Patent Application
20220280912
The present disclosure is directed to metal ion-containing zeolitic compositions, preferably transition metal ion-containing, more preferably zinc ion-containing zeolitic compositions that are useful for scavenging carbon dioxide (CO2) from low-CO2-content gaseous source mixtures (feed streams), including air, and methods of making and using the same. In some preferred embodiments, the compositions comprise zinc ion-doped zeolites having AEI, AFX, or CHA topologies capable of efficiently removing carbon dioxide from low-CO2-content gaseous source mixtures.
Mitigation of the increasing concentration of CO2 in the atmosphere has been recognized as one of the most serious global challenges in the 21st century. The level of global atmospheric CO2 surpassed 409 ppm in 2018, and predictions suggest that it could reach 500 ppm by 2050. See “Climate Change: Atmospheric Carbon Dioxide|NOAA Climate.gov,” can be found under https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide). Even if drastic measures are taken to completely halt anthropogenic CO2 emissions by 2040, the climate risks posed by high atmospheric CO2 concentration are likely to persist for decades afterward. See D. W. Keith, Science 2009, 325, 1654-1655; D. Archer, et al., Annu. Rev. Earth Planet. Sci. 2009, 37, 117-134. Therefore, active removal of CO2 from air using direct air capture (DAC) is one strategy (amongst many) being considered to assist in the battle to limit further increases in CO2 concentration in the atmosphere. See K. S. Lackner, et al., Proc. Natl. Acad. Sci. 2012, 109, 13156-13162. Compared to the conventional point-source CO2 capture from cement plants, power stations, iron/steel industry installations, and oil refineries, DAC could mitigate CO2 emissions from all sources, and in turn, enable onsite technologies that require CO2 as a feedstock (thereby eliminating the need for storage and transport infrastructure). See C. Brady, et al. Proc. Natl. Acad Sci. 2019, 116, 25001-25007; C. Breyer, et al. Joule 2019, 3, 2053-2057; E. S. Sanz-Pérez, et al. Chem. Rev. 2016, 116, 11840-11876.
Carbon dioxide (CO2) capture is being investigated as an important approach to limit further increases in CO2 concentration in the atmosphere. See K. S. Lackner, et al. Proc. Natl. Acad Sci. 2012, 109, 13156-13162. The conventional approaches for capturing high concentration (>10%) CO2 are being developed for addressing emissions from point sources, such as cement plants, power stations, iron/steel industry installations, and oil refineries. However, point source capture by itself will not be able to reduce atmospheric CO2 as ca. 50% of the anthropogenic emissions are from mobile sources. See E. S. Sanz-Pérez, et al. Chem. Rev. 2016, 116, 11840-11876. Direct air capture (DAC) may be able to aid in mitigating global CO2 amounts originating from point source and non-point source emissions, and allow for onsite technologies for CO2 storage or unitization (thereby eliminating the need for storage and transport infrastructure). See E. S. Sanz-Pérez, et al. Chem. Rev. 2016, 116, 11840-11876; C. Brady, et al. Proc. Natl. Acad. Sci. 2019, 116, 25001-25007; C. Breyer, et al. Joule 2019, 3, 2053-2057. DAC is also promising for capture of leaked CO2 from carbon capture and storage (CCS) point sources and/or geologic CO2 storage sites. See X. Shi, et al. Angew. Chem. Int. Ed 2019, 59, 6984-7006. DAC requires capture from low concentrations of CO2, ca. 400 ppm CO2. In addition to DAC, efficient removal of low concentration CO2 may be useful for other situations such as air purification in space stations and future human space environments, aircraft, submarine, and office buildings, and in medicine, e.g., anesthesia machines. See O. Shekhah, et al. Nat. Commun. 2014, 5, 4228; S. Mukherjee, et al. Sci. Adv. 2019, 5, eaax9171. In order to create efficient capture technologies for low concentration CO2 environments, there is a need for new adsorbents.
Development of low cost physisorbents may be useful for CO2 capture because they have the potential for fast kinetics and low energy requirements for regeneration that could drastically reduce the cost of operations. See A. Kumar, et al. Angew. Chem. Int. Ed. 2015, 54, 14372-14377; S. Choi, et al. ChemSusChem 2009, 2, 796-854. These properties will likely be particularly significant in applications involving trace CO2 capture, as the low concentrations of CO2 often result in both low diffusion rates and low CO2 capacities. See J. Liu, et al. ACS Sustain. Chem. Eng. 2019, 7, 82-93. Zeolites are used in many commercial applications including catalysis, adsorption and separation due to their physical and chemical stabilities as well as other merits attributed to their unique structures. See M. Flanigen, et al. in Zeolites in Industrial Separation and Catalysis (Ed.: S. Kulprathipanja), Wiley-VCH, Weinheim, 2010, pp. 1-26; Y. Li, L. Li, J. Yu, Chem 2017, 3, 928-949; M. E. Davis, Nature 2002, 417, 813-821. They can be synthesized at very large scale over a broad range of properties, e.g., very hydrophilic to very hydrophobic. Zeolites already have shown promising performance for CO2 capture in post-combustion carbon capture processes as well as CO2 removal in air pre-purification processes (including the international space station). See S. Choi, et al. ChemSusChem 2009, 2, 796-854; K. T. Chue, et al. Ind Eng. Chem. Res. 1995, 34, 591-598; S. Sircar, W. C. Kratz, 1981, U.S. Pat. No. 4,249,915A; R. Kay, SAE Trans. 1998, 107, 514-522.
Capture of CO2 requires an effective and economic sorbent that possesses merits such as moderate CO2-binding affinity, fast sorption kinetics, high capacity, good selectivity against other components in the air, easy regeneration with minimal energy input, long-term stability, and low cost. See S. Choi, et al. ChemSusChem 2009, 2, 796-854. To this end, DAC efforts in the past decade or so have involved a variety of sorbent types; chemisorbents using amine-based materials (see E. S. Sanz-Pérez, et al. Chem. Rev. 2016, 116, 11840-11876; S. A. Didas, et al. Acc. Chem. Res. 2015, 48, 2680-2687; J. J. Lee, et al. Langmuir 2018, 34, 12279-12292; A. R. Sujan, et al. ACS Sustain. Chem. Eng. 2019, 7, 5264-5273), moisture-swing sorbents (see X. Shi, et al., Angew. Chem. Int. Ed 2019, 59, 6984-7006; M. Oschatz and M. Antonietti, Energy Environ. Sci. 2018, 11, 57-70), and physisorbents like zeolites (see A. Kumar, et al. Angew. Chem. Int. Ed 2015, 54, 14372-14377; S. M. W. Wilson and F. H. Tezel, Ind Eng. Chem. Res. 2020, 59, 8783-8794), and metal-organic frameworks (MOFs), see P. M. Bhatt, et al. J. Am. Chem. Soc. 2016, 138, 9301-9307; K. Sumida, et al., Chem. Rev. 2012, 112, 724-781; D. M. D'Alessandro, et al., Angew. Chem. Int. Ed 2010, 49, 6058-6082. Chemisorbents have been extensively studied for DAC of CO2 due to their high CO2 uptake. This type of sorbent is currently being used by several companies such as Carbon Engineering, ClimeWorks, and Global Thermostat. See H. Azarabadi and K. S. Lackner, Appl. Energy 2019, 250, 959-975. These sorbents either require elevated temperatures (100-900° C.) for regeneration or they suffer from time-dependent oxidation, and can expel toxic volatiles into the atmosphere. See E. S. Sanz-Pérez, et al. Chem. Rev. 2016, 116, 11840-11876; A. Kumar, et al. Angew. Chem. Int. Ed 2015, 54, 14372-14377. DAC via physisorption is attractive because of the potential for high selectivity, fast kinetics and low energy requirements for recycling. A. Kumar, et al. Angew. Chem. Int. Ed 2015, 54, 14372-14377.
Porous materials, in particular zeolites, are one class of adsorbent material with potential for DAC. Zeolites are crystalline, aluminosilicate materials that have a proven track record of use in industry for catalysis, adsorption and separation due to their physical and chemical stabilities. See S. Kulprathipanja, Wiley—VCH Verl. GmbH Co KGaA 2010, 620. The charge mismatch between the framework Si4+ with Al3+ results in a net negative charge that can be balanced by alkali metal, alkaline earth metal, proton and ammonium cations or some type other positively charged species. The abundance of cation exchangeable sites in their pore networks enables this class of material to adsorb a wide variety of gas molecules, including acidic gas molecules such as CO2. See S. Choi, et al. ChemSusChem 2009, 2, 796-854. Indeed, zeolites are promising sorbents for CO2 capture in post-combustion carbon capture processes as well as CO2 removal in air pre-purification processes and are used in a number of locations including the international space station. See S. Choi, et al. ChemSusChem 2009, 2, 796-854; K. T. Chue, et al., Ind Eng. Chem. Res. 1995, 34, 591-598; S. Sircar and W. C. Kratz, Removal of Water and Carbon Dioxide from Air, 1981, U.S. Pat. No. 4,249,915A; R. Kay, SAE Trans. 1998, 107, 514-522.
Although numerous zeolites have been investigated for carbon capture (see A. Khelifa, et al. Microporous Mesoporous Mater. 1999, 32, 199-209; V. P. Shiralkar, S. B. Kulkarni, Zeolites 1985, 5, 37-41; K. S. Walton, et al. Microporous Mesoporous Mater. 2006, 91, 78-84; T.-H. Bae, et al. Energy Environ. Sci. 2012, 6, 128-138; Y. Zhou, et al. Science 2021, 373, 315-320), the research for capture of low concentrations of CO2 has mainly been focused on low-silica FAU-type zeolites (Si/Al of less than 2). See A. Kumar, et al. Angew. Chem. Int. Ed. 2015, 54, 14372-14377; N. R. Stuckert, R. T. Yang, Environ. Sci. Technol. 2011, 45, 10257-10264; S. M. W. Wilson, F. H. Tezel, Ind Eng. Chem. Res. 2020, 59, 8783-8794. Low-silica zeolites are hydrophilic so they have high water capacity as well as low hydrothermal stability that likely will present challenges for large scale commercialization of carbon capture technologies. See N. S. Wilkins, J. A. Sawada, A. Rajendran, Adsorption 2020, 26, 765-779. Zeolites with higher Si/Al give higher hydrophobicity, yet they are known to have low CO2 capacity.
Low-silica zeolites with the FAU (13X and Y as trade names) and LTA (4A as the trade name) framework topologies are among the most commonly used adsorbents in industrial gas adsorption and separations. See A. Khelifa, et al., Microporous Mesoporous Mater. 1999, 32, 199-209; V. P. Shiralkar and S. B. Kulkarni, Zeolites 1985, 5, 37-41; K. S. Walton, et al., Microporous Mesoporous Mater. 2006, 91, 78-84; T.-H. Bae, et al., Energy Environ. Sci. 2012, 6, 128-138. However, their strong CO2 binding energy via both physisorption and chemisorption as well as their hydrothermal stability can lead to difficulties with regeneration, and thus lead to low recyclability even under vacuum regenerating conditions.[15,24,31] See S. M. W. Wilson and F. H. Tezel, Ind. Eng. Chem. Res. 2020, 59, 8783-8794; T. D. Pham, et al., Langmuir 2013, 29, 832-839; P. J. E. Harlick, F. H. Tezel, Microporous Mesoporous Mater. 2004, 76, 71-79. Recently, a high-silica zeolite, SSZ-13, possessing the CHA framework topology, has gained attention, as it is now successfully commercialized for selective catalytic reduction of NOX with ammonia in vehicle emissions. See J. H. Kwak, R. G. Tonkyn, D. H. Kim, J. Szanyi, C. H. F. Peden, J. Catal. 2010, 275, 187-190; I. Bull, et al., Copper CHA Zeolite Catalysts, 2009, U.S. Pat. No. 7,601,662B2. Both experimental results and computer simulations have shown promising adsorption capacity and CO2/N2 selectivity of cation exchanged SSZ-13 zeolites for CO2 capture. See T. D. Pham, et al., Langmuir 2013, 29, 832-839; M. R. Hudson, et al., J. Am. Chem. Soc. 2012, 134, 1970-1973; J. Shang, et al., J. Am. Chem. Soc. 2012, 134, 19246-19253; T. Du, Research on Chemical Intermediates volume 2017, 1783-1792; M. Sun, et al., Chem. Eng. J. 2019, 370, 1450-1458; J. Zhang, et al., Microporous Mesoporous Mater. 2008, 111, 478-487; M. Debost, et al., Angew. Chem. Int. Ed. 2020, 59, 23491-23495; J. K. Bower, et al., ACS Appl. Mater. Interfaces 2018, 10, 14287-14291. Yet, there are no studies reported for DAC of CO2 with SSZ-13.
