Method for synthesizing mesoporous nano-sized ultra-stable Y zeolite
Through one-pot synthesis method and ammonium hexafluorosilicate treatment of nano-Y zeolite, the problems of complexity and cost of traditional methods are solved, and the efficient synthesis of mesoporous nano-size ultra-stable Y zeolite is achieved, which improves the mass transfer performance and economicality of the catalyst.
Patent Information
- Application Number
- CN202380081845.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-29
- Filing Date
- 2023-11-16
- Publication Date
- 2025-07-04
AI Technical Summary
The prior art is difficult to economically synthesize mesoporous nano-size ultra-stable Y zeolites. The traditional methods are complex and costly, and cannot effectively enhance the mass transfer performance of the catalyst.
The nano-sized Y zeolite was treated with ammonium hexafluorosilicate, and the mesoporous nano-sized ultra-stable Y zeolite was formed by controlling the hydrogel composition and autoclave treatment, combined with water washing and calcining steps.
The total surface area and mesoporous volume of the catalyst are increased, the synthesis cost is reduced, and the performance and economic feasibility of the catalyst are enhanced.
Smart Images
Figure BDA0005421806900000091
Abstract
Description
[0001] Cross - reference to related applications
[0002] This application claims priority to U.S. Patent Application Serial No. 18 / 059,728, filed on November 29, 2022, titled "Method for Synthesizing Mesoporous Nanoscale Ultrastable Y 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 uses of these compositions, and more particularly to a method for synthesizing mesoporous nanoscale ultrastable Y zeolite, including treating nanocrystalline Y zeolite directly with ammonium hexafluorosilicate. Background art
[0004] Y - type zeolites are crystalline aluminosilicates that are widely used in heavy oil conversion processes such as hydrocracking and fluid catalytic cracking processes. The feedstocks for these processes are 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 greater. 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. And microporous materials exhibit a pore size distribution in the range of 0.5 nm to 2 nm. Conventional Y - type zeolites have pore sizes less than 2 nm, which do not allow large molecules to diffuse in and react at the active sites located inside the zeolite. Increasing the pore size and decreasing the zeolite particle size are two effective ways to enhance mass transfer and thus significantly improve catalyst performance.
[0005] Ultrastable Y zeolites have been produced, but their synthesis has traditionally been based on micron - sized Y zeolites rather than nanoscale Y zeolites, and on sequential dealumination and desilication, which require additional steps and processes and hinder the economic viability of mesoporous zeolite manufacture. Summary of the invention
[0006] Accordingly, there has long been a need to provide more economical schemes for synthesizing mesoporous ultrastable Y zeolites. In addition, there has long been a need to provide a scheme for synthesizing mesoporous nanoscale ultrastable Y zeolites to take advantage of the enhanced properties brought about by the reduced particle size. The present disclosure addresses this long - standing need by generating mesoporous nanoscale ultrastable Y zeolites according to a method that utilizes nanoscale Y zeolites and a one - pot synthetic post - treatment with ammonium hexafluorosilicate.
[0007] According to one embodiment of the present disclosure, a method for synthesizing mesoporous nanosized ultrastable Y zeolite includes mixing sodium hydroxide and water to form an aqueous NaOH solution; adding sodium aluminate and colloidal silica to the aqueous NaOH solution and mixing to form a hydrogel, wherein the hydrogel has the following molar ratio composition: 8 to 12 of Na2O:Al2O3:14 of SiO2:200 to 400 of H2O; transferring the hydrogel to an autoclave operating at 50 °C to 70 °C for 10 hours to 20 hours; further operating the autoclave at 80 °C to 120 °C for 10 hours to 20 hours to form a zeolite precursor; and filtering and washing the zeolite precursor with water until the pH reaches 8 to 9 to form nanosized Y zeolite. The method further includes combining the nanosized Y zeolite with 30 mL to 1000 mL of water per gram of nanosized Y zeolite on a dry basis to form a nanosized Y zeolite slurry mixture, and heating the nanosized Y zeolite slurry mixture to 70 °C to 100 °C; adding an aqueous solution of ammonium hexafluorosilicate of 0.1 M to 2.0 M to the nanosized Y zeolite slurry mixture within 1 hour to 2 hours to form a dealumination solution; maintaining the dealumination solution at 70 °C to 100 °C for an additional 1 hour to 8 hours; filtering and washing the dealumination solution with water to form an ultrastable Y zeolite precursor; drying the ultrastable Y zeolite precursor at 80 °C to 150 °C for 6 hours to 24 hours to form a dried zeolite precursor; and calcining the dried zeolite precursor at 250 °C to 600 °C for 1 hour to 8 hours to form nanosized ultrastable Y zeolite.
