Sorbent structure for carbon dioxide capture

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 carbonate in an amount ranging from greater than 5% by weight to up to 50% by weight. The carbonate is at least one of (i) an alkali metal (X2CO3) and (ii) an alkaline earth metal (YCO3). The channel wall further comprises a metal-containing support in an amount ranging from 40 wt% to up to 95 wt%. The metal-containing support is selected from the group consisting of metal alloys, metal oxides, metal-non-metal alloys, ceramics, and any combination thereof. The metal-containing support has a total accessible porosity ([epsilon]) in the range of 0.4 to 0.8.

Description

Technical Field

[0001] This specification relates generally to the field of carbon dioxide capture, and more particularly to sorbent structures for capturing carbon dioxide (CO2) from gas streams and methods of making and using the same. Background Art

[0002] This section is intended to introduce various aspects of the art that may be associated with the exemplary embodiments of the present invention. It is believed that this discussion helps provide a framework for better understanding certain aspects of the present invention. Therefore, it should be understood that this section should be read in this light and not necessarily as an admission of any prior art.

[0003] The increase in the level of carbon dioxide (CO2) in the atmosphere is at least partially due to emissions from various sources, including industrial sites (such as thermal power plants, refineries) and other processing plants, such as cement processing plants, steel processing plants, aluminum processing plants, etc. The increase in the level of carbon dioxide (CO2) in the atmosphere is related to global warming. As a preventive measure to address global warming, various technologies are being used and / or developed to reduce the amount of CO2 emitted into the atmosphere. In addition, governments of various countries have formulated or plan to formulate programs and / or regulations that aim to provide economic incentives to reduce CO2 emissions, all of which are encouraging the development of CO2 capture technology.

[0004] One type of CO2 reduction technology involves the use of adsorbents to capture or remove CO2 from gas streams. Adsorbents typically account for a significant portion of total capital and operating costs, particularly in terms of adsorbent replacement. Adsorbent performance (including capacity and stability) has a direct economic impact. For example, a method that requires only a smaller amount of a better performing (more efficient) adsorbent to capture a similar amount of CO2 from the same volume of gas stream may result in reduced capital and operating costs. However, currently known adsorbents and methods for capturing CO2 from gas streams still suffer from low efficiency and / or high cost.

[0005] For example, many adsorbents use organic amines to capture carbon dioxide, but organic amines are easily oxidized, increasing the likelihood of adsorbent degradation and causing a loss of CO2 adsorption capacity over time. These adsorbents include WO2010027929A1, WO2017009241A1, WO2010091831A1, and WO21189042A1.

[0006] WO21189042A1 also discloses a solid block formed from sintered dense mesoporous particles that are sintered together so as to be structurally coherent; wherein each particle is mesoporous, and the solid sintered block is macroporous. The solid block also includes a plurality of longitudinal channels that extend between and through opposing faces of the solid block to form openings. The exposed walls of these channels are formed from sintered mesoporous particles, and a CO2 adsorbent is contained within the pores thereof. WO21189042A1 discloses a variety of coating methods to achieve sintered coatings of the mesoporous particles, but these methods may result in lower volumetric CO2 capture capacity.

[0007] Another group of adsorbents uses potassium carbonate as a CO2 adsorbent, which addresses the potential for increased amine oxidation. However, they disclose the use of adsorbent particles to capture CO2 from a gas stream. For example, the adsorbent particles of WO2016185387A1 are transported from an adsorber to a desorber in a circulating fluidized bed. The adsorbent material, which includes a support impregnated with potassium carbonate, is crushed and sieved to form particles. Similarly, US20210016220 discloses multiple fixed adsorbent beds containing an alkaline adsorbent.

[0008] Similarly, US2021187480A1 discloses a granular activated carbon material for capturing CO2 from air. The granular activated carbon is impregnated with an alkali metal carbonate, such as K2CO3. Additionally, the paper "Sorption of carbon dioxide by the composite sorbent 'potassium carbonate in a porous matrix'" (Okunev, A. et al., Russian Chemical Bulletin 2003, 52, 359-363) discloses potassium carbonate granules supported on alumina for flue gas capture.

[0009] 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 coated with K2CO3 and treated with wet N2 to hydrate it.

[0010] Therefore, there remains a need to provide sorbents that can efficiently capture CO2 from gas streams. Summary of the Invention

[0011] According to certain aspects, there is provided an adsorbent structure for capturing carbon dioxide from a gas mixture, the adsorbent structure comprising: a first end and a second end; a plurality of flow channels; and a plurality of channel walls. The flow channels are formed by at least one channel wall, and the flow channels extend from the first end to the second end. The channel walls comprise: (i) a carbonate in an amount ranging from greater than 5 wt% to up to 50 wt%, preferably greater than 5 wt%, including 10 wt% to up to 30 wt%, based on the total weight of the channel walls, wherein the carbonate is at least one of (i) an alkali metal (X2CO3) and (ii) an alkaline earth metal (YCO3); and (ii) a metal-containing support in an amount ranging from 40 wt% to up to 95 wt%, based on the total weight of the channel walls. The metal-containing support comprises a metal and is selected from a metal alloy, a metal oxide, a metal-non-metal alloy, a ceramic, and any combination thereof. The metal-containing support also has a total accessible porosity (ε) in the range of 0.4 to 0.8, preferably 0.5 to 0.7. 载体 ).

[0012] The total accessible porosity (ε 载体 ) may be determined at least in the following ways:

[0013] ε carrier = WPV carrier / (WPV carrier + 1 / ρ carrier)

[0014] Among them WPV 载体 is the gravimetric aqueous pore volume of the metal-containing support (ml / g), and where p 载体 is the gravimetric skeletal density of the metal-containing support.

[0015] Optionally, the metal-containing support (WPV 载体 The gravimetric water pore volume (ml / g) of the water column can be determined at least as follows:

[0016] WPV carrier = (M2-M1) / ρ liquid / (M1)

[0017] where M1 is the mass (in grams) of a dry sample of the metal-containing support,

[0018] wherein M2 is the mass (in grams) of the wet sample of the metal-containing support, and

[0019] ρ 液体 is the gravimetric density of the liquid used to wet the sample.

[0020] Alternatively, the adsorbent structure may comprise a residual total accessible porosity (ε ) in the range of 5% to 75%, preferably 10% to 65%, more preferably 20% to 65%. 残余 ). Optionally, ε 残余 This can be determined by at least the following means:

[0021] ε 残余 =ε 载体 -(w 碳酸盐 / (1-w 碳酸盐 ))*(1-ε 载体 )*ρ 载体 / ρ 碳酸盐

[0022] where ε 载体 is the total accessible porosity of the metal-containing support, and

[0023] Where W 碳酸盐 is the mass loading of carbonate on the adsorbent (wt %), and

[0024] where ρ 载体 is the gravimetric skeletal density (g / ml) of the metal-containing support, and

[0025] where ρ 碳酸盐 is the gravimetric density of the carbonate metal (g / ml).

