Molecular sieve SSZ-91, method for preparing SSZ-91, and use of SSZ-91.

Abstract

To provide a family of new crystalline molecular sieves designated as SSZ-91, a method for making SSZ-91 and use of SSZ-91.SOLUTION: A molecular sieve SSZ-91 is structurally similar to sieves belonging to molecular sieves of a ZSM-48 family, and is characterized as: (1) having a low degree of defects, (2) having a low aspect ratio that inhibits hydrocracking as compared to conventional ZSM-48 materials having an aspect ratio of greater than 8, and (3) being substantially pure phase.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This application relates to U.S. Patent Applications No. 14 / 837,071, No. 14 / 837,087, No. 14 / 837,108, and No. 14 / 837,094, all of which were filed on 27 August 2015 and are incorporated herein by reference.

[0002] This specification describes a novel family of crystalline molecular sieves named SSZ-91, a method for preparing SSZ-91, and the use of SSZ-91. [Background technology]

[0003] Crystalline molecular sieves and molecular sieves are particularly useful in applications such as hydrocarbon conversion, gas drying, and separation due to their unique sieving properties and catalytic properties. While numerous different crystalline molecular sieves have been disclosed, there is a continuous demand for novel molecular sieves with desirable properties for gas separation and drying, hydrocarbon and chemical conversion, and other applications. Novel molecular sieves, containing novel internal pore structures, can provide improved selectivity in these processes.

[0004] Molecular sieves have distinct crystal structures, as indicated by their individual X-ray diffraction patterns. These crystal structures define the characteristic cavities and pores of different species.

[0005] Molecular sieves are classified by the Structural Committee of the International Zeolite Association in accordance with the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, structurally established skeletal-type zeolites and other crystalline microporous molecular sieves are assigned a three-letter code and listed in the "Atlas of Zeolite Framework Types," 6th Revision, Elsevier (2007), and in the molecular sieve structure database on the International Zeolite Association website (http: / / www.iza-online.org).

[0006] The structure of a molecular sieve can be ordered or disordered. Molecular sieves with an ordered structure have periodic constituent units (PerBUs) that are periodically ordered in all three dimensions. Structures that are structurally disordered exhibit periodic ordering in fewer than three dimensions (i.e., in 2, 1, or 0 dimensions). Disorder occurs when PerBUs are connected in different ways, or when two or more types of PerBUs grow together within the same crystal. A crystal structure created from PerBUs is called an edge-component structure if periodic ordering is achieved in all three dimensions.

[0007] In disordered materials, planar stacking faults occur when the material contains two-dimensional ordering. Planar faults disrupt channels formed by the material's pore system. Planar faults located near the surface restrict diffusion pathways otherwise necessary to allow the supply material components to approach the catalytically active portions of the pore system. Consequently, the catalytic activity of the material typically decreases as the degree of defects increases.

[0008] For crystals with planar defects, interpreting the X-ray diffraction pattern requires the ability to simulate the effects of stacking disorder. DIFFaX is a computer program based on a mathematical model for calculating the intensity from crystals containing planar defects. (See MMJTreacy et al., Proceedings of the Royal Chemical Society, London, A (1991), Vol. 433, pp. 499-520). DIFFaX is a simulation program selected and available from the International Zeolite Association for simulating XRD powder patterns for inter-growing phases of molecular sieves. (See "Collection of Simulated XRD Powder Patterns for Zeolites" by MMJTreacy and JBHiggins, 2001, 4th edition, published for the Structural Committee of the International Zeolite Association). DIFFaX has also been used to theoretically study the intergrowth phases of AEI, CHA, and KFI molecular sieves, as reported by KPLillerud et al. in "Studies in Surface Science and Catalysis," 1994, Vol. 84, pp. 543-550. DIFFaX is a well-known and established method for characterizing disordered crystalline materials with planar defects, such as intergrowth molecular sieves.

[0009] The symbol ZSM-48 represents a family of disordered materials, each characterized by having a one-dimensional 10-membered ring-tubular pore system. The pores are formed from a rolled-up honeycomb-like sheet of condensed tetrahedral 6-membered ring structures, and the pore openings contain 10 tetrahedral atoms. Zeolites EU-2, ZSM-30, and EU-11 are classified as zeolites of the ZSM-48 family.

[0010] According to Lobo and Koningsveld, the ZSM-48 family of molecular sieves consists of nine polytypes (see J.Am.Chem.Soc.2002, 124, 13222-13230). These materials have very similar but not identical X-ray diffraction patterns. Lobo and Koningsveld's paper describes their analysis of three ZSM-48 samples provided by Dr. Alexander Kuperman of Chevron Corporation. Each of the three labeled samples, A, B, and C, was prepared using three different structural modifiers. Comparative Examples 2 and 3 below correspond to samples A and B described in Lobo and Koningsveld's paper.

[0011] The paper by Lobo and Koningsveld states that sample A is polytype 6 and sample B is defective polytype 6. The paper further states that the morphology of sample A consists of needle-shaped crystals with a diameter of approximately 20 nm and a length of approximately 0.5 μm. The morphology of sample B consisted of long, thin crystals with a width of approximately 0.5 μm and a length of 4 to 8 μm. Scanning electron microscope images of samples A and B are shown herein in Figures 3 and 4, as shown in Comparative Examples 2 and 3 below.

