Patent Application
20250145480
The embodiments described herein generally relate to porous materials and, more particularly, to zeolites.
Materials that include pores, such as zeolites, may be utilized in many petrochemical industrial applications. For instance, such materials may be utilized as catalysts in a number of reactions that convert hydrocarbons or other reactants from feed chemicals to product chemicals.
Zeolites may be characterized by a microporous structure framework type. Various types of zeolites have been identified over the past several decades, where zeolite types are generally described by framework types, and where specific zeolitic materials may be more specifically identified by various names such as ZSM-5 or zeolite-Y.
Zeolite containing catalysts and adsorbents have widespread uses in many diverse industries. Exemplary industries include the petrochemical industry in refinery, gas separation, and carbon dioxide separation and capture processes. In the petroleum industry, for example, zeolite containing catalysts may be included in processes such as fluid catalytic cracking (FCC) and hydrocracking to catalyze reactions such as hydrogenation, dehydrogenation, isomerization, alkylation, and cracking, for example. Zeolite containing adsorbents may be utilized in the separation of paraffins or aromatic isomers, and in drying processes to remove water and other impurities from hydrocarbon streams.
Embodiments of the present disclosure are directed to methods of making zeolite-Y particles, where the zeolite-Y particles may have relatively small particle sizes (e.g., on the nano-sized scale as described herein). In particular, the methods of making zeolite-Y particles may comprise a crystallization process that utilizes two separate heat treatments and adding a structure directing agent and a swelling agent between the two heat treatments. The combination of at least these features may allow for the formation of zeolite-Y particles with relatively high uniformity of mesopores and a relatively short synthesis process, at least as compared to conventional methods.
According to one or more embodiments, a method for making zeolite-Y particles may comprise forming a zeolite precursor solution comprising an alumina source material and a silica source material in a solvent. The method may also comprise heating the zeolite precursor solution at a temperature of from 50° C. to 70° C. for a time period of from 12 hours to 24 hours to form an intermediate mixture and adding a structure directing agent and a swelling agent to the intermediate mixture. Following the adding of the structure directing agent and the swelling agent to the intermediate mixture, the intermediate mixture may be heated at a temperature of from 50° C. to 120° C. for a time period of from 12 hours to 24 hours to form the zeolite-Y particles.
It is to be understood that both the preceding general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. Additional features and advantages of the embodiments will be set forth in the detailed description and, in part, will be readily apparent to persons of ordinary skill in the art from that description, which includes the accompanying drawings and claims, or recognized by practicing the described embodiments. The drawings are included to provide a further understanding of the embodiments and, together with the detailed description, serve to explain the principles and operations of the claimed subject matter. However, the embodiments depicted in the drawings are illustrative and exemplary in nature, and not intended to limit the claimed subject matter.
One or more embodiments presently described herein are directed to methods of making zeolite-Y particles. In some embodiments, the zeolite-Y particles are nano-sized, as described herein. The methods are described in detail hereinafter, along with properties and physical characteristics of the formed zeolite-Y particles.
As used throughout this disclosure, “zeolites” or “zeolite materials” generally refer to micropore-containing inorganic materials with regular intra-crystalline cavities and channels of molecular dimension, as would be understood by those skilled in the art. Zeolites generally comprise a crystalline structure, as opposed to an amorphous structure. The microporous structure of zeolites may render large surface areas and desirable size-/shape-selectivity, which may be advantageous for catalysis. Accordingly, zeolites may be utilized in many petrochemical industrial applications, such as, for instance, reactions that convert hydrocarbons or other reactants from feed chemicals to product chemicals by cracking.
Generally, zeolites may be characterized by a microporous framework type, which defines their microporous structure. Framework types are described in, for instance, “Atlas of Zeolite Framework Types” by Christian Baerlocher et al., Sixth Revised Edition, published by Elsevier, 2007, the teachings of which are incorporated by reference herein.
As described herein, the zeolites formed are zeolite-Y. Zeolite-Y generally comprises an FAU framework type. Zeolite-Y described herein may be characterized, in some embodiments, as ultra-stable zeolite-Y (USY). As used herein, “zeolite-Y” and “USY” refer to a zeolite having a FAU framework type according to the IZA zeolite nomenclature and consisting majorly of silica and alumina, as would be understood by one skilled in the art.