Zinc-exchanged CHA has been reported for CO2 capture. See Du, T., et al. Preparation of zinc chabazite (ZnCHA) for CO2 capture. Res Chem Intermed 43, 1783-1792 (2017). https://doi.org/10.1007/s11164-016-2729-y; Mingzhe Sun, et al., Transition metal cation-exchanged SSZ-13 zeolites for CO2 capture and separation from N2, Chemical Engineering Journal, Volume 370, 2019, 1450-1458, ISSN 1385-8947, https://doi.org/10.1016/j.cej.2019.03.234. However, these materials have been examined for CO2 capture from flue gasses which comprise large proportions of CO2. An adsorbent that is effective for capturing CO2 from gasses having a high CO2 do not necessarily demonstrate similar performance in the context of gasses having relatively low CO2 concentrations. Indeed, the preparation method of the CHA with Si/Al=2.2 did not show good performance (CO2 uptake) for 400 ppm CO2. See Zn-CHA2(a)-1.91E in Table 2 herein.
Thus, a need exists for efficient adsorbents for DAC of CO2 from feed gasses having relatively low CO2 concentrations, such as, for example, atmospheric air.
The present disclosure provides metal ion-doped crystalline microporous aluminosilicate compositions comprising:
(a) a three-dimensional aluminosilicate framework containing α-cages with 8-MR openings that are sized to accommodate the molecular dimensions of carbon dioxide (3.3 Å);
(b) the framework further comprising d6r (or D6MR) composite building blocks having 6-membered rings that face (are part of) or connect the α-cage of the framework;
wherein the crystalline microporous aluminosilicate contains 1.2 to 8 metal ions per unit cell, wherein the ratio of metal ions to aluminum within the unit cell is from 0.33 to 0.85; and
wherein the metal ion-doped crystalline microporous aluminosilicate composition adsorbs carbon dioxide when exposed to a gaseous mixture comprising carbon dioxide.
The present disclosure also is directed to compositions useful for capturing carbon dioxide (CO2) from low-CO2-content gaseous source mixtures (feed streams), including air, and methods of making and using the same. In certain embodiments, the compositions comprise metal ion-doped crystalline microporous aluminosilicate compositions comprising:
(a) a three-dimensionally aluminosilicate framework containing α-cages interconnected by 8-MR openings that are appropriately sized for accommodating the molecular dimensions of carbon dioxide (3.3 Å);
(b) the framework further comprising d6r (or D6MR) composite building blocks having 6-membered rings that face (are part of) the α-cage of the framework;
wherein the crystalline microporous aluminosilicate contains metal ions, preferably transition metal ions, more preferably zinc ions, positioned within the framework lattice; and
wherein the metal ion-doped crystalline microporous aluminosilicate composition adsorbs carbon dioxide more than the otherwise same crystalline microporous aluminosilicate composition that does not contain the metal ions when subjected to the same gaseous source mixture under the same conditions.
In certain independent aspects:
(a) the aluminosilicate framework has a AEI, AFT, AFX, CHA, EAB, KFI, LEV, or SAS topology, preferably a AEI, AFX, or CHA (e.g., SSZ-13) topology;
(b) the aluminosilicate framework have a Si:Al atomic ratio is in a range of from 1:1 to 20:1, or any one of the ranges defined elsewhere herein;
(c) the metal ions positioned within the framework lattice comprise a transition metal ion, preferably iron, cobalt, nickel, copper, zinc, or silver, more preferably zinc;
(d) the (transition) metal ions are present within the framework lattice in a ratio of from 0.5 to 6 metal ions per unit cell, or any one of the ranges defined elsewhere herein;
(e) the compositions contain or have the capacity to contain carbon dioxide in a range of from 0.5 to 0.55 to 1.7 mmol adsorbed CO2 per unit cell, when the metal ion-doped crystalline microporous aluminosilicate composition is exposed to a gas source having (i) a total pressure in a range of from 50 kPa to 125 kPa, or any one of the ranges or values defined elsewhere herein, and (ii) a CO2 content in a range of from 350 to 425 ppm, or any one of the ranges or values defined elsewhere herein;
(f) in those compositions containing carbon dioxide, the carbon dioxide is desorbed at a temperature of less than 130° C., less than 125° C., less than 120° C., less than 115° C., less than 110° C., or less than 100° C.;
(g) the composition adsorbs less than 15 wt %, less than 10 wt %, or less than 5 wt % water, relative to the weight of the anhydrous metal ion-doped crystalline microporous aluminosilicate composition; and/or
(h) in those compositions containing water, the water desorbs at a temperature of less than 250° C., less than 225° C., less than 200° C., less than 175° C., or less than 150° C.
In certain independent aspects:
(a) the aluminosilicate framework has a AEI, AFT, AFX, CHA, EAB, KFI, LEV, or SAS topology, preferably a AEI, AFX, or CHA (e.g., SSZ-13) topology;
(b) the aluminosilicate framework have a Si:Al atomic ratio is in a range of from 1:1 to 20:1, or any one of the ranges defined elsewhere herein;
(c) the metal ions positioned within the framework lattice comprise a transition metal ion, preferably iron, cobalt, nickel, copper, zinc, or silver, more preferably zinc;
(d) the (transition) metal ions are present within the framework lattice in a ratio of from 0.5 to 6 metal ions per unit cell, or any one of the ranges defined elsewhere herein;
(e) the compositions contain or have the capacity to contain carbon dioxide in a range of from 0.5 to 0.55 to 1.3 mmol adsorbed CO2 per unit cell, when the metal ion-doped crystalline microporous aluminosilicate composition is exposed to a gas source having (i) a total pressure in a range of from 50 kPa to 125 kPa, or any one of the ranges or values defined elsewhere herein, and (ii) a CO2 content in a range of from 350 to 425 ppm, or any one of the ranges or values defined elsewhere herein;
(f) in those compositions containing carbon dioxide, the carbon dioxide is desorbed at a temperature of less than 130° C., less than 125° C., less than 120° C., less than 115° C., less than 110° C., or less than 100° C.;
(g) the composition adsorbs less than 15 wt %, less than 10 wt %, or less than 5 wt % water, relative to the weight of the anhydrous metal ion-doped crystalline microporous aluminosilicate composition; and/or
(h) in those compositions containing water, the water desorbs at a temperature of less than 250° C., less than 225° C., less than 200° C., less than 175° C., or less than 150° C.
Certain embodiments provide that the compositions set forth herein can be prepared by methods comprising contacting a precursor crystalline microporous aluminosilicate with an aqueous solution of a salt of a suitable metal ion, and optionally rinsing the resulting metal ion-doped crystalline microporous aluminosilicate with water and/or optionally drying the metal ion-doped crystalline microporous aluminosilicate, wherein the salt is any one of the salts described elsewhere herein, and the method steps are optionally those described herein.
Certain embodiments provide methods of capturing carbon dioxide from a gaseous source mixture, such methods comprising contacting the gaseous source mixture with any one or more of the metal ion-doped crystalline microporous aluminosilicate compositions set forth herein so as to adsorb the carbon dioxide into the composition, and optionally desorbing the carbon dioxide from the carbon-dioxide laden metal ion-doped crystalline microporous aluminosilicate.
In certain independent aspects of these methods:
(a) the contacting of the metal ion-doped crystalline microporous aluminosilicate with the gaseous source mixture is done in the absence or without the use of an added desiccant; and/or
(b) the contacting of the metal ion-doped crystalline microporous aluminosilicate with the gaseous source mixture is done in the presence or with the use of an added desiccant.
Certain additional embodiments provide for the material configurations that allow for the practice of these methods.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
The present application is further understood when read in conjunction with the appended drawings. For the purpose of illustrating the subject matter, there are shown in the drawings exemplary embodiments of the subject matter; however, the presently disclosed subject matter is not limited to the specific methods, devices, and systems disclosed. In addition, the drawings are not necessarily drawn to scale.
In the present disclosure the singular forms “a,” “an,” and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “a material” is a reference to at least one of such materials and equivalents thereof known to those skilled in the art, and so forth.
When a value is expressed as an approximation by use of the descriptor “about,” it will be understood that the particular value forms another embodiment. In general, use of the term “about” indicates approximations that can vary depending on the desired properties sought to be obtained by the disclosed subject matter and is to be interpreted in the specific context in which it is used, based on its function. The person skilled in the art will be able to interpret this as a matter of routine. In some cases, the number of significant figures used for a particular value may be one non-limiting method of determining the extent of the word “about.” In other cases, the gradations used in a series of values may be used to determine the intended range available to the term “about” for each value. Where present, all ranges are inclusive and combinable. That is, references to values stated in ranges include every value within that range. For example, a range defined as from 400 to 450 ppm includes 400 ppm and 450 ppm as independent embodiments.
It is to be appreciated that certain features of the invention which are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. That is, unless obviously incompatible or specifically excluded, each individual embodiment is deemed to be combinable with any other embodiment(s) and such a combination is considered to be another embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. Finally, while an embodiment may be described as part of a series of steps or part of a more general structure, each said step may also be considered an independent embodiment in itself, combinable with others.
The transitional terms “comprising,” “consisting essentially of,” and “consisting” are intended to connote their generally in accepted meanings in the patent vernacular; that is, (i) “comprising,” which is synonymous with “including,” “containing,” or “characterized by,” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps; (ii) “consisting of” excludes any element, step, or ingredient not specified in the claim; and (iii) “consisting essentially of” limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed invention. Embodiments described in terms of the phrase “comprising” (or its equivalents), also provide, as embodiments, those which are independently described in terms of “consisting of” and “consisting essentially of.” For those embodiments provided in terms of “consisting essentially of,” the basic and novel characteristic(s) is the facile operability of the methods or compositions/systems to provide the aluminosilicate compositions at meaningful yields (or the ability of the systems using only those ingredients listed. Other components or steps may be included, as long as these additional components or steps do not materially affect the basic and novel characteristic(s) of the claimed invention.
When a list is presented, unless stated otherwise, it is to be understood that each individual element of that list, and every combination of that list, is a separate embodiment. For example, a list of embodiments presented as “A, B, or C” is to be interpreted as including the embodiments, “A,” “B,” “C,” “A or B,” “A or C,” “B or C,” or “A, B, or C,” as separate embodiments, as well as C1-3.
Throughout this specification, words are to be afforded their normal meaning, as would be understood by those skilled in the relevant art. However, so as to avoid misunderstanding, the meanings of certain terms will be specifically defined or clarified.
The terms “method(s)” and “process(es)” are considered interchangeable within this disclosure.
The terms “separating” or “separated” carry their ordinary meaning as would be understood by the skilled artisan, insofar as they connote physically partitioning or isolating of one material from another or the selective capture of one component from a broader mixture. For example, in the case where the terms are used in the context of gas processing, the terms “separating” or “separated” connote a partitioning of the gases by adsorption or by permeation based on size or physical or chemical properties, as would be understood by those skilled in the art.
