Zeolite synthesis

Abstract

To provide a method of synthesizing a zeolite with a silica-to-alumina ratio (SAR) of 10 or greater.SOLUTION: The method comprises: forming a reaction mixture including at least one alumina source, at least one silica source, and at least one organic structure directing agent, wherein the reaction mixture has a solid content of about 10% or greater; and crystallizing the reaction mixture at a temperature of 100°C or less at atmospheric pressure to form a zeolite.SELECTED DRAWING: Figure 1B

Description

[Background technology]

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 937,572, filed November 19, 2019, the contents of which are incorporated herein by reference in their entirety.

[0002] FIELD OF THE DISCLOSURE This disclosure relates generally to the field of selective catalytic reduction (SCR) catalysts and methods of preparing and using such catalysts to selectively reduce nitrogen oxides.

[0003] Diesel engine emissions include particulate matter (PM), nitrogen oxides (NO x ), unburned hydrocarbons (HC), and carbon monoxide (CO). x is a term used to describe various chemical species of nitrogen oxides, including nitric oxide (NO) and nitrogen dioxide (NO2), among others. The two major components of exhaust particulate matter are the soluble organic fraction (SOF) and the soot fraction. SOF condenses in a layer on top of soot and is generally derived from unburned diesel fuel and lubricating oil. SOF can exist in diesel exhaust as a vapor or aerosol (i.e., fine droplets of liquid condensate), depending on the exhaust gas temperature. Soot is primarily composed of carbon particles. The HC content of exhaust can vary depending on engine type and operating parameters, but typically includes various short-chain hydrocarbons, such as methane, ethene, ethyne, and propene.

[0004] NO x Various methods are used to treat contaminated gas mixtures to reduce air pollution. One type of treatment involves catalytic reduction of nitrogen oxides. There are two processes: (1) nonselective reduction processes, in which carbon monoxide, hydrogen, or hydrocarbons are used as reducing agents, and (2) selective reduction processes, in which ammonia or an ammonia precursor is used as a reducing agent. In selective reduction processes, a high degree of nitrogen oxide removal can be achieved with a small amount of reducing agent.

[0005] Catalysts used in SCR processes should ideally be able to maintain good catalytic activity under hydrothermal conditions over a wide temperature range, e.g., from 200°C to over 600°C. SCR catalysts are commonly exposed to high-temperature hydrothermal conditions, such as during the regeneration of soot filters, a component of exhaust gas treatment systems used to remove particulates.

[0006] Molecular sieves such as zeolites have been used in the selective catalytic reduction of nitrogen oxides (SCR) with reducing agents such as ammonia, urea, or hydrocarbons in the presence of oxygen. Zeolites are crystalline materials with fairly uniform pore sizes ranging from about 3 to about 10 angstroms in diameter, depending on the type of zeolite and the type and amount of cations contained in the zeolite. Zeolites with eight-ring pore openings and double six-ring secondary building blocks, such as those with cage-like structures, are well suited for use as SCR catalysts. A particular type of zeolite with these properties is chabazite (CHA), a small-pore zeolite with eight-ring pore openings (about 3.8 angstroms) accessible through three-dimensional porosity. The cage-like structure results from the connection of double six-ring structural units by four rings. Molecular sieves having a CHA framework structure can be prepared, for example, according to the methods disclosed in U.S. Pat. Nos. 4,503,024, 4,544,538, and 6,709,644, and in "Verified Synthesis of Zeolites Second Edition," Elsevier 2001, p. 123, each of which is incorporated herein by reference.

[0007] Typical methods for preparing certain CHA zeolites (e.g., zeolites having SAR values ​​of 10 or greater) involve hydrothermal synthesis under relatively harsh conditions. For example, in the above-referenced '538 patent, the zeolites are typically prepared by hydrothermal crystallization under pressure in an autoclave. Similarly, the above-referenced '644 patent describes a hydrothermal crystallization process for preparing CHA (SSZ-64) crystals at temperatures between 100°C and 200°C, e.g., under autogenous pressure over a course of about 3 to about 20 days. While less harsh conditions are known for preparing certain zeolites, these methods are generally limited to preparing zeolites having lower silica-to-alumina ratio (SAR) values.

[0008] Therefore, alternative methods for the production of CHA (and other zeolites) of various SARs without the harsh conditions previously described are needed. [Brief explanation of the drawings]

[0009] To provide an understanding of certain embodiments of the present disclosure, reference is made to the accompanying drawings, which are not necessarily drawn to scale, and in which reference numerals indicate components of exemplary embodiments of the present disclosure. The drawings are provided merely as examples and should not be construed as limiting the scope of the present disclosure.

[0010] [Figure 1A] 1 shows a perspective view of a honeycomb-type substrate that may include the catalyst composition of the present disclosure. [Figure 1B] 1B shows a partial cross-sectional view enlarged relative to FIG. 1A and taken along a plane parallel to an end face of the carrier of FIG. 1A, showing an enlarged view of a plurality of gas flow channels shown in FIG. 1A. [Figure 2] 1 shows a cross-sectional view of a portion of a wall flow filter substrate. [Figure 3] 1 shows a schematic diagram of an embodiment of an emissions treatment system in which the catalyst of the present disclosure is utilized. [Figure 4]Provided are X-ray diffraction (XRD) patterns of samples taken during crystallization at 97°C in a stirred reflux vessel at 150 rpm (Figure 4A) and 350 rpm (Figure 4B). [Figure 5] (Figure 5A (scale bar: 5 μm) and Figure 5B (scale bar: 500 nm)) Provides micrographs of CHA crystallized at 97°C in a stirred reflux vessel at 350 rpm. [Figure 6] The SCR performance of selected samples is illustrated in the experimental section below.

[0011] The present disclosure provides methods for synthesizing zeolites using less harsh conditions than those typically used to produce, for example, CHA zeolites with high silica-to-alumina (SAR) ratios. In particular, the methods outlined herein may enable such production at lower and / or correspondingly lower temperatures. Advantageously, the disclosed processes may be carried out without the need for autogenous pressure and / or in a simple stirred vessel (e.g., at atmospheric pressure). The present disclosure further provides corresponding zeolite products thus prepared, as well as emission treatment systems and methods of exhaust gas treatment that utilize the zeolite product(s).

[0012] These and other features, aspects, and advantages of the present disclosure will become apparent in the following detailed description taken in conjunction with the accompanying drawings, which are briefly described below. The present disclosure includes any combination of two, three, four, or more of the embodiments, as well as combinations of any two, three, four, or more features or elements described in the present disclosure, unless the context clearly dictates otherwise. The present disclosure is intended to be read as a whole such that any separable features or elements of the disclosure are to be considered combinable in any of its various aspects and embodiments, unless the context clearly dictates otherwise. Other aspects and advantages of the present disclosure will become apparent hereinafter.