[0026] Alternatively, the sum of the amount of the carbonate salt and the amount of the metal-containing support may be at least 95 wt%, preferably 97 wt%, more preferably 99 wt% of the adsorbent structure.

[0027] Alternatively, X may be selected from K + 、Na + 、Cs + 、Li + and any combination thereof, and Y is selected from Mg 2+ , Ca 2+ 、Sr 2+ 、Ba 2+and alkaline earth metal cations thereof. Alternatively, the metal of the metal-containing support may be selected from aluminum, silicon, titanium, zirconium, magnesium, calcium, iron, and any combination thereof; Alternatively, the metal-containing support is selected from silica, alumina, titania, zirconia, cordierite, mullite, silicon carbide, aluminosilicates, preferably zeolites, and any combination thereof. Alternatively, the carbonate may be selected from one or more alkali metals, and the metal-containing support is selected from titania and / or zirconia. Optionally, the carbonate is selected from one or more alkali metals, and the metal-containing support is alumina, preferably heat-treated alumina, more preferably selected from potassium aluminate, sodium aluminate (2NaAlO2═Na2O*Al2O3), hydrated alumina (boehmite, Al2O3*H2O), bayerite, gibbsite, boehmite, pseudo-boehmite, bauxite, γ-alumina, δ-alumina, χ-alumina, ρ-alumina, κ-alumina, η-alumina, θ-alumina, magnesium aluminate, trine, bermire and any combination thereof.

[0028] Optionally, the metal-containing support may further comprise a reinforcing material to improve or facilitate mechanical strength and / or manufacturing process, with the amount of the reinforcing material being less than 20 wt % of the total weight of the metal-containing support.

[0029] Optionally, 40% to up to 100% of the total accessible porosity has pore sizes less than or equal to 50 nm, and 0% to up to 60% of the total accessible porosity has pore sizes greater than 50 nm. Optionally, 0% to up to 20% of the total accessible porosity has pore sizes greater than 500 nm. Optionally, the adsorbent structure may also have a cell density in the range of 50 cells per square inch (cpsi) up to 400 cpsi, preferably in the range of 50 cpsi up to 300 cpsi, and an open frontal area in the range of 60% to up to 85%, preferably in the range of 65% to 75%. Optionally, the channel walls may also have an average thickness in the range of 150 microns up to 1000 microns.

[0030] According to another aspect, the present disclosure provides a method for capturing carbon dioxide from a gas mixture. The method comprises: (a) providing an embodiment of an adsorbent structure disclosed herein; (b) passing a gas containing carbon dioxide (CO2-containing gas) through at least a portion of a flow channel, including the entire flow channel; and reacting at least a portion of the CO2 in the CO2-containing gas with a carbonate to produce an at least partially loaded (including fully loaded) adsorbent structure. Optionally, the CO2-containing gas stream consists essentially of air.

[0031] Optionally, the step of passing the CO2-containing gas through at least a portion of the flow channel is carried out at or near atmospheric pressure. Optionally, the method may further comprise (d) contacting at least a portion of the loaded adsorbent structure with steam to regenerate the adsorbent structure, wherein the steam is introduced at or near atmospheric pressure, or at a slightly elevated pressure slightly above atmospheric pressure (e.g., >1 bar), suitably about 1.3 bar / 130 kPa (about 18.9 psi), and at a temperature of about 100°C to 130°C.

[0032] Typically, to capture carbon dioxide from a gas stream, it is desirable that the adsorbent material impose a minimal pressure drop on the gas stream in order to minimize the energy required to move the gas stream through the removal process, while achieving maximum contact between the adsorbent and the gas stream, thereby maximizing the mass transfer rate of the CO2 to be removed from the gas stream. In cases where the gas stream from which the carbon dioxide is captured is atmospheric air, the concentration of CO2 available for capture in atmospheric air is very low, currently between 400 ppm and 420 ppm, and expected to rise in the future. In such cases, to extract effective amounts of CO2, very large volumes of air must be flowed through any capture system. Moving large volumes of air through the system while maintaining the desired CO2 capture efficiency results in increased energy requirements, which is one of the primary factors in achieving economic viability.

[0033] As described herein, an adsorbent structure and various embodiments thereof provide for the removal of carbon dioxide, wherein a relatively small volume of the adsorbent structure can absorb a large amount of carbon dioxide in a short period of time. This is attributable at least to the relatively high total accessible porosity, which enables a relatively high carbonate loading to capture CO2. The required small volume of the adsorbent structure reduces the costs associated with building and operating a carbon dioxide removal system. The structure, particularly the parallel channels, also reduces the pressure drop experienced by the process gas as it passes through the adsorbent structure. The reduced pressure drop reduces operating costs because the fan power required to move the gas through the adsorbent structure is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Depicted are illustrative perspective views of exemplary embodiments of adsorbent structures according to certain aspects described herein.

[0035] Figure 2 Depicted are adsorbent structures according to certain aspects described herein (such as Figure 1 An illustrative enlarged perspective view of an embodiment of the adsorbent structure depicted in FIG.

[0036] Figure 3 Depicted is an illustrative perspective partial cross-sectional view along a length of another exemplary embodiment of an adsorbent structure according to certain aspects described herein.

[0037] Figure 4 is a SEM (scanning electron microscope) image of a portion of a channel wall of an embodiment of a metal-containing support of an adsorbent structure according to certain aspects disclosed herein.

[0038] Figure 5 A schematic diagram of an exemplary DAC system is shown in which embodiments of the sorbent structures disclosed herein may be employed. DETAILED DESCRIPTION

[0039] The present invention will now be described in detail with reference to the embodiments of the invention as shown in the accompanying drawings. References to "one embodiment," "an embodiment," "an exemplary embodiment," etc. indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is considered to be within the knowledge of those skilled in the art that such feature, structure, or characteristic may be affected in conjunction with other embodiments, whether or not explicitly described. Other suitable modifications and adjustments of the various conditions and parameters commonly encountered in the art, and which will be apparent to those skilled in the art, are within the spirit and scope of the present invention.

[0040] Although the description herein provides numerous specific details set forth for a thorough understanding of the illustrative embodiments, it will be apparent to those skilled in the art that the 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 so as not to unnecessarily obscure the invention. Features and advantages of the embodiments may be better understood with reference to the drawings and the following discussion.

[0041] In addition, when similar elements are used in one or more figures, the same reference numeral will be used in each figure, and a detailed description of the element will be provided only when the element first appears. For the sake of clarity, some features or components of the systems or processes described herein may be omitted in some depicted configurations.