[0008] Other features and advantages of the techniques disclosed herein will be set forth in the detailed description that follows, and in part will be apparent to those of ordinary skill in the art upon examination of the following or upon practice of the techniques described herein, including the detailed description which follows and the 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 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 ultrastable Y 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 prevent large molecules in the heavy oil fraction from diffusing into the active sites located inside the zeolite, thus having a negative impact on the performance of the catalyst. 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 a mesoporous ultrastable Y zeolite composition having an average pore diameter greater than 4 nm and a particle size less than 200 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 ultrastable Y zeolite catalyst affects the performance of the ultrastable Y zeolite catalyst.
[0013] Previous methods for synthesizing mesoporous ultrastable Y zeolite have mainly focused on generating micron-sized Y zeolite. For the purposes of this disclosure, micron-sized Y zeolite is considered to be Y zeolite having a particle size greater than 500 nanometers (nm). In addition, post-synthesis or "top-down" modification of Y zeolite, such as steaming and acid dealumination or chemical dealumination techniques, has been used to improve the hydrothermal stability of Y zeolite to prepare USY (ultrastable Y) zeolite. There have also been attempts to combine framework desilication using known techniques with subsequent dealumination with ammonium hexafluorosilicate (AHFS) or steaming to generate USY zeolite with defect-guided mesoporosity. However, this sequential desilication-dealumination treatment is both time-consuming and increases the complexity and cost of the synthesis process. An alternative method for synthesizing mesoporous nanosized ultrastable Y zeolite has been developed according to an embodiment of the present disclosure, which uses a one-pot synthesis method and post-synthesis modification of nanosized Y zeolite with ammonium hexafluorosilicate. This upgrading synthesis method increases the total surface area, external surface area, and mesopore volume, reduces the operating cost, and enhances the economic feasibility of manufacturing mesoporous nanosized ultrastable Y zeolite.
[0014] Embodiments of Y-type zeolites that can be incorporated into hydrotreating catalysts are generally described in this disclosure. 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 that can be carried out prior to 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 ultrastable Y 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 the zeolite (e.g., pore diameters of 0.3 nm to 1 nm) can provide a large surface area and the desired size / shape selectivity, which can be beneficial for catalysis. 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 zeolites currently described can be characterized as Y-type (i.e., having an aluminosilicate FAU 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 ultrastable Y zeolites includes mixing sodium hydroxide and water to form an aqueous NaOH solution and adding sodium aluminate and colloidal silica to the aqueous NaOH solution and mixing to form a hydrogel. Transfer the hydrogel to an autoclave operating at 50 °C to 70 °C for 10 hours to 20 hours, and then at 80 °C to 120 °C for 10 hours to 20 hours to form a zeolite precursor. Filter and wash the zeolite precursor until the pH reaches 8 to 9 to form nanosized Y zeolites. Combine the nanosized Y zeolites with 30 mL to 1000 mL of water per gram of nanosized Y zeolites on a dry basis to form a nanosized Y zeolite slurry mixture, and then heat the nanosized Y zeolite slurry mixture to 70 °C to 100 °C. Add an aqueous solution of ammonium hexafluorosilicate at 0.1 M to 2.0 M to the nanosized Y zeolite slurry mixture over 1 hour to 2 hours to form a dealumination solution. Hold the dealumination solution at 70 °C to 100 °C for an additional 1 hour to 8 hours, then filter and wash the dealumination solution with water to form an ultrastable Y zeolite precursor. Finally, dry the ultrastable Y zeolite precursor at 80 °C to 150 °C for 6 hours to 24 hours to form a dried zeolite precursor, and calcine the dried zeolite precursor at 250 °C to 600 °C for 1 hour to 8 hours to form nanosized ultrastable Y zeolites. The method for synthesizing mesoporous nanosized ultrastable Y zeolites and each specific step are discussed in further detail below.