[0012] Kirschhock and his collaborators have described the successful synthesis of pure-phase polytype 6 (see Chem.Mater.2009, 21, 371-380). In that paper, Kirschhock and his collaborators describe that their pure-phase polytype 6 material (which they call COK-8) has a morphology consisting of long, needle-like crystals (15-80 nm wide; 0.5-4 μm long) with a very large length-to-width ratio, growing along the direction of interconnected pores.

[0013] As shown in Kirschhock's paper, molecular sieves from the ZSM-48 family consist of a 10-membered ring, one-dimensional pore structure, where the channels formed by interconnected pores extend perpendicular to the long axis of the needle-like crystal. Thus, the channel openings are located at the short ends of the needle-like crystals. As the length-to-diameter ratio (also known as the aspect ratio) of these needle-like crystals increases, the diffusion pathways for the hydrocarbon feed material also increase. As the diffusion pathways increase, the residence time of the feed material in the channels also increases. Longer residence times result in an increase in undesirable hydrocracking of the feed material, accompanied by a decrease in selectivity. [Overview of the project] [Problems that the invention aims to solve]

[0014] Therefore, there is currently a need for ZSM-48 molecular sieves that exhibit a lower degree of hydrogenolysis than known ZSM-48 molecular sieves. Furthermore, there is an ongoing need for ZSM-48 molecular sieves that are pure or substantially pure and have a low degree of disorder (low defect rate) within their structure. [Means for solving the problem]

[0015] The following is a family of crystalline molecular sieves with distinctive properties, referred to herein as “Molecular Sieve SSZ-91” or simply “SSZ-91”. Molecular Sieve SSZ-91 is structurally similar to sieves belonging to the ZSM-48 family of zeolites, and is characterized by (1) a low defect rate, (2) a low aspect ratio that suppresses hydrocracking compared to conventional ZSM-48 materials with an aspect ratio greater than 8, and (3) being substantially pure phase.

[0016] As shown in the following examples, ZSM-48 materials lacking any one of the three characteristic combinations of SSZ-91 (low aspect ratio, low EU-1 content, and high polytype 6 composition) exhibit poor catalytic performance.

[0017] In one embodiment, a molecular sieve is provided having a silicon oxide to aluminum oxide molar ratio of 40 to 200. In its as-manufactured form, the X-ray diffraction line shown in Table 2 of this specification serves as an indicator of SSZ-91.

[0018] As determined by DIFFaX simulations and as described by Lobo and Koningsveld in J.Am.Chem.Soc.2012, 124, 13222-13230 (where disorder is regulated by three different defect probabilities), the SSZ-91 material consists of at least 70% polytype 6 of the total ZSM-48 type material present in the product. It should be noted that the phrase "at least 70%" includes the case where no other ZSM-48 polytypes are present in the structure, i.e., the material is 100% pure phase polytype 6.

[0019] In another embodiment, SSZ-91 is substantially a pure phase. SSZ-91 contains a further EUO-type molecular sieve phase in an amount between 0 and 3.5% by weight of the total product (including).

[0020] Molecular sieve SSZ-91 has a morphology characterized as a polycrystalline aggregate, where each aggregate is characterized as being composed of crystallits collectively having an average aspect ratio between 1 and 8 (including). SSZ-91 exhibits a lower degree of hydrocracking than ZSM-48 material with a higher aspect ratio. An aspect ratio of 1 is the ideal minimum, in which case the length and width are the same.

[0021] In another embodiment, a method for preparing a crystalline material is provided, comprising contacting (1) a source of at least one silicon oxide; (2) a source of at least one aluminum oxide; (3) a source of at least one element selected from Group 1 and Group 2 of the periodic table; (4) hydroxide ions; and (5) a hexamethonium cation under crystallization conditions.

[0022] In yet another aspect, a method for preparing a crystalline material having the X-ray diffraction profile of Table 2 as-produced, comprising: (a) preparing a reaction mixture comprising (1) at least one source of silicon oxide, (2) at least one source of aluminum oxide, (3) at least one source of an element selected from Group 1 and Group 2 of the Periodic Table, (4) hydroxide ions, (5) hexamethonium cations, and (6) water; (b) maintaining the reaction mixture under crystallization conditions sufficient to form crystals of the molecular sieve. The above method is provided thereby. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] [Figure 1] A diagram showing the powder X-ray diffraction (XRD) pattern of as-synthesized molecular sieve prepared in Comparative Example 1.

[0024] [Figure 2] A scanning electron micrograph of as-synthesized molecular sieve prepared in Comparative Example 1.

[0025] [Figure 3] A scanning electron micrograph of as-synthesized molecular sieve prepared in Comparative Example 2.

[0026] [Figure 4] A scanning electron micrograph of as-synthesized molecular sieve prepared in Comparative Example 3.

[0027] [Figure 5] A diagram showing the powder XRD pattern of as-synthesized molecular sieve SSZ-91 prepared in Example 7.

[0028] [Figure 6]This is a scanning electron microscope image of the as-synthesized molecular sieve SSZ-91 prepared in Example 7.

[0029] [Figure 7] This is a scanning electron microscope image of the as-synthesized molecular sieve prepared in Example 8.

[0030] [Figure 8] This figure shows plots of several simulated XRD patterns created with DIFFaX, and the powder XRD pattern of the as-synthesized molecular sieve SSZ-91 prepared in Example 8.

[0031] [Figure 9] This figure shows plots of several simulated XRD patterns created with DIFFaX, and the powder XRD pattern of the as-synthesized molecular sieve prepared in Example 11.

[0032] [Figure 10] This figure shows plots of several simulated XRD patterns created with DIFFaX, and the powder XRD pattern of the as-synthesized molecular sieve prepared in Comparative Example 1.