[0042] Figure 1 Schematically depicted is a perspective view of an adsorbent structure 100 , which is an exemplary embodiment of the adsorbent disclosed herein for capturing carbon dioxide from a gas mixture. Figure 2 A magnified view of the adsorbent structure 100 is schematically depicted, and Figure 3A cross-sectional view of the adsorbent structure 100 along its length 112 is schematically depicted. Although the adsorbent structure 100 is depicted as having a generally rectangular block shape (or cuboid), it should be understood that the adsorbent structure 100 may have any suitable cross-sectional shape, including geometric shapes such as trapezoidal, triangular, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Figures 1 to 3 In the illustrated embodiment, the adsorbent structure 100 includes a first end 102 and a second end 104. Figure 2 The adsorbent structure 100 further includes a plurality of flow channels 106 and a plurality of channel walls 108 .

[0043] The flow channel 106 is formed by at least one channel wall 108 and extends from the first end 102 to the second end 104. The flow channel 106 has a shape formed by at least one (such as two or more) channel wall. The shape of the flow channel 106 is preferably polygonal, more preferably selected from a triangle, square and hexagon, trapezoidal, rectangular, sinusoidal or circular, such as an elliptical or circular shape. The flow channel 106 preferably provides parallel flow channels extending from the inlet face (e.g., 102) of the substrate to the outlet face (e.g., 104), such that the channels are open to allow fluid to flow through the adsorbent structure 100.

[0044] As described herein, substantially all of the flow channels 106 may have substantially the same shape, or, in addition or alternatively, a portion of the flow channels 106 may have a different shape than the remainder of the flow channels 106, depending on other specifications, such as the overall configuration of the adsorbent structure 100. For example, at least a major portion (>50%, preferably >80%) of the flow channels 106 (including all of the flow channels) may have a polygonal or circular shape; if polygonal, it may be preferably selected from the group consisting of triangular, rectangular, square, hexagonal, and any combination thereof. For example, in an embodiment in which the adsorbent has a cylindrical shape, it will be understood that the interior flow channels around the center may have a different shape (such as a square) than the flow channels at the circular edges defined by the circular outer channel walls.

[0045] The flow channels 106 preferably occupy a relatively large amount of front cross-sectional area so that the flow resistance of the gas through these channels is relatively low, thereby minimizing the pressure drop, which is the energy required to force the gas through the adsorbent structure 100. For example, referring to Figure 2, the adsorbent structure 100 preferably has an open frontal area (OFA) or free cross-sectional area in the range of 60% to as high as 85%, and more preferably 65% ​​to 75%. As used herein, "open frontal area" or "free cross-sectional area" has its ordinary meaning. For example, an adsorbent structure having an OFA of 60% means that 60% of the cross-sectional area of ​​the frontal region (e.g., 102 or 104) is open to allow gas to flow through the adsorbent structure. That is, the cross-sectional area of ​​the flow channels 106 accounts for 60% of the cross-sectional area of ​​the adsorbent structure. One way to characterize the number of flow channels 106 that make up the OFA of the adsorbent structure 100 is cell density, where certain dimensions of the flow channels 106 (or "cells") can be designed to meet various goals, including OFA.

[0046] For example, reference Figure 1 and Figure 2 An exemplary suitable adsorbent structure, such as structure 100, having a cross-sectional square shape of 150 mm x 150 mm may have 1,600 cells or flow channels 106 (40 cells x 40 cells), wherein each cell opening (d) is approximately 3.2 mm, and an OFA of 72.8%. Alternatively, structure 100 may have a cell density in the range of 50 cells per square inch (cpsi) up to 400 cpsi, preferably in the range of 50 cpsi up to 300 cpsi, and an open frontal area in the range of 60% up to 85%, preferably in the range of 65% to 75%. Additionally or alternatively, at least a portion of the channel walls 108 may have an average thickness in the range of 150 microns up to 1,000 microns. It should be understood that the thickness of the channel walls 108 may vary from one portion of the adsorbent structure 100 to another, including whether or not a particular channel wall is an exterior wall.

[0047] Optionally, the adsorbent structure 100 may comprise at least 10 x 10 mm 2 (such as 50×50mm 2 Up to 600×600mm 2 within the range, preferably 100×100mm 2 Up to 500×500mm 2 within the range, more preferably within 150×150 mm 2 Up to 300×300mm 2 ) (e.g., if the adsorbent structure has a square or cylindrical cross-sectional shape, the nominal cross-sectional area is Figure 1 D in 2 or Figure 3 π(0.5D) in 2 (where D represented by 110 is the side length or diameter respectively).

[0048] Optionally, the adsorbent structure 100 comprises a length 112 (L) in the range of 50 mm to 2000 mm, preferably in the range of 100 mm to 1000 mm, and most preferably in the range of 200 mm to 500 mm.

[0049] Preferably, the adsorbent structure 100 is self-supporting and comprises a monolithic unit, such as a honeycomb structure, having parallel flow channels 106 extending from a first end 102 to a second end 104 (e.g., flowing through the monolith). For example, the metal-containing support provides structural integrity (serving as a substrate) and serves as part of the active material to promote the adsorption of CO2 by carbonates. Such monolithic units can be formed using methods known in the art, such as extrusion, co-milling, 3D printing, and / or impregnation.

[0050] The channel walls 108 comprise at least one carbonate of (i) an alkali metal having the chemical formula X2CO3 and (ii) an alkaline earth metal having the chemical formula YCO3, in an amount ranging from 5 wt% up to 50 wt%, preferably from greater than 5 wt% to 30 wt%, based on the total weight of the channel walls. Preferably, X is selected from K + 、Na + 、Cs + 、Li + (thereby forming K2CO3, Na2CO3, Cs2CO3, Li2CO3) and any combination thereof. Preferably, Y is selected from Mg 2+ , Ca 2+ 、Sr 2+ 、Ba 2+ (thereby forming alkaline earth metal cations of MgCO3, CaCO3, SrCO3, BaCO3) and any combination thereof. The weight is preferably determined when the carbonate is in anhydrous form.

[0051] The weight percent amount of carbonate in anhydrous form is preferably calculated from the weight percent amount of carbonate determined by chemical analysis, preferably X-ray fluorescence spectroscopy (XRF). Prior to analysis of the weight percent of carbonate, the sample to be tested is dried, preferably at about 300° C. for at least one hour, to determine the mass of the dried sample. The weight percent amount of carbonate can be calculated using the following equation (A):

[0052] W 碳酸盐 =W 金属 / f(A)

[0053] Where W 碳酸盐 is the mass loading of carbonate on the adsorbent (wt%), W 金属is the mass loading of carbonate metal on the adsorbent structure as determined by XRF (wt %), and f is the mass fraction of carbonate metal in anhydrous or salt form, which can be calculated using the following equation (B):

[0054] f=M 金属 *n 金属 / M 碳酸盐 (B)

[0055] Among them, M 金属 is the molar mass of the metal (g / mol), M 碳酸盐 is the molar mass of the carbonate, and n 金属 is the number of moles of metal per mole of carbonate (e.g. for potassium carbonate (K2CO3), n 金属 =2; and for magnesium carbonate (MgCO3), n 金属 =1).