[0016] In one or more embodiments, an aqueous NaOH solution is formed. Specifically, sodium hydroxide and water are mixed to form an aqueous NaOH solution. According to various embodiments, sodium hydroxide and water are mixed in a weight ratio of 1:1 to 1:10, 1:2 to 1:10, 1:3 to 1:8, 1:4 to 1:8, 1:5 to 1:7, or 1:5 to 1:6. Sodium hydroxide and water are mixed until the sodium hydroxide is completely dissolved to form an aqueous NaOH solution.
[0017] In one or more embodiments, sodium aluminate and colloidal silica are added to the aqueous NaOH solution and mixed to form a hydrogel. In various embodiments, sodium aluminate, colloidal silica, and the aqueous NaOH solution may be mixed for at least 1 hour, at least 5 hours, at least 10 hours, at least 15 hours, or 15 hours to 25 hours. In one or more embodiments, the mixing of sodium aluminate, colloidal silica, and the aqueous NaOH solution can be completed at 25 °C to 40 °C. It is understood that the mixing time must be sufficient to convert sodium aluminate, colloidal silica, and the aqueous NaOH solution into a hydrogel. It should be noted that after crystallization, silicon from colloidal silica and aluminum from sodium aluminate form a zeolite framework, and sodium is used as a balancing atom on the zeolite.
[0018] In one or more embodiments, the aqueous NaOH solution, sodium aluminate, and colloidal silica are provided in appropriate volumes or weights such that the hydrogel has the following molar ratio composition: 8 to 12 of Na2O:Al2O3:14 of SiO2:200 to 400 of H2O. Specifically, when the aqueous NaOH solution, sodium aluminate, and colloidal silica are combined to form a hydrogel, the relative proportions of the components required to form the desired molar ratio can be understood. In a further embodiment, the hydrogel can have the following molar ratio composition: 5 to 15 of Na2O:Al2O3:7 to 20 of SiO2:200 to 400 of H2O.
[0019] In various embodiments, the colloidal silica can be provided as 30 weight percent (wt.%) to 50 wt.%, 30 wt.% to 45 wt.%, 35 wt.% to 50 wt.%, 35 wt.% to 45 wt.%, or about 40 wt.% of colloidal silica.
[0020] In one or more embodiments, the hydrogel is transferred to an autoclave, and the hydrogel crystallizes in the autoclave to form a zeolite precursor. Inside the autoclave, silica and aluminum substances form nuclei as basic units, and then more silica and aluminum aggregate on the basic units to form zeolite units. Subsequently, the zeolite units grow into large particles until all the silica and aluminum substances are consumed.
[0021] In various embodiments, the hydrogel is heated in an autoclave operating at a first temperature of 50°C to 70°C, 50°C to 65°C, 55°C to 70°C, 55°C to 65°C, or about 60°C. After heating at the first temperature, the temperature in the autoclave can be increased to a second temperature of 80°C to 120°C, 90°C to 120°C, 80°C to 110°C, 90°C to 110°C, or about 100°C. Additionally, in various embodiments, the hydrogel can be heated in the autoclave at the first temperature for 10 hours to 20 hours, 10 hours to 18 hours, 10 hours to 16 hours, 10 hours to 14 hours, or about 12 hours. Similarly, in various embodiments, the hydrogel can be heated in the autoclave at the second temperature for 10 hours to 20 hours, 10 hours to 18 hours, 10 hours to 16 hours, 10 hours to 14 hours, or about 12 hours. For example, the autoclave can initially operate at 50°C to 70°C for 10 hours to 16 hours and then at 90°C to 110°C for an additional 10 hours to 16 hours to form a zeolite precursor. In one or more embodiments, the autoclave remains stationary in the oven without rotating.
[0022] In one or more embodiments, the zeolite precursor formed by heating and crystallizing the hydrogel in the autoclave is filtered and washed with water to form nanosized Y zeolite. The water used to wash the zeolite precursor colloid is preferably deionized water to avoid side reactions or contamination of the resulting nanosized Y zeolite. Filtering and washing the zeolite precursor removes any uncrystallized reactants or other unwanted reaction products from the desired product.
[0023] In one or more embodiments, washing the zeolite precursor with water to form nanosized Y zeolite includes separating the solid product from the autoclave from any liquid product formed in the autoclave using a centrifuge. The solid product is then mixed with water to wash the solid product. Subsequently, the resulting solution is separated using a centrifuge. In various embodiments, the washing and separation can be repeated 1, 2, 3, 4, or 5 times in total. Alternatively, the washing and separation can be repeated until the resulting solution has a pH less than 9.0 or a pH in the range of 8.0 to 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 tube, which represents the resulting solution having a pH less than 9.0.
