Method for synthesizing mesoporous nano-sized beta zeolites

Abstract

Methods for the synthesis of mesoporous nano-sized beta zeolites are described. A method may include mixing an aqueous alkaline solution with cetyltrimethylammonium bromide (CTAB) to form a first solution; nano-sized zeolite particles having a particle size of less than or equal to 100 nm are added to the first solution to form a second solution. The nano-sized zeolite particles comprise a microporous skeleton comprising a plurality of micropores having a diameter of less than or equal to 2 nm and a BEA skeleton type. The method may also include transferring the second solution to an autoclave operating at 25 DEG C to 200 DEG C for 3 hours to 24 hours to form a colloid; drying the colloid at 100 DEG C to 200 DEG C for 8 hours to 36 hours without washing the colloid to form a zeolite precursor; and calcining the zeolite precursor at 250 DEG C to 600 DEG C for 1 to 8 hours to form a mesoporous 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 / 059,712, filed on November 29, 2022, entitled "Method for Synthesizing Mesoporous Nanoscale Beta Zeolite", the entire content of which is incorporated herein by reference. Technical field

[0003] The present disclosure generally relates to nanoscale mesoporous zeolite compositions, as well as methods of synthesizing and using these compositions, and more particularly to methods for synthesizing mesoporous nanoscale beta zeolite without an intermediate washing step. Background art

[0004] Beta zeolite is a crystalline aluminosilicate that is widely used in heavy oil conversion processes such as hydrocracking and fluid catalytic cracking processes. The feedstock for these processes is a portion of crude oil with 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 ranging from 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 traditionally requires an intermediate washing step, which reduces the yield and thus hinders the economic stability of mesoporous zeolite manufacturing. Summary of the invention

[0006] Accordingly, there has long been a need to provide a more economical solution for synthesizing mesoporous nanoscale beta zeolite. The present disclosure meets this long - standing need by generating mesoporous nanoscale beta zeolite according to a method that eliminates all intermediate washing steps during zeolite preparation. It is understood that eliminating the washing step both increases the zeolite yield and reduces the operating cost through fewer process operations.

[0007] According to an embodiment of the present disclosure, a method for synthesizing mesoporous nanosized beta zeolite includes: mixing an alkaline aqueous solution with cetyltrimethylammonium bromide (CTAB) to form a first solution; adding nanosized zeolite particles having a particle size less than or equal to 100 nm to the first solution to form a second solution, wherein the nanosized zeolite particles include a microporous framework and a BEA framework type, and the microporous framework includes a plurality of micropores having a diameter less than or equal to 2 nm; transferring the second solution to an autoclave operating at 25°C to 200°C for 3 hours to 24 hours to form a colloid; drying the colloid at 100°C to 200°C for 8 hours to 36 hours without washing the colloid to form a zeolite precursor; and calcining the zeolite precursor at 250°C to 600°C for 1 hour to 8 hours to form mesoporous nanosized beta zeolite.

[0008] Other features and advantages of the technology disclosed herein will be set forth in the detailed description that follows, and in part will be apparent to those skilled in the art from the description or recognized by practicing the technology described herein, including the detailed description that follows and the appended claims.

[0009] It should be understood that the foregoing 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 nanosized mesoporous zeolite compositions and methods for synthesizing these compositions.

[0011] The description may use the phrases "in some embodiments", "in various embodiments", "in one embodiment", or "in embodiments", which may each refer to one or more of the same or different embodiments. Additionally, 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 contents such as sulfur, nitrogen, and metals, and to convert large molecular weight hydrocarbons (complex aromatics or unsaturated hydrocarbons) into naphtha, kerosene, gasoline, diesel, or high-quality lubricating oil. The catalyst used for the hydrogenation operation has 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 catalyst. 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 an average pore diameter greater than 3 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 the zeolite catalyst affects the performance of the zeolite catalyst.

[0013] Previous methods for synthesizing mesoporous nanosized beta zeolite generated mesopores by desilication via NaOH or NH3 and hydrothermal treatment. However, such methods also require separation and washing steps after hydrothermal treatment to remove substances before calcining the zeolite. An alternative method for synthesizing mesoporous nanosized beta zeolite has been developed according to the embodiments of the present disclosure, which makes full use of NaOH or NH3 for desilication but does not require an intermediate washing step. This improved synthesis method increases the yield of the synthesized zeolite, reduces the operating cost, and enhances the economic feasibility of manufacturing mesoporous nanosized beta zeolite.