[0033] [Figure 11] This is a scanning electron microscope image of the as-synthesized molecular sieve prepared in Example 13.

[0034] [Figure 12] This figure shows plots of several simulated XRD patterns created with DIFFaX, and the powder XRD pattern of the as-synthesized molecular sieve prepared in Example 13. [Modes for carrying out the invention]

[0035] introduction The term "active source" means a reagent or precursor material capable of supplying at least one element in a reactive form that can be incorporated into a molecular sieve structure. The terms "source" and "active source" may be used interchangeably herein.

[0036] The terms “molecular sieve” and “zeolite” are synonymous and include (a) intermediate and (b) final or target molecular sieves and molecular sieves produced by (1) direct synthesis or (2) post-crystallization treatment (secondary modification). Secondary synthesis techniques enable the synthesis of target materials from intermediate materials by heteroatomic lattice substitution or other techniques. For example, aluminosilicates can be synthesized from intermediate borosilicates by post-crystallization heteroatomic lattice substitution from B to Al. Such techniques are publicly known, for example, as described in U.S. Patent No. 6,790,433, issued September 14, 2004, by CYChen and Stacey Zones.

[0037] " * The terms "MRE-type molecular sieve" and "EUO-type molecular sieve" include all molecular sieves and their isotypes assigned to the International Zeolite Association's framework, as described in the "Atlas of Zeolite Framework Types," edited by Ch. Baerlocher, LBMcCusker and DHOlson, Elsevier, 6th revision, 2007, and the database of zeolite structures on the International Zeolite Association's website (http: / / www.iza-online.org).

[0038] The term “periodic table” refers to the IUPAC version of the periodic table of elements dated June 22, 2007, and the numbering scheme for the groups of the periodic table is as described in Chem.Eng.News, 63(5), 26-27(1985).

[0039] For the purposes of this specification and the accompanying claims, unless otherwise indicated, all numerical values ​​representing quantities, percentages or ratios and other numerical values ​​used herein are understood to be modified in all cases by the term “approximately.” Therefore, unless otherwise indicated, the numerical parameters shown in the following specification and the accompanying claims are approximations and may vary depending on the desired characteristics to be obtained. Note that, as used herein and in the accompanying claims, the singular forms “a,” “an,” and “the” include multiple references unless specifically and explicitly limited to one reference. As used herein, the term “include” and its grammatical variations are non-exclusive; therefore, the enumeration of items into a list does not exclude other similar items that may be substituted for or added to the enumerated item. As used herein, the term “comprising” includes the element or step specified following the term, but any such element or step is not exhaustive, meaning that one embodiment may include other elements or steps.

[0040] Unless otherwise specified, individual components or mixtures of components may be selected. Details of elements, materials, or other component types include all possible lower general combinations of the listed components and their mixtures. Furthermore, all numerical ranges presented herein include their upper and lower limits.

[0041] The patentable scope is defined by the claims and may include other embodiments that a person skilled in the art could conceive of. Such other embodiments are within the scope of the claims if they have structural elements that are not different from the literal meaning of the claims, or if they include equivalent structural elements that differ only slightly from the literal meaning of the claims. Unless otherwise inconsistent with this specification, all references made herein are incorporated by reference.

[0042] Reaction mixture and crystallization In the preparation of SSZ-91, at least one organic compound selected for synthesizing molecular sieves from ZSM-48 family zeolites is used as a structure-controlling agent ("SDA"), also known as a crystallization template. An SDA useful for producing SSZ-91 is shown in the following structure (1) [ka] It is represented by [this].

[0043] The SDA cation is typically accompanied by an anion, which may be any anion that does not impair molecular sieve formation. Representative examples of anions include hydroxide ions, acetate ions, sulfate ions, carboxylate ions, and halide ions, such as fluoride ions, chloride ions, bromide ions, and iodide ions. In one embodiment, the anion is a bromide ion.

[0044] Generally speaking, SSZ-91 is, (a) A step of preparing a reaction mixture containing (1) at least one silicon oxide source; (2) at least one aluminum oxide source; (3) at least one element selected from Group 1 and Group 2 of the periodic table; (4) hydroxide ions; (5) hexamethonium cations; and (6) water. (b) The step of maintaining the reaction mixture under crystallization conditions sufficient to form crystals of molecular sieves. It is prepared by [method].

[0045] The composition of the reaction mixture in which molecular sieves are formed is specified in relation to molar ratios in Table 1 below. [Table 1] In the table, (1) M is selected from the group consisting of elements from Group 1 and Group 2 of the periodic table, (2) Q is a structural modifier represented by structure 1 above.

[0046] Useful sources of silicon as used herein include fumed silica, precipitated silica, silica hydrogel, silicic acid, colloidal silica, tetraalkyl orthosilicates (e.g., tetraethyl orthosilicates), and silica hydroxide.

[0047] Useful sources of aluminum as used herein include aluminates, alumina, and aluminum compounds such as AlCl3, Al2(SO4)3, Al(OH)3, kaolin clay, and other zeolites. An example of a source of aluminum oxide is LZ-210 zeolite (a type of Y zeolite).

[0048] As described above in this specification, for each embodiment described herein, the reaction mixture may be formed by containing at least one source (referred to herein as M) of elements selected from Group 1 and Group 2 of the periodic table. In one lower embodiment, the reaction mixture is formed using a source of elements from Group 1 of the periodic table. In another lower embodiment, the reaction mixture is formed using a source of sodium (Na). Any M-containing compound that does not impair the crystallization process is suitable. Sources for such Group 1 and Group 2 elements include their oxides, hydroxides, nitrates, sulfates, halides, oxalates, citrates, and acetates.