[0024] In one or more embodiments, nanosized Y zeolite is combined with water to form a nanosized Y zeolite slurry mixture. In various embodiments, the nanosized Y zeolite can be combined with 30 milliliters (ml) to 1000 ml, 100 ml to 800 ml, 100 ml to 600 ml, 100 ml to 500 ml, 100 ml to 400 ml, 100 ml to 300 ml, or 100 ml to 200 ml of water per gram of nanosized Y zeolite on a dry basis to form a nanosized Y zeolite slurry mixture. Subsequently, in various embodiments, the nanosized Y zeolite slurry mixture is heated to 70 °C to 100 °C, 75 °C to 100 °C, 70 °C to 95 °C, 80 °C to 95 °C, or approximately 90 °C with stirring. During the AHFS treatment, heating can accelerate the removal of aluminum from the zeolite framework, and at the same time, the silicon in the AHFS can backfill the voids left after the removal of aluminum. If the temperature is not high enough, the reaction rate may be unacceptably slow and difficult to meet practical applications.
[0025] In one or more embodiments, ammonium hexafluorosilicate (AHFS) is added to the nanosized Y zeolite slurry mixture to remove aluminum from the nanosized Y zeolite and form a dealuminated solution. Specifically, in various embodiments, an aqueous solution of AHFS at 0.1 M to 2.0 M, 0.1 M to 1.0 M, 0.2 M to 0.8 M, or 0.4 M to 0.5 M is added to the nanosized Y zeolite slurry mixture. In one or more embodiments, the weight ratio of ammonium hexafluorosilicate forming the dealuminated solution to the nanosized Y zeolite on a dry basis is in the range of 0.1 to 1.0.
[0026] In one or more embodiments, AHFS is added to the nanosized Y zeolite slurry mixture over 1 hour to 2 hours to form a dealuminated solution. The addition of AHFS can be considered to be carried out drop by drop. When adding AHFS on an industrial scale, a liquid pump with precise flow control is used.
[0027] In one or more embodiments, during the addition of AHFS to form a dealuminated solution, the nanosized Y zeolite slurry mixture is maintained at 70 °C to 100 °C. In various further embodiments, during the addition of AHFS to form a dealuminated solution, the nanosized Y zeolite slurry mixture can be maintained at 75 °C to 100 °C, 80 °C to 100 °C, 80 °C to 95 °C, 80 °C to 90 °C, or approximately 90 °C.
[0028] In one or more embodiments, the dealumination solution is maintained at 70 °C to 100 °C for an additional 1 hour to 8 hours. In various further embodiments, the dealumination solution is maintained at 70 °C to 95 °C, 80 °C to 100 °C, 85 °C to 95 °C, or 90 °C to 95 °C for an additional 1 hour to 6 hours, 1 hour to 4 hours, 1 hour to 3 hours, or approximately 2 hours. For example, in one or more embodiments, an aqueous solution of ammonium hexafluorosilicate at 0.1 M to 2.0 M can be added to the nanosized Y zeolite slurry mixture over 1 hour to 2 hours while maintaining the nanosized Y zeolite slurry mixture at 80 °C to 90 °C to form the dealumination solution, and the dealumination solution can be maintained at 90 °C to 95 °C for an additional 1 hour to 8 hours. Additionally, in various embodiments, the dealumination solution can be stirred while maintaining the high temperature.
[0029] In one or more embodiments, the dealumination solution is filtered and the collected product is washed with water to form a ultrastable Y zeolite precursor. Filtering and washing the dealumination solution includes separating the solid product from any liquid product in the dealumination solution using a centrifuge or other filtering scheme. The solid product is then mixed with water to wash the solid product. The resulting solution is then separated using a centrifuge. In various embodiments, the washing and separation can be repeated a total of 1, 2, 3, 4, or 5 times.