[0014] Embodiments of BEA framework type zeolites, such as beta zeolites, are generally described in this disclosure, and such zeolites can be incorporated into hydrotreating catalysts. This disclosure relates to methods for producing such zeolites and the properties and structures of the produced zeolites. In some embodiments, the hydrotreating catalyst can be used to crack aromatics in heavy oil during a pretreatment process, which can be carried out before steam cracking or other downstream processing. According to one or more embodiments, the zeolite compositions formed according to this disclosure can include relatively small particle sizes and can have mesoporosity. Such zeolite materials can be referred to throughout this disclosure as "mesoporous nanosized beta zeolites". As used throughout this disclosure, "zeolite" refers to a microporous inorganic material having regular intracrystalline cavities and molecular-sized channels. The microporous structure of zeolites (e.g., pore diameters of 0.3 nm to 1 nm) can provide a large surface area and desirable size / shape selectivity, which is advantageous in catalytic applications. The described mesoporous zeolites can include, for example, aluminosilicates, titanosilicates, or pure silicates. In one or more embodiments, the described zeolites can include micropores (present in the microstructure of the zeolite) and additionally include mesopores. As used throughout this disclosure, micropores refer to pores in the zeolite structure having a diameter less than or equal to 2 nm and greater than or equal to 0.1 nm, and mesopores refer to pores in the zeolite structure having a diameter greater than 2 nm and less than or equal to 50 nm. The currently described zeolites can be characterized as beta (i.e., having an aluminosilicate BEA framework type).

[0015] Disclosed herein are specific synthesis methods for these nanosized mesoporous zeolite compositions. According to this disclosure, a method for synthesizing mesoporous nanosized beta zeolites includes: mixing an alkaline aqueous solution with cetyltrimethylammonium bromide (CTAB) to form a first solution; and adding nanosized zeolite particles having a particle size less than or equal to 100 nm to the first solution to form a second solution, wherein the nanosized zeolite particles include a microporous framework and a BEA framework type, and the microporous framework includes a plurality of micropores having a diameter less than or equal to 2 nm; and transferring the second solution to an autoclave operating at 25 °C to 200 °C for 3 hours to 24 hours to form a colloid. Subsequently, the colloid is dried at 100 °C to 200 °C for 8 hours to 36 hours to form a zeolite precursor. It should be noted in particular that after the colloid is taken out of the autoclave, it is dried without intermediate washing. Finally, the zeolite precursor is calcined at 250 °C to 600 °C for 1 hour to 8 hours to form mesoporous nanosized beta zeolites. The synthesis method of mesoporous nanosized beta zeolites and its specific steps will be discussed in detail below.

[0016] In one or more embodiments, a first solution is formed. Specifically, an aqueous alkaline solution is mixed with cetyltrimethylammonium bromide (CTAB) to form the first solution. In one embodiment, the aqueous alkaline solution includes one or more of NaOH or NH3. According to various embodiments, the aqueous alkaline solution is a 0.1M to 1.0M NH3 solution, a 0.1M to 0.8M NH3 solution, a 0.3M to 1.0M NH3 solution, a 0.3M to 0.6M NH3 solution, or an approximately 0.5M NH3 solution. According to various embodiments, the aqueous alkaline solution is a 0.1M to 1.0M NaOH solution, a 0.1M to 0.8M NaOH solution, a 0.3M to 1.0M NaOH solution, a 0.3M to 0.6M NaOH solution, or an approximately 0.5M NaOH solution.

[0017] In various embodiments, the aqueous alkaline solution and CTAB can be mixed for 1 minute to 30 minutes, 5 minutes to 30 minutes, 5 minutes to 15 minutes, or approximately 10 minutes. It should be understood that the mixing time needs to be sufficient to completely dissolve CTAB in the aqueous alkaline solution to generate the first solution.