According to the methods for making zeolite-Y particles described herein, in general, a zeolite precursor solution may be formed and the zeolite precursor solution may be heated in a first heating step to form an intermediate mixture. A structure directing agent and a swelling agent may be added to the intermediate mixture and the intermediate mixture may then be heated in a second heating step following the addition of the structure directing agent and the swelling agent to from zeolite-Y particles.
As described hereinabove, in one or more embodiments, in an initial step, a zeolite precursor solution is formed. Generally, zeolite precursor solutions may refer to those that include the materials that will form the zeolite, such as silicon, aluminum, and oxygen atoms. Zeolite precursor solutions may include a solvent and at least an alumina source material and a silica source material. The zeolite precursor solution may further comprise a basic compound, as described herein. The solvent may be water, but other solvents are not necessarily excluded from the scope of the presently disclosed methods.
Without limitation, the alumina source materials may comprise one or more of alumina, NaAlO2, Al2(SO4)3, Al(NO3)3, AlCl3, or Al2O3. Also, without limitation, the silica source material may comprise one or more of colloidal silica, fumed silica, or tetraethyl orthosilicate (TEOS), or Na2SiO3. It should be understood that molecules of source materials may disassociate in solution, and that the initial zeolite precursor solution comprising an alumina source material or a silica source material may refer to the initial zeolite precursor solution comprising the initial molecules of the source materials or disassociated components of these molecules. The basic compound may be chosen from NaOH, KOH, Mg(OH)2, and the basic compound composition is not necessarily limited. In some embodiments, the alumina source material may not be aluminum isopropoxide.
According to one or more embodiments, the zeolite precursor solution may generally be prepared by mixing the alumina source material and the silica source material into a solvent. For example, the alumina source material may be mixed into a solvent, the silica source material may be mixed into another solvent, and these two mixtures may be combined. The ordering of the mixing of the alumina source material and the silica source material into the solvent is not necessarily limited. Similarly, a basic compound may be mixed into the solution that includes the alumina source material and silica source material, or may be added already mixed with the solvent.
According to one or more embodiments, the mixture that includes the alumina source material and silica source material may be aged to form the zeolite precursor solution. Aging may be for a period of time of at least 10 hours, such as from 10 hours to 48 hours, from 10 hours to 30 hours, or from 15 hours to 25 hours. The aging may include agitating the mixture, such as stirring the mixture. In some embodiments, the aging may be at an elevated temperature, such as about 30° C., but in other embodiments, the aging may be at ambient temperature such as about 25° C. Without being bound by theory, while it is not believed that the overall chemical composition substantially changes in the mixture during aging, it is believed that aging may form zeolite nuclei from which zeolitic particles may be formed in downstream steps by crystallization. In general, final crystal sizes may be smaller when more nuclei are formed during aging, and relatively small crystal size and particle size may be desired.
In one or more embodiments, the molar ratio of components in the zeolite precursor solution may be 8-12 Na2O: 1 Al2O3: 6-20 SiO2: 200-400 H2O. Molar ratios of any two of these components are contemplated herein based on the described molar ratio of Na2O, alumina, silica, and water.
Following the forming of the zeolite precursor solution, the zeolite precursor solution may be heated to form an intermediate mixture. According to one or more embodiments, the zeolite precursor solution may be heated at a temperature of at least 50° C., such as from 50° C. to 70° C. For example, the heating may be at a temperature of from 50° C. to 55° C., from 55° C. to 60° C., from 60° C. to 65° C., from 65° C. to 70° C., or any combination of one or more of these ranges. In one or more embodiments the heating may be for a time period of from 12 hours to 24 hours, such as from 12 hours to 14 hours, from 14 hours to 16 hours, from 16 hours to 18 hours, from 18 hours to 20 hours, from 20 hours to 22 hours, from 22 hours to 24 hours, or any combination of one or more of these ranges.
