Method for synthesizing nano-sized beta zeolites

Abstract

Methods for synthesizing nano-sized beta zeolites are described. The method may include mixing alumina with tetraethylammonium hydroxide to form an aluminum solution; mixing silica, additional TEAOH, and water to form a silica slurry; and adding an aluminum solution to the silica slurry and mixing to form an aluminosilicate gel. The method may also include transferring the aluminosilicate gel to an autoclave operating at 120 DEG C to 160 DEG C at a rotational speed of 60 to 100 revolutions per minute for 2 to 4 days to form a zeolite precursor colloid; washing the zeolite precursor colloid with water to form a washed colloid; drying the washed colloid at 80 DEG C to 150 DEG C for 6 hours to 24 hours to form a zeolite precursor; and calcining the zeolite precursor at 400 DEG C to 650 DEG C for 2 hours to 8 hours to form the nano-sized beta zeolite.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority of U.S. Patent Application Serial No. 18 / 059,705, titled "Method for Synthesizing Nanoscale Beta Zeolite", filed on November 29, 2022, the entire content of which is incorporated herein by reference. Technical field

[0003] The present disclosure generally relates to nanoscale mesoporous zeolite compositions and methods of synthesizing and using these compositions, and more particularly to methods for synthesizing nanoscale beta zeolite using alumina as an aluminum source. Background art

[0004] Beta zeolite is a crystalline aluminosilicate and is widely used in heavy oil conversion processes such as hydrocracking and fluid catalytic cracking processes. The feedstock for these processes is a part of crude oil, which has an initial boiling point of 350 degrees Celsius (°C) and an average molecular weight of about 200 to 600 or higher. Macroporous materials have a pore size distribution between 50 nanometers (nm) and 1000 nm. Mesoporous materials have a medium pore size distribution, between 2 nm and 50 nm. Microporous materials have a pore size distribution range of 0.5 nm to 2 nm. Conventional beta zeolite has a pore size of less than 2 nm, which does not allow large molecules to diffuse in and react at the active sites located inside the zeolite. Increasing the pore size and reducing the zeolite particle size are two effective ways to enhance mass transfer and thus significantly improve the catalyst performance.

[0005] Nanoscale beta zeolites have been produced, but their synthesis has traditionally utilized expensive elemental aluminum or aluminum isopropoxide as the aluminum source for generating the zeolite. Summary of the invention

[0006] Accordingly, there has long been a need to provide more economical schemes for synthesizing nanoscale beta zeolite. The present disclosure addresses this long - standing need by generating nanoscale beta zeolite according to methods that allow alumina to serve as the aluminum source for generating the zeolite. It is readily understood that alumina is not only readily available and inexpensive, thus providing an economical way to generate nanoscale beta zeolite.

[0007] According to one embodiment of the present disclosure, a method for synthesizing nano-sized beta zeolite includes: mixing alumina with tetraethylammonium hydroxide (TEAOH) to form an aluminum solution; mixing silica, additional TEAOH, and water to form a silica slurry; adding the aluminum solution to the silica slurry and mixing for at least 1 hour to form an aluminosilicate gel, wherein the aluminosilicate gel has the following molar ratio composition: SiO2 of 20 to 500: TEAOH of 8 to 300: Al2O3: H2O of 17 to 700; transferring the aluminosilicate gel to an autoclave operating at 120 °C to 160 °C at a rotation speed of 60 to 100 revolutions per minute for 2 to 4 days to form a zeolite precursor colloid; washing the zeolite precursor colloid with water to form a washed colloid; drying the washed colloid at 80 °C to 150 °C for 6 to 24 hours to form a zeolite precursor; and calcining the zeolite precursor at 400 °C to 650 °C for 2 to 8 hours to form nano-sized beta zeolite.

[0008] Other features and advantages of the techniques disclosed herein will be set forth in the following detailed description, and in part will be apparent to those skilled in the art from reading the detailed description or practicing the techniques described herein (including the following detailed description and the appended claims).

