EP4658399A1

EP4658399A1 - Sorbent structures for carbon dioxide capture and methods for making thereof

Info

Publication number: EP4658399A1
Application number: EP24701893.0A
Authority: EP
Inventors: Lennart VAN HAANDEL; Alexander Willem Van Der Made; Peter John Van Den Brink; Sayee Prasaad BALAJI; Santosh GANJI; Ravi Agrawal
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2023-02-03
Filing date: 2024-01-24
Publication date: 2025-12-10
Also published as: AU2024216218A1; CL2025002294A1; CN120659666A; WO2024160606A1

Abstract

A sorbent structure comprising: a first end and a second end; a plurality of flow channels; and a plurality of channel walls. The channel walls comprise a carbonate in an amount in a range from greater than 5 wt% and up to 50 wt%. The channel walls further comprise a metal-containing support in an amount in a range from 40 wt% and up to 95 wt%. The metal-containing support is selected from the group consisting of a metal alloy, metal oxide, metal-non-metal alloy, ceramic, and any combination thereof. The metal- containing support comprises a total accessible porosity (ε) in a range from 0.4 – 0.8. A surface of the metal-containing support comprises a reaction product between the metal-containing support and a passivating material, wherein the reaction product being less reactive to the carbonate than the metal-containing support without the reaction product.

Description

SP2905 SORBENT STRUCTURES FOR CARBON DIOXIDE CAPTURE AND METHODS FOR MAKING THEREOF Field of the Invention [1] The present specification generally relates to the field of carbon dioxide capture, and more specifically, to sorbent structures for capturing carbon dioxide (CO2) from a gas stream and methods for making and using same. Background of the Invention [2] This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of any prior art. [3] The atmospheric carbon-dioxide (CO₂) level is increasing at least in part due to emissions from various sources, including industrial sites like thermal power plants, oil refineries, and other processing plants such as cement, steel, aluminium, and the like. The increased level of atmospheric carbon-dioxide (CO2) has been linked to global warming. Various technologies are being used and/or developed to reduce the amount of CO2 emitted into the atmosphere as one precautionary measure to address global warming. In addition, various governments have established or plan to establish programs that either provide economic incentives to reduce CO₂ emissions and/or regulations limiting CO₂ emissions, all of which encourage the development of CO2 capture technologies. [4] One such type of CO₂-reduction technologies involves capturing or removing CO2 from a gas stream using a sorbent. The sorbent typically comprises a significant portion of the overall capital and operating costs, particularly in sorbent replacement. The performance of the sorbent, in terms of capacity and stability, has a direct economic impact. For instance, a process would need less amount of a better performing (more efficient) sorbent to capture a similar amount of CO2 from the same volume of gas stream, which can result in lower capital and operating costs. Current known sorbents and processes for capturing CO2 from a gas stream, however, still suffer from low efficiency and/or are too costly. [5] For instance, a number of sorbents employ organic amines to capture carbon dioxide, which are prone to oxidation, thereby increasing the chance of sorbent degradation SP2905 and loss of CO2 sorption capacity over time. These sorbents include WO2010027929A1, WO2017009241A1, WO2010091831A1, and WO21189042A1. [6] WO21189042A1 further discloses a solid mass formed of sintered, compact, mesoporous particles, the particles being sintered together so as to be structurally coherent; wherein each of the particles is mesoporous and the solid sintered mass is macroporous. The solid mass further comprising a plurality of longitudinal channels extending between and opening through opposing faces of the solid mass. The exposed walls of the channels are formed of the sintered mesoporous particles and contain a sorbent for CO2 in its mesopores. WO21189042A1 discloses various coating methods to achieve the sintered coating of mesoporous particles, which can lead to lower volumetric CO2 capture capacity. [7] Another set of sorbents use potassium carbonate as a sorbent for CO₂, which addresses the increased chance of oxidation of amine. They, however, disclose capturing carbon-dioxide from a gas stream using adsorbent particulates. For instance, the adsorbent particulates of WO2016185387A1 are transported from the adsorber to the desorber in a circulating fluidized bed. The adsorbent material comprising potassium carbonate impregnated support is crushed and sieved to form the particulates. Likewise, US20210016220 discloses a plurality of fixed sorbent beds that contain an alkalized sorbent. [8] Similarly, US2021187480A1 discloses a particulate activated carbon material for capturing CO2 from air. The particulate activated carbon is impregnated with alkali carbonate salt such as K₂CO₃. Also, the paper “Sorption of carbon dioxide by the composite sorbent ‘potassium carbonate in porous matrix’” (Okunev, A. et al., Russian Chemical Bulletin 2003, 52. 359-363) discloses particulates of potassium carbonate on alumina for flue gas capture. [9] The paper by Rodríguez-Mosqueda et al. (Parametrical Study on CO₂ Capture from Ambient Air Using Hydrated K2CO3 Supported on an Activated Carbon Honeycomb, Ind. Eng. Chem. Res.2018, 57, 3628−3638, 6) discloses an activated carbon honeycomb monolith that was coated with K2CO3 and treated with moist N2 to hydrate it. [10] Moreover, large-scale carbon dioxide capture generally involves a large number of adsorption and regeneration cycles for the sorbent (such as at least 500 cycles), which can introduce structural instability to the sorbent (e.g., wear and tear over time after a large number of cycles). While stability of certain material has been examined, it has been under extreme conditions, such as very high temperatures and/or pressures and do not relate to an application in carbon dioxide capture. On the other hand, direct air capture generally takes SP2905 place in ambient temperature and atmospheric pressure for adsorption and slightly higher temperature and pressure than ambient for regeneration. An example of a reference examining thermal stability of certain material includes Tijburg, Ivo Ignatius Maria, John Wilhelm Geus and H. W. Zandbergen. “Application of lanthanum to pseudo-boehmite and 5 γ-Al2O3.” Journal of Materials Science 26 (1991): 6479-6486. [11] As such, there still exists a need for sorbents that provide efficient capturing of CO2 from a gas stream. [12] Summary of the Invention 10 [13] According to one aspect, there is provided a method for reducing reactivity between a metal-containing support and a carbonate of a sorbent structure for capturing carbon dioxide from a gas mixture. The method comprises: (a) providing a material to form a metal-containing support; wherein the metal- containing support material comprises a metal and is selected from the group 15 consisting of a metal alloy, metal oxide, metal-non-metal alloy, ceramic, and any combination thereof, (b) adding a passivating material or a precursor thereof to the metal-containing support material from step (a) to form a combined formulation of metal- containing support material and passivating material, wherein the passivating 20 material being present in an amount in a range from 0.1 wt% and up to 20 wt% and the metal-containing support material being present in an amount from 40 wt% and up to 99.9 wt%, based on the total weight of the combined formulation; (c) forming a structure from the combined formulation, wherein the structure 25 comprises: o a first end and a second end; o a plurality of flow channels; and o a plurality of channel walls, wherein the flow channels are formed by at least one channel wall, 30 wherein the flow channels extend from the first end to the second end, wherein optionally, step (b) occurs before or after step (c); (d) heating the formed structure to produce a treated structure, wherein the heating causes at least a portion of the metal-containing support material to react with at SP2905 least a portion of the passivating material to form a reaction product on at least a portion of a surface of the metal-containing support of the treated structure (e) providing a carbonate to the metal-containing support material or the metal- containing support to generate a sorbent structure, wherein the sorbent structure comprises a plurality of channel walls comprising (i) a metal-containing support comprising the metal-containing support material and (ii) the reaction product and carbonate on a surface of the metal-containing support; wherein optionally, step (e) occurs simultaneously with steps (a) and (b) or step (e) occurs after step (d) wherein the metal-containing support of the sorbent structure comprises a total accessible porosity (ε_support) in a range from 0.4 – 0.8, preferably 0.5 – 0.7; wherein the total accessible porosity of the metal-containing support (εsupport) is determined at least by: εsupport = WPVsupport/(WPVsupport + 1/ρsupport) where WPV_support is the gravimetric water pore volume (ml/g) of the metal-containing support and where ρsupport is the gravimetric skeletal density of the metal-containing support wherein the carbonate is provided in an amount in a range from greater than 5 wt% and up to 50 wt%, preferably greater than 5 wt%, including from 10 wt% and up to 30 wt%, based on the total weight of the channel walls of the sorbent structure, wherein the carbonate being at least one of (i) an alkali metal (X₂CO₃) and (ii) an alkaline earth metal (YCO₃); wherein the reaction product being less reactive to the carbonate than the metal- containing support material. [14] Optionally, the passivating material is one or more lanthanides, wherein the one or more lanthanides being selected from a group consisting of lanthanum (La), Praseodymium (Pr), Dysprosium (Dy), Lutetium (Lu), Cerium (Ce), an oxide of each of the foregoing, and any combination thereof. [15] Optionally, the passivating material is selected from the group consisting of boron (B), boron oxide, phosphorus (P), phosphorus oxide, and any combination thereof. [16] Optionally, the passivating material being selected from zinc, zinc oxide, or a combination thereof, wherein step (e) occurs after step (d). SP2905 [17] Optionally, the metal-containing support comprises alumina in an amount in a range from 80 wt% and up to 99.9 wt% of the total weight of the metal-containing support. [18] Optionally, the step of providing the metal-containing support with a passivating material comprises heating the metal-containing support in a gaseous stream comprising ammonia. [19] Optionally, the passivating material is provided in an amount in a range from 0.1 wt% and up to 5 wt%. [20] Optionally, the passivating material is provided in an amount in a range from 0.5 wt% and up to 20 wt%. [21] Optionally, the heating step comprises heating the formed structure at a temperature in a range from 300 °C and up to 1100 °C. [22] According to another aspect, there is provided a sorbent structure for capturing carbon dioxide from a gas mixture. The sorbent structure comprises: ^ a first end and a second end; ^ a plurality of flow channels; and ^ a plurality