Following the heating of the zeolite precursor solution to form the intermediate mixture, a structure directing agent and a swelling agent may be added to the intermediate mixture. As described herein, a “structure directing agent” may refer to a compound or compounds that self-assemble in a solution to form an ordered meso-structure from which a zeolite may crystallize around the structure directing agent's structure to form a zeolite with the desired framework. According to some embodiments, the structure directing agent may be chosen from one or more of cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide (DTAB), cetyltripropylammonium bromide (CTPABr), and tri-n-propylamine. As described hereinabove, a swelling agent may be added to the intermediate mixture. As described herein a “swelling agent” may refer to a compound or compounds that may increase the size of micelles formed within a solution. According to some embodiments, the swelling agent may be chosen from one or more of 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, xylene, and toluene.
Without being bound by theory, it is believed that the addition of a structure directing agent and a swelling agent between the two heating treatments may improve the uniformity of the mesopores formed in the final zeolite-Y particles. It is believed that the structure directing agent may form micelles within the solution and the swelling agent may interact with these micelles to “swell” the micelles to a larger size. The zeolite-Y particles may begin to form by crystallizing around the surface of these swollen micelles forming mesopores within the zeolite-Y structure. Further, it is believed, the interaction between the structure directing agent and the swelling agent may form relatively more consistent sized micelles allowing for a more uniform structure of the zeolite-Y particles formed around these micelles when compared to zeolites formed without the use of a structure directing agent and a swelling agent.
In one or more embodiments, a second silica source material may be added to the intermediate mixture prior to heating the intermediate mixture. The second silica source material may be added at the same time as one or both of the swelling agent and the structure directing agent or may be added separately from one or both of the swelling agent and the structure directing agent. In one or more embodiments, the second silica source material may comprise one or more of colloidal silica, fumed silica, tetraethyl orthosilicate (TEOS), or Na2SiO3.
In one or more embodiments, a basic compound may be added to the intermediate mixture prior to heating the intermediate mixture. The basic compound may be chosen from one or more of NaOH, KOH, Mg(OH)2, and the basic compound composition is not necessarily limited.
In one or more embodiments, a co-solvent may be added to the intermediate mixture prior to heating the intermediate mixture. In one or more embodiments the co-solvent may be chosen from ethyl alcohol, isopropanol, methanol, and the co-solvent composition is not necessarily limited
Following the addition of the structure directing agent and the swelling agent to the intermediate mixture, the intermediate mixture may be heated at a temperature of at least 50° C. For example, the intermediate mixture may be heated at a temperature of from 80° C. to 120° C., such as from 80° C. to 85° C., from 85° C. to 90° C., from 90° C. to 95° C., from 95° C. to 100° C., from 100° C. to 105° C., from 105° C. to 110° C., from 110° C. to 115° C., from 115° C. to 120° C., or any combination of one or more of these ranges. In one or more embodiments, the intermediate mixture may be heated for a time period of from 12 hours to 24 hours, such as from 12 hours to 14 hours, from 14 hours to 16 hours, from 16 hours to 18 hours, from 18 hours to 20 hours, from 20 hours to 22 hours, from 22 hours to 24 hours, or any combination of one or more of these ranges.
In one or more embodiments, the heating of the initial zeolite precursor solution forms the crystalized zeolite-Y particles in a residual liquid solution. In one or more embodiments, following the formation of the zeolite-Y particles in residual liquid solution, the zeolite-Y particles are separated from the residual liquid solution. Separation may be by a wide variety of techniques, and generally phase separation techniques may be suitable since the zeolite-Y particles are solids and the residual liquid solution is a liquid. For example, centrifugation may be utilized to separate the zeolite-Y particles from the residual liquid solution. Separation of the zeolite-Y particles may be complete or incomplete where, for example, some small amount of zeolite-Y particles remain in the residual liquid solution, but this is not desirably the case.
Following separation of the zeolite-Y particles from the residual liquid solution, the zeolite-Y particles may be washed and/or dried. Washing may be with water, and may be conducted until the pH of the zeolite-Y particles is from about 8 to 9. Drying may be by presence in ambient conditions or by heating, such as relatively low temperature heating. Following drying, the zeolite-Y particles may be calcinated by exposure to heat. The calcination may be performed by exposure to temperatures of from 300° C. to 500° C. for 4 to 10 hours.