[0009] It should be understood that the above general description and the following detailed description both present embodiments of the present technology and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed present technology. Additionally, the following description is for illustrative purposes only and is not intended to limit the scope of the claims in any way. Detailed Description

[0010] The present disclosure describes various embodiments related to nano-sized mesoporous zeolite compositions and methods for synthesizing these compositions.

[0011] The phrases "in some embodiments", "in various embodiments", "in one embodiment", or "in embodiments" may be used in the description, which may respectively refer to one or more of the same or different embodiments. In addition, the terms "comprising", "including", "having", etc. used with respect to the embodiments of the present disclosure are synonyms.

[0012] Zeolite catalysts are commonly used in heavy oil conversion processes such as hydrocracking and fluid catalytic cracking processes. For example, crude oil can first be hydrotreated and then passed through a hydrocracking catalyst to remove unwanted components such as sulfur, nitrogen, and metals, and to convert large molecular weight hydrocarbons (complex aromatic or unsaturated hydrocarbons) into naphtha, kerosene, gasoline, diesel, or high-quality lubricating oil. The catalysts used in the hydrogenation operation have two functions: one is to crack large molecular weight hydrocarbons, and the other is to hydrogenate unsaturated molecules. However, the small pore diameters of the most widely used zeolites (beta zeolite and Y zeolite) in hydrocracking catalysts have an adverse effect on the performance of the catalysts. The small pore diameters prevent large molecules in the heavy oil fraction from diffusing into the active sites located inside the zeolite. This results in a decrease in catalyst activity and possible catalyst deactivation. The low diffusion efficiency of large molecules can be improved by increasing the pore diameter of the zeolite catalyst, or by reducing the particle size of the zeolite catalyst, or by combining these two characteristics. Disclosed herein is an ordered mesoporous zeolite composition having a pore diameter between 2 nm and 60 nm and a particle size less than 100 nm. By increasing the external surface area of the catalyst and shortening the diffusion path of reactants and products, reducing the particle size during the synthesis of zeolite catalysts affects the performance of the zeolite catalysts.

[0013] The traditional hydrothermal synthesis of nanosized beta zeolite has many problems associated with the presence of alkali metal cations during the preparation process, including the irregularity of zeolite catalysts caused by the aggregation of nanosized particles, and the reduction in the yield of the final product due to the need for ion exchange and separation steps to obtain the H-type zeolite product or proton zeolite form. Current techniques for overcoming the irregularity problem include introducing a steaming step or performing a hot alkaline treatment on a mixture of nanosized precursors and micellar solutions containing a structure-directing agent (SDA). By controlling the SDA concentration and temperature during the synthesis process, nanosized zeolite particles with ordered mesoporosity are produced. Previous techniques also include using an ethanol surfactant solution for flocculation, which results in the need for a subsequent filtration process to separate the zeolite.

[0014] Previous methods for synthesizing nanosized beta zeolite have also traditionally utilized expensive aluminum sources such as metallic aluminum or aluminum isopropoxide. However, the embodiments according to the present disclosure demonstrate that nanosized beta zeolite can be synthesized using a significantly cheaper aluminum source, namely alumina (Al2O3).

[0015] Disclosed herein is a specific synthesis method of these nano-sized mesoporous zeolite compositions. According to the present disclosure, the method for synthesizing nano-sized beta zeolite includes: mixing alumina with tetraethylammonium hydroxide (TEAOH) to form an aluminum solution; mixing silica, additional TEAOH, and water to form a silica slurry; and adding the aluminum solution to the silica slurry and mixing for at least 1 hour to form an aluminosilicate gel, wherein the aluminosilicate gel has the following molar ratio composition: SiO2 of 20 to 500: TEAOH of 15 to 40: Al2O3: H2O of 17 to 700. Subsequently, the aluminosilicate gel is transferred to an autoclave operating at 120 °C to 160 °C at a rotation speed of 60 to 100 revolutions per minute for 2 days to 4 days to form a zeolite precursor colloid; the zeolite precursor colloid is washed with water to form a washed colloid; the washed colloid is dried at 80 °C to 150 °C for 6 hours to 24 hours to form a zeolite precursor. Finally, the zeolite precursor is calcined at 400 °C to 650 °C for 2 hours to 8 hours to form nano-sized beta zeolite. The synthesis method of nano-sized beta zeolite and its specific steps will be discussed in detail below.