of channel walls, wherein the flow channels are formed by at least one channel wall, wherein the flow channels extend from the first end to the second end, and wherein the channel walls comprise: o a carbonate in an amount in a range from greater than 5 wt% and up to 50 wt%, preferably greater than 5 wt%, including from 10 wt% and up to 30 wt%, based on the total weight of the channel walls, wherein the carbonate being at least one of (i) an alkali metal (X₂CO₃) and (ii) an alkaline earth metal (YCO3); o a metal-containing support in an amount in a range from 40 wt% and up to 95 wt%, based on the total weight of the channel walls; wherein the metal-containing support comprises a metal and is selected from the group consisting of a metal alloy, metal oxide, metal-non-metal alloy, ceramic, and any combination thereof, wherein the metal-containing support comprises a total accessible porosity (εsupport) in a range from 0.4 – 0.8, preferably 0.5 – 0.7; wherein the total accessible porosity of the metal-containing support (ε_support) is determined at least by: SP2905 εsupport = WPVsupport/(WPVsupport + 1/ρsupport) where WPV_support is the gravimetric water pore volume (ml/g) of the metal-containing support and where ρsupport is the gravimetric skeletal density of the metal-containing support wherein a surface of the metal-containing support comprises a reaction product between the metal-containing support and a passivating material, wherein the reaction product being less reactive to the carbonate than the metal-containing support without the reaction product. [23] Optionally, the passivating material is one or more lanthanides, optionally the one or more lanthanides being selected from a group consisting of lanthanum (La), Praseodymium (Pr), Dysprosium (Dy), Lutetium (Lu), Cerium (Ce), an oxide of each of the foregoing, and the reaction product is selected from lanthanum aluminum oxides (such as LaAlO3, beta-LaAl11O18, xAl2O3*yLa2O3), praseodymium aluminum oxides (such as Pr AlO₃, xAl₂O₃*yPr₂O₃), dysprosium aluminum oxides (such as DyAlO₃, Dy₃Al₅O₁₂ or xAl2O3*yDy2O3), lutetium aluminum oxides (LuAlO3, Lu3Al5O12 and Lu4Al2O9 or xAl2O3*yLu2O3) (Lu), cerium aluminum oxides (CeAlO3 or xAl2O3*yCe2O3), and any combination thereof. [24] Optionally, the passivating material is selected from the group consisting of boron (B), boron oxide, phosphorus (P), phosphorus oxide, and any combination thereof and the reaction product is selected from aluminum borates (such as AlBO3, Al18B4O33, Al4B2O9 or xAl₂O₃*yB₂O₃), aluminum phosphates (such as orthophosphate (AlPO₄), aluminum metaphosphate (Al(PO3)3 and xAl2O3*yP2O5), and any combination thereof. [25] Optionally, the passivating material being selected from zinc, zinc oxide, or a combination thereof and the reaction product is xAl2O3*yZnO, such as ZnAl2O4 spinels. [26] Optionally, the passivating material is nitrogen and the reaction product is aluminum oxynitride. [27] Optionally, the metal-containing support further comprises silica. Optionally, the passivating material is nitrogen and the reaction product is silicon oxynitride. [28] Generally, for capturing carbon dioxide from a gas stream, it is desirable for the sorbent material to impose minimal pressure drop on the gas flow to minimize the energy required for moving the gas stream through the removal process and at the same time achieve maximum contact between the sorbent and the gas stream to maximize the mass transfer SP2905 rates of the CO2 to be removed from the gas stream. If the gas stream from which carbon dioxide is being captured is atmospheric air, the concentration of CO₂ available for capture is very low, in the atmospheric air, currently between 400 and 420 ppm, which is expected to rise in the future. In such scenario, very large air volumes have to flow through any capture system to extract a meaningful amount of CO2. The increase in energy demands from moving large amounts of air through the system while maintaining the desired CO2 capture efficiency is one of the primary factors in achieving economic feasibility. [29] As described herein, the sorbent structure and its various embodiments provides removal of carbon dioxide where a comparably small volume of sorbent structure can absorb a large amount of carbon dioxide in a short period of time. This is at least due to the relatively high total accessible porosity that enables the relatively high loading of carbonate to CO2 capture. The small volume of sorbent structure required decreases costs associated with building and operating carbon dioxide removal systems. The described structure, particularly parallel channels, also reduces the pressure drop experienced by the process gas passing through the sorbent structure. The reduced pressure drop reduces the operating cost due to the reduced fan power required to move the gas through the sorbent structure. [30] In addition, the present disclosure provides certain embodiments that mitigate the reactivity between the carbonate and the metal-containing support under certain direct air capture (DAC) conditions, particularly adsorption conditions such as: CO2 concentration of approximately 400 ppmv and ambient conditions (around atmospheric pressure of about 1 bar and temperature of the surrounding environment in a range of -20 °C to 50 °C), and desorption conditions: TSA process with regeneration temperatures 80 - 150 °C, steam as stripping medium. [31] For effective adsorption of CO₂, typical conditions include a relatively high pH in the total accessible porosity provided by the carbonate where it has at least a pH of 10. At such high pH, certain metal-containing support, such as alumina, is more soluble than at neutral pH. As such, the metal-containing support of various embodiments of the sorbent structure is reactive to the conditions created by the carbonate and/or the carbonate itself. For the sake of brevity, it should be understood that reference to reactivity to the carbonate includes reactivity to the conditions created by the carbonate. [32] Not wishing to be bound by theory, it is believed that the increased solubility is due to the metal-containing support, such as alumina, being more likely to form anionic species (Al(OH₄)- species), especially when subject to multiple adsorption and desorption SP2905 DAC cycles. The increased solubility of the metal-containing support, including alumina, can lead to continuous dissolution of certain component in different locations, which can cause several undesired effects. One example of such undesired effect is accelerated aging which involves dissolution of aluminium at places with high curvature (i.e. small positive 5 radii) and settlement of the dissolved aluminium at places with low (or negative) curvature. This phenomena is also known as Ostwald Ripening. Another example is phase changing. As a result of the dissolution, a meta stable aluminium oxide may recrystallize as a more stable aluminium hydroxide (e.g. gypsite). Specifically, if carbonate and alkali metal ions are present, the more stable phase may be Dawsonite (NaAlCO₃(OH)₂ or KAlCO₃(OH)₂), 10 which not only will modify the metal-containing support but also scavenge part of the active material (such as the carbonate). [33] Both processes (ripening and phase transition), which is believed to be related to the increased solubility of certain embodiments of the metal-containing support, can have detrimental influence on the structural dimensions and the structural integrity of the metal- 15 containing support. Brief Description of the Drawings [34] FIG.1 depicts an illustrative perspective view of an exemplary embodiment of a sorbent structure according to certain aspects described herein. [35] FIG.2 depicts an illustrative enlarged perspective view of an embodiment of a 20 sorbent structure according to certain aspects described herein, such as the sorbent structure depicted in FIG.1. [36] FIG.3 depicts an illustrative perspective, partial cross-sectional view along the length of another exemplary embodiment of a sorbent structure according to certain aspects described herein. 25 [37] FIG. 4 is an SEM (scanning electron microscope) image of a portion of the channel wall of an embodiment of a metal-containing support of the sorbent structure according to certain aspects disclosed herein. [38] FIG.5 illustrates a schematic representation of an exemplary DAC system in which embodiments of the sorbent structure disclosed herein can be employed. 30 [39] FIG.6 is a graph of anticipated results for Prophetic Example 5. Detailed Description of the Invention SP2905 [40] The present invention will now be described in detail with reference to embodiments thereof as illustrated in the accompanying drawings. References to “one embodiment”, “an embodiment” “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every 5 embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or 10 not explicitly described. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the art, are within the spirit and scope of the invention. [41] Although the description herein provides numerous specific details that are set forth for a thorough understanding of illustrative embodiments, it will be apparent to one 15 skilled in the art that embodiments may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention. The features and advantages of embodiments may be better understood with reference to the drawings and discussions that follow. 20 [42] In addition, when like elements are used in one or more figures, identical reference characters will be used in each figure, and a detailed description of the element will be provided only at its first occurrence. Some features or components of the systems or processes described herein may be omitted in certain depicted configurations in the interest of clarity. 25 [43] FIG.1 schematically depicts a perspective view of sorbent structure 100, which is an exemplary embodiment of the sorbents for capturing carbon dioxide from a gas mixture disclosed herein. FIG.2 schematically depicts an enlarged view of sorbent structure 100, and FIG.3 schematically depicts a sectional view of sorbent structure 100 along its length 112. Although sorbent structure 100 is depicted as having a generally rectangular block30 shape (or cuboid), it is understood that sorbent structure 100 can have any suitable cross- sectional shape, including geometrical shapes such as trapezoidal, triangular, rectangular, square, sinusoidal, hexagonal, oval, circular, and the like. In the embodiment shown in FIGS.1 - 3, sorbent structure 100 comprises first end 102 and second end 104. Referring SP2905 to FIG.2, sorbent structure 100 further comprises a plurality of flow channels 106, and a plurality of channel walls 108. [44] Flow channels 106 are formed by at least one channel wall 108 and extend from first end 102 to the second end 104. Flow channels 106 have a shape formed by at least one 5 (such as two or more) channel wall. The shape of flow channels 106 is preferably a polygon, more preferably selected from triangle, square, and hexagon, trapezoid, rectangular, sinusoid, or round like oval or round. Flow channels 106 preferably provide parallel flow passages extending from an inlet face (e.g., 102) to an outlet face (e.g., 104) of the substrate such that passages are open for fluid to flow through sorbent structure 100. 