[0013] The present disclosure is not limited to the details of configuration or process steps set forth in the following description. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways. It is to be understood that the exemplary embodiments described herein are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed method and apparatus without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is intended to cover modifications and variations that come within the scope of the appended claims and their equivalents.

[0014] In one aspect of the present disclosure, a method for synthesizing an aluminosilicate zeolite having a silica-to-alumina ratio (SAR) of 10 or greater is provided, comprising: i) forming a reaction mixture comprising at least one alumina source, at least one silica source, and at least one organic structure directing agent, wherein the reaction mixture has a solids content of about 10% or greater (e.g., by weight); and ii) crystallizing the reaction mixture in a container open to the atmosphere at a temperature of 100° C. or less to form the aluminosilicate zeolite.

[0015] The method can be used to provide various types of aluminosilicate zeolite products. For example, in some embodiments, the aluminosilicate zeolite includes a zeolite having an 8-ring pore size. In some embodiments, the aluminosilicate zeolite includes a zeolite having a framework comprising double 6-ring (D6r) subunits. In some embodiments, the aluminosilicate zeolite includes a zeolite having a framework selected from AEI, AFX, CHA, LEV, AFT, EAB, KFI, SAT, TSC, SAV, ERI, LTA, and any combination of the foregoing. In some embodiments, the aluminosilicate zeolite includes a zeolite having a CHA crystalline framework.

[0016] For example, in some embodiments, the aluminosilicate zeolite includes at least one zeolite having an 8-ring pore size. In some embodiments, the aluminosilicate zeolite includes at least one zeolite having a framework comprising double 6-ring (D6r) subunits. In some embodiments, the aluminosilicate zeolite includes at least one having a framework selected from AEI, AFX, CHA, LEV, AFT, EAB, KFI, SAT, TSC, SAV, ERI, and LTA. In some embodiments, the aluminosilicate zeolite includes at least one zeolite having a CHA crystalline framework.

[0017] In some embodiments, the method provides an aluminosilicate zeolite having a relatively high silica-to-alumina ratio (SAR) value, but the method is not limited thereto. In some embodiments, the aluminosilicate zeolite has an SAR of 15 or greater. In some embodiments, the aluminosilicate zeolite has an SAR of 20 or greater. In some embodiments, the aluminosilicate zeolite has an SAR of 10-30.

[0018] In some embodiments, the solids content of the reaction mixture is about 15% by weight or greater. The at least one alumina source of the reaction mixture can vary, and in some embodiments, includes a zeolite, such as a zeolite having an FAU, LTL, LTA, or MOR crystalline framework. In some embodiments, the at least one alumina source includes a zeolite having an FAU crystalline framework in the form of zeolite Y. The at least one organic structure-directing agent can also vary, and in some embodiments, the at least one organic structure-directing agent is a quaternary ammonium salt having a substituent selected from alkyl substituents, aromatic substituents, and any combination of the foregoing. In some embodiments, the at least one organic structure-directing agent is a quaternary ammonium salt having at least one substituent selected from alkyl substituents, aromatic substituents, and any combination of the foregoing. One non-limiting example of the at least one organic structure-directing agent is tetramethylpiperidinium. The at least one silica source can also vary, and in some embodiments, the at least one silica source includes an alkali metal silicate solution.

[0019] The parameters of the disclosed methods can be varied. For example, the temperature at which the crystallization step is carried out can vary, such that in some embodiments, the crystallization step is carried out at a temperature of about 95°C to 100°C. In some embodiments, the disclosed methods do not require that the crystallization step be carried out in an autoclave. In some embodiments, the crystallization step is carried out in a stirred vessel equipped with a reflux condenser. Agitation of the reaction mixture can be advantageous, and in some embodiments, the crystallization step is carried out with stirring.

[0020] The methods provided herein, in some embodiments, include one or more additional method steps. For example, the methods, in some embodiments, include calcining an aluminosilicate zeolite to form a zeolite-containing silicate. + Form or Na +The method may further include ion-exchanging the aluminosilicate zeolite with a promoter metal to form an ion-exchanged zeolite catalyst. In some embodiments, the method may further include ion-exchanging the calcined zeolite with a promoter metal to form an ion-exchanged zeolite catalyst. Such promoter metals may vary and may be, for example, Fe or Cu.

[0021] Definition: The following definitions are provided for terms used in this disclosure.

[0022] References throughout this specification to "one embodiment," "a particular embodiment," "one or more embodiments," or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of phrases such as "in one or more embodiments," "in a particular embodiment," "in one embodiment," or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment(s) of the present disclosure. Furthermore, particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0023] The articles "a" and "an" are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0024] All ranges cited herein are inclusive, that is, the endpoints are included within the range unless otherwise specified.

[0025] The term "about" is used throughout this specification to describe and account for small variations. For example, the term "about" can refer to ±5% or less, such as ±2% or less, ±1% or less, ±0.5% or less, ±0.2% or less, ±0.1% or less, or ±0.05% or less. All numerical values ​​are modified by the term "about," whether explicitly stated or not. Values ​​modified by the term "about" include the specified value. For example, "about 5.0" includes 5.0.

[0026] The terms "catalyst" or "catalytic material" or "catalytic material" refer to a material that promotes a reaction.

[0027] As used herein, the term "catalytic article" refers to an element used to promote a desired reaction. For example, a catalytic article may include a washcoat including a catalytic species, such as a catalyst composition, on a substrate, such as a honeycomb substrate.

[0028] As used herein, the term "washcoat" has its ordinary meaning in the art of a thin, adherent coating of catalyst or other material applied to a support substrate material, such as, for example, a honeycomb-type support member, that is sufficiently porous to permit the passage of a gas stream to be treated. As understood in the art, a washcoat may be obtained from a dispersion of particles in a slurry, which may be applied to a substrate, dried, and calcined to provide a porous washcoat.

[0029] As used herein, the term "substrate" refers to a monolithic material onto which a catalytic material is deposited, typically in the form of a washcoat.

[0030] As used herein, the term "stream" broadly refers to any combination of flowing gases that may include solid or liquid particulate matter. As used herein, the term "gas stream" or "exhaust gas stream" refers to a flow of gaseous components, such as, for example, engine exhaust, which may include entrained non-gaseous components, such as liquid droplets, solid particulates, etc. Engine exhaust gas streams may further include combustion products, incomplete combustion products, nitrogen oxides, combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen.