[0016] Finally, these compositions are synthesized using a mixture of fumed silica or colloidal silica and alumina. The method does not include using aluminum salts or silica salts to form zeolite precursors. The nano-sized beta zeolite can be an H-type mesoporous nano-sized beta zeolite. The nano-sized beta zeolite combines the advantages of mesoporous materials and nano-sized particles. In this method, no sodium ions or other impurities are introduced, and thus, according to the method of the embodiments of the present disclosure, subsequent ion exchange steps, such as the exchange of ammonium ions, are not required. Due to the elimination of post-ion exchange in the traditional method, the loss of zeolite during the sodium ion removal process is eliminated, and thus the dry gel conversion improves the synthesis efficiency and product yield.

[0017] In one or more embodiments, an aluminum solution is formed. Specifically, alumina is mixed with tetraethylammonium hydroxide (TEAOH) to form an aluminum solution. As mentioned above, the aluminum source in the aluminum solution is alumina, which saves a large amount of cost compared with the traditionally used expensive aluminum sources (such as metallic aluminum or aluminum isopropoxide). It should be understood that the formation pathway for generating the intermediate aluminate (AlO2 - ) in zeolite formation varies depending on the aluminum source. For example, compared with the pathway for generating aluminate using alumina as described in Reaction 2, Reaction 1 illustrates the pathway for generating aluminate using elemental aluminum. It should be noted that the formation of zeolite nuclei and crystal growth typically occurs through a solution-mediated mechanism, in which silicon and aluminum precursors dissolve in the solution, first generating nuclei, and then silicon and aluminum species transfer to the nuclei to enable crystal growth. Therefore, the dissolution differences of Al and Al2O3 in an alkaline solution affect the rates of zeolite nucleus formation and crystallization.

[0018] Al+OH -→Al(OH)3 + OH - →AlO2 - Reaction 1

[0019] Al2O3 + OH - →AlO2 - Reaction 2

[0020] In one or more embodiments, a silica slurry is formed. Specifically, silica is mixed with additional tetraethylammonium hydroxide (TEAOH) and water to form a silica slurry. In one embodiment, the silica source is fumed silica. In another embodiment, the silica source is colloidal silica. Using these silica sources in place of alkali metal salts of silica and using alumina in place of alkali metal salts of aluminum eliminates the need for a subsequent ion exchange step and directly forms the β-zeolite product.

[0021] In one or more embodiments, an aluminum solution is added to the silica slurry and mixed to form an aluminosilicate gel. In various embodiments, the aluminum solution and the silica slurry can be mixed for at least 1 hour, at least 1.5 hours, at least 2 hours, or at least 3 hours. It should be understood that the mixing time must be sufficient to fully combine the aluminum solution and the silica slurry to form a gel.

[0022] The formation of the aluminum solution and the silica slurry is completed such that the aluminosilicate gel has the following molar ratio composition: SiO2 from 20 to 500: TEAOH from 8 to 300: Al2O3: H2O from 17 to 700. Specifically, since the aluminum solution and the silica slurry are combined to form the aluminosilicate gel, the relative ratios of silica, TEAOH, alumina, and water in the aluminum solution and the silica slurry can be understood. For example, for each mole of alumina used to form the aluminum solution, 20 to 500 moles of silica should be used to form the silica slurry. In a further embodiment, the aluminosilicate gel can have the following molar ratio composition: SiO2 from 20 to 500: TEAOH from 8 to 300: Al2O3: H2O from 17 to 700. In an even further embodiment, the aluminosilicate gel can have the following molar ratio composition: SiO2 from 20 - 100: TEAOH from 8 - 60: Al2O3: H2O from 200 - 500.