[0049] For each embodiment described herein, the molecular sieve reaction mixture may be supplied by two or more sources. Similarly, two or more reaction components may be supplied by one source.

[0050] The reaction mixture can be prepared in batches or continuously. The crystal size, morphology, and crystallization time of the molecular sieves described herein may vary depending on the properties of the reaction mixture and the crystallization conditions.

[0051] The reaction mixture is kept at a high temperature until molecular sieve crystals form. Generally, zeolite hydrothermal crystallization is carried out under pressure, usually in an autoclave at a temperature between 125°C and 200°C for 1 to 18 hours or more, subjecting the reaction mixture to self-generated pressure and possibly being stirred.

[0052] As described herein, SSZ-91 is a substantially pure phase material. As used herein, the term “substantially pure phase material” means that the material is completely free of zeolite phases other than those belonging to the ZSM-48 family of zeolites, or present in amounts that do not have a measurable effect on the selectivity of the material or impart any defects to the material. Two common phases that cocrystallize with SSZ-91 are EUO-type molecular sieves such as EU-1, as well as magadiite and kenyaite. These additional phases may exist as separate phases or may grow together with the phases of SSZ-91. As shown in the following examples, the presence of large amounts of EU-1 in the product is detrimental to the selectivity for hydrogenation isomerization by SSZ-91.

[0053] In one embodiment, the SSZ-91 product contains an additional EUO-type molecular sieve phase in an amount between 0 and 3.5% by weight. In one sub-embodiment, SSZ-91 contains EU-1 between 0.1 and 2% by weight. In another sub-embodiment, SSZ-91 contains EU-1 between 0.1 and 1% by weight.

[0054] The ratio of powder XRD peak intensities changes linearly as a function of the weight fractions of any two phases in the mixture: (Iα / Iβ)=(RIRα / RIRβ)*(xα / xβ), where the RIR (reference intensity ratio) parameter is known to be found in the International Centre for Diffraction Data's powder diffraction file (PDF) database (http: / / www.icdd.com / products / ). The weight percentage of the EUO phase is therefore calculated by measuring the ratio between the peak intensity of the EUO phase and the peak intensity of the SSZ-91 phase.

[0055] The total formation of the EUO phase is suppressed by selecting the optimal hydrogel composition, temperature, and crystallization time that minimize EUO phase formation while maximizing the yield of the SSZ-91 product. The following examples provide guidance on how variations in these process variables minimize EU-1 formation. For those skilled in zeolite production, these variables depend on the size of the production run, the available equipment capacity, the desired target yield, and the acceptable level of EU-1 material in the product, so it is easy to select the process variables necessary to minimize EU-1 formation.

[0056] During the hydrothermal crystallization step, molecular sieve crystals can spontaneously nucleate from the reaction mixture. Using molecular sieve crystals as a seed material can be advantageous in reducing the time required for complete crystallization to occur. Furthermore, seed addition can result in a higher purity of the resulting product by promoting molecular sieve formation in preference to nucleation and / or any unwanted phases. However, when seed addition is used, it has been found that the seed must be a very pure SSZ-91 phase to avoid the formation of large amounts of EUO phase. When used as a seed, the seed crystals are added in an amount between 0.5% and 5% by weight of the silicon source used in the reaction mixture.

[0057] The formation of magadiite and kenyaite can be minimized by optimizing the hexamethonium bromide / SiO2 ratio, controlling the hydroxide concentration, and minimizing the sodium concentration, as magadiite and kenyaite are layered sodium silicate compositions. The following examples provide guidance on how to minimize EU-1 formation by changing gel conditions.

[0058] After molecular sieve crystals are formed, the solid product is separated from the reaction mixture by standard mechanical separation techniques such as filtration. The crystals are washed with water and then dried to obtain as-synthesized molecular sieve crystals. The drying step can be carried out under atmospheric pressure or vacuum.

[0059] Post-crystallization treatment Molecular sieves can be used as-synthesized, but are typically thermally treated (calcined). The term “as-synthesized” refers to the molecular sieve in its crystallized form before the removal of SDA cations. SDA can be removed by heat treatment (e.g., calcination), preferably in an oxidizing atmosphere (e.g., air, a gas with an oxygen partial pressure greater than 0 kPa), at a temperature readily determined by those skilled in the art sufficient to remove SDA from the molecular sieve. SDA can also be removed by ozone treatment and photodegradation techniques (e.g., exposing the SDA-containing molecular sieve product to light with a wavelength shorter than visible light or electromagnetic radiation under conditions sufficient to selectively remove organic compounds from the molecular sieve), as described in U.S. Patent No. 6,960,327.

[0060] Next, the molecular sieves may be calcined in steam, air, or an inert gas at a temperature in the range of 200°C to 800°C for 1 to 48 hours, or for a longer period. Typically, the extraskeletal cations (e.g., Na) are removed by ion exchange. + It is desirable to remove the ions and replace them with hydrogen, ammonium, or any desired metal ion.

[0061] If the formed molecular sieve is an intermediate molecular sieve, the target molecular sieve can be realized using post-synthesis techniques such as heteroatom lattice substitution techniques. The target molecular sieve (e.g., silicate SSZ-91) can also be realized by removing heteroatoms from the lattice using known techniques such as acid leaching.