[0031] As used herein, the terms "particulate filter" and "soot filter" refer to filters designed to remove particulate matter, such as soot, from an exhaust gas stream.

[0032] As used herein, the term "BET surface area" has its ordinary meaning associated with the Brunauer-Emmett-Teller (BET) method for determining surface area by N adsorption. Pore size and pore volume can also be determined using BET-type N adsorption or desorption experiments, as will be understood by those skilled in the art.

[0033] As used herein, "support" in the context of a catalytic material or catalyst washcoat refers to a material that receives a catalyst (including, for example, precious metals, stabilizers, promoters, binders, etc.) by precipitation, association, dispersion, impregnation, or other suitable method.

[0034] As used herein, the term "selective catalytic reduction" (SCR) refers to a catalytic process that uses a nitrogenous reductant to reduce nitrogen oxides to dinitrogen (N). As used herein, "nitrogen oxides" and "NO x The term "oxidizer" refers to oxides of nitrogen. SCR processes typically use catalytic reduction of nitrogen oxides with ammonia to form nitrogen and water according to the following reaction: 4NO+4NH3+O2→4N 2+ 6H2O (standard SCR reaction) 2NO2 + 4NH3 → 3N2 + 6H2O (slow SCR reaction) NO + NO2 + 2NH3 → 2N2 + 3H2O (high-speed SCR reaction)

[0035] As used herein, the term "zeolite" refers to a specific example of a molecular sieve containing silicon and aluminum atoms. Zeolites are substantially crystalline materials having relatively uniform pore sizes ranging from about 3 to about 10 angstroms in diameter, depending on the type of zeolite and the type and amount of cations contained in the zeolite lattice.

[0036] Reference herein to an "aluminosilicate zeolite" framework type limits the material to molecular sieves that do not contain phosphorus or other metals substituted into the framework. However, for clarity, as used herein, "aluminosilicate zeolite" excludes aluminophosphate materials such as, for example, SAPO, ALPO, and MeAPO materials, and the broader term "zeolite" is intended to include aluminosilicates and aluminophosphates.

[0037] Zeolite CHA-framework type molecular sieves, also referred to herein as "CHA zeolites," have the approximate formula: (Ca,Na,K,Mg)AlSi0 12Included are zeolite groups having 6H2O (e.g., hydrated calcium aluminum silicate). Three synthetic forms of zeolite CHA-framework type molecular sieves are described in "Zeolite Molecular Sieves" by DW Breck, published by John Wiley & Sons in 1973, which is incorporated herein by reference. The three synthetic forms reported by Breck are Zeolite KG, described in J. Chem. Soc., p. 2822 (1956), Barrer et al.; Zeolite D, described in British Patent No. 868,846 (1961); and Zeolite R, described in U.S. Pat. No. 3,030,181, each of which is incorporated herein by reference. The synthesis of another synthetic form of the zeolite CHA-framework type, SSZ-13, is described in U.S. Pat. No. 4,544,538, which is incorporated herein by reference.

[0038] As used herein, the term "promoted" refers to a metal component (e.g., a "promoter metal") that is intentionally added to the molecular sieve material, as opposed to an inherent impurity in the molecular sieve. Thus, a promoter is intentionally added to improve the activity of the catalyst compared to a catalyst that does not have the intentionally added promoter. In one or more embodiments, a suitable metal(s) is independently exchanged onto the molecular sieve to promote the selective catalytic reduction of nitrogen oxides in the presence of ammonia.

[0039] Example of embodiment: Some embodiments of the present disclosure include, but are not limited to, the following. 1. A method for synthesizing an aluminosilicate zeolite having a silica-to-alumina ratio (SAR) of 1.10 or greater, comprising: forming a reaction mixture comprising at least one alumina source, at least one silica source, and at least one organic structure directing agent, wherein the reaction mixture has a solids content of about 10% or greater; and crystallizing the reaction mixture in a container open to the atmosphere at a temperature of about 100°C or less to form an aluminosilicate zeolite. 2. The method of embodiment 1, wherein the aluminosilicate zeolite comprises a zeolite having an 8-ring pore size. 3. The method of embodiment 1 or 2, wherein the aluminosilicate zeolite comprises a zeolite having a framework comprising double hexacyclic (D6r) subunits. 4. The method of any one of forms 1-3, wherein the aluminosilicate zeolite comprises a zeolite having a framework selected from AEI, AFX, CHA, LEV, AFT, EAB, KFI, SAT, TSC, SAV, ERI, LTA, and any combination of the foregoing. 5. The method of any one of embodiments 1-4, wherein the aluminosilicate zeolite comprises a zeolite having a CHA crystalline framework. 6. The method of any one of embodiments 1-5, wherein the aluminosilicate zeolite has an SAR of 15 or greater. 7. The method of any one of embodiments 1-6, wherein the aluminosilicate zeolite has an SAR of 20 or greater. 8. The method of any one of embodiments 1-5, wherein the aluminosilicate zeolite has an SAR of 10 to 30. 9. The method of any one of embodiments 1-8, wherein the solids content of the reaction mixture is about 15% or greater. 10. The method of any one of embodiments 1-9, wherein the at least one alumina source comprises a zeolite having a FAU, LTL, LTA, or MOR crystalline framework. 11. The method of embodiment 10, wherein the zeolite having an FAU crystalline framework is zeolite Y. 12. The method of any one of embodiments 1-11, wherein the at least one organic structure directing agent is a quaternary ammonium salt having at least one substituent selected from alkyl substituents, aromatic substituents, and combinations of any of the foregoing. 13. The method of any one of embodiments 1-12, wherein at least one organic structure directing agent is tetramethylpiperidinium. 14. The method of any one of embodiments 1-13, wherein the temperature ranges from about 95°C to about 100°C. 15. The method of any one of embodiments 1-14, wherein the vessel is a stirred vessel equipped with a reflux condenser. 16. The method of any one of embodiments 1-15, wherein crystallizing the reaction mixture is carried out with stirring. 17. The method of any one of embodiments 1-16, wherein the at least one silica source comprises an alkali metal silicate solution. 18. Calcining aluminosilicate zeolites to form H + Form or Na + 18. The method of any one of embodiments 1 to 17, further comprising forming a calcined zeolite in the form 19. The method of embodiment 18, further comprising ion-exchanging the calcined zeolite with a promoter metal to form an ion-exchanged zeolite catalyst. 20. The method of any one of embodiments 1-17, further comprising ion-exchanging the aluminosilicate zeolite with a promoter metal to form an ion-exchanged zeolite catalyst. 21. The method of embodiment 19 or 20, wherein the promoter metal is Fe or Cu. 22. A substrate comprising a metal-promoted zeolite catalyst composition prepared by the method of any one of embodiments 18-21. 23. The substrate of embodiment 22, wherein the metal-promoted zeolite catalyst composition is coated on the substrate. 24. The substrate of embodiment 23, wherein the metal-promoted zeolite catalyst composition is coated on the substrate in the form of a washcoat. 25. The substrate of embodiment 24, wherein the washcoat comprises a binder selected from silica, alumina, titania, zirconia, ceria, and combinations of any of the foregoing. 26. The substrate of embodiment 25, wherein the binder loading is from about 0.1% to about 10% by weight based on the weight of the washcoat. 27. The substrate of any one of embodiments 22-26, wherein the substrate is selected from a flow-through honeycomb monolith and a particulate filter. 28. The substrate of any one of embodiments 22-27, wherein the substrate is a ceramic or metal having a honeycomb structure. 29. The substrate of any one of embodiments 22-27, wherein the substrate is a gasoline particulate filter or a soot filter. 30. The substrate of any one of embodiments 22-29, comprising one or more catalyst layers on the inlet and / or outlet walls of the substrate. 31. The substrate of any one of embodiments 22-30, comprising a combination of at least two catalyst layers on the inlet and / or outlet walls of the substrate. 32. An exhaust gas treatment system comprising an engine and a catalyst composition prepared by the method of any one of embodiments 18-21. 33. The exhaust gas treatment system of embodiment 32, wherein the engine is a lead-burn engine. 34. The exhaust gas treatment system of embodiment 32 or 33, wherein the engine is a diesel engine or a lean-burn gasoline engine. 35. A method for treating an engine exhaust gas stream, comprising: placing a catalyst downstream from an engine, the catalyst comprising a metal-exchanged zeolite prepared by the method of any one of embodiments 18 to 21; and flowing the engine exhaust gas stream over the catalyst. 36. The method of embodiment 35, wherein the engine is a lead-burn engine. 37. The method of embodiment 35 or 36, wherein the engine is a diesel engine or a lean-burn gasoline engine. 38. The method of any one of embodiments 35-37, further comprising placing an additional catalytic component downstream of the engine.

