Honeycomb substrate having high porosity and surface area and method of making same

Abstract

Embodiments of a honeycomb substrate are provided. The honeycomb substrate comprises a plurality of intersecting walls forming a plurality of channels extending through the honeycomb substrate from a first end to a second end. The honeycomb substrate comprises 40 wt% or greater sintered glass beads. The honeycomb substrate comprises a porosity of 60% or greater, and the honeycomb substrate comprises a surface area of 5 m2 / g or greater as measured according to Braunauer-Emmett-Teller methodology. Embodiments of the disclosure also relate to a method of preparing same.

Description

Attorney Docket No.: SP24-293PCT HONEYCOMB SUBSTRATE HAVING HIGH POROSITY AND SURFACE AREA AND METHOD OF MAKING SAMECROSS-REFERENCE TO REEATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.Provisional Application No. 63 / 720,363 filed November 14, 2024, the content of which is incorporated herein by reference in its entirety.BACKGROUND

[0002] The disclosure relates to honeycomb substrates and, more particularly, to a honeycomb substrate with a high surface area and to a method of making same.

[0003] Honeycomb substrates are versatile structures that can be used in a variety of contexts to filter, absorb, adsorb, catalyze, or otherwise interact with compounds in a gas stream. For example, honeycomb substrates can be used in the exhaust systems of combustion engines to remove particulate, and in another example, honeycomb substrates can be used to adsorb carbon dioxide from the air in direct air captures systems. Advantageously, honeycomb substrates are typically formed from ceramic materials that are mechanically stronger and that can be used at higher temperatures than other substrate materials.SUMMARY

[0004] According to a first aspect, embodiments of the disclosure relate to a honeycomb substrate. The honeycomb substrate comprises a plurality of intersecting walls forming a plurality of channels extending through the honeycomb substrate from a first end to a second end. The honeycomb substrate comprises 40 wt% or greater sintered glass beads. The honeycomb substrate comprises a porosity of 60% or greater, and the honeycomb substrate comprises a surface area of 5 m2 / g or greater as measured according to Braunauer-Emmett-Teller methodology.

[0005] According to a second aspect, embodiments of the disclosure relate to a carbon capture element comprising the honeycomb substrate of the first aspect.

[0006] According to a third aspect, embodiments of the disclosure relate to a method of preparing a honeycomb substrate. In the method, a green body is extruded. The green body comprises a plurality of intersecting walls forming a plurality of channels extending through the green body from a first end to a second end. The green body comprises a solids component,Attorney Docket No.: SP24-293PCT a binder component, and water. In the method, the green body is sintered to remove the binder component and the water to form a sintered structure having a porosity of at least 60%. The sintered structure has a first surface area as measured according to Braunauer-Emmett-Teller (BET) methodology. Further, in the method, the sintered structure is treated with acid to provide the sintered structure with a second surface area as measured according to BET methodology in which the second surface area is greater than the first surface area. In the method, the solids component comprises glass beads.

[0007] According to a fourth aspect, embodiments of the disclosure relate to a method of capturing carbon dioxide from a gas stream. In the method, the gas stream is directed through the carbon capture element according to the second aspect from the first end of the honeycomb substrate to the second end of the honeycomb substrate. The gas stream comprises a first concentration of carbon dioxide at the first end and a second concentration of carbon dioxide at the second end. The second concentration of carbon dioxide is less than the first concentration of carbon dioxide.