[0062] Molecular sieves produced by the methods disclosed herein can be formed into a wide range of physical shapes. Generally, molecular sieves can be in the form of powders, granules, or molded articles such as extruded products having a particle size sufficient to pass through a 2-mesh (Tyler) sieve and be held in a 400-mesh (Tyler) sieve. When the catalyst is molded by extrusion molding with an organic binder, the molecular sieves may be extruded before drying, or dried or partially dried and then extruded.

[0063] Molecular sieves can be compounded with other materials that are resistant to the temperatures and other conditions used in the organic conversion process. Such matrix materials include active and inactive materials, as well as synthetic or naturally occurring molecular sieves, and inorganic materials such as clay, silica, and metal oxides. Examples of such materials and methods for using them are disclosed in U.S. Patents 4,910,006 and 5,316,753.

[0064] Next, one or more active metals selected from the group consisting of metals from Groups 8 to 10 of the periodic table may be further added to the extruded material or particles using techniques such as impregnation or ion exchange to enhance the hydrogenation function. It is desirable to co-impregnate the modified metal and one or more Groups 8 to 10 metals simultaneously, as disclosed in U.S. Patent No. 4,094,821. In one embodiment, at least one active metal is selected from the group consisting of nickel, platinum, palladium, and combinations thereof. After metal addition, the metal-added extruded material or particles may be calcined in air or an inert gas at a temperature of 200°C to 500°C. In one embodiment, the metal-added extruded material is calcined in air or an inert gas at a temperature of 390°C to 482°C.

[0065] SSZ-91 is useful in various hydrocarbon conversion reactions, including hydrocracking, dewaxing, olefin isomerization, alkylation, and isomerization of aromatic compounds. SSZ-91 is also useful as an adsorbent for general separation purposes.

[0066] Characterization of molecular sieves Molecular sieves produced by the methods disclosed herein have an SiO2 / Al2O3 molar ratio (SAR) of 40 to 200. The SAR is determined by inductively coupled plasma (ICP) elemental analysis. In one sub-embodiment, SSZ-91 has an SAR between 70 and 160. In another sub-embodiment, SSZ-91 has an SAR between 80 and 140.

[0067] The SSZ-91 material is composed of at least 70% polytype 6 of the total ZSM-48 type material present in the product, as determined by DIFFaX simulation and as described by Lobo and Koningsveld in J.Am.Chem.Soc.2012, 124, 13222-13230 (where disorder is regulated by three different defect probabilities). It should be noted that the phrase "at least X%" includes the case where no other ZSM-48 polytypes are present in the structure, i.e., the material is 100% polytype 6. The structure of polytype 6 is as described by Lobo and Koningsveld (see J.Am.Chem.Soc.2002, 124, 13222-13230). In one embodiment, the SSZ-91 material is composed of at least 80% polytype 6 of the total ZSM-48 type material present in the product. In another embodiment, the SSZ-91 material is composed of at least 90% polytype 6 of the total ZSM-48 type material present in the product. The structure of polytype 6 is defined by the Structural Committee of the International Zeolite Association as a skeletal code. * MREs have been assigned.

[0068] Molecular sieves SSZ-91 have a morphology characterized by polycrystalline aggregates having diameters between approximately 100 nm and 1.5 μm, each aggregate containing a collection of crystallits collectively having an average aspect ratio between 1 and 8. As used herein, the term diameter represents the shortest length on the short end of each crystallit under consideration. SSZ-91 exhibits a lower degree of hydrocracking than ZSM-48 material with higher aspect ratios. In one sub-embodiment, the average aspect ratio is between 1 and 5. In another sub-embodiment, the average aspect ratio is between 1 and 4. In yet another sub-embodiment, the average aspect ratio is between 1 and 3.

[0069] Molecular sieves synthesized by the methods disclosed herein can be characterized by their XRD patterns. The powder XRD linears in Table 2 are representative examples of as-synthesized SSZ-91 prepared according to the methods disclosed herein. Slight variations in the diffraction pattern may result from variations in the molar ratio of skeletal species in a particular sample due to changes in the lattice constant. Furthermore, sufficiently small crystals will affect the shape and intensity of the peaks, resulting in significant peak broadening. Slight variations in the diffraction pattern may also result from variations in the organic compounds used in preparation and from variations in the Si / Al molar ratio for each sample. Sintering may also result in slight shifts in the XRD pattern. Despite these slight perturbations, the fundamental crystal lattice structure remains unchanged. [Table 2]

[0070] The X-ray diffraction pattern linearities in Table 3 are representative examples of calcined SSZ-91 produced according to the method described herein. [Table 3]

[0071] Powder X-ray diffraction patterns presented herein were collected using standard techniques. The radiation was CuK αThis is radiation. The peak height and position (as a function of 2θ, where θ is the Black angle) can be read from the relative intensity of the peak (adjusted for background), and d (the grid plane spacing corresponding to the recorded linearity) can be calculated. [Examples]

[0072] The following exemplary examples are non-limiting.

[0073] Summary of Examples The following examples demonstrate that ZSM-48 materials lacking any one of the three specific combinations of properties of SSZ-91 (low aspect ratio, low EU-1 content, and high polytype 6 composition) exhibit poor catalytic performance. Table 4 below summarizes the hydrogenation performance for the various examples outlined below. Only Example 8 (SSZ-91) showed superior performance, i.e., superior selectivity and low gas generation compared to the other three examples. The remaining materials of the other three examples tested each exhibited poor performance because they lacked at least one of the three specific combinations of properties that define SSZ-91. [Table 4]

[0074] (Comparative Example 1) Synthesis of ZSM-48 The products in this example were prepared using available reagents in accordance with the teachings of U.S. Patent No. 5,075,269 issued on December 24, 1991, by Thomas F. Degnan and Ernest W. Valyocsik (Mobil Oil Corp.).