As described herein, the zeolite-Y is formed as particles. The particles may be shaped particles, such as spheres, or may be inconsistent in shape or otherwise globular in shape, and shape of the particles is not necessarily limited in embodiments described herein. As described herein, the size of a particle refers to the maximum length of a particle from one side to another, measured along the longest distance of the particle. For example, a spherically shaped particle has a size equal to its diameter, or a rectangular prism shaped particle has a maximum length equal to the hypotenuse stretching from opposite corners. Particle size may be measured by a variety of known techniques such as laser diffraction analysis or microscopy. In one or more embodiments, the zeolite-Y particles may be nano-sized meaning that they have an average particle size of less than 1 micron. In some embodiments, the zeolite-Y particles may have an average diameter of from 150 nm to 300 nm, such as from 150 nm to 160 nm, from 160 nm to 170 nm, from 170 nm to 180 nm, from 180 nm to 190 nm, from 190 nm to 200 nm, from 200 nm to 210 nm, from 210 nm to 220 nm, from 220 nm to 230 nm, from 230 nm to 240 nm, from 240 nm to 250 nm, from 250 nm to 260 nm, from 260 nm to 270 nm, from 270 nm to 280 nm, from 280 nm to 290 nm, from 290 nm to 300 nm, or any combination of one or more of these ranges.
In one or more embodiments, the zeolite-Y particles described may include, in addition to micropores (present in the microstructure of a zeolite), mesopores, and the zeolite-Y particles may be mesoporous by having an average pore size of greater than 2 nm and less than or equal to 50 nm. Unless otherwise described herein, the “pore size” of a material refers to the average pore size, but materials may additionally include mesopores having a particular size that is not identical to the average pore size. The average pore size of a material can be measured using BET analysis, as is widely understood to those in the art. According to one or more embodiments, the zeolite-Y particles may have an average pore size of greater than 2 nm, such as from 2.5 nm to 4 nm, such as from 2.5 nm to 3 nm, from 3 nm to 3.5 nm, from 3.5 nm to 4 nm, or any combination of one or more of these ranges.
In one or more embodiments, the zeolite-Y may have an average micropore volume and/or an average mesopore volume, where the total pore volume is the sum of these two. The mesopore and micropore volumes may be calculated according to the Barrett-Joiner-Halenda (BJH) method of determining mesopore volume known to one having skill in the art. Details regarding the t-plot method and the BJH method of calculating micropore volume and mesopore volume respectively are provided in Galarneau et al., “Validity of the t-plot Method to Assess Microporosity in Hierarchical Micro/Mesoporous Materials”, Langmuir 2014, 30, 13266-13274, for example. In one or more embodiments, the zeolite-Y particles may have a total pore volume of from 0.4 ml/g to 0.7 ml/g, such as from 0.4 ml/g to 0.45 ml/g, from 0.45 ml/g to 0.5 ml/g, from 0.5 ml/g to 0.55 ml/g, from 0.55 ml/g to 0.6 ml/g, from 0.6 ml/g to 0.65 ml/g, from 0.65 ml/g to 0.7 ml/g, or any combination of one or more of these ranges.
In one or more embodiments, the zeolite-Y particles may have an average surface area of at least 650 m2/g, such as at least 550 m2/g, at least 600 m2/g, at least 650 m2/g, at least 700 m2/g, or even at least 750 m2/g, as determined through the Brunauer-Emmett-Teller (BET) method (average BET surface area).
As described herein, crystallinity is a measurement of the degree of structural order in a solid. A more crystalline solid will have its atoms and molecules arranged in a more regular and periodic manner than a less crystalline solid. Crystallinity is typically determined by x-ray diffraction. A particular diffraction peak can be selected and its intensity normalized. Zeolites can be analyzed and the diffraction intensity normalized against the standard producing a relative crystallinity based on a standard zeolite structure. In one or more embodiments, the zeolite-Y particles may have a relative crystallinity based on the crystallinity of CBV-100, available from Zeolyst International, of greater than 100%.