[0018] In one or more embodiments, nano-sized zeolite particles are added to the first solution to form a second solution. In various embodiments, the nano-sized zeolite particles can have an average particle size less than or equal to 100 nm, less than or equal to 90 nm, less than or equal to 85 nm, or less than or equal to 80 nm. Additionally, the nano-sized zeolite particles include a BEA framework type, such as beta zeolite. Further, the nano-sized zeolite particles include a microporous framework that includes a plurality of micropores having an average diameter less than or equal to 2 nm. However, it should be understood that the nano-sized zeolite particles can also include mesopores.

[0019] It should be understood that various nano-sized zeolite particles can be utilized, and the method of the present disclosure improves the mesoporosity of such nano-sized zeolite particles. In one or more embodiments, the nano-sized zeolite particles can include a surface area of 590 m 2 / g, a pore volume of 0.83 ml / g, an average pore diameter of 2.8 nm, and an average particle size of 80 nm, and the pore volume is divided into a micropore volume of 0.15 ml / g and a mesopore volume of 0.68 ml / g.

[0020] In various embodiments, before heating the second solution in an autoclave, the second solution may be mixed for 1 minute to 60 minutes, 5 minutes to 40 minutes, 10 minutes to 30 minutes, or about 20 minutes after adding the nanosized zeolite particles to the first solution. During the mixing of the second solution, the alkaline aqueous solution present in the first solution removes silicon from the zeolite structure of the nanosized zeolite particles, thereby obtaining mesoporosity. The CTAB included in the first solution can fill the voids and act as a templating agent to maintain the zeolite structure and mesoporosity during further processing.

[0021] In various embodiments, the mass ratio of CTAB in the second solution to the nanosized zeolite particles ranges from 0.1 to 1.0, 0.1 to 0.8, 0.1 to 0.5, 0.2 to 0.5, or is about 0.3. It should be understood that if too little CTAB is present, the CTAB is not sufficient to function as a stabilizer to avoid damage to the zeolite structure during desilication with the alkaline solution. Additionally, an excessive amount of CTAB brings higher costs, more CTAB is lost during the washing process, and this discharge also brings corresponding environmental problems.

[0022] In various embodiments, the ratio of the volume of the alkaline aqueous solution to the mass of the nanosized zeolite particles in the second solution ranges from 2 to 40, 5 to 40, 8 to 30, or 10 to 20. It should be understood that if this ratio is too small, the silicon removed from the zeolite framework is insufficient, resulting in a decrease in the mesoporosity brought about. On the contrary, if this ratio is too large, too much silicon may be removed, resulting in the destruction of the zeolite structure.

[0023] In one or more embodiments, the second solution is transferred to an autoclave to form a colloid. Specifically, during the treatment in the autoclave, the alkaline aqueous solution desilicates the nanosized zeolite particles in the second solution.

[0024] In various embodiments, the second solution is heated in an autoclave operating at 25°C to 200°C, 80°C to 175°C, 90°C to 150°C, 120°C to 160°C, 140°C to 160°C, or about 150°C. Additionally, in various embodiments, the second solution can be heated in the autoclave for 3 hours to 24 hours, 4 hours to 20 hours, 5 hours to 18 hours, 6 hours to 14 hours, 8 hours to 12 hours, or about 10 hours.

[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 for quenching the autoclave, which does not come into contact with the contents of the autoclave, 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. In a further embodiment, the autoclave can be allowed to cool naturally to room temperature.

[0026] In one or more embodiments, the colloid is dried to form a zeolite precursor. In various embodiments, the colloid can be dried at a high drying temperature of from 100 °C to 200 °C, 100 °C to 180 °C, 100 °C to 160 °C, 110 °C to 150 °C, 100 °C to 140 °C, 100 °C to 130 °C, 100 °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 from 6 hours to 36 hours, 10 hours to 30 hours, 12 hours to 24 hours, 6 hours to 18 hours, 8 hours to 14 hours, or 8 hours to 12 hours. Alternatively, the period of drying at the high drying temperature can be considered to be overnight.

[0027] It should be noted specifically that, according to the embodiments of the present disclosure, the colloid formed by heating in the autoclave is not washed. However, in one or more embodiments, the colloid is treated in a centrifuge to remove excess water before drying the colloid.