[0056] For example, XRF analysis of a sample of the adsorbent structure according to aspects described herein showed that potassium metal (W K The mass loading of potassium carbonate on the metal-containing support can be calculated using equations (A) and (B) shown below.

[0057] f=39.10(g / mol)*2 / 138.205g / mol=0.566(B)W 碳酸钾 = 0.433 wt% / 0.566 = The amount of K2CO3 in anhydrous form in the analyzed adsorbent structure sample is 7.66 wt% (A).

[0058] Carbonates are hygroscopic salts that tend to absorb moisture from the air and hydrate. The hygroscopicity of each carbonate can vary depending on the specific metal cation. Both anhydrous and hydrated carbonates readily react with carbon dioxide and water to form bicarbonate, thereby capturing carbon dioxide as bicarbonate. Therefore, carbonates are used as adsorbents for CO2.

[0059] The channel wall 108 also comprises a metal-containing support, the amount of which is based on the total weight of the channel wall, in the range of 40 wt % to as high as 95 wt %. The metal-containing support is preferably an inorganic material and comprises a metal. The metal-containing support is preferably selected from metal alloys, metal oxides, metal-nonmetal alloys, ceramics and any combination thereof. The metal is selected from aluminum, calcium, silicon, titanium, zirconium, magnesium, iron and any combination thereof. Preferably, the metal-containing support is selected from silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, cordierite, mullite, silicon carbide, aluminosilicate (preferably zeolite), aluminum phosphate and any combination thereof. More preferably, the metal-containing support is selected from aluminum oxide, titanium dioxide and any combination thereof.

[0060] Carbonates and metal-containing supports are considered active materials as known to those skilled in the art.The present disclosure provides adsorbent structures comprising a majority (greater than 50 wt%, more preferably greater than 80 wt% of the total weight of the adsorbent structure) of active material.

[0061] A preferred embodiment of the adsorbent 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 is least reactive with the alkali metal salt during carbon capture conditions. Examples of such metal-containing supports include titania or zirconia. For example, a preferred embodiment is an adsorbent structure wherein the carbonate is selected from one or more alkali metal carbonates, and wherein the metal-containing support is selected from titania, zirconia, or a combination thereof.

[0062] In another aspect, the reaction between the carbonate and the metal-containing support can be minimized at least by using a metal-containing support, particularly alumina, that has been heat-treated. Preferably, the metal-containing support can be selected from potassium aluminate, sodium aluminate (2NaAlO2═Na2O*Al2O3), hydrated alumina (boehmite, Al2O3*H2O), bayerite, gibbsite, boehmite, pseudoboehmite, bauxite, gamma-alumina, delta-alumina, chi-alumina, rho-alumina, kappa-alumina, eta-alumina, theta-alumina, magnesium aluminate, trine, bermire, and any combination thereof.

[0063] The metal-containing support is porous, which means that it contains pores or spaces. In particular, the metal-containing support has a total accessible porosity (ε) in the range of 0.4 to as high as 0.8, preferably 0.5 to as high as 0.7. 载As is known in the art, these ranges of total accessible porosity (ε) of the metal-containing support can also be expressed as a percentage of 40% up to 80%, preferably 50% 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) (i.e., open pores) in a substance that is accessible to water. For the purposes of 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.

[0064] The higher the total accessible porosity, the more accessible pores there are on the surface of the material, which means that the rigidity of the material is lower, and vice versa. Despite the lower rigidity, having more accessible pores enables higher loadings of the target material. Without wishing to be bound by theory, the inventors have found that a preferred range of at least 0.5, including 0.5 up to 0.7 or 0.8, provides more accessible space or voids in the support or channel walls to accommodate carbonates, thereby allowing relatively larger loadings of carbonates while still allowing the metal-containing support to provide structural integrity to enable such embodiments to be self-supporting.

[0065] Total accessible porosity of the metal-containing support (ε 载体 ) is preferably determined by the following equation (C):

[0066] ε 载体 =WPV 载体 / (WPV 载体 +1 / ρ 载体 )(C)

[0067] Among them WPV 载体 is the gravimetric aqueous pore volume of the metal-containing support (ml / g), and ρ 载体 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 does not include the total accessible pores (ε 载体 ), but includes the volume of inaccessible pores. Gravimetric skeletal density can be measured using helium pycnometry according to ASTM D3766.

[0068] The water pore volume (WPV) of the metal-containing support is preferably determined by the following equation (D):

[0069] WPV support = (M2 - M1) / ρ liquid / (M1) (D) M1 is the mass of a dry sample of the metal-containing support in grams. M1 is preferably determined by providing a sample of the metal-containing support in the range of 5 grams up to 100 grams, drying the sample at an operating temperature of about 300° C. for at least 60 minutes, and then weighing the dried sample using a two-digit scale.

[0070] M2 is the mass (in grams) of the wet sample containing the metal support. This is determined as follows. After the dried sample is weighed to define M1, the sample is placed in a container and water is slowly added to the sample until the sample is submerged. After the sample 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 bubbles appear in the sample, and the pressure is switched back to ambient pressure (which refers to the pressure of the surrounding environment, typically about 1 bar). It is usually necessary to apply pressure for about 30 minutes until no more bubbles appear in the sample.

[0071] 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 to be removed from the flow path of the sample, preferably on a grade 4 filter paper for about two minutes. After removing excess water from the flow path, the wet sample is weighed to provide M2.

[0072] In equation (D), ρ 液体 is the density of the liquid used, which is usually water with a density of 1.0 g / ml. 载体 The water pore volume (WPV) of the metal-containing support can then be calculated using equation (D) 载体 ). In known WPV 载体 and ρ 载体 The total accessible porosity (ε) of the metal-containing support can be calculated using equation (C) given the value of 载体 ).

[0073] The pores of the metal-containing support accommodate the carbonate, thereby providing support for the carbonate. That is, the carbonate is present in the total accessible pores (ε 载体 ) or occupy at least a portion of the total accessible pores of the metal-containing support, thereby reducing ε 载体 and provide the adsorbent structure with a value less than ε 载体 The residual total accessible porosity (ε 残余 During CO removal operations using the adsorbent structure, a CO-containing gas (such as air) flows through the flow channels and contacts the carbonates in the channel walls, where the CO in the gas reacts with the carbonates and is extracted. The residual total accessible porosity (ε residual ) of the adsorbent structure is preferably calculated using the following equation (E):

[0074] ε residual = ε carrier - (w carbonate / (1 - w carbonate)) * (1 - ε carrier) * ρ carrier / ρ carbonate (E)

[0075] where ε 载体 is the total accessible porosity of the metal-containing support as defined by equation (C)

[0076] Where W碳酸盐 is the mass loading of carbonate on the adsorbent (wt%)

[0077] where ρ 载体 is the gravimetric skeletal density (g / ml) of the metal-containing support as defined elsewhere herein, and

[0078] where ρ 碳酸盐 is the gravimetric density of the carbonate metal (g / ml). This value is widely available and known to those of ordinary skill in the art.