[0023] In one or more embodiments, the aluminosilicate gel is transferred to an autoclave to form a zeolite precursor colloid. It should be understood that heating in the autoclave causes silicon and aluminum species to form zeolite nuclei, which then further crystallize to form zeolite crystals.

[0024] In various embodiments, the aluminosilicate gel is heated in an autoclave operating at 120 °C to 160 °C, 125 °C to 155 °C, 130 °C to 150 °C, 135 °C to 145 °C, or about 140 °C. Additionally, in various embodiments, the aluminosilicate gel can be heated in the autoclave for 2 days to 4 days, 2.5 days to 4 days, 2 days to 3.5 days, 2.5 days to 3.5 days, or about 3 days. Further, in various embodiments, the aluminosilicate gel can be rotated in the autoclave at a speed of 60 to 100 revolutions per minute (rpm), 60 to 90 rpm, 60 to 80 rpm, 60 to 70 rpm, or about 60 rpm.

[0025] In one or more embodiments, the autoclave is quenched with water. It should be understood that quenching immediately stops any reaction in the autoclave and ensures that the reaction times for all synthesis reactions are consistent over multiple production runs. It should also be understood that the water used to quench the autoclave, which does not come into contact with the aluminosilicate gel or the resulting zeolite precursor colloid, need not be limited to distilled water, tap water, or purified water. In one or more embodiments, the water can be cold water, which for the purposes of this disclosure is defined as water at a temperature of 30 °C or lower. In various embodiments, the autoclave can be quenched for 1 hour, 1.5 hours, 2 hours, 3 hours, or 4 hours.

[0026] Conventional methods for preparing nanosized zeolites involve using ethanol or an ethanol surfactant solution to obtain a zeolite precursor, and these conditions include longer stirring times without pH adjustment. This results in the formation of a flocculant that must be filtered before subsequent processing. During the filtration process, a significant amount of silica and aluminum substances are removed. As a result, subsequent hydrothermal treatment leads to the local formation of zeolites. The crystallinity of the zeolites is reduced, and most of them are amorphous materials and not zeolites. In embodiments of the method disclosed herein, the first step is to form a zeolite precursor building unit as an aluminosilicate gel. There is no separation step, so all silica and aluminum substances remain in the system. After hydrothermal treatment, almost all of the silica and aluminum are converted into beta zeolite rather than being washed away from the system.

[0027] In one or more embodiments, the zeolite precursor colloid produced by heating in an autoclave is washed with water to form a washed colloid. The water used to wash the zeolite precursor colloid is preferably distilled water to avoid reaction or contamination of the resulting washed colloid. However, it should be understood that any purified water free of impurities such as Mg, Na, Ca, Cl, etc. can be used, and distilled water is not required in all embodiments. These impurities, especially Mg, Ca, and Na cations, may deposit on the zeolite to neutralize the acidic sites and thus reduce the zeolite acidity and potentially reduce the zeolite stability. Washing the zeolite precursor colloid removes any silica, TEAOH, alumina, silica, or other unwanted reaction products from the desired product, thereby producing beta zeolite or crystalline SiO2 - Al2O3. If the alumina and silica substances are not removed, they will become amorphous silica - alumina after drying and calcination, thus reducing the crystallinity and zeolite purity of the final product.

[0028] In one or more embodiments, washing the zeolite precursor colloid with water to form a washed colloid includes separating the solid and colloid product from the autoclave from any liquid product formed in the autoclave using a centrifuge. The solid and colloid product are then mixed with water to wash the solid and colloid product. Water can be added to the solid and colloid product, and the weight ratio of water to the product is approximately 10:1, and the mixture can be stirred for about 30 minutes. The resulting solution is then separated using a centrifuge. In various embodiments, the washing and separation can be repeated, for a total of 1, 2, 3, 4, or 5 washes. Alternatively, the washing and separation can be repeated until the resulting solution removed during centrifugation has a pH less than 9.0. Specifically, after centrifugation, the solid product settles at the bottom of the centrifuge tube, and a clear solution is present at the top of the centrifuge tube, which represents the resulting solution having a pH less than 9.0.