10 [45] As described herein, essentially all flow channels 106 can have substantially the same shape, or additionally or alternatively, a portion of flow channels 106 may take on different shapes as compared to the remaining portion of flow channels 106, depending on other specifications, such as the overall configuration of sorbent structure 100. For instance, at least a major portion (>50%, preferably >80%), including all, of flow channels 15 106 has a polygon or circular shape; if polygon, preferably selected from the group consisting of a triangle, rectangle, square, hexagon, and any combination thereof. For example, in an embodiment where the sorbent has a cylindrical shape, it is understood that the inner flow channels around the center may have different shape (such as square) than the flow channels at the circular edge, which are defined by a circular outer channel wall. 20 [46] Flow channels 106 preferably occupies a relatively large amount of the front cross-sectional area such that resistance of the flow of gas through the channels is relatively low, thus minimizing the pressure drop which is the energy needed to force the gas through sorbent structure 100. For instance, referring to FIG.2, sorbent structure 100 preferably comprises an open frontal area (OFA) or free cross-sectional area in a range from 60% and 25 up to 85%, and more preferably in the range 65% to 75%. As used herein, “open frontal area” or “free cross-sectional area” has its ordinary meaning. For instance, a sorbent structure that has an OFA of 60%, it means that 60% of the cross-sectional area of the frontal area (e.g., 102 or 104) is open for the flow of a gas through the sorbent structure. That is, the cross-sectional area of flow channels 106 occupies 60% of the cross-sectional area of the 30 sorbent structure. One way the number of flow channels 106 making up the OFA of sorbent structure 100 can be characterized is cell density, where certain dimensions of flow channels 106 (or “cell”) can be designed to meet various objectives, including OFA. SP2905 [47] For instance, referring to FIGS.1 and 2, an exemplary suitable sorbent structure, such as structure 100, with a cross-sectional square shape of 150 mm by 150 mm can have 1600 cells or flow channels 106 (40 cells by 40 cells), where each cell opening (d) is about 3.2 mm, and OFA of 72.8 %. Optionally, structure 100 can comprise a cell density in a range from 50 and up to 400 cells per square inch (cpsi), preferably in a range from 50 and up to 300 cpsi and open frontal area in a range from 60% and up to 85%, preferably in the range 65% to 75%. Additionally or alternatively, at least a portion of the channel walls 108 can further comprise an average thickness in a range from 150 microns and up to 1000 microns. It is understood that the thickness of channel walls 108 can vary from one portion of sorbent structure 100 to another portion, including whether a particular channel wall is an exterior wall. [48] Optionally, sorbent structure 100 can comprise a nominal cross-sectional area (for instance D² in FIGS 1 or π(0.5D)² in FIG.3 (with D being 110 as a side or diameter, respectively) if the sorbent structure had a square or cylindrical cross-sectional shape, respectively) of at least 10 x 10 mm², such as in a range from 50 x 50 mm² to 600 x 600 mm², preferably in a range from 100 x 100 mm² to 500 x 500 mm², more preferably in a range from 150 x 150 mm² to 300 x 300 mm². [49] Optionally, sorbent structure 100 comprises a length 112 (L) in a range of 50 mm to 2000 mm, preferably in a range from 100 mm to 1000 mm, and most preferably in a range from 200 mm to 500 mm. [50] Preferably, sorbent structure 100 is a monolithic unit that is self-supporting and comprises parallel flow channels 106 that extend from first end 102 to second end 104 (e.g., flow through monolith), such as a honeycomb structure. For instance, the metal-containing support provides structural integrity (functioning as a substrate) as well as functions as part of the active material to facilitate the sorption of CO2 by the carbonate. Such a monolithic unit may be formed using methods known in the art such as extrusion, co-mulling, 3-D printing and/or impregnation. [51] Channel walls 108 comprise a carbonate of at least one of (i) an alkali metal with a chemical formula of X2CO3 and (ii) an alkaline earth metal with a chemical formula YCO3 in an amount in a range from 5 wt% and up to 50 wt%, preferably greater than 5 wt% to 30 wt%, based on the total weight of the channel walls. Preferably, the X is an alkali metal cation selected from the group consisting of K⁺, Na⁺, Cs⁺, Li⁺, (thereby forming K2CO3, Na₂CO₃, Cs₂CO₃, Li₂CO₃), and any combination thereof. Preferably the Y is an alkaline SP2905 earth metal cation selected from the group consisting of Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, (thereby forming MgCO₃, CaCO₃, SrCO₃, BaCO₃) and any combination thereof. The recited weight amounts are preferably determined when the carbonate is in anhydrous form. [52] The wt% amount of carbonate in anhydrous form is preferably calculated from the wt% amount carbonate as determined by chemical analysis, preferably X-ray Fluorescence Spectroscopy (XRF). Before analysis of the wt% of carbonate is performed, the sample for testing is dried, preferably at around 300 °C for at least one hour, to determine the dry sample mass. The wt% amount of carbonate can be calculated using the following equation (A): Wcarbonate = Wmetal / f (A) where W_carbonate is the mass loading of carbonate on the sorbent (wt%), W_metal is the mass loading of the metal of the carbonate on the sorbent structure as determined by XRF (wt%) and f is the mass fraction of the metal of the carbonate in anhydrous or salt form, which can be calculated using the following equation (B): f = M_metal * n_metal / M_carbonate (B) where Mmetal is the molar mass of the metal (g / mol), Mcarbonate is the molar mass of the carbonate and nmetal is the number of moles of metal per mole of carbonate salt (for instance nmetal = 2 for potassium carbonate (K2CO3) and nmetal = 1 for magnesium carbonate (MgCO3). For instance, a sample of a sorbent structure according to aspects described herein was analysed with XRF, which showed a mass loading of the metal potassium (WK) on a dry basis of 4.33 wt%. The carbonate loading of potassium carbonate on the metal- containing support can be calculated using equations (A) and (B) as shown below. f = 39.10 (g/mol) * 2 / 138.205 g/mol = 0.566 (B) Wpotassium carbonate = 0.433 wt%/0.566 = 7.66 wt% of K2CO3 in anhydrous form in the sample of the sorbent structure analyzed (A). [53] The recited carbonates are hygroscopic salts with a tendency to absorb moisture from the air and becomes hydrated. The hygroscopicity of each carbonate can vary depending on the particular metal cation. Both the anhydrous and hydrated forms of the carbonates are prone to react with carbon dioxide and water to form a bicarbonate, thereby capturing the carbon dioxide as the bicarbonate. As such, the recited carbonates function as sorbents for CO2. SP2905 [54] Channel walls 108 further comprise a metal-containing support in an amount in a range from 40 wt% and up to 95 wt%, based on the total weight of the channel wall. The metal-containing support is preferably an inorganic material and comprises metal. The metal-containing support is preferably selected from the group consisting of a metal alloy, 5 metal oxide, metal-non-metal alloy, ceramic, and any combination thereof. The metal is selected from the group consisting of aluminium, calcium, silicon, titanium, zirconium, magnesium, iron, and any combination thereof. Preferably, the metal-containing support is selected from the group consisting of silica, alumina, titania, zirconia, cordierite, mullite, silicon carbide, aluminosilicates, preferably zeolites, aluminium phosphate, and any 10 combination thereof. More preferably, the metal-containing support is selected from the group consisting of alumina, titania, and any combination thereof. [55] The carbonate and metal-containing support are considered to be active material as known to one of ordinary skill. The present disclosure provides for sorbent structures that comprise a majority (greater than 50 wt%, more preferably greater than 80 wt% of the 15 total weight of the sorbent structure) of active material. [56] One preferred embodiment of the sorbent structure comprises an alkali metal salt, more preferably potassium carbonate and/or sodium carbonate, as the carbonate. For embodiments employing an alkali metal salt, it is preferred that the metal-containing support is one that minimally reacts with the alkali metal salt during carbon capture conditions. 20 Examples of such metal-containing support includes titania or zirconia. For instance, a preferred embodiment is a sorbent structure where the carbonate is selected from one or more alkali metal carbonate and where the metal-containing support is selected from titania, zirconia, or a combination thereof. [57] In another aspect, the reaction between the carbonate and metal-containing 25 support can be minimized at least by using a metal-containing support, particularly alumina, that has been thermally treated. Preferably, the metal-containing support can be selected from the group consisting of potassium aluminate, sodium aluminate (2NaAlO2═Na2O*Al2O3), hydrated alumina (Boehmite, Al2O3*H2O), bayerite, gibbsite, boehmite, pseudo-boehmite, bauxite, gamma-alumina, delta-alumina, chi-alumina, rho- 30 alumina, kappa-alumina, eta-alumina, theta-alumina, magnesium aluminate, trine, bermire, and any combination thereof. [58] The metal-containing support is porous, meaning it contains pores or spaces. In particular, the metal-containing support comprises a total accessible porosity (ε_support) in a SP2905 range from 0.4 and up to 0.8, preferably from 0.5 and up to 0.7. As known in the art, these ranges for the total accessible porosity (ε) of the metal-containing support can be expressed as percentages as well, from 40% and up to 80%, preferably from 50% and up to 70%. As used herein, the term “total accessible porosity” has its ordinary meaning, which includes the percentage or fraction of void space (i.e., pores) in a substance that is accessible to water (i.e., open pores). For this disclosure, the total accessible porosity of the metal-containing support refers to the percentage or fraction of void space in the metal-containing support that is accessible to water. [59] The higher the total accessible porosity the more accessible pores are present on the surface of a substance, which means the less rigid the substance, and vice versa. Although less rigid, having relatively more accessible pores enables a higher loading of a material of interest. Without wishing to be bound by theory, the inventors have found that the preferred range of at least 0.5, including from 0.5 and up to 0.7 or 0.8, provides more accessible space or voids in the support or channel walls to contain the carbonate, thereby allowing for relatively greater amounts of loading of the carbonate while still allowing the metal-containing support to provide structural integrity to enable such embodiments to be self-supporting. [60] The total accessible porosity of the metal-containing support (εsupport) is preferably determined by the following equation (C): ε_support = WPV_support/(WPV_support + 1/ρ_support) (C) where WPVsupport is the gravimetric water pore volume (ml/g) of the metal-containing support and ρ_support is the gravimetric skeletal density (g/ml) of the metal-containing support. As used herein, the term “gravimetric skeletal density” means the density of the metal-containing support which excludes the volume occupied by the total accessible porosity (εsupport) but includes the volume of inaccessible porosity. The gravimetric skeletal density can be measured using the Helium pycnometry method according to ASTM D3766. [61] The water pore volume (WPV) of the metal-containing support is preferably determined by the following equation (D): WPVsupport = (M2−M1)/ρliquid/(M1) (D) [62] M₁ is the mass (in grams) of a dry sample of the metal-containing support. M₁ is preferably determined by providing a sample of the metal-containing support in a range SP2905 from 5 grams and up to 100 grams, drying the sample for at least 60 minutes at an operating temperature of about 300 °C, and then weighing the dried sample with a two-digit scale. [63] M2 is the mass (in grams) of the wet sample of the metal-containing support. This is determined as follows. After the dried sample is weighed to define M1, it is placed in a container and water is slowly added to the sample until it is immersed. After it is immersed in water, a vacuum of at least 0.1 bar is applied to the container, which expands any air inside the immersed sample. Pressure is applied at least until no more air bubbles come out of the sample and the pressure is switched back to ambient pressure (which refers to the pressure of the surrounding environment, typically around 1 bar). It generally takes around 30 minutes of applying pressure until no more air bubbles come out of the sample. [64] After the pressure is switched back to ambient pressure, the immersed sample is removed from the container and placed on paper to allow excess liquid from the flow channels of the sample to be removed, preferably for about two minutes on a filter paper grade 4. After removal of excess water in the flow channels, the wet sample is weighed to provide M₂. [65] In equation (D), ρliquid is the density of the liquid used, which typically is water with a density of 1.0 g/ml. After M1, M2, and ρsupport are determined, then the water pore volume of the metal-containing support (WPVsupport) can be calculated using equation (D). With the values of WPVsupport and ρsupport known, the total accessible porosity of the metal- containing support (ε_support) can be calculated using equation (C). [66] The pores of metal-containing support hold the carbonate, thereby providing support to the carbonate. That is, the carbonate is present in or occupies a least a portion of the total accessible porosity of the metal-containing support (εsupport), thereby reducing the ε_support and providing the sorbent structure with a residual total accessible porosity (ε_residual) that is less than the εsupport. During CO2 removal operation using the sorbent structure, CO2- containing gas (such as air) flows through the flow channels and comes in contact with the carbonate in the channel walls, where the CO2 in the gas reacts with the carbonate and gets extracted. The residual total accessible porosity (εresidual) of the sorbent structure is preferably calculated using the following equation (E): εresidual = ^support - (wcarbonate / (1- wcarbonate))*(1- ^ ^support)* ρsupport/ρcarbonate (E) ^ where εsupport is total accessible porosity of the metal-containing support as defined by equation (C) where Wcarbonate is the mass loading of carbonate on the sorbent (wt%) SP2905 where ρsupport is the gravimetric skeletal density (g/ml) of the metal-containing support as already defined elsewhere herein, and where ρcarbonate is the gravimetric density of the metal of the carbonate (g/ml). This value is widely available and known to one of ordinary skill in the art. [67] Optionally, the residual total accessible porosity (εresidual) of sorbent structure 100 is in a range from 5% to 75%, preferably from 10% to 65%, more preferably from 20% to 65%. [68] Preferably, impregnation is used to load at least a portion of total accessible porosity of the metal-containing support with the carbonate, as described herein. As used herein, “impregnated” or “impregnation” refers to permeation of the carbonate into the total accessible porosity of the support. [69] With the total accessible porosity as described (such as in a range from 0.4 and up to 0.8), the metal-containing support provides high loading of the carbonate, which enables good contact and CO2 efficiency as the CO2-containing gas can pass through flow channels 106, while still resulting in a low pressure drop, which provides for low operating costs. [70] Preferably, the sum of the amount of the carbonate and the amount of the metal- containing support is at least 95 wt%, preferably 97 wt%, more preferably 99 wt%, of the total weight of channel wall 108. That is, sorbent structure 100 is preferably self-supporting where channel walls 108 preferably comprise mostly (i.e., at least 95 wt%), including consisting essentially, of the carbonate and the metal-containing support. Preferably, sorbent structure 100 (with its first and second ends) comprises mostly (at least 95 wt%) of channel walls 108 forming flow channels 106. [71] FIG.4 is an electronic microscope image of the various pores for an exemplary embodiment of the metal-containing support as described herein, which relate to the total accessible porosity ( ^support) and the space in at least a portion of which holds the carbonate. [72] Optionally, from 40% and up to 100% (preferably at least 50% and up to 100%) of the total accessible porosity ( ^_support) comprises a pore size of 0.5 nm and up to 50 nm. For instance, the black holes in FIG. 4 are pores of roughly 20 nm. Additionally or alternatively, from 0% and up to 60% of the total accessible porosity ( ^_support) comprises a pore size of greater than 50 nm. Additionally or alternatively, from 0% and up to 20% of the total accessible porosity ( ^support) comprises a pore size of greater than 500 nm. As used herein, pore size refers to the pore width or diameter. The optional distribution of pore SP2905 sizes in the total accessible porosity ( ^support) ensures adequate void space in the nano-scale to contain the carbonate, thereby improving the volumetric carbon dioxide capture capacity of embodiments of the disclosed sorbent structure as compared to those with (i) less total accessible porosity and/or (ii) a smaller percentage of the total accessible porosity having a pore size 0.5 nm and up to 50 nm. [73] The fraction of the total accessible porosity of the metal-containing support ( ^support) having a pore size of less than or equal to 50 nm (F<50nm) is preferably determined using the following equation (G): F<50nm = (WPVsupport-(PV>50nm))/WPVsupport (G) where WPV is determined using equation (B) and PV>50nm is the pore volume of pores with a diameter above 50 nm as preferably determined using mercury porosimetry. [74] The PV>50nm value, meaning the fraction of the total accessible porosity having a pore size of greater than 50 nm (F>50nm), is preferably determined using the method described in ASTM D4284 (Determining pore volume distribution of catalysts and catalyst carriers by mercury intrusion porosimetry). When applying a contact angle of 140° using this method of ASTM D4284, the diameter of 50 nm corresponds to 296 bar (4240 PSI). PV>50nm therefore will correspond to the mercury volume that intruded between 0 and 296 bar. [75] The fraction of the total accessible porosity having a pore size of greater than 500 nm (F>500nm) is preferably determined using the method described in ASTM D4284. When applying a contact angle of 140° using the method of ASTM D4284, F>500nm corresponds to the mercury volume that intrudes between 0 and 29.6 bar. [76] It is understood that the metal-containing support can comprise materials that are known in the art to improve or facilitate the mechanical strength and/or fabrication process. Examples of such materials include tungsten trioxide, aluminum oxide, silicon dioxide, fibers, such as glass fibers, ceramic fibers (aluminosilicates), silicon carbide. The amount of these material is typically less than 20 wt%, 15 wt%, preferably less than 10 wt%, of the total weight of the metal-containing support. [77] For embodiments that are self-supported monolith structures, the external surface area per unit volume is directly associated to the mass transfer rate. The external surface area of self-supported monoliths is proportional to the cell density and wall thickness. The cell density has a typical unit of cells per square inch. SP2905 [78] The present disclosure provides for methods of using the sorbent structures described herein (such as sorbent structure 100) to capture carbon dioxide from any gas stream containing CO2. The method comprises providing sorbent structure 100 that comprises first end 102 and second end 104, and a plurality of flow channels 106, and a plurality of channel walls 108. The method further comprises passing a gas comprising carbon dioxide (CO2-containing gas) through at least a portion, including all, of flow channels 106. As the CO2-containing gas passes through flow channels 106, it comes in contact with channel walls 108, including the carbonate and metal-containing support. The method further comprises allowing at least a portion of the CO₂ in the CO₂-containing gas to react with the carbonate in channel walls 108. Preferably, the CO2-containing gas stream comprises carbon dioxide in an amount of less than 500 ppm, more preferably from 300 and up to 500 ppm. More preferably, CO2-containing gas consists essentially of atmospheric air (generally a mixture of gases comprising the Earth’s atmosphere). [79] Suitable equipment (such as reactors) and operating conditions are known to one of ordinary skills. Examples of such suitable equipment and conditions can be found in EP2173322.3, EP21207908.1. For instance, FIG.5 shows a representation of a direct air capture (DAC) carbon dioxide adsorber unit 100 in top or plan view. The exemplary adsorber unit 100 comprises one or multiple rows of monolith beds or slabs 501 that are comprised of one or more embodiments of the sorbent structure disclosed herein. Preferably, the embodiment of the sorbent structure employed is a monolith where feed gas 550 comprising carbon dioxide is drawn through flow channels 106 (not shown in FIG. 5) by suitable equipment, such as impellers 503, such as fans. Typically, the feed gas 550 is air but in embodiments of the invention it may comprise a conditioned gas enriched with carbon dioxide, such as a flue exhaust gas from an industrial or biological process. As the feed gas 550 passes across the surfaces comprised within the monolith, at least a portion of the carbon dioxide reacts with the carbonate and is captured, thereby providing carbon dioxide depleted gas 560 leaving the monolith and vented to the atmosphere. [80] Eventually as the sorbent material approaches desired saturation with adsorbed carbon dioxide there is a need to regenerate the sorbent material and strip away the carbon dioxide. The adsorber unit 500 can include a movable regenerator unit 502 that is able to move along a track and encompasses an adjacent pair of monolith blocks at any given time whilst allowing neighbouring monolith blocks to continue to adsorb carbon dioxide. In this way the cycle of adsorption and regeneration within the DAC unit can occur continuously SP2905 without interruption and