[0079] Optionally, the residual total accessible porosity (ε 残余 ) is in the range of 5% to 75%, preferably 10% to 65%, more preferably 20% to 65%.

[0080] Preferably, the carbonate is loaded into at least a portion of the total accessible pores of the metal-containing support using an impregnation method, as described herein. As used herein, "impregnated" or "impregnation" refers to the penetration of the carbonate into the total accessible pores of the support.

[0081] At total accessible porosity as described above (such as in the range of 0.4 to as high as 0.8), the metal-containing support provides high loading of carbonate, achieving good contact and CO2 efficiency as the CO2-containing gas can pass through the flow channels 106 while resulting in low pressure drop, thereby providing low operating costs.

[0082] Preferably, the sum of the amount of carbonate and the amount of metal-containing support is at least 95 wt.%, preferably 97 wt.%, and more preferably 99 wt.%, of the total weight of the channel walls 108. That is, the adsorbent structure 100 is preferably self-supporting, wherein the channel walls 108 preferably comprise primarily (i.e., at least 95 wt.%) carbonate and metal-containing support, including consisting essentially of carbonate and metal-containing support. Preferably, the adsorbent structure 100 (having its first and second ends) comprises primarily (at least 95 wt.%) the channel walls 108 forming the flow channels 106.

[0083] Figure 4 is an electron microscopy image of various pores of an exemplary embodiment of a metal-containing support as described herein, the image relating to the total accessible pores (ε 载体 ) and space to accommodate carbonates in at least a portion of the total accessible pore space.

[0084] Optionally, a total accessible porosity (ε 载体 ) have a pore size ranging from 0.5 nm to as high as 50 nm. For example, Figure 4The black holes in are approximately 20 nm holes. Additionally or alternatively, 0% to up to 60% of the total accessible porosity (ε 载体 ) having a pore size greater than 50 nm. Additionally or alternatively, 0% to up to 20% total accessible porosity (ε 载体 ) has a pore size greater than 500 nm. As used herein, pore size refers to the pore width or diameter. Total accessible porosity (ε 载体 ) ensures that there is sufficient nanoscale void space to accommodate carbonates, thereby improving the volumetric carbon dioxide capture capacity of embodiments of the disclosed adsorbent structure compared to adsorbent structures having i) a lower total accessible porosity and / or ii) a smaller percentage of total accessible porosity having pore sizes ranging from 0.5 nm to up to 50 nm.

[0085] The total accessible porosity (ε) of the metal-containing support having a pore size less than or equal to 50 nm (F < 50 nm) 载体 ) is preferably determined using the following equation (G):

[0086] F<50nm=(WPV 载体 -(PV>50nm)) / WPV 载体 (G)

[0087] wherein WPV is determined using equation (B), and PV>50 nm represents the pore volume of pores having a diameter greater than 50 nm, which pore volume is preferably determined using mercury intrusion porosimetry.

[0088] The PV>50nm value refers to the fraction of the total accessible porosity having pore diameters greater than 50 nm (F>50 nm), which is preferably determined using the method described in ASTM D4284 (Pore Volume Distribution of Catalysts and Catalyst Supports by Mercury Intrusion Porosimetry). When a contact angle of 140° is applied using this method of ASTM D4284, a diameter of 50 nm corresponds to 296 bar (4240 PSI). Therefore, PV>50nm will correspond to a volume of mercury intruded between 0 bar and 296 bar.

[0089] The fraction of the total accessible porosity having a pore size greater than 500 nm (F>500 nm) is preferably determined using the method described in ASTM D 4284. When a contact angle of 140° is applied using the method of ASTM D 4284, F>500 nm corresponds to a mercury volume intruded between 0 bar and 29.6 bar.

[0090] It should be understood that the metal-containing support may contain materials known in the art to improve or facilitate mechanical strength and / or manufacturing processes. Examples of such materials include tungsten trioxide, aluminum oxide, silicon dioxide, fibers such as glass fibers, ceramic fibers (aluminosilicates), and silicon carbide. The amount of these materials is typically less than 20% by weight, 15% by weight, and preferably less than 10% by weight of the total weight of the metal-containing support.

[0091] For embodiments of the self-supporting monolithic structure, the external surface area per unit volume is directly related to the mass transfer rate. The external surface area of ​​the self-supporting monolith is proportional to the pore density and wall thickness. The pore density has a typical unit of pores per square inch.

[0092] The present disclosure provides a method for capturing carbon dioxide from any CO2-containing gas stream using an adsorbent structure described herein, such as adsorbent structure 100. The method includes providing an adsorbent structure 100 comprising a first end 102 and a second end 104, and a plurality of flow channels 106 and a plurality of channel walls 108. The method also includes passing a gas containing carbon dioxide (CO2-containing gas) through at least a portion of the flow channels 106, including all of the flow channels. As the CO2-containing gas passes through the flow channels 106, the gas contacts the channel walls 108 comprising carbonates and a metal-containing support. The method also includes reacting at least a portion of the CO2 in the CO2-containing gas with the carbonates in the channel walls 108. Preferably, the CO2-containing gas stream comprises carbon dioxide in an amount of less than 500 ppm, more preferably from 300 ppm to as much as 500 ppm. More preferably, the CO2-containing gas consists essentially of atmospheric air (typically a gas mixture comprising the Earth's atmosphere).

[0093] Suitable equipment (such as reactors) and operating conditions are known to those of ordinary skill in the art. Examples of such suitable equipment and conditions can be found in EP2173322.3, EP21207908.1. For example, Figure 5 A top or plan view of a direct air capture (DAC) carbon dioxide adsorber unit 100 is shown. The exemplary adsorber unit 100 includes one or more rows of monolithic beds or plates 501 constructed from one or more embodiments of the adsorbent structure disclosed herein. Preferably, the embodiment of the adsorbent structure employed is a monolithic, wherein a feed gas 550 containing carbon dioxide is drawn through the flow channels 106 ( Figure 5Typically, the feed gas 550 is air, but in embodiments of the present invention, it may include a conditioned gas rich in carbon dioxide, such as flue gas from an industrial or biological process. As the feed gas 550 passes through surfaces contained within the monolith, at least a portion of the carbon dioxide reacts with the carbonates and is captured, causing a carbon dioxide-lean gas 560 to exit the monolith and be exhausted to the atmosphere.