[0075] 76.51 g of NaOH (50%), 846 g of deionized water, 124.51 g of HI-SIL 233 silica (PPG Industries), and 63 g of hexamethonium bromide ("HMB", Sigma Aldrich) were added to a 1-gallon autoclave liner. After all solids had dissolved, 396 g of aluminum stock solution, prepared by dissolving 4.35 g of Al2(SO4)3·18H2O and 63 g of concentrated H2SO4 in 733.52 g of deionized water, was added. Finally, 0.45 g of SSZ-91 seed crystals from Example 7 were added. The mixture was stirred until homogeneous. The composition of the prepared aluminosilicate gel had the following molar ratios. [Table 5]

[0076] The liner was transferred to a 1-gallon autoclave and heated to 160°C for 8 hours, while being stirred at a speed of 150 rpm under self-generated pressure. After 80 hours, the product was filtered, washed with deionized water, and dried. The resulting solid was determined to be ZSM-48 material by XRD (Figure 1). XRD showed the presence of an undetectable amount of EU-1 in the product (likely less than 1% EU-1). SEM showed aggregated, elongated needle-shaped crystals of ZSM-48 crystals with aspect ratios of 7–12 (Figure 2).

[0077] (Comparative Examples 2 and 3) As described above, the paper by Lobo and Koningsveld describes their analysis of three ZSM-48 samples provided by Dr. Alexander Kuperman of Chevron Corporation. Each of the three samples, samples A, B, and C, was prepared using three different structural modifiers. The paper by Lobo and Koningsveld describes sample A as polytype 6 and sample B as defective polytype 6. The paper further describes that the morphology of sample A (Figure 3) consists of thin needle-shaped crystals with a diameter of approximately 20 nm and a length of approximately 0.5 μm. The morphology of sample B (Figure 4) consists of long, thin crystals with a diameter of approximately 30 nm and a length of 4–8 μm. Despite Dr. Kuperman's material being reported to have a high concentration of polytype 6, the samples are characterized as having an aspect ratio (length / diameter) of 25 for sample A and an aspect ratio in the range of 133–266 for sample B.

[0078] (Examples 4-11) Synthesis of SSZ-91 with varying EU-1 concentrations in the product. Each of Examples 4 through 11 was prepared by adding NaOH (50%), deionized water, HI-SIL 233 silica (PPG Industries), and hexamethonium bromide (Sigma Aldrich) to an autoclave liner. After all solids had dissolved, an aluminum stock solution prepared by dissolving 4.18 g of Al2(SO4)3·18H2O and 45.58 g of concentrated H2SO4 in 540.6 g of deionized water was added. The mixture was stirred until homogeneous. The molar ratio to the aluminosilicate gel and the heating period are listed in Table 6 below. [Table 6]

[0079] The liner was transferred to an autoclave and heated to 160°C for 8 hours, while being stirred at a speed of 150 rpm under self-generated pressure. After the crystallization period, the product was filtered, washed with deionized water, and dried. The resulting solid was analyzed by XRD to determine the product and the level of EU-1 in the product. The bulk SiO2 / Al2O3 molar ratio and EU-1 content are listed in Table 7 below. [Table 7]

[0080] Products from Examples 1 and 4-11 were analyzed by XRD and SEM. The XRD pattern for Example 7 is shown in Figure 5, which is an example of the XRD patterns collected for the remaining Examples 4-11.

[0081] SEM images for Examples 7 and 8 are shown in Figures 6 and 7, respectively, which are illustrative examples of SEM images for the remaining Examples 4-11. Figures 6 and 7 show that the SSZ-91 material consists of polycrystalline aggregates, each aggregate composed of crystallits, where each crystallit has a characteristic average aspect ratio of less than 8. In contrast, the ZSM-48 material of Comparative Examples 1-3 (Figures 2-4) contained long needle-like crystals and fibrous morphologies, and the presence of these morphologies consistently resulted in poor catalytic performance.

[0082] Calcination and ion exchange of molecular sieves The as-synthesized products from Comparative Example 1 and Examples 4-11 were converted to the sodium form by heating to 120°C at a rate of 1°C / min and holding for 120 minutes in a dry air atmosphere, followed by a second temperature increase of 1°C / min to 540°C and holding at this temperature for 180 minutes, and finally a third temperature increase of 1°C / min to 595°C and holding at this temperature for 180 minutes. The samples were then cooled to below 120°C. Each of these calcined samples was then converted to the ammonium form as follows: Ammonium nitrate equal to the mass of the sample to be exchanged was completely dissolved in 10 times the mass of the sample in deionized water. The sample was then added to the ammonium nitrate solution, the suspension was sealed in a flask, and heated overnight in a 95°C oven. The flask was removed from the oven, and the sample was immediately recovered by filtration. The ammonium exchange procedure was repeated with the recovered samples, washed with a large amount of deionized water until the conductivity was less than 50 μS / cm, and finally dried in a 95°C oven for 3 hours.

[0083] Hydrogenation treatment test Palladium ion exchange was performed on ammonium-exchanged samples from Examples 1 and 4-11 using tetraamminepalladium(II) nitrate (0.5 wt% Pd). After ion exchange, the samples were dried at 95°C and then calcined in air at 482°C for 3 hours to convert tetraamminepalladium(II) nitrate to palladium oxide.