[0008] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0009] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment s), and together with the description serve to explain principles and operation of the various embodiments. In the drawings:

[0011] FIG. 1 depicts an embodiment of a honeycomb substrate, according to an exemplary embodiment of the present disclosure;

[0012] FIG. 2 is a flow diagram of a method of forming a honeycomb substrate, according to an exemplary embodiment of the present disclosure;Attorney Docket No.: SP24-293PCT

[0013] FIG. 3 schematically represents etching of ions from the sintered glass beads of the honeycomb substrate, according to an exemplary embodiment;

[0014] FIG. 4 is a graphical representation of the bulk density and surface area as a function of acid treatment time, according to exemplary embodiments;

[0015] FIGS. 5A-5D are SEM images of sintered honeycomb substrates after different acid treatment times, according to exemplary embodiments; and

[0016] FIGS. 6A and 6B are SEM images of sintered honeycomb substrates comprising clay after different acid treatment times, according to exemplary embodiments.DETAILED DESCRIPTION

[0017] Reference will now be made in detail to various embodiments of a honeycomb substrate with enhanced porosity and surface area and a method of making the honeycomb substrate, examples of which are illustrated in the accompanying drawings. As will be discussed more fully below, the presently disclosed honeycomb substrate is comprised of sintered glass beads, particularly hollow glass microspheres, and upon sintering the walls of the glass beads rupture, creating a very porous structure (e.g., 60% porosity or greater). According to the present disclosure, Applicant has found that treating this sintered structure with acid will greatly increase the surface area of the honeycomb substrate, allowing more space for sorbent loading. Specifically, Applicant has found that acid treating increases the surface area from less than 1 m2 / g to as much as 50 m2 / g or more depending on the length of the treatment. These and other aspects and advantages of the disclosed honeycomb substrate and method of making same will be described in relation to the embodiments provided below and in the drawings. These embodiments are presented by way of example and not by way of limitation.

[0018] FIG. 1 depicts a honeycomb substrate 100 according to one or more embodiments of the present disclosure. The honeycomb substrate 100 includes an outer wall 102 defining an outer perimeter shape of the honeycomb substrate 100. As shown in FIG. 1, the outer wall 102 defines substantially circular end faces at a first end 104 and at a second end 106, thus giving the honeycomb substrate 100 an overall cylindrical shape. However, the outer wall 102 may define other two-dimensional end face shapes, such as rectangles, triangles, pentagons, hexagons, ellipses, obround, and other polygonal and / or curved shapes. In general, the end faces will be the same shape and size, thereby defining an elongated or prismatic three-dimensional shape of the honeycomb substrate 100.Attorney Docket No.: SP24-293PCT

[0019] In one or more embodiments, the outer wall 102 comprises an average maximum cross-sectional dimension (e.g., diameter) as measured across the outer wall is in a range from 2 cm to 20 cm, in particular in a range from 5 cm to 15 cm.

[0020] Within the outer wall 102 is a plurality of intersecting walls 108. As shown in the embodiment of FIG. 1, the intersecting walls 108 are arranged in a grid in which first walls extend across the end face in a first direction and second walls extend across the end face in a second direction, substantially perpendicular to the first direction. In this way, the intersecting walls 108 define a plurality of channels 110. The intersecting walls 108 and, thus, the channels 110 extend along the length of the honeycomb substrate 100 from the first end 104 to the second end 106.

[0021] In one or more embodiments, the plurality of channels comprises a cell density ranging from about 6 cells per square inch (cpsi) to about 1200 cpsi, in particular about 20 cpsi to about 1000 cpsi. In one or more embodiments, the intersecting walls define a cross-sectional shape of the plurality of channels, the cross-sectional shape being rectangular, hexagonal, circular, ovate, elliptical, and other regular or irregular polygonal or curved shapes. In one or more embodiments, a thickness of each wall of the plurality of intersecting walls is in a range of about 0.001 inches to about 0.1 inches, in particular in a range from about 0.001 inches to about 0.05 inches.

[0022] According to the present disclosure, the honeycomb substrate 100 is comprised of sintered glass beads in which, after sintering, the honeycomb substrate 100 undergoes an acid treatment. In particular, the honeycomb substrate 100 comprises 40 wt% or greater sintered glass beads. In one or more embodiments, the honeycomb substrate 100 comprises sintered glass beads in an amount in a range from 40 wt% to 80 wt%. In one or more embodiments, the sintered glass beads comprise hollow glass microspheres. In one or more embodiments, the glass beads comprise a median particle size d50 in a range of 10 pm to 50 pm, in particular in a range of 10 pm to 30 pm. The particle size of the glass beads can be used to influence the final pore size of the honeycomb substrate by using a smaller median particle size to produce a smaller pore size and a larger median particle size to produce a larger pore size.