[0040] In some embodiments, the disclosed zeolites are promoted with a promoter metal selected from alkali metals, alkaline earth metals, Group IIIB, IVB, VB, VIB, VIIB, VIIIB, IB, and IIB transition metals, Group IIIA elements, Group IVA elements, lanthanides, actinides, and combinations of any of the foregoing. In some embodiments, promoter metals (e.g., additional promoter metals, etc.) that can be used to prepare the promoted zeolites of the disclosed catalyst compositions include, but are not limited to, copper (Cu), cobalt (Co), nickel (Ni), lanthanum (La), manganese (Mn), iron (Fe), vanadium (V), silver (Ag), cerium (Ce), neodymium (Nd), praseodymium (Pr), titanium (Ti), chromium (Cr), zinc (Zn), tin (Sn), niobium (Nb), molybdenum (Mo), hafnium (Hf), yttrium (Y), tungsten (W), and combinations of any of the foregoing. In one or more embodiments, the promoter metal content, calculated as oxide, independently ranges from about 0.01 wt. % to about 15 wt. %, from about 0.5 wt. % to about 12 wt. %, or from about 1.0 wt. % to about 10 wt. %, based on the total weight of the corresponding calcined zeolite (including the promoter metal), reported on a volatiles-free basis. In some embodiments, the promoter metal is copper or iron.

[0041] The promoter metal can be exchanged into the zeolite by a liquid-phase exchange process, in which soluble metal ions (e.g., one or more soluble metal ions) are exchanged for protons or ammonium or sodium ions (e.g., one or more ions independently selected from protons, ammonium, or sodium ions) associated with the zeolite. The exchange can also be carried out by a solid-state process, in which solid particles of the promoter metal oxide or metal salt are mixed with zeolite powder and treated under a specific temperature and gas environment, which may or may not include steam. The exchange process can also be accomplished via an in situ process during slurry preparation, in which fine metal oxide particles are suspended in a zeolite slurry under conditions favorable for solid-liquid interaction.

[0042] In one aspect, the present disclosure provides a method for forming zeolites under reasonably mild conditions. Surprisingly, as outlined herein below, it has been discovered that even zeolites with high SAR values ​​(e.g., SAR values ​​of 10 or greater) can be crystallized under such conditions.

[0043] In some embodiments, the method of the present disclosure includes forming a reaction mixture including at least one alumina source comprising a zeolite, at least one silica source, at least one organic structure directing agent, and optionally a secondary alkali metal cation source. The secondary alkali metal cation source can increase the alkali metal content of the reaction mixture. In some embodiments, the reaction mixture is provided under alkaline aqueous conditions. The ratios of the various components, particularly the OH:SiO ratio and the Na / SiO ratio, can be adjusted, for example, by adding an acid source (e.g., sulfuric acid, etc.) and / or a sodium source (e.g., sodium sulfate, etc.).

[0044] The at least one silica source can vary and is generally selected from sources including alkali metal silicate solutions and / or colloidal silica. The alkali metal, if present in at least one silica source, can be, for example, lithium, sodium, potassium, rubidium, cesium, or francium. In certain embodiments, the alkali metal is sodium or potassium (e.g., when at least one silica source includes sodium silicate or potassium silicate). When at least one silica source includes an alkali metal silicate, the individual metal (M) / Si molar ratio is at least about 0.4, or at least about 0.5, or at least about 0.6, or at least about 0.7, or at least about 0.8, with non-limiting ranges being about 0.4 to about 1.2, or about 0.6 to about 1.0, or about 0.7 to about 0.9.

[0045] The zeolite included in the at least one alumina source may vary and may include various zeolite materials known in the art, such as various aluminosilicate zeolites. In certain embodiments, a zeolite having the FAU crystal structure is used, which is formed by a 12-ring structure and has channels of approximately 7.4 Å. Non-limiting examples of such zeolites include faujasite, zeolite X, zeolite Y, LZ-210, and SAPO-37. Such zeolites are characterized by a three-dimensional pore structure with pores running perpendicular to each other in the x, y, and z planes, with secondary building units of 4, 6, and 6-6. Examples of SAR ranges for bulk FAU zeolite materials are from about 3 to about 6, with typical unit cell sizes ranging from 24.35 to 24.65, as determined by XRD. Zeolite Y is useful in certain embodiments of the present disclosure. FAU zeolites, for example, contain Na + In one particular embodiment, the FAU zeolite is in the sodium form and contains about 2.5% to about 13% NaO by weight.