In the context of CO2 content in a gaseous source mixture, the terms “low concentration” or “low-CO2-content” refers to embodiments where the CO2 content of is in a range of from 100 ppm to 1000 ppm, or more preferably in an amount approximating the content of CO2 in our atmosphere (i.e., ca. 400 ppm), but also the higher levels found in buildings. In some specific embodiments, the CO2 content in a gaseous source mixture may range from 300 to 350 ppm, 350 to 400 ppm, 400 to 450 ppm, 450 to 500 ppm, 500 to 600 ppm, 600 to 700 ppm, 700 to 800 ppm, 800 to 900 ppm, 900 to 1000 ppm, or the CO2 content may be defined in terms of any of the foregoing values or two or more of the foregoing ranges. The term “gaseous source mixture” or the like refers to the gas from which the CO2 is being extracted, typically air or, in the case of testing, helium, optionally in the presence of argon present as an internal standard. The gaseous source mixture is typically present at ambient atmospheric pressure (i.e., 101 kPa) or within 10% or 20% of that pressure, though higher pressures (i.e., up to 202 kPa) may also be considered in the present context.
The term “microporous,” according to IUPAC notation refers to a material having pore diameters of less than 2 nm. Similarly, the term “macroporous” refers to materials having pore diameters of greater than 50 nm. And the term “mesoporous” refers to materials whose pore sizes are intermediate between microporous and macroporous. Within the context of the present disclosure, the material properties and applications depend on the properties of the framework such as pore size and dimensionality, cage dimensions and material composition.
“Optional” or “optionally” means that the subsequently described circumstance may or may not occur, so that the description includes instances where the circumstance occurs and instances where it does not. For example, the phrase “optionally heated” refers to both embodiments where the material is and is not heated. Similarly, the term “optionally present” refers to both embodiments where the component is and is not present. Each of these embodiments (is and is not heated or is and is not present) represents individual and independent embodiments.
As used herein, the term “crystalline microporous solids” or “crystalline microporous aluminosilicate” are crystalline structures having very regular pore structures of molecular dimensions, i.e., under 2 nm. The maximum size of the species that can enter the pores of a crystalline microporous solid is controlled by the dimensions of the openings. These materials are sometimes referred to as “molecular sieves,” having very regular pore structures of molecular dimensions, i.e., under 2 nm. The term “molecular sieve” refers to the ability of the material to selectively sort molecules based primarily on a size exclusion process. The maximum size of the species that can enter the pores of a crystalline microporous solid is controlled by the dimensions of the openings. These are conventionally defined by the ring size of the aperture, where, for example, the term “8-MR” or “8-membered ring” refers to a closed loop that is typically built from eight tetrahedrally coordinated silicon (or aluminum) atoms and 8 oxygen atoms. These rings are not necessarily symmetrical, due to a variety of effects including strain induced by the bonding between units that are needed to produce the overall structure, or coordination of some of the oxygen atoms of the rings to cations within the structure. As used herein, in the context of the invention, the term “8-MR” or 8-MR zeolite” refers only to those aluminosilicate crystalline materials, or optionally substituted derivatives, having frameworks comprising 8-membered rings as the largest ring for entrance of molecules into the intracrystalline void space. Exemplary structures can identified in Baerlocher, et al., Atlas of Zeolite Framework Types, Sixth Revised Edition (2007), this reference being incorporated by reference herein for this teaching. In the present disclosure, the terms can also refer specifically to one or more compositions having AEI, AFX, and CHA topologies or any of the other topologies cited herein.
AEI topology is a three-dimensional interconnected channel system, bound by 8-membered rings 8MRs (3.8×3.8 Å) and basket-shaped cages, which are connected by double 6-membered rings (D6Rs).
AFX topology is made up of elongated larger aft cages (0.55×1.35 nm) and smaller gme cages (0.33×0.74 nm), which each joined by D6Rs units.
CHA topology is composed of D6Rs in an AABBCC sequence. All D6Rs have the same orientation, and link to other D6Rs to give a structure that contains the cha cage. Each cha cage is linked to six others via 8MR windows.
FAU topology is built by linking sodalite (SOD) cages through D6Rs, which creates a large cavity in FAU called the “supercage” accessible by a three-dimensional 12MR pore system.
LTA topology is built by linking SOD cages through double 4-membered rings, which creates a large cavity in FAU called the “supercage” accessible by a three-dimensional 8MR pore system.
The term “metal ion-doped” is intended to confer the same meaning as “metal ion-containing” in the context of the metal ions set forth elsewhere herein.
The term “silicate” refers to any composition including silicate (or silicon oxide) within its framework. It is a general term encompassing, for example, pure-silica (i.e., absent other detectable metal oxides within the framework), aluminosilicate, borosilicate, ferrosilicate, germanosilicate, stannosilicate, titanosilicate, or zincosilicate structures. The term “aluminosilicate” refers to any composition including both silicon and aluminum oxides within its framework. The term “zeolite” refers to an aluminosilicate composition that is a member of this family. For this reason, the terms “metal ion-doped zeolitic composition(s)” and “metal ion-doped crystalline microporous aluminosilicate composition(s)” are considered equivalent and are used interchangeably herein. Such aluminosilicates may be “pure-aluminosilicates (i.e., absent other detectable metal oxides within the framework) or optionally substituted (i.e., containing other metal oxides within the lattice framework). When described as “optionally substituted,” the respective framework may contain boron, gallium, germanium, hafnium, iron, tin, titanium, indium, vanadium, zinc, zirconium, or other atoms substituted for one or more of the atoms not already contained in the parent lattice or framework.
As used herein, the term “transition metal” refers to any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table, as well as the elements of the f-block lanthanide and actinide series. This definition of transition metals specifically encompasses Group 4 to Group 12 elements. In certain other independent embodiments, the transition metals comprises an element of Groups 6, 7, 8, 9, 10, 11, or 12. In still other independent embodiments, the transition metal comprises scandium, yttrium, titanium, zirconium, vanadium, manganese, chromium, molybdenum, tungsten, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, or mixtures thereof, preferably iron, cobalt, nickel, copper, silver, and zinc.
In some cases herein, the term “metal ion-doped crystalline microporous aluminosilicate compositions” are referred to as “zeolitic compositions” or “metal-doped zeolitic compositions,” and the like.
The present disclosure is directed to new compositions of matter useful for extracting carbon dioxide (CO2) from feed streams, especially feed streams containing low levels of CO2, including air. Such new compositions comprise transition metal-containing zeolites, including those zeolites having the framework characteristics set forth herein, including those provided in C. Baerlocher, Atlas of Zeolite Framework Types, 6th Revised Edition 2007, which is incorporated by reference for its teaching of such frameworks, and preferably those compositions where the transition metal is zinc and the zeolites have AEI, AFX, and CHA topologies. The disclosure is also directed to methods of making and using these compositions, including configurations useful for using these compositions to extract the CO2 from gaseous feed streams.
The present invention may be understood more readily by reference to the following description taken in connection with the accompanying Figures and Examples, all of which form a part of this disclosure. It is to be understood that this invention is not limited to the specific products, methods, conditions, or parameters described or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of any claimed invention. Similarly, unless specifically otherwise stated, any description as to a possible mechanism or mode of action or reason for improvement is meant to be illustrative only, and the invention herein is not to be constrained by the correctness or incorrectness of any such suggested mechanism or mode of action or reason for improvement. For example, though the some of the present disclosure comments on the placement of the transition metal (zinc) ions in the zeolitic framework, the present inventions are not constrained by the correctness or incorrectness of these comments as to the placement. Throughout this text, it is recognized that the descriptions refer to compositions and methods of making and using said compositions. That is, where the disclosure describes or claims a feature or embodiment associated with a composition or a method of making or using a composition, it is appreciated that such a description or claim is intended to extend these features or embodiment to embodiments in each of these contexts (i.e., compositions, methods of making, and methods of using).
In some aspects, the disclosure is directed to metal ion-doped crystalline microporous aluminosilicate compositions comprising:
(a) a three-dimensional aluminosilicate framework containing α-cages with 8-MR openings that are sized to accommodate the molecular dimensions of carbon dioxide (3.3 Å);
(b) the framework further comprising d6r (or D6MR) composite building blocks having 6-membered rings that face (are part of) or connect the α-cage of the framework;
wherein the crystalline microporous aluminosilicate contains 1.2 to 8 metal ions per unit cell, wherein the ratio of metal ions to aluminum within the unit cell is from 0.33 to 0.85; and
wherein the metal ion-doped crystalline microporous aluminosilicate composition adsorbs carbon dioxide when exposed to a gaseous mixture comprising carbon dioxide.
In some embodiments, the compositions are useful for extracting CO2 from gaseous sources, including air, that can be described in compositional or functional terms, or in a combination of compositional and functional terms. In functional terms, the compositions share an enhanced capacity to capture CO2 from gas mixtures, including those gas mixtures themselves having low CO2 levels, for example having CO2 contents approximating the levels of CO2 found in air.
The crystalline microporous aluminosilicate compositions (e.g., zeolitic compositions) described herein share at least the following compositional and structural similarities:
(1) They are described in terms of crystalline microporous aluminosilicate compositions comprising a three-dimensional framework having pores defined by 8-membered rings (i.e., 8-MR openings) that are appropriately sized for accommodating the molecular dimensions of carbon dioxide (3.3 Å). These 8-MR openings interconnect cavities that are larger than the 8-MR openings themselves, these cavities also referred to as the α-cages of the zeolites.
(2) They show a substantial increase in their ability to capture CO2 under the test conditions when doped with metal ions, including transition metal ions, such as zinc ions, relative to their non-doped condition.
(3) The structures of the zeolites further comprise double 6-membered rings (d6r or D6MR) composite building blocks whose 6-membered rings face (are part of) the α-cage of the zeolite (e.g., AEI, AFX, and CHA).
Topologies that exhibit at least these structural characteristics (i.e., containing α-cages with interconnecting 8-MR openings with facing 6-membered rings associated with d6r building blocks) include AEI, AFT, AFX, CHA, EAB, KFI, LEV, and SAS. Other zeolites that exhibit at least these structural characteristics are considered within the scope of this disclosure, including those provided in C. Baerlocher, Atlas of Zeolite Framework Types, 6th Revised Edition 2007, which is incorporated by reference for its teaching of such frameworks. Those zeolites having AEI, AFX, and CHA topologies (or similar; with d6r building blocks facing the openings/cages that are accessible to CO2 molecules) are shown herein to exhibit substantially increased capacities for CO2 when appropriately doped with zinc ions.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein the three-dimensional aluminosilicate framework has an AEI, AFT, AFX, CHA, EAB, KFI, LEV, or SAS topology.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein the three-dimensional aluminosilicate framework has AEI, AFX, or CHA topology.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein the three-dimensional aluminosilicate framework has AEI topology.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein the three-dimensional aluminosilicate framework has AFX topology.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein the three-dimensional aluminosilicate framework has CHA topology.
In some embodiments in which the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure has CHA topology, the CHA topology is synthetic CHA. As used herein, “synthetic CHA” refers to CHA that has a Si/Al ration that may be greater than or less than 4. CHA with an Si/Al>4 has the tradename SSZ-13. (Zones, S.I. U.S. Pat. No. 4,544,538A).
Other zeolites comprising sodalite (sod) building blocks, which do not have d6r building blocks or have d6r building blocks that do not face the α-cage do not exhibit the enhanced CO2 absorption with zinc-doping (considered representative of other transition metal-doping). Indeed, and by sharp contrast, zinc-doping is shown herein to substantially inhibit the ability of these LTA zeolites to adsorb CO2. For example, zeolites of EMT and FAU topology have 12-MR openings and both d6r and sod building blocks. These frameworks comprise 6-membered rings in their 12-MR α-cages, but these 6-membered rings are associated only with the sod, but not the d6r, building blocks, and these zeolites not only fail to respond to zinc doping with enhanced CO2 absorption, but instead exhibit substantially reduced CO2 absorption with zinc-doping. Zeolites with the LTA topology do not have d6r building blocks also fail to respond to zinc doping with enhanced CO2 absorption, and exhibit substantially reduced CO2 absorption with zinc-doping.