[0029] In one or more embodiments, the washed colloid is dried to form a zeolite precursor. In various embodiments, the washed colloid can be dried at a high drying temperature of 80°C to 150°C, 90°C to 150°C, 100°C to 150°C, 110°C to 150°C, 80°C to 140°C, 80°C to 130°C, 80°C to 120°C, 90°C to 120°C, or 100°C to 110°C. Additionally, in various embodiments, the washed colloid can be dried at the high drying temperature for a period of 6 hours to 24 hours, 10 hours to 24 hours, 12 hours to 24 hours, 6 hours to 18 hours, or 8 hours to 14 hours. Alternatively, the period of drying at the high drying temperature can be considered overnight.

[0030] In one or more embodiments, a zeolite precursor is calcined to form nanosized beta zeolite. In various embodiments, the zeolite precursor can be calcined at a high calcination temperature of 400 °C to 650 °C, 450 °C to 650 °C, 500 °C to 650 °C, 550 °C to 650 °C, 500 °C to 600 °C, or 550 °C to 600 °C. Additionally, in various embodiments, the zeolite precursor can be calcined at the high calcination temperature for a period of 2 hours to 8 hours, 2 hours to 6 hours, 3 hours to 6 hours, 4 hours to 8 hours, 4 hours to 5 hours, or approximately 4 hours. In one or more embodiments, the heating rate during calcination is 2 °C per minute.

[0031] Properties of the nanosized beta zeolite include an average particle size of 10 nm to 100 nm. The average particle size is based on SEM measurements. In some embodiments, the nanosized beta zeolite has a particle size of 10 nm to 90 nm, 20 nm to 100 nm, 30 nm to 100 nm, 40 nm to 100 nm, or 50 nm to 100 nm. The surface area of the nanosized beta zeolite can be 500 square meters per gram (m 2 / g) to 800 m 2 / g. In some embodiments, the nanosized beta zeolite can be in the range of 500 m 2 / g to 700 m 2 / g, 500 m 2 / g to 600 m 2 / g, 550 m 2 / g to 800 m 2 / g, or 550 m 2 / g to 700 m 2 / g. The pore volume of the nanosized beta zeolite can be 0.5 milliliters per gram (ml / g) to 1.0 ml / g. In some embodiments, the pore volume of the nanosized beta zeolite can be 0.6 ml / g to 1.0 ml / g, 0.75 ml / g to 1.0 ml / g, 0.5 ml / g to 0.9 ml / g, or 0.75 ml / g to 0.9 ml / g. The pore diameter of the nanosized beta zeolite can be 3 nm to 10 nm. In some embodiments, the pore diameter of the nanosized beta zeolite can be 3 nm to 8 nm, 4 nm to 10 nm, 4 nm to 8 nm, or 5 nm to 7 nm. Using the Brunauer-Emmett-Teller technique and the pore volume, the pore diameter can be determined from the surface area.

[0032] Embodiments of the presently disclosed method for synthesizing nanosized β-zeolite do not require a step to remove alkali metal cations (such as sodium or other cations) because these substances are not introduced to form the initial aluminosilicate mixture. Since the silica source is fumed silica or colloidal silica, the method does not require a subsequent ion exchange step. In addition, alumina is used instead of elemental aluminum or other more expensive substances. By eliminating one or more steps of the traditional zeolite process and using cheaper starting materials, the synthesis cost of the zeolite is reduced while the zeolite yield is increased.

[0033] Examples

[0034] The method for synthesizing nanosized β-zeolite will be further illustrated by the following examples. The examples are illustrative in nature and should not be construed as limiting the subject matter of the present disclosure.

[0035] Two samples of nanosized β-zeolite were prepared to compare the synthesis via the traditional method with the synthesis according to the method of the present disclosure. Comparative Example 1 provides the synthesis of nanosized β-zeolite using a traditional aluminum source. Inventive Example 2 provides the synthesis of nanosized β-zeolite using alumina as the aluminum source.