significant downtime. It will be appreciated that the configuration of a movable regenerator unit 502 depicted in FIG.5 is merely exemplary and alternative assemblies of monoliths and regenerator units are possible, for example, as mentioned previously United States Patent No.10,512,880 describes an arrangement whereby monolith beds are arranged in a rotating drum around a static regeneration unit. [81] The regenerator unit 502 comprises an inlet that is in fluid communication with a source of a regenerant vapour, such as steam via a low-pressure (LP) steam line 570. Typically, the steam may be derived from an external heat exchange system that is able to heat a supply of water by way of a boiler and generate output of LP steam. The LP steam may also be obtained as output from a back pressure turbine or reclaimed from one or more parallel industrial processing apparatus and systems that generate excess or waste energy, suitably in the form of thermal energy, such as comprised within steam or other heated fluids. [82] The regenerator unit further comprises at least one outlet that is in fluid communication with a vent line 580 that comprises a vacuum pump 504. In this way steam may be introduced and drawn into the regenerator unit from the LP steam line via reduction of pressure. Alternatively, steam of slightly elevated pressure just above atmospheric pressure (e.g. >1 bar), suitably around 1.3 bar/130 KPa (around 18.9 psi), and at a temperature of around 100 to 130 ˚C may be introduced directly into the regenerator unit. That is, in certain embodiments, the sorbent structure is regenerated at least via temperature- swing adsorption (TSA) rather than pressure-swing adsorption (PSA). [83] Accordingly, the present disclosure provides a method for capturing carbon dioxide from a gas mixture. The method comprises: (a) providing an embodiment of the sorbent structure disclosed herein, including sorbent structure 100; (b) passing a gas comprising carbon dioxide (CO₂-containing gas) through at least a portion, including all, of the flow channels (e.g., 108) of the structure; and (c) allowing at least a portion of the CO2 in the CO₂-containing gas to react with the carbonate to produce at least partially loaded (including fully loaded) sorbent structures. Optionally, the CO2-containing gas stream consists essentially of air. [84] Optionally, the step of passing the CO2-containing gas through at least a portion of the flow channels is conducted at or near atmospheric pressure, which is known to one of ordinary skill and typically is 1 atm +/- 5%. Additionally or alternatively, the method further comprises (d) contacting the at least partially loaded sorbent structures with steam to regenerate the sorbent structures, wherein the steam is introduced at or near atmospheric SP2905 pressure or has a slightly elevated pressure just above atmospheric pressure (e.g. >1 bar), suitably around 1.3 bar/130 KPa (around 18.9 psi), and at a temperature of around 100 to 130 ˚C. [85] According to another aspect, the present disclosure also provides methods of 5 making a sorbent structure as described herein for capturing carbon dioxide from a CO2- containing gas. In embodiments wherein the metal-containing support is produced separately (such as through extrusion or 3D printing), the carbonate can be applied to the metal-containing substrate using impregnation. The method of wash-coating is not preferred because the material is applied on top of the surface of the sorbent structure as a layer, which 10 tends to unnecessarily reduce the total accessible porosity of the metal-containing substrate. On the other hand, impregnation applies the carbonate in the total accessible porosity without unnecessary reduction of pore space and/or width of the flow channels 106 as compared to wash-coating, thereby allowing for better accessibility to the carbonate by the carbon dioxide and/or improved gas flow through the sorbent structure 100. 15 [86] In various embodiments, the metal-containing support material and the carbonate material may be combined, for example in a paste, and extruded together to form the sorbent structure. In this embodiment, the carbonate may be dispersed throughout the metal- containing support when the combined paste is extruded into a monolithic form to achieve the desired physical and structural properties. One advantage of combining the metal- 20 containing support material and the carbonate material in one single step is that fewer process steps are required. A further advantage is that it is easier to obtain a good mixing and distribution of the metal-containing support material and the carbonate material when they are combined and formed together (such as via extrusion or 3D printing). [87] According to another aspect, there is provided methods to reduce the reactivity 25 between the metal-containing support and the carbonate (including the undesired effects on the metal-containing support from conditions created by the carbonate) by providing a passivating material to an embodiment of the metal-containing support (as described herein, in an amount in a range from 0.1 wt% and up to 20 wt% of the total weight of the metal- containing support, and causing at least a portion of the metal-containing support to react 30 with at least a portion of the passivating material to form a reaction product on at least a portion of a surface of the metal-containing support, where the reaction product being less reactive to the carbonate than the metal-containing support without the reaction product. According to another aspect, there is provided an embodiment of the sorbent structure SP2905 described herein in which the surface of the metal-containing support comprises a reaction product between the metal-containing support and a passivating material, where the reaction product is less reactive to the carbonate than the metal-containing support without the reaction product. 5 [88] Optionally the passivating material is one or more lanthanides or lanthanum oxide (an oxide of a lanthanide, not just an oxide of lanthanum) compounds to provide both elements of lanthanide and oxygen to form the reaction product. As understood by one of ordinary skills, “lanthanides” has its ordinary meaning and generally refers to one or more of the fifteen metallic elements from lanthanum to lutetium in the periodic table. 10 Preferably, the one or more lanthanides can be selected from a group consisting of lanthanum (La), Praseodymium (Pr), Dysprosium (Dy), Lutetium (Lu), Cerium (Ce), and any combination thereof. Optionally, the one or more lanthanides is provided in an amount from 0.1 wt% and up to 5 wt% of the total weight of the metal-containing support. [89] Any suitable methods can be used to provide the metal-containing support with 15 one or more lanthanides and/or its respective precursor(s) and causing a reaction between the metal-containing support and the passivating material to form a reaction product. Optionally, a suitable method can be selected from the group consisting of impregnation, co- mulling, (selective) adsorption, and any combination thereof. Broadly speaking, the factors influencing the selected concentration of lanthanide(s) include the selected lanthanide(s) and 20 its precursor, the desired stabilizing effect, the preparation method, and any combination thereof. One general aim is to maximize the contact area between the selected lanthanide and the surface of the metal-containing support to enable a reaction between the two, typically under high temperature, to form the reaction product. For instance, with all things being relatively equal, one suitable way to maximize the contact area is at least by having a 25 high lanthanide(s) dispersion during preparation. A metal-containing support with a better dispersion of lanthanide(s) should require less lanthanide(s) as compared to one that has poor dispersion. [90] An example of a suitable method involving impregnation can include at least preparing a solution of a suitable precursor of one or more selected lanthanide(s) and 30 impregnating it onto an embodiment of the metal-containing support, such as one comprising at least 80 wt% alumina. For an embodiment where the one or more lanthanide(s) includes lanthanum, suitable examples of lanthanum precursor can include lanthanum nitrate (La(NO₃)₃*6H₂O) and other salts such as lanthanum chloride (LaCl₃) are also possible. After SP2905 impregnation, the sample is dried (under conditions known to one of ordinary skill), thereby resulting in alumina with the lanthanum salt (La(NO₃)₃) dispersed on the surface. Subsequently, the sample is calcined at a temperature from 300 °C and up to 1100 °C, preferably from 500 and up to 900 °C, at about 1 atm. During calcination, the lanthanum ions are released from the salt to react with the metal-containing support (such as alumina) to form the reaction product of at least LaAlO3. While the description refers to lanthanum specifically, the other lanthanides, such as Praseodymium (Pr), Dysprosium (Dy), Lutetium (Lu), Cerium (Ce), and any combination thereof can be substituted in as known by one of ordinary skill. Example 2 below is an example of impregnation with lanthanum nitrate. [91] Another suitable example includes adsorption, which is, in principle, similar to impregnation, except it includes at least an extra step to prepare the impregnation solution. This extra step is the preparation of a lanthanum complex with a suitable chelator, such as ethylenediaminetetraacetic acid (EDTA). There are other chelators known to one of ordinary skill, such as nitrilotriacetic acid (NTA), citric acid (H3Cit), acetic acid, ethylenediamine, and others. The base conjugates of the acids may work equally well, such as sodium EDTA (Na4EDTA) or sodium citrate (Na3Cit). The solution of the lanthanum chelate is then impregnated on the metal-containing support, dried and calcined similar to normal impregnation. The chelators facilitate a better dispersion of the lanthanum ions on a molecular level. [92] Preferably, a selected chelating agent is one that forms a negatively charged ion with the lanthanide. For instance, if the lanthanide includes lanthanum and the metal- containing support comprises at least 80 wt% of alumina, then EDTA is a preferred chelating agent because it forms a negatively charged ion with lanthanum (La³⁺ + [EDTA]^4- = [La(EDTA)]-). The formed negatively charged ion can selectively adsorb on the positively charged surface when the pH of the solution containing the precursor (with or without the chelating agent)is below the isoelectric point (IEP) of the alumina support (IEP for alumina is 7-8). This is in contrast to, for example, lanthanum citrate (LaCit) which is neutral and does not form a negatively charged ion with lanthanum. [93] Another suitable method includes co-mulling, which also follows a similar principle as impregnation and adsorption. At least one difference involves adding the solution containing the lanthanide precursor (with and/or without the chelating agent) is added to the powder of the metal-containing support material, such as alumina, to form a SP2905 paste. The paste is extruded to form the shaped support, which is dried and calcined similarly to impregnated and/or (selective) adsorption samples. [94] Although deposition precipitation can be used to obtain the reaction product, it is not preferred since it obtains a bulk phase of the reaction product in addition to formation