[0046] A non-limiting example of an organic structure-directing agent for this synthesis is adamantyltrimethylammonium hydroxide, although other amines and / or quaternary ammonium salts may be substituted or added. Non-limiting examples include quaternary ammonium cations having substituents (e.g., one or more substituents) selected from alkyl, adamantyl, cyclohexyl, aromatic, and any combination of the foregoing. Further non-limiting examples of organic structure-directing agents include cyclohexyltrimethylammonium, benzyltrimethylammonium, and dimethylpiperidinium hydroxide.

[0047] Hydroxide ions are the only necessary mineralizer required in the reaction mixture, and the amount of hydroxide required to achieve the above ratios can be provided solely from the alkali metal silicate solution and, to a lesser extent, from the organic structure directing agent source. If desired, the hydroxide ion content can be supplemented with an additional hydroxide ion source, such as NaOH or KOH.

[0048] In some embodiments of the present disclosure, the reaction does not require the use of high pressures (e.g., reactions in autoclaves, etc.) as are typically required for the production of various zeolites. As mentioned above, it is known that some zeolites can be produced without such harsh conditions, but it is generally understood that the preparation of zeolites with higher SAR values ​​(e.g., about 10 or greater) requires these harsh conditions.

[0049] Thus, the disclosed methods generally involve crystallizing the reaction mixture under no applied pressure (e.g., at atmospheric pressure). For example, in certain embodiments, the crystallization reaction can be carried out in a vessel open to the air, such as a vessel equipped with a reflux condenser. The method can include heating the reaction mixture using a non-limiting example reaction temperature in the range of about 100°C to about 160°C (e.g., about 110°C to about 160°C).

[0050] Higher temperatures may, in some embodiments, result in a greater rate of crystallization (i.e., greater conversion to product), all other parameters being equal. The rate of crystallization has also been observed to increase significantly with decreasing water-to-silica molar ratio, i.e., HO / SiO ratio (increasing solids content). The solids content of a zeolite gel is defined in the following manner: % solids content = (moles of Al2O3 equivalents in gel) x (101.96 g / mol) + (moles of SiO2 equivalents in gel) x (60.08 g / mol) x 100 / (total mass of gel)

[0051] It has been surprisingly discovered that by adjusting the solids content of the reaction mixture and the crystallization temperature, a suitable degree of crystallization can be achieved at atmospheric pressure. Typical reaction times can vary depending on, for example, the solids content and temperature, but are generally from about 30 hours to about 3 days.

[0052] In some embodiments, about 50% or greater crystallization can be obtained at moderately high solids contents (e.g., HO / SiO ratios of about 15 or less) at atmospheric pressure and temperatures of about 110°C or greater. In some embodiments, about 50% or greater crystallization can be obtained at atmospheric pressure and lower solids contents (e.g., HO / SiO ratios greater than about 15, such as from about 15 to about 30), at correspondingly higher reaction temperatures (e.g., about 130°C or greater). Higher crystallization percentages (e.g., greater than 90%) can be obtained by further increasing the temperature and / or solids content. For example, in some embodiments, greater than 90% crystallization can be obtained with reaction mixtures having HO / SiO ratios of about 15 or less at temperatures of at least about 120°C. In some embodiments, greater than 90% crystallization can be obtained with reaction mixtures having higher solids contents (e.g., HO / SiO ratios greater than about 15, such as from about 15 to about 30), but at higher temperatures relative to the previous embodiments, e.g., temperatures of about 140° C. or greater.

[0053] Optionally, the product may be centrifuged. Organic additives may be used to aid in handling and isolation of the solid product. Spray drying is an optional step in the processing of the product. The solid zeolite product so obtained may be heat treated or calcined in air or nitrogen. Typical calcination temperatures range from about 400°C to about 850°C (e.g., about 500°C to about 700°C) for periods of 1 to 10 hours. Following the initial calcination, the zeolite product generally contains zeolite primarily in the alkali metal form (e.g., Na + Optionally, the single or multiple ammonia ion exchanges are performed on the NH4 + This can be used to obtain the form, which can be optionally further calcined to obtain H +Forms a shape.

[0054] In certain embodiments, the zeolite is further ion-exchanged with a promoter metal to form a metal-promoted zeolite catalyst. For example, copper or iron can be ion-exchanged to form a copper- or iron-exchanged zeolite. The ion-exchange can be carried out using conventional methods. For example, copper can be ion-exchanged, in some embodiments, using copper oxide or copper acetate. The resulting copper loading can be defined, for example, based on the Cu / Al molar ratio, which can be, for example, about 0.2 to about 0.5 Cu / Al.

[0055] In some embodiments, the zeolite crystals resulting from the disclosed crystallization can be about 80% to about 99% crystalline or about 90% to about 97% crystalline. The method, in some embodiments, can be useful for preparing zeolite products having a CHA structure. However, this is not limiting. In some embodiments, the disclosed method can be used to produce aluminosilicate zeolite crystal seeds with 8-ring pore sizes having a structure selected from AEI, AFX, CHA, LEV, AFT, EAB, KFI, SAT, TSC, SAV, ERI, LTA, and any combination of the foregoing. In some embodiments, the method can be used to produce ZSM-5 zeolites.

[0056] Zeolite products can be characterized by an SAR range. As described, in some embodiments, the disclosed methods can be used to produce zeolites having a range of SAR values; however, they are particularly relevant in the context of producing zeolites with higher SAR values ​​because these have not previously been prepared under mild conditions. Thus, while the methods are broadly applicable, in certain embodiments, they are used to produce zeolite products with SARs of about 10 or greater, about 12 or greater, about 15 or greater, or about 20 or greater, such as products with SARs of about 10 to about 30, about 12 to about 30, about 15 to about 30, about 18 to about 30, or about 20 to about 30.

[0057] In certain embodiments, metal-promoted zeolite materials prepared according to the methods outlined herein can be characterized by their SCR activity at various temperatures. In certain embodiments, the metal-promoted zeolites provided herein exhibit comparable SCR activity at various temperatures compared to comparable metal-promoted zeolites prepared via conventional methods (i.e., those requiring high pressure). In particular, the disclosed methods can provide metal-promoted zeolite materials characterized by SCR activity after thermal aging treatment (e.g., about 650°C (HDD) or about 800°C (LDD)), and the NOx content of the metal-promoted zeolite-metal materials of the present disclosure can be improved. x The conversion rate is within about 10% or about 20% of a comparative metal-promoted zeolite material having the same metal loading at one or both of exhaust gas temperatures of about 200° C. and about 600° C., the comparative zeolite being prepared using a comparative process described in the Examples (e.g., Sample B). For example, the comparative metal-promoted zeolite material can be a zeolite material made using a reaction mixture that is crystallized under autogenous pressure.

