and is incorporated herein by reference.EXAMPLE 1

[0051] 0.88 g of deionized water, 0.70 g of a IN NaOH solution, 3.33 g of (6R, 105)-6,10-dimethyl-5-azaspiro[4.5]decane hydroxide (ROH) solution, 0.02 g of Na2B4O7·10H2O, 0.51 g of fumed silica (CAB-O-SIL® M5, from Cabot Corporation), and 0.01 g of boron beta zeolite seeds (SiO2 / B2O3 molar ratio of about 30) were mixed together in a Teflon liner. The synthesis mixture had the following composition in terms of molar ratios:l. OSiCh: 0.25ROH: O. OIB2O3: 0.05Na20: 0.35OH’: 30H2O.

[0052] The liner was then capped, sealed inside a 23 -mL autoclave, and heated at 160°C under tumbling conditions (43 rpm) inside a convection oven for 5-11 days. The solids were then isolated by centrifugation, washed with deionized water, and dried in an oven at 95°C.

[0053] FIG 1 shows the powder XRD pattern of the as-synthesized product and is consistent with the product being SSZ-43 zeolite. The powder XRD pattern of the product appears to show broad features characteristic of materials with very small crystals.

[0054] The resulting material shows nano-sized small crystallites (about 100 nm). FIG.2 shows the SEM image of the as-synthesized product.

[0055] The as-synthesized product had a SiO2 / B2O3molar ratio of 84, as determined by ICP-AES.

[0056] The as-synthesized material was then calcined in nitrogen by placing a thin bed of material in a calcination dish and heated in a muffle furnace from room temperature to 120°C at a rate of l°C / minute and held at 120°C for 3 hours. Then, the temperature was ramped up to 540°C at a rate of l°C / minute to 595°C and held at 595°C for 5 hours. The material was then allowed to cool to room temperature. The calcined material was then converted to the ammonium form by heating in a solution of ammonium nitrate (typically, 1 g NH4NO3 / 1 g zeolite in 10 mL of H2O at 85°C for at least 3 hours). The material was then filtered. This was repeated twice for a total of 3 exchanges. At the end, the material was washed with deionized water to a conductivity of less than 100 pS / cm dried in air at 85°C.

[0057] FIG. 3 shows the powder XRD pattern of the calcined material.

[0058] The micropore volume of the ion-exchanged and dried material was 0.10 cm3 / g.

[0059] The acid site density was characterized using n-propylamine TPD and found to be 42.38 μmol H+ / g.

Claims

CLAIMS1. A borosilicate zeolite having an SSZ-43 framework structure, wherein the zeolite has a mean crystal size of less than 500 nm.

2. The zeolite of claim 1, wherein the zeolite has a mean crystal size 50 nm to 400 nm.

3. The zeolite of claim 1, wherein the zeolite has a mean crystal size 50 nm to 200 nm.

4. The zeolite of claim 1, wherein the zeolite has a SiO2 / B2O3molar ratio of 50 to 150.

5. The zeolite of claim 1, wherein the zeolite has a SiO2 / B2O3molar ratio of 75 to 125.

6. The zeolite of claim 1, comprising (6R, 105)-6,10-dimethyl-5-azaspiro[4.5]decane cation in its pores.

7. A method of making a borosilicate zeolite having an SSZ-43 framework structure with a mean crystal size of less than 500 nm, the method comprising:(a) preparing a synthesis mixture comprising a boron atom source, a silicon atom source, a structure directing agent (Q) comprising a (6R, 105)-6,10-dimethyl-5-azaspiro[4.5]decane cation, a source of hydroxide ions (OH), a source of an alkaline and / or alkaline-earth metal (M), beta zeolite seeds, and water;(b) heating the synthesis mixture under crystallization conditions including a temperature of from 100°C to 200°C for a time sufficient to form crystals of the borosilicate zeolite; and(c) recovering at least a portion of the borosilicate zeolite from step (b).

8. The method of claim 7, wherein the synthesis mixture has the following composition in terms of molar ratios:SiO2 / B2O3 30 to 150M / SiO20.01 to 0.15 Q / SiO20.01 to 1.00 OH / SiO20.01 to 0.75 H2O / SiO21 to 1009. The method of claim 7, wherein an amount of beta zeolite seeds in the synthesis mixture is from 0.1 wt. % to 10 wt. %, based on the weight of the silicon atom source in the synthesis mixture.

10. The method of claim 7, further comprising calcining the zeolite recovered in step (c) to produce a calcined zeolite.

11. A process of converting an organic compound to a conversion product comprises contacting the organic compound with the borosilicate zeolite of claim 1.

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