of the reaction product on the surface of the metal-containing support. [95] When the metal-containing support, particularly one that comprises alumina, preferably in an amount in a range from 80 wt% and up to 99.9 wt% of the total weight of the metal-containing support, is provided with one or more lanthanides as the passivating material, the metal-containing support reacts with the passivating material and forms a reaction product that can include lanthanum aluminum oxides (such as LaAlO3, beta- LaAl₁₁O_18, xAl₂O_3*yLa₂O₃), praseodymium aluminum oxides (such as PrAlO₃, xAl2O3*yPr2O3), dysprosium aluminum oxides (such as DyAlO3, Dy3Al5O12 or xAl₂O₃*yDy₂O₃), lutetium aluminum oxides (LuAlO₃, Lu₃Al₅O₁₂ and Lu₄Al₂O₉ or xAl2O3*yLu2O3) (Lu), cerium aluminum oxides (CeAlO3 or xAl2O3*yCe2O3), and any combination thereof. The “x” and “y” represents the stoichiometry of the two respective elements in the reaction product. It is believed that the reaction product has reduced reactivity with the carbonate (including conditions caused by the carbonate) as compared to the metal-containing support without the reaction product, particularly under DAC conditions. Not wishing to be bound by theory, the reduced reactivity to the carbonate believed to be exhibited by the reaction product is due at least in part to the low solubility of the reaction product at high pH and/or the delayed transition from gamma alumina to alpha alumina in the reaction product. As such, the surface of a metal-containing support with the reaction product is believed to be less reactive when it comes in contact with the carbonate, and hence be more stable through multiple DAC adsorption and regeneration cycles as compared to a metal-containing support without the reaction product. [96] Alternatively, the passivating material can be selected from the group consisting of boron (B) or boron oxide, phosphorus (P) or phosphorus oxide, and any combination thereof to provide both the boron and/or phosphorus and oxygen to form the reaction product. Any suitable methods can be used to provide the metal-containing support with boron (B) and/or phosphate (P) and/or its respective precursor and causing a reaction between the metal-containing support and the passivating material to form a reaction product. Optionally, a suitable method can be selected from the group consisting of impregnation, co-mulling, and any combination thereof. The general aim of maximizing SP2905 the contact area between the boron and/or phosphate and the surface of the metal-containing support and high dispersion during preparation are similarly applicable here. One suitable manner to achieve high dispersion is at least by selecting a soluble B or P precursor. Suitable precursors for P or phosphorus oxide can be selected from the group consisting of phosphoric acid, K3PO4, K2HPO4, KH2PO4, Na3PO4, Na2HPO4, NaH2PO4, ammonium phosphates (such as (NH4)3PO4, (NH4)2HPO4, (NH4)H2PO4), and any combination thereof, with phosphoric acid being a preferred precursor. Suitable precursors for boron or boron oxide can be selected from the group consisting of boric acid, potassium borate (K3BO3), potassium metaborate (KBO₂) and potassium tetraborate (K₂B₄O₇ or K₂B₄O₇*4H₂O), their sodium analogues, ammonium borates (such as (NH4)3BO3 and (NH4)B5O8*4H2O (ammonium pentaborate)), and any combination thereof, with boric acid being a preferred precursor. The descriptions above with respect to impregnation and co-mulling as suitable methods to provide embodiments of the metal-containing support with the one or more lanthanide(s) and/or its respective precursors are equally applicable here for the boron, phosphorus, and/or its respective precursors, except the temperature for calcining is in a range from 300 °C and up to 950 °C, preferably from 400 °C and up to 800 °C. Optionally, the boron and/or phosphate (or boron and/or phosphorus oxide) is provided in an amount in a range from 0.1 wt% and up to 5 wt%, based on the total weight of the metal-containing support. [97] For instance, Examples 3 and 4 below describe the co-mulling of a metal- containing support consisting essentially of alumina with boric acid or phosphoric acid in which the acid was dissolved in water and mixed with alumina (or boehmite) powder into a paste that was extruded. The extruded product was then dried and calcined to obtain P-Al2O3 or B-Al₂O₃. [98] When the metal-containing support, particularly one that comprises alumina, preferably in an amount in a range from 80 wt% and up to 99.9 wt% of the total weight of the metal-containing support, is provided with boron and/or phosphate as the passivating material, which is heated, a reaction product between the metal-containing support and the passivating material can include xAl2O3*yB2O3 (one or more examples being aluminum borates (such as AlBO3, Al18B4O33, Al4B2O9)), xAl2O3*yP2O5 (one or more examples being aluminum phosphates (such as aluminum orthophosphate (AlPO₄), aluminum metaphosphate (Al(PO3)3)), and any combination thereof. These reaction products are SP2905 believed to be generally more stable at high pH as compared to the metal-containing support without the reaction product, such as alumina. [99] Alternatively, the passivating material is nitrogen and the step of providing the passivating material and causing a reaction between the metal-containing support and the 5 passivating material comprises heating the metal-containing support, optionally at a temperature in a range from 500 °C to 1000 °C at a pressure of around 1 atm, in a gaseous stream comprising ammonia. Preferably, the concentration of ammonia in the gaseous stream can be in a range of 5 % and up to 100%. Optionally, the nitrogen is provided in an amount in a range from 0.5 wt% and up to 20 wt%, based on the total weight of the metal- 10 containing support. [100] When the metal-containing support, particularly one that comprises alumina, preferably in an amount in a range from 80 wt% and up to 99.9 wt% of the total weight of the metal-containing support, is heated in a gaseous stream comprising ammonia, where the nitrogen acts as the passivating material, a reaction product between the metal-containing 15 support and the passivating material can include aluminum oxynitride (AlON), which is believed to be generally more stable at high pH as compared to the metal-containing support without the reaction product, such as alumina. If the metal-containing support comprises silica and is heated in a gaseous stream comprising ammonia, where the nitrogen acts as the passivating material, a reaction product between the metal-containing support and the 20 passivating material can include silicon oxynitride (SiON), which is believed to be generally more stable at high pH as compared to the metal-containing support without the reaction product, such as silica. [101] Alternatively, the passivating material can be a zinc oxide compound to provide both elements of zinc and oxygen to form the reaction product. Any suitable methods can 25 be used to provide the metal-containing support with zinc, zinc oxide, and/or respective precursor and causing a reaction between the metal-containing support and the passivating material to form a reaction product. Optionally, a suitable method can be selected from the group consisting of impregnation, co-mulling, and any combination thereof to mix the material to form the metal-containing support, such as alumina, with a Zn²⁺ precursor and 30 then heating it to high temperature so that the zinc ions can diffuse into an alumina lattice. The general aim of maximizing the contact area between the passivating material discussed elsewhere and the surface of the metal-containing support and high dispersion during preparation are similarly applicable here. One suitable manner to achieve high dispersion SP2905 is at least by selecting a soluble zinc precursor, such as zinc nitrate (Zn(NO3)2 or Zn(NO₃)₂*6H₂O) , so it can be well dispersed (in solution) over the surface of the metal- containing support to achieve desirable contact between the two compounds. Another suitable method involves at least mixing finely dispersed zinc oxide powder, which is insoluble, with the powder material for an embodiment of the metal-containing support, such as alumina powder, to achieve good contact between the two compounds. The co-mulled or combined mixture is heated to obtain the reaction product comprising xAl2O3*yZnO, such as ZnAl2O4 spinels. Another suitable option for co-mulling includes at least zinc phosphate (Zn₃(PO₄)₂), which is also insoluble. Heating allows the transition metal (Zn) to diffuse into the metal-containing lattice (such as alumina) to form the spinel. [102] The descriptions above with respect to impregnation and co-mulling as suitable methods to provide embodiments of the metal-containing support with the one or more lanthanide(s) and/or its respective precursors are equally applicable here for zinc, and/or its respective precursors, except the heating temperature is in a range from 300 °C and up to 1100 °C, preferably from 600 °C and up to 950 °C. Optionally, the zinc and/or zinc oxide is provided in an amount in a range from 0.5 wt% and up to 20 wt%, based on the total weight of the metal-containing support. ZnAl2O4 is believed to have lower solubility at high pH as compared to the metal-containing support without the reaction product, such as alumina. [103] Alternatively, the passivating material can be selected from the group consisting of one or more lanthanides, phosphate, and any combination thereof. [104] Alternatively, the passivating material can be selected from the group consisting of P, Zn, and any combination thereof. [105] Alternatively, the passivating material can be selected from the group consisting of one or more lanthanides, B, P, N, Zn, and any combination thereof. [106] The reaction product can also comprise spinels comprising alkaline earth or transition metals (such as MgAl2O4, BaAl2O4, iron alumina, cobalt alumina, nickel alumina, copper alumina). As used herein, “spinels” has its ordinary meaning and generally refers to a mixed oxide represented by the composition formula MAl2O4, where M is a divalent cation selected from the group consisting of an alkaline earth metal (Mg²⁺, Ca²⁺, etc), a transition metal (Zn²⁺, Co²⁺, Ni²⁺, etc), and any combination thereof. Alternatively, the reaction product can be selected from the group consisting of zinc alumina spinels, aluminum phosphates, and any combination thereof. SP2905 [107] Additionally or alternatively, the surface of an embodiment of the metal- containing support can be provided with a more stable substance, such as titania, aluminosilicate, a carbon/hydrocarbon overlayer, and any combination thereof, to mitigate the reactivity between the metal-containing support (without one or more of these 5 substances) and the carbonate. [108] Accordingly, the present disclosure provides a method for reducing reactivity between a metal-containing support and a carbonate of a sorbent structure, which is used for capturing carbon dioxide from a gas mixture. The method comprises providing a material to form a metal-containing support, where the metal-containing support material comprises10 a metal and is selected from the group consisting of a metal alloy, metal oxide, metal-non- metal alloy, ceramic, and any combination thereof. A passivating material is added to the metal-containing support material to form a combined formulation of metal-containing support material and the passivating material. In the combined formulation, the passivating material is present in an amount in a range from 0.1 wt% and up to 20 wt% and the metal- 15 containing support material being present in an amount from 40 wt% and up to 99.9 wt%, based on the total weight of the combined formulation. A structure can be formed from the combined formulation. The structure comprises: a first end and a second end; a plurality of flow channels; and a plurality of channel walls, where the flow channels are formed by at least one channel wall and the flow channels extend from the first end to the second end. 20 The descriptions around the sorbent structure (including channel walls, metal-containing support and its properties, carbonate), heating conditions (such as various temperature ranges), passivating material (including precursors), and reaction product, as well as other reasonably related disclosures are understood to equally apply here when similar or the same words are used. The details not been reiterated for the sake of brevity. 