The ability of the crystalline microporous aluminosilicate (zeolitic) compositions that react positively to metal doping (i.e., that exhibit this enhanced CO2 capacity) is shown to depend both on the Si:Al ratios of the zeolites and the transition metal ion (e.g., zinc ion) content in the zeolite.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 1:1 to 20:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 2:1 to 8.5:1, or from 2:1 to 7.5:1, or from 5.5:1 to 8.5:1, or from 6.5:1 to 7.5:1, or from 7.5:1 to 8.5:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 5.5:1 to 8.5:1, or from 6.5:1 to 7.5:1, or from 7.5:1 to 8.5:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 2:1 to 8.5:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 2:1 to 7.5:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 2:1 to 6:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 2:1 to 4:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 5.5:1 to 8.5:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 6.5:1 to 7.5:1.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a Si:Al atomic ratio in a range of from 7.5:1 to 8.5:1.
Si:Al ratios in a range of from 5.5:1 to 8.5:1 work well, or from 6.5:1 to 7.5:1, or about 7:1 especially in the presence of zinc ions. But even zeolitic compositions containing lower Si:Al ratios (i.e., having Si:Al ratios as low as about 2:1 or about 4:1—e.g., having a range of from 2:1 to 8.5:1) if prepared in such a way as to ensure pore volumes comparable to their higher Si:Al ratio analogues (e.g., in a range of from 0.15 to 0.25 or about 0.2 cm3/g), such as otherwise set forth herein.
More generally, in certain embodiments, the zeolitic compositions have an Si:Al atomic ratio of about 1:1 or in a range of from 1:1 to 1.5:1, from 1.5:1 to 2:1, from 2:1 to 2.5:1, from 2.5:1 to 3:1, from 3:1 to 3.5:1, from 3.5:1 to 4:1, from 4:1 to 4.5:1, from 4.5:1 to 5:1, 5:1 to 5.5:1, from 5.5:1 to 6:1, from 6:1 to 6.5:1, from 6.5:1 to 7:1, 7:1 to 7.5:1, from 7.5:1 to 8:1, from 8:1 to 8.5:1, from 8.5:1 to 9:1, 9:1 to 9.5:1, from 9.5:1 to 10:1, from 10:1 to 11:1, from 11:1 to 12:1, 12:1 to 13:1, from 13:1 to 14:1, from 14:1 to 15:1, from 15:1 to 20:1, or a range defined by the combination of two or more of the foregoing ranges, for example from 1.5:1 to 3:1, 2:1 to 4:1, about 2:1, about 3:1, about 4:1, from 4:1 to 8:1, from 8:1 to 12:1, from 5.5:1 to 8.5:1, about 5:1, about 6:1, about 7:1, about 8:1, or from 1.5:1 to 8.5:1.
In certain embodiments, the aluminosilicate framework may be substituted with one or more of boron oxide, cerium oxide, gallium oxide, germanium oxide, hafnium oxide, iron oxide, tin oxide, titanium oxide, indium oxide, vanadium oxide, or zirconium oxide.
In some aspects, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain at least one metal ion, present in a range of from 0.1 to 0.5 metal ion per unit cell, from 0.5 to 1 metal ion per unit cell, from 1 to 1 to 1.25 metal ions per unit cell, from 1.25 to 1.5 metal ions per unit cell, from 1.5 to 1.75 metal ions per unit cell, from 1.75 to 2 metal ions per unit cell, from 2 to 2.25 metal ions per unit cell, from 2.25 to 2.5 metal ions per unit cell, from 2.5 to 2.75 metal ions per unit cell, from 2.75 to 3 metal ions per unit cell, from 3 to 3.25 metal ions per unit cell, from 3.25 to 3.5 metal ions per unit cell, from 3.5 to 3.75 metal ions per unit cell, from 3.75 to 4 metal ions per unit cell, from 4 to 4.25 metal ions per unit cell, from 4.25 to 4.5 metal ions per unit cell, from 4.5 to 4.75 metal ions per unit cell, from 4.75 to 5 metal ions per unit cell, from 5 to 5.25 metal ions per unit cell, from 5.25 to 5.5 metal ions per unit cell, from 5.5 to 5.75 metal ions per unit cell, from 5.75 to 6 metal ions per unit cell, from 6 to 6.5 metal ions per unit cell, from 6.5 to 7 metal ions per unit cell, from 7 to 7.5 metal ions per unit cell, from 7.5 to 8 metal ions per unit cell, or a range defined by two or more of the foregoing ranges, for example, from 1.5 to 4 metal ions per unit cell. Loadings of about 2.25 to 3 metal ions per unit cell (e.g., about 2.5 atoms per unit cell of CHA-7) or 7 to 8 metal ions per unit cell (e.g., about 7.5 atoms per unit cell of CHA-2) appears especially attractive. Metal ion content is conveniently determined by EDS.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 1.2 to 8 metal ions per unit cell.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 1.2 to 4 metal ions per unit cell.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 1.21 to 2.6 metal ions per unit cell.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 1.5 to 4 metal ions per unit cell.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 1.2 to 3 metal ions per unit cell.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 1.2 to 3 metal ions per unit cell.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 2.25 to 3 metal ions per unit cell.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 4 to 8 metal ions per unit cell.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 6 to 8 metal ions per unit cell.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain 7 to 8 metal ions per unit cell.
In some embodiments, the metal ion is a transition metal ion.
In some embodiments, the metal ion in the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure comprises zirconium, iron, cobalt, nickel, copper, zinc, or silver.
In other embodiments, the metal ion in the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure comprises iron, cobalt, nickel, copper, zinc, or silver.
In some embodiments, the metal ion in the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure comprises zinc.
In some embodiments, the zeolitic compositions (crystalline microporous aluminosilicate compositions) of the disclosure contain at least one transition metal ion, present in a range of from 0.1 to 0.5 transition metal ion per unit cell, from 0.5 to 1 transition metal ion per unit cell, from 1 to 1 to 1.25 transition metal ions per unit cell, from 1.25 to 1.5 transition metal ions per unit cell, from 1.5 to 1.75 transition metal ions per unit cell, from 1.75 to 2 transition metal ions per unit cell, from 2 to 2.25 transition metal ions per unit cell, from 2.25 to 2.5 transition metal ions per unit cell, from 2.5 to 2.75 transition metal ions per unit cell, from 2.75 to 3 transition metal ions per unit cell, from 3 to 3.25 transition metal ions per unit cell, from 3.25 to 3.5 transition metal ions per unit cell, from 3.5 to 3.75 transition metal ions per unit cell, from 3.75 to 4 transition metal ions per unit cell, from 4 to 4.25 transition metal ions per unit cell, from 4.25 to 4.5 transition metal ions per unit cell, from 4.5 to 4.75 transition metal ions per unit cell, from 4.75 to 5 transition metal ions per unit cell, from 5 to 5.25 transition metal ions per unit cell, from 5.25 to 5.5 transition metal ions per unit cell, from 5.5 to 5.75 transition metal ions per unit cell, from 5.75 to 6 transition metal ions per unit cell, from 6 to 6.5 transition metal ions per unit cell, from 6.5 to 7 transition metal ions per unit cell, from 7 to 7.5 transition metal ions per unit cell, from 7.5 to 8 transition metal ions per unit cell, or a range defined by two or more of the foregoing ranges, for example, from 1.5 to 4 transition metal ions per unit cell. Loadings of about 2.25 to 3 transition metal ions per unit cell (e.g., about 2.5 transition atoms per unit cell of CHA-7) appears especially attractive. Metal ion content is conveniently determined by EDS.
In some embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 1.2 to 8 transition metal ions per unit cell.
In other embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 1.2 to 4 transition metal ions per unit cell.
In other embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 1.2 to 3 transition metal ions per unit cell.
In other embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 1.21 to 2.6 transition metal ions per unit cell.
In other embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 1.5 to 4 transition metal ions per unit cell.
In other embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 2.25 to 3 transition metal ions per unit cell.
In some embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 4 to 8 transition metal ions per unit cell.
In some embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 6 to 8 transition metal ions per unit cell.
In some embodiments, the crystalline microporous aluminosilicate compositions of the disclosure contain 7 to 8 transition metal ions per unit cell.
In some aspects, the crystalline microporous aluminosilicate compositions of the disclosure transition are characterized by the metal ions per Al and these are considered independent embodiments. These ratios can be determined experimentally or, to a good approximation by using the number of atoms in the unit cell in combination with the Si:Al ratios of the underlying zeolite. These ratio ranges, as determined by comparing the metal ions per unit cell and the Si/Al atoms in the corresponding unit cell, represent additional or alternative embodiments. For example, a pure CHA7 aluminosilicate unit cell framework containing 2.5 Zn ions per unit cell (a CHA unit cell framework nominally has 36 atoms of Si and Al) and having an Si:Al ratio of 7:1 contains 36/8 or 4.5 Al atoms per unit cell, corresponding to about 0.56 Zn atoms/Al atoms. A range of 2.25 to 3 metal ions per CHA7 unit cell would correlate to 0.5 to 0.67 Zn atoms/Al atoms. A pure CHA2 aluminosilicate unit cell framework containing 7.5 Zn ions per unit cell (a CHA unit cell framework nominally has 36 atoms of Si and Al) and having an Si:Al ratio of 2:1 contains 36/3 or 12 Al atoms per unit cell, corresponding to about 0.63 Zn atoms/Al atoms. A range of 7 to 8 metal ions per CHA2 unit cell would correlate to 0.58 to 0.67 Zn atoms/Al atoms.
In some embodiments, the crystalline microporous aluminosilicate compositions of the disclosure are characterized by the transition metal ions per Al and these are considered independent embodiments. These ratios can be determined experimentally or, to a good approximation by using the number of atoms in the unit cell in combination with the Si:Al ratios of the underlying zeolite. These ratio ranges, as determined by comparing the transition metal ions per unit cell and the Si/Al atoms in the corresponding unit cell, represent additional or alternative embodiments. For example, a pure SSZ-13-7 aluminosilicate unit cell framework containing 2.5 Zn ions per unit cell (a CHA unit cell framework nominally has 36 atoms of Si and Al) and having an Si:Al ratio of 7:1 contains 36/8 or 4.5 Al atoms per unit cell, corresponding to about 0.56 Zn atoms/Al atoms. A range of 2.25 to 3 transition metal ions per SSZ-13-7 unit cell would correlate to 0.5 to 0.67 Zn atoms/Al atoms.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a ratio of metal ions to aluminum within the unit cell is from 0.34 to 0.58, such as, for example, a ratio of metal ions to aluminum within the unit cell that is 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, or 0.58.
In other embodiments the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure have a ratio of metal ions to aluminum within the unit cell is from 0.59 to 0.85, such as, for example, a ratio of metal ions to aluminum within the unit cell that is 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, or 0.85.
Additionally or alternatively, the zeolitic compositions contain one or more ions of strontium, magnesium, calcium, indium, or barium in a range of from 0.5 to 1 ions per unit cell, from 1 to 1 to 1.25 ions per unit cell, from 1.25 to 1.5 ions per unit cell, from 1.5 to 1.75 ions per unit cell, from 1.75 to 2 ions per unit cell, from 2 to 2.25 ions per unit cell, from 2.25 to 2.5 ions per unit cell, from 2.5 to 2.75 ions per unit cell, from 2.75 to 3 ions per unit cell, from 3 to 3.25 ions per unit cell, from 3.25 to 3.5 ions per unit cell, from 3.5 to 3.75 ions per unit cell, from 3.75 to 4 ions per unit cell, from 4 to 4.25 ions per unit cell, from 4.25 to 4.5 ions per unit cell, from 4.5 to 4.75 ions per unit cell, from 4.75 to 5 ions per unit cell, from 5 to 5.25 ions per unit cell, from 5.25 to 5.5 ions per unit cell, from 5.5 to 5.75 ions per unit cell, from 5.75 to 6 ions per unit cell, or a range defined by two or more of the foregoing ranges, for example, from 2.25 to 3 ions per unit cell, or from 1.5 to 4 ions per unit cell.