[0023] The glass beads, in particular hollow glass microspheres, are used to create the structure of the honeycomb substrate 100 and as the former of the pores in the honeycomb substrate 100. Using such glass beads will provide greater porosity as compared to solid glass particles, flakes, or fibers.Attorney Docket No.: SP24-293PCT

[0024] The glass composition of the glass beads is not particularly limited. In one or more embodiments, the glass composition comprises primarily silica (SiCh), i.e., at least 50 wt% silica, in particular at least 60 wt% silica, and most particularly at least 70 wt% silica. In one or more embodiments, the glass beads are formed from a glass composition comprising 65 wt% to 85 wt% SiCh; 1 wt% to 10 wt% CaO; 1 wt% to 10 wt% B2O3; and 1 wt% to 10 wt% Na2O. In embodiments, the glass composition may comprise up to 3 wt% of one or more other components, including MgO and AI2O3.

[0025] In one or more embodiments, the honeycomb substrate 100 further comprises graphite. In one or more embodiments, the honeycomb substrate 100 comprises from 0 wt% to 50 wt%, in particular 10 wt% to 30 wt%, of graphite. Advantageously, the graphite may provide a continuous network within the honeycomb substrate 100. In this regard, the graphite has a much higher combustion point than the softening or melting point than the glass beads, and at the sintering temperatures used to form the honeycomb substrate, the graphite will not combust, helping to prevent shrinkage of the honeycomb substrate 100 during sintering. Additionally, in such embodiments, the graphite may be used to provide an electrically conductive network within the honeycomb substrate 100. Notwithstanding, in one or more other embodiments, the sintering temperature can be increased to burn out more graphite to make the honeycomb substrate nonconductive.

[0026] In one or more embodiments, the honeycomb structure further comprises clay. In one or more embodiments, the honeycomb structure comprises from 0 wt% to 50 wt%, in particular clay. In one or more embodiments, the clay may be used to replace a portion of the glass beads within the structure of the honeycomb substrate 100. Accordingly, in one or more embodiments, the combined amount of glass beads and clay is in a range from 50 wt% to 100 wt%, in particular in a range from 60 wt% to 90 wt%. Advantageously, including clay enhances the extrudability of the honeycomb substrate and improves the mechanical strength; although, including clay also tends to decrease the porosity and achievable surface area. Notwithstanding, the clay, along with the glass beads, is etched to generate surface area.

[0027] The type of clay used is not particularly limited. In one or more embodiments, the clay is at least one of a kaolinite, montmorillonite, smectite, or illite. In one or more embodiments, the clay is calcined. For example, the clay may be calcined kaolin, which is kaolin clay that has been calcined to drive off the water of hydration. Advantageously, calcined kaolin is more stable, harder, denser, and less absorbent, and the calcined kaolin can help control shrinkage and cracking of the honeycomb substrate 100 during sintering.Attorney Docket No.: SP24-293PCT

[0028] In one or more embodiments, the honeycomb substrate 100 comprises a porosity of 60% or greater, in particular 70% or greater. In one or more embodiments, the porosity is measured using mercury intrusion porosimetry. In one or more embodiments, the pores comprise a median pore size d50 in a range of 5 pm to 20 pm.

[0029] In one or more embodiments, the honeycomb substrate 100 comprises a surface area of 5 m2 / g or greater as measured according to Braunauer-Emmett-Teller (BET) methodology, a methodology known in the art for measuring surface area. In one or more embodiments, the surface area is 15 m2 / g or greater, in particular 50 m2 / g or greater. In one or more embodiments, the surface area is as high as 80 m2 / g.