25 [109] The passivating material can be added to the metal-containing support material before or after the structure being formed. For instance, if co-mulling is employed, then the passivating material (in solution or solid form) can be combined to form the combined formulation from which the structure is formed (such as through extrusion). If impregnation is employed, then the metal-containing support material can be formed into 30 the structure first, and the passivating material is added at least via impregnation. [110] The formed structure is heated to produce a treated structure. The heating causes at least a portion of the metal-containing support material to react with at least a portion of the passivating material to form a reaction product on at least a portion of a surface of the SP2905 metal-containing support of the treated structure. As described above, the heating temperatures can vary depending on the type of passivating material(s) that are selected. [111] A carbonate as described herein is provided to generate an embodiment of the sorbent structure described herein, where the sorbent structure comprises a plurality of 5 channel walls comprising (i) a metal-containing support comprising the metal-containing support material and (ii) the reaction product and carbonate on a surface of the metal- containing support. The carbonate can be provided to the metal-containing support material along with the passivating material as part of the combined formulation before the structure is formed treated (such as through co-mulling and subsequently extrusion then heating to 10 cause a reaction to form the reaction product). Alternatively, the carbonate can be added to the treated structure comprising the metal-containing support material and reaction product, such as through impregnation of the carbonate to a metal-containing support comprising alumina and ZnAl₂O₄). [112] An advantage of the various embodiments described herein is that the sorbent 15 structure of the present disclosure provides for efficient contact between the gas mixture flowing through the sorbent structure and the sorbent structure (both metal-containing support material and carbonate) on a micro-scale level, and the metal-containing support provides for efficient transport of the process gas through the sorbent structure itself on a macro-scale level, without the need for a separate substrate, which can lead to increased 20 production costs as well as reduced flow. [113] Various embodiments of the sorbent structures disclosed herein enables enhanced flow paths and provides higher volumetric efficiency in the configurations as compared to packed adsorbent beds employing catalyst in particulate form or to structures that employ substrates (that is, does not contain a majority of active material) or apply active 25 material through washcoating. The packed adsorbent beds have higher pressure drops and slower mass transfer rates which are inefficient in operating the adsorption or catalytic processes for large volume gas separation processes, such as those employed in direct air capture processes. The sorbent structures of the present disclosure are particularly suitable for large volume gas separation processes that rely upon low pressure drop and high 30 volumetric efficiency through rapid cycling. [114] Examples [115] Example 1 Preparation of 10% K2CO3 on Al2O3 [116] 8.1 g of a porous straight-channel monolithic Al2O3 substrate was used as a support having 100 cpsi, 0.45 mm walls, an open frontal area of 0.58, a porosity of 0.68 and an average pore size of 12 nm.27.8 g of K2CO3 was dissolved in demineralized water to obtain a solution volume of 200 ml. The monolith was completely immersed in the solution for 30 minutes. Excess water from the channels and on the outer surface of the monolith was removed with a compressed air nozzle. The sample was subsequently dried in air flow at 65°C for 15 minutes, followed by drying at 120 °C for 2 hours and calcination at 300 °C for 2 hours. The sorbent contains 10.0% K2CO3 on Al2O3. The residual porosity was 0.51. [117] The salt loading is defined as K₂CO₃, which does not necessarily represent the final state of the alkali metal precursor on the sorbent. Sorbents were prepared from 7.5% K₂CO₃ on γ- Al₂O₃ to 40% K₂CO₃ on γ- Al₂O₃. Sorbent preparations were also carried out with carbonates, bicarbonates, hydroxides, acetates, and citrates as precursor compounds. [118] Example 2 Preparation of 10% K2CO3 on La- Al2O3 [119] 10.0 g of a porous straight-channel monolithic Al2O3 substrate was used as a support having 100 cpsi, 0.45 mm walls, an open frontal area of 0.58, a porosity of 0.68 and an average pore size of 12 nm.3.93 g of La(NO3)3.6H2O was dissolved in demineralized water to obtain a solution volume of 200 ml. The monolith was completely immersed in the solution for 30 minutes. Excess water from the channels and on the outer surface of the monolith was removed with a compressed air nozzle. The sample was subsequently dried in air flow at 65°C for 15 minutes, followed by drying at 120 °C for 2 hours and calcination at 550 °C for 2 hours. The monolith contains 3 wt% La on Al2O3 (La- Al2O3) and has a porosity of 0.65. [120] 27.8 g of K2CO3 was dissolved in demineralized water to obtain a solution volume of 200 ml. The La- Al₂O₃ monolith was completely immersed in the solution for 30 minutes. Excess water from the channels and on the outer surface of the monolith was removed with a compressed air nozzle. The sample was subsequently dried in air flow at 65°C for 15 minutes, followed by drying at 120 °C for 2 hours and calcination at 300 °C for 2 hours. The sorbent contains 10.0% K2CO3 on La- Al2O3. The residual porosity was 0.41. [121] Example 3 Preparation of 10% K2CO3 on B- Al2O3 [122] 810 gr of alumina pseudo-boehmite powder was taken in a 250 ml Sigma mixer. Then 73.36 gr of boric acid was added slowly under mixing conditions. The dry mixing was done for 10 minutes to ensure homogeneous mixing of the ingredients. Separately a solution was prepared by adding 12.1 gr of acetic acid and 23.9 gr of nitric acid to 700 ml of water. This solution was added slowly to Sigma-type mixer under mixing condition. The mulling continued for 30 min, while the 3 gr of methylcellulose and 6 gr of polyacrylamide added in the last 5 minutes. This mull mix was extruded into 1.3 mm TL shaped extrudates. The extrudates were dried at 125 °C for 2 hours, followed by calcination at 483 °C for 1 hour. The Boron modified carrier (B- Al2O3) has a porosity of 0.75. 2.78 gr of K2CO3 dissolved in 15 ml of water. Once the solution is clear, amount of water to bring up the volume to 20 ml.25 gr of B- Al2O3 was taken in 250 ml PP bottle and 20 ml of K₂CO₃ solution was added to it. Then the sample kept on a rollerbank for 30 min rotation. This allows the solution to be impregnated into carrier. Then the sample dried at 120 °C for 2 hours, followed by 300 °C calcination for 2 hours. The residual porosity was 0.67. [125] Example 4 Preparation of 20% K2CO3 on P- Al2O3 [126] 128.94 gr of alumina pseudo-boehmite powder was taken in a 250 ml Sigma mixer. Then 6.32 gr of boric acid was added slowly under mixing conditions. The mixing was done for 5 minutes to ensure homogeneous mixing of the ingredients. Separately a solution was prepared by adding 3.8 gr of nitric acid to 105 ml of water. This solution was added slowly to a Sigma-type mixer under mixing condition. The mulling continued for 30 min, while the 0.5 gr of methycellulose and 1 gr of polyacrylamide added in the last 5 minutes. This mull mix was extruded into 1.3 mm TL shaped extrudates. The extrudates were dried at 125 °C for 2 hours, followed by calcination at 483 °C for 1 hour. The P- modified carrier (P- Al₂O₃) has a porosity of 0.74. [127] 8.23 gr of K2CO3 dissolved in 20 ml of water. Once the solution is clear, remaining amount of water to bring up the volume to 25 ml.33 gr of P- Al₂O₃ was taken in 250 ml PP bottle and 25 ml of K2CO3 solution was added to it. Then the sample kept on a rollerbank for 30 min rotation. This allows the solution to be impregnated into carrier. Then the sample dried at 120 °C for 2 hours, followed by 300 °C calcination for 2 hours. The residual porosity is 0.52. [128] Prophetic Example 5 – CO² Capacity and Stability Test [129] Sorption capacity is tested for 1000 adsorption-desorption cycles in a fixed bed setup with a sorbent volume of 10 cm³. The setup is equipped with calibrated mass flow controllers to control gas flow (air, nitrogen) and a vapor generator with static mixer to humidify the gasses. During adsorption 200 NL/h humid air with 18% relative humidity at SP2905 30 °C is passed over the sorbent bed for 120 minutes. Then the sorbent is regenerated at 120 °C for 1 hour in diluted steam (40 vol% H₂O in N₂) at 200 NL/h. After regeneration, the sorbent bed is cooled again to 30 °C in humid air (18% R.H. at 30 °C) for the next adsorption cycle. Subsequent cycles are carried out according to the same protocol. The off gasses are passed through a condenser and an IR analyzer to measure the CO2 breakthrough profile. CO2 capacity is determined by integration of the CO2 breakthrough profile and is reported based on the dry mass of the sample. FIG.6 summarizes the CO2 desorption capacities of two sorbents over numerous cycles. An embodiment of the stabilized sorbent structure produced as described in Example 3 and an embodiment of the sorbent structure without stabilization produced as described in Example 1 are tested according to the protocol set forth in this Prophetic Example 5. FIG.6 shows the anticipated results of such test where the line for Sample 1 refers to the embodiment of the stabilized sorbent structure (Example 3) and the line for Sample 2 refers to the embodiment of the sorbent structure without stabilization (Example 1). As can be seen in FIG.6, the CO2 capacity of Sample 2 (without stabilization) is expected to deteriorate quicker than that of Sample 1 (with stabilization). [130] While specific embodiments have been described herein, it is understood that such descriptions are not intended to limit the described embodiments. Instead, any combination of the features and elements provided above, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the aspects, features, embodiments and advantages described herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s).