[0028] In one or more embodiments, the zeolite precursor is calcined to form mesoporous nanosized β-zeolite. In various embodiments, the zeolite precursor can be calcined at a high calcination temperature of from 250 °C to 600 °C, 300 °C to 600 °C, 400 °C to 600 °C, 450 °C to 600 °C, 500 °C to 600 °C, 550 °C to 600 °C, or approximately 550 °C. Additionally, in various embodiments, the zeolite precursor can be calcined at the high calcination temperature for a period of from 1 hour 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 from 2 °C to 4 °C per minute.

[0029] The properties of mesoporous nanosized beta zeolite include an average particle size of 10 nm to 100 nm. This average particle size is based on SEM measurements. In some embodiments, the mesoporous 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 mesoporous nanosized beta zeolite can be from 500 square meters per gram (m 2 / g) to 800 m 2 / g. In some embodiments, the surface area of the mesoporous nanosized beta zeolite can be from 500 m 2 / g to 700 m 2 / g, from 500 m 2 / g to 650 m 2 / g, from 550 m 2 / g to 800 m 2 / g, from 550 m 2 / g to 700 m 2 / g, or from 600 m 2 / g to 650 m 2 / g. This average particle size is based on Brunauer - Emmett - Teller (BET) measurements. The pore volume of the nanosized beta zeolite can be from 1.0 milliliter per gram (ml / g) to 2.0 ml / g. In some embodiments, the pore volume of the mesoporous nanosized beta zeolite can be from 1.0 ml / g to 1.8 ml / g, 1.0 ml / g to 1.6 ml / g, 1.0 ml / g to 1.5 ml / g, or 1.0 ml / g to 1.4 ml / g. The average pore diameter of the mesoporous nanosized beta zeolite can be greater than 3 nm, for example, in the range of 3 nm to 50 nm. In some embodiments, the average pore diameter of the mesoporous nanosized beta zeolite can be 2 nm to 40 nm, 5 nm to 30 nm, 5 nm to 50 nm, 5 nm to 30 nm. Alternatively, in various embodiments, the average pore diameter of the mesoporous nanosized beta zeolite can be greater than 4 nm, greater than 5 nm, greater than 6 nm, or greater than 7 nm. The pore diameter can be determined from the surface area and pore volume.

[0030] Most of the pore volume of the mesoporous nanosized beta zeolite is mesopore volume. In various embodiments, at least 60 volume %, at least 65 volume %, at least 70 volume %, at least 75 volume %, or at least 80 volume % of the pore volume of the mesoporous nanosized beta zeolite is mesopore.

[0031] Embodiments of the presently disclosed methods for synthesizing mesoporous nanosized beta zeolite do not require a step of washing the colloid to remove alkali metal cations. Elimination of such a washing step increases the yield and reduces the operating cost. Specifically, since one or more steps in the conventional zeolite process are eliminated, the operating cost is reduced and the yield of the synthesized zeolite is increased, which enhances the manufacturing economy of the mesoporous nanosized beta zeolite.

[0032] Examples

[0033] The method for synthesizing mesoporous nanosized beta 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.

[0034] Four samples of mesoporous nanosized beta zeolite were prepared and the synthesis via the conventional method was compared with the synthesis according to the method of the present disclosure. Comparative Example 1 and Comparative Example 3 provide the synthesis of mesoporous nanosized beta zeolite using the conventional method, including at least one washing step. Inventive Example 2 and Inventive Example 4 provide the synthesis of mesoporous nanosized beta zeolite, omitting all washing steps. It should be noted that Inventive Example 2 includes a simple separation via a centrifuge, but it is expressly provided that the preparation method omits all washing steps.

[0035] Comparative Example 1

[0036] For Comparative Example 1, mesoporous nanosized beta zeolite was prepared, including a washing step. In a first container, 2.1 ml of concentrated ammonia water (15 M NH3·H2O) from Sigma Aldrich was added to 60.4 g of H2O. The water was purified water free of impurities such as Mg, Na, Ca, Cl, etc. It should be noted that it is not desirable to introduce impurities, especially Mg, Ca, Na cations, because these impurities may deposit on the zeolite to neutralize the acidic sites, reduce the zeolite acidity, and possibly reduce the zeolite stability. It should be noted that the concentrated ammonia water and water formed 62.5 g of 5 M NH3·H2O. To obtain 62.5 g of 5 M NH3·H2O, 1.12 g of CTAB was added and the resulting first solution was stirred for 10 minutes. After mixing, 4.56 g of nano beta zeolite was added to the first solution and stirred for 20 minutes to form a second solution. The nano-sized beta zeolite was the nano-sized beta zeolite disclosed by L. Ding et al. in Microporous and Mesoporous Materials 94 (2006) 1-8. Subsequently, the second solution was transferred to a PTFE-lined stainless steel autoclave, sealed and heated. The autoclave was operated at 100 °C for ten hours and then quenched with water. Then the colloid formed in the autoclave was washed three times in a high-speed centrifuge. 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.