[0030] In one or more embodiments, the honeycomb structure comprises a bulk density in a range from 0.5 g / cm3to 0.7 g / cm3. As will be discussed more fully below, the bulk density is influenced by the composition of the honeycomb substrate 100. In particular, adding clay to or increasing the amount of clay in the composition of the honeycomb substrate 100 will increase the density. Further, as will be discussed below, increasing acid treatment time will decrease the density.

[0031] In one or more embodiments, the honeycomb substrate 100 as described above is used as a carbon capture element, in particular for direct air capture. In particular, the honeycomb substrate 100, having the disclosed enhanced surface area, can be loaded with a sorbent material, such as polyethyleninime, sodium carbonate, or metal-organic frameworks (MOF). In one or more embodiments, the sorbent is loaded into the honeycomb substrate 100 using a process such as washcoating.

[0032] Having described the structure of the honeycomb substrate, embodiments of a method 200 of preparing the honeycomb substrate are now described in relation to the flow diagram of FIG. 2. In the method 200, a green body is extruded in a first step 201. The green body is formed from a slip composition comprising a solids component, a binder component, and water. The slip composition is extruded through an extrusion die that forms the plurality of intersecting walls and channels extending through the green body from a first end to a second end.

[0033] In the slip composition, the solids component includes the glass beads, graphite, and optionally clay as described above. As mentioned above, inclusion of clay in the slip composition helps to improve the extrudability of the slip composition. In one or more embodiments, the binder component comprises a methylcellulose compound, a lubricant, andAttorney Docket No.: SP24-293PCT a nitrate salt. The methylcellulose helps to keep the solids component from settling in the slip composition. An example of a suitable methylcellulose is Culminal™ MHPC 724 (available from Ashland Inc., Wilmington, DE). In one or more embodiments, the lubricant is at least one of a mineral oil, tall oil, fatty acid, or sodium stearate, amongst other possibilities. In one or more embodiments, the lubricant further comprises an antioxidant; although, an antioxidant can be added separately, too. The lubricant facilitates extrusion of the slip composition. An example of a suitable lubricant is MOX30A, available from S & S Chemical, Northport, NY. In the slip composition, the nitrate salt lowers the firing temperature and improves mechanical strength. In one or more embodiments, the nitrate salt is lithium nitrate (LiNCh) or sodium nitrate (NaNCh). Lithium nitrate, in particular promotes crystal formation, maintaining the structure of the honeycomb substrate and reducing shrinkage, and sodium nitrate lows the melting temperature of the glass.

[0034] In one or more embodiments, the binder component comprises the methylcellulose compound in an amount in a range of 5 parts per hundred weight (pph) to 20 pph of the solids component. In one or more embodiments, the binder component comprises the lubricant in an amount in a range of 5 pph to 20 pph of the solids component. In one or more embodiments, the binder component comprises the nitrate salt in an amount in a range of 5 pph to 20 pph of the solids component.

[0035] In one or more embodiments, the slip composition comprises water in an amount in a range of 35 pph to 65 pph.

[0036] In a second step 202 of the method 200, the green body is sintered to remove the binder component and the water to fuse the solids components to form a sintered structure having a porosity of at least 60%. In one or more embodiments, the sintering is performed at a temperature in a range of 500 °C to 800 °C, in particular in a range of 550 °C to 700 °C, for a time in a range of 5 hours to 50 hours, in particular in a range of 10 hours to 20 hours. During sintering, the walls of the glass beads deteriorate, rupturing to open the interior structure of the glass beads. Indeed, when viewed using scanning electron microscopy, remnants of the spherical glass beads can still be seen in which the wall of the glass bead has ruptured

[0037] After the second step 202, the sintered structure has a first surface area as measured according to BET methodology. In one or more embodiments, the first surface area is less than 5 m2 / g, in particular 1 m2 / g or less.Attorney Docket No.: SP24-293PCT

[0038] Thereafter, in a third step 203 of the method 200, the sintered structure is treated with acid to provide the sintered structure with a second surface area as measured according to BET methodology. The second surface area is greater than the first surface area. As discussed above, the second surface area is 5 m2 / g or greater, in particular, 15 m2 / g or greater, and most particularly 50 m2 / g or greater.