[0084] 0.5 g of each palladium-exchanged sample from Example 11 was loaded into the center of a 23-inch long, 0.25-inch outer diameter stainless steel reactor tube, with alundum loaded upstream of the catalyst for preheating the feed material (total pressure 1200 psig; descending hydrogen rate 160 mL / min (measured at 1 atm, 25°C); descending liquid feed rate 1 mL / hour). All materials were first reduced in a hydrogen stream at approximately 315°C for 1 hour. Products were analyzed every 30 minutes by online capillary gas chromatography (GC). Raw data from GC were collected by an automated data collection / processing system, and hydrocarbon conversion rates were calculated from the raw data.

[0085] The catalyst was first tested at approximately 260 °C to determine the temperature range for the next set of measurements. The full temperature range resulted in a wide range of hexadecane conversions, with maximum conversions just below and exceeding 96%. At each temperature, at least five online GC injections were collected. Conversion was defined as the amount of hexadecane that reacted to produce other products (including isomers). Yield was expressed as the weight percent of products other than n-C 16 and included iso-C 16 as the yield product. The results are included in Table 8.

Table 8

[0086] For the preferred materials of the present invention, the desirable isomerization selectivity at 96% conversion is at least 85%. The good balance between isomerization selectivity and temperature at 96% conversion has significant meaning for the present invention. The desirable temperature at 96% conversion is less than 605 °F. The lower the temperature at 96% conversion while still maintaining at least 85% isomerization selectivity, the more desirable the catalyst. The best catalyst performance is determined by the synergy between isomerization selectivity and temperature at 96% conversion. A large amount of impurities results in an undesirable cracking with a high amount of accompanying gas production, as reflected in Table 8 by high levels of C4 - cracking. The desirable C4 - cracking for the materials of the present invention is less than 2.0%. Note that the selectivity begins to decrease at 6.82% EU-1 as the increasing concentration of EU-1 promotes cracking.

[0087] Polymorph distribution ​​Using DIFFaX, simulated XRD patterns were created for ZSM-48 materials having polytype 6 between 70% and 100%, and compared with XRD patterns collected for molecular sieve products from Examples 8 and 11. The simulated and product XRD patterns are shown in Figures 8 and 9 of this specification, respectively. Comparing the product XRD patterns with the simulated patterns, it is evident that the products synthesized in Examples 8 and 11 contain more than 90% polytype 6.

[0088] Using DIFFaX, simulated XRD patterns were created for ZSM-48 materials having polytype 6 between 70% and 100%, and compared with the XRD patterns collected for molecular sieve products from Comparative Example 1. The simulated and product XRD patterns are shown in Figure 10 of this specification. Comparing the product XRD pattern with the simulated pattern, it is shown that the product synthesized in Comparative Example 1 contains 80% polytype 6.

[0089] The material synthesized in Comparative Example 1 was subjected to the hexadecane hydrogenation treatment test outlined in Examples 4-11 above. The material from Comparative Example 1 showed an isomerization selectivity of 78% at a 96% conversion rate at a temperature of 614°F. As shown in Table 9 below, C4 - Decomposition was 2.8%. The isomerization selectivity at 96% conversion rate for the material of Comparative Example 1, which had a polytype 6 content of only 80%, was inferior to that of Examples 4 to 10 shown in Table 7 above, even though the material of Comparative Example 1 contained an immeasurable amount (<1%) of EU-1. This indicates that the materials of Comparative Example 1 and Example 11 exhibited two of the three properties of SSZ-91 (low aspect ratio, low EU-1 content, and high polytype 6 content), but the lack of the third property contributed to the poor catalytic performance of the materials. [Table 9]

[0090] (Examples 12-13) Synthesis of SSZ-91 using alternative silica sources The material for Example 12 was prepared by adding NaOH (50%), deionized water, CAB-O-SIL M-5 silica (Cabot Corporation), and hexamethonium bromide (HMB) to an autoclave liner. After all the solids had dissolved, anhydrous Riedel de Haen sodium aluminate was added. Finally, an SSZ-91 slurry similar to the slurry from Example 4 was added. The mixture was stirred until homogeneous. The resulting aluminosilicate gel composition had the following molar ratios. [Table 10]

[0091] The liner was transferred to an autoclave and heated to 160°C for 8 hours, while being stirred at a speed of 150 rpm under self-generated pressure. After 48 hours, the product was filtered, washed with deionized water, and dried. The obtained solid was determined by XRD to be SSZ-91 and to contain 0.30 wt% EUO. The bulk SiO2 / Al2O3 molar ratio was found to be approximately 102.

[0092] The materials for Example 13 were prepared by adding NaOH (50%), deionized water, commercially available NALCO 2327 colloidal silica (40.3% SiO2), and hexamethonium bromide to an autoclave liner. After all the solids had dissolved, Al2(SO4)3·18H2O, which had been pre-dissolved in some water, was added. The mixture was stirred until homogeneous. The resulting aluminosilicate gel composition had the following molar ratios. [Table 11]

[0093] The liner was transferred to an autoclave and heated to 160°C for 8 hours, while being stirred at a speed of 150 rpm under self-generated pressure. After 35 hours, the product was filtered, washed with deionized water, and dried. The obtained solid was determined by XRD to be SSZ-91 and to contain 3.16 wt% EU-1. The bulk SiO2 / Al2O3 molar ratio was found to be approximately 155. The material of Example 13 was analyzed by scanning electron microscopy, and the SEM image from the analysis is shown in Figure 11.