[0037] Inventive Example 2

[0038] According to an embodiment of the present disclosure, for Inventive Example 2, mesoporous nanosized β-zeolite was prepared without including a washing step. In a first container, 4.2 ml of concentrated ammonia water (15 M NH₃·H₂O) from Sigma Aldrich was added to 120.9 grams of H₂O. The water was the same purified water used in Comparative Example 1 and was purified using reverse osmosis (RO) water purification technology. It should be noted that the concentrated ammonia water and water formed 125 grams of 5 M NH₃·H₂O. To obtain 125 grams of 5 M NH₃·H₂O, 2.3 grams of CTAB was added and the resulting first solution was stirred for 10 minutes. After mixing, 9.12 grams of nanosized β-zeolite was added to the first solution and stirred for 20 minutes to form a second solution. It should be noted that the nanosized β-zeolite was the same as the nanosized β-zeolite used in Comparative Example 1. Subsequently, the second solution was transferred to a PTFE-lined stainless steel autoclave, sealed and heated. The autoclave was operated at 100 °C for ten hours and then quenched with water. Then the colloid formed in the autoclave was separated from the excess water once via a centrifuge. However, it should be specifically noted that the colloid was not washed or rinsed. 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.

[0039] The synthesis parameters of Comparative Example 1 and Inventive Example 2 are provided in Table 1 below. It should be noted that the zeolite contains approximately 17.8% water. Therefore, when calculating the ratio of the alkaline solution to the zeolite, if the zeolite is on a dry basis, its moisture content must be considered. Specifically, 4.56 grams of zeolite includes 3.75 grams of zeolite on a dry basis, so the volume-weight ratio of the alkaline solution to the zeolite is 16.67. Similarly, the ratio of CTAB to the zeolite is also calculated based on the dry basis of the zeolite.

[0040] Table 1: Synthesis parameters of Comparative Example 1 and Inventive Example 2

[0041]

[0042] Comparative Example 3 and Inventive Example 4

[0043] Except that the autoclave was operated at 150 °C, additional colloids were formed in the same manner as in Invention Example 2 and divided into two sub-samples for further processing. For Comparative Example 3, one sub-sample was washed three times in a high-speed centrifuge, and the excess water was removed after each centrifugation cycle. The solid zeolite product was then dried overnight at 110 °C and calcined at 550 °C for 4 hours at a heating rate of 2 °C / minute to form the mesoporous nano-sized β-zeolite of Comparative Example 3. In contrast, for Invention Example 4, the remaining sub-sample was dried overnight at 110 °C without an intermediate washing and centrifugation process. The dried sample was then calcined at 550 °C for 4 hours at a heating rate of 2 °C / minute to form the mesoporous nano-sized β-zeolite of Invention Example 4.

[0044] The nano-β-zeolites used in Comparative Example 1, Comparative Example 3, Invention Example 2, and Invention Example 4 respectively had a surface area of 590 m 2 / g, a pore volume of 0.83 ml / g, an average pore diameter of 2.8 nm, and an average particle size of 80 nm. The pore volume was divided into a micropore volume of 0.15 ml / g and a mesopore volume of 0.68 ml / g.

[0045] The synthesis parameters of the mesoporous nano-sized β-zeolites of Comparative Example 3 and Invention Example 4 are provided in Table 2 below.

[0046] Table 2: Synthesis Parameters of Comparative Example 3 and Invention Example 4

[0047]

[0048] The properties of the mesoporous nano-sized β-zeolites of Comparative Example 1, Invention Example 2, Comparative Example 3, and Invention Example 4 are provided in Table 3 below. The average particle size was based on SEM measurements. The average pore diameter was determined from the surface area using the Brunauer-Emmett-Teller (BET) technique and the pore volume. The XRD crystallinity was determined using CP-814E (Zeolyst International) as a reference.