[0039] In one or more embodiments, the acid used for the treating comprises at least one of sulfuric acid, a chlorine acid (e.g., hydrochloric acid, hypochi orous acid, chlorous acid, chloric acid, or perchloric acid), or nitric acid.

[0040] In one or more embodiments, the treating is performed at a temperature in a range from 50 °C to 100 °C. In one or more embodiments, the treating is performed for a time of 2 hours or less, in particular 1 hour or less.

[0041] As shown in FIG. 3, the acid treatment of the third step 203 leaches ions, such as calcium (Ca2+), sodium (Na+), and boron (B3+), out from the sintered honeycomb substrate, leaving the silica framework. The removal of the ions from the sintered honeycomb substrate causes a decrease in the density of the honeycomb substrate 100 as well as increasing the roughness and, thus, surface area of the intersecting walls 108 of the honeycomb substrate 100. In one or more embodiments, sintering (second step 202) is performed before acid treatment (third step 203) in order to create phase separation between the different oxides of the glass network, allowing for the acid to selectively leach the non-silica portions of the honeycomb substrate 100.

[0042] As mentioned above, after forming the honeycomb substrate 100, the honeycomb substrate 100 can be loaded with a sorbent material through a process such as washcoating. The disclosed honeycomb substrate 100 advantageously provides high porosity for gas diffusion and high surface area for sorbent loading.

[0043] Accordingly, the present disclosure also relates to a method of capturing carbon dioxide from a gas stream. In the method, the gas stream is directed through the honeycomb substrate according to the present disclosure from the first end to the second end. The gas stream comprises a first concentration of carbon dioxide at the first end and a second concentration of carbon dioxide at the second end. The second concentration of carbon dioxide is less than the first concentration of carbon dioxide. In one or more embodiments, the gas stream is ambient air such that the method of capturing carbon dioxide is a method of direct air carbon capture.

[0044] EXPERIMENTAL EXAMPLESAttorney Docket No.: SP24-293PCT

[0045] Two example honeycomb substrates according to the present disclosure were prepared. The example honeycomb substrates were prepared from the slip compositions described in Table 1, below.Table 1. Slip Compositions for Honeycomb Substrates

[0046] Green honeycomb substrates formed form the slip compositions of Examples 1 and 2 were extruded. The green honeycomb substrate of Example 1 was fired 600 °C for 2 hours, and the green honeycomb substrate of Example 2 was fired at 700 °C for 2 hours. The firing burned off the binder component and evaporated the water, leaving a sintered honeycomb substrate comprised of the fused solids component. The sintered honeycomb substrate was cut into samples, including a control sample for each of the compositions of Example 1 and Example 2 and multiple samples that were subsequently treated with acid. The acid treatment involved submerging the samples in an acid bath of 20 wt% H2SO4 at a temperature of 90 °C. The time of acid treatment as well as the resultant porosity, mean pore size, bulk density, and surface area (BET) are summarized in Table 2, below.Table 2. Properties of Sintered Honeycomb SubstrateAttorney Docket No.: SP24-293PCT

[0047] As can be seen from Table 2, the sintered honeycomb substrate of Example 1 without acid treatment had a baseline porosity of 74% but a surface area of about 0 m2 / g. After acid treatment for just 15 minutes, the porosity decreases slightly, but the surface area increases by 9.55 m2 / g. After acid treatment for 30 minutes and 60 minutes, the porosity is slightly higher than the untreated sample, and the surface area increases to about 17% and 65%, respectively. Thus, without substantially affecting porosity, the acid treatment vastly increases the surface area of the honeycomb substrate, allowing more surface for deposition of a carbon capture material and thus for a greater degree of carbon capture. Further Table 2 demonstrates that the median pore diameter d50 decreases, which represents the opening up of smaller pores in the sintered honeycomb structure, thereby shifting the median pore diameter downward. Additionally, the bulk density decreases as a function of treatment time, which is expected as the acid causes dissolution of the glass beads.