[0030] In one or more embodiments, the wet filter cake comprising the ultrastable Y zeolite precursor is dried to form a dried zeolite precursor. In various embodiments, the ultrastable Y zeolite precursor can be dried at a high drying temperature of 80 °C to 150 °C, 90 °C to 140 °C, 90 °C to 130 °C, 90 °C to 120 °C, 95 °C to 120 °C, 100 °C to 120 °C, 100 °C to 115 °C, or 100 °C to 110 °C. Additionally, in various embodiments, the ultrastable Y zeolite precursor can be dried for a period of 6 hours to 24 hours, 8 hours to 18 hours, 10 hours to 18 hours, 6 hours to 18 hours, 8 hours to 14 hours, or 8 hours to 12 hours at the high drying temperature. Alternatively, the period of drying at the high drying temperature can be considered overnight.
[0031] In one or more embodiments, the zeolite precursor is calcined after drying to form nanosized ultrastable Y zeolite. In various embodiments, the dried zeolite precursor can be calcined at a high calcination temperature of 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 about 550 °C. Additionally, in various embodiments, the dried zeolite precursor can be calcined for a period of 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 about 4 hours at the high calcination temperature. In one or more embodiments, the heating rate during calcination is 1 °C to 3 °C per minute.
[0032] The properties of the nanosized ultrastable Y zeolite include an average particle size of 100 nm to 200 nm. The average particle size is based on SEM measurement. In some embodiments, the mesoporous nanosized ultrastable Y zeolite has a particle size of 100 nm to 180 nm, 100 nm to 160 nm, 100 nm to 140 nm, 100 nm to 130 nm, or 110 nm to 130 nm. The surface area of the nanosized ultrastable Y zeolite can be greater than 600 m 2 / g. In some embodiments, the surface area of the nanosized ultrastable Y zeolite can be 600 m 2 / g to 800 m 2 / g, 600 m 2 / g to 760 m 2 / g, 600 m 2 / g to 700 m 2 / g, or 600 m 2 / g to 650 m 2 / g. The average particle size is measured based on the Brunauer - Emmett - Teller (BET) technique. The pore volume of the nanosized ultrastable Y zeolite can be 0.6 milliliters per gram (ml / g) to 0.8 ml / g. In some embodiments, the pore volume of the nanosized ultrastable Y zeolite can be 0.65 ml / g to 0.8 ml / g, 0.7 ml / g to 0.8 ml / g, 0.6 ml / g to 0.75 ml / g, or 0.65 ml / g to 0.75 ml / g. The average pore diameter of the nanosized ultrastable Y zeolite can be 4 nm to 6 nm. In some embodiments, the average pore diameter of the nanosized ultrastable Y zeolite can be 4 nm to 5.5 nm, 4 nm to 5 nm, or 4.25 nm to 4.75 nm. Alternatively, in one or more embodiments, the average pore diameter of the nanosized ultrastable Y zeolite can be greater than 4 nm. The pore diameter can be determined by the surface area and pore volume.
[0033] In various embodiments, the mesoporous nano-sized ultrastable Y zeolite comprises a mesopore volume of at least 0.3 ml / g, at least 0.35 ml / g, or at least 0.4 ml / g. In one or more embodiments, the majority of the pore volume of the mesoporous nano-sized ultrastable Y zeolite is the mesopore volume. In various embodiments, at least 50 vol%, at least 54 vol%, at least 56 vol%, or at least 58 vol% of the pore volume of the nano-sized ultrastable Y zeolite is mesoporous.
[0034] Examples
[0035] The method for synthesizing the mesoporous nano-sized ultrastable Y 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.
[0036] Two samples of mesoporous Y zeolite were prepared to compare the synthesis using micro-sized Y zeolite with the synthesis using nano-sized Y zeolite according to the method of the present disclosure. Comparative Example 1 provided the synthesis of mesoporous Y zeolite using micro-sized Y zeolite. Inventive Example 2 provided the synthesis of mesoporous nano-sized ultrastable Y zeolite using nano-sized Y zeolite.
[0037] Comparative Example 1
[0038] For Comparative Example 1, mesoporous Y zeolite was prepared by subjecting micro-sized Y zeolite to AFHS treatment after synthesis. In a first container, 6.7 grams of CBV-300 zeolite (available from Zeolyst International, Conshohocken, PA) and 300 ml of deionized water were mixed and heated to 90 °C. In a separate container, an aqueous solution of ammonium hexafluorosilicate was prepared by mixing 1.65 grams of AHFS with 200 ml of water. Then, the aqueous solution of ammonium hexafluorosilicate was added dropwise to the first container containing the zeolite solution over a 2-hour period. Then, the temperature of the mixture in the first container was raised to 90 °C to 95 °C and maintained for 2 hours with stirring. Stirring was stopped, and the mixture was allowed to settle for about 10 minutes. Subsequently, the resulting product was washed 3 times, each time using about 500 ml of water. The obtained wet filter cake was dried overnight at 110 °C and then calcined at 550 °C for 4 hours at a heating rate of 2 °C per minute.