[0049] Table 3: Properties of Mesoporous Nano-Sized β-Zeolites

[0050]

[0051] As shown in Table 3, the zeolites prepared via the conventional synthesis method including a washing step (Comparative Example 1 and Comparative Example 3) are similar to the zeolites prepared via the method according to the present disclosure without a washing step (Inventive Example 2 and Inventive Example 4). Specifically, by comparing Comparative Example 1 with Inventive Example 2, it can be seen that even if the washing step is omitted, the desired zeolite product can still be obtained. Similarly, by comparing Comparative Example 3 with Inventive Example 4, it can be seen that even if the washing step is omitted, the desired zeolite product can still be obtained. Therefore, it is confirmed that according to the method of the present disclosure, the conventional washing step existing in the zeolite preparation process can be omitted to produce mesoporous nanosized β-zeolite.

[0052] In summary, it should now be understood that various aspects of a method and system for producing aromatics and light olefins from a mixed plastic stream are disclosed herein.

[0053] According to a first aspect of the present disclosure, a method for synthesizing mesoporous nanosized β-zeolite includes: mixing an alkaline aqueous solution with cetyltrimethylammonium bromide (CTAB) to form a first solution; adding nanosized zeolite particles having a particle size less than or equal to 100 nm to the first solution to form a second solution, wherein the nanosized zeolite particles include a microporous framework and a BEA framework type, and the microporous framework includes a plurality of micropores having a diameter less than or equal to 2 nm; transferring the second solution to an autoclave operating at 25 °C to 200 °C for 3 hours to 24 hours to form a colloid; drying the colloid at 100 °C to 200 °C for 8 hours to 36 hours without washing the colloid to form a zeolite precursor; and calcining the zeolite precursor at 250 °C to 600 °C for 1 hour to 8 hours to form mesoporous nanosized β-zeolite.

[0054] A second aspect includes the method according to the first aspect, wherein, based on SEM measurement, the mesoporous nanosized β-zeolite includes an average particle size of 10 nanometers to 100 nanometers.

[0055] A third aspect includes the method according to the first aspect or the second aspect, wherein, based on BET measurement, the mesoporous nanosized β-zeolite includes 500 m 2 / g to 800 m 2 / g of specific surface area.

[0056] A fourth aspect includes the method according to any one of the first aspect to the third aspect, wherein the mesoporous nanosized β-zeolite includes a pore volume of 1.0 ml / g to 2.0 ml / g.

[0057] A fifth aspect includes the method according to any one of the first aspect to the fourth aspect, wherein at least 60 volume % of the pore volume is mesopores.

[0058] The sixth aspect includes the method according to any one of the first to fifth aspects, wherein the mesoporous nano-sized β zeolite has an average pore diameter greater than 3 nm.

[0059] The seventh aspect includes the method according to any one of the first to sixth aspects, wherein the alkaline aqueous solution includes one or more of NaOH or NH3.

[0060] The eighth aspect includes the method according to any one of the first to seventh aspects, wherein the alkaline aqueous solution is a 0.1 M to 1.0 M NH3 solution or NaOH solution.

[0061] The ninth aspect includes the method according to any one of the first to eighth aspects, wherein the alkaline aqueous solution is a 0.5 M NH3 solution.

[0062] The tenth aspect includes the method according to any one of the first to ninth aspects, wherein in the second solution, the mass ratio of CTAB to the nano-sized zeolite particles is in the range of 0.1 to 1.0.

[0063] The eleventh aspect includes the method according to any one of the first to tenth aspects, wherein the ratio of the volume of the alkaline aqueous solution to the mass of the nano-sized zeolite particles in the second solution is in the range of 2 to 40.

[0064] The twelfth aspect includes the method according to any one of the first to eleventh aspects, wherein the first solution is mixed for 1 minute to 30 minutes before adding the nano-sized zeolite particles to form the second solution.

[0065] The thirteenth aspect includes the method according to any one of the first to twelfth aspects, wherein the second solution is mixed for 1 minute to 60 minutes before heating the second solution in an autoclave.