[0048] FIG. 4 provides a graphical representation of the acid treatment of the honeycomb substrate of Example 1. As can be seen from FIG. 4, the bulk density of the samples decreases with increasing treatment time, and the surface area increases with increasing treatment time.

[0049] FIGS. 5A-5D provide SEM images of the honeycomb substrates prepared according to the four samples of Example 1. In particular, FIG. 5 A is an SEM image of the untreated sample (i.e., 0 minutes of treatment from Table 2), and FIG. 5B is an SEM image of the sample treated for 15 minutes. As can be seen in a comparison of the SEM images, the sample treated for 15 minutes has greater roughness, greater depth of pores, and more small pore openings. As the length of acid treatment increases to 30 minutes and 60 minutes as shown in FIGS. 5C and 5D, respectively, the roughness, depth of the pores, and number of pore openings continues to increase. Thus, the SEM images of FIGS. 5A-5D demonstrate that the acid treatment causes the surface area to increase proportional to the time of treatment.

[0050] The sintered honeycomb substrate of Example 2 had a baseline porosity of about 65%, but a surface area of only 0.9 m2 / g. After acid treatment for 72 minutes, the porosity increased to about 72%, and the surface area increased to about 56 m2 / g.Attorney Docket No.: SP24-293PCT

[0051] FIGS. 6A and 6B provide SEM images of the honeycomb substrate prepared according to the two samples of Example 2. As with the previous set of SEM images, the SEM images of FIGS. 6A and 6B demonstrate that acid treatment leads to an increase in roughness and surface area. The microstructure of the samples of Example 2 is different as compared to the sintered and acid treated honeycomb substrate of Example 1 because of the presence of clay in the solids component.

[0052] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article "a" is intended to include one or more than one component or element, and is not intended to be construed as meaning only one.

[0053] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosed embodiments. Since modifications, combinations, sub-combinations, and variations of the disclosed embodiments incorporating the spirit and substance of the embodiments may occur to persons skilled in the art, the disclosed embodiments should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

Attorney Docket No.: SP24-293PCT What is claimed is:

1. A honeycomb substrate, comprising:a plurality of intersecting walls forming a plurality of channels extending through the honeycomb substrate from a first end to a second end; andwherein the honeycomb substrate comprises 40 wt% or greater sintered glass beads, a porosity of 60% or greater, and a surface area of 5 m2 / g or greater as measured according to Braunauer-Emmett-Teller methodology.

2. The honeycomb substrate of claim 1, wherein the sintered glass beads comprise hollow glass microspheres.

3. The honeycomb substrate of claim 1 or claim 2, wherein the sintered glass beads comprise a plurality of glass beads with ruptured glass walls.

4. The honeycomb substrate of any of claims 1-3, wherein a median particle size d50 of the glass beads is in a range of 10 pm to 50 pm.

5. The honeycomb substrate of any of claims 1-4, wherein the glass beads are formed from a glass composition comprising at least 60 wt% of silica.

6. The honeycomb substrate of any of claims 1-5, wherein the honeycomb substrate comprises graphite.

7. The honeycomb substrate of claim 6, wherein the honeycomb substrate comprises the graphite in an amount up to 50 wt%.Attorney Docket No.: SP24-293PCT 8. The honeycomb substrate of claim 6 or claim 7, wherein the honeycomb substrate comprises clay.

9. The honeycomb substrate of claim 8, wherein the honeycomb substrate comprises the clay in an amount up to 50 wt%.

10. The honeycomb substrate of any of claims 1-9, wherein the surface area is 15 m2 / g or greater.

11. The honeycomb substrate of any of claims 1-10, wherein the surface area is 50 m2 / g or greater.

12. The honeycomb substrate of any of claims 1-11, wherein a bulk density of the honeycomb substrate is in a range from 0.5 g / cm3to 0.7 g / cm3.