The zeolite-Y particles described herein may be utilized alone or in combination with other materials as catalyst used in hydrocracking processes. Such a catalyst may have at least two functions: cracking of high molecular weight hydrocarbon and hydrogenating the unsaturated molecules. However, the relatively small pore size (e.g. average pore size less than 2 nm) of most conventional zeolites Y materials in hydrocracking catalysts generally does not favor the transport of large molecules in heavy oil fractions to diffuse into the active sites located inside the zeolite. This may cause low activity, and a possible deactivation of the catalyst. Additionally, the poor diffusion efficiency of bulky molecules can be avoided by reduced zeolite particle size due to increased external surface area and shortened diffusion path of the molecules. However, the relatively small particle size of the presently disclosed zeolite-Y materials may enable for better access of reactive molecules to catalytic sites.
The various embodiments of methods described will be further clarified by the following examples. The examples are illustrative in nature, and should not be to limit the subject matter of the present disclosure.
First 6.800 g of sodium hydroxide (NaOH) was stirred and dissolved in 39.24 g of water in a glass bottle and then allowed to cool. To this mixture 1.640 g of sodium aluminate (NaAlO2) and 21.00 g of 40 wt. % colloidal silica was added and stirred for 1 hour. The mixture was then stirred and aged at 30° C. for 20 hours. The resulting hydrogel mixture was next autoclaved at 60° C. for 12 hours. Then, the colloidal product mixture was cooled to room temperature and set aside. Following this process, 5.000 g of CTAB along with 1.000 g of NaOH, 10.00 mL of ethyl alcohol as a cosolvent, 10.00 g of TEOS, and 20.00 g of distilled water were added to a separate beaker and mixed for 30 minutes. This resulting product was then mixed with the colloidal product that had been set aside and mixed for 30 minutes. The resulting hydrogel mixture was then crystallized at 100° C. for 12 hours. The product was then filtrated and washed with water until its pH reached between 8 and 9. The resulting solid product was subsequently dried at 110° C. for 24 hours and then calcinated at 500° C. for 4 hours (2° C./min ramp).
First 6.800 g of NaOH was stirred and dissolved in 39.24 g of water in a glass bottle and then allowed to cool. To this mixture 1.640 g of NaAlO2 and 21.00 g of 40 wt. % colloidal silica was added and stirred for 1 hour. The mixture was then stirred and aged at 30° C. for 20 hours. The resulting hydrogel mixture was next autoclaved at 60° C. for 12 hours. Then, the colloidal product mixture was cooled to room temperature and set aside. Following this process, 5.000 g of CTAB along with 1.000 g of NaOH, 0.8300 g of 1,2,4-trimethybenzene (TMB) as a swelling agent, 10.00 mL of ethyl alcohol as a cosolvent, 10.00 g of TEOS, and 20.00 g of distilled water were added to a separate beaker and mixed for 30 minutes. This resulting product was then mixed with the colloidal product that had been set aside and mixed for 30 minutes. The resulting hydrogel mixture was then crystallized at 100° C. for 12 hours. The product was then filtrated and washed with water until its pH reached between 8 and 9. The resulting solid product was subsequently dried at 110° C. for 24 hours and then calcinated at 500° C. for 4 hours (2° C./min ramp).
As shown in Table 1, the addition of a swelling agent, as in EX-1, led to a decreased particle size, increased mesopore surface area, increased mesopore volume, and an increased total pore volume and total surface area when compared to both the commercially available zeolite, CBV-100 (available from Zeolyst International), and the zeolite formed in CE-1 without the use of a swelling agent. Accordingly, the addition of both a swelling agent and a structure directing agent may lead to desired physical properties of the synthesized zeolite-Y particles.
This disclosure includes numerous aspects. One aspect is a method of making zeolite-Y particles, the method comprising: forming a zeolite precursor solution comprising an alumina source material and a silica source material in a solvent; heating the zeolite precursor solution at a temperature of from 50° C. to 70° C. for a time period of from 12 hours to 24 hours to form an intermediate mixture; adding a structure directing agent and a swelling agent to the intermediate mixture; and following the adding of the structure directing agent and the swelling agent to the intermediate mixture, heating the intermediate mixture at a temperature of from 50° C. to 120° C. for a time period of from 12 hours to 24 hours to form the zeolite-Y particles.