Additionally or alternatively, the ion content of the zeolitic compositions may be defined in terms of the corresponding ion content per gram or unit volume of the corresponding zeolite.
Additionally or alternatively, in certain embodiments, the zeolitic compositions are defined in terms of their carbon dioxide content or carbon dioxide capacity.
In some embodiments, the content or capacity of carbon dioxide in the zeolitic compositions are defined in terms of molecules of CO2 per unit cell. In certain of these embodiments, the carbon dioxide content or carbon dioxide capacity of the ion-doped (preferably zinc-doped) zeolitic compositions are in a range of from 0.5 to 0.55, from 0.55 to 0.6, from 0.6 to 0.65, from 0.65 to 0.7, from 0.7 to 0.75, from 0.75 to 0.8, from 0.8 to 0.85, from 0.85 to 0.9, from 0.95 to 1.0, from 1.0 to 1.05, from 1.05 to 1.1, from 1.1 to 1.15, from 1.15 to 1.2, from 1.2 to 1.25, from 1.25 to 1.3, from 1.3 to 1.7 molecules adsorbed CO2 per unit cell of the doped zeolite, when the doped zeolite is exposed to a gas source having a total pressure in a range of from 50 kPa to 75 kPa, from 75 kPa to 100 kPa, from 100 kPa to 125 kPa, from 125 kPa to 150 kPa, or a range defined by two or more of the foregoing ranges, and having a CO2 content in a range of from 350 to 375 ppm, from 375 to 400 ppm, from 400 ppm to 425 ppm, or a range defined by two or more of the foregoing ranges.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure contain, or have the capacity to contain, carbon dioxide in a range of from 0.3 to 1.7 molecules adsorbed CO2 per unit cell; or in a range of from 0.4 to 0.6 molecules adsorbed CO2 per unit cell; or in a range of from 0.6 to 1.25 molecules adsorbed CO2 per unit cell; or in a range of from 1.26 to 1.7 molecules adsorbed CO2 per unit cell.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein exposure of the crystalline microporous aluminosilicate composition to a gas source having (a) a total pressure in a range of from 50 kPa to 125 kPa, such as, for example, a total pressure in a range of from 50 kPa to 75 kPa, or from 75 kPa to 100 kPa, or from 100 kPa to 125 kPa, or from 125 kPa to 150 kPa, and (b) a CO2 content in a range of from 350 to 425 ppm, such as, for example, 350 to 375 ppm, or from 375 to 400 ppm, or from 400 ppm to 425 ppm, results in adsorption of carbon dioxide in a range of from 0.3 to 1.7 molecules adsorbed CO2 per unit cell, such as, for example, from 0.4 to 6 molecules adsorbed CO2 per unit cell, from 0.6 to 1.25 molecules adsorbed CO2 per unit cell, or from 1.25 to 1.7 molecules adsorbed CO2 per unit cell.
In other embodiments, the content of carbon dioxide in the zeolitic compositions are defined in terms of millimoles of CO2 per gram of zeolite. In certain of these embodiments, the carbon dioxide content or carbon dioxide capacity of the metal ion-doped (preferably zinc ion-doped) zeolitic compositions of the disclosure are in a range of from 0.25 to 0.3, from 0.3 to 0.35, from 0.35 to 0.4, from 0.4 to 0.45, from 0.45 to 0.5, from 0.5 to 0.55, from 0.55 to 0.6, from 0.6 to 0.65, from 0.65 to 0.7 mmol adsorbed CO2 per gram doped zeolite, or a range defined by two or more of the foregoing ranges, when the metal ion-doped zeolite is exposed to a gas source having a total pressure in a range of from 50 kPa to 75 kPa, from 75 kPa to 100 kPa, from 100 kPa to 125 kPa, from 125 kPa to 150 kPa, or a range defined by two or more of the foregoing ranges, and having a CO2 content in a range of from 350 to 375 ppm, from 375 to 400 ppm, from 400 ppm to 425 ppm, from 425 ppm to 450 ppm, from 450 ppm to 500 ppm, from 500 ppm to 1000 ppm, or a range defined by two or more of the foregoing ranges.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate composition of the disclosure are those wherein exposure of the metal ion-doped crystalline microporous aluminosilicate composition to a gas source having (a) a total pressure in a range of from 50 kPa to 125 kPa, such as, for example, from 50 kPa to 75 kPa, from 75 kPa to 100 kPa, from 100 kPa to 125 kPa, from 125 kPa to 150 kPa, or about 100 kPa; and (b) a CO2 content in a range of from 350 to 425 ppm, such as, for example, from 350 to 375 ppm, from 375 to 400 ppm, from 400 ppm to 425 ppm, or about 400 ppm; results in adsorption of carbon dioxide in a range of from 0.2 to 0.7 mmols, such as, for example, from 0.2 to 0.5 mmol, from 0.3 to 0.7 mmol, or from 0.5 to 0.7 mmol, adsorbed CO2 per gram of metal ion-doped crystalline microporous aluminosilicate composition.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate composition of the disclosure are those wherein passage of a gas having (a) a total pressure in a range of from 50 kPa to 125 kPa, and (b) a CO2 content in a range of from 350 to 425 ppm, through a tube containing a fixed bed of the metal ion-doped crystalline microporous aluminosilicate composition, results in complete breakthrough of CO2 after adsorption of 0.2-0.7 mmol, such as, for example, such as, for example, from 0.2 to 0.5 mmol, from 0.3 to 0.7 mmol, or from 0.5 to 0.7 mmol of CO2 per gram of metal ion-doped crystalline microporous aluminosilicate composition. In some embodiments, the gas source is 400 ppm CO2/400 ppm Ar balanced by He at a flow rate of 20 mL·min−1 at 30° C. In other embodiments, the gas source is 400 ppm CO2/1% Ar/20% O2/N2, at a flow rate of 14 mL·min−1 at 30° C.
As used herein, “complete breakthrough (or saturation)” refers to the condition at which the CO2 concentration in the gas entering the fixed bed of the metal ion-doped crystalline microporous aluminosilicate composition is the same as the CO2 concentration in the gas exiting the fixed bed.
In other embodiments, the metal ion-doped crystalline microporous aluminosilicate composition of the disclosure are those wherein passage of a gas having (a) a total pressure in a range of from 50 kPa to 125 kPa, and (b) a CO2 content in a range of from 350 to 425 ppm, through a tube containing a fixed bed of the metal ion-doped crystalline microporous aluminosilicate composition, results in complete breakthrough of CO2 after adsorption of an amount of CO2 (on a mmol/g basis) that is 1.4-1.6 times greater than the amount of CO2 adsorbed by an equal weight of zeolite 13X before complete breakthrough of CO2 occurs under the same conditions. In some embodiments, the gas source is 400 ppm CO2/400 ppm Ar balanced by He at a flow rate of 20 mL·min−1 at 30° C. In other embodiments, the gas source is 400 ppm CO2/1% Ar/20% O2/N2, at a flow rate of 14 mL·min−1 at 30° C.
Additionally or alternatively, the content or capacity of the metal ion-doped zeolitic compositions are defined in terms of the amount of carbon dioxide adsorbed or adsorbable when subjected to a gas source having a given partial pressure of CO2 at a given ambient temperature. In exemplary embodiments, a zeolitic compositions containing or having the capacity to adsorb 0.4 mmol CO2 per gram of ion-doped zeolite at 30° C. (303K) from an gas at one atmosphere (101 kPa) containing 400 ppm CO2 (4×0.0001×101 kPa) has a content or capacity corresponding to a partitioning of 10 mmol adsorbed CO2 per gram zeolite per kPa CO2 source at 303K. The foregoing CO2 contents/capacities at the pressures indicated (50 kPa to 150 kPa, including sub-ranges therein, with CO2 contents in a range of from 350 to 1000 ppm, and sub-ranges therein) can be viewed also in these ratio terms.
Additionally or alternatively, in separate independent embodiments, the metal ion doped zeolitic compositions can be or are defined in their ability to desorb CO2. In certain of these embodiments, the metal ion doped zeolitic compositions containing CO2 desorb their CO2 at temperatures less than 130° C., less than 125° C., less than 120° C., less than 115° C., less than 110° C., or less than 100° C.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein adsorbed CO2 is completed desorbed at a temperature that is lower than the temperature required to completely desorb CO2 from zeolite 13X under the otherwise same conditions.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein the metal ion-doped crystalline microporous aluminosilicate composition has a selectivity for CO2 over N2 of at least 800:1.
As used herein, selectivity for CO2 over N2 is the ratio of CO2 to N2 divided by the ratio of their partial pressures or volume fractions in the streams, i.e., (QCO2/QN2)/(FCO2/FN2) where QCO2 is CO2 uptake, FCO2 is the CO2 fraction, QN2 is N2 uptake, FN2 is the N2 fraction.
In some embodiments, the metal ion-doped crystalline microporous aluminosilicate compositions of the disclosure are those wherein the metal ion-doped crystalline microporous aluminosilicate composition has a selectivity for CO2 over N2 of at least 900:1.
Additionally or alternatively, in separate independent embodiments, the metal ion doped zeolitic compositions adsorb less water than do their corresponding pristine (i.e., containing no metal ion dopants) zeolites. In some embodiments, the metal ion doped zeolitic compositions adsorb less than 15 wt %, less than 10 wt %, or less than 5 wt % water, relative to the weight of the anhydrous metal ion doped zeolitic compositions
Additionally or alternatively, in separate independent embodiments, the metal ion doped zeolitic compositions can be or are defined in their ability to desorb occluded water. In certain of these embodiments, the metal ion doped zeolitic compositions containing water desorb water at temperatures less than 250° C., less than 225° C., less than 200° C., less than 175° C., or less than 150° C.
This combination of high CO2 absorptions, facile CO2 desorptions, low hydrophilicity, and facile water desorption at mild temperatures provides good recyclability (upwards of 10 absorption/desorption cycles at ambient atmospheric pressure) of these materials for CO2 capture applications.
Every combination of the foregoing descriptions of topology, Si:Al ratio, metal ion and metal ion content, CO2 content or capacity, and CO2 or water absorption or desorption characteristics are considered separate and independent embodiments, as if separately explicitly defined and enumerated as such. That is, the metal ion-doped crystalline microporous aluminosilicate composition can be independently defined with respect to any of the prescribed topologies, Si:Al ratios, metals, metal loadings and/or CO2/water contents set forth elsewhere herein. For example, the compositions may be described in terms of a metal ion-doped crystalline microporous aluminosilicate composition comprising:
(a) a three-dimensionally aluminosilicate framework having α-cages interconnected by 8-MR openings that are appropriately sized for accommodating the molecular dimensions of carbon dioxide (3.3 Å);
(b) the framework further comprising d6r (or D6MR) composite building blocks having 6-membered rings that face (are part of) the α-cage of the framework; wherein the metal ion-doped crystalline microporous aluminosilicate composition is characterized by one or more of the following features:
(c) wherein the framework is a AEI, AFT, AFX, CHA, EAB, KFI, LEV, or SAS topology, preferably a AEI, AFX, and CHA topology;
(d) optionally wherein the aluminosilicate has an Si:Al ratio in a range of from 1:1 to 8.5:1, from 1.5:1 to 2.5:1, about 2:1, from 5.5:1 to 8.5:1, or from 6.5:1 to 7.5:1, or about 7:1, or any one of the values, ranges, or sub-ranges elsewhere set forth herein;
(e) wherein the crystalline microporous aluminosilicate contains metal ions, preferably transition metal ions, more preferably zinc ions;
(f) optionally wherein the composition contains from 1.5 to 4 transition metal ions per unit cell, or from about 2.25 to 3 transition metal ions per unit cell;
(g) wherein the metal ion-doped crystalline microporous aluminosilicate composition exhibits an increased capacity for CO2 relative to the metal-free crystalline microporous aluminosilicate composition when subjected to a low-CO2-content gaseous source mixtures, for example air.