[0094] Hydrogenation treatment test Palladium addition tests and catalyst tests were performed on the SSZ-91 materials synthesized in Examples 12 and 13, as described in the above examples. The results of the catalyst tests are shown in Table 12 below. These two examples, prepared by changing the raw materials used, demonstrate the versatility of SSZ-91 preparation. Example 12 showed another good example with a desirable isomerization selectivity of 88% at 96% at a considerably lower temperature. Example 13, although in the pure phase, showed poor catalytic performance and crystal behavior with an unfavorable aspect ratio of crystals. [Table 12]

[0095] Using DIFFaX, simulated XRD patterns were created for the ZSM-48 material having polytype 6 between 70 and 100%, and compared with the XRD patterns collected for the molecular sieve product from Example 13. The simulated and product XRD patterns are shown in Figure 12 of this specification. SEM images from this analysis are shown in Figure 11. Comparing the product XRD pattern with the simulated pattern, it is shown that the product synthesized in Comparative Example 1 contains more than 90% polytype 6. This indicates that although the material in Example 13 has the essential low EU-1 content and the desired polytype distribution, the high aspect ratio contributed to the poor catalytic performance of the material. Example 13 again demonstrates that the absence of any one of the three properties of SSZ-91 (low aspect ratio, low EU-1 content, and high polytype 6 content) contributes to the poor catalytic performance of the material. Furthermore, the present invention includes the following preferred embodiments. (1) A molecular sieve belonging to the ZSM-48 family of zeolites, The molar ratio of silicon dioxide to aluminum oxide is 40 to 200. At least 70% of the total ZSM-48 type material present in the product is polytype 6, and Further EUO-type molecular sieve phase in amounts between 0 and 3.5% by weight of the total product Includes, It has a morphology characterized by polycrystalline aggregates containing crystallits that collectively have an average aspect ratio between 1 and 8. The above molecular sieve. (2) In its as-synthesized form, it substantially has the X-ray diffraction pattern shown in the following table. [Table 1] JPEG0007893933000014.jpg94161 (1) Molecular sieves as described above. (3) A molecular sieve according to (1) or (2), having a silicon oxide to aluminum oxide molar ratio of 70 to 160. (4) A molecular sieve according to any one of (1) to (3), having a silicon oxide to aluminum oxide molar ratio of 80 to 140. (5) A molecular sieve according to any one of (1) to (4), comprising at least 80% polytype 6 of the total ZSM-48 type material present in the product. (6) A molecular sieve according to any one of (1) to (5), containing EU-1 between 0.1 and 2% by weight. (7) A molecular sieve described in any of (1) to (6), wherein the crystallits collectively have an average aspect ratio between 1 and 5. (8) A molecular sieve according to any one of (1) to (7), comprising at least 90% polytype 6 of the total ZSM-48 type material present in the product. (9) A molecular sieve described in any of (1) to (8), wherein the crystallits collectively have an average aspect ratio between 1 and 3. (10) A method for preparing a molecular sieve according to any one of (1) to (9), comprising the steps of: preparing a reaction mixture containing at least one silicon source, at least one aluminum source, at least one source of an element selected from Group 1 and Group 2 of the periodic table, hydroxide ions, hexamethonium cations, and water; and subjecting the reaction mixture to crystallization conditions sufficient to form crystals of a molecular sieve. (11) Molecular sieves are as follows with respect to molar ratio: [Table 2] JPEG0007893933000015.jpg3485 [In the table, M is selected from the group of elements consisting of Groups 1 and 2 of the periodic table; Q is the hexamethonium cation.] The method according to (10), which is prepared from a reaction mixture containing the following: (12) Molecular sieves are as follows with respect to molar ratio: [Table 3] JPEG0007893933000016.jpg3485 [In the table, M is selected from the group of elements consisting of Groups 1 and 2 of the periodic table; Q is the hexamethonium cation.] The method according to (10), which is prepared from a reaction mixture containing the following: (13) A method for converting hydrocarbons, comprising the step of contacting a hydrocarbon feed material with a catalyst comprising a molecular sieve as described in any of (1) to (9) under hydrocarbon conversion conditions. (14) Use of molecular sieves according to any one of (1) to (9) for converting hydrocarbons under hydrocarbon conversion conditions.

Claims

1. A molecular sieve belonging to the ZSM-48 family of zeolites, The molar ratio of silicon oxide to aluminum oxide is 118 to 200. At least 70% of the total ZSM-48 type material present in the product is polytype 6, and Further EUO-type molecular sieve phase in an amount between 0 and 3.5% by weight of the total product Includes, It has a morphology characterized by a polycrystalline aggregate containing crystallits that collectively have an average aspect ratio between 1 and 5, and In its as-synthesized form, it substantially possesses the X-ray diffraction patterns shown in the table below. Table 1 The above molecular sieve.

2. A method for preparing a molecular sieve according to claim 1, comprising the steps of: preparing a reaction mixture containing at least one silicon source, at least one aluminum source, at least one source of an element selected from Group 1 and Group 2 of the periodic table, hydroxide ions, hexamethonium cations, and water; and subjecting the reaction mixture to crystallization conditions sufficient to form crystals of a molecular sieve.

3. A method for converting hydrocarbons, comprising the step of contacting a hydrocarbon-based supply material with a catalyst containing a molecular sieve as described in claim 1, under hydrocarbon conversion conditions.

4. Use of the molecular sieve according to claim 1 for converting hydrocarbons under hydrocarbon conversion conditions.

Images