[0039] Inventive Example 2
[0040] According to an embodiment of the present disclosure, for Invention Example 2, mesoporous nanosized ultrastable Y zeolite was prepared by subjecting nanosized Y zeolite to AFHS treatment after synthesis. An aqueous sodium hydroxide solution was initially prepared by mixing 6.8 g of NaOH from Sigma Aldrich and 39.2 g of water in a beaker. With stirring, 1.64 g of NaAlO2 from Sigma Aldrich and 21 g of 40 wt.% colloidal silica (Ludox AS-40 colloidal silica) from Sigma Aldrich were added to the sodium hydroxide solution. The temperature was maintained at 30 °C and stirred for 20 hours to form a hydrogel. The hydrogel was transferred to an autoclave and crystallized at 60 °C for 12 hours, then heated to 100 °C for an additional 12 hours. The resulting product was filtered and washed with water until the pH reached 8 to 9 to obtain nanosized Y zeolite.
[0041] The nanosized Y zeolite prepared was further processed in substantially the same manner as Comparative Example 1 to produce mesoporous nanosized ultrastable Y zeolite. In a first container, the nanosized Y zeolite was combined with 300 ml of deionized water and mixed and heated to 90 °C. In a separate container, an aqueous solution of ammonium hexafluorosilicate was prepared by mixing 16.5 g of AHFS with 200 ml of water. Then, the aqueous solution of ammonium hexafluorosilicate was added dropwise to the first container containing the zeolite solution over a 2-hour period. Then the temperature of the mixture in the first container was raised to 90 °C to 95 °C and held for 2 hours with stirring. Stirring was stopped and the mixture was allowed to settle for about 10 minutes. Subsequently, the resulting product was washed 3 times, each time using about 500 ml of water. The obtained wet filter cake was dried overnight at 110 °C and then calcined at 550 °C for 4 hours with a heating rate of 2 °C per minute.
[0042] The properties of the mesoporous Y zeolites of Comparative Example 1 and Invention Example 2 are provided in Table 1 below. The average particle size was based on SEM measurements. The average pore diameter was determined by surface area using the Brunauer-Emmett-Teller (BET) technique and pore volume. CBV-100 (Zeolyst International) was used as a reference to determine the XRD crystallinity.
[0043] Table 1: Properties of Mesoporous Nanosized Y Zeolite
[0044]
[0045] As shown in Table 1, the zeolite of Invention Example 2 exhibits improved properties relative to the zeolite of Comparative Example 1. Specifically, the comparison between Comparative Example 1 and Invention Example 2 shows that the use of nano-scale Y zeolite according to the present disclosure achieves smaller particle size, larger surface area, and larger pore volume compared to micron-scale Y zeolite. Notably, the crystallinity of 98 to 100 represents a significant improvement over hydrothermal treatment and other methods for producing Y zeolites with high silica / alumina ratios, where the crystallinity is generally below 75%.
[0046] Based on the above, it should now be understood that various aspects of a method for synthesizing mesoporous nano-sized ultrastable Y zeolite are disclosed herein.
[0047] According to a first aspect of the present disclosure, a method for synthesizing mesoporous nano-sized ultrastable Y zeolite includes mixing sodium hydroxide and water to form an aqueous NaOH solution; adding sodium aluminate and colloidal silica to the aqueous NaOH solution and mixing to form a hydrogel, wherein the hydrogel has the following molar ratio composition: 8 to 12 of Na2O:Al2O3:14 of SiO2:200 to 400 of H2O; transferring the hydrogel to an autoclave operating at 50°C to 70°C for 10 hours to 20 hours; further operating the autoclave at 80°C to 120°C for 10 hours to 20 hours to form a zeolite precursor; filtering and washing the zeolite precursor with water until the pH reaches 8 to 9 to form nano-sized Y zeolite; combining the nano-sized Y zeolite with 30 mL to 1000 mL of water per gram of nano-sized Y zeolite on a dry basis to form a nano-sized Y zeolite slurry mixture, and heating the nano-sized Y zeolite slurry mixture to 70°C to 100°C; adding an aqueous solution of ammonium hexafluorosilicate at 0.1 M to 2.0 M to the nano-sized Y zeolite slurry mixture within 1 hour to 2 hours to form a dealumination solution; maintaining the dealumination solution at 70°C to 100°C for an additional 1 hour to 8 hours; filtering and washing the dealumination solution with water to form an ultrastable Y zeolite precursor; drying the ultrastable Y zeolite precursor at 80°C to 150°C for 6 hours to 24 hours to form a dried zeolite precursor; and calcining the dried zeolite precursor at 250°C to 600°C for 1 hour to 8 hours to form nano-sized ultrastable Y zeolite.