13. The honeycomb substrate of any of claims 1-12, wherein the honeycomb substrate comprises a perimeter wall and an average maximum cross-sectional dimension as measured across the perimeter wall is in a range from 2 cm to 20 cm.

14. A carbon capture element comprising the honeycomb substrate of any of claims 1-13.

15. The carbon capture element of claim 14, wherein the honeycomb substrate is loaded with a sorbent.

16. The carbon capture element of claim 15, wherein the sorbent comprises at least one of polyethylenimine, sodium carbonate, or a metal-organic framework.Attorney Docket No.: SP24-293PCT 17. A method of preparing a honeycomb substrate, comprising:extruding a green body comprising a plurality of intersecting walls forming a plurality of channels extending through the green body from a first end to a second end, the green body comprising a solids component, a binder component, and water;sintering the green body to remove the binder component and the water to form a sintered structure with a porosity of at least 60%, the sintered structure comprising a first surface area as measured according to Braunauer-Emmett-Teller (BET) methodology; and treating the sintered structure with acid to provide the sintered structure with a second surface area greater than the first surface area as measured according to BET methodology; andwherein the solids component comprises glass beads.

18. The method of claim 17, wherein the solids component comprises 40 wt% or greater of the glass beads.

19. The method of claim 17 or claim 18, wherein the glass beads comprise hollow glass microspheres.

20. The method of any of claims 17-19, wherein the solids component further comprises graphite.

21. The method of claim 20, wherein the sintered structure comprises the graphite in an amount up to 50 wt%.

22. The method of any of claims 17-21, wherein the binder component comprises lithium nitrate to inhibit shrinkage during the sintering.

23. The method of claim 22, wherein the solids component does not comprise clay.Attorney Docket No.: SP24-293PCT 24. The method of claim 20 or claim 21, wherein the solids component comprises clay.

25. The method of claim 24, wherein the sintered structure comprises the clay in an amount up to 50 wt%.

26. The method of claim 24 or claim 25, wherein the binder component comprises sodium nitrate to decrease a melting temperature of a glass material of the glass beads.

27. The method of any of claims 17-26, wherein the binder component comprises a methylcellulose compound, a lubricant, and a nitrate salt.

28. The method of any of claims 17-27, wherein the sintering is performed at a temperature in a range of 500 °C to 800 °C for a time in a range of 5 hours to 50 hours.

29. The method of any of claims 17-28, wherein the acid used for the treating comprises at least one of sulfuric acid, a chlorine acid, or nitric acid.

30. The method of any one of claims 17-29, wherein the treating is performed at one or more temperatures in a range from 50 °C to 100 °C.

31. The method of any one of claims 17-30, wherein the treating is performed for a time of 2 hours or less.

32. The method of any one of claims 17-31, wherein the first surface area is less than 5 m2 / g and the second surface area is 5 m2 / g or greater.

33. The method of claim 32, wherein the second surface area is 15 m2 / g or greater.Attorney Docket No.: SP24-293PCT 34. The method of claim 32 or claim 33, wherein the second surface area is 50 m2 / g or greater.

35. The method of any of claims 17-34, wherein the sintered structure comprises a bulk density in a range from 0.5 g / cm3to 0.7 g / cm3.

36. The method of any of claims 17-35, wherein after the treating, the method further comprises loading the sintered structure with a sorbent.

37. The method of claim 36, wherein the loading comprises washcoating the sintered structure with the sorbent.

38. The method of claim 36 or claim 37, wherein the sorbent is at least one of polyethylenimine, sodium carbonate, or a metal-organic framework.

39. A method of capturing carbon dioxide from a gas stream, comprising:directing the gas stream through the carbon capture element of any of claims 14-16 from the first end of the honeycomb substrate to the second end of the honeycomb substrate; andwherein the gas stream comprises a first concentration of carbon dioxide at the first end and a second concentration of carbon dioxide at the second end less than the first concentration of carbon dioxide.

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