[0058] Base material In one or more embodiments, the metal-promoted zeolite catalyst composition provided herein is disposed on a substrate. The washcoat is formed by preparing a slurry containing the catalyst at a specific solids content (e.g., 30% to 90% by weight) in a liquid, which is then coated onto the substrate and dried to provide a washcoat layer. Washcoats containing the metal-promoted molecular sieves provided herein can optionally contain a binder selected from silica, alumina, titania, zirconia, ceria, and combinations of any of the foregoing. The binder loading is typically about 0.1 to 10% by weight, based on the weight of the washcoat.

[0059] In one or more embodiments, the substrate is selected from a flow-through honeycomb monolith and a particulate filter, and the catalytic material(s) are applied to the substrate as a washcoat.

[0060] 1A and 1B illustrate an exemplary substrate 2 in the form of a flow-through substrate coated with a catalyst composition as described herein. Referring to FIG. 1A, the exemplary substrate 2 has a cylindrical shape, including a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 identical to end surface 6. The substrate 2 has a plurality of fine, parallel gas flow passages 10 formed therein. As can be seen in FIG. 1B, the passages 10 are defined by walls 12 and extend through the carrier 2 from the upstream end surface 6 to the downstream end surface 8, with the passages 10 being unobstructed to allow a fluid, such as a gas stream, to flow longitudinally through the carrier 2 and through the gas flow passages 10. As can be more easily seen in FIG. 1B, the walls 12 are sized and configured such that the gas flow passages 10 have a substantially regular polygonal shape. As shown, the catalyst composition can be applied as multiple, separate layers, if desired. In the illustrated embodiment, the catalyst composition is comprised of both a discrete bottom layer 14 adhered to the wall 12 of the support member and a second discrete top layer 16 coated on the bottom layer 14. The present disclosure may be practiced with one or more (e.g., two, three, or four, etc.) catalyst layers and is not limited to the two-layer embodiment illustrated in FIG. 1B.

[0061] In one or more embodiments, the substrate is a ceramic or metal having a honeycomb structure. Any suitable substrate can be used, such as a monolith substrate of the type having fine, parallel gas flow passages extending from the inlet or outlet face of the substrate so that the passages are open and allow fluid to flow therethrough. The passages, which are essentially straight-line paths from the fluid inlet to the fluid outlet, are defined by walls onto which a catalytic material is coated as a washcoat so that gas flowing through the passages comes into contact with the catalytic material. The flow passages in the monolith substrate are thin-walled channels that can be of any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such structures can contain from about 60 to about 900 or more gas inlet openings (i.e., cells) per square inch of cross section.

[0062] The ceramic substrate can be made from any suitable refractory material, such as cordierite, cordierite-α-alumina, silicon nitride, zircon-mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, α-alumina, aluminosilicate, etc. Substrates useful for the catalysts of the present disclosure can also be metallic in nature and can be composed of one or more metals or metal alloys. Metal substrates can include any metal substrate, such as those with openings or "punchouts" in the channel walls. Metal substrates can be used in various shapes, such as pellets, corrugated sheets, or monolithic forms. Non-limiting examples of metal substrates include heat-resistant base metal alloys, such as alloys in which iron is a substantial or major constituent. Such alloys may include one or more elements selected from nickel, chromium, and aluminum, the sum of which metals may comprise at least about 15% by weight of the alloy, for example, about 10% to 25% by weight of chromium, about 1% to 8% by weight of aluminum, and about 0% to about 20% by weight of nickel, in each case based on the weight of the substrate.

[0063] In one or more embodiments in which the substrate is a particulate filter, the particulate filter can be selected from a gasoline particulate filter or a soot filter. Particulate filters include, but are not limited to, honeycomb wall-flow filters, partial filtration filters, wire mesh filters, wound fiber filters, sintered metal filters, and foam filters. In certain embodiments, the particulate filter is a catalyzed soot filter (CSF). The catalyzed CSF, for example, comprises a substrate coated with the catalyst composition provided herein.

[0064] Wall flow substrates useful for supporting the catalytic material of one or more embodiments may have a plurality of fine, substantially parallel gas flow passages extending along the longitudinal axis of the substrate. In some embodiments, each passage is blocked at one end of the substrate body, with alternate passages blocked at the opposite end face. Such monolith substrates may contain up to about 900 or more passages (or "cells") per square inch of cross section, although much smaller numbers may be used. For example, substrates may have about 7 to about 600 cells per square inch ("cpsi"), more typically about 100 to about 400 cells per square inch ("cpsi"). Porous wall flow filters used in embodiments of the present disclosure may be characterized in that the walls of the porous wall flow filter have a platinum group metal thereon or therein. The catalytic material may be present only on the inlet side, only on the outlet side, on both the inlet and outlet sides of the substrate wall, or the wall itself may be composed entirely or partially of catalytic material. In another embodiment, the substrate may include one or more catalyst layers and a combination of at least two catalyst layers on the inlet and / or outlet walls of the substrate.

[0065] As seen in FIG. 2 , the example substrate has multiple passages 52. The passages are tubularly surrounded by the interior wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. Alternate passages are blocked at the inlet end by inlet plugs 58 and at the outlet end by outlet plugs 60, forming an inverted checkerboard pattern at the inlets 54 and outlets 56. Gas flow 62 enters through unblocked channel inlets 64, is stopped by outlet plugs 60, and diffuses through the (porous) channel walls 53 to the outlet end 66. Gas cannot pass back to the inlet side of the wall because of the inlet plugs 58. Porous wall-flow filters used in this disclosure may be characterized by the substrate walls having one or more catalyst materials thereon.

[0066] Exhaust Gas Treatment Systems A further aspect of the present disclosure is directed to an exhaust gas treatment system. In one or more embodiments, the exhaust gas treatment system includes an engine, such as a diesel engine or a lean-burn gasoline engine, e.g., a lean-burn engine, and a catalyst composition of the present disclosure downstream of the engine.