[0066] The fourteenth aspect includes the method according to any one of the first to thirteenth aspects, wherein the autoclave operates at 90 °C to 150 °C for 8 hours to 12 hours.

[0067] The fifteenth aspect includes the method according to any one of the first to fourteenth aspects, wherein the colloid is dried at 100 °C to 120 °C for 8 hours to 12 hours.

[0068] The sixteenth aspect includes the method according to any one of the first to fifteenth aspects, wherein the zeolite precursor is calcined at 550 °C to 600 °C for 3 hours to 6 hours to form the mesoporous nano-sized β zeolite.

[0069] The seventeenth aspect includes the method according to any one of the first to sixteenth aspects, wherein the heating rate during calcination is 2 °C to 4 °C per minute.

[0070] The eighteenth aspect includes the method according to any one of the first aspect to the seventeenth aspect, wherein the colloid is processed in a centrifuge to remove excess water before drying the colloid.

[0071] 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, as long as these modifications and variations are within the scope of the appended claims and their equivalents.

[0072] Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural referents.

[0073] Throughout this disclosure, ranges are provided. 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 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 constitute a range of that property, and all combinations of ranges formed by all the described quantitative values of a given property are contemplated in this disclosure.

[0074] As used in this disclosure and the appended claims, the words "comprising", "having", and "including" and all their grammatical variants are intended to have an open, non - restrictive meaning, excluding no additional elements or steps.

[0075] Throughout the description of 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, in order not to obscure the various embodiments, the illustrations of the various embodiments may omit certain features or details.

Claims

1. A method for synthesizing mesoporous nanosized β-zeolite, the method comprising: Mixing an alkaline aqueous solution with cetyltrimethylammonium bromide (CTAB) to form a first solution; Adding nanosized zeolite particles having a particle size less than or equal to 100 nm to the first solution to form a second solution, wherein the nanosized zeolite particles comprise a microporous framework and a BEA framework type, and the microporous framework comprises a plurality of micropores having a diameter less than or equal to 2 nm; Transferring the second solution to an autoclave operating at 25°C to 200°C for 3 hours to 24 hours to form a colloid; Drying the colloid at 100°C to 200°C for 8 hours to 36 hours without washing the colloid to form a zeolite precursor; And Calcining the zeolite precursor at 250°C to 600°C for 1 hour to 8 hours to form the mesoporous nanosized β-zeolite.

2. The method according to claim 1, wherein Based on SEM measurement, the mesoporous nanosized β-zeolite comprises 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 mesoporous nanosized 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 mesoporous nanosized β-zeolite comprises a pore volume of 1.0 ml / g to 2.0 ml / g.

5. The method according to any one of claims 1 to 4, wherein at least 60 vol% of the pore volume is mesopores.

6. The method according to any one of claims 1 to 5, wherein the mesoporous nanosized β-zeolite comprises an average pore diameter greater than 3 nm.

7. The method according to any one of claims 1 to 6, wherein the alkaline aqueous solution comprises one or more of NaOH or NH3.

8. The method according to any one of claims 1 to 7, wherein the alkaline aqueous solution is a 0.1 M to 1.0 M NH3 solution or NaOH solution.

9. The method according to any one of claims 1 to 8, wherein the alkaline aqueous solution is a 0.5 M NH3 solution.

10. The method according to any one of claims 1 to 9, wherein in the second solution, the mass ratio of CTAB to the nanosized zeolite particles is in the range of 0.1 to 1.

0.

11. The method according to any one of claims 1 to 10, wherein the ratio of the volume of the alkaline aqueous solution to the mass of the nanosized zeolite particles in the second solution is in the range of 2 to 40.

12. The method according to any one of claims 1 to 11, wherein before adding the nanosized zeolite particles to form the second solution, the first solution is mixed for 1 minute to 30 minutes.

13. The method according to any one of claims 1 to 12, wherein before heating the second solution in the autoclave, the second solution is mixed for 1 minute to 60 minutes.

14. The method according to any one of claims 1 to 13, wherein the heating rate during calcination is 2°C to 4°C per minute.

15. The method according to any one of claims 1 to 14, wherein before drying the colloid, the colloid is treated in a centrifuge to remove excess water.

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