Another aspect is any above aspect or combination of aspects, wherein the method further comprises adding a second silica source material to the intermediate mixture prior to heating the intermediate mixture.
Another aspect is any above aspect or combination of aspects, wherein the second silica source material is tetraethyl orthosilicate.
Another aspect is any above aspect or combination of aspects, wherein the structure directing agent is one or more of cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide, cetyltripropylammonium bromide, and tri-n-propylamine.
Another aspect is any above aspect or combination of aspects, wherein the swelling agent is one or more of 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, xylene, and toluene.
Another aspect is any above aspect or combination of aspects, wherein the method further comprises adding one or more of NaOH, KOH, or Mg(OH)2 to the intermediate mixture prior to heating the intermediate mixture.
Another aspect is any above aspect or combination of aspects, wherein the method further comprises adding a co-solvent to the intermediate mixture prior to heating the intermediate mixture.
Another aspect is any above aspect or combination of aspects, wherein the alumina source material is chosen from one or more of NaAlO2, Al2(SO4)3, Al(NO3)3, AlCl3, or Al2O3.
Another aspect is any above aspect or combination of aspects, wherein the silica source material is chosen from one or more of colloidal silica, fumed silica, tetraethyl orthosilicate, or Na2SiO4.
Another aspect is any above aspect or combination of aspects, wherein forming zeolite precursor solution comprises: mixing a basic compound, the silica source material, and the alumina source material into a solvent to form a mixture; and aging the mixture by stirring the mixture for at least 10 hours.
Another aspect is any above aspect or combination of aspects, wherein the solvent is water.
Another aspect is any above aspect or combination of aspects, wherein aging the mixture comprises stirring the mixture at a temperature of from 20° C. to 40° C.
Another aspect is any above aspect or combination of aspects, wherein aging the mixture comprises stirring the mixture for from 10 hours to 30 hours.
Another aspect is any above aspect or combination of aspects, wherein the zeolite-Y particles have a ratio of mesopore surface area to total surface area of at least 38%.
Another aspect is any above aspect or combination of aspects, wherein the zeolite-Y particles have an average particle size of from 150 nm to 300 nm.
Another aspect is any above aspect or combination of aspects, wherein the zeolite-Y particles have an average pore size of from 2.5 to 4 nm.
Another aspect is any above aspect or combination of aspects, wherein the zeolite-Y particles have a total pore volume of from 0.4 ml/g to 0.7 ml/g.
Another aspect is any above aspect or combination of aspects, wherein the zeolite-Y particles have an average surface area of at least 650 m2/g.
Another aspect is any above aspect or combination of aspects, wherein the zeolite-Y particles have a relative crystallinity of greater than 60%.
Another aspect is any above aspect or combination of aspects, wherein the method further comprises washing the zeolite-Y particles; drying the zeolite-Y particles; and calcinating the zeolite-Y particles.
Having described the subject matter of the present disclosure in detail and by reference to specific embodiments, it is noted that the various details described in this disclosure should not be taken to imply that these details relate to elements that are essential components of the various embodiments described in this disclosure, even in cases where a particular element is illustrated in each of the drawings that accompany the present description. Rather, the claims appended hereto should be taken as the sole representation of the breadth of the present disclosure and the corresponding scope of the various embodiments described in this disclosure. Further, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims.
It is noted that one or more of the following claims utilize the term “wherein” as a transitional phrase. For the purposes of defining the present technology, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.”
It should be understood that any two quantitative values assigned to a property may constitute a range of that property, and all combinations of ranges formed from all stated quantitative values of a given property are contemplated in this disclosure. It should be appreciated that compositional ranges of a chemical constituent in a stream or in a reactor should be appreciated as containing, in some embodiments, a mixture of isomers of that constituent. For example, a compositional range specifying butene may include a mixture of various isomers of butene. It should be appreciated that the examples supply compositional ranges for various streams, and that the total amount of isomers of a particular chemical composition can constitute a range.