[0067] One example of an emissions treatment system is illustrated in FIG. 3, which shows a schematic diagram of an emissions treatment system 20. As shown, the emissions treatment system can include multiple catalyst components in series downstream of an engine 22, such as a lean-burn gasoline engine. At least one of the catalyst components can be an SCR catalyst of the present disclosure. The catalyst compositions provided in accordance with the present disclosure can be combined with a number of additional catalyst materials and can be located in various positions relative to the additional catalyst materials. FIG. 3 illustrates five catalyst components 24, 26, 28, 30, and 32 in series; however, the total number of catalyst components can vary, and five components is merely a non-limiting example.

[0068] Without limitation, Table 1 presents various exhaust gas treatment system configurations of one or more embodiments. Note that each catalyst is connected to the next catalyst via an exhaust conduit such that the engine is upstream of catalyst A, which is upstream of catalyst B, which is upstream of catalyst C, which is upstream of catalyst D, and which is upstream of catalyst E (if present). References to components A-E in the table may be cross-referenced with the same symbols in FIG. 3.

[0069] The DOC catalysts listed in Table 1 can be any catalyst conventionally used to reduce carbon monoxide (CO) and hydrocarbon (HC) pollutants in engine exhaust gases and can include platinum group metals (PGMs) supported on a refractory metal oxide support (e.g., alumina, etc.).

[0070] The LNT catalysts listed in Table 1 xThe catalyst can be any catalyst conventionally used as a trap, including basic metal oxides (such as BaO, MgO, CeO, etc.) and platinum group metals (such as Pt and Rh) for catalytic oxidation and reduction of NO. x It may include a sorbent composition. [Table 1]

[0071] References in the table to DPF refer to a diesel particulate filter, which may consist of a wall flow filter adapted to filter particulate matter in the exhaust gases.

[0072] References to SCR in the tables refer to an SCR catalyst, which may include an SCR catalyst composition comprising a metal-exchanged zeolite described herein. References to SCRoF (or SCR on filter) refer to a particulate or soot filter (e.g., a wall-flow filter, etc.) that may include an SCR catalyst composition provided herein. When both an SCR and an SCRoF are present, one or both may include an SCR catalyst provided herein, or one of the catalysts may include a conventional SCR catalyst. The emissions treatment system may optionally include an injector positioned upstream of the SCR catalyst and adapted to inject ammonia or an ammonia precursor (e.g., urea, etc.) into the exhaust stream.

[0073] References to AMOx in the tables refer to an ammonia oxidation catalyst that may be provided downstream of the metal-exchanged zeolite-containing catalyst described herein to remove any fugitive ammonia from the exhaust gas treatment system. In certain embodiments, the AMOx catalyst may include a PGM component. In one or more embodiments, the AMOx catalyst may include a bottom coat including a PGM component and a top coat with SCR functionality.

[0074] As will be appreciated by those skilled in the art, in the configurations listed in Table 1, any one or more of components A, B, C, D, or E can be disposed on a particulate filter, such as a wall-flow filter, or on a flow-through honeycomb substrate. In one or more embodiments, the engine exhaust system includes one or more catalyst compositions mounted in a location near the engine (direct-coupled location, CC), with an additional catalyst composition in an underbody location (underfloor location, UF).

[0075] How to treat engine exhaust Another aspect of the present disclosure is directed to a method for treating an exhaust gas stream from an engine, such as a lean-burn engine. The method may include disposing a catalyst downstream of the engine, the catalyst including a metal-exchanged zeolite prepared according to one or more embodiments of the present disclosure, and flowing the engine's exhaust gas stream over the catalyst. In one or more embodiments, the method further includes placing additional catalyst components downstream of the engine, as described above.

[0076] The present disclosure will now be described with reference to the following example(s). [Example]

[0077] First, studies were conducted at various temperatures and various solids contents (H2O / SiO2) to evaluate whether any crystallization was observed at atmospheric pressure to form the CHA product. Trimethyladamantylammonium hydroxide (TMAdaOH) was used as the organic structure-directing agent (OSDA), sodium silicate was used as the silica source, and Na-FAU was used as the alumina source. SiO2:0.0219Al2O3:0.095TMAda + :0.84Na + :0.52OH - :11.7~33.6H2O

[0078] The OH / SiO2 and Na / SiO2 ratios were adjusted by adding sulfuric acid and sodium sulfate, respectively, using the following standard addition order: HO, AdaOH, Na2SO4, HO2SO4, Na-FAU, and sodium silicate. Initial temperature studies (Table 2) at 15 h crystallization time were conducted in a stirred autoclave (150 revolutions per minute (rpm)) and showed that the rate of CHA formation increased significantly with decreasing HO / SiO2 ratio (increasing solids content of the gel) at all temperatures. Notably, traces of CHA were detected after crystallization at 100 °C in the gel with the highest solids content (HO / SiO2 = 11.7). [Table 2]

[0079] Subsequent crystallization of the latter was attempted in a stirred glass vessel (150 or 350 rpm) equipped with a reflux condenser at 97° C. Samples were removed periodically during crystallization and analyzed via XRD, as described below.

[0080] Two tests were carried out to evaluate the feasibility of preparing such a CHA zeolite at atmospheric pressure by stirring at different rpm values. The diffraction patterns of these samples are shown in Figures 4A and 4B for two crystallization tests at 150 rpm (Figure 4A) and 350 rpm (Figure 4B). At 150 rpm, crystallization of CHA began after 45 h and was complete by 93 h at temperature. Apart from FAU and CHA, no other phases or amorphous material were observed in the samples. By increasing the stirring speed to 350 rpm, complete conversion of FAU is achieved at 97 °C in 45–65 h. Micrographs of the final CHA product (SAR = 20) obtained from the gel crystallized at 350 rpm are shown in Figures 5A and 5B. The material exhibits a high degree of crystallinity (95% CHA) and a corresponding high surface area (ZSA = 560 m). 2 / g, MSA=40m 2 / g).

[0081] The as-prepared CHA product from the 150 rpm crystallization was calcined (540 °C) to remove OSDA and subsequently ammonium exchanged. + The form was calcined (450°C) and + CuO was introduced to achieve a CuO loading of 4.6 wt% (Sample A). Note that ambient pressure crystallization (97°C for 72-100 hours) of conventional CHA zeolite gels, which are known to yield SAR 20 CHA products under hydrothermal conditions (140-170°C for 15-30 hours), did not yield a crystalline product.

[0082] A comparative sample (Comparative Sample B) was prepared by hydrothermal crystallization (170°C, 30 hours). This gel, referred to as "Comparative Gel," was prepared using the following composition (without a zeolitic alumina source), using aluminum triisopropoxide and colloidal silica as the alumina and silica sources, respectively: SiO2:0.0506Al2O3:0.07TMAda + :0.13Na + :0.2OH - :11.6H2O

[0083] This comparative sample was then calcined, ammonium exchanged, calcined, and ion exchanged with CuO (as in sample A) to give a crystallized SAR=20 CHA at 5.1 wt % CuO loading.