(h) optionally wherein the carbon dioxide adsorbed by metal ion-doped crystalline microporous aluminosilicate composition desorbs at a temperature of less than 130° C., less than 125° C., less than 120° C., less than 115° C., less than 110° C., or less than 100° C.; and/or
(i) optionally wherein any water adsorbed by metal ion-doped crystalline microporous aluminosilicate composition desorbs at a temperature of less than 250° C., less than 225° C., less than 200° C., less than 175° C., or less than 150° C.
Further, any of the materials or combinations of materials or steps set forth in the Examples are also considered independent embodiments of the present disclosure.
The zeolitic frameworks can be prepared by methods known in the art (including, e.g., U.S. Pat. Nos. 3,140,249; 3,140,251; and 3,140,253), some of which are set forth herein.
These zeolitic frameworks can be further modified, for example, by incorporating metal ions (also referred to herein as dopants), such as set forth above, in the frameworks by methods also known in the art, such as are described herein. Acetates, halides (e.g., chlorides), and nitrates are preferred sources of these doping metals. Acetate salts (or salts of other carboxylic acids) appear to be preferred; for example, zinc acetate (or other organic acid) appears to be a preferred source of zinc.
As set forth in the Examples, different metal loadings can be achieved by washing the precursor zeolite (either pristine—no added metal—or previously loaded with metals) with aqueous solutions of specific concentrations of the metal salt(s). The aqueous salt solutions may comprise a single metal cation or multiple metal cations. The pH of the aqueous salt solution may be controlled, for example using dilute strong acid, dilute strong base, or buffer, or may be left uncontrolled. After exposure to the aqueous salt solution, the metal ion containing zeolite may be optionally rinsed with a second salt solution and/or one or more rinses of water, preferably distilled water, before drying and/or calcining the metal ion containing zeolite to remove occluded water.
In some aspects, the disclosure is directed to methods of preparing a metal ion-doped crystalline microporous aluminosilicate composition, the method comprising contacting a calcined precursor crystalline microporous aluminosilicate with an aqueous solution of a salt of the metal ion, and optionally rinsing the resulting metal ion-doped crystalline microporous aluminosilicate with water and/or optionally drying the metal ion-doped crystalline microporous aluminosilicate.
In some embodiments, the calcined precursor crystalline microporous aluminosilicate has an AEI, AFX, or CHA topology.
In other embodiments, the calcined precursor crystalline microporous aluminosilicate has an AEI topology. In other embodiments, the calcined precursor crystalline microporous aluminosilicate having an AEI topology is SSZ-39.
In some embodiments, the calcined precursor crystalline microporous aluminosilicate has an AFX topology. In other embodiments, the calcined precursor crystalline microporous aluminosilicate having an AFX topology is SSZ-16.
In some embodiments, the calcined precursor crystalline microporous aluminosilicate has a CHA topology. In other embodiments, the calcined precursor crystalline microporous aluminosilicate having a CHA topology is SSZ-13. In yet other embodiments, the calcined precursor crystalline microporous aluminosilicate having an CHA topology is synthetic CHA.
In some embodiments of the methods of preparing a metal ion-doped crystalline microporous aluminosilicate composition, the metal ion in the aqueous solution of a salt of the metal ion is one or more of Zn(OAc)2, ZnCl2, Zn(NO3)2, ZnSO4, or ZnBr2.
In some embodiments of the methods of preparing a metal ion-doped crystalline microporous aluminosilicate composition, the metal ion in the aqueous solution of a salt of the metal ion is Zn2+.
The metal ion-doped zeolitic compositions as disclosed herein are described as useful in extracting CO2 from gaseous source mixtures or to otherwise separate gases. For example, these can be used to separate water and carbon dioxide from fluid streams, such as from air. Typically, the molecular sieve is used as a component in a membrane that is used to separate the gases. Examples of such membranes are disclosed in U.S. Pat. No. 6,508,860.
For each of the preceding processes described, additional corresponding embodiments include those comprising a device or system comprising or containing the materials described for each process. For example, in the gas of the gas trapping, additional embodiments include those devices known in the art as direct air capture devices In such devices, carbon dioxide is captured and stored until subject to conditions for desorption. The devices may also comprise membranes comprising the metal ion-doped zeolitic compositions useful in the processes described.
In certain embodiments, the metal ion-doped compositions may be present and/or used in a fixed bed arrangement, either suitable for its intended purpose by itself or with another material. For example, in some embodiments, the metal ion-doped compositions may be suitable for use in extracting CO2 from the atmosphere without the need for additional desiccant material(s). In such cases, the metal ion-doped compositions may be present in a fixed bed or other suitable arrangement that allows a gaseous source mixture to pass through, over, or otherwise around these compositions. The metal ion-doped compositions may be present or used in the absence of a separate desiccant material, whether the separate desiccant material is present upstream (optionally proximate to, for example in a tandem fixed bed arrangement) or intermingled with the configured metal ion-doped compositions set forth herein. In other embodiments, the metal ion-doped compositions may be present or used with a separate desiccant material, either in a tandem bed (or functionally equivalent) arrangement or intermingled together. When present or used with a separate desiccant material, for example in a tandem or dual bed arrangement, the materials are configured to allow a gaseous source mixture to pass through the desiccant before passing through the metal ion-doped compositions set forth herein.
In either case, the metal ion-doped zeolitic compositions may be configured in such a way as to allow a gaseous source mixture to pass through, over, or otherwise around these compositions.
In some aspects, the disclosure is directed to methods of capturing carbon dioxide from a gaseous source mixture, the method comprising contacting the gaseous source mixture with a metal ion-doped crystalline microporous aluminosilicate of the disclosure such that carbon dioxide in the gaseous source mixture is adsorbed by the metal ion-doped crystalline microporous aluminosilicate.
In some embodiments, the methods of the disclosure further comprise desorbing the carbon dioxide from the carbon-dioxide laden metal ion-doped crystalline microporous aluminosilicate.
In some embodiments, contacting the metal ion-doped crystalline microporous aluminosilicate with the gaseous source mixture is done in the absence of, or without the use of, an added desiccant.
In other embodiments, contacting the metal ion-doped crystalline microporous aluminosilicate with the gaseous source mixture is done in the presence of, or with the use of, an added desiccant.
In some embodiments, contacting the gaseous source mixture with the metal ion-doped crystalline microporous aluminosilicate comprises passing the gaseous source mixture through a fixed-bed of adsorbent comprising the metal ion-doped crystalline microporous aluminosilicate.
In some embodiments, contacting the gaseous source mixture with the metal ion-doped crystalline microporous aluminosilicate occurs at a temperature of less than 50° C., such as, for example, a temperature of less than 45° C., a temperature of less than 40° C., a temperature of less than 35° C., a temperature of less than 30° C., a temperature of less than 25° C., a temperature of less than 20° C., or a temperature of less than 15° C.
In some embodiments, desorbing the carbon dioxide from the carbon-dioxide laden metal ion-doped crystalline microporous aluminosilicate occurs at a temperature less than 130° C., such as for example, a temperature less than 125° C., a temperature less than 120° C., a temperature less than 115° C., a temperature less than 110° C., or a temperature less than 100° C.
In some embodiments, the gaseous source mixture comprises water.
In some embodiments, the methods of the disclosure further comprise desorbing water from the metal ion-doped crystalline microporous aluminosilicate at a temperature less than 250° C., such as, for example, a temperature less than 225° C., a temperature less than 200° C., a temperature less than 175° C., or a temperature less than 150° C.
While each Example is considered to provide specific individual embodiments of composition, methods of preparation and use, these teachings should be considered representative of the more general disclosure; i.e., none of the Examples should be considered to limit the more general embodiments described herein.
In the following examples, efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental error and deviation should be accounted for. Unless indicated otherwise, temperature is in degrees C., pressure is at or near atmospheric.
SSZ-13 is a “high-silica composition” with Si/Al>4, and described in Zones, S.I. U.S. Pat. No. 4,544,538, 1985. Reference to this material defines embodiments both specific to this material and representative of the CHA and other topologies set forth herein.
CHA-type zeolites possess the CHA framework topology (
Alkali cation containing SSZ-13 zeolites have been shown to adsorb CO2 due to the strong electric field and acid-base interaction induced by the ions. The results presented herein (
As it was not possible to obtain high CO2 capacity using Na-CHA zeolites, alternative cation types were investigated for CO2 adsorption in CHA-type zeolites. Transition metals can be used for catalytic processes such as CO2 hydrogenation. Here, transition metals were explored for DAC. Several transition metals exchanged into CHA-type zeolites exhibited increased CO2 adsorption capacities as shown in
The Zn-CHA-type materials exhibit faster adsorption kinetics than 13×, as illustrated by the sharper breakthrough profile for Zn-CHA7-1.91E compared to 13× (
A series of Zn-CHA7 samples were prepared with fixed Al composition (Si/Al=7) and Zn/U.C. ranging from 0 to 6.60 (Table 5), where Zn/U.C. denotes the number of Zn ions per CHA unit cell, i.e., Zn ion density. As shown by the data in
The environments and states of Zn ions were examined to understand the CO2 adsorption behavior. As shown in
Quantitative analysis of 1H MAS NMR data suggests that Zn2+ (Tables 6-7) ions are the predominate species for at stage I that is with high adsorption efficiency, i.e., CO2/Zn. Correlation of the numbers of Zn2+ and CO2/U.C. gives a linear relation (
In order to assess the impact of framework topology on CO2 adsorption performance, several other zeolites were prepared that possess significant variations in topologies. Two groups of materials were selected: Group I (
Thus, the addition of Zn ions into CHA-type zeolites, e.g., SSZ-13, produced greatly enhanced performance for adsorbing low concentrations of CO2. The Zn ion containing zeolites exhibited higher CO2 capacity, faster kinetics, lower desorption energy than the standard low-silica 13× zeolites. Control of the state and location of Zn ions in the CHA cages was crucial to the high CO2 adsorption capacity. Zn2+ ions located at the D6MRs of SSZ-13 with Si/Al=ca. 7 gave an adsorption capacity of 0.51 mmol CO2/g-zeolite, a 17-fold increase compared to the parent H-form. Lowering the Si/Al to ca. 2 resulted in an increase of capacity to 0.67 mmol CO2/g-zeolite. The framework topology of the zeolite plays a key role in the performance of the Zn-exchanged materials by governing the position of divalent ions.
X-ray diffraction: The crystallinity of the materials was examined using powder X-ray diffraction (XRD). The XRD patterns were collected using a Rigaku Miniflex II desktop instrument with a Cu radiation source, Kα=1.5418 Å.
Scanning electron microscopy: The morphology of the materials was measured using scanning electron microscopy (SEM, ZEISS 1550 VP FESEM). The SEM was equipped with an Oxford X-Max SDD. Energy dispersive X-ray spectroscopy (EDS) used for determining the element contents (e.g., Si/Al ratios) of each sample. Before measurement, all zeolites were coated with Pt of ca. 10 nm thickness to avoid charging effects.