[0036] Comparative Example 1

[0037] According to the traditional method, for Comparative Example 1, elemental aluminum powder was utilized in the preparation of nanosized β-zeolite. In a first container, 0.27 grams of metallic Al powder from Sigma Aldrich was combined with 25 grams of tetraethylammonium hydroxide (TEAOH) (Aldrich, 35% aqueous solution). The resulting mixture was stirred at room temperature until the Al powder was completely dissolved and a clear solution was formed. In a second container, 15 grams of fumed silica ( 200, from Evonik Industries Ag (Essen, Germany)) was combined with 38 grams of 35% TEAOH and 4.05 grams of purified water to form a slurry. Then the aluminum solution in the first container was added to the slurry in the second container and mixed at room temperature for 4 hours to form an aluminosilicate gel. Subsequently, the aluminosilicate gel was transferred to a PTFE-lined stainless steel autoclave, sealed and placed in a rotary oven. The autoclave was rotated at 60 rpm at 140 °C for three days and then quenched with cold water for 1 hour. Then the colloidal formed in the autoclave was repeatedly washed in a high-speed centrifuge until a pH of approximately 9.0 was reached. Then the solid zeolite product was dried overnight at 110 °C and calcined at 550 °C for 4 hours at a heating rate of 2 °C / minute.

[0038] Inventive Example 2

[0039] According to an embodiment of the present disclosure, for Invention Example 2, alumina is utilized in the preparation of nano-sized beta zeolite. In a first container, 0.51 grams of alumina ( Sasol) is combined with 25 grams of tetraethylammonium hydroxide (TEAOH) (Aldrich, 35% aqueous solution). The resulting mixture is stirred at room temperature until the alumina is completely dissolved and a clear solution is formed. In a second container, 15 grams of fumed silica ( 200, from Evonik Industries Ag (Essen, Germany)) is combined with 38 grams of 35% TEAOH and 4.05 grams of purified water to form a slurry. Then the aluminum solution in the first container is added to the slurry in the second container and mixed at room temperature for 4 hours to form an aluminosilicate gel. Subsequently, the aluminosilicate gel is transferred to a PTFE-lined stainless steel autoclave, sealed, and placed in a rotary oven. The autoclave is rotated at 60 rpm at 140 °C for three days and then quenched with cold water for 1 hour. Then the colloids formed in the autoclave are repeatedly washed in a high-speed centrifuge until a pH of approximately 9.0 is reached. Then the solid zeolite product is dried overnight at 110 °C and calcined at 550 °C for 4 hours at a heating rate of 2 °C / minute.

[0040] The properties of the nano-sized beta zeolite of Comparative Example 1 and Invention Example 2 are provided in Table 1 below. The average particle size is based on SEM measurements. The average pore diameter is determined by the surface area using the Brunauer-Emmett-Teller (BET) technique and pore volume. The XRD crystallinity is determined using CP-814E (Zeolyst International) as a reference.

[0041] Table 1: Properties of Nano-sized Beta Zeolite

[0042] Comparative Example 1 Inventive Example 2 Aluminum source Elemental aluminum <![CDATA[Al2O3]]> <![CDATA[Si:Al2 (mole)]]> 25 25 XRD crystallinity 95.0 94.8 SEM average particle size, nm 80 83 <![CDATA[BET surface area, m 2 / g]]> 596 592 Pore volume, ml / g 0.81 0.83 Average pore diameter, nm 5.44 5.61

[0043] As shown in Table 1, the zeolite prepared via the conventional synthesis method (Comparative Example 1) is similar to the zeolite prepared via the method according to the present disclosure (Invention Example 2). Thus, it is confirmed that alumina can be used as a lower-cost substitute for elemental aluminum as an aluminum source to produce nano-sized beta zeolite.

[0044] In summary, it should now be understood that various aspects of methods and systems for producing aromatics and light olefins from a mixed plastic stream are disclosed herein.