Claims

SP2905 C L A I M S 1. A method for reducing reactivity between a metal-containing support and a carbonate of a sorbent structure for capturing carbon dioxide from a gas mixture, the method comprising: 5 (f) providing a material to form a metal-containing support; wherein the metal- containing support material comprises a metal and is selected from the group consisting of a metal alloy, metal oxide, metal-non-metal alloy, ceramic, and any combination thereof, (g) adding a passivating material or a precursor thereof to the metal-containing10 support material from step (a) to form a combined formulation of metal- containing support material and passivating material, wherein the passivating material being present in an amount in a range from 0.1 wt% and up to 20 wt% and the metal-containing support material being present in an amount from 40 wt% and up to 99.9 wt%, based on the total weight of the combined 15 formulation; (h) forming a structure from the combined formulation, wherein the structure comprises: o a first end and a second end; o a plurality of flow channels; and 20 o a plurality of channel walls, wherein the flow channels are formed by at least one channel wall, wherein the flow channels extend from the first end to the second end, wherein optionally, step (b) occurs before or after step (c); (i) heating the formed structure to produce a treated structure, wherein the heating 25 causes at least a portion of the metal-containing support material to react with at least a portion of the passivating material to form a reaction product on at least a portion of a surface of the metal-containing support of the treated structure (j) providing a carbonate to the metal-containing support material or the metal- containing support to generate a sorbent structure, wherein the sorbent structure 30 comprises a plurality of channel walls comprising (i) a metal-containing support comprising the metal-containing support material and (ii) the reaction product and carbonate on a surface of the metal-containing support; wherein optionally, SP2905 step (e) occurs simultaneously with steps (a) and (b) or step (e) occurs after step (d) wherein the metal-containing support of the sorbent structure comprises a total accessible porosity (εsupport) in a range from 0.4 – 0.8, preferably 0.5 – 0.7; wherein the total accessible porosity of the metal-containing support (εsupport) is determined at least by: εsupport = WPVsupport/(WPVsupport + 1/ρsupport) where WPVsupport is the gravimetric water pore volume (ml/g) of the metal-containing support and where ρsupport is the gravimetric skeletal density of the metal-containing support wherein the carbonate is provided in an amount in a range from greater than 5 wt% and up to 50 wt%, preferably greater than 5 wt%, including from 10 wt% and up to 30 wt%, based on the total weight of the channel walls of the sorbent structure, wherein the carbonate being at least one of (i) an alkali metal (X₂CO₃) and (ii) an alkaline earth metal (YCO₃); wherein the reaction product being less reactive to the carbonate than the metal- containing support material. 2. The method of claim 1, wherein the passivating material is one or more lanthanides, wherein the one or more lanthanides being selected from a group consisting of lanthanum (La), Praseodymium (Pr), Dysprosium (Dy), Lutetium (Lu), Cerium (Ce), an oxide of each of the foregoing, and any combination thereof. 3. The method of any one of claims 1 - 2, wherein the passivating material is selected from the group consisting of boron (B), boron oxide, phosphorus (P), phosphorus oxide, and any combination thereof. 4. The method of any one of claims 1 - 3, wherein the passivating material being selected from zinc, zinc oxide, or a combination thereof, wherein step (e) occurs after step (d). 5. The method of any one of claims 1 - 3, wherein the metal-containing support comprises alumina in an amount in a range from 80 wt% and up to 99.9 wt% of the total weight of the metal-containing support. 6. The method of any one of claims 1 - 5, wherein the step of providing the metal- containing support with a passivating material comprises heating the metal- containing support in a gaseous stream comprising ammonia. SP2905 7. The method of any one of claims 1 – 3 wherein the passivating material is provided in an amount in a range from 0.1 wt% and up to 5 wt%. 8. The method of any one of claims 1, 4 – 6, wherein the passivating material is provided in an amount in a range from 0.5 wt% and up to 20 wt% 9. The method of any one of claims 1 – 8, wherein the heating step comprises heating the formed structure at a temperature in a range from 300 °C and up to 1100 °C. 10. The method of claim 1, wherein from 40% and up to 100% of the total accessible porosity (εsupport) comprises a pore size of 0.5 nm and up to 50 nm, and/or wherein from 0% and up to 60% of the total accessible porosity ( ^_support) comprises a pore size of greater than 50 nm, and/or from 0% and up to 20% of the total accessible porosity ( ^support) comprises a pore size of greater than 500 nm. 11. A sorbent structure for capturing carbon dioxide from a gas mixture, the sorbent structure comprising: ^ a first end and a second end; ^ a plurality of flow channels; and ^ a plurality of channel walls, wherein the flow channels are formed by at least one channel wall, wherein the flow channels extend from the first end to the second end, and wherein the channel walls comprise: o a carbonate in an amount in a range from greater than 5 wt% and up to 50 wt%, preferably greater than 5 wt%, including from 10 wt% and up to 30 wt%, based on the total weight of the channel walls, wherein the carbonate being at least one of (i) an alkali metal (X2CO3) and (ii) an alkaline earth metal (YCO₃); o a metal-containing support in an amount in a range from 40 wt% and up to 95 wt%, based on the total weight of the channel walls; wherein the metal-containing support comprises a metal and is selected from the group consisting of a metal alloy, metal oxide, metal-non-metal alloy, ceramic, and any combination thereof, wherein the metal-containing support comprises a total accessible porosity (ε_support) in a range from 0.4 – 0.8, preferably 0.5 – 0.7; wherein the total accessible porosity of the metal-containing support (εsupport) is determined at least by: SP2905 εsupport = WPVsupport/(WPVsupport + 1/ρsupport) where WPV_support is the gravimetric water pore volume (ml/g) of the metal-containing support and where ρsupport is the gravimetric skeletal density of the metal-containing support wherein a surface of the metal-containing support comprises a reaction product between the metal-containing support and a passivating material, wherein the reaction product being less reactive to the carbonate than the metal-containing support without the reaction product. 12. The sorbent of claim 10 , wherein the passivating material is one or more lanthanides, optionally the one or more lanthanides being selected from a group consisting of lanthanum (La), Praseodymium (Pr), Dysprosium (Dy), Lutetium (Lu), Cerium (Ce), an oxide of each of the foregoing, and the reaction product is selected from lanthanum aluminum oxides (such as LaAlO3, beta-LaAl11O18, xAl₂O₃*yLa₂O₃), praseodymium aluminum oxides (such as Pr AlO₃, xAl2O3*yPr2O3), dysprosium aluminum oxides (such as DyAlO3, Dy3Al5O12 or xAl2O3*yDy2O3), lutetium aluminum oxides (LuAlO3, Lu3Al5O12 and Lu4Al2O9 or xAl2O3*yLu2O3) (Lu), cerium aluminum oxides (CeAlO3 or xAl2O3*yCe2O3), and any combination thereof. 13. The sorbent of any one of claims 11 - 12, wherein the passivating material is selected from the group consisting of boron (B), boron oxide, phosphorus (P), phosphorus oxide, and any combination thereof and the reaction product is selected from aluminum borates (such as AlBO3, Al18B4O33, Al4B2O9 or xAl2O3*yB2O3), aluminum phosphates (such as orthophosphate (AlPO₄), aluminum metaphosphate (Al(PO3)3 and xAl2O3*yP2O5), and any combination thereof. 14. The sorbent of any one of claims 11 - 13, wherein the passivating material being selected from zinc, zinc oxide, or a combination thereof and the reaction product is xAl2O3*yZnO, such as ZnAl2O4 spinels. 15. The sorbent of any one of claims 11 - 14, wherein the passivating material is nitrogen and the reaction product is aluminum oxynitride. 16. The sorbent of any one of claims 11 - 16, wherein the metal-containing support further comprises silica. SP2905 17. The sorbent of claim 16, wherein the passivating material is nitrogen and the reaction product is silicon oxynitride.