[0094] Eventually, when the adsorbent material approaches the desired saturation of adsorbed carbon dioxide, it is necessary to regenerate the adsorbent material and strip the carbon dioxide. The adsorber unit 500 may include a mobile regenerator unit 502 that is capable of moving along a track and encompassing a pair of adjacent monoliths at any given time while allowing the adjacent monoliths to continue adsorbing carbon dioxide. In this manner, the adsorption and regeneration cycles within the DAC unit may occur continuously without interruption and significant downtime. It should be understood that Figure 5 The depicted configuration of the movable regenerator unit 502 is merely exemplary, and alternative assemblies of monolith and regenerator units are possible, for example, as previously mentioned, U.S. Patent No. 10,512,880 describes an arrangement in which a monolith bed is arranged in a rotating drum surrounding a static regeneration unit.

[0095] The regenerator unit 502 includes an inlet that is in fluid communication with a source of regenerant steam, such as steam, via a low-pressure (LP) steam line 570. Typically, the steam can be derived from an external heat exchange system that can heat a water supply via a boiler and produce an output of LP steam. The LP steam can also be obtained as output from a back-pressure turbine or recovered from one or more parallel industrial process equipment and systems that generate excess or waste energy, suitably in the form of thermal energy, such as contained in steam or other heating fluids.

[0096] The regenerator unit also includes at least one outlet in fluid communication with an exhaust line 580 comprising a vacuum pump 504. In this manner, steam can be introduced and pumped into the regenerator unit from the LP steam line via a pressure reduction. Alternatively, steam at a slightly higher pressure slightly above atmospheric pressure (e.g., >1 bar), suitably about 1.3 bar / 130 kPa (about 18.9 psi) and a temperature of about 100° C. to 130° C., can be introduced directly into the regenerator unit. That is, in certain embodiments, the adsorbent structure is regenerated at least via temperature swing adsorption (TSA) rather than pressure swing adsorption (PSA).

[0097] Thus, the present disclosure provides a method for capturing carbon dioxide from a gas mixture. The method includes: (a) providing an embodiment of an adsorbent structure disclosed herein, including adsorbent structure 100; (b) passing a gas containing carbon dioxide (CO2-containing gas) through at least a portion of a flow channel of the structure, including all of the flow channel (e.g., 108); and (c) reacting at least a portion of the CO2 in the CO2-containing gas with a carbonate to produce an at least partially loaded (including fully loaded) adsorbent structure. Optionally, the CO2-containing gas stream consists essentially of air.

[0098] Optionally, the step of passing the CO2-containing gas through at least a portion of the flow channel is carried out at atmospheric pressure or near atmospheric pressure, which atmospheric pressure is known to those of ordinary skill and is typically 1 atm + / - 5%. Additionally or alternatively, the method further comprises (d) contacting at least a portion of the loaded adsorbent structure with steam to regenerate the adsorbent structure, wherein the steam is introduced at atmospheric pressure or near atmospheric pressure, or at a slightly elevated pressure slightly above atmospheric pressure (e.g., >1 bar), suitably about 1.3 bar / 130 KPa (about 18.9 psi), and at a temperature of about 100° C. to 130° C.

[0099] According to another aspect, the present disclosure also provides a method of preparing an adsorbent structure as described herein for capturing carbon dioxide from a CO2-containing gas. In embodiments where the metal-containing support is produced separately (such as by extrusion or 3D printing), the carbonate can be applied to the metal-containing substrate using impregnation. Wash coating is not preferred because the material is applied as a layer on top of the adsorbent structure surface, which tends to unnecessarily reduce the total accessible porosity of the metal-containing substrate. In another aspect, compared to wash coating, impregnation applies the carbonate in the total accessible pores without unnecessarily reducing the pore space and / or width of the flow channels 106, thereby allowing the carbon dioxide to better react with the carbonate and / or improve the gas flow through the adsorbent structure 100.

[0100] In various embodiments, metal-containing support material and carbonate material can be combined, for example, in paste form, and extruded together to form an adsorbent structure. In this embodiment, when the combined paste is extruded into a monolithic form to achieve desired physical and structural properties, carbonate can be dispersed throughout the metal-containing support. An advantage of combining metal-containing support material and carbonate material in a single step is that fewer process steps are required. Another advantage is that, when metal-containing support material and carbonate material are combined and formed together (such as via extrusion or 3D printing), it is easier to obtain good mixing and distribution of metal-containing support material and carbonate material.

[0101] An advantage of the various embodiments described herein is that the adsorbent structures of the present disclosure provide efficient contact between the gas mixture flowing through the adsorbent structure and the adsorbent structure (both the metal-containing support material and the carbonate salt) at a microscale level, and the metal-containing support provides efficient transport of the process gas through the adsorbent structure itself at a macroscale level without the need for a separate substrate which may result in increased production costs and reduced flow rates.

[0102] Various embodiments of the adsorbent structures disclosed herein can enhance flow paths and provide higher volumetric efficiency in configurations compared to packed adsorbent beds employing catalysts in particulate form or structures employing substrates (i.e., that do not contain the majority of the active material) or structures that apply the active material by washcoating. Packed adsorbent beds have higher pressure drops and slower mass transfer rates, which can lead to inefficient operation of the adsorption or catalytic process in large-volume gas separation processes, such as those employed in direct air capture processes. The adsorbent structures disclosed herein are particularly well-suited for large-volume gas separation processes that rely on rapid cycling to achieve low pressure drops and high volumetric efficiency.

[0103] Example

[0104] Example 1 Preparation of 10% K2CO3 Supported on TiO2 (Adsorbent Structure A)

[0105] As the metal-containing support, 12.2 g of a porous straight channel monolithic titania substrate having 100 cpsi, 0.35 mm walls, 0.74 open frontal area, a total accessible porosity (ε) of 0.50 was used. 载 The monolith (containing the metal support) was completely immersed in the solution for 30 minutes to impregnate the carbonate. Excess liquid on the flow channels and the outer surface of the monolith was removed using a compressed air nozzle. The sample was then dried at 120°C for 2 hours and calcined at 300°C for 2 hours to produce adsorbent structure A. A sample of adsorbent structure A was analyzed and the results showed that it contained 10.0% K2CO3 in anhydrous form supported on TiO2 (as the metal-containing support). The residual total accessible porosity (ε) of adsorbent structure A was calculated using the method disclosed herein. 残余 ) is 0.41.

[0106] Example 2 Preparation of 20% K2CO3 Supported on TiO2 (Adsorbent Structure B)

[0107] As the metal-containing support, 12.2 g of a porous straight channel monolithic titania substrate having 100 cpsi, 0.35 mm walls, 0.74 open frontal area, a total accessible porosity (ε) of 0.50 was used. 载The monolith (containing the metal support) was completely immersed in the solution for 30 minutes to impregnate the carbonates. Excess liquid on the flow channels and the outer surface of the monolith was removed using a compressed air nozzle. The sample was then dried in an air stream at 65°C for 15 minutes, then dried at 120°C for 2 hours and calcined at 300°C for 2 hours. A sample of adsorbent structure B was analyzed and shown to contain 20.0% K2CO3 in anhydrous form supported on TiO2 (as the metal-containing support). The residual total accessible porosity (ε) of adsorbent structure B was calculated using the method disclosed herein. 残余 ) is 0.31.