[0048] A second aspect includes the method described in the first aspect, wherein, based on SEM measurement, the mesoporous nano-sized ultrastable Y zeolite includes an average particle size of 100 nm to 200 nm.
[0049] A third aspect includes the method described in the first or second aspect, wherein based on BET measurement, the mesoporous nano-sized ultrastable Y zeolite includes a surface area greater than 600m 2 / g.
[0050] The fourth aspect includes the method according to any one of the first to third aspects, wherein the mesoporous nano-sized ultrastable Y zeolite has a pore volume of 0.6 ml / g to 0.8 ml / g.
[0051] The fifth aspect includes the method according to any one of the first to fourth aspects, wherein the mesoporous nano-sized ultrastable Y zeolite has an average pore diameter of 4 nm to 6 nm.
[0052] The sixth aspect includes the method according to any one of the first to fifth aspects, wherein the mesoporous nano-sized ultrastable Y zeolite has a mesopore volume of at least 0.3 ml / g.
[0053] The seventh aspect includes the method according to any one of the first to sixth aspects, wherein sodium aluminate, colloidal silica, and an aqueous NaOH solution are mixed at 25°C to 40°C for 15 hours to 25 hours to form a hydrogel.
[0054] The eighth aspect includes the method according to any one of the first to seventh aspects, wherein the hydrogel is transferred to an autoclave, which is initially operated at 50°C to 70°C for 10 hours to 16 hours, and then at 90°C to 110°C for an additional 10 hours to 16 hours to form a zeolite precursor.
[0055] The ninth aspect includes the method according to any one of the first to eighth aspects, wherein the weight ratio of ammonium hexafluorosilicate for forming the dealumination solution to the nano-sized Y zeolite on a dry basis is 0.1 to 1.0.
[0056] The tenth aspect includes the method according to any one of the first to ninth aspects, wherein an aqueous ammonium hexafluorosilicate solution of 0.1 M to 2.0 M is added to the nano-sized Y zeolite slurry mixture within 1 hour to 2 hours, while maintaining the nano-sized Y zeolite slurry mixture at 80°C to 90°C.
[0057] The eleventh aspect includes the method according to any one of the first to tenth aspects, wherein the dealumination solution is maintained at 90°C to 95°C for an additional 1 hour to 8 hours.
[0058] The twelfth aspect includes the method according to any one of the first to eleventh aspects, wherein the ultrastable Y zeolite precursor is dried at 100°C to 120°C for 8 hours to 12 hours.
[0059] The thirteenth aspect includes the method according to any one of the first to twelfth aspects, wherein the zeolite precursor is calcined at 550°C to 600°C for 3 hours to 6 hours to form a mesoporous nano-sized ultrastable Y zeolite.
[0060] The fourteenth aspect includes the method according to any one of the first to thirteenth aspects, wherein the heating rate during calcination is 1°C to 3°C per minute.
[0061] The fifteenth aspect includes the method according to any one of the first aspect to the fourteenth aspect, wherein the colloidal silica is colloidal silica of 30% to 50% by weight.
[0062] The sixteenth aspect includes the method according to any one of the first aspect to the fifteenth aspect, wherein the hydrogel has the following molar ratio composition: 5 to 15 of Na2O:Al2O3:7 to 20 of SiO2:200 to 400 of H2O.
[0063] 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.
[0064] Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural referents.
[0065] Throughout this disclosure, ranges are provided. It is contemplated that each discrete value included in the range is also included. Additionally, it is equally contemplated that ranges formed by each discrete value included in the explicitly disclosed range are also included. For the sake of brevity, this general indication is provided without explicit indication after each disclosed range. Further, 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.
[0066] 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.