All-solid-state, magic-angle spinning nuclear magnetic resonance: All-solid-state, magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra were obtained on a Bruker AVANCE 500 MHz (11.2 T) spectrometer using a 4 mm zirconia rotor with a Kel-F cap. 1H MAS NMR spectroscopy experiments were conducted on representative samples. Prior to the measurement, samples were loaded in the rotor and dehydrated under vacuum (10−2 Torr) at 400° C. for 12 h using a Schlenk manifold. The spectra were acquired at 500.1 MHz and a spinning rate of 12 kHz using a 90° pulse length of 4 s with varied cycle delay times depending on the relaxation time, and then were deconvoluted using Origin 9.1. Signal intensities corresponding to the Brønsted acid sites were referenced to hexamethyl benzene and normalized by the sample mass to quantify the acid site density (mmol/g). The 1H-decoupled 29Si MAS NMR spectra were acquired without dehydration at 99.3 MHz and a spinning rate of 8 kHz using a 90° pulse length of 4 μs with a cycle delay time of 60 s. Framework Si/Al ratios were calculated using eq. S1, where I denotes the intensity of the 29Si NMR signal and nmax=2 in the present case. See C. A. Fyfe, et al., Zeolites 1985, 5, 179-183. Equation 51:
aElemental analysis of ca. 40 crystals using EDS.
bThe values were calculated from 29Si NMR.
Solid-state NMR (13C and 29Si) spectra were obtained using a Bruker DSX-500 spectrometer (11.7 T) and a Bruker 4 mm MAS probe. The spectral operating frequencies were 500 MHz, 125.7 MHz, and 99.4 MHz for 1H, 13C, and 29Si nuclei, respectively. Spectra were referenced to external standards as follows: tetramethylsilane (TMS) for 1H and 29Si and adamantane for 13C as a secondary external standard relative to tetramethylsilane. Samples were spun at 14 kHz for 1H NMR and 8 kHz for 13C and 29Si MAS and CPMAS NMR experiments.
Fourier transform infrared spectroscopy: Fourier transform infrared (FT-IR) spectra were collected on zeolite samples using a Nexus 470 FT-IR spectrometer equipped with a s deuterated, L-alanine doped triglycine sulfate (DTGS) detector. Catalyst samples (˜10-12 mg) were pressed into a self-supporting wafer (ca. 1.2 cm in diameter) and placed in a custom-built FT-IR cell. The wafers were treated in flowing dry air at 723 K for 120 min, and then cooled to RT for CO2 adsorption under flowing dry air for 30 min. Spectra were collected with a resolution of 4 cm−1 and averaged over 64 scans. The baseline correction and spectrum normalization follow previously reported method by Gounder et. al. using the framework Si—O—Si combination/overtone band between 2100 and 1750 cm−1. See C. Paolucci, A. A. et al., J. Am. Chem. Soc. 2016, 138, 6028-6048.
UV-Vis diffuse reflectance spectroscopy: UV-Vis Diffuse reflectance (DR) spectra were recorded on a Cary 5000 UV-Vis-NIR spectrometer in a 200-800 nm wavelength range.
Thermogravimetric analysis (TGA) was performed on a Perkin Elmer STA 6000 with a ramp of 10° C. min−1 to 900° C. under air atmosphere. Samples (0.01-0.06 g) were placed in aluminum crucible and heated at 10 K/min in a flowing stream (0.333 cm3/s) comprised of compressed air (Airgas).
Unless otherwise noted, all reagents were purchased from commercial sources and were used as received. Unless otherwise noted all, reactions were conducted in flame-dried glassware under an atmosphere of argon.
All materials for synthesizing zeolites were used as-received without further purifications from the stated vendors. The moisture contents of the solid sources were determined by thermogravimetric analysis (TGA). Ludox-AS40 (40 wt % silica dispersed in water, Sigma-Aldrich) and sodium silicate (homemade, SiO2: 38.3 wt %, SiO2/Na2O: 3.22) were used as silica source. Aluminum sources are aluminum isopropoxide (≥98%, Sigma-Aldrich), aluminum hydroxide powder (63 wt % Al2O3, Pfaltz & Bauer), Reheiss F2000 (Al(OH)3, 45% H2O) and FAU zeolites with a Si/Al ratio of 12 (denoted as FAU2). The organic structure directing agents (OSDAs) are N,N,N-trimethyl-1-adamantammonium hydroxide (25 wt % in H2O, TMAdaOH, Sachem), N,N-dimethyl-2,6-dimethylpiperidiunim hydroxide (home synthesized), 1,4-diazabicyclo[2.2.2]octane-C4-diquat dibromide. Alkaline aqueous solutions are NaOH (10 wt %, homemade), NaOH (50 wt %, Sigma-Aldrich), NaOH (1M, VWR), KOH (45 wt %, Sigma-Aldrich). The salts used for ion exchange are zinc(II) acetate dihydrate (Zn(CH3CO2)2.2H2O, ≥98%, Sigma-Aldrich), copper(II) nitrate trihydrate (Cu(NO3)2.3H2O, 99-104%, Sigma-Aldrich), zirconium(IV) oxynitrate hydrate (ZrO(NO3)2.xH2O, 99%), indium(III) nitrate hydrate (In(NO3)3.xH2O, 99.9%, Sigma-Aldrich), iron(III) nitrate nonahydrate (Fe(NO3)3.9H2O, 99.95%, Sigma-Aldrich), cobalt(II) nitrate hexahydrate (Co(NO3)2.6H2O, ≥98%, Aldrich).
CHA-Type Zeolites (SSZ-13 and High Aluminum CHA-Type)
The synthesis of SSZ-13 zeolite with Si/Al ratio higher than 5 was modified from the method in international zeolite association (http://www.iza-online.org/synthesis/default.htm). A molar ratio of 1 SiO2/X Al2O3/0.2 TMAdaOH/0.2 NaOH/44 H2O was used in the synthesis solution (X was calculated based on the targeting Si/Al). Typically, a 25% solution of the OSDA (TMAdaOH) was added to NaOH aqueous solution and stirred for 10 min at room temperature (RT). Then aluminum isopropoxide was added. After 21 h stirring at RT, Ludox-40 was added and stirred 26 h before charging the solution into Teflon-lined Parr autoclaves. SSZ-13 zeolites with lower Si/Al ratio (Si/Al=5) was synthesized following the method from Deimund et al. See M. A. Deimund, et al., ACS Catal. 2016, 6, 542-550. The molar composition of the synthesized gel is: 1 SiO2/0.078 Al2O3/0.2 TMAdaOH/0.2 NaOH/40 H2O. Reheiss F2000 and fumed silica were the aluminum and silicon source, respectively. The gel was stirred until it was homogeneous. The solution was placed in a Teflon-lined Parr autoclave and heated in a rotating oven to 160° C. for approximately 7 days.
High-aluminum CHA-type zeolites (Si/Al=ca. 2, CHA2) were synthesized using the method reported by Liu et al. See B. Liu, et al. Microporous Mesoporous Mater. 2014, 196, 270-276. The molar ratio in the gel was: 1SiO2:0.2Al2O3: 0.39K2O:0.3NH4F:35H2O. First, aluminum hydroxide was dissolved in a KOH aqueous solution, which was under heating at 80° C. After cooling down, required amount of ammonium fluoride and colloidal silica were added. This mixture was stirred at room temperature for 6 h to form a milk-like gel. The gel was loaded into Teflon-lined Parr autoclaves and hydrothermally treated at 150° C. for 7 days. It should be noted that CHA-type zeolites with Si/Al=2 (denoted as CHA2(a)) were also prepared from the hydrothermal conversion of zeolite Y (FAU-type) following the International Zeolite Association synthesis method. In a typical synthesis, 26.42 g of deionized water was mixed with 3.58 g of a potassium hydroxide solution (45 wt %, Sigma-Aldrich), to which 3.33 g of CBV500 (a NH4-form zeolite Y with Si/Al of 2.6 from Zeolyst) were added. The mixture was shaken for about 30 s and heated in a sealed polypropylene vessel at 100° C. for 14 days under static conditions. However, the CHA material converted from FAU showed small pore volume (0.05 m3/g, Table 3) after zinc loading, consistent with the recent results from Hong et al. See J. G. Min, K. C. Kemp, K. S. Kencana, S. B. Hong, Microporous Mesoporous Mater. 2021, 323, 111239.
The synthesis of K-SSZ-13 zeolite, denoted as CHA(K)7, follows the reported method by Gounder et al. See J. R. Di Iorio, S. Li, C. B. Jones, C. T. Nimlos, Y. Wang, E. Kunkes, V. Vattipalli, S. Prasad, A. Moini, W. F. Schneider, R. Gounder, J. Am. Chem. Soc. 2020, 142, 4807-4819. A molar ratio of 1 SiO2/0.0167 Al2O3/0.1 TMAdaOH/0.4 KOH/44 H2O was used in the synthesis solution. In a typical synthesis, an aqueous solution of TMAdaOH (25 wt %, Sachem) was added to distilled water and stirred for 15 minutes under ambient conditions. Then, an aqueous KOH solution (45 wt % in deionized water, Sigma-Aldrich) was added to the TMAdaOH solution and stirred at ambient conditions for 15 minutes. Next, aluminum hydroxide powder (63 wt % Al2O3, Pfaltz & Bauer) was added and stirred for 15 minutes under ambient conditions. Finally, an aqueous colloidal silica solution (Ludox AS40, 40 wt %, Sigma-Aldrich) was added and the contents were covered and stirred for 2 h under ambient conditions. The resulting mixture was charged into Teflon-lined Parr autoclaves and heated to 160° C. for 6 days under static conditions.
SSZ-39 (AEI)
The synthesis of SSZ-39 follows the previously reported method by the Davis group. See M. Dusselier, et al., Chem. Mater. 2015, 27, 2695-2702. A molar ratio of 1 SiO2/0.0167 Al2O3/0.14 OSDA/0.57 NaOH/28 H2O was used in the synthesis solution. First, 3.00 g of home synthesized organic OSDA (N,N-dimethyl-2,6-dimethylpiperidinium hydroxide, 0.7008 mmol/g aqueous solution) were combined with 0.13 g NaOH (10 wt % aqueous solution) and 2.89 g water in a 23 mL Teflon-lined Parr autoclave followed by 20 min stirring under ambient condition. Then, 2.95 g home-made silica source (sodium silicate, SiO2 27.97 wt %, Na2O 8.66 wt %, H2O 63.38 wt %) as well as aluminum source (CBV500, a NH4-form zeolite Y with Si/Al of 2.6 from Zeolyst) were added. After 1 h vigorous stirring, a homogeneous gel was obtained. The Teflon-lined Parr autoclave was then sealed and placed in a rotating oven at 140° C. for 7 days.
SSZ-16 (AFX)
Zeolite SSZ-16 was synthesized using the method reported by Zones et al. See S. I. Zones, Zeolite SSZ-16, 1985, U.S. Pat. No. 4,508,837A. A homogeneous solution was prepared by mixing 0.22 g of 1,4-diazabicyclo[2.2.2]octane-C4-diquat dibromide, 0.41 g of the FAU12, 0.99 g of homemade sodium silicate reagent (38% SiO2, SiO2/Na2O=3.3), 4.5 g of 1 N NaOH solution and 0.7 g of water. This mix gives an overall OH−/SiO2 of 0.80. The solution is charged into Teflon-lined Parr autoclaves and heated to 135° C. for 4 days in a rotatory oven.
Zeolite 13X (FAU-type) and 4A (LTA-type)
4A and 13X were obtained from Sigma-Aldrich.
After the synthesis of materials containing OSDAs was finished, the resulting solids were washed three times with distilled water followed by acetone washing. The crystals were dried overnight at 80° C. before calcining in air at 580° C. for 8 h, with a ramp rate of 1.0° C.min−1, to remove the OSDAs. Crystallinity was evaluated by XRD.