[0108] Example 3 Preparation of 10% K2CO3 Supported on Al2O3 (Adsorbent Structure C)

[0109] As the metal-containing support, 8.1 g of a porous straight channel monolithic Al2O3 substrate having 100 cpsi, 0.45 mm wall, 0.58 open frontal area, 0.68 total accessible porosity (ε 载 The monolith (containing the metal support) was completely immersed in the solution for 30 minutes to impregnate the carbonates. Excess liquid on the channels and the outer surface of the monolith was removed using a compressed air nozzle. The sample was then dried in an air stream at 65°C for 15 minutes, then dried at 120°C for 2 hours and calcined at 300°C for 2 hours. A sample of adsorbent structure C was analyzed and shown to contain 10.0% K2CO3 in anhydrous form supported on Al2O3 (as the metal-containing support). The residual total accessible porosity (ε) of adsorbent structure C was calculated using the method disclosed herein. 残余 ) is 0.63.

[0110] Example 4 Preparation of 25% K2CO3 Supported on Al2O3 (Adsorbent Structure D)

[0111] As the metal-containing support, 20 g of a porous straight channel monolithic Al2O3 substrate having 100 cpsi, 0.45 mm wall, 0.68 open frontal area, 0.70 total accessible porosity (ε 载体) and an average pore size of 12 nm, wherein 100% of the total accessible porosity has a pore size less than or equal to 50 nm. 34.8 g of K2CO3 were dissolved in deionized water to obtain a solution volume of 100 ml. The monolith (containing metal support) was completely immersed in the solution for 30 minutes to impregnate the carbonate. Excess liquid on the flow channels and the outer surface of the monolith was removed using a compressed air nozzle. The sample was then dried at 120°C for 2 hours and calcined at 300°C for 2 hours. A sample of adsorbent structure D was analyzed and the results showed that it contained 25.0% K2CO3 in anhydrous form supported on Al2O3 (as the metal-containing support). The residual total accessible porosity (ε) of adsorbent structure D was calculated using the method disclosed herein. 残余 ) is 0.52.

[0112] Example 5 Preparation of 10% Na2CO3 Supported on Al2O3 (Adsorbent Structure E)

[0113] 20 g of a porous straight channel monolithic Al2O3 substrate having 100 cpsi, 0.45 mm wall, 0.68 open frontal area, 0.70 porosity and an average pore size of 12 nm, with 100% of the total accessible porosity having pore sizes less than or equal to 50 nm, was used as a support. 13.9 g of Na2CO3 was dissolved in deionized water to obtain a solution volume of 100 ml. The monolith was completely immersed in the solution for 30 minutes. Excess water on the channels and the outer surface of the monolith was removed using a compressed air nozzle. The sample was then dried at 120°C for 2 hours and calcined at 300°C for 2 hours. The adsorbent contained 10.0% Na2CO3 supported on Al2O3. The residual porosity was 0.63.

[0114] The carbonate loading on a particular metal-containing support is defined as the anhydrous form of KCO and does not necessarily represent the final state of the alkali metal precursor on a particular adsorbent structure. Various adsorbent structures were prepared using loadings ranging from 7.5% KCO on γ-AlO to 40% KCO on γ-AlO. Adsorbent preparations were also performed using carbonates, bicarbonates, hydroxides, acetates, and citrates as precursor compounds.

[0115] Example 6: CO2 Capacity Fixed Bed Test

[0116] The adsorbent volume is 5 cm 3The adsorption capacity was tested by 5 adsorption-desorption cycles in a fixed bed apparatus of 100 nm. The apparatus was equipped with a calibrated mass flow controller for controlling the gas flow (air, nitrogen), and a membrane steam generator for humidifying the gas. Before the adsorption and desorption cycles, the sample was dried in argon at 120°C for 2 hours. The bed was then cooled to 30°C, and wet nitrogen with a relative humidity of 18% and a temperature of 30°C was passed through the adsorbent bed for 75 minutes. The bed temperature was kept at 30°C and the air flow was switched to air containing 380ppm to 420ppm CO2 and a relative humidity of 18% and a temperature of 30°C. The wet air was passed through the adsorbent bed at a gas hourly space velocity (at atmospheric pressure) of 24,000h-1 for 2 hours. The air flow was then switched to nitrogen, and the bed was flushed for 15 minutes to remove any physically adsorbed water. The adsorbent was then heated to 120°C in nitrogen for 30 minutes and subsequently heated in a mixture of 5% steam with the remainder nitrogen for 45 minutes to regenerate the adsorbent and desorb CO2. Afterwards, the adsorbent was cooled to 30°C to complete the first adsorption-desorption cycle. Subsequent cycles were performed according to the same protocol. The exhaust gas was passed through an IR analyzer to measure the CO2 and H2O breakthrough curves. The gas line was heated to prevent water condensation. The CO2 capacity was determined by integrating the CO2 breakthrough curve and reported based on the dry mass of the sample. Table 1 summarizes the CO2 desorption capacity of various adsorbents in the 5th cycle.

[0117] Table 1: Summary of adsorbent CO2 capacities

[0118]

[0119] *As reported by Rodríguez-Mosqueda et al. (“Parametrical Study on CO2 Capture from Ambient Air Using Hydrated K2CO3 Supported on an Activated Carbon Honeycomb,” Ind. Eng.

[0120] Chem. Res. 2018, 57, 3628-3638) 6

[0121] Adsorbents generally exhibit higher CO2 capacities in the first adsorption-desorption cycle. Therefore, we tested the adsorbents over five adsorption-desorption cycles and report the CO2 desorption capacities of the final cycle in Table 1. Adsorbent structure A impregnated with 10% K2CO3 supported on a titania honeycomb substrate (as described in Example 1) exhibited a residual porosity of 41%. The CO2 capacity of adsorbent structure A was 1.06 g CO2 / 100 g adsorbent (1.06 wt%), which is higher than the capacity of a reference sample of activated carbon honeycombs impregnated with K2CO3 tested at 30°C and 28% relative humidity, as reported by Rodríguez-Mosqueda et al.

[0122] Adsorbent structure B impregnated with 20% K2CO3 supported on a titanium dioxide honeycomb substrate (as described in Example 2) had a residual porosity of 31%. Adsorbent structure B had a capacity of 2.14 g CO2 / 100 g adsorbent (2.14 wt%). Unexpectedly, both adsorbent structures A and B maintained significantly better performance than the reference sample. It is believed that adsorbent structures A and B should be able to fully function in terms of structural integrity and CO2 capacity in subsequent adsorption-desorption cycles beyond the five cycles tested in these examples. In contrast, Rodríguez-Mosqueda et al. observed unstable adsorbents that failed after several cycles. Without wishing to be bound by theory, it is believed that in the reference sample, the carbonates undergo a phase transition from one set of adsorption-desorption cycles to the next (carbonates reacting with CO2 to bicarbonates during adsorption and dissolving and recrystallizing due to humidity fluctuations during desorption). These phase changes place stress on the activated carbon material, which is believed to cause it to break down after a few cycles.Unexpectedly, similar detrimental reactions are not observed for embodiments of the structured adsorbents described herein.