[0067] 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, to avoid obscuring the various embodiments, the illustrations of the various embodiments may omit certain features or details.
Claims
1. A method for synthesizing mesoporous nanosized ultrastable Y zeolite, the method comprising: Mixing sodium hydroxide and water to form an aqueous NaOH solution; Adding sodium aluminate and colloidal silica to the aqueous NaOH solution and mixing to form a hydrogel, wherein the hydrogel has the following molar ratio composition: 8 to 12 of Na2O:Al2O3:14 of SiO2:200 to 400 of H2O; Transferring the hydrogel to an autoclave operating at 50 °C to 70 °C for 10 hours to 20 hours; Further operating the autoclave at 80 °C to 120 °C for 10 hours to 20 hours to form a zeolite precursor; and Filtering and washing the zeolite precursor with water until the pH reaches 8 to 9 to form nanosized Y zeolite; Combining the nanosized Y zeolite with 30 ml to 1000 ml of water per gram of the nanosized Y zeolite on a dry basis to form a nanosized Y zeolite slurry mixture, and heating the nanosized Y zeolite slurry mixture to 70 °C to 100 °C; Adding an aqueous solution of ammonium hexafluorosilicate at 0.1 M to 2.0 M to the nanosized Y zeolite slurry mixture within 1 hour to 2 hours to form a dealumination solution; Maintaining the dealumination solution at 70 °C to 100 °C for an additional 1 hour to 8 hours; Filtering and washing the dealumination solution with water to form an ultrastable Y zeolite precursor; Drying the ultrastable Y zeolite precursor at 80 °C to 150 °C for 6 hours to 24 hours to form a dried zeolite precursor; and Calcining the dried zeolite precursor at 250 °C to 600 °C for 1 hour to 8 hours to form the nanosized ultrastable Y zeolite.
2. The method according to claim 1, wherein the mesoporous nanosized ultrastable Y zeolite comprises an average particle size of 100 nanometers to 200 nanometers based on SEM measurement and a surface area of greater than 600 m 2 / g based on BET measurement.
3. The method according to claim 1 or 2, wherein the mesoporous nanosized ultrastable Y zeolite has a pore volume of 0.6 ml / g to 0.8 ml / g.
4. The method according to any one of claims 1 to 3, wherein the mesoporous nanosized ultrastable Y zeolite has an average pore diameter of 4 nm to 6 nm.
5. The method according to any one of claims 1 to 4, wherein the mesoporous nanosized ultrastable Y zeolite has a pore volume of at least 0.3 ml / g.
6. The method according to any one of claims 1 to 5, wherein sodium aluminate, the colloidal silica and the aqueous NaOH solution are mixed at 25 °C to 40 °C for 15 hours to 25 hours to form the hydrogel.
7. The method according to any one of claims 1 to 6, wherein the hydrogel is transferred to an autoclave, the autoclave is initially operated at 50 °C to 70 °C for 10 hours to 16 hours, and then operated at 90 °C to 110 °C for an additional 10 hours to 16 hours to form the zeolite precursor.
8. The method according to any one of claims 1 to 7, wherein the weight ratio of ammonium hexafluorosilicate for forming the dealumination solution to the nanosized Y zeolite on a dry basis is 0.1 to 1.
0.
9. The method according to any one of claims 1 to 8, wherein the 0.1 M to 2.0 M aqueous solution of ammonium hexafluorosilicate is added to the nanosized Y zeolite slurry mixture within 1 hour to 2 hours while maintaining the nanosized Y zeolite slurry mixture at 80°C to 90°C.
10. The method according to any one of claims 1 to 9, wherein the dealumination solution is maintained at 90°C to 95°C for an additional 1 hour to 8 hours.
11. The method according to any one of claims 1 to 10, wherein the ultrastable Y zeolite precursor is dried at 100°C to 120°C for 8 hours to 12 hours.
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 hours to 6 hours to form the mesoporous nanosized ultrastable Y zeolite.
13. The method according to any one of claims 1 to 12, wherein the heating rate during calcination is 1°C to 3°C per minute.
14. The method according to any one of claims 1 to 13, wherein the colloidal silica is 30 wt% to 50 wt% colloidal silica.
15. The method according to any one of claims 1 to 14, wherein the hydrogel has the following molar ratio composition: 5 to 15 of Na2O:Al2O3: 7 to 20 of SiO2: 200 to 400 of H2O.