[0045] According to a first aspect of the present disclosure, a method for synthesizing nanosized beta zeolite includes: mixing alumina with tetraethylammonium hydroxide (TEAOH) to form an aluminum solution; mixing silica, additional TEAOH, and water to form a silica slurry; adding the aluminum solution to the silica slurry and mixing for at least 1 hour to form an aluminosilicate gel, wherein the aluminosilicate gel has the following molar ratio composition: SiO2 from 20 to 500: TEAOH from 8 to 300: Al2O3: H2O from 17 to 700; transferring the aluminosilicate gel to an autoclave operating at 120 °C to 160 °C at a rotational speed of 60 to 100 revolutions per minute for 2 days to 4 days to form a zeolite precursor colloid; washing the zeolite precursor colloid with water to form a washed colloid; drying the washed colloid at 80 °C to 150 °C for 6 hours to 24 hours to form a zeolite precursor; and calcining the zeolite precursor at 400 °C to 650 °C for 2 hours to 8 hours to form nanosized beta zeolite.

[0046] A second aspect includes the method described in the first aspect, wherein, based on SEM measurement, the nanosized beta zeolite has an average particle size of 10 nanometers to 100 nanometers.

[0047] A third aspect includes the method described in the first or second aspect, wherein, based on BET measurement, the nanosized beta zeolite has a surface area of 500 m 2 / g to 800 m 2 / g.

[0048] A fourth aspect includes the method described in any one of the first to third aspects, wherein the nanosized beta zeolite has a pore volume of 0.5 ml / g to 1.0 ml / g.

[0049] A fifth aspect includes the method described in any one of the first to fourth aspects, wherein the nanosized beta zeolite has an average pore diameter of 3 nm to 10 nm.

[0050] A sixth aspect includes the method described in any one of the first to fifth aspects, wherein the autoclave is quenched with cold water before washing the zeolite precursor colloid with water.

[0051] A seventh aspect includes the method described in any one of the first to sixth aspects, wherein washing the zeolite precursor colloid with water to form a washed colloid is completed in a centrifuge.

[0052] An eighth aspect includes the method described in any one of the first to seventh aspects, wherein the washed colloid has a pH of about 9.0.

[0053] A ninth aspect includes the method described in any one of the first to eighth aspects, wherein the silica is fumed silica.

[0054] The tenth aspect includes the method described in any one of the first to eighth aspects, wherein the silica is colloidal silica.

[0055] The eleventh aspect includes the method described in any one of the first to tenth aspects, wherein the autoclave operates at a rotation speed of 60 to 80 revolutions per minute at 130°C to 150°C for 2 to 4 days.

[0056] The twelfth aspect includes the method described in any one of the first to eleventh aspects, wherein the colloidal gel after washing is dried at 100°C to 110°C.

[0057] The thirteenth aspect includes the method described in any one of the first to twelfth aspects, wherein the zeolite precursor is calcined at 550°C to 600°C for 3 to 6 hours to form nano-sized β-zeolite.

[0058] The fourteenth aspect includes the method described in any one of the first to thirteenth aspects, wherein the heating rate during calcination is 2°C per minute.

[0059] The fifteenth aspect includes the method described in any one of the first to fourteenth aspects, wherein the aluminosilicate gel has the following molar ratio composition: SiO2: 20 to 500, TEAOH: 15 to 40, Al2O3, H2O: 17 to 700.

[0060] The sixteenth aspect includes the method described in any one of the first to fourteenth aspects, wherein the aluminosilicate gel has the following molar ratio composition: SiO2: 20 - 100, TEAOH: 8 - 60, Al2O3, H2O: 200 - 500.

[0061] Those skilled in the art should understand that various modifications and variations can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter. Therefore, this specification is intended to cover various modifications and variations of the described embodiments, provided that these modifications and variations are within the scope of the appended claims and their equivalents.

[0062] Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural referents.