[0123] Although specific embodiments have been described herein, it should be understood that such description is not intended to limit the embodiments described. Rather, it is contemplated that any combination of the features and elements provided above (whether or not relating to different embodiments) can be used to implement and practice the contemplated embodiments. Furthermore, although the embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether a particular advantage is achieved by a given embodiment does not limit the scope of the invention. Therefore, the aspects, features, embodiments, and advantages described herein are merely illustrative and are not considered to be elements or limitations of the appended claims unless expressly recited in a claim.

Claims

1. An adsorbent structure for capturing carbon dioxide from a gas mixture, the adsorbent structure comprising: A first end and a second end; Multiple flow channels; and Multiple channel walls, wherein the flow channel is formed by at least one channel wall, wherein the flow channel extends from the first end to the second end, and wherein the channel wall comprises: o a carbonate in an amount ranging from greater than 5 wt% up to 50 wt%, preferably greater than 5 wt%, including 10 wt% up to 30 wt%, based on the total weight of the channel walls, wherein the carbonate is at least one of (i) an alkali metal (X2CO3) and (ii) an alkaline earth metal (YCO3); o a metal-containing support, the amount of the metal-containing support ranging from 40 wt% 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 metal alloys, metal oxides, metal-nonmetal alloys, ceramics, and any combination thereof, wherein the metal-containing support has a total accessible porosity (ε) in the range of 0.4 to 0.8, preferably 0.5 to 0.7 载体 ); wherein the total accessible porosity (ε 载体 ) is determined at least by: e 载体 =WPV 载体 / (WPV 载体 +1 / p 载体 ) Among them WPV 载体 is the gravimetric water pore volume of the metal-containing support (ml / g), where ρ 载体 is the gravimetric skeletal density of the metal-containing support, and wherein 40% up to 100% of said total accessible porosity has pore sizes less than or equal to 50 nm, and 0% up to 60% of said total accessible porosity has pore sizes greater than 50 nm.

2. The adsorbent structure according to claim 1, wherein the metal-containing support (WPV 载体 The gravimetric water pore volume (ml / g) of the water is determined at least as follows: WPV 载体 =(M2-M1) / ρ 液体 / (M1) wherein M1 is the mass (in grams) of the dry sample of the metal-containing support, where M2 is the mass (in grams) of the wet sample containing the metal support, and p 液体 is the gravimetric density of the liquid used to wet the sample.

3. The adsorbent structure according to any one of the preceding claims, having a residual total accessible porosity (ε) in the range of 5% to 75%, preferably 10% to 65%, more preferably 20% to 65%. 残余 ).

4. The adsorbent structure according to claim 3, wherein the ε 残余 Determined at least by: e 残余 =e 载体 -(w 碳酸盐 / (1-w 碳酸盐 ))*(1-e 载体 )*r 载体 / r 碳酸盐 where ε 载体 is the total accessible porosity of the metal-containing support, and Where W 碳酸盐 is the mass loading of carbonate on the adsorbent (wt %), and where ρ 载体 is the gravimetric skeletal density (g / ml) of the metal-containing support, and wherein p 碳酸盐 is the gravimetric density of the carbonate metal (g / ml).

5. The adsorbent structure according to any one of the preceding claims, wherein the sum of the amount of the carbonate salt and the amount of the metal-containing support is at least 95 wt.-%, preferably 97 wt.-%, more preferably 99 wt.-% of the adsorbent structure.

6. The adsorbent structure according to any one of the preceding claims, wherein X is selected from K + 、Na + 、Cs + 、Li + and any combination thereof, and Y is selected from Mg 2+ , Ca 2+ 、Sr 2+ 、Ba 2+ and alkaline earth metal cations in any combination thereof.

7. The adsorbent structure according to any one of the preceding claims, wherein the metal of the metal-containing support is selected from the group consisting of aluminum, silicon, titanium, zirconium, magnesium, calcium, iron, and any combination thereof; alternatively, wherein the metal-containing support is selected from the group consisting of silica, alumina, titania, zirconia, cordierite, mullite, silicon carbide, aluminosilicates, preferably zeolites, and any combination thereof.

8. The adsorbent structure according to claim 7, wherein the carbonate is selected from one or more alkali metals, and the metal-containing support is selected from titania and / or zirconia.

9. The adsorbent structure of claim 7, wherein the carbonate is selected from one or more alkali metals and the metal-containing support is alumina, preferably heat-treated alumina, more preferably selected from 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-alumina, kappa-alumina, eta-alumina, theta-alumina, magnesium aluminate, trine, bermire, and any combination thereof.

10. The adsorbent structure according to any one of the preceding claims, wherein the metal-containing support further comprises a reinforcing material to improve or facilitate mechanical strength and / or manufacturing process, the amount of the reinforcing material being less than 20 wt% of the total weight of the metal-containing support.

11. The adsorbent structure according to any one of the preceding claims, wherein 0% up to 20% of the total accessible porosity has pore sizes greater than 500 nm.

12. The adsorbent structure according to any of the preceding claims, further having a cell density in the range of 50 cells per square inch (cpsi) up to 400 cpsi, preferably in the range of 50 cpsi up to 300 cpsi, and an open frontal area in the range of 60% up to 85%, preferably in the range of 65% to 75%.

13. The adsorbent structure of any one of the preceding claims, wherein the channel walls further have an average thickness in the range of 150 microns up to 1000 microns.

14. A method for capturing carbon dioxide from a gas mixture, the method comprising: - Providing an adsorbent structure according to any one of claims 1 to 13; - passing a gas containing carbon dioxide (CO2-containing gas) through at least a portion of the flow channel, including the entirety of the flow channel; as well as - reacting at least a portion of the CO 2 in the CO 2 -containing gas with the carbonate to produce an at least partially loaded adsorbent structure.

15. The method of claim 14, wherein the CO2-containing gas stream consists essentially of air.

16. The method of any one of claims 14 to 15, wherein the step of passing the CO2-containing gas through at least a portion of the flow channel is performed at or near atmospheric pressure, the method further comprising: contacting the at least partially loaded adsorbent structure with steam to regenerate the adsorbent structure, wherein the steam is introduced at or near atmospheric pressure, or at a slightly elevated pressure slightly above atmospheric pressure (e.g. >1 bar), suitably about 1.3 bar / 130 kPa (about 18.9 psi), and at a temperature of about 100°C to 130°C.

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