Aqueous-Phase Ion-Exchange of Zeolites
Metal-zeolites were prepared by aqueous phase cation ion exchange of calcined zeolites with corresponding salt solutions. Typically, 600 mg of zeolites were added to 30 mL of salt solutions, which were then stirred at 80° C. for 24 h. Metal-zeolites were recovered via centrifugation with or without 6 times washing using distilled H2O, and the materials were named with and without IE correspondingly. For FAU-type and LTA-type zeolites, ion exchange was performed at room temperature (RT) for 2 days to prevent the dissolution of the materials. The exchanged crystals were dried at 100° C. in ambient air in a free convention oven overnight.
A similar ion exchange procedure was used to prepare samples for the study of speciation of zinc ions in SSZ-13. Depending on the targeting zinc exchange level, 30 mL of 0.001 M to 0.05 M aqueous zinc acetate solution were used as the precursor. The Zn2+ solution was adjusted to a pH value of 4.92±0.02 before dispersing NH4-SSZ-13 zeolites using 0.1 M HCl aqueous solution, and then the solution was stirred at 80° C. for 24 h. The materials were recovered by centrifugation and washed 6 times with copious amount of distilled water. The exchanged crystals were dried at 100° C. overnight.
To titrate the paired aluminum sites in the double six membered rings (D6MRs) in CHA zeolites using Co2+, (see J. R. Di Iorio, R. Gounder, Chem. Mater. 2016, 28, 2236-2247; C. T. Nimlos, et al. Chem. Mater. 2020, 32, 9277-9298) the as prepared CHA-type zeolites were first NH4+-exchanged followed by converting to their proton form (H-form) by heating to 580° C. under flowing dry air for 8 h, with a ramp rate of 1.0° C.min−1. Then the H-form CHA was added to a 0.25 M aqueous solution of Co(NO3)2 (150 mL·g, >98 wt %, Aldrich) and stirred at 80° C. for three times (5 h, overnight and 5 h) without pH control. This procedure is closely similar to Gounder's method. See C. T. Nimlos, et al., Chem. Mater. 2020, 32, 9277-9298. This process was repeated three times (5 h, overnight, 5 h) followed by 6 times wash with copious amount of distilled water.
aElemental analysis was performed using EDS.
bMicropore volumes were calculated from N2 adsorption data. The results show comparable micropore pore volumes (0.18-0.21 cm3/g) for Zn-CHA7 with Zn loading lower than 6.60 Zn/U.C.
cThe CHA2(a) and CHA2 materials were converted from FAU zeolites and directly synthesized from amorphous gel respectively.
The zeolite performance for CO2 adsorption was tested using fixed bed column breakthrough experiments (
aZn-CHA7-0.5IE denotes CHA zeolites with a Si/Al ratio of 7 was exchanged by 0.5M Zn2+ aqueous solution. If IE was not included, the material was not washed with distilled water after ion exchange.
bThe adsorption experiments were performed at 30° C. for a gas mixture of 400 ppm CO2/400 ppm Ar (internal standard)/He.
cThe CHA2(a) and CHA2 materials were converted from FAU zeolites and directly synthesized from amorphous gel, respectively. The low capacity for Zn-CHA2(a)-1.9IE is due to the small pore volume (Table 3).
The TPD experiments were carried out in the same setup as in the column breakthrough measurements. Zeolites with comparable dry mass (ca. 77.61 mg, sieved size: 160-600μm) were loaded in a quartz tubing. Prior to TPD experiments, the samples of zeolites were outgassed at 550° C. for 24 h under a 20 mL·min−1 flow of 500 Ar/He gas. After the temperature was lowered to 30° C., the samples were saturated with a gas stream of 400 ppm CO2/400 ppm Ar (internal standard)/He at a flow rate of 20 mL·min−1. After saturation, TPD experiments were carried out by switching the gas stream to 5% Ar/He at a flow rate of 20 mL·min−1 and heating up with a constant ramp rate (2, 5, 10, 15, 20° C.min−1). Simultaneously, the signal of CO2 was detected using a mass spectrometer with m/e=44 amu.
Desorption kinetic parameters of CO2 from 13X and Zn-CHA7-1.9IE zeolites were estimated using temperature programmed desorption (TPD). The method developed by Cvetanovic and Amenomiya was applied with assumption of 1st order desorption and homogeneous adsorption surfaces. See R. J. Cvetanović, Y. Amenomiya, in Adv. Catal. (Eds.: D. D. Eley, H. Pines, P. B. Weisz), Academic Press, 1967, pp. 103-149. Generally, a linear relationship between 2 ln(Tm)−lnβ and 1/Tm can be established (equation 2).
Where Tm is the temperature of peak maximum (in K), β is the constant heating rate (in K.s−1), Ed is the activation energy for desorption, A is pre-exponential factor for desorption, R is universal gas constant (8.314 J.K−1.mol−1). Therefore, the activation energy (Ed) and pre-exponential factor (A) for desorption can be obtained from the slope and intercept of a plot of 2 ln(Tm)−lnβ=f(1/Tm), respectively. The activation energy (Ed) for desorption obtained is contributed from the intrinsic activation energy for desorption, diffusion and readsorption. See R. E. Richards, L. V. C. Rees, Zeolites 1986, 6, 17-25. In particular for porous materials like zeolites, where diffusion and readsorption from the micropores are inevitable. See X. Xia, et al., J. Phys. Chem. C 2007, 111, 6000-6008.
The interaction strength between CO2 and zeolites is often indicated using isosteric heat/entropy of adsorption, Qst or ΔHads, that is derived from two to three isotherms measured at different temperatures. In the present work, TPD experiments were performed to directly evaluate the energy required for desorption of CO2 from zeolites. As shown in Table 4, the desorption energy is 47.93 kJ.mol−1 for 13× after saturated with 400 ppm CO2. This value is within the range of adsorption energy (46-49 kJ.mol−1) for CO2 in zeolites at zero coverage. See A. Khelifa, et al., Microporous Mesoporous Mater. 1999, 32, 199-209; T.-H. Bae, et al., Energy Environ. Sci. 2012, 6, 128-138. In the situation of physisorption the adsorption heat released from the adsorption process is the reverse of the desorption heat. See A. Nuhnen, C. Janiak, Dalton Trans. 2020, 49, 10295-10307. As CO2 molecules primarily/exclusively physisorbed in zeolites, the results obtained from TPD also reflects the adsorption heat. Therefore, the consistency between the desorption energy measured in this work and the reported adsorption energy validates the method used herein.
aIon exchange experiments were performed in Zn2+ aqueous solution with pH adjusted to 4.92 by adding 0.1M HCl aqueous solution. If not labeled, pH was not controlled for those materials during ion exchanges.
bThe adsorption experiments were performed at 30° C. for a gas mixture of 400 ppm CO2/400 ppm Ar (internal standard)/He.
The state of the Zn ions was qualitatively analyzed by studying the OH stretch region (
Further, the fraction of Zn2+ and Zn(OH)+ was quantitatively calculated using the residual H+ density obtained from the 1H NMR results (
aIon exchange experiments were performed in Zn2+ aqueous solution with pH adjusted to 4.92 by adding 0.1M HCl aqueous solution. If not labeled, pH was not controlled for those materials during ion exchanges.
As the data shown in
aIon exchange experiments were performed in Zn2+ aqueous solution with pH adjusted to 4.92 by adding 0.1M HCl aqueous solution. If not labeled, pH was not controlled for those materials during ion exchanges.
bMeasured by EDS mapping of the area containing at least 100 crystals.
cTotal Zn ions per unit cell SSZ-13 calculated from the EDS results.
dZn2+ or Zn(OH)+ cations per unit cell SSZ-13 calculated from the EDS results and 1H density in Table 6.
Previous studies suggest that paired aluminum sites are preferentially located in the D6MRs in the CHA cages for SSZ-13 zeolites synthesized using methods similar to this work with Na+as the inorganic mineralizer. See J. R. Di Iorio, et al., J. Am. Chem. Soc. 2020, 142, 4807-4819; C. Paolucci, A. A. et al., J. Am. Chem. Soc. 2016, 138, 6028-6048. Moreover, Co2+ titration of the density of paired aluminum sites in the D6MRs shows a CO2+/Al ratio of 0.20 (Table 8). See J. R. Di Iorio, et al., J. Am. Chem. Soc. 2020, 142, 4807-4819.
This value is the same to the highest Zn2+/Al obtained at the end of stage II. Therefore, the pre-formed Zn(OH)+in the D6MRs may then be converted into Zn2+. This transformation is responsible for the increase of Zn2+ at stage II. Thus, it contributes to a relatively constant fraction of Zn2+ species as well as adsorption efficiency. Although Na+ can also stabilize paired aluminum sites in the 8MRs, see J. R. Di Iorio, et al., J. Am. Chem. Soc. 2020, 142, 4807-4819, these sites would be excluded for accommodating Zn2+ in the present work for the following reasons: 1) The paired aluminum density in the D6MRs is equal to the highest Zn2+ density obtained; 2) Using K+ directed CHA as a control, it was demonstrated that Zn2+ in the 8MRs is likely inactive for CO2 adsorption, while a sharp increase of CO2 capacity is observed at stage II in
Control experiments were performed to further identify the adsorption sites in Zn-CHA zeolites. The state and location/environment of Zn ions are crucial for CO2 adsorption. To further study this, CHA zeolites were prepared with a Si/Al of ca. 7 with the K+ as the mineralizer, denotated as CHA(K)7. Gounder et al. has demonstrated the predominate presence of isolated aluminum in the D6MRs in K-directed CHA with a Si/Al of 10 and that this material is unable to coordinate bivalent cations in the D6MRs. See J. R. Di Iorio, et al., J. Am. Chem. Soc. 2020, 142, 4807-4819. CHA(K)7 zeolites were prepared using the same method. Co2+-titration showed (Table 8) a Co/Al ratio of 0.02±0.02, suggesting that the CHA(K)7 is free of paired aluminum sites in the D6MRs.
Similar to the CHA7 material, Zn ions were exchanged into CHA(K)7 with various loadings. FT-IR spectra (
aIon exchange experiments were performed in Zn2+ aqueous solution with pH adjusted to 4.92 by adding 0.1M HCl aqueous solution. If not labeled, pH was not controlled for those materials during ion exchanges.
bMeasured by EDS mapping of the area containing at least 100 crystals.
cCalculated from 1H MAS NMR spectra.
dTotal Zn ions per unit cell CHA calculated from the EDS results.
eZn2+ or Zn(OH)+ ions per unit cell SSZ-13 calculated from the EDS results and 1H density in Table 8.
The CO2 adsorption performance was examined for Zn-CHA(K)7 zeolites with various Zn loadings. The results (Table 9 and
With this discussion, one may argue that Zn(OH)+ could be the primary sites for CO2 molecules adsorbed in CHA cages. However, it should be noted that the adsorption capacity for CO2 in Zn-CHA7 and Zn-CHA(K)7 are greatly different, with the former showing almost two-fold capacity (0.51 vs. 0.28 mmol/g) under the same ion exchange condition. Moreover, the present work shows that all Zn2+ in the D6MRs are active adsorption sites for CO2 molecules, while only limited fraction Zn(OH)+ in the D6MRs are able to adsorb CO2. Therefore, these results suggest that Zn2+ ions in the D6MRs are the primary adsorption sites and that Zn(OH)+ species at D6MRs are extra possible sites. Therefore the Al distribution in the framework with maximizing Al located in D6MRs as 2Al sites has a critical effect on enhanced CO2 adsorption performance.
As those skilled in the art will appreciate, numerous modifications and variations of the present invention are possible in light of these teachings, and all such are contemplated hereby. All of the references cited herein are incorporated by reference herein for all purposes, or at least for their teachings in the context presented.
In some embodiments, the disclosure is directed to the following aspects:
This application claims the benefit of U.S. Provisional Application No. 63/154,334, filed Feb. 26, 2021, and U.S. Provisional Application No. 63/237,180, filed Aug. 26, 2021. Each of the aforementioned applications is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63154334 | Feb 2021 | US | |
| 63237180 | Aug 2021 | US |