[0084] Sample A and Comparative Sample B, catalytic coatings containing alumina and zirconium oxide binder, were disposed via a washcoat process on cellular ceramic monoliths having a cell density of 400 cpsi and a wall thickness of 6 mil. The coated monoliths were dried at 130°C and calcined at approximately 550°C for 1 hour. The coating process was carried out at a rate of 2.2 g / in 3 The catalyst loading was 5% alumina and 5% zirconium oxide binder. The coated monoliths were hydrothermally aged at 650°C for 50 hours in the presence of 10% HO / air (HDD). The NO of the 650°C aged sample wasx The conversion was carried out under pseudo-steady-state conditions for 120,000 h in a gas mixture of 1000 ppm NO, 1000 ppm NH, 10% O, 10% H, O, and the balance N, with a temperature increase of 2.5°C / min from 175°C to 600°C. -1 The gas volumetric hourly space velocity was measured in a laboratory reactor.

[0085] The NOx conversion at 175°C and 600°C after aging at 650°C for the coated catalysts containing Sample A and Comparative Sample B is shown in Figure 6. As shown, slightly less but comparable performance after HDD aging is observed for Sample A compared to Comparative Sample B; this difference may be due to the lower CuO content of Sample A.

[0086] It will be readily apparent to those skilled in the relevant art that suitable modifications and adaptations to the compositions, methods, and applications described herein can be made without departing from the scope of any embodiment or aspect thereof. The provided compositions and methods are intended to serve as examples and are not intended to limit the scope of the embodiments. All of the various embodiments, aspects, and options disclosed herein can be combined in all variations. The scope of the compositions, formulations, methods, and processes described herein includes all actual or potential combinations of the embodiments, aspects, options, and examples herein. All patents and publications cited herein are incorporated by reference for their specific teachings, as described, unless other specific incorporated descriptions are specifically provided.

Claims

1. 1. A method for synthesizing an aluminosilicate zeolite having a silica-to-alumina molar ratio (SAR) of 10 or greater, comprising: forming a reaction mixture comprising at least one alumina source, at least one silica source, and at least one organic structure directing agent, the reaction mixture having a solids content of about 10% or greater; and H ２ O / SiO ２ a molar ratio of about 15 or less; and crystallizing the reaction mixture at a temperature of about 100° C. or less in an open vessel open to the atmosphere at atmospheric pressure to form the aluminosilicate zeolite; the at least one alumina source comprises a zeolite having a FAU, LTL, LTA, or MOR crystalline framework; method.

2. 10. The method of claim 1, wherein the aluminosilicate zeolite comprises a zeolite having an 8-ring pore size.

3. 2. The method of claim 1, wherein the aluminosilicate zeolite comprises a zeolite having a framework comprising double hexacyclic (D6r) subunits.

4. 2. The method of claim 1, wherein the aluminosilicate zeolite comprises a zeolite having a framework selected from AEI, AFX, CHA, LEV, AFT, EAB, KFI, SAT, TSC, SAV, ERI, LTA, and combinations of any of the foregoing.

5. 10. The method of claim 1, wherein the aluminosilicate zeolite comprises a zeolite having a CHA crystalline framework.

6. 10. The method of claim 1, wherein the aluminosilicate zeolite has an SAR of 15 or greater.

7. 10. The method of claim 1, wherein the aluminosilicate zeolite has an SAR of 20 or greater.

8. 10. The method of claim 1, wherein the aluminosilicate zeolite has an SAR of 10 to 30.

9. 10. The method of claim 1, wherein the solids content of the reaction mixture is about 15% or greater.

10. 2. The method of claim 1, wherein the zeolite having the FAU crystalline framework is zeolite Y.

11. 10. The method of claim 1, wherein the at least one organic structure directing agent is a quaternary ammonium salt having at least one substituent selected from alkyl substituents, aromatic substituents, and combinations of any of the foregoing.

12. 10. The method of claim 1, wherein the at least one organic structure directing agent is tetramethylpiperidinium.

13. The method of claim 1 , wherein the temperature ranges from about 95° C. to about 100° C.

14. 10. The method of claim 1, wherein the vessel is a stirred vessel equipped with a reflux condenser.

15. 10. The method of claim 1, wherein the crystallizing of the reaction mixture is carried out with stirring.

16. The method of claim 1 , wherein the at least one silica source comprises an alkali metal silicate solution.

17. The aluminosilicate zeolite is calcined to form H ＋ Form or Na ＋ 10. The method of claim 1, further comprising forming a calcined zeolite in the form

18. 18. The method of claim 17, further comprising ion-exchanging the calcined zeolite with a promoter metal to form an ion-exchanged zeolite catalyst.

19. 10. The method of claim 1, further comprising ion-exchanging the aluminosilicate zeolite with a promoter metal to form an ion-exchanged zeolite catalyst.

20. 20. The method of claim 19, wherein the promoter metal is Fe or Cu.

21. The water to silica ratio of the reaction mixture is H ２ O / SiO ２ 10. The method of claim 1, wherein the molar ratio is less than 12.

22. 1. A method for synthesizing an aluminosilicate zeolite having a silica-to-alumina molar ratio (SAR) of 10 or greater, comprising: forming a reaction mixture comprising at least one alumina source, at least one silica source, and at least one organic structure directing agent, the reaction mixture having a solids content of about 10% or greater; and H ２ O / SiO ２ a molar ratio of about 15 or less; and crystallizing the reaction mixture at a temperature of about 100° C. or less in a vessel open to the atmosphere at atmospheric pressure to form the aluminosilicate zeolite; the at least one silica source comprises an alkali metal silicate solution; method.

23. 1. A method for synthesizing an aluminosilicate zeolite having a silica-to-alumina molar ratio (SAR) of 10 or greater, comprising: forming a reaction mixture comprising at least one alumina source, at least one silica source, and at least one organic structure directing agent, the reaction mixture having a solids content of about 10% or greater; and H ２ O / SiO ２ a molar ratio of about 15 or less; and crystallizing the reaction mixture at a temperature of about 100° C. or less in an open vessel open to the atmosphere at atmospheric pressure to form the aluminosilicate zeolite; The aluminosilicate zeolite is calcined to form H ＋ Form or Na ＋ forming a calcined zeolite in the form method.

24. 24. The method of claim 23, further comprising ion-exchanging the calcined zeolite with a promoter metal to form an ion-exchanged zeolite catalyst.

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