[0063] This disclosure provides ranges throughout. It is contemplated that each discrete value encompassed by the range is also included. Additionally, it is equally contemplated that ranges formed by each discrete value encompassed by the explicitly disclosed range are also included. For the sake of brevity, this general indication is provided without explicit indication after each disclosed range. Furthermore, it should be understood that any two quantitative values assigned to a property can form a range of that property, and all combinations of ranges formed by all the stated quantitative values of a given property are contemplated in this disclosure.

[0064] As used in this disclosure and the appended claims, the words "comprising," "having," and "including," and all grammatical variations thereof, are intended to have an open, non-limiting meaning, excluding no additional elements or steps.

[0065] Throughout this specification, numerous details are set forth in order to provide a thorough understanding of the various embodiments. In other instances, well-known processes, devices, and systems may not be described in particular detail so as not to unnecessarily obscure the various embodiments, but these are available to those skilled in the art. Additionally, to avoid obscuring the various embodiments, the illustrations of the various embodiments may omit certain features or details.

Claims

1. A method for synthesizing nano-sized β-zeolite, the method comprising: Mixing alumina with tetraethylammonium hydroxide (TEAOH) to form an aluminum solution; Mixing silica, additional TEAOH, and water to form a silica slurry; Adding the aluminum solution to the silica slurry and mixing for at least 1 hour to form an aluminosilicate gel, wherein the aluminosilicate gel has the following molar ratio composition: 20 to 500 of SiO2: 8 to 300 of TEAOH: Al2O3: 17 to 700 of H2O; Transferring the aluminosilicate gel to an autoclave operating at 120 °C to 160 °C at a rotational speed of 60 to 100 revolutions per minute for 2 to 4 days to form a zeolite precursor colloid; Washing the zeolite precursor colloid with water to form a washed colloid; Drying the washed colloid at 80 °C to 150 °C for 6 to 24 hours to form a zeolite precursor; and Calcining the zeolite precursor at 400 °C to 650 °C for 2 to 8 hours to form the nano-sized β-zeolite.

2. The method according to claim 1, wherein, Based on SEM measurement, the nano-sized β-zeolite has an average particle size of 10 nanometers to 100 nanometers.

3. The method according to claim 1 or 2, wherein Based on BET measurement, the nano-sized β zeolite has a surface area of 500 m 2 / g to 800 m 2 / g.

4. The method according to any one of claims 1 to 3, wherein the nano-sized β-zeolite has a pore volume of 0.5 ml / g to 1.0 ml / g.

5. The method according to any one of claims 1 to 4, wherein the nano-sized β-zeolite has an average pore diameter of 3 nm to 10 nm.

6. The method according to any one of claims 1 to 5, wherein the autoclave is quenched with cold water before washing the zeolite precursor colloid with water.

7. The method according to any one of claims 1 to 6, wherein the washed colloid has a pH of about 9.

0.

8. The method according to any one of claims 1 to 7, wherein the silica is fumed silica.

9. The method according to any one of claims 1 to 7, wherein the silica is colloidal silica.

10. The method according to any one of claims 1 to 9, wherein the autoclave operates at 130 °C to 150 °C at a rotational speed of 60 to 80 revolutions per minute for 2 to 4 days.

11. The method according to any one of claims 1 to 10, wherein the washed colloid is dried at 100 °C to 110 °C.

12. The method according to any one of claims 1 to 11, wherein the zeolite precursor is calcined at 550 °C to 600 °C for 3 to 6 hours to form the nano-sized β-zeolite.

13. The method according to any one of claims 1 to 12, wherein the heating rate during calcination is 2 °C per minute.

14. The method according to any one of claims 1 to 13, wherein the aluminosilicate gel has the following molar ratio composition: 20 to 500 of SiO2: 15 to 40 of TEAOH: Al2O3: 17 to 700 of H2O.

15. The method according to any one of claims 1 to 13, wherein the aluminosilicate gel has the following molar ratio composition: 20 - 100 of SiO2: 8 - 60 of TEAOH: Al2O3: 200 - 500 of H2O.